Effects of Grain Boundary Segregation on Grain Boundary Diffusion and Chemical Kinetics in Olivine Aggregates

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。马歇尔桑德伯格博士已被授予美国国家科学基金会地球科学博士后奖学金，在明尼苏达大学开发研究和教育的综合计划。本实验研究将量化晶界化学和结构对Mg 2+，O2-和Si 4+晶界扩散的影响。合成的细粒镁橄榄石聚集体将掺杂有受控量的Ca、Pr和Ni。在高温/高压退火之后，将测量30 Si、26 Mg和18 O的示踪剂扩散曲线，以计算这些阳离子在掺杂和未掺杂样品中的体扩散率。这项研究的一个重要目标是评估微量元素在影响岩石动力学行为方面的作用，从而更好地将实验室实验的结果应用于地球。晶界偏聚的动力学效应将有助于更好地理解晶界结构和性能，其潜在应用范围广泛，如细晶材料的断裂韧性，快离子导体，固态电解质的动力学，以及陶瓷，金属和合金的高温蠕变强度。教育计划将包括固体地球动力学的研究生/本科层次的研讨会，其中将包括这些实验的结果。Sundberg将通过该部门目前运行的夏季研究计划（REU）指导本科生进行这项调查。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Dr. Marshall Sundberg has been granted an NSF Earth Sciences postdoctoral fellowship to develop an integrated program of research and education at the University of Minnesota. This experimental study will quantify the effects of grain boundary chemistry and structure on grain boundary diffusion of Mg2+, O2-, and Si4+. Synthetic, fine-grained forsterite aggregates will be doped with controlled amounts of Ca, Pr, and Ni. Following high-temperature/high-pressure anneals, tracer diffusion profiles of 30Si, 26Mg, and 18O will be measured in order to calculate the bulk diffusivity of these cations in both doped and un-doped samples. One important goal of this research is to evaluate the role that trace elements play in influencing the kinetic behavior of rocks and thus better apply the results of laboratory experiments to the Earth. The kinetic effects of grain boundary segregation will facilitate a better understanding of grain boundary structure and properties, with potential applications as diverse as the fracture toughness of fine-grained materials, fast-ion conductors, the kinetics of solid-state electrolytes, and the high-temperature creep strength of ceramics, metals, and alloys.The education plan will consist of graduate/undergraduate level seminar in solid-earth kinetics, in which the results of these experiments will be included. In addition, Dr. Sundberg will mentor undergraduate students in this investigation through the summer research program (REU) currently run by the Department.