CN1562886A

CN1562886A - AMmonium hydroxide p4recipitation method fr preparing nano powder of Y 203 and transparent ceramics

Info

Publication number: CN1562886A
Application number: CN 200410021455
Authority: CN
Inventors: 孙旭东; 闻雷; 修稚萌; 霍地; 左良
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2004-03-24
Filing date: 2004-03-24
Publication date: 2005-01-12
Anticipated expiration: 2024-03-24
Also published as: CN1290798C

Abstract

In the invention, Y(NO3) solution with density 0.1-0.4 mol/L composed by 5N Y2O3 crude powder and analyse pure hydrogen nitrade and NH4OH with density 0.3-2M are used as raw material to do titration, at same time, (NH4)2SO4 (weight is 1-10 percent of reaction material total weight) is added in cold water showering in temp. 0-4 deg.C to do positive titrating, NH4OH precipitating agent with density 0.3-2 M is titrated into Y(NO3) solution with density 0.1-0.4 mol/L, the titrating speed is 2-15 mol/min, final pH value is 7.6-8.3, then continuous stirring in temp 0-4 deg.C, washing by using water and alcohol, drying 24 hours in temp. 60 deg.C. Ground dry precipitant is burned 2-10 hours in temp. 900-1100 deg.c to produce Y2O3 nanometre powder with particle size about 20-60 nm. Said nanometre is composed of green bodies by 150-230 Mpa isostatic pressure and is fired in temp. 1600-1800 deg.C in vacuum to produce Y2O3 transparent ceramics.

Description

Preparation of Y2O3Ammonium hydroxide precipitation method for nano powder and transparent ceramic

Technical Field

The invention belongs to the technical field of preparation of fine ceramics of transparent products containing rare earth oxides according to the international patent classification table, and particularly relates to preparation of Y₂O₃Ammonium hydroxide precipitation method of nanometer powder and transparent ceramic.

Background

Yttrium oxide (Y)₂O₃) The high-temperature infrared material and the electronic material are excellent, the melting point is higher than 2400 ℃, the dielectric constant is 12-14, and the transparency is good. Due to Y₂O₃The structural type, higher melting point and corrosion resistance make it capable of operating under more severe conditions than alumina transparent ceramics. Of greater significance is the inclusion of Nd₂O₃Y of (A) is₂O₃A base transparent ceramic material. The ceramic can be used for a solid laser used at a wavelength of 1.06 mu m in laser technology. Y called Yttralox₂O₃Transparent ceramics were first developed by Grescovich and Woods, a common electric company, usa. The material is 10% ThO₂-90％Y₂O₃The light transmittance of the solid solution of (2) is similar to that of glass, but the use temperature is extremely high. The ceramic is prepared from high-purity 99.99%, Y₂O₃Powder as initial material and ThO₂As an additive, the primary raw material is sintered at 2170 ℃ under normal pressure to prepare Y with high light transmittance₂O₃A transparent ceramic. U.S. Pat. No. 3873657, Nippon Nissan K.K., G.Toda, I.Matsuyama and Y.Tsukuda describes a Y additive containing 0.1 to 0.8 mol% of BeO₂O₃The base transparent ceramic material has a sintering temperature of about 2000 ℃. Rhodes from GTE corporation of America made a highly transparent high density Y₂O₃Based on multiple crystals (U.S. patent 4,115,134). The polycrystal is mainly composed of Y₂O₃Composition and containing about 6 to 14 mol% of La₂O₃The sintering temperature is 2150 ℃, and the annealing is carried out at 1900 ℃. The experiments of Tsukuda and Muta show that sintering at 2270 ℃ and normal pressure can be carried out without additivesPreparation of Y₂O₃A transparent ceramic. Preparation of Y₂O₃The methods for transparent ceramics mostly require higher sintering temperatures or doping with ThO₂Or toxic or radioactive additives such as BeO, etc., which cause difficulties in preparation.

Disclosure of Invention

Aiming at the problems of the prior art, in order to prepare Y without using additives and at lower temperature₂O₃Nano powder and transparent ceramic, the present invention uses Y (NO)₃)₃Solution with NH₄OH is used as raw material, and Y is prepared by chemical precipitation₂O₃Nanometer powder, and method for controlling reaction process, PH value and doping small amount of sulfate ions to obtain Y₂O₃And (4) nano powder. Then sintering the mixture for several hours at 1600-1800 ℃ in a vacuum atmosphere to obtain Y₂O₃A transparent ceramic. Prepared Y₂O₃The transparent ceramic has excellent optical performance.

The process flow is shown in the attached drawing:

the technological process is divided into six steps, and each step needs to have control conditions:

(1)Y(NO₃)₃and NH₄OH is reacted while adding (NH)₄)₂SO₄: using 0.1-0.4 mol/L Y (NO)₃)₃Solution of 0.3-2M NH₄OH is a precipitating agent. The method can greatly reduce the agglomeration of powder by doping sulfate ions into the system. The obtained powder has fine and uniform powder particles, and the average particle sizes of the Y are about 20nm and 60nm₂O₃And (3) powder. Therefore, 1-10% of the total weight of the reactants (NH) needs to be added₄)₂SO₄. The reaction is carried out in an ice water bath with constant temperature of 0-4 ℃ by stirring, and is a forward titration. The following reactions occur:

x varies from 0 to 1, Y₂(OH)_6-x(NO₃)_x·nH₂The solubility of O in the aqueous solution was 5.2X 10^-22～8.1×10^-23And then precipitate, which is called precursor precipitate. In general may be Y₂(OH)₅NO₃·H₂O denotes a precursor precipitate.

The forward titration mode is to add the precipitant to the salt solution, and the reverse titration mode is to add the salt solution to the precipitant. Due to the difference in titration order, the change in pH was clearly distinguishable between the two systems. During the back titration, since ammonia is present in large excess, it is present in Y (NO)₃)₃During the titration of the solution, the pH value is changed from high to low, and the change is not obvious. Whereas the positive titration is opposite, NH₄OH to Y (NO)₃)₃During the titration of the solution, the pH value is changed from low to high. The morphology of the precursor precipitate also varied significantly with changes in PH. Forward titration at low PH, the precursor precipitate is a flocculent aggregate, exhibiting a card house structure (card house structure), at high PH, the precursor precipitate card house structure characteristic is reduced and the particles become finer. Precursor precipitate card housing structures when titrated in the reverse direction are not as distinct in character and are predominantly equiaxed grains.

The method is determined as normal pressure forward titration, and the concentration of Y (NO) per liter is 0.1-0.4 mol/L₃)₃Titrating the solution with NH concentration of 0.3-2M₄The titration speed of the OH precipitant is 2-15 ml/min, and the pH value of the reaction end point is 7.6-8.3. A deposit of the card house structure is generated, which is beneficial to Y₂O₃Preparing nanometer powder and transparent ceramic.

(2) After titration, aging is carried out for 0.5-2 hours, stirring is carried out continuously, and the temperature of a reaction system is maintained at 0-4 ℃.

(3) The precursor precipitate was then washed with distilled water and absolute ethanol. Washing the precursor precipitate with distilled water for 4 times to remove NH as by-product₄NO₃(ii) a Then, the mixture is cleaned by absolute ethyl alcoholWashing for 2 times to remove water in the precursor precipitate so as to prevent the precursor precipitate from generating serious agglomeration in the drying process.

(4) After cleaning, drying for 24h at 60 ℃ under normal pressure.

(5) And grinding the dried precursor precipitate by using an alumina mortar, putting the ground precursor precipitate into a quartz crucible, and calcining the quartz crucible for 4 hours at 900-1150 ℃. Y with uniform particle size, average particle size of about 20nm and good dispersibility of 60nm is obtained₂O₃And (4) nano powder.

(6) Pressing the prepared nano powder into a green body by 150-230 Mpa isostatic pressing, and then sintering the green body in vacuum at 1600-1800 ℃ for 2-10 h with the vacuum degree of 1 multiplied by 10^-3Pa, obtaining Y₂O₃The light transmittance of the transparent ceramic in a visible light region with the wavelength of 1000nm can reach 60-75%.

Drawings

Process chart for preparing yttrium oxide nano powder and transparent ceramic by ammonium hydroxide precipitation method

Detailed Description

Y₂O₃Coarse powder (5N) and analytically pure concentrated HNO₃Preparing Y (NO) with concentration of 0.26mol/L as raw material₃)₃500ml of the solution. Preparing NH with the concentration of 1M₄OH is used as a precipitating agent. Reacting NH₄OH titrates to vigorously stirred Y (NO)₃)₃In solution. During the reaction, the system is placed in an ice-water mixture water bath, the temperature of the reaction system is controlled to be 0 ℃, the titration speed is 5ml/min, andthe final pH value of the system is 8.0. After the titration was completed, stirring was continued for 0.5h while maintaining the temperature of the reaction system. After the aging is finished, washing the precursor precipitate for 4 times by using distilled water to remove a reaction by-product NH₄NO₃Then, the precursor precipitate was washed with absolute ethanol 2 times to remove water. And (4) cleaning the precursor precipitate, and drying in an oven at 60 ℃ for 24 h. The dried precursor precipitate was ground with an alumina mortar and then calcined in a quartz crucible at 1100 ℃ for 4 hours. The obtained powder is subjected toPressing into green body at 200MPa, vacuum sintering at 1700 deg.C for 4 hr with sintering furnace vacuum degree of 1 × 10^-3Pa, obtain Y₂O₃A transparent ceramic.

And observing the appearance of the precursor precipitate and the primary particles of the powder under different calcining conditions by adopting a Philips EM400 type Transmission Electron Microscope (TEM). The light transmittance of the ceramic was measured using a DMR-22 spectrophotometer.

Y₂O₃The powder has uniform size, the average particle size is about 20nm and 60nm respectively, and the dispersion is good. Y is₂O₃The transmittance measurement of the transparent ceramic showed that the transmittance in the visible light region of 1000nm wavelength reached 75%.

Claims

1. Preparation of Y₂O₃The ammonium hydroxide precipitation method of nano powder and transparent ceramic is characterized by using Y (NO)₃)₃And NH₄OH is used as a raw material to prepare Y through five steps₂O₃Nano powder, and then the transparent Y is prepared by the sixth step of high-temperature vacuum sintering₂O₃A ceramic;

(1) generating Y₂(OH)₅NO₃·H₂O precursor precipitate, and the reaction control conditions are as follows: stirring in ice-water bath at 0-4 ℃, carrying out normal pressure forward titration, and adding NH₄OH drop into Y (NO)₃)₃In solution, Y (NO) at a defined concentration per liter₃)₃Titration of a defined concentration of NH in solution₄The titration speed of the OH precipitator is 2-15 ml/min. The reaction is carried out while adding a prescribed amount of (NH)₄)₂SO₄The pH value of the titration end point is 7.6-8.3;

(2) after titration, continuously maintaining stirring at 0-4 ℃, and aging for 0.5-2 hours;

(3) washing with water-ethanol, wherein the washing is distilled water washing for 4 times, and absolute ethanol washing for 2 times;

(4) precursor precipitate Y after cleaning₂(OH)₅NO₃·H₂O, drying for 24 hours at the temperature of 60 ℃ and under normal pressure;

(5) to pairCalcining the ground and dried precipitate in a quartz crucible at 900-1100 ℃ for 2-10 hours to generate Y with good dispersibility and average particle sizes of 20nm and 60nm₂O₃And (4) nano powder.

(6) Will Y₂O₃Pressing the nano powder into a green body under 150-230 MPa isostatic pressure, and heating at 1600-1800 ℃ in a vacuum firing furnace at 1 × 10^-3Sintering for 4 hours under Pa vacuum degree to generate Y₂O₃A transparent ceramic.

2. Preparation Y according to claim 1₂O₃Precipitation of nanopowders and transparent ceramics by ammonium hydroxide, in a first step titration is performed while adding (NH)₄)₂SO₄Which is added (NH)₄)₂SO₄Characterized in that it is added in an amount of Y (NO)₃)₃And NH₄1-10% of the total weight of the OH reactant.

3. Preparation Y according to claim 1₂O₃Precipitation of nano-powder and transparent ceramic with ammonium hydroxide using Y (NO)₃)₃And NH₄OH as a starting material, characterized by Y (NO)₃)₃The concentration of (A) is 0.1-0.4 mol/L, NH₄The OH concentration is 0.3-2M; y (NO)₃)₃Should be Y as from 5N₂O₃Reacting the coarse powder with analytically pure nitric acid to obtain a pure solution, using NH₄OH should be, for example, NH analytically pure₄OH to prepare a pure solution.