جستجوی مقالات مرتبط با کلیدواژه "بازپخت" در نشریات گروه "علوم پایه"

The giant magneto impedance (GMI) effect is a large variation in the electrical impedance of a magnetic conductor when subjected to a static magnetic field. The sensitivity to the direction (AGMI) and magnitude of applied  magnetic field    and also linearity levels   of this  effect are three important parameters in magnetic sensors application. A suitable annealing procedure can be used to achieve an optimum response of GMI by reducing the quenched-in internal stresses and induces transverse magnetic anisotropy.  In this research the effect of irradiation of gamma rays from two gamma sources (60Co, 137Cs) on the asymmetry of GMI  of Co68.15Fe4.35Si12.5B15  amorphous alloy is studied. The optimum asymmetry of studied sample obtained after 30 (24) hours irradiation by photons emitted by 60Co (137Cs) source. The X-ray diffraction pattern shows a transition from amorphous phase to a crystalline phase in  samples. Results  show that induced changes by irradiation with 137Cs source leads to a better sensitivity  to  direction of applied magnetic field especially in case of irradiated sample for 24 hours. This sample can be considered a good magnetic sensor candidate.

Well-aligned ZnO nanorods array have been synthesized through chemical bath deposition at law temperature (less than 120oC) using seed layer under different condition such as bath concentration and temperature, growth time, thickness of seed layer and it’s annealing. Structural, morphological, chemical and optical properties of ZnO nanorods array were studied by X-ray diffractometry, field emission-scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDX) and UV-Vis-near IR optical absorption spectroscopy, respectively.The post-synthesized thermal treatment results in increased crystalline quality of nanorods as vertical c preffered orientation. The height, mean diameter and density of strongly well-oriented ZnO nanorods array are 190nm, 31-52 nm and 290-413 rods/μm2 on ZnO seed layer, respectively. The annealing of nanorods at 400oC causes to decrease in bandgap energy from 3.29eV for the as-grown nanorods to 3.19 eV. The increase in bath temperature to 110oC results in random direction of nanorods and decreasing in bandgap energy. The annealing of seed layer at temperature range of 200-600oC causes to increase in mean diameter and decrease in nanorods height and concentration and bandgap energy. The decrease in seed layer thickness causes to decrease in nanorods concentration.

In this paper, the effects of temperature on the refractive index layer of magnesium fluoride, MgF2, is investigated. The layers, using the electron gun, in temperatures of different 25,100,200,300 °C and were deposited on the glass substrate (BK7). In all samples, the deposition rate was Å/C. Transmission spectra of samples, using a spectrophotometer at wavelengths 400-800nm were determined. The sample produced at room temperature was annealed for 2 hours at 300°C. Then, indexes of refraction of samples were calculated using three methods. The refractive indexes according to the methods were in a good agreement with one another. The results showed that by increasing the temperature from laboratory temperature to 300 °C, the refractive index of magnesium fluoride increased as a linear function from n=1.32 to n=1.39. Moreover, the index of refraction of the annealed sample increased conspicuously while the annealed sample showed some absorption.

In this research, Ni50Mn34In16 ferromagnetic shape memory alloy has been prepared by mechanical alloying method. XRD patterns of the samples showed that after 10 hours of ball milling, the alloy structure was completely formed and continuing of the milling process led to more fine particle size. Also the role of annealing on improvement of the alloy properties was studied. It was found that the sample annealing at 900ºC followed by quenching improves the crystal structure and helps to reach L21 structure. Ac susceptibility measurements showed that for the occurrence of magnetic transition, annealing and quenching process on the ball milled powder is necessary.

CdS: Mn nanocrystals were obtained by nucleation and growth in colloidal solution. Their mean size range between 3.96 nm and 4.90 nm. The structural properties were studied by the use of X-ray diffraction (XRD). Phase transition between the hexagonal structure and cubic structure was evidenced to be a function of synthesis temperature. The mechanism of the phase transition also was revealed by two-step annealing for 2h.