Mechanical electrodeposition of bright nanocrystalline nickel

A new mechanical electrodeposition technology was proposed, and nanocrystalline nickel deposit with bright and smooth surface was prepared in the bath without any additive agents. Unlike traditional methods, the novel technology employed dynamical hard particles to continuously polish the cathode surface and disturb the nearby solution during electrodepositing. Experimental results showed that the polishing effect of hard particles can effectively prevent the hydrogen bubbles and impurities from adhering on the deposit surface and avoid the production of pits, pinholes and nodules. Furthermore, comparing with the deposit prepared by traditional methods, the one prepared by the novel technology was substantially refined with grain size ranging from 30 to 80 nm. Every diffraction peak’s intensity of the deposit was reduced, the preferential orientation degree of (200) decreased and those of (111) and (220) increased. The microhardness notably increased. The magnetic properties were also changed with decreased saturation magnetization and increased coercive force. It was also found that variation of current density and cathode rotational speed could affect the structure and properties of the nickel deposits prepared by this technology. Supported by the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2004005)     

低碳钢表面激光涂覆WC+Co的工艺研究

本文研究了利用激光作为热源在低碳钢表面涂覆WC+Co的工艺。利用光镜、扫描电镜、能谱成分分析及显微硬度等手段对涂层合金的组织和性能进行了分析。认为在低碳钢表面涂覆硬质合金的涂层组织性能取决于激光涂覆工艺与预涂层的质量。在较低的激光输出功率和较慢的扫描速率下,可以得到WC颗粒弥散分布于γ为基的固溶体上的组织,其硬度可达1400HV.较高的功率条件下,涂层组织是WC全部熔解重新生成的η+γ共晶组织,硬度降至1000HV.较快的扫描下涂覆层合金不易涂覆在基体上。     

高能脉冲冷焊Fe基合金改性层的组织及性能

为了进一步提高核泵用钢的耐磨性能及抗空蚀性能,采用高能脉冲冷焊技术在304不锈钢表面制备了Fe基合金改性层.利用扫描电子显微镜和X射线衍射仪分别对改性层的显微组织和相结构进行了分析,利用显微硬度计、摩擦磨损试验机及超声波振荡空蚀仪分别对改性层的显微硬度、耐磨性与抗空蚀性能进行了研究.结果表明,改性层组织细密,且主要由基体相α-Fe和硬质碳化物相Cr_(23)C_6和Cr_7C_3组成,改性层的最高显微硬度可达510 HV,相对耐磨性为3.88.空蚀5 h后,改性层的失重量和表面粗糙度分别约为304不锈钢基材的1/5和1/6.     

两步法合成MCFC复合阴极及其性能研究

基于前期研究,采用电泳沉积技术将摩尔比为1∶1的LiCoO2和LiFeO2两种纳米颗粒同时修饰至制得的抗形变/溶解复合材料Ⅰ表面（镍阴极材料内通过机械混合法掺杂质量分数2%、4%、6%Co3O4纳米颗粒）制成复合基体阴极Ⅱ。采用扫描电镜对制得的复合基体Ⅱ进行表面形貌分析,筛选出形貌较好的复合基体阴极Ⅱ及其电泳沉积条件。在模拟MCFC运行条件下,复合工作阴极Ⅱ具有良好的热稳定性和电活性,其中掺杂比为4%的复合工作阴极Ⅱ在100h溶解实验测试中溶出的镍离子浓度几乎为0。     

Microstructure of Ni / WC surface composite layer on gray iron substrate

The surface infiltrated composite (Ni/WC) layers on gray iron substrate were fabricated through a vacuum infiltration casting technique (VICT) using Ni-based composite powder with different WC particles content as raw materials.The microstructures of surface infiltrated composite layer,the interface structures between surface composite layer and the substrate,the changes of macro-hardness with the increasing of WC content and the micro-hardness distribution are investigated.The infiltrated composite layer includes a surface composite layer and a transition layer,and the thickness of the transition layer decreases with the increasing content of WC.The thickness of transition layer with 20%WC content in the surface infiltrated composite layer was 170 μm which was the thickest for all transition layers with different WC content.The surface composite layer was mainly composed of WC,W2C,FeB and NiB,along with Ni-Cr-Fe,Ni (Cr) solid solution,Ni (Si) solid solution and Ni (Fe) solid solution.The transition layer was composed of Ni (Cr) solid solution,Ni (Fe) solid solution,Ni (Si) solid solution,Fe (Ni) solid solution and eutectic.The surface macro-hardness and micro-hardness of the infiltrated layer had been evaluated.The macro-hardness of the surface composite layer decreases with the WC content increasing,and the average macro-hardness is HRC60.The distribution of micro-hardness presents gradient change.The average micro-hardness of the infiltrated layer is about HV1000.     

连续碳纤维增强金属基复合材料增材制造工艺

针对连续碳纤维增强金属基复合材料增材制造工艺开展系统性实验探索,研究结果表明：在对碳纤维进行表面改性后,可以实现打印过程中熔融金属基体与碳纤维的良好浸润复合;送丝速度对单道沉积路径表面质量、路径宽度及其纤维体积分数影响较大,当送丝速度为4 mm/s时,沉积路径表面质量较好,路径宽度约为1.5 mm,碳纤维体积分数约为3.43%;沉积路径搭接率对打印单层表面质量影响较大,当搭接率为50%时,单层表面质量较好;基于优化后的实验参数,实现了连续碳纤维增强金属基复合材料薄壁件以及拉伸样件的直接增材制造,薄壁件内碳纤维与金属基体形成了较好结合,而且连续碳纤维对于复合后材料的抗拉强度起到了显著增强作用.     

原位自生TiC颗粒对铁基耐磨堆焊金属的影响

为了研究原位自生TiC颗粒对堆焊层组织与性能的影响,采用药芯焊丝明弧堆焊方法在Q235钢表面制备了Fe-Cr-Ti-C堆焊合金.利用X射线衍射仪、扫描电子显微镜、洛氏硬度计和湿砂磨损试验机对堆焊合金进行了分析.结果表明,加入的Ti元素可在堆焊层中原位生成TiC硬质相颗粒,并促进M7C3硬质相的生成,从而起到细化晶粒的作用.当生成的TiC和M7C3硬质相数量较多且弥散分布于金属基体中时,这些硬质相可起到相应的抗磨骨架作用,从而提高了堆焊金属的耐磨性.当药芯焊丝中Ti元素的质量分数为7%时,堆焊层性能最佳,其硬度值为61.6HRC,磨损量为0.3904g.     

A NOVEL MODIFICATION TECHNIQUE FOR METAL SURFACE

A novel solultion-arc discharge surface modi-fication technique has been introduced in this paper, In thismodification technique,the speed of mass transport in surfaceand diffusion layer is much higher than that of other ways,such as ion implantation,PVD,CVD,PCVD,glow dischargeplasma treatment,etc.The solution-arc discharge plasma be-longs to a plasma in high air pressure.Its cathode electricfield,electric charge densiry and current density are muchlarger than those of low temperature plasma.The voltage-current characteristic has been measured.Mechanical and elec-trochemical propertiks of same steel treated with solution-arcdischarge have been studied.As to the mechanism of thts tech-nique,an analysis has been given.     

Novel Nanosized Adsorbing Composite Cathode Materials for the Next Generational Lithium Battery

A novel carbon-sulfur nano-composite material was synthesized by heating sublimed sulfur and high surface area activated carbon （HSAAC） under certain conditions. The physical and chemical per- formances of the novel carbon-sulfur nano-composite were characterized by scanning electron microscopy （SEM）, Brunauer-Emmett-Teller （BET） and X-ray diffraction （XRD）. The electrochemical performances of nano-composite were characterized by charge-discharge characteristic, cyclic voltammetry and electrochemical impendence spectroscopy （EIS）. The experimental results indicate that the electrochemical capability of nano- composite material was superior to that of traditional S-containing composite material. The cathode made by carbon-sulfur nano-composite material shows a good cycle ability and a high specific charge-discharge capacity. The HSAAC shows a vital role in adsorbing sublimed sulfur and the polysulfides within the cathode and is an excellent electric conductor for a sulfur cathode and prevents the shuttle behavior of the lithium-sulfur battery.     

Wear-resistance Performance of Spray-welding Coating by Plasma Weld-surfacing

Alloy powders including Ni60, WC, Cr_3C_2, and TiC with different mass ratios were deposited on medium carbon low alloy steel by plasma welding. Through the experiments, the optimal alloy powder reinforcing cutter tool surface properties were discovered. The wear resistance properties were investigated on the impact abrasive wear tester. The experimental results show that in terms of microstructure, there exists the shape of herringbone, spider mesh, broken flower structures in coatings. In addition, fusion area of four specimens surfacing welding layer displays a large number of acicular martensite with a small amount of austenite. The coating mainly consists of Ni-Cr-Fe austenitic phase and the other precipitates. TiC density is smaller, its content is less in alloy powder, in the process of surfacing welding, TiC is melted fully, which is mainly distributed in surface layer and middle layer of hard facing layer. The content of TiC gradually reduces from surface layer of hard facing layer to the fusion area. Compared to TiC, the density of tungsten carbide and chromium carbide is larger, there exist tungsten carbide and chromium carbide particles, which are not completely melted near the fusion area. The micro-hardness presents gradient change from the fusion area to the surface layer of hard facing layer, and the hardness of the middle layer is slightly lower than that of the fusion area, and the hardness increases near the surface layer.     

喷射电铸快速成型技术的试验研究

介绍了喷射电铸快速成型技术的原理与系统组成，通过实验研究与分析了喷射电铸的特点，用喷射电铸快速成型设备制备了具有简单形状的纳米晶金属铜零件。用扫描电镜（SEM）和X射线衍射手段对其微观形貌和组织结构进行了分析。     

LaB6复合型场发射阵列阴极的结构设计

为了提高传统Spindt型场发射阵列阴极的稳定性,提出了一种新型的LaB₆复合型场发射阵列阴极结构,该结构包括非晶硅电阻层、钼过渡层和六硼化镧发射体层。基于ANSYS平台模拟了该阴极中电阻层、过渡层和发射体层厚度对热应力场分布的影响,并根据仿真结果进行了实验验证。仿真结果表明,电阻层厚度不影响热应力场的分布,只是改变热应力的大小;随着电阻层厚度的增加,阴极最大热应力会减小;过渡层可以有效减缓发射层的热应力,且过渡层的厚度会影响热应力场的分布;当电阻层厚度为72 nm,过渡层厚度为200 nm,发射层厚度为728 nm时,阴极最为稳定。薄膜热应力测试结果与模拟结果基本一致,证实了引入过渡层和电阻层对于减小阴极热应力的可行性。     

航空薄壁框类零件铣削加工表面质量研究

刀具-薄壁深腔框类零件是一个弱刚性系统,在铣削力作用下,刀具及框类零件的薄壁结构发生挠曲,出现欠切与过切,从而使加工厚度产生偏差,严重影响工件加工精度和表面质量.首先介绍铣削力的计算方法,在此基础上研究刀具弯曲、壁板挠曲对加工表面质量的影响.采用有限元法依次计算任意加工点处刀具及壁板的刚度,推导铣削薄壁框类零件时厚度偏差的计算,提出极限铣削力概念.通过数值算例,研究减小加工偏差的方法,提高航空薄壁零件加工精度.     

分散方式对Ni-Si_3N_4纳米复合电镀层显微组织和性能的影响

采用超声波分散加机械搅拌技术在纯铜板上制备了含有纳米Si3N4颗粒的镍基纳米复合镀层,研究了分散方式对复合镀层中纳米颗粒含量、复合镀层组织结构、显微硬度和磨损性能的影响。利用扫描电镜(SEM)和X-射线衍射仪(XRD)分析了镀层表面的显微组织及相结构,通过磨损实验机检测了复合镀层的耐磨性能。结果表明,采用超声波分散技术可获得组织细密、高显微硬度的纳米复合镀层,其显微硬度最高可达996 HV,耐磨性能较未经超声波分散处理的镀层有显著提高。     

基于信号与系统理论的多媒体故障分析方法研究

多媒体系统因其设备与线路较为繁杂,发生故障时往往难以定位设备故障或线路问题。根据信号与系统理论,提出了多媒体故障的信号路径分析方法,归纳了该方法的两个操作步骤,简要分析其通用性,并综合运用该方法对常见的多媒体教学系统故障进行了示例分析,证明了该方法的有效性。     

微弧氧化技术在高压齿轮水泵中的应用

为了在良好的加工工艺和高性价比前提下,提高水压元件的摩擦磨损特性和耐蚀性能,利用微弧氧化技术在常规液压元件的工作表面制备陶瓷化涂层,使其能直接应用于水压传动系统.应用该技术在材质为ADC12的高压齿轮泵的浮动侧板表面原位生成致密的陶瓷氧化层,其厚度可达130m以上,硬度可达HV1000以上.将经过陶瓷化处理的高压齿轮泵用于水压传动试验表明,该泵工作运行稳定,最高出口压力可达16MPa.在现阶段整体工程陶瓷元件应用于水压传动尚不成熟的情况下,使用微弧氧化技术进行元件表面改性是一种经济可行的方法.     

Optimization of material removal strategy in milling of thin-walled parts

The optimal material removal strategy can improve a geometric accuracy and surface quality of thin-walled parts such as turbine blades and blisks in high-speed ball end milling.The dominant conception in the material removal represents the persistence of the workpiece cutting stiffness in operation to advance the machining accuracy and machining efficiency.On the basis of theoretical models of cutting stiffness and deformation,finite element method (FEM) is applied to calculate the virtual displacements of the thin-walled part under given virtual loads at the nodes of the discrete surface.With the reference of deformation distribution of the thin-walled part,the milling material removal strategy is optimized to make the best of bracing ability of still uncut material.This material removal method is summarized as the lower stiffness region removed firstly and the higher stiffness region removed next.Analytical and experimental results show the availability,which has been verified by the blade machining test in this work,for thin-walled parts to reduce cutting deformation and meliorate machining quality.     

吸附法制备CuO/SiO2纳米复合材料

为了研究和控制CuO粒子的生长，提出了一种利用吸附相纳米反应器制备纳米粒子的新方法.在SiO2表面的吸附层反应器中得到CuO纳米粒子，由络合滴定法测定了Cu离子的吸附速度，利用XRD、TEM、EDX和溶剂置换的方法研究了反应和吸附过程的特性.结果表明，Cu离子的吸附在1 h内达到平衡，60%的Cu离子被吸附到SiO2表面.随着温度的升高，吸附层体积会减小且络合吸附作用得到加强.由于吸附层度的限制，CuO晶粒粒径会减小.反庆在吸附层内发生，随水量的增加，SiO2表面环境发生突变，Cu量迅速达到最大值并不再改变.     

航空机匣零件加工变形量预测与控制

航空机匣类零件通常由航空难加工材料制成,壁薄、刚性差、难加工,极易发生切削变形。因 此,以航空薄壁机匣零件为研究对象,基于切削加工力学建模,采用有限元分析方法,实现了对航空薄壁机 匣零件车削加工变形量的预测。在此基础上,采用加工变形量主动补偿方法,通过对每次走刀的切削深度进 行补偿以减少加工变形量。有限元仿真与切削试验结果均显示,采用该方法可以大大减少加工变形误差并使 其分布更加均匀,可有效地控制切削加工变形量。     

Al_2O_3包覆对富锂锰基正极材料Li_(1.2)Mn_(0.54)Co_(0.13)Ni_(0.13)O_2的电化学性能影响

采用水热法合成富锂三元正极材料,探究了最佳包覆比例下Al_2O_3包覆对材料的电化学性能影响.采用扫描电镜(SEM)和X射线衍射仪(XRD)表征了富锂三元正极材料的表面形貌和结构,通过循环伏安(CV)、交流阻抗(EIS)技术分析了材料电化学性的影响因素.结果表明,通过异丙醇铝水解制得了氧化铝包覆层,提高了材料的比容量,稳定了材料的结构.