Alteration of Structure and Properties of Thin Polyimide Films and Coatings by Plasma and Thermal Treatment

The influence of alternating radiofrequency-plasma and heat treatment on the structure and bulk properties of polyimide films and coatings with a thickness of 3.5 m was studied. It was shown that plasma treatment leads to the enhancement of the specific surface energy due to the polar component and to an increase in the diffusion coefficient and in the amount of sorbed water. The subsequent thermal treatment leads to the recovery of the polyimide surface and bulk properties to almost their initial magnitudes. It was assumed that these effects are caused by a change in the structure of thin films and coatings and by the buildup of negatively charged particles at the surface and in mesopores of the polymer upon RF plasma treatment and due to annealing upon thermal treatment.     

Reaction of formaldehyde with the Wilkinson complex in the presence of carboxylic acid amides

N,N-Dimethylacetamide and N, N-dimethyformamide react with RhCl(PPh₃)₃ with displacement of PPh₃ and the formation of a complex with the amide. Formamide and N-propylacetamide do not form similar complexes under similar conditions. In contrast to the reaction of RhCl(PPh₃)₃, which leads to the formation of RhCl(CO)(PPh₃)₂ due to decarbonylation of CH₂O, stabilization of the ₂-CH₂O form of the CH₂O coordinated with rhodium is likely in the reaction of formaldehyde with a rhodium complex containing an N-bonded amide. Under the conditions of hydroformylation of CH₂O in a solution of the Wilkinson complex in an unsubstituted amide the dominating pathway of the transformation of formaldehyde is its reaction with the solvent or the ammonia formed via decarbonylation of the unsubstituted amide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2670–2673, December, 1989.     

An improved method for selective catalytic reduction of nitrogen oxides in exhaust gases

The selective catalytic reduction (SCR) of nitrogen dioxide in an air flow modeling the exhaust gas from an internal combustion engine is studied. Granulated V₂O₅ (13.5%)–MnO₂ (0.7–1.0%)/Al₂O₃ powder (AVK-10M catalyst) and ammonia injected into a SCR catalytic cell are used as a heterogeneous catalyst of NO₂ reduction and a reducing agent, respectively. If the efficiency of NO₂ removal is high enough and satisfies the requirements of the State Sanitary Standards for the maximum permissible concentrations of substances emitted into the atmosphere (\(MP{C_{N{O_2}}}\) = 0.085 mg/m³), the reducing agent (ammonia) is not completely consumed during SCR, so a considerable amount of NH₃ can be released into the atmosphere. Therefore, a strict control of both NO₂ and unreacted ammonia emissions is needed. The dependences of the concentrations of [NH₃] and [NO₂] on the [NH₃]/[NO₂] ratio for the model air flow passed through the AVK-10M granular heterogeneous catalyst are measured. It is found that the maximum degree of removal of NO₂ from the air takes place at [NH₃]/[NO₂] = 1.3. In the conventional process, the concentration of [NO₂] drop from 530.00 to 0.07 mg/m³, i.e., below the \(MP{C_{N{O_2}}}\). At the same time, the ammonia concentration increases to [NH₃] = 3.4 mg/m³, which becomes 85 times the \(MP{C_{N{O_2}}}\), 0.04 mg/m³. To remove unreacted ammonia from air flows, we developed [P–(SO₃ ^-)₂ · Me²⁺] sulfocationites, where Me are the Cu and/or Ca ions, P is a styrene–divinylbenzene copolymer. It is shown that the concentration of ammonia passed through the adsorption cell filled with a freshly sulfocationite drops below \(MP{C_{N{H_3}}}\) = 0.04 mg/m³. The dependences of the dynamic exchange capacity (DEC) before ammonia breakthrough for the [P–(SO₃ ^-)₂ · Cu²⁺] delta-sulfocationite on the air flow rate, [NH₃] concentration, and humidity are measured. The maximum value of the DEC, δ = 59.5 mg/cm³, is observed at an air flow velocity of 2.171 m/s, [NH₃] = 0.0035 mg/L, and 75% humidity. To illustrate practical applications of the proposed improved SCR method, it is shown that a 3-L replaceable [P–(SO₃ ^-)₂ · Cu²⁺] sorbent cartridge in a SCR exhaust gas purifier for a car internal combustion engine does not need replacement more frequently than every 50000 km.     

Study of carbon nanostructures obtained by pyrolytic synthesis

The structure and phase composition of a carbon nanomaterial obtained by the thermal decomposition of toluene-ferrocene mixtures are studied by Mössbauer spectroscopy, high-resolution electron microscopy, and x-ray diffraction. Variations in the structural state of the catalyst and in the quantitative yield of the nanomaterial are analyzed as functions of the synthesis time.     

Joint bounds for the Perron roots of nonnegative matrices with applications

Given a finite set {A_x}_{x ∈ X} of nonnegative matrices, we derive joint upper and lower bounds for the row sums of the matrices D⁻¹ A^(x) D, x ∈ X, where D is a specially chosen nonsingular diagonal matrix. These bounds, depending only on the sparsity patterns of the matrices A^(x) and their row sums, are used to obtain joint two-sided bounds for the Perron roots of given nonnegative matrices, joint upper bounds for the spectral radii of given complex matrices, bounds for the joint and lower spectral radii of a matrix set, and conditions sufficient for all convex combinations of given matrices to be Schur stable. Bibliography: 20 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 334, 2006, pp. 30–56.     

Temperature dependence of fluorescence spectra of derivatives of 1,4-distyrylbenzene in polymethyl methacrylate film

Journal of Applied Spectroscopy -     

System for recording and analysis of reflection high-energy electron diffraction patterns

An efficient and fast system for recording and analysis of reflection high-energy electron diffraction (RHEED) patterns is described. The software developed for this system includes three program packages: one for operating in the single-window mode, one for operating in the four-window mode, and one for the linear regime. Examples are given of the use of the system for monitoring and control of growth of III–V semiconductor compounds by molecular-beam epitaxy. Using this system, we discovered an effect wherein a periodic splitting of the RHEED peaks occurs during the growth of GaAs (100). Zh. Tekh. Fiz. 67, 111–116 (August 1997)