铁-镍纳米粉末的制备及其表征

通过差热分析、透射电镜和X射线衍射分析等方法，对以硝酸铁和硝酸镍为主要原料，采用溶胶-凝胶法和化学共还原法制取的镍质量分数分别为10％和20％的铁-镍纳米粉末进行了表征，同时比较聚乙二醇和柠檬酸在制备凝胶时的分散效果。结果表明：以柠檬酸为分散剂，制备的铁-镍纳米粉末的粒径在：30nm左右，成分为(Fe，Ni)和少量(Ni，Fe)Fe2O4的混合物，无其他杂质。     

石墨烯/碳纳米管气凝胶的制备及其弹性性能

以Hummers法制备的氧化石墨烯和管径为30~50nm、长50~100μm的碳纳米管为原料,采用水热还原法及冷冻干燥处理制备了石墨烯气凝胶和石墨烯/碳纳米管气凝胶,研究了气凝胶的物相组成、微观形貌和弹性性能,分析了碳纳米管对弹性性能的影响机理。结果表明:两种气凝胶均具有三维多孔结构,碳纳米管均匀地分布在石墨烯上,并且缠绕在石墨烯片层的内壁和片层间的连接点处;石墨烯/碳纳米管气凝胶的可回复压缩变形量高达90%,远大于石墨烯气凝胶的;碳纳米管可以有效地防止层叠石墨烯片层间的滑动,提高石墨烯的结构稳固性。     

以MCM-41分子筛为催化剂载体制备碳纳米管

通过比较水热法和室温法制得的MCM-41分子筛的不同性能, 选择适于催化合成碳纳米管的MCM-41的制备方法, 以MCM-41分子筛为催化剂载体用CVD法制备碳纳米管,并分析其所制备的碳纳米管的特点和生长机理。使用XRD、低温N2吸附、SEM、TEM等测试手段对MCM-41分子筛、催化剂材料及合成碳纳米管产物进行表征。结果表明,水热法合成的MCM-41分子筛较适合用来作为制备碳纳米管的催化剂载体,其介孔结构对碳纳米管的生长起到了一定的模板控制作用,所制备的碳纳米管具有管径小、尺寸单一等特点。     

碳纳米管薄膜的制备及其超疏水性研究

采用化学气相沉积法在平面硅基体上制备碳纳米管薄膜,并通过扫描电子显微镜、透射电子显微镜和接触角测量仪对样品进行形貌结构和浸润性质的表征。结果表明:碳纳米管的定向性主要由基体上催化剂粒子的分布控制,并遵循顶部生长生长机制;2种碳纳米管薄膜都具有较大的接触角,获得的定向碳纳米管表面具有微纳米复合结构是产生超疏水的主要原因。     

碳纳米管在润滑脂中的摩擦学性能及机制研究

以碳纳米管为添加剂制备锂基润滑脂,并探究碳纳米管含量、管径及管长对其摩擦学性能的影响。结果表明:碳纳米管可明显提高润滑脂的摩擦学性能;随碳纳米管质量分数的增加,润滑脂的摩擦学性能先提高后下降,碳纳米管质量分数为0.05%时润滑脂的摩擦学性能最佳;添加管径小、管长大的碳纳米管时润滑脂表现出更优秀的摩擦学性能,这是因为管径小、管长大的碳纳米管可能更容易被填充到表面微凸体的凹槽中。磨斑XPS结果显示,润滑膜中有氧化铁及碳纳米管的存在,氧化铁与碳纳米管等边界膜起到减摩抗磨的作用。     

生长温度对TCVD法制备定向碳纳米管薄膜影响

本文通过磁控溅射技术在单晶硅上制备了Ni薄膜作为催化剂,采用热化学气相沉积法(TCVD)以乙炔为碳源,合成了定向碳纳米管薄膜.通过扫描电子显微镜(SEM)和透射电子显微镜(TEM)表征了碳纳米管薄膜的表面微观形貌和内部结构,考察了温度对氨刻蚀催化剂膜和定向生长碳纳米管薄膜过程的影响.结果表明:在其他工艺参数条件一定的情况下,只有反应温度在750℃左右时,颗粒大小适中、分布均匀、催化活性适当、管型较准直;由透射电镜分析发现,在单晶硅上生长的碳纳米管为顶端生长模式,并初步讨论了制备取向碳纳米管的生长机理.     

纳米Mn-Zn软磁铁氧体的制备与性能研究

纳米Mn-Zn软磁铁氧体以硝酸铁、硝酸锌、硝酸锰和柠檬酸为原料,利用溶胶-凝胶凝胶自蔓延燃烧工艺合成纳米级Mn-Zn铁氧体粉体.用X-衍射(XRD)分析了粉体的粒径大小和强度是否符合标准,利用高压投射电子显微镜、振动样品磁强计(VSM)、研究了烧结MnZn铁氧体的成相状态、磁性能.通过分析得到最佳制备条件:Mn:Zn=0.55:0.45、pH值为5、煅烧温度为200℃、煅烧时间为90 min.     

BaTi03/铁氧体复合材料的制备及性能

采用传统溶胶-凝胶法和改进的柠檬酸盐溶胶-凝胶法制得了钦酸钡,并对其进行了比较.采用柠檬酸-EDTA的联合络合溶胶-凝胶法制得了针状纳米锶铁氧体磁性微粒,并将钛酸钡和锶铁氧体进行了复合.利用XRD对样品的物相进行分析,利用TEM对样品形貌和粒径进行表征,利用振荡样品磁强计(VSM)对样品进行了磁性能研究,并利用矢量网络分析仪对粉末的电磁波吸收性能进行了表征.结果表明,在2～6GHz范围内,钛酸钡质量分数为30%的复合材料在850℃煅烧2h后吸波性能最佳,最大吸收量为28dB,10dB频带宽度为1.7GHz.     

凝胶-热分解法制备NiFe_2O_4纳米粉末及其性能表征

以硝酸铁、硝酸镍以及柠檬酸为原料,采用凝胶-热分解法制备出了尖晶石NiFe2O4纳米粉末。研究了凝胶-热分解法的反应机理和反应过程,讨论了热处理温度对颗粒平均尺寸以及性能的影响。利用X射线衍射(XRD)、TEM以及VSM对样品物性进行表征,结果表明,所制样品为纯相的NiFe2O4纳米颗粒,颗粒的大小为35～65 nm,且颗粒的粒径随热处理温度的升高而增大,当热处理温度为700℃时,颗粒大小均匀、分散性好,比饱和磁化强度达到54.63 emu/g。同时,作者也对反应的动力学原理进行了研究,得出NiFe2O4纳米颗粒形成的活化能为16.15 kJ/mol。     

基于碳纳米管-纳米金甲醛气体电化学传感器的研究

多孔气体扩散电极的制备是甲醛电化学传感器开发的关键所在.通过柠檬酸三钠还原法合成了纳米金-碳纳米管催化剂,制备了甲醛电化学传感器多孔气体扩散电极,并对催化剂和多孔扩散电极进行SEM、EDS、XRD表征.在甲醛气体浓度为0.24 mg/m3和0.63 mg/m3时对组装的传感器进行了响应性能测试.甲醛浓度在0.10～0.84 mg/m3时,传感器的线性方程为:y=10.291x+4.4161(R2=0.9960),响应时间大约80 s.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....