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231.
The room-temperature isomer shifts of iron in nickel aluminides have been measured. A single Mössbauer-resonance line is observed for alloys of composition (NiAl)100-cFec, 0 ? c ? 5 at. %, and Al50Ni50-cFec, 2 ? c ? 50 at. %. The isomer shift for dilute Fe concentration in stoichiometric NiAl is compared with that for FeAl at stoichiometric composition. 相似文献
232.
A method is reported for the fabrication of wires with extended pore structures. Nanospheres are initially infiltrated into the one-dimensional channels of alumina or polymer porous membranes. Metal is then electrochemically deposited within the channels. Removal of the membrane and nanospheres results in porous wires. The production of 1-mum diameter wires with 300- or 500-nm diameter pores and 300-nm diameter wires with 140-nm pores illustrates the utility of this approach. Contacts between the spheres and the channel wall result in openings on the surface of the wires, and contacts between the spheres themselves produce openings between adjacent pores. Some short-range ordering of the spheres within the channels, as reflected in the wire pore structure, is evident. Characterization of the porous wires by electron microscopy is presented, and the potential applications of materials is discussed. 相似文献
233.
234.
Richard H. Wiley 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1797-1818
The mass spectral characteristics of pivalolactone and its polymer have been determined. The monomeric lactone (MW 100) shows no molecular ion peak but does show peaks at 70 and 42 m/e associated with the loss of formaldehyde and then carbon monoxide and at 56 and 41 associated with the loss of isobutene and carbon dioxide. Only weak peaks, corresponding to the presence of traces of oligomers, are observed above m/e 71. The polymer, at volatilization temperatures of 250-350°C, gives fragments of up to 1242 m/e with a pattern recurring over intervals of 100 m/e units. The principal peaks occur at X42, X70, X83, and X01 m/e. Above 301, the X42 and X70 peaks are observable up to X = 12. The X70 fragment is assigned an acylium isobutyrate radical ion structure and the X42 fragment is assigned an isobutyl radical ion structure. The degradation products are accounted for as being formed from volatilized cyclic oligomers. 相似文献
235.
The free radical copolymerization of styrene and other vinyl monomers to produce cross-linked, network polymers is of technological importance in the production of ion-exchange resins, packings for gas-liquid and gel permeation chromatography, cross-linked latex polymers, and other products. The principal multifunctional cross-linking monomers which are used in this connection are ethylene glycol dimethacrylate and divinylbenzenes, and accurate values for reactivity ratios in their reactions with bifunctional monomers are essential for the design of copolymerization processes and products. Wiley and co-workers have reported reactivity ratios for the copolymerizations of these monomers with styrene and with methyl methacrylate [1]. In these studies the reactivity ratios were calculated from the raw data using a graphical “method of intersections” [2]. In this procedure the differential copolymer equation is put into the form 相似文献
236.
Field desorption mass spectra of oligomers show peaks of mass up to 2400 amu. 相似文献
237.
The copolymerization reactivity ratios for styrene/m- and styrene/p-divinylbenzene have been determined at high conversions (<35%) using the integrated form of the copolymerization equation. Values of r1 (s) = 1.11, r2 (m) = 1.00; and r1 (s) = 0.20, r2 (p) = 1.00 were obtained. These values indicate the same relative behavior but are quantitatively different from the differential data. The data confirm that the para isomer is incorporated more rapidly into the growing polymer chain than is the meta isomer. 相似文献
238.
239.
Based on the insights gained from previous published works, a series of multi-layer spacer designs for use in spiral wound membrane modules are proposed and evaluated via computational fluid dynamics simulations. The filament diameter to channel height ratio of traditional cylindrical filaments is reduced from 0.6 to 0.4 and 0.3, and one or two layers of elliptical filaments with various attack angles are introduced in the middle region of the channel. The mass transport equations are solved in conjunction with the momentum and continuity equations for a solute with Schmidt number of 600, and the hydraulic Reynolds number is varied from 50 up to 800. Spacer performance is evaluated via a basic permeate processing cost analysis. The proposed designs did not lower processing costs when operating at hydraulic Reynolds numbers above 200, but showed potential for reducing costs in the steady laminar flow regime, at hydraulic Reynolds numbers equal to or less than 200. Implications for design improvements of spacer meshes, such as extra layers of spacer filaments to direct the bulk flow towards the membrane walls, and changes to the filament profiles to reduce form drag are discussed. 相似文献
240.
Garrison JC Panzner MJ Custer PD Reddy DV Rinaldi PL Tessier CA Youngs WJ 《Chemical communications (Cambridge, England)》2006,(44):4644-4646
The reaction of 4-ethynyl-pyridine with tert-butyl lithium followed by its addition to (Me3tacn)RhCl3 affords the facial octahedral complex (Me3tacn)Rh(CCPy)3, condensation of which with the square planar complex cis-(DCPE)Pt(NO3)2 results in a self-assembled trigonal bipyramidal cage with Rh(III) and Pt(II) atoms occupying the vertices. 相似文献