Search

Titanium alloys are often used in engineering fields including aerospace, cryogenic technologies, and weaponry due to their remarkable qualities. However, several issues including a high coefficient of friction, weak wear resistance, and low hardness hinder their widespread usage. Despite several efforts to enhance their tribology, achieving ultra-low friction on titanium alloy surfaces remains a challenging problem in materials science. Here, we report on the superlubricity of a MoS2 + a-C:H (Mo-a films) composite film, prepared by magnetron sputtering and spraying to lubricate titanium alloy surfaces. Robust superlubricity was achieved by the Mo-a composite films with a coefficient of friction (COF) below 0.007 in a helium environment. Compared to the reference titanium alloy substrates, the introduction of Mo-a composite film reduced the friction coefficient to roughly 1%, and the a-C:H film reduced wear by three orders of magnitude. High-resolution characterizations indicate that this enhanced tribology can be attributed to the formation of transfer film, which is enriched with nanostructured graphene sheets and MoS2 nanoscrolls, and is formed due to shear stress-induced structural transformation of a-C:H films and MoS2 nanosheets. This transfer film transitioned the initial high-resistance steel-to-a-C:H contact to super low-resistance steel-to-transfer film contact, thus achieving superlubricity and a remarkable wear reduction. This work outlines a pathway to solving the poor wear resistance and high friction coefficient problem of titanium alloy surfaces, which can be an important guideline for applications of titanium alloys in mechanical engineering. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous carbon films (a-C : H) were prepared by d.c.-pulse plasma chemical vapor deposition using CH4 and H2 gases. The microstructure and hardness of the resulting films were investigated at different deposition pressures (6, 8, 11, 15, and 20 Pa). The growth rate increased sharply from 3.2 to 10.3 nm/min with increasing the pressure from 6 to 20 Pa. According to Raman spectra, XPS, and Fourier transform infrared analysis, the films deposited at the pressure of 6 and 8 Pa have high sp3 content and show typical diamond-like character. However, the microstructures and bond configuration of the films deposited at 11, 15, and 20 Pa have high sp2 content and favored fullerene-like nanostructure. The hardness and sp2 content were shown to reach their minimum values simultaneously at a deposition pressure of 8 Pa and then increased continuously. The film with fullerene-like nanostructure obtained at 20 Pa displays a high Raman ID/ IG ratio (~1.6), and low XPS C 1 s binding energy (284.4 eV). The microstructural analysis indicates that the films are composed of a hard and locally dense fullerene-like network, i.e. a predominantly sp2-bonded material. The rigidity of the films is basically provided by a matrix of dispersed cross-linked sp2 sites. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A highly sunlight active Ni-loaded TiO2 nanocomposite (Ni/TiO2) is successfully prepared by a simple chemical reduction method using tetrabutyl titanate as a precursor, Ni(NO3)2·6H2O as a nickel source, and N2H4·H2O as a reductant, respectively. The crystal structure, morphology and UV–vis diffuse reflectance characteristics are investigated by XRD, TEM, and UV–vis diffuse reflectance spectroscopy, while the photocatalytic performance of Ni/TiO2 is evaluated by photocatalytic degradation of methyl orange solution under UV and sunlight irradiation. Results show that the crystal structure of TiO2 is not changed upon the loading of Ni, the photocatalytic performance of TiO2 under both UV-light and sunlight, however, is enhanced greatly. The enhancement of the photocatalytic performance of Ni/TiO2 is attributed to the increase of the photogenerated electron–hole separation efficiency and the advanced absorption of light due to surface plasmon effect of Ni nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: A new ternary composite MnO2 nanosheet array/reduced graphene oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (MnO2/rGO/PEDOT:PSS) is prepared by a two-step process. Its potential application in supercapacitor electrode materials was evaluated. Electrochemical tests reveal that the MnO2/rGO/PEDOT-PSS material exhibits a high specific capacitance of 169.1Fg−1 at a current density of 0.2Ag−1, good rate capability with a capacitance of 28.3Fg−1 even at a high current density of 10Ag−1, as well as excellent cycle stability with capacitance retention of 66.2% at 2Ag−1 after 2000 cycles. Therefore, this ternary composite material may have great potential in supercapacitor electrode applications. [Copyright &y& Elsevier]