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Number of results: 11
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Abstract

Describes how to obtain a soluble sodium silicate with a density of 1.40 g/cm3, 1.45 g/cm3, 1.50 g/cm3, and silica module M = 2.1 obtained from the silica- sodium glass with module M = 3.3 and M = 2.1. Residual (final) strength of molding samples made with these binders, were determined at temperatures corresponding to the characteristic temperatures of phase and temperature transitions of silica gel. Indicated the type of soluble sodium silicate capable of obtain the smallest value of the final strength of molding sand in the specified range of temperatures.
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Abstract

In this paper the chemo-rheological behavior of aqueous TiC suspension and physical properties of gelcasted green body were investigated. The monomer system used in this project was acrylamide (AM) and methylenebisacrylamide (MBAM). Polymerisation reaction was promoted by the addition of tetramethyl ethylenediamine as a catalyst and ammonium persulfate as a initiator. The effects of tetramethylammonium hydroxide (TMAH), polyethylenimine (PEI) and polyethylene glycol (PEG) dispersants on the premix solution containing TiC powder have been studied via observation of the zeta potential and rheological behavior. The optimal amount of TMAH was achieved 0.4 wt.% at pH 9. The chemorheological results showed that the gelation time decreased and viscosity increased with increasing the monomer content, solid loading, initiator amount and temperature. The highest flexural strength of gel casted green body was obtained with 50 vol% solid loading and 25 wt.% monomers content.
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Abstract

U-type ferrite typified by Ba4Co2Fe36O60 is used as a RAM (Radar Absorbing Materials) in the X-band (8-12 GHz). Ba4Co2Fe36O60 is known to have a complex crystal structure, which makes it difficult to obtain single phase and have low reproducibility. Previously known U-type ferrites have been fabricated based on a ceramic process that mixing (by a ball mill), calcining, grinding, binder mixing, drying, sieving, pressing and sintering. In contrast, the process of preparing the powder by the sol-gel method and its heat-treating is advantageous in that it can reduce the process steps and the required time. In addition, the precise stoichiometric control by the sol-gel method can effectively evaluate the effect of added or substituted elements. In this study investigates the crystal structure of Ba4Co2Fe36O60 synthesized by the sol-gel method and the morphology of U-type ferrite nano-powders according to various heat treatment conditions. Analysis of the crystal structure is used for XRD. Morphology and size are observed by SEM. In addition, VSM is performed to confirm the change of magnetic properties according to various heat treatment conditions.
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Abstract

Hydroxyapatite (HAp) has been attracting widespread interest in medical applications. In a form of coating, it enables to create a durable bond between an implant and surrounding bone tissues. With addition of silver nanoparticles HAp should also provide antibacterial activity. The aim of this research was to evaluate the composition of hydroxyapatite with silver nanoparticles in a non-destructive and non-contact way. For control measurements of HAp molecular composition and solvent evaporation efficiency the Raman spectroscopy has been chosen. In order to evaluate dispersion and concentration of the silver nanoparticles inside the hydroxyapatite matrix, the optical coherence tomography (OCT) has been used. Five samples were developed and examined ‒ a reference sample of pure HAp sol and four samples of HAp colloids with different silver nanoparticle solution volume ratios. The Raman spectra for each solution have been obtained and analyzed. Furthermore, a transverse-sectional visualization of every sample has been created and examined by means of OCT.
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Abstract

The paper contains the results of the initial surface treatment influence on the properties of the medical Ti-6Al-7Nb alloy with a modified zirconium oxide layer deposited on its surface by sol-gel method. In the paper, the analysis of results of potentiodynamic studies is presented as well as its resistance to pitting corrosion and electrochemical impedance spectroscopy (EIS), macroscopic observation of the surface of samples and analysis of geometrical structure with the use Atomic Force Microscope (AFM) were performed. The studies were performed on two groups of samples depending on the graduation of the sand used in sandblasted process – 50 μm and 250 μm. Based on the obtained results it can be concluded that the type of the initial surface treatment preceding the surface modification of the Ti-6Al-7Nb has a significant effect on its properties.
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Abstract

GZO/IZO semiconductor thin films were prepared on the ITO substrate via sol-gel spin coating method for using in the dyesensitized solar cells (DSSCs). For this purpose, GZO and IZO thin films were optimized by the percentage of doping gallium and indium in zinc oxide and were studied their electrical, optical and structural properties. After that, the layers with the best performance were selected for use in the DSSCs. The concentration of all solutions for spin coating processes was 0.1 M and zinc oxide has been doped with gallium and indium, with different doping percentages (0, 0.5, 1, 2 and 4 volume percentage). So, by studying the properties of the fabricated thin films, it was found the films with 0.5%GZO and 0.5%IZO have the best performance and hence, the optimized dual-layer (0.5% GZO/0.5% IZO (GIZO)) were prepared and studied their electrical and optical properties. The synthesized optimized dual-layer film was successfully used as the working electrode for dye-sensitized solar cells. The sample with 0.5%IZO shows the 9.1 mA/cm2 short-circuit current density, 0.52 V open circuit voltage, 63% fill factor and 2.98% efficiency.
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Abstract

The ethylene vinyl acetate (EVA) is widely used for solar modules encapsulation. During lamination process EVA melts and chemical bonds between polymer chains are created. Its number is tightly related to cross-linking degree and it is consider as a major quality reference for module encapsulation. The lamination can be described as a process with two stages: melting and curing where the typical temperature for curing is in the range from 145 to 175°C. In the present study, for the first time, comparison of three commercial available EVA foils with low curing temperature EVA (EVA LOW). For this reason, the temperature of following lamination processes was set from a range from 115 to 175°C. The behavior of cured EVA films under investigation EVA was determined with two approaches: with extraction and with optical methods. The results indicate the applicability of these methods for the EVA cross-linking characterization. Finally, the extraordinary behavior of EVA LOW foil was noticed.
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Abstract

Y2O3-MgO nanocomposites are one of the most promising materials for hypersonic infrared windows and domes due to their excellent optical transmittance and mechanical properties. In this study, influence of the calcination temperature of Y2O3-MgO nanopowders on the microstructure, IR transmittance, and hardness of Y2O3-MgO nanocomposites was investigated. It was found that the calcination temperature is related to the presence of residual intergranular pores and grain size after spark plasma sintering. The nanopowders calcined at 1000°C exhibits the highest infrared transmittance (82.3% at 5.3 μm) and hardness (9.99 GPa). These findings indicated that initial particle size and distribution of the nanopowders are important factors determining the optical and mechanical performances of Y2O3-MgO nanocomposites.
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