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51.
52.
稀土元素在LD30铝合金真空钎焊中的作用 总被引：4，自引：1，他引：4
研究了添加La和Ce的Al-Si基钎料真空钎焊LD30铝合金接头的力学性能，微观组织形貌和EDS，并与未添加稀土元素的Al-Si基钎料真空钎焊接头进行对比。结果表明，添加稀土元素的LD30铝合金真空钎焊接头抗拉强度为288MPa，达母材抗拉强度的97．6％，明显高于未添加稀土的LD30合金真空钎焊接头。其机制在于La,Ce能够明显提高Al-Si基钎料与LD30铝合金的润湿性能，改善LD30铝合金真空钎焊接头焊缝及其基体中杂质元素的分布，促进钎料和母材中各元素的均匀扩散，从而提高真空钎焊接头的力学性能。 相似文献
53.
P. Sagan G. Wisz B. Tsizh I. Virt I. Rudy 《Molecular Crystals and Liquid Crystals》2018,671(1):148-155
AbstractThe structure, morphology and optical transmittance spectra of pentacene films on the (glass/ITO) surface were studied. The films were grown by two methods - the thermal vacuum deposition (TVD) and pulsed laser deposition (PLD). The electron diffraction pattern from thermally deposited pentacene films confirms their polycrystalline structure while the diffraction pattern of PLD-coated layers has a diffusion character. The results obtained showed that layers deposited by the TVD method has an optical spectrum that is characteristic for the pentacene film in contrary to the layers deposited by the PLD method. It is found a sensitivity of the optical transmittance of pentacene films to the ammonia action, which may be used for development the optical gas sensor. 相似文献
54.
Fang Xia Joël Brugger Gujie Qian Yung Ngothai Brian O'Neill Jing Zhao Stewart Pullen Scott Olsen Allan Pring 《Journal of Applied Crystallography》2012,45(2):166-173
A large‐volume single‐pass flow‐through cell for in situ neutron diffraction investigation of hydrothermal crystallization processes is reported. The cell is much more versatile than previous designs owing to the ability to control independently and precisely temperature (up to 673 K), pressure (up to 46 MPa), flow rate (0.01–10 ml min−1) and reaction‐fluid volume (≥65 ml). Such versatility is realized by an innovative design consisting of a room‐temperature and ambient‐pressure external fluid supply module, a high‐pressure reaction module which includes a high‐temperature sample compartment enclosed in a vacuum furnace, and a room‐temperature and high‐pressure backpressure regulation module for pressure control. The cell provides a new avenue for studying various parameters of hydrothermal crystallizations independently, in situ and in real time at extreme hydrothermal conditions (e.g. supercritical). The cell was successfully commissioned on the high‐intensity powder diffractometer beamline, Wombat, at the Australian Nuclear Science and Technology Organisation by investigating the effect of pressure on the hydrothermal pseudomorphic conversion from SrSO4 (celestine) to SrCO3 (strontianite) at a constant temperature of 473 K and flow rate of 5 ml min−1. The results show that the increase of pressure exerts a nonlinear effect on the conversion rate, which first increases with increasing pressure from 14 to 20 MPa, and then decreases when pressure further increases to 24 MPa. 相似文献
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B. Niethammer 《ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik》2010,90(4):259-270
We review recent progress on the derivation and analysis of higher order corrections to the classical mean‐field theory of Lifshitz, Slyozov, and Wagner for domain coarsening. Most research on this subject in the applied literature has focussed on the effect of screening induced fluctuations, however some of the resulting models lack self‐consistency. We discuss here recent work in which a self‐consistent model for fluctuations is derived and compare it to a model that has first been suggested in the original paper by Lifshitz and Slyozov. This model takes the effect of encounters between domains into account, but has seemingly gone unnoticed in the literature. Contrary to common expectations self‐similar solutions of this model predict a much larger coarsening rate than the models accounting for fluctuations. 相似文献
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M. Sridharan Sa. K. Narayandass D. Mangalaraj Hee Chul Lee 《Crystal Research and Technology》2003,38(6):479-487
Cd0.96Zn0.04Te thin films are deposited onto thoroughly cleaned glass substrates (Corning 7059) kept at room temperature by vacuum evaporation. The films are found to have good stoichiometry as analyzed by Rutherford Backscattering Spectrometry. The films exhibited zinc blende structure with predominant (111) orientation. The surface morphology of the films is studied by Atomic Force Microscopy. The rms roughness of the films evaluated by AFM is 3.7 nm. The pseudodielectric‐function spectra, ε(E) = ε1(E) + i ε2(E) at room temperature are measured by spectroscopic ellipsometry. The measured dielectric function spectra reveal distinct structures at energies of the E1, E1+ Δ1 and E2 critical points. The band gap energy of the films measured by optical transmittance measurement is 1.523 eV. The PL spectrum of the films shows intense emission due to free and bound exciton recombination and no emission associated with crystal imperfection and deeper impurity levels. The PL line shapes give indications of the high quality of the layers. 相似文献
59.
C. Viswanathan V. Senthilkumar R. Sriranjini D. Mangalaraj Sa. K. Narayandass Junsin Yi 《Crystal Research and Technology》2005,40(7):658-664
Thin films of InSe were obtained by thermal evaporation techniques on glass substrates maintained at various temperatures (Tsb = 30°, 400°C). X‐ray diffraction analysis showed the occurrence of amorphous to polycrystalline transformation in the films deposited at higher substrate temperature (400°C). The polycrystalline films were found to have a hexagonal lattice. Compositions of these films have been characterized by EDAX and the surface analysis by scanning electron microscopy. Optical properties of the films, investigated by using spectrophotometer transmittance spectra in the wavelength range (300 – 1100 nm), were explained in terms of substrate temperatures. Films formed at room temperature showed an optical band gap (Egopt) 1.56 eV; where as the films formed at 400°C were found to have a Egopt of 1.92 eV. The increase in the value of Egopt with Tsb treatment is interpreted in terms of the density of states model as proposed by Mott and Davis. The analysis of current ‐Voltage characteristics, based on space charge limited currents (SCLC) measurements, confirms the exponential decrease of density of states from the conduction band edge towards the Fermi level for both the amorphous and polycrystalline films. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
60.