AU605143B2

AU605143B2 - A base material for producing ceramic materials

Info

Publication number: AU605143B2
Application number: AU70939/87A
Authority: AU
Inventors: Peter Dr. Kleinschmit; Anh Thu Dr. Liu
Original assignee: Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 1986-04-05
Filing date: 1987-04-01
Publication date: 1991-01-10
Anticipated expiration: 2007-04-01
Also published as: EP0241647A2; EP0241647A3; JPS62260721A; AU6595490A; DE3611449A1; AU7093987A

Description

UI FORM 10 U)b o AL H OAiSTRA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: SPRUSON FERGUSON

LIA

This document contains the amendments made under Section 49 and is correct for printing 70q3q i Ir Class Int. Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: Name of Applicant: S Address of Applicant: Actual Inventor(s): Address for Service: Degussa Aktiengesellschaft Weissfrauenstrasse 9, Frankfurt, Federal Republic of Germany PETER KLEINSCHMIT and AN" TU LAU Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, Australia for the invention entitled: Complete Specification "A BASE MATERIAL FOR PRODUCING CERAMIC MATERIALS" The following statement is a full description of this invention, including the best method of performing it known to us SBR/JS/0109W ~1 -1- Abstract A Base Material for Producing Ceramic Materials A base material when used for the manufacture of non-porous ceramic material, wherein the base material is characterized in that it contains a pyrogenically produced mixed oxide of zirconium oxide and silicon dioxide dispersed in water and spray-dried, and which base material is not obtained as a gel.

a a o 000 0 0 0 0 000o 0000 0 0 000000 0 0 d 0 0 0 S o :9y KNK:939y 4 i 2 2 TECHNICAL FIELD The invention relates to a base material for producing ceramic materials.

BACKGROUND OF THE INVENTION It has been known to produce base materials for the manufacture of ceramic materials by spray-drying aqueous dispersions of zirconium oxide sols mixed with oxides pyrogenlcally produced by flame hydrolysis of silicon compounds (British Patent 2,011,366).

It is the disadvantage of these base materials that they are obtained as gels and, in addition, that they contain important amounts of anionic contaminants (usually nitrate ions). These Initial products are converted into the corresponding oxides only by heating to high temperatures; on this occasion, nitrogen oxides, which pollute the environment, are released.

These disadvantages are overcome by directly producing the mixed oxides in a flame.

0 0 00 SUMMARY OF THE INVENTION The object of the present invention is a base material for the manufacture of ceramic materials, wherein the base material is characterized in that it contains a pyrogenically produced mixed oxide of 20 zirconium oxide and silicon dioxide which was dispersed in water and spray dried.

000 0 Another object of the invention is a pyrogenically produced mixed zirconium oxide, which was obtained by flame hydrolysis and 0000 which contains from 5 to 95% by weight of silicon dioxide as a component of the mixed oxide.

S, According to a broad form of the present invention there is provided a base material when used for the manufacture of non-porous ceramic material, wherein the base material is characterized in that it contains a pyrogenically produced mixed oxide of zirconium oxide and silicon dioxide dispersed in water and spray-dried, and which base material is not obtained as a gel.

The process of producing the pyrogenically produced mixed zirconium oxide, which was obtained particularly by flame hydrolysis and contains from 5 to 95% by weight of silicon dioxide as a component of the mixed oxide, is characterised In that anhydrous zirconium chloride is evaporated, transferred with an inert gas such as nitrogen into the mixing region of a conventional burner, therein mixed with hydrogen and silicon tetrachlorlde KWK:939y I- Il i i li i_ I i i ll i -3in a ratio resulting in the correspondingly composed mixed zirconium oxide, that the four-component mixture is burnt in a reaction chamber, and that thereafter the corresponding solid mixed zirconium oxide is separated from the gaseous reaction product and, if necessary, liberated from hydrogen chloride by heating in moist air.

Another process for producing the pyrogenically produced mixed zirconium oxide, which was obtained particularly by flame hydrolysis and which contains from 5 to 95% by weight of silicon dioxide as a component of the mixed oxide, is characterised in that the silicon tetrachloride is mixed with hydrogen and that the resulting mixture is introduced into the flame via an annular nozzle at the burner nozzle.

In another embodiment of the invention the base metal may further contain a pyrogenically produced zirconium oxide, which was obtained particularly by flame hydrolysis, and which, if necessary, is doped with 0 i^ 15 rare-earth oxides.

°OoO In a special embodiment of the invention, the zirconium oxide can have a surface area ranging from 45+10 to 100+10 m 2 The tamped density can amount to 750-1000 g/liter.

oo. The molar ratio of rare-earth oxide to zirconium oxide can range from 0.5 to 8%.

The rare-earth elements La, Y, and Ce can be contained in the zirconium oxide.

The process of producing the pyrogenic zirconium oxide, obtained particularly by flame hydrolysis and, if necessary, doped with rare-earth Uo 25 oxides, is characterized in that pyrogenically produced zirconium oxide, obtained particularly by flame hydrolysis, is dispersed in water, doped, if o. °ta necessary, with salts of rare-earth elements such as yttrium, and spray dried.

In an embodiment of the invention, a compound of the group formed by 30 polyvinyl alcohols and polyvinyl glycols, a combination of the two, can be added as a binder to the aqueous dispersion. The concentration of the aqueous dispersion can range from 10 to 50% by weight.

In another embodiment of the present invention the base material may further contain a pyrogenically produced mixed oxide of zirconium oxide and titanium dioxide, obtained particularly by flame hydrolysis.

KWK:939y n ~1 -4- The mixed oxide of zirconium oxide and titanium dioxide can be manufactured in the same fashion as the mixed oxide of zirconium oxide and silicon dioxide after replacing silicon tetrachloride by titanium tetrachloride.

In another embodiment of the present invention the base material may further contain a pyrogenically produced mixed oxide of aluminium oxide and titanium oxide obtained particularly by flame hydrolysis.

The mixed oxide of aluminium oxide and titanium oxide can be produced in the same fashion as the mixed oxide of zirconium oxide and titanium oxide after replacing zirconium tetrachloride by anhydrous aluminium chloride.

In another embodiment of the present invention the base material may further contain a pyrogenically produced mixed oxide of zirconium oxide and silicon dioxide, obtained specifically by flame hydrolysis.

.0"'15 In a particular embodiment of the invention, the mixed oxide of o oo zirconium oxide and silicon dioxide can have a surface area of from 45±5 m 2 /g to 350+10 m 2 The tamped density can amount to 250-1500 g/liter.

The mixed oxide of zirconium oxide and silicon dioxide can be oo0c° manufactured as follows by dispersing in water pyrogenically produced mixed oxide of zirconium oxide and silicon dioxide, obtained particularly by flame hydrolysis, by adding ammonia, if necessary, and by spray-drying.

In another embodiment of the invention the base material may further contain a pyrogenically produced silicon dioxide, obtained particularly by 0 flame hydrolysis, which is dispersed in water, mixed with ammonia, if necessary, and spray-dried.

In a particular embodiment of the invention, the silicon dioxide may have the following physicochemical characteristics: specific surface area ranging from 45±5 'tg to 370+10 m 2 /g and tamped density ranging from 200 to 420 g/liter In another embodiment of the present invention the base material may further contain a pyrogenically produced silicon dioxide which was obtained particularly with the arc process, is dispersed in water, mixed with ammonia, if necessary, and spray-dried.

In a particular embodiment of the invention, the silicon dioxide can have the following physiochemical characteristics: specific surface area 150±30 m 2 /g and tamped density 500±50 g/liter.

KHK:939y 4A In another embodiment of the present invention, the base material may further contain a pyrogenically produced zirconium oxide, which was obtained particularly by flame hydrolysis, is mixed in aqueous dispersion with pyrogenically produced silicon dioxide obtained particularly by flame hydrolysis, mixed with ammonia, if necessary, and spray-dried.

0 t0 00 o n o 0 00 D 0 0 0 0 i J J 0 0 0 00 Sooo0 S o o 3 d 0 0 a 4 0I I, 4 £I

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In a particular embodiment, the mixed oxide can have the following 2 physicochemical characteristics: specific surface area 45±5 m /g and tamped density 200-1500 g/liter.

The substances of the invention can be advantageously used to produce ceramic materials. The specific advantages are: 1. The products are very fine-grained and therefore can be easily fused.

2. The products are of high pu-ity (C1 can be quantitatively removed by deacidification).

3. The mixed oxides can be produced in any proportion of the ingredients; a highly homogeneous dispersion of the oxides is obtained.

4. The oxides usually develop in their high-temperature phases which, in the case of oxides precipitated from a solution, are obtained only by calcination at high temperatures.

The process is a continuous process and therefore economically advano tageous.

o, 6. In spray-drying, the well-defined primary particles and the crystal S structure of the pyrogenically produced oxides or mixed oxides, obtained 00. particularly by flame hydrolysis, remain unchanged. The products experience o o o° only microgranulation; in this way dense structures, suitable for fusing, are obtained without previous particle growth.

DETAILED DESCRIPTION OF EXAMPLES 0a 0 Example 1 °oo By flame hydrolysis of zirconium tetrachloride, zirconium oxide, ZrO 2 is produced as the initial material.

oo The conditions of the reaction are as follows: air of the reaction: 1.0 Nm 3 /h

H

2 0.4 Nm 3 /h carrier gas N 2 1.0 Nm 3 /h ZrCl 4 evaporator: 350 °C initial material: 400 n ZrCl 4 /h surface area: 104 m 2 /g powder density: 53 g/liter analyses: 2.66 C1-, 160 ppm Si0 2 Crystal structure analysis reveals tetragonal ZrO 2 (ASTM No.

17.923) as the principal phase of the product and small admixtures of monoclinic ZrO 2 (ASTM No. 13.307). Photographs obtained with transmission electron microscopy show agglomerated spherical particles with an average diameter of 8-10 nm (Figure 1).

5 Example 2 Four g of polyethylene glycol (PEG 20,000 of the company Merck) and 1 g of polyvinyl alcohol (Mowiol 3-83 of the company Hoechst) are dissolved in 500 ml water and 100 g of zirconium oxide of Example 1 are added by stirring. After that, the suspension is mixed with 165.7 ml of an yttrium acetate solution having a concentration of 38.7 g Y/liter. The concentration of solids was adjusted to 10% by addition of water, and the dispersion was homogenised and spray-dried. The product has a powder density of 1015 g/liter or a tamped density of 1180 g/liter and a specific surface area of m Phase analysis based by x-ray diffraction reveals an unmudified tetragonal crystal structure of the zirconium oxide. The appended rasterelectron microscopical picture (Figure 2) shows the tight packing of the primary particles in the microgranulates.

Example 3 A mixed aluminium-titanium oxide is produced by joint flame S hydrolysis of A1C1 3 and TiC1 4 The conditions of the reaction are as follows: air of the reaction: 0.5 Nm 3 /h

H

2 0.2 Nm 3 /h carrier gas A1C1 3 0.8 Nm 3 /h S carrier gas TiC1 4 30 liter/h S AlC13 evaporator: 235 °C TiC1 4 receiver: 137 °C initial materials: 286 g/h AIC1 3 117 ml/h TiC1 4 analyses: 6 4

~LI-

Example 4 The mixed zirconium-titanium oxide is produced by joint flame hydrolysis of zirconium chloride and titanium chloride.

The conditions of the reaction are as follows: air of the reaction: 0.5 Nm 3 /h

H

2 0.2 Nm 3 /h carrier gas ZrCl 4 0.5 Nm 3 /h carrier gas TiCl4: 30 liter/h ZrCl 4 evaporator: 350 °C TiC14 receiver: 139 °C initial materials: 214 g/h ZrCl 4 167 ml/h TiC1 4 analyses: powder density 54 g/liter, surface area 66 m /g o Example 5 Zr0 2 /TiO 2 o Unless otherwise specified, reaction conditions as in Example 4.

000 S Air of the reaction: 1.0 Nm 3 /h S H2: 0.4 Nm 3 /h initial materials: 789 g/h ZrCl 4 279 ml/h TiC1 4 analyses: surface area 66 m2/g o°oExample 6 ZrO 2 /TiO 2 o 2 Conditions of the reaction: S air of the reaction:

H

2 carrier gas ZrC1 4 carrier gas TiC1 4 ZrCl 4 evaporator: TiC14 receiver: initial materials: analyses: powder density 0.75 Nm 3 /h 0.30 Nm 3 /h 0.50 Nm 3 /h 30 liter/h 345 °C 139 °C 88 g/h ZrCl 4 521 ml/h TiC1 71 g/ter, surface area 50 m 71 g/liter, surface area 50 m2/g 7 Example 7 Zr02/Si0 2 Conditions of the reaction: air of the reaction:

H

2 carrier gas ZrC1 4 carrier gas SiC1 4 ZrCl 4 evaporator: SiC1 4 receiver: initial materials: analyses: powder de 1.0 Nm 3 /h 0.4 Nm3/h 0.8 Nm3/h 30 liter/h 400 °C 58 OC 330 g/h ZrCl 4 23 ml/h SiC1 nsity 60 g/iter, surface area 109 m /g nsity 60 g/liter, surface area 109 m2/g 0 Cr i 20 01 Example 8 Zr02/SiO2 Conditions of the reaction: air of the reaction:

H

2 carrier gas SiC14: carrier gas ZrC14: ZrC1 4 evaporator: SiCl 4 receiver: initial materials: 0.6 Nm 3 /h 0.25 Nm3/h 30 liter/h 0.4 Nm 3 /h 400 °C 58 °C 70 g/h ZrCl 4 340 ml/h SiCl1 0.24% C1-, powder density 24 g/liter analyses: surface area 333 m2/g, 0000 o0 Example 9 Zr0 2 /Si0 2 See Example 11 for the conditions of the reaction.

ZrCl 4 evaporator: 400 °C SiC1 4 receiver: 54 °C initial materials: 350 g/h ZrCl 4 ml/h SiCl analyses: powder density 50 g/liter, 0.62 C, surface area 80 m analyses: powder density 50 g/liter, 0.62% C1, surface area 80 m2/g 8 Example 10 ZrO 2 /SiO 2 See Example 11 for the conditions of the reaction.

ZrCl 4 evaporator: 400 00 SiCl 4 receiver: 60 00 initial materials: 120 glh ZrCl 4 550 liter/h SiCl 4 2 analysi s: surface area 253 m /g Example 11 ZrO 2 /SiO 2 Conditions of the reaction: air of the reaction: 0.6 Nm 3 /h H 2 0.25 Nm 3 /h carrier gas ZrCl 4 0.4 Nm 3 /h carrier gas Sil 430 liter/h ZrCl 4 evaporator: 400 00 Sicl 4receiver: 59 00 initial materials: 70 g ZrCl 4 275 ml SiCl 4 2 analyses: powder density 30 g/liter, 0.33% CY-, surface area 264 m /g 0 0 0 0 10 D0 0 C,00 0 040 9-

I

Example 12 One hundred g of a commercial silicic acid (Aerosil® 200), obtained by flame hydrolysis, or of a likewise commercially available silicic acid (TK 9000), obtained in an arc, were stirred into water in the concentrations listed in Table 1; the dispersions were adjusted to pH 8 with ammonia, if necessary, and spray-dried. The characteristics which the products had before and after the treatment, can be inferred from Table 1.

Table 1 Comparative data of the pyrogenic silicon dioxides oxide concentration by weight) of solids pH specific surface area (m 2 /g) tamped density (g/liter) A 200 initial material 201 (silicic acid 10 3.6 187 180 prod. by flame 10 8 196 210 hydrolysis 20 3.4 183 400 TK 900 initial material 150 100 (silicic 10 3.8 152 470 acid prod. 10 8.0 136 540 with an arc) 20 3.5 154 550 Photograph obtained of product with appended (Figure 3).

raster-electron microscope is Example 13 One hundred gram of the zirconium oxide of Example 1 were suspended in 850 ml and the equimolar amount (48.8 g) of a commercial silicon dioxide obtained by flame hydrolysis (Aerosil® 200) was added in portions to the suspension. The mixture was homogenised with the Thurax mixer and spray-dispersed. The product has a specific surface area of 125 m2/g and a tamped density of 475 g/liter.

0 L Example 14 Mixed Zr02/SiO 2 oxide was produced by flame hydrolysis under the following reaction conditions: air of the reaction: 0.6 Nm 3 /h

H

2 0.25 Nm 3 /h carrier gas ZrC1 4 0.4 Nm 3 /h carrier gas SiC1 4 30 liter/h ZrCl 4 evaporator: 400 °C SiC14 receiver: 58 °C initial materials: 190 g ZrCl 4 ml SiC1 4 analyses: powder density 39 g/liter, surface area 130 m 2 0.17% C1 One hundred g of the mixed oxide obtained in this fashion were stirred into 900 ml water and spray-dried. The spray-dried product had a specific surface area of 142 m 2 /g and a powder density of 370 g/liter or a tamped density of 440 g/l.

o 0 11

Claims

1. A base material when used for the manufacture of non-porous ceramic material, wherein the base material is characterized in that it contains a pyrogenically produced mixed oxide of zirconium oxide and silicon dioxide dispersed in water and spray-dried, and which base material is not obtained as a gel.

2. A base materiai according to claim 1, characterized in that the mixed oxide is produced by flame hydrolysis.

3. A base material according to claim 1 or claim 2 further characterized in that it contains at least one of: pyrogenically produced zirconium oxide whicn was dispersed in water and spray-dried; pyrogenically produced zirconium oxide and titanium dioxide which was dispersed in water and spray dried; pyrogenically produced aluminium oxide and titanium oxide which was dispersed in water and spray-dried; pyrogenically produced silicon dioxide which was dispersed in water and spray-dried; pyrogenically produced zirconium dioxide which was dispersed in an aqueous liquid with a pyrogenically produced silicon dioxide and spray-dried thereafter.

4. A base material according to claim 3, characterized in that (a) to are produced by flame hydrolysis.

A base material according to claim 3, characterized In that (d) is produced by the arc process.

6. A base material according to any one of claim 3 to characterized in that is doped with rare-earth salts.

7. A base material according to claim 6, characterized in that the rare-earth salts are yttrium salts.

8. A base material according to claim 2, characterized in that the mixed oxide contains from 5 to 95% by weight of silicon dioxide and 95 to by weight of zirconium oxide.

9. A process of producing a base material as defined in claim 8 which process comprises evaporating anhydrous zirconium chloride, transferring the anhydrous zirconium chloride with an inert gas into a mixing region of a conventional burner, therein mixing with hydrogen and silicon tetrachloride In a ratio resulting In a pyrogenlcally produced KK:939y 13 mixed zirconium oxide, the mixture is then burnt in a reaction chamber to produce the mixed zirconium oxide and a gaseous product, and thereafter the solid mixed oxide is separated from the gaseous reaction product and, whenever necessary, liberated from hydrogen chloride by heating in moist air.

A process according to claim 9, characterized in that the inert gas is nitrogen.

11. A process according to claim 9 or claim 10, characterized in that the silicon tetrachloride is mixed with hydrogen and that the resulting mixture is introduced into a flame of the conventional burner via an annular nozzle at a burner nozzle of the conventional burner.

12. A base material when used for the manufacture of ceramic materials, substantially as hereinbefore described with reference to any one of Examples 8 to 11 or 14. DATED this TWENTY-NINTH day of AUGUST 1990 Degussa AG Patent Attorneys for the Applicant SPRUSON FERGUSON s i KNK:939y