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排序方式: 共有186条查询结果,搜索用时 31 毫秒
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《Physics letters. A》2019,383(19):2290-2295
Cooling rate is critical in synthesizing nanoparticles (NPs), which determines the microstructure and the corresponding mechanical, thermal and electrical properties. This research, as the most initiative one, studies microstructure formation of three different sized high entropy alloy (HEA) NPs under three different cooling rates, employing molecular dynamics (MD). Through analysis of potential energy, “common neighbor analysis”, radial distribution function, and also the mean square displacement, it is found that phase transition temperature is independent of HEA NP size, and as cooling rate decrease, more amorphous atoms transform to fcc and hcp orders, which can alternate the mechanical and thermodynamic properties of the final structure. The Cr atoms are found to aggregate into one cluster inside the NP and also try to migrate to the surface of the HEA NP, due to the large diffusivity. This research provides new insights in the size dependency of the nanoparticles, which may motivate more applications in which the strong size dependency is not desirable. 相似文献
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用流变震荡模式研究了10 wt%浓度的弹道明胶在冷却和等温下的老化行为.对明胶从sol-gel点冷却到某个目标温度的过程,通过不同冷却速率的实验,建了一个弹性模量与温度的线性关系.不同温度下明胶的等温老化实验表明,弹性模量-时间曲线具有相似的形状.依据Normand提出的二级反应动力学模型,引入一个表征明胶老化行为的速率常数,构建了一个预测弹道明胶在老化初级阶段的弹性模量演化的模型.该模型中模量-温度关系在初始和无穷大时是直线,其他模量-温度线是近似直线,并交于sol-gel点.老化速率常数和过冷度之间符合Flory-Weaver方程.对弹性模量和老化时间进行归一化处理,可将不同温度下的老化曲线叠加成一条主曲线. 相似文献
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Kee-Hyeon Cho Won-Pyo Chang Moo-Hwan Kim 《International Journal of Heat and Fluid Flow》2011,32(6):1186-1198
The present paper reports on a numerical simulation and experimental validation of fluid flow and conjugate heat transfer characteristics of new vascular channels, whose cross-sections are semi-circular. The numerical analysis covers the Reynolds number range of 30−2000, with a cooling channel volume fraction of 0.04, pressure drop range of 30−105 Pa. Six flow configurations were considered: first, second, and third constructal structures with optimized hydraulic diameters and non-optimized hydraulic diameter for each system size 10 × 10, 20 × 20, and 50 × 50, respectively. The numerical results of the proposed vascular channels show that the channel configurations of the optimized constructs show much lower flow resistance and temperature distribution than those of the non-optimized constructs. It is also shown that the power component in the power-law relationship between mass flow rate and pressure drop decreases as the system size and mass flow rates increase. The numerical results are validated by experimental data, and with the two exhibiting excellent agreement in all cases. The validation study against the experimental data shows that the presented numerical model is a reliable tool for predicting the performance of cooling plates under practical operating conditions and for the design of self healing or cooling system. 相似文献
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Corrosion and passivation behavior of Mg-Zn-Y-Al alloys prepared by cooling rate-controlled solidification 总被引:1,自引:0,他引:1
Michiaki Yamasaki Shogo IzumiYoshihito Kawamura Hiroki Habazaki 《Applied Surface Science》2011,257(19):8258-8267
Highly corrosion-resistant nanocrystalline Mg-Zn-Y-Al multi-phase alloys have been prepared by consolidation of rapidly solidified (RS) ribbons. The relation between corrosion behavior and microstructure evolution of Mg-Zn-Y-Al alloys with a long period stacking ordered phase has been investigated. In order to clarify the influence of rapid solidification on the occurrence of localized corrosion such as filiform corrosion, several Mg96.75Zn0.75Y2Al0.5 (at.%) alloys with different cooling rates are fabricated by the gravity casting, copper mould injection casting and melt-spinning techniques and their corrosion behavior and microstructures are examined by the salt water immersion test, electrochemical measurements, GDOES, XRD, SEM and TEM. To clarify the effect of aluminium addition on the improvement in corrosion resistance of the alloys, several Mg97.25−xZn0.75Y2Alx alloys with different aluminium contents are fabricated by consolidating RS ribbons and the formation of corroded films on the Mg-Zn-Y-Al alloys have been investigated. Rapid solidification brings about the grain refinement and an increase in the solid solubility of zinc, yttrium and aluminium into the magnesium matrix, enhancing microstructural and electrochemical homogeneity, which in turn enhanced corrosion resistance. The addition of aluminium to magnesium can modify the structure and chemical composition of surface films and improves the resistance to local breakdown of the films. 相似文献
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反斯托克斯荧光制冷 (Anti StokesFluorescentCooling)也被称为激光制冷 (LaserCooling)。自 1 995年以来 ,该项研究取得了飞速的发展。目前 ,人们利用激光制冷的方法已经得到了比家用冰箱冷冻室还低的温度 ,并能够利用半导体量子阱材料得到低于液氮温区的降温。由于这项技术具有全光性 ,它的制冷器具有体积小、重量轻、无电磁辐射、无振动、无噪声等特点 ,因此也就具有了非常诱人的应用前景和符合军事、空间、集成光学、微电子、医学等领域的特殊要求 ,而被国外研究者所重视。做为一项基本技术 ,激光制冷研究的突破必然会导致许多对温度有特殊要求的高技术实用化 ,推动那些领域向前发展。本文详细地介绍了反斯托克斯荧光制冷研究的历史和最新进展 ,详细地介绍了该项研究中的方法和理论。着重介绍了激光制冷的热力学限制、发光过程的热力学理论 ,探讨激光制冷产生的机制和制冷理论。最后 ,对激光制冷器的发展前景和设计依据进行了讨论 ,尝试性地探讨了线圈型制冷器、用于芯片的制冷器和单分子 光子泵型制冷器的应用考虑。 相似文献
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Shichao Wang 《International Journal of Polymer Analysis and Characterization》2014,19(4):287-295
Titanium dioxide (TiO2) particles were introduced to improve the solar reflectance of high-density polyethylene (HDPE). The organic-inorganic hybrids were fabricated by melt blending. A series of characterizations were taken to study the crystallization behavior, morphology, solar reflectance, and real cooling property. TiO2 particles acted as nucleation agents in the HDPE matrix and made the HDPE form thick lamellar crystals. TiO2 particles could disperse well into the HDPE matrix under 2.5 wt.% loading but agglomerated with 3 wt.%. Solar reflectance was related to the reflective index of TiO2 and the microstructure of HDPE. The real cooling property depended on the solar reflectance and the dispersion of the TiO2 particles in the HDPE matrix. 相似文献
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介绍了 HL-2M 装置冷却水系统的组成以及各子系统的循环流程、运行原理和运行参数。 相似文献
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Florian J. Stadler Tatsuhiro Takahashi Koichiro Yonetake 《European Polymer Journal》2011,(5):1048-1053
Ethene-/α-olefin copolymers having a wide range of comonomers between 8 and 26 carbon atoms in length were characterized by wide angle X-ray diffraction (WAXD). It was found that the crystallinities for the shorter comonomers (C8, C12) matched fairly well with the crystallinities from DSC and volumetric measurements, while for the longer comonomers (C18, C26) distinct differences between the three methods were found. This was explained by the presence of an additional crystalline phase of the side chains slightly deforming the amorphous peak. 相似文献