Papers by Keyword: Thermal Property

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Authors: Chao Xu, Dong Chen
Abstract: The structural and elastic properties of the cubic spinel Ge3N4 semiconductor have been investigated using the ab initio scheme within the generalized gradient approximation in the framework of density functional theory. Quantities such as lattice constants and elastic constants of interest are calculated. A good agreement is found between our results and the other data. Through the lattice dynamics, in which the finite displacement method is used, we have obtained successfully the thermal properties such as the phonon curve, free energy, heat capacity and Debye temperature in the whole temperature range from 0 to 1000K. It is the authors ambition that these results will inspire further experimental study on the Ge-based semiconductors. * Corresponding author: CHEN Dong
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Authors: Xin Tan, Yu Qing Li, Xue Jie Liu
Abstract: With a motivation to understand microscopic aspects of TiN relevant to the electronic structure, phonon and thermal properties of transition metal nitride TiN superlattices, we determine its electronic structure, phonon spectra and thermal properties using first-principles calculations based on density functional theory with a generalized gradient approximation of the exchange correlation energy. We find that the electronic bands crossed by EF are half occupied, TiN has the ability of taking part in chemical reactions and also has the surface activity; A large gap in its phonon spectra, anomalies in the phonon dispersion of metallic TiN, manifested as dips in acoustic branches, but it do not contain soft modes in any direction; The specific heat (Cv) of TiN rises rapidly at low temperatures, the Cv values of the material, is identical to the Dulong-Petit value at high temperatures. Under the quasi-harmonic approximation (QHA), the thermal expansion, specific heat and bulk modulus B(T) are obtained, and the B(T) decreases along with the increase of temperature.
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Authors: Yi Chuan Chen, C. Y. A. Tsao, Sy Cherng Yang, Chang Chuan Hsu
Abstract: Rapid solidification process was employed to make 6061 Al alloy powder. Powder size distribution was analyzed with SEM. Powder densities, i.e. apparent density and tap density, were measured. Thermal properties were measured via DSC. Surface condition and microstructures and their chemical compositions were characterized with XRD, OM, SEM/EDX. Nanoindentation was employed to obtain the hardness and Young’s modulus of the powders. The relationships among the atomization parameters, powder shapes and sizes, powder densities, thermal properties, microstructures and the mechanical properties were analyzed and rationalized.
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Authors: Tehreem Kanwal, Rub Nawaz Shahid, Naeem Ul Haq Tariq, Fahad Ali, M. A. Rafiq, Muhammad Iqbal, J.I. Akhter, Bin Awais Hasan
Abstract: The ceramic-metal composites that have all phases continuous throughout the structure are known as Interpenetrating Phase Composites (IPCs) and they have many applications in various fields. In this investigation ZrO2-Ni IPCs of varied compositions were synthesized using tubular furnace and microwave furnace routs. Samples were Characterized using BET surface area, Pycnometer density, dilatometry and scanning electron microscopy. The Electrical parameters of the composites were measured using impedance spectrometer. Results indicate that threshold percolation reached at 40 volume percent of Ni in both cases. Moreover, no significant difference was observed in BET surface area and CTE of composites prepared by conventional and microwave sintering processes.
293
Authors: Himadri R. Soni, Prafulla K. Jha
Abstract: Using first principles density functional theoretical calculations within the generalized gradient approximation (GGA), the present paper reports thermal properties such as constant volume lattice specific heat, Gibbs free energy, internal energy, and entropy of Yb-pnictides such as YbN, YbP and YbAs in its rocksalt phase. The variation of lattice specific heat with temperature obeys the classical Dulong-Petits law at high temperature while at low temperature it obeys Debye T3 law. The internal energy, entropy and free energy show a gradual variation with temperature. The specific heat at constant volume at lower temperature increases as going from N to P to As. *Corresponding author Email: pkj@bhavuni.edu, prafullaj@yahoo.com Telephone: +91-278-2422650 Fax: +91-278-2426706
353
Authors: Mei Po Ho, Hao Wang, Chun Kit Ho, Kin Tak Lau
Abstract: Silk fibre has been popularly used for bio-medical engineering and surgically-operational applications because of its biocompatible and bio-resorbable properties for centuries. Using silk fibre as reinforcement for some bio-polymers to enhance the stiffness of scaffolding and bone implant plates has been developed. However, its dynamic mechanical properties with the biodegradable properties have not yet well understood. In this paper, the dynamic mechanical and thermal properties of degraded and non-degraded silk fibre reinforced Polylactic acid (PLA) composites are discussed.
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Authors: Zdenĕk Jonšta, Pavel Koštial, Ivan Ružiak, Peter Jonšta, J. Jurčiová, Zora Jančíková, Jiri David, Ivan Kopal
Abstract: In the paper we present measurements of transport physical parameters such as thermal conductivity, diffusivity and specific heat capacity and dc electrical conductivity as well as the mechanical values E*, tg δ for rubber compounds filled by different ratio of silica - carbon black fillers. From presented results it is possible to see that proper filler concentration (rubber blend - silica - carbon black) rising all thermal parameters as well as mechanical properties represented by complex Young’s modulus and so, maintains the good mechanical parameters of the blend and finally it also lowers the electrical resistance. All trends are favourable for the improvement of useful rubber blends properties.
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Authors: Bo Xu, Ji Ping Liu
Abstract: Two aluminum hydride polymorphs (α-AlH3 and β-AlH3) were prepared by desolvation of AlH3-etherate based on the organometallic synthesis method and the thermal properties of them were investigated using TG-DSC and ex situ XRD under heating and isothermal processes. The results suggest that the α polymorph is more stable than the β polymorph, and the decomposition of the less stable polymorph, β-AlH3, occurs by an exothermic transformation to the α phase followed by the decomposition of α-AlH3 into Al and H2, with partial direct decomposition occurring in the process of phase transition at low temperatures (<100 C).
333
Authors: Xin Min Hao, Wen Juan Ma, Ge Gan, Peng Cheng Zhao, Yuan Yang, Rui Wang
Abstract: This paper introduces the study of structure on EVA (ethylene-vinyl acetate)/hemp stem powder compound system. The micro behavior of EVA/hemp system was measured by SEM (Scanning Electron Microscopy), and its thermal properties were measured by DSC (Differential Scanning Calorimetry ). It indicates that hemp stem core has entered into EVA foaming system successfully when measured by FT-IR (Fourier Transform Infrared).
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Authors: Shi Chao Xiu, Shi Qiang Gao, Zhi Li Sun
Abstract: Hybrid journal bearings are used in the high and super high speed cases mainly, such as the super-high speed spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of the bearing is a major reason to lower the accuracy of the main shaft system and limit the bearings working speed higher, as a result, restrict the bearing applications. In this paper, the thermal properties and the heat mechanism of such bearings are analyzed. The mathematical model of hybrid journal bearing is established to analyze the mechanism of generating heat. In addition, the temperature field distribution for the certain hybrid journal bearing at speed of 10000 rpm is studied by means of software ANSYS considering the heat transfer characters between fluid and solid. An improved measure about temperature rise of hybrid journal bearing is presented.
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