Search results for: Ali Shakouri
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Journal of Electronic Materials > 2019 > 48 > 11 > 7312-7319
Thermoelectric generators directly convert heat into electricity, typically made from bulk solid thermoelectric materials. They are a widely used technology in exhaust gas heat recovery from automotive vehicles or radioisotope power generation in space satellites. We propose a film-laminated device structure for lower cost and higher volume production. The film-laminated thermoelectric generator design...
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SN Applied Sciences > 2019 > 1 > 9 > 1-10
One of the most common methods for determining elastic moduli of rocks is the acoustic velocity log. The elastic moduli of reservoir rocks are widely used in geomechanical modeling, borehole stability analysis, and hydraulic fracture design. In the carbonate reservoirs, the effect of the fluid type on the dynamic elastic modulus under high pressure conditions have rarely been investigated. Carbonate...
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Breakdown processes in polymer dielectrics pose a limitation to energy storage and high-power operation of many electronic devices. These processes have been studied for many decades, and a great deal of progress has been made in developing phenomenological models [1]. Nonetheless, many open questions remain, particularly regarding the development of a single, unified theory to describe all stages...
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Thermal characterization of nano-featured devices is a critical challenge for the development of high performance devices. Although far-field thermoreflectance imaging is limited in spatial resolution by the optical diffraction limit, it is more amenable to absolute temperature calibration of plasmonic devices than existing near-field scanning probe tip methods. We have built an advanced thermoreflectance...
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As the size of electric and optoelectronic devices is reduced to nanoscale, self-heating becomes a major reliability concern. Leveraging designs that could intrinsically remove or reduce the heat and in turn decrease temperature is desirable. In this work, twin nanoscale heater lines with four-probe electrical measurement combined with full-field thermal imaging are used to elucidate the departure...
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Thermoreflectance thermal imaging technique uses light in the visible wavelength range and has a diffraction limit of ∼250nm. Despite that TR is still capable of acquiring temperature signal from devices smaller in size down to ∼3x below diffraction limit. Below diffraction limit, the detected thermoreflectance signal underestimates the true measured temperature by 360%. Image blurring was used in...
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2017 IEEE International Reliability Physics Symposium (IRPS) > 5C-3.1 - 5C-3.7
Thermoreflectance imaging microscopy is demonstrated for pre-breakdown thermal and material analysis of power AlGaN/GaN MOSHEMTs stressed to catastrophic break-down. Optical and thermal images with submicron spatial resolution reveal evolution of self-heating and mechanical degradation on the MOSHEMT gate metal for both the full-ON and full-OFF operating states, with VD up to 155 V. Strong correlation...
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Applied Thermal Engineering > 2017 > 114 > C > 1366-1371
A novel concept using thermoelectric direct power generators (TEGs) integrated into a 1kW scale miniature Brayton cycle is investigated based on an analytical study. The work considers a residential scale application aiming to achieve 40% primary energy efficiency in contrast to the state-of-the-art miniature gas turbine alone, which can only achieve <16%. A topping cycle TEG for a hot gas temperature...
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This paper presents a novel method for obtaining optimized, accurate, and fully calibrated images of the thermal behavior of complex semiconductor devices with submicron features. To thermally analyze the growing number of high power devices, such as microwave amplifiers for wireless mobile applications, a technique is required for high speed transient and high spatial resolution thermal characterization...
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Thermoelectric energy recovery from waste heat in glass melting process is investigated without any detrimental design or process changes. Melting glass pellets require a furnace with temperature over 1500 °C for downstream glass shaping processes and hence a large amount of exergy is available but currently destroyed. Due to high temperature gradients, parasitic losses are investigated in conjunction...
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Extreme Mechanics Letters > 2016 > 9 > Part 3 > 386-396
Crystalline thermoelectric nanowires with well controlled chemical composition, defects and grain structures are desired for their thermoelectric performance. Here, P-type thermoelectric (TE) nanowires, BixSb2−xTe3, are deposited in anodized aluminum oxide (AAO) templates at room temperature by pulsed laser assisted electrochemical deposition (ECD). Evident differences in the ECD processes resulting...
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Transient thermal characterization by thermal imaging in our earlier work demonstrated its ability to extract key information about the thermal response of transistors under operating conditions. We investigate a non-equilibrium response to a short time pulse for very high frequency devices, e.g. hetero-junction bipolar transistors (HBTs). Characterizing high speed thermal signals from devices with...
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Shrinking features and growing device complexity with today's advanced devices has led to increased challenges of gaining a full understanding of device thermal behavior. At the same time, with higher power densities having a full understanding of the device static and dynamic thermal behavior is essential for ensuring optimal tradeoffs between performance and device reliability. Thermal imaging based...
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Shrinking features and growing device complexity with today's advanced devices has led to increased challenges of gaining a full understanding of device thermal behavior. At the same time, with higher power densities having a full understanding of the device static and dynamic thermal behavior is essential for ensuring optimal tradeoffs between performance and device reliability. Thermal imaging based...
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Harvesting heat from the skin surface of humans or homoeothermic animals will provide a great opportunity for implementing wireless communication sensors and/or monitoring devices without the use of batteries. One of the bio-energy harvesting approaches, the thermoelectric generator is a promising candidate for converting the temperature difference between the body skin and the ambient air into electricity...
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To achieve the required performance with high speed switching transistors, the gate feature length in communication devices is as small as a few tens of nanometers in multi finger configurations and transistors are arrayed in a Monolithic Microwave Integrated Circuit (MMIC). The technology therefore, makes thermal characterization more and more difficult. We employ a transient thermal imaging technique...
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Industrial energy consumption represents a large part of the energy flow in the United States and it would probably be similar in many other countries. Coal or gas fired furnaces are a major component of the energy consumption to supply high temperatures. Refractory wall is indispensable along the furnace pathway designed for melting or processing materials. Unfortunately, more than a fraction of...
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Transient thermal response provides rich information about the thermal behavior of advanced transistors and devices. We present the transient thermal modeling and analysis based on an instantaneous thermal imaging technology with transistor level spatial resolution for a high power GaN HEMT. The time responses show the clear separations of sources in temperature rises. At the transistor level or die...
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Computer Applications in Engineering Education > 24 > 3 > 428 - 442
Computational simulations, which are also expert tools, can be used as virtual laboratories for supporting inquiry‐based learning in engineering education. However, little is known of what are effective ways to implement them, particularly for online learning. The purpose of this study is to investigate the effect of computational simulations for student understanding of thermoelectric devices in...
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In this chapter we review recent advances in nanoengineered materials for thermoelectric energy conversion. We start by a brief overview of the fundamental interactions between heat and electricity, i.e., thermoelectric effects. A key requirement to improve the energy conversion efficiency is to increase the Seebeck coefficient (S) and the electrical conductivity (σ ), while reducing the thermal conductivity...
