2.11.2.1 Introduction

Apart from its use as a neutron reflector and modera­tor in nuclear reactors, beryllium is in strong demand for use in X-ray windows of medical and industrial equipment, acoustic speaker diaphragms, galvano mir­rors for laser drilling, reflected electron guard plates in semiconductor production equipment, and various other applications. It is also widely used in the electri­cal and electronic industry, particularly in beryllium — copper alloys for wrought metal production and for molds and other forging tools and dies. In electronics, in particular, the need for beryllium has been growing rapidly in recent years with the trend toward lighter, thinner, and smaller electronic components. In the following sections, we outline the methods of its pro­duction and processing and discuss its basic properties.

2.11.2.2 Production and Processing Methods1

Among the 30 or so naturally occurring ores, the most economically important is beryl, which contains 10-14% beryllium oxide (BeO). At present, the two main industrial processes used to extract BeO from beryl are the fluoride method and the sulfuric acid method. Both of these yield BeO of industrial-grade purity, which is used as a raw material for Be-Cu mother alloys, electronics manufacture, refractories, and other fields of application. For use in nuclear reactors, BeO is further purified by recrystallization or precipitation.

Metallic beryllium (Be) is produced from BeO or Be(OH)2 by either of two industrial processes. One involves the formation of BeF2 followed by its ther­mal reduction with Mg to produce Be pebbles, and the other involves the formation of BeCl2 followed by its electrolysis to produce Be flakes. The resulting pebbles and flakes are high in Mg and Cl2 content, respectively, and these impurities are removed by vacuum melting.

The principal techniques of Be processing are molding by powder metallurgy, warm or hot working, and joining or welding. In hot-press sintering, which has been widely developed for Be molding, the start­ing material is commonly —200 mesh Be powder, which is inserted between graphite dies and then pressure molded in vacuum at high temperatures (1323 K). The resulting moldings are commonly called ‘hot-press blocks,’ and can be obtained with high integrity and near theoretical density. Other molding methods that may be employed include spark plasma sintering and cold-press sintering.

Cold working of Be at room temperature is extremely difficult because of its low elongation, and it is accordingly formed into plates, rods, or tubes by ‘warm working’ at 773-1173 Kor ‘hot work­ing’ at 1273-1373 K. In either case, the Be must be covered with mild steel or some other material and the intervening air withdrawn before it is heated, as it readily oxidizes at high temperatures.

Various methods have been developed for Be join­ing and welding. These include mechanical joining and resin bonding, electron-beam and diffusion weld­ing, and brazing and soldering. Because of its high oxygen affinity, however, any process in which the Be is heated must be performed under an appropriate inert gas or vacuum.