Showing papers on "Friction sensitivity published in 2019"

Synthesis of Thermally Stable and Insensitive Energetic Materials by Incorporating the Tetrazole Functionality into a Fused-Ring 3,6-Dinitropyrazolo-[4,3-c]Pyrazole Framework.

Abstract: A series of fused-ring energetic materials, i.e., 3,6-dinitro-1,4-di(1H-tetrazol-5-yl)-pyrazolo[4,3-c]pyrazole (DNTPP, compound 2) and its ionic derivatives (compounds 3-8), were designed and synthesized in this study. The molecular structures of compounds 2, 3, 6, 7·2H2O, and 8 were confirmed using single-crystal X-ray diffraction. Their physicochemical and energetic properties, such as density, thermal stability, heat of formation, sensitivity, and detonation properties (e.g., detonation velocity and detonation pressure), were also evaluated. The results indicate that DNTPP and most of its ionic derivatives are extremely thermally stable and insensitive toward mechanical stimuli. In particular, the thermal decomposition temperature of compound 3 is up to 329 °C, while compounds 7 and 8 are very insensitive (impact sensitivity: >20 J; friction sensitivity: >360 N). Compounds 2, 3, and 6 possess good comprehensive properties, including excellent thermal stability, remarkable low sensitivities, and favorable detonation performance. These features show that DNTPP and its ionic derivatives have considerable promise as thermally stable and insensitive energetic materials.

Supercritical Antisolvent Processing of Nitrocellulose: Downscaling to Nanosize, Reducing Friction Sensitivity and Introducing Burning Rate Catalyst

Abstract: A supercritical antisolvent process has been applied to obtain the nitrocellulose nanoparticles with an average size of 190 nm from the nitrocellulose fibers of 20 μm in diameter. Compared to the micron-sized powder, nano-nitrocellulose is characterized with a slightly lower decomposition onset, however, the friction sensitivity has been improved substantially along with the burning rate increasing from 3.8 to 4.7 mm·s−1 at 2 MPa. Also, the proposed approach allows the production of stable nitrocellulose composites. Thus, the addition of 1 wt.% carbon nanotubes further improves the sensitivity of the nano-nitrocellulose up to the friction-insensitive level. Moreover, the simultaneous introduction of carbon nanotubes and nanosized iron oxide catalyzes the combustion process evidenced by a high-speed filming and resulting in the 20% burning rate increasing at 12 MPa. The presented approach to the processing of energetic nanomaterials based on the supercritical fluid technology opens the way to the production of nitrocellulose-based nanopowders with improved performance.

C8N12O10: a promising energetic compound with excellent detonation performance and desirable sensitivity

Abstract: Among energetic materials, there is a significant challenge faced by researchers to seek an optimal balance between high performance and safety. By combination of furoxan and 1,2,4-oxadiazole backbones and C–NO2 moieties, a promising energetic molecule, bis(4-nitro-1,2,5-oxadiazole-2-oxid-3-yl)-azo-1,2,4-oxadiazole (6), was prepared and characterized by IR, multinuclear NMR spectroscopy, elemental analysis, DSC measurements and single crystal X-ray diffraction. It has a high density (1.92 g cm−3), an acceptable thermal stability (182 °C) and a high heat of formation (1188.8 kJ mol−1/2.8 kJ g−1). The calculated detonation performance (D = 9666 m s−1 and P = 42.8 GPa) is comparable to that of CL-20 (9706 m s−1 and 45.2 GPa). More importantly, it shows desirable impact and friction sensitivity (IS: 12 J and FS: 180 N), which is less sensitive than HMX (IS: 7.4 J and FS: 120 N). Furthermore, a detonation test of compound 6 was conducted. The results indicate that compound 6 is more powerful than the commonly used secondary explosive RDX (D = 8795 m s−1 and P = 34.9 GPa). The combination of advanced performances and desirable safety makes this substance a potential secondary explosive.

5-(4-Azidofurazan-3-yl)-1-hydroxytetrazole and its derivatives: from green primary to secondary explosives

Abstract: 5-(4-Azidofurazan-3-yl)-1-hydroxytetrazole (4) and its ammonium (4a), hydroxylammonium (4b), and hydrazinium (4c) salts were synthesized. Each compound was characterized by X-ray single crystal structure diffraction, infrared (IR), and 1H and 13C NMR spectroscopy, elemental analyses, thermal stability, and sensitivity to external stimulants. Crystal structures and packing coefficients were analyzed and compared with respect to π–π stacking and hydrogen bonding. Due to the presence of lattice water in compound 4, the impact sensitivity (IS = 15 J) and friction sensitivity (FS = 120 N) are notably lower than those of the anhydrous material (IS = 3 J, FS = 20 N), which could act as a primary explosive. In this way, the primary explosive could be synthesized, transported, and stored more safely than traditional primary explosives. The detonation properties determined by EXPLO 6.02 software show that among the four compounds, 4b has superior detonation velocity (Vd = 9201 m s−1) and pressure (P = 36.0 GPa) values which are comparable to those of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). The impact sensitivity (10 J) is less-sensitive than HMX (7.5 J), which suggests compound 4b as a potential alternative to HMX.

Preparation of multi-scale FOX-7 particles and investigation of sensitivity and thermal stability

Abstract: Multi-scale ultrafine 1,1-diamino-2,2-dinitroethene (FOX-7) samples with different particle size were fabricated and specifically, nano-FOX-7 was successfully prepared by a green mechanophysical milling method. All samples were characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Impact and friction sensitivities of the samples were tested and thermal analysis was performed by differential scanning calorimetry (DSC) and thermogravimetry (TG). Ultrafine particles with a mean size of 40 nm, 0.9 μm and 3.4 μm respectively showed less sensitivity than raw FOX-7, whose particles size was about 20 μm. The critical drop height H50 of ultrafine FOX-7 increased from 129 cm to 172 cm, 142 cm and 136 cm, respectively and the friction sensitivity reduced from 32% to 8%, 16% and 20%, respectively. Furthermore, the apparent activation energy of ultrafine particles increased compared with raw materials, which suggested the thermal stability of the ultrafine particles was improved.

Fabrication and Characterization of Submicron Scale Spherical RDX, HMX, and CL-20 without Soft Agglomeration

Abstract: In this study, a novel spray drying-assisted self-assembly (SDAS) technology was proposed to prepare submicron elemental explosives with good morphology, uniform dispersion, and low sensitivity and spherical submicron RDX, HMX, and CL-20 particles without soft agglomeration were fabricated via such a method. Structural characterizations and thermal stability of the composites were systematically studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimeter (DSC). Moreover, safety performance was analyzed by qualitative testing of impact sensitivity and friction sensitivity. The XRD analysis demonstrated that HMX and CL-20 refined by SDAS maintained the crystal structure of β-HMX and e-CL-20 before and after refinement, whereas the HMX crystal structure after spray recrystallization refinement was transformed from β-HMX to α-HMX. The DSC results indicated that the thermal decomposition peak temperature of the three particles refined by the SDAS technology had a minimum advancement, and the thermal stability of the particles was relatively superior. More importantly, the of the RDX, HMX, and CL-20 refined by this novel method was increased to 48.3 cm, 44.6 cm, and 31.1 cm, and the probability of friction explosion was decreased to 62%, 62%, and 80%, respectively, thus significantly improving the safety performance as compared with the sample refined by spray recrystallization.

Preparation and characterization of nitrogen-rich bis-1-methylimidazole1 H ,1′ H -5,5′-bistetrazole-1,1′-diolate energetic salt

Abstract: A new nitrogen-rich energetic salt of bis-1-methylimidazole 1H,1′H-5,5′-bistetrazole-1,1′-diolate salt, (1-M)2BTO, was synthesized and characterized (FT-IR, 1H NMR, 13C NMR, elemental analysis, and X-ray single-crystal diffraction). Results indicated that (1-M)2BTO crystallizes in the triclinic space group P-1. The thermal decomposition behavior of (1-M)2BTO was determined by differential scanning calorimetry (DSC) and thermogravimetric tandem infrared spectroscopy. The decomposition peak temperature of (1-M)2BTO was 530 K, which suggested that the salt is strong heat resistance. The apparent activation energies were 130.56 kJ mol−1 (Kissinger’s method) and 132.50 kJ mol−1 (Ozawa’s method), respectively. The enthalpy of formation for the salt was calculated as 917.3 kJ mol−1. The detonation velocity and detonation pressure of (1-M)2BTO were 7448 m s−1 and 20.7 GPa, respectively, using the Kamlet-Jacobs equation. Furthermore, the sensitivity test results showed that its impact sensitivity is greater than 50 J and friction sensitivity is 180 N, indicating that it has a lower sensitivity.

Device and method for improving accuracy of friction sensitivity test

Abstract: The invention relates to a device and method for improving the accuracy of a friction sensitivity test. The device and method mainly solve the problem of poor accuracy of a test in the prior art due to subjective judgment. The device for improving the accuracy of the friction sensitivity test comprises a steel base, a balance weight, a load arm, a porcelain plate, a bracket, an adjustment rod, a handle and a signal collector; the balance weight and the load arm are connected to the bracket, the porcelain plate is fixed to the bracket, and a switch, the handle and the bracket are fixed to the steel base; and according to the technical scheme, the device and method for improving the accuracy of the friction sensitivity test well solves the above problem, and can be used for improving the accuracy of the friction sensitivity test.

Method for improving accuracy of friction sensitivity test

Abstract: The invention relates to a method for improving the accuracy of a friction sensitivity test. The method mainly solves the problem that in the prior art, a test has poor accuracy due to subjective judgment. According to the method for improving the accuracy of the friction sensitivity test, a friction sensitivity test device is adopted to perform the friction sensitivity test, and the device comprises a steel base, a balance weight, a load arm, a porcelain plate, a bracket, an adjustment rod and a handle; the balance weight and the load arm are connected to the bracket, the porcelain plate is fixed to the bracket, and a switch, the handle and the bracket are fixed to the steel base; and according to the technical scheme, the method for improving the accuracy of the friction sensitivity testwell solves the above problem, and can be used for improving the accuracy of the friction sensitivity test.

Friction speed control device for friction sensitivity test and control method thereof

Abstract: The invention discloses a friction speed control device for detecting friction sensitivity and a control method thereof, and belongs to the technical field of testing of energetic materials. The device solves the problem that steady control of friction speed in the existing friction sensitivity test process of insensitive explosive cannot be achieved. The friction speed control device comprises aspeed governing motor, a surpassing centrifugal clutch, a rack friction plate and rack friction plate guiding devices, the output end of the speed governing motor is connected with one end of the surpassing centrifugal clutch, a gear is installed on a connection shaft of the other end of the surpassing centrifugal clutch, the gear is engaged with the rack friction plate, the rack friction plate isinstalled in the rack friction plate guiding devices, and the rack friction plate is slidably connected with the rack friction plate guiding devices.