Uniform Surface Roughness Research Articles

Control of surface edge roughness for an aluminum alloy mirror based on sub-aperture polishing

With current polishing methods, it is hard to guarantee roughness uniformity between the edge and inner regions of the surface. Hence, this paper develops a sub-aperture polishing method based on chemical mechanical action to remove turning periodic marks and improve surface roughness uniformity. A compliant polishing pad with a rigid tool holder is proposed to ensure that the pressure in the contact area remains constant when the polishing tool moves out the edge of the workpiece. The optimal process parameters were investigated in the full aperture polishing experiment. Numerical simulation was implemented to analyze the relationship between the overhang ratio and removal uniformity and optimize the polishing trajectory parameters. The polishing experiments with aluminum alloy mirrors reveal that the impurities inside the aluminum alloy restrict the further improvement of surface roughness. The average surface roughness is improved from 8.82 nm to 1.71 nm, and the peak and valley roughness value is reduced from 2.51 nm to 0.71 nm, which indicates the proposed sub-aperture polishing method can improve the surface roughness uniformity.

Tailoring Optical Performance of Polyvinyl Alcohol/Crystal Violet Band-Pass Filters via Solvent Features

Optical filters are essential components for a variety of applicative fields, such as communications, chemical analysis and optical signal processing. This article describes the preparation and characterization of a new optical filter made of polyvinyl alcohol and incremental amounts of crystal violet. By using distinct solvents (H2O, dimethyl sulfoxide (DMSO) and H2O2) to obtain the dyed polymer films, new insights were gained into the pathway that underlies the possibility of tailoring the material’s optical performance. The effect of the dye content on the sample’s main properties was inspected via UV–VIS spectroscopy analysis combined with colorimetry, refractometry and atomic force microscopy experiments. The results revealed that the colorimetric parameters are affected by the dye amount and are dramatically changed when the solvent used for film preparation is different. The rise in the refractive index upon polymer dyeing was due to the synergistic effect of the larger polarizability of the dye and the occurrence of hydrogen bonds among the system components. Spectral data evidenced that samples prepared in H2O and DMSO preserve the absorption characteristics of the added dye, whereas H2O2 acts as an oxidizing agent and enhances transparency. Also, for the first two solvents, multiple absorption edges were noted as a result of dye incorporation, which was responsible for the occurrence of new exciton-like states, hence the band gap reduction. The films processed in H2O were able to block radiations in the 506–633 nm range while allowing other wavelengths to pass with a transmittance above 90%. The samples attained in DMSO presented similar properties, with the difference that the domain of light attenuation was shifted towards higher wavelengths. Atomic force microscopy showed the dye’s effect on the level of surface roughness uniformity and morphology isotropy. The dyed polymer foils in non-oxidizing agents have suitable features for use as band-pass filters.

Crystallographic, macromolecular, thermal, and mechanical properties of Bambusa balcooa fibers: effect of two-step chemical modification

AbstractNatural fibers (NFs) are becoming more and more interesting to research, because of their numerous benefits, sensitivity, biodegradability, and capacity to provide sustainable products that encourage technological innovation and a variety of industrial applications. In this study, a two-step treatment approach was adopted to chemically modify NF obtained from Bambusa balcooa. First ethanol (C2H6O) was utilized for pre-treatment, followed by potassium permanganate (KMnO4)-acetone solution at different concentration and treatment durations. The influence of this modification on the crystallographic, thermal, macromolecular, morphological, and mechanical properties of the B. balcooa fibers (BFs) were assessed using X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and mechanical characterization using both treated and untreated BF. The XRD analysis revealed notable alterations in the crystalline properties of the fiber. FTIR analysis confirmed that wax, hemicellulose, and lignin had been partially eliminated. The findings of the TGA investigation showed that the modified BF could be processed with polymers at low temperatures. Under ideal circumstances, the treated single BF tensile strength increased, and SEM morphology indicated that uniform surface roughness had been attained. This study demonstrated that two-step treatment of BF has the prospective of been used as reinforcement in a range of bio-composites for certain industrial and innovative uses under the right treatment conditions.

Solid dielectric electrochemical polishing of 3D-printed parts: Performance and mechanisms

Surface post-processing of metal additive manufacturing components is challenging due to their typically complex geometries (e.g., curved surfaces) coupled with high initial surface roughness. Herein, we propose an efficient solid dielectric electrochemical polishing (SDECP) method employing ion exchange resin particles with a porous structure that absorbs and stores electrolytes as a conductive medium. This method enhances the surface quality of additively manufactured components with Bézier curved surfaces to a mirror finish, achieving improvements in Sa, Sq, and Sz of 91.5%, 91.7%, and 86.9%, respectively. Planetary motion strategies are implemented to optimize mass transfer on the anode surface in the discontinuous solid dielectric. Results indicate that bidirectional planetary motion (BPR) in SDECP effectively improves the uniformity of surface roughness and material removal across different regions of the part. Furthermore, we quantitatively describe the relationship between material removal rate (MRR) and average current in SDECP. The intermittent material removal mechanism of SDECP is elucidated utilizing discrete element method (DEM) simulations. Our work offers innovative insights into the material removal mechanisms of SDECP, presenting an efficient approach for overall surface post-processing of metal additive manufacturing components.

Structural analysis of selective laser melted copper-tin alloy

Additively manufactured complex geometries from copper alloys with high thermal and mechanical properties have drawn the attention of researchers. The present contribution explores the additive manufacturing (AM) of copper-based alloys from powder particles intended for heat sink and heat exchange applications. Selective laser melting (SLM) parameters featuring low laser beam power (160 W), moderate scanning speed (320 mm/s), and high energy density (200 J/mm³) were employed to fabricate dense components from CuSn10 particles. The present work deal with structural analysis and precision investigation of microfabrication, particularly in Struts, Tubes, and Fins. Mechanical properties (compression and hardness) for Strut structure, differential pressure evaluations for Tube structure, and analyses of thermal and electrical conductivities for Fin structure were investigated. The results showed an improvement in strength compared to those of pure copper, facilitating ease of AM. The obtained results affirm the feasibility of AM, demonstrating the successful creation of complex and combined solid-porous structures using SLM process from Cu alloys. A comprehensive structural investigation and characterization of the Cu–Sn alloy is presented here, aiming to establish a standardized approach for analysing Cu alloys. The results indicate that small-scaled structures fabricated via CuSn10 alloy exhibits a thermal conductivity of 34.3 W·m⁻¹·K⁻¹, an electrical conductivity of 4.72×10⁶ S/m, a hardness of 119 HV-50, a uniform surface roughness of 6 µm, and can withstand a force loading of 1 kN.

A NEW ABRASIVE DISC DESIGNED FOR GRINDING GRANITE

The aim of the work is to develop a new effective design and material of the disc for abrasive machining of granite. The task was undertaken in order to shorten the time of the machining operation of surface grinding by ensuring a uniform post-machining surface roughness for a given cycle , shortening the time for a given grain group of abrasive segments. For the purpose of the task, an analysis of the effectiveness of the impact of the working surface of the disc of known geometric solutions and a new solution of the disc geometry was carried out. Recipes for material composition and technology for making prototypes of discs with a new geometry of abrasive segments were developed, for which laboratory tests were performed.

Fabrication of pH-Responsive PDPAEMA Thin Film Using a One-Step Environmentally Friendly Plasma Enhanced Chemical Vapor Deposition

In recent years, there has been growing interest in pH-responsive polymers. Polymers with ionizable tertiary amine groups, which have the potential to be used in many critical application areas due to their pKa values, have an important place in pH-responsive polymers. In this study, poly(2-Diisopropyl aminoethyl methacrylate) (PDPAEMA) thin films were coated on various substrates such as glass, fabric, and silicon wafer using a one-step environmentally friendly plasma enhanced chemical vapor deposition (PECVD) method. The effects of typical PECVD plasma processing parameters such as substrate temperature, plasma power, and reactor pressure on the deposition rate were studied. The highest deposition rate was obtained at a substrate temperature of 40 °C, a reactor pressure of 300 mtorr, and a plasma power of 60 W. The apparent activation energy was found to be 17.56 kJ/mol. Based on the results of this study, uniform film thickness and surface roughness were observed in a large area. The PDPAEMA thin film was exposed to successive acid/base cycles. The results showed that the pH sensitivity of the thin film produced by the PECVD method is permanent and reversible.

Microwave-assisted alkali treatment of sisal fiber for fabricating composite as non-structural building materials

Currently, the world needs sustainable materials to replace and minimize the use of synthetic materials in order to reuce environmental pollution. In this context, natural fiber-reinforced composites (NFRCs) are in high demand. However, the low thermal and mechanical properties have limited their application spectrum. The current research investigation explores the effectiveness of alkali treatment and microwave-assisted alkali treatment (MAAT) on sisal fiber and sisal/high-density polyethylene (HDPE) composites. The MAAT was performed at three different power levels (300, 640 and 800 W) and treatment time was kept constant (10 min); the power level was optimized based on the fiber’s performance. The chemical analysis of treated fibers showed an increased ratio of cellulose percentage in the fibers when compared to untreated fibers. The MAAT (at 640W10) showed improvement in the thermal stability of sisal fiber as compared to untreated and alkali treated fibers. The single fiber test showed the highest (21.92% and 45.77%) increase in tensile strength for MAAT (at 640W10) as compared to alkali treated and untreated sisal fibers, respectively. Scanning electron microscopy (SEM) showed the effectiveness of the MAAT (at 640W10) in terms of a more uniform surface roughness on the fiber surface. The research also focused on using time efficient microwave-assisted molding (MAM) method for the fabrication of NFRCs. Vector network analyzer (VNA) was used to determine the dielectric constant of the fibers as it plays a critical role in heat generation during microwave heating. Mechanical, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) tests were performed on the fabricated composites. It was observed that the MAAT sisal fiber (at 640 W) reinforced HDPE composites (640W10/HDPE) had recorded the best performance as they showed increased thermal stability, percentage crystallinity (3.56% and 10.26%), tensile strength (14.93% and 32.04%) and flexural strength (10.28% and 28.60%) as compared to alkali treated sisal fiber reinforced HDPE composites (NTSF/HDPE) and untreated sisal fiber reinforced HDPE composites (USF/HDPE), respectively. From the results, it is observed that MAAT has strong potential to be commercially employed for the time-efficient treatment of natural fibers before fabricating the sustainable construction components, parts, and products.

Experimental study on heat transfer performance using a hybrid cooling method combined of a flat-plate heat pipe and spray cooling

A hybrid cooling system consists of spray cooling as condensing end and flat-plate heat pipe (FPHP) as heat-transfer medium was previously studied on the effects of the volume flow rate and the inlet temperature. As an extension, this paper using multi-nozzle arrays to promote the forced convection heat transfer and changing the surface roughness of the FPHP to improve the phase change heat transfer. It was found that the impinging energy and drainage channel formed by multi-nozzle arrays were the main reasons for the enhancement in convection region. However, in the phase-change section, a uniform thin liquid film and surface roughness apparently improved the evaporation and nucleate boiling. Relative to our previous study, a maximum heat flux removal was increased from 70 W/cm2 to 90 W/cm2 at surface roughness (Ra = 1.62 μm) with a surface superheat only 4.17℃, the heat transfer coefficient of 21.6 W·cm-2·K-1 and an enhancement of 28.6 % were obtained. Furthermore, the transition temperature and the temperature change rate were studied to explore the vapor flow modes and thermal response characteristics of the FPHP. As the transition temperature Ttr = 251 K, and the Knusden number＜0.01, the FPHP consistently maintained a continuum flow regime during startup, stabilization, and dry-out processes. Impressively, the temperature change rate of the FPHP remained below 0.015℃/s, resulting in a temperature change of only 0.9℃ within one minute. This exceptional temperature stability ensured reliable operation for electronic components.

Intelligent Additive Manufacturing Architecture for Enhancing Uniformity of Surface Roughness and Mechanical Properties of Laser Powder Bed Fusion Components

In the Laser Powder Bed Fusion (L-PBF) process, 3D components with complex geometries are fabricated in a layer-by-layer fashion by using a controlled laser beam to selectively melt particular regions of the metal powder bed. However, due to the stochastic nature of the L-PBF process, the top surface roughness of each solidified layer tends to be different even when the optimal processing conditions for the different positions on the build plate are employed. As a result, the mechanical properties of the built components frequently vary from one component to the next. Accordingly, this study proposes an Intelligent Additive Manufacturing Architecture (IAMA) for controlling the surface roughness of each build layer through an appropriate adjustment of the laser re-melting parameters. The IAMA architecture comprises five modules, namely In-Situ Metrology (ISM), Ex-Situ Metrology (ESM), Automatic Virtual Metrology (AVM), Additive Manufacturing Simulation (AMS) and Intelligent Compensator (IC). The feasibility of the proposed architecture is demonstrated by comparing the top surface roughness of cubic and mechanical strengths of tensile test samples built using the proposed method with those built using a traditional L-PBF approach without surface roughness control. It is found that the samples fabricated using the IAMA approach have an average top surface roughness of 1.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m and a standard deviation is 0.7 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m. By contrast, the samples produced using the traditional L-PBF approach have an average surface roughness of 13.45 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m and a standard deviation of 2.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m. In addition, the specimens produced with the assistance of IAMA architecture have an average tensile strength of 1013 MPa with a standard deviation of 69.5 MPa, while those printed without surface roughness control have an average tensile strength of 903 MPa with a standard deviation of 101.4 MPa <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —As L-PBF produce part in a layer-by-layer manner, therefore, the roughness on the top surface of previous layer have a strong influence on the printing quality of current layer. The variations of surface roughness will lead to the fluctuation of mechanical properties of the fabricated components. Additionally, to the best of author’s knowledge, current commercial L-PBF machines can not actively control the surface roughness of samples during the process. The proposed IAMA in this work can predict and control the roughness on the top surface of each layer during L-PBF process. Therefore, the constructed architecture has strong potential for integrating into the commercial L-PBF machine for controlling the surface roughness on the top of the parts during the manufacturing process. As a result, the quality of the fabricated components is expected to be in consistent. Accordingly, L-PBF machine equipped with IAMA will have a strong potential in applying for mass production of the components in aerospace and automobile industries.

A Novel Apparatus to Standardize the Polishing Protocol to Achieve Different Roughness of Titanium and Zirconia Disc Surfaces.

To propose and evaluate standardized polishing protocols for in vitro experiments using a custommade apparatus under controlled force to create consistent surface roughness on titanium and zirconia discs. A total of 160 discs were manufactured with a diameter of 10 mm, 80 titanium (Ti) and 80 zirconium oxide (Zr). Specimens were categorized into two groups: controlled force (CF) and without controlled force (WCF). Specimens in the CF group were polished with a custom apparatus incorporating a tension gauge on the Ti and Zr disc surfaces to achieve consistent roughness. The WCF group was polished without the use of a tension gauge. Each group had four subgroups (n &#61; 10): control/machined with no polishing (C), rough (R), smooth (S), and very smooth (VS). The subgroups were processed using a sequence of diamond-impregnated polishing burs and polishing paste. The CF group showed consistent surface roughness and a gradual decrease in surface roughness. Control in Ti (Ra &#61; 6.5 ± 0.03 μm) and in Zr (Ra &#61; 5.4 ± 0.04 μm); R in Ti (Ra &#61; 3.5 ± 0.06 μm) and in Zr (Ra &#61; 3.2 ± 0.07 μm); S in Ti (Ra &#61; 1.5 ± 0.04 μm) and in Zr (Ra &#61; 1.1 ± 0.06 μm); and VS in Ti (Ra &#61; 0.05 ± 0.002 μm) and in Zr (Ra &#61; 0.02 ± 0.005 μm). There were significant differences for R, S, and SV under CF and WCF in Ti and Zr surfaces. The specimens polished under control force produced significantly more uniform surface roughness than those polished without controlled force and were produced with a higher degree of consistency.

Friction and lubrication modelling in sheet metal forming: Influence of local tool roughness on product quality

To improve the accuracy of forming simulations, advanced friction models are increasingly used in the industry. These models account for the physical properties of the sheet, tool and lubrication and describe the tribological conditions during the forming operation. One of the main influencing factors on the tribology system, and therefore the friction coefficient, is the surface roughness of the tools. Until now, it is often assumed all tools have the same uniform surface roughness. In reality however, the tool might have different surface conditions dependent on the type and location of the tool. That is, the blank holder might be differently polished than the punch, and sharp radii might have a different tool roughness compared to flat areas. This paper investigates a significant number of tool measurements from different tool sets from Volvo Cars, and quantifies the effect of local surface conditions on product quality.

Sheath &amp; Dilator 카테터 내 폴리머 튜브의 원형도 및 표면 개선에 관한 연구

As the market for minimally invasive procedures developed rapidly, there was an increase in the demand for high-precision, high-performance catheter fabrication technology. Sheath and dilator tubes are essential intervention devices for procedures, in which catheters are used and require precise dimensional accuracy, and uniform roundness and surface roughness. Polyethylene is used in sheath and dilator limitation for processability, which causes low melt flow index and side effects. Therefore, in the extrusion process using polyethylene, it is important to study the manufacturing of tubes with improved roundness and surface roughness. In this study, we proposed a calibrator for precise production with an aim to manufacture 5Fr micro-puncture tubes, and studied the changes in the roundness and surface roughness of tubes by changing the cooling water temperature and water disk thickness. As a result, it was found that the cooling water temperature and wafer disk thickness had an effect on the roundness and surface roughness, and the roundness had an effect on the formation of the wall thickness. Therefore, these experimental results were used as a study for the production of improved Sheath and Dilator tubes.

A 2-Stage Root Analog Implant with Compact Structure, Uniform Roughness, and High Accuracy

Immediate implant placement has the advantages of shortening the operation time, reducing the treatment cycle and cost. At present, this technology has been used widely, but the indications of immediate implantation are still limited. Here, a novel type of root analog implant (RAI) was manufactured by selective laser melting technology to address the limitation. Under optimized condition, RAIs were printed with the internal density of 99.73% and the uniform surface roughness of 11 μm (Sa). Besides, the deviation between RAI specimen and design models is controlled within 0.15 mm after optimizing scanning parameters. The substrate printed could promote human bone marrow stromal cell proliferation, spreading, and osteogenic differentiation. The bone–implant contact (BIC, 75% ± 7%) and bone volume/total volume (BV/TV, 74% ± 7%) of RAIs were significantly higher than that of conventional implants (BIC, 66% ± 5%; BV/TV, 62% ± 5%) in in vivo experiments. Further, customized abutments were designed for the RAIs, improving the masticatory ability of the beagle dogs after crown restoration. This study aims to design a personalized 2-stage RAI with compact structure and uniform roughness, in order to achieve better fracture resistance, initial osseointegration efficiency, and dispersed stress in immediate implantation. It provides a certain guiding value for standardizing the manufacture and clinical application of RAI in immediate implantation.

Control design of a reciprocating high-speed wire feed system for 7-axis robotic electric discharge machining

For decades, researchers have struggled to solve 6-axis robotic vibration while machining hard-to-cut materials. On the other hand, wire electric discharge machining (WEDM) stands out as a non-conventional machining process able to cut large and complex profiles of any conductive hard-to-cut material with minor non-contact forces. Thus, WEDM is a promising process to be combined into a robot to overcome vibration and low accuracy. However, the robot characteristics of a high degree of freedom combined with payload limitation oblige to separate the heavy wire winding system from the robot end-effector, demanding an equally high degree of freedom and unconventional solutions to feed and control the wire electrode. This study designs and reports experimental findings of the first robotic WEDM apparatus based on a high-speed winding system with 600 m of wire length, capable of controlling the wire speed from 1 to 10 m/s and wire tension from 0.1 to 10 N. The system adopts flexible outer cases to travel and reciprocate the wire into a 7-axis robotic system composed of a 6-axis robot and an external rotating axis. The proposed design is a highly dynamic process whose wire tension and speed are achieved by a hybrid controller to cope with the non-linear relation of speed and tension provided by the magnetic clutch. It combines a regression open-loop control for optimality and wire breakage avoidance with a closed-loop control to guarantee admissibility while coping with wire friction disturbances. The findings review a novel wire winding system capable of controlling usual wire disturbance and stepped surface of reciprocating high-speed WEDM as well as additional friction and elastic behaviour of the flexible case, delivering wire tension of ± 12% along with stable EDM process and uniform surface roughness between wire reciprocation areas with a Ra of 2.94 μm. Potential adoption of the method can finally make 6-axis robots a feasible and advantageous technique compared to computer numeric control (CNC) while shaping monolithic and complex workpieces of conductive and hard-to-cut materials.

Study of the Polishing Characteristics by Abrasive Flow Machining with a Rotating Device

Since only uni-direction motion is produced by traditional abrasive flow machining (AFM), so the polishing effects of the inner hole is not easy to achieve uniform roughness of the whole surface after polishing. Therefore, in this study, a rotating device with a DC servo motor was set up in the AFM to increase the tangential forces on the machining surface, and therefore, improve the uniform surface roughness and polishing efficiency. The rotating device was designed by a group of transmission gear set and a DC servo motor to create a rotational finishing path for the abrasive medium. The rotational motion of an abrasive can create different tangential forces on the working surface, inducing a more complex polishing path than that of traditional AFM. In addition to rotational speed, a servo motor can also change rotation directions in one working process, causing an abrasive medium to create many irregular finishing paths in the AFM. The experimental results showed that the surface roughness of the workpiece was significantly decreased with an increase in the rotational speed. Additionally, the results also showed that the surface roughness (SR) of the inner hole decreased from 0.61 μm Ra to 0.082 μm Ra after 20 machining cycles, the surface roughness improvement rate reached 87% at 15 rpm rotational speed, by applying a 1.5:1 silicone gel/abrasive concentration ratio and #60 abrasive mesh in the experiments. This study created excellent polishing efficiency by using a servo rotational device with AFM to produce good surface quality.

Performance deterioration of axial compressor rotor due to uniform and non-uniform surface roughness

Surface roughness is a significant source of performance loss in gas turbine engines. The fan and compressor, being the initial components of the gas turbine engine, are more prone to surface roughness effects due to the ingestion of debris at low atmospheric conditions. This paper attempts to numerically study the impact of uniform and non-uniform surface roughness on axial compressor rotor performance. NASA rotor 37 is used as the validation test case for the numerical methodology, and the results show a good match between the experimental and computational fluid dynamics data. Detailed flow field analysis indicates that there is a reduction in rough blade performance and the overall flow turning that reduces the work done by the rotor. The location sensitivity studies shock location is the major contributor to the overall loss in the performance. Also, the study of non-uniform roughness on blade performance shows that roughness on the leading edge is the major contributor to the loss as compared to the trailing edge and so does roughness on the shroud as compared to the roughness on the hub. An interesting observation is that for the given configuration and roughness height, near the shroud, the role of the tip vortex is more pronounced than the role of surface roughness on the performance.

The effect different of hydrochloric acid concentrations on the cleaning of Ni foam substrate: Structural and morphological studies

Recently, much attention has been focused on nickel (Ni) as current collectors for supercapacitor applications. The cleaning of Ni current collector is mandatory before it can be utilized in supercapacitor devices. The cleaning of the Ni foam substrate is essential for removing contaminations and modifying the surface morphology of the foam. In this study, Ni foam substrates were cleaned via sonication in different concentrations of HCl solution and the formation of the oxide layer on the surface of the Ni foam was investigated. The formation of oxide layer on the Ni foams was characterized of its morphology, elemental and structural analyses. The cleaning of the Ni foam with HCl solution leads to the formation of oxide layer on the Ni foam surface. The cleaning of Ni foam substrate with a 2.5 M of HCl solution gave an oxide layer with uniform thickness (0.034 μm) before the layer was detached. Cleaning with 5.0 M HCl concentration produced the thickest oxide layer formation (0.327 μm). However, a cracked line (black line) was also observed for 4.0 and 5.0 M HCl concentrations, indicating that the attachment of these oxide layers on the surface of the Ni foam was poor and susceptible to detachment. From the structural analyses, no impurity peaks were detected in the diffraction pattern and the intensity peaks of Ni were decreased and broaden with the increase in the HCl concentration. It is proven that the Ni foam have uniform surface roughness of the oxide layer when cleaned with HCl solution lower than 2.5 M but the thick oxide layer was detached at concentrations higher than 2.5 M which deteriorates the supercapacitor systems.

Tailoring Patterned Visible-Light Scattering by Silicon Photonic Crystals.

Searching for the relationship between the nanostructure and optical properties has always been exciting the researchers in the field of optics (linear optics as well as non-linear optics), energy harvesting (anti-reflective Si solar cells, perovskite solar cells, ..., etc.), and industry (anti-reflection coating on car windows, sunglasses, etc.). In this work, we present an approach for nanostructuring the silicon substrate to silicon photonic crystals. By precisely controlling the etching time and etching path after using nanoimprint lithography, ordered arrays of inverted Si nanopyramids and Si nanopillars with good homogeneity, uniform surface roughness, high reproducibility of pattern transfer, and a controllable aspect ratio are prepared. Experimental investigation of the optical properties indicates that the reflections of these Si nanostructures are mainly determined by the aspect ratio as well as the period of nanostructures. Furthermore, we have experimentally observed visible-light scattering (V-LS) patterns on inverted Si nanopyramids and Si nanopillars, and their corresponding patterns can be precisely controlled by the patterned nanostructures. The V-LS pattern, background, and "ghost peaks" on the angle-resolved scattering results are caused by constructive interference, destructive interference, and the interference situation between both. This controllable nanopatterning on crystalline Si substrates with precisely tunable optical properties shows great potential for applications in many fields, for example, optics, electronics, and energy.

Effects of Cu-alloying in minute quantities on the corrosion-induced mechanical degradation behaviors of medium C-based ultrahigh-strength steel in aqueous environments

This study examined the applicability of Cu-alloying in minute quantities to medium C-based ultrahigh-strength automotive steel with a tensile strength of more than 2000 MPa to improve the resistance to mechanical degradation caused by aqueous corrosion. Cu-alloying of this steel favored the precipitation of fine-(Ti,Mo)C particles, leading to a smaller prior-γ grain size (PAGS) and inter-lath size, resulting in higher tensile strain. In addition, Cu-alloyed steel showed the surface inhibiting characteristics in a neutral aqueous condition based on higher corrosion resistance (i.e., larger polarization resistance and less weight loss). The smaller particle size of corrosion scale (CuxFe3-xO4), more uniform surface roughness, and smaller PAGS can be the major mechanistic reasons for suppressing the reduction in the mechanical properties of Cu-alloyed ultrahigh-strength steel in the corrosive environment.