CN112079640A - MoSi2@ZrO2Preparation method of core-shell structure - Google Patents

Abstract

The invention discloses a method for preparing a MoSi ₂ @ZrO ₂ core-shell structure, comprising the following steps: (1) adding MoSi ₂ powder and SDS into a beaker with mechanical ultrasonic stirring, and using water or alcohol as a dispersion medium; (2), After dispersing for a certain period of time, add zirconium source to the suspension, and dropwise add alkaline solution NH ₃ ·H ₂ O or NaOH until the pH is between 7 and 14; continue to stir for a certain period of time until the mixture is uniform; (3), mix The prepared suspension is placed in a reaction kettle, the curing time is 12-48h, and the curing temperature is 160-220°C; heated in an oven, and the suspension is kept at a certain temperature through a certain heating rate; (4), hydrothermal reaction After synthesis, the powder is obtained by filtering, washing, drying, and sieving; (5), calcining the prepared powder in a calcining device for 1-6 hours, and the holding temperature is 300-400 °C; (6), after the above-mentioned step, the MoSi ₂ @ZrO ₂ core-shell structure is obtained, and the volume fraction of the synthesized ZrO ₂ powder is 10-30 vol%. The invention adopts the hydrothermal method, which is pollution-free, reduces equipment requirements, and is environmentally friendly.

Description

Preparation method of MoSi2@ZrO2 core-shell structure

technical field

The invention relates to the technical field of preparation of high-performance ceramic matrix composite material powder, in particular to a preparation method of a MoSi ₂ @ZrO ₂ core-shell structure.

Background technique

MoSi2 has the advantages of high melting point ( _2303K ), high strength and good thermal conductivity, and is a candidate material for the next generation of high temperature materials. In particular it is considered a promising high temperature coating for aerospace, nuclear industry, metallurgy and electronics, among others. MoSi ₂ is brittle at low temperature (BDTT at 900-1000°C), and has insufficient high-temperature strength above 1300°C, especially its creep resistance is relatively low. Moreover, at about 400-600 °C, MoSi ₂ undergoes accelerated oxidation, and finally turns from a dense body to a powder, which is called the Pest phenomenon. These shortcomings limit the application of MoSi2 as a high _- temperature structure. Therefore, room temperature toughening and high temperature reinforcement, as well as inhibiting low temperature Pest are the key problems to be solved urgently for _MoSi2 .

The hydrothermal method is an important method to prepare ZrO ₂ powder, which is characterized in that the preparation process is completed at one time under high temperature and high pressure, and no later crystallization treatment is required, and the obtained powder has a narrow particle size distribution and pure composition.

Core-shell nanoparticles are a composite multi-component structure formed by a particle with a size ranging from microns to nano-films as the core, and several layers of uniform nano-films are coated on its surface. The functions are connected to each other. The chemical inertness of the coating layer in the core-shell composite material can improve the stability of the nanoparticles, so the core-shell structure material exhibits more excellent physical and chemical properties than when a single central particle exists, and has broad application prospects.

In the present invention, the MoSi ₂ @ZrO ₂ core-shell structure is obtained by mechanical stirring and dispersion and hydrothermal synthesis. The purpose of coating several layers of ZrO ₂ is to prevent MoSi ₂ from oxidizing at low temperature (400-600 ℃) and enhance the room temperature strength and fracture toughness. It lays the foundation for the wide application of MoSi2 _- based composites.

SUMMARY OF THE INVENTION

The problem to be solved by the present invention is: to provide a method for preparing a MoSi ₂ @ZrO ₂ core-shell structure, using MoSi ₂ as a matrix, by adding ZrOCl ₂ ·8H ₂ O in the hydrothermal synthesis process, synthesizing ZrO ₂ , and then coating MoSi ₂ . To eliminate the hazard of low temperature oxidation of MoSi ₂ during the sintering process, ZrO ₂ is generated by hydrothermal reaction, thereby obtaining a MoSi ₂ @ZrO ₂ core-shell structure. This prepares for further improvement of the mechanical properties of composite materials in the future.

The technical solution provided by the present invention to solve the above problems is: a method for preparing a MoSi ₂ @ZrO ₂ core-shell structure, the method comprising the following steps:

(1), add a certain proportion of MoSi ₂ powder and SDS into the beaker with mechanical ultrasonic stirring, and use water or alcohol as the dispersion medium;

(2) After dispersing for a certain period of time, add a certain amount of zirconium source to the suspension, and dropwise add alkaline solution NH ₃ ·H ₂ O or NaOH until the pH is between 7 and 14; continue to stir for a certain period of time until the mixture is mixed uniform;

(3), place the prepared suspension in the reaction kettle, the curing time is 12-48h, and the curing temperature is 160-220°C; use an oven to heat, and keep the suspension at a certain temperature through a certain heating rate;

(4), after the hydrothermal reaction synthesis, by filtration, washing, drying, sieving, obtain powder;

(5), calcining the prepared powder in the calcining equipment for 1-6 hours, and the holding temperature is 300-400 °C;

(6) After the above steps, a MoSi ₂ @ZrO ₂ core-shell structure is obtained, and the volume fraction of the synthesized ZrO ₂ powder is 10-30 vol%.

Preferably, the dispersion time in the step (2) is 1-6h.

Preferably, the calcination equipment in the step (5) is an atmosphere tube furnace, a high temperature vacuum furnace and a microwave sintering furnace.

Preferably, in the step (5), the heating rate of calcination is 5-20° C./min, the holding time is 30-180 min, and the calcining atmosphere is vacuum, argon atmosphere or nitrogen atmosphere.

Compared with the prior art, the advantages of the present invention are:

(1) Disperse MoSi ₂ powder by mechanical stirring method to avoid powder agglomeration and obtain a uniform suspension.

(2) The hydrothermal method is adopted, which is pollution-free, reduces equipment requirements, and is environmentally friendly.

(3) The preparation process is completed at one time under high temperature and high pressure, and no subsequent crystallization treatment is required, and the obtained powder has a narrow particle size distribution and pure composition.

Description of drawings

The accompanying drawings described herein are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

Figure ₁ is the XRD pattern of the MoSi2@ZrO2 core _- shell structure.

FIG. 2 is a TEM image of the MoSi ₂ @ZrO ₂ core-shell structure prepared in Example 1. FIG.

Detailed ways

The embodiments of the present invention will be described in detail below with the accompanying drawings and examples, so as to fully understand and implement the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects.

Example 1

Add the ball _- milled 2.5g MoSi powder and 1.6g/L SDS as a dispersant into a beaker containing 200ml of distilled water for mechanical ultrasonic stirring, using water as the dispersion medium; after dispersing for 6h, add 1.5338g of zirconium source ZrOCl to the suspension _2.8H2O , calculated as ₂₀ % vol _ZrO2 . The alkaline solution NH ₃ ·H ₂ O was added dropwise to pH=9. Continue to stir for 3h until the mixture is uniform. The prepared suspension was placed in a reaction kettle, heated to 200°C using an oven, curing time was 24h, and curing temperature was 200°C. After the hydrothermal reaction is synthesized, the composite powder is obtained by filtering with distilled water and alcohol, washing three times each, then drying, and sieving through a 200-mesh sieve. The prepared powder was calcined in an atmosphere tube furnace for 3 h at a holding temperature of 380 °C. After the above steps, the MoSi ₂ @ZrO ₂ core-shell structure was obtained.

The above only describes the best embodiments of the present invention, but should not be construed as limiting the claims. The present invention is not limited to the above embodiments, and the specific structure thereof can be changed. All changes made within the protection scope of the independent claims of the present invention are all within the protection scope of the present invention.

Claims (4)

1. MoSi₂@ZrO₂The preparation method of the core-shell structure is characterized by comprising the following steps: the method comprises the following steps of,

(1) certain proportion of MoSi₂Adding the powder and SDS into a beaker, mechanically and ultrasonically stirring, and using water or alcohol as a dispersion medium;

(2) after dispersing for a certain time, adding a certain amount of zirconium source into the suspension, and dropwise adding an alkaline solution NH₃·H₂O or NaOH until the PH value is between 7 and 14; continuously stirring for a certain time until the mixture is uniformly mixed;

(3) placing the prepared suspension in a reaction kettle, and curing for 12-48 h at 160-220 ℃; heating by using an oven, and keeping the temperature of the suspension after the suspension reaches a certain temperature through a certain heating rate;

(4) after hydrothermal reaction synthesis, filtering, washing, drying and sieving to obtain powder;

(5) calcining the prepared powder in calcining equipment for 1-6 hours at the heat preservation temperature of 300-400 ℃;

(6) obtaining MoSi through the steps₂@ZrO₂Core-shell structure of synthetic ZrO₂The volume fraction of the powder is 10-30 vol%.

2. MoSi according to claim 1₂@ZrO₂The preparation method of the core-shell structure is characterized by comprising the following steps: and (3) the dispersion time in the step (2) is 1-6 h.

3. MoSi according to claim 1₂@ZrO₂The preparation method of the core-shell structure is characterized by comprising the following steps: and (5) calcining equipment is an atmosphere tube furnace, a high-temperature vacuum furnace and a microwave sintering furnace.

4. MoSi according to claim 1₂@ZrO₂The preparation method of the core-shell structure is characterized by comprising the following steps: the temperature rise rate of the calcination in the step (5) is 5-20 ℃/min, the heat preservation time is 30-180 min, and the calcination atmosphere is vacuum, argon atmosphere or nitrogen atmosphere.

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