Nanoporous metals and applications

This dissertation consists of three parts: fabrication of nanoporous metal thin films, study of the dealloying models and Kinetic Monte Carlo simulation and the fabrication of a hydrogen sensor using nanoporous platinum thin films.;In the first part of the dissertation, we reported the fabrication of different metallic nanoporous films by dealloying and studied their structural properties. Nanoporous films are of interest in a wide range of applications such as catalysis, sensing, microfluidic control and filtration. The objective of this study is to synthesize and characterize different nanoporous structures by chemical etching. The experiments were conducted on four different materials: 6-carat white gold leaf, solder wire, imitation Italian gold leaf and sputtered CuPt alloy thin films. The dealloyed CuPt films were coarsened at different temperatures to obtain pore sizes ranging from a few nanometers to tens of nanometers. The porous films have been analyzed by field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDX), and high quality x-ray mapping (XRM). Our experiments resulted in sponge-like Au nanoporous of 10-200 nm, Pb pores of 10-300 nm, and Cu pores of 10-100 nm. The results showed a technically improved fabrication of different nanoporous materials with large surface area and well defined pore morphology.;The second part of the dissertation was the study of various models to explain the evolution of porosity by dealloying and the development of a KMC simulation model to verify experimental results. A KMC model was developed to simulate the dealloying of CuPt in H2SO4 and coarsening of the dealloyed film in vacuum at various temperatures. The output was compared with the experimental results.;The third part of the dissertation was the fabrication of a nanoporous platinum (np-Pt) thin film based hydrogen sensor. A sensor device with four electrodes was fabricated on the np-Pt thin films using a stainless steel mask by sputtering copper. The electrical characteristics of the sensor exhibit marked sensitivity or current changes in the presence of hydrogen. A resistance transient method was used to measure the sensitivity of these thin films in different hydrogen concentrations using air as the carrier gas. The effect of temperature and pore size on the sensitivity and response time were studied. Sensitivity of 3.5% was obtained for 1000ppm of hydrogen at room temperature for the largest fabricated pore size of 35nm. The fabricated sensors showed quick response and repeatability in their sensing mechanism. The results demonstrate that np-Pt thin films configured as a gas sensor have high sensitivity to hydrogen.