Sintered silicon carbide/carbon composite ceramic body having a homogeneous very fine grain microstructure with at least 50 percent of its silicon carbide grains having a size not exceeding about 5 microns and an aspect ratio less than about 3, with graphite grains having an average size not exceeding that of the silicon carbide grains uniformly dispersed throughout the matrix of silicon carbide and having a density of at least 75 percent of theoretical can be made by firing of an infiltrated, microporous shaped green body having prior to infiltration a density of at least about 45 percent of theoretical, the shaped green body being infiltrated with an organic material which can be coked at elevated temperatures to form carbon, a sintering aid selected from the group consisting of aluminum, beryllium or boron or compounds containing any one or more of these or a mixture of any of the foregoing elements or compounds, silicon carbide having a surface area of from about 5 to about 100 square meters/gram and, optionally, a temporary binder at a sintering temperature of from about 1900° C. to about 2300° C. in an inert atmosphere or vacuum. The process for making such pressureless-sintered composite bodies is relatively undemanding of exact temperature/time control during sintering. Certain embodiments of such composite sintered bodies may be electrical-discharge machined. Fully dense composite bodies exhibiting no open porosity may be formed.

Sintered silicon carbide/carbon composite ceramic body having fine microstructure

Substrates are disclosed having an ultra-smooth surface finish thereon rendering them useful in making high density magnetic storage components, such as a computer hard disk or thin-film head which can read and/or write data on such disks. The substrates are comprised of a non-oxide ceramic base which is coated with a smoothing layer comprised of amorphous, non-stoichiometric silicon carbide corresponding to the formula SiCx, wherein x is the molar ratio of carbon to silicon and is greater than 1. Also disclosed are processes for making the substrates and components.

Ceramic substrates and magnetic data storage components prepared therefrom

A silicon carbide ceramic body having a high degree of lubricity as a result of large graphite inclusions in the body. The graphite inclusions have an average size of at least about 100 micrometers. The graphite-loaded silicon carbide component is preferably formed by spray drying graphite particles independent of the silicon carbide, blending the graphite agglomerates and silicon carbide to form a raw batch, forming the raw batch into a green body, and sintering the green body to produce a graphite-loaded silicon carbide ceramic body having good density and good strength.

Graphite-loaded silicon carbide

Silicon carbide sintered bodies having controlled porosity in the range of about 3-25 vol % are prepared from raw batches containing a multimodal distribution of silicon carbide particles and comprised of at least a first set of particles having one average grain size and a second set of particles having another average grain size larger than the first set of particles. The resulting pores are 3-5 microns in the largest dimension, with an aspect ratio between about 1/1 and about 3/1 . The porous bodies, e.g., in the form of mechanical seal members, exhibit good tribological properties.

Porous silicon carbide

A dense, self-sintered silicon carbide/carbon-graphite composite material and a process for producing the composite material is disclosed. The composite material comprises a silicon carbide matrix, between 2 and 30 percent by weight carbon-graphite, and small amounts of sintering aids such as boron and free carbon. The silicon carbide has an average grain size between 2 and 15 νm, and the carbon-graphite has an average grain size between 10 and 75 νm, the average grain size of the carbon-graphite being greater than the average grain size of the silicon carbide. The composite material has a density of at least 80 percent of theoretical density as determined by the rule of mixtures for a composite material. This density is achieved with minimal microcracking at a high graphite loading with large graphite particles. The composite material exhibits good lubricity and wear characteristics, resulting in improved tribological performance. The process for producing the composite material uses a carbon-bonded graphite comprising at least 5 percent by weight carbon-precursor binder.

Dense, self-sintered silicon carbide/carbon-graphite composite and process for producing same

Sintered silicon carbide/graphite/carbon composite ceramic body having a homogeneous fine grain microstructure with at least 50 percent of its silicon carbide grains having a size not exceeding about 8 microns and an aspect ratio less than about 3, with graphite grains having an average size not exceeding that of the silicon carbide grains microns uniformly dispersed throughout the matrix of silicon carbide and having a density of at least 75 percent of theoretical can be made by firing of a shaped green body having a density of at least about 45 percent of theoretical, the shaped green body containing graphite of fine particle size, a sintering aid selected from the group consisting of aluminum, beryllium or boron or compounds containing any one or more of these or a mixture of any of the foregoing elements or compounds, silicon carbide having a surface area of from about 5 to about 100 square meters/gram and, optionally, a temporary binder at a sintering temperature of from about 1900° C. to about 2300° C. in an inert atmosphere or vacuum. The process for making such pressureless-sintered composite bodies is relatively undemanding of exact temperature/time control during sintering. Contain embodiments of such composite sintered bodies may electrical-discharge machined.

Boecker Wolfgang Dietrich Geor

Papers

Sintered silicon carbide/graphite/carbon composite ceramic body having ultrafine grain microstructure