Papers by Keyword: Silica Coating

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Authors: Yun Cang Li, Jian Yu Xiong, C.S. Wong, Peter D. Hodgson, Cui E Wen
Abstract: In the present study, titanium (Ti) samples were surface-modified by titania (TiO2), silica (SiO2) and hydroxyapatite (HA) coatings using a sol-gel process. The bioactivity of the film-coated Ti samples was investigated by cell attachment and morphology study using human osteoblast-like SaOS-2 cells. Results of the cell attachment indicated that the densities of cell attachment on the surfaces of Ti samples were significantly increased by film coatings; the density of cell attachment on HA film-coated surface was higher than those on TiO2 and SiO2 film-coated surfaces. Cell morphology study showed that the cells attached, spread and grew well on the three kinds of film-coated surfaces. It can be concluded that the three kinds of film coatings can bioactivate the surfaces of Ti samples effectively. Overall, Ti sample with HA film-coated surface exhibited the best bioactivity.
Authors: Y. Kobayashi, K. Misawa, M. Takeda, N. Ohuchi, A. Kasuya, M. Konno
Abstract: Silica-coating of AgI nanoparticles with a Stöber method was carried out to find out reaction conditions for control of the shell thickness. The AgI nanoparticles were prepared from AgClO4 and KI with the use of 3-mercaptopropyltrimethoxysilane (MPS) as a silane coupling agent and dimethylamine (DMA) catalyst for alkoxide hydrolysis. The silica-coating was performed at 4.5×10-6-4.5×10-5 M MPS, 11-20 M water, 0.002-0.1 M DMA and 0.005-0.04 M tetraethylorthosilicate at AgI concentrations of 0.1-1 mM. Consequently, AgI-silica core-shell particles could be prepared with the use of 4.5×10-5 M MPS, 20 M water, 0.01 M DMA and 1 mM AgI. Silica shell thickness could be varied from 15 to 28 nm with an increase in the TEOS concentration from 0.005 to 0.04 M.
Authors: Jong Chul Park, Jae Hwan Pee, Yoo Jin Kim, Woo Seok Cho
Abstract: The colored TaON and Ta3N5 were synthesized by ammonolysis of amorphous Ta(OH)5 in the temperature range of 800-1000°C. Ta(OH)5 were prepared by titration process from TaCl5. TaON were synthesized at 900°C for 2 hr, and Ta3N5 were synthesized at 1000°C for 5 hr. In general, Ta3N5 powders were easily oxidized at 500°C with changing colority from red to white. To minimize the oxidation problem of Ta3N5 powders, we proposed silica coated system using TEOS and APTES as a surfactant. Tonality of silica coated Ta3N5 has very little changing which means silica coating actually minimizes the oxidation of the Ta3N5 particles.
Authors: Christian R. Simon, R. Haugsrud, M. Musiani, S. Barison, John Charles Walmsley, T. Jacques, R. Bredesen
Authors: Wanchart Suprompituk, Thana Radpakdee, Nantiwat Pholdee, Papot Jaroenapibal
Abstract: This paper demonstrates a technique to synthesize silica-coated single-walled carbon nanotubes (SWNTs@SiO2) based on sodium dodecyl sulfate (SDS), 3-aminopropyltriethoxysilane (APTES), ammonium hydroxide (NH4OH) and tetraethyl orthosilicate (TEOS). The coating of silica is done to promote bond strength between SWNTs@SiO2 and other materials. The anionic surfactant used in the coating process helps create linkages between the silica coupling agent and the SWNTs’ walls without compromising the excellent properties of SWNTs. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray spectroscopy (EDX) were employed to characterize the sizes of SiO2 particles, the structure of SWNTs@SiO2, and the elements existed in the materials. The size of SiO2 particles has shown to be dependent on the amount of TEOS concentration and reaction time. Higher TEOS concentration and longer reaction time led to larger SiO2 particles. Successful coatings of SiO2 on SWNTs have been demonstrated. Silica appeared to be uniformly coated on the SWNTs surfaces. The thickness of the coating layer was found to be approximately 3-7 nm.
Authors: Miao Liu, Si Fang Li, Daniel Umereweneza
Abstract: The acid resistance of ultramarine blue was greatly enhanced by silica coatings. Sodium metasilicate nonahydrate was used as silica precursor and ammonium chloride was used to react with it. Fourier transform infrared (FT-IR) spectroscopy was used to characterize surface structure on the coating layer. The effects of coating conditions on acid resistances of the coated ultramarine blue were investigated. The acid resistance was evaluated by immersing the pigment in 10 wt% hydrochloric acid. The results showed the optimal mass ratio of silicate to ultramarine was 3.75 and the proper solid content was 60 g/L. Under above conditions, the silica coated ultramarine blue exhibited an acid resistance of 8, while the uncoated ultramarine blue only showed an acid resistance of 1.
Authors: Ahmed Mohamed El-Toni, Shu Yin, Tsugio Sato
Abstract: Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products because of its excellent UV light absorption property and low catalytic ability for the oxidation of organic materials superior to undoped ceria. The performance of calcia doped ceria needs more enhancement through further control of its oxidation catalytic activity and improvement of its covering ability. In order to reduce the oxidation catalytic activity further, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization technique. Generally, nanoparticles of calcia doped ceria do not provide a good coverage for human skin because of the agglomeration of the nanoparticles. The platy particles are required to enhance the covering ability of calcia doped ceria. This can be accomplished by synthesis of calcia-doped ceria/plate-like material (e.g., potassium lithium titanate (K0.8Li0.27Ti1.73O4) and mica) nanocomposite with subsequent silica coating. Calcia-doped ceria/plate-like material was prepared by soft chemical method followed by silica coating via seeded polymerization technique. Silica coated calcia-doped ceria/plate-like material nanocomposite was characterized by X-ray diffraction, SEM, TEM, XPS and FT-IR.
Authors: Wanchart Suprompituk, Papot Jaroenapibal
Abstract: This work demonstrated the improvement of belite cement compressive strength by incorporating nanosilica coated single-walled carbon nanotubes (SWNTs@SiO2) into the cement paste. The structure and chemical compositions of SWNTs@SiO2 materials were characterized by transmission electron microscopy and energy dispersive X-ray spectroscopy techniques, respectively. Belite cement composites were prepared by mixing belite cement paste with different loadings of SWNTs@SiO2 ranging from 0.02 – 0.1 wt%. In order to measure the early strength of cement composites, the samples were aged for 7 days, and then subjected to compression tests. Effects of uncoated SWNTs and silica coated SWNTs loadings on the compressive strength of belite cement composites were studied. Without pre-coating SWNTs with nanosilica, the SWNTs additives led to large decrease in compressive strength of belite cement composite. Improvements in compressive strength of belite cement are shown in samples that incorporated SWNTs@SiO2 loadings. The coating layer helps enhance bonding strength between reinforced SWNTs and the matrix, as well as promote hydration reactions in the cement paste. The highest increase in the compressive strength of 18.8 % is found in the sample with the minimal SWNTs@SiO2 loading of 0.02%.
Authors: Cyril O. Ehi-Eromosele, J.A.O. Olugbuyiro, A. Edobor-Osoh, A.A. Adebisi, O.A. Bamgboye, J. Ojeifo
Abstract: Coating of magnetic nanoparticles (MNPs) is usually a requirement prior to their utilization in biomedical applications. However, coating can influence the magneto-structural properties of MNPs thereby imparting their applications. The present work highlights the combustion synthesis of Na-doped lanthanum manganites (LNMO) and the influence of silica coatings on the magneto-structural properties, colloidal stability and antimicrobial properties of LNMO MNPs with their biomedical applications in mind. The crystalline perovskite structure was the same both for the bare and silica coated LNMO samples while there was a slight increase in crystallite size after coating. The FTIR spectral analysis, reduction in agglomeration of the particles and the elemental composition of the coated nanoparticles confirmed the presence of silica. The magnetization values of 34 emu/g and 29 emu/g recorded for bare and coated LNMO samples, respectively show that LNMO MNPs retained its ferromagnetic behaviour after silica coating. The pH dependent zeta potentials of the coated sample is-22.20 mV at pH 7.4 (physiological pH) and-18 mV at pH 5.0 (cell endosomal pH). Generally, silica coating reduced the antibacterial activity of the sample except for Bacillus spp where the antibacterial activity was the same with the bare sample. These results showed that while silica coating had marginal effect on the crystalline structure, size and magnetization of LNMO MNPs, it reduced the antibacterial activity of LNMO MNPs and enhanced greatly the colloidal stability of LNMO nanoparticles. Keywords: Na-doped lanthanum manganites, Silica coating, magnetic nanoparticles, biomedical applications, antimicrobial properties, colloidal stability
Authors: Ahmad Farooq, Ali Abd El-Aty
Abstract: Silica coated alumina abrasives, used for abrading the surface of Yttria stabilized tetragonal zirconia polycrystal ceramics, were produced in order to achieve successful bonding with resin luting cement. The source of the silica coating was from Silicon Nanoparticles (SiNPs) that were produced from spark erosion in high pressure flushing of deionized water. SEM images verified average size distribution of the SiNPs to be between 30-50nm. In contrast to the tribochemical methods that are used widely to produce such abrasives, a completely novel dry physical process was opted for this experiment. By optimization of the conditions, 2g of purified SiNPs was mixed with 20g of alumina μ-particles (approximated diameter of 100μm), in presence of 25ml ethanol, mixed thoroughly to form slurry. Heated up to 120°C for 20 minutes to evaporate the ethanol, the resultant powder mix was compacted and uploaded in furnace at temperature of 1100°C for 2hrs. This formed an oxide layer on the SiNPs which consequently formed bonding with the alumina particles. SEM/EDS results validate substantial amount of coating of silica on alumina. The paper hereby demonstrates a novel method of producing silica coated alumina abrasives, which is a dry and cleaner substitution method compared to tribochemical approach.
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