The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

This work investigated the influence of graphite on the wear behavior of Al 7075/Al 2 O 3 /5 wt.% graphite hybrid composite. The investigation reveals the effectiveness of incorporation of graphite in the composite for gaining wear reduction. The Al 7075 (aluminium alloy 7075) reinforced with Al 2 O 3 –graphite were investigated. The composites were fabricated using liquid metallurgy route. Ceramic particles along with solid lubricating materials were incorporated into aluminium alloy matrix to accomplish reduction in both wear resistance and coefficient of friction. The Al 7075/Al 2 O 3 /graphite hybrid composite was prepared with 5 wt.% graphite particles addition and 2, 4, 6 and 8 wt.% of Al 2 O 3 . The hardness, tensile strength, flexural strength and compression strength of the Al 7075–Al 2 O 3 –graphite hybrid composites are found to be increased by increased weight percentage of ceramic phase. The wear properties of the hybrid composites containing graphite exhibited the superior wear-resistance properties.

Study on mechanical and wear properties of Al 7075/Al2O3/graphite hybrid composites

In the present investigation, the influence of B 4 C on the mechanical and Tribological behavior of Al 7075 composites is identified. Al 7075 particle reinforced composites were produced through casting, K 2 TiF 6 added as the flux, to overcome the wetting problem between B 4 C and liquid aluminium metal. The aluminium B 4 C composites thus produced were subsequently subjected to T6 heat treatment. The samples of Al 7075 composites were tested for hardness, tensile, compression, flexural strengths and wear behavior. The test results showed increasing hardness of composites compared with the base alloy because of the presence of the increased ceramic phase. The wear resistance of the composites increased with increasing content of B 4 C particles, and the wear rate was significantly less for the composite material compared to the matrix alloy. A mechanically mixed layer containing oxygen and iron was observed on the surface, and this acted as an effective insulation layer preventing metal to metal contact. The coefficient of friction decreased with increased B 4 C content and reached its minimum at 10 vol% B 4 C.

Influence of B4C on the tribological and mechanical properties of Al 7075–B4C composites

Electrodeposition of Ni-Fe alloys, composites, and nano coatings–A review

Stress corrosion cracking behaviour of 7xxx aluminum alloys: A literature review

Aluminum alloy 7075 has been widely studied, due to its excellent mechanical properties developed by age hardening and their extensive uses in the aircraft structure. Tensile test specimens were tested in various preaging conditions (100, 120, 140 °C) and various retrogression temperatures T 7 (160, 180, 200 °C) in order to evaluate the effect of heating cycles on the mechanical as well as corrosion properties. The optimum condition was preaging at T 6 120 °C and retrogressing at T 7 200 °C, which gave the highest hardness and tensile properties. The corrosion behavior of three-point-loaded specimens after 7 days of immersion in 3.5% NaCl solution, using modified electrochemical cell, was studied. The most resisting condition for SCC was preaging at T 6  = 100 °C and retrogression at T 7  = 160 °C for 250 min. Specimens retrogressed at 200 °C for 8 min showed low resistance to stress corrosion cracking.

Improvements in mechanical and stress corrosion cracking properties in Al-alloy 7075 via retrogression and reaging

Nanocrystalline Ni-Fe deposits with different composition and grain sizes were fabricated by electrodeposition. Deposits with iron contents in the range from 7 to 31% were obtained by changing the Ni2+/Fe2+ mass ratio in the electrolyte. The deposits were found to be nanocrystalline with average grain size in the range 20-30 nm. The surface morphology was found to be dependent on Ni2+/Fe2+ mass ratio as well as electroplating time. The grains size decreased with increasing the iron content, especially in case of short time electroplating. Increasing the electroplating time had no significant effect on grain size. The microhardness of the materials followed the regular Hall-Petch relationship with amaximum value (762 Hv) when applying Ni2+/Fe2+ mass ratio equal to 9.8.

/pdf/electrodeposition-and-characterization-of-nanocrystalline-ni-2hxral5sgs.pdf

Electrodeposition and characterization of nanocrystalline Ni-Fe alloys

Instrument of chloride ions on the pitting corrosion of electroplated steel alloy 4130

The performance of weathering decay of uncoated and Ni, Cu and Cd coated steel alloy 4130 in 3.5 wt. % NaCl solution was anticipated. The Ni-coated sample showed greater corrosion inhibition effect than both Cu-coated and Cd-coated depending on the obtained results of open circuit potential, polarization curves, cyclic voltammetry, and impedance spectroscopy. The surface of uncovered and covered electrodes are described by subjecting to scanning electron microscopy prior and afterward engagement in a salt solution. The best corrosion resistance and surface morphology achieved in Ni-coated steel alloy. The inhibition efficiencies of tested samples were 90.7, 89.1 and 56.9 for the Ni-coated, Cu-coated, and Cd-coated respectively.

https://ejchem.journals.ekb.eg/article_39769_56e19f1e02f4d2503a27063f276107b9.pdf

Effect of Plating Materials on the Corrosion Properties of Steel Alloy 4130

Two series of Al sheets are coated with different thicknesses of copper-deposited film from 10 to 40 µm by the electroplating technique. The first group is the fresh cast Al sheets, and the other is the recycled water-atomized Al powder prepared by the technique of powder metallurgy. Microstructure and phase structure were examined by XRD, optical microscopy and FESEM. Electrical conductivity, thermal conductivity and coefficient of thermal expansion (CTE) were investigated. The XRD showed that only Al and Cu peaks appeared for the cast Al sheet samples, but for the recycled ones other peaks corresponding to Al2O3 were also detected. The microstructure indicated that the coated Cu layer had a dendritic structure in a continuous pattern, but for the recycled samples the dendritic structure was not clear but continuous. Both the thermal and electrical conductivities were gradually increased along with the increase in the Cu thickness, while the CTE was decreased.

Electrochemical Surface Modification of Aluminum Sheets Prepared by Powder Metallurgy and Casting Techniques for Printed Circuit Applications

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