固态氧化铝碳热还原反应研究进展

固态氧化铝碳热还原反应在陶瓷材料及铝冶金领域得到广泛的应用和研究,但其反应机理至今未能得到统一的认识。介绍氧化铝碳热还原过程形成的固态、气态产物,阐述3种主要反应机理。提出固-固相反应机理缺乏直接证据,气-固相反应机理与热力学分析及实验不符,而氧化铝分解反应机理较合理。可能的反应机理如下:氧化铝分解为含铝气体和氧气,碳与氧气反应以降低氧分压,含铝气体再次反应形成最终产物,在减压或氩气下形成碳化铝、碳氧化铝等,在氮气下形成氮化铝。并提出了系统解释固态氧化铝碳热还原反应需要继续研究的方向。     

电热法生产高铝的铝硅合金

第一部分:电热法生产铝硅合金及其目前发展状况;电热法的优点和缺点;制取高铝的铝硅合金来改善电热法。第二部分:在温度1600～2200℃范国内的 Al—Si—C—O 四元系状态图是电热还原粘土的理论基础;四元系的研究,生产不含碳化物的高铝的铝硅合金;建立一种新型电炉应用于用碳还原高岭土—氧化铝混合物,以生产70%Al 以上的铝硅合金。     

高岭石与氧化铁在还原焙烧过程中的反应行为（英文）

铝硅酸盐矿物中氧化硅和氧化铝的预先分离对从高硅含铝物料中提取氧化铝具有重要意义。本文作者研究高岭石与氧化铁在还原焙烧过程中的反应行为。热力学计算以及还原焙烧实验结果表明,由氧化铁还原得到的氧化亚铁优先与高岭石中的氧化铝反应而生成铝酸亚铁;与此同时,高岭石中的氧化硅转变为石英固溶体或者方石英固溶体。在有足量碳粉存在的条件下,过量的氧化亚铁和氧化硅反应生成的硅酸亚铁随着焙烧温度的升高进一步还原成氧化硅和金属铁。然而,升高焙烧温度及降低Fe_2O_3/Al_2O_3的摩尔比均能促进莫来石的形成。控制高岭土、赤铁矿和煤灰中Fe_2O_3/Al_2O_3/C摩尔比为1.2:2.0:1.2,在1373 K下还原焙烧60 min即可实现高岭石完全转变为独立的氧化硅和铝酸亚铁。研究结果有望为铝硅酸盐矿物中氧化铝和氧化硅的综合利用提供新技术。     

氧化铝的真空碳热还原—氯化—歧化反应(英文)

通过XRD物相分析和热力学分析研究氧化铝的真空碳热还原—氯化—歧化反应。以氧化铝和石墨为原料,在真空下、1643-1843K的温度范围内进行实验。结果表明,AlCl3(g)与氧化铝碳热还原产生的Al2O(g)或Al(g)反应生成AlCl(g),该AlCl(g)在较低温度下歧化分解为金属铝和AlCl3(g);当压力为100Pa、温度为980K时,AlCl(g)的歧化反应率达到90%。生成的金属铝可以吸附催化CO歧化为C和CO2,并可以与CO二次反应形成Al4C3、Al2O3、C和CO2,导致铝产物中含有C、Al4C3和Al2O3。产物铝中所含的这些杂质随着AlCl(g)歧化反应温度的降低而减少。AlCl3(g)在接近室温的温度下冷凝下来。     

1000°～1800°K温度范围内Al-C-O系的热力学分析

本文对1000～1800°K 温度范围内的 Al—C—O 系进行了热力学分析。以稳定性标准和化学计量极限为基础,在所研究的整个温度范围内,确定了用石墨还原氧化铝的平衡条件。实验资料和计算数据表明,氧化铝和石墨反应生成碳化铝,碳化铝再还原氧化铝。在可实现的还原体系中,高温和相当小的 P_(Al) 和 P_(CO)值有利于这些反应的进行。本研究中确定的稳定的碳氧化物平衡与其它作者所断定的那些稳定反应不相符合。因此,文中报导的是对体系的动力学而不是对稳定平衡有利的那些反应。按照直接还原过程的要求,探讨了低价卤化物反应的热化学性质。验证了借生成一氯化铝以分离还原的铝的可能性。指出了这一方法在还原时是有效的,但此法在氧化铝还原工艺中尚未采用。     

高铝粉煤灰生料配比对熟料烧成温度及溶出性能的影响研究

本文以高铝粉煤灰预脱硅后脱硅灰为原料,研究了不同钙比(1.90、2.10)、铁铝比(0.032、0.050)对熟料烧成温度范围及溶出性能的影响;试验结果表明:铝硅比1.6、铁铝比0.032、碱比0.93、0.95、1.00的条件下高钙熟料相对于低钙熟料氧化铝溶出率提高1.6%~2.3%,氧化钠溶出率提高0.98%~1.4%;铝硅比1.6、铁铝比0.050、碱比0.93、0.95、1.00的条件下高钙熟料相对于低钙熟料氧化铝溶出率提高1.5%~2.25%,氧化钠溶出率提高0.22%~1.75%;高钙熟料相对于低钙熟料可扩宽熟料烧结温度范围10℃,生料铁铝比由0.032提高至0.050可降低熟料烧成温度20℃,可扩宽熟料烧成温度范围10℃。     

铝硅铁合金可溶阳极电解提取金属铝的研究

以低品位含铝资源或含铝固体废弃物为原料用碳热还原制取的铝硅铁合金作为可溶性阳极、以NaCl-KCl-Na_3AlF_6为电解质体系、采用熔盐电解法从铝硅铁合金中提取金属铝进行了试验研究。通过X射线衍射物相分析和扫描电解分析对铝硅铁合金及电解提取的铝和电解剩余物进行了分析,结果表明,以铝硅铁合金为可溶阳极,在电流密度为0.60 A/cm~2,电解温度为690℃,极距为3 cm,电解时间5 h的最优条件下,试验的电流效率可达到70%以上。电解后得到的阴极产品中Al的含量为93.21%,Si含量为4.54%,Fe含量为1.21%。阴极产品中硅铁杂质主要来源于铝硅铁合金阳极中铝硅共晶低熔点合金的掉落。     

真空氯化亚铝歧化法从氧化铝中提取铝

研究了以氧化铝和石墨为原料真空氯化亚铝歧化法提取铝的条件,包括反应温度、预反应和冷凝器的结构。结果表明：在1643~1843 K的温度范围内,氧化铝与碳的反应程度随着反应温度的升高而提高,但铝的提取率首先随着反应温度的升高而提高,在1743 K时达到最高,继续升高反应温度,铝的提取率反而降低;氧化铝与碳进行预反应可以提高金属铝的提取率;金属铝与CO的接触面积越小、冷凝温度越低,C、Al4C3和Al2O3杂质的含量越低,这取决于冷凝器的结构。     

碳氢协同还原-碳化法制备纳米WC粉的工艺及机理研究

针对传统还原-碳化工艺中WC粉颗粒的长大问题,采用碳氢协同还原-碳化法制备纳米级球形WC粉,研究前驱体配碳比和反应温度对WC粉性能的影响。结果表明,WC的碳含量与前驱体的配碳比密切相关,最佳配碳比（即n(C)/n(W)值）为3.6。W向WC的转变具有结构遗传性,WC的平均粒径与还原温度和碳化温度密切相关。随着还原温度由680 ℃升高至800 ℃,还原水蒸气与碳反应生成CO和H2,显著降低体系中水蒸气的分压,从而抑制中间产物W颗粒的挥发-沉积长大,WC的平均粒径随还原温度升高而减小。碳化过程中的高温促进WC颗粒的晶界迁移和纳米W颗粒之间的烧结合并长大,WC的平均粒径随碳化温度的升高而增大。n(C)/n(W)为3.6的前驱体粉末经800 ℃还原和1100 ℃碳化后,得到平均粒径为87.3 nm的球形WC粉。     

碳氢协同还原-碳化法制备纳米WC粉的工艺及机理

针对传统还原-碳化工艺中WC粉颗粒长大的问题,采用碳氢协同还原-碳化法制备纳米级球形WC粉,研究了前驱体配碳比和反应温度对WC粉性能的影响。结果表明,WC粉的碳含量与前驱体的配碳比密切相关,最佳配碳比(即n(C)/n(W)值)为3.6。W转变为WC具有结构遗传性,WC粉的平均粒径与还原温度和碳化温度密切相关。随着还原温度由680℃升高至800℃,还原水蒸气与碳反应生成CO和H_2,显著降低体系中水蒸气的分压,从而抑制中间产物W颗粒的挥发-沉积长大,WC粉的平均粒径随还原温度升高而减小。碳化过程中的高温促进WC颗粒的晶界迁移和纳米W颗粒之间的烧结合并长大,WC粉的平均粒径随碳化温度的升高而增大。n(C)/n(W)为3.6的前驱体粉末经800℃还原和1100℃碳化后,得到平均粒径为87.3 nm的球形WC粉。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.