- Titanium powder production by preform reduction process (PRP)
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To develop an effective process for titanium powder production, a new preform reduction process (PRP), based on the calciothermic reduction of preform containing titanium oxide (TiO2), was investigated. The feed preform was fabricated from slurry, which was made by mixing TiO2 powder, flux (e.g. CaCl2) and binder. Various types of preforms in the form of plates, spheres, or tubes were prepared using a conventional technique, and the fabricated preform was sintered at 1073 K before reduction in order to remove the binder and water. The sintered solid preform containing TiO2 was then placed in a stainless steel container, and reacted with calcium vapor at a constant temperature ranging between 1073 and 1273 K for 6 h. Titanium powder was recovered from the reduced preform by leaching it with acid. As a result, pure titanium powder with 99 mass% purity was obtained. This process was found to be suitable for producing a homogeneous fine powder when the composition of flux and the size of the preform are controlled.
- Okabe, Toru H.,Oda, Takashi,Mitsuda, Yoshitaka
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- Thermal decomposition of Ti5(Se,Te)8 in argon and nitrogen atmospheres
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Chalcogenides TiSe1.60-x Tex (0 ≤.x ≤ 1.60), forming a continuous series of hexagonal solid solutions, were prepared by the direct ampule procedure. The thermal decomposition of TiSe1.60-x Tex was studied for the samples with x = 0, 0.16, 0.80, 1.44, and 1.60 in Ar and N2 atmospheres in the course of heating from 25 to 1000°C. The selenide undergoes no weight loss under Ar, in contrast to the telluride which disproportionates and loses weight owing to the formation of volatile TiTe2. At high temperatures, tellurides are more sensitive than selenides to the presence of nitrogen: The disproportionation is accompanied by the reaction of TiTe2 with N2, yielding low-volatile titanium nitride and free tellurium. Titanium selenide and telluride as components of the solid solutions behave similarly to the corresponding individual chalcogenides. 2005 Pleiades Publishing, Inc.
- Pankratova,Zvinchuk,Suvorov,Hatanpaa,Kozlov,Leskela
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- Revealing dehydrogenation effect and resultant densification mechanism during pressureless sintering of TiH2 powder
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The use of TiH2 powder as a sintering precursor can produce nearly full-density titanium and titanium alloys with good mechanical properties. Unfortunately, there is a lack of research on the effect of lattice defects generated during the dehydrogenation of TiH2 powder, and the underlying sintering diffusion mechanism and activation energy have yet to be determined. In this work, we report a two-step sintering strategy to reveal the dehydrogenation effect and resultant densification mechanism during the pressureless sintering of a TiH2 powder precursor. The results show that, compared with hydrogenated-dehydrogenated (HDH) Ti powder, TiH2 powder, an intermediate of HDH-Ti powder, exhibited a higher instantaneous densification rate, greater onset relative density, rapid grain growth, and thus a smaller grain size. It also showed a grain boundary diffusion mechanism below 91% relative density and half the sintering activation energy in the intermediate sintering stage. Fundamentally, this was attributed to lattice defects generated during the dehydrogenation of TiH2 powder, which was confirmed by the greater relative density of a sintered TiH2 compact due to the two-step sintering strategy designed herein. Interestingly, the sintered sample obtained from the TiH2 powder precursor has a satisfying combination of strength and ductility that is far superior to other bulk Ti materials, especially sintered bulk Ti obtained from HDH-Ti powder. The results obtained in this paper provide theoretical guidance for using pressureless sintering to produce nearly full-density Ti and Ti alloys with good mechanical properties for structural applications.
- Chen,Yang,Liu,Ma,Kang,Wang,Zhang,Li,Li,Li
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- Magnesium reduction of titanium tetrachloride
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The reasons for the slow rate of reaction between TiCl4 vapor and a clean Mg surface are clarified, and the role of the magnesium reduction of titanium chlorides in the gas phase and liquid magnesium chloride film is discussed. The mechanisms for the formation of spongy titanium and its deposition on the walls of commercial reactors are elucidated. A continuous procedure is proposed for the preparation of titanium powder.
- Evdokimov,Krenev
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- Preparation of strong and ductile pure titanium via two-step rapid sintering of TiH2 powder
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The present work demonstrates the feasibility of preparing bulk-Ti, with high strength and good ductility, via spark plasma sintering of TiH2 powders. The microstructure and mechanical properties of bulk titanium prepared under two different pr
- Sharma, Bhupendra,Vajpai, Sanjay Kumar,Ameyama, Kei
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- Kinetics of the iodide titanium process by the thermal decomposition of titanium tetraiodide
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An extensive study of the kinetics of the iodide titanium process, performed in a flow system by the thermal decomposition of titanium tetraiodide over a tungsten filament substrate, is presented in this paper. The influence of the substrate temperature, TF, and reactant pressure, PTiI(4)o, on the process rate has been analyzed. It has been found that the overall process is rate limited by the transfer of gases in the neighborhood of the substrate. In addition, it has been determined that the rate of titanium transfer is modulated at the filament surface by a certain deposition efficiency that depends on reactant pressure and reaction temperature. The available thermodynamic data for the gaseous titanium iodides at high temperatures fail to explain such an efficiency factor, although the calculations described herein indicate that such data are probably incorrect. Eventually, the titanium growth rate results from the noninterfering contributions of titanium deposition and evaporation rates. The overall reaction rate for the process can be expressed as a function of the operational parameters by the following equation: rG(TF, PTiI(4)o) = 0.9εD(TF, PTiI(4)o)PTiI(4)oTF-rE(TF) mg cm-2 min-1. εD represents the determined deposition efficiency and rE the titanium evaporation rate in vacuum. Owing to the similarities between the iodide process for titanium and zirconium, the general characteristics for the titanium growth kinetics here described are expected to be also fulfilled for the zirconium case.
- Cuevas,Fernandez,Sanchez
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- Electrochemical reduction of TiO2 in molten LiCl-Li2O
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An investigation into the electrochemical reduction of TiO2 to Ti in molten LiCI-Li2O has been performed. Analysis of the time-dependent changes of a phase composition shows that the reduction proceeds through lithium-containing intermediates consisting of LiTi2O 4 and LiTiO2. The reduction of TiO2 in molten LiCl-Li2O allows a much lower reaction temperature compared to the conventional reduction process in molten CaCl2. Copyright
- Hur, Jin-Mok,Lee, Su-Chul,Jeong, Sang-Mun,Seo, Chung-K
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- A new, energy-efficient chemical pathway for extracting ti metal from ti minerals
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Titanium is the ninth most abundant element, fourth among common metals, in the Earth's crust. Apart from some high-value applications in, e.g., the aerospace, biomedicine, and defense industries, the use of titanium in industrial or civilian applications has been extremely limited because of its high embodied energy and high cost. However, employing titanium would significantly reduce energy consumption of mechanical systems such as civilian transportation vehicles, which would have a profound impact on the sustainability of a global economy and the society of the future. The root cause of the high cost of titanium is its very strong affinity for oxygen. Conventional methods for Ti extraction involve several energy-intensive processes, including upgrading ilmenite ore to Ti-slag and then to synthetic rutile, high-temperature carbo-chlorination to produce TiCl4, and batch reduction of TiCl4 using Mg or Na (Kroll or Hunter process). This Communication describes a novel chemical pathway for extracting titanium metal from the upgraded titanium minerals (Ti-slag) with 60% less energy consumption than conventional methods. The new method involves direct reduction of Ti-slag using magnesium hydride, forming titanium hydride, which is subsequently purified by a series of chemical leaching steps. By directly reducing Ti-slag in the first step, Ti is chemically separated from impurities without using high-temperature processes.
- Fang, Zhigang Zak,Middlemas, Scott,Guo, Jun,Fan, Peng
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- Fabrication of a micro-porous Ti-Zr alloy by electroless reduction with a calcium reductant for electrolytic capacitor applications
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A metallic titanium and zirconium micro-porous alloy for electrolytic capacitor applications was produced by electroless reduction with a calcium reductant in calcium chloride molten salt at 1173 K. Mixed TiO2-70 at%ZrO2 oxides, metallic calcium, and calcium chloride were placed in a titanium crucible and heated under argon atmosphere to reduce the oxides with the calcium reductant. A metallic Ti-Zr alloy was obtained by electroless reduction in the presence of excess calcium reductant and showed a micro-porous morphology due to the sintering of each of the reduced particles during the reduction. The residual oxygen content and surface area of the reduced Ti-Zr alloy decreased over time during the electroless reduction. The element distributions were slightly different at the positions of the alloy and were in the composition range of Ti-69.3 at% to 74.3 at%Zr. A micro-porous Ti-Zr alloy with low oxygen content (0.20 wt%) and large surface area (0.55 m2 g-1) was successfully fabricated by electroless reduction under optimal conditions. The reduction mechanisms of the mixed and pure oxides by the calcium reductant are also discussed.
- Kikuchi, Tatsuya,Yoshida, Masumi,Taguchi, Yoshiaki,Habazaki, Hiroki,Suzuki, Ryosuke O.
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- Reactions of ground state Ti atoms with NO: Insertion versus complexation. An IR matrix isolation study
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The reaction of ground state Ti atoms with NO during condensation in solid argon has been reinvestigated. The NTiO molecule, already characterized in reactions of laser-ablated Ti, is the only product observed for the reaction between one Ti atom and one nitric oxide molecule. Isotopic data on ν1, ν2, ν3, 2ν1 and 2ν2 have been measured in the mid- and far-infrared regions. This enables a complete harmonic force-field calculation based on a bent geometry, in agreement with the conclusions of the previous study. No evidence is found, however, of a metastable nitrosyl complex intermediate, as previously proposed. This study confirms that the insertion reaction proceeds directly from the ground electronic state reagents, with no or very little activation energy. (C) 2000 Published by Elsevier Science B.V.
- Krim, Lahouari,Prot, Christophe,Alikhani, Esm? M.,Manceron, Laurent
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- Mechanochemically synthesized Al2O3-TiC nanocomposite
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Al2O3-TiC nanocomposite was synthesized by ball milling of aluminum, titanium oxide and graphite powder mixtures. Effect of the milling time and heat treatment temperatures were investigated. The structural evolution of powder particles after different milling times was studied by X-ray diffractometry and scanning electron microscopy. The results showed that after 40 h of ball milling the Al/TiO2/C reacted with a self-propagating combustion mode producing Al2O3-TiC nanocomposite. In final stage of milling, alumina and titanium carbide crystallite sizes were less than 10 nm. After annealing at 900 °C for 1 h, Al2O3 and TiC crystallite sizes remained constant, however increasing annealing temperature to 1200 °C increased Al2O3 and TiC crystallite size to 65 and 30 nm, respectively. No phase change was observed after annealing of the synthesized Al2O3-TiC powder.
- Mohammad Sharifi,Karimzadeh,Enayati
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- Effects of TiCl4 purity on the sinterability of Armstrong-processed Ti powder
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The sintering behavior of titanium powder produced via the Armstrong process from two different grades of TiCl4 was investigated by a combination of thermal, chemical, and microstructural analysis techniques. It was found that the use of lower
- Weil,Hovanski,Lavender
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- Conversion of titanium hydride to titanium nitride during mechanical milling
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The response of a stable titanium hydride to severe mechanical milling treatments at room temperature was studied in different gaseous environments using different milling media. Structural details were monitored by Reitveld refinements using x-ray-diffraction data and hydrogen compositions were measured by decomposition at 850 °C in a constant volume system. Milling in an argon atmosphere produces only nanocrystalline TiHx with a reduction in hydrogen content proportional to the milling time. Milling in steel and Co bonded WC vials in air gave a more rapid loss of H and simultaneous formation of TiN. The lattice parameters of both the TiHx and the Ti formed by decomposition support a mechanism based on solid solution of N in the TiHx followed by partition into two phases. This resembles a chemically enhanced version of the solid-solution pumping mechanism previously described for the nitrogenation of pure Ti milled in air. Experiments with different milling media and minor additions of Fe and or Co suggest that 3d transition metal is necessary for the nitrogenation to occur, most likely by promoting dissociative chemisorption of N2.
- Zhang, Heng,Kisi, Erich H.
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- Electrolysis of Ti2CO solid solution prepared by TiC and TiO2
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TiO2 can be reduced by TiC at temperatures in excess of 1000 °C, under vacuum conditions. The resulting product was found to show the structures of a Ti2CO solid solution, which has excellent conductivity like a metal. A series of experiments have been performed on the possibility of titanium electrolysis, using a Ti2CO solid solution as an anode, in a NaCl-KCl melt. Carbon monoxide (CO) was monitored at the anode during electrolysis when the potential was kept constant. The product on the cathode was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that titanium powders can be prepared through electrolysis of a Ti2CO solid solution. The oxygen content of the titanium powders was measured and the result shows that it is lower than 300 ppm.
- Jiao, Shuqiang,Zhu, Hongmin
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- Obtaining of high-purity titanium, zirconium, and hafnium by the method of iodide refining in industrial conditions
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The processes of obtaining high-purity titanium, zirconium, and hafnium by the method of thermal dissociation of iodides are discussed. The data on cleaning of the metals from impurities in glass and metal closed-type vessels are presented. The types of v
- Kotsar,Morenko,Shtutsa,Akhtonov,Aleksandrov,Ziganshin,Indyk,Kucheryavenko,Lazarenko,Lapidus,Pogadaev,Popov
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- Reduction of titanium dioxide to metallic titanium conducted under the autogenic pressure of the reactants
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We report on a reaction to convert titanium dioxide to titanium. The reduction reaction was done under the autogenic pressure of the reactants at 750 °C for 5 h. The MgO, a by- product, was removed by acids to obtain pure metallic titanium.
- Eshed, Michal,Irzh, Alexander,Gedanken, Aharon
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- Formation of Al-Y oxide during processing of γ-TiAl
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While processing Y2O3 dispersed γ-TiAl, Y2O3 particles which dissolved during hot isostatic pressing (HIP'ing) were found to precipitate during the heat treatment in the form of a mixed Al-Y oxide. To understand the chemical reaction that occurs between Y2O3 and γ-TiAl during the heat treatment cycle, a powder mixture comprising of γ-TiAl and 10 wt.% Y2O3 was mechanically alloyed (MA'd) for 8 h and the milled powder was subjected to differential thermal analysis (DTA) at 1150 °C prior to analyzing it using X-ray diffraction technique. The present study clearly demonstrates that aluminum in the combined form either as γ-TiAl or Al2O3 reacts in a similar manner with Y2O3 when milled and heat treated at 1150 °C. In either case there is formation of Al2Y4O9 (2Y2O3.Al2O3).
- Trivedi,Patankar,Froes,Baburaj
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- Extraction of titanium from different titania precursors by the FFC Cambridge process
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Cheap titania precursors including titania dust, metatitanic acid (solid) and titanium-rich slag were tested as the feeding materials in the FFC Cambridge process (laboratory scale). Porous pellets (~20 mm in diameter, 2.0-3.0 mm in thickness) of the prec
- Ma, Meng,Wang, Dihua,Wang, Wenguang,Hu, Xiaohong,Jin, Xianbo,Chen, George Z.
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- On the necessary experimental conditions to grow titanium films on hot tungsten filaments using titanium tetraiodide
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An experimental system has been built to grow titanium films on hot tungsten filaments by the pyrolytic decomposition of titanium tetraiodide. Different procedures are examined in this system to establish the necessary experimental conditions to promote t
- Cuevas,Fernandez,Alguero,Sanchez
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- Electrodeposition of Ti from TiCl4 in the ionic liquid 1-methyl-3-butyl-imidazolium bis (trifluoro methyl sulfone) imide at room temperature: Study on phase formation by in situ electrochemical scanning tunneling microscopy
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Titanium was electrodeposited from a nominal 0.24 M TiCl4 in 1-methyl-3-butyl-imidazolium bis (trifluoro methyl sulfone) imide ([BMIm]BTA) at room temperature on a Au(1 1 1) substrate. The process of electrodeposition was studied by cyclic voltammetry, chrono amperometry and in situ scanning tunneling microscopy (STM). In a first step TiCl4 is reacted to TiCl2, which is subsequently reduced to metallic Ti. Two dimensional (2D) clusters form preferentially on the terraces in the under potential deposition range. 2D clusters presumably of TiCl3 precipitates grow and coalesce to cover the whole substrate with a 2D film at a substrate potential below -1.1 V versus ferricenium/ferrocene ([Fc]+/[Fc]) redox couple. At a potential of -1.8 V a dense layer of three dimensional (3D) clusters of titanium of 1-2 nm thickness is formed. The features of the I-U tunneling spectra and the relative reduction of the effective tunneling barrier by 0.8 eV with respect to gold clearly indicate the metallic character of Ti deposits. Observation of circular holes on the Au(1 1 1) substrate after dissolution of the deposited Ti indicates the formation of Au-Ti surface alloying.
- Mukhopadhyay,Aravinda,Borissov,Freyland
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- Catalytic properties of silica supported titanium, vanadium and niobium oxide nanoparticles towards the oxidation of saturated and unsaturated hydrocarbons
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The catalytic properties of silica supported titanium, vanadium and niobium oxide nanoparticles towards the oxidation of different organic substrates (cyclohexane, cyclohexene, 1-hexene) using tertbutylhydroperoxide (TBHP) and molecular oxygen as the oxid
- Martínez-Méndez, Susana,Henríquez, Yurgenis,Domínguez, Olgioly,D'Ornelas, Lindora,Krentzien, Heinz
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- Electrochemical deposition of Pd, Ti, and Ge for applications in GaAs technology
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The electrolytic deposition of Pd, Ti, and Ge is demonstrated. A process for depositing smooth surfaces of layers from 10 to 100 nm and thicker is described. Applications of this technology for Schottky and ohmic contacts are shown and the advantages to similar evaporated metallization schemes are listed.
- Schuessler,Statzner,Lin,Krozer,Horn,Hartnagel
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- Thermal behaviour of titanium seleno-telluride Ti5Ch8 in Ar and N2 atmospheres
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A series of TiSe1.60-xTex, where 0 ≤ x ≤ 1.60, was prepared. The samples were characterized by powder X-ray diffraction and thermogravimetric analysis in Ar and N2 atmospheres. The XRD measurements showed that the titanium seleno-tellurides form a continuous solid solution of a hexagonal structure. Thermal behaviour of the compounds was studied by thermogravimetric analysis for samples x = 0, 0.16, 0.80, 1.44, 1.60 in the temperature interval from 25 to 1273 K. After heating in Ar, no mass loss was observed in selenide (x = 0). In contrast, for telluride (x = 1.60) mass loss took place due to a formation of ditelluride. For seleno-tellurides in nitrogen atmosphere both disproportion reaction and a reaction of ditelluride with N2 occurred simultaneously.
- Pankratova,Stepanova,Zvinchuk,Suvorov,Hatanpaa,Kozlov,Leskela
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- Ultrafine-grained titanium of high interstitial contents with a good combination of strength and ductility
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A dehydrided Ti powder of very high oxygen content was successfully consolidated using back pressure equal channel angular processing into a fully dense bulk ultrafine-grained Ti showing apparent compressive ductility as well as high true yield and ultimate strengths of 1350 and 1780 MPa, respectively. Interstitial solid solution strengthening contributed to the majority of the increase in strength with additional contribution from ultrafine grains. Significantly, the material also exhibited much improved ductility for such a high interstitial content, thanks probably to the nonequilibrium grain boundaries and bimodal grain structure introduced during severe plastic deformation.
- Xu,Wu,Sadedin,Wellwood,Xia
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- Production of titanium powder directly from TiO2 in CaCl 2 through an electronically mediated reaction (EMR)
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Production of titanium powder directly from titanium dioxide (TiO 2) through an electronically mediated reaction (EMR) using calcium as a reductant was investigated. Feed material (TiO2 powder or preform) and reductant (Ca-Ni alloy) were charged in electronically isolated locations in a molten calcium chloride (CaCl2) salt at 1173 K, and the current flow through an external circuit between the feed and reductant locations was monitored during reduction of TiO2. The voltage between feed electrode and reductant alloy was intermittently measured during the reduction experiment to monitor the reduction process. After the reduction experiment, pure titanium powder with low nickel content was obtained even though liquid Ca-Ni alloy was used as a reductant. These results demonstrate that titanium metal powder can be produced without direct physical contact between the feed and reductant. In some experimental conditions, pure titanium powder with 99.5 mass% purity was successfully obtained.
- Park, Il,Abiko, Takashi,Okabe, Toru H.
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- Combustion of TiO2-Mg and TiO2-Mg-C systems in the presence of NaCl to synthesize nanocrystalline Ti and TiC powders
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The combustion process of TiO2-Mg and TiO2-Mg-C systems with sodium chloride as an inert diluent was investigated. The values of combustion parameters and temperature distribution on a high-temperature wave according to the amount of sodium chloride were obtained by the thermocoupling technique. The leading stages of combustion processes are found and the sizes of reactionary zones were estimated. It is shown that the introduction of NaCl in an initial mixture promotes the formation of a nanocrystalline structure of the final products. As a result, nanosized titanium, and titanium carbide powders have been successfully obtained.
- Nersisyan,Lee,Won
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- Formation of Ti or TiC nanopowder from TiO2 and carbon powders by electrolysis in molten NaCl-KCl
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A new route to produce pure Ti powder or TiC nanopowder with diameters of ~50 nm by electrolysis in molten KCl-NaCl using TiO2 and carbon powder was reported in this paper. This electrochemical experiment was carried out with an innovative equipment unitizing the chlorination and electrolyzation. A fine titanium powder was obtained after electrolysis at 4.0 V for 5 h at 850 °C. TiC nanopowder could be prepared in the anode chamber with the cell voltage up to 4.5 V. Furthermore, the product was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that pure Ti or TiC nanopowder can be prepared after electrolysis. The TiC nanopowder exhibited a polymorphic structure, and it had good thermal stability and oxidation resistance below 345 °C in air investigated by TGA and DSC. Cyclic voltammograms were carried out and the electrode reaction mechanisms during the electrolysis process were discussed in the paper.
- Zhao, Kun,Wang, Yaowu,Peng, Jianping,Di, Yuezhong,Liu, Kejia,Feng, Naixiang
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- Three-dimensional nanoporous TiO2 network films with excellent electrochemical capacitance performance
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The three-dimensional (3D) nanoporous hydrogenated TiO2 (denoted as H-TiO2) network film on titanium substrate was fabricated by a novel and controllable method. The fabrication process involved dealloying, alkaline reflux and hydrogenation. The dealloying produced the 3D nanoporous titanium film with open pores and interconnected nanoflakes nearly perpendicular to the substrate. The oxidation of the 2D titanium nanoflakes in the alkaline reflux resulted in the formation of the TiO2 nanotubes with an inner diameter of 5-10 nm and a length larger than 1.5 μm. The 3D nanoporous TiO2 network film was formed by the self assembly of these long and thin TiO2 nanotubes. Hydrogenation induced the formation of oxygen vacancies and more hydroxyl groups on the H-TiO2 surface. The 3D nanoporous H-TiO2 network film presented a capacitance of 1.05 mF cm-2 at the scanning rate of 100 mV s- 1. Furthermore, the H-TiO2 network film electrode also showed remarkable rate capability as well as excellent electrochemical cycling stability with a capacitance reduction of less than 7% after 1000 charge-discharge cycles at the current density of 100 μA cm- 2. The prominent electrochemical capacitance properties of the 3D H-TiO2 network film electrode could be attributed to its unique structural characteristics.
- Zhou, Huan,Zhong, Yuan,He, Zhishun,Zhang, Liying,Wang, Jianming,Zhang, Jianqing,Cao, Chu-Nan
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- In-situ observation on the magnesiothermic reduction of TiCl4 around 800 °C by microfocus X-ray fluoroscopy
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In the industrial smelting process for titanium metal, liquid TiCl4 is supplied on molten magnesium and reduced to porous titanium in a closed steel or stainless steel container at 800–900 °C. In the present study, in-situ observation on the magnesiothermic reduction of TiCl4 was performed by microfocus X-ray fluoroscopy. We successfully observed that the molten magnesium creeps up on container walls rapidly and that porous titanium is mainly deposited and grows on the walls by reduction of gaseous TiCl4 by the magnesium. This unique behavior of magnesium is attributed to the capillary action of molten magnesium through pores of titanium deposited on the walls.
- Kishimoto, Akihiro,Uda, Tetsuya
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- Investigation of the electrochemical reduction of Na2Ti3O7 in CaCl2 molten salt
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Sodium titanate (Na2Ti3O7), as an intermediate product for producing TiO2 through alkaline process, was used as precursor to prepare Ti metal successfully by FFC Cambridge Process. For the aim to gain insight into the electro-reduction mechanism, the sintered Na2Ti3O7 pellets(~1.83 mm thinkness, open porosity ~20%) were electrolysed using them as cathodes against graphite counter electrode in the molten CaCl2. The experiments were carried out at 900 °C and the applied voltage was 3.1V. Partially reduced samples were prepared by terminating the reduction process after different electrolysis times. The obtained samples were characterised by means of X-ray diffraction analysis, SEM and EDS. The results show that Na2Ti3O7 reacts easily with molten CaCl2 as 2Na2Ti3O7 + 2CaCl2 → Ca2Ti2O6 + 4TiO2 + 4NaCl and Ca2Ti2O6 → 2CaTiO3. The electrochemical reduction of sodium titanate proceeds via sequential formation of CaTiO3, titanium sub-oxides (such as Ti4O7, Ti3O5, Ti2O3 and TiO), CaTi2O4, Ti-O solid solution and Ti. The whole reduction can be divided into three stages: the first stage is that Ca2+ ions from electrolyte are inserted into Na2Ti3O7 particles leading to the formation of titanium sub-oxides and calcium titanates(CaTiO3 and CaTi2O4); the second stage is that calcium titanates are reduced into Ti-O solid solution from outside to inside of the pellets; the third stage is that the formed Ti-O solid solution is further deoxidised to form Ti metal.
- Liu, Kejia,Wang, Yaowu,Di, Yuezhong,Peng, Jianping
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p. 236 - 243
(2019/06/24)
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- Thermal characterization of titanium hydride in thermal oxidation process
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We investigated the thermal behavior of titanium hydride with different particle size at the different atmospheres using the thermal analysis techniques. The results demonstrated that the smaller particle has larger reactivity and showed less stable at hi
- Samal, Sneha,Cho, Sunghwan,Park, Dong Wha,Kim, Hyungsun
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- Effect of mechanically induced modification on TiH2 thermal stability
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Interrupted thermal desorption and X-ray diffraction techniques were used to study the effect of graphite and boron additives on non-equilibrium decomposition of mechanically activated commercial TiH2. The phase transformation sequence is described as a number of consecutive reactions corresponding to desorption peaks. The process is compared to non-equilibrium decomposition of commercial TiH2. The mechanical pre-treatment with additives significantly eases and accelerates decomposition of TiH2 to αTi(H), but hinders the stage of αTi(H) → αTi transformation. Only a small portion of pure αTi was detected for as-milled TiH2 and TiH2/B powders after the final TPD. No αTi was formed in the case of as-milled TiH2/C.
- Morozova,Khomenko,Borchers, Ch.,Leonov
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p. S754-S758
(2011/10/31)
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- A direct electrochemical route from oxides to Ti-Si intermetallics
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The titanium silicide intermetallics have been directly prepared from the mixture of titanium oxide (TiO2) and silicon oxide (SiO2) powder by using the solid-oxygen-ion-conducting membrane (SOM) electrolysis process. The electrochemical process was carried out in a molten flux CaCl2 at 950 °C with a potential of 3.5-4.0 V. The effects of the stoichiometry of the initial mixture on the electrolysis characteristics and the final product compositions were investigated. It has been found that the molar ratio of TiO2:SiO2 dominates the composition of final products. A single-phase silicide Ti5Si3 intermetallic was obtained when the TiO2:SiO2 molar ratio is 5:3; the TiSi was identified as the dominant phase with a minor amount of TiSi2 at TiO2:SiO2 molar ratio 1:1; three silicide phases, Ti5Si4, Ti5Si3 and TiSi, were found coexisting in the final product produced from TiO2-SiO2 mixture of molar ratio 5:4; the product of electrolysis consisted of the compound Ti5Si3 and the pure metal Ti as TiO2:SiO2 molar ratio equals to 3:1; and two silicide phases, TiSi and TiSi2, are formed as TiO2:SiO2 molar ratio equals to 1:2. The preliminary experimental results suggest that the electro-deoxidization process is fast and the current efficiency reached 75%.
- Zou, Xingli,Lu, Xionggang,Li, Chonghe,Zhou, Zhongfu
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p. 5173 - 5179
(2010/08/22)
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- Hydrogen storage in magnesium-metal mixtures: Reversibility, kinetic aspects and phase analysis
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The sorption capacity and kinetics of mechanically activated binary mixtures of Mg with nine different metals (Al, Cu, Fe, Mn, Mo, Sn, Ti, Zn, Zr) have been studied to determine whether these metals act as catalyzing/destabilizing agents in formation/decomposition of Mg hydrides. Identification of crystalline phases before and after the absorption/desorption processes assists our understanding of the different behaviors displayed by the studied compounds. Cu, Al and Zn take active part in Mg hydrogenation/dehydrogenation, but only the addition of Cu is actually effective in MgH2 destabilization, leading to a substantial decrease of the desorption temperature of this phase (down to 270 °C), and to an improved desorption kinetics. With the other metals, the hydrogen release usually occurs at a significant rate only above 320 °C and the kinetics of the absorption/desorption processes are slower than in the Mg/MgH2 system.
- Milanese,Girella,Bruni,Berbenni,Cofrancesco,Marini,Villa,Matteazzi
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p. 396 - 405
(2009/02/07)
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- On the quest for new mixed-metal μ-oxo-bridged complexes: Synthesis of compounds containing transition metal-oxygen-main group metal motifs M-O-M 1 (M = Ti, Zr; M1 = Al, Ga) without cyclopentadienyl ligands
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The reaction of TiBz4 (Bz = benzyl) with LAIMe(OH), L = (2,6-iPr2C6H3NC(Me))2CH, afforded LAIMe(μ-O)TiBz3 (1) and [LAIMe(μ-O)]2TiBz 2 (2), whereas the corresponding reaction with ZrBz4 resulted only in the formation of the trinuclear species [LAIMe(μ-O)] 2ZrBz2 (3). The reaction of (Mes2Ga(OH)) 2·THF (Mes = 2,4,6-Me3C6H2) with Ti(NEt2)4 yielded the cluster compound TiGa 6O7(NEt2)2(Mes)6 (4). All compounds have been characterized by elemental analysis, NMR spectroscopy, and mass spectrometry. Additionally, single crystal X-ray structure data of 1, 3, and 4 are reported. Compounds 1-4 show low catalytic activities in the polymerization of ethylene. Revisiting known μ-oxo-bridged complexes containing the M-O-M1 (M = Ti, Zr, Hf; M1 = Al, Ga) skeleton revealed that the application of polynuclear group 13 hydroxides and oxo bridged complexes possesses a potential for the preparation of new polyoxometal clusters.
- Nikiforov, Grigory B.,Roesky, Herbert W.,Schulz, Thomas,Stalke, Dietmar,Witt
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p. 6435 - 6443
(2009/02/05)
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- A new method for thin silver coating reaction using Ag2O and polyethylene glycol 400
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A new method for thin silver coating reactions using Ag2O and polyethylene glycol 400, an environmentally benign solvent, was devised. The reactions were investigated using 1H NMR, IR, UV-vis, SEM, and XPS measurements. Copyright
- Tanemura, Kiyoshi,Koike, Takanobu,Komatsu, Shigeki,Goto, Shin-Ichi,Nishida, Yoko,Suzuki, Tsuneo,Horaguchi, Takaaki
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p. 782 - 783
(2008/02/09)
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- Mechanism and kinetics of processes occurring at TiO2 cathode in CaCl2-CaO melt
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Preparation of titanium by the electrochemical reduction of titanium dioxide in a CaCl2-CaO melt in a diaphragm electrolyzer using a graphite anode was studied.
- Lebedev,Sal'nikov,Sizikov,Rymkevich
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p. 1503 - 1508
(2008/03/15)
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- Physiochemical pathway for cyclic dehydrogenation and rehydrogenation of LiAlH4
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A five-step physiochemical pathway for the cyclic dehydrogenation and rehydrogenation of LiAlH4 from Li3AlH6, LiH, and Al was developed. The LiAlH4 produced by this physiochemical route exhibited excellent dehydrogenation kinetics in the 80-100 °C range, providing about 4 wt % hydrogen. The decomposed LiAlH4 was also fully rehydrogenated through the physiochemical pathway using tetrahydrofuran (THF). The enthalpy change associated with the formation of a LiAlH4· 4THF adduct in THF played the essential role in fostering this rehydrogenation from the Li3AlH6, LiH, and Al dehydrogenation products. The kinetics of rehydrogenation was also significantly improved by adding Ti as a catalyst and by mechanochemical treatment, with the decomposition products readily converting into LiAlH4 at ambient temperature and pressures of 4.5-97.5 bar.
- Wang, Jun,Ebner, Armin D.,Ritter, James A.
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p. 5949 - 5954
(2007/10/03)
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- Use of an organometallic compound to protect and/or strengthen a keratin material, and treatment process
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The use of a composition comprising at least one organometallic compound which may be obtained by partial or total hydrolysis, and partial or total condensation, of at least one metallic precursor, to at least one of protect and strengthen a keratin material.
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- Preparation and surface science characterization of model Ziegler-Natta catalysts. Role of undercoordinated surface magnesium atoms in the chemisorption of TiCl4 on MgCl2 thin films
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Two new synthetic routes for the preparation of model Ziegler-Natta catalysts under UHV conditions are described. The exposure of metallic magnesium to TiCl4 produced titanium chloride films with Ti in the 4+, 3+, 2+, and 0 oxidation states. Stable titanium chloride films could also be obtained by TiCl4 and Mg codeposition on MgCl2 and Au. A TiCl4/TiCl2 film was obtained in this case. The reaction of these systems with AlEt3 produced model catalysts for the polymerization of both ethylene and propylene. XPS is a proper technique for the characterization of the oxidation state of Ti in a variety of titanium chloride surface species. The stability of MgCl2 surfaces with a high concentration of undercoordinated Mg atoms was studied in UHV by Mg gas-phase deposition on a MgCl2 multilayer film. The Mg adatoms were readily coordinated by the Cl ions diffusing from the halide bulk to the surface. Mg-containing MgCl2 faces are thermodynamically unstable, and the fast diffusion of the Cl ions in the MgCl2 matrix allows the recovery of the chlorine termination to lower the system surface energy. The high mobility of the chlorine ions is of central importance for the molecular level understanding of the dynamic equilibrium among the MgCl2 surface, TiCl4, and the electron donors used in the synthesis of high performance microporous Ziegler-Natta catalysts. The deposition of MgCl2 in the presence of TiCl4 was studied for the stabilization of high Miller index faces during the MgCl2 film growth. The interaction between the two halides is too weak to influence the MgCl2 deposition, and TiCl4 could not be chemisorbed at 300 K.
- Magni, Enrico,Somorjai, Gabor A.
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p. 8788 - 8795
(2007/10/03)
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- New syntheses with magnesium hydride. Part 3: Preparation of nanocrystalline or amorphous metals by hydride reduction
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The tribochemical reduction of metal halides by magnesium hydride in organic solvents allows the synthesis of nanosize or amorphous metals.
- Knott, Wilfried,Frommeyer, Georg,Klapdor, Astrid,Windbiel, Dagmar
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p. 459 - 468
(2007/10/03)
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- Reaction of TiO2-Al-C in the combustion synthesis of TiC-Al2O3 composite
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Reaction mechanisms and the thermal structure in the reaction zone during the combustion of TiO2, Al, and C to form TiC-Al2O3 composite were studied. The reaction between each component was studied and the combustion wave
- Choi,Rhee
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p. 986 - 992
(2008/10/08)
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- Dioxygen Complexes of 3d Transition-Metal Atoms: Formation Reactions in the Gas Phase
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Reactions of ground-state 3d transition-metal atoms including Ti, Mn, Co, Ni, and Cu with molecular oxygen in Ar buffer gas have been investigated in the pressure range 5-700 Torr at 296 K.Attention has been given to termolecular association reactions in which mono(dioxygen) complexes are formed.A pulsed laser photolysis-laser fluorescence technique is used where metal atoms are produced by visible multiphoton dissociation of a volatile organometallic precursor in a static pressure reaction cell, and reactions of metal atoms are monitored by resonance fluorescence excitation at variable time delay following the photolysis pulse.The pres ent study completes a survey of the reactions of 3d transition-metal atoms with O2 under room temperature conditions, from which it emerges that reactivity with respect to complex formation is correlated with a dns1 valence electron configuration of the metal atom.Simplified RRKM calculations have been used to interpret termolecular rate constants for the association reactions in terms of a trend in the binding energies of the dioxygen complexes.
- Brown, Carl E.,Mitchell, S. A.,Hackett, Peter A.
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p. 1062 - 1066
(2007/10/02)
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- Synthesis of [μ-1,9,10,11-η:4,5,6,12-η-tricyclo[7.1.1.1 4,6]dodeca-1(11),4,6-(12),9-tetraene]bis(tricarbonyliron): The smallest cyclophane with metal-stabilized antiaromatic decks
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The synthesis and structure of [μ-1,9,10,11-η:4,5,6,12-η-tricyclo[7.1.1.1 4,6]dodeca-1(11),4,6(12),9-tetraene]bis(tricarbonyliron) (1), a small cyclophane containing iron-stabilized antiaromatic decks of cyclobutadiene, is reported. Complex 1 crystallizes in the monoclinic space group P21/a, a = 12.455 (6) A?, b = 9.769 (4) A?, c = 7.156 (2) A?, β = 92.88 (3)°, and d(calcd, Z = 2) = 1.665 g cm-3. The structure was resolved by direct methods using MULTAN80 and refined by least squares to Rf = 4.2% (Rw = 5.2%). The physical properties of 1 were examined and compared to [2.2]paracyclophane. The cyclobutadiene ligands are parallel to and lie directly over each other with no ring distortion, and there is a 20.6° out-of-plane bending of the aliphatic bridges away from the metal. The intradeck distance of 2.7 A? is the smallest observed for the cyclophanes. The carbonyl moieties are in the staggered conformation.
- Adams, Christopher M.,Holt, Elizabeth M.
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p. 980 - 986
(2008/10/08)
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- TITANIUM (O) REAGENTS; 4. A SELECTIVE AND EFFICIENT REDUCTION OF NITROPYRIDINE DERIVATIVES
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Following the successful applications of a titanium (O) slurry in the deoxygenation of aromatic N-oxides, we attempted to achieve this method for the reduction of a nitro- group in pyridine derivatives.In general, only aminopyridine derivates were formed in 85-98percent yield.The advantage of this excellent reducing agent consists in mild reaction conditions and high yields of products, as well as in the selectivity of the reaction.
- Malinowski, Marek
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- Reduction of bis(triorganotin) oxides by metals: An easy route to hexaorganoditins
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Bis(triorganotin) oxides have been reduced in high yield to hexaorganoditins by titanium, magnesium, potassium, and sodium.
- Jousseaume, Bernard,Chanson, Evelyne,Pereyre, Michel
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p. 1271 - 1272
(2008/10/08)
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- ELECTROLYTIC REDUCTION OF TiF62 - IN CHLORIDE MELTS WITH DIFFERENT ACID-BASE PROPERTIES.
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The mechanism and kinetics of the TiF//6**2** minus electrolytic reduction process were investigated in molten alkali metal chlorides. It was shown that the overcharging reaction is preceded by the TiF//6**2** minus thermal dissociation process with formation of TiF//4. Electrolytic reduction of the latter occurs with formation of divalent titanium fluoride compounds, difficulty soluble in the melt. The overcharging process depends significantly on acid-base properties of the melt. Reduction of TiF//6**2** minus to the metal under the experimental conditions occurs irreversibly in one stage.
- Taranenko,Shapoval,Nerubashchenko
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- ELECTROCHEMICAL BEHAVIOR OF TiCl4 SOLUTIONS IN LOW-MELTING ORGANIC MEDIA.
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The electrochemical behavior of TiCl//4 was studied in carbamide, acetamide, and ammonium sulfamate and acetate at 150 degree by potentiodynamic and chronopotentiometric methods. A continuous coating of a pale grey color, containing up to 10% metallic titanium, was obtained upon electrolysis of carbamide and acetamide melts on steel and solid VK-8 and VK-6 alloys. The obtained coating exceeds in quality the coatings, deposited from sulfamate and acetate melts.
- Tumanova,Sarnavskii,Bogdanovich,Bel'dii,Novitskaya
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