燃烧剂对二硼化钛晶体形态的影响

以(Mg+Al)+B_2O_3+TiO_2为基础配系,通过改变燃烧剂中Mg和Al相对比例,研究不同燃烧剂对二硼化钛晶体形态的影响,探讨二硼化钛的晶体特征及其生长机理。研究表明,采用自蔓延高温合成法所获得的二硼化钛粉末,其晶体形态除了呈不规则颗粒状外,还存在着片状、柱状和晶须阵列等形态,典型的二硼化钛晶体形态呈六棱柱状。以Al粉部分取代Mg粉,可以有效增加柱状二硼化钛晶体的相对量。二硼化钛晶体的生长倾向一方面取决于其晶体结构本身,同时也取决于二硼化钛晶体生长时周围的成分起伏、能量起伏等环境条件。一维二硼化钛的形成对于增强硼化钛基陶瓷材料的韧性具有重要的意义。     

硼化物和硼化物-钢阴极导电棒

硼化物的性质广泛研究了作为阴极材料的二硼化钛和二硼化锆。并对这些材料进行了烧结、热压,亦用改进的热压技术进行了制造。表1和表2分别列出了二硼化钛和二硼化锆的性质。     

铝热还原氟钛酸钠法制备钛铝合金的酸洗除氧研究

二段铝热还原氟钛酸钠法制备钛及钛合金具有流程短、成本低、绿色化的特点，有一定的工业化应用前景。但在工业规模试生产中发现，部分钛铝合金产物存在氧含量过高等问题。依据酸洗可溶解钛铝合金表面自然形成的氧化膜从而降低氧含量的原理，探究草酸+盐酸的混合酸浓度、液固比、浸出时间、反应温度、粉末粒度等工艺条件对酸洗除氧效果的影响。结果表明：在1%草酸+5%盐酸、液固比10∶1、浸出时间6 h、反应温度30℃、粉末粒度<75μm的条件下酸洗除氧效果最佳，可将钛铝合金中的氧含量从1.79%降低至0.79%。该酸洗工艺也同样适用于低氧钛铝合金，可将氧含量从0.366%降低至0.178%。     

放电等离子烧结法制备二硼化钛多孔陶瓷

以二硼化钛微粉为原料，采用放电等离子烧结技术，通过控制烧结温度、保温时间、施加压力等工艺参数，成功的制备出具有高强度和高气孔率的二硼化钛多孔陶瓷。采用浸泡介质法，三点弯曲法测试了材料的气孔率，开口气孔率及强度；用扫描电镜对材料断口进行了观察。实验结果表明：在1300-1500℃的烧结温度下，获得了气孔率33％～45％，最大抗弯强度〉60MPa的二硼化钛多孔陶瓷。扫描电镜结果显示，二硼化钛颗粒间有明显的颈部烧结。     

硼化钛工业性试制与生产

硼化钛是制造硼化钛阴极的主要原料。以前我国没有硼化钛工业生产、实验室生产的少量硼化钛粉成本高，难地推广应用。兰江冶炼厂与中南工业大学合作进行了用高温电阻炉直接合成硼化钛的工业性试验，并建成了月产５００ｋｇ硼化钛的生产线，为铝电解工业推广应用硼化钛阴极创造了良好条件。本文具体介绍了硼化钛的试制方法和产品的质量分析结果。     

新槽衬材料的开发

1　二硼化钛试验槽美国西弗吉尼亚世纪铝公司与EMEC咨询公司、SGL碳公司、肯特基世纪铝公司以及果尔登西北铝公司合作 ,在美国能源部的支持下联合攻关 ,旨在降低铝电解槽阴极碳和铝界面处的电阻 ,该项科研课题的作法是要在阴极中提供一个可补充的硼源 ,使硼与铝水中掺有的钛发生反应 ,在阴极处生成一层二硼化钛。该课题的目标是要建立起这样一种二硼化钛表层以实现降低电耗、提高产量、延长电解槽使用寿命的目的。该项课题可分为三个研究阶段。第二阶段已于 2 0 0 2年完成。其内容是用三块浸渍有二氧化硼的碳块来更换三块标准碳块。第三…     

铝-钛-硼中间合金熔制方法

一、专利申请范围本发明是关于铝-钛-硼中间合金的熔制方法,合金中含硼0.2～0.8％, (Ti—2.2B)≥3.9％,余量为铝。基体铝是由大量的30微米以下的晶粒构成,沿晶界,高度分散着粒度平均为1微米的二硼化钛晶粒。本方法的特点如下: (a) 溶解在冰晶石中的氧化硼和氧化钛,     

钢凝固过程超细钛氧化物析出的热力学分析

某些类型超细钛氧化物能促进针状铁素体的形成,细化晶粒钛氧化物夹杂的析出类型受钢液中的氧含量、合金元素成分的影响.以X80管线钢成分为研究对象,从热力学角度分析了微合金元素及钢液中的氧浓度对其析出类型的影响.结果显示,在钢液凝固温度区间,相同温度和氧含量时,Ti的氧化物中,Ti3O5是最稳定的,其次为Ti2O3.钢中铝对...     

机械化学置换反应合成碳化钛和二硼化钛

碳化钛和二硼化钛的熔点、硬度和强度都很高,而且具有很高的化学稳定性,生成热的绝对值也高。通常在高温下采用置换反应、碳热反应、直接反应、自扩散高温合成方法制备。近来,采用机械化学合成法通过钛粉分别与碳粉和硼粉的燃烧反应成功制得了碳化钛和二硼化钛。然而,这些传统的制备方法要求在高温下和(或)以昂贵的钛粉末为原材料来实现。 利用还原金属来实现机械化学置换反应(MDR)的方法已可用来制备WC,但是,还未能用于制备过渡金属的碳化物与硼化物。对碳化钛和二硼化钛来说,TiO2+2Ca=Ti+2CaO、Ti+C=TiC和Ti+2B=TiB2的反应焓分别…     

氧对铸造Ti-6Al-4V合金机械性能的影响

钛是活性金属之一,在熔融状态下对氧的亲和力甚大。每经一次真空熔融都会使钛中氧含量有所增加。由于钛铸件一般要比变形件多熔化一次,因而经常有许多钛铸件的氧含量超过其标准中所规定的允许限度0.15％。 一、试验过程 研究用的母合金锭是在真空自耗电极电     

新型损伤容限型钛合金TC21稀土催化固体渗硼

采用固体粉末渗硼法对新型损伤容限型钛合金TC21表面进行稀土催化化学热处理,通过扫描电镜(SEM)、X射线衍射(XRD)、能谱(EDS)与金相显微镜(OM)研究了渗层组织形貌和物相组成。结果表明:钛基表面渗硼层包括以整体薄壁状在基体外层分布的TiB2和以须状晶形式在次表层分布的TiB双强化渗层,渗层与基体结合紧密;渗剂中稀土含量对渗层性能的影响存在有最佳值;且发现此方法实现了钛合金TC21表面B、C共渗。     

Copper-titanium diboride coatings obtained by plasma spraying reactive micropellets

Electrotribological applications require materials with both high electrical conductivity and wear resisance. For this purpose, a copper- base plasma sprayed coating containing titanium diboride particles was developed. The process for fabricating this CU- TiB₂ coating consists of plasma spraying reactive powders that contain a Cu- Ti alloy and boron. The reaction between the copper alloy and boron proceeds in different steps going from solid- state diffusion of titanium and copper to the synthesis of TiB₂ in a liquid below 1083 ‡C. Plasma sprayed copper coatings contain finer TiB₂ crystals than Cu- TiB₂ materials synthesized in a furnace at 1200 ‡C. Coatings with 25 vol% TiB2 have hardnesses that are comparable to Cu- Co- Be and Cu- Ni- Be alloys and to Cu- W and Cu- Mo alloys used in spot welding. Their low electrical resistivity of 52 ΜΩ cm could be increased by lowering the oxygen content with coatings and controlling the formation of TiB₂ clusters, the titanium content in solution in copper remaining low after the synthesis reaction.     

Densification of titanium diboride by hot isostatic pressing and production of near-net-shape components

Hot isostatic pressing (HIP) was applied to the production of titanium diboride (TiB₂) parts. Cylinders were first produced to select the best starting powder (of two possible choices) and the processing conditions. Transverse strength, hardness, and toughness measurements were carried out on the densified products. Results were equivalent or better than data published in the literature, showing that HIP is an efficient method of processing ceramic powders. Constitutive equations representing the rheology of porous materials are presented and applied to the selected titanium diboride powder. Hot pressing and sinter forging tests were carried out to obtain the parameters of the constitutive equations. These equations were used in a finite-element program to simulate the forming of TiB₂ crucibles by HIP. These parts were actually processed using graphite or titanium inserts to produce a hollow, cylindrical part with a closed end. Observed and calculated final shapes were compared, showing good agreement. In addition, the finite-element program allowed the calculation of residual stresses after processing, of eventual remaining porosity. It then became possible to optimize processing routes, can, and insert geometries.     

镀膜金刚石膜层的俄歇分析

镀膜金刚石在现代金刚石制品中的应用愈来愈重要,我们对镀铬和镀钛两种金刚石的镀层作了俄歇分析。结果表明:俄歇能较准确分析膜层元素原子数分数、膜层厚度;所用镀铬和镀钛金刚石,镀层中分别除碳、铬元素,碳、钛元素外,均含有氧元素,这是镀层表面氧化所致;所用镀铬和镀钛金刚石,相对稳定的镀层厚度分别约为25 nm,360 nm。XRD线谱分析,镀铬金刚石镀层由于太薄,未发现衍射相,镀钛金刚石镀层却有TiC为基的固溶体形成。     

真空二次还原精炼法制备低氧高钛铁合金的研究

以铝热法生产的高钛铁为原料,以Al为还原剂进行真空还原精炼制备低氧高钛铁。研究了精炼温度、精炼时间等因素对精炼效果的影响,采用XRD、SEM及化学元素分析等手段对高钛铁合金进行了表征。结果表明:精炼后的高钛铁主要含有TiFe2、Fe2TiO5、TiO、Al2O3、TiAl、Fe0.942O等相,精炼后合金的微观结构均匀致密,夹杂物得到有效去除,氧含量大幅降低。但精炼温度过高,精炼时间过长,会恶化精炼效果。精炼后合金中钛含量(质量分数)为(69.00～71.00)%,铝含量低于2.50%,硅含量低于2.63%,氧含量低于3.52%,完全符合优质高钛铁的技术指标。     

Corrosion of alumina/titanium diboride composites in neutral and acidic chloride solutions

This research concerns the study of the corrosion behaviour of monolithic titanium diboride and the composites 50%Al₂O₃/50%TiB₂ (50/50) and 70%Al₂O₃/30%TiB₂ (70/30) in 3.5% NaCl solutions, at pH 7 and 3 (adjusted by HCl additions). The test temperature is 45 ± 1°C. Both electrochemical and chemical techniques are applied. Scanning electron microscope (SEM) observations are also used to investigate the corrosion attack morphology. Polarization curve recording evidences that at short immersion times both composites exhibit a passive behaviour. The stability of these passive conditions decreases at increasing volume fractions of titanium diboride in the material and is minimum in the monolithic material. The analyses of the aggressive solutions during 30 days of immersion of 50/50 under free corrosion conditions are in agreement with the hypothesis that at both pH values passivity is due to the presence of a titanium‐containing insoluble surface film, probably constituted by hydrated titanium oxide. SEM observations evidence the presence of a third phase in the composites, beside titanium diboride and alumina, that is constituted by an aluminum borate, formed during sinterization. This phase undergoes a chemical attack during exposures to the aggressive solutions, under free corrosion conditions. The relative importance of chemical towards electrochemical corrosion, as assessed by coupling potentiostatic tests and chemical analyses, increases when passive conditions are maintained.     

Phase equilibria in TiB2-reinforced high modulus steel

An application of thermodynamic calculations to the phase equilibria in TiB₂-reinforced high modulus steel (HMS) is described. Titanium diboride (TiB₂) has been verified as the best reinforcement for improving isotropic Young’s modulus of steels. The TiB₂ particles can be synthesized in-situ in a ferrite matrix using a combination of ferrotitanium and ferroboron powders. The calculations reveal that impurities, such as oxygen, could promote the iron boride (Fe₂B) formation in a Fe-TiB₂ pseudobinary system, especially for the HMS processed through this powder metallurgical technique. Modification of the steel matrix of HMS by an addition of ferrite formers is encouraged based on the calculated (Fe-TiB₂)-X diagrams that show no significant change in the stability of TiB₂. In the development of HMS with an Fe-Cr matrix, the phase constitution was predicted successfully, and the highest Young’s modulus is reached with a proper control of titanium content.     

Phase equilibria in TiB2-reinforced high modulus steel

An application of thermodynamic calculations to the phase equilibria in TiB₂-reinforced high modulus steel (HMS) is described. Titanium diboride (TiB₂) has been verified as the best reinforcement for improving isotropic Young’s modulus of steels. The TiB₂ particles can be synthesized in-situ in a ferrite matrix using a combination of ferrotitanium and ferroboron powders. The calculations reveal that impurities, such as oxygen, could promote the iron boride (Fe₂B) formation in a Fe-TiB₂ pseudobinary system, especially for the HMS processed through this powder metallurgical technique. Modification of the steel matrix of HMS by an addition of ferrite formers is encouraged based on the calculated (Fe-TiB₂)-X diagrams that show no significant change in the stability of TiB₂. In the development of HMS with an Fe-Cr matrix, the phase constitution was predicted successfully, and the highest Young’s modulus is reached with a proper control of titanium content.     

铝热自蔓延法制备低氧高钛铁合金及表征

以金红石、钛精矿、Al为原料采用铝热自蔓延法制备出低氧高钛铁。研究相关反应体系的热力学及动力学问题,考察配料比、熔渣类型、发热剂等对铝热自蔓延过程的影响,采用XRD,SEM以及化学分析等技术对高钛铁合金进行表征。结果表明:反应体系的绝热温度大于1800K,反应能自我维持进行;Al还原TiO2反应的表观活化能为93.676kJ.mol-1,反应级数为0.01,Al还原TiO2和Fe2O3的表观活化能为300.740kJ.mol-1,反应级数为1.20;合金主要由TiFe2、TiFe以及Fe2TiO0.13等钛铁低氧固溶体相组成,夹杂相存在是导致合金中氧含量高及微观缺陷存在的直接原因;合金中钛、铝、铁、硅含量分别为:60.0%～62%、7.0%～11.0%、21.0%～25.0%以及3.0%左右;合金中的氧被有效去除,最低为1.85%。     

Titanium diboride thin films produced by dc-magnetron sputtering: Structural and mechanical properties

The use of titanium diboride films as protective coatings was proposed for several applications because of its mechanical and tribological properties, as well as chemical and thermal stabilities. The aim of this work is to evaluate the effects of the deposition parameters on the microstructure and mechanical properties of titanium diboride films. All films were deposited on silicon substrates by dc-magnetron sputtering from a stoichiometric TiB2 target in argon atmospheres. The chemical composition was determined by Rutherford backscattering spectroscopy (RBS), while structural information was obtained by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The intrinsic stress of the films was determined by measuring the change of the substrate curvature due to film deposition. Surface roughness was studied by Atomic Force Microscopy (AFM). The film hardness and elastic modulus were determined by nanoindentation measurements. The correlation between the mechanical properties with the film density is presented. The internal stress reduction occurs with substantial reduction of the film hardness, and it occurs for films with low mass density.