The process of bubble formation in the hot isostatic pressing treated,doped molybdenum wire

Entrapped materials in the bubbles formed in the K- and Si-doped and hot isostatically pressed molybdenum wire were examined by means of scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy. Solidified particles entrapped in the bubbles were identified as Al-K-Si leucite-type oxide. After reheating these solidified particles at 1900 °C for 5 minutes under atmospheric pressure, however, a portion of the particle was homogeneously volatilized. The remainder was identified as an Al-K-Si mullite-type oxide. Therefore, it can be concluded that the added dopants form a single phase upon annealing, and the formation of bubbles in the doped molybdenum wire is due to volatilization of Al-K-Si oxides, not pure elements constituting the oxides.     

Recrystallization of molybdenum wire doped with potassium-silicate

The doping effect of the bubble formation oxide on the recrystallization of Mo wire was investigated. Five different wires of 1 mm in diameter were prepared through sintering, swaging, and drawing processes. Each wire was doped with various amounts of potassium (K) plus silicon (Si), i.e., 0, 0.028, 0.14, 0.28, and 0.49 by weight percent, and annealed for 30 minutes at given temperatures. To understand the overall recrystallization phenomena, changes in hardness and in optical microstructures were examined. Transmission electron micrographs were taken for the specimens in the as-drawn state and at the beginning of the decrease in hardness. And also, the relative excess resistivity was measured as a function of heating temperature to confirm the occurrence of the abnormal grain growth. During the grain growth, bubble dispersion was evaluated through fractography by scanning electron microscopy (SEM). Primary re-crystallization started at 750 °C regardless of the amount of dopants. For the specimens doped with 0.14 and 0.28 (K + Si), large elongated and interwoven grain structures indicating ab-normal grain growth developed over 1400 °C and 1600 °C, respectively. For the specimens doped with 0.028 and 0.49 (K + Si), however, small equiaxial grain structure developed similar to pure molybdenum wire. Such a difference was understood through the relationship between grain structures and bubble dispersion parameters (the average bubble diameter, the bubble row density, the columnar bubble spacing, and the bubble row distance). It was concluded that two of the most important parameters to develop a grain structure of high aspect ratio were bubble row density and bubble row distance. At a high bubble row density, irregularity in bubble row distance induced the higher aspect ratio (length/width (L/W)) of grain.     

脉冲激光切丝工艺制备球形钼粉

为了获得高性能的实心球形颗粒钼粉原料,采用脉冲激光切丝法制备球形钼粉。通过筛分、光学显微镜和扫描电子显微镜等研究了所制备钼粉的粒度、形貌、微观组织等物理性能。结果表明,脉冲激光切丝法制备的钼粉形貌呈球形或近球形,表面光滑,没有卫星颗粒或颗粒粘接聚集现象。在试验工艺参数范围内,90%以上的钼粉颗粒粒径在150 μm以上,其中粒径在150～300 μm范围的颗粒占比最大,超过60%。粒径400 μm以下的钼粉通常是内部致密的,而在一些粒径较大的钼粉颗粒中出现内部孔洞,并初步分析了钼粉颗粒及其内部孔洞的形成机制。     

Si、Al、K掺杂钼丝的组织和性能研究

通过透射电镜(TEM)、扫描电镜(SEM)、能谱分析(EDS)对Si、Al、K掺杂烧结钼条和退火钼丝的组织形貌进行了跟踪检测分析;通过DSC和硬度试验检测Si、Al、K掺杂钼丝的再结晶温度;通过热模拟试验对纯钼条和Si、Al、K掺杂钼条的高温综合力学性能进行了对比分析.结果表明:Si、Al、K掺杂使钼条的高温综合力学性能得到了明显的改善;在本试验条件下,Si、Al、K掺杂使钼丝的再结晶温度提高约550～600℃,再结晶后由长径比大的晶粒形成燕尾搭接状链锁结构组织;Si、Al、K掺杂钼丝的强化相是K泡和硅酸铝钾颗粒.     

Orthodontic wire: a continuing evolution

Previous studies have shown that large doses of vitamin A potentiate chemical-induced liver injury and that the Kupffer cell is directly involved in this potentiation. Therefore, these studies were designed to determine if Kupffer cells isolated from vitamin A treated male Sprague-Dawley rats (75 mg/kg/day for 3-7 days as all- trans-retinol) had altered activity and function. Respiratory activity of Kupffer cells isolated from rats treated with vitamin A for 3 to 7 days markedly increased. Similarly, phagocytic activity was significantly elevated (up to 9-fold) after exposure to vitamin A for 3 to 7 days. Production of reactive oxygen species, measured by luminol-enhanced chemiluminescence of Kupffer cells isolated after 7 days of vitamin A exposure, was significantly higher than that of control cells when stimulated with opsonized zymosan. Also, the release of superoxide anion by individual Kupffer cells isolated from vitamin A treated rats was nearly three times greater than that of control cells. Basal production of tumor necrosis factor-alpha (TNF-alpha) and prostaglandin E2 (PGE2) production were significantly elevated in Kupffer cells isolated from rats treated with vitamin A. Lastly, peripheral blood monocytes (PBMC) isolated from rats treated with vitamin A for 7 days had a significantly greater respiratory activity, as well as TNF-alpha and PGE2 production, than PBMC isolated from control rats. Our data suggest that large doses of vitamin A enhance both Kupffer cell and PBMC function. Upregulation of the activity by these phagocytic cells may play a role in the vitamin A potentiation of chemical-induced liver injury.     

The bubble,drop, and particle unit (BDPU)

The Bubble, Drop, and Particle Unit (BDPU) is an instrument conceived to study the dynamics of transparent fluid mixtures in Spacelab’s microgravity environment. The scientific objectives of BDPU in its present configuration will essentially be the investigation of (1) bubbles, drops, and particles in liquids with nonuniform temperature and concentration fields, (2) formation and dynam-ics of the solidification fronts, and (3) interaction between intrusions and solidification fronts. The heart of the facility is the exchangeable test container which can, within some limits, be adapted to the investigator’s requirements. The diagnostics of the fluid under investigation are essentially opti-cal: direct view, slice view, Schlieren, interferometry, and thermography. Several devices are used for fluid management and production of bubbles and drops in liquid matrices. BDPU is a candidate for the IML-2 mission. This paper is based on a presentation made in the symposium “Experimental Methods for Microgravity Materials Science Research” presented at the 1988 TMS-AIME Annual Meeting in Phoenix, Arizona, January 25-29, 1988, under the auspices of the ASM/MSD Thermo-dynamic Data Committee and the Material Processing Committee.     

Si和La元素对Mo丝显微组织与力学性能的影响

系统研究了La、Si单元掺杂和复合掺杂对钼丝的显微组织和力学性能的影响及其作用机制,优化出具有优异力学性能的Mo-Si-La合金丝的成分为Mo-0.15Si-(0.5～0.8)La.MoSi2与Mo原位反应生成Mo5Si3和Mo3 Si硬质相,起到良好的晶粒细化作用和弥散强化作用.La2O3颗粒通过延迟微裂纹的形成和扩...     

氮掺杂碳负载超细碳化钼析氢电催化剂

近年来，碳化钼（Mo₂C）因其良好的稳定性及类Pt催化特性而广泛应用于电解水析氢领域，但Mo₂C在高温制备条件下易过度生长导致其催化活性降低。为解决上述问题，以多糖瓜尔豆胶为碳源，利用其分子结构中丰富的羟基与钼酸根的强烈配位作用，抑制钼原子在高温处理过程中的团聚；同时，氮元素的引入能够进一步提高碳基底的电子转移速率及催化特性。结果表明，在800 ℃高温下可获得超细Mo₂C@氮掺杂碳纳米片复合结构，该产物在碱性介质中，在10 mA/cm2的电流密度的过电位为163 mV，塔菲尔斜率为64.8 mV/（°）。同时材料体系表现出良好的稳定性，经过12 h的耐久性测试，电极材料电流密度无明显衰减。该制备方法的提出有望为其他超细金属碳化物体系的合成提供新的思路。      

The evolution of annealing textures in 90 Pct drawn copper wire

An electrolytic copper rod was drawn in 24 passes to a 90 pct reduction in area and subsequently annealed under various conditions. The global texture of the drawn wire, as measured by X-ray methods, showed a fiber texture approximated by a strong 〈111〉 and a weak 〈100〉 component. However, its microtexture, as measured by electron backscattered diffraction (EBSD), indicated that the major 〈111〉+minor 〈100〉 duplex fiber texture was dominant only in the center region, while a relatively diffuse texture developed with a somewhat higher density of orientations having a 〈11w〉//wire axis in the middle and surface regions. The inhomogeneous texture in the as-deformed wire gave rise to an inhomogeneous microstructure and texture after annealing. When annealed at 300 °C or 600 °C for 3 hours, the wire developed a duplex fiber texture consisting of major 〈100〉+minor 〈111〉 components in the center region, a strong 〈100〉 fiber texture in the middle region, and a weak texture consisting of 〈111〉 and 〈100〉 components with the 〈111〉 component being slightly stronger in the surface region. When the drawn wire was annealed at the high temperature of 700 °C, the texture at short annealing times was similar to that of the wire annealed at the lower temperatures of 300 °C and 600 °C for 3 hours, but prolonged annealing gave rise to a texture ranging from the 〈111〉 to 〈112〉 components due to abnormal grain-growth that started in the surface region. The recrystallization texture consisting of the major 〈100〉+minor 〈111〉 components was explained by the strain-energy-release maximization (SERM) model, in which the recrystallization texture is determined such that the absolute maximum principal stress direction due to dislocations in the deformed state is along the minimum elastic-modulus direction in recrystallized grains. On the other hand, the abnormal grain-growth texture was attributed to grain-boundary mobility differences between differently oriented grain.     

H08A焊丝钢夹杂物演变规律分析

为了提高H08A焊丝钢的拉拔性能和焊接性能,对该钢种全流程进行取样分析,利用扫描电镜观察夹杂物的形貌,统计数密度,利用夹杂物自动分析系统对夹杂物成分变化和成分分布进行分析,利用FactSage热力学软件分析夹杂物低熔点区域分布.结果表明,钢中全氧含量可间接反映出夹杂物数密度水平,若没有LF精炼和中间包保护浇铸,铸坯中全...     

Dopant Occupancy in MgO-Codoped Lithium Niobate Crystals

On the basis of the bond valence model, the preferential occupancy of various dopant such as Mn2 , Eu3 , Er3 , Nd3 , Lu3 , Yb3 , In3 , Cr3 , Fe3 and Ti4 in the ideal stoichiometric lithium niobate (SLN) crystallographic frame was investigated in a viewpoint of chemical bonds. Theoretical analysis indicates that the dopant occupancy is significantly influenced by the anti-site Nb4 Li. Our work also shows that Mg-like ions (Mg2 , Zn2 , In3 , Sc3 ) have a repulsive effect on Nb4 Li ions. When removing Nb4 Li ion by codoping Mg-like ions, the dopant occupancy in the LN crystallographic frame is determined by the natural characteristics of dopant, which is consistent well with the result in the ideal SLN crystals.     

电弧增材制造HSLA钢的组织演变行为与力学性能

 电弧增材制造是成形高性能HSLA钢构件的重要新方法。为了明晰HSLA钢在电弧增材制造时的组织演变行为,研究了构件在堆积成形时的温度场、热循环、热影响区分区及其组织转变。结果表明,电弧增材制造过程中,HSLA钢堆积金属包含凝固区与热影响区,热影响区可分为粗晶区、正火区和回火区。凝固区在热循环作用下先后转变为粗晶区、正火区,最终成为回火区;同时,堆积金属中的残留铁素体晶核、夹杂物附近的高密度位错、铁素体感生形核、第二相质点钉扎晶界和连续动态再结晶共同促进组织细化,使粗大的柱状晶、块状铁素体、侧板条铁素体以及少量针状铁素体、珠光体演变为细小的等轴铁素体和珠光体,有利于提高构件强韧性并抑制力学性能各向异性。构件垂直与水平抗拉强度分别为519.6、520.8 MPa,-20 ℃冲击功分别为124.7、122.1 J。     

过氧化钠熔融-硫氰酸铵差示光度法测定钼精矿和钼焙砂中钼

研究了用过氧化钠在高铝坩埚中700 ℃熔融样品5～10 min,用硫氰酸铵差示光度法测定了钼精矿和钼焙砂中钼含量的方法。对样品的熔融条件、样品溶液的制备条件和测定条件进行了优化。通过加入无水乙醇消除了MnO^2-₄的干扰,采用三氯化铁溶液沉淀吸附和酒石酸钠掩蔽的方式消除了钨(Ⅵ)、铬(Ⅵ)和钒(Ⅴ)等其它共存离子的影响。结果表明,于吸收波长λ=480 nm处,钼质量浓度在14.0～26.0 μg/mL范围内符合比尔定律,检出限为4.2×10^-2 μg/mL。将本法用于钼精矿管理样品GLY-01、钼精矿和钼焙砂生产样品中钼的测定,测定值与参考值或重量法测得结果一致,相对标准偏差(RSD,n=11)为0.10%～0.14%。     

复杂钼矿石中钼的化学物相分析

目前我国针对钼矿石进行物相分析时一般主要选择先溶解氧化钼,将留在残渣中的钼相计为硫化钼,但对于复杂钼矿石,这种操作会导致部分难溶的胶态氧化钼被计为硫化钼而使测定结果不准确,误导选矿工艺的制定。准确分离硫化钼和这部分难溶矿物中钼是钼矿石化学物相分析方法和选矿工艺亟待解决的问题。某地钼矿石因含有与金红石嵌连关系十分复杂的胶态氧化钼,无法通过传统化学物相分析方法浸出。实验以该地区的钼矿石为研究对象,通过实验探讨了使用王水作为浸取剂分离硫化钼和这部分难溶矿物中钼的方法,实现了硫化钼的准确定量分析。结果表明,采用45%(V/V)王水,于80℃水浴上反应2.0h的条件浸取硫化钼,能较好地分离出硫化钼。对钼矿各相态结果进行精密度考察,硫化钼相的钼测定结果的相对标准偏差(RSD,n=6)为0.13%,残渣部分难溶矿物中钼的RSD(n=6)为1.8%;相态合量与总钼测定结果一致;且分离测定的硫化钼分布率69.56%与经矿物自动解离分析仪(MLA)鉴定结果70%一致,实验结果能正确指导选矿工艺。