真空熔炼AZ91镁合金过程中Mg元素的蒸发行为

在真空Ar气氛中熔炼AZ91镁合金，测定了不同精炼温度下Mg元素的蒸发速率。结果表明，随着精炼温度的升高，Mg元素的蒸发量增大。通过计算可知，Mg的蒸气压是Al的10^9倍，是Zn的46倍，因此主要是Mg的蒸发而导致合金其他元素含量升高。XRD分析表明，蒸发物是Mg元素。结合Mg元素的蒸发机制，在该试验条件下推导出Mg元素蒸发率的计算公式以及Mg元素的表观传质系数、蒸发率与精炼温度的关系，计算得出Mg元素蒸发率为0．86×10^-3-1．35×10^3g／cm^2·s，Mg元素的表观传质系数在2×10^-5-24×10^-5cm／s范围内。     

Si纳米纤维的等离子体制备工艺

本文利用电弧等离子体蒸发制备了纳米Ｓｉ纤维，通过沉积温度场的调节，确定了纤维的最佳沉积温度约６００℃，同时表征了纤维的生长过程，在一定的温度下，Ｓｉ团聚体颗粒间的“颈连接”及颗粒表面的非晶层是导致团聚体自扩散和表面扩散一维生长的直接条件。     

Induction plasma spheroidization of tungsten and molybdenum powders

The melting, evaporation and oxidation behaviors as well as the solidification phenomena of tungsten and molybdenum in induction plasma were studied. Scanning electron microscopy was used to examine the morphology and the cross section of plasma-processed powders. X-ray diffraction was used to analyze the oxides formed on the particle surface of these two metals. The influence of spray chamber pressure on the spheroidization and oxidation phenomena was discussed. The results show that fewer Mo particles than W particles are spheroidized at the same powder feed rate under the same plasma spray condition although molybdenum has a lower melting point. A small fraction of tungsten is evaporized and condensed either on the surface of tungsten particles nearby or on the wall of spray chamber. Tungsten oxides were found in tungsten powder processed under soft vacuum condition. Extremely large grains form inside some spheroidized particles of tungsten powder.     

Effect of surface modification of metal hydride electrode on performance of MH/Ni batteries

A novel method was applied to the surface modification of the metal hydride(MH)electrode of MH/Ni batteries.Both sides of the electrode were plated with a thin silver film about 0.1μm thick using vacuum evaporation plating technology,and the effect of the electrode on the performance of MH/Ni batteries was examined.It is found that the surface modification can enhance the electrode conductivity and decrease the battery ohimic resistance.After surface modification,the discharge capacity at 5C(7.5A)is increased by 212 mA.h and the discharge voltage is increased by 0.11 V,the resistance of the batteries is also decreased by 32%.The batteries with modified electrode exhibit satisfactory durability.The remaining capacity of the modified batteries is 89%of the initial capacity even after 500 cycles.The inner pressure of the batteries during overcharging is lowered and the charging efficiency of the batteries is improved.     

蒸发法制备Ni－Ti纳米非晶合金粒子

采用气相蒸发法制备纳米量级的Ｎｉ－Ｔｉ非晶合金粒子，研究了各种因素对Ｎｉ－Ｔｉ纳米非晶合金粒子形成的影响，并用透射电子显微镜，高分辨电子显微镜，Ｘ射线衍射仪和能谱等多种手段对纳米非晶合金粒子进行了表征．结果表明，当粒子成分在共晶区Ｎｉ（４０）Ｔｉ（６０）附近时，容易形成非晶；较低惰性气体压力和较高蒸发温度有利于Ｎｉ－Ｔｉ纳米非晶粒子的形成．     

Spin-valve magnetoresistance in Co/Si/（Co/Cu/Co） multilayers

A series of Co/Si/（Co/Cu/Co） multilayers and Co/Si/Co sandwiches were prepared by high vacuum electron-beam evaporation. It was found that a Si spacer （≥0.9 nm） could greatly decrease the interlayer coupling in Co/Si/Co sandwiches and there was no magnetoresistance（MR） or spin-valve MR in them due to the high resistivity of Si spacer. While in Co/Si/（Co/Cu/Co） multilayers, we observed a spin-valve MR of about 0.5% through a nominal 2.7 nm Si spacer at room temperature. The spin-valve MR in Co/Si/（Co/Cu/Co） multilayers was attributed to the enhanced spin polarization of conduction electrons caused by the top Co/Cu/Co sandwich with GMR mechanism and high spin-dependent scattering at Co/Cu interface.     

薄膜厚度对HfO2薄膜残余应力的影响

HfO2薄膜是用电子束蒸发方法制备的，利用ZYGO干涉仪测量了基片镀膜前后曲率半径的变化，计算了薄膜应力。对样品进行了XRD测试，讨论了膜厚对薄膜残余应力的影响。结果发现不同厚度HfO2薄膜的残余应力均为张应力，应力值随薄膜厚度的增加而减小，当薄膜厚度达到一定值后，应力值趋于稳定。从微观结构变化对实验结果进行了分析，发现微结构演变引起的本征应力变化是引起薄膜残余应力改变的主要因素。     

The influence of thermal annealing on residual stresses and mechanical properties of arc-evaporated TiCxN1−x (x=0, 0.15 and 0.45) thin films

We report the stress relaxation behavior of arc-evaporated TiC_xN_1−x thin films during isothermal annealing between 350 and 900°C. Films with x=0, 0.15, and 0.45, each having an initial compressive intrinsic stress σ_int=−5.4 GPa, were deposited by varying the substrate bias V_s and the gas composition. Annealing above the deposition temperature leads to a steep decrease in the magnitude of σ_int to a saturation stress value, which is a function of the annealing temperature. The corresponding apparent activation energies for stress relaxation are E_a=2.4, 2.9, and 3.1 eV, for x=0, 0.15, and 0.45, respectively. TiC_0.45N_0.55 films with a lower initial stress σ_int=−3 GPa, obtained using a high substrate bias, show a higher activation energy E_a=4.2 eV. In all the films, stress relaxation is accompanied by a decrease in defect density indicated by the decreased width of X-ray diffraction peaks and decreased strain contrast in transmission electron micrographs. Correlation of these results with film hardness and microstructure measurements indicates that the stress relaxation is a result of point-defect annihilation taking place both during short-lived metal-ion surface collision cascades during deposition, and during post-deposition annealing by thermally activated processes. The difference in E_a for the films of the same composition deposited at different V_s suggests the existence of different types of point-defect configurations and recombination mechanisms.     

Characterization of nanocrystalline AlTiN coatings synthesized by a cathodic-arc deposition process

Graded and multilayered Al_xTi_1−xN nanocrystalline coatings were synthesized by using cathodic-arc evaporation (CAE) process. Ti₃₃Al₆₇ and Ti₅₀Al₅₀ alloy cathodes were used for the deposition of Al_xTi_1−xN nanocrystalline coatings with different Al/(Ti+Al) ratios. Optical emission spectra of the plasma species including atomic and ionized Ti, atomic Al, excited and ionized nitrogen (N₂ and N₂⁺) revealed that the excitation, ionization and charge transfer reactions of the Al-Ti-N plasma occurred during the Al_xTi_1−xN coating process. A preferred (111) orientation was shown in the Al_0.67Ti_0.33N with high Al/(Ti+Al) atomic content ratio (0.63) and small grain size (29 nm). The graded Al_0.67Ti_0.33N/TiN possessed the highest hardness of Hv_25 g 3850 ± 180. However, the multilayered Al_0.67Ti_0.33N/TiN coating supported a longer tool life with lower residual stress. It has been found that the wear performance and mechanical properties of the films were correlated with the Al/(Ti+Al) content ratio and multilayered structure.     

钠基膨润土防水毯在滹沱河防洪整治中的试验研究

结合滹沱河防洪综合整治工程,对钠基膨润土防水毯建立试验模型,着重研究不同试验水头、外界环境条件(温度、风力等因素)对钠基膨润土防水毯的渗水量、水分蒸发量和渗透系数的变化规律。研究结果表明:试验水头与渗透系数成非线性关系,且渗水量随水位的增加而增加,渗透系数随水位的增加而减小。通过模型试验验证了钠基膨润土防水毯高密实、高防水等特点,为类似的防洪综合整治工程提供了技术支撑。