Cheng Zhiqiang [SMM Annual meeting] expert post: the development status and application of analytical preparation technology of high-performance alumina ceramics are taught in an all-round way!

SMM12 March 3: at the 2020 non-ferrous metals industry annual meeting and long-term carnival jointly held by SMM (SMM) and China Renewable Resources Industry Technology Innovation Strategic Alliance, Cheng Zhiqiang, vice president of Shandong Industrial Ceramic Research and Design Institute, gave a comprehensive explanation on the development status and application of high-performance alumina ceramics, alumina ceramic industry chain and preparation technology.

I. brief introduction of alumina ceramics

Alumina ceramic (alumina ceramics) is a kind of ceramic material with α-Al2O3 as the main crystal phase-- one of the earliest research, the most widely used and the largest output.

It is mainly divided into high purity type: Al2O3 content > 99.9%, sintered T as high as 1650-1900 ℃, and ordinary type (75-99%): 75 porcelain, 85 porcelain, 90 porcelain, 99 porcelain and so on.

There are 12 kinds of isomorphous variants, such as α, β, γ, δ, ε, ζ, η, θ, κ, λ, ρ and amorphous alumina. The most common ones are α-Al2O3, β-Al2O3 and γ-Al2O3.

2. Preparation technology of alumina ceramics.

technological process

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

Sintering, including sintering system-the shortest firing curve (heating, heat preservation, cooling) to achieve the best performance at the lowest firing temperature, atmosphere: inertia, oxidation, reduction, vacuum, air; pressure; firing mode (hot pressing, hot isostatic pressing, microwave heating, Discharge plasma, self-flaming)

The forming technology includes dry method, plastic method, wet method, adding material manufacturing (3D printing).

New technology of precision machining-plastic processing technology: grinding + laser, grinding + ultrasonic wave

Ceramic augmented manufacturing (3D printing) 3D printing technology, also known as augmented manufacturing, rapid prototyping, formless prototyping and so on.

Based on 3D digital model, the technology of layer-by-layer manufacturing and layer-by-layer superposition is adopted to form 3D solid (layer-by-layer shaping method).

Analysis of Global 3D Printing Market

According to the latest report from Grand View Research, the global ceramic 3D printing market is expected to approach $160 million by 2025.

It is estimated that by 2025, the market for 3D printing of ceramics for aerospace end-use will reach US $26.1 million, and the annual growth rate of related demand in the medical field will be about 35.4%.

Properties and applications of alumina ceramics

It has high mechanical strength, good electrical insulation, high hardness and melting point, good corrosion resistance, excellent chemical stability, and good optical properties and ionic conductivity under certain conditions.

It has a wide range of applications, mainly in mechanical, electronic, electric, chemical and medical aspects.

Mechanical aspects (high strength, high hardness, wear resistance)-cutting tools, ball valves, abrasives, bearings, wire drawing parts

Alumina ceramic cutting tools: hard cutting, high-speed dry cutting, ultra-high-speed cutting

With the advantages of high heat resistance, high hardness and wear resistance and excellent chemical stability, it is one of the most important cutting tools in cutting, and its machining efficiency is 10 times higher than that of traditional tools.

Valves for alumina ceramic industry (seal)

Plug valve: in oil exploitation, transportation and refining equipment, it is also widely used in petrochemical, coal chemical, natural gas and other industrial fields.

Gate valve, globe valve: tap water, sewage, construction, petroleum, chemical industry, food, medicine, textile, electric power, ship, metallurgy, energy system, etc.

Ball valve: especially suitable for media with bad working conditions, such as oxygen, hydrogen peroxide, methane, ethylene, strong acid, etc.

Electronics and power (high strength, good insulation)-substrates, transparent ceramics, electrical insulating ceramics, spark plugs, etc.

Alumina ceramic substrate (high temperature resistance, high electrical insulation, low dielectric constant and dielectric loss, high thermal conductivity, good chemical stability)

Ultra-high voltage pillar insulators (high strength, high resistance, high dielectric strength, low dielectric constant and dielectric loss, good chemical stability)

Chemical industry (high temperature resistance, good chemical stability, strong acid and alkali resistance and organic solvent corrosion)-chemical fillers, Bubble, honeycomb, micropores, mesoporous ceramics (membranes), corrosion resistant coatings, etc.-filling, supporting and purifying separation materials

Chemical fillers (high temperature resistance, corrosion resistance, high specific surface area)

Different structures and shapes: Rasi ring, Bauer ring, cross diaphragm ring, stepped ring, moment saddle ring, different saddle ring and so on. Used in drying towers, absorption towers, cooling towers, washing towers, regeneration towers, etc., in chemical, metallurgical, gas, oxygen production and other industries.

Ceramic film (high specific surface area, high temperature resistance, corrosion resistance)-environmental protection, biochemistry, food and medicine, catalytic reaction, chemical industry, metallurgy, water treatment, seawater desalination, etc.

Medical aspects (high strength, high hardness, good chemical stability, biological inertia)-artificial bones, artificial joints, artificial teeth, etc.

Al2O3-HAP composite material-good biological properties, stable physical and chemical properties, hardness, bending strength and fracture toughness are close to human bone-- it is expected to be the most ideal bone graft material.

Transparent alumina ceramics

Definition of transparent ceramics: ceramics that can pass through light and can be imaged. Light includes ultraviolet light, visible light, infrared light and so on.

Basic conditions for light transmission of ceramics

Density > 99.5% of theoretical density

There is no gap at the grain boundary or the size of the gap < < the wavelength of incident light.

There are no impurities and glass phases at the grain boundary, or their optical properties are similar to those of microcrystals.

The grains are small and uniform, in which there are no voids.

The selective absorption of incident light by the crystal is very small.

The surface is smooth and clean.

Classification of transparent ceramics

Transparent ceramic

Translucent alumina-transparent alumina-submicron transparent alumina

Mid-infrared transparent ceramics form a series of all kinds of materials.

Including: YAG, Y2O 3, submicron crystal Al2O3, AlON, MgAl2O4, etc.

V. opportunities and challenges

The stage of high-quality development: the key period of changing the mode of development, optimizing the economic structure and changing the driving force of growth.

The present situation of China's new material industry: as a whole, it is "big but not strong", which is reflected in the following points.

Unreasonable product structure

The supply of high-end materials is seriously insufficient.

There are many low-level repetitive construction and overcapacity of low-end varieties.

The Ministry of Industry and Information Technology: a survey of more than 130 key materials shows that 32% are in a domestic blank and 52% rely on imports-- "2018 National Manufacturing Power expert Forum"

The core technology is controlled by others, and the transformation of achievements is slow.

The original innovation ability is insufficient, and the R & D and supporting ability of common technology is not strong.

The core technologies in some areas are controlled by the United States, Japan and Germany, and key components and equipment still rely heavily on imports.

Weak competitiveness in the international market

Insufficient cooperation between enterprises and regions

Except that the technology and equipment of some backbone enterprises approaches or reaches the international advanced level, most of the small and medium-sized enterprises are backward in technology and equipment.

Attach importance to the development of new materials industry: at present, the policy pyramid for the development of new materials has been constructed through programmatic documents, guidance documents, planning and development goals and tasks.

New materials, including alumina powder and high-performance alumina ceramics, are key basic raw materials! It is an indispensable and important support for energy saving and environmental protection, new generation information technology, aerospace and so on. High-end alumina powder and new materials including high-performance ceramics have a bright future.