Pulsed electrodeposition of hydroxyapatite on titanium substrate in solution containing hydrogen peroxide

Hydroxyapatite(HAP) coatings were prepared on the titanium substrate in the electrolyte containing H2O2 by the pulse electrodeposition. The introduction of H2O2 restrains the evolution of H2 and improves the adhesive strength between coatings and substrate. The results of pulse electrodeposition show that the relaxation time of the pulse is beneficial to growth of HAP because it makes ions diffuse from bulk to the surface of electrode and reduces concentration polarization in the next pulse time. It is beneficial to the increase of the duty circle of the pulse for deposition of HAP, but the result is not good if it is increased excessively. With increasing potential, it is good for the growth of HAP coatings. If the potential is too high, it is easy for HAP coatings to drop off during the process of electrodeposition under too intensive polarization, such as -1.0 V (vs SCE), and there is not many coatings on the substrate. The combination of pulse electrodeposition and addition of hydrogen peroxide can assuredly improve the physico-chemical properties of hydroxyapatite coatings.

In situ construction of protonated g-C3N4/Ti3C2 MXene Schottky heterojunctions for efficient photocatalytic hydrogen production

Converting sustainable solar energy into hydrogen energy over semiconductor-based photocatalytic materials provides an alternative to fossil fuel consumption.However,efficient photocatalytic splitting of water to realize carbon-free hydrogen production remains a challenge.Heterojunction photocatalysts with well-defined dimensionality and perfectly matched interfaces are promising for achieving highly efficient solar-to-hydrogen conversion.Herein,we report the fabrication of a novel type of protonated graphitic carbon nitride(PCN)/Ti3C2 MXene heterojunctions with strong interfacial interactions.As expected,the two-dimensional(2D)PCN/2D Ti3C2 MXene interface heterojunction achieves a highly improved hydrogen evolution rate(2181μmol∙g‒1)in comparison with bulk g-C3N4(393μmol∙g‒1)and protonated g-C3N4(816μmol∙g‒1).The charge-regulated surfaces of PCN and the accelerated charge transport at the face-to-face 2D/2D Schottky heterojunction interface are the major contributors to the excellent hydrogen evolution performance of the composite photocatalyst.

Hot compressive deformation behavior of an in-situ TiB whisker reinforced Ti matrix composite

An in-situ TiB whisker reinforced Ti matrix (TiBw/Ti) composite is fabricated by powder metallurgy technique followed by hot extrusion. Hot compressive deformation behavior of the composite, in which the TiB whiskers were oriented along the extruded direction, is investigated. The results indicate that the hot compressive resistance of the TiBw/Ti composite is higher than that of the unreinforced Ti, and hot compressive resistance of the composite in the direction parallel to the whisker orientation is higher than that in the direction perpendicular to the whisker orientation. The hot compressive resistance of the composite increases with increasing strain rate and decreasing temperature. With increasing test temperature, the rate of the decrement of the compressive flow stress of the composite is higher than that of the unreinforced Ti. With increasing amount of compressive deformation, more and more TiB whiskers rotate and break during deformation. The rotation of the whiskers is easier at higher temperature, while, at lower temperature it becomes more difficult and whisker breakage becomes much more serious.

Effects of TiCN Composite Die with Low Thermal Conductivity on Hot Forging Performances

Titanium carbonitride based composite （TiCN-metallic binder） was developed as die material for replacement of cemented tungsten carbide. The effects of thermal conductivity characteristic of the TiCN composite on hot forging performances were investigated using a servo press with ram motion control. Three types of the die materials; （a） tool steel for hot working, （b） cemented tungsten carbide with high thermal conductivity and （c） TiCN composite with low thermal conductivity were compared. In hot upsetting of a chrome steel workpiece, the TiCN composite die was confirmed to reduce the forging load by approximately 20% at slow forging speed. This is because the die with low thermal conductivity could prevent the workpiece from rapid cooling induced by heat transfer at the die-workpiece interface. In addition, the material flow of the workpiece to a die cavity was improved. Furthermore, the wear depth/wear coefficient of the TiCN composite was lower than that of the tool steel and the cemented tungsten carbide in the numerical analysis of wear due to the combination of low thermal conductivity and high hardness.

Role of adsorbed proteins on hydroxyapatite-coated titanium in osteoblast adhesion and osteogenic differentiation

The method of plasma-spray coating of hy- droxyapatite （HA） onto pure titanium has been demon- strated to be effective to enhance the osteogenic differentiation and accelerate bone regeneration. Yet it is still a big challenge to figure out the interplay among im- plant surface properties, adsorbed proteins and cell-surface interactions. In this study, the plasma-sprayed HA-coated titanium （HA-Ti） surface was compared with the titanium substrate in terms of protein adsorption, cell adhesion and differentiation. The phase composition, wettability and to- pography were characterized. Compared to the Ti substrate, the HA-Ti had a smaller water contact angle, but larger micro-scale roughness, and showed a poorer ability to ad- sorb fibronectin （Fn）, bovine serum albumin （BSA） and serum proteins. However, it could adsorb larger amount of recombinant human bone morphogenetic protein 2 （BMP- 2）. The osteoblasts and bone marrow mesenchymal stem cells （BMSCs） tended to adhere on the Ti substrate. By contrast, the BMSCs cultured on the HA-Ti showed a stronger tendency toward osteogenesis differentiation.