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ABSTRACT: Silver flakes are the most widely applied conductive fillers in electrically conductive adhesives (ECAs) because of their
high conductivity and stable chemical properties. It is expected that there are advanced ECAs with both high electrical conductance
and good adhesive strength. The high filler loadings can improve the conductance of ECAs, whereas the adhesive strength is
decreased. Silver nanostructures are incorporated for the purpose of electrical conductance and adhesive strength improvement
of ECAs. A simple method has enabled the synthesis of silver nanostructures by reducing silver nitrate with ethylene glycol
in the presence of poly(N-vinylpyrrolidone). They are added to ECAs by dispersing them in ethanol while it is used as the diluent to adjust the volatility
of ECAs, preventing them from the aggregation. This proposed process offers the possibility to effectively use silver nanostructures
for improving the conductivity of ECAs at the low content of conductive fillers while good adhesive strength may be obtained.
Journal of Materials Science Materials in Electronics 04/2012; 21(5):486-490. · 1.08 Impact Factor
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ABSTRACT: Here we report a facile, surfactant-free and template-free synthesis process of highly uniform dendritic silver nanostructures with high catalytic activity for the reduction of p-nitrophenol. By controlling the concentration of AgNO(3) aqueous solution and the reaction time, various shapes of silver nanodendrites (SNDs) could be obtained easily. The effects of different parameters such as concentrations of the reagents and reaction time on the morphology and structure of as-prepared tree-like nanostructures have also been investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Also, the X-ray photoelectron spectroscopy (XPS) has been used to identify the oxidation state of SNDs. In addition, the catalytic activity of the as-prepared SNDs samples at 200 mM AgNO(3) aqueous solution was evaluated by a redox reaction of p-nitrophenol in the presence of an excess amount of NaBH(4). It was found that the highly symmetrical SNDs with roughly 60-120 nm in stem and branch diameter and 3-12 μm in length obtained after 120 s reaction time do have higher catalytic activity than other SNDs prepared at different reaction time, several times stronger catalytic activity in the sodium borohydride reduction of p-nitrophenol to p-aminophenol, compared to some other silver nanoparticles reported in literature. The crystallinity provided by X-ray diffraction (XRD) analysis indicates that the improvement of the crystallinity is also very crucial for SNDs' catalytic activities. The SNDs are very promising catalytic candidates for the reduction of p-nitrophenol because of easily simple preparation route and high catalytic activity.
Journal of hazardous materials 03/2012; 217-218:36-42. · 4.14 Impact Factor
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ABSTRACT: A modified chemical-precipitation method is proposed to synthesize MgO nanopowders with high crystallinity at a low temperature of 400 degrees C using acetic acid as a modifier. The as-obtained intermediates and final products were investigated by Fourier-transformed infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and transmission electron microscopy, respectively. The influence of acetic acid in the MgO preparation process was also investigated by a comparison of the samples without acetic acid, and the mechanism of acetic acid modification is also proposed. The carboxyl group of acetic acid could coordinate with Mg atom in a monodentate mode to form a new organic ligand intermediate Mg(OH)(OCOCH3), which facilitates the thermal decomposition of the intermediate at low temperature and enhances the crystallization of MgO.
Journal of Nanoscience and Nanotechnology 03/2012; 12(3):1919-23. · 1.56 Impact Factor
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ABSTRACT: Ti-doped magnesium oxide powders were prepared by a chemical coprecipitation technique using magnesium nitrate hexahydrate and titanium tetrabutoxide as starting materials and ammonia hydroxide as precipitator. The influence of titanium doping on the structure and morphology of MgO powders was investigated by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy and transmission electron microscopy. The results show that titanium ion (Ti4+) was successfully incorporated into the MgO crystal lattice, and consequently, caused the changing of MgO crystal lattice parameter. However, titanium doping resulted in varied particle sizes, and enhanced slightly the particle aggregation. It is attributed to the difference between the solubility product (Ksp) of the two precursors, Mg(OH)2 and TiO(OH)2, which is one of important factors in the chemical coprecipitation process.
Materials Characterization. 60(8):858-862.
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ABSTRACT: The study was carried out to investigate the effects of two different coupling agents on the properties of epoxy-based electrically conductive adhesives (ECAs). For the investigation, a novel mixture of solvent and diluted acid was designed to remove the lubricants on the surface of silver flakes fully and each of the following two commercially available coupling agents, a silane coupling agent and one titanate coupling agent, was used as an additive for the ECA. It was found that with the full removal of lubricants on the surface of silver flakes, the electrical conductivity is improved at the same weight filler loading. It was also found that the adding of coupling agents has different effects on the electrical, aging and lap shear properties of ECAs. According to this study, the use of silane coupling agent had a significant electrical conductivity improvement and lap shear strength increase before and after the aging test. But for the titanate coupling agent, the properties of the ECA have no significant change. Scanning electron microscopy studies revealed a strong adhesion/bonding between the filler and the matrix for coupling agent-added ECA.
International Journal of Adhesion and Adhesives.
