Lingping Zhou

Effects of Al coating on corrosion resistance of sintered NdFeB magnet

Abstract Pure Al coating was deposited on sintered NdFeB magnet by direct current (DC) magnetron sputtering to improve the corrosion resistance of magnet. The influences of coating thickness and sputtering power on microstructure and corrosion resistance of Al coating were investigated. The surface morphology of Al coating was characterized by scanning electron microscopy (SEM). The corrosion properties were investigated by potentiodynamic polarization curves and neutral salt spray (NSS) test. The formation of the uniform and compact Al coating is a necessary condition to achieve excellent corrosion resistance. And the optimal corrosion resistance can be obtained in the sample with 6.69 μm thick Al coating deposited at 51-82 W.

Wear behavior of Ag implantation GH4169 alloy by ion beam assisted bombardment

The wear behavior of Ag implantation GH4169 alloy by ion beam assisted bombardment was measured under lower applied load and sliding speed. The wear rate of GH4169 alloy decreased from 2.58 × 10−4 mm3·m−1 to 6.25 ×10−5 mm3·m−1 after Ag implantation. The friction coefficient had not mostly been changed. After Ag implantation, Ag and Ag2O were detected on the worn surface of GH4169 alloy, which benefits the formation of continuous lubrication and protected layers. The predominant wear mechanism changed from abrasion and adhesion wear to oxidation and adhesion wear. In addition, the hardness increased. So, the wear resistance of GH4169 alloy under lower applied load and sliding speed can be improved with Ag implantation by ion beam assisted bombardment.

WEAR BEHAVIOR OF NANOSTRUCTURED HYPOEUTECTIC Fe–B ALLOY

The wear behavior of nanostructured hypoeutectic Fe94.3B5.7 alloy was investigated in comparison with coarse grained counterpart. The friction coefficient of the Fe94.3B5.7 alloy changed slightly with grain size. While the wear rate decreased as the grain size decreased to nano scale. Both Fe2O3 and Fe2SiO4 oxides were found on the worn surfaces in the nanostructured Fe94.3B5.7 alloy, but only a few oxide films were observed for the coarse grained counterpart. These results suggested that the nanostructured eutectic was conducive to forming oxide films on the worn surface of the Fe94.3B5.7 alloy, and improved the wear resistance.

Study on Silver-plated Molybdenum Interconnected Materials for LEO Solar Cell Array

Atomic oxygen (AO) is one of the most important environmental factors that affected the performance of low earth orbit spacecraft in orbit. In which, silver was the most common materials as the interconnected materials. However, with the poor AO resistance of silver, the interconnectors could be failure easier, and the lifetime of the spacecraft was also reduced. In this paper, the silver-plated molybdenum interconnected materials made by Ag thin films deposited on the Mo foils by vacuum deposition methods was studied. And the effects of the preparation process on the micro-structure of the Ag thin films, the interfacial adhesive strength and the electrical conductivity of the composites were investigated. It was found that the Ag thin films deposited on the Mo substrates coated the Ag thin films by ion beam assisted deposition(IBAD) methods exhibited a perfectly (200) preferred orientation. The interfacial adhesive strength had been increased to 18.58MPa. And the composites also have excellent electrical performance.

Enhancement of the Adhesive Strength between Ag Films and Mo Substrate by Ag Implanted via Ion Beam-Assisted Deposition

Silver-coated molybdenum is an optimum material selection to replace pure silver as solar cell interconnector. However, the low adhesive strength between Ag films and Mo substrate hinders the application of the interconnector, because it is difficult to form metallurgical bonding or compound in the film/substrate interface using conventional deposition. In order to improve the adhesion, some Ag particles were implanted into the surface of Mo substrate by ion beam-assisted deposition (IBAD) before the Ag films were deposited by magnetron sputtering deposition (MD). The objective of this work was to investigate the effect of different assisted ion beam energy on the film/substrate adhesive properties. In addition, the fundamental adhesion mechanism was illustrated. The results revealed that the adhesion between Ag films and Mo substrate could be greatly enhanced by IBAD. With the increase of the assisting ion beam energy, the adhesive strength first increased and then decreased, with the optimum adhesion being able to rise to 25.29 MPa when the energy of the assisting ion beam was 30 keV. It could be inferred that the combination of “intermixing layer” and “implanted layer” formed by the high-energy ion bombardment was the key to enhancing the adhesion between Ag films and Mo substrate effectively.

Excellent Tribological Properties of Lower Reduced Graphene Oxide Content Copper Composite by Using a One-Step Reduction Molecular-Level Mixing Process

Reduced graphene oxide (RGO) composite copper matrix powders were fabricated successfully by using a modified molecular-level mixing (MLM) method. Divalent copper ions (Cu2+) were adsorbed in oxygen functional groups of graphene oxide (GO) as a precursor, then were reduced simultaneously by one step chemical reduction. RGO showed a distribution converting from a random to a three-dimensional network in the copper matrix when its content increased to above 1.0 wt.% The tribological tests indicated that the friction coefficient of the composite with 1.0 wt.% RGO decreased markedly from 0.6 to 0.07 at an applied load of 10 N, and the wear rate was about one-third of pure copper. The excellent tribological properties were attributed to a three-dimensional and uniform distribution, which contributes to improving toughness and adhesion strength.

A hierarchical carbon modified nano-NiS2 cathode with high thermal stability for a high energy thermal battery

Nanocrystallization is widely used to improve the discharge performances of LIBs. While its lower thermal stability limits the operating time, especially for the thermal battery system, which discharges at high temperatures (usually 500–550 °C). In this paper, NiS2 particles were coated with amorphous carbon. Then they accumulated into submicron particles and were connected/fixed by a carbon network. The initial decomposition temperature of nano-NiS2 increased from 400 °C to 590 °C after this hierarchical carbon modification. The hierarchical carbon modified nano-NiS2 cathode revealed excellent discharge performances in thermal batteries at high temperatures. Specifically with 0.1 A cm−2 at 500 °C, the specific capacity and energy reach 610 mA h g−1 and 1082 W h kg−1, respectively, at a cut-off voltage of 1.4 V. The specific energy retains about 503 W h kg−1 even at 700 °C. The multiple protective effects of hierarchical carbon modification not only effectively improve the conductivity and thermal stability, but also inhibit the dissolution and shuttling of products. So, hierarchical carbon modification makes nano-NiS2 more suitable for high specific energy and long operating life thermal batteries.

Corrosion−wear behavior of nanocrystalline Fe88Si12 alloy in acid and alkaline solutions

The corrosion−wear behavior of a nanocrystalline Fe88Si12 alloy disc coupled with a Si3N4 ball was investigated in acid (pH 3) and alkaline (pH 9) aqueous solutions. The dry wear was also measured for reference. The average friction coefficient of Fe88Si12 alloy in the pH 9 solution was approximately 0.2, which was lower than those observed for Fe88Si12 alloy in the pH 3 solution and in the case of dry wear. The fluctuation of the friction coefficient of samples subjected to the pH 9 solution also showed similar characteristics. The wear rate in the pH 9 solution slightly increased with increasing applied load. The wear rate was approximately one order of magnitude less than that in the pH 3 solution and was far lower than that in the case of dry wear, especially at high applied load. The wear traces of Fe88Si12 alloy under different wear conditions were examined and analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the tribo-chemical reactions that involve oxidation of the worn surface and hydrolysis of the Si3N4 ball in the acid solution were restricted in the pH 9 aqueous solution. Thus, water lubrication can effectively improve the wear resistance of nanocrystalline Fe88Si12 alloy in the pH 9 aqueous solution.