Carbothermal Method Research Articles

Fabrication of a TiC0.5O0.5 anode using the carbothermal method under a non-vacuum atmosphere and its application in metal titanium electrolysis

Fabrication of a TiC0.5O0.5 anode using the carbothermal method under a non-vacuum atmosphere and its application in metal titanium electrolysis

Carbothermal synthesis of nano-iron-carbon composites for arsenate removal from high-arsenic acid wastewater

The current carbothermal method involves impregnation and reduction of ferric salt with the problems of low product activity and high cost, limiting the large-scale production and application of nano-zero-valent iron (nZVI). In this work, the nano-iron-carbon composites (CB-nZVI) were successfully synthesized at a high efficiency, low consumption and batch production process and showed a rapid and efficient As(V) removal from high-arsenic acid wastewater (pH<2 and As(V)> 5 g/L). More than 99.77% As(V) was removed by CB-nZVI under optimum reaction conditions of pH 1.7, initial As(V) concentration 5 g/L and nZVI dosage 11 g/L at 40 ℃ with approximately 11 mg/L As(V) still remained in the filtrate. A novel continuous two-stage treatment process was proposed with only 0.12 mg/L As(V) remained in the filtrate, which met the demands specified in Emission Standard of Pollutants for the Sulfuric Acid Industry issued by Ministry of Environmental Protection of China (GB26132–2010), and solid wastes were greatly reduced at the same time. The iron species distributed on the CB-nZVI core-shell structure possessed a high chemical reduction potential gradient driving force which resulted in the adsorbed As(V) would further be reduced to As(III) and As(0) and then diffusing across the thin oxide layer, leading to accumulating or immobilizing the arsenic at the CB-nZVI. Moreover, strongly acidic condition and Fe/C micro-electrolysis could accelerate the corrosion of CB-nZVI and generate iron oxides for As(V) adsorption. These results suggested that CB-nZVI has great potential for the disposal of strongly acidic wastewater with high concentration in the smelting industry.

Product control and a study of the structural change process during the recycling of lithium-ion batteries based on the carbothermic reduction method

Carbothermal reduction to recover lithium-ion batteries is an environmentally friendly recycling method. This work provides a theoretical analysis of the thermodynamics and an experimental verification process for the carbon thermal reduction recovery of lithium cobaltate (LiCoO2), as well as an explanation of the microstructural changes. The reaction conditions are controlled to obtain the ideal recovery product. A thermodynamic graph of the possible reaction between LiCoO2 and graphite (C) and the reduction of cobalt oxide (CoO, Co2O3, Co3O4) by carbon monoxide (CO) is obtained by thermodynamic analysis. The feasibility of the carbothermic reduction reaction of LiCoO2 at high temperature is studied under standard atmospheric pressure. By controlling the reaction temperature (800 °C) and the ratio of the reactants (LiCoO2/C = 4:5), the reduction products cobalt monoxide (CoO) and lithium carbonate (Li2CO3) are obtained, and the recovery rates are 89% and 84%, respectively. From the perspective of the crystal structure, the reduction process of LiCoO2 is analyzed. The Li-O bond in the LiCoO2 crystal structure is destroyed by CO, which promotes destruction of the Li-O octahedral structure and the formation of a Co-O octahedron. The Li-O octahedron is transformed into a tetrahedral structure in Li2O, and Li2O then reacts with CO2 to form Li2CO3; the Co-O octahedrons combine to form a CoO crystal structure. When the temperature continues to rise, CoO is reduced to Co. The carbothermic reduction recovery method does not require any additional hazardous chemicals and can avoid secondary pollution during the recovery process. This research provides theoretical support for the industrial recycling of lithium-ion batteries.

SUBSTANTIATING THE PROCESS OF PRODUCTION OF FERROMOLYBDENUM FROM TEGHUT MOLYBDENITE CONCENTRATE UNDER PRODUCTION CONDITIONS

Studies of the production process of ferromolybdenum under industrial conditions feom Teghut molybdenite concentrate by using different reducing materials are carried out. Molybdenum can be reduced by carbon at low energy costs. However, the reduction of molybdenum oxides with carbon is accompanied by the formation of undesirable carbides Mo2C and MoCl-x. Due to the limitation of the carbon content in ferromolybdenum (≤0.05…0.5% C), it is obtained by the metallothermal method. In production, ferromolybde¬num is smelted by the out-of-furnace silicoaluminothermal method with an upper fuse from fired molybdenum concentrate (50.% Mo) and the use of ferro-silicon-aluminum (FSA) containing 60…65% Si and 10…12% Al, aluminum grains, iron ore, steel shavings and lime. The process takes place only due to the heat released by the reduction reactions of molybdenum, iron and other elements oxides with silicon and aluminum. From the standpoint of thermodynamics, the reduction reaction of molybdenum oxides by the carbothermal method has a positive value of enthalpy and entropy (due to the formation of CO), the total value of the change in Gibbs energy (∆G_T^0) remains negative and becomes smaller in absolute terms. That is why carbohydrate recovery requires external energy expenditure. On the contrary, when reducing by the aluminothermic and silicothe¬r¬m¬ic methods, the reactions are too negative, since these reactions are highly exothermic, and here the entropy factor does not affect the negative value of the change in Gibbs energy (∆G_T^0) (all reactants and the resulting products are in solid form), therefore the reactions are recovered due to the exothermicity of their own reactions and do not require external energy costs, which is the potential advantage of this method.

Исследование термических свойств шихтовых материалов для выплавки ферросплава с титаном карботермическим способом

This paper presents the results of studies of the thermal properties for charge materials investigated for the smelting of a ferroalloy with titanium by the carbothermal method. The following charge materials were involved and studied in the work: ilmenite concentrate from the Shokash deposit (Aktobe region, Martuk district), high-ash coals, indispensable for domestic purposes for their intended purpose. Derivatographic analysis was used to study the thermal properties of the charge. To compare the electrical resistance of coals in order to select an effective reducing agent, in this work, measurements of the electrical resistance of high-ash coals from the Saryadyr, Borly and Ekibastuz deposit were carried out. As a result, it was found that for the smelting of a new complex titanium-containing ferroalloy, high-ash coal from the Saryadyr deposit is most applicable.

Синтез карбида и диборида титана для металлообработки и получения керамики

Introduction. Titanium carbide and diboride are characterized by high values of hardness, chemical inertness and for this reason are widely used in modern technology. This paper provides information on the synthesis of titanium carbide and diboride by carbothermal and carbide-boron methods, respectively, on the use of titanium carbide as an abrasive and in the manufacture of tungsten-free hard alloys, carbide steels, wear-resistant coatings, as well as titanium diboride in the production of cutting tools and ceramics based on boron carbide The aim of this work is to study the processes of synthesis of highly dispersed powders of titanium carbide and diboride, which are promising for the manufacture of cutting tools, wear-resistant coatings, abrasives and ceramics. Research methods. Titanium oxide TiO2, nanofibrous carbon (NFC), and highly dispersed boron carbide were used as reagents for the synthesis of titanium carbide and diboride. Experiments to obtain titanium carbide were carried out in a resistance furnace, and titanium diboride in an induction furnace. X-ray studies of the phase composition of titanium carbide and diboride samples were carried out on an ARL X-TRA diffractometer (Thermo Electron SA). The determination of the content of titanium and impurities in the samples of titanium carbide and diboride was carried out by the X-ray spectral fluorescence method on an ARL-Advant'x analyzer. The total carbon content in the titanium carbide samples was determined on an S-144 device from LECO. The content of boron and other elements for titanium diboride samples was determined by inductively coupled plasma atomic emission spectrometry (ICP AES) on an IRIS Advantage spectrometer (Thermo Jarrell Ash Corporation). The surface morphology and particle sizes of the samples were studied using a Carl Zeiss Sigma scanning electron microscope (Carl Zeiss). The determination of the particle/aggregate size distribution was performed on a MicroSizer 201 laser analyzer (BA Instruments). Results. The paper proposes technological processes for obtaining highly dispersed powders of titanium carbide and diboride. The optimum synthesis temperature for titanium carbide is 2,000…2,100 oC, and for titanium diboride 1,600…1,700 oC. The content of the basic substance is at the level of 97.5…98.0 wt. %. Discussion. A possible mechanism for the formation of titanium carbide and diboride is proposed, which consists in the transfer of vapors of titanium oxides to the surface of solid carbon (synthesis of titanium carbide) and vapors of boron and titanium oxides to the surface of solid carbon (synthesis of titanium diboride). Due to the high purity and dispersion values, the resulting titanium carbide powder can be used as an abrasive material and for the manufacture of tungsten-free hard alloys, carbide steels, wear-resistant coatings, and titanium diboride powder can be used for the preparation of cutting tools and ceramics based on boron carbide.

Generation of high-density nanoparticles in the carbothermal shock method.

The carbothermal shock (CTS) method has attracted considerable attention in recent years because it enables the generation of finely controlled polyelemental alloy nanoparticles (NPs). However, fabricating high surface coverage of NPs with minimized exposure of the carbon substrate is essential for various electrochemical applications and has been a critical limitation in CTS method. Here, we developed a methodology for creating NPs with high surface coverage on a carbon substrate by maximizing defect sites of cellulose during CTS. Cu NPs with high surface coverage of ~85%, various single NPs and polyelemental alloy NPs were densely fabricated with high uniformity and dispersity. The synthesized Cu NPs on cellulose/carbon paper substrate were used in electrocatalytic CO2 reduction reaction showing selectivity to ethylene of ~49% and high stability for over 30 hours of reaction. Our cellulose-derived CTS method enables the greater availability of polyelemental NPs for a wide range of catalytic and electrochemical applications.

Experience of mixed nitride uranium–plutonium fuel fabrication at the siberian chemical plant jsc site

The “Proryv” project is significant for the Russian Federation and relates to the activity that has been assigned the status of “especially important” for the Rosatom State Corporation. It is planned to develop a new generation of nuclear energy technologies based on the closed nuclear fuel cycle of fast neutron reactors with a lead coolant and mixed nitride uranium-plutonium nuclear fuel as a part of this direction (hereinafter – MNUP fuel).The first method for MNUP fuel producing was the direct synthesis of nitrides from starting metals and alloys of uranium and plutonium (hydrogenation-nitration), implemented in laboratory conditions. The disadvantage of this method is its explosion and fire hazard.A method for carbothermal reduction in the atmosphere of nitrogen from the initial oxides of uranium and plutonium is proposed for the production of MNUP fuel on an industrial scale.According to the results of the literature data analysis of considered above methods, carbothermic reduction in a nitrogen atmosphere from the starting oxides of uranium and plutonium is the most optimal for the industrial production of MNUP fuel.Based on the foregoing as part of the «Proryv» project the concept of MNUP fuel production by the carbothermic synthesis method was adopted as the main method at the site of Siberian Chemical Plant (Joint stock company). For this purpose in 2012 a set of experimental facilities (a unique platform for the pilot industrial production of fuel components (from pellets to fuel assemblies) of fast reactors) was created.During this period for the first time in the world at the set of experimental facilities full-scale nuclear fuel assemblies based on MNUP fuel composition were made, data for verifying the technological model of the processes for manufacturing MNUP fuel were prepared, using experimental models of the equipment a complex technological process with experimental scaling of the manufacturing technology of MNUP fuel was developed, an automatic algorithm sorting of tablets and systems for providing and controlling the parameters of the box atmosphere was developed, as well as construction materials of furnaces for the synthesis and sintering of nitride fuel were tested. In total, 24 nuclear fuel assemblies — more than 1000 fuel elements of various designs with different shells — were transferred for loading into the BN-600 reactor. Successfully completed irradiation of 21 nuclear fuel assemblies.

Synthesis of monodisperse and high-purity α-Si3N4 powder by carbothermal reduction and nitridation

Carbothermal reduction-nitridation method is an effective means for synthesizing Si3N4 powder. Herein, spherical monodisperse silica was used as silicon source. The effects of reaction temperature, nitrogen flow rate and Si3N4 seeds content on the products were studied. It was found that high-purity α-Si3N4 (>99.0 wt%) was synthesized from C/SiO2 = 3:1 at 1400 °C, reaction time of 6 h and nitrogen flow rate of 800 ml/min. The powder, with an average size of 0.5 μm, showed good dispersity and regular morphology because spherical monodisperse silica could be completely coated with carbon. The more contact sites between SiO2 and C, the higher concentration of SiO(g) would be produced in the initial stage. It also indicated that the nucleation rate of α-Si3N4 increased, thereby inhibiting the formation of an agglomerate phase and suppressing the grain growth of α-Si3N4. Furthermore, higher nitriding temperature and Si3N4 seeds content both decreased the grain size and increased β-Si3N4 content. The forming mechanism of non-agglomerated and submicron-sized α-Si3N4 was clarified.

Recovery of high-grade copper matte by selective sulfurization of CuO–Fe2O3–SiO2–CaO system

The separation of Cu from the Cu x O-Fe x O containing waste (such as copper slag and electroplating sludge) is always intractable by using pyrometallurgy method. The carbothermic reduction methods, as well as the conventional sulfurization technology by using sulfurization agent FeS 2 , will introduce lots of iron into the prepared Cu–Fe alloy or Cu–Fe–S matte, and this results in the difficulty in further separation of Cu from Fe. In this work, CaS is utilized as the new sulfurization agent, and the iron content of prepared Cu–Fe–S matte is lower than 5%, while the copper grade is improved to about 76–79%. Such products could be used as the raw materials for producing metallic copper. According to the experimental results, at 1450 °C, the copper oxides in CuO–Fe 2 O 3 –SiO 2 –CaO system is selectively sulfurized by CaS, and Cu 2 S dominated product is formed and separated from slags. The recovery extent of copper reaches 98% when the CaS addition is 1.15 times (1.15CaS) of the stoichiometric quantity required. However, the increase of CaS addition (1.6CaS) will lead to the sulfurization of iron oxides, and make the iron content in Cu–Fe–S matte increase to 15%. Besides, when the Cu/Fe ratio (in mass) of synthetic waste is 0.5, part of the CaS is oxidized by Fe 2 O 3 , which results in the recovery extent of Cu to only about 73.30%. However, the copper recovery extent could be improved to 97% by adding extra reductant carbon.

Fabrication of in-situ Ti(C,N) phase toughened Al2O3 based ceramics from natural bauxite

Al2O3–Ti(C,N) ceramics were fabricated via carbothermal reduction nitridation method with high-titania special-grade bauxite as the raw material. The formation mechanism of in-situ Ti(C,N) phase and its effect on the properties of materials are discussed. After nitrided at 1700 °C, Ti(C,N) phase could be formed in-situ with appropriate C/TiO2 molar ratio. Due to the residual stress field formed by Ti(C,N) particles, the path of crack propagation is changed, leading to the crack deflection and pinning. Therefore, the mechanical properties of the materials are improved by forming in-situ Ti(C,N) phase. With a C/TiO2 molar ratio of 2.2 and nitridation temperature of 1700 °C, Al2O3–Ti(C,N) ceramic with a hardness of 13.9 GPa, a fracture toughness of 8.28 MPa m1/2 and a flexural strength of 387 MPa could be fabricated.

Cycling properties of Na3V2(PO4)2F3 as positive material for sodium-ion batteries

The research into sodium-ion battery requires the development of high voltage cathodic materials to compensate for the potential of the negative electrode materials which is usually higher than the lithium counterparts. In this framework, the polyanionic compound Na3V2(PO4)2F3 was prepared by an easy-to-scale-up carbothermal method and characterized to evaluate its electrochemical performances in half cell vs. metallic sodium. The material shows a specific capacity (115 mAh g−1) close to the theoretical limit, good coulombic efficiency (>99%) and an excellent stability over several hundred cycles at high rate. High-loading free-standing electrodes were also tested, which showed interesting performances in terms of areal capacity and cyclability.

Thermal insulation TiN aerogels prepared by a combined freeze-casting and carbothermal reduction-nitridation technique

With the rapid development of energy sources and aerospace engineering, high-performance thermal insulation materials with multiple functions are attracting more and more attentions. Non-oxide ceramic aerogels have application potential in thermal insulation under harsh conditions owing to their good thermal insulation performance and chemical stability. In this work, TiN aerogels were prepared by a combined freeze-casting and carbothermal reduction-nitridation method utilizing TiO2 and chitosan as raw materials, at 1473 K for 3 h, with a C/TiO2 molar ratio of 3/1. They showed a specific surface area of 167 m2/g and ultralow density of 0.07 g/cm3 (the relative density of 1.3 %). Their thermal conductivity value was only 0.166 ± 0.0054 W/(m K at 673 K (TiO2 solid content of 5 wt%). Moreover, the prepared aerogels possessed reasonably high mechanical strength and good high-temperature service performance, suggesting that they can be used under high-temperature conditions as an insulation material.

Carbothermal conversion of boric acid into boron-oxy-carbide nanostructures for high-power supercapacitors

In this study, we report a facile carbothermal method for the preparation of boron-oxy-carbide (BOC) nanostructures and explore their properties towards electrochemical energy storage devices.

Synthesis of Transition Metal Carbide Catalysts for Vanadium Redox Flow Batteries

Vanadium redox flow batteries (VRFBs) proposed by Skyllas-Kazacos’ group in the 1980s [1] have recently attracted considerable attention for large-scale energy storage due to their desirable features such as flexible and safe design, high efficiency, and long cycle life. Graphite or carbon materials have been the most common catalysts for VRFBs [2]. However, they often show limited activity and reversibility. This issue may be circumvented with the development of new and efficient catalysts. Transition metal carbides are regarded as attractive candidates because they possess good electronic conductivity, low cost, high abundance, and outstanding thermal and chemical stabilities [3]. However, transition metal carbides fabricated by traditional carbothermal reaction methods exhibit a small specific surface area and inevitable aggregation at high reaction temperatures.A transition metal carbide fabrication process is under development at Hawaii Natural Energy Institute, which favors the formation of nano-sized particles that are expected to possess a large specific surface area. Figure 1a shows X-ray diffraction patterns for graphite as carbon source and the resulting vanadium carbide. The dominant phase is V8C7 and the particle size is approximately 50 nm. As shown in Figure 1b, cathodic currents for both electrodes in 3 M H2SO4 are due to the hydrogen evolution reaction. Although the cathodic current remarkably increases for graphite in 1 M (V2++V3+) + 3 M H2SO4 in Figure 1c, a significant anodic current is not detected indicating that the reversibility of the graphite toward the V2+/V3+ redox reactions is poor. In contrast, anodic and cathodic currents substantially increase on vanadium carbide, signifying an improvement in catalytic activity and reversibility toward the negative electrode reactions in comparison to graphite. The undesired hydrogen evolution reaction appears to have an important influence on the V3+ to V2+ reduction reaction. This influence was removed to more clearly show the vanadium V2+/V3+ redox reactions partial currents. Figure 1d shows the catalytic activity of graphite and vanadium carbide after background current subtraction. Vanadium carbide reveals more pronounced redox peaks than graphite signaling that vanadium carbide has a higher catalytic activity and enhanced reversibility toward V2+/V3+ redox reactions than graphite. The vanadium carbide composition, structure, morphology, and particle size will be tuned to improve activity.Figure 1. (a) X-ray diffraction patterns and (b, c, d) cyclic voltammograms (positive scan) for vanadium carbide and graphite. Acknowledgments Authors are grateful to the Office of Naval Research (award N00014-18-1-2127) and the Hawaiian Electric Company.

Nano-Si/C Composite Via Carbothermal Shock for Lithium Ion Battery Anode

Nowadays, Li-ion batteries are ubiquitous and dominate the portable storage market. However, their utilizations for high-energy applications are limited and they present huge social challenges for the future, especially for the applications to electric and hybrid electric vehicles (EVs and HEVs respectively). One strategy, praised by both academics and industry, the high capacity electrode materials, notably silicon, as it is considered an attractive graphite substitute in Li-ion battery anode. Silicon (Si) is recognized as a representative anode material for next-generation lithium-ion batteries due to properties, such as a high theoretical capacity, suitable working voltage, and high natural abundance. However, inherently, a large volume expansion (~ 400%) during lithiation/delithiation introduces poor electrical conductivity and unstable solid electrolyte interfaces (SEI) films, the Si-based anodes possess serious stability problems hindering practical applications. To overcome the issue, Si-nanoparticles(Si-NPs) has been proposed as a promising solution to overcome the volume expansion and the flowing fracturing problems of the micron-size particles. Thus, various nanoparticles and nano-objects (0D, 1D, 2D and 3D) have been tried for the Li battery anode in the last decade.1, 2 It has been demonstrated that Si-NPs smaller than 150 nm can be avoided the further fracturing upon the repeating lithiation.We propose a technology for preparations of novel Si-NPs/carbon(Si/C) composites on the basis of thermal shock of the carbon materials such as natural and artificial graphites. We developed a facile, one-step carbothermal shock method for transformations from micro-Si to Si-NPs less than 150 nm size and well dispersed on carbon matrix (Figure 1.). The particle size distribution of the Si-NPs was narrow and the dispersion was uniform. The Si/C composite anode exhibited a high specific capacity (>1,000 mAh/g) and predominant fast charging behavior. Reference [1] R. Chen, T. Zhao, X. Zhang, L. Li and F. Wu, Advanced cathode materials for lithium-ion batteries using nanoarchitectonics, Nanoscale Horiz., 2016, 1, 423-444[2] D. Ma, Z. Cao and A. Hu, Si-Based Anode Materials for Li-Ion Batteries: A Mini Review, Nanomicro Lett., 2014, 6(4), 347-358Figure 1. SEM images of Si-NPs/carbon (Si/C) composites Figure 1

A Creative “Spark” for High-Entropy Alloys

In this issue of Matter, Feng et al. make a breakthrough understanding of an aerosol system for manufacturing unprecedented alloys with excellent catalytic properties. This work will inspire improved 3D nanoprinting techniques for creating new matter forms for broad applications, including additive manufacturing, catalysts, and metallurgy.

Obtaining of niobium-containing ferroalloys from the Russian ore raw materials

The possibility of processing niobium-containing pyrochlore-apatite concentrates obtained from ores of Beloziminskoye deposit has been studied. A two-stage scheme for selective reduction of phosphorus into a metal phase to obtain low-phosphorus niobium-containing slag was suggested. The reduction of phosphorus and iron was carried out by a carbothermic method using coke and pig iron carbon as the reducing agent. Pig iron chip and magnetite product (80 % Fe2O3) were used as the precipitating agent. In laboratory and semi-industrial conditions the basic possibility of selective separation and sedimentation of phosphorus (to 91 %) and iron from a niobic concentrate without considerable reduction of niobium (up to 1–2 %), according to the two-stage scheme with minimum possible temperature of process during the first period (∼ 1260 °C) and hot soak at the increased temperature (∼ 1450 °C) during the second period were shown. Obtained low-phosphorus niobium-containing slag after crushing can be used for ferroniobium production according to existing technological schemes.

Enhanced microwave absorption properties under synergism of 0-D TiB2 particles and 1-D TiB2 fibers prepared by carbothermal process

Titanium boride (TiB2) particles and fibers were synthesized by the carbothermal method with different calcination temperatures and time. Subsequently, the effects of calcination temperatures and time on microstructure and the yield of TiB2 fibers were investigated. Further, the dielectric and microwave absorption (MA) properties of TiB2/paraffin composites within 2–18 GHz were discussed. As a result, the yield of TiB2 fibers reached a maximum at 1400 °C for 180 min. The content of TiB2 was directly proportional to permittivity. The sample containing 80 wt % TiB2 particles and fibers indicated that the minimum reflection loss (RLmin) attained − 46.5 dB at 11.6 GHz when the thickness was 1.45 mm and the effective absorption bandwidth (EAB) was 4.64 GHz (RL<–10 dB) with the thickness of 1.25 mm. The related MA mechanisms were also discussed. The excellent stability, simple production procedure, thin absorbing layer, and wide EAB make TiB2 become an ideal candidate for microwave absorbing materials applied in high temperatures.

Ultrafine AlN synthesis by alumina carbothermal reduction under vacuum: Mechanism and experimental study

Ultrafine AlN powders were synthesized by carbothermal reduction nitridation method under vacuum (VCRN) in a double temperature zones vacuum furnace with alumina and carbon black as raw materials. The mechanism of the process was investigated. The results show that when the soaking time was 1.5 h at 1650 °C, 300 Pa N2 pressure, the purity ultrafine AlN powders were obtained. By analyzing the results of density function theory (DFT) calculation and XRD, the mechanism of VCRN can be identified as Al2O3 → Al2OC/Al4C3 → Al6C3N2/AlN → AlN. The results of theoretical study further proved that the compound of Al6C3N2 can be nitrogenized quickly through the reaction of Al6C3N2 + 2 N2(g) → 6AlN + 3C.