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• BiVO 4 was used for the first time in the field of thermites. • Al/BiVO 4 exhibits a unique reaction mechanism. • Al/BiVO 4 exhibits superior pressure performance and ignition characteristics. • The superior reactivity is attributed to the gaseous and condensed phase products. Thermites has garnered significant attention due to its high energy density and elevated reaction temperature. However, in most cases, thermites reactions predominantly generate heat and high temperatures while yielding less gas production. Although Al/Bi 2 O 3 exhibits abundant gas generation, it demonstrates lower heat release and is too sensitive. In this study, bismuth vanadate (BiVO 4) is introduced as the oxidizer in thermites for the first time. Al/BiVO 4 exceeds both Al/ Bi 2 O 3 and Al/V 2 O 5 in terms of jetting distance, and the maximum pressure attained by Al/BiVO 4 is nearly double that of Al/ Bi 2 O 3. Additionally, we investigate the reaction mechanism of the Al/BiVO 4 system by means of thermal reaction pathway analysis and characterization of combustion and thermal analysis products. This study unveils a distinctive reaction mechanism during the combustion of Al/BiVO 4 , with bismuth undergoing reduction prior to vanadium. Throughout the entire reaction process, gaseous substances are forcefully released, and the high-temperature solids enhance the generation of gaseous products, resulting in the formation of a flame characterized by a high-temperature particle swarm. The impressive high temperature particle swarm flame and significant pressure output performance and flame jetting distance of the Al/BiVO 4 system confer advantages to its ignition capability. We posit that Al/BiVO 4 holds great potential for various applications in propellants, explosives, and pyrotechnic products. [ABSTRACT FROM AUTHOR]

• A new type of fluorine-containing oxidant BiOF was synthesized. • The n-Al/BiOF system exhibits excellent ignition and combustion properties. • The pre-ignition reaction between BiOF and n-Al promotes energy release. • The energy release of n-Al/BiOF depends on the Al-O/Al-F synergistic mechanism. The reduced diffusion distance of nano-thermite results in an exceptionally high energy release rate and intense exothermic reactions upon ignition, which has drawn significant interest from researchers in the field of energetic materials. With the deepening of research, metal fluorides are gradually favored by researchers because of their unique reaction characteristics. This paper presents the synthesis of a new fluorine-containing oxidant, BiOF, and its use in the preparation of a novel nano-thermite with n-Al. BiOF crystals exhibit a unique microscopic morphology and are interlaced into "nanoflower" microspheres, which allows for good interfacial contact between the oxidant and fuel during the recombination process. The resulting n-Al/BiOF system displays excellent ignition and combustion performance, with a combustion temperature higher than the boiling point of its main combustion products, AlF 3 and Bi. Compared with n-Al/CuO and n-Al/MoO 3 systems, n-Al/BiOF exhibits a higher flame propagation rate under confinement. In addition, the ignition threshold of the n-Al/BiOF system is also smaller than that of the n-Al/CuO and n-Al/MoO 3 systems. Furthermore, the paper examines the reaction mechanism of the n-Al/BiOF system through thermal reaction path analysis and combustion and thermal analysis product characterization. The paper discovers a "pre-ignition" reaction mechanism before the ignition temperature, where the strongly electronegative fluorine in BiOF corrodes the Al 2 O 3 shell, promoting the release of aluminum energy. The synergistic and effective interaction between oxygen, fluorine, and fuel aluminum in the n-Al/BiOF system results in efficient energy release performance, making BiOF a promising candidate for n-Al based reactive materials in propellants, explosives, and pyrotechnic products. [ABSTRACT FROM AUTHOR]

• Eutectic silicon makes the combustion of Al-Si/CuO more stable than Al/CuO. • The increased solid phase products of Al-Si/CuO guarantees good ignition ability. • The eutectic silicon leads to an advanced and enhanced heat release of Al-Si alloy. • Al-Si/CuO thermites ignite Mg/Teflon/Viton (MTV) column faster than Al/CuO. The unstable energy release efficiency hinders the application of Al/CuO metastable intermixed composites (MICs) in pyrotechnic applications to some extent. To overcome this issue, systematic experiments of Aluminum-Silicon (Al-Si) alloy-thermites with different Si content (12 wt% and 20 wt%) have been investigated in the context of regulating the energy release process. Optical diagnosis methods were applied synchronously to measure the flame propagation velocity and temperature field variation. Scanning electron microscopy and differential scanning calorimetry were used to observe the morphology and analyze the thermal process. Results indicated that the introduction of silicon significantly stabilized the combustion process of Al-Si/CuO due to the fewer gas-phase products and slower reaction rate of Si with CuO, while the flame temperature changed little. Excess silicon wafer blocks observed by SEM on Al-20Si led to an enhanced transport of oxygen and fuel. This explained the abnormal reactivity of hypereutectic alloy. The total heat releases of Al-20Si and Al-12Si were respectively enhanced by 110.2% and 93.1% in comparison with that of Al under DSC tests. Infrared temperature measurement of the Mg/Teflon/Viton (MTV) column revealed that Al-12Si and Al-20Si alloy thermites ignited MTV column 569.06 and 540.48 ms faster than Al/CuO, respectively, as the energy output mainly existed in the form of high-temperature residues. These improvements are attributed to the synergistic effect of the reactivity of silicon and aluminum, as well as the phase change during reaction which provides a controllable energy release process of alloy thermite and a better ignition performance. These findings are expected to facilitate the development of the nature of Al alloys and are especially promising for the thermite technology driven by reliable energy release rates. [ABSTRACT FROM AUTHOR]

The energy performance of nanothermites in aqueous conditions is commonly restricted by the rapid heat dissipation and corrosion of nano-Al. Here we report studies on the fabrication and submerged ignition for the super-hydrophobic nanothermite film based upon the Co 3 O 4 /Al core/shell nanowires (NWs). The Co 3 O 4 NWs arrays, which are synthesized using a facile hydrothermal-annealing method, serve as templates for the deposition of Al shells by magnetron sputtering. The super-hydrophobic surface is subsequently realized by the fluoroalkylsilane coating. The tests of the laser-induced underwater ignition reveal that the super-hydrophobic modification effectively could lead to the ignition of the nanothermite film. Furthermore, the anti-aging behaviors of the obtained super-hydrophobic nanothermite film in aqueous conditions are investigated in detail to compare the heat-release and ignition characteristics at different submersion times. Impressively, the resultant super-hydrophobic composite could still hold about 50% of the original energy even after an underwater storage of 2 days. [ABSTRACT FROM AUTHOR]

• CFO/Al/Bi 2 O 3 is formed by long-range electrostatic force and covalent interactions. • CFO/Al/Bi 2 O 3 used as energetic electric-thermal conversion component. • Replacement of the Ni-Cr or SCB to solve the problems caused by film interfaces. • To detonate RDX reliably without other bridges. Carbon fiber is used to construct an energy conversion component with the purpose of high reliability, safety and potential application in micro size. The carbon fiber oxidant (CFO) is endowed as the carrier for the assembly of CFO/Al/Bi 2 O 3 while long-range electrostatic force and covalent interactions are analyzed as the main force. The self-assembly can function with a voltage as low as 15.34 V and can detonate RDX successfully without using primary explosives and traditional bridge film unit. The ignition mechanism is deduced that carbon fibers have a transient high conductivity when the voltage is charged. The one-dimensional structure and micro-size make the puncture easily and reliably. Moreover, the integration of Al/Bi 2 O 3 enhanced its initiation power and reliability. The research broadens the understanding of carbon fiber as one-dimensional material, and more applications are expected in this new field by considering the variety of carbon fiber size, different sorts of reactive materials and so on. [ABSTRACT FROM AUTHOR]