对氧化铝碳热还原-氯化法炼铝过程中碳化铝的氯化反应研究

采用热力学分析及X射线衍射、扫描电子显微镜及能谱仪等方法与手段,系统研究了中真空条件下碳化铝与氯化铝的反应。通过热力学研究,在10～100 Pa,温度低于1773 K时,Al与C生成Al4C3的反应及Al4C3与AlCl3的反应满足反应发生的热力学条件。实验研究表明,Al4C3可以通过Al与C反应制得;在1773 K、10～100 Pa下,Al4C3与AlCl3可以发生反应,并在冷凝区得到金属铝,热力学研究与实验研究完全一致。在真空碳热-氯化法炼铝过程中存在着Al4C3与AlCl3发生的反应,其是氯化过程中的重要反应之一。     

Al-TiO2-B2O3-C系XD合成铝基复合材料的反应机理及力学性能

研究了Al-TiO2-B2O3-C反应系XD合成铝基复合材料的反应机理.结果表明在Al-TiO2-B2O3-C系中,当B2O3/TiO2摩尔比=0.5,C/TiO2摩尔比=0时,TiO2和B2O3分别与Al结合生成热力学稳定的Al2O3和活性Ti原子、B原子,B原子和Ti原子分别穿过各自反应层结合生成热力学稳定的TiB2,过剩的Ti原子则与Al结合生成棒状物Al3Ti;加入碳粉后,Ti原子将优先与C和C与Al的化合物Al4C3反应生成TiC,Al3Ti逐渐减少,在C/TiO2摩尔比为0.5时,Al3Ti相基本消失,力学性能得到改善,其拉伸强度和延伸率分别从266MPa和3%增加到315MPa和7%.     

低价氯化铝法从氧化铝直接碳还原炼铝的机理分析

碳热过程的热力学分析表明,系统压力为100 Pa时,生成Al4O4C与Al4C3以及Al4O4C与C结合生成Al4C3的初始温度分别为1690,1711,1472 K;碳热-氯化过程的热力学分析表明,在101 Pa,1500 K时,氧化铝直接碳热-氯化的吉布斯自由能为-20.041 kJ;系统压力为100 Pa时,Al4O4C,Al4C3以及Al2O3联合Al4O4C,Al4C3参与氯化反应的初始温度分别为1459,1378,1416 K。实验结果显示:碳热过程在50~100 Pa、高于1693 K时,Al4O4C与Al4C3开始生成且含量随着温度的升高而增加;随着温度的继续升高或系统压力的减小,Al2O3及Al4O4C碳热转化为Al4C3。在50~100 Pa,1693 K时进行了实验,证明了该过程没有发生碳热-氯化反应。在70~150 Pa,1753~1853 K的范围时进行实验,均得到金属铝,说明要发生碳热-氯化反应必须先发生氧化铝与碳的碳热反应,即生成Al4O4C与Al4C3。     

Al-TiO2-C系XD合成铝基复合材料的反应机理及拉伸性能

本文讨论了热扩散反应法制备Al-TiO2-C系铝基复合材料的反应机理及拉伸性能.热力学分析表明Al-TiO2-C系的合成反应是放热并可自发进行,反应产物中α-Al2O3生成自由能最低,热力学最稳定,当温度高于500K时,TiC优先于Al4C3生成.实验结果表明,当C/TiO2摩尔比为零时,增强体由α-Al2O3和Al3Ti组成,α-Al2O3为细小颗粒,呈偏聚状态,Al3Ti呈棒状,分布相对均匀.随着C/TiO2摩尔比的增加,Al3Ti逐渐减少,在C/TiO2摩尔比等于1时,Al3Ti基本消失,反应产物中未见Al4C3相,其拉伸性能也随之得到改善,拉伸强度和延伸率分别从273.4MPa和3%上升到350.7MPa和6%.     

低价氧化铝真空碳热氯化反应机理研究

为研究低价氧化铝、三氯化铝以及碳在真空下反应的机理,对该反应进行热力学计算,计算结果表明反应在1760K,60 Pa的条件下可以进行。采用基于密度泛函框架下的第一性原理平面波赝势法,计算得到Al2O与C、Al Cl3与C以及Al2O与Al Cl3和C的稳定结构。并用从头算分子动力学的方法模拟了它们在1760 K,60 Pa的条件下的反应过程,结果表明Al2O、Al Cl3分别在C(001)表面时,Al2O更容易发生解离,同时在C表面时Al Cl3会先发生离解,最后有吸附态的Al Cl分子和CO分子生成。     

Ti3AlC2的高温临氢行为

研究了Ti3Al C2体材料在氢气氛中的高温(1100~1400℃)热稳定性。采用XRD、SEM、SIMS和Raman分析等手段对Ti3Al C2临氢反应前后的物相组成、表面形貌进行了表征;使用热力学软件Factsage计算了反应过程中的气态产物。结果表明,在1100~1400℃氢气氛条件下有少量H溶解在Ti3Al C2材料中,Ti3Al C2发生了以Al元素缺失为特征的有限程度的分解反应。缺失的Al元素与气氛中极微量的氧反应形成了均匀但不致密的Al2O3膜;而当反应温度为1400℃时,Al2O3膜发生了明显的脱落。使用热力学软件的计算结果预测,部分缺失Al元素与H2反应生成气体产物Al H。初步的研究结果表明,在1300℃以下Ti3Al C2具有较好的耐氢性能。     

在电场中燃烧合成Al2O3-TiC-Al复合材料的结构形成机理

以3TiO2 3C (4 x)Al为反应体系,用电场激发燃烧合成技术并使用合成中形成的液态Al对产物的渗透作用,制备出致密度为92.5%的Al2O3-TiC-Al复合材料,采用燃烧波峰淬熄法研究了原位合成Al2O3-TiC-Al复合材料的结构形成机理.结果表明:电场提供的焦耳效应可提高体系的绝热燃烧温度,从而可突破该体系只能在x＜10 mol下发生SHS反应的热力学限制;在Al2O3-TiC-Al复合材料动力学过程中,首先Al粉熔融,进而加速与TiO2的反应生成Al2O3;然后Al与TiO2反应还原出Ti并与C反应生成TiC;液态Al的渗透将Al2O3和TiC颗粒粘结起来,形成致密的复合材料组织.     

真空法从铟矿中制备铟的机理研究

在真空条件下,本文采用热力学分析方法计算真空下铟矿碳热还原反应过程中发生的反应的吉布斯自由能以及起始反应温度。结果表明,当压力为10 Pa、温度高于380 K时,In2O3与C的反应满足反应发生的热力学条件。在同一体系压力下,物料In2O3:C摩尔比为1:3时,反应生成单质In所需的温度是最低的。在碳量充足条件下In2O3可直接被还原生成单质铟,随着碳的消耗,In2O3的碳热反应会生成中间产物。由此,推算在真空碳热反应过程中,碳热还原In2O3的顺序首先生成In,随着碳耗及升温生成In2O,最后生成In O。In2O3热分解生成In2O,随着体系压力的降低,反应起始温度降至423 K;中间产物In2O热分解生成单质In,当体系压力降至10 Pa时,起始温度降为781 K;In O与生成物CO反应,随着体系压力降低,吉布斯自由能增加,因此,降压不利于In O与CO反应。本文从热力学角度探讨真空制备铟热力学可行性,为下一步实际生产提供相应的理论基础。     

Ni3Al在低氯分压和低氧分压混合气氛中的高温腐蚀行为

研究了Ni3Al在800℃,PCl2=1×10-4Pa,Po2=2.34×10-15Pa氯氧混合气氛中的高温腐蚀行为.应用热重分析方法研究了Ni3Al在该环境中的动力学行为,借助SEM、金相显微镜和X衍射分析来研究反应后样品的表面形貌和断面形貌以及分析反应生成的腐蚀产物,并用热力学平衡相图对Ni3Al在该环境下的高温腐蚀机理进行了探讨.     

SiO2在真空低价氟化法炼铝过程的分布

热力学研究得出:当系统残余压力为100~10 Pa时,SiO2与碳反应在1465~1353 K以上即可生成Si和CO;在1329~1225 K以上即可生成SiC和CO;SiO2和还原剂碳及氟化铝在1464~1353 K以上反应生成SiF4和CO及铝。实验考察了真空低价氟化法炼铝过程中SiO2的分布。XRD表明:SiO2在低价氟化法炼铝过程中有五种走向:(1)被还原成SiC,存在于残渣相;(2)被还原为单质硅,再与还原出的铁生成硅铁,存在于残渣相;(3)SiO2与冰晶石生成铝硅酸盐进入气相中;(4)SiO2与冰晶石生成气态SiF4,再与冰晶石分解的氟化钠形成Na2SiF6进入冷凝相;(5)形成气态低价氧化硅,再在合适温度下分解为单质硅进入冷凝相。     

Wear resistant carbon coatings deposited at room temperature by pulsed laser deposition method on 7075 aluminum alloy

This paper presents the results of a study on the influence of the parameters (pressure and composition of the process atmosphere) of the deposition of carbon coatings on aluminum alloy 7075 by the PLD method on their selected mechanical properties. The study correlated the sp²/sp³ ratio and the relative fraction of CH₂/CH₃ groups formed during coating deposition with the hardness distribution, adhesion, friction and wear resistance of the analyzed systems. Carbon coatings with a titanium interlayer were found to be characterized by the highest adhesion (Lc = 6.9 mN). The introduction of nitrogen at the stage of the deposition of both the interlayer and/or the final carbon layer decreased the maximum adhesion of the coating, while, in this system, the highest value of adhesion Lc was obtained in the presence of nitrogen at the stage of the deposition of both the TiN interlayer and the a:CN carbon coating (Lc = 4.6 mN).     

CF连续涂覆SiC／AlN

设计并组装了用于溶液浸渍渍烧成工艺的连续涂覆装置；用所制备聚合物先驱体溶液，以６ｍ．ｍｉｎ＾－１的运行速度在碳纤维表面实施连续涂覆ＳｉＣ／ＡｌＮ涂层；比较了涂层纤维与纤维的性能。结果表明，涂层不影响纤维的柔顺可编程性和力学强度，但使纤维的抗热氧化性及其与铝的复合丝的拉伸强度均有较大提高。     

铝合金二氧化碳气瓶爆炸事故分析

介绍一起铝合金二氧化碳气瓶爆炸事故,对爆炸事故按照树形结构从检验、充装、运输、使用等多个环节,按照安全技术规范和标准从管理、监察、检验、充装、力学性能和理化手段、安全附件等多方面分析了产生爆炸的原因,进而提出了事故教训。     

Fabrication of aluminum foam stabilized by copper-coated carbon fibers

Short copper-coated carbon fibers were used as novel stabilizer for aluminum foam. Aluminum foams containing 0.35, 1.0, 1.7 vol.% copper-coated carbon fibers were fabricated by a melt route. Foaming behavior and microstructure of these foams were observed. Results show that copper-coated carbon fibers can stabilize aluminum foam by preventing cell wall rupture and reducing coalescence. The fibers are mostly located inside cell wall and form a network structure, which can generate separating force and prevent cell wall from rupture. The volume fraction of copper-coated carbon fibers needed to stabilize aluminum foam is as low as 0.35 vol.%, and the foam is more stable when more fibers are used.     

Processing of Sliding Hybrid Composites with Aluminum Alloy Matrix Containing Solid Lubricants

This paper presents the information about manufacturing processes of hybrid composites with aluminum alloy matrix containing glassy carbon as a solid lubricant. Two methods have been described: the method based on mixing glassy carbon and ceramic particles with a liquid metal matrix; and the precursor method. In the precursor method, carbon is introduced into a composite with the application of liquid precursor and porous ceramic foams. It is then followed by precursor pyrolysis where, as the result, glassy carbon is obtained. Ceramic foams help liquid precursor penetrate the ceramic spheroid pores by forming a thin film of glassy carbon on their walls. Composites produced by the both methods feature good tribological properties. Sliding friction coefficient in air of the new obtained by mixing method composite against cast iron (μ = 0.08 ? 0.17 at wearing in and 0.12 after wearing in by reciprocating sliding and 0.14 ? 0.17 by rotating sliding) is much lower than in the case of composite containing only ceramic foam as a reinforcing phase (μ = 0.28 ? 0.36 by reciprocating sliding and 0.28 ? 0.40 by rotating).     

Fabrication and mechanical properties of Cu-coatedwoven carbon fibers reinforced aluminum alloy composite

Cu-coatedwoven carbon fibers/aluminum alloy composite (C_f/Al) was prepared by spark plasma sintering. Microstructure and mechanical properties of the composite were investigated. Microstructure observation indicates that the interface reaction is evidently inhibited by Cu coating. Woven carbon fibers are adhered to the matrix alloy by anchor locking effect of matrix alloy immersing into the interstices between carbon fibers. Under the quasi-static and dynamic compressive conditions, the composite exhibits excellent ductility even when the strain reaches 0.8. Adding carbon fibers into ZL205A alloy has no obvious influence on compressive flow stress of the composite. The compressive true stress–true strain curves show that the composite is a strain rate insensitive material. During the tensile tests, the elongation of the composite shows a sharp increase from 4.5% to 13.5% due to the adding of woven carbon fibers. Meanwhile, the tensile strength of the composite is increased slightly from 168 MPa to 202 MPa compared to that of ZL205A alloy. The good ductility of the composite is ascribed to the cracks deflection, fibers pulling out, debonding and breakage mechanisms.     

Microstructural characteristics and mechanical properties of carbon nanotube reinforced aluminum alloy composites produced by ball milling

The influence of milling time on the structure, morphology and thermal stability of multi-walled carbon nanotubes (MWCNTs) reinforced EN AW6082 aluminum alloy powders has been studied. After structural and microstructural characterization of the mechanically milled powders micro- and nano-hardness of the composite powder particles were evaluated. The morphological and X-ray diffraction studies on the milled powders revealed that the carbon nanotubes (CNTs) were uniformly distributed and embedded within the aluminum matrix. No reaction products were detected even after long milling up to 50 h. Nanotubes became shorter in length as they fractured under the impact and shearing action during the milling process. A high hardness of about 436 ± 52 HV is achieved for the milled powders, due to the addition of MWCNTs, after milling for 50 h. The increased elastic modulus and nanohardness can be attributed to the finer grain size evolved during high energy ball milling and to the uniform distribution of hard CNTs in the Al-alloy matrix. The hardness values of the composite as well as the matrix alloy compares well with that predicted by the Hall–Petch relationship.     

碳纤维表面处理对铝电解用硼化钛阴极涂层性能的影响

硼化钛阴极涂层是铝电解用可润湿性阴极材料中的一种，具有优良的抗钠渗透性和对铝液润湿性，可以有效地延长铝电解槽寿命。碳纤维是硼化钛涂层材料的增强剂之一．对硼化钛阴极涂层的性能影响很大。本文研究了不同工艺的液相碳纤维表面氧化处理法对硼化钛阴极涂层抗拉强度和粘接强度的影响。采用PTIR检测碳纤维处理后表面含氧基团的变化，寻找影响硼化钛阴极涂层性能的原因，从而达到最有效地提高TiB2阴极涂层抗拉强度和粘接强度的目的。结果表明，采用工艺(1)(10％HNO3，80℃、恒温5min．超声波、5min)对碳纤维进行表面处理最合理，处理后碳纤维表面含氧基团的含量最高．用其制备硼化钛阴极涂层的抗拉强度、粘接强度最大。