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Hu D.,South China University of Technology | Wang Y.,Key Laboratory of Specially Functional Materials
Advanced Materials Research | Year: 2012

This paper utilized a novel oxidative co-precipitation method to synthesis hexagonal Fe 3O 4 nanometer particles, which assisted by a weakly magnetic field. The crystallinity, morphology, particle size distribution, compositions and magnetic properties of the as-prepared particles were investigated using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), ultrasonic particle sizer (UPS), X-ray photoelectron spectra (XPS) and vibrating sample magnetometer (VSM). The formation mechanism of the hexagonal Fe 3O 4 nanometer particles, which assisted by a weakly magnetic field was also discussed. The results shown that the as-prepared hexagonal particles were purity magnetite (Fe 3O 4), and the weakly magnetic field could accelerate the phase transformation from goethite (a-FeOOH) to magnetite (Fe 3O 4), increase the particle size and uniform the morphology. The values of saturation magnetization (Ms) and coercivity (H) of the hexagonal magnetic particles are 71.05 emu·g-1 and 474.3 Oe, respectively, which contributed to the morphology anisotropy of the particles. © (2012) Trans Tech Publications, Switzerland. Source


Zhang J.,South China University of Technology | Zhang J.,Key Laboratory of Specially Functional Materials | Lei B.,South China University of Technology | Lei B.,Key Laboratory of Specially Functional Materials | And 6 more authors.
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2011

In this paper, nanoscale bioactive glass particles with different morphologies were prepared through adding citric acid in a sol-gel process. The structure of as-prepared samples was characterized using specific surface area analysis apparatus, SEM and TEM. The results indicate that just using citric acid as hydrolysis catalyst can easily control the nanostructure and morphology of bioactive glass and is in favor of preparing the bioactive glass with smaller particle size, larger specific surface area and pore volume. This procedure can serve a simple mean with low cost to produce nanoscale bioactive glass and control its morphology. Source


Yu T.,Key Laboratory of Specially Functional Materials | Yu T.,South China University of Technology | Ye J.,Key Laboratory of Specially Functional Materials | Gao C.,Key Laboratory of Specially Functional Materials | And 2 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2010

In the present study, the effect of biomedical organic compounds (starch, sodium alginate, chitosan and gelatin) on the hydration of calcium phosphates was studied using X-ray diffraction, infrared spectroscopy, scanning electron microscopy and XPS analysis. Amorphous calcium phosphate (ACP) was prepared by a mechanochemical route and mixed with biomedical organic compounds. A solidification reaction occurred between ACP and dicalcium phosphate dihydrate (DCPD); the hydration product was poorly crystallized hydroxyapatite (HA). During the setting reaction of ACP and DCPD, the presence of biomedical organic compounds had an effect on the hydration product: the bonding energies of the primary elements (Ca, P) in the hydration product (HA) were changed; also different hydration morphologies, self-setting properties, rheological properties and mechanical strength of the cement were obtained. This work will allow advances in the synthesis of bionic composite calcium phosphate cement (CPC). © 2009 Elsevier B.V. All rights reserved. Source


Nkurikiyimfura I.,South China University of Technology | Nkurikiyimfura I.,Kigali Institute of Science and Technology | Wang Y.,South China University of Technology | Wang Y.,Key Laboratory of Specially Functional Materials | And 2 more authors.
Renewable and Sustainable Energy Reviews | Year: 2013

Magnetic nanofluids (MNF) constitute a special class of nanofluids that exhibit both magnetic and fluid properties. The interests in the use of MNF as a heat transfer medium stem from a possibility of controlling its flow and heat transfer process via an external magnetic field. This review presents recent developments in this field with the aim of identifying major affecting parameters and some novel applications. This review emphasizes on thermal conductivity enhancement and thermomagnetic convection in devices using MNFs as heat transfer media. © 2013 Elsevier Ltd. Source


Nkurikiyimfura I.,South China University of Technology | Nkurikiyimfura I.,Kigali Institute of Science and Technology | Yanmin Wang,South China University of Technology | Yanmin Wang,Key Laboratory of Specially Functional Materials | And 3 more authors.
ICMREE2011 - Proceedings 2011 International Conference on Materials for Renewable Energy and Environment | Year: 2011

This paper investigated the enhancement of thermal conductivity of engine oil based magnetite (Fe3O4) nanofluids, which were prepared via a co-precipitation method with and without ultrasound assistance, in the presence of external magnetic field. The thermal conductivity was determined using a thermal constants analyzer. Effects of particle size, particle volume fraction and magnetic field on the thermal conductivity ratio of the magnetic nanofluids were analyzed. The results showed that the thermal conductivity could be enhanced with the finer magnetite particles used in the nanofluid at a greater particle volume fraction. In addition, the thermal conductivity enhancement was found to be related to magnetic field parallel to temperature gradient. © 2011 IEEE. Source

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