Mn对Mg-4Zn变形镁合金组织与性能的影响

目的 研究Mn对Mg-4Zn合金再结晶组织演变和力学性能的影响,发展高性能Mg-Zn-Mn变形镁合金。方法 以Mg-Zn镁合金为研究对象,利用Mn元素的固溶强化增塑、刺激再结晶形核和钉扎再结晶晶界的特点,通过Mg-Zn-Mn挤压镁合金的显微组织以及室温力拉伸和压缩力学性能测试,分析挤压过程中显微组织的演变和成分对力学性能的影响。结果 Mg-4Zn-2Mn合金平均晶粒尺寸为~7 μm,其拉伸屈服强度、抗拉强度、伸长率、压缩屈服强度和拉压不对称性分别为226 MPa,316 MPa,17%,171 MPa,0.75。结论 合金化元素Mn可有效细化变形镁合金的再结晶组织,随Mn元素含量的增加,Mg-Zn合金再结晶组织不断细化,未再结晶区域增加,合金力学性能增加,拉压不对称性改善。     

Growth and some properties of Zn5In2S8 single crystal

Zn₅In₂S₈ has been synthesized in the form of single hexagonal platelets. This compound is the fifth member of the layered semiconductor family Zn_xIn₂S_3+x. Optical measurements are used for the evaluation of the energy gap at room temperature. This was found equal to 2.84 eV. The presence of extended composition faults was indicated by the a²-hv diagrams and proved by electron microscopy techniques. Some electrical properties have been studied and an electron trap at E_x=E_c−0.4 eV, with a concentration of about 10¹² cm⁻³ was found to exist. An anisotropy of about 10⁶ was measured in the two directions: Parallel to the layers and vertically to them.     

VDMOSFET HEF degradation modelling considering turn-around phenomenon

Gate oxide failure of power VDMOSFET has been researched for a long time. For BTI parameter degradation, some models are proposed. However, the degradation modelling of HEF still have challenges, one of which is the turn-around phenomenon. Due to the existence of the turn-around point, the threshold voltage degradation model under HEF cannot be described using classical models. Aiming at this problem, the experimental study and the argument are proposed in this paper. First, the theoretical model assumption is discussed based on the degradation mechanism. Second, the HEF stress experiments are carried out to acquire experimental data. Then the model fitting is processed. A three-phase model is proposed to describe threshold voltage degradation under HEF stress.     

Effects of solid loading on the fabrication of ceramic microparts by soft molding

The effects of solid loading on the fabrication of ceramic microparts by soft molding were studied. Alumina microchannel parts of different dimensions (60–160 µm) were fabricated from well-dispersed suspensions with different solid loadings (70, 75 and 80 wt%). The structural integrity of the green microchannel parts was examined to study the moldability of the suspensions. It was found that the minimum feature size and linear shrinkage of the microchannel parts decreased with increasing solid loading, while the green density and sintered density showed the opposite trend. The reasons for incomplete filling and demolding failures were also discussed.     

Densification and properties of ZrO2 nanoparticles added magnesia–doloma refractories

In this work the effect of nano- and microZrO₂ addition on the densification and hydration resistance of MgO–CaO refractories was investigated. 0, 2, 4, 6 and 8 wt% ZrO₂ was added to MgO–CaO refractories that contain 35 wt% CaO. The crystalline phases and microstructure characteristics of specimens sintered at 1650 °C for 5 h in an electric furnace were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The physical properties are reported in terms of bulk density, apparent porosity and hydration resistance. Results show that with addition of ZrO₂ the bulk density and hydration resistance of the samples increased while apparent porosity decreased. Also the hydration resistance of the samples was appreciably improved by the addition of ZrO₂ due to its effect on decreasing the amount of free CaO in the refractories, promotion of densification as well as modification of the microstructure. Also it revealed that the nanoZrO₂ addition was more effective than microZrO₂ due to its higher activity.     

An exploration for the degradation behavior of 2-D electrostatic microscanners by accelerated lifetime test

Failure analysis for the MEMS device is a crucial step in understanding the root causes of failure and improving the performance of the device. In order to explore the degradation failure mechanisms of 2-D electrostatic microscanners, three steps were addressed in this paper. Firstly, the stress distribution of the microscanner under its operation state was simulated using the finite element method (FEM), and the results showed that the middle part on the frame torsion beam was the most critical place. In the second step, accelerated lifetime test (ALT) was performed to shorten the time-to-failure period. Thirty well-conditioned devices participated in the experiment with continuous operation modes. Finally, five failures were observed by scanning electron microscope (SEM), and pull-in was found to be the main failure mode. In particular, a new appearance (wrinkling) was found at the most critical place obtained by previous simulation, and the natural frequencies of failed microscanners declined in accordance with the characteristic degradation trend before they failed. In this paper, it was proved that for electrostatic microscanners, the degradation of the mechanical properties after a long period of cyclic torsion work was the cause that induced pull-in failure, and the degradation was embodied by the wrinkling appearance. Besides, based on the experimental data, a working life of 15.8 years at 298 K for microscanners was obtained by further calculation.     

电炉半钢转杯离心粒化制备铁粉工艺

摘要：为了实现钛精矿电炉冶炼副产品半钢的高附加值利用,提出了以半钢为原料,采用转杯与冷却水幕相结合的转杯离心粒化工艺制备铁粉,并作为硫酸法钛白还原剂的新工艺。实验研究了转杯直径和转速对铁粉粒度的影响规律,结果表明铁粉粒度随着转杯直径和转速的增大而减小;转杯直径为150mm、转速为1800r/min时,颗粒粒径小于0.45mm 的铁粉占比达到90.45%（质量分数）;建立了适用于转杯离心粒化颗粒粒度的预测模型,平均相对误差为 11.43%;利用扫描电镜观察了铁粉颗粒截面的显微结构,铁粉颗粒表面存在一层铁的氧化物;利用热重分析法研究了水幕对铁粉颗粒氧化程度的影响。论文最后提出了铁粉制备、余热回收与钛白制备相结合的新工艺。     

First-principles study of influence of Ti vacancy and Nb dopant on the bonding of TiAl/TiO2 interface

Influence of defects (Ti vacancy and Nb dopant) on the bonding of TiAl/TiO₂ interface was studied via first-principles calculations. It was shown that the bonding strength and the stability of TiAl/TiO₂ interface were weakened by the presence of Ti vacancy and dopant Nb. The defects could also change the relative stability of the interface with different couplings between the two compounds. Electronic structure of the interface was analyzed and the influence mechanisms of defects on the bonding of interface were presented.     

Effect of Si doping on the photocatalytic activity and photoelectrochemical property of TiO2 nanoparticles

Si-doped TiO₂ nanoparticles with anatase crystalline phase were prepared by a hydrothermal method using acetic acid as the solvent. Photoelectrochemical studies showed that the photocurrent value for the 15% Si-doped TiO₂ electrode (54.4 μA) was much higher than that of the pure TiO₂ electrode (16.7 μA). In addition, the 15% Si-doped TiO₂ nanoparticles displayed the highest photocatalytic activity under ultraviolet light irradiation. So doping suitable amount of Si in TiO₂ nanoparticles was profitable for transferring photogenerated electrons and inhibiting the recombination of photogenerated electrons and holes. As a result, the photocatalytic activity of TiO₂ nanoparticles was improved.