Montana State University

Paul S. Gentile, PhD, PE

Mechanical and Industrial Engineering Department
P.O. Box 173800
Bozeman, MT 59717-3800

Tel: (406) 994-2680
Fax: (406) 994-6292
Office: ROBH 112

paul.gentile@me.montana.edu

Paul S. Gentile, PhD, PE

Research Interests

Mechanical engineering and materials science research interests: nano-engineered materials for energy applications, electro-chemical conversion, high resolution imaging & spectroscopy, thermodynamic modeling and numerical methods. Teaching initiatives: problem based learning, interactive classroom, systems based approach and international engineering education.

Analytical Techniques:

Analytical and design techniques: MATLAB, computer aided drafting (CAD), finite element analysis (FEA), , thermodynamic equilibrium modeling, field emission microscopy (FEM), elemental mapping, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), mass spectroscopy, thermal gravimetric analysis, dilatometry, and electro-chemical performance testing.

Consulting Interests

Professional engineering consultation interests include combined heat and power plants, gasification, responsible use of natural gas in lieu of flaring, and recovery of waste bio-products for stationary and portable applications.

Professional Publications

Intl J of Appl Ceram Tech

[1] Paul S. Gentile, Stephen W. Sofie, Camas F. Key and Richard J. Smith, "Silicon Volatility from Alumina and Aluminosilicates under Solid Oxide Fuel Cell Operating Conditions ," Int. J. Appl. Ceram. Technol. (October 2011).

Abstract

Thermodynamic equilibrium modeling indicates the introduction of H2O in oxidizing environments decreases Si stability due to formation of volatile hydroxide and oxy hydroxides.  3Al2O3·2SiO2 bond offers only a slight improvement on silicon stability over SiO2 in humidified oxidizing environments.  In reducing atmospheres Si stability is improved by the presence of H2O and Al2O3, transitioning from SiO and silane as the dominant volatile species to hydroxides, oxy hydroxides and SiO with increasing water vapor partial pressure.  Transpiration, thermal gravimetric and dilatometry studies reveal initial rapid releases of Si from SOFC refractory materials followed by slower solid state diffusion limited release.  

Journal of Power Sources

[2] Paul S. Gentile and Stephen W. Sofie, "Investigation of Aluminosilicate as a Solid Oxide Fuel Cell Refractory," J. Power Sources, 196 [10] 4545-4554 (May 2011).

Abstract

Aluminosilicate represents a potential low cost alternative to alumina for solid oxide fuel cell (SOFC) refractory applications. The objectives of this investigation are to study: (1) changes of aluminosilicate chemistry and morphology under SOFC conditions, (2) deposition of aluminosilicate vapors on yttria stabilized zirconia (YSZ) and nickel, and (3) effects of aluminosilicate vapors on SOFC electrochemical performance. Thermal treatment of aluminosilicate under high temperature SOFC conditions is shown to result in increased mullite concentrations at the surface due to diffusion of silicon from the bulk. Water vapor accelerates the rate of surface diffusion resulting in a more uniform distribution of silicon. The high temperature condensation of volatile gases released from aluminosilicate preferentially deposit on YSZ rather than nickel. Silicon vapor deposited on YSZ consists primarily of aluminum rich clusters enclosed in an amorphous siliceous layer. Increased concentrations of silicon are observed in enlarged grain boundaries indicating separation of YSZ grains by insulating glassy phase. The presence of aluminosilicate powder in the hot zone of a fuel line supplying humidified hydrogen to an SOFC anode impeded peak performance and accelerated degradation. Energy dispersive X-ray spectroscopy detected concentrations of silicon at the interface between the electrolyte and anode interlayer above impurity levels.

ASME

[3] Paolo R. Zafred, Stephen W. Sofie and Paul S. Gentile, "Progress in understanding silica transport process and effects in solid oxide fuel cell performance," in Proceedings of the ASME Eight International Fuel Cell Science, Engineering & Technology Conference, Brooklyn, New York, USA, June 14-16, 2010.

Abstract

One of the enabling technologies required for commercialization of high efficiency solid oxide fuel cell (SOFC) stacks is the development of low cost ceramic refractories capable of withstanding the harsh environment during start-up and steady state operation. Although low density, high purity fibrous alumina materials have been used for more than two decades in manufacturing of SOFC stack components, their low mechanical strength and high cost have precluded their use in the next generation pre-commercial generator modules. A current trend in SOFC stack design is to use high strength, low purity mullite bonded, cast ceramics which can be produced in large volume at a relatively low cost. Sufficient strength is required to provide structural support of the stack and its upper internals in addition to withstanding the severe thermal gradients in both steady state and transient conditions. To reduce costs while achieving suitable mechanical strength, thermal shock, and creep resistance, certain levels of silica and other impurities are present in the refractory ceramic. Silica, however, has been established to poison SOFC anodes thus degrading cell performance and stack life. Therefore, silica transport within the stack has become a dominant issue in SOFC generator design. As a result, an important design requirement for the stack ceramic materials is to develop a fundamental understanding of the silicon species transport process based on refractory composition and gas atmosphere in effort to minimize silicon species volatilization through the porous material. The vaporization behavior of the Al-Si-O system has been investigated in numerous studies and verified experimentally. It is well known that when aluminum silicate components are exposed to a reducing atmosphere, the partial pressure of oxygen is low, therefore this causes formation of volatile SiO(g). This SiO(g) gaseous phase is transported by the fuel stream to the anode/electrolyte interface and electrochemically oxidizes back into SiO2 over the triple phase boundaries (TPB) by the oxygen transported via the fuel cell. This re-deposition process of SiO2, known also as Si poisoning, blocks the reaction of fuel oxidation as it takes over the reactive sites, leading to noticeable degradation in cell performance. In this paper, the status of research on formation of volatile silicon species in aluminosilicate SOFC insulation materials is examined. The formation of volatile SiO(g), SiO(OH)(g), and SiO(OH)2(g) are indicated to facilitate silicon transport in anode fuel streams. Silica deposition is shown to degrade fuel cell anode performance utilizing a novel SOFC silicon poisoning test setup, and silica deposition is only observed on YSZ in the electrochemically active regions of the cell.

 

[4]

Paul S. Gentile, Stephen W. Sofie, Richard J. Smith and Camas F. Key, "Silicon Volatility and Transport in Aluminosilicate Refractory for SOFC Applications," in American Chemical Society 65th Southwest Regional Meeting, El Paso, TX, 2009.

[5]

Paul S. Gentile and Stephen W. Sofie, "High Performance Interleaved Electrolyte Supported Solid Oxide Fuel Cell," in MS&T Environmental & Energy Issues Symposium, Pittsburgh, PA, 2008.

[6]

Paul S. Gentile and Stephen W. Sofie, "Development of a Novel High Performance Electrolyte Supported Solid Oxide Fuel Cell," in MS&T Material Science & Technology Conference & Exhibition, Detroit, MI, 2007.

[7]

Paul S. Gentile, Stephen W. Sofie and Johannes Buscher, "Copper Based Metallic Braze for Hermetic SOFC Sealing," in 31st International Conference & Exposition on Advanced Ceramics & Composites, Daytona, FL, 2007.

[8]

Sherry L. Cady, Paul Stoodley, Paul S. Gentile and Peter Suci, "The Mobile Biofilm Unit (MBU): A Technological Innovation in Geomicrobial Studies," in Biomineralization in Terrestrial Hot Springs: The Preservation of Thermophiles in Past and Present-Day Systems. Geological Society of America., Denver, CO, 2004.

[9]

Peter Suci, Sherry L. Cady, Paul S. Gentile and Paul Stoodley, "Mobile Biofilm Unit (MBU)," in ASM Biofilms, Victoria, BC, 2003.