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Lu J.,Beijing Institute of Technology | Cheng X.,Xiamen University | Cheng X.,Fujian Key Laboratory of Advanced Materials
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2017

The porous silicon samples were fabricated on the p-type single crystal silicon wafers in 40% hydrofluoric acid solution under a nitrogen atmosphere by applying a constant current density of 30 mA/cm2 for 1, 3 and 5 min, respectively. The surface morphologies and microstructures of the freshly prepared porous silicon layers were investigated. The relative amounts of large single crystal, nanocrystalline and amorphous silicon related to the extent of crystallinity transformation and the change of crystallite diameter involved during porous silicon formation were evaluated via multi-peak fitting Raman spectra. The results reveal that the sponge-like nanoporous structures are formed on the silicon surfaces at different polarization time. The apparent changes in crystal structure and crystallite diameter occur during the porous silicon formation, leading to the coexistence of large single crystal, nanocrystalline and amorphous silicon. The crystallite diameter reduces to 0.65 nm from 1.41 nm for the initial growth. The degree of lattice distortion could be contributed to the crystallinity transformation and crystallite diameter variation. © 2017, Editorial Department of Journal of the Chinese Ceramic Society. All right reserved.


Jia Y.H.,Xiamen University | Wu Y.B.,Xiamen University | Huang Y.,Xiamen University | Huang Y.,Fujian Key Laboratory of Advanced Materials | And 3 more authors.
IOP Conference Series: Materials Science and Engineering | Year: 2017

Nano powders with high reflectivity in near-infrared waveband have broad applications as thermal insulation materials. In this study, nano bismuth titanate powders with the reflectance to near-infrared of as high as 89.5% in average were prepared via a sol-gel method by using tetrabutyl titanate, bismuth nitrate as raw materials and citric acid, acetic acid as reaction adjuvant reagents. Furthermore, to control the reflectivity in the visible light waveband, the as-prepared nano bismuth titanate powders were further coated with nano-Ag by using NaBH4 as a reduction agent. The influence of different dispersants on reflectivity and on powder dispersibility has also been studied. SEM characterization demonstrates that PEG1000, worked as a dispersant, significantly enhances the dispersion of bismuth titanate powders comparing with non-dispersant system. UV-Vis-NIR spectra reveal that with addition amount of AgNO3 of 1.5 ml and PEG1000 as the dispersant, the Ag-coated bismuth titanate nano powders can reach about 60% of reflectance to near-infrared, while the reflectance of visible light can be controlled as low as around 14%. It is very promising for such nano powders to be used in thermal insulation glass materials. © Published under licence by IOP Publishing Ltd.


Zhang X.Q.,Xiamen University | Wu Y.P.,Xiamen University | Huang Y.,Xiamen University | Huang Y.,Fujian Key Laboratory of Advanced Materials | And 3 more authors.
IOP Conference Series: Materials Science and Engineering | Year: 2017

Anatase TiO2 nanoparticles with different amounts of fluorine doping were synthesized by a hydrothermal method using hydrogen titanate nanotubes as a precursor and applied as mesoporous layer for preparing perovskite solar cell. The morphology and structures were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), meanwhile, the properties and performances were tested by photoluminescence spectrum (PL) and current density and voltage (J-V) curve. It was found that doping fluorine into TiO2 made the photoelectric conversion efficiency (PCE) of perovskite solar cell (PSC) to be improved. The best PCE of PSC based on a F-doped TiO2 was 13.06% and increased by 51% compared to an un-doped TiO2. The study provided a direction for the exploration of high performance electron transport layer of perovskite solar cell. © Published under licence by IOP Publishing Ltd.


Huang L.,Xiamen University | Huang L.,Fujian Key Laboratory of Advanced Materials | Zhu Z.,Xiamen University | Cheng X.,Xiamen University | And 3 more authors.
Key Engineering Materials | Year: 2017

Rotational rheometer has been widely used in studying rheological properties of materials. However, the conventional rheological measurements may not be applicable for some non-traditional materials with characteristic properties. Polycarbosilane (PCS) is an oligomer and in the form of solid state at room temperature. A large amount of air bubbles are evolved during the heating process of PCS, which is extremely harmful for rheological measurements of PCS melt and detrimentally influences the accuracy of rheological data. In this work, a series of PCS raw samples were pretreated with different heating processes by the advanced rheometric expansion system at 315°C before the rheological measurements at 295°C. The softening point temperatures and molecular weight distributions of different PCS samples were obtained before and after the preheating processes. The experimental data collected with the in-situ preheating and ex-situ preheating for 1 h were compared. © 2017 Trans Tech Publications, Switzerland.


Wu Y.,Xiamen University | Zhou Z.,Xiamen University | Zhou Z.,Fujian Key Laboratory of Advanced Materials | Tuo Y.,Xiamen University | And 3 more authors.
Materials Letters | Year: 2013

Self-assembled BiOI microrings composed of nanoplatelets have been successfully fabricated via a simple hydrothermal method using an oleic acid contained solvent as a reaction medium. For a comparison, only BiOI microplatelets were obtained without oleic acid. Oleic acid acts critically as a trigger for the assembly of microrings through an interaction between carboxylate anion and Bi3+ ion (3COO--Bi3+). The complex (3COO--Bi3+) adsorbed onto the planes of BiOI nuclei, controlling the orientated crystal growth, and the microrings formed through a self-assembly of nanoplatelets. The photocatalytic activity of the obtained BiOI microrings was found to be about 30% higher than that of microplatelets. The novel way may also be extended to preparation of a wide range of self-assembled microrings composed of nanoplatelets. © 2013 Elsevier B.V.


Shao Z.,Xiamen University | Zhang Y.,Xiamen University | Zhang Y.,Fujian Key Laboratory of Advanced Materials | Cheng X.,Xiamen University | Cheng X.,Fujian Key Laboratory of Advanced Materials
Progress in Chemistry | Year: 2014

As a three-dimensional nanoporous material with low density and high porosity, silica aerogel exhibits a low thermal conductivity at room temperature and becomes an ideal nanoporous super thermal insulating material. However, the poor mechanic property and fragment occurred during ambient pressure drying have greatly limited the practical applications of silica aerogel. The apparent enhancements in integrity, strength and flexibility are achieved with the new-type of silica aerogels prepared by compositing or crosslinking, which makes it possible to be applied alone in the form of monolith as thermal insulating materials. In this paper, the porous structures, basic properties and thermal insulation principles of silica aerogels are briefly introduced. The research progress of newly developed fiber reinforced composite silica aerogels, polymer crosslinked silica aerogels, and the other combined silica aerogels as monolithic thermal insulation materials are focused. Finally, the key problems in the field of silica aerogels are summarized and the future research trends are highlighted.


Lu J.-M.,Beijing Institute of Technology | Cheng X.,Xiamen University | Cheng X.,Fujian Key Laboratory of Advanced Materials
Wuli Huaxue Xuebao/ Acta Physico - Chimica Sinica | Year: 2016

The electrochemical responses of heavily doped n-type single-crystal silicon (CSi) during the formation of porous silicon (PSi) layers in hydrofluoric acid-based electrolytes were investigated. A series of PSi layers were fabricated by constantly applying different anodic current densities, which were selected according to the linear polarization curve. The surface and cross-sectional morphologies of the PSi layers were studied by scanning electron microscopy. The electrochemical behavior of CSi and PSi electrodes was compared by linear sweep polarization and chronopotentiometry techniques. The important parameters associated with the electrochemical reactions at the electrodes were evaluated by analyzing the Tafel plots and chronopotentiograms obtained before and after the PSi formation. Structural models of the CSi electrode/electrolyte and PSi electrode/ electrolyte interfaces were suggested based on the experimental data. Accordingly, the interfacial characteristics of CSi and PSi electrodes were discussed. © Editorial office of Acta Physico-Chimica Sinica.


Wu Y.,Xiamen University | Zhou Z.,Xiamen University | Zhou Z.,Fujian Key Laboratory of Advanced Materials | Wang W.,Xiamen University | And 3 more authors.
Materials Letters | Year: 2013

Crystalline-disordered core-shell anatase (La, F)-TiO2 with high photocatalytic activity has been successfully fabricated by (La, F)-codoping via a simple hydrothermal method. The surface disordered shell of the (La, F)-TiO2 nanoparticles is attributed to (La, F)-codoping with La 3+ ions occupying interstitials and F- ions substituting O2- positions in the lattice. The results show that the disordered shell can effectively trap photogenerated holes, therefore, the (La, F)-TiO 2 semiconductors exhibit excellent photocatalytic properties probed by the degradation of methyl orange (MO) under UV irradiation. The strategy employed shows a novel way and can also be extended to other crystalline-disordered core-shell anatase TiO2 systems. © 2013 Elsevier B.V. All rights reserved.


Wang K.,Xiamen University | Huang M.,Xiamen University | Huang Y.,Xiamen University | Huang Y.,Fujian Key Laboratory of Advanced Materials | And 3 more authors.
Materials Science Forum | Year: 2016

Anti-fogging functional coatings have a broad application prospective in the fields of construction and transportation vehicles. In this study, superior water absorbing and anti-fogging coatings were prepared by a cure reaction using epoxy resins as water absorbent resins, hydroxyethyl ethylenediamine as a curing agent, γ-ammonia propyl triethoxy silane as a coupling agent, organic silicon sol as filler. The impact of additional polyethylene glycol (PEG) on the properties of water absorbing and antifogging coating has also been studied. The anti-fogging experiments were conducted in a 40 ℃ water steam bath, and the result shows that the sample with additional 4.0% PEG has an anti-fogging time of 315 seconds (s), which is better than that without PEG (the anti-fogging time being 240s). Infrared spectroscopy and scanning electron microscope structure characterization indicate that the sample with additional PEG has an obvious three-dimensional network structure with hydroxyl groups, which leads to a great saturated water quantity and a superior anti-fogging performance. © 2016 Trans Tech Publications, Switzerland.


Wang D.,Xiamen University | Zhou Z.-H.,Xiamen University | Zhou Z.-H.,Fujian Key Laboratory of Advanced Materials | Yang H.,Xiamen University | And 4 more authors.
Journal of Materials Chemistry | Year: 2012

TiO 2 loaded with crystalline nano silver (c-Ag/TiO 2) was successfully synthesized by a one-step low-temperature hydrothermal method in aqueous solution using tetra-n-butyl titanate and AgNO 3 as precursors. The structure and morphology were characterized by Auger electron spectroscopy (AES), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis absorption spectra (UV-Vis) and fluorescence spectra (FS). The photocatalytic activity was tested with photocatalytic degradation of hydrogen sulfide (H 2S) gas. The results show that the nano silver particles of Ag/TiO 2 prepared by the one-step low-temperature hydrothermal method are crystalline, while they are amorphous when prepared by the conventional UV reduction deposition method (a-Ag/TiO 2). The photocatalytic activity of the c-Ag/TiO 2 prepared by the hydrothermal method was found to have a significant improvement for H 2S degradation, being more than 2 times over that of the a-Ag/TiO 2 prepared by the conventional method. © The Royal Society of Chemistry 2012.

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