CN1069846C - Sol-gel method for preparing yttrium oxide blended zirconium oxide ceramic micro filter film - Google Patents

Abstract

The present invention relates to a sol-gel method for preparing inorganic ceramic films, which comprises: ZrOCI2.8H2O and Y2O3 are used as initial raw materials for preparing a mixed water solution; polyethylene glycol is used as an additive; ammonia water is used for the coprecipitation of yttrium and zirconium; a hydrochloric acid peptization method is used for preparing the coprecipitation containing yttrium and zirconium; a hydrochloric acid peptization method is used for preparing sol containing yttrium and zirconium, and the sol is coated on the surface of a base bottom; after the sol is placed for dehydration drying in certain humidity, the sol is slowly heated to the temperature of 460 to 850 DEG C in a furnace, and the temperature is preserved for over 1.5 hours; next, the is cooled according to the temperature of the furnace, and prepared zirconium oxide solid solution ceramic microfiltration films doped with yttrium oxide have the advantages of even film layers and narrow pore diameter distribution.

Description

A sol-gel method for preparing yttria-doped zirconia ceramic microfiltration membrane

The invention belongs to the technical field of inorganic ceramic membrane and sol-gel method.

Generally, the inorganic ceramic membrane adopts a multilayer structure, with a coarse-porous ceramic support as the bottom layer, and a layer of membrane layer with a pore size of 0.1-1 μm is coated on it to form a microfiltration membrane that can be used for separation. The layer membrane is called the middle layer or the transition layer; if a top layer membrane with a smaller pore size (2nm to 100nm) is formed on it, an ultrafiltration membrane is formed. Inorganic ceramic membranes can be used in food, beverage, metallurgy, medicine, bioengineering, environmental governance, petrochemical and several high-tech fields.

The composite oxide system of yttria and zirconia is an excellent high temperature ceramic material. When the Y content is 2-5 mol%, a partially stable zirconia tetragonal solid solution (TZP ceramics) is formed, which is a high-performance tough ceramic; when the Y content is 8-25 mol%, a cubic structure is formed. Yttria-stabilized zirconia solid solution (YSZ for short), which is a high-temperature oxygen ion conductor, has excellent thermal and chemical stability at high temperatures. An optimal material that allows oxygen to penetrate and can be used at high temperatures (above 1000°C) required by the process. In the field of inorganic ceramic membranes that has risen in recent years, zirconia-based materials are also very eye-catching. The main reason is not only the ionic conductivity of the Y ₂ O ₃ -ZrO ₂ solid solution system, but also its high-temperature chemical corrosion resistance and structural integrity. The stability is better than the alumina ceramic membrane which has been extensively researched and applied. However, there are very few research reports on ZrO ₂ ceramic membranes in the world at present, and there are even fewer research reports on Y ₂ O ₃ -ZrO ₂ system ceramic membranes.

According to Sweden's "Key Engineering Materials" (Key Engineering Materials) 1991, volume 61-62, page 383, the γ-Al ₂ O ₃ film phase from γ-Al ₂ O ₃ to α-Al ₂ O ₃ occurs above 850 °C Change, the pore size will increase abnormally, which will cause damage to the film performance and affect the film quality. In addition, the γ-Al ₂ O ₃ film layer has poor corrosion resistance to strong acid and alkali, and the γ-Al ₂ O ₃ film coated with zirconia layer, its thermal stability is significantly better than that of zirconia ceramic film, and it is resistant to high temperature chemical corrosion. However, this paper only reports the research on ZrO ₂ ceramic membranes, and does not involve the Y ₂ O ₃ -ZrO ₂ system.

The American Journal of Materials Research (Journal of Materials Research) reported on page 1073, Volume 6, Issue 5, 1991, that zirconium alkoxide compounds were used as raw materials and a sol-gel method of alkoxide hydrolysis was used to obtain nano-sized zirconia ceramic membranes. However, the alkoxide of zirconium (and yttrium) is expensive, and there is no commercial sale in China; and the sol particles formed by the hydrolysis of the alkoxide are too small to easily penetrate into the pores of the ceramic substrate and cause blockage.

The purpose of the present invention is to propose a kind of cheap and easy-to-obtain starting raw material, adopt sol-gel method, select suitable non-ionic surfactant as additive, prepare high-quality yttrium oxide-zirconia composite oxide ceramic microfiltration Membrane or interlayer approach.

The method for preparing yttrium oxide-doped zirconia ceramic microfiltration membrane or intermediate layer is characterized in that it comprises the following steps:

1. Using ZrOCl ₂ 8H ₂ O and Y ₂ O ₃ as starting materials, it is prepared into a mixed solution containing Zr and Y at a concentration of 0.1-1.0 mol/l and containing 2-10% by weight of polyethylene glycol, wherein Y and Zr The molar ratio is 0.02-0.25;

2. Zirconium yttrium sol was prepared by co-precipitation followed by peptization;

At a temperature of 80-90°C and stirring conditions, slowly add ammonia water containing 1-10% polyethylene glycol dropwise to the above-mentioned zirconium-yttrium mixed solution until a precipitate is formed, and then add hydrochloric acid dropwise until the precipitate disappears, forming a zirconium-yttrium sol;

3. To form a gel film on a substrate:

The above-mentioned zirconium yttrium sol is coated on the surface of the selected base material to form a sol film, and placed under constant humidity conditions of room temperature and relative humidity of 55-85% to dehydrate until the weight is basically constant to form a gel film.

4. Burning to form a ceramic microfiltration membrane:

Put the above-mentioned material for forming a gel film in an electric furnace, raise the temperature to 460-850°C at a rate lower than 20°C/hour, then keep the temperature for not less than 1.5 hours, and cool with the furnace to obtain yttria-doped zirconia Solid solution ceramic microfiltration membrane.

In order to make the gel film layer uniform and have an appropriate thickness, the process of sol coating in the above step 3 and dehydration at room temperature and humidity can be repeated several times;

In order to better avoid the agglomeration of the precipitate formed when ammonia water is dripped into the yttrium-zirconium mixed solution, and ease the stress of the gel film during the dehydration and drying process, and prevent the film layer from cracking, 2-10 The molecular weight of % weight is polyethylene glycol of 200-400, and the polyethylene glycol of molecular weight of 1000-2000 that accounts for 1-10% by weight is added in ammoniacal liquor;

The method can be used to prepare yttria-doped zirconia ceramic microfiltration membranes on dense or porous ceramics, quartz, silicon wafers, glass or metal material substrates.

Since the present invention uses ZrOCl ₂ 8H ₂ O, which is easy to obtain in China and relatively cheap in price, as the starting material, the cost of preparing microfiltration membranes is reduced, and the technology is easy to popularize, apply and implement; The method for preparing yttrium-zirconium-containing sol is simple and easy to control, supplemented by adding two polyethylene glycols with different molecular weights, the prepared sol has good dispersion, high stability, and uniform particle size, which improves the performance of the gel film layer. Defects such as cracks and holes are not easy to appear during drying; the present invention adopts the gel film formed by dehydration and drying at room temperature and constant humidity, adopts a slower heating rate of less than 20°C/hour to an appropriate temperature, and then heats it for more than 1.5 hours. The process of furnace cooling can ensure that the prepared ceramic film has no cracks, no holes, and a narrow range of pore size distribution. By adopting the method of the present invention, Y ₂ O ₃ — ZrO ₂ composite oxide ceramic membrane, this ceramic membrane can be used as a high-temperature microfiltration membrane that can resist strong acid and alkali corrosion, and the yttrium-zirconium membrane layer can also be used as an intermediate layer (transition layer) to further prepare a smaller pore size and a larger size. On the nanometer or sub-nanometer top membrane, an ultrafiltration membrane or a dense membrane is formed to meet the needs of gas separation, selective oxygen permeability or oxygen enrichment. If it is on a high-quality ceramic substrate with a smooth surface, it is easier to obtain a uniform high-quality film layer. The zirconia microfiltration membrane or interlayer membrane doped with yttrium oxide prepared by the method of the present invention has more advantages than the existing γ-Al ₂ O ₃ membrane, and this membrane avoids the phase transition of the aluminum oxide membrane at high temperature The defects that cause damage to the membrane performance can withstand high temperature, strong acid and strong alkali corrosion, good chemical stability, especially good oxygen ion penetration performance that aluminum oxide membranes do not have, so that they can meet the needs of low energy consumption oxygen enrichment and Special needs of organic chemical processes involving partial oxidation.

Below is an embodiment of the present invention:

Dissolve ZrOCl ₂ ·8H ₂ O in water to prepare an aqueous solution of ZrOCl ₂ with a concentration of 0.8016M; dissolve Y ₂ O ₃ with hydrochloric acid to prepare an aqueous solution of YCl ₃ with a concentration of 0.6160M.

Take 50ml of the above-mentioned ZrOCl ₂ aqueous solution and 12ml of YCl ₃ aqueous solution. After mixing, add 4g of polyethylene glycol (PEG200) with a molecular weight of 200. After dissolving, pour it into a flask and heat it to 90°C in an oil bath. Under stirring, slowly drop into the ammonia water containing 5% polyethylene glycol with a molecular weight of 1540 and a concentration of 5M until the milky white sticky paste precipitate no longer disappears, and continue to slowly dissolve under stirring conditions at 90 ° C. Add hydrochloric acid with a concentration of 3M dropwise until the precipitate completely disappears, forming a clear colloidal solution of yttrium and zirconium. The prepared sol was sealed and stored for later use.

Take an α-Al ₂ O ₃ porous ceramic substrate with a thickness of 2 mm, a porosity of 42%, and a pore diameter of 2-4 μm, first clean it with ethanol and then with deionized water, and dry it until it is fully dry, and then immerse it in the above prepared In the colloidal solution of yttrium and zirconium, take it out after immersing for 20 seconds, put it in a constant humidity chamber with a saturated saline solution (relative humidity is 70% at 25°C), place it at room temperature for a day and night, take it out, and put it in the yttrium-zirconium again Immerse in the colloidal solution for 20 seconds, and then place it in a constant humidity chamber with saturated saline solution for a day and night. After taking it out, put it into a muffle furnace, raise the temperature from room temperature to 600°C at a rate of 10°C/hour, keep the temperature constant for 2 hours, take it out after cooling with the furnace, and obtain the yttria-stabilized zirconia microfiltration membrane.

Attached Figure 1 is a scanning electron micrograph of a typical YSZ film section on a porous α-Al ₂ O ₃ substrate. The pore size of the substrate is 2-4 μm, and the thickness of the YSZ film is about 3 μm. It can be seen from the photos that the YSZ film layer has a good bite with the α-Al ₂ O ₃ substrate, but it does not diffuse into the pores of the substrate layer.

Accompanying drawing 2 is the X-ray diffraction spectrogram of baseless gel grinding into powder without burning at different temperatures, showing that the YSZ film layer is a standard face-centered cubic structure, measured after burning the baseless gel, and the pore size is 100nm.

Claims (1)

1. the preparation method of the zirconium oxide ceramic micro filter film of a Yttrium oxide doping is characterized in that with ZrOCl ₂8H ₂O and Y ₂O ₃Be starting raw material, be mixed with and contain Zr and Y concentration 0.1-1.0mol/l that contain the mixing solutions of polyoxyethylene glycol 2-10% weight, wherein the mol ratio of Y and Zr is 0.02-0.25; 80-90 ℃ and stir under, in the solution of above-mentioned Y of containing and Zr, drip contain polyoxyethylene glycol 1-10% weight ammoniacal liquor to becoming precipitation, dripping hydrochloric acid is to precipitating disappearance again; The sol coating that forms is formed dissolved glue film on base material, be that to be placed to weight under the 55-85% condition constant substantially in room temperature and relative humidity, forms gel-film; Be warming up to 460-850 ℃ with the speed that is lower than 20 ℃/hour in electric furnace, insulation is more than 1.5 hours, furnace cooling.

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