Dr. Srinivas Dharavath
Our research group will design and synthesize various nitrogen-rich azoles, fused and strained rings containing small molecules which are highly dense, thermally stable, and insensitive towards mechanical stimuli for 'Green' and 'Environmentally friendly' high energy materials (HEM) applications. So far, we have synthesized various poly-nitrogen containing small energetic molecules and salts from commercially available cheap starting materials as HEMs in a simple and straightforward manner. Few synthesized molecules are a better replacement for the existing benchmark energetic materials that meet the requirements of present and future civil, defense, and space applications.
Design and synthesis of high-performing energetic materials
In material science, high energy materials (HEMs) are among the most essential functional substances and are widely utilized for various military and civilian purposes. HEMs are designed to store enormous amounts of energy in the chemical structure in a condensed phase releasing rapidly (in the case of an explosive) or gradually (in the case of propellants) and exerting abrupt change in heat-pressure on the surroundings. Since the discovery of black powder and the subsequent development of nitroglycerine, nitrocellulose, TNT, TATB, RDX, HMX, CL-20, etc., the demand for new materials has increased with desired properties for civil, defence, and space exploration programs.
HEMs with specific and modifiable physicochemical and energetic properties are essential for their precise applications. New HEMs with tunable performance and safety have been the subject of an extensive investigation by researchers worldwide. Some of the present challenges in the field of HEMs are (i) Demand for green energetic materials with nitrogen-rich heterocyclic backbone as a replacement for TNT, RDX and HMX since they produce an enormous amount of toxic gases (CO and CO2) on detonation. (ii) Insensitivity towards heat, impact, friction, and electrostatic discharge is an essential and fate-deciding parameter for HEMs. (iii) Development of higher-performing melt-castable ingredients that are more energetic than TNT and DNAN. (iv) Combining high performance with less sensitivity i.e., minimizing energy-safety contradiction.
The heterocyclic backbone plays an excellent role in the design and synthesis of HEMs. Developing new and convenient synthetic routes, high energy-safety balance, and environmentally benign nature has tremendous value to the wider materials community.
Dr. Srinivas Dharavath
Amine and nitramine functionalization of imidazole-triazine and triazole-triazine skeletons: Exploring for potential multipurpose energetic materials (Special issue)
A series of five and six-membered C-C bonded energetic materials (2-7) based on a combination of imidazole-triazine and triazole-triazine backbones were designed, synthesized, and characterized using NMR, IR, and TGA DSC studies. Further, the structure of compound 4 was supported by single-crystal X-ray analysis. All the newly synthesized energetic compounds exhibited good density, excellent thermal stability, good detonation performance, and low mechanical sensitivity toward impact and friction. Among all, the nitrate salt 4 exhibits balanced properties, including high density (1.80 g cm-3), excellent thermal stability (254 ℃), good detonation velocity (8178 m s-1) and low sensitivity towards impact and friction. The facile synthetic feasibility, thermal stability, energetic performance and insensitivity of all the molecules suggest they can be used as an insensitive secondary explosive in various defence and civilian applications.
Synthesis of advanced pyrazole and N-N bridged bistriazole-based secondary high energy materials
In this work, we have synthesised 3,5-dihydrazinyl-4-nitro-1H-pyrazole (2), 9-nitro-1H-pyrazolo[3,2-c:5,1-c']bis([1,2,4]triazole)-3,6-diamine (3), N-N bonded N,N'-([4,4'-bi(1,2,4-triazole)]-3,3'-diyl)dinitramide (5) and its stable nitrogen-rich energetic salts in a single and two-steps with quantitative yields from commercially available inexpensive starting material 4,6-dichloro-5-nitropyrimidine (1). Along with the NMR, IR, DSC, and elemental analysis (EA) characterization, the structures of 2, 4, 5, 6, 7 and 8 were confirmed by single crystal X-ray diffraction. Interestingly, 5, 6, 7 and 8 show excellent thermal stability (242, 221, 250, 242 ℃) than RDX (210 ℃). Detonation velocities of 2, 4, 6 and 7 ranges from 8992 to 9069 m s-1 which are better than RDX (8878 m s-1) and close to HMX (9221 m s-1). All these compounds are insensitive to impact (10 to 35 J) and friction (360 N) sensitivity. These excellent energetic performances, stability and synthetic feasibility make compounds 2, 4, 6 and 7 promising candidates as secondary explosives and potential replacements to the presently used benchmark explosives RDX, and HMX.