Papers by Keyword: Thermal Treatment

Abstract: In this research, titanium dioxide (TiO₂) nanoparticles were immobilized into polyvinyl alcohol (PVA) matrix without and with surfactants via solution casting film combined with thermal treatment method. The dispersion and distribution of TiO₂ nanoparticles presented by scanning electron microscopy (SEM) showed the uniform distribution of TiO₂ nanoparticles in PVA matrix with surfactant. Fourier-transform infrared spectroscopy (FTIR) showed increasing intensity peak at 560-800 cm^-1 corresponding to Ti-O stretching vibration indicating interaction between PVA and TiO₂ after thermal treatment. X-ray diffraction (XRD) result showed peak of PVA crystal structure due to the thermal treatment, and the addition of surfactant could decrease the average crystallite size of TiO₂ in PVA/TiO₂ nanocomposite films. Photocatalytic activity was determined from the film efficiency on removal of methylene blue (MB) under ultraviolet (UV). The results showed the greater MB removal efficiency of the PVA/TiO₂ nanocomposite films with surfactant and thermal treatment than those without surfactant and thermal treatment.

Abstract: The properties of steel 42HMFA, which has been tempered in various environments at thermal improvement, are investigated. Advantages of application to training of water solutions of polymers are shown. Training in synthetic environments provides higher rates of mechanical properties of steel products. As a result of training in water solutions of polymer, the maximum level of hardenability on the section of product and fatigue strength of detail is reached.

Abstract: This article presents the development of energy-saving induction heating technology to accelerate significantly the process of heat treatment of steel wire. The analysis of international trends and prospects of the use of induction heating shows a steady expansion of the applied induction technologies in metallurgy. The article considers the advantages of induction heating in comparison with other competitive technologies. Heat treatment in electro-technical induction units is determined by the interrelated electrical and thermal processes in them, the complex nature of the distribution of internal heat sources, the dependence of the nature of the power distribution of the induction unit on the temperature of the products processed. The features of the applicated in the induction method of heating in the hardware industry for objects previously unused: such as coils of wire and riots of calibrated steel. The results of the study show the influence of the induction method of heating on temperature-time factors to the formation of the structure, to increase the uniformity of heating and the quality of heat treatment of steel wire, calibrated steel in riots, taking into account the technological problem. The authors give the assessment of the effectiveness of medium and high-frequency induction heating of steel wire of various diameters. The evaluation of the increase in the efficiency of an induction heating unit with the simultaneous heat treatment of several filaments of steel wire of the same diameter, combined into a bundle, was made.

Abstract: Self-compacting high-strength concrete (SCHSC) is an innovative concrete that has superior physical and mechanical properties, and does not require vibration for placing and compaction. Heat treatment (HT) of SCHSC can significantly accelerate the strength growth during cast-in-situ construction, and allows to reduce the turnover of formwork, the labor costs for construction, and the construction period. The issue of strength development of SCHSC during HT has been studied. SCHSC of R₂₈ = 100 MPa was studied. Test specimens were cured with HT by infrared rays for 7, 9, 11, 13, 16 and 24 hours. Then warmed specimens were tested for compressive strength after 0.5, 4, 12 and 24 hours of cooling period. Study was carried out on the basis of analyzing, generalizing and evaluations of experimental data. A mathematical model is proposed for determining the compressive strength of SCHSC after one day of curing with HT.

Abstract: The hydrophilic-hydrophobic surface area of alumina powder (Al₂O₃) oxidized at different temperatures was determined on the base of adsorption of water and butane vapor at 25°C. In the order to study the influence of thermal oxidation upon hydrophilic/hydrophobic character of the surface, samples of Al₂O₃ were characterized using granulometry, SEM and BET surface area measurement. SEM results showed that the thermal treatment does not affect the morphology of the Alunima. However, the increase of treatment temperature from 250 to 900°C results in changing of the hydrophilic-hydrophobic balance of Al₂O₃ surface.

Abstract: This study focuses on the role of Mo addition on the mechanical properties of an Al-Si-Cu-Mg alloy in as-cast and heat-treated condition at ambient and elevated temperature. Addition of 0.4 to 0.6 wt.% Mo forms Mo-bearing dispersoid particles which have a relatively high melting point and improve high temperature tensile strength. Ductility suffered in the presence of Mo-bearing particles. Trace addition of Mo up to 0.6 wt.% has a negligible influence on the yield strength and hardness of Al-Si-Cu-Mg alloy in as-cast and heat-treated conditions at ambient temperature and 250 °C.

Abstract: Fiber coatings for BN/SiC-and BN/Si₃N₄-bilayer systems were developed for the use in SiC/SiC composites. All coatings were produced with high process velocities of 500 m/h by a continuous roll-to-roll dip-coating process. The fiber surface was fully covered with a homogeneous coating and without fiber bridging. Tensile tests of fiber bundles were used to examine potential degradation of the fiber properties due to the application of the coatings. The coated fiber bundles showed a reduction of the maximum tensile load to 90.0 % for the BN/Si₃N₄ and to 86.7 % for the BN/SiC coating in comparison to the fiber bundle in the as-received state. A thermal treatment of the coated fiber bundles up to 1650 °C led to no reduction of their maximum tensile load. SiC/SiC composites were fabricated by polymer infiltration and pyrolysis. The flexural strength and strain of composites with BN/SiC fiber coating were improved to 467 MPa and 0.42 % in comparison to the composites without fiber coating. The composites with BN/SiC coating showed toughened fracture behavior with fiber pull-out effects.

Abstract: In this work, the thermal treatment temperature effect on phase formation and bioactivity of glass-ceramics based on the SiO₂-Na₂O-CaO-P₂O₅ system has been studied. The chemical composition of the system is 45 wt.% SiO₂, 24.5 wt.% Na₂O, 24.5 wt.% CaO and 6 wt.% P₂O₅ (45S5). The rice husk ash is used as the natural raw materials instead of commercial SiO_2. All of the investigated compositions were prepared by melting the glass mixtures at 1350°C for 3 h. The resulting glass samples were heated at different thermal treatment temperatures ranging from 750 to 1050°C with fixed dwell-time for 4 h for crystallization. Phase identification of the 45S5 glass ceramics was carried out by X-Ray diffraction (XRD). Moreover, the physical properties such as density, porosity and mechanical properties were systematically investigated. It was found that, the increasing of heat treatment temperature led to the increasing of the Na₂Ca₂Si₃O₉ phase and obtaining better bioactive behavior after incubation of glass-ceramics in simulated body fluid (SBF) for 7 days. The maximum hardness value of 4.02 GPa was achieved after heating at 1050°C for 4 h. However, the density value has slightly changed with various heat treatment temperatures.

Abstract: Multi-angular branched ZnO microstructures with rods-shaped tips and nanopushpins with hexagonal cap on top have been synthesized by a simple thermal treatment process of compacted ZnS powder used as starting material and substrate. The structures have been grown at different temperatures (800, 900 and 1000 °C) for 60 min, in a constant nitrogen environment at atmospheric pressure via a catalyst-free process. XRD results of the as-grown products from ZnS powder show a significant reduction in the cubic zincblende phase to the hexagonal wurtzite phase with the increase of treatment temperature, as compared to the bulk value. Post-anneal analyses indicated that the transformation of morphologies of the as-grown structures also depends strongly on the treatment temperature. The proposed method represents an easy and economical way to grow complex structures of ZnO, with a relatively short time, furthermore, without the neediness of use an external substrate to grow. These new and interesting nanostructures have potential in applications such as optoelectronics.

Abstract: Mechanical engineering is the leading business unit, capable of giving impetus to innovation development of all industry sectors virtually, so restructuring and development of innovative production in engineering industry is an objective and urgent problem of modern times.