JP2008281582A - Particle size distribution measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and accurately perform measurement of a high-concentration sample by forming a sample layer having an appropriate thickness which never causes multiple scattering. <P>SOLUTION: A sample cell used in a laser diffraction scattering particle size distribution measuring device includes a groove 61 formed in a transparent plate to extend from one end to the other end thereof as a sample storage part for high-concentration sample. The width W of the groove is set larger than the width of laser beam, and the height of the groove is set almost equal to the size of the largest particle contained in a measurement sample group. A sample layer having an appropriate thickness which causes multiple scattering can be formed by placing a sample on the groove 61 and removing the excess sample by a scraper. After completion of one sample measurement, the sample left in the groove can be easily removed by a brush or the like. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a particle size distribution measuring apparatus for measuring the size distribution of powder particles. In particular, a sample particle group dispersed in a liquid is irradiated with laser light, and the spatial intensity distribution of diffracted light or scattered light from the sample particle group is measured, and Fraunhofer's diffraction theory or Mie scattering is determined from the distribution. The present invention relates to a laser diffraction scattering type particle size distribution measuring apparatus for calculating a particle size distribution of a sample particle group by calculation based on theory.

  When measuring the particle size distribution of high-concentration samples such as pastes and slurries using a laser diffraction / scattering particle size distribution measuring device, the thickness of the high-concentration sample is adjusted in the optical axis direction of the laser light to reduce the generation of multiple scattered light. It needs to be very thin.

  Therefore, as a sample cell, there is a method (Patent Document 1) in which a high-concentration sample is sandwiched between two light-transmitting glass plates and compressed to stretch the sample into a thin layer. Since the thickness of the sample layer varies depending on the size, the measurement data varies greatly. There has also been proposed a method (Patent Document 2) in which a concave portion is formed in a glass plate and a high concentration sample is accommodated therein.

Utility Model Registration No. 2598857 (FIG. 1) JP-A-9-72841 (FIG. 1)

  The sample cell described in Patent Document 2 is satisfactory in terms of measuring a high-concentration sample, but is somewhat problematic in terms of ease of making the sample cell and ease of cleaning at the stage of use. That is, in the sample cell described in Patent Document 2, for example, a circular hole is formed in one plate and another plate formed in the same shape as that is fitted. This is somewhat difficult to manufacture in that the accuracy of fitting between the two plates is required.

  Further, in the sample cell described in Patent Document 2, a recess formed in the center of one plate finally becomes a sample storage portion. When trying to use the same sample cell for the next measurement, there is a problem in that the inside of the recess is inevitably difficult to clean, so that it takes time for cleaning.

  Furthermore, when a sample is put into a thin sample container, the sample is apt to be unevenly placed. In particular, when the measurement particle group is not dispersed in the liquid medium but placed on the sample cell holding portion as a powder, it is considered that the distribution of the sample is often not uniform on the sample cell.

  The present invention has been made in view of the above problems, and an object thereof is to make it possible to measure a high-concentration sample easily and with high accuracy, and to simplify the cleaning of a sample cell. It is another object of the present invention to enable accurate particle size distribution measurement even when the sample is not uniformly distributed on the sample cell.

  In order to solve the above problems, the present invention irradiates a sample cell containing a sample particle group with laser light, measures the spatial intensity distribution of light diffracted or scattered from the sample group, and determines the particle size of the sample particle group. In the particle size distribution measuring apparatus for calculating the distribution, the sample cell is composed of a translucent plate material, and the surface of the plate material is a sample particle group having a groove shape having a bottom surface penetrating from one end of the plate material to the other end. It has an accommodating part, The bottom face of the groove | channel is an optical plane (Claim 1), It is characterized by the above-mentioned.

  Since the sample cell is accommodated in the groove formed in the sample cell and the excess sample can be easily removed, the sample thickness in the optical axis direction of the laser beam can be set to an appropriate thickness for the high concentration sample. Further, since this groove penetrates from one end of the plate material constituting the sample cell to the other end, the previous sample can be easily swept out when the sample cell is used next time, and cleaning is easy.

  The depth of the groove formed in the sample cell can be approximately the same as the maximum particle diameter of the particles contained in the sample particle group, or about several times the maximum particle diameter. By doing so, it is possible to substantially reduce the accumulation of particles in the depth direction of the groove, that is, in the optical axis direction of the laser beam, and to greatly reduce multiple scattering.

  The groove of the sample cell can be formed as a groove by polishing the surface of one glass material, for example. Although it is somewhat difficult to optically polish only the center of a single plate to form a recess, the groove of the present invention penetrates from one end of the plate material to the other, so that the polishing tool can escape and optical polishing is performed. It is easy to form a groove.

  Moreover, the groove | channel of said sample cell can form a groove | channel by bonding together the board | plate material which has one optical plane which forms the bottom face of a groove | channel, and the other two board | plate materials (Claim 2). More specifically, the sample cell can be configured by adhering a plate material having a thickness corresponding to the depth of the groove so as to be sandwiched from the left and right with respect to one plate material placed in the center. As another method, two plate members having a thickness corresponding to the depth of the groove may be bonded to one surface of one plate member, and a groove may be formed between the two plate members. Such a method for producing a sample cell is generally cheaper than a method for forming grooves by polishing, and the accuracy as an optical plane can be increased.

  Furthermore, the particle size distribution measuring apparatus of the present invention further includes an irradiation position moving unit that relatively moves the irradiation position of the laser light irradiated to the sample cell inside the groove, and a space of light to be diffracted or scattered. When measuring the intensity distribution, the irradiation position moving unit is operated to average the measured intensity (Claim 3). Since the sample cell used in the present invention has a groove penetrating from one end to the other end of the plate material, a sufficient distance for averaging can be secured. Even when the sample is not evenly distributed in the groove that is the sample storage unit, the scattered light intensity is averaged and the correct particle size distribution can be obtained because the scattered light is measured while driving the irradiation position moving unit. .

  In the particle size distribution measuring apparatus according to claim 1, since the groove that is the sample storage portion has a shape penetrating from one end to the other end of the plate material constituting the sample cell, it is easy to manufacture and easy to clean even when used. It is.

  In addition, since the depth of the groove is substantially the same as the maximum particle diameter of the particles contained in the sample particle group or about several times, for example, the sample protruding from the groove height can be easily removed with a scraper. The sample thickness in the optical axis direction of the laser beam can be set to a thickness suitable for a high concentration sample.

  Further, in the particle size distribution measuring apparatus according to claim 2, since the groove is formed only by the combination of the three plates, the groove is formed and optical polishing for making the bottom surface an optical plane is not necessary and inexpensive. A sample cell can be fabricated.

  Further, in the particle size distribution measuring apparatus according to claim 3, since the laser light is irradiated to particles existing in various parts using the groove length of the sample cell and the scattered light is averaged and taken in, the sample A correct particle size distribution of the particle group can be obtained.

  The particle size distribution apparatus of the present invention will be described with reference to the schematic configuration diagram shown in FIG. In this configuration example, the optical axis 10 of the laser beam is arranged in a substantially vertical direction, and the laser light is emitted from the bottom to the top. The laser light emitted from the laser light source 1 is formed into a parallel beam having a predetermined beam diameter by the collimator 2 and then irradiated to the sample cell 6 through the transparent cover 3 for dust prevention. The dust-proof cover 3 is not always necessary. In a sample storage section of a sample cell 6 described later, a group of particles to be measured is dispersed in a liquid medium and a sample is placed. The laser light applied to the sample is emitted in a direction away from the optical axis 10 by scattering or diffraction by the powder particles contained in the sample, and the scattered light is condensed on the surface of the ring detector 8 by the condenser lens 7. Is done.

  The ring detector 8 is composed of a large number of light detection elements arranged in a ring shape with the optical axis 10 as the center, and can detect the intensity of scattered light generated by the powder particles in the sample cell 6 for each scattering angle. it can. The output of the ring detector 8 is taken into the control device 9 via a data sampling circuit or the like for each scattering angle. The control device 9 is a device including a computer. The control device 9 performs an operation based on the Mie scattering theory or the Fraunhofer diffraction theory from the spatial intensity distribution of the scattered light obtained as described above, and is dispersed in the sample cell 6. The particle size distribution of the powder sample is calculated.

  The sample cell 6 is used for measurement by being placed on a mounting base 4 having a hole through which laser light can pass, and this mounting base 4 is moved in one direction indicated by an arrow A by the drive unit 5. It is possible. The sample cell placed thereon moves with respect to the optical axis 10 by moving the mounting table 4, and the scattered light from samples at various locations in the sample cell can be measured and averaged. it can.

  2A and 2B are diagrams for explaining the shape of the sample cell 6, where FIG. 2A is a perspective view and FIG. The sample cell 6 has a substantially rectangular parallelepiped plate shape made of translucent transparent glass or the like, and a groove 61 serving as a storage portion for storing a measurement sample is formed on the surface thereof. The material of the sample cell is preferably quartz glass, but it is also possible to use a transparent plastic such as an acrylic plate. The overall size of the sample cell is not particularly limited, but is about 30 mm wide, 50 mm long, and 2 mm thick. The cross section of the groove 61 is a rectangle having a width W and a height (depth) H, and penetrates from one end of the sample cell 6 to the other end. The bottom surface 62 of the groove 61 is polished, is an optically smooth flat surface, and is transparent. Since both ends of the groove 61 penetrate to the end of the sample cell, there is a clearance for the polishing tool, and the bottom surface 62 can be easily polished.

  The width W of the groove 61 is larger than the diameter of the irradiated laser beam and is about 5 to 20 mm. Although the height H of the groove 61 is extremely shallow, it is desirable that the height H be approximately the same as or several times the diameter of the largest particle in the sample particle group to be measured. By doing so, all of the measurement particles can be accommodated in the groove 61, and multiple scattering can be reduced. Specifically, although it varies depending on the sample to be measured, it is about 0.05 to 0.5 mm. The dimension of the groove | channel 61 described here is an example, Comprising: It determines suitably according to a laser beam diameter and a measuring object sample.

  When measuring the sample to be measured, an appropriate amount of the suspension containing the sample particle group is placed in the groove 61 which is the sample storage unit. Thereafter, when the surface of the sample cell 6 on which the groove 61 is formed is traced by a scraper having a straight edge, the suspension protruding from the groove 61 is removed, and the sample to be measured remains in the groove 61 only. At this time, there are no walls at both ends of the groove 61 and they are open. However, the sample to be measured will not spill out due to the surface tension of the sample liquid unless it is reversed.

  The sample to be measured is not dispersed in the liquid medium but can be accommodated in the groove 61 by the same operation even if it is in the form of paste or slurry. If the sample to be measured is the powder itself, after sprinkling an appropriate amount of powder so that it is scattered on the bottom surface of the groove 61, the excess sample can be removed with a scraper or the like as described above. Good.

  When one measurement is completed and the sample cell is reused for the next measurement, it is a matter of course that the previous sample should not remain in the sample cell. If the sample cell 6 shown in FIG. 2 is used, the groove 61 which is a sample accommodating portion penetrates from one end to the other end. In order to remove the previous sample remaining in the groove 61, a brush or cloth is used. Therefore, the sample cell 6 can be cleaned very easily and surely to every corner.

  The sample cell 6 can be formed not only by polishing a groove serving as a sample storage part but also by combining three plates. The material of the plate can be a transparent glass plate or a plastic plate. An example of a sample cell manufacturing method will be described with reference to FIG.

  In FIG. 3A, one plate cell with a groove is formed by bonding another plate 72 having a larger thickness to both sides of a plate 71 serving as a bottom surface of the groove 73 from both sides. The height of the plate 72 is larger than the height of the plate 71 by the height of the groove 73, and the groove 73 is formed by sticking them together from the left and right with one surface as a common surface. The width of the groove 73 is the same as the width of the plate 71, and the height of the groove 73 is the difference between the height of the plate 72 and the plate 71.

  In FIG. 3B, one sample cell with a groove is formed by bonding two plates 75 having the same thickness as the height of the groove to the surface of the plate 74 serving as the bottom surface of the groove 76 and separating them at both ends. . The height of the plate 75 is selected to be the same as the height of the groove to be formed, and the grooves 76 are formed by adhering them to the left and right sides of one surface of the plate 74 at an appropriate interval. The width of the groove 76 is the same as the distance between the two plates 75, and the height of the groove 76 is the same as the thickness of the plate 75.

  When the sample cell having the structure shown in FIG. 3B is manufactured, the plate 75 is pasted to the plate 74 using a material that is thicker than the target groove height, and then the surface of the plate 75 is adhered. May be ground to a desired thickness. In this case, it is relatively easy to grind the surface of the plate 75 which is the outer surface of the sample cell.

  As shown in FIG. 3, when a sample cell is manufactured by bonding three plates, there is a merit in terms of manufacturing cost. That is, it is generally easier to make the surface of the plate optically smooth than to optically polish the inside of the groove. In the case of the sample cell of FIG. 3, since the surface which becomes the bottom surface of the groove is the surface of one plate itself, if the sample cell is manufactured using a plate having an optically smooth plane in advance, optical polishing in the subsequent process will be performed. There is no need to spend time. Therefore, the sample cell can be manufactured at a low cost. The other two plates that do not become the bottom surfaces of the grooves are not necessarily plates having an optical plane. In some cases, the material may not be the same as the plate constituting the bottom surface. Furthermore, the plate which does not become the bottom surface of the groove may not be transparent.

  The irradiation position moving unit will be described. In the example described with reference to FIG. 1, the drive unit 5 and the installation base 4 form the irradiation position moving unit in the claims, and the sample cell is moved with respect to the fixed laser beam. The sample cell is placed on the installation table 4 so that the moving direction A coincides with the longitudinal direction of the groove 61 of the sample cell described in FIG. By doing so, the irradiation position irradiated with the laser beam relatively moves in the groove 61. When measuring the scattered light intensity distribution, if the scattered light is measured while moving the installation base 4 by the drive unit 5, even if the sample in the groove 61 is biased, the data is integrated and averaged. As a result, the particle size distribution of the entire sample can be measured correctly.

  Regarding the movement of the irradiation position, not only a method of moving and changing the sample cell but also the laser beam may be moved while the sample cell is fixed. For example, a laser light irradiation system including a laser light source and a collimator may be driven with respect to the sample cell.

  The apparatus described with reference to FIG. 1 is a vertical particle size distribution measuring apparatus in which the optical axis direction of the laser beam is oriented in the vertical direction, but the present invention is a horizontal particle size distribution in which the optical axis direction of the laser beam is the horizontal direction. It can also be applied to a distribution measuring device. The above sample cell can be used as it is for a paste-like sample or a slurry sample. In the case of a sample dispersed in a medium, the sample suspension can be prevented from falling by covering the upper surface of the sample cell with a transparent cover plate.

It is a schematic block diagram of the particle size distribution measuring apparatus of this invention. It is a figure of the sample cell used for this invention. It is a figure explaining the manufacturing method of a sample cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser light source, 2 ... Collimator, 3 ... Cover, 4 ... Installation stand, 5 ... Drive part, 6 ... Sample cell, 7 ... Condensing lens, 8 ... Ring detector, 9 ... Control apparatus, 10 ... Optical axis, 61 …groove

Claims (3)

  In the particle size distribution measuring apparatus for irradiating the sample cell containing the sample particle group with laser light, measuring the spatial intensity distribution of light diffracted or scattered from the sample group, and calculating the particle size distribution of the sample particle group, the sample The cell is composed of a light-transmitting plate material, and the surface of the plate material has a sample particle group containing portion in the shape of a groove that penetrates from one end to the other end of the plate material and has a bottom surface, and the bottom surface of the groove is optical. Particle size distribution measuring apparatus characterized by being a flat surface.   2. The particle size distribution measuring apparatus according to claim 1, wherein the sample cell is formed by bonding a single plate material forming the bottom surface of the groove and the other two plate materials to form a groove. A particle size distribution measuring device.   3. The particle size distribution measuring apparatus according to claim 1, further comprising an irradiation position moving unit that relatively moves an irradiation position of the laser light irradiated to the sample cell inside the groove, and is diffracted or scattered. A particle size distribution measuring apparatus characterized in that when the spatial intensity distribution of light is measured, the irradiation position moving unit is operated to average the measured intensity.

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