The Experts below are selected from a list of 18423 Experts worldwide ranked by ideXlab platform
Tsungyuan Kuo - One of the best experts on this subject based on the ideXlab platform.
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effects of Laser Power Level on microstructural properties and phase composition of Laser clad fluorapatite zirconia composite coatings on ti6al4v substrates
Materials, 2016Co-Authors: Chisheng Chien, Chengwei Liu, Tsungyuan KuoAbstract:Hydroxyapatite (HA) is one of the most commonly used materials for the coating of bioceramic titanium (Ti) alloys. However, HA has poor mechanical properties and a low bonding strength. Accordingly, the present study replaces HA with a composite coating material consisting of fluorapatite (FA) and 20 wt % yttria (3 mol %) stabilized zirconia (ZrO2, 3Y-TZP). The FA/ZrO2 coatings are deposited on Ti6Al4V substrates using a Nd:YAG Laser cladding system with Laser Powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min, and 1200 W/600 mm/min, respectively. The experimental results show that a significant inter-diffusion of the alloying elements occurs between the coating layer (CL) and the transition layer (TL). Consequently, a strong metallurgical bond is formed between them. During the cladding process, the ZrO2 is completely decomposed, while the FA is partially decomposed. As a result, the CLs of all the specimens consist mainly of FA, Ca4(PO4)2O (TTCP), CaF2, CaZrO3, CaTiO3 and monoclinic phase ZrO2 (m-ZrO2), together with a small amount of θ-Al2O3. As the Laser Power is increased, CaO, CaCO3 and trace amounts of tetragonal phase ZrO2 (t-ZrO2) also appear. As the Laser Power increases from 400 to 800 W, the CL hardness also increases as a result of microstructural refinement and densification. However, at the highest Laser Power of 1200 W, the CL hardness reduces significantly due to the formation of large amounts of relatively soft CaO and CaCO3 phase.
Chisheng Chien - One of the best experts on this subject based on the ideXlab platform.
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effects of Laser Power Level on microstructural properties and phase composition of Laser clad fluorapatite zirconia composite coatings on ti6al4v substrates
Materials, 2016Co-Authors: Chisheng Chien, Chengwei Liu, Tsungyuan KuoAbstract:Hydroxyapatite (HA) is one of the most commonly used materials for the coating of bioceramic titanium (Ti) alloys. However, HA has poor mechanical properties and a low bonding strength. Accordingly, the present study replaces HA with a composite coating material consisting of fluorapatite (FA) and 20 wt % yttria (3 mol %) stabilized zirconia (ZrO2, 3Y-TZP). The FA/ZrO2 coatings are deposited on Ti6Al4V substrates using a Nd:YAG Laser cladding system with Laser Powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min, and 1200 W/600 mm/min, respectively. The experimental results show that a significant inter-diffusion of the alloying elements occurs between the coating layer (CL) and the transition layer (TL). Consequently, a strong metallurgical bond is formed between them. During the cladding process, the ZrO2 is completely decomposed, while the FA is partially decomposed. As a result, the CLs of all the specimens consist mainly of FA, Ca4(PO4)2O (TTCP), CaF2, CaZrO3, CaTiO3 and monoclinic phase ZrO2 (m-ZrO2), together with a small amount of θ-Al2O3. As the Laser Power is increased, CaO, CaCO3 and trace amounts of tetragonal phase ZrO2 (t-ZrO2) also appear. As the Laser Power increases from 400 to 800 W, the CL hardness also increases as a result of microstructural refinement and densification. However, at the highest Laser Power of 1200 W, the CL hardness reduces significantly due to the formation of large amounts of relatively soft CaO and CaCO3 phase.
Shields, Jeffrey Allan - One of the best experts on this subject based on the ideXlab platform.
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The scattering of high-frequency acoustic phonons in silicon and gallium arsenide
2024Co-Authors: Shields, Jeffrey AllanAbstract:The production and propagation of high-frequency acoustic phonons in silicon and GaAs are studied at low temperatures ($\le$2K) using the phonon imaging technique. In this technique, a heat source is provided by a focused Laser beam which is raster scanned across the surface of the sample which is immersed in liquid helium. After they propagate across the sample, the acoustic phonons produced by the heat source are detected by a small superconducting detector. The spatial distribution of the ballistic phonon flux is highly anisotropic due to the phonon focusing effect.In this thesis, the characteristics of the phonon source produced by the focused Laser beam have been studied extensively in silicon. The phonon source consists of a small region in the crystal in which the phonon occupation number is elevated with respect to the rest of the crystal. The lifetime and frequency distribution of the phonon source are found to vary dramatically with different boundary conditions, such as whether the surface is of the sample is metalized or whether the excitation surface is in contact with liquid helium. The Laser Power Level also has profound effects on the characteristics of the phonon source, and a threshold of some sort has been observed at low Power.The phonon frequency determines the likelihood that the phonon will traverse the sample ballistically since the elastic scattering rate depends on the phonon frequency to the fourth Power. A special sample geometry allows the first direct measurement of the elastic scattering rate in silicon by comparing the experimental data with Monte Carlo calculations of the elastic scattering.The phonon focusing pattern changes at very high phonon frequencies due to lattice dispersion. Observations of dispersive effects in the phonon focusing pattern of silicon have been made and the effect of various lattice dynamics models on the Monte Carlo calculations of the elastic scattering in silicon are presented.Phonon scattering from defects in GaAs has been studied and dramatic effects in the phonon focusing pattern have been observed with near infrared irradiation of the crystal. Previous studies have indicated that the EL2 defect is changed from its normal state into a metastable state under irradiation with infrared light. We observe changes in the phonon scattering after irradiation which indicate a decrease in inelastic phonon scattering with the transition to the metastable state.U of I OnlyETDs are only available to UIUC Users without author permissio
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The scattering of high-frequency acoustic phonons in silicon and GaAs
2024Co-Authors: Shields, Jeffrey AllanAbstract:The production and propagation of high-frequency acoustic phonons in silicon and GaAs are studied at low temperatures (~ 2K) using the phonon imaging technique. In this technique, a heat source is provided by a focused Laser beam which is raster scanned across the surface of the sample which is immersed in liquid helium. After they propagate across the sample, the acoustic phonons produced by the heat .source are detected by a small superconducting detector. The spatial distribution of the ballistic phonon flux is highly anisotropic due to the phonon focusing effect. In this thesis, the characteristics of the phonon source produced by the focused Laser . beam have been studied extensively in silicon. The phonon source consists of a small region in the crystal in which the phonon occupation number is elevated with respect to the rest of the crystal. The lifetime and frequency distribution of the phonon source are found to vary dramatically with different boundary conditions, such as whether the surface is of the sample is metalized or whether the excitation surface is in contact with liquid helium. The Laser Power Level also has profound effects on the characteristics of the phonon source, and a threshold of some sort has been observed at low Power. The phonon frequency determines the likelihood that the phonon will traverse the sample ballistically since the elastic scattering rate depends on the phonon frequency to the fourth Power. A special sample geometry allows the first direct measurement of the elastic scattering rate in silicon by comparing the experimental data with Monte Carlo calculations of the elastic scattering. The phonon focusing p~ttern changes at very high phonon frequencies due to lattice dispersion. Observations of dispersive effects in the phonon focusing pattern of silicon have been made and the effect of various lattice dynamics models on the Monte Carlo calculations of the elastic scattering in silicon are presented. Phonon scattering from defects in GaAs has been studied and dramatic effects in the phonon focusing pattern have been observed with near infrared irradiation of the crystal. Previous studies have indicated that the EL2 defect is changed from its normal state into a metastable state under irradiation with infrared light. We observe changes in the phonon scattering after irradiation which indicate a decrease in inelastic phonon scattering with the transition to the metastable state.U of I OnlyThesi
Chengwei Liu - One of the best experts on this subject based on the ideXlab platform.
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effects of Laser Power Level on microstructural properties and phase composition of Laser clad fluorapatite zirconia composite coatings on ti6al4v substrates
Materials, 2016Co-Authors: Chisheng Chien, Chengwei Liu, Tsungyuan KuoAbstract:Hydroxyapatite (HA) is one of the most commonly used materials for the coating of bioceramic titanium (Ti) alloys. However, HA has poor mechanical properties and a low bonding strength. Accordingly, the present study replaces HA with a composite coating material consisting of fluorapatite (FA) and 20 wt % yttria (3 mol %) stabilized zirconia (ZrO2, 3Y-TZP). The FA/ZrO2 coatings are deposited on Ti6Al4V substrates using a Nd:YAG Laser cladding system with Laser Powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min, and 1200 W/600 mm/min, respectively. The experimental results show that a significant inter-diffusion of the alloying elements occurs between the coating layer (CL) and the transition layer (TL). Consequently, a strong metallurgical bond is formed between them. During the cladding process, the ZrO2 is completely decomposed, while the FA is partially decomposed. As a result, the CLs of all the specimens consist mainly of FA, Ca4(PO4)2O (TTCP), CaF2, CaZrO3, CaTiO3 and monoclinic phase ZrO2 (m-ZrO2), together with a small amount of θ-Al2O3. As the Laser Power is increased, CaO, CaCO3 and trace amounts of tetragonal phase ZrO2 (t-ZrO2) also appear. As the Laser Power increases from 400 to 800 W, the CL hardness also increases as a result of microstructural refinement and densification. However, at the highest Laser Power of 1200 W, the CL hardness reduces significantly due to the formation of large amounts of relatively soft CaO and CaCO3 phase.
Fubin Wang - One of the best experts on this subject based on the ideXlab platform.
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femtosecond Laser ablation Power Level identification based on the ablated spot image
The International Journal of Advanced Manufacturing Technology, 2018Co-Authors: Fubin Wang, Yang Liu, Ding FengAbstract:When using a femtosecond Laser to process the microchannel on silicon wafers in order to determine the machining speed in the X axis and feed rate in the Y axis, a large number of the spot ablation experiments on the surface of silicon wafer sample are needed. To determining the relationship between the size of spot mark and the corresponding Power Level, this paper presents a method based on image features of spot mark and Support Vector Machine (SVM). Firstly, we propose a preliminary segmentation strategy for spot mark image based on the K-means clustering, the image is clustered into backgrounds, halos, and targets, the image corrosion method is used to remove the interference around the target, and according to the deterministic characteristics of convex hull method to extract the target marks, consequently, the spot target with different ablation Power has a uniform segmentation criterion. Secondly, we extract the geometric feature parameters of a spot mark image, such as pixel area, height, width, inner radius, and outer radius, and then construct the geometric parameters sample set of spot mark image. Finally, taking the geometric feature parameters of spot mark image as the input vector and the corresponding Laser Power Level as the output vector, the recognition model of Laser Power Level based on SVM is constructed.
