Influence Of Surface Structure Research Articles

Exploring mechanisms of asymmetric droplet impact dynamics on roughness gradient surface

Droplet impact on surfaces with varying roughness and wettability is a common phenomenon in both natural and industrial environments. While previous studies have primarily examined asymmetric droplet rebound driven by impact velocity or Weber number, the influence of surface structure and associated impact mode transitions has received less attention. In this study, molecular dynamics simulations and detailed analyses are employed to investigate the mechanisms governing droplet rebound on nanopillar arrays with gradient distributions. Results reveal that nanopillar height significantly influences rebound direction, with two distinct directional transitions occurring as the height increases. Additionally, the effects of surface structure and Weber number on impact patterns, rebound velocity, and contact time are systematically evaluated, with contact angle calculations shedding light on the underlying force mechanisms. A phase diagram is developed to illustrate the relationship between rebound direction, Weber number, and nanopillar height. The study further extends the analysis to substrates with bidirectional gradient distributions, demonstrating consistency with single-directional gradient results and validating the broader applicability of the findings. This research provides critical insights into droplet dynamics on roughness gradient surfaces, emphasizing the role of nanopillar height and impact mode in controlling droplet behavior and highlighting potential applications in the design of structured array surfaces.

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.

High-Pressure CO2 and CH4 Transport in Smooth Crystalline Silica Mesopores: A Molecular Dynamics Study.

In this study, we use molecular dynamics (MD) simulation to study pressure-driven CO2 and CH4 flows and their slippage behaviors in β-cristobalite mesopores. The result illustrates that both CO2 and CH4 have an apparent adsorption layer on pore surface. However, significant differences in gas slippage are observed: CH4 flow shows considerable slippage, while it is negligible for CO2 flow. This disparity is attributed to the collective effect of gas molecular configurations and surface structure. The linear molecular structure of CO2 allows it to align perpendicular to the surface, even penetrating into the surface. Notably, the perpendicular orientation of CO2 molecules is energetically favored near the center of the equilateral triangle formed by adjacent oxygen atoms on β-cristobalite surface. Conversely, the symmetric molecular structure of CH4, coupled with its larger size, prevents its penetration into pore surfaces. Therefore, despite smooth crystalline surfaces, CO2 topological accessible plane is much more curved than that of CH4. Consequently, CO2 displays hesitating motions undergoing rotational movements, which significantly hinders its slippage. This study highlights the collective influences of gas molecular characteristics and surface structure on gas slippage, affording important insights into gas sequestration and the development of functional materials for gas separation.

Influence of Catalyst Surface Structure on the Electrochemical Hydrogenation of Cis,Cis-Muconic Acid

Adipic acid (AA) production from petroleum-based cyclohexane is one of the largest chemical processes in terms of annual volumetric turnover accounting for 3 million tons as of 2022. The current commercial approach to synthesize AA is through the oxidation of petroleum-derived cyclohexane using nitric acid. The release of N2O in stoichiometric amounts makes it one of the most significant greenhouse gas (GhG) emitting processes. The abundance of biomass in the Midwestern United States has driven significant research efforts to synthesize bio-derived and sustainable commodity products and lower the chemical industry’s carbon footprint.1 cis,cis-Muconic acid (ccMA), a biobased C6 diunsaturated diacid platform molecule can be transformed to commodity chemicals like caprolactam, adipic acid, and terephthalic acid, with AA being of particular interest for the synthesis of nylon 6,6.2 For the first time in literature, we demonstrate appreciable production of AA (conversion: 91%, selectivity: >95%) through electrochemical hydrogenation (ECH) of ccMA on PGM catalysts. Carbon-supported palladium (Pd/C) and platinum (Pt/C) selectively produced AA while bulk Pd and Pt yielded the monounsaturated trans-3-hexenedioic acid (t3HDA) intermediate and H2 under all tested conditions. Such an influence of surface structure on the electrochemistry of organics is not unprecedented. Koper et. al3 studied Pt single crystals for the electrochemical hydrogenation of acetone and showed how activity, selectivity, and extent of catalytic poisoning are highly sensitive to the Pt surface structure. Similarly, we used density functional calculations to elucidate the structure-sensitive nature of ccMA ECH and its intermediates by identifying thermodynamically preferred reaction pathways as a function of surface geometry (terrace vs steps). The energetics coupled with experimental observations suggest that the reduction of ccMA to t3HDA occurs through an outer sphere proton-coupled electron transfer mechanism, while the reduction of HDA to AA preferentially occurs on Pd and Pt (111), the most abundant facet in Pd/C and Pt/C. Our calculations also explain the exceptional performance of Pd/C compared to Pt/C by the weaker binding of Pd terrace sites compared to Pt. Overall, combining renewable electricity, in-situ hydrogen generation from water, and a biologically-produced intermediate enabled us to open a sustainable route for bio-adipic acid production. This allows us to further design and optimize the catalyst for the selective production of biobased AA.

Electrochemical Monitoring of Respiratory Infectious Disease on Nanostructured Surface Functionalized with Biosynthetic Multimer Aptamers

Multivalent aptamers have gained substantial interest owing to their enhanced affinity towards target analytes compared to their monomeric counterparts due to their capability to bind simultaneously to diverse regions of a target molecule, fostering more robust and enduring interactions. This study focuses on engineering the surface-based production and modification of multivalent aptamers through room temperature rolling circle amplification technique and chemically modified primers. This process starts with immobilizing modified primers onto an electrode to generate and arrange biosynthesised multivalent aptamers. These bio-engineered multivalent aptamers are utilized as bio-receptors for capturing a specific target (in this case, the SARS-CoV-2 spike protein). The entire surface amplification procedure is extensively characterized using electrochemical, microscopy, and spectroscopy methods, determining the optimal amplification duration for biosensing applications. Impressively, multivalent aptasensors shows substantially increased response signals and affinity compared to monomeric aptasensors. Moreover, the influence of surface structures on response signals is explored by employing both flat screen-printed gold electrodes and nano-/microisland (NMI) electrodes. NMIs-based multimeric aptasensors demonstrate notably heightened sensitivity in detecting SARS-CoV-2 spike protein within the range of 10 to 106 fg/mL in saliva and buffer media. Finally, the signal of the proposed aptasensor has been successfully assessed using several patient samples.

Influence of surface structure and tube material on the condensation heat transfer coefficient of n-butane on horizontal single tubes and in tube bundles

The present study examines the condensation heat transfer coefficient αcond of n-butane on the outside of different horizontal tubes and in corresponding tube bundles. Experiments were conducted with a smooth tube, finned tubes with various fin densities, fin heights and tube materials, and a high-performance condensation tube (HPT) at vapor temperatures of (40 and 78) °C and varying heat flux densities q̇. The influence of inundation on αcond was systematically investigated by varying the mass flow of liquid condensate at q̇ of (20 and 60) kW·m−2. Differences between the experimental results from this work and previous ones for propane on the same condensation tubes could be explained with the help of the thermophysical properties and, thus, the retention angle of the condensate in the channels between the fins and the condensate layer thickness. For single copper tubes, αcond increased with increasing fin densities from (19 to 48) fins per inch and was between 9 and 17 times larger than for the smooth tube. This enhancement factor even reached a value of about 24 for the HPT. These increases can be attributed in part to the increased surface area, but the strongest effect appears to be related to surface tension-driven drainage of the condensate. In addition to the experimental investigations, αcond of the finned condensation tubes was predicted using an analytical model for the condensation heat transfer on finned tubes. Here, excellent agreement with an average deviation from the experimental results of 6.6 % could be found. Studies of the inundation effect have shown that the expected decrease in αcond due to the additional condensate impinging on the tubes inside bundles and increasing the film thickness often holds, but is partially counteracted by other effects and depends on the tube geometry.

Razor clam (Pinna bicolor) structural mimics as drivers of epibenthic biodiversity; a manipulative experiment

Shellfish ecosystems facilitate important ecological functions and communities, but overexploitation and mismanagement have contributed to their decline worldwide. Within recent decades, coastal management efforts have increasingly sought to understand and reinstate valuable ecological functions provided by habitat-forming bivalves including oysters, mussels and pinnids. However, many bivalve species are critically understudied, limiting restoration and ecological engineering opportunities. Pinnids, specifically, are an underappreciated bivalve group, with razor clams (Pinna bicolor) forming dense aggregations, and potentially supporting important ecological functions. This study, conducted in an urban Australian estuary, was a manipulative experiment that investigated whether artificial razor clam shells could facilitate beneficial ecological functions through the provision of structural habitat. Specifically, we investigated the influence of intertidal benthic structures, including the micro-habitat influences of surface structure associated with mortality status (open or closed shell), and the short-term response of the benthic and epifaunal communities. Within 12 weeks, the structural razor clam mimics rapidly changed the aboveground ecological community, relative to the bare habitat controls. Both open and closed artificial shells provided a settlement surface for epiphytic organisms and supported enhanced epifaunal biodiversity. Contrastingly, the artificial structures did not significantly alter sediment characteristics or infaunal macroinvertebrate composition in the surrounding benthos. These results provide important insights into the rapid ecological response to the installation of intertidal pinnid structures in dynamic estuarine ecosystems. Furthermore, we provide a case study for understanding the ecological functions of an understudied habitat-forming species, which could be used to inform future restoration and management efforts.

Comparison of Chromatic Assimilation Effects Depending on Printing Substrate in the Munker-White Model

Understanding the influence of paper surface structures on color perception is crucial for the printing industry. This research investigates the impact of horizontal and vertical parallel lines on chromatic assimilation using the Munker-White grid model. The study employs the perceived ∆E00 metric to quantify color differences and determine whether these textures affect perceived color accuracy and consistency differently. Results reveal variations in color perception due to surface textures. The biggest color difference (ΔE00) occurred at 60% RTV coverage for cyan, where the vertical structure showed a significantly lower value than the horizontal. For the yellow primary stimulus, the greatest difference was observed at 20% RTV coverage, with both structures showing high initial values that decrease with increased coverage. These findings provide valuable insights for improving color management practices and enhancing the quality and reliability of color reproduction on various substrates, contributing to advancements in printing technology and color science.

Boosting the adsorption capacity and anti-impurity performance of zeolitic imidazolate frameworks for antimony(III) in water through the synthesis of leaf-shaped structures

In recent years, the search for effective antimony adsorption materials has been unyielding. However, the exploration of zeolite imidazolate frameworks (ZIFs) as potential adsorbents, along with the influence of material surface structure and water chemistry on their performance remain under explored. In this study, various molar ratios of Zn2+ and 2-methylimidazole are employed to synthesize three distinct shapes of ZIFs: cube, leaf, and dodecahedron. The experimental outcomes reveal that Leaf-ZIFs, exhibit exceptional adsorption capabilities for Sb(III), the maximum adsorption capacity of Leaf-ZIFs was 57.3 mg g−1. The adsorption kinetics adhere to the pseudo-second-order model, and equilibrium is achieved in approximately 10 h. Additionally, the adsorption isotherm curve is consistent with the Freundlich model. Through comprehensive batch experiments, we thoroughly examined the impact of varying solution pH levels, coexisting ions, and the coexistence of humic acids on the adsorption of Sb(III). The Leaf-ZIFs exhibited remarkable adaptability in neutral, alkaline, and low-concentration heteroionic environments, while demonstrating minimal interference from humic acid present in the solution. Analysis using SEM, XPS, and FTIR techniques revealed that the adsorption mechanism of Leaf-ZIFs primarily involved the partial breakage of the Zn-N bond within the material's structure. This breakage led to the formation of Zn-OH groups, which subsequently reacted with Sb(III) molecules through the -OH groups. The culmination of this process was the formation of Zn-O-Sb bonds, resulting in the effective adsorption of Sb(III) from aqueous solutions.

Influence of Metal Surface Structures on Composite Formation during Polymer–Metal Joining Based on Reactive Al/Ni Multilayer Foil

Progressive developments in the field of lightweight construction and engineering demand continuous substitution of metals with suitable polymers. However, the combination of dissimilar materials results in a multitude of challenges based on different chemical and physical material properties. Reactive multilayer systems offer a promising joining method for flexible and low‐distortion joining of dissimilar joining partners with an energy source introduced directly into the joining zone. Within this publication, hybrid lap joints between semicrystalline polyamide 6 and surface‐structured austenitic steel X5CrNi18–10 (EN 1.4301) are joined using reactive Al/Ni multilayer foils of the type Indium–NanoFoil. The main objective is to examine possibilities of influencing crack initiation in the foil plane by variation of joining pressure and different metal surface structures with regard to geometry, density, and orientation. Thus, the position of foil cracks is superimposed onto the metal structure and associated filling with molten plastic is improved. Consequently, characterization of occurring crack positions as a function of joining pressure and metal structure, analysis of the composite in terms of structural filling and joint strength, as well as possible causes of crack initiation are evaluated.

Investigation on Influence of Surface Structuring on Brazed Joint between Tungsten Carbide and Steel

The aim of this project is to investigate the effects of surface structuring on brazed joints made of steel and tungsten carbide as well as how these effects affect the joints' mechanical characteristics. The industry uses brazing as a common connecting method, although brazing is known to produce considerable residual strains because of cooling thermal gradients. The strength, longevity, and fatigue resistance of the brazed joint can be impacted by the existence of residual stress, which might be crucial for applications in aerospace and automotive. The impact of several brazing parameters on the development of residual stress will be examined in this study, including temperature, heating rate, cooling rate, and material choice. To describe the residual stress state and assess the mechanical characteristics of the joint, experimental methods such X-ray diffraction and Shear Strength test will be used. The results of this project can be applied to numerous sectors to optimize the brazing procedure and enhance the performance and dependability of brazed components.

Wetting and spreading of bulk liquid and precursor film of molten AgCuTi on ultrafast laser structured surface of Ti

In order to reveal the influence of special surface structures on the wetting and spreading of Ag/Ti system and the precursor film, micro-bumps, micro-pits, micro-grooves and micro-thread surface structures were machined on a grade 2 commercially-pure Ti (TA2) surface by using ultrafast laser. In situ wetting experiments of AgCuTi filler metal on TA2 surfaces with different special structures were conducted. The results showed that the wetting morphology of AgCuTi over original TA2 surface is special double ring (small circle inside and ring outside). The special surface structures can effectively change the wetting characteristics of Ag/Ti system, including the spreading rate and the final spreading area. It also affects the structure and composition of the wetting interface. In Ag/Ti system, different components are affected to different degrees by the surface structures, resulting in uneven distribution of the bulk liquid region and the precursor film region of the wetting interface. The micro-bumps and micro-pits structures can effectively promote the wetting and spreading of AgCuTi on TA2, while micro-thread structures can inhibit its wetting spread. For the micro-grooves, the AgCuTi spreads rapidly and almost completely along the direction of the groove, while in the vertical direction, it is difficult for the AgCuTi to spread through the groove. By studying the wetting spreading process and interface behavior of molten filler metal on complex surfaces, it is expected to provide important guiding significance for using special surface microstructure to control the wetting spreading process and interface reaction of brazing system.

Influence of surface structure and tube material on the condensation heat transfer coefficient of propane on horizontal single tubes and in tube bundles

The condensation heat transfer of propane on the outside of single horizontal tubes and in tube bundles was investigated by determining the condensation heat transfer coefficient αcond in a newly designed experimental setup. To study the influence of different surface structures and tube materials, experiments were conducted with a smooth tube, finned tubes with various fin densities and heights, and a high-performance condensation tube at vapor temperatures of 30 and 40 °C and varying heat flux densities. In addition, the influence of inundation on αcond was systematically investigated by varying the mass flow of liquid condensate at heat flux densities of 20 and 60 kW·m−2. The experimental setup was successfully validated using smooth tubes by a comparison of the resulting αcond with literature data and Nußelt's film theory. For the single copper tubes with fin densities from 19 to 48 fins per inch, αcond increased and was by factors of 9 to 21 larger than for the smooth tube at the same heat flux density. Investigations of the inundation effect have shown that the additional condensate can lead to an increasing condensate film thickness, which decreases αcond due to its increased thermal resistance, and/or can lead to turbulences in the condensate film, which increases αcond. The interplay of the two effects depends highly on the surface geometry. An increasing fin height always enhanced αcond, whereas a lower thermal conductivity of the tube material leads to a smaller αcond.

The Influence of Mesoscopic Surface Structure on the Electrocatalytic Selectivity of CO2 Reduction with UHV-Prepared Cu(111) Single Crystals.

The key role of morphological defects (e.g., irregular steps and dislocations) on the selectivity of model Cu catalysts for the electrocatalytic reduction of CO2 (CO2RR) is illustrated here. Cu(111) single-crystal surfaces prepared under ultrahigh vacuum (UHV) conditions and presenting similar chemical and local microscopic surface features were found to display different product selectivity during the CO2RR. In particular, changes in selectivity from hydrogen-dominant to hydrocarbon-dominant product distributions were observed based on the number of CO2RR electrolysis pretreatment cycles performed prior to a subsequent UHV surface regeneration treatment, which lead to surfaces with seemingly identical chemical composition and local crystallographic structure. However, significant mesostructural changes were observed through a micron-scale microscopic analysis, including a higher density of irregular steps on the samples producing hydrocarbons. Thus, our findings highlight that step edges are key for C-C coupling in the CO2RR and that not only atomistic but also mesoscale characterization of electrocatalytic materials is needed in order to comprehend complex selectivity trends.

Effect of alkali-metal cation on oxygen adsorption at Pt single-crystal electrodes in non-aqueous electrolytes.

The effect of Group 1 alkali-metal cations (Na+, K+, and Cs+) on the oxygen reduction and evolution reactions (ORR and OER) using dimethyl sulfoxide (DMSO)-based electrolytes was investigated. Cyclic voltammetry (CV) utilising different Pt-electrode surfaces (polycrystalline Pt, Pt(111) and Pt(100)) was undertaken to investigate the influence of surface structure upon the ORR and OER. For K+ and Cs+, negligible variation in the CV response (in contrast to Na+) was observed using Pt(111), Pt(100) and Pt(poly) electrodes, consistent with a weak surface-metal/superoxide complex interaction. Indeed, changes in the half-wave potentials (E1/2) and relative intensities of the redox peaks corresponding to superoxy (O2-) and peroxy (O22-) ion formation were consistent with a solution-mediated mechanism for larger cations, such as Cs+. Support for this finding was obtained via in situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). During the ORR and in the presence of Cs+, O2- and weakly adsorbed caesium superoxide (CsO2) species were detected. Because DMSO was found to strongly interact with the surface at potentials associated with the ORR, CsO2 was readily displaced at more negative potentials via increased solvent adsorption at the surface. This finding highlights the important impact of the solvent during ORR/OER reactions.

Revealing the characteristics of biofilms on different polypropylene plastic products: Comparison between disposable masks and takeaway boxes

The increasingly severe plastic pollution issue was intensified by the enormous plastic emissions into ecosystems during the Covid-19 pandemic. Plastic wastes entering the environment were swiftly exposed to microorganisms and colonized by biofilms, and the plastic-biofilm combined effects further influenced the ecosystem. However, the non-woven structure of disposable masks discarded carelessly during the COVID-19 pandemic was different from those of plastics with flat surface. To reveal the potential effects of plastic structure on colonized biofilms, white disposable surgical masks (DM) and transparent takeaway boxes (TB), both made of polyethylene, were selected for the incubation of organic conditioning films and biofilms. The results indicated that the non-woven structure of disposable mask was destroyed by the influence of water infiltration and biofilm colonization. The influence of surface structure on conditioning films led to a relatively higher proportion of tryptophan-like substances on DM than those on TB samples. Therefore, biofilms with significantly higher microbial biomass and carbon metabolic capacity were formed on DM than those on TB samples owing to the combined effects of their differences in surface structure and conditioning films. Moreover, abundant functional microorganisms associated with stress tolerance, carbon metabolism and biofilm formation were observed in biofilms on disposable mask. Combining with the results of partial least squares regression analysis, the selective colonization of functional microorganisms on disposable masks with uneven surface longitudinal fluctuation was revealed. Although the predicted functions of biofilms on disposable masks and takeaway boxes showed more similarity to each other than to those of free-living aquatic microorganisms owing to the existence of the plastisphere, biofilms on disposable masks may potentially trigger environmental risks different from those of takeaway boxes by unique carbon metabolism and abundant biomass.

Nanoisland Formation on the Low Index Planes of Pt By Repeated Electro-Oxidation and-Reduction

Pt-based electro-catalysts are the most common cathode material in proton exchange membrane fuel cells given their high oxygen reduction reaction activity and stability. However, practical applications are limited by catalyst performance loss and degeneration. A main cause for this is nanoscale Pt surface restructuring, which occurs upon formation and reduction of a Pt surface oxide. During oxidation, a fraction of the Pt surface atoms are extracted in a process known as “place-exchange” from the electrode and are bound at specific sites in an oxide about 1 – 4 Å above the surface [1]. Upon subsequent oxide reduction, these atoms as well as the vacancies from which they originate can agglomerate, leading to the nucleation of adatom and vacancy islands. If this process is repeated, nanoislands with a well-defined lateral size of about 20 – 60 Å are grown [2-6]. Detailed studies of this growth process have been performed on the Pt(111) electrode [2-6], revealing two distinct growth regions which are characterized by different vertical scaling exponents [3].For the development of catalysts with superior long-term stability, a more detailed knowledge of the restructuring of the other low index planes of Pt is required. In our recent study of the Pt oxides on Pt(111) and Pt(100) we already showed a strong dependence of the structural stability of the surface on differences in the atomic-scale oxide structure formed on those two surface orientations [1]. However, the influence of surface structure on the nanoisland growth after repeated oxidation and reduction is largely unclear.We present a comparative operando grazing incidence small angle X-ray scattering (GISAXS) study of the nanoisland formation on Pt(111), Pt(100) and Pt(110) in acidic electrolyte. The GISAXS measurements of the nanoisland growth were performed at a high photon energy of >70 keV, which lowered background scattering from the electrolyte, enabling us to resolve the islands after the very first ox./red. cycle. Differences in island shape and growth behaviour on the low index planes will be discussed.We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft via project no. 418603497, MA 1618/23-1 and the BMBF via 05K19FK3.References Fuchs et al., Nat. Catal. 3, 754–761 (2020)Sugawara and K. Itaya, J. Chem. Soc., Faraday Trans. 185, 1351-1356 (1989)Jacobse et al., Nat. Mater. 17 (3), 277-282 (2018)J. Rost, et al., Nat. Commun. 10, 5233 (2019)Ruge et al., J. Am. Chem. Soc. 139, 4532 (2017)Jacobse, et al. ACS Cent. Sci. 5 (12), 1920–1928 (2019)

Sol-gel coatings for solar cover glass: Influence of surface structure on dust accumulation and removal

Soiling of solar cover glass is a major cause for efficiency loss of solar photovoltaic modules. Anti-soiling coatings can be used to reduce the rate of soiling and lower cleaning costs. The efficiency of these coatings has been demonstrated in laboratory and field tests, but the mechanisms and relevant parameters are still not well understood.In this article, we present a study on the influence of surface structure of hydrophilic sol–gel coatings on their anti-soiling performance in terms of both, dust accumulation and subsequent indoor tests for dust removal by wind. The surface structure of the films originates from the addition of colloidal silica particles of different sizes to the sols used for film preparation. In the dust deposition experiments, standardized test dust and dust collected from solar installations were used. Repeated tests were conducted under controlled humidity.In the case of dust deposition, the accumulation of dust particles larger than ∼10 µm is strongly reduced, in relation to bare glass, by the anti-soiling effect of all coatings regardless of their surface structure.For the dust removal via wind, coatings that bear a smoother surface structure are cleaned more easily than coatings with a rougher surface structure.Additionally, larger and rounder dust particles are removed more easily from coatings with a rougher surface structure (structure height over ∼40 nm), while smaller and more irregularly shaped dust particles are removed more easily from coatings with a smoother surface structure.

Adhesion property of municipal solid waste incinerator bottom ash and limestone with asphalt based on surface energy theory

ABSTRACT The aim of this paper is to investigate the adhesion of municipal solid waste incinerator bottom ash (MSWIBA) and limestone to asphalt using the principles of surface energy theory. MSWIBA asphalt mixes are known for their satisfactory water stability, with adhesion being a crucial factor, as demonstrated in previous freeze-thaw splitting tests. Contact angles of ground MSWIBA and limestone were measured using a capillary rise test, eliminating the influence of material surface structure. Subsequently, adhesion work and spalling work were calculated to correlate with water-induced damage. The results showed that the sequence of adhesion work was fine MSWIBA > limestone > coarse MSWIBA, while the sequence of spalling work was coarse MSWIBA > limestone > fine MSWIBA. The adhesion of MSWIBA asphalt mixes was evaluated using the water boiling test image method to validate the findings of surface energy theory. In both asphalt tests, the spalling rate followed this sequence: coarse MSWIBA > limestone > fine MSWIBA. The Adhesion index ER ranked as follows: ER Fine MSWIBA > ER limestone > ER coarse MSWIBA. These results suggest that the water stability of MSWIBA asphalt mixes is influenced by the surface energy of the components. Consequently, indices derived from surface energy theory can be applied in formulating and predicting the properties of MSWIBA asphalt mixes.

Drying behaviour of nanofluid sessile droplets on self-affine vis-à-vis corrugated nanorough surfaces.

In recent years, evaporative self-assembly of sessile droplets has gained considerable attention owing to its wide applicability in many areas. While the phenomenon is well studied for smooth and isotropically rough (self-affine) surfaces, investigations comparing the outcomes on self-affine vis-à-vis corrugated surfaces remains to be done. In this experimental work, we compare the wetting and evaporation dynamics of nano-colloidal microlitre droplets on self-affine and corrugated nanorough surfaces having identical roughnesses and interface properties. The coupled influence of particle size, concentration, and surface structuring has been explored. Differences in wettability and evaporation dynamics are observed, which are explained via the interaction between wetting fluid and anisotropic surface roughness. Our findings exhibit different temporal behaviour of contact radius and angle in the evaporation process of the droplets. Further, the corrugated surface exhibits anisotropic wettability with a monotonic change in droplet shape as evaporation proceeds, finally giving rise to irregular dried patterns. The scaled rim width and crack spacing of the particulate deposits are examined. Our results can inspire fabrication of surfaces that can facilitate direction-dependent droplet motion for specific applications.