JP5330047B2 - Method for producing ceramic powder with improved dispersibility and method for producing dispersion of ceramic powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing dispersion of ceramic powder which provides the dispersion of ceramic powder with good dispersibility to impart high density of a molding. <P>SOLUTION: The method for manufacturing the dispersion of ceramic powder comprises incorporating the raw material ceramic powder and a dispersant for dispersing the raw material ceramic powder into a predetermined dispersing medium, in a liquid medium S that can produce a radical species, and producing the radical species in the medium while allowing the medium in which the raw material ceramic powder and the dispersant were incorporated to flow. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a ceramic powder having improved dispersibility, and a method for producing a ceramic powder dispersion.

  In many cases, a ceramic molded body is manufactured by the following steps: Dispersing ceramic powder in a predetermined medium, molding the obtained dispersion into an appropriate shape, and firing the molded body.

  By the way, in order to form this type of ceramic molded body uniformly and at a high density, it is necessary to improve the dispersibility of the ceramic powder in the dispersion (that is, to make the dispersion state uniform). In order to improve dispersibility, a dispersant is generally added to the medium.

  In order to further improve the dispersibility, an attempt may be made to increase the amount of the dispersant adsorbed on the surface of the ceramic particles. At this time, generally, for example, a relatively large amount of a low molecular weight dispersant is added, or a so-called high molecular dispersant is added. However, in this method, there is a concern that a relatively large amount of surplus dispersant (that is, a free dispersant not adsorbed on the surface of the ceramic particles) is generated in a relatively large amount, thereby reducing the density of the molded body.

上記式において、Ｍは材料粒子表面の分散剤の吸着サイト、Ｄは分散剤、Ｍ−Ｄは吸着サイトに分散剤が吸着したもの、Ｋは平衡定数を示す。上記式の通り、吸着サイトに分散剤が吸着したものＭ−Ｄと、吸着していないフリーの分散剤Ｄとは、平衡関係にある。吸着量を多くするためには分散剤を多く添加する必要がある一方、分散剤を多く添加すると、上述の平衡関係のため、同時にフリーの分散剤が増加してしまう。

In the above formula, M is the adsorption site of the dispersing agent on the surface of the material particles, D is the dispersing agent, M-D is the adsorption site of the dispersing agent, and K is the equilibrium constant. As shown in the above formula, the sample MD with the dispersant adsorbed on the adsorption site and the free dispersant D not adsorbed are in an equilibrium relationship. In order to increase the amount of adsorption, it is necessary to add a large amount of dispersant, but when a large amount of dispersant is added, the amount of free dispersant increases at the same time due to the above-described equilibrium relationship.

  The present invention has been made to address the above-described problems. That is, an object of the present invention is to provide a ceramic powder and a dispersion thereof having good dispersibility and capable of increasing the density of a molded body.

  A feature of the present invention is to produce a ceramic powder with improved dispersibility by the following method: (1) Raw material ceramic powder and raw material ceramic powder in a liquid medium capable of generating radical species (2) In the state that the medium containing the raw material ceramic powder and the dispersant is flowed, while heating the medium, the medium is heated in the medium. To produce the radical species.

  In addition, a feature of the present invention is that the powder (modified ceramic powder) obtained by the steps (1) and (2) is dispersed in the dispersion medium, thereby dispersing the ceramic powder having good dispersibility. It is to produce a liquid.

  The heating and the generation of radical species described above are performed, for example, by applying a voltage (alternating current or pulsed) between a pair of electrodes immersed in the medium to generate plasma (in-liquid plasma). Can be done at the same time. The above-described heating can be performed separately from the generation of the radical species (for example, using ultrasonic heating or the like). Moreover, the above-mentioned heating may be local (for example, heat generation by the above-mentioned plasma generation in liquid) or may be overall.

  When an aqueous solution is used as the medium, the radical species is typically OH · or H ·. In addition, as the dispersant, one having a carboxyl group can be used.

  When producing a ceramic powder with improved dispersibility (recovering the modified ceramic powder from the treated medium), a drying step is finally performed (usually prior to this drying step). A cleaning process is performed, but it is not essential.) In the drying step, any drying process such as hot air drying, spray drying, freeze drying, or the like can be used. Then, by dispersing the modified ceramic powder obtained through the drying step in the dispersion medium, a ceramic powder having good dispersibility can be obtained.

  In the method of the present invention, the radical species is generated in the medium while the medium in which the raw material ceramic powder and the dispersant are added is flowed (stirred) while the medium is heated. . Specifically, for example, when a voltage is applied between the pair of electrodes immersed in the medium to generate plasma (liquid plasma) in the medium, the medium is generated in the plasma generation region. The radical species are generated while being in a high temperature / high pressure state (supercritical state).

  By the action of this heat and radical species, the dispersant adheres firmly (irreversibly) to the surface of each particle of the raw ceramic powder. In this case, it is considered that a radical reaction occurs between the surface and the dispersant, and dehydration bonding or chemical bond-like adhesion corresponding to this occurs.

  According to the method of the present invention, the amount of the dispersant adhering to the surface can be effectively increased without increasing the amount of the dispersant input (that is, with a smaller amount of input than before). . Alternatively, according to the method of the present invention, residual impurities such as excess dispersant and coupling agent can be effectively suppressed.

  Even if the powder obtained by the present invention (the modified ceramic powder) is washed, the residual impurities are effectively suppressed. This is because the dispersing agent adheres firmly (irreversibly) to the surface of each particle (K becomes very large in the above formula), so that almost no detachment of the dispersing agent by washing occurs. Furthermore, by using a process premised on washing, it is possible to stably modify all the adsorption sites (to form a dispersion agent bonded).

  When a slurry obtained by dispersing the powder obtained by the method of the present invention (the modified ceramic powder) in the dispersion medium to prepare a slurry, extremely good dispersibility is exhibited. In addition, as described above, the slurry is such that the residual impurities such as the excess dispersant and coupling agent are extremely suppressed. Therefore, according to the present invention, it is possible to provide a ceramic powder and a dispersion thereof having good dispersibility and capable of increasing the density of a molded body.

  Further, according to the present invention, firm (irreversible) adhesion of the dispersant on the surface of each particle of the modified ceramic powder is uniformly performed on almost the entire surface of the particle. Furthermore, carelessly changing the crystal state and the particle size distribution can be effectively suppressed.

  When the radical species are generated by submerged plasma, a shock wave acts in the vicinity of the plasma. Therefore, the modification can be performed while the weak aggregates are crushed by the shock wave. In this case, even if the powder concentration is high (for example, 0.1 vol% or more), almost the entire surface of the particles can be uniformly modified.

  The method of the present invention can be performed not only as a batch process but also as a continuous process using a distribution system. Further, the method of the present invention can be suitably used for improving the dispersibility of the oxide ceramic powder. In particular, even when the particle diameter is small, it is possible to effectively suppress the occurrence of aggregation by increasing the adhesion amount of the dispersant.

It is the schematic which shows the principal part structure of an example of the apparatus for enforcing the manufacturing method of this invention. It is a graph which shows the thermogravimetric analysis result of an Example and a comparative example. It is a FT-IR spectrum of an example and a comparative example. It is the schematic which shows the principal part structure of the other example of the apparatus for enforcing the manufacturing method of this invention. It is the schematic which shows the principal part structure of another example of the apparatus for enforcing the manufacturing method of this invention.

  Embodiments and representative examples of the present invention will be described below with reference to the drawings as appropriate. In addition, the description about the following embodiment is specific to the extent possible, merely an example of the embodiment of the present invention in order to satisfy the description requirement (description requirement / practicability requirement) of the specification required by law. It is only what is described in.

  Therefore, as will be described later, it is quite natural that the present invention is not limited to the specific configurations of the embodiments described below. Various modifications that can be made to the present embodiment are listed together at the end, as they would interfere with the understanding of the consistent description of the embodiment if inserted during the description of the embodiment. .

<Outline of apparatus configuration for carrying out manufacturing method of embodiment>
FIG. 1 is a schematic diagram showing the main configuration of an example of an apparatus for carrying out the manufacturing method of the present invention. The manufacturing apparatus 1 includes a storage tank 2, a stirrer 3, and an in-liquid plasma generator 4.

  A medium S that is an aqueous solution with adjusted conductivity is stored in the storage tank 2. The stirrer 3 causes the medium S to flow (stir) in the storage tank 2.

  The in-liquid plasma generator 4 includes a pair of electrodes 4a. The pair of electrodes 4 a is provided in the storage tank 2 so as to be immersed in the medium S stored in the storage tank 2. Further, the pair of electrodes 4a is arranged so that radical species are generated by applying a voltage between the pair of electrodes 4a to generate plasma (in-liquid plasma) in the medium S.

  Specifically, the electrode 4a is fixed to the electrode holder 4b so that the tip is exposed. The pair of electrode holders 4b are supported by support means (not shown) so that the pair of electrodes 4a face each other with a predetermined gap therebetween. The pair of electrodes 4a is electrically connected to the power source 4c.

<Outline of Manufacturing Method of Ceramic Powder with Improved Dispersibility of Embodiment>
The method for producing a ceramic powder with improved dispersibility according to this embodiment includes the following steps.
(1) A raw material ceramic powder and a dispersing agent are put into a medium S that is an aqueous solution capable of generating OH · or H · as radical species.
(2) While the medium S in which the raw material ceramic powder and the dispersing agent are charged is flowed (stirred) by the stirrer 3, a voltage is applied between the pair of electrodes 4 a to generate plasma (liquid plasma) in the medium S. Is generated. Then, the medium becomes a high temperature / high pressure state (supercritical state) in the plasma generation region. Accordingly, the medium S is heated and OH · or H · is generated in the medium S.

  Due to the action of OH. Or H. produced in the medium S and heat, the dispersant adheres firmly (irreversibly) to the surface of each particle of the raw ceramic powder. In this case, it is considered that a radical reaction occurs between the surface and the dispersant, and dehydration bonding or chemical bond-like adhesion corresponding thereto occurs.

  According to the method of the present embodiment, it is possible to effectively increase the adhesion amount of the dispersant without increasing the amount of the dispersant input (that is, with a smaller amount of input than before). Or the residue of impurities, such as an excessive dispersing agent and a coupling agent, can be suppressed effectively.

  Hereinafter, specific process contents and evaluation results of an example of the manufacturing method of the present invention will be described in contrast to a comparative example.

<Example>
(A) By adding KCl to ion-exchanged water, a medium that is a KCl aqueous solution with conductivity adjusted to 1 mS / cm was prepared.
(B) 5 g of PZT (Pb (Zr _0.52 Ti _0.48 ) O ₃ ) powder is added to 100 ml of medium, and dispersion treatment is performed for 2 minutes with a 300 W ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusyo Co., Ltd .: product number US-300T). went.
(C) 5 g of hexanoic acid as a dispersant was added to the above dispersion.
(D) The dispersion after addition of the dispersant was put into a 200 ml beaker serving as the storage tank 2, and plasma in liquid was generated while stirring with a magnetic stirrer (5 minutes).
(E) The dispersion after the above treatment is subjected to suction filtration to collect a solid content, and the solid content is repeatedly washed with butyl acetate and suction filtered several times, and then dried at 100 ° C. A later ceramic powder was obtained.

  The submerged plasma generation conditions in the above step (D) are as follows: the electrode 4a is a tungsten electrode having a diameter of 1 mm (tip is cylindrical), the gap between the electrodes is 1 mm, and the voltage is a pulsed voltage of 0 V / 2 kV ( 20 kHz, pulse width 1.7 μsec, power output 200 W).

The PZT powder was synthesized as follows: PbO, ZrO ₂ , and TiO ₂ in powder form were weighed so as to have the above composition, and these were then calibrated in a polyethylene pot. Wet mixed using ₂ mm ZrO ₂ beads, dried and heat treated. As a result of observing the synthesized powder with a scanning electron microscope, the particle diameter of the powder was about 100 nm, and the isoelectric point was about pH = 6.0. The isoelectric point is obtained by measuring the zeta potential of powder in water at 5 points of pH = 2, 4, 6, 8, and 10.

<Comparative Example 1>
(B ′) 5 g of PZT powder was added to 100 ml of a medium composed of ion-exchanged water, and a dispersion treatment was performed for 2 minutes with a 300 W ultrasonic homogenizer (same as above).
(C) 5 g of hexanoic acid as a dispersant was added to the above dispersion.
(D ′) The dispersion after addition of the dispersant was subjected to a dispersion treatment for 2 minutes using a 300 W ultrasonic homogenizer (same as above).
(E) The dispersion after the above treatment is subjected to suction filtration to collect a solid content, and the solid content is repeatedly washed with butyl acetate and suction filtered several times, and then dried at 100 ° C. A later ceramic powder was obtained.

<Comparative example 2>
(B ′) 5 g of PZT powder was added to 100 ml of a medium composed of ion-exchanged water, and a dispersion treatment was performed for 2 minutes with a 300 W ultrasonic homogenizer (same as above).
(C · D ″) Autoclave (Om Lab Tech Co., Ltd .: Product No. MMJ-500) A 5 ml container of Hastelloy (registered trademark) and 5 g of the above dispersion and hexanoic acid as a dispersant are added to the autoclave. Then, the mixture was hydrothermally treated at 400 ° C. and 25 MPa for 5 minutes while stirring with an agitator attached to the autoclave.
(E) The dispersion after the above treatment and cooling is suction filtered to collect a solid content, and after washing and solid filtration with butyl acetate several times, the solid content is dried at 100 ° C. A modified ceramic powder was obtained.

<Evaluation result 1: Thermogravimetric analysis>
FIG. 2 and Table 1 show the results obtained by analyzing the powders obtained in the above Examples and Comparative Examples with a thermogravimetric analyzer (manufactured by Rigaku Corporation: product number TGA50). This analysis was performed under the following conditions: room temperature to 500 ° C. (temperature increase rate: 10 ° C./min) under air flow.

  The results in Table 1 correspond to the amount of dispersant firmly adhered to the surface of the ceramic particles to the extent that they are not desorbed even by the step (E). As is apparent from this result, the amount of the dispersant attached to the surface of the ceramic particles by the in-liquid plasma treatment in the example was much larger than those in Comparative Examples 1 and 2.

  As shown in FIG. 2, the behavior during the thermogravimetric analysis was that Comparative Example 1 was decomposed at the lowest temperature, Comparative Example 2 was decomposed at the highest temperature, and the Example was in the middle. When comprehensively considering this result and the FT-IR analysis result described later, it is considered that the manner in which the dispersant is attached to the surface of the ceramic particles is different between the example, the comparative example 1 and the comparative example 2.

<Evaluation result 2: FT-IR analysis>
Samples prepared by diluting and mixing the powders obtained by the above-mentioned Examples and Comparative Examples and the raw ceramic powder before treatment with KBr powder to form tablets were prepared using an FT-IR analyzer (manufactured by Perkin Elmer Co., Ltd.). FIG. 3 shows the result of analysis by the diffuse reflection method according to the product name spectrum 2000).

As shown in FIG. 3, the peak (3680 cm ⁻¹ ) corresponding to the isolated hydroxyl group observed in the raw ceramic powder before treatment disappears in the examples and the comparative examples. On the other hand, in Examples and Comparative Examples, peaks at 1540 and 1420 cm ⁻¹ due to COO stretching vibration appear. Therefore, in the processing of Examples and Comparative Examples (D, D ′, and D ″), the dispersant having a carboxyl group is attached (bonded) to the above-mentioned isolated hydroxyl group in an ionic or dehydrating manner. It is possible.

The example, comparative example 1 and comparative example 2 are different in the shapes of 3000 to 3700 cm ⁻¹ peak due to OH stretching vibration and 1540 and 1420 cm ⁻¹ peaks due to COO stretching vibration. Further, as described above, the decomposition behavior during thermogravimetric analysis is also different between the example, the comparative example 1, and the comparative example 2. Therefore, as described above, the manner in which the dispersant is attached to the surface of the ceramic particles is considered to be different between the example, the comparative example 1, and the comparative example 2.

In the example, unlike each comparative example, a peak of 1710 cm ⁻¹ due to C═O stretching vibration appeared strongly. However, the peak at 2900 to 3000 cm ⁻¹ due to CH stretching vibration is not strong. Therefore, it is considered that the adhesion between the particles and hexanoic acid in the examples is not a physical adsorption but a chemical bond as described above (in this example, adhesion in a form close to an ester).

  Further, the FT-IR analysis result corresponds to the result of the thermogravimetric analysis described above in which the amount of adsorption is in the order of Example, Comparative Example 1, and Comparative Example 2.

That is, as described above, in Comparative Example 2, the peak corresponding to the isolated hydroxyl group is reduced as compared with the raw material ceramic powder before treatment. In Comparative Example 1, in addition to Comparative Example 2, a broad hydroxyl peak near 3200 cm ⁻¹ is reduced. Furthermore, in the Examples, in addition to Comparative Example 1, the hydroxyl peak near 3400 cm ⁻¹ is reduced. And it is thought that such a reduction | decrease aspect of a hydroxyl group peak corresponds to the adsorption amount (result of the above-mentioned thermogravimetric analysis).

<Evaluation result 3: Dispersibility>
When the powder obtained by the above-mentioned Example was added in toluene and dispersed for 2 minutes with a 300 W ultrasonic homogenizer (same as above), a good and stable dispersible slurry was obtained.

  Here, when the powder obtained by the Example, the comparative example 1, and the comparative example 2 was mixed in the two-phase-separated solution of water / toluene, and the dispersibility was confirmed, the example, the comparative example 1, and In any of Comparative Examples 2, the obtained powder was dispersed on the toluene phase side. This means that in any of the powders obtained in Examples, Comparative Example 1 and Comparative Example 2, hexanoic acid as a surface modifier is adhered to the particle surface.

  However, when the water / toluene two-phase separation solution evaluated above was allowed to stand for 1 day and then shaken and mixed again, in Comparative Example 2, the powder moved to the aqueous phase. On the other hand, in Example and Comparative Example 1, the powder did not move to the aqueous phase. This is because hexanoic acid adhered firmly in Example and Comparative Example 1 but weakly adhered in Comparative Example 2 so that hexanoic acid was detached and the powder moved to the aqueous phase. Means. In addition, only the powder of the comparative example 2 was settled in the toluene phase after standing.

  Considering this dispersibility evaluation result and the above-described FT-IR analysis result in a comprehensive manner, Comparative Example 1 is more irreversible due to reaction with hydroxyl groups other than isolated hydroxyl groups than Comparative Example 1 and Comparative Example 1. It can be said that more intense strong adsorption occurs.

  By the way, the approach distance of the powder to the plasma generation part is an important parameter for effectively using radical reaction, thermal energy, and shock wave. Therefore, the relationship between the approach distance and the reaction state was evaluated by changing the stirring conditions.

  When stirring is carried out at 20 rpm, the powder is only rotated around the bottom of the container 40 mm away from the plasma generating portion. In that state, the processing did not proceed at all, and the same result as in Comparative Example 2 was obtained. The stirring speed was gradually increased, and improvement in dispersibility was observed at about 40 rpm. The distance between the powder and the electrode at that time was close to about 20 mm.

  Further, when the stirring speed was increased to 1000 rpm, the powder was supplied to the vicinity of the plasma, specifically, less than 1 mm by the vortex. In that case, however, the powder turned black. The reason seems to be that the powder was pyrolyzed and carbonized due to excessive supply of thermal energy.

  From the above, the preferable condition is that the approach distance of the powder to the plasma generating portion is 1 mm or more and 20 mm or less. In addition, from this result, in the Example, stirring was implemented at 200 rpm.

<List of examples of modification>
Note that the above-described embodiments and examples are merely examples of typical implementations of the present invention that the applicant has considered to be the best at the time of filing of the present application, as described above. Therefore, the present invention is not limited to the above-described embodiments and examples. Therefore, it goes without saying that various modifications can be made to the above-described embodiments and examples without departing from the essential part of the present invention.

  Hereinafter, some typical modifications will be exemplified. However, it goes without saying that the modifications are not limited to those listed below. In addition, all or some of the plurality of modified examples can be combined with each other as appropriate within a technically consistent range.

  The present invention (especially those expressed functionally and functionally in the constituent elements constituting the means for solving the problems of the present invention) is based on the above-described embodiment and the description of the following modifications. Should not be interpreted as limited. Such a limited interpretation is unacceptable and improper for imitators, while improperly harming the applicant's interests (rushing to file under a prior application principle).

  The present invention is not limited to the specific apparatus configuration shown in the above embodiment.

  For example, the material and shape of the electrode 4a, the gap width, the type and conductivity of the medium S, and the like are not particularly limited as long as plasma is generated.

  The medium S is heated by the generation of plasma in the liquid, and the radical addition reaction is promoted by this heat. At this time, it is preferable to control the temperature of the medium S to be substantially constant while suppressing the temperature of the medium S below the boiling point by a method such as cooling the storage tank 2 from the outside. As a result, the thermal energy of the plasma for promoting the addition reaction of radicals can be kept constant (if the thermal energy is small, the reaction does not proceed easily, and if the thermal energy is large, bubbles are generated and the radical cannot be used effectively).

The material for adjusting the conductivity is not particularly limited as long as it dissolves in water. For example, a water-soluble salt (H, K, Na, NH ₄ as a cation, Cl, NO ₃ , SO ₄ as an anion) , OH) or the like. In particular, the reactivity can be improved by adjusting the pH so that the surface charge of the powder is reduced. This is because the surface charge inhibits the access of radical species. Specifically, the pH is preferably within ± 3 of the isoelectric point.

  About stirring conditions: The powder must be supplied in the vicinity of the radical generation site. In order to efficiently transmit three types of energy of radical, heat, and shock wave, it is preferable to supply the powder within 1 mm or more and within 20 mm from the radical generation part. If it is less than 1 mm, the heat energy is too strong, and the modifier is thermally decomposed. When it is larger than 20 mm, no reaction occurs.

About powder type: The powder is not limited as long as it has a hydroxyl group on the surface, but the more hydroxyl group, the better. This is because the reaction amount also increases, and as a result, dispersion is improved. Specifically, oxide ceramics represented by ZrO ₂ , TiO ₂ , Al ₂ O ₃ , CeO ₂ , SiO ₂ , Fe ₂ O ₃ , Nb ₂ O ₅ , Y ₂ O ₃ , NiO, BaTiO ₃ , Examples thereof include composite oxides typified by Pb (Zr _x Ti _1-x ) O ₃ and LiCoO ₂ . Further, the particle diameter may be smaller than the size that can be dispersed in the liquid.

  As the applied voltage, an arbitrary voltage such as high frequency or microwave can be used. A waveform having a peak not only on the positive potential side but also on the negative potential side can be used. However, when the output is too large, the organic component tends to decompose, and when it is small, the plasma does not tend to be generated, so the range of 10 W to 500 W is preferable.

  FIG. 4 is a schematic view showing the main configuration of another example of an apparatus for carrying out the manufacturing method of the present invention. As shown in FIG. 4, the manufacturing apparatus 1 may further include a medium circulator 5. The medium circulator 5 includes a medium circulation path 5a, a flow pump 5b, and a wet crusher 5c.

  An inlet 5 a 1 in the medium circulation path 5 a is provided so as to open at the bottom of the storage tank 2. Further, the outlet 5 a 2 in the medium circulation path 5 a is provided so as to open at the upper part of the storage tank 2. That is, the medium circulation path 5 a is provided so as to lead out the medium S from the bottom of the storage tank 2 and return the derived medium S to the upper part of the storage tank 2.

  The flow pump 5b is interposed in the medium circulation path 5a so as to send the medium S from the inlet 5a1 to the outlet 5a2 in the medium circulation path 5a. The wet crushing / pulverizing machine 5c is interposed in the medium circulation path 5a and crushes / crushes the ceramic powder aggregate in the medium S.

  In the manufacturing apparatus 1 having such a configuration, the medium S flows in the storage tank 2 by the operation of the flow pump 5b (therefore, the stirrer 3 can be omitted in the configuration shown in FIG. 4). At this time, the ceramic powder aggregate in the medium S is pulverized / pulverized by the wet pulverization / pulverization machine 5c.

  According to the flow-type apparatus configuration of this modification, it is possible to simultaneously and continuously perform crushing and strong adhesion of the dispersant.

  FIG. 5 is a schematic view showing the main configuration of still another example of an apparatus for carrying out the manufacturing method of the present invention. As shown in FIG. 5, the in-liquid plasma generator 4 may be interposed in the medium circulation path 5a. That is, in this modification, the in-liquid plasma generation tank 4d is interposed in the medium circulation path 5a. A pair of electrode holders 4b holding the electrodes 4a are attached to the submerged plasma generation tank 4d.

  Also in the configuration of the present modification, crushing and reforming can be performed simultaneously and continuously as in the above-described modification (see FIG. 4). Furthermore, according to the configuration of the present modification, it is possible to uniformly and satisfactorily perform the reforming process on most particles in the medium S passing through the medium circulation path 5a by the operation of the medium circulator 5. .

  The raw material ceramic powder used in the present invention may be in the form of powder or slurry when it is put into the medium. In the latter case, since the ceramic powder is dispersed and put into the medium, the modification is performed more uniformly. As a dispersion method in this case, a general wet method such as wet pulverization using beads, a homogenizer using a jet mill or ultrasonic waves, or the like can be used. The dispersion medium for obtaining this slurry may be the same as or different from the medium at the time of modification, and a material having good compatibility with the powder to be used can be used as appropriate.

  The modified dispersion may be used as it is, or may be pulverized by drying, or may be made into a paste by concentration or the like.

  Other modifications not specifically mentioned are naturally included in the scope of the present invention as long as they do not change the essential part of the present invention. In addition, in each element constituting the means for solving the problems of the present invention, elements expressed functionally and functionally include the specific structures disclosed in the above-described embodiments and modifications, It includes any structure that can realize this action / function. Furthermore, the disclosure content (including the specification and drawings) of the prior applications and publications cited in this specification may be incorporated as a part of this specification.

DESCRIPTION OF SYMBOLS 1 ... Manufacturing apparatus 2 ... Reservoir 3 ... Stirrer 4 ... Submerged plasma generator 4a ... Electrode 4b ... Electrode holder 4c ... Power source 4d ... Submerged plasma generator 5 ... Medium circulation machine 5a ... Medium circulation path 5a1 ... Inlet 5a2 ... Outlet 5b ... Fluid pump 5c ... Wet crusher S ... Medium

JP 2001-30227 A JP 2001-106578 A JP 2001-130968 A JP 2008-13810 A Japanese Patent No. 3925932

Claims (12)

A method for producing a ceramic powder with improved dispersibility, comprising:
In a liquid medium capable of generating radical species, raw material ceramic powder, and a dispersant for dispersing the raw material ceramic powder in a predetermined dispersion medium,
A ceramic with improved dispersibility, wherein the radical species are generated in the medium while heating the medium in a state where the medium into which the raw material ceramic powder and the dispersant are introduced is flowed Powder manufacturing method. A method for producing a ceramic powder with improved dispersibility according to claim 1,
The raw ceramic powder is preliminarily made into a slurry and then charged into the medium.
A method for producing ceramic powder with improved dispersibility. A method for producing a ceramic powder having improved dispersibility according to claim 1 or 2,
By generating a plasma in the medium by applying a voltage between a pair of electrodes immersed in the medium, the radical species is generated in the medium while heating the medium,
A method for producing a ceramic powder with improved dispersibility, characterized in that the raw ceramic powder is supplied within a range of 1 mm to 20 mm from a plasma generating portion. A method for producing a ceramic powder with improved dispersibility according to any one of claims 1 to 3,
The method for producing a ceramic powder with improved dispersibility, wherein the medium is an aqueous solution. A method for producing a ceramic powder with improved dispersibility according to claim 4,
The method for producing a ceramic powder having improved dispersibility, wherein the radical species is OH · and / or H ·. A method for producing a ceramic powder with improved dispersibility according to any one of claims 1 to 5,
The method for producing a ceramic powder with improved dispersibility, wherein the dispersant has a carboxyl group. A method for producing a dispersion of ceramic powder,
In a liquid medium capable of generating radical species, raw material ceramic powder, and a dispersant for dispersing the raw material ceramic powder in a predetermined dispersion medium,
The surface of the raw ceramic powder is dispersed by generating the radical species in the medium while heating the medium in a state in which the medium in which the raw ceramic powder and the dispersant are charged is flowed. Obtain the modified ceramic powder modified by the agent,
The obtained modified ceramic powder is dispersed in the dispersion medium,
A method for producing a dispersion of ceramic powder. A method for producing a dispersion of ceramic powder according to claim 7,
The raw ceramic powder is preliminarily made into a slurry and then charged into the medium.
A method for producing a dispersion of ceramic powder. A method for producing a dispersion of ceramic powder according to claim 7 or claim 8,
By generating a plasma in the medium by applying a voltage between a pair of electrodes immersed in the medium, the radical species is generated in the medium while heating the medium,
A method for producing a dispersion of ceramic powder, characterized in that the raw material ceramic powder is supplied within a range of 1 mm to 20 mm from a plasma generating portion. A method for producing a dispersion of ceramic powder according to any one of claims 7 to 9,
The method for producing a dispersion of ceramic powder, wherein the medium is an aqueous solution. A method for producing a dispersion of ceramic powder according to claim 10,
The method for producing a dispersion of ceramic powder, wherein the radical species is OH · and / or H ·. A method for producing a dispersion of ceramic powder according to any one of claims 7 to 11,
The method for producing a dispersion of ceramic powder, wherein the dispersant has a carboxyl group.

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