Energetic Applications Research Articles

Probing the performance of DFT in the structural characterization of [FeFe] hydrogenase models.

In this work, a series of DFT and DFT-D methods is combined with double-ζ basis sets to benchmark their performance in predicting the structures of five newly synthesized hexacarbonyl diiron complexes with a bridging ligand featuring a μ-S2C3 motif in a ring-containing unit functionalized with aromatic groups. Such complexes have been considered as [FeFe] hydrogenase catalytic site models with potential for eco-friendly energetic applications. According to this assessment, r2SCAN is identified as the density functional recommended for the reliable description of the molecular and crystal structures of the herein studied models. However, the butterfly (μ-S)2Fe2 core of the models demonstrates a minor deformation of its optimized geometry obtained from both molecular and periodic calculations. The FeFe bond length is slightly underestimated while the FeS bonds tend to be too long. Adding the D3(BJ) correction to r2SCAN does not lead to any improvement in the calculated structures.

Vibrational Energy Transfer in Energetic Ionic Liquid 4-Amino-1H-1,2,4-triazolium Nitrate: Ab Initio Molecular Dynamics Simulations.

Energetic ionic liquids (EILs) represent a distinctive class of energetic materials with substantial research significance and promising energetic applications. In this work, we delved into the vibrational energy transfer mechanism within the EILs, specifically focusing on 4-amino-1H-1,2,4-triazolium nitrate (ATN), utilizing ab initio molecular dynamics simulations. Our work illustrates distinct energy transfer patterns for different vibrational modes. Upon exciting the stretching vibration of the NH group in the cationic group, vibrational energy preferentially migrates to the neighboring CH bond within the aromatic ring on the femtosecond to picosecond time scales and notably in an in-phase coherent energy transfer fashion. In contrast, exciting the stretching vibration of the N9H11 bond triggers the transfer of vibrational energy to its neighboring N9H10 bond in an out-of-phase coherent fashion. Conversely, exciting the stretching vibration of the N9H10 bond leads to energy transfer predominantly through intermolecular pathways due to the hydrogen-bonding interaction between this bond and the anion. The vibrational energy of the excited N9H10 stretch is shown to dissipate very rapidly, displaying a fast component (with a time constant as short as ca. 7 fs) and a slow component (ca. 230 fs).

Ignition and combustion of AlH3-nanoparticles: A molecular dynamics study

AlH3 has tremendous potential for hydrogen energy storage and energetic applications. The structure and thermodynamic properties of core-shell AHNP with different oxidation degrees from ignition to combustion are studied using ReaxFF molecular dynamics simulations. Two models covered by different alumina shells are built. Results indicate that the thinner shell is ready to form an Al-rich environment, which is crucial for accelerating ignition and subsequent combustion processes. In ignition period, the influence of shell is investigated by comparing surface oxygen adsorption rates, oxidation degree of Al and H atoms, and stress evolution of AHNP. AHNP with thinner shell exhibits a higher O adsorption rate to form an O-rich environment, which accelerates the oxidation process of Al atoms. A thicker shell significantly inhibits the thermal diffusion of core Al and H atoms, while H atoms are still able to penetrate it with a low diffusion rate. Stress analysis shows the thickness of the shell directly affect the thermal diffusion rate of Al atoms. The combustion of AHNP can be divided into three stages: rapid, slow, and self-sustaining combustion. The combustion process is controlled by the particle and external O atoms diffusion behaviors. A detailed structural evolution process during AHNP combustion has also been clarified through the displacement analysis. The findings provide a theoretical foundation for the diffusion-dominated combustion mechanism of AHNP from an atomic view. Novelty and Significance StatementAlH3 has tremendous potential for hydrogen energy storage and energetic applications. At present, the combustion mechanism of AlH3-nanoparticles (AHNP) is still not well understood, and the atomic-scale evolution process and reaction mechanism are also poorly studied, which is difficult to obtain in experiments. In this study, the ignition and combustion mechanisms of AHNP is revealed based on the ReaxFF molecular dynamics simulations, and the influence of oxidation degree on the ignition and combustion of AHNP is also clarified, which can provide theoretical guidance for the application of AHNP as a clean fuel and preparing for the combustion research of AHNP coated with different materials.

Graphitic Carbon Nitride Enters the Scene: A Promising Versatile Tool for Biomedical Applications.

Graphitic carbon nitride (g-C3N4), since the pioneering work on visible-light photocatalytic water splitting in 2009, has emerged as a highly promising advanced material for environmental and energetic applications, including photocatalytic degradation of pollutants, photocatalytic hydrogen generation, and carbon dioxide reduction. Due to its distinctive two-dimensional structure, excellent chemical stability, and distinctive optical and electrical properties, g-C3N4 has garnered a considerable amount of interest in the field of biomedicine in recent years. This review focuses on the fundamental properties of g-C3N4, highlighting the synthesis and modification strategies associated with the interfacial structures of g-C3N4-based materials, including heterojunction, band gap engineering, doping, and nanocomposite hybridization. Furthermore, the biomedical applications of these materials in various domains, including biosensors, antimicrobial applications, and photocatalytic degradation of medical pollutants, are also described with the objective of spotlighting the unique advantages of g-C3N4. A summary of the challenges faced and future prospects for the advancement of g-C3N4-based materials is presented, and it is hoped that this review will inspire readers to seek further new applications for this material in biomedical and other fields.

Metal Sulfide‐Based Nanoarchitectures for Energetic and Environmental Applications

Despite their numerous excellent properties, metal sulfides are not particularly efficient at converting energy and purifying the environment, which limits their further applications. Fortunately, the energy conversion and environmental purification efficiencies of these materials have experienced notable advancements in recent years, accompanied by an improved understanding of their underlying mechanisms. Herein, progress in experimental researches in recent years on the engineering of single component metal sulfides by controlling morphology, construction of heterojunctions, and incorporating elements is reviewed. Methods to design and prepare metal sulfide‐based composites by building binary or ternary heterojunctions of metal sulfide/semiconductor/conductor are also discussed in detail. These materials are used in energy conversion and environmental purification systems, where they act as photocatalytic materials not only to split water, reduce carbon dioxide or nitrogen, but also to degrade pollutants (organic and inorganic) in water and gas. Finally, it is concluded by summarizing the research frontiers of metal sulfide nanomaterials in energy and environmental applications, as well as proposing potential challenges and future research directions. This work may contribute to a better understanding of metal sulfide nanocomposites and provide clues for the fabrication of more efficient metal sulfide‐based nanostructures for clean energy production and environmental remediation.

Characterization and calibration of a piezo-energetic composite film as a reactive gauge

The field of multifunctional energetics encompasses a range of materials including propellants, explosives, and pyrotechnics that possess the ability to be manipulated through various characteristics that can be switched between go and no-go, or those that have controllable energy release levels or have additional functions beyond energetic output. The development of multifunctional energetics harnessing electromechanical or piezoelectric properties of polymeric materials or binder systems has garnered increasing interest in recent years. Among polymers, fluoropolymers such as poly(vinylidene fluoride) (PVDF) and copolymers such as poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)], which are used as the binder and oxidizer in the energetic formulations, have demonstrated the highest piezoelectric coefficients. In this study, we fabricated piezo-energetic composite films using aluminum nanopowders (10 wt. % active content) as fuel and P(VDF-TrFE) (70/30) as an oxidizer and investigated the piezoelectric response using a small-scale drop weight setup. Additionally, we employed a shaker setup to investigate the response of the films to vibrations. Our findings demonstrate that these piezo-energetic films can replicate the behavior of a commercial PVDF gauge at relatively low-pressure impacts, indicating their potential use as shock or pressure sensors in various fields, as well as an accelerometer gauge. Additionally, aging studies of up to one year indicated minimal loss in the energetic content of the created films, enabling the use of energetic gauges for an extended period. Our findings support the effectiveness of piezo-energetic composite films as pressure sensors or accelerometers and highlight their potential for energetic applications.

Highly energetic formulations of boron and polytetrafluoroethylene for improved ignition and oxidative heat release

Boron (B) is desirable for energetic applications due to high gravimetric and volumetric energy densities. However, their use is limited because the native oxide shells on their surfaces limit oxidation and heat release by acting as a diffusion barrier and dead weight that does not contribute to heat release during oxidation. This paper reports a facile and efficient method of blending B with perfluoro additives to obtain materials with augmented heat release. We use polytetrafluoroethylene (PTFE) as a fluorine source that reacts with the oxide layer exothermally and use thermochemical analysis to identify the optimum composition of PTFE to extract high energy from B as a result of synergistic oxidation and fluorination reactions. The reduction in ignition temperatures of B is also observed due to its blending with PTFE. In this work, we determined B/PTFE blends with lower ignition temperature and higher oxidative heat release. These effects are due to the gasification of native surface oxide by fluorine via exothermic reactions that facilitate the enhanced reactions in the exposed metal core by eliminating the kinetic/thermodynamic barrier in the diffusion of the oxidizer to the B particle core. The study demonstrates the optimized formulation of highly energetic blends of B/PTFE for energetic applications.

Oxidation behavior and combustion characteristics of micro- and nano-sized titanium boride for energetic applications

This study explored the characteristics of TiB2 powders as an additive fuel of energetic materials. Results revealed that the whole oxidation of TiB2 was divided into two stages before and after the melting of B2O3. The effect of Ti on the onset oxidation temperature and low-temperature oxidation efficiency of TiB2 highlighted energy output features. The mass gain of the first stage, the combustion heat, the peak pressure, and the maximum pressurization rates of nano-sized TiB2 were larger than those of micro-sized TiB2. These properties of TiB2 provide evidence for the synergistic effect between Ti and B, which could promote its application in energetic formulations.

Challenges and prospects in energetic application of Pithecellobium dulce (Roxb.) Benth as a bioenergy tree

AbstractA report on the Pithecellobium dulce tree is provided in this review. The main characteristics of the tree, its chemical composition, traditional applications and future application in the bioenergy area are addressed. Pithecellobium dulce is a leguminous tree characterized by being fast growing, nitrogen fixing and largely available. In addition, it is distinguished by growing in different types of soils from acid to alkaline and with little water. This review could serve as a scientific basis to promote and carry out new research work focused on individual and comprehensive use for various bioenergetic processes, from the different parts that make up the P. dulce tree such as its leaves, pods, branches, flowers, fruit and seeds. Among the bioenergetic processes that could be developed are the production of bioethanol, biodiesel, biogas, heterogeneous catalysts, biochar, activated carbon and nanoparticles, among other applications.

Recent Progress of Ru Single‐Atom Catalyst: Synthesis, Modification, and Energetic Applications

AbstractIn recent years, single‐atom catalysts (SACs) have become the most active part of the catalytic field due to their excellent catalytic activity. Among them, Ru SACs exhibit excellent performance in many catalytic applications due to their high atomic utilization efficiency, catalytic activity and selectivity, and relatively low cost. In order to understand the structure–performance relationship and potential catalytic mechanism of Ru SACs, this review summarizes the research progress of Ru SACs in the fields of electrocatalytic water splitting, fuel cells, nitrogen reduction, and nitrate reduction in recent years. The catalytic process of Ru single atom in different synthesis methods and modification strategies is summarized. Finally, some opportunities and challenges for the future development of Ru SACs are prospected.

Probing the evolution in catalytic graphitization of biomass-based materials for enduring energetic applications

Catalytic processing of biomass and its derivatives to produce graphitizable materials offers a transformative method for converting renewable resources into bio-energy and valuable carbon-based materials.

Metal-organic frameworks as photocatalysts in energetic and environmental applications.

Metal-organic frameworks (MOFs) are an exciting new class of porous materials with great potential for photocatalytic applications in the environmental and energy sectors. MOFs provide significant advantages over more traditional materials when used as photocatalysts due to their high surface area, adaptable topologies, and functional ability. In this article, we summarize current developments in the use of MOFs as photocatalysts for a variety of applications, such as CO2 reduction, water splitting, pollutant degradation, and hydrogen production. We discuss the fundamental properties of MOFs that make them ideal for photocatalytic applications, as well as strategies for improving their performance. The opportunities and challenges presented by this rapidly expanding field are also highlighted.

Management of Agri-Food Waste Based on Thermochemical Processes towards a Circular Bioeconomy Concept: The Case Study of the Portuguese Industry

Sustainable biomass production has a significant potential for mitigating greenhouse gas emissions, providing an alternative to produce eco-friendly biofuels, biochemicals, and carbonaceous materials for biological, energetic, and environmental applications. Biomass from agroforestry and agricultural wastes is the richest natural carbon source and a sustainable option for woody biomass from a circular economic perspective. The European Union (EU) is estimated to produce 1.3 billion tons of agri-food waste annually. Portugal has a large supply of residual biomass, as well as other byproducts and wastes from forestry, agriculture, and the food industry, and has a high availability of residual biomass. By using biomass waste to create high-value products, Portugal envisages an improvement in its economic performance, while reducing its dependence on energy imports and fossil fuel use. This review explores the potential of agri-food waste obtained from Portuguese industries through thermochemical conversion technologies as a promising sustainable substitute for wood-based biomass for the development of eco-friendly biofuels, biochemicals, and high-value carbonaceous materials, and their applications. This strategy, based on the circular bioeconomy concept, can help reduce reliance on fossil fuels, reduce greenhouse gas emissions, fulfil the needs of the growing population, and offer a sustainable waste management solution.

Doping HTPB binder with cellulose nitrate: A promising strategy for advanced energetic material applications

This study explored the characteristics of hydroxyl-terminated polybutadiene (HTPB) supplemented with cellulose nitrate (NC), as a high-energy density binder. The effect of NC doping and its content on the chemical structure, morphology, energetic, and thermokinetic behavior of HTPB–NC binder highlighted attractive features such as good compatibility, improved density, homogeneity, and fiber dispersion. Additionally, HTPB–NC exhibited excellent thermal stability with significant energy release and notable chemical reactivity. These interesting properties of the HTPB–NC binder, provide evidence for the excellent synergistic effect between HTPB and NC, which could promote its application in the next generation of energetic propellant formulations.

Technical Feasibility of Sorghum Biomass for Briquettes Production

Vegetable biomass has been widely used for bioenergy generation, including sorghum, which has been the object of research for presenting high biomass productivity in the field in a short period of time and its in natura form is an option in sugar and energy plants during the off-season. The use of raw biomass has a number of disadvantages and its densification, through the production of briquettes, improves its energy and physical-mechanical characteristics. The objective of this study was to characterize the in natura biomass and briquettes of two hybrids of biomass sorghum: the commercially used BRS 716 and CMSXS 7016 still in test phase. The cultivation of the two hybrids was carried out at the experimental station of Embrapa Milho e Sorgo, located in the municipality of Sete Lagoas, in Minas Gerais, Brazil, in the 2016/2017 crop, with conventional cultural management for sorghum. The values found for the two hybrids of sorghum biomass are quite satisfactory compared to the values found in the literature for forest and agricultural species that are normally used for energy purposes, except for the ash content, being a viable alternative for energy production. The in natura biomass of hybrid CMSXS 7016 presents similar characteristics to the commercial hybrid BRS 716, and can be used commercially energetic applications. The briquettes of sorghum hybrids biomass are technically feasible for energetic generation, with energy and physical-mechanical characteristics superior to the biomass in natura, with apparent and energy density about 7-8 times higher.

Preparation and Characterization of Physically Activated Carbon and Its Energetic Application for All-Solid-State Supercapacitors: A Case Study.

Biomass-derived activated carbons have gained significant attention as electrode materials for supercapacitors (SCs) due to their renewability, low-cost, and ready availability. In this work, we have derived physically activated carbon from date seed biomass as symmetric electrodes and PVA/KOH has been used as a gel polymer electrolyte for all-solid-state SCs. Initially, the date seed biomass was carbonized at 600 °C (C-600) and then it was used to obtain physically activated carbon through CO2 activation at 850 °C (C-850). The SEM and TEM images of C-850 displayed its porous, flaky, and multilayer type morphologies. The fabricated electrodes from C-850 with PVA/KOH electrolytes showed the best electrochemical performances in SCs (Lu et al. Energy Environ. Sci., 2014, 7, 2160) application. Cyclic voltammetry was performed from 5 to 100 mV s-1, illustrating an electric double layer behavior. The C-850 electrode delivered a specific capacitance of 138.12 F g-1 at 5 mV s-1, whereas it retained 16 F g-1 capacitance at 100 mV s-1. Our assembled all-solid-state SCs exhibit an energy density of 9.6 Wh kg-1 with a power density of 87.86 W kg-1. The internal and charge transfer resistances of the assembled SCs were 0.54 and 17.86 Ω, respectively. These innovative findings provide a universal and KOH-free activation process for the synthesis of physically activated carbon for all solid-state SCs applications.

Engineered Surface Chemistry and Enhanced Energetic Performance of Aluminum Nanoparticles by Nonthermal Hydrogen Plasma Treatment.

Extracting the maximum chemical energy from aluminum nanoparticles (Al NPs) during oxidation is essential for their use in energetic applications. However, the shell of native Al2O3 limits the release of chemical energy by acting as a diffusion barrier and dead weight. Engineering the surface properties of Al NPs by modifying their shell chemistry can reduce the inhibiting effects of the oxide shell on the rate and heat release of oxidation. Here, we employ nonthermal hydrogen plasma at high power and a short time to alter the shell chemistry by doping it with Al-H, as examined and confirmed by HRTEM, FTIR, and XPS. Thermal analysis (TGA/DSC) shows that Al NPs with modified surfaces exhibit augmented oxidation and heat release (33% higher than those of untreated Al NPs). The results demonstrate the promising effect of nonthermal hydrogen plasma in engineering the shell chemistry of Al NPs to improve their overall energetic performance during oxidation.

Mechanistic understanding of the participation effect of carbon in the combustion of PTFE/n-Al: Combining experimental verification with reactive molecular dynamics simulation

Owing to the high energy density, polytetrafluoroethylene/aluminum nanoparticles (PTFE/n-Al) has been considered as the promising composite in energetic applications, but the limited combustion efficiency restricts its practical uses. Undoubtedly, for the further improvement of combustion efficiency, mechanistic understanding of the combustion of PTFE/n-Al is fundamentally necessary. However, the participation effect of non-fluorine species (i.e., carbon) on combustion has been overlooked, leading to the lack of generalized framework for combustion mechanism. By using a combined experimental verification and reactive molecular dynamics (RMD) simulation approach, this work focuses on the participation effect of carbon and involved reaction mechanism in the combustion of PTFE/n-Al. The thermal reactivity and combustion performance of four PTFE/n-Al composites with F/Al molar ratio of 1.0 (R1), 2.0 (R2), 3.0 (R3) and 4.0 (R4) have been investigated by thermal analyses (TGA-DSC-MS) and combustion experiments (flame images, heat of reaction and condensed combustion products). The heat of reaction decreases in the order of R2 (7.89 kJ/g), R1 (7.67 kJ/g), R3 (7.33 kJ/g) and R4 (6.55 kJ/g), and a similar trend has been found for the flame intensity. Moreover, the carbon deposition percentage (%) in combustion of R1, R2, R3 and R4 reaches 76.5%, 76.4%, 90.2% and 123.3%, which shows a negative effect on combustion performance. Based on experimental results, the RMD simulations for the reactions of n-Al and Al core with trafluoroethylene (TFE) and related fluorocarbon atmospheres have been performed. It is found that, going from R1 to R4, the elevated active fluorocarbon species play a double-edged sword role in combustion. On one side, they exhibit a promoting role in accelerating the crack of Al2O3 shell, the dispersion and heat releasing kinetics of Al core. On the other side, they also result in extensive carbon deposition on unreacted n-Al, showing a hindering role in further reaction and lowering combustion efficiency. Accordingly, in experiments, optimal combustion performance of PTFE/n-Al has been observed with suitable composition (R2). Finally, the generalized reaction mechanism involving participation effects of carbon and fluorine has been proposed for PTFE/n-Al, which is beneficial for perfecting combustion mechanism and improving combustion efficiency of fluorocarbon/metal composites.

Thermal analysis study of ammonium nitrate in the presence of NiCuCr2O4 additive

Nickel-copper chromite (NiCuCr2O4) was synthesized by the co-precipitation method using sodium hydroxide as a precipitating agent. The composition of ammonium nitrate (AN):NiCuCr2O4 (mass ratio 98:2) was used for the comparative thermal analysis study. The results suggested that ammonium nitrate containing nickel-copper chromite (AN + NiCuCr2O4) can act as a potential energetic material to replace AN in energetic applications. The activation energy of AN + NiCuCr2O4 was decreased by 85.7 kJ mol−1 compared to pure AN along with a reduction in the peak decomposition temperature. The lower activation energy and low pre-exponential factor can fasten AN + NiCuCr2O4’s decomposition at a lower temperature.

Study on GAP Adhesive-Based Polymer Films, Energetic Polymer Composites and Application

To lay the foundation for environmentally friendly energetic polymer composites, GAP (glycidyl azide polymer) adhesive-based polymer films with different curing parameter R (mol ratio of hydroxyl/isocyanate) and energetic polymer composites with different RDX contents were studied. GAP/TDI (toluene diisocyanate)/GLY(glycerol) was selected as the adhesive system. The tensile strength and elongation at the break of the polymer film with R = 2.2, was 14.34 MPa and 176.86%, respectively, as observed by an AGS-J electronic universal testing machine. A relatively complete cross-linking network and high hydrogen bonding interaction were observed by LF-NMR (low-field nuclear magnetic resonance, where the cross-linking density was 11.06 × 10-4 mol/cm3) and FT-IR (fourier transform infrared spectroscopy, where the carbonyl bonding ratio was 64.84%). Forty percent RDX(hexogen) was added into the adhesive system. The tensile strength was 4.65 MPa, and the elongation at the break was 78.49%; meanwhile, the heat of the explosive was 2.87 MJ/kg, and the residue carbon rate was only 2.47%. The tensile cross-sections of energetic polymer composites were observed by SEM (Scanning electron microscopy).