Synthesis of titanium carbide by thermo-chemical methods with TiH2 and carbon black powders

A new synthesizing method for producing submicron TiC powders was studied by using TiH₂ and carbon black powders. It is well known that hydrogen absorption transforms titanium from metal (h.c.p.) to brittle hydride (f.c.c.) powders by ball-milling. This research focused on obtaining submicron-sized TiC powders from the ball-milled mixture of TiH₂ and carbon black by thermal treatment. The hydrogen, carbon, iron, and oxygen composition changes in the mixed powders were analyzed. Thereafter, a differential thermal analysis (DTA) test was performed to observe change of phase with ball-milling time. The TiC powders were obtained by heat treating the powders milled for 5h at various temperatures (600–1200°C). The phase microstructure was investigated via DTA, X-ray diffraction (XRD), and scanning electron microscope (SEM). The mixture milled for 2h had an f.c.t. structure containing 66.73 at. %H transformed to f.c.c. by milling for 4h. After 5h of ball-milling, submicron-sized particles of 273 nm were obtained. At the isothermal heat-treating temperature of 500°C, the Ti single phase was formed completely, and the TiC phase of lattice parameter 0.310 nm was completely formed over the temperature of 1000°C.     

化学法制备Al2O3包覆TiH2颗粒发泡剂

利用非均匀成核法 ,以 pH缓冲溶液作沉淀剂 ,研究了Al2 O3 包覆TiH2 粉末的包裹技术。结果表明 ,Al3 浓度对包覆层显微结构有影响 ,当Al3 浓度为 0 .0 5mol/L ,pH值为 4.5时 ,可以获得好的氧化铝前驱体包覆TiH2 颗粒 ,经 35 0℃煅烧可得到均匀、致密的Al2 O3 /TiH2 包覆颗粒。当包覆层厚大于 1.42 μm时 ,Al2 O3 /TiH2 包覆颗粒释放氢气过程被显著地延迟 ,这种延迟效应对泡沫铝制备具有重要的实用价值。采用Al2 O3 /TiH2包覆粉体作为发泡剂 ,成功制备出多孔泡沫铝材料。     

Kinetic models of controllable pore growth of anodic aluminum oxide membrane

An anodized Al₂O₃ (AAO) membrane with apertures about 72 nm in diameter was prepared by two-step anodic oxidation. The appearance and pore arrangement of the AAO membrane were characterized by energy dispersive x-ray spectroscopy and scanning electron microscopy. It was confirmed that the pores with high pore aspect ratio were parallel, well-ordered, and uniform. The kinetics of pores growth in the AAO membrane was derived, and the kinetic models showed that pores stopped developing when the pressure (??) trended to equal the surface tension at the end of anodic oxidation. During pore expansion, the effects of the oxalic acid concentration and expansion time on the pore size were investigated, and the kinetic behaviors were explained with two kinetic models derived in this study. They showed that the pore size increased with extended time (r=G·t+G??), but decreased with increased concentration (r = ?K·lnc-K??) through the derived mathematic formula. Also, the values of G, G??, K, and K?? were derived from our experimental data.     

高能球磨制备超细TiH_2粉研究

利用氢化钛的氢脆性,在室温下通过高能球磨制备超细氢化钛粉。研究不同球磨条件对粉末粒度和形貌的影响,并对制备的粉末进行了扫描电镜分析。结果表明,球磨时间对粉末粒度的影响很大,粉末粒度在球磨初期迅速减小,球磨2min粉末迅速细化,粒度约为5μm~10μm。粒度为40μm的氢化钛粉,用庚烷保护湿磨30min时粒度达到1μm以下,球磨60min即可制得粒度为0.1μm的超细氢化钛粉。     

泡沫铝用SiO2/TiH2包覆型发泡剂的制备

以硅酸钠(NaSiO3*9H2O)和盐酸(HCl)为原料,采用非均匀形核法,通过控制反应条件可以在氢化钛(TiH2)表面均匀地包覆一层SiO2,作为发泡剂用于泡沫铝的制备.实验结果表明,经过包覆的发泡剂释氢时间可延迟60 s以上.用这种SiO2/TiH2包覆型发泡剂能制备出孔洞均匀的泡沫铝制品.     

多层片式PTCR热敏陶瓷注凝成型工艺

研究了用注凝成型工艺制备片式PTCR热敏陶瓷.采用PMAA-NH4为分散剂,丙三醇为增塑剂,并加入适量的有机单体AM制备了高固相含量、低粘度的BaTiO3半导瓷浆料,研究了浆料粘度及坯体的性能与浆料固相体积分数、有机单体含量及增塑剂含量之间的关系.研究表明:浆料固相体积分数对坯体的干燥及烧结行为有较大影响,当浆料固相体积分数在45%以上时,可有效避免制品干燥和烧结过程中收缩过大而产生的变形开裂缺陷;当有机单体的质量分数为2%～4%,丙三醇的体积分数为3%～6%时,可获得有一定强度和柔韧性的生坯;研究了注凝成型PTCR陶瓷的微观结构及陶瓷元件的PTCR性能,成功地制备了层数为5、室温电阻为0.8Ω、电阻温度系数为13.40%/℃、升阻比大于105的多层片式PTCR元件.     

Wetting behavior of Al alloys on a TiH2 substrate

The wetting behavior of Al–Ge alloys on TiH₂ substrates was investigated by an improved sessile drop method under high vacuum and in a temperature range of 773–818 K. Results indicate that the equilibrium contact angles of Al–Ge/TiH₂ increase linearly with temperature according to the following formula: θ = 0.2882T ? 85.04, and decrease linearly as the Ge content increases from 25.2% to 36.2% according to the formula: θ = 214 ? 200Ge (wt.%). The worst wetting behavior was obtained for a pure Al/TiH₂ system at its foaming temperature (973 K). TiH₂ particles were prone to aggregate and were thus difficult to disperse. This could be one of the reasons for closed-cell aluminum foam products having non-uniform pores.     

TiH2粉末的高能行星球磨及超细晶钛烧结

研究TiH 2粉末的高能行星球磨规律,然后使用制备出的球磨粉末开展压制?真空烧结,评价烧结样品的显微组织特征。结果表明,TiH 2粉末的高能球磨可划分为3个基本阶段：球磨初期粉末粒度迅速细化;球磨中期粉末粒度逐步趋向最小极限尺寸,同时粉末粒径的均匀性和分布集中程度明显改善;在球磨的后期,粉末粒径又会发生粗化现象。因此,TiH2粉末的高能行星球磨存在一组最佳的工艺参数。高能球磨会改变TiH2粉末的脱氢特征温度,且粉体的D 50越小,特征温度下降幅度越大,与原料粉末相比,最大差值达83℃。对烧结样品的显微组织分析显示,通过由球磨TiH 2粉末所获得的烧结钛合金的晶粒度得到了显著地细化;当采用优化的工艺开展球磨TiH 2粉末制备时,通过压制和真空烧结可获得平均晶粒度在5μm以下的超细晶钛。     

TiH2对合成Al-Ti-B合金组织及细化行为的影响

应用激光引燃自蔓延高温合成技术制备添加TiH2及不添加TiH2的两种Al—Ti-B中间合金。采用X射线衍射仪、电子探针、扫描电镜和差热分析仪等检测两种中间合金的相组成、分布、组织形貌及自蔓延反应热分析过程。结果表明：在合成Al—Ti—B中间合金过程中，TiH2对自蔓延反应具有明显的促进作用，分析认为TiH2受热分解出高活性Ti原子及具有催化作用的H原子，从而降低了自蔓延的反应温度，并改变了TiAl3和TiB2的形态和分布（TiB2的平均直径小于0．5μm），减小了TiB2的聚集倾向。添加TiH2的中间合金组织构成及形貌更适合细化处理，因而其对工业纯铝的细化效果优于不添加TiH2的中间合金。     

加热氧化处理对TiH2释氢行为的影响

通过直接集气法和X射线衍射分析,研究了TiH2在空气中加热氧化处理前后的释氢行为.结果表明:经高于450℃空气中加热处理后TiH2于Ar气氛中释氢,TiH1.97和TiH1.92向TiH1.5转变的相变开始温度有明显的升高趋势,表明氧化产物对TiH2有较好的缓释效果;氧化温度对TiH2缓释效果的影响程度明显大于保温时间的影响.TiH2在氧化过程中随温度和保温时间的变化有明显的颜色变化,呈灰色→金绿色→金黄色→紫色→蓝色的变化趋势;颜色的变化不仅表明了氧化产物厚度和相的变化,而且还表明氧化是一个渐进的过程.     

Porosity and mechanical properties of porous titanium fabricated by gelcasting

Porous Ti compacts with large size and complex shape for biomedical applications were fabricated in the porosity range from 40.5% to 53.8% by controlling gelcasting parameters and sintering conditions. The experimental results show that the total porosity and open porosity of porous titanium compacts gelcast from the Ti slurry with 34 vol.% solid loading and sintered at 1100℃ for 1.5 h are 46.5% and 40.7%, respectively, and the mechanical properties are as follows： compressive strength 158.6 MPa and Young＇s modulus 8.5 GPa, which are similar to those of human cortical bone and appropriate for implanting purpose.     

钛醇盐水解-沉淀法制备纳米二氧化钛粉体(英文)

以钛酸四丁酯为原料,采用水解-沉淀法制备TiO2纳米粉体,利用BET、XRD、IR、SEM和激光粒度分析仪等测试手段对制备TiO2粉体晶粒大小、粉体的粒度分布情况等进行了研究,并讨论原料配比,烧成温度,pH值与晶粒大小,物相组成等之间的关系。结果表明:在600°C到800°C之间,TiO2粉体由锐态矿转变为金红石,经800°C加热2h的物相主要为金红石,粉体呈类球形;pH为3.03,n(H2O):n[Ti(C4H9O)4]=30,400°C热处理2h后制备的TiO2粉末晶粒平均尺寸为80nm,粉体的平均粒度为580nm,比表面积为117.2631m2/g。     

Effect of TiH2 on preparation of closed-cell aluminum foam and its compressive behavior

The vesicant problem during the process of preparing closed-cell aluminum foam by molten body transitional foaming process was discussed and the effect of granularity and addition of TiH2 on porosity of closed-cell aluminum foam was investigated. The static compressive behavior of closed-cell aluminum foam and the influence of porosity on static compressive property of closed-cell aluminum foam were researched as well. The results show that with increasing granularity of TiH2, the porosity of closed-cell aluminum foam firstly increases and then decreases gradually, the granularity should be controlled in the range of 38-74μm which can result in higher porosity. The porosity of closed-cell aluminum foam increases with the increasing addition of TiH2, and the addition of TiH2 should be controlled fi＇om 1.5% to 2.5% which can result in homogeneous cell and moderate strength of closed-cell aluminum foam. The compressive process of closed-cell aluminum foam obviously displays linear elastic phase, plastic collapse phase, and densification phase, and the compressive strength grows with decreasing porosity.     

泡沫铝二次发泡工艺用先驱体中TiH2发泡剂的分散性

研究二次发泡泡沫铝工艺用熔体路径发泡先驱体中TiH2的分散性,包括熔体粘度测量、工艺参数对发泡剂分散性影响等。结果表明,610℃是ZLD104合金熔体粘度变化的转折点,低于610℃熔体粘度随温度的变化较大,高于610℃熔体粘度随温度的变化较小;随分散温度、搅拌速度、分散时间的提高,发泡剂分散均匀性提高,但在3 000 r/min,分散30 s的条件下,发泡剂的团聚现象仍然存在;在粘度-温度非敏感区分散发泡剂,并采用挤压使发泡先驱体致密化,以及采用3 000 r/min以上的搅拌速度分散发泡剂,可提高熔体路径发泡先驱体发泡剂均匀性。     

Rapid fabrication of alumina-based ceramic cores for gas turbine blades by stereolithography and gelcasting

Injection moulding is accepted as one of the most important methods for shaping complex ceramic cores, which are used to form intricate internal cooling passages of gas turbine blades. But the relatively long lead time and high costs involved in the fabrication of hard tooling render it uneconomical for new products development and low-volume production. In the study, a rapid prototyping process is developed to fabricate complex-shaped alumina-based ceramic core by combining stereolithography (SL) with gelcasting. SL is utilized to fabricate an integral sacrificial resin mold, and gelcasting is utilized to form a wet ceramic core green body through polymerization of aqueous ceramic slurry. The freeze-drying process is adopted to treat the wet green body surrounded by the resin mold, the drying shrinkage is decreased, and the generation of crack can be prevented. The sintering shrinkage of ceramic core is controlled by adding magnesium oxide power and developing a novel sintering process. After the resin mold is burnt out, the complex-shaped alumina-based ceramic core is obtained.     

工业纯钛TA2的焊接

通过对工业纯钛TA2焊接特点的分析及焊接温度场的确定,拟定了TA2钨极氩弧焊焊接工艺,着重对其钨极氩弧焊的保护措施、焊接规范参数的选择进行了实验与分析。通过实验对比,制定出了合理的规范参数,得到了满意的焊缝质量。     

基于冷喷涂的多孔钛与钛合金的制备与表征

基于冷喷涂技术的优点,结合喷涂后热处理开发了一种新的多孔钛与钛合金制备工艺.研究了热处理对所制备多孔钛与钛合金块材的组织与结合强度的影响.结果表明,所得多孔块材的气孔率与粉末本身及喷涂条件有关,气孔率在10%～50%之间变化.热处理态的气孔率代表了冷喷涂制备块材的实际气孔率.所得多孔块材喷涂态的结合强度在10～30 MPa之间变化.热处理后粒子间接触界面通过扩散达到冶金结合,多孔块材的结合强度均明显增加(超过55 MPa).     

TiH2的表面处理对释氢的影响及泡沫铝孔结构的控制

用化学方法制备了Al2O3溶胶,采用溶胶-凝胶和机械搅拌的方法在TiH2表面形成了Al2O3凝胶层.进行了发泡剂的释氢实验和两步法制备泡沫铝实验.结果表明:利用铝熔胶对发泡剂进行表面预处理可有效延缓其分解时间并改善其润湿性,涂覆后TiH2可在溶体中均匀分布,从而实现两部制备工艺,获得孔隙结构比较均匀的泡沫铝样品.