Smitesh Bakrania

Catalysis of methanol-air mixture using platinum nanoparticles for microscale combustion

High surface area, active catalysts containing dispersed catalytic platinum nanoparticles (dp ∼11.6 nm) on a cordierite substrate were fabricated and characterized using TEM, XRD, and SEM. The catalyst activity was evaluated for methanol oxidation. Experimental results were obtained in a miniature-scale continuous flow reactor. Subsequent studies on the effect of catalyst loading and reactor flow parameters are reported. Repeat tests were performed to assess the stability of the catalyst and the extent of deactivation, if any, that occurred due to restructuring and sintering of the particles. SEM characterization studies performed on the postreaction catalysts following repeat tests at reasonably high operating temperatures (∼500°C corresponding to ∼0.3Tm for bulk platinum) showed evidence of sintering, yet the associated loss of surface area had minimal effect on the overall catalyst activity, as determined from bulk temperature measurements. The potential application of this work for improving catalytic devices including microscale reactors is also briefly discussed.

The Effects of Two Thick Film Deposition Methods on Tin Dioxide Gas Sensor Performance

This work demonstrates the variability in performance between SnO2 thick film gas sensors prepared using two types of film deposition methods. SnO2 powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes were investigated, and a new binder-less deposition procedure was developed and characterized. The binder recipes yielded sensors with poor film uniformity and poor structural integrity, compared to the binder-less deposition method. Sensor performance at a fixed operating temperature of 330 °C for the different film deposition methods was evaluated by exposure to 500 ppm of the target gas carbon monoxide. A consequence of the poor film structure, large variability and poor signal properties were observed with the sensors fabricated using binders. Specifically, the sensors created using the binder recipes yielded sensor responses that varied widely (e.g., S = 5 – 20), often with hysteresis in the sensor signal. Repeatable and high quality performance was observed for the sensors prepared using the binder-less dispersion-drop method with good sensor response upon exposure to 500 ppm CO (S = 4.0) at an operating temperature of 330 °C, low standard deviation to the sensor response (±0.35) and no signal hysteresis.

A study on the influence of rich versus traditional classroom response system (CRS) questions on concept retention

Clickers in classrooms have been shown to increase student engagement. With the emergence of touch-based smart devices, such as iPhones and iPads, there is a move towards migrating the functionality offered by the clickers to these advanced response systems. Apart from being a convenient alternative, do these advanced touch-based devices offer anything new with respect to student learning? For a start, beyond the traditional multiple-choice and true/false responses, these advanced clickers provide several new question modalities that the traditional button-based clickers do not offer. It can be hypothesized that the rich interactions offered by touch-based devices can enhance student engagement even further than the traditional clickers currently do and contribute towards improvements in student learning. To explore this hypothesis, a study was designed to investigate the difference in concept retention among students who use the traditional versus rich classroom response systems (CRS). The study was conducted using a custom-designed iPhone app during an engineering lecture. While no significant difference in retention was evident, several insights were gained in favor of the rich interactions offered by the new CRS. This work highlights the distinct features that make advanced clickers conducive to student engagement and guides future developments in such next generation classroom technologies.

Combustion Synthesis of Fe-Incorporated SnO2 Nanoparticles Using Organometallic Precursor Combination

Synthesis of nanomaterials within flames has been demonstrated as a highly scalable and versatile approach for obtaining a variety of nanoparticles with respect to their chemistry, composition, size, morphology, and dimensionality. Its applicability can be amplified by exploring new material systems and providing further control over the particle characteristics. This study focused on iron-incorporated SnO2 nanoparticles generated using an inverse coflow diffusion flame burner that supported a near-stoichiometric methane-air combustion. A liquid organometallic precursor solution of Sn(CH3)4 and Fe(CO)5 was used to produce 11–14 nm nanocrystalline particles. Synthesized particles were analyzed using TEM, XRD, and XEDS to characterize for size and composition. A flame temperature field was obtained to map particle evolution within the flame. A range of conditions and parameters were studied to specifically generate targeted particles. The study augments related research towards increasing the production potential of combustion synthesis.

A study of fuel and reactor design for platinum nanoparticle catalyzed microreactors

Typical microcombustion-based power devices entail the use of catalyst to sustain combustion in less than millimeter scale channels. This work explores the use of several other candidate fuels for ∼8 nm diameter Pt particle catalyzed combustion within 800 µm channel width cordierite substrates. The results demonstrate while commercial hydrocarbon fuels such as methane, propane, butane, and ethanol can be used to sustain catalytic combustion, room temperature ignition was only observed using methanolair mixtures. Fuels, other than methanol, required preheating at temperatures >200°C, yet repeated catalytic cycling similar to methanol-air mixtures was demonstrated. Subsequently, a new reactor design was investigated to couple with thermoelectric generators. The modified reactor design enabled ignition of methanol-air mixtures at room temperature with the ability to achieve repeat catalytic cycles. Preliminary performance studies achieved a maximum temperature difference ΔT of 55°C with a flow rate of 800 mL/min. While the temperature difference indicates a respectable potential for power generation, reduced exhaust temperature and improved thermal management could significantly enhance the eventual device performance.

CorePal: A standards-based content hub for STEM fields

In an effort to generate and retain student interest in STEM fields, this work focused on providing middle school teachers with resources to engage students using hands-on activities and demonstrations directly related to the state science standards. The project involved generating a library of content for 8th grade physical science standards. The demonstrations and activities were specifically selected to promote interest and engage students, while being easy-to-implement for the teachers. The resources were packaged as a mobile app, called CorePal, to make the content highly accessible. CorePal was designed to allow teachers to track their progress and more importantly serve as a powerful guide to integrate science and engineering activities within their curriculum. Since the project was inspired by feedback from middle school teacher workshops for incorporating hands-on activities in classrooms, local science teachers participated in focus group discussions, workshops and surveys to inform CorePals development. This paper introduces this standards-based hub for middle-school teachers to engage students within the STEM fields. The paper details CorePals design philosophy and development. Initial feedback from teachers is included to provide context for these efforts. Even though the feedback has been positive, success of CorePal rests on its ability to build a collaborative community around it. Upon its launch, CorePal will exist as the only standards-based content tool on a mobile platform.