CN104230316A - Method for preparing aluminum oxide ceramic - Google Patents

Abstract

The invention provides a method for preparing aluminum oxide ceramic and belongs to the technical field of ceramic preparation. The method for preparing aluminum oxide ceramic is achieved by the following technical scheme comprising: (1) evenly mixing 10-30% by weight of thermoplastic plastic or a resin organic binder with aluminum oxide powder at a temperature of 150-200 DEG C; and (2) carrying out dry pressing molding and sintering in the presence of high-temperature and high-pressure gas serving as a transmission medium, wherein the particle size of the aluminum oxide powder is between 60mu m and 60-200 meshes. By adopting the method for preparing the aluminum oxide ceramic, which is disclosed by the invention, the sintering is carried out by adopting the high-temperature and high-pressure gas serving as the transmission medium; the method has the advantage of uniform heating in all directions and is suitable for sintering articles with a complex shape;, since the structure is uniform, the performance of materials is respectively improved by 30-50% compared with the performance of a material prepared by cold-pressing and sintering and is improved by 10%-15% compared with a material prepared by general hot-pressing and sintering; the prepared aluminum oxide ceramic has the excellent performances such as high melting point, high hardness, good mechanical properties, corrosion resistance and insulation and the like.

Description

The making method of alumina-ceramic

Technical field

The invention belongs to technical field of ceramic preparation, particularly relate to a kind of making method of alumina-ceramic.

Background technology

Current pottery has not only been widely used the field of domestic ceramics (crockery, tea set) and the art pottery (ceramic vase, sculpture), is also more applied to other aspects.

Alumina-ceramic is divided into high-purity type and coventional type two kinds at present.The stupalith of high-purity type alumina-ceramic system Al2O3 content more than 99.9%, because its sintering temperature is up to 1650-1990 DEG C, transmission peak wavelength is 1 ~ 6 μm, is made generally in melten glass to replace platinum crucible: utilize its light transmission and can be used as sodium vapor lamp pipe by alkaline-resisting metal protection; Can be used as ic substrate and high-frequency insulation material in the electronics industry.Coventional type alumina-ceramic system is divided into the kinds such as 99 porcelain, 95 porcelain, 90 porcelain, 85 porcelain by Al2O3 content difference, and Al2O3 content also divides common alumina-ceramic series into 80% or 75% sometimes.Wherein 99 alumina ceramics materials are for making high-temperature crucibles, fire-resistant boiler tube and special high-abrasive material, as ceramic bearing, ceramic seal and water valve plate etc.; 95 alumina ceramics are mainly used as corrosion-resistant, wear parts; Owing to often mixing part talcum in 85 porcelain, improve electrical property and physical strength, can with the metal sealing such as molybdenum, niobium, tantalum, what have is used as electrovacuum device device.

Summary of the invention

The invention provides a kind of making method of alumina-ceramic.The present invention is realized by following technical proposals:

(1) weight ratio account for 10-30% thermoplastic plastic or resin organic binder bond and alumina powder jointed at 150-200 DEG C of temperature Homogeneous phase mixing, powder granule is greater than 60 μm, between 60 ~ 200 orders;

(2), after dry-pressing formed, high temperature and high pressure gas sinters as pressure transfer medium.

Adopt the making method of alumina-ceramic of the present invention, high temperature and high pressure gas is adopted to sinter as pressure transfer medium, there is each advantage to thermally equivalent, be well suited for the sintering of complex-shaped goods, due to even structure, material property, than cold-rolled sintered raising 30 ~ 50%, improves 10 ~ 15% than general hot pressed sintering, and obtained alumina-ceramic has the good characteristics such as high-melting-point, high rigidity, good mechanical property, anti-corrosion, insulation.

Embodiment

Below by specific embodiment, the present invention is further illustrated.

One powder preparation:

The aluminum oxide powder entering factory is prepared into powder body material according to different product requirements from different moulding process.Powder granularity, below 1 μm, if manufacture high-purity alumina ceramic goods alumina purity outside 99.99%, also needs superfine grinding and makes its even particle size distribution.When adopting extrusion molding or injection molding, need in powder to introduce binding agent and plasticizer, be generally weight ratio 10-30% thermoplastic plastic or resin organic binder bond should with alumina powder jointed at 150-200 DEG C of temperature Homogeneous phase mixing, be beneficial to forming operation.The shaping powder raw material of heat pressing process is adopted then not need to add binding agent.According to semi-automatic or full-automatic dry is molded, there is special processing requirement to powder, need to adopt spray granulation to process powder, make it present spherical shape, be beneficial to improve powder fluidity and be convenient to shaping middle automatic filling die wall.In addition, for reducing the friction of powder and die wall, lubricant (as stearic acid) and the binding agent PVA of interpolation 1 ~ 2% is also needed.

For to powder mist projection granulating, need wherein introduce polyvinyl alcohol as binding agent time dry-pressing formed.A kind of water-soluble paraffin of Shanghai institute exploitation is in recent years used as the binding agent of Al2O3 mist projection granulating, under heating state, have good mobility.Powder after mist projection granulating must possess good fluidity, density is loose, and flow angle friction temperature is less than 30 DEG C.The conditions such as grain composition ratio is desirable, to obtain larger biscuit density.

Two forming methods:

Aluminium oxide ceramic products forming method has the multiple methods such as dry-pressing, slip casting, extruding, isostatic cool pressing, injection, curtain coating, hot pressing and hip moulding.Developed again both at home and abroad in recent years pressure filtration molding, Direct Coagulation Casting, gel casting, centrifugal grouting shaping with Solid Freeform etc. forming technique method.The forming method that different shape of products, size, complex model are different from the product needed of precision.Pluck its conventional shaping introduction:

Dry-pressing formed: the dry-pressing formed technology of alumina-ceramic is only limitted to the simple and inner wall thickness of shape more than 1mm, and length-to-diameter is not more than the object of 4: 1.Forming method has uniaxially or two-way.Press has fluid pressure type, mechanical type two kinds, can be semi-automatic or full-automatic molding mode.Press peak pressure is 200MPa.Output per minute can reach 15 ~ 50.Because fluid pressure type press stroke pressure is even, therefore rolled-up stock height is different when powder is filled with difference.And mechanical type press applying pressure size changes because powder filling is how many, easily cause sintering rear dimensional contraction and produce difference, affect quality product.Therefore in dry-pressing process, powder granule is uniformly distributed mould filling extremely important.Whether accurate the fill-up alumina-ceramic parts size precision control effect to manufacturing be very large.Powder granule, to be greater than 60 μm, can to obtain maximum unrestricted flow effect between 60 ~ 200 orders, obtains best pressure forming effect.

Slip casting: injection forming is the forming method that alumina-ceramic uses the earliest.Owing to adopting plaster mould, cost low and being easy to the parts of shaping large size, complex contour.The key of injection forming is the preparation of alumina slurry.Usually be flux medium with water, then add dispergator and binding agent, the final vacuum of fully grinding, then fall in injection plaster mould.Because plaster mould kapillary is to the absorption of moisture, slurry is solidificated in mould then.During drain casting, when die wall absorption slurry reaches required thickness, also need additional size to pour out.For reducing base substrate shrinkage, high concentration slurry should be used as far as possible.

Also needing to add organic additive in alumina-ceramic slurry makes slip stable suspersion not precipitate to make slip particle surface form electrostatic double layer.Need in addition to add binding agent and the dispersion agents such as polypropylene amine, Sudan Gum-arabic such as vinyl alcohol, methylcellulose gum, marine alga acid amide, object is all to make slurry be suitable for injection forming operation.

Three firing technologies:

By particulate ceramic blank Densification and the technological method forming solid material sintering.Sinter and get rid of by cavity between base substrate endoparticle, a small amount of gas and impurity organism are got rid of, makes mutually to grow combination between particle, form the method for new material.

The heating unit burning till use widely uses electric furnace most.Except normal pressure-sintered (i.e. pressureless sintering), hot pressed sintering and hot isostatic pressing is also had to burn till.Although continuous hot-press sintering improves output, equipment and mold expense is too high, and in addition owing to belonging to axial direction heated, article length is restricted.Hot isostatic pressing burns till and adopts high temperature and high pressure gas to make pressure transfer medium, has each advantage to thermally equivalent, is well suited for the sintering of complex-shaped goods.Due to even structure, material property is than cold-rolled sintered raising 30 ~ 50%.10 ~ 15% are improved than general hot pressed sintering.Therefore, at present some high added value alumina ceramic products or defence and military need special component, adopt hot isostatic pressing process for calcining as the goods such as ceramic bearing, speculum, nuclear fuel and gun barrel, field.

In addition, microwave sintering method, arc plasma sintering process, self-propagating sintering technology are also just in development research.

Four precision work and packaging process:

Some alumina ceramic material, after completing sintering, is still needed and is carried out precision work.As the goods that can be used as artificial bone require surface to have very high smooth finish, as minute surface, to increase oilness.Because alumina ceramic material hardness is higher, precision work need be done with harder grinding and polishing brick to it.As SiC, B4C or diamond drill etc.The grinding step by step of usual employing abrasive material from coarse to fine, final surface finish.The Al2O3 micro mist of < 1 μm or diamond drill cream generally can be adopted to carry out grinding and polishing.In addition the method for laser processing and ultrasonic machining grinding and polishing also can adopt.

Claims (1)

1. a making method for alumina-ceramic, is characterized in that comprising the following steps:

(1) weight ratio account for 10-30% thermoplastic plastic or resin organic binder bond and alumina powder jointed at 150-200 DEG C of temperature Homogeneous phase mixing, powder granule is greater than 60 μm, between 60 ~ 200 orders;

(2), after dry-pressing formed, high temperature and high pressure gas sinters as pressure transfer medium.