Crystal Size Effects on the Lattice Parameter of Nano-scaled Oxides

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NON-TECHNICAL DESCRIPTION: Prof. Siu-Wai Chan is examining how nanosized crystals expand or contract at the atomic level, and how they are affected by crystal size, temperature, pressure, and the presence of structural irregularities. The intellectual value of her research lies in understanding how small structural changes make profound changes in material behavior. This enhanced understanding will help in the development of new materials with improved properties. A better understanding of bonding should contribute to the development of nanoparticle synthesis methods with greater control over critical properties. Insight into the structure and defects in metal oxide nanoparticles may provide a knowledge base for the rational design of more efficient and less costly catalysts for cleaner air and sustainable energy. Undergraduate, master's, and doctoral students are being trained in conducting research, and new demonstration units (that incorporate the results of this study) are being developed for a New York City high school visitation program.TECHNICAL DESCRIPTION: Prof. Siu-Wai Chan is examining changes in the lattice parameter of metal oxides with crystallite-size, defect formation, temperature, and pressure. She employs both traditional and synchrotron-based, time-resolved X-ray diffraction. The coefficient of thermal expansion is calculated through measurements of the lattice in response to temperature variations. Similarly, measuring how the lattice responds to pressure allows for a calculation of the bulk modulus. She is interested in determining if these quantities are dependent on particle size in the nanoscale regime. The intellectual value of her research lies in the fact that small structural changes often generate profound changes in properties. Therefore, this project will provide a window to view the nature of bonding in nanoparticles and will enable a better understanding of surface stress and surface energy to be gained. It will also help to determine if the macroscopic based theory of surface stress, which has successfully predicted the lattice contraction in noble metal crystallites, can be used for ionic solids. The opportunity to tackle these issues is timely because mono-dispersed nanoparticles are now widely available.