Advances in
Nanotechnology
Even though
popular conceptions of nanotechnology are not always clear or
well defined, one thing is certain — it will have a significant
impact on science and technology in the near
future. According to the National Science Foundation, funding
available through its nanotechnology initiative will increase
to more than $1 billion within five years.
Researchers at the URI College of Engineering and beyond are helping drive advances in nanotechnology. Some examples of the nanotechnology research underway at URI include:
Dr. William Euler, professor of chemistry, is working with the Sensors and Surface Technology Partnership to use carbon nanotubes for device applications. In collaboration with scientists from Emitech, Inc., the researchers have fabricated near-infrared photoconductors and electromechanical actuators using carbon nanotubes as the critical, active component. In particular, the actuators rely upon the high-surface area and unique properties of the nanotubes to power devices that work under low voltage and low power conditions. These devices are expected to be used in anti-viion systems or microfluidic applications.
Dr. Arun Shukla, professor of mechanical engineerin
g,
has recently fabricated polyester/TiO2 nanocomposites and has
initiated an investigation to characterize their dynamic fracture
constitutive behavior. A relationship between dynamic stress intensity
factor, KI, and crack tip velocity has been established. As well,
the behavior of the nanocomposites has been compared with that
of the virgin polyester matrix. Fractographic analysis has been
conducted to correlate fracture surface characteristics to experimental
values. Crack propagation velocities in nanocomposites were found
to be 50% greater than those in polyester. Crack-arrest toughness
in the nanocomposites was 60% greater than in polyester.
Dr. Otto Gregory and his research team have developed a nanocomposite coating that has proven to be effective in extending the lifetime and performance of TBCs (thermal barrier coatings). TBCs are used extensively in the aircraft engine and power-generation industry to protect turbine components from the high gas temperatures encountered during operation. TBCs usually employ a bond coat for adhesion and a ceramic overcoat for thermal protection. These coatings are typically applied by thermal spray techniques. However, the difference in thermal expansion between these materials ultimately leads to delamination/decohesion failure at the interface. The metallic bond coat is very rough in the as-sprayed condition, and tends to exaggerate the stresses due to the mismatch in thermal expansion. A nanocomposite coating with an intermediate thermal expansion coefficient was effective in reducing the mismatch between the NiCoCrAlY bond coat and the alumina overcoat. This relatively thin coating effectively reduced the interfacial stresses derived from heating and cooling cycles and substantially increased the thermal fatigue life of TBC’s. The nanometer dimensions of the particles comprising the intermediate coating proved effective in-filling the valleys of the rough conformation at the bond coat / topcoat interface. The thermal fatigue life of TBC’s using this optimized TCE nanocomposite coating was increased by more than a factor of four.
Dr. Arijit Bose is working on “soap-like” molecules, called surfactants, that have a dual characteristic (a part of the molecule likes a solvent, and the other dislikes it). When added to water, these molecules tend to self-assemble into many interesting aggregate morphologies that balance the molecules’ tendency to stay dispersed (entropy) with its penchant for protecting its hydrophobic entities from water (enthalpy). These aggregates are nanometers in dimension, and range from spheres, cylinders, vesicles and liquid crystalline gels. Visualization of these microstructures is essential if they are to be exploited for any applications, yet this is a challenge because of their size (2-100nm), and because any vacuum-based technique will cause solvent evaporation and irreversibly destroy the aggregate. One part of the research is focused on imaging these microstructures using special techniques such cryogenic transmission electron microscopy (see figures) and freeze fracture direct imaging (URI is the second in the world to develop this), as well as light and small angle neutron scattering. Once the microstructures have been determined, they are used as templates for materials synthesis. In particular, the team has looked at a gel phase formed by adding two surfactants into a mixture of oil and water, and discovered that it contains nanochannels of water dispersed along with oil nanochannels. The nanochannel network of aqueous and organic phases has been exploited for templated synthesis of macroporous silica using hydrolysis of tetraethoxysilane and for the formation of polystyrene and polymethylmethacralate by free radical polymerization. SANS has revealed that the surfactant template is robust, being retained during silica synthesis as well as polymerization. The highly viscous aqueous/organic phase for forming nanocomposites where inorganic nanoparticles are homogeneously distributed without agglomeration within a polymer matrix. These materials have several applications, including multifunctional membranes, high-strength transparent coatings, and as drug delivery vehicles.
Dr. Michael Greenfield is leading a research group that is studying how changes in the molecular architecture impact the structure and arrangements of polymer chains and fluid molecules over nanometer length scales, with a particular interest in the effects of small to moderate molecular weight additives. In a project supported by Ford Motor Company, positions of ultraviolet absorber molecules – protective ingredients that prevent automotive paint photodegradation – within nanoscale free volume holes are calculated using a geometric computational analysis of configurations taken from molecular simulations. Preliminary results suggest that subtle differences in chain-UVA nanopacking could exert large effects on macroscale UV absorption efficiency, with implications for the design and selection of UVA/polymer combinations.
future. According to the National Science Foundation, funding
available through its nanotechnology initiative will increase
to more than $1 billion within five years.Researchers at the URI College of Engineering and beyond are helping drive advances in nanotechnology. Some examples of the nanotechnology research underway at URI include:
Dr. William Euler, professor of chemistry, is working with the Sensors and Surface Technology Partnership to use carbon nanotubes for device applications. In collaboration with scientists from Emitech, Inc., the researchers have fabricated near-infrared photoconductors and electromechanical actuators using carbon nanotubes as the critical, active component. In particular, the actuators rely upon the high-surface area and unique properties of the nanotubes to power devices that work under low voltage and low power conditions. These devices are expected to be used in anti-viion systems or microfluidic applications.
Dr. Arun Shukla, professor of mechanical engineerin
g,
has recently fabricated polyester/TiO2 nanocomposites and has
initiated an investigation to characterize their dynamic fracture
constitutive behavior. A relationship between dynamic stress intensity
factor, KI, and crack tip velocity has been established. As well,
the behavior of the nanocomposites has been compared with that
of the virgin polyester matrix. Fractographic analysis has been
conducted to correlate fracture surface characteristics to experimental
values. Crack propagation velocities in nanocomposites were found
to be 50% greater than those in polyester. Crack-arrest toughness
in the nanocomposites was 60% greater than in polyester.Dr. Otto Gregory and his research team have developed a nanocomposite coating that has proven to be effective in extending the lifetime and performance of TBCs (thermal barrier coatings). TBCs are used extensively in the aircraft engine and power-generation industry to protect turbine components from the high gas temperatures encountered during operation. TBCs usually employ a bond coat for adhesion and a ceramic overcoat for thermal protection. These coatings are typically applied by thermal spray techniques. However, the difference in thermal expansion between these materials ultimately leads to delamination/decohesion failure at the interface. The metallic bond coat is very rough in the as-sprayed condition, and tends to exaggerate the stresses due to the mismatch in thermal expansion. A nanocomposite coating with an intermediate thermal expansion coefficient was effective in reducing the mismatch between the NiCoCrAlY bond coat and the alumina overcoat. This relatively thin coating effectively reduced the interfacial stresses derived from heating and cooling cycles and substantially increased the thermal fatigue life of TBC’s. The nanometer dimensions of the particles comprising the intermediate coating proved effective in-filling the valleys of the rough conformation at the bond coat / topcoat interface. The thermal fatigue life of TBC’s using this optimized TCE nanocomposite coating was increased by more than a factor of four.
Dr. Arijit Bose is working on “soap-like” molecules, called surfactants, that have a dual characteristic (a part of the molecule likes a solvent, and the other dislikes it). When added to water, these molecules tend to self-assemble into many interesting aggregate morphologies that balance the molecules’ tendency to stay dispersed (entropy) with its penchant for protecting its hydrophobic entities from water (enthalpy). These aggregates are nanometers in dimension, and range from spheres, cylinders, vesicles and liquid crystalline gels. Visualization of these microstructures is essential if they are to be exploited for any applications, yet this is a challenge because of their size (2-100nm), and because any vacuum-based technique will cause solvent evaporation and irreversibly destroy the aggregate. One part of the research is focused on imaging these microstructures using special techniques such cryogenic transmission electron microscopy (see figures) and freeze fracture direct imaging (URI is the second in the world to develop this), as well as light and small angle neutron scattering. Once the microstructures have been determined, they are used as templates for materials synthesis. In particular, the team has looked at a gel phase formed by adding two surfactants into a mixture of oil and water, and discovered that it contains nanochannels of water dispersed along with oil nanochannels. The nanochannel network of aqueous and organic phases has been exploited for templated synthesis of macroporous silica using hydrolysis of tetraethoxysilane and for the formation of polystyrene and polymethylmethacralate by free radical polymerization. SANS has revealed that the surfactant template is robust, being retained during silica synthesis as well as polymerization. The highly viscous aqueous/organic phase for forming nanocomposites where inorganic nanoparticles are homogeneously distributed without agglomeration within a polymer matrix. These materials have several applications, including multifunctional membranes, high-strength transparent coatings, and as drug delivery vehicles.
Dr. Michael Greenfield is leading a research group that is studying how changes in the molecular architecture impact the structure and arrangements of polymer chains and fluid molecules over nanometer length scales, with a particular interest in the effects of small to moderate molecular weight additives. In a project supported by Ford Motor Company, positions of ultraviolet absorber molecules – protective ingredients that prevent automotive paint photodegradation – within nanoscale free volume holes are calculated using a geometric computational analysis of configurations taken from molecular simulations. Preliminary results suggest that subtle differences in chain-UVA nanopacking could exert large effects on macroscale UV absorption efficiency, with implications for the design and selection of UVA/polymer combinations.