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In this study, a high-hardness and wear-resistant ceramic coating was prepared on the surface of 319S aluminum alloy using the micro-arc oxidation (MAO) technique. The effects of pulse width, negative voltage, and KOH concentration on the MAO coating were investigated, and the microhardness and surface roughness of the coating were measured. The morphology, elemental distribution, and phase composition of the coating were analyzed using SEM, EDS, XRD, and digital microscopy. The influence of the MAO coating on the wear of the 319S aluminum alloy was evaluated using a friction-wear tester. The results showed that in the sodium silicate solution system, with an increase in pulse width, the thickness of the coating gradually increased and the surface hardness initially increased and then decreased. With an increase in negative voltage, the density of the coating first increased and then decreased, the thickness of the dense layer initially increased and then decreased, and the surface hardness initially increased and then decreased. With an increase in the KOH concentration, the coating thickness increased and the roughness initially decreased and then increased. When the pulse width was 3000 ms, the negative voltage was 130 V, and the KOH concentration was 1 g/L, the coating exhibited the best density, with the highest surface hardness of 1426.8 HV and the thickest dense layer of 55 μm. The reduction in surface cracks and improvement in density indicated an enhancement in the hardness and wear resistance of the coating. The decrease in width and depth of the wear scars demonstrated the excellent wear resistance of the coating. [ABSTRACT FROM AUTHOR]

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In this study, the 10B21 steel was treated by micro-arc oxidation (MAO) in the electrolyte consisting of aluminate and phosphate to enhance its corrosion resistance. The effect of negative voltage on corrosion resistance of the MAO coating obtained has mainly been analyzed through their phase composition, microstructure, interfacial bonding strength, salt spray and electrochemical testing. The result indicates that with negative voltages applied to the MAO coating, Fe-Al transition layers arise between coating layer and matrix. Furthermore, different negative voltages bring forward different α-Al2O3 contents contained in the MAO coatings and when it reaches −100 V, the amount of α-Al2O3 appears as the largest. The surface porosity of the coating was also significantly decreased. In addition, the corrosion current density of the coating is only 3.64 μA·cm−2, which is two orders of magnitude lower than that of the substrate. After 72 h of salt spray corrosion, it is found that the coating substrate is less corroded when the negative voltage of 100 V is applied. Therefore, −100 V has been proven as the optimum performance for improving the corrosion resistance of 10B21 steel. [ABSTRACT FROM AUTHOR]

This work reports the design of nano-level starch-gelatin biopolymeric blends incorporated with nano-TiO2 for energy storage applications in areas which need to utilise negative voltages. Six different activated nanoarchitectures were designed, push coated on nickel foam substrates and characterized with FTIR, a Zeta sizer, XRD, TEM, CV, EIS, and GCD techniques for structural, functional and electrochemical properties respectively. The COC glucosidic linkage, amide A bond, TiO bond were seen at 1068, 2783, 602 cm−1 to confirm the succesful synthesis of starch-gelatin-TiO2 nanohybrids, while TEM confirmed well dispersed TiO2 NPs dispersed within the crystalline starch nanoparticles and oval shaped nano-gelatin NPs. XRD analysis revealed crystallite sizes to be in the range of 21–98 nm for all nano-architectures, and confirmed the prescence of highly ordered phases suitable for energy storage, after activation. The zeta sizer investigations determined that the samples were nanoparticulates with sizes below 100 nm. The highest specific capacitances obtained at 5 mVs−1 were 237, 246, 349, 686, 691, 808F/g in the three electrodes configuration and 194, 204, 287, 541, 570, 617F/g in the two electrodes configurations for AS-NPs, AG-NPs, ASG-NHs, AS-TiO2 NHs, AG-TiO2-NHs and ASG-TiO2-NHs respectively. When the samples were tested using a three-electrode and two-electrode configuration, the activated starch-gelatin-TiO2 nanohybrid showed the lowest Rct of 0.28 Ω and 0.51 Ω, energy densities of 208.3 and 176.4 Wh/Kg, and power densities of 6213 and 5406 W/Kg. All samples had retention capacities of 86–95%, with the activated starch-gelatin-TiO2 nanohybrid having values of 95% and 92% for the GCD experiments run using three and two electrode configurations. This work demonstrates that biopolymer nanohybrids can be effective electrodes for supercapacitors devices in energy storage applications.

[Display omitted] • A highly compact ceramic coating is formed on SiC p /Al composite surface by PEO. • The coating obtained at +500 V/−80 V (i.e., N80) has high electrical insulation. • The compact coating structure provides a good long-term anti-corrosion ability. • The coatings display a high infrared emissivity value in the waveband of 8–20 μm. PEO coating microstructure on SiC p /Al composites under the influence of negative pulse are comparatively studied. Results show that the cross-sectional porosity is significantly reduced to 5.1%. The electrical insulation performance of coatings initially improves and then declines as the negative voltage rises from 0 V to 120 V, which is attributed that either an excessively low or excessively high negative voltage is insufficient to improve the internal defects of the coating. Among all the coatings, the coating obtained at +500 V/−80 V (i.e., N80) possesses better electrical insulation (with breakdown voltage of 736 ± 15 V, dielectric strength of 16.3 ± 0.3 V/μm, electrical resistivity of 1.51 × 1011 Ω∙cm), better dielectric performance, higher optical band gap value, making it appropriate for usage as electronic packaging or dielectric materials. The impedance modulus at low frequency of N80 coating is two to three times higher than that of N0, N40, and N120 coating, providing a long-term anti-corrosion ability for the substrate, during the 72-hour immersion. Additionally, the coatings display a high infrared emissivity in the waveband of 8–20 μm (>0.9) to achieve good radiation and heat dissipation effect. Thus, a reasonable negative voltage used in coating preparation does effectively diminish internal structural defects, enhancing coating performance. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Coatings were prepared on 5005 Al alloy surfaces at various negative voltages by plasma electrolytic oxidation, with addition of red mud (RM, 2 g L−1). The effects of the negative voltage on the coating composition, structure, and corrosion resistance were investigated. Various effects were observed with increasing negative voltage. The current density on the sample surface increased, the breakdown function was enhanced, and the RM concentration in the coating increased. The color of the ceramic layer changed from white to reddish brown and continuously deepened, consistent with the RM color. The coating grew faster and the thickness increased, and the overall compactness first increased and then decreased. The coating surface roughness gradually decreased and the surface porosity fluctuated greatly. A negative voltage of 100 V gave the best surface porosity and overall compactness. The XRD patterns showed that the coating consisted mainly of γ-Al 2 O 3 when the negative voltage was small, an increase in the negative voltage led to formation of α-Al 2 O 3 and CaCO 3. Fe 2 O 3 , CaTiO 3 , and SiO 2 were identified in the coatings by a combination of XRD and EDS analyses, and their contents increased. The coating corrosion resistance first increased and then decreased; a negative voltage of 100 V gave the best corrosion resistance. The presence of RM constituents in the coating with a dense composite structure effectively reduced the corrosion depth of the coating. Graphical abstract Unlabelled Image Highlights • Colored PEO coatings with added red mud were prepared. • Red mud particles improved the coatings composition. • Negative voltage effects on coating structure and corrosion resistance were studied. • Optimal negative voltage to obtain the best corrosion resistance was determined. • Corrosion depth was affected significantly by the presence of red mud particles. [ABSTRACT FROM AUTHOR]

The characteristics of PEO processes on SiC p /Al composite in aluminate electrolyte under the influence of negative pulse were comparatively investigated, aiming to tailor the soft sparking discharge states, thus achieving the compact ceramic coating and providing a deep understanding of the mechanisms involved. Tracking the variation trend of element optical emission intensity by OES technology reflects the influence of negative voltage on the evolution of the spark state, and the results show that large negative voltage accelerates the transition from arc sparking discharge to soft sparking discharge. When the PEO process completely enters the soft spark discharge state, the lowest electron density can also be kept at 1.06 × 1022 m−3, reaching the local thermodynamic equilibrium condition. At this time, the electron temperature in the plasma discharge zone is about 4000 K. In addition, the coating surface roughness value decreases with the increase of negative voltage, and the introduction of negative voltage effectively reduces the irregular convex structures and the macropores in the coating, due to inhibiting destructive high-intensity spark discharge by the soft sparking discharge. [Display omitted] • A highly compact ceramic coating is prepared on SiC p /Al composite surface via the soft sparking discharge. • The transition from arc sparking discharge to soft sparking discharge is accelerated with increasing negative voltage. • PEO enters the soft sparking accompanied by electron density at 1.06 ×1022 m-3 and electron temperature of 4000 K. [ABSTRACT FROM AUTHOR]

Electrospun nanofibrous scaffolds providing local delivery of vascular endothelial growth factor (VEGF) have distinctive advantages for vascular tissue engineering. However, more than 90% of VEGF were normally released from scaffolds formed by conventional positive-voltage emulsion electrospinning (PVEES) within the initial 3 days. VEGF molecules bear positive charge. In this investigation, emulsion electrospinning using power supplies of different polarities was studied for producing scaffolds bearing specific electric charge. VEGF-containing poly(lactic-co-glycolic acid) scaffolds with initial potential of −87 and −202 V were formed by negative-voltage emulsion electrospinning (NVEES) at −10 and −20 kV, respectively, which enabled steady and sustained release up to 18 days, exhibiting effective modulation for VEGF release. Compared to VEGF-containing scaffolds formed by PVEES, NVEES-formed scaffolds showed superior performance in promoting endothelial cell functions. [ABSTRACT FROM AUTHOR]

A stacked field-effect transistor (FET) linear cellular antenna switch adopting a transistor layout with odd-symmetrical drain–source metal wiring and an extremely low-power biasing strategy has been implemented in silicon-on-insulator CMOS technology. A multi-fingered switch-FET device with odd-symmetrical drain–source metal wiring is adopted herein to improve the insertion loss (IL) and isolation of the antenna switch by minimizing the product of the on-resistance and off-capacitance. To remove the spurious emission and digital switching noise problems from the antenna switch driver circuits, an extremely low-power biasing scheme driven by only positive bias voltage has been devised. The proposed antenna switch that employs the new biasing scheme shows almost the same power-handling capability and harmonic distortion as a conventional version based on a negative biasing scheme, while greatly reducing long start-up time and wasteful active current consumption in a stand-by mode of the conventional antenna switch driver circuits. The implemented single-pole four-throw antenna switch is perfectly capable of handling a high power signal up to +35 dBm with suitably low IL of less than 1 dB, and shows second- and third-order harmonic distortion of less than -45 dBm when a 1-GHz RF signal with a power of +35 dBm and a 2-GHz RF signal with a power of +33 dBm are applied. The proposed antenna switch consumes almost no static power. [ABSTRACT FROM PUBLISHER]

Abstract: Ceramic coatings were fabricated on ZK60 magnesium alloy by microarc oxidation (MAO) with different negative voltages. The coating degradability and bioactivity were evaluated by simulated body fluid (SBF) soaking test. A scanning electron microscope (SEM) and an X-ray diffractometer (XRD) were employed to characterize the coating morphology and phase composition. The electrochemical workstation was used to investigate the electrochemical corrosion properties of the samples. The results show that the coating growth mechanism can be influenced by the introduction and increase of negative voltage through affecting the direction and speed of ions transferring. With increase of negative voltage in the range of 0–100V, the coating electrochemical corrosion property is improved, the coating degradation rate is reduced, and the combination property of coating corrosion resistance and apatites forming ability is enhanced. [Copyright &y& Elsevier]

Positive voltage electrospinning (PVES) has been mainly used for forming fibrous polymer scaffolds for different applications including tissue engineering. There is virtually no report on negative voltage electrospinning (NVES) of tissue engineering scaffolds. In this study, NVES of four biopolymers, namely, gelatin, chitosan, poly(lactic -co-glycolic acid) (PLGA), and polybutylene terephthalate (PBT), to form nanofibrous membranes was systematically investigated. For comparisons, PVES of these polymers was also conducted. It was found that chitosan fibers could not be produced using NVES. Under NVES or PVES, the fiber diameter of electrospun scaffolds generally increased with increasing needle inner diameter and polymer solution concentration but decreased with increasing working distance for all four polymers. Neither NVES nor PVES altered the chemical structure of gelatin, PLGA, and PBT. PVES and NVES resulted in fibrous membranes bearing positive charges and negative charges, respectively. PLGA and PBT fibrous membranes retained around 30% and 50%, respectively, of the initial charge one week after electrospinning. Charges on gelatin and chitosan fibrous membranes were almost completely dissipated within 60 min of electrospinning. For all four polymers, under either PVES or NVES, the retained charges on fibrous membranes increased with increasing applied electrospinning voltage. This study explored a new approach for forming fibrous scaffolds by using NVES and has opened a new area for developing negatively charged fibrous scaffolds for tissue engineering applications. [ABSTRACT FROM AUTHOR]

• The voltage can be reduced to less than breakdown voltage by negative pulse. • Effect mechanism of negative pulse is explained by analyzing electrical waveforms. • A suitable negative pulse can reduce damage to coating and improve the compactness. • Energy consumption can be reduced by setting a reasonable ratio of negative pulse. A bipolar pulse mode is usually used in the plasma electrolytic oxidation (PEO) process of aluminum alloys. The negative pulse can eliminate the cavity and improve the compactness of the PEO coating. However, the effect mechanism of negative pulse on the electrical signal of PEO is not clearly understood. In this study, a method of improving the compactness of PEO coating and reduce energy consumption under different transient voltages and current waveforms is established and discussed. An equivalent circuit of RC series corresponding to the coating and the electric double layer during the PEO process was proposed to analyze the effect of negative pulse on the compactness of the PEO coating. Results showed that the voltage in the T+ off stage can be rapidly reduced to less than the breakdown voltage by introducing negative pulses, and the discharge of unextinguished sparks on the sample surface was inhibited, resulting in a relatively compact PEO coating. The time constants RC decreases with increased negative currents. The decline of the time constant RC indicates the rapid response of the oxidation reaction to the electric signal, which can improve the coating's compactness and reduce the energy consumption. In actual production, the energy consumption can be reduced by setting up a reasonable ratio of positive and negative pulse voltages in the PEO. [ABSTRACT FROM AUTHOR]

[Display omitted] This work reports the design of nano-level starch-gelatin biopolymeric blends incorporated with nano-TiO 2 for energy storage applications in areas which need to utilise negative voltages. Six different activated nanoarchitectures were designed, push coated on nickel foam substrates and characterized with FTIR, a Zeta sizer, XRD, TEM, CV, EIS, and GCD techniques for structural, functional and electrochemical properties respectively. The C O C glucosidic linkage, amide A bond, Ti O bond were seen at 1068, 2783, 602 cm−1 to confirm the succesful synthesis of starch-gelatin-TiO 2 nanohybrids, while TEM confirmed well dispersed TiO 2 NPs dispersed within the crystalline starch nanoparticles and oval shaped nano-gelatin NPs. XRD analysis revealed crystallite sizes to be in the range of 21–98 nm for all nano-architectures, and confirmed the prescence of highly ordered phases suitable for energy storage, after activation. The zeta sizer investigations determined that the samples were nanoparticulates with sizes below 100 nm. The highest specific capacitances obtained at 5 mVs−1 were 237, 246, 349, 686, 691, 808F/g in the three electrodes configuration and 194, 204, 287, 541, 570, 617F/g in the two electrodes configurations for AS-NPs, AG-NPs, ASG-NHs, AS-TiO 2 NHs, AG-TiO 2 -NHs and ASG-TiO 2 -NHs respectively. When the samples were tested using a three-electrode and two-electrode configuration, the activated starch-gelatin-TiO 2 nanohybrid showed the lowest R ct of 0.28 Ω and 0.51 Ω, energy densities of 208.3 and 176.4 Wh/Kg, and power densities of 6213 and 5406 W/Kg. All samples had retention capacities of 86–95%, with the activated starch-gelatin-TiO 2 nanohybrid having values of 95% and 92% for the GCD experiments run using three and two electrode configurations. This work demonstrates that biopolymer nanohybrids can be effective electrodes for supercapacitors devices in energy storage applications. [ABSTRACT FROM AUTHOR]