Azlin M. Biaggi-Labiosa

Shape-controlled synthesis of palladium and copper superlattice nanowires for high-stability hydrogen sensors.

For hydrogen sensors built with pure Pd nanowires, the instabilities causing baseline drifting and temperature-driven sensing behavior are limiting factors when working within a wide temperature range. To enhance the material stability, we have developed superlattice-structured palladium and copper nanowires (PdCu NWs) with random-gapped, screw-threaded, and spiral shapes achieved by wet-chemical approaches. The microstructure of the PdCu NWs reveals novel superlattices composed of lattice groups structured by four-atomic layers of alternating Pd and Cu. Sensors built with these modified NWs show significantly reduced baseline drifting and lower critical temperature (259.4 K and 261 K depending on the PdCu structure) for the reverse sensing behavior than those with pure Pd NWs (287 K). Moreover, the response and recovery times of the PdCu NWs sensor were of ~9 and ~7 times faster than for Pd NWs sensors, respectively.

Field Emission and Radial Distribution Function Studies of Fractal-like Amorphous Carbon Nanotips

The short-range order of individual fractal-like amorphous carbon nanotips was investigated by means of energy-filtered electron diffraction in a transmission electron microscope (TEM). The nanostructures were grown in porous silicon substrates in situ within the TEM by the electron beam-induced deposition method. The structure factorS(k) and the reduced radial distribution functionG(r) were calculated. From these calculations a bond angle of 124° was obtained which suggests a distorted graphitic structure. Field emission was obtained from individual nanostructures using two micromanipulators with sub-nanometer positioning resolution. A theoretical three-stage model that accounts for the geometry of the nanostructures provides a value for the field enhancement factor close to the one obtained experimentally from the Fowler-Nordheim law.

The development of micro/nano chemical sensor systems for aerospace applications

Aerospace applications require a range of chemical sensing technologies to monitor conditions related to both space exploration and aeronautic aircraft operations. These applications include leak detection, engine emissions monitoring, fire detection, human health monitoring, and environmental monitoring. This paper discusses efforts to produce microsensor platforms and Smart Sensor Systems that can be tailored to measure a range of chemical species. This technology development ranges from development of base sensor platforms to the evaluation of more mature systems in relevant environments. Although microsensor systems can have a significant impact on aerospace applications, extensive application testing is necessary for their long-term implementation. The introduction of nanomaterials into microsensor platforms has the potential to significantly enable improved sensor performance, but control of those nanostructures is necessary in order to achieve maximum benefits. Examples will be given of microsensor platform technology, Smart Sensor Systems, application testing, and efforts to integrate and control nanostructures into sensor structures.

Nanostructured material sensor processing using microfabrication techniques

Purpose – The development of chemical sensors based on nanostructures, such as nanotubes or nanowires, depends on the capability to reproducibly control the processing of the sensor. Alignment and consistent electrical contact of nanostructures on a microsensor platform is challenging. This can be accomplished using labor‐intensive approaches, specialized processing technology, or growth of nanostructures in situ. However, the use of standard microfabrication techniques for fabricating nanostructured microsensors is problematic. The purpose of this paper is to address this challenge using standard photoresist processing combined with dielectrophoresis.Design/methodology/approach – Nanostructures are suspended in photoresist and aligned between opposing sawtooth electrode patterns using an alternating current (AC) electric field (dielectrophoresis). The use of photoresist processing techniques allow the burying of the nanostructures between layers of metal, thus improving the electrical contact of the nano...

Aircraft Ground Demonstration of Engine Emissions Monitoring System Based on a Gas Microsensor Array

This paper presents a gas microsensor array for monitoring the emissions produced by an aircraft engine. This engine emissions monitoring system, which is intended for on-board engine implementation, includes the capability to measure multiple emission byproducts. The intent is to use this emissions information to assist in assessing the health state of the engine, including the diagnosis of engine deterioration and faults. Results from the application of the system to an aircraft turbofan engine are presented and discussed. This includes both nominal engine operating scenarios and seeded fault scenarios. The system is shown to hold promise for detecting the existence of a simulated oil leak as well as bleed actuator faults. Follow-on maturation plans are also discussed.

Cathodoluminescence of modified porous silicon for field emission displays applications

Intense Cathodoluminescence (CL) emission is obtained for Electron Modified Porous Silicon films when excited with electron beams of kinetic energies below 2KeV, supporting the applicability of such material as light emitter in field emission display devices. Porous Silicon films were irradiated with an electron beam producing a collapsed nanostructure of reduced porosity. The CL intensity from the excited pixels made of such material reduced in less than 10% during a continuous burning of 10 hours. The CL spectra of the films correlate with its photoluminescence showing that the origin of the CL is the quantum confinement effect in the silicon nanoparticles. In situ SIMS analyses before and after prolonged e-beam excitation, as well as of the electron-eroded material from the sample, showed minor compositional changes of the film and reduced sputtering of the silicon nanoparticles due to the electron irradiation. In situ bombardment of the porous material with Hydrogen beams induced changes on the surface passivation of the nanoparticles through which we were able to maximize the CL of the films.