Preparation, Configurations and N.M.R. Dates of the Acids CH3(SR)CHCOOH (R C6H5, CH2C6H5, CH2COOH) The cis and trans isomers of the acids CH3(SR)CHCOOH (R C6H5, CH2C6H5, CH2COOH) were prepared by addition of HSR to CH3CCCOOH in alkaline water solution and by alkaline hydrolysis of CH3C(SR)2CH2COOC2H5 (R C6H5, CH2C6H5, CH2COOC2H5). The oxidation products CH3C(SO2R) CHCOOH (R C6H5, CH2COOH) were also prepared. The n.m.r. dates of the acids were obtained and some relations between them were discussed. 相似文献
Isothermal storage and reduction of NO2 with CO, C3H6 and H2 as reducing agents on a lean NOx adsorber was investigated by temperature programmed desorption (TPD) and temperature programmed reduction (TPR) studies. The reduction of NOx was clearly favoured with H2 as reducing agent. Carbon monoxide and C3H6 showed fairly low reduction of NOx. The NOx reduction at low temperatures with H2 as reducing agent was found to be effective, clearly much more effective than for CO. 相似文献
Scratching of thin film/substrate structures is studied theoretically and numerically. The results are discussed in connection to delamination initiation and in particular subsequent growth at scratching. The material behavior of the film is described by classical elastoplasticity accounting for large deformations. The deformation of the substrate is neglected indicating that the results are pertinent to soft thin films. The numerical investigation is performed using the finite element method (FEM) and the numerical strategy is discussed in some detail. The results from this study show that delamination growth at thin film scratching is a stable feature with crack arrest occurring at a decreasing load. 相似文献
Pt/Al2O3 catalysts with platinum contents of 0.1, 1.0 and 3.0 wt% were used for the low temperature combustion of methanol in the absence and the respective presence of a trace amount of ammonia. It is observed that ammonia inhibits the combustion of methanol, which is due to competition between methanol and ammonia for the same sites. For a fixed space velocity and without ammonia in the gas, the performances of the catalysts increase up to a Pt loading of 1.0 wt%. In the presence of ammonia, however, no upper limit of performance is observed with increased Pt content. The results are discussed in terms of both Pt–support interface and the Pt surface being active. 相似文献
The problem of steady-state rolling contact between two cylinders with dry friction was formulated into standard linear complementarity problems (LCPs) using the explicit physical definition. For normal contacts, the complementarity variables are the normal pressure and the gap. For the tangential contact, the traction distribution and relative slip are the variables obtained by solving the LCP. The frictional behavior is assumed to be governed by the Coulomb friction law, and LCP formulations of both similar elastic (Carter problem) and dissimilar elastic rolling contacts are presented in this work. Good agreement was found between the current LCP approach and publicly available software for both the rolling contact of similar elastic and dissimilar elastic cylinders. Moreover, the surface roughness was taken into account in this article by the verified approach. The results show the initial slope of the traction-relative creepage curve decreases as the surface roughness increases. 相似文献
In this article, the problem of 3D steady-state rolling contacts with dry friction for circular Hertzian contacts is formulated mathematically as a linear complementarity problem (LCP). The complementarity variables are the traction and the relative slip of contact regions, in which a polyhedral friction law is employed. The present work uses the general expressions describing the surface deformations due to uniform traction over a rectangular area on an elastic half-space to derive the influence coefficient matrix for rolling contact problems. Three possible creepage types—that is, longitudinal, lateral, and spin creepage—are considered in this work. Firstly, the numerical results are verified against the existing numerical solutions and good agreement has been found. Secondly, the anisotropic friction is studied by the verified approach. Some numerical examples are provided to illustrate the current LCP method for both isotropic and anisotropic friction in which the combined effects of the three kinds of creepage on the traction distribution are shown. 相似文献
Combustion of CO, ethyl acetate and ethanol was studied over CuOx/Al2O3, CuOx–CeO2/Al2O3, CuMn2O4/Al2O3 and Mn2O3/Al2O3 catalysts. It was found that modification of the alumina with ceria before subsequent copper oxide deposition increases the activity for combustion of CO substantially, but the effect of ceria was small on the combustion of ethyl acetate and ethanol. The activity increases with the CuOx loading until crystalline CuO particles are formed, which contribute little to the total active surface. The CuOx–CeO2/Al2O3 catalyst is more active than the CuMn2O4/Al2O3 catalyst for the oxidation of CO but the CuMn2O4/Al2O3 catalyst is more active for the combustion of ethyl acetate and ethanol.
Thermal ageing and water vapour in the feed caused a modest decrease in activity and did not affect the CuOx–CeO2/Al2O3 and CuMn2O4/Al2O3 catalysts differently. In addition, no difference in intermediates formed over the two catalysts was observed.
Characterisation with XRD, FT-Raman and TPR indicates that the copper oxide is present as a copper aluminate surface phase on alumina at low loading. At high loading, bulk CuO crystallites are present as well. Modification of the alumina with ceria before the copper oxide deposition gives well dispersed copper oxide species and bulk CuO crystallites associated to the ceria, in addition to the two copper oxide species on the bare alumina. The distribution of copper species depends on the ceria and copper oxide loading. The alumina supported copper manganese oxide and manganese oxide catalysts consist mainly of crystalline CuMn2O4 and Mn2O3, respectively, on Al2O3. 相似文献
Controlling the release rate of biocides (antifouling agents) from a paint coating is a key issue for the development of multi-season antifouling marine coatings. One promising approach is the use of nanoparticles onto which biocides are adsorbed to prevent premature depletion of the biocide. Adsorption of one novel (Medetomidine) and six commercially available and widely used antifouling biocides (Chlorothalonile, Dichlofluanid, Diuron, Irgarol, Seanine, Tolylfluanid) onto oxide nanoparticles (Al2O3, CuO, MgO, SiO2, TiO2, ZnO) was investigated by HPLC and NMR in different organic solvents. Large differences in adsorption strength depending on the type of nanoparticle and solvent employed were observed. It was shown that nanoparticles coordinate preferentially with the imidazole moiety of Medetomidine. Independent of the type of particle this interaction was considerably stronger in comparison to the other biocides. However, the interaction strength was strongly dependant on the type of solvent, where the largest strongest interaction was achieved in o-xylene. In addition field tests were performed where a considerable decrease in release rate was displayed from coatings containing Medetomidine adsorbed to nanoparticles compared to coatings containing Medetomidine as single additive. 相似文献
The linear thermal expansions (LTE) of bulk nanocrystalline ingot iron (BNII) at six directions on rolling plane and conventional polycrystalline ingot iron (CPII) at one direction were measured from liquid nitrogen temperature to 300 K. Although the volume fraction of grain boundary and residual strain of BNII are larger than those of CPII, LTE of BNII at the six measurement directions were less than those of CPII. This phenomenon could be explained with Morse potential function and the crystalline structure of metals. Our LTE results ruled out that the grain boundary and residual strain of BNII did much contribution to its thermal expansion. The higher interaction potential energy of atoms, the less partial derivative of interaction potential energy with respect to temperature T and the porosity free at the grain boundary of BNII resulted in less LTE in comparison with CPII from liquid nitrogen temperature to 300 K. The higher LTE of many bulk nanocrystalline materials resulted from the porosity at their grain boundaries. However, many authors attributed the higher LTE of many nanocrystalline metal materials to their higher volume fraction of grain boundaries. 相似文献
Kinetic measurements at low temperatures (310–360 K) using gas chromatography (GC) for benzene hydrogenation on Pt(100) and
Pt(111) single crystal surfaces have been carried out at Torr pressures. These kinetic measurements demonstrated a linear
compensation effect for the production of cyclohexane. A detailed application of the model of selective energy transfer to
the experimentally obtained results yields the vibrational frequency of the adsorbate leading to reaction. This frequency
is attributed to ring distortion modes. The vibrational frequency of the heat bath, or catalyst, is ascribed to a Pt-H mode.
An approximate heat of adsorption of the reacting molecule is also calculated from the model. 相似文献