Selloni (Princeton), S. Son (Purdue), V. Yang (Georgia Tech), M. Zachariah, B. Eichhorn (UMD)

Transcription

1 Smart Functional Nanoenergetic Materials R.A. Yetter, S. Thynell (PSU), I. Aksay, A. Selloni (Princeton), S. Son (Purdue), V. Yang (Georgia Tech), M. Zachariah, B. Eichhorn (UMD) Energetic Material Design to Control High Pressure Dynamics Workshop UCLA IPAM Center

2 Why Nanoenergetic Materials Important Components to Energetic Materials High Energy Density Fuel Components to Propellants, Fuels, and Explosives (High Concentrations) Burning Rate Modifiers (Low Concentrations) Gelling Agents for Hazards Reduction, MEMs systems, and others Unique Properties Increased Specific Surface Area Increased Reactivity Increased Catalytic Activity Lower Melting Temperatures Lower Heats of Fusion, Increased Heats of Reaction Implications to Propulsion Increased Burning Rates (> factor 5) Higher Efficiency (more efficient particle combustion, less two phase flow losses, for solids Isp 10s) Reduced Sensitivity Min/low smoke energetic materials

3 Condensed phase agglomerates can contribute to twophase flow losses Two-phase flow losses can reduce motor performance by as much as 10% [a] Inclusion modified fuels or other composites can lead to smaller product particles, and potentially lower 2- phase flow loss Motivation [a] H. Cheung, N. S. Cohen, Performance of solid propellants containing metal additives, 1965, 3, Image: Y. M. Timnat, Advanced Chemical Rocket Propulsion, Academic Press, Orlando, FL 1987.

4 Example of Burning Propellants 2 ~1.8 s increase in r b 9% nal (ALEX) / 9% μal 1.5 r = 2.538P b s 5 mm s 1 43 μm Al 80 nm Al Combustion of μm Al far from surface Combustion of nm Al close to surface 0.5 r b = 2.092P % μal log (P) [MPa] T. R. Sippel, S. F. Son, L. J. Groven, Aluminum agglomeration reduction in a composite propellant using tailored Al/PTFE particles, Combustion and Flame 161 (2014) Mench, M.M., Yeh, C.L., and Kuo, K.K., Propellant Burning Rate Enhancement and Thermal Behavior of Ultra fine Aluminum Powders (ALEX), in Proc. of the 29th Annual lconference of ICT, 1998, pp G. V. Ivanov, and F. Tepper, Challenges in Propellants and Combustion 100 Years after Nobel, pp , (Ed. K. K. Kuo et al., Begell House, 1997).

5 Example of Burning Propellants: the Surface μmal agglomerate aggregate of nmal surface 500 μm 50 μmal spherical agglomerate formed by inflammation of an aluminized aggregate 50 μm nmal emerging from surface as aggregates (preagglomerate) L. T. De Luca, L. Galfetti, F. Severini, L. Meda, G. Marra, A. B. Vorozhtsov, V. S. Sedoi, and V. A. Babuk, Burning of Nano Aluminized Composite Rocket Propellants, Combustion, Explosion, and Shock Waves, Vol. 41, No. 6, pp , 2005

6 Al Burning Times Experiment 1173 K ng Time [m ms] Burni K K d 1 Anticipated Times Diameter [μm] d 2

7 Issues and Motivation Current Status: The fullextent of the anticipated gains from nanoscale energetic materials has not been realized in large part due to: Low sintering temperatures, High surface area leading to large aggregates, Limited solids loading with nanoparticles, Oxide coatings lowering active metal content, Lack of fundamental understanding of burning process Motivation: 3 D, hierarchical, ordered structures, controlled reactivity, addressable, improved processing combustion propellant p surface high solids loading propellant μm hierarchical composite particle energetic, gasifying, passivating agent nm particle distributed combustion w/o sintering of primary nm particles near propellant surface

8 Approach and Organization

9 Why Tetrazines and FGS? Substituted tetrazines are readily synthesized. Can be tailored to application (energetics, fluorophores, coordination chemistry) Covalent bonds formed via nucleophilic substitution of hydroxyls Tetrazine-based energetic materials are described by Los Alamos as a promising class of compounds materials for propellants and explosives. High density, high nitrogen compounds with unusual combustion mechanisms due to high heats of formation Ready addition of substituents for increased stability (more carbon) or increased energetics (more nitrogen) Functionalized graphene sheets (FGSs) are a reduced form of graphene oxide, containing high energy lattice defects and various oxygen functional groups distributed across a high surface area sheet. FGSs are catalysts for monopropellant combustion through hydroxyls on defect sites Defect sites and oxygen functionalities provide a variety of sites for chemical modification of the FGS Graphene gels--3d high surface area porous matrices--can be used as containers for gases, liquids, id and solids Tetrazines have been attached to FGSs via simple nucleophilic aromatic substitution and as covalent links between FGSs Heat of formation = 481 kj/mol 1,2,4,5-tetrazine Heat of formation = 536 kj/mol 3,6-dihydrazino- 1,2,4,5-tetrazine Heat of formation = 1101 kj/mol 3,6-diazido-1,2,4,5-tetrazine 9 Functionalized graphene sheet

10 Cachan/Princeton Tetrazines Covalently Bind to FGS FGS 2 FGS-Tz2 FGS-Tz3 FGS-Tz4 %C %N %O %Cl Aims for bridging i sheets with bound tetrazines: Porous matrix (graphene gel) Energetic links to decompose and fragment matrix (increased nitrogen content) Thermally and electrically conductive matrix Effect of binding tetrazines: Are covalently bound tetrazines more stable? What is the effect on the rate of tetrazine fragmentation? Does this change the rate of energy release? What are the reaction products?

11 Covalent Bonds Stabilize Tetrazines to Achieve More Decomposition C-H (undefined) Pure Tz4 Biphenyl rings C-H FGS-Tz4 (undefined) Confined rapid thermolysis (PSU): Rapid heating rate (2000 /s) prevents vaporization of condensed phase Reaction products past through infrared spectrometer for identification When heated to temperature high enough to initiate decomposition, bound tetrazines decompose into smaller molecular species 11

12 Covalently Bound Tetrazines Decompose at Higher Onset Temperature Only partial decomposition of Tz4 H 2 O + Large mass fragments 300 C More rapid decomposition of Tz4 in FGS-Tz4 H 2 O + 28 amu CO C Temperature rapidly increases with time (10 5 /s) Fragments analyzed by mass spectroscopy Pure tetrazines start to decompose at lower T, but produce large mass fragments Tetrazines bound to FGS start to decompose at higher T, but with higher rate of decomposition to form smaller mass fragments UMd/Princeton 12

13 Bound Tetrazines Quickly Fragment into Smaller Molecules under Rapid Heating Pure Tz4 H 2 O + FGS-Tz4 Onset T = 300 C Onset T = 440 C H 2 O + N 2+, CO CO 2 + Fragmentation of compounds under extremely rapid heating (10 5 /s) Pure tetrazines begin to decompose at lower temperature but generate large mass fragments, indicating incomplete decomposition The decomposition of tetrazines bound to FGS begins at higher temperature with lower mass fragments, indicating more complete decomposition 13

14 2700 K 0 ps Free Tz4 tetrazine Tz4 and Bound Tz4 Decompose through Different Mechanisms 0.31 ps 0.64 ps E E 462 kj/mol 472 kj/mol 0 ps 0.28 ps Tz4 tetrazine bound to FGS E 1 st tetrazine ring fragments 2 nd tetrazine ring fragments E 0.61 ps 1915 kj/mol Both tetrazine rings fragment along with biphenyl group 1610 kj/mol Fragmentation and product formation continues Molecular dynamic model: temperature raised instantaneously to 2700 K to ensure tetrazine decomposition Bound tetrazine rapidly and more completely decomposes; fragmentation proceeds on or near FGS Faster rate of reaction for tetrazine decomposition leads to higher rate of energy production Hypothesis: vibrational state of bound tetrazine very high local temperature much higher than ambient why?

15 Graphene additive to rocket fuels Some liquid rocket motors use fuel in cooling passages fuel film cooling produces coke variability in heat transfer and clogging. Additives may lower fuel decomposition temperature to enhance cooling without coking. n-c 12 2H 26 Conve ersion, % wt%-Pt/FGS MPa, 50 ppmw FGS, 10 ppmw Pt C 500 C 530 C no additive FGS Pt-FGS Graphene w and w/o catalyst may be used to accelerate decomposition kinetics. Particle pinning to surface remains intact and therefore additive may subsequently be used to enhance gas-phase combustion. Low concentrations may be suspended in liquid rocket fuels more reactive catalyst desired. Applications to ionic liquids should be considered. BEFORE supercritical pyrolysis at 800 K & 4.75 MPa AFTER: Pt remains pinned & discretized.

16 Effects of Particles in Combustion Sprays Fuel propellant sprays are studied at low and elevated pressures (sub and supercritical) without and with combustion. The effects of the nanocomposite additives on the spray characteristics, ignition, and combustion are studied. Re=1,400 Re=3,500 Pure MCH MCH + Pt-FGS (50 ppm) P=600 psi

17 Reaction Modeling of Graphene and Al Based Clusters/Composites in C/H/O/N Systems Thermal decomposition modeling results of graphene with n-dodecane using ReaxFF consistent with experiments (with H. Sim and Adri van Duin, PSU) Dehydrogenation of n-dodecane: C 53 H 20 O 2 (graphene) + C 12 H 26 C 53 H 21 O 2 + C 12 H 25 C-C scission followed by the dehydrogenation to form smaller products: C 12 H 25 C 4 H 8 + C 8 H 17 Number of n dodecane w or w/o oxidized graphene (C 53 H 20 O 2 ) at 1800 K (density = 0.12 and 0.31 g/cc) 30 No of n-dodecan ne no particle_at 0.12 g/cc no particle at 0.31 g/cc w/ oxid graphene at 0.12 g/cc w/ oxid graphene at 0.31 g/cc Time (ns) In preparation to model the oxidation of Al clusters and composite particles, thermal oxidation i of Al nanoparticles was performed using ReaxFF (with S. Hong and Adri van Duin, PSU) 0.5 ps X section 0.0 ps Low oxygen density at 300 K 1.0 ps 5 ReaxFF reactive force has been developed for Al/C/H/O systems. HotsH t spots were observed at outer surface of nm (864 atom) particle during oxide formation for NVT simulations at 300, 500, and 900 K. Hot spots generated voids, which accelerated transport and reaction by reducing reaction barrier for diffusion i from 36 kcal/mol l to 2.9 kcal/mol

18 Modeling and Simulation of Heat Transport and Combustion of Nanoenergetic Materials Atomistic Scale Modeling of Heat Transport in Nano-Particle Laden Fluids study heat transport in nano-particle laden fluids using MD simulations and calculate transport properties results serve as inputs to macro-scale combustion models Macro-Scale Modeling of Combustion of Metal-Based Heterogeneous Reactive Materials investigate mechanisms that control burning rate of mixtures explored the effects of particle entrainment and agglomeration on burning properties of nano-aluminum and water mixtures nano-aluminum and water mixtures aluminum, water, and hydrogen peroxide mixtures nickel-clad clad aluminum pellets

19 Effect of Particle Entrainment and Agglomeration on Combustion of Nano-Al/Water Mixtures Does nano-al agglomerate during combustion? Does particle motion affect burning behaviors? Aluminum particles can be entrained by the flow water vapor generated by water vaporization n Particle velocity: up = rb( ρl / ρg), 0 n 1 n = 0: no entrainment; n =1: complete entrainment Burning rate: r b = ap m Diffusion regime: 0 < m <0.5 Kinetics: 0.5 < m < 1 Pressure dependence of burning rate due to combustion mechanism (burn time: t b ~ p -q ) particle entrainment Entrainment lowers burning rate by increasing flame thickness and decreasing heat flux Particles cluster and agglomerate (d~3-5 μm) due to inter- & intra-particle attractive forces Favorable agreement with experimental data only when entrainment & agglomeration are considered Pressure Expo onent, m Burning Rate (r b ), cm/s Kinetic Diffusion Present Study Zaseck Son s et group al. [12] Sundaram Our previous et al. work [7] r b =ap m Entrainment Index, n Experiment Yetter s group [13] Kinetic (q = 1.0, n = 0.0, d p = 80 nm) Kinetic (q = 0.58, n = 0.0, d p = 80 nm) Kinetic (q = 0.58, n = 0.4, d p = 80 nm) Diffusion (n = 0.5, d ag = 4 μm) Pressure (p), 21 January MPa 2015

20 Heat Transport in Metal-Based Energetic Materials How does particle size affect thermal conductivities of particle & particle-laden fluid? Can macro-scale models be directly applied for systems with nano-particles? Equilibrium MD (EMD) λ 1 = 2 k BVT 0 J ( t). J (0) 3 Non-equilibrium i MD (NEMD) q λ = dt / dx Models validated d for bulk solid argon For aluminum, potential function exerts significant effect on predictions Predicted thermal conductivities orders of magnitude lower than bulk value (230 W/m-k) Classical MD treats only phonon mode dt Thermal conductivity y, W/m-K MD - NVT Christen - Pollack Clayton - Batchelder Krupskii White - Woods NEMD Argon Temperature, K Potential Aluminum Thermal Conductivity (W/m- K) EMD NEMD Lenard-Jones Sutton-Chen Cleri-Rosato Glue Mishin January

21 Mike Zachariah h (Metallic Clusters and Mesoscopic Aggregates) Steve Son (Integration of Nanoenergetic Composite Ingredients/Mixtures and their Reactive Characterization) Stef Thynell (Experimental and QM Investigation of Decomposition and Early Chemical Kinetics of Ammonia Borane)

22 Extras

23 Research Approach 1 s 100sAtoms (Periodic Systems) Combustion Characteristics, Propulsive Behaviors, Burning Properties Meso-Scale Models 1 ns Inter-Atomic Potential Molecular Functions Dynamics 1 fs Quantum Mechanics QM/MD Models Thermodynamic and Transport Properties, Ignition Characteristics, Reaction Mechanisms 1 Å 10 nm Length Scales 1 m

24 Significant Accomplishments Explored the effects of particle entrainment and agglomeration on burning properties of nano-aluminum and water mixtures Studied the effects of hydrogen peroxide on combustion of aluminum and water mixtures Investigated the effect of packing density on burning properties of metal-based energetic materials Developed equilibrium and non-equilibrium MD simulation frameworks to study heat transport in metal-based nanoenergetic materials

25 Combustion of Aluminum/Water/Hydrogen Peroxide Mixtures What is the effect of hydrogen peroxide on burning properties of Al/water mixtures? Model is employed is investigate burning bh behaviors of Al/water/H /H 2 O 2 system Pressure: 1-20 MPa; Particle size: 3-70 μm O/F: ; H 2 O 2 conc.: 0-90 % Particle entrainment phenomenon is considered Results compared with experimental data of Son s group (Purdue) For large particles, pressure dependence of burning rate is attributed to particle entrainment effect (and not reaction kinetics) Transition from diffusion to kinetically-controlled conditions causes the exponent to increase from 0.35 at 70 μmto1.04at3μm Burning rate nearly doubled when the concentration of hydrogen peroxide increases from0to90% Burning Rate(r b ), cm/s onent,m PressureExp H-15 [14] (Son s Son group) et al. H-30 [14] (Son s group) H-15 H-30 H-50 Kinetic Regime H-60 n= % H 2 O 2 O/F = Pressure (p), MPa Diffusioni Regime Particle Diameter, μm

26 Effect of Packing Density on Burning Properties of Nickel-Clad Aluminum Pellets How does packing density affect burning rates of metal-based energetic materials? Flame propagation of nickel-coated aluminum particles il in argon environment studied did Particle size is 79 µm and pressure is 1 atm Energy conservation for the pellet 2 T T ρmcp m = λm + Q Q Q t x, 2 gen conv rad Conduction & radiation heat losses to ambiance MD diffusion i coefficients i inputs to the model Five different models of thermal conductivity employed to identify the most accurate model Maxwell-Eucken-Bruggeman thermal conductivity model offers best predictions treats both random (Bruggeman) and dispersed (Maxwell) particle distributions ib ti Burning rate increases sharply at a packing density of 60 %. Burning Rate e,mm/s Burning Ra ate, mm/s Ticha Bruggeman Parallel MEB 120 Predictions Duetal. [47],c=6 100 Predictions Du et al. [47], c = 15 Yetter s Experiment Dean et group al. [13] Maxwell Pellet Density, ρ/ρ TMD d p =79μm δ s =7μm Pellet Density, ρ/ρ TMD

27 Publications 1. D.S. Sundaram and V. Yang, Effect of Packing Density on Flame Propagation of Nickel-Coated Aluminum Particles, Combustion and Flame, Vol. 161, 2014, pp D.S. Sundaram and V. Yang, Combustion of Micron-Sized Aluminum Particle, Liquid Water, and Hydrogen Peroxide Mixtures, Combustion and dflame, Vol. 161, 2014, pp D.S. Sundaram and V. Yang, Effects of Entrainment and Agglomeration of Particles on Combustion of Nano- Aluminum and Water Mixtures, Combustion and Flame, Vol. 161, 2014, pp D.S. Sundaram, P. Puri, V. Yang, Thermochemical Behavior of Nano-Sized Aluminum-Coated Nickel particles, Journal of Nanoparticle Research, Vol. 16, No. 2392, 2014, pp D.S. Sundaram, V. Yang, Y. Huang, G.A. Risha, R.A. Yetter, Effects of Particle Size and Pressure on Combustion of Nano-Aluminum Particles and Liquid Water, Combustion and Flame, Vol. 160, 2013, pp D.S. Sundaram, P. Puri, V. Yang, Pyrophoricity of Nascent and Passivated Aluminum Particles at Nano Scales, Combustion and Flame, Vol. 160, 2013, pp D.S. Sundaram, P. Puri, V. Yang, Thermochemical Behavior of Nickel-Coated Nanoaluminum particles, Journal of Physical Chemistry C, Vol. 117, 2013, pp D.S. Sundaram, V. Yang, T.L. Connell Jr., G.A. Risha, R.A. Yetter, Flame Propagation of Nano/Micron-Sized Aluminum Particles and Ice (ALICE) Mixtures, Proceedings of the Combustion Institute,, Vol. 34, 2013, pp D.S. Sundaram, V. Yang, and V.E. Zarko, Combustion of Nano Aluminum Particles: A Review, to appear in Combustion, Explosion, and Shock Waves. 10. D.S. Sundaram and V. Yang, A General Theory of Ignition and Combustion of Aluminum Particles, Combustion and Flame, to be submitted. 11. D.S. Sundaram, V. Yang, and R.A. Yetter, Metal-Based Nanoenergetic Materials: Synthesis, Properties, and Applications, Progress in Energy and Combustion Science, to be submitted.

28 Increased Rate and Extent of Fragmentation for Bound Tetrazines Pure Tz4 FGS-Tz Heat ting Rate (K K/s) Endotherm 250 C Heat ting Rate (K K/s) Endotherm 400 C Time (s) Time (s) Nanocalorimetry (UMd/NIST): Endotherms from sample fragmenting on sample pad during extremely rapid heating (10 5 /s); only bond breaking observed Products of fragmentation leave sample pad, ported to mass spectrometer for analysis Onset of fragmentation delayed to higher T tetrazine more stable with respect to higher temperature when bound to FGS Larger amount of energy absorbed upon fragmentation, indicating a larger extent of fragmentation in tetrazines bound to FGS 28

29 Pure Tz3 More Complete Fragmentation a General Mechanism for Bound Tetrazines m/z = 149 amu Methyl-adamantane substitutent (MW = 149 amu) FGS-Tz3 (bound tetrazine) No methyl-adamantane fragments Effect of binding tetrazines to FGS is similar regardless of tetrazine used Bound tetrazines are stable to higher temperature, but When fragmentation begins, it is rapid and more complete. This results in a faster rate of reaction leading to higher rates of energy release. 29

30 Summary and Targets bis-tetrazines covalently bind to FGSs Tz4 effective and rigid bridging agent Covalent bond confirmed by CV, XPX, FTIR, thermal analysis, and modeling Tetrazines covalently bound to FGS decompose at higher temperature and more completely Models indicate a directed decomposition pathway Higher rate of energy release shown in experiment and model Targets: Define the mechanism for bound tetrazine decomposition Develop new hybrid materials with higher h nitrogen content t Combine hybrid materials with liquid and solid propellants o Ignition and combustion o Hypergolic fuels o 3-dimensional graphene gels Incorporate hybrids into printable, conductive inks o Energetic devices: addressable igniters 30

31 Research Area Overview Solid and liquid propellants p with energetic additives Characterization of combustion behavior of composite additives and propellants containing additives Reaction analysis and model development of propellants with composite particles Analysis of transport properties Reaction analysis and model development of propellants with composite particles Reaction analysis of interstitial ingredients Reaction analysis of primary particles and supports Analysis of entrainment, sintering, and agglomeration Strand Solid Propellant Reaction analysis of composite particles Condensed phase reactions Advanced Diagnostics Multiscale Modeling Analysis of transport properties Analysis of entrainment, sintering, and agglomeration Droplet Reaction analysis of interstitial ingredients Liquid Propellant