Oxide beryllium

Beryllium Oxide and Oxides with the Wurtzite Structure 

Early studies on BeO single crystals by Bentle and Miller [51] identified four slip systems basal slip, (0001)(1120) prismatic slip, 1100 (1120) and 1100 [0001] and pyramidal slip, Il22 (1123). Not surprisingly, significant plastic anisotropy was found. At 1000 °C, the yield stresses for these systems were as follows 35 MPa for basal slip 49 and llOMPa for prismatic slip along (1120) and [0001], respectively and 250 MPa for pyramidal slip. More recent studies on creep deformation in BeO 

By way of contrast, temperatures of 1650 to 1850 °C had to be used for samples compressed along [1100] and [000Ij. Although most of the [1100] samples buckled, it was possible to determine a creep rate of 7.2 x 10 s for one sample at a stress of 50 MPa at 1650°C, and this increased to 1.6 x 10 s for a stress of 100 MPa. Fora [OOOlj-orientedsample, an upper boundforthecreeprateof 1.7 x 10 s atl750°C and 100 MPa could be determined. 

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. 

Typical application fields are casting molds for molded vanadium components, crucibles for high frequency induction furnaces and substrates for integrated circuits. In nuclear reactor technology beryllium oxide is mixed with nuclear fuel as a moderator for fast neutrons. 

Beryllium oxide (BeO, beryllia) is the only material apart from diamond which combines high thermal-shock resistance, high electrical resistivity, and high thermal conductivity at a similar level. Hence its major application is in heat sinks for electronic components. BeO is highly soluble in water, but dissolves slowly 

Mechanical properties Symbol Units Beryllium oxide, dense 

Zirconium dioxide (Zr02), commonly called zirconium oxide, forms three phases, with a monoclinic, a tetragonal, and a cubic crystal structure. Dense parts may be obtained by sintering of the cubic or tetragonal phase only. In order to stabilize the cubic phase, stabilizers such as MgO, CaO, Y2O3, and Ce02 are added. 

An important class of zirconium dioxide ceramics is known as partially stabilized zirconia (PSZ), 

INTRODUCTION This data sheet contains information for single crystal beryllium oxide. 

MECHANICAL PROPERTIES, (298 K) Young s Modulus, (psi) 53 x 10 Hardness, (Knoop) 

---

These ion lasers are very inefficient, partly because energy is required first to ionize the atom and then to produce the population inversion. This inefficiency leads to a serious problem of heat dissipation, which is partly solved by using a plasma tube, in which a low-voltage high-current discharge is created in the Ar or Kr gas, made from beryllium oxide, BeO, which is an efficient heat conductor. Water cooling of the tube is also necessary. 

It had beryllium oxide [1304-56-9] BeO, moderator and nickel tubes, through which ran a molten salt fuel consisting of fluorides of Na, Be, and U. 

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. 

Inhalation of certain fine dusts may constitute a health hazard. Eor example, exposure to siUca, asbestos, and beryllium oxide dusts over a period of time results ki the potential risk of lung disease. OSHA regulations specify the allowable levels of exposure to kigestible and respkable materials. Material Safety Data Sheets, OSHA form 20, available from manufacturers, provide information about hazards, precautions, and storage pertinent to specific refractory products. 

Beryllium Carbide. Beryllium carbide [506-66-17, Be2C, maybe prepared by heating a mixture of beryllium oxide and carbon to 1950—2000°C,... 

Beryllium carbide slowly hydroly2es to beryllium oxide and methane in the presence of atmospheric moisture although months may be requited to complete the reaction. Any carbon contained in beryllium metal is present as the carbide because the solubiUty of carbon in beryllium is extremely low. 

Beryllium Nitrate. BeryUium nitrate tetrahydrate [13516-48-0], Be(N02)2 4H2O, is prepared by crystallization from a solution of beryUium hydroxide or beryllium oxide carbonate in a slight excess of dilute nitric acid. After dissolution is complete, the solution is poured into plastic bags and cooled to room temperature. The crystallization is started by seeding. Crystallization from more concentrated acids yields crystals with less water of hydration. On heating above 100°C, beryllium nitrate decomposes with simultaneous loss of water and oxides of nitrogen. Decomposition is complete above 250°C. 

Beryllium Oxide. Beryllium oxide [1304-56-9], BeO, is the most important high purity commercial beryllium chemical. In the primary industrial process, beryllium hydroxide extracted from ore is dissolved in sulfuric acid. The solution is filtered to remove insoluble oxide and sulfate impurities. The resulting clear filtrate is concentrated by evaporation and upon cooling high purity beryllium sulfate, BeSO 4H20, crystallizes. This salt is... 

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. 

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

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. 

Refractories for Electric Reduction Furnaces. Carbon hearth linings are used in submerged-arc, electric-reduction furnaces producing phosphoms, calcium carbide, all grades of ferrosilicon, high carbon ferrochromium, ferrovanadium, and ferromolybdenum. Carbon is also used in the production of beryllium oxide and beryllium copper where temperatures up to 2273 K ate requited. 

Beryllium oxides Baghouses or high-efficiency particulate air (HEPA) filters... 

Beryllium oxide dust Baghouses and HEPA filters... 

Staeking faults and sometimes proper polytypism are found in many inorganic compounds - to pick out just a few, zinc sulphide, zinc oxide, beryllium oxide. Interest in these faults arises from the present-day focus on electron theory of phase stability, and on eomputer simulation of lattice faults of all kinds investigators are attempting to relate staeking-fault concentration on various measurable character-isties of the compounds in question, such as ionicity , and thereby to cast light on the eleetronic strueture and phase stability of the two rival structures that give rise to the faults. 

Chemical Reactivity - Reactivity with Water Reacts vigorously as an exothermic reaction. Forms beryllium oxide and hydrochloric acid solution Reactivity with Common Materials Corrodes most metals in the presence of moisture. Flammable and explosive hydrogen gas may collect in confined spaces Stability During Transport Stable Neutralizing Agents for Acids and Caustics Flush with water and rinse with dilute solution of sodium bicarbonate or soda ash Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

Fire Hazards - Flash Point Not pertinent. This is a combustible solid Flammable Limits in Air (%) Not pertinent Fire Extinguishing Agents Graphite, sand, or any other inert dry powder Fire Extinguishing Agents Not To Be Used Water Special Hazards of Combustion Products Combustion results in beryllium oxide fumes whieh are toxic to inhalation Behavior in Fire Powder may form explosive mixture in air Ignition Temperature (deg. F) Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

Water as an impurity is known to promote the breakaway corrosion of a number of metals in addition to iron in CO2 the effect has been reported for magnesium (hydrocarbons have more effect on the oxidation of this metal), beryllium, zirconium and sodium. In the latter case water is known to convert the oxide to deliquescent NaOH but acceleration of beryllium oxidation probably results from hydride formation and mechanical damage to the oxide. 

In its general corrosion behaviour, beryllium exhibits characteristics very similar to those of aluminium. Like aluminium, the film-free metal is highly active and readily attacked in many environments. Beryllium oxide, however, like alumina, is, a very stable compound (standard free energy of formation = —579kJ/mol), with a bulk density of 3-025g/cm as compared with 1 -85 g/cm for the pure metal, and with a high electronic resistivity of about 10 flcm at 0°C. In fact, when formed, the oxide confers the same type of spurious nobility on beryllium as is found, for example, with aluminium, titanium and zirconium. 

The possible employment of beryllium in nuclear engineering and in the aircraft industry has encouraged considerable investigation into its oxidation characteristics. In particular, behaviour in carbon dioxide up to temperatures of 1 000°C has been extensively studied and it has been shown that up to a temperature of 600°C the formation of beryllium oxide follows a parabolic law but with continued exposure break-away oxidation occurs in a similar fashion to that described for zirconium. The presence of moisture in the carbon dioxide enhances the break-away reaction . It has been suggested that film growth proceeds by cation diffusion and that oxidation takes place at the oxide/air interface. ... 

Dry hydrogen chloride gas readily attacks solid beryllium above about 500° C with the formation of volatile beryllium chloride. Beryllium carbide and nitride are similarly attacked, but not beryllium oxide this behaviour is of use in one method for the determination of beryllium-oxide in metallic beryllium. 

Determination of beryllium by precipitation with ammonia solution and subsequent ignition to beryllium oxide Discussion. Beryllium may be determined by precipitation with aqueous ammonia solution in the presence of ammonium chloride or nitrate, and subsequently igniting and weighing as the oxide BeO. The method is not entirely satisfactory owing to the gelatinous nature of the precipitate, its tendency to adhere to the sides of the vessel, and the possibility of adsorption effects. 

---