Narrowing sputtered nanoparticle size distributions

1993 ◽  
Vol 8 (5) ◽  
pp. 995-1000 ◽  
Author(s):  
F.H. Kaatz ◽  
G.M. Chow ◽  
A.S. Edelstein
Keyword(s):  
Size Distribution ◽  
Mean Free Path ◽  
Particle Formation ◽  
Distribution Functions ◽  
Size Distributions ◽  
Narrow Size Distribution ◽  
Linear Arrangement ◽  
Nanocrystalline Particle ◽  
The Mean ◽  
Potential Use

By adjusting the sputtering rate and gas pressure, it is possible to form nanoparticles of different sizes, phases, and materials. We have investigated the spatial distribution of sputtered particle formation using a vertical, linear arrangement of substrates. Collecting the particles soon after they are formed, before they have time to grow and agglomerate, allows one to obtain a narrow size distribution. In the case of molybdenum, a narrow distribution of cubic particles is formed at relatively large distances (8 cm) from the source. These cubic particles collide and self-assemble in the vapor into arrays of larger cubic particles. The particle size histograms are fitted to lognormal distribution functions. How supersaturation occurs is discussed qualitatively as a function of the distance from the substrate, sputtering rate, and the mean free path in the vapor. This method of nanocrystalline particle formation has potential use in magnetic and opto-electronic (quantum dot) applications, where a narrow size distribution is required.

Effects of grain size distribution on Cole-Cole plots of polycrystalline spinels

2001 ◽  
Vol 699 ◽  
Author(s):  
M. P. Gutiérrez-Amador ◽  
R. Valenzuela
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mean Free Path ◽  
Size Distributions ◽  
Frequency Range ◽  
Impedance Response ◽  
Grain Size Distributions ◽  
The Mean ◽  
Different Grain Size

AbstractSpinel ferrites of composition Ni0.5Zn0.5Fe2O4 were prepared by coprecipitation. Different grain size and grain size distributions were obtained by various heat treatments. Their electrical properties were investigated by impedance spectroscopy in the temperature range 25-200°C and in the frequency range of 5Hz-13MHz. A decrease in resistivity was observed as grain size increased, which can be explained by an increase in the mean free path of electrons. Cole-Cole plots showed two well-resolved semicircles for samples with a narrow grain size distribution. As the width of the distribution increased, the semicircles exhibited a deformation and eventually became unresolved. These results are interpreted on the basis of a distribution of time-constant of the impedance response, associated with the grain size distribution.

Characterization of Booming Sands

2002 ◽  
Vol 759 ◽  
Author(s):  
Katherine S. Brantley ◽  
Melany L. Hunt ◽  
Christopher E. Brennen ◽  
Steven S. Gao
Keyword(s):  
United States ◽  
Moisture Content ◽  
Size Distribution ◽  
Sand Dunes ◽  
The United States ◽  
Size Distributions ◽  
Narrow Size Distribution ◽  
Dune Sands ◽  
The Mean

ABSTRACTMany sand dunes – at least seven in the United States – make loud booming noises when they avalanche. Records of the sound are centuries old, but the cause remains a mystery. This study examines properties of both the sand and the sound.Properties of the sand reveal clues about the source of the booming. Sand must be extremely dry to boom, but low moisture content alone is not sufficient to facilitate booming. Although the mean grain diameters of both booming and silent dune sands range from 0.20 – 0.40mm, the booming samples have smaller standard deviations. However, synthetic sands with similar size distributions do not boom, so a narrow size distribution cannot be solely responsible for the booming. Studies of the roundness and sphericity of the grains are currently underway.Air microphone and geophone recordings of the booming indicate that the fundamental frequency varies between 80–105 Hz depending on the dunes. This is consistent with previous measurements. Laboratory recordings of the “burping” sound that booming sand makes when shaken in a jar reveal a broad peak between 150–300 Hz.

scholarly journals Quantifying aerosol size distributions and their temporal variability in the Southern Great Plains, USA

2019 ◽  
Vol 19 (18) ◽  
pp. 11985-12006 ◽  
Author(s):  
Peter J. Marinescu ◽  
Ezra J. T. Levin ◽  
Don Collins ◽  
Sonia M. Kreidenweis ◽  
Susan C. van den Heever
Keyword(s):  
Size Distribution ◽  
Great Plains ◽  
Diurnal Cycle ◽  
Particle Formation ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
New Particle Formation ◽  
Scanning Mobility Particle Sizer ◽  
Southern Great Plains ◽  
Particle Sizer

Abstract. A quality-controlled, 5-year dataset of aerosol number size distributions (particles with diameters (Dp) from 7 nm through 14 µm) was developed using observations from a scanning mobility particle sizer, aerodynamic particle sizer, and a condensation particle counter at the Department of Energy's Southern Great Plains (SGP) site. This dataset was used for two purposes. First, typical characteristics of the aerosol size distribution (number, surface area, and volume) were calculated for the SGP site, both for the entire dataset and on a seasonal basis, and size distribution lognormal fit parameters are provided. While the median size distributions generally had similar shapes (four lognormal modes) in all the seasons, there were some significant differences between seasons. These differences were most significant in the smallest particles (Dp<30 nm) and largest particles (Dp>800 nm). Second, power spectral analysis was conducted on this long-term dataset to determine key temporal cycles of total aerosol concentrations, as well as aerosol concentrations in specified size ranges. The strongest cyclic signal was associated with a diurnal cycle in total aerosol number concentrations that was driven by the number concentrations of the smallest particles (Dp<30 nm). This diurnal cycle in the smallest particles occurred in all seasons in ∼50 % of the observations, suggesting a persistent influence of new particle formation events on the number concentrations observed at the SGP site. This finding is in contrast with earlier studies that suggest new particle formation is observed primarily in the springtime at this site. The timing of peak concentrations associated with this diurnal cycle was shifted by several hours depending on the season, which was consistent with seasonal differences in insolation and boundary layer processes. Significant diurnal cycles in number concentrations were also found for particles with Dp between 140 and 800 nm, with peak concentrations occurring in the overnight hours, which were primarily associated with both nitrate and organic aerosol cycles. Weaker cyclic signals were observed for longer timescales (days to weeks) and are hypothesized to be related to the timescales of synoptic weather variability. The strongest periodic signals (3.5–5 and 7 d cycles) for these longer timescales varied depending on the season, with no cyclic signals and the lowest variability in the summer.

Size decrease of detonation nanodiamonds by air annealing investigated by AFM

MRS Advances ◽  
2016 ◽  
Vol 1 (16) ◽  
pp. 1067-1073 ◽  
Author(s):  
Stepan Stehlik ◽  
Daria Miliaieva ◽  
Marian Varga ◽  
Alexander Kromka ◽  
Bohuslav Rezek
Keyword(s):  
Size Distribution ◽  
Annealing Temperature ◽  
Detonation Nanodiamonds ◽  
Particle Analysis ◽  
Detonation Synthesis ◽  
Size Distributions ◽  
Force Microscopy ◽  
Atomic Force ◽  
Mean Size ◽  
The Mean

ABSTRACTNanodiamonds (NDs) represent a novel nanomaterial applicable from biomedicine to spintronics. Here we study ability of air annealing to further decrease the typical 5 nm NDs produced by detonation synthesis. We use atomic force microscopy (AFM) with sub-nm resolution to directly measure individual detonation nanodiamonds (DNDs) on a flat Si substrate. By means of particle analysis we obtain their accurate and statistically relevant size distributions. Using this approach, we characterize evolution of the size distribution as a function of time and annealing temperature: i) at constant time (25 min) with changing temperature (480, 490, 500°C) and ii) at constant temperature (490°C) with changing time (10, 25, 50 min). We show that the mean size of DNDs can be controllably reduced from 4.5 nm to 1.8 nm without noticeable particle loss and down to 1.3 nm with 36% yield. By air annealing the size distribution changes from Gaussian to lognormal with a steep edge around 1 nm, indicating instability of DNDs below 1 nm.

scholarly journals On the sub-micron aerosol size distribution in a coastal-rural site at El Arenosillo Station (SW – Spain)

2011 ◽  
Vol 11 (21) ◽  
pp. 11185-11206 ◽  
Author(s):  
M. Sorribas ◽  
B. A. de la Morena ◽  
B. Wehner ◽  
J. F. López ◽  
N. Prats ◽  
...  
Keyword(s):  
Size Distribution ◽  
Particle Formation ◽  
Rural Site ◽  
Aerosol Size Distribution ◽  
Land Breeze ◽  
Air Masses ◽  
Desert Dust ◽  
Median Size ◽  
The Mean ◽  
Marine Air

Abstract. This study focuses on the analysis of the sub-micron aerosol characteristics at El Arenosillo Station, a rural and coastal environment in South-western Spain between 1 August 2004 and 31 July 2006 (594 days). The mean total concentration (NT) was 8660 cm−3 and the mean concentrations in the nucleation (NNUC), Aitken (NAIT) and accumulation (NACC) particle size ranges were 2830 cm−3, 4110 cm−3 and 1720 cm−3, respectively. Median size distribution was characterised by a single-modal fit, with a geometric diameter, median number concentration and geometric standard deviation of 60 nm, 5390 cm−3 and 2.31, respectively. Characterisation of primary emissions, secondary particle formation, changes to meteorology and long-term transport has been necessary to understand the seasonal and annual variability of the total and modal particle concentration. Number concentrations exhibited a diurnal pattern with maximum concentrations around noon. This was governed by the concentrations of the nucleation and Aitken modes during the warm seasons and only by the nucleation mode during the cold seasons. Similar monthly mean total concentrations were observed throughout the year due to a clear inverse variation between the monthly mean NNUC and NACC. It was related to the impact of desert dust and continental air masses on the monthly mean particle levels. These air masses were associated with high values of NACC which suppressed the new particle formation (decreasing NNUC). Each day was classified according to a land breeze flow or a synoptic pattern influence. The median size distribution for desert dust and continental aerosol was dominated by the Aitken and accumulation modes, and marine air masses were dominated by the nucleation and Aitken modes. Particles moved offshore due to the land breeze and had an impact on the particle burden at noon, especially when the wind was blowing from the NW sector in the morning during summer time. This increased NNUC and NAIT by factors of 3.1 and 2.4, respectively. Nucleation events with the typical "banana" shape were characterised by a mean particle nucleation rate of 0.74 cm−3 s−1, a mean growth rate of 1.96 nm h−1 and a mean total duration of 9.25 h (starting at 10:55 GMT and ending at 20:10 GMT). They were observed for 48 days. Other nucleation events were identified as those produced by the emissions from the industrial areas located at a distance of 35 km. They were observed for 42 days. Both nucleation events were strongly linked to the marine air mass origin.

scholarly journals Density and Size Distribution of the Sea Cucumber, Holothuria scabra (Jaeger, 1935), at Six Exploited Sites in Mahout Bay, Sultanate of Oman

2007 ◽  
Vol 12 ◽  
pp. 43 ◽  
Author(s):  
Khalfan M. Al-Rashdi ◽  
Michel R. Claereboudt ◽  
Saud S. Al-Busaidi
Keyword(s):  
Size Distribution ◽  
Sea Cucumber ◽  
Size Distributions ◽  
Sultanate Of Oman ◽  
Population Densities ◽  
Sea Cucumbers ◽  
Holothuria Scabra ◽  
Mean Size ◽  
Males And Females ◽  
The Mean

A rapid survey of the density and size distribution of recently exploited populations of Holothuria scabra in Mahout Bay (Ghubbat Hashish Bay) was carried out at six fishing sites. The results showed that population densities varied between 1170 and 4000 individuals ha-1 and biomass ranged between 393 and 2903 kg ha-1. The mean size of sea cucumbers and population densities were much lower in populations closer to human settlements, suggestive of overfishing. The sex ratio was estimated to be 1:1 and the size distributions of males and females did not differ significantly. The length-weight relationship for both sexes was calculated as W (g) = 0.033 Length (mm) 2.178. 

Size distribution functions of submicron aerosol and approximation based on the direct Kolmogorov equation

2020 ◽  
Author(s):  
Otto Chkhetiani ◽  
Evgeny Gledzer ◽  
Natalia Vazaeva
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Aerosol Particles ◽  
Distribution Functions ◽  
Dust Aerosol ◽  
Fragmentation Process ◽  
Aral Sea ◽  
Kolmogorov Equation ◽  
Radiation Budget ◽  
Size Distributions

&lt;p&gt;The particle size distribution function is one of the characteristics reflecting the composition of aerosol during sand lifting and removal in desert regions. This characteristic, in addition to known practical applications, is important in describing radiation processes during the exchange of heat fluxes and in forming cloud systems in the models of atmospheric dynamics. Fine dust-aerosol fractions (less than 2 &amp;#181;m in diameter) are especially important for the atmospheric radiation budget, because such fractions (having a significant lifetime) most efficiently interact with short-wave solar radiation. One of the central regularities in considering the size distributions of simulated dust-aerosol particles is the following formula based on the so-called fragmentation process and verified using a large amount of empirical data &lt;em&gt;N &lt;/em&gt;(&lt;em&gt;d&lt;/em&gt;) ~ &lt;em&gt;d &lt;/em&gt;&lt;sup&gt;-2&lt;/sup&gt;. Similar dependence for particles with size &lt;em&gt;d &lt;/em&gt;&gt; 1 &amp;#181;m is associated with the consideration of the fragmentation process as a particle splitting according to the log-normal distribution.&lt;/p&gt;&lt;p&gt;Results of field measurements taken in the near&amp;#8211;Caspian (2002, 2003, 2007, 2009, 2010, 2011, 2013, 2014, 2016 years) and near&amp;#8211;Aral-sea (1998) deserts under the conditions of weak winds (almost in the absence of saltation processes) and strong heating of the land surface are given. These results show that the fine mineral dust aerosol (0.1-1 &amp;#181;m) considerably contributes to the total aerosol content of the atmospheric surface layer under such conditions. The scaling of daytime mean size &lt;em&gt;d&lt;/em&gt; distribution at a height of 2 m is close to &lt;em&gt;d &lt;/em&gt;&lt;sup&gt;-5&lt;/sup&gt;&amp;#160;in contrast to the law &lt;em&gt;d &lt;/em&gt;&lt;sup&gt;-2&lt;/sup&gt; for fraction&amp;#160;&lt;em&gt;d&lt;/em&gt; &gt;1 &amp;#181;m.&lt;/p&gt;&lt;p&gt;Different compositions of aerosol particles at 0.1 &lt; &lt;em&gt;d &lt;/em&gt;&lt; 1 &amp;#181;m, and &lt;em&gt;d&lt;/em&gt; &gt;1 &amp;#181;m, including multicomponent fractions (less than 1 &amp;#181;m) may result in different probabilities of their integration and disintegration, which, finally, determine equilibrium particle size distributions. The simplest distribution approximations based on the Kolmogorov direct differential equation are given.&amp;#160;&lt;/p&gt;&lt;p&gt;This study was supported by the RFBR (19-05-50110) and the Presidium of the Russian Academy of Sciences (programs 12 and 20).&lt;/p&gt;

Size Distribution in Periphyton

1987 ◽  
Vol 44 (11) ◽  
pp. 2025-2028 ◽  
Author(s):  
Antonella Cattaneo
Keyword(s):  
Size Distribution ◽  
Fish Community ◽  
Size Class ◽  
Size Distributions ◽  
Size Classes ◽  
Rule Of Thumb ◽  
Littoral Fish ◽  
Order Of Magnitude ◽  
The Mean

When periphytic organisms growing on artificial plants were grouped in logarithmically increasing size classes, patterns in the distribution of biomass were consistent over the season and under different grazing regimes, despite taxonornical changes in the dominant taxa of algae and invertebrates. The amount in each size class was not constant, and instead, certain classes tended to have values consistently lower or higher than the mean. The locations of these peaks and troughs in the size distributions coincided with those observed in lake plankton. Despite these irregularities, the hypothesis that the biomass in logarithmic size classes is constant apparently applies at a crude level, for the biomass of most size classes lay within an order of magnitude of the mean. This rule of thumb also applies to the littoral fish community, for the minnow biomass was approximately that in a periphyton size class.

scholarly journals Departure from MHD prescriptions in shock formation over a guiding magnetic field

2017 ◽  
Vol 35 (3) ◽  
pp. 513-519 ◽  
Author(s):  
A. Bret ◽  
A. Pe'er ◽  
L. Sironi ◽  
M.E. Dieckmann ◽  
R. Narayan
Keyword(s):  
Magnetic Field ◽  
Free Path ◽  
Mean Free Path ◽  
Distribution Functions ◽  
Shock Formation ◽  
Physical Analysis ◽  
Particle In Cell ◽  
The Mean ◽  
Collective Plasma ◽  
Aligned Magnetic Field

AbstractIn plasmas where the mean-free-path is much larger than the size of the system, shock waves can arise with a front much shorter than the mean-free-path. These so-called “collisionless shocks” are mediated by collective plasma interactions. Studies conducted so far on these shocks found that although binary collisions are absent, the distribution functions are thermalized downstream by scattering on the fields, so that magnetohydrodynamics prescriptions may apply. Here we show a clear departure from this pattern in the case of Weibel shocks forming over a flow-aligned magnetic field. A micro-physical analysis of the particle motion in the Weibel filaments shows how they become unable to trap the flow in the presence of too strong a field, inhibiting the mechanism of shock formation. Particle-in-cell simulations confirm these results.

The Determination of Crystallite Size and Size Distribution from Broadened X-Ray Diffraction Lines

1961 ◽  
Vol 5 ◽  
pp. 94-103 ◽  
Author(s):  
H. F. Quinn ◽  
P. Cherin
Keyword(s):  
Harmonic Analysis ◽  
Size Distribution ◽  
Fourier Coefficients ◽  
Distribution Functions ◽  
Composite Sample ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mean Size ◽  
The Mean

AbstractMagnesium oxide crystallites having mean dimensions in the range of 25–1000 A can be prepared by controlled thermal decomposition of the carbonate.Following some earlier investigations of Birks and Friedman, we have determined the mean size and size distribution of several such MgO samples from the broadened X-ray diffraction lines which they exhibit. Contrary to the procedure of the above investigators, the harmonic analysis due to Stokes has been used to correct for instrumental broadening and values of mean-size and size-distribution functions obtained from the Fourier coefficients by the methods of Warren and Averbach.The results obtained are compared with average sizes and distributions obtained by direct examination of the samples in an electron microscope.A composite sample has been prepared by mixing known quantities of the sample previously studied. The distribution function obtained by harmonic analysis of one diffraction line of the composite sample is compared with the function calculated from the distributions of its components.Conclusions are drawn concerning the significance of the results obtained by the Warren technique: in particular, the average sizes obtained by this method are compared with those given by the approximate method used by Birks and Friedman.

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