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Hydrothermal Route (hydrothermal + route)
Selected AbstractsControlled Synthesis of Cobalt Flowerlike Architectures by a Facile Hydrothermal RouteEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2008Ya-jing Zhang Abstract Cobalt flowerlike architectures composed of hexagonal nanoplatelets have been synthesized by a simple hydrothermal reduction method. The architectures are fabricated by the reaction of CoCl2 with NaOH at 140,180 °C in the presence of sodium dodecyl benzenesulfonate (SDBS), with NaH2PO2·H2O as reducing agent. The diameters of the flowers range from 8 to 10 ,m, and the average thickness of the hexagonal sheets is about 100 nm. Higher reaction temperatures and the proper concentration of sodium hydroxide (NaOH) are key requirements for the fabrication of the flowerlike architectures. A growth mechanism for these architectures is proposed on the basis of the characterization by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The magnetic hysteresis loops at 5 K and 295 K of the cobalt flowerlike architectures show ferromagnetic characteristics with coercivities of 371 Oe and 197 Oe, respectively. Our work may shed light on the designed fabrication of complex 3D architectures of other materials.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Hydrothermal Route for Cutting Graphene Sheets into Blue-Luminescent Graphene Quantum DotsADVANCED MATERIALS, Issue 6 2010Dengyu Pan Water-soluble graphene quantum dots (GQDs, ca. 10 nm in diameter) that exhibit bright blue photoluminescence (PL) are prepared by hydrothermal (chemical) cutting of oxidized graphene sheets (see figure). The mechanisms of the cutting and luminescence are discussed. This discovery of PL of GQDs may extend the range of application of graphene-based materials to optoelectronics and biological labeling. [source] Morphogenesis and Crystallization of ZnS Microspheres by a Soft Template-Assisted Hydrothermal Route: Synthesis, Growth Mechanism, and Oxygen SensitivityCHEMISTRY - AN ASIAN JOURNAL, Issue 1 2009Liangbao Yang Abstract Almost monodisperse ZnS microspheres have been synthesized on a large scale by a hydrothermal route, in which tungstosilicate acid (TSA) was used as a soft template. By controlling the reaction conditions, such as reaction temperature, pH value of the solutions, and the reaction medium, almost monodisperse microspheres can be synthesized. The structure of these microspheres is sensitive to the reaction conditions. The growth mechanism of these nearly monodisperse microspheres was examined. Oxygen sensing is realized from ZnS microspheres. The current through the ZnS microspheres under UV illumination increases as the oxygen concentration decreases. [source] Magnetic-Field-Induced Phase-Selective Synthesis of Ferrosulfide Microrods by a Hydrothermal Process: Microstructure Control and Magnetic Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2006Z. He Abstract Microrods of the ferrosulfide minerals greigite (Fe3S4) and marcasite (FeS2) are selectively synthesized by an in,situ magnetic-field-assisted hydrothermal route. Each complex microrod is composed of fine building blocks with different shapes. The unique magnetic properties of the microrods and electrical performance of a single microrod are studied. The results demonstrate that the magnetic properties of the ferrosulfide minerals are strongly related to their corresponding microstructures. The value of the low-temperature transition increases as the greigite component in the product decreases. The combination of small-molecule sulfur precursors and an applied magnetic field makes possible the selective synthesis of ferrosulfide minerals with different phases and distinct microstructures, underlining the fact that the magnetic field can be a useful tool as well as an independent parameter for the phase-selective synthesis and self-assembly of inorganic building blocks in solution chemistry. [source] Hydrothermal Synthesis and Spark Plasma Sintering of (K, Na)NbO3 Lead-Free PiezoceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Nan Liu A facile hydrothermal route was adopted for synthesis of lead-free piezoceramics (K, Na)NbO3 powders. The influences of temperature and KOH/NaOH concentration on the resultant powders were investigated. Although two similar perovskite phases appeared when K/Na ratio tended toward 1:1, the two-phase coexistence tendency was weakened by increasing hydrothermal reaction temperature, and consequently only one phase could be obtained after spark plasma sintering. Reasonably good ferroelectric and piezoelectric properties were obtained for the samples after postannealing, whose piezoelectric constant (d33) reached 135 pC/N. The optimal remnant polarization (Pr) and mechanical quality factor (Qm) were 26.2 ,C/cm2 and 164, respectively, which were both twice as much as those of the samples using powders prepared from solid-state reaction. [source] Synthesis and Mechanism of Ferroelectric Potassium Tantalate Niobate Nanoparticles by the Solvothermal and Hydrothermal ProcessesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007Nian Wei High-purity KTa0.3Nb0.7O3 nanoparticles have been successfully synthesized by hydrothermal and solvothermal methods. The KOH concentration and the solvent composition have significant effects on the final products. The synthesis mechanism was discussed. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy investigations show that the typical samples solvothermally synthesized are nanosized, well crystallized, and single crystalline. The KTa0.3Nb0.7O3 shows a pseudo-cubic to tetragonal transition with increasing crystallite size. It is believed that supercritical isopropanol plays an important role in synthesizing KTa0.3Nb0.7O3 nanoparticles under milder conditions than the hydrothermal route. The present solvothermal method provides a new potential route for synthesizing ferroelectric potassium tantalate niobate material. [source] Morphogenesis and Crystallization of ZnS Microspheres by a Soft Template-Assisted Hydrothermal Route: Synthesis, Growth Mechanism, and Oxygen SensitivityCHEMISTRY - AN ASIAN JOURNAL, Issue 1 2009Liangbao Yang Abstract Almost monodisperse ZnS microspheres have been synthesized on a large scale by a hydrothermal route, in which tungstosilicate acid (TSA) was used as a soft template. By controlling the reaction conditions, such as reaction temperature, pH value of the solutions, and the reaction medium, almost monodisperse microspheres can be synthesized. The structure of these microspheres is sensitive to the reaction conditions. The growth mechanism of these nearly monodisperse microspheres was examined. Oxygen sensing is realized from ZnS microspheres. The current through the ZnS microspheres under UV illumination increases as the oxygen concentration decreases. [source] Morphology-Dependent Gas-Sensing Properties of ZnO Nanostructures for ChlorophenolCHEMISTRY - AN ASIAN JOURNAL, Issue 8 2010Zhipeng Li Abstract The crystal-plane effect of ZnO nanostructures on the toxic 2-chlorophenol gas-sensing properties was examined. Three kinds of single-crystalline ZnO nanostructures including nanoawls, nanorods, and nanodisks were synthesized by using different capping agents via simple hydrothermal routes. Different crystal surfaces were expected for these ZnO nanostructures. The sensing tests results showed that ZnO nanodisks exhibited the greatest sensitivity for the detection of toxic 2-chlorophenol. The results revealed that the sensitivity of these ZnO samples was heavily dependent on their exposed surfaces. The polar (0001) planes were most reactive and could be considered as the critical factor for the gas-sensing performance. In addition, calculations using density functional theory were employed to simulate the gas-sensing reaction involving surface reconstruction and charge transfer both of which result in the change of electronic conductance of ZnO. [source] | |||||||||||||