Materials Science Forum Vols. 745-746

Abstract: Ag nanoparticles (NPs) have prominent local surface plasma resonance effect (LSPR), and Ag NPs exhibit sharpest and strongest bands among all metals. Diamond-like carbon (DLC) film have good biological compatibility and also have high transmissibility in the visible and near-infrared region. A new LSPR interface between Ag NPs and ultra-thin DLC film was formed by Plasma Enhanced Chemical Vapor Deposition. The morphologies and properties of the Ag NPs coated with DLC film were studied with SEM and AFM. The results indicated that the thickness of DLC film increased with the deposition time. LSPR peak became sharper after depositing for 1 or 2 min. DLC film was prior to nucleate on the surface of Ag NPs, and it has high content of sp² bonds near the interface. The sensitivity of new LSPR interface deposited for 20s was about the half of the sensitivity of bare Ag NPs and the sensitivity significantly decreased with deposition time. This result is helpful to understand the behavior of the new LSPR interface and to improve its sensitivity.

Abstract: Porous ceramics foamed by aerogens with pores of specific characteristics in shape and size can be widely applied in many fields such as biological engineering, enzyme engineering, environmental engineering, etc. However, the Preparation is prone to structure defects such as inequality of pore size and distribution, crack, contraction deformation, etc. Four-level orthogonal tests based on three improving factors such as water content and carboxymethyl cellulose (CMC) and stirring time (ST) were carried out to improve the method of preparing porous ceramic body foamed by aerogens at ordinary temperature. It is concluded that water content is the key improving factor followed by stirring time and CMC content, and the optimized formula could be A3B3C1 or A3B4C2. Microscopic analysis indicates that there are about 107 pores within 100μm² with diameter below 10μm and about 117 pores within 10000μm² with diameter range from 20μm to 100μm in the sample.

Abstract: Silver particles were synthesized by reducing silver ions with copper metal. The as-synthesized silver particles were characterized by scanning electron microscope (SEM). The effects of synthesis conditions on particle morphology were studied. The results showed that dendritic structures were readily synthesized when the silver nitrate solution kept stationary. The low concentration of silver ion was benefit to get perfect silver dendrite. The use of ammonium made the silver shape transferring from dendritic to spherical. The ultrasonic wave accelerated the diffusion of mass and produced spherical silver particles. These results indicated that dendritic silver particles were easy to obtain in non-equilibrium condition while the shape of silver rod-like or spherical was easy to get in equilibrium condition. The morphology and the size of silver particles depend on the synthesis conditions. The formation mechanism of dendritic silver particles were also deduced.

Abstract: The nanostructured ZnS, CdS/CdCO₃ and MnCO₃ were prepared by the hydrothermal method with gravity field of 1000 /g in the oil/water system at 100-150 for 0.5h. The products were characterized by eld-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and BET method. The results showed that the ZnS samples obtained using ZnCl₂ and Na₂S₂O₃ as precursors at 100-120 for 0.5h were the polycrystalline microspheres self-assembled by the crystallites with the size of 3-25nm. The pore volume of polycrystalline microspheres decreased with the increase of the size of the applied gravity forces. The morphology of CdS/CdCO₃ samples obtained at 100 for 0.5h was the flower-like structure, while the as-prepared samples at 120 for 0.5h were the nanoceramic microspheres in shape. The gravity force favors the formation of CdS/CdCO₃ samples. Moreover, the MnCO₃ polycrystalline flake can be obtained at 100-120 for 0.5h under gravity field of 1000 /g.

Abstract: Room temperature ionic liquid [1-butyl-3-methylimidazoliuBF4 was prepared under microwave irradiation. Platinum (Pt) nanoparticles were synthesized in the ionic liquid with ethanol as reductant. The structure and morphology of the Pt nanoparticles were characterized by SEM, FTIR and TG-DTA. The results show that the mean diameter of the nanoparticles was about 10nm and the surface was modified with the room temperature ionic liquid. The catalytic property was evaluated by hydrogenation of benzaldehyde in ethanol and the conversion reached up to 80% under hydrogen pressure.

Abstract: VO₂ thin films were obtained from V₂O₅ thin film in the thermal decompose process. V₂O₅ thin films were prepared in the spin-coating way and with V₂O₅ sol-gels as raw materials fabricated by the reformative inorganic sol-gel method. The effects of the viscosity of colloid on the fabrication of V₂O₅ film and the thermal decomposing temperature on the fabrication of VO₂ film were studied. The results show that the appropriate viscosity of colloid to obtain well-distributed V₂O₅ film was in the range of 30g/L-40g/L and suitable thermal decomposing temperature was about 500°C.

Abstract: Crystal structure and microstructure of La_0.7-xHo_xSr_0.3MnO₃ (x=0.2,0.6) prepared by usual ceramic techniques and grinding procedure were investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). When doping amount x equals to 0.2, incorporation of Ho atoms contributed to phase separation and coexistence of rhombohedral (La_0.7Sr_0.3MnO₃) and hexagonal (HoMnO₃) phases. La_0.7Sr_0.3MnO₃ phase is of typical perovskite structure, whereas, HoMnO₃ phase is non-perovskite structure. As x reaches 0.6, the volume fraction of HoMnO₃ phase was significantly increasing. Meanwhile, an orthorhombic lattice with perovskite structure and space group Pnma can be observed. It prevented from partial substitution of La ³⁺ or Sr²⁺ by Ho³⁺ and the distortion of Mn-O octahedra.

Abstract: A series of xBiFeO₃-(1-x) NiCuZn ferrite multiferroic composites have been prepared by solid state reaction method, in which x is 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0. Composites are densified at 700 °C for 3 h. XRD results show that ferroelectric phase and ferromagnetic phase can be co-existed in the composites. The density of composites increases with an increase of BiFeO₃ content. SEM results reveal that the bigger grains are BiFeO₃ and the smaller grains are NiCuZn ferrite. Composites exhibits the typical magnetic hysteresis loops. Increasing x, the saturation magnetization of composites linearly decrease. The real part of permeability for composites decreases with increasing x. Meanwhile, the peak of imaginary part of permeability shifts toward higher frequency.

Abstract: In this work, 0.33BaTiO₃-0.67BiFeO₃ multiferroic ceramics doped with x mol% MnO₂ (x= 0.1-1.0) were fabricated by solid-state reaction method, and their microstructure and dielectric property were also investigated. The perovskite phase structure of the solid solutions was confirmed by X-ray diffraction patterns, and the formation of minor impure phase of Bi₂Fe₄O₉ was prevent effectively by Mn-doping. With increasing the Mn-doped concentration, the dielectric constants of Mn-doped 0.33BaTiO₃-0.67BiFeO₃ multiferroic ceramics first increased, and reached a maximum value of 340 (measured @1MHz) at the Mn-doped concentration of 0.60 mol%, and then decreased. On the other hand, the dielectric losses first decreased, and reached the minimum value at the Mn-doped concentration of 0.30 mol%, and then increased along with increasing the Mn-doped concentrations. The ferroelectric domain structures in the Mn-doped 0.33BaTiO₃ - 0.67BiFeO₃ multiferroic ceramics with rhombohedral symmetry were also revealed by TEM image and selected area electron diffraction patterns, and tweed-like domain structures were observed.

Abstract: BiFeO₃ nanoparticles were synthesized by a NaNO₃-assisted low-heating temperature solid state reaction method. The effects of the molar ratio of added NaNO₃ and the calcination temperature on the characteristics of the products were discussed. The structure, morphology, magnetic, optical and electrical properties of BiFeO₃ were characterized by XRD, SEM, VSM and UV-VIS. The experimental results showed that the introduction of leachable inert inorganic salt as a hard agglomeration inhibitor in the mixture precursor led to the formation of BiFeO₃ nanoparticles with uniform size. With the addition of NaNO₃ in the process, the particle morphology decreased from a diameter of 300-500 nm to 80-100 nm. The BiFeO₃ attained at 600 °C showed a smaller band gap (2.12 eV) and weak ferromagnetism at room temperature with a remnant magnetization value (Mr) of approximately 3.1×10^-5 emu/g and a coercive filed value (Hc) of nearly 20 Oe.