Metallothermic Process Research Articles

Preparation and Study of Carbide-Sialon Composite in SiC-SiAlON-Al2O3 System

Goal: Synthesis of SiAlON by reaction coating method using aluminosilicate natural raw material geopolymer (kaolin), corundum and silicon carbide and on its basis obtaining a composite with high physical and technical properties by hot pressing for use in armor and rocket technology. For the intensification of sialon formation and sintering processes, the influence of various additives was studied, such as: aluminum powder, elemental silicon, yttrium and magnesium oxides. Method: A SiAlON-containing composite with an open porosity of 15% - 16% was obtained by the metallothermic process and the method of reactive annealing in nitrogen. The resulting material was milled to a dispersion of 1 - 3 μm and hot pressed at 1620°C to obtain a product with high density and performance properties. We studied the process of sialon formation and the microstructure of the composite by X-ray phase, optical and electronmicroscopy analysis methods. Result: In the selected composition the β-SiAlON was formed at 1400°C instead of 1800°C, which was due to the mutual influence of the initial raw materials:geopolymer kaolin, perlite, corundum, aluminum, silicon, SiC, the development of the process is facilitated by the vitreous dopant perlite (96 glass phase). The use of perlite, which is eutectic with geopolymer at low temperatures, creates a good prerequisite for intensive diffusion processes with other components. Conclusion: A SiAlON-containing composite with high physical and technical properties was obtained in the SiC-SiAlON-Al2O3 system by the method of reactive sintering and hot pressing, with the following properties: the strength limit in compression is 1940 MPa, and in bending it is 490 MPa. The process of making sialon has been studied using X-ray phase and electron microscopy analysis methods. The physical and technical properties of the obtained composite are studied by modern research methods.

Joint metallothermic reduction of titanium and rare refractory metals of V group

The features of phase formation during the joint aluminothermic reduction of titanium, niobium, tantalum, vanadium from their oxides using methods of thermodynamic modeling, differential thermal and X-ray phase analysis were studied. Computer thermodynamic modeling made it possible to predict the optimal temperature conditions in the metallothermic process, composition and ratio of reagents in the charge, behavior of elements and sequence of phase formation. Thermodynamic calculations were supplemented by differential thermal studies using the combined scanning calorimetry method to identify the kinetic and thermochemical components of the process. An analysis of theoretical and experimental data allowed us to establish that the interaction of aluminum with titanium dioxide proceeds through the stage of titanium monoxide formation and features by the formation of TixAly intermetallic compounds of various compositions (TiAl3, TiAl, Ti2Al) depending on the Al and TiO2 ratio in the charge. When titanium dioxide is partially replaced by niobium, tantalum and vanadium oxides, the metallothermic process during interactions in the Al–TiO2–Nb2O5, Al–TiO2–Ta2O5 and Al–TiO2–V2O5 systems has a similar nature, enters the active phase once liquid aluminum appears, is accompanied by exothermic effects and features by the priority formation of titanium aluminides and binary and ternary intermetallic aluminum compounds with Group 5 rare refractory metals – AlNb3, Al3Nb, Al3Ta, Al3(Ti1–х, Taх), Al3(Ti0,8V0,2). The joint conversion of titanium dioxide and rare refractory metal pentoxides during the reduction process is carried out through sequential and parallel stages of the formation of simple and complex element oxides with low oxidation states.

Novel sustainable silicothermic synthesis of phase-pure TiB2 fine powder

Abstract Phase pure TiB2 powder of 100–400 nm was synthesized at 1100 °C via a novel sustainable silicothermic reduction technique using TiO2, Na2B4O7 and Si powders as starting materials. By introducing sodium salts as source of Na2O into the reactant mixture, the original water-insoluble byproduct SiO2, which is hard eliminated from resultant product in the conventional silicothermic reduction process, was transformed into water-soluble Na2Si2O5, making it much easy to remove it from the reacted mass via simple hot water washing. Consequently, a ‘‘post reduction’’ leaching process with a strong acid, generally required by the conventional metallothermic processes, was successfully avoided, and the relevant environmental concerns could be alleviated. Moreover, the aqua Na2Si2O5 could be readily recycled and used as a precursor for preparing many other types of valuable materials. Evaporation loss of silicon in the reduction process was dominated by SiO (g) resultant from the interactions between Si, SiO2 and Na2Si2O5 at test temperatures. By using 5 wt% excessive Si, TiO2 and Na2B4O7 were completely converted into TiB2 at 1100 °C.

Production of Magnesium-Strontium Alloys Through Vacuum Metallothermic Process

Vacuum metallothermic reduction is the main method to produce magnesium (Mg) metal from Mg-containing ores. In the process, a mixture of ore and reductant material is charged in retorts, which provide a vacuum atmosphere of about 100 Pa (1 mbar) in the process. The accounts in the literature stated that the process is viable for the metallothermic reduction of strontium (Sr) as well. The main problem for the reduction of the Sr is the high affinity of Sr to oxygen. Moreover, the Sr is an important metal for Mg alloying. In the present study, production of Mg-Sr alloy from oxide raw materials was studied through the vacuum metallothermic process. Thus, it was aimed to develop a simple and commercially viable method to directly produce Mg-Sr alloys, and the Sr content would be in the form of Mg17Sr2 intermetallic alloy. In the experiments, calcined dolomite ore and SrO were used as raw materials. Investigated parameters were reductant type (FeSi and Al), process temperature, and process time on the recovery ratios of Mg and Sr in produced alloys. The highest recovery ratios, 97.1 pct for the Mg and 81.2 pct for the Sr, were obtained in the experiment conducted at 1250 °C for 480 minutes. The reductant material was the Al, and the Sr-Al addition ratio was 5 wt pct in the experiment.

Reduction Conditions of Metallic Calcium from Magnesium Production Residues

In this paper, the theoretical and industrial definitions of metallic calcium production by the metallothermic process in a vacuum atmosphere were investigated. In the experiments, Al is the only reductant used for metallothermic calcium production. The effects of Al stoichiometry, time variances, and temperature changes were investigated. The experiments were carried out at 1200 °C, 1250 °C, and 1300 °C, and with 100% Al, 125% Al, and 150% Al stoichiometry to produce metallic calcium from the residue of metallic magnesium production. Both the raw materials and the residue phases were characterized by atomic absorption spectrometry (AAS), X-ray diffraction (XRD) spectrometry, and chemical analysis techniques. Experimental results were investigated to determine the highest efficiency of reduction conditions. From the results of the experiments, reaction kinetics and activation energy were calculated. According to the experimental results, the highest recovery rate parameters for the reduction of calcium are 150% stoichiometric Al for 480 min at 1300 °C, with 72% recovery.

Thermodynamic simulation and validation experiment of neodymium oxide reduction into metallic neodymium by metallothermic process

Neodymium (Nd) is one of the rare-earth elements (REEs) found in significant amount within monazite and bastnasite minerals. Nd is a ferromagnetic metal that is often used as a material to produce magnet, commonly known as a permanent magnet. Neodymium is alloyed with other metals such as iron and boron to form one of the strongest types of permanent magnet. This research aim is to study the reduction process of Nd-oxide into Nd-metal through the metallothermic process. The Nd metal product is expected to fulfill the material specification for a permanent magnet. Thermodynamics simulation of Nd reduction into its metal was conducted using ITB’s licensed Factsage software. A validation experiment was conducted only to the Nd metal resulting simulation. The simulations involved some parameters, i.e. temperatures (600, 700, 800, 900, 1000, 1100 and 1200 °C), types of fluxes (CaCl 2 and Ca(OH) 2 ), composition of the reducing agent (1x, 2x dan 3x of the stoichiometric calculations), types of the reducing agents (Ca and Mg), and types of feeds used (Nd-oxide and Nd-chloride). The thermodynamic simulation shows that Nd metal was produced in a condition where the temperature should be1100-1200 °C using Ca as the reducing agent and CaCl 2 as the flux, while the amount of reducing agent has no effect on the resulted product. Validation result of the simulations shows that the Nd metal is formed up to 49% metal in a non-oxidative condition.

Effect of Reductant Type on the Metallothermic Magnesium Production Process

AbstractThis paper is a contribution to the theoretical and quantitative understanding of the processes for the production of magnesium metal by metallothermic process in vacuum (Pidgeon Process). In the present study, effects of reductant type and amount were investigated. CaC2 is a low-cost alternative to FeSi (ferrosilicon) which is the common reductant in the Pidgeon Process. CaC2 slightly decreases the Mg recovery ratios but it remarkably decreases the process cost. The experimental study, conducted with the change of mass % FeSi–CaC2 ratio at 1,250 °C for 360 min, the optimum Mg recovery was measured as 94.7 % at 20 % CaC2 addition. Also aluminum, as a reductant, allows conducting the process at lower temperatures than that of FeSi. For the experiments conducted with Al addition, the highest Mg recovery ratio was measured as 88.0 % in the conditions for 300 min process duration and 100 % stoichiometric Al addition at 1,200 °C.

Synthesis and Structural Studies of Nanowires Composite Materials from Rice Husk Ash by Metallothermic Processes

Nanowires composite materials were synthesized from rice husk ash using by two metallothermic processes. The rice husk ash and carbon charcoal were mixed with Mg and Sn metals by various ratios and heated at 700℃ and 1000℃ under atmosphere of nitrogen gas. The formed products were studied by scanning electron microscope (SEM) and X-rays diffraction (XRD) technique. SEM images showed the structures of nanowires composite materials with diameter around 50-300 nm and length of more a few 10 μm. XRD patterns indicated the crystal structures of composite materials consisting of Si, MgO, Mg2SiO4 phase and SiC, SnO2 phase.

Protective Mo2NiB2–Ni coatings by centrifugal metallothermic SHS

Cast Mo2NiB2–Ni metal-matrix composites and protective coatings thereof were fabricated by centrifugal metallothermic SHS process. The quality of SHS surfacing was found to depend on process parameters such as the mass of green mixture per unit surface area of substrate and centrifugal acceleration. The hardness of synthesized coatings was rather high and attained as large values as 800–1200 H V. Optimal conditions for deposition of high-quality protective coatings onto a steel substrate were found experimentally. The process can be recommended for practical implementation in production of cutting tools, tribological materials, molds, and deposition of protective coatings. The present results can be expected to make a theoretical background for industrial-scale manufacturing of new tungsten-free MMCs and protective coatings with valued service parameters.

Thermodynamics of Iron Metallothermy

Besides other possible applications, the thermitic compositions based on iron oxides are meant to the achieving of the permanent joints of the railroad tracks. In addition to the iron oxides, the thermitic kit include also the reducing agent – aluminum powder, a carbon source to adjust the percent of this element in the obtained steel and a flux with a view to allow the steel composition and temperature control. The metallothermic process efficiency is given by strictness in the selection of ratio of the thermitic components and mainly in that of the iron oxides types. Their correct dosage makes possible the estimation and rigorous control of the thermal effect of reactions. In this work, using thermodynamic calculations, is analyzed and quantified the development of the thermal effect of the metallothermic reduction reactions of iron oxides depending on the iron oxides proportions in the thermitic composition.

Properties of the intermetallic phase Nb3Al prepared by a calcium hydride reduction process

This paper demonstrates the feasibility of and examines the main steps in preparing the Nb3Al compound by a metallothermic process: by heating a mixture of niobium and aluminum oxides and calcium hydride (calcium hydride reduction process). Our calculations indicate that, when thermodynamic equilibrium sets in during the reaction between the components of a starting mixture, the oxygen content of the intermetallic phase may be very low. We obtained experimental Nb3Al intermetallic powders of nearly 100% purity and investigated their physicochemical and technological properties.

Study of the Utilization of Chromium Plating Waste by Mechanical Activation

In this study, the production of metallic chromium via metallothermic process was investigated. A chromium oxide-rich residue from chromium plating industry was characterized. Aluminothermic reduction was performed in lab-scale using an open graphite crucible. The plating residue and the aluminum powder were processed in a SPEX mill, in order to promote its effective mixing and mechanical activation. Energy dispersive X-Ray (EDX) analyses in the scanning electron microscope (SEM) have shown the presence of metallic chromium in the reaction products.

Challenges in light metals production

Light metals have great potential for application in the automotive and aerospace industries because of their excellent physical properties. The usage of aluminium, titanium and magnesium is limited by relatively high costs of production, associated energy costs and large ecological footprint. In the case of aluminium, significant improvement to the Hall–Héroult process is still achievable through advances in cell design, materials and process control. Alternative production processes, including carbothermic reduction and low temperature routes are also possible. Magnesium and titanium production are currently dominated by batch metallothermic processes and new process routes are required to develop these industries. Research at CSIRO, through the Light Metals Flagship, is currently focused on step change improvements in the production of light metals, aiming at lowering energy usage, increasing productivity and reducing the overall environmental impact. In the present paper, the overall status of the existing technologies will be described, highlighting areas that are being developed around the world and at CSIRO.

Drying of Inorganic Particulate Compounds

ABSTRACT Inorganic particulates are usually dried in a fixed bed, fluidized bed, or spray dryers. These compounds are easy to dry, once their physical structure, with high porosity, allows moisture content removal with low resistances. For fluidized bed of alumina particle evaluations, a laboratory-scale drying unit was built. The drying experiments were carried out with alumina particles with different diameters to evaluate temperature and air flow rate effects on drying kinetics and bed height. In another case, the dehydration of a mixture of rare-earth chlorides in a fluidized bed was studied, aiming at the production of anhydrous rare-earth chlorides, used to obtain mischmetal by electrolytic and metallothermic processes. The spray drying experiments were carried out in a pilot plant. Spray drying is a technique largely applied in industrial processes to dry solutions or suspensions, converting their solid parts into a dried powder. A set of rare-earth drying experiments was carried out, aiming at the development of techniques to obtain a powder that could satisfy international morphological requirements. The results allowed evaluating the effects of air flow rate, feed concentration, atomizer model, rotation velocity, and atomization pressure on powder density and particle size distribution.

Refractory Metals Extraction by Fused Salt Electrolysis, the Present Status and the Future Prospects

The refractory metals, which are characterised by high melting points and sensitivity towards interstitial impurities, are produced invariably by the metallothermic processes. As the metallic reductants are obtained by electrolytic routes, a need has been felt to develop these processes for their production of. The paper discusses the present status of electroextraction of these metals and highlights the future trends of producing them through these routes.

Carbothermic Reduction Using Liquid Metal Solvents

The use of liquid metal solvents has broadened the application-potential of carbothermic reduction in the areas of ore reduction reactions and reactive separations. A properly chosen solvent permits pyrometallurgical reductions at temperatures far below those possible with processes that do not employ a solvent metal. Product contamination is inhibited as well. Further, solvated carbothermic reduction appears to consume substantially less energy than conventional electrochemical and metallothermic processes.