CN111267219A

CN111267219A - AlON ceramic gel-casting vacuum degassing method

Info

Publication number: CN111267219A
Application number: CN202010241111.7A
Authority: CN
Inventors: 田庭燕; 王颖; 王海丽; 滕祥红
Original assignee: Beijing Sinoma Synthetic Crystals Co Ltd
Current assignee: Sinoma intraocular lens Research Institute Co., Ltd; Beijing Sinoma Synthetic Crystals Co Ltd
Priority date: 2020-03-31
Filing date: 2020-03-31
Publication date: 2020-06-12
Anticipated expiration: 2040-03-31
Also published as: CN111267219B

Abstract

The AlON ceramic gel casting vacuum degassing method adopts an AlON ceramic gel casting vacuum degassing device to carry out degassing and comprises two degassing cabins which are identical in structure and are arranged in a mutually vertical mode, a vacuum degassing chamber is formed at the vertical connection position of the degassing cabins, a movable push plate with a push rod is arranged on one side of a cavity in the degassing cabin, a rotating shaft with blades is arranged at the position close to the vacuum degassing chamber, and a degassing mechanism is arranged on the inner wall of the vacuum degassing chamber. Inject into horizontal degasification cabin die cavity with AlON ceramic slurry, promote the push pedal and remove slurry toward the opposite side, pivot rotation paddle stirs slurry, and the bubble is stirred out and is broken the suction, and slurry gets into the die cavity in second degasification cabin, rotates 90 the above-mentioned process degasification of repetition with the device. The invention ensures that each part of slurry is stirred by the paddle when passing through the rotating shaft and is exposed in a vacuum environment, gas can be fully separated out, degassing is efficient, and the product performance and the yield are improved.

Description

AlON ceramic gel-casting vacuum degassing method

Technical Field

The invention relates to the technical field of ceramic material gel casting, in particular to a vacuum degassing method for AlON ceramic gel casting.

Background

Aluminium oxynitride (AlON) is Al₂O₃A stable single-phase solid solution in the binary AlN system, a transparent polycrystalline ceramic with a strength and hardness of 380MPa and 1800kg/mm²Second to single crystal sapphire, the AlON transparent ceramic has good optical transmittance from near ultraviolet (0.2 mu m) to intermediate infrared (5.0 mu m), so the AlON transparent ceramic can be applied to application fields such as light protection and armor which have strict requirements on material hardness, toughness and light transmittance.

The AlON transparent ceramic product mainly comprises two preparation methods, wherein the first method is to prepare the AlON transparent ceramic by using alumina and aluminum nitride as raw material powder and adopting a reaction sintering method, the process is simple, but sintering is affected due to the difference in sintering performance, particle size distribution and the like, the product is basically semitransparent, and the transmittance is not high; the other method is to prepare AlON powder by adopting a high-temperature solid-phase reaction method or an aluminum oxide reduction nitridation method, and sinter the AlON powder after forming. In the forming method, the AlON transparent ceramic mainly comprises methods such as dry pressing forming, slip casting forming and the like.

The gel casting is to add organic monomer and cross-linking agent into the ceramic slurry, and the organic monomer in the slurry is subjected to in-situ polymerization reaction to form a firm three-dimensional network structure, so that the suspension is cured and formed in situ to obtain a uniform, high-strength and near-net-size ceramic blank. Then demoulding, drying, binder removal and densification sintering are carried out, and the required ceramic part can be prepared. But the literature of preparing AlON transparent ceramics by gel casting is less. At present, in the gel casting process, initial slurry contains a certain amount of bubbles, and if the bubbles cannot be removed fully, the bubbles left in the blank can form air holes, so that the product performance is seriously influenced. The prior ceramic slurry bubble removing method mainly adopts a packing auger with blades to realize vacuum stirring on slurry, and the packing auger is matched with vacuum ultrasonic vibration or adopts a vibrating screen and the like to ensure that bubbles are broken or reach the surface of the slurry and are sucked away by a vacuum mechanism, but the whole slurry is only contacted with the surface of the slurry in a vacuum environment, the contact surface is smaller, and simultaneously, because the slurry has higher viscosity, the bubbles inside or at the bottom are difficult to completely reach the surface of the slurry and be removed in a certain stirring or vibrating time, and the problem of low efficiency caused by long-time stirring or vibration is solved. For raw materials of several kilograms scale used in a laboratory, firstly, the cost for purchasing the device is very high, and secondly, a large amount of slurry must be prepared each time to use the device, so that serious waste is caused, and therefore, a simple, efficient and effective degassing device and method which are suitable for being used in the laboratory scale are necessary.

Disclosure of Invention

In order to solve the technical problem, the invention provides a vacuum degassing method for AlON ceramic gel injection molding.

The complete technical scheme of the invention comprises the following steps:

a vacuum degassing method for AlON ceramic gel casting is characterized in that a vacuum degassing device for AlON ceramic gel casting is adopted for degassing, the vacuum degassing device for AlON ceramic gel casting comprises a first degassing cabin and a second degassing cabin which are identical in structure and are arranged vertically, a vacuum degassing chamber is formed at the vertical connection position of the first degassing cabin and the second degassing cabin, a cavity for containing slurry is arranged in the degassing cabin, a push plate with a push rod is arranged at one side in the cavity and can push the push plate to move back and forth in the cavity by the push rod, a rotating shaft with blades is arranged at the position, close to the vacuum degassing chamber, of the other side of the cavity, the rotating shaft is connected in a mounting hole in the inner wall of the cavity and can rotate in the hole, degassing mechanisms are arranged on two inner walls of the vacuum degassing chamber, each degassing mechanism comprises a filter screen arranged on the inner wall and a vacuum pipeline connected with the filter screen, the vacuum pipeline is connected with a vacuum pump.

The whole AlON ceramic gel injection molding vacuum degassing device is arranged on the frame through a shaft and can rotate 90 degrees along the shaft, and a corresponding positioning mechanism is arranged on the frame.

The specific steps of vacuum degassing are as follows: first pour into the first degasification cabin die cavity that the level set up with AlON ceramic slurry into, open the vacuum pump, promote the push rod afterwards, and promote the push pedal and remove slurry toward the opposite side, when slurry passes through the pivot, it rotates to drive the pivot, the paddle stirs slurry simultaneously, make the bubble in the slurry broken by stirring out, gas is by vacuum degassing mechanism suction, slurry falls down under the action of gravity simultaneously, get into the die cavity in second degasification cabin, along with the push pedal removes pivot one side, first time degasification process is accomplished, with the push pedal return this moment, rotate 90 with whole AlON ceramic gel injection molding vacuum apparatus along the axle, make second degasification cabin become the level, first degasification cabin becomes perpendicular, promote the above-mentioned process of push pedal repetition in the second degasification cabin, make slurry carry out the degasification of the second time.

And repeating the process until the bubbles in the slurry are reduced to meet the requirements, discharging the slurry, and performing the next procedure.

Compared with the prior art, the improvement of the invention is as follows: in the aspect of raw material preparation, the applicant introduces a fluidized bed method on the basis of an alumina reduction nitridation method, a gas suspension system from bottom to top is formed in a reaction chamber, AlON powder with a very small particle size is obtained, and the performance of the product is improved by obtaining AlON ceramic in a gel film injection molding mode on the basis. However, because the particle size of the synthesized AlON powder is quite small, a great amount of gas can be brought in during the gel injection molding process, and the bubbles are difficult to be completely removed by adopting the traditional vacuum stirring degassing, so that the efficiency is low and the yield is low. Therefore, the invention designs the AlON ceramic gel injection molding vacuum degassing device aiming at the situation, and compared with the vacuum stirring degassing device in the prior art, the invention adopts the slurry moving mode to ensure that each part of slurry is stirred by the paddle when passing through the rotating shaft and is exposed in the vacuum environment, the gas can be fully separated out, the degassing process can be repeated by rotating the whole vacuum degassing device by 90 degrees, the device has small structure, simple structure, high efficiency and easy operation, and is very suitable for preparing raw materials for small-scale experiments in laboratories.

Drawings

FIG. 1 is a schematic structural view of an AlON ceramic gel injection molding vacuum degassing apparatus according to the present invention.

In the figure, 1-a first degassing cabin, 2-a second degassing cabin, 3-a push plate, 4-a push rod, 5-a rotating shaft, 6-a blade, 7-a filter screen, 8-a vacuum pump, 9-a vacuum pipeline, 10-a vacuum degassing chamber and 11-a pin shaft.

Detailed Description

The invention is further described with reference to the following figures and detailed description.

As shown in figure 1, the AlON ceramic gel casting vacuum degassing device disclosed by the invention comprises a first degassing cabin 1 and a second degassing cabin 2 which have the same structure and are arranged vertically, a vacuum degassing chamber 10 is formed at the vertical connection position of the first degassing cabin 1 and the second degassing cabin 2, a cavity for containing slurry is arranged in the cabin body, a push plate 3 with a push rod 4 is arranged at one side in the cavity, the push plate can be pushed by the push rod to move back and forth in the cavity, the other side of the cavity is provided with a rotating shaft 5 with a blade 6 at a position close to the vacuum degassing chamber, the rotating shaft is connected in a mounting hole on the inner wall of the cavity, and can rotate in the hole, two mutually vertical inner walls of the vacuum degassing chamber are provided with degassing mechanisms, this degasification mechanism is including being equipped with filter screen 7 on the inner wall, the vacuum line 9 of being connected with the filter screen, and vacuum line 9 can adopt rubber or plastic hose in order to do benefit to the rotation, and vacuum line 9 connects vacuum pump 8.

The whole AlON ceramic gel injection molding vacuum degassing device is arranged on a beam of the frame through a pin shaft 11 and can rotate 90 degrees along the shaft, and a corresponding limiting block 12 is arranged on the frame.

When carrying out the vacuum degassing, at first pour into the first degasification cabin die cavity that the level set up with AlON ceramic thick liquids into, open the vacuum pump, promote the push rod afterwards, and promote the push pedal and remove thick liquids toward the opposite side, thick liquids when the pivot, it rotates to drive the pivot, the paddle stirs thick liquids simultaneously, make the bubble in the thick liquids broken by stirring out, gas is by vacuum degassing mechanism suction, thick liquids fall down under the action of gravity simultaneously, get into the die cavity in second degasification cabin, along with the push pedal removes pivot one side, the first time degasification process is accomplished, with the push pedal return this moment, along the round pin axle with whole AlON ceramic gel injection molding vacuum degassing unit rotation 90, and fix on the stopper, make the second degasification cabin become the level, first degasification cabin becomes perpendicular, promote the above-mentioned process of push pedal repetition in the second degasification cabin, make the thick liquids carry out the degassing of second time.

Compared with the vacuum stirring degassing device in the prior art, the AlON ceramic gel injection molding vacuum degassing device disclosed by the invention adopts a slurry moving mode, so that each part of slurry is stirred by the paddle when passing through the rotating shaft and is exposed in a vacuum environment, gas can be fully separated out, and meanwhile, after the first degassing process is finished, the whole vacuum degassing device can be repeated by rotating 90 degrees, and the device is simple in structure and high in efficiency. Set up the filter screen on the vacuum degassing chamber inner wall, prevent that thick liquids from being inhaled vacuum line, the pivot need not external drive, passes through the in-process at thick liquids and is rotated by automatic drive, drives the paddle and stirs thick liquids. The push rod may be driven manually or by a motor.

The invention also discloses an AlON gel injection molding method which is suitable for the vacuum degassing device, comprising the following steps:

(1) and (3) AlON powder synthesis: by using Al₂O₃The powder and carbon source are used as raw materials, nitrogen is introduced into a boiling bed to be used as boiling gas, and partial Al is caused to be generated₂O₃Formation of gaseous Al by reduction of a carbon source₂O or Al, and then reacting with nitrogen to form AlN and Al₂O₃The mixed powder of (1); then continuously raising the temperature in the boiling bed reaction chamber to ensure that Al₂O₃AlON is generated by solid phase reaction with AlN at high temperature; cooling to obtain AlON powder.

(2) Selecting 99-99.5 parts of AlON ceramic powder and Y by weight parts₂O₃+La₂O₃0.5-1 part of powder, wherein the average grain diameter of AlON ceramic powderIs about 6-10 μm, Y₂O₃、La₂O₃The average particle size of the powder is 150-200nm, the powder is mixed and put into a planetary ball mill, absolute ethyl alcohol is added as a solvent for ball milling, and the ball milled powder is put into a vacuum drying oven for drying to prepare mixed powder. Wherein AlON ceramic powder is used as a sintered substrate, Y₂O₃And La₂O₃The powder is used as a sintering aid, and after repeated tests are carried out on the content and the granularity of the sintering aid components in experiments, the sintering temperature can be well reduced, the sintering density is improved, and the comprehensive effect of the mechanical property and the optical property of the product is properly improved under the content and the granularity. The effect is not obvious when the addition content of the auxiliary agent is low, and the addition content is too high, so that a second phase in an AlON matrix is generated, and the performance is reduced. And (3) carrying out hydration resistance treatment on the powder, adding the mixed powder into distilled water containing 1 wt% of orthophosphoric acid, dispersing for 20min at 75 ℃ by using a constant-temperature magnetic stirrer, filtering out excessive water, and drying to obtain the hydration resistance-resistant mixed powder.

(3) 10g of acrylamide, 0.9g of N, N' -methylenebisacrylamide and 1.2g of JA-281 were added to 100g of deionized water to form a premix, and 82g of the premix was taken for use. Adding the mixed powder into 82g of premix liquid in batches, specifically adding 80g of mixed powder firstly, placing the mixed powder in a quick mill for ball milling for 30 minutes, then adding 120g of mixed powder, placing the mixed powder in the quick mill for ball milling for 30 minutes to prepare slurry with the solid phase volume content of 35-45 vol% and the viscosity of 60-100 mPa.s. On the basis that the inventor carries out calculation design on the dosage, the powder adding amount and the time of each component in the AlON ceramic powder gel forming process on the basis of carrying out early-stage research on the polymerization effect of the monomer and the cross-linking agent, so that the finally obtained slurry has the solid phase volume content of 35-40 vol% and the viscosity of 60-100mPa & s, is beneficial to vacuum exhaust and has good formability.

(4) And then, carrying out vacuum degassing on the slurry in a designed vacuum degassing device, adding 1.7g of tetramethylethylenediamine and 2.5g of ammonium persulfate into the obtained slurry, uniformly stirring, injecting into a mold, curing at 50 ℃ for 2 hours, demolding to obtain a biscuit, and then drying at 80 ℃ for 20 hours.

(5) And (3) heating the dried biscuit to 750 ℃ at the speed of 15 ℃/min, preserving the heat for 3 hours, removing gel substances in the biscuit, and then sintering the biscuit for 10 hours at 1920 ℃ without pressure to obtain the AlON transparent ceramic.

Specifically, the AlON powder used in the invention adopts Al₂O₃Powder and carbon source are used as raw materials, an ebullated bed method is introduced on the basis of an alumina reduction nitridation method, nitrogen is introduced into the ebullated bed to be used as boiling gas, and partial Al is made₂O₃Formation of gaseous Al by reduction of a carbon source₂O or Al, and then reacting with nitrogen to form AlN and Al₂O₃The mixed powder of (1); then continuously raising the temperature in the boiling bed reaction chamber to ensure that Al₂O₃AlON is generated by solid phase reaction with AlN at high temperature; cooling to obtain AlON powder. One specific process flow is as follows:

(1) preparing materials: by purity of>99.99 percent of high-purity gamma-Al with the particle size distribution D50 of 60nm₂O₃Powder, and purity>99.99 percent of carbon black with the particle size distribution D50 of 180-200nm as a raw material, and Al₂O₃The mass ratio of the carbon black to the carbon black is 16: 1;

(2) carbon black is put into a heating chamber, preheated to 750 ℃, and nitrogen with the purity of 99.99 percent and the pressure of 0.8MPa is introduced into a reaction chamber of a fluidized bed at the same time, so that the reaction chamber is in a nitrogen atmosphere;

(3) followed by high purity gamma-Al₂O₃Mixing the powder with the preheated carbon black powder and feeding the mixture into a reaction chamber through a material inlet, wherein the thickness of a powder bed layer is about 0.08 m;

(4) the temperature in the boiling bed reaction chamber reaches 1600 ℃, and the purity is introduced from a blower at the bottom of the boiling bed reaction chamber>99.99%, nitrogen gas with pressure of 1.1MPa as boiling gas, nitrogen flow rate of 0.7m/s, and maintaining for 20min, wherein part of Al is added during the process₂O₃Formation of gaseous Al by reduction of carbon black₂O or Al, and then reacting with nitrogen to form AlN and Al₂O₃The mixed powder of (1);

(5) then, the temperature in the reaction chamber of the fluidized bed reaches 1800 ℃, the nitrogen pressure is increased to 2.0Mpa, the nitrogen flow rate is 1.0m/s, the temperature is kept for 15min, and Al in the process₂O₃Carrying out solid phase reaction with AlN at high temperature to generate gamma-AlON;

(6) and conveying the reacted gamma-AlON powder to a cyclone separator by an air blower, separating, and cooling to obtain AlON powder.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A vacuum degassing method for AlON ceramic gel casting is characterized in that a vacuum degassing device for AlON ceramic gel casting is adopted for degassing, the vacuum degassing device for AlON ceramic gel casting comprises a first degassing cabin and a second degassing cabin which are identical in structure and are arranged vertically, a vacuum degassing chamber is formed at the vertical connection position of the first degassing cabin and the second degassing cabin, a cavity for containing slurry is arranged in the degassing cabin, a push plate with a push rod is arranged at one side in the cavity and can push the push plate to move back and forth in the cavity by the push rod, a rotating shaft with blades is arranged at the position, close to the vacuum degassing chamber, of the other side of the cavity, the rotating shaft is connected in a mounting hole in the inner wall of the cavity and can rotate in the hole, degassing mechanisms are arranged on two inner walls of the vacuum degassing chamber, each degassing mechanism comprises a filter screen arranged on the inner wall and a vacuum pipeline connected with the filter screen, the vacuum pipeline is connected with a vacuum pump.

The specific steps of vacuum degassing are as follows: first pour into the first degasification cabin die cavity that the level set up with AlON ceramic slurry into, open the vacuum pump, promote the push rod afterwards, and promote the push pedal and remove slurry toward the opposite side, slurry is when the pivot, it rotates to drive the pivot, the paddle stirs slurry simultaneously, make the bubble in the slurry broken by stirring out, gas is by vacuum degassing mechanism suction, slurry falls into the die cavity in second degasification cabin under the action of gravity simultaneously, along with the push pedal removes pivot one side, first degassing process is accomplished, with the push pedal return this moment, rotate 90 with whole AlON ceramic gel injection molding vacuum degassing unit along the axle, make second degasification cabin become the level, first degasification cabin becomes perpendicular, promote the above-mentioned process of push pedal repetition in the second degasification cabin, make slurry carry out the degassing of second time.