High-Pressure Phase Transition of Hexagonal Alkali Pnictides

High-pressure studies of Li₃P, Na₃Sb, and Na₃Bi at room temperature show that these compounds undergo a reversible transition from a hexagonal phase to a denser, cubic phase. The lattice parameters of the cubic phases are determined at pressures of up to 9.0 GPa.     

一种RDX基PBX炸药力学性能和本构关系研究

利用分离式霍普金森压杆(SHPB)对一种RDX基PBX炸药进行了高应变率加载试验,得到了其在不同应变率(300~1 200 s-1)范围内的力学性能,并用扫描电子显微镜(SEM)对回收样品进行了微观分析。结果表明:材料的力学性能和损伤均具有明显的应变率效应。采用含损伤的ZWT非线性黏弹性本构模型,对试验数据进行了拟合,拟合曲线和试验曲线吻合良好。     

High-Pressure Phase Transitions of LaF3and CeF3

The effect of high pressure on the structure of LaF₃ (tysonite), CeF₃, and nonstoichiometric LaF₃-based solid solutions (rhombohedral system, P c1, Z = 6) is discussed. In the systems MF₂–LaF₃ with M = Pb and Sr, fluorite-like M_{1 –x} La _x F_{2 + x} solid solutions (Fm3m, Z = 4) are obtained in the composition range 0.5 x 0.75 by quenching from 1500–1700 K at p = 10 GPa. By extrapolating the composition dependences of the lattice parameter for these cubic solid solutions, the lattice parameter of cubic LaF₃ is estimated at a= 5.86 ± 0.02 Å. High-pressure x-ray diffraction studies indicate that CeF₃ undergoes a first-order phase transition similar to that revealed recently in LaF₃. At p = 20.6 GPa, the lattice parameters of orthorhombic CeF₃ (Cmma, Z= 8) are a = 8.062 ± 0.006 Å, b = 8.457 ± 0.009 Å, and c = 5.091 ± 0.006 Å. The transition is accompanied by a 7.3% decrease in volume. The high-pressures structure of LaF₃ and CeF₃ can be thought of as a distorted modification of the structure of a hypothetical fluorite-like trifluoride. The lattice parameters of the orthorhombic and cubic cells are related by a _ortho b _ortho a _cubic and c _ortho a _cubic.     

Novel Phase Behavior in Quantum Rotors

A system of quantum linear rotors in a crystal field is found to display a novel type of phase diagram. At a certain value of the crystal field a discontinuity point appears at the orientational phase transition line. As the crystal field increases this point splits into two critical points with a single-phase-state discontinuity (hole) between them. This remarkable feature is common both for a system where all angular momentum states are allowed and for one where the angular momentum is restricted to have even values despite the fact that general aspects of the transformations induced by the crystal field differ considerably for the two systems.     

双相钢的疲劳行为（上）

本文评述了近年来国内外有关双相钢疲劳行为方面的文献资料,并提出了尚待解决的问题。     

双相钢的疲劳行为（下）

评述了近年来国内外有关双相钢疲劳行为方面的文献资料,并提出了尚待解决的问题。     

不同Cr含量的Fe-Cr合金高温高压水蒸气氧化行为

Fe-Cr合金钢广泛用于锅炉的受热面管,但目前研究多针对Cr在高温常压环境中的氧化行为,对高温高压下的研究较少。对Cr的质量分数分别为9%、12%、18%、25%的Fe-Cr合金试样在650℃、25 MPa的高压水蒸气环境中的氧化行为进行研究,并与Cr-9的常压水蒸气氧化进行对比,采用扫描电镜(SEM)观察形貌、能谱分析成分变化、X射线衍射仪(XRD)分析物相组成并称重绘制氧化动力学曲线,以此来探究不同Cr含量的Fe-Cr合金的氧化膜生长规律和压强对其氧化行为的影响。结果表明:随着Cr含量的提高,Fe-Cr合金的孕育期增长,抗氧化能力得到提高;Cr含量的增加对氧化行为有一定影响,氧化66.0 h,Cr-9与Cr-12氧化动力学符合抛物线规律,在氧化初期就出现内外氧化层分层,内层为尖晶石FeCr2O_4,外层为Fe_3O_4,而Cr-18、Cr-25则仍处于孕育期,动力学几乎处于稳定状态,这个阶段主要是元素的扩散准备,氧化物的出现只是附加产物;表面的氧化物并不能构成一层完整的氧化膜,外加压强能够增加Fe-Cr合金位错和空位浓度,从而提高氧化速率,并且压强影响了氧化膜的形貌,在压应力的作用下,氧化膜主要由粒状氧化物构成。     

Predicting the High-Pressure Phase Equilibria of Binary Mixtures of n-Alkanes Using the SAFT-VR Approach

The phase behavior of selected alkane binary mixtures is studied using SAFT-VR, a version of the statistical associating fluid theory for potentials of variable attractive range (SAFT). We treat the n-alkane molecules as chains formed from united-atom hard-sphere segments with square-well potentials of variable range to describe the attractive interactions. We use a simple relationship between the number of carbon atoms in the n-alkane molecule and the number of segments in the united atom chains in order to predict the phase behavior of n-butane with other n-alkanes. The calculated vapor pressures and saturated liquid densities of the pure components are fitted to experimental data from the triple point to the critical point. These optimized parameters are rescaled by the respective experimental critical points and used to determine the critical lines and phase behavior of the mixtures. We use the Lorentz-Berthelot combining rule for the unlike interactions. We predict the phase behavior of n-butane + n-alkane binary mixtures, concentrating mainly on the critical region. The gas-liquid critical lines predicted by SAFT-VR for the n-alkane mixtures are in excellent agreement with the experimental data, and improve significantly on the results obtained with the simpler SAFT-HS approach where the attractive interactions are treated at the mean-field level.     

植酸与亚硝酸二环己胺气相缓蚀性能的比较

通过在植酸中加入氨水后不同pH值的气相缓蚀试验和在不同涂布量时的腐蚀失重试验,确定植酸作为气相防锈纸缓蚀剂使用时的最佳pH值为9左右,涂布量为20－30g/m^2。以亚硝酸二环己胺为参照,通过密闭空间挥发减量试验、气相快速甄别试验和湿热试验对其缓蚀性能进行了研究。结果表明植酸对黑色金属、镀锡钢板、镀锌钢板等缓蚀性能良好,优于亚硝酸二环己胺,但涂布量过高或过低时,容易引起过腐蚀,是危险型缓蚀剂。     

磁流变弹性体的磁致性能

设计了一种聚氨酯基磁流变弹性体,利用设计的磁致力学性能测试装置,对剪切状态下磁流变弹性体的磁流变效应进行了系统的测试。结果表明,相对磁流变效应随着外加磁场强度的增大而增大,随着激励振幅的增大而减小。预加载位移的大小直接决定这相对磁流变效应,过大的变形会导致相对磁流变效应急剧减小。激励频率对相对磁流变效应影响不大。     

Non-Fermi Behavior Near Ferromagnetic Quantum Phase Transition

We propose a model for the explanation of the non-Fermi behavior near the ferromagnetic quantum phase transition. The scaling equations have been used to calculate the specific heat and we showed that the quantum effects are responsible for the T ln T term from the specific heat. The results are in agreement with recent experimental data obtained in the Ni_xPd_{1 – x} system. The relation with the other approaches was also discussed.     

国外热塑性弹性体的进展

本文介绍了国外聚烯烃系（ＴＰＯ）、苯乙烯系（ＳＢＣ）、聚氨酯系（ＴＰＵ）、聚酯系（ＴＰＥＥ）、聚酰胺系（ＴＰＡＥ）和聚氯乙烯系（ＴＰＶＣ）等六大类热塑性弹性体（ＴＰＥ）的研究开发进展。     

Phase Change Behavior of Nitinol Shape Memory Alloys

Among other special characteristics Shape Memory Alloys (SMAs) have the ability to return to a predetermined shape when heated. In fact, the phase change of an existing element can strongly be influenced by thermal and thermo‐mechanical treatments. Up to now, SMEs have been discovered in various materials, which can generally be classified into noble‐metal based, Cu‐based, Fe‐based, Ni‐Ti‐based alloy systems and non‐metallic SMAs. In this paper a general overview of the Ni‐Ti system and a detailed review over the Ni‐Ti‐Cu system will be given with special regard to the influence of heat treatments upon the phase change behavior.     

High-Pressure Viscosity and Density Behavior of Ternary Mixtures: 1-Methylnaphthalene+n-Tridecane+2,2,4,4,6,8,8-Heptamethylnonane

The dynamic viscosity and the density of the ternary system, n-tridecane+1-methylnaphthalene+2,2,4,4,6,8,8-heptamethylnonane, were measured as a function of temperature from 293.15 to 353.15 K in 10 K increments at pressures up to 100 MPa. A falling body viscometer was used for measuring the dynamic viscosity above 0.1 MPa, while at 0.1 MPa the viscosity was obtained with an Ubbelohde viscometer. The overall uncertainty in the reported data is less than 1 kg·m^–3 for densities and 2% for viscosities, except at 0.1 MPa where the uncertainty is less than 1%. The experimental results correspond to 882 values of viscosity. With reference to the 126 values published previously for the pure compounds and 882 values for the three associated binaries, the system is globally described by 1890 experimental values as a function of pressure, temperature, and composition. The results for the viscosity are discussed in terms of mixing laws and the excess activation energy of viscous flow.     

磁流变弹性体的研究现状及工程应用

磁流变弹性体是一种新型磁流变材料,其特点是流变性能可控可逆、响应时间非常短,而且稳定性好、结构设计简单,因而在智能化减振降噪、电磁传感器和主动控制等领域具有广阔的应用前景。系统介绍了国内外磁流变弹性体的研究现状,包括磁流变弹性体的力学模型、磁致力学性能及影响因素和工程应用,并提出了今后应深入研究的几个问题。     

水相中银纳米粒子的制备及动力学行为研究

以油酸钠为表面活性剂、AgNO3为前驱剂、N,N-甲基甲酰胺(DMF)为还原剂,在水相体系制备银纳米粒子.采用紫外-可见分光光度计测定了不同反应时间银纳米粒子的吸收曲线,系统地考察了反应温度以及DMF加入量等因素对银纳米粒子生成过程动力学行为的影响.结果表明,未加DMF时,该反应体系不能生成银纳米粒子,随着DMF加入量的增加和反应温度的升高,体系中银纳米粒子的吸收强度逐渐增大,在100℃、DMF加入量为3mL时,银纳米粒子的吸收强度大幅度提高.透射电子显微镜的结果表明,所得的银纳米粒子具有球形形貌,且具有较窄的尺寸分布.     

Pairing Phase Diagram of Three Holes in the Generalized Hubbard Model

The pairing problem of a three electrons system has been studied by using a real-space method and the generalized Hubbard Hamiltonian. This method includes the correlated hopping interactions as an extension of the previously proposed mapping method, and is based on mapping the correlated many-body problem onto an equivalent site- and bond-impurity tight-binding one in a higher dimensional space, where the problem was solved in a non-perturbative way. In a linear chain, we analyzed the pairing phase diagram of three correlated holes for different values of the Hamiltonian parameters. For some values of the hopping parameters we obtain an analytical solution for all kind of interactions.     

聚氨酯弹性体的结构与力学性能

室温催化合成了一系列不同结构的聚氨酯弹性体,研究了软硬链段的化学结构对聚氨酯弹性体形态结构和力学性能的影响规律,结果表明,由MDI合成的PU弹性体的力学性能和阻尼性能优于相应的由TDI合成的PU弹性体,对称结构的MDI易规整排列,提高了力学强度,软硬链段之间的相容性和较强的相互作用有利于提高弹性体的力学性能。     

快速凝固高温Al－Fe－Mo－Si－Zr－Ti合金强化相结构及其热粗化行为

用Ｘ－ｒａｙ衍射、系统倾转、会聚束，能谱分析确定了Ａｌ－Ｆｅ－Ｍｏ－Ｓｉ－Ｚｒ－Ｔｉ合金强化相的晶体结构，点阵常数、空间群及化学式，系统研究了该强化相在４２７℃、４７７℃，５９７℃时的粗化规律及机制，以及稀土元素Ｇｄ、Ｙ对该强化相热粗化行为的影响。