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This research focuses on optimising the process of preparing metallic dysprosium through calcinothermic reduction. The study employed response surface methodology (RSM) based on a central composite face-centred (CCF) design to model the interactive effects of three independent variables: reduction temperature, Ca/DyF3 molar ratio, and reduction time, on the dependent response, which was the reduction yield. Initially, experiments were conducted to determine the experimental matrix or planning region. Subsequently, experimental studies were carried out within this matrix to develop a quadratic response surface methodology - central composite face (RSM-CCF) model for the calcinothermic reduction of DyF3 using MODDE 5.0 software. The resulting model demonstrated good agreement between calculated and actual data, establishing a reliable framework for the calcinothermic reduction process. Further analysis involved assessing the contributions of the model’s coefficients to the dependent response to optimise the process. The findings indicate that reduction temperature plays a significant role in governing the calcinothermic reduction. The optimal parameters for the calcinothermic reduction of DyF3 were identified as a reduction temperature of 1450-1460°C, a reduction time of 50 minutes, and a Ca/DyF3 molar ratio of 2.15. Under these conditions, the maximum reduction yield achieved was 85.7%.

Calcium vapor reduction of niobium oxide compounds has been studied at temperatures from 1023 to 1123 K. The adiabatic temperature of calcium reduction of niobium pentoxide (3020 K) and the Mg4Nb2O9 niobate (2525 K) has been determined by thermodynamic modeling with the TERRA software suite. We have assessed the effects of process temperature, reduction time, and precursor powder particle size on the degree of reduction, specific surface area, and pore structure of the niobium powders. [ABSTRACT FROM AUTHOR]

Calcium vapor reduction of Ta2O5 and Mg4Ta2O9 has been studied at temperatures from 750 to 850°C. We have found out specific features of the pore structure of the calciothermic tantalum powders and assessed the effect of precursor particle size on the degree of reduction. To reduce the Mg4Ta2O9 tantalate with an average particle size of 2 μm, holding at a temperature of 800°C for at least 4 h was needed. Reducing the average particle size to 0.15 μm allowed us to reach complete reduction at a temperature of 750°C in just 1 h. [ABSTRACT FROM AUTHOR]

In this study, calciothermic single phase iron boride(Fe2B) production was investigated in a scalable molten salt system, starting from inexpensive, easily accessible oxide materials. First, the formation of Fe2B was examined in detail in the light of thermodynamic data and literature. After, effects of CaO amount (0-10 wt.%) and time (30-60 min) on particle synthesis were investigated under at constant 3.0 V cell voltage and 1273 K temperature. It was determined that the average current increased continuously with the increase in the amount of CaO, and the current efficiency increased up to 7% by weight of CaO. After the CaO ratio was determined, the effect of the electrolysis duration was examined. In durations experiments, it has been observed that, in 30 minutes’ duration, the particles are composed of Fe, Fe2B and FeB, and by increasing the experiment time to 60 min, single-phase Fe2B particles are obtained. The magnetic properties of the single-phase Fe2B particles obtained at the end of the experiment period of 60 minutes were investigated by VSM. The saturation magnetization, permanent magnetization and coercivity values of the Fe2B particles were determined as 90.718 emu/g, 33.311 Oe, 1.684 emu/g, respectively.

An aging global population is accelerating the need for better, longer-lasting orthopaedic and dental implants. Additive manufacturing can provide patient-specific, titanium-alloy-based implants with tailored, three-dimensional, bone-like architecture. Studies using two-dimensional substrates have demonstrated that osteoblastic differentiation of bone marrow stromal cells (MSCs) is enhanced on surfaces possessing hierarchical macro/micro/nano-scale roughness that mimics the topography of osteoclast resorption pits on the bone surface. Conventional machined implants with these surfaces exhibit successful osseointegration, but the complex architectures produced by 3D printing make consistent nanoscale surface texturing difficult to achieve, and current line-of-sight methods used to roughen titanium alloy surfaces cannot reach all internal surfaces. Here, we demonstrate a new, non-line-of-sight, gas/solid-reaction-based process capable of generating well-controlled nanotopographies on all open (gas-exposed) surfaces of titanium alloy implants. Dense 3D-printed titanium-aluminum-vanadium (TiAl6V4) substrates were used to evaluate the evolution of surface nanostructure for development of this process. Substrates were either polished to be smooth (for easier evaluation of surface nanostructure evolution) or grit-blasted and acid-etched to present a microrough biomimetic topography. An ultrathin (90 ± 16 nm) conformal, titania-based surface layer was first formed by thermal oxidation (600 °C, 6 h, air). A calciothermic reduction (CaR) reaction (700 °C, 1 h) was then used to convert the surface titania (TiO2) into thin layers of calcia (CaO, 77 ± 16 nm) and titanium (Ti, 51 ± 20 nm). Selective dissolution of the CaO layer (3 M acetic acid, 40 min) then yielded a thin nanoporous/nanorough Ti-based surface layer. The changes in surface nanostructure/chemistry after each step were confirmed by scanning and transmission electron microscopies with energy-dispersive X-ray analysis, X-ray diffraction, selected area electron diffraction, atomic force microscopy, and mass change analyses. In vitro studies indicated that human MSCs on CaR-modified microrough surfaces exhibited increased protein expression associated with osteoblast differentiation and promoted osteogenesis compared to unmodified microrough surfaces (increases of 387% in osteopontin, 210% in osteocalcin, 282% in bone morphogenic protein 2, 150% in bone morphogenic protein 4, 265% in osteoprotegerin, and 191% in vascular endothelial growth factor). This work suggests that this CaR-based technique can provide biomimetic topography on all biologically facing surfaces of complex, porous, additively manufactured TiAl6V4 implants. [ABSTRACT FROM AUTHOR]

We have studied characteristics of powders prepared by nitriding products of calcium vapor reduction of Ta2O5, Nb2O5, Mg4Та2O9, and Mg4Nb2O9. The process was run in two steps: (1) reduction of the oxide compounds at 750, 800, 850, and 900°C for 1–6 h and (2) holding of the reduction products in a nitrogen atmosphere at the same temperatures for 1–5 h. The use of Ta2O5 as a precursor led to the formation of products containing, in addition to tantalum, the θ-TaN and Ta2N nitrides. Tantalum nitrides were difficult to synthesize from Mg4Та2O9 reduction products. If Nb2O5 was used as a precursor, the nitridation products contained, in addition to niobium, the NbN and Nb2N nitrides with hexagonal close-packed lattices. In the case of nitridation of Mg4Nb2O9 reduction products, the percentage of the nitrides was a factor of 6–10 smaller than in the case of reduction and nitridation of niobium pentoxide, which can be accounted for in terms of specific features of the pore structure of the powders. Raising the reduction temperature from 750 to 850°C reduced the specific surface area of the nitrided powders from 26.2 to 11.6–14.5 m2/g. The powders had a mesoporous structure. [ABSTRACT FROM AUTHOR]

Uranium ingot is produced by metallothermic reduction of uranium tetrafluoride using magnesium or calcium as reductant. Presence of oxygen containing compounds viz. uranyl fluoride and uranium oxide in the starting uranium fluoride has a significant effect on the firing time, final temperature of the charge, slag-metal separation and hence the metal recovery. As reported in the literature, the maximum tolerable limit for uranyl fluoride in the UF4 is 2.5 wt% and limit for uranium oxide content is in the range 2–3 wt%. No theoretical or experimental basis is available till date for these limits. Analyses have been carried out in this study to understand the effect of UO2F2 concentration in the starting fluoride on the final temperature of the products and thus the reduction characteristics. UF4 having uranyl fluoride concentration, less than as well as more than 2.5 wt%, have been investigated. Thermodynamic calculations have been carried out to arrive at a general expression for the final temperature attained by the products during calciothermic reduction of UF4. Finally, an upper limit for the oxygen containing impurities has been estimated using the CaO–CaF2 phase diagram.

The synthesis of group IV transition metals (TMs) such as Ti, Zr, and Hf from their respective oxides (TMO 2) poses significant challenges with current methods. There is an urgent need for an environmentally friendly and versatile approach to establish sustainable, efficient, and adaptable TM synthesis technology from TMO 2. In this study, the LN process (Lee-Nersisyan), a novel and straightforward approach that employs CaMg 2 as the reductant for TMO 2 powders is introduced. This innovative strategy involves the thermal processing of TMO 2 + k CaMg 2 mixtures (with k values ranging from 2 to 5 moles) in an argon atmosphere at temperatures between 800 and 1200 °C. The process yields high-purity TM powder with particle sizes in the range of 5–25 μm and oxygen content of less than 0.2 wt%. We apply density-functional theory (DFT) to elucidate the interaction energies and equilibrium interatomic distances between Ti-Ca, Ti-Mg, Ca-Mg, Mg-Mg, Ca-Ca, and Ti-Ti metallic pairs. Additionally, we discuss the growth behavior of TM particles through molecular dynamics simulation (MD) employing LAMMPS. Our LN process represents a promising solution for efficient and sustainable TM synthesis from TMO 2. • An innovative method for producing TM (Ti, Zr, Hf) powders from oxides is presented. • Utilizing CaMg 2 as reductant results TM particles with 0.2 wt% of oxygen is obtained. • Calciothermic reduction of TMO 2 is found to be the primary driving force of reaction. • The interaction energies and interatomic distances of M-M pairs are calculated by DFT. • TM particles sintering and growth behavior based on MD simulation is highlighted. [ABSTRACT FROM AUTHOR]

The processes of calciothermic reduction of metals from iron (FeTa2O6) and manganese (MnTa2O6) tantalates as well as tantalum oxide (Ta2O5) were studied in this work. According to the results of thermodynamic analysis performed in the temperature range of 373–2773 K, the interaction of FeTa2O6 and MnTa2O6 with calcium proceeds with complete reduction of metals. The calculation and comparison of the logK equilibrium constants for the reactions of alumino- and calciothermic reduction of iron and manganese tantalates showed the thermodynamic advantage of using metallic calcium as a reducing agent. Experimental investigations of calciothermal reduction on samples of synthesized oxides were carried out by the method of combined thermogravimetry and differential thermal analysis in the mode of nonisothermal heating to 1473 K in an argon flow. X-ray powder diffraction was used to determine the phase composition of the initial samples and interaction products. It was shown that the calciothermic reduction of metals from the synthesized manganese tantalate proceeds actively at temperatures above 1196 K, while iron tantalate and tantalum oxide with the appearance of molten calcium. Tantalum and its solid solutions with iron or manganese, corresponding to the structural type Ta7Fe6, were included in the main metal components of the products of the interaction of FeTa2O6 and MnTa2O6 with calcium. [ABSTRACT FROM AUTHOR]

In this study, calciothermic single phase iron boride(Fe2B) production was investigated in a scalable molten salt system, starting from inexpensive, easily accessible oxide materials. First, the formation of Fe2B was examined in detail in the light of thermodynamic data and literature. After, effects of CaO amount (0-10 wt.%) and time (30-60 min) on particle synthesis were investigated under at constant 3.0 V cell voltage and 1273 K temperature. It was determined that the average current increased continuously with the increase in the amount of CaO, and the current efficiency increased up to 7% by weight of CaO. After the CaO ratio was determined, the effect of the electrolysis duration was examined. In durations experiments, it has been observed that, in 30 minutes’ duration, the particles are composed of Fe, Fe2B and FeB, and by increasing the experiment time to 60 min, single-phase Fe2B particles are obtained. The magnetic properties of the single-phase Fe2B particles obtained at the end of the experiment period of 60 minutes were investigated by VSM. The saturation magnetization, permanent magnetization and coercivity values of the Fe2B particles were determined as 90.718 emu/g, 33.311 Oe, 1.684 emu/g, respectively. [ABSTRACT FROM AUTHOR]

The reduction of TiO2 and CaTiO3 in a mixture with calcium has been studied in an argon atmosphere and vacuum at temperatures in the range 1023–1123 K. The adiabatic temperature of the reduction reactions involved has been calculated as a function of the excess of calcium in the starting mixture and its initial temperature. The presence of a thin CaCl2 film on calcium particles and the use of calcium titanate as a precursor have been shown to increase the reduction rate. The use of a CaTiO3 precursor and CaCl2-activated calcium has made it possible to obtain titanium powders containing 0.5 wt % oxygen and having a specific surface area of 1.2 m2/g via reduction at a temperature of 1073 K for 6 h. [ABSTRACT FROM AUTHOR]

For several decades, the metallurgical industry and the research community worldwide have been challenged to develop energy-efficient and low-cost titanium production processes. The expensive and energy-consuming Kroll process produces titanium metal commercially, which is highly matured and optimized. Titanium’s strong affinity for oxygen implies that conventional Ti metal production processes are energy-intensive. Over the past several decades, research and development have been focusing on new processes to replace the Kroll process. Two fundamental groups are categorized for these methods: thermochemical and electrochemical. This literature review gives an insight into the titanium industry, including the titanium resources and processes of production. It focuses on ilmenite as a major source of titanium and some effective methods for producing titanium through extractive metallurgy processes and presents a critical view of the opportunities and challenges.

We have determined the adiabatic temperature of the calcium reduction of ZrO2 and CaZrO3 (1525 and 1040 K, respectively) and the reaction onset temperature. In a mixture of reagents under an argon atmosphere in a reactor, it is about 1123 K and is determined by the calcium melting onset. If calcium particles with CaCl2 film on their surface are used as a reducing agent, reduction begins at a temperature of 1023 K in an argon atmosphere and at 973 K in vacuum. By reduction for 3 h at a temperature of 1023 K, we have obtained zirconium powder containing 0.36% oxygen and having a specific surface area of 0.35 m2/g. [ABSTRACT FROM AUTHOR]

Combustion of thermite TiO2/ZrO2–Ca mixtures in nitrogen gas was studied upon variation in green composition and nitrogen pressure P in the presence/absence of added calcium iodate Ca(IO3)2. The addition of calcium iodate was found to increase combustion temperature and extend combustibility limits. For compositions in which calcium was completely replaced by calcium nitride Ca3N2, the combustion temperature decreased with increasing P. The combustion of ZrO2 was found to proceed in two stages, the first stage being associated with the decomposition and gasification of calcium iodate. [ABSTRACT FROM AUTHOR]

Abstract This paper reports the preparation of Ti microparticles that are angular and spherical in shape through the combustion of a TiO 2 + αCa (where α is moles of Ca) exothermic mixture in an inert atmosphere. The relationship between the combustion parameters and the properties of the resultant Ti particles is discussed with consideration of the effect of Ca concentration. Using excess amounts of Ca in the experiment was effective in modifying the shape of the particles from angular to spherical. The Ti powder was found to be well-dispersed and the diameter of individual particles ranged from 5 µm to 50 µm. Based on the combustion parameters, the activation energy for the redox reaction was calculated as ∼ 138 kJ/mol. This paper discusses the chemistry of the reduction process and highlights the effects of combustion temperature and the amount of liquid calcium on the characteristics of the Ti particles. Graphical abstract The combustion process in TiO 2 + Ca mixture developed a maximum temperature of about 1820 °C and resulted in Ti spherical particles. fx1 [ABSTRACT FROM AUTHOR]

Abstract A new process to fabricate porous titanium by calcium vapor in-situ reduction of titanium sespuioxide was presented in this paper. The mixture of Ti 2 O 3 and CaCl 2 powders was preformed and reduced by calcium vapor. The porous titanium structure was obtained after leaching reduction products with hydrochloric acid and deionized water. The pore structure, morphology, composition of reduction products were investigated by SEM-EDS and XRD. The influence of different contents of anhydrous calcium chloride on porosity was discussed. The results show metallic titanium products with two types of pore structures and vacuum sintering treatment strengthened effectively connection between titanium particles. The porosity of porous titanium samples was 62%–82% and more than 90% of pores are open-pores. Highlights • A facile method was proposed to preparation of porous titanium by using Ti 2 O 3. • The diameter of closed-loop pore is about 5–10 μm and tunnel diameter is about 25–120 μm in porous titanium sample. • Over 90% of pores are open-pores and the porosity of samples are the range of 62%–82%. • With the increase of CaCl 2 in raw materials, the porosity of samples would become bigger gradually. [ABSTRACT FROM AUTHOR]

This study reports a room temperature mechanochemical route for the synthesis of LaB6 powders originated from related metal oxide powders as La2O3 and B2O3. Ca granules and B2O3 powders were respectively used as reducing agent and boron source in the experiments. This study is actually meaningful to create added value by using the native boron source of Turkey for the production of high-technology boron materials. Milling duration as the most important parameter of mechanochemistry was examined to reveal the ideal production conditions. Mechanochemically synthesized powders were subjected to selective HCl leaching in order to eliminate unwanted phases. Thermochemical software of HSC ChemistryTM program was utilized to determine the reaction probability and to estimate the predicted products. Characterization investigations were carried out by X-ray diffractometer (XRD), differential scanning calorimeter (DSC), particle size analyzer (PSA), stereomicroscope (SM), scanning electron microscope (SEM), transmission electron microscope/energy dispersive spectrometer (TEM/EDS) and atomic absorption spectrometer (AAS). Nanosized LaB6 powders were achieved with/without an insignificant amount of Ca3(BO3)2 phase via mechanochemistry in a high-energy ball mill for 3 h and via leaching with 4 M and 6 M HCl. Lastly, the experimental outputs obtained by a calciothermic reduction were compared with those of magnesiothermic reduction.

A metallurgical material integration concept, using porous calcium titanate (CaTiO 3 ) as raw material, was put forward for preparation of metallic titanium powder and porous titanium by calciothermic reduction. Porous metallic titanium was prepared by calcium vapor reduction at 1273 K for 6 h with two types of interconnected pores in titanium samples. The interconnected macropores about 50–300 μm were inherited from porous CaTiO 3 , and the micropores about 5–40 μm were made by leaching removal of byproduct CaO in reduction products. Metallic porous titanium was fabricated in Ca-dissolved CaO-CaCl 2 molten salt mixtures by self-sintering and had a good interconnectivity inside with thickness about 155 μm and the porosities of the porous titanium are 65–81%. [ABSTRACT FROM AUTHOR]

The compound CaCl2 plays a significant role in the process of direct calciothermic reduction of Ti2O3 to prepare porous titanium. In this paper, the effect of CaCl2 on reduction products by calciothermic reduction of Ti2O3 was investigated. Results show that the distribution of CaCl2 in reduction preform influences particle size and morphology differences in reduction products both on the surface and the inside. The CaCl2 is transferred to the surface of the Ti2O3 preform due to its volatilization before and throughout reduction. The content of CaCl2 in the surface zone of Ti2O3 preform is significantly higher than that in the interior during the reduction process, contributing to the formation of large Ti particles with a smooth shape on the surface, and small Ti particles with inherited morphology of Ti2O3 inside. More CaCl2 causes the aggregation of Ti particles to form large Ti particles which are advantageous as they connect and form a more solid porous titanium structure. The presence of a small amount of CaCl2 in the interior also results in the coexistence of small Ti and CaO particles, forming a loose structure with uniform distribution. [ABSTRACT FROM AUTHOR]

A new branched morphology of metallic niobium powder particles was produced by calciothermic reduction of niobium oxides in molten CaCl 2 . The influence of some reaction parameters on the powder particle morphology was studied, and the formation mechanism was investigated. It was found that the formation of intermediate complex niobium oxides (Ca x Nb 2 O y ) was crucial in the formation of niobium powder particles with the branched morphology. Based on this finding, the formation mechanism of the branched morphology in four stages was proposed. These Nb powder particles with microscopic branches can prevent particle sintering during the fabrication process of electric capacitors, allowing the latter to exhibit a higher capacitance. [ABSTRACT FROM AUTHOR]

The compound CaCl2 plays a significant role in the process of direct calciothermic reduction of Ti2O3 to prepare porous titanium. In this paper, the effect of CaCl2 on reduction products by calciothermic reduction of Ti2O3 was investigated. Results show that the distribution of CaCl2 in reduction preform influences particle size and morphology differences in reduction products both on the surface and the inside. The CaCl2 is transferred to the surface of the Ti2O3 preform due to its volatilization before and throughout reduction. The content of CaCl2 in the surface zone of Ti2O3 preform is significantly higher than that in the interior during the reduction process, contributing to the formation of large Ti particles with a smooth shape on the surface, and small Ti particles with inherited morphology of Ti2O3 inside. More CaCl2 causes the aggregation of Ti particles to form large Ti particles which are advantageous as they connect and form a more solid porous titanium structure. The presence of a small amount of CaCl2 in the interior also results in the coexistence of small Ti and CaO particles, forming a loose structure with uniform distribution.

The reduction of yttrium fluoride (YF3) by calcium in a molybdenum crucible was investigated. A visual observation technique was used to monitor the reduction process. It was observed that the reaction initiated immediately after the melting of calcium. Based on the results, a two-step reduction sequence was attempted. First, the charge was heated to 950°C to minimise the calcium loss by vaporisation and to ensure completion of reaction. The products were then fast heated to 1600°C for slag/metal separation. Molybdenum content of yttrium was found to be in a range of 3.5-4.75 wt-%, which is much lower than the equilibrium content predicted by Mo-Y phase diagram. The yttrium/molybdenum interface was studied using an electron probe microanalyser, which confirmed that the overall equilibrium was not reached, indicating the possibility of lowering the molybdenum contamination further by process optimisation. [ABSTRACT FROM AUTHOR]

This study reports a room temperature mechanochemical route for the synthesis of LaB6 powders originated from related metal oxide powders as La2O3 and B2O3. Ca granules and B2O3 powders were respectively used as reducing agent and boron source in the experiments. This study is actually meaningful to create added value by using the native boron source of Turkey for the production of high-technology boron materials. Milling duration as the most important parameter of mechanochemistry was examined to reveal the ideal production conditions. Mechanochemically synthesized powders were subjected to selective HCl leaching in order to eliminate unwanted phases. Thermochemical software of HSC Chemistry™ program was utilized to determine the reaction probability and to estimate the predicted products. Characterization investigations were carried out by X-ray diffractometer (XRD), differential scanning calorimeter (DSC), particle size analyzer (PSA), stereomicroscope (SM), scanning electron microscope (SEM), transmission electron microscope/energy dispersive spectrometer (TEM/EDS) and atomic absorption spectrometer (AAS). Nanosized LaB6 powders were achieved with/without an insignificant amount of Ca3(BO3)2 phase via mechanochemistry in a high-energy ball mill for 3 h and via leaching with 4 M and 6 M HCl. Lastly, the experimental outputs obtained by a calciothermic reduction were compared with those of magnesiothermic reduction. [ABSTRACT FROM AUTHOR]

Explored was the phenomenology of calciothermic reduction in model green mixtures containing metal oxides with strong (TiO) and weak (MoO) Me-O bonds. In case of high affinity metal (Ti), the process occurs in two stages: (1) combustion reaction of Ca with N yielding calcium nitride and (2) calciothermic reduction of TiO to give TiN. In case of low affinity metal (Mo), the above reactions proceed in parallel, without noticeable time delay. [ABSTRACT FROM AUTHOR]

Submicrometer-sized Sm-Co powders have been prepared by the calciothermic reduction and subsequent solid-state diffusion of a nanostructured Sm-Co-O/Co-O precursor. The Sm and Co containing precursor was prepared by an autocombustion process. X-ray diffraction identified the product as a mixture of SmCoO3 and Co3 O4. This powder was mixed in a 1:2 mass ratio with CaO (which served as a thermal ballast and aggregation inhibitor) and milled to reduce the particle size below 1 micrometer. Ca metal was added to the mixed powder in amounts between 2 and 6 times those required to reduce the Sm and Co oxides, and sealed in Nb tubes for heat treatment at 900^\circC for various lengths of time. After cooling to room temperature, metallic Sm-Co particles were isolated from the undesired reaction products by a series of washing steps in acetic acid and ethyl alcohol. [ABSTRACT FROM AUTHOR]

Abstract: A nitriding method defined as, “calciothermic assisted immersion nitriding (CAIN)” has been developed to modify the surface of titanium alloys and improve their tribological properties. The CAIN process described here involves the heat treatment of titanium alloy specimens (Ti–6Al–4V) in an air environment within a sealed vessel containing a molten flux of calcium and calcium chloride, resulting in the preferential diffusion of nitrogen atoms into the samples. The nitriding process was found to produce a consistent TiCxNyOz surface layer, where the exact chemical composition was dependent on the processing conditions. The tribological properties of the surface layers were tested using a high frequency reciprocating rig under dry lubrication conditions and demonstrated that the CAIN process can be used to produce layers with good adhesion to the Ti–6Al–4V substrate and wear resistance comparable to industrially produced physical vapour deposition (PVD) coatings. [Copyright &y& Elsevier]

To develop an effective process for titanium powders production, a calciothermic reduction process of pigment titanium dioxide ( w(TiO)>98%), based on the preform reduction process (PRP), was investigated by means of XRD, SEM and EDS. In this process, the mixture of TiO powder and CaCl was pressed into pieces as feed preform and was reduced by calcium vapor. Titanium powders was recovered after leaching from the reduced preform with hydrochloric acid and deionized water. The results indicate when the mass ratio of CaCl to TiO is about 1:4 and at a constant temperature of 1 273 K for 6 h in vacuum furnace, titanium powders with 99.55% purity by EDS analysis and irregular shape (8-15 μm in particle size) are obtained. [ABSTRACT FROM AUTHOR]

Investigated was the effect of particle size of starting powder material on the calciothermic reduction of TiO in the TiO-Ca system. According to XRD results, TiO did not react with Ca after 40 h of ball milling. DTA data indicated that a decrease in the particle size of starting material resulted in lower reaction temperatures between molten Ca and TiO (decrease from 1073 to 1044°C). The XRD results showed that titanium metal can be produced from nanosized starting material, and the reduction reaction progressed at lower temperatures upon a decrease in the particle size of TiO. Also, the particle size of the products decreased with decreasing particle size of starting TiO. The concentration of residual oxygen depended on the particle size of TiO due to increasing surface of contact with deoxidizer (Ca). [ABSTRACT FROM AUTHOR]

Abstract: A new production system for rare-earth-based hydrogen storage alloys is proposed. We applied self-ignition combustion synthesis (SICS) utilizing hydrogenation heat of metallic calcium. The required primary energy and total exergy loss (EXL) for the production of 1kg of LaNi5 alloy with the proposed and conventional systems were evaluated. The results revealed that the production of raw materials accounted for more than 90% of the total EXL in both systems. Specifically, the use of calcium had decisive effects on the total EXL of the system for producing LaNi5 alloy. The proposed system reduced the total EXL by 14.6MJ/kg-LaNi5 as compared with the conventional system. The SICS was remarkably exergy-saving because the heating temperature was decreased by utilizing the hydrogenation heat of calcium and the product absorbed hydrogen without an activation treatment. [Copyright &y& Elsevier]

Abstract: Metallic nickel powders with low and uniform residual oxygen content were produced from NiO using the molten salt electrolysis of CaO in CaCl2 melt. Suitable amount of CaO for the reduction was in the range of 0.5–3.0mol% CaO. The electrical isolation of NiO from both electrodes could produce metallic Ni in CaCl2 melt. Separating the metal oxides from the cathode confirmed the mechanism of calciothermic reduction that the electrolysis of dissolved CaO in CaCl2 melt produces Ca, and that the dissolved Ca in molten CaCl2 successfully reduces NiO to metallic Ni. An average of about 600ppm oxygen in Ni sample was achieved directly from oxide, when NiO was detached from the cathode. [Copyright &y& Elsevier]

Abstract: This paper describes self-ignition combustion synthesis (SICS) of LaNi5 in a pressurized hydrogen atmosphere using metallic calcium as both the reducing agent and the heat source. In this study, the effects of hydrogen on the ignition temperature and the hydrogenation properties of the products were mainly examined. In the experiments, La2O3, Ni, and Ca were dry-mixed in the molar ratio of 1:10:6 and then heated up at a hydrogen pressure of 1.0MPa until the ignition due to the hydrogenation of calcium. For the sake of comparison, the same experiments were performed in a normal argon atmosphere. The results showed that the ignition temperature was drastically lowered by hydrogen; it was only 600K in the case of hydrogen as compared to 1100K in the case of argon. The products also exhibited high initial activity and hydrogen storage capacity of 1.54mass%. The proposed method offers many benefits for using cost-effective rare-earth oxide, saving productive time and energy, improving initial activity of the product and applying to any AB5-type hydrogen storage alloy. [Copyright &y& Elsevier]

The effect of oxygen partial pressure and basicity on the solubility of Sc 2 O 3 in the CaO–CaCl 2 flux is studied. As a result, the solubility of Sc 2 O 3 only depends on basicity of the flux and the stable ionic state of which is ScO 2.5 2 − . The thermodynamic simulation on the alloy composition of calciothermic reduction is also studied and shows consistency with experimental results. [ABSTRACT FROM AUTHOR]

Abstract: Hafnium oxide was reduced to metal by using Ca dissolved in the molten CaCl2–NaCl mixture. The investigations were carried out at a temperature lower than the melting point of Ca which ensured minimum reductant loss through evaporation .The oxygen content in the produced metal was lowered under 1000ppm level and it was highly depended on the amount of Ca and the amount of salt. Various salt compositions have been studied in order to select the best composition for the reduction process and it was found that the system containing 30mol% NaCl could produced hafnium metal with 960ppm oxygen. [Copyright &y& Elsevier]

Sm 2 Fe 17 alloy was prepared via direct calciothermic reduction using SmF 3 as raw material and iron as inducer. [Display omitted] • A novel method for preparing Sm 2 Fe 17 alloy was proposed by iron-induced SmF 3 through calciothermic reduction. • Sm 2 Fe 17 alloy with low content of impurities calcium and oxygen was prepared. • The optimum technological parameters for Sm 2 Fe 17 alloy fabrication were determined. • The induced mechanism of iron on preparing Sm 2 Fe 17 alloy was investigated. SmF 3 cannot be directly reduced to metallic samarium by calcium. In this work, we presented the thermodynamic calculation and preperation of Sm 2 Fe 17 alloy by calciothermic reduction. The composition, crystal structure, elements distribution, chemical valence and induced mechanism of Sm 2 Fe 17 alloy were analyzed and characterized by ICP, XRD, SEM, EDS and XPS. The results show that the feasibility of preparing Sm 2 Fe 17 alloy by iron-induced SmF 3 calciothermic reduction. The Sm and Fe component of SmFe alloy approximates the nominal composition of Sm 2 Fe 17 alloy with 10% excess of SmF 3 over the stoichiometry. The micrograph of the SmFe ingot exhibits fish-bone-like morphology and is composed of α-Fe, Sm 2 Fe 17 and SmFe 3 phases. The Sm and Fe elements of the samples demonstrate zero valency. Electrons from metallic Sm are drawn toward to the orbits of Fe and an Sm-Fe bond with ionic bond property is formed and being reduced by calcium to obtain Sm 2 Fe 17 alloy. [ABSTRACT FROM AUTHOR]

For several decades, the metallurgical industry and the research community worldwide have been challenged to develop energy-efficient and low-cost titanium production processes. The expensive and energy-consuming Kroll process produces titanium metal commercially, which is highly matured and optimized. Titanium's strong affinity for oxygen implies that conventional Ti metal production processes are energy-intensive. Over the past several decades, research and development have been focusing on new processes to replace the Kroll process. Two fundamental groups are categorized for these methods: thermochemical and electrochemical. This literature review gives an insight into the titanium industry, including the titanium resources and processes of production. It focuses on ilmenite as a major source of titanium and some effective methods for producing titanium through extractive metallurgy processes and presents a critical view of the opportunities and challenges. [ABSTRACT FROM AUTHOR]

A combined process of electrolysis of CaO in molten CaCl2 and calciothermic reduction, the so called OS process, was applied to prepare metallic vanadium directly from V2O3. Fine metallic powder containing 1860 wt ppm oxygen was obtained using a 0·5 mol.-%CaO–CaCl2 melt following processing for 10·8 ks (3 h) at 1173 K. The oxygen level did not decrease further even when the applied charge was doubled. Because metallic vanadium can be electrochemically deoxidised to 10 ppm oxygen from 1·48%, the high oxygen content in the reduced powder was attributed to the large amount of byproduct CaO due to reduction and the large surface area of the fine particles. [ABSTRACT FROM AUTHOR]

A combined process of electrolysis of CaO in molten CaCl2 and calciothermic reduction, the so called OS process, was applied to prepare metallic vanadium directly from V2O3. Fine metallic powder containing 1860 wt ppm oxygen was obtained using a 0·5 mol.-%CaO–CaCl2 melt following processing for 10·8 ks (3 h) at 1173 K. The oxygen level did not decrease further even when the applied charge was doubled. Because metallic vanadium can be electrochemically deoxidised to 10 ppm oxygen from 1·48%, the high oxygen content in the reduced powder was attributed to the large amount of byproduct CaO due to reduction and the large surface area of the fine particles. [ABSTRACT FROM AUTHOR]

Abstract: Almost single-phase ternary Ni50Ti50−x Zr x alloys with x =5 and 10at.% zirconium nominal contents have been successfully produced using the alternative powder metallurgical VPCR process. This process, based on the solid-state sintering of Ni, TiH2 and ZrH2 powder mixtures under highly reducing atmosphere (Ca reducing vapor), prevents efficiently the complex oxide formations. Furthermore, the produced Ni50Ti50−x Zr x alloys do not show the well-known secondary intermetallic phases belonging to the binary Ni–Ti and Ni–Zr systems as well as to the ternary Ni–Ti–Zr system. X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray (SEM/EDS) analyses show that the chemical homogeneity of the produced NiTiZr alloys was similar to that of corresponding melt-cast alloys but some residual porosity was still present. [Copyright &y& Elsevier]

Abstract: “Broccoli”-like morphology of Ta powder was found when Ca reduces Ta2O5 in the molten CaCl2. It consisted of fine particles and branches, and it was different from the conventional spherical particles. The formation of this morphology depended on the stacking methods of the starting materials. Eight types of filling methods proved that the branch was formed when the CaO-enriched region was locally produced near the oxide. [Copyright &y& Elsevier]

Abstract: Ti-rich NiTi shape-memory alloys have been fabricated from elemental powders using an alternative powder metallurgical method based on the use of a reducing metal vapor during sintering. The produced alloys show high chemical homogeneity, low porosity and large shape-memory effects with recovery strains up to 3.9% for an applied stress of 80MPa. [Copyright &y& Elsevier]