JPH01270558A - Production of ceramic - Google Patents

Abstract

PURPOSE:To obtain ceramic in high yield while preventing cracks and fractures during thermal decomposition of binder by blending ceramic material powder with binders having different thermal decomposition temperatures, granulating, molding and calcining. CONSTITUTION:In production of ceramic by blending ceramic material powder with a binder, granulating, forming a molded article consisting of the granules and calcining the molded article, two or three binders having different thermal decomposition temperatures is used as the binder and the ceramic material powder is granulated. In the above-mentioned method, since two or three binders having different thermal decomposition temperatures are used, thermal decompositions successively occur in the order of the binder having a lower thermal decomposition temperature under a calcining condition at ordinary heating rate. Consequently, in the decomposition process, moderate thermal decomposition is advanced half stepwise and almost continuously during heating up to calcination temperature, so that abrupt expansion of calcined material can be avoided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing ceramics, particularly for power storage, magnetic levitation trains, superconducting propulsion cars, electromagnetic propulsion ships, electric wire materials, high-speed semiconductor devices, medical magnetocardiograms, etc. The present invention relates to a method for manufacturing ceramics having superconductivity used in high-sensitivity magnetoencephalography magnetometers and the like.

[Prior Art] Conventionally, in the manufacturing method of ceramics, there is a molding step before the final firing step, and a binder is used in the granulation step during this molding.

PVA (polyvinyl alcohol) or the like is used alone as a binder, and the selection of its addition amount and its effects (effects on the sintered body), etc., are explained in detail in the following literature. .

[Ceramic dielectric engineering]; Written by Kiyoshi Okazaki, Gakkensha, (1
969-9-15 first edition) P, 83-92, P
], 30-1.3 L.

As shown on page 84 of this document, the amount of binder added is, for example, 0.5, 1.0'+3
．． Depending on the specific surface area and specific gravity of the powder added, that is, the ceramic raw material powder, such as 0.0 and 5.0 wt%,
It was determined partly by experience.

Further, the temperature increase rate during firing is usually about 150 to bhr.

[Problem to be solved by the invention] However, in the conventional binder selection method as described above, only one type of binder is used during firing, so the usual firing conditions (temperature increase rate of 150°C to 300°C/hr) are used. In this case, thermal decomposition of the binder occurs rapidly, and 130~ of the above-mentioned document
As described on page 13, there was a problem in that the generated thermal decomposition residue (such as CO2) sometimes caused cracks in the fired body, that is, ceramics. Note that the temperature increase rate should be slowed down to <(30°C/
If the firing time is 5 to 10 times longer than the usual firing time, the efficiency of using the firing furnace becomes extremely poor.

An object of the present invention is to provide a method for manufacturing ceramics having superconducting properties, which can prevent the occurrence of cracks and cracks due to thermal decomposition of a binder and can provide a high yield.

[Means for Solving the Problems] The present invention provides a method for producing ceramics having superelectricity, in which a step of adding two or three types of binders having different thermal decomposition temperatures to ceramic material powder is performed during the granulation step. It was designed to have the following characteristics.

[Function] In the method for manufacturing ceramics according to the present invention, two to three types of binders having different thermal decomposition temperatures are used in the granulation process.
Since the binder uses seeds, thermal decomposition occurs sequentially starting from the binder with the lowest thermal decomposition temperature under the firing conditions with the normal heating rate, so the rapid thermal decomposition of the binder is suppressed, and the decomposition process is slowed down to the firing temperature. When the temperature is increased during the heating period, gradual thermal decomposition occurs in a semi-stepwise and almost continuous manner, thereby avoiding rapid expansion of the fired body.

[Example] First, as an example of the present invention, a method for manufacturing a ceramic having superconductivity and the performance of the obtained ceramic will be sequentially explained.

Erbium oxide (Er) with a purity of 99.9% is used as a starting material.
a), barium carbonate (13aCO3), cupric oxide (C
uO) was weighed to give LrBa2Cus06.5 and mixed for 40 minutes in an agate mortar or shaker.
Next, it was calcined in air at 900°C for 5 hours. Is calcined powder nE again? It was ground for 30 minutes using a TA machine. Next, the granulation is carried out with -B - First, Ceramo 1.03, a water-soluble binder manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
and Ceramo 1B27B, and Ceramo EB60 were calcined powder 1
00 parts by weight, weigh 1 part by weight of each, and add 400 parts by weight of pure water.
Stir until the parts by weight are uniform. Thereafter, it was granulated using a spray dryer. This is designated as sample A. The binders mentioned above have thermal decomposition temperatures that increase in the order of Ceramo LO3, Ceramo 11327B, and Ceramo EI160.

Here, for comparison, we will use the conventional manufacturing method, that is, only the following types of binders: in this case, Ceramo 1,
A system in which 3 parts by weight of 03 was added to 100 parts by weight of calcined powder was granulated using a spray dryer in the same manner as Sample A. This is designated as sample B.

The granulated powders of Samples A and B obtained as described above were molded using a hydraulic press using a mold at a pressure of 1 ton/min.
Molding was carried out at 2 am to obtain a molded product of 16φ×31 mm. Firing was performed on a platinum plate at a heating rate of 250°C/11mm.
, in air at 950° C. for 20 hours, and a perfect superconducting ceramic was obtained for sample (A). This is sample B.
The super-4 conductive ceramic obtained by firing under the same conditions as Sample A developed cracks as described below, so a perfect ceramic was not obtained.

Superconducting properties of the superconducting ceramic obtained by firing Sample A were measured. In this case, a copper wire was connected to the ceramic surface via silver paste as an electrode. The electrical resistance was measured by a four-terminal method, with a constant voltage of 71111 being applied. As a result, the temperature at which the electrical resistance becomes completely zero, that is, the critical temperature T, was 88 K.

Next, the quality of the superconducting ceramic obtained in this example, that is, the appearance, and the experimental results that support the excellent effects shown by the manufacturing method of the present invention will be explained.

First, FIG. 3 is a reproduction of a plan view photograph of the ceramic obtained by firing Sample A. The firing conditions were 950° C. for 20 hours. As in this case, when three types of binders with different thermal decomposition temperatures were used, the ceramic could be fired without generating any cracks or cracks, and a ceramic with good superconducting properties could be obtained.

On the other hand, FIG. 4 is a reproduction of a plan view photograph of the ceramic obtained by firing Sample B. The firing conditions were exactly the same as for sample A in FIG.

As is clear from Figure 4, when ceramics are formed using one type of binder with a relatively low thermal decomposition temperature, as in the conventional method, many cracks and cracks occur, making the ceramics unusable. All I got was something.

FIG. 1 is a diagram showing the relationship between the temperature until the firing temperature (for example, 95.0'C) is reached and the weight loss rate of the binder. In the figure, the horizontal axis is the temperature, and the vertical axis is the weight loss rate, that is, the weight loss rate due to thermal decomposition of the binder.

In the experiment, the weight loss rate at each temperature was determined for three molded body samples to which the same amount of each of the three types of binders used in sample A was added. Each curve is due to the difference in binder, white circles are Ceramo LO3 and triangles are Ceramo 182.
7B, the black circle corresponds to Ceramo EB60. The temperature at which the weight loss rate is 50% is 275°C for Cera 03,
The temperature was 340°C for (? -7 mol B27B O') and 425°C for Ceramo EB[io.

FIG. 2 is a diagram showing the relationship between the temperature up to the sintering temperature and the weight loss rate of the molded bodies of samples A and B of the above example. In the figure, the horizontal axis is the temperature, and the vertical axis is the weight loss rate as in FIG.

Through this experiment, it was possible to determine the progress of thermal decomposition of the binder.
As in the case shown in the figure, it can be determined from the weight loss rate.

As shown in the curve of sample B, only one type of ceramo I, 0
When No. 3 is used as a binder, thermal decomposition proceeds rapidly. On the other hand, as can be seen from the curve of sample A under the same experimental conditions, when three types of binders having different thermal decomposition temperatures are used, the thermal decomposition of the binder proceeds slowly and occurs in stages.

This gradual thermal decomposition of the binder helps improve the density and homogeneity of the fired ceramics, and can be applied to methods of manufacturing ceramics with complex compositions, such as those with superconductivity.

In addition, although the above example describes the case where three types of binders are used, even when two types of binders with different thermal decomposition temperatures = 7 - are used, the same result can be achieved by appropriately selecting the type of binder. It is possible to produce ceramics without cracks or cracks.

[Effects of the Invention] As explained above, according to the present invention, by adding two to three types of binders having different thermal decomposition temperatures in the granulation process before obtaining a ceramic molded body, Ceramic firing conditions (heating rate 150°C
~300°C/hr), it is effective to eliminate cracks and cracks caused by rapid thermal decomposition, and to efficiently produce high-quality ceramics.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the temperature up to the firing temperature and the weight loss rate of various binders, and Figure 2 shows the relationship between the temperature up to the firing temperature and the weight loss rate of the molded bodies of samples A and B. line diagram,
FIG. 3 is a schematic diagram of a plan view photograph of the ceramic obtained by firing Sample A, and FIG. 4 is a schematic diagram of a plan view photograph of the ceramic obtained by firing Sample B. Agent Patent Attorney Toshiaki Suzuki Method of this invention (Teyoro Ceramics 3rd Invention Pot Sample A Tenkabuto Imouto 950'C20hrs Sample B Smoke Rear Spear) 1 \X)g ■V 1 Niwakama method 1 Teyoi Ceramics 4th Cause 950'C20hrs

Claims (1)

[Claims] A method for manufacturing ceramics in which a binder is added to ceramic material powder and granulated to form a molded body made of the granulated material, and then the molded body is fired. A method for manufacturing ceramics, comprising a granulation step of granulating the ceramic material powder using two or three types of the binders.