Thermodynamic properties of melts of Bi—Eu system

The thermochemical properties of alloys were determined for the first time by calorimetry Bi—Eu system at a temperature of 1200 K in the range of 0 ≤ xBi ≤ 0,2 and 0,77 ≤ xBi ≤ 1,0. It is established that the minimum value of the enthalpy of mixing is equal to –61,7 ± 0,5 kJ / mol at xBi = 0,5. = –184,7 ± 16,7 kJ / mol, = = –206,9 ± 21,8 kJ / mol. The activities of the components were calculated according to the model of an of the ideal associated solution (IAR), using the thermochemical properties of the melts of the Bі—Eu. system. It has been established that the activities of the components show large negative deviations from ideal solutions. To predict the enthalpies of formation of LnBi compounds, the available literature data on these parameters are analyzed and the most reliable ones are presented as a dependence on ∆fH = f(ZLn). It is established that the enthalpies of formation LnBi change smoothly and monotonically with the exception of Bi—Eu and Bi—Yb systems. This is due to the large size factors for the last two systems. To combine all the enthalpy data of Ln—Bi intermetallic formation of Ln—Bi systems depending on the sequence number Ln, we need similar values for the Eu—Bi compound. But at present they are not known, so based on the above, it was assumed that the value of the minimum enthalpy of mixing will be close to the enthalpy of formation of this compound. This hypothesis is confirmed by data on the enthalpies formation of phase YbBi and equiatomic melts of binary of Yb—Bi system. To confirm the thermodynamic data, we compare the known melting temperatures of the formed intermediate phases, known from the diagrams state Bi—Ln system. The obtained dependences correlate with ∆fH = f(ZLn ) і ∆V = f(ZLn). This means that the predictions of thermochemical properties accurately reflect the nature of the considered melts of the Bi—Eu system. Keywords: thermochemical properties, melts, compounds, Bi, Eu.

Assessing cellulose dissolution efficiency in solvent systems based on a robust experimental quantification protocol and enthalpy data

Dissolution of microcrystalline cellulose (MCC) in pure ionic liquids (ILs) and IL/dimethyl sulfoxide (DMSO) mixtures (mole fraction χDMSO = 0.2–0.9) was quantified using a specially constructed mechanical stirring system that allows reproducible agitation speed; temperature control, and minimum solution-air contact. The electrolytes employed were: 1-(n-butyl)-3-methylimidazolium acetate (C4MeIm AcO), 1-(methoxyethyl)-3-methylimidazolium acetate (C3OMeIm AcO), 1,8-diazabicyclo[5.4.0]undec-7-enium acetate (DBU AcO), tetramethylguanidinium acetate (TMG AcO), and tetra(n-butyl)ammonium fluoride hydrate (TBAF·xH2O). The effects on MCC dissolution of IL/DMSO composition, and temperature (50, 70°C) were studied. C4MeIm AcO and C4MeIm AcO/DMSO were more efficient solvents than their C3OMeIm AcO counterparts, due to “deactivation” of the ether oxygen of C3OMeIm AcO. MCC dissolution by C4MeIm AcO/DMSO was compared with DBU AcO/DMSO, TMG AcO/DMSO at χDMSO = 0.6, and TBAF·xH2O/DMSO at χDMSO = 0.95. The relative efficiency was (solutions in DMSO): C4MeIm AcO > C3OMeIm AcO > DBU AcO > TMG AcO > TBAF·xH2O. The efficiency of C4MeIm AcO relative to C3OMeIm AcO is due to higher solution basicity. Isothermal titration calorimetry was used to study cellobiose-solvent interactions. Except for TBAF·xH2O/DMSO, these interactions are exothermic; the relative solvent efficiency increases with increasing dissolution |enthalpy|. Using the mole fraction concentration scale to report cellulose dissolution avoids possible ambiguities.

Spatial variability of enthalpy in rabbit house with and without ridge vent

ABSTRACT The profitability of a rabbit farming system must consider the rabbit’s breed, nutrition, management, sanitation and mainly the thermal environment that the animal will be exposed during the productive period. The aim of this study was to compare the internal thermal environment of two rabbit houses, one with ridge vent and the other without ridge vent. Geostatistical technique was used to evaluate the spatial variability of enthalpy. Data were collected at 48 points in each house during eight days at the end of summer season 2016. Measurements of dry-bulb temperature, relative humidity and wind speed were made for 1 min at three times a day at 7:00 a.m., 12:00 a.m. and 5:00 p.m. In addition, the enthalpy was calculated and a data analysis was performed using geostatistical tools and isocolor maps through interpolation by kriging. Based on results from geostatistics, it was possible to characterize the variability magnitude and structure of this variable inside the rabbits’ houses with and without ridge vent. The heterogeneity of the spatial distribution of enthalpy in several regions of two houses was also observed through generated isocolor maps. The ridge vent assisted in obtaining a more favorable internal environment for rabbit breeding because this house showed more comfortable conditions of enthalpy values, besides lower heterogeneity of the spatial distribution of enthalpy.

Modeling Superionic Behavior of Plutonium Dioxide

The Bredig transition to the superionic phase indicated with the $$\lambda $$-peak in $${C_p}$$ was highly expected for plutonium dioxide ($${\rm{Pu}}{{\rm{O}}_2}$$) as other actinide dioxides. However, least-square fit and local smoothing techniques applied to the experimental enthalpy data of PuO2 in 1980s could not detect a $$\lambda $$-peak in specific heat that might be due to too scattered and insufficient experimental data. Therefore, this issue has not been yet put beyond the doubts. In the current article, a superionic model of $${\rm{Pu}}{{\rm{O}}_2}$$ is developed with partially ionic model of a rigid ion potential. Thermophysical properties were calculated in constant pressure–temperature ensemble using molecular dynamics simulation. The Bredig transition with vicinity of a $$\lambda $$-peak in specific heat was successfully observed for the model system at about 2,100 K. Moreover, the experimental enthalpy change was well reproduced before and after the estimated transition temperature.