JP2009046361A - Process for producing slurry and slurry produced by the process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing slurry producible a necessary amount of the slurry in a short time. <P>SOLUTION: The process for producing the slurry comprises a step (1) of obtaining storage slurry containing a first pulverized powder which is a pulverized raw material powder formed by pulverizing a raw material mixture containing the raw material powder using grinding media and a step (2) of obtaining slurry containing a second pulverized powder derived from the first pulverized powder by wet jet-milling a necessary amount out of the storage slurry. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a slurry production method that can be put to practical use, a slurry produced thereby, a dry powder of the slurry, a powder molded body using the slurry, and a fired body thereof.

  The powder firing process to produce a product by firing a powder compact obtained by forming a raw material powder into a predetermined shape has the advantage that a product with a complicated shape can be manufactured efficiently and inexpensively. Widely used in the industrial field.

  In the powder firing process, the quality, shape, and accuracy of the resulting product are greatly affected by the powder compact before firing. For example, when the density of the powder compact is low, the shrinkage of the substance constituting the powder compact during firing becomes large, and it becomes difficult to control the shape and accuracy of the product. If voids remain in the powder compact, the quality of the product is significantly reduced. In addition, when the density of the powder compact is uneven, the shrinkage rate is partially different, resulting in uneven shrinkage and cracks in the product during firing. Therefore, in order to obtain a good product, it is extremely important to produce a powder compact having a high density and a uniform density distribution.

  Various methods for forming a powder compact are known, and roughly classified into a dry process and a wet process. The dry process includes, for example, a technique such as pressing that applies high temperature and high pressure to the raw material powder. However, when obtaining a high-density powder molded body using fine particles, the dry process requires high temperature and high pressure, which increases the size of the apparatus and the cost. In addition, due to the demand for higher performance and higher performance of materials and components in accordance with recent developments in industrial technology, raw material powders are being refined. This is also a risk of reduced workability and powder explosion. Problems such as increased performance, worsening of the working environment, and extrusion process. On the other hand, wet processes include, for example, a slurry casting process in which a raw material powder and a solvent are mixed to produce a slurry and then cast into a porous mold, and an injection process in which the mold is injected at a high pressure. The wet process does not require special and expensive equipment, and can produce a large complex shaped product.

  However, there is a need for a net shape that allows more complex parts to be manufactured with higher accuracy and a higher density of the powder compact. As a method for increasing the density of a powder compact, there are a method resulting from a molding process and a method resulting from a slurry used for molding. Methods resulting from the molding process include, for example, pressure cast molding in which an external force is applied during molding, centrifugal molding in which centrifugal force is applied, and vibration molding in which vibration is applied (see, for example, Patent Documents 1 and 2). However, the improvement of the method resulting from the molding process generally increases the size of the apparatus, and the consumption of the mold and the apparatus becomes severe. Further, there is a case where the density of the powder compact that can be expected is not achieved.

  Methods resulting from the slurry used for molding include, for example, a method of increasing the particle size distribution width of the raw material powder, a method of adjusting the solvent, pH, amount of dispersant, and the like of the slurry (for example, Patent Documents 3 and 4). reference). Although the method of adjusting the solvent, pH, amount of dispersant and the like of the slurry can achieve a slight density increasing effect, it is difficult to obtain a desired high-density powder compact. This is partly due to the instability of the slurry such as an increase in the viscosity of the slurry and reaggregation of particles in the slurry production process.

JP-A-8-99306 JP-A-2-141455 JP 2000-128625 A JP-A-3-169506 Japanese Patent Laid-Open No. 11-113544 JP-A-11-147714 JP 2006-248876 A

  In general, a slurry is manufactured by mixing raw material powder and a solvent and performing ball mill treatment using a crushing medium called a medium. The reason why this manufacturing method is adopted is that a large amount of processing work is possible and a slurry can be manufactured at low cost. However, when ball milling is performed, the crystal structure and surface state of the raw material powder are damaged by collision with a medium having a large mass, and the raw material powder is agglomerated due to an increase in surface energy. Aggregation of the raw material powder increases the viscosity of the slurry and causes aggregation over time, so it is not preferable to use a stored slurry. Conventionally, slurry production was performed for each batch, and unused slurry was discarded. In the manufacturing process, several hours to several days are required. Therefore, the conventional manufacturing method has problems in terms of time, economy, and environment.

  In addition, due to collisions between media, the media wear powder is mixed into the slurry as impurities. If the amount of impurities mixed is large, it may reach 1 wt%. Such impurities hinder firing and cause deterioration of the properties of the resulting product. Therefore, it is not preferable to re-disperse the stored slurry in order to re-disperse it during use, such as ball milling or the like, which leads to an increase in impurities in the slurry.

  Now, regarding wet jet mill processing, an invention applicable in the food industry has been disclosed (see, for example, Patent Document 5). In addition, an invention of a wet jet mill treatment that focuses on refining raw material powders such as ceramic powders and metal powders is also disclosed (see, for example, Patent Document 6). Since the slurry produced by the wet jet mill treatment has low viscosity and low re-agglomeration property, the invention relates to the slurry produced by the wet jet mill treatment, its production method, its high density formed body, and its high strength sintered body. Is disclosed (for example, see Patent Document 7).

  However, a slurry production method that performs wet jet milling is not preferred in terms of processing capacity for mass production.

  This invention is made | formed in view of the problem which such a prior art has, The place made into the subject is providing the slurry manufacturing method which can manufacture a required quantity of slurry in a short time. Moreover, the place made into the subject of this invention is providing the slurry which has low re-aggregation property. Furthermore, the place made into the subject of this invention is providing the powder which can manufacture a high-density powder compact. Moreover, the place made into the subject of this invention is providing the powder molded object which can manufacture the sintered body with few defects. Furthermore, the place made into the subject of this invention is providing the sintered body with few defects.

  As a result of intensive studies to achieve the above-mentioned problems, the inventors of the present invention produce a storage slurry using a crushed medium such as a mass-manufacturable medium, and produce a slurry by timely wet jet milling the necessary amount of the storage slurry. Thus, the present inventors have found that the above-described problems can be achieved, and have completed the present invention.

  That is, according to the present invention, the following slurry production method, slurry, powder, powder molded body, and fired body are provided.

  [1] A step (1) of using a crushing medium to crush a raw material mixture containing raw material powder to obtain a storage slurry containing a first crushed powder obtained by crushing the raw material powder; And a step (2) of obtaining a slurry containing a second crushed powder derived from the first crushed powder by subjecting the necessary component to a wet jet mill.

  [2] The method for producing a slurry according to [1], wherein the slurry having a viscosity change amount of 10 mPa · s / h or less per unit time is obtained.

  [3] The wet jet mill treatment is a treatment in which the stored slurry is pumped to a nozzle disposed in a sealed state in a pressure resistant container and is split, and the split stored slurry collides and joins with each other. The method for producing a slurry according to [1] or [2].

  [4] The slurry production method according to any one of [1] to [3], wherein the surface state of the second crushed powder is equivalent to the surface state of the raw material powder.

  [5] A slurry produced by the slurry production method according to any one of [1] to [4].

  [6] The slurry according to [5], in which the amount of change in viscosity per unit time is 10 mPa · s / h or less.

  [7] A powder obtained by drying the slurry according to [5] or [6].

  [8] A powder compact having a relative density of 65 to 74%, obtained by casting the slurry according to [5] or [6].

  [9] A fired body obtained by firing the powder compact according to [8], having a density of 95% or more and a linear shrinkage rate of 12% or less.

  [10] The fired body according to [9], wherein the strength measured according to JIS R1601 is 570 MPa or more.

  The slurry production method of the present invention is economical and has an effect of conforming to environmental harmony. Moreover, the slurry of this invention has the effect that it has a low viscosity and low re-aggregation property, and can manufacture a high-density powder compact. Furthermore, the powder of the present invention has an effect that a high-density powder compact can be produced. Moreover, the powder molded body of the present invention has an effect that a fired body with few defects can be produced. Furthermore, the fired body of the present invention has the effect of being practical with few defects.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and is based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

(I) Slurry production method The slurry production method of the present invention uses a crushing medium, crushes a raw material mixture containing raw material powder, and obtains a storage slurry containing the first crushed powder obtained by crushing the raw material powder. A step (1) and a step (2) of obtaining a slurry containing a second crushed powder derived from the first crushed powder by wet jet milling a necessary part of the stored slurry. . By having these two steps, it is possible to provide a method for producing a slurry that is economical and in harmony with the environment.

  Since the manufacturing method of the slurry of this invention has a process (1) which uses a crushing medium and obtains the storage slurry containing the 1st crushing powder by crushing the raw material mixture containing a raw material powder, and crushing the raw material powder Large quantities of storage slurry can be produced.

  As the crushing medium, a known medium capable of crushing in a large amount can be used. Specific examples of the crushing medium include a ball mill, a planetary ball mill, and a bead mill.

  Examples of the raw material powder include metal powder; intermetallic compound powder; ceramic powder such as oxide, carbide, and nitride; mixed powder thereof; and the like. Moreover, it is preferable that the number average particle diameter of raw material powder is a number average particle diameter which can produce a storage slurry by the crushing process using a crushing medium from nano size to micron size.

  The raw material mixture usually contains a solvent together with the raw material powder. As the solvent, for example, a conventionally used solvent such as water, alcohols, ketones, oils and amines is preferably used, and water is more preferably used from the viewpoint of environmental harmony. More specifically, distilled water, ion exchange water, tap water, industrial water, and the like can be used as water. Moreover, as long as the effects of the present invention are not impaired, it is also preferable to add known additives in order to improve the properties of the obtained powder compact in addition to the raw material powder. Known additives include, for example, polymer additives such as polyacrylic acid ammonium salt, polymethacrylic acid ammonium salt, polyethyleneimine, methylcellulose, and polyvinyl alcohol.

  The concentration of the raw material powder contained in the raw material mixture is preferably 1 to 60 vol%, more preferably 1 to 50 vol%. If it is less than 1 vol%, the wall thickness in casting may be thin. On the other hand, if it exceeds 60 vol%, the stored slurry may not have fluidity that allows wet jet milling.

  A storage slurry contains the 1st crushed powder which crushed the raw material powder in a raw material mixture using the crushing medium. The storage slurry usually has high re-aggregation property, and the viscosity change per unit time is 10 mPa · s / h or more. Thus, it can be said that the first crushed powder in the storage slurry reaggregates with time. For this reason, it is not preferable to use the stored slurry as it is for the production of a powder compact, since this tends to lead to uneven density of the powder compact.

Here, the first crushed powder preferably has a number average particle diameter of 1 to 10 ⁴ nm, and more preferably 1 to 10 ³ nm.

  By having a step (2) of obtaining a slurry containing a second crushed powder derived from the first crushed powder by wet jet milling the necessary portion of the stored slurry obtained in the step (1). A necessary amount of practical slurry can be produced in a short timely manner. Accordingly, the slurry production method of the present invention is economical and conforms to environmental harmony.

  The wet jet mill process is a process that breaks up the powder contained in the split flow by effectively utilizing the turbulent flow, shearing and cavitation effects caused by the high-speed flow due to the collision between the high-speed split flows or between the flow and the flow path wall. is there. By performing wet jet mill treatment, the storage slurry is turbulent and sheared when passing through the flow path at high speed or while colliding, so that the re-agglomerated powder contained in the storage slurry is crushed. Is done. Further, when the pressure is released immediately after the collision, a cavitation effect occurs, and the powder in the slurry is further crushed by a shock due to sudden pressure release to become a slurry containing the second crushed powder.

  Examples of wet jet mills that perform such treatment include a type that uses high-speed jetting with a valve plate that is commercially available as a “high-pressure homogenizer”, a type that collides at high speed in a slit-shaped flow path, and a 90 ° phase. A type that causes high-speed collisions within each single-character flow path that has been connected to each other, a type that causes multiple collisions between fluids within the same nozzle, and a type that causes collisions by jetting from opposing orifices into an aspherical structure room And a type in which a liquid-phase jet stream collides at high speed. There are some differences in the mixing, dispersion, and crushing effects due to the characteristics of each device type, but the type of storage slurry containing re-agglomerated powder, that is, the first crushed powder, collides from the front. Is preferred.

  More specifically, as the wet jet mill, a wet jet mill is preferably used which is pumped to a nozzle disposed in a sealed state in a pressure-resistant vessel and is shunted so that the shunts collide with each other.

  The processing pressure of the pump when performing the wet jet mill treatment is preferably 10 MPa or more, more preferably 50 MPa or more, and particularly preferably 100 MPa or more. When the processing pressure of the pump is less than 10 MPa, the effects of mixing, dispersion, and crushing may not be sufficient. The number of wet jet mill treatments is not particularly limited, and the treatment can be repeated any number of times until a slurry having desired characteristics is obtained. In addition, although it does not specifically limit about the upper limit of the process pressure of a pump, It is preferable that it is 500 Mpa or less substantially.

  The slurry is obtained by wet jet milling the storage slurry and contains the second crushed powder. The slurry has a low re-aggregation property, and the viscosity change per unit time is preferably 10 mPa · s / h or less, and more preferably 5 mPa · s / h or less. When the change in viscosity per unit time is more than 10 mPa · s / h, the re-aggregation property of the second crushed powder is high, and the slurry density may be nonuniform. The lower limit of the change in viscosity per unit time is not particularly limited, but may be substantially 0 mPa · s / h or more.

Here, the second crushed powder preferably has a number average particle diameter of 1 to 10 ⁴ nm, and more preferably 1 to 10 ³ nm. If the number average particle size of the second crushed powder is more than 10 ⁴ nm, the re-agglomerated powder in the storage slurry may be clogged with the nozzle of the wet jet mill. On the other hand, if the thickness is less than 1 nm, the surface energy may be large, so that crushing and dispersion cannot be performed. The surface state of the second crushed powder is preferably equivalent to the surface state of the raw material powder. The surface states of the second crushed powder and the raw material powder can be compared, for example, based on the measurement results of the respective powders such as the infrared absorption spectrum and the scanning electron microscope. Here, “the surface state is equivalent” means that there is no substantial difference in these measurement results, that is, the peak intensity of the infrared absorption spectrum, the state of the amorphous layer that can be formed on the powder surface, and the like. .

(II) Slurry The slurry of the present invention is a slurry produced by the above-described slurry production method. The slurry of the present invention has a low viscosity and a low re-aggregation property, and can produce a high-density powder compact.

  The slurry of the present invention has a low re-aggregation property, and the viscosity change per unit time is preferably 10 mPa · s / h or less, and more preferably 5 mPa · s / h or less. When the viscosity change per unit time is more than 10 mPa · s / h, the reaggregation property is high, and the relative density of the powder compact may be lowered. The lower limit of the change in viscosity per unit time is not particularly limited, but is substantially preferably 0 mPa · s / h or more.

  The slurry has a low viscosity, and more specifically, the viscosity is preferably 50 mPa · s or less, and more preferably 45 mPa · s or less. When the viscosity of the slurry exceeds 50 mPa · s, rearrangement of the second crushed powder during casting may be hindered, and the relative density of the powder compact may be reduced. The lower limit of the viscosity is not particularly limited, but it is preferably substantially 1 mPa · s / h or more.

(III) Powder The powder is a powder obtained by drying the slurry, and is the same as the second crushed powder. By producing powder, a high-density powder compact can be produced. Here, the drying method of the slurry is not particularly limited, and examples thereof include natural drying, reduced pressure drying, and high temperature drying.

(IV) Powder compact A powder compact is obtained by casting a slurry. The mold for casting may be a mold having water absorption, such as a plaster mold or a resin mold, and a known porous mold can be used. As casting methods, there are, for example, waste mud casting, solid casting, vibration casting, pressure casting, reduced pressure casting, centrifugal casting, etc., and known methods can be used.

  The powder compact preferably has a relative density of 50 to 74%, more preferably 65 to 74%. When the relative density of the powder molded body is less than 50%, the density of the powder molded body is low, and it may be difficult to control the shape and accuracy of the fired body. On the other hand, if the relative density of the powder compact exceeds 74%, abnormal grain growth may be caused in grain growth accompanying firing.

(V) Fired body The fired body is obtained by firing a powder compact. The firing method is not particularly limited, and various firing furnaces, firing atmospheres, firing times, firing temperatures, and the like can be selected according to the raw material powder.

  The sintered body preferably has a density of 95% or more, and more preferably 96% or more. When the density of the fired body is less than 95%, the strength of the fired body may not be sufficient. The upper limit of the density of the fired body is not particularly limited, but it is preferably substantially 100% or less. The linear shrinkage of the fired body is preferably 14% or less, and more preferably 12% or less. When the linear shrinkage rate of the fired body is more than 14%, there may be a problem in the shape of the fired body.

  Moreover, it is preferable that the intensity | strength measured based on JISR1601 is 570 Mpa or more, and, as for a sintered compact, it is still more preferable that it is 600 Mpa or more.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified. Moreover, the measuring method of various physical-property values and the evaluation method of various characteristics are shown below.

  [Viscosity Measurement]: Viscosity was measured using a “vibrating viscometer” manufactured by A & D.

  [Infrared absorption spectrum measurement]: Measurement was performed using “Fourier transform infrared absorption spectrum” manufactured by PerkinElmer.

  [Three-point bending strength test]: Measured according to JIS R1601.

Example 1
Aluminum oxide powder (number average particle diameter of 570 nm) is used as a raw material powder, distilled water is used as a solvent, and weighed and mixed so that the alumina concentration is 30 vol%, and is used for mass production of conventional slurries. Storage slurry was manufactured by processing for 24 hours with a ball mill. One week later, an appropriate amount of stored slurry was taken out and wet-milled once at a processing pressure of 200 MPa to produce a slurry. The graph which plotted the frequency with respect to the number average particle diameter of the 2nd crushed powder contained in a slurry is shown with a broken line of FIG. Moreover, the graph which plotted the viscosity with respect to time is shown by (b) in FIG.

(Example 2)
The slurry produced according to Example 1 was dried to produce a powder. A chart showing the measurement results of the infrared absorption spectrum of this powder is shown in FIG.

(Example 3)
Casting molding was performed using the slurry produced in Example 1, and a plate-like powder compact of 100 × 100 × 10 mm was produced. The relative density was measured with respect to the obtained powder compact. The results are shown in Table 1.

Example 4
A fired body was produced by firing the powder compact produced in Example 3 at 1450 ° C. The relative density and shrinkage rate of the obtained fired body were measured. The results are shown in Table 2. In addition, a three-point bending strength test was performed on the obtained fired body. The results are shown in Table 3. Furthermore, a scanning electron micrograph showing the microstructure of the fired body is shown in FIG. 4B.

(Example 5)
A fired body was manufactured by firing the powder compact manufactured in Example 3 at 1500 ° C. The relative density and shrinkage rate of the obtained fired body were measured. The results are shown in Table 2.

(Comparative Example 1)
Aluminum oxide powder (number average particle diameter of 570 nm) is used as a raw material powder, distilled water is used as a solvent, and weighed and mixed so that the alumina concentration is 30 vol%, and is used for mass production of conventional slurries. Storage slurry was manufactured by processing for 24 hours with a ball mill. The graph which plotted the frequency with respect to the number average particle diameter of the 1st crushing powder contained in a storage slurry is shown by the continuous line of FIG. Moreover, the graph which plotted the viscosity with respect to time is shown by (a) in FIG.

(Comparative Example 2)
The storage slurry produced according to Comparative Example 1 was dried to produce a powder. A chart showing the measurement results of the infrared absorption spectrum of this powder is shown in FIG.

(Comparative Example 3)
The raw material powder, aluminum oxide powder, was dried to produce a powder. A chart showing the measurement results of the infrared absorption spectrum of this powder is shown in FIG.

(Comparative Example 4)
Casting molding was performed using the storage slurry produced in Comparative Example 1 to produce a plate-like powder compact of 100 × 100 × 10 mm. The relative density was measured with respect to the obtained powder compact. The results are shown in Table 1.

(Comparative Example 5)
A fired body was produced by firing the powder compact produced in Comparative Example 4 at 1450 ° C. The relative density and shrinkage rate of the obtained fired body were measured. The results are shown in Table 2. In addition, a three-point bending strength test was performed on the obtained fired body. The results are shown in Table 3. Further, a scanning electron micrograph showing the microstructure of the fired body is shown in FIG. 4A.

(Comparative Example 6)
A fired body was produced by firing the powder compact produced in Comparative Example 4 at 1500 ° C. The relative density and shrinkage rate of the obtained fired body were measured. The results are shown in Table 2.

(Comparative Example 7)
A storage slurry produced in the same manner as in Comparative Example 1 was taken out after one week, and an appropriate amount of storage slurry was taken out and ball milled again to produce a slurry. The slurry was cast and molded to produce a 100 × 100 × 10 mm plate-like powder compact. The relative density was measured with respect to the obtained powder compact. The results are shown in Table 1.

(Comparative Example 8)
A fired body was produced by firing the powder compact produced in Comparative Example 7 at 1450 ° C. The relative density and shrinkage rate of the obtained fired body were measured. The results are shown in Table 2. A scanning electron micrograph showing the microstructure of the fired body is shown in FIG. 4C.

(Comparative Example 9)
A fired body was produced by firing the powder compact produced in Comparative Example 8 at 1500 ° C. The relative density and shrinkage rate of the obtained fired body were measured. The results are shown in Table 2.

  The particle size distributions of the second and first crushed powders contained in the slurry produced in Example 1 and Comparative Example 1 were measured. A graph plotting the frequency against the number average particle diameter is shown in FIG. In FIG. 1, the solid line indicates the measurement result for Comparative Example 1, and the broken line indicates the measurement result for Example 1. From FIG. 1, the number average particle diameters of the first and second crushed powders coincide with each other at 570 nm, and the number average particle diameter of the aluminum oxide powder as the raw material powder coincides with 570 nm. From this, it can be said that by performing wet jet mill treatment, it is possible to pulverize the powder that has been agglomerated by storage and redisperse the slurry.

  The change with time of the viscosity of the slurry produced in Example 1 and Comparative Example 1 was measured. A graph plotting viscosity against time is shown in FIG. In FIG. 2, (a) shows the viscosity of the slurry produced in Comparative Example 1, and (b) shows the viscosity of the slurry produced in Example 1. The viscosity of the slurry produced in Comparative Example 1 is 45 mPa · s immediately after the ball mill treatment, and then increases. This means that the first crushed powder contained in the storage slurry is re-agglomerated. On the other hand, the viscosity of the slurry produced in Example 1 is substantially constant within a measurement time of 180 m at 45 mPa · s. This means that the re-aggregation property of the second crushed powder contained in the slurry after the wet jet mill treatment is low. That is, it can be said that a storage slurry that tends to aggregate can be modified into a stable slurry with low aggregation.

  Infrared absorption spectra of the powders produced in Example 2 and Comparative Examples 2 and 3 were measured. The chart which shows the measurement result of the infrared absorption spectrum of each powder is shown in FIG. 3, (a) is the infrared absorption spectrum of the powder produced in Comparative Example 3, (b) is the infrared absorption spectrum of the powder produced in Example 2, and (c) is produced in Comparative Example 2. The infrared absorption spectrum of powder is shown. It can be seen that the infrared absorption spectrum of the powder produced in Comparative Example 2 has a stronger peak intensity indicating hydroxyl groups present on the surface of the aluminum oxide than the infrared absorption spectrum of the powder produced in Comparative Example 3. On the other hand, the infrared absorption spectrum of the powder produced in Example 2 almost coincides with the infrared absorption spectrum of the powder produced in Comparative Example 3, and no difference is observed in the peak intensity indicating hydroxyl groups. That is, it can be said that the surface state of the powder contained in the crushed slurry is equivalent to the surface state of the raw material powder by the wet jet mill treatment. This can be said that the coagulable slurry modified by the ball mill treatment is modified into a stable slurry, that is, a slurry having low reagglomeration property.

  Table 1 shows the relative densities of the powder compacts produced in Example 3 and Comparative Examples 4 and 7. From Table 1, the relative density 67.0% of the powder compact produced in Example 3 is a higher value than the relative densities 61.2% and 59.5% of the powder compact produced in Comparative Examples 4 and 7. is there. From this, it can be said that the powder compact manufactured in Example 3 is in a homogeneous and highly filled state.

  Table 2 shows the relative density and shrinkage ratio of the fired bodies produced in Examples 4 and 5 and Comparative Examples 5, 6, 8, and 9. The relative density and shrinkage of the fired bodies produced in Examples 4 and 5 were 96.2% and 10.2%, 98.5% and 11.1%, respectively, whereas Comparative Example 5 and The relative density and shrinkage of the fired bodies produced at 6,8,9 were 92.1% and 14.6%, 94.5% and 15.2%, 91.6% and 13.9%, 94.7% and 14.6%.

  Further, the microstructures of the fired bodies manufactured in Example 5 and Comparative Examples 5 and 8 were observed with a scanning electron microscope. Scanning electron micrographs showing the microstructures of the fired bodies produced in Example 5 and Comparative Examples 5 and 8 are shown in FIGS. 4A, 4B, and 4C, respectively. 4A is a scanning electron micrograph showing the microstructure of the fired body manufactured in Comparative Example 5, and FIG. 4B is a scanning electron micrograph showing the microstructure of the fired body manufactured in Example 5. FIG. 4C is a scanning electron micrograph showing the microstructure of the fired body produced in Comparative Example 8. It can be seen that the fired bodies produced in Comparative Examples 5 and 8 have many pores, and the densification has not progressed completely (FIGS. 4A and C). On the other hand, the fired body produced in Example 5 was densified without abnormal grain growth, and no defects such as pores were observed (FIG. 4B).

  Further, a three-point bending strength test based on JIS R1601 was performed on the fired bodies manufactured in Example 4 and Comparative Example 5. The results are shown in Table 3. The three-point bending strength of the fired body manufactured in Example 4 was 616.3 MPa, whereas the three-point bending strength of the fired body manufactured in Comparative Example 5 was 474.0 MPa.

  From these results, it can be seen that the fired bodies produced in Examples 4 and 5 are dense, low shrinkage fired bodies having a dense and homogeneous microstructure.

  TECHNICAL FIELD The present invention relates to a method for producing a slurry that can be practically used and a slurry produced thereby, a dry powder of the slurry, a powder molded body using the slurry, and a fired body thereof, and a linear shrinkage ratio of the fired body. Is 12% or less, it can greatly contribute to high reliability, high performance, and near net shape when used as various members. In addition, since the density of the compact can be increased, the firing temperature can be reduced and the firing time can be shortened, and reduction of the environmental burden and cost reduction of powder firing can be expected. Furthermore, since the slurry can be stored, it can be expected to be manufactured at low cost such as effective use of materials such as time reduction of the slurry manufacturing process and disposal of unused slurry for slurry production for each conventional batch. . Moreover, the produced slurry has low viscosity and low re-aggregation property, and application to processes other than casting (for example, inkjet) is also expected.

It is the graph which plotted the frequency with respect to the number average particle diameter. It is the graph which plotted the viscosity with respect to time. It is a chart which shows the measurement result of the infrared absorption spectrum of each powder. 6 is a scanning electron micrograph showing the microstructure of a fired body produced in Comparative Example 5. 4 is a scanning electron micrograph showing the microstructure of a fired body produced in Example 4. FIG. 10 is a scanning electron micrograph showing the microstructure of a fired body produced in Comparative Example 9.

Claims (10)

Using a crushing medium, crushing the raw material mixture containing the raw material powder to obtain a storage slurry containing the first crushed powder obtained by crushing the raw material powder;
A step (2) of obtaining a slurry containing a second crushed powder derived from the first crushed powder by wet jet milling a necessary part of the stored slurry;
The manufacturing method of the slurry which has this.   The manufacturing method of the slurry of Claim 1 which obtains the said slurry whose variation | change_quantity of the viscosity per unit time is 10 mPa * s / h or less. The wet jet mill treatment is
The storage slurry is pumped to a nozzle arranged in a sealed state in a pressure vessel and is divided.
The method for producing a slurry according to claim 1 or 2, which is a process of causing the stored slurry that has been split to collide and merge with each other.   The method for producing a slurry according to any one of claims 1 to 3, wherein a surface state of the second crushed powder is equivalent to a surface state of the raw material powder.   The slurry manufactured by the manufacturing method of the slurry as described in any one of Claims 1-4.   The slurry according to claim 5, wherein the amount of change in viscosity per unit time is 10 mPa · s / h or less.   The powder obtained by drying the slurry of Claim 5 or 6.   A powder compact having a relative density of 65 to 74%, obtained by casting the slurry according to claim 5 or 6.   A fired body obtained by firing the powder compact according to claim 8 and having a density of 95% or more and a linear shrinkage rate of 12% or less.   The fired body according to claim 9, wherein the strength measured in accordance with JIS R1601 is 570 MPa or more.