Preparation and Properties of Chemically Bonded Ceramic Coatings Reinforced by GO-TiO2 composites

Russian Journal of Applied Chemistry - Graphene oxide (GO) decorated by titanium dioxide (TiO2) was fabricated and introduced into the chemically bonded ceramic coatings as a nanofiller. The...     

纳米Ni－B非晶态合金的催化性质研究

纳米Ｎｉ－Ｂ非晶态合金的催化性质研究杨军,崔黎丽,邓景发（复旦大学化学系,第二军医大学药学院,上海,２００４３３）关键词纳米材料,非晶态合金,催化性质纳米非晶材料融合了纳米晶与非晶材料的特性,既有很高的表面原子比,又呈高度几何无序状态。与普通非晶材料...     

Preparation and Chromatographic Properties of Some Chemically Bonded Phases for Reversed-Phase Liquid Chromatography

Abstract

Four different monomeric chemically bonded phases suitable for reversed-phase liquid chromatography have been prepared. Duplicate preparations, elemental analysis, post-treatment with TMS and chromatographic properties all indicate that maximum coverage has been obtained. The chromatographic activity of the silica surface is discussed on the basis of TMS-phases with various surface coverages. It is observed that logarithmic retention data for homologous series and different RP-phases-partially taken from the literature—form a set of straight lines with a common intersection point.     

Organopolysiloxanes as Chemically Sensitive Coatings for Optical Fibers

Various types of UV-curable organically modified siloxanes have been synthesized by the sol-gel method with the aim of fabricating chemically sensitive coatings for silica optical fibers. The refractive index of the coating material can be tailored in the range from 1.46 to 1.56 and sensitivity towards CO2 is achieved by incorporation of amino groups. The interaction of the cured layers with CO2 or with hydrocarbons has been studied in immersion experiments. Both the reaction of CO2 with incorporated amino groups and the penetration of hydrocarbons into the layer induce changes of the light absorption coefficient and the refractive index of the coating which are detected by measuring the output light intensity from the fiber.     

An STM Study of Chemically Deposited Silver Nanoclusters on Mixed Self-Assembled Monolayers

Small silver clusters Ag _n (primarily probably Ag₄ clusters which aggregate to Ag_n (400<n<2000)) are generated in the immediate vicinity of a four-electron reducing agent (based on hydroquinone) which is incorporated in a monolayer of long-chain alkanethiols. The hydroquinone derivative is oxidized to quinone (see the picture). Molecularly resolved scanning tunneling microscopy (STM) images were obtained of self-assembled monolayers with and without silver clusters.     

Thermochemical Properties of Chemically Modified Zeolite

Zeolites chemically modified with 1, 4 or 6 M aqueous solutions of NaOH were studied by DTA, TG and ETA (emanation thermal analysis) in the temperature range 201–200°C. The structural changes in the modified zeolites at room temperature and in the modified zeolites annealed at 1000°C were studied by XRD analysis. Thermal analysis demonstrated dehydration, dehydroxylation, structural changes and a glass transition. A gradual loss in crystallinity of the chemically modified zeolites was also observed. XRD analysis revealed structural changes caused by chemical treatment and also by annealing.This revised version was published online in November 2005 with corrections to the Cover Date.     

The Hemolytic Properties of Chemically Modified Cyclodextrins

The hemolytic properties of naturalcyclodextrins, especially of the more commoncyclomaltoheptaose entity, severely hamper theirpotential use as carriers in pharmaceuticalapplications where parenteral administration isconcerned. A systematic investigation on the role ofchemical modifications with regard to the hemolyticcharacter was carried out involving C-6 branchedneutral, anionic, cationic and amphoteric derivatives.From these data, conclusions have been drawnabout the charge and the geometry of the modification: (i)Substitution at primary hydroxyl groups usuallydecreases the hemolytic character and the geometry ofthe substituent affects the hemolytic property; (ii)introduction of an amino group, resulting in apositive charge at physiological pH, decreases thehemolytic character; (iii) negative charges arecomparatively less effective in reducing the hemolyticcharacter; (iv) zwitterionic groups seem to enhancethe hemolytic character of the cyclodextrin molecule.     

电脉冲沉积铝化物及铝化物-Y_2O_3涂层

采用电脉冲沉积技术在 2 0碳钢表面上获得了冶金结合的晶粒尺寸约为几十到几百纳米的铝化物和铝化物 弥散Y2 O3复合微晶涂层。60 0℃空气中氧化 10 0h的结果表明 ,电脉冲沉积获得的两种涂层均可显著地降低 2 0碳钢的氧化速率并提高氧化层的抗剥落性能。用AFM ,SEM ,EDS和XRD对铝化物涂层及氧化层进行了分析 ,并讨论了两种涂层提高抗氧化性能的作用机制     

化学改性环氧树脂水基涂料的研究-涂膜性能

化学改性环氧树脂水基涂料的研究-涂膜性能     

Physical Properties of Sol-Gel Coatings

One of the most important applications of sol-gel technology is the fabrication of coatings. This is because of the possibility of applying oxide coatings with practically all types of chemical compositions at low ambient temperatures on many substrates of various shapes through the use of liquid solutions. Both oxides and different types of organic-inorganic hybrid coatings have been reported. Both oxides and hybrid coatings are usually amorphous at ambient temperatures but some oxides can be converted to the crystalline phase with heating. Regardless of the intended applications of the coatings their physical properties are always of importance. For instance, an anti-reflective coating for an automobile mirror is of little practical value unless it is fairly scratch-resistant. In this review which covers published information in the past fifteen years, some of the more important results of physical properties of sol-gel derived coatings are discussed firstly for oxides and then for organic-inorganic hybrids. It appears that properties such as the hardness of oxide coatings are inadequate unless the heat-treatment temperatures are in excess of about 400°C. The hybrid coatings, especially when they contain a dispersed phase of a hard solid like colloidal silica, can be processed at temperatures below about 150°C and can improve the performance of organic plastics such as the polycarbonates. There is insufficient scientific understanding of the relationship between physical properties and other interdependent variables such as processing conditions, chemistry and coating thickness. More research in this area will undoubtedly contribute to the availability of better and new coatings via the sol-gel approach.     

Silane-Based Coatings on Polypropylene,Deposited by Atmospheric Pressure Glow Discharge Plasmas

The aim of this paper is to show the possibility to synthesize silicon-based deposits on a polypropylene substrate, using a glow dielectric barrier discharge at atmospheric pressure, and to correlate the gas phase behavior with the properties of the thin film deposits. The discharge is generated in a mixture of nitrous oxide and silane, diluted in nitrogen. The influence of the [N₂O]/[SiH₄] ratio on the layer characteristics is mainly studied. Deposits are analyzed by XPS, SSIMS, AFM and wetting angle measurements. The discharges are also characterized by their optical emission spectra. Measurements are made as a function of the distance from the gas inlet, and they allow one to correlate these spectra with the film thickness and its chemical composition. Finally, chemical kinetics of the reactive gas decomposition reactions are proposed.     

Protecting Properties of Composite Fluoroplastic Coatings

Preparation of protecting fluoroplastic coatings at varied composition of the reaction mixture was studied. Introduction of quarternary pyridinium poly salt and various pigments into the polytrifluorochloroethylene composition allows variation of the process parameters of coating deposition on the cathode and preparation of modified fluoroplastic coatings with good anticorrosive properties.     

Visible Light Reductive Photocatalysis of Azo-Dyes with n–n Junctions Based on Chemically Deposited CdS

New composite photocatalysts have been obtained by chemical bath deposition of CdS on top of either nanostructured crystalline ZrO₂ or TiO₂ films previously deposited on conductive glass FTO. Their morphological, photoelectrochemical and photochemical properties have been investigated and compared. Time resolved spectroscopic, techniques show that in FTO/TiO₂/CdS films the radiative recombination of charges, separated by visible illumination of CdS, is faster than in FTO/ZrO₂/CdS, evidencing that carrier dynamics in the two systems is different. Photoelectrochemical investigation evidence a suppression of electron collection in ZrO₂/CdS network, whereas electron injection from CdS to TiO₂ is very efficient since trap states of TiO₂ act as a reservoir for long lived electrons storage. This ability of FTO/TiO₂/CdS films is used in the reductive cleavage of N=N bonds of some azo-dyes by visible light irradiation, with formation and accumulation of reduced aminic intermediates, identified by ESI-MS analysis. Needed protons are provided by sodium formate, a good hole scavenger that leaves no residue upon oxidation. FTO/TiO₂/CdS has an approximately 100 meV driving force larger than FTO/ZrO₂/CdS under illumination for azo-dye reduction and it is always about 10% more active than the seconds. The films showed very high stability and recyclability, ease of handling and recovering.     

High Temperature Corrosion Resistance of Coatings Deposited by Hvof for Application in Steam Turbines

The geothermal steam turbines are exposed to mechanisms of corrosion/erosion that weakens its components and reduces their useful life. Due to this problem work has been done in application and characterization of coating in solid state by means of the technique of high-velocity Oxygen Fuel (HVOF), evaluating the corrosion rate (V_corr) at high temperature of MCrAlY and Diamalloy 4006 coatings deposited on stainless steel SS304. Test was performance in an Autoclave at 170 ⁰C using a modified geothermal fluid as electrolyte. Open circuit potential was monitoring during 24 hours until the system reached the equilibrium. After that, Polarization and Impedance Spectroscopy techniques were used to evaluate the specimens. For microstructure characterization; X–ray Diffraction (XRD), electron sweep microscope (SEM) and Optical microscope were applied. Results show that both coatings (Diamalloy 4006 and MCrAlY), have low current density compare with the substrate, which is an indicative of a lower corrosion rate due to the passive behavior of the species deposited on the Surface of the coating.     

Corrosion Behavior in Acid and Alkaline Media of Nickel Coatings Deposited at Room Temperature

Impedance spectroscopy, chronovoltammetry, chronopotentiometry, scanning electron microscopy, and atomic-force microscopy were used to examine the corrosion behavior in acid and alkaline media and the morphology of nickel coatings electrodeposited from acetate, tartrate, and isobutyrate electrolytes at a temperature of 20–25°C. Models describing the nickel corrosion processes in H₂SO₄ and NaOH solutions were suggested. It was found that nickel coatings formed from isobutyrate electrolytes have the highest corrosion resistance.     

Tribological Performance of Chemically Bonded Phosphate Ceramic Coatings with Different Curing Agents on Mild Steel

Russian Journal of Applied Chemistry - To enhance the compactness of the chemically bonded phosphate ceramic coatings (CBPCs), different inorganic curing agents (MgO, CaO, and ZnO) are selected as...     

超疏水聚硅氧烷涂层的制备及其性能

采用溶胶-凝胶法,以甲基三乙氧基硅烷(MTES)为有机硅前驱体,通过酸-碱催化水解-缩合得到聚有机硅氧烷凝胶,经浸涂-提拉成膜技术在玻璃表面制备超疏水聚硅氧烷涂层。通过红外光谱(FT-IR)、水接触角(WCA)和场发射扫描电子显微镜(FE-SEM)等分析技术对涂层进行了结构表征、疏水性测试和表面形貌观察。结果表明,涂层内部形成带有甲基和残余硅羟基基团的网络结构。当n(MTES)∶n(EtOH)∶n(H2O)分别为1∶35∶8和1∶45∶8时,在室温制备的涂层对水的接触角可分别高达160°和162°,滚动角均低至7°,并且涂层在250℃以下的热处理过程中,其疏水性基本保持不变。FE-SEM观察证实了涂层表面分布着许多孔径为0.5～1.0μm的微孔和粒径为50～100 nm的纳米颗粒聚集体,具有微-纳米尺寸相结合的双重结构。此外涂层还具有较高的透明性、对腐蚀性液体具有超疏水性。研制得到的超疏水涂层有望用于玻璃、织物、金属和塑料等基底表面作为保护和防腐蚀涂膜。     

化学沉积Ni-P-Al2O3和Ni-P-SiC复合材料的微观组织与物理性能

采用化学沉积方法,可以制备以镍磷合金为基质的复合硬质相粒子的复合材料［１］．镍磷合金颇受青睐之处在于可以调整成分和时效处理温度来改变其组织结构,进而获得广泛变化的性能［２,３］．本文报道化学沉积获得的ＮｉＰ氧化铝和ＮｉＰ碳化硅复合材料的微观组织与...     

Composition, Structure, and Corrosion–Electrochemical Properties of Chromium Coatings Deposited from Chromium(III) Electrolytes Containing Formic Acid and Its Derivatives

To study electrocatalytic properties of chromium, its deposits are obtained from Cr(III) electrolytes containing formic acid and its four derivatives (formaldehyde, methyl alcohol, formamide, dimethylformamide) and comprehensively examined. Amorphous structure of the deposits is established with an x-ray diffraction analysis. The valence state of chromium and major extrinsic elements is studied by x-ray photoelectron spectroscopy. The carbon reduction degree and the organization of carbon particles in deep layers of the deposits (chainlike or graphite-like structures) is shown to depend on the nature of organic compounds added into the chromium-plating electrolyte. The corrosion–electrochemical behavior of the obtained deposits in 0.5 M H₂SO₄ is compared to that of polycrystalline chromium and deposits plated from sulfate–oxalate Cr(III) electrolytes.     

掺铈纳米二氧化铅修饰电极色谱电化学用于单胺类神经递质的研究

研制了一种新型掺铈纳米二氧化铅修饰电极，用X射线衍射（XRD）和扫描隧道 显微镜（STM）进行了表征。该修饰电极对单胺类神经递质及其代谢产物有良好的 电催化作用，灵敏度高，稳定性和重现性好，将其作为电化学检测器与液相色谱和 微渗析技术联用，测定了帕金森氏症病人脑脊液中单胺类神经递质及其代谢产物的 含量。取得了满意的结果并初步探讨了帕金森氏症的致病机理。