ToF‐SIMS observation of PTFE surfaces modified by α‐particle irradiation

The surface structure of polytetrafluoroethylene (PTFE) upon α‐particle irradiation has been investigated at doses in the range of 1 × 10⁷ to 1 × 10¹¹ Rad and compared with the surface structure of the unirradiated polymer. Both neat and 25% fiberglass content PTFE were studied. The samples, maintained at nominal room temperature, were irradiated in vacuum by 5.5 MeV ⁴He²⁺ ions generated in a tandem accelerator beam line. Static time‐of‐flight SIMS (ToF‐SIMS) was employed to probe chemical changes at the surface as a function of the irradiation level. In general, the data are indicative of increased cross‐linking at α‐doses less than 1 × 10⁹ Rad, followed by increased fragmentation and unsaturation at α‐doses greater than 1 × 10⁹ Rad. Throughout the irradiation regime, scission is a constant factor promoting cross‐linking, branching, and unsaturation. However, at α‐doses greater than 1 × 10¹⁰ Rad, extreme structural degradation of the polymer becomes evident and is accompanied by conversion to oxygen‐functionalized and aliphatic compounds. Thus, for PTFE in an α‐particle field, an upper exposure limit of ～10¹⁰ Rad is essential for nominal retention of molecular structure. Finally, a quantitative relationship between α‐dose and characteristic fragment ion intensity is developed. Copyright © 2005 John Wiley & Sons, Ltd.     

TiO2表面电子结构及其光催化活性

利用ＨＣｌ和ＨＣｌＯ４对不同方法制备的ＴｉＯ２进行了表面修饰,发现经强酸修饰后ＴｉＯ２的光催化活性有明显提高,其中ＨＣｌ的修饰效果好于ＨＣｌＯ４。     

Surface Modification of Colloidal Silica by Sulfonation Route for Super-Hydrophilicity

Colloidal silica was chemically modified by a two-step method including an olefin sulfonation route as a preliminary study for super-hydrophilic applications. The hydrophobic vinyl groups were initially bonded chemically to the hydroxylated silica surface using the trichlorosilane coupling agents. The vinyl-terminated silica was then sulfonated by addition reaction with chlorosulfonic acid. The modified silica was investigated using DRIFT, TGA, element analysis, solid-state ²⁹Si- and ¹³C CP-MAS NMR. The vinyl-terminated specimen showed a characteristic IR absorption band at 1600 cm^–1 and a weight loss of approximately 3% starting at 350°C while the ²⁹Si NMR peaks at 70.9 and 79.8 ppm and ¹³C NMR at 136 ppm and 129.8 ppm were assigned to a vinyl group bonded to silica. Elemental analysis of the sulfonated silica indicated the presence of sulfur, carbon and hydrogen. Thermal decomposition in range 150–600°C was due to the presence of sulfonated organics and unreacted vinyl groups while the new signals on ¹³C NMR, which were in the range 70–15 ppm, were assigned to sulfonated carbons.     

Scanning electron microscopic studies on different habits of gel grown doped manganese carbonate crystals

The effect of impurities on the growth of manganese carbonate crystals has been studied. Stereophotogrammetric analysis showed that all crystal faces have the same Miller indices and the peanut-shaped forms are twins with twin axis 0001.     

黑米花色苷酰化修饰红外光谱分析

黑米花色苷易受外部环境影响发生降解致使局部分子结构破坏而使营养价值和保健功能有所下降。利用有机酸提供酰基对黑米花色苷进行修饰来提高花色苷结构的稳定性。利用红外光谱分析经咖啡酸酰化修饰黑米花色苷的结构变化。结果表明：黑米花色苷酰化修饰前后于官能团区3 650~3 200和1 680~1 620 cm-1处均有吸收峰，且其于指纹区1 282.68和1 277.51 cm-1处出现酚羟基吸收峰，于1 056.07和1 054.03 cm-1处出现醇羟基吸收峰，719.90和719.71 cm-1处出现苯环上C-H面外弯曲振动吸收峰。由此可见，黑米花色苷酰化修饰后主要结构框架仍为花色苷的芳环结构。此外，黑米花色苷酰化修饰前后于1 900~1 650 cm-1间1 714.28和1 728.13 cm-1处均出现共轭羰基的特征吸收峰，对应于可直接连接在苯环上的α-羰基结构，由此说明黑米花色苷结构中存在着酰基基团。黑米花色苷经酰化修饰后红外图谱于1 517.20 cm-1处出现新吸收峰，其正好处于1 800~900 cm-1双键(不含氢)伸缩振动区，指纹区876.65 cm-1处亦出现了苯环上的C-H面外弯曲振动吸收峰。与之相呼应在经二阶导数处理后红外光谱图中在2 500～2 000 cm-1间出现了新的波动，此波段为累积双键伸缩振动区，而官能团区3 650~3 200 cm-1间3 370.20 cm-1处的吸收峰正好处于多分子缔合区。由此可见，在咖啡酸作为酰基供体，酰化修饰黑米花色苷时由于分子间的重新缔合于结构中引入了新的酰基基团而呈现出一种双酰化的空间结构。黑米花色苷酰化结构中有机酸与糖链相连，将有机酸置于2-苯基苯并吡喃骨架的表面，这种堆积作用模式可以较好地抵抗水的亲核攻击和其他降解反应进而提高黑米花色苷结构的稳定性。     

Conventional processes and membrane technology for carbon dioxide removal from natural gas:A review

Membrane technology is becoming more important for CO 2 separation from natural gas in the new era due to its process simplicity,relative ease of operation and control,compact,and easy to scale up as compared with conventional processes.Conventional processes such as absorption and adsorption for CO 2 separation from natural gas are generally more energy demanding and costly for both operation and maintenance.Polymeric membranes are the current commercial membranes used for CO 2 separation from natural gas.However,polymeric membranes possess drawbacks such as low permeability and selectivity,plasticization at high temperatures,as well as insufficient thermal and chemical stability.The shortcomings of commercial polymeric membranes have motivated researchers to opt for other alternatives,especially inorganic membranes due to their higher thermal stability,good chemical resistance to solvents,high mechanical strength and long lifetime.Surface modifications can be utilized in inorganic membranes to further enhance the selectivity,permeability or catalytic activities of the membrane.This paper is to provide a comprehensive review on gas separation,comparing membrane technology with other conventional methods of recovering CO 2 from natural gas,challenges of current commercial polymeric membranes and inorganic membranes for CO 2 removal and membrane surface modification for improved selectivity.     

Influence of the e-beam irradiation and photo-oxidation aging on the structure and properties of LDPE-OMMT nanocomposite films

In this paper two systems, polyethylene (LDPE) and polyethylene/commercial organo-modified montmorillonite (LDPE/OMMT) nanocomposite, were subjected to e-beam irradiation at different doses and both the molecular modifications and mechanical properties have been investigated through solubility, FT-IR, calorimetric and tensile tests. Moreover, in some of the irradiated systems photo-oxidation aging was performed and its effects were studied. The results show an enhancement with irradiation of the positive effect of the nano-filler loading, related to the increase of the mechanical properties, due to the increase of the nano-filler polymer interaction.Nevertheless calorimetric and FT-IR data indicate that the well known reduction of LDPE/OMMT nanocomposite resistance to photo-oxidation ageing, with respect to LDPE, is amplified by ionizing radiation.     

Preparation of sinapinaldehyde modified mesoporous silica materials and their application in selective extraction of trace Pb(II)

A new solid phase extractant, sinapinaldehyde (SA) modified SBA-15 mesoporous silica, was developed for selective extraction and preconcentration of trace Pb(II) from aqueous solutions. The successful immobilization of SA on SBA-15 and the strong interaction between SA-SBA-15 and Pb(II) were characterized and confirmed by FTIR spectroscopy and scanning electron microscopy. Parameters such as solution pH, shaking time, eluent condition and sample volume were optimized so that the maximum removal of Pb(II) from solution could be achieved. At pH 4.0, the maximum adsorption capacity of the sorbent for Pb(II) was found to be 33.6?mg?g^?1 and the adsorbed Pb(II) could be completely eluted using a mixed solution of 2?M HCl and 5% CS(NH₂)₂. Some common metal ions such as K(I), Na(I), Mg(II), Ca(II), Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) did not interfere with the adsorption of trace Pb(II). The detection limit of the present method was found to be 1.3?ng?mL^?1 and the relative standard deviation was less than 2.0% (n?=?8). These results suggested that this new sorbent is very efficient and selective for the removal of trace Pb(II) in water samples.