Modification Of Surface Structure Research Articles

Surface structures and wettability: Their roles in enhancing nucleate boiling heat transfer of refrigerants

Nucleate boiling is an effective heat transfer mechanism. Previous studies have demonstrated that modifying surface structure or wettability can independently improve nucleate boiling efficiency; however, the combined effects and optimal modification sequence remain underexplored. This research aims to comprehensively analyze the influence of surface structure and wettability on the nucleate boiling heat transfer performance of refrigerants. Different surface structures and wettability were prepared using surface polishing, laser ablation, mechanical cutting, and a combination that involved initially employing laser ablation, followed by the application of chemical etching, and finishing with the treatment using materials possessing low surface energy. The static contact angles on these surfaces were measured via the capillary rise method, followed by pool boiling experiments and bubble behavior visualization. The results show that increasing surface wettability can enhance bubble departure frequency and capillary wicking, thereby improving critical heat flux and heat transfer coefficient. The key to optimizing surface modification to enhance critical heat flux involves constructing alternating high and low nucleation core regions to reduce interactions between bubbles; for enhancing heat transfer coefficient, the key lies in constructing compact nanoscale structures that expand the heat transfer and nucleation area, followed by improving wettability.

Thermal Plasma‐Induced Surface Modifications Correlated With the Field Emission Properties of Copper

ABSTRACTThe present work deals with the Argon (Ar) Thermal plasma‐induced surface modification of Cu and its correlation with the electrical and field emission (FE) properties. Polycrystalline Cu targets were treated with Ar thermal plasma under atmospheric pressure at different treatment times ranging from 5 min to 30 min. XRD patterns revealed the absence of new phase in treated samples. However, significant variation in peak intensities and shifting is observed, which is explained on the basis of thermal plasma ions induced defect generation and annihilation processes. The electrical conductivity of processed Cu targets measured by four‐probe method ranges from 1.9 MS/m to 70 MS/m and is well correlated with the crystallite size variation. Surface modification induced work function alternations investigated by employing Scanning Kelvin Probe (SKP) technique are in the range of 4.69 eV 4.97 eV. The irradiated morphology explored by optical and scanning electron microscopy analyses revealed the formation of localized melt pools, grains, hillocks, spheroids, and sputtered patches, which are explainable on the basis of Coulomb's explosion, thermal spike model, plasma‐induced sputtering, and re‐deposition. FE properties of thermal plasma‐treated Cu are measured in diode configuration by measuring I‐V characteristics of target under ultra‐high vacuum condition. The improved FE parameters such as turn‐on field (Eo), field enhancement factor (β), and maximum current density (Jmax) come out to be in the range of 3–7.5 V/μm, 1715–3223, and 284–872 nA/cm2, respectively and their correlation with plasma‐induced surface structural, morphological and work function modifications is discussed.

Gas adsorption analysis for quantifying the edge sites of graphite

The edge plane exposed on the surface of carbon materials is the active site that determines their properties. When graphite is used as the negative electrode in lithium-ion batteries, the edge plane acts as an access point for lithium insertion/desorption. However, because of the low specific surface area and amorphous carbon coating of graphite particles, accurately estimating the number of edge planes is challenging. Therefore, we propose a technique for determining graphite edge planes based on the stepwise adsorption of Kr onto the hexagonal carbon network surface. Graphite particles with highly modified surface structures were prepared by controlling the particle size, heat treatment temperature, and amorphous carbon coating. Electrochemical evaluation revealed significant differences in charge-transfer resistance, an indicator of edge planes. The edge plane determination results obtained using conventional methods such as X-ray diffractometry and Raman spectroscopy did not correlate well with charge-transfer resistance. Meanwhile, Kr adsorption measurements revealed that the stepwise adsorption behavior, because of the interaction of Kr with the energetically homogenous surface, varied significantly depending on the surface properties of graphite particles. The number of edge planes estimated by gas adsorption strongly correlated with charge-transfer resistance. Consequently, we determined that the graphite edge plane tied to the electrochemical index can be derived using gas adsorption analysis. This edge plane determination technique would be applicable not only to graphite but also to highly crystalline carbon materials with an exposed hexagonal carbon network surface.

In Situ Surface Coatings and Structural Modifications for Reducing Residual Lithium and Stabilizing Lattice on Ultrahigh Ni Cathodes

In Situ Surface Coatings and Structural Modifications for Reducing Residual Lithium and Stabilizing Lattice on Ultrahigh Ni Cathodes

Intensifying interfacial oscillations in falling film flows over rectangular corrugations

Unsteady film flows play an important role in intensifying heat and mass transfer processes, with applications, e.g., in falling film absorbers or reactors. In this context, the influence of surface structure modification on the wave dynamics of falling film flows is experimentally investigated based on localized film thickness time series data. Arrays of rectangular ridges oriented perpendicular to the main flow direction are considered, and an optimum ridge distance is identified, at which particularly strong interfacial oscillations are induced in the falling film. These potentially result from the interaction of the flow with a statically deformed base film under resonance-like conditions. The transient destabilization is amplified in the case of narrow ridge sizes, where inertia-driven flow features are particularly pronounced. With regard to mass transfer applications, the structure-induced increase in gas–liquid interfacial area may be of secondary importance compared to changes in internal flow conditions.

Zinc blende ZnS (001) surface structure investigated by XPS, LEED, and DFT

The formation and stability of the zinc blende ZnS (001) single crystal surface have been examined by x-ray photoemission spectroscopy (XPS), low-energy electron diffraction (LEED), and density-functional theory (DFT) calculations. LEED patterns obtained from the ZnS (001) surface prepared in ultrahigh vacuum conditions at 1420 K reveal the formation of a (1 × 2) reconstructed structure. Surface chemical characterization performed by XPS indicates that the surface region consists of a Zn-deficient (sulfur-rich) phase. Our DFT theoretical calculations confirm that the ZnS (001) (1x2) surface structure is energetically favorable and consists of a Zn-terminated topmost surface layer stabilized by Zn-vacancies. The calculations also suggest that the remaining Zn-cations on the surface are displaced inward, driven by surface energy minimization related to zinc-blend ZnS (001) polar nature. Notably, the observed surface structural modifications have potential implications for the ZnS physical and chemical properties.

Experimental study on the effect of tube surface modifications and in-channel baffle plates on falling film evaporator heat transfer properties for sever cabinets

To effectively alleviate the high energy consumption associated with traditional cooling strategies in data centers, this research synoptically designs an innovative and energy-efficient integrated structure combining a falling film evaporator with a cabinet. An experimental setup with a water film tube in a rectangular channel is constructed, and the impacts of liquid film temperature, spray density, and inlet air Reynolds number on heat transfer properties in the cases of the tube's surface structure modifications and baffle plates presence in the channel are explored, respectively. Two significant findings that enable low energy consumption-oriented cooling strategy development are derived. (1) Decreasing the spray density can reduce energy consumption when liquid film integrity is maintained. Upon quadrupling the inlet spray density for the smooth and finned tubes, the heat transfer rate and heat transfer coefficient between the tubes and airflow in the baffled and unbaffled channels only increase by 23.1 to 29.9% and 18.6 to 28.3%, respectively. (2) The tube surface modifications and baffles presence can significantly improve the heat transfer performance. The performance evaluation criterion between the airflow and finned tube in the channel with baffles is 2.5–4.0 times higher than those between the airflow and smooth tube in the baffle-free channel.

Harnessing ion beam erosion engineering for controlled self-assembly and tunable magnetic anisotropy in epitaxial films

The engineering of the surface morphology and the structure of the thin film is one of the essential technological assets for regulating the physical properties and functionalities of thin film-based devices. This study presents an easy and handy approach to tailor the surface structure of epitaxial thin films utilizing low-energy ion beam. Here, we investigate the evolution of the surface structure and magnetic anisotropy (MA) in epitaxial Fe/MgO (001) model systems subjected to multiple cycles of ion beam erosion (IBE) after thin film growth. The growth of Fe film occurs in the form of three–dimensional islands and exhibits intrinsic biaxial MA. Following a few cycles of IBE, an induced uniaxial magnetic anisotropy leads to a split in the hysteresis loop, and the film displays almost uniaxial magnetic switching behavior. More distinctly, we present a clear and conclusive evidence of (2 × 2) reconstruction of the Fe surface due to the atomic rearrangement by IBE. Furthermore, 57Fe isotope sensitive nuclear resonance scattering measurement provides insight into the depth-resolved magnetic information due to the modified surface topography. We also demonstrate that thermal annealing can reversibly tune the surface reconstruction and induced UMA. The feasibility of the IBE technique by adequately selecting IBE parameters for surface structure modification has been highlighted apart from conventional tailoring of the morphology for the tuning of UMA and introduces a new dimension to our understanding of self-assembled surface morphology evolution by IBE.

Plasma-induced, N-doped, and reduced graphene oxide–incorporated NiCo–layered double hydroxide nanowires as a high-capacity redox mediator for sustainable decoupled water electrolysis

Although the recent emergence of decoupled water electrolysis prevents typical H2/O2 mixing, the further development of decoupled water electrolysis has been confined by the lack of reliable redox mediator (RM) electrodes to support sustainable H2 production. As energy storage electrodes, layered double hydroxides (LDHs) possess inherently poor conductivity/stability, which can be improved by growing LDHs on graphene substrates in situ. The proper modification of the graphene surface structure can improve the electron transport and energy storage capacity of composite electrodes, while current methods are usually cumbersome and require high temperatures/chemical reagents. Therefore, in this study, dip coating was adopted to grow graphene oxide (GO) on nickel foam (NF). Then, the GO was reduced using nonthermal plasma (NTP) to reduced GO (rGO) in situ while simultaneously implementing N doping to obtain plasma-assisted N-doped rGO on NF (PNrGO/NF). The uniform conductive substrate ensured the subsequent growth of less-aggregated NiCo-LDH nanowires, which improved the conductivity and energy storage capacity (5.93 C/cm2 at 5 mA/cm2) of the NiCo-LDH@PNrGO/NF. For the decoupled system, the composite RM electrode exhibited a high buffering capacity for 1300 s during the decoupled H2/O2 evolution, and in the conventional coupled system, the necessary input voltage of 1.67 V was separated into two lower ones, 1.42/0.33 V for H2/O2 evolutions, respectively. Simultaneously, the RM possessed outstanding redox reversibility and structural stability during long-term cycling. This work could offer a feasible strategy for using NTP to synthesize excellent RM electrodes for application to decoupled water electrolysis.

Hydrogen Sensing with Palladium-Based Materials: Mechanisms, Challenges, and Opportunities.

Palladium morphologies are prominently used in Hydrogen gas sensing applications owing to their unique characteristics and properties. In this review article, Palladium nanoparticles, thin films, and alloys were designated as the scope of Palladium morphologies. The aim of this review article is to explore Hydrogen sensing using Palladium, focusing on the recent advancements in the field.. The principles underlying Hydrogen sensing mechanisms with Palladium are discussed initially, highlighting the unique properties of Palladium that make it a promising material for this purpose. Special attention is given to the surface interactions and structural modifications that influence the sensitivity and selectivity of Palladium-based sensors The study also addresses key challenges and recent innovations in the field which contribute to the enhancement of Palladium-based Hydrogen sensing capabilities. The current state of research is critically examined to identify gaps in knowledge and future research directions are highlighted. The prospects and challenges associated with the use of Palladium for Hydrogen sensing, emphasizing its pivotal role in advancing sensor technologies for Hydrogen detection are also discussed.

In-situ construction of epitaxial phase for boosting zinc nucleation on three-dimensional interface

Interface modification of zinc (Zn) metal anode with conductive three-dimensional (3D) structure is widely utilized in zinc ion batteries. However, the uniformity of zinc nucleation on surface microstructure is rarely investigated which exacerbates the tip effect and raises unstable risk. Herein, a strategy via the initial copper (Cu) alloying and following sulfurization treatment is reported to accomplish boosted uniform nucleation of zinc on the modified layer with dense microstructures. This epitaxial sulfide phase not only improves the wetting area to revitalize the microstructural surface, but also forms a bifunctional zincophilic Cu2S/CuZn alloy interface layer, which combines the merits of guided local ions diffusion and improved zinc nucleation environment. As a result, a homogeneous growth of zinc on the 3D structural substrate can be realized, and cycling stability of the achieved Cu2S/CuZn electrode with a practical capacity of 1 ​mAh cm−2 under 1 ​mA ​cm−2 or amplified current density of 10 ​mA ​cm−2 is significantly enhanced. This work provides an epitaxial strategy in constructing a bifunctional zincophilic interface layer for boosting zinc nucleation, and offers a new perspective on the modification of 3D surface structure for stabilization of zinc anode.

Investigation of Dielectric Properties and Structural Changes in XLPE Composite Insulation of Covered Conductor due to Thermal Aging

Investigating the dielectric characteristics and structural alterations in XLPE composites, commonly employed in the insulation of covered conductors, stands as a pivotal research focus. In this study, we examined the variation in dielectric loss (tanδ) concerning frequency and voltage, influenced by thermal aging in XLPE insulation. To achieve this, the samples underwent aging at 120°C for six periods, a total of 450 hours. Furthermore, we conducted PD tests, FTIR, and SEM assessments on the insulation both before and after the aging process. A comprehensive analysis of the material's property changes during thermal aging was performed by comparing the PD test results with the tanδ measurements. In order to delve deeper into the interpretation of these findings because of thermal aging, we explored both internal and surface structural modifications, which directly impact tanδ and PD values, utilizing FTIR and SEM techniques.

Study of changes in the surface structure of tungsten irradiated by helium plasma

One of the important aspects is the interaction of plasma with the surface of a material, especially in the conditions of a fusion facility. The current work presents the preliminary results of the study of tungsten surface structure modification under helium plasma irradiation. A small-sized linear simulator KAZ-PSI with a plasma-beam setup was designed and assembled, where helium was used as a working gas. The main elements of the linear plasma simulator are an electron beam gun with a LaB6 cathode, a plasma-beam discharge chamber, an interaction chamber, a target device, and an electromagnetic system consisting of electromagnetic coils. It was revealed that under irradiation on the surface of the samples there is a relief with defective structure consisting of chaotically arranged ledges and pits of various shapes with average size (100‒600) nm and pore sizes (0.1‒1.5) μm with visible areas of flaking and sputtering. It was found that when the negative potential on the target is varied by –500V/–1000V/–1500V, the formation of dislocation with chaotic and cellular structure of tungsten with an average grain size of (1‒25) μm is observed; it was revealed that the total values of elastic and plastic components of deformation across the tungsten grain differ from each other by about 2.5 times.

Post-fry oil distribution in batter coated fried foods

This study investigated the impact of post-frying treatments on oil distribution of meat-analog based batter coated foods. Wheat and rice flour-based batter systems were used to coat a meat-analog (MA) model food. The product was fried at 180 °C for 2, 4 and 6 min in canola oil. Hot air blow (HAB), pressure assisted absorbent paper (PAP), and centrifuge assisted absorbent paper (CAP) were used as post-fry de-oiling treatment. Results showed that batter-coated MA possess distinct spatial (surface, matrix and total) fat profiles compared to non-coated MA. Surface fat (SF) of MA-based coated products were dependent to both batter formulations and frying time. Post-fry de-oiling treatments effectively reduced SF, matrix fat (CrMF) and crust total fat (CrF) of MA-based products, without distorting texture and color. Impact of de-oiling treatments were more obvious for products with higher SF. ATR-FTIR spectroscopic analysis revealed that surface fat of batter-coated fried MA was comparatively static and removable during post-fry holding. The CAP treatment reduced CrF to the highest extent, followed by PAP and HAB. Effectiveness of de-oiling treatments greatly influenced by surface microstructure. Batter formulations and frying time are the key to regulate oil distribution in MA-based batter coated fried foods, via surface structural modification.

THE EFFECT OF HARDENING TECHNIQUES ON WEAR RESISTANCE AND FATIGUE LIFE OF DUCTILE CAST IRON

Many hardening methods have been developed and proposed as an effective technology to produce microstructural modification and improvement of mechanical properties of variety metallic materials. In this experimental study, the effects of applying laser peening (LP) and friction stir processing (FSP) methods on wear resistance and fatigue properties of selected cast iron ASTM A536, grade (80-55-06) with ferrite/pearlite microstructure were investigated. Microscopic study revealed evident refinement and crashing of graphite nodules as 50% of the basic size with FSP and 32% with LP within the processed surfaces hence improving average microhardness by 100% and 48% respectively. The wear resistance and fatigue life were increased by 33% and 122% after FSP whereas, the corresponding increments were 15% and 22% after LP in comparison with the basic ductile iron. These improvements were linked to surface hardening, compressive stresses and structural modification by the employed processes.

Near-infrared Ⅱ light-assisted Cu-containing porous TiO2 coating for combating implant-associated infection

Treatment implant-associated infections remains a severe challenge in the clinical practice. This work focuses on the fabrication of Cu-containing porous TiO2 coatings on titanium (Ti) by a combination of magnetron sputtering and dealloying techniques. Additionally, photothermal therapy is employed to enhance the effect of Cu ions in preventing bacterial infection. After the dealloying, most of Cu element was removed from the magnetron sputtered Cu-containing films, and porous TiO2 coatings were prepared on Ti. The formation of porous nanostructures significantly enhanced the photothermal conversion performance under NIR-II light irradiation. The combined effect of hyperthermia and Cu ions demonstrated enhanced antibacterial activity in both in vitro and in vivo experiments, and the antibacterial efficiency can reach 99% against Streptococcus mutans. Moreover, the porous TiO2 coatings also exhibited excellent biocompatibility. This modification of the titanium surface structure through dealloying changes may offer a novel approach to enhance the antimicrobial properties of titanium implants.

Effect of GNP/Ni-TiO2 Nanocomposite Coated Copper Surfaces Fabricated by Electro Chemical Deposition under Nucleate Pool Boiling Regime: A Comprehensive Experimental Study

Current study presents an experimental analysis of nucleate pool boiling on the GNP/Ni-TiO2 (GNP-graphene nano particle) nano-composite coated copper surfaces. In order to produce the microporous surfaces, a two-step electro-deposition process is used. This deposition results in the formation of a modified surface structure, and various surface morphological characteristics of this modified structure, like wettability, roughness and surface structure are studied. The results reveal an improvement in CHF (critical heat flux) and BHTC (boiling heat transfer coefficient) in case of GNP/Ni-TiO2 coated surfaces. The main elements influencing the improved heat transfer of the GNP/Ni-TiO2nano-composite coating are its increased wettability, roughness, and high thermal conductivity. The SNCCC (superhydrophilic nano-composite coated copper) surfaces have the maximum BHTC of 97.52 (kW/m2K) and CHF of 2043 (kW/m2), which are 93% and 88% higher than the base Cu surfaces respectively. Here, it is analysed how the performance of SNCCC surfaces are enhanced by the impact of different parameters, like the roughness of the surface and wettability. The bubble characteristics at the time of boiling is noticed using a high-speed camera, and several factors such as nucleation site density, bubble departure diameter, and bubble emission frequency are statistically studied for SNCCC surfaces.

Investigation of α-Fe2O3 catalyst structure for efficient photocatalytic fenton oxidation removal of antibiotics: preparation, performance, and mechanism.

Currently, the surface structure modification of photocatalysts is one of the effective means of enhancing their photocatalytic efficiency. Therefore, it is critically important to gain a deeper understanding of how the surface of α-Fe2O3 photocatalysts influences catalytic activity at the nanoscale. In this work, α-Fe2O3 catalysts were prepared using the solvothermal method, and four distinct morphologies were investigated: hexagonal bipyramid (THB), cube (CB), hexagonal plate (HS), and spherical (RC). The results indicate that the hexagonal bipyramid (THB) exhibits the highest degradation activity towards tetracycline (TC), with a reaction rate constant of k = 0.0969 min-1. The apparent reaction rate constants for the cube (CB), hexagonal plate (HS), and spherical (RC) morphologies are 0.0824, 0.0726, and 0.0585 min-1, respectively. In addition, it has been observed that the enhancement of photocatalytic activity is closely related to the increase in surface area, which provides more opportunities for interactions between Fe2+ and holes. The quenching experiments and electron paramagnetic resonance (EPR) results indicate that the ˙O2, ˙OH and h+ contribute mainly to the degradation of TC in the system. This research contributes to a more comprehensive understanding of catalyst surface alterations and their impact on catalytic performance.

Nano-protrusions in intercalated graphite: understanding the structural and electronic effects through DFT.

Complex phenomena characterize the intercalation of ions inside stratified crystals. Their comprehension is crucial in view of exploiting the intercalation mechanism to change the transport properties of the crystal or obtaining a fine control of crystal delamination. In particular, the relationship between the concentration and nature of intercalated ions and surface structural modifications of the host stratified crystal is still under debate. Here, we discuss a theoretical effort to provide a rationale for some structural changes observed on the highly oriented pyrolytic graphite (HOPG) surface after electrochemical treatment in perchloric and sulphuric acid solutions. The formation of the so-called nano-protrusions on the basal plane of intercalated graphite was previously observed with scanning tunneling microscopy (STM). In this work, we employed both STM and density functional theory (DFT) simulations to elucidate the physical and chemical mechanisms driving the emergence of these nano-protrusions. The DFT results show that, in a bilayer graphene system, the presence of a single ion can generate a nano-protrusion with 2.49 Å height and 21.27 Å width. In the deformed area, the C-C bond length is stretched by about 2.5% more than the normal graphene bond. These values are of the same dimensional scale as those reported in previous STM experimental results.25 However, the simulated STM images obtained by increasing the amount of intercalated ions per area suggest that the presence of more than one ion is needed for the deformation of the uppermost graphite layer during the early stages of intercalation. In contrast, in a multilayer graphene system, no significant surface deformation is detected when ions are intercalated between the third and fourth layers. Charge analysis indicates an altered distribution of the charges as a consequence of the intercalation. The charge transfer from graphene layers to the intercalated ions results in a surface layer more prone to oxidation.

The effect of pretreatment and surface modification of porous transport layer (PTL) on the performance of proton exchange membrane water electrolyzer

The surface properties of the anode porous transport layer (PTL) significantly impact the performance of a proton exchange membrane water electrolyzer (PEMWE). The pretreatment (ultrasonic cleaning and acid etching) of a pristine titanium (Ti) felt before it is used as the anode PTL and the surface structural modification of a PTL are two critical methods to improve the performance of an electrolyzer. However, the mechanisms for the pretreatment and surface modification need to be clarified. In this paper, five electrolyzers with five different-fabricated-ways anode PTLs are tested and compared based on I–V curves, EIS curves, and physical characterization techniques. X-ray photoelectron spectroscopy (XPS) results show that the ultrasonic cleaning pretreatment of PTL can improve hydrophilicity by increasing the amount of hydroxyl. In addition, EIS results indicate the significant charge transfer resistance of electrolyzer taking pristine titanium felt as PTL. Adopting the carbon paper as a microporous layer (MPL) or treated titanium felt with acid etching can eliminate or reduce the charge transfer resistance of the electrolyzer. Finally, the mechanism of surface pretreatment and modification of PTL are disclosed to cast light on the improvement of PTLs in further study.