Surface Diffusion Research Articles

Advancing service life estimation of reinforced concrete considering the coupling effects of multiple factors: Hybridized physical testing and machine learning approach

Chloride-induced corrosion is the primary factor that significantly impacts the service life of reinforced concrete structures. Therefore, it is crucial to investigate the transportation behavior of chloride ions within concrete structures to accurately estimate their service life. Previous studies have mostly examined the diffusion of chloride ions through physical tests on concrete specimens. Some data-driven models have also been developed to predict the chloride ion concentration at different depths in concrete structures. However, these prediction models often considered random factors in materials and the environment separately, neglecting their coupled effects. As a result, there can be a significant disparity between the predicted results and the actual test outcomes. To achieve a more precise evaluation of the service life, this study conducted a physical test to investigate the diffusion behavior of chloride ions in plain concrete specimens. Factors such as water-cement ratio (W/C), coarse aggregate volume fraction (v) (ratios of the mass of coarse aggregates to the total mass of concrete specimen), ratios of environmental temperature to maintenance standard temperature (T/T0), ratios of environmental humidity to maintenance humidity (h/h0), and ratios of exposure time to maintenance time (t/t0) were considered in the test. Based on the test results, machine learning approaches were employed to determine the influence of each factor on the chloride diffusion coefficient (D) and surface chloride concentration (Cs). Subsequently, a prediction model was developed using the second Fick's law, with the chloride ion concentration at each depth as the output and the aforementioned factors as the inputs. Furthermore, by analyzing the above results, the study examined the impacts of various factors on the service life of reinforced concrete structures. The findings indicate that W/C and v are the most significant factors affecting D and Cs. As W/C and T/T0 increase, both D and Cs also increase. Conversely, the volume fraction of coarse aggregate has a hindering effect on the diffusion of chloride ions in concrete structures. Additionally, the study explored the effect of each input factor on the service life of reinforced concrete structures considering the effect of the above factors. Overall, these findings provide valuable insights into improving the accuracy of estimating the service life of reinforced concrete structures by considering the coupled effects of materials and environmental factors.

On De Gennes narrowing of fluids confined at the molecular scale in nanoporous materials.

Beyond well-documented confinement and surface effects arising from the large internal surface and severely confining porosity of nanoporous hosts, the transport of nanoconfined fluids remains puzzling in many aspects. With striking examples such as memory, i.e., non-viscous effects, intermittent dynamics, and surface barriers, the dynamics of fluids in nanoconfinement challenge classical formalisms (e.g., random walk, viscous/advective transport)-especially for molecular pore sizes. In this context, while molecular frameworks such as intermittent Brownian motion, free volume theory, and surface diffusion are available to describe the self-diffusion of a molecularly confined fluid, a microscopic theory for collective diffusion (i.e., permeability), which characterizes the flow induced by a thermodynamic gradient, is lacking. Here, to fill this knowledge gap, we invoke the concept of "De Gennes narrowing," which relates the wavevector-dependent collective diffusivity D0(q) to the fluid structure factor S(q). First, using molecular simulation for a simple yet representative fluid confined in a prototypical solid (zeolite), we unravel an essential coupling between the wavevector-dependent collective diffusivity and the structural ordering imposed on the fluid by the crystalline nanoporous host. Second, despite this complex interplay with marked Bragg peaks in the fluid structure, the fluid collective dynamics is shown to be accurately described through De Gennes narrowing. Moreover, in contrast to the bulk fluid, the departure from De Gennes narrowing for the confined fluid in the macroscopic limit remains small as the fluid/solid interactions in severe confinement screen collective effects and, hence, weaken the wavevector dependence of collective transport.

Ta/Nb doping motivating cubic phase stability and CO2 tolerance of Sr2Co1.6Fe0.4O6-δ double perovskite for high-performing SOFC cathode

Developing cathodes that are both phase-stable and tolerant to carbon dioxide (CO2) is a crucial and challenging task for solid-oxide fuel cells (SOFCs) operating at reduced temperatures. The activity of oxygen reduction reaction (ORR) in SOFC cathodes is typically influenced by factors such as geometric features and oxygen vacancies. In this study, new and robust cathodes for SOFCs, Sr2Co1.5Fe0.4Ta0.1O5+δ (SCFT) and Sr2Co1.5Fe0.4Nb0.1O5+δ (SCFN) are developed by doping a small amount of niobium (Nb) and tantalum (Ta) into Sr2Co1.6Fe0.4O5+δ (SCF) using a simple solid-state reaction technique. The effects of Nb/Ta doping on the crystal structure, oxygen vacancies, electrical conductivity, and electrochemical properties of SCFT and SCFN are investigated. The results reveal that these materials possess a fully cubic structure in the Fm-3m space group, with improved oxygen vacancy and electrical conductivity. They also exhibit good chemical compatibility with electrolytes at 1100 °C for 8 h and remain thermally stable when exposed to air and CO2 at 700 °C, without any additional phase formation. The area-specific resistance (ASR) of the SCFT cathode is found to be only 0.06 Ω cm2, whereas the SCFN cathode has an ASR of 0.10 Ω cm2. The superior performance of SCFT can be attributed to the higher oxygen vacancy, which enhances oxygen surface exchange kinetics and diffusivity compared to SCFN. When tested in a single cell using humidified H2 as the fuel and ambient air as the oxidant, the SCFT cathode achieves a power density of 656 mW cm−2 at 700 °C, while the SCFN cathode reaches 559 mW cm−2, indicating the potential of SCFT as a promising cathode material for SOFCs. The excellent performance of these materials can be attributed to their mixed electronic-ionic conduction properties, unique structural features, and high observed oxygen vacancy, which contribute to their remarkable electronic conductivity and significant ionic mobility.

Beyond Constant Current: Origin of Pulse-Induced Activation in Phase-Transforming Battery Electrodes.

Mechanistic understanding of phase transformation dynamics during battery charging and discharging is crucial toward rationally improving intercalation electrodes. Most studies focus on constant-current conditions. However, in real battery operation, such as in electric vehicles during discharge, the current is rarely constant. In this work we study current pulsing in LiXFePO4 (LFP), a model and technologically important phase-transforming electrode. A current-pulse activation effect has been observed in LFP, which decreases the overpotential by up to ∼70% after a short, high-rate pulse. This effect persists for hours or even days. Using scanning transmission X-ray microscopy and operando X-ray diffraction, we link this long-lived activation effect to a pulse-induced electrode homogenization on both the intra- and interparticle length scales, i.e., within and between particles. Many-particle phase-field simulations explain how such pulse-induced homogeneity contributes to the decreased electrode overpotential. Specifically, we correlate the extent and duration of this activation to lithium surface diffusivity and the magnitude of the current pulse. This work directly links the transient electrode-level electrochemistry to the underlying phase transformation and explains the critical effect of current pulses on phase separation, with significant implication on both battery round-trip efficiency and cycle life. More broadly, the mechanisms revealed here likely extend to other phase-separating electrodes, such as graphite.

Exploring oversampling in RBF least-squares collocation method of lines for surface diffusion

Exploring oversampling in RBF least-squares collocation method of lines for surface diffusion

Nanoporous gold with microporous structure prepared by sodium dodecyl sulfate-mediated electrochemical dealloying

Nanoporous gold (NPG) is a promising catalytic material for the oxidation of CO and methanol applications. However, NPGs are prone to extensive macroscopic cracking that often decrease mechanic properties of NPGs and depresses their catalytic action. To produce crack-free NPG with an ultra-finer porosity in room temperature, the anionic surfactant sodium dodecyl sulfate (SDS) was added in electrochemical dealloying process. SDS has the effect of reducing the surface diffusion of gold which hinder the initial coarsening of ligaments and prevents interior silver atoms from being exposed and dissolved. As a result, the pore and ligment size are finer, but higher residual silver of NPG samples. NPG with pore size down to 2 nm and the ligament 4.0 nm was successfully fabricated with 13.32 mM SDS in perchloric acid solution. The surface diffusion coefficient of Au atoms was 1.6 × 10−24 m2·s−1, nearly 3 orders of magnitude smaller than that of Au atoms in the absence of SDS (2.8 × 10−21 m2·s−1). Nanoindentation results demonstrated that high residual silver content made NPG samples harder and stiffer，the specific surface areas of NPG with 6.66 mM SDS was 190 m2 g−1 by BET. This work provided very important clues on how to control the crack free ultrafine nanoporous structure of other materials.

Morphological Relaxation of Strained Epitaxial Films for Stripe‐Geometry Devices

AbstractOne of the major issues when reducing the channel length in strained transistors is the stress relaxation that significantly degrades the carriers mobility. A new morphological evolution is reported here, describing the relaxation of a strained epitaxial film deposited on a pattern characterized by stripe geometry, both paradigmatic of two‐dimensional (2D) like systems, and characteristic of many devices. The thermodynamic surface diffusion framework accounting for elasticity and capillarity is investigated. The former is solved in two dimensions thanks to the Airy formalism. The resulting dynamical Schrödinger‐like equation governing the film shape evolution is then solved thanks to a decomposition on eigenmodes. It reveals different developments depending upon the system's geometric parameters and the time scale. Mass transfer occurs toward the relaxed areas and creates a ridge at the nanolayers edges, controlled by the geometry and the scale of the structure. These results allow to refine the potential control of electronic properties via the geometry of a system.

A Dynamic Permeability Model in Shale Matrix after Hydraulic Fracturing: Considering Mineral and Pore Size Distribution, Dynamic Gas Entrapment and Variation in Poromechanics

Traditional research on apparent permeability in shale reservoirs has mainly focussed on effects such as poromechanics and porosity-assisted adsorption layers. However, for a more realistic representation of field conditions, a comprehensive multi-scale and multi-flowing mechanism model, considering the fracturing process, has not been thoroughly explored. To address this research gap, this study introduces an innovative workflow for dynamic permeability assessment. Initially, an accurate description of the pore size distribution (PSD) within three major mineral types in shale is developed using focussed ion beam-scanning electron microscopy (FIB-SEM) and nuclear magnetic resonance (NMR) data. Subsequently, an apparent permeability model is established by combining the PSD data, leading to the derivation of dynamic permeability. Finally, the PSD-related dynamic permeability model is refined by incorporating the effects of imbibition resulting from the fracturing process preceding shale gas production. The developed dynamic permeability model varies with pore and fracture pressures in the shale reservoir. The fracturing process induces water blockage, water-film formation, and water-bridging phenomena in shale, requiring additional pressure inputs to counteract capillary effects in hydrophilic minerals in shale, But also increases the overall permeability from increasing permeability at larger scale pores. Unlike traditional reservoirs, the production process commences when the fracture is depleted to 1–2 MPa exceeds the pore pressure, facilitated by the high concentration of hydrophobic organic matter pores in shale, this phenomenon explains the gas production at the intial production stage. The reduction in adsorption-layer thickness resulting from fracturing impacts permeability on a nano-scale by diminishing surface diffusion and the corresponding slip flow of gas. this phenomenon increases viscous-flow permeability from enlarged flow spacing, but the increased viscous flow does not fully offset the reduction caused by adsorbed-gas diffusion and slip flow. In addition to the phenomena arising from various field conditions, PSD in shale emerges as a crucial factor in determining dynamic permeability. Furthermore, considering the same PSD in shale, under identical pore spacing, the shape factor of slit-like clay minerals significantly influences overall permeability characteristics, much more slit-shaped pores(higher shape factor) reduce the overall permeability. The dynamic permeability-assisted embedded discrete fracture model (EDFM) showed higher accuracy in predicting shale gas production compared to the original model.

The surface diffusivity of nanoparticles physically adsorbed at a solid-liquid interface.

This work proposes an analytical model considering the effects of hydrodynamic drag and kinetic barriers induced by liquid solvation forces to predict the translational diffusivity of a nanoparticle on an adsorbing surface. Small nanoparticles physically adsorbed to a well-wetted surface can retain significant in-plane mobility through thermally activated stick-slip motion, which can result in surface diffusivities comparable to the bulk diffusivity due to free-space Brownian motion. Theoretical analysis and molecular dynamics simulations in this work show that the surface diffusivity is enhanced when (i) the Hamaker constant is smaller than a critical value prescribed by the interfacial surface energy and particle dimensions, and (ii) the nanoparticle is adsorbed at specific metastable separations of molecular dimensions away from the wall. Understanding and controlling this phenomenon can have significant implications for technical applications involving mass, charge, or energy transport by nanomaterials dispersed in liquids under micro/nanoscale confinement, such as membrane-based separation and ultrafiltration, surface electrochemistry and catalysis, and interfacial self-assembly.

Sintering behavior and activation energy calculation of nanoparticulate Fe3O4: a molecular dynamics simulation

This study employs molecular dynamic simulations to investigate the sintering mechanisms of Fe3O4 nanoparticles and determine the sintering activation energy. The melting temperature has been calculated using atomic volume to verify the accuracy of this EAM function and its parameters. Neck width has been defined to demonstrate the sintering degree under different temperatures, from 1373 K to 1773 K. Following sections divide the whole evolution into three mechanisms: surface diffusion, grain boundary diffusion and viscous flow according to the atomic migration vector. Finally, the sintering activation energy has been figured out based on the neck diameter ratio which later has been employed to predict the neck growth curve at 1523 K. Therefore, this investigation reveals the sintering mechanisms and introduces a method to predict the growth rate using activation energy.

Wafer-scale synthesis of two-dimensional ultrathin films.

Two-dimensional (2D) materials, consisting of atomically thin layered crystals, have attracted tremendous interest due to their outstanding intrinsic properties and diverse applications in electronics, optoelectronics, and catalysis. The large-scale growth of high-quality ultrathin 2D films and their utilization in the facile fabrication of devices, easily adoptable in industrial applications, have been extensively sought after during the last decade; however, it remains a challenge to achieve these goals. Herein, we introduce three key concepts: (i) the microwave assisted quick (∼1 min) synthesis of wafer-scale (6-inch) anisotropic conducting ultrathin (∼1 nm) amorphous carbon and 2D semiconducting metal chalcogenide atomically thin films, (ii) a polymer-assisted deposition process for the synthesis of wafer-scale (6-inch) 2D metal chalcogenide and pyrolyzed carbon thin films, and (iii) the surface diffusion and epitaxial self-planarization induced synthesis of wafer-scale (2-inch) single crystal 2D binary and large-grain 2D ferromagnetic ternary metal chalcogenide thin films. The proposed synthesis concepts can pave a new way for the manufacture of wafer-scale high quality 2D ultrathin films and their utilization in the facile fabrication of devices.

FRACTAL ANALYSIS FOR PERMEABILITY OF MULTIPLE SHALE GAS TRANSPORT MECHANISMS IN ROUGHENED TREE-LIKE NETWORKS

In this work, a new gas transport model for shale reservoirs is constructed by embedding randomly distributed roughened tree-like bifurcation networks into the matrix porous medium. We constructed apparent permeability models for different shale gas flow mechanisms based on fractal theory, taking into account the effects of relative roughness and surface diffusion. The effects of bifurcation structure parameters as well as shale gas parameters on different apparent permeabilities are systematically analyzed. It is found that the permeability generally shows a decreasing trend with the increase in pore pressure, but the effect on viscous flow is inconsiderable. In addition, larger porosity, fractal dimension and bifurcation levels lead to increased permeability of different mechanisms. Whereas, the increase in the bifurcation levels implies a greater flow resistance, resulting in a decreased permeability. In addition, The relative roughness hinders the development of total permeability but favors surface diffusion permeability. Moreover, larger length ratios and diameter ratios are beneficial to the shale gas flow.

Development of an easy to solve phenomenological model including pore and surface diffusions applied to batch adsorption

This work introduces the Quadratic Pore Volume and Surface Diffusional Model (QPVSDM), which incorporates quadratic functions to approximate the average intraparticle concentration profiles of adsorption processes. It was developed to batch adsorption operations assuming instantaneous reaction (local equilibrium given by the Langmuir isotherm), external mass transfer, and intraparticle pore and surface diffusions. It consists of an ordinary differential equation that is simple to solve numerically. Experimental data from distinct real systems reported in the literature were reproduced by the QPVSDM (R2 > 0.92), which was compared with the Pore Volume and Surface Diffusional Model (PVSDM) consisting of a partial differential equation system. Both models reached the exact same equilibrium condition successfully. To encourage the testing and application of the QPVSDM, as well as to compare it with the PVSDM, an easy-to-use executable program written in python is available at GitHub platform.

Oxidation of fine aluminum particles: thermally induced transformations in particle shells and kinetics of oxide nucleation.

This paper investigates the process of oxidation of fine aluminum powder, consisting of spherical Al particles of 'metal core/oxide shell' type, when heated in air at temperatures below 550 °C. The highly dispersed aluminum powder 'Alex' used in this work (particle size: 0.05-1.5 μm and number average particle diameter (DN): 0.11 μm) was produced by electric explosion of a thin Al wire in argon with subsequent passivation in an oxygen-containing atmosphere. For the first time, the influence of the particle size on the oxidation process has been identified. During the reaction, individual γ-Al2O3 oxide nuclei grow at the surface of Al particles with diameters less than 300 nm without laterally overlapping to form a protective passivating layer, as typically occurs during the oxidation of micron-sized particles or bulk metal. The localization of γ-Al2O3 nuclei is determined by the regions where peeling of the primary amorphous oxide film from the surface of the metal core of an Al particle occurs due to the thermal decomposition of aluminum hydroxides (T ≈ 350 °C) present within the particle shells. A significant increase in the contributions of the following factors leads to a high oxidation rate: the diffusion within the disordered structure of a particle core and the surface diffusion of cations (Ea = 80.6 ± 5.3 kJ mol-1, 400-450 °C), the surface and grain boundary diffusion of oxygen during the growth of γ-Al2O3 crystallites (Ea = 108.3 ± 11.2 kJ mol-1, 470-500 °C) and the surface and grain boundary transport of anions through an amorphous and underlying nanocrystalline oxide layer with a constant thickness (Ea = 205.1 ± 8.6 kJ mol-1, 520-550 °C). The results obtained make it possible to expand the theoretical understanding of the manifestations of the size effect in solid-phase reactions and take into account its influence in practice.

Wafer scale growth of single crystal two-dimensional van der Waals materials.

Two-dimensional (2D) van der Waals (vdW) materials, including graphene, hexagonal boron nitride (hBN), and metal dichalcogenides (MCs), form the basis of modern electronics and optoelectronics due to their unique electronic structure, chemical activity, and mechanical strength. Despite many proof-of-concept demonstrations so far, to fully realize their large-scale practical applications, especially in devices, wafer-scale single crystal atomically thin highly uniform films are indispensable. In this minireview, we present an overview on the strategies and highlight recent significant advances toward the synthesis of wafer-scale single crystal graphene, hBN, and MC 2D thin films. Currently, there are five distinct routes to synthesize wafer-scale single crystal 2D vdW thin films: (i) nucleation-controlled growth by suppressing the nucleation density, (ii) unidirectional alignment of multiple epitaxial nuclei and their seamless coalescence, (iii) self-collimation of randomly oriented grains on a molten metal, (iv) surface diffusion and epitaxial self-planarization and (v) seed-mediated 2D vertical epitaxy. Finally, the challenges that need to be addressed in future studies have also been described.

Assimilating experimental data of a mean three-dimensional separated flow using physics-informed neural networks

In this article, we address the capabilities of physics-informed neural networks (PINNs) in assimilating the experimentally acquired mean flow of a turbulent separation bubble occurring in a diffuser test section. The training database contains discrete mean pressure and wall shear-stress fields measured on the diffuser surface as well as three-component velocity vectors obtained with particle image velocimetry throughout the volumetric flow domain. Imperfections arise from the measurement uncertainty and the inability to acquire velocity data in the near-wall region. We show that the PINN methodology is suited to handle both of these issues thanks to the incorporation of the underlying physics that, in the present study, are taken into account by minimizing residuals of the three-dimensional incompressible Reynolds-averaged Navier–Stokes equations. As a result, measurement errors are rectified and near-wall velocity profiles are predicted reliably. The latter benefits from the incorporation of wall shear-stress data into the PINN training, which has not been attempted so far to the best of our knowledge. In addition to demonstrating the influence of this novel loss term, we provide a three-dimensional, highly resolved, and differentiable model of a separating and reattaching flow that can be readily used in future studies.

Significance of slow vital capacity, difference between slow and forced vital capacity, ratio of FEV1/SVC with increasing age and BMI in healthy males and females

Background: The slow vital capacity (SVC), forced vital capacity (FVC) difference, and forced expiratory volume in one second (FEV1)/SVC ratio are crucial for understanding respiratory health, especially in mild airway obstruction. These parameters are more reliable than traditional measures and are influenced by age and body mass index (BMI). Investigating their relationship can improve diagnostic accuracy and health-care interventions. Aims and Objectives: (i) To record peak expiratory flow rate (PEFR), FVC, FEV1 of expiration, FEV1/FVC ratio, forced expiratory flow rate (FEF25-75%), mean forced expiratory flow rate from 0.2 to 1.2 l of volume expired (FEF.2-1.2), SVC, and find the difference between SVC and FVC, ratio of FEV1/SVC. (ii) To correlate SVC, SVC-FVC, FEV1/SVC, and other pulmonary function tests (PFTs) with age, gender, and BMI emphasizing their importance in detecting airway obstruction. (iii) To assess these known indicators of airflow obstruction in healthy individuals to gain knowledge of changing lung health with respect to advancing age, gender, and BMI. Materials and Methods: The study included 200 individuals, comprising both men and women aged between 18 and 60 years, who were in good health. The sample was divided into five age groups, and participants were classified into categories of underweight, normal weight, overweight, and obese based on their BMI. Standard procedures were employed to record anthropometric measurements. PEFR was measured using Wright’s peak flow meter, whereas FVC, FEV1, FEV1/FVC ratio, forced expiratory flow between 25 and 75% of FVC (FEF25-75%), forced expiratory flow at 2-1.2 l (FEF.2-1.2), and SVC were assessed using an expirograph (Helios 401, RMS, India). Adequate statistical analysis was conducted on the gathered data. Results: There was a highly significant difference in the means of SVC, SVC-FVC, FEV1/SVC, and other PFTs (P < 0.000) over the five age groups by ANOVA and a significant difference between younger and older age groups analyzed by post hoc test. It also showed a highly significant difference in the mean values of SVC, FEV1/SVC, and other PFTs over the categories of BMI and a significant difference between normal and obese groups by multiple comparisons. A small increase in mean values of SVC-FVC was seen in overweight, obese, and underweight compared to the normal BMI group. Females showed reduced mean values of SVC, FEV1/SVC, and other PFTs compared to males. (P < 0.000). The mean value of SVC-FVC in females is greater than in males (P < 0.01), which suggest that the tendency for airway obstruction may be greater in women compared to men due to smaller airway diameter and diffusion surface. PEFR, FVC, FEV1, FEV1/FVC, FEF25-75%, FEF.2-1.2, SVC, and FEV1/SVC were negatively correlated with age. SVC-FVC was positively correlated with age (r = 0.338, P < 0.000). There was a negative correlation between PEFR, FVC, FEV1, FEF25-75%, FEF.2-1.2, SVC, and BMI. Conclusions: PFT serves as a crucial diagnostic tool in assessing respiratory health, with parameters such as FVC and FEV1 commonly utilized. However, SVC is gaining recognition for its nuanced insights into lung function. This article delves into the significance of SVC, highlights the differences between SVC and FVC, and explores the relationship between FEV1/SVC ratio, age, and BMI in healthy individuals. The current research was undertaken due to a scarcity of existing studies and demonstrated that SVC, the ratio of FEV1/SVC, and other PFTs diminish with age progression and increasing BMI. In addition, females exhibited decreased lung function, with a greater disparity between SVC and FVC than males.

High areal-capacitance based extremely stable flexible supercapacitors using binder-free exfoliated graphite paper electrode

The highly porous and binder-free flexible paper electrodes can enhance the specific capacitance of symmetric supercapacitors (SCs) due to their large surface and effective ion diffusion pathways. We synthesized the exfoliated graphite (ExG) by the thermal exfoliation method of chemically treated graphite flakes and compressed it into a paper-like thin sheet (binder-free) of ∼0.15 mm thickness. The coin cell SCs with copper (Cu) and stainless steel (SS) as current collectors have been fabricated for the electrochemical measurement. The cyclic voltammetry and galvanostatic charge/discharge measurements are investigated at various scan rates and current densities. The SCs with Cu foil as a current collector perform better than SS-based SCs. The Cu current collector-based SCs showed a specific capacitance of 37.08 mF cm−2, whereas it was ∼29.98 mF cm−2 for SS-based SCs at a 0.01 V s−1 scan rate across a 0–0.6 V potential window. Approximately no degradation in charge storage capacity for more than 15 000 cycles at 0.1 V s−1 shows the ultra-stability of the flexible ExG-based binder-free electrodes. A digital watch is powered using the fabricated pouch cell supercapacitor with copper-based current collectors to show the potential of SCs.

Time-resolved force microscopy using the delay-time modulation method

We developed a time-resolved force microscopy technique by integrating atomic force microscopy using a tuning-fork-type cantilever with the delay time modulation method for optical pump-probe light. We successfully measured the dynamics of surface recombination and diffusion of photoexcited carriers in bulk WSe2, which is challenging owing to the effect of the tunneling current in time-resolved scanning tunneling microscopy. The obtained results were comprehensively explained with the model based on the dipole-dipole interaction induced by photo illumination.

Fast calculation of radiative heat transfer coefficient between diffuse and non-diffuse surfaces

Fast calculation of radiative heat transfer coefficient between diffuse and non-diffuse surfaces