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T.w. Clyne - One of the best experts on this subject based on the ideXlab platform.
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measurement of Interfacial Fracture Energy by single fibre push out testing and its application to the titanium silicon carbide system
Acta Materialia, 1998Co-Authors: A.f. Kalton, S.j. Howard, Jolanta Janczakrusch, T.w. ClyneAbstract:Abstract A Fracture mechanics model is presented for the advance of an Interfacial crack during push-out testing. The effects of thermal residual stresses and Interfacial frictional sliding are included. The model is based on the approach of Majumdar and Miracle (Key Eng. Mater., 1996, 116/117, 153) and leads to mathematical results which are very similar to those of Liang and Hutchinson (Mech. Mater., 1993, 14, 207). The equations presented can be used to obtain a value for the Interfacial Fracture Energy from the applied load at which a crack of known length is observed to propagate. Such information can in many cases be deduced from load–displacement data obtained during push-out testing. It is assumed that the Interfacial crack propagates from the top (loaded) face of the specimen. However, for cases where propagation occurs from the bottom face, the model can still be applied to give a lower bound on the Interfacial Fracture Energy. Experimental data are presented from push-out testing of titanium reinforced with SiC monofilaments. These data have been obtained over a range of test temperatures. This has allowed exploration of the effect of varying the residual stress state within the specimen. The experimental data have been interpreted using the analytical model. Some finite element modelling has also been carried out. It is concluded that the Interfacial Fracture Energy in these composites can be lower bounded at about 10 J m−2, or at a somewhat lower value at elevated temperature. Information is also presented about the average shear stress at which Interfacial sliding occurs. This is strongly dependent on the (thermal) radial clamping stress and falls from about 150 MPa at room temperature to about 10 MPa at 800°C.
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Measurement of Interfacial Fracture Energy by single fibre push-out testing and its application to the titanium–silicon carbide system
Acta Materialia, 1998Co-Authors: A.f. Kalton, S.j. Howard, Jolanta Janczak-rusch, T.w. ClyneAbstract:Abstract A Fracture mechanics model is presented for the advance of an Interfacial crack during push-out testing. The effects of thermal residual stresses and Interfacial frictional sliding are included. The model is based on the approach of Majumdar and Miracle (Key Eng. Mater., 1996, 116/117, 153) and leads to mathematical results which are very similar to those of Liang and Hutchinson (Mech. Mater., 1993, 14, 207). The equations presented can be used to obtain a value for the Interfacial Fracture Energy from the applied load at which a crack of known length is observed to propagate. Such information can in many cases be deduced from load–displacement data obtained during push-out testing. It is assumed that the Interfacial crack propagates from the top (loaded) face of the specimen. However, for cases where propagation occurs from the bottom face, the model can still be applied to give a lower bound on the Interfacial Fracture Energy. Experimental data are presented from push-out testing of titanium reinforced with SiC monofilaments. These data have been obtained over a range of test temperatures. This has allowed exploration of the effect of varying the residual stress state within the specimen. The experimental data have been interpreted using the analytical model. Some finite element modelling has also been carried out. It is concluded that the Interfacial Fracture Energy in these composites can be lower bounded at about 10 J m−2, or at a somewhat lower value at elevated temperature. Information is also presented about the average shear stress at which Interfacial sliding occurs. This is strongly dependent on the (thermal) radial clamping stress and falls from about 150 MPa at room temperature to about 10 MPa at 800°C.
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Stiffness, residual stresses and Interfacial Fracture Energy of diamond films on titanium
Diamond and Related Materials, 1997Co-Authors: X.l. Peng, Y.c. Tsui, T.w. ClyneAbstract:Abstract Diamond films were deposited on tungsten and titanium substrates using hot filament CVD, with methane concentrations ranging from 0.3 to 1.5% and substrate temperatures ranging from 725 to 875°C. The deposited diamond films were characterised by X-ray diffraction and SEM. Young's moduli of the diamond films were determined by the cantilever beam bending method. In the range studied, methane concentration had a strong influence on the Young's modulus, but deposition temperature did not. Values ranged from 532 GPa for 1.5% methane to 954 GPa for 0.5% methane. Intrinsic (deposition) stresses were calculated using measured Young's modulus values and experimental data for the net curvature changes on deposition of the films. Account was taken of the curvature changes owing to differential thermal contraction during post-deposition cooling. The intrinsic stress was found to range from + 0.2 to 0.9 GPa. The value first increased and then decreased as the methane content was raised. A similar trend was observed on raising the deposition temperature. These effects are explained on the basis of the expected levels of sp 2 carbon and carbon vacancies. By monitoring the temperature at which thick films spontaneously debonded during cooling, and using the measured intrinsic stress levels, the Interfacial Fracture Energy between diamond films and titanium substrates (commercial purity and Ti-6Al-4V) was measured. The values obtained were all in the vicinity of about 70 J m −2 . Substrate composition and deposition temperature apparently have little effect on the Interfacial toughness for the cases studied.
John W. Halloran - One of the best experts on this subject based on the ideXlab platform.
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influence of microstructure and temperature on the Interfacial Fracture Energy of silicon nitride boron nitride fibrous monolithic ceramics
Journal of the American Ceramic Society, 1999Co-Authors: Rodney W. Trice, John W. HalloranAbstract:The microstructure and Interfacial Fracture Energy of silicon nitride/boron nitride fibrous monoliths, GammaBN, were determined as a function of starting silicon nitride composition and temperature using the method described by Charalambides. The glassy phase created by the sintering aids added to the silicon nitride cells was shown to migrate into the boron nitride cell boundaries during hot-pressing. The amount of glassy phase in the boron nitride cell boundaries was shown to strongly influence GammaBN at room temperature, increasing the Fracture Energy with increasing amounts of glass. Similar trends in the Interfacial Fracture Energy as a function of temperature were demonstrated by both compositions of fibrous monoliths, with a large peak in GammaBN observed over a narrow temperature range. For silicon nitride cells densified with 6 wt% yttria and 2 wt% alumina, the room-temperature Interfacial Fracture Energy was 37 J/m2, remaining constant through 950°C. A sharp increase in GammaBN, to 60 J/m2, was observed between 1000° and 1050°C. This increase was attributed to interactions of the crack tip with the glassy phase in the boron nitride cell boundary. Measurements at 1075°C indicated a marked decrease in GammaBN to 39 J/m2. The Interfacial Fracture Energy decreased with increasing temperature in the 1200° to 1300°C regime, plateauing between 17 to 20 J/m2. A crack propagation model based on linkup of existing microcracks and peeling/cleaving boron nitride has been proposed.
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Influence of Microstructure and Temperature on the Interfacial Fracture Energy of Silicon Nitride/Boron Nitride Fibrous Monolithic Ceramics
Journal of the American Ceramic Society, 1999Co-Authors: Rodney W. Trice, John W. HalloranAbstract:The microstructure and Interfacial Fracture Energy of silicon nitride/boron nitride fibrous monoliths, GammaBN, were determined as a function of starting silicon nitride composition and temperature using the method described by Charalambides. The glassy phase created by the sintering aids added to the silicon nitride cells was shown to migrate into the boron nitride cell boundaries during hot-pressing. The amount of glassy phase in the boron nitride cell boundaries was shown to strongly influence GammaBN at room temperature, increasing the Fracture Energy with increasing amounts of glass. Similar trends in the Interfacial Fracture Energy as a function of temperature were demonstrated by both compositions of fibrous monoliths, with a large peak in GammaBN observed over a narrow temperature range. For silicon nitride cells densified with 6 wt% yttria and 2 wt% alumina, the room-temperature Interfacial Fracture Energy was 37 J/m2, remaining constant through 950°C. A sharp increase in GammaBN, to 60 J/m2, was observed between 1000° and 1050°C. This increase was attributed to interactions of the crack tip with the glassy phase in the boron nitride cell boundary. Measurements at 1075°C indicated a marked decrease in GammaBN to 39 J/m2. The Interfacial Fracture Energy decreased with increasing temperature in the 1200° to 1300°C regime, plateauing between 17 to 20 J/m2. A crack propagation model based on linkup of existing microcracks and peeling/cleaving boron nitride has been proposed.
Rodney W. Trice - One of the best experts on this subject based on the ideXlab platform.
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influence of microstructure and temperature on the Interfacial Fracture Energy of silicon nitride boron nitride fibrous monolithic ceramics
Journal of the American Ceramic Society, 1999Co-Authors: Rodney W. Trice, John W. HalloranAbstract:The microstructure and Interfacial Fracture Energy of silicon nitride/boron nitride fibrous monoliths, GammaBN, were determined as a function of starting silicon nitride composition and temperature using the method described by Charalambides. The glassy phase created by the sintering aids added to the silicon nitride cells was shown to migrate into the boron nitride cell boundaries during hot-pressing. The amount of glassy phase in the boron nitride cell boundaries was shown to strongly influence GammaBN at room temperature, increasing the Fracture Energy with increasing amounts of glass. Similar trends in the Interfacial Fracture Energy as a function of temperature were demonstrated by both compositions of fibrous monoliths, with a large peak in GammaBN observed over a narrow temperature range. For silicon nitride cells densified with 6 wt% yttria and 2 wt% alumina, the room-temperature Interfacial Fracture Energy was 37 J/m2, remaining constant through 950°C. A sharp increase in GammaBN, to 60 J/m2, was observed between 1000° and 1050°C. This increase was attributed to interactions of the crack tip with the glassy phase in the boron nitride cell boundary. Measurements at 1075°C indicated a marked decrease in GammaBN to 39 J/m2. The Interfacial Fracture Energy decreased with increasing temperature in the 1200° to 1300°C regime, plateauing between 17 to 20 J/m2. A crack propagation model based on linkup of existing microcracks and peeling/cleaving boron nitride has been proposed.
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Influence of Microstructure and Temperature on the Interfacial Fracture Energy of Silicon Nitride/Boron Nitride Fibrous Monolithic Ceramics
Journal of the American Ceramic Society, 1999Co-Authors: Rodney W. Trice, John W. HalloranAbstract:The microstructure and Interfacial Fracture Energy of silicon nitride/boron nitride fibrous monoliths, GammaBN, were determined as a function of starting silicon nitride composition and temperature using the method described by Charalambides. The glassy phase created by the sintering aids added to the silicon nitride cells was shown to migrate into the boron nitride cell boundaries during hot-pressing. The amount of glassy phase in the boron nitride cell boundaries was shown to strongly influence GammaBN at room temperature, increasing the Fracture Energy with increasing amounts of glass. Similar trends in the Interfacial Fracture Energy as a function of temperature were demonstrated by both compositions of fibrous monoliths, with a large peak in GammaBN observed over a narrow temperature range. For silicon nitride cells densified with 6 wt% yttria and 2 wt% alumina, the room-temperature Interfacial Fracture Energy was 37 J/m2, remaining constant through 950°C. A sharp increase in GammaBN, to 60 J/m2, was observed between 1000° and 1050°C. This increase was attributed to interactions of the crack tip with the glassy phase in the boron nitride cell boundary. Measurements at 1075°C indicated a marked decrease in GammaBN to 39 J/m2. The Interfacial Fracture Energy decreased with increasing temperature in the 1200° to 1300°C regime, plateauing between 17 to 20 J/m2. A crack propagation model based on linkup of existing microcracks and peeling/cleaving boron nitride has been proposed.
Taeksoo Kim - One of the best experts on this subject based on the ideXlab platform.
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Cooptimization of Adhesion and Power Conversion Efficiency of Organic Solar Cells by Controlling Surface Energy of Buffer Layers.
ACS applied materials & interfaces, 2017Co-Authors: Inhwa Lee, Jonghyeon Noh, Jung-yong Lee, Taeksoo KimAbstract:Here, we demonstrate the cooptimization of the Interfacial Fracture Energy and power conversion efficiency (PCE) of poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT)-based organic solar cells (OSCs) by surface treatments of the buffer layer. The investigated surface treatments of the buffer layer simultaneously changed the crack path and Interfacial Fracture Energy of OSCs under mechanical stress and the work function of the buffer layer. To investigate the effects of surface treatments, the work of adhesion values were calculated and matched with the experimental results based on the Owens–Wendt model. Subsequently, we fabricated OSCs on surface-treated buffer layers. In particular, ZnO layers treated with poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) simultaneously satisfied the high mechanical reliability and PCE of OSCs by achieving high work of adhesion and optimized work function.
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Enhancing Adhesion of Screen‐Printed Silver Nanopaste Films
Advanced Materials Interfaces, 2015Co-Authors: Jae-han Kim, Kwang-seok Kim, Kr Jang, Seung-boo Jung, Taeksoo KimAbstract:The Interfacial Fracture Energy of screen-printed silver nanopaste films is quantitatively measured, and the fundamental adhesion mechanism is investigated. It is found that the Interfacial Fracture Energy at the Ag film/silicon substrate interface is critically affected by the sintering condition. The sintering temperature tunes the Interfacial surface morphology of Ag films and the amount of organic residues at the interface. These factors determine the degree of Interfacial toughening between the Ag film and the substrate, which directly affects the adhesion properties. The increased surface roughness of the Ag film with sufficient organic residues leads to a larger Interfacial toughening at the film/substrate interface, and subsequently to an enhanced Interfacial Fracture Energy of screen-printed Ag nanopaste films.
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Effects of hydrophobic agent content in macro-porous substrates on the Fracture behavior of the gas diffusion layer for proton exchange membrane fuel cells
Journal of Power Sources, 2014Co-Authors: Sanwi Kim, Byeong-heon Jeong, Bo Ki Hong, Taeksoo KimAbstract:Abstract Although the adhesion between the macro-porous substrate (MPS) and micro-porous layer (MPL) of a gas diffusion layer (GDL) is a critical factor that affects the reliability and durability of proton exchange membrane fuel cells, systematic studies quantifying the Interfacial Fracture Energy of GDL have not yet been reported. Therefore, in this study, the Interfacial Fracture Energy of GDLs with different contents of hydrophobic agents in the MPS is quantitatively measured. GDL samples with 0, 5, 10, and 20 wt% of hydrophobic agent content are tested using double cantilever beam Fracture mechanics tests. It is observed that the Interfacial Fracture Energy of the GDLs increases as the content of hydrophobic agent increases, due to more favorable interactions between the hydrophobic agents of the MPL and MPS. Optical microscope, scanning electron microscope, and Energy-dispersive X-ray spectroscope analyses are performed on the bare and delaminated surfaces in order to investigate the mechanism of the Interfacial Fracture Energy increase of the GDLs.
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Interfacial toughening of solution processed Ag nanoparticle thin films by organic residuals
Nanotechnology, 2012Co-Authors: Inhwa Lee, Sanghyeok Kim, Jeonghoon Yun, Inkyu Park, Taeksoo KimAbstract:Reliable integration of solution processed nanoparticle thin films for next generation low-cost flexible electronics is limited by mechanical damage in the form of delamination and cracking of the films, which has not been investigated quantitatively or systematically. Here, we directly measured the Interfacial Fracture Energy of silver nanoparticle thin films by using double cantilever beam Fracture mechanics testing. It was demonstrated that the thermal annealing temperature and period affect the Interfacial Fracture Energy. Also it was found that the Interfacial Fracture resistance can be maximized with optimized annealing conditions by the formation of organic residual bridges during the annealing process.
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annealing induced Interfacial Fracture Energy of silver nanoparticle films on substrate for reliable printed electronics
The Electrochemical Society Meeting, 2012Co-Authors: Inhwa Lee, Sanghyeok Kim, Jeonghoon Yun, Inkyu Park, Taeksoo KimAbstract:Solution-based printing methods without conventional microfabrication processes attract a significant attention as the next generation manufacturing processes. Therefore, in recent years, various solutionbased printing methods such as inkjet, gravure/flexography, and nanoimprinting have been developed for micro/nano-scale patterning of solutionbased metal inks. Nanoparticle-based ink solutions are typically used as the materials for the printed electronics fabrication process. However, flexible electronics have a fatal problem such as large deformation caused by severe mechanical loading and mismatch of coefficients of thermal expansion (CTE) for metal thin film and polymer substrates by temperature swing in spite of importance of mechanical adhesion of thin films to substrate. These result in the delamination and cracking of thin films from flexible substrates but quantitative research related to the adhesion of nanoparticle-based thin films has not been conducted so far to the best knowledge of the authors. In the present study, we demonstrated how thermal annealing temperature and period affect the Interfacial Fracture Energy and found the Interfacial Fracture resistance can be maximized with optimized annealing condition by organic residuals. We further demonstrate that the organic residuals segregated onto the substrate during annealing process and they formed organic bridging which is believed to strengthen the interface between silver nanoparticle film and substrate.
A.f. Kalton - One of the best experts on this subject based on the ideXlab platform.
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measurement of Interfacial Fracture Energy by single fibre push out testing and its application to the titanium silicon carbide system
Acta Materialia, 1998Co-Authors: A.f. Kalton, S.j. Howard, Jolanta Janczakrusch, T.w. ClyneAbstract:Abstract A Fracture mechanics model is presented for the advance of an Interfacial crack during push-out testing. The effects of thermal residual stresses and Interfacial frictional sliding are included. The model is based on the approach of Majumdar and Miracle (Key Eng. Mater., 1996, 116/117, 153) and leads to mathematical results which are very similar to those of Liang and Hutchinson (Mech. Mater., 1993, 14, 207). The equations presented can be used to obtain a value for the Interfacial Fracture Energy from the applied load at which a crack of known length is observed to propagate. Such information can in many cases be deduced from load–displacement data obtained during push-out testing. It is assumed that the Interfacial crack propagates from the top (loaded) face of the specimen. However, for cases where propagation occurs from the bottom face, the model can still be applied to give a lower bound on the Interfacial Fracture Energy. Experimental data are presented from push-out testing of titanium reinforced with SiC monofilaments. These data have been obtained over a range of test temperatures. This has allowed exploration of the effect of varying the residual stress state within the specimen. The experimental data have been interpreted using the analytical model. Some finite element modelling has also been carried out. It is concluded that the Interfacial Fracture Energy in these composites can be lower bounded at about 10 J m−2, or at a somewhat lower value at elevated temperature. Information is also presented about the average shear stress at which Interfacial sliding occurs. This is strongly dependent on the (thermal) radial clamping stress and falls from about 150 MPa at room temperature to about 10 MPa at 800°C.
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Measurement of Interfacial Fracture Energy by single fibre push-out testing and its application to the titanium–silicon carbide system
Acta Materialia, 1998Co-Authors: A.f. Kalton, S.j. Howard, Jolanta Janczak-rusch, T.w. ClyneAbstract:Abstract A Fracture mechanics model is presented for the advance of an Interfacial crack during push-out testing. The effects of thermal residual stresses and Interfacial frictional sliding are included. The model is based on the approach of Majumdar and Miracle (Key Eng. Mater., 1996, 116/117, 153) and leads to mathematical results which are very similar to those of Liang and Hutchinson (Mech. Mater., 1993, 14, 207). The equations presented can be used to obtain a value for the Interfacial Fracture Energy from the applied load at which a crack of known length is observed to propagate. Such information can in many cases be deduced from load–displacement data obtained during push-out testing. It is assumed that the Interfacial crack propagates from the top (loaded) face of the specimen. However, for cases where propagation occurs from the bottom face, the model can still be applied to give a lower bound on the Interfacial Fracture Energy. Experimental data are presented from push-out testing of titanium reinforced with SiC monofilaments. These data have been obtained over a range of test temperatures. This has allowed exploration of the effect of varying the residual stress state within the specimen. The experimental data have been interpreted using the analytical model. Some finite element modelling has also been carried out. It is concluded that the Interfacial Fracture Energy in these composites can be lower bounded at about 10 J m−2, or at a somewhat lower value at elevated temperature. Information is also presented about the average shear stress at which Interfacial sliding occurs. This is strongly dependent on the (thermal) radial clamping stress and falls from about 150 MPa at room temperature to about 10 MPa at 800°C.