Papers by Keyword: Sol-Gel Technology

Abstract: This paper deals with sol-gel process and application in no cement castables based on andalusite. The use of calcium free binder increases the refractory parameters of material and allows its faster drying. Six colloidal sols from CWK Bad Köstritz based on SiO₂ were tested, which differed not only in concentration and particle size, but also in pH. The influence of silica sols on the consistency of fresh castable, initial setting and final setting times were investigated. Furthermore, basic parameters after firing, such as bulk density, apparent porosity, flexural and compressive strength, were tested.

Abstract: The aim of research was developed area of nanoporous ceramic matrials of ternary - ZrO₂-TiO₂-SiO₂ system. The ceramic materials of system ZrO₂-TiO₂-SiO₂ was synthesized via sol-gel technology by hydrolysis of tetraethylorthosilicate (TEOS), zirconia propoxide and titanium isporopoxide solutions. The sols were polymerized at room temperature to obtain gels. Then gels were dried at 100 ^OC 72 hours. Xerogel was milled 1 or 6 hours and the powder was axial pressed for nanoporous ceramic samples. All the samples were sintered at 800 ^OC or 1000 ^OC in air. 1M HYPERLINK "res://\\\\ld1062.dll/type=1_word=hydrochloric%20acid" hydrochloric acid (HCl) and destilled water were used as a catalyst to promote the hydrolysis and condensation reactions. All samples were characterized by X-rays (XRD) diffraction, particle size distribution and compressive strength. Apparent density and specific surface area of ceramic samples were determined by a Brunauer, Emmett and Teller (BET) nitrogen adsorption-desorption isotherms.

Abstract: The aim of the research was to develop the area of mesoporous thin films of a binary TiO₂–SiO₂ system. Sol was synthesized from tetraethylorthosilicate as the silica source and titanium isopropoxide solution as the TiO₂ source, while triblock copolymer surfactant (Pluronic F 127 (10% solution in water, (P))) was used as the mesostructure-directing agent. In this paper we present sol-gel obtained TiO₂–SiO₂ with a mesoporous structure. The effects of added titanium on the mesostructure and on the porosity are presented and discussed. Four different molar percentage ratios of Ti: Si were used for the synthesis of mixed TiO₂–SiO₂ mesoporous thin films on glass substrate. The mesoporous structure of thin films was characterized by X-ray diffraction (XRD) patterns, atomic force microscopy (AFM), scanning electron microscopy (SEM) and the water contact angle. These mesoporous TiO₂–SiO₂ thin films could have many potential applications in many areas such as separation membranes, catalysis, optics, and self-cleaning surfaces.

Abstract: Antibacterial activity of zinc oxide (ZnO) or strengthening of hydroxylapatite whisker (HAPw) had been studied and applied widely. However, antibacterial property of ZnO-HAPw was scarcely researched nowadays. The aim of this study was to further investigate several kinds of morphologies of ZnO-HAPw prepared by sol-gel technology at different pondus hydrogenii (pH) value and temperature. Four kinds of morphologies of ZnO-HAPw were granule, triangle, short rod and gongs nail at 70°C and pH=6.4, 37°C and pH=6.6, 70°C and pH=6.6, 70°C and pH=6.6. The SEM images of HAPw and ZnO-HAPw samples showed that the HAPw surface was smooth and no difference after annealing treatment. In addition, different shapes of nanoZnO fused uniformly on the HAPw surface. The EDS indicates nanoZnO fuses on HAPw surface.

Abstract: Considering the grit aggregation of fixed abrasive and the environmental pollution of free abrasive machining tools, a kind of ultra-fine abrasive polishing pad was fabricated by means of sol-gel technology. The effects of drying method, gel reaction time, sodium alginate concentration and pad thickness which determine the property of the polishing pad were respectively investigated. And the polishing pad fabricated under the optimized condition was utilized to polish silicon wafer on a nano-polishing machine to evaluate the tool performance.

Abstract: This study applies the principle of silane coupling agent (SG-Si900) of alkane chain steric hindrance effect ,using SG-Si900, tetrabutyl titanate and TEOS as the main raw materials synthesizes self-cleaning organic Ti-Si compound materials by hydrolysis, constant temperature polycondensation and distillation. To improve the comprehensive performance, we can adjust the synthesis temperature and some main reaction parameters, such as H2O/Si, SG-Si900/TEOS, Si/Ti. The experiment proves that the best preparation conditions of compound materials is at the synthesis temperature of 80°C, the ratio of H2O/Si is 8, the ratio of Si/Ti is 9, the ratio of SG-Si900/TEOS is 1. The viscosity of the compound materials which were mutually soluble with water at any ratio is 40.9 S and the contact angle of water against composite films based glass which are made by pulling method is less than 5°.

Abstract: In order to transform the diamagnetism of expanded graphite (EG) to ferrimagnetism and improve its electromagnetic interferential capability, nano γ-Fe₂O₃/EG magnetic composite materials was prepared by sol-gel and low temperature self-combustion technique. The as prepared samples were characterized by SEM, XRD and Magnetic hysteresis cycle test. The results indicated that the composite materials had ferrimagnetism property after the embedding of γ-Fe₂O₃, but the average conductivity of the composites decreases gradually with the increase of γ-Fe₂O₃. Different mixing ratio of ferrite gel and graphite intercalation compounds produced ferric oxide with different crystal form and shape. When the content of ferrite sol was low, spherical γ-Fe₂O₃ with the mean size of 31.69nm was formed, and spread unevenly on the surface and interformational micelles of EG. High content of ferrite sol (83wt%) produced more perfect crystal γ-Fe₂O₃ of pentahedron shape with the mean size of 44.68nm, and a few of α-Fe₂O₃ occurred which lead to the decline of the magnetic property of the composite materials.

Abstract: In this study, thin films of CaBi₄Ti₄O₁₅ with preferential crystal orientation were prepared by the chemical solution deposition (CSD) technique on a SiO₂/Si substrate. The films consisted of a crystalline phase of bismuth-layer-structured dielectric. The as-deposited CaBi₄Ti₄O₁₅ thin films were crystallized in a conventional furnace annealing (RTA) under the temperature of 700 to 800°C for 1min. Structural and morphological characterization of the CBT thin films were investigated by X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM). The impedance analyzer HP4294A and HP4156C semiconductor parameters analyzer were used to measurement capacitance voltage (C-V) characteristics and leakage current density of electric field (J-E) characteristics by metal-ferroelectric-insulator- semiconductor (MFIS) structure. By the experimental result the CBT thin film in electrical field 20V, annealing temperature in 750°C the CBT thin film leaks the electric current is 1.88x10^-7 A/cm² and the memory window is 1.2V. In addition, we found the strongest (119) peak of as-deposited thin films as the annealed temperature of 750°C

Abstract: A short review of recent investigations of the authors on the Ru(II)-based optical oxygen sensors is presented focused on the influence of: (i) type of the supporting matrix (SiO2 or polymethylmetacrylate based), (ii) precursors used (tetraethoxysilane, ormosil-type alkoxosilanes, methylmetacrylate, polymethylmetacrylate), (iii) method applied for the matrix synthesis, (iv) method for films deposition (dip- and spin coating), (v) chromophore leaching as a result of storage of the films in potentially aggressive media (water, diluted acidic and basic solutions) and (vi) working environment nature on the: a) films morphology, b) the analytical characteristics of the sensing component (linearity of the Stern-Volmer dependence, sensitivity of the device, reproducibility of the results), c) admissible parameters (pH, temperature) of the working medium. Special attention is paid on the effect of sol-sonication (as a tool against dye microcrystallization). The results obtained permit optimal precursors, sol preparation conditions and coating procedure to be recommended for gas and for dissolved oxygen measurement, respectively. The sonication of the sol ensures a rather significant improvement of the sensor performance. The strong quenching of the chromophore in the case of in-situ polymerization of the methylmetacrylate is observed.The sensing films are successfully applied for oxygen determination in natural lake waters and beer.

Abstract: In situ synthesis technique of β-tricalcium phosphate(β-TCP)/ Na-doped 58S bioglass composite powders were investigated. Firstly, the β-TCP ultra-micro powders are synthesized via wet chemical method. β-TCP/Na doped 58S bioglass composite powders were synthesized in situ by sol-gel technique, using tetraethyl orthosilicate(TEOS), triethyl phosphate(TEP), calcium nitrate tetrahydrate(Ca(NO3)2•4H2O), sodium nitrate(NaNO3) as starting materials. The composite powders were characterized by XRD, EDX　and SEM. The bioactivity of the synthesized powders was analyzed by immersion studies in simulated body fluid (SBF). The results show that the composite powders are made up of good crystalline β-TCP and amorphous bioglass, and it was conformed that the material had good osteoproduction and bioactivities, that is an indication of bioactive potential in vivo. It is believed that the β-TCP/ Na-doped 58S bioglass (58SN) composite by sol-gel technique in situ could be a desirable biomaterial for preparing scaffold of bone tissue engineering.