Transferred Arc Thermal Plasma Research Articles

Upcycling of silicon scrap collected from photovoltaic cell manufacturing process for lithium-ion batteries via transferred arc thermal plasma

As the supply of photovoltaic industry products increases rapidly, measures to solve the upcoming related waste problem are urgently required. In particular, the fabrication process of Si wafers leads to significant Si scrap residue, and approximately 40% of crystalline Si ingots are wasted as Si scrap. Here, a feasibility study was conducted to investigate the recycling of Si scrap waste collected during the solar panel manufacturing process using the transferred arc thermal plasma. Si-NP with a particle size of 100 nm or less applicable as an anode material for lithium-ion batteries (LIBs) was successfully upcycled by the transferable arc thermal plasma method, and the developed LIB showed excellent electrochemical performance. Si-NPs electrodes show a discharge capacity of 2920 mAh g−1 at 0.1 A g−1, and 2167 mAh g−1 at 0.4 A g−1. In addition, silicon-graphite (Si-G) composites were also prepared to improve the electrochemical properties of LIBs. Furthermore, the possible pros and cons of the method proposed in this study were discussed including economic evaluation. These results show that the transferred arc thermal plasma is a simple, eco-friendly, and cost-effective method of upcycling Si-NPs anode material from Si scrap waste for high-performance LIBs.

Synthesis of Nanoparticles of Aluminium–Boron complex for Radiation Sensor

Radiation sensors based on thermo luminescence from nanoparticles of aluminium-boron complex for gamma radiation have been reported. Crystal chemistry of aluminium boride is quite complicated and is derived from complex tetragonal modification of boron. The crystal structure varies with the method of preparation and energy band gap contains defect states governed by the temperature during synthesis. There are various methods of preparing nanoparticles like boll milling, sol-gel and RF-thermal plasma. In the present studies Aluminum boron complex nanoparticles were synthesized by DC- transferred arc thermal plasma method. The DC-transferred arc thermal plasma has been received great attention as a useful method to synthesize nanoparticles. Since a substance is easily evaporated in large volume of thermal plasma. A pure aluminium and boron powders were mixed together and made to evaporate from water cooled graphite after impinging thermal plasma plume. Argon with flow rate of 3L/min was used as a plasma forming gas for the evaporation of raw powder mixture in Ar ambient in the plasma reactor. The obtained nanoparticles of aluminum –boron complex were characterized using X-ray diffraction technique for structural analysis, Transmission electron microscopy (TEM) for morphological analysis and energy dispersive analysis by X-ray (EDAX) for elemental analysis. The aluminum boron complex so obtained was investigated for thermoluminscence properties.

Environmental Benign Process for Production of Molybdenum Metal from Sulphide Based Minerals

Molybdenum is a strategic and high temperature refractory metal which is not found in nature in free state, it is predominantly found in earth’s crust in the form of MoO3/MoS2. The main disadvantage of the industrial treatment of Mo concentrate is that the process contains many stages and requires very high temperature. Almost in every step many gaseous, liquid, solid chemical substances are formed which require further treatment. To overcome the above drawback, a new alternative one step novel process is developed for the treatment of sulphide and trioxide molybdenum concentrates. This paper presents the results of the investigations on molybdenite dissociation (MoS2) using microwave assisted plasma unit as well as transferred arc thermal plasma torch. It is a single step process for the preparation of pure molybdenum metal from MoS2 by hydrogen reduction in thermal plasma. Process variable such as H2 gas, Ar gas, input current, voltage and time have been examined to prepare molybdenum metal. Molybdenum recovery of the order of 95% was achieved. The XRD results confirm the phases of molybdenum metal and the chemical analysis of the end product indicate the formation of metallic molybdenum (Mo 98%).

Preparation of Nano Aluminium Powder (NAP) using a Thermal Plasma: Process Development and Characterization

A bottom up approach for the preparation of Nano Aluminium Powder (NAP) using a Transferred Arc Thermal Plasma Reactor (TAPR) is described. The aluminium block is subjected to evaporation by the application of a thermal plasma. The aluminium vapour produced is rapidly quenched to room temperature resulting in crystallization of the aluminium vapour in nano-particulate form. Various process parameters, such as the plasma torch power, reactor pressure and plasma gas composition were optimized. This paper also describes the characterization of NAP by analytical methods, for the estimation of the Active Aluminium Content (AAC), Total Aluminium Content (TAC), XRD, bulk density, BET surface area, HR-TEM etc. The results are compared with those for samples prepared in other thermal plasma reactors, such as the DC Arc Plasma Reactor (DCAPR) and the RF Induction Thermal Plasma Reactor (RFITPR), and for commercially available NAP samples (ALEX, prepared by the EEW technique).

Carbothermal reduction of sillimanite in a transferred arc thermal plasma reactor

Conversion of sillimanite to value-added ceramic materials was investigated by transferred arc plasma processing using nitrogen as the plasma gas. Plasma processing was carried out using sillimanite and sillimanite–carbon mixtures at different power levels. The products were characterized by XRD, SEM and FTIR techniques. Thermodynamic analysis using free energy minimization principle was used to predict the products formed and also analyze the experimental results. The results of these investigations showed that sillimanite can be converted to mullite, or alumina and silicon carbide by careful choice of the operating conditions and sillimanite–carbon ratio.

Phase controlled structure formation of the nanocrystalline zirconia using thermal plasma technique

Nanocrystalline ZrO2 powder was synthesized by dc transferred arc thermal plasma reactor by homogeneous gas phase condensation mechanism. ZrO2 is an oxide ceramic with a high melting point, good chemical resistance and high mechanical strength. When doped with certain oxides, ZrO2 shows high ionic conductivity. ZrO2 is also recognized as a superior thermal barrier material. Thermal plasma synthesis of oxide nano materials shows pressure dependent crystalline phase and crystallite size. The X-ray diffraction analysis clearly shows that as the ambient oxygen gas pressure increases from 100 Torr to 1000 Torr the abundance of tetragonal phase goes on increasing. The morphology of the as synthesized ZrO2 powder was found to be spherical and independent on the ambient gas pressure as seen from the Scanning Electron Microscopy studies. The specific surface area of powder was calculated using the nitrogen gas adsorption Brunauer, Emmett, Teller surface area analysis technique and found no much variation.

Large-scale synthesis of nanopowders by transferred arc thermal plasma

The present work describes the preliminary results on large-scale synthesis and characterisation of copper (Cu) and aluminium nitride (AlN) nano powders by transferred arc thermal plasma technique. The transferred arc was used to vaporise the precursor materials (Cu, Al metal 99.9% pure). Nano particles are formed in the gas phase as a result of homogeneous nucleation. The vapours of Al were allowed to react with NH3 gas for the synthesis of AlN. Rapid quenching using Ar/N2 then produced the desired nano powders. For the generation of Cu nano powders, argon was used as a quench gas. The resultant nano-powders of Cu, AlN were collected under the controlled atmosphere. TEM and AFM results show the particle size ranging between 70 nm and 100 nm. These particles possess exotic applications in defence systems, armour for aircraft and vehicles, aeronautical systems, power electronics, microelectronics etc.

Growth of nano-particles of Al 2O 3, AlN and iron oxide with different crystalline phases in a thermal plasma reactor

The paper presents the experimental results showing that the crystalline phase of the nano-particles, synthesized in a DC transferred arc thermal plasma reactor, critically depend on the operating pressure in the reaction zone. The paper reports about the changes in crystalline phases of three different compounds namely: aluminium oxide (Al 2O 3), aluminium nitride (AlN) and iron oxide (Fe x O y ) synthesized at 760 Torr and 500 Torr of operating pressures. The major outcome of the present work is that the phases having higher defect densities are more probable to form at the sub-atmospheric operating pressures. The variations in the crystalline structures are discussed on the basis of the change in the temperature during the nucleation process, prevailing at the boundary of the plasma, on account of the ambient pressures. The as-synthesized nano-particles were examined by X-ray diffraction analysis and transmission electron microscopy. In addition, the confirmatory analysis of the crystalline phases of iron oxides was carried out with the help of Mössbauer spectroscopy.

Microstructure and properties of flame sprayed tungsten carbide coatings

This article reports on feasibility experiments carried out with oxy-acetylene spray system with various oxygen to fuel ratios using two different tungsten carbide powders and powder feeding methods, to evaluate the newly developed fused WC, synthesised by transferred arc thermal plasma method. Transferred arc thermal plasma method is more economical and less energy intensive than the conventional arc method and results in a fused carbide powder with higher hardness. The microstructure and phase composition of powders and coatings were analysed by optical and scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Carbon content of the powders and coatings were determined to study the decarburisation of the material during spraying process. Coatings were also characterised by their hardness and abrasive wear. The effects of metallurgical transformation and phase content are related to wear performance. The results demonstrate that the powders exhibit various degree of phase transformation during the spray process depending on the type of powder, powder feeding and spray parameters. The carbon loss during the spray process in excess of 45% resulted in reduced hardness and wear resistance of the coatings. Coatings with high amount of WC and W 2C along with FeW 3C showed higher wear resistance. Thus, coatings of high wear resistance can be produced using fused tungsten carbide powder with WC and W 2C phases, which can be economically synthesised by thermal plasma transferred arc method.

Fine silica powder preparation by use of a transferred arc thermal plasma reactor

Highly dispersed fine silica powder has been prepared from the quartzite mineral and petroleum coke by reactive evaporation in the thermal plasma and condensation from the vapour phase. The process made use of an indigenously developed dc plasma reactor in transferred arc mode. Silicon monoxide gas produced by heating the above mixture was condensed in the presence of steam. The product obtained was in the form of very fine agglomerates and characterized by scanning electron microscopy (SEM) and laser particle size analysis. BET surface area and viscosity measurements were also carried out.