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With the progress in science and technology, non-oxide ceramics (NOCs) are playing a vital role in various fields at high temperature. However, under harsh service conditions, NOCs tend to be confronted with complicated interface reactions with different media, leading to an acceleration in material failure. Among which, the gas-solid reaction is the most common one accompanied by the highest reaction rate, and the corresponding principles and methods are always applicable to solid-solid and liquid-solid reactions. Therefore, deep understanding of the gas-solid interface reaction behavior is significantly important. Herein, contemporary aspects of gas-solid interface reaction of NOCs are reviewed to show how efficient different approaches are to understand the reaction behavior and mechanism. This review covers theoretical approaches based on kinetic models, experimental approaches using advanced instruments as testing and characterization techniques, and simulative approaches with the help of first-principle calculation and molecular dynamics. Different kinetic models applied to different reaction types are introduced and compared, which have a unique advantage in describing and predicting the gas-solid interface reaction behavior of NOCs. Various techniques are illustrated to show the intuitive observation of changes in microstructure and phase composition at the reaction interface. Based on the above two aspects, the effects of external environment on the gas-solid interface reaction are explained and the significance of interface evolution of NOCs themselves is recognized. To reveal the internal reaction essence, the typical application of recently rising simulative approaches is illustrated to show their potentials in observing the reaction path at the atomic and molecular scale and revealing the reaction mechanism. Finally, some research areas worthy being carried out are pointed out. This review will give a deep understanding of the gas-solid interface reaction and provide scientific designing basis for the performance improvement of NOCs. [ABSTRACT FROM AUTHOR]

Hyperthermal atomic oxygen (AO) bombardment to thermal protection system surface has been identified to impact the aerodynamic heating significantly, due to complex chemical reactions at the gas–solid interface, e.g., surface catalysis recombination, oxidation, and ablation. Previous investigations have focused on the surface effects of the AO collision process, while the influence of impacting gas characteristics remains unclear under various non-equilibrium aerodynamic conditions. This work conducts a reactive molecular dynamics (RMD) study of AO collisions over graphene surface, by considering the incoming gas at different translational energies (0.1 ≤ Ek ≤ 10 eV), incident angles (θ = 15°, 30°, 45°, 60°, 75°, and 90°), and O/O2 ratios (χO2 = 0.00, 0.25, 0.50, 0.75, and 1.00). The RMD results indicate that for AO normal incidence, the predominant reactive products of O2, CO, and CO2 molecules are produced due to the synergistic catalytic recombination and surface ablation reaction effects. A maximum recombination performance is identified around 5-eV AO incidence. For off-normal AO incidence, the recombination coefficient increases with the increase in incidence angle from 15° to 60° due to the larger perpendicular components of translational energy and then decreases smoothly. With the increase in O2 mole fraction, the surface reflection probabilities increase, which result in the decrease in both catalytic recombination and ablation activities. Via revealing the atomistic-scale mechanism of gas effects on the surface under hypersonic non-equilibrium conditions, this work sheds light for the future design and optimization of thermal protection materials. [ABSTRACT FROM AUTHOR]

The mechanical effects of dilute liquid inclusions on the solid-liquid composite are explored, based on an analytical circular inclusion model incorporating the internal pressure change of the liquid and the surface tension of the interface. Several simple explicit dependences of the stress field and effective stiffness on the bulk modulus and the size of the liquid, the surface tension, and Poisson's ratio of the matrix are derived. The results show that the stresses in the matrix are reduced, and the stiffness of the solid-liquid composite is enhanced with the consideration of either the surface tension or the internal pressure change. Particularly, the effective Young's modulus predicted by the present model for either soft or stiff matrices agrees well with the known experimental data. In addition, according to the theoretical results, it is possible to stiffen a soft solid by pressured gas with the presence of the surface tension of the solid-gas interface. [ABSTRACT FROM AUTHOR]

The demand for DC gas-insulated switchgear/gas-insulated transmission line (GIS/GIL) becomes more and more urgent in recent years owing to the rapid development of high voltage direct current (HVDC) transmission systems. Insulators in DC GIS/GIL could easily accumulate a large number of charges on its surface during long-term operation, which might lead to overstressing of polymeric insulation or surface flashover. Therefore, it is of great significance to propose an effective method for dissipating extra surface charges. However, achieving charge dissipation without opening the tank is still a great challenge to SFC6-insulated equipment for a long time. In this paper, a novel method, which is named X-ray based non-contact charge dissipation method (XNCDM) for insulators in SF6-insulated equipment, is proposed. The effects of X-ray irradiation on the charges dissipation and the influences of irradiation dose were experimentally investigated in SF6. The mechanisms underlying are discussed in detail. Results show that surface charges on the insulator can be almost completely dissipated after short-time X-ray irradiation with enough dose, owing to the significant enhancement of electric conduction along the insulator surface and charge neutralization by gas ions near the gas-solid interface. This paper provides a novel technique for realizing rapid surface charge dissipation on the insulator, which is of great significance for a variety of engineering applications of DC GIS/GIL. [ABSTRACT FROM AUTHOR]

Adsorption of gas molecules in metal-organic frameworks is governed by many factors, the most dominant of which are the interaction of the gas with open metal sites, and the interaction of the gas with the ligands. Herein, we examine the latter class of interaction in the context of CO2 binding to benzene. We begin by clarifying the geometry of the CO2-benzene complex. We then generate a benchmark binding curve using a coupled-cluster approach with single, double, and perturbative triple excitations [CCSD(T)] at the complete basis set (CBS) limit. Against this △CCSD(T)/CBS standard, we evaluate a plethora of electronic structure approximations: Hartree-Fock, second-order Møller-Plesset perturbation theory (MP2) with the resolution-of-the-identity approximation, attenuated MP2, and a number of density functionals with and without different empirical and nonempirical van der Waals corrections. We find that finite-basis MP2 significantly overbinds the complex. On the other hand, even the simplest empirical correction to standard density functionals is sufficient to bring the binding energies to well within 1 kJ/mol of the benchmark, corresponding to an error of less than 10%; PBE-D in particular performs well. Methods that explicitly include nonlocal correlation kernels, such as VV10, vdW-DF2, and ωB97X-V, perform with similar accuracy for this system, as do ωB97X and M06-L. [ABSTRACT FROM AUTHOR]

Charging of insulators modifies local electric field distribution and increases potential threat to the safety of the gas insulated equipment. In this paper, surface charge tailoring techniques are classified and reviewed by introducing a Dam-flood model. Technical solutions of different charge tailoring methods are compared and discussed. The outlook of potential solutions to suppress charge accumulation is recommended and discussed based on industrial consideration. This paper serves as a guide handbook for engineers and researchers into the study of charge tailoring methods. Meanwhile, we hope that the content of this paper could shed some lights upon charge-free insulators to promote the industrial application of HVDC GIL/GIS. [ABSTRACT FROM AUTHOR]

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Despite technological advancements, probing gas‐solid interfaces at the nanoscale is still a formidable challenge. New nano‐spectroscopic methods are needed to understand the guest–host interactions of functional materials during gas sorption, separation, and conversion. Herein, we introduce in situ Photoinduced Force Microscopy (PiFM) to evidence site‐specific interaction between Metal‐Organic Frameworks (MOFs) and water. To this end, we developed amphiphilic Surface‐anchored MOF (SURMOF) model systems using self‐assembly for the side‐by‐side hetero‐growth of nanodomains of hydrophilic HKUST‐1 and hydrophobic ZIF‐8. PiFM was used to probe local uptake kinetics and to show D2O sorption isotherms on (defective) HKUST‐1 paddlewheels. By monitoring defect vibrations, we visualized in real‐time the saturation of existing defects and the creation of D2O‐induced defects. This work shows the potential of in situ PiFM to unravel gas sorption mechanisms and map active sites on functional (MOF) materials. [ABSTRACT FROM AUTHOR]

Comprehensive knowledge and understanding of the breakdown behavior of solid–gas interfaces are important for the development, optimization, and coordination of insulation in practical high-voltage (HV) gas-insulated systems (GISs) that are widely used in the power and pulsed power industries. However, despite significant research efforts focused on the characterization of the breakdown parameters and properties of complex gas-filled HV systems, the basic mechanisms that underpin the development of discharges in such solid–gas topologies are not fully understood. This lack of knowledge is particularly noticeable in the case of solid–gas interfaces stressed with HV impulses. This study is aimed at the experimental investigation of the breakdown behavior of solid–gas interfaces, formed between solid dielectrics and common gases: dry air, N2, and CO2 at atmospheric pressure. Four different solid-dielectric materials, PTFE, HDPE, Delrin, and Macor, with relative permittivities in the range from 2.1 to 6.3, were used in this work. The solid–gas interfaces formed by these dielectric materials and the surrounding gases were stressed with positive and negative HV impulses. The breakdown voltage and time to breakdown were obtained for all combinations of solid–gas interfaces using both positive and negative impulses, with a nominal rise time of $\sim 1.9~\mu \text{s}$. A digital camera operated in the open-shutter regime was used to obtain images of the breakdown spark channels that were classified according to their propagation paths. The results obtained in this study will help in further understanding of the breakdown behavior of solid–gas interfaces and can be used in the development and optimization of dielectric topologies for use in GISs. [ABSTRACT FROM AUTHOR]

The use of CO2 as a natural refrigerant in data center cooling, oil recovery and in CO2 capture and storage is gaining traction in recent years which involves heat transfur between CO2 and the base fluid. A need arises to improve the thermal conductivity of CO2 to increase the process efficiency and reduce cost. One way to improve the thermal conductivity is through nanoparticle addition in the base fluid. The nano fluid in this study consists of alumina (Al2O3) nanoparticle and CO2 as a base fluid. The experimental data on thermal conduciivity of CO2 based nanoffuid is not available. In this study, the effect of the formation of a nan61ayer (or molecular layering) at the gas-solid interface on thermal conductivity is investigated using equilibrium molecular dynamics (EMD) simulations. This study also investigates the diameter effect of nanoparticle on the nanolayer, thermal conductivity (k) and self-diffusion coefficient (D). In addition to this, diffusion coefficients are calculated for base fluid and nanoffuid to investigate the Brownian motion effect. We found that it decreases with increase in particle size. Thickness of the dense semi-solid layer formed at the nanoparticle-gas interface is studied through radial distribution function (RDF) and density distribution around nanoparticle. This thickness is found to increase with nanoparticle diameter. The thermal conductivity enhancement of the nanofluid was 20%, 46% and 62% for 1 nm, 2 nm and 3 nm diameter, respectively. The output of the current work demonstrates the enhancement in thermal conductivity due to nanoparticles addition which may improve data center cooling efficiency and CO2 capture and storing. [ABSTRACT FROM AUTHOR]

Sulfur hexafluoride (SF6) is widely used in the power industry because of its excellent insulation and arc extinguishing performance. However, the high greenhouse effect of this material is being restricted by many countries around the world, thereby discouraging its usage. As a potential alternative to SF6, the compatibility of C5F10O with conductive copper materials used in electrical equipment is of great significance in ensuring the safe and stable operation of environmentally friendly gas-insulated equipment. In this paper, the interaction among C5F10O/N2, C5F10O/air gas mixture, and copper was studied via experiments and simulations. When the C5F10O/N2 (or air) gas mixture comes in contact with copper at the gas–solid interface, a small portion of C5F10O is decomposed to form C3F6 (or C3F6 and C3F6O) at high temperatures. Meanwhile, at low temperatures (120 °C), the C5F10O/air gas mixture becomes more compatible with copper than with the C5F10O/N2 gas mixture. When the experiment temperatures range between 170 °C and 220 °C, the compatibility of the C5F10O/air gas mixture with copper is significantly inferior to its compatibility with copper. Under high temperatures, the C5F10O/air gas mixture shows severe corrosion on the copper surface due to the presence of O2, forms a thick cubic grain, and emits irritating gases. The simulations show that the carbonyl group in C5F10O is chemically active and can be easily adsorbed on the copper surface. An anti-corrosion treatment must be performed on copper materials in manufacturing equipment. The findings provide an important reference for the application of C5F10O gas mixture. [ABSTRACT FROM AUTHOR]

In this paper, a simplified model for erosion in un-bonded flexible pipes caused by the sand entrained in the produced fluid is established. Flow field analysis is performed based on the governing equations of die continuous fluid and die discrete particles. A two-way coupled Eulerian-Lagrangian approach is employed to solve die gas-solid flow in the pipe bend. To eliminate the influence of die length of the straight pipe section on the stability of the flow field in the pipe, the flow' field distribution under different lengdis is analyzed to determine die optimal straight pipe lengdi. Six commonly used erosion models are adopted to predict die erosion rate. After comparing the prediction results with experimental data, die most accurate Oka model is selected to calculate the effect of the fluid and structure parameters on erosion. Effects of particle parameters and pipe structural parameters on die erosion rate of curved flexible pipes are numerically fitted, and the quantitative description is given. [ABSTRACT FROM AUTHOR]

The electric field distributions along gas-solid interfaces determine the reliability, lifetimes and sizes of gaseous insulated switchgears/pipelines (GIS/GIL), which also affect the reliability of power systems. In this study, the characteristics of steady and transient electric field distributions were first introduced, followed by the concept of functionally graded materials (FGMs). The development histories of FGM applied in electrical engineering and the related optimisation methods were described in detail. The field regulation effect and fabrication technology of different FGM insulators were also compared. To overcome the limitations of traditional FGM insulators, the design of surface FGM (SFGM) was proposed, together with their preparation methods and electrical performance. Furthermore, the future development prospects of FGM and SFGM insulators for compact GIS/GIL were summarised.

The exploration and development of unconventional resources have been of growing interest in the industry in recent years. It is widely known that the adsorption and desorption mechanisms of unconventional gas have great significance for gas accumulation and exploration. However, major researches based on the mechanism of solid-gas interface have failed to reveal it completely, which introduce large discrepancies between actual and predicted production. In this paper, the mechanism of solid-liquid-gas adsorption and desorption interface is enlightened to describe the characteristics of unconventional gas. The validity of the proposal was verified preliminarily by building a conceptual model which redefines the gas-water distribution. Furthermore, the possibility of production of gas trapped in micropores was first investigated. The findings of this study can help for better understanding of the adsorption, desorption, and production mechanisms and in unconventional gas system. Accordingly, the explanation of variation between experiment result and actual production rate even with physical parameters was reasonable in theory. Therefore, this work should provide a basis for improving the accuracy of production predictions in actual reservoirs and should assist analysts in determining reasonable unconventional gas target. [ABSTRACT FROM AUTHOR]

During the past few decades, resonant Auger spectroscopy (RAS) has presented some advantages in elucidating the electronic structure of free molecules, liquids, and solids. To further extend the application of RAS in complex in situ environments, the ambient pressure system should be developed to characterize the gas–solid and liquid–solid interfaces. In this paper, we describe the design and performance of an ambient pressure mapping of resonant Auger spectroscopy (mRAS) system newly developed at BL02B01 at the Shanghai Synchrotron Radiation Facility. This system is unique in that the ambient pressure soft x-ray absorption spectroscopy (sXAS) can be measured in Auger electron yield with kinetic energy (KE) resolved. We can obtain a mapping of the resonant Auger spectroscopy (mRAS) in the near ambient pressure environment. This approach provides an additional dimension of information along the KE of Auger electrons to reveal details of the valence and unoccupied states at the vicinity of the absorption edge. Complementary to the photoemission spectroscopy that probes the core levels, in situ two-dimension mRAS characterization is useful in studying the electronic structure of complex interfaces of gas–solid and liquid–solid under realistic operating conditions. We herein present the in situ oxidation of Cu(111) in the ambient oxygen environment as demonstration of the mRAS capability. Specifically, resolving the Auger features gives valuable clues to the molecular level understanding of chemical bonding and the evolution of orbital hybridization. In addition, the mRAS results of spatial resolution and mbar range gas pressure are shown and discussed. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of gas-solid two-phase flow and water vaporization in a 3D powder-particle spouted bed (PPSB) by means of the combined approach of the Eulerian-Eulerian two-fluid model (TFM) and kinetic theory of granular flows (KTGF). The simulation shows that the gas temperature in the injection area is higher than water and particles, and the three-phase temperatures in other areas are similar. The water vaporization rate is higher at the junction of the injection area and the annulus area, lower in the center of the injection area, and lowest in the annulus area. By increasing gas velocity and liquid temperature, reducing gas humidity, promoting water vaporization. [ABSTRACT FROM AUTHOR]

The purpose of the article is to analytically solve the conjugate problem of heat transfer in a viscous shock layer on a blunt object and thermal conductivity in an anisotropic half-space. A feature of the flow around such bodies near the critical point is that in this case, the boundary layer equations are not satisfied and it is necessary to solve the Navier-Stokes equations together with the equations of continuity, state, and energy, however, in a stationary formulation of an incompressible flow. The problem of coupled heat transfer between a viscous shock gasdynamic layer and anisotropic half-space with the assumption of incompressibility of the gasdynamic flow behind the normal part of the shock wave is posed. An analytical solution to this problem is obtained with a boundary condition at the gas-solid object interface in the form of a parameter – temperature, as well as an analytical solution to the thermal conductivity problem in an anisotropic half-space with the same boundary condition. [ABSTRACT FROM AUTHOR]

Numerous experimental data are available on contact angles. However, the majority of them concern sessile droplets, although bubbles are more interesting from the point of view of colloid science, because a sessile bubble is distinguished by the existence of an equilibrium thin liquid film at a gas–solid interface. This paper presents the totality of modern thermodynamic equations necessary for describing the contact angle of a bubble of an arbitrary size. However, in view of their complexity, specific relationships are derived and analyzed for small although macroscopic bubbles. The dependences of a bubble contact angle on the temperature, pressure in a liquid, composition of a liquid phase, and roughness of a solid surface are considered. In the case of a pure liquid, when a gaseous phase consists of its vapor, the obtained relations are of significance for the cavitation theory. The study as a whole has a framework character, and so only the general basic results are presented. Their detailing is possible in combination with experimental data. [ABSTRACT FROM AUTHOR]

Pressurized circulating fluidized beds are applied in a range of applications because of intensified heat and mass transfer and chemical reaction. The gas density increases linearly with the pressure, which influences the gas-solid flow characteristics. In this work, the effects of operating pressure (0.1 MPa–0.6 MPa) on the distribution of particle volume fraction and gas-solid slip velocity in the riser are studied under different conditions. The particle belongs to Geldart B group, the solids circulation rate ranges from 20 to 50 kg/(m2.s), and the fluidizing gas velocity ranges from around 2 to 8 m/s. With an increase in pressure from 0.1 to 0.6 MPa, in order to achieve the same solids circulation rate, the fluidizing gas velocity decreases approximately to a half. Under pressurized conditions, the profile of particle volume fraction along the axial direction shows a similar trend, while the particle volume fraction in the bed central zone at the upper riser increases slightly. Under different pressures, the plot of the nondimensional gas-solid slip velocity against the particle volume fraction converges on a power correlation. The present study is a first step towards the aim of correlating the solids circulation rate and gas-solid slip velocity with operating parameters under pressurized conditions. Unlabelled Image • Gas-solid flow in a pressurized circulating fluidized bed up to 0.6 MPa is studied. • The fluidizing gas velocities at different pressures are obtained for the same solids circulation rate. • The profile of particle volume fraction along the axial and radial are presented. • The gas-solid slip velocity decreases rapidly with the increase of pressure. • The nondimensional gas-solid slip velocities at different pressures are analyzed. [ABSTRACT FROM AUTHOR]

Displacement reactions between binary and ternary ceramics in the Ti–W–C system and reactive gaseous atmospheres are investigated in this work. Specifically, WC and 50:50 wt% TiC:WC solid solution powders were exposed to flowing hydrogen gas, or equilibrated against an excess of titanium in the presence of iodine, to form metallic tungsten and TiC solid products. In the case of pure WC reacting with hydrogen, transformation to metallic tungsten occurred as a result of removal of chemically bound carbon as gaseous hydrocarbons. In the case of pure WC reacting with titanium iodide vapors, transformation was accompanied by the appearance of TiC as a solid product formed at the gas‐solid interface. In the case of 50:50 wt% TiC:WC solid solution powders, hydrogen was generally found to be an ineffective displacing reagent, whereas reaction with titanium iodide vapors was observed to proceed virtually to completion, resulting in a two phase product mixture comprising metallic tungsten and TiC. For the latter case, a variety of microstructures could be observed within a given batch, including tungsten platelets and/or lamellae in a TiC matrix, or coarse tungsten grains interspersed with TiC grains. These morphological variations are speculated to arise from compositional variation in the starting material and the occurrence of local rapid coarsening along fast diffusion pathways within reacting agglomerates and polycrystalline primary particles. The observed reaction products and relative efficacy of gaseous reagents to promote displacement reactions in the Ti–W–C system are rationalized on the basis of thermodynamic predictions. The reaction between 50:50 wt% TiC:WC solid solution powders and titanium iodide vapors constitutes the first known report of an internal displacement reaction proceeding via gaseous intermediates in a nonoxide ceramic system. [ABSTRACT FROM AUTHOR]

A physically rigorous computational algorithm is developed and applied to calculate subcontinuum thermal transport in structures containing semiconductor-gas interfaces. The solution is based on a finite volume discretization of the Boltzmann equation for gas molecules (in the gas phase) and phonons (in the semiconductor). A partial equilibrium is assumed between gas molecules and phonons at the interface of the two media, and the degree of this equilibrium is determined by the accommodation coefficients of gas molecules and phonons on either side of the interface. Energy balance is imposed to obtain a value of the interface temperature. The classic problem of temperature drop across a solid-gas interface is investigated with a simultaneous treatment of solid and gas phase properties for the first time. A range of transport regimes is studied, varying from ballistic phonon transport and free molecular flow to continuum heat transfer in both gas and solid. A reduced-order model is developed that captures the thermal resistance of the gas-solid interface. The formulation is then applied to the problem of combined gas-solid heat transfer in a two-dimensional nanoporous bed and the overall thermal resistance of the bed is characterized in terms of the governing parameters. These two examples exemplify the broad utility of the model in practical nanoscale heat transfer applications. [ABSTRACT FROM AUTHOR]

• Investigating hydrogen heterogeneous reaction takes place in catalytic combustor with a blunt body. • Introducing the blunt body into the catalytic combustor enhances the hydrogen conversion ratio. • Strengthening heat and mass transfer characteristics is observed as the blockage ratio increases. • By exploring field synergy effects, the optimal performance parameters of the combustor with a blunt body are determined. A numerical investigation has been conducted to explore the effect of an inserted blunt body on the heterogeneous reaction (HTR) characteristics in a micro-catalytic combustor operating with premixed hydrogen/air. The two-dimensional numerical model incorporates a comprehensive heterogeneous reaction mechanism of hydrogen employed by experimental verification. The influences of blockage ratio at various inlet velocities have been investigated to obtain optimized design parameters of the combustor. The findings of this research highlight analysis of the positive influence of an inserted blunt body within the combustor, including enhancement of chemical reaction rate and hydrogen conversion ratio. Numerical results shows that the gaseous mixture between the blunt body and catalytic surface noticed a considerable velocity increase, leading to a greater adsorption–desorption of bulk species on the catalytic surface. At the same inlet velocity, the hydrogen conversion ratio gradually increases with higher blockage ratios. When the blockage ratio is less than or equal to 0.6, the average inner wall temperature is positively affected by the increased blockage ratio. However, the effect becomes negative at higher blockage ratios (0.8). The Pr (Prandtl number) number near the gas–solid interface adjacent to the blunt body initially decreases and then increases, while Nu/Nu0 (Nusselt number) and Pe (Peclet number) exhibit an initial increase followed by a decrease. The presence of the blunt body leads to a reduction in the cross-sectional area of the channel, causing an acceleration in fluid velocity near the blunt body and exerting an impact on the boundary layer near the gas–solid interface. This indicates that the addition of the blunt body reduces the boundary layer thickness and enhances the mass and heat transfer characteristics in the region. The study reveal that as the blockage ratio increases, the overall field synergy of the combustor initially increases and then decreases. The peak field synergy is attained at an optimal blocking ratio of 0.6. The findings of this study have important implications for the design of micro-scale combustors. [ABSTRACT FROM AUTHOR]

As people are paying more attention to the health and comfort of the indoor environment, the sensors detecting the relative humidity (RH) and volatile organic compounds (VOCs) have attracted widely research interests. However, how to improve the sensitivity and selectivity remains a challenge, especially for flexible sensors working at room temperature (around 25 ℃). In this work, the controlling of solid-gas interface was found to be able to enhance the sensitivity and the manipulation of solid-solid interface increased the selectivity of the sensor for VOC detection. The flexible sensor based on electrospinning cellulose (EC) show high sensitivity for humidity detection due to its large solid-gas interface, which can be used for real-time monitoring of human breathing and speech recognition, simultaneously, it can also detect a variety of VOCs. By introducing silver nanowires (AgNWs) to establish solid-solid interface between silver and expanded graphite (EG), the selectivity of the sensor for VOCs detection was improved, which shown higher sensitivity for EtOH with faster response/recovery time, as well as long-term cycle stability and bending insensitivity. Furthermore, the sensor also can be decomposed by burning, offering a sustainable disposal method. This versatile, low-cost and environmentally friendly flexible electronic device may be used for wearable air monitoring and environmental controlling. [Display omitted] • A Room-temperature-operated gas sensor was developed for RH and VOCs detection. • The specific surface area of the sensor is increased by electrospinning to improve the sensitivity. • AgNWs is introduced to improve the selectivity of the sensor for VOCs detection. • The sensor has long-term cycle stability and bending insensitivity. • The sensor can be disposed by burning. [ABSTRACT FROM AUTHOR]

Combustion of the AP/HTPB composite propellant at the mesoscale is simulated by a partitioned numerical framework, in which the unsteady solid-phase conduction, gas-solid interface regression, and gaseous combustion are sequentially calculated on two sets of overlapped grids. The gas-solid interface is traced by the level-set method. The mass and species exchange conditions at the gas-solid interface are converted into source terms by the immersed-boundary method. Effectiveness of the entire framework is justified by applying the integrated solver to a Miller pack example. The predicted burning rates show good agreement with experimental data over a wide range of pressure conditions, and the gas-phase temperature field clearly depicts the final diffusion flame. The flame zone closely above the regressing interface can be identified by the fluctuation of the projected velocity components perpendicular to the main stream direction. Statistical results conditional on Lagrangian tracing of fluid parcels released from the AP and binder parts show distinction between the oxidizer-rich and fuel-rich flames in terms of the reaction intensity and the flame structure. From the algorithm/simulation perspective: a partitioned numerical solution framework is built upon overlapped structured (for the gas phase) and unstructured (for the solid phase) meshes; the level-set approach is used on the unstructured mesh to identify solid-gas interface with complex geometry. From the analysis perspective: the flame front is newly defined in terms of the tangential velocity components; the fuel/oxidizer evolution pattern is analyzed from conditional statistics based on Lagrangian tracing; new insights in heterogeneous combustion include, for instance, effects of pressure on the tangential velocity fluctuation and flame properties conditional on different ingredients. [ABSTRACT FROM AUTHOR]

[Display omitted] • A DFT-based rate equation is developed to predict CaO carbonation with CO 2. • The surface reaction is coupled with structural transformation in DFT calculations. • A multiscale model is established on 'atom → surface → grain → particle' scales. • Nucleation kinetics predicts the negative activation energy close to equilibrium. Calcium oxide (CaO), a CO 2 sorbent and key ingredient in the process of making cement, exhibits excellent potential for carbon capture, utilization, and storage (CCUS) applications through calcium looping and integrated carbon capture and utilization, owing to its outstanding kinetic properties and high recyclability. From a fundamental standpoint, it is important to establish a comprehensive and precise carbonation kinetic model for CaO. In the present study, a density functional theory (DFT)-based rate equation was developed to predict the gas–solid reaction kinetics of CaO carbonation with CO 2 in calcium looping. The reaction pathway of CaO carbonation, including surface reactions and structural transformations, was obtained by a transition state search of DFT calculations, and the transition state theory was used to calculate the reaction rate constants. The nucleation model was implemented in the mean-field surface reaction model to describe the nucleation of the CaCO 3 product at the gas–solid interface. A grain model was developed to couple the surface reaction and CO 2 diffusion through the product layer. The developed theory was validated using a wide range of experimental data, and the negative activation energy of CaO carbonation close to equilibrium was accurately predicted. The developed first principle-based rate equation provides a detailed theoretical framework for predicting CaO performance and optimizing the microstructure of Ca-based sorbents. [ABSTRACT FROM AUTHOR]

The excitation of a surface plasmon polariton (SPP) wave on a metal-air interface by a diffraction grating under monochromatic normal illumination is investigated numerically. The influence of the different experimental parameters (grating thickness, period, and duty cycle) is discussed in detail for a semi-infinite metal and a thin film. Both engraved (grooves) and deposited (protrusions) gratings are considered. The most efficient coupling to the SPP is obtained for a groove grating which duty cycle is about 0.5. Furthermore a small grating depth of some tens of nanometers is sufficient to excite a SPP mode with a coupling efficiency higher than 16% in each direction. Implications for practical SPP experiments are discussed. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD), a chemical vapor deposition technique based on sequential self-terminating gas–solid reactions, has for about four decades been applied for manufacturing conformal inorganic material layers with thickness down to the nanometer range. Despite the numerous successful applications of material growth by ALD, many physicochemical processes that control ALD growth are not yet sufficiently understood. To increase understanding of ALD processes, overviews are needed not only of the existing ALD processes and their applications, but also of the knowledge of the surface chemistry of specific ALD processes. This work aims to start the overviews on specific ALD processes by reviewing the experimental information available on the surface chemistry of the trimethylaluminum/water process. This process is generally known as a rather ideal ALD process, and plenty of information is available on its surface chemistry. This in-depth summary of the surface chemistry of one representative ALD process aims also to provide a view on the current status of understanding the surface chemistry of ALD, in general. The review starts by describing the basic characteristics of ALD, discussing the history of ALD—including the question who made the first ALD experiments—and giving an overview of the two-reactant ALD processes investigated to date. Second, the basic concepts related to the surface chemistry of ALD are described from a generic viewpoint applicable to all ALD processes based on compound reactants. This description includes physicochemical requirements for self-terminating reactions, reaction kinetics, typical chemisorption mechanisms, factors causing saturation, reasons for growth of less than a monolayer per cycle, effect of the temperature and number of cycles on the growth per cycle (GPC), and the growth mode. A comparison is made of three models available for estimating the sterically allowed value of GPC in ALD. Third, the experimental information on the surface chemistry in the trimethylaluminum/water ALD process are reviewed using the concepts developed in the second part of this review. The results are reviewed critically, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials. Although the surface chemistry of the trimethylaluminum/water ALD process is rather well understood, systematic investigations of the reaction kinetics and the growth mode on different substrates are still missing. The last part of the review is devoted to discussing issues which may hamper surface chemistry investigations of ALD, such as problematic historical assumptions, nonstandard terminology, and the effect of experimental conditions on the surface chemistry of ALD. I hope that this review can help the newcomer get acquainted with the exciting and challenging field of surface chemistry of ALD and can serve as a useful guide for the specialist towards the fifth decade of ALD research. [ABSTRACT FROM AUTHOR]

We employ Monte Carlo simulations in the grand canonical ensemble (GCEMC) to investigate the impact of nonplanarity of a solid substrate on the locus of the prewetting phase transition. The substrate is modelled as a periodic sequence of furrows of depth D and periodicity s[sub x] in the x direction; the furrows are infinitely long in the y direction. Our results indicate that a necessary prerequisite for a prewetting transition is the formation of a(n approximately) planar interface between molecularly thin films and an adjacent (bulk) gas. Thus, in general the prewetting transition is shifted to larger chemical potentials because the formation of a planar film–gas interface is more difficult next to a nonplanar compared with a planar solid surface. However, this shift turns out to be nonmonotonic depending on D on account of subtle packing effects manifested in the deviation of the local density Δρ(x,Δz;D) at the nonplanar solid surface from that at a planar substrate. If D becomes sufficiently large prewetting as a discontinuous phase transition is suppressed because inside the furrow a highly ordered film forms that prevents a planar film–gas interface from forming. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the wetting behavior of a sessile cylinder of a Lennard-Jones liquid in equilibrium with its vapor and in contact with a solid substrate. Alteration of the solid-fluid potential interaction relative to the fluid-fluid potential; Influence of temperature on equilibrium wetting; Dynamic spreading for various types of solids.

This paper describes a zero-dimensional model for evaluating the mass flow rate history of a solid rocket motor igniter. Based on the results of an igniter-firing experiment, in which the igniter is the only source of combustion gas and no propellant is ignited, the proposed model can be used to compute the mass flow rate of the igniter. Different species and temperature-dependent properties, such as the specific heat for each species, are considered. The coupling between the flow field variables in the combustion chamber and the heat transfer at the gas-solid interface is computed in a segment way. Calculations are performed for different species and properties, and the errors are discussed. Using the computed igniter mass flow rate as a boundary condition, a two-dimensional calculation is performed for validation purposes. The results are in good agreement with experimental data. The proposed model can be used to provide reasonable boundary conditions for solid rocket motor simulations and to evaluate the performance of igniters. Although derived on the basis of a small-scale solid rocket motor, the model has the potential to be used in large-scale systems. [ABSTRACT FROM AUTHOR]

The paper presents the studies, research and results obtained using ultrasounds in the field of industrial air filtration. In this regard, there are two types of air filter that have been designed for use in the air filtration system in the paint booths. The first type of filter uses vibrations from a classic system consisting of transducer, amplifier, and activated element. The second filter is based on the ultrasonic cavitation phenomenon. For both types of filtering systems, finite element analysis is useful, and it is very useful in selecting vibration modes and vibration frequencies to be used. Besides these are presented elements of the practical realization of the filters as well as some of the experimental results obtained. The main phenomena that occur in the propagation of ultrasounds through a gaseous medium: propagation velocity; compressing and scaling the environment according to the nature of ultrasonic waves; reflection and refraction of ultrasonic waves at the solid-gas interface; the creation of stationary waves and the emergence of pressure knots and antinodes; diffraction and diffusion of ultrasonic waves; attenuation of ultra-acoustic energy; ultraacoustic absorption; ultrasonic cavitation, etc. it is proposed to use the effects of their propagation in the filtration and purification process and the construction of ultrasonic filters operating on the principle of "ultrasonic agglomeration" on the principle of "ultrasonic shaking" or combined. [ABSTRACT FROM AUTHOR]

Copyright of Latin-American Journal of Physics Education is the property of Latin-American Physics Education Network and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Adsorption plays a critical role in surface and interface processes. Fractional surface coverage and adsorption free energy are two essential parameters of molecular adsorption. However, although adsorption at the solid–gas interface has been well‐studied, and some adsorption models were proposed more than a century ago, challenges remain for the experimental investigation of molecular adsorption at the solid–liquid interface. Herein, we report the statistical and quantitative single‐molecule measurement of adsorption at the solid–liquid interface by using the single‐molecule break junction technique. The fractional surface coverage was extracted from the analysis of junction formation probability so that the adsorption free energy could be calculated by referring to the Langmuir isotherm. In the case of three prototypical molecules with terminal methylthio, pyridyl, and amino groups, the adsorption free energies were found to be 32.5, 33.9, and 28.3 kJ mol−1, respectively, which are consistent with DFT calculations. [ABSTRACT FROM AUTHOR]

The gas-solid interface is generally considered to be the weakest part in gas-insulated systems. The flashover voltage of a gas-solid interface is difficult to predict because it involves an extremely complex physical process affected by multiple factors. In this paper, we employ the support vector regression (SVR) method based on mass data on the features of the electric field that are indicators of the flashover voltage. We cast 48 kinds of epoxy resin post insulators as samples, and 61 features are extracted to characterize the surface electric field distribution and the flashover voltage under standard lightning impulse voltage. Four indicators that may be useful in predicting the flashover voltage were obtained; the maximum electric field along the surface of the insulator (E max), the normal electric field components of E max (E n_Emax), the maximum gradient of the surface tangential electric field component (E t_gm), and the integral of the area in which the E value exceeds x% of E max along the insulator surface (V t60). We establish an SVR flashover voltage prediction model with these four features, whose average deviation is 7% in 10,000 predictions. It is expected that this study may provide a reference for the continued study of the gas-solid surface flashover mechanism. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An understanding of interfacial barriers underpinning fluid transport in nanoporous membranes is critical for the design of efficient next generation membranes, to harness their potential for industrial scale separations. Such barriers include the contribution of external and internal interfacial barriers, and strongly depend on smoothness of the pore surface, pore size, shape, tortuosity, structural defects such as pore blockage and thermodynamic state of the fluid. We review recent progress in the transport of a fluid through nanoporous membrane materials such as zeolites and carbon nanotubes, which hold promise for industrial significance, but their application is subject to strong interfacial barriers. The contribution of interfacial barriers to the overall transport in these membrane materials is found to be particularly significant when the pore surface is uniform as well as at low temperatures and pressures. Further, such barriers that arise from internal defects such as grain boundaries are found to be remarkable and detrimental to separation kinetics. The internal interfacial barriers are found to be significant, and are enhanced when a dense medium such as a polymer is present at the interface, suggesting that interfacial barriers can play a key role in mixed matrix membranes and is an important area requiring further attention. [ABSTRACT FROM AUTHOR]

• CFD is applied to study the performance of a novel partition-cavity solar reactor. • Gap size increase leads to a temperature drop on the gas-solid interfaces. • Thinner catalyst derives higher temperature under concentrated solar radiation. • Best efficiency found for design with 30 mm gap and 30 mm catalyst thickness. Solar thermochemical processes utilize inexhaustible solar energy as a thermal driving force to provide heat and motivate reactions, which offer pathways to store solar energy as chemical fuels. Some elevated temperature reactions, like thermal decomposition, gasification, and methane reforming, are anticipated in solar reactors which have the ability to provide extremely high temperatures. Presently, the dominating considerations in the design of solar reactors are heat and mass transfer with reaction mechanisms. A novel partition cavity-receiver reactor concept is proposed in this paper. In order to provide a longer pathway of interaction between the catalyst and reactants, a partition is introduced in this cavity-receiver reactor. A numerical computational fluid dynamics (CFD) analysis is performed to study the influences of geometric factors (i.e. gap size between partition and bottom, inlets/outlets position, catalyst thickness) under both uniform and model-generated distribution of concentrated radiant fluxes. A two-step solar thermochemical redox reaction using ceria as a catalyst to split CO 2 is modeled in the partition cavity-receiver reactor to investigate the relationship between geometric factors and reaction rates. Based on the comparisons and analysis of results, optimized geometric factors and corresponding operating conditions are discussed. [ABSTRACT FROM AUTHOR]

The anode gas diffusion layer plays an important role on mass transport. By adjusting the assembly pressure, the structure of gas diffusion layer can be controlled to investigate the two-phase behavior. The electrochemical test indicates that increasing the assembly pressure causes increase in mass transport resistance. Inhomogeneous compression of gas diffusion layer is observed by three-dimensional imaging technology. Based on the experimental data, a two-phase model is established. The simulated results show that the increment of surface roughness and the reduction of porosity, both derived from compression of gas diffusion layer, exacerbate CO 2 blockage of the cell. Lowering polytetrafluoroethylene content of anode gas diffusion layer alleviates CO 2 blockage by reducing the difference of surface tension between liquid-solid and gas-solid interface as well as the negative capillary pressure of gas diffusion layer. Thus, the peak power density climbs from 60.61 to 49.94 mW cm−2 to 74.79 and 70.47 mW cm−2 at the assembly pressure of 1.00 and 2.00 MPa, respectively. The optimal assembly pressure locates at where good contact between membrane electrode assembly and bipolar plate is achieved, with the least gas diffusion layer deformation possible. Image 1 • The 3D structural data of GDL are measured for modeling analysis. • Inhomogeneous compression of GDL increases mass transport resistance. • The increased roughness and reduced porosity of GDL hinder CO 2 removal. • Structural optimization of GDL improves peak power density by 23% and 41%. [ABSTRACT FROM AUTHOR]

We have developed a torsion balance to detect the rotation of a cell containing spin-polarized gaseous atoms to study angular momentum transfer from gaseous atoms to solid. A cesium vapor cell was hung from a thin wire in a vacuum chamber, and irradiated from the bottom with circularly polarized light tuned to the D2 transition to polarize cesium atoms in the cell. By varying the light helicity at the resonance frequency of the torsion balance, we induced forced rotational oscillation of the cell and detected radiation torque exerted on the cesium vapor cell through the cesium atoms inside. The torque was particularly large when both hyperfine levels of cesium atoms were optically pumped with application of a longitudinal magnetic field. Further detailed study will provide new insights into spin-transfer processes at the gas-solid interface. [ABSTRACT FROM AUTHOR]

• Typical powder regimes were observed at different pressures. • A distinct gas-slid interface will be formed at high pressure. • The flow representations of pressure sub-signals were redistricted. • Wavelet analysis can give more details of gas-solid flow than standard deviation. Powder propellant feeding system is the key part of powder engine, and the powder fluidization process is quite complex due to the comprehensive effects of intake type, piston and compressible dense gas-solid flow in tank. In order to explore the regimes and fluidization characteristics at high pressure, in this paper, visualization technique with pressure transducer are applied, and the pressure signals have been analyzed by using standard deviation and wavelet transform methods. It is found that in powder tank the fluidization regime will be changed with the increase of pressure: from partial powder fluctuation at low pressure (0.4 MPa) to steady gas-solid interface at high pressure (2.5 MPa), and the regime phenomenon can be explained roughly by standard deviation analysis of pressure signals. Meanwhile, the flow representations of pressure sub-signals were redistricted through wavelet energy method based on ten-level decomposition: the approximation sub-signal a10 (0–4.88 Hz) represents the fluidized gas intake, sub-signals d8–d10 (19.53–39.0625 Hz) represent the powder flow structure changing, gas-solid interaction is represented by d6–d7(39.0625–156.25.Hz), and sub-signals d1–d5 (156.25–5000 Hz) can be used for gas turbulence flow representation. Where gas turbulence and powder fluctuation were determined as the main contributions to pressure fluctuation in the tank. Otherwise, the wavelet energies of sub-signals except for approximation decrease with pressure increase, but there exist large differences for that with the increase of particle mean diameter with different leading force, and the easier entrainment for different size powder, the slighter effects of gas turbulence and gas-solid interaction. [ABSTRACT FROM AUTHOR]

Thermal localization leads to reaction initiation in granular materials. Observations show that it occurs in the vicinity of large pores and, thus, depends on a material's microstructure. Since the spatial variability of the latter cannot be ascertained in all its relevant details, we treat the material's initial porosity as a random field. The so-called "hotspots" are then modeled as rare events in a complex nonlinear dynamical system. Their probability of occurrence is quantified by the tails of the distributions of the temperature and the corresponding reaction rate. These are computed via Monte Carlo simulations of a two-phase five-equation dynamic compaction model, which are supplemented with a mesoscale model of the thermal localization at the solid-gas interface. Our results demonstrate a strong nonlinear dependence of the probability of hotspot initiation on the variance of the initial porosity. [ABSTRACT FROM AUTHOR]

Abstract A simple, low-cost, electroless, and industrially scalable solution/vapor two-step strategy for the synthesis of highly-transparent and conductive CuI thin films is presented. The process is based in the coupling of the versatile chemical solution deposition technique to a gas–solid reaction method. It consists of the chemical deposition of CuS 2 thin films (which can be performed over any kind of substrate) and their subsequent halidization by a gas–solid reaction with iodine vapor. The CuI obtained by this route is as transparent and conductive as the ones obtained by physical techniques coupled to an iodination reaction. Particularly, we present a 60-nm CuI sample obtained by iodination of a chemical-solution-deposited 21-nm CuS 2 , which is practically similar to the best reported in the literature, in terms of absence of the common frosted-glass-like appearance. The integrated transmittance in the visible region of this CuI thin film is 0.85, compared with the 0.91 of the glass slide used as a substrate, which is an indication of the high transparence of the synthesized CuI material. Hall-Effect and optical characterization of a thicker CuI thin film (146 nm) obtained by the solution/vapor two-step process presented here resulted in a p -type conductivity, a resistivity equal to 1.1 Ω cm, a hole concentration of 1.3 × 1019 cm–3, a hole mobility of 0.43 cm2/V·s, an integrated transmittance in the visible region of 0.65, and, according to the Z 1,2 exciton absorption, an energy band gap of 3.05 eV. Analyses by XPS and XRD, as well as a rigorous chemical analysis and an accurate Rietveld refinement, confirmed that the composition of the obtained material is Cu 0.85±0.06 I with a zincblende structure, thus presenting copper vacancies; this composition explains the p -type conductivity of the synthesized material. All these results demonstrate that the two-step process presented here is a promising alternative to those including conventional physical techniques. The CuI thin films present enough quality to be studied for both photovoltaics and transparent electronics applications. [ABSTRACT FROM AUTHOR]

Highlights • Gas mean residence time is 13.5 s in the blast furnace investigated. • Gas flow is divided into two representative streams after entering the furnace through a tuyere. • The mainstream of gas flow features piston-type flow. • The second stream of gas flow indicates draggy distribution in RTD curves. Abstract Gas residence time distribution (RTD) is an effective and convenient indicator for evaluating the performance of complex multiphase chemical reactors including ironmaking blast furnaces (BFs). However, in the open literature, there lacks the systematic RTD research for BFs. In this study, an integrated mathematical model is developed for describing the gas RTD of a BF. The model combines a steady multi-fluid model for describing the in-furnace state of flow and thermo-chemical behavior of gas-solid-liquid phases and a transient model for describing the dynamic behavior of tracer materials. The results show that the gas flow field inside the BF is quite complex, resulting from many factors such as furnace geometry and coupled thermo-chemical behaviors of other phases. The tail of gas RTD curve resulted from the lagging phenomenon of tracer flow inside BFs, is captured. The gas RTD is discussed by using mean residence time, dispersion of molecules distribution, cumulative distribution function and residence time intensity function. Under the given BF conditions, mean residence time and space time of gas fluids are predicted as 13.5 s and 16.3 s, respectively. The existence of stagnant flow in the BF can be both derived and directly identified. Moreover, it is indicated the gas flow patterns in the BF are composed of piston-type flow, stagnant flow and limited mixing flow. This study provides a cost-effective tool for better understanding BF gas flow dynamics and optimizing BF operations. [ABSTRACT FROM AUTHOR]

Highlights • A novel continuum theory accurately predicts aggregation in a gas-solid flow. • The continuum theory accurately predicts entrainment of cohesive particles. • Aggregation leads to increased granular temperature and breakup of agglomerates. Abstract In this work, a continuum theory for cohesive particles developed recently (Kellogg et al., 2017) is applied to lightly-cohesive particles in an unbounded, gas-solid riser. The novelty of this recent theory is its fundamental incorporation of the effects of the granular temperature (i.e., continuum measure of impact velocity) and the material and cohesion properties on the rates of aggregation and breakage of agglomerates. Here, we extend this theory to multiphase systems and place particular emphasis on its ability to predict entrainment rate, as past empirical correlations vary by orders of magnitude when applied to the same system (Chew et al., 2015). Specifically, continuum predictions of entrainment rates and agglomerate fraction are compared with Discrete Element Method (DEM) simulations of lightly-cohesive particles in a gas-solid flow. The agreement obtained for these quantities provides preliminary validation for the use of the continuum theory for cohesive particles in gas-solid flows. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water vapor splitting by using n‐type semiconductor electrodes with a proton exchange membrane (PEM) enabled pure hydrogen production from humidity in ambient air. We proved a design concept that the gas–electrolyte–semiconductor triple‐phase boundary on a nanostructured photoanode is important for the photoinduced gas‐phase reaction. A surface coating of solid‐polymer electrolyte on a macroporous titania‐nanotube array (TNTA) electrode markedly enhanced the incident photon‐to‐current conversion efficiency (IPCE) at the gas–solid interface. This indicates that proton‐coupled electron transfer is the rate‐determining step on the bare TNTA electrode for the gas‐phase PEC reaction. The perfluorosulfonate ionomer‐coated TNTA photoanode exhibited an IPCE of 26 % at an applied voltage of 1.2 V under 365 nm ultraviolet irradiation. The hydrogen production rate in a large PEM‐PEC cell (16 cm2) was 10 μmol min−1. [ABSTRACT FROM AUTHOR]

This study investigated the carbonation behaviour of a calcium‐based sorbent in the calcium‐looping CO2 capture process as a non‐catalytic gas‐solid reaction using a modified grain size distributed (GSD) model. In GSD model, the calcium‐based particle consisted of numerous spherical grains with variable size distribution. The GSD model was modified by considering a variable diffusion coefficient of the gaseous reactant through the development of the product layer. The overall conversion over the reaction time was calculated by a mathematical modelling. The overall sorbent conversion obtained by using the modified GSD model showed better agreement with the experimental data with the average absolute deviation of 4.2 % than the results obtained using the grain model with the average absolute deviation 9.4 %. In the modified GSD model, the physical microstructure of the sorbent particle changes due to the molar volume expansion during the carbonation reaction. The model also predicted accurately the change of particle structural properties such as porosity, molar density, and specific surface area during the carbonation reaction. [ABSTRACT FROM AUTHOR]