Roughness Density Research Articles

Structure and Functional Characteristics of Novel Polyurethane/Ferrite Nanocomposites with Antioxidant Properties and Improved Biocompatibility for Vascular Graft Development.

Novel ferrite/polyurethane nanocomposites were synthesized using the in situ polymerization method after the addition of different spinel nanoferrite particles (copper, zinc, and copper-zinc) and examined as potential coatings for medical devices and implants in vascular tissue engineering. The influence of the nanoferrite type on the structure and functional characteristics of the polyurethane composites was investigated by FTIR, SWAXS, AFM, TGA, DSC, nanoindentation, swelling behavior, water contact angle, and water absorption measurements. Biocompatibility was evaluated by examining the cytotoxicity and adhesion of human endothelial cells and fibroblasts onto prepared composites and performing a protein adsorption test. The antioxidant activity was detected by UV-VIS spectroscopy using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay. Embedding the different types of nanoparticles in the polyurethane matrix increased phase mixing, swelling ability, and DPPH scavenging, decreased surface roughness, and differently affected the stiffness of the prepared materials. The composite with zinc ferrite showed improved mechanical properties, hydrophilicity, cell adhesion, and antioxidant activity with similar thermal stability, but lower surface roughness and crosslinking density compared to the pristine polyurethane matrix. The in vitro biocompatibility evaluation demonstrates that all nanocomposites are non-toxic, exhibit good hemocompatibility, and promote cell adhesion, and recommends their use as biocompatible materials for the development of coatings for vascular implants.

Low-cost photogrammetry solutions for surveying confined underground spaces: testing the traditional set-up against 360° camera on Tombs of the Kings archaeological site

Abstract. This study explores low-cost photogrammetry solutions for surveying confined underground spaces, focusing on Tomb 7 at the UNESCO World Heritage Site, Tombs of the Kings in Paphos, Cyprus. The research, part of the ENGINEER project, compares traditional photogrammetric methods using frame cameras against a 360° multi-lens camera. The aim is to identify reliable, low-cost methods for 3D documentation of archaeological sites, which can be used for structural analysis and systematic monitoring.Three photogrammetric acquisition methodologies were tested: handheld with frame camera, standard with frame camera, and relaxed with 360° camera. The study evaluates the accuracy of these acquisition methods by comparing dense point clouds generated from each dataset against a reference dataset obtained via terrestrial laser scanning (TLS). Metrics such as cloud-to-cloud distance, roughness, and point cloud density were used for comparison.Results indicate that while the 360° camera offers ease of use and high data density, it also introduces more noise and variability. Traditional methods, though more time-consuming, provide more consistent and accurate results. The findings suggest that combining both approaches could optimize data quality and acquisition efficiency, making the 360° multi-lens camera a viable low-cost photogrammetry option for heritage documentation.

Enhancing power density in D-mode GaN HEMT direct-current triboelectric nanogenerators through ICP-etched surface engineering

In the evolving landscape of energy harvesting, the refinement of friction properties in metal-semiconductor direct current triboelectric nanogenerators (MSDC TENGs) has garnered significant attention. While prior research predominantly concentrated on achieving superior performance in MSDC TENGs through material manipulation, structural adjustments, and friction mode optimization, there has been a noticeable dearth of investigations into surface engineering or modification of semiconductor materials. In this paper, the surface patterning of depletion mode GaN-based high electron mobility transistor (D-GaN HEMT) as friction materials is done by inductively coupled plasma etching method, involving both mechanism analysis and experimental exploration. Through modulation of etching depth and pattern density, a systematically arranged diamond pattern is created on the surface, augmenting surface roughness and charge density. Consequently, the surface-patterned D-GaN HEMT TENG achieves a maximum short-circuit current of 60 µA and a peak power density of 4.05 W/m², which is about 2.8 times greater than the pristine D-GaN HEMT TENG. Furthermore, the power supply capabilities of the surface-patterned D-GaN HEMT TENG are scrutinized, revealing its proficiency in capacitive charging and discharging. The successful activation of a deep ultraviolet LED underscores its potential applications in ultraviolet disinfection. This research holds substantial significance in optimizing the power generation efficiency and performance of MSDC TENGs employing D-GaN HEMT.

Fabrication and anti-fouling performance assessment of micro-textured CNT-PDMS nanocomposites through the scalable roll-coating process

This study investigates the micro-topographic surfaces as a benign anti-fouling/fouling-release method. The bio-inspired engineered surfaces were manufactured by controlling the viscoelastic instabilities of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS) nanocomposites using a customized, scalable two-roll coating process. The effects of manufacturing conditions, i.e., roller speed and roller radius-to-gap ratio, on surface properties, such as Wenzel roughness factor, peak density, water contact angle, and the tensile testing of the nanocomposite, were studied. The results showed that decreasing roller gap distance would significantly increase the hydrophobicity of the samples. Moreover, a positive correlation was observed between surface peak density and roughness factor. A textured sample was manufactured that significantly outperformed the non-textured CNT-PDMS, indicating a correlation between surface roughness and diatom attachment density. The dynamic diatom attachment assay showed up to 35% reduction in surface coverage of textured samples by the Navicula perminuta diatom compared to the non-textured CNT-PDMS control samples.

(Invited) Silicon Carbide Technology Scaling: Challenges and Opportunities across the Value Chain

Silicon Carbide (SiC) technology has emerged as a promising solution to address the growing demand for high-performance power electronics in various applications, ranging from automotive to renewable energy systems. As the industry continues to push the boundaries of SiC technology, scaling opportunities and challenges arise across the entire value chain, from material to device fabrication and new package architectures. In addition, it should be noted that scientific understanding, especially in the areas of defect behaviour in the SiC epitaxy layer, threshold voltage instability, interface trap density, and integrity of the gate insulator, would be increasingly important and necessary for the further development of SiC power devices. To address the economics, and mass produce ultra-high-power electronics devices with improved performance and reliability, we partnered with ecosystem players across the value chain from substrate to power module packaging and set up a 200mm SiC specialty open innovation process line.This talk will provide an overview of the key challenges and opportunities associated with SiC technology. We will discuss the high grow rate (≥50µm/hr) SiC epitaxy process and share methodologies to achieve high-quality epitaxy layer with good doping control (≤10%), tight thickness uniformity (≤3%), low surface roughness (≤3Å) and low crystal defect densities (≤0.4 cm-2) on 200mm 4H-SiC substrate. Moving on to the metal oxide semiconductor (MOS) device interface engineering, we will discuss strategies for achieving low interface trap densities (~1011eV-1 cm-2) and improved threshold voltage instability. Beyond device fabrication, we will highlight the importance of the power module packaging technique in realizing the full potential of SiC technology. This includes the double-side liquid cooling system and the power dissipation capability with different designs and material options for the proposed 6-in-1 power module.Overall, by addressing these challenges collaboratively, we can accelerate the adoption of SiC technology and unlock its full potential to drive power semiconductor technology and beyond. Figure 1

Revisiting a Drag Partition Model For Canopy-Like Roughness Elements

Turbulent flows over a large surface area (S) covered by n obstacles experience an overall drag due to the presence of the ground and the protruding obstacles into the flow. The drag partition between the roughness obstacles and the ground is analyzed using an analytical model proposed by Raupach (Boundary-Layer Meteorol 60:375-395, 1992) and is hereafter referred to as R92. The R92 is based on the premise that the wake behind an isolated roughness element can be described by a shelter area A and a shelter volume V. The individual sizes of A and V without any interference from other obstacles can be determined from scaling analysis for the spread of wakes. To upscale from an individual roughness element to n/S elements where wakes may interact, R92 adopted a background stress re-normalizing instead of reducing A or V with each element addition. This work demonstrates that R92’s approach results in a linear background stress reduction in A and V only when the ratio of n/S is small, due to a low probability of wake interactions. This probabilistic nature suggests that up-scaling from individual to multiple roughness elements can be re-formulated using stochastic averaging methods proposed here. The two approaches are shown to recover R92 under plausible conditions. An alternative scaling for the shelter volume is also proposed here using thermodynamic arguments of work and dissipation though the final outcome remains similar to R92. Comparisons between R92 and available data spanning more than two decades after R92 on blocks and vegetation-like roughness elements confirm the practical utility of R92. The agreement between R92 and this updated databases of experiments and simulations confirm the potential use of R92 in large-scale models provided that the relevant parameters accommodate certain features of the roughness element type (cube versus vegetation-like) and, to a lesser extent, their configuration throughout S. Last, a comparison between R92 and models based on first-order closure principles with constant mixing length suggests that R92 can outperform such models when evaluated across a wide range of roughness densities.

Effect of energy density on down surface characteristics of AlSi10Mg alloy fabricated via selective laser melting

The correlation between surface roughness and energy density in the down surface area of AlSi10Mg alloy manufactured by selective laser melting was analyzed. This study investigated the relationship between the contour melt pool shape and surface roughness in the down surface area across an energy density range of 10–150 J/mm³. As the energy density increased, the contour melt pool in the down surface area became more stable, which significantly influenced surface roughness. Low energy density resulted in the unstable formation of the contour melt pool, leading to a deterioration in surface quality, whereas high energy density promoted the stable formation of the melt pool. Sufficient energy density is essential for the complete formation of the contour melt pool on the down surface, which plays a crucial role in reducing surface roughness. However, within the energy density range where the contour melt pool is fully formed, keyhole defects may occur, and it can be anticipated that these defects may worsen at energy densities exceeding the critical threshold.

Effects of Leafy Flexible Vegetation on Bed‐Load Transport and Dune Geometry

AbstractThe development of sustainable river management strategies requires knowledge of the effect of vegetation on hydrodynamics and sediment transport. To date, the complex physical processes involving the combined effects of leafy flexible vegetation and mobile bedforms are not completely understood. Most sediment transport models have been developed for bare bed conditions so that their performance in the presence of leafy flexible vegetation remains unclear. On the other hand, recently developed models consider vegetated conditions but they typically account only for the presence of rigid cylinders and in some cases scour at their base. For this purpose, laboratory experiments were conducted with mobile dune bed conditions and artificial flexible plants with varying Leaf Area Index to investigate the effect of flexible vegetation on bed morphology and sediment transport. Sediment transport rates and bedform characteristics such as height, wavelength and celerity, were measured in specifically designed experimental runs. The collected data show that the presence of leafy vegetation alters bed morphology, tending to reduce the average dune wavelength and leading to the formation of complex 3D geometries. Bed‐shear‐stress‐based models for predicting sediment transport were verified to be valid under conditions of low vegetation roughness density. On the contrary, the collected data emphasize that the measured bed‐load transport rate increased in the presence of leafy flexible vegetation with higher frontal area. Recent bed‐load models for vegetated channels provide a better interpretation for dense leafy vegetation but are less effective when predominant effects related to dunes are present.

Accelerated Singular Spectrum Analysis and Machine Learning to investigate wood machining acoustics

The use of monitoring in manufacturing has increased the necessity for effective signal pre-processing methods to remove redundant data. Singular Spectrum Analysis (SSA) can decompose signals and time-series data into summable and physically interpretable reconstructed components. The high computational complexity has impeded the popularity of this method, as it could only be used for small datasets. In this study, significant work was put into the acceleration of SSA to enable the decomposition of acoustic emissions and airborne sound signals collected by monitoring wood machining. Important computational improvements were highlighted by benchmarking the accelerated SSA against the classical approach. Further results showed that the combination of SSA and Machine Learning enhanced the accuracy of predicting surface roughness (RSSA2=0.96 | RRAW2=0.89) and sample density (RSSA2=0.93 | RRAW2=0.88), while also improving the classification of cutting speeds (ACCSSA=100% | ACCRAW=86.34%) and wood species (ACCSSA=93.12% | ACCRAW=89.39%). The interpretation of the results showed that SSA enabled the selective filtering of redundant information from the monitored acoustics.

Effect of biofilm physical characteristics on their susceptibility to antibiotics: impacts of low-frequency ultrasound

Biofilms are highly resistant to antimicrobials, often causing chronic infections. Combining antimicrobials with low-frequency ultrasound (LFU) enhances antimicrobial efficiency, but little is known about the underlying mechanisms. Biofilm physical characteristics, which depend on factors such as growth conditions and age, can have significant effects on inactivation efficiency. In this study, we investigated the susceptibility of Pseudomonas aeruginosa biofilms to tobramycin, with and without LFU treatment. The biofilms were grown under low and high fluid shear to provide different characteristics. Low-shear biofilms exhibited greater thickness, roughness, and porosity and lower density, compared to high-shear biofilms. The biofilm matrix of the high-shear biofilms had a three times higher protein-to-polysaccharide ratio, suggesting greater biofilm stiffness. This was supported by microrheology measurements of biofilm creep compliance. For the low-shear biofilms without LFU, the viability of the biofilms in their inner regions was largely unaffected by the antibiotic after a 2-hour treatment. However, when tobramycin was combined with LFU, the inactivation for the entire biofilm increased to 80% after 2 h. For the high-shear biofilms without LFU, higher LFU intensities were needed to achieve similar inactivation results. Microrheology measurements revealed that changes in biofilm inactivation profiles were closely related to changes in biofilm mechanical properties. Modeling suggests that LFU changes antibiotic diffusivity within the biofilm, probably due to a “decohesion” effect. Overall, this research suggests that biofilm physical characteristics (e.g., compliance, morphology) are linked to antimicrobial efficiency. LFU weakens the biofilm while increasing its diffusivity for antibiotics.

Effects of Ar ion bombardment on the structure and properties of β-quartz

β-quartz is an important component that affects the physical and chemical properties of glass-ceramics. The material removal process of ion beam machining is complicated as one of the ultra-precision machining forms. Therefore, it is important to understand the removal mechanism of ion beam machining materials. The methods of molecular dynamics (MD) and first-principles were adopted to investigate the microscopic mechanism of ion beam bombardment of the β-quartz structure. The damage evolution of structures and the evolution of material properties caused by defects respectively from the atomic and electronic levels. Through MD analysis, we find that the random collision between incident ions and matrix atoms can lead to the formation of sputtered atoms. The incidence of ions will increase the disorder degree of the matrix, and the influence on the disorder degree at different depths of the matrix is different. The degree of disorder increases obviously in the range of 50–70 Å from the surface of the matrix. It has a significant impact on the surface topology of the matrix, the number of defects, surface roughness, and matrix density. The results of first-principle calculation show that the refraction, absorption and other characteristics of the system are significantly different with different doping forms, and the energy loss is most affected by substituted doping. And the substituted doping defects have the most significant effects on the structural energy loss. Among, the Ar-substituted O doping structure leads to higher energy loss, and the peak energy loss intensity reaches 5.146. In contrast, the Ar-substituted Si doping structure causes the least energy loss, the intensity is 2.543. This study provides a theoretical basis for the selection of parameters and the realization of ultra-smooth surface in actual ion beam machining.

Effect of laser process parameters on the pores, surface roughness, and hardness of laser selective melting of dental cobalt-chrome alloys.

To address the quality problems caused by high porosity in the preparation of dental cobalt-chrome alloy prosthetics based on selective laser melting (SLM) technology, we investigated the influence mechanism of different forming process parameters on the microstructure and properties of the materials. Moreover, the range of forming process parameters that can effectively reduce defects was precisely defined. The effects of laser power, scanning speed, and scanning distance on the pore properties, surface roughness, and hardness of dental cobalt-chrome alloy were investigated by adjusting the printing parameters in the process of SLM. Through metallographic analysis, image analysis, and molten pool simulation, the pore formation mechanism was revealed, and the relationship between the porosity and energy density of SLM dental cobalt-chrome alloy was elucidated. When the linear energy density was higher than 0.18 J/mm, the porosity defect easily appeared at the bottom of the molten pool. When the laser energy density was lower than 0.13 J/mm, defects occurred in the gap of the molten pool due to insufficient melting of powder. In particular, when the linear energy density exceeded the threshold of 0.30 J/mm or was below 0.12 J/mm, the porosity increased significantly to more than 1%. In addition, we observed a negative correlation between free surface roughness and energy density and an inverse relationship between macroscopic hardness and porosity. On the basis of the conditions of raw materials and molding equipment used in this study, the key process parameters of SLM of molding parts with porosity lower than 1% were successfully determined. Specifically, these key parameters included the line energy density, which ranged from 0.13 J/mm to 0.30 J/mm, and the scan spacing should be strictly controlled below 90 μm.

Flow Through a Passage With Scaled Additive Manufacturing Roughness Representing Different Printing Orientations

Abstract Components with internal passages created using some laser-sintering based, additive manufacturing (AM) systems can exhibit anisotropic surface features with an appearance of three-dimensional roughness superimposed on two-dimensional, rib-like features. This paper presents an investigation of flow over roughness representing internal cooling passages printed at different angles to the AM printing plane. A roughness geometry was acquired using an X-ray tomography scan of a direct-metal-laser-sintering (DMLS) created coupon with internal cooling passages. The base surface scan was then used to create four surfaces with notional rib-like features positioned at different angles relative to the spanwise flow direction. The flow resistance of each surface was measured using the roughness internal flow tunnel. The mean flow velocity profiles for the cases with ReDh ≤ 30,000 were characterized using a four-camera, tomographic, and particle tracking system. The results demonstrate roughness orientation effects include (1) reduced bulk flow resistance as the alignment angle from the spanwise direction increases, (2) generated flow in the spanwise direction and increased tunnel flow swirl as the alignment angle increases, and (3) velocity profile changes as the flow migrates away from the rough side of the tunnel to the opposing smooth wall. The particle tracking system also demonstrates that the mean streamwise flow profiles change significantly between the 30 deg and 45 deg roughness orientations. Finally, the equivalent sandgrain roughness measurements for the four surfaces were found to follow the trends predicted using the correlations of Bons (2002, “St and cf Augmentation for Real Turbine Roughness With Elevated Freestream Turbulence,” ASME J. Turbomach., 124(4), pp. 632–644.) and Sigal and Danberg (1990, “New Correlation of Roughness Density Effect on the Turbulent Boundary Layer,” AIAA J., 28(3), pp. 554–556.).

Electromagnetohydrodynamic (EMHD) flow of Jeffrey fluid through a rough circular microchannel with surface charge-dependent slip.

This research examines the electromagnetohydrodynamic (EMHD) flow of Jeffrey fluid in a rough circular microchannel while considering the effect of surface charge on slip. The channel wall corrugations are described as periodic sinusoidal waves with small amplitudes. The perturbation method is employed to derive solutions for velocity and volumetric flow rate, and a combination of three-dimensional (3D) and two-dimensional (2D) graphical representations is utilized to effectively illustrate the impacts of relevant parameters on them. The significance of the Reynolds number in investigations of EMHD flow is particularly emphasized. Furthermore, the effect of wall roughness and wave number on velocity and the influence of wall roughness and surface charge density on volumetric flow rate are primarily focused on, respectively, at various Reynolds numbers. The results suggest that increasing the wall roughness leads to a reduction in velocity at low Reynolds numbers ( ) and an increment at high Reynolds numbers ( ). For any Reynolds number, a roughness with an odd multiple of wave number ( ) will result in a more stable velocity profile compared to one with an even multiple of wave number ( ). Decreasing the relaxation time while increasing the retardation time and Hartmann number can diminish the impact of wall roughness and surface charge density on volumetric flow rate, independent of the Reynolds number. Interestingly, in the existence of wall roughness, further consideration of the effect of surface charge on slip leads to a 15% drop in volumetric flow rate at and a 32% slippage at . However, in the condition where the effect of surface charge on slip is considered, further examination of the presence of wall roughness only results in a 1.4% decline in volumetric flow rate at and a 1.6% rise at . These findings are crucial for optimizing the EMHD flow models in microchannels.

A simple and efficient technique of interlayer interface Ar+ etching to enhance tribological properties in TiSiN/TiAlN coating

In this paper, a simple and efficient technique of interlayer interface Ar+ etching is presented to regulate the microstructure and properties of the TiSiN/TiAlN coating deposited by arc ion plating. SEM, AFM, XRD, and EIS of the TiAlN coating indicate that Ar+ bombardment can reduce the roughness and porosity density. HR-TEM reveals the presence of epitaxial growth at the interlayer interface. The TiSiN/TiAlN coating exhibits high bonding force (Lc3 around 118.7 N) and excellent toughness (CPRs around 2230.2 N2) at − 300 V etching. The wear rate and COF of the coating are reduced to 4.26 × 10−5 mm3∙N−1∙m−1 and 0.295. The results demonstrate that interlayer interface Ar+ etching can effectively optimize the interlayer quality and enhance the wear resistance of the multilayer coating.

Dissipative and thermal aspects in cyclic loading of additive manufactured AISI 316L

This study presents a comprehensive understanding of the fatigue behavior of 316L stainless steel specimens produced using the laser powder bed fusion (PBF-LB/M) method. The investigation has been conducted through a multifaceted approach that includes surface roughness analysis, density measurements, microstructural examination, fatigue testing, strain measurements, and thermographic analysis. Thermographic data processing models, i.e. the bi-power law (TCM-modified) model and the TCM method, are applied to fatigue test results of standard samples to evaluate fatigue limit values. The fatigue limit of the samples was estimated using the Murakami Method (MM), Constant Amplitude Loading (CAL) and Step Loading (SL) tests. The proposed methodology allows exploration of the entire stress level range within a single test, which could allow evaluation of the fatigue limit of components within only one test. This study is the starting point for a rapid evaluation method for estimating the fatigue limit using thermography, offering a cost-effective, time-efficient, and non-destructive means of assessing the fatigue performance of materials produced using additive manufacturing processes.

A Study on Powder Spreading Quality in Powder Bed Fusion Processes Using Discrete Element Method Simulation

Powder deposition is a very important aspect of PBF-based additive manufacturing processes. Discrete Element Method (DEM) is commonly utilized by researchers to examine the physically complex aspects of powder-spreading methods. This work focuses on vibration-assisted doctor blade powder recoating. The aim of this work is to use experiment-verified DEM simulations in combination with Taguchi Design of Experiments (DoE) to identify optimum spreading parameters based on robust layer quality criteria. The verification of the used powder model is performed via angle of repose and angle of avalanche simulation–experiment cross-checking. Then, four criteria, namely layer thickness deviation, surface coverage ratio, surface root-mean-square roughness and true packing density, are defined. It has been proven that the doctor blade’s translational speed plays the most important role in defining the quality of the deposited layer. The true packing density was found to be unaffected by the spreading parameters. The vertical vibration of the doctor blade recoater was found to have a beneficial effect on the quality of the deposited layer. Ultimately, a weighted mean quality criteria analysis is mapped out. Skewness and kurtosis were proven to function as effective indicators of layer quality, showing a linear relation to the weighted means of the defined quality criteria. The specific weights that optimize this linearity were identified.

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.

Investigation of microstructural, micromorphology, and surface plasmon resonance characteristics in Ni/Al, Ni/Cu, and Ni/SS thin films.

As the first boundary between the environment and the material, the surface plays an important role in their interaction with each other, therefore, the use of appropriate tools and analysis to examine the mechanical properties and morphology of surfaces has particular importance in industry and research. In this research, a thin film of nickel was deposited on metal substrates made of aluminum, copper, and steel by using the RF magnetic cathode. Then, using a non-contact atomic force microscope, the morphological properties of the nickel film with static parameters, Minkowski functionals (MF's), fractal, and multifractal were extracted to be analyzed and studied. After that, using parameters such as root mean square (RMS) roughness, skewness, and kurtosis, it was determined how the surface roughness, distribution, and probability density of particles on the film surface alters with the change of the substrate. Next, by examining and analyzing the Δα and Δf parameters obtained from the multifractal section, the morphology of the produced film on the metal substrates was investigated. Then, the change in the surface plasmon resonance (SPR) peak position is changed for the prepared film in the range of the absorption spectrum due to the substrate effect and the microstructural properties of the formed film. HIGHLIGHTS: Ni film has been deposited by Rf magnetron sputtering. The effect of metal substrates on the topography, fractality, and optical properties was studied. Minkowski functionals were used to investigate the surface morphology of the samples. Substrate's material and the topography of the formed film can changed the surface plasmon resonance position.

Effective parameters on polydimethylsiloxane/graphene composite-based triboelectric nanogenerator performance

ABSTRACT This paper systematically investigates the effective parameter on the performance of polydimethylsiloxane/graphene (PDMS@Gr)-based triboelectric nanogenerators (TENGs) as well as their applications. PDMS@Gr films containing 0, 0.05, 0.5, 1, and 1.5 wt.% graphene are synthesized, and their surface characteristics, mechanical behavior, and electrical properties are characterized. Vertical contact-separation mode TENGs are fabricated, and their performance is evaluated. The results demonstrate that the surface roughness and surface charge density are the most critical parameters for the performance of PDMS@Gr-based TENGs compared to the electrical and mechanical properties of the friction layers. The PDMS@Gr-based TENG with 1 wt.% graphene shows the highest power output of 2.6 W/m2 at an optimized working condition (5 Hz and 15 N). It also exhibits stable power output until 15,000 working cycles and displays battery-free applications by powering a light-emitting diode (LED) array, a calculator, a digital watch, and a digital thermometer.