What’s the alumina ceramic?

Alumina ceramics are a very widely used material. It has a lot of great features, and it’s very cheap.Many people want to know more about alumina ceramics. So we wrote this article hoping to help everyone.

  • What is alumina ceramic?
  • History of alumina ceramic
  • History of alumina ceramic
  • Classification of Aluminum Oxide Ceramics
  • Manufacturing Technology of Aluminum Oxide Ceramics
  • How to Choose Suitable Aluminum Oxide Ceramic Products
  • How to choose the right alumina ceramic manufacturer
  • Applications of alumina ceramics
  • Development trends of alumina ceramics

1、What is alumina ceramic?

Alumina ceramic is a type of ceramic material mainly composed of aluminum oxide (Al2O3), used as an insulating material for electrical components. Alumina ceramic has good conductivity, mechanical strength, and high-temperature resistance. Its characteristics make it one of the most widely used ceramics in structural, wear, and corrosive environments.

Alumina ceramic is usually made from bauxite and can be produced using injection molding, pressing, isostatic pressing, slip casting, diamond machining, and extrusion. Like other important engineering materials such as silicon nitride, alumina can be produced by dry pressing and sintering or by hot pressing with appropriate sintering aids.

Alumina ceramic belongs to technical ceramics due to its performance and cost-effectiveness. Alumina ceramic is classified based on its aluminum oxide content, ranging from 70% to 99.9%. The higher the purity of alumina, the stronger its wear resistance and corrosion resistance.

2、History of alumina ceramic

In 1931, Siemens Halske in Germany first applied alumina ceramic to spark plug materials and obtained the “Sinter Korund” patent. At that time, it was a new material with superior performance compared to other materials and attracted people’s attention. However, the manufacturing technology of alumina ceramic products was not mature at that time, and there were few applications that could fully utilize its excellent performance, so the development was slow. With the advancement of manufacturing technology, people gradually recognized the excellent properties of alumina ceramic materials such as heat resistance and electrical insulation, especially in the past decade, alumina ceramic products have developed rapidly.

3、Characteristics of alumina ceramic

High hardness: Its Rockwell hardness is HRA80-90, second only to diamond, far exceeding the wear resistance of wear-resistant steel and stainless steel.

Excellent wear resistance: Its wear resistance is equivalent to 266 times that of manganese steel and 171.5 times that of high-chromium cast iron.

Light weight: Its density is 3.5g/cm3, only half that of steel, which can greatly reduce equipment load.

Wide range of applications: It can be used in all machinery with high wear and tear, and different types of products can be selected according to different needs.

4、Classification of Aluminum Oxide Ceramics

Aluminum oxide ceramics are classified into two types: high-purity and ordinary.

High-purity aluminum oxide ceramics are ceramic materials with an Al2O3 content of over 99.9%. Due to their high sintering temperature of 1650-1990°C and their transmittance wavelength of 1-6 μm, they are generally used to make melting glasses instead of platinum crucibles. They are also used as sodium lamp tubes due to their transparency and resistance to alkali metal corrosion, and as integrated circuit substrates and high-frequency insulation materials in the electronics industry.

Ordinary aluminum oxide ceramics are divided into different varieties according to their Al2O3 content, such as 99 ceramics, 95 ceramics, 90 ceramics, and 85 ceramics. Sometimes, those with an Al2O3 content of 80% or 75% are also included in the ordinary aluminum oxide ceramic series. Among them, 99% aluminum oxide ceramics are used to make high-temperature crucibles, refractory furnace tubes, and special wear-resistant materials, such as ceramic bearings, ceramic sealing components, and water valve discs. 95% aluminum oxide ceramics are mainly used as corrosion-resistant and wear-resistant components. 85 ceramics, due to the addition of some talc, improve their electrical performance and mechanical strength. They can be sealed with metals such as molybdenum, niobium, and tantalum and are used as electric vacuum device components.

5、Manufacturing Technology of Aluminum Oxide Ceramics

Raw material processing: using green and efficient processing technology and high-energy equipment, including high-purity, ultra-fine, distribution, and morphology aspects.

Sintering includes the firing system, which is the shortest firing curve (heating, holding, and cooling) that obtains the best performance at the lowest firing temperature, atmosphere: inert, oxidizing, reducing, vacuum, air; pressure; firing method (hot pressing, hot isostatic pressing, microwave heating, discharge plasma, self-propagating high-temperature synthesis).

Forming technology includes dry, plastic, wet, and additive manufacturing (3D printing).

New technologies have emerged in the precision processing link, such as the plastic processing technology of grinding + laser and grinding + ultrasonic.

Ceramic additive manufacturing (3D printing) technology, also known as additive manufacturing, rapid prototyping, and moldless manufacturing. Based on the 3D digital model, it uses layer-by-layer manufacturing to form a three-dimensional solid object (layered manufacturing method).

6、How to Choose Suitable Aluminum Oxide Ceramic Products

Industrial wear has always been a problem. Different equipment has different wear conditions, and the specific degree is determined by its working conditions. Suitable wear-resistant materials should be selected to solve equipment wear problems.

Nowadays, aluminum oxide ceramics have become widely used wear-resistant materials due to their high wear resistance and corrosion resistance. When selecting wear-resistant ceramics, the conveying method and working conditions of the material should be considered first, generally with pneumatic conveying or material conveying with a large impact force.

In a pneumatic conveying system, the equipment is subjected to greater wear but not much impact force. In this case, wear-resistant ceramics with high hardness should be considered to reduce equipment wear.

In the material conveying with a large impact force, such as a large drop, greater impact force is exerted, and wear-resistant ceramics with better toughness should be selected to resist material impact. Secondly, it is also necessary to consider the properties of the material, the size of the material, etc.

7、How to choose the right alumina ceramic manufacturer

7.1 Inspect the factory:

Alumina ceramic processing is quite difficult, so the requirements for processing equipment are very high. These high-precision advanced equipment are very expensive. If the production manufacturer is small in scale and the production workshop looks simple, then the processing equipment is definitely not high-precision, and the quality of the processed alumina ceramics cannot be effectively guaranteed.

7.2 Inspect the production process:

Having equipment alone is not enough to guarantee product quality. We cannot consult customer service or sales with mature and exquisite production processes. We can ask the other party to introduce the production process and processing flow or ask for samples. Alumina ceramics produced by strong manufacturers are not only smooth, wear-resistant, and corrosion-resistant, but also have good high-temperature resistance, acid and alkali resistance, and other advantages.

7.3 Inspect the raw materials:

A trustworthy alumina ceramic manufacturer will use modern engineering ceramic materials as raw materials. This type of ceramic material has high hardness and better wear resistance. The choice of materials will also play an important role in the quality of alumina ceramics.

7.4 Inspect the length of operation:

Excellent companies can stay in a field for a long time. Through time accumulation and precipitation, it is believed that products produced by such companies are more reliable and trustworthy. Such manufacturers will also provide more complete and thoughtful after-sales service.

8、Applications of alumina ceramics:

In the electronics industry, alumina ceramics are used in interconnects, resistors, and capacitors. They are an economical and durable material used for substrates in hybrid integrated circuits, surface mount devices, and sensors. Alumina ceramic cutting tools have strength and thermal conductivity. Although they are very expensive, disposable materials have been designed using composite materials to be cost-effective and manufactured through sintering and pressing. Alumina ceramics’ high impact resistance makes them suitable for body armor in protective tanks, helicopters, and bulletproof jackets in military applications. Due to their inertness, insolubility in chemical agents, wear resistance, and ability to have a highly polished surface, alumina ceramics can be used as a biological material. They are used in artificial joints, bone spacers, cochlear implants, and dental implants. Tubes and scientific products are also made from alumina ceramics.

9、Development trends of alumina ceramics:

As the most widely used material in advanced ceramics, alumina ceramics exhibit the following development trends along with the industry’s overall development:

9.1 Technological equipment level will improve rapidly:

The development of computer technology and digital control technology has promoted the technical progress and rapid development of the advanced ceramic material industry. Advanced complete sets of equipment, such as automatic control continuous sintering furnaces, high-power and high-capacity grinding equipment, and high-performance powder-making and granulating equipment, have significantly improved the industry’s overall level in production efficiency and product quality.

9.2 Product quality level will continue to improve:

Chinese microcrystalline alumina ceramic products have gone through a rapid development process, from non-existent to small-scale production, and from low to higher product quality.

9.3 Industry scale will expand rapidly:

As a basic material for other industries or fields, microcrystalline alumina ceramic products are influenced and restricted by the development level of other industries. From the application of alumina ceramics, their application range is becoming wider, and the amount used is increasing, especially in anti-wear engineering and the production of building ceramics, the increase in usage will be more significant.

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