Rodney W. Trice

Research Interests

Development of Processes to Fabricate Complex Shaped Ceramics

We are investigating approaches to fabricate ceramics into complex shapes, building upon our Ceramic Suspension Gel (CeraSGel) technology that was developed at Purdue by Profs. Trice and Youngblood. CeraSGels are a combination of ceramic powder (greater than 50 vol.%), 3-4 wt.% water soluble polymer, water and dispersant.

There are several advantages to forming with CeraSGels. First, no heating or cooling of the CeraSGel is required as it is flowable at room temperature. Second, only a small amount of polymer is required, virtually eliminating defects that can arise due to binder burnout. Third, formed bodies in the green state can be machined very easily as they have sufficient green body strength for handling. Fourth, the stresses applied to the suspensions during forming can be used to align microstructural features. One research thrust in a recently funded Army Research Office (ARO) grant is to aligning b-Si3N4 seeds during injection molding, which in turn will influence the b-Si3N4 grains formed during sintering.

The approach to using CeraSGels to form complex ceramics is to design the rheology of the gel such that it has the requisite properties required for the particular forming process used. For example, the rheology of a CeraSGel suspension for injection molding is different than one used for 3D printing. To date we have formed with CeraSGels of Al2O3, B4C, Si3N4, and ZrB2 powders, however, the process is amenable to any powder system. Another aspect of the ARO grant is the development of complex shaped body armor made from B4C.

We have included several video links showing forming with the CeraSGel process. In the first, an alumina CeraSGel is being injection molded. In the second, an alumina CeraSGel is being 3D printed using a modified syringe style printer.

 3D Printing Video

 Injection Molding Video

Design of High Emissivity Rare-Earth Oxides For Hypersonic Performance Informed by Atomistic Simulations

Hypersonic vehicles require sharp featured nose tips and wing leading edges to reduce drag on the vehicle. However, the geometry of these edges increase the convective heat flow to the surface, ultimately increasing the overall temperature of the component to temperatures as high as 2300 K. The current work sponsored by AFOSR is investigating approaches to reduce the heat the heat flow to these critical components. Further details on this work are available by contacting Prof. Trice.

Effect of Biofuels on Gas Turbine Engines

The gas turbine engine is of utmost importance for generating electrical power and/or thrust in Naval aircraft. The hot sections of gas turbines are typically comprised of superalloy turbine blades, many of which have additional thermal protection provided by a ceramic thermal barrier coating or TBC. Both the superalloy blades and TBC can be attacked by corrosive species found in the fuel and environment. The current fuel for these aircraft is a kerosene-based jet propellant deemed JP8. In aviation gas turbine fuels, the sulfur content is relatively low, e.g., approximately 0.05-0.24 wt%. When combined with sodium, however, sulfur forms corrosive deposits of Na2SO4 that are detrimental to the life of turbine parts.[i] Uncoated metal regions, which often occur where the blade attaches to the platform, are particularly susceptible to Na2SO4 corrosion.  In addition to Na2SO4, Ca-Mg-Al silicates or CMAS can be ingested into the gas turbine from volcanic ash or sandy particulate, and depending on the operation temperature, can melt and infiltrate into a porous coating. Upon cooling the change in compliance of the coating can cause it to spall off. Ultimately, hot corrosion of blades and coatings can result in the loss of engine efficiency and increased downtime for maintenance, which can add substantially to the overall cost to maintain an aircraft. Looking ahead, the Navy roadmap includes a switch to aviation fuels containing a mixture of 50 vol.% biofuels by 2016. This change has the potential to create new challenges for the Navy, particularly with regards for gas turbine applications.

The contaminants found in various biofuels are known to include oxides of alkali and alkaline earth metals including calcium, magnesium, sodium, potassium, along with sulfur, phosphorus and silicon oxides. Furthermore, a recent study on the impurities of biofuel revealed Na and K impurities that can be converted to oxides, sulfates, hydroxides or carbonates. During combustion, an inorganic ash may be left behind. Several important observations can be made based on this list of impurities. First and foremost is that the type of impurity found in the biofuel will be significantly affected by the source of the biomass. Thus, it will be absolutely essential to understand the interplay between the biomass source and impurity type.  Second, while CMAS is typically ingested as particulate in middle-east theaters or from volcanic ash, the impurity list includes the necessary elements to form CMAS without exposure to either of these two environments. This is very significant as CMAS is particularly destructive for operating temperatures above its melting temperature (~1250oC), particularly affecting TBC lifetimes. Third, the presence of low temperature glass formers like P2O5 is disconcerting. The glass transition temperature of P2O5-based glasses can be as low as 400oC, well below the operating temperature of a gas turbine. This has the potential to create many new problems in the gas turbine engine either via interaction with the superalloy or via infiltration of the porous TBC, in a manner similar to that of the CMAS infiltration.

Preparation of Ultra-Low Thermal Conductivity Coatings via Suspension Plasma Spray Using a Deefect Clustering Approach (NSF CMMI-0853297):

The objective of this research is to investigate a novel processing method to produce ultra-low conductivity thermal barrier coatings that would overcome deficiencies of current yttria-stabilized zirconia coatings. Thermal barrier coatings are used in gas turbine engines to thermally protect the superalloy blades in the combustion area, affording hotter, more efficient operating temperatures. Our approach for preparing next generation thermal barrier coatings couples for the first time two newly developed techniques: suspension plasma spray and defect clustering. In suspension plasma spray, nanosized powders are dispersed in ethanol to form a colloidal suspension; the suspension is then sprayed into a hot plasma plume to evaporate the solvent and melt the powder. The second technique, defect clustering, involves doping yttria-stabilized zirconia with paired rare-earth ions (such as ytterbium and neodymium) to create immobile clusters in the plasma-sprayed coating. The presence of these clusters in a thermal barrier coating scatters phonons, reducing coating thermal conductivity by over one-half compared to current yttria-stabilized zirconia-only coatings.

Electrophoretic Deposition of Solid Oxide Fuel Cell Electrolytes

Solid oxide fuel cells (SOFCs) are a promising element of comprehensive energy policies due to their direct mechanism for converting the oxidization of fuel, such as hydrogen, into electrical energy. One emphasis of SOFC research is the development of dense, thin electrolytes in order to reduce internal ohmic loss and facilitate reduced operating temperatures that improve practical SOFC feasibility. Electrophoretic deposition (EPD) is a low cost and expeditious method to attain dense, thin electrolytes, requiring less investment than many competing technologies, such as the varieties of vapor and plasma deposition. At Purdue University, EPD has been used to create yttria -stabilized zirconia (YSZ) electrolytes of <10 µm thickness, which have been used in SOFC’s achieving 900 mW/cm2 power density at 800 °C. This work is performed in collaboration with Prof. Elliott Slamovich.

Current Funding Sources

  • U.S. Army Research Office (Dr. David Stepp Program Manager):  “Fabrication of Complex-Shaped Ceramic Components by Room-Temperature Injection Molding of Ceramic Suspension Gels”

  • Air Force Office of Scientific Research (Dr. Ali Sayir Program Manager ) :  “Design and Assessment of Multifunctional Coatings for Ablation and Emissivity Performance”

  • Rolls-Royce Corporation: "Hot Corrosion Studies of Various High Temperature Materials"

  • Office of Naval Research: "Fundamental Studies on Composition/Performance Correlations for Aviation Fuels"

Select Publications