CeO_2添加剂对等离子ZrO_2涂层抗热震性的影响

在ZrO2陶瓷涂层中加入适量的CeO2,使陶瓷涂层的抗热震性能得到提高,这主要是由于CeO2的加入,涂层的微小孔隙增加、涂层产生细微的网状裂纹,增加了微裂纹密度,从而降低了涂层的弹性模量,释放了涂层中的应力,提高了涂层的裂纹失稳扩展时的临界温差ΔTc,并可阻止裂纹沿单方向的快速扩展,使涂层的抗热震起裂性能和抗热震失效能力得到提高。其中,CeO2加入量为9%效果最佳,过量加入CeO2,会过早地促进裂纹的扩展、断裂,不利于提高涂层的抗热震性能。     

Controlled free radical polymerization of styrene initiated from the alkoxyamine-functionalized silicon surface

Manipulation of surface properties of wafer is im- portant in technologies of biotechnology and advanced microelectronics[1,2]. A number of methods have been developed to modify the surface properties[3]. Among them, polymer brush is a well recognized met…     

Sol-gel coatings of BaO-TiO2-SiO2 compositions

New alkali resistant BaO-TiO₂-SiO₂ coatings have been developed via the sol-gel process. In the solutions and in the gels (T<300°C) an infrared absorption band at 930 cm^–1 gives the possible evidence of mixed Si-O-Ti bonds, which have not been found in the system SiO₂-TiO₂-ZrO₂. Baking the films at about 500°C for less than 1 h leads to stable layers with negligible residual carbon contents. Compositions near 20 BaO-40 TiO₂-40 SiO₂ showed the best performance.     

Characterization of La0.8Sr0.2MnO3 Produced by a Reactive DC Thermal Plasma Spray System

An atmospheric pressure, reactive DC plasma spray system was used to evaluate a process for depositing porous, complex oxide thin films. A mixture of La₃O₃, SrCO₃, and MnCo₃ was used to produce a porous cathode layer for potential application in planar solid oxide fuel cells. The coated lanthanum strontium manganite (LSMO) layer made from the mixture was compared to ones generated using a pre-reacted LMSO powder made by solid-state reaction. The results showed that the crystallization of the reactive-spray formed coating layer on the zirconia substrate was higher than that of the coating layer on the mild steel from the pre-reacted LMSO powder. It is both a simpler process and gave better crystallization. The controlled porous coating layers with open pore size of less than 1 m were successfully produced in a reactive DC plasma spray system from the mixture of raw materials.     

Room-Temperature Mirror Preparation Using Sol-Gel Chemistry and Laminar-Flow Coating Technique

The CEA/DAM megajoule-class pulsed Nd:glass laser devoted to Inertial Confinement Fusion (ICF) research will require 240 cavity-end mirrors. The approved laser design necessitates 42-cm × 46-cm × 9-cm highly-reflective (HR)-coated substrates representing more than 50 m² of coated area. Prototypes of these dielectric mirrors were prepared with interference quaterwave stacks of SiO₂ and ZrO₂-PVP (PolyVinylPyrrolidone) thin films starting from sol-gel colloidal suspensions (sols). Low refractive index material was based on nanosized silica particles and high refractive index coating solution was made of a composite system. The colloidal/polymeric ratio in the composite system has been optimized regarding refractive index value, laser damage threshold and chemical interactions have been studied using FT-IR spectroscopy. A deposition technique so-called Laminar Flow Coating (LFC) has been associated to sol-gel chemistry for HR laser damage-resistant sol-gel coating development. This novel coating method confirmed its main advantages compared to dipping or spinning processes: coating large flat square substrates at room temperature with small solution consumption, good thickness uniformity, weak edge-effects, induced stress-free coating, good optical properties and laser damage resistance fulfilling.     

Sol-gel zirconia coatings aimed at dust suppression in aluminosilicate high temperature insulating blankets

The feasibility of reducing the amount of loftable fibres in aluminosilicate blankets by coating with sol-gel zirconia was studied. A zirconium alkoxide based solution was employed to coat small samples of blanket using a dip-coating technique. The zirconia coatings and two grades of blanket were analysed using DTA, XRD, SEM and optical microscopy techniques to characterize any reactions and phase changes occurring in the system over a range of temperatures. It was found that dip-coated samples fired at temperatures of 700–800°C displayed reasonably coherent coatings providing an anchoring effect at the surface of the material by bonding loose surface fibres in a network of zirconia.     

Mechanism of electroless deposition of Ni–W–P alloys by adding surfactants

This paper describes an electroless deposition method for the formation of a thin metallic film containing mainly nickel with significant amounts of tungsten (up to 25%) and phosphorus (5–10%). The film was deposited from an aqueous electrolyte that contained sodium tungstate as a source of tungsten, nickel sulphate as a source of nickel and hypophosphite as the reducing agent and a source of phosphorus. The surfactants were p‐hexyloxy‐p‐sodium sulphonate azobenzene (HSA) with the formula H₁₃C₆OC₆H₄N₂ C₆H₄SO₃Na and p‐hexylbenzyltriethanol ammonium chloride (HBC) with the formula H₁₃C₆H₄CH₂N⁺ (C₂H₄OH)₃Cl^?, added as stabilizers. In this study the process parameters of typical solutions, such as temperature, pH and concentration of tungstate salt and the concentration of different surfactants, were presented and discussed. Adsorption of the surfactants on a metal surface was dependent, among other things, on the structure of their hydrophobic and hydrophilic portions. The effect of adsorption of these surfactants on a metal surface was examined above and below the critical micelle concentration (CMC). The deposition process involves several reactions that occur simultaneously and are described in detail in this work. The mechanism for interaction of the surfactants with the steel surface was proposed through the isotherm for adsorption from aqueous solution. Furthermore, the surface properties of the surfactants were measured, particularly the CMC, the surface tension reduction and the maximum surface excess Γ_max. The tungsten percentage in the deposit layer was strongly influenced by the plating conditions and the critical concentration of each surfactant. The results were discussed according to the surface properties of the additive. The thin film of Ni–W–P achieved high crystal refinement and high hardness, it was smooth and uniform and it exhibited superior corrosion resistance. Copyright © 2003 John Wiley & Sons, Ltd.     

New method for the preparation of small diameter columns with polymeric stationary phases for open tubular liquid chromatography

The purpose of this report is to introduce a new method for use in coating polymeric stationary phase films on the inside wall of small bore diameter fused silica capillary tubing. This technique is being developed for use in fabricating capillary columns for open tubular liquid chromatography.     

Control of Wall Thickness and Extraordinarily High Hydrothermal Stability of Nanoporous MCM‐41 Silica

Wall thickness of siliceous MCM‐41 could be controlled systematically up to 36.1 Å. A reasonable model explaining formation of thicker MCM‐41 walls, not enlarging pore channel is proposed on the basis of TGA and ¹³C MAS NMR data of samples. Thermal restructuring process under mild basic condition favors the silica redeposition on silica wall and building up thicker wall. Most mesostructure of calcined MCM‐41 with thicker wall was retained even after hydrothermal treatment in boiling water for 14 days. To our best knowledge, the excellent hydrothermal stability of the MCM‐41 silica reported herein has not been described before and facilitates practical applications of mesoporous molecular sieves in future.     

Negatively charged sol-gel column with stable electroosmotic flow for online preconcentration of zwitterionic biomolecules in capillary electromigration separations

A negatively charged sol-gel coating was developed for on-line preconcentration of zwitterionic biomolecules in capillary electrophoresis (CE), using asparagine and myoglobin as representative zwitterionic bioanalytes. The sol-gel coating was created by using a solution containing three precursors: mercaptopropyltrimethoxysilane (MPTMS), tetramethoxysilane (TMOS), and n-octadecyltriethoxysilane (C18-TEOS). The resulting sol-gel coating contained chemically bonded mercaptopropyl functional groups that were further oxidized by hydrogen peroxide to the corresponding sulfonic acid moieties. Such a surface-bonded sol-gel coating can carry a negative charge over a wide range of pH due to the presence of deprotonated sulfonic acid groups. Under favorable pH conditions, the negatively charged sol-gel coating can facilitate the extraction of positively charged analytes from a zwitterionic sample through electrostatic interaction. This principle was employed to extract myoglobin and asparagine by passing aqueous samples of these zwitterionic analytes through a negatively charged sol-gel column. The extracted analytes were then desorbed and focused via local pH change and stacking. The local pH change was accomplished by passing a buffer solution with a pH above the solute p/ value, while a dynamic pH junction between the sample solution and the background electrolyte was utilized to facilitate solute focusing. The sorption/desorption phenomena could, perhaps, also be explained on the basis of ion-exchange and local pH junction effects. On-line preconcentration and analysis results obtained on sulfonated sol-gel columns were compared with those obtained on an uncoated fused silica capillary of identical dimensions using conventional sample injections. Using UV detection, the presented sample preconcentration technique provided a sensitivity enhancement factor (SEF) on the order of 3 x 10(3) for myoglobin, and 7 x 10(3) for asparagine.