Bulk nanocrystalline Al prepared by cryomilling

Bulk nanocrystalline Al was fabricated by mechanically milling at cryogenic temperature (cryomilling) and then by hot pressing in vacuum. By using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), the microstructure evolution of the material during cryomilling and consolidation was investigated. With increasing the mill- ing time, the grain size decreased sharply and reduced to 42 nm when cryomilled for 12 h. The grains had grown up, and the colum- nar grain was formed under the hot pressing and extrusion compared with the cryomilled powders. The grain size of as-extruded specimen was approximately 300-500 nm. The reason of high thermal stability of this bulk was attributed primarily to the Zener pin- ning from the grain boundary of the AlN arising from cryomilling and the solute drag of the impurity. Tensile tests show that the strength of nanocrystalline Al is enhanced with decreasing grain size. The ultimate tensile strength and tensile elongation were 173 MPa and 17.5%, respectively. It appears that the measured high strength in the cryomilled Al is related to a grain-size effect, disper- sion strengthening, and dislocation strengthening.     

Na2CO3对CaO粉体的钝化效果影响

为提高相关CaO系材料的抗水化性能,通过在CaO粉体中加入Na2CO3添加剂,对其进行碳酸化处理,使其表面形成一层碳酸钙保护膜,并利用正交试验法探讨了如何引入Na2CO3添加剂为最佳组合条件的研究。结果表明,加热温度为500℃,水蒸气温度为40℃,CO2流量在3.5 L/min,通气时间30 min的条件下,存在Na2CO3添加剂的CaO粉体抗水化性效果较好,总增重率可降至13%,而吸水率可降至0.313%。     

太阳能级硅粉在等离子体中纯化研究

给出了本研究中所采用工业硅的要求和太阳电池功率高达14%的P型硅材料中单一杂质的阀值。针对太阳能级硅的纯化要求和工业硅的特性,提出了等离子体对硅粒“刻蚀提纯”的新概念。增加鞘层厚度将使硅粉浸泡于高动能离子中的几率增加,钝化效应消失从而达到提高纯化速率的目的。所研制的新型纯化系统能够满足硅粒自旋、长沉降时间和重复纯化的条件,所给出的工艺参数能满足鞘层宽、离子浓度高的要求。实验结果显示这种新的提纯方法可望用于太阳能级硅的制备。     

硅粉质量对甲基氯硅烷选择性的影响

根据有机硅单体合成反应机理和反应动力学,研究了原料硅粉质量、粒度及粒度分布对二甲基二氯硅烷选择性的影响,并对提高二甲基二氯硅烷选择性提出了建议.     

二氧化硅粉末的润湿性能与浸湿功

通过用动态法研究浸润粉层的液体重量随时间的变化规律,测定了甲、乙、丙、丁、戊醇对SiO2粉末层的平均毛细管半径、弯曲率、接触角及浸湿功.结果表明,醇对SiO2粉层的毛细管平均半径随碳氢链的增长而增加,除甲醇外.前进接触角亦随之增加.     

化学反应法钝化金属镁粒的试验研究

采用化学反应法对镁粒进行钝化处理,用正交试验法研究钝化剂组分、性质和钝化工艺参数等对阻燃时间的影响,确定了最佳钝化剂组成和钝化工艺参数。经检测,制备的钝化镁粒阻燃时间为18．21s,燃点为904K,活性镁含量达97．6％,满足铁水脱硫的工艺要求。SEM观察发现,钝化处理后镁粒表面生成了致密均匀的钝化层。试验采用的钝化工艺具有钝化成本低、活性镁含量高等特点。     

片状锌粉的可控钝化及电性能研究

采用水/酒精、双氧水溶液为氧化剂,制备了表面钝化Zn(OH)2的片状锌粉.采用X射线衍射(XRD)、热重分析(TG)、扫描电镜(SEM)对钝化锌粉进行了表征,考察了钝化增重对锌粉压片电阻率和漏电流密度的影响.结果表明,锌粉钝化后在表面形成鼓包状组织,随着氧化剂浓度和时间的增加,锌粉钝化增加;随着钝化膜的增厚,钝化锌粉的电阻率增加,漏电流密度减小.     

氢氧化铝超细粉体填料表面改性

研究了表面改性剂配比，用量，改性时间等对氢氧化铝超细粉体填料表面改性效果的影响及改性机理，实验结果表明最佳改性方案为：改性剂用纯丙三醇，改性剂对填料的液固比为15；改性温度为120℃，改性时间为4h。     

Synthesis of nanocrystalline NiCrC alloy feedstock powders for thermal spraying by cryogenic ball milling

Nanocrystalline NiCrC alloy powders with a qualified particle size distribution for thermal spraying were synthesized us-ing the cryogenic ball milling (cryomilling) method.The morphology,microstructure,size distribution,and phase transformation of the powders were characterized by scanning electron microscopy (SEM),laser scattering for particle size analysis,X-ray diffraction (XRD),and transmission electron microscopy (TEM).After cryomilling for 20 h,the average grain size of the as-milled powders ap-proached a constant value of 30 nm by XRD measurement.The average particle size slightly increased from 17.5 to 20.3 μm during the 20-h milling.About 90vo1% of the powders satisfied the requirement for thermal spraying with the particle dimension of 10-50 grn,and most of the powders exhibited spherical morphology,which were expected to have good fluidity during thermal spraying.The Cr2O3 phase formed during the cryomilling process as revealed in the XRD spectra,which was expected to enhance the thermal stability of the as-milled powders during the followed thermal spraying or other heat treatment.     

纳米锌锡氧化物的制备与表征

以四氯化锡和氯化锌(摩尔比4:1)为起始原料,在配制的一定浓度的水溶液体系中滴加氨水,于一定的焙烧温度下处理,获得了晶粒完整、粒度在20 nm左右的四方相锌锡氧化物晶体;借助热重差热分析(TG—DTA),X-射线衍射(XRD),对锌锡氧化物超细粉末的晶相组成、大小、烧结过程进行了分析.试验结果表明:pH值的调节、锌锡比是影响溶胶稳定的关键因素.XRD衍射表明,锌锡氧化物保持了SnO2原有的四方晶体结构.Zn2 的掺杂引起了晶格畸变.在400℃烧结时,Zn2 是进入O2-形成的间隙位置,形成间隙固溶体.在600℃烧结时,Zn2 进入Sn4 的晶格位子形成置换固溶体.     

燃烧合成法制备Si3N4粉体及其相组成影响因素的研究

氮化硅陶瓷材料因具有优异的热、力、电学性能，现已得到广泛应用，其原料制备也更加受到重视.现阶段的几种氮化硅粉体的制备方法存在着很多不足，因此采用燃烧合成工艺制备氮化硅粉体.燃烧合成工艺具有反应速度快、节能、产物纯度高等优点，但很难控制产物的相组成.主要介绍了燃烧合成反应的热力学及动力学；借助x 射线衍射仪和扫描电镜，在采用“归一法”定量计算的基础上探讨了α-Si₃N₄、β-Si₃N₄的形成机理和相组成的影响因素.     

激光能量对掺铒纳米Si晶薄膜形貌的影响

采用XeCl脉冲准分子激光器,保持激光脉冲比为1:2,分时烧蚀Er靶和高阻抗单晶Si靶。改变激光能量,在真空中沉积了掺Er非晶Si薄膜。在氮气保护下,分别在950℃,1010℃和1100℃温度下进行30min热退火处理,得到掺Er纳米晶Si薄膜。扫描电子显微镜的结果表明,高的退火温度或高的激光能量均会导致迷津结构的形成。     

Powder Extrusion Molding of Nanocrystalline WC-10Co Composite Cemented Carbide

The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 （ wt% ） composite powders were prepared by the spray thermal decomposition-continuous reduction and carburization technology. In order to improve the properties of rods shaped by using powder extrusion molding, the cold isostatic pressing （CIP） technology was used before or after debinding. Specimens were siutered by vacuum siutering and hot isostatic pressing （HIP）. The density, Rockwell A hardness, magnetic coercivity , and magnetic saturation induction of siutered specimen were measured. The microstructure of the green bodies and the siutered specimens was studied by scanning electron microscopy （SEM）. Results show that the rod formed by using powder extrusion molding after debinding and followed by cold isostatic pressing can be siutered to 99.5% density of composite cemented carbide rods with an average grain size of about 200- 300 nm, magnetic coercivity of 30.4 KA / m, Rockwell A hardness of 92.6 and magnetic saturation induction of 85% . Superfine WC- 10 Co cemented carbide rods with excellent properties were obtained.     

Preparation of spherical microfine silicon powder

Under certain conditions of proper temperature and pH value, sodium silicate was hydrolyzed in liquid ammonia chloride, and spherical microfine SiO2 powder in micrometer-size was prepared. In this experiment, the relationship between needed time and proper pH value, temperature, density of the solution, and its current capacity were found .The optimum conditions are pH 8.5, 70 ~C, and the concentration of sodium silicate is 0.6 mol/L for the density of the solution. The structure of spherical microfine silicon was characterized by SEM and XRD.     

表面处理对反相微乳液中II-VI族量子点的影响

以对二甲苯为连续相,水为分散相,聚(氧乙烯)-聚(氧丙烯)-聚(氧乙烯)嵌段聚合物为表面活性剂,制备ZnSe和ZnMnSe量子点.在量子点表面覆盖一层Zn(OH)2使其发生钝化,再加水引起相分离,选择合适的有机溶剂可从反相微乳液中成功分离出上述量子点,分离后的量子点保持荧光特性且量子点荧光有显著增强.经11-巯基十一烷酸表面修饰,分离的量子点可分散在水中形成透明溶液.采用X-射线衍射、透射电镜、动态激光光散射和荧光光度计表征晶体结构、形貌、尺寸分布和荧光特性,讨论了使量子点稳定的表面保护机理.研究结果表明,嵌段聚合物分子吸附在量子点表面,阻碍了其氧化进程,表面钝化可修补晶体部分缺陷,使分离的量子点荧光增强,稳定期达数月之久.

Abstract：

The successful extractions of ZnMnSe as well as ZnSe quantum dots (QDs) from a reverse micelle template were reported. The recovered QDs kept their functionality with distinct enhancement in photoluminescence. After being coated with a possible layer of Zn(OH)2 within the template, the QDs were extracted from the template by adding water to induce phase transition and employing specific organic solvent. Thereafter, the extracted QDs were capped with mercapto-undecanoic acid for dispersion in water to render crystal clear solution. Analytical techniques such as X-ray diffraction, transmission electron microscopy, dynamic light scattering, and fluorometer were employed to characterize the crystal structure, morphology, average particle size, and photoluminescence of the samples. The mechanism of the surface protection towards QDs was investigated and discussed. A mechanism was proposed as block copolymer molecular being adsorbed to the QDs surface that retards the oxidation process of QDs during the extraction. Consequently, the extracted QDs demonstrated invariable photoluminescence and consistent stability for months.     

亚微米碳化硅超细粉碎实验研究

通过实验研究,对碳化硅用搅拌磨粉碎形式下的粉体粒度、粒度分布、比表面积叶应研磨时间的相互关系进行了分析.对实验数据进行回归分析拟合,得出了搅拌磨超细粉碎过程中的粉体中位径与比表面积、中位径与研磨时间、粒度分布与研磨时间的函数关系模拟方程式.理论计算曲线与实验数据吻合程度很好.根据推导出的函数关系方程式,可以预测碳化硅搅拌磨超细研磨过程中的产品性能,为实际生产放大模拟提供了理论依据.     

碳化硅粉体表面乳液聚合处理及特性研究

利用乳液聚合方法对碳化硅粉体表面进行聚电解质包覆改性，处理后碳化硅粉体表面特性发生改变，不易团聚，可以制成固相含量较高的稳定的悬浮液。分析了聚电解质处理后的碳化硅粉体悬浮液的特性，结果表明：碳化硅粉体表面的疏水性越好，其沉降性越好，悬浮液的固相含量就越高。     

Surface Modification of Silicon Carbide Powders with Aminoorganosilanes

To study the surface modification of SiC powders with aminoorganosilanes, high solid loading and low viscosity SiC slurry was prepared. Three kinds of aminoorganosilanes were used in the experiment. Infrared Fourier transform spectrometry （Nicolet20SX, America） was applied to analyze the surface characterization of modified SiC powders. The largest solid loading of SiC coated with WD-52 slurry had increased to 54.5vo1% and the stabilization also increased remarkably. At the same time, the viscosity of SiC slurry declined. Comparing with WD-50 and WD-57, WD-52 is most effective for modification of SiC powders.     

电势对硅片摩擦电化学材料去除特性的影响

为了提高硅片抛光效率,改善抛光表面质量,采用电化学交流阻抗谱法实验研究了极化电势对硅片表面钝化作用的影响规律,结合摩擦电化学实验探讨了极化电势对硅片表面摩擦系数及材料去除特性的影响．结果表明,在碱性CeO₂抛光液中,对硅片施加1 V阳极极化电势能够促进其表面形成抑制腐蚀的钝化层,极化电势过高会破坏表面钝化层,过低则抑制钝化层形成．良好的硅片表面钝化层能够有效增大其摩擦系数,提高摩擦电化学实验过程中的材料去除率．     

长脉冲激光辐照单晶硅的表面形态

针对长脉冲激光在空气中对单晶硅进行辐照所产生的表面形态问题,研究了不同能量密度的激光辐照后单晶硅的表面形态变化及其形成机理.结果表明:单晶硅表面的涟漪波纹状微结构与光的散射和干涉有关;随着激光能量密度的增加,单晶硅表面出现解理现象,其主要是由较高的温度梯度而引起的应力所致;熔融和汽化时的单晶硅表面形态主要是由载流子动力及等离子体波引起的;激光辐照单晶硅中心点温度曲线在单晶硅熔点和沸点附近时出现平台期,这是由于材料在熔融和气化过程中要吸收潜热;激光能量密度越大,单晶硅表面的损伤面积越大.