Helmut Takahiro Uchida | Tokai University (original) (raw)
Papers by Helmut Takahiro Uchida
Polymers
In an interlayered carbon fiber-reinforced polycarbonate polymer (CFRPC) composite composed of th... more In an interlayered carbon fiber-reinforced polycarbonate polymer (CFRPC) composite composed of three sized of CF plies, alternating between four PC sheets, designated [PC]4[CF]3, and a new process of activating CF cross-weave cloth plies directly on both sides with homogeneous low-energy electron beam irradiation (HLEBI) before lamination assembly and hot pressing at 6.0 MPa and 537 K for 8 min was produced. Experimental results show that a dose of 215 kGy of HLEBI raised the bending strength, σb, at each experimental accumulative probability, Pa, with the σb at a median Pa of 0.50, increasing by 25% over that of the untreated sample. Three-parameter Weibull analysis showed that when quality can be controlled, a dose of 215 kGy of HLEBI can raise the statistically lowest bending strength, σs, at Pa = 0 (94.3 Mpa), with a high correlation coefficient. This is because, although it had a higher bending strength than that in the other experimental conditions, the weakest sample of the 2...
Defect and Diffusion Forum, Jul 1, 2015
Pd-H system is a model system suitable for studying interactions of hydrogen with metals. In the ... more Pd-H system is a model system suitable for studying interactions of hydrogen with metals. In the present work, we studied hydrogen-induced buckling of thin Pd films deposited on various substrates with different bonding strengths (sapphire, glimmer) and also the effect of deposition temperature. Lattice expansion and phase transitions were investigated by X-ray diffraction of synchrotron radiation. The influence of substrate and microstructure of the film on the buckling process and phase transformation to palladium hydride are discussed.
Acta Materialia, Aug 1, 2016
For thin metal films adhered to rigid substrates hydrogen uptake results in compressive stresses ... more For thin metal films adhered to rigid substrates hydrogen uptake results in compressive stresses in the GPa range. Stresses affect the thermodynamics as well as the durability of thin films, but many films can release stress above critical stress values. Depending on the films' thickness, microstructure and adhesion to the substrate, which determine the energy available in the nano-sized system, stress release is conducted via different release mechanisms. To evaluate the different mechanisms, Palladium thin films ranging from 10 nm to 350 nm and with three different types of microstructures (nanocrystalline, multioriented epitaxy and threefold epitaxy) are studied with special focus on the mechanical stress. In-situ substrate curvature measurements, XRD stress analyses and acoustic emission (AE) measurements are conducted to determine intrinsic stresses, hydrogen-induced stress changes and stress release signals. By this complementary experimental approach, different stress release mechanisms (named channels) are identified. Discrete stress relaxation (DSR) events are found already within the overall linear elastic stress-strain regime. Energies to stimulate DSRs lay well below the formation energy of dislocations, and may allow the movement of defects pre-existing in the films. For higher strain energies, all studied films can release stress by the formation of new dislocations and plastic deformation. When the adhesion to the substrate is small, an alternative release channel of film buckling opens for thick films.
Journal of Advanced Science, 2023
As the hydrogen society progresses, Fuel Cell Vehicles (FCVs) are rapidly becoming more widesprea... more As the hydrogen society progresses, Fuel Cell Vehicles (FCVs) are rapidly becoming more widespread. Metal hydrogen permeable membranes, which are the essential parts of the hydrogen fuels for polymer electrolyte fuel cells (PEFCs), require an alternative material to palladium from a cost point of view. Austenitic stainless steel, which is low cost, corrosion resistant, and easy to prepare for manufacture, has been considered unsuitable as a hydrogen permeable membrane because its passive film inhibits hydrogen permeation. However, destabilization of the surface oxide film and thin processing can be expected to improve its permeability. In this work, 18mass%Cr-8mass%Ni-2mass%Mo-Low Carbon (0.02mass%) stainless steel alloy (SUS316L) foils were irradiated with electron beam (EB) in a nitrogen atmosphere to investigate the effect of EB treatment on hydrogen permeability. The diffusion coefficient of hydrogen in the passive layer on the surface of stainless steel irradiated at 250 kV and 600 kGy was calculated to be promoted about 8 times compared to the untreated one, by applying Schmitz's multilayer hydrogen diffusion permeation model. Based on the results obtained, partial destabilization of the surface oxide film by irradiation treatment is suggested.
Materials Science Forum
Achieving a strong bond between carbon fiber (CF) and recyclable thermoplastic polymer (TP) has a... more Achieving a strong bond between carbon fiber (CF) and recyclable thermoplastic polymer (TP) has always been highly sought after. So far, applying electron beam (EB) irradiation with optimal dose and cathode potential (Vc) has shown success in increasing mechanical properties of interlayered CFRTPs. However, with concern for durability and safety, higher strength is desired. Therefore, EB setting applying electron beam (EB) irradiation with cathode potential (Vc) to 170, 210, 225 or 250 kV was applied to CFRTPA (carbon fiber reinforced thermoplastic polyamide) articles just before shipping. Specimens were 9 CF plies alternating between 10 PA (polyamide) sheets, designated [TPA]10[CF]9. When optimal EB dose of 43.2 kGy is applied to both finished specimen surfaces after fabrication, experimental results show higher Vc setting of 250 kV can increase impact strength of the [TPA]10[CF]9 over that at 170 kV. In summary, the 250 kV-EB (250 kV) strengthens [TPA]10[CF]9 significantly, about ...
Materials
New types of hybrid aluminum joints: Al-acrylonitrile butadiene styrene (ABS) carbon fiber reinfo... more New types of hybrid aluminum joints: Al-acrylonitrile butadiene styrene (ABS) carbon fiber reinforced thermoplastic polymer (CFRTP) designated Al/Ni-CFP/ABS, and Al-18-8 Stainless steel, Al/Ni-CFP/18-8, by Ni-plated carbon fiber plug (Ni-CFP) insert not before seen in the literature have been fabricated. The goal is to take advantage of extremely high ~6 mm CF surface area for high adhesion, to enhance the safety level of aircraft and other parts. This is without fasteners, chemical treatment, or glue. First, the CFP is plated with Ni. Second, the higher melting point half-length is spot welded to the CFP; and third, the remaining half-length is fabricated. The ultimate tensile strength (UTS) of Al/Ni-CFP/ABS was raised 15 times over that of Al/ABS. Normalized cUTS according to CFP cross-section by Rule of Mixtures for cAl/Ni-CFP/18-8 was raised over that of cAl/Ni-CFP/18-8 from 140 to 360 MPa. Resistance energy to tensile deformation, UT, was raised 12 times from Al/ABS to Al/Ni-CF...
Materials
Impact by hailstone, volcanic rock, bird strike, or also dropping tools can cause damage to aircr... more Impact by hailstone, volcanic rock, bird strike, or also dropping tools can cause damage to aircraft materials. For maximum safety, the goal is to increase Charpy impact strength (auc) of a carbon-fiber-reinforced thermoplastic polyphenylene sulfide polymer (CFRTP-PPS) composite for potential application to commercial aircraft parts. The layup was three cross-weave CF plies alternating between four PPS plies, [PPS-CF-PPS-CF-PPS-CF-PPS], designated [PPS]4[CF]3. To strengthen, a new process for CFRP-PPS was employed applying homogeneous low voltage electron beam irradiation (HLEBI) to both sides of PPS plies prior to lamination assembly with untreated CF, followed by hot press under 4.0 MPa at 573 K for 8 min. Experimental results showed a 5 kGy HLEBI dose was at or near optimum, increasing auc at each accumulative probability, Pf. Optical microscopy of 5 kGy sample showed a reduction in main crack width with significantly reduced CF separation and pull-out; while, scanning electron m...
Journal of Advanced Science, 2017
Adhesion induced by homogeneous low voltage EB-irradiation (HLEBI) under O2 partial pressure from... more Adhesion induced by homogeneous low voltage EB-irradiation (HLEBI) under O2 partial pressure from 0.02 mol% to 20 mol% in N2 gas atmosphere of CFRP/Al lamination has been successfully developed. Its adhesive tensile shear strength of CFRP/Al with 0.30 MGy-HLEBI under optimal O2 partial pressure in N2 atmosphere of 0.2 mol% is 8.2 MPa, which is about 1.4 times higher than that (5.9 MPa) of CFRP/Al untreated.
Materials
Strong adhesion between recyclable thermoplastic (TP) polymer and carbon fiber (CF) has always be... more Strong adhesion between recyclable thermoplastic (TP) polymer and carbon fiber (CF) has always been highly sought after. Therefore, for an interlayered CF reinforced TP polypropylene (CFRTPP) composite composed of 3 sized CF plies, alternating between 4 PP sheets, designated [PP]4[CF]3, a process of activating CF plies directly on both sides with homogeneous low energy electron beam irradiation (EBI) under N2 gas, prior to lamination assembly and hot press of 4.0 MPa at 493 K for 3 min was carried out. Experimental results showed EBI dose of 43.2, 129, or 216 kGy significantly raised Charpy impact values, auc at all fracture probabilities, Pf. The 129 kGy dose appeared to be at or near optimum increasing auc 103%, 83%, and 65% at low-, median-, and high-Pf = 0.07, 0.50, and 0.93; while raising statistically lowest impact value, as at Pf = 0 calculated by 3-dimensional Weibull equation about 110%, indicating increased safety and reliability. It is assumed dangling bonds generated by ...
Materials, Apr 29, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
MATERIALS TRANSACTIONS, 2019
A new process of internal activation of carbon fiber reinforced thermoplastic polymer (CFRTP) of ... more A new process of internal activation of carbon fiber reinforced thermoplastic polymer (CFRTP) of polypropylene (PP) by applying electron beam irradiation (EBI) under oxygen (O 2)rich nitrogen gas (N 2) atmosphere to CF chopped strand matt (CSM) layers prior to assembly and hot press to strengthen the typically weak CF/thermoplastic polymers (TPs) adhesion was proposed. Samples were interlayered composite with layup of alternating PP and CF plies, [PP] 4 [CF] 3. Composite fabrication was performed by one directional hot-press under constant pressure of 4.0 MPa at 473 K for 1 min. Results showed applying an optimum 0.22 MGy-EBI under protective N 2 gas with O 2 concentrations between 200 ppm and 200,000 ppm mostly improved the bending strength (• b) while reducing strain at the bending strength (• b) apparently increasing the elasticity. The method appears to work well for the weakest samples in the data sets: at low accumulative probability P f = 0.06 by median rank method, • b was apparently improved by the 200 ppm and 2,000 ppm O 2 atmospheres. Namely, 0.22 MGy-EBI under N 2 gas atmosphere with 200 ppm to 2,000 ppm-O 2 improved • b at P f = 0.06 (57 MPa) about 21%, over that of untreated (47 MPa). Strength increase could be explained by mutual entangling of both sizing epoxy film on CF and PP with strong covalent bonding, which formation of direct CF: C:C :PP induced by EBI and oxygen assisted CF: C:O:C :PP by concentrating the O 2 gas molecules from 200 ppm to 2,000 ppm-O 2 in N 2 atmosphere, rather than weak molecular bonding CF-(H 2 O, N 2 , O 2)-PP for the untreated samples. Moreover, the action of the EBI apparently acts to clean residual H 2 O, N 2 , and O 2 to purify and activate the CF surface increasing polar group and active site density. They most likely contributed to bending strength enhancement. The 0.22 MGy-EBI in O 2-rich N 2 atmosphere appears to be a viable method to increase carbon fiber-thermoplastic polypropylene adhesion enhancing reliability and safety of the PP-CFRTP.
The Japan Institute of Metals and Materials, Feb 3, 2021
Journal of Advanced Science
Magnetostrictive materials are widely used to build actuators, sensors, and vibration energy harv... more Magnetostrictive materials are widely used to build actuators, sensors, and vibration energy harvesting devices. Generally, the interfacial adhesion between the substrate and thin films plays important roll from the practical point of view. Therefore, establishing precise techniques to evaluate the interfacial adhesion energy are quite important as basic technologies in the applications. In this study, we focused on the in-plane stress control by tuning the hydrogen content via electrochemical hydrogen loading. Effect of hydrogen absorption on Sm-Fe thin films were studied by in-situ measurement of electrochemical hydrogen loading combined with acoustic emission. The step-by-step electrochemical hydrogen loading was applied to Sm-Fe films and the electromotive force (EMF) between the Saturated Calomel Electrode (SCE) and Sm-Fe thin film in equilibrium state was measured at each hydrogen concentration. Acoustic emission (AE) measurements revealed that when hydrogen concentration over a certain value increase of AE counts. At the same time, EMF tended to increase above a certain hydrogen concentration. Delamination of the Sm-Fe film from the substrate (buckling) was also observed after electrochemical hydrogen loading technique.
Journal of Composite Materials
A new process of activating sizing film free (removed sizing) carbon fiber (SFF-CF) mats directly... more A new process of activating sizing film free (removed sizing) carbon fiber (SFF-CF) mats directly with electron beam irradiation (EBI) under oxygen-rich nitrogen gas prior to lamination assembly and hot-press was found to increase bending strength of CFRTP (CF reinforced thermoplastic polypropylene (PP)) interlayered composite composed of 3 SFF-CF mats between 4 PP sheets, [PP]4[SFF-CF]3. The hot-press fabrication was performed under 4.0 MPa at 473 K for 1 min. Experimental results showed optimal condition of 0.22 MGy-EBI under 2,000 ppm-O2-rich, protective N2 atmosphere improved bending strength, σb at all accumulative probabilities, Pf over that of untreated. This could be explained by maximum number of the strong covalent bonds of CF:C:C:PP and oxygen assisted CF:C:O:C:PP bonds adhering bare SFF-CF surface to PP, instead of the weak intermolecular bonding of CF(H2O, N2, O2)PP of untreated. The optimal concentration of O2 molecules together with the EBI probably purified the SFF-C...
Defect and Diffusion Forum, 2013
Hydrogen absorption and diffusivity in high quality ZnO crystals were investigated in this work b... more Hydrogen absorption and diffusivity in high quality ZnO crystals were investigated in this work by X-ray diffraction combined with slow positron implantation spectroscopy and electrical resistometry. ZnO crystals were covered by a thin Pd over-layer and electrochemically charged with hydrogen. It was found that absorbed hydrogen causes plastic deformation in a sub-surface region. The depth profile of hydrogen concentration introduced into the crystal was determined by nuclear reaction analysis. Enhanced hydrogen concentration was found in the sub-surface region due to excess hydrogen atoms trapped at defects introduced by plastic deformation. Hydrogen diffusion in ZnO crystals with various orientations was studied by in-situ electrical resistometry. It was found that hydrogen diffusion in the c-direction is faster than hydrogen diffusion in the a-direction most probably due to open channels existing in the wurtzite structure along the c-axis.
Journal of Alloys and Compounds, 2015
ABSTRACT Gas phase loading of nanocrystalline and epitaxial 20 nm Pd films deposited on single cr... more ABSTRACT Gas phase loading of nanocrystalline and epitaxial 20 nm Pd films deposited on single crystalline sapphire substrates was studied in this work. The nanocrystalline film was deposited at room temperature and the epitaxial film deposited at 800 °C. The nanocrystalline film suffers from in-plane compressive stress imposed by atomic peening processes. The epitaxial film exhibits tensile stress caused by the different thermal expansion coefficients of Pd and sapphire substrate. Coherent phase transition into the hydride phase was observed both for the nanocrystalline and for the epitaxial film. For both films, the lattice parameters continuously increase during the phase transition to the hydride phase. Both films exhibit enhanced hydride formation pressure compared to bulk Pd. Misfit dislocations are formed at interface between Pd film and substrate during hydrogenation. This leads to irreversible change of stress state of the films subjected to sorption and desorption cycle with hydrogen.
Scripta Materialia, 2011
ABSTRACT The hydrogenation of nanocrystalline Mg films on Si- and Pd substrates was studied by el... more ABSTRACT The hydrogenation of nanocrystalline Mg films on Si- and Pd substrates was studied by electromotive force and X-ray diffraction measurements. A strong loading current dependency of the hydrogenated volume was found. While for high current densities i > 1 × 10−6 A cm−2 only about 10 nm could be hydrogenated, about 200 nm could be reached for small current densities i < 4 × 10−7 A cm−2. For a 2.1 μm Mg film on a Pd substrate, a thickness of 1.3 μm could be hydrogenated.
Journal of Nano Research, 2013
Hydrogen interaction with defects and structural development of Pd films with various microstruct... more Hydrogen interaction with defects and structural development of Pd films with various microstructures were investigated. Nanocrystalline, polycrystalline and epitaxial Pd films were prepared and electrochemically loaded with hydrogen. Structural changes of Pd films caused by absorbed hydrogen were studied by in-situ X-ray diffraction combined with acoustic emission and measurement of electromotorical force. Development of defects during hydrogen loading was investigated by positron annihilation spectroscopy. It was found that hydrogen firstly fills open volume defects existing already in the films and subsequently it occupies also interstitial sites in Pd lattice. Absorbed hydrogen causes volume expansion, which is strongly anisotropic in thin films. This introduces high stress into the films loaded with hydrogen. Acoustic emission measurements revealed that when hydrogen-induced stress achieves a certain critical level rearrangement of misfit dislocations takes place. The stress wh...
Polymers
In an interlayered carbon fiber-reinforced polycarbonate polymer (CFRPC) composite composed of th... more In an interlayered carbon fiber-reinforced polycarbonate polymer (CFRPC) composite composed of three sized of CF plies, alternating between four PC sheets, designated [PC]4[CF]3, and a new process of activating CF cross-weave cloth plies directly on both sides with homogeneous low-energy electron beam irradiation (HLEBI) before lamination assembly and hot pressing at 6.0 MPa and 537 K for 8 min was produced. Experimental results show that a dose of 215 kGy of HLEBI raised the bending strength, σb, at each experimental accumulative probability, Pa, with the σb at a median Pa of 0.50, increasing by 25% over that of the untreated sample. Three-parameter Weibull analysis showed that when quality can be controlled, a dose of 215 kGy of HLEBI can raise the statistically lowest bending strength, σs, at Pa = 0 (94.3 Mpa), with a high correlation coefficient. This is because, although it had a higher bending strength than that in the other experimental conditions, the weakest sample of the 2...
Defect and Diffusion Forum, Jul 1, 2015
Pd-H system is a model system suitable for studying interactions of hydrogen with metals. In the ... more Pd-H system is a model system suitable for studying interactions of hydrogen with metals. In the present work, we studied hydrogen-induced buckling of thin Pd films deposited on various substrates with different bonding strengths (sapphire, glimmer) and also the effect of deposition temperature. Lattice expansion and phase transitions were investigated by X-ray diffraction of synchrotron radiation. The influence of substrate and microstructure of the film on the buckling process and phase transformation to palladium hydride are discussed.
Acta Materialia, Aug 1, 2016
For thin metal films adhered to rigid substrates hydrogen uptake results in compressive stresses ... more For thin metal films adhered to rigid substrates hydrogen uptake results in compressive stresses in the GPa range. Stresses affect the thermodynamics as well as the durability of thin films, but many films can release stress above critical stress values. Depending on the films' thickness, microstructure and adhesion to the substrate, which determine the energy available in the nano-sized system, stress release is conducted via different release mechanisms. To evaluate the different mechanisms, Palladium thin films ranging from 10 nm to 350 nm and with three different types of microstructures (nanocrystalline, multioriented epitaxy and threefold epitaxy) are studied with special focus on the mechanical stress. In-situ substrate curvature measurements, XRD stress analyses and acoustic emission (AE) measurements are conducted to determine intrinsic stresses, hydrogen-induced stress changes and stress release signals. By this complementary experimental approach, different stress release mechanisms (named channels) are identified. Discrete stress relaxation (DSR) events are found already within the overall linear elastic stress-strain regime. Energies to stimulate DSRs lay well below the formation energy of dislocations, and may allow the movement of defects pre-existing in the films. For higher strain energies, all studied films can release stress by the formation of new dislocations and plastic deformation. When the adhesion to the substrate is small, an alternative release channel of film buckling opens for thick films.
Journal of Advanced Science, 2023
As the hydrogen society progresses, Fuel Cell Vehicles (FCVs) are rapidly becoming more widesprea... more As the hydrogen society progresses, Fuel Cell Vehicles (FCVs) are rapidly becoming more widespread. Metal hydrogen permeable membranes, which are the essential parts of the hydrogen fuels for polymer electrolyte fuel cells (PEFCs), require an alternative material to palladium from a cost point of view. Austenitic stainless steel, which is low cost, corrosion resistant, and easy to prepare for manufacture, has been considered unsuitable as a hydrogen permeable membrane because its passive film inhibits hydrogen permeation. However, destabilization of the surface oxide film and thin processing can be expected to improve its permeability. In this work, 18mass%Cr-8mass%Ni-2mass%Mo-Low Carbon (0.02mass%) stainless steel alloy (SUS316L) foils were irradiated with electron beam (EB) in a nitrogen atmosphere to investigate the effect of EB treatment on hydrogen permeability. The diffusion coefficient of hydrogen in the passive layer on the surface of stainless steel irradiated at 250 kV and 600 kGy was calculated to be promoted about 8 times compared to the untreated one, by applying Schmitz's multilayer hydrogen diffusion permeation model. Based on the results obtained, partial destabilization of the surface oxide film by irradiation treatment is suggested.
Materials Science Forum
Achieving a strong bond between carbon fiber (CF) and recyclable thermoplastic polymer (TP) has a... more Achieving a strong bond between carbon fiber (CF) and recyclable thermoplastic polymer (TP) has always been highly sought after. So far, applying electron beam (EB) irradiation with optimal dose and cathode potential (Vc) has shown success in increasing mechanical properties of interlayered CFRTPs. However, with concern for durability and safety, higher strength is desired. Therefore, EB setting applying electron beam (EB) irradiation with cathode potential (Vc) to 170, 210, 225 or 250 kV was applied to CFRTPA (carbon fiber reinforced thermoplastic polyamide) articles just before shipping. Specimens were 9 CF plies alternating between 10 PA (polyamide) sheets, designated [TPA]10[CF]9. When optimal EB dose of 43.2 kGy is applied to both finished specimen surfaces after fabrication, experimental results show higher Vc setting of 250 kV can increase impact strength of the [TPA]10[CF]9 over that at 170 kV. In summary, the 250 kV-EB (250 kV) strengthens [TPA]10[CF]9 significantly, about ...
Materials
New types of hybrid aluminum joints: Al-acrylonitrile butadiene styrene (ABS) carbon fiber reinfo... more New types of hybrid aluminum joints: Al-acrylonitrile butadiene styrene (ABS) carbon fiber reinforced thermoplastic polymer (CFRTP) designated Al/Ni-CFP/ABS, and Al-18-8 Stainless steel, Al/Ni-CFP/18-8, by Ni-plated carbon fiber plug (Ni-CFP) insert not before seen in the literature have been fabricated. The goal is to take advantage of extremely high ~6 mm CF surface area for high adhesion, to enhance the safety level of aircraft and other parts. This is without fasteners, chemical treatment, or glue. First, the CFP is plated with Ni. Second, the higher melting point half-length is spot welded to the CFP; and third, the remaining half-length is fabricated. The ultimate tensile strength (UTS) of Al/Ni-CFP/ABS was raised 15 times over that of Al/ABS. Normalized cUTS according to CFP cross-section by Rule of Mixtures for cAl/Ni-CFP/18-8 was raised over that of cAl/Ni-CFP/18-8 from 140 to 360 MPa. Resistance energy to tensile deformation, UT, was raised 12 times from Al/ABS to Al/Ni-CF...
Materials
Impact by hailstone, volcanic rock, bird strike, or also dropping tools can cause damage to aircr... more Impact by hailstone, volcanic rock, bird strike, or also dropping tools can cause damage to aircraft materials. For maximum safety, the goal is to increase Charpy impact strength (auc) of a carbon-fiber-reinforced thermoplastic polyphenylene sulfide polymer (CFRTP-PPS) composite for potential application to commercial aircraft parts. The layup was three cross-weave CF plies alternating between four PPS plies, [PPS-CF-PPS-CF-PPS-CF-PPS], designated [PPS]4[CF]3. To strengthen, a new process for CFRP-PPS was employed applying homogeneous low voltage electron beam irradiation (HLEBI) to both sides of PPS plies prior to lamination assembly with untreated CF, followed by hot press under 4.0 MPa at 573 K for 8 min. Experimental results showed a 5 kGy HLEBI dose was at or near optimum, increasing auc at each accumulative probability, Pf. Optical microscopy of 5 kGy sample showed a reduction in main crack width with significantly reduced CF separation and pull-out; while, scanning electron m...
Journal of Advanced Science, 2017
Adhesion induced by homogeneous low voltage EB-irradiation (HLEBI) under O2 partial pressure from... more Adhesion induced by homogeneous low voltage EB-irradiation (HLEBI) under O2 partial pressure from 0.02 mol% to 20 mol% in N2 gas atmosphere of CFRP/Al lamination has been successfully developed. Its adhesive tensile shear strength of CFRP/Al with 0.30 MGy-HLEBI under optimal O2 partial pressure in N2 atmosphere of 0.2 mol% is 8.2 MPa, which is about 1.4 times higher than that (5.9 MPa) of CFRP/Al untreated.
Materials
Strong adhesion between recyclable thermoplastic (TP) polymer and carbon fiber (CF) has always be... more Strong adhesion between recyclable thermoplastic (TP) polymer and carbon fiber (CF) has always been highly sought after. Therefore, for an interlayered CF reinforced TP polypropylene (CFRTPP) composite composed of 3 sized CF plies, alternating between 4 PP sheets, designated [PP]4[CF]3, a process of activating CF plies directly on both sides with homogeneous low energy electron beam irradiation (EBI) under N2 gas, prior to lamination assembly and hot press of 4.0 MPa at 493 K for 3 min was carried out. Experimental results showed EBI dose of 43.2, 129, or 216 kGy significantly raised Charpy impact values, auc at all fracture probabilities, Pf. The 129 kGy dose appeared to be at or near optimum increasing auc 103%, 83%, and 65% at low-, median-, and high-Pf = 0.07, 0.50, and 0.93; while raising statistically lowest impact value, as at Pf = 0 calculated by 3-dimensional Weibull equation about 110%, indicating increased safety and reliability. It is assumed dangling bonds generated by ...
Materials, Apr 29, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
MATERIALS TRANSACTIONS, 2019
A new process of internal activation of carbon fiber reinforced thermoplastic polymer (CFRTP) of ... more A new process of internal activation of carbon fiber reinforced thermoplastic polymer (CFRTP) of polypropylene (PP) by applying electron beam irradiation (EBI) under oxygen (O 2)rich nitrogen gas (N 2) atmosphere to CF chopped strand matt (CSM) layers prior to assembly and hot press to strengthen the typically weak CF/thermoplastic polymers (TPs) adhesion was proposed. Samples were interlayered composite with layup of alternating PP and CF plies, [PP] 4 [CF] 3. Composite fabrication was performed by one directional hot-press under constant pressure of 4.0 MPa at 473 K for 1 min. Results showed applying an optimum 0.22 MGy-EBI under protective N 2 gas with O 2 concentrations between 200 ppm and 200,000 ppm mostly improved the bending strength (• b) while reducing strain at the bending strength (• b) apparently increasing the elasticity. The method appears to work well for the weakest samples in the data sets: at low accumulative probability P f = 0.06 by median rank method, • b was apparently improved by the 200 ppm and 2,000 ppm O 2 atmospheres. Namely, 0.22 MGy-EBI under N 2 gas atmosphere with 200 ppm to 2,000 ppm-O 2 improved • b at P f = 0.06 (57 MPa) about 21%, over that of untreated (47 MPa). Strength increase could be explained by mutual entangling of both sizing epoxy film on CF and PP with strong covalent bonding, which formation of direct CF: C:C :PP induced by EBI and oxygen assisted CF: C:O:C :PP by concentrating the O 2 gas molecules from 200 ppm to 2,000 ppm-O 2 in N 2 atmosphere, rather than weak molecular bonding CF-(H 2 O, N 2 , O 2)-PP for the untreated samples. Moreover, the action of the EBI apparently acts to clean residual H 2 O, N 2 , and O 2 to purify and activate the CF surface increasing polar group and active site density. They most likely contributed to bending strength enhancement. The 0.22 MGy-EBI in O 2-rich N 2 atmosphere appears to be a viable method to increase carbon fiber-thermoplastic polypropylene adhesion enhancing reliability and safety of the PP-CFRTP.
The Japan Institute of Metals and Materials, Feb 3, 2021
Journal of Advanced Science
Magnetostrictive materials are widely used to build actuators, sensors, and vibration energy harv... more Magnetostrictive materials are widely used to build actuators, sensors, and vibration energy harvesting devices. Generally, the interfacial adhesion between the substrate and thin films plays important roll from the practical point of view. Therefore, establishing precise techniques to evaluate the interfacial adhesion energy are quite important as basic technologies in the applications. In this study, we focused on the in-plane stress control by tuning the hydrogen content via electrochemical hydrogen loading. Effect of hydrogen absorption on Sm-Fe thin films were studied by in-situ measurement of electrochemical hydrogen loading combined with acoustic emission. The step-by-step electrochemical hydrogen loading was applied to Sm-Fe films and the electromotive force (EMF) between the Saturated Calomel Electrode (SCE) and Sm-Fe thin film in equilibrium state was measured at each hydrogen concentration. Acoustic emission (AE) measurements revealed that when hydrogen concentration over a certain value increase of AE counts. At the same time, EMF tended to increase above a certain hydrogen concentration. Delamination of the Sm-Fe film from the substrate (buckling) was also observed after electrochemical hydrogen loading technique.
Journal of Composite Materials
A new process of activating sizing film free (removed sizing) carbon fiber (SFF-CF) mats directly... more A new process of activating sizing film free (removed sizing) carbon fiber (SFF-CF) mats directly with electron beam irradiation (EBI) under oxygen-rich nitrogen gas prior to lamination assembly and hot-press was found to increase bending strength of CFRTP (CF reinforced thermoplastic polypropylene (PP)) interlayered composite composed of 3 SFF-CF mats between 4 PP sheets, [PP]4[SFF-CF]3. The hot-press fabrication was performed under 4.0 MPa at 473 K for 1 min. Experimental results showed optimal condition of 0.22 MGy-EBI under 2,000 ppm-O2-rich, protective N2 atmosphere improved bending strength, σb at all accumulative probabilities, Pf over that of untreated. This could be explained by maximum number of the strong covalent bonds of CF:C:C:PP and oxygen assisted CF:C:O:C:PP bonds adhering bare SFF-CF surface to PP, instead of the weak intermolecular bonding of CF(H2O, N2, O2)PP of untreated. The optimal concentration of O2 molecules together with the EBI probably purified the SFF-C...
Defect and Diffusion Forum, 2013
Hydrogen absorption and diffusivity in high quality ZnO crystals were investigated in this work b... more Hydrogen absorption and diffusivity in high quality ZnO crystals were investigated in this work by X-ray diffraction combined with slow positron implantation spectroscopy and electrical resistometry. ZnO crystals were covered by a thin Pd over-layer and electrochemically charged with hydrogen. It was found that absorbed hydrogen causes plastic deformation in a sub-surface region. The depth profile of hydrogen concentration introduced into the crystal was determined by nuclear reaction analysis. Enhanced hydrogen concentration was found in the sub-surface region due to excess hydrogen atoms trapped at defects introduced by plastic deformation. Hydrogen diffusion in ZnO crystals with various orientations was studied by in-situ electrical resistometry. It was found that hydrogen diffusion in the c-direction is faster than hydrogen diffusion in the a-direction most probably due to open channels existing in the wurtzite structure along the c-axis.
Journal of Alloys and Compounds, 2015
ABSTRACT Gas phase loading of nanocrystalline and epitaxial 20 nm Pd films deposited on single cr... more ABSTRACT Gas phase loading of nanocrystalline and epitaxial 20 nm Pd films deposited on single crystalline sapphire substrates was studied in this work. The nanocrystalline film was deposited at room temperature and the epitaxial film deposited at 800 °C. The nanocrystalline film suffers from in-plane compressive stress imposed by atomic peening processes. The epitaxial film exhibits tensile stress caused by the different thermal expansion coefficients of Pd and sapphire substrate. Coherent phase transition into the hydride phase was observed both for the nanocrystalline and for the epitaxial film. For both films, the lattice parameters continuously increase during the phase transition to the hydride phase. Both films exhibit enhanced hydride formation pressure compared to bulk Pd. Misfit dislocations are formed at interface between Pd film and substrate during hydrogenation. This leads to irreversible change of stress state of the films subjected to sorption and desorption cycle with hydrogen.
Scripta Materialia, 2011
ABSTRACT The hydrogenation of nanocrystalline Mg films on Si- and Pd substrates was studied by el... more ABSTRACT The hydrogenation of nanocrystalline Mg films on Si- and Pd substrates was studied by electromotive force and X-ray diffraction measurements. A strong loading current dependency of the hydrogenated volume was found. While for high current densities i > 1 × 10−6 A cm−2 only about 10 nm could be hydrogenated, about 200 nm could be reached for small current densities i < 4 × 10−7 A cm−2. For a 2.1 μm Mg film on a Pd substrate, a thickness of 1.3 μm could be hydrogenated.
Journal of Nano Research, 2013
Hydrogen interaction with defects and structural development of Pd films with various microstruct... more Hydrogen interaction with defects and structural development of Pd films with various microstructures were investigated. Nanocrystalline, polycrystalline and epitaxial Pd films were prepared and electrochemically loaded with hydrogen. Structural changes of Pd films caused by absorbed hydrogen were studied by in-situ X-ray diffraction combined with acoustic emission and measurement of electromotorical force. Development of defects during hydrogen loading was investigated by positron annihilation spectroscopy. It was found that hydrogen firstly fills open volume defects existing already in the films and subsequently it occupies also interstitial sites in Pd lattice. Absorbed hydrogen causes volume expansion, which is strongly anisotropic in thin films. This introduces high stress into the films loaded with hydrogen. Acoustic emission measurements revealed that when hydrogen-induced stress achieves a certain critical level rearrangement of misfit dislocations takes place. The stress wh...