Ngk Insulators, Inc.

Issei Hayakawa

Tadaaki Matsuhisa

Noriyuki Ukai

Mithuru Miyamoto

Isao Oda

Shigenori Ito

Masayuki Kaneno

High density fine ceramic sintered bodies are disclosed, which have a maximum pore diameter of not more than 10 .mu.m and a porosity of not more than 0.5%. A process for producing such high density fine ceramic sintered bodies comprises the steps of mixing a ceramic raw material powder with a sintering aid, grinding the resultant, mixture granulating and shaping the mixture, and firing the shaped body. The granulated powder is once forcedly dried, and upon necessity is added with water and/or sieved to obtain a uniform granulated powder having a given amount of water.

Silicon nitride ceramic sintered bodies

A high hardness silicon nitride sintered body which includes 10.about.50% of a .alpha.-Si.sub.3 N.sub.4 per total weight of silicon nitride and has a Knoop hardness of not less than 15.5 Gpa, and is use as a bearing material or the like.

High hardness silicon nitride sintered bodies

A homogeneous Si.sub.3 N.sub.4 sintered body is produced having a proportion of a grain boundary crystalline phase to the whole grain boundary of 50% or less, maximum pore diameter of 10 .mu.m or less and a porosity of 0.5% or less. A process for manufacturing each an Si.sub.3 N.sub.4 sintered body is, in conventional processes wherein a starting material for Si.sub.3 N.sub.4 is mixed with a sintering aid, pulverized, granulated, then molded and subsequently fired, characterized in that a temperature lowering rate from a firing temperature to 1,000.degree. C. is made to be 30.degree. C./min. Another process of the invention is, in the above conventional process, characterized in that Si.sub.3 N.sub.4 containing at least 90% of .alpha.-Si.sub.3 N.sub.4 as a starting material and a sintering aid, both having an average grain diameter of 1 .mu.m or less, are used, the granulated powder is once forcedly dried and then, if required, water is added, before the molding and firing.

Homogenous silicon nitride sintered body

A homogeneous silicon nitride sintered body produced by placing a shaped body of silicon nitride powder into a high density silicon carbide sagger having particular properties and then firing under particular conditions.

Method of producing homogeneous silicon nitride sintered bodies

High density fine ceramic sintered bodies are disclosed, which have a maximum pore diameter of not more than 10 .mu.m and a porosity of not more than 0.5%. A process for producing such high density fine ceramic sintered bodies comprises the steps of mixing a ceramic raw material powder with a sintering aid, grinding the resulting mixture granulating and shaping the mixture, and firing the shaped body. The granulated powder is once forcedly dried, and upon necessity is added with water and/or sieved to obtain a uniform granulated powder having a given amount of water.

Ceramic sintered bodies and a process for manufacturing the same

Disclosed herein is a method of manufacturing dense cordierite, which includes steps of molding a powder mainly consisting of cordierite crystals and having an average particle size of not more than 5 .mu.m, firing a resulting molding at a temperature of from 1,350.degree. to 1,430.degree. C., whereby the sintered body having a porosity of not more than 6% and a bulk specific gravity of not less than 2.4 is obtained.

Method of manufacturing dense cordierite

Disclosed herein is a ceramic insert cast piston for an internal combustion engine which includes a head made of ceramic, a metal ring fitted around the peripheral portion of the ceramic head, and a piston body made of a metal by casting a metal around the ceramic head with the metal ring thereon, wherein an air insulating layer in the form of an annular groove is formed at the inner periphery of the metal ring and a buffer member is interposed between the ceramic head and the casting metal piston body.

Ceramic insert cast piston

Polycrystalline spinel sintered body consisting mainly of Al.sub.2 O.sub.3 and MgO in a molar ratio of Al.sub.2 O.sub.3 /MgO of ranging from 0.52/0.48 to 0.70/0.30 and containing 0.001-0.1% by weight of LiF has a high in-line transmission. The sintered body can be obtained by calcining a powdery mixture of Al.sub.2 O.sub.3 and MgO in a specifically limited molar ratio, molding the calcined mixture into a shaped article together with a specifically limited amount of LiF, and firing the shaped article under a specifically limited temperature condition.

Growing community of inventors

Nagoya, Japan

Issei Hayakawa