STRUCTURE,CHEMICAL BONDS AND THER MOELECTIC PROPERTY OF Si DOPED BORON CARBIDES

Thecorrelation between composition, structure, chemical bond, and thermoelectric proper tiesof Si doped boroncarbidesisstudied using SCF DV Xαmethod. Thecalculationsshow that Siatom firstlysubstitutes Bor Catomson theend of boron carbidechain, then may occupyinterstitialsites when Siis dopedin boron carbide, anditisdifficultfor SitosubstituteBor Catom in thecenter of chain orintheicosahedron. Arepresentativestructural unitcontain ing an Si atom is 〔C B Si〕ε+ 〔B11 C〕ε , whilethe structural unit without Siis 〔C B B ( C)〕δ 〔B11 C〕δ+ . Afteradding Sitotheboroncarbides,theenergyrequired bythe dispro portionation reaction decreases,theconcentrationofthecarriersincreases,andthereare more pathsfor the bipolaron to hopping. At thesametime, the covalent bond becomes weaker, andthethermal conductivity decreases. Therefore, thethermoelectric property of Si dopedboron carbidesisimproved .

THERMODYNAMIC PROPERTIES Cu-Ce-S AND Cu-Y-S LIQUID SOLUTIONS

The thermodynamic properties of Cu-Ce-S and Cu-Y-S liquid solutions were studied by the chemical equilibrium technique at 1200℃. The equilibrium constants and the standard free energies of formation of CeS and YS were determined for the reactions: CeS=[Ce]+[S] and YS = [Y]+[S] . For the solution of Ce_(1) and Y_(l) in pure Cu according to the reactions: Ce_(1)= [Ce] and Y_(1)= [Y] , the standard free energies of solutions were obtained. The first order and second order interaction coefficients between solute elements as well as the activity coefficients γ_(Ce)~0 and γ_Y^0 in liquid Cu were also determined.

THE PREPARATION,STRUCTURE AND PROPERTES OF Sr_(0.5)Ca(0.5)CuO_2

Sr_(0.5)Ca_(0.5)CuO_2 has been synthesized by the solid state reaction.The compound crystallizes in an orthorhombic unit cell,space group D_(2h)^(17)-Cmcm with a=3.444 ,b=16.11 ,c=3.868 .It decomposes shove 1038℃. Sr_(0.5)Ca_(0.5)CuO_2 is s black p-type semiconductor with resistivity 53Ω.cm at room tempersture.

Investigation of Illumination Effects on the Electrical Properties of Au/GO/p-lnP Heterojunction with a Graphene Oxide Interlayer

In this work,the electrical property of Au/graphene oxide/p-InP hetero-structure has been evaluated by 1-V and C-V measure-ments in dark and iluminated conditions(visible light).The diode exhibited significant rectifying behavior,thus indicating the heterojunction-lype diode.The key electrical parameters of heterojunction diode including ideality factor(n),series resistance(R),shunt resistance(Rsh),and barrier height(Фb)are estimated from I-V data based on the theory of thermionic emission.The modifed Norde and Cheung's methods were utilized to evaluate the electrical parameters and compared the results.The current conduction mechanism at different voltage regions of I-V has also been investigated.The variation of 1/C versus voltage signifies linearity at high frequency(1 MHz),indicating that the type of heterojunction can be abrupt.The experimental outcomes of this study revealed that the performance of heterojunction diode in dark is considerably good as compared to the ilumination condition with respect to the lower values of Фp,n,R,and interface state density(Nss).

Reduced Graphene Oxide Supported Bimetallic CobaltPalladium Nanoparticles with High Catalytic Activity towards Formic Acid Electro-oxidation

In this work,we report the growth of uniformly dispersed bimetallic cobalt-palladium nanoparticles(NPs) on reduced graphene oxide(RGO) nanosheets to prepare CoPd-RGO composites via a two-step procedure,where firstly formed Co NPs are used as seeds for the subsequent growth of Pd.The generation of Co NPs on RGO is performed by an in-situ reduction reaction with the reducer ethylene glycol under oil bath at180 ℃.According to composition,size and microstructure analyses,NPs in the resulting CoPd-RGO have an average particle size of 5 nm,and Pd is added to one side of Co NPs,thus forming Co-Pd bimetallic interfaces.The involved formation mechanism is suggested.The composite is used as an electro-catalyst for the formic acid oxidation in alkaline electrolyte,and the catalytic performance is investigated by cyclic voltammetry and chronopotentiometry etc.The results show that the composite has the highest electrocatalytic activity,the best electrochemical stability and the highest resistance to CO poisoning than those of the monometallic composite and commercial Pd black at the same loading.This is due not only to the small size of NPs with Co-Pd bimetallic interfaces providing more active atoms accessible for reactants,but also to the electric synergistic effect between metals and graphene.