Mei Han Wang

Preparation and Characterization of Graphite Oxide

The preparation of graphite oxide is one of essential steps for graphene by oxidation reduction method. Graphite oxide was acquired from the oxidation of graphite by improved Hummers method and characterized by X-ray diffraction, scanning electron microscope, Fourier transform infrared absorbance spectroscopy and thermogravimetric analysis. It was showed that the graphite interlayer distance of graphite oxide increased for a large amount of oxygen containing functional groups. Shift and broaden of diffraction peaks were observed after oxidation and the original graphite peaks disappeared.

Preparation and Characterization of Graphene by Oxidation-Reduction Method

Graphene was prepared by using hydrazine hydrate to reduce the exfoliated graphite oxide nanosheets in the aqueous colloidal suspension. The prepared graphene were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD) and scanning electron microscope (SEM), respectively. The results showed that part of oxygen containing groups of the exfoliated graphite oxide nanosheets disappeared and the conjugated p bond recovered after reduction. The thickness and size of the graphene nanosheets decreased.

Cu2+ Removal by Hydroxyapatite Nanorods Prepared by Surfactant-Templated Method

Nanohydroxyapatite (HA) with rod-like shape was synthesized by a cationic surfactant-templated method. Batch adsorption experiments were conducted to investigate its copper adsorption property from aqueous solution. The effect of initial copper ion concentration and contact time were studied. Results showed that HA adsorption capacity increased from 25.6 mg/g to 81.4 mg/g with the increase of initial copper ion concentration from 20 mg/L to 200 mg/L. Meanwhile, the removal efficiency decreased from 64.1% to 20.3%. Moreover, it also revealed that the removal efficiency of Cu2+ increased with the increasing contact time and the initial adsorption process is rapidly increased within 15 min and the equilibrium was attained after 15 min.

Preparation and Adsorption Property of Nano-Rods Hydroxyapatite Using Cationic Surfactant Templates

Nano-rods hydroxyapatite (HA) was synthesized by hydrothermal method using Ca(NO3)2·4H2O and H3PO4 as precursors and cationic surfactant (CTAB) as a template. The effect of pH value and reaction temperature on the phase and morphology of HA were investigated. HA samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that high pH values resulted in high purity of HA. HA morphology changed from irregular round shape to nano-rod shape with the increase of the reaction temperature from 80°C to 120°C. The prepared HA was utilized as adsorbent to remove copper ion from aqueous solution. The adsorption results showed that nano-rod HA had a rapid Cu2+ adsorption rate and good removal efficiency (>99%).

Lamination of Green Ceramic Tapes in the Manufacturing of Multilayer Ceramic Devices

Lamination of green ceramic tapes is one of the most important technological processes in the manufacturing of multilayer ceramic devices and it has determined influence on the quality of the devices. Therefore, choosing proper lamination technique is very important to a designed structure. The development of lamination techniques of green ceramic tapes is of great significance for the electronic communication industry and it has become a hot spot in the research. In this paper, the main lamination techniques in the present research and practice are overviewed. As to the development prospect and direction of the lamination of green ceramic tapes, the own opinions are given on the basis of lamination study in recent years.

Lamination of Green Ceramic Tapes with Adhesive at Ambient Temperature

In this paper, green ceramic tapes are joined together by adhesive based lamination technique. The effects of adhesive concentration, pressure on the lamination and sintering temperature on the laminate are mainly discussed. The parameters are also optimized. It was shown that the effect of adhesive concentration and pressure on the lamination is obvious and the effect of sintering temperature is not big. 10 layers of cordierite tapes can be laminated under 2MPa with a dwell time of 3min with PVA by adhesive based lamination. The adhesive based lamination can be used to be an alternative of thermo-compressive lamination.

Fluorescence and Energy Transfer in Er3+/ Nd3+ Co-Doped Oxyfluoride Tellurite Glass

Er3+/Nd3+ co-doped oxyfluoride tellurite glass was prepared successfully by the conventional melting method. Luminescent properties of Er3+/Nd3+ co-doped oxyfluoride tellurite glass were studied in the NIR spectral range. There existed strong absorption peaks of Nd3+ ions at 580 nm, 743 nm, 800 nm and 874 nm and obvious absorption peaks of Er3+ ions at 580 nm, 743 nm, 800 nm and 874 nm. Er 3+ /Nd 3+ co-doped glass performed excellent fluorescence properties at 1.53 μm and 1.06 μm. There existed energy transfer between Nd3+ ions and Er3+ ions, that is 4I9/2 (Er 3+ ) + 4I9/2 (Nd3+) → 4I15/2 (Er3+) + 4F5/2 (Nd3+). Owing to the energy transfer from Er3+ ions to Nd3+ ions, multi-phonon relaxation or up-conversion radiations, emission intenisty of Er3+/ Nd3+ co-doped glass was weaker than that of Er3+ single-doped glass at 1.53 μm.

Synthesis and Characterization of Novel Polyfluorene Derivatives

A novel series of copolymers containing fluorene units are synthesized by Sonogashira coupling reaction in mild condition. Benzene, naphthalene and anthracene are co-polymerized with ethynylfluorene, respectively. The structures are confirmed by NMR, Mass, Elemental analysis and GPC. The polymers have good thermal properties with glass-transition temperature of 90-155°C(Tg), and they have bandgaps from 2.21-2.77 eV. The results of photoluminescence in solid state show that introduction of huge chromophore could effectively suppress the formation of aggregates and excimers which typically cause red-shifted or new emission.