Guang Ming Wu

Effect of Calcium Sulfate on the Formation of Ettringite in Calcium Aluminate and Sulfoaluminate Blended Systems

The formation of ettringite and the expansion associated with it were studied on paste made from Portland cement, two Al-bearing compounds such as calcium aluminate cement and calcium sulphoaluminate cement, and calcium sulfate with different reactivities (anhydrite, α-hemihydrate and gypsum). The hydration process and formation of ettringite in the binders with different content of calcium sulfate was investigated by free expansion testing, isothermal conduction calorimetry, X-ray diffraction (XRD) and environmental scanning electronic microscope (ESEM). Results showed that the reactivity and amount of the calcium sulfate determined the balance between the hydration products of ettringite and monosulfate, and also the early hydration kinetics including the formation content, size and location of ettringite. It was also found that all the ternary systems with higher addition of calcium sulfate expand significantly. When a higher content of α-hemihydrate was added, besides ettringite much secondary gypsum also forms in voids between cement granules, which exerted adverse effects on the properties of ternary systems. However, the formation content of ettringite appeared to have no connection with the expansion value.

Structural Study of WO3 and MoO3 Compound Films in H2 Gasochromism

Sol-gel tequnique was used to prepare disordered tungsten oxide and molybdenum oxide sols. A series ratio of W:Mo compound sols were obtained via mettalic powder co-peroxided by H2O2 as precursors in ethonal. Compound films were achieved by dip-coating method. Fourier Transform Infrared Spectroscopy, Raman Spectroscopy were taken to characterize the structure of these compound films. Uv-visible Spectroscopy was used to test the gasochromic property. The results showed that the gasochromics property was much different from that of pure tungsten oxide and molybdenum oxide sol-gel thin films. The effect was origined from the structrue alteration, which was not due to the spectrum superposition but the co-reaction of W and Mo.

Electrochemical Performance of V2O5 Nano-Porous Aerogel Film

Nano-porous V2O5 aerogel films were prepared by dip-coating vanadium oxide sol onto ITO substrate, using V2O5 powder, Benz alcohol, Isopropanol as precursor materials. The nano pores were characterized by scaning electron microscope (SEM). The electrochemical properties were investigated by chronopotenyiometry(CP) and cyclic voltammograms(CV). Results showed that this porous V2O5 aerogel film exhibited good cycling stability with initial discharge capacity of 143mAh/g and 128 mAh/g after 18 cycles, staying 89.5 % of the initial discharge capacity, at a charge/discharge current density of 200 mA/g.

Preparation and Properties of Super Insulation Material SiO2 Aerogel

Nano-porous monolithic SiO2 aerogel as insulation material was prepared from silicon alkoxide as the precursor materials, followed by ethanol supercritical drying in this paper. In order to improve the mechanical properties of silica aerogel monoliths, the ceramic fibers were mixed in the pure aerogel, or integrating inorganic fiber materials as skeleton materials with low thermal conductivity supporting. Instron 5566, 5500R Material Testing Machine was used to measure the mechanical intensity. SEM was used to characterize the morphology of the silica aerogel monoliths. The thermal properties of the silica aerogels were determined by using the Hot Disk device. The results show that new type composite materials had a low effect on the thermal conductivities of the silica aerogel monoliths, but improved the mechanical intensity clearly. It made a great progress in the practical application of the SiO2 aerogel monoliths.

Surface Modification and Properties of SiO2 Nano Porous Aerogels

Surface modification is a process in which Si-CH3 groups of trimethylchlorosilane (TMCS) replace -OH groups on the inner surface of SiO2 aerogels, so the surface property of aerogels has shown hydrophobic performance which could be changed back to hydrophilic by 450 heat treatment. This aerogels with surface property controlled are prepared via sol-gel process with polyethoxydisiloxanes (E-40) used as precursor, and have typical porous structures dried at ambient pressure: high porosity (above 90 %), super specific surface area (about 1000 m2/g), low bulk density (down to 3.03 kg/m3) and average pore size is about 20 nm. This paper presents adsorption mechanisms in aerogels and illustrates that the adsorption capacity of aerogels is three or four times as much as that of activated carbon fiber (ACF) and granule of activated carbon (GAC). So SiO2 aerogels are potentially important to be used as absorbents being quite efficient to adsorb toxic substances.

Characterization and Electrochemical Performances of Vanadium Oxide Films Doped with Metal Ions

Vanadium oxide films were prepared via the sol–gel process and dip coating method, using V2O5 as raw materials and H2O2 (volume fraction 30) as the solvent. Mn and Ni ions were added to vanadium oxide sol to prepare doping vanadium oxide films. The films were characterized by atomic force microscopy, FT-IR, X-ray diffraction and electrochemical techniques. The add-on of Metal ions will not affect the morphology of the vanadium oxide films, but change the valence of vanadium ion and vanadium oxide crystal phase. Furthermore, cyclic voltammetry curves show that metal ions doping vanadium oxide films exhibit reversible electrochemical reaction. But electrochemical impedance spectroscopy indicates pure vanadium oxide film has a better diffusion rate.

The Process Optimization and Structural Analysis of Gasochromic Thin Films Derived by Peroxopolytungstic Acid

The sol-gel method with a combination of dip-coating process was employed to prepare peroxopolytungstic acid gasochromic thin films. The influence of preparation process on the structural and gasochromic durability was then discussed. We found that hydrogen peroxide content shown a significant impact on the structure of tungsten oxide thin films, which directly determined the gasochromic durability

Mechanism of Annealing Treatment Effect on the Gasochromic Properties of WO3 Bulks and Films

Nanostructural WO3 materials exhibit excellent gasochormism performance under the action of the hydrogen gas. In this paper, we study the mechanism of annealing treatment effect on the gasochromic properties both of the WO3 bulks and WO3 films. WO3 bulks were prepared from WO3 sol and dried under ambient pressure, which was previously synthesized via sol-gel method. The WO3 films were prepared using dip-coating method. UV-visible spectroscopy, Raman spectroscopy, Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction spectra (XRD) were utilized to investigate components, structures and gasochromic properties. And we find that the mechanism of the thermal treatment on the gasochromic performance depends on H+ diffusion velocity which largely relies on the structural water content.

A Composite Film of V2O5 and Multiwall Carbon Nanotubes as Cathode Materials for Lithium-Ion Batteries

In this paper, V2O5-Multiwall Carbon Nanotubes (MWCNTs) composite film is prepared through sol-gel technique and dip-coating method. MWCNTs pretreated by mixed acid, H2O2 and cheap V2O5 powder are used as raw materials. The morphology, structure and components of the composite film are characterized by corresponding testing instruments. The final electrochemical measurements indicate that: the V2O5-MWCNTs composite film as cathode materials for lithium batteries exhibits better electrochemical performance than ordinary V2O5 film.