Novel artificial hip joint: A layer of alumina on Ti-6Al-4V alloy formed by micro-arc oxidation.

In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high wear resistance. However, it is liable to fracture under load bearing operations in artificial joints. We propose a promising way to overcome this limitation by forming a dense alumina layer onto a relatively tough substrate such as Ti-6Al-4V alloy to obtain high wear resistance on a material that can sustain relatively high toughness. For this purpose, Al metal powders were deposited onto Ti-6Al-4V alloy by cold spraying in N2 atmosphere. Interfacial adhesion between Al and the Ti alloy was improved by the formation of a reaction layer of Al3Ti between them by heating at 640 °C for 1h in air. Subsequently, micro-arc oxidation treatment was performed to oxidize Al. The oxidized layer was composed of an outer porous layer of γ-alumina and inner-most dense layer of α-alumina. The α-alumina layer was almost fully densified and exhibited high Vickers hardness almost equal to that of alumina ceramics used as the femoral head. Thus, the newly developed dense alumina/Ti alloy can be potentially used to produce the reliable bearing surfaces of artificial hip joint.

Synthesis of carbon fibers with branched nanographene sheets for electrochemical double layer capacitor application.

We demonstrate a one step technique to synthesis the carbon fibers (CNFs) with branched nanographene sheets by the pulsed discharge (PD) plasma chemical vapor deposition (CVD) process. Highly crystalline branched nanographene sheets were directly grown from the surface of the carbon fibers to obtain a three dimensional (3D) nanostructure. The growth process can be explained from the catalyst support growth of the CNFs, and subsequently nucleation and growth of the nanographene sheets from the crystalline surface of the CNF. The deposited nanostructured films with different pulse discharge were used as an electrode for electrochemical double-layer capacitors (EDLC). It is observed that the capacitance is dependent on the morphology of the electrode materials and an optimum capacitance is obtained with the branched nanographene on CNFs.

A photoinduced charge transfer composite of graphene oxide and ferrocene.

We demonstrate the formation of a photoinduced charge transfer composite with graphene oxide (GO) and ferrocene (Fc) molecules. Derived insulating GO was partially reduced to improve the conductivity and modified with the Fc molecules. Transmission electron microscopy (TEM), elemental mapping, X-ray photoelectron and UV-visible spectroscopy studies confirm that the Fc molecules were well grafted to the surface of a GO sheet. Photoresponsivity of the prepared GO-Fc composite was investigated by fabricating a metal/GO-Fc/metal device. The fabricated device shows enhanced current density under light illumination, suggesting a photo-induced charge transfer process in the developed GO-Fc composite.

Poly(3-octylthiophene)/fullerene heterojunction solar cell incorporating carbon nanotubes.

Here, we report incorporation of multiwalled carbon nanotubes (MWNTs) in Poly(3-octylthiophene)/fullerene heterojunction solar cells. Multi-walled carbon nanotubes (MWNTs) were functionalized by oxygen plasma treatment. Photoelectron spectroscopy study of oxygen plasma treated MWNTs shows surface modification with hydroxyl and carboxyl groups. Plasma treated MWNTs were combined with Poly(3-octylthiophene) and solar cell was fabricated with the structure Au/P3OT + MWNTs/C60/FTO. Fabricated device shows short circuit current density (Jsc) open circuit voltage (Voc), fill factor and conversion efficacy as 0.04 mA/cm2, 0.355 V, 21% and 0.003%. Solar cell fabricated with incorporation of MWNTs shows much better device performance, then that of the device without MWNTs. MWNTs in the polymer composite act as exciton dissociation site and provide efficient hole transportation, and thereby improving device performance.