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Sung R. Choi - One of the best experts on this subject based on the ideXlab platform.

  • Foreign Object Damage in Gas-Turbine Grade Silicon Nitrides by Silicon Nitride Ball Projectiles
    Volume 1: Aircraft Engine; Ceramics; Coal Biomass and Alternative Fuels; Controls Diagnostics and Instrumentation; Education; Electric Power; Awards a, 2009
    Co-Authors: Sung R. Choi
    Abstract:

    Foreign object damage (FOD) behavior of two gas-turbine grade Silicon Nitrides (AS800 and SN282) was determined with a considerable sample size at ambient temperature using impact velocities ranging from 50 to 225 m/s by 1.59-mm diameter Silicon nitride ball projectiles. The degree of impact damage as well as of post-impact strength degradation increased with increasing impact velocity, and was greater in SN282 than in AS800 Silicon nitride. The critical impact velocity in which target specimens fractured catastrophically was remarkably low: about 200 and 130 m/s, respectively, for AS800 and SN282. The difference in the critical impact velocity and impact damage between the two target Silicon Nitrides was attributed to the fracture toughness of the target materials. The FOD by Silicon nitride projectiles was significantly greater than that by steel ball projectiles. Prediction of impact force was made based on a yield model and compared with the conventional Hertzian contact-stress model.

  • foreign object damage of two gas turbine grade Silicon Nitrides at ambient temperature
    26th Annual Conference on Composites Advanced Ceramics Materials and Structures: A: Ceramic Engineering and Science Proceedings Volume 23 Issue 3, 2008
    Co-Authors: Sung R. Choi, Michael J Pereira, Lesley A Janosik, Ramakrishna T Bhatt
    Abstract:

    Foreign object damage (FOD) behavior of two commercially available gas-turbine grade Silicon Nitrides (AS800 and SN282) was determined at ambient temperature through extensive strength testing of flexure test specimens impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 220 to 440 m/s. AS800 Silicon nitride exhibited a greater FOD resistance over SN282, primarily due to its greater value of fracture toughness (K IC ). This key factor (K IC ) affecting FOD resistance was further evidenced by the indentation strength response of both materials as well as by a quasi-static phenomenological impact model. The damage generated by projectile impact seemed to be in the forms of well- or ill-developed cone cracks and of lateral cracks.

  • Foreign object damage in disks of gas-turbine-grade Silicon Nitrides by steel ball projectiles at ambient temperature
    Journal of Materials Science, 2004
    Co-Authors: Sung R. Choi, Lesley A Janosik, J. M. Pereira, Ramakrishna T Bhatt
    Abstract:

    Foreign object damage (FOD) behavior of two commercial gas-turbine-grade Silicon Nitrides, AS800, SN282, was determined at ambient temperature through postimpact strength testing of target disks impacted by steel ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 Silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness ( K _Ic). The critical impact velocity V _c for which the corresponding postimpact strength was the lowest was V _c ≈ 440, 300 m/s for AS800, SN282, respectively. A unique lower strength regime was typified for both Silicon Nitrides depending on impact velocity, was attributed to significant radial cracking. The damage generated by projectile impact was typically in the form of ring, radial, cone cracks with their severity, combination being dependent on impact velocity. Unlike the thick (3 mm) flexure bar target specimens used in previous studies, the thin (2 mm) disk target specimens exhibited a unique back-side radial cracking on the reverse side just beneath the impact sites at, above impact velocities of 160 m/s for SN282, 220 m/s for AS800.

  • foreign object damage in flexure bars of two gas turbine grade Silicon Nitrides
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004
    Co-Authors: Sung R. Choi, Michael J Pereira, Lesley A Janosik, Ramakrishna T Bhatt
    Abstract:

    Abstract Foreign object damage (FOD) behavior of two commercial gas-turbine grade Silicon Nitrides, AS800 and SN282, was determined at ambient temperature through strength testing of flexure test specimens impacted by steel ball projectiles with a diameter of 1.59 mm in a velocity range from 220 to 440 m/s. AS800 Silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness ( K Ic ). The use of an additional equiaxed, fine-grained Silicon nitride (NC132) showed that fracture toughness was a key material parameter affecting FOD resistance. The observed damages generated by projectile impact were typically in the forms of well- or ill-developed ring and cone cracks with little presence of radial cracks.

  • foreign object damage of two gas turbine grade Silicon Nitrides in a thin disk configuration
    ASME Turbo Expo 2003 collocated with the 2003 International Joint Power Generation Conference, 2003
    Co-Authors: Sung R. Choi, Michael J Pereira, Lesley A Janosik, Ramakrishna T Bhatt
    Abstract:

    Foreign object damage (FOD) behavior of two commercial gas-turbine grade Silicon Nitrides, AS800 and SN282, was determined at ambient temperature through post-impact strength testing for thin disks impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 Silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (KIC ). The critical impact velocity in which the corresponding post-impact strength yielded the lowest value was Vc ≈ 440 and 300 m/s for AS800 and SN282, respectively. A unique lower-strength regime was typified for both Silicon Nitrides depending on impact velocity, attributed to significant radial cracking. The damages generated by projectile impact were typically in the forms of ring, radial, and cone cracks with their severity and combination being dependent on impact velocity. Unlike thick (3 mm) flexure bar specimens used in the previous studies, thin (2 mm) disk target specimens exhibited a unique backside radial cracking occurring on the reverse side just beneath the impact sites at and above impact velocity of 160 and 220 m/s for SN282 and AS800, respectively.Copyright © 2003 by ASME

Hisanori Yamane - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis, Crystal Structure, and Photoluminescence of the Boron-Aluminum-Silicon Nitride Phosphor Sr3BAl5Si9N20:Eu.
    Inorganic Chemistry, 2018
    Co-Authors: Fumitaka Yoshimura, Hisanori Yamane
    Abstract:

    Single crystals of new boron–aluminum–Silicon Nitrides, Sr3BAl5Si9N20 and Sr2.91Eu0.09BAl5Si9N20, were synthesized by heating binary nitride mixtures at 2030 °C under a N2 pressure of 0.85 MPa. The X-ray diffraction spots from single crystals of these two compounds were indexed with the trigonal cell parameters a = 22.7406(8) A, c = 5.7066(2) A and a = 22.7439(8) A, c = 5.7050(2) A, respectively, and the crystal structures were determined to have the space group P3c1, with B atoms situated at planar 3-fold-coordinated N sites. A three-dimensional framework structure is constructed for these materials based on the sharing of N atoms of Al/Si–N4 tetrahedra and B–N3 triangles. In this framework, Sr/Eu atoms are located at three sites, surrounded by 10 N atoms. Single crystals of Sr2.91Eu0.09BAl5Si9N20 emitted yellow light with a peak wavelength of 565 nm and a full width at half-maximum of 106 nm under 450 nm light irradiation. The emission intensity of these crystals at 200 °C was found to be 12% of the int...

  • Synthesis, Crystal Structure, and Photoluminescence of the Boron–Aluminum–Silicon Nitride Phosphor Sr3BAl5Si9N20:Eu
    2018
    Co-Authors: Fumitaka Yoshimura, Hisanori Yamane
    Abstract:

    Single crystals of new boron–aluminum–Silicon Nitrides, Sr3BAl5Si9N20 and Sr2.91Eu0.09BAl5Si9N20, were synthesized by heating binary nitride mixtures at 2030 °C under a N2 pressure of 0.85 MPa. The X-ray diffraction spots from single crystals of these two compounds were indexed with the trigonal cell parameters a = 22.7406(8) Å, c = 5.7066(2) Å and a = 22.7439(8) Å, c = 5.7050(2) Å, respectively, and the crystal structures were determined to have the space group P3c1, with B atoms situated at planar 3-fold-coordinated N sites. A three-dimensional framework structure is constructed for these materials based on the sharing of N atoms of Al/Si–N4 tetrahedra and B–N3 triangles. In this framework, Sr/Eu atoms are located at three sites, surrounded by 10 N atoms. Single crystals of Sr2.91Eu0.09BAl5Si9N20 emitted yellow light with a peak wavelength of 565 nm and a full width at half-maximum of 106 nm under 450 nm light irradiation. The emission intensity of these crystals at 200 °C was found to be 12% of the intensity at 25 °C

  • eu2 doped strontium aluminum Silicon Nitrides having α sialon and polytypoid structures
    Journal of the American Ceramic Society, 2017
    Co-Authors: Fumitaka Yoshimura, Hisanori Yamane
    Abstract:

    Yellow single crystals of aluminum Silicon Nitrides containing strontium and europium were prepared by heating starting mixtures of Sr3N2, Si3N4, AlN, and EuN at 2050°C and 0.85 MPa of N2 for 8 h. Single crystal X-ray diffraction revealed that prismatic crystals 20–100 μm in size were Sr0.31Al0.62Si11.38N16:Eu (trigonal, a = 7.7937(2) A, c = 5.6519(2) A, space group P31c), which are isotypic with Sr-α-SiAlON, Srm/2Alm+nSi12-m-nN16-nOn, with m = 0.62 and n = 0. The Eu2+ content was approximately 1 at% of Sr contained in the framework of corner-sharing (Al/Si)N4 tetrahedra with an occupancy of 0.154(2). Block-shaped crystals with a side length of 50–300 μm were a new polytypoid of Sr-α-SiAlON, Sr2.97Eu0.03Al6Si24N40. Streak lines were observed in the direction of the c* axis in the X-ray oscillation photographs, indicating stacking faults of the structure. The fundamental X-ray reflections were indexed with a hexagonal cell (a = 7.9489(3) A, c = 14.3941(6) A). The structure was analyzed with a model of space group P6¯ in which one of the six Al/Si sites was statistically split into two sites with occupancies of 0.673(5) and 0.227(5). The atomic arrangements in the layers of the structure were similar to those of Sr-α-SiAlON, but the stacking sequences of the layers were different. The peak wavelengths and full widths at half maximum of emission spectra measured for the single crystals of Sr0.31Al0.62Si11.38N16:Eu and Sr2.97Eu0.03Al6Si24N40 were 583 nm and 87 nm, and 584 nm and 91 nm, respectively, under 400 nm wavelength light excitation at room temperature. This article is protected by copyright. All rights reserved.

Fumitaka Yoshimura - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis, Crystal Structure, and Photoluminescence of the Boron-Aluminum-Silicon Nitride Phosphor Sr3BAl5Si9N20:Eu.
    Inorganic Chemistry, 2018
    Co-Authors: Fumitaka Yoshimura, Hisanori Yamane
    Abstract:

    Single crystals of new boron–aluminum–Silicon Nitrides, Sr3BAl5Si9N20 and Sr2.91Eu0.09BAl5Si9N20, were synthesized by heating binary nitride mixtures at 2030 °C under a N2 pressure of 0.85 MPa. The X-ray diffraction spots from single crystals of these two compounds were indexed with the trigonal cell parameters a = 22.7406(8) A, c = 5.7066(2) A and a = 22.7439(8) A, c = 5.7050(2) A, respectively, and the crystal structures were determined to have the space group P3c1, with B atoms situated at planar 3-fold-coordinated N sites. A three-dimensional framework structure is constructed for these materials based on the sharing of N atoms of Al/Si–N4 tetrahedra and B–N3 triangles. In this framework, Sr/Eu atoms are located at three sites, surrounded by 10 N atoms. Single crystals of Sr2.91Eu0.09BAl5Si9N20 emitted yellow light with a peak wavelength of 565 nm and a full width at half-maximum of 106 nm under 450 nm light irradiation. The emission intensity of these crystals at 200 °C was found to be 12% of the int...

  • Synthesis, Crystal Structure, and Photoluminescence of the Boron–Aluminum–Silicon Nitride Phosphor Sr3BAl5Si9N20:Eu
    2018
    Co-Authors: Fumitaka Yoshimura, Hisanori Yamane
    Abstract:

    Single crystals of new boron–aluminum–Silicon Nitrides, Sr3BAl5Si9N20 and Sr2.91Eu0.09BAl5Si9N20, were synthesized by heating binary nitride mixtures at 2030 °C under a N2 pressure of 0.85 MPa. The X-ray diffraction spots from single crystals of these two compounds were indexed with the trigonal cell parameters a = 22.7406(8) Å, c = 5.7066(2) Å and a = 22.7439(8) Å, c = 5.7050(2) Å, respectively, and the crystal structures were determined to have the space group P3c1, with B atoms situated at planar 3-fold-coordinated N sites. A three-dimensional framework structure is constructed for these materials based on the sharing of N atoms of Al/Si–N4 tetrahedra and B–N3 triangles. In this framework, Sr/Eu atoms are located at three sites, surrounded by 10 N atoms. Single crystals of Sr2.91Eu0.09BAl5Si9N20 emitted yellow light with a peak wavelength of 565 nm and a full width at half-maximum of 106 nm under 450 nm light irradiation. The emission intensity of these crystals at 200 °C was found to be 12% of the intensity at 25 °C

  • eu2 doped strontium aluminum Silicon Nitrides having α sialon and polytypoid structures
    Journal of the American Ceramic Society, 2017
    Co-Authors: Fumitaka Yoshimura, Hisanori Yamane
    Abstract:

    Yellow single crystals of aluminum Silicon Nitrides containing strontium and europium were prepared by heating starting mixtures of Sr3N2, Si3N4, AlN, and EuN at 2050°C and 0.85 MPa of N2 for 8 h. Single crystal X-ray diffraction revealed that prismatic crystals 20–100 μm in size were Sr0.31Al0.62Si11.38N16:Eu (trigonal, a = 7.7937(2) A, c = 5.6519(2) A, space group P31c), which are isotypic with Sr-α-SiAlON, Srm/2Alm+nSi12-m-nN16-nOn, with m = 0.62 and n = 0. The Eu2+ content was approximately 1 at% of Sr contained in the framework of corner-sharing (Al/Si)N4 tetrahedra with an occupancy of 0.154(2). Block-shaped crystals with a side length of 50–300 μm were a new polytypoid of Sr-α-SiAlON, Sr2.97Eu0.03Al6Si24N40. Streak lines were observed in the direction of the c* axis in the X-ray oscillation photographs, indicating stacking faults of the structure. The fundamental X-ray reflections were indexed with a hexagonal cell (a = 7.9489(3) A, c = 14.3941(6) A). The structure was analyzed with a model of space group P6¯ in which one of the six Al/Si sites was statistically split into two sites with occupancies of 0.673(5) and 0.227(5). The atomic arrangements in the layers of the structure were similar to those of Sr-α-SiAlON, but the stacking sequences of the layers were different. The peak wavelengths and full widths at half maximum of emission spectra measured for the single crystals of Sr0.31Al0.62Si11.38N16:Eu and Sr2.97Eu0.03Al6Si24N40 were 583 nm and 87 nm, and 584 nm and 91 nm, respectively, under 400 nm wavelength light excitation at room temperature. This article is protected by copyright. All rights reserved.

Ramakrishna T Bhatt - One of the best experts on this subject based on the ideXlab platform.

  • foreign object damage of two gas turbine grade Silicon Nitrides at ambient temperature
    26th Annual Conference on Composites Advanced Ceramics Materials and Structures: A: Ceramic Engineering and Science Proceedings Volume 23 Issue 3, 2008
    Co-Authors: Sung R. Choi, Michael J Pereira, Lesley A Janosik, Ramakrishna T Bhatt
    Abstract:

    Foreign object damage (FOD) behavior of two commercially available gas-turbine grade Silicon Nitrides (AS800 and SN282) was determined at ambient temperature through extensive strength testing of flexure test specimens impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 220 to 440 m/s. AS800 Silicon nitride exhibited a greater FOD resistance over SN282, primarily due to its greater value of fracture toughness (K IC ). This key factor (K IC ) affecting FOD resistance was further evidenced by the indentation strength response of both materials as well as by a quasi-static phenomenological impact model. The damage generated by projectile impact seemed to be in the forms of well- or ill-developed cone cracks and of lateral cracks.

  • Foreign object damage in disks of gas-turbine-grade Silicon Nitrides by steel ball projectiles at ambient temperature
    Journal of Materials Science, 2004
    Co-Authors: Sung R. Choi, Lesley A Janosik, J. M. Pereira, Ramakrishna T Bhatt
    Abstract:

    Foreign object damage (FOD) behavior of two commercial gas-turbine-grade Silicon Nitrides, AS800, SN282, was determined at ambient temperature through postimpact strength testing of target disks impacted by steel ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 Silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness ( K _Ic). The critical impact velocity V _c for which the corresponding postimpact strength was the lowest was V _c ≈ 440, 300 m/s for AS800, SN282, respectively. A unique lower strength regime was typified for both Silicon Nitrides depending on impact velocity, was attributed to significant radial cracking. The damage generated by projectile impact was typically in the form of ring, radial, cone cracks with their severity, combination being dependent on impact velocity. Unlike the thick (3 mm) flexure bar target specimens used in previous studies, the thin (2 mm) disk target specimens exhibited a unique back-side radial cracking on the reverse side just beneath the impact sites at, above impact velocities of 160 m/s for SN282, 220 m/s for AS800.

  • foreign object damage in flexure bars of two gas turbine grade Silicon Nitrides
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004
    Co-Authors: Sung R. Choi, Michael J Pereira, Lesley A Janosik, Ramakrishna T Bhatt
    Abstract:

    Abstract Foreign object damage (FOD) behavior of two commercial gas-turbine grade Silicon Nitrides, AS800 and SN282, was determined at ambient temperature through strength testing of flexure test specimens impacted by steel ball projectiles with a diameter of 1.59 mm in a velocity range from 220 to 440 m/s. AS800 Silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness ( K Ic ). The use of an additional equiaxed, fine-grained Silicon nitride (NC132) showed that fracture toughness was a key material parameter affecting FOD resistance. The observed damages generated by projectile impact were typically in the forms of well- or ill-developed ring and cone cracks with little presence of radial cracks.

  • foreign object damage of two gas turbine grade Silicon Nitrides in a thin disk configuration
    ASME Turbo Expo 2003 collocated with the 2003 International Joint Power Generation Conference, 2003
    Co-Authors: Sung R. Choi, Michael J Pereira, Lesley A Janosik, Ramakrishna T Bhatt
    Abstract:

    Foreign object damage (FOD) behavior of two commercial gas-turbine grade Silicon Nitrides, AS800 and SN282, was determined at ambient temperature through post-impact strength testing for thin disks impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 Silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (KIC ). The critical impact velocity in which the corresponding post-impact strength yielded the lowest value was Vc ≈ 440 and 300 m/s for AS800 and SN282, respectively. A unique lower-strength regime was typified for both Silicon Nitrides depending on impact velocity, attributed to significant radial cracking. The damages generated by projectile impact were typically in the forms of ring, radial, and cone cracks with their severity and combination being dependent on impact velocity. Unlike thick (3 mm) flexure bar specimens used in the previous studies, thin (2 mm) disk target specimens exhibited a unique backside radial cracking occurring on the reverse side just beneath the impact sites at and above impact velocity of 160 and 220 m/s for SN282 and AS800, respectively.Copyright © 2003 by ASME

Frédéric Danoix - One of the best experts on this subject based on the ideXlab platform.

  • Mechanism of Si3N4 precipitation in nitrided Fe-Si alloys: A novel example of particle-stimulated-nucleation
    Materials Letters, 2017
    Co-Authors: Andrius Martinavičius, Hugo P. Van Landeghem, Raphaële Danoix, Abdelkrim Redjaïmia, Mohamed Gouné, Frédéric Danoix
    Abstract:

    Atom probe tomography (APT) was employed to investigate the precipitation process of Si3N4 particles after plasma assisted nitriding and subsequent annealing of Fe-Si alloy. The nitriding was done using 15N2 medium to enable quantitative analysis of Si and N by APT. Al, as a minor alloying element, is found to play an important role in the precipitation sequence. It is shown that Al forms Al-N clusters before Si3N4 precipitation takes place, and provides nucleation sites for the precipitation of Si3N4. Composition measurements show that Silicon Nitrides are enriched in Al, Ti and Mn as compared to the matrix.