The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform
George D Quinn - One of the best experts on this subject based on the ideXlab platform.
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dye impregnation method for revealing machining crack geometry
Journal of the American Ceramic Society, 2001Co-Authors: Wataru Kanematsu, Mutsuo Sando, Ryna B Marinenko, L.k. Ives, George D QuinnAbstract:The palladium nitrate dye penetrant method for revealing surface microcracks was investigated and applied to display the geometry of machining cracks in silicon Nitride flexure test specimens. This method used elemental mapping with an electron probe microanalyzer to detect the presence of the dye and, thereby, display the crack geometry. A previously used bending method and a method developed in this study in which the specimen surface is exposed to the dye under pressure were used to facilitate dye penetration. Prior to applying the method to study machining cracks, carefully controlled Knoop indentation cracks introduced into flexure specimens were used to verify penetration of the dye to the crack tip. During these experiments it was found that the palladium nitrate dye resulted in a reduction in flexure strength, which, on further study, was attributed to the dilute nitric acid solution used to formulate the dye. Exposure to carbon tetrafluoride plasma etching prior to applying the pressurized dye method also resulted in a detectable decrease in flexure strength. Although there was clear evidence that exposure to dye and plasma etching resulted in a small but measurable decrease in flexure strength for the silicon Nitride Material studied, there was no detectable change in observed crack geometry. The reduction in flexure strength was apparently caused by a decrease in resistance to initiate crack propagation. It was concluded that the palladium nitrate dye method is an accurate and useful means for determining the geometry of small, otherwise difficult to observe surface microcracks. Nevertheless, caution should be exercised with the use of this method during strength measurements. When applied to machining cracks, the complex nature of these shallow, elongated, sometimes joining cracks was unambiguously revealed.
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dye impregnation method for revealing machining crack geometry
Journal of the American Ceramic Society, 2001Co-Authors: Wataru Kanematsu, Mutsuo Sando, Ryna B Marinenko, L.k. Ives, George D QuinnAbstract:The palladium nitrate dye penetrant method for revealing surface microcracks was investigated and applied to display the geometry of machining cracks in silicon Nitride flexure test specimens. This method used elemental mapping with an electron probe microanalyzer to detect the presence of the dye and, thereby, display the crack geometry. A previously used bending method and a method developed in this study in which the specimen surface is exposed to the dye under pressure were used to facilitate dye penetration. Prior to applying the method to study machining cracks, carefully controlled Knoop indentation cracks introduced into flexure specimens were used to verify penetration of the dye to the crack tip. During these experiments it was found that the palladium nitrate dye resulted in a reduction in flexure strength, which, on further study, was attributed to the dilute nitric acid solution used to formulate the dye. Exposure to carbon tetrafluoride plasma etching prior to applying the pressurized dye method also resulted in a detectable decrease in flexure strength. Although there was clear evidence that exposure to dye and plasma etching resulted in a small but measurable decrease in flexure strength for the silicon Nitride Material studied, there was no detectable change in observed crack geometry. The reduction in flexure strength was apparently caused by a decrease in resistance to initiate crack propagation. It was concluded that the palladium nitrate dye method is an accurate and useful means for determining the geometry of small, otherwise difficult to observe surface microcracks. Nevertheless, caution should be exercised with the use of this method during strength measurements. When applied to machining cracks, the complex nature of these shallow, elongated, sometimes joining cracks was unambiguously revealed.
Wataru Kanematsu - One of the best experts on this subject based on the ideXlab platform.
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dye impregnation method for revealing machining crack geometry
Journal of the American Ceramic Society, 2001Co-Authors: Wataru Kanematsu, Mutsuo Sando, Ryna B Marinenko, L.k. Ives, George D QuinnAbstract:The palladium nitrate dye penetrant method for revealing surface microcracks was investigated and applied to display the geometry of machining cracks in silicon Nitride flexure test specimens. This method used elemental mapping with an electron probe microanalyzer to detect the presence of the dye and, thereby, display the crack geometry. A previously used bending method and a method developed in this study in which the specimen surface is exposed to the dye under pressure were used to facilitate dye penetration. Prior to applying the method to study machining cracks, carefully controlled Knoop indentation cracks introduced into flexure specimens were used to verify penetration of the dye to the crack tip. During these experiments it was found that the palladium nitrate dye resulted in a reduction in flexure strength, which, on further study, was attributed to the dilute nitric acid solution used to formulate the dye. Exposure to carbon tetrafluoride plasma etching prior to applying the pressurized dye method also resulted in a detectable decrease in flexure strength. Although there was clear evidence that exposure to dye and plasma etching resulted in a small but measurable decrease in flexure strength for the silicon Nitride Material studied, there was no detectable change in observed crack geometry. The reduction in flexure strength was apparently caused by a decrease in resistance to initiate crack propagation. It was concluded that the palladium nitrate dye method is an accurate and useful means for determining the geometry of small, otherwise difficult to observe surface microcracks. Nevertheless, caution should be exercised with the use of this method during strength measurements. When applied to machining cracks, the complex nature of these shallow, elongated, sometimes joining cracks was unambiguously revealed.
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dye impregnation method for revealing machining crack geometry
Journal of the American Ceramic Society, 2001Co-Authors: Wataru Kanematsu, Mutsuo Sando, Ryna B Marinenko, L.k. Ives, George D QuinnAbstract:The palladium nitrate dye penetrant method for revealing surface microcracks was investigated and applied to display the geometry of machining cracks in silicon Nitride flexure test specimens. This method used elemental mapping with an electron probe microanalyzer to detect the presence of the dye and, thereby, display the crack geometry. A previously used bending method and a method developed in this study in which the specimen surface is exposed to the dye under pressure were used to facilitate dye penetration. Prior to applying the method to study machining cracks, carefully controlled Knoop indentation cracks introduced into flexure specimens were used to verify penetration of the dye to the crack tip. During these experiments it was found that the palladium nitrate dye resulted in a reduction in flexure strength, which, on further study, was attributed to the dilute nitric acid solution used to formulate the dye. Exposure to carbon tetrafluoride plasma etching prior to applying the pressurized dye method also resulted in a detectable decrease in flexure strength. Although there was clear evidence that exposure to dye and plasma etching resulted in a small but measurable decrease in flexure strength for the silicon Nitride Material studied, there was no detectable change in observed crack geometry. The reduction in flexure strength was apparently caused by a decrease in resistance to initiate crack propagation. It was concluded that the palladium nitrate dye method is an accurate and useful means for determining the geometry of small, otherwise difficult to observe surface microcracks. Nevertheless, caution should be exercised with the use of this method during strength measurements. When applied to machining cracks, the complex nature of these shallow, elongated, sometimes joining cracks was unambiguously revealed.
Shouhua Feng - One of the best experts on this subject based on the ideXlab platform.
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a graphene like oxygenated carbon Nitride Material for improved cycle life lithium sulfur batteries
Nano Letters, 2015Co-Authors: Wanfei Li, Limei Duan, Xin Li, Lei Ji, Zhibin Geng, Keke Huang, Luhua Lu, Lisha Zhou, Wei Chen, Shouhua FengAbstract:Novel sulfur (S) anchoring Materials and the corresponding mechanisms for suppressing capacity fading are urgently needed to advance the performance of Li/S batteries. Here, we designed and synthesized a graphene-like oxygenated carbon Nitride (OCN) host Material that contains tens of micrometer scaled two-dimensional (2D) rippled sheets, micromesopores, and oxygen heteroatoms. N content can reach as high as 20.49 wt %. A sustainable approach of one-step self-supporting solid-state pyrolysis (OSSP) was developed for the low-cost and large-scale production of OCN. The urea in solid sources not only provides self-supporting atmospheres but also produces graphitic carbon Nitride (g-C3N4) working as 2D layered templates. The S/OCN cathode can deliver a high specific capacity of 1407.6 mA h g–1 at C/20 rate with 84% S utilization and retain improved reversible capacity during long-term cycles at high current density. The increasing micropores, graphitic N, ether, and carboxylic O at the large sized OCN sheet f...
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a graphene like oxygenated carbon Nitride Material for improved cycle life lithium sulfur batteries
Nano Letters, 2015Co-Authors: Limei Duan, Zhibin Geng, Keke Huang, Lisha Zhou, Wei Chen, Jinghai Liu, Zongrui Liu, Liwei Liu, Shouhua FengAbstract:Novel sulfur (S) anchoring Materials and the corresponding mechanisms for suppressing capacity fading are urgently needed to advance the performance of Li/S batteries. Here, we designed and synthesized a graphene-like oxygenated carbon Nitride (OCN) host Material that contains tens of micrometer scaled two-dimensional (2D) rippled sheets, micromesopores, and oxygen heteroatoms. N content can reach as high as 20.49 wt %. A sustainable approach of one-step self-supporting solid-state pyrolysis (OSSP) was developed for the low-cost and large-scale production of OCN. The urea in solid sources not only provides self-supporting atmospheres but also produces graphitic carbon Nitride (g-C3N4) working as 2D layered templates. The S/OCN cathode can deliver a high specific capacity of 1407.6 mA h g(-1) at C/20 rate with 84% S utilization and retain improved reversible capacity during long-term cycles at high current density. The increasing micropores, graphitic N, ether, and carboxylic O at the large sized OCN sheet favor S utilization and trapping for polysulfides.
Dariya Dontsova - One of the best experts on this subject based on the ideXlab platform.
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potassium poly heptazine imides from aminotetrazoles shifting band gaps of carbon Nitride like Materials for more efficient solar hydrogen and oxygen evolution
Chemcatchem, 2017Co-Authors: Aleksandr Savateev, Sergey Pronkin, Jan Dirk Epping, Marc Georg Willinger, Christian M Wolff, Dieter Neher, Markus Antonietti, Dariya DontsovaAbstract:Potassium poly(heptazine imide) (PHI) is a photocatalytically active carbon Nitride Material that was recently prepared from substituted 1,2,4-triazoles. Here we show that the more acidic precursors, such as commercially available 5-aminotetrazole, upon pyrolysis in LiCl/KCl salt melt yield PHI with the greatly improved structural order and thermodynamic stability. Tetrazole-derived PHIs feature long range crystallinities and unconventionally small layer-stacking distances leading to the altered electronic band structures as shown by Mott-Schottky analyses. Under the optimized synthesis conditions, visible light driven hydrogen evolution rates reach twice the rate provided by the previous golden standard, mesoporous graphitic carbon Nitride having much higher surface area. More interestingly, the up to 0.7 V higher valence band potential of crystalline PHI compared to the ordinary carbon Nitrides makes it an efficient water oxidation photocatalyst which works even in the absence of any metal-based co-catalysts under visible light. To our knowledge, this is the first case of a metal free oxygen liberation from water as such.
Aleksandr Savateev - One of the best experts on this subject based on the ideXlab platform.
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potassium poly heptazine imide transition metal free solid state triplet sensitizer in cascade energy transfer and 3 2 cycloadditions
Angewandte Chemie, 2020Co-Authors: Aleksandr Savateev, Nadezda V Tarakina, Volker Strauss, Tanveer Hussain, Katharina Ten Brummelhuis, Jose Manuel Sanchez Vadillo, Yevheniia Markushyna, Stefano Mazzanti, A P Tyutyunnik, Ralf WalczakAbstract:Polymeric carbon Nitride Materials have been used in numerous light-to-energy conversion applications ranging from photocatalysis to optoelectronics. For a new application and modelling, we first refined the crystal structure of potassium poly(heptazine imide) (K-PHI)-a benchmark carbon Nitride Material in photocatalysis-by means of X-ray powder diffraction and transmission electron microscopy. Using the crystal structure of K-PHI, periodic DFT calculations were performed to calculate the density-of-states (DOS) and localize intra band states (IBS). IBS were found to be responsible for the enhanced K-PHI absorption in the near IR region, to serve as electron traps, and to be useful in energy transfer reactions. Once excited with visible light, carbon Nitrides, in addition to the direct recombination, can also undergo singlet-triplet intersystem crossing. We utilized the K-PHI centered triplet excited states to trigger a cascade of energy transfer reactions and, in turn, to sensitize, for example, singlet oxygen (1 O2 ) as a starting point to synthesis up to 25 different N-rich heterocycles.
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potassium poly heptazine imides from aminotetrazoles shifting band gaps of carbon Nitride like Materials for more efficient solar hydrogen and oxygen evolution
Chemcatchem, 2017Co-Authors: Aleksandr Savateev, Sergey Pronkin, Jan Dirk Epping, Marc Georg Willinger, Christian M Wolff, Dieter Neher, Markus Antonietti, Dariya DontsovaAbstract:Potassium poly(heptazine imide) (PHI) is a photocatalytically active carbon Nitride Material that was recently prepared from substituted 1,2,4-triazoles. Here we show that the more acidic precursors, such as commercially available 5-aminotetrazole, upon pyrolysis in LiCl/KCl salt melt yield PHI with the greatly improved structural order and thermodynamic stability. Tetrazole-derived PHIs feature long range crystallinities and unconventionally small layer-stacking distances leading to the altered electronic band structures as shown by Mott-Schottky analyses. Under the optimized synthesis conditions, visible light driven hydrogen evolution rates reach twice the rate provided by the previous golden standard, mesoporous graphitic carbon Nitride having much higher surface area. More interestingly, the up to 0.7 V higher valence band potential of crystalline PHI compared to the ordinary carbon Nitrides makes it an efficient water oxidation photocatalyst which works even in the absence of any metal-based co-catalysts under visible light. To our knowledge, this is the first case of a metal free oxygen liberation from water as such.