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1.
Scandia doped tungsten powders were prepared by spray drying combined with two-step hydrogen reduction.The particle size of doped tungsten powder,powder morphology and doped tungsten matrix were characterized by scanning electron microscope,X-ray diffrac-tion and laser diffraction particle size analyzer,respectively.The reduction behavior of Sc2O3 doped tungsten oxide and the effect of Sc2O3 on the property of tungsten powder were studied by the temperature programmed reduction.The experimental results showed that the pre-cursor powders prepared by spray drying had spherical shape.The addition of Sc2O3 could decrease the reduction temperature of tungsten oxide.The scandia doped tungsten powder had sub-micrometer size in the range of 0.1 to1 μm and scandium distributed evenly in the powder.By using this kind powder,sub-microstructure cathode matrices with semispherical grains and homogenous distribution of scan-dium were obtained. 相似文献
2.
Scandia doped tungsten powders were prepared by spray drying combined with two-step hydrogen reduction. The particle size of doped tungsten powder, powder morphology and doped tungsten matrix were characterized by scanning electron microscope, X-ray diffraction and laser diffraction particle size analyzer, respectively. The reduction behavior of Sc2O3 doped tungsten oxide and the effect of Sc2O3 on the property of tungsten powder were studied by the temperature programmed reduction. The experimental results showed that the precursor powders prepared by spray drying had spherical shape. The addition of Sc2O3 could decrease the reduction temperature of tungsten oxide. The scandia doped tungsten powder had sub-micrometer size in the range of 0.1 to1 μm and scandium distributed evenly in the powder. By using this kind powder, sub-microstructure cathode matrices with semispherical grains and homogenous distribution of scandium were obtained. 相似文献
3.
V. N. Chuvil’deev A. V. Nokhrin G. V. Baranov M. S. Boldin A. V. Moskvicheva N. V. Sakharov D. N. Kotkov Yu. G. Lopatin V. Yu. Belov Yu. V. Blagoveshchenskii N. A. Kozlova D. A. Konychev N. V. Isaeva 《Russian Metallurgy (Metally)》2014,2014(3):215-228
The structure and mechanical properties of nano- and ultradispersed mechanically activated heavy W-Ni-Fe and W-Ni-Fe-Co tungsten alloys (VNZh and VNZhK alloys, respectively) are studied. Mechanically activated nano- and ultradispersed charge powders are sintered by free sintering (thermally activated) and spark plasma sintering. The dependence of the density of the alloys made of the mechanically activated powders on the sintering temperature is found to have a nonmonotonic character with a maximum corresponding to the optimum sintering temperature. It is shown that an increase in the mechanical activation time and the acceleration of the milling bodies during mechanical activation lead to a decrease in the alloy particle size and the formation of nonequilibrium solid solutions and are accompanied by a decrease in the optimum sintering temperature of heavy tungsten alloys. Ultrahigh-strength tungsten alloys the mechanical properties of which are substantially higher than those of standard coarse-grained analogs are fabricated due to the optimization of the conditions of ball milling and high-rate spark plasma sintering of W-Ni-Fe powders. 相似文献
4.
钨粉形貌与粒度分布对成形性和压坯强度的影响 总被引:2,自引:0,他引:2
林高安 《粉末冶金材料科学与工程》2009,14(4):260-264
钨制品的压制行为依赖于原料粉末的性能.采用3种不同氧含量的氧化钨为原料,通过H2还原得到了3种平均粒度相同但粒度分布与颗粒形貌不同的钨粉.用模压法制成强度测试用样品,采用三点弯曲法测定压坯的抗弯强度,并观察样品的形貌,研究钨粉的粒度分布和颗粒形貌对钨粉成形性和压坯强度的影响.结果表明,通过控制氧化钨原料中各种物相的比例,可以有效地控制钨粉的粒度分布与形貌:在粉末费氏粒度相当的条件下,原料粉末中细颗粒含量越高,颗粒形貌越不规则,其成形性越好,压坯强度越高. 相似文献
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6.
以钨酸钠和盐酸为原料,碳纳米管为载体,采用一步法将钨酸颗粒直接沉积在碳纳米管管壁上,形成钨酸-碳纳米管(H2WO4-CNTs)复合物.或采用二步法将钨酸沉淀与碳纳米管复合,形成H2WO4-CNTs复合物.之后,在氧气气氛下进行煅烧,生成了氧化钨粉末.经物理性能测试,2种方法制备的H2WO4-CNTs复合物中钨酸颗粒的平均粒径分别为10 nm和100 nm.氧化钨粉末的平均粒径分别为250 nm和2μm,比表面积分别为36.53 m2/g和13.99 m2/g.采用紫外可见分光光度计测定了氧化钨的光催化性能,在11 W的日光灯照射下,当光照时间为30 min时,脱色率分别达到93.8%和79.1%.结果表明,一步法制备的氧化钨因具有更小的平均粒径和更大的比表面积,表现出更好的物理吸附性能和光催化性能. 相似文献
7.
L. A. Vermenko O. I. Get'man S. P. Rakitin V. V. Skorokhod 《Powder Metallurgy and Metal Ceramics》1983,22(9):703-707
Conclusions An increase in the size of pores determined by the Barus-Bechgold method in porous specimens from fine tungsten and tungsten-nickel powders takes place during heating to the isothermal sintering temperature. The addition of nickel to tungsten activates the pore size growth process. The size of the increased pore channels in porous solids from W and W-0.46% Ni powders in the temperature range 1000–1300°C depends on the particle size and sintering temperature. A correlation has been found between the integral shrinkage during isothermal sintering and the capillary stresses acting on the attainment of the isothermal sintering temperature in compacts from W-0.46% Ni powders of various particle sizes. The rates of isothermal shrinkage are the same, being independent of the previous history of the powders.Translated from Poroshkovaya Metallurgiya, No. 9(249), pp. 18–23, September, 1983. 相似文献
8.
以钨酸铵溶液为原料,加入含Li、Na和K碱金属盐的添加剂,在湿氢条件下还原制备粗晶球形钨粉.研究了碱金属盐的种类、含量及还原时间对仲钨酸铵粉末及钨粉的影响.通过扫描电镜、能谱仪、X射线衍射仪和检验分析筛对仲钨酸铵及粗晶钨粉的形貌、成分、物相组成及粒度分布进行表征.研究表明,采用钨酸铵溶液为原料,添加剂(NaCl、KCl和Li2CO3)为3 g·L-1,在1000℃湿氢条件下还原180 min,可直接制备出流动性良好、近球形、晶粒发育完整且均匀的粗晶钨粉.其平均粒径达到67μm,最大粒径可达150μm,最大松装密度为13.41 g·cm-3,最佳流动性为每50 g粗晶钨粉用时9 s. 相似文献
9.
通过改变球磨时间,获得不同粒度分布的钨粉颗粒,分析球磨时间对钨粉粒度分布和形貌特征的影响,提高粒度分布在目标区间(5~11 μm)的钨粉颗粒体积分数。结果表明,球磨的前2 h对原料中大颗粒钨粉的影响较大,钨粉颗粒最大粒径由134 μm迅速下降到20 μm左右。随着球磨时间的增加,钨粉粒度分布指标减缓下降,除粒径变小外,颗粒形貌基本无变化,但是在球磨10 h后开始出现团聚现象。综合分析可知,球磨时间的改变对钨粉粒度分布指标影响较大,球磨时间为8 h时,可获得粒度分布最窄的钨粉颗粒,在目标区间的钨粉颗粒体积分数达到75%。 相似文献
10.
Effect of size and shape of tungsten particles on dynamic torsional properties in tungsten heavy alloys 总被引:3,自引:0,他引:3
Dong-Kuk Kim Sunghak Lee Heung-Sub Song 《Metallurgical and Materials Transactions A》1999,30(5):1261-1273
The effect of the size and shape of tungsten particles on dynamic torsional properties in tungsten heavy alloys was investigated.
Dynamic torsional tests were conducted on seven tungsten alloy specimens, four of which were fabricated by repeated sintering,
using a torsional Kolsky bar, and then the test results were compared via microstructure, mechanical properties, adiabatic shear banding, and deformation and fracture mode. The size of tungsten particles
and their hardness were increased as sintering temperature and time were increased, thereby deteriorating fracture toughness.
The dynamic torsional test results indicated that in the specimens whose tungsten particles were coarse and irregularly shaped,
cleavage fracture occurred predominantly with little shear deformation, whereas shear deformation was concentrated into the
center of the gage section in the conventionally fabricated specimens. The deformation and fracture behavior of the specimens
having coarse tungsten particles correlated well with the observation of the in situ fracture test results, i.e., cleavage crack initiation and propagation. These findings suggested that there would be an appropriate tungsten particle
size because the cleavage fracture mode would be beneficial for the “self-sharpening” of the tungsten heavy alloys. 相似文献
11.
超细钨粉是生产硬质合金的重要原料,目前工业上制备超细钨粉的方法主要是氧化钨氢还原法.如何低成本、大规模的生产出均匀的超细钨粉一直是一个研究热点.文中采用控制变量法,进行蓝钨氢还原实验,探究还原温度、氢气流量和还原时间对产物钨粉形貌的影响.当还原温度为700℃,氢气流量为150 mL/min,还原时间为55 min,此时... 相似文献
12.
将微量硅酸钠以不同浓度的水溶液形式掺杂到蓝色氧化钨中并在相同的条件下还原成钨粉。结果表明,还原钨粉的粒度随硅酸钠掺杂量的增加而增加,少量掺杂还使还原钨粉的松装密度增加。对还原钨粉表面的扫描电镜及x射线光电子能谱分析结果显示,掺杂到蓝色氧化钨中的硅酸钠最终以Na_2SiO_3和SiO_2二种分子形式存在并以微粒状分布在还原钨粉的表面。掺杂微量硅酸钠还使还原钨粉中的二次颗粒增加。 相似文献
13.
超细钨粉是目前制备多种硬质合金和结构材料的重要原料,其主要制备方法为氢还原法.在对大量文献资料进行查阅及分析的基础上,综述了氧化钨氢还原动力学的研究现状,包括氧化钨氢还原的基本原理、不同动力学条件下的还原历程以及物相转换.介绍了国内外学者在不同钨氧化物的氢还原过程中,通过改变动力学参数对产物钨粉的粒度、形貌、结构和性能的影响,以及实际工业生产的现状和存在的问题.重点介绍了目前氢还原动力学的几种模型及其方程,并对可能适用于氧化钨氢还原动力学研究的动力学模型进行了展望. 相似文献
14.
以碳热预还原和氢气深还原两步制备的纳米钨粉作为烧结原料,即先通过碳黑还原脱除三氧化钨中的大部分氧,再以氢还原脱除残留的氧。该方法制备的钨粉颗粒呈球形形貌,平均晶粒度可达90 nm。同时,向钨粉中掺杂质量分数为1%和2%的氧化铝,探究了氧化铝对钨粉烧结行为的影响。通过烧结样品的断口形貌和晶粒的平均尺寸分析发现,氧化铝对烧结后期的晶粒长大有明显的抑制作用,相同的烧结温度下晶粒的尺寸随着氧化铝含量的上升而减小。在1600 ℃时,纯钨粉烧结坯的晶粒平均尺寸为2.75 μm,但添加质量分数为1%和2%氧化铝的烧结样品晶粒平均尺寸约为1.5 μm,这是由于氧化铝能有效地抑制烧结后期的钨粉晶粒长大。纯钨粉和掺杂氧化铝钨粉的烧结坯的硬度随温度升高具有不同的趋势。掺杂钨粉烧结坯的硬度随着温度的升高而升高,且其最大值高于800 HV。但是,纯钨粉烧结坯的硬度随烧结温度增加而先增加后降低,在1400 ℃时取得最大值(473.6 HV),这是由纯钨粉烧结坯的晶粒在高温下急剧长大所导致。在烧结温度为1600 ℃时,纯钨粉、掺杂质量分数1%和2%的氧化铝掺杂的钨粉的烧结坯的相对密度依次为98.52%、95.43%和93.5%。 相似文献
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16.
对铵钨青铜((NH_4)_(0.5)WO_3,ATB)、氢钨青铜(H_(0.33)WO_3,HTB)、紫色氧化钨(W_(18)O_(49),TVO)和蓝色氧化钨(WO_3+WO_(2.9),TBO)4种氧化钨粉的氮气吸附/脱附等温线数据的分析,获得了其表面积、微孔体积、微孔分布、中孔体积、平均孔径和分数维维数等物理参数。结果表明:TVO粉末具有最大的中孔体积、最小的微孔体积、最窄的孔径分布、最小的分数维维数和最大的平均孔径,有利于氢还原制取超细钨粉,而不利于掺杂工艺。HTB粉末具有最大的微孔体积,最宽的孔径分布,最高的分数维维数和最小的平均孔径,对于掺杂工艺来说是有利的。ATB和TBO的上述参数介于TVO和HTB的参数之间。 相似文献
17.
Dynamic deformation behavior of an oxide-dispersed tungsten heavy alloy fabricated by mechanical alloying 总被引:14,自引:0,他引:14
Sanghyun Park Dong-Kuk Kim Sunghak Lee Dong-Kuk Kim Ho Jin Ryu Soon Hyung Hong Ho Jin Ryu 《Metallurgical and Materials Transactions A》2001,32(8):2011-2020
The objective of this study is to investigate the dynamic deformation and fracture behavior of an oxide-dispersed (OD) tungsten
heavy alloy fabricated by mechanical alloying (MA). The tungsten alloy was processed by adding 0.1 wt pct Y2O3 powders during MA, in order to form fine oxides at triple junctions of tungsten particles or at tungsten/matrix interfaces.
Dynamic torsion tests were conducted for this alloy, and the test data were compared with those of a conventional liquid-phase
sintered (LPS) specimen. A refinement in tungsten particle size could be obtained after MA and multistep heat treatment without
an increase in the interfacial area fraction between tungsten particles. The dynamic test results indicated that interfacial
debonding between tungsten particles occurred over broad deformed areas in this alloy, suggesting the possibility of adiabatic
shear-band formation. Also, oxide dispersion was effective in promoting interfacial debonding, since the fine oxides acted
as initiation sites for interfacial debonding. These findings suggest that the idea of forming fine oxides would be useful
for improving self-sharpening and penetration performance in tungsten heavy alloys. 相似文献
18.
采用等离子旋转电极雾化技术(PREP)制备球形钨粉,利用激光粒度分析仪、氧氮分析仪、扫描电子显微镜(SEM)对钨粉末的粒径分布、氧含量、微观形貌、表面组织进行分析。结果表明:球形钨粉粒度集中分布在45~150μm,呈单峰分布,理论中位粒径85.5μm与实测粒径80μm接近。钨粉氧增量均小于0.001 5%,其中45~150μm粉末比15~53μm的粉末氧增量更低,仅为0.000 38%。15~53μm钨粉表面光洁,几乎无空心粉。钨粉物理性能优异,且粒径在45~150μm的钨粉性能优于15~53μm的。 相似文献
19.
氧化钨氢气还原制备超细钨粉的研究现状 总被引:1,自引:0,他引:1
郭峰 《粉末冶金材料科学与工程》2007,12(4):205-210
超细钨粉以其显著的优点,早已成为多种重要功能材料和结构材料的主要原料,但以喷雾干燥法等常规制粉工艺制得的钨粉末均为前驱复合氧化物粉末,必须对其进行氢还原才能最终制备出超细钨基复合粉末或钨基复合材料.为此,该文作者综述了氧化钨及其复合氧化物粉末的还原工艺、原理及不同条件下还原后所得粉末的特性,分析了采用不同特征的氧化钨及其复合氧化物做原料可得到不同性能还原W粉的原因,并对氢气还原过程中粉末粒度及其均匀性的影响等因素进行了详细论述,获得了一些参考性认知. 相似文献