DE10392574T5 - Process for the preparation of reaction-bonded silicon carbide - Google Patents

Abstract

Process for producing reaction bonded silicon carbide comprising the steps of:
Providing a silicon feed body of a predetermined shape containing silicon powder and phenolic resin, furfuryl alcohol resin or epoxy resin as a binder;
Providing a silicon carbide / carbon preform;
Contacting the silicon delivery body with a surface of the preform in a reaction bonding furnace; and
Heat treating it at a temperature higher than the melting temperature of the silicon under vacuum or inert atmosphere to infiltrate molten silicon in the silicon feed body into the preform.

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 silicon carbide acts as a binder around the silicon carbide particles in the preform interconnect and pores between the silicon carbide particles to fill up with the silicon.

One Method of feeding from molten silicon to a silicon carbide / carbon preform for Preparation of a reaction-bonded silicon carbide consists in immersing the preform in a crucible in which the filled with molten silicon is, and in the feeding of the molten silicon over the entire preform Capillary tube of the preform. However, in this case, a heating device for melting silicon, a crucible for receiving molten Silicon, a device for supplying molten silicon from a crucible to a specimen, etc. required, therefore the manufacturing process complex is and increases the cost become.

in the In the case of a simply shaped preform, a molten silicon may be used 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 become silicon powder particles at a higher temperature melted as the melting point, so that they due to surface tension clump together. Furthermore, the molten silicon, if it is clumped to a mass, not the entire surface, which fed to the silicon should, cover, and in some cases The lump may fall down due to gravity.

at the aforementioned conventional Method of feeding of silicon, when molten silicon clumps, the silicon far from the desired one Contact point away, and therefore the feed distance of the molten Silicon magnified and the infiltration area reduced. additionally should a silicon source at a constant position on a specimen be fixed. Furthermore, molten silicon has a very large surface tension and low viscosity. It thus has a tendency to stick together, so that it is his surface reduced. 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. Even though molten silicon for Reaction-bonded silicon carbide is important, it is difficult to evenly melted silicon the entire specimen according to the conventional Supply process.

Main technical point of the present invention

Therefore It is an object of the present invention to provide a process for the economical production of a reaction-bound Silicon carbide.

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.

Yet Another object of the present invention is to reduce the processing time while maintaining a uniform rate of infiltration over the entire surface, by having a uniform spatial Distribution of molten silicon is maintained.

Detailed description the invention

To the Solve the Objects of the present invention is a process for the preparation provided by reaction bonded silicon carbide, which comprising: Providing a Siliziumzuführungskörpers with Silicon powder particles and a thermosetting resin as a binder; Providing a silicon carbide / carbon preform; in contacting the silicon supply body with a surface the preform in an oven; and heating to the melting point of Silicon under vacuum or inert atmosphere, around the molten silicon in the silicon feed body in to infiltrate the preform.

Brief description of the drawings

It demonstrate:

1A to 1D a process for producing reaction-bonded silicon carbide according to the present invention; 1A a state in which a silicon feed coupon and a silicon carbide 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 / 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 effectively free molten silicon the shape, size and thickness a reaction-bonded silicon carbide are supplied. A cohesion of the molten silicon can be prevented and the molten silicon be supplied evenly.

It there is provided a process for the production of reaction bonded silicon carbide, which includes the steps: Providing a Siliziumzuführungskörpers with a predetermined shape, the silicon powder and a curable Contains resin as a binder; Providing a silicon carbide / carbon preform; contacting of the silicon feed body with a surface the preform in an oven; and heating to the melting point of Silicon under vacuum or inert atmosphere, around molten silicon in the silicon feed body in to infiltrate the preform.

Of the Silicon feeding or supplying bodies, called silicon feed body for short, is prepared by adding a slurry by mixing 70 to 99 weight percent Silicon powder with a part size of 10 to 5000 μm and 1 to 10% by weight curable resin as a binder in a solvent is produced, granules or a granule is achieved by drying the slurry, and the Granules are formed in a predetermined shape.

The curable Resin, which is a higher Residual carbon content; such as. Phenol resin has, is used as a binder used. The binder may further be 1 to 10% by weight thermoplastic resin, e.g. PVB (polyvinyl butyral), contained, around the specimen to give a warm conversion. When the thermoplasticity imparted to the silicon feed coupon is made by the thermoplastic resin with the thermosetting resin as a binder can be added, the reaction-bonded preform with the entire uneven surface the infiltration surface be contacted, even if the infiltration uneven is trained. additionally can when 1 to 10 weight percent plasticizer to increase the Warm conversion are added, the feed sample easily according to the form the infiltration surface itself be converted at low temperature.

Furfuryl alcohol resin and epoxy resin can be used as a curable resin besides phenolic resin. Polyvinyl alcohol (PVA), polyvinyl acetate (PVRc), polymethyl methacrylate (PMMA), etc. can be used as thermo plastic resins besides the PVB can be used, and dibutyl phthalate (DBP), benzyl-butyl phthalate (BBP), polyethylene glycol (PEG), dimethyl phthalate (DMP), di-octyl phthalate (DOP), glycerin, etc. can be used as the plasticizer.

The Binder becomes with the silicon in the body in the initial state of Reaction bond for forming a silicon carbide network structure reacted, causing a clumping 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 hot conversion 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 Silicon carbide (preform) standing, 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 are larger than the silicon carbide powder particles of the reaction-bonded preform. In the present Invention will be the difference between the particles of the silicon powder and the silicon carbide powder increased as much as possible to the infiltration rate of the molten silicon to accelerate, and thereby the Greatly reduce reaction time. The ratio between the silicon powder and the silicon carbide powder is suitably 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 prepared by mixing the silicon powder with the hardenable resin having a higher residual carbon content, such as phenolic resin, and the silicon supply body is made by plasticizing the granules. The silicon feed body is brought into contact with a location of the silicon carbide / carbon preform which, as in FIG 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 / carbon preform 20 The silicon feed body 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 and the silicon carbide / carbon preform are heat-treated in a reaction sintering furnace under vacuum or in an inert atmosphere so that at least one of their surfaces is in contact. The curable resin is thermally decomposed in the temperature range of 400 to 500 ° C during the heat treatment, so that carbon 23 in the silicon feed body as shown in FIG 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 completely connects the molten silicon in the silicon supply body and prevents the molten silicon from clumping or running off to one side; so that the molten silicon evenly on the shear surface 15 is distributed, where the preform and the silicon supply body in contact. As a result, the molten silicon in the silicon supply body is uniformly infiltrated into the silicon carbide preform. The silicon supply body finally leaves the silicon carbide frame structure 13 as shown in 1C , In the silicon carbide preform, the molten silicon infiltrated from the silicon supply body is reacted with the carbon particles to form 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 a low strength, and thus can be easily separated from the reaction-bonded body. The reaction-bonded silicon carbide 20 can by a simple processing as shown in 1D to be obtained.

As described above, when the reaction-bonded silicon carbide manufactured using the Siliziumzuführungskörpers is the reaction between those obtained from the bonding agent in the Siliziumzuführungskörper Carbon and silicon particles an exothermic reaction, and This allows the uniform melting of silicon induced and the cohesion of silicon due the surface tension be prevented. Therefore, the area through which the molten Silicon is infiltrated into the silicon carbide preform, maximum being held.

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. the retention time can be minimized. There is also an additional one Device for the feeder of the molten silicon is not required. Thus, the costs for the processing plant and the kiln are reduced.

embodiments

A Silicon carbide / carbon preform is made by mixing silicon carbide with a size of 1 to 10 μm and Soot from 10 to 40 μm made so that they Soot from 0 to 30% by volume, and by adding phenolic resin as a binder.

Of the Melt silicon feed body is using silicon powder of 70 to 2000 microns and the Phenolharzbindemittel made.

First are 1 to 15 weight percent phenolic resin and 0 to 15 weight percent DBP based on the weight of the material powder dissolved in alcohol, which Dissolve phenolic resin can. The silicon powder is added to the above solution to remove the slurry manufacture. After the addition of the silicon powder, these become evenly a strong stirring, Milling or ultrasonic processing mixed and then the context separated. When the porridge in distilled water, which is at 50 up to 80 ° C heated is dropped, there is a rapid solvent replacement, and the Dripped porridge turns into a hard state. The remaining 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.

When Another method is the desired amount of silicon powder and phenolic resin mixed in a dry manner, and then for 1 to 8 hours in a ball mill ground dry. Then the granules are mixed in a relatively uniform manner State won. However, the ideal mixed state of the granules can by the wet mixing method be achieved.

The produced granules is at 5 to 400 MPa in the temperature range from room temperature to 120 ° C compressed to obtain the fused silica supply body.

In the reaction bonding furnace is the 0 to 30.3 volume percent carbon black containing reaction-bonded silicon carbide preform of 50 mm × 50 mm Size with the Melt silicide delivery body of the same size in contact and then these are in the temperature range of 1410 up to 1460 ° C under vacuum atmosphere heat treated, to infiltrate the molten silicon into the silicon carbide preform. Thereby the reaction-bonded silicon carbide is recovered.

Table 1 illustrates the plastic density and sintering density of the reaction bonded silicon carbide according to the present invention. Table 1

2A and 2 B illustrate a fine structure of the silicon carbide / carbon preform with carbon black of 30.3 percent by volume ( 2A ) and a fine structure of the 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. the heating 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 reaction sintering furnace for the heating of the Silicon up to the melting temperature is required. Therefore, can the reaction-bonded silicon carbide produced economically become.

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 cause a clumping of the molten silicon due the surface tension to prevent, therefore, the infiltration surface of the molten silicon can be kept maximum. In addition, the uniform infiltration speed over the entire infiltration surface be maintained by the spatial distribution of the molten silicon maintained evenly becomes. Therefore, the total infiltration time, i.e., the processing time, be minimized.

SUMMARY

The present invention is inter alia based on the object of providing a process for the economic production of a reaction-bonded silicon carbide, which process comprises the following process steps:
Providing a silicon feed body of a predetermined shape containing silicon powder and phenolic resin, furfuryl alcohol resin or epoxy resin as a binder;
Providing a silicon carbide / carbon preform;
Contacting the silicon delivery body with a surface of the preform in a reaction bonding furnace; and
Heat treating it at a temperature higher than the melting temperature of the silicon under vacuum or inert atmosphere to infiltrate molten silicon in the silicon feed body into the preform.
( 1A - 1D )

Claims (10)

A method of producing reaction bonded silicon carbide comprising the steps of: providing a silicon feed body of a predetermined shape containing silicon powder and phenolic resin, furfuryl alcohol resin or epoxy resin as a binder; Providing a silicon carbide / carbon preform; Contacting the silicon delivery body with a surface of the preform in a reaction bonding furnace; and heat treating it at a temperature higher than the melting temperature of the silicon under vacuum or inert atmosphere to infiltrate molten silicon in the silicon feed body into the preform. The method of claim 2, wherein the silicon supply body is manufactured is made by adding a pulp by mixing 70 to 99 weight percent Silicon powder and hardenable Resin with 1 to 10 weight percent as a binder in a solvent to be mixed; Drying the slurry to obtain granules; and plasticizing the granules, to obtain a predetermined shape. The method of claim 2, wherein the size of the silicon powder particles about 10 to 5000 microns is. Process according to claim 2, wherein the plasticizing temperature is in the range of room temperature to 120 ° C. The method of claim 2, 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. The method of claim 2, wherein the binder contains a plasticizer with 1 to 10 weight percent, which from dibutyl phthalate (DBT), benzyl-butyl phthalate (BBT), polyethylene glycol (PEG), di-metyl phthalate (DMP), di-octyl phthalate (DOP) and glycerol selected becomes. A method according to claim 5 or 6, wherein the plasticizing temperature in the range of 60 to 120 ° C lies. The method of claim 1, wherein a silicon carbide frame structure by Reaction of the silicon particles and the binder in the Siliziumzuführungskörper due the heat treatment is produced. The method of claim 1, wherein the heat treatment temperature between 1410 and 1550 ° C lies. The method of claim 1, wherein a ratio between the dimensions of the particles of the silicon powder and the silicon carbide powder 5: 1 to 25: 1.