MXPA00010861A - Metal powders produced by the reduction of the oxides with gaseous magnesium - Google Patents

Abstract

Metal powder Ta and/or Nb, with or without one or metals from the group Ta, Nb, Ti, Mo, W, V, Zr and Hf, is made in a fine powder form by reduction of metal oxide by contact with a gaseous reducing agent, preferably an alkaline earth metal, to near complete reduction, leaching, further deoxidation and agglomeration, the powder so produced being sinterable to capacitor anode form and processable to other usages.

Description

METALLIC POWDERS PRODUCED BY REDUCTION BE THEIR OXIDES WITH GASEOUS MAGNESIUM FIELD AND BACKGROUND OF THE INVENTION This invention relates to the production of tantalum, niobium and other metal powders and their alloys by reduction of the corresponding metal oxide with gaseous active metals, such as Mg, Ca and other gaseous reducing materials, both in elemental form and in the form of compounds. Tantalum and niobium are elements of a group of metals that are difficult to isolate in free state as a consequence of the stability of their compounds, especially some of their oxides. A review of the methods developed to produce tantalum will serve to illustrate the history of a typical production procedure for these metals. The tantalum metal powder was first produced on a commercial scale in Germany at the beginning of the 20th century by reduction of the double salt, potassium heptafluortantalate (K.2TaF7) with sodium. Small pieces of sodium were mixed with the salt containing tantalum and the mixture was sealed in a steel tube. The tube was heated at the top with an annular burner and, after ignition, the reduction proceeded rapidly down the tube. The reaction mixture was allowed to cool and the solid mass, consisting of tantalum metal powder, unreacted K2TaF and sodium, as well as other products of the reduction, was manually removed using a chisel. The mixture was triturated and then leached with dilute acid to separate the tantalum from the components. The procedure was difficult to control, dangerous and produced coarse, contaminated dust, but nevertheless suggested, in later years, the way for what would become the main means of production of high purity tantalum. Commercial production of tantalum metal in the United States began in the 1930s. A melted mixture of K2TaF7 containing tantalum oxide (Ta2? 5) was electrolyzed at 700 ° C in a steel retort. After the reduction, the system was cooled and the solid mass was removed from the electrolysis cell, after which it was ground and leached to separate the coarse tantalum powder from the other reaction products. Dendritic powder was not suitable for direct use in applications of Ref: 124473 capacitors. The modern method of tantalum production was developed in the late 1950s by Hellier and Martin (Hellier, E.G. and Martin, G.L., US Patent 2950185, 1960). After Hellier and Martin and hundreds of other embodiments or variations described below, a molten mixture of K2TaF7 and a diluent salt, usually NaCl, was reduced with molten sodium in a stirred reactor. Using this system, it was feasible to control the important reaction variables, such as reduction temperature, reaction rate and reaction composition. Over the years, the process was refined and perfected to the point where high quality powders with a surface area greater than 20,000 cm / g were produced, with those materials having a surface area of the order of 5000-8000 being typical. cm2 / g. The production process still requires the separation of the solid reaction products from the retort, the separation of the tantalum powder from the salts by leaching and the carrying out of treatments, of the agglomeration type, to improve the physical properties. Most capacitor grade tantalum powders are also deoxidized with magnesium to minimize oxygen content (Albrecht, WW, Hoppe, H., Papp, V. and Wolf, R., US Patent 4537641, 1985). . Pre-agglomeration artifacts are also known today from the form of primary particles to the form of secondary particles and of doping with materials to improve capacitance (for example, P, N, Si and C). Although the reduction of K2TaF7 with sodium has allowed the industry to produce tantalum powder of high quality and high performance, according to Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Volume A 26, p. 80, 1993, the consumption of tantalum for capacitors had already reached a level greater than 50% of the world tantalum production of about 1000 tons per year, while essentially no use had been made of niobium for capacitors, even at Although the raw material base for niobium is considerably more abundant than the raw material for tantalum and despite the fact that most publications referring to powder preparation and capacitor production methods mention niobium in addition to tantalum.

Some of the difficulties that arise in the application of said process to niobium are as follows: Although the production process of the type shown in Hellier and Martin (US 2950185) for the reduction of potassium heptafluortantalate by means of sodium in a salt melt it can be used in principle for the production of high purity niobium powders via potassium heptafluorniobate, in practice said process does not behave well. This is due, in part, to the difficulty of precipitating the corresponding heptafluorniobate salts and, in part, to the aggressively reactive and corrosive nature of said salts, so that the niobium produced by that process is very impure. In addition, niobium oxide is normally unstable. See, for example, N.F. Jackson et al, Electrocomponent Science & Technology, Vol. 1, pp. 27-37 (1974). Consequently, niobium has only been used in the capacitor industry to a very small extent, predominantly in areas where quality requirements are lower. However, the dielectric constant of niobium oxide is about 1.5 times as high as that of a similar layer of tantalum oxide, which would in principle allow a greater capacitance of the niobium capacitors, subject to considerations of stability and other factors. As regards tantalum itself, despite the success of the K ^ TalVsodium reduction procedure, there are several drawbacks in this method. It is a discontinuous procedure subject to the inherent variability of the system; as a result, it is difficult to maintain consistency from one batch to another. The post-reduction processing (mechanical and hydrometallurgical separations, filtration) is complex, requiring the use of considerable human and economic resources and also being a long-term procedure. The distribution of large quantities of reaction products containing fluorides and chlorides can be a problem. Of fundamental importance, the procedure has evolved to a state of maturity such that the prospects for important advances in the behavior of the tantalum powder produced are limited.

Over the years, numerous attempts have been made to develop alternative routes for the reduction of tantalum and similar metal compounds, including Nb compounds to the metallic state (Miller, GL "Tantalum and Niobium", London, 1959, pp. 188 -94; Marden, JW and Rich, MH, US Patent 1728941, 1927; and Gardner, D., US Patent 2516863 1946; Hurd, US Patent 4687632). Among these attempts was the use of active metals other than sodium, such as calcium, magnesium and aluminum, and raw materials such as tantalum pentoxide and tantalum chloride. As can be seen in Table I below, the negative changes in the free energy of Gibbs indicate that the reduction of the oxides of Ta, Nb and other metals with magnesium to the metallic state is favorable; the speed and method of reaction determine the possibility of using this approach to produce high quality powders on a commercial scale. To date, none of these measures were commercialized in an important way because they did not produce high quality powders. Apparently, the reason these measures failed in the past was because the reductions were carried out by mixing the reducing agents with the metal oxide. The reaction took place in contact with the molten reducing agent and under conditions of impossibility of controlling the temperature of highly exothermic reactions. Therefore, the morphology of the products and the residual content in reducing metal can not be controlled.

Table 1 Change in Free Energy of Gibbs for the Reduction of Metal Oxides with Magnesium MxOy (s) + yMg (g)? yMgO (s) + xM (s) It is well known to use magnesium to deoxidize or reduce the oxygen content of the tantalum metal. The process comprises mixing the metal powder with 1, 3% magnesium and heat to get the reduction procedure. Magnesium is in the molten state during part of the heating time. In this case, the objective is to separate 1000-3000 ppm of oxygen and only a low concentration of MgO is produced. However, when a much larger amount of tantalum oxide is reduced, a large amount of magnesium oxide is generated. The resulting mixture of magnesium, tantalum oxide and magnesium oxide, under poorly controlled temperature conditions, can form tantalum-magnesium-oxygen complexes that are difficult to separate from the tantalum metal. A principal object of the invention is to provide a new technique for the production of tantalum and niobium powders of high performance and quality for capacitors, which technique provides a means of eliminating one or more, preferably all, of the problems encountered. in the traditional reduction of double salt and later processed. Another object of the invention is to provide a continuous production method. A further object of the invention is to provide improved metal shapes. A further object of the invention is to provide niobium / tantalum alloy powders with quality and morphology for use in capacitors. SUMMARY OF THE INVENTION The applicant entity has discovered that the problems of the state of the art can be eliminated when metal oxides such as Ta2's and Os and sub-oxides are reduced in massive amounts with magnesium in gaseous form, substantially or preferably in its entirety. The oxide source should be substantially or preferably solid in its entirety. The oxide is provided in the form of a porous solid with high access through its entire mass by the gaseous reducing agent. The metals that can be produced in an efficient manner individually or multiple (co-produced) by the present invention are from the group consisting of Ta, Nb and Ta / Nb alloy, either alone or with an additional inclusion of Ti, Mo, V, W, Hf and Zr incorporated or produced together. The metals can also be mixed or alloyed during or after, from production and / or shaped to useful compounds of such metals. As sources, the respective stable and unstable forms of oxides of such metals can be used. Metal alloys can be produced from alloyed oxide precursors, for example, those resulting from the coprecipitation of a suitable precursor for the oxide. Below are the steam pressures of alj? One of the reducing agents: The reduction temperature varies significantly depending on the reducing agent used. The temperature ranges for oxide reduction (Ta, Nb) are: With Mg (mgas) -800-1100 ° C, Al ^) -1100-1500 ° C, Li ^) -1000-1400 ° C, By variations of the temperature and other processing conditions, within the effective reduction range, different physical properties as well as different morphology of the metallic powder produced by reduction can be achieved. One embodiment of the invention includes a first step of reducing an oxide source of the metal or metal substantially selected to release 80-100% (by weight) of the metal contents in said sources as primary powder particles, subsequent leaching or other hydrometallurgical steps to separate the metal from the residual reducing agent oxide and from other by-products of the reduction reaction and the residual condensing reducing agent (optionally), followed by one or more oxidation steps under less concentrated conditions of reagents than in the first a coarse reduction stage (and with a better tolerance the molten state of the reducing agent) then proceeding to an additional separation as may be necessary. According to this first embodiment, the invention provides a one-stage reduction process for the production of metal powders as mentioned above, comprising the steps of: (a) providing a mixed oxide or oxides of the metal or metals, the own oxide in a form that can be traversed by the gas; (b) generating a gaseous reducing agent at a point outside the oxide mass and passing the gas through the mass at an elevated temperature, wherein (c) the reactants, the porosity of the oxide, the temperature and the time of The reduction reaction is selected to achieve a substantially complete reduction of the oxide or oxides to release the metal portion thereof, the residual oxide of the reducing agent formed in the reaction being easily separated, thereby forming a metal powder high surface area flowable in a process that essentially avoids the use of melt reducing agent in the production of metal or alloy powders Preferred reducing agents used in this method of reducing the first embodiment are Mg, Ca and / or its hydrides. In particular, Mg is preferred. The production of metals Nb and / or Ta, optionally allied with each other and / or with alloying elements, selected from the group consisting of Ti, Mo, W, Hf, V and Zr is preferable. A second embodiment of the invention provides a reduction method in two stages, comprising the steps of: (a) providing a mixed oxide or oxide of the metal or metals, the oxide being in a form that can be traversed by a gas; (b) passing a gas containing hydrogen, alone or with gaseous diluent, through the mass at an elevated temperature in a manner that the partial reduction of the oxide or oxides is achieved; wherein (c) the porosity of the oxide, the temperature and the time of the reduction reaction are selected to remove at least 20% of the oxygen contained in the oxide and thus produce a suboxide; (d) reducing the suboxide with a metal or reducing metals and / or hydrides of one or more reducing metals, thereby reducing the substantially complete ibrma oxide to release the metal portion thereof. Preferably, the metals and / or hydrides of reducing metals are brought into contact with the suboxide in gaseous form Preferred reducing metals in the second step of reduction of this second mode are Mg and / or Ca and / or their hydrides, particularly preferred Mg The reduction temperature is preferably chosen (for Mg) between 850 ° C and the normal boiling point (1150 ° C). The process according to the present invention (both embodiments) has been developed specifically to provide tantalum and niobium and tantalum and niobium alloy with quality for capacitors and materials or applications of Ta / Nb of equivalent purity and / or morphology needs. The enormous gap of the state of the art that exists in this respect is thus filled in part by the availability of quality niobium for capacitors that this invention allows, but also a segment of the technique relating to tantalum is improved with this invention. In all cases, tantalum and / or niobium can be improved by its alloy or combination with other materials during the production of tantalum / niobium by reduction or later. Among the requirements for such powders is the need to have an agglomerated, presintered structure of high specific surface of approximately spherical primary particles which, after pressing and sintering, gives rise to a coherent porous mass which provides an interconnected system of porous channels of a gradually narrower diameter to allow easy entry of the forming electrolyte for anodization and of manganese nitrate solution [Mn (NO3) 2] for the manganization. The reduction of oxides with gaseous reducing agents, at least during the initial reduction phase, allows an easy control of the temperature during the reduction to avoid excessive presintering. Furthermore, in comparison with the proposals of the state of the art using liquid reducing metals, the controlled reduction with gaseous reducing metals does not lead to the contamination of the reduced metal with the reducing metal by incorporation in the crystallographic network of the reduced metal. It has been found that this contamination occurs mainly during the initial reduction (in the case of Nb) of Nb? Os to NbO2. This in principle seems to be surprising because the niobium suboxide (NbO?) Only contains 20% less oxygen than niobium pentoxide (NbO ^ s) - This effect was attributed to the fact that the suboxide forms a crystal lattice considerably denser than pentoxide. The density of NbOzs is 4.47 g / cm3, while that of bÜ2 is 7.28 g / cm3, that is, the density is increased by 1.6 times by the separation of only 20% of the oxygen. Taking into account the different atomic weights of niobium and oxygen, a volume reduction of 42% is associated with the reduction of Nb? 2.5 to NbO2. Therefore, the applicant entity establishes (without thereby limiting the scope of the invention) that the effect according to the invention can be explained by the fact that during the reduction of pentoxide, the magnesium in contact with the oxide is capable of diffusing from a relatively easy mode to the interior of the crystalline network, where it has a high mobility, while the mobility of the magnesium in the crystal lattice of the suboxide is significantly reduced. Consequently, during the reduction of the suboxide, the magnesium remains substantially above the surface and is accessible to attack by the washing acids. The above applies even in the case of a controlled reduction with gaseous magnesium. Obviously, in this case, the reduction also occurs during the initial critical reduction to suboxide only at the surface of the oxide, and the magnesium oxide formed during the reduction does not enter the oxide or suboxide powder. The preferred temperature during the reduction with magnesium gaseous is comprised between 900 and 1100 ° C, very particularly between 900 and 1000 ° C. The temperature can be increased up to 1200 ° C once at least 20% of the oxygen has been separated, in order to improve the pre-sintering. The reduction of pentoxide with hydrogen produces a suboxide that is already sintered with the formation of agglomerates comprising stable sintered bridges, which have a favorable structure to be used as material for capacitors. Lower temperatures require longer reduction times. In addition, the degree of sintering of the metal powders to be produced can be adjusted in a predeterminable way by selecting the temperature and time of the reduction. The reactors are preferably coated with a sheet of molybdenum or by a ceramic material which is not reduced by H ?, in order to avoid contamination. On the other hand, the reduction time and the reduction temperature should be selected so as to separate at least 20% of the oxygen from the pentoxide. The greater degrees of reduction are not harmful. Nevertheless, in general it is not possible to reduce more than 60% of the oxygen within practicable time scales and tolerable temperatures. Once a degree of reduction of 20% or more is reached, the suboxide is present. According to this method of the process, the reduction product is preferably kept still (annealing) for some time, very preferably for about 60 to 360 minutes, at a temperature above 1000 ° C. It seems that this allows it to be can form and stabilize the new dense crystal structure. Since the rate of reduction decreases very considerably depending on the degree of reduction, it is sufficient to heat the sub-oxide to the reduction temperature under hydrogen, optionally with a slight decrease in temperature. Normally, the reduction and annealing times of 2 to 6 hours are sufficient within the temperature range of 1100 to 1500 ° C. In addition, the reduction with hydrogen has the advantage that impurities such as F, Cl and C, which are Critical to capacitor applications, they are reduced to less than 10 ppm, preferably less than 2 ppm. The suboxide is subsequently cooled to room temperature (<100 ° C) in the reduction apparatus, the suboxide powder is mixed with finely divided powders of the metals or reducing metal hydrides and the mixture is heated under an inert gas at the reduction temperature of the second stage. The reducing metals or metal hydrides are preferably used in a stoichiometric amount with respect to the residual oxygen of the acidic earth metal suboxide and, most preferably, they are used in an amount which is slightly in excess of the stoichiometric amount. A particularly preferred method is to use a stirred bed in the first stage and carry out the second stage, without intermediate cooling, in the same reactor by introducing the metals or reducing metal hydrides. If magnesium is used as the reducing metal, the magnesium is preferably introduced as gaseous magnesium, since in this way the forming reaction of the metal powder can be easily controlled. Once the reduction is completed, according to the reduction procedure of both a single stage and two stages, the metal is cooled and the inert gas is subsequently passed through the reactor with an increasing oxygen content in order to deactivate the metallic powder. The oxides of the reducing metals are separated in a manner known in the art by acid washing. The tantalum and niobium pentoxides are preferably used in the form of finely divided powders. The primary grain size of the pentoxide powders should correspond to approximately 2-3 times the desired primary grain size of the metal powders to be produced. The pentoxide particles preferably consist of free-flowing agglomerates with an average particle size of 20 to 1000 μm, including a specific preference of a narrower range of particle sizes of very preferably 50 to 300 μm. The reduction of niobium oxide with gaseous reducing agents can be carried out in a stirred or static bed, such as a rotary kiln, a fluidized bed, a grid oven or in a sliding plate furnace. If a static bed is used, the depth of the bed should not exceed 5-15 is, so that the reducing gas can penetrate the bed. It is possible to use larger bed depths in case a bed fill is used through which the gas flows from the bottom. For tantalum, the preferred chosen facilities are described in Example 2 and in the paragraph between the following Examples 2 and 3, with reference to Figures 1-4. The niobium powders that are particularly preferred according to the invention are obtained in the form of agglomerated primary particles with a primary particle size of 100 to 1000 nm, wherein the agglomerates have a particle size distribution, determined by Matersizer (ASTM). -B822), corresponding to DIO = 3 to 80 μm, preferably 3 to 7 μm, D50 = 20 to 250 μm, in particular 70 to 250 μm, more preferably 130 to 180 μm and D90 = 30 to 400, very particularly from 230 to 400 μm and very especially from 280 to 350 μm. The powders according to the invention exhibit outstanding flow properties and resistances in the pressed state, which determines their processability to produce capacitors. The agglomerates are characterized by stable sintered bridges, which ensure a favorable porosity after processing to form capacitors. Preferably, the niobium powder according to the invention contains oxygen in quantities of 2500 to 4500 ppm / m2 surface and, in addition to the low oxygen content, contains up to 10000 ppm of nitrogen and up to 150 ppm of carbon, and without taking into account the content of alloying metals has a maximum content of 350 ppm of other metals, wherein the metal content is that mainly of the reducing metal or the metal of the hydrogenation catalyst. The total content in other metals amounts to no more than 100 ppm. The total content in F. Cl, S is less than 10 ppm. Capacitors can be produced from the niobium powders which are preferred according to the invention, immediately after deactivation and sieving through a sieve with a mesh size of 400 μm. After sintering at a density in the pressed state of 3.5 g / cm3 at 1100 ° C and forming at 40V, these capacitors have a specific capacitance of 80000 to 250000 μFV / g (measured in phosphoric acid) and a density of specific spontaneous discharge current less than 2 nA / μFV. After sintering at 1150 ° C and forming at 40 V, the specific capacitance of the capacitor is from 40000 to 150000 μFV / g with a specific spontaneous discharge current density of less than 1 nA / μFV. After sintering at 1250 ° C and forming at 40 V, capacitors are obtained that have a specific capacitance (measured in phosphoric acid) of 30,000 to 80000 μFV / g and a specific spontaneous discharge current density of less than 1 nA / μFV . Preferred niobium powders according to the invention have a BET specific surface area of 1.5 to 30 m2 / g, preferably 2 to 10 m2 / g. It has been found, surprisingly, that capacitors can be produced from Nb / Ta alloy powders in such a way that the capacitors have a specific capacitance appreciably higher than that obtained from capacitors produced with pure Nb powders and of pure Ta or that anticipated for an alloy by simple linear interpolation. The capacitances (μFV) of capacitors with sintered powder anodes of Nb and sintered powder anodes of Ta having the same surface area are approximately equal. The reason for this is that the higher dielectric constant of the niobium oxide insulating layer (41 compared to 26 of the tantalum oxide) is compensated for by the greater thickness of the oxide layer per volt (anodizing voltage) formed during the anodization The thickness of the oxide layer per volt of Nb is approximately twice as thick as that formed on Ta (about 1.8 nm / V in the case of Ta and around 3.75 nm / Ven the case of Nb) . The present invention can provide a capacitance related to the surface (μFV / m2) of alloy powder capacitors that is up to about 1.5-1.7 higher than the expected value from the linear interpolation between powder capacitors of Nb and Ta dust capacitors. This seems to indicate that the thickness of the oxide layer per volt anodizing voltage of the alloy powders of the invention is closer to that of Ta, while the dielectric constant of the oxide layer is closer to that of Nb. The above surprisingly high capacitance of the alloy may be associated with a different structural form of oxide of the components of the alloy compared to the structure of oxides on the surface of pure powders of Nb. In fact, preliminary measurements have revealed that the growth of the oxide layer of an alloy of 15 at .-% Ta - 85 at .-% Nb is almost 2.75 nm / volt. The present invention also comprises, therefore, an alloy powder useful in the manufacture of electrolytic capacitors consisting mainly of niobium and containing up to 40 at .-% tantalum, based on the total content of Nb and Ta. The alloy powder according to the present invention is intended to mean that the minor component Ta will be present in an amount greater than the amount of ordinary impurity of niobium metal, for example, in an amount greater than 0.2% by weight (2000 ppm , copespondent to 2 at .-% for Ta). Preferably, the content in Ta is at least 2 at .-% tantalum, in particular at least 5 at .-% tantalum, more preferably at least 12 at .-% tantalum, based on the total content in Nb and Ta.

Preferably, the tantalum content of the alloy powders according to the invention is less than 34 at .-% tantalum. The effect of the increase in capacitance gradually increases to a ratio of atoms of Nb to atoms of Ta of about 3. An amount greater than 25 at .-% of Ta, based on the total content of Nb and Ta, only increases slightly in fact the effect. The alloy powders according to the invention preferably have surfaces BET multiplied by the density of the alloy between 8 and 250 (m2 / g) x (g / cm3), in particular between 15 and 80 (m / g) x (g / cm3). The density of the alloy material can be calculated from the respective atomic ratio of Nb and Ta multiplied by the densities of Nb and Ta respectively. The effect of the increase in capacitance of the alloy is not limited to powders having the structure of agglomerated spherical grains. Therefore, the alloy powders according to the invention can have a morphology in the form of agglomerated flakes preferably having BET surface values multiplied by the density comprised between 8 and 45 (m2 / g) x (g / cm3). Particularly preferred alloyed powders are agglomerates of substantially spherical primary particles having a BET x density of 15 to 60 (m / g) x (g / cm 3). The primary alloyed powders (grains) can have average diameters between 100 and 1500 nm, preferably between 100 and 300 nm. Preferably, the diameter deviation of the primary particles from the mean diameter is less than a factor of 2 in both directions. The agglomerated powders can have an average particle size, determined according to ASTM-B 822 (Mastersizer), as described for niobium powders above. Particularly preferred alloying powders have a density ratio Scott and alloy density comprised between 0.09 and 0.18 (g / cm 3) / (g / cm 3). Any production method known in the art can be used for the production of quality tantalum powder for capacitors, with the proviso that a precursor which is an alloy precursor containing niobium and tantalum is used approximately in the atomic ratio of Nb and Ta. desired in the metal powder alloy instead of a precursor that only contains tantalum. Useful alloy precursors can be obtained from the coprecipitation of (Nb, Ta) compounds in aqueous solutions containing water-soluble Nb and Ta compounds, for example, coprecipitation of (Nb, Ta) oxyhydrate in aqueous solution of heptafluor-complexes by the addition of ammonia and subsequent calcination of the oxyhydrate to the oxide. Flake powders can be obtained by electron beam fusion of a mixture of high purity tantalum and niobium oxides, reduction of the molten ingot, hydration of the ingot at elevated temperature, spraying of the brittle alloy, dehydration of the alloy powder and conformation of the same in flakes. The flakes are then agglomerated by heating at temperatures of 1100 to 1400 ° C in the presence of a reducing metal such as Mg, optionally with P and / or N doping. This process for the production of "ingot-derived" powder has been given US Pat. No. 4,740,238 for the production of flaked tantalum powder and WO 98/19811 for flake niobium powder. Particularly preferred Nb-Ta alloy powders having the morphology of agglomerated spherical grains are obtained from mixed oxides of (Nb, Ta) by reduction with a gaseous reducing agent as described herein. The metal powders produced are suitable for use in electronic capacitors and in other applications including, for example, the production of complex electro-optical, superconductive compounds and other metal and ceramic compounds, such as PMN and metal structures and high temperature forming oxides. . The invention comprises said powders, the production methods thereof, certain derivative products produced from such powders and methods for the production of said derivative products. The use in capacitors may be accompanied by other known capacitor production aids such as doping with agents to retard the sintering densification or to otherwise improve the capacitance, dispersion and disruptive discharge of the final product.

The invention allows several different paths in several of its various fields of application. In the first place, the well-known high-performance tantalum powder for the manufacture of quality solid electrolytes for computers / telecommunications, small-size capacitors (high capacitance per unit) can be produced now, with significant net cost, complexity and time savings. volume unit and stable behavior characteristics). Secondly, other reactive metals, especially Nb and alloys, for example Ta-Nb, Ta-Ti, Nb-Ti, can be introduced as substitutes for the Ta in capacitors for certain applications with a cost saving, or as substitutes for the high finished Al market with a much better performance, allowing in particular much smaller sizes for an equivalent capacitance and use of solid electrolytes. Commercial aluminum electrolytic capacitors use wet electrolyte systems. Other objects, features and advantages will become apparent from the following detailed description of preferred embodiments, considered in combination with the accompanying drawings, wherein: BRIEF DESCRIPTION OF THE DRAWINGS Figures 1-4 show schematic drawings of processing systems for the implementation of the present invention. Figures 5A-12C are electronic scanning micrographs (SEMs) of powders produced in accordance with the present invention, including some SEMs of the state of the art or comparative examples of metal powders produced in a manner different from the present invention. Figures 13 and 14 are flow diagrams illustrating various uses of the powder and derivatives. Figure 15 is a schematic representation of a final article according to its use as a capacitor (one of several forms of use as a capacitor). Figure 16 is a graphical plot of the capacitance and surface area of Ta-Nb alloy powders in relation to the composition of the alloy.

DETAILED DESCRIPTION OF PREFERRED MODALITIES Example 1 (Comparative) A mixture of Ta2? S and magnesium was charged in a tantalum tray and covered with aluminum foil. The magnesium stoichiometry was 109% of that required to completely reduce the tantalum oxide. The mixture was heated at 1000 ° for 6 hours in an argon atmosphere. The mixture was not stirred during the reduction process. After cooling, the products were passivated by the scheduled addition of oxygen. The result of the reduction procedure was a black spongy material that was difficult to disintegrate. The product was leached with dilute mineral acid to separate the magnesium oxide, after which it was dried and sieved. The yield in coarse material (+40 mesh) was as high as 25%. In the following Table 1.1 the content of impurities (as% or ppm) and the surface areas (SA, cm2 / g) of each of the fractions +40 and -40 are given. Both magnesium and oxygen contents were high. The large percentage of coarse material and poor product quality made it unsuitable for use in capacitor applications. Table 1.1 Example 2 With reference to Figure 1, a bed (3) of 200 g of tantalum pentoxide was placed in a porous tantalum plate 4 suspended above magnesium metal shavings (5) contained in a tantalum jar. The container was covered with a tantalum lid and placed in a sealed retort, passing argon (Ar) through the sealed volume via the nozzle (6). The can was heated and maintained at 1000 ° C for 6 hours in a gaseous atmosphere of argon / magnesium using a bed (5) of solid magnesium chips maintained in a region completely separated from the oxide bed.

After cooling to room temperature, the product mixture is passive by introducing argon / oxygen mixtures containing 50.8, 101.6, 203.2, 381 mm (Hg, partial pressure) of O2 (g), respectively, inside the oven. Each mixture was contacted with the powder for 30 minutes. The retention time for the last passivation with air was 60 minutes. The magnesium oxide was separated from the tantalum powder by leaching with dilute sulfuric acid and then rinsed with high purity water to remove acidic residues. The product was a powder that flowed freely. Figures 5A, 5B, 5C show electronic scanning microphotographs (SEMs) of product samples (designated as Ta GR-2D) at 15700, 30900 and 60300 magnifications, respectively, taken in an electron microscope operated at 15 kilovolts. Figures 5D and 5E provide a comparison consisting of SEMs at 70000 magnification (x) of tantalum powder produced by sodium reduction. The properties of the tantalum powder of Figures 5 A, 5B, 5C are given in the following Table 2.1. Table 2.1 The ratio of oxygen concentration to surface area was only in agreement with the surface oxygen, indicating that the tantalum oxide had been completely reduced. In Figures 2-4 alternative reactor shapes are shown as illustrated in Figure 1 (and set forth in Example 2). Figure 2 shows an instantaneous reduction reactor 20 with a vertical tube surrounded by a heater 24, a metal oxide power source 25 and a reducing agent vapor source 26 (eg, Mg) (mixed in argon), a argon outlet 26 'and a collector 28 for metal and oxide of the reducing agent. Valves VI, V2 are provided. The oxide particles fall through the tube and are instantly reduced. Figure 3 shows a rotary kiln 30 with an inclined rotating pipe 32, a heater 34, an oxide hopper 35; a source of gas 36 (reducing agent and diluent, eg, argon) and an outlet 36 ', and a manifold 38 for the metal and reducing agent oxide. Figure 4 shows a multi-solenoid furnace 40 with a retort 42 containing rotating trays 43 and grooved vanes 43 ', heater 44, oxide source 45, gas source and outlet 46, 46' and manifold 48. In addition, also employing other reactor plants such as the fluid bed furnace reactors already known per se or the Contop types, KIVCET. Example 3 Tantalum powder with a surface area of 57000 cm2 / g produced according to the procedure of Example 2 was deoxidized by mixing the powder with 2% w / w Mg and heating at 850 ° C for 2 hours in an argon atmosphere . The separation of the source of reducing agent and oxide is not necessary after this deoxidation step. The deoxidized powder was allowed to cool and was then passivated, leached and dried. Figure 7A shows an SEM (100000 x) of the deoxidized powder (finished) and in Figure 7B an SEM (70000 x) of reduced powders with finished sodium appears. The differences in morphology are evident. After doping with 100 ppm P by adding the appropriate amount of NHJH? POJI, the powder was pressed into pellets of 0.14 g in weight at a pressing density of 5.0 g / cc. In Figure 6 an SEM of the deoxidized powder is additionally provided. The pellets were sintered in vacuum at 1200 ° C for 20 minutes. The pellets were anodized at 30 volts in a 0.1% w / w solution of H3PO4 at 80 ° C. The formation current density was 100 mA / g and the retention time in the formation voltage was two hours . The average capacitance of the anodized pellets was 105000 μF (V) / g and the spontaneous discharge current, measured after 5 minutes of application of 2 IV, was 0.1 nA μF (V). Example 4 A powder with a surface area of 133000 cm2 / gm and an apparent density of 27.3 g / m3 prepared as described in Example 2 was treated as in Example 3. In Figure 7C an SEM (56600 x ) of the finished powder. Pellets produced from the deoxidized powder were anodized at 16V using the conditions of Example 3. The average capacitance of the anodized pellets was 160000 μF (V) / g. Example 5 900 grams of Ta2? 5 were reduced with magnesium gas at 900 ° C for two hours. The magnesium oxide was separated from the reduction product by leaching with dilute sulfuric acid. The resulting powder had a surface area of 70000 cm / g and was deoxidized at 850 ° C for 2 hours using 8% w / w magnesium. To the charge was added 1% w / w of NFLC1 to nitrate the tantalum. The deoxidized powder was treated in the manner described in Example 3. The level of doping with P was 200 ppm. The powder was deoxidized again using the same time and temperature profile with 2% w / w Mg and no C1-NH. Magnesium and residual magnesium oxide were separated by leaching with dilute mineral acid. The chemical properties of the powder are given in the following Table 5.1. The powder had a surface area of 9000 cm2 / g and excellent flowability. The pressed pellets were sintered at 1350 ° C for 20 minutes and anodized at 16V in 0.1% v / v of H3PO at 80 ° C. The capacitance of the anodized pellets was 27500 μF (V) / g and the discharge current spontaneous was 0.43 nA / μF (V). Table 5.1 Chemical Element (ppm) O N C Cr Fe Ni Na K Ca Si 2610 2640 95 8 18 < 5 1 < 10 < 2 41 Example 6 500 grams of TA2O5 were reduced at 1000 ° C for six hours with magnesium gas. The properties of the primary powder thus produced are given in the following Table 6.1. Table 6.1 The primary powder was deoxidized at 850 ° C for two hours. 4% w / w Mg and 1% w / w NHtCl were added. The MgO was leached with mineral acid. Next, the powder was doped at 200 ppm P by addition of the equivalent amount of NH H2PO4. The powder was deoxidized a second time at 850 ° C for two hours and then nitrided at 325 ° C by the addition of a gas mixture containing 80% argon and 20% nitrogen. In the following Table 6.2 some properties of the finished powder are offered. Table 6.2 Pellets were prepared from the powder at a pressing density of 5.0 g / cc. The sintered pellets were anodized at 80 ° C to 16 volts in 0.1% w / w solution of H3PO4. In the following Table 6.3 the capacitances and spontaneous discharge currents are offered as a function of the sintering temperature. Table 6.3 Example 7 (Comparative) Potassium heptafluorniobate (K2NbF7) was reduced with sodium using a stirred reactor molten salt method similar to those described by Hellier et al. and Hildreth et al., US Patent 5,442,978. The diluent salt was sodium chloride and the reactor was built in Inconel alloy. The niobium metal powder was separated from the salt matrix by leaching with dilute nitric acid (HNO3) and then rinsed with water. The following Table 7.1 shows selected physical and chemical properties. The very high concentrations of metallic elements, nickel, iron and chromium, make the powders unsuitable for use as quality material for capacitors. The contamination arose as a consequence of the inherently coxy nature of K2NbF7. This property makes the sodium reduction process unsuitable for the production of quality niobium powder pair capacitors. Table 7.1 SBD = Apparent density Scott (g / cm3), FAPD = Mean particle diameter Fisher (μ) Example 8 200 grams of niobium pentoxide were reduced in the manner described in Example 2. The resulting product was a black powder that flowed freely and that had a surface area of 200800 cm2 / g. The passivated product was leached with dilute nitric acid solution to remove residual magnesium oxide and magnesium and then with high purity water to remove residual acid. This material was mixed with 10% w / w Mg and deoxidized at 850 ° C for 2 hours. In the following Table 8.1 physical and chemical properties of the powder are offered. The powder was doped with 100 ppm P in the manner described in Example 3. Table 8.1 Physical and Chemical Properties of Niobium Powder Figures 8 A and 8B show SEMs (70000 x), grass, for niobium powders produced by reduction with liquid sodium (Example 7) and gaseous magnesium (Example 8). The grouping of small particles can be observed as barnacles being the larger ones much more pronounced in Figure 8B than in the Figure 8A. Figures 8C, 8D are SEMs (2000 x) of, respectively, niobium powder produced by reduction with sodium and reduction with gaseous magnesium. The niobium powder produced by reduction with liquid sodium has large (> 700 nm) bonded (300 nm +) protruding grains as well as listels that cause the product to have a compact shape and fine-grained material (of the order of 10 nm, but some of up to 75 nm) as barnacles, while the niobium powder produced by reduction with gaseous magnesium has a base grain size of around 400 nm and many smaller grains of around 20 nm on it, many of which smaller grains form agglomerates by themselves of a size of up to 100 nm Example 9 Pellets of 0.14 gram weight were prepared from the niobium powder produced in Example 8. The pellets were anodized in 0% solution., 1% v / v of H3PO4 at 80 ° C. The current density was 100 mA / g and the retention time in the formation voltage was 2 hours. In the following Table 9.1 the electrical results are given as a function of the density of pressing, formation voltage and sintering temperature of the pellets Table 9.1 Summary of electrical properties (capacitance, spontaneous discharge current) of the niobium powder at densities of Pressed 3.0, 3.5 (g / cc) Example 10 Niobium oxide was reduced with gaseous magnesium in the manner described in Example 8. The resulting powder was deoxidized twice. During the first deoxidation, 2% w / w of NF ^ Cl was added to the charge to nitrate the powder. The deoxidation conditions were 850 ° C for two hours with 7% w / w Mg. After leaching and drying, the powder was doped with 200 ppm P. The second deoxidation was carried out at 850 ° C for 2 hours using 2.5% w / w Mg. The finished product has a surface area of 22000 cm2 / g and a good flow capacity. The chemical properties are given in the following Table 10.1. Pellets were anodized at 16 volts in 0.1% w / w solution of H3PO at 80 ° C using a current density of 100 mA / g and a retention time of two hours. The electrical properties are given in the following Table 10.2. Table 10.1 Table 10.2 Example 11 a) The Nb? Os used had a particle size of 1.7 μm as determined by FSSS (Fisher Sub Sieve Sizer) and comprised the following impurity contents: Total (Na, K, Ca, Mg) 11 ppm Total (Al, Co, Cr, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Sb, Sn, Ti, V, W, Zn, Zr) 19 ppm Ta 8 ppm Si 7 ppm C < 1 ppm Cl < 3 ppm F 5 ppm S < 1 ppm The Nb2O5 was passed, inside a molybdenum canister, through a sliding plate furnace, under a slowly flowing hydrogen atmosphere, and kept in the hot zone of the furnace for 3.5 hours. The suboxide obtained had a composition corresponding to NbO ?. b) The product was placed in a fine mesh grid under which a crucible containing magnesium was located at 1.1 times the stoichiometric amount with respect to the oxygen content of the suboxide. The installation comprising the grid and the crucible was treated for 6 hours at 1000 ° C under an argon protective gas In the course of this procedure, the magnesium was evaporated and reacted with the underlying sub-oxide. The furnace was subsequently cooled (<100 ° C) and air was introduced gradually in order to passivate the surface of the metal powder. The product was washed with sulfuric acid until magnesium could no longer be detected in the filtrate and then washed until neutral with deionized water and dried. The analysis of the niobium powder provided the following contents in impurities: O 20000 ppm (3300 ppm / m2) Mg 200 ppm Fe 8 ppm Cr 13 ppm Ni 3 ppm Ta 110 ppm C 19 ppm N 4150 ppm The particle size distribution, determined by Mastersizer, corresponded to: DIO 4.27 μm D50 160.90 μm D90 318.33 μm The primary grain size was visually determined at a value of around 500 nm. The apparent density Scott was 0.95 g / cm3. The BET surface area was 6.08 m2 / g. The flow capacity, determined as the Flow Hall, it was 38 seconds. c) From the niobium powder, anodes with a diameter of 3 mm, a length of 5.66 mm, an anodic mass of 0.14 g and a density in the pressed state of 3.5 g / cm3 were produced by sintering on a niobium wire during the times and at the temperatures shown in Table 11.1. The strength in the pressed state of the anodes, determined according to Chatillon, was 6.37 kg. The anodes were formed at 80 ° C in an electrolyte containing 0.1% by volume of H3PO4 at a current density of 100/150 mA and at the voltage indicated in Table 11.1 and the characteristics of the capacitor were determined; see Table 11.1.

Table 11.1 Example 12 Example 11 was repeated with the difference that the temperature in the first reduction stage was 1300 ° C. The metal powder had the following properties: Mastersizer DIO 69.67 μm D50 183, 57 μm D90 294.5 μm Primary grain size (visual) 300-400 nm Specific surface BET 5 m2 / g Free Flow Capacity. The strength in the pressed state was extremely high: 13 kg at a density in the pressed state of 3.5 g / cm3, and 8 kg at a density in the pressed state of 3 g / cm3. After sintering at 1100 ° C for 20 minutes (density in the pressed state 3 g / m and after forming at 40 V, a capacitance of 222498 μFV / g and a spontaneous discharge current of 0.19 nA / μPV were measured. 13 This example shows the effect of the reduction temperature in the first stage on the properties of niobium powder: Three batches of niobium pentoxide were treated for 4 hours under hydrogen at 1100 ° C, 1300 ° C or 1500 ° C, under conditions that were otherwise the same. The batches were subsequently reduced to niobium metal with gaseous Mg (6 hours, 1000 ° C). The MgO that formed during the course of the reaction, together with excess Mg, were separated by washing with sulfuric acid. The following powder properties were obtained. Reduction Temperature 1100 ° C 1300 ° C 1500 ° C Sub-xid: BET m2 / g1} 1.03 049 0.16 Hall Flow) without flow 63.5 g cm 63.5 g cm without flow 48 sec 20 sec Niobium metal: BET m2 / g 9.93 7.8 5.23 FSSS μm3) 0.6 0.7 6.8 Hall Flow without flow 63.5 g cm 63.5 g cm without flow 85 sec 19 sec SD g / cc4) 1.02 1.00 1.02 Mg ppm 240 144 210 O ppm 40000 28100 16600 J) Specific surface BET 2) Flow capacity 3 Particle size determined by Fisher Sub Sieve Sizer 4) Bulk density Example 14 A precursor of (Nbx, Ta ^ Os is prepared by coprecipitation of oxyhydrate from (Nb, Ta) in mixed aqueous solution of heptafluor-niobium complexes and tantalum by the addition of ammonia with stirring and subsequent calcination of the oxyhydrate to the oxide. A batch of the mixed oxide powder having a nominal composition of Nb: Ta = 90:10 (weight ratio) was placed in a molybdenum canister and passed through a sliding plate furnace under a flowing hydrogen atmosphere. slowly and kept in the hot zone of the oven for 4 hours at 1300 ° C. After cooling to room temperature, the composition was determined from the weight loss, being approximately (Nbo, 944Tao, o54) O. The suboxide was placed on a fine mesh grid below which was placed a crucible containing magnesium at 1.2 times the stoichiometric amount with respect to the oxygen content of the suboxide. The installation comprising the grid and the crucible was treated for 6 hours at 1000 ° C under argon protective gas. The furnace was subsequently cooled to a temperature below 100 ° C and air was gradually introduced in order to passivate the surface of the metal powder. The product was washed with sulfuric acid until magnesium could no longer be detected in the filtrate and then washed until neutral with deionized water and dried. The analysis of the alloy powder gave a tantalum content of 9.73% by weight and the following contents in impurities (ppm): O: 20500, Mg: 24, C: 39, Fe: 11, Cr: 19, Ni: 2, Mo: 100. The primary grain size determined visually was approximately 450 nm. The BET surface area was 6.4 m2 / g, the Scott density was 0.92 g / cm3, the particle size (FSSS) was 0.87 μm. From the alloy powder, anodes with a diameter of 2.94 mm, a length of 3.2 mm and a density in the pressed state of 3.23 g / cm3 were produced by sintering on a niobium wire for 20 minutes at 1150. ° C. The density in the sintered state was 3.42 g / cm3. The electrodes were anodized in an electrolyte containing 0.25% H3PO up to a final voltage of 40 V. The characteristics of the capacitor were determined using a 10% aqueous solution of H ^ 0, »as follows: Capacitance: 209117 μFV / g , Spontaneous discharge current: 0.55 nA / μFg. Example 15 An alloy powder was prepared as in Example 4 using an oxide powder with the nominal composition of Nb: Ta = 75:25 (weight ratio). The analysis of the metallic alloy powder gave a tantalum content of 26.74% by weight and the following contents in impurities (ppm): O: 15000, Mg: 25, C: 43, Fe: 9, Cr: 20, Ni : 2, Mo: 7, N: 247. The primary grain size visually determined was around 400 nm. The BET surface area was 3.9 m2 / g, the Scott density was 1.09 g / cm3, the particle size (FSSS) was 2.95 μm and the Hall Flow was 27 s. From the alloy powder, anodes with a diameter of 2.99 mm, a length of 3.23 mm and a density in pressed state of 3, 05 g / cm3 by sintering on a niobium wire for 20 minutes at 1150 ° C. The density in the sintered state was 3.43 g / cm 3. The electrodes were anodized in an electrolyte containing 0.25% H. PO4 up to a final voltage of 40 V. The characteristics of the capacitor were determined using a 10% aqueous solution as follows: Capacitance: 290173 μFV / g, Spontaneous discharge current: 0.44 nA / μFg. EXAMPLE 16 Tantalum hydroxide was precipitated in an aqueous solution of tantalum complex fluorine by the addition of ammonia. The precipitated hydroxide was calcined at 1100 ° C for 4 hours to provide a precursor of Ta2O5 with the following physical data: mean particle diameter according to Fisher Sub Sieve Sizer (FSSS): 7.3 μm, bulk density (Scott): 1, 7 g / cm3, specific surface area (BET): 0.36 m2 / g, particle size distribution by laser diffraction in Master Sizer S, measured with ultrasound: DIO = 15.07 μm, D50 = 23.65 μm, D90 = 34.03 μm. The morphology of the agglomerated spheres are shown in Figures 9A-9C (SEM photographs). 300 g of the precursor pentoxide was placed on the screen and at the bottom of a retort, as shown in Figure 1, 124 g of Mg were placed (1.5 times the stoichiometric amount necessary to reduce the pentoxide to metal). The vacuum was made in the retort and then filled with argon and heated to 950 ° C for 12 hours. After cooling to a temperature below 100 ° C and subsequent passivation, the product was leached with an aqueous solution containing 23% by weight of sulfuric acid and 5.5% by weight of hydrogen peroxide, and then washed with water until neutrality. The product was dried overnight at 50 ° C and sieved <400μm. The tantalum powder showed the following analytical data: Average particle size (FSSS): 1.21 μm, Apparent density (Scott): 1.5 g / cc, BET surface area: 2.20 m2 / g, Good flow capacity MasterSizer DIO = 12.38 μm, D50 = 21.47 μm, D90 = 32.28 μm, Morphology: see Figures 10A-10C (SEM photographs) Chemical analysis: O: 7150 ppm N: 488 ppm H: 195 ppm C: 50 ppm Si: 30 ppm F: 2 ppm Mg: 6 ppm Na: 1 ppm Fe: 3 ppm Cr: < 2 ppm Ni: < 3 ppm The powder was impregnated with gentle stirring with a solution of NHUH? PO-j containing 1 mg P per ml, dried overnight at 50 ° C for doping with 150 ppm P and sieved < 400μm Capacitor anodes were prepared from 0.047 g of Ta powder each to a density in the pressed state of 5.0 g / cm3 by sintering to 1260 ° C with a retention time of 10 minutes. The formation current density was 150 mA / g with 0.1% by weight solution as a forming electrolyte at 85 ° C up to a final voltage of 16 V which was maintained for 100 minutes.

Test Results: Density in sintered state '. 4.6 g / cm3, Capacitance: 100577 μFV / g Spontaneous discharge current: 0.73 nA / μFV. Example 17 Ta2O5 of optical quality and high purity was first calcined at 1700 ° C for 4 hours and then for 16 hours at 900 ° C to provide more compact and coarser precursor particles. The physical properties of the pentoxide powder are: Average particle size (FSSS): 20 μm Apparent density (Scott): 2.4 g / cc Granulometry: 400-500 μm 8.7% 200-400 μm 63.6% 125 -200 μm 15.0% 80-125 μm 7.2% 45-80 μm 3.8% < 45 μm 1.7% Morphology is shown in Figures 11 A-1 IC (SEM photographs). The oxide powder was reduced to metal in the manner described in Example 16, but at 1000 ° C for 6 hours. Leaching and doping with P were performed as in Example 16. The tantalum powder showed the following analytical data: Average particle size (FSSS): 2.8 μm, Apparent density (Scott): 1.7 g / cc , BET Surface: 2, 11 m2 / g, Flow capacity through a funnel not vibrated with an angle of 60 ° and an opening of 2.54 mm: 25 g in 35 seconds, MasterSizer DIO = 103.29 μm, D50 = 294.63 μm, D90 = 508.5 μm, Morphology: see Figures 12A-12C (SEM photographs) Chemical analysis: O: 7350 ppm N: 207 ppm H: 174 ppm C: 62 ppm Mg: 9 ppm Fe: 5 ppm Mg: 6 ppm Cr: < 2 ppm Ni: < 3 ppm P: 150 ppm Capacitor anodes were prepared and anodized as in Example 16.

Results of the test: Density in sintered state: 4.8 g / cm3, Capacitance: 89 201 μFV / g Spontaneous discharge current: 0.49 nA / μFV. A second series of capacitors was prepared in the same way but with an increase in sintering temperature to 1310 ° C. Test Results: Density in sintered state: 5.1 g / cm3, Capacitance: 84 201 μFV / g Discharge current spontaneous: 0.68 nA / μFV. Example 18 Several samples, each of approximately 25 g, of WO3, ZrO2 and V2O3 were individually reduced with magnesium gas at 950 ° C for 6 hours. The reduction products were leached with dilute sulfuric acid to remove residual magnesium oxide. The product was a black metallic powder in each case. The tungsten and zirconium powders had oxygen content of 5.9 and 9.6% p / p, respectively, indicating that the metal oxides were reduced to the metallic state. The present process seems to represent the only proven way to produce chemically reduced and high quality niobium powder. The reduction of the metal oxide with a gaseous reactive agent, such as magnesium, as here shown, is thus particularly suitable for the production of powders that can be used as substrates for metal-oxide metal capacitors. Although the reduction process was carried out with the metal oxide in a bed in contact with a source of gaseous magnesium, the reduction can take place in a fluidized bed, in a rotary kiln, in a reactor of instantaneous reduction, in systems of several sills or similar systems as long as the magnesium or other reducing agent is in a gaseous state. The procedure will also work with other metal oxides or mixtures of metal oxides for which the reduction reaction with gaseous magnesium or other reducing agent has a negative change in Gibbs free energy. There are several advantages in the gas reduction processes described here. The treatment of the reduction products is much less complicated and expensive than the post-reduction elaboration of tantalum powder produced by reactions in liquid phase, such as the reduction with sodium of K2TaF in a molten salt system. No residues of fluorides or chlorides are produced in the present process. This eliminates a potentially serious distribution problem or the need to institute a costly waste recovery system. The reduction of metal oxides with gaseous reducing agents gives rise to powders with much larger surface areas than the powders produced by the reduction process with molten salt / sodium. The new procedure easily provides powders with a very high surface area compared to the traditional method; The potential for the production of quality powders for very high performance capacitors is great with magnesium or another gaseous reducing agent. The present invention further demonstrates for the first time the superiority of Ta-Nb alloy powders for use in the production of capacitors. Figure 16 shows the ratio of the maximum obtainable capacity (μFV / g) and BET surface of the powder (m2 / g) with respect to the alloyed composition. A and C represent pure powders of Ta, Nb, respectively, as measured in the present Example 16. B represents the highest known values of pure powder Ta capacitors as described in WO Examples 2, 5 and 7. 98/37249. Line 1 represents the values that can be expected for alloy powder capacitors from the linear interpolation between pure dust capacitors of Ta and Nb. E represents u? fictitious Nb powder capacitor where the insulating oxide layer has the same thickness per volt as in Ta dust capacitors, but where the dielectric constant of niobium oxide differs. Line 11 represents the linear interpolation between B and E. D represents a measured value of an alloy powder capacitor of 25% by weight of Ta / 75% by weight of Nb, as presented in Example 15 above. Curve III represents the estimated dependence of the capacitance on the alloy composition of alloy powder capacitors according to the present invention. Figure 13 is a block diagram of steps for achieving an electrolytic capacitor application according to the invention. The steps comprise: reduction of the metal oxide with gaseous reducing agent; separation of the reducing agent oxide from a resulting metal mass; disintegration to the powder form and / or to a primary powder particle size; classification; optionally, presinterization to establish agglomerated secondary particles (to establish the agglomerates the controlled mechanical methods and the control of the original reduction or separation stages are also effective); deoxidation to reduce the concentration of oxygen; compaction of the primary or secondary particles to a porous coherent mass by cold isostatic pressing with or without the use of compaction binders or lubricants; sintering to a porous anode shape (which may have an elongated cylindrical shape, a plate shape or a short length shape such as a chip); lead coupling at the anode by embedding at the anode before sintering or welding to the sintered anode compact; formation of metal surfaces exposed within the porous anode by electrolytic oxidation to establish a dielectric oxide layer; impregnation of the solid electrode impregnating precursors in the porous mass and pyrolyzing in one or more stages or by other impregnation methods; cathode termination; and packaging. Other various cleaning and testing stages are not shown. The final product is illustrated (in cylindrical form) in Figure 15 as a Ta or Nb (or Ta-Nb) alloy capacitor 101 in partial section as a porous anode of Ta or ^ Jb (or of Ta alloy). -Nb) 102, impregnated with a solid electrolyte, surrounded by a counter-electrode (cathode) 104 and packaging coating 105 with a dense lead wire 106 of Ta or Nb (which generally coincides with the composition of the powder) which is joins the anode by means of a solder joint 107. As indicated above, by means of the present invention it is possible to have access to other forms of capacitors known per se (different form factors, different metals, different electrolyte systems, different junctions). of anodic lead, etc.). Figure 14 is a block diagram that jointly illustrates the production of some of the other products and uses derived from the invention, including the use of powders as enamelling baths, in molding and in loose packed form for subsequent reaction and / or consolidation by means of sintering, hot isostatic pressing (H.I.P.) or in sintering methods / H.I.P. Powders per se and / or in a consolidated state can be used in the production of composite materials, in combustion, in chemical synthesis (as reactants) or in catalysis, in alloy operations (for example, femometalurgy) and in coatings. The consolidated powders can be used to produce rolling products and processed products. In some cases, the end-use products prepared using the powders produced by gas reduction resemble the products of the prior art prepared with powders of the state of the art (for example, reduced) and, in other cases, the products they will be new and will present unique physical, chemical or electrical characteristics resulting from the unique forms described herein of powders produced by reduction by gaseous reducing agents. The processes that go from the production of the dust to the final product or final use are also modified in the measure in which the powders and their production methods produce profiles of impurity and modified morphology. The lamination products and produced products produced may involve remelting, molding, annealing, dispersing, consolidating and other well-known operations per se. The final products produced through the final reaction of the metal powders can produce high purity products such as oxides, nitrides, silicides and other derivatives such as complex ceramic products used in ferroelectrics and in optical applications, for example PMV compounds of perovskite structure. It will now be apparent to those skilled in the art that other modifications, improvements, details and uses are possible in accordance with the letter and spirit of the foregoing description and within the scope of this invention, which is limited only by the following claims, interpreted in accordance with patent law, and including the doctrine of equivalents. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (4)

1. REVINDICATIONS Having described the invention as above, the content of the following claims is claimed as property: 1.- Procedure for the production of metal powders selected from the group consisting of Ta and Nb, and all their alloys, alone or with one or more selected metals of the group consisting of Ti, Mo, W, Hf, V and Zr added to them or produced together with them, characterized in that I understood; the steps of: (a) providing an oxide or mixed oxides of the metal or metals, the oxide itself being in a form that can be traversed by the gas; (b) generating a gaseous reducing agent at a point outside the oxide mass and passing the gas through the mass at an elevated temperature; wherein (c) the reactants, the oxide porosity, the temperature and the time of the reduction reaction are selected to achieve a substantially complete reduction of the oxide or oxides to release the metal portion thereof, the residual oxide being easily separated of the reducing agent formed in the reaction; whereby a high surface area flowable metal powder is formed in a process that essentially avoids the use of a melt reducing agent in the production of metal or alloy powders.
2. 2. Process for the production of metal powders selected from the group consisting of Ta and / or Nb and all their alloys, alone or with one or more metals selected from the group consisting of Ti, Mo, W, Hr, V and Zr, characterized because it comprises the steps of (a) providing a mixed oxide or oxide of the metal or metals, the oxide being in a form that can be traversed by a gas; (b) passing a gas containing hydrogen, alone or with gaseous diluent, through the mass at an elevated temperature in a manner that the partial reduction of the oxide or oxides is achieved; wherein (c) the oxide porosity, temperature and time of the reduction reaction are selected to remove at least 20% of the oxygen contained in the oxide and thereby produce a suboxide, (d) reduce the suboxide with a metal or reducing metals and / or hydrides of one or more reducing metals, thereby substantially reducing the oxide to release the metal portion thereof.
3. 3. Process according to claim 1 or 2, characterized in that the reducing agent is selected from the group consisting of Mg, Ca, Al, Li, Ba, Sr and the hydrides thereof. 4. Method according to any of claims 1 to 3, characterized in that the powder of metal or alloy is processed to a secondary agglomerated form. 5. Process according to any of claims 1 to 4, characterized in that the metal powder is further deoxidized by a new exposure to a gaseous reducing agent. 6. Method according to claim 2, characterized in that the reduction of the first stage is carried out at least until the volume of solid matter is reduced by 35-50%. Method according to claim 2 or 6, characterized in that the reduction of the first stage is carried out up to MeOx where Me represents Ta and / or Nb and x assumes a value from 1 to 2. 8. Process according to any of the claims 2, 6 or 7, characterized in that the reaction product of the first stage is maintained at the reduction temperature for approximately 60-360 more minutes. 9 - Process according to any of claims 2 or 6 to 8, characterized in that, in the second stage, Mg, Ca and / or hydrides thereof are used as reducing agents. 10. Process according to any of claims 1 to 9, characterized in that the metal consists essentially of tantalum and the oxide is tantalum pentoxide. 11. Process according to any of claims 1 to 10, characterized in that the metal comprises niobium and the oxide comprises niobium pentoxide or a niobium suboxide. 12 - Method according to claim 11, characterized in that the oxide contains tantalum in an amount of up to 50 at .-% based on the total content of metals. 13. Method according to any of claims 1 to 12, characterized in that the shape of the oxide mass that can be traversed by gas provides a void volume of at least 90%. 14.- Method according to any of claims 1 to 13, wherein the oxide is provided in particulate form of agglomerated primary oxide with diameters between 100 to 1000 nm and an average agglomerate size of 10 to 1000 microns (Mastersizer D50 ). 15. Process according to any of claims 1 to 14, characterized in that the reducing agent is magnesium. 16. Method according to any of claims 1 to 15, characterized in that the high temperature during the passage of the gaseous reducing agent through the oxide mass is below 0.5 TM, where TM represents the melting point of the metallic powder. 17. Method according to claim 16, characterized in that the temperature is below 0.
4. 4 TM. 18. Method according to any of claims 1 to 17, characterized in that the primary metal powder is subjected to an additional deoxidation treatment to produce a finished powder. 19. Process according to claim 18, characterized in that one or more finishing deoxidation steps are provided as an extension of the reduction reaction. 20. Method according to claim 19, characterized in that the finishing deoxidation consists of a separate treatment. 21. Process according to any of claims 1 to 20, characterized in that the metallic powder is processed to a secondary agglomerated form. 22. - Process according to claim 21, characterized in that a deoxidation step is applied to the agglomerated secondary form of the powder. 23. Method according to any of claims 1 to 22, characterized in that the metal powder is additionally shaped to a coherent porous mass. 24.- Niobium powder in the form of agglomerated primary particles with a particle size of 100 to 1000 nm, characterized because the agglomerates have a particle size corresponding to DIO = 3 to 80 μm, D50 = 20 to 250 μm and D90 30 to 400 μm, determined by Mastersizer. 25. Niobium powder according to claim 24, characterized in that it contains up to 40 at .-% Ta only or with one or more of at least one metal selected from the group consisting of Ti, Mo, W, Hf, V and Zr, based on the total content in metal. 26 -. 26 - Niobium powder according to claim 25, characterized in that it contains at least 2 at .-% of the other or other metals. 27. Niobium powder according to claim 25, characterized in that it contains at least 3.5 at .-% of the other or other metals. 28. Niobium powder according to claim 25, characterized in that it contains at least 5 at .-% of the other or other metals. 29 - Niobium powder according to claim 25, characterized in that it contains at least 10 at .-% of the other or other metals. 30. Niobium powder according to claims 25 to 29, characterized in that it contains up to 34 at .-% of the other or other metals. 31 - Niobium powder according to any of claims 25 to 30, characterized in that it contains tantalum like the other metal. 32. Dust according to any of claims 24 to 31, characterized in that it has the form of agglomerated primary substantially spherical particles with a diameter of 100 to 1500 nm. 33 - Dust according to any of claims 24 to 32, characterized in that the product of the BET surface and the alloy density is from 8 to 250 (m2 / g) x (g / cm3). 34.- Dust according to any of claims 24 to 33, characterized in that the ratio of the Scott density to the alloy density is 0.09 to 0.14 (g / cm3 / (g / cm3). according to claim 32, characterized in that it has an agglomerated particle size of 20 to 300 μ determined as the D50 value according to Mastersizer 36.- Niobium powder according to any of claims 24 to 35, characterized in that it contains oxygen in quantities of 2500- 4500 ppm / m of BET surface, up to 10000 ppm of nitrogen, up to 150 ppm of carbon and less than a total of 500 ppm of metallic impurities 37.- Niobium powder according to any of claims 24 to 35, characterized in that, after of the sintered at 1100 ° C and 40 V formation, exhibits a capacitor-specific capacitance of 8000 to 250000 μFV / g and a specific spontaneous discharge current density of less than 2nA / μFV 38 - Niobium powder according to any of claims 2 4 to 35, characterized in that, after sintering at 1250 ° C and forming at 40 V, it exhibits a capacitor-specific capacitance of 30000 to 80000 μFV / g and a specific spontaneous discharge current density of 1 nA / μFV. 39. A capacitor anode characterized in that it is obtained by sintering, of a powder according to any of claims 24 to 38 and subsequent anodization. 40. A capacitor, characterized in that it contains an anode according to claim 39. 41. A capacitor according to claim 40 as a solid electrolyte capacitor. 42.- An alloy powder useful in the production of electrolytic capacitors, characterized in that it consists essentially of niobium and contains up to 40% t-tantalum based on the total content of Nb and Ta. 43. Powder according to claim 42, characterized in that it contains at least 2 at-% of tantalum. 44.- Dust according to claim 43, characterized in that it contains at least 3.5 at -% of tantalum. 45.- Powder according to claim 43, characterized in that it contains at least 5 at-% of tantalum. 46.- Dust according to claim 43, characterized in that it contains at least 10 at .-% of tantalum. 47. - Dust according to claim 42, characterized in that it contains from 12 to 34 at .-% of tantalum. 48. Powder according to any of claims 42 to 47, characterized in that it has the form of agglomerated flakes having a product of the surface area BET by the alloy density of 8 to 45 (m2 / g) x (g / cm3). 49. Powder according to any of claims 42 to 47, characterized in that it has the form of agglomerated primary substantially spherical particles having a diameter of 100 to 1500 nm and having a product of the BET surface at a density of 15 to 60 ( m / g) x (g / cm). 50 - Powder according to claim 7 or 8, characterized in that it has a value D50 of the average particle size, according to Mastersizer, from 20 to 250 μm. 51. Powder according to any of claims 42 to 50, characterized in that it has a density Scott of 0.09 to 0.18 (g / cm3) / (g / cm3). 52. A capacitor anode, characterized in that it is obtained by sintering, of a powder according to any of claims 42 to 51 and subsequent anodization. 53. A capacitor, characterized in that it comprises an anode according to claim 52. 54 -. 54 - Process for the production of an alloy powder according to claim 48, characterized in that it comprises the steps of: (a) Hydruration of a molten alloy ingot with electron beam containing Nb and up to 40 at .-% Ta based in the total content of Nb and Ta; (b) Spraying said hydride alloy ingot; (c) Dehydration of the pulverized alloy obtained in step (b); (d) Shaping said pulverized alloy into flakes; (e) Agglomeration of said flakes at a temperature of 800 to 1150 ° C in the presence of an alkaline metal as a reducing agent; and (f) Leaching and washing the agglomerated alloy flakes to remove any residual product from the reducing agent. 55.- Method according to claim 54, characterized in that during the agglomeration stage, the alloy powder is doped with phosphorus and / or nitrogen. 56 -. 56 - A powder of niobium-tantalum alloy capable of achieving, after sintering and forming, a ratio of the specific capacity to the BET surface of the powder greater than 65000 (μFV / g) / (m2 / g) with greater preference of 7000 (μFV / g) / (m2 / g).