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961.
A novel Eu3+‐ and self‐activated vanadate phosphor of Ca4La(VO4)3O with oxyvanadate apatite structure 下载免费PDF全文
Ruijin Yu Jung Hyun Jeong Yin‐Feng Wang 《Journal of the American Ceramic Society》2017,100(12):5649-5658
Pure and Eu3+‐activated Ca4La(VO4)3O phosphors were prepared via three‐step solid‐phase synthesis. The phase formation and structure were investigated by X‐ray diffraction (XRD) with Rietveld refinements. All the samples crystallized in an apatite‐type structure. The morphological properties were measured via by SEM and EDS measurements. Ca4La(VO4)3O is a new vanadate optical material with a direct band feature and a band energy of 3.1 eV. The undoped Ca4La(VO4)3O phosphor presents self‐activated yellow luminescence from 400 nm to 750 nm with a maximum wavelength of 525 nm originating from VO4 groups. Luminescence characteristics of Ca4La(VO4)3O indicate that the phosphor is not sufficient for practical applications. In Eu3+‐activated Ca4La(VO4)3O, there is an efficient energy transfer from VO4 to Eu3+ ions. The luminescence spectra, concentration quenching, decay curves, color chromaticity, and quantum efficiencies (QE) of Ca4La(VO4)3O:Eu3+ were investigated. The phosphor presents optimal Eu3+ doping concentration of about 20 mol%. The dominant red emission in Ca4La(VO4)3O:Eu3+ is 615 nm from electronic 5D0→7F2 dipole transitions. The quantum efficiency and the luminescence stability of the pure and Eu‐activated Ca4La(VO4)3O were reported. The luminescence was discussed on the structural characteristics. 相似文献
962.
Sehwan Song Jiwoong Kim Dooyong Lee Jisung Lee Taewon Min Jong‐Ah Chae Jong‐Seong Bae Jaekwang Lee Jeong‐Soo Lee Sungkyun Park 《Journal of the American Ceramic Society》2017,100(9):3928-3934
The structural, electrical, and chemical properties of Sn‐doped Fe2O3 powders were investigated. Various quantities of Sn‐doped Fe2O3 powders were synthesized using solid‐state reactions. Rietveld analysis for the powders that were doped below 2% revealed a phase‐pure Sn‐doped Fe2O3 structure (i.e., identical to Fe2O3 structure). Alternatively, the analysis for the powders that were doped more than 3% exhibited secondary phase. The unit cell volume and electrical conductivity of the phase‐pure samples increased with an increase in the doping concentration. X‐ray photoelectron spectroscopy measurements showed an increased Fe2+ state with the increase in Sn doping concentration. Therefore, the improved electrical conductivity and unit cell volume with the increase in doping concentration of the phase‐pure powders might be related to the increased Fe2+ state. 相似文献
963.
Jeong Min Park Sangin Keel Jinhan Yun Ji Hye Yun Sang-Sup Lee 《Korean Journal of Chemical Engineering》2017,34(8):2204-2210
The co-combustion of dried sewage sludge with coal is a promising method to dispose of and treat sewage sludge waste. Because sewage sludge has a different elemental composition than coal, the co-combustion of sewage sludge with coal may have different combustion characteristics than the single combustion of coal. In this study, the co-combustion of dried sewage sludge with coal was tested varying heating rates and mixing ratios of the dried sewage sludge. The results were analyzed using thermogravimetric (TG) and derivative thermogravimetric (DTG) curves and modeled using Ozawa-Flynn-Wall and Vyazovkin models. The mixed samples of coal and dried sewage sludge showed similar TG curves to the coal sample. The co-combustion showed activation energies close to that of the single coal combustion. This suggests that the co-combustion of coal and dried sewage sludge has similar combustion behavior to the single combustion of coal for mixing percentages of dried sewage sludge up to 20%. 相似文献
964.
Taekyung Lee Hyoungjae Kim Sangjik Lee Chuljin Park Doyeon Kim Haedo Jeong 《Journal of Mechanical Science and Technology》2017,31(12):5649-5655
Single-sided lapping is crucial in sapphire wafering processes for improving flatness and achieving the target wafer thickness using loose abrasives. In single-sided lapping process, the Material removal rate (MRR) is a key factor for reducing process time and cost. However, the MRR is limited when using loose abrasives because abrasives mostly act by rolling and sliding. Many researchers have studied fixed abrasives to increase the MRR, but the MRR decreases with time. To solve this problem, the self-dressing effect was studied with various pressures, velocities, cutting fluids and wafers. The MRR decreased due to the wear of abrasives, and the pressure and velocity have little effect on the self-dressing. Lapping experiments were done using cutting fluid with a lapped wafer and sawed wafer. The MRR, plate roughness and thickness were measured to study the wear of the abrasive and the self-dressing effect. The cutting fluid delayed the wear of the abrasives and thus improved the decrease in MRR, but it had little effect on the self-dressing effect, like in the case when water was used. When using cutting fluid and a sawed wafer, the MRR was high and did not decrease. A concentrated load on the plate caused by shape error and saw marks on the sawed wafer could produce the self-dressing effect. We verified that a sawed wafer could produce the self-dressing effect on even a worn plate. 相似文献
965.
Sung Kim Ung-Been Jeong Kyoung-Yong Lee Jin-Hyuk Kim Joon-Yong Yoon Young-Seok Choi 《Journal of Mechanical Science and Technology》2017,31(11):5099-5106
During design optimization, the impeller and diffuser of a mixed-flow pump are generally optimized separately. In such cases, the total head can be overdesigned. In this study, the designs of the impeller and diffuser were optimized simultaneously by using computational fluid dynamics and the Response surface method (RSM). Design variables were defined according to the vane plane development of the impeller and diffuser. Three-dimensional Reynolds-averaged Navier–Stokes equations for the shear stress transport turbulence model were discretized by finite volume approximations and solved on hexahedral grids to analyze the flow in the pump. The total head and total efficiency were selected as objective functions, with four design variables related to the impeller outlet angles and diffuser inlet angles used for optimization. The RSM was constructed based on the objective functions with design points generated from the central composite method. The hydraulic performance of the optimum model was analyzed. 相似文献
966.
Micro texturing was fabricated on polyoxymethylene surfaces using laser texturing, and the tribological characteristics were studied. Micro texturing was proven to be very effective in lowering the coefficient of friction, regardless of the texturing depth used in this study. Laser texturing was practical and efficient owing to its fast process time with reasonable machined shapes. An optimum aspect ratio and area density of texturing would exist under the conditions used in this study. Wear of polyoxymethylene was negligible. 相似文献
967.
Energy Harvesting: High‐Performance Piezoelectric,Pyroelectric, and Triboelectric Nanogenerators Based on P(VDF‐TrFE) with Controlled Crystallinity and Dipole Alignment (Adv. Funct. Mater. 22/2017) 下载免费PDF全文
968.
Superstructures: Enzyme‐Driven Hasselback‐Like DNA‐Based Inorganic Superstructures (Adv. Funct. Mater. 45/2017) 下载免费PDF全文
969.
Electrocatalyts: Controlled Fabrication of Hierarchically Structured Nitrogen‐Doped Carbon Nanotubes as a Highly Active Bifunctional Oxygen Electrocatalyst (Adv. Funct. Mater. 9/2017) 下载免费PDF全文
970.
Polymer hydrogels consist of a three-dimensional (3D) structure with cross-linked networks rich in a huge amount of water through hydrogen-bonding interactions, making them highly hydrophilic. Due to their impressive hydrophilic characteristics and cell non-cytotoxicity, polymer hydrogels are useful tissue engineering tools for the organization of cells and tissues and organ regeneration. Many biomedical engineers and researchers have recently begun to utilize polymer hydrogels as tissue or cell culture environments and as scaffolds for the stable growth of organs in tissue engineering and regeneration medicine. This paper focuses on skin regeneration in polymer hydrogels where skin is a means of protecting the body from infection or physical or chemical damage. Generally, skin tissue that has incurred minor damage or wounds can regenerate and heal in a relatively short time, while severe injuries may require transplantation or artificial skin. For those purposes, skin culturing in an in vitro environment is essential, and the environment produced using polymer hydrogel scaffolds needs to be both similar to the real environment and safe for skin cell growth. This paper reviews post-2000 skin regeneration research in the field of tissue engineering, focusing specifically on polymer hydrogels; it also discusses some of the central perspectives and key issues. 相似文献