Mai Liqiang

Preparation and optical properties of V2O5 nanotube arrays

V2 O5 nanotube arrays in porous anodic alumina (PAA) template were obtained from V2 O5 sols prepared by melt quenching method. X-ray powder diffraction and selected area electron diffraction investigations demonstrate that V2 O5 nanotubes are orthorhombic. Results by scanning electron microscopy and transmission electron microscopy results show that V2 O5 nanotubes with a uniform diameter form highly ordered arrays. The diameter and length of the nanotubes depend on the pore diameter and the thickness of the PAA template used. It is proved that the sol-gel template process is a cost-saving, simple and readily-controlled method to prepare metal oxides nanomaterials. Owing to the quantum size effect, the optical absorption edge of V2 O5 nanotubes in PAA exhibits a significant blue shift with respect to that of bulk V2 O5.

Novel preparation and XPS analysis of V2O5 xerogel

The V2O5 sol was fabricated by ultra-fast quenching. The vanadium with low valence (V4+) was found in V2O5 xerogel films by XPS analysis. The technology of oxygen top-blown was applied to analyze the XPS spectrum difference of V2O5 xerogel when the powder of V2O5 was melting in air or in oxygen atmosphere. The results show that the different melting atmosphere has certain influences on the chemical valence of V2O5 xerogel.

Nonlinear dynamic characteristics of combustion wave in SHS process

The characteristic of combustion wave and its change were analyzed by numerical value calculation and computer simulation, based on the combustion dynamical model of SHS process. It is shown that with the change of condition parameters in SHS process various time-space order combustion waves appear. It is concluded from non-linear dynamical mechanism analysis that the strong coupling of two non-linear dynamical processes is the dynamical mechanism causing the time-space order dissipation structures.

Nanowire device for electrochemical energy storage

Reducing capacity fading, increasing energy density and improving rate capability are the worldwide challenges in the development of electrochemical energy storage devices. Developing novel high-performance nanomaterials and devices is one of the effective solutions to overcome the challenges and explore the next-generation power batteries with high power density, high energy density and excellent cycling performance. Compared with bulk materials, nanowire electrode materials have more advantages in the assembly and in situ characterization of electrochemical devices for energy storage since unique anisotropy, fast axial electron transport and radial ion diffusion. Based on the new advance in this field and Mai groups work, we review that the single nanowire solid-state electrochemical device is designed and assembled, revealing the intrisinic principles of capacity fading with the decreasing of conductivity and deterioration of the structure through in situ characterization. Following the above discovery, chemical pre-intercalation and topotactical substitution as well as orderly oriented assembly are provided to improve the conductivity of the electrode materials, cycling stability and rate performance of the electrochemical devices by optimizing the intrinsic transport properties of the electrodes. In addition, hierarchical structure and one-dimensional buffer-effect hybrid structure are designed and constructed, which increase the specific surface area, active sites and minimized the structure degradation of nanowire during cycles, resulting in the enhancement of energy density, power density and lifespan. The above results lay a foundation for the development and applications of large-scale energy storage device and microdevices and even nanodevices.

Chemical Lithiation and Electroactivity of Nanomaterials

High capacity and good cycling stability of the electrode materials are the key points to develop high-performance lithium ion battery. Based on the latest research over the world, especilly from our group, in this paper we summarized the progress in chemical lithiation and electroactivity of nanomaterials. Firstly, we introduced the preparation of high capacity nanomaterials (molybdenum oxide, vanadium oxides, selenium hydrates, etc) and the chemical problems in lithiation process. Then we summed up the progress in assembly, chemical lithiation and electroactivity of single nanowire devices and nanowire lithium ion battery. Finally, we pointed out that assembly of single nanowire (nanobelts, nanotubes, etc.) device, in situ probe of lithium ion transport, design and construction of ordered array and complex structure, investigation of lithiation mechanism, electrostatic coupling, interface interaction, etc. are effective methods to deeper exploration of the relationship between chemical lithiation and electroactivity of nanomaterials and main directions of nanoscale lithium ion battery research field.

Self-assembling synthesis of vanadium oxide nanotubes and simple determination of the content of V(IV)

High-yielding low-cost vanadium oxide nanotubes were prepared by the hydrothermal self-assembling process from vanadium pentoxide and organic molecules as structure-directing templates. Moreover, a new method was discovered for determining the content of V (IV) in vanadium oxide nanotubes by thermogravimetric analysis (TGA). This method is simple, precise and feasible and can be extended to determine the content of low oxidation state in the other transition metal oxide nanomaterials.