Determination of Interfacial Amorphicity in Functional Powders.

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Particle surface properties critically influence performance in pharmaceutical, food, and polymer applications, affecting flow, dissolution, and tabletability.
• Surface amorphization, a change in crystalline material structure, significantly impacts powder blend performance.
• Characterizing bulk amorphous content is established, but nanoscale surface amorphicity measurement is challenging.

Purpose of the Study:

• To develop and validate novel methods for characterizing surface amorphicity at the nanoscale using Atomic Force Microscopy (AFM).
• To investigate the mechanical changes associated with amorphization and recrystallization events on particle surfaces.
• To present a methodology for interpreting heterogeneous surface data and track humidity-induced surface recrystallization.

Main Methods:

• Utilized AFM PeakForce Quantitative Nanomechanical (QNM) technique to measure energy dissipation (eV) variations on particle surfaces.
• Developed a cumulative distribution analysis of dissipation data to differentiate crystalline and amorphous states.
• Compared AFM/QNM data with conventional AFM and Scanning Electron Microscopy (SEM) for topographical analysis.
• Monitored surface recrystallization over time by tracking dissipation response in specific surface regions.

Main Results:

• AFM PeakForce QNM effectively measured nanoscale mechanical changes related to surface amorphization and recrystallization.
• The cumulative distribution method provided a coherent interpretation of heterogeneous surface dissipation data.
• Dissipation data correlated with topographical differences observed via conventional AFM and SEM.
• Humidity exposure induced significant surface recrystallization, confirmed by changes in dissipation over time.

Conclusions:

• AFM PeakForce QNM is a powerful tool for quantifying surface amorphicity at the nanoscale.
• The presented data analysis methodology enhances the interpretation of complex surface nanomechanical properties.
• Surface amorphicity is dynamic and susceptible to environmental factors like humidity, leading to recrystallization.