Molding silicon carbides

Silicon carbide, SiC or carborundum, has the diamond structure, and it is widely used as an abrasive in grinding wheels. These are made by crushing the SiC, adding clay, then heating the material in molds. Silicon carbide is prepared by the reaction... 

This process is more popular in polymers. For the injection molding of ceramics, a thermoplastic polymer is required to the extent of 40 vol.%. This is called the binder. For example, to injection mold silicon carbide, ethyl cellulose is one such binder that is used. During the firing process, a binder removal soak, called binder burnout, is given to eliminate the polymer from the final product. 

Other linear polysilanes can also be used as ceramic precursors. Solid objects of silicon carbide are manufactured by Nippon Soda Co. from polysilastyrene and finely divided silicon carbide powder.133 These materials are blended, injection molded to the... 

Silicon combines with carbon to form silicon carbide or carborundum, SiC, and forms are known that have the wurtzite and zinc blende structures. It is a very hard, tough material that is used as an abrasive and a refractory. The powdered material is crushed after mixing with clay and heated in molds to make grinding wheels. It is prepared by the reaction... 

Each of the Pyramid foundry sets comes complete with furnace chamber and lid, electric motor, blower-mixer, blower tube, flexible hose, crucible tongs, flask and sand to match size of furnace set that Is ordered, flour silica and a high grade silicon carbide crucible of the proper size. An instruction booklet is included which explains the operation of the furnace, and the method of making molds for metal casting. Each of the above sets is equipped with the supplies shown in the photo, except set No. 1 which Is equipped with 12" assay type tongs. 

Sintered silicon carbides are formed by all the traditional methods as well as standard plastic forming techniques such as injection molding. These compacts are sintered with small amounts of additives at very high temperatures in inert atmospheres to form essentially a single phase silicon carbide structure. 

It is technically easier to manufacture a molded component from SiC-powder by slip casting or dry pressing, working it mechanically and then sintering pressureless at 1950 to 2000°C. Due to the low sintering activity of silicon carbides, such processes have only been recently successfully carried out with the advent of fine particulate SiC-powders (specific surface area > 5 m /g) with low oxygen-contents (< 0.2%). Boron or aluminum and free carbon or boron carbide are added as sintering aids. 

Dense SiC platelet reinforced silicon carbide composites were recently fabricated [52]. The highest sintered densities of 97-98% TD were achieved with 20% platelet contents using hot molding as the thermoplastic forming technique [53]. 

This opened up an inexpensive method of producing dense and complex parts consisting of pure silicon carbide (SSiC). The powders (see Fig. 8) can be molded into a green body by any of the methods used in ceramic molding [93,94], depending on the shape required and the number of pieces involved (see Table 5). Sintering is... 

K.M. Taylor, Cold Molded Dense Silicon Carbide Articles and Methods of Making the Same," U.S. Pat. No. 3 205 043. Sept 7,1965. 

A A glass sphere is molded into an optical lens by pressing against an optically smooth silicon carbide surface under heat and pressure. In order to avoid surface irregularities and distortions due to friction between the two surfaces, a lubricant must be employed. Under the conditions of the process, what lubricating mechanism would you predict to be most effective What characteristics should the lubricant have Explain your conclusions. 

Self-bonded silicon carbide materials in molded form and of high SiC content have been available only from the late 1960s onwards. These are being increasingly used for structural components in mechanical engineering, and have proved to be highly successful for use under extreme abrasive, corrosive, and thermal conditions due to their excellent mechanical, chemical, and physical properties. 

Silicon carbide and boron carbide to a lesser degree are important industrial materials which are produced on a large scale in the form of powders, molded shapes, and thin films. 

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