Highly reactive metastable intermixed composites (MICs) have attracted much attention in the past decades. The MIC family of materials mainly includes traditional metal-based nanothermites, novel core-shell-structured, 3D ordered macroporous-structured, and ternary nanocomposites. By applying special fabrication approaches, highly reactive MICs with uniformly dispersed reactants, "layer-by-layer" or "core-shell" structures, can be prepared. Thus, the combustion performance can be greatly improved, and the ignition characteristics and safety can be precisely controlled by using a certain preparation strategy. Here, the preparation and characterization of the MICs that have been developed during the past few decades are summarized. Traditional preparation methods for MICs generally include physical mixing, high-energy ball milling, sol-gel synthesis, and vapor deposition, while the novel methods include self-assembly, electrophoretic deposition, and electrospinning. Various preparation procedures and the ignition and combustion performance of different MIC reactive systems are compared and discussed. In particular, the advantages of novel structured MICs in terms of safety and combustion efficiency are clarified, based on which suggestions regarding the possible future research directions are proposed.

Highly Reactive Metastable Intermixed Composites (MICs): Preparation and Characterization

Wearable piezoresistive pressure sensors based on 3D graphene

Energetic materials, including explosives, pyrotechnics, and propellants, are widely used in mining, demolition, automobile airbags, fireworks, ordnance, and space technology. Nanoenergetic materials (nEMs) have a high reaction rate and high energy density, which are both adjustable to a large extent. Structural control over nEMs to achieve improved performance and multifunctionality leads to a fascinating research area, namely, nanostructured energetic materials. Among them, core-shell structured nEMs have gained considerable attention due to their improved material properties and combined multiple functionalities. Various nEMs with core-shell structures have been developed through diverse synthesis routes, among which core-shell structured nEMs associated with explosives and metastable intermolecular composites (MICs) are extensively studied due to their good tunability and wide applications, as well as excellent energetic (e.g., enhanced heat release and combustion) and/or mechanical properties. Herein, the preparation methods and fundamental properties of the abovementioned kinds of core-shell structured nEMs are summarized and the reasons behind the satisfactory performance clarified, based on which suggestions regarding possible future research directions are proposed.

Core–Shell Structured Nanoenergetic Materials: Preparation and Fundamental Properties

Energetic materials have been widely investigated experimentally and theoretically for decades, but there are still many unanswered questions concerning their thermal decomposition mechanisms that ...

Thermal decomposition of energetic materials using TG-FTIR and TG-MS: a state-of-the-art review

In this work, a multi-material selective laser melting (SLM) prototype system is demonstrated with the capability of mixing two metallic powders at different compositions on demand. The flexible system can operate for in-situ alloying of different elements as well as producing composite materials. In this preliminary work, Fe/Al-12Si component manufacturing is demonstrated. Initially, pure Fe and Al-12Si powders are studied separately. At a second phase the 55/45 volumetric ratio of Fe/Al-12Si mixture is processed. Finally, deposition of parts composed of Fe, Fe/Al-12Si, and Al-12Si layers is carried out demonstrating the feasibility of the powder-bed fusion based additive manufacturing method for multi-material manufacturing.

Multi-material selective laser melting of Fe/Al-12Si components

Synthesis, thermolysis, and sensitivities of HMX/NC energetic nanocomposites.

In this work, an energetic composite fiber, in which 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) nanoparticles intimately incorporated with a nitrocellulose/glycidyl azide polymer (NC/GAP) fiber, was prepared by the electrospinning method. The morphology and structure of the nanofiber was characterized by scanning electron microscopy (SEM), energy dispersive X-Ray (EDX), fourier transform infrared spectroscopy (IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET). The nanofibers possessed a three-dimensional (3D) net structure and a large specific surface area. Thermal analysis, energetic performance, and sensitivities were investigated, and they were compared with NC/GAP and LLM-105 nanoparticles. The NC/GAP/nano-LLM-105 nanofibers show higher decomposition rates and lower decomposition temperatures. The NC/GAP/nano-LLM-105 decomposed to CO2, CO, H2O, N2O, and a few NO, -CH2O-, and -CH- fragments, in the thermal-infrared spectrometry online (TG-IR) measurement. The NC/GAP/nano-LLM-105 nanofibers demonstrated a higher standard specific impulse (Isp), a higher combustion chamber temperature (Tc), and a higher specialty height (H50). The introduction of nano-LLM-105 in the NC/GAP matrix results in an improvement in energetic performance and safety.

https://www.mdpi.com/2079-4991/9/6/854/pdf

An Electrospun Preparation of the NC/GAP/Nano-LLM-105 Nanofiber and Its Properties.

Nanometer triaminoguanidine nitrate (TAGN) with mean size of 218.7 nm was fabricated, and its structures were characterized by scanning electron microscopy, X-ray diffraction, IR, and X-ray photoelectron spectroscopy analyses. As an energetic accelerator for thermal decomposition of ammonium perchlorate (AP) and ammonium nitrate (AN), 10% nano TAGN blended with AP and AN, and samples “[90% AP + 10% (nano TAGN)]” and “[90% AN + 10% (nano TAGN)]” were obtained, respectively. Differential scanning calorimetry (DSC) analyses were employed to investigate the decomposition kinetics and thermodynamics of the samples. The results indicated that [90% AP + 10% (nano TAGN)] presented a higher activation energy (152.34 kJ mol–1) than pure AP (117.21 kJ mol–1) and [90% AN + 10% (nano TAGN)] possessed a lower activation energy (147.51 kJ mol–1) than pure AN (161.40 kJ mol–1). All activation free energies (ΔG≠) were positive values. This means that activation of the molecules was not a spontaneous process. The decomposi...

Thermal Behavior and Decomposition Mechanism of Ammonium Perchlorate and Ammonium Nitrate in the Presence of Nanometer Triaminoguanidine Nitrate

http://www.ysxbcn.com/down/2014/01_en/36-p0263.pdf

Mechanism for thermite reactions of aluminum/iron-oxide nanocomposites based on residue analysis

By milling 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) together, a nano CL-20/RDX co/mixed crystal explosive with a mean particle size of 141.6 nm is prepared from the raw materials, and the co/mixed crystals are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) and thermal-infrared spectrometry online (DSC-IR) technology; furthermore, the impact, friction and thermal sensitivity of the samples are tested. The results show that after milling, the morphology of the co/mixed crystal explosive is near-spherical, and the particle size reveals a normal distribution. The milled sample showed the same molecular structure and surface elements as the raw materials, but the XRD test shows that CL-20/RDX has a new crystal phase and the Raman and IR spectra gave a supplementary confirmation for the existence of a cocrystal phase in the milled sample. The activation energy of the thermal decomposition of CL-20/RDX is 206.49 kJ mol−1 higher than that of raw RDX. DSC-IR analysis showed that the thermolysis of CL-20/RDX produces a large amount of CO2 and N2O and a small amount of H2O, NO2 and NO. The mechanical sensitivity of CL-20/RDX is very low. In impact sensitivity tests with a 5 kg hammer, the special height (H50) is 51.43 cm, which is higher than the values of 36.43 cm for raw CL-20 and 9.78 cm for raw RDX. In the friction sensitivity tests, the explosion probability (P) is 56%; however, the thermal sensitivity of CL-20/RDX is higher than that of the raw materials, with its 5 s burst point being only 243.51 °C.

/pdf/mechanochemical-fabrication-and-properties-of-cl-20-rdx-nano-1f1elozvuw.pdf

Xiaolan Song

Papers

Synthesis, thermolysis, and sensitivities of HMX/NC energetic nanocomposites.

An Electrospun Preparation of the NC/GAP/Nano-LLM-105 Nanofiber and Its Properties.

Thermal Behavior and Decomposition Mechanism of Ammonium Perchlorate and Ammonium Nitrate in the Presence of Nanometer Triaminoguanidine Nitrate

Mechanism for thermite reactions of aluminum/iron-oxide nanocomposites based on residue analysis

Mechanochemical fabrication and properties of CL-20/RDX nano co/mixed crystals