Steady-state kinetics of the NO-CO reaction on Rh(111): extrapolation from 10−10 to 1 bar

Ultrahigh vacuum studies indicate that the mechanism of the NO-CO reaction on Rh(111) involves reversible adsorption of NO and CO, NO decomposition, nitrogen desorption, and a Langmuir-Hinshelwood reaction between CO and oxygen. Employing available experimental data for the rate constants of these steps, we have calculated the steady-state reaction kinetics in a wide range of pressures and temperatures. At relatively high pressures (P _NOP _CO0.01 bar), the results of simulations are in marginal agreement with the experimental data. Analyzing the difference between the theory and experiment makes it possible to understand the type of changes which might be introduced into the model in order to improve the agreement with the experiment.     

A method for the determination of the volumes of arbitrarily-spaced local defects during eddy-current testing of cylindrical items by a multi-unit probe

The design of a data-analysis algorithm in the eddy-current testing of cylindrical items by a multi-unit probe, which allows the automatic determination of the volume of local defects between single probes that are included in a multi-unit probe, has been described. The effectiveness of the algorithm is confirmed by its repeatability studies.     

EFFECTIVE PROPERTIES OF POROUS AND COMPOSITE MATERIALS

Based on a previously modified version of Bruggerman's method, a dependence of the effective diffusion coefficient in porous media on the porosity is deduced and compared with available experimental data. Based on the same method, a dependency of the effective elastic coefficients of composite materials on the volume fraction of inclusions is deduced in the case of different types of inclusions. Comparison with available experimental data shows good agreement between the theory predictions and the experimental data. In the case of the elastic properties of laminated composite materials, application of the same method yields results identical to those obtained using the averaging procedure. A theory of effective viscosity of concentrated suspensions is applied for calculations of dependency of effective viscosity on applied shear rate using available experimental data.     

Influence of surface layer conditions of multiwall carbon nanotubes on their electrophysical properties

We have investigated temperature σ(T) and magnetic field σ(B) dependences of the conductivity of multiwalled carbon nanotubes (MWNTs) with different average outer diameter d? and composite materials on the bases of these MWNTs in dielectric polymethyl methacrylate matrix (PMMA). It was shown that the percolation threshold of the electrical conductance for MWNT/PMMA composites lies in the range of concentration of MWNTs lower than 0.5 wt.%. From the joint analysis of σ(T) and σ(H) we have found that quantum corrections to the conductivity for interaction electrons is dominated in MWNTs with average outer diameters d? ～ 23 nm and MWNT/PMMA composite materials. We determined the constant of electron–electron interaction λ from quantum correction to σ(T) and σ(H). In the result we have found that λ depends on the concentration of MWNTs in MWNT/PMMA materials. This fact demonstrates that the interaction of the dielectric material of PMMA with surface atoms of MWNTs leads to the change of the λ in MWNTs. For MWNTs with average outer diameters d? ≤ 13 nm and for composite on the base of these MWNTs we have observed the domination of one dimensional variable range hopping conductivity (VRHC) at a temperature below 20 K. From the data of VRHC we estimated the density of localized states at the Fermi level N(E_F) and demonstrated that N(E_F) is decreasing in composite materials.