蒸发——冷凝法制备超细金属粉末

在低压惰性气体中,用蒸发—冷凝法可制备多种金属和合金超细粉末。文中概叙了蒸发温度、气氛及其压力等因素对粉末平均粒径及粒度分布的影响。     

雾化法制备高品质钛合金粉末技术研究

研究了惰性气体雾化法和等离子旋转电极法两种雾化法制备工艺所得TA15钛合金粉末的化学成分、粒度分布、颗粒形貌及微观组织。结果表明,雾化法制备的粉末间隙元素增量低,而且颗粒球形度高,颗粒内部是细小的胞状显微组织;惰性气体雾化法制备的粉末细粉收得率较高,有较多的吸附颗粒,颗粒内部有气孔;等离子旋转电极法制备的粉末粒度分布范围窄,颗粒呈规则的球形,表面光亮、圆滑。     

微波碳化法制备纳米WC粉末及其机理

传统制备WC粉末的方法都是依靠发热体的辐射、能量对流、传导等方式加热W、C混合粉末到一定温度,热量由外向内传递,具有加热温度高、周期长、WC颗粒长大明显等缺点。本研究以纳米钨粉和活性炭为原料,采用微波加热法在1 000℃快速制备纳米WC粉末。用XRD分析不同碳化温度产物的物相组成,并用SEM和TEM对产物进行形貌和粒度分析。结果表明:平均粒径50 nm的钨粉经微波碳化法在1 000℃保温10 min,能够制备出平均粒径为86.5 nm的单相WC粉末,纳米WC颗粒表面光滑,形貌呈近球形。分析微波碳化法制备纳米WC粉末的机理表明,微波碳化过程为扩散控制,WC颗粒的长大速率随碳化温度的升高而加快。     

选区激光熔化成形用GH4169合金粉末的性能

采用真空熔炼-惰性气体雾化法制备了GH4169合金粉末,分析了粉末的粒度分布、颗粒形貌特征,利用选区激光熔化成形技术(SLM)制备了金相、拉伸试样,并分析了显微组织及力学性能。结果表明:气雾化法制备的GH4169合金粉末粒度呈正态分布,粒径主要在25～40μm之间,颗粒为球形或近球形,并且存在一部分"卫星球"粉末;SLM成形的GH4169合金试样退火前的平均屈服强度和抗拉强度分别为637 MPa,981 MPa,平均断后伸长率和收缩率为27.5%,50.0%,退火后屈服强度和抗拉强度增大,断后伸长率和断面收缩率有所减小,拉伸断口主要呈现韧性断裂特征。     

纳米级WO3粉末制备工艺的研究

将H2WO4溶于含氨的碱性水溶液中，用超声喷雾热转换装置制备了纳米级WO3非晶态粉末。通过XRD及TEM研究了WO3非晶粉末的物相组成、颗粒形貌及粒径范围。用DSC-TG研究了纳米WO3前驱体粉末从非晶到微晶的转变温度和粉末热分解过程中的失重规律。结果表明，采用超声喷雾热转换法可制得平均粒度为30nm的WO3粉末，颗粒形貌近球形。     

Fe3+掺杂纳米TiO2的表征及其光催化性能的研究

[目的]提高TiO2的可见光响应和光催化活性.[方法]采用溶胶凝胶法制备掺铁纳米TiO2粉体,进而研究掺铁TiO2的光催化活性.[结果]450 ℃煅烧后掺铁TiO2出现了很明显的TiO2特征衍射峰,且峰形尖锐,结晶良好,均没有出现铁的掺杂新相.随着掺铁量的提高,TiO2的粒径逐渐减小,当掺杂量为0.4%时,TiO2的粒径最小,减少至纯TiO2的45%.掺铁抑制了锐钛矿向金红石矿的转变.随着焙烧温度的升高,TiO2的粒径逐渐增大.用溶胶-凝胶法制备的TiO2均为纳米级,基本成球形颗粒.纯TiO2粒子分布不是很均匀,团聚现象明显;掺铁TiO2颗粒分布均匀,没有明显的团聚现象;掺铁使TiO2在紫外灯和太阳光下的降解性能都有着不同程度的提高.[结论]溶胶-凝胶法制备的掺铁纳米TiO2细化了晶体晶粒,抑制了锐钛矿向金红石矿的转变.     

Al-Ni-Y合金雾化粉末的超高压固结成形及其机理研究

采用紧耦合惰性气体雾化技术制备具有非晶和纳米晶结构的Al82Ni10Y8(%)合金粉末, 粒径小于26μm粉末为非晶和纳米晶结构, 而粒径小于15μm粉末为非晶单相结构。在250, 310, 360, 400, 450℃5个不同温度下对粉末进行了超高压固结成形, 并对致密化后合金的显微结构进行了分析。致密化后粉末颗粒基本保持原有粉末形貌, 但随着致密化温度的升高, 晶化和晶化相长大愈发明显, 合金密度呈增高趋势。对粉末致密化的机理进行了讨论, 认为非晶相的粘滞流动是低温下获得高致密度的主要原因。     

真空蒸发-冷凝法制备片状CU粉

采用蒸发-冷凝法在真空条件下制备了片状Cu粉,并用激光粒度分析仪(SL)、扫描电镜(SEM)、辉光放电质谱仪(GDMS)和X射线衍射仪(XRD)对片状Cu粉进行表征.结果表明,制备的Cu粉为面心立方结构,表面平整,分散性好,粒径为10～30μm,厚1～2μm.试验考察了蒸发温度、真空度、保温时间和冷凝高度4个因素对片状...     

铟深加工—纳米级ITO粉末的研制

用液相共沉淀法制备了纳米级ITO粉末，通过在底液中添加分散剂A，有效地防止了团聚现象的发生。用X射线衍射仪分析了粉末的XRD谱图，证实粉末呈单一相，为立方晶系，粉末用透射电镜分析，粒径40-50nm，呈球形。     

纳米二硫化钼制备过程中硫源及分散剂的研究

纳米二硫化钼具有优异的性能,其应用前景广阔。制备纳米二硫化钼粉末的方法很多,特点各异,并各有其优缺点。液相还原法制备纳米二硫化钼因具有实验设备简单、操作方便、流程短和制得的颗粒粒径较小等优点近年来受到广泛的关注。本文通过对应用该法制备非晶态二硫化钼过程中的收率、粒径和形貌的分析,确定了制备过程的最佳硫源和分散剂分别为硫代乙酰胺和聚乙二醇。     

Structure and properties of nanocrystalline rare earth bulks prepared by spark plasma sintering

A series of rare earth bulks with the ultrafine nanocrystalline structure were prepared by applying an "oxygen-free" (an environmental oxygen concentration less than 0.5 ppm) in-situ synthesis system, where the inert-gas condensation was combined with the spark plasma sintering technology into an entirely closed system. The thermal and mechanical properties of the prepared ultrafine nanocrystalline bulks were characterized and compared with those of the raw polycrystalline bulks. It was found that the speci...     

高Ce 含量的速凝带及其磁性能

近年来,Nd-Fe-B磁体需求量的与日俱增间接地造成了稀土Ce 金属的大量积压,为提高稀土Ce 的利 用率,并降低Nd-Fe-B磁体的生产成本,可采取双主相合金法制备（Nd, Ce）-Fe-B磁体,为解决上述难题提供 了一种有效途径。通过对高Ce 含量速凝带的成分及速凝工艺的探索,成功制备出了具有较好枝晶且几乎 不含α-Fe 相的Ce-Fe-B 和（Nd, Ce）-Fe-B 速凝带。在制备的烧结磁体中,（Nd, Ce）-Fe-B 磁体的剩磁达到了 11.33 kGs,Ce-Fe-B磁体的剩磁达到了8.037 kGs,为后期制定制备高Ce 含量的高性能双主相磁体的热处理工 艺提供了数据参考。     

稀土金属脱除氧杂质的新技术及驱动机制研究进展

介绍了活泼金属除气法、等离子体熔炼法和固溶氢原子除气法等稀土金属脱除氧杂质的新方法,详细归纳了将氧杂质含量限制在5×10-5以下的工艺条件.重点介绍新方法中引入活泼金属、氢等离子体、活性固溶氢原子等各种外部驱动因素的设计思想,提出提纯新技术的同时探究了痕量杂质的迁移规律及去除机制,深化对杂质存在形式、行为规律及提纯机理的认识.采用FAST-2D与Stefan数值模拟技术、18O₂示踪同位素标记技术、CALPHAD相图数据库模拟计算技术对稀土金属高纯化的新工艺提供理论指导与评价,加深对提纯驱动机制的理解.      

Effect of the sintering temperature and time on the structure and phase composition of temperature stable hard magnetic materials of the REM–Fe–Co–B system

The structure, the phase composition, and the distribution of alloying elements in the structure of temperature stable hard magnetic materials of the REM–Fe–Co–B system (REM = rare-earth metals), which are prepared under different manufacturing conditions, namely, at different sintering temperatures and times, have been studied. The phase composition, the local chemical composition of phases, the volume fraction of pores, and the manufacturing conditions that allow one to prepare the structure ensuring high magnetic properties have been determined.     

Influence of rare-earth modification on the formation of nonmetallic inclusions in high-carbon steel

The content of nonmetallic inclusions when rail and wheel steel is produced by intensive modern technology and modified by rare-earth metals is analyzed. The composition, morphology, dimensions, and distribution of the inclusions in the steel are determined in the case without oxidation by aluminum or treatment by silicocalcium and also with treatment of aluminum-bearing steel by both rare-earth metals and silicocalcium. Modification with rare-earth metals reduces the content of oxide inclusions in the rail and wheel steel. That improves the plasticity and impact strength of the products.     

Crystal-chemical properties of sulfides of the rare-earth metals and actinides

Summary The crystal-chemical and physical properties of sulfides and oxysulfides of rare-earth metals and actinides are reviewed, and the principal regular relationships in the correlation of these properties with the peculiarities of the electron structure of rare-earth metal and actinide atoms are shown. A hypothesis is advanced regarding the nature of the chemical bond between atoms of the rare-earth metals and actinides and sulfur, as well as between the sulfur atoms in sulfides, and the changes occurring in passing from high-metal phases to high-sulfur phases.     

Rational design of novel carboxylic acid functionalized phosphonium based ionic liquids as high-performance extractants for rare earths

Developing the novel ionic liquids as the potential substitutes for conventional organic solvents in extraction of the rare-earth metals is highly desirable but challenges still remain. In this study, the well-designed carboxylic acid functionalized phosphonium based ionic liquids, (4-carboxyl)butyl-trioctyl-phosphonium chloride/nitrate, were synthesized and characterized. The as-prepared samples were tested as the undiluted hydrophobic acidic extractant for rare-earth metal ions, affording the maximal loading of 3 mol/mol towards Nd(III) in aqueous solution and the remarkable stripping performance. The results also reveal their excellent extractability and selectivity for Sc(III) in the mixtures of six rare-earth ions, as well as the outstanding separation properties between rare-earth and first row transition-metal ions (i.e., La/Ni, Sm/Co). Moreover, the extraction mechanism indicates that the extracted rare-earth complex via a proton exchange in the ionic liquid phase is structurally similar to the complexes obtained with neutral extractants. This work presents a prototype for the fabrication of the hydrophobic cation-functionalized ionic liquids for highly efficient rare-earth extraction and provides the future application in recycling of rare-earth metals from the spent magnets.     

Influence of Microalloying on the Strength and Corrosion of Low-Carbon Stainless Steel

Attention focuses on how nitrogen and rare-earth metals modify the mechanical properties and corrosion characteristics of unstabilized low-carbon Fe–Cr–Ni stainless steel, additionally alloyed with silicon and molybdenum. The influence of the selected microalloying method on the mechanical properties of unstabilized low-carbon chromonickel stainless steel and its resistance to local corrosion is studied experimentally. Nitrogen-bearing 03X17H9AC2, 03X17H9AM3, and 03X18H15AM3 stainless steel microalloyed with rare-earth metals is investigated.     

Use of rare earth elements in single-atom site catalysis:A critical review——Commemorating the 100th anniversary of the birth of Academician Guangxian Xu

Rare earth metals are strategic resources with potential applications in optics,metallurgy and catalysis.In recent years,single-atom site catalysts(SASCs) have attracted increasing attention owing to their 100%atom efficiency and unique catalytic performances.Over the past decade,rare earth elements,including rare earth metals and their oxides,have shown great potential in SASCs.However,systematic analyses of data are still handful.In this mini-review,the use of rare earth metals and their oxides in SASCs was summarized and the results are discussed.A particular focus was paid to the synthetic strategies,characterization of rare earth-containing SASCs,and applications as catalysis supports,promoters and active sites.Current issues faced by rare-earth metals and their oxides in SASCs,as well as future prospects were also provided.