Iron removal and recovery in the titanium dioxide feedstock and pigment industries

Titanium and iron are closely related in nature. Therefore, for both environmental and economic reasons, the fate of iron may be very crucial for the titanium extraction industry. Smelting of ilmenite to produce titania slag allows for the recovery of iron as high purity pig iron. However, in the production of synthetic rutile from ilmenite sands, iron is returned to the mine site as a fine oxide/hydroxide residue. Some projects to recover iron from these residues never reached the industrial scale. In the titanium dioxide (TiO₂) pigment industry, iron is deported as sulfate or chloride salt, which is usually neutralized and rejected at a considerable cost. In the past few years, ferrous sulfate heptahydrate (or copperas) and iron chloride have found a few applications, but still the demand for these iron salts is not enough to cover the production volumes. The review of some new processes currently under development clearly shows that iron recovery is essential for the long-term viability of any new ilmenite upgrading or TiO₂ pigment production process.     

The technologies of titanium powder metallurgy

Titanium alloys exhibit attractive mechanical properties but they are expensive. This paper reviews the current status of titanium powder metallurgy which offers near-net shape cost-effective approaches to the fabrication of components. For more information, contact F.H. Froes, University of Idaho, McClure Bldg., Room 437, Moscow, ID 83844-3026, e-mail imap@uidaho.edu.     

Ultra-fine Cu clusters decorated hydrangea-like titanium dioxide for photocatalytic hydrogen production

Hydrogen,with the merits of zero emissions and high energy density,is one of the promising green energy sources.Seeking for high efficiency and low-cost catalysts is one of the key issues for hydrogen evolution and its practical applications.Nano-structured metal cocatalysts are widely used to improve the photocatalytic performance via surface electronic structure/properties optimization of the catalyst.Herein,we report ultra-fine(*1 nm)Cu clusters decorated hydrangea-like TiO₂systems for photocatalytic hydrogen evolution.The pristine hydrangea-like TiO₂support shows a promising performance of hydrogen evolution(1.8 mmol·h^-1·g^-1),which is*10.7 times higher than that of the commercial P25(168 lmol·h^-1·g^-1).After ultra-fine Cu clusters decoration,a maximal hydrogen evolution performance(3.7 mmol·h^-1·g^-1)is achieved in the optimized system 6Cu–TiO₂(6 wt%).Experimental and theoretical studies demonstrate that the ultra-fine Cu clusters decoration could promote the charge separation and transfer process effectively.The Cu clusters also act as reaction sites for reduction of H₂O to H2.These results are of great importance for the study of Cu-based co-catalyst systems and also shed light on the development of other non-noble metal co-catalysts in photocatalysis hydrogen evolution.     

粉末冶金钛合金的制备

钛合金性能优异．但不易对其进行机加工。粉末冶金已成为生产钛合金复杂形状零件的合适工艺。本文综述了采用传统粉末冶金方法和金属注射成形方法生产钛合金的工艺过程。     

粉末冶金钛合金的制备与力学性能

采用元素混合法制备粉末冶金Ti-Al-Mo-V-Ag合金.通过X射线衍射、金相观察、扫描电镜及力学性能测试等方法,研究Ag的添加及烧结温度对基体合金的显微组织与力学性能影响,并对其作用机制进行探讨.结果表明:添加5%～10% Ag(质量分数)可提高基体合金的压坯成型性,最终使烧结合金的致密度与力学性能得到提高;Ti-5Al-4Mo-4V-5Ag合金经过1 250 ℃真空烧结4 h后,抗压缩强度及相对密度分别达到1 656 MPa及96.3%.     

粉末冶金多孔钛表面生物活化的研究

采用粉末冶金法制备了具有适合人体组织长入孔径的多孔钛,并对其进行生物活化处理.利用EPMA、SEM、XRD等研究了不同预处理方法和浸泡时间对多孔钛表面羟基磷灰石(HA)的形貌及形成速度的影响.结果表明,多孔钛的表面以及孔的内表面上均有纳米晶TiO2生成,预钙化处理能够明显提高多孔钛表面生成羟基磷灰石的速率,促进HA的形核长大,预钙化后磷含量增加明显,验证了Na2HPO4在预处理中对多孔钛的活化是有利的.     

低成本高性能粉末冶金钛合金

粉末冶金是短流程制备低成本、高性能钛及钛合金的有效方法。低成本氢化脱氢（HDH）钛粉可用于制备粉末冶金钛合金制件,但由于受间隙原子含量高、烧结致密度低和微观组织粗大等因素影响,使粉末冶金钛制品的组织性能优势得不到发挥。实验采用氢化脱氢钛粉—冷等静压—真空烧结的技术路线制备了Ti-6Al-4V烧结坯,间隙原子含量低（O<0.16 wt.%, N<0.05 wt.%, H<0.015 wt.%）,具有均匀细小的近等轴?组织,良好的室温拉伸性能（UTS>930 MPa, YS>870 MPa, El>14%）。实验同时表明了HDH工艺制备低间隙原子含量钛粉的可行性,间隙原子含量的增加主要源于粉末及压坯的操作、转移和储存过程。得益于粉末冶金钛合金的细晶和近终成形特点,它无需通过开坯锻造,并且近成型的烧结坯能够提高材料利用率,减少后续热加工变形量及加工道次。因此,以粉末钛合金烧结坯替代锻坯进行后续的塑性加工能够大幅度降低钛合金构件及型材的成本。     

氢处理技术在钛合金粉末冶金中的应用及影响

氢处理技术是铁合金的一种特有的热处理方式,粉束冶金是生产铁合金复杂形状零件的合适工艺.钦合金粉来冶金结合氢处理技术是一种独特的成形工艺.本文综述了氢处理技术在钦合金粉未冶金中的一些应用及其影响机理.     

The pre-alloyed powder metallurgy of titanium with boron and carbon additions

Discontinuously reinforced titanium alloys have been produced by gasatomizing Ti-6Al-4V (in weight percent) with additions of boron and/or carbon to make a pre-alloyed, in-situ reinforced titanium-alloy powder. The rapid cooling that takes place during atomization results in a fine and uniform dispersion of titanium carbide and titanium boride. The atomized powder can be consolidated using standard titanium powder consolidation methods such as hot isostatic pressing or extrusion and further processed to produce standard mill forms. Mechanical properties of the consolidated product show room-temperature tensile strengths up to 1,470 MPa with an elastic modulus of approximately 140 GPa. For more information, contact C.F. Yolton, Crucible Research LLC, 6003 Campbells Run Road, Pittsburgh, PA 15205; (412) 923-2955; fax (412) 788-4665; e-mail cfyolton@crucibleresearch.com.     

超声波辐照对水合二氧化钛晶体结构和煅烧二氧化钛粒度的影响

介绍在硫酸氧钛水解过程初期引入超声波辐照,采用透射电子显微镜、X射线衍射仪和激光粒度测试技术对水解产物-水合二氧化钛及其在650℃的煅烧产物二氧化钛进行表征.结果表明:超声波辐照作用不仅促进了硫酸氧钛的水解过程而且使水解产物的晶格参数发生改变,特别是锐钛型四方晶胞的c轴从0.951 4 nm缩短到0.918 1 nm,同时,晶胞体积缩小,晶粒度减小.在煅烧以后,c轴伸长明显使原有的晶格畸变消失.与未受超声波辐照的水解产物不同,受过超声波作用的水合二氧化钛在煅烧之后其平均颗粒度减小的趋势达10%,从水合二氧化钛的0.712μm减小为0.639 μm.     

Opportunities in the electrowinning of molten titanium from titanium dioxide

The value chain of titanium products shows that the difference between the cost of titanium ingot and titanium dioxide is about $9/kg titanium. In contrast, the price of aluminum, which is produced in a similar way, is only about $1.7/kg. Electrowinning of molten titanium from titanium dioxide is therefore believed to have significant potential to reduce the cost of titanium products. The process is hampered by the high operating temperatures and sophisticated materials of construction required; the high affinity of titanium for carbon, oxygen, and nitrogen; and physical and chemical properties of the different titanium oxide species when reducing titanium from Ti₄₊ to metallic titanium. For more information, contact D.S. van Vuuren, CSIR, Materials and Manufacturing Technology Department, Meiring Naude Road, Pretoria, Gauteng 0181, South Africa; +27 12-841 2375; fax +27 841 2135; e-mail dvvuuren@csir.co.za.     

Soviet titanium research and production

An exclusive interview on what the Russians are doing about titanium as revealed by Dr. John P. Nielsen, Chairman of the Dept. of Metallurgy of New York University, who recently returned from his second tour of metallurgical research laboratories and plants in the USSR.     

Roles of titanium dioxide and ion-doped titanium dioxide on photocatalytic degradation of organic pollutants (phenolic compounds and dyes) in aqueous solutions: A review

Water pollution by organic pollutants is an ever increasing problem for the global concerns. This paper presents a critical review on the abatement of organic pollutants, dyes and phenolic compounds in particular, using photocatalytic reaction by titanium dioxide (TiO₂). Mechanism of photocatalytic reaction is briefly discussed. A detailed search of published reports on the advancement in photocatalytic degradation of organic pollutants in wastewater by doping titanium dioxide with foreign species such as metal and non-metal component has also been carried out and analyzed in this paper.     

Preparation of titanium dioxide photocatalytic hollow spheres

With coaxial nozzle system, TiO2 hollow spheres were prepared and the optimum parameters of forming TiO2 hollow spheres were fix on as follows： acrylamide （AM） was used as monomer up to 30.3%, acetone was used as vesicant, the mass fraction of initiator was 0.4%, the forming temperature was in the range from 90 ℃ to 95 ℃. The photocatalistic performance of TiO2 hollow spheres was characterized by degradation of methyl orange. Compared with nano-TiO2 powders, hollow spheres can be recycled after cleanout and drying, taking on similar efficiency ofphotocatalistic.     

二氧化钛包覆微细金刚石的制备及表征

以聚乙烯吡咯烷酮（PVP）为偶联剂,钛酸四丁酯（TBOT）为TiO₂前驱体,氨水为催化剂,通过St?ber法制备核-壳结构的二氧化钛包覆微细金刚石（UFD@TiO₂）,研究溶液pH值、氨水及去离子水的加入量对UFD@TiO₂的影响。采用XRD、SEM及DSC-TG等手段对UFD@TiO₂进行表征,利用三点弯曲法测定添加UFD或UFD@TiO₂的陶瓷结合剂试样的抗折强度,通过SEM观察陶瓷结合剂试样断口的微观形貌。实验结果表明:当溶液pH值约为8,氨水体积分数为0.8%,去离子水体积分数为0.8%时,TBOT水解生成的TiO₂易在金刚石表面异质形核,可获得致密均匀的TiO₂膜层;UFD@TiO₂的起始氧化温度为650℃,比UFD的起始氧化温度583℃提高了67℃;UFD@TiO₂-陶瓷结合剂试样的抗折强度比UFD-陶瓷结合剂试样的抗折强度提高了20.9%。      

Self-assembled polyaniline nanotubes and nanoribbons/titanium dioxide nanocomposites

Self-assembled polyaniline (PANI) nanotubes, accompanied with nanoribbons, were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in an aqueous medium, in the presence of colloidal titanium dioxide (TiO₂) nanoparticles of 4.5 nm size, without added acid. The morphology, structure, and physicochemical properties of the PANI/TiO₂ nanocomposites, prepared at various initial aniline/TiO₂ mole ratios, were studied by scanning (SEM) and transmission (TEM) electron microscopies, FTIR, Raman and inductively coupled plasma optical emission (ICP-OES) spectroscopies, elemental analysis, X-ray powder diffraction (XRPD), conductivity measurements, and thermogravimetric analysis (TGA). The electrical conductivity of PANI/TiO₂ nanocomposites increases in the range 3.8 × 10^?4 to 1.1 × 10^?3 S cm^?1 by increasing aniline/TiO₂ mole ratio from 1 to 10. The morphology of PANI/TiO₂ nanocomposites significantly depends on the initial aniline/TiO₂ mole ratio. In the morphology of the nanocomposite synthesized using aniline/TiO₂ mole ratio 10, nanotubes accompanied with nanosheets prevail. The nanocomposite synthesized at aniline/TiO₂ mole ratio 5 consists of the network of nanotubes (an outer diameter 30–40 nm, an inner diameter 4–7 nm) and nanorods (diameter 50–90 nm), accompanied with nanoribbons (a thickness, width, and length in the range of 50–70 nm, 160–350 nm, and ～1–3 μm, respectively). The PANI/TiO₂ nanocomposite synthesized at aniline/TiO₂ mole ratio 2 contains polyhedral submicrometre particles accompanied with nanotubes, while the nanocomposite prepared at aniline/TiO₂ mole ratio 1 consists of agglomerated nanofibers, submicrometre and nanoparticles. The presence of emeraldine salt form of PANI, linear and branched PANI chains, and phenazine units in PANI/TiO₂ nanocomposites was proved by FTIR and Raman spectroscopies. The improved thermal stability of PANI matrix in all PANI/TiO₂ nanocomposites was observed.     

综合利用钛铁矿制备二氧化钛、钛酸锂和磷酸铁锂

以钛铁矿为原料,经机械活化-盐酸浸出得到水解钛渣和富铁浸出液;用H2O2将水解钛渣中的Ti配位溶出,得到配位浸出液,并以其为反应物制备纳米级片状的过氧钛化合物;该过氧钛化合物经洗涤、煅烧制备得到纳米级片状的TiO2,其纯度高达99.31%(质量分数)。将过氧钛化合物与Li2CO3混合,球磨后煅烧合成性能优良的锂离子电池负极材料Li4Ti5O12。以富铁浸出液为原料,经选择性沉淀制备含少量Al和Ti的FePO4.xH2O,并以其为前驱体制备了Al-Ti掺杂的LiFePO4。该LiFePO4在1C和2C倍率下的首次放电比容量分别达151.3和140.1(mA.h)/g,循环100次之后容量无衰减。该方法也可用于钛白粉副产品硫酸亚铁的回收利用,制备性能优异的LiFePO4。     

Electronic structure and momentum density distribution of titanium dioxide

LCAO calculations have been performed for the electronic and structural properties of the rutile TiO₂ under the periodic HF and DFT schemes. The methods have been applied to study Compton profiles and the structure factors. The experimental Compton profile based on Am²⁴¹ Compton spectrometer for polycrystalline TiO₂ has been compared with the calculations. The calculated Compton profile from HF-LCAO has been found to be in good agreement with the measurement compared to the ionic model and DFT-LCAO method. The published experimental X-ray structure factors support the FLAPW method more than the periodic HF-LCAO method. Signatures of charge transfer on compound formation are observed. Partial ionic as well as covalent character of bonding is observed on the basis of structure factor as well as momentum density analysis. The present work enables to examine the DFT and HF approaches in terms of structure factor and the Compton profile studies.