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Influence of agglomerate morphology on micro cold spray of Ag nanopowders
Journal of Aerosol Science ( IF 3.9 ) Pub Date : 2021-01-01 , DOI: 10.1016/j.jaerosci.2020.105648
J.J.H. McCallister , M.D. Gammage , J.W. Keto , M.F. Becker , D. Kovar

Abstract The micro-cold spray process produces thick patterned films by impacting powders consisting of nano-to-sub-micron particles at velocities from 300 to over 1400 m/s. This process has been used extensively to produce ceramic films but has been employed only on a very limited basis to produce metallic films. The fine powders used in micro-cold spray are invariably agglomerated to some degree, but the influence of agglomerate morphology has not previously been studied for metallic particles. Here we study the effect of pre-treatments of the powder in the temperature range from room temperature to 200 °C on the powder morphology and resulting film properties of Ag. Experiments show that as the pre-treatment temperature is increased, the agglomerated powders do not densify significantly, but changes in the agglomerate morphology increase the fractal dimension. There is also evidence that increased pre-treatment temperatures increase the size of the necks between primary particles. Although the calculated impact velocities are reduced slightly for pre-treated powders compared to films produced from untreated powders, experimental results show that using pre-treated powders produces films with higher relative densities (up to 80%) and increased as-deposited conductivities (up to 3.5 S/μm). It is postulated that the pre-treated agglomerates utilize a larger fraction of the impact energy for deformation of the primary particles rather than fragmentation of the agglomerates due to increased bonding between primary particles.

中文翻译:

团聚形态对纳米银粉微冷喷涂的影响

摘要 微冷喷涂工艺通过以 300 到 1400 m/s 的速度撞击由纳米到亚微米颗粒组成的粉末来产生厚的图案薄膜。该工艺已广泛用于生产陶瓷薄膜,但仅在非常有限的基础上用于生产金属薄膜。微冷喷涂中使用的细粉总是在一定程度上结块,但以前没有研究过金属颗粒结块形态的影响。在这里,我们研究了在从室温到 200°C 的温度范围内对粉末进行预处理对粉末形态和 Ag 薄膜性能的影响。实验表明,随着预处理温度的升高,团聚的粉末不会显着致密,但是团聚体形态的变化增加了分形维数。还有证据表明,增加预处理温度会增加初级颗粒之间的颈部尺寸。尽管与未处理粉末制成的薄膜相比,预处理粉末的计算冲击速度略有降低,但实验结果表明,使用预处理粉末产生的薄膜具有更高的相对密度(高达 80%)和增加的沉积电导率(高达到 3.5 S/μm)。据推测,由于初级粒子之间的结合增加,预处理的团聚体利用较大比例的冲击能量使初级粒子变形,而不是使团聚体破碎。还有证据表明,增加预处理温度会增加初级颗粒之间的颈部尺寸。尽管与未处理粉末制成的薄膜相比,预处理粉末的计算冲击速度略有降低,但实验结果表明,使用预处理粉末产生的薄膜具有更高的相对密度(高达 80%)和增加的沉积电导率(高达到 3.5 S/μm)。据推测,由于初级粒子之间的结合增加,预处理的团聚体利用较大比例的冲击能量使初级粒子变形,而不是使团聚体破碎。还有证据表明,增加预处理温度会增加初级颗粒之间的颈部尺寸。尽管与未处理粉末制成的薄膜相比,预处理粉末的计算冲击速度略有降低,但实验结果表明,使用预处理粉末产生的薄膜具有更高的相对密度(高达 80%)和增加的沉积电导率(高达到 3.5 S/μm)。据推测,由于初级粒子之间的结合增加,预处理的团聚体利用较大比例的冲击能量使初级粒子变形,而不是使团聚体破碎。实验结果表明,使用预处理的粉末产生的薄膜具有更高的相对密度(高达 80%)和增加的沉积电导率(高达 3.5 S/μm)。据推测,由于初级粒子之间的结合增加,预处理的团聚体利用较大比例的冲击能量使初级粒子变形,而不是使团聚体破碎。实验结果表明,使用预处理的粉末产生的薄膜具有更高的相对密度(高达 80%)和增加的沉积电导率(高达 3.5 S/μm)。据推测,由于初级粒子之间的结合增加,预处理的团聚体利用较大比例的冲击能量使初级粒子变形,而不是使团聚体破碎。
更新日期:2021-01-01
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