Heat Treatment In Argon Atmosphere Research Articles

Effect of Heat Treatment in Different Atmospheres on Thermally Evaporated ZnS films

In this study, the properties of ZnS films which can be used as a buffer layer in photovoltaic thin film solar cell technologies were tried to be improved by applying post-production heat treatments. ZnS films were subjected to annealing processes in Nitrogen, Argon and Air atmospheres with an atmosphere-controlled heat treatment system and the effects of these atmospheres on the films were investigated. As a result of XRD analysis, it was determined that all films show a preferential orientation towards the (111) ZnS plane. The crystallite size of the ZnS film increased with the applied heat treatment. It was also confirmed by transmittance measurements that the ZnS film annealed in air is partially oxidized and contains the secondary ZnO phase in its structure. Optical band gap values for ZnS films were found to be 3.53–3.56 eV. The refractive index values of the films were determined by spectroscopic ellipsometry. Two-probe technique was used to determine the electrical resistivity and heat treatment caused a decrease in the resistivity values of the films. Surface analyzes of the films were performed with the help of AFM and SEM measurements. As an outcome of this study, it has been revealed that the surfaces of ZnS films can be modified by heat treatment in Argon atmosphere. The production of ZnS films and their optimization with subsequent heat treatments were carried out, and ZnS films with high transmittance and improved morphology were obtained. These materials can be used as buffer layer or window layer in CZTS, CIGS and CdTe based solar cells.

Effective combination of CuFeO2 with high temperature resistant Nb-doped TiO2 nanotube arrays for CO2 photoelectric reduction

Herein, we report a simple approach to synthesize CuFeO2/TNNTs photocathodes composed of high-temperature resistance n-type Nb-doped TiO2 nanotube arrays (TNNTs) and p-type CuFeO2 for CO2 reduction. TNNTs were prepared by anodic oxidation on TiNb alloy sheets and CuFeO2/TNNTs were then prepared by coating precursor liquid onto TNNTs followed by heat treatment in argon atmosphere. The microstructures of CuFeO2/TNNTs and TNNTs before and after heat treatment were investigated by SEM and TEM. The phase compositions of CuFeO2/TNNTs were studied by XRD and XPS, and the light absorption performance were tested by UV–vis diffuse reflectance spectrum. Results show that TNNTs exhibit a regular nanotube arrays structure and this structure is well remained after the calcination at 650 °C. In addition, TNNTs show similar semiconductor properties to n-type TiO2, which enables them to be integrated with p-type CuFeO2 to obtain composite photocathodes with a p-n junction. The synthesized CuFeO2/TNNTs photocathode is well crystallized because no other crystalline iron or copper compounds are included in the prepared photocathode. Furthermore, the photocathode shows high light absorption and fast carrier transport due to the appropriate band gap and p-n junction. As a result, high photoelectrocatalytic CO2 reduction performance with high selectivity to ethanol is obtained on this photocathode.

High-performance, flexible planar microsupercapacitors based on crosslinked polyaniline using laser printing lithography

With the latest trend of miniaturization of modern portable electronic devices, the development of small-sized, flexible power sources is in great demand. Herein, we report the fabrication of flexible and high-performance planar microsupercapacitors (MSCs) on a poly-ethylene terephthalate substrate as portable energy storage devices. We employed a facile laser printing technology and thermal crosslinking route to fabricate crosslinked polyaniline (PANI) based MSCs, taking advantage of the low processing cost and high cyclic stability. The flexible PANI MSCs after heat treatment in Argon atmosphere exhibited a remarkably high areal capacitance of 54 mF cm−2 at the current density of 0.3 mA cm−2, which is much higher than that of PANI MSCs reported so far elsewhere. 79.8% of the initial capacitance was retained after 1000 cycles, indicating the excellent cyclic stability of the devices. This innovative approach provides a new strategy for the facile fabrication of flexible and high-performance planar energy storage devices.

Facile synthesis of lithium-vanadium-molybdenum oxide nanocomposite as high-performance anode material for lithium ion batteries

A lithium-vanadium-molybdenum-oxide composite has been prepared by a soft chemical route with mechanical activation assistance followed by low-temperature heat treatment in argon atmosphere. The X-ray diffraction reveals that the synthesized sample is made up of Li3V(MoO4)3 and LiVOMoO4 crystal phases. The SEM images show the fine particles ~300nm in size. HRTEM image shows a clear crystal boundary between the two phases. The composite possesses good electrochemical performance as anode material. Particularly, it delivers an initial charge capacity of 927 mAh g−1 at 50mAg−1 with a high initial coulombic efficiency of 81.2% and maintains 87.8% of its initial capacity after 50 cycles. Even if tested at 1000mAg−1, it can deliver a reversible capacity of 542mAhg−1.

Synthesis of binary and multinary metal sulphides by precipitation and their characterisation

CuS, In2S3, CuInS2 and CuGaS2 semiconductors have been synthesised in powder form by precipitation reaction using Na2S·3H2O as a precipitating agent. Precipitated at about 313K in aqueous medium, the powders of CuS crystallise in covellite (hexagonal) phase and those of In2S3, CuInS2 and CuGaS2 in tetragonal phase on heat treatment in argon atmosphere. The formation of CuS or In2S3 takes place due to the reaction between the metal and bisulphide ions in aqueous phase while that of CuInS2 or CuGaS2 involves solid state reaction between CuS and In2S3 or GaxSy during heat treatment and is accompanied with the evolution of SO2 gas. The powders are nearly monophasic, exhibit nanometric morphology and bear their respective stoichiometric compositions. The direct band gaps of CuS, In2S3, CuInS2 and CuGaS2 measure 2.06, 2.3, 1.34 and 2.38eV respectively. The method is simple and is extended to the synthesis of CuIn0.8Ga0.2S2 as well.

Kinetics of carbide formation in the molybdenum–tungsten coatings used in the ITER-like Wall

The kinetics of tungsten carbide formation was investigated for tungsten coatings on carbon fibre composite with a molybdenum interlayer as they are used in the ITER-like Wall in JET. The coatings were produced by combined magnetron sputtering and ion implantation. The investigation was performed by preparing focused ion beam cross sections from samples after heat treatment in argon atmosphere. Baking of the samples was done at temperatures of 1100 °C, 1200 °C, and 1350 °C for hold times between 30 min and 20 h. It was found that the data can be well described by a diffusional random walk with a thermally activated diffusion process. The activation energy was determined to be (3.34 ± 0.11) eV. Predictions for the isothermal lifetime of this coating system were computed from this information.

Synthesis and characterization of zirconium carbide nanorods at low temperature

A novel chemical synthetic method at low temperature was developed for the synthesis of ZrC nanorods, using ZrCl4 and sodium metal in the presence of naphthalene as the carbon source. The results showed that the ZrCl4, after heat treatment in argon atmosphere at temperatures above 500°C, can be completely converted into ZrC nanorods. However, the initial formation temperature of ZrC was as low as 400°C whereas ZrO2 as an intermediate product was also produced from the precursor at 300°C, and the mixture was finally transformed into pure ZrC at 700°C. The synthesized ZrC nanorods exhibited cubic lattice structure.

Edge Absorption of thin Films –Ga2O3

Fundamental absorption edge of b–Ga2O3 thin films, obtained by radio-frequency ion-plasmous sputtering, was investigated, using the method of optical spectroscopy. It was ascertained that the optical band gap Eg increases from 4.60 to 4.65 eV after the heat treatment films in argon atmosphere and to 5.20 eV after the reduction of annealed films in a hydrogen atmosphere. Consolidated effective mass of free charge carriers in b–Ga2O3 films after annealing and after reduction in hydrogen was estimated. It was found that the concentration of charge carriers after heat treatment in argon atmosphere is 7.30´1017 cm–3 and after reduction in hydrogen, is 2.62´1019 cm–3, which is typical for degenerated semiconductors. It was shown that the shift of fundamental absorption edge in thin films b–Ga2O3 after reduction in hydrogen is caused by Burstein-Moss effect.

Effect of heat treatment on superconducting properties of FeSe wire fabricated by PIT method

We report on successful fabrication of superconducting FeSe wire using hot gas extrusion (HGE) ex-situ PIT (powder in tube) method. Length of the obtained wire was about 60cm with cross-sectional superconducting core area nearly 2.5 × 10−3 cm2. For the wire sample we observed superconducting transition temperature, Tonsetc ≈ 11 K, about 1.2K lower compared to preliminary prepared FeSe powder. Heat treatment in argon atmosphere at 350oC resulted in transition width decrease from ΔT(10% − 90%) ≈ 1.75 K in sample without heat treatment down to ΔT ≈ 0.9 K in annealed samples. Estimated derivative of the upper critical field as a function of temperature of the sample annealed during 72h in argon atmosphere at 350oC is dHc2/dT ∼ −2.9 T/K. Applying WHH theory to our data allows to define Hc2(0K) = 0.69Tc × (dHc2/dT) ≈ 19.8T. The untreated wire shows critical current density, Jc ∼ 75 A/cm2 at T=4.0 K in zero field. Increasing annealing time up to 72 hours at 350oC in argon atmosphere gives rise to Jc increase of about 60% approaching 120 A/cm2 at T=4.0K and H=0T . Also Jc measurements were made in magnetic fields up to 9T. Our results show applicability of the HGE PIT method for fabrication of superconducting wires based on FeSe compound. Long-range heat treatment is necessary to improve superconducting properties of the samples.

Explosively Consolidated Powder-In-Tube MgB$_{2}$ Superconductor Aided by Post-Thermal Treatment

A MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> superconductor was prepared from Mg flakes or powders and B powders using the powder-in-tube technique with explosive consolidation. Compaction of Mg and B powders resulted in a two-phase alloy, due to the relatively low temperature developed during compaction as well as the very short duration of the process. Formation of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> was obtained after subsequent heat treatment in argon atmosphere at a maximum temperature of 950degC.

Directional solidification, microstructure and properties of the [formula omitted]– [formula omitted] eutectic

The Al–Nb system exhibits a eutectic transformation at 1595 . 2 ∘ C , which results in Al 3 Nb ( D 0 22 ) and Nb 2 Al ( D 8 b ) phases. This paper is concerned with the processing of this eutectic by directional solidification. Alloys were prepared by arc melting and directionally solidified in Bridgman-type equipment. The resulting samples were utilized to evaluate the solidification microstructure and morphology regarding the growth conditions. Eutectic microstructures obtained were regular with lamellar morphology. Variations of the growth rate showed that an increase in this parameter causes a decrease in the lamellar spacing. With further increase in the growth rate, eutectic cells were observed as a result of constitutional undercooling. Oxidation tests of eutectic microstructures showed that this alloy suffers severe microstructure instability, with growth kinetics of the oxide scale of linear type. This indicates that the Al in the Nb–Al eutectic alloy is insufficient to form protective oxide films, such as, α - Al 2 O 3 . Finally, the heat treatment in argon atmosphere showed that the eutectic alloy presents a high degree of microstructure stability at 1200 ∘ C .

Effect of RF power on optical and electrical properties of ZnO thin film by magnetron sputtering

Zinc oxide is an important fluorescence material due to its excellent luminescence efficiency and low voltage required to produce green light. In this study, the RF reactive magnetron sputtering system was used to deposit the transparent (ZnO:Zn) thin films on glass substrates. The effect of RF sputtering power and heat treatment on the photoluminescence (PL) and resistivity were studied. It has been found that increasing RF sputtering power improves the PL efficiency. After heat treatment in argon atmosphere, the crystalline structure of the ZnO film is improved and the (0 0 0 2) preferred orientation is enhanced. The resistivity of the as-deposited film cannot be detected. After annealing, the resistivity is in the range 10 −1–10 −3 Ω cm −1.

Alteration of band structure in Si nanocrystals

The photoluminescence of Si nanocrystals with dimensions ranging from 70 to 250 nm was investigated. Grains were prepared by mechanical ball-milling and subsequent sedimentation steps in order to segregate them in size. This was followed by heat treatment in argon atmosphere at 1000°C to reduce the density of dislocations introduced during milling. At the same temperature, an oxidation process in air was carried out in order to create a stable SiO 2/Si interface and reduce the dimensions of the grains. Crystallinity of the samples was checked by X-ray diffraction and transmission electron microscopy-related techniques. Two emission bands have been determined. One was identified with the D1 center usually assigned to dislocations. The second one is identified as being due to an excitonic recombination and shows phonon replicas characteristic for bulk silicon. This band is reported here for the first time. In the fraction of the smallest silicon grains, a gradual upshift of the excitonic line was observed with diminishing average grain diameter. This was associated with band structure perturbation due to size-confinement.

Structural, thermal and magnetic properties of Pr-123 polycrystalline and thin film superconductors

We report the structural, thermal and magnetic properties of superconducting PrBa 2Cu 3O 7− δ (Pr-123). The existence of superconductivity in samples of Pr-123 is still a polemic subject. To further study this problem, we have measured thin films and high-quality polycrystalline bulk samples by following a sol–gel method, associated with heat treatment in argon atmosphere. The present results confirm the occurrence of superconductivity in Pr-123 polycrystalline and thin film samples.

Electrodeposition and characterization of CdS thin films on stainless steel and tin oxide substrates

Cadmium sulphide films are electrodeposited from dimethylsulphoxide (DMSO) and propylene carbonate (PC) on stainless steel and tin oxide substrates. The physical properties of the films grown in both solvents have been studied. The thickness, grain size and morphology of the CdS films have been examined using X-ray diffractometer patterns and scanning electron microscopy. Heat treatment in argon atmosphere improves the electrical conductivity of the samples.