No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Production of rutile from ilmenite by room temperature ball-milling-induced sulphurisation reaction
Abstract
Rutile (TiO2) was produced at room temperature from mineral ilmenite (FeTiO3) by high energy ball milling of an ilmenite-sulphur mixture. A mechanochemical reaction, sulphurisation of iron in ilmenite producing TiO2 and FeS2, occurred during the milling process. During the subsequent annealing, the nanocrystalline TiO2 obtained from milling recrystallised and FeS2 decomposed at 600°C. Pure TiO2 powder was obtained by a simple selective chemical leaching with HCl acid solution. The results indicate that mechanochemistry is a useful room temperature process of material production.
... However, ilmenite and leucoxene became prominent feed materials The X-ray diffraction patterns of activated and unactivated ilmenite are similar, with no new phases forming during mechanical activation Li, Liang, and Wang, 2008b;Sasikumar et al., 2004Sasikumar et al., , 2007Shojaei et al., 2014;Tan, Hu, and Zhang, 2011;Wei et al., 2009;Wu et al., 2011a;. However, ilmenite milled with sulphur as a reducing agent shows weak reflections from new phases formed during attrition (Chen et al., 1996;Subasinghe and Ratnayake, 2021). Ball milling can induce alteration of the lattice structure (i.e., rearrangement of grains and increments of strain). ...
... Several authors have highlighted the benefits of reducing agents during the high-energy ball milling of titanium ores (Chen et al., 1996(Chen et al., , 2013a; Chen, Tang, and Xiao, 2015;Shahien et al., 2015;Wijewardhana, Subasinghe, and Ratnayake, 2021). For example, ilmenite undergoes sulphurization reduction (Equation [1]) with the formation of pyrite (FeS2) during prolonged milling in the presence of sulphur at room temperature (Chen et al., 1996;Subasinghe and Ratnayake, 2021). ...
... Several authors have highlighted the benefits of reducing agents during the high-energy ball milling of titanium ores (Chen et al., 1996(Chen et al., , 2013a; Chen, Tang, and Xiao, 2015;Shahien et al., 2015;Wijewardhana, Subasinghe, and Ratnayake, 2021). For example, ilmenite undergoes sulphurization reduction (Equation [1]) with the formation of pyrite (FeS2) during prolonged milling in the presence of sulphur at room temperature (Chen et al., 1996;Subasinghe and Ratnayake, 2021). Chen et al. (1996) also claimed that milling ilmenite with sulphur for 200 hours successfully produces TiO2 at room temperature. ...
Synopsis In this study, we review the role of mechanical activation in the pyrometallurgical, hydrometallurgical, and electrometallurgical processing of titanium feedstock. Mechanical activation has been shown to decrease the activation energy of chemical reactions, thus enhancing process efficiency and product quality by reducing processing time and energy consumption. Pyrometallurgical processing is energy-intensive and time-consuming. Hydrometallurgy is costly, requires high-grade feed material, and generates toxic waste. Waste generation and process complexity are the major drawbacks of electrometallurgy and solvent extraction. Bioleaching via a mechanically activated pyrometallurgical process can be identified as an alternative method, but the lengthy processing time is the major disadvantage. Mechanically activated titanium concentrate can be used in a finely tuned combined metallurgical process to overcome the challenges and drawbacks in these technologies. Mechanical activation and physicochemical factors controlling pyrometallurgical, hydrometallurgical, and electrometallurgical processing of titanium ore: A review.
... Ball milling of the ilmenite-sulfur mixture at room temperature in a vacuum was also investigated [61]. Upon ball milling broadening of the diffraction peaks in the XRD pattern ( Fig. 4 (a)) corresponding to ilmenite was observed due to the reduction in crystallite size of ilmenite induced by ball pulverization. ...
... Interestingly, the sample annealed at 800 C showed the presence of only TiO 2 . Pure rutile powder was obtained by acid leaching the sample annealed at 600 C in 10% HCl and Fe 9 S 10 was leached suggesting that this low-temperature extraction process is a simple and low-cost alternative for producing rutile from ilmenite [61]. ...
... (a) XRD patterns recorded from the mixtures of ilmenite and sulfur milled for different periods. Adapted from Ref.[61]. (b) XRD patterns of milled and unmilled samples. ...
Ilmenite is a naturally available mineral that is highly applicable in the synthesis of pure TiO2. Titania mainly presents in four polymorphs as rutile, anatase, brookite and TiO2–B. Titania could be mined from minerals such as ilmenite, leucoxene and rutile among which ilmenite is the main source. Ball milling is a mechanical activation method used before subjecting ilmenite to chemical treatment methods to produce titanium based materials. Effect of milling time, milling intensity, milling atmosphere, the introduction of reducing agents on the particle size, surface area, annealing temperature, and the crystal structure of the products are reviewed. The effect of ball milling on acid digestion of ilmenite in hydrochloric acid and sulfuric acid is discussed. Further, the effect of mechanical activation on hydrothermal treatment of ilmenite is explained in detail.
... Zhao and Shadman, 1990;Terry and Chinyamakobvu, 1991;Chen and Williams, 1996;Welham, 1996;Chen et al., 1997;Welham and Williams, 1999;Dewan et al., 2011;Shahien et al., 2015;Wijewardhana et al., 2021). Chen et al. (1996aChen et al. ( , 1996b and Welham (1998) introduced the sulphurisation reaction by milling pure sulphur and ilmenite for 100 h and 200 h at room temperature. However, few previous studies have focussed on combined carbothermic and sulphurisation reductions. ...
... Formation of FeS 2 in milled ilmenite-sulphur (IS) and ilmenite-sulphur-graphite (ISG) samples indicates the beginning of the sulphurisation reaction (e.g. Chen et al., 1996aChen et al., , 1996b. Occurrence of new TiO 2 peaks with weaker and broad reflections also implies the formation of disordered crystalline structures in samples milled for 6 h (Mizutani and Lee, 1990;Lu and Lai, 1995). ...
... Consequently, several mechanisms can be triggered for sulphurisation reaction during ball milling at room temperature (e.g. Chen et al., 1996aChen et al., , 1996bChen, 1997;Š epelák et al., 2013). ...
Sri Lanka is a major global producer of raw material-heavy minerals from beach placer deposits. This study focusses on upgrading Sri Lankan ilmenite sands to synthetic rutile via a mechanochemical method. Ball milling-induced sulphurisation and carbothermic reductions were examined using several geochemical techniques. Raw ilmenite concentrate contained over 95 wt% FeTiO3, ∼2 wt% SiO2, and ∼ 1 wt% Al2O3. Ilmenite was mixed with additives (i.e. sulphur, vein graphite, and a 1:1 mix of sulphur and vein graphite), separately in three ratios by weight, namely 1:1, 2:1 and 4:1, respectively. Each mixture was milled for 4 and 6 h. A high percentage of ilmenite/sulphur + graphite (ISG) was converted to nanoparticles (average particle size = 124 nm) in samples milled for 6 h. X-ray diffraction (XRD) spectra indicate that the intensities of sulphur and graphite peaks decrease after ball milling. This suggests possible dissolution of sulphur and graphite into the ilmenite structure, with the formation of mixed composite structures. The optimum ilmenite to additives ratio for ilmenite to rutile conversion was found to be 4:1. The occurrence of pyrite and pseudorutile peaks in XRD spectra of milled samples indicates that ilmenite reduction was initiated during ball milling. Fourier-transform infrared (FTIR) spectra of milled samples confirm the octahedral metal-ion stretching vibrations of carbon-incorporated ilmenite structures. The ilmenite-additive mixtures containing both sulphur and graphite (ISG) showed the best results. Consequently, ISG samples (mixing ratio of 4:0.5:0.5, and milled for 6 h) were isothermally annealed at 800 °C, 1000 °C and 1200 °C, respectively. Sharpening of rutile peaks and disappearance of pyrrhotite peaks in the annealed samples indicated the completion of the mechanochemical reactions that were initiated during ball milling. The optimum temperature for ilmenite reduction was determined to be 1000 °C. At that temperature pseudorutile peaks had disappeared from the XRD spectra of the annealed samples, whereas brookite and rutile peaks appeared. The method introduced in this study thus can be utilised to convert ilmenite to synthetic rutile.
... According to XRD patterns, the broad amorphous peaks (i.e., the baseline beginning with higher intensity and decreasing gradually) can be observed in each mixture containing activated carbon (Fig. 4b) and carbonized carbon derived from coconut shells (Fig. 4c) even after ball milling. Carbothermic reduction initiates upon the formation of new mineral phases within the samples [10,13,31,33]. However, the formation of new phases was not observed in XRD patterns of the studied ball milled raw ilmenite and ilmenite-carbon mixtures (Fig. 4). ...
Carbothermic reduction reduces ilmenite into TiO2 or acid-soluble intermediates. This method gained more attention due to several industrial applications of TiO2 and metal Ti. However, the efficiency of carbothermic reduction of ilmenite into synthetic rutile is poorly investigated for different carbon sources. In this study, several advanced characterization techniques were used to examine the effect of carbon on the carbothermic reduction of ilmenite via ball milling and isothermal annealing. Fourier transform infrared spectroscopic (FTIR) analysis showed new broad bands appearing in ball milled mixtures (ranging from ∼650 cm−1 to 1200 cm−1), due to temporary bonding of Ti–O–C overlapped with Ti–O–Ti bonding. Scanning electron microscopic (SEM) analysis also suggested that carbon was incorporated in the crystal lattice of ilmenite during ball milling. However, no new phases were observed in the X-ray diffraction (XRD) patterns of ball milled ilmenite-carbon mixtures. Therefore, the energy transferred during ball milling is not sufficient to overcome the activation energy of carbothermic reduction of ilmenite. Phase transformation of ilmenite occurred after annealing at 1000 °C by forming new phases such as rutile, pseudorutile, and pseudobrookite. Intermediate phases such as pseudorutile and pseudobrookite decreased with the use of carbon. Consequently, the efficiency of carbothermic reduction decreased in the order of coconut shells (amorphous) > activated carbon > vein graphite (crystalline). The absence of temporary bonding of Ti–O–C in annealed samples further confirmed the phase transformation of ilmenite. This study also showed that ball milled, and annealed samples resulted in highly crystalline rutile. Thermodynamic behavior of carbothermic reduction was finally simulated using the calculated enthalpy, entropy, and the Gibb’s free energy for each reaction.
... Mechanochemical techniques have also been explored in a few notable studies in the creation of ceramic powders and titanium. An early study by Chen et al. observed the creation of rutile (TiO2) from ball milling ilmenite (FeTiO3) through a sulfurization reaction induced by a planetary ball mill, where FeS2 and TiO2 were produced [34]. Rutile is a common source for titanium and is also used to manufacture TiB2, which is a common component in high-temperature coatings and crucibles [35]. ...
While reactions driven by mechanical force or stress can be labeled mechanochemical, those specifically occurring at a sliding interface inherit the name tribochemical, which stems from the study of friction and wear: tribology. Increased perception of tribochemical reactions has been gained through technological advancement, and the development of new applications remains on-going. This surprising physico-kinetic process offers great potential in novel reaction pathways for synthesis techniques and nanoparticle interactions, and it could prove to be a powerful cross-disciplinary research area among chemists, engineers, and physicists. In this review article, a survey of the history and recent usage of tribochemical reaction pathways is presented, with a focus on forging new compounds and materials with this sustainable synthesis methodology. In addition, an overview of tribochemistry’s current utility as a synthesis pathway is given and compared to that of traditional mechanochemistry.
... Meanwhile, mechanical ball-milling process is one of effective methods for cooperating with acid leaching process for the activation of ilmenite ore due to lowcost, room-temperature-operation and suitability for industrial scale. Based on this fact, acid leaching process accompanying mechanical milling and for TiO 2 production from ilmenite ore is of interest and practical due to the overall leaching limiting control by surface chemical reaction [17][18][19][20][21][22][23]. It is believed that the particle size and crystalline structure of ilmenite ore can be changed after ball-milling process relating to the increase of active site surface area and lattice strain. ...
In this work activated ilmenite nanoparticles were prepared by chemical-assisted in mechanical ball-milling process from ilmenite ore as starting raw material. The effect of milling process on their phase composition, particle size, surface morphology and local structure were investigated. Phase identification and crystalline structure of ilmenite mineral, milled samples and subsequent leached residues were characterized by x-ray diffraction (XRD). Meanwhile, the distorted octahedral structure and the oxidation state of relevant elements in ilmenite ore and activated ilmenite obtained by different process conditions were analyzed by x-ray absorption spectroscopy (XAS). Particle size and morphologies of the samples were monitored by field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). Three dominant peaks of TiO2 rutile, FeTiO3, and Fe2TiO4 are obviously adulterated in XRD patterns after mechanical milling with water and acid solution when comparing to precursor mineral. However, the contaminated phase of FeTiO3 and Fe2TiO4 was readily decreased by acid-assisted mechanical ball-milling. The enhancement in leaching process of ilmenite residue after milling can be obtained with sulfuric acid. This result suggests that iron contaminated phase could be leached from the sample resulting to the decrease in Fe environment around Ti atom.
... At high pO 2 and pS 2 , the behaviour of quaternary system could therefore be predicted by considering the reactions of the Fe-S and Fe-Ti-O sub-systems and an iron-rich liquid sulphide phase which was formed at higher temperature. More recently, Welham (1998) and Chen et al. (1996) carried out sulphidation experiments on ilmenite with sulphur at room temperature through ball milling action and found pyrite (FeS 2 ) and TiO 2 to be the stable phases after milling. Annealing of the products at 600uC showed the decomposition of pyrite to pyrrhotite in both experimental studies. ...
This study provides an assessment of the high temperature thermochemical reactions of ilmenite and chromite with sulphur and uses the information to analyse the possibility of selective sulphidation of chrome-bearing spinels as a new route for chromite removal from ilmenite concentrates. The work includes both systematic thermodynamic assessment and targeted experimental investigations. Thermodynamic calculation results studying the effect of reactants composition, temperature and different sulphur sources (H 2 S and elemental S) showed that chromite can be selectively sulphidised at a controlled atmosphere of partial pressure of oxygen (pO 2) below 10 210 atm and partial pressure of sulphur (pS 2) above 10 26 atm. The addition of carbon with sulphur was found to be useful for the chromite sulphidation reaction. The optimum quantity of sulphur reactant to carbon was found to be 3 : 1 (in mole) for 1 mol of chromite. Sulphidation experiments on a mixture of natural ilmenite and chromite at 1100uC for 5 h using 5%H 2 S as a sulphur source showed that the ilmenite was preferentially sulphidised first, which was also in a good agreement with the thermodynamic assessment. Sulphidation of a naturally occurring chrome spinel contaminated ilmenite concentrate showed that the degree of weathering also played a role in the sulphidation of the chrome spinel. It was also concluded that H 2 S is not suitable for selective sulphidation of chrome spinel from the ilmenite concentrate and that tightly controlled pS 2 and pO 2 conditions are required.
... The sextets with hyperfine field values of 51 T and 33 T correspond to hematite and to metallic Fe respectively. One of the three doublets, having the characteristic hyperfine parameters of natural ilmenite, appears together with the other two which only come out in ilmenite obtained by high-energy ball milling [23]. This effect could be due to the distorted structure and the small crystalline grains induced by the mechanical process. ...
The mechanochemical activation of Ti/Fe2O3 powder mixtures with molar ratio 1 and 1.5 was performed with the aim of understanding the effects of the starting composition on the reactivity and structure of the produced phases. The solid mixture was characterized by scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry and Mössbauer spectroscopy. The consumption of the reactants and the formation of metallic iron are observed at short activation times. After 3 h, the redox reaction completes, yielding a composite powder formed by nanocrystalline Fe particles dispersed in an oxide matrix. The mixture with the highest Ti/Fe ratio leads to the formation of a TiO2 matrix, whereas the other composition forms FeTiO3. Both composite materials have very high saturation magnetization and moderate coercivities. Under subsequent thermal treatment at 700 °C, the activated solids show a progressive crystalline ordering with partial oxidation of Fe (mainly to FeTiO3 and Fe2O3) and crystallization into the rutile phase of TiO2. This leads to a significant decrease of magnetization and coercivity.
The reserves of ilmenite are abundant in India; however, it needs to be upgraded to synthetic rutile. The carbothermic reduction is one of the most effective processing methods to produce TiO2. However, it is more energy intensive method as is carried out at high temperature. The present paper studies the carbothermic reduction of Manavalakurichi ilmenite concentrate by charcoal in the presence of sodium carbonate. The sodium carbonate as catalyst has significant effect on kinetics of reduction. It is able to save energy by reducing the reduction temperature for same degree of reduction at high temperature without catalyst.
A novel microwave roast process for synthesizing rutile TiO2 having high crystallinity from Panzhihua sulphate titanium slag is developed in the present work. Properties of samples at various stages of reactions including the crystal structure, microstructure and molecular structure, were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman techniques, respectively. The work also addressed the phase transformation of sulphate titanium slag before and after microwave heating. The result of XRD showed that under the microwave roasting process, the sulphate titanium slag was decomposed following acidification of the sodium titanates. The SEM analysis showed morphology transformations during the whole process and the short rod-like structure of rutile after the treatment. The Raman spectroscopy demonstrated that the peaks of 141 cm− 1, 254.8 cm− 1, 428.8 cm− 1, and 606.2 cm− 1 corresponded to the characteristic patterns of rutile TiO2. Based on the above results, this process could be an efficient way for rutile TiO2 preparation utilizing Panzhihua sulphate titanium slag.
The generic concept of “Thiometallurgy” was introduced showing that use of sulfur, both as afuel and as a reductant, facilitates efficient process design with low effluents including low green house gas emissions. The need to capture sulfur oxides, a by-product, as a result of oxidation during processing, is essential to offset the production cost. Thiometallurgy can beextended to the production of low cost titanium dioxide from titanium ores, ilmenite or oxidized iron containing leucoxene, using sulfur as a reductant. Titanium dioxide is needed in making many of the low cost titanium powder production technologies based on electrolysis/reductionof titanium oxides. Currently carbon is used as reductant in industry that produces CO2 closer to 11kg CO2/kg Ti metal but using sulfur has the potential to lower the emissions. The paper addresses the production of titanium dioxide with marketable by-products including least amount of waste and effluents. This approach of minimizing the cost makes this a “Sustainable production process”.
Upgrading of a low-grade titanium slag (∼55% TiO2) with high silica, calcia, magnesia and iron contents has been studied using sulphation roasting technique using SO2/air gas mixture followed by hydrochloric acid leaching. XRD analysis of the sulphated slag reveals the presence of kennedyite (Fe2O3. MgO. 3TiO2), rutile (TiO2), calcium sulphate (CaSO4) and calcium silicate (3CaO.SiO2) phases. The residue after leaching contains mainly kennedyite, rutile phases and free silica with traces of calcium silicate phase. Synthetic rutile that has about 83% TiO2 can be produced at the optimum conditions. Thermodynamic calculations give rational explanations of the obtained results.
In this paper, the effects of mechanical activation on the microwave absorbing characteristics of ilmenite were systematically investigated using the microwave cavity perturbation technique and the digital signal processing technique. The relationships between dielectric loss and the microwave absorbing characteristics of the mechanical activated ilmenite were studied. The crystal structures and surface chemical functional groups of ilmenite were characterized using XRD and FT-IR, respectively. The results indicated that the microwave absorbing characteristics of mechanical activated ilmenite are better than that of untreated ilmenite. The optimum experiment parameters were found as follows: mechanical activation time of 120 min.
Temperature rising characteristics of titania-rich slag under microwave irradiation were obtained. The effects of microwave power, mean particle sizes of samples and sample weight on temperature rising characteristics of titania-rich slag were systematically investigated. The crystalline compounds of sample before and after microwave heating were characterized by X-ray diffractometry. The results show that the titania-rich slag has a good microwave absorption property. The titania-rich slag sample can be reach 1200 °C after 60 min at 3.0 kW in microwave field. The XRD characterization results show that untreated titania-rich slag mainly consists of crystalline compounds of anatase TiO2 phase; while the microwave heating treated sample is mainly composed of crystalline compounds of rutile TiO2 phase. It can be inferred that anatase TiO2 phase is completely converted to rutile TiO2 phase in microwave heating.
Mechanochemistry as a branch of solid state chemistry enquires into processes which proceed in solids due to the application of mechanical energy. This provides a thorough, up to date overview of mechanochemistry of solids and minerals. Applications of mechanochemistry in nanoscience with special impact on nanogeoscience are described. Selected advanced identification methods, most frequently applied in nanoscience, are described as well as the advantage of mechanochemical approach in minerals engineering. Examples of industrial applications are given. Mechanochemical technology is being applied in many industrial fields: powder metallurgy (synthesis of nanometals, alloys and nanocompounds), building industry (activation of cements), chemical industry (solid waste treatment, catalyst synthesis, coal ashes utilization), minerals engineering (ore enrichment, enhancement of processes of extractive metallurgy), agriculture industry (solubility increase of fertilizers), and pharmaceutical industry (improvement of solubility and bioavailability of drugs). This reference serves as an introduction to newcomers to mechanochemistry, and encourages more experienced researchers to broaden their knowledge and discover novel applications in the field.
The work addresses phase transformation of titania slag using microwave irradiation. Properties of samples before and after microwave irradiation including thermal stability, crystal structures, microstructure, surface chemical functional groups and molecular structures, have been investigated by TG/DTA, XRD, SEM, FT-IR and Raman, respectively. The results of TG/DTA showed that titania slag have two phase transformation, one at 578.0 degrees C and another at 850.0 degrees C. It was confirmed that at roasting temperature in excess of 600 degrees C, anatase starts to transform as rutile. The property changes can be attributed to microwave irradiation, which causes the crystal transformation.
Anatase TiO2 powders used as photocatalysts were prepared by ball milling process at various milling time and annealed in nitrogen atmosphereat different temperatures. Commercial TiO2 powders were ball-milled with ethanol at room temperature. After ball milling process, the samples were annealed in nitrogen atmosphere. The particle sizes and surface area of milled powders were measured by particle analyzer and Brunauer Emmet Teller method(BET). Effect of milling time and annealing temperature on structural properties of TiO2 powders was investigated by X-ray diffraction(XRD) and scanning electron microscope(SEM). The degradation of aquous RhB dye by ball-milled TiO2 powder photocatalyst was investigated under UV light irradiation. Comparing to P-25, TiO2 powder prepared via ball milling process at 24 hr demonstrated significant enhancement in its photocatalytic activity under UV light due to the increasing active surface area after ball milling process.
Extractive metallurgy has used free or combined sulfur as both the raw material and the energy material in carrying out economical manufacture of several metals in millions of tons per year quantities over the past century. This has controlled carbon emissions in an unintentional fashion and out of necessity as the ores in many cases have been sulfides to start with. And the benefits of heat generation by the sulfides reacting with oxygen in the process steps have avoided the use of carbon as a fuel in providing the reaction temperatures. In this article, we will show the inherent benefits of "thiometallurgy," which uses sulfur in the extraction of metals in alleviating CO2 and water vapor-greenhouse gas (GHG) emissions, as well as its ability to provide a cost-effective energy material solution. Such solutions are not only applicable to existing base metal production but, as the authors will show, also are applicable to newer processes in the production of other metals and chemicals, such as alkaline earth metals, titanium, and to an extent aluminum in an indirect fashion. Iron ores can also be treated with thiometallurgy to meet the ULCOS criterion of ultra-low carbon dioxide steel being studied in Europe. The concept of generating "thiopower" as an alternative energy approach is also introduced by the authors.
In this work, response surface methodology (RSM) based on five-level,
three-variable, and central composite design (CCD) was used to optimize
the synthesis of synthetic rutile. With the TiO2 content as
the dependent variable, the effects of three independent variables, i.e.
temperature, time, and mass, were investigated. The effects of several
parameters on the TiO2 content were systematically
investigated to identify the optimal experimental conditions. In
addition, Raman spectroscopy was used to characterize the synthetic
rutile under the optimum condition. The results showed that the obtained
second-order polynomial equation explains adequately the non-linear
nature of the modeled response. The optimal conditions found to be at
the temperature of 1358.30 K, time of 58.77 min, and mass of 80.97 g.
Under optimum conditions, the predicted TiO2 content of
synthetic rutile was 88.81% while the experimental date was 88.16%. The
experimental value after process optimization was found to agree
satisfactory with the predicted value. The demonstration of response
surface methodology can be applied effectively and efficiently to the
synthesis processing of synthetic rutile.
In this present study, the effects of mechanical activation on the characterization of titania slag were systematically investigated. The crystal structures, surface chemical functional groups, and microstructure of the samples were characterized before and after mechanical activation using XRD, FT-IR, and Raman spectroscopy techniques, respectively. It was found that untreated titania slag under mechanical activation was mainly composed of Fe3Ti3O10 and rutile TiO2, but that of being treated by mechanical activation was mainly composed of Fe3Ti3O10, Ti2O3 and rutile TiO2. Ti2O3 is transformed partially from Fe3Ti3O10 under moderate mechanical activation conditions for 12 h. The demonstration of mechanical activation techniques can be applied effectively and efficiently to the treatment processing of titania slag.
Natural ilmenite samples (containing both FeTiO3 and Fe2Ti3O9 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 Mössbauer 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.
Mechanochemical reactions in the system FeTiO3 –Si have been investigated as functions of the powder composition and milling conditions, using x-ray diffraction and thermal analyses. Reduction reactions of FeTiO3 by Si were observed during room-temperature milling with the formation of α–Fe, amorphous SiOx, nanocrystalline TiO2, or intermetallic compounds, depending on the Si content. The mechanochemical reaction process consists of a mechanical activation stage and a reaction stage. Higher milling intensity leads to a shorter activation step and a higher reaction rate.
The mineral ilmenite (FeTiO3) has been ball milled at room temperature in air. The oxidation of ilmenite in the process of milling was investigated by examining the milled samples with powder X-ray diffractometry, X-ray fluorescence spectrometry and thermal analysis. The ilmenite was fully converted to thermally metastable Fe2Ti3O9 and γ-Fe2O3 phases after 100 h of ball milling in air. The oxidation process of an ilmenite in a pure thermally activated process consists of a slow low-temperature reaction (600 °C–1000 °C) with the formation of intermediate phases (Fe2Ti3O9 and Fe2O3) and the fast high-temperature reactions (> 1000 °C) with the production of the final stable phases(Fe2TiO5 and TiO2). The observed oxidation reaction during ball milling at room temperature corresponds to the low-temperature reaction in a thermally activated process. The high-temperature reactions were not observed during milling, even during a prolonged milling or under a higher milling intensity. It seems that the process of the oxidation of ilmenite induced by high energy ball milling is a non-equilibrium process and is favourable for the formation of thermally metastable phases.
Mechanical milling of a stoichiometric mixture of Bi2O3and V2O5yielded nanosized powders of bismuth vanadate, Bi2VO5.5(BiV). Structural evolution of the desired BiV phase, through an intermediate product (BiVO4), was monitored by subjecting the powders, ball milled for various durations to X-ray powder diffraction (XRD), differential thermal analysis (DTA), and transmission electron microscopic (TEM) studies. XRD studies indicate that the relative amount of the BiV phase present in the ball-milled mixture increases with increase in milling time and its formation reaches completion within 54 h of milling. Assynthesized powders were found to stabilize in the high-temperature tetragonal (γ) phase. DTA analyses of the powders milled for various durations suggest that the BiV phase-formation temperature decreases with increase in milling time. The nanometric size (30 nm) of the crystallites in the final product was confirmed by TEM and XRD studies. TEM studies clearly demonstrate the growth of BiV onBi2O3crystallites.
An ilmenite (FeTiO3) concentrate has been milled with sulfur in a laboratory-scale ball mill for 100 h under a variety of conditions. X-Ray diffraction and thermal processing have shown that reaction occurs within the mill forming pyrite (FeS2) and rutile (TiO2). The reaction was of greatest extent in a mill run under 400 kPa of inert gas; some reaction occurred in a mill under 10(-2) Pa, whereas little reaction was observed when either water or air was present. Annealing of the product powders showed that reaction to TiO2 and FeS2 could be achieved in a closed system after 1 h at 400 degrees C but with the evolution of SO2, whereas annealing at 800 degrees C also gave TiO2 and FeS2, but without formation of SO2 which was thought to have disproportionated to form iron sulfate(VI). Closed-tube annealing of unmilled sulfur and milled ilmenite showed the same reactions as milled powders but of much greater extent.
At the official dinner of a. meeting in May 1939, I was seated next to Max Hansen. When I congratulated him on the well deserved success of his "Aufbau der Zweistoff-Legierungen," he smiled: "yes, it was a struggle with the hydra, and so it has taken me seven years," meaning that whenever he had thought to have finished the phase diagram of a particular system, new evidence would turn up like the new heads of the Greek monster. There is no need to point out the importance of assessed phase diagrams to metallurgists or even anyone concerned with the technology and applica tion of metals and alloys. The information contained therein is fundamental to considerations concerning the chemical, physical and mechanical properties of alloys. Hansen's German monograph was followed by a revised English edition in 1958 with K. Anderko and the supplements by R.P. Elliott (1965) and F.A. Shunk (1969). All those who have made use of these volumes will admit that much diligent labour has gone into this work, necessary to cope with the ever increasing number of publications and the consequent improvements."
The system Fe-Sn has been studied by numerous authors [1‒14]. The diagram shown in Fig. 80 is essentially that suggested by Hansen [A]. Its main features are a broad miscibility gap in the liquid state above a monotectic temperature of 1,130°C [2, 7], a solution in γ(Fe) in the shape of a closed loop [3, 5, 11, 12], and five intermediary phases represented by the formulae Fe3Sn, Fe3Sn2, FeSn, FeSn2 and γ (NiAs structure).
The isomer shift and the quadrupole splitting of 57Fe in the pyrite-type dichalcogenides, FeS2-CoS2-NiS2-NiSe2 and CoSe2, were measured at room temperature. It is concluded that the effects of atomic distance and electronegativity of ligand make comparable contributions to the isomer shift of a divalent iron in low spin state. In high spin state, the contribution of atomic distance is smaller than that of electronegativity. The lattice term of electric field gradient gives a large contribution to the quadrupole splitting. The isomer shift and the quadrupole splitting of Fe1-yCoyS2 change around y=0.5 where the concentration dependence of resistivity changes. In NiS2-xSex, the quadrupole splitting of 57Fe becomes small with increasing x at the metal-semiconductor phase boundary.
Metal oxides are considered more thermally stable than metal nitrides. Thus for conventional nitriding processes that involve heating at high temperature in N[sub 2]/NH[sub 3] under pressure, it is impossible to produce nitrides in an atmosphere of oxygen. However, mechanical alloying has been well recognized as a process that produces non-equilibrium phases. In the case of gas-solid reactions, a supersaturated nitrogen solid solution and a high-temperature phase have been produced at room temperature. Further, TiN and ZrN, which are metastable compared with their corresponding oxides, have been formed by ball milling of pure elemental powders in a leaking mill into which air penetrated. It has also been reported that ball milling of titanium powder in air induced the formation of TiNO[sub 0.5]. These results suggest that oxidation is not always a dominant reaction and that nitridation can be more favorable under mechanical attrition. To study the possibility of nitridation reaction of an oxide, a crystalline silica SiO[sub 2] was ball milled in a pure nitrogen atmosphere. The crystalline silica structure is more reactive than an amorphous silica during milling. [alpha]-Si[sub 3]N[sub 4] is stable to oxidation reactions below 1,400 C.
Solid state room temperature reduction and exchange reactions of metal (M) sulphides are described. Reactions are driven by ball mining powder mixtures of the sulphide and the reductant (R) or exchange compound (CaO). Reduction reactions show a complete reduction of the metal sulphide with formation of M-Rsulphide nanocomposites. Exchange reactions with CaO show the formation of Moxide-CaS nanocomposites. Reactions having positive enthalpy or even positive free-energy changes in a wide temperature range are shown to occur. The effect of milling iron sulphide alone is also reported. Milling was performed for 24 h to assess the feasibility of the various reactions involved. X-ray diffraction and Mössbauer spectroscopy for iron-containing systems were used to characterize the powders before and after processing.
The occurrence of simple solid-state displacement reactions during mechanical alloying has been investigated. The reduction
of cupric oxide to pure copper metal by a variety of metallic reducing agents was studied, and the powders were examined by
X-ray diffractometry and electron microscopy. When milled with a liquid process control agent, the reaction progressed gradually
with time, whereas an unstable combustion reaction occurred when no such control agent was employed. A minimum adiabatic temperature
of 1300 K is necessary for combustion to occur in these systems. The reaction enthalpy is an important factor in determining
the precombustion period. The as-milled powders consisted of finely divided, nanometer-sized crystallites with an extremely
high defect density. It is proposed that the increased reactivity of the system arises through the unique conditions prevailing
during mechanical alloying.
Elemental powders of nickel and zirconium were mechanically alloyed over a wide concentration range 10 to 90 at % Zr. The amorphous single phase was formed over the range 20 to 80 at % Zr. The effect of the excessive mechanical alloying on the glass formation was studied by continuing ball-milling beyond the completion of the glass formation for the powders with the average compositions Ni30Zr70, Ni50Zr50 and Ni70Zr30. A partial crystallization took place in all three cases and its initiation was the fastest in Ni30Zr70 and was delayed with decreasing zirconium content. The critical factor for triggering the crystallization was attributed to the oxygen contamination for the zirconium-rich Ni30Zr70 powders and to the reduction in glass-forming ability for the nickel-rich Ni70Zr30 powders. The latter conclusion is drawn from the facts that the impurity concentrations arising from the debris of the stainless steel balls and the vial are gradually accumulated with increasing milling time and that the effective zirconium concentration is reduced below the critical concentration of approximately 20 at % as a result of alloying with the elements iron, chromium and nickel in the stainless steel.
Amrrdinn Purcrtt 241 110
- R G Iysk
- Bccher
May 21. IYSK.
151 R.G. Bccher. Amrrdinn
Purcrtt 241 110. IWd.
[hl R.Ci. Bucher. R.G. Canning. B.A. Gnodhuat and S. Uusna.
- J J Honn
- J A Barclay
J.J. Honn and J.A. Barclay. J. Appl. Cht. Rintechl..
25
(1975) %I.
- G Schaffcr
- P G Mccormick
G.B+ Schaffcr and P.G. McCormick. Metal/. Trmts. A. 31 (1990)
2789.
US fwrnr 2 YS-i,'7X Septcmbcr 27
- A J E Gaskin
- Ringwood
November 13. IYSh.
131 A.J. Gaskin and A.E. Ringwood, US fwrnr
2 YS-i,'7X Septcmbcr 27. 1960.
Amrrdinn Purcrtt 241 110. IWd
- R G Bccher
R.G. Bccher. Amrrdinn
Purcrtt 241 110. IWd.
[hl R.Ci. Bucher. R.G. Canning. B.A. Gnodhuat and S. Uusna.
Proc. Ausr. hr. Mh Mfr..,714 (INS) 21.
- P Mattuazzi
- G Lr Cacr
P. Mattuazzi and G. Lr Cacr. Mow, Sci. Eug. A. 1% (1992)
229.
'
Iron-Rinrrry Phuw Diqr
[ I6! 0. Kuhaschcwski.
Iron-Rinrrry
Phuw
Diqr[?nls.
Springer,
Serlin, 1982, p. 125.
Chemical Corporation, UK Patent 795 164
- Columbia-Southern
Australian Patent 241 110
- R G Becher