Beryllides

Beryllides with less Be have simpler structures, e.g. the Laves phases MBe2 with M = Cr, Mo, or Fe with a C14 structure and M = Ti, Nb, or Ta with a Cl5 structure (see Sec. 8.1), the B2 phases NiBe and TiBe (see Sec. 4.4), or the A15 phase MojBe (see Sec. 7.1). Basic data can be found in early compilations (Shaffer, 1964 Samsonov and Vinitskii, 1980). 

The mechanical behavior of these Be-rich phases and its variation with temperature has been studied by means of hardness tests, bending stress-rupture tests, tension tests and compression tests (Ryba, 1967 Marder and Stonehouse, 1988 Fleischer and Zabala, 1990 c Nieh and Wadsworth, 1990 Bruemmer etal., 1993). The observed brittle-to-ductile transition temperatures are of the order of 1000°C. The low-temperature fracture toughness has been found to be between 2 and 4 MN/m with practically no macroscopic ductility (Bruemmer et al., 1993), though there are indications of local plasticity at 

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Table 1. High Temperature Oxidation Resistant Beryllides...

The beryllides, being intermetaUic compounds, are hard, strong materials which exhibit Httie ductihty at room temperature. Strength properties increase gradually as a function of temperature up to about 870°C, above which a sharp increase in strength occurs, peaking in the region of 1260°C the modulus of mpture values exceed 280 MPa (40,000 psi) at this latter temperature. 

Beryllide system Compound formula CAS Registry Number Melting point, °C X-ray density, a/hi I. Be, wt %... 

The beryllides continue to be of interest for high temperature aerospace applications because of their oxidation resistance, low density, and high strength at elevated temperature (7). The limited strain capacity of the materials, particulady at low temperatures, has thus far prevented actual use. 

CARBIDES-INDUSTRIALHARD CARBIDES] (Vol 4) - [MOLYBDENUM AND MOLYBDENUMALLOYS] (Vol 16) -beryllides of [BERYLLIUM COMPOUNDS] (Vol 4) -catalyst [MALONIC ACID AND DERIVATIVES] (Vol 15) -by-products of copper mining [COPPER] (Vol 7)... 

Neptunium is fairly reactive and forms some interesting compounds. Examples include neptunium dialuminide (NpAl2) and neptunium beryllide (NpBc3). These compounds are unusual because they consist of two metals joined to each other. Normally, two metals do not react with each other very easily. Neptunium also forms a number of more traditional compounds, such as neptunium dioxide (Np02), neptunium trifluoride (Npp3), and neptunium nitrite (NPNO2). 

Be beryllium beryllium (general) Be+, beryllium(l+) Be2+, beryllium(2+) beryllide beryllido... 

Beryllides and Borides. CrBe2 and CrBj have been prepared by the reactive hot-pressing method and studied by X-ray diffraction. The crystal structure of the interstitial boride, CrB j, has been determined. The results suggest that the Cr atom occupies a high symmetry position.The ternary complex boride UCrB has been shown by two independent crystallographic studies to have the YCrB -type structure. ... 

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