DE19820832A1 - Production of a solid body used, e.g., as brake disk - Google Patents

Abstract

Production of a solid body comprises using a raw material containing one or more additives selected from monosaccharides, oligosaccharides and polysaccharides in a molding process followed by a solidification process above the decomposition temperature of the saccharides added.

Description

The present invention relates to a method for manufacturing of a solid body, a raw material offset, the raw one Contains powder and at least one aggregate first a molding process and then a solidification process under is pulled. The present invention further relates to a through this process manufacturable body as well as the use of a such body.

Generic body made of sintered or recrystallized materials such. For example, silicon carbide (RSiC) boron carbide (RB ₄ C) or boron nitride (RBN) are known. They are generally obtained by sintering raw material offsets that contain raw material particles and possibly aggregates.

The most common material is silicon carbide; in the form of sintered silicon carbide (SSiC) or recrystallized silicon carbide (RSiC). The SSiC is obtained from fine crystalline SiC particles with the addition of binders, sintering additives to the Ak Activation and carbon for sealing sintering (for example, add ze of boron and carbon or aluminum and carbon). Of the Raw material offset is subjected to a shaping process. In the right  the resulting green body is the raw material powder with the help of the bin solidified. The green body is depressurized at approx. 2000 ° C sintered. You get a dense product with over 96% of theo retic density. The compression that occurs during sintering however, leads to shrinkage. Recrystallized silicon Umcarbide (RSiC) is obtained by sintering silicon carbide par particles preferably bimodal grain distributions. This procedure ren is z. Example from US 2,964,823, DE-OS 28 37 900 and DE 31 49 796 known. These particles become egg at approx. 2000 ° C sintered in a porous body. You may need a bandage medium to solidify the green body, but no sinteraddi tive. No compaction takes place during sintering, so that no shrinkage is observed. You get pure, non sealed porous silicon carbide.

The problem here is that the green body in use conventional ceramic binder when heating to the sintering temperature passes through a gap in strength, that is, at Temperatu ren becomes unstable at around 200 ° C. The green body can even disintegrate.

The object of the invention is therefore a method and products the above Provide way with which on simple and cheap Ways solid bodies are available that have no strength gap have and below about 200 ° C when heating thermopla possess statistical properties.

The solution is a procedure with the characteristics of the contractor Proverb 1 and the products that can be made from it.  

In the following, the term "saccharide" is used as a generic term for Monosaccharides, oligosaccharides and polysaccharides are used.

The method according to the invention is therefore characterized in that that as a binder one or more monosaccharides, oligosaccha ride or polysaccharides are used in their decomposition solidify the raw material powder. The inventive method ren leads to solid bodies by the decomposition of the saccha The resulting carbon contain, are dimensionally stable and kei have a strength gap. Saccharides are in contrast to conventional binders such. E.g. resins easy to process ten, do not require organic solvents and are easy to use ch, uncritical thermal behavior. You are non-toxic, one easy to handle, cheap and easily available. When warming up show a thermoplastic behavior, the viscosity can can be controlled via the temperature curve. The raw material offset can therefore also be pressed during solidification and thus further ver be sealed, since the admixed saccharides at higher temperatures Soften the fittings first before they decompose. Furthermore The gases generated during the decomposition lead to a uniform open porosity that be a liquid infiltration favorable.

The strength of the body according to the invention is sintered Bodies comparable. The body according to the invention can without Sintering can be processed further. The nope for the consolidation temperatures are much lower than the usual sinter temperatures. So that the inventive method and follow  Lich the product available with it also cheaper and such suitable for wide industrial applications.

Advantageous further developments result from the dependent claims chen. The molding process is preferably at a tempera tur below about 500 ° C, for example. In a range of about 50 to 250 ° C, the solidification process at a temperature of about 120 performed up to about 1000 ° C.

A preferred embodiment of the method according to the invention sees the use of saccharides or saccharide solutions, preferably aqueous solutions. Suitable water soluble Saccharides are, for example, glucose, fructose, sucrose, in particular in the form of ordinary table sugar and soluble starch (Amylose), but also other water-soluble mono-, oligo- and Po lysaccharides. The concentration of the saccharide solution should be before preferably 10 to 80 wt .-%. Already with a 10% The solution is observed to solidify. In the production of high concentrated solutions, it is recommended that the saccharide or dissolve the saccharides with gentle warming. Highly concentrated Te saccharide solutions can have a slightly syrupy consistency point.

Any raw material powder or raw material powder mixtures can be used for the production of raw material offsets for the inventive Bodies are used to set certain properties len. For example, silicon carbide, boron carbide, aluminum umnitrid- and / or titanium carbide powder or mixtures of one or more of these powders are used.  

Basically, two Ver suitable driving variants. A first variant provides for one Submit saccharide solution and thus the raw material powder preferably up to about 70% by weight, based on the saccharide solution, and if necessary to mix additional aggregates. In a second Va riante first becomes a slip from the raw material powder and, if necessary, Aggregates produced and then the or the saccharides be mixed. The amount of saccharide should be about 10 to 80% by weight, based on the amount of liquid contained in the slip, be.

With the grain size distribution you have the choice between several Possibilities. It can be monomodal, but also bimodal with one Fine grain and a coarse grain fraction. Also a trimodal Structure with a fine, a medium-coarse and a coarse grain is conceivable. In the manufacture of fiber-reinforced ceramics te the grain size preferably matched to the fiber diameter be.

In this context, the older, not pre-published light patent application 197 36 560.4-45, whose Offenba tion is hereby incorporated into the present application.

There are numerous ways of shaping each Green body. Production in slip casting is preferred drive. Die casting and foil casting are also conceivable. Do you have one pasty starting material, extrusion processes are suitable, Injection molding, isostatic pressing, axial pressing, hot pressing,  RAM presses and comparable processes. Are important at The use of long fibers or fiber fabrics also the classic ones known winding and laying techniques in which the fiber or the fabric is immersed in a slurry of raw material offset and then wound or laid and pressed or otherwise is widely processed.

To adjust the pore size and pore structure are in addition to Grain size and the grain distribution also the respective shaping process for producing the green bodies. At The matrix is also used to manufacture fiber reinforced bodies and stored in the fiber bundle and thereby keeps infiltrati on channels open. The fibers are completely in the porous Ma trix embedded.

The body obtainable by the method according to the invention can then with inorganic or organic substances, e.g. Carbon, carbon precursors or other substances, e.g. Metals are filled. For manufacturing, for example, fiber-reinforced Silicon carbide ceramics become the porous body with carbon or impregnated with a carbon precursor. The Koh Lenstoff offer on the Precorsortyp, so its coal Yield or over the degree of dilution of the carbon or Precursors controlled in the solvent or suspending agent become. The subsequent siliconization takes place under the usual Conditions.

All are suitable for producing the fiber-reinforced bodies known fibers reinforcing fibers, including whiskers or pla  telets. These include carbon fibers, ceramic fibers, oxi fibers and non-oxide fibers. These fibers can do so probably as short fibers as well as continuous fibers, also in Form of fiber fabrics are introduced.

Exemplary embodiments of the present invention are described below dung described in more detail with the help of the attached figures. It demonstrate:

Figures 1 and 2 polished sections of various bodies according to the invention, which were obtained from different silicon carbide Ver sets with different saccharide content.

FIGS. 3 and 4 Anschliffbilder various inventive composites, the chem by silicidation of matrices of silicon carbide offsets with differing saccharide were obtained.

First of all, the production of a silicon carbide body should be exemplary be described in the slip casting process. The Schlic Kergußverfahren is known per se and in the above. Block letters described. However, the use of this method is not imperative.

First, water is mixed with a condenser. It can it is a liquefier based on ammonium hydroxide or act on an organic basis. The pH of those with ammonium hydroxide liquefied solution is adjusted to 11.4. A mo  Nomodal silicon carbide offset with a medium grain size about 1 µm is stirred into the solution. That way a homogeneous aqueous slurry with a solids content of made about 50 to 60%. In the slip is more common Table sugar stirred in. The resulting raw material offset is dewatered in a porous form and then at about 50 to 110 ° C dried. The molded body is then 4 hours 200 ° C solidified in air. The resulting invention Body cannot be broken with bare hands.

The resulting solid was washed with a phenolic resin in Va vacuum impregnated and cured at 175 ° C and 7 bar in an autoclave tet. The body was then at a temperature of Pyrolyzed 1000 ° C under protective gas. The following rivers sigilization was carried out by wick infiltration at 1560 ° C. The Holding time was 10 minutes.

In the raw material offset, reinforcing fibers and. the like to be mixed in. The saccharide content of the raw material offset advantageously at least about 10 wt .-% be carry.

As part of a series of measurements with the Ver drive solid bodies from a raw material offset with a sugar content of 10, 20, 30, 40, 50, 60 and 70 wt .-% manufactured and measured. A raw material offset without bandage was used as a zero sample medium processed.  

In particular, the fiber-reinforced materials are for tribologi cal applications, such as B. brake units and sliding elements and for structural applications, e.g. E.g. in automobile construction and racing, Suitable for engine construction and space travel.

Claims (19)

1. A process for producing a solid body, wherein a raw material batch containing a raw material powder and at least one additive is first subjected to a shaping process and then a solidification process, characterized in that a raw material batch is used which contains one or more additives , which is selected from the group consisting of nonosaccharides, oligosaccharides and polysaccharides and the solidification process is carried out above the decomposition temperature of the saccharide or saccharides added. 2. The method according to claim 1, characterized, that the molding process at a temperature below about 500 ° C is carried out. 3. The method according to any one of the preceding claims, characterized, that the solidification process at a temperature of about 120 ° C to about 1000 ° C is carried out.   4. The method according to any one of the preceding claims, characterized, that the solidification process is carried out under increased pressure becomes. 5. The method according to any one of the preceding claims, characterized, that the saccharides are used in solid form as an additive become. 6. The method according to any one of claims 1 to 4, characterized, that a solution, preferably an aqueous solution of at least a monosaccharide, oligosaccharide and / or polysaccharide or from a mixture of one or more of these sub punching is used. 7. The method according to claim 6, characterized, that uses a saccharide solution of about 10 to 80% by weight becomes. 8. The method according to any one of the preceding claims, characterized, that as water-soluble saccharides glucose, fructose, water soluble starch (amylose) or sucrose, preferably in Form of common table sugar. 9. The method according to any one of the preceding claims,  characterized, that to produce the raw material offset, a Sac Charid solution is submitted and then the raw material powder and possibly other additives. 10. The method according to claim 9, characterized, that about up to 70 wt .-% raw material powder based on the previous placed saccharide solution are mixed. 11. The method according to any one of claims 1 to 8, characterized, that to produce the raw material offset first a preferably aqueous slurry from raw material powder and possibly white other additives and then the or the saccharides are mixed into the slip. 12. The method according to claim 11, characterized, that about 10 to 80 wt .-% saccharide (s) based on the rivers proportion of the slip presented. 13. The method according to any one of the preceding claims, characterized, that any raw material powder, preferably silicon carbide and / or Boron carbide and / or aluminum nitride and / or titanium carbide powder is used. 14. The method according to any one of the preceding claims,  characterized, that one or more types of reinforcing fibers, preferably wise short fibers and / or continuous fibers such as Langfa star and / or fiber fabric, with the raw material offset and processed further. 15. The method according to claim 14, characterized, that as reinforcing fibers carbon fibers and / or kera mix fibers and / or oxidic fibers and / or nonoxidi cal fibers are used. 16. The method according to any one of the preceding claims, characterized, that one of the following processes is used as the shaping process is set: slip casting, die casting, foil casting, extrusion driving, injection molding, isostatic pressing, axial pressing, Hot presses, RAM presses and comparable processes as well Wrapping and laying techniques. 17. The method according to any one of the preceding claims, characterized, that the resulting solid body with an organic or inorganic substance, preferably a carbon donor and / or is infiltrated with liquid metal. 18. Solid body, obtainable by a method according to one of the Claims 1 to 17.   19. Use of a by a method according to any one of the claims 1 to 17 available solid, preferably fiber-reinforced Body for further processing for tribological applications, in particular plain bearings, sliding elements, brake discs, brakes coverings and for further processing for structural applications applications, especially as a material in automotive and drive systems plant construction and in space travel.