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Liu M.,Fujian Normal University | Qin W.,Fujian Normal University | Liu R.,Fujian Normal University | Liu Y.,Fujian Normal University | And 2 more authors.
Gaofenzi Cailiao Kexue Yu Gongcheng/Polymeric Materials Science and Engineering | Year: 2014

A series of porous poly(L-lactic acid) (PLLA) films were fabricated from PLLA/DMF solutions by thermally induced phase separation. The crystallization temperatures of PLLA/DMF solutions and thermal properties of porous PLLA films were examined by DSC. The morphology and crystal form of PLLA films were measured by SEM and XRD, respectively. The results show that the crystallization temperature gradually increases with PLLA concentration increasing. The film with nanofibrous network structure is obtained from low concentration solution, while film with porous microspheres is obtained from high concentration solution; the crystal form is α' and α-form, respectively; the formation mechanism for the PLLA nanofibrous network and microspheres is liquid-liquid phase separation, nucleation and crystal growth, respectively. In addition, Tm of PLLA films increases slightly with increase of PLLA concentration. Source


Lin Y.B.,Fujian Normal University | Lin Y.B.,Fujian Provincial Key Laboratory of Polymer Materials | Huang Z.G.,Fujian Normal University | Yang Y.M.,Fujian Normal University | And 4 more authors.
Applied Physics A: Materials Science and Processing | Year: 2011

(La0.7Sr0.3MnO3)x/YBa 2Cu3O7)y composites were prepared by mixing La0.7Sr0.3MnO3 powders and the sol-gel-derived YBa2Cu3O7 matrix, followed by high-temperature calcinations. Their structural, magnetic properties and magnetoresistance effect have been investigated systematically. A giant positive magnetoresistance (PMR) at low magnetic field is observed at low temperatures. In the case of (La0.7Sr0.3MnO3) 1/(YBa2Cu3O7)9 composite, the PMR achieves 260% under a magnetic field of 5800 Oe. However, the PMR value sharply decreases with increasing temperature and no magnetoresistance effects are found above metal-insulator transition temperature. The enhancement of spin-dependent scattering at the grain boundaries should be responsible for the observed PMR. In addition, the temperature dependence of resistance under magnetic field could be explained by the competition between diamagnetism and paramagnetism in YBCO phase. At low temperature, the diamagnetism is predominant over paramagnetism and the interface scattering between LSMO grains is enhanced correspondingly. As a result, the low-temperature resistance increases and large PMR appears. © 2010 Springer-Verlag. Source


Xiong X.,Xiamen University | Xiong X.,Fujian Provincial Key Laboratory of Polymer Materials | Wang Y.,Xiamen University | Zou W.,Xiamen University | And 2 more authors.
Journal of Chemistry | Year: 2013

By dispersing aqueous precipitant in liquid paraffin to prepare a W/O emulsion then adding chitosan (CS) solution, CS microcapsules have been successfully prepared. It is a facile way to prepare polymer microcapsules by using aqueous precipitant or nonsolvent as template, which avoids the removal of template and would free from the necessity to cross-link the microcapsule as usual methods to directly form dense shell. The hollow feature of the obtained materials is revealed. The diameter of the microcapsules ranges from several μm to over 100 μm. Magnetic CS microcapsules have been prepared in this way when Fe 3+ and Fe 2+ were mixed with CS to prepare a mixture starting solution. The appearance and microstructure of the composite microcapsules were studied. The results indicate that the formed Fe 3O 4 nanoparticles are embedded in the CS matrix evenly due to strong interaction between the Fe 3O 4 nanoparticles and the CS molecules. The Fe 3O 4 content and the magnetic properties of the composite microcapsule were measured. The composite microcapsules were calcined in air at 700°C to prepare pure inorganic hollow microspheres. It is general to prepare hollow polymeric or composite particles by using this method. © 2013 Xiaopeng Xiong et al. Source


Zhang W.,Fujian Normal University | Zhang W.,Fujian Provincial Key Laboratory of Polymer Materials | Tu G.,Fujian Normal University | Tu G.,Fujian Provincial Key Laboratory of Polymer Materials | And 6 more authors.
Materials Letters | Year: 2014

Mesoporous ZnO particle with high specific surface area was synthesized by a reverse microemulsion-based evaporation-induced self-assembly (EISA) technique, using zinc nitrate as metal precursor and sucrose as porogen, respectively. Structural and morphological characterization indicated that the resulting ZnO possesses a wurtzite structure and spherical morphology with an average particle size of about 150 nm. And, the effect of the molar ratio of sucrose to Zn2+ on the mesoporosity and antibacterial activity of the resulting ZnO was also investigated. The results of low temperature N 2 adsorption-desorption analysis confirmed the formation of the mesoporous ZnO. When the molar ratio of sucrose to Zn2+ was 1.5, the resulting ZnO possessed the highest specific surface area of 233.56 m 2 g-1 and the largest pore volume 0.89 cm3 g-1, respectively. The inhibition zone tests revealed that the mesoporous ZnO particle exhibits a strong antibacterial activity against both a Gram-negative bacterium Escherichia coli and a Gram-positive bacterium Staphylococcus aureus. © 2013 Elsevier B.V. Source


Lin Y.B.,Fujian Normal University | Lin Y.B.,Fujian Provincial Key Laboratory of Polymer Materials | Yang Y.M.,Fujian Normal University | Yang Y.M.,Fujian Provincial Key Laboratory of Polymer Materials | And 6 more authors.
Physica B: Condensed Matter | Year: 2010

Room-temperature ferromagnetic Mn-doped ZnO films have been deposited on Si(0 0 1) substrates by plasma enhanced chemical vapor deposition technique. The microstructure, structure, optical and magnetic properties were investigated systematically. X-ray diffraction and transmission electron microscopy reveal that the all samples have a wurtzite polycrystalline structure and no secondary phase is found in films. Magnetization measurements indicate that Zn1-xMnxO films show room temperature ferromagnetism. In order to elucidate the origin of the ferromagnetism, Zn1-xMnxO films were annealed under different atmosphere. The results show that photoluminescence spectra are strongly dependent on defects in films and the interface between grains. © 2009 Elsevier B.V. All rights reserved. Source

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