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81.
82.
The enthalpies of solution of pure silver halides AgCl and AgI and a composite material with molar composition 0.5 AgCl-0.5 AgI were measured at 298 K in a mixture of Na2S2O3 (1 M) and NH4OH (1 M). X-ray diffraction patterns showed that the composite material contained the metastable γ-AgI phase; different mechanisms for its stabilization were discussed. The phase transition enthalpies of AgI modifications and the enthalpy of formation of the composite material were deduced from the measurements. The latter could be related to a change of interfacial enthalpies. 相似文献
83.
N. Petit V. Garnier V. Ta Phuoc R. Caillard A.-M. Frelin A. Ruyter I. Laffez J.-C. Soret A. Maignan F. Gervais 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(4):423-429
The reflectivity spectra of an oriented ceramic of Bi-2223 has been investigated by polarized infrared reflectivity spectroscopy
in the energy range 0.005-2.2 eV. It is shown that the data for the polarization parallel to the c axis cannot be fitted with a one-component Drude or extended-Drude model. The conductivity spectrum is then obtained from
the best fit of a “double-damping Drude” model to reflectivity spectra, itself derived from the factorized form of the dielectric
function, and by a Kramers-Kronig inversion as well. The data and their analysis give a new insight of the 2D character of
the system.
Received 26 April 2001 and Received in final form 28 August 2001 相似文献
84.
Pierre Krausz Jean Guillerez Francis Garnier 《Journal of organometallic chemistry》1978,161(1):97-108
The cis-trans interconversion of olefins in the system W(CO)6 + CCl4 + 2-butene is studied, both with initial irradiation of a solution of W(CO)6 in CCl4 (photoinduction), and with continuous irradiation of the system, for cis- and trans-butene concentrations between 0.09 and 6.0 M. Analysis of the results of the photoinduction experiments (rate of conversion and kinetic law as a function of the initial concentration of the olefin) allowed us to propose a simple kinetic scheme comprising a cis-trans interconversion of 2-butene and olefin-catalyzed destruction of the catalytic entity (k2 = (0.62 ± 0.06)x10?4 M s?1). In the continuous irradiation experiments the final distribution of the olefin was independent of the initial butene concentration (cis-2-butene/trans-2-butene 3.0) and the reaction kinetics are of first-order (kobs = (3±1) x10?4 s?1. Comparison of the two experiments suggests continuous photochemical regeneration of the catalytically active entity. The first-order reaction kinetics are in agreement with a carbene-metal carbonyl structure of the intermediate 相似文献
85.
Dilatation thermique anormale et caractere en couches des metavanadates MV2O6 (M = Ca,Cd, Zn,Mg, Pb)
The variations of cell parameters and thermal expansion tensors of metavanadates MV2O6 have been measured in the range 77–295 K. The thermal expansion anisotropy is characteristic of layer structures especially for brannerite-type structures (M = Cd, Zn, Mg); this anisotropy is explained by the presence of [VO5] polyhedra, such as occur in the V2O5 layer structure. For CaV2O6 the variation of thermal expansion as a function of temperature is abnormal: peaks, typical of a diffuse transition, are observed at 260 K for α1(T) and α3(T) curves. The temperature anomaly is reduced when cadmium is substituted for calcium. 相似文献
86.
J. Carre P. Claudy M. Kollmannsberger J. Bousquet E. Garnier P. Barberi 《Journal of fluorine chemistry》1978,11(6):613-627
Tellurium Tétrafluoride has been prepared and various analysis (chemical, thermal, Xray) have been performed. Heat of fusion (δHfus = 3,02 Kcal.mol-1), and calorific capacity of solid TeF4 from 298 to 402°K (Cps = 30 cal.K-1. mol-1) and of liquide TeF4 at 423°K (Cp1 = 31, 1 cal.K.-1.mol-1) have been determined Enthalpic values are given. 相似文献
87.
Solla-Gullón J Vidal-Iglesias FJ López-Cudero A Garnier E Feliu JM Aldaz A 《Physical chemistry chemical physics : PCCP》2008,10(25):3689-3698
Reactivity towards methanol and formic acid electrooxidation on Pt nanoparticles with well characterised surfaces were studied and compared with the behaviour of single crystal electrodes with basal orientations. Polyoriented and preferential (100), (111) and (100)-(111) Pt nanoparticles were synthesised, cleaned preserving its surface structure, characterised and employed to evaluate the influence of the surface structure/shape of the Pt nanoparticles on these two relevant electrochemical reactions. The results pointed out that, in agreement with fundamental studies with Pt single crystal electrodes, the surface structure of the electrodes plays an important role on the reactivity of both oxidation processes, and thus the electrocatalytic properties strongly depend on the surface structure/shape of the nanoparticles, in particular on the presence of sites with (111) symmetry. These findings open the possibility of designing new and better electrocatalytic materials using decorated shape-controlled Pt nanoparticles as previously described with Pt single crystal electrodes. 相似文献
88.
Louis Y Cmuk P Omanović D Garnier C Lenoble V Mounier S Pizeta I 《Analytica chimica acta》2008,606(1):37-44
The influence of an adsorbed layer of the natural organic matter (NOM) on voltammetric behaviour of copper on a mercury drop electrode in natural water samples was studied. The adsorption of NOM strongly affects the differential pulse anodic stripping voltammogram (DPASV) of copper, leading to its distortion. Phase sensitive ac voltammetry confirmed that desorption of adsorbed NOM occurs in general at accumulation potentials more negative than −1.4 V. Accordingly, an application of negative potential (−1.6 V) for a very short time at the end of the accumulation time (1% of total accumulation time) to remove the adsorbed NOM was introduced in the measuring procedure. Using this protocol, a well-resolved peak without interferences was obtained. It was shown that stripping chronopotentiogram of copper (SCP) in the depletive mode is influenced by the adsorbed layer in the same manner as DPASV. The influence of the adsorbed NOM on pseudopolarographic measurements of copper and on determination of copper complexing capacity (CuCC) was demonstrated. A shift of the peak potential and the change of the half-peak width on the accumulation potential (for pseudopolarography) and on copper concentration in solution (for CuCC) were observed. By applying a desorption step these effects vanished, yielding different final results. 相似文献
89.
马丽娜 《纯粹数学与应用数学》2007,23(4):549-555
通过构造两个非负鞅证明了一个强极限定理,然后把它应用到本文所定义的广义Bethe树上的奇偶马尔可夫链场上,从而获得了此马氏链场上的一类强极限定理. 相似文献
90.
Andrieux D Gaspard P Ciliberto S Garnier N Joubaud S Petrosyan A 《Physical review letters》2007,98(15):150601
The time-reversal symmetry of nonequilibrium fluctuations is experimentally investigated in two out-of-equilibrium systems: namely, a Brownian particle in a trap moving at constant speed and an electric circuit with an imposed mean current. The dynamical randomness of their nonequilibrium fluctuations is characterized in terms of the standard and time-reversed entropies per unit time of dynamical systems theory. We present experimental results showing that their difference equals the thermodynamic entropy production in units of Boltzmann's constant. 相似文献