Nanoenergetic Materials Research Articles

Enhancing the Energy Release Performance of Al/CuO Nanothermites through Hierarchical Structure

ABSTRACT The objective of this study is to enhance the mixing uniformity and contact efficiency between nano-Al and oxidizers through structural control, while suppressing the “pre – ignition fusion” effect of nanothermites. We employed biotemplate approach, utilizing Lycopodium japonicum Thunb. spores (LP) and Papilio maackii wings (PW) as sacrificial templates, to successfully fabricate hierarchically structured Al/PW-CuO and Al/LP-CuO nanothermites. At a stoichiometric ratio of Ф = 1.5, Al/PW-CuO exhibited the highest heat release of 2278.00 J/g, whereas Al/LP-CuO also achieved a substantial heat release of 1969.08 J/g. These outstanding performances are attributed to the unique structures of PW-CuO and LP-CuO, especially the spine-like plate structure of PW-CuO, which provides more reaction sites, thereby enhancing spatial utilization and heat release efficiency. This study provides new insights for the design and application of highly active nanoenergetic materials.

Nanoenergetic Materials: From Materials to Applications.

Both nanoscience and nanotechnology have undoubtedly contributed significantly to the development of thermite-based nanoenergetic materials (NEMs) with tunable and tailorable combustion performance and their subsequent integration into devices. Specifically, this review article reflects the immense paybacks in designing and fabricating ordered/disordered assembly of energetic materials over multiple length scales (from nano- to milli-scales) in terms of realization of desired reaction rates and sensitivity. Besides presenting a critical review of present advancements made in the synthesis of NEMs, this article touches upon aspects related to various applications concomitantly. The article concludes with the author's summary of the insurmountable challenges and the road ahead toward the deployment of nanoenergetic materials in practical applications. The real challenge lies in the ability to preserve the self-assembly of fuel and oxidizer nanoparticles achieved at the nanoscale while synthesizing macroscale energetic formulations using advanced fabrication techniques both in bulk and thin film forms. Most importantly, these self-assembled NEMs have to exhibit excellent combustion performance at reduced sensitivity to external stimuli such as electrostatic discharge (ESD), friction and impact.

Targeted nano-energetic material exploration through active learning algorithm implementation

This paper presents an active learning-based method designed to guide experiments towards user-defined specific regions, termed ”regions of interest,” within vast and multi-dimensional thermite design spaces. Thermites composed of metallic reactant coupled to an inorganic oxidizer are non-explosive energetic materials which stay inert and stable until subjected to a sufficiently strong thermal stimulus, after which they undergo fast burning with release of high amount of chemical energy (up to 16 kJ.cm−3). They represent an interesting class of nano-engineered energetic material because of their high adiabatic flame temperature (> 2600 °C) and customizable combustion properties. We introduced a new acquisition function combining linearly two factors with the usual standard deviation of a Gaussian Process Regression algorithm. A first factor guides the sampling towards the defined zone of interest, and a second, is an incentive function that encourages the exploration of under-sampled regions of the design space. We found that our algorithm effectively provides up to several tens of nanothermites that achieve specific desired properties well-distributed within the design space, after only 200 samplings, whereas, Latin Hypercube Sampling procedure samples less than 10 points of interest. Our framework is tailored for typical discrete search spaces involving multiple measured physical properties and when only a small dataset is available, as it is the case in thermite materials. But more generally, this research represents a significant advancement for large-scale problems in energetic materials science and engineering, where predicting the effect of feature modification is desired but limited simulations or experiments can be afforded due to their high cost.

Hot Bridge-Wire Ignition of Nanocomposite Aluminum Thermite Synthesized Using Sol-Gel-Derived Aerogel with Tailored Properties for Enhanced Reactivity and Reduced Sensitivity

The development of nano-energetic materials has significantly advanced, leading to enhanced properties and novel applications in areas such as aerospace, defense, energy storage, and automobile. This research aims to engineer multi-dimensional nano-energetic material systems with precise control over energy release rates, spatial distribution, and temporal and pressure history. In this context, sol–gel processing has been explored for the manufacture of nanocomposite aluminum thermites using aerogels. The goal is to produce nano-thermites (Al/Fe2O3) with fast energy release rates that are insensitive to unintended initiation while demonstrating the potential of sol–gel-derived aerogels in terms of versatility, tailored properties, and compatibility. The findings provide insightful conclusions on the influence of factors such as secondary oxidizers (KClO3) and dispersants (n-hexane and acetone) on the reaction kinetics and the sensitivity, playing crucial roles in determining reactivity and combustion performance. In tandem, ignition systems contribute significantly in terms of a high degree of reliability and speed. However, the advantages of using nano-thermites combined with hot bridge-wire systems in terms of ignition and combustion efficiency for potential, practical applications are not well-documented in the literature. Thus, this research also highlights the practicality along with safety and simplicity of use, making nano-Al/Fe2O3-KClO3 in combination with hot bridge-wire ignition a suitable choice for experimental purposes and beyond.

Achieving superior ignition and combustion performance of Al/I2O5 biocidal nanoenergetic materials by CuO addition

It was found that all iodine-containing biocidal energetic materials has a relatively long ignition delay upon combustion. A shorter ignition time (from the thermal trigger to the peak pressure) for Al/iodine oxides might further boost their combustion performance due to their high reactivity and high gas release rate. To achieve this goal, a secondary oxidizer, CuO, is incorporated into Al/I2O5 at different mass content keeping the overall thermite stoichiometry constant. The ternary Al/I2O5/CuO thermites were characterized in ignition using a T-jump ignition temperature set up, and in combustion in a constant volume combustion cell. Consequently, all ternary thermites outperform traditional Al/I2O5 counterpart with an optimum for 80/20 wt% of I2O5/CuO. This later composition ignites in 0.01 ms (30 times shorter than Al/I2O5) and produces peak pressure and pressurization rate of ∼4 and 26 times greater than those produced by Al/I2O5. A series of additional characterizations using Fourier-transform infrared spectroscopy, Differential Scanning Calorimetry, Electrical/Thermal conductivity measurement, etc., permitted to unravel the cause of such improvement and to propose a reaction mechanism for this ternary Al/I2O5/CuO system. From an applications point of view, this study proposes a facile, inexpensive and efficient way to enhance the combustion performance of Al/I2O5 biocidal nanoenergetic materials.

Construction of high-performance azide films with Macro size appropriate for the micro-initiator

Micro-nano energetic materials generally have advantages such as high reactivity and high energy density due to their special micro-nano structure, but the macroscopic construction of micro-nano energetic materials is the biggest bottleneck hindering their development. In this paper, a layer-by-layer superposition method combining electrospinning and electrospray is proposed. Metal salt microspheres are embedded into nanofibers, and a three-dimensional azide film (3D CA@C and 3D LA@C) is obtained through high-temperature calcination and in situ azide process. Because azide microspheres are evenly dispersed in the carbon skeleton with good thermal and electrical conductivity, and are limited by the frame structure, they are not susceptible to external stimuli, so as to have better sensitivity performance. The electrostatic sensitivity of 3D CA@C increased from 0.05 mJ to 2.72 mJ of raw material, and the flame sensitivity of 3D LA@C increased from 8 cm to 31 cm of raw material. At the same time, the 3D azide films can still maintain good initiation performance and meet the actual initiation requirements. This work gives full play to the advantages of energetic materials with micro-nano structure, and at the same time realizes the construction of macroscopic size of materials. While maintaining its micro-nano characteristics, the film obtained can be easily processed, which is more in line with the requirements of the MEMS process. This provides the latest idea and experience for the preparation of micro and nano energetic materials at the macro scale.

Carbon Nanotubes for Confinement-Induced Energetic Nanomaterials.

Oxidized carbon nanotubes obtained by catalytic chemical vapor deposition were filled with an aqueous solution of nano-energetic materials using a very simple impregnation method. The work compares different energetic materials but focuses especially on an inorganic compound belonging to the Werner complexes, [Co(NH3)6][NO3]3. Our results show a large increase in released energy upon heating, which we demonstrate to be related to the confinement of the nano-energetic material either directly by filling of the inner channel of carbon nanotubes or to insertion in the triangular channels between adjacent nanotubes when they form bundles.

Exotic Inverse Kinetic Isotopic Effect in the Thermal Decomposition of Levitated Aluminum Iodate Hexahydrate Particles

Aluminum iodate hexahydrate ([Al(H2O)6](IO3)3(HIO3)2; AIH) represents a novel, oxidizing material for energetic applications. Recently, AIH was synthesized to replace the aluminum oxide passivation layer of aluminum nanoenergetic materials (ALNEM). The design of reactive coatings for ALNEM-doped hydrocarbon fuels in propulsion systems requires fundamental insights of the elementary steps of the decomposition of AIH. Here, through the levitation of single AIH particles in an ultrasonic field, we reveal a three-stage decomposition mechanism initiated by loss of water (H2O) accompanied by an unconventional inverse isotopic effect and ultimate breakdown of AIH into gaseous elements (iodine and oxygen). Hence, AIH coating on aluminum nanoparticles replacing the oxide layer would provide a critical supply of oxygen in direct contact with the metal surface thus enhancing reactivity and reducing ignition delays, further eliminating decades-old obstacles of passivation layers on nanoenergetic materials. These findings demonstrate the potential of AIH to aid in the development of next-generation propulsion systems.

Nanoenergetic Composites with Fluoropolymers: Transition from Powders to Structures.

Over the years, nanoenergetic materials have attracted enormous research interest due to their overall better combustion characteristics compared to their micron-sized counterparts. Aluminum, boron, and their respective alloys are the most extensively studied nanoenergetic materials. The majority of the research work related to this topic is confined to the respective powders. However, for practical applications, the powders need to be consolidated into reactive structures. Processing the nanoenergetic materials with polymeric binders to prepare structured composites is a possible route for the conversion of powders to structures. Most of the binders, including the energetic ones, when mixed with nanoenergetic materials even in small quantities, adversely affects the ignitability and combustion performance of the corresponding composites. The passivating effect induced by the polymeric binder is considered unfavorable for ignitability. Fluoropolymers, with their ability to induce pre-ignition reactions with the nascent oxide shell around aluminum and boron, are recognized to sustain the ignitability of the composites. Initial research efforts have been focused on surface functionalizing approaches using fluoropolymers to activate them further for energy release, and to improve the safety and storage properties. With the combined advent of more advanced chemistry and manufacturing techniques, fluoropolymers are recently being investigated as binders to process nanoenergetic materials to reactive structures. This review focuses on the major research developments in this area that have significantly assisted in the transitioning of nanoenergetic powders to structures using fluoropolymers as binders.

Electrostatic spraying construction strategy and performance of NGEC-based core-shell nanoenergetic material

Recently, a novel kind of thermal plastic energetic cellulose binder nitrate glycerol ether cellulose (NGEC) exhibits promising application in enhancing the mechanical property of propellants. In this study, a series of NGEC-based core-shell nanoenergetic composites were prepared by electrostatic spray technology, including RDX@NGEC, HMX@NGEC, and CL-20@NGEC. The findings revealed that NGEC was coated uniformly on the surface of energetic crystals and presented favorable spherical morphology. The thermal decomposition demonstrated that the polymorphic phase transition of HMX and CL-20 almost disappeared, and the activation energy (Ea) was also calculated. Comparing with original energetic crystals, the Ea of RDX@NGEC (133.44 kJ/mol) and HMX@NGEC (326.65 kJ/mol) were increased by 11.39 kJ/mol and 38.58 kJ/mol, respectively, while that of CL-20@NGEC (155.59 kJ/mol) was decreased by 76.18 kJ/mol. Finally, the impact sensitivity has been reduced dramatically. Hence, this fabrication strategy of NGEC-based nanoenergetic composites has profound basic theory research significance and may provide promising application propellants.

2D-WO3/nAl Nanoenergetic Materials: Preparation and Energetic Properties

2D-WO₃/nAl Nanoenergetic Materials: Preparation and Energetic Properties

Continuous flow resonance acoustic mixing technology: a novel and efficient strategy for preparation of nano energetic materials

Recently, microfluidic technology has been widely applied to the preparation of nano-energetic materials. The mixing efficiency of fluid is one of the significant factors which could affect the particle size and particle size distribution (PSD) of products. In this report, a novel strategy to enhance the mixing performance of fluid is developed by combining continuous flow microfluidic and resonant acoustic mixing (RAM) technologies. The results of the fluid visualization and 3D-Computational fluid dynamics (CFD) simulation showed that the new continuous flow resonance acoustic mixing (CFRAM) technology has better mixing efficiency than the traditional microfluidic approach. To demonstrate the utility of this CFRAM technology, it was implemented in the continuous preparation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) nanoparticles. Compared with previous reported results, nano TATB prepared by CFRAM technology has a smaller average particle size (D50 = 50.8 nm) and a narrower particle size distribution (D10 = 33.0 nm; D90 = 69.6 nm). The XRD spectrum shows that the crystal structure of nano TATB has not changed. DSC test results show that the apparent activation energy of nano TATB is 177.8 kJ/mol, which is 6.5 kJ/mol lower than the raw TATB, and has good thermal stability. We expect that this strategy may open a new avenue for the efficient preparation of nano energetic materials with narrow PSD.

Enhanced Energetic Performance of Aluminum Nanoparticles by Plasma Deposition of Perfluorinated Nanofilms.

The performance of Al as nanoenergetic material in solid fuel propulsion or additive in liquid fuels is limited by the presence of the native oxide layer at the surface, which represents a significant weight fraction, does not contribute to heat release during oxidation, and acts as a diffusion barrier to Al oxidation. We develop an efficient technique in which the oxide layer is effectively turned into an energetic component via a reaction with fluorine that is coated in the form of a fluorocarbon nanofilm on the Al surface by plasma-enhanced chemical vapor deposition. Perfluorodecalin vapors are introduced in a low-pressure plasma reactor to produce nanofilms on the surface of Al nanoparticles, whose thickness is controlled with nanolevel precision as demonstrated by high-resolution transmission electron microscopy images. Coated particles show superior heat release, with a maximum enhancement of 50% at a thickness of 10 nm. This significant improvement is attributed to the chemical interaction between Al2O3 and F to form AlF3, which removes the oxide barrier via an exothermic reaction and contributes to the amount of heat released during thermal oxidation. The chemistry and mechanism of the enhancement effect of the plasma nanofilms are explained with the help of X-ray photoelectron spectroscopy, X-ray diffraction, high-angle annular dark-field scanning transmission electron microscopy-energy dispersive spectroscopy, thermogravimetric analysis, and differential scanning calorimetry.

Nanoenergetic Materials: Enhanced Energy Release from Boron by Aluminum Nanoparticle Addition.

Boron has the highest enthalpy of oxidation per unit mass (and volume) among metals and metalloids and is an excellent candidate as a solid fuel. However, the native oxide present on the surface limits the available energy and rate of its release during oxidation. Here, we report a simple and effective method that removes the oxide in situ during oxidation via an exothermic thermite reaction with aluminum that enriches the particle in B at the expense of Al. B/Al blends with different compositions are optimized using thermogravimetry and differential scanning calorimetry, and the best sample in terms of energy release is characterized by high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, and X-ray diffraction. All compositions release more energy than the individual components, and the blend containing 10% Al by weight outperforms pure B by 40%. The high energy release is due to the synergistic effect of B oxidation and thermite reaction between Al and B2O3. We demonstrate the formation of ternary oxide by the oxidation of the B/Al blend that provides porous channels for the oxidation of B, thereby maximizing the contact of the metal and oxidizer. Overall, the results demonstrate the potential of using B/Al blends to improve the energetic performance of B.

Application of microfluidic technology on preparation of nano LLM-105

ABSTRACT Current methods, including ball milling and spray drying, are subject to some restrictions in application for preparing nano 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), such as too large volume of dangerous goods, unstable temperature as well as discontinuous industrial production. In this study, continuous and safe preparation of nano-LLM-105 was achieved using microfluidic technology. Several influence factors had been studied on the particle size of LLM-105 including supersaturation, microreactor structure, solvent/non-solvent ratio, the total flow rate, reactor temperature, as well as the number of plates. Results showed that supersaturation of solution and structure of the microreactor played a critical role in the formation of nano-scale LLM-105. Further analysis on these nano-particles revealed its D50 was 124.95 nm with a spherical-like narrow shape through scanning electron microscopy and particle size distribution curve. X-ray diffraction results show that the crystal structure of nano-LLM-105 has not changed, and the differential scanning calorimeter test results show that nano-LLM-105 still maintains good thermal stability compared to raw-LLM-105. In short, this protocol provides a new route for continuous and safe preparation of nano-level LLM-105, which could be potentially applied to other nano-energetic materials, such as HMX and CL-20.

Tailoring Vibrational Signature and Functionality of 2D-Ordered Linear-Chain Carbon-Based Nanocarriers for Predictive Performance Enhancement of High-End Energetic Materials.

A recently proposed, game-changing transformative energetics concept based on predictive synthesis and preprocessing at the nanoscale is considered as a pathway towards the development of the next generation of high-end nanoenergetic materials for future multimode solid propulsion systems and deep-space-capable small satellites. As a new door for the further performance enhancement of transformative energetic materials, we propose the predictive ion-assisted pulse-plasma-driven assembling of the various carbon-based allotropes, used as catalytic nanoadditives, by the 2D-ordered linear-chained carbon-based multicavity nanomatrices serving as functionalizing nanocarriers of multiple heteroatom clusters. The vacant functional nanocavities of the nanomatrices available for heteroatom doping, including various catalytic nanoagents, promote heat transfer enhancement within the reaction zones. We propose the innovative concept of fine-tuning the vibrational signatures, functionalities and nanoarchitectures of the mentioned nanocarriers by using the surface acoustic waves-assisted micro/nanomanipulation by the pulse-plasma growth zone combined with the data-driven carbon nanomaterials genome approach, which is a deep materials informatics-based toolkit belonging to the fourth scientific paradigm. For the predictive manipulation by the micro- and mesoscale, and the spatial distribution of the induction and energy release domains in the reaction zones, we propose the activation of the functionalizing nanocarriers, assembled by the heteroatom clusters, through the earlier proposed plasma-acoustic coupling-based technique, as well as by the Teslaphoresis force field, thus inducing the directed self-assembly of the mentioned nanocarbon-based additives and nanocarriers.

Energetic characteristics of hydrogenated amorphous silicon nanoparticles

• Plasma-synthesized amorphous Si NPs ( a -nSi) incorporate abundant hydrogen. • The reactivity of a -nSi/KClO 4 increases by a factor of six compared with nAl. • The energetic performance of nSi is correlated with its hydrogen content. • In situ release of hydrogen from hydrides enhances the reactivity. In this work, we utilize a low-temperature non-equilibrium plasma to nucleate and grow sub-10 nm Si particles with varying degrees of crystallinity by tuning the level of power coupled into plasma discharge. Temperature-programmed desorption spectroscopy shows that as-prepared amorphous Si nanoparticles ( a -nSi) incorporate more hydrogen than crystalline Si nanoparticles ( c -nSi). Further, hydrogen is incorporated in the material in the form of higher silicon hydrides with a lower desorption temperature. Combustion cell measurements show that when formulated with KClO 4 , a -nSi outperforms its crystalline counterpart with respect to pressure output. The pressurization rate of a -nSi/KClO 4 composite increases by a factor of six compared with nAl to 0.66 MPa·μs −1 . Evidence of hydrogen release (∼730 K) from Temperature-jump time-of-flight mass spectrometry (T-Jump TOFMS) of a -nSi/KClO 4 suggests the creation of Si dangling bonds prior to ignition (∼820 K), which then react exothermically with oxygen liberated from KClO 4 , leading to ignition. Explosive reaction of H 2 /O 2 mixture likely contributes to the rapid pressure rise. The enhanced energetic performance of hydrogenated a -nSi compared to its crystalline counterpart suggests that incorporation of hydrogen is a promising strategy for improving the performance of nanoenergetic materials.

Engineered nanoparticles (ENPs): Unexplored potential and limitations

The rapid growing industry of global economic importance is exploring the novel material synthesized at the nanoscale. Engineered nanoparticles (ENPs) have been manufactured with specific shape, size, surface properties and unique functionalities such as catalytic behaviour, increased strength, improved thermal and electrical conductivity. These advancements have opened the door to new applications in biomedicine, nanoenergetic materials and functional nanocomposites including cancer therapy, drug delivery, tissue engineering, regenerative medicine, biomolecule detection, and antimicrobial activities. In cancer therapies, nanoparticulate delivery systems allow ENPs greater penetration of therapeutic and diagnostic substances within the body while posing fewer risks than conventional cancer therapies. Evidences suggested that ENPs offer some substantial danger to the environment by its toxicological effects when they are exposed to the environment, which leads to the chronic issues of nanopollution. The aquatic environment is at the greatest risk from ENPs, as it serves as a sink for nearly all environmental contaminants. Despite these challenges, ENPs holds promise to in different field as well as minimize environmental pollution, by employing the innovative environmental remediation methods. There are gaps in understanding the fate of ENPs in the environment hence more stringent and critical research is the need of the hour. It also call for the advancement of tools and techniques that can accurately quantify and analyze the uptake of ENPs into biological systems.This review includes the different types of ENPs their sources and physiochemical characteristics and the ultimate fate of these ENPs in the environment.

Preparation of Energetic Composites Materials via Sol-Gel

In this research, nitrocellulose / magnesium borohydride nanomaterials (NC / Mg(BHx)y) nanoenergetic composite materials are synthesized through sol-gel method and the freeze-drying technology. Among them, nitrocellulose (NC) is used as a gel matrix to load Mg(BHx)y particles. Scanning electron microscopy (SEM) results show that Mg(BHx)y is embedded and uniformly dispersed in the NC matrix. The particle size of the high-energy composite material is about 2 μm. The results of FT-IR showed that the hydrogen storage alloy was successfully loaded around the NC without destroying the cellulose structure. The composite material decomposition reaction (Temperature-Time) curve is obtained through the adiabatic accelerated calorimeter (ES-ARC) test.

Preparation and characterisation of the NBC/CL-20/AP nanoenergetic composite materials

ABSTRACT In this study, a novel nitrated bacterial cellulose/2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/ammonium perchlorate nanoenergetic composite was successfully prepared by the sol–gel method and the freeze-drying technology. The structure and composition were characterised by means of scanning electron microscope, X-ray diffractometer and Fourier-transform infrared. The results demonstrated that the structure of the gel nanoparticles was granted with unique network cross-linked porous, wherein the hexaazaisowurtzitane and ammonium perchlorate nanoparticles were embedded and dispersed uniformly in the gel matrix. The thermal decomposition properties of composites were analysed by differential scanning calorimeter-thermogravimetric analysis, and the results revealed that the composites exhibited only two exothermal peaks which correspond to the nitrated bacterial cellulose/hexaazaisowurtzitane and ammonium perchlorate. In addition, the impact and friction sensitivities of composites were also performed and showed outstanding safety performance. Hence, this preparation strategy of nitrated bacterial cellulose-based nanocomposite energetic materials may provide promising application in high-performance and low-sensitivity propellants.