Uniform Surface Treatment Research Articles

Green electrochemical polishing of EBM Ti6Al4V samples with preliminary fatigue results

Additive manufacturing technologies have several well-known advantages; however, the surface quality of the printed parts is poor, compromising the corrosion and mechanical properties. Thus, surface finishing treatments are necessary. The most post-processing treatments proposed in the literature are mechanical or chemical. The formers are contact techniques and cannot be suitable for complex geometry, while the latter use strong and dangerous reagents. This paper is aimed to investigate the effect of the electropolishing treatment, a contactless technique, using an eco-friendly electrolytic solution in reducing the roughness and improving the fatigue properties of Ti6Al4V specimens produced by electron beam melting technology. Several parameters affecting the effectiveness of the electropolishing treatment have been investigated, as interelectrode distance, stirring rate and duration time. An optimal combination of them allowed a uniform surface treatment and a significant roughness reduction (64% of Sa reduction for cylindrical specimens). Under sinusoidal loading conditions with a maximum stress of 378 MPa and a stress ratio equal to R = 0.1, the mean fatigue life of electropolished dog-bone specimens was 250% longer than that of as-built specimens.

Precision beam shaping by spatial frequency filtering

Flattop beams are in high demand for a variety of applications, including uniform surface treatment, interference laser processing, repairing and skin therapy. In this experiment, we optimized the direction of phase grating to spatially separate the beam into extracted and residual components in the Fourier plane, and spatially filtered the components to form a square or hexagonal flattop beam with no wave-like structure inside and high edge steepness.

Graph-Analytical Method for Determining the Untreated and Treated with the Herbicide Area around the Stem with Over-lapping When the Working Body is Made in the Form of a Probe

In order to solve the problem of uniform surface treatment of bored areas of perennial plantations (treatment with herbicides) the graph-analytical method of examination of treatment quality (determination of untreated and treated area around the overlapped die) is proposed. To do this, you need to specify the diameter of the stamp of perennial planting, the overall size of the deflector in the form of a stylus, its position in the space relative to the diameter of the stamp of perennial planting, the size of the overlap zone when treating with herbicides in the gardens, the distance between the dies and the operating speed of the unit to determine the geometric and operating parameters of the sprayer. The whole stage of the working device (probe), when it is working in the nozzle zone is divided into 4 stages. Analysis of the graphical image of the stylus trajectory during movement around the stamp gives an idea of the surface treatment process with herbicides during spraying. In the first stage, part of the borehole zone is treated with overlap, while in the third stage, the untreated area around the die is left untreated. The dependencies of determining these areas depending on the geometric dimensions of the dies, their location in the gardens, the length and angle of the stylus and the operating speed of the unit are derived. According to the different trajectories of movement, in the process of influence of a stylus on a stamp there is a change of direction of an air-droplet stream, as a result of which the flow of a working liquid and accordingly the processed area changes. It is possible to determine the deviation of the actual rate of fluid flow from the specified rate at different points in the borehole area by calculating the areas treated with overlap and untreated. All obtained dependencies will serve for optimization of geometrical and mode parameters of the working device (feeler gauge) during its operation in the borehole zone.

Development of a Highly Densified Magnetic Sheet for Inductors and Advanced Processes through Silane Surface Treatment of Fe Nanopowder

For developing subminiature and highly integrated multilayer inductors, soft magnetic powder was used; however, its ferrite magnetic component is characterized by high resistivity and reduced direct current saturation, leading to the deterioration of the inductor under high currents. Therefore, herein, to improve the electromagnetic properties of thin-film inductors, Fe nanopowder was used to increase the volume fraction of magnetic sheets. Surface treatment was performed by using silane coupling agents, which improved the bonding strength and dispersibility of the Fe nanopowder with a heterogeneous epoxy binder. For uniform surface treatment on the nanopowder, the silane-treated powder was aged for 24 h, at a temperature of 3 °C. The surface-treated Fe nanopowder was used with a mixing ratio of the soft magnetic powder (coarse:fine:nano) of 7:2.5:0.5 wt.%; this was successful in producing a flexible and highly densified magnetic sheet. As a result, the volume fraction of the magnetic sheet for thin-film inductors to which a low-temperature aging-treated nanopowder was applied was significantly improved.

Formation of Porous Alumina Film By Indirect Oxidation Under AC Electric Field

In recent years, there has been renewed interest in bipolar electrochemistry, which deals with reactions occurring on unconnected conductive objects placed between outer electrodes, due to its potential applications in various fields ranging from sensing to the fabrication of functional materials. In most of the studies regarding bipolar electrochemistry, a direct current (DC) electric field is applied between the driving electrodes, and an inhomogeneous reaction field on the bipolar electrode is used. Based on the polarization of both sides of a bipolar electrode under a DC electric field, the electrochemical redox reactions on each part of a bipolar electrode can be controlled. In our previous study, we investigated the application of an alternating current (AC) electric field for surface coating of aluminum and successfully formed porous alumina films on unconnected aluminum by indirect oxidation under an AC electric field without a direct electrical connection (“AC-bipolar anodization”) 1, 2). A common strategy applied in bipolar anodization is to use the interfacial potential differences between the driving electrodes under a DC electric field, resulting in the asymmetrical formation of oxide films (e.g., gradients in the thickness of the porous layer and pore diameter) on a metal substrate used as a bipolar electrode. On the other hand, we focused on bipolar anodization under an AC electric field as uniform surface treatment for aluminum. With the above background, we continued our preliminary work and tried to fabricate Pt/alumina composite on an unconnected aluminum substrate using one-pot electrochemical synthesis in a single electrolyte 3). This synthetic approach overcomes the drawbacks of conventional methods in terms of the operation efficiency and will lead to the development of various functional composites using one-pot synthesis. In terms of basic research, potential applications of our developed method will be also discussed. H. Asoh, M. Ishino, H. Hashimoto, RSC Adv., 6, 90318 (2016).H. Asoh, M. Ishino, H. Hashimoto, J. Electrochem. Soc., 165, C295 (2018).H. Asoh, S. Miura, H. Hashimoto, ACS Appl . Nano Mater., in press (2019).

Nanoporous silver cathode surface-treated by aerosol-assisted chemical vapor deposition of gadolinia-doped ceria for intermediate-temperature solid oxide fuel cells

Herein, a nanoporous silver surface treated with gadolinia-doped ceria (GDC) is evaluated as a cathode for intermediate-temperature solid oxide fuel cells operating below 500 °C. For uniform surface treatment on the porous silver, aerosol-assisted chemical vapor deposition (AACVD) is used; it is a non-vacuum process and is considered as an economical alternative to the expensive vacuum-environment thin-film fabrication methods. Consequently, a uniform coating of AACVD GDC on the Ag surface is successfully achieved, which is confirmed by high-resolution transmission electron microscopy. The optimized amount of AACVD GDC enhances fuel cell performance compared to cells with bare Ag, in terms of the power and long-term stability measured by current–voltage characteristics, electrochemical impedance spectroscopy, and potentiostatic amperometry. This performance is even more significant than that from the cell with a platinum cathode, which, to our best knowledge, is known as the best-performing catalyst for solid oxide fuel cells in the intermediate- and low-temperature regimes. The power enhancement is attributed to the improved kinetics with the GDC surface coating; moreover, this oxide decoration is proven effective in preventing the thermal agglomeration of Ag, as confirmed by the morphology comparison before and after the long-term test.

Experimental study on the microwave processing of waste tyre rubber aggregates to enhance their surface properties for their use in rubberized bituminous mixtures

AbstractThis experimental study uses the microwave technology to process the waste tyre rubber aggregates to enhance the interaction properties of waste rubber and bitumen by smoothing its surface. This was to make the waste rubber less reactive to the bitumen sample at the elevated temperatures of around 140–170°C. Parameters such as the microwave power, the height of the sample inside the processing chamber, and the processing time have been considered and optimized. The results show that the microwave processing technique designed in this study has significantly smoothened the surface of waste rubber. Scanning electron microscope surface analysis has been carried out to confirm the changes and smoothness of the rubber surface in comparison with the untreated waste rubber aggregates. In addition, microwave spectroscopy analysis has been carried out to confirm the reduction in the absorption properties of waste rubber. The microwave curves of the bitumen samples extracted from the treated rubber–bitumen blend are comparable with the pure bitumen sample with minute shifts in the resonant peaks. The results show the potential of the technique and recommends designing a dedicated processing unit to further improve it through parameters such as volumetric and uniform surface treatment, penetration depth of the microwaves.

High-voltage electrode optimization towards uniform surface treatment by a pulsed volume discharge

In this study, the shape and material of the high-voltage electrode of an atmospheric pressure plasma generation system were optimised. The research was performed with the goal of achieving maximum uniformity of plasma treatment of the surface of the low-voltage electrode with a diameter of 100 mm. In order to generate low-temperature plasma with the volume of roughly 1 cubic decimetre, a pulsed volume discharge was used initiated with a corona discharge. The uniformity of the plasma in the region of the low-voltage electrode was assessed using a system for measuring the distribution of discharge current density. The system's low-voltage electrode - collector - was a disc of 100 mm in diameter, the conducting surface of which was divided into 64 radially located segments of equal surface area. The current at each segment was registered by a high-speed measuring system controlled by an ARM™-based 32-bit microcontroller. To facilitate the interpretation of results obtained, a computer program was developed to visualise the results. The program provides a 3D image of the current density distribution on the surface of the low-voltage electrode. Based on the results obtained an optimum shape for a high-voltage electrode was determined. Uniformity of the distribution of discharge current density in relation to distance between electrodes was studied. It was proven that the level of non-uniformity of current density distribution depends on the size of the gap between electrodes. Experiments indicated that it is advantageous to use graphite felt VGN-6 (Russian abbreviation) as the material of the high-voltage electrode's emitting surface.

Formation of relief on a metallic target surface under the action of compression-plasma flows

The results of experimental and theoretical investigations of relief formation on the surface of a steel target (grade St 3 steel, GOST (State Standard) 380) during treatment by compression-plasma flows are represented. The density of energy absorbed by the target varied in the range from 15 to 25 J/cm2, the pulse duration was 100 μs, and the pulse number was N = 1, 3, 5, 7. The experiment revealed the expansion of boundaries of the central area (the area on which the plasma flow is incident normally to the surface) with increasing pulse number. This is explained by the more uniform surface treatment at a greater pulse number. It is shown that to describe relief formation in the central area there is a need to take into account the pressure of the plasma flow on the target surface, apart from surface tension forces and energy dissipation due to viscosity.

An atmospheric-pressure plasma brush driven by sub-microsecond voltage pulses

An atmospheric-pressure room-temperature plasma brush, which can deliver uniform surface treatment effects, is reported. The plasma structure, which includes the negative glow, Faraday dark space and positive column, is clearly visible to the naked eye. The width of the Faraday dark space diminishes with decreasing gap distance and this phenomenon is different from that observed from low-pressure glow discharge plasmas. High-speed photographs taken at an exposure time of 2.5 ns show that the plasma propagates from the nozzle to the object in about 100 ns and 10 ns for gap distances of 6 mm and 2 mm, respectively, and the results are consistent with electric measurements. The emission spectra reveal N2(B–A) bands in addition to those of O, , N2(C–B) and He, indicating that the plasma source is reactive and suitable for applications such as surface modification and materials processing.

자장 여과 아크 이온빔 식각 공정을 이용한 WC-Co 및 SCM415 금속 소재 표면 구조 제어 연구

The surfaces of WC-Co and SCM415 were etched to form a micro size protrusion for oil based ultra low friction applications using an ion bombardment process in a filtered vacuum arc plasma. WC-Co species showed that a self-patterned surface was available by the ion bombarding process due to the difference of sputtering yield of WC and Co. And the increasing rate of roughness was 0.6 nm/min at -600 V substrate bias voltage. The increasing rate of roughness of SCM415 species was 1.5 nm/min at -800 V, but the selfpatterning effect as shown in WC-Co was not appeared. When the SCM415 species pretreated by electrical discharge machining is etched, the increasing rate of roughness increased from 1.5 nm/min to 40 nm/min at -800 V substrate bias voltage and the uniform surface treatment was available.

Investigation of surface treatment of conductive wire in cylindrical atmospheric pressure plasmas

Polyethylene insulated electric wire was treated in He and Ar dielectric barrier discharge atmospheric pressure plasmas generated in a quartz tube wound with tubular electrodes. The wire was put penetrating through the high voltage and the grounded electrodes, improving the discharge and facilitating uniform surface treatment. In this work, the influences of conductivity of the wire on the effects of surface treatment and discharge behavior were investigated. Surface properties of the wire samples were analyzed by means of surface energy measurement and X-ray photoelectron spectroscopy. In order to reveal the mechanism for treating the conductive wire, I– V discharge waveforms were measured and time-resolved plasma images were taken. It was demonstrated that the conductive wire was involved in the discharge process, reducing the breakdown voltage significantly and enhancing the discharge. It shows that the discharge mode was strongly dependent on the conductivity of a wire. Intensive surface discharges developed along the conductive wire were found to be mainly responsible for noticeable improvement in the treatment effect.

Atmospheric Dielectric-Barrier Discharges Scalable From 1 mm to 1 m

Three types of atmospheric dielectric-barrier discharges are presented to illustrate their potential for uniform surface treatment with a length scale spanning from 1 mm to 1 m. As these atmospheric discharges are scaled up in size, it is increasingly difficult to sustain their plasma stability. By using nanosecond images, it is shown that the use of high excitation frequencies is beneficial in achieving excellent uniformity and robust plasma stability, which are both desirable for uniform and reproducible surface treatment.

Persistence and fate of 2,3,4,6-tetrachlorophenol and pentachlorophenol in limnocorrals

Three separate limnocorral experiments were conducted to assess the fate and effects of a commercial 2,3,4,6-tetrachlorophenol (TeCP) formulation (DIATOX®; 19.4% TeCP, 4.8% pentachlorophenol [PCP], 75.8% “inert” buffers) in an aquatic ecosystem. Nominal treatment concentrations for experiments 1 and 2 were 0.075 and 0.75 mg active ingredient (a.i.)/L and 0.75 and 1.50 mg a.i./L DIATOX®, respectively, with three replicates of each treatment. Pesticide was applied in the morning for experiment 1 and in the evening for experiment 2. For Experiment 3, unreplicated concentrations of 0.1, 0.25, 0.5, 1.0, 2.0, 4.0, and 7.3 mg a.i./L DIATOX® were chosen; pesticide was applied in the evening. In all three experiments, the pesticide was applied as a single, uniform surface treatment. Both TeCP and PCP dissipated rapidly from the water of treated limnocorrals. Times to 50% dissipation for TeCP and PCP in the integrated water column were generally similar within experiments but ranged from 0.4 to 1.1 d following the morning application of experiment 1 to 3.4 to 7.3 d following the evening applications of experiments 2 and 3. The faster initial dissipation of TeCP and PCP from the water following the morning application implicated photolysis as the primary degradation mechanism, as did the faster dissipation of chlorophenols from the surface layer than from other water depths during experiment 2. Aqueous dissipation rates for both compounds from the integrated water column were similar in all three experiments after the initial mixing period (1–4 d); the three-experiment average first-order rate coefficient for either compound after day 4 was 0.09/d. From a mass balance perspective, the majority of the chlorophenols remained in the water column. Neither compound accumulated in the sediments to any significant extent ( 99% of the applied chlorophenols had dissipated from the water of treated enclosures by the end of the various experiments (42–63 d).

PERSISTENCE AND FATE OF 2,3,4,6-TETRACHLOROPHENOL AND PENTACHLOROPHENOL IN LIMNOCORRALS

Three separate limnocorral experiments were conducted to assess the fate and effects of a commercial 2,3,4,6-tetrachlorophenol (TeCP) formulation (DIATOX®; 19.4% TeCP, 4.8% pentachlorophenol [PCP], 75.8% “inert” buffers) in an aquatic ecosystem. Nominal treatment concentrations for experiments 1 and 2 were 0.075 and 0.75 mg active ingredient (a.i.)/L and 0.75 and 1.50 mg a.i./L DIATOX®, respectively, with three replicates of each treatment. Pesticide was applied in the morning for experiment 1 and in the evening for experiment 2. For Experiment 3, unreplicated concentrations of 0.1, 0.25, 0.5, 1.0, 2.0, 4.0, and 7.3 mg a.i./L DIATOX® were chosen; pesticide was applied in the evening. In all three experiments, the pesticide was applied as a single, uniform surface treatment. Both TeCP and PCP dissipated rapidly from the water of treated limnocorrals. Times to 50% dissipation for TeCP and PCP in the integrated water column were generally similar within experiments but ranged from 0.4 to 1.1 d following the morning application of experiment 1 to 3.4 to 7.3 d following the evening applications of experiments 2 and 3. The faster initial dissipation of TeCP and PCP from the water following the morning application implicated photolysis as the primary degradation mechanism, as did the faster dissipation of chlorophenols from the surface layer than from other water depths during experiment 2. Aqueous dissipation rates for both compounds from the integrated water column were similar in all three experiments after the initial mixing period (1–4 d); the three-experiment average first-order rate coefficient for either compound after day 4 was 0.09/d. From a mass balance perspective, the majority of the chlorophenols remained in the water column. Neither compound accumulated in the sediments to any significant extent (< 0.1% of applied mass), but sediment-associated residues did dissipate at a considerably slower rate than residues in the water column. From 97 to >99% of the applied chlorophenols had dissipated from the water of treated enclosures by the end of the various experiments (42–63 d).

Surface modification and coating of powders by ion beam techniques

Powdered materials are widely used in industry. Many of the properties of powders are determined by their surface. Therefore, surface modification techniques such as those based on ion beams are promising techniques for powder modification. Ion beam techniques are typical line-of-sight processes. Only that part of a powder particle which is turned directly towards the source of the ion beam and is not shaded is treated properly. This renders uniform surface treatment of powders difficult. More or less sophisticated facilities for agitating the powder in the ion beam have to be used. In the present paper, a set-up is described for ion beam treatment of powders based on a rotating drum with wings which move the powder grains through the ion beam line. The features of this facility and the processes which take place in it during ion irradiation of powders are discussed. As an example, results of ion implantation and ion beam sputter deposition of gold onto alumina powder are presented. The amount of implanted or deposited gold, depending on rotation speed of the drum and number and type of ions, was determined using neutron activation analysis. The powder grain surfaces with deposited gold atoms were inspected with electron microscopy in combination with X-ray analysis.