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10 minutes to understand alumina ceramic

Alumina ceramic is the most well-known and most commonly used fine ceramic material. It has the same sintered crystal body as sapphire and ruby. Alumina ceramic is a kind of ceramic material with alumina (Al2O3) as the main body.  As alumina ceramics have a series of advantages such as high-temperature resistance, corrosion resistance, wear resistance, high hardness, etc., they can replace metal materials and organic polymer materials for harsh working environments.

As an indispensable important material, it has broad application prospects in the fields of energy, aerospace, machinery, automotive, electronics, and chemistry. These alumina ceramics are made into ceramic heating, alumina ceramic rod, ceramic shaft for pump, ceramic seals for water pumps.

This ceramic is made of AL2O3 as the main component (AL2O3 mass fraction is> 45%). According to the content of AL2O3, it can be divided into 75% alumina ceramics, 95% alumina ceramics, and 99% alumina ceramics.


ceramic seals for pumps


Properties of alumina ceramics



Advantages:


1. High mechanical strength (bending strength) and hardness;

2. High abrasion resistance

3. Resistant to chemical attack by strong acids and bases, even at high temperatures;

4. High stiffness

5. Excellent insulation performance;

6. Low thermal expansion coefficient;

7. Good fracture toughness;

8. Good thermal conductivity;

9. Good biocompatibility.


Disadvantages:


1. Brittle

2. Poor impact resistance

3. Poor thermal shock resistance

4. Difficult to shape

5. High processing costs


Production process and cost analysis


The production process of alumina ceramics

process of making alumina ceramics

In the four steps, molding is the core process. It determines the processing method of the raw materials, the sintering method, and the size of the processed amount.


Alumina ceramic forming method


Alumina ceramic products can be formed by dry pressing, grouting, extrusion, cold isostatic pressing, injection, casting, hot pressing, and hot isostatic pressing. In recent years, the alumina ceramic industry has developed more molding techniques such as filter press molding, direct solidification injection molding, gel injection molding, centrifugal grouting, and solid free molding. Products with different product shapes, sizes, complex shapes, and accuracy require different molding methods. The following mainly introduces common molding methods of alumina ceramics.


1. Dry pressing


Raw material: granulated powder

Sintering: high-temperature sintering

Alumina ceramic dry pressing technology is limited to objects' inner wall thickness exceeding 1mm, the ratio of length to diameter is not greater than 4: 1, and simple shapes such as rings, squares, and flat plates.

There are two types of presses: hydraulic and mechanical. They can be semi-automatic or fully automatic. Because the stroke pressure of the hydraulic press is uniform, the height of the pressed parts is different when there is a difference in the powder filling.

However, the amount of pressure applied by a mechanical press varies depending on how much the powder is filled, which can easily lead to differences in dimensional shrinkage after sintering and affect product quality. But the automatic mechanical molding is extremely efficient. Therefore, the uniform distribution of powder particles during dry pressing is very important for mold filling. The accuracy of the filling amount has a great influence on the dimensional accuracy control of the manufactured alumina ceramic parts.


2. Hot injection molding


Raw material: Paraffin alumina powder mixture

Sintering: Discharge paraffin

                High-temperature sintering

The hot injection molding method is a relatively extensive production method for producing alumina ceramics. The basic principle is the use of paraffin heating and melting and cooling solidification characteristics. Alumina powder and hot paraffin liquid are evenly mixed to form a non-plastic ceramic powder. The flowable slurry is then poured into a metal mold, and after the wax slurry is cooled and solidified, the formed green body is removed from the mold. After proper trimming of the body, it is buried in an adsorbent and heated for dewaxing. Finally, the dewaxed body is sintered into a final product.


3. Isostatic pressing method


Raw material: powder

Sintering: high-temperature sintering

The isostatic pressing method refers to a method in which a compressed sample is placed in a high-pressure container, and the sample is uniformly pressurized from all directions by using the incompressible characteristics of the liquid medium and the uniform pressure transmission characteristics. According to the principles of fluid mechanics, the pressure is transmitted uniformly and uniformly in all directions. Therefore, the pressure on the powder in the high-pressure container in all directions is uniform and consistent in size. By the above method, a dense green body can be formed with inferior powder, and finally, an alumina ceramic product is formed.


Cost analysis


The excellent properties of ceramic materials can be used in many places, but often the cost limits the scope of use of ceramic materials. Product performance and production cost are two contradictions that cannot be adjusted.

The main reasons for cost:

1. Difficulty of molding

the main component of alumina ceramics has poor molding ability, and the use of additives will affect the performance of the product.

2. Processing difficulty

because of the high hardness and high brittleness of alumina ceramic, it can only be processed with diamond.

3. Product irreversibility

The product of alumina ceramic is irreversible during production, so the scrap rate cannot be reduced.

products of alumina ceramics

Choosing the right molding method will greatly reduce costs and improve product quality.

 


Classification and application of alumina ceramic


Small changes in alumina content in the formula can cause very large changes in ceramic properties. Several common alumina ceramics will be introduced below.

 


75% Alumina


This is a highly versatile alumina ceramic with great mechanical, electrical, thermal, and chemical properties.

Featuring:

Low thermal expansion

Good mechanical strength and hardness

Chemical and corrosion resistance

Consistent electrical and mechanical properties

Thermal stability

Dense, non-porous and vacuum tight

These features make this alumina ceramics become an excellent choice for gaskets, resistors, and heating elements industry which require good mechanical, electrical and thermal performance. The ceramic heating and ceramic gasket are the common products made of 75% alumina ceramic.

No processing, standard block cost:(2.5)USD/kg


95% Alumina


This is high purity alumina ceramic with excellent mechanical, electrical, thermal, and chemical properties.

Features:

Superior electrical properties

High mechanical strength and wear resistance

Moly-manganese metallisable

Chemical and corrosion resistance

Excellent dielectric properties

Dense, non-porous and vacuum tight

The features of this alumina ceramic make this the right choice for applications such as electrical inductors, switches, bushings, electronic packages, bearings, and wear-resistant components. The ceramic seal ring and ceramic pump seal are the common products made of 95% alumina ceramic.

No processing, standard block cost:(4.5)USD/kg


99% alumina


This 99% alumina ceramic material was developed for abrasive resistance and mechanical strength in chemically aggressive environments.

Features:

Excellent resistance to corrosion and chemical attack

Exceptionally hard-wearing and abrasion-resistant

Dense, non-porous and vacuum tight

Excellent dimensional stability across a wide temperature range

This hard-wearing alumina ceramic material used in many pumping products, including wear-resistant components for rotary and reciprocating pumps handling chemically aggressive media: shafts, bearings, thrust washers, plungers, seals, etc. The ceramic shaft and ceramic mechanical seal are the common products made of 99% alumina ceramic.

No processing, standard block cost:(10)USD/kg

 



Mingxing Ceramics Factory is a ceramic component manufacturer providing ceramic parts made of alumina ceramic material including ceramic rod, ceramic shaft, ceramic seal ring, ceramic pump seal, ceramic disc valve, ceramic piston, and ceramic hone. If you have any needs, please contact us !


ceramic shaft for pump


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Fenghua Mingxing Ceramics Factory is a company that produces all kinds of ceramic structural parts. The main products include ceramic shaft rods, ceramic plungers, ceramic valve, ceramic rings, etc. 

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