{"63676":{"#nid":"63676","#data":{"type":"event","title":"MSE Ph.D. Proposal - Stan Davis","body":[{"value":"\u003Cp\u003ETitle: Study of the\nStress Relaxation Mechanisms Enabling Shape Preserving Silica Magnesiothermic\nReduction \u003C\/p\u003E\u003Cp\u003EShape preserving\nsilica magnesiothermic reduction makes use of gas-silica displacement chemistry\nto convert intricately shaped, hierarchically ordered, three-dimensional silica\nstructures into porous silicon replicas while maintaining complex features of\nthe starting silica template down to ~15 nm.\u0026nbsp; This technique has been used\nto convert a number of starting silica templates into porous silicon replicas\nincluding diatom frustules, inverse opals, nanospheres, micropatterned\nstructures, etc., which exhibit enhanced surface area and porosity due to the\nnature of the silicon conversion chemistry.\u0026nbsp; \u003C\/p\u003E\n\n\u003Cp\u003EDespite the\nprogress made in applying silica magnesiothermic reduction to a wide range of\nsilica templates, understanding of the mechanisms enabling shape preservation\nis still poor.\u0026nbsp; In particular, large compressive stresses (~2-5 GPa) are\nevolved in the products of silica magnesiothermic reduction due to large\nchanges in molar volume upon reaction (~20-60% depending upon silica\npolymorph\/crystallinity).\u0026nbsp; Despite these stresses, geometric distortion\nbetween the silica templates and porous silicon replicas is only very\nmodest.\u0026nbsp; This implies that a stress relaxation mechanism operates\nconcurrently with the reaction, which enables the process to be shape\npreserving.\u0026nbsp; This investigation hopes to gain a better understanding of\nthe nature of this stress relaxation mechanism.\u0026nbsp; Silica wafers will be\nmagnesiothermically treated to produce thin product films on the surface which\nwill be characterized using XRD (sin2\u03c8 method)\nto quantify the compressive stress evolved in these product films.\u0026nbsp; Annealing\ntreatments at the reaction temperature will then be applied to induce stress\nrelief in the product films.\u0026nbsp; Microstructural changes in the product films\nwill then be characterized to discern correlations between the microstructural\nevolution of the product films and the rate of stress relief during annealing,\nrevealing the nature of the stress relaxation mechanism operating during silica\nmagnesiothermic reduction.\u0026nbsp; It is hoped that this work will provide a\nbetter understanding of the silica magnesiothermic reduction process which can\nbe used to attain better replication of starting silica templates as the\ncomplexity of these templates increases.\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EMSE Ph.D. Proposal\n- Stan Davis \u003C\/p\u003E\n\n\n\n\u003Cp\u003ETitle: Study of the\nStress Relaxation Mechanisms Enabling Shape Preserving Silica Magnesiothermic\nReduction \u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"MSE Ph.D. Proposal - Stan Davis"}],"uid":"27388","created_gmt":"2011-01-18 14:36:08","changed_gmt":"2016-10-08 01:53:48","author":"Bill Miller","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2011-01-28T14:00:00-05:00","event_time_end":"2011-01-28T17:00:00-05:00","event_time_end_last":"2011-01-28T17:00:00-05:00","gmt_time_start":"2011-01-28 19:00:00","gmt_time_end":"2011-01-28 22:00:00","gmt_time_end_last":"2011-01-28 22:00:00","rrule":null,"timezone":"America\/New_York"},"extras":[],"groups":[{"id":"1238","name":"School of Materials Science and Engineering"}],"categories":[],"keywords":[{"id":"10802","name":"MSE_Interal_Event"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Ca href=\u0022mailto:stan.davis@gatech.edu\u0022\u003Estan.davis@gatech.edu\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":[],"slides":[],"orientation":[],"userdata":""}}}