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81.
Small quantities (<2%) of various metal oxides are incorporated into the lattice of β-C2S during the high temperature preparation. The effect which these stabilizers have on the hydration rate is examined. A model involving the charge/radius ratio of the metal ion is developed to explain altered hydration rates. This charge/ radius ratio model also proves useful in describing the crystal-chemical stabilization of β-C2S. In addition, the solubility of Cr2O3 in β-C2S is determined by a novel differential thermal analysis technique. 相似文献
82.
Zheng Ya-Jun; Merz Kenneth M. Jr; Farber Gregory K. 《Protein engineering, design & selection : PEDS》1993,6(5):479-484
Two mechanisms for an aldoseketose isomerization havebeen examined using high level ab initio and semiempirical molecularorbital methods. The proton transfer pathway via an enediolintermediate is shown to be favored in the absence of a metalion, while the hydride transfer pathway becomes favored in thepresence of a metal ion. Our calculations explain why the protontransfer pathway is operative in most aldoseketose isomerizationreactions. These calculations also provide further support forthe previously proposed metal ion-mediated hydride transfermechanism for xylose isomerase. 相似文献
83.
Gordon B. A. Lim Kenneth S. McGuire Douglas R. Lloyd 《Polymer Engineering and Science》1993,33(9):537-542
Non-isothermal crystallization growth rates of nucleated and non-nucleated isotactic polypropylene (iPP) in dotriacontane were determined experimentally by thermal optical microscopy. Adipic acid was used as the nucleating agent. The non-isothermal growth rates of the nucleated and non-nucleated systems were compared with experimentally determined isothermal growth rates. The Lauritzen and Hoffman growth rate equation, originally developed for isothermal crystallization, was modified to describe the non-isothermal growth. The modified Lauritzen-Hoffman equation was used to predict isothermal growth rates from non-isothermal crystallization for the nucleated and non-nucleated polymer-diluent mixtures. This study is the first to deal with polymer-diluent-nucleating agent systems vital to membrane production. 相似文献
84.
Towards an Environmentally Acceptable Heterogeneous Catalytic Method of Producing Adipic Acid by the Oxidation of Hydrocarbons in Air 总被引:1,自引:0,他引:1
Raja Robert Lee Sang-Ok Sanchez-Sanchez Manuel Sankar Gopinathan Harris Kenneth D.M. Johnson Brian F.G. Thomas John Meurig 《Topics in Catalysis》2002,20(1-4):85-88
A survey is given of the catalytic methods potentially available for the production of adipic acid by the oxidation of readily available hydrocarbon precursors under environmentally benign conditions. Encouraging results are reported using H2O2 as oxidant and microporous FeAlPO-5 as catalyst at moderate temperatures. 相似文献
85.
Bryan D. Vogt Christopher L. Soles Hae-Jeong Lee Eric K. Lin Wen-li Wu 《Polymer》2005,46(5):1635-1642
Moisture absorption into ultrathin poly(vinyl pyrrolidone) (PVP) films with varying thickness was examined using X-ray reflectivity (XR) and quartz crystal microbalance (QCM) measurements. Two different surfaces were used for the substrate: a hydrophilic silicon oxide (SiOx) and a hydrophobic hexamethyldisilazane (HMDS) treated silicon oxide surface. The total equilibrium moisture absorption (solubility) was insensitive to the surface treatment in the thickest films (≈150 nm). However, strong reductions in the equilibrium uptake with decreasing PVP film thickness were observed on the HMDS surfaces, while the SiOx surface exhibited thickness independent equilibrium absorption. The decreased absorption with decreasing film thickness is attributed a depletion layer of water near the polymer/HMDS interface, arising from hydrophobic interactions between the surface and water. The diffusivity of water decreased when the film thickness was less than 60 nm, independent of the surface treatment. Changes in the properties of ultrathin polymer films occur even in plasticized films containing nearly 50% water. 相似文献
86.
Kenneth J. Balkus Jr. Alexei G. Gabrielov Netanya Sandler 《Journal of Porous Materials》1995,1(2):199-206
The clathrate type molecular sieve SAPO-16 was prepared via a hydrothermal synthesis using bis(cyclopentadienyl)cobalt(III) hydroxide, Cp2CoOH, as a template and characterized by XRD, FT-IR, UV-Vis and SEM. Additionally, the preparation and characterization of possibly new isostructural SAPO-UTD-3 and CoAPO-UTD-3 materials is reported.NSF Presidential Young Investigator 1991–1996. 相似文献
87.
Several fatty derivatives with bulky moieties were prepared by treatment of epoxidized isopropyl oleate with a number of alcohols
in the presence of sulfuric acid catalyst to provide a series of α-hydroxy ethers in good yield. The materials were analyzed
for cold flow performance through cloud point and pour point determinations. The most promising α-hydroxy ether produced in
this study, with respect to both low temperature behavior and economic criteria, was isopropyl 9(10)-(2-ethylhexoxy) 10(9)-hydroxystearate,
which has a cloud point of −23°C and pour point of −24°C. 相似文献
88.
Preparation and Characterization of Mordenite Thin Films via Pulsed Laser Deposition 总被引:1,自引:0,他引:1
Zeolite thin films are interesting for their potential application in membrane based separations, catalysis, and molecular sensing. Mordenite is a one-dimensional channel type zeolite that has been used in alcohol/water separations. Pulsed-laser deposition has been used to prepare partially oriented, crystalline mordenite thin films on stainless steel foil, and frits as well as carbon fibers and DAM-1 particles. Preliminary results for pervaporation of isopropanol/H2O mixtures using mordenite membranes indicate separation factors of 133 and 459 at room temperature and 76°C, respectively. 相似文献
89.
The application of a low temperature ashing method for estimating total residual organic matter (toluene insolubles) in oil sands is described. A linear correlation exists between organic carbon content and loss on ignition at 400 ± 10 °C of solvent extracted oil sands. The ratio between total organic carbon and the weight loss on ignition (CT/LOl) owing to the removal of residual organic matter is much lower than that obtained for toluene soluble bitumen fractions, indicating very different chemical composition for the residual organic matter. The measured carbon content of the residual organic matter in oil sands suggests that this material could be a mixture of various fractions contained in resins, asphaltenes, asphaltic acids and humic acids. 相似文献
90.