CS196509B1 - Ceramic composition for technical and electrotechnical products or for utility ceramic products - Google Patents

Description

The invention relates to ceramic materials suitable for technical, electrotechnical or utility ceramics processed by casting, plastic forming, pressing, hydrostatic pressing.

Corundum porcelain with high mechanical strength requires special properties for preparation of working mixtures of raw materials, especially fluxes. They are nephelin-syenlty, phonolite or keratophyre with highly active alkaline component, which during firing has a positive effect on the actual sintering process of corundum porcelain and by dissolving into glass it removes random quartz grains introduced into clay clay mixtures. This eliminates the weak points of the fired body and increases its overall mechanical strength. However, the use of phonolites, keratoire, or other raw materials from Czechoslovakia (especially clays and calcined flakes) brings with it a significant increase in the content of iron oxide (Fe ₂ O ₃ ) in the fired shard, which is unfavorable especially in corundum porcelain. unglazed products and degrading the appearance of white glazed products. Carbrown color is caused by the formation of a thin layer of iron oxides.

The disadvantages of the prior art are overcome by the invention, which is based on the fact that the ceramic mass contains 15.1 to 65% by weight of alumina (AlgO4).

196 509

198 599 .a and / or bauxite, calcined or mineralized or electro-melted, 1 to 35% by weight of a silica component, of which 80% of the particles (crystals) are below 40 µm, consisting of quartz, quartz, quartz, limnocarcite, quartz, amorphous silica (SiOg), high SiOg β clay, ground quartz glass, either alone or in admixture, 5 to 40% by weight of feldspar, phonol, nepheline-syenite, keratophyr, granite, pegraf, feldspar pegmatite, tufa, either individually or in admixture.

It is an advantage of the invention that the added silica component, which is very fine-grained (in particular worm and quartzite), is rapidly melted into the melt when the porcelain mixture is fired and chemically binds the iron compounds present, resulting in a noticeable effect. The surface of the fired cullet is considerably improved not only in terms of its whiteness, but also its mechanical properties are improved, both by removing some of the surface defects (due to the reduction of Pe ₂ O ₃ ^{on the} surface of the culled cullet) from partially etched grains of corundum and the dissolved silica component. Increased formation of fine secondary mullite increases the total content of crystalline phases in the fired body.

The invention will be explained in more detail by means of four possible embodiments:

Example 1

In a first example of a particular embodiment, the mixture is:

% Al ₂ 0 ₃ % silica component of quartzite quartz and 30% fluxes of Halámky feldspar were milled in a ball mill for the remainder in the range of 0.2 to 0.6% to 0.063 sieves. The mass was dewatered in a spray drier. Semi-finished products were prepared by isostatic pressing technology. Insulators prepared from semifinished products by machining were fired to 1360 ° C after glazing. The fired body reached meehn-bend strength of 130 to 170 MPa, mechanical bending strength of more than 2.0 mJ. mm ^-2 and electrical breakdown strengths exceeding 25 kV.

-1 mm ·

Example 2

In a second example of a particular embodiment, the mixture is:

% kaolin and clays,% mineralized AlgO4,% quartzite quartz (silica component),% calcined shale ZP lib (Mullitl component),% feldspar II and 6% jingle , 2 to 0.6%. The mass was dewatered by calolysis, homogenized on the draw bar. Semi-finished products and e-drawers on the vacuum drawing press • 198 509

They were processed by plastic creation technology. The products were fired at 1360 ° C.

Example 3

In a third example of a particular embodiment, the mixture:

% of kaolins and clays,% of mineralized AlgOp, 10% of the Council of Sagittarius,% of zirconailiate (ZrSiO ₄ )% of keratophyll and% of feldspar II were processed in a similar way as in Example 1. The fired shard reached in both cases the bending strengths of the impact will increase as

2,5 mJ. mm and electrical breakdown strengths greater than 30 kV / mm.

Example 4

In a fourth example of a particular embodiment, the mixture is:

% kaolins and clays,% mineralized AlgO4,% quartzite Bánská Bělá,% jingle Želenice and 16% feldspar ŽP I were ground in a ball mill with the addition of 1% kercortan. The mixture was dewatered in a spray drier and granulated Jimota and hydrostatically pressed blanks that were dry machined. The firing of the products was conducted at temperatures of 1350 to 1380 ° C. The fired burr of this corundum porcelain exhibited a mechanical bending strength of 180 to 230 MPa, an electrical breakdown strength higher than 25 kV / mm.

The whiteness of the unglazed baked cane was good and comparable in all examples with a ceramic shard of classical composition.

Claims (9)

1. Ceramic material for technical, electro-technical or utility ceramics, processed by plastic production technology and by all kinds of pressing and casting, characterized in that it contains 15.1 to 65% by weight of aluminum cyanide (AlgO4) and / or baaxl, calcined or mineralized or electro-melted, from 1 to 35% by weight of a silica component, of which 80% of the particles are less than 40 µm in size, consisting of quartz, quartzite, sandstone, limo-quartzite, silica, diatomaceous earth, amorphous silica (SiO ₂ ); SiO ₂ , ground quartz glass, either individually or in admixture, 5 to 40% by weight of feldspar, feldspar, nepheiin-eyonite, keratophyr, granite, pegraph, feldspar pegmatite, tuff, either individually or in admixture . 2. Ceramic mass according to claim 1, characterized in that it contains 5 to 60% by weight of clay composed of kaolins, clays, non-calcined chips, halloyeites or bentonites, or additions of organic plasticizers and reinforcing agents. 3. Ceramic composition according to claim 1 and / or 2, characterized in that it contains from 2 to 40% by weight of a synthetic component consisting of synthetic mullite, calcined kaolin, calcined clay, calcined halloyeite, calcined flake, porcelanite, fireclay, fired ceramic shards. either separately or in admixture. 4. Ceramic mass according to claims 1 to 3, characterized in that it contains from 1 to 40% by weight of zirconium silicate (ZrS10O). 5. A ceramic composition as claimed in any one of claims 1 to 4 comprising from about 0.5 to about 20% by weight of magnesium component, based on magnesium oxide, of talc, calcined talc, synthetic enstatite, steatite burnt cullet, cordierite cullet, dolomite, magnesite, serpentine, foreterite, magnesium oxide, synthetic magnesium flux or glass, either singly or in combination. 6. A ceramic composition as claimed in any one of claims 1 to 5 comprising about 0.5 to about 10% by weight of calcium component based on calcium oxide, consisting of synthetic calcium flux or glass, natural or synthetic wollaetonite, limestone, marlstone, calcined marlstone, and It is either alone or in combination. 7. Ceramic composition according to claim 1, characterized in that it contains 0.2 to 5% by weight of barium component, based on barium oxide, preferably barium carbonate. 8. Ceramic material according to claims 1-7, characterized in that it contains 0.1 to 5 weight% of titanium, e preferably TiO ₂ or BaTiO ^. 9. Ceramic composition according to claims 1 to 8, characterized in that it contains 0.5 to 15% by weight of the zinc component, based on zinc oxide, preferably synthetic zinc flux.