{"63065":{"#nid":"63065","#data":{"type":"event","title":"Schenck Wiley - PhD Proposal Defense","body":[{"value":"\u003Cp\u003EThesis Title: Synergistic Methods for the Production of High-Strength\nand Low-Cost Boron Carbide\u003C\/p\u003E\n\n\n\n\u003Cp\u003EAbstract:\u003C\/p\u003E\n\n\u003Cp\u003E\u0026nbsp; Boron carbide\n(B4C) is a non-oxide ceramic in the same class of nonmetallic hard materials as\nsilicon carbide and diamond. The high hardness, high elastic modulus and low\ndensity of B4C make it a nearly ideal material for personnel and vehicular\narmor. B4C plates formed via hot-pressing are currently issued to U.S. soldiers\nand have exhibited excellent performance; however, hot-pressed articles contain\ninherent processing defects and are limited to simple geometries such as\nlow-curvature plates.\u003C\/p\u003E\n\n\u003Cp\u003ERecent advances in the pressureless sintering of B4C have\nproduced\u003C\/p\u003E\n\n\u003Cp\u003Etheoretically- dense and complex-shape articles that also\nexhibit superior ballistic performance.\u003C\/p\u003E\n\n\u003Cp\u003EHowever, the cost of this material is currently high due\nto the powder shape, size, and size distribution that are required, which\nlimits the economic feasibility of producing such a product. Additionally, the\nlow fracture toughness of pure boron carbide may have resulted in historically\nlower transition velocities (the projectile velocity range at which armor\nbegins to fail) than competing silicon carbide ceramics in high-velocity\nlong-rod tungsten penetrator tests. Lower fracture toughness also limits\nmulti-hit pro- tection capability. Consequently, these requirements motivated\nresearch into methods for improving the densification and fracture toughness of\ninexpensive boron carbide composites that could result in the development of a\nsuperior armor material that would also be cost-competitive with other\nhigh-performance ceramics.\u003C\/p\u003E\n\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\n\n\u003Cp\u003E\u0026nbsp; The primary\nobjective of this research was to study the effect of titanium and car- bon\nadditives on the sintering and mechanical properties of inexpensive B4C\npowders.\u003C\/p\u003E\n\n\u003Cp\u003EThe boron carbide powder examined in this study was a\nsub-micron (0.6 \u03bcm median particle size) boron carbide powder produced by H.C.\nStarck GmbH via a jet milling process. A carbon source in the form of phenolic\nresin, and titanium additives in the form of 32 nm and 0.9 \u03bcm TiO2 powders were\nselected. Parametric studies of sinter- ing behavior were performed via\nhigh-temperature dilatometry in order to measure the in-situ sample contraction\nand thereby measure the influence of the additives and their amounts on the\noverall densification rate. Additionally, broad composition and\nsintering\/post-HIPing studies followed by characterization and mechanical\ntesting elucidated the effects of these additives on sample densification,\nmicrostructure de- velopment, and mechanical properties such as Vickers\nhardness and microindentation fracture toughness.\u003C\/p\u003E\n\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\n\n\u003Cp\u003E\u0026nbsp; Based upon this\nresearch, a process has been developed for the sintering of boron carbide that\nyielded end products with high relative densities (i.e., 100%, or theo- retical\ndensity), microstructures with a fine (2-3\u003C\/p\u003E\n\n\u003Cp\u003E\u03bcm) grain size, and high Vickers microindentation\nhardness values. In addition to possessing these improved physical properties,\nthe costs of producing this material were substantially lower (by a factor of 5\nor\u003C\/p\u003E\n\n\u003Cp\u003Emore) than recently patented work on the pressureless\nsintering and post- HIPing of phase-pure boron carbide powder. This recently\npatented work developed out of our laboratory utilized an optimized powder\ndistribution and yielded samples with high relative densities and high hardness\nvalues.\u003C\/p\u003E\n\n\u003Cp\u003EThe current work employed the use of titanium and carbon\nadditives in specific ratios to activate the sintering of boron carbide powder\npossessing an approximately mono-modal particle size distri- bution. Upon\nheating to high temperatures, these additives produced fine-scale TiB2 and\ngraphite inclusions that served to hinder grain growth and substantially\nimprove overall sintered and post-HIPed densities when added in sufficient\nconcentrations.\u003C\/p\u003E\n\n\u003Cp\u003EThe fine boron carbide grain size manifested as a result\nof these second phase inclu- sions caused a substantial increase in hardness;\nthe highest hardness specimen yielded a hardness value (2884.5 kg\/mm^2)\napproaching that of phase-pure and theoretically- dense boron carbide (2939 kg\/mm^2).\u003C\/p\u003E\n\n\u003Cp\u003EAdditionally, the same high-hardness composi- tion\nexhibited a noticeably higher fracture toughness (3.04 MPa\u00b7m^1\/2) compared to\nphase-pure boron carbide (2.42 MPa\u00b7m^1\/2), representing a 25.6% improvement. A\npotential consequence of this study would be the development of a superior\narmor material that is sufficiently affordable, allowing it to be incorporated\ninto the general soldier\u0027s armor chassis.\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003ESchenck Wiley - PhD Proposal Defense\u003C\/p\u003E\u003Cp\u003ESynergistic Methods for the Production of High-Strength\nand Low-Cost Boron Carbide\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Schenck Wiley - PhD Proposal Defense"}],"uid":"27388","created_gmt":"2010-12-06 11:46:47","changed_gmt":"2016-10-08 01:53:32","author":"Bill Miller","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2010-12-10T14:00:00-05:00","event_time_end":"2010-12-10T16:00:00-05:00","event_time_end_last":"2010-12-10T16:00:00-05:00","gmt_time_start":"2010-12-10 19:00:00","gmt_time_end":"2010-12-10 21:00:00","gmt_time_end_last":"2010-12-10 21:00:00","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:cswiley@gatech.edu\u0022\u003ESchenck Wiley\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":[],"slides":[],"orientation":[],"userdata":""}}}