Search Results

You are looking at 1 - 10 of 143 items for :

  • "Thermodynamic data" x
Clear All
Journal of Thermal Analysis and Calorimetry
Authors: V. I. Pet’kov, E. A. Asabina, A. V. Markin, N. N. Smirnova and D. B. Kitaev

Summary The thermodynamic data for NZP compounds MZr2(PO4)3 (M=Na, K, Rb, Cs, Zr0.25) and Na5D(PO4)3 (D=Ti, Zr) are reported. The heat capacities of the phosphates were measured between T=7 and T=640 K. The standard enthalpies entropies, and Gibbs functions of formation at T=298.15 K were derived. The obtained thermodynamic characteristics of phosphates of the NZP type structure and literature data are summarized. Thermodynamic functions of reactions of solid-state synthesis were calculated and the usability of ceramic technology for obtaining NZP compounds was proved.

Restricted access

The temperature-dependence of the specific heat near to the glass temperature was investigated for several Te- and As-based chalcogenide glasses, the latent heats of melting and crystallization of the former alloys also being measured. No thermal change could be detected in the transformation of the As-based alloys from the solid to the liquid state.

Restricted access

Abstract  

Decarbonation curve for the synthetic dolomite analogues; (Cd-dolomites) were determined for CdMg(CO3)2, CdMn(CO3)2 and CdZn(CO3)2 under CO2 pressure of up to 2.5 kbar. All the three double carbonates were completely disordered at the decomposition temperatures and hence the thermodynamic data (Standard enthalpy; ΔH f o, Standard free energy; ΔG f o) retrieved from the univariant decarbonation curve corresponds to the disordered phases. They are: article image The mixing enthalpies and free energies for the formation of the disordered 1∶1 solid solution phases are: article image The thermodynamic data (ΔH f o, ΔG f o and ΔH r o, ΔG r o) showed a positive correlation with the decomposition temperatures. The mixing energies of the disordered double carbonates also show a direct correlation with the cationic size differences.

Restricted access

Abstract  

Data on synthesis, thermal behavior and thermodynamic properties for the NZP phosphates NaMe2(PO4)3 and Na5Me(PO4)3 (Me=Ti, Zr, Hf) are reported. The compounds were synthesized by sol-gel method and solid-state reactions and characterized by X-ray powder diffraction, IR spectroscopy, electron microprobe and chemical analysis. Their thermal behavior was studied by the DTA measurements. The heat capacities of the phosphates were measured between temperatures 7 and 650 K. The fractal dimensions for the phosphates were calculated. The obtained thermodynamic characteristics of these phosphates and also literature data for the compounds of NZP type structure are summarized.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Luiza N. H. Arakaki, V. H. A. Pinto, V. L. S. Augusto Filha, M. G. Fonseca, J. G. P. Espínola, Tomaz Arakaki and Claudio Airoldi

this cation. This geometry, proceeding from the pronounced distortion caused due to the Jahn–Teller effect, is more significant for cations having a d 9 configuration, such as [Cu (II)] [ 20 ]. In the present case, the thermodynamic data

Restricted access

Abstract  

Bentonite was investigated to remove Ni(II) from aqueous solutions because of its strong sorption ability. Herein, bentonite was modified with sodium carboxymethylcellulose (CMC) and used as an adsorbent to remove Ni(II) from aqueous solutions. The results indicated that CMC-bentonite had higher sorption capacity than bare bentonite in the sorption of Ni(II) from aqueous solutions. Sorption of Ni(II) on CMC-bentonite was mainly dominated by ion exchange or outer-sphere surface complexation at low pH values, but by inner-sphere surface complexation or surface precipitation at high pH values. The thermodynamic data calculated from temperature dependent sorption isotherms indicated that the sorption of Ni(II) to CMC-bentonite hybrids was an spontaneous process and enhanced with increasing temperature.

Restricted access

Abstract  

This work examines the sequestration of 64Cu(II) by sorption process onto plasma-induced polyaniline (PANI)-grafted multiwalled carbon nanotubes (denoted as MWCNTs/PANI) prepared by an plasma-induced grafting technique. The role of a variety of environmental conditions such as pH, ionic strength, natural organic matter (NOM) in the sorption of 64Cu(II) onto MWCNTs/PANI is studied. The results indicate that the sorption is strongly dependent on pH but independent of ionic strength. A positive effect of NOM on 64Cu(II) sorption is found at pH <7.5, whereas a negative effect is observed at pH >7.5. The sorption isotherms in the absence and presence of NOM can be better described by Freundlich model than Langmuir model. Sorption isotherms of 64Cu(II) at higher initial NOM concentrations are higher than those at lower NOM concentrations. The thermodynamic data calculated from temperature-dependent sorption suggest that the sorption is spontaneous and enhanced at higher temperature. Results of this work suggest that MWCNTs/PANI may be a promising candidate for cost-effective treatments of 64Cu(II)-contaminated wastewaters.

Restricted access

Abstract  

Micelle/water partition coefficients were obtained for procaine hydrochloride using micellar liquid chromatography (MLC) to illustrate the potential application of this technique to compounds of pharmaceutical interest. Experiments were conducted over a temperature range which led to calculation of a Gibbs free energy, enthalpy and entropy of transfer for procaine hydrochloride. Successful application of this technique was confirmed using a second compound over a range of temperatures, namely caffeine. Overall, this work confirms that MLC can be used to determine precise and accurate partition coefficients that possibly more closely mimic biological membranes than traditional in vitro systems, namely octanol/water.

Restricted access

Abstract  

Micelle/water partition coefficients for three dialkyl phthalate esters — dimethyl phthalate ester (DMP), diethyl phthalate ester (DEP) and dipropyl phthalate ester (DPP) were obtained by micellar liquid chromatography (MLC). Experiments were conducted over a temperature range which led to calculation of a Gibbs free energy, enthalpy and entropy of transfer for the phthalate esters. In addition, small angle neutron scattering (SANS) experiments were conducted with no substantial change observed in micelle size before and after phthalate ester incorporation. Overall, a novel method for obtaining thermodynamic information, based on partitioning data, has been developed for dialkyl phthalate esters using micellar liquid chromatography.

Restricted access