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Silica Coating (silica + coating)
Selected AbstractsRecent Progress on Silica Coating of Nanoparticles and Related NanomaterialsADVANCED MATERIALS, Issue 11 2010Andrés Guerrero-Martínez Abstract In recent years, new strategies for silica coating of inorganic nanoparticles and organic nanomaterials, which differ from the classical methodologies, have emerged at the forefront of materials science. Silica as a coating material promises an unparalleled opportunity for enhancement of colloidal properties and functions by using core,shell rational designs and profiting from its synthetic versatility. This contribution provides a brief overview of recent progress in the synthesis of silica-coated nanomaterials and their significant impact in different areas such as spectroscopy, magnetism, catalysis, and biology. [source] Formation of Hydrophobic Silica Coatings on Stones for Conservation of Historic SculpturesCHINESE JOURNAL OF CHEMISTRY, Issue 8 2010Feigao Xu Abstract The conservation of historic sculptures is receiving growing attention because of the increasing air pollution. A hydrophobic silica coating was synthesized to protect historic sculptures from weathering by starting from a solution of tetraethoxyorthosilicate (TEOS) precursor using hexadecyltrimethoxysilane (HDTMS) as hydrophobic modifier in the presence of ammonia as a catalyst. The molar ratio of ethanol, TEOS, H2O and NH4OH was kept constant at 8:0.045:3:2.8 and the molar ratio of HDTMS/TEOS (M) was varied from 0 to 0.458. The organic modification was confirmed by infrared spectroscopic studies, and the hydrophobicity of the coating was tested by the contact angle measurements. The stone surface morphology of sample treated with silica coating was characterized. The results showed that the nanocomposites were composed of spherical particles with grain size of about 190 nm in diameter. After the limestone's surface was modified, the contact angle of limestone increased from 20° to 100° for M0.458. The protective performance evaluated with its ability to resist acid rain reveals that the protective effects are satisfying. [source] Luminescent Core/Shell Nanoparticles with a Rhabdophane LnPO4 - xH2O Structure: Stabilization of Ce3+ -Doped Compositions,ADVANCED FUNCTIONAL MATERIALS, Issue 3 2006V. Buissette Abstract The core/shell strategy has been successfully developed for rhabdophane lanthanide phosphate aqueous colloids. The growth of a LaPO4 - xH2O shell around Ce,Tb-doped core nanoparticles increases their stability against oxidation. A bright green luminescence is thus preserved in sol,gel films whose fabrication requires silica coating and thermal treatment of the core/shell nanoparticles. [source] Recent Progress on Silica Coating of Nanoparticles and Related NanomaterialsADVANCED MATERIALS, Issue 11 2010Andrés Guerrero-Martínez Abstract In recent years, new strategies for silica coating of inorganic nanoparticles and organic nanomaterials, which differ from the classical methodologies, have emerged at the forefront of materials science. Silica as a coating material promises an unparalleled opportunity for enhancement of colloidal properties and functions by using core,shell rational designs and profiting from its synthetic versatility. This contribution provides a brief overview of recent progress in the synthesis of silica-coated nanomaterials and their significant impact in different areas such as spectroscopy, magnetism, catalysis, and biology. [source] Metallodielectric Photonic Crystals Assembled from Monodisperse Spherical Colloids of Bismuth and Lead,ADVANCED MATERIALS, Issue 4 2006Y. Wang Monodisperse metallic and metallodielectric spherical colloids have been synthesized in large quantities and explored as building blocks for fabricating three-dimensional metallodielectric photonic crystals. Both measurements and calculations revealed large photonic bandgaps covering optical wavelengths from the visible up to the near-IR region for the metallic (Bi and Pb) and metallodielectric (with a silica coating) colloids (see Figure). [source] Comparison of Repair Methods for Ceramic-Fused-to-Metal CrownsJOURNAL OF PROSTHODONTICS, Issue 5 2006Mutlu Özcan DMD Purpose: The objective of this study was to evaluate the effect of four repair methods on the fracture load of repaired ceramic-fused-to-metal crowns. Materials and Methods: Metal-ceramic crowns were fractured, and the failure load was measured. The fractured metal-ceramic crowns (n = 9) were assigned randomly to the following treatment groups: (1) hydrofluoric acid (9.5%) etching, (2) air-particle abrasion (50 ,m Al2O3), (3) silica coating (30 ,m SiOx), and (4) the application of a layer of glass fiber-reinforced composite (FRC) (thickness: 0.12 mm) on the repair surface. The crowns were repaired with a highly filled resin composite and subjected to 3 repair cycles (n = 27). All specimens were stored in water at 37°C for 24 hours and then thermocycled (6000 cycles, 5°C to 55°C). The fracture load values for final failure of intact and repaired crowns were measured with a universal testing machine, and failure types were recorded. Results: No significant differences ( p > 0.05) were found between the final failure values for the groups treated with 9.5% hydrofluoric acid (376 N) and airborne particle abrasion with either Al2O3 (432 N) or SiOx (582 N) followed by silanization, respectively. Significantly, higher ( p < 0.0001) final failure values (885 N) were obtained with the use of the FRC layer when compared with the other repaired groups. There was no significant difference ( p > 0.05) between the final fracture load of intact crowns (872 N) and those repaired with FRC (885 N) (One-way ANOVA with repeated measures, Bonferroni test). No significant difference in fracture loads was found between the 1st, 2nd, and 3rd repair cycles (558 N, 433 N, 485 N, respectively). Failure sites were predominantly at the alloy/veneering resin interface in Group 1; Groups 2 and 3 both showed more cohesive failures than Group 1. In the case of FRC, the failure pattern was exclusively cohesive between the two laminates of FRC layer. Conclusions: The conditioning methods (Groups 1 to 3) of the repair surfaces did not show differences between each other; each resulted in mean fracture loads at lower levels than that of the intact crowns. Addition of an FRC layer increased the fracture load to the level of intact crowns. This suggests that the use of FRC in repairs of metal-ceramic crowns might be a viable option. [source] A Practical Method for Chairside Repair of Debonded Porcelain Denture TeethJOURNAL OF PROSTHODONTICS, Issue 1 2006Mutlu Özcan DMD The bonding of porcelain denture teeth to polymethylmethacrylate remains a clinical problem. In this article an alternative chairside method, based on silica coating and silanization for adhesion of denture tooth porcelain to polymethylmethacrylate is described. [source] Formation of Hydrophobic Silica Coatings on Stones for Conservation of Historic SculpturesCHINESE JOURNAL OF CHEMISTRY, Issue 8 2010Feigao Xu Abstract The conservation of historic sculptures is receiving growing attention because of the increasing air pollution. A hydrophobic silica coating was synthesized to protect historic sculptures from weathering by starting from a solution of tetraethoxyorthosilicate (TEOS) precursor using hexadecyltrimethoxysilane (HDTMS) as hydrophobic modifier in the presence of ammonia as a catalyst. The molar ratio of ethanol, TEOS, H2O and NH4OH was kept constant at 8:0.045:3:2.8 and the molar ratio of HDTMS/TEOS (M) was varied from 0 to 0.458. The organic modification was confirmed by infrared spectroscopic studies, and the hydrophobicity of the coating was tested by the contact angle measurements. The stone surface morphology of sample treated with silica coating was characterized. The results showed that the nanocomposites were composed of spherical particles with grain size of about 190 nm in diameter. After the limestone's surface was modified, the contact angle of limestone increased from 20° to 100° for M0.458. The protective performance evaluated with its ability to resist acid rain reveals that the protective effects are satisfying. [source] Surface-Protected Etching of Mesoporous Oxide Shells for the Stabilization of Metal NanocatalystsADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Qiao Zhang Abstract Nanoparticles of transition metals, particularly noble metals, are widely used in catalysis. However, enhancing their stability during catalytic reactions has been a challenge that has limited the full use of the benefits associated with their small size. In this Feature Article, a general "encapsulation and etching" strategy for the fabrication of nanocatalyst systems is introduced in which catalyst nanoparticles are protected within porous shells. The novelty of this approach lies in the use of chemical etching to assist the creation of mesopores in a protective oxide shell to promote efficient mass transfer to encapsulated metal nanoparticles. The etching process allows for the direct transformation of dense silica coatings into porous shells so that chemical species can reach the catalyst surface to participate in reactions while the shells act as physical barriers against aggregation of the catalyst particles. By using the surface-protected etching process, both yolk,shell and core,satellite type nanoreactors are synthesized and their utilization in liquid- and gas-phase catalysis is demonstrated. The thermal and chemical stability of the metallic cores during catalytic reactions is also investigated, and further work is carried out to enhance recyclability via the introduction of superparamagnetic components into the nanoreactor framework. [source] Atmospheric Pressure Plasma Deposition of Adhesion Promotion Layers on AluminiumPLASMA PROCESSES AND POLYMERS, Issue S1 2009Philipp Bringmann Abstract The paper presents investigations on the deposition of plasma polymerised films at atmospheric pressure as a pretreatment for painting and adhesive bonding of aircraft aluminium structures. Two different plasma jet sources are employed, one based on a controlled arc discharge and air as process gas, and another based on a dielectric barrier discharge (DBD) and He as plasma gas. The organosilicon precursors HMDSO, TEOS and OMCTS are used with both plasma sources. Deposition in the arc discharge plasma jet leads to almost carbon-free silica coatings, whereas coatings deposited with the DBD jet source contain a high amount of carbon, varying with precursor type. The obtained results of corrosion investigations and adhesion tests are promising, as some representative aircraft industry requirements could be achieved. However, the investigations show a strong dependency on the used precursor and type of polymer (paint or adhesive) applied on the plasma polymerised film. [source] | ||||||||||