Office: WO 2262
Phone: (419) 530-1505
Fax: (419) 530-4033
Prediploma, 1996, Bergische Universität Wuppertal
M.S. 1999, Ph.D., 2001, Georgia Institute of Technology
Postdoctoral Associate, 2001-2003, Cornell University
Synthesis and characterization of new and improved solids; non-hydrolytic sol-gel chemistry; negative thermal expansion materials; sulfides; polymer composites; powder x-ray methods; Rietveld method.
The Lind-Kovacs group will be pursuing research in the following target areas: 1) Synthesis and characterization of new negative thermal expansion (NTE) materials in the Sc2W3O12 family, 2) Incorporation of NTE materials into polymers, 3) Application of non-hydrolytic sol-gel methods to the synthesis of improved sulfide materials, and 4) Development of in situ methods for the preparation of inorganic/polymer composites.
Negative thermal expansion (NTE) materials
While most solids expand upon heating, a few classes of materials shrink with increasing temperature. This unusual property is based on the compounds' crystal structures. It has attracted growing attention during the last decade, as it can be used to counterbalance the normal, positive thermal expansion of other materials through the preparation of composites.
There are many factors that influence the usefulness of NTE materials for composites (temperature range over which NTE is observed, occurrence of temperature or pressure induced phase transitions, ease of preparation etc.). For each specific application, additional factors like magnitude of the expansion coefficient, compatibility with other composite components, and stability under the expected processing conditions, need to be considered. To date, no "ideal" NTE material has been prepared, limiting the choice of composite components to the "most suitable" NTE material instead.
Research in our group will focus on the preparation of new materials in the Sc2W3O12 family. This family shows the strongest dependence of expansion behavior on cation identity. The use of non-hydrolytic sol-gel chemistry allows the incorporation of a larger variety of cations than those accessible by traditional ceramic methods, and facilitates the preparation of highly homogenous mixed cation compounds. The expansion behavior of the resulting materials will be characterized by variable temperature powder x-ray diffraction in combination with Rietveld analysis.
Weare collaborating with the Coleman group in chemical engineering to prepare polymer composites containing the NTE material cubic ZrMo2O8. For the preparation of composites, control of particle size and shape are important. In addition, the surface of the oxide particles has to be modified with groups that allow a favorable interaction with the polymer matrix.
New sulfide materials prepared by "non-hydrolytic" sol-gel chemistry
Non-hydrolytic sol-gel (NHSG) chemistry of oxides has been promoted as a method that leads to highly homogenous mixed metal oxide gels, and frequently allows crystallization of metastable materials at low temperatures. Few attempts have been made to extend this useful process to non-oxide materials. However, there is a growing demand for low temperature methods that will allow the preparation of metastable materials, higher purity products, or samples with controlled morphologies (e.g. particle size, thin films). The Lind group will work on adapting the established NHSG methods for oxides to the preparation of new and improved sulfide materials. Our main focus will be on sulfides with interesting optical properties, as these are especially sensitive towards impurities. The goals of this project are two-fold: i) to establish "non-hydrolytic" sol-gel methods for the synthesis of sulfides, and ii) to prepare and characterize new and improved sulfide materials.
Development of in situ methods for the preparation of inorganic/polymer composites
The preparation of inorganic/polymer composites often involves multiple synthesis steps that lead to preformed inorganic particles and/or preformed polymer, followed by modifications to achieve compatibility between the two components, before the final mixing step that results in composites. We have recently started to explore the feasibility of developing true one-pot in situ methods for the preparation of inorganic/polymer composites, in which the inorganic phase and the polymer form simultaneously under mutually compatible conditions.