36 research outputs found
Tabular Two-Dimensional Correlation Analysis for Multifaceted Characterization Data
We propose tabular two-dimensional correlation 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
datasets of carbon nanotube (CNTs) films annealed at various temperatures and
revealed the complexity of their hierarchical structures, which include
elements like 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 8 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 like 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.Comment: 15 pages, 4 figure
Very high-cycle fatigue properties of 90° unidirectional CFRP laminates and evaluation of fatigue limits by free volume measurement using positron microscopy
The objective of this study was to experimentally evaluate the fatigue limit of 90° unidirectional carbon fiber reinforced plastic (CFRP) laminates. The very high-cycle fatigue properties of the specimens were evaluated using ultrasonic and electromagnetic fatigue testing machines. Ultrasonic fatigue tests were conducted to obtain the fatigue properties under the giga-cycle regime. The specimen geometry was designed to resonate at 20 kHz, the specimen consisted of CFRP laminate and a metal tab to connect to the horn end of the testing machine. Additionally, the free volume of the matrix material, namely, epoxy resin, of the CFRP laminates was evaluated using the positron annihilation method. A slit was introduced in the specimen surface to identify the location of damage development, which facilitated the free volume measurement by positron microscopy. The obtained S-N curves reveal that failure did not occur at strain levels lower than ξmax = 0.75% at the slit tip for all specimens up to N = 1.0 à 109 cycles. The free volume measurement for a specimen set above the threshold strain level revealed that the free volume increased in size and decreased in amount as the number of cycles increased. The test results revealed that the opposite trend existed below the threshold, which suggests that a fatigue limit may exist
Transport of small and neutral solutes through reverse osmosis membranes: Role of skin layer conformation of the polyamide film
The polyamide skin layer of reverse osmosis (RO) membranes was characterised using advanced and complementary analytical techniques to investigate the mechanisms underlying the permeation of contaminants of emerging concern in potable water reuse ? N-nitrosodimethylamine (NDMA) and N-nitrosomethylethylamine (NMEA). This study used five RO membrane samples with similar membrane properties. The five RO membrane samples spanned over a large range of water permeance (0.9?5.8 L/m2 h bar) as well as permeation of NDMA (9?66%) and NMEA (3?29%). Despite these differences among the five RO membranes, characterisations of the skin layer using positron annihilation lifetime spectroscopy, atomic force microscopy and field emission scanning electron microscopy revealed almost no variation in their free-volume hole-radius (0.270?0.275 nm), effective surface area (198?212%) and thickness (30?35 nm) of the skin layer. The results suggest that there could be other RO skin layer properties, such as the interconnectivity of the protuberances within the polyamide skin layer additional to the free-volume hole-size and thickness of the skin layer, which can also govern water and solute permeation
Increase in the beam intensity of the linac-based slow positron beam and its application at the Slow Positron Facility, KEK
Recent developments of the Slow Positron Facility at the Institute of Materials Structure
Science, High Energy Accelerator Research Organization (KEK) are reported. We have
modified the converter/moderator assembly for slow positron beam production, yielding an
increase of an order of magnitude in the intensity of the beam. The first observation of
the photodetachment of the positronium negative ion (Psâ), and the installation
of a reflection high-energy positron diffraction (RHEPD) station and the initial data
obtained are reported