CN100582003C

CN100582003C - Sol-gel process for preparing Yb2SiO5 powder

Info

Publication number: CN100582003C
Application number: CN200710041229A
Authority: CN
Inventors: 温海明; 董绍明; 丁玉生; 张翔宇; 和平
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2007-05-25
Filing date: 2007-05-25
Publication date: 2010-01-20
Anticipated expiration: 2027-05-25
Also published as: CN101066764A

Abstract

The present invention relates to sol-gel process of preparing Yb2SiO5 powder, and features that Yb2SiO5 precursor sol is first obtained with ethyl acetate and ytterbium nitrate as materials and through hydrolysis and condensation reaction in water and alcohol solution, and then heat treated at 1200 deg.c to obtain Yb2SiO5 powder. The process is simple and has high repeatability, and the prepared Yb2SiO5 powder in submicron level is hopeful in application as the oxidation and degradation resisting coating material for fiber reinforced SiC-base composite material.

Description

Yb 2SiO 5The sol-gel process for preparing of powder

Technical field

The invention belongs to Prepared by Sol Gel Method ceramic ultrafine powder body field, be specifically related to a kind of monodispersed submicron level ytterbium silicate (Yb ₂SiO ₅) the collosol and gel preparation technology of powder.

Background technology

Fiber reinforcement SiC ceramic matric composite, for example SiC fiber reinforcement SiC (SiC/SiC), C fiber reinforcement (C/SiC) might replace the hot junction structure unit that Ni base superalloy is used to aero-turbine because of it has superior mechanical behavior under high temperature with stability.Yet a subject matter of existence is its deficient in stability in containing the high-speed fuel gas environment of high-temperature vapor.Adding coating at composite material surface is effective ways of head it off.Units such as NASA have carried out big quantity research to this.The result shows, in various coated materials, rare earth silicate, especially ytterbium silicate, because of it possess superior resistance to elevated temperatures, in water vapour high stability and become with the chemistry of SiC and mechanical compatibility one of candidate material of application prospect arranged most.Preparation rare earth silicate powder is used solid phase method usually at present, and synthesis temperature is more than 1600 ℃, and the gained powder is a micron order.Sol-gel method is a kind of common methods for preparing superfine powder, advantages such as synthesis temperature is low, the gained diameter of particle is little that it has.The collosol and gel preparation method of yttrium silicate, silicic acid lutetium powder has appeared in the newspapers and has led, and the collosol and gel preparation method of ytterbium silicate powder still is not reported.

Summary of the invention

The objective of the invention is to propose a kind of Yb ₂SiO ₅The collosol and gel preparation technology of powder.

The submicron order Yb that the present invention proposes ₂SiO ₅The collosol and gel preparation technology of powder is to be raw material with tetraethoxy (TEOS), ytterbium nitrate, and hydrolysis and condensation reaction take place in water and alcoholic solution, obtains Yb ₂SiO ₅Aqueous precursor gel obtains Yb by high-temperature heat treatment again ₂SiO ₅Submicron powder.Operational path as shown in Figure 1.Concrete steps are as follows:

(1) with ytterbium nitrate Y _b(NO ₃) ₃NH ₂O (n=6～7) is dissolved in ethanol under 70-80 ℃ of water bath condition, get the ytterbium nitrate ethanolic soln of concentration range at 1.0～7.0mol/L.After solution temperature is dropped to room temperature (15～20 ℃);

(2) at ambient temperature, TEOS is added in the ytterbium nitrate ethanolic soln, stirring mixes it, control TEOS: H ₂O: C ₂H ₅OH (mol ratio) is in 1: 12: 5～1: 12: 30 scope;

(3) (volume percent hydrochloric acid/TEOS=3%) dropwise join in the above-mentioned solution obtains reaction mixture with a certain amount of catalyzer hydrochloric acid under whipped state;

(4) with above-mentioned reaction mixture vigorous stirring 5min～24h under 70-80 ℃ of water bath condition, obtain faint yellow transparent colloidal sol;

(5) with colloidal sol at room temperature ageing 10h～30h get wet gel;

(6), and in mortar, be ground into fine powder with wet gel dry xerogel in 200 ℃ of baking ovens;

(7) dry gel powder is calcined 1h down at 1200 ℃ and get Yb ₂SiO ₅Powder.

The present invention adopts sol gel process in technical scheme, (1200 ℃) have made single dispersion Yb at a lower temperature ₂SiO ₅Sub-micro ground rice.Whole process is roughly as follows:

Hydrolysis and polycondensation take place in TEOS, generate the Si-O-Si key.While Yb ³⁺Can participate in the hydrolysis condensation reaction of TEOS, break the Si-O-Si key and form the Si-O-Yb key.Along with further carrying out of hydrolytie polycondensation, the three-dimensional, amorphous network of Si-O-Yb forms, and promptly obtains Yb ₂SiO ₅Aqueous precursor gel.Gel is that colloidal particle interconnects into skeleton and the space reticulated structure that forms, and has filled up liquid in skeleton structure, but the liquid that is full of between rack can not flow, and the colloidal particle that constitutes rack has certain kindliness, and semi-solid state demonstrates flexibility.Yb ₂SiO ₅Aqueous precursor gel removed weak bonded water and ethanol molecule before this in heat treatment process, remove strong bonded water molecules thereafter, and the nitrate radical generation decomposition reaction in the network.Then be and the decomposition of the alkoxy grp (owing to hydrolysis condensation reaction does not exist fully) of Si atomic linkage and the burning of residual carbon.At 700 ℃, gel remains amorphous state substantially, but a small amount of Yb is arranged ₂O ₃And SiO ₂Generate.The crystallization of Si-O-Yb random network takes place in gel about 1000 ℃, generate Yb ₂SiO ₅, but also have Yb ₃SiO ₅And Yb ₂Si ₂O ₇Two kinds of thing phases.Gel 1200 ℃ the calcining 1h after, Yb ₃SiO ₅And Yb ₂Si ₂O ₇Eliminate, only have Yb ₂SiO ₅, and crystallization fine (shown in Fig. 2 X ray diffracting spectrum).

Because of using ytterbium nitrate Y among the present invention _b(NO ₃) ₃NH ₂O (n=6～7) makes raw material, has determined water and TEOS mol ratio to be approximately 12: 1.Ethanol and TEOS mol ratio have remarkable influence to sol-gel process.Ethanol and TEOS mol ratio are high more, and hydrolysis condensation reaction is slow more, final resulting Yb ₂SiO ₅The powder footpath is more little.Yet ethanol and the too high meeting of TEOS mol ratio cause the colloidal sol that generates stable always and can not be transformed into aqueous precursor gel.

Have that technology is simple, good reproducibility and prepared Yb ₂SiO ₅The particle diameter of powder is characteristics such as submicron order.Be expected to be applied to the anti-oxidant and degeneration coated material of fibrous reinforcement SiC ceramic matric composite.

Description of drawings

Fig. 1 Prepared by Sol Gel Method Yb provided by the invention ₂SiO ₅The operational path of powder

Fig. 2 Yb ₂SiO ₅The X ray diffracting spectrum of powder

Yb among Fig. 3 embodiment 1 ₂SiO ₅The TEM figure of powder

Yb among Fig. 4 embodiment 2 ₂SiO ₅The TEM figure of powder

Embodiment

Further describe technical scheme of the present invention below by specific embodiment.

Embodiment 1:

(1) with 70.06g ytterbium nitrate Y _b(NO ₃) ₃NH ₂O (n=6～7) is dissolved in the 70.03g ethanol under 70 ℃ of water bath condition, after solution temperature is dropped to room temperature, strength of solution is 1.70mol/L, TEOS: H ₂O: C ₂H ₅OH=1: 12: 20;

(2) at ambient temperature, 15.62gTEOS is added in the ytterbium nitrate ethanolic soln, stirring mixes it;

(3) under whipped state, will dropwise join in the above-mentioned solution, obtain reaction mixture as the hydrochloric acid 0.5ml of catalyzer;

(4) with above-mentioned reaction mixture vigorous stirring 12h under 70 ℃ of water bath condition, obtain transparent colloidal sol;

(5) with colloidal sol at room temperature ageing 24h get gel;

(6) wet gel dry 8h in 200 ℃ of baking ovens is got xerogel, and in mortar, be ground into fine powder;

(7) dry gel powder is calcined 1h down at 1200 ℃ and get the Yb that particle diameter is 200～300nm ₂SiO ₅Powder, its transmission electron microscope (TEM) is schemed as shown in Figure 3.

Embodiment 2:

(1) with 35.03g ytterbium nitrate Y _b(NO ₃) ₃NH ₂O (n=6～7) is dissolved in the 12.42g ethanol under 80 ℃ of water bath condition, after solution temperature is dropped to room temperature, strength of solution is 4.77mol/L, TEOS: H ₂O: C ₂H ₅OH=1: 12: 7;

(2) at ambient temperature, 7.8gTEOS is added in the ytterbium nitrate ethanolic soln, stirring mixes it;

(3) under whipped state, will dropwise join in the above-mentioned solution, obtain reaction mixture as the hydrochloric acid 0.25ml of catalyzer;

(4) with above-mentioned reaction mixture vigorous stirring 10min under 70 ℃ of water bath condition, obtain transparent colloidal sol;

(5) with colloidal sol at room temperature ageing 16h get gel;

(7) dry gel powder is calcined 1h down at 1200 ℃ and get the Yb that particle diameter is about 1 μ m ₂SiO ₅Powder, its transmission electron microscope (TEM) is schemed as shown in Figure 4.

Claims

1, a kind of Yb ₂SiO ₅The sol-gel process for preparing of powder is characterized in that with tetraethoxy, ytterbium nitrate be raw material, and hydrolysis and condensation reaction take place in water and alcoholic solution, obtains Yb ₂SiO ₅Aqueous precursor gel obtains Yb by thermal treatment again ₂SiO ₅Make powder; Concrete steps are:

1. ytterbium nitrate is dissolved in ethanol, concentration is the ytterbium nitrate ethanolic soln of 1.0-7.0mol/L, is cooled to room temperature then;

2. TEOS is added in the ytterbium nitrate ethanolic soln that 1. step prepare, stir and make its mixing, TEOS: H ₂O: C ₂H ₅Mol ratio between the OH is 1: 12: 5～1: 12: 30;

3. again under whipped state, will dropwise join as the hydrochloric acid of catalyzer in the solution that 2. step prepare, the volume ratio that obtains reaction mixture hydrochloric acid and TEOS is 3%;

4. stir under the reaction mixture water bath condition that 3. step is made, obtain faint yellow transparent colloidal sol;

5. the colloidal sol that 4. step is prepared ageing at room temperature makes wet gel;

6. oven dry makes xerogel under 200 ℃ of conditions of the wet gel that 5. step is made, and grinds to form fine powder;

7. the dry gel powder that 6. step is made makes submicron order Yb 1200 ℃ of calcinings ₂SiO ₅Powder.

2, by the described Yb of claim 1 ₂SiO ₅The sol-gel process for preparing of powder is characterized in that described ytterbium nitrate is dissolved in ethanol and carries out under water bath condition, bath temperature is 70-80 ℃.

3, by the described Yb of claim 1 ₂SiO ₅The sol-gel process for preparing of powder, it is characterized in that step 1. or 5. described room temperature be 15-20 ℃.

4, by the described Yb of claim 1 ₂SiO ₅The sol-gel process for preparing of powder, the temperature of water-bath is 70-80 ℃ when it is characterized in that stirring under the 4. described water bath condition of step.

5, by claim 1 or 4 described Yb ₂SiO ₅The sol-gel process for preparing of powder is characterized in that the time that 4. step stirs is 5min-24h.

6, by the described Yb of claim 1 ₂SiO ₅The sol-gel process for preparing of powder is characterized in that the 5. described digestion time of step is 10h-30h.