Variation of the creep limit and structure of a welded joint in PT-3V titanium alloy under the effect of cyclic loading. Report 2

Comparative analysis of the characteristics of amplitude-dependent internal friction (IF) was carried out to explain reasons leading to an increase of the creep limit of the butt welded joint in PT-3V titanium alloy (PT-2V filler material) after cyclic loading. IF was measured by the method of the direct torsional pendulum on cylindrical specimens representing the gage part of the specimens subjected to preliminary cyclic loading. The data were processed using the Granato-Lucke theory. The results show that the reduction of IF after cyclic loading took place as a result of an increase of the number and redistribution of pinning points of the dislocations. Consequently, the density of mobile dislocations decreases by 8% and the length of dislocation segments by 18%. These processes of stabilization of the structure were completed within 5·10 ⁴ cycles of preliminary loading. Stabilization of the dislocation structure of the material of the welded joint increases its creep limit.Translated from Problemy Prochnosti, No. 4, pp. 35–40, April, 1996.     

New sleeve filters for cleaning fluids in the production of movie film

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 10, p. 2, October, 1992.     

New 2,2-difluoro-1,3,2(2H)oxazaborines and merocyanines derived from them

Synthetic methods have been developed to prepare oxazaborines, the azaanalogues of 2,2-difluoro-1,3,2(2H)dioxaborines, which can form merocyanine dyes. The first oxazaborine merocyanines with the isomeric position of the coordinating nitrogen atom have also been obtained. Comparing the spectral properties of donor-acceptor dioxa- and oxazaborine dyes, it is seen that substitution of the 3-O atom by the NH group in the chelate ring has a slight effect on absorption and fluorescence band positions but causes the intensity redistribution between the 0-0 and 0-1 vibronic absorption peaks and thus induces a change in the absorption band shape due to the enhanced solvation of oxazaborines. Substitution of the 1-O ring atom by the NPh group leads to a bathochromic shift and a manifold increase in the fluorescence quantum yield for the corresponding boron chelate dyes.     

Crucial Role of Weak Acid Sites for Catalytic Performance of Zeolites in Ethyl tert-butyl Ether Synthesis

Catalytic activity of different zeolites: H,NH₄-form of mordenite-containing rock (H-CMK) and H-Beta with a Si/Al ratio of 15–407 (H-ВЕА) in ethyl tert-butyl ether (ETBE) synthesis in a packed-bed flow reactor at 80–180°C and 1?MPa has been studied. Acid characteristics of zeolites were determined by stepwise (Quasi-Equilibrium) ammonia thermodesorption. Three types of acid sites of different strength has been found, which is marked as weak (E_NH3?=?60–75?kJ/mol), medium (E_NH3?=?86–123?kJ/mol), and strong (E_NH3?=?112–145?kJ/mol). The correlation between ETBE productivity and the concentration of weak acid sites has been found. Thereby, it was established that weak acid sites of zeolites are the active sites in ETBE synthesis.     

Changes induced in a ZnS:Cr-based electroluminescent waveguide structure by intrinsic near-infrared laser radiation

The causes of changes that occur in a thin-film electroluminescent metal-insulator-semiconductor-insulator-metal waveguide structure based on ZnS:Cr (Cr concentration of ～4 × 10²⁰ cm^?3) upon lasing (λ ≈ 2.6 μm) and that induce lasing cessation are studied. It is established that lasing ceases because of light-scattering inhomogeneities formed in the structure and, hence, optical losses enhance. The origin of the inhomogeneities and the causes of their formation are clarified by studying the surface topology and the crystal structure of constituent layers of the samples before and after lasing. The studies are performed by means of atomic force microscopy and X-ray radiography. It is shown that a substantial increase in the sizes of grains on the surface of the structure is the manifestation of changes induced in the ZnS:Cr film by recrystallization. Recrystallization is initiated by local heating by absorbed laser radiation in existing Cr clusters and quickened by a strong electric field (>1 MV cm^?1). The changes observed in the ZnS:Cr film are as follows: the textured growth of ZnS crystallites, an increase in the content of Cr clusters, and the appearance of some CrS and a rather high ZnO content. Some ways for improving the stability of lasing in the ZnS:Cr-based waveguide structures are proposed.