高能球磨法制备不锈钢-TiC纳米复合粉末的研究

在真空条件下采用高能球磨法以不锈钢粉末、钛粉和碳粉为原料制备了不锈钢-TiC超细复合粉末.X射线、扫描电子显微镜、比表面积评价等分析技术被用来对球磨过程中粉末的微观状态进行了分析.结果表明,随着球磨时间的增加,不锈钢复合粉末逐渐细化,用X射线衍射方法计算的最终晶粒可达到20nm.同时,钛粉和碳粉在球磨过程中发生反应形成TiC,可获得纳米级的不锈钢-TiC复合粉末.     

化学镀法制备纳米Ni-B包覆Al复合粉末

以硼氢化钾(KBH4)为还原剂,采用化学镀法制备了纳米Ni-B包覆Al复合粉末,研究了镀液组分及工艺对包覆效果的影响,获得了制备复合粉末的优化条件。采用SEM,XRD,ICP和BET对复合粉末的表面形貌、物相结构、元素组成和比表面积进行了表征分析。结果表明:纳米Ni-B在Al表面包覆连续、均匀,且纳米Ni-B呈非晶态,粒径80~100nm,化学组成约为Ni72B28,纳米Ni-B/Al复合粉末比表面积达到了26.21m2.g-1。     

机械合金化法制备W—Cu合金的研究

采用高能球磨的机械合金化法制备W—Cu合金,对其在实验过程中的工艺条件进行了研究。结果表明：随着球磨时间的延长,粉末的粒度逐渐细化,比表面积逐渐增大。球磨过程分为三个阶段。最佳工艺条件是：当球料比为5：1,W：Cu为8：2,球磨时间达到30h时,铜粉和钨粉基本形成固溶体。球磨过程加入少量的无水乙醇,防止在球磨过程中粉末被氧化。     

金属微粉的制备及其颗粒特性

采用高能机械球磨法制备了金属铁、钨微粉 ,分析了铁、钨粉末产品的粒度分布特性、比表面积变化情况及颗粒形貌。     

高活性中孔型纳米二氧化硅粉末制备新工艺的探索

用溶胶－凝胶法制备出SiO2凝胶后，首次结合并采用低温热处理以及球磨工艺制备出高活性中孔型纳米SiO2粉末。利用TEM等手段分析了热处理温度、球磨对其显微结构及其物性的影响。结果表明，选择合适的热处理机制和适当的球磨时间可制备出具有很高表面能和表面活性的中孔型纳米SiO2粉末。本方法设备要求及操作过程简单，是一种具有发展前景的新型工艺。     

高能球磨法制备铁、钨金属微粉的研究

用高能机械球磨法制备了金属铁、钨微粉，对振动磨的结构及破碎原理作了简要介绍，分析了铁、钨粉末产品的粒度分布特性、比表面积变化情况，讨论了原料性质、球磨时间、球磨强度、球料比等因素对高能球磨过程的影响。     

溶胶-球磨超细W-Cu复合粉末烧结性能研究

采用溶胶-球磨法制备W-10Cu、W-20Cu复合粉末,研究了球磨工艺对粉末粒度、形貌和烧结性能的影响。研究结果表明,球磨粉末呈现双峰粒度分布,球磨20h的W-10Cu、W-20Cu粉末的粒度分别为1.03和1.15μm。球磨过程中,粉末比表面积变换式ln[(Sm-S0)/(Sm-S)]与球磨时间t符合线性关系。W-10Cu、W-20Cu复合粉末球磨20h,可以在1380℃一步液相烧结达到近全致密,显微组织细小且均匀。     

纳米复合碳化钨-钴粉末的分散与粒度表征

为研究纳米复合碳化钨-钴粉末的分散稳定性和粒度表征方法，以一定量分散介质和分散剂作用于纳米复合碳化钨-钴粉末，利用氮吸附法(BET)、光子相关光谱法(PCS)和电位分析仪分别测试了粉末的比表面积、粒度及其分布和粉末的ξ电位．研究结果表明：高比重的纳米复合碳化钨-钴粉末经一定工艺处理后具有相当的分散稳定性，但长时间球磨对分散并非有利；用BET可表征一次粒径，而PCS则表征二次粒径。     

热喷涂球磨法制备超细铜锌粉

本文将热喷涂法与机械球磨法相结合,提出一种新的超细铜锌粉末的制备方法.讨论了热喷涂工艺参数、球磨时间、球磨助剂、热处理条件对粉末性质的影响,并采用扫描电镜法、X射线衍射法、筛分法对粉末的粒度、形貌、成分等进行了分析,得出最佳工艺参数.该方法可以制备出粒度分布均匀、性质稳定、粒度为200～500nm的超细铜锌粉末.     

反应球磨钛与尿素制备氮化钛的反应机理研究

将Ti粉与尿素在室温下进行反应球磨制备了TiN粉末,对球磨不同时间后的粉末进行XRD分析,采用TG-FTIR技术分析了尿素的分解温度与产物,利用TEM及EELS观察和分析了球磨70h粉末的微观形貌、结构及成分. 结果发现,球磨70h合成了纳米TiN粉末,晶粒度为6~7nm,Ti/N原子比约为1.0∶0.6. 经800℃,5h真空退火处理后粉末的XRD谱图表明粉末组成为单相TiN. 在反应球磨过程中,Ti与尿素的分解产物NH₃与HNCO发生反应形成TiN,随球磨时间延长,Ti的缺陷能增大、活性增加,N在Ti中的扩散激活能减小,在球磨作用下N的扩散距离变短,TiN的含量逐渐增加形成晶核并逐渐长大形成纳米晶.     

锡掺杂的氧化铟纳米粉体的表面修饰与改性

为了提高锡掺杂的氧化铟纳米粉体在有机单体甲基丙烯酸甲酯(MMA)中的分散效果,采用球磨、辅助超声等方法,选用PEG4000、KH570、油酸和十八醇等作为分散剂,对纳米粉体进行表面修饰和改性.研究了分散剂种类、添加量及球磨时间对纳米粉体分散稳定性的影响.找出了在MMA单体中分散最好的纳米粉体改性工艺条件:以乙二醇为分散介质、锡掺杂氧化铟纳米粉体摩尔分数为0.1%的KH570和0.016%的一缩二乙二醇为分散剂,球磨10 h,辅助超声30 min,红外干燥.采用高分辨透射电镜(HRTEM)和红外光谱(FT-IR)等对其结构和包裹性能进行了表征,结果显示粉体粒径约为50 nm,表面被无定形分散剂所包裹,颗粒之间无明显团聚现象,分散性好.     

纳米石墨的制备方法(英文)

简要概述了现有的纳米石墨制备方法,这些方法从材料来源上可以分为2类,一类由鳞片石墨来制备,另一类由富碳材料合成.由鳞片石墨制备纳米石墨的方法主要有球磨法、超声波粉碎法、爆轰裂解法和电化学插层法;由富碳材料合成纳米石墨的方法主要包括爆轰合成法、化学气相沉积法、激光脉冲沉积法和化学合成法.     

Microwave synthesis and sintering of Mg4Nb2O9 nanoceramics

Mg₄Nb₂O₉ nanopowders were prepared from MgO and Nb₂O₅ mixtures by using a high energy ball milling method, combined with subsequent annealing at low temperatures by microwave heating. After milling for 20 h, pure phase Mg₄Nb₂O₉ nanopowders with an average grain size of 127 nm were obtained at 850, 130 °C lower than that required by a conventional solid state reaction process. Mg₄Nb₂O₉ ceramics sintered at a low temperature of 1,300 °C using microwave heating showed almost full density and excellent microwave dielectric properties (ε_r = 12.9, Q × f = 174,200 GHz and τ_f = ?68).     

Mechanical synthesis of high purity Cu–In–Se alloy nanopowder as precursor for printed CISe thin film solar cells

Mechanical alloying and ball milling are low cost, up-scalable techniques for the preparation of high purity chalcogenide nanopowders to be used as precursor material for printing thin film solar cells. In this study, high purity copper indium selenium (Cu–In–Se) alloy nanopowders with 20–200 nm particle size were synthesized from macroscopic elemental Cu, In and Se powders via mechanical alloying and planetary ball milling. The particle size distribution, morphology, composition, and purity level of the synthesized Cu–In–Se alloy nanopowders were investigated. Thin Cu–In–Se alloy nanopowder ink coatings, deposited on Mo-coated glass substrates by doctor blading, were converted into a CuInSe₂ semiconductor film by selenization heat treatment in Se vapor. The CuInSe₂ film showed semiconducting band gap around 1 eV measured by photoluminescence spectroscopy. CuInSe₂ absorber layer based thin film solar cell devices were fabricated to assess their performance. The solar cell device showed a total efficiency of 4.8%, as measured on 0.25 cm² area cell.     

Enhanced thermoelectric figure-of-merit in p-type nanostructured bismuth antimony tellurium alloys made from elemental chunks

By ball milling alloyed bulk crystalline ingots into nanopowders and hot pressing them, we had demonstrated high figure-of-merit in nanostructured bulk bismuth antimony telluride. In this study, we use the same ball milling and hot press technique, but start with elemental chunks of bismuth, antimony, and tellurium to avoid the ingot formation step. We show that a peak ZT of about 1.3 in the temperature range of 75 and 100 degrees C has been achieved. This process is more economical and environmentally friendly than starting from alloyed bulk crystalline ingots. The ZT improvement is caused mostly by the lower thermal conductivity, similar as the case using ingot. Transmission electron microscopy observations of the microstructures suggest that the lower thermal conductivity is mainly due to the increased phonon scattering from the increased grain boundaries of the nanograins, precipitates, nanodots, and defects. Our material also exhibits a ZT of 0.7 at 250 degrees C, similar to the value obtained when ingot was used. This study demonstrates that high ZT values can be achieved in nanostructured bulk materials with ball milling elemental chunks, suggesting that the approach can be applied to other materials that are hard to be made into ingot, in addition to its advantage of lower manufacturing cost.     

Fe-Cu 系机械球磨合金化研究

目的为了实现Fe粉和Cu粉的合金化及观察其过程变化。方法采用机械球磨的方法,利用扫描电子显微镜等仪器,对球磨过程中的组织演变过程及微观形貌进行了研究。结果通过球磨得到了十几个纳米尺寸的晶粒。结论通过球磨可以得到过饱和固溶体。     

Barium titanate nanoparticles produced by planetary ball milling and piezoelectric properties of corresponding ceramics

Barium titanate (BaTiO₃) nanocrystalline powders were prepared by solid state reaction route starting from BaCO₃ and TiO₂ powders accompanied by high-energy ball milling. Different samples were prepared by varying the milling time from 1 h to 30 h, keeping the milling speed fixed at 250 rpm. All the milled powders were examined with TEM. The particle size first decreases from 105 nm to a minimum of 28 nm as the milling time increases from 1 h to 20 h and then increases to 38 nm with further increase of milling time to 30 h. Dense ceramics were formed by sintering the nanopowders at 1350 °C for 4 h. With decreasing particle size of the starting nanopowders, the ceramics exhibit gradual increase in density from 5.65 g/cc to 5.84 g/cc, coercive field (E_c) from 2.25 kV/cm to 4.77 kV/cm and piezoelectric charge constant (d₃₃) from 99pC/N to 121pC/N.     

Fabrication and characterization of nanostructured Ti6Al4V powder from machining scraps

In recent years researches on properties of nanocrystalline materials in comparison with coarse-grained materials has attracted a great deal of attention. The present investigation has been based on production of nanocrystalline Ti6Al4V powder by means of high energy mechanical milling. In this regard, Ti6Al4V powder was produced by ball milling of machining scraps of Ti6Al4V. The structural and morphological changes of powders were investigated by X-ray diffraction, scanning electron microscopy, and microhardness measurements. The results revealed that ball milling process reduced the size of the coherent-scattering region of Ti6Al4V to approximately 20 nm. Also a remarkable change in morphology and particle size was occurred during ball milling. Moreover, phase evolution during milling was taken into consideration. The as-milled Ti6Al4V powder exhibited higher microhardness comparing to the original samples.     

NH_3BH_3/NaH复合物及其水解特性

以NaH为诱导剂,通过高能球磨工艺制备NH3BH3和NaH的复合物,分析研究了复合物的物相、颗粒形态及其水解性能。结果表明在球磨过程中NH3BH3和NaH反应生成NaBH4新相,但反应并不完全,复合物中的NH3BH3包覆在NaH和生成的NaBH4颗粒表面并发生部分非晶化。诱导剂NaH的加入能有效地改善NH3BH3的水解放氢性能。当NH3BH3/NaH为2.5：1,60℃下,0.1g该复合物10min内放出125mL的H2,约为10.2%（质量分数）,其中一半来源于H2O。     

Enhanced thermoelectric figure of merit of p-type half-Heuslers

Half-Heuslers would be important thermoelectric materials due to their high temperature stability and abundance if their dimensionless thermoelectric figure of merit (ZT) could be made high enough. The highest peak ZT of a p-type half-Heusler has been so far reported about 0.5 due to the high thermal conductivity. Through a nanocomposite approach using ball milling and hot pressing, we have achieved a peak ZT of 0.8 at 700 °C, which is about 60% higher than the best reported 0.5 and might be good enough for consideration for waste heat recovery in car exhaust systems. The improvement comes from a simultaneous increase in Seebeck coefficient and a significant decrease in thermal conductivity due to nanostructures. The samples were made by first forming alloyed ingots using arc melting and then creating nanopowders by ball milling the ingots and finally obtaining dense bulk by hot pressing. Further improvement in ZT is expected when average grain sizes are made smaller than 100 nm.