Relevant Surface Research Articles

A new exvivo human skin model for the topographic and biological analysis of cosmetic formulas.

Existing methods to evaluate skin care products suffer limitations. This is the case for exvivo skin explants, a first-choice 3D model. While essential to analyse mid- to long-term biological effects, this classical model hinders assessing microrelief variations. To circumvent these limitations, we developed an exvivo PERFused EXplant setup (Perfex) that maintains the outer skin surface in the open air, closely mirroring physiological conditions. A custom-designed reservoir enables perfusing the dermal side of explants with buffered, temperature-controlled medium, while the epidermis is subjected to "normal" conditions. Skin tension and characteristics of the stratum corneum, microrelief, histology and immunohistology (collagen types I and III, elastin and fibrillin-1) were analysed and compared to those of explants maintained under conventional conditions or invivo skin. The effects of skin care formulas intended to induce short- and/or mid- to long-term effects were also assessed. Skin explants maintained with the Perfex setup exhibit characteristics (firmness, elasticity, hydration and barrier function) closer to those of invivo skin than with conventional conditions. Moreover, Perfex-maintained explants present no alteration in histology after 7 days and slight variation in the expression of key protein markers. Microrelief characteristics also remain mostly stable over 7 days. Formula applications corroborate that skin tensor-containing products primarily induce short-term changes in the microrelief, while those with biologically active ingredients mainly lead to mid- to long-term effects on the histology and expression of molecular markers. Furthermore, maintaining skin explants with a physiologically relevant skin surface enabled analysing the relationship between microrelief and key markers, showing that fibrillin-1 is the protein most correlated with microrelief characteristics. The Perfex setup allows for similar preservation of skin explant histology and key protein expression as the conventional system, yet it maintains a skin surface close to that of invivo skin. Therefore, it is valuable to analyse both the short- and mid- to long-term impacts of skin care formulas and better comprehend their effects. The Perfex system also offers a new tool for investigating fundamental questions, such as the link that can exist between dermal proteins and skin surface properties.

The Effects of Short-Range Intermolecular Repulsive Forces on Hamaker Constant Estimation Using Atomic Force Microscopy.

The atomic force microscope (AFM), as it is able to characterize surface topography as well determine the AFM cantilever tip-surface force, proves effective at estimating the value of the Hamaker constant, A, for a given solid material. Two main AFM-based methods have been proposed for estimating values of A. In the approach-to-contact (AtC) method, Hamaker constants are inferred from the deflections at which the AFM tip first jumps into contact with the substrate. In the pull-off (PO) method, the deflections that arise when the AFM tip is finally pulled away from the substrate are used to estimate values of A. In prior applications of these two methods, the short-range intermolecular repulsive forces that are known to arise between the AFM tip and the substrate were, however, ignored. Upon invoking a physically relevant description of these short-range and steeply repulsive forces, we investigate the effects of repulsive interactions on the values of A estimated from the existing AtC and PO methods when applied to neutrally charged systems under low humidity or vacuum conditions. For experimentally relevant surfaces, we find that repulsive forces have a modest effect on the AtC method, although they still need to be accounted for in order to generate improved estimates of the Hamaker constant. On the other hand, repulsive forces have a significant effect on the Hamaker constants inferred from the PO method, and must be properly accounted for when using this approach. Our analysis also includes an explicit incorporation of surface roughness into the PO method, which is not typically done in most prior applications of the PO method.

Unraveling a Molecular Adhesion Mechanism at Complex Polymer-Metal Interfaces.

Controlling polymer-metal adhesion is critical in ensuring that materials can be cleanly separated during production processes without residue, which is crucial for various industrial applications. Accurately characterizing adhesion on industrial-grade surfaces is complex due to factors like surface roughness and actual contact area between surfaces and the polymer. In this study, we quantified the adhesive behavior of stainless-steel samples with varying surface treatments against a polymer using the surface forces apparatus (SFA) in reflection geometry, as well as X-ray photoelectron spectroscopy (XPS). We compared adhesive properties with the penetration depth of oxygen and the hydroxide-to-oxide ratio, which were modified by plasma and thermal treatments. Our results indicate that both treatment types enhance the deadhesive properties of the materials compared to native passive films, due to decreasing hydroxide functionality on the surface. Thermal treatment reduces adhesion further, due to an even lower hydroxide content, which reduces hydrogen bonding between the surface and polymer. Furthermore, we show that van der Waals forces, which depend on the density, have marginal to no influence on the adhesive behavior. This study not only advances our understanding of the factors influencing polymer-metal adhesion but also demonstrates the application of the SFA in reflection geometry for characterizing industrially relevant rough surfaces.

A proteogenomic surfaceome study identifies DLK1 as an immunotherapeutic target in neuroblastoma

Cancer immunotherapies produce remarkable results in B cell malignancies; however, optimal cell surface targets for many solid cancers remain elusive. Here, we present an integrative proteomic, transcriptomic, and epigenomic analysis of tumor and normal tissues to identify biologically relevant cell surface immunotherapeutic targets for neuroblastoma, an often-fatal childhood cancer. Proteogenomic analyses reveal sixty high-confidence candidate immunotherapeutic targets, and we prioritize delta-like canonical notch ligand 1 (DLK1) for further study. High expression of DLK1 directly correlates with a super-enhancer. Immunofluorescence, flow cytometry, and immunohistochemistry show robust cell surface expression of DLK1. Short hairpin RNA mediated silencing of DLK1 in neuroblastoma cells results in increased cellular differentiation. ADCT-701, a DLK1-targeting antibody-drug conjugate (ADC), shows potent and specific cytotoxicity in DLK1-expressing neuroblastoma xenograft models. Since high DLK1 expression is found in several adult and pediatric cancers, our study demonstrates the utility of a proteogenomic approach and credentials DLK1 as an immunotherapeutic target.

Biomimetic Cooling: Functionalizing Biodegradable Chitosan Films with Saharan Silver Ant Microstructures.

The increasing occurrence of hot summer days causes stress to both humans and animals, particularly in urban areas where temperatures can remain high, even at night. Living nature offers potential solutions that require minimal energy and material costs. For instance, the Saharan silver ant (Cataglyphis bombycina) can endure the desert heat by means of passive radiative cooling induced by its triangular hairs. The objective of this study is to transfer the passive radiative cooling properties of the micro- and nanostructured chitin hairs of the silver ant body to technically usable, biodegradable and bio-based materials. The potential large-scale transfer of radiative cooling properties, for example, onto building exteriors such as house facades, could decrease the need for conventional cooling and, therefore, lower the energy demand. Chitosan, a chemically altered form of chitin, has a range of medical uses but can also be processed into a paper-like film. The procedure consists of dissolving chitosan in diluted acetic acid and uniformly distributing it on a flat surface. A functional structure can then be imprinted onto this film while it is drying. This study reports the successful transfer of the microstructure-based structural colors of a compact disc (CD) onto the film. Similarly, a polyvinyl siloxane imprint of the silver ant body shall make it possible to transfer cooling functionality to technically relevant surfaces. FTIR spectroscopy measurements of the reflectance of flat and structured chitosan films allow for a qualitative assessment of the infrared emissivity. A minor decrease in reflectance in a relevant wavelength range gives an indication that it is feasible to increase the emissivity and, therefore, decrease the surface temperature purely through surface-induced functionalities.

Microstructure and mechanical properties of 3D‐printed zirconia bone scaffold: Experimental and computational analysis

AbstractMicroextrusion‐based additive manufacturing of zirconia‐based bioceramics is capable of fabricating design‐specific architectures with high mechanical strength properties and relative density. We developed a novel organic residue‐free binder system for zirconia paste printing (ZP2) with the shear‐thinning properties apropos to microextrusion‐based 3D printing. Based on thermogravimetric analysis, debinding protocol was established followed by high‐temperature heat treatment under four sintering conditions. Quantitative linear shrinkage (32.3%–42.7% ranging from in‐plane to vertical direction), density (83.3%–87.5%), and surface roughness (7.7–13.8 µm from the parallel to the perpendicular to the infill direction) as a factor of sintering conditions (1400°C–1500°C for 3–4 h) were analyzed. Whereas qualitative phase assemblage demonstrated “sintering condition independent” phase stability; grain growth and reduction in porosity were observed in the microstructure with increment in sintering temperature and hold time. Interestingly, at higher temperature and hold time, the compressive (46–72.4 MPa) and tensile strength (16.2–23.1 MPa) properties experienced a trade‐off between grain growth and reduction in porosity. The ZP2 scaffolds sintered at lower temperature and hold time qualified for the bone scaffold applications having interconnected porosities, biologically relevant surface roughness, and human bone mimicking mechanical properties. With a unique finite element analysis recipe, the mechanical behavior of the “life‐like” reconstructed computer aided design (CAD) geometries identical to real 3D‐printed‐sintered ZP2 scaffolds was quantitatively predicted.

B-090 Efficient Hydrophilic Surface Coating with Low Concentrations of Bovine Gamma Globulins

Abstract Background Bovine Gamma Globulin (BGG) is a high purity immunoglobulin fraction of bovine serum. BGG is used as a blocker to prevent non-specific binding in immunoassays and, due to the mixture of immunoglobulins, its blocking capabilities differ from traditional blockers like Bovine Serum Albumin (BSA). Our objective was to evaluate the adsorption characteristics of BGG to In vitro diagnostic relevant hydrophilic surfaces compared to BSA. A bead-based immunoassay was utilized to quantify the mass of protein coating a bead surface and atomic force microscopy (AFM) to analyze physical properties of the protein-surface layer. Methods The mass of BGG bound to hydrophilic beads (Dynabeads M-270 Carboxylic Acid) was determined across varying concentrations ranging from 0.1% to 1.0% in pH 7.0 phosphate buffer. Coated beads were heated in 1x SDS loading dye to dissociate bound protein, then ran on a nonreducing SDS-PAGE gel. The total protein was measured using densitometry against a standard curve, using ImageJ, and analyzed with GraphPad Prism. This methodology was also used for BSA. AFM was used to image a topographical view of BGG binding to a silica surface. Samples were prepared at concentrations from 0.1% to 1.0% in phosphate buffer at pH 7.0. Followed by a series of washes to remove non-bound molecules, the surface was allowed to dry, then scratched with an AFM cantilever. The surface was then analyzed for roughness and thickness of BGG adsorption for each concentration. Results BGG and BSA have notable differences in their coating properties at a concentration of 1.0%. In the bead assay, the protein-surface binding is enhanced ∼4.8-fold for BGG compared to BSA. Interestingly, even at 0.1% BGG bound ∼0.8-fold more than BSA at 1.0%. Despite a 6-fold increase in mass bound to the bead surface with 1.0% BGG compared to 0.1%, AFM revealed a 1.3-fold and 1.8-fold decrease in height and roughness at the lower concentration, while maintaining effective coating. These results suggest that higher BGG concentrations result in thicker, rougher surface coating. This could lead to steric hindrance and obstruction of binding sites, affecting assay performance. Therefore, a lower concentration of BGG may lead to better surface coating and prevent reduced sensitivity and accuracy within immunoassays. Conclusions The bead binding assay demonstrates that BGG displays surface adsorption with comparable or improved results with lower concentrations compared to BSA. At 0.1%, BGG exhibits effective binding to a hydrophilic surface equivalent to that achieved by BSA at 1.0%. Additionally, AFM data suggest that even at 0.1%, BGG effectively coats the silica surface and potentially reduces steric hinderance compared to BGG at 1%. While BSA remains a reliable choice for many applications, our findings suggest that BGG can be an effective blocker for immunoassay applications. The choice of a suitable blocker varies depending on factors such as assay high background, sensitivity, and specificity. By tailoring the choice of blocker to the specific requirements of the assay, researchers can optimize assay performance by improving the accuracy and the reliability of the assay.

Bending fatigue behavior of metastable and stable austenitic stainless steels with different surface morphologies

AbstractThe surface morphology has a significant influence on the fatigue behavior of components. For austenitic stainless steels (ASSs), this issue is even more pronounced due to their metastability. Based on the complex deformation mechanisms of metastable ASSs, which include dislocation slip, deformation twinning, and deformation‐induced martensitic phase transformation, the metastable stainless steel AISI 347 was investigated in this study together with the stable AISI 904L as a reference material. Four‐point bending fatigue tests with load ratio R = 0.1 and testing frequency f = 10 Hz at ambient temperature were carried out on specimens with five technically relevant surface morphologies: mechanical polished, milled, microshot peened, laser shock‐peened, and ultrasonic modified. Systematic material characterizations were carried out to elucidate the crucial role of surface roughness and deformation‐induced α′‐martensite in the fatigue behavior of both metastable and stable materials. While surface roughness is a well‐known key factor in conventional fatigue cases, deformation‐induced martensite layers implemented by various surface modification methods were proven to improve the fatigue life in metastable austenitic steels, opening new perspectives to extend the lifetime of ASS components.

The role of the water contact layer on hydration and transport at solid/liquid interfaces

Understanding the structure in the nanoscopic region of water that is in direct contact with solid surfaces, so-called contact layer, is key to quantifying macroscopic properties that are of interest to e.g. catalysis, ice nucleation, nanofluidics, gas adsorption, and sensing. We explore the structure of the water contact layer on various technologically relevant solid surfaces, namely graphene, MoS[Formula: see text], Au(111), Au(100), Pt(111), and Pt(100), which have been previously hampered by time and length scale limitations of ab initio approaches or force field inaccuracies, by means of molecular dynamics simulations based on ab initio machine learning potentials built using an active learning scheme. Our results reveal that the in-plane intermolecular correlations of the water contact layer vary greatly among different systems: Whereas the contact layer on graphene and on Au(111) is predominantly homogeneous and isotropic, it is inhomogeneous and anisotropic on MoS[Formula: see text], on Au(100), and on the Pt surfaces, where it additionally forms two distinct sublayers. We apply hydrodynamics and the theory of the hydrophobic effect, to relate the energy corrugation and the characteristic length-scales of the contact layer with wetting, slippage, the hydration of small hydrophobic solutes and diffusio-osmotic transport. Thus, this work provides a microscopic picture of the water contact layer and links it to macroscopic properties of liquid/solid interfaces that are measured experimentally and that are relevant to wetting, hydrophobic solvation, nanofluidics, and osmotic transport.

Rapid and sensitive determination of residual prion infectivity from prion-decontaminated surfaces.

Prion diseases are untreatable fatal transmissible neurodegenerative diseases that affect a wide range of mammals, including humans, and are caused by PrPSc, the infectious self-templating conformation of the host-encoded protein, PrPC. Prion diseases can be transmitted via surfaces (e.g., forceps, EEG electrodes) in laboratory and clinical settings. Here, we use a combination of surface swabbing and real-time quaking-induced conversion (RT-QuIC) to test for residual surface-associated prions following prion disinfection. We found that treatment of several prion-contaminated laboratory and clinically relevant surfaces with either water or 70% EtOH resulted in robust detection of surface-associated prions. In contrast, treatment of surfaces with sodium hypochlorite resulted in a failure to detect surface-associated prions. RT-QuIC analysis of prion-contaminated stainless steel wires paralleled the findings of the surface swab studies. Importantly, animal bioassay and RT-QuIC analysis of the same swab extracts are in agreement. We report on conditions that may interfere with the assay that need to be taken into consideration before using this technique. Overall, this method can be used to survey laboratory and clinical surfaces for prion infectivity following prion decontamination protocols.IMPORTANCEPrion diseases can be accidentally transmitted in clinical and occupational settings. While effective means of prion decontamination exist, methods for determining the effectiveness are only beginning to be described. Here, we analyze surface swab extracts using real-time quaking-induced conversion (RT-QuIC) to test for residual prions following prion disinfection of relevant clinical and laboratory surfaces. We found that this method can rapidly determine the efficacy of surface prion decontamination. Importantly, examination of surface extracts with RT-QuIC and animal bioassay produced similar findings, suggesting that this method can accurately assess the reduction in prion titer. We identified surface contaminants that interfere with the assay, which may be found in clinical and laboratory settings. Overall, this method can enhance clinical and laboratory prion safety measures.

MiR-1915-3p regulates megakaryocytic and erythroid differentiation by targeting SOCS4

BackgroundProper control of the lineage bias of megakaryocytic and erythroid progenitor cells (MEPs) is of significant importance, the disorder of which will lead to abnormalities in the number and function of platelets and erythrocytes. Unfortunately, the signaling pathways regulating MEP differentiation largely remain to be elucidated. This study aimed to analyze the role and the underlying molecular mechanism of miR-1915-3p in megakaryocytic and erythroid differentiation.MethodsWe utilized miRNA mimics and miRNA sponge to alter the expression of miR-1915-3p in megakaryocytic and/or erythroid potential cells; siRNA and overexpression plasmid to change the expression of SOCS4, a potential target of miR-1915-3p. The expression of relevant surface markers was detected by flow cytometry. We scanned for miR-1915-3p target genes by mRNA expression profiling and bioinformatic analysis, and confirmed the targeting by dual-luciferase reporter assay, western blot and gain- and lost-of-function studies. One-way ANOVA and t-test were used to analyze the statistical significance.ResultsIn this study, overexpression or knockdown of miR-1915-3p inhibited or promoted erythroid differentiation, respectively. Accordingly, we scanned for miR-1915-3p target genes and confirmed that SOCS4 is one of the direct targets of miR-1915-3p. An attentive examination of the endogenous expression of SOCS4 during megakaryocytic and erythroid differentiation suggested the involvement of SOCS4 in erythroid/megakaryocytic lineage determination. SOCS4 knockdown lessened erythroid surface markers expression, as well as improved megakaryocytic differentiation, similar to the effects of miR-1915-3p overexpression. While SOCS4 overexpression resulted in reversed effects. SOCS4 overexpression in miR-1915-3p upregulated cells rescued the effect of miR-1915-3p.ConclusionsmiR-1915-3p acts as a negative regulator of erythropoiesis, and positively in thrombopoiesis. SOCS4 is one of the key mediators of miR-1915-3p during the differentiation of MEPs.

Langmuir monolayers provide an effective strategy for studying molecular recognition of nucleobases using alkylated nucleotides

Molecular Recognition in nucleotides is crucial for medicine, underpinning precise interactions in genetic replication and therapy. Alkylated nucleotides, in particular, play a key role in modifying DNA to inhibit cancer cell growth. In this study, we focused on an alkylated nucleotide, PNM2 (3′,4′,6’-O-tristearoyl uridine or uridine tri-stearate), to investigate the interaction between adenine molecules in the aqueous subphase and PNM2 Langmuir monolayers. Utilizing techniques such as tensiometry, Brewster angle microscopy, infrared spectroscopy, surface potential measurements, and dilatational surface rheology, we found compelling evidence of molecular Recognition between the polar head of the insoluble amphiphile (uridine) in the monolayer and adenine in the aqueous subphase, attributed to hydrogen bonding. These interactions significantly influenced the physicochemical properties of the air-water interface, including monolayer expansion upon molecular recognition, decreased dilatational modulus, increased tensiometric stability of the monolayer when compressed to relevant surface pressures, and decreased surface potential. These findings are noteworthy for drug development, providing crucial insights into the mechanisms of nucleotide interactions.

Tracking ultrafast non-adiabatic dissociation dynamics of the deuterated water dication molecule.

We applied reaction microscopy to elucidate fast non-adiabatic dissociation dynamics of deuterated water molecules after direct photo-double ionization at 61eV with synchrotron radiation. For the very rare D+ + O+ + D breakup channel, the particle momenta, angular, and energy distributions of electrons and ions, measured in coincidence, reveal distinct electronic dication states and their dissociation pathways via spin-orbit coupling and charge transfer at crossings and seams on the potential energy surfaces. Notably, we could distinguish between direct and fast sequential dissociation scenarios. For the latter case, our measurements reveal the geometry and orientation of the deuterated water molecule with respect to the polarization vector that leads to this rare 3-body molecular breakup channel. Aided by multi-reference configuration-interaction calculations, the dissociation dynamics could be traced on the relevant potential energy surfaces and particularly their crossings and seams. This approach also unraveled the ultrafast time scales governing these processes.

Tribocharged solids in protoplanetary discs: internal and external discharge time-scales

ABSTRACT Particles regularly tribocharge in collisions. Here, we study how long charges can persist on such particles in the environment of a protoplanetary disc. We set up three complementary experiments to quantify discharge time-scales. We first directly measure the time dependency of charge on triboelectrically charged objects. For this aspect, we performed two long-time experiments under different environmental conditions. We find that the charge persists on the tribocharged bodies on time-scales between minutes and years. Discharge might be mediated by external ions or internally, by conduction. To constrain the latter, we also determined the specific electric resistance of dust samples as simulants for dust aggregates in protoplanetary discs. In this third experiment, we see an increase in resistivity at decreasing ambient pressure up to the limit of the instrument. These findings are consistent with the assumption that water on all relevant surfaces including dust grains within the pore space of aggregates is the main driver of discharge. Under disc conditions, the charge might persist for weeks to years. This leaves net-charged isolated grains in dense parts of the mid-plane of protoplanetary discs charged in between collisions.

Improvement of the thermionic emission properties of C12A7 electride

Calcium aluminate electride (named as C12A7) has become an active topic as a material for electron emission in the research field of electron sources, especially for electric propulsion, in recent years. Whereas the initially predicted, extremely low work function of 0.6 eV could not be confirmed experimentally at technically relevant surface current densities, the material remains an attractive emitter. Besides C12A7 emitting electrons at lower temperatures compared to LaB6, it appears to be resistant to poisoning and even iodine compatible as only known low work function material. On the other hand, the ceramic electride nature of the emitter introduces challenges related to the thermal, mechanical and electrical properties. Therefore, C12A7 has been investigated experimentally as a candidate material for thermionic emitters in space applications. The aim of this study was to enhance the thermionic emission by material modifications such as surface treatments, electrical contacting methods and doping of the C12A7. The performance improvement was quantified in a thermionic diode configuration, in which the emission current was determined as a function of temperature over multiple heating cycles to observe time dependent effects. The surface treatment such as grinding or polishing affects the emission properties of the C12A7 negatively. In contrary, the doping of the C12A7 lattice as well as the contacting of the back side (heater side) significantly improved the emission as well as the measured current density.

A New Perspective on Internal Turbine Blade Cooling by Perforated Blockages and Pin-Fins

Abstract The cooling configuration, sequentially combining perforated blockages (forming blockage jets) and a pin-fin array inside the trailing-edge of a turbine blade has been perceived unsuitable due to the presumed inferior thermal performance (η < 1.0). In the present study, we provide a new perspective on this particular cooling configuration, based on fluidic mechanisms, newly established in a better representative setup for blockage jets aligned with pin-fins, accounting for relevant heat transfer surfaces. To this end, heat transfer on the blockage, pin-fin, and end-wall surfaces was measured at a selected Reynolds number of ReD = 26,000 using a thermochromic liquid crystal technique. Flow field mapping by particle image velocimetry and oil–dye flow visualization were supplementally performed. We demonstrate, contrary to previous studies that the thermal performance of the blockage pin-fin configuration can be e.g., η = 1.1 if the blockages and pin-fins are arranged to maximize both elements' thermofluidic advantages. Our data further suggest that unlike conventional pin-fin configurations subjected to uniform coolant stream, the blockage pin-fin configuration can offer a better performance with fewer pin-fin rows used.

Density functional theory analysis of the stability of H[formula omitted]O and CO[formula omitted]-derived surface species over low-index Ni facets

Analysis of stability of chemical species over catalytic surfaces is crucial for understanding the surface-specific effects to reach optimal catalyst composition. With reference to CO2 hydration, we undertook the task of unravelling the same over Ni surfaces, and examined the effect of exposed surface facets on the stability of relevant surface species. By examining H2O and CO2-derived surface species over Ni(100), Ni(110), and Ni(111) surface facets, we investigated the adsorption and dissociation of H2O and CO2-derived surface, enabling a thorough comparison of facet effects. A linear scaling relationship between the adsorption energy of the adsorbates and Bader charges was observed, providing an evidence that the binding energy of surface species originating from H2O and CO2 was closely correlated to the degree of electron transfer from Ni to the adsorbed species. Understanding of the binding and stability of H2O and CO2-derived species over Ni surfaces was furthered by the analysis of the charge density iso-surfaces. Stability plots and reaction paths highlighted Ni(100) and Ni(110) to be superior to Ni(111). Ni(110) exhibited the lowest H2O dissociation barrier, while Ni(100) showed favourable CO2 dissociation barriers citing Ni(110) surface facet as the most suited plane for selective CO2 hydration.

Valorization of agricultural olive waste as an activated carbon adsorbent for the remediation of water sources contaminated with pharmaceuticals

The present study investigates the performance of activated carbon from olive pomace (ACOP) in the removal of hydrophilic organic pharmaceutical micropollutants such as the antibiotic sulfamethoxazole (SMX) from water. The adsorption behavior of two chemically modified ACOP was investigated considering their interesting textural properties, relevant surface functions and charges. The performances in terms of adsorption capacity were investigated and optimized with respect to the main operating conditions. Comparison of SMX adsorption capacities on ACOP with commercial powdered activated carbon and nanoporous carbonaceous materials prepared from argan shells revealed that ACOP enabled the highest adsorption capacities (39.68 mg g−1). The adsorption behavior was attributed not only to the textural properties, such as the large surface area (1857 m2 g−1) and porosity, but also to the charge and functional groups of the surface.

Development and experimental evaluation of surface enhancement methods for laser powder directed energy deposition microchannels

ABSTRACT This research evaluates Laser Powder Directed Energy Deposition (LP-DED) for producing fine feature internal microchannels. This study is focused on enhancing and characterising the surfaces of microchannels produced using techniques such as abrasive flow machining, chemical milling, chemical mechanical polishing, electrochemical machining, and thermal energy method to modify internal surfaces of microchannels made from NASA HR-1 Fe-Ni-Cr alloy. Flow testing for discharge coefficient measurement is conducted on processed microchannel samples, followed by characterisation through optical microscopy, Scanning Electron Microscopy (SEM), and Computed Tomography. Findings reveal variations in surfaces due to powder adherence, melt pool undulations, and polishing mechanisms. The study emphasises the significance of removing material equivalent to the mean powder diameter to reduce surface roughness and impact the discharge coefficient. The research proposes a ratio for planarising roughness and waviness peak height and density, offering insights for tailored surface adjustments in specific applications requiring reduced flow resistance. Highlights Internal microchannels with thin-walls were fabricated using the laser powder directed energy deposition process. Various surface enhancements and polishing processes were developed to modify the surface texture of the LP-DED channels. Flow testing was conducted to determine the discharge coefficient. Post-test characterisation was completed to obtain cross sectional area, perimeter, surface texture, and general surface condition to analyse results. Ratio of roughness and waviness peak and density (Spk/Spd and Wp/WPc) is proposed as a relevant surface characterisation parameter. Tailored surface modifications for specific end-use applications.

Experimental Analysis of the Time-Wise Compressor Fouling Phenomenon

Abstract Compressor fouling is still an unforeseen phenomenon. Gas turbines for heavy-duty and propulsion applications are subject to performance degradation due to fouling, erosion, and corrosion mechanisms. Unlike the last two, the fouling phenomenon is recoverable depending on weather, operating conditions, and operator actions. It is generated by the adhesion of micro-sized particles on the relevant surfaces, generating blade shape and surface roughness variations. Fouling could affect the machine performance differently. The interaction between machine characteristics, airborne contaminants, and environmental conditions determines fouling prediction challenges. An experimental campaign has been carried out in the present analysis to study the overtime modification of compressor performance and mass deposits on the blade and vane surfaces. The axial unit has been operated to control the performance and deposition process by keeping the contamination and the relative humidity constant during the time. The test matrix has been based on two relative humidity values and four exposure time intervals. The results have shown the action of the competitive phenomena as adhesion and detachment, generating a non-linear trend of the deposited mass−time relation depending on impact characteristics and humidity values. Compressor performance follows similar behavior and shows a non-linear trend instead of constant contamination. Data interpretation and generalization are reported to increase the possibility of better predicting the effects of particle adhesion on gas turbine performance degradation.