GB931335A - Improvements in or relating to boron phosphide - Google Patents

Abstract

Cubic crystalline boron phosphide may be prepared by reacting together a boron halide, hydride or alkyl compound with a phosphorus halide or hydride in the gas phase at a temperature above 1100 DEG F. Suitable boron compounds are:- BCl3, B Br3, BI3, mixed halides, Me3B, Et3B, tri normal propyl boron, tri iso propyl boron, tri tert butyl boron, ethylated decaborane, diborane, pentaborane, decaborane. In a modification phosphorus and hydrogen may be used with one of the above boron compounds. The proportions are preferably 1-1,5 mols. of phosphorus (calculated as the monatomic form) and from 1,5-5 mols. of hydrogen per each mol. of boron compound. In both cases the process is carried out in a high temperature furnace and the compounds introduced into two separate gas streams to undergo turbulent mining, the temperature being in the range 1600 DEG -2700 DEG F. and the boron phosphide being deposited on the walls of the collecting vessel or as a coating on a metal or graphite surface or on a prototype of molybdenum. The crystalline boron phosphide may be shaped by hot pressing, e.g. at 500-20,000 psig and 1000 DEG -6000 DEG F., or cold pressing, may be diffused into metal or ceramic shapes by packing round the shape and heating to 1500 DEG -6000 DEG F., may be applied as a coating of particles by flame spraying, electrophoresis, or from a slurry, or may be slip cast and subsequently fired. In all cases fluxes and bonding agents may be added, e.g. Cr, Fe, Ni, Co, Nb, Ta, Ti, Zr, W, Mo, Hf, Al2O3, ZrO2, HfO2, SiO2, BeO2, TiO2, ThO2, alkali metal borates or phosphates, boron phosphate or sodium silicate. Porosity may be produced by adding naphthalene, cork or asbestos. The shape or coating may be densified and sintered, and may be subsequently subjected to reduction with H2, where metal oxides are also present, or oxidation. For slurry coating the boron phosphide is dispersed in water with carbonymethyl cellulose. Examples of applications for the resulting temperature and chemical resistant boron phosphide or composition as an article or coating are:-crucibles, missile nose cones, rocket fuel tanks and pump impellers, jet nozzles, Venturi throats, exhaust deflectors, grinding wheels, shaping tools, turbine blades and nozzles, observation windows for furnaces, nuclear reactors, or space ships, burners, agitators, nuclear reactor shields, semi conductors, strengthened metal wear plates, or radiation meters. Porous material may be used as filters or to provide cooling by passage of liquids. Specification 923,860 also is referred to.ALSO:Cubic crystalline boron phosphide may be prepared by reacting together a boron halide, hydride or alkyl compound with a phosphorus halide or hydride (see Group III) at above 1100 DEG F. The crystalline boron phosphide may be shaped by hot pressing, e.g. at 500-20,000 p.s.i. g. and 1000-6000 DEG F., or cold pressing, may be diffused into metal or ceramic shapes by packing round the shape and heating to 1500-6000 DEG F., may be applied as a coating of particles by flame spraying, electrophoresis, or from a slurry, or may be slip cast and subsequently fired. In all cases fluxes and bonding agents may be added e.g. Cr, Fe, Ni, Co, Nb, Ta, Ti, Zr, W, Mo, Hf, Al2O3, ZrO2, HfO2, SiO2, BeO2, TiO2, ThO2, alkali metal borates or phosphates, boron phosphate or sodium silicate. Porosity may be produced by adding naphthalene, cork, or asbestos. The shape or coating may be densified and sintered, and may be subsequently subjected to reduction with H2, where metal oxides are also present, or oxidation. For slurry coating the boron phosphide is dispensed in water with carboxymethylcellulose. Examples of application for the resulting temperature and chemical resistant boron phosphide or composition as an article or coating are:- crucibles, missile nose cones, rocket fuel tanks and pump impellers, jet nozzles, venturi throats, exhaust deflectors, grinding wheels, shaping tools, turbine blades and nozzles, observation windows for furnaces, nuclear reactors or space ships, burners, agitators, nuclear reactor shields, semiconductors, strengthened metal wear plates, or radiation meters. Porous material may be used as filters or to provide cooling by passage of liquids. Specification 923,860 also is referred to.