Yoshitsugu Tomokiyo - Profile on Academia.edu (original) (raw)
Papers by Yoshitsugu Tomokiyo
In-situ observations of irradiation-induced phase transformations
Ultramicroscopy, Nov 1, 1994
Abstract High-voltage and high-resolution electron microscopy approaches the resolving power of 0... more Abstract High-voltage and high-resolution electron microscopy approaches the resolving power of 0.1 nm and is expected to develop new fields of materials science and engineering. In order to look over future advances, the present paper introduces the progress of our studies on irradiation-induced phase transformations in alloys based on conventional high-voltage electron microscopy. This paper also shows phase transformations at or near surface of α-Al 2 O 3 induced by an intense electron beam in clean high-vacuum microscopes which give insight into irradiation-induced phenomena in new high-voltage and high-resolution electron microscopy.
Energy filtering transmission electron microscopy using the new JEM-2010FEF
Journal of Microscopy, Apr 1, 1999
ABSTRACT
Journal of Nuclear Materials, Mar 1, 1991
Irradiation-induced amorphization and swelling of ceramics including graphite have been studied t... more Irradiation-induced amorphization and swelling of ceramics including graphite have been studied through in-situ observation of electron microscopy, electron energy loss spectroscopy and convergent beam electron diffraction. Amorphization occurs below 500 K for highly-oriented pyrolytic graphite (HOPG) and below 300 K for Sic under electron irradiation. The amorphization fluences of HOPG and Sic required for full amorphization show no flux dependence. The displacement threshold energy is determined to be 12 eV for HOPG from the electron energy dependence of the amorphization fluence which is equivalent to 1 dpa. An atomistic model for describing the irradiation-induced amorphization and swelling of graphite is proposed. A high concentration of C, molecules and their clusters between basal planes induce abrupt swelling along the c-axis within 4 X 10e3 dpa and fade the periodical structural image at 4~ 10m2 dpa. The concentration of vacancies increases gradually up to 1 dpa at which amorphization is completed.
High Resolution Electron Microscopy of Sintered YBa2Cu3O7-x
Sintered specimens have been observed through high resolution electron microscopy. Lattices of or... more Sintered specimens have been observed through high resolution electron microscopy. Lattices of orthorhombic structure are slightly distorted in the vicinity of a twin boundary. Three types of grain boundaries (GBs) are present: (1)Some grain boundaries are parallel to a C-plane of one grain where a lot of stacking faults is concentrated along the GB. (2) The others have amorphous layers of 1∼4 nm in thickness at the boundaries. Lattice distortion and stacking faults were not found near the GBs. (3)A coincidence tilt boundary accompanies neither stacking fault nor amorphous layer, but an axial length varys near the GB. Cracks parallel to a C-plane are frequently presnt. A width of crack is in the range of 1 nm ∼ several tens of nm. A stacking fault present in an interior of grain consists of extra planes of Ba layer and Cu-O chain. The lattice distortion at a twin boundary, a nano-crack and an isolated stacking fault in the internal region of a grain may act as an effective pinning center but most of the structures mentioned above seem to be responsible for low Jc value.
Omega filter installed in the 1MV microscope of Kyushu University
Micron, Aug 1, 2008
A 1.25MV high-voltage electron microscope with a B-type omega filter has been successfully instal... more A 1.25MV high-voltage electron microscope with a B-type omega filter has been successfully installed at Kyushu University. An image detection chamber has been set inside a concrete block below the ground level without changing the frame structure for anti-vibration. Nearly the same design as that for the 200kV microscope has been kept for the present omega filter except for its size. A new pre- and post-filter lens system with rotation-free imaging has been designed. Energy resolution, beam shape and stability of the filter have been measured. Some application data have been obtained to demonstrate the performance of the filter.
2-110 Training and education of researchers for electron microscopy at the Research Laboratory for High Voltage Electron Microscopy in Kyushu University
工学・工業教育研究講演会講演論文集, Jul 28, 2006
Ultramicroanalysis for the Development of Nanomaterials
Dependence of critical voltages in Cu-based alloys on composition, temperature and short range order
Proceedings, annual meeting, Electron Microscopy Society of America, 1978
Introduction Since the critical voltage effect in electron microscopy was discovered [1, 2], a nu... more Introduction Since the critical voltage effect in electron microscopy was discovered [1, 2], a number of its applications have been proposed [3-9]. As the critical voltage Vcof an alloy depends primarily on the scattering factors of constituent atoms, not only the compositional change but also the degree of order and the mean square displacement (msd) of the atoms affect the value of Vc. In the present paper the effect of alloying on Vc is studied in Cu-based alloys containing 14.8 at% Al, 4.9 or 14.9 at% Au. These alloys are of interest because Al is lighter and Au heavier than Cu atom, and furthermore the alloys develop a short range order. The critical voltages were determined using JEM-1000 HVEM by observing of the minimum intensity of 2g Kikuchi line and the reversal of the contrast of middle line at lg spot. The measured Vc was analyzed by the 10-beam dynamical theory.
Observation of faint contrast at planar faults in alloys
Proceedings, annual meeting, Electron Microscopy Society of America, 1978
The contrast in electron microscopic images of planar faults in a crystal is characterized by a p... more The contrast in electron microscopic images of planar faults in a crystal is characterized by a phase factor , where is the reciprocal lattice vector of the operating reflection, and the lattice displacement due to the fault under consideration. Within the two-beam theory a planar fault with an integer value of is invisible, but a detectable contrast is expected when the many-beam dynamical effect is not negligibly small. A weak fringe contrast is also expected when differs slightly from an integer owing to an additional small displacement of the lattice across the fault. These faint contrasts are termed as many-beam contrasts in the former case, and as ε fringe contrasts in the latter. In the present work stacking faults in Cu-Al alloys and antiphase boundaries (APB) in CuZn, FeCo and Fe-Al alloys were observed under such conditions as mentioned above, and the results were compared with the image profiles of the faults calculated in the systematic ten-beam approximation.
Journal of the Japan Institute of Metals, 1968
Microstructural and Mechanical Properties of TiC, TiB2 and VC with Low Carbon Steel Surface Alloy Fabricated by High Energy Electron Beam Irradiation
Materials Science Forum, 2005
Because of its excellent process advantages such as high energy efficiency, short irradiation tim... more Because of its excellent process advantages such as high energy efficiency, short irradiation time and rapid heating, high energy electron beam (HEEB) irradiation is becoming of interest as a future surface modification technology. In this study, surface alloying of TiC, TiB2 and VC ceramic particles with a low carbon steel substrate was carried out using HEEB of 1.4 MeV. Surface alloyed layers of all the specimens were about 2 mm thick and consisted of a melted region, an interface region, a heat affected zone (HAZ) and the matrix. In all the specimens, the hardness at the surface was the highest, and then decreased sharply into the interior reaching the lowest values at the matrix. A remarkable increase in the mechanical properties was observed for the VC surface alloyed specimen. Vanadium carbides of large (~ 5 µm) and fine sizes (~ 20 nm) were formed uniformly, which resulted in an increase of hardness to 2-3 times of that of the matrix, and highest wear resistance.
Higher order Laue zone patterns and determination of local lattice parameter
Microstructures of Dielectric Ba_xSr_ TiO3 Prepared by RF Sputtering
まてりあ : 日本金属学会会報, Dec 20, 2001
Microstructure control in HDDR process for higher anisotropic Nd-Fe-B magnet powders
Homogenized Nd-Fe-Co-B-Zr(-Ga) alloys are treated by hydrogenation (HD-process) and dehydrogenati... more Homogenized Nd-Fe-Co-B-Zr(-Ga) alloys are treated by hydrogenation (HD-process) and dehydrogenation (DR-process) with various treatment conditions, followed by quenching in argon gas flow. After the HDDR process, the specimens are crashed into powders. The magnetic properties of the powder and bonded magnets are measured with a vibrating sample magnetometer and a B-H tracer. The microstructural changes are also analyzed by electron microscopy (FE-SEM and TEM) and discussed with special reference to the behavior of boron.
Applications of Convergent Beam Electron Diffraction to Extract Quantitative Information in Materials Science
Journal of Electron Microscopy, Dec 1, 1992
Convergent beam electron diffraction (CBED) provides more quantitative, precise and local informa... more Convergent beam electron diffraction (CBED) provides more quantitative, precise and local information on crystals than the traditional selected-area diffraction (SAD). Some of the results of our applications of CBED will be shown, with an emphasis on quantitative analyses of crystal structure in materials science: (i) The critical voltage and the intersecting Kikuchi line methods are combined with the CBED technique to accurately determine the structure factors and temperature factors; (ii) a large angle CBED is applied to determine the atomic coordinates in a unit cell; (iii) higher order Laue zone patterns are used to determine absolute lattice parameters and local lattice distortion
Scripta Materialia, Apr 1, 2003
Quantitative characterizations of nanostructures in FePt granular thin films were achieved by tra... more Quantitative characterizations of nanostructures in FePt granular thin films were achieved by transmission electron microscopy with various analytical methods. Significant amounts of Fe and Pt atoms are dissolved within the matrix of Al 2 O 3 in the as-deposited states. These solutioned Fe and Pt atoms play important roles of the structural changes during thermal annealing process.
Transmission electron microscope analysis of epitaxial growth processes in the sputtered β-FeSi2/Si(001) films
Thin Solid Films, Aug 1, 2004
The crystallographic orientation relationships and the formation process of β-FeSi2/Si(001) films... more The crystallographic orientation relationships and the formation process of β-FeSi2/Si(001) films were investigated by transmission electron microscopy. A film produced by sputtering pure iron onto a silicon substrate at 600 °C consists of α- and β-FeSi2 particles. The crystallographic relationships obtained are: (112)α‖(111)Si and (101)β‖(111)Si or (110)β‖(111)Si. The grains of α- and β-FeSi2 grown inside the substrate adopt the epitaxy to Si(111), irrespective of the surface orientation of the substrate. At 500 °C, on the contrary, there are few α-FeSi2 grains and some grains of β-FeSi2 with (100)β‖(001)Si [010]β‖[110]Si. These results demonstrate that the lower temperature and the higher Fe concentration suppress the formation of α-FeSi2 and promote the formation of β-FeSi2 on/below the substrate surface.
CBED Determination of The Atomic Positions in A Cu-1212 Layered Copper Oxide Crystal
Journal of Microscopy, Jul 1, 2001
Convergent beam electron diffraction, energy filtering, high resolution electron microscopy, high... more Convergent beam electron diffraction, energy filtering, high resolution electron microscopy, high T c superconductor, oxygen deficiency, phase transformation, twin boundary, YBa 2 Cu 3 O y .
Defects occurring at or near surfaces in α-Al2O3 during electron irradiation
Ultramicroscopy, Nov 1, 1991
Abstract A new type of defect introduced during electron irradiation in an α-Al 2 O 3 single crys... more Abstract A new type of defect introduced during electron irradiation in an α-Al 2 O 3 single crystal has been investigated through in situ high-resolution electron microscopy (HREM). The defects are observed as a black line contrast parallel to the (006) lattice plane in HREM images along the [110] direction but they are invisible in images along [001]. Line contrasts of the defects can also be observed in a bright-field or dark-field image under excitation of the systematic row of (006) reflection. Electron-diffraction patterns show streaks and extra spots suggesting the presence of planar defects inside the specimen as well as the surface. The defects do not appear during irradiation at 200 kV, but do appear at 400 kV after irradiation of several minutes. The defects occur in a thick area as well as in a thin area of specimen edge and some of them grow or disappear abruptly during irradiation. Examples of multi-layer and complex-layer defects are also shown.
In-situ observations of irradiation-induced phase transformations
Ultramicroscopy, Nov 1, 1994
Abstract High-voltage and high-resolution electron microscopy approaches the resolving power of 0... more Abstract High-voltage and high-resolution electron microscopy approaches the resolving power of 0.1 nm and is expected to develop new fields of materials science and engineering. In order to look over future advances, the present paper introduces the progress of our studies on irradiation-induced phase transformations in alloys based on conventional high-voltage electron microscopy. This paper also shows phase transformations at or near surface of α-Al 2 O 3 induced by an intense electron beam in clean high-vacuum microscopes which give insight into irradiation-induced phenomena in new high-voltage and high-resolution electron microscopy.
Energy filtering transmission electron microscopy using the new JEM-2010FEF
Journal of Microscopy, Apr 1, 1999
ABSTRACT
Journal of Nuclear Materials, Mar 1, 1991
Irradiation-induced amorphization and swelling of ceramics including graphite have been studied t... more Irradiation-induced amorphization and swelling of ceramics including graphite have been studied through in-situ observation of electron microscopy, electron energy loss spectroscopy and convergent beam electron diffraction. Amorphization occurs below 500 K for highly-oriented pyrolytic graphite (HOPG) and below 300 K for Sic under electron irradiation. The amorphization fluences of HOPG and Sic required for full amorphization show no flux dependence. The displacement threshold energy is determined to be 12 eV for HOPG from the electron energy dependence of the amorphization fluence which is equivalent to 1 dpa. An atomistic model for describing the irradiation-induced amorphization and swelling of graphite is proposed. A high concentration of C, molecules and their clusters between basal planes induce abrupt swelling along the c-axis within 4 X 10e3 dpa and fade the periodical structural image at 4~ 10m2 dpa. The concentration of vacancies increases gradually up to 1 dpa at which amorphization is completed.
High Resolution Electron Microscopy of Sintered YBa2Cu3O7-x
Sintered specimens have been observed through high resolution electron microscopy. Lattices of or... more Sintered specimens have been observed through high resolution electron microscopy. Lattices of orthorhombic structure are slightly distorted in the vicinity of a twin boundary. Three types of grain boundaries (GBs) are present: (1)Some grain boundaries are parallel to a C-plane of one grain where a lot of stacking faults is concentrated along the GB. (2) The others have amorphous layers of 1∼4 nm in thickness at the boundaries. Lattice distortion and stacking faults were not found near the GBs. (3)A coincidence tilt boundary accompanies neither stacking fault nor amorphous layer, but an axial length varys near the GB. Cracks parallel to a C-plane are frequently presnt. A width of crack is in the range of 1 nm ∼ several tens of nm. A stacking fault present in an interior of grain consists of extra planes of Ba layer and Cu-O chain. The lattice distortion at a twin boundary, a nano-crack and an isolated stacking fault in the internal region of a grain may act as an effective pinning center but most of the structures mentioned above seem to be responsible for low Jc value.
Omega filter installed in the 1MV microscope of Kyushu University
Micron, Aug 1, 2008
A 1.25MV high-voltage electron microscope with a B-type omega filter has been successfully instal... more A 1.25MV high-voltage electron microscope with a B-type omega filter has been successfully installed at Kyushu University. An image detection chamber has been set inside a concrete block below the ground level without changing the frame structure for anti-vibration. Nearly the same design as that for the 200kV microscope has been kept for the present omega filter except for its size. A new pre- and post-filter lens system with rotation-free imaging has been designed. Energy resolution, beam shape and stability of the filter have been measured. Some application data have been obtained to demonstrate the performance of the filter.
2-110 Training and education of researchers for electron microscopy at the Research Laboratory for High Voltage Electron Microscopy in Kyushu University
工学・工業教育研究講演会講演論文集, Jul 28, 2006
Ultramicroanalysis for the Development of Nanomaterials
Dependence of critical voltages in Cu-based alloys on composition, temperature and short range order
Proceedings, annual meeting, Electron Microscopy Society of America, 1978
Introduction Since the critical voltage effect in electron microscopy was discovered [1, 2], a nu... more Introduction Since the critical voltage effect in electron microscopy was discovered [1, 2], a number of its applications have been proposed [3-9]. As the critical voltage Vcof an alloy depends primarily on the scattering factors of constituent atoms, not only the compositional change but also the degree of order and the mean square displacement (msd) of the atoms affect the value of Vc. In the present paper the effect of alloying on Vc is studied in Cu-based alloys containing 14.8 at% Al, 4.9 or 14.9 at% Au. These alloys are of interest because Al is lighter and Au heavier than Cu atom, and furthermore the alloys develop a short range order. The critical voltages were determined using JEM-1000 HVEM by observing of the minimum intensity of 2g Kikuchi line and the reversal of the contrast of middle line at lg spot. The measured Vc was analyzed by the 10-beam dynamical theory.
Observation of faint contrast at planar faults in alloys
Proceedings, annual meeting, Electron Microscopy Society of America, 1978
The contrast in electron microscopic images of planar faults in a crystal is characterized by a p... more The contrast in electron microscopic images of planar faults in a crystal is characterized by a phase factor , where is the reciprocal lattice vector of the operating reflection, and the lattice displacement due to the fault under consideration. Within the two-beam theory a planar fault with an integer value of is invisible, but a detectable contrast is expected when the many-beam dynamical effect is not negligibly small. A weak fringe contrast is also expected when differs slightly from an integer owing to an additional small displacement of the lattice across the fault. These faint contrasts are termed as many-beam contrasts in the former case, and as ε fringe contrasts in the latter. In the present work stacking faults in Cu-Al alloys and antiphase boundaries (APB) in CuZn, FeCo and Fe-Al alloys were observed under such conditions as mentioned above, and the results were compared with the image profiles of the faults calculated in the systematic ten-beam approximation.
Journal of the Japan Institute of Metals, 1968
Microstructural and Mechanical Properties of TiC, TiB2 and VC with Low Carbon Steel Surface Alloy Fabricated by High Energy Electron Beam Irradiation
Materials Science Forum, 2005
Because of its excellent process advantages such as high energy efficiency, short irradiation tim... more Because of its excellent process advantages such as high energy efficiency, short irradiation time and rapid heating, high energy electron beam (HEEB) irradiation is becoming of interest as a future surface modification technology. In this study, surface alloying of TiC, TiB2 and VC ceramic particles with a low carbon steel substrate was carried out using HEEB of 1.4 MeV. Surface alloyed layers of all the specimens were about 2 mm thick and consisted of a melted region, an interface region, a heat affected zone (HAZ) and the matrix. In all the specimens, the hardness at the surface was the highest, and then decreased sharply into the interior reaching the lowest values at the matrix. A remarkable increase in the mechanical properties was observed for the VC surface alloyed specimen. Vanadium carbides of large (~ 5 µm) and fine sizes (~ 20 nm) were formed uniformly, which resulted in an increase of hardness to 2-3 times of that of the matrix, and highest wear resistance.
Higher order Laue zone patterns and determination of local lattice parameter
Microstructures of Dielectric Ba_xSr_ TiO3 Prepared by RF Sputtering
まてりあ : 日本金属学会会報, Dec 20, 2001
Microstructure control in HDDR process for higher anisotropic Nd-Fe-B magnet powders
Homogenized Nd-Fe-Co-B-Zr(-Ga) alloys are treated by hydrogenation (HD-process) and dehydrogenati... more Homogenized Nd-Fe-Co-B-Zr(-Ga) alloys are treated by hydrogenation (HD-process) and dehydrogenation (DR-process) with various treatment conditions, followed by quenching in argon gas flow. After the HDDR process, the specimens are crashed into powders. The magnetic properties of the powder and bonded magnets are measured with a vibrating sample magnetometer and a B-H tracer. The microstructural changes are also analyzed by electron microscopy (FE-SEM and TEM) and discussed with special reference to the behavior of boron.
Applications of Convergent Beam Electron Diffraction to Extract Quantitative Information in Materials Science
Journal of Electron Microscopy, Dec 1, 1992
Convergent beam electron diffraction (CBED) provides more quantitative, precise and local informa... more Convergent beam electron diffraction (CBED) provides more quantitative, precise and local information on crystals than the traditional selected-area diffraction (SAD). Some of the results of our applications of CBED will be shown, with an emphasis on quantitative analyses of crystal structure in materials science: (i) The critical voltage and the intersecting Kikuchi line methods are combined with the CBED technique to accurately determine the structure factors and temperature factors; (ii) a large angle CBED is applied to determine the atomic coordinates in a unit cell; (iii) higher order Laue zone patterns are used to determine absolute lattice parameters and local lattice distortion
Scripta Materialia, Apr 1, 2003
Quantitative characterizations of nanostructures in FePt granular thin films were achieved by tra... more Quantitative characterizations of nanostructures in FePt granular thin films were achieved by transmission electron microscopy with various analytical methods. Significant amounts of Fe and Pt atoms are dissolved within the matrix of Al 2 O 3 in the as-deposited states. These solutioned Fe and Pt atoms play important roles of the structural changes during thermal annealing process.
Transmission electron microscope analysis of epitaxial growth processes in the sputtered β-FeSi2/Si(001) films
Thin Solid Films, Aug 1, 2004
The crystallographic orientation relationships and the formation process of β-FeSi2/Si(001) films... more The crystallographic orientation relationships and the formation process of β-FeSi2/Si(001) films were investigated by transmission electron microscopy. A film produced by sputtering pure iron onto a silicon substrate at 600 °C consists of α- and β-FeSi2 particles. The crystallographic relationships obtained are: (112)α‖(111)Si and (101)β‖(111)Si or (110)β‖(111)Si. The grains of α- and β-FeSi2 grown inside the substrate adopt the epitaxy to Si(111), irrespective of the surface orientation of the substrate. At 500 °C, on the contrary, there are few α-FeSi2 grains and some grains of β-FeSi2 with (100)β‖(001)Si [010]β‖[110]Si. These results demonstrate that the lower temperature and the higher Fe concentration suppress the formation of α-FeSi2 and promote the formation of β-FeSi2 on/below the substrate surface.
CBED Determination of The Atomic Positions in A Cu-1212 Layered Copper Oxide Crystal
Journal of Microscopy, Jul 1, 2001
Convergent beam electron diffraction, energy filtering, high resolution electron microscopy, high... more Convergent beam electron diffraction, energy filtering, high resolution electron microscopy, high T c superconductor, oxygen deficiency, phase transformation, twin boundary, YBa 2 Cu 3 O y .
Defects occurring at or near surfaces in α-Al2O3 during electron irradiation
Ultramicroscopy, Nov 1, 1991
Abstract A new type of defect introduced during electron irradiation in an α-Al 2 O 3 single crys... more Abstract A new type of defect introduced during electron irradiation in an α-Al 2 O 3 single crystal has been investigated through in situ high-resolution electron microscopy (HREM). The defects are observed as a black line contrast parallel to the (006) lattice plane in HREM images along the [110] direction but they are invisible in images along [001]. Line contrasts of the defects can also be observed in a bright-field or dark-field image under excitation of the systematic row of (006) reflection. Electron-diffraction patterns show streaks and extra spots suggesting the presence of planar defects inside the specimen as well as the surface. The defects do not appear during irradiation at 200 kV, but do appear at 400 kV after irradiation of several minutes. The defects occur in a thick area as well as in a thin area of specimen edge and some of them grow or disappear abruptly during irradiation. Examples of multi-layer and complex-layer defects are also shown.