The Effects of Soluble Impurities on the Flow and Fabric of Polycrystalline Ice

BAKER/1141411本奖项支持一个项目，该项目旨在系统研究可溶杂质，特别是硫酸对多晶冰蠕变的影响，作为温度、应变率和杂质浓度的函数。工作假设是，与高纯度冰相比，可溶杂质会增加多晶冰的流动速度，这种影响与温度有关，并且杂质通过影响重结晶和颗粒生长将改变冰的组构。无论是掺入硫化氢的冰，还是高纯度的多晶冰，都将通过冻结冰片、将其破碎、筛选冰粒，然后在模具中将其烧结成直径至少有10个颗粒的细粒圆柱形样品来生产。所得到的微结构(位错结构、晶粒度和形状、晶界特征和酸的微结构位置)将使用各种技术进行表征，包括：光学显微镜、扫描电子显微镜，包括二次电子成像、电子背散射图案、能量色散X射线光谱、电子沟道对比成像和X射线形貌。掺H_2SO_4和高纯多晶冰的蠕变将在一定的温度和应力范围内进行。采用多种方法相结合的方法研究了冰S对蠕变变形(晶界滑动、位错运动、重结晶、晶界迁移、杂质重分布)的响应。蠕变行为将被模型化，并与微观结构相关。特别令人感兴趣的是杂质如何影响蠕变的激活能。这项工作的学术价值是，它将导致对冰川冰更好的理解，并将使冰川学家能够对杂质对多晶冰中流动和组构发展的影响进行建模。该项目的更广泛影响包括将获得的关于杂质对冰流影响的知识，这将使古气候学家能够更好地解释冰芯数据，并使科学家能够开发预测模型，以更好地处理各种气候变化情景下的冰盖流动。该项目还将对一名博士生、几名本科生和一些高中生进行教育和培训。研究结果将发表在相关期刊上。几个本科生，通常是每年两个，也将执行这项工作。达特茅斯积极争取所有学位水平的少数族裔学生，我们将为这个项目寻找女性或少数族裔本科生。本科生将得到达特茅斯？S国家荣誉科学女性项目或REU基金的资助。本科生呢？研究将与博士生S紧密结合起来研究。汉诺威高中的学生也将参与该项目，并开发一套教育工具，向学生介绍冰的特性。这项研究的结果将发表在参考期刊上，并在会议上发表。

Baker/1141411 This award supports a project to undertake a systematic examination of the effects of soluble impurities, particularly sulfuric acid, on the creep of polycrystalline ice as function of temperature, strain rate and impurity concentration. The working hypothesis is that soluble impurities will increase the flow rate of polycrystalline ice compared to high-purity ice, that this effect will be temperature dependent and that the impurities by affecting the re-crystallization and grain growth will change the fabric of the ice. Both H2SO4-doped and high-purity poly-crystalline ice will be produced by freezing sheets of ice, breaking them up, sieving the ice particles and then sintering them in a mold into fine-grained cylindrical specimens with at least ten grains across their diameter. The resulting microstructures (dislocation structure, grain size and shape, grain boundary character and micro-structural location of the acid) will be characterized using a variety of techniques including: optical microscopy, scanning electron microscopy, including secondary electron imaging, electron backscattered patterns, energy dispersive X-ray spectroscopy, electron channeling contrast imaging, and X-ray topography. The creep of both the H2SO4-doped and the high-purity polycrystalline ice will be undertaken at a range of temperatures and stresses. The ice?s response to the creep deformation (grain boundary sliding, dislocation motion, re-crystallization, grain boundary migration, impurity redistribution) will be studied using a combination of methods. The creep behavior will be modeled and related to the microstructure. Of particular interest is how impurities affect the activation energy for creep. The intellectual merit of the work is that it will lead to a better understanding of glacier ice and will enable glaciologists to model the influence of impurities on the flow and fabric development in polycrystalline ice. The broader impacts of the project include the knowledge that will be gained of the effects of impurities on the flow of ice which will allow paleoclimatologists to better interpret ice core data and will allow scientists developing predictive models to better address the flow of ice sheets under various climate change scenarios. The project will also lead to the education and training of a Ph.D. student, several undergraduates and some high school students. Results from the research will be published in refereed journals. Several undergraduates, typically two per year, will also perform the work. Dartmouth aggressively courts minority students at all degree levels, and we will seek women or minority group undergraduates for this project. The undergraduates will be supported by Dartmouth?s nationally-honored Women In Science Project or by REU funding. The undergraduates? research will integrate closely with the Ph.D. student?s studies. Hanover High School students will also be involved in the project and develop an educational kit to introduce students to the properties of ice. Results from the research will be published in refereed journals and presented at conferences.