Tabular Two-Dimensional Correlation Analysis for Multifaceted Characterization Data.

We propose tabular two-dimensional correlation spectroscopy analysis for extracting features from multifaceted characterization data, essential for understanding material properties. This method visualizes similarities and phase lags in structural parameter changes through heatmaps, combining hierarchical clustering and asynchronous correlations. We applied the proposed method to data sets of carbon nanotube (CNT) films annealed at various temperatures and revealed the complexity of their hierarchical structures, which include elements such as voids, bundles, and amorphous carbon. Our analysis addresses the challenge of attempting to understand the sequence of structural changes, especially in multifaceted characterization data where 11 structural parameters derived from eight characterization methods interact with complex behavior. The results show how phase lags (asynchronous changes from stimuli), and parameter similarities can illuminate the sequence of structural changes in materials, providing insights into phenomena such as the removal of amorphous carbon and graphitization in annealed CNTs. This approach is beneficial even with limited data and holds promise for a wide range of material analyses, demonstrating its potential in elucidating complex material behaviors and properties.

Neutron flat-panel detector using In-Ga-Zn-O thin-film transistor.

Neutron imaging is a powerful tool for observing the internal structure of an object without destroying the object. Neutron imaging (neutron radiography) is a prominent application of neutrons but still requires significant improvements, for example, in sensitivity, resolution, radiation hardness, and handling of neutron imaging detectors. This paper presents the development and the first neutron imaging results of a neutron flat-panel detector (nFPD) based on an In-Ga-Zn-O (IGZO) thin-film transistor (TFT)/photodiode array coupled with a LiF/ZnS scintillator sheet. Direct photo-coupling to the scintillator increases the light collection efficiency. Moreover, unlike lens-coupled neutron cameras, the proposed detector is compact and easy to handle. Owing to the high off-state resistance of IGZO TFTs, their leakage current is lower than that of conventional TFTs, enabling the IGZO TFTs to hold an accumulated charge for a longer period of time and allowing longer exposure times for imaging. This would be a powerful feature for imaging at compact neutron sources with limited flux. This paper reports on the first neutron imaging results with an IGZO nFPD, its performance evaluation, and a demonstration of three-dimensional computed tomography with neutrons.

Evaluation methodology of diffusion coefficient of guest substances associated with angstrom-scale open spaces in materials by slow positron beam.

The knowledge of elemental migration associated with angstrom-scale open spaces is a prerequisite for sophisticated material design with respect to nanodispersion as well as a better understanding of molecular migration in a geological environment. Here, we show the methodology for evaluating the diffusion coefficient of guest substances focusing on angstrom-scale open spaces, where the depth-variation of open spaces caused by elemental diffusion in the micrometer-scale surface region is examined by the variable-energy slow positron beam. The present methodology determines a low diffusion coefficient of ∼10-14 cm2 s-1 for potassium at 533 K in SiO2 glass within the framework of Fick's principle providing the evidence that ∼2.5 Šopen spaces intrinsically present in the glass matrix govern the diffusion process.