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.     

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.     

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.     

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.     

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.     

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.     

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.     

复合钛白的制备技术现状与趋势

综述了近年来国内外制备复合钛白的简单机械混合法、强力机械研磨法、粒一粒包覆改性法、TiCl4水解法、TiOSO4水解法、氟化法、微波合成法和碳酸化法等八种方法的原理及工艺技术,评价了其工艺流程、产品成本、产业化前景和推广价值．对其发展进行了展望。     

Low cycle fatigue improvement of powder metallurgy titanium alloy through thermomechanical treatment

A low-cost β type Ti-1.5Fe-6.8Mo-4.8Al-1.2Nd （mass fraction, %）（T12LCC） alloy was produced by blended elemental powder metallurgy（P/M） method and subsequent thermomechanical treatment. Low cycle fatigue（LCF） behavior of P/M T12LCC alloy before and after thermomechanical treatment was studied. The results show that the LCF resistance of P/M titanium alloy is significantly enhanced through the thermomechanical treatment. The mechanisms for the improvement of LCF behavior are attributed to the elimination of residual pores, the microstructure refining and homogenization.     

Characteristics and wear behavior of cenosphere dispersed titanium matrix composite developed by powder metallurgy route

The cenosphere dispersed Ti matrix composite was fabricated by powder metallurgy route, and its wear and corrosion behaviors were investigated. The results show that the microstructure of the fabricated composite consists of dispersion of hollow cenosphere particles in α-Ti matrix. The average pore diameter varies from 50 to 150 μm. The presence of porosities is attributed to the damage of cenosphere particles due to the application of load during compaction as well as to the hollow nature of cenospheres. A detailed X-ray diffraction profile of the composites shows the presence of Al₂O₃, SiO₂, TiO₂ and α-Ti. The average microhardness of the composite (matrix) varies from HV 1100 to HV 1800 as compared with HV 240 of the as-received substrate. Wear studies show a significant enhancement in wear resistance against hardened steel ball and WC ball compared with that of commercially available Ti–6Al–4V alloy. The wear mechanism was established and presented in detail. The corrosion behavior of the composites in 3.56% NaCl (mass fraction) solution shows that corrosion potential (φ_corr) shifts towards nobler direction with improvement in pitting corrosion resistance. However, corrosion rate of the cenosphere dispersed Ti matrix composite increases compared with that of the commercially available Ti–6Al–4V alloy.     

The use of titanium in production automobiles: Potential and challenges

Titanium offers a number of attractive features for use in high-production-volume automobiles; however, high cost has been a barrier to application, thus far. This article discusses the potential and challenges for the use of titanium in the family automobile. A.M. Sherman earned his Ph.D. in metallurgy at the Massachusetts Institute of Technology in 1972. He is currently senior staff technical specialist at Ford Motor Company. Dr. Sherman is a member of TMS. C.J. Sommer earned his B.S. in metallurgical engineering at University of Pittsburgh in 1982. He is currently manager of automotive marketing at Timet. F.H. Froes earned his Ph.D. in physical metallurgy at Sheffield University in 1967. He is currently the director of the Institute for Materials and Advanced Processes at the University of Idaho. Dr. Froes is also a member of TMS.