ISO-13321-1996.pdf
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1、INTE RNATIONAL STANDARD IS0 13321 First edition 1996-07-o I Particle size analysis - Photon correlation spectroscopy Analyse granulom B max c G2) f-2 Nv 77 r ;lo e P 8 P2 maximum value of the intercept B for a given setting of the detection optics; concentration of particulate material, in moles per
2、 litre; intensity autocorrelation function; refractive index of the dispersion medium; number of particles in scattering volume V; viscosity of the dispersion medium; decay rate; laser wavelength in vacua (632,8 nm for He-Ne laser); particle volume fraction; particle density; scattering angle; secon
3、d cumulant. 4 Principle A monochromatic and coherent laser light beam illuminates a representative sample for particle size analysis, dispersed at a suitable concentration in a liquid. The light scattered by the particles at an angle (typically 90) is recorded by a detector whose output is fed to a
4、correlator. The decay of the autocorrelation function of the scattered intensity is interpreted in terms of average particle size and polydispersity index by the so-called cumulants method. Annex C provides some theoreticai background for particle sizing by PCS. Copyright International Organization
5、for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/17/2007 21:32:55 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 13321:1996(E) is0 5 Apparatus beam is on. Observe local regulations for laser ra
6、diation safety. The main components of a typical photon correlation spectrometer are listed below. NOTE 2 - Commercial or “home-made” instruments that meet the requirements of this International Standard may be used. There are several significant differences, both in hardware and software, not only
7、between instruments from different manufacturers but also between different types from one manufacturer. The instrument specifications do not always give adequate information for proper assess- ment of its specific features. Therefore, annex D has been provided to recommend specifications for PCS in
8、struments. 5.1 Laser, monochromatic, emitting light polarized with its electric field component perpendicular to the plane formed by the incident and detected rays (vertical polarization), e.g. a He-Ne laser capable of 2 mW to 5 mW power output. 5.2 Sample holder, allowing control and measure- ment
9、of the temperature to within + 0,3 “C. 53 . Primary beam stop. 5.4 Optics and detector, to collect and digitize the radiation scattered by the sample at an angle of, e.g., 90”. If a polarization analyzer is included, it shall be positioned in the vertical position, i.e. with a maximum transmission f
10、or light polarized with its electrical field perpendicular to the plane of incident and scattered beams. 5.5 Correlator. 5.6 Computation unit. 6 Preliminary procedures 61 . Instrument location The instrument shall be placed in a clean environment, free from excessive electrical noise and mechanical
11、vibration and out of direct sunlight. If organic liquids are used (e.g. as an index-matched liquid and/or as the suspension medium), there shall be due regard to local health and safety requirements, and the area shall be well ventilated. The instrument shall be placed on a rigid table or bench to a
12、void necessity for fre- quent realignment of the optical system. NOTE 3 - Alternatively, it may incorporate a rigid optical bench internally. WARNING - PCS instruments are equipped with low or medium power lasers whose radiation can cause permanent eye damage, Never look into the direct path of the
13、laser beam or its reflections. Do not use highly reflecting surfaces when the laser 6.2 Sample preparation and inspection 6.2.1 Samples shall consist of well-dispersed par- ticles in a liquid medium. The dispersion liquid shall fulfil following requirements: a) b) cl d) d f 1 it shall be transparent
14、 (non-absorbing) at the laser wavelength; it shall be compatible with the materials used in the instrument; it shall not dissolve, swell or coagulate the particu- late material; it shall have a refractive index different from that of the particulate material; its refractive index and viscosity shall
15、 be known with an accuracy better than 0,5 %; it shall be well filtered. Water is often used as a dispersion medium. The use of freshly distilled water (the still shall be built from quartz glassware) or of deionized and filtered (pore size 0,2 pm) water is recommended. Since long-range particle int
16、eraction may affect the results for strongly charge-stabilized dispersions, a trace of salt c(NaCI) about IO-3 mol/l may be added to such samples to reduce the range of particle interaction. Large fluctuations in recorded scattered time- averaged signals (count rate) on short time scales (e.g. 0,l s
17、 intervals) with bursts of high count rates indicate the presence of contaminating dust. The appearance of sparkling centres in the beam also usually indicates a dusty sample. Such liquids shall be further cleaned (by filtration and/or distillation) before use. Detailed recommendations for sample pr
18、eparation are given in annex E. The dispersion liquid alone shall give no (or very low) scattered signal when checked in the instrument for dust or contaminants. 6.2.2 The concentration of particulate material shall be above some minimum level and shall not exceed a maximum level. The minimum level
19、is determined by the following two requirements: 1) The scattered intensity (count rate) of the sample containing the dispersed particles shall be at least 10 times higher than the signal scattered by the dispersion medium alone. 2) The number NV of particles in the scattering vol- ume shall be at l
20、east about 1 000 (any number in the range 500-I 000 is acceptable). 2 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/17/2007 21:32:55 MDTNo reproduction or networking permitted without
21、license from IHS -,-,- IS0 IS0 13321:1996(E) 3) 4) 5) NOTE 4 -This number can be estimated from the av- erage PCS diameter xpcs, from the particle volume frac- tion and from the value Vof the measuring volume by NV = 6qiWlm,$, A typical order of magnitude of V is 1 O-6 cm3 (its value can be found in
22、 the specifications provided by the in- strument manufacturer). This equation relates to monosized materials only; for polydisperse samples the actual number of particles in the scattering volume may be much larger than predicted by this equation. If this larger number density compromises the single
23、- scattering criteria 3) to 5), it may be that further dilution is necessary, leading to a requirement that either the coherence aperture in the receiver be increased or the incident laser beam made larger to increase the measurement volume. A subsequent reduction in measured intercept will then be
24、incurred. This com- promise is not permitted for the purposes of calibration and verification. The maximum level is mainly determined by the condition that only single scattering shall be ob- served, i.e. no multiple scattering. The absence of significant contributions from multiple scattering shall
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