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H2 Atmosphere (h2 + atmosphere)

Distribution by Scientific Domains
Polymers and Materials Science75%

Selected Abstracts

Patterned Synthesis of Pd4S: Chemically Robust Electrodes and Conducting Etch Masks

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2010
Boya Radha
Abstract A simple, one-step process to synthesize Pd4S films is reported here along with their characterization using X-ray diffraction, electron microscopy, and electrical measurements. The synthesis involves thermolysis of a single-source precursor, namely palladium alkanethiolate, in H2 atmosphere at 250,°C for 3,h. The films are highly conducting and resistant to strong acidic, alkali, and oxidizing environments. The precursor allows patterning of the Pd4S films by electron beam lithography and micromolding, an attribute that has been employed in making chemically resistant electrodes and etch masks. The conversion of palladium thiolate to other sulfide phases is also achieved. [source]

Fabrication and Luminescent Properties of Nd3+ -Doped Lu2O3 Transparent Ceramics by Pressureless Sintering

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009
Ding Zhou
The fabrication of transparent Nd3+ ion-doped Lu2O3 ceramics is investigated by pressureless sintering under a flowing H2 atmosphere. The starting Nd-doped Lu2O3 nanocrystalline powder is synthesized by a modified coprecipitant processing using a NH4OH+NH4HCO3 mixed solution as the precipitant. The thermal decomposition behavior of the precipitate precursor is studied by thermogravimetric analysis and differential thermal analysis. After calcination at 1000°C for 2 h, monodispersed Nd3+:Lu2O3 powder is obtained with a primary particle size of about 40 nm and a specific surface area of 13.7 m2/g. Green compacts, free of additives, are formed from the as-synthesized powder by dry pressing followed by cold isostatic pressing. Highly transparent Nd3+:Lu2O3 ceramics are obtained after being sintered under a dry H2 atmosphere at 1880°C for 8 h. The linear optical transmittance of the polished transparent samples with a 1.4 mm thickness reaches 75.5% at the wavelength of 1080 nm. High-resolution transmission electron microscopy observations demonstrate a "clear" grain boundary between adjacent grains. The luminescent spectra showed that the absorption coefficient of the 3 at.% Nd-doped Lu2O3 ceramic at 807 nm reached 14 cm,1, while the emission cross section at 1079 nm was 6.5 × 10,20 cm2. [source]

Revisit to the Origin of Grain Growth Anomaly in Yttria-Doped Barium Titanate

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2001
Jung-Kun Lee
In this study, the effect of atmosphere during calcining and sintering of Y2O3 -doped BaTiO3 was investigated to reveal the origin of the anomaly of grain growth and conductivity as a function of Y2O3 content. Samples with various atmospheric histories were prepared. Microstructural and electrical variations were observed using SEM, dielectric (,r vs T) and thermopower measuring techniques, and impedance spectroscopy. An abrupt decrease in grain growth and a transition from semiconducting to insulating behavior were observed when the Y2O3 concentration exceeded 0.3 mol% and the samples were heat-treated in an O2 atmosphere. In contrast, the samples treated under N2+ 5% H2 atmosphere revealed neither grain growth anomaly nor conductivity anomaly even though the Y2O3 concentration was much greater than 3 mol%. The undoped BaTiO3 samples also demonstrated increased average grain size with increased oxygen partial pressure. Therefore, it was suggested that the grain growth anomaly did not result from the formation of cation vacancies V,Ba or V,,Ti. To investigate the origin of the grain growth anomaly, the Curie temperature, concentration of free electrons, and impedance spectra were measured. The grain growth anomaly and conductivity anomaly were associated with abrupt changes in all the measurements. These abrupt changes could be explained by the partial incorporation of donor dopants. Consequently, the origin of the anomaly in the microstructure and electrical properties are discussed in terms of grain-boundary segregation of the donor dopant. [source]

Diode-pumped passively mode-locked Yb3+ -doped yttrium lanthanum oxide ceramic laser

LASER PHYSICS LETTERS, Issue 8 2009
W. Li
Abstract A diode-pumped picosecond laser was demonstrated with Yb3+ -doped yttrium lanthanum oxide transparent laser ceramic Yb:(Y1,xLax)2O3 (x = 0.1), which was fabricated with nanopowders and sintered in H2 atmosphere. Passive modelocking was realized for the first time to our knowledge with a semiconductor saturable absorber mirror, generating pulses of 174 ps at the central wavelength 1032.5 nm with the average output power 162 mW under a diode-laser pump power of 3.2 W. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]