Water activity and freezing points in aqueous solutions of manganese nitrate: experimental and modeling

The water activities of manganese nitrate solutions were measured using a humidity sensor instrument up to almost the saturation molality at 298.15 K; the thermodynamic properties of the system were described by the Pitzer model and specific interaction theory (SIT). The evaluation of the ion interaction parameters for the Pitzer model and SIT were carried out using experimental freezing points and osmotic coefficients of manganese nitrate aqueous solutions, collected from the open literature, and the water activity data measured in this work. A set of Pitzer and SIT parameters were estimated using a temperature dependency, that enables us to cover wider temperature ranges, and consequently calculate system properties to higher molalities. Both approaches represent very satisfactorily, and with similar accuracy, the experimental data and the calculated manganese nitrate molal activity coefficients are comparable to those already published for analogous systems. Additionally, the Pitzer model was also able to calculate the ice curve and the solubility branch of manganese nitrate hexahydrate up to a salt solution 6.5 mol-kg-1.This work was developed in the scope of the projects POCI-01-0145-FEDER- 006984—Associate Laboratory LSRE-LCM both funded by European Regional Development Fund (ERDF) through COMPETE2020—Programa Operacional Competitividade e Internacionalização (POCI)—and by national funds through FCT—Fundação para a Ciência e a Tecnologia. This work is also a result of project ‘‘AIProcMat@N2020—Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020’’, with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through ERDF.info:eu-repo/semantics/publishedVersio

Etude physico-chimique du systeme ternaire eau-nitrate d'aluminium-nitrate d'ammonium : application au stockage de l'energie frigorifique

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Partition of metallic cations between aqueous solutions and mixed crystals of hydrated cobalt and nickel nitrates: Modelling of the influence of temperature and composition

International audienc

Dielectric properties of copolymers based on cyano monomers and methyl α-acetoxyacrylate

International audienceWith the aim of developing dielectric polymers containing CN groups with strong dipole moment, alternating and statistical copolymers of the cyano monomers vinylidene cyanide (VCN), acrylonitrile and methacrylonitrile with methyl α-acetoxyacrylate (MAA) were synthesized and characterized. The copolymer's composition and microstructure were analysed by NMR spectroscopy, SEC and elemental analysis. The reactivity ratios calculated from the Q-e Alfrey-Price parameters for these copolymers indicated the alternating and statistical structures confirmed by NMR analysis. The copolymers have glass transition temperatures Tg in the range 83-146 °C and are stable up to 230 °C. The thermal stability of the copolymers depends on the nature of the cyano monomers. Their molecular dynamics were investigated by dielectric relaxation spectroscopy. We revealed a weak relaxation β at sub-Tg temperature for poly(VCN-co-MAA) usually originating from molecular motions that are restricted to the scale of a few bond lengths. Strong α-relaxation processes occurred above Tg for these copolymers. This primary relaxation was associated with cooperative movements of the polar groups (CN) at the time of mobility of the principal chains. The activation energy of the α-relaxation process was also calculated. The values of the dielectric increment Δε for these copolymers were determined by Cole-Cole plots and indicated that the copolymers exhibit interesting dielectric properties compared with similar cyano materials. The polarity-permittivity relationship was also established

Solvation phenomena and revision of solid–liquid equilibria in aqueous solutions of two precursors of mixed oxides, the hydrates of cobalt and nickel nitrates

International audienc

Widespread Solid Solutions of Hexahydrated Cobalt and Nickel Nitrates: Solid–Liquid Equilibria at 273.15 and 303.15 K and Characterization of Mixed Crystals of Homogeneous Composition

The isothermal solubility curves of the H₂O–Co­(NO₃)₂–Ni­(NO₃)₂ ternary system were studied at 273.15 and 303.15 K, using a synthetic method based on conductivity measurements. The analysis of the equilibrium phases’ composition was conducted by UV–visible spectroscopy. The solid phases were first characterized by powder X-ray diffraction, which showed the formation of two substitutional solid solutions: Co_(1−σ)Ni_σ(NO₃)₂·6H₂O, which has a monoclinic structure, and Ni_(1−ω)Co_ω(NO₃)₂·6H₂O, which has a triclinic structure. Then the evolution of the lattice parameters of the crystals at 303.15 K, depending on the solid solution composition, was studied by single-crystal X-ray diffraction. The shrinkage of the monoclinic lattice increases with the increase of the nickel ions in the structure. The stability area of this solid solution is very wide as more than 7 cobalt ions in 10 could be replaced by nickel ions. However, the variation of the lattice parameters of the triclinic solid solutions remains limited, although a small shift of the diffraction peaks is observed. This is consistent with a limited composition area of the triclinic solid solution, where less than 1 nickel ion in 10 could be replaced by cobalt ions