Abstract: A pigmented silicon nitride composition suitable for hot pressing into near shape articles of manufacture having a cosmetically uniform color. The composition comprises high purity, sub-micrometer, alpha silicon nitride powder mixed with a sintering aid and a pigmenting material. In a preferred embodiment the pigmenting material comprises molybdenum carbide, although carbides of other elements are applicable as well. The resulting hot pressed article is cosmetically superior to non-pigmented silicon nitride. Such articles are especially useful for processing semiconductor components where appearance in the form of color uniformity is a strict requirement for the manufacturer and the customer.

Abstract: In-situ Si.sub.3 N.sub.4 whisker growth mechanisms have enhanced the microstructure of ceramic materials such as SiC through controlled growth of elongated beta-type Silicon Nitride grains. During liquid phase sintering at temperatures not exceeding 1850.degree. C., alpha-type Silicon Nitride dissolves into the liquid phase and reprecipitates as an elongated or acicular beta modification. The Si.sub.3 N.sub.4 reinforced microstructures can be formed by the controlled recrystallization of beta-type Silicon Nitride. In-situ whisker growth is enhanced or optimized through the use of thermal treatments and/or additions of seed materials. Finely divided beta-type Silicon Nitride particles which are insoluble in the liquid phase during sintering, and therefore have been used to provide nucleation sites for whisker growth are employed. Thermal treatments have been designed to promote directional growth (elongation) as opposed to development of less elongated type grains.

Abstract: In-situ Si.sub.3 N.sub.4 whisker growth mechanisms have enhanced the microstructure of ceramic materials such as SiC through controlled growth of elongated beta-type Silicon Nitride grains. During liquid phase sintering at temperatures not exceeding 1850.degree. C., alpha-type Silicon Nitride dissolves into the liquid phase and reprecipitates as an elongated or acicular beta modification. The Si.sub.3 N.sub.4 reinforced microstructures can be formed by the controlled recrystallization of beta-type Silicon Nitride. In-situ whisker growth is enhanced or optimized through the use of thermal treatments and/or additions of seed materials. Finely divided beta-type Silicon Nitride particles which are insoluble in the liquid phase during sintering, and therefore have been used to provide nucleation sites for whisker growth are employed. Thermal treatments have been designed to promote directional growth (elongation) as opposed to development of less elongated type grains.

Abstract: The present invention relates to improved materials for fabricating can bodies. In particular, the present invention relates to can tooling components fabricated from whisker-reinforced silicon nitride having from about 5 to about 15 weight percent whiskers with an average diameter of at least about 0.75 micrometers. The material preferably has a thermal expansion coefficient of less than about 3.5.times.10.sup.-6 per .degree.C. and a friction coefficient of from about 0.20 to about 0.24. The present invention also provides a method for reducing the trim height of can bodies formed using a can tooling apparatus.

Abstract: The present invention relates to improved materials for fabricating can bodies. In particular, the present invention relates to can tooling components fabricated from whisker-reinforced silicon nitride having from about 5 to about 15 weight percent whiskers with an average diameter of at least about 0.75 micrometers. The material preferably has a thermal expansion coefficient of less than about 3.5.times.10.sup.-6 per .degree.C. and a friction coefficient of from about 0.20 to about 0.24. The present invention also provides a method for reducing the trim height of can bodies formed using a can tooling apparatus.

Abstract: A new silicon carbide material is made following a procedure including hot pressing to provide a finished product having a microstructure with an optimal grain size of less than 7 micrometers. The material exhibits a dominant failure mode of intergranular fracture requiring significant energy for crack propagation. The method of manufacturing is cost-effective by allowing the use of "dirty" raw materials since the process causes impurities to segregate at multi-grain boundary junctions to form isolated pockets of impurities which do not affect the structural integrity of the material. End uses include use as protective projectile-resistant armor.

Abstract: A new silicon carbide material is made following a procedure including hot pressing to provide a finished product having a microstructure with an optimal grain size of less than 7 micrometers. The material exhibits a dominant failure mode of intergranular fracture requiring significant energy for crack propagation. The method of manufacturing is cost-effective by allowing the use of "dirty" raw materials since the process causes impurities to segregate at multi-grain boundary junctions to form isolated pockets of impurities which do not affect the structural integrity of the material. End uses include use as optical and electronic substrate materials.

Abstract: A silicon carbide material is made following a procedure including hot pressing to provide a finished product having a microstructure with an optimal grain size of less than 7 micrometers. The material exhibits a dominant failure mode of intergranular fracture requiring significant energy for crack propagation. The method of manufacturing is cost-effective by allowing the use of "dirty" raw materials since the process causes impurities to segregate at multi-grain boundary junctions to form isolated pockets of impurities which do not affect the structural integrity of the material. End uses include use as protective projectile-resistant armor.

Abstract: A method is disclosed of fully densifying a plurality of preformed ceramic plates by axial compression of the billets along a wall defining a cylinder and cavity. A series of the plates are stacked along the wall with the smallest dimension of the billets aligned with the axis of the cavity. The billets have a ratio of the smallest dimension to the largest dimension in the range of 1:3 to 1:40. The largest dimension of each of the plates is less than the lateral dimension of the cavity to leave an annular space; the space is filled with a pseudo isostatic pressing medium. The assembly is hot pressed under sufficient pressure and heat to convert the plates to billets of substantially full density.

Abstract: A new silicon carbide material is made following a procedure including hot pressing to provide a finished product having a microstructure with an optimal grain size of less than 7 micrometers. The material exhibits a dominant failure mode of intergranular fracture requiring significant energy for crack propagation. The method of manufacturing is cost-effective by allowing the use of "dirty" raw materials since the process causes impurities to segregate at multi-grain boundary junctions to form isolated pockets of impurities which do not affect the structural integrity of the material. End uses include use as optical and electronic substrate materials.

Abstract: A method of making a silicon nitride comprising object by use of a low density reaction bonded body is disclosed. An uncompacted mixture of silicon powder and a fluxing agent is heated in a nitrogen atmosphere to react the mixture with the atmosphere to form a body consisting essentially of silicon nitride and having a dimension greater than and a density less than the finished product. The nitrided mixture is then hot pressed to produce a silicon nitride comprising object of desired dimension and density, which material is useful as a cutting tool material for machining metals.

Abstract: A method of making a reaction bonded/hot pressed silicon nitride comprising object is disclosed. Second phase crystallites are formed prior to hot pressing. A mixture of silicon, SiO.sub.2, and 0.4-2.3 molar percent (by weight of the silicon) of oxygen carrying agents, i.e., Y.sub.2 O.sub.3 and Al.sub.2 O.sub.3, is performed and reaction nitrided to form discs or billets having at least 60% alpha Si.sub.3 N.sub.4 and a high proportion of second phase crystallites which displace substantially all silicate glass except for a controlled small quantity. The reactive amounts of Y.sub.2 O.sub.3, Al.sub.2 O.sub.3 and SiO.sub.2 are controlled to assure formation of substantially Y.sub.1 SiO.sub.2 N as the second phase crystallite. Al.sub.2 O.sub.3 is controlled in an amount of 0.4-4% by weight to ensure that the small proportion of glass serves to protect the oxynitrides against linear oxidation kinetics. The hot pressed material has no visual mottle porosity associated therewith.

Abstract: A method is disclosed of making a plurality of dimensionally accurate hot pressed ceramic bodies. A plurality of Si.sub.3 N.sub.4 plates having a thickness to width ratio of 1:3 to 1:40 are stacked in a hot pressing assembly (40-41-42-43). The plates are arranged in groups of progressively decreasing number so that (a) for a plate group (10-11-12-13-14) residing in a zone of compression (15) that will experience the least movement along the pressing direction the stacked number of plates is greatest within such group, and (b) for a plate group residing in a zone of compression (22) that will experience the most movement along the pressure direction the stacked number of plates (21) within such group is the lowest, each group being separated from adjacent groups by an inert rigid spacer.

Abstract: A method of improving the quality of hot pressed Si.sub.3 N.sub.4 bodies is disclosed. Unpurified silicon powder and admixed oxygen carrying agents are compacted to form a preform. The preform is nitrided, facilitated by the presence of certain impurities, to agglomerate the mixture to an increased density no greater than 2.7 gm/cm.sup.3. The nitrided preform is immersed in one or more stages in one or more leaching solutions of effective concentration to remove the selected impurities. The treated preform is then hot pressed to full density accompanied by a substantial reduction or absence of undesirable impurities such as iron silicide, which can conventionally form during hot pressing.

Abstract: A method of making a compacted body useful in the fabrication of an improved, fully densified silicon nitride ceramic is disclosed. Silicon powder, oxygen carrying agents, and a dry lubricant (an aliphatic acrylate resin) are admixed. The lubricant is selected to have a low surface energy value less than 28 dyne/cm, have a glass transition temperature of -43.degree. to -82.degree. C., and a molecular weight equal to or less than 5000. The admixture is milled to a desired average particle size no greater than 35 microns. The milled mixture is then formed into a compact which can be nitrided and hot pressed to form a fully dense silicon nitride object.

Abstract: A method is disclosed for simultaneously and uniformly densifying a plurality of semidense ceramic powder bodies. The bodies are hinged together with a uniform space therebetween to form a cluster. The spaces in each cluster are filled with an isostatic pressure medium and then the clusters are stacked in a predetermined alignment along a pressing axis and hot pressed to substantially full density. The bodies are then ruptured from said clusters so as to be in a condition for use as a tool.

Abstract: A method is disclosed for making a more densified silicon nitride comprising object under less stringent heating conditions without sacrificing physical properties. A mixture of silicon powder, 6-18% yttrium silicon oxynitride (a major proportion of which is the Y.sub.10 Si.sub.6 O.sub.24 N.sub.2 phase), 0.4-3% Al.sub.2 O.sub.3, and possibly up to 2% of an oxynitride forming oxide (Y.sub.2 O.sub.3) is compacted, nitrided, and sintered to produce a silicon nitride/YSiO.sub.2 N comprising object of relatively high density.

Abstract: A method is disclosed of densifying a silicon nitride comprising compact having 5-17% by weight yttrium silicon oxynitride and having a density of 2.0-2.6 gm/cm.sup.3. The method comprises (a) partially sintering the compact at a temperature of 3000.degree.-3200.degree. F. for a period of 0.5-72 hours to form a semidense body with a density of 2.9-3.15 gm/cm.sup.3, and (b) hot pressing a stacked assembly of said bodies in the hot zone of a hot pressing cavity to form fully dense anisotropic products, each body being separated from the other within the assembly by a distance no greater than 0.03 inch, and the stacked assembly occupying substantially the entire length of the hot zone of the hot pressing cavity.

Abstract: A method of making a powder additive consisting of yttrium silicon oxynitrides, preferably of the Y.sub.10 Si.sub.6 O.sub.24 N.sub.2 or YSiO.sub.2 N phases, is disclosed. Stoichiometric amounts of Y.sub.2 O.sub.3, SiO.sub.2, and Si.sub.3 N.sub.4 are mixed and arranged in intimate reactive contact, the amounts being to form a desired oxynitride according to the formula Y.sub.a Si.sub.b O.sub.c N.sub.d, where a, b, c and d represent the required element parts of the compound in equilibrium with the mixture elements. The mixture is heated in an inert atmosphere to a temperature and for a time sufficient to convert the stoichiometric amounts of the mixture to the desired yttrium silicon oxynitride. The heat agglomerated mixture is then ground to a powder.

Abstract: A method of making a densified silicon nitride/oxynitride composite is disclosed. The method comprises: (a) shaping a substantially homogeneous powder mixture of silicon nitride, 6-18% yttrium silicon oxynitride of the Y.sub.10 Si.sub.6 O.sub.24 N.sub.2 phase in an amount to form a viscous solution with at least a portion of the silicon nitride, and (b) densifying the body by heat fusion, with or without the use of mechanical pressure, to a density and a dimension required for the final product.