Computer Simulations of Faceted Nanoparticles and Carbon Nanotubes in Liquid Crystals

The purpose of this research is to investigate the use of liquid crystals (LCs) to manipulate and organize faceted nanoparticles and carbon nanotubes (CNTs). Computer simulations at different levels of detail are used to study these systems. Results from this project will be relevant for potential applications of these systems in displays, nanoscale electronics, electro-optical switches, and in the development of composites with unique mechanical, thermal and/or electronic properties. In this research, two independent but directly related projects were carried out. In the first part of the research, we investigated the torque that develops when faceted nanoparticles, namely cubes and triangular prisms, are immersed in a nematic LC. We used a mesoscale theory in terms of the tensor order parameter Q(r) to model the nematic. Homeotropic anchoring condition of the NLC is imposed on the surfaces of faceted nanoparticles. Our results indicate that, when the particle is oriented at an out-of-plane orientation (i.e. unstable configuration), it moves away immediately from that state and then slowly orients itself back to the stable configuration (i.e. in-plane orientation). The magnitude of the out-of-plane torques is similar to that of in-plane torques. In case of an isolated nanoprism system, the torque reaches maximum when the particle orients with one of its rectangular sides parallel to the far field director n(r). In contrast, the torque of an isolated nanocube system reaches maximum when the particle orients with its four lateral faces parallel to the far field director n(r). In the second part of our research, we investigated the effect of varying the molecular structure and the phase of the LC on the CNTs interactions by performing MD simulations. Our results suggest that increasing the chain length of the hydrophobic tail of the nCB LC molecule decreases the tendency of aggregation for CNTs in nCB LCs. Additionally, varying the phase of the nCB LC is insufficient to decrease the tendency of aggregation for CNTs

Our Primary Goal is to Develop an Efficient and Cost-effective Photobioreactor

"Global climatic conditions have changed by fossil fuel utilization, and this change has serious impact on humankind and nature. The amount of CO2 emitted into the atmosphere has increased by ~ 30% in a decade since 2006. This rise is due to the continued increasing need of fuel. Fossil fuel based global carbon emission, which is the largest contributor of CO2 into the atmosphere (approx. 57%), increased by over 16 times since 1990 [1]. In the 21st century, the planet will become warmer with detrimental environmental effects on our lives, since the global average surface temperature has risen by 0.3 – 0.6 oC (0.5 – 1.1 oF) [2]. For example, Indonesia will move its capital city as its current one is sinking, average wildlife populations have dropped by 60 percent in just over 40 years, and excessive heat exposure contributed to more than 8000 premature deaths in the United States from 1979 to 2003. The major challenge policy makers, government and scientists around the world currently tackle is the global warming issues linked with fossil fuel consumption. Hence, to achieve a healthier and cleaner environment, the priority should be mitigating greenhouse gas (GHG), mainly CO2, and use renewable sources for fuel.

Numerical Simulations of a Postulated Methanol Pool Fire Scenario in a Ventilated Enclosure Using a Coupled FVM-FEM Approach

Numerical investigations have been carried out for a postulated enclosure fire scenario instigated due to methanol pool ignition in a chemical cleaning facility. The pool fire under consideration is radiation-dominated and poses a risk to the nearby objects if appropriate safety requirements are not met. The objective of the current study was to numerically evaluate the postulated fire scenario and provide safety recommendations to prevent/minimize the hazard. To do this, the fire scenario was first modeled using the finite volume method (FVM) based solver to predict the fire characteristics and the resulting changes inside the enclosure. The FDS predicted temperatures were then used as input boundary conditions to conduct a three-dimensional heat transfer analysis using the finite element method (FEM). The coupled FVM–FEM simulation approach enabled detailed three-dimensional conjugate heat transfer analysis. The proposed FVM–FEM coupled approach to analyze the fire dynamics and heat transfer will be helpful to safety engineers in carrying out a more robust and reliable fire risk assessment