High Roughness Research Articles

Maximizing Roughness Factors in Oxide-Derived Copper Coatings through Electrodeposition Parameters for Enhanced Electrocatalytic Performance

The pursuit of novel techniques for obtaining dispersed copper-based catalysts is crucial in addressing environmental issues like decarbonization. One method for producing nanostructured metals involves the reduction of their oxides, a technique that has found widespread use in CO2 electroreduction. Currently, the intrinsic activities of oxide-derived copper electrocatalysts produced via different routes cannot be compared effectively due to the lack of information on electrochemically active surface area values, despite the availability of electrochemical methods that enable estimation of surface roughness for highly dispersed copper coatings. In this study, we aim to explore the potential of oxide-derived copper to achieve a high electrochemically active surface area by examining samples obtained from acetic and lactic acid deposition solutions. Our results revealed that Cu2O oxides had distinct morphologies depending on the electrodeposition solution used; acetate series samples were dense films with a columnar structure, while electrodeposition from lactic acid yielded a fine-grained, porous coating. The roughness factors of the electroreduced films followed linear relationships with the deposition charge, with significantly different slopes between the two solutions. Notably, a high roughness factor of 650 was achieved for samples deposited from lactic acid solution, which represents one of the highest estimates of electrochemically active surface area for oxide-derived copper catalysts. Our results highlight the importance of controlling the microstructure of the electrodeposited oxide electrocatalysts to maximize surface roughness.

Strength of a Zirconia- Reinforced Glass-Ceramic After Diamond Bur Adjustment.

Adjustments with diamond burs on the ceramic surface can affect its roughness and decrease flexural strength. This study evaluated the effect of polishing or glazing on the surface roughness and biaxial flexural strength of a zirconia-reinforced lithium silicate glass-ceramic upon adjustment with diamond burs. Seventy disks were prepared according to ISO 6872 and divided into seven groups (n = 10) according to different adjustments and finishing processes. Surface roughness was measured prior to biaxial flexural strength testing. The topography was analyzed using an atomic force microscope , fracture markings were identified using a stereomicroscope and representative specimens were analyzed using scanning electron microscopy. The use of diamond burs significantly increased the surface roughness and decreased the strength of the evaluated ceramic (p⟨0.05). Polishing reduced the ceramic's roughness but resulted in flexural strength similar to that of the groups with wear (p⟩0.05). The glaze-treated specimens showed flexural strength statistically similar to the control group (p>0.05) but higher roughness, similar to those with wear. Polishing reduced the surface roughness but did not affect the biaxial flexural strength of the ZLS ceramic. At the same time, the application of glaze after wear increased the strength.

Roughness Factors of Electrodeposited Nanostructured Copper Foams

Copper-based electrocatalytic materials play a critical role in various electrocatalytic processes, including the electroreduction of carbon dioxide and nitrate. Three-dimensional nanostructured electrodes are particularly advantageous for electrocatalytic applications due to their large surface area, which facilitates charge transfer and mass transport. However, the real surface area (RSA) of electrocatalysts is a crucial parameter that is often overlooked in experimental studies of high-surface-area copper electrodes. In this study, we investigate the roughness factors of electrodeposited copper foams with varying thicknesses and morphologies, obtained using the hydrogen bubble dynamic template technique. Underpotential deposition (UPD) of metal adatoms is one of the most reliable methods for estimating the RSA of highly dispersed catalysts. We aim to illustrate the applicability of UPD of lead for the determination of the RSA of copper deposits with hierarchical porosity. To find the appropriate experimental conditions that allow for efficient minimization of the limitations related to the slow diffusion of lead ions in the pores of the material and background currents of the reduction of traces of oxygen, we explore the effect of lead ion concentration, stirring rate, scan rate, monolayer deposition time and solution pH on the accuracy of RSA estimates. Under the optimized measurement conditions, Pb UPD allowed to estimate roughness factors as high as 400 for 100 µm thick foams, which translates into a specific surface area of ~6 m2·g−1. The proposed measurement protocol may be further applied to estimate the RSA of copper deposits with similar or higher roughness.

Diffuser optimization for enhancing light extraction from light-emitting electrochemical cells

Light-emitting electrochemical cells (LECs) have enabled many novel solution-processable, low-cost, and flexible emission applications. Nevertheless, relatively inferior device efficiencies render LECs less competitive with other emission technologies. Light extraction would be a promising approach to enhance the device efficiencies of LECs. The diffuser film composed of a transparent photoresist layer doped with large and small TiO2 nanoparticles (NPs) embedded between the indium-tin-oxide layer and the glass substrate has shown superior light extraction performance (>2.5X). However, the physical insight of optimization, e.g., adjusting the concentration of small TiO2 NPs in diffuser film, has not been explored yet. In this work, increasing the concentration of small TiO2 NPs is found to increase the thickness, roughness, and refractive index of the diffuser film. The optical simulation indicates that the thickness of the diffuser film has little effect on the light extraction. However, a higher roughness but a lower refractive index is preferred for the diffuser film to achieve better light extraction. As such, it is rational to expect that a proper concentration of small TiO2 NPs to reach a high enough roughness but still keep a relatively low refractive index is required for diffuser optimization. This study clarifies the physical mechanism responsible for diffuser optimization and thus shows a high potential for lighting applications of LECs.

Cake layer discrepancy triggered by different pore sizes in an anaerobic membrane bioreactor

Cake layer formation is a key contributor to anaerobic membrane bioreactor (AnMBR) fouling. This study identified the discrepancy in the cake layer formation triggered by the pore size of the AnMBR. Five membrane modules with different pore sizes of 0.1, 0.22, 0.45, 1, and 5 μm were operated synchronously in the same AnMBR over a 120-day period. The transmembrane pressure (TMP) was observed and classified into three stages for each membrane. Pore size did not cause an obvious cake layer discrepancy at the initial stage, where the TMP increased. However, the membranes with larger pore sizes had a longer weak rise in the TMP during cake layer formation. The cake layer on the membranes with smaller pore sizes formed rapidly, but the cake layer on the membranes with bigger pore sizes could mitigate the TMP jump. The 0.45 μm membrane had the highest roughness and most severe cake layer formation. Acinetobacter showed obvious growth during cake layer formation, especially with a higher bacterial capacity on the membranes with smaller pore sizes. Pore size did not cause a genus-level discrepancy. However, there was a variation in bacterial percentage during cake layer formation.

Analysis of physical, chemical, mechanical, and microbiological properties of Ti–35Nb–7Zr–5Ta and Ti–6Al–4V discs obtained by machining and additive manufacturing

The objective was to compare the physical, chemical, mechanical, and microbiological properties between discs (n = 10) of Ti–6Al–4V and Ti–35Nb–7Zr–5Ta (TNZT) obtained by Machining (M) and additive manufacturing (AM) by Laser Powder Bed Fusion technique to identify the influence of chemical composition and processing technique on material properties. Using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), x-ray diffraction (XRD), wettability, surface free energy, roughness by confocal laser microscopy and atomic force microscopy (AFM), Vickers microhardness (VM), and colony forming units (CFU) against S. aureus. Two-way ANOVA (p < 0.05) was applied. Higher roughness and irregularity were observed in the AM discs. The chemical composition of the EDX alloys was compatible with the concentrations expected and available in the literature. For TNZT the manufacturing technique interfered in the present phases (α and β) due to different cooling rates. The wettability and surface free energy of TNZT was higher than that of Ti–6Al–4V, and there was no significant difference for the manufacturing techniques. Ti–6Al–4V showed greater hardness than TNZT and the M technique greater than AM. There was no difference in S. aureus CFU between the groups. It was concluded that TNZT alloy showed higher hydrophilicity, surface free energy, roughness, lower hardness, manufacturing techniques that interfered in its phases, and no differences for CFU compared to Ti–6Al–4V. The AM technique generated more irregular and rough surfaces, and lower hardness, without significant changes concerning M in terms of chemical composition, wettability, surface free energy, and bacterial formation.

Influence of a D-enantiomeric peptide on the anticorrosion ability of titanium with different surface roughness against Streptococcus mutans biofilms

ObjectiveTo investigate the effectiveness of a d-enantiomeric antibiofilm peptide (DJK-5) on the anticorrosion ability of titanium (Ti) with different surface roughness against Streptococcus mutans biofilms. MethodsCommercially pure Ti disks with machined (MA, smooth) or sandblasted + acid-etched (SLA, rough) surfaces were prepared and characterized. All disks were divided into three groups: a positive control (PC) group with S. mutans, a DJK-5-treated group, and a negative control (NC) group without S. mutans. Biofilm formation and corrosion on Ti surfaces were determined by confocal laser scanning microscopy and scanning electron microscopy after 2 and 6 days, and the electrochemical properties were evaluated. ResultsTen μg/mL of DJK-5 killed 83.3 % and 87.4 % of biofilms on SLA and MA Ti surfaces, respectively after 2 days, and 72.9 % and 77.7 % after 6 days, with more bacteria surviving on SLA surfaces with higher roughness (p < 0.05). DJK-5 treatment induced less surface defects with tiny pit corrosion than PC. DJK-5 treatment when compared to PC, led to electrochemical properties more reflecting NC surfaces, including significantly less negative corrosion potential, lower corrosion current, and higher passive film resistance (p < 0.05). SLA surfaces exhibited higher current density and lower resistance than MA surfaces (p < 0.05). ConclusionDJK-5 effectively enhanced the corrosion resistance of Ti with different surface roughness while killing S. mutans biofilms, and smooth surfaces were more susceptible to peptide treatment. Clinical significanceThe antibiofilm peptide is promising for promoting the anticorrosion ability of Ti against biofilms, thereby preventing biofilm-related infections.

Analysis of Surface and Physicochemical Properties of Novel Hydrogel Materials Supported with Magnetic Nanoparticles

Nanotechnology is a field of science that has been growing rapidly in recent times. The use of this science in medicine makes it possible to develop new innovative therapies and materials with therapeutic effects. The topic of controlled delivery of therapeutic substances using appropriate carriers is extremely important. Such carriers can be, among others, magnetic nanoparticles. In the present study, magnetic nanoparticles coated with nanosilver were obtained. This carrier was then placed in a hydrogel matrix. The study shows that the properties of the obtained materials indicate their high application potential as transdermal systems. In this work, hydrogel materials modified with magnetic nanoparticles with silver were subjected to a physicochemical analysis. The sorption capacity of these materials was determined, and they were subjected to infrared spectroscopy analysis and incubation tests in simulated body fluids. In addition, the surface of these materials was characterized in detail. The results indicated that all the materials exhibit excellent sorption capacities, and their surfaces are characterized with high roughness.

Hydrophobic-oleophobic polyurethane with mechanical reinforcement: Synthesized by thiol-ene click chemistry

Polyurethane (PU) is a universal polymer material with excellent performance, widely used as foam materials, adhesives, coatings, rubber, etc. Nevertheless, the considerable presence of ester and ether bonds in the polyurethane backbone, combined with the hydrophilic –OH group located at the end of molecular chain, renders it intrinsically hydrophilic. This inherent hydrophilicity presents substantial constraints on its potential utilization in flexible electronic displays, wearable electronic devices, and various other fields. It is a great challenge for hydrophobic polyurethane to simultaneously achieve mechanical reinforcement. Herein, the fluorinated chain extenders were introduced into PU, which not only resulted in low surface energy but also improved the surface roughness through the microphase separation due to the difference in the solubility parameters between the fluorine-containing side chain and the main chain. The long-chain perfluorinated extender was achieved via thiol-ene click chemistry, thus regulating the fluorine content by adjusting the amount of chain extender. The low surface energy and high roughness, developed by microphase separation, make the DFX-PU films exhibit excellent hydrophobicity (120°) and oleophobicity (121°). Additionally, the fluorine-containing side chains aggregate to form physical cross-linking points, reinforcing the mechanical properties of the film. When the fluorine-containing chain extender accounted for 10% (DF0.5-PU), the PU film showed the best mechanical properties. Compared with the control group, tensile strength is enhanced by 165%, the toughness is increased by 287%, and the elongation-at-break was improved by 156%.

Rolling contact fatigue failure mechanism of bearing steel on different surface roughness levels under heavy load

It is inherent knowledge that rolling contact fatigue (RCF) failure of subsurface-initiated spalls usually occur under optimum surface under heavy load. However, our previous work has revealed surface-initiated RCF failure mechanism under heavy load and initial high roughness surface. The formation of surface crack caused by RCF is a complicated phenomenon that is accompanied by surface morphology and lubrication condition, as well as stress distribution and microstructure evolution. To clarify the main failure mechanism, this study carried out systematic RCF tests with different surface roughness specimens and conducted characterization of superficial microstructure for specimens of pre-service and post-service by Focused Ion Beam (FIB). The results clearly suggest precursor of collapsed morphology and nanocrystalline layer are the main factor that causes the RCF life with high roughness is lower than that with low roughness. While the spalling failure initiating from low roughness surface under heavy load are strongly relied on surface plastic deformation. Two main plastic deformation mechanisms are conductive to formation of surface cracks: the micro-plastic deformation and the local severe plastic flow. A newly failure mechanism that spalling failure initiates from surface has been proposed to link surface roughness and microstructure evolution.

Structure and Mechanical Properties of Milled and 3D-Printed Ti-6Al-4V Alloys for Subtractive and Additive CAD/CAM Manufacturing in Dentistry

The mechanical properties, structure, and morphology of milled and 3D-printed Ti-6Al-4V alloys produced by selective laser melting were investigated in this study. The mechanical properties were investigated by means of nanoindentation, a tensile test, and a three-point bending test. An Atomic Force Microscope (AFM) was used to study the surface topography and roughness of both titanium alloys. The surface structure and phase analyses were studied by a scanning electron microscope (SEM) and through powder X-ray diffraction (XRD). The results from the nanoindentation experiments showed that the 3D-printed sample has higher indentation hardness and modulus than the milled one. The AFM observation of the surface topography of the samples showed that the milled sample has a higher roughness than the 3D-printed one. The tensile test results showed that the 3D-printed sample by means of Selective Laser Melting (SLM) technology has about 26% higher tensile strength and smaller elongation than the milled one. The three-point bending test revealed that the 3D-printed Ti-6Al-4V sample has higher flexural strength than the milled one. It was found that the 3D-printed sample has a smaller crystal size than the milled one, which, according to the Hall–Petch relationship, leads to its higher indentation hardness.

Influence of Surface Preparation on the Microstructure and Mechanical Properties of Cold-Sprayed Nickel Coatings on Al 7075 Alloy

This work presents the effect of surface roughness (Al 7075) on the microstructure and mechanical properties of cold-sprayed nickel coatings. Coating analysis included substrate surfaces and coating geometry, microstructure characterization, microhardness, nanohardness, elastic modulus, and adhesion. The results show that the surface preparation had a significant effect on coating adhesion and microstructure. The coating deposited at the highest gas temperature revealed a dense microstructure, showing very good adhesion of the impacting powder particles to the substrate and good bonding between deposited layers. The Ni grains with different shapes (elongated, equiaxed) and sizes of a few dozen to several hundred nanometres were present in the splats. An increase in temperature caused significant growth in coating thickness as a result of the powder grains’ higher velocity. Moreover, higher gas temperature resulted in the enhancement of micro- and nanohardness, elastic modulus, and adhesion. The adhesive bond strength of Ni coatings in the tested temperature ranges from 500 °C to 800 °C increased with the increase in the surface roughness of the substrate. For the Al 7075 coarse grit-blasted (CG) substrate with the highest roughness, the adhesion reached the highest value of 44.6 MPa when the working gas was at a temperature of 800 °C. There were no distinct dependencies of surface roughness and thickness on the mechanical properties of the cold-sprayed nickel coating.

Surface wettability patterning of metal additive manufactured parts via laser-assisted functionalization

Additive manufacturing (AM) has revolutionized the production of complex geometries with superior properties compared with traditional manufacturing methods. However, the high roughness and poor wettability of as-produced surfaces of AM parts limit their suitability for certain applications. To address this, we present a maskless laser-assisted surface functionalization method to improve the wettability of metal 3D printed parts. This study explores the potential of combining metal AM with surface wettability patterning, a promising technique in fluid-related fields. Large-area AlSi10Mg parts were fabricated using laser powder bed fusion (L-PBF), followed by an innovative laser-assisted functionalization (LAF) method to achieve patterned wetting surfaces. The LAF method consists of laser texturing and chemical modification steps, and two strategies were demonstrated to fabricate different types of wettability patterns. Strategy I helps produce two types of superhydrophobicity, while strategy II helps create a superhydrophobic-superhydrophilic patterned surface. The study demonstrates the simplicity, robustness, and feasibility of the process and analyzes the processing mechanism, surface topography, and surface chemistry. The integration of surface wettability patterning and 3D-printing can optimize components to enhance performance and efficiency by creating intricate fluid flow pathways. Overall, this work highlights the potential of combining metal AM with surface wettability patterning, providing a pathway to produce high-performance parts with tailored wettability properties. This research has significant implications for fluid-related industries such as aerospace, automotive, and energy, as it offers unparalleled design freedom and the ability to create complex geometries.

Large-Eddy Simulations of the Tropical Cyclone Boundary Layer at Landfall in an Idealized Urban Environment

Abstract Populated urban areas along many coastal regions are vulnerable to landfalling tropical cyclones (TCs). To the detriment of surface parameterizations in mesoscale models, the complexities of turbulence at high TC wind speeds in urban canopies are presently poorly understood. Thus, this study explores the impacts of urban morphology on TC-strength winds and boundary layer turbulence in landfalling TCs. To better quantify how urban structures interact with TC winds, large-eddy simulations (LESs) are conducted with the Cloud Model 1 (CM1). This implementation of CM1 includes immersed boundary conditions (IBCs) to represent buildings and eddy recycling to maintain realistic turbulent flow perturbations. Within the IBCs, an idealized coastal city with varying scales is introduced. TC winds impinge perpendicularly to the urbanized coastline. Numerical experiments show that buildings generate distinct, intricate flow patterns that vary significantly as the city structure is varied. Urban IBCs produce much stronger turbulent kinetic energy than is produced by conventional surface parameterizations. Strong effective eddy viscosity due to resolved eddy mixing is displayed in the wake of buildings within the urban canopy, while deep and enhanced effective eddy viscosity is present downstream. Such effects are not seen in a comparison LES using a simple surface parameterization with high roughness values. Wind tunneling effects in streamwise canyons enhance pedestrian-level winds well beyond what is possible without buildings. In the arena of regional mesoscale modeling, this type of LES framework with IBCs can be used to improve parameters in surface and boundary layer schemes to more accurately represent the drag coefficient and the eddy viscosity in landfalling TC boundary layers. Significance Statement This is among the first large-eddy simulation model studies to examine the impacts of tropical cyclone–like winds around explicitly resolved buildings. This work is a step forward in bridging the gap between engineering studies that use computational fluid dynamics models or laboratory experiments for flow through cities and mesoscale model simulations of landfalling tropical cyclones that use surface parameterizations specialized for urban land use.

Temperature-dependent dielectric investigation of dual-ions doped hydroxyapatite nanoparticles

Different metal ions doped hydroxyapatite (HAp) nanoparticles were prepared by the sol–gel method. The phase analysis and the average surface roughness are determined using powder.X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The synthesized dual-ions doped hydroxyapatite nanoparticles exhibit a stable HAp structure without any impurity peaks. The higher roughness (Ra) value of 65.839 nm and the lower roughness (Ra) value of 4.5276 nm were obtained for Magnesium-Zinc HAp (Mg-ZnHAp) and Copper-Zinc HAp (Cu-Zn-HAp) samples, respectively. We found the hardness value increased with the addition of dual dopant ions in HAp. The decrease in hardness of the (Mg-ZnHAp) sample is found to be due to a decrease in the density of dopant ions in HAp. The modification in the dielectric properties of dual-ions doped HAp by varying the temperature as a function of frequency is analyzed. Temperature-dependent dielectric studies unveiled the non-Debye-type relaxation behaviour in the synthesized samples. The dielectric values as a function of frequency show the deviations in peaks are due to polarization with respect to different temperatures.

Comparative investigation on organosilicon film growth by cyclonic plasma using hexamethyldisilazane and hexamethyldisilazane/nitrogen gas mixture

This study aimed to discover the surface characteristics of cyclonic plasma‐deposited films and the effect of nitrogen gas addition. The influence of nitrogen gas addition on the surface characteristics of organosilicon films in hexamethyldisilazane (HMDSN) and HMDSN/nitrogen (HMDSN/N2) cyclonic plasmas at atmospheric pressure was evaluated. It was found that the addition of nitrogen gas is a crucial factor affecting organosilicon film growth in the plasma cyclone in one atmosphere. SEM, AFM, and ATR‐FTIR results indicated that on adding nitrogen gas, the surface morphology became rougher, the peak corresponding to the Si–O–Si group was detected at approximately 1050 cm−1, the degree of porosity was relatively low, and the proportion of the SiCHx group decreased. In general, the surface energies of the films deposited in the HMDSN discharge and the HMDSN/N2 gas mixture discharge exhibited similar features. SEM and AFM evaluations showed high roughness values of 44.5 nm for the film formation in the HMDSN/N2 gas mixture discharge, while the films grown in the HMDSN discharge exhibited a relatively flat surface with a roughness of 24.5 nm. Based on ATR‐FTIR detection, cyclonic plasma‐deposited films deposited in the HMDSN discharge obtained organic moieties, while the films generated in the HMDSN/N2 gas mixture discharge exhibited strong Si–O–Si absorption signals. A possible nano‐organosilicon film growth that prevails in atmospheric pressure plasma deposition is proposed based on atmospheric‐pressure plasma chemistry, nitrogen gas addition, and experimental observations.

Development and characterization of new formulation of biodegradable emulsified film based on polysaccharides blend and microcrystalline wax

Abstract The aim of the present work is the development and characterization of new formulation of emulsified films based on soluble starch/sodium alginate blend and microcrystalline wax. The developed films were studied in order to use them as new formulations to produce food packaging. The obtained films were generally homogeneous, thin, and slightly flexible. These films appeared more opaque compared to the non-emulsified film. Incorporation of microcrystalline wax was caused modifications of mechanical properties of films; these modifications were principally due to the formation of amylose–lipid complex. It was found that microcrystalline significantly reduced film water vapor permeability (WVP) of emulsified films. Atomic force microscope (AFM) was used to evaluate surface topography and roughness of the films. The surface topography was significantly affected, in the other word high roughness values were obtained. Microemultion formation in which the microcrystalline wax particles are distributed homogeneously within the polymer matrix was investigated by scanning electron microscopy (SEM). Moreover, the polysaccharides blend/microcrystalline wax emulsified films can be useful as a biodegradable packaging material to maintain the quality of food products.

Pre-treatment of steel slag and its applicability in asphalt mixtures for sustainable pavements

The secondary utilization of steel slag is significant for land occupation reduction, natural aggregate conservation, and environmental protection. This study aims to enhance the utilization of steel slag aggregate (SSA) in pavement engineering by providing guidance on selecting efficient and rapid pre-treatment methods. It compares the macroscopic morphological characteristics of basalt, SSA, and SSA prepared using various pre-treatment methods. The chemical composition and surface micromorphology of the samples were investigated by X-ray fluorescence spectrometry and scanning electron microscopy. The effects of the pre-treatment methods on the SSA and the performance of its asphalt mixture were comparatively evaluated based on laboratory tests. The carbon dioxide equivalent (CO2e) and cost associated with steel slag asphalt mixtures were quantified in this study. The findings revealed that the high angularity and roughness of the SSA make it an ideal candidate for use in pavement layer aggregates. Pre-treatment methods such as thermal water and acetic acid soaking expedited the hydration and oxidation reactions. Furthermore, applying a silane coupling agent resulted in the forming of a polymer membrane on the SSA surface, significantly enhancing its volume stability and adhesive properties. All these methods present compelling alternatives to natural aging. Compared with the original SSA, the performance of asphalt mixtures prepared using pretreated SSA was optimized, particularly concerning the volumetric stability and moisture damage resistance. In general, although the CO2e from using SSA for pavement construction increased compared to those using other substances, the CO2e was significantly lower than those from SSA lying idle, which positively impacts the alleviation of SSA accumulation and promotes sustainable development.

Heat Transfer in an Injector-Scaled Additively Manufactured Fuel Passage

Abstract Knowledge of heat transfer in fuel wetted passages is important for informing injector design and life estimates due to the effects of temperature on fuel degradation. Future injectors will be manufactured using additive methods in an effort to reduce production costs and time, while also facilitating more agile design practices. Additive manufacturing (AM) is known to result in increased surface roughness compared to conventional manufacturing techniques, however limited data exist on how this roughness impacts heat transfer, particularly in liquid flows. This paper solves the inverse heat conduction problem for heat transfer coefficient in liquid flows through rough 90 deg channel bends typical of the pilot gallery in a lean direct-injection fuel spray nozzle. Heat transfer distributions across two rough surfaces are compared to an equivalent smooth surface. The two rough surfaces have different morphologies but have the same relative effective sand grain roughness which is matched to a prototype AM fuel injector. The sand grain roughness is predicted from a correlation that has been adapted for the high relative roughness scales characteristic of additively manufactured fuel passages. The effective sand grain roughness estimated from surface measurements of a prototype AM fuel gallery was ∼13% of the passage hydraulic diameter. For the two rough surfaces, the heat transfer enhancement is up to three times the smooth surface value for the straight section preceding the bend and up to four times around the bend. Heat transfer distributions across the two rough surfaces are similar, but the magnitudes differ by ∼17% depending on the surface morphology. This highlights the importance of the heat transfer effectiveness of surface features, which unlike the sand grain roughness is not matched for the two surfaces considered. Adjusting the data for differences in heat transfer effectiveness corrects the average heat transfer for the rough surfaces to within 7%.

Rapid Surface Modification of Stainless Steel 304L Electrodes for Microbial Electrochemical Sensor Application.

Electrogenic microorganisms serve as important biocatalysts for microbial electrochemical sensors (MESes). The electrical signal produced is based on the rate of electron transfer between the microbes and electrodes, which represents the biotoxicity of water. However, existing MESes require complex and sophisticated fabrication methods. Here, several low-cost and rapid surface modification strategies (carbon powder-coated, flame-oxidized, and acid-bleached) have been demonstrated and studied for biosensing purposes. Surface-modified MESe bioanodes were successfully applied to detect multiple model pollutants including sodium acetate, ethanol, thinner, and palm oil mill effluent under three different testing sequences, namely, pollutant incremental, pollutant dumping, and water dilution tests. The carbon powder-coated bioanode showed the most responsive signal profile for all the three tests, which is in line with the average roughness values (Ra) when tested with atomic force microscopy. The carbon powder-coated electrode possessed a Ra value of 0.844, while flame-oxidized, acid-bleached, and control samples recorded 0.323, 0.336, and 0.264, respectively. The higher roughness was caused by the carbon coating and provided adhesive sites for microbial attachment and growth. The accuracy of MESe was also verified by correlating with chemical oxygen demand (COD) results. Similar to the sensitivity test, the carbon powder-coated bioanode obtained the highest R2 value of 0.9754 when correlated with COD results, indicating a high potential of replacing conventional water quality analysis methods. The reported work is of great significance to showcase facile surface modification techniques for MESes, which are cost-effective and sustainable while retaining the biocompatibility toward the microbial community with carbon-based coatings.