Nahid Mohajeri

Chemochromic hydrogen detection

Hydrogen is becoming an increasingly important fuel source as fossil fuel supplies decline. The low explosive limit of hydrogen makes leak detection a priority when dealing with this fuel. In an effort to support the use of hydrogen, a chemochromic sensor has been developed which is robust, simple to use, and does not require active operation. It can be made into a thin film or tape which can be conveniently used for leak detection at unions, valves, or outlets. There are two forms of the sensor, a reversible and an irreversible, allowing a variety of applications based on individual situations. The irreversible sensor is useful during hazardous operations when personnel cannot be present, while the reversible is ideal for monitoring the status of a leak in person or via a camera. Testing the irreversible sensor against environmental effects has been completed and results indicate this material is suitable for outdoor use in the harsh beachside environment of Kennedy Space Center. The environmental testing has led to increased sensitivity of the irreversible chemochromic sensor. In an effort to advance this technology further, this chemochromic sensor will be integrated into a sensor system using an electrical or optical signal.

Accelerated Durability Testing of Perfluorosulfonic Acid MEAs for PEMFCs

There is a strong interest in durability studies of proton exchange membrane fuel cells (PEMFC) because, along with cost, the long-term stability of PEMFC is a limiting factor in their commercialization. Examining the characteristics of a membrane electrode assembly (MEA) over a prescribed amount of time under accelerated degradation conditions can give an indication of the degradation behavior of each MEA. Testing under low humidities and/or high temperatures or by humidity or temperature cycling are techniques that accelerate degradation.

Effect of Equivalent Weight of Phosphotungstic Acid-Incorporated Composite Membranes on the High Temperature Operation of PEM Fuel Cells

Fuel cells have shown great promise for future power sources and there has been substantial advancement in the technology of fuel cells over the past decades. For automobile application, however, there are still challenging issues related to its performance and durability. It is highly desirable to operate fuel cells at high temperature because of a number of benefits, e.g., improved reaction kinetics and carbon monoxide tolerance. Since the conventional polymer electrolytes such as Nafion are not stable at high temperatures, the development of novel membranes that are mechanically, thermally, and electrochemically stable at high temperatures while providing good conductivity under low relative humidity condition is one of the most challenging areas of research for automobile applications of fuel cells. In fact, extensive research efforts have been made to design new proton exchange materials that can overcome the limitations of conventional polymer electrolytes.

A review of manufacturing metrology for improved reliability of silicon photovoltaic modules

In this work, the use of manufacturing metrology across the supply chain to improve crystalline silicon (c-Si) photovoltaic (PV) module reliability and durability is addressed. Additionally, an overview and summary of a recent extensive literature survey of relevant measurement techniques aimed at reducing or eliminating the probability of field failures is presented. An assessment of potential gaps is also given, wherein the PV community could benefit from new research and demonstration efforts. This review is divided into three primary areas representing different parts of the c-Si PV supply chain: (1) feedstock production, crystallization and wafering; (2) cell manufacturing; and (3) module manufacturing.

Regeneration of Ammonia-Borane Complex for Hydrogen Storage

At the Florida Solar Energy Center (FSEC), a research program is underway for developing a high-density hydrogen storage system based on amine-borane (AB) complexes. Due to their high hydrogen capacity, these hydrides have been employed, in the past, as disposable hydrogen sources for fuel cell applications. However, to meet the requirements for hydrogen storage onboard vehicles, it is essential that cost effective and energy efficient methods for the regeneration ( i.e. hydrogenation) of the spent (dehydrogenated) AB complexes can be found that utilize only hydrogen and/or electricity ( i.e. the only plausible hydrogen economy energy carriers). We are studying two ammoniaborane (NH 3 BH 3 )-based systems with high hydrogen storage capacity. The first system employs a borazine-cyclotriborazane cycle. Borazine is a product of NH 3 BH 3 thermolysis. Cyclotriborazane is the inorganic analog of cyclohexane. The second system employs polymeric AB complexes such as poly-(aminoborane) and polyborazylene. Poly-(aminoborane), an inorganic analog of polyethylene, is also a product of amoniaborane thermolysis whilepolyborazylene is the product of borazine thermolysis. For the two systems above, we are developing regeneration ( i.e. reduction of borazine, poly-(aminoborane) and polyborazylene) schemes based on: 1) catalytic hydrogenation and 2) indirect (multi-step) synthesis techniques.