Polishing Characteristics of Transparent Polycrystalline YAG Ceramics Using Magnetic Field-Assisted Finishing

2016 ◽  
Author(s):  
Daniel Ross ◽  
Yanming Wang ◽  
Hadyan Ramadhan ◽  
Hitomi Yamaguchi
Keyword(s):  
Magnetic Field ◽  
Material Removal ◽  
Colloidal Silica ◽  
Yttrium Aluminum Garnet ◽  
Surface Characteristics ◽  
Grain Structure ◽  
Laser Applications ◽  
Ceramic Surfaces ◽  
Yttrium Aluminum ◽  
Diamond Abrasive

Transparent polycrystalline yttrium aluminum garnet (YAG) ceramics have garnered an increased level of interest for high-power laser applications due to their ability to be manufactured in large sizes, and doped in relatively substantial concentrations when compared to traditional single-crystalline gain media. However, surface characteristics have a direct effect on the lasing ability of these materials, and a lack of a fundamental understanding of the polishing mechanisms of these ceramics remains a challenge for their utilization. The aim of this paper is to study the polishing characteristics of YAG ceramics using magnetic field-assisted finishing (MAF). An experimental setup was developed, through the refinement of the MAF process, for YAG ceramic workpieces. Using this equipment with diamond abrasives, the YAG ceramic surfaces were polished to sub-nanometer scale. Polishing trials with fine diamond abrasive and colloidal silica were then performed on this sub-nanometer surface and the material removal mechanisms were analyzed. Polishing with 0–0.1 μm diameter diamond abrasive caused increasing roughness with polishing time due to the continuous cycle of relatively substantial chipping followed by minor smoothing. Polishing with colloidal silica caused valleys to widen with increased polishing time and the grain structure of the ceramic influenced the material removal.

scholarly journals Polishing Characteristics of Transparent Polycrystalline Yttrium Aluminum Garnet Ceramics Using Magnetic Field-Assisted Finishing

2016 ◽  
Vol 4 (4) ◽  
Author(s):  
Daniel Ross ◽  
Yanming Wang ◽  
Hadyan Ramadhan ◽  
Hitomi Yamaguchi
Keyword(s):  
Magnetic Field ◽  
Material Removal ◽  
Colloidal Silica ◽  
Yttrium Aluminum Garnet ◽  
Surface Defects ◽  
Surface Characteristics ◽  
Grain Structure ◽  
Initial Surface ◽  
Laser Applications ◽  
Yttrium Aluminum

Transparent polycrystalline yttrium aluminum garnet (YAG) ceramics have garnered an increased level of interest for high-power laser applications due to their ability to be manufactured in large sizes and to be doped in relatively substantial concentrations. However, surface characteristics have a direct effect on the lasing ability of these materials, and a lack of a fundamental understanding of the polishing mechanisms of these ceramics remains a challenge to their utilization. The aim of this paper is to study the polishing characteristics of YAG ceramics using magnetic field-assisted finishing (MAF). MAF is a useful process for studying the polishing characteristics of a material due to the extensive variability of, and fine control over, the polishing parameters. An experimental setup was developed for YAG ceramic workpieces, and using this equipment with diamond abrasives, the surfaces were polished to subnanometer scales. When polishing these subnanometer surfaces with 0–0.1 μm mean diameter diamond abrasive, the severity of the initial surface defects governed whether improvements to the surface would occur at these locations. Polishing subnanometer surfaces with colloidal silica abrasive caused a worsening of defects, resulting in increasing roughness. Colloidal silica causes uneven material removal between grains and an increase in material removal at grain boundaries causing the grain structure of the YAG ceramic workpiece to become pronounced. This effect also occurred with either abrasive when polishing with iron particles, used in MAF to press abrasives against a workpiece surface, that are smaller than the grain size of the YAG ceramic.

Achieving Best Visual Outcomes with a Monofocal Intraocular Lens

2011 ◽  
Vol 04 (01) ◽  
pp. 30
Author(s):  
James A Davison ◽  
Keyword(s):  
Epithelial Cell ◽  
Intraocular Lens ◽  
Yttrium Aluminum Garnet ◽  
Surface Characteristics ◽  
Replacement Surgery ◽  
Architectural Features ◽  
Single Piece ◽  
Yttrium Aluminum ◽  
Monofocal Iol

Specific monofocal intraocular lens (IOL) design features have been integrated over time to provide improved vision performance after lens replacement surgery. Features of the AcrySof® IQ single-piece monofocal IOL (SN60WF, Alcon Laboratories) include architectural, chemical, and surface characteristics that improve performance over earlier designs. The architectural features include single-piece construction with low resistance to compression, 3D haptics for easy implantation, and predictable and stable long-term positioning. The foldable hydrophobic acrylic plastic provides efficient light focus and incorporates ultraviolet (UV) radiation and light-normalized spectrum transmission characteristics. The plastic’s surface incites minimal post-operative uveitis and capsule reaction and also resists epithelial cell proliferation. The biconvex optic is asymmetric with most of the power incorporated into the anterior surface to reduce dysphotopsia. The posterior surface has a base convexity and incorporates an aspheric modification. The optic’s square edge provides a barrier that discourages epithelial cell invasion and consequent posterior capsule opacification and need for neodymium-doped yttrium–aluminum–garnet (Nd:YAG) posterior capsulotomy, and is frosted to reduce dysphotopsia.

Effect of Binder Content on Hybrid Magnetic Tool Behavior

2017 ◽  
Author(s):  
Max Stein ◽  
Hitomi Yamaguchi
Keyword(s):  
Magnetic Field ◽  
Magnetic Particles ◽  
Yttrium Aluminum Garnet ◽  
Target Surface ◽  
Binder Content ◽  
Water Soluble ◽  
Form Accuracy ◽  
Transition Speed ◽  
Yttrium Aluminum ◽  
Tool Transformation

This paper proposes the use of a hybrid magnetic tool, consisting of magnetic particles bonded with water-soluble glue, to improve both surface roughness and form accuracy of brittle materials such as ceramics. As the binder gradually dissolves into the lubricant, the bonded hybrid magnetic tool transforms to a particle brush in a magnetic field, increasing the deformability of the tool and its ability to conform to the target surface. This paper describes the effects of the tool transformation — from a bonded tool to a particle brush — on the characteristics of finished yttrium aluminum garnet (YAG) laser ceramics. The bonded tool removes material to flatten and smooth the target surface at the start of the process, gradually transitions to a particle brush (starting at the tool periphery), and finally smooths the surface as a flexible particle brush. The tool deformability and transition speed are adjustable by the binder content.

Yag Single Crystals for Scintillators of Stem

1990 ◽  
Vol 48 (1) ◽  
pp. 166-167
Author(s):  
M. Hibino ◽  
K. Irie ◽  
R. Autrata ◽  
P. schauer
Keyword(s):  
Single Crystals ◽  
Yttrium Aluminum Garnet ◽  
Light Guide ◽  
Detection System ◽  
Polished Surface ◽  
Detective Quantum Efficiency ◽  
Backscattered Electrons ◽  
Electron Detection ◽  
Yttrium Aluminum ◽  
Phosphor Screens

Although powdered phosphor screens are usually used for scintillators of STEM, it has been found that the phosphor screen of appropriate thickness should be used depending on the accelerating voltage, in order to keep high detective quantum efficiency. 1 It has been also found that the variation in sensitivity, due to granularity of phosphor screens, makes the measurement of fine electron probe difficult and that the sensitivity reduces with electron irradiation specially at high voltages.In order to find out a preferable scintillator for STEM, single crystals of YAG (yttrium aluminum garnet), which are used for detecting secondary and backscattered electrons in SEM were investigated and compared with powdered phosphor screens, at the accelerating voltages of 100kV and 1 MV. A conventional electron detection system, consisting of scintillator, light guide and PMT (Hamamatsu Photonics R268) was used for measurements. Scintillators used are YAG single crystals of 1.0 to 3.2mm thicknesses (with surfaces matted for good interface to the light guide) and of 0.8mm thickness (with polished surface), and powdered P-46 phosphor screens of 0.07mm and 1.0mm thicknesses for 100kV and 1MV, respectively. Surfaces on electron-incidence side of all scintillators are coated with reflecting layers.

EDM with USM Combination Process of Sintered NdFeB Permanent Magnet

2010 ◽  
Vol 44-47 ◽  
pp. 1066-1069
Author(s):  
Li Li ◽  
Li Ling Qi ◽  
Zong Wei Niu
Keyword(s):  
Permanent Magnet ◽  
Material Removal ◽  
Removal Rate ◽  
Surface Characteristics ◽  
Dielectric Fluid ◽  
Machined Surface ◽  
Combination Process ◽  
Electro Discharge Machining ◽  
Ndfeb Permanent Magnet ◽  
Machining Characteristics

This paper presents an experimental investigation of the machining characteristics of sintered NdFeB permanent magnet using a combination process of electro-discharge machining (EDM) with ultrasonic machining (USM). Concentration of abrasive in the dielectric fluid is changed to explore its effect on the material removal rate (MRR). MRR of EDM /USM, conventional EDM are compared, machined surface characteristics are also compared between them. It is concluded that the combination EDM/USM process can increase the MRR and decrease the thickness of the recast layer. In the combination process, an appropriate abrasive concentration can improve its machining efficiency.

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