JPH065610Y2 - Centrifugal sedimentation type particle size distribution measuring device - Google Patents

Description

[Detailed Description of Device] a. TECHNICAL FIELD The present invention relates to a centrifugal sedimentation type particle size distribution measuring device suitable for measuring the particle size distribution of ultrafine particles.

B. BACKGROUND ART A centrifugal sedimentation type particle size distribution measuring apparatus stores a sample in which a powder is dispersed in a liquid in a container, and a centrifugal force is applied to the sample to force the particles to settle, thereby reducing the time required for measuring the particle size distribution. It is intended to be shortened.

By the way, in this kind of particle size distribution measuring apparatus, since the measurement of the sedimentation state of particles depends on an optical method in which measurement accuracy is relatively easy to obtain, the container for storing the sample is made of a transparent material such as quartz or tempered glass. Due to the fact that it is manufactured in, there is a limit to the centrifugal force that can act on the sample in consideration of breakage, and it is usually suppressed to about 5000 rpm for 1 minute at most.

For this reason, when targeting a particle size of about 0.02 μm, which is a problem in the field of fin ceramics and composite materials, for example, even when sample particles having a density of 2 are dispersed in water, it takes a long time of 8 hours to complete the measurement. There was a problem that required.

C. The present invention has been made in view of the above problems, and an object of the present invention is to provide a centrifugal sedimentation type particle size distribution measuring apparatus capable of measuring the particle size distribution of ultrafine particles in a short time. is there.

D. SUMMARY OF THE INVENTION That is, the feature of the present invention is that the region for detecting the sedimentation state of particles can be adjusted by centrifugal force.

E. Embodiments Details of the present invention will be described below based on illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a sample cell holder housed in a rotating body 4 mounted on a rotating shaft 3 driven by a variable speed electric motor 2. ,
One end is attached to the other end of the spring member 5 fixed to the rotary shaft 3 side, and is configured to be movable in the radial direction of the rotating body 4 by the guide members 6, 6. Further, on the wall surface of the rotating body 4 facing the sample cell 7 housed in the holder 1, a light transmitting element 8 is provided, and a light emitting element 9 and a light receiving element 10 are arranged so as to sandwich the rotating body 4. It is configured to form the optical path of the particle detector. A data processing circuit 11 receives a signal from the position detector 12 attached to the rotary shaft 3 and a signal from the light receiving element 10 to calculate a particle size distribution from the light transmittance. In addition, reference numeral 13 in the drawing denotes a dummy weight for balancing with the measuring unit.

Next, the operation of the apparatus thus configured will be described with reference to FIG.

A sample in which sample particles to be measured are uniformly dispersed in a liquid is housed in the sample cell 7, the weight W thereof is measured, and then the sample holder 1 is set (I).

At the stage of completing such preparation, the motor 2 is rotated at the rotation speed R.
_When rotated by ₁ , the spring member 5 receives the centrifugal force acting on the sample cell 7 and the holder 1 and extends by the length Δl ₁ (II). Needless to say, since the weights of the sample cell 7 and the cage 1 are known, this length Δl ₁ is also known.
When the rotation is continued by this rotation speed R ₁ , the particles start to settle from the large particles P ₁ and P ₂ and sequentially pass through the optical path L-L of the light receiving element 10, and the concentration of the particles is increased by the light receiving element 10. To be detected. In this way, when the rotation speed of the sample cell 7 is increased to R ₂ when the particles P ₁ and P ₂ having large particle diameters have settled (III in the same figure), the spring member 5 causes the action of the increased centrifugal force. In response to this, it is extended by Δl ₂ . Thereby, the upper end of the measuring cell 7 and the optical path L-L of the light receiving element 10
The relative distance between the light receiving element 10 and the optical path L-
L crosses the upper end portion of the ultrafine particles P ₃ which cannot be completely settled. Needless to say, ultra-fine particles P ₃ and P ₄ will, in some initial rotational speed R ₁ could not be settled to the light path L-L, therebetween under the action of centrifugal force generated by the rotation speed R ₁ Since the difference in the sedimentation amount is relatively generated, the amount of change in the signal level of the light receiving element 10 caused by the change in the rotation speed from R ₁ to R ₂ represents the concentration of the ultrafine particles P _3. Become.

That is, when the particles are uniformly dispersed in the medium solution and a centrifugal force is applied to the particles, the particles settle in the direction of the centrifugal force, and the settling distance l within a certain time t is r from the center of rotation to the upper end of the particles. When the rotation speed is ω, the solvent liquid density is ρ, the particle density is ρ ′, the particle diameter is D, and the medium solution viscosity is η, (Where K is a constant), the larger the particle diameter D, the faster the particles settle, and the settling distance l is also proportional to the measurement duration t. Therefore, by increasing the rotation speed, the distance from the center of rotation to the upper end of the target particle P ₃ , that is, the apparent settling distance becomes large as r + Δl _1, and there is no need to wait for the settling of the target particle itself. Moves to the optical path L-L of the light receiving element 10.

When the rotation speed of the sample cell 7 is increased to R ₃ at the time when the detection of the particles P ₃ is completed (IV), the spring member 5 further increases Δ.
Only l ₃ extra elongation upper end P ₄ of the small particles P ₄ particle diameters to pass through the optical path L-L, the concentration change is detected by the light receiving element 10.

Hereinafter, without waiting for the fine particles to settle in this way, the position of the light receiving element 10 is gradually moved to the rotating shaft 3 side by gradually increasing the rotation speed to detect the relative difference in the settling amount.

In addition, in this embodiment, one end of the spring member 5 is fixed to the rotary shaft 3, but as shown in FIG.
The spring member 13 is provided between the peripheral wall surface 4a and the sample cell holder 1.
The same operation can be achieved even if the above is provided.

F. Effect As described above, according to the present invention, since the sample cell is elastically held in the direction of the centrifugal force, the particle detection point can be moved according to the sedimentation situation.
In particular, not only can the time required for measuring the particle size distribution of ultrafine particles be significantly shortened, but the amount of movement can be adjusted precisely because the detection region is moved by utilizing centrifugal force. In addition, since it does not need to rotate at high speed, it is possible to measure a group of particles having a large particle diameter in a highly decomposed state. Furthermore, since the sample cell is supported via a spring member, this serves as a buffer member. As a result, the sample cell can be protected from a shock or the like.

[Brief description of drawings]

1 (a) and (b) are a cross-sectional view and a front view of an apparatus showing an embodiment of the present invention, FIG. 2 is an explanatory view showing the operation of the same apparatus, and FIG. It is sectional drawing which shows the Example of. 1 ... Sample cell holder, 2 ... Variable speed electric motor 4 ... Rotating body, 5 ... Spring member 10 ... Light receiving element, 13 ... Spring member

Claims (1)

[Scope of utility model registration request] 1. A sample cell is attached to a rotating body driven by a variable speed electric motor through an elastic member which is expandable / contractible in a radial direction, and an optical detector for detecting particles of the sample cell is installed in the electric motor. Centrifugal sedimentation type particle size distribution measuring device which is arranged at a certain distance from the rotation axis.