Faculty

Publications

Hongmei An, Paul J. McGinn. Catalytic Behavior of Potassium Containing Compounds for Diesel Soot Combustion. Applied Catalysis B, 62:46-56, 2006. view abstract // link Alkali doped oxides were synthesized and tested as catalysts for diesel soot combustion using a combinatorial method. It has been found that potassium shows better promotion of the catalytic activity than other alkali elements, and most of the potassium-rich oxides showed similar catalytic behaviors when catalysts and soot were mixed in a slurry. The influence of different mixing methods, including loose contact, tight contact and slurry (wet) mixing with different soot suspensions, on the catalytic behavior of some transition metal oxides, alkali metal carbonates and potassium-containing oxides were studied through thermogravimetry and XRD. The high activity of potassium-containing catalysts is found to be due to the intimate contact between soot and potassium cations caused by polar solvents. Potassium containing catalysts degraded after repeated thermal cycles due to the loss of potassium. It was also found that the addition of transition elements can inhibit the loss of potassium.

James S. Cooper, Guanghai Zhang, Paul J. McGinn. A plasma sputtering system for deposition of thin film combinatorial libraries. Review of Scientific Instruments, 76:25745, 2005. view abstract // link The design of a plasma sputtering system for the deposition of combinatorial libraries is described. A rotating carousel is used to position shadow masks between the targets and the substrate. Multilayer films are built up by depositing sequentially through various masks. Postdeposition annealing is used to promote interdiffusion of the layered structures. Either discrete or compositional gradient libraries can be deposited in this system. Samples appropriate for characterization with a scanning electrochemical microscope or a multichannel microelectrode array system can be produced. The properties of some deposited Pt–Ru films for fuel cell applications are described.

C. Zhou, P. J. McGinn. The Effect of Oxidation on the Processing of Mesocarbon Microbeads. Carbon, 44:1673-1681, 2006. view abstract // link Mesocarbon microbeads have proved to be an excellent precursor for high-density carbon materials. In this article, the impact of oxidation on carbonization behavior and mechanical property of the graphitized pellets are studied. Thermal analysis shows that the oxidation is the competition between weight gain, due to the incorporation of oxygen into the structure and weight loss caused by the consumed carbon and hydrogen during reaction with oxygen. Thermogravimetry-mass spectroscopy showed that the chemical process associated with the hydrogen release is responsible for the major shrinkage event. On the other hand, the weight loss due to carbon monoxide release dominates the weight loss when microbeads are oxidized at 250 °C or higher. X-ray analysis revealed that oxidation pretreatment inhibits the growth of mesophase structure at temperatures around 450 °C during carbonization. When compacted under pressure higher than 100 MPa, cracks were found in pellets made from original microbeads, while for microbeads oxidized at 150 °C or higher no cracks were discovered after carbonization. The cracks were formed when microbeads had the lowest viscosity, as evidenced in the dilatometry experiments. Fracture toughness of the graphitized pellets decreases continuously with an increase in oxidation temperature, indicating that oxidation should be avoided when maximum fracture property is desired.

James S. Cooper, Paul J. McGinn. Combinatorial Screening of Thin Film Electrocatalysts for a Direct Methanol Fuel Cell Anode. Journal of Power Sources, 163:330-338, 2006. view abstract // link The Pt-Ru-W and Pt-Ru-Co ternary alloy systems were investigated for use as anode catalysts in direct methanol fuel cells. Plasma sputtering through shadow masks was used to deposit discrete composition combinatorial libraries. Post-deposition annealing promoted multilayer homogenization, with interdiffusion of the layers confirmed by X-ray diffraction. The short term methanol oxidation activities of the different compositions were compared in parallel by cyclic voltammetry with a multichannel electrochemical cell. It was found that the optimum composition changed from initial to final tests. Initially Pt25Ru0W75 and Pt17Ru17Co66 outperformed the best binary Pt-Ru catalyst by 3× and 20×, respectively. Cycling the potential at 60 °C was found to change the performance of some compositions. The performance of Pt-Ru binary catalysts were improved by this conditioning and the optimum ternary compositions shifted to Pt44Ru12W44 and Pt12Ru50Co38. The optimum Pt-Ru-W composition had a peak methanol oxidation current density that was 1.5× more than the best Pt-Ru binary composition. The peak methanol oxidation current density of the best Pt-Ru-Co composition was 2.5× more than the best Pt/Ru binary composition and had a substantially lower onset potential.

James S. Cooper, Min Ku Jeon, Paul J. McGinn. Combinatorial screening of ternary Pt-Ni-Cr catalysts for methanol electro-oxidation. Electrochemistry Communications, 10:1545-1547, 2008. view abstract // link Methanol electro-oxidation activity of ternary Pt–Ni–Cr system was studied by using a combinatorial screening method. A Pt–Ni–Cr thin-film library was prepared by sputtering and quickly characterized by a multichannel multielectrode analyzer. Among the 63 different composition thin-film catalysts, Pt28Ni36Cr36 showed the highest methanol electro-oxidation activity and good stability. This new composition was also studied in its powder form by synthesizing and characterizing Pt28Ni36Cr36/C catalyst. In chronoamperometry testing, the Pt28Ni36Cr36/C catalyst exhibited "decay-free" behavior during 600 s operation by keeping its current density up to 97.1% of its peak current density, while the current densities of Pt/C and Pt50Ru50/C catalysts decreased to 14.0% and 60.3% of their peak current densities, respectively. At 600 s operation, current density of the Pt28Ni36Cr36/C catalyst was 23.8 A gnoble metal−1, while that of those of the Pt/C and Pt50Ru50/C catalysts were 2.74 and 18.8 A gnoble metal−1, respectively.

James S. Cooper, Paul J. McGinn. Combinatorial screening of fuel cell cathode catalyst compositions. Applied Surface Science, 254:662-668, 2007. view abstract // link An improved fuel cell cathode catalyst composition was pursued by fabricating and screening thin film combinatorial libraries. Results from the Pt-Ru, Pt-Co-Ti, Pt-Co-Cu and Pt-Co-Cr systems are reported. The discrete composition combinatorial libraries were fabricated by plasma sputtering through shadow masks. Each combinatorial library was tested by cyclic voltammetry in a multichannel electrochemical cell. Compositions were ranked based on the onset potential of the oxygen reduction reaction. Several compositions exhibited better onset potentials than pure Pt. The optimum composition from the Pt-Co-Ti system was Pt44Ti12Co44 but showed signs of corrosion after prolonged testing. A wide range of Pt-Co-Cu compositions also outperformed Pt initially, but ultimately failed due to poor corrosion resistance. Among all of the compositions that were screened, the best performance was demonstrated by Pt28Co36Cr36, with an onset potential 107 mV higher than pure Pt and no sign of corrosion.

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Courses

• CBE 40461 - Structure of Solids - This class seeks to provide students with an understanding of the structure of solids, primarily as found in metals, alloys, and ceramics applied in technological applications. The structure of cry... more >
• CBE 41362 - Laboratory Technology in Materials Science - This course is intended for junior chemical engineering majors who are participating in the materials certificate program. The goal of the course is to introduce students to instrumentation they wi... more >
• CBE 60561 - Structure of Solids - This class seeks to provide students with an understanding of the structure of solids, primarily as found in metals, alloys, and ceramics applied in technological applications. The structure of cry... more >
• CBE 60910 - Selected Topics in Material Processing - This course covers a limited number of materials processing techniques used by materials researchers as well as industrial manufacturers. The primary areas to be covered include thin film processin... more >

Images

Pulsed laser deposition (PLD) system for synthesis of combinatorial libraries