Surface Roughness Factor Research Articles

Impedance study of hydrogen evolution on Ni/Zn and Ni–Co/Zn stainless steel based electrodeposits

A study on the electrocatalytic performance of Ni/Zn and Ni–Co/Zn alloys for hydrogen evolution reaction (HER) in alkaline media (30 wt.% KOH solution) has been carried out. After preparing by electrodeposition on stainless steel supports, the alloys were leached of to remove part of the zinc and generate a porous layer. For the developed electrodes, the surface roughness factor, R f , was evaluated by electrochemical impedance spectroscopy (EIS). The HER on these electrodes was evaluated by means of steady-state polarization curves and EIS. The obtained electrodes were characterized by large R f for HER, and very low overpotentials at the current density of 250 mA cm −2, η 250 ∼ 0.138 V at 30 °C. The high electrode activity was mainly attributed to the high surface area of the developed electrodes.

Fluorine-Ion-Mediated Electrodeposition of Rhombus-Like ZnFOH Nanorod Arrays: An Intermediate Route to Novel ZnO Nanoarchitectures

Novel rhombus-like ZnO nanorod (NR) arrays were achieved via a facile two-step synthesis strategy based on first a low-temperature aqueous electrodeposition of vertically aligned rhombic ZnFOH NR arrays in the presence of fluoride and second a pyrolysis of ZnFOH intermediate into ZnO with the same morphology. The fluorine-ion-mediated electrodeposition mechanism of ZnFOH was confirmed for the first time, and the proposed formation process that the rhombus-like ZnO NRs characterized by mesoporous structure derived from the electrodeposited ZnFOH intermediate was corroborated by systematic structural characterization of the as-prepared products. A dye-sensitized solar cell (DSSC) based on the rhombus-like ZnO NR arrays with a larger surface roughness factor was assembled, and a higher conversion efficiency of 0.69% was attained in comparison to 0.47% of the DSSC based on the hexagon-like ZnO NR arrays electrodeposited in the absence of fluoride. Further, we demonstrate that the unique two-step synthesis strategy also possessed the capability of constructing complex nanoarchitectures with 1D rhombus-like ZnO NRs as the building blocks.

Thickness dependency of sol-gel derived ZnO thin films on gas sensing behaviors

ZnO thin films were fabricated by a sol-gel method using Zn(CH 3COO) 2·2H 2O as starting material in order to prepare an acetone gas sensor. A homogeneous and stable solution was prepared by dissolving the zinc acetate in a solution of ethanol and monoethanolamine. The sol-gel solution is coated on alumina substrates with various thicknesses by spin coating technique and heat treated to grow crystalline ZnO thin films. The effect of thickness on physical and electrical properties of as deposited ZnO thin films has been studied. The as deposited ZnO thin films were characterized by X-ray diffraction spectroscopy, field emission scanning electron microscopy and atomic force microscopy. The root mean square surface roughness factors increase with thickness of the films and found 3.9, 6.6, 9.0, and 11.28 nm for 80-, 220-, 450- and 620-nm-thin films respectively. The activation energies of the films are calculated from the resistance temperature characteristics. The sensitivities of the ZnO films towards the acetone gas were determined at an operating temperature of 200 °C. The sensitivity towards acetone vapor is strongly depending on surface morphology of the ZnO thin films.

Taguchi Analysis of surface roughness and delamination associated with various cemented carbide K10 end mills in milling of GFRP

This Paper presents a study of surface roughness, precision and delamination factor in use of Ti-Namite carbide K10 end mill, Solid carbide K10 end mill and Tipped Carbide K10 end mill. A plan of experiment based on Taguchi was established with prefixed cutting parameters and the machining was performed. An Surfcoder to examine the surface roughness and Infrared Thermography to examine the delamination of chopped Glass fiber-reinforced plastic (GFRP) laminates was used. Earlier works reports that cutting velocity and feed rate makes significant contribution to overall performance. But, the experimental results of this paper indicates that the depth of cut are recognised to make the most significant contribution to the overall performance as compared to cutting velocity and feed rate. The objective was to establish a correlation between cutting velocity, feed rate and depth of cut with surface roughness and delamination in a GFRP laminate. The correlation was obtained by multiple-variable linear regression using Minitab14 software.

Electrochemical properties of porous bismuth electrodes

The properties of Bi surfaces with different roughnesses were characterized by electron microscopy, cyclic voltammetry, and impedance spectroscopy. Two different strategies were used for preparation of porous bismuth layers onto Bi microelectrode surface in aqueous 0.1 M LiClO 4 solution. Firstly, treatment at potential E < −2 V (vs. Ag|AgCl in sat. KCl) has been applied, resulting in bismuth hydride formation and decomposition into Bi nanoparticles which deposit at the electrode surface. Secondly, porous Bi layer was prepared by anodic dissolution ( E = 1 V) of bismuth electrode followed by fast electroreduction of formed Bi 3+ ions at cathodic potentials E = −2 V. The nanostructured porous bismuth electrode, with surface roughness factor up to 220, has negligible frequency dispersion of capacitance and higher hydrogen evolution overvoltage than observed for smooth Bi electrodes.

EIS Characterization of Ni/Zn and Ni-Co/Zn Stainless Steel Based Electrodeposits for the Hydrogen Evolution Reaction

A study on the electrocatalytic performance of Ni/Zn and Ni-Co/Zn alloys for hydrogen evolution reaction (HER) in alkaline media has been carried out. After preparing, by electrodeposition on stainless steel supports, the alloys were leached of to remove part of the zinc and generate a porous surface. For the developed electrodes, the surface roughness factor, Rf, one of the most important problems in electrocatalysis, was evaluated by Electrochemical Impedance Spectroscopy (EIS). The HER on these electrodes was evaluated by applying steady-state polarization curves and EIS. The obtained electrodes were characterized by large roughness factors for HER, Rf ~ 5000 and very low overpotentials at the current density of 250 mA cm-2, η250 ~ 0.32 mV at 30 ºC. The high electrode activity was mainly attributed to the high surface area of the developed electrodes.

The Hydrogen Evolution Reaction on Electrolytic Nickel-Based Coatings Containing Metallic Molybdenum

Ni-Mo and Ni+Mo coatings were prepared by electrodeposition under the galvanostatic conditions, in such a manner that the coatings contain the same quantity of molybdenum. The electrochemical activity of these coatings was studied in the process of hydrogen evolution reaction (HER) from 5 M KOH solution using steady-state polarization and electrochemical impedance spectroscopy (EIS) methods. Basing on the results of EIS measurements, the rate constants of the HER as well as the surface roughness factors were determined. It was found that Ni+Mo composite coating is characterized by enhanced electrochemical activity towards hydrogen evolution as compared with Ni-Mo alloy coating. Improvement of the electrocatalytic performance of Ni+Mo composite coating could be attributed to the increase in its real surface area as well as to the catalytic effect in points of contact of molybdenum and nickel matrix. Thus obtained composite coating may be useful in application as electrode materials for the hydrogen evolution reaction.

Wetting of the (0001) α-Al2O3 Sapphire Surface by Molten Aluminum: Effect of Surface Roughness

The wetting of molten aluminum on the “c”-plane (0001) of single-crystal α-Al2O3 (sapphire) was studied by the sessile drop technique from 800 °C (1073 K) to 1200 °C (1473 K). Systematically increasing the (0001) surface roughness by SiC abrasion increased the wetting contact angle, resulting in reduced wetting. The surface roughness factor R originally defined by Wenzel, was determined as a function of the abrasion, temperature, and time. The wetting decreases as the surface roughness increases. Rough surfaces also create time and temperature effects on wetting, changing those for a smoothly polished surface. The existence of a high-temperature surface structural transition for (0001) of α-Al2O3, which has been previously suggested, was confirmed. Increased roughness R accents the effect of the surface structural transition, increasing the wetting contact angle changes during the transition.

AC Breakdown Voltage Simulation of SF 6 /N 2 Mixture in Non-Uniform Field and Its Comparison with Experimental Values

is the most commonly used insulating gas in electrical systems. But In these days mixtures and alternative gas has been studied because of global warming. so although many studies have been carried out about binary gas mixtures with , few studies were presented about breakdown characteristics of mixtures. At present study the breakdown characteristics of mixtures in Non-uniform field was performed. In this paper, The simulation value are compared with experiment values. Streamer breakdown criterion was used for predicting breakdown voltage. For accurate simulation this simulation apply utilization factor using CST(computer simulation technology) EM program. AC breakdown experiments in non-uniform field was performed to compare with the breakdown simulation values. The pressure range of gas mixtures was 0.4 MPa to 0.7 MPa. The rod-plane was used and mixture ratio is 20% : 80%. The gap lengths are 10mm to 70mm. As the pressure increase, this simulation value does not correspond to the experiment value. So this simulation need surface roughness factor. As a result of applying surface roughness factor this simulation decrease a relative error (|experiment value - simulation value| /simulation value).

Sensitivity study of frictional behavior by dimensional analysis in cold forging

In metal forming operations, material flow and quality of the product depend on the conditions at the billet/tools interface friction, lubrication, and surface finish. Of these parameters, friction is the most difficult to characterize and its influence is often difficult to predict because of its dependency on a variety of factors. Recently, through a number of investigations conducted, a linear relationship among shear friction factor, dimensionless load and tip distance was obtained. The aim of the present study is to see whether the linear relationship obtained in the previous works was fortuitous or genuine by applying a dimensional analysis introducing processing parameters such as contact pressure, ram velocity, viscosity of the lubricant, load, surface roughness and shear friction factor. From the dimensional analysis based on Buckingham π theorem and the data obtained from the tip test experiment, the present theoretical work derives dimensionless parameters and analysis of variance determines any correlation between the dimensionless parameters obtained. This work reconfirms the theoretical background of the previous experimental findings in the literature.

Surfactant-free assembling of functionalized single-walled carbon nanotube buckypapers

The electrical and textural properties of single-walled carbon nanotube buckypapers were tunned through chemical functionalization processes. Single-walled carbon nanotubes (SWCNTs) were covalently functionalized with three different chemical groups: Carboxylic acids (–COOH), benzylamine (–Ph–CH2–NH2), and perfluorooctylaniline (–Ph–(CF2)7–CF3). Functionalized SWCNTs were dispersed in water or dimethylformamide (DMF) by sonication treatments without the addition of surfactants or polymers. Carbon nanotube sheets (buckypapers) were prepared by vacuum filtration of the functionalized SWCNT dispersions. The electrical conductivity, textural properties, and processability of the functionalized buckypapers were studied in terms of SWCNT purity, functionalization, and assembling conditions. Carboxylated buckypapers demonstrated very low specific surface areas (<1m2/g) and roughness factor (Ra=14nm), while aminated and fluorinated buckypapers exhibited roughness factors of around 70nm and specific surface areas of 160–180m2/g. Electrical conductivity for carboxylated buckypapers was higher than for as-grown SWCNTs, but for aminated and fluorinated SWCNTs it was lower than for as-grown SWCNTs. This could be interpreted as a chemical inhibition of metallic SWCNTs due to the specificity of the diazonium salts reaction used to prepare the aminated and fluorinated SWCNTs. The utilization of high purity as-grown SWCNTs positively influenced the mechanical characteristics and the electrical conductivity of functionalized buckypapers.

TiO2 Branched Nanostructure Electrodes Synthesized by Seeding Method for Dye-Sensitized Solar Cells

We report TiO2 branched nanostructure photoelectrodes for dye-sensitized solar cells (DSSCs). The TiO2 branch-type nanoparticle is synthesized by means of a seeding method with TiO2 nanowire as a seed. During the seeding process, the TiO2 nanostructure is evolved from a nanowire (NW) to nanobranch (NB) shape. It is also found that rutile TiO2-NB shows such a three-dimensional structure with branches grown along backbones of rutile TiO2-NW as confirmed by high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD) analysis. In photocurrent−voltage measurements, short-circuit current density, and cell efficiency of TiO2-NW and TiO2-NB increase from 6.25 to 12.18 mA/cm2 and increase from 2.6 to 4.3%, respectively, due to both increased specific surface area and roughness factor.

Preparation of a superhydrophobic film with UV imprinting technology

Superhydrophobic surfaces with an advancing water contact angle (CA) larger than 150 and a water sliding angle (SA) less than 10 are found on lotus leaves and butterfly wings. These surfaces are interesting because of their various applications for water-repellence and anti-sticking properties. The lotus leaf is especially well known for its selfcleaning ability. Rolling water droplets wash off contaminants and dust due to low surface adhesion. According to previous studies, the surface dewetting is governed by the surface energy of coating material and roughness of the surface. Poly(dimethylsiloxane) (PDMS) and fluorocarbon based materials have been used to artificially modify a surface due to their low surface free energies. Nanotubes, nanofibers, nanorods, and porous structures have been introduced to create complex nano structures. Theoretically, two distinct models (Wenzel and Cassie models) were proposed to explain the effect of roughness on a hydrophobic surface. Because roughness impacts contact angles, they introduced the surface roughness factor (r), which is defined as the ratio between the actual and projected surface areas. Wenzel derived a theoretical relationship from the Young equation, which correlates the ‘apparent’ or measured contact angle on a rough surface with a flat substrate (Young’s model). His equation shows that an increased r can enhance surface wettability, allowing water to penerate the surface. Cassie and Baxter, on the other hand, propose that an r above a critical level leads to a great decrease in CA hysteresis, therefore increasing the receding angle. In the Cassie model, water droplets partially sit on surface air pockets and can easily roll off. In the previous study, we showed a simple method to imitate the hierarchical lotus leaf structure using sol-gel technology. Briefly, we used a micro lens array (MLA) pattern to create ordered, micron-sized, large hills and porous silica aerogel to create disordered nano structure, and then chemically modified the surface with a PDMS coating solution. Nano-imprint lithography (NIL) is a promising technique to fabricate patterned structures with high precision and throughput in the micro/nanometer scale region. Additionally, NIL is inexpensive and does not require a complicated apparatus. In conventional NIL technology, hard molds, such as silicon, dielectric material (e.g., silicon dioxide or silicon nitride), and metal material (e.g., nickel) were used. Recently, flexible mold technology was introduced, replacing hard molds, making it easier to release the mold from the polymer surface, providing better conformal contact with the substrate to be patterned, and reducing the pressure needed during imprinting. In a previous study, Kim et al. introduced a simple NIL method to create a superhydrophobic surface with a flexible mold made from anodic aluminium oxides (AAOs). Furthermore, Lee et al. produced well-defined, large, nanostructured polymeric and metallic surfaces with nanoembossing or nanofibers and controlled aspect ratios by employing AAOs or textured Al surfaces as a replication master. In this study, we present a superhydrophobic flexible film preparation with ultraviolet (UV) NIL technology using a flexible master substrate with ordered micronsized patterns and disordered nano structure. The advantage of this study is that it removes the surface treatment step that is required in conventional imprinting. The surface treatment allows for easy demolding due to the low surface energy of the superhydrophobic and modifiedPDMS coating surface.

Fatigue crack initiation and propagation behavior of forging die steels

In this paper, fatigue crack initiation and propagation behavior of forging die steels are reviewed mainly on the basis of the author’s experimental results. First of all, low cycle fatigue strength, fatigue crack propagation behavior and thermal fatigue properties of the representative hot forging die steel SKD62 are summarized with respect to testing temperature, steel hardness, stress concentration factor of the specimen and surface treatments effect. Then, the emphasis is focused upon the recently obtained experimental results on low cycle, high cycle and giga cycle fatigue behavior of cold forging die steels. Fatigue crack initiation and propagation behavior of cold forging die steels is discussed with respect to steel hardness, surface roughness and stress concentration factor of specimen. Characteristics of fatigue fracture surface morphology is summarized and related to fatigue crack initiation and propagation mechanism of hot and cold forging die steels. Finally, recommended studies on fatigue of forging die steels are touched on briefly.

Experimental Research on the Electrochemical Abrasive Belt Grinding 0Cr17Ni4Cu4Nb Stainless Steel

This article introduces a new way combining electrochemical and traditional abrasive grinding belt called Electrochemical Abrasive Belt Grinding. Through the study of grinding the 0Cr17Ni4Cu4Nb stainless steel, analyzes the influence of all the key factors for surface roughness during the process of electrochemical abrasive belt grinding by means of multivariate orthogonal experimental methods and single factor experimental method.

Gold supported catalytic layer: An intermediate step between fundamental and applied fuel cell studies

We report the preparation and electrochemical characterization of gold supported catalytic layer electrodes which have been prepared using a similar methodology to that employed in the preparation of conventional catalyst coated membranes. Consequently, the so-prepared catalytic layers have comparable properties (morphology and thickness) than those employed in direct liquid fuel cells. Using this working electrode configuration, and the so-called hydrogen adsorption–desorption region, fundamental electrochemical parameters such as electrochemically accessible Pt surface area, roughness factor and Pt-catalyst utilization of the catalytic layer have been evaluated. The electrochemically accessible Pt surface area, roughness factor and Pt-catalyst utilization have been found independent of the metal loading in the range of 0.1–0.5 mg Pt cm −2. However for 1 mg Pt cm −2, an important decrease on electrochemically accessible Pt surface area and Pt-catalyst utilization has been observed. On the other hand, when formic acid electrooxidation is used, a sudden decrease on the electrocatalytic activity has been observed as metal loading increases. These results clearly indicate that the formic acid electrooxidation process is strongly dependant of the accessibility of the reactant into the inner part of the electrodes, highlighting its mass-transport controlled reaction properties. These findings point out that, from an applied point of view, it is recommendable using catalytic layers as thinner as possible as well as high formic acid concentrations. These experimental conditions will maximize the Pt-catalyst utilization by minimizing the accessibility problems of the reactant into the inner part of the electrodes.

Photoactivity of Transparent Nanocrystalline Fe2O3 Electrodes Prepared via Anodic Electrodeposition

Highly transparent nanocrystalline α-Fe2O3 films were prepared via anodic electrodeposition using a slightly acidic aqueous medium (pH 4.1). The deposition mechanism involved oxidation of Fe2+ ions to Fe3+ ions followed by precipitation of Fe3+ ions as amorphous γ-FeOOH films. The as-deposited films were then converted to transparent nanocrystalline α-Fe2O3 films by annealing at 520 °C in air. The as-deposited and annealed films were characterized by Raman and UV−vis spectroscopy, X-ray diffraction, and scanning electron microscopy. The photoactivity of the as-deposited and annealed films was studied by measuring short-circuit photocurrents in a 60:40 solution of propylene carbonate:acetonitrile containing 0.5 M tetrabutylammonium iodide and 0.04 M iodine. Both films show n-type behavior generating anodic photocurrent. α-Fe2O3 films with various thicknesses were prepared to study the effect of film thickness on photon absorption and photocurrent. The short-circuit photocurrent of α-Fe2O3 films increased gradually as the film thickness increased to 400−500 nm because of the corresponding increase in photon absorption and surface area of the films. However, when the film thickness exceeded 400−500 nm, aggregation of Fe2O3 particles at the film/substrate interface became severe. This increased recombination losses near the collector electrode, and with no significant gain in photon absorption, led to an overall decrease in photocurrent. α-Fe2O3 films were also prepared by annealing FeOOH films produced via anodic deposition in a neutral medium (pH 7.5). The film prepared from the neutral medium was two times thicker and possessed a surface roughness factor two times higher than the film prepared from the acidic medium when the two films contained the same amount of α-Fe2O3. Comparing photocurrent of these films allowed for better understanding the effect of electrode structures (i.e., surface area, film thickness) on photocurrent generation in α-Fe2O3 electrodes with poor charge transport properties.

Optimum damage and surface roughness prediction in end milling glass fibre-reinforced plastics, using neural network and genetic algorithm

This paper presents an approach for the determination of the optimal cutting parameters (spindle speed, feed rate, and depth of cut) and end mill flutes leading to minimum surface roughness and delamination factor in end milling of glass fibre reinforced plastics (GFRP) by coupling neural network (NN) and genetic algorithm (GA). In this regard, the advantages of statistical experimental design technique, experimental measurements, artificial neural network, and genetic optimization method are exploited in an integrated manner. The genetically optimized neural network system (GONNS) is proposed for the selection of the optimal cutting conditions from the experimental data when an analytical model is not available. GONNS uses back-propagation (BP) type NNs to represent the input and output relations of the considered system. The GA obtains the optimal operational conditions through using the NNs. From this, it can be clearly seen that a good agreement is observed between the predicted values and the experimental measurements.

Mirror Finishing of Austenitic Stainless Steel with a Cermet Insert

Stainless steel SUS304 is one of the typical difficult-to-cut materials due to strong tendency to adhesion and work hardening. Therefore finished surface becomes rough in machining operations. In this report, precision cutting of SUS 304 is discussed. Surface roughness depends on accuracy of the machine tool, adhesion and roughness of tool flank. We analyzed the factors of surface roughness in turning of SUS304 on an engine lathe. M20 tungsten carbide inserts, coated carbide inserts and cermet inserts were used. Peak-to-valley height of machined surface included approximately 1μm of machine error. Surface profile reflected roughness of tool flank. Polished flank decreased the roughness of finished surface. Adhesion was least in the case of cutting with cermet inserts. We also conducted face turning of SUS304 on an ultra-precision lathe with cermet inserts. Flank of the inserts were polished to 100nmRz. We obtained 50nm of minimum peak-to-valley height and 220nmRz of surface roughness.

Effects of paste storage on the properties of nanostructured thin films for the development of dye-sensitized solar cells

The effects of paste storage on the properties of nanostructured thin films were investigated in the present study. To this aim, dye-sensitized solar cells were fabricated using nanostructured TiO 2 thin films and an organic dye as a sensitizer. Aggregation of TiO 2 nanoparticles was observed when paste was stored until deposition affecting film's porosity and surface roughness factor and as a consequence, reducing the efficiency of the solar cells. On the other hand, fewer cracks were developed during the drying process of the film when stored paste was used for film deposition instead of freshly prepared paste. This is due to the presence of large pores on films with significant particle agglomeration, which enhance evaporation of acetyl acetone and water, thereby reducing cracks. The development of cracks on the film's surface results to a decrease in the efficiency of the cell, albeit a slight one. One of the main aims of the present study was also the investigation of different methods for developing counter electrodes, as the properties of the counter electrodes can affect the efficiency of the solar cells considerably. Counter electrodes were prepared by two different methods, namely by electrodeposition using an aqueous solution of H 2PtCl 6 (0.002 M) and by thermal decomposition of H 2PtCl 6 from isopropanol (5 mM). Electrodeposited counter electrodes were found to present several advantages over electrodes prepared by thermal decomposition, such as increased photocurrent, reduced sheet resistance, as well improved fill factor for the resulting solar cell.