Showing papers by "Simon S. Park published in 2016"

Thermal conductivity of carbon nanotube and hexagonal boron nitride polymer composites

Abstract: This paper investigates the thermal conductivity of nanocomposites of carbon nanotubes (CNT) and hexagonal boron nitride (hBN) polymer composites using a three-dimensional random walk algorithm and effective medium approach (EMA) method. For CNT nanocomposites, the influence of the orientation of CNTs (semi-aligned and randomly-dispersed) on the thermal conductivity was quantified. For hBN nanocomposites, thermal conductivity values were studied in random dispersion of inclusions. Hybrid nanocomposites containing both hBN and CNT were also investigated using a random walk method and experiments. To verify the calculated thermal conductivities, nanocomposite samples were fabricated. Both the modeling and experimental results showed that the concentration of nanoparticulates (random dispersion) in composites increases thermal conductivity up to 170% and 300% for 13.1 vol% CNT and 6.3 vol% hBN, respectively. It was found that the alignment of CNTs may enhance thermal conductivity of CNT composites. For composites with a 13.1 vol% of CNTs, the increase in thermal conductivity of the semi-aligned composites is approximately 210%. However, for hybrid composites with a 3.1 vol% of CNT/hBN (1.55 vol% each), a 290% increase is observed. At 3.1 vol%, thermal conductivity enhancements are 170% and 250% for single-filled composites of CNT and hBN, respectively.

Hybrid Copper–Silver Conductive Tracks for Enhanced Oxidation Resistance under Flash Light Sintering

Abstract: We developed a simple method to prepare hybrid copper–silver conductive tracks under flash light sintering. The developed metal nanoparticle-based ink is convenient because its preparation process is free of any tedious washing steps. The inks were composed of commercially available copper nanoparticles which were mixed with formic acid, silver nitrate, and diethylene glycol. The role of formic acid is to remove the native copper oxide layer on the surface of the copper nanoparticles. In this way, it facilitates the formation of a silver outer shell on the surface of the copper nanoparticles through a galvanic replacement. In the presence of formic acid, the copper nanoparticles formed copper formate, which was present in the unsintered tracks. However, under illumination by a xenon flash light, the copper formate was then converted to copper. Moreover, the resistance of the copper-only films increased by 6 orders of magnitude when oxidized at high temperatures (∼220 °C). However, addition of silver nitra...

Environmentally friendly preparation of nanoparticle-decorated carbon nanotube or graphene hybrid structures and their potential applications

Abstract: Nanoparticle-modified carbon nanotubes or graphene structures have recently been developed for use in various applications, such as drug delivery systems, biosensors, batteries, energy storage, and nanoelectronics. However, highly hazardous materials may be produced and released during the synthesis reaction and sample preparation of these nanostructures under existing methods. In order to overcome the problem, many scientists are working on the development of environmentally friendly and user-friendly preparation methods for decorating carbon nanostructures with nanomaterials. This review introduces several synthesis strategies that may lead toward more eco-friendly approaches. Potential applications in various fields for nanoparticle-decorated carbon nanotubes or graphene prepared using an environmentally friendly method are also a focus of the article.

Effects of foaming through leaching on the electrical behavior of polystyrene/carbon nanotube composites

Abstract: The aim of this study was to investigate the effects of foaming on the electrical properties of carbon nanotube (CNT)-reinforced polystyrene (PS). A pseudo-three-dimensional (3D) model based on random walk simulation was developed for predicting the electrical properties of CNT nanocomposites. The electromagnetic interference shielding effectiveness (EMI SE) of foamed PS/CNT composites was also studied through a network analyzer, measuring the EMI SE of specimens through reflection and absorption mechanisms. Six types of nanocomposites, including foamed and nonfoamed PS/CNT composites with a CNT loading of 2.1 vol% and different void contents, were manufactured using compression molding and leaching techniques. To realize the effects of foaming on the electrical conductivity of PS/CNT composites, electrochemical impedance spectroscopy analyses were carried out and compared with the pseudo-3D model. We also found that foaming via the leaching method improved the EMI shielding properties of the composites u...

Minimally invasive pseudo-continuous blood glucose monitoring: Results from in-vitro and in-vivo testing of the e-Mosquito

Abstract: This paper presents the eTac, a smart shoe for autonomous blood glucose monitoring (BGM) that aims at replacing finger-pricking tests used by diabetic patients. The device works as the user is walking: an actuator mechanism harnesses natural forces exerted by the user's body weight to drive an electronically-controlled lancet penetrating the skin at the toe tip, and to aid in the extraction of a whole blood sample from subcutaneous capillaries. The blood sample is then collected and blood glucose concentration (BGC) is measured directly from it in-situ. In-vivo human testing results demonstrate the feasibility of the method.

Remediation of contaminated soil and water using enhanced stimulators

Abstract: A contaminated medium (such as soil and/or groundwater) contaminated with petrogenic and/or other organic contaminants such as petroleum hydrocarbons, light non- aqueous phase liquids (NAPLs), dense non-aqueous phase liquids (DNAPLs), persistent organic pollutants (i.e. sulfolane), chlorinated compounds, and volatile organic compounds, can be mixed with enhanced stimulators and be thermally remediated. The enhanced stimulators are heat induced to undergo exothermic reactions, which initiate a series of in-situ chemical reactions to such as to produce hydrogen gas. The hydrogen gas causes hydrocracking of heavy hydrocarbons to produce light hydrocarbons which can be recovered such as for future use.

Electromagnetic wave concentrated heating and heat-activated chemical reactions of enhanced sensitizers for enhanced oil recovery

Abstract: Methods, systems and apparatus for enhanced oil recovery utilizing enhanced sensitizers with chemical blowing agents (CBAs) includes irradiation of electromagnetically activated sensitizers with electromagnetic (EM) waves The injected enhanced sensitizers absorb the energy from EM waves which increases the temperature The elevated temperature then activates chemical blowing agents to aid in fluidity of heavy oil or bitumen extractions The released gases from CBAs also aid in upgrading by releasing desired gases which in turn reduces long hydrocarbon chains at elevated temperature along with catalysts