Effect of the burning temperature on the phase composition,photovoltaic response,and electrical properties of Ag/Pd resistive films

Silver-palladium (Ag/Pd) films were grown by thick-film technology using a resistive paste consisting of Pd, Ag2O, and glass on ceramic substrates at burning temperatures of 878, 1013, and 1113 K. The effect of the burning temperature and Pd content in the initial paste on the phase composition, resistivity, photovoltaic properties of films, free carrier concentration, and mobility was studied. It was found that the films grown at a burning temperature of 878 K have the greatest factor of conversion of the pulsed laser power to the photovoltaic signal, which depends on the direction of the incident radiation wave vector. Using X-ray diffraction, X-ray photoelectron spectroscopy, and thermodynamic modeling, it was shown that the AgPd alloy and PdO oxide are the main components of the Ag/Pd film with photovoltaic properties.     

Transformation of perfluorinated benzocycloalkenes and alkylbenzenes to their carbonyl derivatives under the action of CF3COOH/SbF5

Perfluorinated benzocycloalkenes (benzocyclobutene, indan, tetralin), alkylbenzocycloalkenes and alkylbenzenes react with CF₃COOH/SbF₅ at 20-50 °C giving the corresponding carbonyl derivatives.     

Carbonylation of Polyfluorobenzocyclobutenones in a SbF5 Medium

Russian Journal of Organic Chemistry - The carbonylation of perfluoro-2-R-benzocyclobutenones (R = F, CF3, C2F5, C6F5) in a CO-SbF5 system is accompanied by transformations of the four-membered...     

Investigation of the structure of nanocrystalline refractory oxides by X-ray diffraction,electron microscopy,and atomic force microscopy

The structures of nanocrystalline fibrous powders of refractory oxides have been investigated by different methods: determination of coherent-scattering regions, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic-force microscopy (AFM). The sizes of nanograins of different crystalline phases of refractory metal oxides have been determined during the formation of these nanograins and the dynamics of their growth during heat treatment in the temperature range 600–1600°C has been studied. The data on the structure of nanocrystalline refractory oxide powders, obtained by different methods, are in good agreement. According to the data on coherent-scattering regions, the sizes of the ZrO₂ (Y₂O₃) and Al₂O₃ grains formed are in the range 4–6 nm, and the particle sizes determined according to the TEM and AFM data are in the ranges 5–7 and 2–10 nm, respectively. SEM analysis made it possible to investigate the dynamics of nanoparticle growth at temperatures above 1000°C and establish the limiting temperatures of their consolidation in fibers.

     

Skeletal transformations of perfluorinated 2,2-diethyl- and 2-ethyl-2-phenyl-benzocyclobutenones under the action of antimony pentafluoride

Perfluoro-2-ethyl-2-phenylbenzocyclobutenone heated with SbF₅ at 70 °C and then treated with water, forms perfluoro-3-ethyl-3-phenylphthalide. In contrast to this, heating of perfluoro-2,2-diethylbenzo-cyclobutenone with SbF₅ at 70 °C gives, after treatment of the reaction mixture with water, perfluoro-2-(pent-2-en-3-yl)benzoic acid. When the reaction temperature is raised to 125 °C, a solution of a salt of perfluoro-4-ethyl-3-methylisochromenyl cation is obtained. Hydrolysis of the solution of the salt gives perfluoro-4-ethyl-3-methylisochromen-1-one.     

Generation of a Polarization Sensitive Photocurrent in a CuSe/Se Nanocomposite Thin Film

JETP Letters - CuSe-based structures are widely used in various fields of photonics and optoelectronics. It has been shown for the first time that a photocurrent depending on the direction of the...     

Photoinduced radical processes on the spinel (MgAl2O4) surface involving methane, ammonia, and methane/ammonia

The present study explored photoinduced radical processes caused by interaction of CH(4) and NH(3) with a photoexcited surface of a complex metal oxide: magnesium-aluminum spinel (MgAl(2)O(4); MAS). UV irradiation of MAS in vacuo yielded V-type color centers as evidenced by the 360 nm band in difference diffuse reflectance spectra. Interaction of these H-bearing molecules with photogenerated surface-active hole states (O(S)(-)?) yielded radical species which on recombination produced more complex molecules (including heteroatomic species) relative to the initial molecules. For the MAS/CH(4) system, photoinduced dissociative adsorption of CH(4) on surface-active hole centers produced ?CH(3) radicals that recombined to yield CH(3)CH(3). For MAS/NH(3), a similar dissociative adsorption process led to formation of ?NH(2) radicals with formation of NH(2)NH(2) as an intermediate product; continued UV irradiation ultimately yielded N(2). For the mixed MAS/CH(4)/NH(3) system, however, interaction of adsorbed NH(3) and CH(4) on the UV-activated surface of MAS yielded ?NH(2) and ?CH(3) radicals, respectively, which produced CH(3)-NH(2) followed by loss of the remaining hydrogens to form a surface-adsorbed cyanide, CN(S), species. Recombination of photochemically produced radicals released sufficient energy to re-excite the solid spinel, generating new surface-active sites and a flash luminescence (emission decay time at 520 nm, τ ~ 6 s for the MAS/NH(3) case) referred to as the PhICL effect.     

Solution of sparse quasi-square rectangular systems by Gaussian elimination

We present a general method for the linear least-squares solutionof overdetermined and underdetermined systems. The method isparticularly efficient when the coefficient matrix is quasi-square,that is when the number of rows and number of columns is almostthe same. The numerical methods for linear least-squares problemsand minimum-norm solutions do not generally take account ofthis special characteristic. The proposed method is based onLU factorization of the original quasi-square matrix A, assumingthat A has full rank. In the overdetermined case, the LU factorsare used to compute a basis for the null space of A^T. The right-handside vector b is then projected onto this subspace and the least-squaressolution is obtained from the solution of this reduced problem.In the case of underdetermined systems, the desired solutionis again obtained through the solution of a reduced system.The use of this method may lead to important savings in computationaltime for both dense and sparse matrices. It is also shown inthe paper that, even in cases where the matrices are quite small,sparse solvers perform better than dense solvers. Some practicalexamples that illustrate the use of the method are included.     

Transformations of Perfluorinated 2-Alkyl- and 2,2-Dialkylbenzocyclobutenones in SbF<Subscript>5</Subscript> and SiO<Subscript>2</Subscript>-SbF<Subscript>5</Subscript>

Perfluorinated 2-methyl- and 2-ethylbenzocyclobutenones on heating in SbF₅ underwent isomerization into perfluoroindan-1-one and perfluoro(2-methylindan-1-one), while their reaction with SiO₂—SbF₅ gave perfluorinated 3-methyl- and 3-ethylphthalides, respectively. Perfluorinated 2-ethyl-2-methyl- and 2,2-diethylbenzocyclobutenones reacted with SbF₅ to produce perfluorinated 2-(but-2-en-2-yl)- and 2-(pent-2-en-3-yl)-benzoic acids, and their transformations in SbF₅ over SiO₂ afforded 5,6,7,8-tetrafluoro-1-oxo-3-trifluoromethyl-1H-isochromene-4-carboxylic acid and perfluoro(4-ethyl-3-methyl-1H-isochromen-1-one), respectively.     

Reaction of perfluoro-1-ethylindan with SiO2/SbF5 and skeletal transformations of perfluoro-3-ethylindan-1-one under the action of SbF5 and SiO2/SbF5

Perfluoro-1-ethylindan heated with excess of SiO₂ in an SbF₅ medium at 75 °C and then treated with water, gives 4-carboxy-perfluoro-3-methylisochromen-1-one. Perfluoro-3-ethylindan-1-one is converted, under the action of SbF₅ at 70 °C, to perfluoro-2-(but-2-en-2-yl)benzoic acid as a mixture of E- and Z-isomers. When the reaction temperature is raised to 125 °C, a solution of salts of perfluoro-3,4-dimethyl-1H-isochromen-1-yl and perfluoro-4-ethyl-1H-isochromen-1-yl cations is obtained. Increase in the reaction time lowers the content of a salt of the latter cation in the solution. Hydrolysis of the solution of the salts gives perfluoro-3,4-dimethylisochromen-1-one and perfluoro-4-ethylisochromen-1-one.