JP7411501B2 - Powder resistivity measuring device and resistivity measuring method - Google Patents

Description

The present invention relates to a powder resistivity measurement device and a resistivity measurement method, and more specifically, to a method for measuring volume resistivity that can be used to evaluate the physical properties of various powders used for electronic materials, electrode materials, etc. The present invention relates to a resistivity measuring device and a resistivity measuring method.

In the production of electronic materials and electrode materials, in order to further improve their performance, it is necessary to not only evaluate the product but also accurately evaluate the physical properties of the raw materials themselves from the material design stage. Many of these raw materials are so-called fine particles that are handled as powders or granules, and one of their physical properties is volume resistivity (hereinafter abbreviated as "resistivity" as appropriate), which represents the electrical resistance per unit volume in an aggregated state. ) is used.

For example, in measuring the volume resistivity of inorganic powder, which is the raw material for electrophotographic photoreceptors, the sample powder is pressure-molded, and a constant voltage is applied between electrodes installed at the top and bottom ends of the compact. By measuring the resistance value of the molded body from the current flowing in the case, the resistivity is calculated based on the volume of the molded body, and the resistivity of the normal sample is estimated by taking into account the porosity of the molded body. (Patent Document 1).

A resistivity measuring device that uses the above principle includes, for example, a cylinder that accommodates powder as a sample, a disk-shaped probe unit that forms the bottom of the cylinder, and a base on which the cylinder and probe unit are mounted. It mainly consists of a pressurizing piston inserted into a cylinder, and a hydraulic jack that moves the piston up and down relative to the base. To measure the resistivity, after storing the powder in a cylinder, the powder in the cylinder is gradually compressed by relatively pushing down the piston, and the thickness and pressing force of the powder in each compression state are measured. and measure the resistance value using the probe unit.

The resistivity measuring device can measure the resistance value of low-resistance samples using a constant current application method using a four-point probe, and for high-resistance samples, it can measure resistance using a ring electrode method. The resistance value can be measured using a constant voltage application method using a probe. The resistivity of powder decreases as the load increases, but when evaluating the physical properties of powder, the change in resistivity with respect to load is usually expressed as a coordinate and used as the physical property. The resistivity measuring device as described above is available, for example, as a powder resistance measuring system (product name: MCP-PD51) manufactured by Nitto Seiko Analytech Co., Ltd. (Non-patent Document 1, Non-patent Document 2). ).

Japanese Patent Application Publication No. 2015-108792

Nitto Seiko Analytech Co., Ltd. website “Resistivity measurement method Volume resistivity” (https://www.mccat.co.jp/instrument/resistivity-meters/ghlup1.html) Nitto Seiko Analytech Co., Ltd. website “Powder resistance measurement system MCP-PD51 type” (https://www.mccat.co.jp/instrument/resistivity-meters/mcp-pd51.html)

By the way, in measuring the volume resistivity as described above, the area where the powder is pressurized, that is, the cross-sectional area of the cylinder that houses the powder, and the thickness of the powder in the pressurized state, that is, the area for pressurizing. Based on the height of the powder in the cylinder measured from the position of the piston and the measured resistance value, the volume resistivity itself can be accurately measured for each compression state.

However, the compression state of the powder in the cylinder due to the depression of the piston, that is, the degree of clogging, differs depending on the shape, particle size, and particle size distribution of the particles that make up the powder. Even when compressed, there is actually a difference in resistance value, and as a result, there is a problem that the index of volume resistivity against load lacks reliability as a standard for evaluating physical properties.

On the other hand, when determining the resistivity of powder in a compressed state, if the bulk density is used as the standard rather than the load, the influence of differences in the powder's compression state can be eliminated, resulting in a more reliable evaluation of physical properties. should be possible. However, in conventional resistivity measuring devices, even though the cylinder contains a certain amount of sample, as the piston is pushed down, air in the powder is released from a small gap between the inner circumference of the cylinder and the piston. At the same time, the powder itself also leaks, and the mass of the sample contained in the cylinder fluctuates, making it difficult to accurately determine the bulk density, and the reality is that the volume resistivity relative to the bulk density cannot be accurately measured.

The present invention has been made in view of the above-mentioned circumstances, and its object is to provide a powder resistivity measuring device and a resistivity measuring method for measuring the volume resistivity of various powders. The object of the present invention is to provide a powder resistivity measuring device and resistivity measuring method that can accurately measure volume resistivity based on bulk density without causing errors due to differences in state, and also to provide a powder resistivity measuring device and resistivity measuring method that can accurately measure volume resistivity based on bulk density. The aim is to provide new indicators for evaluating

In order to solve the above problems, in the present invention, a certain amount of powder as a sample is stored in a cylinder, and when the piston is pushed down to gradually compress the powder in the cylinder, a vacuum pump is used to compress the powder in the cylinder. By compressing while forcibly exhausting the air inside the cylinder, that is, the air contained in the powder, through a small gap provided at the bottom, the powder is prevented from leaking from the cylinder, and this prevents the powder from leaking during compression. The bulk density in each state was specified, and the resistance value at that time was measured.

That is, the present invention consists of two main points, the first of which is a powder resistivity measuring device for measuring volume resistivity with respect to bulk density, which includes a cylinder containing a powder as a sample; A disk-shaped probe unit that fits into the cylinder and forms the bottom of the cylinder, a base on which the cylinder and the probe unit are mounted together with a cylinder support block that fixes the cylinder, and a base that slides on the inner peripheral surface of the cylinder. a pressurizing piston inserted into the cylinder in contact with the cylinder; a lifting mechanism that moves the piston up and down relative to the base; and a height gauge that measures the insertion length of the piston into the cylinder. The probe unit is arranged with a gap provided to the inner circumference of the cylinder to allow air to pass through without powder leaking, and the cylinder support block is provided with an exhaust flow path leading to the gap. The present invention resides in a powder resistivity measuring device characterized in that the air in the cylinder can be evacuated by connecting a vacuum pump to the exhaust flow path.

The second gist of the present invention is a method for measuring the resistivity of powder using the above-mentioned resistivity measuring device, in which a certain amount of powder as a sample is stored in a cylinder, and then a vacuum pump is applied. While operating the cylinder to exhaust air, the piston is relatively pushed down to gradually compress the powder in the cylinder, and the thickness of the powder in each compressed state is measured using a height gauge. The present invention resides in a powder resistivity measuring method characterized by measuring the volume resistivity of the powder in each compressed state with respect to the bulk density by measuring the resistance value of the powder with a probe unit.

According to the present invention, when the powder in the cylinder is gradually compressed, the air contained in the powder is forcibly evacuated by a vacuum pump through the minute gap between the inner circumference of the cylinder and the probe unit at the bottom of the cylinder. By compressing the powder while compressing it, leakage of the powder from the cylinder can be prevented and the mass of the powder that was initially measured can be maintained, so the bulk density can be measured at any time while the powder is being compressed, and the resistance value at that time can be measured. This allows the relationship between the bulk density and volume resistivity of the powder to be determined with high precision. Therefore, according to the present invention, when evaluating the physical properties of various powder samples, it is possible to provide a highly reliable index of volume resistivity relative to bulk density.

1 is a vertical cross-sectional view schematically showing a configuration example of a main part of a powder resistivity measuring device according to the present invention, which is equipped with a four-point probe. 1 is a vertical cross-sectional view schematically showing a configuration example of a main part of a powder resistivity measuring device according to the present invention, which includes a ring electrode type probe. FIG. 1 is an explanatory diagram showing the entire system of a powder resistivity measuring device according to the present invention. 1 is a graph showing the relationship between bulk density and load using the powder resistivity measuring device and resistivity measuring method according to the present invention. 1 is a graph showing the relationship between volume resistivity and bulk density using the powder resistivity measuring device and resistivity measuring method according to the present invention. 2 is a graph showing the relationship between bulk density and load using a conventional resistivity measuring device and resistivity measuring method. 1 is a graph showing the relationship between volume resistivity and bulk density using a conventional resistivity measuring device and resistivity measuring method.

Embodiments of a powder resistivity measuring device (hereinafter abbreviated as “measuring device”) and a powder resistivity measuring method (hereinafter abbreviated as “measuring method”) according to the present invention will be explained based on the drawings.

First, the measuring device of the present invention will be explained. The measuring device of the present invention indicated by reference numeral 1 in FIG. 3 is a device for measuring volume resistivity with respect to bulk density of powder, and constitutes a resistivity measuring system. Such a resistivity measuring system mainly includes a hydraulic pump 51, a vacuum pump 6, a computer 80 for control and analysis, a resistance measuring device 81, and a controller 82, in addition to the main body of the measuring device 1.

As shown in FIG. 1, the measuring device 1 of the present invention includes a cylinder 2 that accommodates a powder S as a sample, a disk-shaped probe unit 3a that fits into the cylinder and forms the bottom of the cylinder 2. A base 11 on which the cylinder 2 and probe unit 3a are mounted, a pressurizing piston 4 inserted into the cylinder in sliding contact with the inner peripheral surface of the cylinder 2, and a piston 4 relative to the base 11. As shown in FIG. 3, these members are housed in a casing 10 having a rectangular parallelepiped shape, for example.

As shown in FIG. 1, the cylinder 2 has a cylindrical inner tube 20 made of an insulating material, and a collar for hooking onto a cylinder support block 17, which will be described later, at the lower end. The sample container is composed of a cylindrical outer tube 21, and the inner tube 20 is usually designed to have an inner diameter of about 5 to 50 mm and a height of about 10 to 50 mm. The cylinder 2 is attached to a cylinder support block 17, and the cylinder support block 17 is constructed by disposing an annular retaining ring 14 on the upper surface of a pedestal 13 having a circular planar shape.

The inner tube 20 of the cylinder 2 has a length such that its lower end protrudes downward from the outer tube 21, and an outer circumferential ring 24 for locating the cylinder 2 at the center of the retaining ring 14 is arranged at the lower end of the inner tube 20. be done. The outer ring 24 is inserted into the retaining ring 14 with a gap of about 0.5 to 2 mm, and the gap is sealed by a sealing material 15 attached to the outer periphery of the outer ring 24. A sealing material holding ring 23 and a fixing ring 25 are arranged on the upper and lower surfaces of the outer circumferential ring 24, respectively, and a screw (not shown) screwed from the lower surface side of the fixing ring 25 is used to attach the inner part to the lower end of the outer cylinder 21. The cylinder 20 is assembled. Furthermore, by setting the thicknesses of the sealing material holding ring 23, the outer ring 24, and the fixing ring 25, a gap of about 0.5 to 2 mm, which will be described later, is formed on the lower surface of the fixing ring 25 at the lower end of the inner cylinder 20. There is.

The above two gaps, that is, the gap between the upper surface of the pedestal 13 and the lower end of the cylinder 2 (lower surface of the fixing ring 25), and the gap between the inner circumferential surface of the retaining ring 14 and the outer circumferential surface of the fixing ring 25, are An exhaust flow path 91 for exhausting air contained in S is configured. Furthermore, an exhaust passage 92 leading to a vacuum pump 6 (see FIG. 3), which will be described later, is provided inside the retaining ring 14, and the exhaust passage 91 is connected to the exhaust passage 92 inside the retaining ring 14. I understand. Note that the exhaust line 61 (see FIG. 3) is connected to the exhaust flow path 92 via a joint 93.

As shown in FIG. 1, the bottom of the cylinder 2 is comprised of a probe unit 3a placed on the top surface of the pedestal 13. The probe unit 3a illustrated in FIG. 1 is a four-point probe unit that measures the resistivity of a powder S with low resistance, and four needle-shaped electrodes are arranged in a straight line on a ceramic disk serving as an insulating material. These four electrodes are brought into contact with the sample, a constant current is passed between the two outer probes, and the potential difference generated between the two inner probes is measured to determine the resistance. Note that a connector 39 is attached to the side surface of the pedestal 13 for connecting the wiring of the probe to a measuring device.

Further, when measuring the resistivity of the powder S having high resistance, as shown in FIG. 2, a ring electrode type probe unit 3b is used as the probe unit instead of the above probe unit 3a. The probe unit 3b is constructed by sequentially stacking a ceramic disc as an insulating material and a disc-shaped electrode, and applies a constant high voltage from an electrode 41b of a piston 4, which will be described later, to cause the powder S to The resistance of the powder S is determined by measuring the current flowing through it. Note that a double ring electrode consisting of an outer guard electrode and an inner main electrode (current detection electrode) can also be arranged as the electrode of the probe unit 3b.

As shown in FIG. 1, the cylinder 2 and the probe unit 3a are mounted on a base 11 together with the above-mentioned cylinder support block 17 that fixes the cylinder 2. As shown in FIG. 3, the base 11 is arranged to be able to move up and down vertically along a guide bar 12 erected at the bottom of the casing 10, and has coil springs and the like arranged at the top of the casing 10. It is constantly urged downward by the elastic body 16. Further, a head portion 42 is provided on the ceiling portion of the casing 10 to relatively pressurize the upper end of the piston 4 when the base 11 is raised. The assembly structure of the cylinder 2, cylinder support block 17, and base 11 in the apparatus illustrated in FIG. 2 is also the same as that in the apparatus shown in FIG.

The pressurizing piston 4 is shown in outline in FIGS. 1 and 2, and when measuring the resistivity of the low-resistance powder S, as shown in FIG. It consists of a ceramic disk, which is an insulating material. On the other hand, when measuring the resistivity of high-resistance powder S, as shown in FIG. A predetermined voltage is applied to the electrode from a resistance measuring device 81 via a connector 49 attached to the head of the piston 4.

The piston 4 described above is inserted into the cylinder 2 containing the powder S, and the tip side of the piston 4 is in sliding contact with the inner peripheral surface of the inner cylinder 20 of the cylinder 2, specifically, by 20 to 50 μm. It is slidably inserted with a dimensional difference (difference between the inner diameter of the inner cylinder 20 and the diameter of the piston 4). As shown in FIG. 3, a hydraulic jack 52 as a lifting mechanism is arranged at the bottom of the casing 10 on the lower surface side of the base 11. , the base 11 is raised. Thereby, the piston 4 hits the head portion 42 and descends relative to the base 11, so that the powder S in the cylinder 2 can be pressurized. Note that the hydraulic jack 52 used has an output of about 5 to 50 kN.

In the measuring device 1 of the present invention, when the piston 4 is pressed down to compress the powder S in the cylinder 2, in order to exhaust the air contained in the powder S, as shown in FIGS. 1 and 2, a probe is used. The units 3a and 3b are arranged with a gap 90 provided in the inner circumference of the inner tube 20 of the cylinder 2 to allow air to pass through without the powder S leaking out. Furthermore, as described above, the cylinder support block 17 is provided with the aforementioned exhaust passages 91, 92 and a joint 93 that communicate with the gap 90, and as shown in FIG. By connecting the pump 6, the air inside the cylinder 2 can be exhausted. Thereby, in the measuring device 1, when compressing the powder S, it is possible to prevent the powder S from leaking from the cylinder 2, that is, from the gap between the cylinder 2 and the piston 4. , the mass of the powder S during measurement can be maintained at a constant amount.

A gap 90 between the inner circumference of the cylinder 2 (the inner circumference of the inner tube 20) and the probe units 3a, 3b is normally set to 20 to 50 μm, preferably 25 to 35 μm. The reason for specifying the size of the gap 90 is as follows. In other words, if the gap 90 is less than 20 μm, the dimensional difference in how the cylinder 2 fits into the inner cylinder 20 is small, making it difficult to assemble the cylinder 2 before measurement, and the exhaust efficiency from the cylinder 2 is poor, resulting in a lower descending speed of the piston 4. Since it is necessary to set the value low, there is a problem that the measurement time becomes long. On the other hand, if the gap 90 exceeds 50 μm, the powder will also be discharged from the gap 90, and the bulk density of the powder S will change, causing a problem that measurement accuracy will decrease.

Further, as shown in FIG. 3, the measuring device 1 is provided with a height gauge 71 for measuring the thickness of the powder S. The height gauge 71 is composed of, for example, an electronic dial gauge equipped with a telescoping bar, and is mounted vertically on the base 11 with the tip of the stem in contact with the shaft extending horizontally from the head portion 42. It will be done. The height gauge 71 has a function of measuring the thickness of the powder S by measuring the height (vertical position) of the cylinder 2, that is, the relative insertion depth of the piston 4 with respect to the cylinder 2. has. Furthermore, in order to specify the measurement point (reference) of the volume resistivity, the head section 42 is provided with a load meter 72 that measures the pressing force of the piston 4, that is, the pressing force applied to the powder S. . Usually, the load cell 72 is a load cell that converts the magnitude of the load into an electrical signal.

As shown in FIG. 3, a hydraulic pump 51, a vacuum pump 6, a computer 80, a resistance measuring device 81, and a controller 82 are connected to the measuring device 1. A hydraulic pump 51 that operates the hydraulic jack 52 is connected to the hydraulic jack 52 via a hydraulic line 53. As the hydraulic pump 51, a plunger pump type hydraulic pump whose piston movement is controlled by a linear actuator is used instead of the manual plunger pump used in conventional measuring devices. A linear actuator is, for example, a mechanism that controls the amount and speed of movement of a moving block attached to a linear guide by rotating a ball screw with a servo motor or stepping motor and reciprocating a ball screw nut. Can be mentioned. Since the hydraulic pump 51 has its piston attached to the moving block of the linear actuator, the supply of hydraulic oil can be precisely adjusted, and the elevation of the hydraulic jack 52 can be accurately controlled.

Although not shown in the drawings, instead of the hydraulic jack 52, the lifting mechanism disposed at the bottom of the casing 10 rotates the base 10 by rotating a screw using a stepping motor or a servo motor whose rotational position and speed can be controlled. It is also possible to use a screw jack to raise and lower the Such a screw type jack, for example, connects a ball screw or a trapezoidal screw to the shaft of a motor through a gear with a relatively large reduction ratio, and connects a nut attached to the lower surface of the base 11 to the screw. By screwing them together, it is configured as a linear motion system that moves the base 11 up and down by the amount that the screw rotates. When a lifting mechanism using a motor is adopted, the device configuration becomes simple and the cost of the motor and control circuit can be reduced.

The vacuum pump 6 is connected to the exhaust flow path 92 via a joint 93 of the cylinder support block 17 shown in FIGS. 1 and 2. As the vacuum pump 6, a diaphragm pump is used because the air to be evacuated from the powder S is small and can be reliably evacuated. Normally, the maximum flow rate of the vacuum pump 6 is about 5 to 20 L/min, and the ultimate degree of vacuum is about -20 to -40 kPa.

Further, as shown in FIG. 3, the resistance measuring device 81 converts the resistance values measured by the probe units 3a and 3b into digital signals, and is connected to transmit the obtained electrical signals to the computer 80. be done. The height gauge 71 and the load meter 72 provided in the measuring device 1 are connected so as to transmit the obtained electric signals to the computer 80 as digital signals via the controller 82 . The computer 80 is then configured to send a control signal to the hydraulic pump 51 via the controller 82.

Next, a measuring method of the present invention using the above measuring device 1 will be explained. In measuring the volume resistivity, as a preparatory work, first, the cylinder 2 is assembled to the cylinder support block 17, and a certain amount of powder S is accommodated in the inner tube 20 of the cylinder 2. Although it varies depending on the type of powder, the amount of powder S accommodated in the cylinder 2 is usually about 0.01 to 10 g. Next, the exhaust line 61 is connected to the joint 93, and the piston 4 is inserted into the cylinder 2 to the extent that its tip contacts the powder S while operating the vacuum pump 6 to exhaust the air inside the cylinder 2. Then, the cylinder support block 17 is placed on the base 11 together with the cylinder 2 and piston 4. Note that, before storing the powder S in the cylinder 2, its mass is measured in advance.

Subsequently, the resistivity measurement operation is started. To measure the resistivity, the vacuum pump 6 is operated again to exhaust the air inside the cylinder 2, while the hydraulic pump 51 is operated and the hydraulic jack 52 is raised to hold the cylinder 2 together with the base 11 at a certain level. Lift with speed. By such an operation, the piston 4 is pushed down relatively by the head portion 42, and the powder S in the cylinder 2 is gradually compressed.

When compressing the powder S, the exhaust flow rate of air from the cylinder 2 is set to 300 to 3000 mL/min by controlling the vacuum pump 6. The reason for setting the exhaust flow rate from the cylinder 2 is as follows. That is, if the exhaust flow rate from cylinder 2 is less than 300 mL/min, the measurement time becomes longer and the analysis efficiency decreases, and if the exhaust flow rate exceeds 3000 mL/min, the inner cylinder 20 of cylinder 2 There is a possibility that the flow velocity in the gap 90 between the inner circumference of the probe unit 3a and the probe units 3a and 3b becomes too high, and the powder is sucked.

In addition, when compressing the powder S, the pressing force by the piston 4, in other words, the compression force on the powder S, is set to a plurality of compression ranges in the range of 0 to 20 kN, for example, and the piston The relative pressing down speed of No. 4 is set in multiple stages, for example, in the range of 75 to 0.1 mm/min. The reason for setting the compressive force for the powder S and the downward speed of the piston 4 is as follows. In other words, during the compression process of the powder S, the distance between the particles becomes closer and the density increases, but if the particles are rapidly compressed, the movement of particles cannot keep up with this, resulting in variations in the density of the powder S and resulting in less uniformity. descend. Therefore, from the viewpoint of increasing the uniformity of the density of the powder S, it is desirable to apply pressure as slowly as possible, but as the depressing speed of the piston 4 is reduced, the measurement time becomes longer, causing a decrease in analysis efficiency. . Furthermore, when measuring the resistance at a target load value, if the depressing speed (compression speed) of the piston 4 is too fast, the target value will be overshot and measurement accuracy will be impaired.

In the measurement method of the present invention, the compression speed and load control for the powder S are important, and it is also necessary to consider the pressing characteristics depending on the hardness of the particles constituting the powder S. For example, in the case of soft powder S, the depressing speed of the piston 4 is set to 75 mm/min in the low load area and 0.2 mm/min in the high load area, and in the case of hard powder S, the depressing speed of the piston 4 is set to The pressing down speed is set to 25 mm/min in the low load area and 0.1 mm/min in the high load area. As described above, by adjusting the pressing down speed of the piston 4 to, for example, 75 mm/min or less, leakage of the powder S from the upper end of the cylinder 2 can be prevented.

In the measuring method of the present invention, as described above, when the powder S is gradually compressed by the relative depression of the piston 4, a preset load value is measured while measuring the load on the powder S with the load meter 72. As a measurement point (reference), the height of the cylinder 2 (insertion length of the piston 4) in each compression state is measured by the height gauge 71, and the resistance value of the powder S in each compression state is measured by the probe unit 3a, 3b.

In that case, the powder S whose mass has been measured in advance is housed in the cylinder 2, the inner diameter of the cylinder 2 is known, and the height of the cylinder 2 measured by the height gauge 71 indicates that when the powder S is compressed, Since the thickness of the powder S can be measured, the volume and bulk density of the powder S can be calculated. By measuring the resistance value of the powder S using the probe units 3a and 3b, it is possible to measure the volume resistivity with respect to the bulk density of the powder S at each measurement point, in other words, in each compressed state.

As described above, in the present invention, when a certain amount of powder S, which is a sample, is gradually compressed in the cylinder 2, the air inside the cylinder 2 is extracted from the minute gap 90 provided at the bottom of the cylinder 2, that is, By compressing the air contained in the powder S while forcibly exhausting it with the vacuum pump 6, leakage of the powder from the cylinder 2 can be prevented and the mass of the powder S that was initially measured can be maintained. , while compressing the powder S, the bulk density can be measured at any time, and the resistance value at that time can be measured. Thereby, the relationship between the bulk density and volume resistivity of the powder S can be specified with high precision. Therefore, according to the present invention, when evaluating the physical properties of various powder samples, it is possible to provide a highly reliable index of volume resistivity relative to bulk density. The present invention can be applied to various materials such as metals, alloys, ceramics such as metal oxides and metal nitrides, carbon materials such as carbon black and carbon nanotubes, inorganic materials, resin powders such as toner, foods, and pharmaceuticals. Can be applied to powder samples.

Example:
By using EC carbon (elementary carbon) as the sample powder S and using the measurement method of the present invention using the measuring device 1 of the present invention, changes in bulk density with respect to load can be confirmed, and volume with respect to bulk density can be confirmed. Resistivity was measured. The measurement was performed seven times by changing the amount of powder S. In each measurement, the amounts of powder S introduced into cylinder 2 were 0.121 g, 0.176 g, 0.252 g, 0.280 g, 0.387 g, 0.446 g, and 0.680 g.

In the measurement, while measuring the load by the piston 4 with the load meter 72, the bulk density is calculated by measuring the thickness of the powder S with the height gauge 71, and at the same time, the resistance value at that time is calculated using the probe unit 3a. The volume resistivity was obtained by measuring with a resistance measuring device 81. As a result, as shown in the graph of FIG. 4, it was confirmed that the changes in bulk density with respect to changes in load were approximately the same for all seven samples. As shown in the graph of FIG. 5, it was confirmed that the volume resistivity relative to the bulk density was also approximately the same for all seven samples.

Comparative example:
Using a conventional measuring device that does not exhaust the air in the sample, the same EC carbon as in the example was used as a sample, and the bulk density was calculated by measuring the load and the thickness of the powder in the same manner as in the example. The resistance value at that time was measured to determine the volume resistivity. The measurement was carried out 11 times with different amounts of powder. In each measurement, the amount of powder introduced into the cylinder was 0.100 g, 0.200 g, 0.300 g at 3 points, 0.400 g, 0.500 g, 0.600 g, and 0.700 g at 3 points. Ta. As a result, as shown in the graph of Figure 6, the change in bulk density with respect to load changes varied among the 11 samples, and as shown in the graph of Figure 7, the volume resistivity with respect to bulk density also varied among the 11 samples. Differences were observed between the samples.

The present invention is suitable for more accurately evaluating the physical properties of powders because it can measure the volume resistivity relative to the bulk density of various powders used in the manufacture of electronic materials and electrode materials with high precision. be.

1: Resistivity measuring device 10: Casing 11: Base 12: Guide bar 13: Pedestal 14: Retaining ring 15: Seal material (O ring)
16: Elastic body (coil spring)
17: Cylinder support block 2: Cylinder 20: Inner cylinder 21: Outer cylinder 23: Seal material holding ring 24: Outer ring 25: Fixed ring 3a: Probe unit (4 probe electrodes)
3b: Probe unit (ring electrode)
39: Connector 4: Piston 41a: Pressure part 41b: Pressure part 42: Head part 49: Connector 51: Hydraulic pump 52: Hydraulic jack (lifting mechanism)
6: Vacuum pump 71: Height gauge 72: Load cell
80: Computer 81: Resistance measuring device 82: Controller 90: Gap 91: Exhaust channel 92: Exhaust channel 93: Joint S: Powder

Claims (7)

This is a powder resistivity measurement device that measures volume resistivity with respect to bulk density, and includes a cylinder that accommodates powder as a sample, and a disk-shaped probe unit that fits into the cylinder and forms the bottom of the cylinder. , a base on which the cylinder and the probe unit are mounted together with a cylinder support block that fixes the cylinder; a pressurizing piston inserted into the cylinder in sliding contact with the inner peripheral surface of the cylinder; and the base. The probe unit includes an elevating mechanism that moves the piston up and down relative to the cylinder, and a height gauge that measures the insertion length of the piston into the cylinder, and the probe unit is configured to is arranged with a gap that allows air to pass through without leaking, and the cylinder support block is provided with an exhaust flow path that communicates with the gap, and a vacuum pump is connected to the exhaust flow path. A powder resistivity measuring device characterized by being configured to be able to exhaust air inside a cylinder. The powder resistivity measuring device according to claim 1, wherein the gap between the inner circumference of the cylinder and the probe unit is set to 20 to 50 μm. 3. The powder resistivity measuring device according to claim 1, wherein the elevating mechanism is a hydraulic jack operated by a plunger pump type hydraulic pump that controls movement of the piston by a linear actuator. 3. The powder resistivity measuring device according to claim 1, wherein the elevating mechanism is a screw type jack in which a screw is rotated by a motor whose rotational position and speed can be controlled. A method for measuring the resistivity of powder using the resistivity measuring device according to any one of claims 1 to 4, comprising: storing a certain amount of powder as a sample in a cylinder, and then operating a vacuum pump. While exhausting the air in the cylinder, the piston is pushed down relatively to gradually compress the powder in the cylinder, and the thickness of the powder in each compressed state is measured with a height gauge, and the powder is A method for measuring the resistivity of powder, characterized in that the volume resistivity of the powder in each compressed state relative to the bulk density is measured by measuring the resistance value of the powder with a probe unit. The method for measuring resistivity of powder according to claim 5, wherein when compressing the powder, the piston is relatively pushed down at a speed of 75 to 0.1 mm/min. The method for measuring resistivity of powder according to claim 5 or 6, wherein when compressing the powder, air in the cylinder is exhausted at a flow rate of 300 to 3000 mL/min.

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