CN101508578A - Preparation Method of Heterogeneous Nucleation of LaPO4 Coated Al2O3, ZrO2 Composite Powder - Google Patents

Abstract

LaPO₄Coated with Al₂O₃、ZrO₂The non-homogeneous nucleation process of preparing composite powder features that Al in certain proportion is first mixed into the composite powder₂O₃、ZrO₂Putting the composite powder into deionized water, adding a dispersing agent for ultrasonic dispersion to prepare a suspension, and adding 50-200 ml of La (NO)₃)₃Adding the aqueous solution into the suspension, magnetically stirring for 30-100 min, and then dropwise adding La (NO) into the suspension under the magnetic stirring₃) ₃Equal volume of equal concentration Na in aqueous solution₃PO₄And (3) adding the aqueous solution at a dropping speed of 5-15 drops/min, keeping the pH value of the suspension constant in the dropping process, continuously stirring for 1-3 hours after the dropping is finished, then cleaning impurity ions in the suspension by using deionized water, drying in a drying box, and finally calcining the powder. The method has simple steps and is easy to control; not only can obtain LaPO₄And Al₂O₃、ZrO₂Weak interface between them, and can reduce soft phase LaPO₄The content of (A) can sacrifice smaller mechanical property to obtain better processing property.

Description

Preparation Method of Heterogeneous Nucleation of LaPO4 Coated Al2O3, ZrO2 Composite Powder

technical field

The invention relates to a preparation method of an inorganic composite powder, in particular to a non-uniform nucleation preparation method of a LaPO ₄ coated Al ₂ O ₃ and ZrO ₂ composite powder.

Background technique

ZTA (ZrO ₂ toughened Al ₂ O ₃ ) composite ceramics has excellent corrosion resistance, thermal shock resistance, high strength and toughness, and it will be possible to solve the reliability and durability problems that limit the application of ceramic materials. application prospects. However, the machinability of ZTA composite ceramics still limits its promotion in many aspects to a large extent. In order to improve the machinability of ZTA ceramic materials, people add LaPO ₄ to Al ₂ O ₃ , ZrO ₂ matrix, which breaks through the limitation of ceramic processing performance and makes ceramic materials have a broader application prospect. This composite ceramic has good chemical compatibility, high melting point and excellent stability in oxidizing atmosphere. However, mixing LaPO ₄ with Al ₂ O ₃ and ZrO ₂ directly requires a large amount of LaPO ₄ , and LaPO ₄ is a weak phase, adding too much will reduce the mechanical properties of the material.

The non-uniform nucleation method is a method commonly used in powder coating. It uses the coated particles as the nucleation matrix. By controlling the concentration of the coating material in the solution to not exceed the limit crystal concentration, that is, to control the non-uniform nucleation Between the critical value required for nucleation and the critical value required for uniform nucleation. Under this condition, the conditions for non-uniform nucleation and growth can be met, thereby realizing the coating process of particles. Although unique to the synthetic environment, it allows precise control of the thickness of the coated particle and its chemical composition. At present, there is no relevant report at home and abroad on the preparation of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder by non-uniform nucleation method.

Contents of the invention

The object of the present invention is to provide a preparation method of non-uniform nucleation of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder, so as to overcome the above-mentioned shortcomings in the prior art.

A kind of heterogeneous nucleation preparation method of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder, characterized in that first a certain proportion of Al ₂ O ₃ , ZrO ₂ composite powder is put into deionized water, add dispersion The agent was ultrasonically dispersed to form a suspension, and then 50-200ml of La(NO ₃ ) ₃ aqueous solution was added to the suspension, stirred magnetically for 30-100min, and then added dropwise with La(NO 3 ) 3 to the suspension under magnetic stirring. NO ₃ ) ₃ aqueous solution with equal volume and concentration of Na ₃ PO ₄ aqueous solution, the dropping rate is 5-15 drops/min, during the dropping process, keep the pH value of the suspension constant, after the dropping, continue to stir for 1~ 3h, then wash the impurity ions in the suspension with deionized water, put it in a drying oven to dry, and finally calcinate the powder.

The present invention is the first to introduce the non-uniform nucleation method into the preparation of LaPO ₄ /ZTA composite material. The steps are simple and easy to control. It can not only obtain the weak interface between LaPO ₄ and Al ₂ O ₃ and ZrO ₂ , but also reduce the soft interface. The content of phase LaPO ₄ , through this design, can sacrifice less mechanical properties to obtain better processing properties, overcome the difficulties in processing LaPO ₄ /ZTA ceramics, and make it further popularized and applied.

Description of drawings

Figure 1 is the X-ray diffraction comparison diagram of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder and uncoated composite powder (a) coated powder (b) uncoated powder.

Fig. 2 is a transmission electron microscope image of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder.

Detailed ways

The present invention selects La(NO ₃ ) ₃ 6H ₂ O, NaPO ₄ 12H ₂ O, Al ₂ O ₃ , and ZrO ₂ as raw materials, and the mass ratio of Al ₂ O ₃ to ZrO ₂ in the composite powder is 4:1. The volume ratio is 6.26:1. Prepare La(NO ₃ ) ₃ ·6H ₂ O and Na ₃ PO ₄ ·12H ₂ O into aqueous solutions with a concentration of 0.01 mol/L respectively. Before the coating process, in order to reduce particle agglomeration and obtain a well-dispersed Al ₂ O ₃ and ZrO ₂ composite powder suspension, weigh 1.5g of Al ₂ O ₃ and ZrO ₂ powder in proportion, and put it into 200ml deionized In water, NaOH solution was used to adjust the pH value of the suspension to 10, and 0.5 wt% dispersant polyammonium methacrylate (PMAA) was added, and ultrasonically dispersed for 120 min. Then 150 ml of La(NO ₃ ) ₃ aqueous solution was added to the suspension, and stirred magnetically with a stirrer for 60 min. Then the above-mentioned Na _{PO aqueous} solution of equal volume and concentration is dropped into the suspension, and the dropping speed must be controlled slowly, because if the dropping speed is too fast, it is easy to make _LaPO produce uniform nucleation and affect the coating effect, so Control the dropping rate at 15 drops/min. The whole dropping process should be carried out under magnetic stirring to keep the suspension of Al ₂ O ₃ and ZrO ₂ particles. After the dropwise addition, the suspension was continuously stirred for 2 hours, and then the impurity ions were washed with deionized water, and dried in a drying oven at 60° C. for 12 hours. Finally, the powder is calcined at 1000° C. for 2 hours to obtain LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder.

In the present invention, the LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder is tested by X-ray diffraction (XRD) and transmission electron microscope (TEM). In Figure 1, b is the XRD pattern of Al ₂ O ₃ and ZrO ₂ composite powder before coating, and a is the XRD pattern of the prepared coated powder, from which Al ₂ O ₃ and ZrO ₂ can be seen After the composite powder is coated with a layer of LaPO4, the intensity of the diffraction peaks decreases obviously, while the diffraction peaks of _LaPO4 are more obvious. The change of the intensity of the diffraction peak indicates that the surface of the α-Al ₂ O ₃ particles has been coated with a layer of LaPO ₄ . It can be seen from the transmission electron microscope photo in Figure 2 that LaPO ₄ is not coated on the surface of the composite powder of Al ₂ O ₃ and ZrO ₂ in the form of a film, but forms nano-scale fine particles and is adsorbed on the surface of the composite powder. surface, but still belongs to the core-shell coating structure, the core is composed of multiple Al ₂ O ₃ and ZrO ₂ particles, and the shell layer is composed of a layer of nano-sized LaPO ₄ particles, with a thickness ranging from 10 to 30nm.

The average particle size of the Al ₂ O ₃ and ZrO ₂ particles described in the present invention is 50-300 nm; the concentrations of the La(NO ₃ ) ₃ ·6H ₂ O and NaPO ₄ ·12H ₂ O aqueous solutions are both 0.001-300 nm. 0.1mol/L; the mass ratio of Al ₂ O ₃ to ZrO ₂ in the composite powder is 2-6:1, and the weight ratio range of Al ₂ O ₃ , ZrO ₂ composite powder to deionized water is 1: 50～300, the concentration of the added dispersant polyammonium methacrylate in the suspension is 0.1～1wt%; the pH range of the suspension in the dropping process is 1～12; the drying temperature is 40 ~100°C, the drying time is 8~16h; the calcination temperature is 800~1200°C, and the calcination time is 1~3h; the dispersant is polyammonium methacrylate, polyethylene glycol or citric acid.

Claims (8)

1, a kind of LaPO ₄ coating Al ₂ O ₃ , ZrO ₂ composite powders non-uniform nucleation preparation method, it is characterized in that at first a certain proportion of Al ₂ O ₃ , ZrO ₂ composite powders are put into deionized water, Add a dispersant for ultrasonic dispersion to make a suspension, then add 50-200ml of La(NO ₃ ) ₃ aqueous solution into the suspension, stir magnetically for 30-100min, and then dropwise add La(NO ₃ ) ₃ aqueous solution, Na ₃ PO ₄ aqueous solution with equal volume and concentration, the dropping rate is 5-15 drops/min. During the dropping process, keep the pH value of the suspension constant. After the dropping, continue to stir 1 to 3 hours, then wash the impurity ions in the suspension with deionized water, put it in a drying oven to dry, and finally calcinate the powder. 2. The non-uniform nucleation preparation method of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder as claimed in claim 1, characterized in that the average particle size of the Al ₂ O ₃ , ZrO ₂ composite powder is The diameter is about 50-300nm. 3. The non-uniform nucleation preparation method of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder as claimed in claim 1, characterized in that said La(NO ₃ ) ₃ ·6H ₂ O and NaPO ₄ ·The concentration of the 12H ₂ O aqueous solution is 0.001-0.1 mol/L. 4. The non-uniform nucleation preparation method of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder as claimed in claim 1, characterized in that Al ₂ in the Al ₂ O ₃ , ZrO ₂ composite powder The mass ratio of O ₃ to ZrO ₂ is 2 to 6:1, the weight ratio of Al ₂ O ₃ and ZrO ₂ composite powder to deionized water is in the range of 1:50 to 300, and the added dispersant polyammonium methacrylate is The concentration in the suspension is 0.1-1 wt%. 5. The non-uniform nucleation preparation method of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder as claimed in claim 1, characterized in that the pH value of the suspension during the dropwise addition ranges from 1 to 12. 6. The non-uniform nucleation preparation method of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder as claimed in claim 1, characterized in that the drying temperature is 40-100°C, and the drying time is 8- 16h. 7. The non-uniform nucleation preparation method of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder as claimed in claim 1, characterized in that the calcination temperature is 800-1200°C, and the calcination time is 1- 3h. 8. The non-uniform nucleation preparation method of LaPO ₄ coated Al ₂ O ₃ , ZrO ₂ composite powder as claimed in claim 1, characterized in that the dispersant is polyammonium methacrylate, polyethylene glycol or citric acid.

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