Metal/ Intermetallic nanoparticles and nanoalloys as energetic nanomaterials (ENMs) for solid propellant applications
Our past studies on the synthesis and energetic behavior of Al nanoparticles (NPs) have led to the development of kinetic Monte Carlo (KMC) simulations to investigate the role of heat release during non-isothermal collision/coalescence of metal NPs grown out of aerosol routes in driving their fractal-like morphologies and in turn, their interfacial oxidation kinetics. Morphological complexities of NP aggregates evolving out of colloidal and/or, aerosol routes are finally dictated by their constituent primary particles formed during saturated vapor phase nucleation - a phenomenon that is theoretically and experimentally irreconcilable and hence, extremely ill-understood till date! Hence, we develop phenomenological and KMC-based models to gain fundamental insight into the mechanistic picture behind homogenous and non-isothermal vapor-phase nucleation of metal NPs without the underlying capillarity approximation (constant surface tension for all cluster sizes), and steady-state assumptions of classical nucleation theory (CNT). In the past, we have also carried out mass spectrometric analysis and developed LIBS as a quantitative analytical tool for in-situ studies of Al NP oxidation. In future, we seek to extend our studies towards the synthesis and characterizations of morphologically and structurally tuned intermetallic NPs that promote large heat release as a result of self-propagating high-temperature synthesis (SHS) reactions during their alloy formation owing to their large negative reaction enthalpies.
Relevant Publications:
Seyyed Ali Davari, and Dibyendu Mukherjee, (2017) “Homogeneous nucleation of metal nanoparticles: A kinetic Monte Carlo model to study the vapor phase synthesis of Al nanoparticles,” AIChE Journal, DOI: 10.1002/aic.15887.
Dibyendu Mukherjee‡, Matthew Wang, and Bamin Khomami, (2012) “Impact of particle morphology on surface oxidation of nanoparticles: A Kinetic Monte Carlo based study”, (‡=Corresponding Author), AIChE Journal, 58(11), 3341.
D. Mukherjee, A. Prakash and M. R. Zachariah, (2006) “The implementation of a discrete nodal model to probe the effect of size-dependent surface tension on nanoparticle formation and growth”, Journal of Aerosol Science, 37, 1388.
D. Mukherjee, A. Rai and M. R. Zachariah, (2006) “Quantitative laser-induced breakdown spectroscopy for aerosols using internal calibration standards: Application to the oxidative coating of aluminum nanoparticles”, Journal of Aerosol Science, 37, 667.
K. Park, D. Lee, A. Rai, D. Mukherjee, and M. R. Zachariah, (2004) “Size resolved kinetics measurements of aluminum nanoparticle oxidation by single particle mass spectrometry”, Journal of Physical Chemistry B, 109, 7290.
D. Mukherjee, C. G. Sonwane and M. R. Zachariah, (2003) “Kinetic Monte-Carlo simulation of the effect of coalescence energy release on the size and shape evolution of nanoparticles grown as an aerosol”, Journal of Chemical Physics, 119, 3391.
S. A. Davari, D. Mukherjee, (2017) “Homogeneous nucleation of metal nanoparticles: A kinetic Monte Carlo model to study the vapor phase synthesis of Al nanoparticles,” AIChE Journal, DOI: 10.1002/aic.15887.
Advanced Laser Induced Breakdown Spectroscopy (LIBS) for quantitative analysis of biomolecules, semiconducting materials and metal/intermetallic nanoparticles
Laser-induced breakdown spectroscopy (LIBS) involves the collection and processing of the spectral signature resulting from high-irradiance pulsed laser generated plasma containing an analyte. Typically, a high-energy pulsed laser is tightly focused onto the analyte sample (solid, liquid or gas) to form a plasma. The laser-induced plasma atomizes and excites the samples through complete thermal vaporization and decomposition of the target materials. The optical emissions resulting from the relaxation of the excited atomic/ionic states are recorded as signature spectral lines via spectrograph and ICCD camera. In the past, we have developed a methodology using internal calibration standards that enables LIBS to carry out quantitative spectrochemical analysis of the atomic constituents of the analyte sample (Q-LIBS technique). We have extended this technique in our lab for the analysis of a wide class of metal/intermetallic nanoparticles, bio-aerosols and semiconducting materials.
- LIBS Analysis of intermetallic nanoparticles/nanocomposites
LIBS has been mostly used for elemental composition analysis of bulk materials. We have expanded LIBS application to quantitative measurment (Q-LIBS) for complex intermetallic (IM) nanoalloy (NAs) and nanocomposites (NCs) as well as advanced metal oxide (MO) nanomaterials. The obtained results are in a good agreement with Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), which indicates LIBS is not only useful for chemical composition detection, but also can be used for quantitative mesearmunts, with minimum sample preparation.
Personnel Involved: Amanda Knopps (PhD Student; CEME)
Funded by: ONR, Department of Defense (DoD).
Relevant Publications:
S.A. Davari, S. Hu, D. Mukherjee, (2017), "Calibration-free quantitative analysis of elemental ratios in intermetallic nanoalloys and nanocomposites using Laser Induced Breakdown Spectroscopy (LIBS)”, Talanta, 164, 330-340
S.A. Davari, S. Hu, E. L. Ribeiro, D. Mukherjee, (2017) "Rapid elemental composition analysis of intermetallic ternary nanoalloys using calibration- free quantitative Laser Induced Breakdown Spectroscopy (LIBS) ", MRS Advances, DOI: 10.1557/adv.2017.303.
- LIBS Analysis of dissolved oxygen content in single crystal Si wafers (Funded by SunEdison Semiconductors)
Interstitial oxygen content of a silicon wafer is an important material characteristic for most modern device technologies. Interstitial oxygen in silicon is typically measured by infrared absorption. The accuracy of these measurements is subject to error. These wafer measurements are time consuming and potentially introduce handling damage or contamination to the finished polished wafer. LIBS has been used for measuring interstitial Oxygen in silicon wafers. Fast mesurmeant, and minimum sample preparation makes LIBS a perfect candidate for this purpose.
Relevant Publications:
S. A. Davari, S. Hu, R. Pamu, D. Mukherjee, (2017) "Calibration-free quantitative analysis of thin-film oxide layers in semiconductors using Laser Induced Breakdown Spectroscopy (LIBS)," Journal of Analytical Atomic Spectrometry, DOI: 10.1039/C7JA00083A.
Design, synthesis and characterization of metastable ceramic nanoparticles (Oxides/Carbides/Nitrides) as advanced ENMs
- Tailoring metastable metal/ceramic-interfaced composite ENMs via controlled LASiS dynamics:
ENMs find applications in solid-state propellants, explosives and pyrotechnics due to the anticipated kinetically controlled ignition arising from large specific surface areas, metastable structures and smaller diffusion lengths in nanoscale regimes. Past works have investigated energetic properties of metal nanoparticles (NPs) (Al, Ni, Si, etc.) and composite Al/oxidizer mixtures for their size-dependent properties and heat release mechanisms at nanoscale. Yet, the large heat release in first-generation ENMs have been offset by hindered detonation rates due to the fuel-oxidizer diffusion lengths and rates being compromised by excessive oxide shell formations and NP aggregations. To this end, few research efforts have tapped into the unique yet diverse possibilities of tuning the reactivity of ENMs by tailoring their metastable states and surface structural rearrangements in shell-core nanostructures that can lead to enhanced thermochemical stability, while allowing for safe activations under desired conditions. Although such efforts would be novel and commendable, weak fundamental understanding and challenges in the design and synthesis of next-generation metastable ENMs whose surface reactivity can be tuned via structural arrangements of interfacial atoms have stymied their potential as future ENMs. This project aims to address the aforesaid knowledge gap via rational design, synthesis and structure-property characterizations of composite metal/ceramic NPs (<10 nm) encapsulated in fullerene-like Carbon nanocages. High-energy LASiS techniques shall be used for manufacturing the composite ENMs whose energetic behaviors will be tailored by tuning their metastable states/interfaces, compositions and crystallinity. Structure-composition properties evolving out of the complex plasma process will be tailored via detailed mechanistic understanding for the chemical dynamics and reaction mechanisms during LASiS. Such efforts will also pave the path for systematic design of advanced metastable ENMs with enhanced safety and reduced sensitivities.
Personnel Involved: Shubham Garg (PhD student; CEME); Amanda Knopps (PhD Student; CEME)
Funded by: ONR, Department of Defense (DoD).
- Synthesis and characterization of metastable amorphous-Al oxides (a-AlOx; 2.5<x<=3.0)
Abundant progress has been made in conventional equilibrium syntheses and predictions of lowest energy ground-state materials with well-defined structures or orders. Yet, a large gamut of materials remains unexplored in the vastly untapped far-from-equilibrium phase space. Binary metal oxides are known to exist in ddiverse polymorphic phases under varying pressure-temperature conditions. Of them, crystalline oxides of Aluminum (Al), the most earth-abundant metal, have been well-studied. But, non-stoichiometric/amorphous Al-oxide structures in metastable states - albeit, theoretically predicted - are rarely reported in experiments due to the inability to kinetically trap and phase-stabilize such targeted structures in useful amounts over practical timescales. We address this grand challenge by employing Laser Ablation Synthesis in Solution (LASiS) as a facile non-equilibrium route to synthesize unusually hyper-oxidized and metastable amorphous-AlOx nanoparticles (a-AlOx NPs) that are remarkably stabilized by interfacial monolayer skins of ordered carbon atoms. Unlike past rare sightings of a-AlOx structures, LASiS allowed one-pot synthesis in a reproducible and scalable fashion to enable extensive bulk and surface characterizations. The formidable task of contriving rational characterization routes for such a rarely observed material guided our unconventional and disparate approaches here for the first-ever comprehensive study on its structural and chemical properties as well as stabilization mechanism.
Personnel Involved: Elijah Davis (PhD, 2024; CBE; UTK) manda Knopps (PhD Student; CEME)
Funded by: AFOSR, Department of Defense (DoD).
- Synthesis and characterization of cubic boron nitride
Boron nitride (BN) bears highly similar structures as carbon nanodiamond (ND) that are well-known as unique nanoparticle (NP) materials finding a myriad of useful applications, e.g., fluorescent biomarkers, electronics, photovoltaics, plasmonics, catalysis. Theoretical investigations on ND and BN NPs suggest the unique possibility of surface structural arrangements that affect core structures, and hence, result in possible large internal stresses in these nanostructures. Specifically, h-BN (Point group = D6h, Space group = P63/mmc) and c-BN (Space group = Fd3m) have generated tremendous scientific and technological interests due to their analogous structures and properties with graphite and diamond, respectively. The c-BN (lattice constant = 0.361nm) and diamond (0.356nm) exhibit strong interatomic potentials that lead to the highest hardness (∼7500 kg mm−2 for c-BN and ∼10,000 kg mm−2 for ND) and stiffness (Young’s modulus ∼700 GPa for c-BN and ∼1000 GPa for ND). Apart from that, c-BN exhibits high thermal conductivity (~12 W cm−1 K−1), close to that of diamond ~20 Wcm−1 K−1, which has one of the highest values including that of copper (~4 W cm−1 K−1), while the coefficient of friction for c-BN and ND is the lowest (less than 0.1) among all known materials. However, c-BN has certain advantages over ND, namely: 1) it is more oxidation-resistant; 2) it has higher thermal stability and hence, less reactive even at high temperatures with ferrous alloys; and 3) it is a wide-band-gap semiconductor (Eb~5.5 eV). Such properties make c-BN coatings the Holy Grail in materials science research for machining alloys, protective shells on energetic materials as well as for advanced semi-conductor materials. Specifically, the origin of unique surface nanostructures of BNNPs, when combined with the aforementioned diverse interfacial properties, can provide paradigm shift in the design of novel NPs with tunable interfacial stresses and activities – for both catalytic and next-generation energetic materials. But a fundamental knowledge gap exists in the rational design and synthesis of such metastable NPs due to the highly challenging and complex synthesis routes involved. We address the aforementioned knowledge gap through high-energy laser ablation-based rational design, and synthesis combined with structure-property characterizations of c-BN NPs (<10 nm sizes) comprising fullerene-like surface nanocage structures.
Relevant Publications:
Coming soon. Stay Tuned!