On 28/7/2019 was discussed the graduate student (doctorate) "Zena Abdul Ameer Salman" on her thesis tagged

“Fabrication of Tri-Metal Oxides Gas Sensors for Medical Applications”

The discussion committee consisted of the following

Abstract

This thesis presents a fabrication of a breath analyzer device based on five gas sensors array to detect NH₃, H₂ and CO gases in human breath that may serve as a diagnostic tool for colonic fermentation, kidney failure, and asthma diseases respectively.

Films were prepared from different tri-metal oxides by using modified chemical spray pyrolysis technique via employed double nozzles. The tungsten salt was used as a basic salt, with four additives, including tin, zinc, iron and chromium salts at three mixing weight ratios of tungsten to additives salts 3:1, 1:1 and 1:3, at molarity 0.1 M using water as a precursors soluble. Then, the solutions were sprayed simultaneously on heated n-silicon substrates, followed by annealing process at 400˚C for one hour.

The produced films are characterized using the following characterization tools: X-ray diffraction was applied to investigate the structural property, and scanning electron microscopy and atomic force microscopy were applied to study the microstructural property. The ultraviolet-visible absorption spectra and Hall Effect measurements were performed to investigate the band gap and the carrier type of thin films. A gas system was used for detecting the gases NH₃, H₂ and CO at concentrations 5, 20, and 5 ppm, respectively to measure the sensitivity and response time of the prepared samples at different operation temperatures of 25, 100, 200 and 300°C in dry air. The calibration was evaluated towards relative humidity H₂O 80% and 500 ppm of CO₂ gas at room temperatures. The XRD results showed that the SnWO₄, ZnWO₄, FeWO₄ tri-metals oxides films grew with different polycrystalline polymorphs. The SEM results revealed the formation of different microstructural morphologies; grainy, porous, micro needles and rods with plane morphology. The sensitivity measurement showed that the highest sensitivity of all sensors was to CO₂, while the lowest response was to NH₃, and the gas sensitivity was improved in the presence of additives. The sensors that have the best gas sensitivity towards H₂, NH₃ and CO were used in the fabrication of the Breath analyzer detector. Breath analyzer detector body was prepared using 3D-printer by linking the sensors with the data acquisition board. A control process was used to transform the gas sensitivity value to a digital signal, where the case of the patient is determined (Normal or Positive) for each disease.

The thesis was evaluated scientifically by Asst. Prof. Dr. Shatha Kazem Abdul Latif / University of Baghdad / College of Engineering Al-Khwarizmi, and linguistically by Asst. Prof. Dr. Samir Ali Amin / University of Technology / Department of Mechanical Engineering.

The discussion took place in the Graduate Hall of Building C / Materials Engineering Department / University of Technology