Absolute Reaction Rate Research Articles

Viscosity of Cu–Ni Melts

The kinematic viscosity of Cu–Ni melts with nickel contents of 10, 20, 30, 40, 50, 60, 70, 80, and 90 at % is measured. Kinematic viscosity is measured using the damped torsional vibrations of a crucible with a melt in the mode of sample cooling. The measuring results are discussed within the theory of absolute reaction rates. The temperatures at which the viscous flow characteristics (and thus the structural state of the melt) change are determined by analyzing the temperature dependences of kinematic viscosity. The patterns of the liquid–liquid transition in metal alloys of the Cu–Ni system that form a continuous series of solid solutions during crystallization are analyzed.

The reaction of hydrated iodide I(H2O)- with ozone: a new route to IO2- products.

We report on an experimental characterization of the isolated reaction of hydrated iodide I(H2O)- with ozone O3 at room temperature performed using a radio-frequency ion trap combined with a quadrupole mass spectrometer. Contrary to the oxidation reaction of the bare I- ion, the hydrated iodide I(H2O)- primarily reacts to form I- and IO2- with significant absolute reaction rate constants of 2.0 ± 0.3 × 10-10 cm3 molecule-1 s-1 and 2.5 ± 0.3 × 10-10 cm3 molecule-1 s-1 while direct pathways to IO- and IO3- are much weaker. Quantum chemical calculations indicate that in aqueous phase and for atmospherically relevant temperatures, the presence of hydrated iodides are favored over bare I- ions, thus suggesting that the chemistry of the hydrated ions is relevant for understanding and modeling atmospheric processes at the air-water interface.

Excess volume and surface tension of some flavoured binary alcohols at temperatures 298.15, 308.15 and 318.15 K

ABSTRACTFrom the measured work of Ching-Ta and Chein-Hsiun Tu, we have presented the theoretical results of Surface tension and excess volume for three binary systems: namely 2-Propanol+Benzyl alcohol(1), 2-Propanol+2-Phenylethnol(2) and Benzyl alcohol+2-Phenylethanol(3) at temperatures 298.15, 308.15 and 318.15 K and atmospheric pressure over the concentration range 0.05–0.95. Theoretical results were computed from Flory model, Ramaswamy and Anbananthan (RA) model and model devised by Glinski, and studied the mixing properties and interactions of these liquids. Deviations in the surface tension (∆σ) were evaluated and fitted to the Redlich–Kister polynomial equation to derive the binary coefficients and standard errors. Moreover, McAllister multi-body interaction model based on Eyring’s theory of absolute reaction rates has also been applied. For liquid mixtures, the free energy of activation is additive, based on the proportions of the different components of the mixture and interactions of like and unlike molecules. The behaviour of the liquids was studied and correlated with the molecular interactions from these liquid state models. Conclusively, these non-associated and associated models were compared and tested for different systems showing that the McAllister multi-body interaction model yields good results as compared to associated models, while Flory model shows more deviations.

Experimental validation of the neutronic parameters in the Jordan subcritical assembly

Following the construction of the Jordan Subcritical Assembly (JSA) on the campus of the Jordan University of Science and Technology (JUST); a detailed experimental study of the facility was performed to measure different reactor parameters. In this paper, the reactivity and activation reaction rate in JSA were determined experimentally and then validated with the calculated results from Monte Carlo Simulation Radaideh et al. (2018a). The reactivity and criticality analysis were implemented using the source jerk method, while the foil activation technique was used for activation reaction rate and flux characterization. The experimental subcritical reactivity in dollars was −5.498 ± 0.045 while keff for the facility was 0.96476 ± 0.00771. The multiplication factor calculated using Monte Carlo codes of JSA was 0.96553 ± 0.00002. In addition, it was found that the source jerk results had large uncertainties due to the counting error. 115In foils were used to measure the activation reaction rate. The absolute axial and radial reaction rates were measured by averaging the measured counts for three photo-peaks of 116mIn. The experimental results were validated by the calculated reaction rates from MCNP5. The error in the activation reaction rate measurements were dominated by the peak area measurement error. The calculated and measured activation reaction rate results demonstrated very good agreement with a maximum deviation of approximately 11% in both directions. In this work, the neutron source strength was experimentally determined using the foil activation technique. The value estimated for the source was 1.02×106±0.9% (n/s) which is very close to the reported value.

Computational validation of the fission rate distribution experimental benchmark at the JSI TRIGA Mark II research reactor using the Monte Carlo method

A fission rate profile benchmark experiment has been performed at the Jožef Stefan Institute TRIGA Mark II reactor. The measurements were made using absolutely calibrated miniature fission chambers developed and manufactured by the Commissariat à l’Énergie Atomique et aux Énergies Alternatives. The aim of the paper is to describe the experimental set-up, fission rate measurements and to present the detailed Monte Carlo computational model of the TRIGA reactor, which was constructed with as used to compute absolute fission rate distributions in the core at a fixed control rod position, taking into account the detailed description of the experimental configuration. The paper focuses on the extensive evaluation of experimental and calculational uncertainties and biases following the International Reactor Physics Experiment Evaluation Project methodology. A comparison between the measured and computed absolute reaction rates concludes the paper, with the agreement being within one sigma standard uncertainty.

Reaction mechanism, rate constants, and product yields for the oxidation of Cyclopentadienyl and embedded five-member ring radicals with hydroxyl

Potential energy surfaces for the C5H5 + OH and C15H9 + OH reactions have been studied by ab initio calculations at the CCSD(T)-F12/cc-pVTZ-f12//B3LYP/6-311G(d,p) and G3(MP2,CC)//B3LYP/6-311G(d,p) levels of theory, respectively, in order to unravel the mechanism of oxidation of the cyclopentadienyl radical and five-member-ring radicals embedded in a sheet of six-member rings with OH. The VRC-TST approach has been employed to compute high-pressure-limit rate constants for barrierless entrance and exit reaction steps and multichannel/multiwell RRKM-ME calculations have been utilized to produce phenomenological pressure- and temperature-dependent absolute and individual-channel reaction rate constants. The calculations allowed us to quantify relative yields of various products in a broad range of conditions relevant to combustion and to generate rate expressions applicable for kinetic models of oxidation of aromatics. The C5H5 + OH reaction is shown to proceed either by well-skipping pathways without stabilization of C5H6O intermediates leading to the bimolecular products ortho-C5H5O + H, C5H4OH (hydroxycyclopentadienyl) + H, and C4H6 (1,3-butadiene) + CO, or via stabilization of the C5H6O intermediates, which then undergo unimolecular thermal decomposition to ortho-C5H5O + H and C4H6 + CO. The well-skipping and stabilization/dissociation pathways compete depending on the reaction conditions; higher pressures favor the stabilization/dissociation and higher temperature favor the well-skipping channels. For the C15H9 + OH reactions, the results demonstrate that embedding decreases the oxidation rate constants and hinder the decarbonylation process; the removal of CO grows less likely as the number of common edges of the five-member ring with the surrounding six-member rings increases.

Viologen-Catalyzed Conversion of Carbohydrates in a Biofuel Cell for Sustainable Energy

Carbohydrates have great potential as a renewable and abundant source of energy. Biofuel cells represent a possible way of exploiting this source of energy in the form of electricity. However, carbohydrate oxidation in biofuel cells faces challenges related to both the rate of conversion and the extent to which the fuel can be converted. This experimental study examines the use of viologen compounds as a homogeneous catalyst to address these challenges. Specifically, the study seeks to quantify the rate and extent of the homogeneous reaction between viologen and carbohydrates as the basis for development of a practical biofuel cell. The heterogeneous electrochemical reaction of viologen is also examined, and issues related to coupling of the homogeneous and heterogeneous reactions are investigated and optimized. Methods for increasing the rate and extent of reaction are also explored. To do this, experiments were performed at different pH values, temperatures, concentrations of catalyst and carbohydrates, and electrode potentials. The homogeneous reaction rate was measured by tracking O2 uptake over time or by spectroscopic measurement of the viologen concentration. When the homogeneous reaction was coupled with electrochemical regeneration of the catalyst, the current provided a direct measurement of the reaction rate. The overall conversion was estimated by integrating the rate data or by measuring the final concentration for experiments without catalyst regeneration. In addition, 13C NMR was used to examine reaction products in order to provide insight into the oxidation mechanism and conversion efficiency. Tests were performed with several different carbohydrates including dihydroxyacetone, glyceraldehyde, xylose and glucose. Experiments with three-carbon carbohydrates showed rapid reaction of the fuel. The extent of reaction for these fuels was approximately 30%; in other words, 30% of the possible electrons were extracted from the fuel relative to the electron removal required for full oxidation to carbon dioxide. NMR data showed Formate as a principal product, and additional tests indicated that the rate of Formate oxidation is sufficiently slow such that it should be considered a “dead-end” product. Coupling of a Formate fuel cell would enhance the process efficiency. The reaction rates observed for the longer carbon chains were considerably slower, and measurement of the extents of reaction are still in progress. These rates are also slow relative to that of the heterogeneous electrochemical reaction; therefore, the homogeneous rate would likely control the performance of the fuel cell for these fuels. An optimal biofuel cell design must account for both the absolute reaction rates and the relative rates of the homogeneous and heterogeneous (electrochemical) reactions. Finally, slow degradation of catalyst was observed under some conditions (e.g., high pH) and catalyst stability is a factor that should be considered in practical system design.

Estimating the parameters of the microheterogeneous structure of metal melts according to viscometric experimental data in terms of the absolute reaction rate theory

The temperature dependences of the viscosity of microheterogeneous metal melts are analyzed in terms of the Frenkel–Eyring theory. Using viscometric experimental data, the sizes of dispersed particles in metal melts whose components undergo eutectic and monotectic interactions are numerically estimated.

The Relation between Vaporization Enthalpies and Viscosities: Eyring's Theory Applied to Selected Ionic Liquids.

Key properties for the use of ionic liquids as electrolytes in batteries are low viscosities, low vapor pressure and high vaporization enthalpies. Whereas the measurement of transport properties is well established, the determination of vaporization enthalpies of these extremely low volatile compounds is still a challenge. At a first glance both properties seem to describe different thermophysical phenomena. However, eighty years ago Eyring suggested a theory which related viscosities and vaporization enthalpies to each other. The model is based on Eyring's theory of absolute reaction rates. Recent attempts to apply Eyring's theory to ionic liquids failed. The motivation of our study is to show that Eyring's theory works, if the assumptions specific for ionic liquids are fulfilled. For that purpose we measured the viscosities of three well selected protic ionic liquids (PILs) at different temperatures. The temperature dependences of viscosities were approximated by the Vogel-Fulcher-Tamann (VFT) relation and extrapolated to the high-temperature regime up to 600 K. Then the VFT-data could be fitted to the Eyring-model. The values of vaporization enthalpies for the three selected PILs predicted by the Eyring model have been very close to the experimental values measured by well-established techniques. We conclude that the Eyring theory can be successfully applied to the chosen set of PILs, if the assumption that ionic pairs of the viscous flow in the liquid and the ionic pairs in the gas phase are similar is fulfilled. It was also noticed that proper transfer of energies can be only derived if the viscosities and the vaporization energies are known for temperatures close to the liquid-gas transition temperature. The idea to correlate easy measurable viscosities of ionic liquids with their vaporization enthalpies opens a new way for a reliable assessment of these thermodynamic properties for a broad range of ionic liquids.

A Paradigm-Shifting Methodology for Sensitivity Analysis of Critical Multiplying Nuclear Systems

Dispensing with the traditional approach to solving the equations modeling multiplying critical nuclear systems as an eigenvalue system, this work proposes a new and comprehensive mathematical framework (C-Framework) that eliminates the need for solving eigenvalue problems when computing the forward and adjoint neutron flux distributions in critical reactors. Consequently, the C-Framework enables the mathematical and computational analysis of critical and noncritical multiplying systems, with or without external sources, in a unified manner. By eliminating the need for solving eigenvalue problems, the C-Framework also enables the use of more efficient numerical methods (than currently used) for computing the forward and adjoint neutron flux distributions in critical reactors. Furthermore, the C-Framework also enables the application of the Comprehensive Adjoint Sensitivity Analysis Methodology (C-ASAM) as a replacement for the so-called generalized perturbation theory (GPT). The C-ASAM is much simpler to apply than the GPT, while not only yielding all of the results that the GPT can deliver, but also delivering results for all of the many—and not “GPT-allowable”—nonlinear responses of interest in reactor analysis that do not satisfy the very restrictive orthogonality relations required by the GPT’s underlying generalized adjoint equation. By dispensing with the need for solving eigenvalue problems involving the inversion of singular operators, the C-ASAM is vastly more general and more efficient than the GPT. These conclusions are underscored by exact analytical results presented for paradigm illustrative problems, which include problems that are solvable using the GPT (e.g., the system’s multiplication factor, ratios of reaction rates responses), and problems that are not solvable using the GPT (e.g., absolute reaction rates, equilibrium xenon concentration responses); all of these problems are shown to be solvable exactly and most efficiently within the C-ASAM framework.

Synthesis, characterization and adsorption behavior of coconut leaf carbon

Adsorption at the liquid–solid interface has numerous applications in the removal of toxic materials and organic pollutants from water. The present work reports the adsorption of maleic acid onto activated carbon obtained from coconut (Cocos nucifera) leaves. Three types of activated carbons were synthesized by different methods: physical, chemical and microwave activation. In this work, we characterized these methods by XRD, SEM, TGA and FTIR spectroscopic analysis. Activated carbons were subjected to adsorption of maleic acid and the process of adsorption was studied as a function of concentration of acid, contact time and temperature. The polar C–O functional group of the carbon surface attracts H+ ions from the acid solution. This interaction is responsible for the adsorption process. The adsorption data were fitted to Freundlich and Langmuir isotherms. The process of adsorption was found to follow second order kinetics. The effect of temperature on adsorption was also studied and the activation energy, change in enthalpy and entropy were calculated based on the theory of absolute reaction rate expressions.

Anomalous viscosity transition of solid He-4 in nanodomains

Verified theory of absolute reaction rate or transition-state (originates from the quantum chemistry approach) as well as boundary perturbation method were applied to capturing the possible jump of shear viscosity for solid 4He (with small 3He impurities) passing through Vycor’s pores which have in average a diameter around 7 nm. Via tuning of activation energies and activation volumes while fixing of forcing parameters we can obtain quantitatively the same temperatures at which the anomalous solid state transitions for flowing solid He-4 (with small He-3 concentrations) in confined nanodomains have been experimentally reported. Current open issues played by the role of He-3 impurities were also discussed.

Calculation of excess Gibbs energy of activation for viscous flow in (ionic liquid + co-solvent)

Recently, a comment was published (J. Chem. Thermodyn. 106 (2017), pp. 216–217) regarding the calculation of the (molar) excess Gibbs energy of activation for viscous flow (ΔGmE∗) in binary mixtures of (ionic liquids+solvent). In that comment, it was suggested that the functional form we reported was in error. Here, we show that direct substitution of Eyring’s Theory of Absolute Reaction Rates into the excess Gibbs energy expression that the functional form presented in our original work indeed holds true.

Tuning the glass transition of asphalt binder based on viscosity criteria under zero shear rates

With the theory of absolute reaction rate or transition-state approach together with the boundary perturbation method we calculate the possible temperature-dependent viscosity of bitumen or asphalt binder via tuning of activation volume as well as activation energy for the first time under zero shear rates. Before we present our novel approach and numerical results we firstly verify our calculations with both ambient temperature and high temperature viscosity measurements for bitumen conducted previously. Our tuning activation volume of bitumen will be useful to the current needs of intelligent compaction and application of nanotechnology to easily handling or processing asphalt binder.

A Unified Constitutive Model for Creep and Cyclic Viscoplasticity Behavior Simulation of Steels Based on the Absolute Reaction Rate Theory

In this work, the viscoplasticity and creep behavior for modified 9Cr-1Mo and 316 stainless steels were investigated. Based on the absolute reaction rate theory, a unified constitutive model incorporating internal state variables was proposed to characterize the evolution of the back stress. Also, the model was implemented by the ABAQUS system with the semi-implicit stress integration. Compared to the experimental data, the results demonstrated that the proposed approach could effectively simulate the cyclic softening and hardening behavior for such structural steels.

Neutron activation analysis using a modified absolute calibration method

In this work a modified absolute calibration method of neutron activation analysis (NAA) was proposed. Reaction rates per atom of elements of interest were calculated by using MCNPX Monte Carlo code with a well established disk surface neutron source. Time dependency of the absolute reaction rate per atom produced during the irradiation was achieved by utilizing a well calibrated neutron monitoring system. Three activation foils with given compositions, namely, Au(1%)/Al, Mn(88%)/Ni and Cu(100%) and a SS304 sample were measured to test the adequacy and performance of this proposed modified absolute calibration method.

Possible anomalous transitional transport of electronic fluids in hydrogen sulphide under high pressures

With the verified quantum chemistry theory of absolute reaction rate or transition state approach, we illustrate the possible enhancing superconducting transition temperature of hydrogen sulphide under high pressures via tuning of activation volume together with activation energy for the first time under zero shear rates. Before we present our novel approach and numerical results we firstly verify our preliminary results with previous Drozdov et al.’s [Nature2015, 525, 73] measurements. After some necessary verifications, we illustrate our novel numerical results via the enhancing of the onset or superconducting transition temperature for electronic liquids in hydrogen sulphide within the same lower pressure regime (compared to previous Drozdov et al.’s experimental data) by decreasing of activation volume: ∼ 10−25m3 decrement under zero shear rates. The latter might also be linked to the glass transition state for electronic fluids in hydrogen sulphide under high pressures once the shear viscosity is calculated.

Copolymerization Kinetics of Glycidol and Ethylene Oxide, Propylene Oxide, and 1,2-Butylene Oxide: From Hyperbranched to Multiarm Star Topology

Copolymerization of established epoxide monomers with glycidol (G) is a key reaction to prepare branched or hyperbranched polyethers. The kinetics of the multibranching anionic ring-opening copolymerization of glycidol (a cyclic latent AB2 monomer) with ethylene oxide (EO), propylene oxide (PO), and 1,2-butylene oxide (BO; cyclic latent AB monomers), respectively, in dimethyl sulfoxide was studied. Online 1H NMR spectroscopy was employed for in situ monitoring of the individual monomer consumption during the entire course of the statistical copolymerization. Varying the counterion, both the cesium alkoxide and potassium alkoxide initiated copolymerization were studied and compared. From the individual monomer consumption, reactivity ratios were calculated. The reactivity ratio of the alkylene oxides decreases from 0.44 to 0.11 with increasing alkyl chain length on going from EO to BO. Unexpectedly, glycidol was found to exhibit a higher reactivity ratio in each copolymerization, with reactivity ratios ranging from 2.34 (with EO) to 7.94 (copolymerization with BO). Different counterions had an impact on absolute reaction rates, however, relative monomer reactivities remained unchanged. The reactivity ratios determine both the molecular weight distribution and the topology as well as the degree of branching (DB) of the respective branched copolymers, implying a change from a hyperbranched random copolymer (glycidol/EO) to a multiarm star structure with increasing side chain length of the alkylene comonomer.

Room-temperature superconducting in sulfur hydrides

With the theory of absolute reaction rate we demonstrate the possible superconducting transition in sulfur hydrides within the room-temperature regime via tuning of activation volume as well as activation energy for the first time under zero shear rates. Before we present our novel approach and numerical results we firstly verify our calculations with previous measurements [Drozdov et al. Nature 525 (2015) 73]. After successful verifications, we illustrate our novel numerical results via the enhancing transition temperature for electronic liquids in sulfur hydrides to within the room-temperature regime (after decreasing of activation volume: ∼10−27m3 decrement or increasing of activation energy under zero shear rates compared to previous Drozdov et al.'s experimental data).

Physicochemical analysis of slip flow phenomena in liquids under nanoscale confinement

Eyring theory employs the statistical mechanical theory of absolute reaction rates to analyse the transport mechanisms in fluids. A physicochemical methodology combining molecular dynamics (MD) and Eyring theory of reaction rates is proposed for investigating the liquid slip on a solid wall in the nanoscale domain. The method involves the determination of activation energy required for the flow process directly from the MD trajectory information and then calculate the important transport properties of the confined fluid from the activation energy. In order to demonstrate the universal applicability of the proposed methodology in nanofluidics, the slip flow behavior of argon, water and ionic liquid confined in various nanostructures has been investigated. The slip length is found to be size dependent in all the cases. The novelty of this method is that the variations in slip length are explained on the basis of molecular interactions and the subsequent changes in the activation energy.