The erosion rates and mechanisms are discussed for several materials in contact with molten silicon near its melting point. Vitreous materials, e.g., vitreous carbon and fused silica, behave similarly and erode primarily by dissolution. Pressed‐powder materials, e.g., silicon carbide and silicon nitride, degrade by a combination of dissolution and particulate erosion (intergranular corrosion).
The fundamental properties of the absorption spectra of KBr:Pb2+ crystals have been studied at various temperatures from the liquid helium range to room temperature. The observed absorption bands are assigned to the so-called A, B, C, and D' bands by analogy with the absorption bands of other s2-configuration ions in alkali halide crystals. The B, C, and D ' bands overlap but have been resolved into their components by nonlinear least squares analysis. A discussion is given of the energy separation between the B and C bands in Sn2+-, TI+-, and Pb2+-doped alkali halide crystals.Les proprietCs fondamentales des spectres d'absorption des cristaux de KBr:Pb2+ ont Ct C Ctudites, pour diverses tempiratures allant de la region de I'helium liquide jusqu'i la temperature ambiante. Les bandes d'absorption observCes sont identifiees avec les bandes dites A, B, C et D', par analogie avec les bandes d'absorption de d'autres configurations s 2 d'ions dans des cristaux d'haloginures alcalins. I1 y a superposition entre les bandes B, C et D'; les composantes peuvent cependant &tre sCparCes par un calcul non-linCaire de moindres carres. On prCsente une discussion de la separation en Cnergie des bandes B et C dans des cristaux d'halogenures alcalins dopis avec SnZ+, TI+ et Pb2+.[Traduit par le journal]Can.
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