Crystallite size analysis of Al/Ni multilayer powder by synchrotron radiation X-ray diffraction

Abstract

The self-propagated exothermic reaction characteristics of Al/Ni multilayer powders can be employed as heat sources and controlled by cold-rolling conditions. This feature depends on the heat propagation inside of crystal grains. Therefore, the crystallographic factor that relates cold-rolling conditions to exothermic characteristics should be identified. To determine the change trend in crystallite size with the increase in the number of rolling passes, the crystallite sizes in the Al/Ni multilayer powder were calculated using Scherrer’s equation, and precise X-ray profiles were obtained using the synchrotron radiation X-ray diffraction method. The results indicate that the crystallite sizes were refined by increasing the number of rolling passes up to 30; from 30 to 40 passes, however, the crystallite sizes increased. It is assumed that, in addition to the Al/Ni multilayer powder being thin and multilayered, the increase in crystallite size at 40 passes allows for the smooth propagation of heat, consequently improving the exothermic characteristics. Therefore, crystallite size is the dominant parameter in the relationship between rolling conditions and exothermic characteristics.

Investigation on the Structure and Morphology of CZTSe Solar Cells by Adjusting Cu–Ge Buffer Layers

“…The fwhm value of the (111) plane belonging to Cu-R and Cu−F is 0.253 and 0.188°, respectively. Because the crystallite sizes are inversely proportional to the fwhm value, 27 their crystallite sizes are estimated to be 33.8 and 45.5 nm, respectively, according to Scherrer's equation. The decrease in reflectance always relates to the increase in surface roughness.…”

Microscale thermal characteristics of cold-rolled aluminum alloy using a thermoreflectance method

“…However, because the free electron is a heat propagation carrier, we assumed that the heat propagation was disturbed by a decrease in the movability of this free electron with an increase in the number of crystallite boundaries due to thinning and multilayering. 28) Therefore, we concluded that the cold-rolling process has both a positive effect that causes an increase in the maximum exothermic temperature and a negative effect that causes a decrease in heat propagation. If the crystallite size of the Al/Ni powder, which is sufficiently multilayered by cold rolling, could be increased by other methods such as heat treatment, further improvement in the exothermic reaction characteristics could be expected.…”

“…In our study, to improve the productivity and convenience of the heat source, an Al/Ni multilayer powder fabricated by the coldrolling and frictional pulverizing methods was developed, and the thermal reaction characteristics were studied. 13,[25][26][27][28] In a previous study, we revealed that the exothermic reaction characteristics, such as the reaction speed and maximum exothermic reaction temperature, increase with an increase in the number of cold-rolling passes. 25) These characteristics can be controlled to some extent by changing the rolling conditions.…”