Surface Review and Letters

The emissions of nitric oxide and carbon monoxide from internal combustion engines generate a large impact on the environment and on people's health. Catalytic reduction of these species using platinum group metals has already shown significant potential for emissions control. Since catalysts often use carbon monoxide to reduce nitric oxide in these devices, accurate models of their interaction are required to advance catalyst simulations in order to meet increasingly stringent emissions regulations. As a result, this paper reviews the literature of the NO–CO reaction over platinum in order to develop more precise detailed and global reaction mechanisms for use in exhaust after-treatment modeling activities. Moreover, it is found that the reaction between NO and CO over platinum yields carbon dioxide and nitrogen as main products and nitrous oxide as an important side product. Hence, this paper additionally describes the mechanism for nitrous oxide production in advance of greenhouse gas regulations.

In this study, the length and width effects of metal films on the stress-induced bending of a surface micromachined cantilever curved grating are systematically investigated. A characterization of cantilever curved gratings with various lengths and widths was conducted to observe out-of-plane deformation. A finite element model was established to analyze the deformation. Finite element analysis and experimental results indicate that the commonly used beam theory formula for predicting the deformation of surface micromachined cantilever curved gratings is not valid for these devices. Experiments show that the shape of a cantilever curved grating and residual stress have a close relationship. As the length increases, the residual stress of the metal increases, resulting in a larger out-of-plane deformation of the cantilever curved grating. The tip deflection gradually decreases as the length-to-width ratio of the cantilever curved grating increases. A more reliable shape design of metal films on the stress-induced bending of surface micromachined cantilever curved gratings can thus be achieved.

The surface of materials plays an important role in their technological applications. In the interest to study the stability of materials and their behavior, we irradiate them by the electrons by using the electron spectroscopy such as the Auger electron spectroscopy (AES) and the electron energy loss spectroscopy (EELS). These methods have proved their good sensitivity to study material surfaces. In this paper, we give some results about the effect of the electron beam irradiating the compounds InP, InSb, InPO₄ and In_xGa_1-xAs. The III–V semiconductors InP and InSb seem to be sensitive to the electron irradiation. This breaks the chemical bonds between the element III and V which leads to an oxidation process at the surface. The AES and EELS spectroscopy are also used to characterize the oxide InPO₄ whose thickness is about 10 Å grown on the substrate InP(100). The irradiation of the system InPO₄/InP(100) by the electron beam of 5 keV energy leads to a structural change of the surface, so that there is breaking of chemical bonds between indium and phosphorus (In–P) and formation of new oxide other than InPO₄. In this study we show an important result concerning the effect of the electron beam on the compound In_xGa_1-xAs by varying the parameter x to obtain In_0.2Ga_0.8As and In_0.53Ga_0.47As. It appears that the electron beam affects In_0.2Ga_0.8As too much in comparison with In_0.53Ga_0.47As. In the case of the irradiation of In_0.2Ga_0.8As, there is breaking of chemical bonds between indium and GaAs leading to formation of indium oxide associated to GaAs.

Bound rubber in carbon black (CB) filled rubber (natural rubber (NR) and styrene–butadiene rubber (SBS)) was prepared by the solvent method. The nanomorphology of CB and rubber/CB soluble rubber was observed by atomic force microscope. The results show that high-structure CB DZ13 has a "grape cluster" structure which consists of many original particles with the grain size of about 30–50 nm. Graphitizing process of CB decreases the amount of bound rubber. The NR/DZ13 soluble rubber with island–rim structure has been obtained, where the islands are DZ13 particles and the rims around the islands are occupied by NR film. But when the graphitized DZ13 particles were used as fillers of rubber, we have only observed that some graphitized DZ13 particles were deposited on the surface of the globular-like NR molecular chains, instead of the spreading of NR molecular chains along the surface of DZ13 particles, indicating that graphitized DZ13 has lower chemical activity than ungraphitized DZ13. Especially, we have already observed an interesting unusual bound rubber phenomenon, the blocked "bracelet" structure with the diameter of about 600 nm in which CB particles were blocked in ring-shaped SBS monomer.

Strontium hexaferrite was widely used in the fabrication of commercial permanent magnets and certain microwave devices. In this study, the strontium hexaferrite nanoparticle coatings were prepared by sol–gel method and using spin coating process on silicon substrate, then the effect of pH value, such as 5, 7 and 9, and calcination temperatures, such as 600°C, 800°C, and 1000°C, on structural and magnetic properties of strontium hexaferrite thin films were investigated by XRD, SEM and VSM measurements. The maximum saturation magnetization value of 57.43 emu/g and coercivity value of 3908 Oe were achieved for the thin film with crystallite size approximately 41 nm, prepared at pH value of 7 and calcinations temperature of 800°C.

Novel cross Bi₂ WO₆ microwafers have been fabricated by a facile acetone-assisted solvothermal method in high quantity. The structure characterizations of the microwafers were investigated in detail by means of X-ray powder diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The results indicate that the orthorhombic phase of Bi₂ WO₆ with high crystallinity can be obtained and each microwafer is polycrystalline in nature and organized by the nanoflake subunits. UV-visible diffuse reflectance spectrum of the prepared Bi₂ WO₆ microwafers demonstrates that they have absorption in the visible light region. The photocatalytic activity of cross Bi₂ WO₆ microwafers toward (Rhodamine B) RhB degradation under visible light was investigated, and it was found to be significantly better than that of Bi₂ WO₆ sample prepared by solid-state reaction (SSR-Bi₂ WO₆).

The kinetics as well as the equilibrium segregation profiles of very low concentrations of Sn (0.14 at.%) and Sb (0.12 at.%) in a polycrystalline Cu sample were measured by Auger electron spectroscopy. These profiles were compared to those from a Cu(100), Sb, Sn ternary single crystal which was subjected to the same experimental conditions. The results are explained in terms of solute segregation to grain boundaries and surface interfaces. The comparison also indicate that not only bulk diffusion, interactions and segregation energies play a role in the surface enrichment of the species, but in polycrystalline samples, the doping order of the specimen is to be considered as well. The differences in interaction energies of Sn and Sb also suggest an indirect method of measuring the concentrations of nonsegregating impurities in polycrystalline samples.

The vibrational properties of the three ordered metallic surface alloys, Cu(100)-c(2 × 2)-Pd, Cu(100)-(2 × 1)-Pd, and Cu(100)-(2 × 2)-Pd, are presented. The phonon dispersions of vibrational modes as well as the local density of phonon states (LDOS) are calculated using matching theory associated with Green's function formalism. The calculated results are discussed and interpreted. In particular, the transfer of charge between the Pd and Cu atoms in the surface alloys modifies the surface boundary force constants, with resultant remarkable differences for the vibrational LDOS on the Pd and Cu atomic sites at the Pd/Cu(100) surface, compared to the LDOS at the pure Cu(100) surface. This may favor new Pd-catalyzed reactions at such surface alloys systems.

An algorithm that provides direct, efficient ND polynomial factorization is presented to solve the numerical issues that arise during the direct inversion of helium atom scattering (HAS) diffraction spectra. For an n-variate polynomial the algorithm directly deflates the polynomial to n-single variable equations by evaluating the ratio of pairs of polynomial coefficients. Error estimation of the coefficients of the 1D polynomials is then performed automatically using standard 1D search techniques. The effectiveness of the technique is demonstrated against bi- and trivariate polynomials and an approximate range of validity for error prone polynomials is demonstrated. To demonstrate the effectiveness of the technique, HAS diffraction spectra for the low coverage (2 × 1)-H/Pd(311) system have been analyzed using direct inversion and have revealed that H binds in a three-fold hollow site.