一种用于太阳能电池背电极的超细球形铝粉浆料

采用具有不同粒径级配的球形铝粉制备了能够与硅片形成性能良好太阳能电池背电极的铝浆,并在硅片上制备了铝电极膜。研究了铝粉粒径级配对铝电极膜性能的影响。结果表明:随着超细球形铝粉(0.5~2.0μm)含量的增多,铝电极膜层的填充性、致密性得到了增强,太阳能电池的光电转换效率η得到了提高;与不含超细球形铝粉的样品相比,w(超细球形铝粉)为8%时的太阳能电池的η提高了约4%。超细球形铝粉含量过多(如15%)时,铝电极膜表面容易析出铝珠,电极膜机械强度降低甚至出现灰化脱落。     

酸洗前处理对叠层片式电感器焊接性的影响

采用电子扫描电镜和能谱分析研究了叠层片式电感器(MLCI)端电极的三层结构对焊接性的影响。利用氢氟酸(HF)具有强氧化性的特点对产品端电极银层进行微蚀前处理以起到整平作用,利于镀层的生长。试验结果证明前处理酸洗工艺能够有效改善产品镀层的焊接性。使用质量分数2%的HF进行酸洗,能够有效去除端电极银镀层上的玻璃相成分(SiO2),从而使电感器镀层表面上锡覆盖率大于90%。     

PEDOT:PSS-CNT Composite Particles Overcome Contact Resistances in Slurry Electrodes for Flow-Electrode Capacitive Deionization

Activated carbon (AC) particles constitute the current material of choice concerning the preparation of flow electrodes for flow-electrode capacitive deionization (FCDI). They are inexpensive, mass-producible, highly conductive, and exhibit a large specific surface area for ion adsorption. However, despite recent advances concerning the modification of AC slurries, their density, and hydrophobicity still constitute major challenges regarding particle aggregation, sedimentation, and pumpability, restricting their particle load to approximately 25 wt.%. Since the particle volume fraction directly correlates to the chance of particle contact, which dictates the charge transfer and hence the degree of flow electrode utilization, the development of AC-based slurries seems to stagnate. This study addresses these challenges by investigating poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based suspensions as an alternative to conventional carbon-based flow electrodes. The corresponding conductive hydrogel particles feature softness, internal porosity, low density, hydrophilicity, and a mass-specific salt adsorption capacity that exceeds AC by up to ten times. FCDI experiments can reveal that, contrary to AC, the inherent properties of PEDOT:PSS-based particles simplify the slurry preparation process and enable flow electrode circulation at significantly higher particle volume fractions. These results suggest that PEDOT:PSS-based hydrogel particles are a promising candidate to overcome the percolation and contact-related challenges of state-of-the-art AC slurries.     

超细铜粉的化学镀锡及其抗氧化性能研究

以水合肼还原法制备出平均粒径约1μm的超细铜粉,并对其进行化学镀锡。研究了镀锡层对复合粉末微观形貌及抗氧化性能的影响。结果表明:镀覆质量分数50%的锡后,复合粉末平均粒径有所减小,但在空气中的氧化起始温度从120℃提高到220℃,与镀银层相比,镀锡层在较低温度区间对铜粉抗氧化具有优势。     

基于等效球形颗粒数的颗粒物质量浓度算法

从Mie散射理论出发,推导了粒子计数器(OPC)测量球形颗粒物质量浓度的计算公式.考虑非球形颗粒,从颗粒群粒度分布概念出发,提出了统计意义上的等效球形颗粒数概念,给出了非球形颗粒物质量浓度的理论公式,并利用该理论公式阐明了OPC测量非球形颗粒物质量浓度计算公式的合理性,进而给出了基于等效球形颗粒数的悬浮颗粒物的质量浓度算法.实验结果表明,该算法的质量浓度计算值与实际值十分吻合,因而为实现OPC在线测量悬浮颗粒物的质量浓度提供了一种可行途径.     

三电极碳纳米管传感器的极间距优化

三电极碳纳米管传感器各电极之间的间距大小是影响检测精度的关键因素之一。在用传感器阵列检测多组分气体混合物时,各传感器的极间距很难确定。为三电极碳纳米管气体传感器提出一种基于粒子群算法(PSO)的极间距优化方法。该方法包括设计极间距、组建由不同极间距的多个传感器组成的传感器阵列、建立包括极间距及检测离子电流的数据库、建立混合气体定量分析模型及极间距优化等步骤。采用多组由不同极间距的三个碳纳米管传感器构成的传感器阵列对NO和SO2 混合气体进行测量,其中各传感器的极间距均采用上述方法优化。实验结果显示,上述极间距优化方法能够有效地选择电极之间的最佳间距,优化极间距后的传感器也获得了更高的检测灵敏度。     

Optimization of thermal interface materials for electronics cooling applications

Thermal interface materials (TIMs) are used in electronics cooling applications to decrease the thermal contact resistance between surfaces in contact. A methodology to determine the optimal volume fraction of filler particles in TIMs for minimizing the thermal contact resistance is presented. The method uses finite element analysis to solve the coupled thermo-mechanical problem. It is shown that there exists an optimal filler volume fraction which depends not only on the distribution of the filler particles in a TIM but also on the thickness of the TIM layer, the contact pressure and the shape and the size of the filler particles. A contact resistance alleviation factor is defined to quantify the effect of these parameters on the contact conductance with the use of TIMs. For the filler and matrix materials considered-platelet-shaped boron nitride filler particles in a silicone matrix-the maximum observed enhancement in contact conductance with the use of TIMs was by a factor of as much as nine.     

机械活化燃烧合成AlN-Al_2O_3复合陶瓷粉

在催化剂氯化铵的作用下,将高能球磨机械活化后的工业铝粉置于空气中自燃,制备出了AlN质量分数约为80%的AlN-Al2O3复合粉体。通过对原始铝粉和球磨铝粉的形貌进行对比分析,探讨了球磨对铝粉的机械力化学效应。借助XRD和扫描电镜分析了燃烧产物的物相、形貌和结构,结果表明,生成的AlN颗粒主要集中于燃烧产物中心部,粒径为2μm;生成的Al2O3颗粒则主要分布于燃烧产物外表面,粒径为100nm。     

同轴载气送粉激光熔覆粉末流参数研究

同轴气动送粉激光熔覆过程中,金属粉末落入熔池的速度、浓度的分布等物理参数对熔覆层的形貌有一定的影响。DPIV(d igital partic le im age veloc im etry)是试验确定粉末流运动规律的有效方法,通过建立DPIV试验装置,对同轴载气送粉装置输送的粉末的速度、浓度进行了取值计算。结果表明,随气体流量的增加粉末的浓度有一定的减少。沿z轴方向,存在发散汇聚在发散的变化,粉末粒子流量与粒子速度在一定范围内有线性关系,超出Mp=0.33g/s~0.83g/s,Vp=0~1.3m/s范围,其影响将减弱。     

基于二次裂变粒子群算法的盲信号分离

针对粒子群算法对盲信号分离存在的问题,提出二次裂变技术。首先将粒子集中的权值按照逐渐递减顺时针的进行排序,减少搜索算法的时间开销;接着选取一定数目大权值的粒子进行裂变繁殖,繁殖后再生的粒子自粒子集权值的低端逆时针依次覆盖原小权值的粒子,数目正比于原来的粒子群;最后对第二次裂变的数目判断,进行相应扩展或者收缩运算。实验仿真结果表明:二次裂变粒子群算法具有分离效果好、收敛速度快的优点。     

Low-voltage lab-on-chip for micro and nanoparticles manipulation and detection: experimental results

In this paper, a low voltage fully integrated Laboratory-on-Chip (LoC) for dielectrophoretic manipulation and capacitive sensing of nano and micro particles is presented. The proposed system is intended to design an implantable LoC. The lowest static power consumption of the implemented Integrated circuit is 650???A with a voltage supply of ?1.10 and +1.8?V. Three different sizes of carboxyl-modified polystyrene particles (diameters of 0.22, 0.97 and 2.04???m) where tested experimentally with three different electrode architectures to achieve dielectrophoretic mixing and separation. U-shaped, L-shaped and octagonal electrodes are used to perform the separation and mixing operations. The biosensing part is designed with a charge based capacitive sensor with an integrated sigma-delta modulator at its output stage. It was tested experimentally with algae and ethanol. The chip size is 1.2 by 1.2?mm and it is connected to a 15?×?30?cm microfluidic design. An efficient particle manipulation was achieved by applying a voltage of 1.7 V peak to peak in the microchannel with 90 and 180° dephased signals.     

Nanoporous Membrane Electrodes with an Ordered Array of Hollow Giant Carbon Nanotubes

This study proposes a next-generation model membrane electrode for fundamental electrochemical research of amorphous-based porous carbon materials. This novel electrode is fabricated by the uniform carbon coating of anodic aluminum oxide formed on an Al substrate and free from a barrier layer. The conformally carbon-coated layer forms vertically aligned giant carbon nanotubes, and their walls comprise low-crystalline stacked graphene sheets. The diameter and the length of the nanopores can be tuned over a broad range of between 10 to 200 nm and 2 to 90 µm, respectively. Moreover, unlike composite electrodes made from other ordered nanoporous carbons, this model electrode exhibits an absence of inter-particle spacing and hence no contact resistance between particles. Thus, this model electrode provides representative nanopores of low-crystalline carbon materials. An atomic-scale structural model of the low-crystalline carbon walls is built with the aid of an in-house temperature-programmed desorption system to enable theoretical simulations to be performed. Using this model electrode, the electrical conductivity of low-crystalline carbon walls and mass transportation in an electric double-layer system are elucidated. This representative model electrode is expected to help clarify the complex electrochemical processes in porous carbon electrodes.     

Modeling of multi-layered structure containing heterogeneous material layer with randomly distributed particles using infinite element method

In the electronics industry, filler particles are added to the epoxy to form a composite material in order to adjust the elastic modulus and the coefficient of thermal expansion (CTE). This paper enhances the infinite element method (IEM) for modeling and analyzing a multi-layered structure such as flip-chip assembly containing a heterogeneous material layer reinforced with randomly distributed multiple particles under thermal loading. The proposed method provides a straightforward and efficient means of modeling multiple particles since only one IE stiffness matrix of particle needs to be calculated for all of the other particles. Moreover, in analyzing the material interface problem, the proposed technique could put many number of element layers to measure the high stresses close to the edge of the multi-layered structure, and was easily applied to compare the maximum interfacial stresses near the corner.A series of problems relating to multi-layered structures containing heterogeneous materials are investigated. Initially, this study investigates the effect of varying the volume fraction of randomly arranged particles in the heterogeneous layer on the effective properties of the layer. The results obtained for the effective properties of the heterogeneous material and their influence on the interfacial stress are compared to those obtained from the Mori-Tanaka analytical method. Finally, in addition to equivalent models, three-dimensional finite element models containing multiple randomly distributed particles were built and studied. It is shown that at the free edge the interfacial stresses decrease when the number of particles close to the interface increases.     

激光熔注WCp/Ti-6Al-4V梯度复合材料层形成机制

采用激光熔注(LMI)技术在Ti-6Al-4V表面制备了WCp/Ti-6Al-4V梯度复合材料(MMC)层,对其形成机制进行了研究.研究结果表明,WC颗粒在复合材料层中的分布与其初始速度v0、穿越熔池表面最小临界速度vmin以及熔池粘度η有关.由于WC陶瓷颗粒密度大,在激光熔注过程中具有较高的动能,熔池粘度不再是决定梯度复合材料层形成的关键因素.对于WC/Ti材料体系,熔池凝固前沿是形成WCp/Ti-6Al-4V梯度复合材料层的重要因素,复合材料层不同深度范围内WC颗粒的数量由这一深度熔池凝同前沿长度所决定.WC颗粒注入位置对其在复合材料层中的分布有很大影响.在WC颗粒由熔池后部"拖尾"注入的情况下,该区域熔池深度较浅,WC颗粒遇到的熔池凝固前沿位于较高的位置,大多数WC颗粒被"冻结"在复合材料层的上部,进而形成了WCp/Ti-6Al-4V梯度复合材料层.     

0-3型压电复合材料的硬球无规堆积模型

根据换能器用０－３型压电复合材料中压电陶瓷颗粒精度相等及分布均匀的特性,建立了０－３型压电复合槽糕的硬球无规堆积模型,阐明了复合材料中包裹压电陶瓷颗粒的聚合物厚度随压电陶瓷体积比的变化,给出了不同制备工艺（流延法、热压法）制备理想换能器用０－３电压复合材料的最大压电陶瓷的体积比。并基于广义自洽模型分析了０－３压电复合材料的中压电陶瓷颗粒的有效极化场。     

电子墨水用SiO2白色电泳颗粒的表面包裹及荷电

采用控制正硅酸乙酯在氨水-无水乙醇中水解的方法,制备出适合电子墨水使用的白色SiO2颗粒。将经H2O2浸泡,由甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)表面改性的SiO2颗粒,与苯乙烯单体分散在异丙醇中,采用自由基共聚法在SiO2颗粒表面包裹不同厚度的聚苯乙烯包4裹层。采用场发射扫描电镜(Field Emission Scanning Electron Micro-scopes)、高分辨率透射电镜(High Resolution Transmission Electron Microscopes)、傅立叶变换红外光谱(Fourier Transform Infrared Ray)、纳米粒度及Zeta电位分析(Zetasizer)等分析方法,研究了包裹前后SiO2颗粒的表面形貌、颗粒尺寸及包裹层厚,包裹后颗粒的表面化学键合情况,颗粒在四氯乙烯中的表面Zeta电位以及在四氯乙烯中的分散性。结果表明:自制SiO2颗粒呈球形,粒径约300 nm,SiO2颗粒表面包裹了聚苯乙烯,包裹层较为均匀完整,层厚约为10～25 nm,并随包裹颗粒时所加苯乙烯单体量增大而变厚,颗粒在四氯乙烯中的表面Zeta电位由-4.26 mV提高到-49.47 mV,包裹后颗粒在电势为9 V的电场下,响应时间理论计算值到达40 ms,颗粒在四氯乙烯中的分散性良好,分散后静置48 h,分散率可达到87%。     

硅片线锯砂浆中硅粉与碳化硅粉的泡沫浮选分离回收

以对碳化硅表面有选择性的脂肪酸作为捕收剂,采用泡沫浮选分离方法来分离回收硅片线锯砂浆中的和碳化硅粉。研究了捕收剂浓度、起泡剂浓度、浮选溶液的温度及pH值对分离效果的影响。当浮选溶液中捕收浓度为0.315mol/L,起泡剂浓度为0.18mol/L,温度为70℃,pH值为4.5时,分离效果最佳:浮起产物中碳化粉质量分数为99.3%,沉淀产物中硅粉质量分数为95.9%。     

Scattering of radiowaves by a melting layer of precipitation inbackward and forward directions

A melting layer of precipitation is composed of melting snowflakes (snow particles); the assumption of spherical particles along with mass conservation is used. The melting layer is studied by deriving the size distribution of the melting snow particles, the thickness of a melting layer, the density of a dry snow particle, and the average dielectric constant of a melting snow particle. Vertical profiles of radar reflectivity and specific attenuation are computed at 1-100 GHz by using the Mie theory for five raindrop size distributions at rain rates below 12.5 mm/h. The radar bright band is explained with computed radar reflectivities at 3-10 GHz. It is shown that the radar bright band can be absent in the melting layer at frequencies above 20 GHz. This agrees with radar observations at 35 and 94 GHz. The specific attenuation, as well as the average specific attenuation of the melting layer, is divided into absorption part and scattering part. The latter is increasingly significant with the increase of frequency. The total zenith attenuation due to stratiform rain is divided into the rain zenith attenuation and the additional zenith attenuation, which is the difference between zenith attenuation, due to the melting layer, and attenuation, due to the same path length of the resulting rain. The additional zenith attenuation increases with the increase of rain rate even at frequencies above 20 GHz. This should be taken into account in radar remote sensing and satellite-Earth communications     

含片状粒子涂层的热辐射

用几何光学绕射理论研究了片状粒子的散射，由非均匀系统的热辐射传输方程求出了含片状粒子涂层的表观比辐射率，讨论了片状粒子的线度、体积化、涂层厚度等因素对涂层系统辐射性能的影响，比较了含片状粒子涂层和含球状粒子涂层的辐射性能。     

片状FeCoZr合金吸收剂吸波性能的正交实验

采用气雾化和机械球磨结合的方法制备片状FeCoZr合金磁粉吸收剂,利用正交实验综合研究了球磨时间、吸收剂粒径和含量对吸波材料在2～18GHz内吸波性能的影响。结果表明:在设计范围内,各因素对吸波材料反射损耗的影响顺序从大到小为:球磨时间、粒径和质量分数;获得的最佳工艺条件:球磨时间为15h、吸收剂粒径小于48μm及其质量分数为75%,从而实现了对吸波材料性能的优化设计。