جستجوی مقالات مرتبط با کلیدواژه « پوسته » در نشریات گروه « مواد و متالورژی »

In this study, ZnO cores were first synthesized by using procedures zinc acetate dehydrate and sodium hydroxide via a co-precipitation method. Then, TiO2 shells were coated on the ZnO nanoparticles by using TTIP through co-precipitation approach to form ZnO/TiO2 core/shell nanocomposites. Structural and elemental studies were performed by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). Nanostructure morphologies were analyzed by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The optical absorption edges and band-gap energies were calculated using UV-vis spectra. Open-aperture z-scan technique was finally used to survey two-photon absorption phenomenon. Obtained results showed an increase in two-photon reverse saturable absorption for the ZnO/TiO2 core/shell nanocomposites compared to pristine ZnO nanoparticles.

In this paper, SnO2/ZnO core - shell nanocomposites were synthesized via sonochemical processing. To achieve this, ZnO nanoparticles were prepared by ultrasonic method. In the next stage, the core-shell nanocomposites in the presence of ZnO particles (prepared in the previous step) and adding precursor SnCl4.5H2O was prepared by ultrasonic. After synthesizing the nanocomposites, their properties were studied by XRD, TG-DTA and TEM analyses. The synthesized SnO2/ZnO core - shell nanocomposites have amorphous structure that can be changed to crystalline structure after calcination at 650 C for 1 hour. Also, the gas sensing characteristics of SnO2/ZnO core- shell nanocomposite was studied. For evaluating the gas sensing properties, the synthesized particles were prepared by pressing the powder into pills and gas sensing test was performed with respect to the various gases such as methanol, CO, and H2. Due to the unique properties of the core - shell semiconductor particles in the mechanism of charge separation, the gas sensing properties of core - shell particles are higher than those of pure oxides.

Due to high strength and stiffness in comparison with their weights، laminated composite materials are widely used in many structures such as aerospace. Therefore to predict their mechanical response، the understanding of their failure mechanisms is very important. The delamination between composite layers and adhesive joints is one of the main damage modes of these materials. In this research، the cohesive zone model is used to predict the damage evaluation of composite wing adhesive joints. The advantage of this method is the modeling of delamination growth without any requirements to the presence of initial crack and remeshing. Moreover to predict the probable damage in composite layers the Ladeveze progressive damage model has been implemented in Abaqus using user defined code (Umat) and also the importance of considering the intralaminar failure on the acceleration in damage initiation and propagation in adhesively bonded joints have been evaluated. The results verify the proper accuracy of implemented method. Furthermore، the results of solid cohesive elements showed to be more accurate in predicting damage initiation and evaluation in comparison to shell elements. Finally effects of adhesive properties such as thickness and quality of bonding in load capability of wing structure have been investigated.

In this paper, ZnO/Cu2O nanostructures were synthesized via molten salt and hydrothermal method. At the first step, the ZnO hierarchical nanostructures were successfullyprepared bymolten salt method at 200 oC without any calcination and post treatment. The hierarchical star-like structures were used as core due to higher light absorption. Secondly, Cu2O nanoparticles were formed on the arms surfaces of ZnO star-like particles via facile hydrothermal method. X ray diffraction, UV-Vis spectrum analyses were used to characterize the phases and optical behavior of core-shell structures. Microstructures of core-shell particles were also analyzed by scanning electron microscopy. Based on the result, the higher light absorption of core-shell structure made them as a good candidate to apply in photoelectrochemical cells.