Bismuth-antimony, density

In this study 99.999% purity bismuth, antimony and tellurium powdered elements were used as starting materials. Hot pressing method was chosen as a sintering process. Hot pressing conditions were 753K, 400kgf/cm, for one hour. Typical sizes of hot-pressed specimen were 1 Omm( ) X 5mm and sliced into 1mm thick disk specimen. The density of specimen measured by Archimedes method were more than 98% of the ideal value. 

The physical properties of bismuth, summarized ia Table 1, are characterized by a low melting poiat, a high density, and expansion on solidification. Thermochemical and thermodynamic data are summarized ia Table 2. The soHd metal floats on the Hquid metal as ice floating on water. GaUium and antimony are the only other metals that expand on solidification. Bismuth is the most diamagnetic of the metals, and it is a poor electrical conductor. The thermal conductivity of bismuth is lower than that of any other metal except mercury. 

If one looks along the strip in the direction of the current, with the magnetic lield directed downward, then, with si rips of antimony, cohall, zinc, or iron, the electric potential drop is toward the right and the effect is said to he positive. With gold, silver, platinum, nickel, bismuth, copper, and aluminum, it is toward the left, and Ihe effect is called negative. The transverse electric potential gradient per anil magnetic lield intensity per unit current density is called the Hall coefficient" for the metal in question Thus, the Hall coeflicienL is delined us... 

Many studies on the direct reaction of methyl chloride with silicon-copper contact mass and other metal promoters added to the silicon-copper contact mass have focused on the reaction mechanisms.7,8 The reaction rate and the selectivity for dimethyldichlorosilane in this direct synthesis are influenced by metal additives, known as promoters, in low concentration. Aluminum, antimony, arsenic, bismuth, mercury, phosphorus, phosphine compounds34 and their metal complexes,35,36 Zinc,37 39 tin38-40 etc. are known to have beneficial effects as promoters for dimethyldichlorosilane formation.7,8 Promoters are not themselves good catalysts for the direct reaction at temperatures < 350 °C,6,8 but require the presence of copper to be effective. When zinc metal or zinc compounds (0.03-0.75 wt%) were added to silicon-copper contact mass, the reaction rate was potentiated and the selectivity of dimethyldichlorosilane was enhanced further.34 These materials are described as structural promoters because they alter the surface enrichment of silicon, increase the electron density of the surface of the catalyst modify the crystal structure of the copper-silicon solid phase, and affect the absorption of methyl chloride on the catalyst surface and the activation energy for the formation of dimethyldichlorosilane.38,39 Cadmium is also a structural promoter for this reaction, but cadmium presents serious toxicity problems in industrial use on a large scale.41,42 Other metals such as arsenic, mercury, etc. are also restricted because of such toxicity problems. In the direct reaction of methyl chloride, tin in... 

Shutov et al. carried out density functional theory (DFT) calculations on E[N(SiMe3)CH2CH2]3N (E = P, Sb, Bi) up to the PBE level of theory <2002IC6147>. The structural data obtained from geometry optimization on antimony and bismuth derivatives reproduced experimental trends, that is, a decrease in the Ndat-E distance from Sb to Bi. The values of electron density in Ndat-E critical point and the Laplacian of charge density for the azabismatrane indicated that a closed-shell interaction existed between Bi atom and Ndat atom. 

A final possibility is that of a semimetal. In this case, there is a zero density of states at the Fermi level, but no band gap. Semimetals differ from semiconductors in that their resistivities have a metallic-like temperamre dependency. Semimetals include selenium, bismuth, arsenic, graphite, and antimony. All of these types of behaviors are illustrated schematically in Figure 6.2, which shows the simplified band picmre and the corresponding DOS for each case. 

The influence of antimony, arsenic and bismuth on the reversibility of the PAM structure has been studied via cycling of cylindrical tubular electrodes filled with PAM powder to a density of 4.15 g cm [47,48]. Current collectors (spines) of Pb or Pb—6.0 wt% Sb alloy are used. Figure 4.22 illustrates the effect of Sb , As and Bi ions in the electrolyte on the specific capacity of the tubular electrodes during the first 20 cycles. 

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