Preparation And Sensing Properties Of Nanocomposites

This paper aims at preparing gas sensing nanocomposites based on SnO₂ with chemical homogeneous and superior thermal stabiltity compared to single-component oxide using solid state adulteration and two steps sol-precipitation method and testing their sensing properties for detection of toxic and noxious gases.The particle size,morphology,specific surface, composition,thermal and phase stability of the nanocomposites were characterized by means of XRD,TEM,BET,EDS and TG-DTA etc.The effect of synthesis reaction conditions,such as total concentration of metal ions,pH value and compositions of nanocomposites on the performance of gas sensing materials based on SnO₂ was studied in this paper and the optimum parameters have been established.From solid state adulteration method,the nanocomopostion of 10%WO₃-90%SnO₂ nanocomposite exhibited the highest sensitivity and selectivity for NO₂.From two steps sol-precipitation method,the results showed that incorporation WO₃ or MoO₃ as a secondary component enhanced their thermal and phase stability resulting in high sensitivity and selectivity for the detection of NO_x,CO and C₂H₅OH.The sensing properties were dependent on the compositon of nanocomposites,operating and calcination temperatures.The sensing performance was greatly enhanced by the introduction of a small amount of noble metal such as Pd,or MgO,Al₂O₃ oxide coating.The electronic defect in the suface of SnO₂ based nanocrystallite and the sensing effect in nanometer lever as well as electronic interaction between gas and material were discussed by temperature-programmed desorption(TPD), Fourier-transform infrared(FT-IR)spectroscopy and X-ray photoelectron spectroscopy(XPS)analysis.All the above discussion will facilitate understanding the gas sensing mechanism of the SnO₂ based nanocomposite and application of materials for gas sensor.