Alkylene-functionality in bridged and fused nitrogen-rich poly-cyclic energetic materials:Synthesis,structural diversity and energetic properties

From the standpoint of chemical structures,the organic backbones of energetic materials can be classified into aromatic rings,nonaromatic rings,and open chains.Although the category of aromatic energetic compounds exhibits several advantages in the regulation of energetic properties,the nonaromatic heterocycles,assembling nitramino explosophores with simple alkyl bridges,still have prevailed in benchmark materials.The methylene bridge plays a pivotal role in the constructions of the classic nonaromatic heterocycle-based energetic compounds,e.g.,hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX)and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine(HMX),whereas ethylene bridge is the core moiety of state-of-the-art explosive 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20).In this context,it is of great interest to employ simple and practical bridges to assemble aromatic and nonaromatic nitrogen-rich heterocycles,thereby expanding the structural diversity of energetic materials,e.g.,bridged and fused nitrogen-rich poly-heterocycles.Furthermore,alkyl-bridged poly-heterocycles highlight the potential for the open chain type of energetic materials.In this review,the development of alkyl bridges in linking nitrogen-rich heterocycles is presented,and the perspective of the newly constructed energetic backbones is summarized for the future design of advanced energetic materials.

Atomic interface regulation of rare-marth metal single atom catalysts for energy conversion

Efficient photocatalysis and electrocatalysis in energy conversion have been important strategies to alleviate energy crises and environmental issues.In recent years,with the rapid development of emerging catalysts,significant progress has been made in photocatalysis for converting solar energy into chemical energy and electrocatalysis for converting electrical energy into chemical energy.However,their selectivity and efficiency of the products are poor.Rare earth(RE)can achieve atomic level fine regulation of catalysts and play an crucial role in optimizing catalyst performance by their unique electronic and orbital structures.However,there is a lack of systematic review on the atomic interface regulation mechanism of RE and their role in energy conversion processes.Single atom catalysts(SACs)provide clear active sites and 100%atomic utilization,which is conducive to exploring the regulatory mechanisms of RE.Therefore,this review mainly takes atomic level doped RE as an example to review and discuss the atomic interface regulation role of RE elements in energy conversion.Firstly,a brief introduction was given to the synthesis strategies that can effectively exert the atomic interface regulation effect of RE,with a focus on the atomic interface regulation mechanism of RE.Meanwhile,the regulatory mechanisms of RE atoms have been systematically summarized in various energy conversion applications.Finally,the challenges faced by RE in energy conversion,as well as future research directions and prospects,were pointed out.

Additive manufacturing of energetic materials:Tailoring energetic performance via printing

Additive manufacturing(AM),also called three-dimensional(3D)printing,has been developed to obtain energetic materials within the past decade.3D printing represents a family of flexible manufacturing techniques that enable fast and accurate fabrication of structures with complex 3D features and a broad range of sizes,from submicrometer to several meters.Various methods have already been explored,including templating,melting extrusion,inkjet printing and electrospray methods.It was demonstrated that the structure achieved by AM could be used to manipulate the reactivity of energetic or reactive materials by changing the flow of gases and entrained particles via architecture.By employing different AM techniques,energetic materials with controllable nanostructures and uniformly dispersed ingredients can be prepared.It is exciting to tailor the energy release without defaulting to change the formulation of the conventional method.The combustion and mechanical properties of conventional energetic materials can be retained at the same time.In this review,the preparation and characterization of AM energetic materials that have been developed in the last decade are summarized.Various AM techniques used in the fabrication of energetic materials are compared and discussed.In particular,formulations of energetic materials applied in AM,metallic fuels,binders and energetic fillers and their advantages in terms of combustion efficiency and other properties are proposed.

Synthesis and Characterization of Fluorodinitrobenzenes with Tunable Melting Point:Potential Low Sensitive Energetic Plasticizer and Melt-Cast Carrier

of main observation and conclusion In order to explore the effects of fluoro substituents on the energy and safety of energetic compounds,a series of fluorodinitrobenzenes including l,3-difluoro-2,4-dinitrobenzene(1),1,5-difluoro-2,4-dinitrobenzene(2),1,2,3-trifluoro-4,6-dinitrobenzne(3)and 1,3,5-trifluoro-2,4-dinitrobenzene(4)were prepared.All the compounds were fully characterized.The structures of 2 and 3 were further confirmed by single crystal X-ray diffraction analysis.The results show that these compounds exhibit comparable detonation properties(D=6703-6978 m s^-1,and p=21.3-23.76Pa)to those of 2,4,6-trinitrotoluene(TNT)due to the significantly increased density of fluorine introduced.Low sensitivity(IS>40 J,and FS>360 N)of these compounds along with different melting points make them potential candidates for different allocation.Among them,1 and 4 with the melting point of 42.5℃and 55.2℃,respectively,show promise for application in the field of energetic plasticizer.Compounds 2 and 3 are potential low sensitive melt-cast carrier due to their similar melting point and superior detonation performance to that of TNT.