KR20070032366A - Yttrium-zirconium mixed oxide powder - Google Patents

Abstract

Nano-scale yttrium-zirconium mixed oxide powder in the form of agglomerated primary particles with the following physical-chemical parameters:-BET surface area: 40 to 100 m ² / g,-d _n = 3 to 30 nm, d _n = average , Number-related primary particle diameter, yttrium content measured by chemical analysis and calculated by yttrium oxide Y ₂ O ₃ , 5 to 15% by weight relative to mixed oxide powder,-measured by TEM-EDX Yttrium content of each primary particle corresponding to the content in the powder, calculated as yttrium oxide Y ₂ O ₃ , ± 10%, content at room temperature for the mixed oxide powder, measured by X-ray diffraction As-monoclinic zirconium oxide <1 to 10% by weight,-tetragonal zirconium oxide to 10 to 95% by weight,-monoclinic zirconium oxide content after heating for 2 hours at 1300 ° C. is less than 1% by weight,-carbon content Less than 0.2% by weight. It is prepared by atomizing a solution of an organic solvent containing an organic zirconium oxide precursor and an inorganic yttrium precursor and burning it in a combustion gas / air flame to separate gas and solid products. It can be used as a ceramic base material.

Nano-scale yttrium-zirconium mixed oxides, monoclinic, tetragonal

Description

Yttrium-zirconium mixed oxide powder {YTTRIUM-ZIRCONIUM MIXED OXIDE POWDER}

The present invention relates to yttrium-zirconium mixed oxide powders, their preparation and use.

Zirconium oxide may exist in three crystal structures, depending on the temperature, monoclinic, tetragonal, and cubic.

Starting from the melt, it is assumed that cubic crystals are formed at about 2680 ° C and tetragonal structures are formed at about 2370 ° C. The change from tetragonal to monoclinic phase occurs at about 1170 ° C. and is accompanied by a volume increase of about 3 to 5%. This volume increase can cause stresses and cracks in the structural components produced above the tetragonal / monoclinic transition temperature.

The phase transition can be suppressed by doping with yttrium oxide, calcium oxide, cerium oxide or magnesium oxide to stabilize the tetragonal structure of zirconium oxide.

Yttrium-stabilized tetragonal zirconium oxide is understood to be zirconium oxide doped with about 3 mol% yttrium oxide. Partially yttrium-stabilized zirconium oxide is zirconium oxide doped with about 3 to 8 mol% yttrium and is understood to consist of a cubic matrix with tetragonal inclusions. Fully yttrium-stabilized zirconium oxide is zirconium oxide doped with about 8 mol% yttrium and is understood to have a cubic crystal structure.

Yttrium-stabilized zirconium oxide can be obtained, for example, by wet-chemistry and pyrogenic reactions.

US 6703334 describes a method for preparing yttrium-stabilized zirconium oxide powders having tetragonal and / or cubic crystal structures, in which zirconium carbonate particles and yttrium compounds are reacted together, wherein the two reaction partners Solid, one solid and one liquid, one solid and one gas, and the resulting product is then calcined. Information on the particle size and specific surface area of the resulting yttrium-stabilized zirconium oxide powder was not presented.

US 5155071 claims partially yttrium-stabilized zirconium oxide powder in the form of aggregated primary particles, where the aggregates have an average diameter of less than 150 nm and yttrium is uniformly dispersed in zirconium oxide. Partially yttrium-stabilized zirconium oxide powders are prepared by burning a uniform mixture consisting of a zirconium precursor and a yttrium precursor. An important feature is that the zirconium oxide precursor, which is generally zirconium tetrachloride, is vaporizable but the yttrium precursor is not vaporizable, the reaction is not carried out. Thus, the yttrium precursor supplies the combustion reaction in solid form. The disadvantage of this method is that a powder with only a low BET surface area is obtained. In addition, it was found that although the yttrium dispersion is not uniform, there exist regions having different yttrium concentrations. Moreover, no information is given on the sintering behavior of partially yttrium-stabilized zirconium oxide powders.

Beierer et al. (Freiberger Forschungsheft 1998, A841, pages 281-295) described a homogeneous solution of zirconium alkoxide with yttrium (II) acetylacetonate, with very high oxygen excess and very short flame residence time (about 1 yttrium-stabilized zirconium oxide obtained by spraying into an oxyhydrogen flame in ms). Depending on the yttrium content, square or cubic zirconium oxide in the form of spherical particles with a BET surface area of 30 m ² / g is obtained. This method is not economical due to high oxygen excess and expensive yttrium precursors.

Juarez et al. (Journal of the European Ceramic Society 20 (2000), pages 133-138) are yttrium-stabilized, obtained by exothermic redox reactions of nitrate and citrate ions in nitrate-citrate gels. Zirconium oxide powders are described. After grinding, the resulting powder has a particle size of 125 nm and monoclinic zirconium oxide content of about 20%. The gel is obtained by dissolving zirconium oxychloride and yttrium acid in nitric acid, removing chlorine, and then adjusting the pH to 7 with citric acid and ammonium hydroxide. The solution is then heated to 200-250 ° C. on a hot plate. At that temperature, an exothermic reaction between nitrate and citrate ions is initiated. The carbon-containing impurities are then removed at 350 ° C. over 1 hour and then calcined at 600 ° C. This method is not very economical and is not suitable for scale up.

EP-A-1285881 can have a BET surface area of 1 to 600 m ² / g, contain less than 0.05% by weight of chloride, and change any phase on monoclinic during storage at room temperature or during annealing (about 900 ° C.). It also claims a tetragonal yttrium-zirconium oxide mixed oxide powder, which is not shown. Mixed oxide powders are prepared by atomizing a zirconium oxide precursor and a yttrium oxide precursor together (two-component nozzle) or separately (three-component nozzle) in an oxyhydrogen flame with the aid of a carrier gas. It was found that yttrium was more uniformly dispersed in zirconium oxide when using a two-component nozzle, but it was found that higher BET surface area and / or higher yttrium content could not be obtained (Examples 1 to 3).

It is an object of the present invention to provide a nano-scale yttrium-stabilized zirconium oxide in which yttrium is dispersed as uniformly as possible in zirconium oxide, and after sintering only small amounts of monoclinic zirconium oxide or monoclinic zirconium oxide do not appear. will be.

It is a further object of the present invention to provide an inexpensive method for producing this powder.

The present invention provides nano-scale yttrium-zirconium mixed oxide powders in the form of aggregated primary particles having the following physical-chemical parameters:

BET surface area: 40 to 100 m ² / g,

d _n = 3 to 30 nm, d _n = mean, number-related primary particle diameter,

A yttrium content measured by chemical analysis and calculated as yttria Y ₂ O ₃ , from 5 to 15% by weight relative to the mixed oxide powder,

The yttrium content of each primary particle corresponding to the content in the powder, measured by TEM-EDX and calculated by yttrium oxide Y ₂ O ₃ , is ± 10%,

As a content at room temperature for the mixed oxide powder, measured by X-ray diffraction

Monoclinic zirconium oxide <1 to 10% by weight,

10 to 95% by weight of tetragonal zirconium oxide,

-After heating for 2 hours at 1300 ℃ monoclinic zirconium oxide content is less than 1% by weight,

A carbon content of less than 0.2% by weight.

X-ray diffraction evaluation is performed according to Rietveld.

More preferably, the BET surface area of the mixed oxide powder according to the present invention may be 45 to 65 m ² / g.

It may also be desirable for the mixed oxide powders according to the invention to have a d _n / d _a ratio of 0.5 to 0.9, where d _n is the average, water-related primary particle diameter, and d _a is the average over the surface One average primary particle diameter.

It may also be desirable for the mixed oxide powders according to the invention to have an average aggregate diameter of less than 200 nm.

It may also be desirable for the mixed oxide powders according to the invention to have an OEM surface area / BET surface area ratio of greater than 1.1. The OEM surface area is expressed as OEM = 6000 / (d _a x Rho), where d _a = particle diameter averaged across the surface, Rho = 6.05 g / cm ³ zirconium oxide. It may be particularly desirable for the ratio of OEM surface area / BET surface area to exceed 1.2.

It may also be desirable for the mixed oxide powders according to the invention to have no micropores and to have a mesopore content of less than 0.2 ml / g in the range of 2 to 30 nm.

The invention also provides a process for the preparation of the mixed oxide powder according to the invention, in which

Organic zirconium oxide precursors and inorganic yttrium oxide precursors dissolved in organic solvents or organic solvent mixtures, respectively, subsequently mixed according to the desired ratio of zirconium and yttrium,

-Atomizing this solution mixture with air (atomic air) or inert gas,

It is mixed with a gas mixture containing combustion gas and air (primary air), allowing it to combust into the reaction space in flames,

Cooling the hot gas and the solid product, then separating the solid product from the gas,

here,

The content of the zirconium oxide precursor in the solution is at least 15% by weight, at most 35% by weight, preferably 20-30% by weight,

In each case, additionally introducing reaction space air (secondary air) or an inert gas in an amount corresponding to 50% to 150% of the amount of primary air,

Lambdas defined as the ratio of oxygen required for the combustion of oxygen / combustion gases present in the air used are from 2 to 4.5,

The residence time of the precursor in the flame is from 5 to 30 ms, preferably from 10 to 20 ms,

The content of the precursor solution in the amount of residual gas obtained after combustion of the combustion gases with air is from 0.003 to 0.006% by volume, preferably 0.004 to 0.005% by volume.

Zirconium (IV) ethanolate, zirconium (IV) n-propanolate, zirconium (IV) isopropanolate, zirconium (IV) n-butanolate, zirconium (IV) tert-butanolate and / or as organic zirconium oxide precursors Zirconium (IV) 2-ethylhexanoate can be used preferably.

Zirconium compounds generally contain 1 to 5% by weight of hafnium compounds. However, zirconium compounds may be prepared to a degree of purity of 99% by weight or more.

Like inorganic yttrium precursors, yttrium nitrate, yttrium hydrochloride, yttrium carbonate and / or yttrium sulfate may be preferably used.

Particular preference is given to using yttrium nitrate tetrahydrate.

In principle, any inorganic solvent can be used provided the inorganic yttrium precursor and the organic zirconium oxide precursor are soluble. Suitable organic solvents are methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, 2-propanone, 2-butanone, diethyl ether, tert-butyl methyl ether, tetrahydrofuran, ethyl acetate, toluene And / or benzine.

The invention also provides a filler of the mixed oxide powder according to the invention, as a carrier, as a catalytically active component, in a fuel cell, as a dental material, as an additive in the silicone and rubber industry, for the preparation of membranes, as liquid systems It relates to the use as color pigments in the surface coatings industry, for thermal protection stabilization, in order to adjust their rheological properties.

analysis:

BET measured according to DIN 66131

TEM / EDX: Energy Dispersive X-Ray Analysis (EDX)

TEM: Jeol 2070-F; EDX: Noran Voyager 4.2.3

Image Analysis: Primary particle and aggregate sizes were measured by image analysis. Image analysis was performed with Hitachi's H 7500 TEM device and SIS's MegaView II CCD camera. The image magnification for evaluation was 30,000: 1 with a pixel density of 3.2 nm. The number of particles evaluated was more than 1000. Prepared according to ASTM3849-89. The lower limit for detection was 50 pixels.

The contents of yttrium oxide and zirconium oxide were measured by X-ray fluorescence analysis and / or chemical analysis.

Precursor solution used:

지르코늄 18: 25.4 중량%의 산화지르코늄, 39.6 중량%의 옥탄산, 3.5 중량%의 2-(2-부톡시에톡시)-에탄올, 31.5 중량%의 화이트 스피리트(white spirit)에 상응하는 지르코늄 옥토에이트.Solution Zr-1: Octa-Soligen

Zirconium 18: zirconium octoate corresponding to 25.4 wt% zirconium oxide, 39.6 wt% octanoic acid, 3.5 wt% 2- (2-butoxyethoxy) -ethanol, 31.5 wt% white spirit .

NPZ: 28.8 중량%의 산화지르코늄, 41.2 중량%의 테트라프로판올레이트, 30 중량%의 1-프로판올에 상응하는 지르코늄 테트라프로판올레이트.Solution Zr-2: Tyzor

NPZ: zirconium tetrapropanol corresponding to 28.8 wt% zirconium oxide, 41.2 wt% tetrapropanolate, 30 wt% 1-propanol.

Solution Y-1: 30.7 wt% Y (NO ₃ ) ₃ * 4H ₂ O, 69.3 wt% acetone

Solution Y-2: 33.8 wt% Y (NO ₃ ) ₃ * 6H ₂ O, 66.2 wt% methanol

Example 1:

A solution Zr-1 in an amount of 312 g / h (based on zirconium oxide) and a solution Y-1 in an amount of 7.0 g / h (based on yttrium oxide) were mixed. The mixture remained stable and no precipitate formed.

The total amount of the mixture 1300 g / h including the solvent was then atomized with air (3.5 Nm ³ / h). The resulting droplets showed a droplet size spectrum d ₃₀ of 5 to 15 μm. The droplets were burned into the reaction space in a flame formed from hydrogen (1.5 Nm ³ / h) and primary air (12.0 Nm ³ / h). 15.0 Nm ³ / h (secondary) air was further introduced into the reaction space. The hot gas and solid product were then cooled in a cooling line. The resulting yttrium-stabilized zirconium oxide was separated in a filter.

Example 2 was carried out in the same manner, but with Zr-2 and Y-1 components. The usage amount is shown in Table 1.

Example 3 was carried out in the same manner as in Example 1. The amount of the used component is shown in Table 1.

Example 4 was carried out in the same manner as in Example 1, but was carried out with components Zr-2 and Y-1. The usage amount is shown in Table 1.

Examples 5 and 6 were carried out in the same manner as in Example 1, but the solutions Zr-2 and Y-2 were separately supplied to the flame.

The powders of Examples 1-4 according to the invention exhibited a composition generally similar to the primary particles for the yttrium and zirconium components. These values were in good agreement with those from powder analysis.

The powders of Examples 1 to 4 according to the invention exhibited a distinctive OEM surface area / BET surface area ratio. This ratio was higher than 1.1, compared to the powders of the comparative and competing samples.

The powders of Comparative Examples 5 and 6 exhibited nonuniform mixed oxide component dispersions, in particular compared to the powders according to the invention. In addition, after the heat treatment at 1300 ° C., they still contained a clear amount of monoclinic zirconium oxide.

Claims (11)

Nano-scale yttrium-zirconium mixed oxide powder in the form of aggregated primary particles having the following physical-chemical parameters: BET surface area: 40 to 100 m ² / g, d _n = 3 to 30 nm, d _n = mean, number-related primary particle diameter, A yttrium content measured by chemical analysis and calculated as yttria Y ₂ O ₃ , from 5 to 15% by weight relative to the mixed oxide powder, The yttrium content of each primary particle corresponding to the content in the powder, measured by TEM-EDX and calculated by yttrium oxide Y ₂ O ₃ , is ± 10%, As a content at room temperature for the mixed oxide powder, measured by X-ray diffraction Monoclinic zirconium oxide <1 to 10% by weight, 10 to 95% by weight of tetragonal zirconium oxide, -After heating for 2 hours at 1300 ℃ monoclinic zirconium oxide content is less than 1% by weight, A carbon content of less than 0.2% by weight. The nano-scale yttrium-zirconium mixed oxide powder according to claim 1, wherein the BET surface area is 45 to 65 m ² / g. 3. The method of claim 1, wherein d _n / d _a = 0.5 to 0.9, where d _n is the average, number-related primary particle diameter, and d _a is the average primary particle diameter averaged over the surface Nano-scale yttrium-zirconium mixed oxide powder, characterized in that). The nano-scale yttrium-zirconium mixed oxide powder according to any one of claims 1 to 3, wherein the average aggregate diameter is less than 200 nm. The method according to any one of claims 1 to 4, wherein the ratio of OEM surface area / BET surface area is> 1.1 and OEM surface area is OEM = 6000 / (d _a x Rho) where d _a = averaged over the surface. Nano-scale yttrium-zirconium mixed oxide powder, characterized by primary particle diameter, Rho = 6.05 g / cm ³ density for zirconium oxide. The nano-scale according to any one of claims 1 to 5, characterized in that it does not have micropores, and the content of mesopores in the range of 2 to 30 nm is less than 0.2 ml / g. Yttrium-zirconium mixed oxide powder. Organic zirconium oxide precursors and inorganic yttrium oxide precursors dissolved in organic solvents or organic solvent mixtures, respectively, subsequently mixed according to the desired ratio of zirconium and yttrium, -Atomizing this solution mixture with air (atomic air) or inert gas, It is mixed with combustion gas and air (primary air) to cause the mixture to burn into the reaction space in a flame, Cooling the hot gas and the solid product, then separating the solid product from the gas, here, The content of zirconium oxide precursors (calculated as ZrO ₂ ) in the solution is at least 15% by weight and at most 35% by weight, In each case, additionally introducing reaction space air (secondary air) or an inert gas in an amount corresponding to 50% to 150% of the amount of primary air, Lambdas defined as the ratio of oxygen required for the combustion of oxygen / combustion gases present in the air used are from 2 to 4.5, The residence time of the precursor in the flame is between 5 and 30 ms, The content of the precursor solution in the amount of gas obtained after combustion of the combustion gas by air is 0.003 to 0.006% by volume Method for producing a nano-scale yttrium-zirconium mixed oxide powder according to any one of claims 1 to 6, characterized in that. 8. The zirconium oxide precursor of zirconium (IV) ethanolate, zirconium (IV) n-propanolate, zirconium (IV) isopropanolate, zirconium (IV) n-butanolate, zirconium (IV) tert- And butanolate and / or zirconium (IV) 2-ethylhexanoate. The method of claim 7 or 8, wherein the inorganic yttrium precursor is selected from the group consisting of yttrium nitrate, yttrium hydrochloride, yttrium carbonate and / or yttrium sulfate. 10. The organic solvent of claim 7, wherein the organic solvent is methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, 2-propanone, 2-butanone, diethyl ether, tert. -Butyl methyl ether, tetrahydrofuran, ethyl acetate, toluene and / or benzine. The filler of the nano-scale yttrium-zirconium mixed oxide powder according to claim 1, as a carrier, as a catalytically active component, in a fuel cell, as a dental material, for the preparation of a membrane And as additives in the rubber industry, as color pigments, in the surface coating industry, for thermal protection stabilization, to adjust the rheological properties of liquid systems.