ABSTRACT
In this chapter, we examine the structural aspects of materials as the basis for substance identification in aviation security X-ray diffraction imaging systems. X-ray diffraction imaging provides details of atomic-level structure tied to materials’ properties. Hence, the processing-structure-property relationship fundamental to materials science establishes the foundation of this security technology. X-ray diffraction features characteristic of crystalline and non-crystalline substances and the imaging modality for both of these material forms are reported. In addition, spectral anomalies from crystalline texture due to processing and physical attributes of commercial goods are discussed. Many of the over 400 X-ray spectra of materials acquired for creation of a reference database are provided in this chapter which includes data for flammable organic solvents, aqueous-based commercial goods, foodstuffs, polymers, metals and alloys, and solid oxidizer compounds. Statistical cluster analysis applied to these database items reveals the discriminating nature of X-ray diffraction for object classification based broadly on crystallinity for limited defined clusters and according to common materials properties/classes for larger data cluster sets.
