what should be the characteristic of high resistivity material
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High resistivity. High melting point. Highmechanical strength. High ductility, so that can be drawn in the form of wire easily.
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Reactive material has been widely studied for more than 40 years [1] and the metal/polymer mixture type reactive materials showed great superiority in the application of weapons and equipment [2]. Metal/polymer mixture type reactive materials are usually composed of two or more metal particles and polytetrafluoroethylene (PTFE). This type of materials is relatively insensitive under normal conditions, but, under high strain rate loading or high-pressure collision conditions, violent chemical reactions will occur and release a lot of chemical energy [3,4]. In 2004, the scientists in the “naval weapon operation center” of the US army found that the damage area on the air target resulted from the reactive fragment was nearly doubled if the reactive and inert fragments have the same size and collision velocity. Some characteristics of the metal/polymer mixture type reactive material are similar to conventional explosives, but the reactive material has better mechanical properties than the explosive, and the overall performance of the external impact loading conditions is blunt, high energy.
Currently, the most widely used PTFE based reactive materials composite formulation is PTFE/Al (73.5%/26.5%), and its unit mass energy and unit volume energy can reach 3.5 times and 5 times tri-nitro-toluene (TNT) explosives [5]. Under the condition of high-speed impact loading, PTFE/Al will undergo violent combustion and detonation reaction, and the reaction rate is roughly between the combustion rate of propellant and the detonation rate of explosive [6,7]. The heat released by the unit mass reaction of PTFE/Al (wt.%: 73.5/26.5) is about 8.53 kJ/g, which is about two times the TNT explosive under the same conditions. To extend the applied scope of PTFE/Al, many works on fabrication method and formulation have been carried out. The tensile strength of PTFE/Al can be increased to 20 MPa after sintering, and the sintered PTFE/Al reactive material can be used as a structural member. The density of PTFE/Al can be increased to more than 10 g/cm3 by adding more heavy-metal powder such as tungsten, and then the penetration ability can be enhanced. Cai [8,9] carried out many mechanical property tests on PTFE/Al and PTFE/Al/W, including quasi-static compression test, drop impact test, and dynamic SHPB test. The results show that, when the particle size of Al powder is 2 μm, a small part of PTFE/Al sample will react in the process of quasi-static compression. As for PTFE/Al/W reactive material, when the particle size and porosity between particles decrease, the compressive strength of the formed sample will increase. In addition, the mechanical behavior of PTFE/Al/W reactive material under the constraint of aluminum shell with different thickness were also studied. The results show that the experimental results of PTFE/Al/W under the impact of drop weight are consistent with the description of the Zerilli–Armstrong constitutive equation, and it was also found that the main reason for the crack generation and propagation in the sample is due to the debonding and separation between the PTFE matrix and W particles. Osborne [10] and Mock [1,11] carried out drop impact test and Taylor impact test for PTFE/Al reactive materials, and the influence of Al particle size on the energy release characteristics of PTFE/Al reactive materials was studied. They found that the PTFE/Al reactive materials with smaller Al particles are more likely to react, because the smaller Al particle size means that the specific surface area of the particles is larger, and the initial energy required to induce the reaction is less.
Currently, the most widely used PTFE based reactive materials composite formulation is PTFE/Al (73.5%/26.5%), and its unit mass energy and unit volume energy can reach 3.5 times and 5 times tri-nitro-toluene (TNT) explosives [5]. Under the condition of high-speed impact loading, PTFE/Al will undergo violent combustion and detonation reaction, and the reaction rate is roughly between the combustion rate of propellant and the detonation rate of explosive [6,7]. The heat released by the unit mass reaction of PTFE/Al (wt.%: 73.5/26.5) is about 8.53 kJ/g, which is about two times the TNT explosive under the same conditions. To extend the applied scope of PTFE/Al, many works on fabrication method and formulation have been carried out. The tensile strength of PTFE/Al can be increased to 20 MPa after sintering, and the sintered PTFE/Al reactive material can be used as a structural member. The density of PTFE/Al can be increased to more than 10 g/cm3 by adding more heavy-metal powder such as tungsten, and then the penetration ability can be enhanced. Cai [8,9] carried out many mechanical property tests on PTFE/Al and PTFE/Al/W, including quasi-static compression test, drop impact test, and dynamic SHPB test. The results show that, when the particle size of Al powder is 2 μm, a small part of PTFE/Al sample will react in the process of quasi-static compression. As for PTFE/Al/W reactive material, when the particle size and porosity between particles decrease, the compressive strength of the formed sample will increase. In addition, the mechanical behavior of PTFE/Al/W reactive material under the constraint of aluminum shell with different thickness were also studied. The results show that the experimental results of PTFE/Al/W under the impact of drop weight are consistent with the description of the Zerilli–Armstrong constitutive equation, and it was also found that the main reason for the crack generation and propagation in the sample is due to the debonding and separation between the PTFE matrix and W particles. Osborne [10] and Mock [1,11] carried out drop impact test and Taylor impact test for PTFE/Al reactive materials, and the influence of Al particle size on the energy release characteristics of PTFE/Al reactive materials was studied. They found that the PTFE/Al reactive materials with smaller Al particles are more likely to react, because the smaller Al particle size means that the specific surface area of the particles is larger, and the initial energy required to induce the reaction is less.
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