蓝色氧化钨组成和相结构

根据定中化学分析和X-射线衍射分折研究结果,蓝色氧化钨(TBO)的组成在很宽的谱线内变化,这种变化浓赖于还原温度、气氛和速度,也依赖于四水合仲钨酸铵还原的实际制备过程。除结晶化合物六方晶系钨青铜(HTB)、WO_3、W_(20)O_(58)和W_(18)O_(49)外,工业生产蓝色氧化钨(TBO)还含30％～55％的X-射线非晶相组分。 首次发现,APT·4H_2O可在130℃下干氢气流中转变成APT～2H_2O相。在250～350℃温度范围内的X-射线非晶相中间体,不单是六方晶系钨青铜(HTB),而且也是结晶氧比钨的起源。 从含HTB的TBO粉通过由K~-取代H~-的阳离子交换而结合了大量钾。用固体高分辨率质子核磁共振(’HNMR)研究TB0,亦可区分含不同阳离子的基团。     

蓝钨生产技术进展

<正> 一、前言所谓蓝色氧化钨(简称蓝钨),并没有统一的分子式,截止到目前,国际上也尚无统一的质量标准。而工业实践中的蓝钨,多为铵钨青铜ATB、WO_(2.9)、W_(20)O_(58)、W_(18)O_(49)、WO_3等的多相混合物,也有单相的六方ATB。由于蓝钨在工艺性能上比黄钨(WO_3)具有化学活性高、掺杂效应好,比表面积大、还原速率快和钨粉粒度易     

超细钨粉的制取及其氧化钨原料和钨粉的粒度测量

选取相成分单一的氢钨青铜(H_(0.33)WO_3)、铵钨青铜((NH_4)_(0.5)WO_3)和紫钨(WO_(2.72))作为原料,研究钨原料对制取超细钨粉的影响;对氧化钨原料和超细钨粉的粒度测量方法作了比较,研究结果表明:紫钨由于有着特殊的结构,其制得的钨粉细而均匀,分散性好,是适合于做微晶硬质合金的原料;对于氧化钨原料的粒度(伪同晶颗粒尺寸,即二次颗粒)测量,推荐使用激光衍射法;对于超细钨粉粒度(一次颗粒)的炉前测量,BET法测球形相当径相当理想。     

蓝色氧化钨,金属钨粉和碳化钨粉

1蓝色氧化钨、金属钨粉和碳化钨粉的特性1.1蓝色氧化钨工业用蓝色氧化钨（TBO）是一种由多种钨化合物组成的粉末状混合物。一般是由铵钨青铜、氢钨青铜、三氧化钨、β-氧化物（WO2.9）和γ-氧化钨（WO2.72）混合组成，其表观颜色随氧指数（O／W）从2．72～3．0紫色向黄色连续变化。它正在逐步取代传统的钨酸和黄色WO3而成为一种重要的钨中间化合物。1.2金属钨粉用还原法获得的钨粉粒度为0．3～30μm．其颜色随粒度粗细而改变，粉末颗粒越细，颜色越黑。粗粒度的钨粉呈灰色并具有金属光泽一亮点；中等粒度钨粉呈灰黑色；超细钨纷呈深黑…     

氧化钨氢还原过程中产物形貌的变化

以蒸发结晶法制得的仲钨酸铵为原料,制备了三氧化钨、蓝色氧化钨、WO_(2.72)、二氧化钨以及 WO_(2.72)-WO_2混合物和WO_2-α-W混合物的样品,用扫描电镜进行了形貌研究。对用固态合成法制备的WO_(2.72)与用氢还原法制备的WO_(2.72)作了形貌比较,说明两者共有的柱状晶是WO_(2.72)的固有晶形,不一定与气相迁移反应有关。氢还原钨粉的粒度在颇大程度上取决于二氧化钨的粒度。从蓝色氧化钨或WO_(2.72)到二氧化钨这一还原阶段,对钨粉粒度具有决定性影响。WO_(2.72)到二氧化钨及二氧化钨到钨粉的还原,并非按核收缩反应模式,还原反应是从假颗粒内外的活性点开始向周围扩展的。     

钨蓝的氧钨比测定

用氧化钨(WO_3、WO_3·H_2O)或仲钨酸铵[5(NH_4)_2O·12WO_3·5H_2O]在氢或氢-氮气流下还原制备金属钨时,首先要求生成低氧含量的蓝色氧化物,俗称钨蓝,介于WO_3与WO_2之间非化学计量的氧化物,包括WO_(2·72)(W_(18)O_(40))及WO_(2·90)(W_(20)O_(58))等.在任意选择的某一温度下终止还原反应,就存在很复杂的相成分,它的氧钨比对以后制备金属钨的性能关系密切.为此,测定钨蓝的氧钨比有其重要的意义.     

APT离解还原与生成物性质

研究了APT离解还原成WO_2的反应过程、微区变化和生成物性质。研究指出:粉末真密度能近似地反映离解还原产物的相成分。离解还原产物的粒度、比表面积和溶解度与粉末的相成分和离解还原温度有一定的关系。含铵量高的铵钨青铜(ATB′)和W_(20)O_(58)有最大的比表面积。批量制得纯相的W_(20)O_(58)和W_(18)O_(49),测得其真密度分别为6.95g/cm~3和7.59g/cm~3。观察到W_(20)O_(58)、W_(18)O_(49)和WO_2三相共存的情况。     

Na元素掺杂方式对超粗晶碳化钨及其合金性能的影响

对比研究了在仲钨酸铵(APT)中掺杂Na元素和在黄钨中掺杂Na元素对钨粉、碳化钨粉及其合金性能的影响规律及作用机制。结果表明:由于APT中掺入的Na_2WO_4·2H_2O在煅烧过程中充分转变为Na_2W_2O_7,利于在后续的黄钨还原过程中生成低熔点的钨青铜Na_2O·xWO_3,易于获得粒度较粗的钨颗粒;APT中掺钠获得的钨粉和碳化钨粉末颗粒粒度均大于黄钨中掺钠的粉末颗粒粒度,且前者制备的超粗晶WC-10Co合金性能优于黄钨掺Na的合金。     

第四届全国金属粉末学术会议论文选摘要

不同相成分的蓝色氧化钨氢还原过程的研究对相成份分别为ATB、W_(20)O_(58)的蓝色氧化钨和黄色氧化钨在不同的温度下进行了氢还原试验,并测试了还原钨粉的BET比表面、FSSS平均粒度及SKC粒度分布,指出,无论在高温或低温下还原蓝色氧化钨均可获得比表面较大、BET粒度较小的钨粉,     

不同氧含量的氧化钨粉对超细钨粉制备的影响

研究了不同氧含量的氧化钨粉对超细钨粉制备的影响。结果表明,以蓝钨(WO_(2.90))为原料制取的钨粉粒度都在1μm左右,以紫钨(WO_(2.72))为原料制备的钨粉的粒度均小于以蓝钨为原材料制备的粉体。不同氧含量的氧化钨粉制备超细钨粉时,影响粉末FSSS粒度的顺序为:还原温度氢气流量装舟量推舟速度。以紫钨为原料,在还原温度700~840℃、推舟速度18min/舟、装舟量0.35kg/舟、氢气流量50~60m3/h的条件下,制备的钨粉粒度为0.3μm左右。     

Synthesis of Mesoporous, Nanocrystalline Lanthanum Phosphate in the Presence of Citric Acid and Stearic Acid

Lanthanum phosphate was prepared in the presence of citric acid and stearic acid under methanolic conditions at pH 4.5 and pH 7, respectively. The samples obtained were intensively characterized using X-ray diffraction, nitrogen adsorption-desorption isotherm study, transmission electron microscopy （TEM）, thermal gravimetric and differential thermal analysis, and Fourier transform infrared （FTIR） analysis . The as-synthesized samples prepared at pH 4.5 showed lamellar mesostruroned form with high crystallinity. Results showed that the pore size and pore volume changed when the materials were prepared under different pH conditions. Morphology of the samples was observed by using TEM, which showed that the samples possessed relatively small particles closely packed together. The as-synthesized samples were investigated using FTIR, and the mesopore formation mechanism was discussed.     

基于图像处理的矿石颗粒三维微观孔隙结构演化

采用高精度显微CT技术及三维图像分析方法研究氧化铜矿石颗粒在酸浸前后内部微观孔隙结构特征及其演变,考察孔隙率、孔隙尺寸分布、孔隙连通度、孔隙分维等参数的变化规律.结果表明:酸浸后矿石颗粒的孔隙率明显增加,孔隙尺寸分布范围更广,出现一定比例的大孔隙,平均孔隙直径增加2~3倍;孔隙连通度在酸浸前基本为零,酸浸后明显增加,并在各方向上呈现空间变异性;孔隙分维数在浸出结束后也有所增大,且在一定范围内与孔隙率及平均孔隙直径呈指数增长关系.借助三维图像分析可实现矿石浸出过程中内部微观孔隙结构的定量描述,从而揭示矿石颗粒孔隙结构的演化规律.      

Effect of tungsten oxide on ceria nanorods to support copper species as CO oxidation catalysts

In this work,tungsten oxide with different concentrations(0,0.4 at%,2.0 at% and 3.2 at%) was introduced to the ceria nanorods via a deposition-precipitation(DP) approach,and copper species of ca.10 at% were sequentially anchored onto the modified ceria support by a similar DP route.The aim of the study was to investigate the effect of the amount of tungsten oxide(0,0.4 at%,2.0 at%,and 3.2 at%) modifier on the copper-ceria catalysts for CO oxidation reaction and shed light on the structure-activity relationship.By the aids of multiple characterization techniques including N_2 adsorption,high-resolution transmission electron microscopy(HRTEM),powder X-ray diffraction(XRD),X-ray absorption fine structure(XAFS),and temperature-programmed reduction by hydrogen(H_2-TPR) in combination with the catalytic performance for CO oxidation reaction,it is found that the copper-ceria samples maintain the crystal structure of the fluorite fcc CeO_2 phase with the same nanorod-like morphology with the introduction of tungsten oxide,while the textural properties(the surface area,pore volume and pore size) of ceria support and copper-ceria catalysts are changed,and the oxidation states of copper and tungsten are kept the same as Cu~(2+)and W~(6+)before and after the reaction,but the introduction of tungsten oxide(WO_3)significantly changes the metal-support interaction(transfer the CuO_x clusters to Cu-[O_x]-Ce species),which delivers to impair the catalytic activity of copper-ceria catalysts for CO oxidation reaction.     

碳溶反应过程焦炭气孔结构变化规律

 利用焦炭反应性装置测定不同温度下焦炭的碳溶反应,采用比表面积及孔径分析仪、SEM表征焦炭的气孔结构参数,分别利用BET方程和BJH法计算焦炭的比表面积、孔体积和平均孔径,由吸附等温线计算焦炭表面分形特征变化,考察焦炭碳溶反应过程中孔结构的变化规律。研究表明,随着温度的升高,焦炭吸附曲线类型由I类向II类吸附等温线转变,比表面积以及孔容均先增加后减小,2～10 nm的孔径变化明显。1 000 ℃之前焦炭的溶损反应过程主要受化学反应速率影响,1 000 ℃之后受扩散控制的主导性提高,不同焦炭的气孔结构变化影响了溶损反应行为。分形维数与孔结构有一定的相关性,可以反映焦炭溶损过程气孔的变化。     

Bi_2WO_6 doped with rare earth ions:Preparation,characterization and photocatalytic activity under simulated solar irradiation

Rare-earth modification Bi_2 WO_6 composites(RE/Bi_2 WO_6) were studied by experimental performance and theory computation based on the different 4 f orbits of selected rare earth elements(La,Ce,Gd,and Yb).The prepared RE/Bi_2 WO_6 was characterized by XRD,SEM/TEM,XPS,UV-vis DRS,and N_2 adsorption to learn their physical-chemical properties.Azo dye Rhodamine B(RhB) was photodegraded as a target pollutant to investigate the photocatalytic activity of prepared RE/Bi_2 WO_6 composites.The results of experiment and computation show that four rare earth elements with different electron configurations retain the phase and morphology of Bi_2 WO_6 and enhance the removal efficiency of RhB under simulated solar irradiation.The optimum doping contents are 0.01%,0.05%,0.05% and 0.01% for La-,Ce-,Gd-,and Yb-doped Bi_2 WO_6,respectively.However,light rare earth La and Ce doped composites indicate some difference in visible light adso rption capacity and mineralization on RhB co mpared with heavy rare earth Gd and Yb doped composites.Both La/Bi_2 WO_6 and Ce/Bi_2 WO_6 possess larger pore size and higher mineralization ability than Gd/Bi_2 WO_6 and Yb/Bi_2 WO_6 under the same experimental conditions while Gd/Bi_2 WO_6 and Yb/Bi_2 WO_6 show stronger red shift to the visible light due to the more 4 f electrons.The hole oxidation plays a major role in the photodegradation of RhB by all RE/Bi_2 WO_6.     

二次压煮工艺提高钨冶炼金属回收率的应用

概述了我国钨冶炼碱压煮工艺的现状。指出采用二次压煮工艺可将钨冶炼企业的金属回收率提高至97％以上，混合渣中的WO2降低至1％左右。     

Phase Behavior of Rare Earth Manganites

Among complex oxides containing rare earth and manganese BaLn2Mn2O7(Ln=rare earth) with the layered perovskite type and Ln2(Mn,M)O7 with pyrochlore-related structure were studied since these compounds show many kinds of phases and unique phase transitions. In BaLn2Mn2O7 there appear many phases, depending on the synthetic conditions for each rare earth. The tetragonal phase of so-called Ruddlesden-Popper type is the fundamental structure and many kinds of deformed modification of this structure are obtained. For BaEuzMn207 at least five phases have been identified from the re-sults of X-ray diffraction analysis with the space group P42/mnm, Fmmm, Immm and A2/m in addition to the fundamental tetragonal 14/mmm phase. In the pyrochlore-related type compounds, LnzMn2-xMxO7(M=Ta,Nb,W etc),there also appear several phases with different crystal structures. With regard to every rare earth, Ln2MnTaO7 phase is stable only for excess Ta and can be obtained under high oxygen partial pressure process. This group has trigonal structure with zirkelite type (P3121 space group). On the other hand Ln2Mn2/3Nb4/307 phase has monoclinic (C2/c space group)and zireonolite type structure. All of these structural models have the fundamental structure based on HTB (hexagonal tungsten bronze) layers formed by the arrangement of oxygen octahedra.     

从硬质合金典型材质发展看中国硬质合金工业的技术进步

中国是世界硬质合金的生产与消耗大国,中国硬质合金工业的技术现状令世人关注.本文从硬质合金典型材质与关键原料制备技术及其微观组织结构与性能特性等方面,展示了近年来中国硬质合金工业的主要技术进展.包括紫钨工艺制备的超细、纳米W粉与WC粉,紫钨工艺与WC-Co纳米复合粉工艺制备的超细晶硬质合金,超粗晶硬质合金以及原位激发自润...     

Synthesis and Characterization of Y-Doped Mesoporous CeO2 Using A Chemical Precipitation Method

Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction （XRD）, energy dispersive analysis of X-rays （EDAX）, transmission electron microscopy （TEM）, infrared （IR） absorbance, and the BET method. For the prepared samples with 20% （molar ratio） Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.     

添加无烟煤对焦炭微晶和气孔结构的影响

根据焦炭的XRD谱图及SCHERRER'S 公式研究了添加无烟煤炼焦后焦炭的微晶结构参数的变化.试验结果表明:添加无烟煤可以促进焦炭中微晶的发展,使焦炭微晶结构参数La、Lc和石墨化度增大.利用氮气吸附方法分析了焦炭气孔结构的变化,结果发现:添加无烟煤炼焦后焦炭的微孔体积、比表面积和平均孔径都有显著的降低.根据FHH模型计算了焦炭的分形维数.结果表明:在焦炭中存在分形结构,添加无烟煤炼焦后焦炭的分形维数降低,焦炭表面变光滑.