JP2008007383A - Method of manufacturing ceramic structure and ceramic structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a ceramic structure free from swelling even under a humid atmosphere where moisture is present in the surroundings. <P>SOLUTION: The method of manufacturing the ceramic structure has the steps of: manufacturing a hard porous carbon material (RB ceramic) powder; forming the RB ceramic powder into a green body having a prescribed shape; and firing the green body, wherein a step of washing the RB ceramic powder and/or the green body with water is provided before the step of firing the green body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a manufacturing method for manufacturing a ceramic structure using a hard porous carbon material (RB ceramics) made from rice bran.

  In recent years, a hard porous carbon material (hereinafter referred to as RB ceramics) using rice bran as a raw material has been developed as a new material that can be used for a sliding member. This manufacturing method of RB ceramics is disclosed by patent document 1, for example.

  Patent Document 1 includes kneading a koji by adding a thermosetting resin and an appropriate amount of an aqueous solution containing paste or water to koji such as rice bran and koji with adjusted particle size, and kneading a thermosetting resin and the like. A process of granulating porridges to a predetermined particle size or less, a step of filling the granule in a desired mold and then molding while pressing and degassing, an inert gas from the molded product demolded from the mold Porous carbon material product comprising the steps of firing and carbonizing by reaching a desired final firing temperature according to a predetermined temperature increase rate in an atmosphere or vacuum, and a step of cooling from the final firing temperature to room temperature at a predetermined temperature decrease rate A manufacturing method is disclosed.

  And RB ceramics manufactured with such a manufacturing method show effects, such as light weight, high intensity, high hardness, and high abrasion resistance. Due to these effects, the sliding member is used as described above.

However, RB ceramics have a problem that they swell by absorbing surrounding moisture. That is, when swelling occurs, the external shape of the entire RB ceramic product changes, and desired sliding characteristics cannot be obtained.
JP-A-10-101453

  This invention is made | formed in view of the said actual condition, and makes it a subject to provide the manufacturing method of the ceramic structure which does not swell also in the humid environment where moisture exists in the circumference | surroundings.

  In order to solve the above-mentioned problems, the present inventors have studied ceramic structures made of RB ceramics, and as a result, paying attention to the fact that water-soluble impurities contained in RB ceramics absorb the surrounding water. It has been found that the above-described problem can be solved by having a step of removing.

  That is, the method for manufacturing a ceramic structure according to the present invention includes the steps of manufacturing an RB ceramic powder, a step of forming the RB ceramic powder into a predetermined shape, and a step of firing the formed body. The method includes a step of washing the RB ceramic powder and / or the molded body with water before the step of firing the molded body.

  The ceramic structure of the present invention includes the steps of producing RB ceramic powder, washing the RB ceramic powder with water, and molding the RB ceramic powder into a predetermined shape and firing the molded body. It is characterized by being applied.

  The production method and ceramic structure of the present invention include a step of washing the RB ceramic powder and / or the molded body with water before firing. By this step, impurities are not contained in the molded body before firing. As a result, the impurities in the RB ceramics do not absorb the surrounding moisture, and a structure in which the shape change is suppressed is obtained.

(Production method)
The production method of the present invention includes a step of producing an RB ceramic powder, a step of shaping the RB ceramic powder into a predetermined shape, and a step of firing the molded body.

  The manufacturing method of RB ceramic powder is not specifically limited, A conventionally well-known manufacturing method, for example, the manufacturing method of said patent document 1, can be used. Further, the particle size of the produced RB ceramic powder is not particularly limited. That is, the particle size can be made such that the ceramic structure can be manufactured. Here, the particle size of the RB ceramic powder is preferably as small as possible because cleaning in the subsequent steps becomes easy.

  The forming method for forming the RB ceramic powder into a desired shape is not particularly limited, and a conventionally known method can be used. Examples of the molding method include CIP molding, hydraulic press molding, injection molding, and extrusion molding.

  The method for firing the compact of the RB ceramic powder is not particularly limited, and a conventionally known method can be used. For example, a method of heating in a furnace adjusted to a predetermined atmosphere can be given.

  And the manufacturing method of this invention has the process of wash | cleaning RB ceramic powder and / or a molded object with water before the process of baking a molded object. When the RB ceramic powder and / or the molded body are washed with water, water-soluble impurities contained in the RB ceramic powder (and / or the molded body) are eluted. Thereby, impurities in the RB ceramic powder (and / or the molded body) are removed. By removing the water-soluble impurities from the RB ceramic powder (and / or the molded body), the ceramic structure produced by performing the subsequent process does not contain water-soluble impurities, and as a result, absorbs moisture. Swelling is suppressed.

  The cleaning of the RB ceramic powder (and / or molded body) is not limited as long as it is a cleaning method capable of eluting water-soluble impurities in the RB ceramic powder (and / or molded body). Absent. For example, even in a method in which RB ceramic powder (and / or compact) is placed in running water and washed continuously, the RB ceramic powder (and / or compact) is charged into the stored water and stirred, and then filtered. Any cleaning method may be used.

  In the production method of the present invention, the water for washing the RB ceramic powder (and / or the molded body) includes not only pure water but also an aqueous solution capable of dissolving a water-soluble substance. More preferably, it is deionized water or pure water.

  The cleaning of the RB ceramic powder and / or the molded body is preferably performed until the electric conductivity of the solution obtained by washing the RB ceramic powder and / or the molded body with water becomes 100 μS / cm or less. By performing water washing until the electrical conductivity of the washed solution (solution after washing) becomes 100 μS / cm or less, water-soluble impurities in the RB ceramic powder (and / or the molded body) can be removed. Here, the electrical conductivity of the washed solution is due to water-soluble impurities in the RB ceramics. More specifically, when washed with water, water-soluble impurities in the RB ceramic are eluted into the washing water. As impurities are eluted, the electrical conductivity of the washing water increases. This electrical conductivity has a correlation with the amount of eluted impurities. That is, when the amount of impurities eluted from the RB ceramic powder decreases, the electrical conductivity decreases. It can be judged that the impurities in the RB ceramic have been eluted when the electric conductivity is 100 μS / cm or less. In the production method of the present invention, the electric conductivity of the solution washed with water is preferably as low as possible, and more preferably 50 μS / cm.

  In the production method of the present invention, it is preferable that the washing step performed before firing is performed before the molded body is molded. That is, by cleaning in the state of the RB ceramic powder, it becomes easy to remove impurities in the RB ceramic.

  In the production method of the present invention, it is preferable to have a step of preliminarily molding the molded body before firing the molded body. By performing preliminary drying, it is possible to suppress the occurrence of a large shape change during firing.

(Ceramic structure)
The ceramic structure of the present invention is a ceramic structure manufactured by the above manufacturing method. That is, a step of washing with water before firing is performed. As a result, the structure does not contain water-soluble impurities, and the structure is suppressed from absorbing and swelling around the surrounding water.

  The ceramic structure of the present invention is preferably a sliding member. Since the RB ceramic itself exhibits effects such as light weight, high strength, high hardness, and high wear resistance, the ceramic structure manufactured using the RB ceramic as a raw material is particularly preferably used for the sliding member. Examples of the sliding member that can form the ceramic structure of the present invention include a Stirling engine piston, sleeve, cylinder, displacer, and lip seal.

  Hereinafter, the present invention will be described using examples.

  As an example of the present invention, a ceramic structure made of RB ceramics was manufactured.

(Example 1)
First, RB ceramics powder was manufactured using rice bran. The production of the RB ceramic powder was performed by the method described below.

  The RB ceramic powder can be produced by mixing defatted bran extracted from rice bran and phenol resin, performing continuous firing in a rotary kiln furnace, pulverizing and sorting. In this example, a commercially available product (manufactured by Sanwa Oil Co., Ltd., trade name: RBC) was used as the RB ceramic powder.

  Subsequently, the produced RB ceramic powder is washed with water. The RB ceramic powder was cleaned by the method described below. This washing was repeated until the washed RB ceramic powder was filtered off and the electric conductivity of the filtrate was 100 μS / cm or less. Here, the cleaning of the RB ceramic powder was performed by suction filtration with an aspirator.

  Then, after drying at 120 degreeC for 12 hours, it grind | pulverized with the ball mill. The RB ceramics after pulverization had an average particle size of about 50 μm.

The RB ceramic powder after pulverization is put into a mold made of paper (corrugated cardboard), and this mold is put in a rubber bag. Thereafter, CIP molding was performed at a molding pressure of 264.9 MPa (2.7 t / cm ² ).

  The molded body was degreased and fired. This degreasing firing was performed by subjecting the molded body to carbonization treatment by heating at 900 ° C. By this heating, degreasing of the phenol resin contained in the molded body was performed.

  Thereby, the ceramic structure of the present Example was able to be manufactured.

(Example 2)
A ceramic structure was produced in the same manner as in Example 1, except that the rice bran was used as the raw material for the RB ceramic powder, and the rice bran generated during the milling for the production of ginjo sake was used. Also in this example, as in Example 1, a commercially available product (manufactured by Sanwa Oil Co., Ltd., trade name: GRBC) was used as the RB ceramic powder. The RB ceramic powder of this example is the same RB ceramic powder as that of Example 1 except that Na is not contained in the raw material phenol resin.

(Example 3)
A ceramic structure was produced in the same manner as in Example 1 except that rice bran was used as the raw material for the RB ceramic powder, and rice bran derived from rice husk was used. Also in this example, as in Example 1, a commercially available product (trade name: RHC, manufactured by Sanwa Oil Co., Ltd.) was used as the RB ceramic powder. The RB ceramic powder of this example is the same RB ceramic powder as that of Example 1 except that Na is not contained in the raw material phenol resin. Rice bran derived from rice husk is a rice bran produced in the process of milling brown rice into white rice, and is mainly composed of a high-molecular substance such as pectin, cellulose, or lyxin.

(Comparative Example 1)
A ceramic structure was manufactured in the same manner as in Example 1 except that the RB ceramic powder was not washed.

(Comparative Example 2)
A ceramic structure was manufactured in the same manner as in Example 2 except that the RB ceramic powder was not washed.

(Comparative Example 3)
A ceramic structure was manufactured in the same manner as in Example 3 except that the RB ceramic powder was not washed.

(Evaluation)
Swellability was evaluated as an evaluation of the ceramic structures of the examples and comparative examples.

  Specifically, the swelling property was evaluated by cutting a 40 × 10 × 10 mm sample from each ceramic structure and holding it at 120 ° C. for 24 hours for drying. Then, this sample was immersed in water kept at room temperature and kept for 24 hours. Thereafter, drying was repeated again at 120 ° C. for 24 hours, and immersion in water at room temperature for 24 hours was repeated and kept at 120 ° C. for 24 hours for drying. The shape after drying was measured, and the rate of change of the length of each side before and after swelling was determined to obtain the swelling rate. The measurement result of the swelling rate is shown in FIG.

  As shown in FIG. 1, it can be seen that the ceramics of each of the examples in which the RB ceramic powder was washed had a reduced swelling rate as compared with the ceramics of each comparative example that was not washed. That is, it can be seen that the ceramics of each example are ceramics in which swelling due to surrounding moisture is suppressed.

  Subsequently, the content of water-soluble impurities (P, Mg) contained in the RB ceramic powder used in the production of each ceramic was measured by a water and moisture method, and the measurement results are shown in FIGS. Specifically, the measurement was performed by wet analysis using a measuring instrument that measures by atomic absorption spectrophotometry and a measuring instrument that measures by spectrophotometry.

  As shown in each of FIGS. 2 to 3, the RB ceramic powder used in the manufacture of the ceramics of each example was water-soluble compared to the RB ceramic powder used in the manufacture of the ceramics of each comparative example that was not cleaned. It can be seen that the content of volatile impurities is greatly reduced. That is, in the ceramics of each example, these impurities are suppressed from absorbing surrounding moisture.

  Further, SEM photographs (100 times) before and after washing with water of the RB ceramic powder used in the production of each example were taken. FIG. 4A shows the RB ceramic powder used in Example 1 before cleaning, and FIG. 4B shows the cleaned RB ceramic powder. FIG. 5A shows a state before the cleaning of the RB ceramic powder used in Example 2, and FIG. 5B shows a state after the cleaning. FIG. 6 (a) shows the RB ceramic powder used in Example 3 before cleaning, and FIG. 6 (b) shows after cleaning.

  As shown in FIGS. 4 to 6, no change in the shape of the RB ceramic powder was observed before and after the cleaning. That is, by cleaning the RB ceramic powder with water, impurities inside could be removed without causing a change in the outer peripheral shape.

  As described above, the ceramic structure of each example was a ceramic structure in which a change in shape such as swelling due to surrounding moisture was suppressed.

It is a graph of the measurement result of the swelling rate of each ceramic. It is a graph of the measurement result of the content rate of P in each RB ceramic powder. It is a graph of the measurement result of the content rate of Mg in each RB ceramic powder. It is a SEM photograph before and behind washing | cleaning of the RB ceramic powder used for Example 1. FIG. 4 is a SEM photograph of the RB ceramic powder used in Example 2 before and after cleaning. 4 is a SEM photograph of the RB ceramic powder used in Example 3 before and after cleaning.

Claims (5)

Producing RB ceramic powder;
Forming the RB ceramic powder into a predetermined shape;
A step of firing the molded body;
In a method for producing a ceramic structure having
A method for producing a ceramic structure, comprising a step of washing the RB ceramic powder and / or the molded body with water before the step of firing the molded body.   2. The ceramic structure according to claim 1, wherein the cleaning of the RB ceramic powder and / or the molded body is performed until an electric conductivity of a solution obtained by washing the RB ceramic powder and / or the molded body with water becomes 100 μS / cm or less. Manufacturing method. Producing RB ceramic powder;
Forming the RB ceramic powder into a predetermined shape;
A step of firing the molded body;
In the manufacturing method having
A ceramic structure comprising a manufacturing method including a step of washing the RB ceramic powder and / or the formed body with water before the step of firing the formed body.   The ceramic structure according to claim 3, wherein the cleaning of the RB ceramic powder and / or the molded body is performed until an electric conductivity of a solution obtained by washing the RB ceramic powder and / or the molded body with water becomes 100 µS / cm or less. .   The ceramic structure according to claim 3, wherein the ceramic structure is a sliding member.

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