Ag-Cu-MoS2复合材料的真空载流磨损性能

采用粉末冶金方法制备了含有不同Cu质量分数(2%~4%)的Ag-Cu-MoS_2复合材料,并对其力学性能、电学性能和真空载流磨损性能进行了研究.结果表明:较高Cu质量分数的Ag-Cu-MoS_2复合材料表现出较高的硬度和抗弯强度;中等Cu质量分数(2.5%和3%)的Ag-Cu-MoS_2复合材料电刷表现出较低的电压降和电噪声;滑动速度的增加会降低材料间的接触稳定性,进而导致较高的电压降和较大的电噪声.在真空载流条件下与Ag合金盘滑动摩擦过程,不同Cu质量分数的Ag-Cu-MoS_2复合材料电刷均表现出较低的磨损,其磨损率在1×10~(–14)m~3/(N·m)~2.5×10~(–14)m~3/(N·m)范围,其磨损机理主要为疲劳磨损以及黏着磨损.     

Enhanced phase sensitivity of an SU(1,1) interferometer with displaced squeezed vacuum light

We study the phase sensitivity of an SU(1,1) interferometer with two input beams in the displaced squeezed vacuum state and the coherent state, respectively. We find that there exists an optimal squeezing fraction of the displaced squeezed vacuum state that optimizes the phase sensitivity. We also examine the effects of some factors, including the loss, mean photon number of the input beams and amplitude gain of the optical parameter amplifiers, on the optimal squeezing fraction so that we can choose the optimal values to enhance the phase sensitivity.     

热注入法合成PbX(X=S,Se)量子点的结构和性能研究

采用热注入的方法在空气氛围中合成PbX(X=S,Se)量子点,液体石蜡和磷酸三丁酯(TBP)作为不同的溶剂优化PbSe量子点的合成;使用六甲基二硅硫烷(TMS)作为硫源合成了第一激子吸收峰在900 ～ 1500 nm分布的PbS量子点.通过透射电镜(TEM)、X射线衍射(XRD)和吸收光谱等测试手段对合成的物质进行成分与光学性能分析表征,对比研究了Ⅳ-Ⅵ族化合物量子点在成核过程中的差异.结果表明在相同的实验条件下PbS量子点的反应条件相对温和,量子限域效应明显;而PbSe量子点的合成对环境的要求更加严苛,反应温度更高,量子点的尺寸分布更宽.     

Initiation of vacuum breakdown and failure mechanism of the carbon nanotube during thermal field emission

The carbon nanotube(CNT)-based materials can be used as vacuum device cathodes. Owing to the excellent field emission properties of CNT, it has great potentials in the applications of an explosive field emission cathode. The falling off of CNT from the substrate, which frequently appears in experiments, restricts its application. In addition, the onset time of vacuum breakdown limits the performance of the high-power explosive-emission-cathode-based diode. In this paper, the characteristics of the CNT, electric field strength, contact resistance and the kind of substrate material are varied to study the parameter effects on the onset time of vacuum breakdown and failure mechanism of the CNT by using the finite element method.     

Hot corrosion behavior of the spray-formed nickel-based superalloy

An investigation of low temperature hot corrosion is carried out on a spray-formed nickel-based superalloy FGH100pre-coated with Na_2SO_4~- NaCl at 700℃ for 100 h. Mass gain measurement, x-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy are used to study the corrosion behavior. Results reveal that corrosion behavior follows a sequence, that is, first rapidly proceeding, then gradually slowing down, and finally forming an outer layer composed of different types of oxides and an inner layer mainly comprised of sulfides. In-depth analysis reveals that the hot corrosion of FGH100 is a combined effect of oxidation-sulfidation and transfer of oxides.     

Effect of pulsed bias on properties of ZrN/TiZrN films deposited by cathodic vacuum arc

ZrN/TiZrN multilayer are deposited by cathodic vacuum arc method with different substrate bias (from 0 to -800 V), using Ti and Zr plasma flows in residual N₂ atmosphere, combined with ion bombardment of sample surfaces. The effect of pulsed bias on structure and properties of films is investigated. Microstructure of the coating is analyzed by X-ray diffraction (XRD), and scanning electron microscopy (SEM). Meanwhile, the nanohardness, Young's modulus, and scratch tests are performed. The experimental results show that the films exhibit a nanoscale multilayer structure consisting of TiZrN and ZrN phases. Solid solutions are formed for component TiZrN films. The dominant preferred orientation of TiZrN films is (111) and (220). At pulsed bias of -200 V, the nanohardness and the adhesion strength of ZrN/TiZrN multilayer reach a maximum of 38 GPa, and 78 N, respectively. The ZrN/TiZrN multilayer demonstrates an enhanced nanohardness compared with binary TiN and ZrN films deposited under equivalent conditions.     

真空环境中油水分离的试验研究

针对真空环境中油水分离问题,以真空滤油机为研究对象,构建了多参数实时耦合的油水分离试验系统,并利用Labview软件进行了数据的采集和处理。分析了油水分离的主要影响因素,结果表明,在试验参数范围内,水的初始含水率对脱水率的影响较大,真空压力和温度对脱水率呈单调变化的趋势,运行时间存在一个较优值30s。上述结果可为深入研究真空滤油机油水分离机理提供参考。     

a-C：H膜的高真空磨损失效机制研究——应力的影响

采用中频非平衡磁控溅射法沉积了含氢无定形碳(ａ-C:H)薄膜,利用球-盘摩擦试验机考察了不同载荷下薄膜在高真空中(5.0×10^-3 Pa)的摩擦磨损行为,通过对磨损表面的分析以及相关的验证实验,探讨了应力(接触应力、薄膜内应力)对薄膜在高真空中摩擦磨损行为的影响.结果表明:在高真空中,随着载荷的增加,薄膜的摩擦系数逐渐降低,而耐磨寿命却急剧缩短;在高真空高接触应力下,无论是摩擦还是静压,薄膜表面均出现了明显的应力释放花样.因此可以认为,薄膜在高真空中的磨损失效与其在高接触应力下的内应力释放有密切关系.     

TiO2-SiO2二维大孔薄膜的制备及其光催化活性研究

本文采用改进的溶胶-凝胶法制备了具有锐钛矿晶型结构和较小晶粒尺寸的TiO₂-SiO₂溶胶,并以聚苯乙烯(PS)小球为模板,采用旋涂法制备了新型大孔TiO₂-SiO₂复合薄膜,探究了煅烧温度、不同硅钛比以及溶胶添加量对所制备的大孔薄膜形貌及光催化活性的影响,并考察了该薄膜真空活化前后(Ti³⁺掺杂后)在紫外及模拟太阳光下光催化降解有机污染物罗丹明B的活性。通过Raman、DRS、SEM、EPR等方法对薄膜进行表征,发现制备的复合薄膜具有高透明度、良好附着力及优异的光催化活性。     

自动真空液相色谱装置的研制及其在五味子成分分离中的应用

为满足天然产物高效分离的需求,本文研制了自动真空液相色谱(AUTO-VLC)装置并用于五味子石油醚萃取物的分离。该装置由自主设计的流动相储备系统、10通分流切换阀、3通切换阀、3个不同规格的动态轴向压缩色谱柱、10通馏分收集阀和馏分收集器组成,采用可编程逻辑控制器(PLC)S7-200实现了分离过程的不同比例流动相切换、不同规格色谱柱选择、分离时间设定及馏分收集的自动控制及监测。应用于五味子成分分离的结果表明:采用150 mm直径动态轴向压缩色谱柱的VLC,从100 g五味子石油醚萃取物中一次分离得到6个组成明显不同的样品(S1~S6)。建立了通过多次薄层色谱(TLC)展开筛选VLC分离条件的方法,并进行了分离验证。VLC分离条件选择方法:自动真空液相色谱的初始洗脱剂的比例以首次TLC展开时全部目标化合物的比移值(R_f)介于0~0.45时展开剂的组成为宜;梯度洗脱比例变化以k值(展开次数(n)与R_f的线性函数斜率)和TLC分离度为依据选择;不同R_f范围内洗脱次数由n≈ ΔR_f/k计算。采用选择的条件从样品S5中分离得到了13个组分和4个纯度在85%以上的化合物,仅耗时17 h。AUTO-VLC的研制对于中药成分的自动和系统性分离具有重要价值。