Study Of The Structure Transformation Of Electrodeposited CoPt And Low Dimensional TiO₂ Materials

Nanostructured materials have potential applications in high technologies and industry due to their novel properties. The control of the structure transformation in the low-dimensional materials is crucial for their practical applications, which requires a basic understanding of the phase transformation of the materials. In the present work, the structural transformations of both electrodeposited CoPt films and low dimensional TiO₂ materials have been investigated by the employment of an x-ray diffractometer (XRD), a transmission electron microscopy (TEM), and a vibration sample magnetometer (VSM).A1+L1₀ nanocomposite CoPt films were prepared by electrodepositon and their microstructure and magnetic behaviors have been investigated. A strong magnetic exchange coupling between the A1 and L1₀ phases is observed after annealing at 650℃for 2.5 h, which yields a large coercivity H_c=14.2 kOe and a high remanence ratio M_r/M_s=0.88 for the nanocomposite films of A1+L1₀ CoPt.Amorphous TiO₂ nanowires with a diameter about 20 nm were prepared by chemical method using the porous anodic alumina templates (PAAT). The free-standing TiO₂ nanowires without PAAT undergo the transformation from anatase to rutile at 600℃, while the phase transition of the amorphous TiO₂ nanowires confined in PAAT occurs at 900℃. The kinetics of the phase transition of anatase TiO₂ nanowires confined in the PAAT was studied by using x-ray diffraction. The confined nanowires show a nucleation energy of En =2.7 eV and a growth energy of Eg=2.8 eV, larger than that of En=1.9 eV and Eg=1.6 eV in amorphous TiO₂ powders. The enhanced structural stability is attributed to the surface suppression of the nucleation.