جستجوی مقالات مرتبط با کلیدواژه « sol-gel » در نشریات گروه « مواد و متالورژی »

In the present research, nanoparticles based on the alumina-yttria system were synthesized using a sol-gel method. Then, the effect of heat treatment on the phase evolution and crystallite size in this composite system was investigated. The produced composite powder was characterized using X-ray diffraction and scanning electron microscopy. Scherrer equation was used to investigate the effect of temperature on crystallite sizes. The composite powder was cold isostatically pressed and subjected to a pressureless sintering process at different temperatures to evaluate its density changes. The X-ray diffraction results showed that the powder sample was initially amorphous. By increasing the temperature, the components of this composite system reacted and Alpha-Al2O3 and Y3Al5O12 phases are formed. The crystallite size of the Theta-alumina phase grew with increasing temperatures up to 1000 C. At higher temperatures, crystallite size decreased due to the decomposition of theta-alumina. The density of the samples increased by increasing the temperature up to 1600 C so that the samples reached a relative density of about 96%. The densification curve of the composite showed three different stages during sintering. Examining the hardness of the samples showed that the hardness increases with the increase of the sintering temperature, and in the sample sintered at 1600 C for 3 hours, the Vickers hardness reached about 14 GPa.

In this study, by selecting the appropriate process conditions and using aluminum cans, the aluminum alkoxide compound was prepared and used as a precursor in aluminum oxide (Al2O3) nanoparticle synthesis processes by sol-gel method. In the production of mesoporous Al2O3 nanoparticle via sol-gel process, the aging temperature of 25, 60, 80 °C and time of 12, 24 and 48 h were selected and investigated as the main parameters in determining the solute particle size and bonding during the gel process. The results showed that the aging temperature is 80 °C and 24h time as the optimal conditions for the synthesis of Al2O3 nanoparticle with superior properties in terms of specific surface area and porosity. The calcination temperature showed that the minimum temperature required to reach the alumina phase is 500 °C. However, due to the necessity of the presence of crystalline phase with maximum ordering in the layout of the atomic plates of 900 °C and 1 hour storage time, the optimum calcination conditions were selected. Scanning and transmission electron microscopy studies of the optimum sample showed that the final product had the same appearance as the nanoparticles, and the particle size distribution was in the range of 20 to 40 nm. It was also found that the synthesized nanoparticles have very distinct crystalline plates, and as a result of the nanoparticles bonding to each other and forming larger masses, porosities in the meso-range were formed in their microstructure which made the end product to be used as a catalyst substrate.

The nickel oxide layer doped with cerium was applied on a glass slide using the solution obtained from two precursors, nickel hexacetate and cerium ammonium hexanitrate with the general formula Ni1-eCexO and heated at different temperatures up to 550 degrees Celsius. Structural studies showed that the coated layers were composed of nickel oxide nanocrystals with a size of 40 to 120 angstroms. The thickness of the applied layer was 600 nm and it was formed with 5 layers. Electrochemical measurements including cyclic voltammetry and electrochemical impedance showed the reversibility of the electrochromic layer in 25 cycles. The ability of lithium ions to enter the tested layer was confirmed by 0.1 M solution of lithium perchlorate in isopropyl alcohol and current measurement compared to the Ag/AgCl electrode. During the conducted studies, the molar ratio of 0.05 to 0.1% was found to be appropriate due to the minimum electrical resistance and slight change in the visible transmission spectrum. Spectroscopy of the layers showed that this coating has near infrared absorption capability of 40% without causing any color change under the glass base, and its use as an optically passive electrode is suitable.

Bioceramics are very popular materials for tissue engineering applications due to their properties such as suitable bioactivity, biocompatibility, excellent compressive strength, and wear resistance. One of the most widely used bioceramics is calcium silicates. Calcium silicates are biocompatible and bioactive with relatively good mechanical properties, but high degradation rate. Elements such as magnesium (Mg), zirconium (Zr), and zinc (Zn) are added to calcium silicates to resolve this problem. Baghdadite (Ca3ZrSi2O9) with good biological properties is one of the calcium silicate based ceramics in which the zirconium element has replaced part of the calcium element. Also, the presence of calcium and zirconium elements has increased the biological and mechanical properties of this material. The purpose of this research was to synthesize Baghdadite powder using the sol-gel process and to characterize it using X-ray diffraction test to study the formed phases, halo test for antibacterial properties investigations, Fourier transform infrared spectroscopy to determine the functional groups, and field emission scanning electron microscope to examine the morphology of the powder. The results showed that the single-phase Baghdadite phase was formed with the particle size of 225 ± 15 nm and lumpy morphology. The elemental analysis test confirmed the presence of the main elements of Baghdadite (Ca, Si, Zr, and O) in the synthesized sample. Moreover, the elemental map analysis confirmed the uniformity of Baghdadite constituent elements. The results of the Disk diffusion test revealed that Baghdadite had no appropriate antibacterial properties against staphylococcus bacteria, but showed a slight antibacterial properties against Escherichia coli bacteria.

In this research, zirconium carbide nanoparticles were synthesized by sol-gel method using pH and temperature parameters and controlling it during the process. Zirconium propoxide and phenolic resin were used as Zr and carbon raw materials, respectively. The effect of pH and temperature parameters in the synthesis process of these nano powders was investigated. The results in the case of tuberculosis showed that by controlling the pH in the range of 5, Zr-containing precursor particles can be synthesized in sizes below 10 nm. In FTIR data, Zr-O and Zr-C bonds were detected in the range of 560 and 1505 cm-1, respectively. The XRD results showed that no zirconium carbide particles were formed at the temperature of 700ºC and the initial compounds containing carbon and zirconia did not perform any chemical reaction yet. At the temperature of 1320 ºC, the initial buds of zirconium carbide have started to form. By increasing the temperature up to 1420 ºC, through carbothermal reactions, raw materials are converted into zirconium carbide. At a temperature of 1420 ºC, the size of the resulting crystallites is about 5 nm. In the characterization of the Raman spectrum, two relatively strong bands are seen in the ranges of 600 and 530 cm-1, which are related to the Zr-C bands of ZrC particles. During the hydrolysis of zirconium alkoxide in the presence of carbon phase and condensation at 60 ºC, a gel with Zr-O-C bonds was formed. These conditions made it possible to obtain the ZrC product at low temperatures, which was confirmed by DTA analysis. DTA/TG analysis showed that the initial buds of ZrC particles were formed in the temperature range of 1320 ºC, which is confirmed by the X-ray diffraction pattern. SEM microstructure images showed that zirconium carbide particles were formed in the range of dimensions below 100 nm and the particle size distribution was in a narrow and uniform range.

Magnetic cobalt ferrite nanoparticles have been widely employed in various applications, such as medical applications due to their desirable characteristics. Although generally magnetic nanoparticles are appropriate for such employments, their applications are restricted due to their toxic properties. Hence, it is tried to decrease the toxic damages by using a biocompatible coating layer. For this purpose, in the present study, it was tried to synthesize Ca2+ and Gd3+ doped cobalt ferrite nanoparticles by the sol-gel auto-combustion method and coat them with chitosan and polyethylene glycol polymers. X-ray diffraction (XRD) pattern along with the Rietveld refinement results confirmed the formation of pure cobalt ferrite nanoparticles with the average crystallite size of 27 nm. Moreover, the results of both thermogravimetry (TGA) test and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a coated layer of chitosan and polyethylene glycol polymers on the surface of nanoparticles. Magnetic characterization of the synthesized nanoparticles indicated that the formation of the coating layer can affect the magnetic properties, so that the saturation magnetization (Ms) increased from 67.93 to 74.61 emu/g. However, the coercivity (Hc) decreased from 982.86 to 908.13 Oe as a result of the formation of the coating layer.

In this study, a 3D bioactive glass composite scaffold containing 2 mol% silver/polycaprolactone (PCL) was synthesized by a 3D printer with the advantages of reproducibility and high flexibility in shape and size. The effective parameters (printer parameters, ratio of glass-phase, polymer phase, and solvent in printer ink) were determined for printing of nanocomposite scaffold by Taguchi method. Characterization of printed scaffolds was performed using X-ray diffraction, scanning electron microscope, infrared spectroscopy, bioactivity test, atomic emission spectroscopy, toxicity test, and cell proliferation. The results related to the synthesis of silver-containing bioglass by sol-gel method and heat treated at 550°C offered nanoparticles with an average diameter of less than 15 nm and a homogeneous distribution of silver in the matrix. Ratio of polymer phase to glass powder equivalent to 0.5, concentration of polymer in solvent of 50%, retraction of 1.5, and drive gear of 1200 are obtained as the optimum conditions for scaffold printing with acceptable quality (percentage, size and distribution of holes, regular structure of layers, and repeatability). The fabricated scaffold in optimal conditions revealed significant antibacterial properties, good bioactivity, acceptable cell viability, and high ALP activity. 3D printed BG/PCL nanocomposite scaffolds with macro (up to 500 µm) and micro size of holes and porosity percentage up to 64% in the structure can be a promising candidate for bone tissue engineering.

In the present research, alumina-ceria particles were synthesized by a sol-gel method. The produced particles were characterized by X-ray diffraction and scanning electron microscopy. Then, alumina matrix composites containing 15 wt.% of ceria were densified under 80 MPa pressure at different temperatures by spark plasma sintering process. X-ray diffraction results showed that the powder produced before heat treatment has an amorphous structure, while alumina and ceria phases are formed after calcination at 800 °C. The produced particles have an average particle size of 250 nm. The effect of sintering temperature on the density of samples, grain size, and hardness of composites was investigated. The samples were densified at about 1400 °C, reaching a density of about 97% of the theoretical density. The microstructure analysis revealed that the composite grains have grown with increasing sintering temperature. The results declared that increasing the temperature and pressure in the sintering process enhances the density of the samples. The Vickers hardness of the composites increased with increasing sintering temperature, as the composite samples sintered at 1400 °C for 20 minutes at a pressure of 80 MPa had the highest Vickers hardness of about 15.3 GPa.

The present project primarily aims to investigate the effect of synthesis method of the bioactive glass powder on the flowability and structural stability of the pastes from it. In this study, 45S5 bioactive glass was synthesized by melting and sol-gel methods. The rheological properties, injectability, washout resistance, and behavior of calcium phosphate deposition formation in the simulated body solution after 21 days were investigated using UV-visible spectroscopy, inductively coupled plasma atomic emission spectroscopy, and scanning electron microscopy. Finally, the cytotoxicity test was carried out, and its dependence on the concentration of the ions released from different pastes was evaluated. The bioactive glass powder prepared through the melting method was non-porous with a specific surface area of about 3 m2g-1 while the powder prepared by the sol-gel method was porous with a specific surface area of about 12 m2g-1. The values of the yield stress, viscosity, and thixotropy in the paste prepared by the sol-gel glass were higher than those of the sample prepared by melting method, and the injection force increased by about five times. Use of sol-gel glass led to the formation of pastes with lower washing resistance and for this reason, the dissolution and release rate of the ions from the paste containing sol-gel glass was higher than those of the same sample with molten glass. Increasing the specific surface area of the powder led to faster formation of the apatite layer on the surface of the samples; however, the rate of cell proliferation decreased due to the high concentration of ions in the environment.

In this research, the process of growth and the optimum length of ZnO nanorods has been studied as a subject of semiconductors, that are used in the photoelectrochemical solar cell made by Sol-Gel and Hydrothermal method.These Nano structures, having suitable gap, cause the decomposition of water into its constructing elements, hydrogen and oxygen.The most length of nanorods achieved by the FTO sublayer and deionized water solvent, at 95°C growth temperature, while 3 hours growing time, and on these conditions caused the length of nanorods to be 1500 nanometers, with the biggest length to width ratio 15.Also, at the final stage, photoelectrochemical experiments and the effects of nanorods length to the decompositionof water was studied. The results of photoelectrochemical experiments showed the optimum quantity for nanorods.The best result of photoelectrochemical has been reached to the maximum ratio of length to width 10, and the maximum length of nanorods 1000 nanometers that has been grown at the temperature of 95°C and during 2 hours.

Electrochemical capacitors have been considered for use in energy storage systems in recent years due to their high power density, high cycling stability, and optimal energy density. Binary metal oxides have been used by researchers to make electrodes due to their desirable morphological properties and better supercapacitive performance. In this study, manganese vanadate (Mn2V2O7) electrode was synthesized using two-step sol-gel and hydrothermal methods. Then, the characterization tests of XRD, FT-IR and SEM were used to determine the crystallographic and morphological properties. Characterization analyses showed that the electrode material of Mn2V2O7 was obtained with a hollow microbial morphology. Electrochemical tests of CV, GCD and EIS showed that the Mn2V2O7 electrode had excellent supercapacitive performance with a specific capacitance of 401 F/g at a current density of 1 A/g.

In recent years, cobalt ferrite nanoparticles have ‎attracted the attention of many researchers due to their vast industrial applications. In this regard, the current study aimed to synthesize ‎CoFe2O4‎ nanoparticles in the presence of different amounts of honey (0, 0.5, 1, ‎‎1.5, 2, and 2.5 g) through the sol-gel auto-combustion method. In order to investigate the microstructure as well as the structural and ‎magnetic properties of the synthesized samples, XRD, DTA/TG, FTIR, ‎FESEM, ‎and VSM analyses were carried out. The phase analysis confirmed that the ‎high-purity cobalt ferrite nanoparticles were formed after the calcination process. The FTIR results showed that ‎the intensity of the organic bands was significantly reduced ‎by adding honey. However, the presence of this agent caused severe changes in the ‎morphology of nanoparticles ‎and also their magnetic properties. Reducing the particle and average grain sizes of the nanoparticles by the addition of ‎honey caused an increase in their coercivity and consequently, their ‎magnetic parameters were enhanced to about 1580 Oe in the sample containing 1.5 g of honey. In addition, the saturation ‎magnetization increased in the ‎presence of honey, compared to the raw sample.

Water pollution is one of the big problems of human societies, and the need to find new ways to remove these pollutants has been given much attention in recent years. One of the methods is the use of photocatalysts. In this research, TiO2 and TiO2-CdO nanoparticles were prepared by a sol-gel method as nano photocatalysts. The produced samples have been used to degrade methylene blue under UV light. To characterize the prepared samples, X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), X-ray Energy Diffraction Spectroscopy (EDS), and Ultraviolet-Visible Spectroscopy (UV-Vis) were used. Microstructural results revealed nanoparticles with dimensions of 18 to 32 nm. XRD results showed that the main phase formed was the anatase. TiO2-4 wt.% CdO nanocomposite showed more photocatalytic activity compared to pure TiO2. Also, the effect of pH, irradiation time, and amount of powder on photocatalytic activity was investigated. The results showed that at pH=9, time of 75 min, and using 0.02 g TiO2-4 wt.% CdO photocatalyst, the maximum photocatalytic activity of about 92 % was obtained.

In this paper, due to the unique capabilities of nanomaterials such as homogeneity in mixing and surface - to - volume ratio, the synthesis and characterization of Zr nanoparticles and the investigation of the milling time on size distribution of the prepared nanoparticles have been investigated. To prepare zirconium dioxide nanoparticles, sol-gel method was used as the basic synthesis method and zirconium tetrachloride precursor was used. The synthesis of pure zirconium powder was carried out using the two-step reduction method of the synthesis of ZrO2 nanoparticles in nitrogen atmosphere. In the first stage of synthesis, ZrO2 powder was calcined with magnesium metal powder after milling in a thermal furnace at 800 . Then, in the final stage of synthesis, calcium metal was used for further refining the powder during milling. The results of EDX analysis at each stage of synthesis show that, after adding a small amount of Ca metal, the oxygen concentration was successfully reduced to about 0.043% by weight, which is in accordance with the standard specifications of zirconium sponge (ASTM B349 / B349M-16). Also, the results of DLS analysis show that the optimal milling time of nanoparticles is 12 hours. This research presents a new process for the production of high-purity metal zirconium nanopowder with the ability to replace the conventional industrial process.

In this study, we investigate calcium aluminate phases that were prepared by three different solid phase synthesis methods and a sol-gel method (with and without EDTA). The purpose of this study is to compare these three methods in terms of achieving higher purity, optimal phase and complexity in the production of the final product. Comparing the results, we found that the sol-gel method is more problematic than the solid-state synthesis. The phases prepared are: (CA), (C12A7), (C3A) and (CA2). In the sol-gel method, we have explored two different innovative regimens with EDTA. The results on the purity of the resulting phases and the effect of adding EDTA showed that, in general, the addition of EDTA leads to better purity. Quantitative x-ray diffraction analysis was used to determine the percentage of prepared calcium aluminate phases. The CA2 phase achieved 100% purity in the first preparation method in all three ways.