Absorption contrast is the conventional mechanism of lab x-ray imaging such as microCTs or X-ray microscopy (XRM). Two major limitations include insufficient contrast to visualize low Z or organic materials and the lack of resolution to visualise pores, cracks or defects below the native spatial resolution of the system.
Sigray has developed a novel lab based multi-contrast X-ray system that operates under absorption contrast, phase contrast, and scattering (darkfield) contrast simultaneously. The novel XRM has a spatial resolution of 0.5 µm in absorption contrast, making it a suitable workhorse for routine 3D tomography applications of a variety of materials. The system is well suited to address current challenges in visualizing organic materials such as polymers, biological tissue and low Z materials using differential phase contrast.
X-ray dark-field imaging on the other hand has potential applications in medical imaging, electronics and non-destructive material testing as the image contrast is formed through the mechanism of small-angle scattering, It provides complementary and otherwise inaccessible structural information about the specimen at the sub-micrometer length scale significantly below the system resolution (sub-resolution) of conventional X-ray imaging systems. Dark field scattering is related to the variations or inhomogeneity in the electron density within the sample where there are cracks, voids or porosity at the sub- and micron-scale.
Applications of this novel imaging approach will be illustrated with CFRP (Carbon Fiber Reinforced Polymers), migration of electrolytes in Li-ion batteries during charge discharge, soft and calcified tissue, defects in electronic components.Due to the restrictions of lab-based equipment, each imaging solution requires its own imaging system. Often, this results in non-correlative imaging workflows – where a similar but different sample or region is imaged in each system to the maximum system resolution capabilities. This poses a number of inherent limitations in obtaining the full understanding of the sample in question: What does the sample look like as a whole and how representative is this region to another? Are there microscale properties that correlate to macroscale features? Additionally, knowing the exact resolution limit required to properly characterize a sample is an important question that can be difficult to answer without observing enhanced resolution of the exact same feature. Combining systems that can achieve different resolutions in a correlative workflow of the same sample also allows for advanced analysis, such as applying properties obtained from high resolution imaging to a large volume obtained from lower resolution imaging. For example, intra- and inter-particle porosity that is not resolved could inherently change simulation results without proper characterization .
We present here results combining two X-ray tomography systems, the Zeiss Xradia Versa and Zeiss Xradia Ultra instruments, into a correlative, multi-length scale analysis workflow through the use of specifically designed hardware and software tools. We demonstrate several applications using this combined approach to enable non-destructive, massively multiscale 3D imaging with minimal sample preparation. Specific examples ranging from biological science to material science are discussed.