TW202214544A - Ceramic spheres - Google Patents

Abstract

Ceramic spheres that include zirconia as a primary component and are 80-95 volume% tetragonal crystals and no more than 5 volume% monoclinic crystals, the ceramic spheres being characterized in that, when average particle diameter is X ([mu]m), the maximum height of waviness Wz ([mu]m) of the line of intersection between a cross-section and the surface of spheres that have a diameter of X/2 ([mu]m) is 0.5%-1.2% of the average particle diameter X ([mu]m). The present invention provides ceramic spheres that can be used as a medium, such as balls or beads, that is for use in a grinder and do not readily break, even when grinding and dispersion are performed at normal temperature and a high water temperature.

Description

ceramic sphere

The present invention relates to ceramic spheroids.

For fine pulverization of powders used for electronic materials or dispersion of pigments for inks, pulverizers such as ball mills, vibration mills, sand mills, and bead mills are widely used for pulverization using a pulverizing medium. The grinding medium (hereinafter also referred to as "medium") such as balls and beads for such a grinder is a ceramic sintered body mainly composed of zirconium dioxide, which is excellent in abrasion resistance, impact resistance, and the like.

The ceramic sintering system with zirconium dioxide as the main component has been disclosed: by limiting the composition ratio of ZrO ₂ and Y ₂ O ₃ , and controlling the amount of Al ₂ O ₃ and SiO ₂ , the durability and wear resistance can be improved. medium (eg, Patent Document 1). [Prior Art Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2001-316178

(The problem that the invention intends to solve)

In recent years, especially for the purpose of improving the performance of the object to be pulverized, the particle size has been further demanded, and the use of micro-diameter media for pulverization of 300 μm or less has been expanded in response to this situation. Micro-diameter media are generally manufactured by, for example, rolling granulation, in-liquid granulation, and plasma fusion molding. Regardless of the granulation method, it is in the process of forming and will be affected by the growth history of particles, Due to the influence of thermal history, surface tension, etc., there is a wave shape on the surface of the medium.

The wave system on the surface of this medium is where the local curvature radius is small. From the results of the review by the inventors of the present invention, it is known that when the media collide with each other, the medium and the object to be pulverized, and the medium and the wall surface of the device, the contact area of the wave area on the surface of the medium is small, and if a higher pressure is applied, the result will be It is easy to generate the cause of damage to the medium. In particular, when the material to be pulverized and the medium are mixed in a pulverizer or the like in water and pulverized/dispersed for a long time, the water temperature may increase, the ceramic sintered body may deteriorate, and breakage may occur easily.

The object of the present invention is to provide a ceramic spherical body that can be used as a medium for grinding balls, grinding beads, etc. in a pulverizer, and is not easily broken even when pulverized/dispersed in a normal temperature state and a state with a high water temperature. (Technical means to solve problems)

That is, in order to solve the above-mentioned problems, the ceramic spherical body of the present invention is mainly composed of zirconium dioxide, the proportion of tetragonal crystal is 80 volume % or more and 95 volume % or less, and the monoclinic crystal proportion system is 5 volume % or less. Wherein, when the average particle size is X (μm), the diameter of the spherical body cross-section with a diameter of X/2 (μm), and the perpendicular line portion to the spherical body surface, the maximum height wave Wz (μm) is the average 0.5% or more and 1.2% or less of the particle size X (μm). (Compared to the efficacy of the prior art)

Even if the ceramic spherical system of the present invention is used for pulverization/dispersion of objects to be pulverized in a normal temperature state or a state with a relatively high water temperature, the effect of suppressing the breakage of the ceramic spherical body can still be exerted.

The ceramic spherical system of the present invention is composed of a ceramic sintered body mainly composed of zirconium dioxide. In addition, in the following specification, the ceramic sintered body of the final product (ie, the intermediate ceramic sintered body obtained by sintering more than one time in the production process other than the grinding medium) is referred to as "intermediate sintered body". In addition, both the final product ceramic sintered body and the intermediate sintered body are simply referred to as "sintered body".

The ceramic spherical system of the present invention is obtained by molding a ceramic raw material powder containing zirconium dioxide as a main component (hereinafter simply referred to as "raw material powder") into a spherical shape. Here, in this specification, "containing zirconium dioxide as the main component" means that the ratio of zirconium dioxide is 90% by weight or more. better.

The content of each component of the ceramic can be obtained as follows. First, a ceramic sample was crushed using a universal testing machine, and about 0.3 g of crushed pieces were placed in a platinum crucible and melted with potassium hydrogen sulfate. This was dissolved in dilute nitric acid and the solution was determined, and each metal element was quantified by ICP emission spectrometry, and the content was determined by converting it into an oxide. Hereinafter, if the components of the ceramic spherical body of the present invention are expressed in terms of metal elements, they may also be expressed in terms of oxides.

Furthermore, the ceramic spherical system of the present invention preferably contains yttrium oxide (Y ₂ O ₃ ), cerium oxide (CeO ₂ ), aluminum oxide (Al ₂ O ₃ ), Magnesium oxide (MgO), calcium oxide (CaO), etc. These stabilizer functions can improve the strength and toughness of the ceramic spherical body. Among them, yttrium oxide is preferably contained. The yttria content is the molar ratio of yttria/zirconia in the ceramic spherical body, preferably 4.6/95.4 or more and 5.6/94.4 or less, more preferably 4.8/95.2 or more and 5.5/94.5 or less.

The proportion of tetragonal crystals in the ceramic spherical system of the present invention is 80% by volume or more and 95% by volume or less, and the proportion of monoclinic crystals is 5% by volume or less. If the content of tetragonal crystals exceeds 80% by volume, when stress is applied, the tetragonal crystals will mutate into monoclinic crystals and expand in volume, which can suppress the cracking of the medium. However, if it is less than 80% by volume, this effect will be reduced. . On the other hand, if the content of tetragonal crystals exceeds 95% by volume, degradation is likely to occur in high-temperature water, so if pulverization/dispersion is performed for a long time, the water temperature may rise, and the ceramic spherical body may be easily damaged. . In addition, from the viewpoint of preventing breakage, the smaller the proportion of monoclinic crystals, the better, and it is preferably 5% by volume or less. More preferably, it is less than 3% of capacity, and particularly preferred is less than 1% of capacity. However, in the production process of the ceramic spherical body, in order to make the surface shape smooth, wet grinding or post-cleaning, which will be described later, is generally performed. , because the monoclinic crystal will form at least 0.1% or more, so it is generally impossible to completely return to zero. The ratio of each crystal phase of the ceramic spherical body can be measured by powder X-ray diffraction.

In the ceramic spherical system of the present invention, when the average particle size is X (μm), the maximum height wave Wz ( μm) is 0.5% or more and 1.2% or less of the average particle diameter X (μm), that is, (Wz/X)×100 is 0.5 or more and 1.2 or less. Generally, the maximum height wave will increase with the particle size, so the present invention uses the quotient of dividing the maximum height wave by the average particle size for evaluation. If (Wz/X)×100 is greater than 1.2, when the ceramic spheres are being crushed, or when the ceramic spheres collide with the object to be crushed, local pressure concentration is generated on the ceramic spheres, resulting in easy breakage. (Wz/X)×100 is preferably 1.0 or less. Furthermore, when (Wz/X)×100 is less than 0.5, the productivity of industrial products is insufficient.

Here, the average particle diameter X can be measured using image analysis and measurement software after photographing the ceramic spherical body. Specifically, it means the value measured as follows. The aggregates of ceramic spheres were photographed with a digital microscope at a magnification of 10 to 200 times. Using image analysis and measurement software, the captured image is binarized based on the brightness of the measurement image. The binarized image is separated from the circular pattern by the least mean square, and the diameter of each separated circle is calculated and set as the diameter of each ceramic sphere. The average particle diameter X was defined as the number average of the diameters of 1000 ceramic spheres.

Furthermore, the "maximum height wave Wz" is based on JIS B 0601:2013, as shown in Fig. 1, for the cross section of the spherical body smaller than the diameter 1 of the ceramic spherical body, which becomes the X/2 diameter of 2, and the positive surface of the spherical body. The intersection 3 can be obtained by observing the ceramic spherical body with a laser microscope from above 4 . As a method of reducing the maximum height wave Wz, for example, rolling for a long time can be performed while adding only water in a rolling granulator described later.

The internal defect rate of the ceramic spherical body of the present invention is preferably 0.5% or less. The term "internal defects" as used herein refers to cracks or voids inside the ceramic spherical body. Internal defect: By grinding the ceramic spherical body, the internal defect rate is 0.5% or less, and the damage of the ceramic spherical body can be further suppressed. The method of setting the internal defect rate to 0.5% or less can be, for example, subjecting the obtained ceramic spherical body to a hot equalization treatment described later, or a step of reducing the surface wave of the molded body described later.

The average particle diameter X of the ceramic spherical body of the present invention is preferably 30 μm or more and 300 μm or less. When the average particle diameter X is 30 μm or more, the separation of the pulverized material and the ceramic spherical body can be easily performed, and the mixing of the ceramic spherical body can be prevented. When the average particle diameter X is 300 μm or less, the object to be pulverized can be pulverized and dispersed uniformly and finely. The average particle diameter X can be set to the above-mentioned range by sieve classification or the like described later.

The minimum particle size of the ceramic spherical body of the present invention is 0.7X (μm) or more, and the maximum particle size is preferably 1.3X (μm) or less. With the minimum particle size of 0.7X or more, the pulverized material and the ceramic spheres can be easily separated, so as to prevent the ceramic spheres from mixing. In addition, when the maximum particle diameter is 1.3X (μm) or less, the pulverized object after pulverization can be made into a uniform particle size distribution. The minimum particle diameter and the maximum particle diameter are the same as the above-mentioned measurement of the average particle diameter X, using image analysis and measurement software, and the minimum value of the diameters of the circles separated by the circular chart is the minimum particle diameter, and the maximum value is set as the The maximum particle size can be determined. The minimum particle diameter and the maximum particle diameter can be set to the above-mentioned ranges by using sieve classification or the like to be described later.

In addition, due to the non-uniformity in the manufacturing process of the ceramic spherical body, it will be difficult to make all the particles into a spherical shape. Generally, the particles with poor sphericity exist at the level of 1 to several%. In particular, the ellipse-shaped object may pass through the grading net whose opening width is smaller than the diameter of the equivalent circle according to the minor axis of the ellipse, or may be caught by the grading net whose opening width is larger than the diameter of the equivalent circle according to the long axis of the ellipse There is also the possibility of shifting the value outside the particle size distribution of ceramic spheres. Therefore, it is better to use the particle size evaluation of sampling, according to the method that can eliminate the influence of the particles with special shapes as above, instead of using the minimum particle size and the maximum particle size, use 1% particle size (D1), 99% particle size and 99% particle size. The definition of (D99) can more accurately grasp the particle size range of the ceramic spherical body, so it is better. Therefore, in the ceramic spherical body of the present invention, D1 is preferably 0.7X (μm) or more, and D99 is 1.3X (μm) or less. D1 and D99 systems can be evaluated in the same manner as the minimum particle size and the maximum particle size.

The ceramic spherical system of the present invention can be manufactured according to various methods. Hereinafter, an example is demonstrated about the detail of the manufacturing example performed by the rolling granulation method.

The raw material powder is first formed into a spherical shape using a rolling granulation method. The rolling granulation method is to form spherical particles by staggeringly adding ceramic raw material powder and a liquid binder containing a binder and moisture in a rotating drum. A method for producing a spherical molded body by growing it.

Next, the step of reducing the surface wave of the obtained formed body is to place the formed body weighing at least 100 kg or more in a rolling granulator, while adding only water, for at least 10 hours or more, preferably about 20 hours, more preferably 30+ hours of rolling. Thereby, the surface of the molded body is flattened, and the surface wave is reduced. In this step, the moisture content in the rolling granulator is preferably set to be 2-5% higher than that when the granulation is grown. In this way, the surface layer of the ceramic spherical body is in a state containing a lot of water, so that the particles can be easily moved (plastically deformed) when subjected to rolling pressure, and as a result, the convex portion can be flattened, and the maximum height wave Wz can be obtained. Smooth ceramic spherical body. In addition, in order to prevent excessive moisture from causing aggregation between particles, it is necessary to visually observe the appearance of the particles in the rolling granulation for grasping the humidified state of the particles at a certain elapsed time, or to sample a small amount of samples to perform microscopic observation of the particle state, or to grasp the state of the particles. The physical quantities, such as moisture content and bulk density, which indicate the humidified state, are rolled while subject to quality control.

Furthermore, the above-mentioned step of reducing the surface wave also has the effect of promoting the densification of the formed body, and can also effectively reduce the internal defect rate.

Since the thus obtained molded body contains moisture, if it is directly supplied and subjected to the sintering step described later, the moisture inside the molded body rapidly evaporates, which may cause cracks in the molded body. Therefore, before the compact is provided for the sintering process, a drying process for gradually reducing the moisture content in the compact is performed using a dryer or the like.

In this way, a ceramic sintered body can be obtained by performing a sintering step of placing the formed body after the drying step in a sagger or the like, and calcining it in a calcining furnace to remove the binder and eliminate the bonding of the powder particles. In the sintering step, it is preferable to perform calcination at 1350-1450° C. for 1-3 hours.

The sintered body that has undergone the sintering step can be used as it is (or after further grinding as described later) as a pulverizing medium. However, in order to further reduce the defects of the pulverizing medium, it is preferable to perform a thermal equalization step described later. Hereinafter, the case where the thermal pressure equalization step is further performed after the sintering step will be described. In addition, in the case where the hot equalization step is not performed, the sintered body after the aforementioned sintering step is not the "intermediate sintered body" of the final product; in the case where the hot equalization step is performed, it is described as "intermediate sintering" in the following description. body".

As described above, the intermediate sintered body obtained by the sintering step is preferably subjected to a hot isostatic pressing step for performing a hot isostatic pressing treatment (hereinafter referred to as "HIP treatment"). HIP treatment is a treatment in which high temperature and isotropic pressure are simultaneously applied to the object to be treated. By applying HIP treatment to the intermediate sintered body, the remaining voids and cracks in the intermediate sintered body can be removed without changing the shape. and other defects.

The HIP treatment is preferably performed at a temperature 0°C to 50°C lower than the sintering temperature in the sintering step. If the temperature is lower, the diffusion of ceramic powders such as zirconium dioxide in the HIP treatment is insufficient, and residual defects may occur. On the other hand, if the temperature of the HIP treatment is higher than the sintering temperature, the grain growth of the intermediate sintered body causes the strength to decrease, and the strength fluctuation may become large. The temperature of the HIP treatment is preferably 0°C to 40°C lower than the sintering temperature in the sintering step, and particularly preferably the temperature is 0°C to 30°C lower.

The pressure of the HIP treatment is sufficient to remove defects, and is preferably a sufficient pressure. If the treatment is carried out at a pressure of 100 MPa or more, the treatment can be carried out without problems. In order to be able to form a high-pressure state, it is preferable to perform the treatment in an Ar gas atmosphere.

The sintering system obtained as described above can be directly used as a pulverizing medium, and a higher-quality pulverizing medium can be obtained by further grinding the surface with devices such as a barrel mill, a ball mill, and a bead mill.

Furthermore, the sintered body is preferably classified by a classification step. The desired average particle size, minimum particle size, and maximum particle size can be set by the classification step. The classification method can be, for example, sieve classification in which a mesh-shaped sieve is used for classification. The sieve classification can also make two layers of sieves overlap, and use one operation to separate the coarse powder with a relatively large particle size and the fine powder with a relatively small particle size.

In addition, with regard to the above-mentioned surface grinding step, the inventors of the present invention have found that, as a result of examination, particularly by using a bead mill apparatus with a higher stirring energy to perform wet grinding, more favorable surface smoothness can be obtained. Surface smoothness is a factor that will greatly affect the amount of wear of ceramic spheres in the wet dispersion process. When colliding with the object to be dispersed, the convex portion is easily ground, and the wear amount of zirconium dioxide, which is the main component of the ceramic spherical body, is increased, and as a result, the quality of the object to be dispersed is greatly affected. In particular, it is known that in the main application of the ceramic spherical body dielectric of the present invention, when the high dielectric raw material for the manufacture of multilayer ceramic capacitors is subjected to the wet dispersion step of the barium titanate powder used, it is known that the wear of the ceramic spherical body will be caused by two factors. When the zirconia component is mixed into the barium titanate, the sintering reaction of the barium titanate will be inhibited, and the uniformity of the primary particle size of the sintered barium titanate will be impaired. The unevenness of the primary particle size can deteriorate the electrical characteristics (capacitance, dielectric loss, etc.) of the capacitor, or promote surface irregularities when forming a thin dielectric layer with a thickness of less than 1 μm per layer, resulting in a flat It becomes a hindrance factor in the process of the build-up structure. Therefore, in the wet dispersion step of barium titanate, the abrasion amount of zirconium dioxide mixed into the object to be pulverized is controlled with high precision, and it is preferable to use a ceramic spherical medium with less abrasion amount and stability. To achieve this, it is necessary to ensure the smoothness of the surface of the ceramic spherical body.

In the grinding step using the above-mentioned bead mill, the important process factors for obtaining good surface smoothness are the type of grinding material (material, particle size), its slurry concentration, stirring speed (peripheral speed), and processing time. In order to make the dead weight as light as the micro-sized ceramic spheres, it is necessary to use higher grinding energy when grinding the surface. The abrasive material is preferably silicon carbide (SiC) or alumina (Al ₂ O ₃ ) with high cutting force. Therefore, it is easier to obtain a smooth surface. Therefore, from the point of view of production efficiency, it is effective to use the abrasive material with larger particle size to perform rough grinding at first, and then use the abrasive material with smaller particle size to perform polishing and grinding. A particle size of about 10 μm is preferably used for polishing and polishing with a particle size of about 0.5 to 2 μm. In addition, the slurry concentration of the abrasives is preferably about 1 to 5% by weight from the viewpoint of preventing aggregation of the abrasives themselves during the polishing process. Similarly, from the viewpoint of preventing aggregation, it is preferable to add about 0.3 to 3% by weight of the dispersant in accordance with the type of abrasive. The stirring speed (circumferential speed) of the operating conditions of the device is as fast as possible from the viewpoint of productivity. However, if it is too fast, residues of abrasives will easily adhere to the surface of the ceramic spherical body. It is in the range of 8~14m/s. The treatment time varies depending on the specifications of the device, the size of the ceramic sphere, the type of abrasives, etc., but is preferably at least 2 hours or more, and more preferably 4 hours or more. In addition, after the grinding process is completed, the residues adhering to the surface of the ceramic spherical body can be removed by using only water without abrasives, or with only water and dispersant, and preferably 0.5~ 2 hours or so.

As a result of performing wet grinding under appropriate conditions using the bead mill as described above, for example, by barrel grinding, the smoothness of Ra=2 to 10 nm can be obtained with respect to the smoothness of the surface roughness Ra=20 to 40 nm. In order to form an abrasive material with a finer particle size below 2nm, grinding is performed for a long time or at a high peripheral speed, but the agglomeration of the abrasive material is likely to occur, and as a result, there will be concerns about mixing into the product, so it is better to use the production method implemented in the present invention. In order to make it into the said surface roughness range. The surface roughness Ra can be evaluated using an atomic force microscope (AFM). In addition, in this invention, 10 ceramic spherical bodies were sampled and evaluated, and the average value was made into the surface roughness value Ra.

When the above-mentioned surface roughness Ra=2~10nm ceramic spherical body is subjected to wet dispersion of barium titanate, the evaluation result of the wear amount shows that if Ra=10nm to 5nm, although it is smooth, the wear amount will also decrease, but if it is less than 5nm, the wear amount will be reduced. almost flat. This phenomenon is considered to be because the zirconia spherical body is subjected to cutting action from barium titanate. For example, even if the initial smoothness is about 2 nm, after use, the smoothness deteriorates to about 5 nm due to cutting damage. From the above results, regarding the wet dispersion application of barium titanate of the present invention, in order to reduce the wear amount of zirconia caused by the ceramic spherical body and stabilize the ceramic spherical body, the surface roughness of the ceramic spherical body is preferably set to Ra=2~ 5nm range. [Example]

Hereinafter, the present invention will be specifically described based on the embodiments, but the present invention is not limited to these embodiments.

(test methods) (average particle size, minimum particle size, maximum particle size, 1% particle size (D1), 99% particle size (D99) The particle size is measured according to the following method. Using a digital microscope VHX-2000 (manufactured by Keyence), an aggregate of ceramic spheres was photographed at a magnification of 10 to 200 times. Image analysis and measurement software WinROOF (registered trademark: manufactured by Mitani Corporation) was used to perform binarization based on the brightness of the measurement image. The binarized image is separated by a circle diagram using the least mean square, and the diameter of each separated circle is calculated and set as the diameter of each ceramic sphere. In addition, let the average particle diameter X be the average number of diameters of 1000 ceramic spherical bodies. In addition, let the minimum value of the diameters of each circle separated by the circular chart be the minimum particle diameter, and the maximum value to be the maximum particle diameter. In addition, count from the smallest end according to the number ratio, set the equivalent diameter of 1% of the cumulative number as 1% particle size (D1), and set the equivalent diameter of 99% of the cumulative number as 99% particle size (D99 ).

針孔 測定範圍：2θ=23°~33°、70°~77° 累計時間：3600秒/幀。 (Crystalline Phase Example) A resin-embedded sample was subjected to cutting and mirror polishing to obtain a measurement sample. This was attached to a sample holder, and the measurement was performed by a wide-angle X-ray diffraction method (micro-part X-ray diffraction). The measurement conditions are as follows: X-ray source: CuK line (using a multilayer mirror) Output: 50 kV, 22 mA Slit system: 100 μm

Pinhole measurement range: 2θ=23°~33°, 70°~77° Cumulative time: 3600 seconds/frame.

From the measurement results, the content of each crystal layer of zirconium dioxide was calculated using the following formula. Monoclinic crystal content (%)=[{I _m (111)+I _m (1-1-1)}/{I _m (111)+I _m (1-1-1)+I _t+c ( 111)}]×100 Cubic crystal content (%)=[I _t+c (111)/{I _m (111)+I _m (1-1-1)+I _t+c (111)}]× [{I _c (400)/{I _c (400) +I _t (400)+I _t (004)}×100 tetragonal content (%)=100-monoclinic content-cubic content where , where I represents the diffraction intensity. The subscripts m, t, and c represent monoclinic, cubic, and tetragonal crystals, respectively. The inner part of the diffraction intensity ( ) represents the index of each crystal.

(Max height wave Wz) The maximum height wave Wz (μm) is based on JIS B 0601:2013. Using a laser microscope VK-X-150 (manufactured by Keyence) for the ceramic spherical body, the diameter from the measurement direction shown in 4 in FIG. 1 (z-axis direction in FIG. 1 ) becomes X shown in 2 in FIG. 1 . /2 (μm) of the cross-section of the spherical body (on the xy plane orthogonal to the z-axis in FIG. 1 ), and the intersection with the surface of the spherical body (that is, the place indicated by 3 in FIG. 1 ), with 10 uncontacted spherical objects, under the conditions of measurement length = average particle diameter X/2 × 3.141 (μm), cutoff value for high frequency component removal λs = 2.5 (μm), and low frequency component removal λc = none , measure the maximum height wave Wz in the z-axis direction, and calculate the average value of the maximum height wave Wz. Here, 5 in FIG. 1 is an example of the measurement distribution of the maximum height wave Wz of the present invention.

(Surface Roughness Ra) The surface roughness Ra (nm) is based on JIS B 0601:2013. 10 particles were randomly sampled from the aggregate of ceramic spheres, and an atomic force microscope (Bruker, NanoScope V) was used to measure the size of a quadrilateral 1/10 of the average particle diameter X of the ceramic spheres according to the scanning speed = 0.3 Hz, A resolution of 256×256 was used to scan the vicinity of the center of the spherical body, and then the obtained image was subjected to one-time Flattening and three-times Plane Fit-x3 processing to obtain an image whose curved surface was fitted and corrected to a flat surface. For the plane-corrected image, the surface roughness Ra is evaluated. The evaluation was performed three times for each particle, and the average value of Ra at 10 particles×3 times=a total of 30 points was defined as the surface roughness value Ra of the ceramic spherical body.

(internal defect rate) The internal defect rate was measured by the following method. The ceramic spherical body is ground to 40~60% of the diameter of the spherical body with a grinding machine, and then polished and ground for more than 10 minutes with a diamond liquid with a particle size of 6 μm to obtain a rough cross-section. The obtained sample was observed at a magnification of 10 to 200 times using a digital microscope VHX-2000 (manufactured by Keyence), and the number of observed cracks was counted. 200 ceramic spheres were observed, and from these, the proportion of ceramic spheres with cracks or point defects was calculated and set as the internal defect rate.

(crushing load value) The crushing load value was measured according to the following method. The ceramic spherical body was clamped by a zirconium dioxide cylindrical fixture with a diameter of 20 mm, and a compressive load was applied at a speed of 0.5 mm/min using an electronic universal testing machine CATY-2000YD (manufactured by Yicang Manufacturing Co., Ltd.), and the load value at the time of failure was measured. The measurement is carried out on 30 ceramic spheres, and the numerical value is an average value. In addition, when the ceramic spherical body is exposed to high temperature water, the strength test system will allow the obtained ceramic spherical body to stand for 50 hours in a water temperature of 90 ° C, and then measure the crushing load value of the ceramic spherical body, and set it as "hydrothermal". Crush load value after test". The measurement is carried out on 30 spheroids, and the numerical system adopts the average value. Also, from {(crushing load value before hydrothermal test)-(crushing load value after hydrothermal test)}/(crushing load value before hydrothermal test)×100, the pressure after hydrothermal test was calculated. Crushed load reduction rate.

(Crack test) The crack test was carried out according to the following method. The aggregate of the obtained ceramic spherical bodies was filled with 220 g of a bead mill device (manufactured by HIROSHIMA METAL & MACHINERY, model UAM-015), 300 g of pure water at 20°C was circulated, and stirring was performed at a peripheral speed of 12 m/s for 24 hours. . After stirring, the ceramic spherical body was taken out, and observed with a digital microscope VHX-2000 (Keyence) at a magnification of 10 to 200 times to confirm the presence or absence of cracks. 1000 ceramic spheres were confirmed, and the number of ceramic spheres with cracks was defined as the number of cracks.

(Evaluation of wear amount and crack evaluation during wet dispersion of barium titanate) The wear amount evaluation of the ceramic spherical body during wet dispersion of barium titanate was carried out by the following method. The aggregate of the obtained ceramic spherical bodies was filled with 220 g of a bead mill device (manufactured by HIROSHIMA METAL & MACHINERY, model UAM-015), and 300 g of barium titanate (SIGMA-ALDRICH) was mixed with 300 g of pure water at 20°C. Company, titanium (IV) barium), and 3 g of dispersant (Tokyo Chemical Industry Co., Ltd., sodium dodecylbenzenesulfonate) were circulated, and wet dispersion was performed for 4 hours at a peripheral speed of 12 m/s. The obtained slurry was dried at 90°C for 24 hours with a hot air dryer, and then the dried barium titanate powder was finely pulverized with a mortar, and then a fluorescent X-ray analyzer (ZSX Primus II, manufactured by Rigaku Electric Co., Ltd.) was used. The amount of zirconium dioxide in the barium titanate powder (ceramic spherical body wear amount) was calculated by obtaining the ratio of the area of the zirconium intensity peak to the area of the intensity peak of titanium and barium. In addition, after this test was carried out, the number of cracks in the ceramic spherical body was confirmed using a digital microscope in the same manner as in the above-mentioned crack test.

[Example 1] In zirconium oxychloride, yttrium chloride was added in such a manner that the oxides in the obtained ceramic spheres were converted into the molar ratio of yttria/zirconia in Table 1, and the raw material powder was prepared according to the co-precipitation method. .

Next, using the above-mentioned raw material powder, according to the rolling granulation molding method, granulation molding was performed until the average particle diameter X after sintering became a size around 50 μm to obtain a molded body.

Next, in the step of reducing the surface wave of the obtained formed body, the surface wave was reduced by rolling for about 40 hours while only adding water so as to maintain a certain moisture content in the rolling granulator.

After drying the formed body obtained as described above, calcination was performed at 1400° C. for 2 hours to obtain an intermediate sintered body (sintering step). Then, the intermediate sintered body was subjected to HIP treatment at 1380° C. and 120 MPa for 1.5 hours (thermal equalization step). The obtained sintered body was subjected to surface grinding using a barrel grinding apparatus, and then subjected to sieve classification to prepare spherical media for grinding shown in Table 1.

[Example 2] Using the raw material powder of Example 1, similarly to Example 1, the rolling granulation method was used to granulate a compact with an average particle diameter X after sintering of about 100 μm, and the step of reducing the surface wave was carried out. The obtained shaped body is dried to remove moisture, and then subjected to calcination and HIP treatment. The obtained sintered body was subjected to surface grinding using a barrel grinding apparatus, and then subjected to sieve classification to prepare spherical media for grinding shown in Table 1.

[Example 3] Using the raw material powder of Example 1, as in Example 1, a compact was granulated by the rolling granulation method until the average particle diameter X after sintering became a size of about 200 μm, and the step of reducing the surface wave was carried out. The obtained shaped body is dried to remove moisture, and then subjected to calcination and HIP treatment. The obtained sintered body was subjected to surface grinding using a barrel grinding apparatus, and then subjected to sieve classification to prepare spherical media for grinding shown in Table 1.

[Example 4] In the same manner as in Example 1, a compact was granulated according to the rolling granulation method until the average particle diameter X after sintering became a size of about 50 μm. Except that the time of the step of reducing the surface wave was shortened to 10 hours, it carried out similarly to Example 1, and produced the spherical medium for pulverization shown in Table 1.

[Example 5] In the same manner as in Example 2, a compact was granulated according to the rolling granulation method until the average particle diameter X after sintering became a size of around 100 μm. Except that the time of the step of reducing the surface wave was shortened to 10 hours, it carried out similarly to Example 2, and produced the spherical media for grinding shown in Table 1.

[Example 6] In the same manner as in Example 3, a compact was granulated according to the rolling granulation method until the average particle diameter X after sintering became a size of around 200 μm. Except that the time of the step of reducing the surface wave was shortened to 10 hours, it carried out similarly to Example 3, and produced the spherical media for grinding shown in Table 1.

[Example 7] In the same manner as in Example 2, a compact was granulated according to the rolling granulation method until the average particle diameter X after sintering became a size of around 100 μm. Except that the treatment temperature of the HIP step was changed from 1380°C to 1300°C, it was carried out in the same manner as in Example 2, and the spherical media for pulverization shown in Table 1 were produced.

[Example 8] The same manufacturing process as in Example 1 was carried out until the HIP treatment, but the grinding step was carried out using a bead mill under the following conditions. The abrasive used was prepared from 3.0% by weight of alumina with a particle size of 3 μm (Tipton Co., Ltd., Light 1A), and 0.5% by weight of sodium polycarboxylate as a dispersant (Zhongjing Oil Co., Ltd., Serna D-305). The slurry was ground for a total of 6 hours with a bead mill at a peripheral speed of 12 m/s, and then used alumina with a particle size of 1 μm (Tipton Co., Ltd., Light 1A) 1.0% by weight, and the dispersant was the same as D-305. : 0.5 wt % of the prepared slurry was polished for 4 hours. Finally, polishing was performed for 2 hours with a slurry prepared only by D-305: 0.5 wt % to remove the surface residues of the ceramic spheres, thereby obtaining ceramic spheres with a surface roughness Ra=2 nm. The subsequent sieve classification was carried out in the same manner as in Example 1.

[Example 9] The same manufacturing process as in Example 1 was carried out until the HIP treatment, but the grinding step was carried out using a bead mill under the following conditions. The abrasive used was prepared from 3.0% by weight of alumina with a particle size of 3 μm (Tipton Co., Ltd., Light 1A), and 0.5% by weight of sodium polycarboxylate as a dispersant (Zhongjing Oil Co., Ltd., Serna D-305). After grinding the slurry for a total of 6 hours according to the bead mill stirring peripheral speed = 12m/s, the slurry prepared by D-305: 0.5% by weight was used for polishing for 2 hours to remove the surface residue of the ceramic spherical body and obtain a rough surface. Ceramic spheres with a degree of Ra=5nm. The subsequent sieve classification was carried out in the same manner as in Example 1.

[Example 10] The same manufacturing process as in Example 1 was carried out until the HIP treatment, but the grinding step was carried out using a bead mill under the following conditions. The abrasive used was prepared from 3.0% by weight of alumina with a particle size of 3 μm (Tipton Co., Ltd., Light 1A), and 0.5% by weight of sodium polycarboxylate as a dispersant (Zhongjing Oil Co., Ltd., Serna D-305). After grinding the slurry for a total of 3 hours according to the bead mill stirring peripheral speed = 12m/s, the slurry prepared by D-305: 0.5% by weight was used for polishing for 2 hours to remove the surface residue of the ceramic spherical body and obtain a rough surface. Ceramic spheres with a degree of Ra=10nm. The subsequent sieve classification was carried out in the same manner as in Example 1.

[Comparative Example 1] In the same manner as in Example 1, a compact was granulated according to the rolling granulation method until the average particle diameter X after sintering became a size of about 50 μm. Except for omitting the step of reducing the surface wave, it was carried out in the same manner as in Example 1, and the spherical media for pulverization shown in Table 1 were produced.

[Comparative Example 2] In the same manner as in Example 2, a compact was granulated according to the rolling granulation method until the average particle diameter X after sintering became a size of around 100 μm. Except that the step of reducing the surface wave was omitted, it was carried out in the same manner as in Example 2, and the spherical media for pulverization shown in Table 1 were produced.

[Comparative Example 3] In the same manner as in Example 3, a compact was granulated according to the rolling granulation method until the average particle diameter X after sintering became 200 μm before and after. Except for omitting the step of reducing the surface wave, it was carried out in the same manner as in Example 3, and the spherical medium for pulverization shown in Table 1 was produced.

[Comparative Examples 4 to 6] In the zirconium oxychloride, yttrium chloride was added so that the oxides in the obtained ceramic spherical body were converted into the ratio shown in the yttria/zirconia molar ratio in Table 1, and the raw material powder was prepared by the coprecipitation method.

Next, using the above-mentioned raw material powder, as in Example 2, the rolling granulation method was used to granulate a compact having an average particle diameter of 100 μm after sintering, and the step of reducing the surface wave was carried out. The obtained molded body is dried to remove moisture, and then subjected to calcination and HIP treatment. The obtained sintered body was subjected to surface grinding using a barrel grinding apparatus, and then subjected to sieve classification to prepare spherical media for grinding shown in Table 1.

[Comparative Example 7] The same production method as in Comparative Example 1 was carried out until the HIP step, but the polishing step was carried out in the same manner as in Example 8 under the polishing conditions using a bead mill to obtain surface smoothness with a surface roughness Ra=3 nm. The sieve classification was also carried out in the same manner as in Example 8.

The evaluation results are shown in Tables 1-2.

As shown in Examples 1 to 6, by reducing the surface wave, a ceramic spherical body that is not easily broken can be obtained. In Example 7, the internal defect rate was increased by lowering the HIP temperature, and the number of cracks was slightly increased, but still within the allowable range.

Comparative Examples 1 to 3 belong to the ceramic spherical bodies which are easily broken due to the large surface waves. Comparative Example 4 belongs to a ceramic spherical body which is easily broken due to the large proportion of monoclinic crystals. In Comparative Example 5, since the ratio of tetragonal crystals is large, the reduction rate of the crushing load value after the hydrothermal test is large, and it belongs to a ceramic spherical body with a high possibility of breakage when the water temperature rises. Comparative Example 6 belongs to a ceramic spherical body which is easily broken because of the small proportion of tetragonal crystals.

Furthermore, as shown in Example 1 and Examples 8 to 10, if the surface roughness Ra = 5 to 20 nm, the wear amount of zirconia during wet dispersion of barium titanate will decrease as Ra decreases, but 5 nm and The 2nm series exhibited the same degree. In addition, the number of cracks in the ceramic spherical body at this time was zero in Examples 1, 8 to 10. In addition, the crack resistance at the time of the crack test was the same as that of Example 1, and also in Examples 8 to 10, the occurrence of cracks was zero.

In Comparative Example 7, although the zirconium dioxide abrasion amount during the wet dispersion of barium titanate was smaller than that of Example 10, it showed a higher value than that of Examples 8 to 9. It was found that the ceramic spherical body had cracks, and it was judged that it might be caused by the mixing of tiny crack fragments into the barium titanate dispersion. The number of cracks in the crack test was not significantly different from that of Comparative Example 1, and cracks occurred.

[Table 1] [Table 1] Average particle size X [μm] Minimum particle size [μm] Maximum particle size [μm] D1 particle size [μm] D99 particle size [μm] Yttria/Zirconium Dioxide Molar Ratio Crystal phase ratio (volume %) scroll time [hour] Maximum height wave Wz [μm] (Wz/X)×100 Surface roughness Ra [nm] HIP temperature [℃] Internal defect rate [%] Square crystal Monoclinic cubic crystal Example 1 50 45 55 46 53 4.8/95.2 89 1 10 40 0.28 0.56 twenty three 1380 0.0 Example 2 106 101 114 103 111 4.9/95.1 91 0 9 40 0.85 0.80 1380 0.0 Example 3 202 194 211 196 209 5.1/94.9 92 0 8 40 1.45 0.72 1380 0.0 Example 4 51 45 59 47 57 4.7/95.3 90 0 10 10 0.59 1.16 1380 0.2 Example 5 106 98 113 99 111 4.5/95.5 91 1 8 10 1.20 1.13 1380 0.2 Example 6 204 192 214 194 211 5.0/95.0 87 2 11 10 2.13 1.04 1380 0.1 Example 7 104 98 109 99 108 4.7/95.3 91 0 9 40 0.83 0.80 1300 0.7 Example 8 51 43 56 45 54 4.9/94.7 90 1 9 40 0.31 0.61 2 1380 0.0 Example 9 50 42 56 43 54 4.8/95.0 91 1 8 40 0.34 0.68 5 1380 0.0 Example 10 51 44 57 46 55 4.8/95.1 90 1 9 40 0.29 0.57 10 1380 0.0 Comparative Example 1 50 44 56 46 54 4.7/95.3 90 1 9 0 0.74 1.48 1380 0.3 Comparative Example 2 104 98 111 100 109 4.8/95.2 89 2 9 0 1.47 1.41 1380 0.3 Comparative Example 3 203 194 213 195 210 4.7/95.3 90 0 10 0 2.80 1.38 1380 0.2 Comparative Example 4 105 96 116 97 114 2.7/97.3 92 8 0 40 0.88 0.84 1380 0.0 Comparative Example 5 106 94 111 95 109 2.5/97.5 98 2 0 40 0.79 0.75 1380 0.0 Comparative Example 6 106 97 112 99 110 5.7/94.3 78 2 20 40 0.85 0.80 1380 0.0 Comparative Example 7 50 43 57 45 55 4.7/94.8 90 1 9 0 0.79 1.58 3 1380 0.0

[Table 2] [Table 2] Crushing load value [kgf] Crushing load value after hydrothermal test [kgf] Crushing load reduction rate after hydrothermal test [%] Number of cracks [pieces] Barium titanate wet dispersion Zr wear concentration [ppm] Barium titanate wet dispersion crack number [ppm] Example 1 0.37 0.36 3 0 1400 0 Example 2 1.66 1.65 1 0 Example 3 5.68 5.64 1 0 Example 4 0.34 0.33 3 0 Example 5 1.54 1.50 3 0 Example 6 5.31 5.25 1 0 Example 7 1.56 1.51 3 2 Example 8 0.39 0.38 3 0 210 0 Example 9 0.38 0.37 3 0 220 0 Example 10 0.38 0.36 5 0 480 0 Comparative Example 1 0.30 0.29 3 7 Comparative Example 2 1.48 1.45 2 10 Comparative Example 3 5.08 5.04 1 11 Comparative Example 4 1.52 1.50 1 6 Comparative Example 5 1.68 1.51 10 0 Comparative Example 6 1.53 1.49 3 8 Comparative Example 7 0.32 0.30 6 8 390 10

1: diameter of ceramic sphere 2: becomes the diameter of X/2 (μm) 3: The intersection of the cross section of the ceramic spherical body with a diameter of X/2 (μm) and the surface of the spherical body 4: Determination direction of maximum height wave Wz 5: Example of measurement distribution of maximum height wave Wz

FIG. 1 is a diagram showing an example of the measurement position, measurement direction, and actually measured wave distribution of the maximum height wave Wz of the ceramic spherical body of the present invention. The maximum height of the wave in the z-axis direction in the figure is measured, and the x-axis and y-axis are the planes perpendicular to it.

Claims (7)

A ceramic spherical body, which is mainly composed of zirconium dioxide, the proportion of tetragonal crystal is more than 80% by volume and less than 95% by volume, and the proportion of monoclinic crystal is less than 5% by volume; wherein, When the average particle size is X (μm), the maximum height wave Wz (μm) is the average particle size in the cross-section of the spherical body with a diameter of X/2 (μm) and the intersection with the surface of the spherical body 0.5% or more and 1.2% or less of X (μm). The ceramic spherical body according to claim 1, wherein the proportion of monoclinic crystals is 0.1% by volume or more. The ceramic spherical body according to claim 1 or 2, wherein the 1% particle size (D1) in the particle size distribution is 0.7X (μm) or more, and the 99% particle size (D99) is 1.3X (μm) or less. The ceramic spherical body according to any one of claims 1 to 3, wherein the minimum particle size is 0.7X (μm) or more, and the maximum particle size is 1.3X (μm) or less. The ceramic spherical body according to any one of claims 1 to 4, wherein the internal defect rate of the ceramic spherical body is 0.5% or less. The ceramic spherical body according to any one of claims 1 to 5, wherein the average particle diameter of the ceramic spherical body is 30 μm or more and 300 μm or less. The ceramic spherical body according to any one of claims 1 to 6, wherein the surface roughness Ra is 2.0 nm or more and 5.0 nm or less, and is used for wet grinding of barium titanate powder.

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