Investigation On The Gas Sensing Properties And Applications Of Nano-ZnO Based Composite Ceramic Thick Films

ZnO nanoparticles have been adopted as the basic gas-sensing materials, it was studied on the effect of doping techniques, such as various doping materials(V2O5 & WO3),doping contents(1 wt%,5 wt%,10 wt%,30 wt%)and sintering temperatures(450℃,650℃,850℃), to ZnO based composite materials'forming, especially on the effect of high doping content to fabricating multiplex composite gas-sensing ceramics. Then some experimental phenomena about resistance and gas sensing properties were clarified combining with materials'microstructure analyzing (XRD& FESEM) and related theories. At last the practicability of nanosized ZnO based thick-film sensing components for detecting concomitant smells when PVC heated was discussed, and their testing ability were evaluated through repetitious experiments.For the adoption of highly surface activation about ZnO nanoparticles, the transformative temperature of liquid curve in ZnO—V2O5 was falled. So liquid phase participated in solid phase sintering, which made the phase ingredients more complex after sintering. Series phases ZnxVyOz, with the representative Zn3(VO4)2, increased their resistance in air and went against their gas sensing properties. Well gas sensing properties of Zn-V-O composite ceramics was ensured by light doping content with 1 wt% and low temperature sintering with 450℃.Comparing to pure nano-ZnO for Zn-W-O composite nanoparticles, it was found that the sensitivity of the multiphase materials shaped by doping the highest content (30 wt%) and low temperature sintering (450℃) to ethanol and benzene was enhanced up to 6 and 4 multiples separately. Subsidiary phases in the composite ceramics played positive actions. Then sensing mechanism enhancing the sensitivity remarkably was proposed as the physical function of bridge contacting caused by WO3's sublimation and condensation, and the chemical action of interactive catalysis caused by the acid cores and alkali cores between WO3 and ZnO. In addition, multiplex phases were transformed in polar WO3 by doping techniques'influencing, which made electrical instability of Zn-W-O composite ceramics and impacted the gas sensing properties thereby.Experiment of detecting associated smells by heating polyvinyl chloride (PVC) with Zn-W-O gas sensing components, exploited the application domains of composite gas sensing ceramics. It was revealed that, thick-film gas sensing components with low doping content and high temperature sintering possessed better coherence comparatively. Referring to the values of standard deviation and relative error as the evaluating parameters, the detectability of gas sensing components was analyzed via 30 times repetitious experimental data.