The TMA-sensitive Performance Of Titanium Dioxide Nanocrystal Material

According to the theory of meso-physics, the property of substance is not only depending on its composition and structure but also depending on its particle size and outline of particle surface. A nanocrystalline material is formed with nano-meter sized particles and can just be described with this theory. The particles in nanocrystalline material have the size of about 1nm to 100nm, and as a result several new effects, such as micro-sized effect, quantum-size effect and macro-quantum tunnelling effect, were discovered.Those effects in turn brings out different characteristics on mechanics, thermodynamics, electricity and chemistry.Those new characteristics have found wind applications in many fields.Therefore from the moment of its appearance , nanocrystalline material had been attracting more and more attentions of scientists on it.The raw powders of two different crystalline TiO2 nanocrystals were synthesized by stearic acid-gel method. Differential thermal analysis-thermogravimetry (DTA-TG),X-ray diffraction (XRD),XPS were used to characterize the synthesis progress and the structure,composition and surface morphology of TiO2 nanocrystals..The results of DTA-TG and XRD indicated that the crystal forms of TiO2 and would gradually change from anatase to rutile with the calcining temperature increasing and calcining time lengthening when the calcining temperature was over 550℃. At the same time the relative content of anatase and rutile can be determined by the intensity of main peak in TiO2 XRD patterns. In these experiments the author also produced trimethylamine gas (TMA) and an Ag/TiO2-sensitive material, with which as the raw material the author further constructed a TMA-sensitive element. The initial performance tests were carried out and the result showed that this Ag/TiO2 element has a good TMA sensitivity when it contains 5% of Ag.Some further tests reveal that with trimethylamine gas concentration of 250 ppm the optimum working current is 135mA, under which this element gives the highest sensitivity and the sensitivity increases with the concentration until the concentration reaches 2000 ppm when the sensitivity becomes constant.