A5032396607- Microstructure and mechanical properties
- Advanced Surface Polishing Techniques
- Diamond and Carbon-based Materials Research
- Semiconductor materials and devices
- Silicon Carbide Semiconductor Technologies
- ZnO doping and properties
- Silicon Nanostructures and Photoluminescence
- Semiconductor materials and interfaces
- Copper-based nanomaterials and applications
- Ion-surface interactions and analysis
- Force Microscopy Techniques and Applications
- Thermal properties of materials
- Advanced materials and composites
- Silicon and Solar Cell Technologies
- Advanced ceramic materials synthesis
- Electrostatic Discharge in Electronics
- Nanopore and Nanochannel Transport Studies
- Electron and X-Ray Spectroscopy Techniques
- Nanowire Synthesis and Applications
- Powder Metallurgy Techniques and Materials
- Metal Alloys Wear and Properties
- Integrated Circuits and Semiconductor Failure Analysis
- Advancements in Semiconductor Devices and Circuit Design
- Gas Sensing Nanomaterials and Sensors
- Metal and Thin Film Mechanics
Kyushu University
2015-2024
Saga University
2024
Materials Science & Engineering
1999-2024
Faculty (United Kingdom)
2017
Engineering (Italy)
2017
Advanced Energy Materials (United States)
2016
Severe plastic deformation (SPD) is effective in producing bulk ultrafine-grained and nanostructured materials with large densities of lattice defects. This field, also known as NanoSPD, experienced a significant progress within the past two decades. Beside classic SPD methods such high-pressure torsion, equal-channel angular pressing, accumulative roll-bonding, twist extrusion, multi-directional forging, various continuous techniques were introduced to produce upscaled samples. Moreover,...
Ultrafine-grained and heterostructured materials are currently of high interest due to their superior mechanical functional properties. Severe plastic deformation (SPD) is one the most effective methods produce such with unique microstructure-property relationships. In this review paper, after summarizing recent progress in developing various SPD for processing bulk, surface powder materials, main structural microstructural features SPD-processed explained including lattice defects, grain...
High-pressure rocksalt ZnO with a band gap of 1.8 eV, which can absorb visible light.
Ceramics are generally brittle at ambient condition and they can hardly be deformed plastically. In this study, severe plastic deformation was successfully imposed on barium titanate ceramic powders by high-pressure torsion. A tetragonal-to-cubic phase transformation occurred, the fraction stability of cubic increased straining because formation nanograins. BaTiO3 exhibited photoluminescence yellow intensity after large grain boundaries. The dielectric constant unusually nanograin while...
Si(100) wafers were subjected to severe plastic deformation under a pressure of 24 GPa using high-pressure torsion (HPT). Si plastically deformed at room temperature. HPT-processed samples composed metastable body centered cubic Si-III and rhombohedral Si-XII phases in the initial diamond Si-I. The volume fraction increased with increasing strain. Successive annealing 873 K led reverse transformation phases. A broad photoluminescence peak about 650 nm appears due Si-III/Si-XII nanograins...
Thermodynamically stable stoichiometric and higher oxidation states are known to be detrimental the electrical optical performances of Ag electrodes. In contrast, thermodynamically less or unstable suboxidation entailing extreme O deficiencies scarcely understood because tenuous null trace in suboxidized domains is difficult detect. This paper presents an experimental confirmation numerical interpretation Ag-layered electrodes influences post-growth reduction on their optoelectrical...
Severe plastic deformation (SPD) has been widely studied in order to enhance the strength and ductility of metallic materials.Among various SPD processing techniques, high-pressure torsion (HPT) can be applied brittle materials including semiconductors.In this overview, we report on HPT Si, Ge, compound semiconductor GaAs.When crystalline Si was subjected HPT, metastable body-centered-cubic (bcc) Si-III rhombohedral Si-XII as well amorphous regions were formed.After annealing, reversely...
Abstract Finding a physical approach for increasing the superconducting transition temperature ( T c ) is challenge in field of material science. Shear strain effects on superconductivity rhenium were investigated using magnetic measurements, X-ray diffraction, transmission electron microscopy, and first-principles calculations. A large shear reduces grain size simultaneously expands unit cells, resulting an increase . Here we show that this new method enhancing differs from hydrostatic...
A vital objective in the wetting of Au deposited on chemically heterogeneous oxides is to synthesize a completely continuous, highly crystalline, ultrathin-layered geometry with minimized electrical and optical losses. However, no effective solution has been proposed for synthesizing an ideal Au-layered structure. This study presents evidence effectiveness atomic oxygen-mediated growth such layer by improving ZnO substrates substantial reduction free energy. The unexpected outcome can be...
Artificially designing the crystal orientation and facets of noble metal nanoparticles is important to realize unique chemical physical features that are very different from those metals in bulk geometries. However, relative their counterparts synthesized wet-chemical processes, vapor-depositing with desired crystallographic while avoiding any notable impurities quite challenging because this task requires breaking away thermodynamically favorable geometry nanoparticles. We used...
Ag wetting on oxides is essential for implementing exceptional layered superstructures with simultaneous ultralow losses in electrical conductance and optical transmittance. This goal difficult to achieve by conventional synthetic techniques involving the incorporation of heterogeneous transition metals or metalloids into as inducers they cause detrimental optoelectrical changes. study provides novel insights use homogeneous seeds improve oxides. We investigated effect atomic O improvement...
Diamond-like carbon (DLC) with significant fraction of tetrahedral sp3 bonds and amorphous structure is generally produced in the form thin films by rapid cooling high-energy atoms vacuum. This study shows that DLC can be directly formed from bulk samples graphite application severe plastic deformation under high pressures. The formation enhanced increasing shear strain, pressure, temperature. It suggested pressure thermodynamically stabilize density lattice defects straining reduces energy...
Germanium has been processed by high-pressure torsion (HPT) under a nominal pressure of 24 GPa at room temperature and cryogenic temperature. The samples were composed diamond-cubic Ge-I phase metastable tetragonal Ge-III phase. formation was significantly suppressed an amorphous phase, in addition to small amount body-centred-cubic Ge-IV, appeared the case HPT processing 100 K. Ge-IV gradually disappeared These results indicated that shear strain thermal energy are important for promoting Ge-III.
Grain refinement of GaAs was achieved by application severe plastic deformation through high-pressure torsion (HPT). Ultrafine-grained structures including nanograins were produced the HPT processing under 24 GPa. An intense photoluminescence (PL) peak in near infrared corresponding to band gap disappeared after but subsequent annealing gave rise not only restoration original band-gap-related also an additional PL visible part spectrum on account quantum confinement nanograins.
We report a dramatic and irreversible reduction in the lattice thermal conductivity of bulk crystalline silicon when subjected to intense plastic strain under pressure 24 GPa using high-pressure torsion (HPT). Thermal HPT-processed samples were measured picosecond time domain thermoreflectance. measurements show that have by factor approximately 20 (from intrinsic single value 142 Wm(-1) K(-1) 7.6 K(-1)). is attributed formation nanograin boundaries metastable Si-III/XII phases which act as...