Study of the Luminescence of Eu-Doped Nanocrystalline Si/SiO2 Systems Prepared by RF Co-Sputtering

1999 ◽  
Vol 581 ◽  
Author(s):  
G.A. Nery ◽  
A. Mahfoud ◽  
L.F. Fonseca ◽  
H. Liu ◽  
O. Resto ◽  
...  
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Particle Sizes ◽  
Photoluminescence Intensity ◽  
Unanswered Question ◽  
Si Nanoparticle ◽  
Si Nanoparticles ◽  
Annealing Effects ◽  
The Eu ◽  
Nanocrystalline Si

ABSTRACTWe prepared Eu-doped films of Si nanoparticles embedded in SiO2 using pellets of Eu2O3 by sputtering. We studied their photoemission, transmission and fluorescence to obtain data about their composition and particle size and the Eu interaction characteristics. We were able to incorporate Eu(III) into the Si nanoparticle / SiO2 host. We also found we obtained Eu(II) in the process. We found a lowering of photoluminescence intensity with lowering of temperature. An as yet unanswered question is the reason for the intense whitish luminescence found in some regions of the samples. Some involvement with Eu(II) is suspected. Eu(IIl) related peaks were only observed where the size distribution peak of the nanoparticles was lower than 1.3nm. Whitish luminescence was related to peak sizes ranging from 1.1nm to 1.4nm. Annealing the samples had clear effects upon their photoluminescence, but did not necessarily involve changes in particle sizes, nor were these size changes necessary to increase luminescence. The Eu doping has a tendency to halt the annealing effects on size and, when changes did occur, the particles generally became smaller.

scholarly journals On microphysical processes of noctilucent clouds (NLC): observations and modeling of mean and width of the particle size-distribution

2010 ◽  
Vol 10 (2) ◽  
pp. 3605-3625
Author(s):  
G. Baumgarten ◽  
J. Fiedler ◽  
M. Rapp
Keyword(s):  
Particle Size ◽  
Linear Relationship ◽  
Size Distribution ◽  
Eddy Diffusion ◽  
Particle Sizes ◽  
Noctilucent Clouds ◽  
Atmospheric Variability ◽  
Distribution Width ◽  
Particle Properties ◽  
Microphysical Processes

Abstract. Noctilucent clouds (NLC) in the polar summer mesopause region have been observed in Norway (69° N, 16° E) between 1998 and 2009 by 3-color lidar technique. Assuming a mono-modal Gaussian size distribution we deduce mean and width of the particle sizes throughout the clouds. We observe a quasi linear relationship between distribution width and mean of the particle size at the top of the clouds and a deviation from this behavior for particle sizes larger than 40 nm, most often in the lower part of the layer. The vertically integrated particle properties show that 65% of the data follows the linear relationship with a slope of 0.42±0.02. For the vertically resolved particle properties (Δz=0.15 km) the slope is smaller and only 0.39±0.03. We compare our observations to microphysical modeling of noctilucent clouds and find that the distribution width depends on turbulence, the time that turbulence can act (cloud age), and the sampling volume/time (atmospheric variability). The model results nicely reproduce the measurements and show that the observed slope can be explained by eddy diffusion profiles as observed from rocket measurements.

scholarly journals MINERAL ABUNDANCE AND PARTICLE SIZE DISTRIBUTION DERIVED FROM IN-SITU SPECTRA MEASUREMENTS OF YUTU ROVER OF CHANG’E-3

2017 ◽  
Vol XLII-3/W1 ◽  
pp. 85-89
Author(s):  
H. Lin ◽  
X. Zhang ◽  
Y. Yang ◽  
X. Wu ◽  
D. Guo
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Landing Site ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Particle Sizes ◽  
The Mean ◽  
The Difference ◽  
Yutu Rover

From geologic perspective, understanding the types, abundance, and size distributions of minerals allows us to address what geologic processes have been active on the lunar and planetary surface. The imaging spectrometer which was carried by the Yutu Rover of Chinese Chang’E-3 mission collected the reflectance at four different sites at the height of ~ 1 m, providing a new insight to understand the lunar surface. The mineral composition and Particle Size Distribution (PSD) of these four sites were derived in this study using a Radiative Transfer Model (RTM) and Sparse Unmixing (SU) algorithm. The endmembers used were clinopyroxene, orthopyroxene, olivine, plagioclase and agglutinate collected from the lunar sample spectral dataset in RELAB. The results show that the agglutinate, clinopyroxene and olivine are the dominant minerals around the landing site. In location Node E, the abundance of agglutinate can reach up to 70 %, and the abundances of clinopyroxene and olivine are around 10 %. The mean particle sizes and the deviations of these endmembers were retrieved. PSDs of all these endmembers are close to normal distribution, and differences exist in the mean particle sizes, indicating the difference of space weathering rate of these endmembers.

Effects of vegetation cover on sediment particle size distribution and transport processes in natural rainfall conditions on post-fire hillslope plots in South Korea

Soil Research ◽  
2016 ◽  
Vol 54 (8) ◽  
pp. 937 ◽  
Author(s):  
Ewane Basil Ewane ◽  
Heon-Ho Lee
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Vegetation Cover ◽  
Rainfall Intensity ◽  
Transport Processes ◽  
Vegetation Recovery ◽  
Particle Sizes ◽  
Sediment Size ◽  
Aggregate Breakdown ◽  
Soil Burn Severity

Sediments were collected from four slow vegetation recovery plots, six fast vegetation recovery plots and five unburned plots at a post-fire site on a rainfall event basis and sorted for size distribution. The aim was to evaluate the effects of vegetation cover, soil aggregate stability, slope and rainfall intensity on sediment size distribution, transport selectivity and erosion processes between the burned and unburned treatment plots. Sediment detachment and transport mechanisms and the particle size transport selectivity of the eroded sediment were assessed based on enrichment ratios (ER) and mean weighted diameter (MWD) methods. The most eroded particle size class in all treatment plots was the 125–250μm class and, generally, the percentage of eroded particle sizes did not increase with slope and rainfall intensity. Higher MWD of the eroded sediment was related to a higher percentage of bare soil exposed and gravel content associated with high soil burn severity and soil disaggregation in the slow vegetation recovery plots. The enrichment of finer clay silt particle sizes increased with varying maximum 30-min rainfall intensity (I30) in the slow vegetation recovery plots, and reflected increased aggregate breakdown and transport selectivity, whereas no good relationship was found in the fast vegetation recovery and unburned plots with varying I30. A minimum I30 of <3.56mmh–1 and a maximum of 10.9mmh–1 were found to be the threshold rainfall intensity values necessary for aggregate breakdown and transport of finer particles by both rainsplash and rainflow in the slow vegetation recovery plots, whereas the response was weak in the fast vegetation recovery and unburned plots following varying I30 dominated only by rainsplash transport closer to the plot sediment collector. The results show that higher vegetation cover in the fast vegetation recovery and unburned plots reduces erosive rainfall energy by 5.6- and 17.7-fold respectively, and runoff energy by 6.3- and 21.3-fold respectively, limiting aggregate breakdown and transport selectivity of finer particles compared with the slow vegetation recovery plots.

scholarly journals Streaming instability of multiple particle species in protoplanetary disks

2018 ◽  
Vol 618 ◽  
pp. A75 ◽  
Author(s):  
Noemi Schaffer ◽  
Chao-Chin Yang ◽  
Anders Johansen
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Protoplanetary Disks ◽  
Single Species ◽  
Stokes Number ◽  
Dust Particles ◽  
Particle Sizes ◽  
Particle Species ◽  
Streaming Instability ◽  
Large Particles

The radial drift and diffusion of dust particles in protoplanetary disks affect both the opacity and temperature of such disks, as well as the location and timing of planetesimal formation. In this paper, we present results of numerical simulations of particle-gas dynamics in protoplanetary disks that include dust grains with various size distributions. We have considered three scenarios in terms of particle size ranges, one where the Stokes number τs = 10−1−100, one where τs = 10−4−10−1, and finally one where τs = 10−3−100. Moreover, we considered both discrete and continuous distributions in particle size. In accordance with previous works we find in our multispecies simulations that different particle sizes interact via the gas and as a result their dynamics changes compared to the single-species case. The larger species trigger the streaming instability and create turbulence that drives the diffusion of the solid materials. We measured the radial equilibrium velocity of the system and find that the radial drift velocity of the large particles is reduced in the multispecies simulations and that the small particle species move on average outwards. We also varied the steepness of the size distribution, such that the exponent of the solid number density distribution, dN∕da ∝ a−q, is either q = 3 or q = 4. Overall, we find that the steepness of the size distribution and the discrete versus continuous approach have little impact on the results. The level of diffusion and drift rates are mainly dictated by the range of particle sizes. We measured the scale height of the particles and observe that small grains are stirred up well above the sedimented midplane layer where the large particles reside. Our measured diffusion and drift parameters can be used in coagulation models for planet formation as well as to understand relative mixing of the components of primitive meteorites (matrix, chondrules and CAIs) prior to inclusion in their parent bodies.

scholarly journals Particle size distribution of sawdust and wood shavings mixtures

2010 ◽  
Vol 56 (No. 4) ◽  
pp. 154-158 ◽  
Author(s):  
T. Vítěz ◽  
P. Trávníček
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Distribution Function ◽  
Network Analysis ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Mass Fraction ◽  
Particle Sizes ◽  
Wood Shavings ◽  
Number Of Particles

Particle size distribution of the sample of waste sawdust and wood shavings mixtures were made with two commonly used methods of mathematical models by Rosin-Rammler (RR model) and by Gates-Gaudin-Schuhmann (GGS model).On the basis of network analysis distribution function F (d) (mass fraction) and density function f (d) (number of particles captured between two screens) were obtained. Experimental data were evaluated using the RR model and GGS model, both models were compared. Better results were achieved with GGS model, which leads to a more accurate separation of the different particle sizes in order to obtain a better industrial profit of the material.

Determination of Particle-Size Distribution in GR-S Latexes

1954 ◽  
Vol 27 (4) ◽  
pp. 1051-1060 ◽  
Author(s):  
Alfred Nisonoff ◽  
W. E. Messer ◽  
L. H. Howland
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Light And Electron Microscopy ◽  
Wide Distribution ◽  
Plant Production ◽  
Particle Sizes ◽  
Laboratory Centrifuge ◽  
Made In

Abstract A method based on Stokes' law, involving the use of an ordinary laboratory centrifuge, is described for the determination of particle size distribution in GR-S latexes. It is shown to be valid by tests for reproducibility and by comparison with the results of light and electron microscopy. In applying the method, several unusually fluid high-solids latexes made in the pilot plant were found to be characterized by a wide distribution of particle sizes. Data on various latexes in plant production are reported.

Effects of Acidity on the Stabilities of Cloudy Apple Juice

2018 ◽  
Vol 789 ◽  
pp. 26-30
Author(s):  
Dan Shi Zhu ◽  
Li Wei Wei ◽  
Xiao Jun Ren ◽  
Xue Hui Cao ◽  
He Liu ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Shelf Life ◽  
Size Distribution ◽  
Apple Juice ◽  
Influence Factor ◽  
Control Group ◽  
Particle Sizes ◽  
Stability Indexes ◽  
The Stability

Acidity is an important influence factor for juice stability. In this study, the effects of acidityon stability of cloudy apple juice were investigated. The stability indexes, such as, turbidity, cloudvalue, cloud stability, and particle size distribution (PSD) were measured at pH 2.0, 2.5, 3.0 and 3.5,along with the untreated juice (pH 3.8) as control group. The results showed that, pH has significanteffects on turbidity, chrome (C*), cloud value, and D50, D90 in PSD of cloudy apple juice. The juicehad a better stabilization at pH 2.5. At this pH condition, the turbidity, cloud value, cloud stability ofjuice was the best. In addition, at pH 2.5, the color of the juice was better, the particles were smaller,and the particle sizes were more uniform. By this study, a theoretical reference could be provided forimproving stability of cloudy apple juice and extending juice shelf life.

scholarly journals Milling Studies in an Impact Crusher I: Kinetics Modelling Based on Population Balance Modelling

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 470
Author(s):  
Ngonidzashe Chimwani ◽  
Murray M. Bwalya
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Population Balance ◽  
Impeller Speed ◽  
Balance Model ◽  
Population Balance Model ◽  
Particle Sizes ◽  
Product Size ◽  
Kinetics Modelling ◽  
Vertical Impact

A number of experiments were conducted on a laboratory batch impact crusher to investigate the effects of particle size and impeller speed on grinding rate and product size distribution. The experiments involved feeding a fixed mass of particles through a funnel into the crusher up to four times, and monitoring the grinding achieved with each pass. The duration of each pass was approximately 20 s; thus, this amounted to a total time of 1 min and 20 s of grinding for four passes. The population balance model (PBM) was then used to describe the breakage process, and its effectiveness as a tool for describing the breakage process in the vertical impact crusher is assessed. It was observed that low impeller speeds require longer crushing time to break the particles significantly whilst for higher speeds, longer crushing time is not desirable as grinding rate sharply decreases as the crushing time increases, hence the process becomes inefficient. Results also showed that larger particle sizes require shorter breakage time whilst smaller feed particles require longer breakage time.

scholarly journals PERMEABILITY OF DIFFERENT SIZE WASTE PARTICLES / SKIRTINGO DYDŽIO ATLIEKŲ DALELIŲ LAIDUMAS DRĖGMEI

2015 ◽  
Vol 7 (4) ◽  
pp. 407-412 ◽  
Author(s):  
Sabina Gavelytė ◽  
Kristina Bazienė ◽  
Nick Woodman ◽  
Anne Stringfellow
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Hydraulic Permeability ◽  
Particle Sizes ◽  
Waste Prevention ◽  
Drainage Layers ◽  
Waste Characteristics ◽  
Waste Particles ◽  
Waste Degradation

The world and life style is changing, but the most popular disposal route for waste is landfill globally until now. We have to think about waste prevention and preparing for re-use or recycling firstly, according to the waste disposal hierarchy. Disposed waste to the landfill must be the last opportunity. In a landfill, during waste degradation processes leachate is formed that can potentially cause clogging of bottom drainage layers. To ensure stability of a landfill construction, the physical properties of its components have to be controlled. The hydrology of precipitation, evaporation, runoff and the hydraulic performance of the capping and liner materials are important controls of the moisture content. The water balance depends also on the waste characteristics and waste particle size distribution. The aim of this paper is to determine the hydraulic permeability in a landfill depending on the particle size distribution of municipal solid waste disposed. The lab experiment results were compared with the results calculated with DEGAS model. Samples were taken from a landfill operated for five years. The samples particle sizes are: >100 mm, 80 mm, 60 mm, 40 mm, 20 mm, 0.01 mm and <0.01 mm. The permeability test was conducted using the column test. The paper presents the results of experiment and DEGAS model water permeability with waste particle size. Gyvenimo būdas kiekvieną dieną keičiasi, bet vienas populiariausių būdų šalinti atliekas yra sąvartynai. Pagal atliekų šalinimo hierarchiją pirmiausia, jas šalindami, turėtumėme galvoti apie tai, kaip išvengti atliekų ir paruošti jas naudoti dar kartą. Šalinti atliekas sąvartynuose turėtų būti paskutinė galimybė. Sąvartyne vykstant biodegradacijai susiformuoja filtratas, kuris dėl sudėtingos sudėties lemia filtrato surinkimo sistemų kolmataciją. Siekdami užtikrinti stabilumą sąvartyne, turime smulkinti ar suslėgti atliekas. Kritulių, garavimo kontroliavimas yra svarbus, užtikrinant tam tikrą komunalinių atliekų drėgnumą. Vandens balansas atliekų masėje taip pat priklauso nuo atliekų savybių ir atliekų dalelių dydžio. Šio darbo tikslas yra nustatyti vandens laidumą sąvartyne priklausomai nuo komunalinių atliekų dalelių dydžio pasiskirstymo. Laboratorinio eksperimento metu gauti rezultatai buvo palyginti su DEGAS modeliu gautais rezultatais. Tyrimui mėginiai buvo paimti iš sąvartyno, kurio amžius yra penkeri metai. Mėginių dalelių dydžiai yra: >100 mm, 80 mm, 60 mm, 40 mm, 20 mm, 0,01 mm ir <0,01 mm. Laidumo tyrimas buvo atliktas taikant kolonėlės testą. Straipsnyje pateikiami eksperimento metu ir taikant DEGAS modelį apskaičiuoti vandens laidumo rezultatai, esant skirtingo dydžio atliekų dalelėms.

Hevea Latex of Large Particle Size

1940 ◽  
Vol 13 (2) ◽  
pp. 415-421
Author(s):  
J. McGavack
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Aqueous Ammonia ◽  
Water Soluble ◽  
Distribution Data ◽  
Particle Sizes ◽  
Volume Changes ◽  
Large Particle Size ◽  
Complete Work

Abstract The purpose of this paper is to report, primarily, the particle size distribution of modified Hevea latices. In addition, the purpose is to show that the amount of nitrogen absorbed by the rubber particles in a latex thoroughly washed by aqueous ammonia depends on the surface exposed. Until the careful and complete work of Lucas (Ind. Eng. Chem. 30, 146 (1938)), there were no reliable particle size distribution data on a normal latex by which the distribution curves of modified latices could be compared. Now, as a result of his excellent technique for measuring all of the particles, even the very small ones, we are able to discuss clearly surface and volume changes when these smaller sized particles are removed. This work was so conducted as to eliminate particle sizes which could not be photographed with microscopical equipment in visible light. It was eventually carried out in such a way as to remove all water-soluble materials not adsorbed on or dissolved in the latex particles which were to be subsequently analyzed for nitrogen.

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