Ultraviolet Photoluminescence from 4H–SiC Nanocrystalline Films Deposited on Silicon Substrate

2002 ◽  
Vol 17 (3) ◽  
pp. 570-574 ◽  
Author(s):  
Zhengping Fu ◽  
Beifang Yan ◽  
Ruchuan Liu ◽  
Yaozhong Ruan
Keyword(s):  
Silicon Oxide ◽  
Luminescence Center ◽  
Silicon Substrates ◽  
Nanocrystalline Films ◽  
Sic Nanoparticles ◽  
Langmuir Blodgett ◽  
Langmuir Blodgett Films ◽  
Mean Size ◽  
The Mean ◽  
Size Of Particles

Preferred-orientated 4H–SiC nanocrystalline films on silicon substrates were successfully prepared by the pyrolysis of the polyimide Langmuir–Blodgett films containing nanometer-sized amorphous silicon nitride powders. Fourier-transform infrared spectra revealed 4H–SiC nanoparticles with interfacial silicon oxide. Ultraviolet photoluminescence with energies above the band gap of bulk 4H–SiC was observed from the films in which the mean size of 4H–SiC particles was 10 nm, while no photoluminescence was observed from the films in which the mean size of particles was 17 nm. A quantum confinement/luminescence center model is suggested to explain the origin of the ultraviolet luminescence.

scholarly journals Models of explosive volcanism

1995 ◽  
Vol 2 (3/4) ◽  
pp. 269-279 ◽  
Author(s):  
A. W. Woods ◽  
S. M. Bower ◽  
M. I. Bursik
Keyword(s):  
Mass Flux ◽  
Subsonic Flow ◽  
Supersonic Jet ◽  
Explosive Volcanism ◽  
Eruption Column ◽  
Flow Temperature ◽  
Mean Size ◽  
The Mean ◽  
Size Of Particles ◽  
Residual Ash

Abstract. We describe a series of models which illustrate the controls upon the evolution of an erupting mixture of ash and gas during an explosive volcanic eruption. For large eruption rates, material typically issues from a crater as a supersonic jet which may entrain and heat sufficient air to become buoyant and form a Plinian eruption column. If a buoyant eruption column is able to form, then this column may ascend to heights of order 10-30 km, depending upon the erupted mass flux. In contrast, for low eruption rates, a shock forms in the crater and the material issues as a slow subsonic flow which generates dense hot ash flows. A new model shows that as such ash flows propagate from the vent, the density of the flow decreases mainly due to sedimentation, until ultimately the residual ash flow becomes buoyant. The distance the flow travels before becoming buoyant increases with the mass flux in the current and the mean size of particles in the current, but decreases with the flow temperature. It also depends upon the mass of air entrained into the collapsing fountain. The mass fraction of solid lifted from such ash flows into the ascending cloud depends mainly upon the mass of air entrained into the collapsing fountain near the volcanic vent. We apply our models to predict run-out distances and deposition patterns produced by erupting volcanoes.

scholarly journals Al2O3 Particles on Titanium Dental Implant Systems following Sandblasting and Acid-Etching Process

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Peter Schupbach ◽  
Roland Glauser ◽  
Sebastian Bauer
Keyword(s):  
Dental Implant ◽  
Sem Analysis ◽  
Acid Etching ◽  
Mean Size ◽  
Bone Level ◽  
Titanium Dental Implant ◽  
The Mean ◽  
Particle Counts ◽  
Size Of Particles ◽  
Implant System

Dental implants with moderately rough surfaces show enhanced osseointegration and faster bone healing compared with machined surfaces. The sandblasting and acid-etching (SA) process is one technique to create moderately rough dental implant surfaces. The purpose of this study was to analyse different commercially available implant systems with a SA-modified surface and to explore the widespread notion that they have similar surface properties regarding morphology and cleanliness. SA-modified surfaces of nine implant systems manufactured by Alpha-Bio Tec Ltd, Camlog Biotechnologies AG, Dentsply Sirona Dental GmbH, Neoss Ltd, Osstem Implant Co. Ltd, Institute Straumann AG, and Thommen Medical AG were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) and examined for surface cleanliness. Six implants from three different lots were selected per each implant system. Mean particle counts for each implant and the mean size of the particles were calculated from three different regions of interest and compared using ANOVA and Tukey’s test. SEM analysis showed presence of particles on the majority of analyzed implant surfaces, and EDX evaluations determined that the particles were made of Al2O3 and thus remnants of the blasting process. SPI®ELEMENT INICELL® and Bone Level (BL) Roxolid® SLActive® implant surfaces showed the highest mean particle counts, 46.6 and 50.3 per area, respectively. The surface of BL Roxolid® SLActive® implant also showed the highest variations in the particle counts, even in samples from the same lot. The mean size of particles was 1120±1011 μm2, measured for USIII CA Fixture implants, while the biggest particle was 5900 μm2 found on a BL Roxolid® SLActive® implant. These results suggest that not all manufacturers are able to produce implant surfaces without particle contamination and highlight that the surface modification process with the SA technique should be appropriately designed and controlled to achieve a clean and consistent final medical device.

Grazing Incidence X-Ray Reflectometry Studies of Cadmium Arachidate Langmuir-Blodgett Films

1991 ◽  
Vol 237 ◽  
Author(s):  
B. K. Tanner ◽  
D. K Bowen ◽  
M. C Petty ◽  
S. Swaminathan ◽  
F. Granfeld
Keyword(s):  
Molecular Layer ◽  
Grazing Incidence ◽  
Interface Roughness ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
X Ray ◽  
Langmuir Blodgett ◽  
Crystal Imperfections ◽  
Langmuir Blodgett Films ◽  
Good Agreement

ABSTRACTGrazing incidence X-ray reflectometry has been used to characterize Langmuir-Blodgett films of cadmium arachidate deposited on silicon substrates. The agreement between layer parameters deduced from the interference fringe period and low angle Bragg peak positions was excellent. Good agreement was found between experimental and simulated reflectivity profiles only when interface roughness and a varying molecular layer thickness was included. Inclusion of interface roughness alone results in a substantial enhancement in the intensity of the Bragg peaks. This effect is identified as being equivalent to the reduction in extinction found in classical X-ray diffraction due to crystal imperfections.

Langmuir-blodgett films of liquid-crystalline heteroaromatic cations associated with diamagnetic (BF4-, CIO4-) or paramagnetic (TCNQ[math]) anions

1988 ◽  
Vol 85 ◽  
pp. 385-389 ◽  
Author(s):  
M. Vandevyver ◽  
J. Richard ◽  
A Barraud ◽  
M. Veber ◽  
C Jallabert ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Langmuir Blodgett ◽  
Langmuir Blodgett Films

Non linear physical properties of langmuir-blodgett films : their possible applications

1988 ◽  
Vol 85 ◽  
pp. 1093-1097 ◽  
Author(s):  
G.G. Roberts ◽  
B. Holcroft ◽  
T. Richardson ◽  
R. Colbrook
Keyword(s):  
Physical Properties ◽  
Langmuir Blodgett ◽  
Non Linear ◽  
Langmuir Blodgett Films

Manufacturing of direct exfoliation graphene-based transparent conducting Langmuir – Blodgett films

2018 ◽  
pp. 17-28
Author(s):  
E. A. Danilov ◽  
◽  
V. M. Samoilov ◽  
V. S. Dmitrieva ◽  
A. V. Nikolaeva ◽  
...  
Keyword(s):  
Langmuir Blodgett ◽  
Transparent Conducting ◽  
Langmuir Blodgett Films

Batch Precipitation of Lead Iodide

1994 ◽  
Vol 59 (6) ◽  
pp. 1301-1304
Author(s):  
Jaroslav Nývlt ◽  
Stanislav Žáček
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Crystal Size ◽  
Lead Nitrate ◽  
Lead Iodide ◽  
Constant Rate ◽  
Mean Size ◽  
The Mean

Lead iodide was precipitated by a procedure in which an aqueous solution of potassium iodide at a concentration of 0.03, 0.10 or 0.20 mol l-1 was stirred while an aqueous solution of lead nitrate at one-half concentration was added at a constant rate. The mean size of the PbI2 crystals was determined by evaluating the particle size distribution, which was measured sedimentometrically. The dependence of the mean crystal size on the duration of the experiment exhibited a minimum for any of the concentrations applied. The reason for this is discussed.

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