جستجوی مقالات مرتبط با کلیدواژه « thermal oxidation » در نشریات گروه « فنی و مهندسی »

In the present work, two- component heterostructure of ZnOnanorods array (ZnO NRs) and CuO nanostructure has been grown. Well-aligned ZnO NRs have been synthesized using seed layer by low temperature wet chemical method. Then, CuOthin film has been form by thermal oxidation ofCu thin film deposited by magnetron sputtering on ZnO NRs to increase and expand optical absorption to visible region. The structure, morphology and chemical, optical, photocatalytic properties of ZnO NRs/CuOheterostructures have been studied by, X-ray diffractometry (XRD), field emission- scanning electron microscope/ energy dispersive X-ray spectroscopy (FE-SEM /EDX), UV-Vis- near IR optical absorption spectroscopy, and current – voltage measurement, respectively.Thermal oxidation of Cu thin film on ZnO NRs in the temperature range 200- 600 °C Cause ZnO NRs/CuO TF heterostructure to form. The ZnO NRs/CuOheterostructures increase and expand optical absorbtion to visible range in comparision to bare ZnO NRs.Photocatalytic activity of ZnO NRs/CuOheterostructure was investigated through Rhodamine B (RhB) photodegrdation under UV- Vis irradiation.Photocatalytic efficiency of ZnO NRs/CuOheterostructure is considerably increased in comparison to bare ZnO NRs

In recent years, much attention has been paid to aerogel materials (especially carbon aerogels) due to their potential uses in energy-related applications, such as thermal energy storage and thermal protection systems. These open cell carbon-based porous materials (carbon aerogels) can strongly react with oxygen at relatively low temperatures (~ 400°C). Therefore, it is necessary to evaluate the thermal performance of carbon aerogels in view of their energy-related applications at high temperatures and under thermal oxidation conditions. The objective of this paper is to study theoretically and experimentally the oxidation reaction kinetics of carbon aerogel using the non-parametric kinetic (NPK) as a powerful method. For this purpose, a non-isothermal thermogravimetric analysis, at three different heating rates, was performed on three samples each with its specific pore structure, density and specific surface area. The most significant feature of this method, in comparison with the model-free isoconversional methods, is its ability to separate the functionality of the reaction rate with the degree of conversion and temperature by the direct use of thermogravimetric data. Using this method, it was observed that the Nomen-Sempere model could provide the best fit to the data, while the temperature dependence of the rate constant was best explained by a Vogel-Fulcher relationship, where the reference temperature was the onset temperature of oxidation. Moreover, it was found from the results of this work that the assumption of the Arrhenius relation for the temperature dependence of the rate constant led to over-estimation of the apparent activation energy (up to 160 kJ/mol) that was considerably different from the values (up to 3.5 kJ/mol) predicted by the Vogel-Fulcher relationship in isoconversional methods

Hydroxyl terminated polybutadien (HTPB resin) is a liquid hydrocarbon polyol that is commonly used in the preparation of solid composite propellants. Because of unsaturated nature of HTPB polymer, it has high potential for oxidative aging. In this paper, the change in the properties of two types of HTPB resin under thermal oxidative aging in the presence and absence of phenolic antioxidant have been investigated. For this purpose, two samples of resin have been stored at 60 °C during four month under atmospheric pressure and the changes of the peroxide value, hydroxyl value, epoxy number, viscosity and molecular weight have been investigated. The results show that crosslinking of radical chains, increase of the molecular weight and hydroxyl functionality of HTPB are the most important oxidative events that occurred during oxidative aging.

In this research, nano-iron oxide was synthesized on the surface and between clay layers using sodium carbonate and iron nitrate after thermal oxidation in 400 ° C. X-ray diffraction from synthesized pigment showed the presence of nano-iron oxide II crystals on the surface of the pigment. Moreover, thermal measurement of nano-iron oxide-clay pigment showed an improvement of thermal stability in comparison with clay. SEM and EDX results showed the presence of chemical elements of Fe, Al and Si on the surface of clay. Reflectance properties of nano-iron oxide-clay pigment showed that the intensity of reflectance in visible region and lightness value of pigment is decreased which is due to deposition of iron oxide nano-particle in the final pigment compound. Results from electromagnetic test showed an increased electromagnetic absorbance in clay/nanoiron oxide pigment in comparison with clay. J. Color Sci. Tech. 8(2014), 1-11©. Institute for Color Science and Technology.

The int erest in dusty plasma research, which is a relatively new field in plasma physics, has increased with the development of m icroelectronics. The dust particles appear as pollutant in this industrial processing. Recent ly, however, they are seen from a different point of views – they can be useful in coatings various technologies for m icroelectronic, optic, electro-opt ic industrial. In this investigation we have concent rated on coating of dust particles by ZnO:Al thin film. D ust particles in the investigation are Zn, Al. Thin films are fabrication by Combination of Plasma Sputtering Zn, Al and T hermal Oxidation. T hese thin films have special physical properties, such as large bond strength, ZnO thin films exhibit high transparency in visible region and low electrical resistively. T he electrical and optical properties of ZnO:Al thin films were evaluated by XRD, RBS, the linear four point probe method and visible spectroscopy. T he best electrical properties obtain and the transparent in 300-800 nm wavelengths is 85 percent.

Aluminium particles were synthesized on clay using two methods of ion exchanged and oxidation. The characteristics of the pigments were investigated by fourier-transform infrared spectra (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscope (SEM), electron dispersive X-ray spectrometer (EDS), reflectance spectrophotometer (RS) and electromagnetic transition instrument (ETI). FTIR spectra showed generation of Aluminium and clay complexes into the clay interlayer. TGA result demonstrated an improvement in thermal stability of clay-Al pigments compared with untreated particles. SEM and EDX results showed that the aluminium aggregates are presented on the surface of clay. Aluminium particles also affected the electromagnetic properties of clay particles.

The effect of thermal oxidation temperature on microstructure, surface chemical composition and corrosion behaviour of commercial pure titanium (CP) are investigated. For this goal and creation of oxide layer with different thickness, the samples of CP tit anium isothermally oxided at temperature range of 400 -800 °C for duration of an hour. Microscopic studies, microhardness measurements, and polarization test in the physiological environment have been applied for characterisation and evaluation of the surfa ce layer. The structure of cross section and oxide layer thickness evaluated by employing optical microscopic examination. Diffusion depth and distribution of oxygen in substrate characterized by glow discharge optical emission spectroscopy (GDOES). Results show that oxide layer thickness and diffusion depth are increased by an increase of oxidation temperature. At oxidation temperature range of 400 -600 °C, increasing oxide layer thickness led to enhancement of corrosion resistance. On the other hand, incre asing of oxidation temperature in the range of 600-800 °C caused decreasing of corrosion resistance due to local spullation phenomenon of oxide layer. Concequently, temperature of 600 ºC was achieved as an optimum temperature for thermal oxidation of commercial pure titanium for corrosion resistance.