Showing papers on "Nickel boride published in 1981"

The effect of crystallite size of nickel on the enantioselectivity of modified nickel catalysts.

Abstract: Enantioselective hydrogenation of methyl acetoacetate to methyl 3-hydroxybutyrate with various unsupported nickel catalysts modified by (2R,3R)-tartaric acid was studied under mild conditions in order to elucidate the dependence of the selectivity upon the surface states of the catalysts. The catalyst with the larger crystallite size has the higher enantioselectivity, presumably because of the higher probability to obtain large ensembles of regularlyarranged nickel atoms in the catalyst surface for the modifier to adsorb strongly and regularly. The nickel boride catalyst has very low enantioselectivity, mainly due to its amorphous structure. The detrimental effect of additives (B, P, and Al in Ni–B, Ni–P, and R–Ni catalysts) was explained as the effect of their lowering the crystallinity of the catalysts.

Partial Hydrogenation of Acetylenes on Modified Nickel Boride Catalysts

Abstract: Ni–B catalysts modified with a small amount of copper(II) salt have a higher selectivity than palladium and modified Raney nickel catalysts for partial hydrogenation of phenylacetylene, 1-heptyne, 1-ethynylcyclohexene, and propargyl alcohol.

Manufacture of nickel boride colloid

Abstract: PURPOSE:To obtain nickel boride colloid showing high activity in the hydrogenation of carbonyl group by treating an Ni salt with an alkali metal borohydride in an alcohol in the presence of an alcohol soluble polymer and adding a basic substance. CONSTITUTION:An Ni salt such as NiCl2.6H2O and an alcohol soluble polymer such as polyvinylpyrrolidone are dissolved in an alcohol such as ethanol deoxidized under a nonoxidizing atmosphere, and an alcoholic soln. of an alkali metal borohydride such as sodium borohydride is dropped. An alcoholic soln. of a basic substance such as NaOH or a solid basic substance is then added, and the mixed soln. is agitated to obtain dark brown uniform nickel boride colloid. Using this colloid as a catalyst the hydrogenation reaction of aldehydes, ketones, etc. proceeds rapidly at ordinary temp. and ordinary pressure.

Metal diborideebase super heattresistant material containing titanium boride as binder

Abstract: PURPOSE:To obtain a super heat resistant sintered material having enhanced heat resistance without causing a strength lowering and capable of being used as a material for a cutting tool, etc. by blending a restricted amount of high m.p. titanium boride as a principal binder into a specified metal diboride followed by sintering. CONSTITUTION:0.01-40wt% titanium boride binder is blended into one or more kinds of metal diborides selected from TiB2, CrB2, TaB2, MnB2, MoB2, YB2, VB2, HfB2, NbB2, AlB2 and ZrB2. To the binder may be added 0.001-30% one or more among nickel boride, iron boride, cobalt boride, manganese boride and Ni-P alloy. The blend is then compacted and sintered by heating to obtain a metal diboride-base heat resistant material having superior relative density, hardness, mechanical strength and heat resistance.

Colloidal nickel boride without protective agent and its catalytic activity for olefin hydrogenation

Abstract: A stable dispersion of colloidal nickel boride was prepared from a dilute solution of nickel(II) chloride in ethanol by sodium borohydride reduction in the absence of protective colloid polymers. The colloid is superior to the conventional poly(vinylpyrrolidone)-protected one in the catalytic activity for the hydrogenation of styrenes and unsaturated carbonyl compounds.

Element for fine-mechanical equipment

Abstract: Element for fine-mechanical equipment, which is exposed to severe abrasion and consists of an alloy which contains from 20 to 65% by weight of cobalt, up to 30% of nickel and chromium, and one or more of the metals iron, molybdenum and tungsten, or from 30 to 80% by weight of nickel, up to 25% by weight of chromium and iron, and additions for age-hardening the alloy, the element having an outer layer which is produced by gas-phase boronization, is tough, abrasion-resistant and has a hardness of up to 3600 kp/mm Said outer layer preferably contains cobalt boride and/or nickel boride and/or a boron layer produced thereon by further gas-phase boronization