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A bulk and dense nanocrystalline (NC) Ni with a mean grain size of 26 nm and a microhardness of 370-382 HV were fabricated by an electro-deposition technique. The microstructure and microhardness of the NC Ni samples were examined. The friction and wear behavior of the NC Ni samples under dry condition both in air and in vacuum were investigated in comparison with a conventional coarse-grained (CG) Ni with a mean grain size of 2.2 μm and a microhardness of 80-90 HV using a pin-on-disk type tribometer. The results show that the NC Ni sample possesses lower friction and higher wear resistance both in air and in vacuum, compared with the CG Ni sample. An important and interesting result is that for the both samples tested, the friction coefficients in vacuum are higher than those in air, while the wear loss occurs reverse case. In the air atmosphere, the NC Ni exhibits a mild wear, and avoids the severe wear that happens on the CG Ni, which is mainly attributed to which is mainly attributed to formation of a mechanical mixed layer on the worn surface of the harder NC Ni. In the vacuum atmosphere, compared with CG Ni, NC Ni shows a significant decrease in the plastic deformation and adhesive wear. [ABSTRACT FROM AUTHOR]

Abstract: The tensile properties of as-fabricated B/Al composites and after thermal–mechanical cycling (TMC) were studied. The results indicate that the Young''s modulus of the B/Al composite decreases significantly with increasing the cycles, and the external stress enhances this tendency. The external stress during the TMC also exerts influence on the tensile strengths of the composite. The mechanism of this effect is analyzed in this study. The microstructural observations indicate that TMC induces firstly the generation and then the recovery effects of dislocations in the aluminum matrix. The interfaces in the B/Al composite change from the strongly bonded toward the appropriately bonded, then to the weakly bonded ones with increasing the cycle number. TMC is a new technique of improving the ultimate tensile strength of B/Al composite. [Copyright &y& Elsevier]

Abstract: Effect of 80KeV proton radiation with fluences of 1014–2×1016 protons/cm2 on the optical properties and microstructure of type-GG17 borosilicate glass as a candidate material for rubidium spectra lamp envelope was investigated. The change in microstructure before and after proton radiation was evaluated by means of UV–vis–NIR spectroscopy, X-ray photoelectron spectroscopy (XPS) and positron annihilation lifetime spectrometer (PALS). The experimental results show that under radiation of 80KeV some broken Si–O bonds were induced and thus the number of non-bridge oxygen (NBO) increased. These irradiation-induced defects caused the degeneration of optical property and loosened glass structure which accelerates rubidium diffusion into lamp envelop. [Copyright &y& Elsevier]

Abstract: Damage effects of proton irradiation on aluminized Kapton films were investigated through ground simulation experiments, in which the energy of protons was 90keV and the flux was 5.0×1011 cm−2 s−1. Changes in surface morphology, optical properties, microhardness and microstructure of Kapton/Al were analyzed. The experimental results show that proton irradiation results in the increase of surface roughness and microhardness, and the degradation of the reflective property in the 500–1200nm range. Raman spectra and XPS analysis demonstrate that changes in chemical structure occurred during irradiation, including the bond breaking of the part of the carbonyl and aromatic ether, ring opening reaction of cyclic imide, and the formation of some new bonds and structure. [Copyright &y& Elsevier]

Abstract: The optical properties and microstructural damage of GG17 glasses, as well as their recovery during annealing at room temperature, are investigated after exposure to 1MeV electrons with various fluences. Experimental results show that the electrons lead to severe optical degradation in the GG17 glass, and induce the formation of paramagnetic defects which can be mainly attributed to the boron–oxygen hole centers. With increasing annealing time at room temperature their decay serves as long-lived defects following first order kinetics. Except for the strong absorption bands located at 334–352nm and 480nm that corresponds to the boron–oxygen hole centers, weaker absorption bands appear at 780nm or 794.6nm after irradiation, inducing a decrease in transmittance by approximately 17% for a fluence of 1×1016 cm−2. It is shown that electron irradiation could cause a harmful effect on rubidium lamps when GG17 glass is used as the lamp envelope material. [Copyright &y& Elsevier]

Abstract: Plasma- and gas-nitrided 2Cr13 samples were characterized using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and microhardness testing techniques. Nitrogen concentration profiles in the cross-sections of the nitrided samples were obtained by glow discharge optical spectroscopy (GDOS). Residual stress profiles along depth of the nitrided samples were measured using an X-ray stress tester. The tribological behaviour of the plasma- and the gas-nitrided samples in vacuum was investigated in order to analyse the effect of nitriding on wear resistance of the 2Cr13 steel. The results show the tribological properties of the 2Cr13 steel in vacuum are improved considerably by plasma nitriding and gas nitriding resulted from microstructure modification and surface hardening during nitriding. The plasma-nitrided samples have better wear resistance than the gas-nitrided samples under 30N, while the gas-nitrided samples have higher wear resistance under 90N. With increasing normal load from 30N to 90N, the wear mechanism shows a transition from mild adhesive and abrasive wear to severe adhesive or even delamination wear. The plasma-nitrided sample has thicker compound layer than the gas-nitrided sample, resulting that it exhibits more intensive delamination under high load of 90N. [Copyright &y& Elsevier]

Abstract: The optical properties and microstructural degradation of a multicomponent glass after exposure to 1MeV electrons for fluences of 1013 to 1016 e−/cm2, as well as the recovery during annealing at room temperature (RT) for the fluence of 1016 e−/cm2, are investigated. The non-bridging oxygen hole centers (NBOHCs), as well as trapped electrons (TEs), are mainly attributed to optical absorption bands and paramagnetic spectra. In comparison of the exponential curves, the in-growth kinetics for each type of defect with increasing fluence are separable, and a new linearly-combined exponential model is used to describe the structural responses during irradiation. Accordingly, RT bleaching curves of defects follow a linearly-combined exponential decay function. Consistent results from optical and paramagnetic signals suggest that this linearly-combined model provides a reasonable kinetic description of the growth and bleaching process of defects. [Copyright &y& Elsevier]

Abstract: A 2Cr13 steel was gas nitrided in pure NH3 gas atmosphere at 793K for 20h. The microstructure, composition and microhardness of the nitrided samples were examined. The tribological behaviour of the nitrided 2Cr13 steel in air and vacuum was investigated in order to analyse effects of the nitriding on wear resistance of the 2Cr13 steel. The results show that the nitrided layer consists of a compound layer and diffusion zone. The nitriding increases both the surface hardness and wear resistance of 2Cr13 steel in air and vacuum, and the anti-wear characteristic of the nitrided 2Cr13 steel in vacuum is much higher than that in air. The nitrided layer exhibits a mild wear in air, and avoids the severe wear that happens on the unnitrided steel. While the adhesion dominates the wear process in vacuum. The material transfer between the wear couples helps to improve the tribological characteristics of the nitrided layer in vacuum. [Copyright &y& Elsevier]