JPH01261257A - Production of one-dimensional particle-oriented material structure - Google Patents

Abstract

PURPOSE:To produce a particle-oriented structure having high anisotropy in one axial direction in high efficiency, by compression-molding a constituent element having low symmetricity at or slightly below the densification temperature of the element while applying an external force in a direction to cause the slippage in one axial direction. CONSTITUTION:A formed article is produced from a substance wherein a part or total of the constituent elements of the substance have microstructural anisotropy of crystal orientation or particle orientation. The opposite faces of the formed article are slantly machined at a prescribed angle (delta) to make the opposite faces to form parallel and slant faces. The article is applied with compression forming external force at or slightly below the densification temperature while applying an external force to the opposite slant faces in a direction to cause a slipping stress in the formed article in a direction of an axis.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a -dimensionally oriented oriented material structure. In particular, it relates to a method for manufacturing a one-dimensional particle-oriented material structure in which a part or all of the constituent elements are uniaxially oriented a material having microstructural anisotropy of crystal structure (orientation) or heterogeneity of particle orientation. .

[Prior art] - The demand for improving the functions of structural materials or electronic materials used in industrial equipment and electronic equipment, etc., and the demand for multifunctionality have become increasingly severe in recent years. For sliding tables of machines, guide plates of precision measuring machines, surface plates, etc., the mechanical strength should be high not in the three-dimensional direction but only in the two-dimensional direction, that is, in the in-plane direction, and the thermal expansion coefficient in the in-plane direction should be increased. A small one is desired. In addition, a material with high wear resistance in the thickness direction is desired, and a material with strong anisotropy and high mechanical strength is also desired.

This tendency is the same for electronic materials, where constituent elements have crystal axis orientations and crystal grain directions, and those that are oriented in a specific direction are required.In other words, so-called differences in crystal orientation For example, the use of materials such as piezoelectric ceramic materials and pyroelectric ceramic materials is increasing.

As a method for producing such a substance having anisotropy in a specific direction, there is a method of controlling the fine structure of the constituent elements, that is, a fine particle orientation technique.

Normally, in metals and ceramic materials, the crystal axes of each particle are in a disordered direction, so even if the constituent elements exhibit anisotropy, I've been able to handle it with this in mind. For this reason, such materials have no directionality in terms of application, and if physical properties in specific directions are to be utilized or expected, it is necessary to control crystal orientation and particle orientation to improve performance. It is necessary to aim for

Methods for aligning crystal orientation and controlling grain orientation (particle orientation technology) include the so-called electrical polarization method, which utilizes the electrical polarity of the constituent elements, and the so-called electrical polarization method, which utilizes the electrical polarity of the constituent elements. A mechanical force is applied in the direction J to cause the particles to slide, and the mechanical force is used to force the three-dimensional crystal orientation and orientation of the particles by an external force from one direction. A so-called Boctoworking method, which controls the orientation in two dimensions, can be considered.

For example, BaTi0. PZT-based peropskite-type ferroelectric materials such as Pb(Zr, Ti)On and Pb(Zr, Ti)On are macroscopically isotropic when subjected to normal firing treatment, but when subjected to polarization treatment by electrical operation, they are given different FJ properties. and transforms into piezoelectric or pyroelectric substances. However, even if such materials are subjected to polarization treatment, it is not possible to effectively utilize the anisotropy associated with ferroelectricity with single crystals.The reason why single crystal materials are desired is as follows. However, in order to bring out the properties of a single crystal to the maximum without impairing its anisotropy as much as possible, there are significant restrictions on the degree of freedom in selecting the composition and shape of the crystal. . In addition, it is not practical due to high costs and restrictions on the method of use, and molded products whose constituent elements are substances with almost no polarity, even if the particle shape of the constituent elements is large. Even if there is anisotropy, the anisotropy of each component element is in a disordered direction, and polarization by electrical processing is difficult, so electrical polarization processing alone as described above will hardly produce anisotropy. No directionality occurs.

Furthermore, even in the case of ferroelectric materials, single crystals have large anisotropy, such as those with a layered microstructure such as Blari, 0++, tungsten bronze type, pyrochlore type, pseudo-ilmenite type, etc. In a ferroelectric material with a structure of
Due to the layered structure, etc.), it is restricted two-dimensionally, and the coercive electric field is too large, making polarization difficult.
The characteristics (piezoelectricity) that can be expected from the properties of the constituent elements cannot be obtained, and for this reason, single crystals are only rarely used in such piezoelectric materials, and are not put into practical use much.

As a method to solve such problems, there is a particle orientation method in which pressure is applied from one direction at high temperature to cause the crystal grains to slide along the grain boundaries, and the grain directions are mechanically forcibly oriented. That is, a hot working method can be considered.

The hot working method includes (υ pot forging (H
ot-Forging), (2) Hot Press (Ho
t-Pressing method, 0) Hot-Extrusion method.

n) method and (4) Hot-Rol method.
ling) method. (2) The following method controls the direction of crystal axes and grain orientation when constituent components crystallize or grow grains by heating to high temperatures.

However, in the method (2), the particles can be oriented to some extent in the two-dimensional (in-plane) direction, but cannot be controlled in the -dimensional direction, and in the methods 0) and (4), the particles can be oriented in the -dimensional Although the orientation can be tolerated, it is not practical as a method for obtaining products with excellent orientation characteristics because the equipment is large-scale and the obtained particle orientation is not suitable for practical use. In contrast, (
The hot forging method described in 1) does not require large-scale equipment and can relatively easily produce products with excellent particle orientation characteristics. Although this method is practical and effective for substances with a large anisotropy of crystal structure, the orientation direction is only controlled in two-dimensional directions and is limited.

FIG. 1 shows a schematic diagram of a hot forging device.

B in FIG.
, E'. When a material with a layered structure is subjected to the hot forging process, slippage occurs at the grain boundaries, and eventually the grains are oriented in a plane perpendicular to the direction in which pressure is applied, with the crystal axes aligned. Substances are obtained. In other words, it shows that the particles are oriented in two dimensions (in-plane).
Therefore, particle orientation in the -dimensional direction cannot be expected at all.

[Problems to be Solved by the Invention] The present invention enables particles with large crystal orientation anisotropy and shape anisotropy (aspect ratio) to be one-dimensionally ( An object of the present invention is to provide a method for manufacturing a particle-oriented structure oriented in the -axis) direction. Therefore,
The present invention eliminates the drawbacks of conventional electrical or mechanical methods for producing grain-oriented materials, and produces crystalline materials with high microstructural anisotropy and materials with different particle shapes and j-characteristics. An object of the present invention is to provide a method for manufacturing a particle-oriented molded body in which the orientation of the particles is controlled with high efficiency in the -axis direction.

[Structure of the Invention] [Means for Solving the Problems] The present invention provides a material in which some or all of the constituent elements have microstructural anisotropy of crystal orientation or anisotropy of particle orientation. forming it into a molded body, cutting the opposing surfaces of the dense molded body diagonally at a predetermined angle,
A one-dimensional particle characterized by comprising a step of making opposing surfaces form parallel and oblique surfaces and applying an external force to the opposing slopes so as to generate a sliding (shear) stress inside the dense molded body. This is a method for manufacturing an oriented material structure.

[Effect]

According to the invention, the second! ! Normally, an atmospheric pressure sintering method is used to produce a densified structure that has microstructural anisotropy in the crystal structure or anisotropy in the particle shape but is macroscopically isotropic. This is a flow sheet showing a comparison with the hot forging method.

When materials with anisotropy in the crystal structure or low-symmetry structured materials with anisotropy in the particle shape used in the present invention are densified by normal pressure sintering, the orientation of the particles becomes disorderly. Therefore, it is macroscopically isotropic and does not exhibit anisotropy on a specific surface.

Figure 3 shows the present invention, which allows a molded body exhibiting macroscopic isotropy to be oriented in a specific direction by applying an external force from one direction while heating it to generate slippage at the grain interface. This figure shows a method of manufacturing a uniaxially oriented structure according to the method of the present invention. That is, in the molded article manufactured according to the flow sheet shown in FIG.
As shown in Fig. 3, when sample 1 is loaded from above and below and an external force is applied, slippage occurs at the particle interface and deformation in the -axial direction is promoted, so that the particle becomes -dimensionally oriented. .

An example of the manufacturing method of the present invention for effectively and smoothly causing this axial sliding is shown in FIG. By cutting at an inclination angle (δ) and applying an external force from one direction while heating the cut in an inverted state, a molded structure oriented in the -axis direction can be obtained. In addition, δ-90-〇.

In general, non-polar crystals are not polarized by electrical processing, even though their microstructures have large shape anisotropy. In the working process, due to the lack of fluidity due to the particle shape during sintering, the particles cannot be oriented at very high temperatures and without applying a large force, which not only requires a large-scale apparatus but is also economically disadvantageous. For this reason, there are many problems that need to be solved for practical use.Also, hot forging methods can achieve two-dimensional (in-plane) orientation, but cannot achieve -dimensional orientation (-axis to direction).
Furthermore, substances that have anisotropy in their microstructurally layered shape, such as BiaffisO+*, and substances that tend to form acicular crystal grains, such as PbNb*Os, have large anisotropy. However, when synthesized using conventional methods, it was not possible to derive useful properties as it was because it was a polycrystalline structure made up of disordered microcrystals. Furthermore,
These mixtures and composites have a major drawback in that a sufficient remanent polarization state cannot be obtained even when electrically polarized. This means that the possible directions of spontaneous polarization are
This is due to the crystal structure (layered or acicular structure), which limits the two-dimensional structure.Also, due to the high Curie point, the coercive electric field is too large, causing electrical breakdown, etc. This is because polarization processing is difficult. The restriction on the 1 degree of freedom of orientation due to the crystal structure is as follows:
Low symmetry nonpolar materials (AIIOs, hexagonal ferrites) and oxygen octahedral groups (bismuth layered structure, tungsten bronze type PbNb, Q, etc., pyrochlore type,
This is a woody problem that occurs when adapting to materials such as pseudo-ilmenite type.

The present inventors have conducted a wide range of research on structured fired bodies whose crystal structures and grain shapes have low microstructural symmetry, and as a result, only the unsatisfactory results described above have been obtained. The reason is that those manufactured by the normal glue method have a structure with low symmetry, and from the viewpoint of directionality, the particles are oriented randomly, and the steric hindrance of the particles themselves and the coefficient of friction at the particle interface are It has been found that this is because due to the large size, sufficient particle orientation cannot occur, and the above-mentioned problems occur in the constituent elements themselves.

From this finding, the inventors have developed a method for constructing components of low symmetry at their W&densification temperature or somewhat below, while applying an external force in a direction such that slip occurs in the -axial direction. The object of the present invention is to provide a method for producing a dense and reliable particle-oriented structure having high uniaxial anisotropy only through a molding process.

Therefore, the present invention eliminates the drawbacks of conventional methods for producing structures with electrically oriented or mechanically oriented particles, and produces crystalline materials with high microstructural anisotropy and anisotropic particles in shape. The object of the present invention is to provide a method for manufacturing with high efficiency a particle-oriented structure in which a substance having a particle orientation is oriented in the -axis direction.

For example, dielectric materials having anisotropy in crystal structure include yttrium oxide (Y*Os), β-alumina,
Mainly used are plate-like crystal α-alumina, magnetic materials include orthogonal ferrite, Ma-Zn ferrite, cubic ferrite, etc., and ferroelectric materials include:
Peropskite-type ferroelectrics such as BaTiOs, Pb(Zr,Ti)On, etc. are also used as low symmetry incubators, such as thin plate-like Bi, iso,, PbB1. N
b, 0. Bismuth layered structures such as tungsten bronze type, pyroa type, and pseudoilmenite type compounds are used.

In another example of the method for manufacturing a uniaxially oriented structure according to the present invention,
The rolling speed is controlled to be different by applying it between rolls with different diameter ratios or rolls with different rotation ratios, or through a die with two surfaces with different slopes, and a sliding force is generated in the rolling direction. .

In addition, in the present invention, a second anisotropic substance that is more easily deformed by external force is mixed with a molded body of a component having a specific crystal anisotropy or particle shape anisotropy. , or a substance that is easily deformed can promote the sliding action and make it possible to create a particle-oriented structure at a lower temperature and with less external force. For this purpose, a mixture of a plurality of substances can be used as long as they provide similar effects.

Next, the method for manufacturing a one-dimensionally oriented structure according to the present invention will be explained in the case of a bismuth layered structure ferroelectric material.
The invention is not limited by the description.

[Example 1] The sample used was 1120 mm by ordinary ceramic technology.
It is a molded body sintered under normal pressure at ℃, and 200 kg is weighed from one direction perpendicular to a specific surface of this sintered compact at the end of sintering.
/ cm'' was applied and held for 3 hours to obtain two-dimensional orientation (in-plane orientation) (so-called pot forging treatment) and the top and bottom surfaces of green molded bodies as shown in Figure 4. Cut it parallel to the inclination of a certain angle (δ), turn it upside down, and sinter it at normal pressure, then heat it at the same sintering temperature of 1120°C and heat it from above at 200°C.
An external pressure of "kg/am" was applied for 3 hours. External pressure was applied to the inclined upper and lower surfaces, and the particles were slid along the grain interface in a uniaxial direction perpendicular to the external pressure to form a structure in which the particles were oriented in the − dimension. Created.

Table 1 and Figure 5 show the ratio of the piezoelectric properties in the vertical direction (K2S(ff)) and the piezoelectric properties in the lateral direction (K2S(:l)) perpendicular to the pressing direction of each sample obtained. : ni33 (vertical)
The results of measuring the degree of orientation using the ratio of / to 33 (3 pieces) and xll are shown.

Cold 1 Stolen Capital 1- Cut Angle <S> Medical Star 1ゑ Cup Blood Normal Pressure Sintered Body 0 1.0 0%17
1.50 1002 In the table, the resection angle indicates the angle at which the upper and lower surfaces are resected as described above, and when the present invention is not used, the resection angle is -0. In addition, the EE electric power ratio is 33 (kuchi) / 33 (
The degree of orientation, which indicates the ratio of horizontal and vertical directions, was measured by the Lotgerling equation using X-ray diffraction.

From these results, it was found that when an external force is applied in the -axis direction, one-dimensional orientation occurs due to slippage at the particle interface, and the properties in the orientation direction are greatly improved.

FIG. 5 is a graph in which the ratio of K2S (vertical)/to 33 (horizontal) is plotted against the resection angle <S). The measurement was carried out under the conditions of Ep-5 [kV 7 wml], Ir-200[''C]te, and Tr-10 minutes.

The sample is a bismuth layered structure ferroelectric material, with 99% Bi*Os, PbO, ff1o*, and Nb*Oi
, NanCO5, La*Os and MnC0, were used as starting materials. Put these into a ball mill with acetone,
Mixed for 10 hours.

Next, the obtained mixture was dried at 80° using a vacuum dryer.
After drying at C for 2 hours, use a mold to produce 80Qkg/c.
The molded product was pressurized for 1 minute at a pressure of 100° C.cs” to form a cylindrical shape.Furthermore, this molded product was calcined at 850'C for 2 hours and then pulverized to obtain a raw material powder for firing.

The raw material powder was mixed with an aqueous solution of polyvinyl alcohol in a ball mill for 20 hours, dried, and then molded into a disc with a diameter of 20 cm and a thickness of 2 cm using a mold at a pressure of 8 Q Okg/csa for 1 minute. It was molded into a sample for sintering.

For comparison, the pressure-fired body was heated to 500°C without any control, held at 500°C for 2 hours, molded, and then heated to 20°C.
The temperature was raised at a temperature increase rate of 0° C./hour, held at the maximum temperature for 3 hours, sintered, and then naturally cooled.

In addition, a hot forged body for comparison was prepared by molding a mixture of calcined raw material powder and polyvinyl alcohol into a mold.
Pressure was applied for 1 minute at 00 kl:/c to form a green body, followed by atmospheric pressure firing in the same manner as above.
A pressure of 200 kg/am8 was applied at 120° C. for 3 hours to cause compression deformation in the forging process, and then the pressure was released and the temperature was lowered at a rate of 200”C/hour.

[Effects of the Invention] The method for manufacturing a one-dimensional oriented structure according to the present invention has the following remarkable technical effects.

First, if the orientation method is applied to a dense body with anisotropy in crystal structure or particle shape, the anisotropy of the constituent elements can be easily adjusted using a simple device and at an economical cost. To provide a manufacturing method that can effectively and significantly extract characteristics.

Second, even in dense bodies containing constituent elements with low microstructural symmetry, anisotropy allows for easy and effective one-dimensional orientation in one axis direction in one step of high-temperature pressure treatment. A method of manufacturing an oriented product is provided.

Thirdly, a highly practical method for producing one-dimensionally oriented structures has therefore been provided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an outline of a conventional hot forging device. FIG. 2 is a flow sheet showing the manufacturing process of isotropic, dense pressureless sintered bodies and biaxially oriented sintered bodies when ceramic/lath raw materials are used. FIG. 3 is a schematic cross-sectional view illustrating the principle of manufacturing a one-dimensionally oriented material structure according to the present invention. FIG. 4 is an example of a sample shape that can be created to have the anisotropic characteristics developed according to the present invention. FIG. 5 is a graph showing anisotropic piezoelectric characteristics developed by the present invention. Patent applicant Mitsubishi Mining Cement Co., Ltd. Agent Patent attorney Hiroshi Kuramochi (one other person) Figure 1 Figure 2 Figure 4 Figure 1. To4A δ (Seat ○ Figure 5

Claims (1)

[Claims] Forming a material in which some or all of the constituent elements have microstructural anisotropy of crystal orientation or anisotropy of particle orientation into a molded body, and forming a material in which opposing surfaces of the molded body are Cut diagonally at a predetermined angle so that the opposing surfaces form parallel and oblique surfaces, and slide uniaxially into the inside of the molded body against the opposing oblique surfaces at the densification temperature or a temperature slightly lower than that. A method for manufacturing a one-dimensional particle-oriented material structure, comprising the step of applying an external force for pressure forming while applying an external force in a direction that does not cause stress.