Abstract

Beryllium carbide, Be₂C, may be prepared by heating a mixture of beryllium oxide and carbon to 1950–2000°C. The reaction is accompanied by a substantial exotherm. The melting point of beryllium carbide is 2250–2400 °C. This compound is a potential first-wall material for fusion reactors, one on the very limited list of possible candidates. Beryllium carbonate tetrahydrate , has been prepared by passing carbon dioxide through an aqueous suspension of beryllium hydroxide. The solid beryllium oxide carbonate intermediates are obtained by a laboratory procedure for preparing pure beryllium salt solutions by reaction with aqueous mineral or organic acids. The beryllium salts of organic acids can be divided into normal carboxylates, Be(RCOO)₂, and beryllium oxide carboxylates, Be₄O(RCOO)₆. The latter are prepared by dissolving beryllium oxide, hydroxide, or the oxide carbonate in an organic acid. The properties of the fluoride differ sharply from those of the chloride, bromide, and iodide. Beryllium fluoride is essentially an ionic compound, whereas the other three halides are largely covalent. Beryllium fluoride, BeF₂, is produced commercially by the thermal decomposition of diammonium tetrafluoroberyllate, (NH₄)₂BeF₄. Beryllium hydride, BeH₂, is best prepared by the controlled pyrolysis of di-t-butyl beryllium, C₈H₁₈Be, at 200°C. Interest in beryllium hydride has centered on its potential use as a solid propellant rocket fuel. Beryllium hydroxide, Be(OH)₂, exists in three forms: a slimy, gelatinous beryllium hydroxide, a stable orthorhombic crystalline form, and an orthorhombic modification precipitated from a sodium beryllate solution. Beryllium forms intermetallic compounds, referred to as beryllides, with most metals by a solid-state reaction of the blended powder constituents at about 1270°C. The properties exhibited by some beryllides include excellent oxidation resistance, high strength at elevated temperature, good thermal conductivity. The beryllides continue to be of interest for high temperature aerospace applications. Beryllium nitrate tetrahydrate, , is prepared by crystallization from a solution of beryllium hydroxide or beryllium oxide carbonate in a slight excess of dilute nitric acid. Beryllium nitride, Be₃N₂, is prepared by the reaction of metallic beryllium and ammonia gas at 1100°C. Beryllium oxalate trihydrate, , is obtained by evaporating a solution of beryllium hydroxide or oxide carbonate in a slight excess of oxalic acid. Beryllium oxalate is important for the preparation of ultrapure beryllium hydroxide, used as a standard for spectrographic analysis of beryllium compounds. Beryllium oxide, BeO, is the most important high purity commercial beryllium chemical. High purity beryllium sulfate, is calcined at carefully controlled temperatures selected to give tailored properties of the beryllium oxide powders as required by the individual beryllia ceramic fabricators. High purity beryllium oxide powder is fabricated by classical ceramic-forming processes such as dry pressing, isostatic pressing, extrusion, tape casting, and slip casting. Beryllia ceramics offer the advantages of a unique combination of high thermal conductivity and heat capacity with high electrical resistivity. Beryllium is principally consumed in the metallic form, either as an alloy constituent or as the pure metal. Consequently, there is no industry associated with beryllium compounds except for beryllium oxide, BeO, which is commercially important as a ceramic material. Care must be taken in the fabrication and processing of beryllium products to avoid inhalation of airborne beryllium particulate matter such as dusts, mists, or fumes in excess of prescribed work place limits. Inhalation of fine airborne beryllium may cause chronic beryllium disease, a serious lung disorder, in certain sensitive individuals.