Advanced Materials Research Vols. 79-82

Abstract: Near full dense B4C ceramic matrix composites were fabricated from Ti-Al-B4C system by combining high energy milling with hot pressing sintering. The effect of different content of Ti-Al on the mechanical properties and microstructure of the as-prepared composites was investigated. A TiAl/B4C composite, whose typical bending strength and fracture toughness are 437.3 MPa and 4.85 MPa•m1/2, respectively, was made. The sintering mechanism and reinforcement mechanism were discussed with the assistant of X-Ray diffraction and electron microscopy.

Abstract: In this paper, we report the fabrication and photoelectric properties of CdTe/TiO2 nanocrystal multilayer. Negatively charged CdTe nanocrystal hydrosols were synthesized in the aqueous phase with 3-mercaptopropionic acid as a surface modifier. The characterization of transmission electron microscopy (TEM) and UV-visible absorption spectrum indicates the resultant CdTe nanocrystal hydrosols are monodisperse and have a very narrow size distribution with a mean diameter of about 5 nm. Clear TiO2 aqueous colloidal nanocrystals with positive surface charges were prepared by using tetrabutyl titanate as precursor. Through the electrostatic interaction between the positive surface charges on TiO2 nanocrystals and those on CdTe nanocrystal hydrosols, multilayer of CdTe/TiO2 nanocrystals were fabricated on the pretreated quartz substrate by layer-by-layer electrostatic self-assembly method. UV-Vis absorption spectrum and atomic force microscopy (AFM) were used to characterize the as-prepared CdTe/TiO2 multilayer. The results show that the surface of the CdTe/TiO2 multilayer are flat and the adsorption intensity in UV-Vis spectrum increases with the layer numbers of the CdTe/TiO2 complex, indicating that CdTe/TiO2 multilayer could be fabricated successfully on the surface of quartz glass and the resultant multilayer have good quality. In the same way, CdTe/TiO2 multilayer were fabricated on the surface of Indium Tin Oxides (ITO) substrate disposed by the poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). The CdTe/TiO2 complex is measured under AM1.5G simulated solar illumination with 100mWcm-2 in air. The results show the maximum open circuit current density (Voc) and short circuit current density (Isc) of CdTe/TiO2 complex on ITO substrate is 0.45V and 0.050mA, which were better than TiO2 or CdTe nanocrystal hydrosols individual due to the interfacial hole-electron converter between the adjacent layers of CdTe and TiO2 nanocrystals.

Abstract: This work focuses on studying a novel polymer/nanocrystal multilayer for the fabrication of donor and accepter typed photovoltaic device. Highly luminescent anionic CdTe nanocrystals were prepared by aqueous synthesis method using 3-mercaptopropionic acid as stabilizer. The resultant CdTe served as electron acceptor and poly(p-phenylene vinylene) (PPV) was used as electron donor. Through the electrostatic interactions between cationic PPV precursor poly(p-xylene tetrahydrothiophenium chloride) and anionic poly(sodium4-styrenesulfonate) (PSS), PPV/PSS complex was fabricated on the surface of pretreated quartz substrate by layer-by-layer electrostatic self-assembly method. UV-Vis spectrum shows that PSS in the PPV/PSS complex make PPV precursors thermally convert into PPV at a lower temperature and less time. PPV/ PSS/PPV/CdTe multilayer were fabricated on the surface of quartz substrate by electrostatic self-assembly method. The surface of the polymer/CdTe complex is flat, which was characterized by atomic force microscopy (AFM). UV-Vis spectrum of the polymer/CdTe complex shows that the absorbance increases with the increase of the number of deposition cycles. In the same way, PPV/PSS/PPV/CdTe multilayer were fabricated on the surface of ITO substrate disposed by the poly(3,4- ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). The resultant polymer/ CdTe complex is measured under AM1.5G simulated solar illumination with 100mW•cm-2 in air. The open circuit current density (VOC) and short circuit current density (JSC) of the polymer/CdTe complex are 0.60 V and 0.305 mA•cm-2 which are better than PPV or CdTe nanocrystal individual. This could be ascribed to interfacial hole-electron converter between the conjugated polymer layer and CdTe nanocrystal layer. Besides, the photovoltaic properties of PPV/CdTe complex can be improved by controlling the layers of PPV/ CdTe nanocrystals complex on the ITO substrate.

Abstract: A series of TiAlN/Si3N4 nano-multilayer films with various Si3N4 layer thicknesses were prepared by reactive magnetron sputtering. These multilayers were then annealed at temperatures ranging from 600 to 900°C in air for 1 hour. The composition, microstructure, and mechanical properties of the films were characterized by energy dispersive x-ray spectroscopy, x-ray diffraction, scanning electron microscopy, and nanoindentation. It reveals that under the template effect of TiAlN layers in multilayers, as-deposited amorphous Si3N4 is crystallized and grows coherently with TiAlN layers when Si3N4 layer thickness is below 0.6 nm. Correspondingly, the hardness and elastic modulus of the multilayers increase significantly. With further increase in the layer thickness, Si3N4 transforms into amorphous, resulting in a decrease of hardness and modulus. The TiAlN/Si3N4 nano-multilayers could retain their superlattice structure even up to 900°C. The small decrease in the hardness of multilayers annealed below 800°C was correlated to the release of compressive stress in multilayers. However, oxidation was found on the surface of multilayers when annealed at 800°C, which resulted in a marked decrease in the hardness of multilayers. The multilayers presented higher hardness as compared with the monolithic TiAlN film.

Abstract: In this paper, the intercalation of methyl-red (MR) into Mg/Al (ratio=2:1) layered double hydroxide (LDH) was carried out using reconstruction method to obtain MRLDH nanocomposite material. Its chemical composition, crystal structure and appearance were characterized by XRD, FT-IR, TEM, TG-DTA and element analysis. It has been found that the MRLDH still keeps the typical lamellar structure, and the guest MR has inserted into the layers of the host LDH. The MRLDH’s disassembly temperature is higher more than 70°C than that of guest molecule MR, so it can be used as a new dye with high thermal stability.

Abstract: The γ-ray co-irradiation method was employed to study the effect of diethanolamine modification on the surface of carbon fiber (CF) and the interfacial properties of CF/epoxy composites. Compared with the original carbon fiber, the surface of modified fibers became rougher. The amount of oxygen-containing functional groups was increased and the nitrogen element was detected after irradiation grafting. The interlaminar shear strength (ILSS) of composites reinforced by carbon fibers irradiated in diethanolamine solution was increased and then decreased as the irradiation dose increased. The ILSS of CF/epoxy composites was enhanced by 16.1% at 200kGy dose, compared with that of untreated one. The γ-ray irradiation grafting is expected to be a promising method for the industrialized modification of carbon fibers.

Abstract: SiO2 /Ni nanocomposite is directly prepared from the silica particle by a controllable method through electroless metallization, which is different from the sol-gel technique. Its fabrication procedure is as follows: first the formation of ligating monolayer by a silane agent coupling with silica, then, binding Pd catalyst with its ligating group, finally, nano-sized Ni deposition occurs on the template. The metallic Ni particles are uniformly deposited on the silica, and they have a net or chain-like structure, just as the silica particles do. The composite inherent coercivity (iHc), saturated magnetization (MS), and residual magnetization (Mr) are 16.5, 10.0 and 1.00 respectively in the as-plated Ni. The chain-like structure causes stronger static magnetization interactions between Ni particles, resulting in a magnetic crystalline anisotropy and the higher iHc value.

Abstract: The magnetic Fe3O4 nanoparticles had been synthesized by co-precipitation process and surface treatment by silane coupling agent (KH570). The magnetic Fe3O4/PMMA nanocomposite films were prepared by blend method, and the chemical structure, mechanical properties, surface morphology and the biocompatibility of the nanocomposite films were studied in this work. The magnetic Fe3O4 nanoparticles were well dispersed in the Fe3O4/PMMA nanocomposite films. The strength of the nanocomposite films, as well as the strain, decreased first and then increased with the increasing of the nanoparticles. The hemolytic ratio indicated that the nanocomposite films had a better blood compatibility.

Abstract: In this paper, nanometer MgO powder was prepared by using MgCl2•6H2O as the raw material, and environmental benign strong-base anion exchange resin as the induced-precipitation regent. The influence of the concentration of MgCl2 solution, drying method, calcination temperature and time on particle size and physico-chemical features of MgO was studied. The optimal technical conditions were obtained. The XRD and SEM results show that the nanometer MgO prepared under the optimal technical conditions has regular hexagonal lamellar structure, and is composed of nanocrystals with average size between 10 to 25 nm. The existence of dry N2 prevented the sintering of MgO during decomposition processing of Mg(OH)2. Compared with the other nanometer MgO preparation methods, ion exchange resin method has the advantages of low cost, low pollution, high yield and environmental benign; therefore, it appears to be a promising method for the industrial manufacturing of nanometer MgO.

Abstract: Fluorescent silica nanoprobe as a biomarker for detection has attracted much attention in the field of nano-biotechnology recently but no further research applications using fluorescent silica nanoparticles (FSNP) combined with antibody molecules reported to detect pathogen detection. In this study, silica nanoparticles were prepared using the water-in-oil (w/o) microemulsion method. The silica nanoparticles were circular in diameter of 50 ± 4.2 nm. The organic dye, tris-2, 2' -bipyridyl dichlororuthenium (II) hexahydrate (Rubpy), could be incorporated efficiently into the core of silica nanoparticles. The fluorescence of Rubpy-doped silica nanoparticles was photostable using a collisional quenching fluorescence test. The Rubpy-doped silica nanoparticles were conjugated with the secondary antibody of goat anti-rabbit immunoglobulin G (IgG) and successfully detected plant pathogen such as Xanthomonas axonopodis pv. vesicatoria that causes bacterial spot disease in Solanaceae plant. These results demonstrated that the fluorescence silica nanoprobe biomarker will have been potential for rapid diagnosis applications on plant diseases.