{"66349":{"#nid":"66349","#data":{"type":"event","title":"MSE Ph.D. Defense Presentation \u2013 Qizhen Liang","body":[{"value":"\u003Cp\u003E\u003Cstrong\u003ETitle:\u003C\/strong\u003E\nPreparation and\nproperties of Thermally\/electrically conductive\u003Cbr \/\u003E\nMaterial architectures based on graphene and other nanomaterials \u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003ESUMMARY\u003C\/strong\u003E:\n\u003C\/p\u003E\n\n\u003Cp\u003EWith\nexcellent electrical, thermal and mechanical properties as well as large\nspecific surface area, graphene has been applied in next-generation\nnano-electronics, gas sensors, transparent electrical conductors, thermally\nconductive materials, and superior energy capacitors\u003Cem\u003E etc.\u003C\/em\u003E Convenient and\nproductive preparation of graphene is thereby especially important and strongly\ndesired for its manifold applications. \u003C\/p\u003E\n\n\u003Cp\u003EChemically\ndeveloped functionalized graphene from graphene oxide (GO) has significantly\nhigh productivity and low cost, however, toxic chemical reduction agents (\u003Cem\u003Ee.g.\u003C\/em\u003E\nhydrazine hydrate) and raised temperature (400-1100\u00b0C) are usually necessary in\nGO reduction yet not preferred in current technologies. Here, microwaves (MW)\nare applied to reduce the amount of graphene oxide (GO) at a relatively low\ntemperature (~165\u003Csup\u003Eo\u003C\/sup\u003EC). Experimental results indicate that resurgence\nof interconnected graphene-like domains contributes to a low sheet resistance\nwith a high optical transparency after MW reduction, indicating the very high\nefficiency of MW in GO\u2019s reduction.\u003C\/p\u003E\n\n\u003Cp\u003EMoreover,\ngraphene is usually recumbent on solid substrates, while vertically aligned\ngraphene architecture on solid substrate is rarely available and less studied.\nFor TIMs, electrodes of ultracapacitors,\u003Cem\u003E \u003C\/em\u003E\u003Cem\u003Eetc\u003C\/em\u003E, efficient heat\ndissipation and electrical conductance in normal direction of solid surfaces is\nstrongly desired. In addition, large-volume heat dissipation requires a joint\ncontribution of a large number of graphene sheets. Graphene sheets must be aligned\nin a large scale array in order to meet the requirements for TIM application.\nHere, thermally conductive fuctionalized multilayer graphene sheets (fMGs) are\nefficiently aligned in a large scale by vacuum filtration method at room\ntemperature, as evidenced by SEM images and polarized Raman spectroscopy. A\nremarkably strong anisotropy in properties of aligned fMGs is observed.\nMoreover, VA-fMG TIMs are prepared by constructing a three-dimensional\nvertically aligned functionalized multilayer graphene architecture between\ncontact Silicon\/Silicon surfaces with pure Indium as a metallic medium.\nCompared with their counterpart from recumbent A-fMGs, VA-fMG TIMs have\nsignificantly higher equivalent thermal conductivity and lower contact thermal\nresistance. \u003C\/p\u003E\n\n\u003Cp\u003EElectrical\nand thermal conductivities of polymer composite are also greatly interested\nhere. Previous researches indicated that filler loading, morphology of fillers,\nand chemical bonding across filler\/polymer interfaces have significant\ninfluence on electrical\/thermal conductivity of polymer composite. Therefore,\nthe research also pays substantial attention to these issues. First, electrical\nresistivity of CPCs is highly sensitive on volume or weight ratio (filler\nloading) of conductive fillers in polymer matrix, especially when filler\nloading is close to percolation threshold (\u003Cem\u003Ep\u003Csub\u003Ec\u003C\/sub\u003E\u003C\/em\u003E). Thermal\noxidation aging usually can cause a significant weight loss of polymer matrix\nin a CPC system, resulting in a filler loading change which can be exhibited by\na prompt alteration in electrical resistivity of CPCs. Here, the phenomena are\napplied as approach for\u003Cem\u003E \u003C\/em\u003E\u003Cem\u003Ein-situ\u003C\/em\u003E monitoring thermal oxidation status\nof polymeric materials is developed based on an electrical sensors based on\nconductive polymeric composites (CPCs). The study developed a model for\nelectrical resistivity of sensors from the CPCs as a function of aging time at\nconstant aging temperature, which is in a good agreement with a\nBoltzmann-Sigmoidal equation. Based on the finding, the sensors show their\ncapability of\u003Cem\u003E \u003C\/em\u003E\u003Cem\u003Ein-situ\u003C\/em\u003E in-situ monitor and\nestimate aging status of polymeric components by a fast and convenient\nelectrical resistance measurement.\u003C\/p\u003E\n\n\u003Cp\u003ESecond,\ninterfacial issues related to these thermal conductive fillers are systemically\nstudied. On the one hand, the study focuses on relationship between morphology\nof h-BN particles and thermal conductivity of their epoxy composites. It is\nfound that spherical-agglomeration of h-BN particles can significantly enhance\nthermal conductivity of epoxy resin, compared with dispersed h-BN plates, by\nsubstantially reducing specific interfacial area between h-BN and epoxy resin.\nOn the other hand, surface of high thermal conductive fillers such as SiC\nparticles and MWNTs are successfully functionalized, which makes their surface reactive\nwith bisphenol A diglycidyl ether and able to form chemical bonding between\nfillers and epoxy resin. By this means, thermal conductivity of polymer\ncomposites is found to be significantly enhanced compared with control samples,\nindicating the interfacial chemical bonding across interface between thermal\nconductive fillers and polymer matrix can promote heat dissipation in polymeric\ncomposites. The finding can benefit a development of high thermal conductive\npolymer composites by interfacial chemical bonding enhancement to meet the\ndemanding requirements in current fine pitch and Cu\/low k technology.\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003ETitle:\nPreparation and\nproperties of Thermally\/electrically conductive\u003Cbr \/\u003E\nMaterial architectures based on graphene and other nanomaterials \u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"MSE Ph.D. Defense Presentation \u2013 Qizhen Liang"}],"uid":"27388","created_gmt":"2011-06-01 13:14:12","changed_gmt":"2016-10-08 01:55:03","author":"Bill Miller","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2011-06-07T14:30:00-04:00","event_time_end":"2011-06-07T16:30:00-04:00","event_time_end_last":"2011-06-07T16:30:00-04:00","gmt_time_start":"2011-06-07 18:30:00","gmt_time_end":"2011-06-07 20:30:00","gmt_time_end_last":"2011-06-07 20:30:00","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":[{"id":"1791","name":"Student sponsored"}],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}