Ceramics beryllium oxide

Table 2. Properties of High Purity Beryllium Oxide Ceramics...

Beryllium, beryllium-containing alloys, and beryllium oxide ceramic in solid or massive form present no hazard whatsoever (31). Solid shapes maybe safely handled with bare hands (32) however, 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 the prescribed workplace exposure limits. Inhalation of fine airborne beryllium may cause chronic beryllium disease, a serious lung disease in certain sensitive individuals. However, the vast majority of people, perhaps as many as 99%, do not react to beryllium exposure at any level (33). The biomedical and environmental aspects of beryllium have been summarized (34). 

Beryllium is used in satellite structures in the form of both sheet and extruded tubing and is a very important material for all types of space optics. Beryllium oxide ceramic applications take advantage of high room temperature thermal conductivity, very low electrical conductivity, and high transparency to microwaves in microelectronic substrate applications. 

Beryllium oxide ceramics have technically valuable properties. Their application is limited due to their high price and poisonou,sness... 

Beryllium oxide ceramics exhibit the highest thermal conductivity of all the ceramic products and are the best electrical insulators at high temperatures. Despite these exceptional properties, beryllium oxide ceramics have only found limited application due to their high cost and poisonousness. They are manufactured by sintering dry or plastically pressed fine particulate beryllium oxide at 1400 to 1450°C in a hydrogen atmosphere. 

Beryllia Beryllium monoxide Beryllium oxide Beryllium oxide (BeO) Bromellete CCRIS 83 EINECS 215-133-1 Gluoina HSDB 1607 Natural bromellite Thermalox Thermalox 995. Used in manufacture of beryllium oxide ceramics, glass in nuclear reactor fuels and moderators electrically resistive catalyst for organic reactions. Electrical conductor but thermal insulator. Light amorphous powder mp = 2530 very sparingly soluble in H2O. 

The aqueous beryllium sulfate is separated from the solids by counter-current decantation thickener operations. A beryllium concentrate is produced by a counter-current solvent extraction process (Maddox and Foos 1966). This concentrate is stripped of its beryllium content with aqueous ammonium carbonate. By heating to 70 °C, aluminum and iron are precipitated and then removed by filtration. Precipitation of beryllium basic carbonate occurs when the solution is heated to 95 °C. The carbonate is filtered, deionized water is added, and heating to 165 °C yields a beryllium hydroxide product which is the common input to beryllium-copper alloy, beryllium oxide ceramics, or pure beryllium metal (Table 2.1-2). 

Uranium beryllium alloy in beryllium oxide ceramic matrix. 

Beryllium is used commercially in three major forms as a pure metal, as an alloy with other metals, and as a ceramic. The favorable mechanical properties of beryllium, e.g., its specific stiffness, have made it a major component for certain aerospace applications in satellites and spacecraft. As a modulator and reflector of neutrons, beryllium is of interest in fusion reactions and for nuclear devices that have defense applications. When a small amount of beryllium is added to copper, the desirable properties of copper (i.e., thermal and electrical conductivity) are kept but the material is considerably stronger. The superior thermal conductivity of beryllium oxide ceramics has made the product useful for circuit boards and laser tubes. A more complete discussion of the applications of beryllium was recently reviewed [2]. 

Cummings KJ, Deubner DC, Day GA, et al. Enhanced preventive programme at a beryllium oxide ceramics facility reduces berylhum sensitisation among new workers. Occup Environ Med 2007 64(2) 134-140. 

Although beryllium oxide [1304-56-9] is in many ways superior to most commonly used alumina-based ceramics, the principal drawback of beryUia-based ceramics is their toxicity thus they should be handled with care. The thermal conductivity of beryUia is roughly about 10 times that of commonly used alumina-based materials (5). BeryUia [1304-56-9] has a lower dielectric constant, a lower coefficient of thermal expansion, and slightly less strength than alumina. Aluminum nitride materials have begun to appear as alternatives to beryUia. Aluminum nitride [24304-00-5] has a thermal conductivity comparable to that of beryUia, but deteriorates less with temperature the thermal conductivity of aluminum nitride can, theoreticaUy, be raised to over 300 W/(m-K) (6). The dielectric constant of aluminum nitride is comparable to that of alumina, but the coefficient of thermal expansion is lower. 

Ceramic-grade beryllium oxide has also been manufactured by a process wherein organic chelating agents (qv) were added to the filtered beryllium sulfate solution. Beryllium hydroxide is then precipitated using ammonium hydroxide, filtered, and carefully calcined to obtain a high purity beryllium oxide powder. 

Beryllium is principally consumed in the metallic form, either as an alloy constituent or as the pure metal. Consequendy, there is no industry associated with beryllium compounds except for beryllium oxide, BeO, which is commercially important as a ceramic material. BeO powder is available at 154/kg in 1991. 

Beryllium Oxide (Bromellite). BeO, mw 25.01, white amorph powd, mp 2530°, bp ca 3900°, d 3.01g/cc. Sol in coned acids and alkalies. V si sol in w. Prepn is by burning BeC03 at 900° in a Pt crucible to the oxide. It is used in nuclear reactor fuels and moderators as well as in powder metallurgy, ceramics, fuel cells and coatings (see above)... 

Beryllium oxide, BeO, is used in place of Si02 or A1203 in performance-sensitive ceramic applications. It is distinguished by having the highest melting point (2507°C) combined with excellent thermal conductivity and poor electrical conductivity. 

Beryllium iodide, 3 663 Beryllium nitrate, 3 664-665 Beryllium nitrate tetrahydrate, 3 664-665 Beryllium nitride, 3 665 Beryllium oxalate, 3 665 Beryllium oxalate trihydrate, 3 665 Beryllium oxide, 3 665-666 5 582 21 491 ceramic insulator, 5 593 energy gap at room temperature,... 

Beryllium oxide shows excellent thermal conductivity, resistance to thermal shock, and high electrical resistance. Also, it is unreactive to most chemicals. Because of these properties the compound has several applications. It is used to make refractory crucible materials and precision resistor cores as a reflector in nuclear power reactors in microwave energy windows and as an additive to glass, ceramics and plastics. 

Beryllium Sulfate. Beryllium sulfate tetrahydrate [7787-56-6], BeS04 4H20, is produced commercially in a highly purified state by fractional crystallization from a beryllium sulfate solution obtained by the reaction of beryllium hydroxide and sulfuric acid. The salt is used primarily for the production of beryllium oxide powder for ceramics. Beryllium sulfate dihydrate [14215-00-0], is obtained by heating the tetrahydrate at 92°C. Anhydrous beryllium sulfate [13510-49-1] results on heating the dihydrate in air to 400°C. Decomposition to BeO starts at about 650°C, the rate is accelerated by heating up to 1450°C. At 750°C the vapor pressure of S03 over BeS04 is 48.7 kPa (365 mm Hg). 

Beryllium sulfate, [CAS 13510-49-1], BeSO 4H2O, is an important salt of beryllium used as an intermediate of high purity for calcination to beryllium oxide powder for ceramic applications. A saturated aqueous solution of beryllium sulfate contains 30.5% BeSC>4 by weight at 303C and 65.2% at 111"C. 

Uses Beryllium (Be) (when pure) is a hard, grayish metal. In nature, beryllium can be found in compounds in mineral rocks, coal, soil, and volcanic dust. The important compounds of beryllium used in industry are beryllium oxide (BeO), beryllium hydroxide (Be(OH)2), beryllium sulfate (BeS04), and beryllium fluoride (BeF2). Beryllium compounds are commercially mined and purified for use in electrical parts, machine parts, ceramics, aircraft parts, nuclear weapons, and mirrors. Beryllium dust is emitted into the air from burning coal and oil. 

Recognizing the applicability of XRD to occupational health chemistry, Lennox and Leroux (1) suggested a number of chemical species which would be suitable for XRD analysis arsenic trioxide, beryllium oxide, mica, vanadium oxides, calcium fluoride in ceramic materials, as well as a number of organics such as DDT, lindane and chlordane. Unfortunately, the general application of XRD to the quantitation of industrial hygiene samples has not been realized and the majority of these analyses are restricted to free silica and to a lesser extent asbestos and talc. 

The USA consumption of beryllium was ca. 300 t/a Be in 1986. Of the beryllium compounds beryllium oxide is, as a result of its high melting point and its high chemical resistance, utilized for oxide-ceramic materials. 

Oxide ceramics are made from oxides of numerous metals including beryllium, aluminum, calcium, and yttrium these metal-oxide bonds are essentially ionic. 

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