玻璃基质与纳米颗粒相互影响的光谱学研究

通过低温选择激发玻璃陶瓷中的LaF3:Tm3+的1D2能级,成功地分开了两种局域环境中Tm3+离子的发射谱,使一些频率的发射谱仅来自于晶相,而另一些则仪来自于玻璃相.讨论了玻璃陶瓷中形成玻璃的氧化物和以晶相析出的氟化物之间的相互作用对两种局域环境中Tm3+离子的光学性能的影响.结果表明:晶粒较大时,氧化物玻璃对处于纳米晶体局域环境的稀土离子的影响减弱,纳米晶体对处于氧化物玻璃局域环境的稀土离子的影响增强;晶粒较小时,氧化物玻璃和晶粒接触面的增加会降低处于纳米晶体局域环境的稀土离子的发光效率,但纳米晶体对处于氧化物玻璃局域环境的稀土离子的影响减弱.晶粒越大,氧化物玻璃对处于纳米品体局域环境的稀土离子的发光影响越小,发光性能越好.玻璃基质中SiO2的含量能影响两种局域环境的Tm3+离子发光效率.     

稀土硅铁雾化与粒化机理的摄影分析

稀土硅铁合金在钢和球墨铸铁中主要作为添加剂使用,稀土元素具有细化晶粒、固溶强化、形成新强化相等作用,可以显著提高钢铁的综合机械性能。 目前稀土硅铁产品是采用机械破碎成粉加入金属之中的。这种制粉工艺浪费较大,且污染环境,危害健康。因此稀土硅铁雾化制粉新工艺的研究已列入国家75重点攻关项目之中。     

高温高压烧结高硬度高致密度块体金属钨及钨基合金W-TiC

采用高温高压烧结方法,烧结纯钨和TiC颗粒弥散增强W-TiC合金材料,对钨及W-TiC合金的烧结致密化行为和力学性能进行了研究。结果表明:在压力为5.0GPa、温度为1 500℃的条件下烧结15min可获得良好的烧结样品,块体钨的致密度达到99.3%,硬度达到6.43GPa;在相同的高温高压烧结条件下,添加质量分数为1.5%的TiC,获得的W-TiC合金致密度达到99.0%,硬度达到7.58GPa。极端高压环境不但能抑制钨及钨合金在烧结过程中的晶粒长大,还能降低烧结温度,提高烧结效率,增加烧结体的致密性。在此基础上进一步探索了钨及钨基合金W-TiC的高压烧结动力学、微观结构、机械性能与烧结压力和烧结温度的关系。     

BPSCCO非晶晶化过程

用 X 射线衍射、透射电镜及电子探针等分析技术研究了熔融淬火法制备的名义成分为Bi_(1.86)Pb_(0.34)Sr_2Ca_2Cu_3O_x 的非晶晶化的相转变过程.并对不同处理温度下的氧化物析出相的形态进行分析,结果表明:在非晶晶化过程中首先析出的是2212,2202相及 CuO,CaO 等氧化物相,然后相互反应生成2223相.2212相及2223相能以交生状态存在.在晶化反应中,不出现 Ca_2CuO_3相.但 CuO,CaO 相弥散分布在超导晶粒里,并随热处理温度的提高,而聚集长大.     

Zr掺杂形式对钨电子发射材料组织性能的影响

采用中频感应加热烧结方法制备了W-1.5%La₂O₃-0.1%Y₂O₃-0.1%ZrO₂和W-1.5%La₂O₃-0.1%Y₂O₃-0.08%ZrH₂电子发射材料,烧结样品的致密度约为95.5%。热电子发射测试结果表明,添加氢化锆的热电子发射材料样品的零场发射电流密度大于添加氧化锆的样品,分析认为是添加的氢化锆在烧结时,发生分解,生成活性的Zr可以捕获钨晶界中的杂质氧,净化晶界,从而提高了电子发射;维氏显微硬度表明添加氢化锆样品的硬度高于添加氧化锆的样品,分析表明是氢化锆的添加有效改善了钨晶粒之间的结合性,提升了钨电子发射材料的硬度。利用SEM,EDS,XRD、金相显微镜等表面分析设备对样品进行了表征,样品结构显示添加氢化锆与添加氧化锆相比,不仅钨晶粒尺寸由13.63 μm降至11.63 μm,而且稀土相尺寸由1.87 μm降至1.66 μm,这种组织结构的变化有利于电子发射。     

一种理想的坩埚材料——弥散强化铂

<正> 光学玻璃通常采用粘土坩埚、铂金坩埚和铂金连熔池炉等方法熔炼。近年来出现了氧化物弥散强化铂,这是一种更为理想的坩埚材料,用这种材料制造的坩埚具有耐高温、变形小、寿命长等特点。弥散强化铂的制造过程是在铂或铂基合金     

电解抛光法制备金属钨箔膜

研究了在硫酸甲醇体系中进行电解抛光制备状态方程(EOS)靶用钨薄膜。分析了钨的阳极极化曲线,对薄膜的表面形貌、晶粒取向、密度和厚度一致性进行了测试和分析,并制备出均方根粗糙度小于50nm、厚度一致性好于99%、能够保持原材料密度的钨箔膜,满足激光驱动材料高温高压状态方程研究的标准靶材料的需求,证明电解抛光是制备低表面粗糙度、块材密度的EOS所用金属箔材的有效手段。     

混合稀土Ho—Ba—Cu—O体系的高温超导电性研究

本文报道了以高钬混合稀土(Ho_2O_3 56.13%)氧化物为原料,利用固态反应法制备混合稀土 Ho-Ba-Cu-O 体系超导体样品的工艺:给出了高温超导电性测量和 X-射线粉末衍射及扫描电镜分析结果.     

碳化物弥散强化钢力学性能及微观组织研究

用碳化物粒子对低活化钢 CLF-1 进行弥散强化。结果表明机械合金化的方法可以制备高强度的碳 化物弥散强化钢,经过 60h 球磨可完成合金化过程,同时添加的碳化物粒子很好地提高了低活化钢 CLF-1 的拉 伸性能,得到了比熔炼低活化钢更高的强度和硬度,同时保持了较好的延伸率。      

纳晶锰氧化物对CO氧化反应的催化活性研究

用γ－射线辐射方法制备了ＭｎＯ２,Ｍｎ２Ｏ３和Ｍｎ３Ｏ４３种纳晶锰的氧化物,它们的平均粒径分别为１０,２０和２２ｎｍ,通过与常规晶粒的相应粉末对比研究发现。纳晶粒末对ＣＯ的氧化反应的催化活性远远高于常规晶粒。经过一次催化实验这后,纳晶锰的氧化物的平均颗粒尺寸虽然有一定程度的增加,但仍保持在纳米范围内,这说明纳晶锰的氧化物作为ＣＯ氧化反应的催化剂是相对稳定的,因此,可以作为廉价和易得的清除ＣＯ的催化     

Influence of impurities on the fracture behaviour of tungsten

Ten tungsten materials with different impurity concentrations and different microstructures have been investigated by Auger electron spectroscopy and scanning electron microscopy with respect to their fracture behaviour. For almost all samples, both inter- and transgranular fracture are observed, and the proportion of each type varies. Due to the difference in their impurity content and grain boundary area, a large variation in the grain boundary impurities can be expected. By analysing the fracture surfaces the effect of grain boundary impurities, especially phosphorous and oxygen, on the fracture resistance of the boundaries was determined. The results indicate that for the analysed tungsten materials, grain boundary impurities do not have a significant influence on the fracture resistance of the boundaries. Other factors such as the size and shape of the grains, the amount of deformation and therefore the density of dislocations within the grains have a greater impact on the fracture behaviour of tungsten.     

Microstructure and thermostability of a W–Cu nanocomposite produced via high-pressure torsion

A coarse-grained W–25% Cu alloy is subjected to high-pressure torsion (HPT) at room temperature to different strains. Evolution of the microstructure during HPT processing is studied using X-ray diffraction analysis, scanning and transmission electron microscopy. It is demonstrated that HPT processing results in fragmentation of the tungsten particles and the formation of a 5–15?nm grain size nanostructure at equivalent strains of ≥256 (saturation). It is shown that the nanostructured W–25% Cu is thermostable up to 500°C, with grain growth up to 50?nm at 720°C. During HPT processing, the lattice parameter of the copper and tungsten was found to increase and decrease, respectively, with increased level of equivalent strain. This is proposed to occur through the interdiffusion of copper atoms into tungsten grains and tungsten atoms into copper grains, as suggested by energy-dispersive X-ray analysis of the individual grains. The formation of a limited solid solution is considered and possible mechanisms for this effect discussed.     

The tungsten powder study of the dispenser cathode

The intercorrelation of tungsten powder properties, such as grain size, distribution and morphology, and porous matrix parameters with electron emission capability and longevity of Ba dispenser cathodes has been investigated for the different grain morphologies. It is shown that a fully cleaning step of the tungsten powder is so necessary that the tungsten powder will be reduction of oxide in hydrogen atmosphere above 700 °C. The porosity of the tungsten matrix distributes more even and the closed pore is fewer, the average granule size of the tungsten powder distributes more convergent. The porosity of the tungsten matrix and the evaporation of the activator are bigger and the pulse of the cathode is smaller when the granularity is bigger by the analysis of the electronic microscope and diode experiment.     

Silicon diffusion through thin tungsten films on silicon,studied with Auger spectroscopy

Silicon out-diffusion through ? 3000 Å tungsten films deposited on silicon by r.f. sputtering was studied using Auger spectroscopy. Silicon first diffuses to the tungsten film surface by grain boundary diffusion and surface migration. The out-diffusion kinetics were most strongly dependent on the thickness of the silicon dioxide layer between tungsten and silicon, and this (native) oxide thickness varied with substrate doping. The out-diffusion rate was independent of tungsten film thickness at 540 Å and 2400 Å. For substrates from which the native oxide was removed by backsputtering just prior to tungsten deposition, no Si out-diffusion to the W film surface was observed until almost the entire film had converted to WSi².     

Influence of high-energy ball milling on the solid-phase sintering kinetics of ultrafine-grained heavy tungsten alloy

The mechanisms for the sintering of ultrafine-grained 95%W–3.5%Ni–1.5%Fe heavy tungsten alloy powders have been investigated. It has been established that a decrease in the activation energy of grain boundary diffusion and the formation of a nonequilibrium solid solution of nickel and iron in the surface layer of tungsten particles upon high-energy ball milling are responsible for the decrease in optimal sintering temperature.     

К ВОПРОУ О ВЛИЯНИИ СР Э дНЭЙ ВЭЛИЧИНЫ зЭРНА wС И СДЭРЗАНИЯ СВЯзЫВАЮ ЩЭЙ КОБ⇓ЛЬТОВОЙ ФАзЫ НА РЭНТГЭНОГРАФИЧЭС КОЭ ИзМЭРЭНИЭ МАКРОН АПЯЖЭНИЙ В ТВЭРДЫХ CПЛАВАХ СИСТ ЭМЫ WС-Со

The influence of the mean grain size of tungsten carbide (in a range of 1–3μm) and the influence of the amount of cobalt binding agent (6–25% weight) in hard metals on the X-ray determination of the elastic macrostresses caused by deflection were studied. A confrontation of the results of X-ray measurements with the values of stresses calculated theoretically from the corresponding deflections and mean elastic constants showed that the values of the stresses determined by X-ray are systematically lower than those calculated theoretically and this difference is greater the larger the mean grain size of tungsten carbide and thus the larger the ratio of the binding cobalt.     

Defect and electrical properties of nanocrystalline tungsten trioxide

Nanocrystalline tungsten trioxide particles were prepared by a wet-chemical method. Transmission electron microscope (TEM) analysis shows that the average grain size is about 15nm. The oxygen deficiency of nanometre-sized sample is higher than that of ordinary tungsten trioxide. The electric conductivity increases because of high oxygen deficiency. Ironic relaxation polarization and crystallographic shear (CS) planes theory were used to explain the unusual dielectric characteristic of nanocrystalline tungsten trioxide.     

Growth, structure and electrical properties of tungsten oxide nanorods

Tungsten trioxide has shown good sensing properties towards various gases. Recently thin nanostructured WO₃ films have been tested. Due to their large surface area to volume ratio they exhibit good sensitivity depending on the grain size. However in conventional WO₃ thin films the average grain size exceeds the thickness of the surface space charge layer, so the electrical conduction is mainly controlled by the carriers transport across the grain boundaries. An alternative way seems to be in a monocrystalline material with nanometric dimensions. Our objective is to fabricate nanosized tungsten oxide rods and to test their sensing properties under gas adsorption. In this work, we focus on the growth, the structure and the electrical properties of tungsten nanorods. The tungsten oxide nanorods were grown by vapour transport from a WO₃ layer onto a substrate (Mica). The nanorods growth was controlled by the temperature gradient between the WO₃ layer and the substrate. Their morphology was investigated by AFM and their structure by TED and TEM. We have investigated the conductivity of the WO₃ nanorods with a technique derived from Atomic Force Microscopy operating in contact mode with a conductive tip (Resiscope).     

钨合金的层裂强度研究

 用压缩空气炮做冲击加载装置研究一种钨合金的层裂特性,加载应力峰值为5~10 GPa,加载应力时间宽度为0.2~0.6 μs。实验用钨合金由粉末热压烧结制成,是一种均匀混合材料。它的成份重量百分比为W（90%）、Ni（6.8%）、Fe（2.7%）和Cr（0.5%）。由锰铜压阻计测量样品靶后界面应力历史表明,此种钨合金的层裂强度与拉伸应力率的平方根呈单调递增关系,与加载应力峰值无关。回收样品的金相分析结果表明,此钨合金的拉伸断裂主要发生在铁镍混合物部位,钨晶粒的穿晶断裂只占很小部分。断口上的“杯状”凹坑表明,它主要属延性断裂机制。