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J. Appl. Cryst.の発刊に際して

비만아 부모의 돌봄 경험: q 방법론

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

About twenty years ago, in the autumn of 1996, the first white light-emitting diodes (LEDs) were offered for sale. These then-new devices ushered in a new era in lighting by displacing lower-efficiency conventional light sources including Edison's venerable incandescent lamp as well as the Hg-discharge-based fluorescent lamp. We review the history of the conception, improvement, and commercialization of the white LED. Early models of white LEDs already exceeded the efficiency of low-wattage incandescent lamps, and extraordinary progress has been made during the last 20 years. The review also includes a discussion of advances in blue LED chips, device architecture, light extraction, and phosphors. Finally, we offer a brief outlook on opportunities provided by smart LED technology.

White light-emitting diodes: History, progress, and future

We present our recent achievement of a transparent ceramic able to produce white light when directly combined with commercially available blue light emitting diodes. The photoluminescence properties of ceramic phosphor (Y1-xCex)(3)Al5O12 are studied as a function of doping fraction (x = 0.0005-0.0020). The emission color is tunable by variations of Ce3+ concentration and ceramic phosphor thickness. A maximum luminous efficacy exceeding 93 lm/W at a low correlated color temperature of similar to 4600 K is obtained, which is superior to samples made from commercial phosphor powders. Hence, the present transparent ceramic phosphor is expected to be an ideal candidate for generating white light. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4742896]

Transparent Ce:Y3Al5O12 ceramic phosphors for white light-emitting diodes

Transparent MgAl2O4 spinel nanoceramics have been sintered at relatively low-temperature (500-700 degrees C) under high pressure (2-5 GPa) using a hydrostatic press with high-temperature-calcined nanopowders. The morphology, nanostructure, optical property, and density of ceramics were analyzed by scanning electron microscopy, transmission electron microscopy, UV-VIS-IR transmission spectrum, and Archimedes draining method. The average grain size (< 100 nm for all samples sintered) depends on the sintering pressure and temperature. The nanoceramics are highly transparent even though their relative densities are all less than 99%, due to the low or negligible light scattering from the nanosized grains and pores. (c) 2006 American Institute of Physics.

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Low-temperature high-pressure preparation of transparent nanocrystalline MgAl2O4 ceramics

Assessment of light scattering by pores in Nd:YAG transparent ceramics

Effect of annealing on the optical properties of Nd:YAG transparent ceramics

Fluorite (F)–pyrochlore (P)–fluorite (F) phase transitions of Gd2Zr2O7 were investigated from 573 K to 1873 K (300 °C to 1600 °C), by means of X-ray diffraction, infrared spectra (IR), and Raman spectra. The low-temperature F phase can stably exist below 1523 K (1250 °C) and the F–P transition occurs at 1523 K to 1573 K (1250 °C to 1300 °C). The ordering process of P phase forms at 1573 K to 1773 K (1300 °C to 1500 °C) and the ordering degree increases with increasing sintering temperature and heat preservation period. High-temperature phase transition from P to F occurs between 1773 K and 1823 K (1300 °C and 1550 °C). IR spectra of samples with different ordering degrees show an interesting shift at 510 cm−1. Raman spectra show that only the A1g
 mode displays a significant change between F and P phases. This ordering degree and phase transition temperature studies would allow a more targeted experimental optimization of Gd2Zr2O7 to use in nuclear waste host, thermal barrier coatings, and solid oxide fuel cells.

Jianqi Qi

Papers

Transparent Ce:Y3Al5O12 ceramic phosphors for white light-emitting diodes

Low-temperature high-pressure preparation of transparent nanocrystalline MgAl2O4 ceramics

Assessment of light scattering by pores in Nd:YAG transparent ceramics

Effect of annealing on the optical properties of Nd:YAG transparent ceramics

Thermal-Driven Fluorite–Pyrochlore–Fluorite Phase Transitions of Gd2Zr2O7 Ceramics Probed in Large Range of Sintering Temperature