Chapters authored
Synthesis Characterization of Nanostructured ZnCo2O4 with High Sensitivity to CO Gas
In this work, nanostructured ZnCo2O4 was synthesized via a microwave-assisted colloidal method, and its application as gas sensor for the detection of CO was studied. Typical diffraction peaks corresponding to the cubic ZnCo2O4 spinel structure were identified at calcination temperature of 500°C by X-ray powder diffraction. A high degree of porosity in the surface of the nanostructured powder of ZnCo2O4 was observed by scanning electron microscopy and transmission electron microscopy, faceted nanoparticles with a pockmarked structure were clearly identified. The estimated average particle size was approximately 75 nm. The formation of ZnCo2O4 material was also confirmed by Raman characterization. Pellets fabricated with nanostructured powder of ZnCo2O4 were tested as sensors using CO gas at different concentrations and temperatures. A high sensitivity value of 305–300 ppm of CO was measured at 300°C, indicating that nanostructured ZnCo2O4 had a high performance in the detection of CO.
Part of the book: Nanostructured Materials
TiO2 Thin Films Produced by Ultrasonic-Agitation Assisted Sol-Gel for Propane Gas Sensor
TiO2 films were deposited by the sol–gel dip coating method assisted by ultra sonic agitation, for their use as propane gas sensors. XRD anlaysis revealed the TiO2 anatase phase for all samples. The film thickness was controlled with the number of the dip-coating immersion cycles, obtaining thicknesses from 10 to 130 nm and a growing rate of 18 nm per immersion. Surface morphology shows that films grow more compact and densely packed as the number of immersion cycles increase. Gas sensing studies indicate that work temperatures above 300°C are needed for sensing activation of the films. Gas sensors sensitivity as a function of propane concentration and film thickness revealed a two-regime behavior: for partial pressures of propane above 400 ppm the sensitivity is not dependent of the film thickness, whereas it is dependent on this parameter at lower partial pressures. Such behavior is attributed to a space charge region and a change in surface structure. For the low concentration regime, the maximum sensitivity was obtained for a film thickness of 110 nm or 5 inmersions.
Part of the book: Thin Films