Research

Seal’s group has been at the forefront of exploring the redox active nature, auto-regenerative, radical scavenging properties and the valence structure of the rare earth cerium oxide when it is present in the nanocrystalline form. By scavenging of the excess reactive oxygen species, these cerium oxide nanoparticle (also called as nanoceria as they are synthesized in the size range of 3-5nm), are able to eliminate the oxidative stress and balancing the cellular oxidative environment and making it more homogenous. In a similar direction, the group has conjugated the highly antioxidative nanoceria with a variety of biomolecules towards its biomedical application. In a similar study, this nanoceria is conjugated it with a small RNA molecule, also known as microRNA molecules which have been to find to play a significant role in regulating the inflammatory response. All together these conjugates have been used towards the diabetic wound healing. The conjugate helps to decrease the inflammation and the oxidative stress resulting in the correction of impaired healing and overall improving the biomechanical properties of healed skin.

Seal’s group further interests are also in the development of nanoceria based anti-inflammatory coatings and its successive application in the development of upcoming prosthetics.

Durip ONR Plasma NanoManufacturing Lab The thermal spray laboratory at UCF houses the state-of-the-art coating and bulk component development facility comprising Plasma and HVOF spray modules. The laboratory is well equipped to develop coatings from ceramic, metallic particles (both micro and nano-size ranges) and solution precursors with applications spanning from corrosion-wearoxidation resistant, a thermal barrier to thermal protection. The laboratory also has the expertise to manufacture bulk nanostructured composites with simple to complex geometries with considerable ease than other processing techniques. Depending on the material and coating/ bulk component properties, the torch and spray parameter combination is chosen from the thermal spray infrastructure. Using a range of plasma spray torches 3 MB (40 kW), 9 MB (80 kW), F4 (60 kW), SG100 torches, the high melting point materials could be processed. HVOF torches (Jet Kote) is useful to shoot the metallic particles at high velocities thereby high dense overlay coatings could be achieved on desired substrates. The torches are mounted on a six-axis robot that could carry the torch to virtually any location in the booth precisely to perform the coating process precisely. Sensors (DPV, Acura Spray, Spray Watch) are available to determine the velocity and temperature of particles during the spray process that can be used to correlate the spray parameters to the particle states and thereby the properties of the end application. Powder feeders (1264 Praxair model and DJ 9MP) and mass flow controllers are available for precise monitoring of the feed rates of powders and gases respectively. Spray drying equipment is available to prepare nano-feedstock powders for effective and safe handling of nanopowders for coatings and components for thermal, catalytic, biomedical and energy applications.

A few examples of our work:

High-Temperature Oxidation Resistance coating using solution precursor plasma spray: Solution precursor plasma spray (SPPS) is used to deposit nanoceria coating on steels. In-house material characterization facility is available to study the microstructure and the surface chemistry using thermodynamic calculations, X-ray photoelectron spectroscopy (XPS), TEM, SEM, FIB, RAMAN, and XRD. Cyclic oxidation at 10000C revealed excellent corrosion resistance of the steel in presence of the SPPS-processed nanoceria coating.

Spray drying of nano alumina and ceramic particles to facilitate plasma spray: Spray drying has been successfully utilized to agglomerate the nanoparticles to facilitate the handling and uniform melting of the agglomerates during the spray. The process variables could be optimized to achieve narrow size agglomerates with a mean size of 25 μm that could be easily fed through the plasma torch and achieve a nanostructured coating. The spray could be optimized to achieve agglomerates of any nanoparticles that have virtual merits with retained nanostructures in the final coating from the point of view wear resistance, high thermal cycles to failure and low thermal conductivity.

Bulk Nanocomposites: Freeform bulk nanocomposites with ceramic and metal matrices with complex geometries have been developed that requires no machining. Some of the properties that have been achieved are high-temperature oxidation resistance using MoSi2-Si3N4, high elastic modulus using W-HfC, high fracture toughness (5 MPa.m1/2) Ni-Alumina, increase ductility in nano-micro alumina, high fracture toughness Carbon nanotube-Alumina, TaC composites, Al-Si alloys, and nano Al-Si components and many others for a variety of high temperature and aerospace applications.

Nanostructure Sensor System for Chemical and Biological Detection We are exploring the chemical-resistance properties of semiconductor oxides for developing gas sensor by integrating into a MEMS device. Our devices are highly sensitive and selective and can operate in low temperature and high humid conditions. Detailed material characterization is performed to understand the surfaces of these nanosensors. We are also developing bio-sensors, where the redox property of nanocrystalline cerium oxide is utilized to detect and measure the production of hydrogen peroxide in the biological environment. This has implication in detecting ROS in various neurodegenerative, cardiac, and metabolic disorders. Research is focused on the surface modification of these nanocrystalline detection elements to prevent sensor ‘bio-fouling’ through protein deposition.

Using the ordered nature and affinity of bio-molecule pairings, technologies are being produced to identify and quantify disease biomarkers in a number of biological systems/models. Device platforms rely on the highly selective and sensitive binding between protein/bio-molecules and specific aptamers or antibodies modified nanomaterials. These platforms are currently being integrated into multi-channel, multiplexed devices (e.g. micro-fluidic, organic electrochemical transistors) to analyze complex bio-media: allowing concurrent, real-time measurements of different analytes from low sample volumes.

High Temperature Corrosion High temperature and high pressure (HT/HP) corrosion test setup have been designed within situ electrochemical impedance spectroscopy (EIS) capability. The cell can be operated at high pressure (20000 Psi) and high temperature (300 oF) in corrosive conditions, which provides important corrosion information of various steels and materials in HT/HP conditions useful to oil and gas industries.

Atomistic Simulation We have revealed novel radiation-sensitive properties of ceria nanoparticles. To understand this, the group is working out an atomistic simulation to understand the interaction of radiation-induced changes in nanocrystalline cerium oxide. Various lattice models are created for cerium oxide and study the effect of radiation by carrying out molecular dynamics simulation. The simulation study is underway in collaboration with the team at Pacific Northwest National Lab. (International partners: Cranfield University)