Thermally reversing window in Ge15Te85 − xInx glasses: Nanoindentation and micro-Raman studies

Nanoindentation studies on Ge₁₅Te_85 ? xIn_x glasses indicate that the hardness and elastic modulus of these glasses increase with indium concentration. While a pronounced plateau is seen in the elastic modulus in the composition range 3 ≤ x ≤ 7, the hardness exhibits a change in slope at compositions x = 3 and x = 7. Also, the density exhibits a broad maximum in this composition range. The observed changes in the mechanical properties and density are clearly associated with the thermally reversing window in Ge₁₅Te_85 ? xIn_x glasses in the composition range 3 ≤ x ≤ 7. In addition, a local minimum is seen in density and hardness around x = 9, the chemical threshold of the system. Further, micro-Raman studies reveal that as-quenched Ge₁₅Te_85 ? xIn_x samples exhibit two prominent peaks, at 123 cm^? 1 and 155 cm^? 1. In thermally annealed samples, the peaks at 120 cm^? 1 and 140 cm^? 1, which are due to crystalline Te, emerge as the strongest peaks. The Raman spectra of polished samples are similar to those of annealed samples, with strong peaks at 123 cm^? 1 and 141 cm^? 1. The spectra of lightly polished samples outside the thermally reversing window resemble those of thermally annealed samples; however, the spectra of glasses with compositions in the thermally reversing window resemble those of as-quenched samples. This observation confirms the earlier idea that compositions in the thermally reversing window are non-aging and are more stable.     

B-Alkylation and Arylation of [(η5-C5Me5Mo)2B5H9]: Synthesis and Characterization of Isomeric [(η5-C5Me5Mo)2B5H9-nRn] (When R = n-Bu, n = 2, 1; R = Ph, n = 2, 1)

Abstract  Reaction of [(η⁵-C₅Me₅Mo)₂B₅H₉], 1 with 5-fold excess of n-BuLi at −70 °C followed by excess of RI (R = n-Bu or Ph) at room temperature yielded B-R inserted metallaboranes [(η⁵-C₅Me₅Mo)₂B₅H₈R] (2: R = n-Bu, 5: R = Ph), [(η⁵-C₅Me₅Mo)₂B₅H₇R₂] (3, 4: R = n-Bu; 6, 7: R = Ph). Isolated yields of mono-alkyl/arylated species are better than di-alkyl/arylated ones. All the new cluster compounds have been characterized by IR, ¹H, ¹¹B, ¹³C NMR and mass spectroscopy as simple substitution derivatives of [(η⁵-C₅Me₅Mo)₂B₅H₉] and the structural types of one of these species, 2 was established by X-ray crystallographic analysis. Graphical Abstract  Reaction of [(η⁵-C₅Me₅Mo)₂B₅H₉], with 5-fold excess of n-BuLi at −70 °C followed by excess of RI (R = n-Bu or Ph) at room temperature yielded B-R inserted metallaboranes [(η⁵-C₅Me₅Mo)₂B₅H_9-nR_n] (When R = n-Bu, n = 2, 1; R = Ph, n = 2, 1).      

ChemInform Abstract: Origin of the Unusual Stability of B12 and B13+ Clusters.

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