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ZnO Powders (zno + powder)

Distribution by Scientific Domains

Physics and Astronomy	55%
Polymers and Materials Science	33%

Selected Abstracts

Facile Gram-Scale Growth of Single-Crystalline Nanotetrapod-Assembled ZnO Through a Rapid Process

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2008
Jianye Li
Abstract From a rapid combustion and catalyst-free method, puresingle-crystalline nanotetrapod-assembled bulk nano-ZnO was grown on a gram-scale for the first time. The gram-scale bulk nano-ZnO is synthesized from ZnO powder with great reliability and repeatability, and also a high conversion efficiency. All four arms of the nanotetrapods are cone shaped and grow in the [001] direction. The photoluminescence properties of the nanotetrapod-assembled ZnO were studied and a mechanism was suggested for the growth of the bulk nanotetrapod-assembled ZnO. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Analysis of Nanocrystalline and Microcrystalline ZnO Sintering Using Master Sintering Curves

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2006
Kevin G. Ewsuk
Master sintering curves were constructed for dry-pressed compacts composed of either a nanocrystalline or a microcrystalline ZnO powder using constant heating rate dilatometry data and an experimentally determined apparent activation energy for densification of 268±25 and 296±21 kJ/mol, respectively. The calculated activation energies for densification are consistent with one another, and with values reported in the literature for ZnO densification by grain boundary diffusion. Grain boundary diffusion appears to be the single dominant mechanism controlling intermediate-stage densification in both the nanocrystalline and the microcrystalline ZnO during sintering from 65% to 90% of the theoretical density (TD). Based on both the consistency of the calculated activation energy as a function of density and the narrow dispersion of the sintering data about the master sintering curve (MSC) for the nanocrystalline ZnO, there is no evidence of either significantly enhanced surface diffusion or grain growth during sintering relative to the microcrystalline ZnO. The MSC constructed for the nanocrystalline ZnO was used to design time,temperature profiles to successfully achieve four different target sintered densities on the MSC, demonstrating the applicability of the MSC theory to nanocrystalline ceramic sintering. The most significant difference in sintering behavior between the two ZnO powders is the enhanced densification in the nanocrystalline ZnO powder at shorter times and lower temperatures. This difference is attributed to a scaling (i.e., particle size) effect. [source]

Incorporation of nitrogen acceptors in ZnO powder

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2006
D. Pfisterer
Abstract We report on the preparation and characterization of N-doped ZnO powders. EPR measurements revealed the presence of N-acceptors similar to those found in single crystals (Aiso = 1.225 mT, Aaniso = 0.864 mT, g, = 1.9953, g, = 1.9633). The photoluminescence of the samples shows donor to shallow acceptor recombinations. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Particle size of powders under hydrothermal conditions

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2003
Wen-Jun Li
Abstract Various non-oxide (CuI, AgI, AgCl, PbS, CuS and ZnS) and oxide (ZnO, TiO2, SnO2, CeO2 and ZrO2) powders were prepared under hydrothermal conditions to investigate the effects of temperature, pH and precursors on the particle size of powders. It was found that the particle sizes of PbS, CuS and ZnS powders were much smaller than that of CuI, AgI and AgCl powders prepared under the same conditions. The particle sizes of TiO2, SnO2, CeO2 and ZrO2 powders are much smaller than that of ZnO powders prepared under the same conditions. It is concluded that the solution conditions have a certain effect on the particle size of powders under the hydrothermal conditions. The particle size of powders increased with the rising of temperature. Additional factors affecting the particle size were uncovered through studying the nucleation mechanism. The particle size was mainly related to the Madelung constant and the electric charge number of ions. Powders with smaller particle size resulted from systems that possessed the larger Madelung constant and ionic charge number. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

UV Random Lasing Action in p-SiC(4H)/i-ZnO,SiO2 Nanocomposite/n-ZnO:Al Heterojunction Diodes

ADVANCED MATERIALS, Issue 13 2006

UV random lasing in p,i,n ZnO-based heterojunction diodes is achieved. The UV emission originates from the use of an intrinsic ZnO,SiO2 nanocomposite layer; the use of ZnO powders can improve the electrical-to-optical conversion efficiency of the heterojunction. The patterned ZnO clusters in the SiO2 matrix enhance the quality of the random media (see figure) thus sustaining the random lasing action. If low-index, p-doped, wide-bandgap materials are used as the hole-injection layer, strong coherent random lasing could be achieved. [source]

Analysis of Nanocrystalline and Microcrystalline ZnO Sintering Using Master Sintering Curves

Random lasing in nanocrystalline ZnO powders

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2010
Heinz Kalt
Abstract We investigate the properties of random lasing in nanocrystalline ZnO powders. The lowest threshold for lasing occurs for average particle diameters of about 260,nm. Reproducible lasing features are achieved for reduced ensemble sizes. Spatially resolved luminescence spectroscopy is used to probe directly the degree of localization of random laser mode. We find that strongly confined and extended modes can co-exist in the same spatial area. However, localized modes appear for small optical gain while extended modes are only supported in the presence of large optical gain, as is expected from theory. Localized and extended random-laser modes co-exist in space but appear in spectral regions of low and high optical gain, respectively. [source]