Thermal Plasma Synthesis Research Articles

Thermal plasma synthesis of Si-multi walled carbon nanotube nanocomposite as an anode for lithium-ion batteries

The Si-MWCNT (multi-walled carbon nanotube) nanocomposite, which is considered a promising replacement for graphite as an anode material for lithium-ion batteries, was prepared using a triple DC thermal plasma jet system. We used micron-size silicon powder and MWCNT powder as raw materials. We varied the main parameters by mixing silicon and MWCNTs or individually injected into the plasma jet and adjusting the mass ratio to 2:1 and 1:2. The location of injection for the raw materials played a critical role in the formation of Si-MWCNT nanocomposites as the temperature at the injection site has a significant impact on the vaporization of silicon and sublimation of carbon nanotubes. Additionally, it was influenced by efficient heat transfer of silicon and the structural change of MWCNT. As a result, the Si-MWCNT nanocomposite was easily produced under separate injection conditions, and silicon nanoparticles of 20 nm or less were attached to the surface of the MWCNT. We evaluated the electrochemical performance of the synthesized material by assembling a CR2032-type coin cell using it as an anode electrode material.

One-step thermal-plasma synthesis of sulphur and nitrogen dual-doped graphene with improved microwave-absorption efficiency

This study presented the one-step synthesis of sulphur (S) and nitrogen (N) dual-doped graphene using atmospheric thermal plasma. The doped graphene was synthesized in the magnetically rotating arc plasma with CS2 as the sulphur source, N2 as the nitrogen source and CH4 as the carbon source. At the same reaction temperature, the concentrations of S and N in S and N dual-doped graphene were higher than those in S/ N -doped graphene, which indicated that the dual-doped mode had a promoting effect on the doping level. In addition, increasing the input power effectively increased the doping levels of S and N atoms, which were up to 15.0 at% and 6.9 at%, respectively, at an input power of 19 kW. The S and N dual-doped graphene displayed excellent microwave absorption capability, with an optimal reflection loss of −56.4 dB at 16.3 GHz, and the effective absorption bandwidth reached 5.7 GHz when the doping levels of S and N atoms were 12.2 at% and 5.1 at%. This simple and rapid method for preparing S and N dual-doped graphene might facilitate the application of heteroatom doped graphene.

A novel dissolution-precipitation strategy to accelerate the sintering of yttrium oxide dispersion strengthened tungsten alloy with well-regulated structure

In this work, accelerated sintering of Y2O3 dispersion strengthened tungsten alloy with a well-regulated structure was achieved by a novel dissolution-precipitation strategy. As indicated, yttrium oxide was firstly dissolved into the lattices of W powder precursor during the thermal plasma synthesis process in a one-step and ultra-fast way, and then homogeneously precipitated out within W grains during sintering. The theoretical calculation reveals that the formation process of Y2O3 dispersoids enhanced the driving force of densification by increasing the sintering stress and declining the macroscopic viscosity, resulting in improved diffusion ability for the W skeleton. The microstructural investigation further confirmed the occurrence of mass inter-diffusion at the W-Y2O3 interface, which provides a fast diffusion pathway for W atoms, and is responsible for the accelerated densification kinetics. Being sintered at 1600 °C for 1 h, the as-obtained alloy possesses a high relative density of 98.26%, together with a refined grain size of 970 nm for W and 50 nm for intragranular Y2O3, respectively.

Non thermal plasma synthesis of ZnO nanoparticles and their corrosion inhibition activity on XC70 mild steel pipeline in 1 M HCl acidic medium

This paper investigates the inhibitory efficiency of zinc oxide nanoparticles (ZnO Nps) as an eco-friendly inhibitor against the corrosion of XC70 mild steel pipelines in a 1 M HCl acidic medium. The ZnO Nps were synthesized using non thermal plasma, in particular the gliding arc discharge-assisted (GAD) method, a chemical solvent free and safe approach that utilizes humid air as the vector gas and distilled water as the solvent. Characterization techniques such as DLS, EDX, SEM, and XRD confirmed the positive zeta potential, hexagonal wurtzite structure, spheroidal shape, and median particle size of 65.6 nm for the synthesized ZnO Nps, respectively. To evaluate the corrosion inhibition efficiency, investigations were conducted utilizing electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques at varying temperature range (298–333K). Results showed that increasing the concentration of ZnO Nps improved their ability to inhibit corrosion, with an optimum concentration of 70 mg/L achieving a high effectiveness of 90.71 % at ambient temperature. SEM analysis confirmed the formation of a protective barrier film on the inhibited substrate, effectively hindering the diffusion of corrosive ions. Furthermore, the DFT method was employed to examine the corrosion mitigation mechanism. These results demonstrate the significant inhibiting properties of ZnO Nps in preventing corrosion of XC70 mild steel in a 1 M hydrochloric acid environment.

Thermal Plasma Synthesis of Forsterite with Cubic Matrix

Thermal Plasma Synthesis of Forsterite with Cubic Matrix

Thermal plasma synthesis of (La,Sr)CoO3-(La,Sr)2CoO4 composite cathodes for intermediate temperature solid oxide fuel cells (IT-SOFC)

(La,Sr)CoO3 and (La,Sr)2CoO4 dual phase powders were synthesized via thermal plasma to be used as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFC). This covered pure (La,Sr)CoO3 as well as the composites where the fraction of (La,Sr)2CoO4 was gradually increased reaching the mid-composition. Powders, all synthesized in the same condition, were extremely small in size, especially at mid-composition where they were close to 30 nm in size. Area specific resistance (ASR) determined from the symmetric cell imply improved cathodic performance at the mid-composition. Taking ASR = 0.15 Ω∗cm2 as benchmark, it was found that the (La,Sr)CoO3: (La,Sr)2CoO4 = 0.53:0.47 cathode may be used at temperatures close 750 °C. Measurements taken from several runs however imply that the cathode performance was not stable and ASR values increases with cycling. This was attributed to the powder form of the cathode which would be expected to coarsen rapidly due to accelerated surface diffusion.

Thermal Plasma Synthesis of Different Alloys and Intermetallics from Ball Milled Al-Mo and Al-Ni Powder Systems.

Lightweight alloys have great importance for car manufacturers that aim to produce safer, lighter, and more environmentally friendly vehicles. As a result, it is essential to develop new lightweight alloys, with superior properties to conventional ones, respecting the demands of the market. Al and its alloys are good candidates for reducing the overall weight of vehicles. The objective of this research was to understand the possibility to synthesize different Al alloys and intermetallics by implementing the plasma system and using two different Al-Ni and Al-Mo powder systems. This was done by separately injecting non-reacted raw Al-Ni and Al-Mo composite powder systems into the plasma reactor. In the first step, the milling parameters were optimized to generate Al-Ni and Al-Mo composite powders, with sizes over about 30 µm, having, respectively, a homogeneous mixture of elemental Al and Ni, and Al and Mo in their particles. Each of the composite powders was then injected separately into the plasma system to provide conditions for the reaction of their elements together. The obtained Al-Ni and Al-Mo powders were then studied using different methods such as scanning electron microscopy, X-ray diffractometry, and energy dispersive X-ray analysis. Regardless of the initially used powder system, the obtained powders were consisting of large spherical particles surrounded by a cloud of fine porous particles. Different phases such as Al, AlNi3, Al3Ni2, and AlNi were detected in the particles of the Al-Ni powder system and Al, Mo, AlMo3, MoO3, and MoO2 in the Al-Mo powder system.

Thermal Plasma Synthesis of Anorthite

Thermal Plasma Synthesis of Anorthite

Thermal plasma synthesized nano-powders of (LaCe)B6 starting from oxide-based precursors and its field electron emission performance

High temperature synthesis process of microcrystalline and nanocrystalline (LaCe)B6 using Self-propagating High temperature Synthesis (SHS) and arc plasma gas phase condensation methods, respectively have been investigated. These methods are rapid and economically viable processes used for the synthesis of technologically important refractory hexaborides. Microcrystalline powders of (LaCe)B6 were synthesized using the SHS process, starting from oxide precursors of lanthanum, cerium, and boron. The powders obtained using SHS process were used as a precursor to getting nanocrystalline (LaCe)B6 using the thermal plasma route. The thermal plasma synthesis was carried out using nitrogen and argon plasmas, respectively. In-situ plasma diagnostics were used to identify evaporated species and determine plasma temperature during the formation of nanocrystalline (LaCe)B6 using optical emission spectroscopy. Further, an effect of plasma input parameters on the structural and optical properties of as synthesized nanocrystalline (LaCe)6 were investigated using XRD analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. A thorough investigation of morphological and structural properties of synthesized nanocrystalline (LaCe)6 was carried out using transmission electron microscopy. Finally, field effect electron emission properties of the microcrystalline and nanocrystalline product were investigated and current density, turn on field, stability of emission performance were determined.

Thermal Plasma Synthesis of Metal-Boride Nanoparticles as a Functional Material for Gamma-Ray Shielding

Thermal Plasma Synthesis of Metal-Boride Nanoparticles as a Functional Material for Gamma-Ray Shielding

고주파 유도결합 열플라즈마를 이용한 IT-SOFC용 LSCF 나노분말 합성 및 전기전도도 특성 평가

고주파 유도결합 열플라즈마를 이용한 IT-SOFC용 LSCF 나노분말 합성 및 전기전도도 특성 평가

Large scale synthesis of copper nickel alloy nanoparticles with reduced compressibility using arc thermal plasma process

Among the various methods employed in the synthesis of nanostructures, those involving high operating temperature and sharp thermal gradients often lead to the establishment of new exotic properties. Herein, we report on the formation of Cu-Ni metallic alloy nanoparticles with greatly enhanced stiffness achieved through direct-current transferred arc-thermal plasma assisted vapour-phase condensation. High pressure synchrotron X-ray powder diffraction (XRPD) at ambient temperature as well as XRPD in the temperature range 180 to 920 K, show that the thermal arc-plasma route resulted in alloy nanoparticles with much enhanced bulk modulus compared to their bulk counterparts. Such a behaviour may find an explanation in the sudden quenching assisted by the retention of a large amount of local strain due to alloying, combined with the perfect miscibility of the elemental components during the thermal plasma synthesis process.

Thermal Plasma Synthesis of Li2S Nanoparticles for Application in Lithium-Sulfur Batteries

Inductively-coupled thermal plasma processes were used to produce nanosized Li2S. Prior to the syntheses, the feasibility of forming Li2S was first evaluated using FactSage by considering the phase diagrams of sulfur and different lithium precursors in reducing atmospheres; Li2O, LiOH·H2O, Li2CO3 and Li2SO4·H2O all showed promises in producing Li2S nanoparticles, as confirmed by experiments. Argon and hydrogen mixtures were used as plasma gases, and a carbothermal reduction was implemented for Li2SO4·H2O. In addition, carbon-coated Li2S nanoparticles were synthesized with downstream injection of methane. Carbon was shown to stabilize Li2S upon contact with ambient air. The Li2S nanoparticles were electrochemically tested in half-cells using electrolytes containing LiNO3 or Li2S6 as additives. It was found that adding LiNO3 to the electrolyte was detrimental to the electrochemical performance of Li2S, whereas the combination of Li2S6 and LiNO3 as additives doubled the charge and discharge capacities of the half-cell over 10 cycles.

High-throughput thermal plasma synthesis of FexCo1-x nano-chained particles with unusually high permeability and their electromagnetic wave absorption properties at high frequency (1-26 GHz).

Herein, we introduce novel 1-dimensional nano-chained FeCo particles with unusually-high permeability prepared by a highly-productive thermal plasma synthesis and demonstrate an electromagnetic wave absorber with exceptionally low reflection loss in the high-frequency regime (1-26 GHz). During the thermal plasma synthesis, spherical FeCo nanoparticles are first formed through the nucleation and growth processes; then, the high temperature zone of the thermal plasma accelerates the diffusion of constituent elements, leading to surface-consolidation between the particles at the moment of collision, and 1-dimensional nano-chained particles are successfully fabricated without the need for templates or a complex directional growth process. Systematic control over the composition and magnetic properties of FexCo1-x nano-chained particles also has been accomplished by changing the mixing ratio of the Fe-to-Co precursors, i.e. from 7 : 3 to 3 : 7, leading to a remarkably high saturation magnetization of 151-227 emu g-1. In addition, a precisely-controlled and uniform surface SiO2 coating on the FeCo nano-chained particles was found to effectively modulate complex permittivity. Consequently, a composite electromagnetic wave absorber comprising Fe0.6Co0.4 nano-chained particles with 2.00 nm-thick SiO2 surface insulation exhibits dramatically intensified permeability, thereby improving electromagnetic absorption performance with the lowest reflection loss of -43.49 dB and -10 dB (90% absorbance) bandwidth of 9.28 GHz, with a minimum thickness of 0.85 mm.

Thermal Plasma Synthesis of Ceramic Nanomaterials

Thermal Plasma Synthesis of Ceramic Nanomaterials

In situ synthesis of core-shell W-Cu nanopowders for fabricating full-densified and fine-grained alloys with dramatically improved performance

In this work, a one-step thermal plasma synthesis route was developed to construct core-shell W-Cu nanoparticles with size about 30 nm. As synthesized nanocomposite powders address the issues of homogeneous elemental distribution and short diffusion distance for Cu to form network around W grains, facilitating fast densification with uniform microstructure and suppressed W grain growth. As a result, compact with high relative density of 99.31% and grain size of 260 nm was obtained at low temperature of 1100 °C, further led to the recorded hardness of 562 Vickers-hardness (Hv) and electrical conductivity of 54.32% International Annealed Copper Standard (IACS), respectively.

Radio frequency thermal plasma-processed Ni-W nanostructures for printable microcircuit electrodes

Nonconventional alloy systems have been actively investigated to find an appropriate electrode candidate for highly integrated microcircuit applications. Here, a Ni-W nanoscale-alloy system is introduced to modulate the unwanted early densification of Ni nanoparticles by adopting a considerable amount of W in the single-step process of radio frequency thermal plasma synthesis. Multiple phases other than Ni phase, i.e., α-W and β-W, were found to coexist when the content of W was presumably beyond its solid solubility limit in Ni. Noticeable retardation of the densification of Ni was observed depending on the content of W in the resultant film electrodes fired at different temperatures up to 1200 °C. As expected, electrical resistivity of the film electrodes depended on the progress of densification. A large variation of electrical resistivity with different W contents was observed at the low temperature of 900 °C while the variation became very small at high temperatures of >1100 °C for all the films. The successful late densification indicates that the Ni-W alloy system is suitable as a microcircuit electrode with a reasonably low electrical resistivity of ~10−5 Ω cm.

Thermal plasma synthesis and electrochemical properties of high-voltage LiNi0.5Mn1.5O4 nanoparticles

The synthesis of LiNi0.5Mn1.5O4 has been reported to change the crystal structure with the oxygen partial pressure and affect the battery characteristics. LiNi0.5Mn1.5O4 involves the formation of impurities, such as LixNi1−xO, LixMn3−xO4, and Li2CO3, at a high temperature range exceeding 700 °C because oxygen loss occurs during synthesis. LiNi0.5Mn1.5O4 electrochemically contains Mn4+, however, Mn3+ is formed because of oxygen deficiency. The Li–Ni–Mn-oxide causes a disproportionation of Mn3+ in an oxygen-deficient state. The synthesized Li–Ni–Mn-oxide nanoparticles at 10,000 K by induction thermal plasma formed spinel-type LiNi0.5Mn1.5O4 (space group Fd3m) of Mn4+. The crystal structure of the cubic-spinel nanoparticles approached a LiNi0.5Mn1.5O4 single phase as the flow rate of O2 increased from 2.5 to 5 l min−1. The formation of LiNi0.5Mn1.5O4 was shown to be accelerated by increasing the O2 gas flow rate. The measured current–voltage characteristics of LiNi0.5Mn1.5O4 nanoparticles appeared at around 4.7–4.8 V as the reaction peak of Ni2+/Ni3+ and Ni3+/Ni4+. In contrast, the Mn of the Li–Ni–Mn-oxide nanoparticles synthesized in the oxygen-deficient state was less than trivalent, which caused disproportionation of Mn. The measured current-voltage characteristics showed peak of an oxygen desorption at near 4.6 V. This study investigated the factors affecting the crystal structure formation and electrochemical properties of high-voltage LiNi0.5Mn1.5O4 nanoparticles formed in thermal plasma.

Thermal Plasma Synthesis of Zirconia Powder and Preparation of Premixed Ca-Doped Zirconia

A novel study about the synthesis of zirconia and calcia-stabilized zirconia powders were carried out by DC thermal plasma starting from cheap precursors as the carbonates. Different operational parameters were investigated to explore the effects of the process conditions, such as the plasma torch power and the gas flow rate on the composition and the morphology of the powders. The products phase changes from a metastable tetragonal to monoclinic/tetragonal mixture. Basically a main tetragonal phase was obtained at low torch power (7 kW) while the amount of monoclinic phase linearly rises with the power, up to 66 wt% at 26 kW of plasma power and high gas flow rate. The gas flow rate also affects the shape and the size of the powder, where high values reduce powder aggregation and enhance the spherical shape. The best results were achieved at 22 kW of plasma power and high gas flow rate, with powders of roundness about 79% and a wide particle size distribution. Adding the calcium carbonate to the zirconium carbonate (corresponding to 8 wt% CaO in the final mixture), the plasma treatment mainly produces a tetragonal phase zirconia, that at 1400 °C in furnace changes in a stable cubic phase. These powders could be made suitable for further industrial applications after proper treatments.

Titanium(III) Sulfide Nanoparticles Coated with Multicomponent Oxide (Ti–S–O) as a Conductive Polysulfide Scavenger for Lithium–Sulfur Batteries

In spite of the high specific capacity and energy density of Li–S batteries based on low-cost sulfur as the active material, their practical use has not yet been realized due to the undesirable formation of soluble polysulfides (PS) during electrochemical cycles and their shuttling effect. In order to minimize this serious issue caused by the active material dissolution, transition metal compounds such as oxides, nitrides, and sulfides have alternatively been used to capture the PS and also to provide electron pathways in the S electrode. However, high-performance additive materials having both high affinity to PS and high electronic conductivity have not been developed thus far. Herein, we report the preparation and application of a new additive material—titanium(III) sulfide (Ti2S3) nanoparticles covered with multicomponent (Ti–S–O) oxide (MO–Ti2S3), which can be synthesized on a large scale using an inductively-coupled thermal plasma synthesis method followed by a simple surface oxidation treatment. MO–Ti2S3 shows much higher PS affinity than other titanium compounds and electronic conductivity that is comparable to that of carbon black. Furthermore, MO–Ti2S3 shows much higher resistance to heat and oxidation while having charge–discharge stability when compared with TiS2. Finally, we show that the cyclability and specific capacity of the Li–S battery can be significantly enhanced by incorporating MO–Ti2S3 in the cathode when compared to utilizing C species.