The effect of sintering and cooling process on geometry distortion and mechanical properties transition of PTFE/Al reactive materials

Wang, Haifu; Geng, Baoqun; Guo, Huan-guo; Zheng, Yuanfeng; Yu, Qian; Ge, Chao

doi:10.1016/j.dt.2019.10.006

Cited by 28 publications

(17 citation statements)

References 27 publications

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“…The reactive material sample during the heating/cooling stage could be assumed as a threedimensional short cylinder under unsteady heat conduction conditions. From the symmetry of the cylinder, for any reactive material shaft section, in the heating/cooling process, the element of the material temperature was only related to its position and sintering time [16]. A long sintering cycle is a benefit for reducing the temperature gradient in the sample and removing the influence of the heating/cooling process.…”

Section: Materials Fabricationmentioning

confidence: 99%

“…The samples are relaxed and sintered for the long-term to remove entrapped air and residual stress [16,23]…”

Section: Materials Fabricationmentioning

confidence: 99%

“…However, insufficiently pressed and sintered reactive materials show different theoretical maximum densities (TMD) and discrepant material properties. Bulk densities of porous reactive materials achieve specific needs [15][16][17]. Moreover, bulk density distributions influenced by pressing and sintering processes are essential for engineering applications, such as double-layered shaped charge liner and reactive material bullet core size design [18,19].…”

Section: Introductionmentioning

confidence: 99%

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Bulk Density Homogenization and Impact Initiation Characteristics of Porous PTFE/Al/W Reactive Materials

Geng

Wang

et al. 2020

Materials

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In this research, the bulk density homogenization and impact initiation characteristics of porous PTFE/Al/W reactive materials were investigated. Cold isostatic pressed (CIPed) and hot temperature sintered (HTSed) PTFE/Al/W reactive materials of five different theoretical maximum densities were fabricated via the mixing/pressing/sintering process. Mesoscale structure characteristics of the materials fabricated under different molding pressures were compared while the effect of molding pressures on material bulk densities was analyzed as well. By using the drop weight testing system, effects of the theoretical maximum densities (TMDs), drop heights and molding pressures on the impact initiation characteristics were studied. Quantitatively, characteristic drop heights (H50) for different types of materials were obtained. The two most significant findings of this research are the density homogenization zone and the sensitivity transition zone, which would provide meaningful guides for further design and fabrication of reactive materials.

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Section: Materials Fabricationmentioning

confidence: 99%

“…The samples are relaxed and sintered for the long-term to remove entrapped air and residual stress [16,23]…”

Section: Materials Fabricationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bulk Density Homogenization and Impact Initiation Characteristics of Porous PTFE/Al/W Reactive Materials

Geng

Wang

et al. 2020

Materials

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“…Through the sintering process, the PTFE can be melted and recrystallized, and the interface between particles disappears due to diffusion. PTFE turns from particles into a dense continuum, and the strength of PTFE is greatly improved [28]. After sintering, PTFE encapsulates the active metal.…”

Section: Introductionmentioning

confidence: 99%

“…When the temperature exceeds 500 • C, PTFE decomposes rapidly. It is generally assumed that the optimum sintering temperature is 380 • C [6,[28][29][30]. Based on the size of the sample and referring to other research [15,17,30], the design sintering process was as follows: the oven temperature was ramped up to 380 • C at a rate of approximately 55 • C/h.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Mechanical Properties and Impact-Induced Reaction Characteristics of PTFE/Al/CuO Reactive Materials

2019

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Metal/fluoropolymer materials are typical reactive materials. Polytetrafluoroethylene (PTFE)/Al/CuO reactive materials were studied in this research. Scanning electron microscopy (SEM), quasi-static compression, the Split Hopkinson pressure bar test, and the drop hammer test were used to study the mechanical properties and induced reaction characteristics of the reactive materials with different Al/CuO thermite contents and different particle sizes. SEM images of the samples demonstrate that the reactive materials were mixed evenly. The compression test results show that, if the particle size of PTFE was too small, the strength of reactive materials after sintering was reduced. After sintering, with the increase in the content of Al/CuO thermite, the strength of the micro-sized PTFE/Al/CuO firstly increased and then decreased. The Johnson-Cook constitutive model can be used to characterize the reactive materials, and the parameters of the Johnson-Cook constitutive model of No. 3 reactive materials (PTFE/Al:Al/CuO = 3:1) were obtained. The reliability of the parameters was verified by numerical simulation. Drop hammer tests show that the addition of Al/CuO aluminothermic materials or the use of nano-sized PTFE/Al reactive materials can significantly improve the sensitivity of the material. The research in this paper can provide a reference for the preparation, transportation, storage, and application of reactive materials.found that adding a high-strength metal material, such as W, with a similar particle size to the PTFE/Al reactive material, can effectively increase the strength of the reactive materials. Cai et al. [12] used a drop hammer to find that the W particle-PTFE interface separation provided initiation and propagation of cracks. In general, the addition of W can increase the strength of the reactive material but reduce the energy density. Thus, people considered adding materials that can release energy, such as Ni. After adding Ni to PTFE/Al, Wu et al. [16] found that Ni makes the reactive material brittle, but it can increase the strain-hardening modulus and compressive strength of the material, while the heat released by the material also increased. However, the energy density of PTFE/Al reactive material is very high, and the energy of PTFE/Al reactive material cannot be significantly increased by adding Ni. If the energy release efficiency of the PTFE reactive materials can be effectively improved, it will be beneficial for their application. PTFE filler metal is a very common type of engineering material. The C-F bonds in PTFE are usually stable and do not react with metals. Under high-temperature conditions, PTFE rapidly decomposes into small-molecule fluorides and undergoes a rapid exothermic reaction with active metals [18]. Experiments by Ames [19] showed that, when the PTFE/Al reactive material impacts the target at a velocity of 1.2 km/s, the energy release efficiency still does not exceed 20%. Therefore, one of the biggest problems with PTFE/Al reactive materials is that the energy release ...

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An approach to distinguish chemical and kinetic energy of reactive materials: PTFE/LiF as an inert substitute to PTFE/Al

Zhou,

Zhao,

Wang

et al. 2024

Propellants Explo Pyrotec

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To distinguish between the kinetic and chemical contributions in the impact of PTFE/Al, this study explores the feasibility of introducing an inert substitute for PTFE/Al by substituting aluminum (Al) with inert materials. Three specimens were fabricated through a process involving mixing, compression, and sintering of raw materials The mechanical properties of these specimens were assessed. Dynamic fragmentation tests of PTFE/Al and PTFE/LiF specimens were performed. These results further substantiate the potential of PTFE/LiF as an inert alternative to PTFE/Al, the two materials exhibit comparable fragmentation distribution characteristics. A preliminary exploration of the energy release in both materials was conducted via vented chamber calorimetry tests. The findings reveal that, at an impact velocity of roughly 650 m/s, only 66.9 % of the materials were deposited into the chamber, with a mere 17.8 % being initiated, about 88.9 % of the total deposited energy results from the chemical reaction energy within the PTFE/Al materials. Importantly, this method demonstrates promise for further application in energy release analysis experiments for various PTFE/Al‐based reactive materials. These findings are beneficial for evaluating the energy release characteristics of reactive fragments on typical targets and lay the foundation for refining energy release models of such materials in future research.

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The effect of sintering and cooling process on geometry distortion and mechanical properties transition of PTFE/Al reactive materials

Cited by 28 publications

References 27 publications

Bulk Density Homogenization and Impact Initiation Characteristics of Porous PTFE/Al/W Reactive Materials

Bulk Density Homogenization and Impact Initiation Characteristics of Porous PTFE/Al/W Reactive Materials

Experimental Study of Mechanical Properties and Impact-Induced Reaction Characteristics of PTFE/Al/CuO Reactive Materials

An approach to distinguish chemical and kinetic energy of reactive materials: PTFE/LiF as an inert substitute to PTFE/Al

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