Department of Materials Science and Engineering, Johns Hopkins University , 3400 N Charles Street, Baltimore, Maryland 21218, United States.
ACS Appl Mater Interfaces. 2017 Jul 5;9(26):22026-22036. doi: 10.1021/acsami.7b03071. Epub 2017 Jun 22.
The use of thin-foil, self-propagating thermite reactions to bond components successfully depends on the ability to suppress gas generation and avoid pore formation during the exothermic production of brazes. To study the mechanisms of vapor production in diluted thermites, thin film multilayer Al-Cu-CuO-Cu foils are produced via magnetron sputtering, where the Cu layer thickness is systematically increased from 0 to 100 nm in 25 nm increments. The excess Cu layers act as diffusion barriers, limiting the transport of oxygen from the oxide to the Al fuel, as determined by slow heating differential scanning calorimetry experiments. Furthermore, by adding excess Cu to the system, the temperature of the self-propagating thermite reactions drops below the boiling point of Cu, eliminating the metal vapor production. It is determined that Cu vapor production can be eliminated by increasing the Cu interlayer thickness above 50 nm. However, the porous nature of the final products suggests that only metal vapor production is suppressed via dilution. Gas generation via oxygen release is still capable of producing a porous reaction product.
使用薄箔自蔓延热反应成功地将组件结合在一起，这取决于在钎料的放热生产过程中抑制气体生成和避免形成孔隙的能力。为了研究稀释热粉中蒸气产生的机理，通过磁控溅射生产了薄膜多层 Al-Cu-CuO-Cu 箔，其中 Cu 层厚度从 0 到 100nm 以 25nm 的增量系统增加。多余的 Cu 层作为扩散屏障，限制了氧从氧化物向 Al 燃料的传输，这是通过缓慢加热差示扫描量热法实验确定的。此外，通过向系统中添加过量的 Cu，自蔓延热反应的温度降至 Cu 的沸点以下，从而消除了金属蒸气的产生。确定通过将 Cu 中间层厚度增加到 50nm 以上，可以消除 Cu 蒸气的产生。然而，最终产物的多孔性质表明，仅通过稀释就可以抑制金属蒸气的产生。通过释放氧气产生气体仍能够产生多孔反应产物。
