Thermal and electrical conductivity properties of some CrIII, MnII and UO 2 II amino alcohol complexes

Cr^III, Mn^II and UO₂ ^II amino alcohol complexes were prepared and analyzed. The IR spectra proved that the ligation occurs via oxygen and nitrogen atoms. The nujol mull electronic absorption spectra joined with the room temperature magnetic moment values proved that the complexes are of O_h geometry. The thermal behaviour of the complexes was studied by DTA and TG techniques. The mechanism of the decomposition was suggested. The thermodynamic parameters of the decomposition were evaluated and discussed. The entropy of activation changes, S*, showed that the transition states are more ordered than the reacting complexes. The D.C. electrical conductivity measurements of Cr- and Mn-amino alcohol complexes are of semiconductor behaviour. Empirical equations were deduced for the conduction of the investigated complexes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal behaviour of complexes of antipyrine derivatives II

Parent and mixed ligand complexes of cobalt(II) and copper(II) ions with N,N-bis-(4-antipyrylmethyl)piperazine or N,N-tetra(4-antipyryl-methyl)-1,2-diaminoethane or/and imidazole as ligand and ClO ₄ ^– or SCN^– as counterion were synthesised and their thermal behaviour was investigated.This work was performed in the framework of cooperation between the Hungarian Academy of Sciences and Romanian Academy and was supported financially, in part, by the Hungarian Scientific Research Foundation (OTKA T 029554).     

Development of SnO2/Sb-based ceramic pigments

The color efficiency of ceramic glaze blue pigments obtained by the Pechini method was presented in this work. The fired pigments and enameled samples were characterized by thermogravimetry (TG) and differential thermal analysis (DTA), XRD, UV-VIS-NIR spectroscopy and CIE-L*a*b* color-measurements. The pigments obtained by the Pechini method present a better solubility in the molten glazes than the pigments obtained by the mechanical mixture of the precursor oxides. This revised version was published online in August 2006 with corrections to the Cover Date.     

Transient oscillations in Soret-driven convection in a colloidal suspension

We present measurements of the transient stage of Soret-driven convective instability. The sample is a diluted colloidal suspension of silica spheres in water with an unusually large negative Soret coefficient S_T. A large temperature gradient (heating from above) is rapidly applied over the sample, while a shadowgraph imaging technique provides images of the convective flow. From the processing of the variance of the intensity of the images we are able to recover the time evolution of the overall intensity of the convective flow. A typical evolution of such signal exhibits, after a latency time, a peak followed by some damped oscillations leading to a steady-state value. Both the onset time _p (the temporal position of the first peak), and the oscillation period _osc show a power law dependence as a function of the solutal Rayleigh number R_s. The exponents found are compared with predictions from existing models.     

Correlation between the Soret coefficient and the static structure factor in a polymer blend

Mutual mass diffusion and thermal diffusion has been investigated in poly(dimethylsiloxane)/ poly(ethylmethylsiloxane) (PDMS/PEMS) polymer blends of equal weight fractions. Molar masses ranged from below 1 to over 20 kg/mol. Both the mutual mass (D) and the thermal diffusion (D_T) coefficient contain a thermally activated factor with an activation temperature of 1415 K. The molar mass dependence of D_T is due to an end-group effect of the local friction coefficient. The thermal diffusion coefficient in the limit of long chains and infinite temperature is D_T^0, = - 1.69×10^-7cm²(sK)^-1. The Soret coefficient S_T of blends far enough away from a critical point is proportional to the static structure factor S(q = 0).     

Preparation of CdO nanoparticles by mechanochemical reaction

CdO nanoparticles of 43 nm in crystal size were successfully synthesized by the mechanochemical reaction (CdCl₂ + Na₂CO₃) with NaCl as a diluent and subsequent thermal treatment at 700°C for 2 h. The samples were characterized by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Effect of calcination temperature on the crystal size of CdO nanoparticles was primarily investigated. The apparent activation energy of CdO nanoparticle formation during thermal treatment was calculated to be 12.2 kJ/mol.     

Atomic Force Microscopy Analysis of Statistical Roughness of GaAs Surfaces Originated by Thermal Oxidation

We have determined the important statistical quantities of the rough boundary between a GaAs single crystal and its oxide film formed by thermal oxidation. Thermal oxidation of the GaAs surfaces was performed at the temperature of 500°C. Using mathematical procedures developed for treating AFM data consisting of a family of the values of the heights of the irregularities of this roughness the values of the important statistical quantities of roughness were determined for 11 samples of the GaAs surfaces created by dissolution of the thermal oxide films originated during thermal oxidation of the smooth GaAs samples (the times of oxidation of these 11 samples were within interval of 20min–8 hours). From the AFM analysis of the roughness of GaAs surfaces it was found that the roughnening of these surfaces was the most pronounced for shorter oxidation times, i.e. for times smaller than about 2 hours.     

Chromatographic impulse response technique with curve fitting to measure binary diffusion coefficients and retention factors using polymer-coated capillary columns

The theoretical basis of a Gaussian-like approximate solution was applied to a chromatographic impulse response technique with curve fitting for measuring binary diffusion coefficients and retention factors using a polymer-coated capillary column. The formulae were derived for evaluating both the accuracy of the approximate solution and the sensitivity of the parameters. The validity of the solution also was confirmed experimentally for pulse injection of phenol in acetone into supercritical carbon dioxide flowing at 313.15 K and 11.6-28.6 MPa. Potential sources for experimental errors of the method are discussed.     

Permanence for a delayed discrete ratio-dependent predator-prey system with Holling type functional response

Sufficient conditions are established for the permanence in a delayed discrete predator-prey model with Holling type III functional response:

     

Acceleration waves analyzed by a new continuum model of solids incorporating microscopic thermal vibrations

Acceleration waves propagating in isotropic solids at finite temperatures are studied by applying the method of singular surfaces to a new continuum model derived statistical-mechanically from a three-dimensional lattice model. The continuum model explicitly takes into account the microscopic thermal vibrations of the constituent atoms as one of the field variables. The propagation speeds and the ratios of mechanical and thermal amplitudes for both longitudinal and transverse waves are consistently determined. The differential equations that govern the time variation of the amplitudes of the waves are also derived. The analytical results, which are valid over a wide temperature range that includes the melting point, are evaluated numerically for several materials, and their physical implications are discussed. One of the findings to be emphasized is that of the singularities of the characteristic quantities at the melting point.Received: 13 March 2003, Accepted: 20 June 2003PACS: 62.30. + d, 65.40.-bM. Sugiyama: Correspondence to Dedicated to Prof. Ingo Müller on the occasion of his 65th birthday.