Structure, internal friction, and Young’s modulus of fractal carbon deposits

We have observed that carbon deposits obtained by atomizing graphite in an electric arc in an atmosphere of argon and helium exhibit porosity and possess fractal structure. The results of measurements of the internal friction Q ⁻¹ and the effective Young’s modulus E as a function of temperature are presented. Data on the resistivity, density, and microhardness of the carbon deposits are presented. A possible mechanism for formation of fractal structures in carbon deposits is discussed. Fiz. Tverd. Tela (St. Petersburg) 40, 584–586 (March 1998)     

Experimental studies on the adhesion strength of a polymer-metal bond depending on the contact zone geometry

Theoretical investigation of the stress-strain state at special points of constructions, e.g., in adhesion joints, has demonstrated that the stress state in the contact zone strongly depends on the configuration of the zone. In order to verify these results, some experiments were carried out. Cylindrical polymer specimens having a circular groove at one of its ends were cemented to steel mushrooms and tested for abruption in tension and cantilever bending. The experiments showed that the adhesive strength depended on the profile of the joint and had a maximum at the optimum value of the angle of the joint and a minimum when the groove was absent. The ratio between the maximum and minimum strength values was 1.5 in tension and 2.5 in bending. The greater effect in the latter case can be explained by the high gradient of the stresses in bending. The experimental results confirmed the possibility of controlling the adhesive strength by changing the contact geometry in accord with the stress-strain calculations.Institute of the Mechanics of Continuous Media, Russian Academy of Sciences, Perm', Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 4, pp. 493–498, July–August, 1999.     

Synthesis and gas transport properties of new aromatic 3F polymers

New aromatic 3F polymers were obtained from condensations of 2,2,2-trifluoroacetophenone (1) with biphenyl (a), terphenyl (b), a mixture of biphenyl with terphenyl (ab), phenyl ether (c) and diphenoxybenzophenone (d). The reactions were performed at room temperature in the Brønsted superacid trifluoromethanesulfonic acid (TFSA) and in a mixture of TFSA with dichloromethane. The polymers show high glass transition temperatures >170 °C, excellent thermal stability (decomposition temperatures ≥475 °C) and good solubility in chlorinated solvents and strong acids. The 3F polymer structures based on biphenyl and terphenyl show attractive permeability coefficients for CO₂ (∼200 Barrers) and H₂ (∼120 Barrers), whereas the 3F polymers that contain ether linkages have permeability coefficients in the typical range of regular polysulfone and polycarbonate. However, in sharp contrast to polysulfone and polycarbonate families, new 3F polymers possess high chemical stability and they have advantages since their reactions, based on commercially available monomers, can be carried out in one-pot at room temperature and offer a large variety of structures not possible to prepare by other synthetic methods.     

Analysis of fringe patterns by the method of integral boundary equations in the solution of plane elastoplastic problems

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 164–170, March–April, 1990.     

Remarkable enhancement of reactivity of carbonyl compounds for polymerizations with non-activated aromatic hydrocarbons

Reaction of carbonyl compounds bearing electron-withdrawing substituents with non-activated aromatic hydrocarbons proceeds selectively in trifluoromethanesulfonic acid (TFSA) at room temperature to give linear, high-molecular-weight polymers.     

Free-space evolution of focused Gaussian beams transformed by conical diffraction in a biaxial crystal

The intensity and polarization pattern of circularly and linearly polarized Gaussian beams transformed by the effect of conical diffraction in a biaxial crystal has been studied experimentally, and compared with the predictions of paraxial theory. Some general regularities in the relative intensity and geometry of beam structures were analyzed. The formation of Mathieu beam profiles from linearly polarized input beams was demonstrated.