Rotary-piston laser engine

The possibility of constructing a rotary-piston laser engine is considered. Its specific advantages over a piston laser engine are cited, and the technical difficulties of its production are noted.Translated from Trudy Fizicheskogo Instituta im. P. N. Lebedeva, Vol. 120, pp. 106–107, 1980.     

Characteristics of membrane-electrode assemblies of hydrogen-air fuel cells with PtCoCr/C catalyst

A cathodic catalyst, which can replace monoplatinum commercial catalyst, is developed and investigated. New catalyst combines a smaller consumption of platinum with a higher mass activity and corrosion resistance. A method of fabrication of ternary (PtCoCr/C) catalyst is improved in order to obtain the catalytic system containing 45–50 wt % platinum. This is necessary to form thinner active layers of cathodes of membrane-electrode assemblies of hydrogen-air fuel cells. The activity of the synthesized PtCoCr/C catalyst is by 1.2–1.5 times higher than that of the monoplatinum catalyst containing 60–70 wt % Pt. According to the accelerated-test data, the corrosion resistance of PtCoCr/C catalyst is also higher than that of Pt/C system.     

Mössbauer study and magnetic properties of M-type barium hexaferrite doped with Co + Ti and Bi + Ti ions

Using X-ray powder diffractions, M?ssbauer spectroscopy, and magnetic measurements, the effect of complex dopants (Co2+ + Ti4+) and (Bi3+ + Ti4+) on the fine structure and magnetic properties of M-type barium hexaferrite prepared by hydroxide and carbonate precipitations has been studied. The distribution of cations over five nonequivalent positions of barium hexaferrite with magnetoplumbite structure is discussed. It has been shown that doped barium hexaferrite can be used for high-coercitivity data storage media.     

Photochromic coumarin spiropyrans

New photochromic spiropyrans (SPP) derived from 4-methyl-7-hydroxy-8-formylcoumarin have been synthesized. The effect of the heterene fragment on the spectral and photochromic properties of the SPP was examined. The photoproduct of the benzodithiolane SPP had the absorption with longest wavelength. Indoline SPP were found to have the most efficient photocoloring. Fluorescence of the cyclic form was found for the SPP.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 601–604, May, 1992     

Effect of poly (lactic acid)‐graft‐glycidyl methacrylate as a compatibilizer on properties of poly (lactic acid)/banana fiber biocomposites

The main aim of this study was to synthesis of poly (lactic acid) (PLA)‐graft‐glycidyl methacrylate (GMA) as well as its influence on the properties of PLA/banana fiber biocomposites. PLA‐graft‐GMA graft copolymer (GC) was synthesized by melt blending PLA with GMA using benzoyl peroxide and dicumyl peroxide as initiators. Graft copolymerization was confirmed by FTIR and ¹H‐NMR spectroscopic studies. PLA/silane treated banana fiber (SiB) biocomposites with various GC concentrations were prepared by melt blending followed by injection molding techniques. The influence of GC content on the mechanical, thermal and moisture resistance properties of the composite was investigated. The addition of 15 wt% GC content in the biocomposite provided optimum tensile and flexural strength, which is attributed to the greater compatibility between fiber and PLA matrix. The thermal properties of biocomposites have been evaluated using thermogravimetric analysis which provided evidence of improved interfacial adhesion between SiB and PLA by the addition of GC. Additionally, GC enhanced the moisture absorption resistance of biocomposites. These results indicated that GC is indeed a good candidate as a compatibilizing agent to improve the compatibility in PLA/fiber biocomposites. Copyright © 2015 John Wiley & Sons, Ltd.     

Study of degradation of membrane-electrode assemblies of hydrogen-oxygen (air) fuel cell under the conditions of life tests and voltage cycling

The degradation processes of HiSPEC 9100 (60% Pt/C) and 13100 (70% Pt/C) cathodic monoplatinum catalysts, which were tested under the model conditions and in the composition of membrane-electrode assemblies (MEA) of hydrogen-air and hydrogen-oxygen fuel cells, are studied. It is shown that, in all cases, the main reason for a decrease in the catalyst activity was a decrease in its surface area, which was caused by the coarsening of platinum nanoparticles, irreversible oxidation of a fraction of active centers, and the destruction of the catalyst due to the carbon support oxidation. The results of electrochemical measurements are supplemented with the structural investigations by the methods of transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). It is found that the degradation processes of MEA in the accelerated stress tests (AST) are similar to those in the long-term life tests. With respect to a decrease in the catalyst active surface area, the application of 2500 cycles in the voltage range of 0.6 to 1.2 V in the AST is equivalent to the life tests for 1010 h. During the fuel cell operation, the destruction of polymer electrolyte proceeds along with the catalyst degradation. This leads to a decrease in the ion-exchange capacity of the membrane and ionomer in the composition of cathode active layer.