微/纳米氧化钨晶须的制备工艺及原理

采用溶胶-水热反应法，通过添加适量的硫化钠结晶体诱导制备了微／纳米氧化钨晶须。利用扫描电镜观察氧化钨样品的形貌特征，并对氧化钨晶须进行能谱测试，用X射线衍射仪对氧化钨样品进行物相分析和晶面测定，用透射电镜观察微／纳米氧化钨晶须／线的生长特征。结果表明：未添加硫酸钠时，在180℃水热反应12～36h只能得到氧化钨颗粒粉末，而添加适量硫化钠后，可制备出直径为0．2～0．3μm、长径比为5～50的氧化钨晶须和直径为10～30nm、长径比为50～200的氧化钨纳米线；氧化钨纳米线晶体结构良好，物相为六方晶系WO3；微／纳米氧化钨晶须／线主要沿〈200〉，〈002〉，〈202〉和〈100〉方向定向生长。     

快速升温法制备Ti-Al合金泡沫材料

利用快速升温法在致密Ti罐或两Ti板夹层中制备Ti-Al合金泡沫夹层材料,通过添加不同量的发泡剂和升温速度控制Ti-Al发泡程度以及孔隙的多少、大小、取向和分布。实验发现：当发泡剂含量大于11%时,开始具有发泡效果,发泡剂含量在13%～15%之间,发泡量、孔径大小和孔径分布比较理想,发泡剂含量大于17%时,形成大孔,且中间的泡最大;当升温速度大于25℃/min时,开始具有发泡现象,随着升温速度继续增加,发泡程度增大,孔隙由少变多,孔径由小变大;当升温速度大于75℃/min时,中间孔隙大部分重合,成大空洞。大量实验发现升温速度是影响孔隙形状、尺寸、取向和分布的主要因素。保温温度和时间是强度大小的主要因素,测试其不同温度下压缩屈服强度,均高于纯钛泡沫材料,具有较高的高温压缩屈服强度。     

氧化钨相成分对超细钨粉均匀性的影响

研究了通过传统氢还原工艺制备超细钨粉末过程中氧化钨原料相组成对超细钨粉均匀性的影响。结果表明：单一相组成的氧化钨能制得超细而均匀的钨粉,多种相组成的氧化钨,由于其在还原过程中存在不同的还原路径和还原速度,制得的钨粉虽细但不均匀。     

TC4钛合金微弧氧化膜层动态热力学性能研究

在锆盐电解液体系中制备出厚度为20μm的微弧氧化膜层,通过动态热机械分析仪研究了TC4钛合金表面的微弧氧化膜层与基体结构的热-机耦合载荷失效行为。结果表明:温度对TC4钛合金微弧氧化膜层服役失效有重要影响。当升温到300℃时,膜层与基体开始出现热膨胀系数不稳定而产生热错配残余应力;当温度到达500℃时,膜层内部出现明显的裂纹,且膜层也在一定程度上与基体发生剥落行为。     

电场作用下预设升温速度对Fe-V-C系燃烧合成的影响

采用Gleeble热模拟机研究了预设升温速度对Fe-V-C体系在电场作甩下燃烧合成的影响。用X射线衍射仪（XRD）以及扫描电镜（SEM）等研究了试样在不同预设升温速度下的相结构和显微组织。结果表明：在电场作用下，该体系的反应起始温度较低。预设升温速度对体系的影响呈阶段变化，当预设升温速度为600℃／s-1000℃／s时，合成过程以及合成产物的变化不大：当预设升温速度升至1400℃／s时，体系的点火温度降低、点火延迟时间缩短，合成产物颗粒变小，硬度提高。     

无压烧结制备YAG多孔陶瓷的工艺及性能

为了能够利用YAG优异的性能开发出更多的功能材料,通过调整无压烧结技术工艺参数成功制备YAG多孔陶瓷材料。结果表明:1500℃烧结的YAG多孔陶瓷的气孔率与1550℃烧结的陶瓷相近,但是1550℃制备的陶瓷具有较多烧结颈使抗压强度较高。保温2 h的样品与保温1 h的样品进行对比表明,保温2 h样品包裹气泡长大使气孔率高,液相较多颗粒联接牢固使抗压强度高。升温速度为5℃/min制备的陶瓷比升温方式10℃/min制备的陶瓷气孔率和抗压强度都高。在800℃排碳所制备的样品的气孔率和抗压强度都比1000℃排碳的高。通过分析工艺参数与性能之间的内在联系,得出烧结温度为1550℃,保温2 h,升温速度为5℃/min,800℃排碳时间1 h制备的YAG多孔陶瓷材料较为适合,其材料气孔率为59.4%,抗压强度为8.55 MPa。     

电场作用下75wt%Fe-25wt%(Ti+C)体系燃烧合成的探讨

采用Gleeble热模拟机对75Fe-25(Ti+C)体系在电场作用下的燃烧合成进行探讨,结果表明:这种不能采用普通SHS技术进行燃烧合成的体系,当预设升温速度为600℃/s时,在电场作用下仍不能实现燃烧合成;而当预设升温速度提高到1 000℃/s时,在电场作用下该体系能在743℃发生燃烧合成反应,合成产物由TiC和Fe组成,其中细小的TiC颗粒有一定程度的团聚现象。     

基于溶胶凝胶法水热合成WO_3纳米材料及气致变色应用（英文）

以钨粉和氧化钨溶胶干粉作为前驱体,通过水热合成以及溶胶凝胶法制备了纳米氧化钨。通过X射线衍射分析仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外分光光度计(FT-IR)以及拉曼光谱(Raman)对水热产物进行了表征和分析。XRD表征显示2种结构分别属于单斜和六角相的氧化钨.电镜表征显示水热产物为纳米短棒和纳米长棒结构。为进一步研究水热产物对氧化钨气致变色性能的影响,通过将溶胶与不同晶相纳米结构复合的方式制备出了同源WO3复合薄膜.通过紫外分光光度计测试其气致变色性能。结果表明:单斜相复合薄膜降低了氧化钨的首次致色时间,六角相的复合薄膜保持了很好的气致循环特性。     

预设升温速度对电场作用下Fe-Ti-C体系燃烧合成的影响

采用Gleeble-1500D热模拟机,研究电场作用下预设升温速度对55wt%(Ti C)-45wt?体系在从室温加热至800℃过程中燃烧合成的影响,结果表明:预设升温速度对体系燃烧合成有较大影响,当预设升温速度为5℃/s时,不能实现燃烧合成;而在10～1500℃/s范围内,体系能实现燃烧合成,且点火温度大幅度降低,在336～742℃之间;随预设升温速度提高,点火温度降低,点火延迟时间缩短;合成产物主要由TiC、Fe和少量C组成,且随预设升温速度提高,TiC颗粒变小,并出现少量Fe2 Ti,但较低和过高的预设升温速度的合成产物中不会出现Fe2Ti.     

7075铝合金汽车支撑摆臂锻件固溶处理温度场模拟

利用ABAQUS有限元软件对7075铝合金汽车支撑摆臂锻件固溶处理过程温度场进行数值模拟,得到了锻件在不同升温方式、不同转运时间以及不同水温淬火下的温度场分布情况。结果表明,锻件随炉升温时,达到预定温度所需时间为112.1 min,最大温差为4.8 ℃;炉子到温后放入锻件升温时仅需71.2 min,最大温差为10.4 ℃。转运时间为3、3.5和4 min时,锻件中冷却最快部位的温度分别下降到384.0、375.9和367.8 ℃,最终确定转运时间不能超过3.5 min。采用25 ℃水淬时,冷却时间为95 s,冷却最快和最慢部位通过淬火温度敏感区的平均冷却速度分别为782.8和19.1 ℃/s,最大温差为237.6 ℃;80 ℃水淬时,冷却时间为56 s,锻件中冷却最快和最慢部分通过淬火温度敏感区的平均冷却速度则分别为587.4和16.8 ℃/s,最大温差为216.0 ℃。     

蓝钨物理性能对钨粉和碳化钨粉性能的影响

仲钨酸铵(APT)对蓝钨性能影响较大,而蓝钨物理性能对钨粉和碳化钨粉的性能影响也较大,通过对APT煅烧前或煅烧后进行特殊处理优选蓝钨原料,可以制取优质碳化钨粉。     

蓝钨循环氧化还原对钨粉末粒度分布的影响

以特纯仲钨酸铵为原料,通过特纯仲钨酸铵在氩气中煅烧获得蓝钨,此蓝钨在纯度为99.99%、露点小于-40℃的氢气中进行还原,蓝钨还原的钨粉在空气中被氧化为三氧化钨,对此三氧化钨再在氢气中还原,然后利用扫描电子显微镜和激光粒度分析仪对试样进行分析,结果表明:经过循环一次氧化和两次还原,制备出了粒径分布在3～10μm之间占83.86%、比表面积为0.180m2/g的中颗粒钨粉。     

Comparison of different tungsten precursors for preparation of tungsten nanopowder by RF induction thermal plasma

Tungsten nanopowders were synthesized using three different precursors: commercial tungsten (W), tungsten trioxide (WO₃), and ammonium paratungstate (APT) by radio-frequency (RF) induction thermal plasma in the presence and absence of H₂. The crystalline structure, morphology, and particle size of the synthesized tungsten nanopowders were analyzed by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The W nanopowder obtained using APT precursor was found to be the most homogeneous and smallest nanoparticles and showed the largest α-W phase (stable) fraction, which is the preferred phase for tungsten because of its superior properties to those of the β-W phase (metastable).     

Modern hydrometallurgical production methods for tungsten

Tungsten is one of the most important refractory metals. It is used in the production of numerous end-use items such as incandescent lamps and hard materials. From its ore concentrates and oxidized scrap, tungsten is processed via a hydrometallurgical route. In the last 100 years there has been a significant change in its processing. This paper reviews the methods employed in the hydrometallurgical production of ammonium paratungstate (APT), the main tungsten compound used in the manufacturing of tungsten metal powder. In addition to discussing tungsten feeds, the paper will review all hydrometallurgical steps typically used in the modern methods of APT production.     

直接碳化技术制备碳化钨粉的研究

本文以两种不同形貌的氧化钨和炭黑为原料,采用加酒精湿磨配炭制取混合料,再经干燥,在中频电炉中,于1 000℃、1 250℃、1 400℃直接碳化,分析碳化产物的相成份、形貌、粒度、炭含量、氧含量。研究发现,不同原料在相同温度直接碳化,碳化产物形貌完全不同;薄片状氧化钨所制得的碳化钨在低倍扫描电镜下观察几乎没有超过50μm的团聚颗粒;在高倍扫描电镜下观察是许多小颗粒的团聚体,并且聚集得很紧密。针状氧化钨原料制得的碳化钨在低倍扫描电镜下观察团粒较多,而且保持着原APT的伪晶形貌,在高倍扫描电镜下观察呈松散的细颗粒聚集体。当直接碳化温度达到1 250℃,反应基本完全,化合碳接近碳化钨理论含碳量。碳化钨粒度随温度的升高而增大。     

Dissolving behavior of ammonium paratungstate in (NH4)2CO3–NH3·H2O–H2O system

The effects of temperature, ammonia concentration and ammonium carbonate concentration on the dissolving behavior of ammonium paratungstate were studied in (NH₄)₂CO₃–NH₃·H₂O–H₂O system. The results show that rising temperature, prolonging duration, increasing ammonia concentration and decreasing ammonium carbonate concentration favor dissolving of ammonium paratungstate at temperature below 90 °C, while the WO₃ concentration decreases after a certain time at temperature above 100 °C. Furthermore, the undissolved tungsten exists in the form of either APT·4H₂O below 90 °C or pyrochlore-type tungsten trioxide above 100 °C. In dissolving process, the ammonium paratungstate dissolves into paratungstate ions followed by partially converting to tungstate ion, resulting in the coexistence of the both ions. This study may provide a new idea to exploit a novel technique for manufacturing ammonium paratungstate and pyrochlore-type tungsten trioxide.     

高纯粉状钨酸制备工艺的研究

APT在水中的难溶性使得酸分解APT制取钨酸的化学反应成为固—液反应 ,从而妨碍了反应均匀有效地进行。在本文所述的研究中 ,通过将APT热离解为偏钨酸铵而显著地改善了原料的水溶解性 ,使得反应成为近似液—液反应。本文还着重讨论了诸如溶浆温度、酸用量、保温时间、陈化时间等工艺参数对酸分解的影响。就以杂质含量很低的APT为原料生产高纯钨酸 ,确立了相应的工艺参数。在所拟工艺条件下制得的高纯钨酸 ,纯度 >99 99% ,平均粒度 0 6 1μm。操作简便、工艺稳定、产品转化率高 ,易实现工业化     

原子吸收光谱法测定钨中铅量

本文以钨粉、钨条、碳化钨、三氧化钨、钨酸、蓝钨、紫钨、仲钨酸铵、偏钨酸铵为分析对象,通过实验,提出了钨及其制品经过适当的溶剂处理后,在碱性条件下,以铁(Ⅲ)为共沉淀剂富集铅,用柠檬酸络合残余钨,以原子吸收光谱法测定钨中质量分数为0.000 3%～0.005 0%的铅量。文章分别对铅分离富集条件、主体元素及共存元素干扰情况、工作曲线的线性关系进行了研究,确定了最佳分析条件。采用优化后的测定条件,用原子吸收光谱法进行钨中铅量的测定,主体元素及其共存元素对测定均无干扰;加标回收率在90.33%～110.00%之间;测定编号为YSS001-96-3和YSS001-96-5三氧化钨标准样品,铅标准值分别为0.000 62%和0.004 1%,实际测得值分别为0.000 63%和0.004 2%;上述三氧化钨标样,通过21次独立测定,其相对标准偏差分别为4.17%和5.18%。方法简便,实用性强。     

Comparing thermal and mechanochemical decomposition of ammonium paratungstate (APT)

In this research, the possibility of mechanochemical decomposition of ammonium paratungstate (APT) has been studied, and compared with thermal decomposition method. For this purpose, APT powders were milled using a planetary ball mill up to 36 h and under air atmosphere. For thermal decomposition, APT powders were heated for 30 minutes at 300 and 450 °C in air atmosphere. X-ray diffraction (XRD), differential scanning calorimeter (DSC), and thermo gravimetric analyzer (TGA) were used to study the decomposition progress, and products. The XRD results showed that APT completely decomposed to WO₃ by thermal decomposition, while the final product of mechanochemical decomposition was WO₃ (H₂O)_0.5. According to DSC and TGA results, during thermal decomposition, ammonia and water released in four steps, and leaved WO₃. By mechanochemical decomposition crystal water and ammonia liberated from APT structure, but structural water of APT remained. In both methods, an X-ray amorphous phase was the intermediate product of APT decomposition.     

Synthesis of Cr-doped APT in the evaporation and crystallization process and its effect on properties of WC-Co cemented carbide alloy

WC grain size has significant effect on WC-Co cemented carbide alloy properties. In order to inhibit WC grain growth during sintering process, grain growth-inhibitor Cr₃C₂ is usually added to tungsten carbide powder in advance through mechanical milling. While, homogeneous distribution of Cr₃C₂ in the tungsten carbide powder is difficult to achieve and result in abnormal growth of WC grains. For this purpose of growth-inhibitor uniform distribution, (CH₃COO)₃Cr is added into ammonium tungstate solution during evaporation and crystallization process to prepare Cr-doped APT powder, which can be used as precursor for ultrafine-grained WC-Co cemented carbide alloy preparation. Compared with conventional APT powder, the Cr-doped APT has smaller particle size and bulk density, moreover, chromium is evenly distributed within it. The Cr-doped APT is then used to produce Cr-doped tungsten powder, which also has smaller particle size than that of conventional tungsten powder. Cr-doped tungsten powder is subsequently prepared into tungsten carbide powder and WC-Co cemented carbide alloy through carbonization and sintering process, respectively. Compared with conventional WC-Co cemented carbide alloy, the obtained WC-Co cemented carbide alloy has smaller mean WC grain size (0.36 μm), and more uniform microstructure. Furthermore, the phenomenon of WC grain abnormal growth during sintering process is not observed, because the grain growth-inhibitor Cr₃C₂ is well dispersed in tungsten carbide and cobalt composite powder. Results show that the obtained WC-Co cemented carbide alloy presents better mechanical properties (HRA, bending strength, coercive force) than those of conventional WC-Co cemented carbide alloy. Accordingly, the novel addition of (CH₃COO)₃Cr during the evaporation and crystallization process is the key factor of ultrafine-grained WC-Co cemented carbide alloy production.