Characterization of thermochemical properties of Al nanoparticle and NiO nanowire composites
© Wen et al.; licensee Springer. 2013
Received: 5 March 2013
Accepted: 27 March 2013
Published: 20 April 2013
Thermochemical properties and microstructures of the composite of Al nanoparticles and NiO nanowires were characterized. The nanowires were synthesized using a hydrothermal method and were mixed with these nanoparticles by sonication. Electron microscopic images of these composites showed dispersed NiO nanowires decorated with Al nanoparticles. Thermal analysis suggests the influence of NiO mass ratio was insignificant with regard to the onset temperature of the observed thermite reaction, although energy release values changed dramatically with varying NiO ratios. Reaction products from the fuel-rich composites were found to include elemental Al and Ni, Al2O3, and AlNi. The production of the AlNi phase, confirmed by an ab initio molecular dynamics simulation, was associated with the formation of some metallic liquid spheres from the thermite reaction.
KeywordsComposite Aluminum nanoparticles NiO nanowires Alumina Nickel aluminide
Metastable intermolecular composites (MICs) are often composed of aluminum nanoparticles (the fuel is usually manufactured with a shell of alumina on each particle) and some oxidizer nanoparticles including CuO [1–12], Fe2O3[13–15], Bi2O3[5, 16], MoO3[5, 17, 18], and WO3[5, 19, 20]. These MICs have drawn much attention recently in developing reliable and high-performance power generation systems due to their nanosized components which allow for the tuning of ignition temperature, reaction propagation rate, and volumetric energy density [12, 17, 21–24]. Applications include gas generators, micro-heaters, micro-thrusters, micro-detonators, and micro-initiators . MICs can be used to fabricate an insert element which is assembled into the conventional solid propellants. This approach helps adjust ignition timing and enhance combustion propagation. However, the challenge remains in identifying a suitable MIC candidate for providing an optimal energetic performance which matches with the properties of the solid propellants.
Generally speaking, better control of the initiation process requires a sufficient heat production rate from the MIC core and a relatively slow pressure increase at the interface between the MIC core and the solid propellant. Gasless thermite reactions are desired for this reason. Gas generation from the thermite reactions is mainly attributed to the formation of vapors of metals (such as Cu, Fe, and Ni), the elemental oxygen (formed from the decomposition of the oxidizer), the gas of metal oxides if the combustion temperature is high enough, and other gaseous reaction products. While the metal vapor forms at a temperature which is above the boiling temperature of the metal, the release of elemental oxygen from the decomposition of the oxidizer component of MICs can be significant as well. Recently, Sullivan and Zachariah characterized the reaction mechanism of a variety of MICs , and they found that, while most oxidizers such as CuO and SnO2 decompose before the thermite reactions occur, which possibly indicates solid-state reactions, the decomposition of Fe2O3 becomes rate-limiting for igniting its thermite reaction. More investigations are needed in order to understand the cause of these different ignition mechanisms. Among the bulk scale thermite reactions, the Al-NiO system was reported to produce less gas . Theoretically, gas (vapor and oxygen) generation from the Al/NiO thermite is about 2% of the gas produced from the Al/CuO thermite and is much lower than other comparable thermite systems. It is therefore worthwhile to investigate the thermochemical properties of the corresponding MIC made of Al and NiO nanostructures. The research objectives of this work were to synthesize and characterize the microstructures of the powder-type Al nanoparticle and NiO nanowire MIC and to investigate its ignition and energy release properties.
In the literature, there are few research papers on the characterization of Al/NiO-based composites. Recently, an Al/NiO MIC was developed on a silicon substrate  for fabricating a two-dimensional geometry. The process started from the thermal oxidation of a Ni film to form a NiO honeycomb. An Al layer was then coated onto this honeycomb by thermal evaporation. The produced Al/NiO MIC exhibited a low ignition temperature and improved the interfacial contact area between Al and NiO. The energy release per mass data was reported, but the method for determining that data was not reported. In that same study, the fabrication method was developed with the presence of a silicon substrate and may not be suitable for other previously mentioned applications. A more detailed investigation on thermochemical behaviors and product microstructures of the powder-type Al/NiO MIC is highly desired.
The reaction properties of a powder MIC depend on the particle size, shape, morphology, and microstructure of its fuel and oxidizer components. A variety of metal oxide nanostructures have been fabricated and implemented in developing high-energy-density MICs, which take the forms of nanospheres , nanowires [2, 30], nanofibers , and nanorods [3, 32]. Usually, the fineness (or particle size) and bulk density of these oxidizers and the degree of their intermixing and interfacial contacting with Al nanoparticles are among the critical factors which influence the ignition mechanism [30, 33]. A recent study showed that the use of CuO nanowires resulted in better mixing between the fuel and oxidizer components of MIC and subsequently facilitated a low-temperature ignition . Their measurements of the pressurization rate from a composite of Al nanoparticles and porous CuO nanowires were about ten times greater than those from the Al and CuO nanoparticle MICs. Other means such as the fabrication of the core-shell nanostructures [2, 34–36] and intermetallic multilayers [22, 37–39] were recently developed to enhance the energetic properties of MICs. Also, the core-shell nanowire- and nanoparticle-based thermites indeed exhibited an improved mixing homogeneity and low activation energy [2, 40]. In this study, NiO nanowires were synthesized, and an effective preparation method to improve intermixing between these NiO nanowires and Al nanoparticles was developed, and then influences of the equivalence ratio of MIC on the ignition process and the energy release value were investigated. The reaction products were examined by electron microscopy and X-ray diffraction in order to identify their chemical compositions and microstructures.
Alumina-passivated Al nanoparticles with a diameter range of 50 to 120 nm were purchased from Sigma-Aldrich Corporation (St. Louis, MO, USA). These nanoparticles were handled in an argon-filled glove box before being mixed with the oxidizer. The thickness of the oxide shell was about 5 to 8 nm which agrees with the reported data on passivated Al nanoparticles [41, 42]. By assuming the averaged nanoparticle diameter of 80 nm, this shell thickness indicates that the content of Al is about 50%. NiO nanowires were synthesized by a hydrothermal method; their average diameters were approximately 20 nm, and their lengths were several microns. Hydrothermal synthesis involved two major steps. First, NiOH nanostructures were formed at 120°C in a weak alkaline solution when Ni(NO3) reacted with a Ni source. NiO nanowires were then produced by annealing NiOH nanostructures at 500°C for 1 h at ambient atmosphere.
Compositions of six Al nanoparticle and NiO nanowire composites
Weight percentage of NiO nanowires (%)
Equivalence ratio ( Φ)a
This measurement revealed the active aluminum content of about 41% to 43%. In this study, the value of 42% was used for determining the equivalence ratio, as shown in Table 1.
The onset temperatures and energy release values were investigated by differential scanning calorimetry (DSC) and using TGA data. These tests were performed in a SDT-Q600 from TA Instruments (New Castle, DE, USA) and compared with the data from a 409 PG/PC NETZSCH (NETZSCH-Gerätebau GmbH, Selb, Germany) simultaneous thermal analysis machine which provides measurements of weight change (TGA) and differential heat flow (DSC) on the same sample. For the SDT-Q600 measurements, the DSC heat flow data were normalized using the instantaneous sample weight at any given temperature. The SDT system was calibrated by following these four steps: (1) TGA weight calibration, (2) differential thermal analysis baseline calibration for the ΔT signal, (3) temperature calibration, and (4) DSC heat flow calibration. In order to remove humidity, these samples were purged in argon for 15 min before thermal scanning. All DSC/TGA experiments were conducted in argon (alpha 2) with a heating rate of 10 K/min, purge flow of 50 ml/min, and temperature range between 35°C and 1,300°C. The obtained mass and heat flow signals were analyzed by the TA analysis software through which the onset temperatures and reaction enthalpies were derived. To determine the compositions of reaction products and their microstructures, the Al/NiO pellets with Φ = 3.5 were heated in argon to 150°C, 450°C, and 800°C on a hot plate. These experiments were performed in a glove box, and the processed pellets were then examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDAX), and X-ray diffraction (XRD). For SEM imaging, the samples were 10 nm gold coated. The XRD patterns were captured using a Rigaku SA-HF3 (1.54 Å CuKα) X-ray source (Rigaku Corporation, Tokyo, Japan) equipped with an 800-μm collimator, operating at an excitation of 50-kV voltage, 40-mA current, and 2-kW power.
where, on the right hand side of the equation, the first term represents the electron-nucleus attraction, the second represents the electron–electron repulsion, and the final term, V NN , represents the nucleus-nucleus repulsion. A large-size box consisting of 25 × 15 × 12.815 Å was used, and gamma point calculations were implemented. The double zeta plus polarization basic set was employed with a very high mesh cutoff of 300 Ry. To reduce the computational cost, the norm-conserving pseudopotentials  were used to replace the complicated effects of the motions of the core (i.e., non-valence) electrons of an atom and its nucleus.
Results and discussion
The dependence of the onset temperatures on the NiO ratios of the composites is shown in Figure 3. It can be observed that increasing the NiO ratio did not significantly change the onset temperature of the exothermic peak. This indicates a narrow size distribution of Al nanoparticles in these composites and sufficient intermixing between Al nanoparticles and NiO nanowires. All measured onset temperatures are smaller than the melting temperature of bulk Al. In the literature, it was suggested that the activation energy of the thermite reaction depends on the diffusion distance over which these metal ions (aluminum and nickel which become available from the decomposition of NiO) need to travel before initiating the reaction .
In summary, the Al/NiO MIC was prepared using the NiO nanowires synthesized hydrothermally with an average diameter of about 20 nm and a length of a few microns. Six fuel-rich samples with different equivalence ratios from 1.7 to 18 were studied. The sonication process of 20 min helped produce the well-dispersed Al nanoparticles decorated on the NiO nanowires. The DSC/TGA measurements showed the onset temperatures of these Al/NiO MICs of about 460°C to 480°C. The ratio of the NiO nanowires in the MIC was found to have a less effect on the onset temperature. The derived energy release value increased significantly from 600 to 1,000 J/g when the NiO amount was increased from 9% to 50%, which were all smaller than the theoretical reaction heat of the Al and NiO thermite reaction. The chemical compositions and microstructures of these MICs were examined using XRD, SEM, and EDAX, which showed the evidence of the AlNi phase, together with the Al, Ni, and Al2O3, from the fuel-rich Al/NiO MICs. The formation mechanism of the AlNi phase was investigated using a preliminary molecular dynamics simulation which showed a diffusion of Al atoms to the Ni cluster.
This work was supported by NSERC Canada, and the authors thank Dr. Robert Stowe for the helpful discussions.
- Apperson S, Shende RV, Subramanian S, Tappmeyer D, Gangopadhyay S, Chen Z, Gangopadhyay K, Redner P, Nicholich S, Kapoor D: Generation of fast propagating combustion and shock waves with copper oxide/aluminum nanothermite composites. Appl Phys Lett 2007, 91: 243109. 10.1063/1.2787972View Article
- Yang Y, Xu DG, Zhang KL: Effect of nanostructures on the exothermic reaction and ignition of Al/CuO x based energetic materials. J. Mater Sci 2012, 47: 1296–1305. 10.1007/s10853-011-5903-zView Article
- Shende R, Subramanian S, Hasan S, Apperson S, Thiruvengadathan R, Gangopadhyay K, Gangopadhyay S, Redner P, Kapoor D, Nicolich S, Balas W: Nanoenergetic composites of CuO nanorods, nanowires, and Al nanoparticles. Propellants Explosives Pyrotechnics 2008, 33: 122–130. 10.1002/prep.200800212View Article
- Jian G, Piekiel NW, Zachariah MR: Time-resolved mass spectrometry of nano-Al and nano-Al/CuO thermite under rapid heating: a mechanistic study. J Phys Chem C 2012, 116: 26881–26887. 10.1021/jp306717mView Article
- Sanders VE, Asay BW, Foley TJ, Tappan BC, Pacheco AN, Son SF: Reaction propagation of four nanoscale energetic composites (Al/MoO3, Al/WO3, Al/CuO, and Bi2O3). J Propul Power 2007, 23: 707–714. 10.2514/1.26089View Article
- Severac F, Alphonse P, Esteve A, Bancaud A, Rossi C: High-energy Al/CuO nanocomposites obtained by DNA-directed assembly. Adv Funct Mater 2012, 22: 323–329. 10.1002/adfm.201100763View Article
- Sullivan KT, Kuntz JD, Gash AE: Electrophoretic deposition and mechanistic studies of nano-Al/CuO thermites. J Appl Phys 2012, 112: 024316. 10.1063/1.4737464View Article
- Umbrajkar SM, Schoenitz M, Dreizin EL: Exothermic reactions in Al-CuO nanocomposites. Thermochimica Acta 2006, 451: 34–43. 10.1016/j.tca.2006.09.002View Article
- Wang J, Hu A, Persic J, Wen JZ, Zhou YN: Thermal stability and reaction properties of passivated Al/CuO nano-thermite. J Phys Chem Solids 2011, 72: 620–625. 10.1016/j.jpcs.2011.02.006View Article
- Weismiller MR, Malchi JY, Yetter RA, Foley TJ: Dependence of flame propagation on pressure and pressurizing gas for an Al/CuO nanoscale thermite. Proc Combust Inst 2009, 32: 1895–1903. 10.1016/j.proci.2008.06.191View Article
- Zhang K, Rossi C, Petrantoni M, Mauran N: A nano initiator realized by integrating Al/CuO-based nanoenergetic materials with a Au/Pt/Cr microheater. J Microelectromech Syst 2008, 17: 832–836.View Article
- Zhou X, Shen R, Ye Y, Zhu P, Hu Y, Wu L: Influence of Al/CuO reactive multilayer films additives on exploding foil initiator. J Appl Phys 2011, 110: 094505. 10.1063/1.3658617View Article
- Cheng JL, Hng HH, Lee YW, Du SW, Thadhani NN: Kinetic study of thermal- and impact-initiated reactions in Al-Fe2O3 nanothermite. Combust Flame 2010, 157: 2241–2249. 10.1016/j.combustflame.2010.07.012View Article
- Park C-D, Mileham M, van de Burgt LJ, Muller EA, Stiegman AE: The effects of stoichiometry and sample density on combustion dynamics and initiation energy of Al/Fe2O3 metastable interstitial composites. J Phys Chem C 2010, 114: 2814–2820. 10.1021/jp910274wView Article
- Plantier KB, Pantoya ML, Gash AE: Combustion wave speeds of nanocomposite Al/Fe2O3: the effects of Fe2O3 particle synthesis technique. Combust Flame 2005, 140: 299–309. 10.1016/j.combustflame.2004.10.009View Article
- Wang L, Luss D, Martirosyan KS: The behavior of nanothermite reaction based on Bi2O3/Al. J Appl Phys 2011, 110: 074311. 10.1063/1.3650262View Article
- Son SF, Asay BW, Foley TJ, Yetter RA, Wu MH, Risha GA: Combustion of nanoscale Al/MoO3 thermite in microchannels. J Propul Power 2007, 23: 715–721. 10.2514/1.26090View Article
- Sun J, Pantoya ML, Simon SL: Dependence of size and size distribution on reactivity of aluminum nanoparticles in reactions with oxygen and MoO3. Thermochimica Acta 2006, 444: 117–127. 10.1016/j.tca.2006.03.001View Article
- Gibot P, Comet M, Vidal L, Moitrier F, Lacroix F, Suma Y, Schnell F, Spitzer D: Synthesis of WO3 nanoparticles for superthermites by the template method from silica spheres. Solid State Sciences 2011, 13: 908–914. 10.1016/j.solidstatesciences.2011.02.018View Article
- Sullivan KT, Chiou W-A, Fiore R, Zachariah MR: In situ microscopy of rapidly heated nano-Al and nano-Al/WO3 thermites. Appl Phys Lett 2010, 97: 133104. 10.1063/1.3490752View Article
- Apperson SJ, Bezmelnitsyn AV, Thiruvengadathan R, Gangopadhyay K, Gangopadhyay S, Balas WA, Anderson PE, Nicolich SM: Characterization of nanothermite material for solid-fuel microthruster applications. J Propul Power 2009, 25: 1086–1091. 10.2514/1.43206View Article
- Howell JA, Mohney SE, Muhlstein CL: Developing Ni-Al and Ru-Al intermetallic films for use in microelectromechanical systems. J Vac Sci Technol B 2011, 29: 042002. 10.1116/1.3607314View Article
- Martirosyan KS: Nanoenergetic gas-generators: principles and applications. J Mater Chem 2011, 21: 9400–9405. 10.1039/c1jm11300cView Article
- Dreizin EL: Metal-based reactive nanomaterials. Progr Energ Combust Sci 2009, 35: 141–167. 10.1016/j.pecs.2008.09.001View Article
- Rossi C, Zhang K, Esteve D, Alphonse P, Tailhades P, Vahlas C: Nano energetic materials for MEMS: a review. J Microelectromech Syst 2007, 16: 919–931.View Article
- Sullivan K, Zachariah MR: Simultaneous pressure and optical measurements of nanoaluminum thermites: investigating the reaction mechanism. J Propul Power 2010, 26: 467–472. 10.2514/1.45834View Article
- Fischer SH, Grubelich MC: Theoretical energy release of thermites, intermetallics and combustion metals. Sandia National Laboratories: Technical report; 1998.View Article
- Zhang K, Rossi C, Alphonse P, Tenailleau C, Cayez S, Chane-Ching J-Y: Integrating Al with NiO nano honeycomb to realize an energetic material on silicon substrate. Appl Phys Mater Sci Process 2009, 94: 957–962. 10.1007/s00339-008-4875-6View Article
- Zhang JT, Liu JF, Peng Q, Wang X, Li YD: Nearly monodisperse Cu2O and CuO nanospheres: preparation and applications for sensitive gas sensors. Chem Mater 2006, 18: 867–871. 10.1021/cm052256fView Article
- Ahn JY, Kim WD, Cho K, Lee D, Kim SH: Effect of metal oxide nanostructures on the explosive property of metastable intermolecular composite particles. Powder Technology 2011, 211: 65–71. 10.1016/j.powtec.2011.03.033View Article
- Siegert B, Comet M, Muller O, Pourroy G, Spitzer D: Reduced-sensitivity nanothermites containing manganese oxide filled carbon nanofibers. J Phys Chem C 2010, 114: 19562–19568. 10.1021/jp1014737View Article
- Thiruvengadathan R, Bezmelnitsyn A, Apperson S, Staley C, Redner P, Balas W, Nicolich S, Kapoor D, Gangopadhyay K, Gangopadhyay S: Combustion characteristics of novel hybrid nanoenergetic formulations. Combust Flame 2011, 158: 964–978. 10.1016/j.combustflame.2011.02.004View Article
- Pantoya ML, Son SF, Danen WC, Jorgensen BS, Asay BW, Busse JR, Mang JT: Characterization of metastable intermolecular composites. In Defense Applications of Nanomaterials. Edited by: Miziolek AW, Karna SP, MatthewMauro J, Vaia RA. Washington, DC: American Chemical Society; 2005:227–240. ACS Symposium Series, vol 891 ACS Symposium Series, vol 891View Article
- Evteev AV, Levchenko EV, Riley DP, Belova IV, Murch GE: Reaction of a Ni-coated Al nanoparticle to form B2-NiAl: a molecular dynamics study. Phil Mag Lett 2009, 89: 815–830. 10.1080/09500830903321384View Article
- Levchenko EV, Evteev AV, Riley DP, Belova IV, Murch GE: Molecular dynamics simulation of the alloying reaction in Al-coated Ni nanoparticle. Comput Mater Sci 2010, 47: 712–720. 10.1016/j.commatsci.2009.10.014View Article
- Prakash A, McCormick AV, Zachariah MR: Tuning the reactivity of energetic nanoparticles by creation of a core-shell nanostructure. Nano Lett 2005, 5: 1357–1360. 10.1021/nl0506251View Article
- Ramos AS, Vieira MT: Intermetallic compound formation in Pd/Al multilayer thin films. Intermetallics 2012, 25: 70–74.View Article
- Lee S-G, Chung Y-C: Molecular dynamics investigation of interfacial mixing behavior in transition metals (Fe, Co, Ni)-Al multilayer system. J Appl Phys 2009, 105: 034902. 10.1063/1.3073899View Article
- Noro J, Ramos AS, Vieira MT: Intermetallic phase formation in nanometric Ni/Al multilayer thin films. Intermetallics 2008, 16: 1061–1065. 10.1016/j.intermet.2008.06.002View Article
- Nguyen NH, Hu A, Persic J, Wen JZ: Molecular dynamics simulation of energetic aluminum/palladium core-shell nanoparticles. Chem Phys Lett 2011, 503: 112–117. 10.1016/j.cplett.2010.12.074View Article
- Revesz A, Lendvai J, Ungar T: Melting point depression and microstructure in ball-milled nanocrystalline aluminium powders. In Metastable, Mechanically Alloyed and Nanocrystalline Materials, Pts 1 and 2. Edited by: Eckert J, Schlorb H, Schultz L. Durnten-Zurich: TTP; 2000:326–331. Wohlbier T (publishing editor) Materials Science Forum, vol 343–346 Wohlbier T (publishing editor) Materials Science Forum, vol 343–346
- Mei QS, Wang SC, Cong HT, Jin ZH, Lu K: Pressure-induced superheating of Al nanoparticles encapsulated in Al2O3 shells without epitaxial interface. Acta Mater 2005, 53: 1059–1066. 10.1016/j.actamat.2004.11.003View Article
- Dubois C, Lafleur PG, Roy C, Brousseau P, Stowe RA: Polymer-grafted metal nanoparticles for fuel applications. J Propul Power 2007, 23: 651–658. 10.2514/1.25384View Article
- Ceperley DM, Alder BJ: Ground-state of the electron-gas by a stochastic method. Phys Rev Lett 1980, 45: 566–569. 10.1103/PhysRevLett.45.566View Article
- Hammer B, Hansen LB, Norskov JK: Improved adsorption energetics within density-functional theory using revised Perdew-Burke-Ernzerhof functionals. Physical Review B 1999, 59: 7413–7421. 10.1103/PhysRevB.59.7413View Article
- Ohkura Y, Liu SY, Rao PM, Zheng XL: Synthesis and ignition of energetic CuO/Al core/shell nanowires. Proc Combust Inst 2011, 33: 1909–1915. 10.1016/j.proci.2010.05.048View Article
- TA Instruments: A review of DSC kinetics methods, TA-073B. http://www.tainstruments.co.jp/application/pdf/Thermal_Library/Applications_Briefs/TA073.PDF
- Puszynski JA: Processing and characterization of aluminum-based nanothermites. Journal of Thermal Analysis and Calorimetry 2009, 96: 677–685. 10.1007/s10973-009-0037-0View Article
- Udhayabanu V, Singh N, Murty BS: Mechanical activation of aluminothermic reduction of NiO by high energy ball milling. J Alloys Compd 2010, 497: 142–146. 10.1016/j.jallcom.2010.03.089View Article
- Sullivan KT, Piekiel NW, Wu C, Chowdhury S, Kelly ST, Hufnagel TC, Fezzaa K, Zachariah MR: Reactive sintering: an important component in the combustion of nanocomposite thermites. Combust Flame 2012, 159: 2–15. 10.1016/j.combustflame.2011.07.015View Article
- Cava S, Tebcherani SM, Souza IA, Pianaro SA, Paskocimas CA, Longo E, Varela JA: Structural characterization of phase transition of Al2O3 nanopowders obtained by polymeric precursor method. Mater Chem Phys 2007, 103: 394–399. 10.1016/j.matchemphys.2007.02.046View Article
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.