六方相/单斜相WO3“异相结”的可控合成及光催化性能

利用沉淀法合成了球形六方相氧化钨(h?WO₃),通过调控六方相向单斜相的相变,可控制备了六方/单斜WO₃(h/m?WO₃)“异相结”催化剂。采用X射线衍射(XRD)、扫描电镜(SEM)和比表面积(BET)等对WO₃催化剂的晶相结构及组成、粒子大小和比表面积进行了表征。光催化分解水产氧的实验结果表明,相较于纯六方相WO₃,具有合适晶相组成的h/m?WO₃展现了显著的光催化性能。结合六方相和单斜相的能带位置,表面光电压表征结果发现,h/m?WO₃“异相结”的形成显著促进了催化剂表面光生电子和空穴的高效分离,进而提高了催化剂的光催化活性。     

石英砂的相变与换向器套筒铸件的变形

用呋喃树脂石英砂工艺生产牵引电机换向器套筒出现变形、裂纹等铸造缺陷,是由石英砂相变膨胀引起,后用高铬刚玉砂代替石英砂得到解决.     

The dynamic evolution of aggregated lithium dendrites in lithium metal batteries

Lithium (Li) metal anodes promise an ultrahigh theoretical energy density and low redox potential,thus being the critical energy material for next-generation batteries.Unfortunately,the formation of Li den-drites in Li metal anodes remarkably hinders the practical applications of Li metal anodes.Herein,the dynamic evolution of discrete Li dendrites and aggregated Li dendrites with increasing current densities is visualized by in-situ optical microscopy in conjunction with ex-situ scanning electron microscopy.As revealed by the phase field simulations,the formation of aggregated Li dendrites under high current den-sity is attributed to the locally concentrated electric field rather than the depletion of Li ions.More specif-ically,the locally concentrated electric field stems from the spatial inhomogeneity on the Li metal surface and will be further enhanced with increasing current densities.Adjusting the above two factors with the help of the constructed phase field model is able to regulate the electrodeposited morphology from aggregated Li dendrites to discrete Li dendrites,and ultimately columnar Li morphology.The methodol-ogy and mechanistic understanding established herein give a significant step toward the practical appli-cations of Li metal anodes.     

高效高功率密度车载双向电能变换器设计

研究设计了一种用于电动汽车电池充放电的车载双向电能变换器。充电状态下,前级采用PWM整流技术,后级采用移相全桥零电压开关电路,实现电气隔离高效的降压变换。放电状态下,双向DC-DC变换器实现升压变换,双向AC-DC作为单相全桥逆变器采用电压前馈、电压电流双闭环控制策略。本系统采用全控型器件GaN控制电流电压通断,能够使得电流电压在正负四象限工作,实现能量的正向和反向的双向传递。依据此方案设计一款开关频率100 kHz、输出功率2 kW的原理样机,经测试该系统能够有效实现能量的双向流动,并且有效提升了效率和功率密度,验证了方案的可行性。     

Avrami exponent and isothermal crystallization of Zr/Ti-based bulk metallic glasses

The isothermal crystallization kinetics of Zr/Ti-based bulk metallic glasses (BMGs) have been investigated by using Avrami exponent. It is a constant nucleation rate and a constant number of quenched-in nuclei that cause the linear John–Mehl–Avrami (JMA) modes in Avrami exponents of Zr₆₂Al₈Ni₁₃Cu₁₇ and Zr₆₅Al₈Ni₁₀Cu₁₇ BMGs, respectively. However, sub-T_g pre-annealing of Zr₆₂Al₈Ni₁₃Cu₁₇, and multiple-step phase transition in Ti₄₃Cu₄₃Zr₇Ni₇ and Ti₄₅Zr₅Cu₄₀Ni_7.5Sn_2.5 make their Avrami exponents deviate from the linear JMA mode. The difference in Avrami exponents maybe provides useful information for performing the microstructure control of BMG composites upon isothermal annealing.     

The high temperature phase transitions of orthorhombic La0.95MnO3

The high temperature phase transitions of orthorhombic La_0.95MnO₃ from room temperature to 1273 K were studied using high temperature XRD technique in air. Two-phase transitions were found in temperature ranges, 373–473 K and 973–1273 K, respectively. The crystal symmetry increases from orthorhombic to rhombohedral then cubic, while the second transition was not completed in the observation of the present study. The first transition could be due to the depression of Jahn–Teller distortion, while the second one could be caused by the ionic oscillation at high temperature. The lattice thermal expansion coefficients of rhombohedral La_0.95MnO₃ from 473 to 973 K were also calculated using lattice parameters.     

颗粒尺度对纳米材料相变的影响

运用Ｈｅｉｓｅｎｂｅｒｇ模型研究了纳米材料相变的尺度效应，建立了相变与颗粒尺度之间的定量关系。模拟结果表明，这一理论与实验数据相符合。     

Investigation of the titanium–indium system

The phase diagram of the Ti–In system was determined using DTA, XRD and EDX analyses. The existence of the phases Ti₂In₅ [Mn₂Hg₅ type structure, space group P4/mbm, a=0.99995(3), c=0.29960(2) nm] and Ti₃In [Ni₃Sn type structure, space group P6₃/mmc, a=0.5978(1), c=0.4812(1) nm] was confirmed. The phase previously labeled Ti₃In₂ was found to exist in a narrow homogeneity region near Ti₅₆In₄₄. Rietveld refinement of the XRD powder pattern yielded solutions compatible with a Cu₃Au-type or a BiIn-type crystal structure, but not with a CuAu-type crystal structure. Furthermore, at 38.5 at.% In, a new phase was observed having a γ-brass related crystal structure [Ti₈In₅, space group , a=0.99578(6) nm]. The intermetallic phases were formed by a cascade of peritectic reactions ending in a eutectic at >99 at.% indium between Ti₂In₅ and (In) at 0.4 K below the melting temperature of pure indium.     

Nd—Pd—Ru三元系富钯区域的相图

用Ｘ射线衍射和金相显微镜分析方法研究了Ｎｄ－Ｐｄ－Ｒｕ三元系的富钯区域，作出部分相图的７００℃等温截面。发现Ｒｕ在（ＮｄＰｄ３）中有高达１３ａｔ％的固溶度。该截面上存在４个单相区：（Ｐｄ），（Ｒｕ），ＮｄＰｄ５和ＮｄＰｄ３；５个二相区：（Ｐｄ）＋（Ｒｕ），（Ｐｄ）＋ＮｄＰｄ５，ＮｄＰｄ５＋ＮｄＰｄ３，ＮｄＰｄ３＋（Ｒｕ）和ＮｄＰｄ５＋（Ｒｕ）；２个三相区：（Ｒｕ）＋ＮｄＰｄ３＋ＮｄＰｄ５和（Ｐｄ）＋（Ｒｕ）＋ＮｄＰｄ５。     

高强耐磨复杂铝黄铜研究

在生产HA164-5-4-2过程中，解决了Fe、Mn的熔化及均匀化、无缺陷铸锭的生产方法、管材直度控制等工艺关键问题。合金的熔点910、4℃，流点949．2℃，相变热焓114．6J／g；热加工性能优良；在高于550℃时其组织是β相，在低于550℃时其组织是α β相，耐磨颗粒是多元富铁相；力学性能分别为σb=796MPa，σ0.2=675MPa，δ5=20％，IIB=218。同时报道了不同热处理条件下组织和性能的关系。