CA2175377A1 - Filter manufactured by micropyrectic synthesis - Google Patents

Abstract

A modular filter for gases liquid and particulate matter is disclosed, the filter comprising at least two porous ceramic or ceramic modules. A regenerative filter is also disclosed comprising a means for filtering; and a means for regenerating said means for filtering, said means for regenerating being integral with said filtering means. A method for coating articles with a conductive coating is also included. Devices which may be used in conjunction with both modular and/or regenerative filters are disclosed.

Description

w o 96/06814 217 5 3 7 7 PCTAUS95/06387 FILTER MANUFACTURED BY MICROPYRECTIC SYNTHESTS

This application is a contin-l~tion-in-part application of PCT application serial number PCT/US95/04935 which is a contin-lAtion-in-part application of application serial llulllbel 08/395,576 which is a continn~tion-in-part application of application serial number 08/297,023 filed August 29, 1994, which is a divisional of appllcation serial number 08/030,586 filed on March 12, 1993, now abandoned. This application is also a continnAtion-in-part application of application serial number 08/369,426 which is a continllAtion-in-part application of application serial number 08/353,727.

FIELD OF THE INVENTION
The present invention relates generally to filter devices for filtering gaseous,liquid and particulate matter. More specifically, the present invention relates to filter S devices having a mo~lllAtP(l design. Even more specifically, the present invention relates to the use of these devices in e~rhAllst emissions af~elLleallllent systems. This invention also relates to a lcgel~lalive filter device cullllJlishlg ceramic, metal-ceramic or inter-m~tAllir composites. More specifically, the present invention relates to an integral heating el~mPnt made in situ with a filtering device. The present10 invention also relates to a process for applying a conductive coating to a ceramic, ceramic composite or inter-m~tAllic structure. The present invention further relates to peripheral and control devices used in conjullclion with the filter devices.

BACKGROUND OF THE INVENTION
During the last few years, several studies have evaluated the health risks associated with exposure to engine exhaust emissions. As a result of these studies, several governm~nt and health o~g~";~AIions have decided to tighten the standards 217S~77 wo 96/06814 PCT/US95/06387 which apply to engine-run vehicles, their fuels and their particulate and gaseous emissions.

On November 15, 1990, the President of the United States signed into law the Clean Air Act Amendments of 1990. Beginning in 1994, the new law sets a performance criteria. Specifically, it requires buses operating more than 70 percent of the time in large urban areas (using any fuel) to cut partir~ te~ by 50 percent compared to conventional heavy duty vehicles. Also, beginning in 1994, the Ellviro~ rnt~l Protection Agency began requiring a yearly testing to d~ e whether buses subject to the standard are meeting the standard in use over their full useful life. Similar provisions exist in other countries and therefore a global effort is underway to find exhaust filters and cleaning devices which would help consumers and the industry in reacting to the stringent standards set by the law.

Rec~ e of the financial and logistical concerns with alL~lllalive fuels, transitauthorities and bus engine m~mlf~rtllrers are seriously considering ~rh.~l.,allllent systems such as trap-oxidizer technology to meet 1993/94 EPA laws and regulations.
Bus engines, for example, run on a stop-and-go cycle which forces the engines tooperate with a dirty, sooty exh~llct Second, these vehicles operate in dense population areas and hence, bus exh~lst and pollution is considered a greater health hazard than over-the-road trucks. Third, environmrnt~ t~ would like to be as clean as possible even if it means going beyond EPA regulations. These and other factors make trap oxidizer technology very attractive, provided that its long-term durability can be proven and provided it is made available at reasonable costs.
The 1993/94 EPA law and regulations are only the first step in a series of ever-tightrning regulations to follow. For the diesel engines industry, the next step in regulation occurs in 1998, when the laws require tighter NO,~ control. Even though NO,~ reduction for 1994 levels was achieved by improved engine design, it is generally accepted that to meet the 1998 levels of 4 g/Bhp-h NO,~, diesel engines will have to use ar~ l,ent systems. As the NO,~ level is re~nre~ however, generally the particulate level increases. Hence, in trying to meet the 1998 low NO,~ levels,

2 1 7 ~i 3 7 7 PCT/US95/06387 -engine m~mlfartllrers are faced with increased partirul~trs, which require further use of arl~,lL~ nt devices such as converters and traps.

AflclLleatlllent devices of the present invention made of ceramic, ceramic 5 composite or inter-metallic filter devices, as well as the heating elements (which may be the identical material as the ceramic, ceramic composite, or inter-mPt~llic filter devices), provide implovcd converters and trap systems which offer the flexibility, efficiency, and cost-effectiveness needed to meet the ch~llenges presented by present (1994) and mPdinm-term (1998), diesel emissions regulations. Preferably a conductive 10 coating may be applied to the filter devices of the present invention. This coating may act as a heating elemPnt. Also preferably, the filter devices may be micl.~ylcLically synth~si7Pd. ''Micrû~yl~,Lics'' or "miclu~ylcLically synthrsi7e~1," as used herein refers to self prop~g~ting high lem~ Lulc synthesis as ~i~cllssed in the review article by Subrall~ll~ly~n et al., in The Journal of Macromolecular Science at Vol. 27, p.p. 6249 - 6273 (1992).

The filter devices used in arl~,lLlc~ nt trap systems are the core of the system and great efforts are being made to fine-tune the existing systems to improve their errcc~ivclless and durability. One of the problems of the current technology is 20 in "regel~ .ting" the filter by burl~ing off the arcllm~ te~ particulate matter.
Tniti~tin~ and controlling the l~el~,lalion process to ensure reliable regeneration without damage to the trap is the central e~-gi~ e~ g problem of trap oxidizer development today. The reason is that over time, the filter becomes loaded with the soot it has trapped and must be cleaned or ''~gellcla~ed''. The process of 25 regeneldtion burns or "oxidizes" the soot collected within the filter. The cleaned filter can be used many times provided it can be succes.~fully regenerated many thousands of times over its lifetime without failure. Another problem faced by the current technology is the need for o~tillli~lion of the filter structure, as in a mo~nl~tr-l design. Yet another problem of the current technology is that ~;ullcllLly 30 available filter materials are not optimally thPrm~lly shock lcsisL~ nor are they highly thrrm~lly cyclable, as in micropyretically m~nllf~rtured materials.

21 Pleselllly, most of the available arLelLledL~ nt trap systems are based on the cellular cordierite ce~amic monolith trap. These traps have not been efficient at collecting soot, or at collecting a large fraction of the particulate soluble organic fMction (SOF). Also, these traps have several other limitations and leave much room 5 for improvement. For example, the straight channeled ("honey-comb") structure of the filters optimizes neither stream line distortion nor surface area, for particulate collection. Further, the cordierite ceramic used in today's filters is expensive.

An initial attempt at solving some of the above described problems in 10 ar~ leal,lle.l~ systems was provided by the ceramic fiber coil traps developed by Mann and Hummel and Daimler Benz in West Gellll~ly. These traps were composed of a number of individual filtering elemPrlt.c, each of which consisted of a number of thi-~nPsses of silica fiber yarn wound on a punched metal support. A number of those fîltering elements were suspended inside a large metal can to make up a trap.
15 However, failures during German field demonstrations appear to have reduced or elimin~tPd further work or application of this system, according to "Diesel Particulate Control Around the World," Michael P. Walsh et al. part of "Global Developments in Diesel Particulate Control" P-240, publ. SAE, Inc. (Feb. 1991).

Numer~us other trapping media have also been tested or proposed, including ceramic foams, corrugated mullite fiber felts, and catalytic coated stainless steel wire mesh.

With respect to regeneration, many dirrel~llL c-)l~e~ are being tested. They range from p.illlili\re off-board l~gel~lalion of the filter in an external oven to sophicti~ted on-board automatic electrical or burner reg~llelalion systems usingelectronic controls and include catalytic injection systems. These approaches toegellerdlion can generally be divided into two groups: passive systems and active systems. Passive systems must attain the conditions required for regeneld~ion during normal operation of the vehicle. Active systems, on the other hand, monitor the build up of particulate matter in the trap and trigger specific actions leading to regeneldtion when nPeded WO 96tO6814 217 ~ 3 7 7 PCT/US95106387 Passive rege~ Lion systems face special problems on heavy duty vehicles.
Fxh~ t It;lllpel~lules from heavy duty diesel engines are normally low, and recent developments such as charge air cooling and increased turbo charger efficiency are reducing them still further. Under some conditions, it would be possible for a truck 5 driver to drive for many hours without ex~ee-1ing the exhaust temperature (around 400-450C) required to trigger regen.,lation. Active systems, on the other hand, are generally e~l ensive, often requiring complex logic and electronics to initiate regell~~lion.

In addition to the problems of the presently available arlelll. atment systems addressed above, the high collcellLl~tion of soot per unit of volume in the cordierite makes these traps sel~ilive to "regelltldlion" conditions. Trap loading, temperature, and gas flow rates must be m~int~in~ within na fairly narrow window. Otherwise, the trap fails to "regenel~le" fully, or cracks or melts to overh~o~tin~ because the high 15 temperature gradients in the filter monolith damage the cordierite structure.

Engine and catalyst m~mlf~tllrers have also e~cl;.l.Pnt~(l with many catalytic con~lt,.~ and with a wide variety of legen~lalive catalytic traps as solutions to the ~r~ le~",~"l problems described above. Precious metal catalytic traps are effective 20 in oxit1i7ing gaseous hydroc&ll,vns and CO as well as the particulate SOF but are relatively ineffective in preventing soot oxidation, a particular problem for diesel engines. Moreover, these metals also promote the oxidation of SO2 to particulateslllf~t~s such as sulfuric acid (H204). Base metal catalytic traps, in contrast, are effective in promoting soot oxidation, but have little effect on hydrocalbvlls, CO, NO
25 or SO2. Another disadvantage of precious metal catalysts is that they are very expensive.

Unlike a catalytic trap, a flowLlllvugh catalytic coll~ el does not collect most of the solid particulate matter, which simply passes through in the exhaust. The 30 particulate control efficiency of the catalytic collvelLel is, of course, much less than that of a trap. One of the major disadvantages of the catalytic converter is the same as with the precious metal catalytic particulate trap: sulfate emissions. The main WO 96/06814 ' PCT/US95/06387 21753~7 object of the catalysts used is to raise the exhaust temperature to a point that could convert the gaseous compounds to safer gaseous emissions. The catalysts undergo chemical reactions which raise the lel,lpel~u,c; of the exhaust gases allowing them to be converted to the safer gases. One of the major reasons which catalytic material and tre~tm~nt~ are used to assist in trap regelleldlion, is that none of the heating systems ~LL~ d, such as diesel fuel burners, electrical heaters and other heaters have been s~cces~ful. However, if there were a rege,~e,~lion system in which a converter or trap could be used without a catalyst for regeneration, the above-listed objects would be achieved.
With respect to processes for the m~mlf~rnlre of porous ceramic articles, U.S.
Pat. No. 3,090,094, issued May 21, 1963 to K. Schw~lL~wdlder et al, discloses a m~thod of making an open-cell porous ceramic article which comprises immersing an open-cell spongy material, preferably polyurethane, in a slurry cont~ining a ceramic coating material to coat cell-defining walls of the spongy material, removing excess slurry from the spongy m~teri~l, and firing the coated spongy material at a t~",~e,~u,e and for a time sufficient to remove the spongy material and form a hardened, vitrified structure. The ceramic coating material may include particulate zirconia, zircon, petalite, mullite, talc, silica and ~lnmin~, having particle sizes l~ngillg from - 80 mesh to - 600 mesh. A binder such as clay, sodium silicate, and calcium ~ e and phosphoric acid, is preferably present in the slurry. Firing is conl1--rted at 500 to 3000 F. (260 to 1650- C.), preferably at 2100 to 2950- F.
(1150- to 1620- C.).

U.S. Pat. No. 3,097,930, issued Jul. 16, 1963 to I. J. Holland, discloses a method of making a porous shape of sintered refractory material which comprises ""~le~sllating a foamed plastic sponge shape with a suspension of refractory particles, drying the illl~,eglldt~d shape, and firing the dried shape in an inert atmosphere to volatilize the sponge material and to sinter the refractory particles. The impregnation and drying steps may be repeated. The foamed plastic sponge may be polystyrene, polyethylene, polyvinyl chloride, latex, or polyu,~Ll~lle, the latter being plere~led.
Refractory materials include clays, minerals, oxides, borides, carbides, silicides, W O 96/06814 2 1 7 ~ ~ 7 7 PCTrUS95/06387 nitrides and mixtures thereof. Specific examples used alumina, beryllia and china clay with particle sizes ranging from less than 1 to greater than 10 microns. Firing was con-lucte(l at 1700 C for alumina and 1350 C for china clay.

U.S. Pat. No. 4,697,632, issued Oct. 6, 1987 to N. G. Lirones, discloses a ceramic foam filter, in~ ting refractory lining, and a melting crucible, and a process for production thereof, which comprises providing an open-cell foam pattern, impregnating the pattern with a ceramic slurry, burning out the foam pattern at a tel~pel~lu~e between 1400 and 2200 F (760 and 1205 C.) to form a ceramic substrate, impregn~ting the ceramic substrate with additional ceramic slurry, and firing the ill~regl~aLed ceramic substrate at a temperature of 2200 to 3400 F.(1205 to 1870 C.). The foam pattern material may be a flexible polyurethane, polyethylene, poly~ropylene or graphite. A suitable ceramic slurry contains from 1 %
to 20% silica (dry weight), and from 99% to 80% alumina (dry weight), with a viscosity belweell 5 and 20 seconds and a film weight belweell 1.0 and 8.0 grams per standard six inch square plate. Preferably the slurry includes a suspending agent, a wetting agent and a defoaming agent. Zirconia may also be used as ceramic material.

U.S. Pat. No. 3,111,396, issued Nov. 19, 1963 to B. B. Ball, discloses a method of making a porous m.ot~llic article which co---l,-ises impregnating a porous organic structure with a suspension of powdered metal, metal alloy or metal compound, and binder, slowly drying the impregnated structure, heating at about 300 -500 F. (150--260- C.) to char the organic structure, and then heating at about 1900- to about 3000 F. (1040- to 1650- C.) to sinter the powder into a porous material.

Other United States patents relating to porous ceramic filters and methods for making them include: 3,893,917 - July 8, 1975 - M. J. Pryor et al; 3,947,363 -March 30, 1976 - M. J. Pryor et al; 3,962,081 - June 8, 1976 - J. C. Yarwood et al;
4,024,056 - May 17, 1977 - J. C. Yarwood et al; 4,081,371 - March 28, 1978 - J.
C. Yarwood et al; 4,257,810 - March 24, 1981 - T. Narumiya; 4,258,099 - March 24, 1981 - T. Nal~lliy~; and 4,391,918 - July 5, 1983 - J. W. Brockmeyer.

175 ~7 None of the above patents disclose or suggest the desirability of using conductive ceramic, metal ceramic or inter-metallic filters, which can also be used as heating elements. The problems associated with the prior art methods are similar to the problems associated with the method described in US Patent No. 5,279,737, S which problems are described in greater detail below.

US Patent No. 5,279,737 ("the '737 patent") discloses a process for producing a porous ceramic, ceramic composite or metal-ceramic structure by micropyretic synthesis wherein a form polymer shape is impregnated with a slurry of ceramic 10 precursors and ignited to initiate micropyretic synthesis, thereby ~tt~ining a ceramic, ceramic composite or metal-ceramic composite article having interconnected porosity.
The '737 patent is incorporated by reference into the present application, in its enli~ y.

Nowhere does USP S,279,737 disclose or suggest a mo~h-l~ted filter comprising at least two porous ceramic or ceramic composite modules. The importance of the mod~ ted design lies in the fact that by having a modulated system one can introduce very thin slices of the ceramic filters with pore sizes of 20 to 30 pores per inch, which are more efficient for particle trapping than larger pore sizes, 20 such as 10 pores per inch. Also, if a whole filter trap co~ rd a single filter unit that was 20 or 30 pores per inch, the ples~ule drop would be too great and the back pressure would cause engine failure. With the mod~ ttqd design, however, it is possible to use these pores sizes and insert therein membranes or slices of the filter of differell~ thirl~ llrC.se to achieve desired results. Some slices can be very thin, but 25 have a very low pore size, for example, 50 pores per inch. A second advantage of the mod-ll~ted design is that in combination with the heating elem~nt~, it is much easier to keep the filters "clean" because smaller pores are geneMlly easier to block and more liffirult to clean. In sum, the mo-l-ll~tr~l design allows for an infinite number of variations of the filters and its applications by varying the pore sizes and 30 the thic~nrs~es of the modules as well as the number of modules in the overall filter.

WO 96/06814 21 7 ~ 7 7 PCT/US95/06387 .
As will be now be described, the coating process of the present invention also con.~titlltes a novel and unobvious improvement over the process described in the '737 patent. The impregnation step in the '737 patent is achieved by dipping the polymeric foam in the slurry with which it is to be impregnated. This step is very cumbersome 5 and awkwa~. Also during processing using the invention of the '737 patent, one has be extremely careful so that the "green structure" (the structure before sintering, micropylclic or otherwise), does not "collapse." Collapse as used herein refers to dissolution of the ceramic in structure, before sintering, before or after burning of the polymeric foam. The process of the '737 patent may also give rise to "distortion".
10 Distortion as used herein means physical distortion which results from large structure sagging under its own weight prior to burning of the polymeric foam. The impregnation of the present process is achieved by (a) flnitli7ing said slurry with steam and ~ yhlg the shape with said fll~ i7e~ slurry or (b) heating said slurry so as to reduce its viscosity and spraying the shape with said reduced viscosity slurry.
15 This method of hllpleg~ion eli".i~ es the above listed problems. Additionally, the steam or hot liquid constituent of the spray better dissolves certain constituents, such as calcium ccul,ol~les and silir~tes (cernf~nt~) such as (CaO)3.(SiO2)2.(H20)3, which lead to a high green and final ~ glll by ~lc~ i~ling out on the deposited surface as a ce~ t. The present process also results in more uniform thir~nrss of the 20 ceramic.

In the past, it was extremely t1ifficlllt to incorporate a heating device into afilter because thermal cycling problems from incompatible thrrm~l expansions of the heating element and filter. This made it ~liffirn1t to have a filter with an integral 25 heating element. The material used for the heating elements are typically molybdenum disilicide based. This material is able to heat to 550C in only a few seconds, which combats the well-known problem of cold-start emissions in motor vehicles. Other superior ~lopellies include high emissivity of approximately 0.9, as compared to other heating elements which have emissivities of 0.4 to 0.75. The fact 30 that the heating element is integMl with the filter provides the advantage of less complexity, less moving parts and less cost. Most other systems depend upon manycomplex systems including logic and electronics to heat the filter or the exh~lst gases, 21~
which is very costly and problematic. All materials made by the micro~ylcLic technique experience a large temperature gradient of more than 1000 centimeters per millim~ter during m~mlf~rtllre. This includes both filters and heating elements made by micro~ylclic technique. Due to the extreme conditions that the materials mustS endure during synthesis, the materials made by the micro~yrcLic technique result in porous ceramics which are extremely th~rm~lly shock resistant, highly thermally cyclable and forgiving when contacted with the heating element. Rec~llce they possess these qualities, they are extremely well-suited for exhaust aflclLlcaLlllent systems.
To date, such rapid heating elements were not available. Non micro~yl~Lic heating el~-m~ntc even though made ~ ally of molybdenum disilicide or silicon carbide are extremely eAycnsive. Furthermore, they cannot heat as rapidly because they are not m~mlf~ctllred by the micl~ylcLic technique. Another reason why 15 heating elem~ntc have not been used in situ with the types of filters most commonly used today, is that the extruded cellular configuration of the plcsellLly available filters is ill suited for integral heating elem~rlt.c. The extruded channels made of the ceramic act as an inclll~tor with respect to the other channels. Thelcrole, one would need many heating elern~ntc, one per cellular channel to have an in situ heating 20 configuration, a highly impractical and extremely eA~ensive proposition.

The in situ heating elem~nt.c would also enhance the catalytic converters already in use, today. Catalytic converters are heated during operation, and the EPA
specifies a ~ -l.-.-- time in which the catalysis bed must reach operating 25 temperature. The standard solution has been to add an "pup" converter -- a second, small collvclL~r ul~SLl.,alll of the main unit. It acts like an igniter, and heats the exh~--ct stream rapidly, but little else about them is .c~ticf~rtory. Even a small converter adds signifir~nt costs. It is often liffl---lt to fit even a sizable converter into limited space, and it creates .chiPl~in~ problems by placing another source of 30 intense heat close to engine components. All of these problems are overcome by the integral in situ heating elem~-ntc of the present invention.

WO 96/06814 2 1 7 5 3 7 7 PCT/US9~/06387 I Several dirrclclll methods have been alLen~lcd to heat catalytic converters, including ~ l,c radio ll~ llliL~el~ that activate a non contact heating device heater,j and additional catalysis. The present invention solves the n~cessity of heating catalysts without the expense and complexity of the prior art.
There is also a great need for technological improvements in catalytic COllvt~ltt~l~ and other engine emission reduction devices because there is a finite limit to the amount of pl~tinllm the most commonly used catalyst. Moreover, pl~tinllm is extremely c~ensive.
The idea of having an in situ heating element within a filter has many applications outside of exhaust systems, as well. One of these applications would be in a simple heating device. One of the major advantages is that the heating element is actually inserted into the filter rather than the heat being supplied from outside the 15 filter.

With respect to the lcgenclalivc aspect of the present invention, US Patent No.
5,094,075, issued March 10, 1992 to Heinrich Berendes, discloses a particulate filter that can be lcgen~ldled by means of a burner working in the main engine exhaust 20 stream. Regell~la~ion is achieved by means of a burner to which fuel and oxygen-cont~ining gas is supplied in a variable proportion. By this means, the burner produQes the output required to achieve the regene~àlion tempe~dlulc in the diesel engine. This patent requires an outside burner, instead of an in situ integral heating element, in order to lcgell~late the filter.
US Patent No. 5,015,381, issued May 14, 1991 to M. FAmllntl Ellion, et al, discloses a fluid filter element, filter, and process for its fabrication, whelein the filter elçm~nt includes a flat base and a thin layer deposited thereupon having a r-h~nn~l~ though which a fluid may flow. In operation, the element is pressed against 30 a flat surface, preferably against the b~r~i(le of another element and a stack of filter elements, whelein the channels become closed conduits. The channels have a mil,;".~.." requirement of thi~kn~oss of the layer so that larger particles may not pass W O96/06814 PCT~US95/06387 217'j377 thelcllllough. Fabrication of the thin layer with the channels therein is preferably accomplished by m~C~ing a pattern corresponding to the channels and then vapor depositing the rem~in~ler of the thin layer, as m~cking and deposition permits actuated control of the heights of the deposited layer and then the mil~i""~", dimension of the S channels. This patent does not disclose the modular design nor does it account for egel~l~ion of soot and particul~tes.

US Patent No. 5,001,899, issued March 26,1991 to Enrique Santiago, et al, discloses a method and appal~l~us for cleaning of a soot filter in the exhaust line of 10 a diesel engine with a combustion chamber placed in front of the soot filter where fuel nozzle and adapted electrical ignition method is built and thereby enabling the aflcll,ulllillg of the exhaust without secondary air. The exhaust in the combustion-chamber is mixed with the fuel which is injected through the fuel nozzle, and ignited by an ignition device with the existing portion of the unburned oxygen. The half15 exh~llst effects the burndown of the ~ccllmlll~tPd soot in the soot filter. The a~al~lus disclosed herein is complex and requires many parts and does not teach a simple integral heating element to burn the soot in the filter.

"Regenel~ion Pelrollllallce Of A Catalyst Versus Non-Catalyst Ceramic Membrane Diesel Particulate Trap", Rich Helfrich, et al, Global Developlllelll~ and Diesel Particulate Control P-240 Society of Automotive Fngin~ers, Inc., 121-132 (February 1991), describes a ceramic foam trap system using a parallel flow stacked element design. The individual el~m~nt.c are bonded together to form subassemblyof 12 to 14 elements. The ceramic foam filter elements are non-retir~ tçd material 25 with a microporous membrane on a down stream (outer) side of the filter element.
The trap itself has a center inlet through which the exhaust flows in the individual elem~ntc by way of the annular inlet ports (formed by adjacent elements). The elements in this invention are all the same size and each have the same function.
The filtration of the gas in such a system is in a 'parallel' fashion and such a filter system is clearly non-motl~ tçd as described and claimed herein.

WO 96/06814 2 17 ~ ~ 7 7 PCT/US95106387 _, US Patent No. 4,400,352, issued August 23, 1983 to Ovea Rehnburg, et al, discloses a method and device for optimi~ing purification of diesel exhaust gases, the purification being carried out by a catalysis. This invention does not disclose modulated design nor does it disclose incorporating a heating element into the filter S for l~,ge~ dlion.

"~A~.Sing Truckers", The Economists New~al)er T.imited, Business Finance and Science: Science and Technology: Pg. 97 describes a particle trap which works like filters in the exh~ t pipe using two traps and switching between them, so one 10 trap filters while the other one burns the collected particles. That article admits, that despite years of research, those traps were still unreliable, strongly indicating the need for reliable particle traps. Although the design described has two separate filter units, it does not teach the modular design of the present invention.

U.S. Patent No. 5,334,570 discloses a porous catalyst support which may be used in a catalytic coll~ el for treating automotive exhaust gases. The desirability of increasing "open frontal area" available for filtration is recognized. However, no mention or suggestion is made of increasing ro~lghn~ss to achieve this objective.

SAE T~ .. ,A~ional No. 930129, entitled Production Experience of a Ceramic Wall Flow Electric Regeneration Diesel Particulate Trap by Kejetin et al., described a dual ceramic wall flow electric regel~ ion diesel particulate trap. No suggestion or disclosing of modulation, conductive coated filter or in-situ heating elements is provided. Also, the electrical heating system disclosed is before (d~wlLsll~alll of) the 25 filter system. No heating element integral with the filter is disclosed or suggested.
Also much greater power is required for the ignition of the filter disclosed in this article as colllpaled to the filters of the present invention.

SAE~ International No. 920140, entitled a Study on Regeneration of Diesel 30 Particle Trapper by Electrical Self-Heating Type Filter describes silicon carbide based filters, which themselves can be heated. While no specific indication of the internAl structure of the filter is given, the article states that the material is formed by 17 S 3 le~xtrusion. When extrusion is used as a means of m~m~farture of ceramics invariably straight walled products are provided. This appears to be borne out by Fig. 3 of the article. Also, 4 KW of energy is required for ignition of a SiC filter because of the extremely high resistivity of SiC.(of the order of lOx106,ll ohm-cm), as opposed to 5 the relatively small energy required for ignition of the filter of the present invention.
Modulation is not disclosed or suggested nor are filters coated with a conductive material.

Several United States patents ~c.~ign~ to Donaldson Coll~dlly, Inc. disclose 10 regenel-dLive filters with separate (non in-situ) heating elements for regeneration purposes. See United States patents 4,878,928; 5,053,062 and 5,224,973.

For the foregoing reasons, there is a need for an af~ lcaLlllent system of high effectiveness, low complexity and low cost, as well as a regellclaLillg system 15 incorporating a heating elern.ont integral with an exhaust ceramic, metal-ceramic or inter-m~t~llir composite filter or a con~ cting coating applied to the filter which then functions as a heating element wh~eill the filter materials are highly thermallycyclable.

While not exclusive, the following describes some of the important features and objectives of the present invention.

An object of the present invention is to provide hllploved catalytic converters 25 and filters using the ceramic, metal-ceramic or inter-mPt~llic composite membranes of the present invention, which meet the United States 1994 and 1998 federal, state and local diesel emission regulations.

Yet another object of the present invention is to initiate and control the 30 regenelaLion process of a filter using ceramic, metal-ceramic or inter-m~ot~llic composites of the present invention, to ensure reliable regel~ldLion without damage to the trap oxidizer.

Another object of the present invention is to make the filter oxidizers less sensitive to regencl~lion conditions.

A further object of the present invention is to reduce the overall costs of filters S used in exhaust systems.

A fur~er object of the present invention is to provide a regenel~tion system in which a converter or a trap oxidizer could be used without the need for using a catalyst for regenelalion.

; Yet another object of the present invention is to provide a heating element integral with a filter, wherein both are highly thermally cyclable and wherein both are ceramic, metal-ceramic or inter-m~t~llic composites.

A further object of the present invention is to provide a heating element which is formed in situ with the filter, both heating element and filter being a ceramic, metal-ceramic or inter-m~t~llic col,lposile.

Yet another object of the present invention is to provide ceramic, metal-20 ceramic composite heating element which heats up extremely rapidly.

It is also an object of the present invention to provide a process for producinga coated structure which obviates the dilJphlg involved in the i",pleg,~ion step in the '737 patent.
It is a further object of the invention to provide a process for producing a coated structure whe~cil~ the impregnation step is less ~wkwald and cumbersome than the impregnation step in the '737 patent.

I t is another object of the invention to provide a process for producing a coated structure which avoids the collapse of the "green structure" during processing, as observed in the '737 patent.

2 1 7 5 ~ 7 7 It is still another object to provide a process for producing a coated structure which avoids the distortion of the formed article during processing, as observed in the '737 patent.

It is a further object of the invention to provide a process for producing a coated structure which better dissolves certain constituents more easily, such as calcium ~ilir~tPs (cPmPnt~) such as (CaO)3.(SiO2)2.(H20)3, which lead to a high green and final sLl~ell~Lh by plecil~iL~Lillg out on the deposited surface.

Yet another object of the present invention is to provide a process for producing a single component coated structure for use as a regellelaLive filter, which structure serves both as a filter and a heating element.

It is also an object of the present invention to provide a process for producinga coated structure for use in exhaust systems, said coating being conductive.

In accordance with the first aspect of the present invention, these is provided,a modulated ceramic, metal-ceramic or inter-metallic composite filter for gaseous, liquid and particulate matter whel~ the modules in said filter are ceramic, metal-ceramic or inter-mPt~llir cGlll~osiLes, said composites having interconnPcted orstraight through porosity and having been m~mlf~rtllred using micropyretic synthesis, the filter Colll~ lg at least two modules. Preferably each module is optimized for extracting dirr~ellL m~tPri~

In accordance with the second aspect of the present invention is provided a regenerator filter comprising a means for filtering and a means for regenerating said means for filtering, said means for regenrdLillg being integral with said filtering means.

According to the invention there is provided in a process for producing a porous ceramic, metal-ceramic or inter-mPt~llir composite structure, comprising the steps of providing a slurry comprising ceramic precursors, impregnating a foamed WO 96tO6814 2 1 7 ~ 3 7 7 PCT/US95/06387 polymer shape with said slurry, heating the slurry-hllplc~lldt~d polymer shape to a temperature sufficient to remove said polymer, and heating said ceramic precursors to obtain said ceramic, metal-ceramic or inter-metallic composite structure, an improvement process for producing a coated porous ceramic, ceramic composite or S inter-m~t~llic structure, the improvement process comprising the steps of: providing a slurry comprising (A) at least one component selected from the group con~i~ting of (a) at least two particulate ceramic precursors capable of undergoing combustionsynthesis, (b) at least one non-miclopy~lic particulate ceramic, (c) at least one metal, (d) at least one inter-m~t~llic, (e) at least one polymeric material, and ~ lu~cs 10 thereof; and (B) hydroplastic materials selected from the group con~ ting of clays, colloidal silica, colloidal ~lllmin~ colloidal zirconia, colloidal ceria and mixtures thereof; impregnating a ceramic, ceramic composite or metal shape with said slurry by (a) flni~ ing said slurry with steam or heated water and spraying said shape with said flni~li7~ slurry or (b) heating said slurry so as to reduce its viscosity and 15 S~ yill~, said shape with said reduced viscosity slurry; and obtaining a coated porous cerami¢, ceramic composite or metal structure by igniting said ceramic precursors to initiate combustion synthesis and/or by heating said non-lllicr~y~etic particulate ceramic, metal, inter-m~t~llic or polymeric material so as to cause said non-microl,y,elic particulate ceramic, metal, inter-m~t~llic or polymeric material to adhere 20 to said porous ceramic, ceramic composite or metal structure.

Acco~ing to the invention there is further provided a process for producing a porous ceramic, metal-ceramic or inter-mPt~llic composite structure, comprising the steps of providing a slurry CC.lll~liSillg ceramic ple~ul~ol~ capable of undergoing 25 combustion synthesis, illl~lcglld~illg a foamed polymer shape with said slurry, heating the slurry-h,ll,lcg,.~d polymer shape to a temperature sufficient to remove saidpolymer, and igniting said ceramic precursors to initiate combustion synthesis, thereby obtaining said ceramic, metal-ceramic or inter-m~t~llic composite structure having .interconnected ~oro~ily and controlled pore size, and improvement process for 30 producmg a porous ceramic, metal-ceramic or inter-metallic composite, the - i,l,plovcl,lent process coll~lisillg the steps of: providing an improved slurry comprising (A) at least one component selecte~ from the group consisting of (a) at 21753~7 least two particulate ceramic precursors capable of undergoing combustion synthesis, (b) at least one non-micro~y~ ic particulate ceramic, (c) at least one metal, (d) at least one inter-m~t~llic, (e) at least one polymeric material, and mixtures thereof; and (B) hydroplastic materials selecte~ from the group consisting of clays, colloidal silica, 5 colloidal alumina, colloidal zirconia, colloidal ceria and mixtures thereof;
impregnating said polymeric shape with said improved slurry by (a) fl~ li7ing said improved slurry with steam or heated water and spraying said shape with said fl~ li7e~ slurry or (b) heating said improved slurry so as to reduce its viscosity and spraying said shape with said reduced viscosity slurry; heating the improved-slurry-10 impregnated polymer shape to a telllpe.alule sufficient to remove said polymer; andobtaining a porous ceramic, ceramic composite or metal structure by igniting said ceramic precursors to initiate combustion synthesis and/or by heating said non-micropyle~ic particulate ceramic, metal, inter-m~t~llic or polymeric material.

In accol.lance with a further aspect of the present invention there is provided a heating element in close contact with a porous body which is itself conductive or to which is applied a conductive coating, which porous body can itself function as a heating element, so as to cause it to heat up if a current is applied through said body and which can also function as a filter due to its porosity, whelcill the heating 20 element function and the filter function of the porous body is accomplished by a single undivided structure.

Another aspect of the present invention provides, in a regenerative filter COlll~liSillg a means for filtering; and a means for legell.,la~ g said means for 25 filtering, said means for regell~ ing being integral with said filtering means, the improvement comprising a pres~ule release safety valve for removing collected particulate matter, the valve being self-lescl~iug or otherwise.

Yet another aspect of the present invention provides a non-regenel~i\re filter 30 means in combination with a pl~S~Ul~ release safety valve for removing collected particulate matter, the valve being self-lese~ g or otherwise.

WO 96/06814 2 1 7 ~ 3 7 7 PCT/USgS/06387 . A further aspect of the present invention provides in a modulated filter for gaseous, liquid and particulate matter, wherein the modules in said filter are porous ceramic, metal-ceramic or inter-m~t~llir composite structures, said structures having interconnPct~d porosity and having been m~mlfactured using micropyretic synthesis, 5 the filter co~ fisillg at least two modules, the improvement including flexible flaps in between or after the modules, said flaps being made of materials selected from the group co"ci~li,l~ of fiber cloth, high tempeMture wools, and flexible boards, said flaps being susceptible to adherence by particulate fines.

Another aspect of the present invention provides in a regenel~tive filter wlll~ g a means for filtering; and a means for regene~Lillg said means for filtering, said means for legellel~li,lg being integral with said filtering means, the improvement comprising fins, met~llic fins, or other conductive fins inside the regeneL~live filter, said fins being used to better distribute heat within the regenerative 15 filter.

An additional aspect of the present invention provides in a modlll~ted filter for gaseous, liquid and particulate matter, whc;rehl the modules in said filter are porous ceramic, metal-ceramic or inter-m~t~llir composite structures, said structures having 20 interconnPcte(l porosity and having been m~mlfac~lred using miclol)yll,lic synthesis, the filter colll~lising at least two modules, the improvement comprising fins, metallic fins, or other conductive fins inside the regenerative filter, said fins being used to better distribute heat within the ~gel~lalive filter.

Figure l(a) is a micrograph of an Al2O3-SiC ceramic m~nllfaçtllred in accordance with USP 5,279,737, Figure l(b) is an enh~nred micrograph of the ceramic of Figure l(a);
Figure 2 is a sçh~ ti~ of Filter I as described herein;

2 17 5 3 7 7 Figure 3 is a sçh~m~tic of mo~ te~ Filter II as described herein;

Figure 4 is a sch~ tir of the test setup used herein for testing filters;

. .
Figure 5 is a micrograph of the filter paper used to collect the exiting material after filtration by a prior art filter; -Figure 6 is a micrograph of the filter paper used to collect the exiting material after filtration by a single module of the present invention;
Figure 7 is a micrograph of the filter paper used to collect the exiting material by a mod--l~ted filter in accordance with the present invention;

Figure 8 shows two filters, with one and two heating elements formed in-situ;
Figure 9 shows a modulated filter co",plising four modules, two with no heating elern-o~t~, one with one heating element and one with two;

Figure 10 shows a filter as incorporated within a casing specifically adapted 20 to be fitted in a land based vehicle;

Figure 11 shows perspective views of the casings having filters incorpoMted therein, specifically adapted to be fitted in a land based vehicle (the filters are not visible in this view);
Figure 12 shows a perspective view of a casing having filters incorporated therein, specifically adopted to be fitted to a 2.5 liter diesel engine, automobile or otherwise; and 30Figure 13 is a graph of le",pe,~lu,e versus resistivity of HR-1550, the heating element material used in Example 1.

WO96/06814 21 7-5 `3 7 7 PCT/US95/06387 DETAILED DESCRIPTION OF THE INVENTION
The plcfc~lcd embodiments of the present invention will now be described in greater detail.

S First Eml)o~li...-..~
This aspect of the present invention provides a modulated ceramic, metal-ceramic or inter-mrt~llic composite filter for gaseous, liquid and particulate matter, wherein the modules in the filter are porous ceramic, metal-ceramic or inter-mPt~llic composites, the modules having interconnected porosity and having been 10 ~ llllr;v~lllcd using miclul~ylc~ic synthesis, wherein the filter comprises at least two such mnd~ s.

Optionally, the mo~ tP~ filter of the present invention also comprises a catalyst, the catalyst being applied-to the filter by coating, impregnating and 15 combinations thereof; and wh~leill the catalyst reacts or is reactive under conditions of vacuum, room lelllpc.~lul~" increased tenl~e~alulc~ ~lCS~ul~ or combinations thereof.

Optionally, each module of the filter is optimized for extracting a dir~elclll 20 material, particularly, partirlll~tes, carbon particles, NO,~, CO, CO2, SO2, hydrocarbons, and combinations thereof.

Also, preferably, the composite is retirlll~trcl. "Rrtir~ ted" as used herein refers to a porous 3-tlimPn~ional structure without straight-through channels.
The greater the ro~ghnP-ss of a filter material, the better the performance of the filter. Therefore, it is plcrellcd that the composite has a rough surface. A"rough" surface as used herein may be understood as a surface with a high frequency of peaks and valleys, the peaks and valleys Cl~dlillg spaces suited for particle30 ll~pillg. See Figures l(a) and (b), which illustrate a typical "rough" composite used as modules in the present embo~imrnt The rollghnrss of the composite can be enh~nred either rhrmir~lly or mrcll~nir~lly.

217 5 3 7 7 Of the several materials disclosed in the '737 patent, it is plefelled that the composite (even in its heating element form), comprises a material selected from the group con~ ting of borides or alnmini~les of ~ , zirconium, niobium, t~nt~hlm, molybdenum, h~fninm, chromium, and v~n~ lm; alnmini(les (except of alllllli"~l"~), S carbides and oxides of lil;l~lilllll, h~fnillm, boron, alll..lill.llll, tantalum, silicon, tungsten, zirconium, niobium, and chl~llliulll; carbonitrides of tit~nillm, niobium, iron, molyb~emlm, v~n~ lm~ and tantalum; nitrides of ~ illl,l, zirconium, boron,all-.lli,..llll, silicon, t~nt~lllm, h~fnillm, and niobium; silicides of molybdenum, l il;."il..", zirconium, niobium, tantalum, tungsten and v~n~ lm; hydrides of l il~
10 zirconium and niobium; Alnminllm oxide~ l." boride; lil;l"i~.", carbide-liLit.,ill."
boride; ~lll."i"..." oxide-ril~ ." boride-lil;lllilllll nitride; alllllli..~-- oxide-lili.llilllll boride-~ iu.ll carbide; boron carbide-~lll.~lil.~lll oxide; molybdenum silicide-~ll.."i"..." oxide; molybdenum boride-all.",i"..." oxide; chromium carbide-alllminllm oxide; van~i-lm nitride-alll-,li" -.,l oxide, ~lllmini~1es of nickel, compounds of 15 pl~tinllm, ruthenium, rhodium, gold, silver, iron, lil;l~,il~." and p~ (lillm in the form of coatings, phosp_ides of nickel, lil~ -nickel~ oxides and oxychlorides of n1thrnillm, mullite, cordierite, 1~.. 11.~.. " chromite, graphite and compounds and mixtures thereof.

G~ )alali~e Example Two alumina-silicon carbide (Al2O3-SiC) filters were made of porous retirlll~tPcl ceramic fabricated by the process of US Patent 5,279,747. The first filter (I) was made by using a ten pores per inch, ~;ylhldlical shaped retir~ tr~ ceramic 25 having a 4" ~ m~ter and 3" height. The ceramic monolith was packed in a steelcasing as shown in Figure 2. See also, Figure 10. The second filter (II) was made by st~c~ing nine, ten pores per inch retir~ te(l ceramic discs of 2" rli~m~oter and 1/2"
thickness, alL.,lllaling them with a steel ring 1/2" long to sepalale the ceramic discs in a 9" long steel casing, making a modular filter (Figure 3).
The two filters for particulate matter were tested on a diesel engine to comparetheir performance with the diesel filters available in the market. Engelhard's 3DVC-WO 96/06814 21 7~3 7 7 PCT/US95/06387 PTX and 4DVC-PTX diesel filters were used for the comparison. These filters havea ceramic monolith with square shaped cells, passing straight through the whole body, with a mean wall thickness of 0. l5mm and 14 pores per inch. This ceramic monolith is manllfactllred by Corning Inc. The setup for the test comprised of a 22HP four 5 stroke diesel engine made by Lister Petter and a paper holder with a filter paper to catch the particles from the engine exhallct See Figure 4. The setup was in the open at an ambient tel~cldlulc of 40F. All the four filters I, II, 3DVC and 4DVC were s~ccessively tested. Each of these filters were conn~octe~ to the engine exhaust pipe as shown in the set up. The filter paper was uniformly sprayed with water to enable 10 the exhaust particles to stick to the surface. The engine was started and was run for two minutes for each filter.

The gain in weight of the paper, which was used for collecting the particles from the exhaust, and visual inspection, were used as the criterion for determining 15 the performance of the filters. Filter I and Filter 4DVC had exactly the same~lim~n~jnns. The gain in weight of the filter paper due to the particles collected from the exhallst of filter I was 0.01g, where as that from filter 4DVC was 0.03g. Also the paper used the filter 4DVC was much darker with more black spots than the one used with filter I. See Figure 5 which is a micrograph of the filter paper used with 20 4DVC; Figure 6 which is a ll,icr~yretic of the filter paper used with filter I; and Figure 7 which is a micrograph of the filter paper used with filter II. Thus, it is clearly demon~l,dted that filter I is much superior in pc~ro~lllance as compared to filter 4DVC.

Filter II was the best filter among the four filters tested. See Figures 5, 6 and 7. The gain in weight was negligible and the paper was slightly yellowed with noblack spots, suggesting a high degree of filtration.

217 ~ 3 7 7 Second Embodiment The second aspect of the present invention provides a regenerative filter comprising: a means for filtering; and a means for regenerating said means for filtering, said means for regeneld~ g being integral with said filtering means.
s Preferably, the means for filtering comprises at least one porous composite having interconn~cte~ porosity and having been m~nllf~ctllred using miclopyl~,tic synthesis. Preferably, the means for regellerdtillg is a heating element. Optionally, the regeneldLulg means may also be a catalyst. Even more preferably, the heating10 element/catalyst can be a porous composite.

The filter/heating element preferably comprises a compound selected from the group con.cicting of metallic material, molybdenum silicides, Fe-Cr-Al, Ni-Cr, SiC
and combinations thereof.
The filter/heating element preferably comprises a material selected from the group concicting of borides or ~hlmini~ s of tit~nillm, zirconium, niobium, t~nt~hlm, molybdenum, hAr";l"", chlollliulll, and van~ -m; ~Illmini~es (except of allll"i".l"~), carbides and oxides of ~ 11illlll, h~r~ boron, al~ lll, t~nt~lllm, silicon, 20 ~ g~le~ hcol iulll, niobium, and chlullliulll; carbonitrides of tit~ninm, niobium, iron, molybdenum, v~n~lillm, and tantalum; nitrides of ~ ,il"", zirconium, boron, alln~ .", silicon, t~nt~lnm, h~fninm, and niobium; silicides of molybdenum, "i~ , zirconium, niobium, t~nt~hlm, lul-g~le~- and van~ lm; hydrides of lil~
zirconium and niobium; ~ l"i"..." oxide-lil~"i,l." boride; lil~"illlll carbide-lil;,l,i,l", 25 boride; ~hlmimlm oxide-lil~l~ill.., boride-lil;lli..." nitride; alll,.~i"~"~ oxide-tit~nil-m boride-liL~ " carbide; boron carbide-~l"."i,-~.ll oxide; molybdenum silicide-alnmimlm oxide; molybdenum boride-all-"li"."" oxide; chlullliulll carbide-alnmimlm oxide; v~n~inm nitride-all--llilllll-l oxide, ~lnmini~es of nickel, compounds ofpl~tinllm, mth~nillm, rhodium, gold, silver, iron, ~ i,l", and pall~tlinm in the form 30 of coatings, phosphides of nickel, lil;lllilll~l-nickel, oxides and oxychlorides of ruthenium, mullite, cordierite, l~ h~ll....~ ch~olllil~, graphite and compounds and mixtures thereof.

WO 96/06814 21 7 ~ 3 7 ~ PCT/US95/06387 Preferably, the regene,d~ g means (the heating element or catalyst) is formed in situ with the composite filter.

Preferably, the composite is reti~ t~d. The catalyst. if present, is applied S to the filter by coating, il"p,egndlh~g, and combinations thereof.

Example 1 A reti~ t~d filter with a pore size of 10 pores per inch (pore sizes ranging 10 from 10-80 pores per inch are most ~,ere"cd for the practice of the invention), m~Mlf~¢tllred according to USP 5,279,737 was made, except that a 3 mm high resistivity heating element m~nllf~tured by Micro~yl~ics Heaters ~ntern~tional under the trade name HR-1550 with terminals was incorporated into the retir~ ted filter prior to combusting the sample. See, Figure 12 which is a resistivity to temperature graph for HR-1550, showing that the resistivity of HR-1550 increases with ten~e,~lule. "High" resistivity means 50-5000 ~ohm-cm, whereas "low" rt;~i~,Livily is understood to be around 1 ~4ohm-cm. "Low" lesislivily heating elements require in excess of 300 amps to be heated up quickly, but a typical 12V automobile battery can only generate less than 100 amps. Therefore, it is important that a high 20 resistivity heating element be used. M~teri~l~ which may be used as high resistivity heating elements are: molybdenum disilicide, silicon carbide, tungsten silicide,zirconium oxide, 1~ c~u~ e, gl~hile, compounds and composites thereof.

$ee, Figure 8 which shows two filters, with one and two heating elements 25 formed in-situ. The final m~t~ri~l of the filter was a composite of Al2O3/SiC when used as a particle trap for exhaust gases was found to effectively trap parti~ul~t~s.
The heating element could be ellergiGed during use and after use as a particle trap to burn off the carbon deposit. Many such filters of size three inches in ~ m~ter and two inches in depth could be used in tandem to give a mod~ ted filter of greater30 length. See, Figure 9, which shows a mo~ te~l filter comprising four modules, two with no heating elements, one with one heating element and one with two. Figure 10 shows a filter as incorporated within a casing specifically adapted to be fitted in 2 1 7~ PCTIUS95/06387 a land based vehicle. Figure 11 shows perspective views of the casings having filters incorporated therein, specifically adapted to be fitted in a land based vehicle (the filters are not visible in this view).

Example 2 A filter with a porous size of five pores per inch, otherwise the same as example one.

Example 3 Same as example one expect the filter had various slurry coatings of nickel compounds (both combustible and non-combustible slurry coatings) applied thereto.

Example 4 Same as example one expect the filter had various coatings of pl~timlm, ruthenium, rhodium, gold, silver, iron, ~ llll and p~ linm and compounds thereof, applied thereto.

Example 5 The heating element was made of silicon carbide, otherwise the same as example 2.

Example 6 The filter was made according to Example 2, but heating element was of a conventional m.ot~llic material such as Fe-Cr-Al alloy or NiCr alloy. However, the heating el~m~nt~ made from molybdenum disilicides were found preferable.

Example 7 A cylindrical shaped membrane filter (Miclo~Jyl~lics Heaters IllL~ ional's DPF)TM, having 2.8 inches ~ m~ter, 3 inches length (several Al203/SiC membranes as in Example 1 were stacked together to yield a modulated filter of 3 inches length) WO 96/06814 2 1 7 5 ~ 7 7 PCT/US9S/06387 and lO!pores per inch, was used for Example 7. This filter had a U shaped HR-1550 element sandwiched in the length of the filter.

Initially, emission tests were con(l~cte~ on an as is 1981 Volkswagon~ Rabbit, 5 with a 1.6L diesel engine. A BEAR~ smokemeter was used to measure the opacity (in m~l3 of the exhaust gases of the Volkswagon~ Rabbitr and a BEAR~ tachometer was used to measure the revolutions per minute of the engine (RPM) of the same.
A ~elc~llL~ge opacity and density of partir~ tes was measured. The smokemeter was connrc~(l using a hose to the vehicle exhaust pipe and the tachometer was connected 10 to the fuel pipe to the engine. This apl,alalus was interfaced with an IBM~ Intell 486 based Col~ L~l to collect real time data. The car was started and warmed for 1/2hour before the tests were con-lllrt~

A standard certification test procedure was used to measure the emission. The 15 procedùre involves a three step process. First, the opacity of the exhaust is measured under idle conditions, i.e. when the engine is just turned on, for a fixed amount of time. Then, the engine is imm~ t~ly acceleMted to the m~ximnm RPM and m~int~in.~ for a given time, after which the engine is deaccelerated to the idle state.
These steps are repeated up to ten times to get the best four results, which are used 20 to obtain the average opacity of the exh~llct The coll~uler decides when it has received at least four ullirollll tests. If the first four are not ul~irollll, then the c~,llll,uter asks for further tests until either four satisfactory results are obtained or a mi..;....~,.. of ten measurements are taken, whichever occurs first. The results given below in Table I are the values obtained at around the highest RPM of the car (approximately 5300), without any filter ~tt~rh~cl to the car.

Next, the filter (mo~llll~ted and rege~ a~i~/e) was in~t~ (l to the exhaust pipeof the car. The opacity test was then repeated. The results are presented in Table II. It was noted that the current dMwn by the heating element was of the order of 25 amps, which is well below the 100 amps easily generated by a 12V battery.

WO 96/06814 PCT/US9~/06387 17 ~ 3 ~ 7 As noted above for all tests, at least four high RPM excursions are required by the co~ uLel. It was noted that when a filter was employed the collll,u~el- was always s~ti~fi~o~ with doing four tests. However when no ~llter was present the coln~ulel had to ask for ten tests.

As is obvious, when the DPF~ membrane filter is used there is a dramatic iln~lovelllent in the exh~ t gas emissions over the case when no filter is used. Also, the engine ran much more con~ e"~ly and uni~llllly when a DPF~ filter was used.
When c~ te~l as the weight of particles reduced per unit volume the results show 10 an average reduction of 0.2 g/m3 when the filter is used.

TABLE I
engine without filter 15TEST ENGINE % OPACITY DENSITY OF
8:54 h SPEED OPACITY m~l PARTICULATES
RPM g/m3 5043 74.4 3.07 0.514 2 5047 81.0 3.75 0.626

3 5071 83.1 4.01 0.669

4 4935 63.8 2.30 0.395 Average: 3.28 0.551 TEST ENGINE % OPACITY DENSITY OF
9:03 h SPEED OPACITY m-' PARTICULATES
RPM g/m3 5334 77.4 3.40 0.559 2 5332 84.4 4.25 0.691 3 5334 79.9 3.67 0.609 4 5335 82.3 3.96 0.648 Average: 3.82 0.627 WO 96/06814 2 1 7 ~ 3 7 7 PCTIUS95106387 TABLE II
using diesel particl~lqte filter (le ~ ive and modulated) at the end of the ~l.q'J~t TEST ENGINE % OPACITY DENSITY OF
10:20 h SPEED OPACITY m~l PARTICULATES
RPM g/m3 4991 39.0 1.14 0.187 2 5073 46.2 1.42 0.234 3 6000 34.9 0.99 0.162 4 5010 36.8 1.05 0.174 Average: 1.15 0.189 TEST ENGINE % OPACITY DENSITY OF
10:24 h SPEED OPACITY m~' PARTICULATES
RPM g/m3 . 1 4935 35.7 1.01 0.168 2 4799 38.2 1.10 0.181 3 5051 37.3 1.07 0.174 4 4980 40.4 1.19 0.193 Average: 1.09 0.179 TEST ENGINE % OPACITY DENSITY OF
10:28 h SPEED OPACITY m~' PARTICULATES
RPM g/m3 6000 34.6 0.97 0.162 2 4955 33.3 0.93 0.150 3 4975 35.2 1.00 0.162 4 4941 36.0 1.03 0.168 Average: 0.98 0.161 TEST ENGINE % OPACITY DENSITY OF
10:32 h SPEED OPACITY m~l PARTICULATES
RPM g/m3 5165 32.0 0.89 0.144 2 5057 33.2 0.93 0.150 2 1 7 ~T6814 ~ 1 7 S 3~ ~ PCTrUS95/06387 3 5005 37.0 1.06 0.174 4 5084 37.3 1.07 0.174 Advantageously, the mod~ t~o~l filter aspect of the present invention may be used in a land-based vehicle, water-based vehicle, in power generation equipment or in an industrial engine. Similarly, the lcgen~ld~ e filter aspect of the present10 invention may also be used advantageously in a land-based vehicle, water-based vehicle, in power geneldtion equipment or in an industrial engine. More generally, the modlll~ted filter aspect of the present invention may be used in a regel~lalive exhaust system. Similarly, the regenel~tive filter aspect of the present invention may also be used in a rege~ dli~le exhaust system. Analogously, the mo~ t~d filter 15 aspect can be used in a catalytic converter.

The mod~ ted filter and/or the regell~ldlive filter, may be used in a diesel engine in combination with a p~hedtel for heating the exhaust gases prior to thegases entering the filter.

In a l~gen.,lalive filter comprising a means for filtering; and a means for egell~lalillg said means for filtering, said means for l~geneldtillg being integral with said filtering means, an improvement is disclosed which comprises a pres~ul~ release safety valve for removing collected particulate matter, the valve being self-resetting 25 or otherwise.

Yet another aspect of the present invention provides a non-regenerative filter means in combination with a pressure release safety valve for removing collectedparticulate matter, the valve being self-resetting or otherwise. The above aspect may 30 be further enh~nretl by including a means for heating the fluid entering the valve.

A further aspect of the present invention provides in a modlll~t~cl filter (as shown in Figure 2), for gaseous, liquid and particulate matter, wherein the modules WO96/06814 21 7 ~ ~ 7 7 PCTIUS95/06387 in said filter are porous ceramic or ceramic composite structures, said structures having interconn~cte(l porosity and having been m~mlf~ctllred using miclo~ylc~icsynthesis, the filter comprising at least two porous ceramic or ceramic composite modules, an improvement including flexible flaps in between or after the modules,

5 said flaps being made of materials selected from the group conci.cting of fiber cloth, high temperature wools, and flexible boards, said flaps being susceptible to adherence by particulate fines. The flaps of the above improvement may preferably be flexible enough so that they are displaced if the flow rate of the fluid to be filtered increases beyond a specified value, but which flaps remove fine particulates at lower flow rates.
Another aspect of the present invention provides, in a regeneldlive filter comprising a means for filtering; and a means for regeneld~h~g said means for filtering, said means for regenerating being integral with said filtering means, an improvement comprising fins, m~t~llic fins, or other conductive fins inside the 15 regeneldLive filter, the fins being used to better distribute heat within the regenerative filter.

An additional aspect of the present invention provides in a modulated filter forgaseous, liquid and particulate matter, whclcill the modules in said filter are porous 20 ceramic or ceramic composite structures, said structures having interconnected porosity and having been m~nllf~chlred using miclopy~clic synthesis, the filter c~"""i~i"g at least two porous ceramic or ceramic composite modules, the improvement comprising fins, m~t~llir fins, or other conductive fins inside the rcgc"."alive filter, said fins being used to better distribute heat within the regencldlive 25 filter.

Preferably the modulated filters and/or the regcl~la~ e filters of the present invention, may be specially (with or without a catalyst), adapted to utilize the heat released from the filters elscwhcre in the land-based vehicle, water-based vehicle, 30 power generation equipment or industrial engine, in which the filters are fitted. In such a case, the filter is adapted to receive external combustible matter for combustion to generate additional heat. The combustible matter may be carbon, 217 5 ~ PCTIUS95/06387 gasoline products, hydrocarbons, metals or any matter which reacts with a positive enthalpy change. The modulated filters and/or the regene,dtive filters of the present invention are designed to increase the residence time of the combustible matter such as carbon particles, so as to allow the combustible matter to be brought to ignition 5 L~ rdlulc and thellcefol~l to be combusted. The modulated filters and/or the regenerative filters of the present invention cause the increased residence time by (1) lld~)pUlg the combustible matter and (2) providing a tortuous path for travel by the gas cal,ying the combustible matter. The importance of a higher residence time is reduced by a hotter substrate (the cell walls of the mod~ ted filters and/or the10 regenelative filters), and/or a hotter means for heating, such as a heating element.
Gradually, the cell walls of the modulated filters and/or the rege~dlive filters get coated with the combustible matter. Combustion of the combustible matter is initi~te~
by ignition, which occurs due to radiation from the means for heating, such as aheating element. Following ignition, spontaneous combustion may occur if the 15 combustible matter is well deposited, which would then proceed along the walls of the mod~ ted filters and/or the ~cgemld~ive filters, requiring no further heat from the means for heating. When the combustible matter burns it radiates heat to the cell walls of the modlll~ted filters and/or the ,egell~,alive filters, which can cause the walls to radiate back and burn more particles or be useful in m~int~ining the 20 combustion process.

Preferably the composites in the modulated and/or ~egel1e,dtive (with or without a catalyst) filters, may be in the form of porous membranes. In such a case, the filters may be advantageously used in furnaces used for producing wax and the 25 like.

Preferably the filters of the present invention can attain temperatures of up to1200- C. Preferably, the filters of the present invention further include a means for g~ging the aging of the catalytic collv~ r.
Preferably the filters when fitted in a land based vehicle, water-based vehicle,power generation equipment or industrial engine, also include a device selected from wo 96/06814 2 i 7 ~ 3 7 7 PCT/US9~/06387 an ignitor, a spark producing means, a heating element, a laser means, a means for inducing a çhP~nic~l reaction and combinations thereof. The above devices may bein addition to or instead of the filter. Preferably, the spark producing means causes intermittent or pulsed sparks or discharges.

In accordance with a further aspect of the present invention, a means for heating is provided such as a heating element being high resi~liviLy and/or highemissivity, an ignitor, a laser, a spark producing means, a means for inducing achPlnir~l reaction and combination thereof, in land-based vehicles, water-based 10 vehicles, power genc,~lion equipment or an industrial engine.

Preferably when the above heating devices are used alone or together with a filter, a surface is not required for combustion of par~ir~ tp~s and/or exhaust gases, as is required in a catalytic converter.
Preferably the lcgellcl~live filter of the present invention further includes one or more heating elPrnPnt and an electrir~l te~ l which may or may not be of the same material as the heating element. Preferably a plurality of heating elements are included in colllbi~lion with a ballast.
Preferably the means for rege~ ivc in a regc,~ldLive filter is a thin film resistor, such as the conductive coatings applied on to the filters as will be described in greater detail below.

Preferabiy the means for regencl~ling includes a device which acts as a solid state switch. The switch may be formed of a piezo electric substance. The piezo electric substance is preferably a spinel ferrite. The ferrite is preferably barium titanate and/or sl~u~ ll titanate. The ~ n~os may or may not be doped. The solid- state switch like device may be used in combination with a heating element. The solid state switch like device may be formed of an electro-optic ceramic substance.

217~377 Preferably the means for regencld~ g includes a device such as thyristors and/or varistors. Also preferably the device may be formed of a substance havinga positive telll~clalulc coefficient.

Preferably the filters (mo~ te~l and/or regenerative) of the present invention further include an energy storage devcie. This devcie may preferably be an inductor or a capacitor. In prior art filters/catalytic converters, used in gasoline engines especially, start up is the worst period from the standpoint of pollution. The filter/catalytic converter is typically "cold" and thelcfore not much combustion/purification occurs. By including an energy storage devcie which is charged during normal use, the stored energy is available for use during the start up period. By col~le~;Lhlg the device so that upon starting the device releases energy to the filter, this problem of low energy is obviated and effective filtration and combustion occurs during start up.
In accoldallce with another aspect of the present invention, there is provided a means for sepdlalillg particles with differing ~len~itiPs whcleill said se~alalillg means is integrally conl-Pc~(l with a heating element. Preferably the means for sepalalillg is a venturi tube or a vortex tube. The means for sepalalillg may or may not be micropyl~ically synth~si7P~.

Membrane T~ ~h. ~ Q, ~
The filters/modules used in the above-described two embo~limPnt~ of the present invention may preferably be in the form of porous ceramic, metal-ceramic or inter-mP-t~llir membranes. Such membranes and their mPthods of m~nllf~rtllre aredescribed in greater detail below. These lll~lllblanes may be thin, two dimensional bodies with a single layer membrane having a thi~ ss within the Mnge of 50 microns to lOmm or can also be much thicker being generally cylindrical in shape.
It is believed that the pores in present membranes can range in si_e from 0.1 micron to 500 microns. Reca~lse the pores have dirr.,~cll~ shapes, pore si_e is usuallydetcllllilled by converting the pore area into an equivalent circular area. Poredensities can be within the range of 20 to 80%.

WO 96/06814 21 7 ~ ~ 7 7 PCT/US95/06387 The basic method for making or synthPsi7ing a porous membrane includes cpalillg a slurry having at least one miclopylcLic substance and at least one liquid carrier for the miclo~yl~,Lic substance. The slurry is preferably applied to the surface of a substrate or article and allowed to dry on the surface into a green form of the 5 membrane. The green form of the membrane is then fired or burned according to micro~yleLic principles in order to form a porous membrane. It is often desirable to modify the slurry with the addition of other substances, referred herein as diluents.
The slurry could have a consistency ranging from very fluid to very powdery. Such slurries according to the present invention can include various combinations of the 10 following constituents:
1.) Micl~yl~Lic substances or agents. These agents are typically particles, fibers, or foils of materials such as Ni, Al, Ti, B, Si, Nb, C, Cr2O3, Zr, Ta, Mg, Zn, MgO, ZnO2, ZrO2, TiO2, B2O3, Fe or combinations thereof which may react to yieldboth heat as well as clean and nascent products from the combustion. Typical 15 reactions could be for example Cr2O3 + Al + B, Ni + Al or Ti + B or C + Al +
SiO2, etc., which react spontaneously to give CrB2, Ni3Al or TiB2 or SiC and Al2O3, respectively, with a large release of heat. The adiabatic telllpeldLUle of such a micro~yrelic reaction could be as high as 6,500-K. Tables I, II, and III give a partial listing of micr~yl~tic reactions (react~nt~ and products) and the approximate amount 20 of heat released in each reaction. AH(KJ/mole) is the enthalpy release for the reaction and T,d K is the ~ h~tic telllp~lalul~ which is exrectP~ to be reached in such reactions. The enthalpy release and the a~ hatir tell~eralulc are not precisely known for all the reactions in Tables I-III. However, all of the reactions listed are believed to be sufficiently exoth~rmir. Table IV gives a list of some micio~ylelic 25 reactions and stoichiometries. It is believed that mixtures of the con~thuPnt~ of Table I-IV are also possible along with the addition of ~iiluentc which could often be the product itself or other materials in powder, foil, fiber or other form of a pre~et~Prmin~ size. It is also believed that each of the re~ct~nt~ and products of the reactions listed in Tables I-III could function as diluents.

~1753 ~' I TABLE I
FORMATION OF REFRACTORY COMPOUNDS

REACTION /~H(KJ/mole) TadK
Ti + 2B = TiB2 -293 3190 Zr + 2B = ZrB2 -263.75 3310 Nb + 2B = NbB2 -207.74 2400 Ti + B = TiB -158.84 3350 Hf + 2B = HfB2 -310.15 3520 Ta + 2B = TaB2 -193.53 3370 Ti + C = TiC -232 3210 3B203 + 10A1 + 3TiO2 = 3TiB2 + SA1203 4000 B203 + 5Mg + Ti02 = TiB2 + 5MgO
B203 + SZn + Ti02 = TiB2 + SZnO
2B203 + SZr + 2Ti02 = 2TiB2 + SZr02 Si+C=SiC -65.3 1800 W+C=WC 40.6 1000 V+C=VC -102 2400 Nb+C =NbC -140 2800 2Nb +C =Nb2C -186 2600 Zr+C=ZrC -202.9 3440 Hf+C=HfC -218.6 3900 Ta+C =TaC -142.9 2700 2Ta+C=Ta2C -202.7 2660 4Al+3C=Al4C3 -208.8 1670 2Mo+C=Mo2C -50 1000 4B+C=B4C -71 1000 V+2B=VB2 2670 La+6B=T ~R6 2800 W+B=WB 1700 WO 96106814 21 7 ~3 7 7 PCT/US95/06387 REACTION ~H(KJ/mole) TadK
2W+B=W2B -87 1400 Cr+2B=CrB2 -94.1 2470 U+4B =UB4 1770 Mo+2B=MoB2 1800 Mo+B=MoB -112.4 1800 Al + 12B =A1Bl2 -200.6 Ti+ 1/2N2=TiN -336.6 4900 3Ti+NaN3=3TiN+Na 3Si +2N2 =Si3N4 -738.1 4300 3Si+4NaN3=Si3N4+4Na Hf+ 1/2N2=HfN -368.7 5100 B + 1/2N2 =BN -254.1 3700 Zr+1/2N2=ZrN 4900 Ta + 1/2N2 =TaN -252.1 3360 2Ta+1/2N2=Ta2N -272.5 3000 V+ 1/2N2=VN -216.9 3500 A1 + 1/2N2=A1N -302.5 2900 La+1/2N2=LaN -299.4 2500 3Be+N2=Be3N2 -564.0 3200 U+ 1/2N2=UN -286.8 3000 3Mg +N2 =Mg3N2 416.1 2900 Nb+1/2N2=NbN -237.8 3500 2Nb+1/2N2=Nb2N -248.3 2670 FORMATION OF INTERMETALLICS

REACTION ~H(KJ/mole) TadK

Ti + Ni=TiNi -278.2 1773 Ti + Pd=TiPd -103.4 1873 Ni + A1 =NiA1 -118.4 1911 Ti + A1=TiA1 -72.8 1654 Ti+Fe=TiFe -40.6 1110 5Ti+3Si =Ti5Si3 -578.9 2500 Ti+2Si=TiSi2 -134.2 1800 Ti+Si=TiSi -130 2000 Mo+2Si=MoSi2 -131.7 3190 W+2Si=WSi2 -92.9 1500 5V+3Si-V5Si3 -461.9 3190 Ta+2Si=TaSi2 -119.1 1800 Zr+Si=ZrSi -155 2100 Zr+2Si=ZrSi2 -153.8 2100 5Zr+3Si=Zr5Si3 -147.6 2800 Nb+2Si=NbSi2 -137.9 1900 2Ni+SiC=Ni2Si+C -76 3Ni +2SiC =Ni3Si2 +2C -98 Cd+S =CdS -149.2 2000 Mn+S=MnS -213.2 3000 Mo+2S =MoS2 -275 2300 25 Ni +2S = NiS2 Ni+P=NiP
Nb+P=NbP
3Ni+A1 =Ni3A1 -153.2 3Ni3Al2+9Ni=6Ni3Al WO 96/06814 21 7 ~ 3 7 7 PCTIUS95/06387 REACTION ~H(KJ/mole) T~dK

Ni+3A1 =NiA13 -162 3Ni +2A1 =Ni3A12 -282.6 Ti+3A1=TiA13 -142.1 1517 Cu+A1=CuA1 899 Cu+2A1 =CuA12 4Cu+3A1 =Cu4A13 3Cu+2A1 =Cu3A12 9Cu+4A1 =CugA14 Fe+A1 =FeA1 -18 3Fe+A1 =Fe3A1 -31.8 Zr+A1=ZrA12 1918 Pd+A1=PdA1 2579 Ti+Ni=TiNi -66.5 1552 Ti+Pt=TiPt -159.5 Ti+Co=TiCo 47.7 1723 Co+A1=CoA1 -110.4 1901 50Ti + (50-x)Ni + xPd = Ti50Ni50 ,~Pd 50Ti+(50-x)Ni+xFe=Ti50Ni50 ,~Fe 50Cu+(50-x)A1 +xNi=Cu50Al50 ,~Ni 50Cu+(50-x)A1 +xMn=Cu50Al50 ,~Mn FORMATION OF COMPOSITES

REACTION ~H(KJ/mole) TadK

Fe203+A1 = A12O3 + 2Fe -836 3753 Cr203+A1 = A12O3 + 2Cr -530 2460 3Cr203 +6A1 +4C = 2Cr3C2+3A1203 - 6500 0.86Ti+1.72B+1.48A1=0.86TiB2+1.48A1 -293 1450 Ti+C+0.68Ni = TiC+0.68Ni -232 1370 Zr+2B+Cu = ZrB2+Cu -263.75 1100 4A1 + 3Si02 + 3C = 2A1203 + 3 SiC
3Fe3O4+8A1=4A12O3+9Fe -816 3509 3NiO+2A1=2A1203+3Ni -928 3546 3MnO2+4A1=2A12O3+3Mn -878 4123 3SiO2+4Al =2Al203+3Si 3TiO2+4A1=2A12O3+3Ti Fe2O3+3Mg=3MgO+2Fe -323 3076 Fe304+3Mg=4MgO+3Fe -316 3184 Cr2O3+3Mg=3MgO+2Cr -221 2181 NiO+Mg=MgO+Ni -353 2579 3MnO2+2Mg=2MgO+Mn -337 3665 2Fe2O3+3Si=3SiO2+4Fe -311 2626 Fe304+2Si =2SiO2+3Fe -298 1808 2NiO+Si=SiO2+2Ni -373 2602 2MnO2+Si=2SiO2+Mn -339 3024 2Fe2O3 + 3Ti = 3TiO2 +4Fe 2Fe2O3 + 3Zr = 3ZrO2 +4Fe 2Cr2O3 + 3Zr = 3ZrO2 +4Cr Ti+2B+aTiB2+bCu=(a+l)TiB2+bCu WO 96/06814 PCT/US9~/06387 217~77 TABLE III (cont'd) REACTION ~I(KJ/mole) TadK
CrO3+Cr2O3+6A1 +2C+3NiO=
Cr3C2+3Al203+3Ni Nb2O5+Al2Zr+vAl203 =
2Nb+ZrO2+A12O3+vAl2O3 Nb2O5+2Al +Zr+vAl203=
2Nb+ZrO2+Al203+vAl2o3 Nb2O5 + 10/3A1 + ~ZrO2 +vA12O3 =
2Nb+~zro2+5l3Al2o3+vAl2o3 B4C+(x+S)Ti=xTiB+4TiB+TiC
2Ti+ C + 2B = TiB2+ TiC
38B + TiAl3 = TiB2 + 3AlB,2 3Tio2+4Al+3c=3Tic+2Al2o3 2300 9TiO + 1 lC +2TiAl3 = 1 lTiC +3Al2O3 3SiO2+4Al+3c=3sic+2Al2O3 3ZrSiO4+4Al+3C=3ZrO2+3SiC+2Al203 WO3+2AI+C=WC+Al203 2B2O3+4Al+C=B4C+2Al203 2ZrO2+4Al+C=Zrc+2Al2o3 2MoO3+Al+3C=3Mo2C+2Al2O3 3B2O3+10A1+3TiO2=3TiB2+5Al2O3 4000 6B+4Al+3Tio2=3TiB2+2Al2o3 4000 lOB203+3TiO2+2B+8TiAl3=
11TiB2 + 12Al203 9TiO2 +26B +4TiAl3 = 13TiB2 +6Al2O3 3Ti + 3B2O3 + 2TiAl3 = 3TiB2 + 3Al2O3 B2O3+ZrO2+10/3Al=ZrB2+5/3Al2O3 2400 MoO3+2Al+B=MoB+Al2O3 -1117.3 4000 217~ TABLE m (cont'd) 3HfO2 +4Al +6B = 3HfB +2Al2O3 REACTION ~H(KJ/mole) TadK

3V2O5+loAl+3N2=6vN+5Al2o3 4800 3TiO2 +2Al +NaN3 = 3TiN +Al2O3 +Na 3TiO2 +4Al + 1.SNaCN =
3TiCo 5No 5 +2Al2O3 + 1.5Na Ti +0.5C +0.167NaN3 = TiCo 5No 5 +0.167Na MoO3+2Al+2Si=MoSi2+Al2O3 3300 2Si3N4+4B2O3+9Al2O3= 4800 8BN+3(3Al203+2SiO2) TiO2+2Mg+C=TiC+2MgO
SiO2+2Mg+C=SiC+2MgO 2300 2B2O3 +6Mg +C =B4C +6MgO
B2O3+5Mg+TiO2=TiB2+5MgO
MoO3 +3Mg+B =MoB +3MgO
MoO3 +Mg +2Si =MoSi2 +3MgO
TiO2+Zr+C=TiC+2ZrO2 SiO2 +Zr+C =SiC +ZrO2 2B2O3+5Zr+2TiO2=2TiB2+5ZrO2 2MoO3+3Zr+2B=2MoB+3ZrO2 2MoO3+3Zr+4Si=2MoSi2+3ZrO2 1/2V2O5 + 11/3B =VB2 +5/6B2O3 2700 l/2Cr203+3B=CrB2+l/2B203 1900 2MoO3 +5B =Mo2B +2B2O3 3000 1/2Fe2O3 +2B =FeB + 1/2B2O3 2400 1/2Fe2O3 +4B +2Fe =3FeB + 1/2B2O3 1800 2MoO3+10Mo+24B=11MoB2+B2O3 2200 217~ 37~ `

TABLE III (cont'd) PbO+MoO2=PbMoO3 1340 PbO2+WO2=PbWO4 2000 WO 96/06814 PCT/US~5/06387 2175~77 TABLE III (cont'd) BaO2+SiO=BaSiO3 1880 BaO2+TiO=BaTiO3 1980 PbO2+TiO=PbTiO3 1440 MnO2+TiO=MnTiO3 1630 MnO2+TiO=MnSiO3 1540 Si+N2+Si3N4+(SiO2)z+AlN=Si~zAlzOzNs z 2673 WO 96/06814 2 1 7 ~ 3 7 7 PCT/US95/06387 TABLE IV
SAMPLE MICROPYRETIC REACTIONS
AND STOICHIOMETRIC WEIGHTS

REACTION WEIGHT %

Ni+Al=NiAl Ni: 68.5, Al: 31.5 3Ni+Al=Ni3Al Ni: 86.7, Al: 13.3 3Cr203+6Al+4C=2Cr3C2+3Al203 Cr203: 69, Al: 24, C: 7 Mo03+2Al+B=M0B+Al203 Mo03: 69, Al: 25.9, B: 5.1 Mo03+2Al+2Si=MoSi2+Al203 Mo03: 57, Al: 21, Si: 22 Ti+2B=TiB2 Ti: 68.9, B: 31.1 STi+3Si+Ti5Si3 Ti: 74, Si: 26 Nb+2Al=NbAl2 Nb: 63.3, Al: 36.7 Zr+2B=ZrB2 Zr: 80.8, B: 19.2 Nb+2B--NbB2 Nb: 81.1, B: 18.9 Fe203+2Al =Al203+2Fe Fe203N: 74.7, Al: 25.3 Cr203+2Al =Al203+2Cr Cr203: 73.8, Al: 26.2 0.86Ti+1.72B+1.48Al=0.86TiB2+1.48 Al Ti: 41.3, B: 18.7, Al: 40 Ti+B=TiB Ti: 81.6, B: 18.4 Hf+2B=HfB2 Hf: 89.2, B: 10.8 Ta+2B=TaB2 Ta: 89.3, B: 10.7 Ti+C=TiC Ti: 80, C: 20 Ti+Ni=TiNi Ti: 44.9, Ni: 55.1 Ti+Pd+TiPd Ti: 31.0, Pd: 69.0 Ti+Al=TiAl Ti: 64, Al: 36 Ti+Fe=TiFe Ti: 46.2, Fe: 53.8 Ti+C+0.68Ni=TiC+0.68Ni Ti: 48, C: 12, Ni: 40 Ni+3Al = NiAl3 Ni: 42, Al: 58 4Al + 3 Si02 + 3C = 2Al203 + 3 SiC Al: 33.29, Si02: 55.59, C:11.2 WO 96/06814 PCT/US9~106387 21~53~
Also included in the referenced slurry used to make the membranes could be the following components:
2) A liquid carrier (i.e., liquid suspending mPtlillm) which could be aqueous or non-aqueous and have either a low or high viscosity. The carrier is most often 5 chosen from a group of plasticizers (i.e., binders in suspension) which may include clays of various sorts such as bentonite, fused silica, kaolinite and related compounds;
silir~tes; borates; stearates and other lubricants including MoS2 and PbS; methyl cellulose and related compounds; organic liquids such as acetone, polyvinyl butyryl, polyvinyl alcohol, polyethylene glycol, oils of various kinds, tetraisoamyloxide, and 10 water. The plasticizer may also be a colloidal liquid such as colloidal alumina, colloidal ceria, colloidal yttria, colloidal silica, colloidal zirconia, mono-~lllll,i.......
phosphate, colloidal cerium acetate or mixtures thereof. Colloidal binders can also be derived from a ~u~el~ion cont~ining colloid precursors and reagents which are solutions of at least one salt such as chlorides, sulfates, nitrates, chlorates,15 perchlorates or metal organic compounds. Colloidal binders will usually be relatively dilute aqueous or non-aqueous suspensions, but the use of concentrated colloids or partly or fully precipitated colloids is also possible. Alternatively, the colloidal binder can be derived from a suspension cont~ining chPl~ting agents such as acetyl acetone and ethyl~retoacet~te. Various mixtures of different carriers are possible.
20 When using colloids, three types of colloidal procec~ing are possible. The first involves the gelation of certain polys~ccll~ri~e solutions. The other two involve colloids and metal organic compounds. These last two involve the mixing of materials in a very fine scale. Colloids may be defined as co~ lishlg a dispersed phase with at least one dimPn~ion between 0.5 nm (nanometer) and about 10 microns 25 (micrometers) in a dispersion m~inm which in the present case is a liquid. The m~gnit~ e of this rlimloncion distinguishes colloids from bulk systems in the following way: (a) an extremely large surface area and (b) a .cignifir~nt percentage of molecules reside in the surface of colloidal systems. Up to 40% of molecules mayreside on the surface.The colloidal systems which are hllL~olL~lL to this invention are 30 both the thermodyn~mir~lly stable lyophilic type (which include macro molecular systems such as polymers) and the kinrtir~lly stable lyophobic type (those that contain particles). In the formation of the slurry, new materials and other agents or diluents may be mixed in with the plasticizers.

3) One diluent may be a powder additive cont~ining carbides, silicides, 5 borides, ~lnminitles, nitrides, oxides, carbonitrides, oxynitrides and combinations thereof. When choosing combinations of powder additives, the particle size selection is important. It is preferable to choose particle sizes below 100 microns and when employing combinations of powder additives, to choose particle sizes which are varied such that the packing of particles is ~Lillli;~ed. Generally, the ratio of the 10 particle sizes will be in the range from about 2:1 to about 5:1. Sometimes packing is op~ ed by choosing one con~tihlPnt size three times smaller than the other constituent, i.e., having a particle ratio size of about 3:1.

4) Metallic particles, intermpt~llir particles or a combination thereof, for 15 example Cu, Ni, Pt, Al, Cr, Zr, Zn, Mg, Fe, Mn, NiAl, NiAl3, CrSi, CrB, etc. The sizes of these particles are also preferably varied to achieve opLilllull~ packing, like with the above powder additives.
5) Metal organic compounds l lincipally metal alkoxides of the general formula M(OR)z, where M is a metal or a complex cation made up of two or more 20 elements, R is an alkyl chain and z is a number usually in the range from 1 to 12.
AlLelllalively, these metal alkoxides can be described as solutions in which molecules of organic groups are bound to a metal atom through oxygen. Examples of metal alkoxides are silicon tetraisoamyloxide, Alll.";"..." butoxide, alll.llill.llll isopropoxide, tetraethyl ortho~ilir~tes~ etc. The organic portions of other metal organic compounds 25 may include formates, ~ret~tes and acetylacetonates.

6) Pyrolizable chlorosilanes, polycarbosilanes, poly.~ 7~nrs and other organosilicon polymers may be used as binders which pyrolize to useful products for oxidation prevention. Such compounds are expected to participate in the micropylclic 30 reaction in a beneficial but complex lllanl~er to increase the yield of useful products with a morphology and size useful for the membrane. Organosilicon polymers WO 96/06814 PCT/US9~/06387 175 3r77pically dissolve in water and therefore should be avoided when producing membranes for filtering aqueous solutions.

7) Alkaline or acitic solutions may be needed to modify the pH of the S slurry. Standard laboratory grade ~lk~lin~os and acids are used.

8) Burnable and/or oxidizable liquid or solid constituents such as polymers (e.g., polyulclllalle, polyester) or carbonaceous materials may be added to the slurry to be eventually burned off leaving behind a prede~ ed pore size and pore volume10 (density) in the membrane.
Tables V and VI give examples of typical slurry compositions.

WO 96/06814 2 1 7 ~ 3 7 7 PCT/US95/06387 ~ ~ ~ o o 2 ~ -oa v U~
o u ~ "~ e y a ~ c O o 'o _ o o o o _ - ~ .~ ' o o _ _ _ _ o ~ ~ ~ ~ ~ ~
~ ~ C.~ ~ ~ ~
U~

U .. ~ a a ~

`' ~ ~ U ~ ~ ~ a "
e c C ~
.e ~a * *

o 21~ 77 Z V o ~

o~
O ~ ~ ~1 -- .~
o o o V o o 5 EV, ~ ~; Z
o V

Z o ZO V.

2 ~
~ o ~ ~ _ ~ ~, CQ

WO 96106814 21 7 ~ ~ 7 7 PCT/I~S95/06387 Once the desired slurry mixture is prepared, the slurry is then dried into a green form having a desired geometric configuration. The slurry may be applied to the surface of a substrate or article. The applied slurry is then dried, such as by air drying or being baked at relatively low telllpcl~tulcs~ for example, in an oven, usually 5 so as not to start the micru~y~clic reaction. There are various methods of applying the slurry including p~inting (by brush or roller), dipping, spraying, or pouring the liquid onto the surface. Typically, each coating of the slurry is allowed to dry before another coating is added. However, the underlying coating does not n~cess~rily need to be entirely dry before the next coating is applied. If one or more coatings with 10 micr~ylelic con.ctit~ent.c are present, then it is preferable to dry these coatings completely prior to firing (i.e., the combustion step). Multiple coatings may benrces,c~ry in order to obtain the desired layer thirl~nPss. Depending upon the slurry composition, additional coatings may be added to already fired layers either for repair or for additional build up. Even when miclo~ylclic constituents are absent, it is 15 ~lcfcllcd to heat the green membrane with a suitable heat source, such as a torch (e.g., butane or oxyacetylene), a laser, a furnace, etc., if il~lovcm-ent in theden.cifir~tion of the membrane is required. Such heating takes place preferably in air but could be in other oxi~li7ing atmospheres or in inert or reducing atmospheres.

In general, the micropylelic layers provide heat for the bonding of several layers as well as bonding to the substrate or article. While membranes with multiple miclupyl.,lic layers can be produced according to the invention, multilayer membranes with one or more non-micr~ylclic layers can also be produced, if desired. These non-micr~ylclic layers could for example be made of polymers.
If desired, bonding of the coatings to the surface of the substrate or article can be enh~nred by treating the surface. The surface may be treated by sandblasting or pickling with acids or fluxes such as cryolite or other combinations of fluorides and chlorides prior to the application of the coating. Similarly, the substrate may be cleaned with an organic solvent such as acetone to remove oily products or otherdebris prior to the application of the coating.

W O 96/06814 PCTrUS9~/06387 217~377 In the case of mic,opyl~lic coatings, an additional step after the drying of theslurry coating(s) will be the firing or combustion of the slurry constituents (i.e., the membrane in its green state). Combustion of the green membrane can be performed by direct flame, concentrated sllnlight, a plasma, a laser or an electron beam. In addition, if the substrate or article is conductive, the green form can be combusted by passing a current through the substrate or article. The coated substrate or article could also be placed inside a furnace at a prede~ d temperature and time or heated by an induction method or by radiant heating. The applied slurry containsparticulate substances which sinter above a given te~ eldLu,e, in particular reactant and/or non-reactant substances that reaction sinter at a te"lpeld~ule greater than about 0.5 Tm, where Tm is the melting point of the lowest melting reaction product.

Additional heat can be applied to a membrane in order to reduce the pore size and pore density in the membrane. The present method is good for obtaining membranes with pore sizes ranging from 10 nanometers to 100 microns. In-situ repair, rather than repl~PmPnt of membranes by using the principles of the present invention is also contemplated.

Conductive Coatin~ App!ir~ti~ c~
Another aspect of the present invention concel,ls a process for applying a conductive coating wherein a slurry- co,ll~,isillg (A) at least one colllpollellL selected from the group co~ g of (a) at least two particulate ceramic ~le~;Ul~Ol:i capable of undergoing combustion ~yllllRsis, (b) at least one non-miclc~y~lic particulate ceramic, (c) at least one metal, (d) at least one inter-m~-t~llic, (e) at least one polymeric material, and mixtures thereof; and (B) hydroplastic materials selected from the group con~i~ting of clays, colloidal silica, colloidal ahlmin~, colloidal zirconia, colloidal ceria and mixtures thereof, is provided. The slurry may contain conventional amounts of suspension agents, surfact~nt~ and anti-foaming agents, e.g., in total up to about 5% by volume, in order to facilitate application, wetting and impregnation of the substrate.

2~7~77 The concentration of ceramic precursors in the aqueous slurry is not critical and may be any amount which will obtain a viscosity such that wetting of the foamed polymer is ensured without excessive run-off. The type of foamed polymer (if used), is not critical, although it is ~rercllcd to select a thermoplastic or thermosetting polymer which will volatilize or decompose at a lcll~ lulc not exceeding about 1100 C. In general, conventional foamed polymers which will volatili_e, decompose or char when heated to a temperature of about 400 to about 1100 C. are suitable,such as polyulcLl~ne, polyvinyl chloride, polyethylene and polypropylene. Cellulose sponge and natural or polymeric fibers in woven or non-woven form may also be used and are int~n-led to be included within the generic term foamed polymer.

The method of application of the slurry to the foamed polymer, i.e., hl~lc~ ion, is what leads to the dramatic hlll,rovclllents afforded this aspect by the present invention over the process of the '737 patent. The impregnation is achieved by (a) flnirli7ing said slurry with steam or heated water and spraying the shape with said flllitli7pd slurry or (b) heating said slurry so as to reduce its viscosity and spraying the shape with said reduced viscosity slurry.

The ull~legl~lion step of this aspect of the present invention obviates the dripping involved in the '737 process, Lllcrcb~ making the process less awkwald and cumbersome. This also avoids the collapse of the "green structure" during processing, as observed in the '737 patent. Fullh( llllore, the present method of impregnation avoids "distortion" of the formed article. Additionally, the steam or heated water or hot liquid col~liluent of the spray better dissolves certain conctitll~ntc more easily, such as calcium silicates (cPm~ntc) such as (CaO)3. (SiO2)2. (H2O)3, which lead to a high green and final ~Llcn~LIl by plccipiL~Lillg out on the deposited surface.

The slurry-illl~lc~,llalcd polymer is heated to a temperature of about 400 to about 1100 C, in order to drive off the polymer. The slurry-impregnated polymer may next again be dipped into the slurry after the heating step and dried. The dipping and drying may be done several times. If it is desired to obtain a coated porous 2 1 7 ~ f PCT/US95/06387 ceramic, ceramic composite or metal structure, a preexisting ceramic, ceramic composite or metal body is impregnated with the slurry as described above.

Finally, the impregnated structure is ignited and/or heated by means of an 5 electric arc, electric spark, flame, welding electrode, laser or in a furnace or by other conventional methods to initiate combustion synthesis and/or to sinter the impregnated structure. The final product is a conductive porous ceramic structure or a coated (the coating being conductive), porous ceramic, ceramic composite or metal structure.Thus, the products of the present invention may act both as filters and, due to their 10 conductiveness, as heating elements. As stated above, because the heating element and filter are one and the same, less heat is lost due to radiation and the heat is available precisely where required, i.e. in the filter (which is also the heating element). It is also possible to incorporate in the conductive body, a "second"
heating element which is a se~alate structure, which further improves the capability 15 of the heating the filter. The "two-in-one" heating element-filter may also be fitted with a plC~i~iUlC release safety valve for removing collected particulate matter, the valve being self-resetting or otherwise.

The ceramic precursors may comprise powder n~ ules cont~ining from about 35% to about 55% mtot~llic all.. i".. ", about 25% to about 35% 1il;11lil.. ,l dioxide (titania), and about 20% to about 30% boric oxide, all l,erccllL~ges being by weight.

Another llli~lUl`C of ceramic precursors in particulate form may comprise from about 65% to about 75% silicon and from about 25% to about 35% graphite, the 25 percentages being by weight.

In another embodiment the ceramic precursors may comprise mixtures cont~ining from about 20% to about 30% m~t~llic ~lll.ni....,n, about 20% to about 25% titania, about 15% to about 25% boric oxide, about 25% to about 30%
30 zirconium oxide, all pel~ lllages being by weight.

wo 96/06814 2 1 7 S 3 7 7 PCT/USg~/06387 The ceramic precursors may further comprise from about 20% to about 30%
mPt~llic ~ nlillllln, about 20% to about 25% titania, about 15% to about 25% boric oxide, and about 25% to about 35% powdered niobium, all percentages being by weight.
s Still another precursor mixture may comprise from about 20% to about 30%
metallic al~ i"~"-, about 20% to about 25% titania, about 15% to about 25% boricoxide, about 20% to about 25% Alllllli"...n oxide, and about 3% to about 10%
zirconium oxide, all pel.;ell~ges being by weight.
Where a miclo~y~lic reaction is involved, the particle size of the ceramic precursors is of illl~,lLance in ~lete~ ining the rate of reaction propagation. For purposes of the present process, particle sizes ranging from about 1 to about 150 microns have been found to be preferable.
It will be understood that the present process is not limited to any particular size or shape of ceramic structure, metal-ceramic composite structure or mPt~llir structure, nor to the pore size thereof, as will be evident from the specific examples which follow. The atmosphere in which combustion synthesis is con-ltlctecl is also 20 not a limitation. In all embo-limPnt~ described herein, combustion synthesis may be carried out in air at ambient ples~ure.

The ceramic, metal-ceramic or inter-mPt~llic composite structure/coating is selected from the group col.~ ;l-g of borides of ~i~;..-i.~.", zirconium, niobium, 25 t~nt~lllm, molyb~lenllm, h~fnillm, ch~llliuul, and v~n~lillm; carbides of tit~nillm, h~fninm, boron, ~l,..,.i.,...~, t~nt~lllm, silicon, l.~,-g~l~n, zirconium, niobium, and ch~ollliulll; calbollillides of ~ ..il..", niobium, and t~nt~hlm; nitrides of li~liulll, zirconium, boron, ~lllllljl,.ll,,, silicon, t~nt~lllm, h~fnillm, and niobium; silicides of molybdenum, ~ ni...n, zirconium, niobium, t~nt~lllm~ en and van~linm;
30 hydrides of ~ .., zirconium and niobium; all.~ oxide-lili...il.", boride;.., carbide~ I,i...ll boride; ~ll.."i..,.." oxide-tit~nil-m boride-~ili...il..ll nitride;
al....,i.,~." oxide-li~ ll boride-~ .,ill." carbide; boron carbide-al~ .ll oxide;

17 5 3 7 7 molybdenum silicide~ -ll oxide; molybdenum boride-al~lmin~m oxide;
chrol,liulll carbide-al~..,i".~"~ oxide, v~n~tlium nitride-al-~min~m oxide, aluminides of nickel, pl~timlm-~lllmimlm compounds, phosphides of nickel, tit~nium-nickel, oxides and oxychlorides of ruthenium, mullite, cordierite and mixtures thereof.

In the following illustrative but non-limiting embodiments of this aspect of theinvention, Examples 1 through 3 relate to the pl~ald~ion of coatings having miclc~yletic con~tit~lent~ while Examples 4 and 5 relate to coatings having non-micro~yl~tiC con~titl~lellt~.

Aqueous slurries were prepared for the following mixtures. All constituents were powders and all ~ l~ges are in weight percent.

55%Ni + 23%Al + 3%C + 10%SiO2 + 2%Pt (catalyst powder form) + 2%CaC03 + 5%clay (the clay is selected from the montmorillonite group of clays, a group cont~ining bentonite, sauconite, nolllloniLe, saponite, hectonite and verm~Yll~te, called three-layered clays) + water (lOml/50g powder) 57%MoO3 + 21%Al + 22%Si + (diluents) + (catalysts such as Pt) (eg MoSi2 or SiC) + colloidal silica(lml/5g) + water (20ml/50g powder) 60%Ti + 15%Si + 5%P + 10%Ni + 5%(SiC fibers) + 3%PtO2 (powder) + 2%RuCl2 (liquid) + colloidal silica + colloidal ~lumin~

+ colloidal zirconia (approx 10ml/50g) W O 96/06814 2 1 7 S 3 7 7 PCTrUS9~/06387 -30%Al203 + 25%SiO2 + 29%ZrO? + 10% (Al203 fibers) +
2%RuCl2(ruthenium chloride) + 3%PtO2 (catalyst) + colloidal silica (lOml/15g) + 0.5%TiO2 + 0.5%MgO

In some cases RuCl2 was added later and heated to 430 C.

50% co~ entc of example 3 and 50% constituents of Example 4 General Procedure The slurries were fl~ i7r(l and were well mixed in stainless steel containers.
A spray machine/steam generator/portable oil fired steam cleaner (model SZ170 made by Dayton Colllpally) is used to gene~e a spray of hot liquid or steam or water. It is a 66 gallon per hour m~rhin~o which opcl~les at up to 180 psi. GeneMlly, the hot liquid or steam or water is splayed on the slurry with a nozzle at a ples~ule of 10ppi.
A polymeric foam cylinder approximately 3" fli~mPter and 4" height was used.
Uniform coating of the foam stems was obtained and the ples~ule of the jet helped to keep the pores open. After each spray a 5 minute drying time was allowed before 20 the next layer was deposited. The layers were allowed to build up until a 0.35 mm stem thirl~n~sc was obtained. The non-distorted mass was then heated to 350 C todrive away the polymer and a green ceramic or ceramic composite structure was obtained. The mass was then placed in a furnace. Furnace telll~ dLu,e for examples 1-3 was 1150-C, for examples 4 and S, it was 1600-C. In all cases, either through 25 miclupylctic silllelillg, or conventional cintering a solid ceramic porous body was obtained. Examples 1 through 3 produced conductive coatings whereas 4 and S werenot conductive.

While specific examples of coating porous ceramic, ceramic composite or 30 metal structures have not been provided, the slurries described above are equally applicable for producing coated articles and the advantages afforded by the 2 1~ 5 ~ impregnation method of the present invention extend to m~mlfarture of coated articles as well.

From the above disclosure of the general principles of the present invention 5 and the prece(ling detailed description, those skilled in the art will readily comprehend the various modifications^to which the present invention is susceptible. Therefore, the scope of the invention should be limited only by the following claims and equivalents thereof.

Claims

Page missing upon filing vanadium; carbides and oxides of tatanium, hafnium, boron, aluminum, tantalum, silicon, tungsten, zirconium, niobium, iron, molybdenum, vanadium and chromium;
carbonitrides of titanium, niobium, and tantalum; nitrides of titanium, zirconium, boron, aluminum, silicon, tantalum, hafnium, and niobium; silicides of molybdenum, titanium, zirconium, niobium, tantalum, tungsten and vanadium; hydrides of tatanium, zirconium and niobium; aluminum oxide-titanium boride; titanium carbide-titanium, boride; aluminum oxide-titanium boride-titanium nitride; aluminum oxide-titaniumboride-titanium carbide; boron carbide-aluminum oxide; molybdenum silicide-aluminum oxide; molybdenum boride-aluminum oxide; chromium carbide-aluminum oxide; vanadium nitride-aluminum oxide, aluminides of nickel, platinum, ruthenium, rhodium, gold, silver, iron, titanium and palladium and compounds thereof in theform of coatings, phosphides of nickel, titanium-nickel, oxides and oxychlorides of ruthenium, mullite, cordierite, lanthanum chlomite, graphite and compounds and mixtures thereof.

9. The modulated filter of claim 1, wherein the pores in said composite are approximately 10-80 pores per inch.

10. The modulated filter of claim 8, wherein each said composite further comprises metallic particles, intermetallic particles and compounds and combinations thereof.

11. The modulated filter of claim 10, wherein said metallic particles, intermetallic particles or combinations thereof are selected from the group consisting of Cu, Ni, Pt, Al, Cr, Zr, Zn, Mg, Fe, Mn, Rh, Ru, NiAl, NiAl3, CrSi, CrB Ti5Si3, NbB, Nb3Al, NbAl3, Nb2Al and compounds and mixtures thereof.

12. A regenerative filter comprising;
a means for filtering including at least one porous ceramic, metal-ceramic or inter-metallic composite having been manufactured using micropyretic synthesis; and a means for regenerating said means for filtering, said means for regenerating being integral with said filtering means.

13. The regenerative filter of claim 12, wherein said regenerating means is formed in situ with said filtering means.

14. The regenerative filter of claim 12, wherein said composite is reticulated.

15. The regenerative filter of claim 12, wherein the means for regenerating comprises a catalyst.

16. The regenerative filter of claim 15, wherein the catalyst is applied to the filter by a method selected from the group consisting of coating, impregnating, and combinations thereof.

17. The regenerative filter of claim 15, wherein the catalyst can react or be reactive under conditions of vacuum, room temperature, increased temperature,pressure or combinations thereof.

18. The regenerative filter of claim 12, wherein said means for regenerating comprises a heating element.

19. The regenerative filter of claim 18, wherein said heating element is formed in situ with said filtering means.

20. The regenerative filter of claim 18, wherein said heating element comprises a compound selected from the group consisting of metallic material, molysilicides, Fe-Cr-Al, Ni-Cr, SiC and compounds and combinations thereof.

21. The regenerative filter of claim 18, wherein said heating element comprises a material selected from the group consisting of borides or aluminides of titanium, zirconium, niobium, tantalum, molybdenum, hafnium, chromium, and vanadium; carbides and oxides of titanium, hafnium, boron, aluminum, tantalum, silicon, tungsten, zirconium, niobium, and chromium; carbonitrides of titanium, niobium, and tantalum; nitrides of titanium, zirconium, boron, aluminum, silicon, tantalum, hafnium, and niobium; silicides of molybdenum, titanium, zirconium, niobium, tantalum, tungsten and vanadium; hydrides of titanium, zirconium and niobium;aluminum oxide-titanium boride;titanium carbide-titanium boride;aluminumoxide-titanium boride-titanium nitride; aluminum oxide-titanium boride-titanium carbide; boron carbide-aluminum oxide; molybdenum silicide-aluminum oxide;
molybdenum boride-aluminum oxide; chromium carbide-aluminum oxide, vanadium nitride-aluminum oxide, aluminides of nickel, platinum, ruthenium, rhodium, gold, silver, iron, titanium and palladium and compounds thereof in the form of coatings, phosphides of nickel, titanium-nickel, oxides and oxychlorides of ruthenium, mullite, cordierite, lanthanum chromite, graphite and compounds and mixtures thereof.

22. The regenerative filter of claim 21, wherein each said composite further comprises metallic particles, intermetallic particles or compounds or combinations thereof.

23. The regenerative filter of claim 22, wherein said metallic particles, intermetalic particles or combinations thereof are selected from the group consisting of Cu, Ni, Pt, Al, Cr, Zr, Zn, Mg, Fe, Mn, Rh, Ru, NiAl, NiAl3, CrSi, CrB Ti5Si3, NbB, Nb3Al, NbAI3, Nb2Al and compounds and mixtures thereof.

24. The regenerative filter of claims 18, 19, 20, or 21 wherein said heating element is a high resistivity heating element with a resistivity of between around 50-5000 µohm-cm.

25. In a land-based vehicle, water-based vehicle, in power generation equipment or in an industrial engine, said vehicles, equipment or engine including a body and an exhaust system, the improvement comprising: a modulated filter for gaseous, liquid and particulate matter, wherein the modules in said filter are porous ceramic, metal-ceramic or inter-metallic composites, said structures having beenmanufactured using micropyretic synthesis, the filter including at least two porous ceramic, metal-ceramic or inter-metallic composites.

26. The improvement of claim 25, wherein the filter includes a catalyst.

27. The improvement of claim 26, wherein the catalyst is applied to the filter by a method selected from the group consisting of coating, impregnating, and combinations thereof.

28. The improvement of claim 26, wherein the catalyst can react or be reactive under conditions of vacuum, room temperature, increased temperature, pressure or combinations thereof.

29. The improvement of claim 26, wherein each said module is optimized for extracting different materials.

30. The improvement of claim 29, wherein said materials are selected from the group consisting of particulates carbon particles, NOx, CO, CO2, SO2, hydrocarbons, and combinations thereof.

31. The improvement of claim 25, wherein said composites have rough surfaces, said roughness being enhanced chemically or mechanically.

32. The improvement of claim 25, wherein said composites are reticulated-33. The improvement of claim 25, wherein each said composite comprises material selected from the group consisting of borides or aluminides of titanium, zirconium, niobium, tantalum, molybdenum, hafnium, chromium, and vanadium;
carbides and oxides of titanium, hafnium, boron, aluminum, tantalum, silicon, tungsten, zirconium, niobium, iron, molybdenum, vanadium, and chromium;
carbonitrides of titanium, niobium, and tantalum; nitrides of titanium, zirconium, boron, aluminum, silicon, tantalum, hafnium, and niobium; silicides of molybdenum, titanium, zirconium, niobium, tantalum, tungsten and vanadium; hydrides of titanium, zirconium and niobium; aluminum oxide-titanium boride; titanium carbide-titaniumboride; aluminum oxide-titanium boride-titanium nitride; aluminum oxide-titaniumboride-titanium carbide; boron carbide-aluminum oxide; molybdenum silicide-aluminum oxide; molybdenum boride-aluminum oxide; chromium carbide-alumimum oxide; vanadium nitride-aluminum oxide, aluminides of nickel, platimum, ruthenium, rhodium, gold, silver, iron, titanium and palladium and compounds thereof in theform of coatings, phosphides of nickel, titanium-nickel, oxides and oxychlorides of ruthenium, mullite, cordierite, lanthanum chromite, graphite and compounds and mixtures thereof.

34. The improvement of claim 33, further comprising metallic particles, intermetallic particles and compounds and combinations thereof.

35. The improvement of claim 34, wherein said metallic particles, intermetallic particles or combinations thereof are selected from the group consisting of Cu, Ni, Pt, Al, Cr, Zr, Zn, Mg, Fe, Mn, Rh, Ru, NiAl, NiAl3, CrSi, CrB Ti5Si3, NbB, Nb3Al, NbAl3, Nb2Al and compounds and mixtures thereof.

36. The improvement of claim 25, wherein the pores in said composite are 10-80 pores per inch.

37. In a land-based vechicle, water-based vehicle, in power generation equipment or in an industrial engine, said vehicles, equipment or engine, including a body and an exhaust system, the improvement comprising: a regenerative filter in the exhaust system including a means for filtering which comprises at least one porous ceramic, metal-ceramic or inter-metallic composite having been manufactured using micropyretic synthesis and a means for regenerating said means for filtering, said means for regenerating being integral with said filtering means.

38. The improvement of claim 37, wherein said regenerating means is formed in situ with said filtering means.

39. The improvement of claim 37, wherein said ceramic, metal-ceramic or inter-metallic composite is reticulated.

40. The improvement of claim 37, wherein said means for regenerating comprises a heating element.

41. The improvement of claim 37, wherein said means for filtering comprises reticulated ceramic, metal-ceramic or inter-metallic composites having been manufactured using miclopyretic synthesis; and said means for regenerating comprises a heating element.

42. The improvement of claim 41, wherein said heating element is formed in situ with said filtering element.

43. The improvement of claim 42, wherein said heating element comprises a compoud selected from the group consisting of metallic material, molysilicides, Fe-Cr-Al, Ni-Cr, SiC and combinations thereof.

44. The improvement of claim 40, wherein said heating element comprises a material selected from the group consisting of borides or aluminides of titanium zirconium, niobium, tantalum, molybdenum, hafnium, chromium, and vanadium;
carbides and oxides of titanium, hafnium, boron, aluminum, tantalum, silicon, tnngsten, zirconium, niobium, and chromium; carbonitrides of titanium, niobium, and tantalum; nitrides of titanium, zirconium, boron, aluminum, silicon, tantalum, hafnium, and niobium; silicides of molybdenum, titanium, zirconium, niobium, tantalum,tungsten and vanadium; hydrides of titanium, zirconium and niobium;
aluminum oxide-titanium boride; titanium carbide-titanium boride; aluminum oxide-titanium boride-titanium nitride; aluminum oxide-titanium boride-titanium carbide;
boron carbide-aluminum oxide; molybdenum silicide-aluminum oxide; molybdenum boride-aluminum oxide; chromium carbide-alumimum oxide, vanadium nitride-aluminum oxide, aluminides of nickel, platinum, ruthenium, rhodium, gold, silver, iron, titanium and palladium and compounds thereof in the form of coatings phosphides of nickel, titanium-nickel, oxides and oxychlorides of ruthenium, mullite, cordierite, lanthanum chromite, graphite and compounds and mixtures thereof.

45. The improvement of claim 44, further comprising metallic particles, intermetallic particles and compounds and combinations thereof.

46. The improvement of claim 45, wherein said metallic particles, intermetallic particles or combinations thereof are selected from the group consisting of Cu, Ni, Pt, Al, Cr, Zr, Zn, Mg, Fe, Mn, Rh, Ru, NiAl, NiAl3, CrSi, CrB Ti5Si3, NbB, Nb3Al, NbAl3, Nb2Al and compounds and mixtures thereof.

47. The improvement of claims 40, 41, 42, or 43 wherein said heating element is a high resistivity heating element, with a resistivity of between around 50-5000 µohm-cm.

48. In a regenerative exhaust system, the improvement comprising:
a modulated filter for gaseous, liquid and particulate matter, wherein the modules in said filter are porous ceramic, metal-ceramic or inter-metallic composites, said composites having been manufactured using micropyretic synthesis, the filter including at least two modules.

49. The improvement of claim 48, wherein the filter includes a catalyst.

50. The improvement of claim 49, wherein the catalyst is applied to the filter by a method selected from the group consisting of coating, impregnating, application of a liquid, application of a gas, application of a pliable solid, and combinations thereof.

51. The improvement of claim 49 wherein the catalyst can react or be reactive under conditions of vacuum, room temperature, increased temperature, pressure or combinations thereof.

52. The improvement of claim 48, wherein each said module is optimized for extracting different materials.

53. The improvement of claim 52, wherein said materials are selected from the group consisting of particulates carbon particles, NOx, CO, CO2, SO2, hydrocarbons, and combinations thereof.

54. The improvement of claim 50, wherein said porous composites have rough surfaces, said roughness being enhanced chemically or mechanically.

55. The improvement of claim 48, wherein said composites are reticulated.

56. The improvement of claim 48, wherein each said composites comprises a material selected from the group consisting of borides or aluminides of of titanium, zirconium, niobium, tantalum, molybdenum, hafnium chromium, and vanadium;
carbides and oxides of titanium, hafnium, boron, aluminum, tantalum, silicon, tungsten, zirconium, niobium, iron, molybdenum, vanadium, and chromium;
carbonitrides of titanium, niobium, and tantalum; nitrides of titanium, zirconium, boron, aluminum. silicon, tantalum, hafnium, and niobium; silicides of molybdenum, titanium, zirconium, niobium, tantalum, tungsten and vanadium; hydrides of titanium, zirconium and niobium; aluminum oxide-titanium boride; titanium carbide-titaniumboride; aluminum oxide-titanium boride-titanium. nitride; aluminum oxide-titanium boride-titanium carbide; boron carbide-aluminum oxide; molybdenum, silicide-aluminum oxide; molybdenum boride-aluminum oxide; chromium carbide-aluminum oxide; vanadium nitride-aluminum oxide, aluminides of nickel, platimlm, ruthenium, rhodium, gold, silver, iron, titanium and palladium and compounds thereof in theform of coatings, phosphides of nickel, titanium-nickel, oxides and oxychlorides of ruthenium, mullite, cordierite, lanthanum chromite, graphite and compounds and mixtures thereof.

57. The improvement of claim 56, further comprising metallic particles, intermetallic particles and compounds and combinations thereof.

58. The improvement of claim 57, wherein said particles, intermetallic particles or combinations thereof are selected from the group consisting of Cu, Ni, Pt, Al, Cr, Zr, Zn, Mg, Fe, Mn, Rh, Ru, NiAl, NiAl3, CrSi, CrB Ti5Si3, NbB, Nb3Al, NbAl3, Nb2Al and compounds and mixtures thereof.

59. The improvement of claim 48, wherein the pores in said composites are 10-80 pores per inch.

60. In a regenerative exhaust system, the improvement comprising:
a regenerative filter comprising a means for filtering which comprises a porous ceramic, metal-ceramic or inter-metallic composite having been manufatured using micropyretic synthesis, and a means for regenerating said means for filtering, said means for regenerating being integral with said filtering means.

61. The improvement of claim 60, wherein said regenerating means is formed in situ with said filtering means.

62. The improvement of claim 60, wherein said ceramic, metal-ceramic or inter-metallic composite is reticulated.

63. The improvement of claim 60, wherein said means for regenerating comprises a heating element.

64. The improvement of claim 63, wherein said heating element is formed in situ with said filtering means.

65. The improvement of claim 64, wherein said heating element comprises a compound selected from the group consisting of metallic material, molycilicides, Fe-Cr-Al, Ni-Cr, SiC and combinations thereof.

66. The improvement of claim 63, wherein said heating element comprises a material selected from the group consisting of borides or aluminides of titanium, zirconium, niobium, tantalum, molybdenum, hafnium, chromium, and vanadium;
carbides and oxides of titanium, hafnium, boron, aluminum, tantalum, silicon, tnngsten, zirconium, niobium, and chromium; carbonitrides of titanium, niobium, and tantalum; nitrides of titanium, zirconium, boron, aluminum, silicon, tantalum, hafnium, and niobium; silicides of molybdenum, titanium, zirconium, niobium, tantalum, tungsten and vanadium; hydrides of titanium, zirconium and niobium;
aluminum oxide-titanium boride; titanium carbide-titanium boride; aluminum oxide-titanium boride-titanium nitride; aluminum oxide-titanium boride-titanium carbide;
boron carbide-aluminum oxide; molybdenum silicide-aluminum oxide; molybdenum boride-aluminum oxide; chromium carbide-aluminum oxide, vanadium nitride-aluminum oxide, aluminides of nickel, platinum, ruthenium, rhodium gold, silver,iron, titanium and palladium and compounds thereof in the form of coatings, phosphides of nickel, titanium-nickel, oxides and oxychorides of ruthenium, mullite, cordierite, lanthanum chromite, grahite and compounds and mixtures thereof.

67. The improvement of claim 66, wherein said composite further comprises metallic particles, intermetallic particles and compounds and combinations thereof.

68. The improvement of claim 67, wherein said particles, intermetallic particles or combinations thereof are selected from the group consisting of Cu, Ni, Pt, Al, Cr, Zr, Zn, Mg, Fe, Mn, Rh, Ru, NiAl, NiAl3, CrSi, CrB Ti5Si3, NbB, Nb3Al, NbAl3, Nb2Al and compounds and mixtures thereof.

69. The improvement of claims 63, 64, 65, or 66, wherein said heating element is a high resistivity heating element, with a resistivity of between around 50-5000 µohm-cm.

70. In a catalytic converter including a catalyst, the improvement comprising: a modulated filter for gaseous, liquid and particulate matter, wherein each of the modules in said filter is a porous ceramic, metal-ceramic or inter-metallic composite, said having been manufactured using micropyretic synthesis, the filter including at least two modules.

71. The improvement of claim 70, wherein the catalyst is applied to the filter by a method selected from the group consisting of coating, impregnating, and combinations thereof.

72. The improvement of claim 70, wherein the catalyst can react or be reactive under conditions of vacuum, room temperature, increased temperature, pressure or combinations thereof.

73. The improvement of claim 70, wherein each said module is optimized for extacting different materials.

74. The improvement of claim 70, wherein said materials are selected from the group consisting of particulates, carbon particles, NOx, CO, CO2, SO2, hydrocarbons, and combination thereof.

75. The improvement of claim 70, wherein said composites have rough surfaces, said roughness being enhanced chemically or mechanically.

76. The improvement of claim 69, wherein said composites are reticulated.

77. The improvement of claim 69, wherein the composite comprises a material selected from the group consisting of borides or aluminides of titanium, zirconium, niobium, tantalum, molybdenum, hafnium, chromium, and vanadium;
carbides and oxides of titanium, hafnium, boron, aluminum, tantalum, silicon, tungsten, zirconium, niobium, and chromium; carbonitrides of titanium, niobium, and tantalum; nitrides of titanium, zirconium, boron, aluminum, silicon, tantalum, hafnium, and niobium; silicides of molybdenum, titanium, zirconium, niobium, tantalum, tungsten and vanadium; hydrides of titanium, zirconium and niobium;
aluminum oxide-titanium boride; titanium carbide-titanium boride; aluminum oxide-titanium boride-titanium nitride; aluminum oxide-titanium boride-titanium carbide;
boron carbide-aluminum oxide; molybdenum, silicide-aluminum oxide; molybdenum boride-aluminum oxide; chromium carbide-aluminum oxide, vanadium nitride-aluminum oxide, aluminides of nickel, platinum, ruthenium, rhodium, gold, silver, iron, titanium and palladium and compounds thereof in the form of coatings, phosphides of nickel, titanium-nickel, oxides and oxychlorides of ruthenium, mullite, cordierite, lanthanum chromite, graphite and compounds and mixtures thereof.

78. The improvement of claim 77, wherein said composite further comprises metallic particles, intermetallic particles and compounds and combinations thereof.

79. The improvement of claim 78, wherein said metallic particles, intermetallic particles or combinations thereof are selected from the group consisting of Cu, Ni, Pt, Al, Cr, Zr, Zn, Mg, Fe, Mn, Rh, Ru, NiAl, NiAl3, CrSi, CrB Ti5Si3, NbB, Nb3Al, NbAl3, Nb2Al and compounds and mixtures thereof.

80. The improvement of claim 70, wherein the pores in said composites are 10-80 pores per inch.

81. A modulated regenerative filter for gaseous, liquid and particulate matter, wherein the modules in said filter are porous ceramic, metal-ceramic or inter-metallic composites, said structures having been manufactured using micropyreticsynthesis, the filter comprising:
at least two porous ceramic or ceramic composite structures; and a means for regenerating said filter, said means for regenerating being integral with said structures.

82. In a land-based vehicle, water-based vehicle, in power generation equipment or in an industrial engine, said vehicles, equipment or engine, including a body and an exhaust system, the improvement comprising: a means for heating selected from the group consisting of a high resistivity heating element, a heating element having high emissivity, a heating element having both high resistivity and high emissivity, an ignitor, a laser, a spark producing means, a mean. for inducing a chemical reaction and combinations thereof.

83. In a land-based vehicle, water-based vehicle, in power generation equipment or in an industrial engine, said vehicles, equipment or engine, including a body and an exhaust system, the improvement comprising: a regenerative filter in the exhaust system comprising a means for filtering which includes at least one porous ceramic, metal-ceramic or inter-metallic composite manufactured using micropyretic synthesis and a heating element having high resistivity, or having high emissivity or having both high resistivity and emissivity, for regenerating said means for filtering, 84. A land-based vehicle, water-based vehicle, power generation equipment or an industrial engine which causes the emission of exhaust gases including particulates, in combination with the filter of claim 1 or claim 13, said vehicles, equipment or engine including a diesel engine and means for preheating the exhaust gases prior to the gases entering said filter, said means for preheating including a high resistivity heating element, or a high emissivity heating element or a heating element having both high resistivity and high emissivity.

85 . A land-based vehicle, water-based vehicle, power generation equipment or an industrial engine which causes the emission of exhaust gases including particulates, in combination with the filter of claim 1, 12 or 15, whereby heated fluids are released from said filter, said vehicles, equipment or engine being adapted to utilize the heat from said fluids elsewhere in vehicles, equipment or engine.

86. The filter of claims 1, 12, or 15, wherein said composites are in the form of porous membranes.

87. A land based vehicle, water-based vehicle, power generation equipment or an industrial engine which causes the emission of exhaust gases including in combination with the filter of claims 1, 12 or 15, a device selected from the group consisting of an ignitor, a spark producing means, a heating element, a laser means, a means for inducing a chemical reaction, electrochemical reaction means, electrospark producing means, electrostatic separation means and combinations thereof.

88. The filter of claim 87, wherein at least two of the listed devices are present.

89. The filter of claim 87, wherein said devices cause the combustion of said particulates and of said exhaust gases.

90. The filter of claim 87, wherein said device is a spark providing means which causes intermittent or pulsed sparks or discharges so as to cause the combustion of said particulates and exhaust gases.

91. The filter of claims 82 or 87 wherein a surface is not required for combustion of said particulates or exhaust gases into innocuous gases.

92. The filters of claims 1, 12, or 15, wherein said filter is capable of attaining an operative temperature of up to 1200°C.

93. The filter of claim 15, further comprising a means for gauging the aging of the catalyst.

94. The filter of claim 12, wherein said means for regenerating comprises a heating element and an electrical terminal.

95. The filter of claim 94, wherein said heating element and electrical terminal and formed of the same material.

96. The filter of claim 12, wherein said means for regenerating comprises a plurality of heating elements in combination with a ballast.

97. The filter of claim 12, wherein said means for regenerating is a thin film resistor.

98. The filter of claim 12, wherein said means for regenerating comprises a device which acts as a solid state switch.

99. The filter of claim 98, wherein said device is formed of a piezo electric substance.

100. The filter of claim 99, wherein said piezo electric substance is a spinel ferrite.

101. The filter of claim 100, wherein said ferrite is barium or strontium titanate or mixtures thereof.

102. The filter of claim 101, wherein said titanates are doped.

103. The filter of claim 98, wherein said means for regenerating further comprises a heating element.

104. The filter of claim 99, wherein said device is formed of an electro-optic ceramic substance.

105. The filter of claim 98, wherein said device is formed of a substance having a positive temperature coefficient.

106. The filter of claim 12, wherein said means for regenerating comprises a device selected from the group consisting of thyristors, varistors or combinations thereof.

107. Use of the filter of claim 86, in furnaces used in producing wax and like substances.

108. The filter of claim 85 being specially adapted for receiving external combustible matter for combustion, so as to generate additional heat.

109. The filter of claim 108, wherein said combustible matter is selected from the group consisting of carbon, gasoline products, hydrocarbons, solid fuels, metals or any matter which reacts with a positive enthalpy change.

110. In a process for producing a porous ceramic or ceramic composite structure, comprising the steps of providing a slurry comprising ceramic precursors, impregnating a foamed polymer shape with said slurry, heating the slurry-impregnated polymer shape to a temperature sufficient to remove said polymer, and heating said ceramic precursors to obtain a ceramic or ceramic composite structure porosity an improvement process for producing a coated porous ceramic, ceramic composite or metal structure, the improvement process comprising the steps of:
providing a slurry comprising (A) at least one component selected from the group consisting of (a) at least two particulate ceramic precursors capable of undergoing combustion synthesis (b) at least one non-micropyretic particulate ceramic, (c) at least one metal, (d) at least one inter-metallic, (e) at least one polymeric material, and mixtures thereof; and (B) hydroplastic materials selected from the group consisting of clays, colloidal silica, colloidal alumina, colloidal zirconia, colloidal ceria and mixtures thereof;

impregnating a ceramic, ceramic composite or metal shape with said slurry by (a) fluidizing said slurry with steam or heated water and spraying said shape with said fluidized slurry or (b) heating said slurry so as to reduce its viscosity and spraying said shape with said reduced viscosity slurry; and obtaining a coated porous ceramic, ceramic composite or metal structure by igniting said ceramic precursors to initiate combustion synthesis and/or by heating said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material so as to cause said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material to adhere to said porous ceramic, ceramic composite or metal structure.

111. The improvement process of claim 110, wherein said shape is selected from the group consisting of fibers, reticulated and non-reticulated foam structures, straight-through ceramic channel structure and porous and non-porous metallic structures.

112. The improvement process of claim 111, wherein said slurry contains at least one of suspension agents, binders, surfactants and anti-foaming agents.

113. In a process for producing a porous ceramic or ceramic composite structure, comprising the steps of providing a slurry comprising ceramic, precursors capable of undergoing combustion synthesis, impregnating a foamed polymer shape with said slurry, heating the slurry-igniting said polymer shape to a temperature sufficient to remove said polymer, and igniting said ceramic precursors to initiate combustion synthesis, thereby obtaining a ceramic or ceramic composite structurehaving interconnected porosity and controlled pore size, an improvement process for producing a porous ceramic or ceramic composite, the improvement process comprising the steps of:
providing an improved slurry comprising (A) at least one component selected from the group consisting of (a) at least two particulate ceramic precursors capable of undergoing combustion synthesis, (b) at least one non-micropyretic particulate ceramic, (c) at least one metal, (d) at least one inter-metallic, (e) at least one polymeric material, and mixtures thereof; and (B) hydroplastic materials selected from the group consisting of clays, colloidal silica, colloidal alumina, colloidal zirconia, colloidal ceria and mixtures thereof;
impregnating said polymeric shape with said improved slurry by (a) fluidizing said improved slurry with steam or heated water and spraying said shape with said fluidized slurry or (b) heating said improved slurry so as to reduce its viscosity and spraying said shape with said reduced viscosity slurry;
heating the improved-slurry-impregnated polymer shape to a temperature sufficient to remove said polymer; and obtaining a porous ceramic, ceramic composite or metal structure by igniting said ceramic precursors to initiate combustion synthesis and/or by heating said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material so as to cause said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material.

114. The process of claim 113, wherein said improved-slurry-impregnated polymer shape is heated to a temperature of about 400 to about 1100°C. in order to volatilize or decompose said polymer.

115. The process of claim 113, including the step of applying a second improved slurry to said improve-slurry-impregnated polymer shape, said second slurry comprising (A) at least one component selected from the group consisting of (a) at least two particulate ceramic precursors capable of undergoing combustionsynthesis, (b) at least one non-micropyretic particulate ceramic, (c) at least one metal, (d) at least one inter-metallic, (e) at least one poly-meric material, and mixtures thereof; and (B) hydroplastic materials selected from the group consisting of clays, colloidal silica, colloidal alumina, colloidal zirconia, colloidal ceria and mixtures thereof.

116. The process of claim 110 or 113, wherein said ceramic or ceramic composite structure/coating comprises a material selected from the group consisting of borides of titanium, zirconium, niobium, tantalum, molybdenum, hafnium, chromium and vanadium; carbides of titanium, hafnium, boron, aluminum, tantalum,silicon, tungsten, zirconium, niobium, and chromium; carbonitrides of titanium, niobium, and tantalum; nitrides of titanium, zirconium, boron, aluminum, silicon, tantalum, hafnium, and niobium; silicides of molybdenum, titanium, zirconium, niobium, tantalum, tungsten and vanadium; hydrides of titanium, zirconium and niobium; aluminum oxide-titanium boride; titanium carbide-titanium boride; aluminum oxide-titanium boride-titanium nitride; aluminum oxide-titanium boride-titaniumcarbide; boron carbide-aluminum oxide; molybdenum silicide-aluminum oxide;
molybdenum boride-aluminum, oxide; chromium carbide-aluminum oxide, vanadium nitride-aluminum oxide, aluminides of nickel, platinum-aluminum compounds, phosphides of nickel, titanium-nickel, oxides and oxychlorides of ruthenium, mullite, cordierite and mixtures thereof.

117. The process of claim 110 or 113, wherein said metal-ceramic composite is chosen from the group consisting of iron-aluminum oxide; aluminum-aluminum, oxide-titanium boride; and titanium-titanium boride.

118. The process of claim 110 or 117, wherein said ceramic precursors comprise a mixture of from about 65% to about 95% by weight titanium and about 5% to about 35% by weight boron, said titanium and boron having average particlesizes ranging from about 1 to about 150 microns.

119. The process of claim 118, wherein said porous ceramic structure is a filter for molten metal, and wherein said ceramic precursors include additives for grain refining of said metal.

120. The process of claim 110, wherein said ceramic precursors comprise a mixture of iron oxide and metallic aluminum in approximately stoichiometric proportions and having average particle sizes ranging from about 1 to about 150 microns.

121. The process of claim 110 or 113, wherein said ceramic precursors comprise a mixture of about 35% to about 55% by weight aluminum, about 25% to about 35% by weight titanium dioxide, and about 20% to about 30% by weight boricoxide.

122. The process of claim 110 or 116, wherein said ceramic precursors comprise a mixture of from about 65% to about 75% by weight silicon and from about 25 % to about 35 % by weight graphite.

123. The process of claim 110 or 113, wherein said ceramic precursors comprise a mixture of from about 20% to about 30% aluminum, about 20% to about 25% titanium dioxide, about 15% to about 25% boric oxide, and about 25% to about35% zirconium oxide, all percentages being by weight.

124. The process of claim 110 or 113, wherein said ceramic precursors comprise a mixture of from about 20% to about 30% aluminum, about 20% to about 25% titanium dioxide, about 15% to about 25% boric oxide, and about 25% to about35 % powdered niobium, all percentages being by weight.

125. The process of claim 110 or 115, wherein said ceramic precursors comprise a mixture of from about 20% to about 30% aluminum, about 20% to about 25 % titanium dioxide, about 15 % to about 25 % boric oxide, about 20% to about 25 %
aluminum oxide, and about 3% to about 10% zirconium oxide, all percentages beingby weight.

126. A porous body which is itself conductive or to which is applied a conductive coating, which porous body can function as a heating element, so as to cause it to heat up if a current is applied through said body, and which can also function as a filter due to its porosity, wherein the heating element function and the filter function is accomplished by a single undivided structure.

127. The porous body of claim 126, wherein said body is itself conductive, said body being manufactured by a process comprising the steps of:
providing an improved slurry comprising (A) at least one component selected from the group consisting of (a) at least two particulate ceramic precursors capable of undergoing combustion synthesis, (b) at least one non-micropyretic particulate ceramic, (c) at least one metal, (d) at least one inter-metallic, (e) at least one polymeric material, and mixtures thereof; and (B) hydroplastic materials selected from the group consisting of clays, colloidal silica, colloidal alumina colloidal zirconia, colloidal ceria and mixtures thereof;
impregnating said polymeric shape with said improved slurry by (a) fluidizing said improved slurry with steam or heated water and spraying said shape with said fluidized slurry or (b) heating said improved slurry so as to reduce its viscosity and spraying said shape with said reduced viscosity slurry;
heating the improved-slurry-impregnated polymer shape to a temperature sufficient to remove said polymer; and obtaining a porous ceramic, ceramic composite or metal structure by igniting said ceramic precursors to initiate combustion synthesis and/or by heating said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material so as to cause said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material.

128. The porous body of claim 126, wherein a conductive coating is applied to said body, said body being a ceramic, ceramic composite or metal structure, the ceramic coating being applied by a process comprising the steps of:
providing a slurry comoprising (A) at least one component selected from the group consisting of (a) at least two particulate ceramic precursors capable of undergoing combustion synthesis, (b) at least one non-micropyretic particulate ceramic, (c) at least one metal, (d) at least one inter-metallic, (e) at least one polymeric material, and mixtures thereof; and (B) hydroplastic materials selected from the group consisting of clays, colloidal silica, colloidal alumina, colloidal zirconia, colloidal ceria and mixtures thereof;
impregnating a ceramic, ceramic composite or metal shape with said slurry by (a) fluidizing said slurry with steam or heated water and spraying said shape with said fluidized slurry or (b) heating said slurry so as to reduce its viscosity and spraying said shape with said reduced viscosity slurry; and obtaining a coated porous ceramic, ceramic composite or metal structure by igniting said ceramic precursors to initiate combustion synthesis and/or by heating said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material so as to cause said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material to adhere to said porous ceramic, ceramic composite or metal structure.

129. A heating element in close contact with a porous body which is itself conductive or to which is applied a conductive coating, which porous body can itself function as a heating element, so as to cause it to heat up if a current is applied through said body and which can also function as a filter due to its porosity, wherein the heating element function and the filter function of the porous body is accomplished by a single undivided structure.

130. The combination heating element porous body of claim 129, wherein said body itself is conductive, said body being manufactured by a process comprising the steps of:
providing an improved slurry comprising (A) at least one component selected from the group consisting of (a) at least two particulate ceramic precursors capable of undergoing combustion synthesis, (b) at least one non-micropyretic particulate ceramic, (c) at least one metal, (d) at least one inter-metallic, (e) at least one polymeric material, and mixtures thereof; and (B) hydroplastic materials selected from the group consisting of clays, colloidal silica, colloidal alumina, colloidal zirconia, colloidal ceria and mixtures thereof;
impregnating said polymeric shape with said improved slurry by (a) fluidizing said improved slurry with steam or heated water and spraying said shape with said fluidized slurry or (b) heating said improved slurry so as to reduce its viscosity and spraying said shape with said reduced viscosity slurry;
heating the improved-slurry-impregnated polymer shape to a temperature sufficient to remove said polymer; and obtaining a porous ceramic, ceramic composite or metal structure by igniting said ceramic precursors to initiate combustion synthesis and/or by heating said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material so as to cause said non-microopyretic particulate ceramic, metal, inter-metallic or polymeric material.

131. The combination heating element-porous body of claim 129, wherein a conductive coating is applied to said body, said body being a ceramic, ceramiccomposite or metal structure, the coating being applied to said body by a process comprising the steps of:
providing a slurry comprising (A) at least one component selected from the group consisting of (a) at least two particulate ceramic precursor capable of undergoing combustion synthesis, (b) at least one non-micropyretic particulate ceramic, (c) at least one metal, (d) at least one inter-metallic, (e) at least one polymeric material, and mixtures thereof; and (B) hydroplastic materials selected from the group consisting of clays, colloidal silica, colloidal alumina, colloidal zirconia, colloidal ceria and mixtures thereof;
impregnating a ceramic, ceramic composite or metal shape with said slurry by (a) fluidizing said slurry with steam or heated water and spraying said shape with said fluidized slurry or (b) heating said slurry so as to reduce its viscosity and spraying said shape with said reduced viscosity slurry; and obtaining a coated porous ceramic, ceramic composite or metal structure by igniting said ceramic precursors to initiate combustion synthesis and/or by heating said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material so as to cause said non-micropyretic particulate ceramic, metal, inter-metallic or polymeric material to adhere to said porous ceramic, ceramic composite or metal structure.

132. A combination heating element-porous body as in claim 126, which comprises a second heating element different in its composition from the first heating element.

133. A combination heating element-porous body as in claim 126, further comprising a pressure release safety valve for removing collected particulate matter, the valve being self-resetting or otherwise.

134. In a regenerative filter comprising a means for filtering; and a means for regenerating said means for filtering, said means for regenerating being integral with said filtering means, the improvement comprising a pressure release safety valve for removing collected particulate matter, the valve being self-resetting or otherwise.

135. A non-regenerative filter means in combination with a pressure release safety valve for removing collected particulate matter, the valve being self-resetting or otherwise.

136. The filter of claim 134 or 135, further including a means for heating the fluid entering the valve.

137. In a modulated filter for gaseous, liquid and particulate matter, wherein the modules in said filter are porous ceramic or ceramic composite structures, said structures having interconnected porosity and having been manufactured using micropyretic synthesis, the filter comprising at least two porous ceramic or ceramic composite modules, the improvement including flexible flaps in between or after the modules, said flaps being made of materials selected from the group consisting of fiber cloth, high temperature wool and flexible boards, said flaps being susceptible to adherence by particulate fines.

138. The improvement of claim 137, wherein said flaps are flexible enough so that they are displaced if the flow rate of the fluid to be filtered increases beyond a specified value, but which flaps remove fine particulates at lower flow rates.
139. In a regenerative filter comprising a means for filtering; and a means for regenerating said means for filtering, said means for regenerating being integral with said filtering means, the improvement comprising fins, metallic fins, or other conductive fins inside the regenerative filter, said fins being used to better distribute heat within the regenerative filter.

140. In a modulated filter for gaseous, liquid and particulate matter, wherein the modules in said filter are porous ceramic or ceramic composite structures, said structures having interconnected porosity and having been manufactured using micropyretic synthesis, the filter comprising at least two porous ceramic or ceramic composite modules, the improvement comprising fins, metallic fins, or other conductive fins inside the regenerative filter, said fins being used to better distribute heat within the regenerative filter.

141. The filter of claims 1, 12 or 15, further comprising an energy storage device.

142. The filter of claim 141, wherein said device is an inductor or a capacitor.

143. A separator for separating particles with different densities, comprising:
a means for separating; and a heating element integrally connected to said means for separating.

144. The separator of claim 143, wherein said separator as a vortex or a venturi tube.

145. The means for separating of claim 144, wherein said separator is micropyretically synthesized.