Correlating Thermal-Conductivity Data for Ternary Liquid Mixtures

The performance of several semi-empirical expressions for correlating the temperature, pressure and composition dependence of the thermal conductivity (λ) of pure organic liquids and mixtures was investigated. The temperature and pressure dependence is adequately represented by Chisholm approximants of order (1, 1) or (2, 1) with five and eight adjustable constants, respectively. The fully predictive Vredeveld equation uses mass fractions as the composition variable. It significantly underestimated λ values for the R32 + R125 + R134a ternary refrigerant system. Binary predictive models with one or two adjustable parameters include the quadratic Scheffé polynomial and its corresponding Padé approximant, the cubic “Margules” model and the theoretical Wassiljewa equation. It was found that the Padé (2, 2) approximant and the Wassiljewa equation satisfactorily correlated the extensive ternary mixture data published by Rowley and coworkers. Best results were obtained when the mole fraction was used as a composition variable. The predictive capability of the models was checked using the R32 + R125 + R134a ternary refrigerant system. Combining rules were used for cross parameters such that the temperature and pressure dependence was incorporated via the pure fluid properties. Model parameters were fixed using binary data alone. In this case, the quadratic Scheffé, Padé (2, 2), and Wassiljewa (with temperature- and pressure-independent parameters) all provided satisfactory predictions for ternary mixtures.     

球磨时间对MA-SPS法制备FeCoCrAlNiB高熵合金微观结构、硬度和断裂韧性的影响

采用机械合金化(MA)和放电等离子烧结(SPS)相结合的方法制备FeCoCrAlNiB高熵合金。研究球磨时间(1、5、10、20、30和40 h)对合金相成分、微观结构、硬度和断裂韧性的影响。结果表明：高能球磨过程中各金属元素的合金化顺序为Al→Co→Ni→Fe→Cr;混合粉末球磨20 h后基本形成了单一的BCC固溶体相,其颗粒尺寸约为20μm。对不同球磨时间的混合粉末进行SPS烧结,获得的FeCoCrAlNiB高熵合金主要由无序BCC+B2(Al-Ni)固溶体相和硼化物相(Fe₂B等)组成。随着球磨时间的延长,合金中硼化物相含量先减少后增加并主要以网状形式分布,BCC相含量则与之相反;合金硬度随球磨时间的延长逐渐提高,主要是因为合金元素间固溶程度越来越高,硼化物相逐渐增多;但硼化物形成的网状结构会破坏基体的连续性,导致合金断裂韧性逐渐降低。当球磨时间为20 h时,获得的FeCoCrAlNiB高熵合金的维氏硬度(HV)为(10.9±0.2) GPa,断裂韧性(K_IC)为(4.4±0.2) MPa·m^1/2,表现出最优的综...     

Optical properties of lithium indium selenide

Conditions of growth of LiInS₂ and LiInSe₂ crystals with high optical quality are studied. Data on the dispersion of refractive indices in red-phase LiInSe₂ crystals are presented. Possible nonlinear three-frequency processes in LiInS₂ and LiInSe₂ crystals used for SHG and OPO are analyzed. Potentials of these crystals for application in OPO devices are shown.     

Canonic-Like HER Activity of Cr1–xMoxB2 Solid Solution: Overpowering Pt/C at High Current Density

Abundant transition metal borides are emerging as substitute electrochemical hydrogen evolution reaction (HER) catalysts for noble metals. Herein, an unusual canonic-like behavior of the c lattice parameter in the AlB₂-type solid solution Cr_1–xMo_xB₂ (x = 0, 0.25, 0.4, 0.5, 0.6, 0.75, 1) and its direct correlation to the HER activity in 0.5 M H₂SO₄ solution are reported. The activity increases with increasing x, reaching its maximum at x = 0.6 before decreasing again. At high current densities, Cr_0.4Mo_0.6B₂ outperforms Pt/C, as it needs 180 mV less overpotential to drive an 800 mA cm⁻² current density. Cr_0.4Mo_0.6B₂ has excellent long-term stability and durability showing no significant activity loss after 5000 cycles and 25 h of operation in acid. First-principles calculations have correctly reproduced the nonlinear dependence of the c lattice parameter and have shown that the mixed metal/B layers, such as (110), promote hydrogen evolution more efficiently for x = 0.6, supporting the experimental results.     

Thin film solar cells based on the ternary compound Cu2SnS3

Alongside with Cu₂ZnSnS₄ and SnS, the p-type semiconductor Cu₂SnS₃ also consists of only Earth abundant and low-cost elements and shows comparable opto-electronic properties, with respect to Cu₂ZnSnS₄ and SnS, making it a promising candidate for photovoltaic applications of the future. In this work, the ternary compound has been produced via the annealing of an electrodeposited precursor in a sulfur and tin sulfide environment. The obtained absorber layer has been structurally investigated by X-ray diffraction and results indicate the crystal structure to be monoclinic. Its optical properties have been measured via photoluminescence, where an asymmetric peak at 0.95 eV has been found. The evaluation of the photoluminescence spectrum indicates a band gap of 0.93 eV which agrees well with the results from the external quantum efficiency. Furthermore, this semiconductor layer has been processed into a photovoltaic device with a power conversion efficiency of 0.54%, a short circuit current of 17.1 mA/cm², an open circuit voltage of 104 mV hampered by a small shunt resistance, a fill factor of 30.4%, and a maximal external quantum efficiency of just less than 60%. In addition, the potential of this Cu₂SnS₃ absorber layer for photovoltaic applications is discussed.     

Microstructural characterization of Mg–Al–Sr alloys

The microstructural details of fourteen Mg–Al–Sr alloys were investigated in the as-cast form by a combination of scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) analysis and quantitative electron probe microanalysis (EPMA). The heat transfer method coupled with the DSC measurement has been utilized to determine the solidification curves of the alloys. The morphology and the chemical composition of the phases were characterized. The microstructure of the alloys is primarily dominated by (Mg) and (Al₄Sr). In the present investigation, ternary solid solubility of three binary compounds extended into the ternary system has been reported and denoted as: (Al₄Sr), (Mg₁₇Sr₂) and (Mg₃₈Sr₉). The (Al₄Sr) phase is a substitutional solid solution represented by Mg_xAl_4–xSr and has a plate-like structure. The maximum solubility of Al in Mg₁₇Sr₂ was found to be 21.3 at%. It was also observed that Mg₃₈Sr₉ dissolved 12.5 at% Al.     

硼白口铸铁的研究进展

白口铸铁的合金化主宰了其发展进程.介绍了硼合金化白口铸铁的研究状况,主要阐述了硼对以碳化物为耐磨相和以硼化物为耐磨相的白口铸铁中组织和性能的影响.硼不改变以碳化物为耐磨相的白口铸铁中碳化物的形态,但能提高碳化物硬度和基体的淬透性,对韧性没有明显改善.以硼化物为耐磨相的白口铸铁组织中含有硬的硼化物耐磨相和强韧的马氏体基体,具有良好的硬度和韧性组合,是一类非常具有前途的新型白口铸铁.     

First principle calculation of physical properties of barium based chalcogenides BaM4S7 (M = Ga,Al); a DFT,DFT-D and hybrid functional HSE06 study

The electronic structure, elastic and optical properties have been calculated for the novel nonlinear optical (NLO) crystals BaQ₄S₇ (Q = Ga, Al) using plane wave pseudo-potential density functional theory (DFT) method as implemented in CASTEP and ABINIT codes. In this study we used both hybrid HSE06 and DFT-D functionals with GGA approximation. These NLO compounds, which belong to the mm2 point group, are particularly interesting because of their transparency in the mid-infrared region and wide energy band gap. We present results for electronic structure, elastic tensor coefficients, refractive indices and second order nonlinear optical susceptibilities. The calculated energy band gap and frequency dependent refractive indices as well as the NLO coefficients of BaGa₄S₇ are in good agreement with the experimental values. With no reported theoretical or experimental energy band gap and optical properties of BaAl₄S₇, we present for the first time its electronic structure and above mentioned optical coefficients. This compound has higher direct band gap with 3.74 eV, better optical birefringence and second-order NLO coefficients than most NLO compounds. The second-order NLO coefficients for BaAl₄S₇ have been calculated as d₃₁ = 3.15 pm/V, d₃₁ = 2.20 pm/V, d₃₃ = −6.31 pm/V.     

High purity synthesis of ZrB2 by a combined ball milling and carbothermal method: Structural and magnetic properties

The present work provides a new insight into the high purity synthesis of zirconium diboride (ZrB₂) powders and a method of controlling impurity during the synthesis process. The single phase ZrB₂ nano-powder was synthesized by a combined ball milling and carbothermal method using zirconium oxide (ZrO₂), boron oxide (B₂O₃) and carbon (C) as starting materials. The reaction pathway, phase purity, and morphology of the ZrB₂ produced are elucidated from X-ray diffraction (XRD) and scanning electron microscopy studies. The details of the impure phases generated during synthesis were obtained from multi-phase Rietveld refinements of XRD data. Experiments revealed that the method of synthesis carried out at 1750?°C involving ZrB₂:B₂O₃:C at a molar ratio of 1:4.5:7.5 could produce highly pure ZrB₂ nano-powders of 67?nm average crystallite size. The magnetometry studies on such pure form of ZrB₂ nano-powders indicated that both paramagnetic and diamagnetic characteristics coexisted in ZrB₂, which could be attributed to its polycrystallinity.     

成分配比对三元硼化物金属陶瓷Mo2FeB2性能的影响

三元硼化物金属陶瓷Mo2FeB2具有良好的硬度和耐磨性，且可通过原位液相反应生成。但不同的成分配比对生成三元硼化物Mo2FeB2性能的影响很大，本文通过实验，对不同Mo／B原子比的三元硼化物金属陶瓷Mo2FeB2的组织结构和硬度进行了对比研究，试验结果表明，当Mo／B原子比为1．1时，三元硼化物金属陶瓷Mo2FeB2具有较好的组织和性能。