Natural Ilmenite Research Articles

Effect of Mo on Properties and Microstructure of Steel-Bonded Cemented Carbide GT35 Produced by In Situ Reduction of Ilmenite

Steel-bonded cemented carbide GT35 was fabricated from natural ilmenite by in-situ carbothermic reduction and vacuum pressureless sintering. The effects of Mo-doped on the mechanical properties and microstructures of GT35 composites were investigated. That the good mechanical properties of steel-bonded cemented carbide GT35 with 9wt% Mo were obtained at the same sintering condition that the density reached 6.223g/cm3 and the average bending strength reached about 1155.6MPa after heat treatment, but the hardness dropped the lowest value HRC 60.94 and the difference was not apparent with the change of Mo content. The additive of Mo is beneficial to be refinement of carbide particle size, sphericity of grains and formation of compact composite. In-situ reduction of natural ilmenite was a feasible way to fabricate good performance composite GT35 with a relative low cost.

Fabrication of Fe-Al Intermetallic/TiC-Al<sub>2</sub>O<sub>3</sub> Ceramic Composites from Ilmenite by Reaction Sintering

Fe-Al intermetallic/TiC-Al2O3 ceramic composites were fabricated by in-situ carbothermic and aluminothermic reduction from natural ilmenite. Synthesis and sintering of the composites were accomplished unanimously in the vacuum hot pressure furnace. The thermodynamic process, the composition, the microstructure as well as the properties of the FeTiO3-Al-C system were studied in detail through theoretical analysis and experimental research. It was shown that the synthesis process started from the melting aluminium, followed by the deoxidation of ilmenite step by step via a series of different valent titanium oxides to form TiC, Al2O3 and Fe-Al as the ultimate productions. The particle sizes are mostly 3-5μm, and their distributions are uniform. Meanwhile, the addition of additives can improve the wettability of alloy to ceramic phases and the combination of the interfaces, giving rise to the properties of the composites as a whole.

Steel-Bonded Cemented Carbide GT35 by In Situ Reduction of Natural Ilmenite

Steel-bonded cemented carbide GT35 was fabricated from natural ilmenite by in-situ synthesis and vacuum pressureless sintering. The thermodynamics of the synthesis process were analyzed. The results indicated that the stable phases were TiC and iron in the FeTiO3-C system. During the synthesis process, ilmenite was reduced by graphite via a series of titanium oxides to obtain hard phase (TiC) and the steel matrix as the ultimate products. The experimental results shown that GT35 had a reasonable phase composition and fine TiC particles embedded uniformly in the steel matrixes. The composites exhibited excellent mechanical properties: the relative density was higher than 97%, the hardness reached HRC 61.5 and the maximal bending strength was about 1270MPa.

The Study of Self-Propagating High-Temperature Synthesis of TiC-Al<sub>2</sub>O<sub>3</sub>/Fe Composites from Natural Ilmenite

In the paper, natural ilmenite (FeTiO3) was used as the main green material to synthesize TiC-Al2O3/Fe composite powder by Self-propagating High-temperature Synthesis (SHS) technology and densified TiC-Al2O3/Fe composites were prepared in a vacuum hot-pressoven. The reaction mechanism in the synthesis process was studied through theoretical thermodynamical analysis and experiment research .The effect of different synthesis conditions on the products was discussed. The relations among synthesis conditions,sintering conditions, phases composition, microstructure and properties of composites were also studied in details. A new way to synthesize the advanced TiC-Al2O3/Fe composites with relatively lower cost was practiced.

Application of 28 GHz Microwave Irradiation to Oxidation of Ilmenite Ore for New Rutile Extraction Process

Microwave heating has been applied to the oxidation in the new rutile extraction process developed by the authors in which rutile is extracted from a natural ilmenite ore by oxidation and magnetic separation followed by leaching with diluted acid. Since ilmenite FeTiO3 and pseudobrookite Fe2TiO5 strongly absorb 28 GHz microwave, Australian ilmenite ore mainly composed of FeTiO3 was rapidly heated up to about 1 273 K and oxidized in air with keeping almost constant temperature. As a result, two equilibrium phases of rutile TiO2 and pseudobrookite were quickly formed at microwave power of 1.5 kW. The growth rate of the pseudobrookite phase in the microwave irradiation was found to be much faster than that of the rutile phase in the conventional resistance furnace, indicating a drastic enhancement of the growth rate by the microwave irradiation.

Feasibility study of the new rutile extraction process from natural ilmenite ore based on the oxidation reaction

Phase relations in the Fe2O3-FeTiO3-TiO2 system were investigated by equilibrating synthetic samples in evacuated sealed quartz tubes at a temperature of 1373 K. The equilibrium partial pressure of oxygen was measured by the electromotive force (EMF) method in the temperature range of 1273 to 1373 K. The phase diagram and oxygen partial pressure diagram in the titanium-iron-oxygen ternary system were then constructed at 1373 K. Rutile extraction from natural ilmenite ore was discussed from the thermodynamic viewpoint. It is found that rutile can be produced from common natural ilmenite ores not only by the reduction as the conventional titanium-rich slag process but also by an oxidation. Then, the oxidation experiment was conducted in air using Australian ilmenite ore to obtain rutile as one of the coexistent phases. Magnetic separation and leaching experiments for synthesized pseudobrookite and reagent rutile were conducted to confirm the possibility of separation of rutile from pseudobrookite. A new rutile extraction process was then proposed.

Combustion synthesis of fine TiFe series alloy powder by magnesothermic reduction of ilmenite

Fine TiFe series alloy powder was fabricated by magnesothermic reduction of ilmenite as main raw material. Adiabatic temperature of the FeTiO 3-Mg system was studied through thermodynamic analysis. Meanwhile, the characteristics of TiFe series alloy were described by XRD, SEM and grading analysis. It is shown that combustion synthesis of the FeTiO 3-Mg system can carry out due to its strong exothermic reaction through adiabatic temperature calculate. Ultrafine TiFe series alloy powder after leached for 5 h has reasonable phases and morphology with the particle distribution of 0.2 to 1 μm. It indicates that in-situ magnesothermic reduction of natural ilmenite is a feasible way to fabricate ultrafine powder with a relatively lower cost.

Reductive kinetics of the reaction between a natural ilmenite and carbon

The reductive degree and rate of Bama ilmenite concentrate by graphite under argon atmosphere were measured by using thermogravimetric analysis system at the temperatures from 850 °C to 1400 °C. The reduction degree of the ilmenite increased with temperature rise, the case similar to reaction rate. The higher the temperature was, the faster the reaction rate was. The phases before and after reduction and the morphology of reduced samples were identified by using X-ray diffraction and optical microscopy analysis, respectively. The reduction degree of the ilmenite decreased due to the presence of impurities. Manganese and magnesium oxide-rich zones formed which prevented complete reduction of Fe 2+. In general, the reaction products were iron, Ti 3O 5, reduced rutiles and pseudobrookite solid solution. The kinetics was also discussed and it was found that the rate-controlling steps were different in the different temperature ranges.

An investigation on electrical properties of microwave treated natural ilmenite (FeTiO3)

It has been observed that microwaves of 2.45 GHz heat dielectric materials. On subjecting natural ilmenite to microwave irradiation, the mineral is observed to heat, with a surface temperature in proportion to the irradiation time. With irradiation times from 40 to 240 seconds (increased in steps of 40 sec), the surface temperature measured on the samples were between 280 and 520 K. Electrical measurements made on the samples before and after irradiation show that the electrical properties are modified by the microwave irradiation. The real conductivity (σ′), dielectric constant (ɛ′) and the dielectric loss (ɛ″) plotted against frequency generally showed universal dielectric behaviour [1 and references therein] similar to that observed in other systems studied in the literature but using conventional heating techniques. Plots of σ′, ɛ′ and ɛ″ against the surface temperature of the sample showed frequency independent peaks around 460 K. The experimental dielectric loss (ɛ″) results fit a peak function of the form: $$\varepsilon^{\prime\prime} = \varepsilon_0 + \frac{A}{\omega_0 T {\sqrt{2\pi}}} \exp \left(-\frac{\big(\ln\big(\frac{T}{T_p}\big)\big)^2}{2\omega_0^2}\right) $$ where ɛ0, A, and ω0 are constants. The fitting of the dielectric loss results gives a frequency independent peak temperature (Tp) as 464 ± 5 K. Plotting the dielectric (γ′) and dielectric loss (γ″) exponents against temperature also gives an estimate of Tp close this value. The possibility of a ferroelectric transition in the samples is investigated by comparison with previous results obtained from synthetic ilmenite samples as it is the case with well known ferroelectric systems such as BaTiO3 [2].

Solid state reduction of a natural ilmenite

An ilmenite concentrate was reduced with graphite under argon gas between 1250 °C and 1350 °C by using a thermogravimetric analysis (TGA) system. Specimens were reacted for various periods of time during which the mass loss values were recorded. Samples representing different reduction stages were examined by optical microscopy, image analyzer, X-ray diffraction and SEM (EDAX) techniques. Reduction of Fe 3+ to Fe 2+, Fe 2+ to Fe and Ti 4+ to Ti 3+ took place within 50% reduction during which a secondary oxide phase was formed and replaced the natural ilmenite. Reduction of Ti 3+ to Ti 2+ took place after 50% reduction which altered the composition of the secondary oxide phase by decreasing its oxygen content. Reduction of Ti 2+ took place while the oxygen deficient TiO 1− x phase formed. Formation of any titanium carbide or oxycarbide phases depended on the completion of the reduction which was not possible at the specified temperatures.

Simultaneous Synthesis of Iron Carbide and Rutile from Ilmenite Ore by Thermochemical Reactions

Simultaneous synthesis of iron carbides (mainly Fe 3 C) and rutile (TiO 2 ) from natural ilmenite ore (mainly FeTiO 3 ) were examined by thermochemical reactions with H 2 -CO or H 2 -CH 4 gas mixtures at temperatures of 1 073-1 273 K. The low sulfur pressures incapable of forming FeS was added to these gas mixtures to make stable iron carbides without free carbon. Iron carbide is currently interesting as alternative pure iron sources in steelmaking. The rutile is also available as a feedstock for titanium industry. First, partial conversion from ilmenite to rutile and metallic iron mostly proceeded and subsequently iron carbidization occurred together with further reduction of rutile. Finally, these processes with both gas mixtures provided iron carbide (Fe 3 C) and lower titanium oxides such as Magneli phases [Ti n O 2n-1 , 4≤n≤9 namely TiO 2-x ) and/or Ti 3 O 5 rather than rutile. Reaction time, H 2 /CH 4 ratio, sulfur potential, and temperature dependence of reaction behavior was examined further. The iron carbidization rates were analysed using the first order rate model. Ilmenite samples prepared from reagents showed slightly slower conversion rates to titanium oxides at 1 073 K than the natural ore ones, though both samples showed similar iron carbidization rates.

Technical note a fast determination of [formula omitted] ratio in industrial minerals

Three-channels data collecting method for the determintion of Fe 3+ Fe 2+ ratio in industrial iron-bearing minerals is proposed using Mössbauer effect spectroscopy. The method has been proved faster (less than five minutes) than the conventional collection of full Mössbauer spectra. Natural Ilmenite, Chromite and Stilpnomelane minerals can be used. The later is used to illustrate the method.

Reduction Kinetics of Natural Ilmenite Ore with Carbon Monoxide

In order to elucidate the reduction kinetics and mechanism of natural ilmenite ore with carbon monoxide, reduction experiments have been carried out using thermogravimetric technique in the temperature range between 1173 and 1323 K with three kinds of natural ilmenite ores from Australia, Malaysia and China. The reduction rate was analyzed in terms of the mixed-control kinetics by applying a shrinking unreacted-core model, on the basis of the observation of cross section of partially reduced ilmenite and X-ray diffraction patterns. The determined reaction rate constant k c and effective diffusivity D e are expressed in the temperature range between 1173 and 1323 K by the following equations: k c /m.s -1 = exp{-113 × 10 3 /(RT) + 5.03} (Australian) k c /m.s -1 = exp{-47.0 × 10 3 /(RT) - 3.04} (Malaysian) k c /m.s -1 = exp{-71.6 × 10 3 /(RT) + 0.554} (Chinese) D c /m 2 .s -1 = exp(-4250/T - 7.54) (Australian) D c /m 2 .s -1 = exp(-3860/T - 7.94) (Chinese) where R: gas constant (J mol -1 K -1 ), T: temperature (K). The activation energy of the reaction is 113, 47.0, 71.6 kJ.mol -1 for Australian, Malaysian and Chinese natural ilmenite ore, respectively. The calculated reduction curves using the rate parameters reproduced the experimental data well. The reduction rate increases with increasing reduction temperature. With respect to the rate-determining step for Australian and Chinese ilmenite ores, the relative contribution of resistance of a mass transfer step through gas film is smaller than that for synthetic ilmenite, while the relative contribution of resistance of a diffusion step of carbon monoxide through pores of the product layer is larger than that for synthetic ilmenite, As for Malaysian ilmenite ore, the overall rate is mainly controlled by a chemical reaction step.

天然イルメナイト鉱石のCOガスによる還元反応速度

In order to elucidate the reduction kinetics and mechanism of natural ilmenite ore with carbon monoxide, reduction experiments have been carried out using thermogravimetric technique in the temperature range between 1173 and 1323 K with Australian, Malaysian, Chinese natural ilmenite ores. The reduction rate was analyzed in terms of the mixed-control kinetics by applying a shrinking unreacted-core model, on the basis of the observation of cross section of the partially reduced ilmenite and X-ray diffraction patterns. Reaction rate constant kc and effective diffusivity De determined are expressed by the following equations:(This article is not displayable. Please see full text pdf.) \ oindentwhere R: gas constant (J·mol−1·K−1), T: temperature (K).The activation energy of the reaction is 113, 47.0, 71.6 kJ·mol−1 for Australian, Malaysian and Chinese natural ilmenite ore, respectively. The calculated reduction curves using the rate parameters finely reproduced the experimental data. The reduction rate increases with increasing the reduction temperature. With respect to the rate-determining step for Australian and Chinese ilmenite ores, the relative contribution of resistance of a mass transfer step through the gas film is smaller than that for synthetic ilmenite, while the relative contribution of resistance of a diffusion step of carbon monoxide through pores of the product layer is larger than that for synthetic ilmenite. As for Malaysian ilmenite ore, the overall rate is mainly controlled by a chemical reaction step.

Increased dissolution of ilmenite induced by high-energy ball milling

High-energy ball milling treatment leads to full dissolution of natural ilmenite sands containing both FeTiO 3 and Fe 2 Ti 3 O 9 phases in a sulphuric acid solution at 100°C. The ilmenite material has been milled for various times in two environments (vacuum and air), and characterised by X-ray diffraction, Mössbauer spectroscopy and surface area analysis. It is found that after milling for only 10 h, 50% of the sample can be dissolved as a result of the increased surface area, nanocrystalline structure and high level of lattice distortion present in the milled sample. Complete dissolution of the ilmenite is obtained on extended milling (200 h) in an oxygen free atmosphere. This occurs as a result of a gradual reduction of the Fe 3+ phase (Fe 2 Ti 3 O 9 ) to the relatively more soluble Fe 2+ phase (FeTiO 3 ) on milling in vacuum. The results overall show that the chemical reactivity of milled materials can be affected significantly by the milling conditions and environment.

Mechanochemical reaction between ilmenite (FeTiO 3) and aluminium

A natural ilmenite (FeTiO 3) and aluminium powder have been mechanically milled together for 100 h in a laboratory ball mill. The as-milled powder and an unmilled powder of identical composition were annealed at up to 1200°C and examined by X-ray diffraction and differential thermal analysis (DTA). The unmilled sample showed aluminium melted prior to an exothermic reaction starting at ∼850°C. The milled powder showed no thermal activity, other than a reversible phase transition at 1067±4°C, indicating that reaction occurred within the mill. The products of both powders were the same, TiAl 3, Fe 4Al 13 and Al 2O 3, although in the milled powder these phases were nanocrystalline until annealing caused crystallite growth. The thermal reaction seemed to occur in two stages, formation of TiAl 3, Al 2O 3 and elemental iron followed by a slower, diffusion controlled reaction between the elemental iron and residual aluminium to form Fe 4Al 13. The reaction during milling was attributed to increased intermixing between the ilmenite and aluminium causing a change in the rate determining step from solid-state diffusion to another, unknown, controlling mechanism.

Mechanochemical Reactions of Ilmenite

Natural ilmenite samples (containing both FeTiO 3 and Fe 2 Ti 3 O 9 phases) have been ball milled in two atmospheres (vacuum and air). Different mechanochemical reactions were observed and the reaction processes were investigated by analysing the as-milled samples using X-ray diffraction and Mossbauer spectroscopy. A reduction reaction occurred during milling in vacuum because of the iron contamination, while an oxidation reaction was induced in the atmosphere of air with formation of thermally metastable phases, which corresponds to a low-temperature oxidation reaction in a thermal annealing process. The different products of milling in two atmospheres result in different chemical reactivities for the milled ilmenite samples.

High-resolution X-ray absorption microspectroscopy of lamellar phases in natural ilmenite

Abstract X-ray absorption microscopy is used to study the surface of a mineral, ilmenite. High-quality surface-sensitive micrographs are easily obtained without special sample preparation beyond that usually used in preparing samples for optical microscopy. The X-ray micrographs show an expected lamellar domain structure that has a very strong contrast change at the iron and titanium L-edges. High-resolution spectroscopy from these two different regions reveals fine structure from iron atoms in two different charge states, and titanium in a single phase. A theoretical analysis and curve-fitting procedure is used to determine the precise stoichiometry of the structures in the two phases detected. These results show that quantitative surface chemistry studies can be performed on natural mineral samples using X-ray photoelectron emission microscopy.

チタン製錬プロセスに関するチタン‐鉄‐酸素系の１，２７３Ｋにおける相平衡

The relation between the phase relations and the equilibrium partial pressures of oxygen in the Ti-Fe-O ternary system has been determined at 1, 273 K using a thermogravimetric method in CO-CO2 gas mixtures and also X-ray diffraction technique for quenched samples after the equilibrium. The possibility of upgrading natural ilmenite ore to a rutile substitute has been discussed and confirmed thermodynamically. The standard Gibbs energy of the reactions at 1, 273 K were also obtained as follows:Fe (s) +FeTiO3 (s) +1/2O2 (g) =Fe2TiO4 (s), -190.9kJ·mol-1, Fe (s) +TiO2 (s) + 1/2O2 (g) =FeTiO3 (s), -202.3kJ·mol-1.Activities of magnetite show negative deviations from Raoult's law in the Fe3O4-Fe2TiO4 solid solutions coexisting with metallic iron at 1, 173-1, 373 K.

A Comparative Study of Radiation Damage In A12O3, FeTiO3, And MgTiO3

AbstractOriented single crystals of synthetic alpha-alumina (α-Α12O3), geikielite (MgTiO3), and natural ilmenite (FeTiO3) were irradiated with 200 keV argon ions under cryogenic conditions (100 K) to assess their damage response. Using Rutherford backscattering spectrometry combined with ion channeling techniques, it was found that ilmenite amorphized readily at doses below 5×1014, alumina amorphized at a dose of 1-2x1015, and geikielite was amorphized at -2x1015 Ar cm-2 . The radiation damage response of the ilmenite crystal may be complicated by the presence of hematite exsolution lamellae and the experimentally induced oxidation of iron. The relative radiation-resistance of geikielite holds promise for similar behavior in other Mg-Ti oxides.