Improvement of copper alloy properties in electro-explosive spraying of ZnO-Ag coatings resistant to electrical erosion

Omara M.A., Nassar I.A.

The electrical energy is transmitted from the generating stations to the consumers through a transmission network. The effectiveness of improving voltage profile yields high transmission network efficiency and increase the capacity of transmission lines, also decrease power losses, voltage drop and unplanned shut down in the big industrial and strategic loads like (oil refining industry). This paper objective presents the suggested solutions for improving voltage profile in electrical network of delta Egypt to achieve a voltage quality. The methodology of suggested solutions are applied on delta Egypt network with voltage levels (66, 11, 6.6, 0.4) kV, the simulations were performed using digital simulation and electrical network calculation (DIgSILENT power factory software) to study the voltage profile. The validation of results was performed by comparing the voltage profile of proposed four different scenarios: 1st: power flow in normal operation (without using any voltage improving devices), 2nd: using Automatic Tap Changer (ATC) of transformers, 3rd: installing a Static Volt Ampere Reactive (VAR) System(SVS) with (ATC), 4th: installing a (SVS), (ATC) and shunt reactive power compensation devices (parallel capacitor / inductor). The best voltage profile achieved by using scenario 4, which supported and improved the voltage profile of all system and brings the magnitudes of all buses in permissible voltage level from (0.79-0.99 P.U.) at normal operation (scenario 1) to (0.9-1.04 P.U.) at (scenario 4). So the system can be operated with more efficiently, stability and improving the capacity of the network after applying the solution stated in scenario 4. • This paper studied the voltage profile in delta Egypt network. • A relation between voltage quality and catastrophic events in oil refining industry. • High quality grid must have voltage stability with in accepted levels at each bus. • Network construction was performed by (DIgSILENT power factory software). • The voltage profile was performed by proposed four different scenarios. Scenario 1: power flow (PF) study in normal operation (base case). Scenario 2: (PF) study using automatic tap changer (ATC). Scenario 3: (PF) study using (ATC)& static Var system (SVS). Scenario 4: (PF) study using (ATC), (SVS) and shunt reactive power control devices. • A comparison between all scenarios results have done to get the optimum solution. • The best voltage profile had achieved by using scenario 4.

Han F., Zhu L., Liu Z., Gong L.

In conventional thermal spraying processes, it is difficult to employ one type of coating process to economically spray materials having greatly different melting points. In this study, wire electrical explosion spraying(WEES) was applied to prepare refractory Ta10W and non-refractory Ni60A coatings by using a self-designed WEES device. The coating microstructure, deposition efficiency and coating thickness, as well as the adhesive strength of both coatings were investigated. A uniform and dense Ta10W coating with the phase of Ta, Ta2N, and FeTaO4 can be obtained when the energy density was 151.6 J/mm3, while the uniform and dense Ni60A coating made up of FeNi and SiO2 phase was got at the energy density of 72.7 J/mm3. The maximum deposition efficiency of Ta10W and Ni60A were 53% and 47% respectively. The thickness increment of both coatings decreased with the explosion frequency. The critical load Lc in the scratch test can be regarded as a criterion of the adhesive strength, the average critical load of Ta10W was greater than 50 N, while the Ni60A was 38.3 N. Through developing a high-efficient spray device and choosing the appropriate process parameter, especially a suitable energy density, the WEES will be capable to produce the commercially available coatings with greatly different melting points.

Hitaj C., Löschel A.

We estimate the impact of a feed-in tariff for renewable power on wind power investment in Germany at the county level from 1996-2010 controlling for windiness and access to the electricity transmission grid. After the Renewable Energy Law (EEG) was passed in 2000, the feed-in tariff became linked to wind power potential, such that more windy locations received a lower incentive per unit of output. We find that a 1 e-cent/kWh increase in the feed-in tariff rate would increase additions to capacity at the national level by 764MWper year from 1996- 2010 or 1,528 MW per year from 2005-2010. We analyze counterfactual scenarios, in which a uniform incentive is offered instead of the wind-dependent EEG incentive. Significantly more wind power plants are installed along the northern coastal counties in the uniform incentive scenario. We find that while the uniform incentive results in greater total wind power output per installed capacity, the EEG is ultimately more efficient by achieving 1% greater wind power output per euro and 3.7% greater reductions in power sector emissions per euro. In addition, we find a significant response from investors to an EEG provision that shifted the cost of transmission system upgrades from wind power developers to grid operators in 2000. The lack of a signal on scarcity of transmission capacity has likely resulted in a distribution of wind power plants that makes suboptimal use of existing infrastructure, necessitating investment in new transmission corridors.

Guzanová A., Brezinová J., Draganovská D., Maruschak P.O.

Abstract The paper focuses on assessment the resistance of hot-sprayed coatings applied by HVOF technology (WC–Co–Cr created using powder of two different grain sizes) against erosive wear by dry-pot wear test in a pin mill at two sample angles. As these coatings are designated for the environment with varying elevated temperatures and often are in contact with the abrasive, the coatings have been subjected to thermal cyclic loading and their erosive resistance has been determined in as-sprayed condition and after the 5th and 10th thermal cycles. The corrosion resistance of coatings was evaluated by linear polarization (Tafel analysis).

Zhou Y.X., Xue Y.L., Zhou K.

Tungsten-copper (WCu) contact materials are the core components of high-voltage electrical switches. However, significant arc ablation effect at high voltage and high current often leads to connection interruption and mechanical loss, which seriously affects the safe operation of appliances. In this paper, the failure mechanisms of tungsten-copper contact materials caused by significant arc ablation in the sulfur hexafluoride (SF6) atmosphere were investigated. Results showed that the arc ablation of contact materials is mainly caused by the evaporation and splashing of copper component which has a low melting point, followed by the ablation and spallation of the tungsten (W) skeleton structure. All of these have roughened the surface of contact materials and then further accelerated the volatilization of copper (Cu) component and the reactions between the contact materials and arc extinguishing medium of SF6. Finally, the contact materials lost their functions of arc extinguishing and current switching. Simulated experimental work has also been performed and it verified the above observed failure mechanisms of contact materials. Due to the instantaneously high temperature and high voltage generated during the arcing, both the Cu and W phases in the WCu alloy have suffered significant evaporation and mass losses.

Li J.

This paper presents optimal sizing algorithms of grid-connected photovoltaic-battery system for residential houses. The objective is to minimize the total annual cost of electricity. The proposed methodology is based on a genetic algorithm involving a time series simulation of the entire system and is validated using data collected through one year. Genetic algorithm jointly optimises the sizes of the photovoltaic and the battery systems by adjusting the battery charge and discharge cycles according to the availability of solar resource and a time-of-use tariff structure for electricity. Houses without pre-existing solar systems are considered. The results show that jointly optimizing the sizing of battery and photovoltaic systems can significantly reduce electricity imports and the cost of electricity for the household. However, the optimal capacity of such photovoltaic battery varies strongly with the electricity consumption profile of the household, and is also affected by electricity and battery prices. Besides individual PV generation and battery storage for each house, this paper also investigates group battery optimizations for communities with different consumption levels or with different energy demand diversity to see their effects on optimal sizing and peak demands for aggregated PV-battery system.

Simshauser P., Akimov A.

From 2004 to 2018 the Regulatory Asset Base (RAB) of electricity networks across Australia's National Electricity Market tripled in value, from $32 billion to $93 billion. The run-up in the capital stock was driven by forecast demand growth and a tightening of reliability standards. But demand contracted from 2010 to 2015. With a rising RAB, contracting demand and a regulated revenue constraint, an adverse cycle of falling demand and sharply rising tariffs appeared to be emerging. Some networks were characterised by significant investment mistakes in retrospect, and perhaps unsurprisingly, various consumer groups and regulatory bodies argued assets should be stranded or written-off with network tariffs reduced. From 2015 to 2018, energy demand increased once again. In this article we present a method for dealing with stranded assets under uncertainty; rather than permanently stranding assets that fail a used and useful test, we reorganise the financial and economic affairs of a template network utility and “Park” excess capacity, issue credit-wrapped bonds to temporarily finance the stranded capital stock, then re-test the Parked Assets at the end of each five-year regulatory determination. Parked Assets can then be “Un-Parked” and returned-to-service in line with connections growth, load growth, or both. This produces an immediate reduction in network tariffs under our generalised assumptions, but scarce government balance sheet capacity is necessarily utilised and recovery risk is transferred from shareholders to taxpayers. Accordingly, a Park and Loan policy is not a costless exercise.

Young S., Bruce A., MacGill I.

Australia has one of the highest penetrations of residential PV in the world and is projected to see substantially more deployment in coming years, with a growing proportion of this being coupled with battery energy storage (BES). Previous analysis of the implications of these residential distributed energy resources (DERs) has tended to focus on the individual private benefits to households that deploy them, their direct technical and revenue impacts on network businesses, or broader electricity industry implications. This paper seeks to quantify the economic impacts of residential PV and BES on electricity network businesses, from residential to wholesale market region level. One key impact is reductions in network business revenues as households purchase less electricity from the grid. However, we also consider the potential savings for network businesses as these PV and BES deployments reduce peak network demand from residential to wholesale market level, a key driver of network investment and hence network business costs. Our findings for the Sydney region suggest that potential network investment cost reductions could even outweigh the loss of revenue. Tariff design will have a key role in ensuring that residential PV and BES deployment offers value both to households as well as network businesses.

Shinde P.P., Adiga S.P., Pandian S., Mayya K.S., Shin H., Park S.

AbstractThe stiff compromise between reliability and conductivity of copper interconnects used in sub-nanometer nodes has brought into focus the choice of encapsulation material. While reliability was the primary driver so far, herein, we investigate how electronic conductivity of Cu(111) thin films is influenced by the encapsulation material using density functional theory and Boltzmann transport equation. Atomically thin 2D materials, namely conducting graphene and insulating graphane both retain the conductivity of Cu films whereas partially hydrogenated graphene (HGr) results in reduction of surface density of states and a reduction in Cu film conductivity. Among transition metal elements, we find that atoms in Co encapsulation layer, which essentially act as magnetic impurities, serve as electron scattering centres resulting in a decrease in conductivity by at least 15% for 11 nm thick Cu film. On the other hand, Mo, Ta, and Ru have more favorable effect on conductivity when compared to Co. The cause of decrease in conductivity for Co and HGr is discussed by investigating the electronic band structure and density of states. Our DFT calculations suggest that pristine graphene sheet is a good encapsulation material for advanced Cu interconnects both from chemical protection and conductivity point of view.

Hutsaylyuk V., Student M., Dovhunyk V., Posuvailo V., Student O., Maruschak P., Koval’chuck I.

The different nature of the effect of hydrogen on the tribological behavior of two carbon steels (st. 45 and st. U8) upon their contact with super solid plasma electrolytic oxidation (PEO) layers synthesized on two light alloys (AMg-6 and D16T alloys as the analogists of the A 95556 UNS USA and AA2024 ANSI USA alloys correspondently) was investigated in the medium of mineral oil of the I-20 type. To compare the effect of hydrogenation on the tribological properties of the analyzed contact pairs, similar tests were also performed on the same mineral oil with clear water or an aqueous solution of glycerine added to its content. A spinel-type film (hercynite) was formed upon friction of two contacting surfaces—the iron-carbon steels and PEO layers synthesized on the AMg-6 alloy. This film was a reliable protection against wear of the surface subjected to the effect of hydrogen. When steels came into contact with the PEO layers synthesized on the D16T alloy, surface protection against wear was ensured by another mechanism. The phenomenon of selective metal transfer in the friction zone (from one to another friction surfaces) was revealed.

Roul M.K., Pradhan S.K., Song K.D., Bahoura M.J.

We report the electrothermal properties of AAA trilayer on polyethylene terephthalate substrate which allowed the development of low-cost high-performance transparent thin-film flexible heater (TTFFH) using RF magnetron sputtering. The structural, electrical, and optical properties of the AAA trilayer were investigated at different thickness of the Ag interlayer. The AAA trilayer-based TTFFH yielded saturation temperatures beyond 100 °C at 10 V at optimized Ag interlayer thickness of 5 nm. The time-dependent temperature profile along with its highly stable and reversible thermal behavior was studied. Most importantly, the AAA trilayer-based TTFFH provides a high-performance alternative to the conventional and expensive ITO electrodes at a much lower cost.

Rejc J.

This paper describes the automated visual inspection system implemented in the production line for mechanical thermostat electrical switch sub-assembly full inspection. The system checks for presence of the electrical switch plates, measures the slant angle of the electrical contact plate holder and measures the contact distance as one of the most important parameters of the mechanical thermostat. The developed system consists of an USB video camera with non-telecentric fixed focal length lens, custom LED line illumination and two laser line illuminations. Also a dedicated user software was written with unique inspection and measurement algorithm. The accuracy and the repeatability of automated visual inspection system was verified with reference objects, previously measured with the reference Mitutoyo profile projector. The verification procedure showed that the measurement accuracy is in a range of ± 0.04 mm and repeatability in a range of ± 0.03 mm.

Ismael S.M., Abdel Aleem S.H., Abdelaziz A.Y., Zobaa A.F.

Currently, renewable energy is rapidly developing across the world in response to technical, economic and environmental developments, as well as political and social initiatives. On the other hand, excessive penetration of distributed generation (DG) systems into electrical networks may lead to various problems and operational limit violations, such as over and under voltages, excessive line losses, overloading of transformers and feeders, protection failure and high harmonic distortion levels exceeding the limits of international standards. These problems occur when the system exceeds its hosting capacity (HC) limit. The HC is a transactive approach that provides a way for the distribution network to be integrated with different types of energy systems. Accordingly, HC assessment and enhancements become an essential target for both distribution system operators and DG investors. This paper provides, for the first time, a systematic and extensive overview of the HC research, developments, assessment techniques and enhancement technologies. The paper consists of four HC principal sections: historical developments, performance limits, perceptions and enhancement techniques. Besides, practical experiences of system operators, energy markets and outcomes gained from real case studies are presented and discussed. It was concluded that success in integrating more distributed generation hinges on accurate hosting capacity assessment.

Koneva N. ., Trishkina L. ., Cherkasova T. .

The paper presents the results of transmission electron microscopic (TEM) studies on the defect substructure of alloys and its modification with an increasing distance from the fracture surface. Cu-Mn polycrystalline FCC solid solutions with Mn contents of 0.4 and 25 аt. % and the average grain size of 100 μm are studied. A test machine INSTRON is used to perform tensile deformation of Cu-Mn samples at room temperature and 2 · 10−2 s−1 strain rate. The strain is measured, the types of the dislocation substructure (DSS) and their parameters are studied with the step of 2 · 10−3 m in the local zones of fractured samples at different distances from the fracture surface. As a result of the experiments, the sequence of changes in the substructure with an increasing distance from the fracture surface are established. In Cu + 0.4 at. % Mn alloy the following substructural sequence is observed: micro-bands, misoriented cells, nonmisoriented cells, and dislocation tangles. Substructural change sequence in Cu + 25 at. % Mn alloy includes microbands, cell-networks with and without misorientations, dislocation pile-ups, and chaotic dislocation distributions. In both alloys terminated subboundaries have a high density near the fracture surface. It is observed that the substructures change gradually depending on the distance to the fracture surface. Substructures that cause the fracture of the alloys at a meso-scale level were also detected. Near the fracture surface, deformation boundaries are misoriented and characterized by a large amplitude of the lattice curvature-torsion. Misoriented cell and microband DSS are observed within the fracture area of Cu + 0.4 at. % Mn alloy. In Cu + 25 at. % Mn alloy the formation of misoriented cellnetwork DSS and microband DSS is observed. Microcracks appear both along the boundaries of misoriented substructures and grain boundaries.

Grechanyuk N.I., Grechanyuk V.G.

The phase composition and structurization of three types of copper and molybdenum composite materials, 0.8 to 5 mm thick, which were condensed from the vapor phase at substrate temperatures 700 and 900°C, are considered: precipitation-strengthened composites, microlayered composites with alternating copper and molybdenum layers 1 to 10 μm thick, and bulk nanocrystalline composites with alternating layers thinner than 0.5 μm. Standard precipitation-strengthened Cu- and Mo-based materials condensed from the vapor phase at substrate temperatures 700–900°C can be produced over a relatively narrow composition range of the strengthening phase (0.1–3 wt.% Mo). When Mo content is 3–5 wt.%, the molybdenum particles change their shape from round to acicular and become discontinuous chains oriented perpendicularly to the vapor flow. If there is more than 5 wt.% of the second phase, the condensed composite materials (CCMs) show a layered structure. The layered structure can be observed in other CCM types (Cu–W, Cu–Cr, NiCrAlTi–Al2O3). Layered copper and molybdenum CCMs, 6 mm thick, produced on a rotating substrate heated to 700 ± 30°C have been experimentally confirmed to belong to bulk nanocrystalline materials.

Meng F., Zhou Y., Zhang H., Wang Z., Liu D., Cao S., Cui X., Nong Z., Man T., Liu T.

Wear-resistant coatings applied to the surface of copper and copper alloys through diverse advanced technologies can substantially enhance their wear resistance and broaden their application spectrum. This paper provides a comprehensive review of the development and current research status of wear-resistant coatings fabricated on copper and its alloys. It presents the research findings on the preparation of wear-resistant coatings using both one-step methods (such as laser cladding, electroplating, thermal spraying, cold spraying, electro-spark deposition, etc.) and two-step methods (chemical plating and heat treatment, electrodeposition and laser cladding, laser cladding and in situ synthesis, etc.). This paper provides an in-depth examination of the characteristics, operating principles, and effects of various coating techniques on enhancing the wear resistance of copper and copper alloys. The advantages and disadvantages of different coating preparation methods are compared and analyzed; meanwhile, a prospective outlook on the future development trends is also offered.

Filyakov A.D., Pochetukha V.V., Romanov D.A., Vashchuk E.S., Gromov V.E.

The microstructure of a new TiB2 – Ag metal matrix composite coating deposited by electrical explosion spraying and modified by electron beam treatment is studied using x-ray diffraction analysis and scanning and transmission electron microscopy. It is shown that the phase composition of the coating depends on the deposition mode, and the subsequent electron beam treatment normalizes it. The main phases of the resulting modified coating are Ag, TiB2 and B2O. After the electron beam treatment, the microstructure of the coating transforms. The nanostructure of the silver matrix is transformed into a nanocrystalline structure with an average crystal size of tens to hundreds of nanometers.

Zhao H., Zhao X., Hui Z., Wang X., Shi H., Huang X.

The present study establishes an experimental platform for investigating arc erosion and explores the erosion characteristics of Ti3AlC2 material under a voltage of 10 kV in SF6/N2, SF6/CO2, and N2/CO2 environments. Our findings reveal that the arc energy and duration exhibit a gradual increase in the sequence of SF6/N2, SF6/CO2, and N2/CO2, while the breakdown strength decreases. Scanning electron microscopy (SEM) and a three-dimensional laser confocal microscope were employed to observe uneven erosion morphology. Additionally, high-speed camera footage captures the arc bending and drifting phenomenon caused by Rayleigh-Taylor instability between the arc and gas. X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis were utilized to characterize the composition of eroded surfaces. Erosion models were proposed for each mixed atmosphere along with comprehensive discussions on their underlying mechanisms. This work expands the application scope of MAX phase materials while providing a theoretical foundation for designing electrical contact materials.

Brahmane S., Hussain S., Sabiruddin K.

A low explosive material such as pyrotechnic mixture made of Al and Ba(NO3)2 powders, commonly known as the flash powder, is used to deposit BaAl2O4-based composite coatings on a flat mild steel surface by using a novel explosive coating setup developed in the laboratory. To achieve the high tribo-mechanical properties of the deposited coating, a suitable mixing ratio of Al to Ba(NO3)2 is to be found. In this work, the Al content of the flash powder is varied from 1 to 2.5 gm for 2 gm of Ba(NO3)2 to study the effect of Al content on the properties of the deposited BaAl2O4-based coatings. The fabricated coatings are characterized in terms of thickness, crystalline phase, microstructure, surface roughness, hardness, and wear resistance by using an optical microscope, X-ray diffractometer (XRD), Field emission scanning electron microscope (FESEM), stylus profilometer, Vickers micro-hardness tester, and linear reciprocating wear tester respectively. Up to 2 gm of Al addition, the hardness of the coatings is found to be enhanced remarkably. However, with further addition of Al, it is found to be decreased significantly. With 2 g of Al content, the major portion of Al powder is utilized well in the chemical reaction to produce mainly hard BaAl2O4 and AlN phases. The highest amount of energy is released from such a composition of feedstock. The presence of pure Ba and Al in the coatings from 1 g to 1.5 g of Al, respectively, have helped to enhance the wear resistance of those by reducing the coefficient of friction values. However, the high wear resistance obtained for the coating obtained from 2 g of Al content is due to the major presence of hard phases and low porosity in it. On the other hand, the high porosity and the major presence of partially melted pure Al particles make the coating from 2.5 g of Al less wear resistant. From a 1:1 mixing ratio of Ba(NO3)2 to Al powders in the flash powder, a hard and monolithic BaAl2O4-based composite coating with minimum defects can be obtained.

Filyakov A.D., Pochetukha V.V., Romanov D.A., Vashchuk E.S.

Due to many factors, the electrical explosion spraying process is not stable, which directly causes unstable coating quality and structure. Electron beam treatment may be used to improve the surface and modified structure of coatings sprayed by electrical explosions. In this study, a new TiB2–Ag metal matrix composite coating was deposited by electrical explosion spraying and modified by electron beam treatment. The prepared coatings were characterized by surface macro- and microanalysis, XDR, cross-section SEM, and TEM. The composition of the spray-coating phase differs from sample to sample. The electron beam treatment normalized the phase composition. Ag TiB2 B2O became the main phase in the modified coating. Increasing the pulse energy density and duration leads to a reduction in the low-melting Ag phase and the formation of copper contact phases due to heating and melting of the copper substrate by excess electron beam energy. The coating structure consists of a silver matrix and TiB2 inclusions. The electron beam treatment did not affect the structure; however, the microstructure of the coating transformed into a cellular crystallization structure. The silver matrix nanostructure was transformed into a nanocrystalline structure with an average crystal size ranging from tens to hundreds of nanometers.

Wang D., Zhu H., Zheng M., Tang Q., Xu J., Wei W., Lu C., Sun Z.

A group of MAX phases including Ti2AlC and Ti2AlN, are candidate reinforcements of Ag-based electrical contact materials. In this work, the interfacial reaction, resistivity, hardness and arc erosion resistance of Ag/Ti2AlX (X = C, N) were investigated comparatively. During the sintering of both Ag/Ti2AlX, Al deintercalated from Ti2AlX and Ag diffused into Ti2AlX. The interfacial reaction was mild in Ag/Ti2AlN while obvious in Ag/Ti2AlC. The first-principles calculation indicated that the higher vacancy formation energy of Al in Ti2AlN led to the mild reaction in Ag/Ti2AlN, which then resulted in a larger decrease in hardness and resistivity, as compared with Ag/Ti2AlC. Moreover, Ag/Ti2AlN showed superior arc erosion resistance, with less evaporation of Ag and oxidation of Ti2AlC. This were attributed to the lower vulnerability of mildly decomposed Ti2AlN, less resistance heat and easier heat dissipation, resulting from the superior electrical and thermal conductivity.

Ou Y.X., Wang H.Q., Ouyang X., Zhao Y.Y., Zhou Q., Luo C.W., Hua Q.S., Ouyang X.P., Zhang S.

Coatings with micro- or nano-scaled structure are always fabricated by various techniques to fulfill the requirements of unique performances according to special working conditions. The differences in preparation techniques always result in large differences in their properties, even for the same coating materials. High-performance coatings are solely up to surface integrity, morphology, microstructure, stress state, interfacial structure, cohesion and adhesion that are all strongly affected by preparation processes. Therefore, how to take advantage of the numerous deposition techniques to design a right preparation process to produce coatings of high performance to meet the demands is the real question. This work set out to answer this question. We first discuss the overall strategies towards making of high-performance coatings including deposition techniques, coatings and characterizations. We then move on to superior performances and durability of protective coatings and functional coatings. These strategies are readily applicable in making of various high-performance protective and functional coatings.

Lu P.A., Manikandan M.R., Yang P.F., He Y.L., Yang F., Dang S.T., Shi Y.C., Lou W.B., Liu R., Wu S.J., Li X.F., Hu Y.C., Shang J., Yin S.Q., Wang X.W.

The development of iron-based supercapacitors has been gaining more attention in the field of energy storage applications due to their non-toxicity, abundance and low cost. In this paper, single phase hematite nanoparticles were synthesized by high temperature thermal decomposition method and directly served as electrochemical supercapacitor electrode material. Structural study (XRD) revealed the single-phase hematite nanoparticles formation with trigonal alpha-Fe2O3 structure. Morphological study (SEM) confirms silkworm chrysalis shape like morphology by many interconnected nanoparticles of the average size of 30 nm. The electrochemical study indicates that the synthesized hematite electrode material can maintain good farad capacitance at 100 mV/s and it shows a specific capacitance of 149.3 F/g at a current density of 1 A/g with the maximum energy and power densities of 4.20 Wh/Kg and 224.90 W/Kg, respectively. Equivalent series resistance and charge transfer resistance of alpha-Fe2O3 electrode material are 1.079 Ω and 9.055 Ω, respectively. This is attributed to the alpha-Fe2O3 nanostructure, which can provide a large contact area between electrode and electrolyte for ionic reaction and transport. The material can still retain 43.8% of the initial specific capacitance after 5000 cycles. The investigation results show that the hematite nanoparticle-based electrode material holds great potential in electrochemical supercapacitors and provides a certain reference in the direction of global energy needs.

Huang K., Song Q., Chen P., Liu Y., Jing Y.

In the present work, Fe/Cu composite coatings were fabricated by electro-explosive spraying technology (EEST), with good lubrication performance and high wear resistance. The microstructure and morphology were characterized by an energy-dispersive spectrometer (EDS), 3D digital microscope, and scanning electron microscope (SEM) coupled with electron backscattered diffraction (EBSD). Mechanical properties and tribological performance were measured using a micro Vickers hardness tester, universal testing machine, and universal friction and wear testing machine. The composite coating had low porosity with a minimum value of 0.7%, high microhardness with a maximum value of 729.9 HV0.2, high bonding strength with a maximum average value of 55.25 MPa, and good wear resistance and self-lubrication, and the ratio of soft metal and hard metal in the coatings was controllable. Under dry friction conditions, the friction reduction mechanism was that there were both metallic oxide particles and soft metal attached in the friction pairs. When the ratio of soft metal in the composite coating was higher, the self-lubricating performance of the coating was better, with adhesive wear as the main wear mechanism; when the ratio of hard metal was higher, the wear resistance was better and the wear mechanism was mainly abrasive wear.

Liu Y., Song Q., Chen P., Huang K., Yang Y.

Abstract In this work, we study the corrosion performance of coatings prepared by electrical explosion spraying of metal wires. 316L metal wire with a diameter of 1.5 mm is used as spray material, and the coating is prepared on the 45# steel substrate by electrical explosion spraying. The oil–water corrosion experiment of the coating is carried out in a constant temperature water bath of 60°C for 168 h. The scanning electron microscopy and energy-dispersive spectroscopy results of the experimental samples have shown that some metal oxides are found inside the coating, most of which are distributed at the grain boundaries with a size range of 30–50 nm. The corrosion rate of the coating is measured by weight loss method with a corrosion rate of 0.079 mm/annum. XRD results show that the corrosion generates CaCO3, Fe3O4, and MgFe2O4. Coating corrosion is mainly caused by the formation of electrochemical corrosion between oxides and non-oxides in the coating, and pitting corrosion and intergranular corrosion in the presence of chloride ions.

Romanov D.A., Pochetukha V.V., Sosnin K.V., Moskovskii S.V., Gromov V.E., Bataev V.A., Ivanov Y.F., Semin A.P.

The article is concerned with analyzing the structure and properties of the Ni–C–Ag–N coating formed on copper by the complex method combining the electroexplosive spraying of coating, its irradiation by a pulsed electron beam and a subsequent nitriding in plasma of a gas discharge of low pressure. The structural constituents of coating's surface after the electroexplosive spraying as well as after the electron-beam processing and nitriding are studied. It is shown that a coating's thickness amounts to ≈90 μm. The wear resistance of a copper sample with the deposited coating exceeds that of the copper without the coating by ≈ 1.6 times. The friction coefficient of samples with the coating (μ = 0.5) is less than that of the copper without the coating (μ = 0.679) by ≈ 1.35 times. It is established that the hardness of the coating increases as the substrate is approached and reaches the maximum value of ≈1780 MPa (the hardness of substrate is 1300 MPa). By means of micro-X-ray-spectral analysis it is detected that the main chemical element of the coating is silver, but copper, nickel, carbon and nitrogen are present in a considerably smaller quantity. It is established by the methods of diffraction electron microscopy that the main phases of the coating are solid solutions.

Ajeesha T.L., Manikandan A., Anantharaman A., Jansi S., Durka M., Almessiere M.A., Slimani Y., Baykal A., Asiri A.M., Kasmery H.A., Khan A., Khan A.A., Madhu P., George M.

Magnetic and optical properties of copper doped spinel calcium ferrite (Ca 1-x Cu x Fe 2 O 4 ; x = 0, 0.2, 0.4, 0.6, 0.8, 1) nanoparticles (NPs) have fascinated the attention of researchers. Spinel Ca 1-x Cu x Fe 2 O 4 NPs were prepared by co-precipiation technique. The as prepared compositions were subjected to structural, magnetic, electrical and optical properties. Cubic spinel phase was observed through powder X-ray diffraction (PXRD) studies and the lattice constant increased with increase in calcium concentration and the average crystallite size in the range 32–19 nm. Transmission Electron microscope (TEM) technique provided information on the morphology of the synthesized ferrites. FT-IR spectral bands observed at 579, 480 and 514 cm −1 confirmed the M−O vibration for Ca–O, Fe–O and Cu–O bands responsible for the formation of spinel. Magnetization, coercivity and retentivity were calculated from vibrating sample magnetometer (VSM) studies. Hysteresis loops revealed the magnetic behavior of the prepared Ca 1-x Cu x Fe 2 O 4 NPs. The adsorption and desorption measurement were achieved from Brunauer–Emmett–Teller (BET) analysis. Band gap of the prepared spinel ferrites were found to be 1.8–2.5 eV revealing semiconducting behaviour of the nanocatalysts. Frequency dependent dielectric studies revealed that at high frequency both dielectric constant and dielectric loss were decreased. The photocatalytic degradation (PCD) of the synthesized spinel ferrites with methylene blue (MB) as organic pollutant and their antibacterial activity was also studied. Ca 0.2 Cu 0.8 Fe 2 O 4 (CCFO-5) nanocatalyst exhibited 96% degradation in 180 min with methylene blue dye.

Romanov D.A., Pochetukha V.V., Gromov V.E., Sosnin K.V.

WN–WC–W2C0.84–Ag coatings are fabricated by a combined method, which combines electroexplosive spraying, nitriding, and electron-beam treatment. The structure, phase composition, nanohardness, Young’s modulus, wear resistance under dry sliding friction conditions, friction coefficient, electrical conductivity, and electroerosion resistance of the coatings are investigated.

Rajendran P.R., Duraisamy T., Chidambaram Seshadri R., Mohankumar A., Ranganathan S., Balachandran G., Murugan K., Renjith L.

High-velocity oxy-fuel (HVOF) spray coating plays a major role in many surface treatment methods, which tend to improve erosion and corrosion resistance properties. HVOF is well known for its dense and high-quality coating ability. This is due to the less in-flight exposure time, which tends to have less oxide content because of its high-velocity properties. Among the number of process parameters, porosity and hardness are predominant factors while considering wear rate and corrosion behaviour analysis. The current study aims to optimise HVOF process parameters to obtain low levels of porosity and high hardness values in the WC-10Ni-5Cr coating sprayed on 35 Mo Cr steel. The flow rates of oxygen, LPG, coating powder feed rate and spray distance are selected in this study as these have a superior influence on the final condition of the coating. Statistical tools such as the design of experiments (DoE), analysis of variants and response surface methodology (RSM) were used to achieve the desired results. As per the result analysis, the oxygen flow rate has a higher effect on the porosity value and microhardness value of the coating.

Romanov D.A., Pochetukha V.V., Sosnin K.V., Moskovskii S.V., Gromov V.E., Bataev V.A., Ivanov Y.F., Semin A.P.

The goal of the research is to analyze the structure and properties of the coating SnO 2 –In 2 O 2 –Ag–N formed on copper by a complex method. The method of coating formation combined the electroerosion spraying, irradiation by pulsed electron beam and subsequent nitriding in plasma of a gas discharge of a low pressure. It is shown that the thickness of the coating amounts to ≈100 μm. The wear resistance of a copper sample with the deposited coating is ≈ 2.8 times higher than that of copper without the coating. The friction coefficient of samples with the coating (μ = 0.479) is ≈ 1.4 times less than that of copper without the coating (μ = 0.679). It is established that the coating hardness increases as the substrate is approached and reaches its maximum value of ≈1400 MPa (substrate hardness is 1270 MPa). By means of micro-X-ray- spectral analysis it is detected that the main chemical element of the coating is silver, with copper, tin, indium, oxygen and nitrogen being present in a much smaller quantity. By the methods of X-ray phase analysis it is revealed that the main phases of the coating are copper-and silver base solid solutions. Tests for the electroerosion resistance showed that the coatings meet the requirements of standards for electromagnet starters with the category of application AC-3 of direct action.