Scholarship

Most of my materials research interests focus on the effect of INTERFACES on material properties.

Nanostructured Materials

Nanostructured materials are generally defined as materials having structural elements with at least one dimension less than 100 nm. (A nm is a billionth of a meter.) Such structural elements could include second phase particles, the thickness of layers in a laminated material, the diameter of in-situ whiskers or fibers, or the grain size in a single phase crystalline material. By comparison, most conventional polycrystalline materials have grain sizes on the order of microns to tens of microns. To put this size difference in perspective, consider the width of a human hair; that dimension is the approximate grain size of some conventional polycrystalline materials. A nanocrystalline material could easily have 1000 grains across the diameter of that human hair!

My research in nanostructured materials focuses on developing a better understanding of several size-dependent phenomena: defect chemistry in oxides and grain boundary segregation, in particular. A recently completed Master's Thesis by Xinlan Shi demonstrated that nanocrystalline TiO2 has an enhanced conductivity and a wide PO2-independent regime relative to conventional TiO2. This behavior is likely due to either enhanced ionic conductivity or conduction of protons; further work is planned to distinguish between these mechanisms.

Another master's student is exploring whether there is a grain size-dependence of the anatase-rutile phase transformation in TiO2. Related research focuses on understanding the thermal stability (or lack thereof) in nanostructured ceramics. If fine grain sizes could be stabilized at elevated temperatures, these materials could see more widespread use.

Recent Publications and Presentations

• C. Demetry and X. Shi, "Grain size-dependent electrical properties of rutile (TiO₂)," Solid State Ionics 118[3-4] 271-79 (1999).Abstract

• C.D. Terwilliger, "Size-Dependent Defect Phenomena in Ultrafine-grained Ceramics," (Invited Talk), Extremely Fine Scaled Ceramics Focused Session, Annual Meeting of the American Ceramic Society, Indianapolis, IN, April 14-18, 1996.

• "Size-Dependent Defect Phenomena in Ultrafine-grained Ceramics," Invited presentation, Institute of Materials Science, University of Connecticut, March 6, 1996.

• C.D. Terwilliger and Y.-M. Chiang, "Measurements of Excess Enthalpy in Ultrafine-grained Titanium Dioxide," Journal of the American Ceramic Society 78[8], 2045-55 (1995). Abstract

• C.D. Terwilliger and Y.-M. Chiang, "Size-Dependent Solute Segregation and Total Solubility in Ultrafine Polycrystals: Ca in TiO2," Acta Metallurgica et Materialia 43[1], 319-328 (1995). Abstract

• C.D. Terwilliger and Y.-M. Chiang, "The Effect of Calcium Segregation on Grain Growth in Nanocrystalline TiO2," NanoStructured Materials 4[6], 651-661 (1994). Abstract

• C.D. Terwilliger and Y.-M. Chiang, "Characterization of Chemically- and Physically-Derived Nanophase Titanium Dioxide," NanoStructured Materials 2, 37-45 (1993). Abstract

Bonded Abrasives

• Carey T. Williams, Chrysanthe Demetry, and Rounan Li, "Structure and Strength of Interfaces in Titanium-Coated Diamond-Glass Composites," pp. 697-704 in Ceramic Science and Engineering Proceedings, Vol. 21, No. 3, 24th Annual Conference on Composites, Advanced Ceramics, Materials and Structures: A (Eds. T. Jessen, E. Ustundag), American Ceramic Society (2000). Abstract

• G.L. Kourtoukova, C. Demetry, S. Ramanath, R. Andrews, D.S. Jacobs, and R.R. Biederman, "Design and Tailoring of Ni-Sn-W Composites for Bonded Abrasive Applications," Materials Science and Engineering A 276[1-2], 58-69 (2000). Abstract

  At the upper left is a scanning electron micrograph of a W particulate-reinforced Ni-Sn composite that was hot pressed from elemental powders. The accompanying x-ray dot maps show the distribution of Ni, Sn, and W in the microstructure. Moving clockwise from the upper right, the maps are for Ni, W, and Sn. Further characterization by EDX showed that there are four phases in the composite: W, a Ni-W intermetallic, Ni-W solid solution, and a Ni-Sn intermetallic. The formation of the intermetallics gives the composite a significantly enhanced elastic modulus relative to a rule-of-mixtures prediction based on the moduli of the unreacted constituents. The wear resistance of the composite, however, is not significantly different than the Ni-Sn matrix. This combination of higher stiffness without significantly greater wear resistance is a desirable combination of properties for some superabrasive grinding wheels that is not possible to achieve with a monolithic material.
  

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  The composite to the right has the same overall composition, but has some W fiber reinforcement replacing half of the W particulate reinforcement. Addition of fibers gives an additional stiffening effect, again without an increase in wear resistance.

  These micrographs were taken by Galina Kourtoukova, who earned a M.S. in Materials Science and Engineering in May 1998.
  

• C. Demetry, F. S. Souto, B. C. Ryden, and J. M. Roy, "Tactile sensing of density uniformity in powder beds after die filling," Powder Technology 99 (1998) 119-124. Abstract

Scholarship in Teaching

Recent Publications, Presentations, and Workshops

• C. Demetry, "Outcomes Assessment of Educational Approaches: Examples for Materials Science Educators," Journal of Materials Education 20 [1-2] 1-8 (1998). Abstract

• C. Demetry, "Alumni-Contributed Materials Selection Projects in an Introductory Materials Science Course," Journal of Materials Education 20 [1-2] 126-133 (1998). Abstract

• C. Demetry, "The WPI-Norton Company Project Center: A University-Industry Partnership in U.S. Undergraduate Education," Industry and Higher Education (Invited Contribution), August 1997, pp. 218-223.Abstract

• C. Demetry and J.E. Groccia, "A Comparative Assessment of Students' Experiences in Two Instructional Formats of an Introductory Materials Science Course," Journal of Engineering Education 86[3], 203-210 (1997). Abstract

• C.D. Terwilliger, "The WPI-Norton Company Project Center: A University-Industry Partnership in Undergraduate Education," pp. 88-92 in Proceedings of the 22nd Annual Conference for Industry and Education Collaboration, American Society for Engineering Education (1997).

• J.E. Miller, D. DiBiasio, C.D. Terwilliger, "Outcomes of the Use of Undergraduate Peer Learning Assistants to Facilitate Cooperative Learning in Introductory Science and Engineering Classes," presented at the Lilly Conference on College Teaching, Miam i University, Oxford, OH, November 21-24, 1996.

• J.E. Miller, D. DiBiasio, C.D. Terwilliger, "The Use of Undergraduate Peer Learning Assistants to Facilitate Cooperative Learning Classes," Workshop presented at the Lilly Conference on College Teaching, Miami University, Oxford, OH, November 21-24, 1996.

• K. O'Connor, N.M. Acuna, R.D. Sisson, Jr., and C.D. Terwilliger, "Engineering Education as Apprenticeship: A Guided Participation Model of Learning," Second Davis Educational Conference, Worcester Polytechnic Institute, May 30, 1996.

• C.D. Terwilliger, "Use of Active and Cooperative Learning in an Introductory Materials Science Course," presented at the Ceramics/Materials Curricula Session, Annual Meeting of the American Ceramic Society, Indianapolis, IN, April 14-18, 1996.

• J.E. Miller, D. DiBiasio, C.D. Terwilliger, "Task Design for Cooperative Learning," Workshop presented at the Lilly Conference on College Teaching, Miami University, Oxford, OH, November 16-19, 1995.

• C.D. Terwilliger, "A Comparative Assessment of Traditional and Active/Cooperative Instructional Formats in an Introductory Materials Science Course," Idea Swap Session, Lilly Conference on College Teaching, Miami University, Oxford, OH, November 16-19 , 1995.

• C.D. Terwilliger and J.E. Groccia, "A Comparative Assessment of Traditional Lecture and Active/Cooperative Instructional Formats in an Introductory Materials Science Course," presented in the Innovations in Materials Education session at the American Society for Engineering Education Annual Meeting, Anaheim, CA, June 25-28, 1995.

• J.E. Miller, D. DiBiasio, W. Farr, C.D. Terwilliger, C. Wills, "Task Design for Cooperative Learning," Worcester Consortium Workshop presented at WPI, March 14, 1995.