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Two-dimensional carbides and nitrides of transition metals, known as MXenes, are a fast-growing family of materials that have attracted attention as energy storage materials. MXenes are mainly prepared from Al-containing MAX phases (where A = Al) by Al dissolution in F-containing solution; most other MAX phases have not been explored. Here a redox-controlled A-site etching of MAX phases in Lewis acidic melts is proposed and validated by the synthesis of various MXenes from unconventional MAX-phase precursors with A elements Si, Zn and Ga. A negative electrode of Ti 3 C 2 MXene material obtained through this molten salt synthesis method delivers a Li + storage capacity of up to 738 C g −1 (205 mAh g −1 ) with high charge–discharge rate and a pseudocapacitive-like electrochemical signature in 1 M LiPF 6 carbonate-based electrolyte. MXenes prepared via this molten salt synthesis route may prove suitable for use as high-rate negative-electrode materials for electrochemical energy storage applications. Two-dimensional transition metal carbides and nitrides, known as MXenes, are currently considered as energy storage materials. A generic Lewis acidic etching route for preparing high-rate negative-electrode MXenes with enhanced electrochemical performance in non-aqueous electrolyte is now proposed.

Addition of molecular cross-links to polymers increases mechanical strength and improves corrosion resistance. However, it remains challenging to install cross-links in low-functionality macromolecules in a well-controlled manner. Typically, high-energy processes are required to generate highly reactive radicals in situ, allowing only limited control over the degree and type of cross-link. We rationally designed a bis-diazirine molecule whose decomposition into carbenes under mild and controllable conditions enables the cross-linking of essentially any organic polymer through double C–H activation. The utility of this molecule as a cross-linker was demonstrated for several diverse polymer substrates (including polypropylene, a low-functionality polymer of long-standing challenge to the field) and in applications including adhesion of low–surface-energy materials and the strengthening of polyethylene fabric.

We present a proof of concept that machine learning techniques can be used to predict the properties of CNOHF energetic molecules from their molecular structures. We focus on a small but diverse dataset consisting of 109 molecular structures spread across ten compound classes. Up until now, candidate molecules for energetic materials have been screened using predictions from expensive quantum simulations and thermochemical codes. We present a comprehensive comparison of machine learning models and several molecular featurization methods - sum over bonds, custom descriptors, Coulomb matrices, Bag of Bonds, and fingerprints. The best featurization was sum over bonds (bond counting), and the best model was kernel ridge regression. Despite having a small data set, we obtain acceptable errors and Pearson correlations for the prediction of detonation pressure, detonation velocity, explosive energy, heat of formation, density, and other properties out of sample. By including another dataset with ≈300 additional molecules in our training we show how the error can be pushed lower, although the convergence with number of molecules is slow. Our work paves the way for future applications of machine learning in this domain, including automated lead generation and interpreting machine learning models to obtain novel chemical insights.

Perovskite oxides have attracted significant attention as energy conversion materials for metal–air battery and solid-oxide fuel-cell electrodes owing to their unique physical and electronic properties. Amongst these unique properties is the structural stability of the cation array in perovskites that can accommodate mobile oxygen ions under electrical polarization. Despite oxygen ion mobility and vacancies having been shown to play an important role in catalysis, their role in charge storage has yet to be explored. Herein we investigate the mechanism of oxygen-vacancy-mediated redox pseudocapacitance for a nanostructured lanthanum-based perovskite, LaMnO 3 . This is the first example of anion-based intercalation pseudocapacitance as well as the first time oxygen intercalation has been exploited for fast energy storage. Whereas previous pseudocapacitor and rechargeable battery charge storage studies have focused on cation intercalation, the anion-based mechanism presented here offers a new paradigm for electrochemical energy storage. Perovskite oxides have attracted significant attention as energy conversion materials owing to their unique physical and electronic properties. Anion-based intercalation pseudocapacitance as well as oxygen intercalation in a nanostructured lanthanum-based perovskite (LaMnO 3 ) have now been exploited for fast energy storage.

The sensitivity of heterogeneous energetic (HE) materials (propellants, explosives, and pyrotechnics) is critically dependent on their microstructure. Initiation of chemical reactions occurs at hot spots due to energy localization at sites of porosities and other defects. Emerging multi-scale predictive models of HE response to loads account for the physics at the meso-scale, i.e. at the scale of statistically representative clusters of particles and other features in the microstructure. Meso-scale physics is infused in machine-learned closure models informed by resolved meso-scale simulations. Since microstructures are stochastic, ensembles of meso-scale simulations are required to quantify hot spot ignition and growth and to develop models for microstructure-dependent energy deposition rates. We propose utilizing generative adversarial networks (GAN) to spawn ensembles of synthetic heterogeneous energetic material microstructures. The method generates qualitatively and quantitatively realistic microstructures by learning from images of HE microstructures. We show that the proposed GAN method also permits the generation of new morphologies, where the porosity distribution can be controlled and spatially manipulated. Such control paves the way for the design of novel microstructures to engineer HE materials for targeted performance in a materials-by-design framework.

Aliphatic nitrate esters are currently the most widely used energetic ingredients in single-, double-, and triple-base propellants. These nitrate esters are unstable at ambient conditions, and stabilizing agents should be incorporated into the energetic compositions to inhibit and slow down the decomposition reactions that can occur. However, the currently used stabilizers present a number of environmental and human health issues. To overcome these shortcomings, many stabilizers have been appeared in the past few decades and continue to be developed. Furthermore, several analytical techniques have been introduced to monitor the stability of nitrate ester-based energetic materials as well, since the existing ones could not be efficiently applied. Therefore, this review paper discusses and summarizes the current and emergent stabilizers as well as their mechanisms of action. A critical and analytical examination of their advantages and drawbacks is made.

Since this century, disruptive innovating technology has developed rapidly and become a significant power of promoting science & technology development and military change, it will also affect energetic materials' development profoundly. In order to realize the impact of disruptive technologies on energetic materials' development, based on tracking the disruptive technology progress of energetic materials field at home and abroad, the disruptive technologies of ultrahigh-energetic materials has been reviewed, and the technological trends of metal hydrogen, all-nitrogen compounds, material genome and nuclear-energy are mainly analyzed, these disruptive technologies will greatly promote the innovative development of ultrahigh-energetic materials.

Flow batteries, in which the electro-active components are held in fluid form external to the battery itself, are attractive as a potential means for regulating the output of intermittent renewable sources of electricity; an aqueous flow battery based on inexpensive commodity chemicals is now reported that also has the virtue of enabling further improvement of battery performance through organic chemical design. Go with the flow batteries Flow batteries differ from the conventional type in that the electro-active components of flow batteries are held in fluid form external to the battery itself, enabling such systems to store arbitrarily large amounts of energy. Flow batteries are therefore attractive as a potential means for regulating the output of intermittent sources of electricity such as wind or solar power. But an important limitation of most such systems is the abundance and cost of the electro-active materials. To overcome this limitation, Brian Huskinson and colleagues have developed an aqueous flow battery on the basis of inexpensive, non-metallic commodity chemicals, with the added advantage of enabling the tuning of key battery properties through chemical design. As the fraction of electricity generation from intermittent renewable sources—such as solar or wind—grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output 1 , 2 . In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form 3 , 4 , 5 . Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts 6 , 7 . Here we describe a class of energy storage materials that exploits the favourable chemical and electrochemical properties of a family of molecules known as quinones. The example we demonstrate is a metal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br 2 /Br − redox couple, yields a peak galvanic power density exceeding 0.6 W cm −2 at 1.3 A cm −2 . Cycling of this quinone–bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals 8 . This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of π-aromatic redox-active organic molecules instead of redox-active metals represents a new and promising direction for realizing massive electrical energy storage at greatly reduced cost.

A novel poly(3,4-ethylenedioxythiophene)-reduced graphene oxide/copper-based metal–organic framework (PrGO/HKUST-1) has been successfully fabricated by incorporating electrochemically synthesized poly(3,4-ethylenedioxythiophene)-reduced graphene oxide (PrGO) and hydrothermally synthesized copper-based metal–organic framework (HKUST-1). The field emission scanning microscopy (FESEM) and elemental mapping analysis revealed an even distribution of poly(3,4-ethylenedioxythiophene) (PEDOT), reduced graphene oxide (rGO) and HKUST-1. The crystalline structure and vibration modes of PrGO/HKUST-1 were validated utilizing X-ray diffraction (XRD) as well as Raman spectroscopy, respectively. A remarkable specific capacitance (360.5 F/g) was obtained for PrGO/HKUST-1 compared to HKUST-1 (103.1 F/g), PrGO (98.5 F/g) and PEDOT (50.8 F/g) using KCl/PVA as a gel electrolyte. Moreover, PrGO/HKUST-1 composite with the longest charge/discharge time displayed excellent specific energy (21.0 Wh/kg), specific power (479.7 W/kg) and an outstanding cycle life (95.5%) over 4000 cycles. Thus, the PrGO/HKUST-1 can be recognized as a promising energy storage material.

Rheological measurements and extrusion tests are used to evaluate the viability of high mass fraction (80% solids content) wet granular materials for extrusion-based 3D printing. Such materials have diverse applications from making dense, strong ceramic custom parts to 3D printing uniquely shaped energetic materials. Traditionally, 3D-printed colloidal materials use much lower mass fraction inks, and hence, those technologies will not work for systems requiring higher mass fraction solids content. These wet granular materials are highly non-Newtonian presenting non-homogenous flows, shear thinning, yield stress, and high elasticity. Such behaviors improve some aspects of print quality, but make printing very difficult. In this work, the relationship between the rheological behavior of wet granular materials and the processing parameters that are necessary for successfully extruding these materials for printing is examined. In the future, such characterizations will provide key indicators on how to alter printer design/operating conditions and adjust material behavior in order to improve printability. This study is a fundamental first step to successfully developing 3D printing technology of wet granular materials.