CN102677174B - A kind of preparation method of Y4Si3O12 whisker - Google Patents

Abstract

The invention relates to a preparation method of Y4Si3O12 crystal whiskers, which comprises the steps of: dissolving Y (NO)3.6H2O and Na2SiO3.9H2O in anhydrous ethanol to obtain solution A; adding ethylenediaminetetraacetic acid (EDTA) and high-density polyethylene (HDPE) into the solution A and magnetically agitating for ultrasonic reaction to obtain solution B; and placing the solution B in a hydrothermal reaction kettle lined with polytetrafluoroethylene for constant-temperature reaction, conducting centrifugal separation, successively washing with distilled water and anhydrous ethanol and finally drying to obtain Y4Si3O12 crystal whiskers. The preparation method of the Y4Si3O12 crystal whiskers has the advantages that the process is simple to control, the cost is lower, the preparation temperature is low, the later-stage crystallization is not required and the possible defects that the crystal grains grow up, are coarsened or curled and the like in the later-stage heat treatment process are avoided to some extent. The appearance control can be realized and the Y4Si3O12 crystal whiskers with high purity and even grain size can be prepared.

Description

A kind of preparation method of Y4Si3O12 whisker

technical field

The invention relates to a method for preparing Y ₄ Si ₃ O ₁₂ with controllable morphology, in particular to a method for preparing Y ₄ Si ₃ O ₁₂ whiskers.

Background technique

The structural characteristics of yttrium silicate material and a series of excellent physical and chemical properties, such as low elastic modulus, low high temperature oxygen permeability, low linear expansion coefficient, low high temperature volatilization rate, chemical corrosion resistance and other characteristics, make it a A high-performance structural material is widely used in the aerospace field. There are three crystal phase structures of yttrium silicate, namely Y ₂ SiO ₅ , Y ₂ Si ₂ O ₇ and Y ₄ Si ₃ O ₁₂ .

At present, although there are very few literature reports on Y ₄ Si ₃ O ₁₂ , and its lattice constant has not yet been reported, but because its melting point is as high as 1950°C, it has extremely low high-temperature oxygen permeability, and Y ₄ Si ₃ O ₁₂ ^{γ -} _Y ^{2 Si} ₂ O ₇ ,amachinable silicate ceramic:mechanical properties and machinability.TheAmerican Ceramic Society,2007,90(8):2535-2541.], and Y ₄ Si ₃ O ₁₂ has good physical and chemical compatibility with SiC [Ogura Y, Kondo M, Morimoto T.Oxygenpermeability of Y ₂ SiO ₅ .Materials Transactions[J],2001,42(6):1124-1130.], so it is considered to be a composite coating with SiC as the inner coating It is one of the most ideal outer coating materials in the structure, and has broad application prospects in high temperature oxidation protection materials.

Huang Jianfeng et al. have successfully prepared a gradient Y ₂ SiO ₅ /Y ₂ Si ₂ O ₇ /Y ₄ Si ₃ O ₁₂ high-temperature anti-oxidation coating on the surface of C/C-SiC [Huang JF, Zeng XR, Li HJ, et al. SiC/yttrium silicate/glass multi-layer oxidation protective coating for carbon/carbon composites[J].Carbon,2004,42(11):2356-2359.] and gradient Y ₂ SiO ₅ /Y ₂ Si ₂ O ₇ /Y ₄ Si ₃ O ₁₂ /glass layer high temperature oxidation resistance coating [Huang JF, Li HJ, Zeng XR.Yttrium silicate oxidation protection coating for SiC coated carbon/carbon composites[J].Ceramics International,2006,32(4):417 -421.], where the gradient Y ₂ SiO ₅ /Y ₂ Si ₂ O ₇ /Y ₄ Si ₃ O ₁₂ /glass coating can effectively protect the C/C composite for 200 h in static air at 1600 °C, and the coating C/ C oxidation weight loss is less than 0.65%. And there are documents [Wang Ya-qin, Huang Jian-feng, Cao Li-Yun et al "Preparation and phase composition optimization of yttrium silicates multi-composition coating for SiC pre-coated carbon/carbon composites" J.Compos.Mater.2011 ,46(4):409-415.] It is reported that the comprehensive advantages of multiphase yttrium silicate coating can be used to solve the problem of oxidation resistance failure of the coating caused by the mismatch of thermal expansion coefficient between the inner and outer coatings. Based on the idea of whisker-toughened ceramics and the very good physical and chemical compatibility between Y ₄ Si ₃ O ₁₂ and SiC inner coating, Y ₄ Si ₃ O ₁₂ whiskers can be used to toughen SiC inner coating at high temperature The field of preparation of anti-oxidation coatings has great prospects.

Contents of the invention

The purpose of the present invention is to realize the preparation method of Y ₄ Si ₃ O ₁₂ whiskers with controllable shape, high purity and relatively uniform particle size by solvothermal method.

In order to achieve the above object, the technical scheme adopted in the present invention is:

1) Take analytically pure Y(NO) ₃ 6H ₂ O and Na ₂ SiO ₃ 9H ₂ O, dissolve them in absolute ethanol according to the molar ratio of Y:Si=1:(1.2~1.8), and prepare Y ³⁺ solution with a concentration of 0.36~0.86mol/L, adjust its pH=7~9 with NaOH solution to obtain solution A;

2) Add analytically pure EDTA and HDPE as templates to solution A according to the molar ratio of Y ³⁺ :EDTA:HEPE=1:(0.4~1.5):(0.05~0.09), and stir magnetically at room temperature for 0.5~2h , mixed evenly, and then ultrasonically reacted for 1~3h, and the ultrasonic power was 300~500W to obtain solution B;

3) Put solution B in a polytetrafluoroethylene-lined hydrothermal kettle, control the filling ratio to 40~60%, then put the reaction kettle into a constant temperature reactor, and react at 140~210°C for 48~72h;

4) The reaction system was naturally cooled to room temperature, centrifuged, washed with distilled water and absolute ethanol for 3 to 5 times, and finally dried in an electric blast drying oven at 50 to 80°C to obtain Y ₄ Si ₃ O ₁₂ whiskers .

The step 1) the concentration of NaOH solution is 3mol/L.

The preparation method of Y ₄ Si ₃ O ₁₂ whiskers of the present invention has simple process control, low cost, low preparation temperature and no need for post-crystallization treatment, which avoids grain growth, coarseness and Defects such as melting or curling.

Shape control can be realized, and high-purity Y ₄ Si ₃ O ₁₂ whiskers with relatively uniform particle size can be prepared.

Since the melting point of Y ₄ Si ₃ O ₁₂ is as high as 1950°C, the thermal expansion coefficient of Y ₄ Si ₃ O ₁₂ (4.31×10 ^-6 K ^-1 ) is very close to that of SiC (4.5×10 ^-6 K ^-1 ), And it has good physical and chemical compatibility with SiC. The Y ₄ Si ₃ O ₁₂ whiskers prepared by the present invention are the most ideal outer coating whiskers in the composite coating structure with SiC as the inner coating. One of the toughest materials, which can effectively improve the oxidation resistance of the coating. In addition, Y ₄ Si ₃ O ₁₂ whiskers have broad application prospects in the fields of electronics industry and information technology.

Description of drawings

Fig. 1 is a scanning electron microscope (SEM) photograph of yttrium orthosilicate (Y ₂ SiO ₅ ) whiskers prepared at a hydrothermal temperature of 140°C in the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Example 1:

1) Take analytically pure Y(NO) ₃ 6H ₂ O and Na ₂ SiO ₃ 9H ₂ O, dissolve them in absolute ethanol according to the molar ratio of Y:Si=1:1.2, and prepare Y ³⁺ concentration of 0.36mol/L solution, with a concentration of 3mol/L NaOH solution to adjust its pH=7 to obtain solution A;

2) Add analytically pure EDTA and HDPE as templates to solution A at a molar ratio of Y ³⁺ :EDTA:HEPE=1:0.4:0.05, stir magnetically at room temperature for 0.5h, mix well, and then ultrasonically react for 1h. The ultrasonic power is 500W to obtain solution B;

3) Put solution B in a polytetrafluoroethylene-lined hydrothermal kettle, control the filling ratio to 40%, then put the reaction kettle into a constant temperature reactor, and react at 210°C for 48h;

4) The reaction system was naturally cooled to room temperature, centrifuged, washed three times with distilled water and absolute ethanol, and finally dried in an electric blast drying oven at 50°C to obtain Y ₄ Si ₃ O ₁₂ whiskers.

Example 2:

1) Take analytically pure Y(NO) ₃ 6H ₂ O and Na ₂ SiO ₃ 9H ₂ O, dissolve them in absolute ethanol according to the molar ratio of Y:Si=1:1.8, and prepare Y ³⁺ concentration of 0.86mol/L solution, with a concentration of 3mol/L NaOH solution to adjust its pH=9 to obtain solution A;

2) Add analytically pure EDTA and HDPE as templates to solution A at a molar ratio of Y ³⁺ :EDTA:HEPE=1:1.5:0.09, stir magnetically at room temperature for 2 hours, mix well, and then ultrasonically react for 3 hours. The power is 300W, and the solution B is obtained;

3) Put solution B in a polytetrafluoroethylene-lined hydrothermal kettle, control the filling ratio to 60%, then put the reaction kettle into a constant temperature reactor, and react at 140°C for 72h;

4) The reaction system was naturally cooled to room temperature, centrifuged, washed with distilled water and absolute ethanol for 5 times, and finally dried in an electric blast drying oven at 80°C to obtain Y ₄ Si ₃ O ₁₂ whiskers.

It can be seen from Figure 1 that the Y ₄ Si ₃ O ₁₂ whiskers that can be obtained by the method described in Example 2 are characterized in that the whisker diameter is about 10-200 nm, and the whisker length is about 3-5 μm.

Example 3:

1) Take analytically pure Y(NO) ₃ 6H ₂ O and Na ₂ SiO ₃ 9H ₂ O, dissolve them in absolute ethanol according to the molar ratio of Y:Si=1:1.5, and prepare Y ³⁺ concentration of 0.61mol/L solution, with a concentration of 3mol/L NaOH solution to adjust its pH=8 to obtain solution A;

2) Add analytically pure EDTA and HDPE as templates to solution A at a molar ratio of Y ³⁺ :EDTA:HEPE=1:0.95:0.07, stir magnetically at room temperature for 1 hour, mix well, and then ultrasonically react for 2 hours. The power is 400W, and solution B is obtained;

3) Put solution B in a polytetrafluoroethylene-lined hydrothermal kettle, control the filling ratio to 50%, then put the reaction kettle into a constant temperature reactor, and react at 175°C for 60h;

4) The reaction system was naturally cooled to room temperature, centrifuged, washed with distilled water and absolute ethanol four times, and finally dried in an electric blast drying oven at 65°C to obtain Y ₄ Si ₃ O ₁₂ whiskers.

Claims (1)

1. a Y ₄si ₃o ₁₂the preparation method of whisker, is characterized in that:

1) analytically pure Y (NO) is got ₃6H ₂o, Na ₂siO ₃9H ₂o, is dissolved in dehydrated alcohol according to the mol ratio of Y:Si=1:1.8, is mixed with Y ³⁺concentration is the solution of 0.86mol/L, regulates its pH=9, obtain solution A by the NaOH solution that concentration is 3mol/L;

2) in solution A, Y is pressed ³⁺: the mol ratio of EDTA:HEPE=1:1.5:0.09 adds analytically pure EDTA and HEPE as template, and at room temperature magnetic agitation 2h, mixes, then ultrasonic reaction 3h, and ultrasonic power is 300W, obtains solution B;

3) solution B is placed in teflon-lined water heating kettle, controlling packing ratio is 60%, then reactor is put into isothermal reactor, at 140 DEG C of reaction 72h;

4) question response system naturally cools to room temperature, centrifugation, and successively wash 5 times separately with distilled water and dehydrated alcohol, finally in the electric drying oven with forced convection of 80 DEG C, drying obtains Y ₄si ₃o ₁₂whisker;

Y ₄si ₃o ₁₂diameter of whiskers is 10 ~ 200nm, and whisker length is 3 ~ 5 μm.