JP2006265571A - Article having ceramic particles oriented and layered thereon, and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an article having flat particles oriented in a fixed direction and deposited thereon. <P>SOLUTION: The article having ceramic particles oriented and layered thereon is produced by the steps of: suspending flat particles of a ceramic, a composite ceramic, a ceramic having a structure containing one or both of an organic matter and a metal in its one part, or a ceramic having its surface modified with one or both of an organic matter and a metal, in a solvent; inserting an electroconductive material in the suspension as a substrate; and applying an electric field onto the suspension to deposit the flat particles in the suspension on the substrate while orienting them. It is possible to deposit the flat particles with higher efficacy by adding a solution of a solated ceramic to the suspension. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, electrophoresis is performed by suspending ceramic-based flat particles having a large vertical and horizontal width and thickness direction difference in a solvent such as water or alcohol, inserting a conductive substrate into the suspension, and applying an electric field. The present invention relates to a ceramic particle oriented laminated body in which particles are oriented and deposited in a certain direction by an electrodeposition method and a method for producing the same.

As for the molding of ceramics using powder raw materials, dry press molding and wet casting are generally used, and most industrial products are produced by these methods.
In addition, the electrophoretic electrodeposition method for ceramics makes it easy to produce a deposition layer with a controlled thickness from a dense thin film to a bulk, and by alternately depositing several different types of suspension, Has been studied as a technique that can be applied to various functions or processing of structural ceramics, and the like.

  For example, as a method for producing a ceramic layer using this type of electrophoretic electrodeposition method, as described in, for example, JP-A-2002-88500, a layered compound having crystal orientation is subjected to a direct current voltage or an organic solvent. As described in JP-A-6-63916, a method for producing a crystallographic layered compound film in which an alternating voltage is applied and electrophoresed to deposit on a substrate, and the deposited layered compound is a thin film, The ceramic raw material particles that are charged by applying a low voltage are immersed in a slurry obtained by dispersing ceramic raw material particles in an organic solvent containing a polyamide-based surfactant, and the electrode and the counter electrode having a predetermined shape are immersed therein. A method for producing a ceramic molded body to be electrodeposited on an electrode has already been disclosed.

  In these ceramic sheet manufacturing methods, spherical particles or rectangular particles are used as ceramic particles. On the other hand, flat particles having a large size in two directions with respect to a size in one direction are difficult to orient, and if used as they are, the material of the product becomes non-uniform. Absent.

  In order to establish a manufacturing technique for utilizing a ceramic sheet using flat particles as a material for an industrial product, it is necessary to align the direction of the particles and improve the uniformity of the product material. In addition, moldings made from spherical particles as raw materials become difficult to mold when the particle size is small. In the case of wet molding, problems such as dry cracking occur due to volume shrinkage after molding due to the influence of the solvent attached to the surface. was there. For this reason, it is very difficult to form nano-sized fine particles that are attracting attention for the development of functional materials.

JP 2002-88500 A JP-A-6-63916 JP 2004-209780 A JP 2003-183891 A JP 2001-316874 A JP 2004-66469 A Special table 2003-532609 gazette Japanese Patent Laid-Open No. 6-219863 JP 2004-131363 A JP-A-8-306985 Special Table 2002-511903 JP-A-6-63915 JP-A-8-78275 JP 2003-13287 A

  In view of the problem of the method for producing a ceramic layer using the conventional electrophoretic electrodeposition method, the present invention uses ceramic particles, and deposits these particles while orienting them in a certain direction. An object of the present invention is to provide a production method for obtaining an oriented laminated body and a ceramic particle oriented laminated body produced thereby.

  When the electrophoretic electrodeposition method is used for the deposition of flat particles, it is possible to produce a stacked deposit in which the directions of particles are aligned under the influence of an electric field. Further, by adding a sol solution of ceramics at that time, the deposition efficiency is increased, the density of the deposit is improved, and an oriented precipitate having a uniform material can be produced.

  Further, the oriented laminate of flat particles can be molded without causing cracks due to drying, since drying shrinkage after deposition is affected by the orientation direction and shrinkage in one direction is increased. Thereby, it becomes possible to manufacture a molded body using a functional material in which the thickness of the flat particles is nano-sized.

The present invention has been made from such a viewpoint, and is composed of ceramics, composite ceramics, ceramics including a part of the structure with organic matter and / or metal, and ceramics modified with organic matter and / or metal on the surface. By suspending the flat particles in a solvent, inserting a conductive material as a substrate, and applying an electric field to the suspension, the flat particles of the suspension are oriented and deposited on the substrate to be ceramic. A particle oriented laminated body is produced.
In this case, by adding a ceramic sol solution to the suspension of flat particles, the deposition efficiency can be increased and deposited.

The present invention is an electrophoretic electrodeposition method in which ceramic-based flat particles having a large difference in width and thickness direction are suspended in a solvent such as water or alcohol, a conductive substrate is inserted, and an electric field is applied. According to the method, a laminate in which each particle is oriented in a certain direction is provided.
BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be specifically described below and will be described in detail with reference to examples.

  Ceramic-based flat particles consist of ceramics, composite ceramics, ceramics that contain organic materials and / or metals as part of the structure, and ceramics that are modified with organic materials and / or metals on the surface. It is a particle whose dimension in the other two directions is larger than the dimension in the direction. Specifically, it is a particle having a large aspect ratio and a large size in the length and width directions compared to the size in the thickness direction.

In addition, a conductive material such as graphite, metal, conductive ceramics, and conductive polymer can be used for the electrophoretic electrodeposition substrate on which these particles are deposited.
To the suspension of flat particles used for electrodeposition, a binder such as polyvinyl alcohol (PVA) can be added as necessary to maintain the shape of the laminate after deposition, or the deposition efficiency can be increased to increase the density. A ceramic sol solution can be added for the purpose of producing a deposit.

  FIG. 1 is a conceptual diagram showing an example of a basic configuration of an electrophoretic electrodeposition apparatus for depositing such particles. A suspension in which flat particles used for electrodeposition are dispersed in a solvent is placed in a container, and a conductive substrate made of, for example, Pd is immersed in this suspension as a substrate for electrophoretic deposition. Further, a counter electrode made of Pt or the like as an auxiliary electrode is immersed in the suspension so as to face this conductive substrate. A power supply device is connected to the conductive substrate immersed in the suspension and a counter electrode, and a DC voltage is applied between the pair of electrodes so that the counter electrode serves as an anode and the conductive substrate serves as a cathode.

  In such an apparatus, by the action of an electric field, the ceramic flat particles in the suspension are deposited on the surface of the conductive substrate while the longitudinal direction of the ceramic flat particles is aligned in a certain direction, and a film-like or sheet-like ceramic A system particle oriented laminate is formed. That is, the particle deposit produced by this method becomes a laminated deposit in which the orientation of the flat particles is uniformly oriented, and it is produced from a thin film to a thick plate-like molded body by changing the electric field application time. It is possible.

In the conventional method for producing a layered product by electrophoretic electrodeposition, the main purpose is to align the crystal direction, the magnetic direction, and other characteristics, and the properties resulting from the atomic structure and the like are aligned.
On the other hand, in the present invention, the purpose is to align the shape of the flat particles in a certain direction. As a result, there is a possibility that the crystal direction and the magnetic direction as described above may be aligned. However, these directions are not necessarily aligned, and the purpose is to align the flat particles in a certain direction.

  As described above, the advantage of aligning the shape direction of the flat particles is that the direction of drying shrinkage is aligned in the manufacturing process or use state of the sheet. In particular, a material composed of fine particles having dimensions on the order of nanometers is expected to have functionality, but since the sheet is liable to crack, the advantage brought about by aligning the shape direction of the flat particles is great.

One preferred embodiment of the present invention is to add a sol solution as an additive to the suspension. If a sol solution having the same composition as the material to be molded is used, a high-quality electrophoretic electrodeposition film can be produced without mixing impurities. For example, when titanium oxide is used for the sheet, the same sol solution of titanium oxide as the sheet component is added to the suspension to produce the electrophoretic electrodeposited sheet.
Examples of these methods are shown below, but this content does not limit the scope of the present invention.

1. Production of Oriented Laminate of Flat Particles by Electrophoretic Electrodeposition As the flat particles, a 100 nm thick titanium oxide nanosheet manufactured by Art Science Co., Ltd. was used. This titanium oxide nanosheet is obtained by the production method described in Japanese Patent Application Laid-Open No. 2004-224623 proposed by the present inventors. That is, a titania nanosheet whose thickness is controlled by a fluid interface sol-gel method in which a 20% solution obtained by polymerizing tetraisopropoxytitanium is dropped and developed on a flowing water surface while quantifying is obtained. This titania nanosheet is a sheet having a structure in which a thermally metastable amorphous or nanocrystal grain having a thickness of 1/5 or less of the sheet thickness is confined in the sheet, and the sheet is easily sinterable. This was dispersed in water at a ratio of 4 g to 100 g to obtain a slurry.

Next, this slurry was put in a container, and a production test of a titania layer was performed under the following two conditions 1 and 2.
(Condition 1) The conductive substrate made of palladium was immersed in the slurry and pulled up after 3 minutes. (Condition 2) As shown in FIG. 1, the conductive substrate made of palladium and the counter electrode made of platinum plate were immersed in the slurry. Then, a DC voltage of 20 V was applied between the two substrates using the platinum plate as the positive electrode and the palladium plate as the cathode.

The results of surface shape observation of the titanium oxide film deposited on the palladium plate under the above conditions with a scanning electron microscope are shown in FIGS.
Condition 1 is a dip method, which is one of the thin film fabrication methods, but as shown in FIG. 2 showing the surface shape of the titanium oxide film, the orientation of the flat particles is not ordered and is a disordered deposition state. I understand. On the other hand, under condition 2 which is the method of the present invention, it is clear from FIG. 3 that the direction of the flat particles is aligned and the effectiveness of the present invention has been confirmed.

2. Addition of ceramic sol solution to suspension of flat particles To the titania slurry used in Example 1, a sol solution of titanium oxide was added to produce an electrophoretic electrodeposition film under the following condition 3, and a deposit ( The state of the film) was evaluated.
(Condition 3) A platinum plate and palladium were added to a solution obtained by adding 5 vol% of titanium oxide sol (titanium tetraisopropoxide 5 wt%, isopropanol 15 wt%, water 80 wt% to a solution of nitric acid 2 wt%) to the slurry. The plate was immersed, and a DC voltage of 20 V was applied between the two substrates using the platinum plate as the positive electrode and the palladium plate as the negative electrode.

  FIG. 4 shows the result of observation of the deposit produced in the same manner as in Example 1 with a scanning electron microscope. As is clear from FIG. 4, it can be seen that the layered alignment material of condition 3 in FIG. 4 is a highly dense deposit with higher orientation and adhesion than the condition 2 of FIG. The effectiveness of adding the ceramic sol solution to the flat particle suspension of the invention was confirmed.

3. Electrophoretic electrodeposition of spherical fine particles P25 manufactured by Degussa Aktien Co., Ltd. was used as spherical fine particles, and a slurry was prepared under the same conditions as in Condition 2 of Example 1 as shown in Condition 4 below.
(Condition 4) A platinum plate and a palladium plate were immersed in a slurry of P25, and a DC voltage of 20 V was applied between the two substrates using the platinum plate as a positive electrode and the palladium plate as a cathode.

  P25 is a fine particle having an average primary particle size of 30 nm, and the deposit produced under Condition 4 cannot be formed into a molded product due to cracking after drying as shown in FIG. It was. On the other hand, the oriented laminate produced under the condition 3 as in Example 2 was able to produce a relatively thick molded body without cracking after drying as shown in FIG.

It is a conceptual diagram which shows an example of the basic composition of the electrophoretic electrodeposition apparatus which deposits particle | grains in one Embodiment of this invention. It is a scanning electron micrograph of the surface shape of the titanium oxide film deposited on the palladium plate under the condition 1 in Example 1 of the present invention. It is a scanning electron micrograph of the surface shape of the titanium oxide film deposited on the palladium plate under the condition 2 in Example 1 of the present invention. It is a scanning electron micrograph of the surface shape of the titanium oxide film deposited on the palladium plate under the condition 3 in Example 2 of the present invention. It is a scanning electron micrograph of the surface shape of the titanium oxide film deposited on the palladium plate under the condition 4 in Example 3 of the present invention. It is a scanning electron micrograph of the surface shape of the titanium oxide film deposited on the palladium plate under the condition 3 in Example 3 of the present invention.

Claims (3)

Suspended flat particles made of ceramics, composite ceramics, ceramics that contain organics and / or metals in part of the structure, and ceramics modified with organics and / or metals on the surface, in graphite, metal, By inserting a conductive material such as conductive ceramics or conductive polymer as a substrate and applying an electric field to the suspension, the flat particles of the suspension are oriented and deposited on the substrate. A method for producing a ceramic particle oriented laminated body. The method for producing a ceramic particle oriented laminated body according to claim 1, wherein a ceramic sol solution is added to the suspension of flat particles to increase the deposition efficiency and deposit. The ceramics and composite ceramics obtained by the manufacturing method according to claim 1 and claim 2, ceramics containing a part of an organic material and / or metal, and ceramics modified on the surface with an organic material and / or metal. A ceramic-based particle oriented laminate, wherein flat particles are oriented and deposited on a substrate.