C. Megaridis - Academia.edu (original) (raw)
Papers by C. Megaridis
Combustion and Flame, 2000
ABSTRACT This experimental investigation analyzes the soot formation effects of oxygen concentrat... more ABSTRACT This experimental investigation analyzes the soot formation effects of oxygen concentration in the oxidizer stream (O2 + N2) ventilating laminar jet nonpremixed methane flames. The base flame incorporates air as the oxidizer; two additional flames, with respective oxygen concentrations of 50% and 100% in the ventilating coflow, are also examined. The microstructure of soot collected from selected flame locations is determined combining thermophoretic sampling and transmission electron microscopy. A laser-light extinction technique is employed along with tomographic inversion to measure the soot volume fraction distributions within the three flames. The results indicate that soot surface growth and oxidation rates in the methane/50% oxygen flame are higher compared to the respective rates in the methane/air base flame. The rate of soot inception becomes stronger with increasing oxygen content in the oxidizer stream. Soot yields diminish with increasing oxygen concentration, as do luminous flame spatial dimensions. Soot aggregate data on the soot annulus suggest a higher degree of agglomeration under oxygen-enriched conditions. Finally, the fractal dimensions of selected soot aggregate samples are measured to be 1.64 (methane/air flame) and 1.65 (methane/50% oxygen flame), being similar to previously published values for carbonaceous soot.
28th Aerospace Sciences Meeting, 1990
A numerical investigation of the fundamental processes governing the energy, mass and momentum ex... more A numerical investigation of the fundamental processes governing the energy, mass and momentum exchanges between the solid, liquid and gas phases of a vaporizing slurry droplet is presented. The configuration studied consists of an isolated slurry droplet containing a single solid particle in its core, and which is vaporizing in a convecting environment. The model allows for independent motion of the solid particle core along the axis of symmetry of the slurry droplet, and it accounts for variable gas-phase properties as well as variable liquid-phase viscosities and latent heat. Additional features of the model include consideration of the surafce blowing effect and droplet surface regression due to vaporization, internal liquid circulation with transient droplet heating, and droplet deceleration with respect to the free flow. The numerical calculation employs an iterative solution procedure that has been successfully used previously for an isolated all-liquid droplet.
The thermal contraction/expansion of an isolated liquid volume inside a closed-end carbon nanotub... more The thermal contraction/expansion of an isolated liquid volume inside a closed-end carbon nanotube is described in terms of high-resolution transmission electron microscope (TEM) observations in real time. The liquid volume is of the order of 1 atto (10^-18) liter. ... Items in iDEA are protected by copyright, with all rights reserved, unless otherwise indicated.
Lab on a Chip, 2014
Inkjet-patterned hydrophilic spots on superhydrophobic paper overlaid with pH indicators to creat... more Inkjet-patterned hydrophilic spots on superhydrophobic paper overlaid with pH indicators to create a point-of-care diagnostic device for droplet sampling at 50 Hz.
Electromagnetic waves in the frequency range of 0.1-10 THz have remained the least explored and d... more Electromagnetic waves in the frequency range of 0.1-10 THz have remained the least explored and developed in the entire spectrum, creating what is widely known as the “Terahertz Gap”. In recent years, THz waves have attracted much attention and continuous interests owning to their prospective applications in many important fields such as astronomy, chemical analysis, biological sensing, imaging and security screening. Among many in-development THz quasi-optical components, THz attenuators, polarizers and filters have been highly demanded in spectroscopy, polarization interferometry, polarimetric detection (e.g. polarization of Cosmic Microwave Background), and other systems. However, conventional methods for realizing the above components usually require complicated microfabrication processes such as photolithography or chemical etching. Therefore, new innovations in materials and processes for cost-effective, and potentially high performance THz quasi-optical components are of imme...
Microscopy and Microanalysis
The opening and filling of carbon nanotubes (CNTs) is of great importance for many applications, ... more The opening and filling of carbon nanotubes (CNTs) is of great importance for many applications, such as electrochemical energy or gas storage systems, biological nanosensors, and nanofludic devices. While filling CNTs can be accomplished by directly sucking liquid or molten materials with capillary force [1] , it is not easy to open the CNTs in a controlled way. Various methods have been developed to open multiwall carbon nanotubes (MWNTs), including chemical treatments with nitric acid or oxidants [2] , thermal treatment by heating in an oxidizing atmosphere [3] and abrasive treatment by rubbing the MWNTs on diamond disks [4]. However, in all these methods the opening only happens at the tips of the MWNTs, and uncontrolled damages to tube walls might occur. There is also no control over the location of the opening on the tube surface. Here we report a new method for opening the side wall of MWNTs by using converged electron beams in a transmission electron microscope (TEM). With this method we can specifically select the positions on nanotubes where we would like to perform the puncture. This is of importance for nanofluidic devices and other applications in which nanotube machining must be done at nanoscale.
The Journal of Undergraduate Research at the University of Illinois at Chicago
Electrospinning is a technique to produce nanofibers more efficiently. In electrospinning, electr... more Electrospinning is a technique to produce nanofibers more efficiently. In electrospinning, electricity spins fibers by extracting the polymer from the solvent and stretching it, all in one continuous electric field. Basics of electrospinning are discussed in sequence from simple homogenous fibers through a single nozzle to heterogeneous core-shell fibers from double, concentric nozzles. Experimental set-up is described and the effect of different variables in the process of electrospinning on nanofiber quality is illustrated. Formation of carbon nanotube fibers with porous walls from polyethylene oxide/polyacrylnitrile (PEO/PAN) core-shell fibers is the definitive objective.Zipped LaTex file
Green Chem., 2016
An environmentally-safe, water-borne coating consisting of titania nanoparticles and fluorine-fre... more An environmentally-safe, water-borne coating consisting of titania nanoparticles and fluorine-free polyethylene copolymers, forming a transparent, substrate-independent, superhydrophobic water barrier.
Interfaces for the 21st Century: New Research Directions in Fluid Mechanics and Materials Science, 2002
Physics of Fluids A: Fluid Dynamics, 1993
This article presents a theoretical study of the deformation of a spherical liquid droplet imping... more This article presents a theoretical study of the deformation of a spherical liquid droplet impinging upon a flat surface. The study accounts for the presence of surface tension during the spreading process. The theoretical model is solved numerically utilizing deforming finite elements and grid generation to simulate accurately the large deformations, as well as the domain nonuniformities characteristic of the
Materials, Nondestructive Evaluation, and Pressure Vessels and Piping, 2006
Interfaces for the 21st Century: New Research Directions in Fluid Mechanics and Materials Science, 2002
Microscale Thermophysical Engineering, 2004
A solution-processable approach in creating gold circuit electrodes with features as fine as 100 ... more A solution-processable approach in creating gold circuit electrodes with features as fine as 100 μm is demonstrated, using a piezoelectrically driven printhead to deposit metallic nanoparticle suspensions. The suspensions consist of gold particles ranging 520 nm in ...
Symposium (International) on Combustion, 1991
Electromagnetic waves in the frequency range of 0.1-10 THz have remained the least explored and d... more Electromagnetic waves in the frequency range of 0.1-10 THz have remained the least explored and developed in the entire spectrum, creating what is widely known as the " Terahertz Gap ". In recent years, THz waves have attracted much attention and continuous interests owning to their prospective applications in many important fields such as astronomy, chemical analysis, biological sensing, imaging and security screening. Among many in-development THz quasi-optical components, THz attenuators, polarizers and filters have been highly demanded in spectroscopy, polarization interferometry, polarimetric detection (e.g. polarization of Cosmic Microwave Background), and other systems. However, conventional methods for realizing the above components usually require complicated microfabrication processes such as photolithography or chemical etching. Therefore, new innovations in materials and processes for cost-effective, and potentially high performance THz quasi-optical components...
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2003
An oscillating-capillary-jet method is presented for the measurement of dynamic surface tension o... more An oscillating-capillary-jet method is presented for the measurement of dynamic surface tension of liquids, and in particular, metal melts, which are susceptible to rapid surface degradation, as caused by adsorption of surface-active elements. The experimental technique captures the evolution of jet swells and necks continuously along the jet-propagation axis, thus adding temporal information to each image. This method is used in conjunction with an existing linear, axisymmetric, constantproperty model to determine the variation of the instability growth rate, and, in turn, surface tension of the liquid as a function of surface age measured from the exit orifice. The conditions investigated focus on a time window of 2-4 ms from the jet orifice. The surface properties of the eutectic 63% Sn-37% Pb solder alloy are investigated in a nitrogen atmosphere containing controlled amounts of oxygen (from 8 to 1000 ppm). The capabilities and advantages, as well as the limitations of the method are discussed in the context of the rapid physical and chemical processes affecting molten-metal capillary-jet instability and break-up.
Polymers for Advanced Technologies, 2009
We report fabrication of thin (100$300 nm) poly(phenylene oxide) (PPO) films and their composites... more We report fabrication of thin (100$300 nm) poly(phenylene oxide) (PPO) films and their composites with poly (styrene) (PS) and silver (Ag) nanoparticles using a one-step electron beam-assisted vapor phase co-deposition technique. Surface morphology and the structure of the deposited polymer thin film composites were characterized by FTIR, Raman, X-ray spectroscopy, and contact angle measurements. As-deposited PPO films and PPO/Ag composites were of porous nature and contrary to solvent casting techniques were free from nodular growth. In the case of PPO/PS thin film polymer composites, however, film morphology displayed nodular growth of PPO with nodule diameters of about $200 nm and height of approximately 50 nm. Unique morphological changes on the porous PPO thin film surface were noticed at different Ag filling ratios. Further, the capacitance of PPO/Ag composites (<16 wt%) were measured under radio-frequency conditions and they were functional up to 100 MHz with an average capacitance density of about 2 nF/cm 2. The fabricated PPO-based composite systems are discussed for their potential applications including embedded capacitor technology.
Combustion and Flame, 2000
ABSTRACT This experimental investigation analyzes the soot formation effects of oxygen concentrat... more ABSTRACT This experimental investigation analyzes the soot formation effects of oxygen concentration in the oxidizer stream (O2 + N2) ventilating laminar jet nonpremixed methane flames. The base flame incorporates air as the oxidizer; two additional flames, with respective oxygen concentrations of 50% and 100% in the ventilating coflow, are also examined. The microstructure of soot collected from selected flame locations is determined combining thermophoretic sampling and transmission electron microscopy. A laser-light extinction technique is employed along with tomographic inversion to measure the soot volume fraction distributions within the three flames. The results indicate that soot surface growth and oxidation rates in the methane/50% oxygen flame are higher compared to the respective rates in the methane/air base flame. The rate of soot inception becomes stronger with increasing oxygen content in the oxidizer stream. Soot yields diminish with increasing oxygen concentration, as do luminous flame spatial dimensions. Soot aggregate data on the soot annulus suggest a higher degree of agglomeration under oxygen-enriched conditions. Finally, the fractal dimensions of selected soot aggregate samples are measured to be 1.64 (methane/air flame) and 1.65 (methane/50% oxygen flame), being similar to previously published values for carbonaceous soot.
28th Aerospace Sciences Meeting, 1990
A numerical investigation of the fundamental processes governing the energy, mass and momentum ex... more A numerical investigation of the fundamental processes governing the energy, mass and momentum exchanges between the solid, liquid and gas phases of a vaporizing slurry droplet is presented. The configuration studied consists of an isolated slurry droplet containing a single solid particle in its core, and which is vaporizing in a convecting environment. The model allows for independent motion of the solid particle core along the axis of symmetry of the slurry droplet, and it accounts for variable gas-phase properties as well as variable liquid-phase viscosities and latent heat. Additional features of the model include consideration of the surafce blowing effect and droplet surface regression due to vaporization, internal liquid circulation with transient droplet heating, and droplet deceleration with respect to the free flow. The numerical calculation employs an iterative solution procedure that has been successfully used previously for an isolated all-liquid droplet.
The thermal contraction/expansion of an isolated liquid volume inside a closed-end carbon nanotub... more The thermal contraction/expansion of an isolated liquid volume inside a closed-end carbon nanotube is described in terms of high-resolution transmission electron microscope (TEM) observations in real time. The liquid volume is of the order of 1 atto (10^-18) liter. ... Items in iDEA are protected by copyright, with all rights reserved, unless otherwise indicated.
Lab on a Chip, 2014
Inkjet-patterned hydrophilic spots on superhydrophobic paper overlaid with pH indicators to creat... more Inkjet-patterned hydrophilic spots on superhydrophobic paper overlaid with pH indicators to create a point-of-care diagnostic device for droplet sampling at 50 Hz.
Electromagnetic waves in the frequency range of 0.1-10 THz have remained the least explored and d... more Electromagnetic waves in the frequency range of 0.1-10 THz have remained the least explored and developed in the entire spectrum, creating what is widely known as the “Terahertz Gap”. In recent years, THz waves have attracted much attention and continuous interests owning to their prospective applications in many important fields such as astronomy, chemical analysis, biological sensing, imaging and security screening. Among many in-development THz quasi-optical components, THz attenuators, polarizers and filters have been highly demanded in spectroscopy, polarization interferometry, polarimetric detection (e.g. polarization of Cosmic Microwave Background), and other systems. However, conventional methods for realizing the above components usually require complicated microfabrication processes such as photolithography or chemical etching. Therefore, new innovations in materials and processes for cost-effective, and potentially high performance THz quasi-optical components are of imme...
Microscopy and Microanalysis
The opening and filling of carbon nanotubes (CNTs) is of great importance for many applications, ... more The opening and filling of carbon nanotubes (CNTs) is of great importance for many applications, such as electrochemical energy or gas storage systems, biological nanosensors, and nanofludic devices. While filling CNTs can be accomplished by directly sucking liquid or molten materials with capillary force [1] , it is not easy to open the CNTs in a controlled way. Various methods have been developed to open multiwall carbon nanotubes (MWNTs), including chemical treatments with nitric acid or oxidants [2] , thermal treatment by heating in an oxidizing atmosphere [3] and abrasive treatment by rubbing the MWNTs on diamond disks [4]. However, in all these methods the opening only happens at the tips of the MWNTs, and uncontrolled damages to tube walls might occur. There is also no control over the location of the opening on the tube surface. Here we report a new method for opening the side wall of MWNTs by using converged electron beams in a transmission electron microscope (TEM). With this method we can specifically select the positions on nanotubes where we would like to perform the puncture. This is of importance for nanofluidic devices and other applications in which nanotube machining must be done at nanoscale.
The Journal of Undergraduate Research at the University of Illinois at Chicago
Electrospinning is a technique to produce nanofibers more efficiently. In electrospinning, electr... more Electrospinning is a technique to produce nanofibers more efficiently. In electrospinning, electricity spins fibers by extracting the polymer from the solvent and stretching it, all in one continuous electric field. Basics of electrospinning are discussed in sequence from simple homogenous fibers through a single nozzle to heterogeneous core-shell fibers from double, concentric nozzles. Experimental set-up is described and the effect of different variables in the process of electrospinning on nanofiber quality is illustrated. Formation of carbon nanotube fibers with porous walls from polyethylene oxide/polyacrylnitrile (PEO/PAN) core-shell fibers is the definitive objective.Zipped LaTex file
Green Chem., 2016
An environmentally-safe, water-borne coating consisting of titania nanoparticles and fluorine-fre... more An environmentally-safe, water-borne coating consisting of titania nanoparticles and fluorine-free polyethylene copolymers, forming a transparent, substrate-independent, superhydrophobic water barrier.
Interfaces for the 21st Century: New Research Directions in Fluid Mechanics and Materials Science, 2002
Physics of Fluids A: Fluid Dynamics, 1993
This article presents a theoretical study of the deformation of a spherical liquid droplet imping... more This article presents a theoretical study of the deformation of a spherical liquid droplet impinging upon a flat surface. The study accounts for the presence of surface tension during the spreading process. The theoretical model is solved numerically utilizing deforming finite elements and grid generation to simulate accurately the large deformations, as well as the domain nonuniformities characteristic of the
Materials, Nondestructive Evaluation, and Pressure Vessels and Piping, 2006
Interfaces for the 21st Century: New Research Directions in Fluid Mechanics and Materials Science, 2002
Microscale Thermophysical Engineering, 2004
A solution-processable approach in creating gold circuit electrodes with features as fine as 100 ... more A solution-processable approach in creating gold circuit electrodes with features as fine as 100 μm is demonstrated, using a piezoelectrically driven printhead to deposit metallic nanoparticle suspensions. The suspensions consist of gold particles ranging 520 nm in ...
Symposium (International) on Combustion, 1991
Electromagnetic waves in the frequency range of 0.1-10 THz have remained the least explored and d... more Electromagnetic waves in the frequency range of 0.1-10 THz have remained the least explored and developed in the entire spectrum, creating what is widely known as the " Terahertz Gap ". In recent years, THz waves have attracted much attention and continuous interests owning to their prospective applications in many important fields such as astronomy, chemical analysis, biological sensing, imaging and security screening. Among many in-development THz quasi-optical components, THz attenuators, polarizers and filters have been highly demanded in spectroscopy, polarization interferometry, polarimetric detection (e.g. polarization of Cosmic Microwave Background), and other systems. However, conventional methods for realizing the above components usually require complicated microfabrication processes such as photolithography or chemical etching. Therefore, new innovations in materials and processes for cost-effective, and potentially high performance THz quasi-optical components...
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2003
An oscillating-capillary-jet method is presented for the measurement of dynamic surface tension o... more An oscillating-capillary-jet method is presented for the measurement of dynamic surface tension of liquids, and in particular, metal melts, which are susceptible to rapid surface degradation, as caused by adsorption of surface-active elements. The experimental technique captures the evolution of jet swells and necks continuously along the jet-propagation axis, thus adding temporal information to each image. This method is used in conjunction with an existing linear, axisymmetric, constantproperty model to determine the variation of the instability growth rate, and, in turn, surface tension of the liquid as a function of surface age measured from the exit orifice. The conditions investigated focus on a time window of 2-4 ms from the jet orifice. The surface properties of the eutectic 63% Sn-37% Pb solder alloy are investigated in a nitrogen atmosphere containing controlled amounts of oxygen (from 8 to 1000 ppm). The capabilities and advantages, as well as the limitations of the method are discussed in the context of the rapid physical and chemical processes affecting molten-metal capillary-jet instability and break-up.
Polymers for Advanced Technologies, 2009
We report fabrication of thin (100$300 nm) poly(phenylene oxide) (PPO) films and their composites... more We report fabrication of thin (100$300 nm) poly(phenylene oxide) (PPO) films and their composites with poly (styrene) (PS) and silver (Ag) nanoparticles using a one-step electron beam-assisted vapor phase co-deposition technique. Surface morphology and the structure of the deposited polymer thin film composites were characterized by FTIR, Raman, X-ray spectroscopy, and contact angle measurements. As-deposited PPO films and PPO/Ag composites were of porous nature and contrary to solvent casting techniques were free from nodular growth. In the case of PPO/PS thin film polymer composites, however, film morphology displayed nodular growth of PPO with nodule diameters of about $200 nm and height of approximately 50 nm. Unique morphological changes on the porous PPO thin film surface were noticed at different Ag filling ratios. Further, the capacitance of PPO/Ag composites (<16 wt%) were measured under radio-frequency conditions and they were functional up to 100 MHz with an average capacitance density of about 2 nF/cm 2. The fabricated PPO-based composite systems are discussed for their potential applications including embedded capacitor technology.