Synthesis and growth of hematite nanodiscs through a facile hydrothermal approach

This study reports a facile hydrothermal method for the synthesis of monodispersed hematite (α-Fe2O3) nanodiscs under mild conditions. The method has features such as no use of surfactants, no toxic precursors, and no requirements of high-temperature decomposition of iron precursors in non-polar solvents. By this method, α-Fe2O3 nanodiscs were achieved with diameter of 50 ± 10 nm and thickness of ~6.5 nm by the hydrolysis of ferric chloride. The particle characteristics (e.g., shape, size, and distribution) and functional properties (e.g., magnetic and catalytic properties) were investigated by various advanced techniques, including TEM, AFM, XRD, BET, and SQUID. Such nanodiscs were proved to show unique magnetic properties, i.e., superparamagnetic property at a low temperature (e.g., 20 K) but ferromagnetic property at a room temperature (~300 K). They also exhibit low-temperature (<623 K) catalytic activity in CO oxidation because of extremely clean surfaces due to non-involvement of surfactants, compared with those spheres and ellipsoids capped by PVP molecules.

Synthesis of single-crystalline LiFePO4 with rhombus-like morphology

In this investigation, carbon-coated LiFePO4 cathode materials were synthesized with a facile hydrothermal method. The structure and electrochemical properties of the materials were investigated by X-ray diffraction (XRD), Roman, transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS), and electrochemical impedance spectroscopy (EIS). By adjusting the mixing concentration of starting materials, a single-crystalline LiFePO4 with an anisotropic rhombus morphology (Space Group: Pmnb No. 62) were successfully synthesized. In addition, the carbon coated on the surface of LiFePO4 material prepared has a lower ID/IG (0.80), which indicates an optimized carbon structure with an increased amount of sp2-type carbon. Electrochemical performance test shows that the carbon-coated LiFePO4 cathode materials have an initial discharge capacity of 146 mAh g−1 at 0.2C.

Study on LiFe1 − xSmxPO4/C used as cathode materials for lithium-ion batteries with low Sm component

LiFe1 − xSmxPO4/C cathode materials were synthesized though a facile hydrothermal method. Compared with high-temperature solid-phase sintering, the method can allow for the fabrication of low Sm content (2 %), a scarce and expensive rare earth element, while the presence of an optimized carbon coating with large amount of sp2-type carbon sharply increases the material’s electrochemical performance. The high-rate dischargeability at 5 C, as well as the exchange current density, can be increased by 21 and 86 %, respectively, which were attributed to the fine size and the large cell parameter a/c as much. It should be pointed out that the a/c value will be increased for the LiFePO4 Sm-doped papered by both of the two methods, while the mechanism is different: The value c is increased for the front and the value a is decreased for the latter, respectively.

Lithium ferrite (Li0.5Fe2.5O4) nanoparticles as anodes for lithium ion batteries

Li0.5Fe2.5O4 nanoparticles of about 80 nm were synthesized through a hydrothermal method, followed by a solid state reaction between LiOH·H2O and Fe2O3. The Li0.5Fe2.5O4 nanoparticles exhibit a remarkable high capacity (up to 1124 mA h g-1), a good cycle stability (650 mA h g-1 after 50 cycles) and excellent coulombic efficiency. © 2014 the Partner Organisations.

Study on LiFe1 − xSm xPO4/C used as cathode materials for lithium-ion batteries with low Sm component

LiFe1 − xSmxPO4/C cathode materials were synthesized though a facile hydrothermal method. Compared with high-temperature solid-phase sintering, the method can allow for the fabrication of low Sm content (2 %), a scarce and expensive rare earth element, while the presence of an optimized carbon coating with large amount of sp²-type carbon sharply increases the material’s electrochemical performance. The high-rate dischargeability at 5 C, as well as the exchange current density, can be increased by 21 and 86 %, respectively, which were attributed to the fine size and the large cell parameter a/c as much. It should be pointed out that the a/c value will be increased for the LiFePO4 Sm-doped papered by both of the two methods, while the mechanism is different: The value c is increased for the front and the value a is decreased for the latter, respectively.

Hydrangea-like multi-scale carbon hollow submicron spheres with hierarchical pores for high performance supercapacitor electrodes

Uniform hydrangea-like multi-scale carbon hollow submicron spheres (HCSSg) are fabricated by a simple hydrothermal method using glucose as carbon source and fibrous silicon dioxides spheres as shape guide. Structure characterization suggests that petal-like partially graphitized carbon nanosheets with the thickness of about 10 nm arranged in three dimensions (3D) to form the hydrangea-like hollow spheres (size ranging from 250 to 500 nm) with mesoporous channels, which can be conducive to be a high specific surface area (934 m2 g-1) and bulk density (0.87 cm g-3), hierarchical pores structure with good conductivity. As a result, the HCSSg has been demonstrated to be a supercapacitor electrode material with high gravimetric (386 F g-1 at 0.2 A g-1) and outstanding volumetric (335 F cm-3) capacitance, good rate capability and cycling stability with 94% capacitance retention after 5000 cycles in aqueous electrolytes, thus suggesting its application potential.

Effect of manufacturing method and aging environment on painted automotive carbon fibre composite surfaces

In this paper, the effect of various aging environments on the painted surface finish of unidirectional carbon fibre composite laminates, manufactured by autoclave and a novel out-of-autoclave technique was investigated. Laminates were exposed to water immersion, 95 % relative humidity and cyclic environments for 552 h and the surface finish was evaluated using visual and wave-scan distinctness of image (DOI) techniques. It was found that the laminate surface finish was dependent on the amount of moisture in the aging test. Minor surface waviness occurred on the laminates exposed to the cyclic test, whereas, surface waviness, print through and DOI values were all significantly higher as the laminates absorbed larger quantities of moisture from the hygrothermal and hydrothermal tests. The water immersion test, which was the most detrimental to the surface finish of the painted laminates, produced dense blistering on the autoclave manufactured laminate surface whereas the out-of-autoclave laminate surface produced only a few. It was found that the out-of-autoclave laminate had high substrate surface roughness which resulted in improved paint adhesion and, therefore, prevented the formation of surface blistering with aging. © 2012 Springer Science+Business Media Dordrecht.