Role In Mass Transport Research Articles

Role of Mass Transport in Electrochemical CO2 Reduction to Methanol Using Immobilized Cobalt Phthalocyanine.

Electrochemical CO2 reduction (CO2R) using heterogenized molecular catalysts usually yields 2-electron reduction products (CO, formate). Recently, it has been reported that certain preparations of immobilized cobalt phthalocyanine (CoPc) produce methanol (MeOH), a 6-electron reduction product. Here, we demonstrate the significant role of intermediate mass transport in CoPc selectivity to methanol. We first developed a simple, physically mixed, polymer (and polyfluoroalkyl, PFAS)-free preparation of CoPc on multiwalled carbon nanotubes (MWCNTs) which can be integrated onto Au electrodes using a poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) adhesion layer. After optimization of catalyst preparation and loading, methanol Faradaic efficiencies and partial current densities of 36% (±3%) and 3.8 (±0.5) mA cm-2, respectively, are achieved in the CO2-saturated aqueous electrolyte. The electrolyte flow rate has a large effect. A linear flow velocity of 8.5 cm/min produces the highest MeOH selectivity, with higher flow rates increasing CO selectivity and lower flow rates increasing the hydrogen evolution reaction, suggesting that CO is an unbound intermediate. Using a continuum multiphysics model assuming CO is the intermediate, we show qualitative agreement with the optimal inlet flow rate. Polymer binders were not required to achieve a high Faradaic efficiency for methanol using CoPc and MWCNTs. We also investigated the role of formaldehyde as an intermediate and the role of strain, but definitive conclusions could not be established.

Impact of geometric features of impermeable discrete bedform on hyporheic exchange

The bedform-driven hyporheic exchange plays a crucial role in mass transport within natural aquatic ecosystems like streams and rivers. This study aimed to unveil the impact of geometric features of impermeable discrete bedforms on hyporheic exchange by experimentally measuring quantitative hyporheic exchange flux data and variation characteristics in an annual flume. The experiments encompassed diverse conditions involving the ratio of bedform wavelength (λ) to wave height (h) and relative submergence. The study also analyzed the dependence of the effective diffusion coefficient on the geometric characteristics of bedform composition elements. The experimental results showed that, in comparison to a permeable flat bed, the presence of an impermeable discrete bedform tended to either attenuate or enhance hyporheic exchange, contingent on the geometric characteristics of bedform composition elements. The hyporheic exchange flux exhibited an initially increase followed by a decrease with increasing λ/h, with turbulence penetration emerging as the dominant mechanism governing hyporheic exchange for cases with relatively denser bedform composition elements (e.g., λ/h = 4.0). The effective diffusion coefficient peaked at λ/h around 6.0–8.0, owing to a significant augmentation in the relative contribution of pumping exchange to gross hyporheic exchange. Furthermore, the hyporheic exchange intensity generally increased with decreasing relative submergence, primarily attributed to the augmented relative contribution of pumping exchange to gross hyporheic exchange.

Flow-induced diffusion in a packed lattice of squirmers

Mass transport in suspensions of swimming microorganisms is one of the most important factors for the colonisation and growth of microorganisms. Hydrodynamic interactions among swimming microorganisms play an important role in mass transport, especially in highly concentrated suspensions. To elucidate the influence of highly concentrated cells on mass transport, we numerically simulated mass transport in lattices of squirmers that were fixed in space and oriented in the same direction. The effects of different volume fractions, Péclet numbers ( $Pe$ ) and lattice configurations on mass transport were quantified by tracking Lagrangian material points that move with background flow with Brownian diffusivity. Although the flow field became periodic in space and each streamline basically extended in one direction, the motion of tracer particles became diffusive over long durations due to Brownian motion and cross-flows. Flow-induced diffusion was anisotropic and significantly enhanced over Brownian diffusion in the longitudinal direction. We also investigated mass transport in random configurations of squirmers to reproduce more general conditions. Similar enhanced diffusion was also observed in the random configurations, indicating that the flow-induced diffusion appears regardless of the configurations. The present flow-induced diffusion did not follow $Pe$ dependency of the conventional Taylor dispersion due to the cross-flows. The time and velocity scales were proposed, which enabled us to predict the flow-induced diffusivity from the data of the flow field and Brownian diffusivity without solving the mass conservation equation. The findings reported here improve our understanding of the transport phenomena in packed suspensions of swimming microorganisms.

A theoretical examination of localized nanoscale induction by single domain magnetic particles

Single domain magnetic nanoparticles are increasingly investigated as actuators of biological and chemical processes that respond to externally applied magnetic fields. Although their localized effects have often been attributed to nanoscale heating, recent experimental evidence suggests the need to consider alternative hypotheses. Here, using the stochastic Landau–Lifshitz–Gilbert equation and finite element modeling, we investigate and critically examine an alternative hypothesis that localized effects may instead involve the induced electric fields arising from the dynamical behavior of individual single domain magnetic particles. We model the magnetization dynamics and resulting induced electric fields for two relevant and distinct cases of magnetic nanoparticles in alternating magnetic fields: (1) magnetogenetic stimulation of channel proteins associated with ferritin and (2) catalytic enhancement of electrochemical hydrolysis. For the first case, while the local electric fields that ferritin generates are shown to be insufficient to perturb the transmembrane potential, fields on the surface of its mineral core on the order of 102–103 V/m may play a more plausible role in mass transport of iron ions that indirectly lead to stimulation. For the second case, our model indicates that the highest interfacial electric field strengths, on the order of 102 V/m, are expected during reversal events. Thus, nanoparticles well suited for hysteresis heating can also act as intermittent sources of localized induced electric fields in response to an alternating applied field. Finally, we compare the magnitude and timescale of these electric fields to technologically relevant phenomena, showing that they are generally weaker and faster.

Voltammetry of Carbon Nanotubes and the Limitations of Particle-Modified Electrodes: Are Carbon Nanotubes Electrocatalytic?

The use of carbon nanotubes (CNTs) as electrocatalysts is summarized; the limitations of using voltammetry based on CNT-modified electrodes is explained; and the role of mass transport, as well as electrode kinetics, with respect to dictating the voltammetric responses is discussed. The use of single-entity electrochemistry to at least complement, if not replace, ensemble voltammetry is advocated along with other caveats, notably purity, with respect to CNT voltammetry.

Role of Mass Transport in the Deposition, Growth, and Transformation of Calcium Carbonate on Surfaces at High Supersaturation.

We demonstrate how combined in-situ measurements and finite element method modeling can provide new insight into the relative contribution of mass transport to the growth of calcium carbonate on two model surfaces, glass and gold, under high-supersaturation conditions relevant to surface scaling. An impinging jet-radial flow system is used to create a high-supersaturated solution at the inlet of different cells: an optical microscope cell presenting a glass surface for deposition and quartz crystal microbalance (QCM) and in-situ IR spectroscopy cells, both presenting a gold surface. The approach described is quantitative due to the well-defined mass transport, and both time-lapse optical microscopy images and QCM data are analyzed to provide information on the growth kinetics of the calcite crystals. Initially, amorphous calcium carbonate (ACC), formed in solution, dominates the deposition process. At longer times, the growth of calcite is more significant and, on glass, is observed to consume ACC from the surface, leading to surface regions depleted of ACC developing around calcite microcrystals. On Au, the mass increase becomes linear with time in this region. Taken together, these microscopic and macroscopic measurements demonstrate that calcite growth has a significant component of mass transport control at high supersaturation. Finite element method (FEM) simulations of mass-transport-limited crystal growth support the strong mass transport contribution to the growth kinetics and further suggest that the observed growth must be sustained by more than just the Ca2+ and CO32– in solution, with dissolution/direct attachment of ACC and/or ion pairs also contributing to the growth process.

History of the solar nebula from meteorite paleomagnetism.

We review recent advances in our understanding of magnetism in the solar nebula and protoplanetary disks (PPDs). We discuss the implications of theory, meteorite measurements, and astronomical observations for planetary formation and nebular evolution. Paleomagnetic measurements indicate the presence of fields of 0.54 ± 0.21 G at ~1 to 3 astronomical units (AU) from the Sun and ≳0.06 G at 3 to 7 AU until >1.22 and >2.51 million years (Ma) after solar system formation, respectively. These intensities are consistent with those predicted to enable typical astronomically observed protostellar accretion rates of ~10-8 M ⊙year-1, suggesting that magnetism played a central role in mass transport in PPDs. Paleomagnetic studies also indicate fields <0.006 G and <0.003 G in the inner and outer solar system by 3.94 and 4.89 Ma, respectively, consistent with the nebular gas having dispersed by this time. This is similar to the observed lifetimes of extrasolar protoplanetary disks.

A Hierarchically Porous Carbazole‐Containing Polymer from [p‐(4‐N‐carbazole)‐C6H4SiO1.5]8 to Load Imidazole for Efficient Proton Conductivity over a Wide Temperature Range

AbstractThe practical application of vehicle fuel cell technology requires solid electrolytes possess not only high proton conductivity, but also stable proton transport channel with a wide operating temperature window. In addition, hierarchically porous materials play a key role in mass transport, such as the concentration and mobility of proton carries. Herein, we present a novel strategy to target this goal. A new hierarchically porous carbazole‐containing polymer (ECUT‐PP) was reported via mechanochemical grinding of [p‐(4‐N‐carbazole)C6H4SiO1.5]8 and anhydrous FeCl3 catalyst at room temperature. Due to the synergistic effects of hierarchical pores, imidazole loaded proton conductor (Im@ECUT‐PP) presents efficient conductivity from 0 °C (2.39×10−7 S/cm) to 200 °C (6.03×10−4 S/cm) under the anhydrous conditions, and its highest temperature is higher than other imidazole‐loaded conductors.

Molecular dynamics characterization of the water-methane, ethane, and propane gas mixture interfaces

The co-existing natural gas and water bulk phases arise in a wide range of technological and environmental processes. The liquid-gas mixture is separated by an interface which plays a crucial role in mass transport across the phases. In this work, we use the molecular dynamics (MD) technique to investigate the molecular organization, solubility, density, and compositions of natural gas-water interfaces. We apply the NPNAT ensemble which is an appropriate statistical methodology to dodge the defects of the conventional ensembles in surface physics, and ultimately, to characterize the interfacial thermodynamics and mechanics. High interfacial density, excess, and radial pair distribution function of the gas components in order of propane, ethane, and methane, respectively, suggest the interfacial adsorption as per favorable interactions with a dense hydrogen bonding network near the surface in the liquid water phase. It is also found that the gas components solubility is negligible. Nevertheless, methane molecules present in natural gas can further dissolve in water, comparing to pure methane. We lastly conclude a heterogeneous formation of structure II hydrate from the adsorption and composition results. Moreover, we systematically increase the pressure from 1 MPa to 50 MPa and the temperature from 273.15 K to 303.15 K to calculate the interfacial tension using the mechanical approach. We observe a decrease in the interfacial tension along with an increase in both pressure and temperature. Given the remarkable hydrocarbon adsorption acting as a surfactant, this interfacial tension attenuation is more highlighted in a natural gas-water system compared to the pure liquid-vapor water or water-pure methane systems at the same temperature and pressure. We employ MD combined with fundamental thermodynamics to predict the interfacial tension via its independent relations with pressure and temperature which agrees with the classical scaling laws, namely, the Eötvös rule. The corresponding molecular mechanisms captured by the microscopic and macroscopic properties at the interfacial regions prospectively demonstrate a sensitivity to both temperature and pressure, which contributes to the developing understanding and applications of the imperative water-natural gas interface.

Study on coalescence dynamics of unequal-sized microbubbles captive on solid substrate

The dynamics of bubble coalescence are of importance for a number of industrial processes, in which the size inequality of the parent bubbles plays a significant role in mass transport, topological change and overall motion. In this study, coalescence of unequal-sized microbubbles captive on a solid substrate was observed from cross-section view using synchrotron high-speed imaging technique and a microfluidic gas generation device. The bridging neck growth and surface wave propagation at the early stage of coalescence were investigated by experimental and numerical methods. The results show that theoretical half-power-law of neck growth rate is still valid when viscous effect is neglected. However, the inertial-capillary time scale is associated with the initial radius of the smaller parent microbubble. The surface wave propagation rate on the larger parent microbubble is proportional to the inertial-capillary time scale.

Light- and Electric-Field-Controlled Wetting Behavior in Nanochannels for Regulating Nanoconfined Mass Transport.

Water wetting behavior in nanoconfined environments plays an important role in mass transport and signal transmission of organisms. It is valuable and challenging to investigate how water behaves in such a nanometer-scale with external stimuli, in particular with electric field and light. Unfortunately, the mechanism of hydrophobic reaction inside the nanospaces is still obscure and lacks experimental support for the current electric-field- or photoresponsive nanochannels which suffer from fragility or monofunctionality. Here, we design functionalized hydrophobic nanopores to regulate ion transport by light and electric field using azobenzene-derivatives-modified polymer nanochannels. With these addressable features, we can control the pore surface wetting behavior to switch the nanochannels between nonconducting and conducting states. Furthermore, we found these hydrophobic nanochannels are rough with a contact angle of 67.3°, making them extremely different from the familiar ones with a smooth pore surface and larger contact angles (>90°). These findings point to new opportunities for studying and manipulating water behavior in nanoconfined environments.

Interfacial wave velocity of vertical gas-liquid annular flow at different system pressures

In two-phase annular flow, the velocity of interfacial waves play a crucial role in mass transport of liquid film, radial velocity distribution of liquid film, friction pressure drop, momentum transfer of two phases and heat-transfer characteristic of liquid film. Majority of existing interfacial wave velocity predictive correlations is established by the experimental data available in literatures which are limited to near atmospheric conditions. So it is necessary to further study the accuracy and applicability of predictive correlations at intermediate and high pressure conditions. The near infrared (NIR) sensor is designed for the interfacial wave velocity measurement in this paper. Air-water annular flow experiments have been conducted at five pressure conditions (from 0.2MPa to 0.9MPa) in a stainless steel tubular test section having an inside diameter 50.0mm. A comparison of the performance of four existing predictive correlations (i.e. Kumar et al. [3] correlation, Omebere-Iyari et al. [5] correlation, Schubring et al. [8] correlation and Al-Sarkhi et al. [9] correlation) based on experimental dataset mentioned above (154 data points) is made. Comparison analysis between the correlations are made and appropriate recommendations drawn (Kumar et al. [3] correlation and Omebere-Iyari et al. [5] correlation). On the basis of the Kumar et al. [3] correlation, both the density increasing of gas core caused by entrained droplet and relative velocities of gas core and liquid film interface are considered, the structure of model is optimized reasonably, a modified wave velocity correlation which could acceptably handle the data of different system pressures is proposed. Laboratory results indicate that the mean absolute error (MAE) of the modified correlation is 5.37% and the relative deviations are within ±10% error band. By extending the data range for empirical contants fitting, the 84.98% relative error of the improved model is within ±20% error band for the all available data (authors' and literature). The improved correlation has a certain extrapolation for different system pressure and pipe diameter conditions.

A numerical shallow-water model for gravity currents for a wide range of density differences

Gravity currents with various contrasting densities play a role in mass transport in a number of geophysical situations. The ratio of the density of the current, ρc, to the density of the ambient fluid, ρa, can vary between 100 and 103. In this paper, we present a numerical method of simulating gravity currents for a wide range of ρc/ρa using a shallow-water model. In the model, the effects of varying ρc/ρa are taken into account via the front condition (i.e., factors describing the balance between the driving pressure and the ambient resistance pressure at the flow front). Previously, two types of numerical models have been proposed to solve the front condition. These are referred to here as the Boundary Condition (BC) model and the Artificial Bed (AB) model. The front condition is calculated as a boundary condition at each time step in the BC model, whereas it is calculated by setting a thin artificial bed ahead of the front in the AB model. We assessed the BC and AB models by comparing their numerical results with the analytical results for a simple case of homogeneous currents. The results from the BC model agree well with the analytical results when ρc/ρa≲102, but the model tends to overestimate the speed of the front position when rho _{mathrm {c}}/rho _{mathrm {a}}gtrsim 10^{2}. In contrast, the AB model generates good approximations of the analytical results for rho _{mathrm {c}}/rho _{mathrm {a}}gtrsim 10^{2}, given a sufficiently small artificial bed thickness, but fails to reproduce the analytical results when ρc/ρa≲102. Therefore, we propose a numerical method in which the BC model is used for currents with ρc/ρa≲102 and the AB model is used for currents with rho _{mathrm {c}}/rho _{mathrm {a}}gtrsim 10^{2}.

Computational and Experimental Analysis of Fluid Transport Through Three-Dimensional Collagen-Matrigel Hydrogels.

A preclinical testing model for cancer therapeutics that replicates in vivo physiology is needed to accurately describe drug delivery and efficacy prior to clinical trials. To develop an in vitro model of breast cancer that mimics in vivo drug/nutrient delivery as well as physiological size and bio-composition, it is essential to describe the mass transport quantitatively. The objective of the present study was to develop in vitro and computational models to measure mass transport from a perfusion system into a 3D extracellular matrix (ECM). A perfusion-flow bioreactor system was used to control and quantify the mass transport of a macromolecule within an ECM hydrogel with embedded through-channels. The material properties, fluid mechanics, and structure of the construct quantified in the in vitro model were input into, and served as validation of, the computational fluid dynamics (CFD) simulation. Results showed that advection and diffusion played a complementary role in mass transport. As the CFD simulation becomes more complex with embedded blood vessels and cancer cells, it will become more recapitulative of in vivo breast cancers. This study is a step toward development of a preclinical testing platform that will be more predictive of patient response to therapeutics than two-dimensional cell culture.

Reaction enhanced channelised fluid-flux along mid- crustal shear zone: An example from Mesoproterozoic Phulad Shear Zone, Rajasthan, India

Fluid infiltration at great depth during regional metamorphism plays a major role in mass transport and is responsible for significant rheological changes in the rock. Calc-silicate rocks of the Kajalbas area of Delhi Fold Belt, Rajasthan, are characterised by foliation parallel alternate bands of amphibole-rich and clinopyroxene–plagioclase feldspar-rich layers of varying thicknesses (mm to decimetre thick). Textural relation suggests that the amphibole grains formed from clinopyroxene and plagioclase in the late phase of regional deformation. Algebraic analysis of the reaction textures and mineral compositions was performed with the computer program C-Space to obtain the balanced chemical reactions that led to the formation of amphibole-rich bands. The computed balanced reaction is 70.74 Clinopyroxene + 27.23 Plagioclase + 22.018 H2O + 5.51 K++ 1.00 Mg2++ 27.15 Fe2+ = 22.02 Amphibole + 67.86 SiO2 aqueous + 36.42 Ca2++ 8.98 Na+. The constructed reaction suggests that aqueous fluid permeated the calc-silicate rock along mm to decimetre thick channels, metasomatized the clinopyroxene–plagioclase bearing rocks to form the amphibole-rich layers. The regional deformation presumably created the fluid channels thereby allowing the metasomatic fluid to enter the rock system. The above reaction has large negative volume change for solid phases indicating reaction-induced permeability. Thermodynamic calculations suggest that the fluid–rock interaction occurred at 665 ±05∘C and 6.6 ±0.25 kbar (corresponding to ∼20 km depth). Textural modeling integrating the textural features and balanced chemical reaction of the calc-silicate rocks of Mesoproterozoic Phulad Shear Zone thus indicate that extremely channelled fluid flow was reaction enhanced and caused major change in the rock rheology.

The role of mass transport in protein crystallization

Mass transport takes place within the mesoscopic to macroscopic scale range and plays a key role in crystal growth that may affect the result of the crystallization experiment. The influence of mass transport is different depending on the crystallization technique employed, essentially because each technique reaches supersaturation in its own unique way. In the case of batch experiments, there are some complex phenomena that take place at the interface between solutions upon mixing. These transport instabilities may drastically affect the reproducibility of crystallization experiments, and different outcomes may be obtained depending on whether or not the drop is homogenized. In diffusion experiments with aqueous solutions, evaporation leads to fascinating transport phenomena. When a drop starts to evaporate, there is an increase in concentration near the interface between the drop and the air until a nucleation event eventually takes place. Upon growth, the weight of the floating crystal overcomes the surface tension and the crystal falls to the bottom of the drop. The very growth of the crystal then triggers convective flow and inhomogeneities in supersaturation values in the drop owing to buoyancy of the lighter concentration-depleted solution surrounding the crystal. Finally, the counter-diffusion technique works if, and only if, diffusive mass transport is assured. The technique relies on the propagation of a supersaturation wave that moves across the elongated protein chamber and is the result of the coupling of reaction (crystallization) and diffusion. The goal of this review is to convince protein crystal growers that in spite of the small volume of the typical protein crystallization setup, transport plays a key role in the crystal quality, size and phase in both screening and optimization experiments.

Properties of Jupiter's magnetospheric turbulence observed by the Galileo spacecraft

AbstractIn collisionless plasmas, turbulence is thought to play an important role in mass transport and energy dissipation. Magnetic fluctuations in the Jovian magnetosphere are essential in a turbulent state. Previous studies of that turbulence have focused on the large scales using low time resolution of magnetic field data. Here we extend those studies to cover a wider range of scales by combining both low and high‐time‐resolution data of Galileo magnetometer. We use particle data from the plasma instrument and include energetic particle contributions to estimate the local plasma parameters. We obtain 11 power spectra of magnetic field in the frequency range of 10−4–1 Hz, which covers both magnetohydrodynamics and ion kinetic scales. The frequencies of the evidenced spectral breaks are found to be relatively well correlated with the characteristic scales of heavy ion. The spectral indices below and above the spectral breaks are found to be broad and cover the ranges of 0.6–1.9 and 1.7–2.5, respectively. An analysis of higher‐order statistics shows an intermittent feature of the turbulence, found to be more prominent in the plasma sheet than in the lobe. Furthermore, a statistical survey of the power of the fluctuations using low‐time‐resolution data suggests a radially varying dawn‐dusk asymmetry: the total power is larger in the duskside (dawnside) at &lt;50 RJ (&gt;80 RJ), which would reflect flow shear and global magnetospheric activity.

Environmental controls and geomorphic importance of a high‐magnitude/low‐frequency snow avalanche event in bødalen, nordfjord, western norway

Snow avalanches are common phenomena in western orway. During the winter–spring period 2011/2012 an extreme snow avalanche occurred within the upper valley part of a steep and glacier‐connected mountain catchment (ødalen) in western orway. Compared with annually occurring regular snow avalanches, so‐called ‘extreme snow avalanche events’ are more difficult to monitor and to study as they are characterized by recurrence intervals often longer than a decade. Morphometric and meteorological controls of a high‐magnitude/low‐frequency snow avalanche event, its geomorphic effects as well as its related relative role in mass transport compared with the annually monitored snow avalanche activity within the ødalen catchment were explored. Maximum values of snow height, velocity and pressure were predicted by applying a numerical run‐out simulation. The formation of this snow avalanche resulted from the combination of extraordinary meteorological conditions and a favourable morphometric setting of the source area. The snow avalanche path covered a total distance of 2900 m, including a stretch of 850 m where the snow avalanche slid downwards on top of the Bødalsbreen outlet glacier. Within the run‐out zone, directly located in front of the ødalen outlet glacier, 2032 stones with b‐axes >5 cm were remobilized which corresponds to a total transferred debris mass of 460 t. Compared with annually occurring snow avalanches within the ødalen drainage basin the relative importance of extreme‐sized snow avalanches is comparably low with respect to direct erosion and sediment transfer along rockwalls at higher slope areas. However, extreme‐sized snow avalanches play a significant role with respect to the remobilization of debris/sediment at lower slope areas as well as to down‐valley transport of sediment, including recognizable transfers of debris into the main stream channels of the drainage basin system whenever extreme snow avalanches reach the main channel.

Numerical simulation on convection-diffusion in an overlapping stenosed artery

Consider an unsteady Newtonian blood flow coupled with mass transport in which flowing through an artery with the presence of an overlapping stenosis. The flowing blood is governed by nonlinear partial differential equations while the convection-diffusion equation to blood is employed to couple with the Newtonian equation in order to characterize the mass transport of blood-borne components such as low-density lipoprotein (LDL). This mass transport refers to the movement of blood-borne molecules from flowing blood into the artery wall, or vice versa. These coupled equations are solved numerically using finite-difference method with an appropriate prescribed initial and boundary conditions. The graphical results of velocity profiles and mass concentration of the solute are presented along the distributions over the entire considered arterial segment. These results show the important role of mass transport in stenosed artery.

Grain boundary grooving in thin films revisited: The role of interface diffusion

Thin nickel (Ni) films were grown on c-plane-oriented sapphire substrates by electron-beam deposition. The as-deposited films exhibited a mazed bicrystal microstructure consisting of interwoven grains of two twinned orientations. Annealing of the specimens at 700°C resulted in the thickening of the Ni film. At the same time a mass deficit in the surface regions near grain boundary thermal grooves was observed. The shape of the observed grooves was very different from that predicted by the classical Mullins model. We developed a model of thermal grooving with simultaneous film thickening due to Ni diffusion along the Ni–sapphire interphase boundary, which agreed well with the experimental results. These findings demonstrate that self-diffusion of metal atoms along the metal–ceramic interface plays an important role in mass transport in thin films. Some implications of fast interphase boundary diffusion for the thermal stability of thin films are discussed.