Isothermal Coefficient Research Articles

Optimal Low Temperature Charging of Lithium-ion Batteries

A lithium-plating side reaction at the lithiated graphite (LiC6) anode leads to poor safety of the lithium-ion battery. Faster charging at normal temperature may lead to a plating side reaction during the end of charging at the anode-separator interface. At lower temperature, the lithium-plating side reaction may become thermodynamically favorable during almost the entire charging period, even at low rates. This paper uses an electrochemical engineering model and dynamic optimization framework to derive charging profiles to minimize lithium plating at low temperatures. Transport parameters for lithium-ion battery are very sensitive at low temperatures. This paper shows the derivation of the optimal charging profile considering strict lower bounds on the plating reaction depending on various thermal insulation conditions (adiabatic, isothermal, and normal heat transfer coefficient) surrounding the battery.

An investigation on Unprotected Loss of Flow Accident in Th–Pu metal fuelled 500 MWe fast reactor

This study focuses on computing static reactivity coefficients and analyzing Unprotected Loss of Flow Accident in a Th–Pu fuelled metal reactor. An attempt is also done to compare the static and dynamic performance of the fresh core with characteristics of U–Pu–6Zr fuelled 500MWe metal reactor. Isothermal temperature coefficient and power coefficients are evaluated in the steady state and found to be negative. The excess reactivity and control rod worth requirements of Th–Pu metal core are assumed similar to that of U–Pu–6Zr metal core. In the Unprotected Loss of Flow Accident (ULOFA) analysis, with flow coast down initiated by station black out, it is found that power to flow ratio is increasing initially up to 53s and then starts to reduce continuously. Power to flow ratio is found to be less than 2 at all times thus ensuring the absence of coolant boiling in the entire core. Sodium voiding starts around 886s in the upper axial blanket and provide negative reactivity. Also it will not propagate to the core center ensuring the probability for core disruptive accident a remote one. Net reactivity feedback is negative and the major contribution is from core radial expansion. Within 12min, the power drops to 32MWt, making it possible for Safety Grade Decay Heat Removal (SGDHR) system to start heat removal from core ensuring safe shutdown of reactor. Sensitivity analysis by considering an uncertainty margin of ±10% in thermo physical properties of fuel composition shows that feedback reactivity of the Th–Pu system is insensitive and the conclusion on the safe shutdown remains unaltered. From this study it is found that inherent safety of Th–Pu metal fuel core is better than that of reactor core fuelled with U–Pu–6Zr metal type under ULOFA condition.

Benchmark Evaluation of Start-Up and Zero-Power Measurements at the High-Temperature Engineering Test Reactor

Benchmark models were developed to evaluate six cold-critical and two warm-critical, zero-power measurements of the high-temperature engineering test reactor (HTTR). Additional measurements of the subcritical configuration of the fully loaded core, core excess reactivity, shutdown margins, six isothermal temperature coefficients, and axial reaction-rate distributions were also evaluated as acceptable benchmark experiments. Insufficient information is publicly available to develop finely detailed models of the HTTR as much of the design information is still proprietary. The uncertainties in the benchmark models are judged to be of sufficient magnitude to encompass any biases and bias uncertainties incurred through the simplification process used to develop the benchmark models. However, use of the benchmark critical configurations of the HTTR for nuclear data adjustment is not recommended as the impact of these biases has not been addressed with rigorous detail. The impact of any simplification biases, if any, is not expected to significantly impact evaluation of the other reactor physics measurement calculations. Dominant uncertainties in the experimental keff for all core configurations come from uncertainties in the impurity content of the various graphite blocks that compose the HTTR. Monte Carlo calculations of keff are between ∽0.9% and ∽2.7% greater than the benchmark values. Reevaluation of the HTTR models as additional information becomes available could improve the quality of this benchmark and possibly reduce the computational biases. High-quality characterization of graphite impurities would significantly improve the quality of the HTTR benchmark assessment. Simulations of the other reactor physics measurements are in good agreement with the benchmark experiment values. The complete benchmark evaluation details are available in the 2014 edition of the International Handbook of Evaluated Reactor Physics Benchmark Experiments.

A unifying model for fluid flow and elastic solid deformation: A novel approach for fluid–structure interaction

Fluid–structure coupling is addressed through a unified equation for compressible Newtonian fluid flow and elastic solid deformation. This is done by introducing thermodynamics within Cauchy׳s equation through the isothermal compressibility coefficient that is experimentally measurable for both fluids and solids. The vectorial resolution of the governing equation, where every component of velocity vectors and displacement variation vectors is calculated simultaneously in the overall multi-phase system, is characteristic of a monolithic resolution involving no iterative coupling. For system equation closure, mass density and pressure are both re-actualized from velocity vector divergence, when the shear stress tensor within the solid phase is re-actualized from the displacement variation vectors. This novel approach is first validated on a two-phase system, involving a plane fluid–solid interface, through the two following test cases: (i) steady-state compression and (ii) longitudinal and transverse elastic wave propagations. Then the 3D study of compressive fluid injection towards an elastic solid is analyzed from initial time to steady-state evolution.

Thermal, structural analysis, Mössbauer and impedance study of copper nickel ferrite nanoparticles synthesized via Tween 80-assisted hydrothermal process

Nanocrystalline nickel ferrite and copper nickel ferrite materials were synthesized through surfactant Tween 80-assisted hydrothermal reaction at low temperature using metallic copper, nickel, and iron as raw materials. Thermogravimetric (TG) and differential thermal analysis (DTA) were used to determine the decomposition of the precursors. Phase composition, microstructural characterization, and distribution of cations in tetrahedral and octahedral sites of crystal structure properties of synthesized ferrite materials were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) absorption, and Mossbauer spectroscopy. The impedance spectroscopic studies of copper nickel ferrite sintered ceramics were carried out at room temperature. TG and DTA of precursors revealed that the crystallization temperature for spinel ferrites phases formation was around 650 °C which were being synthesized through Tween 80-assisted hydrothermal process in highly basic reaction at 180–200 °C for 11–13 h in PTFE-lined stainless steel autoclave. XRD analysis and Rietveld refinement study confirm the formation of single-phase cubic spinel nickel ferrite (NiFe2O4) and copper nickel ferrite (Ni0.5Cu0.5Fe2O4) with cell parameters 8.3385, 8.3595 A and space group Fd3 m, respectively. The synthesized ferrite products showed extensive XRD line broadening, and the average crystallite sizes of NiFe2O4 and Cu0.5Ni0.5Fe2O4 ferrites were in range of 21–29 nm and 18–23 nm, respectively. Mossbauer parameters are characteristic of substituted Cu-Ni-Fe2O4 ferrite material. Isothermal shrinkage characteristic and coefficient of thermal expansion were determined by dilatometry. The ferrite specimens showed excellent densification at 1,050 °C temperature, and uniformly fine grain-sintered ceramics with submicron grain size (10–18 μm) were obtained after sintering at 850 and 1,050 °C. Sintering at 1,050 °C, results in the formation of depletion layer at grain boundaries which act as trapping centers for the carriers and an increase in the impedance values are conferred.

High temperature stability of onion-like carbon vs highly oriented pyrolytic graphite.

The thermodynamic stability of onion-like carbon (OLC) nanostructures with respect to highly oriented pyrolytic graphite (HOPG) was determined in the interval 765–1030 K by the electromotive force (emf) measurements of solid electrolyte galvanic cell: (Low) Pt|Cr3C2,CrF2,OLC|CaF2s.c.|Cr3C2,CrF2,HOPG|Pt (High). The free energy change of transformation HOPG = OLC was found positive below 920.6 K crossing the zero value at this temperature. Its trend with temperature was well described by a 3rd degree polynomial. The unexpected too high values of jointly to the HR-TEM, STEM and EELS evidences that showed OLC completely embedded in rigid cages made of a Cr3C2/CrF2 matrix, suggested that carbon in the electrodes experienced different internal pressures. This was confirmed by the evaluation under constant volume of by the ratio for OLC (0.5 MPa K−1) and HOPG (8 Pa K−1) where and are the isobaric thermal expansion and isothermal compressibility coefficients, respectively. The temperature dependency of the pressure was derived and utilized to calculate the enthalpy and entropy changes as function of temperature and pressure. The highest value of the internal pressure experienced by OLC was calculated to be about 7 GPa at the highest temperature. At 920.6 K, and values are 95.8 kJ mol−1 and 104.1 JK−1 mol−1, respectively. The surface contributions to the energetic of the system were evaluated and they were found negligible compared with the bulk terms. As a consequence of the high internal pressure, the values of the enthalpy and entropy changes were mainly attributed to the formation of carbon defects in OLC considered as multishell fullerenes. The change of the carbon defect fraction is reported as a function of temperature.

Viscoelastic, Surface, and Volumetric Properties of Ionic Liquids [BMIM][OcSO4], [BMIM][PF6], and [EMIM][MeSO3

Thermophysical properties viz. surface tension, viscosity, density, and ultrasonic velocity of three ionic liquids 1-butyl-3-methyl imadazolium octyl sulfate [BMIM][OcSO4], 1-butyl-3-methyl imadazolium hexafluorophosphate [BMIM][PF6], and 1-ethyl-3-methyl imadazolium methanesulfonate [EMIM][MeSO3] have been measured in a wide temperature range. Experimental data so obtained have been used to calculate isentropic compressibility, isothermal expansion coefficient, surface entropy, surface enthalpy, and critical temperature (temperature where the distinction between liquid and gas phase vanishes and the surface tension tends to zero). Structure–property correlation for different ILs is also discussed.

EFFECT OF ENZYMES ON GLUCOSE ISOMERIZATION NONLINEAR REACTION CHROMATOGRAPHY

Adsorption isotherms play an important role in preparation chromatography, which is the basis of procedure design and optimization. For a binary competitive system, the adsorption isotherm constant G is generally derived from linear chromatography. However, the adsorption isotherm coefficient b is difficult to measure, especially for separations accompanied by a reaction. In previous studies, the effect of enzymes has often been simplified or ignored due to its complexity. In the present paper, b was calculated using nonlinear reaction chromatography theory and the reaction rate constant k r . The obtained results were compared using several experimental methods, such as the elution method and the dynamic Michaelis–Menten method, the results of which were generally in agreement. The feasibility of the method was discussed. The method presented herein might provide a simple way to determine the adsorption isotherm of reaction chromatography when enzymes are involved.

Measurement of isothermal temperature reactivity coefficient at research reactor with IRT-4M fuel

Transients analyses is of high importance for reactor safety studies. The temperature reactivity coefficients belong to key input parameters for such studies. However, the amount of experimental data for validation of such parameters for the conditions of research reactors operated with LEU fuel is limited. To improve the situation, a tailor-made experimental instrumentation has been recently developed at zero power research reactor VR-1 that allows for detailed measurement of temperature reactivity effects in lattices with IRT-4M fuel. The instrumentation enables by external water heater to change the temperature of fuel and surrounding water moderator in 2×2 positions of reactor grid in the range from 20 to 40°C. Using the instrumentation the isothermal temperature reactivity effect was measured for a group of four eight-tube fuel assemblies in the above mentioned temperature range. Results were compared to MCNP calculations with the precise model of the VR-1 reactor. The MCNP code was further used for deeper analysis of experimental data.

Ehrenfest scheme forP−Vcriticality of higher dimensional charged black holes, rotating black holes, and Gauss-Bonnet AdS black holes

To provide an analytic verification of the nature of phase transition at the critical point of $P-V$ criticality, the original expressions of Ehrenfest equations have been introduced directly. By treating the cosmological constant and its conjugate quantity as thermodynamic pressure and volume respectively, we carry out analytical check of classical Ehrenfest equations. To show that our approach is universal, we investigate not only higher-dimensional charged AdS black holes, but also rotating AdS black holes. Not only are the examples of Einstein gravity shown, but also the example of modified gravity is presented for Gauss-Bonnet AdS black holes. The specific heat at constant pressure $C_P$, the volume expansion coefficient $\alpha$ and the isothermal compressibility coefficient $\kappa_T$ are found to diverge exactly at the critical point. It has been verified that both Ehrenfest equations hold at the critical point of $P-V$ criticality in the extended phase spaces of AdS black holes. So the nature of the critical point of $P-V$ criticality of AdS black holes has been demonstrated analytically to be a second-order phase transition. These results are consistent with the nature of liquid-gas phase transition at the critical point. In this sense, our research would deepen the understanding of the relations of AdS black holes and liquid-gas systems. Moreover, our successful approaches to introduce the original expressions of Erhenfest equations directly into black hole phase transition research demonstrate again that black hole thermodynamics is closely related to classical thermodynamics, which allows us to borrow techniques from classical thermodynamics to investigate the thermodynamics of black holes.

Ehrenfest scheme for the extended phase space of f(R) black holes

In this letter, the original expressions of Erhenfest equations have been introduced directly into the black-hole research by treating the cosmological constant and its conjugate quantity as thermodynamic pressure and volume, respectively. The nature of phase transition at the critical point of criticality of AdS black holes in f(R) gravity has been investigated as an example. The specific heat at constant pressure CP, the volume expansion coefficient α and the isothermal compressibility coefficient are found to diverge at the critical point. An analytical check of Ehrenfest equations has been carried out and it has been proved that both Ehrenfest equations are satisfied. So AdS black holes in f(R) gravity undergo a second-order phase transition at the critical point. This result is consistent with the nature of liquid-gas phase transition at the critical point and would help deepen the understanding of the relations between AdS black holes and liquid-gas system. Moreover, the influences of f(R) correction on the thermodynamics and the phase transition of AdS black holes in f(R) gravity have also been shown in this letter.

Prediction of volumetric properties of polymer melts using new perturbed hard-chain equation of state

A perturbed hard-sphere equation of state (PHS EOS) has been previously employed for modeling the volumetric properties of some molten metals and ionic liquids (S.M. Hosseini, M.M. Papari, F. Fadaei-Nobandegani, J. Moghadasi, J. Non-Cryst. Solids 358 (2012) 1753–1758). In this work, the chained version of our previous PHS EOS has been developed for predicting the volumetric properties of 19 polymer melts including homopolymers and copolymers. The performance of the proposed EOS has been checked by comparing the results with 2273 literature data points for the specific volumes over wide temperature and pressure range, the overall average absolute relative deviation (AARD) was found to be 0.33%. Uncertainty of specific volume calculations was of the order of ±2.0%. Isothermal compressibility coefficient (κT), of studied polymer melts has also been estimated and compared with those obtained by the use of Tait equation; from 1349 data points examined, the AARD was found to be 3.91%.

Thermal, structural, and impedance analysis of nanocrystalline magnesium chromite spinel synthesized via hydrothermal process

Nanocrystalline magnesium chromite spinel was synthesized through hydrothermal reaction of metal nitrate solutions in stoichiometric amount at different pH, temperature and time intervals. The synthesized products were characterized for crystallinity, phase identification, and surface morphology by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns showed that as-synthesized product remained amorphous up to 250 °C. However, well-crystallized magnesium chromite spinel structure is formed after calcination at 850 °C. Rietveld refinement study confirms the formation of single-phase cubic structure MgCr2O4 with lattice parameter a = 8.3347 A, and Fd3m space group. The as-processed MgCr2O4 products showed extensive XRD line broadening, and the mean crystallite size of such crystals was found to be mainly in size range of 85–124 nm. Surface SEM images of calcined specimens revealed that the matrix is uniform, and no separation of secondary phase was detected. Thermal stability was examined by thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry. TG/DTA reveals that MgCr2O4 is thermally stable above 700 °C. Fourier transform infrared (FTIR) spectra studies shows two strong bands, one around 600 cm−1 which is attributed to the intrinsic vibrations of tetrahedral and other at 400 cm−1 is due to octahedral one. FTIR confirms the formation of metal oxides. The bandgap energy was estimated by absorption spectroscopy in ultraviolet–visible range and was found to be 0.693 eV for MgCr2O4 specimen sintered at 1,000 °C. Isothermal shrinkage characteristic and coefficient of thermal expansion were determined by dilatometry. The powder specimens showed excellent densification at 1,250 °C temperature and uniformly fine grain sintered ceramics (>90 % relative density) with submicron grain size (2–5 μm) were obtained after sintering at 1,000–1,250 °C. Impedance studies were carried out at room temperature and equivalent circuit model (R1Q1) (R2Q2) (R3Q3) is used to explain different relaxation processes. We report largest impedance values i.e., 6.74 × 108 Ω, reduced dielectric constant (≈1.0), and low tangent loss (0.8) for MgCr2O4 sintered at 1,250 °C.

Efficient adsorption of congo red dye from aqueous solution using green synthesized coinage nanoparticles coated activated carbon beads

In this paper, the removal of congo red (CR) dye by adsorption on coinage nanoparticles [silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs)] coated activated carbon (AC) has been discussed. The effect of various process parameters has been investigated by following the adsorption technique. Equilibrium adsorption data of CR were carried out at room temperature. The equilibrium time is independent of the initial CR concentration and the percentage removal of CR increased with increase in contact time. The adsorption data were analyzed by using adsorption isotherm studies. The characteristic parameters for isotherm and related correlation coefficients were determined from graphs of their linear equations. Kinetic studies showed that the adsorption of CR followed pseudo-first-order kinetics. AgNPs- and AuNPs-coated AC is found to be suitable adsorbent for the adsorption of CR. CR was effectively removed 88.0 ± 0.8 % from aqueous solution using AuNPs beads as the adsorption process. Desorption studies were made to elucidate recovery of the adsorbate and adsorbent for the economic competitiveness of the removal system. The PVP-supported AgNPs and AuNPs-coated AC were successfully recycled for ten successive adsorption–desorption cycles indicating its high reusability.

USE OF RESPONSE SURFACE METHODOLOGY TO STUDY THE COMBINED EFFECT OF VARIOUS PARAMETERS ON HEXAVALENT CHROMIUM ADSORPTION

Response surface methodology (RSM) was applied as an experimental design for evaluating the effect of various operational parameters, namely contact time, pH, adsorbent dose, and initial adsorbate concentration, on hexavalent chromium (Cr(VI)) ion uptake from aqueous synthetic chromium solutions using granular activated carbon (GAC). Furthermore, the optimized processing conditions for adsorption of chromium on activated carbon were found on the basis of a multiple-response method called desirability. The best chromium removal was achieved at pH of 2.1, adsorbent dose of 5.16 g, and initial chromium concentration of 36.49 mg L−1 for a contact time of 239.86 min. Also, investigations were carried out to determine the appropriate adsorption isotherm, kinetics models, and mass transfer coefficient of chromium (VI) adsorption on GAC in optimum conditions. The obtained results showed that the adsorption of chromium (VI) follows the Langmuir isotherm equation. In addition, the kinetics of the adsorption process follows pseudo-first-order kinetics.

Potentiometric determination of iron in polluted water samples using new modified Fe(III)-screen printed ion selective electrode

This article is focused on the determination of Fe(III) ion as an important factor in water pollution. A potentiometric method based on screen-printed ion-selective electrode was described for the determination of Fe(III) ion in different polluted water samples. It is based on incorporation of the Fe-phosphotungstate ion-associate in a screen-printed electrode (SPE) composition and tricresylphosphate (TCP) as plasticizer. The influences of the paste composition, different conditioning parameters and foreign ions on the electrode performance were investigated. The reversibility and also response time of the electrode have been studied. The electrode showed Nernstian response of 19.20±0.73mVdecade−1 in the concentration range of 1×10−7–2.5×10−2molL−1. The electrode was found to be usable within the pH range of 3–7.5 and exhibited a fast response time (about 7s), low detection limit (1.57×10−7molL−1), long lifetime (>6 months) and good stability. The isothermal temperature coefficient (dE0/dt) of the electrode was calculated. The electrode was successfully applied for the determination of Fe(III) ion in pure solutions and polluted water samples (formation, tab and sea water samples) using potentiometric determination technique. The results obtained applying this potentiometric electrode is comparable with those obtained using inductive coupled plasma technique.

Measurement of the power and temperature reactivity coefficients of the RTP TRIGA reactor

This paper presents the experimental results of the power and temperature coefficients of reactivity of the RTP TRIGA reactor at the Malaysian Nuclear Agency. The power coefficient of reactivity obtained was approximately −0.26¢kW−1 (−1.81×10−5kW–1), and the measured temperature reactivity coefficient of the reactor was −0.82¢°C−1 (−5.77×10−5°C−1) and −1.15¢°C−1 (−8.08×10−5°C−1) in IFE C12 and IFE F16, respectively. The power defect, which is the change in reactivity taking place between zero power and the power of 850kW was ∼2.19$. Because of the negative temperature coefficient, a significant amount of reactivity is needed to compensate for the temperature change and allows the reactor to operate at the higher power levels in steady state. Throughout this experiment, it is the temperature of the fuel that was measured, not the isothermal temperature coefficient (ITC), which comprises both moderator and fuel.

Isobaric, isothermal theoretical investigation and examination of different prediction equations on some physicochemical properties in PEG liquid polymer system

Densities, viscosities and refractive indices of the {poly(ethylene glycol) 200+ethanol} binary liquid system were determined at three temperatures of (298.15, 303.15, and 308.15)K. From the experimental results, the excess molar volume was obtained and correlated with the Prigogine–Flory–Patterson (PFP) and Extended Real Associated Solution (ERAS) models. Several isobaric and isothermal properties consisting of the isobaric thermal expansion coefficient, excess molar isobaric expansion, excess molar isobaric heat capacity, isothermal coefficient of excess molar enthalpy, activation energy of flow, electron polarizibility, and Gibbs energy of activation were calculated from the experimental measurements. Moreover, the viscosity and refractive index values were correlated and predicted with different semi-empirical equations. To assess the validity of these proposed equations, comparisons were made between the experimental and predicted values.

Determination of betamethasone sodium phosphate in pharmaceuticals by potentiometric membrane sensor based on its lidocaine ion pair

Betamethasone sodium phosphate (BMNaP) has been employed as an electroactive material in the design of an ion-selective electrode (ISE). The electrode incorporates PVC membrane with betamethasone sodium phosphate-lidocaine ion pair complex. The influences of membrane composition, temperature, pH of the test solution, and the interfering ions on the electrode performance were investigated. The sensor exhibits a Nernstian response for betamethasone sodium phosphate ions over a relatively wide concentration range (1.0 × 10−1 to 1.0 × 10−5 M) with a slope of 28.4 ± 0.9 mV per decade at 25°C. It can be used in the pH range 4.0–10.0. The isothermal temperature coefficient of this electrode amounted to −0.0008 V/°C. The membrane sensor was successfully applied to the determination of betamethasone sodium phosphate in pharmaceutical products.

Thermodynamic and acoustic properties of binary mixtures of 1-butanol with 1,2-butanediol. The comparison with the results for 1,3-, and 1,4-butanediol

Densities and isobaric heat capacities have been measured for (1-butanol+1,2-butanediol) over the temperature range from (293.15 to 308.15)K and (282.15 to 320.15)K, respectively. The speed of sound at the temperature 298.15K has been measured as well. Using these results, the molar volumes, isentropic and isothermal compressibility coefficients, molar isentropic and isothermal compressibilities, molar isobaric and isochoric heat capacities as well as internal pressures were calculated. Also the corresponding excess and deviation values were calculated and expressed by Redlich–Kister polynomials. The results are discussed in terms of variations of the structure of the system caused by the participation of the two alcohols (with the same carbon chain but different hydroxyl groups) in the dynamic intermolecular association process through hydrogen bonding at various temperatures. Present findings are also compared with the previous results for 1,3-, and 1,4-butanediol.