Papers by Keyword: Crystallographic Structure

Abstract: Polymer blends, particularly those containing Polybutylene terephthalate (PBT) and Polycarbonate (PC), are extensively utilized in various industrial applications due to their favorable mechanical and thermal properties. Enhancing the performance of such blends necessitates an understanding of the relationship between their crystalline structure and wear behavior. This study investigates the correlation between wear characteristics and structural aspects of PBT/PC blends having varying PC content. Additionally, techniques such as X-ray diffraction (XRD) and optical microscopy of the worn-out surface are employed. The findings reveal a strong connection between the wear behavior of PBT/PC blends and their crystallographic structure. This study provides useful insights into the wear mechanism and crystallization behavior of PBT/PC blends. Specifically, it is observed that with increasing PC content in the blends, the wear resistance is influenced by the size of crystallites, wherein smaller crystallites demonstrate a greater ability to withstand abrasive action-induced damage. The wear performance of the PBT/PC blend with 70% PC improves by ~37% as a result of the formation of a semi-orderly chain structure with a smaller crystallite size. A mechanism is also explained herein related to the change in the nature of crystallization of PBT/PC blends with increasing PC content. In conclusion, this study underscores the importance of considering crystallographic structure when assessing the wear behavior of polymer blends such as PBT/PC.

Abstract: The Bi₂(Sn_0.95Mn_0.05)₂O₇ compound existing simultaneously in two polymorphic modifications, namely, orthorhombic and cubic has been synthesized for the first time by solid-phase synthesis. The magnetic, dielectric and electrical properties of the compound have been studied. Anomalies in the temperature dependences of the electrical resistance and magnetic propoties have been found. These features are explained as martensitic phase transitions.

Abstract: The nanostructural characteristics of direct-current magnetron sputter-deposited Ni₄Al alloy films were studied during in situ isothermal annealing in a transmission electron microscope (TEM). An expansion of the lattice by nearly 5% was observed for the synthesized films in their low-thickness and as-deposited state. The lattice size approaches the bulk value when the film thickness increases or after vacuum annealing heat-treatment. The Ni₄Al films have a nanocrystalline structure in which the ordered L1₂ phase appears upon annealing at above 500°C. A grain coalescence trend was found for the Ni₄Al films during the in situ annealing above 500°C. This can be the main reason for the abnormal grain growth of these films at these high temperatures.

Abstract: Commercially available Multiwalled Carbon Nanotubes (MWCNTs) were refluxed with nitric acid in order to improve the density of the acidic surface functional groups. The formation of oxygen containing functional groups may lead to surface enhancement of MWCNTs for further modifications. The crude MWCNTs were refluxed in nitric acid at 100 °C for time ranging between 3 to 24 h. The influence of treatment time on crystalline structure was investigated using X-Ray Diffraction (XRD); the results confirmed that all treated MWCNTs are crystalline. The density of the surface functional groups on treated MWCNTs was examined by Fourier Transform Infrared (FTIR). The FTIR spectrums revealed a strong vibration band at 1739, 1219, 1369 cm^-1 that indicates covalently bound acidic surface functional groups existed on the treated MWCNTs. The amount of acidic groups increased with the reflux time up to 15 h treatment as measured by an acid-base Boehm titration. The vibrational spectroscopy of these functional groups also increased with the increasing reflux time.

Abstract: Polycrystalline samples of Bi₂Sn₂O₇ have been synthesized by conventional solid-state reaction method. According to the X-ray powder diffraction research, our sample co-existing of two polymorphs phases: cubic and rhombic, concurrently. The real dielectric permeability Re (ε) monotonic grows versus temperature and the imaginary dielectric permeability Im (ε) nonmonotonic is increased at the heating. There are maxima at Т=450 K on both temperature dependences Im (ε) and Re (ε) reveal. Anomalies in the temperature dependence of electrical resistivity at temperatures are found and to be correlated with the α→ β structural phase transition temperature.

Abstract: This paper explains the influence of oxygen partial pressure on crystallographic structure, surface morphology and sensing properties of sputtered MoO₃ thin films. The MoO₃ thin films were deposited by DC reactive magnetron sputtering technique on glass substrate at different oxygen partial pressures in the range of 5×10^-5-4×10^-4 mbar. X-ray diffraction (XRD) results showed that all prepared films were polycrystalline of α-MoO₃ stable orthorhombic phase. Atomic force microscopy (AFM) images depicted a needle-like structure for deposited film at lowest oxygen partial pressure (5×10^-5 mbar) and a granular structure for formed samples at higher oxygen partial pressures (1×10^-4 and 2×10^-4 mbar). These results also showed that increasing of oxygen partial pressure up to 2×10^-4 mbar caused increasing of grains size and surface roughness, while an increase in oxygen partial pressure to the highest pressure (4×10^-4 mbar) had an inverse effect. The electrical response of samples was measured in vacuum and NO environments in the temperature range of 150-350 K. This study showed that the NO gas detection sensitivity of MoO₃ thin films improved with increasing of oxygen partial pressure up to 2×10^-4 mbar, and then decreased.

Abstract: The crystallographic structural characteristics and magnetic properties of Ho₃Fe_29-xT_x (T=V and Cr) compounds have been investigated by using Rietveld refinement analysis of X-ray diffraction (XRD) pattern and magnetic measurements. The calculated results indicate that among the 11 different kinds of Fe sites in these Ho-Fe compounds the preferential sites of the stabilizing elements V and Cr are quite different. The refined lattice parameters of these compounds are in good agreement with the experimental data. Spin reorientations of easy magnetization direction (EMD) are observed at around 150 K for Ho₃Fe₂₇V₂ and Ho₃Fe_25.5Cr_3.5. At the around 1.7 T critical fields (HCR) first order magnetization process (FOMP) occurs in magnetization curves at 4.2 K for the magnetically aligned samples of Ho₃Fe₂₇V₂ and Ho₃Fe_25.5Cr_3.5.