Preparation of Highly Energetic Coordination Compounds with Rich Oxidants and Lower Sensitivity Based on Methyl Groups.

Revamping the structure of energy storage is an efficient strategy for striking a balance between the performance and sensitivity of energetic materials to achieve high energy and reduced sensitivity. In continuation of prior research, this study utilized the ligand 3,5-dimethyl-1H-pyrazole-4-carbonhydrazide (DMPZCA) and innovatively designed and synthesized the compound ECCs [Cu(HDMPZCA)2(ClO4)2](ClO4)2·2H2O (ECCs-1·2H2O). Compared with the former research, solvent-free compound ECCs-1 refers to an innovative material characterized by a dual structure involving ionic salts and coordination compounds. Due to these unique structures, ECCs-1 exhibits an increased [ClO4-] content, a higher oxygen balance constant (OB = -7.9%), and improved mechanical sensitivity (IS = 8 J, FS = 32 N). Theoretical calculations support the superior detonation performance of ECCs-1. Additionally, experimental results confirm its ignition capability through lower-threshold lasers and highlight the outstanding initiation potential and explosive power, making it a suitable candidate for primary explosives.

Regulating the Coordination Environment by Using Isomeric Ligands: Enhancing the Energy and Sensitivity of Energetic Coordination Compounds.

Transforming the energy storage structure is an effective approach to achieve a balance between the detonation performance and the sensitivity of energetic compounds, with a goal of high energy and low sensitivity. Building upon previous work, this study employed an isomeric compound 1H-pyrazole-3-carbohydrazide (3-PZCA) as a ligand and creatively designed the energetic coordination compound (ECC) Ag(3-HPZCA)2(ClO4)3 (ECC-1). It is a novel material with a dual structure of ionic salts and coordination compounds, which represents the first report of such a structure in Ag(I)-based ECCs. With its unique structures, ECC-1 exhibits a larger [ClO4-] content, a higher oxygen balance constant (OB = 0%), and superior mechanical sensitivity (IS = 13 J and FS = 40 N). Theoretical calculations indicate that ECC-1 has a higher detonation performance compared to previous work. Furthermore, the explosive experiment testing results demonstrate that it can be ignited by lower-threshold lasers and possesses excellent initiation capability and explosive power, making it suitable not only as a primary explosive but also as a secondary explosive.

Periodate-Based Perovskite Energetic Materials: A Strategy for High-Energy Primary Explosives.

The requirements for high energy and green primary explosives are more and more stringent because of the rising demand in the application of micro initiation explosive devices. Four new energetic compounds with powerful initiation ability are reported and their performances are experimentally proven as designed, including non-perovskites ([H2 DABCO](H4 IO6 )2 ·2H2 O, named TDPI-0) and perovskitoid energetic materials (PEMs) ([H2 DABCO][M(IO4 )3 ]; DABCO=1,4-Diazabicyclo[2.2.2]octane, M=Na+ , K+ , and NH4 + for TDPI-1, -2, and -4, respectively). The tolerance factor is first introduced to guide the design of perovskitoid energetic materials (PEMs). In conjunction with [H2 DABCO](ClO4 )2 ·H2 O (DAP-0) and [H2 DABCO][M(ClO4 )3 ] (M=Na+ , K+ , and NH4 + for DAP-1, -2, and -4), the physiochemical properties of the two series are investigated between PEMs and non-perovskites (TDPI-0 and DAP-0). The experimental results show that PEMs have great advantages in improving the thermal stability, detonation performance, initiation capability, and regulating sensitivity. The influence of X-site replacement is illustrated by hard-soft-acid-base (HSAB) theory. Especially, TDPIs possess much stronger initiation capability than DAPs, which indicates that periodate salts are in favor of deflagration-to-detonation transition. Therefore, PEMs provide a simple and feasible method for designing advanced high energy materials with adjustable properties.

Tuning the Energetic Performance of CL-20 by Surface Modification Using Tannic Acid and Energetic Coordination Polymers.

The energetic performance of hexanitrohexaazaisowurtzitane (CL-20) was modulated with two energetic coordination polymers (ECPs), [Cu(ANQ)2(NO3)2] and [Ni(CHZ)3](ClO4)2, in this study by a two-step method. First, tannic acid polymerized in situ on the surface of CL-20 crystals. Then, [Cu(ANQ)2(NO3)2] and [Ni(CHZ)3](ClO4)2 were hydrothermally formed on the surface of CL-20/TA, respectively. Explosion performance tests show that the impact sensitivity of the coated structure CL-20/TA/[Cu(ANQ)2(NO3)2] is 58% less than that of CL-20 with no energy decrease. On the other hand, CL-20/TA/[Ni(CHZ)3](ClO4)2 can be initiated by a low laser energy of 107.3 mJ (Nd:YAG, 1064 nm, 6.5 ns pulse width), whereas CL-20 cannot be initiated by even 4000 mJ laser energy. This study shows that it is feasible to modify the performance of CL-20 by introducing energetic CPs with certain properties, like high energy insensitive, laser-sensitive, etc., which could be a prospective method for designing high energy insensitive energetic materials in the future.

Preparation of Laser Energetic Coordination Polymers Based on Urazine by Self-Crystallization.

A practical and brilliant way of preparing laser energetic coordination polymers based on crystallization chemistry and coordination theory is proposed in this paper. Design and successful synthesis of urazine (C2H4N4O2, H2ur, 1) by the theory of "cyclization of semicarbazides" are reported. Using the "acid-controlled self-crystallization" synthesis method, with H2ur as the ligand, we successfully synthesized [Ag(H2ur)2ClO4·H2O]n (3) and confirmed its composition and 1D structure. In addition, 3 was subjected to a simple drying operation to obtain a solvent-free [Ag(H2ur)2ClO4]n (4). Also, 4 has the best abilities in physics and chemistry, such as excellent thermal stability, insensitivity to light, mechanical insensitivity, and good corrosion resistance. In particular, thermogravimetric analysis-differential scanning calorimetry-Fourier transform infrared spectroscopy and powder X-ray diffraction were employed to analyze the thermal decomposition products of 4 and demonstrated that the main decomposed products are AgCl, N2, and H2O. Moreover, the calculated predictions show that 4 has an acceptable detonation performance (P = 22.5 GPa; D = 6.9 km s-1). Furthermore, the hot needle examination and detonation experiment show that 4 can be used as a primary explosive. More importantly, as a laser-detonated light-sensitive material, 4 has a significant application value in safety detonators (E = 100 mJ, P = 10 W, and τ = 10 ms).

A novel energetic framework combining the advantages of furazan and triazole: a design for high-performance insensitive explosives.

A series of tetracyclic furazan-triazole compounds have been synthesized and fully characterized. The predicted detonation performance and tested mechanical sensitivities showed their high-energy performance and insensitive features. Quantum chemical calculations and crystal structure analysis were applied to study the intrinsic structure-property relationship among these compounds. In addition, the detonation test shows their promising potential as secondary explosives.

Evolution of Oxidizing Inorganic Metal Salts: Ultrafast Laser Initiation Materials Based on Energetic Cationic Coordination Polymers.

An effective and novel design strategy for ultrafast laser-initiating materials has been established on the basis of coordination chemistry for the first time in the present work. In view of the positive effect of Ag ion and perchlorate on laser sensitivity, silver perchlorate as a representative of oxidizing inorganic metal salts was used to construct energetic cationic coordination polymers (ECCPs), which solved the inconvenient situation caused by the difficulty in applying these salts directly in energetic materials because of the unavoidable hygroscopicity and the inhomogeneity of physical mixtures of oxidants and reductants. With the nonenergetic nitrogen-rich ligand 3-amino-1H-1,2,4-triazole-5-carbohydrazide (ATCA), one new laser-sensitive Ag(I)-based ECCP [Ag(ATCA)ClO4]n (1) was successfully synthesized with a compact helical structure proved by X-ray single-diffraction crystal data. The physicochemical property evaluation revealed that this Ag-ECCP was not only completely devoid of the undesirable properties of the silver perchlorate and displayed excellent tolerance to moisture and noncorrosive properties to metal shells, but was also endowed with good thermal stability and excellent safety for mechanical stimulation. Moreover, theoretical calculations based on the standard molar enthalpy of formation and the lead plate explosive test as the actual damage experiment have proved that the compound has a superior detonation performance (up to 6800 m s-1 and 0.511 kcal g-1) compared to the traditional primary explosives. More importantly, the laser-initiation-experiment-based femtosecond laser-testing system and high-speed photography demonstrated that this ECCP was an energetic material with great potential for application in the safety detonator as an ultrafast photosensitive initiating material for laser direct initiation, whose initiation delay time is as low as 73 ms using only 200 mJ initiation energy.

Polynitro-Functionalized Triazolylfurazanate Triaminoguanidine: Novel Green Primary Explosive with Insensitive Nature.

Exploring a green and safe primary explosive to replace very toxic and sensitive lead azide and lead styphnate takes great efforts. Here, a series of polynitro-functionalized triazolylfurazanate energetic materials have been reported. These new compounds were fully characterized by infrared, multinuclear NMR spectra, mass spectra, elemental analysis, and differential scanning calorimetry measurements. The structure of mono-diaminoguanidinium salt (17) was determined by single-crystal X-ray diffraction. Inspired by the high pressurization rate and fast energy release in triaminoguanidinium salts, some suitability evaluation for primary explosives has been applied. Di(triaminoguanidinium) 3-nitramino-4-(3-(dinitromethanidyl)-1,2,4-triazol-5-yl)furazanate exhibits an excellent gas-generating capability (Pmax = 9.03 Mpa) and combustion performance (dP/dtmax = 201.5 GPa s-1) close to fast thermite Al/CuO (Pmax = 8.49 Mpa, dP/dtmax = 252.2 GPa s-1). Moreover, the good initiation capacity (60 mg for 500 mg RDX) coupled with insensitivity in this compound (IS = 17.4 J, FS = 240 N, ESD > 0.225 J) make it a promising green and insensitive primary explosive.

Amino-nitramino functionalized triazolotriazines: a good balance between high energy and low sensitivity.

Using a simple and efficient approach, a series of fused triazolo-triazine compounds, namely, 2,5-dinitramide-7-amino-[1,2,4]triazolo[1,5-a][1,3,5]triazine (2) and its energetic salts (4-9, 11-13), were prepared by nitration of 2,5,7-triamine [1,2,4]triazolo[1,5-a][1,3,5]triazine (1) with 100% nitric acid, followed by reacting with the corresponding bases. All new compounds were comprehensively characterized. Structures of 2 and 4 were further confirmed by single crystal X-ray diffraction. Based on the measured densities and calculated heats of formation (Gaussian 09), detonation pressures and velocities were evaluated by EXPLO5, falling in the range of 21.5-34.2 GPa and 7823-9313 m s-1, respectively. Notably, impact and friction tests show that these compounds are very insensitive (IS > 40 J; FS > 360 N). Moreover, two representative compounds 5 and 6 with high decomposition temperature (5: 194 °C; 6: 199 °C), excellent detonation properties (vD = 9313, 9088 m s-1; P = 33.9, 34.1 GPa) as well as rarely low sensitivities (IS > 40 J; FS > 360 N) are promising candidates as high-energy and insensitive explosives.

C8 N26 H4 : An Environmentally Friendly Primary Explosive with High Heat of Formation.

The synthesis and characterization of the metal-free polyazido compounds 3,6-bis-(2-(4,6-diazido-1,3,5-triazin-2-yl)-hydrazinyl)-1,2,4,5-tetrazine (2) and 3,6-bis-(2-(4,6-diazido-1,3,5-triazin-2-yl)-diazenyl)-1,2,4,5-tetrazine (4) are presented. Two compounds were characterized by NMR spectra, IR spectroscopy, mass spectrometry, and differential scanning calorimetry (DSC). Additionally, the structure of 2 was confirmed by single-crystal X-ray diffraction. Compounds 2 and 4 exhibit measured densities (1.755 g cm-3 and 1.763 g cm-3 ), good thermal stabilities (194 °C and 189 °C), high heat of formation (2114 kJ mol-1 and 2820 kJ mol-1 ), and excellent detonation performance (D, 8365 m s-1 and 8602 m s-1 ; P, 26.8 GPa and 29.4 GPa). Furthermore, compounds 2 and 4 have been tested for their priming ability to detonate RDX. The results indicate that the title compound 2 is a potential environmentally friendly alternative candidate to lead-based primary explosives.

Theoretical studies on the thermodynamic properties, densities, detonation properties, and pyrolysis mechanisms of trinitromethyl-substituted aminotetrazole compounds.

Trinitromethyl-substituted aminotetrazoles with -NH2, -NO2, -N3, and -NHC(NO2)3 groups were investigated at the B3LYP/6-31G(d) level of density functional theory. Their sublimation enthalpies, thermodynamic properties, and heats of formation were calculated. The thermodynamic properties of these compounds increase with temperature as well as with the number of nitro groups attached to the tetrazole ring. In addition, the detonation velocities and detonation pressures of these compounds were successfully predicted using the Kamlet-Jacobs equations. It was found that these compounds exhibit good detonation properties, and that compound G (D = 9.2 km/s, P = 38.8 GPa) has the most powerful detonation properties, which are similar to those of the well-known explosive HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocine). Finally, the electronic structures and bond dissociation energies of these compounds were calculated. The BDEs of their C-NO2 bonds were found to range from 101.9 to 125.8 kJ/mol(-1). All of these results should provide useful fundamental information for the design of novel HEDMs.

Theoretical investigation of a novel high density cage compound 4,8,11,14,15-pentanitro-2,6,9,13-tetraoxa-4,8,11,14,15-pentaazaheptacyclo[5.5.1.1(3,11).1(5,9)] pentadecane.

A novel polynitro cage compound 4,8,11,14,15-pentanitro-2,6,9,13-tetraoxa-4,8,11,14,15-pentaazaheptacyclo [5.5.1.1(3,11).1(5,9)]pentadecane(PNTOPAHP) has been designed and investigated at the DFT-B3LYP/6-31(d) level. Properties, such as electronic structure, IR spectrum, heat of formation, thermodynamic properties and crystal structure have been predicted. This compound is most likely to crystallize in C2/c space group, and the corresponding cell parameters are Z = 8, a = 29.78 Å, b = 6.42 Å, c = 32.69 Å, α = 90.00°, ß = 151.05°, γ = 90.00° and ρ = 1.94 g/cm(3). In addition, the detonation velocity and pressure have also been calculated by the empirical Kamlet-Jacobs equation. As a result, the detonation velocity and pressure of this compound are 9.82 km/s, 44.67 GPa, respectively, a little higher than those of 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazaisowurtzitane(TEX, 9.28 km/s, 40.72 GPa). This compound has a comparable chemical stability to TEX, based on the N-NO(2) trigger bond length analysis. The bond dissociation energy ranges from 153.09 kJ mol(-1) to 186.04 kJ mol(-1), which indicates that this compound meets the thermal stability requirement as an exploitable HEDM.

[Research on SCB discharge behavior with atomic emission spectroscopy].

Semiconductor bridge (SCB) was utilized to ignite energetic materials with thin film discharge and characterized of low input energy, high safety and logic control possibility. SCB discharge was diagnosticated with atomic emission spectroscopy. Firstly, discharge temperature was acquired with copper atom spectral lines 510.5 and 521.8 nm, and electron density was calculated with silicon atom spectral line 390.5 nm and corresponding ion line 413.0 nm. As for resistance 1.0 omega of SCB with the discharge voltage of 20 V and capacity of 47 microF, its discharge temperature was about 2 500-4 300 K and electron density 10(16) cm(-3). Meanwhile, the temperature and density V(s) time distributions were acquired simultaneously. And then with the diagnosis results, the discharge behaviors of two sorts of SCB were judged according to plasma space-dimension and time-dimension restrictions. This research set up an efficient technique for the diagnosis of transient small-size discharge behavior and provided instructions for the design of SCB and discharge condition.

[Emission spectroscopy diagnostics of plasma electron temperature].

Electron temperature is one of the important parameters of plasma. It is very difficult to measure the electron temperature exactly and instantly owing to its complexity during discharge. As a plasma diagnostics technique, emission spectroscopy is widely applied in the study and diagnosis of any kind of plasma, because of its simple instrument system, noninterference of measurement, high sensitivity and fast responsibility. In the present paper, some methods for plasma electron temperature diagnosis, such as two lines method, multiline slope method, isoelectronic line method, Saha-Boltzmann equation, absolute intensity method, were introduced. And the applications of these methods were reviewed to provide reference for choosing appropriate methods in practice.