FeO熔化曲线的分子动力学模拟

利用壳层模型分子动力学方法,研究了高温高压条件下FeO的熔化温度,同时还计算了温度在300K及压强上升到140 GPa时FeO的状态方程.作者在研究中,考虑了分子动力学模拟熔化存在的过热现象,通过晶体的现代熔化理论,对FeO的分子动力学模拟熔化温度进行了修正,获得了高温高压下FeO正确的熔化温度.因此,为常压下利用壳层模型分子动力学研究物质熔化提供了一种较好的方法,该方法亦可进一步推广应用到其它物质的高压熔化研究工作.     

高压下3C SiC的电子结构、弹性与热力学性质

运用密度泛函理论的超软赝势平面波方法对3C SiC晶体结构进行了几何优化,得到与实验值相符的晶格参数,在压强为0～100GPa范围内对3C SiC的电子结构与弹性进行了计算,结果表明晶体结构是稳定的,且带隙随着压强的增大而减小。然后利用准谐德拜模型研究了3C SiC在温度为0～2100K、压强为0～100GPa范围内的热力学性质,结果表明其等容热容、热膨胀系数及熵函数都随温度的升高而增大,随压强的增大而减小,而德拜温度随温度的升高而减小,随压强的增大而增大。     

高压下黄铜矿CuInS2的电子结构、弹性参数、热学和电学性质的第一性研究

采用第一性原理方法,研究了高压下黄铜矿半导体CuInS2的电子结构、弹性参数、热学和电学性质.研究结果表明CuInS2是直接能隙半导体,其能隙值随着压强的增大而增大,能隙随压强变化的一阶系数值为54.31 meV/GPa;其弹性参数满足高压下的机械稳定性的条件,并且材料的韧性随着压强的增加而增强. 基于弹性参数计算了体系的德拜温度和最小热导率,德拜温度随着压强的增大而逐渐减小,而最小热导率随着压强的增加而增大. 通过对塞贝克系数和功率因子比弛豫时间的研究,发现增加压强和调节载流子的浓度可以改善CuInS2的电学性能.     

氮化铪的弹性与热力学性质的第一性原理计算

运用基于密度泛函理论的超软赝势平面波方法对HfN晶体结构进行了几何优化,得到与实验值相符的晶格参数。在压强为0～150GPa范围内对HfN的弹性常量进行了计算,它们均满足晶体力学稳定性条件B=(C11+2C12)/3>0,说明在这个压强范围内晶体结构是稳定的。利用准谐德拜模型计算了HfN在温度为0～2 200K、压强为0～150GPa范围内的热力学性质。发现:等容热容、热膨胀系数和熵函数都随温度的升高而增大,随压强的增大而减小;而德拜温度随温度的升高而减小,随压强的增大而增大。     

真空断路器分断金属液桥形成的数值模拟

为研究高压真空断路器触点分断电弧的产生机理,考虑触点表面微观形貌,建立真空环境下铜触点电接触的几何模型和数学模型。数值模拟真空断路器分断时金属液桥的形成过程,其中金属液桥的熔化电压与铜材料的熔化电压近似相等,证明建立仿真模型的正确性。得出金属液桥形成中的温度分布及熔化相变体积变化;探究触点初始分断电流、表面粗糙高度及初始接触压力对金属液桥形成的影响。数值计算结果表明:金属液桥的电势差由电接触位置向电极两边逐渐减小;模型最高温度出现在电接触位置;金属液桥的形变受热膨胀力与表面张力共同作用,随着熔化相变体积的增大,影响金属液桥形变的主导因素从热膨胀力逐渐过渡为表面张力,因此其形状由最初的圆柱形变为哑铃型;金属液桥熔化所需时间随触点初始分断电流和触点表面粗糙高度的增大而减小,随触点初始接触压力的增大而增大。为进一步研究真空金属蒸气电弧的形成机理及提高断路器的可靠性和寿命提供理论支持。     

物质熔化温度的粒度效应

用热力学方法,推导出适用于高分散度球形和非球形物质的熔化温度随粒度变化的关系式,本文所得方程式定量地描述了高分散度物质的熔化温度随粒度减小而降低的关系,所得结果对比于M.Hasegawa等人的理论计算能更好地符合于Coo_(14)be_2对铅的实验结果。     

CrN弹性和热力学性质的第一性原理研究

本文采用平面波赝势密度泛函理论方法研究了立方相CrN平衡态的结构和弹性性质,计算结果与已有的实验值和理论值符合较好.首次利用准谐德拜模型计算了CrN的热力学性质,得到了不同温度下,CrN的体积随压强的变化关系,以及德拜温度、摩尔热容量、熵和内能随压强及温度的变化关系.     

Ni铁磁粒子熵和热容量的影响因素分析

应用统计物理和固体理论,推导了外磁场中镍铁磁粒子的熵、热容量等热力学函数,并利用Mathematica软件进行了数值计算．结果表明：镍铁磁粒子的磁矩与外磁场相互作用引起的熵随温度升高而减小,随外磁场增大而增大;其热容量随温度的升高而增大,随外磁场强度的增大而减小;晶格振动和表面自由能引起的熵和热容量均随温度的升高而增大;温度较低时变化趋势更为显著．     

荷电旋量玻色气体热力学性质的研究

在平均场理论的框架下,讨论了荷电旋量玻色气体的热力学性质,结果表明系统的熵和比热容随朗德因子的增大而减小.熵和比热容均随温度单调增加直至饱和,并且它们随温度的演化没有出现相变点.     

伯塞活脱气体的热力学性质

伯塞活脱气体是实际气体的一种模型,根据状态方程,运用热力学方法导出伯塞活脱气体的内能、熵和热容量都是温度和体积的函数,临界压缩因子小于1,转换温度随体积的膨胀而升高,以及随压强的增大在三种情形下分别升高、降低或不变。     

A novel investigation on the influence of Cu–P modifier on the microstructure,mechanical performance,and melting process of Al–50Si alloys treated by overheating

As an efficient modifier, phosphorus (P) can significantly reduce the size of primary silicon (Si) crystals. However, modifier can aggregate when the P content exceeds a certain proportion, which decreases refining efficiency. In this study, the evolution of microstructures and mechanical properties of Al–50Si alloy have been studied by combining superheating and modification treatments. After modification, the mean size of the primary Si phase increased with superheating temperature, while the hardness decreased with increased superheating. Although the alloy was in an over-modified state when the modified content was 7 ?wt%, the overall alloy hardness was the highest. Nanoindentation tests were used to examine the mechanical properties of each alloy phase and the results showed that the nano-hardness of Al₂Cu phase was 5.52 ?GPa, three times that of an Al matrix, and was considered to be the reason for increased alloy hardness after over-modification. This phenomenon indicated that, except for size and distribution of the primary Si phase, intermetallic compounds, such as Al₂Cu, also played important roles in modifying alloy mechanical properties. The alloy melting process was observed in-situ using a laser confocal high-temperature scanning microscope and results indicated that the melting temperature of α-Al decreased with increased matrix Cu content. A model for calculating distortion energy was proposed and its rationality verified. Calculation results showed that, with increased matrix Cu content, the distortion energy gradually increased, which was the main reason for decreased matrix melting temperature. Moreover, the existence of distortion energy was verified using the EBSD method.     

机械合金化法制备Al-Ni-La-Cu非晶合金

用机械合金化法制备了不同成份的 Al- Ni- L a- Cu非晶合金 .经 X射线衍射仪、透射电子显微术和示差扫描量热仪 (DSC)热分析研究表明 ,随着合金中 Cu含量的增加 ,Al- Ni- L a- Cu的非晶形成能力逐渐增强 ,晶化温度逐渐降低 .     

La0.7Mg0.3Ni3.4-x(Al0.3Co0.4)0.2+x(x=0~0.3)合金电极电化学性能研究

在氩气保护下,采用悬浮熔炼法制备La0.7Mg0.3Ni3.4（Al0.3Co0.7）x（x=0,0.2,0.4,0.6）储氢合金,用X射线衍射仪测试相组成,并用MDI Jade 5.0软件分析相组成和晶胞参数,用开口三电极法测试电极电化学性能。结果表明,合金相主要由LaNi5、LaMg2Ni9、La2Ni7和LaNi2.28相组成,随着合金中Al和Co含量的增加,合金放氢平台压下降,最大吸氢量为1.43%（x=0）,合金电极最大放电容量Cmax为381mA.h.g-1（x=0）,合金电极100个充放循环后的容量保持率S100从53.0%（x=0）增加到57.1%（x=0.3）,循环稳定性增强。当x=0.1时,合金电极的电化学动力学性能较好。     

Effect of stoichiometry and Cu-substitution on the phase structure and hydrogen storage properties of Ml-Mg-Ni-based alloys

To improve the electrochemical properties of rare-earth-Mg-Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the alloys were studied. Nonsubstituted Ml_0.80Mg_0.20(Ni_2.90Co_0.50-Mn_0.30Al_0.30)_x (x=0.68, 0.70, 0.72, 0.74, 0.76) alloys and Cu-substituted Ml_0.80Mg_0.20(Ni_2.90Co_0.50-y Cu_y Mn_0.30Al_0.30)_0.70 (y=0, 0.10, 0.30, 0.50) alloys were prepared by induction melting. Phase structure analysis shows that the nonsubstituted alloys consist of a LaNi₅ phase, a LaNi₃ phase, and a minor La₂Ni₇ phase; in addition, in the case of Cu-substitution, the Nd₂Ni₇ phase appears and the LaNi₃ phase vanishes. Thermodynamic tests show that the enthalpy change in the dehydriding process decreases, indicating that hydride stability decreases with increasing stoichiometry and increasing Cu content. The maximum discharge capacity, kinetic properties, and cycling stability of the alloy electrodes all increase and then decrease with increasing stoichiometry or increasing Cu content. Furthermore, Cu substitution for Co ameliorates the discharge capacity, kinetics, and cycling stability of the alloy electrodes.     

Effects of scandium addition on microstructure and mechanical properties of ZK60 alloy

Series of rod samples of Zr55Al10Ni5Cu30 alloy were prepared by magnetic suspend melting and copper mold suction casting method.The effect of thermal rate treatment(TRT) process on glass forming ability(GFA),mechanical properties and microstructure of Zr-based bulk metallic glass were investigated.It shows that GAF,mechanical properties and microstructure of as-cast Zr55Al10Ni5Cu30 BMGs alloy to a large extent is related to TRT process.GFA and thermal stability of as-cast Zr55Al10Ni5Cu30 alloy increase w...     

Effect of TRT process on GFA, mechanical properties and microstructure of Zr-based bulk metallic glass

The effect of yttrium addition on the glass-forming ability(GFA) and mechanical properties of the Zr-based (Zr_(0.525)Al_(0.1)Ti_(0.05)Cu_(0.179)Ni_(0.146))_(100-x)Y_x and(Zr_(0.55)Al_(0.15)Ni_(0.1)Cu_(0.2))_(100-x)Y_x(x=0,0.2,0.4 0.6,1,2) alloys was studied.Micro-alloying of 0.6%yttrium enhances the room temperature ductility as well as the GFA of the Zr-based alloys.The mechanism of enhancing the GFA and room temperature ductility was analyzed.It is indicated that proper yttrium addition stabilizes the...     

高压变熔点过冷大体积近快速凝固

依据压力可以改变某些金属的熔点的原理,设计了高压大体积凝固工艺,对液态金属施加高压,提高熔点,其凝固过程不依赖于散热速度,而只取决于加压速度,从而实现大体积的近快速凝固,对高压凝固过程的相关参数进行了数值模拟,并对过晶Ａｌ－Ｓｉ合金的高压凝固组织进行了初步探讨。     

X射线荧光光谱法测定海底钴结壳的方法研究

采用粉末压片制样,X-射线荧光光谱法直接测定钴结壳中Fe、Mn、Co、Ni、Si、Al、Ca、K、Na、Ti、P、Mg、Cu、Pb、Mo、Sr、V、Zn、Zr、Y、Ba等元素。重点讨论用熔融法定值部分样品,然后用加以定值的钴结壳标准及样品、国家岩石、土壤、水系沉积物系列标准用粉末压片制样,做工作曲线,一次测量钴结壳中二十余种元素,并用定值样品做精密度与准确度试验,各元素统计结果为RSD％（n=12）除V的RSD〈4％外,其余元素的RSD均小于2％,测定结果与标准值和ICP-MS测量值相符。     

纯铜表面Al-Ni基自熔合金粉末共渗研究

用Al-Ni25自熔合金粉末共渗工艺，对纯铜进行了表面硬化处理。研究了渗层显微组织和Al,Ni,Cu的成分分布及硬化层的显微硬记度特性，并对渗层中各元素作用进行了分析。结果表明，渗层由沉积层和扩散层（过共析＋共折＋亚共折＋α固溶体）构成；同单元渗铝层相比，Ni的渗入降低了表层铝含量，改变了表层组织形貌，从而使表层脆性得到明显改善。     

室温单轴压缩断裂后块状非晶局部自由体积增加的直接观察

利用透射电子显微术，研究了Zr55Al10Ni5Cu30块状非晶室温单轴压缩断裂后样品微观结构变化特征，实验观察到由于塑性形变的集中导致的局部区域内自由体积增加现象，表明局部自由体积增加主导着非晶合金的形变行为。