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Xu R.L. Particle Characterization.. Light Scattering Methods (Kluwer,2000)(ISBN 0792363000)(T)(409s).djvu |
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Size 7.0Mb Date Feb 9, 2005 |
"sizing" module contains a strip photodiode and the "acceptance" module has a
linear photodiode array...
For dry powders, particles must be suspended in a gaseous medium
which forms a relatively quiescent cloud in the case of small particles or a
powder stream of constant velocity by means of a vibratory inclined trough
feeder for large particles...
On the other hand, liquids containing gas will change
viscosity, boil, or vaporize under reduced pressure, as occurs during aspiration...
The stream expands
between the exit of the upper nozzle and the entrance to the lower nozzle...
Recently, high density charge-coupled devices
(CCD) have also been used for submicron particle detection, in which charge
storage is utilized to buffer each data frame transferred from the CCD...
Relative particle scattering intensity over the solid angular range 5°-10° at X = 650
nm and no= 1.0...
In situations where a focused or sheathed flow cannot
be used, such as in in-situ measurements or in high vacuum measurements, not
all particles passing through the sensing zone follow the same trajectory...
As shown in these figures, the extinction efficiency for large or highly
absorptive particles approaches the value of 2...
For liquid measurements, the
latex suspension can be used directly if a proper concentration is chosen...
Comparison of latex size distributions using a modified HIAC optical particle
counter and a Coulter Counter® [33] (reproduced by permission of The Royal
Society of Chemistry)...
Therefore, if the calibration material
has different optical properties from that of the sample material, significant
variation in results can be expected from different instruments...
PARTICLE SIZE RESOLUTION
In particle size analysis the term "resolution" as used is defined how well an
instrument is able to differentiate populations of particles of similar size...
Through deconvolution
of the orientation effects in the measured data (similar to that given in Eq...
For small particles with
dimensions much smaller than that of the sensing zone, if the product of
the number concentration (the number of particles per unit volume) and
the volume of the sensing zone is smaller than 0.1, the deviation of the
measured distribution from the true distribution will be relatively small
and can often be neglected when compared to other unavoidable errors...
As shown in Figure 4.29, a choice of 50% counting efficiency
results in the same threshold setting for counters of different size resolution but
a large shift in the threshold when choosing a 90% counting efficiency...
Therefore, the sensing zone volume for the
smaller particle is about 2.5 times smaller than that for the larger particle...
The detected scattering may be from individual particles (single scattering), or
from the multiple scattering in a concentrated solution or suspension...
Yet
another cell design eliminates the need to know the refractive index of the
medium [11]...
By changing
232
CHAPTER 5
the direction of the incident beam (moving the mirror M2), the optics can cover
a continuous scattering angular range, in this case from 3.6° to 144.1° [13]...
This electron-hole pair is then swept out of the depletion region
between two differently doped semiconductor regions and a photocurrent is
produced...
; i.e., multiplying every pair of numbers that are separated by a delay time
jAt and averaging them over the measurement time (NsAt) to form one data
point in the ACF...
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