高能球磨制备纳米TiO2/纳米晶Cu超细复合粉体

采用高能球磨法制备了TiO2/Cu复合粉体并采用X射线衍射(XRD)、显微图像分析仪等测试分析方法,对球磨过程中复合粉末相结构、组织形貌和粒度分布的变化进行了研究.结果表明:球磨24 h后可形成纳米TiO2粉体/纳米晶Cu复合粉体,Cu粉晶粒达59 nm;随着球磨时间的增加,纳米TiO2团聚体逐渐嵌入Cu颗粒中,被很好地分散开,呈弥散分布;同时复合粉体粒度细化到300 nm以下,比表面积大大增加,粉体也由球形逐渐地过渡到多角形.     

超声和微波作用下制备纳米氧化铜

以氢氧化铜为前驱体，在超声和微波作用下制备纳米氧化铜。借助透射电镜（TEM）、X射线衍射（XRD）、粒度分析等手段，研究了超声、分散剂、微波等制备条件的影响。结果表明：采用该法可以制备粒径小（15nm）、分散良好的纳米氧化铜粉体；超声可使前驱体Cu（OH）2转变为CuO，并粉碎颗粒间形成的团聚；分散剂通过表面修饰抑制颗粒的团聚；微波加热促进了前驱体的转化，并抑制颗粒的长大。     

直流氢电弧等离子体蒸发法制备纳米锡粉

采用高纯锡,通过自行设计的直流电弧等离子体蒸发设备制备了纯净的纳米锡粉。利用X射线衍射（XRD）、透射电子显微镜（TEM）和选区电子衍射（ED）以及Simple PCI软件对样品的成分、形貌、晶体结构和粒径分布进行了分析。结果表明：在本文制备工艺参数条件下,该设备可以成功制备平均粒径为26至49nm的纳米锡粉;粉体的产率和粒径随充气压力升高而增大。所制备的纳米锡粉颗粒细小,纯净,为多晶结构;通过分析不同腔体内的粉体粒径,发现距离钨电极越远,所形成的颗粒尺寸越大。     

热注入法制备银纳米颗粒及其性能表征

采用热注入法,以AgNO3为前躯体,乙二醇为还原剂,聚乙烯吡咯烷酮为稳定剂和分散剂,制备银纳米颗粒。利用透射电子显微镜（TEM）、X射线衍射仪（XRD）和紫外-可见光分光光度计（UV-Vis）对产物银颗粒的尺寸形貌、晶体结构以及光学性能进行了表征,同时根据Mie散射理论对消光谱进行模拟计算。结果表明,同传统的一步化学还原法相比,利用热注入法制备的银纳米颗粒粒径分布更加均匀,分散性更好。所制备的银颗粒呈类球形,粒度约为20 nm,其共振吸收谱线同模拟计算的结果基本符合。     

阳极弧等离子体制备镍纳米粉的性能表征

采用阳极弧放电等离子体方法成功制备了高纯镍纳米粉末;利用X射线衍射（XRD）、透射电子显微镜（TEM）和选区电子衍射（SAED）、BET吸附法测试手段对试样的成分、形貌、晶体结构、比表面积、粒度及其分布进行性能表征,并采用元素分析仪测定C,H,N含量,采用X射线能量色散分析谱仪（EDS）测定试样所含的元素及其相对含量,用红外吸收光谱（FT-1R）对结构组成进行定性分析.实验结果表明：本法所制备的镍纳米粉末的晶体结构与相应的块体材料基本相同,为fcc结构的晶态,平均粒径为47 nm,粒度范围分布在20 nm～70 nm,呈规则的球形链状分布,比表面积为14.23 m2/g,试样纯度高且具有很强吸附性.     

X射线小角散测量氮化铁磁性液体中颗粒的粒度

通过X射线小角散射测定了氮经铁磁性液体中氮化铁纳米级磁性颗粒的粒度分布和平均粒度。通过和透射电镜检测得到的粒度结果进行比较,发现两者得到的检测数据误差不超过10％。由此可以证明X射线小角散射方法可以适用于磁性液体中纳米粉末的粒度分布和平均粒度测量。     

Bi-2223/Ag超导带材前驱粉与热处理的匹配问题

研究了Bi-2223／Ag高温超导带材的前驱粉与后续热处理工艺之间的匹配问题。实验采用A，B，C3种不同的前驱粉。A粉是成分配比为2223的喷雾热分解单粉，B粉和C粉都是2212加CaCuO，组分的2223双粉。B粉和C粉的区别在于，2212加CaCuO，混合后的除碳处理工艺不同。B粉为800℃，3h，C粉为830℃，10h。利用激光粒度分析仪（RSA）和扫描电镜（SEM）对这3种前驱粉的粒度进行了表征，并用X射线衍射仪（XRD）对用这3种粉分别制成的带材经第1次热处理（HT1）后的2223成相率和相结构进行分析，从而找出它们各自对应的最佳HT1工艺。采用四引线法在77K，0T下测试经中间轧制和第2次热处理（HT2）后的临界电流（五），以确定其对应之最佳HT2工艺。RSA和SEM分析表明：A粉颗粒度明显细小，平均中径粒度为1．5μm，且粒径分布区域集中，B粉约3μm，粒径分布较分散，而C粉为4-5μm。研究结果证明：前驱粉的特性直接影响着超导带材的最终超导性能。一种特定的前驱粉，对应着一种特定的最佳HT1和HT2工艺。只有在二者匹配良好前提下，才能使前驱粉的性能得以发掘。     

钒元素对纳米钨粉在高温加热过程中颗粒长大的抑制作用

采用V（NO3）5为抑制剂，分别加入到溶胶-凝胶反应前的钨酸铵溶液中及溶胶反应后的凝胶体中，制备含V前躯体粉，并经二阶段低温还原法制备纳米W粉。采用XRD表征了纳米W粉经650—950℃保温30min处理过程物相的组成及相的变化，用FESEM观察分析了纳米W粉的颗粒形貌。用定量金相测定了不同处理温度下的颗粒尺寸。初步探讨了以V（NO3）5为抑制剂对纳米W粉在还原阶段及加热保温阶段长大的抑制效果。结果表明，V（NO3）5作为抑制剂的加入可有效抑制纳米W粉在还原阶段及加热保温阶段的长大。     

化学共沉淀法制备钨铜合金

首先采用化学共沉淀法制备钨铜复合氧化物粉末,再用氢还原得到纳米级钨铜复合粉末,经成形和烧结得到超细弥散分布钨铜合金.研究结果表明,采用化学共沉淀法结合氢还原工艺制备的W-20%Cu纳米复合粉,W颗粒粒度为30～50 nm,形状呈多边形,Cu相均匀分布在W相之间将W颗粒粘结.所制得的钨铜复合粉表现出高的烧结活性,经1250℃烧结其相对密度达到99.7%,热导率达到223.1 W/m·K,导电性、抗弯强度以及硬度等性能也比传统产品有大幅度提高.     

表面钝化处理对纳米Zn粉抗氧化性能的影响

采用高频感应线圈加热 ,以蒸发—冷凝法制备了纳米Zn粉 ,粉末平均粒径 30nm。借助X射线衍射、X射线光电子能谱和差热失重分析等测试手段 ,研究了表面钝化处理对纳米Zn粉抗氧化热稳定性能的影响。研究结果表明 ,经过表面钝化处理的纳米Zn粉在低于熔点温度的条件下具有较好的抗氧化性能     

Characterization of nanometer tungsten powders

Three types of tungsten powders were prepared by hydrogen reduction of three precursor powders at low temperature,which were used as samples,and were then characterized by Brunauer-Emmer-Teller (BET) method,scanning electron microscopy (SEM),transmission electronic microscopy (TEM),small angle X-ray scattering (SAXS),and field-emission scanning electron microscopy (FESEM) respectively.The results showed that although BET and SEM could not characterize the particle size of nanometer powders,they were important means of assistance to exclude non-nanometer powders.TEM and FESEM could directly measure the particle size of nanometer powders,but this needs a lot of time,to count the average particle size and particle size distribution.SAXS could not describe the state of agglomeration.By the combination of FESEM and SAXS,the particle size,particle size distribution,and particle shape of nanorneter powders could be preciscly characterized.     

Synthesis of nanosized tungsten carbide from phenol formaldehyde resin coated precursors

Nanosized tungsten carbide was synthesized from phenol formaldehyde resin (PF) coated tungsten precursors.The process has three steps in which nanosized tungsten particles were first coated with PF,then the precursors were carburized at 950℃,and finally the carburized powders were treated in flowing wet hydrogen atmosphere at 940℃ to remove the uncombined carbon.The obtained powders were characterizedusing X-ray diffraction analysis (XRD),field-emission scanning electron microscopy (FESEM),small angle X-ray scattering (SAXS),andcombustion-gas-volume method.The results indicated that single-phase WC could be synthesized using excessive PF as carburizer at a muchlower temperature compared with using mixed carbon black.After wet hydrogen treating,the mean size of the obtained WC particles was 94.5nm and the total carbon content was 6.18 wt.%.     

纳米稀土金属Gd的制备及其粒径评估

采用惰性气体保护蒸发凝聚技术，制备了粒径为４～１５ｎｍ的稀土金属Ｇｄ微粉。利用小角Ｘ射线散射（ＳＡＸＳ）、Ｘ射线衍射曲线宽化（ＸＲＤ）、喇曼散射光谱（ＲＳＳ）及电子显微镜（ＴＥＭ）对所制备的纳米Ｇｄ微粉（ｎｍ－Ｇｄ）进行了较广泛和深入的微观分析，探讨了ｎｍ－Ｇｄ微粉的粒径分布及其结构特征。ｎｍ－Ｇｄ体系的平均粒径ｄ与制备气压Ｐ符合如下线性关系：ｄ＝ａ＋ｂｌｎＰ。粒径分布函数符合Ｒａｙｌｅｉｇｈ统计分布，这不同于一般文献中采用ＴＥＭ方法分析得出的对数正态分布。此外还对ｎｍ－Ｇｄ体系的比表面积、表面原子百分比及界面体积分数等结构参数进行了评估，以揭示它们与平均粒径ｄ的关系。实验结果与理论计算曲线能较好吻合     

纳米银粉的水热LSS法制备与表征

以乙醇和油酸为液相(L),油酸钠为固相(S),硝酸银水溶液为溶液相(S),用水热LSS相转移法制备了纳米银粉并对其进行表征。正交实验表明,影响纳米银粉产率的因素依次为水热处理时间乙醇用量油酸用量油酸钠用量,优化条件下所得纳米银粉产率达75.4%;用XRD、TEM和SAXS对制备的银粉进行表征,结果显示所得纳米银粉为形状规则的近球形纯银颗粒,粒度均匀且无明显团聚,平均粒径约23.7 nm。     

Microstructural characterization of the V-doped nano-titania

A new modified sol–gel method has been developed to synthesize undoped nano-titania and vanadium-doped nano-titania. XRD data and the Raman spectra indicate that even after 10 mol% doping of vanadium in the crystal lattice sites of TiO₂, the samples are phase pure with the anatase structure. The average particle size of these materials is about 11.5 nm, as calculated from the XRD peak broadening and TEM. Small angle X-ray scattering (SAXS) was also used for the determination of the particle size of these vanadium-doped titania samples. The SAXS parameters were determined assuming near spherical particle shape. The SAXS results were in agreement with the particle size as obtained by TEM. A negligible variation in the particle size was observed as a function of doping percentage upto a limiting value of 5 mol% doping of vanadium in the TiO₂ lattice. The results of the SAXS are in good agreement with the XRD and the TEM results.     

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 carbon source on the carbothermal reduction nitridation for synthesis of (Ti, W, Mo, V)(C, N) nanocrystalline powders

The effect of carbon source on the carbothermal reduction-nitridation during synthesizing (Ti, W, Mo, V)(C, N) nanocrystalline powders was investigated. For a systematic comparison, activated carbon, graphite and two kinds of carbon black powder were used as reducing agents in this study. Ultrafine (Ti, W, Mo, V)(C, N) powders with a particle size of ~ 200-500 nm have been produced at 1450 °C for 2 h by using nanosized carbon black source with small particle size. The presence of phases in the reaction products was characterized with X-ray diffraction (XRD) and the microstructure of carbon source powders and final products was studied by scanning electron microscopy (SEM). The results show that the formation of the Ti(C, N) phase is strongly dependent on the particle size of carbon source powders, and the synthesizing temperature of the Ti(C, N) phase decreases significantly from 1750 °C to 1300 °C by using nanosized carbon black, as compared with micron graphite. In addition, activated carbon with a particle size of 5-50 μm does not favor the dissolution of tungsten or molybdenum carbides into Ti(C, N) despite its large specific surface area.     

Microstructure and properties of liquid-phase sintered tungsten heavy alloys by using ultra-fine tungsten powders

The microstructure and properties of liquid-phase sintered 93W-4.9Ni-2.1Fe tungsten heavy alloys using ultra-fine tungsten powders (medium particle size of 700 nm) and original tungsten powders (medium particle size of 3um) were investigated respectively. Commercial tungsten powders (original tungsten powders) were mechanically milled in a high-energy attritor mill for 35 h. Ultra-fine tungsten powders and commercial Ni, Fe powders were consolidated into green compacts by using CIP method and liquid-phase sintering at 1465℃ for 30 rain in the dissociated ammonia atmosphere. Liquid-phase sintered tungsten heavy alloys using ultra-fine tungsten powders exhibit full densification (above 99% in relative density) and higher strength and elongation compared with conventional liquidphase sintered alloys using original tungsten powders due to lower sintering temperature at 1465℃ and short sintering time. The mechanical properties of sintered tungsten heavy alloy are found to be mainly dependent on the particles size of raw tungsten powders and liquid-phase sintering temperature.