Ford Motor Company Limited

Cercom, Inc.

Ceradyne, Inc.

Golden Technologies Company, Inc.

Ceradyne Advanced Products, Inc.

Andre Ezis

Elaine C Beckwith

Krishnamoorthy Subramanian

Shyam K Samanta

Howard D Blair

Warren B Copple

John Michael Nicholson

Roblee L Talbott

Chester J Dziedzic

C James Shih

David Moskowitz

James C Uy

Chienchung James Shih

John J Schuldies

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.

Pigmented silicon nitride

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.

In-situ grown whisker reinforced ceramics

Method of making in-situ grown whisker reinforced ceramics

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.

Can tooling components

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.

Monolithic, fully dense silicon carbide material, method of

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.

Monolithic, fully dense silicon carbide mirror and method of

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.

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.

Making hot pressed silicon nitride by use of low density reaction bonded

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.

Method of making reaction bonded/hot pressed Si.sub.3 N.sub.4 for use as

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.

Method of fabricating hot pressed silicon nitride billets

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.

Method of improving quality of hot pressed Si.sub.3 N.sub.4 bodies

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.

Growing community of inventors

Grosse Ile, MI, United States of America

Andre Ezis