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Effect of functional groups on the crystallization of ferric oxides/oxyhydroxides in suspension environment
Qiong ZHOU, Olga ALBERT, Hua DENG, Xiao-Long YU, Yang CAO, Jian-Bao LI, Xin HUANG
Front Mater Sci. 2012, 6 (4): 297-303.
https://doi.org/10.1007/s11706-012-0178-0
This paper investigated the effects of five kinds of Au surfaces terminated with and without functional groups on the crystallization of ferric oxides/oxyhydroxides in the suspension condition. Self-assembled monolayers (SAMs) were used to create hydroxyl (--OH), carboxyl (--COOH), amine (--NH2) and methyl (--CH3) functionalized surfaces, which proved to be of the same surface density. The immersion time of substrates in the Fe(OH)3 suspension was divided into two time portions. During the first period of 2 h, few ferric oxide/oxyhydroxide was deposited except that ?-Fe2O3 was detected on--NH2 surface. Crystallization for 10 h evidenced more kinds of iron compounds on the functional surfaces. Goethite and maghemite were noticed on four functional surfaces, and maghemite also grew on Au surface. Deposition of ?-Fe2O3 was found on--OH surface, while the growth of orthorhombic and hexagon FeOOH were indicated on--NH2 surface. Considering the wide existence of iron compounds in nature, our investigation is a precedent work to the study of iron biomineralization in the suspension area.
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Supported La1--xCexMnO3 perovskite catalysts: preparation, characterization and catalytic performance in methane combustion
Ying SHAO, Xiao-Fei WANG, Min AO, Cai-Rong GONG, Guo-Liang FAN, Hai-Feng CHEN
Front Mater Sci. 2012, 6 (4): 304-310.
https://doi.org/10.1007/s11706-012-0179-z
A serials of La1--xCexMnO3 (x = 0, 0.2, 0.4, 0.6 and 0.8) catalysts have been prepared via a sol--gel process using citric acid as a chelating agent. The phase composition and morphology of the catalysts are characterized by XRD, SEM and TEM. La1--xCexMnO3/γ-Al2O3/cordierite catalyst has also been prepared by immersion process using cordierite honeycomb ceramic as carrier and γ-Al2O3 as support agents. The effect of Ce-doping on the structure of perovskite and catalytic property of methane combustion is explored. The results show that with the increase of Ce substitution, the crystal structure of perovskite changes from the tetragonal system to the orthorhombic system and when the x is equal to 0.2, the catalytic property in methane combustion is the best.
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Preparation and properties of poly HTBN-based urethane--urea/organo reactive montmorillonite nanocomposites
Zai-Feng LI, Yuan WU, Fu-Tao ZHANG, Yu-Yang CAO, Shou-Peng WU, Ting WANG
Front Mater Sci. 2012, 6 (4): 338-346.
https://doi.org/10.1007/s11706-012-0185-1
With ultrasonic assistant mixing way, an intercalated mixture of polyol/organo reactive montmorillonite (ORMMT) was pretreated. The prepolymer composed MMT clay was prepared by reaction of polyol/ORMMT mixture with toluene diisocyanate (TDI). The resultant prepolymer reacted with extender (DMTDA) and then the polyurethane--urea/organo reactive montmorillonite (PUU/ORMMT) nanocomposites were obtained. The structure, morphology and properties of PUU/ORMMT nanocomposites were characterized by FT-IR, TEM, AFM, strain-stress machine, TGA, and dynamic mechanical analysis (DMA). The results showed that when the OMMT content is 3%, the PUU/ORMMT nanocomposities performed super mechanical properties. Because of the presence of ORMMT, both Tg of the soft segment and tanδ of the PUU increased, and the decomposition temperature for the first step and the second step increased respectively. TEM images showed that the organophilic MMT particles in the PUU composite exhibit a high degree of intercalation and exfoliation.
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Preparation and properties of adjacency crosslinked polyurethane---urea elastomers
Yuan WU, Yu-Yang CAO, Shou-Peng WU, Zai-Feng LI
Front Mater Sci. 2012, 6 (4): 347-357.
https://doi.org/10.1007/s11706-012-0184-2
Adjacency crosslinked polyurethane--urea (PUU) elastomers with different crosslinking density were prepared by using hydroxyl-terminated liquid butadiene-nitrile (HTBN), toluene diisocyanate (TDI) and chain extender 3,5-dimethyl thio-toluene diamine (DMTDA) as raw materials, dicumyl peroxide (DCP) as initiator, and N,N'-m-phenylene dimaleimide (HVA-2) as the crosslinking agent. The influences of the crosslinking density and temperature on the structure and properties of such elastomers were investigated. The crosslinking density of PUU elastomer was tested by the NMR method. It is found that when the content of HVA-2 is 1.5%, the mechanical properties of polyurethane elastomer achieve optimal performance. By testing thermal performance of PUU, compared with linear PUU, the thermal stability of the elastomers has a marked improvement. With the addition of HVA-2, the loss factor tanδ decreases. FT-IR spectral studies of PUU elastomer at various temperatures were performed. From this study, heat-resistance polyurethane could be prepared, and the properties of PUU at high temperature could be improved obviously.
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