R1 A 2 Characterization of Energetic Materials Under

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Appendix A Project Reports, ALERT Thrust R1 Characterization Elimination of Illicit Explosives. Phase 2 Year 5 Annual Report Project R1 A 2, PETN in dynamic diamond anvil cell d DAC which is capable of precise controls of pressure compression. rates and shear strains, Understanding the phase and chemical stabilities of energetic materials at blast relevant pressure tempera. ture conditions has been a central theme to the present project Continuing this emphasis we have investi. gated high pressure stability of triaceton triperoxide TATP the explosive used in the recent terror attacks. in Paris 2015 and Brussels 2016 in collaboration with Project R1 C2 at the University of Rhode Island. URI The URI research group has provided the sample material while the Washington State University. WSU project has examined the phase and chemical stability of TATP under high pressures using micro Ra. man spectroscopy and synchrotron X ray diffraction The results have shown that TATP undergoes pres. sure induced structural changes initially to a new crystalline phase at 7 GPa and then to amorphous solid. above 30 GPa To gain physical chemical insights into the observed phase transitions the additional experi. ments are planned, This project provided the opportunity for three graduate and one undergraduate students to gain hands on. experience with cutting edge technologies and technical issues associated with fundamental research on. energetic materials related to Department of Homeland Security DHS and Department of Defense DoD. programs This project also produced one new PhD Dr Sakun Duwal in May 2018 in Chemistry WSU who. will join the Los Alamos National Laboratory this summer. B State of the Art and Technical Approach, B 1 Aluminum Dispersed Teflon Preparation of Composites and Short Pulse Laser Ignition.
The dynamic response of reactive composite such as metal dispersed explosives is complex and undergoes. very complex energetic processes ranging from simple decomposition to deflagration and detonation 1. The characteristics of these processes strongly depend on the extrinsic properties of reactive composites. such as the density microstructure particle sizes and defects Therefore to obtain a consistent and mean. ingful result it is critical to prepare high quality well characterized reactive composites In this project we. are targeting for the synthesis of reproducible metal dispersed reactive composites including Al dispersed. in Teflon Ammonium Nitrate AN and Ammonium Perchlorate AP Here we describe the synthesis of high. quality Al Teflon composites in Figure 1, Figure 1 Preparation of Al 120 nm dispersed in Teflon 200 nm. We used three different sizes of Al nanoparticles 50 80 and 120 nm in diameter with a few nm oxide layers. made by a short pulse plasma process and Teflon nanoparticles 200 nm in diameter These particles. Appendix A Project Reports, ALERT Thrust R1 Characterization Elimination of Illicit Explosives. Phase 2 Year 5 Annual Report Project R1 A 2, have tendency to clump together resulting in highly irregular heterogeneous mixtures Therefore we mixed. and sonicated these particles in hexane Fig 1b and then evaporated hexane to produce homogeneously. dispersed powder mixtures Fig 1c Then the mixtures were cold sintered to a small pellet 10 mm in. diameter and 1 mm thick of Al teflon composite Fig 1d using a hydraulic press The composites were pre. pared with three Al Teflon ratios 70 30 50 50 and 30 70 each with four packing densities 0 3 0 5 0 7. and 0 9 for systematic investigations, Time dependent data of thermal chemical and mechanical properties of high explosives are critical to ob. tain in depth insights of shock initiation and detonation 2 4 The temperature is by far the most important. thermodynamic variable controlling the physical and chemical changes of shock compressed high explosives. in many regards 5 For example it is the most sensitive probe for the energy balance of chemical reactions. Both the rate and pathway of chemical reactions vary significantly with temperature typically following an. exponential dependence Importantly high temperature resulting from exothermic chemical reactions is one. of the main driving forces leading to high explosive detonation However it is often a challenge to determine. temperature especially the evolution of temperature from detonating explosives in real time because of. highly transient and energetic nature of shock initiation and detonation For this reason detonation tempera. tures have typically been calculated in many cases by using various thermochemical models 6 7 of which. results need to be validated experimentally, Therefore we have examined a feasibility of measuring time re.
solved temperatures of blasting Al Teflon composites Our results. were quite promising as shown in Figure 2 We used a short pulse. laser Q switched 10 ns Nd Yag laser pulse at 532 nm to ignite. Al teflon composites and the temperature were determined by. fitting the measured thermal emission to a gray body radiation. formula 8 A six channel optical fiber was used to collect and. deliver thermal emission from the sample to a spectropyrometer. system which consists of six sets of photomultiplier tubes PMTs. narrow beam pass filters and neutral density ND filters The. PMTs were set at six discrete wavelengths centered at 340 400. 450 506 598 and 700 nm 340 and 400 nm are not shown in Fig. 2a each with a full band pass width of 50 nm The PM tube out. puts were optimized to be about 100 mV by using an appropriate. set of ND filters and were recorded at a gigahertz sampling rate on. three four channel digital scope analyzers DSAs at various ver. tical sensitivities Prior to the actual laser ignition the entire sys. tem including the sample assembly optical fiber PMTs etc was. calibrated against a known black body radiation source which. correlates the DSA vertical outputs to the spectral radiance These. calibrated DSA outputs were then fitted to a gray body radiation. equation at every one microsecond time step providing one mi. Figure 2 Time resolved temperature of, Al teflon composite a as determined on crosecond time resolved temperature data for about 2 ms long. the PMT and b converted to temperatures enough for the blast event of interest In this study we assume that. by fitting the a to the grey body formula the emissivity is independent of wavelength The time resolved. in the inset data shows that the blasting Al teflon composite undergoes a wide. range of temperature change ranging from the peak temperature. of 2400 K to a steady burning temperature of 1850 K Importantly the present optical pyrometric system is. good for a faster ns time resolution within the optical window of a few ms limited by the sampling number. points of the DSA We will continue the time resolved temperatures of laser blasted Al teflon composites as. Appendix A Project Reports, ALERT Thrust R1 Characterization Elimination of Illicit Explosives. Phase 2 Year 5 Annual Report Project R1 A 2, well as Al AN and Al AP composites using a similar method in Figure 1 with a faster time resolution 1 10 ns. B 2 Pressure induced Phase and Chemical Transformations in PETN. Mechanical issues associated with the state of stress microstruc. ture grain boundary heterogeneity etc are all very important. to understand shock initiation and detonation in high explosives. 9 10 It is well known that PETN exhibits a strong orientation. dependence of its initiation and detonation under shock compres. sion 11 12 Aimed at gaining the insights into shock sensitivity. we have investigated PETN under quasi hydrostatic and non hy. drostatic conditions The results are shown in Figure 3. Figure 3a plots the pressure induced shifts of C H vibrational Ra. man peaks of PETN to 50 GPa in an Ar pressure transmitting me. dium Soft Ar provides a quasi hydrostatic condition in this pres. sure range The plot clearly shows an abrupt peak shift at 12. GPa which occurs reversibly upon the pressure cycling In con. trast nonhydrostatically compressed PETN behaves completely. differently and shows the evidence for chemical decomposition at. 10 GPa Figure 3b shows the microphotograph images of PETN. taken before and after the chemical reaction at 10 GPa and ambi. ent temperature Note that the reaction occurs rapidly within a. frame time of CCD camera 30 ms and exothermically evident. from the sudden movement of small Ruby particles at the gasket. edge shown in the frame a and produces black carbon particles. over a time scale of several seconds noted in each frame in s Figure 3 a Pressure induced Raman shifts. This reaction is probably related to an increase in shear with in of PETN in hydrostatic Ar pressure medium. creasing pressure Chemical reactions in non hydrostatic condi showing a phase transition at 12 GPa and. tions have been observed previously in nitromethane 13 HMX b photographic images of PETN in non. 14 and 1 4 dinitrocubane 15 all of which can be considered hydrostatic condition showing an abrupt. chemical reaction at 10 GPa, broadly as a shear induced chemical reaction The hydrostatic. data on the other hand indicates no apparent chemical reactions. but a structural phase transition at 12 GPa a similar pressure. associated with chemical decomposition, In order to understand the relationship between the structural phase transition and the chemical reaction.
we now investigate PETN in dynamic diamond anvil cell d DAC which can produce well controlled pres. sure compression rates and dynamic shear strains 16 coupled with time resolved spectroscopic methods. C Major Contributions, The fundamental research outlined here will also result in scientific discoveries and technological innova. tions of great value to defense research needs while enabling DHS to respond to both short and long term. national needs in the areas of explosive characterization and evaluation Major contributions of this project. to the overall ALERT research program are as follows. Completion of the investigation of chemical sensitivity of AN mixtures at high pressures and tempera. tures including ammonium nitrate fuel oil ANFO and Ammonal. Appendix A Project Reports, ALERT Thrust R1 Characterization Elimination of Illicit Explosives. Phase 2 Year 5 Annual Report Project R1 A 2, Work in progress on the systematic studies of main group I peroxides in comparison with H2O2. Completed the phase diagram of AP over the extended region of pressures and temperatures. Accomplished the systematic understanding of high pressure temperature behaviors of the main group. I peroxides, Completed the investigation of AP and Li2O2 under static conditions over a wide range of pressure tem. perature regimes, Developed a fast time resolved six channel pyrometer for the investigation of reactive metals and com.
posites undergoing energetic metal combustions and thermite and metathesis reactions. Completed the investigation of TATP under static conditions to 60 GPa using Raman and synchrotron. X ray diffraction, Determined the structural evolution of reactive composites Al dispersed BN using the TRX experiments. Made significant progress on Al dispersed Teflon especially in preparation of high quality reactive com. posites and time resolved temperature measurements of laser ignited reactive composites. Investigated high pressure behaviors of pentaerythritol tetranitrate PETN under quasi hydrostatic and. non hydrostatic conditions,D Milestones, Our major research accomplishments are on the investigation of phase and chemical stabilities of energetic. materials under both static and dynamic high PT conditions The accomplishment realized in static condi. tions included the following efforts, Mapped out the phase diagram and melting decomposition curves of the two most commonly used. nonconventional energetic materials ammonium nitrates AN published in Journal of Chemical Physics. 2011 2012 and 2013 and ammonium perchlorates AP published in Journal of Chemical Physics 2016. Determined crystal structures phase transitions and chemical stabilities of Group I alkali metal perox. ides including H2O2 Li2O2 and Na2O2 under static high pressures published in Journal of Chemical Physics. 2008 and 2017, Investigated static high pressure properties of triaceton triperoxide TATP the explosive used in the. recent terrorist attacks in Paris and Brussels in collaboration with Project R1 C 2 University of Rhode. Island URI The URI group led by Professor Oxley have provided the sample and we have examined. the phase and chemical stability of TATP under high pressures using micro Raman spectroscopy and. synchrotron X ray diffraction, We have investigated high pressure behaviors of pentaerythritol tetranitrate PETN under quasi hydro.
static and non hydrostatic conditions PETN is one of the most powerful explosives in use today and is. known to exhibit highly anisotropic shock sensitivity. The accomplishments realized in the dynamic conditions included the following efforts. Developed Time Resolved synchrotron X ray diffraction TRX TR Spectroscopy TRS and TR Pyrom. etry TRP for studies of reactive materials These technologies are capable of probing structural and. chemical evolutions of energetic materials subjected to dynamic thermal and mechanical ignitions as. Appendix A Project Reports, ALERT Thrust R1 Characterization Elimination of Illicit Explosives. Phase 2 Year 5 Annual Report Project R1 A 2, described in several publications in Review of Scientific Instruments 2012 Journal of Applied Physics. high quality metal dispersed reactive composite Al dispersed in Teflon AN and AP and a fast time resolved optical pyrometric method to measure the temperature evolution of short pulse laser blasted Al Teflon com posites as described in Section B 1 The presence of shear in explosives plays a critical role to control shock initiation and sensitivity of ener getic materials To understand

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