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During the 1886 MW 7.3 Charleston, South Carolina, earthquake, three railroads emanating from the city were exposed to severe shaking. Expansion joints in segmented railroad tracks are designed to allow railroad infrastructure to withstand a few parts in 10,000 of thermoelastic strain. We show that, in 1886, transient contractions exceeding this limiting value buckled rails, and transient extensions pulled rails apart. Calculated values for dynamic strain in the meizoseismal region are in reasonable agreement with those anticipated from the relation between strain and moment magnitude proposed by Barbour et al. (2021) and exceed estimated tectonic strain released by the earthquake by an order of magnitude. Almost all of the documented disturbances of railroad lines, including evidence for shortening of the rails, can thus be ascribed to the effects of dynamic strain changes, not static strain. Little or no damage to railroads was reported outside the estimated 10-4 dynamic strain contour. The correspondence between10-3 and 2 × 10-4 contours of dynamic strain and Mercalli intensity 9 and 8, anticipated from the dependence of each quantity on peak ground velocity, suggests it may be possible to use railroad damage to quantitatively estimate shaking intensity. At one location, near Rantowles, -20 km west of Charleston, a photograph of buckled track taken one day after the earthquake has been cited as evidence for shallow dextral slip and has long focused a search for a causal fault in this region. Photogrammetric analysis reveals that the buckle was caused by transient contraction of <10 cm with no dextral offset. Our results further weaken the evidence for faulting in the swamps and forests south of the Ashley River in 1886, hitherto motivated by the photograph and limited macroseismic evidence for high-intensity shaking. [ABSTRACT FROM AUTHOR]

A prerequisite for the development or optimization of heterogeneous catalysts is a comprehensive understanding of the reaction mechanism and kinetics at the level as elementary as possible. In comparison with steady‐state catalytic tests typically used for this purpose, non‐steady‐state (transient) studies provide deeper insights due to higher time resolution. For several decades, temporal analysis of products (TAP) and steady‐state isotopic transient kinetic analysis (SSITKA) have been successfully applied to the analysis of various heterogeneous reactions. In this review, we highlight the contributions made by TAP and SSITKA studies between 2017 and 2023 to the understanding of reaction mechanisms and to the derivation of microkinetics. The versatility of these methods is illustrated by the examples of oxidative coupling of methane, CO/CO2 hydrogenation to hydrocarbons or methanol, metathesis of ethylene with 2‐butenes to propene, acrolein oxidation to acrylic acid, methanol conversion to olefins and non‐oxidative propane dehydrogenation to propene. We also provide our personal views on possible developments in this area. [ABSTRACT FROM AUTHOR]

The finite elements method (FEM) is used to improve the extended dynamic plane source (EDPS) method to obtain more accurate values of the thermal conductivity and diffusivity of the specimen. A method of transformation of the FEM-calculated response into an analytical form, which can be used in fitting the measured temperature response, has been described and verified. Furthermore, a modification of the EDPS method designated as EDPS1 is designed, where only one piece of specimen is used. Since there is no analytical formula for the new method, the analytical formula for EDPS is used. Hence, the initial estimates of the specimen parameters for the EDPS1 method are very rough and the FEM numerical evaluations must be repeated several times until the estimates reach relative errors of around 1%. [ABSTRACT FROM AUTHOR]

In this study, soil hydraulic conductivity (K) and soil sorptivity (S) values estimated by applying various steady- and unsteady-flow methods using cumulative infiltration data of three disturbed soils (sandy loam, loam, clay) obtained from a disc infiltrometer in the laboratory at various negative pressure heads were compared. The steady-flow methods used were those of Ankeny et al. and Reynolds and Elrick as well as Logsdon and Jaynes, while the unsteady-flow methods were those of Haverkamp et al. (two-term (2T) and three-term (3T) infiltration equations) and Zhang. The method of White et al., which is a steady-flow method but also uses unsteady-flow infiltration data, was also examined. The results showed that the three steady-flow methods, as well as the Zhang equation, for values of the van Genuchten coefficient n > 1.35, tend to give similar values of K. The 2T infiltration equation with β = 0.6 provided hydraulic conductivity values greater than those estimated by the steady-state methods but gave negative K values in some cases. The values of the coefficients C1 and C2 of the 2T equation were affected by the infiltration time. The coefficient C1 increased while C2 decreased with increasing time when the cumulative linearization method (CL) was applied, but the change in C1 tended to be smaller than that in C2. The inverse solution of the 3T equation using the Excel Solver application for β = 0.75 and β = 1.6, when positive values of K were obtained, approached better the K values estimated by the steady-flow methods compared with those estimated using β = 0.6. Regarding the estimation of S from the unsteady-flow equations (2T, 3T, Zhang), comparable S values were obtained by all equations. The differences between the S values of the various methods are smaller compared to those of K, and S is less affected than K in terms of time. The problem of negative estimates of K might be attributed to the fact that the soils used in this study are classified as soils situated in the domain of lateral capillarity or are not completely homogeneous or soil compaction is observed at some depth. In the case where the soils are not completely homogeneous, the Sequential Infiltration Analysis (SIA) method with β = 0.75 corresponding to the soil types studied was proved to be effective in estimating K values. [ABSTRACT FROM AUTHOR]

The present review describes the up-to-date state of the evaluation of thermophysical properties (TP) of materials with three different procedures: modeling (also including inverse problems), measurements and analytical methods (e.g., through computing from other properties). Methods to measure specific heat and thermal conductivity are described in detail. Thermal diffusivity and thermal effusivity are a combination of the previously cited properties, but also for these properties, specific measurement and calculation methods are reported. Experiments can be carried out in steady-state, transient, and pulse regimes. For modeling, special focus is given to the inverse methods and parameter estimation procedures, because through them it is possible to evaluate the thermophysical property, assuring the best practices and supplying the measurement uncertainty. It is also cited when the most common data processing algorithms are used, e.g., the Gauss–Newton and Levenberg–Marquardt least squares minimization algorithms, and how it is possible to retrieve values of TP from other data. Optimization criteria for designing the experiments are also mentioned. [ABSTRACT FROM AUTHOR]

In this study, soil hydraulic conductivity (K) and soil sorptivity (S) values estimated by applying various steady- and unsteady-flow methods using cumulative infiltration data of three disturbed soils (sandy loam, loam, clay) obtained from a disc infiltrometer in the laboratory at various negative pressure heads were compared. The steady-flow methods used were those of Ankeny et al. and Reynolds and Elrick as well as Logsdon and Jaynes, while the unsteady-flow methods were those of Haverkamp et al. (two-term (2T) and three-term (3T) infiltration equations) and Zhang. The method of White et al., which is a steady-flow method but also uses unsteady-flow infiltration data, was also examined. The results showed that the three steady-flow methods, as well as the Zhang equation, for values of the van Genuchten coefficient n > 1.35, tend to give similar values of K. The 2T infiltration equation with β = 0.6 provided hydraulic conductivity values greater than those estimated by the steady-state methods but gave negative K values in some cases. The values of the coefficients C1 and C2 of the 2T equation were affected by the infiltration time. The coefficient C1 increased while C2 decreased with increasing time when the cumulative linearization method (CL) was applied, but the change in C1 tended to be smaller than that in C2. The inverse solution of the 3T equation using the Excel Solver application for β = 0.75 and β = 1.6, when positive values of K were obtained, approached better the K values estimated by the steady-flow methods compared with those estimated using β = 0.6. Regarding the estimation of S from the unsteady-flow equations (2T, 3T, Zhang), comparable S values were obtained by all equations. The differences between the S values of the various methods are smaller compared to those of K, and S is less affected than K in terms of time. The problem of negative estimates of K might be attributed to the fact that the soils used in this study are classified as soils situated in the domain of lateral capillarity or are not completely homogeneous or soil compaction is observed at some depth. In the case where the soils are not completely homogeneous, the Sequential Infiltration Analysis (SIA) method with β = 0.75 corresponding to the soil types studied was proved to be effective in estimating K values.

The paper addresses the influence of the heat source capacity and structure on the accuracy of the thermophysical parameters measurements within several transient methods. First, the New Plane Source (NPS) method is improved by taking into account the heat source capacity. The results of measurement are compared with those of Step Wise Transient (SWT) method and the relative differences for glass and polymethylmethacrylate (PMMA) are better than 0.5 %. The second part is devoted to the Transient Plane Source (TPS) method. The results of measurement are compared with those of SWT method. The relative differences for glass are less than 0.5 %, but for PMMA 6 %, which is explained by specimen anisotropy. Finally, the reliability of the analytical model of TPS method is supported by comparing it with the numerical one obtained by Finite Elements Method (FEM), where three models of material composition of the heat source are used. The temperature functions are determined from numerical responses obtained by FEM and analytical solution. The coefficients of variation of all four determinations of the thermal diffusivity and conductivity of glass and PMMA are less than 0.4 %. [ABSTRACT FROM AUTHOR]

The present review describes the up-to-date state of the evaluation of thermophysical properties (TP) of materials with three different procedures: modeling (also including inverse problems), measurements and analytical methods (e.g., through computing from other properties). Methods to measure specific heat and thermal conductivity are described in detail. Thermal diffusivity and thermal effusivity are a combination of the previously cited properties, but also for these properties, specific measurement and calculation methods are reported. Experiments can be carried out in steady-state, transient, and pulse regimes. For modeling, special focus is given to the inverse methods and parameter estimation procedures, because through them it is possible to evaluate the thermophysical property, assuring the best practices and supplying the measurement uncertainty. It is also cited when the most common data processing algorithms are used, e.g., the Gauss–Newton and Levenberg–Marquardt least squares minimization algorithms, and how it is possible to retrieve values of TP from other data. Optimization criteria for designing the experiments are also mentioned.

In order to fulfil the increasing demands of indoor comfort and energy efficiency requirements of buildings, innovative materials with good thermal properties have been developed, such as thermal insulating mortars with incorporation of lightweight aggregates and nanomaterials. In the present work, the thermal conductivity of thermal insulating mortars, with EPS and silica-based aerogel, were evaluated for hardened state (28 days of curing), dry state and different moisture content values. Moreover, several methods were performed: two steady-state and two transient methods. For comparison purposes, all of the obtained thermal conductivity values were converted to 23 °C. It is concluded that the results are highly dependent on the temperature and the moisture content of the samples, and the measuring method. This study also shows that the thermal conductivity presents values with variations up to 21% and 14%, with different methods for the mortar’s formulations with and without silica aerogel. It is also concluded that the thermal conductivity evaluation methods have differences regarding the sample’s size, testing time, operation and apparatus’ accuracy and reproducibility. This must be considered, particularly when developing innovative materials, where the material availability or the measurement range of the method can limit the thermal conductivity measurement. [ABSTRACT FROM AUTHOR]

Thermal properties of cement composite with Mixed Fly Ash (MFA) from different parts of Municipal Solid Waste Incineration (MSWI) process as a partial replacement of Portland cement are researched in the paper. MFA is applied in the amount of 10 %, 20 % and 30 % of the mass of cement, while sand and water quantities are kept constant. For the sake of comparison, a reference mixture with Portland cement as the only binder is studied as well. For the characterization of studied materials, their basic physical properties as bulk density, matrix density and total open porosity are measured using gravimetric method combined with helium pycnometry. Among the thermal properties, thermal conductivity, thermal diffusivity and specific heat capacity are accessed by two transient methods having different experimental arrangement and time of measurement. The measured data obtained by the particular methods are compared and the applicability of the methods for the measurement of thermal properties of solid building materials is discussed. [ABSTRACT FROM AUTHOR]

BACKGROUND Environmental regulations are moving to tighter control of NOx emissions produced at both stationary and mobile sources. Selective catalytic reduction ( SCR) of NOx with NH3 is an efficient treatment technique capable of operating at high gas flow rates (e.g. using monolithic catalysts) and a wide range of NO concentrations. The aim of this work is to provide guidelines for designing this kind of reactor taking into account both intrinsic kinetics and mass transfer. RESULTS Experiments have been done in lab-scale (0.5 g) and bench-scale (430 g) reactors operating under different conditions: temperature (150-320 °C), space velocity ( WHSV 5360-16100 mol h−1 kgcat−1), oxygen concentration (0-21%) and NH3/ NO ratio (0.2-1.2). Temperature has a great influence on the reaction rate, and at least 300 °C is required at a WHSV of 16100 mol h−1 kgcat−1. Oxygen is required in the feed because it participates as reactant in SCR. CONCLUSIONS Data obtained from the lab-scale reactor in the absence of mass transfer limitations have been used to fit an intrinsic kinetic model of the SCR reaction. A more complex model has been used for the bench-scale reactor accounting for reaction kinetics and mass transfer (internal effectiveness factor was determined) in the monolithic catalyst. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Different experimental techniques were developed and proposed for determining the thermal conductivities of metals in the eighteenth and nineteenth centuries. Each one reflects the ingenious application of a number of physical principles, some of which only emerged in the panorama of the physical sciences of the moment. The production in recent decades of many revolutionary materials with structures that vary on the length scale of several nanometers, with applications in electronic and optoelectronic devices, have driven a natural evolution in the experimental techniques from steady-state to transient methods, involving modern theoretical models, advanced instrumentation, and ingenious practical developments. This article presents a historical-technical account of the whole evolution, highlighting the main advantages and disadvantages of those most important, some of the technological circumstances that prompted the emergence of new techniques, as well as their comparative estimation capabilities. [ABSTRACT FROM AUTHOR]

Highlights: [•] Extension of the adaptive Huber method for electrochemical integral equations. [•] It applies to integral equations for the expanding plane model of the DME. [•] Solutions are obtained automatically with a prescribed accuracy. [•] The method is tested on simple models of D.C. and A.C. polarography. [ABSTRACT FROM AUTHOR]

Highlights: [•] Extension of the adaptive Huber method for electrochemical integral equations. [•] It applies to integral equations for diffusion inside cylindrical domains. [•] Solutions are obtained automatically with a prescribed accuracy. [•] The method is tested on models of chronoamperometry and voltammetry. [Copyright &y& Elsevier]

Abstract: Diffusion of reactants inside spherical spatial domains, in the absence of homogeneous reactions, is characteristic of some electrochemical systems, such as amalgam mercury drop electrodes. Simulation of transient experiments in such systems can be performed by the classical integral equation method [see, for example, R.S. Nicholson, I. Shain, Anal. Chem. 36 (1964) 706]. This requires an accurate computation of a specific integral transformation kernel function and its moment integrals. Based on formerly known series expansions, highly accurate (16 digits) and cost-optimised procedures serving for this purpose have been designed in this work. The procedures have been combined with the adaptive Huber method developed by the present author. The resulting simulation technique has been tested on simple examples of relevant integral equations, including models of potential step chronoamperometry and cyclic voltammetry. The method is shown to provide automatic solutions, with a user-selected target accuracy. Errors corresponding to the range from about 10-2 of the maximum solution value, down to about 10-7 or even smaller, can be easily obtained at a modest computational cost. [Copyright &y& Elsevier]

Abstract: Digital simulation of transient experiments at channel and tubular electrodes can be performed approximately but relatively cheaply, by means of the integral equation based approach introduced by Singh and Dutt [J. Electroanal. Chem. 182 (1985) 259]. Unfortunately, the use of the series expansion for the relevant integral transformation kernel, suggested by Singh and Dutt, makes such calculations overly slow. A new series expansion is proposed in the present study, which, when combined with the former expansion, yields inexpensive approximations to the kernel and its moment integrals. The relative error of these approximations is at the level of 10−16. The approximations are incorporated into the adaptive Huber method, developed by the present author. The method is shown to provide automatic solutions to the representative integral equations describing chronoamperometry for irreversible charge transfer and cyclic voltammetry for irreversible and reversible charge transfer. Desired accuracy of the solutions is selected simply by specifying a value of the error tolerance parameter. Errors corresponding to the range from about 10−2 of the maximum solution value, down to about 10−7 or even smaller, can be easily obtained at a modest computational cost. [Copyright &y& Elsevier]

Abstract: Integral equations describing controlled-potential transient experiments at planar interfaces, and under conditions of diffusion in one-dimensional finite space, occur in various areas of electrochemistry. Former simulation methods used to solve such equations were rather crudely approximate and non-automatic. In the present work computationally inexpensive approximations to the integral transformation kernels occurring in these equations are determined, that possess the best accuracy achievable within the standard floating point arithmetic. The approximations are combined with the recently developed adaptive Huber method for solving electrochemical integral equations of the Volterra type. The resulting algorithm is tested on representative examples of transient experiments: potential step chronoamperometry for irreversible electron transfer, and cyclic voltammetry for irreversible and reversible electron transfers. The performance of the method is found similar to that previously reported for integral equations involving kernels specific for semi-infinite diffusion. Desired accuracy of the solutions is achieved automatically, depending on user-selected values of the error tolerance parameter. Errors corresponding to the range from about 10−2 of the maximum solution value, down to about 10−7 or even smaller, can be easily achieved at a modest computational cost. [Copyright &y& Elsevier]

Abstract: Electrochemical reduction of metal ions at glassy carbon and tungsten electrodes in molten KCl–LiCl eutectic was studied by linear sweep voltammetry (LSV), convolutive potential sweep voltammetry (CPSV), chronopotentiometry and chronoamperometry. The metal–metal ion systems studied consisted of Pb/Pb(II), Zn/Zn(II) and Mg/Mg(II). In the case of lead deposition, an initial nucleation stage was found to influence the shape of the voltammetric current peak. Because of this, CPSV was believed to be a more reliable method than LSV for the calculation of the diffusion coefficient of the Pb(II) ion. Such types of complications were not observed for zinc and magnesium, since the nucleation overpotentials for these metals were significantly lower than for lead. The convolution voltammograms for magnesium were difficult to interpret because of lithium co-deposition at these negative potentials. Chronopotentiometry and voltammetry yielded practically identical results for D Pb(II). Chronopotentiometric results for reduction of Zn(II)-ions and Mg(II)-ions did not obey the Sand equation very well due to residual currents. Neither was determination of diffusion coefficients from single potentiostatic current transients and the Cottrell equation found to be very reliable for such determinations. LSV seemed to be the most accurate method for determining diffusion coefficients for Zn(II) and Mg(II) ions. Empirical expressions for the temperature dependency of the diffusion coefficient in the temperature range 400–500°C were calculated for all three ions. [Copyright &y& Elsevier]

An oscillating boundary temperature (OBT) method is proposed to simultaneously determine transient thermal properties including thermal conductivity, thermal diffusivity, internal heat generation, and volumetric heat capacity for exothermic solids and semi-solids over a narrow, controlled temperature range by using internal temperature measurements of the thermal wave. A comparison of this method and a transient hot-wire (THW) method is conducted in the presence of heat generation using physical properties which change over time. The advantages and disadvantages of both methods are discussed. The OBT method is potentially useful for the analysis of exothermic solid or semi-solid materials such as hydrating (freshly mixed) cement and concrete, polymers and composites undergoing polymerization reactions, and biological tissues. [ABSTRACT FROM AUTHOR]

Recent standardization developments within the European Union relating to masonry and block systems now allow calculation of thermal performance to be undertaken based on the block configuration and reliable values of the material thermal conductivity. In general, to attain the optimum thermal resistance of a block a minimum amount of material is used such that the webs and faces bounding the air spaces are usually of the order of 6—8 mm. However, the current standard measurement methods are not suitable or precise enough for direct measurement on thin specimens cut from blocks. As a result the masonry industry requested that CEN TC89 investigate and recommend candidate alternative methods suitable for standardization.A working group was established and following consideration of the issues involved, including, in particular, the thermal conductivity range, simplicity, small size, and short operating times, two methods were proposed for further investigation. The first was the steady-state guarded heat flow meter and the second the transient hot strip in both its linear and disc configurations. In order to verify their applicability both methods were used in an initial inter-comparison involving a total of nine organizations. Measurements were made at or close to room temperature on uniform thin test specimens fabricated from a batch of one typical masonry material.This article contains details of the distinctive features and suitability of each method for the task, the participants, the material and test criteria, and includes a summary and discussion of the results that includes unexpected effects due to anisotropy in the particular material. Overall, the results were very promising such that a further series of intercomparison measurements is now underway on some typical materials within the total conductivity range for masonry type products. [ABSTRACT FROM PUBLISHER]

This article deals with the theory and performance of a sensor for measuring thermal conductivity. The sensor, in the form of a small ball, generates heat and simultaneously measures its temperature response. An ideal model of the hollow sphere in an infinite medium furnishes a working equation of the hot-ball method. A constant heat flux through the surface of the ball generates the temperature field. The thermal conductivity of the surrounding medium is to be determined by the stabilized value of the temperature response, i.e., when the steady-state regime is attained. Error components of the sensor are discussed due to analysis of the deviations of the real hot-ball construction from the ideal model. The functionality of a set of hot balls has been tested, and the calibration for a limited range of thermal conductivities was performed. A working range of thermal conductivities of tested materials has been estimated to be from 0.06 W· m · K up to 1 W· m · K. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an overview of the evolution, advancements, and capabilities of the temporal analysis of products (TAP) reactor system as a unique catalyst characterization tool. The origination of the TAP reactor based on molecular beam scattering experiments is briefly mentioned. The advancement in TAP reactor design from the TAP-1 system to the TAP-3 system is introduced to highlight its relevance as a valuable tool for elucidating mechanistic and kinetic aspects of adsorption, diffusion, and reaction in gas–solid systems. Since the invention of the TAP reactor system, a series of TAP microreactor configurations has been introduced with different amounts of catalyst packing starting from the one-zone microreactor to the most recent introduction, the single particle microreactor in which a single Pt particle is packed among 100,000 inert quartz particles. An advantage to decreasing the catalyst zone inside the microreactor is to eliminate non-uniformity in the active zone while still achieving high conversions (95%). Experimental designs and results coupling the TAP reactor to other experimental systems such as a time-of-flight mass spectrometer and atomic beam deposition system is also presented. Key results from recent TAP experiments are presented to show how the TAP reactor is used to answer fundamental questions in catalysis such as bridging the pressure gap between industrial catalysis and surface science, understanding the surface lifetimes of reactive adspecies in TAP pump-probe experiments, finding kinetic rate constants related to changes in catalyst composition and its performance. [Copyright &y& Elsevier]

The field quality of the GSI SIS-100 magnet is influenced by the eddy currents generated in the conductive beam tube during ramping. The eddy-current losses are computed on the basis of a transient 2D finite-element model. A sufficient accuracy is guaranteed by adaptively refining the mesh and by the use of error-controlled adaptive time integrators. The 2D model is accomplished by an analytical model dealing with the closing of the currents at the end parts of the beam tube and thus incorporating the most significant 3D effect. The time dependence of the field quality reveals significant differences at low aperture fields, especially for the sextupole component at the beginning of the ramping. Also without conductive beam tube and for low field values, the relative sextupole and decapole components depend on the magnitude of the field, which indicates the presence of a nonlinear effect. When the magnet operates at an injection field, the magnetic flux density in the bridge of the iron yoke is already saturated. Hence, the saturation pattern in and around this bridge changes immediately at the start of the ramping, resulting in a changing field quality. [ABSTRACT FROM AUTHOR]

Abstract: In situ time-resolved X-ray absorption spectroscopy and mass spectrometry were used to correlate changes in catalyst surface composition with catalytic activity for methane oxidation over alumina supported Pt. Different transient experiments (i.e., pulsing of oxygen or hydrogen to an otherwise constant gas composition) were performed to study the methane oxidation kinetics. Changes in the surface O/Pt ratio were monitored by the introduction of a new analysis method of the white line area corresponding to the Pt LIII-edge XANES spectra. The relevance of the method was confirmed by first-principles calculations demonstrating how hydrogen and oxygen adsorbates modify the electronic structure of Pt. The experimental results show that during the gas-phase transients, the surface O/Pt ratio changes, which in turn affects the methane oxidation rate. Activity maxima are observed for an intermediate surface O/Pt ratio. An oxygen-rich surface seems to hinder the dissociative adsorption of methane, leading to low methane oxidation activity at oxygen excess. [Copyright &y& Elsevier]

Abstract: This manuscript concisely reviews the significance of the temporal analysis of products (TAP) technique in catalysis research from its introduction to the scientific community in the late 1980s. Evolutionary aspects of this time-resolved transient pulse method are presented, highlighting its relevance for elucidation of mechanistic and kinetic aspects of adsorption, diffusion, and reaction in gas–solid systems. The high-temperature ammonia oxidation over noble metal catalysts is used to underline key advantages of the TAP reactor in mechanistic studies, narrowing the often-encountered pressure and materials gaps between techniques operating at ambient pressure and in ultra-high vacuum. Perspectives to further enhance the capabilities of this technique are briefly put forward. [Copyright &y& Elsevier]

Abstract: A detailed mechanistic study of acetone oxidation using ozone was performed on a 10 wt% silica-supported manganese oxide catalyst using in situ Raman spectroscopy. Two adsorbed intermediates were identified at reaction conditions: an acetone species with a band at 2930 cm−1 and an adsorbed peroxide species on the manganese oxide with a band at 890 cm−1. Quantitative temperature-programmed desorption measurements showed that the acetone species resided on the silica support, which thus acted as a noninnocent support. The rates of the acetone and ozone reactions at 318–373 K were equally well described by the power-rate law and Langmuir–Hinshelwood expressions. Transient experiments showed that the rates of formation and reaction of the peroxide surface species did not correspond to the overall reaction rate, and it was concluded that it was not directly involved in the main reaction pathway. A mechanism is proposed involving the migration of the adsorbed acetone intermediate from the silica support to manganese centers, where it reacts with atomically adsorbed oxygen species to form complete oxidation products. [Copyright &y& Elsevier]

The interfacial properties of the steel–concrete system are examined via a new approach for evaluation of galvanostatic pulse data. This methodology allows for rapid determination of the corrosion activity of steel, and readily yields values for parameters related to corrosion such as the polarisation resistance and interfacial capacitance. The method of analysis is based on the iterative fitting of a non-exponential model based on a modified Kohlrausch–Williams–Watt (KWW) formalism. The transient behaviour of steel in concrete is non-exponential in its form and, when analysed this way, an exponent β can be determined characterising the exponential non-ideality of the transient. This non-ideality parameter is found to differ significantly for actively corroding and passive specimens, thereby serving as a useful index to the level of corrosion being experienced. Furthermore, the investigation of the interfacial characteristics of the system, previously unobtainable in a reproducible manner via other electrochemical methods, reveal information regarding the kinetic factors governing corrosion of steel in concrete. [Copyright &y& Elsevier]

Although the spectroscopic detection of electrochemically generated pyrene cation radical (PY⋅+) is generally difficult at room temperature in acetonitrile (AN), we could successfully observe the time changes in the absorption spectra of short-lived PY⋅+ using an electron transfer stopped-flow (ETSF) method by adopting the tris(2,4-dibromophenyl)amine cation radical (TDBPA⋅+) as a reaction initiator. The decrease of PY⋅+ was observed to be complete within 30 ms after generating PY⋅+ via the mixing of the AN solutions of PY and TDBPA⋅+. This decay reaction of PY⋅+ can be attributed to the reaction with a trace amount of water in AN. Thus, the reactions of 1-substituted pyrene cation radicals (XPY⋅+) with water were systematically analyzed using the ETSF method by adding a constant amount of water. Consequently, the reactions were confirmed to be second-order in the cation radicals in all the cases. Among the derivatives, the higher stability of 1-aminopyrene⋅+ was confirmed on the basis of the slow reaction rates, and the order of the reactivity toward water was clarified to be pyrene⋅+>1-bromopyrene⋅+>1-methylpyrene⋅+>1-aminopyrene⋅+. The present results of XPY⋅+ were compared with our previous results on the reactions of 9-substituted anthracene derivative cation radicals. [Copyright &y& Elsevier]

The electrochemical behaviour of iron present in molten enamel is studied at a platinum disc electrode with cyclic and square wave voltammetry and at a platinum rotating disc electrode using chronoamperometry. Fe(III) is reduced in two steps to a Pt–Fe alloy, which disturbs the oxidation behaviour of Fe(II) considerably. Proof is shown for the formation of the alloy. Indications were found that the chemical equilibrium between Fe(III) and Fe(II) in homogeneous solution is attained slowly, which means that Fe(III) actual concentrations are measured instead of analytical concentrations. A consequence is that the diffusion coefficients determined with cyclic and/or square wave voltammetry and reported in the literature must be corrected. This was shown by using rotating disc chronoamperometry. [Copyright &y& Elsevier]

The reactions of 9-substituted anthracene cation radicals (XA+⋅s) with water and methanol in acetonitrile were analyzed using an electron transfer stopped-flow (ETSF) method. By adopting the tris(2,4-dibromophenyl)amine cation radical (TDBPA+⋅) as a reaction initiator, five XA+⋅s, i.e. phenyl, bromo, acetyl, benzyl, and methyl derivatives, could be generated quantitatively by mixing XA with TDBPA+⋅, and the chemical reaction processes of XA+⋅s with water or methanol (ROH) could then be followed by observing dynamic transformation processes of the absorption spectra. Consequently, the reaction orders of XA+⋅ and ROH as well as the reaction rates could be determined. The order of the reactivity was anthracene+⋅>9-methylanthracene+⋅>9-benzylanthracene+⋅>9-acetylanthracene+⋅, 9-bromoanthracene+⋅>9-phenylanthracene+⋅, and diverse changes in the reaction orders of both XA+⋅ and ROH were observed indicating some mechanistic changes. The order of the reactivity was difficult to explain only on the basis of the character of XAs or XA+⋅s. However, as a hypothesis, it can be assumed that when the electron transfer between XA+⋅ and XA(ROH)+⋅ is favorable to formation of XA(ROH)2+, the reaction order of [XA+⋅] is second, and the reaction rates become faster. [Copyright &y& Elsevier]

Li+ charge transfer and the colouration dynamics in an electrochromic tungsten trioxide film electrode have been studied by the potentiostatic intermittent titration technique (PITT) and simultaneous in-situ optical transmittance at one fixed wavelength (670 nm). Relaxation transients of the optical density and of the total integrated charge after potential steps have been measured in intercalation as well as in deintercalation up to a Li composition x of 0.4. The experimental colouration efficiency (CE) (≤80 cm2 C−1) has been deduced as a function of x in such experiments and compared with the efficiency calculated according to the site-saturation model. The small departure of the data from the calculated efficiency was explained in terms of a partially irreversible cathodic reaction, which accounts also for some charge retention in the electrode after a complete cycle. Both charge intercalation and colouration dynamics appeared to follow a diffusion controlled process with a diffusivity of the order of 5×10−11 cm2 s−1. The optical data collected in a complete charge–discharge cycle showed a smaller hysteresis than the electrochemical data, and the colour diffusivity was always higher than the charge diffusivity, in particular at the end of either insertion or deinsertion processes (large x and small x, respectively). Such a small but systematic discrepancy between the optical and electrochemical kinetic data suggests that part of the charge is diverted from the main electrochromic process into a secondary electrochemical process. [Copyright &y& Elsevier]

A numerical simulation and optimization tool for pulsed current electroplating processes is applied to the industrial preparation of high quality Tl-203 deposits. Reliable predictions on current efficiency and deposit quality are enabled by the construction of an adequate reaction mechanism for Tl deposition from highly basic solutions (pH >12.5) in the presence of the EDTA complexing agent. In order to account for multi-ion mass transfer effects near the electrode, the diluted electrochemical ionic system model is to be solved without simplifications, in combination with electron transfer and homogeneous complex forming reactions as defined by the proposed reaction mechanism. Physical and chemical parameters for this model are achieved by comparing and tuning simulated steady-state polarization and efficiency curves at a rotating disc electrode (RDE) with experimental data. [Copyright &y& Elsevier]

The patch-adaptive strategy for electrochemical kinetic simulations, with extensions described in Part 10, is applied to three representative examples of time-dependent kinetic models in one-dimensional space geometry, characterised by the simultaneous presence of spatially distributed and localised unknowns. The models describe: potential step chronoamperometry for a diffusion-controlled charge transfer reaction accompanied by the adsorption of reactants at the electrode; cyclic voltammetry for an electrochemical deposition–precipitation mechanism; and double potential step chronoamperometry for an oscillatory system involving a diffusion-controlled charge transfer reaction having a negative polarisation resistance, in the presence of double layer charging, and ohmic potential drops. The strategy provides accurate, efficient and nearly automatic solutions for these examples, which confirms the overall adequacy of the extensions of the strategy, associated with the handling of localised unknowns. In the third example, the adaptive simulations are very detailed and informative. They confirm the occurrence of numerical artefacts in the literature results of fixed grid simulations for this example. [Copyright &y& Elsevier]

The finite-difference patch-adaptive strategy for electrochemical kinetic simulations, described in Part 5 of this series of papers, is extended to time-dependent models in one-dimensional space geometry, involving spatially localised unknowns at the boundaries, multiple space intervals, and non-local boundary conditions. These extensions are of interest, among others, for the modelling studies of: electrochemical adsorption and/or electrocatalytic reactions, liquid ∣ liquid interfaces, amalgam electrodes, electrochemical biosensors, and pattern formation at electrodes. The following new features are included in the strategy. Grid objects, used by the spatial grid adaptation algorithm, are decomposed into interior and boundary subgrid objects, keeping discrete values of the spatially distributed and localised unknowns, respectively. Linear algebraic equation systems, characterised by quasi-block-tridiagonal matrices having variable block dimensions, and isolated block-pentadiagonal rows, are solved by a specially developed variant of the Thomas algorithm, previously published by the present author. Relative error control is applied to localised unknowns. The calculation of consistent boundary solutions takes into account temporal derivatives present in boundary conditions. Accurate a posteriori calculation of temporal derivatives of the localised unknowns is enabled. [Copyright &y& Elsevier]

The quartz crystal microbalance (QCM) is seeing a rapid increase in new applications and new instrumentation techniques. It is increasingly evident that this sensor provides not only mass data, but can provide information relative to the mechanical properties of deposited films as well. Determining film properties from the measured electrical properties of the QCM resonator requires a modeling of the effects of the film on the electrical behavior of the resonator. We show that the complete electro-mechanical model can provide descriptions of the effects of film properties on resonator behavior in a number of formats to include not only the standard steady-state behavior, but also the transient responses used in a recent new measurement technique. The use of a single model for all techniques will permit comparisons among the results. [Copyright &y& Elsevier]

The initial kinetics of electrochemical deposition of palladium on an Au(111) electrode in 0.1 M H2SO4 solution containing K2PdCl4 have been investigated quantitatively by cyclic voltammetry (CV) and potentiostatic current transient measurements. A cathodic current maximum was observed in the initial stage of Pd deposition process in 0.1 mM K2PdCl4 solution. The analysis shows that the deposition of palladium in this solution proceeds by an instantaneous nucleation and two-dimensional (2D) growth mode. When the concentration of K2PdCl4 became higher, a potential-dependent cathodic current ‘plateau’ after the current maximum was observed. Simple nucleation-growth models cannot fit the transients in the region of the ‘current plateau’. The present current transient results were discussed in comparison with the results obtained by in situ scanning tunneling microscopy (STM). [Copyright &y& Elsevier]