惰气熔融-红外吸收法测定钽钨合金中氢

通过对助熔剂、称样量、分析功率和积分时间的研究,建立了惰气熔融-红外吸收法测定钽钨合金中氢含量的方法。实验结果表明,称取0.15 g钽钨合金样品,放入镍囊,投入脱气后的石墨套坩埚中,设置分析功率为4 000 W,积分时间为60 s,可实现惰气熔融-红外吸收法对钽钨合金中氢含量的测定。方法检出限为0.000 03%,定量限为0.000 1%。将实验方法应用于钽钨合金样品中氢含量的测定,结果的相对标准偏差(RSD,n=11)为16.5%。按照实验方法对另一钽钨合金样品中氢含量进行测定,并加入适量钛标样GBW(E)020187进行加标回收试验,得加标回收率为94%~101%。     

氧化钽喷涂及涂层熔炼实验

液态铈非常活泼,与很多涂层都发生反应。将钽坩埚表面氧化后熔炼铈已有比较满意的结果,但在石墨坩埚表面喷涂Ta2O5涂层的研究报道却很少。本文总结了石墨坩埚表面等离子及火焰喷涂Ta2O5涂层工艺。在大气中通过热震试验考核了氧化钽涂层相稳定性,在真空感应加热环境下对火焰喷涂氧化钽涂层进行了进一步的热震稳定性考核,采用SEM分析了涂层表面微观形貌,同时采用XRD技术分析了加热前后氧化钽涂层的组成变化,分析表明,火焰喷涂能够制备单一的Ta2O5涂层。石墨坩埚表面Ta2O5涂层熔炼实验表明,液态铈不侵蚀Ta2O5涂层。     

钼制新型坩埚

日本专家制成了一种以钼材料为主的新型坩埚。这种坩埚的表面有扩散的钽和铌(含钽2.6%、含铌1.4%),将它用于熔炼玻璃,对玻璃有良好的湿润性,在高温条件下,对玻璃的氮氧化物反应性极低,而且非常耐用。钼制新型坩埚@李有观     

坩埚对高温合金中氧氮及氢分析结果的影响

应用4台仪器考察坩埚对高温合金中氧、氮及氢分析的影响,首先从空白实验开始,进口和国产石墨坩埚氧空白稳定在0.0Xμg/g,氮空白稳定在0.Xμg/g,可以满足高温合金中氧和氮的分析需求。国产石墨坩埚达到国际同类坩埚水平,可以满足实验针对坩埚应用研究的基本要求。实验表明:石墨套坩埚氧空白值最低,石墨套坩埚与单坩埚氮空白值相同,石英坩埚氢空白值最低。借助于钢中氧氮氢联测标样(502-863),比较石墨套坩埚和单坩埚在3台仪器上氧氮分析的差异,结果显示:用同一条内置标线进行计算,套坩埚对氧和氮分析结果比单坩埚低;按套坩埚和单坩埚自行建立的两条对应标线进行计算,两种坩埚对氧和氮分析结果基本一致。而对氢的分析检测,石墨单坩埚数据严重偏离而被禁用,套坩埚可以应用于较高含量氢(不小于0.6μg/g),钢标样中超低氢分析仅石英坩埚数据最佳。应用现有标钢已建立的标线和方法,3种坩埚、4台仪器实测高温合金样品中氧氮及氢含量,每组45点以上数据显示:高温合金实际样品中氧含量数据最分散,氮的测定值相对集中,不同坩埚之间氢的分析结果差别非常大。自带的高温合金内控样分析数据显示:石墨单坩埚氧氮测定值略高于套坩埚氧氮测定值,而3仪器间的差别很小。对高温合金中氢进行测定时,石墨坩埚与样品相互作用产生干扰,比石英坩埚数值虚高,特别是石墨单坩埚产生的干扰比石墨套坩埚更大,不建议使用。石英坩埚成为高温合金中超低氢分析的最佳选择。由于坩埚损坏和鼓泡导致的异常数据可以通过观察用后坩埚及时发现和剔除,不失为降低坩埚不良影响的有效手段之一。     

碱熔-电感耦合等离子体质谱法测定地质样品中铍铯镓铊铌钽锆铪铀钍

采用氢氧化钾碱熔法处理样品,以铑校正铍、铯、铊、铪、铀、钍,以铼校正镓、铌、钽、锆,建立了电感耦合等离子体质谱法测定铍、铯、镓、铊、铌、钽、锆、铪、铀、钍10种元素的方法。分别选用银坩埚、镍坩埚、刚玉坩埚熔融空白样品进行试验,结果表明,采用银坩埚时各元素的空白响应信号值与镍坩埚和刚玉坩埚相比均较低。对熔融条件进行了优化,确定熔融温度为600℃、熔融时间为8min。分别采用去离子水、2%(体积分数)硝酸上机测量,并记录各元素的响应信号值,与测定地质实际样品中各元素的响应信号值进行对比,结果表明,其对测定结果的影响可以忽略不计。在优化的实验条件下,各元素校准曲线线性相关系数均在0.9990以上,方法的检出限为0.023~0.049μg/g,测定下限为0.078~0.16μg/g。采用实验方法对岩石成分分析标准物质中铍、铯、镓、铊、铌、钽、锆、铪、铀、钍10种元素进行测定,测定结果与认定值基本一致,相对误差(RE)在-8.3%~9.6%之间,相对标准偏差(RSD,n=11)均不大于4.2%。采用实验方法对2个从野外采回的地质实际样品进行测定,并加入岩石成分分析标准物质进行加标回收试验,上述10种元素的回收率在96%~102%之间。     

坩埚冷却系统改造对中间合金熔炼的影响

以Zr-Sn—Fe—Cr—Ni合金为研究对象,通过2次非自耗真空电弧熔炼制备出中间合金,对熔炼中间合金时所采用的坩埚的冷却系统进行了改造,对比了改造前后中间合金的熔炼过程,并采用OM、EDS研究了中间合金的组织及化学成分,冉以添加中间合金扣方式压制电极,利用真空自耗电极熔炼方式制备出吨级锆合金铸锭,并对成品铸锭的成分进行跟踪。结果表明：在坩埚中加入导流槽后,中间合金的熔炼效率得到了提高,熔炼时难脱模现象大大缓解;采用加导流槽后的坩埚经过2次熔炼可以制备出成分均匀的中间合金,合金组织由柱状品和树枝晶组成,与未加导流槽时所熔炼的合金相比,组织及成分更加均匀;采用冷却系统改造后的坩埚熔炼的中间合金可以制备出成分均匀的工业规模级锆合会铸绽。     

熔炼金属合金用坩埚材料之选择

在整个熔炼过程中,坩埚材料与金属熔体之间处于还原反应过程,还原反应的强烈程度,取决于熔炼合金的化学成分、冶炼过程的温度、持续时间、介质气氛(或真空度)、坩埚材料及其致密度等。金属合金往往被坩埚材料玷污,含氧量(用岩相分析氧化物夹杂)增加使其性能下降。然而,影响因素是复杂的,至今尚未全部搞清楚。金属合金熔炼时,必须慎重地选择坩埚材料和保护介质。炉衬(坩埚)耐火材料与金属熔体接触时,其热稳定性按下列顺序增     

钽对K_9铸造高温合金组织性能的影响

含钽的K_9铸造高温合金具有良好的综合性能、在长期使用过程中不产生有害于性能的TCP相。本文探讨了钽对该合金组织性能的影响。试料经真空感应炉熔炼(成份见表1)并精密铸造成型。试样于1080℃、     

钛合金熔炼用AZrO3（A=Ba,Sr,Ca）坩埚的制备及其使用性能研究

综述了3种新型复合氧化物(CaZrO3、SrZrO3和BaZrO3)坩埚的制备工艺,分析了3种坩埚熔炼TiNi合金后的效果和界面反应情况。合金熔体与耐火材料间无元素扩散,3种耐火材料均对合金熔体具有良好的反应惰性。此外,通过对比3种耐火材料坩埚与熔体间的界面反应层厚度,发现BaZrO3对TiNi合金熔体具有最高的化学稳定性。进一步使用BaZrO3制备成工业用25kg级坩埚并熔炼TiNi、TiFe、TiAl铸锭,发现铸锭杂质含量较低,说明BaZrO3是一种极具潜力的钛合金熔炼用新型耐火材料。     

感应加热熔炼Cu-Cr合金的凝固行为

采用电弧熔炼和感应加热熔炼研究了不同组成Cu-Cr合金的凝固行为.结果表明:由于高温下Cu-Cr合金与坩埚材料发生反应,氧化铝坩埚中感应加热熔炼Cu-Cr合金受到污染,澄清了Müller与Li的争议;当合金中Cr的摩尔分数大于40%时,感应加热熔炼Cu-Cr合金出现了液相分离,合金与坩埚材料的反应生成物促进了Cu-Cr合金的液相分离.     

Development of a Ceramic-Lined Crucible for the Separation of Salt from Uranium

As part of the spent fuel treatment program at the Idaho National Laboratory, alternate crucible materials are being developed for the processing of uranium and salt. The separation of salt (LiCl/KCl based) from uranium is performed in an inductively heated furnace capable of distillation under vacuum conditions. Historically, salt and uranium have been processed in graphite crucibles coated with a zirconia mold wash. Although the coated crucibles have performed adequately considering the reactive nature of salt and uranium at high temperature, the operations required for multiple use of the crucibles are quite labor intensive. Thus, an alternate ceramic-lined crucible has been developed to simplify remote operations. Two ceramic-lined crucibles have been tested using irradiated materials to verify their compatibility and determine an ultimate life cycle. Although minor process losses and crucible deterioration have occurred with the ceramic-lined crucibles, the overall performance of the crucibles has been adequate for the separation of salt during uranium processing.     

高频燃烧红外吸收法测定金属材料中碳和硫的研究进展

高频燃烧红外吸收法已广泛用于金属材料中碳和硫的测定,然而,国内关于设备的报道较少,坩埚、助熔剂等也未见系统介绍,测试新型金属时,主要依据条件实验确定测量参数,异标校正较普遍,准确度主要依赖加标回收,较少关注基体效应以及不同类设备间的比对等,对国外的相关工作也较少涉猎。基于此,文章对国内外工作进行系统梳理比较。首先,介绍设备的主要进展,从设备起源开始,说明原有设备的不足及更新后的亮点,特别强调基体不同时,燃烧效果有差异,易导致基体效应;随后,对坩埚及助熔剂进行梳理,介绍其发展历程及关键技术点;最后,介绍国内外的相关测试研究工作,指出,需重视基体效应对测试的影响,而常规样品中超低碳和硫含量的测试以及新型物质分析时,借助其他类检测设备验证,不仅可以提高分析准确度,同时,可解释异常现象,加深对该技术的认识。     

铜精矿样品的高压密封微波消解方法研究

研究了采用高压密封微波消解技术消解用于成分分析的铜精矿样品的方法。依据铜精矿矿物组成、物相结构,分别选取了有机物含量高、硅含量高和金属氧化物含量高的样品进行试验,试验内容包括消解试剂种类和用量选择,样品完全消解的条件等。根据研究结果建立了适于铜精矿化学成分分析的高压密封微波消解方法。通过对不同矿物组分、不同物相结构的铜精矿样品的完全消解验证实验,证明了该消解方法的实用性。采用该方法消解铜精矿,然后用ICP-AES法检测试液中砷、汞、铅、镉和氟离子选择电极法检测试液中氟,分析结果与国家标准方法的测定结果一致。     

X-Ray Observation of Gas Evolution, Flotation, and Emulsification of Molten Carbon Steel Immersed in Mold Flux

At two interfacial-tension measurement experiments with the same experimental conditions, steel samples and mold flux samples of the same compositions were melted in crucibles from the same batch. During the first experiment, the steel drop melted far below its liquidus and then was emulsified. At the second experiment, the steel melted at the expected temperature but did not emulsify. The difference that can be identified is the mass of the steel samples.     

Deoxidation with silicon and the control of oxide inclusions in electrical steels

The oxygen solubility in Fe-Si melts in equilibrium with SiO₂ at 1873 K has been determined in a concentration range of 0.1–70 wt % Si. Model alloys are melted in quartz crucibles in an argon atmosphere. The oxygen content in analytical samples is determined by the inert-gas reducing-fusion method after careful sample preparation. The results obtained have been processed using a thermodynamic model that can calculate the oxygen activity and solubility in Fe-Si melts up to 100 wt % Si. The effects of the heating rate and the silicon content on the carbon concentration in carbonyl iron and Fe-Si alloys are studied using the inert-gas reducing-fusion method in the temperature range 1673–2373 K. Oriented electrical steels are investigated using fractional gas analysis. The main forms of oxygen in these steels are found to be silicates, Al₂O₃, and MgAl₂O₄.     

Multiple cracking of tantalum by hydrogenation

The fracture behavior and microstructure changes of pure Ta by hydrogenation have been investigated to elucidate the fundamentals for hydrogen pulverization, which can be used for producing fine Ta powder with high purity and low cost. Concentric cracks are introduced in a recrystallized Ta plate, with a grain size of about 100 μm, when the Ta plate is annealed at 1473 K and cooled in a hydrogen atmosphere. On the other hand, no crack is observed when the Ta plate is annealed at 1473 K in a hydrogen atmosphere and cooled in an argon atmosphere. It is suggested that the surface activation caused by annealing in a hydrogen atmosphere at 1473 K facilitates hydrogen absorption at lower temperatures, and the volume expansion and the hydride formation generated by hydrogen absorption lead to multiple cracking. The multiple cracking in the Ta plate occurs in the following sequence: (1) hydrogen absorption, (2) strain generation by volume expansion and hydride formation, and (3) crack nucleation and propagation.     

Investigation of rare earth sealing of porous micro-arc oxidation coating formed on AZ91D magnesium alloy

Magnesium and its alloys have been used in many industries, but they are reactive and require protection against aggressive envi-ronments. In this study, oxide coatings were applied on AZ91D magnesium alloy using micro-arc oxidation (MAO) process. Then, in order to seal the pores of the MAO coatings, the samples were immersed in cerium bath for different times. The surface morphologies and composi-tions of the coatings were analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS), respectively. The corrosion behavior of the coatings was investigated with electrochemical impedance spectroscopy (EIS) and potentiodynamic polariza-tion tests in 3.5 wt.% NaCl solution. The amount of the porosity of the coating was measured by electrochemical method. It was found that the sealing treatments by immersion in cerium bath successfully sealed the pores of the MAO coatings. The results of the corrosion tests showed that the MAO coating which was sealed in Ce bath for 10 min enhanced the corrosion resistance of the substrate significantly. Fur-thermore, this coating had the lowest amount of the porosity among the coatings.)     

Laves phase precipitation in Fe-Ta alloys

Development of an iron-base alloy hardened by particles of an intermetallic compound rather than a carbide is a desirable goal because of the greater thermal stability of such a dispersion. As a first step in the development of iron-base alloys hardened with the Laves phase, structural studies of binary Fe-Ta alloys have been undertaken. The structures of two phase Fe-Ta alloys have been studied by means of optical and transmission electron microscopy, X-ray diffraction, electron beam microprobe analysis, and scanning electron microscopy. The hardness change as a function of time at 600°, 700°, and 800°C has been determined for binary alloys with 1 at. pct Ta and 2 at. pct Ta in iron. Also, the uniaxial tensile strengths of solution treated, quenched, and aged samples have been determined. These studies suggest that the compound, Fe₂Ta, is isomorphous with the structure type, MgZn₂, (C14) and has a range of compositional homogeneity. The latter results correspond with the predictions of the Engel-Brewer correlation. Also, it has been found that precipitation occurs at grain boundaries, dislocations, and randomly throughout the matrix. Particles which form at dislocations have a (100)α habit plane; whereas a (110)α habit plane has been reported by others^1,3 for the hexagonal Laves phase in α iron. Hypereutectoid composition alloys quenched from the ö phase field have a completely retained § structure. Isothermal decomposition at 600°, 700°, and 800°C of alloys with the retained § structure results in a sizable hardness increase in 2 at. pct Ta alloys but only a modest increase in 1 at. pct Ta alloys. Brittle fracture of aged tensile specimens tested at room temperature reveals that the ductile-brittle transition temperature in tension is above room temperature.     

火试金法测定锡阳极泥中金银

研究建立了火试金法测定锡阳极泥中金和银的分析方法。将锡阳极泥样品与试剂混合后在坩埚中熔融、灰吹,合粒用硝酸分解,采用ICP-AES法分别测定金以及分金液中的杂质,合粒质量减去金量和杂质总量计算得到银量。对于银含量低而杂质含量高的样品,采用准确加银保护合粒。该方法测定金和银的相对标准偏差分别为1.00%~2.59%和0.27%~1.11%,与硫氰酸钾滴定法测定银结果吻合。方法的准确度和精密度均能满足分析需要,具有较强的实用性。     

Phase relationships in the Al-Ta system

Phase relationships have been investigated in the Al-Ta system in the region between Al and AlTa₂. Al-Ta alloys with compositions between 20 and 60 at. pct Ta were prepared using different processing routes. Following appropriate heat treatments, the alloys were characterized microstructurally, by quantitative electron probe microanalyses, X-ray diffraction, and differential thermal analysis. Based on our observations, a revised Al-Ta phase diagram is proposed. Significant revisions include the verification of Al₃Ta as a line compound, the absence of a eutectic transformation in the region between Al₃Ta and AlTa₂, and the conclusive identification of a phase designated as AlTa near the equiatomic composition.