电子束真空精炼直接定向凝固制备高纯铜的研究

以电子束真空熔炼直接定向凝固技术制备5N高纯铜大铸锭为研究目标,利用电子束熔炼原材料,熔体直接定向凝固后得到高纯铜铸锭.采用GDMS-VG9000辉光放电质谱仪和TCH600氧氢分析仪研究了金属杂质及氧氢元素的去除效果,通过EPMA-1600电子探针研究了提纯后元素的分布情况.结果表明:真空电子束熔炼直接定向凝固技术可将原料为4N(99.9988711％)的电解阴极铜板,制备出纯度5N(99.9997235％)、Φ59 mm大尺寸高纯铜铸锭,杂质元素总量降低了75.506％,中间凝固组织为单晶;五种含量较高的元素Ag、Cu、O、P和S均匀分布,没有出现杂质的偏聚现象;与原材料相比,0、H元素分别降低了86.47％,85.00％.研究表明真空电子束精炼直接定向凝固技术能够制备氧氢含量较低的5N大尺寸高纯铜铸锭.     

冶金法提纯工业硅的研究

以冶金级硅为原料进行了制备高纯多晶硅锭的研究,自行设计了真空感应熔炼与定向凝固设备、电子束熔炼设备.通过酸洗、真空感应熔炼与第一次定向凝固、电子束熔炼、真空感应熔炼与第二次定向凝固等组合步骤对工业硅进行提纯.利用电感耦合等离子体发射光谱仪(ICP-AES)进行成分分析,实验结果表明,定向凝固有效去除了金属杂质,电子束对蒸汽压高的元素,尤其是磷元素的去除作用明显.Al的浓度降低到了0.4×10~(-6),Fe、Ca、Ti、Mn、Cu、Zn等金属杂质的浓度降到了0.1×10~(-6)以下,P含量降低到1.5×10~(-6).     

多晶硅冶金法除磷的研究进展

磷是多晶硅中的一种主要杂质元素,目前国内外采用冶金法除磷的工艺主要包括酸洗除磷、合金定向凝固除磷和真空除磷工艺.其中,酸洗除磷工艺可以很有效地去除磷杂质,但仍未达到太阳能级多晶硅小于0.1×10-4%(质量分数)的要求.采用合金定向凝固工艺可以去除80%以上的磷杂质,但目前对凝固后硅中残留溶剂金属的去除方法还有待进一步的研究.通过真空感应熔炼实验已将磷含量从15×10-4%(质量分数)降低至0.8×10-5%(质量分数),并对除磷的热力学条件进行了初步探索.     

多晶硅真空电磁感应熔炼除磷及其过程研制

磷是多晶硅中的主要杂质元素之一,目前采用的酸洗以及定向凝固工艺无法将其含量降低到太阳能级多晶硅所要求的范围之内。采用自行设计的真空电磁感应熔炼炉及定向凝固炉研究了真空度、精炼时间和精炼温度对除磷效果的影响。研究结果表明当炉内压强为5.0×10-1 Pa时,精炼温度和时间分别为1723K和60min时,精炼后硅中磷含量由原来的2.0×10-5（质量分数）降低到1.8×10-6（质量分数）;研究推导出了在压强为5×10-1Pa下磷的含量随精炼时间和精炼温度的关系式如下：XP=X0Pexp[（-1.43×10-4-3.1×10-7T）t]同时还对真空感应熔炼除磷过程进行了热力学与动力学分析。     

冶金法制备太阳能级多晶硅的耦合除杂研究

以工业硅为原料,利用介质熔炼、定向凝固和电子束熔炼三种熔体处理技术对工业硅中的B、P和金属杂质进行了去除,制备出了99.9999%级多晶硅材料,其中,杂质B和P的含量分别低于0.20 ppmw（parts per million (weight),百万分之一质量）,金属杂质总含量（TM）低于0.23 ppmw。研究发现,介质熔炼去除杂质B的过程中,熔体中发生氧化还原反应可以有效去除大部分的杂质Al和Ca;电子束熔炼过程中,利用饱和蒸气压原理可以有效去除挥发性杂质P、Al、Ca,同时降束诱导多晶硅定向凝固,可将其他金属杂质进一步去除。本研究通过各技术间的耦合除杂,减少了冶金法提纯多晶硅的工序,为连续化、规模化生产提供了技术支撑。     

电子束熔炼去除冶金级硅中磷、铝、钙的研究

采用电子束熔炼方法提纯了冶金级硅材料。实验结果表明随熔炼时间延长,硅中挥发性杂质元素P、Al、Ca的含量逐渐降低。熔炼40min后,硅中P含量可以降至2.2×10-5%(质量分数);Al、Ca的最低含量为8.5×10-5%和1.5×10-4%(质量分数)。P、Al、Ca的挥发去除为一阶反应过程,反应速率常数分别为0.11、0.12和0.13min-1。     

电子束熔炼冶金级硅除铝研究

采用电子束熔炼工艺提纯了冶金级硅材料。硅中重要杂质元素Al在制备铸锭中的分布不均匀,呈现出由底部到顶部、由边缘到中心的富集趋势。铸锭边缘部位的杂质Al含量最低,已经低于ICP-AES的探测极限(1×10~(-5)%)。对杂质Al的挥发去除过程进行了理论分析。由Langmuir方程和Henry定律导出了杂质Al的去除率与熔体表面温度、熔炼时间的关系式,该关系式表明杂质Al的去除率会随着熔体表面温度升高、熔炼时间延长而增加,其理论计算值与实测结果符合的较好。     

提纯工业硅除铝的实验研究

为了去除工业硅中的杂质制备太阳能级硅,根据工业硅凝固过程中铝在固相和液相中溶解度的差异,采用定向凝固法去除工业硅中的杂质铝.实验结果表明,铝的去除效率可达98%,说明利用定向凝固法去除工业硅中的铝是可行的.但由于在结晶过程中晶界上会富集部分铝元素,因而定向凝固法并不能除去这一部分杂质.结合金相实验中样品腐蚀前后晶界上的变化,可以知道利用酸浸可以除去晶界上的杂质铝.还研究了先酸浸后定向凝固法相结合除铝,实验结果表明铝的含量可以降到1.6×10-5,铝的去除率达98.6%.     

电子束熔炼炉连铸系统设计

电子束熔炼是一种优异的真空冶金技术。设计的目的是研制一种用于难熔金属熔炼的电子束熔炼炉连铸系统。本文描述了电子束熔炼炉连铸系统总体设计和详细结构设计,在设计中采用水平送料方式实现多根棒料的供给;旋转下降的拖锭机构实现铸锭向下成形;下进下出冷却方式的坩埚实现铸锭凝固。最终得到的电子束熔炼炉连铸系统各项指标均满足设计要求,并进行了初步的熔铸实验。     

电子束束流密度对冶金硅中杂质磷的影响

采用电子束设备对多晶硅进行熔炼,设计熔炼功率和时间相同、降束时间不同的三组实验,评价硅中杂质磷在熔炼及凝固过程中的去除效果。根据熔炼后硅锭的杂质分布特点推导出表征硅中杂质磷的去除率公式,经计算得到去除率为80%以上,并由磷的蒸发方程计算出在本实验中当电子束熔炼多晶硅锭的束流密度在235mA之上时,硅中的磷都可以被蒸发去除。     

Production of ultrahigh purity copper using waste copper nitrate solution

The production of ultrahigh purity copper (99.9999%) by electrolysis in the presence of a cementation barrier has been attempted employing a waste nitric copper etching solution as the electrolyte. The amount of copper deposited on the cathode increased almost linearly with electrolysis time and the purity of copper was observed to increase as the electrolyte concentration was increased. At some point, however, as the electrolyte concentration increased, the purity of copper decreased slightly. As the total surface area of cementation barrier increased, the purity of product increased. The electrolyte temperature should be maintained below 35 degrees C in the range of investigated electrolysis conditions to obtain the ultrahigh purity copper. Considering that several industrial waste solutions contain valuable metallic components the result of present study may support a claim that electrowinning is a very desirable process for their treatment and recovery.     

Purification of cadmium up to 5N+ by vacuum distillation

Cadmium was refined by vacuum distillation, a technique suitable for low boiling and melting point materials, to remove the heavy and low vapour pressure impurities at ppm level. The detailed analysis of the purified Cd as well as raw Cd was done by ICP-OES techniques for 27 impurity elements. Purification was carried out in an efficient high-yield vacuum distillation system designed and fabricated for purifying 3N+ purity indigenous cadmium to 5N+ (99.999%). Analysis confirmed the reduction of total impurity content from 134 ppm (3N7) for raw Cd to 3 ppm (5N7) upon vacuum distilled Cd. The present study shows that the analysis of impurities such as Fe, Mg and Ca are contributed from environmental effect, whereas impurities such as Pb, Bi, Ag, Ni, Cu, Zn and Tl require adaptation of elemental analysing technique to counter dilution effect. The Hg trace analysis can however be carried out by hydride generation techniques.     

Energy and charge distributions in nanosecond vacuum spark plasma flux

The characteristics of vacuum sparks formed under the action of a 4-ns high-voltage pulse with an amplitude of 150 kV have been studied. Ions of a cathode material (copper or graphite) with energies of up to 150 keV were found in the flux of plasma from the cathode region. In the case of a graphite cathode, only singly charged carbon ions with a dome-shaped energy distribution were observed. For a copper cathode, differently charges ions (+1, +2, +3) were detected and their energy distribution exhibited several maxima. The characteristic ion energies depended on the interelectrode distance.     

Process methodology for the small scale production of m6N5 purity zinc using a resistance heated vacuum distillation system

Ultra high purity Zn (m6N5) was obtained through triple vacuum distillation using an m4N5 Zn as input material. High-volatile impurities were removed from the zinc matrix by vacuum evaporation, while traces having lower volatility than the matrix remained in the residual material after finishing of the entire purification process. The time required for the removal of the main high-volatile impurity (Cd) was monitored using a connected gas source mass spectrometer. During distillation the Zn vapor of the distillate was condensed on the cap of a glassy carbon crucible which was water cooled by a movable copper block. The temperatures were optimized for the removal of the volatiles and for the distillation process using vapor pressure data. High resolution glow discharge mass spectrometry was applied for the analysis and purity evaluation of the distilled and input zinc. The analysis confirmed the reduction of the metallic impurities from 43 mg kg⁻¹ to 0.5 mg kg⁻¹ (m6N5) after three consecutive vacuum distillations. An increase in the grain size and a decrease in the micro-hardness were observed for the purified Zn material.     

Recent progress on RE2O3-Mo/W emission materials

RE2O3-Mo/W cathodes were prepared by powder metallurgy method. La2O3-Y2O3-Mo cermet cathodes prepared by traditional sintering method and spark plasma sintering (SPS) exhibit different secondary emission properties. The La2O3-Y2O3-Mo cermet cathode prepared by SPS method has smaller grain size and exhibits better secondary emission performance. Monte carlo calculation results indicate that the secondary electron emission way of the cathode correlates with the grain size. Decreasing the grain size can decrease the positive charging effect of RE2O3 and thus is favorable for the escaping of secondary electrons to vacuum. The Scandia doped tungsten matrix dispenser cathode with a sub-micrometer microstructure of matrix with uniformly distributed nanometer-particles of Scandia has good thermionic emission property. Over 100 A/cm2 full space charge limited current density can be obtained at 950Cb. The cathode surface is covered by a Ba-Sc-O active surface layer with nano-particles distributing mainly on growth steps of W grains, leads to the conspicuous emission property of the cathode.     

Application of vacuum refining in copper production

Abstract

his literature review was prepared in order to determine the state of the art with respect to the vacuum refining of copper. There have been numerous reported laboratory investigations of copper refining by vacuum treatment since the 1940s. Most studies have been carried out with the aim of eliminating deleterious impurities, such as arsenic, antimony, bismuth, lead, sulphur, and oxygen, from copper to levels appropriate to marketable grades, thereby improving the quality of the copper produced. It is interesting to note that the majority of work in this area has been carried out by Japanese and Soviet researchers: Japanese authors have generally tried to explain their results by means of kinetic or thermodynamic analyses, whereas the Soviet ones have merely given experimental results. This review contains three sections. In the first, the theory of vacuum treatment is discussed. The second presents information currently available (to 1980) on vacuum refining and is divided into three subsections, based on the type of copper treated, namely: (i) treatment of blister copper (or crude copper); (ii) treatment of anode copper and/or cathode copper; and (iii) treatment of copper matte. Finally, a patent survey has been carried out, which is reported in the third section.

MST/54     

Cathode spot movement on a continuous carbon fiber reinforced Cu matrix composite in vacuum

The cathode spot movements on a carbon fiber reinforced copper matrix composite (C_f/Cu) were investigated by a scanning electron microscope and a digital high-speed video camera. The composite was prepared by infiltrating a Cu alloy doped with Ti and Cr into a porous carbon/carbon composite in vacuum. It is found that the carbon fibers have a higher ability to withstand the vacuum arc erosion than the Cu matrix. The cathode spot walks randomly on the matrix, rather than on the carbon fibers. The cathode spots are restricted on the Cu matrix in C_f/Cu. The directional movement in the high-speed images is caused by the restricted random walk of the cathode spots. A gradient distribution in the size and density of the cathode spot is present on the Cu matrix. The average arc spreading velocity is estimated to be about 0.36 m/s and the transient arc spreading velocity is in the range of 0.12–0.7 m/s.     

Microstructure,Properties and Wear Behaviors of (Ni_3Al)_p Reinforced Cu Matrix Composites

Pure copper and its composites reinforced with Ni 3 Al particles were produced by powder metallurgy(PM).Ni 3 Al powders were produced by mechanical ball milling from vacuum arc melted compounds.The Ni 3 Al powders were characterized by X-ray diffraction(XRD).The microscopy examinations revealed that the Ni 3 Al particles were distributed uniformly in the matrix.The effects of the particle fraction on the density,electrical conductivity,strength and dry sliding wear resistance of composite were investigated.It was found that the density and electrical conductivity of the composites decrease while the compression yield strength and wear resistance of composites increase with an increase in the particle fraction.The dry sliding wear tests were performed with pin-on-disk geometry.After sliding wear tests,the worn surfaces were examined by scanning electron microscopy(SEM) equipped with an energy dispersive X-ray spectrometer(EDS).Results have shown that the wear mechanism is oxidative and adhesive.     

Al2O3 Particle Size Effect on Reinforced Copper Alloys: An Experimental Study

Abstract: Bonding between dissimilar metallic (copper) and non‐metallic particles (Al₂O₃) was successfully achieved. The mechanical properties of the copper composite nano‐structure with different Al₂O₃ particle sizes ranging from 100 nm to 20 μm were investigated. The alloys were prepared by using electro‐less precipitation and particle metallurgy technique at three different sintered temperatures, 900, 950 and 1000 °C. The chemical composition of composites were 85 atomic % Cu and 15 atomic % Al₂O₃, of which commercially available Al₂O₃ particles with a purity of 99.5% were used. The microstructure, hardness and compressive stress–strain behaviours were determined. A pin‐on‐disc system was used to study wear. Electrical resistivity was also measured.     

Determination of plasma parameters with a probing magnetic field pulse

An experimental technique for the determination of electric conductivity and temperature of plasma is presented. The technique is based on comparing the signals that are produced by a pulsed magnetic field in the circuits of two probes located within the studied plasma and outside of it. The proposed technique for the measurement of plasma parameters was tested experimentally in the context of measuring the electric conductivity and temperature of plasma flux formed in cathode spots of a high-current pulsed vacuum arc with a magnesium cathode.