Abstract: High purity 2,4'-dihydroxydiphenylsulfones useful as developers for thermal recording paper can be produced efficiently and with high selectivity by reacting one or more phenols and sulfuric acid in the presence as of at least one of phosphonic acid, phosphinic acid and salts thereof, in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130.degree. to 200.degree. C., and then purifying the thus-produced crude 2,4'-dihydroxydiphenylsulfones using a mixed solvent containing (1) 5 to 20 weight % of at least one lower aliphatic alcohol and 95 to 80 weight % of at least one aromatic hydrocarbon which does not contain halogen, (2) 10 to 40 weight % of at least one ketone and 90 to 60 weight % of at least one aromatic hydrocarbon which does not contain halogen or (3) 10 to 40 weight % of at least one ester of acetic acid and 90 to 60 weight % of at least one aromatic hydrocarbon which does not contain halogen.

Abstract: A light emitting diode of silicon carbide having a p-n junction comprising an n-type layer doped with donor impurities, a first p-type layer doped with acceptor impurities, and a second p-type layer doped with acceptor impurities and donor impurities. The first p-type layer has a thickness less than the diffusion length of electrons having flowed from the n-type layer. In this way, the first p-type layer effects light emission related to the acceptor impurities which recombine with the electrons having flowed from the n-type layer, and the second p-type layer effects light emission by donor-acceptor pairs which recombine with the electrons having flowed from the n-type layer.

Abstract: This invention is a multi-layer pn type silicon carbide light emitting diode. A first n-type silicon carbide layer is deposited on an n-type substrate. The first n-type silicon carbide layer has an electron concentration larger than 1.times.10.sup.15 cm.sup.-3 and smaller than the electron concentration of the substrate and has a thickness of between 0.1 to 20 .mu.m. A second n-type silicon carbide layer is disposed over the first n-type layer. A first p-type silicon carbide layer is disposed on the second n-type layer to form a PN junction layer.

Abstract: A sintered titanium boride ceramic body consists essentially of a matrix having a three-dimensional net-work structure and consisting essentially of TiC and at least one MB selected from transition metals in a mixing crystals and solid solutions condition, TiB.sub.2 particles separately placed in the matrix, and a grain boundary formed in the periphery of each of the TiB.sub.2 particles. The grain boundary is in a mixing crystals and solid solutions condition of TiB.sub.2 and M boride. M denotes a metal.

Abstract: A sintered metal boride ceramic body consists essentially of: a metal boride matrix consisting essentially of MB or MB.sub.2 and TiC in a and solid solution and TiB.sub.2 particles dispersed in the metal boride matrix, wherein M denotes a metal such as Ni and Cr.

Abstract: A sintered metal boride ceramic body manufactured by mixing 75-99 wt. % of TiB.sub.2 powder with 1-25 wt. % in total of Ni powder and C powder to thereby make a mixture, shaping the mixture together with a binder to thereby make a shaped ceramic body, and firing the shaped ceramic body in a non-oxidizing atmosphere.

Abstract: A method for manufacturing a metal boride ceramic material, includes mixing metal boride powder with 1-20 wt. % metal powder and 0.1-10 wt. % carbon powder, shaping the mixture and firing it. Alternatively, the metal boride powder may be mixed with 0.1-89 wt. % metal carbide powder thereby make a mixture, followed by shaping the mixture and firing it.

Abstract: A fuel supplied through a fuel feed bore of a burner plug and a spray medium supplied through spray medium feed holes thereof are mixed initially in primary mixing chambers in a burner plate and further mixed in a secondary mixing chamber in a burner tip and the fuel mixture thus obtained is sprayed through spray holes of the burner tip. Each of the primary mixing chambers is inclined at a predetermined angle relative to the axis of the burner plate so that the fuel mixture is caused to swirl in a secondary mixing chamber; or the burner plate and the burner tip are so interconnected to each other that the extension of the axis of each primary mixing chamber in the burner plate intersects substantially the midpoint between the adjacent spray holes of the burner tip and consequently the fuel mixture discharged from the primary mixing chambers impinges on the inner wall of the secondary mixing chamber in the burner tip, whereby the ability to atomize a slurry fuel is improved.

Abstract: Silicon nitride whiskers having a long fiber length in which .beta. type silicon nitride is well developed are produced by reacting a mixture of silica, carbon and cryolite in the specific molar ratio in a mixed gas atmosphere of N.sub.2 and NH.sub.3 by heating the mixture at a temperature of 1,250.degree.-1,450.degree. C. Kira of a ceramic industry waste may be used in place of silica and in this case N.sub.2 alone is used as a nitriding atmosphere.

Abstract: In the production of fibrous potassium titanate by the hydrothermal reaction of a mixture of a tetravalent titanium compound and a potassium compound in an aqueous alkaline solution at a high temperature under a high pressure, the hydrothermal reaction is carried out in the presence of at least one member selected from the group consisting of compounds of titanium having less than four valencies, metallic titanium and mixtures thereof, while removing a part of water formed during the reaction from the reaction system.