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991.
Aijun Wang Shun-Li Shang Yong Du Li Chen Jianchuan Wang Zi-Kui Liu 《Journal of Materials Science》2012,47(21):7621-7627
Thermodynamic properties as well as the miscibility gap (binodal) and spinodal decompositions of the cubic Ti1-x Al x N, Ti1-x Zr x N, and Zr1-x Al x N coating alloys have been computed using first-principles calculations. Herein, the cluster expansion method and especially the special quasirandom structure are employed to describe the disordered alloys. The effects of pressure and lattice vibration on the miscibility gaps and spinodal decompositions of the above alloys have been investigated by means of Helmholtz free energy with the vibrational contribution depicted with the Debye-Grüneisen model. It is found that the application of hydrostatic pressure promotes the isostructural decomposition of Ti1-x Al x N, Ti1-x Zr x N, and Zr1-x Al x N alloys, whereas the vibrational contribution decreases the consolute temperature of the phase separation. Our results indicate that the improved age-hardening behavior of cubic Ti1-x Al x N coatings with the addition of Zr arises from the enlarged composition range of binodal and spinodal curves at specified temperatures. Our results are in good agreement with the available experimental data and provide a useful insight into the investigation of age-hardening and characterization of Ti–Al–Zr–N-based coatings for high-temperature applications. 相似文献
992.
Phosphating is a widely adopted treatment in industry for many purposes. In this paper, carbon steel was pretreated with sodium silicate before phosphating. X‐ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements were used to evaluate the pretreatment effect by sodium silicate on the phosphating layer. The results demonstrate that the phosphate layer pretreated by sodium silicate has a better corrosion resistance as compared with the un‐pretreated ones. More compact and uniform coatings composed of finer crystals were obtained with the pretreatment of sodium silicate. 相似文献
993.
Yingfeng Shao Ruiqi Du Xiaofeng Wu Fan Song Xianghong Xu Chiping Jiang 《Journal of Materials Science》2013,48(18):6431-6436
The effect of porosity on the crack characteristics of ceramics after water-quenching is studied by measuring the cracks in ceramic sheets. The result reveals that the pore volume fraction has a slight effect on the enhancement of thermal shock resistance of ceramics when the porosity ranges from 0 to 20 %, because the length and density of the long crack in porous alumina are always slightly less than that in dense alumina. This result is in agreement with the prediction based on the minimum potential energy principle using experimentally measured data. Moreover, the proportion of the strength reduction in the third regime decreases significantly with increasing porosity, because the strength of unquenched specimens decreases more rapidly than that of quenched specimens with increasing porosity. The results of this study may help to further understand the thermal shock behavior of ceramics. 相似文献
994.
We performed dynamic Monte Carlo simulations of isothermal crystallization of bulk polymers at a high temperature, which was induced by a homogeneous stretching with a constant strain rate over a wide range of strains. We observed that the crystallites exhibit variable trends of chain folding in three sequential regions of strains, revealing hierarchical mechanisms of strain-induced polymer crystallization: in the first region, sporadic stretched segments initiate intermolecular crystal nucleation with less chain folding at higher strains; in the second region, massive less-stretched segments perform crystal growth with more chain folding at higher strains; in the third region, those folded chains extend via a melting-recrystallization process, again with less chain folding at higher strains. Different trends of chain-folding between crystal nucleation and growth appear intrinsic and ultimately lead to shish-kebab crystals. Our observations provided a molecular-level rationale to understand various experimental phenomena upon the processing for oriented semi-crystalline polymers. 相似文献
995.
对于只能通过定期检查发现故障的可维修备用系统,由于可维修时间的不连续性,无法使用一般方法进行可靠性预计的情况,给出了一种可靠性预计方法,并通过实例说明了此方法的合理性。 相似文献
996.
An intelligent toolpath (processing sequence) planning for fabricating aircraft structural parts is developed to obtain a minimum-length toolpath while maintaining the required machining time. The problem is first solved in the following ways. Firstly, an abstraction of the machining process is proposed to pick up the feed/retract points of each feature to be machined as the toolpath calculation basis. Secondly, the chaotic simulated annealing method is improved through storing the optimal solution, adding the control condition and selecting each parameter reasonably during the iteration of the algorithm so as to enhance its performance. What’s more, three solution-generating methods are used chaotically to obtain a better result. Lastly, the verification is conducted on four different aircraft structural parts, and the results prove that the proposed algorithm performs very well in terms of toolpath quality and computation time. 相似文献
997.
Kaihua Su Xianyong Yao Sheng Sui Zhaoxu Wei Junliang Zhang Shangfeng Du 《International Journal of Hydrogen Energy》2014
The effects of ionomer contents were investigated in composite electrodes with in-situ grown single crystal Pt nanowires (Pt-NWs) for PEMFCs, including the amount in the carbon matrix and impregnated on the surface of the electrocatalyst layer. The electrocatalyst layer was prepared by growing Pt-NWs directly on the carbon matrix with a simple one-step wet chemical approach at room temperature. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), polarization curve tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were employed to evaluate the ionomer effects. The experimental results showed that the ionomer in the carbon matrix had an influence on the ionic conductivity and aggregation and distribution of the Pt-NWs, and the ionomer impregnated on the surface of the electrocatalyst layer affected the mass transport and ionic conductivity. The performance of the MEA was improved by optimizing the ionomer contents. 相似文献
998.
Hard roof is the main factor that induces rock-burst.In view of the present obvious weakness of control measures for hard roof rockburst in domestic collieries,the mechanism and field application of di... 相似文献
999.
1000.
Du Qiang Bao Tana Li Yi Huang Youdan Shao Long 《Clean Technologies and Environmental Policy》2019,21(7):1499-1514
Clean Technologies and Environmental Policy - In recent years, the industrialization of construction has been promoted to achieve sustainable development within the construction industry;... 相似文献