JPS6247984A - Manufacture of low expansion substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method for manufacturing a dense substrate with a low coefficient of thermal expansion.

(Technical background of the invention and its problems) Cordierite has been known as a ceramic with a small coefficient of thermal expansion, and is used for substrates of planar heating elements.

However, since cordierite has a narrow sintering temperature range, it is difficult to sinter it as a single body using normal means, and a porosity of less than 1.0% cannot be obtained. Therefore, an appropriate sintering aid such as ittria is added, but even in this case, the sintering temperature is as high as 1400°C, the sintering temperature range is narrow at about 50°C, and the raw material cost is high. There is.

Furthermore, when forming such sheet-like materials, methods such as press forming and doctor blade method are used, but the former requires a blade press pressure of at least 70 Qkg/cd and is not suitable for mass production. In addition, the latter method uses an organic binder, a solvent, etc., which poses problems in the working environment, and also has the disadvantage that the binder removal step during sheet firing is extremely complicated and difficult. .

(Purpose of the Invention) The present invention provides a method for manufacturing a ceramic substrate that is dense, has a small coefficient of thermal expansion, and can be manufactured at low cost by eliminating the above-mentioned drawbacks.

(Summary of the invention) That is, the present invention adds ceramic raw materials such as clay, feldspar, talc, and kaolin to a raw material powder having a cordierite composition, and mixes inorganic fibers such as asbestos and alumina fiber thereto to form an aqueous slurry. By agglomerating and paper-making, a sheet-like product made of the above raw material powder, ceramic raw material, and inorganic fiber is obtained,
This is a method for producing a dense low-expansion substrate, which is characterized by firing this at 1300°C to 1400°C.

(Detailed Description of the Invention) Specifically, in the present invention, ceramic raw materials such as clay, feldspar, talc, and kaolin are added to cordierite, which is a low expansion material, and
This is mixed with inorganic fibers such as asbestos and alumina fibers to form an aqueous slurry, which is then agglomerated and paper-formed to obtain ceramic green sheets. The cordierite material that could not be sintered was heated to 1300°C to 1400°C.
It provides a method for densification over a wide range of firing temperatures.

To explain this point specifically, ceramic raw materials such as clay, feldspar, talc, and kaolin improve the plasticity of the aqueous ceramic green sheet obtained by the papermaking method, and further promote the sintering of the raw material cordierite. 5 for purpose
~35% by weight is added. At this time, if the amount of ceramic raw materials added is 5% by weight or less, the composition will deviate greatly from the green sheet light composition obtained by papermaking, and the sintered body will not have a low coefficient of thermal expansion.

Note that the paper-making method used here refers to the use of powdered general ceramic materials such as clay, feldspar, pottery stone, talc, and kaolin, and organic fibers such as wood pulp or inorganic fibers such as asbestos. An aqueous slurry containing 40 wt% is prepared, the solid content is adsorbed and aggregated by fibers by adding a flocculant, and the aggregate is poured onto a filter plate or a net to have a uniform thickness, and then subjected to natural filtration. This is a method of obtaining a sheet-like material by performing filtration using a method such as vacuum filtration. In the present invention using this papermaking method, inorganic fibers such as asbestos, alumina fibers, ceramic fibers, and rock wool act as carriers that hold particles, literally playing the role of fibers in paper. Furthermore, by sufficiently stirring the aqueous slurry at the stage of making the aqueous slurry, the raw material powder, ceramic raw materials, and inorganic fibers are mixed homogeneously, so that the sheet-like material produced is in a homogeneous state that is suitable for sintering. This is the result.

The inorganic fibers are added in an amount of 3 to 40% by weight, preferably 5 to 20% by weight, based on the raw material powder.

If the amount of inorganic fiber added is less than 3% by weight based on the raw material powder, it will be difficult to form a sheet by the papermaking method, and conversely, if it is less than 40% by weight, it will be difficult to obtain a dense sintered body.

The role of the inorganic fiber is not only to serve as a carrier for the powder, but also to serve as one of the constituent elements of the sintered low-expansion substrate. This is different from methods that use organic fibers such as pulp or synthetic fibers as fibers, and organic fibers burn out during firing, leaving voids where the fibers were, so a dense sintered body cannot be produced. On the other hand, in the present invention, inorganic fibers remain in the sintered product as fibers or in a once-dissolved form, contributing to the creation of a dense substrate.

Furthermore, in addition to inorganic fibers, clay, feldspar, talc,
Additives such as kaolin form a liquid phase near the sintering temperature and promote sintering of the substrate at relatively low temperatures and over a wide range (1300-1400'G).

In other words, the present invention facilitates molding and sintering of cordierite in an aqueous system, which has been difficult in the past, and provides a dense, low-expansion substrate with a much simpler process than when using a solvent system. It is.

The present invention will be explained below based on specific examples. In addition, all compositions are weight ratios.

[Example 1] (A) Preparation of sample (Bj flocculant: first, put Cordiera in any alumina pot mill) 3
7. Add 10 parts of 5 parts clay and add appropriate amount of water.24
Time-powdering and -mixing. After crushing, asbestos 2.5
1 part and further water to make a total of 1000 parts to make an aqueous slurry.

A pre-prepared sulfuric acid band aqueous solution is added to this aqueous slurry and stirred to adjust the pH of the solution to 2 to 6, preferably 3.
After adjusting to ~4, add the aqueous solution 12 of polyacrylamide polymer flocculant that was also prepared in advance.
Add 0 parts and stir for 3 seconds to coagulate. The sample agglomerated in the above manner was made into paper using a paper making machine, and
Make a sheet of 1.5 to 2.2 square meters in thickness.

The material processed into an appropriate shape is placed in an electric furnace and fired in an oxidizing atmosphere for 1,380 mm to sinter the ceramic.

When the thermal expansion coefficient of the ceramic plate thus obtained was examined, it was found to be 23×10 −7 (1/′C), porosity 0.2%, and bending strength 4BO kg/d.

[□Example 2] (Preparation of Al sample (13) Coagulant Using the above composition (B), in the same manner as in Example 1, and fired at 1350'C for 4 hours, low expansion was obtained. The substrate is completed.The coefficient of thermal expansion at this time is 18X 10
-7 (1/”C), porosity 0.3%, bending strength 6
00 kg/m.

[Example 3] (Preparation of Al sample (Preparation of Al sample (Al) with a composition similar to that of a Bl flocculant (Al), using (13) and firing at 1330°C for 5 hours in the same manner as in Examples (1) and (2), a low The expansion board is ready.The coefficient of thermal expansion at this time is 20X
10-7 (1/℃), porosity 0.3%, and bending strength so kgA+! Met.

(Effects of the invention) According to the present invention, feldspar, kaolin, talc, frog's eye clay,
Furthermore, by adding asbestos, alumina fiber, etc., cordierite, which is difficult to sinter, can be easily densified with a porosity of 1% or less, and a thermal expansion coefficient of 35x.
It can be made as low as 1O"(1/"c) or less.

Moreover, since the present invention uses paper-making technology that uses inorganic fibers to form the sheet for firing, it is thin, has good workability, can be molded into any shape, is lightweight, strong, and heat-resistant. The ceramic substrate has the advantage of being resistant to impact.

In addition, compared to conventional methods, the process is simpler and the firing temperature is lower, so it is useful for energy saving and can be supplied at low cost.

The thus obtained low-1 expansion substrate with excellent thermal shock resistance can be used as a substrate for planar heaters, heat-resistant plates for household use, barbecue plates, or industrial fields such as medical, food, and chemical industries. Suitable for use as a substrate:

Claims (2)

[Claims] (1) Clay, feldspar,
Ceramic raw materials such as talc and kaolin are added at a ratio of 5 to 35% by weight, and inorganic fibers such as asbestos and alumina are mixed with this to form an aqueous slurry, which is agglomerated and paper-formed to combine the raw material powder with the ceramic raw material. 1. A method for producing a dense substrate with a low coefficient of thermal expansion, which comprises obtaining a sheet-like material made of inorganic fibers and firing the sheet-like material at 1,300 to 1,400°C. (2) The method for manufacturing a dense substrate with a low coefficient of thermal expansion according to claim 1, wherein the amount of inorganic fiber added is 3 to 40% by weight based on the raw material powder.