This paper describes a simple and convenient procedure for fabricating polycrystalline titania nanofibers with controllable diameter and porous structures. By combining sol-gel technique and electrospinning, nanofibers made of poly(vinyl pyrrolidone) (PVP) and amorphous TiO2 were firstly obtained by electrospinning an ethanol solution containing both PVP and titanium tetraisopropoxide under appropriate high voltages. These nanofibers could be subsequently converted to anatase without changing their morphology via calcination in air at 500°C. The average diameter of these ceramic nanofibers could be controlled in the range from 20 to 200 nm by varying a number of parameters such as the voltage, the feeding rate of the precursor solution, the ratio between PVP and titanium tetraisopropoxide, and their concentrations in the alcohol solution. Titanium tetraisopropoxide could be transferred to titania nanofibers with ~100% yield by using this technique.
Self-assembly as a novel method to prepare ultrathin functional films has drawn more and more attention in recent years. The preparation methods, structure, characterization and NO2 gas sensing properties of polyaniline (PAN) ultrathin films are studied in this paper. Firstly, PAN, bpolyphthalocyanine and polycation were prepared as raw materials for self-assembling PAN ultrathin films. The self- assembled PAN ultrathin flims with polymeric and phthalocyanines were prepared based on doping-induced deposition effect. These films were characterized by UV/visible spectroscopy. The study on self-assembling mechanism show that it is acids that drives the self- assembling process, which is dependent on the PAN solution property, the types of solvents and polymeric acids, the molecular weight of polymers and temperature. At last, the NO2 gas sensing properties is studied in this paper.
Electroactive polyaniline (PANI)/MoO3 nanocomposite ultrathin films were fabricated by a novel molecular self-assembly process based on the alternate deposition of PANI and inorganic polyanion isopolymolybdic acid (IPMA). Unlike the already-used layer-by- layer process based on electrostatic attraction, the process was based on acid-base reaction (or doping) of emeraldine base and IPMA. The process was monitored by UV/Vis spectroscopy and ellipsometry measurement.
This paper describes the effect of electromechanical phase on electrical resistivity of a composite
consisting of magnetostrictive phase, conductive phase and insulating phase. It is found that the
resistance of three-phase composite increases with increase of applied magnetic field beyond a certain
va1e ot magnetic field. This resistivity vs. magnetic field characteric seems to be a novel
magnetoresistance effect, which is different from the conventional magnetoresistors. The mechanism of
resistance variation of three-phase composite with applied magnetic field is analysed, and the influence
of material parameter of the polymer matrix like elastic modulus on the resistance vs. magnetic field
characterics is discussed.
A novel sensing material has been developed for constructing a sensor of solvent vapours using chemical
coupling effect of composite, which is different from conventional electron-moving chemiresistors for
use as gas sensors. The composites consisting of polymer loaded with conductive filler near the
percolation threshold exhibit sensitive characters comparable to that of conventional semiconductor gas
sensor but can be realized with much simpler technology and operated at room temperature. This sensor
can also obtain better selectivity by choosing different polymer matrix. Theoretic analysis and
experimental results show sensitive properties of composite sensor greatly depend on composition of
composite and grain size of conducting particles. In general resistance variation R/Rin the presence of
vapor is more for higher volume fraction offiller and larger grain size of conducting particles.