J.M. Hong

Synthesis of K2Ti6O13 whiskers by the method of calcination of KF and TiO2 mixtures

Potassium hexatitanate (K2Ti6O13) whiskers with an average thickness of less than 100 nm were synthesized by calcinating KF and TiO2 mixtures and subsequent boiling water treatment and reheating. The influences of heating temperature and weight ratio of KF to TiO2 in the mixture on the formation of K2Ti6O13 whiskers were investigated. The suitable experiment condition for whisker formation is a weight ratio of KF to TiO2 of about 2:1 and a heating temperature of about 720 degrees C. The resultants of reactions between KF and TiO2 at 720 degrees C were investigated by selected area diffraction (SAD) technique. Some new structures having a monoclinic structure with b = 0.38 nm were found. All these compounds transformed into K2Ti6O13 after boiling water treatment and reheating, (C) 2000 Elsevier Science Ltd.

Synthesis and characterization of rutile TiO2 nanowhiskers

Rutile TiO2, nanowhiskers have been synthesized by annealing a precursor powder in which NaCl and Ti(OH), particles were homogeneously mixed. The precursor powder was prepared by mixing three kinds of inverse microemulsions (mu E) containing TiCl4, aqueous solution, ammonia, and NaCl aqueous solution, respectively, followed by washing with acetone. Annealing temperature and packing density of Ti(OH), in the precursor powder influenced the formation of rutile nanowhiskers. The optimum temperature was 750 degrees C. TiO2, nanowhiskers obtained by annealing a precursor powder in which the molar ratio of sodium to titanium was 400 at 750 degrees C for 2 h had diameters of 10-50 nm and lengths of several micrometers. They were straight rods with square cross sections, and the side surfaces were composed of four equivalent (110) planes.

Phase character and structural anomaly of Bi4Ti3O12 nanoparticles prepared by chemical coprecipitation

Abstract Nanoparticles of Bi4Ti3O12 have been prepared by chemical coprecipitation. The phase structure was investigated by X-ray diffraction (XRD) and refined using the Rietveld method. Orthorhombic Bi4Ti3O12 particles were obtained after heating at 700 and 800 °C; however, for the particles calcined at 500–650 °C, the results suggested the presence of a high-temperature tetragonal phase at room temperature. This structural anomaly was further confirmed by differential thermal analysis (DTA).

Synthesis of cobalt disulfide nanoparticles in polymer matrix

Abstract Amorphous rod-like and needle-like nanoparticles of cobalt disulfide were prepared by the reaction of CoCl2·6H2O with thiourea in the presence of some hydrazine in aqueous solution. The reaction was undertaken in an open reflux system at a relatively low temperature. Polycrystalline cobalt disulfide nanorods were obtained by a similar reaction in an alcohol/water mixed solution. The products were characterized by Fourier transform infrared spectrometer (FTIR), X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The effects of solvent, temperature and time of the reaction on the formation of cobalt disulfide nanocrystalline were discussed. It was found that hydrazine played an important role in shaping rod- or needle-like nanoparticles, and the reflux temperature and time mainly influenced the crystallization of nanoparticles. In addition, the microwave (wavelength λ=3 cm) absorption property of this nanocomposite at room temperature was also investigated.

Synthesis and characterization of K2Ti6O13 whiskers with diameter on nanometer scale

nanjing univ, natl lab solid state microstruct, nanjing 210093, peoples r china. acad sinica, inst met res, atom imaging solids lab, shenyang 110015, peoples r china. nanjing univ, modern anal ctr, nanjing 210093, peoples r china.;li, gl (reprint author), nanjing univ, natl lab solid state microstruct, nanjing 210093, peoples r china

Composition change during bainite transformation in Cu-based shape memory alloys

Abstract In Cu-based shape memory alloys the presence of Zn-depleted regions in the parent phase during the bainitic incubation period is confirmed and the minimum of the Zn content in the region is nearly the same as that in bainite. A shear stress field was found to be present in the growing stage of bainite.