Spectroscopic evidence for the formation of CHx species in the hydrogenation of carbidic carbon on Ni(100)

The CH _x species formed on Ni(100) by hydrogenation of carbidic carbon have been detected using high resolution electron energy-loss spectroscopy (HREELS). Exposures of carbidic carbon to 1×10^–7 Torr H₂ and D₂ at 313 K for 20 min produce CH _x and CD _x species, respectively. These species are identified by two energy-loss peaks for CH _x at 2970 and 1380 cm^–1 and only one peak for CD _x at 1980 cm^–1. Because of the existence of the intense peak at 1380 cm^–1, in the range of a scissors mode for CH₂ and a symmetric deformation mode for CH₃, the CH _x species are tentatively ascribed to CH₂ and/or CH₃. The CD _x species undergo decomposition at 330–370 K in UHV as well as in hydrogen below 10^–7 Torr. No stable CH _x species are observed above 400 K, which is lower than the normal reaction temperature of the methanation reaction (500 K).     

Ultra-structural characterization of enamel–resin interface using FIB-TEM technology

This study evaluated the enamel–resin interface of three adhesive resins (ARs) by a transmission electron microscope (TEM) after milling with focused ion beam (FIB). Simple Class-I cavities (0.5?mm within enamel depth, 4?mm length, and 2?mm width) were prepared on human caries-free molars. The enamel of two groups was conditioned by one-step self-etch bonding system (Scotchbond^?/Single Bond Universal [SBU], and Xeno V^®+ [XV⁺]), while the enamel of the third group was etched by phosphoric acid, and then treated by two-step self-priming etch-rinse system (Prime&Bond^® NT [PBNT]). The application of the adhesive systems was carried out according to their respective manufacturer’s instructions. The cavities were restored by a nanofill resin composite (Filtek^? Z350 XT Universal; 3?M ESPE) in one bulk-fill, and cured for 40?s at 550?mW/cm² by a halogen light (Optilux 501, Demetron/Kerr, Danbury, USA). The specimens were milled by FIB into 100?nm thickness slices, and then observed under TEM. The transmission electron micrographs showed an adequate adhesion of both two-step etch-rinse (PBNT) and one-step self-etch (SBU) to enamel surface. The deeply etched enamel prisms were impregnated by the etch-rinse PBNT adhesive. A relatively inadequate adhesion associated with some areas of bond degradation underneath the hybrid layer and within the adhesive was noted for the XV⁺ AR. Apart from the mild acidic adhesives of one-step self-etch and two-step etch-rinse investigated, the highly hydrophilic and acidic water-based one-step self-etch adhesive (XV⁺) proved to be less effective enamel bond by ultra-structural characterization technique using FIB-TEM.     

Native celluloses on the basis of two crystalline phase (Iα/Iβ) system

A survey by X-ray diffractometry was carried out to confirm the two crystalline phase Iα/Iβ(triclinic/monoclinic) system of native celluloses. We have investigated cellulose samples from 12 different origins and measured the d-spacings with reasonable precision. The samples were then subjected to the hydrothermal annealing that brings the cellulose crystals to the monoclinic type; d-spacings were reevaluated afterward. From the statistical analysis using observed d-spacings, all the cellulose samples were categorized into the two groups that coincide with the two crystalline phase systems: one is the algal-bacterial type rich in triclinic phase and the other is the cotton-ramie type of the monoclinic phase. © 1993 John Wiley & Sons, Inc.     

几株采油菌驱油性能的物模试验

对B1-4、Ⅳ、TB褐、长Ⅱ、DY一1、LJ1、Z-2六株菌开展了单一菌种和复配菌种岩心驱替模拟实验.首先,开展了单菌种在不同驱油阶段的岩心驱油模拟实验.在整个驱替阶段无论发酵原液或稀释液均可以提高原油采收率,因此,从经济方面考虑微生物驱宜采用培养基稀释的茵液.其次,通过复配菌种模拟实验,确定了微生物和弱凝胶联合作用时,不同段塞微生物的选择和配比.通过开展岩心模拟实验,为今后开展微生物驱油和弱微联作提供可借鉴的有利信息,为华北油田微生物采油的发展提供有力的支持.     

Influence of Pt–Ba Proximity on NO x Storage–Reduction Mechanisms: A Space- and Time-Resolved In Situ Infrared Spectroscopic Study

The influence of Pt–Ba proximity on the performance and mechanism of NO _x storage–reduction (NSR) was investigated by a comparative study of Pt–Ba/CeO₂, Pt/CeO₂ and mechanically mixed Pt/CeO₂–Ba/CeO₂. NO _x storage capacity, regeneration activity and selectivity to nitrogen and ammonia during periodic lean (NO + O₂)–rich (H₂) cycles were evaluated and the chemical gradients along the axial direction of the catalyst beds were monitored by space- and time-resolved in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The presence of Ba and its proximity to Pt greatly influenced the NSR process. In particular, the proximity was crucial to achieve better utilization of bulk Ba components as well as enhancing selectivity to N₂. The space-resolved approach is shown to be a powerful tool to understand the impact of the proximity of Pt and Ba constituents on the final NSR performance.     

一种具有部分高介电常数介质调制效应的IGBT

提出了一种具有高介电常数介质填充沟槽的绝缘栅双极晶体管(IGBT).分析了高介电常数介质调制效应.结果表明,与普通场阻型IGBT相比,该器件的击穿电压提高了 8％,通态压降减小了 8％,关断损耗降低了 11％;在相同通态压降下,该器件的关断损耗降低了 35％.在栅极与原HK介质之间增加介电常数更高的介质,进一步提升了该...