The preparation of electrochromic nickel oxide ( NiO
x
) films, which are
colorless in an as-deposited state, has been carried out in Ar/O2/H2 mixed
gas by the rf-sputtering method. Highly transparent films of as-deposited nickel oxide
could be prepared in the sputtering atmosphere consisting of Ar:O2:H2=50:10:40.
From IR and XPS measurements, the as-deposited films were found to be hydrated and to
have the component of Ni(OH)2. When these films were electrochemically colored,
NiOOH was known to remain in the films. The coloration efficiency of the films at the
wavelength of 633 nm was nearly independent of hydrogen content in sputtering atmosphere
up to 40%, but it depended on sputtering pressure. The maximum value of coloration efficiency
was 36 cm2/C for films prepared at hydrogen content of 40% and total pressure of 8 Pa.
WO3-based semiconductor-type gas sensors were fabricated, and their sensing properties to methylmercaptan (CH3SH) were examined in this study. The Ru loading on WO3 was an effective way of an increase in the CH3SH response. In addition, the CH3SH response increased with a decrease in the operating temperature as well as with an increase in the thickness of the Ru-loaded WO3 sensing layer. The increase in the porosity of the Ru-loaded WO3 sensors, which were fabricated by utilizing polymethylmethacrylate microspheres as a template, was also effective in improving the CH3SH response, especially at a low temperature of 150°C. In addition, the lamination of the Ru-loaded WO3 sensor with an α-Al2O3 film improved the CH3SH response at 200°C. Moreover, the Ru loading on the WO3 powder increased the catalytic activities of CH3SH oxidation, and CH3SH was partially oxidized to CH3SSCH3 at temperatures less than 330°C. It was suggested that the increase in the positively charged adsorption of the partially oxidized products onto the bottom part of the sensing layer is effective for enhancing the CH3SH response, especially at lower operating temperatures.
Department of Mining Engineering, and NIT Rourkela who gave me the golden opportunity to do this wonderful project on the topic "Real Time Monitoring System for Mine Safety using Wireless Sensor Network (Multi-Gas Detector)". I find words inadequate to thank him for his encouragement and valuable suggestions during the course of this work. I am also grateful to all faculty members and staff of Mining Department, NIT Rourkela. I express my special thanks to Mr. H. K. Naik, HOD, Department of Mining Engineering for their assistance. I would take the opportunity to thank my friends for helping me in conduction of experiment. I acknowledge my indebtedness to all of them whose works have been referred in understanding and completion of this project.I also thank to all my well-wishers who have patiently extended all sorts of help and moral support for accomplishing this dissertation.
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