This paper describes the results of the determination of some thermal and structural parameters of glasses from the Cu_{x}(As_2Se_3)_{100-x} system for x=0, 1, 5, 10 and 15 at.%. Based on the differential scanning calorimetry curves taken at different heating rates, glass transition temperature T_{g}, onset temperature of crystallization T_{onset}, and melting temperature T_{m} of crystalline units formed are determined. The values of activation energy E_{g} of glass transition process are calculated. These characteristic temperatures served as the basis for the calculation of the parameters of thermal stability of the glasses towards crystallization.
Glass-ceramic materials were developed from gabbro including MgO and Al_2O_3 additives. Heat treatments for phase transformation from glassy matrix to glass-ceramic were carried out at 1000C for 3 h. X-ray diffraction studies conducted on the glass-ceramic samples revealed that the phases formed in the glass-ceramics were cordierite, anorthite, diopsitic augite, forsterite and andesine. Glass and glass-ceramic materials were tested for wear properties against a harder alumina counterface using by a ball-on-disc tribometer at dry sliding condition. Wear tests were realized under the loads of 2.5, 5, and 7.5 N and at the sliding speeds of 0.1, 0.2, and 0.3 m/s. Wear rate of the glass and glass-ceramics ranged from 7.324 × 10^{-7} and 2.150 × 10^{-3}-9.971 × 10^{-7} and 4.982 × 10^{-5} mm^3/m, respectively. It was shown that the crystallization treatment caused the decrease of wear rate.
Thermal properties of glasses from the system Ag_x(As_{40}S_{30}Se_{30})_{100-x} for x=0, 0.5, 1, 3, and 5 at.% were investigated by differential scanning calorimetry. The DSC curves were obtained under non-isothermal conditions which allowed determination of the glass transition temperature T_{g} (onset temperature), crystallization temperature T_{p} (corresponding to the crystallization peak maximum), melting temperature T_{m}, crystallization enthalpy H_{c}, and melting enthalpy H_{m}. The DSC curves obtained at the same heating rate were analyzed in order to study the variation of glass transition temperature with Ag concentration. Observed T_{g} shift toward higher values, with increase in the heating rate, is in agreement with the Lasocka equation. Samples with 3 at.% and 5 at.% Ag were further thermally treated at different heating rates with the aim of analyzing kinetic processes of crystallization. The Moynihan and Kissinger models were used to calculate the activation energy of glass transition and activation energy of crystallization. For the samples that showed the crystallization processes an assessment of the thermal stability was done based on different criteria.
2,2-dimethylbutan-1-ol, known as neohexanol, was studied by adiabatic calorimetry and dielectric spectroscopy. Details of complex solid state polymorphism and relaxational dynamics were identified and described. System of phases of neohexanol was found to be monotropic with three orientationally disordered crystalline phases besides isotropic liquid and ordered crystal. Moreover, two subsequent glass transition anomalies of heat capacity C_{p}(T) were detected on heating in one of the supercooled orientationally disordered crystalline phases. Thermodynamical properties of neohexanol are described in relation to the dielectric relaxation processes found.
In the current study, the effect of boron waste addition on some properties of fly ash based glass and glass-ceramics were investigated. The powder compositions including 10, 30, and 50 wt% boron waste was prepared. All the investigated compositions were melted at 1500C by using electrical furnaces. Melting structures were cast into the graphite mold. Thus, fly ash-boron waste based glass materials were produced. To transform the glass-ceramic, crystallization process was performed. Crystallization and glass-transition temperatures were determined by differential thermal analysis. Highly dense and crystalline materials, predominantly composed of diopside and augite together with tincalconite and residual glassy phase, were detected by X-ray diffraction analysis after heat treatment at 800, 900, and 1000C for 1 h. For the glass and glass-ceramic samples, mechanical tests such as hardness and fracture toughness were realized. A boron waste addition has a positive effect on the hardness of the specimens unlike the fracture toughness results. Furthermore, produced glass-ceramic materials were characterized via scanning electron microscopy.
In this study, we reveal the crystallography, crystallinity, and amorphization of low-dimensional crystals of the topological insulator and phase change material Sb₂Te₃ within both discrete and bundled single walled carbon nanotubes with a diameter range spanning 1.3-1.7 nm by a combination of electron diffraction, aberration-corrected high resolution imaging, and variable dose electron beam irradiation. We further reveal that electron diffraction indicates that the crystallinity of the host single walled carbon nanotubes is largely unaffected by this process indicating that mass loss during the observed in situ glass transition had not occurred and that the template had maintained its structural integrity. Such a transition would not be possible with any other common nanoporous template for which the pores would be enlarged due to likely sintering.
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