Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session H7: Materials I: Synthesis and Phase Transformations |
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Chair: Naresh Thadhani, Georgia Institute of Technology Room: Regency Ballroom F |
Tuesday, July 11, 2017 9:15AM - 9:30AM |
H7.00001: Visualization of hot spot formation in energetic materials under periodic mechanical excitation using phosphor thermography Alex Casey, Gabriel Fenoglio, Humberto Detrinidad Under mechanical excitation, energy is known to localize within an energetic material resulting in `hot spot' formation. While many formation mechanisms have been proposed, additional insight to heat generation mechanisms, the effect of binder/crystal interfaces, and predication capabilities can be gained by quantifying the initiation and growth of the hot spots. Phosphor thermography is a well established temperature sensing technique wherein an object's temperature is obtained by collecting the temperature dependent luminescence of an optically excited phosphor. Herein, the phosphor thermography technique has been applied to Dow Corning Sylgard\textsuperscript{\textregistered} 184/octahydro 1,3,5,7tetranitro1,3,5,7tetrazocine (HMX) composite materials under mechanical excitation in order to visualize the evolution of the temperature field, and thus hot spot formation, within the binder. [Preview Abstract] |
Tuesday, July 11, 2017 9:30AM - 9:45AM |
H7.00002: Hot Spots from Generated Defects in HMX Crystals Christian Sorensen, Nicholas Cummock, Caitlin O'Grady, I. Emre Gunduz, Steven Son There are several hot spot initiation mechanisms that have been proposed. However, direct observation of shock or impact compression of these mechanisms at macroscopic scale in explosives is difficult. Phase contrast imaging (PCI) may be applied to these systems. Here, high-speed video was used to record optical spectrum and for x-ray Phase Contrast Imaging (PCI) of shockwave interaction with low defect HMX crystals and crystals with engineered defects. Additionally, multiple crystals were arranged and observed under shock loading with PCI and optical high-speed video. Sample preparation techniques for generating voids and other engineered defects will be discussed. These methods include drilled holes and laser machined samples. Insight into hot spot mechanisms was obtained. [Preview Abstract] |
Tuesday, July 11, 2017 9:45AM - 10:00AM |
H7.00003: Germanium under Shock Waves: A Study of Some Physical Properties by First Principles Method Enamul Haque We have explored some physical properties of germanium under shock waves, such as elasticity and compressibility, with first principles method, conductivity, susceptibility, and heat absorbability in Comsol environment. The equations of state used for investigation of the above properties relating phase transitions between crystal structures are based on ab initio predictions of the electron in ground states. The deduced equations of state have matched in reasonable range with data on the shock Hugoniot and the calculated physical parameters have coincided in reasonable error with the available value. However, electromagnetic properties of germanium have varied significantly under shock waves, with applied pressure 5GPa. The variation of band energy with pressure has been calculated. The elastic properties have also verified with density functional theory (DFT) which shows excellent accuracy of the result. The possible explanation of these physical properties of germanium is briefly described. [Preview Abstract] |
Tuesday, July 11, 2017 10:00AM - 10:15AM |
H7.00004: Deaggregation, Modification, and Developing Applications for Detonation Nanodiamond Vadym Mochalin Nanodiamond powder (ND) is one of the most promising materials for advanced composites and biomedical applications [1]. It is also a commercial precursor for carbon nanoonions -- material for high power micrometer size supercapacitors and potentially, Li-ion batteries. ND is produced by detonation of explosives with negative oxygen balance in a closed chamber, where extremely high pressures and temperatures develop during detonation. ND consists of diamond particles of \textasciitilde 5 nm diameter, combining fully accessible large surface and rich and tailorable surface chemistry. ND has unique properties including optical, electrical, thermal, and mechanical, and is biocompatible and non-toxic. Due to numerous surface functional groups, ND has catalytic and electrochemical activity. Several techniques have been proposed for ND deaggregation based on milling with costly ceramic microbeads, leaving difficult to remove contaminations in the resulting ND suspension. We have recently discovered a novel, green technique for ND deaggregation using sonication in aqueous sodium chloride slurry [2]. Upon completion of the process sodium chloride can be easily washed out with water leaving behind no contaminants and yielding stable single-digit ND colloids. Modification and development of applications for ND in composites, drug delivery, biomedical imaging, etc., will be also discussed.\\ \\$[1]Mochalin, V. N. et al. Nat. Nanotechnol., 2012, 7, 11\newline [2]Turcheniuk, K. et al. ACS Appl. Mater. Interfaces, 2016, 8, 25461 [Preview Abstract] |
Tuesday, July 11, 2017 10:15AM - 10:30AM |
H7.00005: Shock-wave induced synthesis of few layer graphene nanosheets Pengwan Chen, Hao Yin, Chunxiao Xu, Xin Gao, Qiang Zhou, Liangti Qu Shock wave action combining shock-induced chemical reaction will cause a series of changes of material physical and chemical properties, which is supposed to be a new method for material synthesis and modification. Using solid CO2 (dry ice) as the carbon source, few layer graphene nanosheets were successful synthesized by reduction of CO2 with calcium hydride under detonation-driven flyer impact loading in this study. Furthermore, by adding ammonium nitrate to the reaction system, nitrogen-doped graphene materials were formed in this one-step shock-wave treatment. Similarly, few layer graphene and nitrogen-doped graphene materials were also prepared through the reaction of calcium carbonate and magnesium induced by shock wave. The shock synthesis of graphene nanosheets requires a balance between the growth rate of graphene materials and the formation rate of carbon atoms. Meanwhile, the pressure and temperature are two important factors affecting the synthesis of few layer graphene nanosheets. [Preview Abstract] |
Tuesday, July 11, 2017 10:30AM - 10:45AM |
H7.00006: Detonation Synthesis of Alpha-Variant Silicon Carbide Martin Langenderfer, Catherine Johnson, William Fahrenholtz, Vadym Mochalin A recent research study has been undertaken to develop facilities for conducting detonation synthesis of nanomaterials. This process involves a familiar technique that has been utilized for the industrial synthesis of nanodiamonds. Developments through this study have allowed for experimentation with the concept of modifying explosive compositions to induce synthesis of new nanomaterials. Initial experimentation has been conducted with the end goal being synthesis of alpha variant silicon carbide ($\alpha $-SiC) in the nano-scale. The $\alpha $-SiC that can be produced through detonation synthesis methods is critical to the ceramics industry because of a number of unique properties of the material. Conventional synthesis of $\alpha $-SiC results in formation of crystals greater than 100 nm in diameter, outside nano-scale. It has been theorized that the high temperature and pressure of an explosive detonation can be used for the formation of $\alpha $-SiC in the sub 100 nm range. This paper will discuss in detail the process development for detonation nanomaterial synthesis facilities, optimization of explosive charge parameters to maximize nanomaterial yield, and introduction of silicon to the detonation reaction environment to achieve first synthesis of nano-sized alpha variant silicon carbide. [Preview Abstract] |
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