Xuming Zhang

Osteogenic activity and antibacterial effects on titanium surfaces modified with Zn-incorporated nanotube arrays

Titanium implants having enhanced osteogenic activity and antibacterial property are highly desirable for the prevention of implant associated infection and promotion of osseointegration. In this study, coatings containing titania nanotubes (NTs) incorporated with zinc (NT-Zn) are produced on Ti implants by anodization and hydrothermal treatment in Zn containing solutions. The amount of incorporated Zn can be adjusted by varying the structural parameters such as the nanotube diameter and length as well as hydrothermal treatment time. The suitable NT-Zn coatings with good intrinsic antibacterial properties can prevent post-operation infection. Excellent osteogenesis inducing ability in the absence of extraneous osteogenic supplements is demonstrated and the ERK1/2 signaling is found to be involved. The NT-Zn structure which is simple, stable, and easy to produce and scale up has immense potential in bone implant applications.

One-step growth and field emission properties of quasialigned TiO2 nanowire/carbon nanocone core-shell nanostructure arrays on Ti substrates

Quasialigned nanoarrays consisting of TiO2 nanowire cores and carbon nanocone shells have been produced directly on titanium foils via a simple one-step thermal reaction under acetone vapor at 850°C. The nanowire cores are single-crystalline rutile TiO2 with diameters of 15–20nm and the conical carbon shells are amorphous with gradually decreasing thicknesses from 200–300nm at the bases to 5–10nm at the tips. Disparity of precipitation and etching of carbon shell give rise to the conical shape. Such TiO2∕C nanocone arrays on a conducting substrate are a new member of the conical nanostructures and promising field electron emitters.

Coaxial PANI/TiN/PANI nanotube arrays for high-performance supercapacitor electrodes

Coaxial PANI/TiN/PANI nanotube arrays prepared by electrochemical polymerization of PANI on nanoporous TiN nanotube arrays exhibit a high specific capacitance of 242 mF cm(-2), excellent rate capability with the capacitance remaining at 69% when the current density is increased 50 times from 0.2 to 10 mA cm(-2), and a long cycling life with less than 0.005% decay per cycle.

Engineering and functionalization of biomaterials via surface modification

It is imperative to control the interactions between biomaterials and living tissues to optimize their therapeutic effects and disease diagnostics. Because most biomaterials do not have the perfect surface properties and desirable functions, surface modification plays an important role in tailoring the surface of biomaterials to allow better adaptation to the physiological surroundings and deliver the required clinical performance. This paper reviews recent progress pertaining to the surface treatment of implantable macro-scale biomaterials for orthopedic and dental applications as well as micro- and nano-biomaterials for disease diagnosis and drug/gene delivery. Recent advances in surface modification techniques encompassing adsorption, deposition, ion implantation, covalent binding, and conversion have spurred more expeditious development of new-generation biomaterials.

High-energy lithium-ion hybrid supercapacitors composed of hierarchical urchin-like WO3/C anodes and MOF-derived polyhedral hollow carbon cathodes

A lithium-ion hybrid supercapacitor (Li-HSC) comprising a Li-ion battery type anode and an electrochemical double layer capacitance (EDLC) type cathode has attracted much interest because it accomplishes a large energy density without compromising the power density. In this work, hierarchical carbon coated WO3 (WO3/C) with a unique mesoporous structure and metal-organic framework derived nitrogen-doped carbon hollow polyhedra (MOF-NC) are prepared and adopted as the anode and the cathode for Li-HSCs. The hierarchical mesoporous WO3/C microspheres assembled by radially oriented WO3/C nanorods along the (001) plane enable effective Li+ insertion, thus exhibit high capacity, excellent rate performance and a long cycling life due to their high Li+ conductivity, electronic conductivity and structural robustness. The WO3/C structure shows a reversible specific capacity of 508 mA h g-1 at a 0.1 C rate (1 C = 696 mA h g-1) after 160 discharging-charging cycles with excellent rate capability. The MOF-NC achieved the specific capacity of 269.9 F g-1 at a current density of 0.2 A g-1. At a high current density of 6 A g-1, 92.4% of the initial capacity could be retained after 2000 discharging-charging cycles, suggesting excellent cycle stability. The Li-HSC comprising a WO3/C anode and a MOF-NC cathode boasts a large energy density of 159.97 W h kg-1 at a power density of 173.6 W kg-1 and 88.3% of the capacity is retained at a current density of 5 A g-1 after 3000 charging-discharging cycles, which are better than those previously reported for Li-HSCs. The high energy and power densities of the Li-HSCs of WO3/C//MOF-NC render large potential in energy storage.

Mitigation of Corrosion on Magnesium Alloy by Predesigned Surface Corrosion.

Rapid corrosion of magnesium alloys is undesirable in structural and biomedical applications and a general way to control corrosion is to form a surface barrier layer isolating the bulk materials from the external environment. Herein, based on the insights gained from the anticorrosion behavior of corrosion products, a special way to mitigate aqueous corrosion is described. The concept is based on pre-corrosion by a hydrothermal treatment of Al-enriched Mg alloys in water. A uniform surface composed of an inner compact layer and top Mg-Al layered double hydroxide (LDH) microsheet is produced on a large area using a one-step process and excellent corrosion resistance is achieved in saline solutions. Moreover, inspired by the super-hydrophobic phenomenon in nature such as the lotus leaves effect, the orientation of the top microsheet layer is tailored by adjusting the hydrothermal temperature, time, and pH to produce a water-repellent surface after modification with fluorinated silane. As a result of the trapped air pockets in the microstructure, the super-hydrophobic surface with the Cassie state shows better corrosion resistance in the immersion tests. The results reveal an economical and environmentally friendly means to control and use the pre-corrosion products on magnesium alloys.

Controlled fabrication of core-shell TiO2/C and TiC/C nanofibers on Ti foils and their field-emission properties.

Core-shell TiO(2)/C and TiC/C nanofibers are fabricated in situ on Ti and Al ion-implanted Ti substrates by a thermochemical reaction in acetone and the growth mechanism is described. Implantation of Al into Ti leads to in situ growth of TiC/C in lieu of TiO(2)/C nanofibers. This is because Al has a higher affinity to oxygen than Ti and Ti reacts preferentially with C to form TiC. The Ti foil serves as both the Ti source and substrate for the core-shell TiO(2)/C and TiC/C NFs to ensure strong bonding and small contact resistance between the Ti substrate and the core-shell field emitters. The core-shell TiC/C and TiO(2)/C nanofibers have similar morphology and structure, but the TiC/C nanofibers possess better field emission properties with a turn on field (E(to)) of 2.2 V/μm compared to an E(to) of 3.2 V/μm measured from the TiO(2)/C nanofibers. The enhanced field-emission property of the TiC/C nanofibers is attributed to the high electrical and thermal conductivity of the TiC inner core, which provides a more effective electron transfer pathway between the cathode and C shell emitters.

Hydrothermal synthesis of perovskite-type MTiO3 (M = Zn, Co, Ni)/TiO2 nanotube arrays from an amorphous TiO2 template

Ordered perovskite-type MTiO3/TiO2 nanotube arrays (NTAs) (M = Zn, Co, Ni) are prepared by a general hydrothermal route based on amorphous TiO2 NTAs via electrochemical anodization of Ti foil. The as-anodized amorphous TiO2 is not stable and can react with H2O in solution producing soluble Ti(OH)62− to form anatase nanoparticles (NPs) via water-induced dissolution and recrystallization. The pH and salt content in the solution play important roles in the morphology and composition of the hydrothermal products. In the presence of a metal acetate, the reaction between Ti(OH)62− and H+ is dramatically restricted and the reaction proceeds preferentially between Ti(OH)62− and M2+ (M = Zn, Co, Ni) to produce insoluble MTiO3 NPs which adhere onto the original architecture in situ to form perovskite-type MTiO3/TiO2 NTAs. This study elucidates the role of the amorphous structure in the formation of MTiO3 and provides a general means of synthesizing nanostructured MTiO3.

Large and porous carbon sheets derived from water hyacinth for high-performance supercapacitors

To elevate the properties of carbon based electrical double-layer capacitors (EDLCs), sheet-like carbon with high porosity is desirable due to enhanced electron transport efficiency and good electrolyte accessibility. In this paper, large porous carbon sheets are fabricated via an acid treatment, pyrolytic carbonization, and alkali activation of water hyacinth (WH) biomass. The WH-derived carbon sheets with a large uniform area have a large specific surface of 1308 m2 g−1 and desirable pore volume of 0.84 cm3 g−1, resulting from the template of the original thin cell walls and large intercellular space, which deliver a high specific capacitance of 273 F g−1 at a current density of 1 A g−1, excellent capacity retention of 75% when the current density is increased from 1 to 50 A g−1, and superior cyclic stability over 10 000 cycles in 6 M KOH. The specific capacitance of the assembled symmetric capacitor based on the large and porous carbon sheets reaches a remarkable 81.5 F g−1 and an energy density of 7.24 W h kg−1 can be achieved at a current density of 1 A g−1. These outstanding electrochemical properties suggest that the WH-derived porous carbon sheets have commercial potential in high-performance supercapacitors and the simple and economical process utilizing the WH waste biomass is environmentally friendly.

Robust Electrodes Based on Coaxial TiC/C–MnO2 Core/Shell Nanofiber Arrays with Excellent Cycling Stability for High-Performance Supercapacitors

A coaxial electrode structure composed of manganese oxide-decorated TiC/C core/shell nanofiber arrays is produced hydrothermally in a KMnO4 solution. The pristine TiC/C core/shell structure prepared on the Ti alloy substrate provides the self-sacrificing carbon shell and highly conductive TiC core, thus greatly simplifying the fabrication process without requiring an additional reduction source and conductive additive. The as-prepared electrode exhibits a high specific capacitance of 645 F g(-1) at a discharging current density of 1 A g(-1) attributable to the highly conductive TiC/C and amorphous MnO2 shell with fast ion diffusion. In the charging/discharging cycling test, the as-prepared electrode shows high stability and 99% capacity retention after 5000 cycles. Although the thermal treatment conducted on the as-prepared electrode decreases the initial capacitance, the electrode undergoes capacitance recovery through structural transformation from the crystalline cluster to layered birnessite type MnO2 nanosheets as a result of dissolution and further electrodeposition in the cycling. 96.5% of the initial capacitance is retained after 1000 cycles at high charging/discharging current density of 25 A g(-1). This study demonstrates a novel scaffold to construct MnO2 based SCs with high specific capacitance as well as excellent mechanical and cycling stability boding well for future design of high-performance MnO2-based SCs.