The Experts below are selected from a list of 43044 Experts worldwide ranked by ideXlab platform
Sumetha Suwanboon - One of the best experts on this subject based on the ideXlab platform.
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the wide band gap of highly oriented nanocrystalline al doped zno thin films from sol gel dip coating
Journal of Alloys and Compounds, 2009Co-Authors: Tanattha Ratana, Pongsaton Amornpitoksuk, Sumetha SuwanboonAbstract:Abstract Undoped and Al doped ZnO thin films were prepared on glass substrate by sol–gel dip coating from PVP-modified zinc acetate dihydrate and aluminium chloride hexahydrate solutions. The XRD patterns of all thin films indexed a highly preferential orientation along c -axis. The AFM images showed the Average Grain Size of undoped ZnO thin film was about 101 nm whereas the smallest Average Grain Size at 8 mol% Al was about 49 nm. The values of direct optical band gap of thin films varied in the range of 3.70–3.87 eV.
Pantelis C. Kelires - One of the best experts on this subject based on the ideXlab platform.
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Softening of ultra-nanocrystalline diamond at low Grain Sizes
arXiv: Materials Science, 2008Co-Authors: Ioannis N. Remediakis, Georgios Kopidakis, Pantelis C. KeliresAbstract:Ultra-nanocrystalline diamond is a polycrystalline material, having crystalline diamond Grains of Sizes in the nanometer regime. We study the structure and mechanical properties of this material as a function of the Average Grain Size, employing atomistic simulations. From the calculated elastic constants and the estimated hardness, we observe softening of the material as the Size of its Grains decreases. We attribute the observed softening to the enhanced fraction of interfacial atoms as the Average Grain Size becomes smaller. We provide a fitting formula for the scaling of the cohesive energy and bulk modulus with respect to the Average Grain Size. We find that they both scale as quadratic polynomials of the inverse Grain Size. Our formulae yield correct values for bulk diamond in the limit of large Grain Sizes.
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Softening of ultra-nanocrystalline diamond at low Grain Sizes
Acta Materialia, 2008Co-Authors: Ioannis N. Remediakis, Georgios Kopidakis, Pantelis C. KeliresAbstract:Ultra-nanocrystalline diamond is a polycrystalline material with crystalline diamond Grains in the nanometer Size regime. We study the structure and mechanical properties of this material as a function of the Average Grain Size, employing atomistic simulations. From the calculated elastic constants and the estimated hardness, we observe softening of the material as the Size of its Grains decreases. We attribute the observed softening to the enhanced fraction of interfacial atoms as the Average Grain Size becomes smaller. We provide a fitting formula for the scaling of the cohesive energy and bulk modulus with respect to the Average Grain Size. We find that both these properties scale as quadratic polynomials of the inverse Grain Size. Our formulas yield correct values for bulk diamond in the limit of large Grain Sizes.
Tanattha Ratana - One of the best experts on this subject based on the ideXlab platform.
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the wide band gap of highly oriented nanocrystalline al doped zno thin films from sol gel dip coating
Journal of Alloys and Compounds, 2009Co-Authors: Tanattha Ratana, Pongsaton Amornpitoksuk, Sumetha SuwanboonAbstract:Abstract Undoped and Al doped ZnO thin films were prepared on glass substrate by sol–gel dip coating from PVP-modified zinc acetate dihydrate and aluminium chloride hexahydrate solutions. The XRD patterns of all thin films indexed a highly preferential orientation along c -axis. The AFM images showed the Average Grain Size of undoped ZnO thin film was about 101 nm whereas the smallest Average Grain Size at 8 mol% Al was about 49 nm. The values of direct optical band gap of thin films varied in the range of 3.70–3.87 eV.
Gerhard Jakob - One of the best experts on this subject based on the ideXlab platform.
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Determining the Average Grain Size of Super-Alloy Micrographs
2006 International Conference on Image Processing, 2006Co-Authors: Wanda Benesova, Alfred Rinnhofer, Gerhard JakobAbstract:This work presents a complex solution for determining the Average Grain Size and additional features in super-alloy (Inconel™ 718) micrographs. A crucial point of each automatic Grain Size measurement system is a reliable segmentation of the Grain boundaries using the methods of image processing. This work introduces a novel method for the marker image calculation, which is an essential part of the grayscale image reconstruction. Unlike the methods of grayscale erosion or image subtraction, our method uses the results of contour classification for the goal-directed calculation of the marker image. The grayscale image reconstruction therefore produces an excellent pre-processed image with removed non-Grain objects. In addition, the homogeneity inside the Grains increases without losing information about the Grain boundaries. When the automated Grain Size measurement using the presented algorithm is compared to the manually evaluated Average Grain Size, we can confirm the acceptance of the proposed method for application in metallurgical praxis.
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ICIP - Determining the Average Grain Size of Super-Alloy Micrographs
2006 International Conference on Image Processing, 2006Co-Authors: Wanda Benesova, Alfred Rinnhofer, Gerhard JakobAbstract:This work presents a complex solution for determining the Average Grain Size and additional features in super-alloy (Inconel ? 718) micrographs. A crucial point of each automatic Grain Size measurement system is a reliable segmentation of the Grain boundaries using the methods of image processing. This work introduces a novel method for the marker image calculation, which is an essential part of the grayscale image reconstruction. Unlike the methods of grayscale erosion or image subtraction, our method uses the results of contour classification for the goal-directed calculation of the marker image. The grayscale image reconstruction therefore produces an excellent pre-processed image with removed non-Grain objects. In addition, the homogeneity inside the Grains increases without losing information about the Grain boundaries. When the automated Grain Size measurement using the presented algorithm is compared to the manually evaluated Average Grain Size, we can confirm the acceptance of the proposed method for application in metallurgical praxis.
David E. Golden - One of the best experts on this subject based on the ideXlab platform.
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Effect of Average Grain Size on the work function of diamond films
Applied Physics Letters, 2001Co-Authors: Patrick Abbott, Edward D. Sosa, David E. GoldenAbstract:The work function of hydrogen-terminated polycrystalline diamond films deposited by electrophoresis on molybdenum was studied using ultraviolet photoelectron spectroscopy with 21.2 eV photons for Average Grain Sizes ranging from 0.32 to 108 μm. The work function has a maximum of about 5.1 eV at 0.32 μm, then decreases with increasing Grain Size to a minimum of about 3.2 eV at an Average Grain Size of about 4 μm and then increases to a value of about 4.8 eV at a Grain Size of 108 μm. The results are consistent with a model in which the work function is controlled by the work function of single crystal diamond (111) at the larger Grain Sizes, graphitic carbon at the smaller Grain Sizes, and by a negative electron affinity that increases with decreasing Grain Size due to defects near diamond (111) crystallite edges for the intervening Grain Sizes. The large change in work function (almost a factor of 2) could be useful to make conductors with different work functions for microelectronic gate structures.
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Variation of field emission and photoelectric thresholds of diamond films with Average Grain Size
Applied Physics Letters, 1999Co-Authors: Ambrosio A. Rouse, John B. Bernhard, Edward D. Sosa, David E. GoldenAbstract:We report a decrease in field emission threshold from 3.8 to 3.4 eV for room temperature electrophoresis grown polycrystalline diamond films on molybdenum tips as the diamond Average Grain Size increases from 0.25 to 6 μm. The field emission thresholds agree with photoelectric work functions determined from photoelectron spectroscopy measurements of similarly grown flat samples. In addition, diamond surface states are observed at 0.4, 0.9, and 1.8 eV above the valence band. The results are consistent with an increasing negative electron affinity with Grain Size due to increased surface hydrogen bonding and with perhaps a contribution from surface defect states.
