Hydrophobization of Melamine Sponges Using Radiation-Synthesized Tetrafluoroethylene Telomers

High Energy Chemistry - The process of hydrophobization of melamine sponges has been investigated. Solutions of radiation-synthesized tetrafluoroethylene telomers, which had different chain lengths...     

Radiation-Chemical Synthesis of Perfluorinated Tetrafluoroethylene Telomers

High Energy Chemistry - The kinetics of radiation-initiated telomerization of tetrafluoroethylene in perfluoromethylcyclohexane and perfluoro-1,3-dimethylcyclohexane has been studied, and new...     

Cellulose from Annual Plants and Its Use for the Production of the Films Hydrophobized with Tetrafluoroethylene Telomers

Cellulose HogC was produced by the modified traditional method with 35% yield from the stem of Sosnovsky hogweed and was characterized by elemental analysis, infrared (IR) spectroscopy, powder X-ray diffractometry, differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). For HogC, the degree of crystallinity (approximately 70%) and the glass transition temperature (105–108 °C) were determined. It was found that the whiteness characteristic in the case of HogC was 92% and this significate was obtained without a bleaching procedure using chlorine-containing reagents. In this paper, the possibility of hydrophobization of HogC films by treatment with radiation-synthesized telomers of tetrafluoroethylene is shown. It was found that the contact angle of the telomer-treated cellulose film surface depended on the properties of the telomers (the chemical nature of the solvent, and the initial concentration of tetrafluoroethylene) and could reach 140 degrees.     

Determination of the Boron/Lead Ratio in Ceramic Materials Based on Electrochemical Quartz Crystal Microbalance

A method for quantitatively determining the relationship boron/lead in ceramic materials is presented. It is based on the attachment of microsamples of ceramic frits to an electrochemical quartz crystal microbalance (EQCM). After a reductive deposition step in the ?0.25 to ?0.85 V (vs. AgCl/Ag) potential range, well‐defined stripping peaks are recorded in 0.10 M NaCl plus 0.10 M mannitol. The deposition of boron and lead from suspensions of solid materials, and its subsequent oxidative dissolution can be monitorized at the EQCM. The quotient between the maximum mass gain and the corresponding charge passed enables for a direct quantitation of the boron/lead molar ratio in ceramic materials. Addition methods based on the EQCM examination of i) sample plus lead white (2PbCO₃.Pb(OH)₂) and ii) sample plus Li₂B₄O₇ mixtures are also presented. Results for boron‐containing ceramic frits are in excellent agreement with those obtained by reference methods.     

A Porous Ceramic Based on Aluminomagnesium Spinel

Powdered precursors of an aluminomagnesium spinel were synthesized by joint crystallization of magnesium and aluminum salts from solutions. The sequence of stages of the MgAl₂O₄ formation was studied in relation to the nature of initial reagents and temperature of heat treatment. Optimal modes of sintering of the aluminomagnesium spinel for obtaining ceramic materials with porosity greater than 50% were determined.     

Influence of Additives on Capillary Absorption of Aqueous Solutions into Asymmetric Porous Ceramic Substrate

The effect of divalent and trivalent salts (CaCl(2), CaBr(2), MgCl(2), MgBr(2), LaCl(3), CeCl(3), La(NO(3))(3), and Ce(NO(3))(3)) on the micelle formation in C(8)-lecithin solutions was investigated using the techniques of static and dynamic light scattering. The critical micelle concentration (cmc), mean hydrodynamic radius (R(h)), gyration radius (R(g)), and weight-average molecular weight of the micelles were measured as functions of salt identity and concentration, amphiphile concentration, and temperature. It was found that the micelles in solutions of magnesium are less likely to form and less stable; their standard enthalpy is less exothermic as the ionic strength increases. On the contrary, the micelles in solutions of calcium and trivalent salts form easily, and are more stable; their standard enthalpy is also more exothermic as the ionic strength increases. Based on our model of the Gibb's free energy for the salt-added solutions, we obtained the following formula for the effect of salts on cmc: ln(cmc)'=ln(cmc)+k(1) I(1/2)+k(2)I, where (cmc)' and (cmc) are the critical micelle concentrations in salt-added and salt-free solutions, respectively, I is the ionic strength, and k(1) and k(2) are the salt effect parameters. The agreement between the formula and the experimental data for all the systems under study shows that the formula is more satisfactory than those suggested previously by other authors in describing the effect of salts on the cmc in the micellar solutions of not only zwitterionic but also nonionic surfactants. Copyright 2001 Academic Press.     

Monte Carlo Simulations of Adsorbed Solutions in Heterogeneous Porous Materials

We present results of a Monte Carlo simulation study of binary mixtures of ethane and methane in silica gel. The molecular model treats the adsorbent as a matrix of silica microspheres. The adsorption isotherms, adsorption selectivities and isosteric heats of adsorption have been determined for these systems. The results are compared with predictions from the ideal adsorbed solution (IAS) theory and with experiment. The heats of adsorption are accurately described by the IAS theory. The adsorption isotherms are accurately described by the IAS theory at low bulk pressure but the IAS theory overpredicts the density at high bulk pressure. This latter effect is opposite to that observed in bulk mixtures of this type where nonidealities generally lead to a density increase on mixing. The pressure dependence of the selectivity does not exhibit a maximum at low pressure. We discuss this effect in terms of the adsorbent microstructure.     

Migration,Crystallization and Dissolution Changes of Salt Solution with Color Rendering Property in Porous Quartz Materials

In order to visually display the migration and crystallization process of salt solution in porous cultural relics, copper sulfate solution with color rendering property was selected to record the migration, crystallization and resolution of salt solution in simulated SiO₂ samples under different environmental conditions in real time through high-resolution recording system, scanning electron microscope system, salt phase X-ray diffraction system, and so on. The results showed the migration of salt solution in porous samples was related to the structural characteristics of the porous samples, the migration rate of salt solution, the evaporation rate and the change frequency of crystallization–resolution, etc., in which the large pore size of the sample, the higher the concentration and the faster migration and evaporation rate of salt solution, the greater the change rate of the brine accumulation zone or salt crystallization zone in the different porous samples. During the humidification–drying cycles of rainfall, the higher the cycle frequency of humidification–drying was, the higher the drying temperature was, the more frequent the crystallization-analysis change of salt in the salt-bearing sample was, and the more extensive the distribution of salt crystal zone was. This is the first time to visualize the salt belt by simulating the changing process of a salt solution with a color rendering property in porous samples. This has scientific theoretical guidance for the study of the migration–crystallization changes of soluble salts contained in porous silicate cultural relics. The visibility analysis results of multilayer salt crystal belts can also provide the preliminary basis for further effective desalination of salt bearing cultural relics.     

Composite Sorbing Materials Based on Porous Carbon Powders

The possibility of synthesizing composite sorbing materials on the basis of porous carbon powders was studied. The sorption and porosimetric characteristics of the composites were examined.     

Hydrophobization of Inorganic Materials by Chemical Modification of the Surface

Russian Journal of Applied Chemistry - General relationships of the hydrophobization of oxide and metal materials by chemical modification of the surface are discussed. Compounds containing an...     

聚合物纤维类吸声材料研究进展

噪声污染问题不但制约着经济的发展,还严重影响着人们的身心健康,因此如何有效地控制噪音,开发出降噪性能优异的吸声材料是一个十分重要且亟待解决的课题.本文从纤维类吸声材料的发展出发,重点论述了该类材料的一个重要分支-聚合物纤维类吸声材料的研究现状,同时结合吸声机理及影响吸声性能因素,阐述了聚合物纤维类吸声材料的结构与其声学...     

Hydrophobization of chitosan-based films with acrolein

The structure of acrolein-modified chitosan films was studied by IR spectroscopy. Modification makes the films more hydrophobic. The physical and mechanical properties of films modified with acrolein solutions of low concentrations are improved relative to the unmodified films. The glass transition and decomposition temperatures of the samples were determined by dynamic mechanical and thermal gravimetric analysis. The possibility of using the materials for the development of matrices for tissue engineering was demonstrated.

     

Electrode Materials Based on Porous Silicon with Platinum Nanoparticles for Chemical Current Sources

Composites on porous silicon with platinum nanoparticles were prepared with the aim of developing structural materials for electrochemical power sources. The size and shape of the nanoparticles in the silicon matrix were examined by atomic force and high-resolution transmission electron microscopy. The catalytic activity of the nanomaterials in hydrogen oxidation and oxygen reduction was evaluated. The models based on the composite electrodes prepared were tested under the conditions of operation of hydrogen–air fuel cells.     

Polymer-Mineral Porous Materials Based on the Wide-Porous Silica and Poly-Hydroxyethylmethacrylate

Polymer-mineral hybrid porous system based on the wide-porous silica and co-polymers of 2-OH hydroxyethylmethacrylate (2-OH EMA) with triethylenglycoldimethacrylate (TEGDMA) and maleinic anhydride (MA) have been studied by means of the BET method. Polymer layer was deposited by means of the “dry polymerization” of the mixture of 2-OH EMA, TEGDMA or 2-OH EMA, MA and TEGDMA monomers on the surface of the wide-porous silica in the presence of the polymerization initiator – dicumyl peroxide (DCP). Maleic anhydride was also introduced to the content of the initial polymer layer by means of the “dry polymerization” method. The observed secondary structure-formation may be explained by pores appearance in the course of the polymerization of the deposited organic mixture. The appearance of the micro-pores is observed in this case along with formation of the meso-pores and this phenomenon may be evaluated by changes of the shapes and size of hysteresis loop on the nitrogen adsorption isotherms on the surface of the obtained porous systems.     

Porous Structure of Activated Carbon Fibers

The dependence of the microporous structure of activated carbon fibers on the carbonization temperature of hydrate-cellulose fibers was studied by BET, TVFMP, and Horvath and Kawazoe techniques and methods of the nonlocal density functional theory. The surface energy distribution function was obtained, together with the micropore size distribution curves. It was shown that the effective micropore sizes calculated by the TVFMP method are close to the maximum of the distribution function found in terms of the theory of the density functional.     

基于间苯三酚及其衍生物构筑新型有机多孔材料

有机多孔材料凭借其高比表面积、孔道可调性、易功能化修饰和结构多样性等特征,在催化、能源、吸附与分离等多个领域中展现了巨大应用潜力.对多官能度有机化合物单体以及高效聚合反应的巧妙应用,为新型有机多孔材料的创制提供了强有力的工具,成为该领域的研究热点.以C₃对称型的间苯三酚及其衍生物为例,综述了其在一系列新型有机多孔材料高效构筑中的最新研究进展.     

Preparation of Zeolite X Membranes on Porous Ceramic Substrates with Zeolite Seeds

Zeolite X membranes were investigated by in-situ hydrothermal synthesis on porous ceramic tubes precoated with zeolite X seeds or precursor amorphous aluminosilicate, and porous α-Al2O3 ceramic tubes with a pore size of 50 200 nm were employed as supports. Zeolite X crystals were synthesized by the classic method and mixed into deionized water as a slurry with a concentration of 0.2 0.5wt%, having a range of crystal sizes from 0.2 to 2μm. Crystal seeds were pressed into the pores near the inner surface of the ceramic tubes, and crystallization took place at 95℃ for 24-96 h. It was also investigated that Boehmite sol added with zeolite X seeds was precoated on ceramic supports to form a layer of γ-Al2O3 by heating, and hydrothermal crystallization could then take place to prepare the zeolite membranes on the composite ceramic tubes. The crystal species were characterized by XRD, and the morphology of the supports subjected to crystallization was characterized by SEM. The composite zeolite membranes have zeolitic top-layers with a thickness of 10-25 μm, and zeolite crystals can be intruded into pores of the supports as deeply as 100μm. The experimental results indicate that the precoating of zeolitic seeds on supports is beneficial to crystallization by shortening the synthesis time and improving the membrane strength. The resulting zeolite X membrane shows permselectivity to tri-n-butylamine((C4H9)3N) over perfluro-tributyl-amine ((C4Fg)3N), and a permeance ratio of 57 for ((C4Hg)3N to (C4F9)3N could be reached at 350℃. Permeances of BZ, EB and TIPB through the zeolite membrane were also measured and were found to slightly increase with temperature.     

Preparation of Zeolite X Membranes on Porous Ceramic Substrates with Zeolite Seeds

Zeolite X membranes were investigated by in-situ hydrothermal synthesis on porous ceramic tubes precoated with zeolite X seeds or precursor amorphous aluminosilicate, and porous α-Al2O3 ceramic tubes with a pore size of 50-200 nm were employed as supports. Zeolite X crystals were synthesized by the classic method and mixed into deionized water as a slurry with a concentration of 0.2-0.5wt%, having a range of crystal sizes from 0.2 to 2μm. Crystal seeds were pressed into the pores near the inner surface of the ceramic tubes, and crystallization took place at 95℃ for 24-96 h. It was also investigated that Boehmite sol added with zeolite X seeds was precoated on ceramic supports to form a layer of r-Al2O3 by heating, and hydrothermal crystallization could then take place to prepare the zeolite membranes on the composite ceramic tubes. The crystal species were characterized by XRD, and the morphology of the supports subjected to crystallization was characterized by SEM. The composite zeolite membranes hav     

二氧化钛纳米粒多孔膜增敏的石英微天平传感器

TiO2纳米粒形成的纳微多孔膜具有比表面积高、透性好的特点。采用TiO2纳微多孔膜作为基体，可将β-环糊精有效地固定在石英微天平表面，与聚苯乙烯包裹β-环糊精的涂层相比，检测对硝基酚的灵敏度提高了12倍。β-环糊精/TiO2纳米粒多孔膜修饰的石英微天平传感器对邻、间、对硝基酚3种异构体具有选择性响应。在pH11、浓度范围0.6-20μmol/L内，其斜率分别是对硝基酚k=71.9Hz/μmol、邻硝基酚49.1HzL/μmol、间硝基酚2.8Hz/μmol。TiO2纳米粒涂层为提高石英微天平传感器的灵敏度和缩短响应时间提供了一个新方法。     

介孔氧化硅膜在多孔陶瓷载体上的组装

采用过滤成膜方式结合溶剂挥发诱导自组装方法在多孔氧化铝中空纤维上制备了介孔氧化硅膜。XRD、TEM和N₂吸附脱附实验结果显示非担载膜具有有序的六方介孔结构。通过对中空纤维担载膜的XRD分析进一步确认介孔氧化硅膜的形成。SEM和EDS线扫描结果显示制备的担载膜表面完整、无缺陷,膜层和载体界面之间结合紧密。在此基础上对介孔膜在多孔陶瓷载体上的形成机理进行了探讨。