JPH0484736A - Method for measuring particle size distribution - Google Patents

Abstract

PURPOSE:To make it possible to determine accurate particle size distribution by dispersing the same sample into two solvents having the different refractive indexes, measuring the angle distributions of the intensities of the scattered light beams from both solvents, and finding the refractive index of a particle. CONSTITUTION:A sample W is uniformly dispersed into a solvent. The sample W is made to flow into a cell 1 under this state. A laser beam having the specified cross section is emitted from an emitting optical system comprising a laser light source 2 and a beam expander 3. The scattered light beams from the sample W are outputted through semiconductor photosensors P1 - Pn of a ring detector 5 and a photosensor Ps for measuring the sideward scattered light. The particle size distribution is outputted from a computor 12 based on the various kinds of relative refractive idexes for the scattering angle thetaof each photosensor and the memories of the theoritical scattered-light intensities of various kinds of particle diameters D. Thus, the accurate particle size distribu tion can be determined.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for measuring the particle size distribution of powder, particularly a light scattering type particle size distribution measuring method.

<Prior Art> Methods for measuring the particle size distribution of powder include a centrifugal sedimentation method and a laser diffraction/light scattering method. The former causes particles to settle while applying centrifugal force.

The particle size distribution is measured using the Stokes equation based on the difference in sedimentation rate, and if the particles are small, the sedimentation rate is slow and the measurement takes time (about 20 to 30 minutes). The latter measures the angular distribution of the intensity of diffracted light/scattered light, and uses the theoretical value of Fraunhofer diffraction for large particles, and the theoretical value of Mie scattering for small particles (10 μm or less) for a short time ( (about 2-3 minutes)
This is what we are trying to measure.

<Problems to be Solved by the Invention> Since the theoretical value of Mie scattering changes depending on the relative refractive index of the two particles with respect to the solvent, it is necessary to input the refractive index of the solvent and the particles in advance to calculate the nine particle size distribution. However, the refractive index of powder particles is often unknown, and the current practice is to enter an appropriate value by referring to the refractive index of substances known in literature, etc. 2. The particle size range and shape of the particle size distribution will change. The present invention has been made in view of these points.

The purpose is to provide a method for measuring accurate particle size distribution.

Means for Solving the Problems> In order to achieve the above objects, the present invention uses the same sample in two solvents, each having a considerably different refractive index, such as water (n+-1,33) and cyclohexanone (n2-1,33).
45), measure the angular distribution of the scattered light intensity, and store these data in, for example, a computer. Also, the refractive index nl+ of the two solvents used at this time
Enter n2 into the computer in advance (.

When the above two sets of data are input, the computer assumes various values for the refractive index M of the nine particles, and first calculates the particle size distribution for various refractive indexes when using solvent 1.

Calculation is relative refractive index mI=M with respect to refractive index n+ of solvent 1
/n1 as a parameter.

This is performed based on actually measured data of the angular distribution of scattered light intensity when using Solvent 1 and Mie's theory.

Subsequently, particle size distributions for various refractive indexes when using Solvent 2 are calculated in the same manner.

The actual particle size distribution of the powder should be unrelated to the type of solvent used, so if you find the refractive index that best matches the particle size distribution for each solvent, that is the actual refractive index of the particles. The particle size distribution with respect to the refractive index becomes the actual particle size distribution.

It is possible to determine whether the particle size distributions in each solvent match by pattern analysis using a computer, so after the measurements with the two types of solvents are completed, all these operations are processed by the computer, and only the final results are analyzed. Output.

Kumi foothill example FIG. 1 is a plan view showing the configuration of two embodiments of the present invention.

Sample particles W are flowed into the cell 1 in a state in which they are uniformly dispersed in a solvent. An irradiation light optical system consisting of a laser light source 2 with a wavelength of 780n- and a beam expander 3 is arranged behind the cell 1, and is capable of irradiating sample particles W in the measurement cell 1 with a laser beam having a predetermined cross section. I can do it. A Fourier exchange lens 4 for condensing light scattered by sample particles W is disposed on the optical axis of the irradiated light in front of the measurement cell 1, and a ring detector 5 is disposed at the focal position of the Fourier exchange lens 4. There is.

The ring detector 5 is composed of n ring-shaped semiconductor photosensors Pl*P2+...Pn, each having a different radius around the optical axis of the irradiated light.

6 is a detector for monitoring the amount of light.

On the sides of the measurement cell 10, there are a photosensor Ps for measuring lateral (90°) scattered light and a photosensor Pb2 for measuring dark current.
is installed.

Photosensor P I + P 2 *... Output of Pn (
iI...1n-1t1n) and Ps*
The output (ts, 1b2) of P b enters a sensitivity correction amplifier 9 via a preamplifier 8.

The sensitivity correction amplifier 9 is adjusted so that the output is the same as when each photo sensor is illuminated with light of the same intensity. This output is sequentially digitized by an A/D converter 11 via a multiplexer 10 and sent to the computer 2.

The computer 2 stores numerical tables of two different relative refractive indexes (mO-; M is the refractive index of the particles, n is the refractive index of the solvent) for the scattering angle θ of each photosensor and theoretical scattered light intensity for various particle sizes. It has a program that can output the particle size distribution by inputting 2m and performing sample measurement.

Figures 2 and 3 use kaolin and titanium white as samples, respectively, and water (refractive index 1.
33), cyclohexanone (refractive index 1.
447), the particle size distribution was obtained by assuming various refractive indexes of the unknown sample. In order to find out the refractive index of a sample whose particle size distribution when water is used as a solvent and the particle size distribution when cyclohexanol is used as a solvent are almost the same, the cumulative total of two particle size distributions is 5 for each assumed refractive index.
Find the particle diameter D50% at which it becomes 0%.

FIG. 4 shows the results of determining the relationship between the assumed refractive index and D50% for each solvent.

The particle shape (D5
0%) changes, i.e. according to Mie's scattering theory, and the shape of the particle size distribution (D50%) changes in the two solvents.
) is the refractive index of the particle. The particle size distribution at that refractive index becomes the particle size distribution of the target sample.

<Effects of the Invention> As explained above, the particle size distribution has conventionally been determined assuming an appropriate refractive index.

If the assumed refractive index is incorrect, it will give an incorrect particle size distribution result, as can be seen from FIG. 2 or 3. However, according to the present invention, data on the angular distribution of scattered light intensity is measured using two types of solvents with different refractive indexes, the results are sent to a computer, and M
By performing simulations based on IE theory,
Since the refractive index of particles can be easily known and the particle size distribution can be determined using that refractive index, accurate particle size distribution results can be obtained.

■ PI, P2... s b2 measurement cell laser light source ring detector Photo sensor (for forward scattered light) Photo sensor (for side scattered light) Photosensor for dark current measurement

[Brief explanation of drawings]

FIG. 1 is a plan view showing the configuration of an embodiment of the present invention, FIG.
FIG. 3 is a diagram showing the results of particle size distribution measurements assuming various refractive indexes of kaolin and titanium white, respectively. FIG. 4 is a diagram showing a method for determining the refractive index of particles from the results of particle size distribution measurements using two types of solvents. Hakenkutsu life clear left (8) Type Qi commission - ne (bu) lie Meng J ￥ 赴埜悱 (ku) ro Tsuru kutsu life - ship (pe)

Claims (1)

[Claims] (a) Step of dispersing the same sample in two solvents 1 and 2 having different refractive indexes and measuring the angular distribution of scattered light intensity for both (b) Refractive index n_1 of solvent 1 relative refractive index m_1
= M/n_1 (where M is the refractive index of the particles) as a parameter, the measured value of the angular distribution of scattered light intensity when using solvent 1 (measured value in step (a)) and various values based on Mie's theory Steps (c) and (b) of determining the particle size distribution with respect to the refractive index M of
Step (d) of determining the particle size distribution for various refractive indices M when using solvent 2 in the same manner as in step (d) (b) and (c). A particle size distribution measuring method consisting of a step of determining the particle size distribution of a sample whose purpose is to determine the particle size distribution.