Ngk Spark Plug Company, Limited

Yo Tajima

Masakazu Watanabe

Satoshi Iio

Jun Otsuka

Kenichi Mizuno

Kenji Nakanishi

Kazuhiro Urashima

Ken-ichi Mizuno

An aluminum oxide based sintered body and a method for manufacturing the same are disclosed. The aluminum oxide based sintered body is composed of silicon compounds in particulate form of from about 5 to about 40 mole %, calculated as a carbide, which is present along grain boundaries as a silicon-containing glass, at least one metal or metal compound of from 0.5 to about 20 mole %, calculated as metals, selected from Ti, Nb, Ta, Cr and Mo, and the remainder of Al.sub.2 O.sub.3, and the molar ratio of the metals with respect to the silicon compounds, calculated as a carbide, is about 4 or less.

Aluminum oxide based sintered body

An aluminum oxide based sintered body and a method for manufacturing the same are disclosed. The aluminum oxide based sintered body is composed of silicon compounds of from about 5 to about 40 mole %, calculated as a carbide, at least one metal or metal compound of from 0.5 to about 25 mole %, calculated as metals, selected from Ti, Nb, Ta, Cr and Mo, and the remainder of Al.sub.2 O.sub.3, and a molar ratio of the metals with respect to the silicon compounds, calculated as a carbide is about 4 or less.

Method for manufacturing an aluminum oxide sintered body

A silicon nitride sintered product for use in cutting tools and the like which has silicon nitride as a predominant phase, and comprises 0.1 to 1% by weight of Al as calculated on the basis of Al.sub.2 O.sub.3, the total amount of sintering aid constituents other than Al being 6% by weight or less on the oxide basis, the content of the grain boundary glassy phase being 8% by volume or less. The silicon nitride sintered product preferably has a relative density of 99% or more.

Silicon nitride sintered product excellent in wear resistance

An aluminum oxide-based sintered object having excellent abrasion resistance includes .alpha.-aluminum oxide, a silicon compound and a tungsten compound, wherein the silicon compound and the tungsten compound are present in amounts based on starting amounts of SiC and W metal of from 5 to 40 mole % and from 0.5 to 25 mole %, respectively, based on the sintered object overall, with a W/SiC molar ratio of 4 or less, and in which particles of at least one of tungsten carbide and tungsten silicide having an average particle diameter of 0.5 .mu.m or less are dispersed as a crystalline phase.

Aluminum oxide-based sintered object and process for producing the same

Silicon nitride base sintered body consists of: 1 to 20 wt % (as oxides) of at least one of rare earth elements; 0.5 to 8 wt % of V (as V.sub.2 O.sub.5); 0.5 to 8 wt % (as oxides) of at least one of Nb, Ta, Cr, Mo and W; sum of the Va and VIa group elements according to the Periodic Table of the International Version (as oxides) being 1 to 10 wt %; and balance silicon nitride. It has high strength of 690-880 MPa (70-90 kgf/mm.sup.2) and high oxidation resistance both at 1350.degree. C. It is produced by 2 stage gas-pressure sintering in pressurized N.sub.2 atmosphere, primarily at 1700.degree.-1900.degree. C. at 1 MPa (10 atm) or less and secondarily at 1600.degree.-1900 C. at 10 MPa (100 atm) or above.

Silicon nitride sintered body and method for producing same

A sintered body of silicon nitride having high strength, toughness and oxidation resistance consists essentially of, by weight percentages, 0.5 to 7.0% of a Mg component calculated as MgO, 0.5 to 7.0% of a Zr component calculated as ZrO.sub.2, 0.5 to 10.0% of a Ce component calculated as CeO.sub.2, and the balance being Si.sub.3 N.sub.4. The sum of Mg, Zr and Ce components calculated as oxides is 3 to 20% by weight. This product is suitable for engine parts or cutting tools.

Silicon nitride sintered body

A sintered silicon nitride product comprises from 72 to 98% by weight of silicon nitride, from 1 to 8% by weight of vanadium pentoxide, and from 1 to 20% by weight of one or more oxides of rare earth elements. The vanadium pentoxide and the oxide of rare earth elements accelerate the densification of the sintered product, and provide high strength at high temperature as well as excellent oxidation resistance to the sintered product.

Sintered silicon nitride products

A silicon nitride sintered product comprises, in % by weight, 1 to 10% Mg, calculated as MgO, 1 to 10% Zr, calculated as ZrO.sub.2, 0.1 to 2.0% of at least one of Al, calculated as Al.sub.2 O.sub.3, Li, calculated as Li.sub.2 O, and Na, calculated as Na.sub.2 O, and the remainder being Si.sub.3 N.sub.4 and unavoidable impurities.

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Nagoya, Japan

Yo Tajima