DE10392574B4 - Manufacturing of reaction-bonded silicon carbide by contacting silicon supplying body to preform, and heat processing contacted body at temperature higher than silicon melting temperature - Google Patents

Abstract

Manufacturing of reaction-bonded silicon carbide comprises preparing silicon supplying body, preparing silicon carbide/carbon preform, contacting the silicon supplying body to one surface of the preform in a reaction bonding furnace, and heat processing the contacted body with preform at temperature higher than melting temperature of silicon under vacuum or inert atmosphere to infiltrate fused silicon in supplying body into the preform. Manufacturing of reaction-bonded silicon carbide comprises preparing silicon supplying body (10), preparing silicon carbide/carbon preform (20), contacting the silicon supplying body to one surface of the preform in a reaction bonding furnace, and heat processing contacted supply body at temperature higher than melting temperature of the silicon under vacuum or inert atmosphere to infiltrate fused silicon in the silicon supplying body into the preform. The silicon supplying body includes silicon powder and bonding agent. The bonding agent is phenol resin, furfuryl alcohol resin, or epoxy resin.

Description

Technical area

The The present invention relates to a process for the preparation of reaction bonded silicon carbide, and more particularly a method for uniform feeding of molten silicon on a fully reaction bonded silicon carbide.

State of the art

Reaction bound or reaction-sintered silicon carbide is made by infiltration from molten silicon to a silicon carbide and carbon containing preform produced. The infiltrated molten silicon is reacted with carbon particles present in the as the silicon carbide to be produced preform are present, and the produced silicon carbide functions as a binder to connect the silicon carbide particles in the preform together and pores between the silicon carbide particles with the silicon fill.

One Method of feeding from molten silicon to a silicon carbide and carbon preform for producing a reaction bonded silicon carbide in the immersion of the preform in a crucible, in which filled in the molten silicon is, and in the feeding of the molten silicon to the entire. Preform over a Capillary tube of the preform. However, in this case, a heating device for melting silicon, a.

melting pot for the Receiving molten silicon, and a device for supplying molten Silicon from a crucible to a specimen required which is why the manufacturing process is complex is and increases the cost become.

in the Trap of a simply shaped preform may be molten silicon in a test piece by stacking silicon powder particles on an upper part of the sample and heating the powder particles over infiltrating the melting point of silicon beyond. In this Process, silicon powder particles are melted, so they itself due to surface tension store together. Furthermore, the molten silicon, if it is too a mass is massed, not the entire surface, which fed to the silicon should, cover, and in some cases collapsing can fall down due to gravity.

at the aforementioned conventional Method of feeding of silicon goes when molten silicon gathers together, the silicon is far from the desired one Contact point away, and therefore the feed distance of the molten Silicon magnified and the infiltration area reduced. Furthermore, molten silicon has a very large surface tension and low viscosity. It thus has a tendency to connect so that it reduces its surface area. The bigger that Measure of cohesion becomes, the more affected gravity this. The cohesion of molten silicon reduces the area in which the silicon is infiltrated, as well as the infiltration of silicon is limited to a certain area.

The US Pat. No. 4,154,787 describes a process for producing a reaction bonded silicon carbide body in which a composite of two compacts is prepared, wherein one of the compacts is a mixture of about 75 to 95 parts by weight of silicon carbide, about 5 to 25 parts by weight of finely divided carbon and about 5 to 15 parts by weight of a and wherein the other compact contains about 90 to 97 parts by weight of finely divided silicon, about 3 to 10 parts by weight of finely divided carbon and about 3 to 10 parts by weight of an organic binder. This composite is heated to a temperature such that the organic binder in the compacts is decomposed. Further, the composite is heated in vacuum or in an inert atmosphere to the melting temperature of the silicon, such that a portion of the silicon reacts with the coal in the second compact to form a brittle and porous silicon carbide matrix and the remainder of the silicon is the first Pressing penetrates, wherein at least a portion of the silicon undergoes a reaction with the coal in the first compact, such that the first compact is converted into a reaction-bonded silicon carbide body. Subsequently, the brittle and porous silicon carbide matrix is removed from the reaction bonded silicon carbide body. The silicon carbide preferably has a particle size of 200 to 1200 grit, the carbon preferably has a particle size in the submicron range, and the silicon preferably has a particle size of 100 to 325 mesh.

The German patent application DE 35 40 254 A1 discloses a method for producing silicon carbide bodies by injection molding, debinding of the binder and reaction sintering, characterized by using a mixture of fine SiC powder, fine Si powder, a binder of a duromer plastic and a sintering aid such as boron or aluminum as Injection or molding compound.

Main technical point of the present invention

The Object of the present invention is to provide a process for the economical production of a reaction-bound Silicon carbide and in reducing the processing time under Maintaining a uniform rate of infiltration over the entire surface, by having a uniform spatial Distribution of molten silicon is maintained.

Further Another object of the present invention is to maintain a maximum infiltration area, when the reaction bonded silicon carbide by uniform melting of silicon and preventing cohesion of silicon due of surface tension will be produced.

Detailed description of the invention

To achieve the objects of the present invention, there is provided a process for producing reaction bonded silicon carbide comprising:
Providing a silicon supply body with silicon powder particles and a thermosetting resin as a binder; Providing a silicon carbide and carbon preform or a silicon carbide preform; contacting the silicon feed body with a surface of the preform in an oven; and heating to the melting temperature of the silicon under vacuum or inert atmosphere to infiltrate the molten silicon in the silicon feed body into the preform. Here, the ratio between the dimensions of the particles of the silicon powder of the silicon supply body and the particles of the silicon carbide powder of the preform is 5: 1 to 25: 1, and the size of the silicon powder particles is 70 to 2000 μm.

Brief description of the drawings

It demonstrate:

1A to 1D a method for producing reaction bonded silicon carbide according to the present invention;

1A a condition; wherein a silicon feed coupon and a silicon carbide and carbon preform are brought into contact;

1B a view in which carbonaceous particles are produced in the silicon feed specimen by heat treatment;

1C a view in which a silicon carbide frame structure is generated in the silicon supply specimen by the heat treatment;

1D a final reaction-bonded silicon carbide to which the molten silicon is supplied;

2A a fine structure of the silicon carbide and carbon preform; and

2 B represents a fine structure of silicon carbide sintering after a reaction bond.

embodiment of the preferred embodiments

According to the present Invention can be a cohesion of the molten silicon and prevents the molten silicon be supplied evenly.

Of the Silicon feed body is made by adding a slurry by mixing 70 to 99 weight percent Silicon powder with a part size of 70 up to 2000 μm and 1 to 10 weight percent thermosetting resin as a binder. in a solvent is produced, granules or a granule is achieved by drying the slurry, and the Granules are formed.

The thermosetting resin, which one higher Residual carbon, such as. As phenolic resin has, is used as a binder used. The binder may further be 1 to 10% by weight thermoplastic resin, such as. As PVB (polyvinyl butyral) included. additionally can, if 1 to 10 weight percent plasticizer are added, the feed sample itself be easily converted at low temperature.

furfuryl and epoxy resin can as a thermosetting one Resin can be used in addition to phenolic resin. Polyvinyl alcohol (PVA), Polyvinyl acetate (PVAc), polymethyl methacrylate (PMMA), etc. can be used as thermoplastic resins are used in addition to the PVB, and dibutyl phthalate (DBP), benzyl-butyl phthalate (BBP), polyethylene glycol (PEG), dimethyl phthalate (DMP), di-octyl phthalate (DOP), glycerine, etc. be used as a plasticizer.

The Binder becomes with the silicon in the body in the initial state of Reaction bonding to form a silicon carbide net or silicon carbide frame structure reacted, causing an agglomeration of the molten Silicon can be prevented.

Of the Silicon feed body is in the range of room temperature to 120 ° C, depending on how controlled the strength of the feeder body is generated. It is desirable that the Process for forming under heat within the range of 60 to 120 ° C. If the percentage is increased in silicon in the silicon supply body, Hardly any contraction occurs due to the heating due to the network of the silicon powder, and therefore molten silicon is formed the entire area of the silicon feed body in contact with the silicon carbide preform.

It For example, a silicon feed body may be used which is complete is combined with a silicon carbide preform by a common Glue is used.

In Contact with a compact body made of silicon carbide (preform) is a silicon supply body within a higher one Temperature as the melting point of silicon, for example 1410 up to 1550 ° C, heated and the molten silicon infiltrates into the silicon carbide preform, to produce the reaction bonded silicon carbide.

Siliziumpulverteilchen of the silicon feed body greater than the silicon carbide powder particles of the reaction bonded preform. In the present invention, the difference between the Particles of the silicon powder and the silicon carbide powder so far as possible enlarged to the infiltration rate of the molten silicon accelerate, thereby greatly reducing the reaction time. The relationship the dimensions between the silicon powder and the silicon carbide powder lies between 5: 1 to 25: 1.

Here in Below are the manufacturing process and the properties of the present invention in more detail with reference to FIGS attached Figures described.

Granules are made by mixing the silicon powder with the thermosetting resin 12 with a higher residual carbon rate, such. As with phenolic resin, prepared, and the Siliziumzuführungskörper 10 is made by plasticizing the granules. The silicon supply body 10 comes with a location of silicon carbide and carbon preform 20 brought into contact, which, as in 1A shown to be reaction bound. In 1A the upper part represents the silicon supply body 10 , and the lower part of the silicon carbide and carbon preform 20 dar. The silicon supply body 10 has the silicon particles 11 and the thermosetting resin 12 on. The preform is made of the silicon carbide particles 21 and the carbon particles 22 produced.

Subsequently, the silicon supply body 10 and heat-treating the silicon carbide and carbon preform in a sintering furnace under vacuum or in an inert atmosphere so that at least one of their surfaces is in contact. The thermosetting resin 12 is decomposed in the temperature range of 400 to 500 ° C during the heat treatment, so that carbon 23 in the silicon supply body 10 as shown in 1B remains. As the heat treatment temperature continues to increase, the residual carbon is burned, undergoes local compression, and reacts with the molten silicon particles as the temperature reaches the melting point of silicon to form the silicon carbide frame structure (see FIG 13 in 1C ) train.

The above frame structure 13 completely bonds the molten silicon in the silicon supply body 10 and prevents the molten silicon from aggregating or to one side runs away, so that the molten silicon evenly on the shear surface 15 is distributed where the preform 20 and the silicon supply body 10 stay in contact. As a result, the molten silicon becomes in the silicon supply body 10 evenly into the silicon carbide preform 20 infiltrated. The silicon supply body 10 finally leaves the silicon carbide frame structure 13 as shown in 1C , In the silicon carbide preform 20 this will be from the silicon feed body 10 Infiltrated molten silicon with the carbon particles 22 reacted to new silicon carbide particles 25 and the infiltrated molten silicon also fills the air gaps 24 between the existing silicon carbide particles 21 out.

On the other hand, the silicon carbide frame structure has 13 a low strength, and therefore can be easily separated from the reaction-bound body. The reaction-bound silicon carbide 20 can by simple processing as shown in 1D to be obtained.

As described above, when the reaction bonded silicon carbide 20 using the silicon feed body 10 is prepared, the reaction between the from the bonding agent in the Siliziumzuführungskörper 10 obtained carbon 23 and silicon particles 11 an exothermic reaction, and thereby the uniform melting of the silicon can be induced and the cohesion of the silicon due to the surface tension can be prevented. Therefore, the area through which the molten silicon can be preformed into the silicon carbide 20 is infiltrated, held at maximum.

Further becomes a uniform spatial Distribution of molten silicon maintained to a uniform infiltration speed over the entire infiltration surface and therefore the total infiltration time, i. H. the retention time can be minimized. Further, an additional device for the feed of the molten silicon is not required. Thus, the costs for the processing plant and the kiln are reduced.

embodiments

A silicon carbide and carbon preform 20 is by mixing silicon carbide 21 with a size of 1 to 10 microns and carbon black of 10 to 40 microns prepared so that it contains carbon black to 30 percent by volume, and phenol resin is added as a binder.

The molten silicon supply body 10 is made using silicon powder 11 from 70 to 2000 microns and the phenolic resin binder.

First, 1 to 15% by weight of phenolic resin and up to 15% by weight of DBP are dissolved in alcohol based on the weight of the material powder, which can dissolve phenolic resin. The silicon powder 11 is added to the above solution to prepare the slurry. After the addition of the silicon powder 11 these are uniformly mixed by means of a strong stirring, milling or ultrasonic processing and then the context is separated. When the slurry is dropped into distilled water heated to 50 to 80 ° C, rapid solvent decomposition occurs and the drenched slurry changes to a hard state. The residual solvent in the granules is minimized by repeated stirring, and then the dripped granules are separated from the solution and dried to obtain the required granules.

As another method, the desired amount of silicon powder 11 and phenolic resin are mixed in a dry manner, and then dry-milled in a ball mill for 1 to 8 hours. Then, the granules are recovered in a relatively uniformly mixed state. However, the ideal mixing state of the granules can be achieved by the wet mixing method.

The produced granules are compressed at 5 to 400 MPa in the temperature range from room temperature to 120 ° C, around the silicon supply body 10 to obtain.

In the furnace, the reaction-bonded silicon carbide and carbon preform 20 of 50 mm × 50 mm in size containing carbon black up to 30 volume percent is attached to the silicon supply body 10 of the same size, and then they are heat-treated in the temperature range of 1410 to 1460 ° C under a vacuum atmosphere to the molten silicon in the silicon carbide preform 20 to infiltrate. As a result, the reaction bonded silicon carbide is recovered.

Table 1 shows the density and density after sintering of the reaction bonded silicon carbide 20 according to the present invention. Table 1 Together powder translation (Vol%) Density (%) Density after sintering (%) SiC soot 100 0 53.9 96.7 91.6 8.4 57.0 97.0 83.8 16.2 58.2 97.4 76.6 23.4 60.3 97.5 69.7 30 62.8 97.8

2A and 2 B illustrate a fine structure of the silicon carbide and carbon preform with soot of 30.3 percent by volume ( 2A ) and a fine structure of. Silicon carbide sintering after the reaction bonding ( 2 B ).

Industrial applicability

As heretofore described, according to the problem solution of present invention, the majority of for preparing the reaction-bonded silicon carbide in the conventional Technology needed Equipment, such as B. the warming device for the Melting of the silicon, the melting pot for the storage of the molten Silicon and the delivery device from the oven to the body not mandatory. Only the sintering furnace for heating the silicon up to the melting temperature is required. Therefore, the reaction-bound Silicon carbide can be produced economically.

Further is in accordance with the present Invention, the reaction between the present in the Siliziumzuführungskörper present Silicon powder and the carbon obtained from the binder an exothermic reaction, which is why the silicon melted evenly can be. Further, the silicon carbide frame structure formed in the silicon lead body is in FIG able to accumulate the molten silicon due to the surface tension to prevent, therefore, the infiltration surface of the molten silicon can be kept maximum. In addition, the uniform infiltration rate over the entire infiltration surface be maintained by the spatial distribution of the molten Maintain silicon evenly becomes. Therefore, the total infiltration time, i. h., the processing time, be minimized.

Claims (8)

Process for the preparation of reaction bonded silicon carbide ( 20 comprising the steps of: providing a silicon delivery body ( 10 ), which silicon powder ( 11 ) and phenolic resin, furfuryl alcohol resin and / or epoxy resin as a binder; Providing a silicon carbide and carbon preform ( 20 ) or a silicon carbide preform; Contacting the silicon delivery body ( 10 ) with a surface of the preform ( 20 ) in a reaction bonding furnace; and heat treating them with a higher temperature than the melting temperature of the silicon ( 11 ) under vacuum or inert atmosphere, so that molten silicon in the silicon feed body ( 10 ) into the preform ( 20 ) infiltrated, characterized in that the ratio between the dimensions of the particles of the silicon powder ( 11 ) of the silicon delivery body ( 10 ) and the particle of silicon carbide powder ( 21 ) of the preform ( 20 ) Is 5: 1 to 25: 1, and wherein the size of the silicon powder particles ( 11 ) Is 70 to 2000 microns. The method of claim 1, wherein the silicon delivery body ( 10 ) is prepared by mixing a slurry by mixing 70 to 99 weight percent silicon powder ( 11 ) and thermosetting resin ( 12 ) are mixed with 1 to 10% by weight as a binder in up to 20% by weight of solvent; Dry the porridge to make granules ( 22 ) to obtain; and curing the granules. The method of claim 2, wherein the curing temperature is in the range of room temperature to 120 ° C. Method according to one of claims 1 to 3, wherein the binder 1 to 10 weight percent thermoplastic resin containing polyvinyl butyral (PVB), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc) and polymethyl methacrylate (PMMA) is selected. Method according to one of claims 1 to 4, wherein the binder a curing agent containing 1 to 10 weight percent, which consists of dibutyl phthalate (DBT), benzyl-butyl phthalate (BBT), polyethylene glycol (PEG), di-methyl phthalate (DMP), di-octyl phthalate (DOP) and glycerol is selected. Method according to one of claims 2 to 5, wherein the curing temperature in the range of 60 to 120 ° C lies. Method according to one of claims 1 to 6, wherein a silicon carbide frame structure ( 13 ) by reaction of the silicon particles ( 11 ) and the binder in the silicon supply body ( 10 ) is generated due to the heat treatment. Method according to one of claims 1 to 7, wherein the heat treatment temperature between 1410 and 1550 ° C lies.