Jiamu Huang

Graphene as a high-capacity anode material for lithium ion batteries

Graphene was produced via a soft chemistry synthetic route for lithium ion battery applications. The sample was characterized by X-ray diffraction, nitrogen adsorption-desorption, field emission scanning electron microscopy and transmission electron microscopy, respectively. The electrochemical performances of graphene as anode material were measured by cyclic voltammetry and galvanostatic charge/discharge cycling. The experimental results showed that the graphene possessed a thin wrinkled paper-like morphology and large specific surface area (342 m2·g−1). The first reversible specific capacity of the graphene was as high as 905 mA·h·g−1 at a current density of 100 mA·g−1. Even at a high current density of 1000 or 2000 mA·g−1, the graphene maintained good cycling stability, indicating that it is a promising anode material for high-performance lithium ion batteries.

ONE-STEP AND CONTROLLABLE SELF-ASSEMBLY OF Au/TiO2/CARBON SPHERES TERNARY NANOCOMPOSITES WITH A NANOPARTICLE MONOSHELL WALL

In this work, stable and well dispersed colloidal Au/TiO2 binary nanoparticles (NPs) were synthesized initially. Meanwhile, they were immobilized simultaneously on colloidal carbon spheres (CSs), one of popular hard templates, to prepare hybrid self-assembly nanostructures. The morphology and crystal structure of these nanocomposites (NCs) were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), thermogravimetric (TGA) and N2 sorption analysis. By controlling the NPs size, ratio of Au/TiO2 NPs, process temperature and time, and concentration of surfactants (e.g., MPA), Au/TiO2@CSs NCs could be tailored into core-shell nanostructures with various surface coverages of Au NPs and/or TiO2NPs. Interestingly, hollow spheres with a binary-nanoparticle monoshell could be achieved by calcinations of typical Au/TiO2@CSs NCs. In principle, these novel hybrid nanostructures with controllable functionality and high-surface-area traits could be very promising photocatalysts for waste water treatment.

Chemical splitting of multiwalled carbon nanotubes to enhance electrochemical capacitance for supercapacitors

Multiwalled carbon nanotubes (MWCNTs) were chemically split and self-assembled to a flexible porous paper made of graphene oxide nanoribbons (GONRs). The morphology and microstructure of the pristine MWCNTs and GONRs were analyzed by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. And the specific surface area and porosity structure were measured by N2 adsorption-desorption. The longitudinally split MWCNTs show an enhancement in specific capacitance from 21 F g-1 to 156 F g-1 compared with the pristine counterpart at 0.1 A g-1 in a 6 M KOH aqueous electrolytes. The electrochemical experiments prove that the chemical splitting of MWCNTs will make inner carbon layers opened and exposed to electrochemical double layers, which can effectively improve the electrochemical capacitance for supercapacitors.

Effect of Al Content on Microstructure and Mechanical Property of Nanocomposite TiAlSiN Thin Films

TiAlSiN thin films exhibit high hardness due to the multicomponent and multiphase structures. Effects of Si on TiAlSiN microstructure and mechanical properties have been well studied. However, there is insufficient information on the effects of Al. Thus, in this work, Al-contained nanocomposite nc-TiN/a-SiNx thin films with Al up to 10 at.% were prepared by magnetron co-sputtering Ti, Al and Si3N4 targets in Ar/N2 gas atmosphere. The effects of Al on TiAlSiN microstructure and mechanical property were well studied. Adjusting Al/(Ti+Al) target power ratio tuned chemical composition, microstructure and consequently mechanical properties. With increase of Al/(Ti+Al) target power ratio from 0 to 0.2, Al content increased from 0 to 10 at.%. X-ray photoelectron spectroscope results showed that aluminum nitride was formed. X-ray diffraction results confirmed that the nanocrystalline phase TiN was with Si and Al in its structure, or (Ti, Al, Si) N. The matrix was amorphous silicon nitride containing aluminum nitride. Nanoindentation hardness of the thin films remained at about 28 GPa till Al addition was increased to 3.1 at.%.

Development of Microarc Oxidation/Sputter CeO2 Duplex Ceramic Anti-Corrosion Coating for AZ31B Mg Alloy

A duplex CeO₂/MAO coating was deposited on AZ31B magnesium alloy through microarc oxidation and reactive radio frequency magnetron sputtering. The microstructure and chemical composition of the proposed coating were investigated through scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The CeO₂/MAO coating was approximately 580 nm in thickness and showed fewer micropores and defects than those the MAO coating presented. The properties of corrosion resistance were assessed using the polarization test, electrochemical impedance spectroscopy, and the neutral salt spray test. The CeO₂/MAO duplex coating had the lowest corrosion current density of 3.25×10-9 A/cm² and the highest polar resistance, approximately four orders of magnitude higher than that of the uncoated sample. Electrochemical measurements suggested that CeO₂ coating can serve as a strong physical barrier between the corrosion medium and the Mg alloy.