What is honeycomb ceramics?
Honeycomb ceramics are a new type of industrial ceramics with a honeycomb like structure as the main structure. Inside, there are many interconnected honeycomb shaped parallel channels, and these honeycomb units are divided into thin walls with different shapes of lattices. From its earliest use in small car exhaust purification to its widespread application in industries such as chemical, power, metallurgy, petroleum, electronics, machinery, etc. today, it is becoming increasingly widespread and has considerable development prospects.
Classification of materials and uses of honeycomb ceramics
Honeycomb ceramics can be made from various materials. The main materials include: cordierite, mullite, aluminum titanate, activated carbon, silicon carbide, activated alumina, zirconia, silicon nitride, and composite matrices such as mullite cordierite and cordierite aluminum titanate. After activated carbon powder or particles are made into honeycomb ceramic shapes, the purification and wastewater treatment capabilities of water treatment are greatly improved, especially in the pharmaceutical industry, where antibiotics, hormones, vitamins, nucleic acid injections, and various injections, drugs, etc. are dehydrated, decolorized, and impurities are removed.
Honeycomb ceramic products can be divided into four categories according to their purpose: heat storage materials, fillers, catalyst carriers, and filter materials.
Performance of honeycomb ceramics
- Large specific surface area
- Lightweight
- Low coefficient of thermal expansion
- Large specific heat capacity
- Acid and alkali resistant
- Good chemical stability
- Good insulation performance
- Good thermal shock resistance
- High porosity
Preparation methods of honeycomb ceramics
1. Extrusion molding method
2. Hot Die Casting Forming
3. Grouting method
4. Suppression method
Among them, hot press casting, injection molding, and compression methods are difficult to prepare high pore density, large size, and thin-walled honeycomb ceramics. In actual production processes, the most widely used method for preparing honeycomb ceramics is extrusion molding.
Common Materials for Honeycomb Ceramics
Aluminum porcelain
Oxide ceramics mainly composed of Al2O3-SiO2 and containing a certain amount of mineralizers such as Ba, Ca, Zr, Mg belong to the category of aluminum ceramics. The content of Al2O3 ranges from 45% to 99%. According to the different main crystal phases, aluminum ceramics can be divided into corundum ceramics (Al2O3>95%), mullite ceramics (Al2O3-50%), and mullite corundum ceramics (Al2O3-75%). Aluminum ceramics are mainly used in petrochemical, metal smelting, desulfurization towers, reaction furnaces, packed towers, etc. They serve as support materials and tower fillers for catalysts in reactors. Due to their good mechanical properties, chemical stability, and heat resistance, aluminum ceramics can adapt well to high temperature, high pressure, and strong corrosive working environments.
Mullite
Mullite is a series of minerals composed of aluminum silicates, mainly including high-purity fused mullite, ordinary fused mullite, all natural bauxite concentrate sintered mullite, and light sintered mullite. Natural mullite crystals are slender needle like and radial cluster like, with a melting temperature of about 1910°C. This type of mineral is relatively rare and is mostly synthesized artificially. Mullite is a mineral formed by aluminum silicate at high temperatures, and it is formed when aluminum silicate is artificially heated. Mullite has the characteristics of high temperature resistance, high strength, low thermal conductivity, and significant energy-saving effects. Among them, its fire resistance is particularly excellent, and it is still stable at 1800°C, and decomposes into corundum and liquid phase at 1810°C. It is mostly used in the production of refractory materials and is widely used in industries such as ceramics, metallurgy, casting, and electronics.
Silicon carbide
Silicon carbide (SiC) is made by smelting raw materials such as quartz sand, petroleum coke (or coal coke), and sawdust (salt is required to produce green silicon carbide) through a resistance furnace at high temperature. It is a type of carbide with high Mohs hardness, with a grade of 9.5, second only to the world's hardest diamond (grade 10), and has excellent thermal conductivity. It is a semiconductor that can resist oxidation at high temperatures. Among contemporary non oxide high-tech refractory raw materials such as C, N, and B, silicon carbide is the most widely used and economical one, which can be called steel sand or refractory sand. Common industrial produced silicon carbide is divided into two types: black silicon carbide and green silicon carbide, both of which are hexagonal crystals with a specific gravity of 3.20-3.25 and a microhardness of 2840-3320kg/mm ². Silicon carbide has the characteristics of stable chemical properties, high thermal conductivity, small thermal expansion coefficient, and good wear resistance. The advanced refractory material made from it is heat-resistant, shockproof, small in size, lightweight, and high-strength, with good energy-saving effect.
Cordierite
Cordierite, also known as water sapphire or dichroite, has the chemical formula Mg2Al4Si5O18; It can contain elements such as Na, K, Ca, Fe, Mn, and H2O. Produced in schist, gneiss, and altered igneous rocks, it is a silicate mineral that can be colorless but usually has a light blue or light purple, glassy luster. Magnesium cordierite can be artificially synthesized for use as refractory materials. Cordierite, due to its good fire resistance and low thermal expansion rate, can be used to make materials such as ceramics and glass. It is now commonly used as a raw material for honeycomb carriers in automotive purifiers.
Zirconium oxide
Zirconia ceramics are widely used in the field of structural ceramics due to their high toughness, high bending strength, high wear resistance, excellent insulation performance, and thermal expansion coefficient similar to steel. In terms of functional ceramics, due to their excellent high-temperature resistance, they are used as the main raw materials for induction heating tubes, refractory materials, and heating elements. In addition, zirconia is widely used in thermal barrier coatings, catalyst carriers, medical, healthcare, refractory materials, textiles, and other fields.
Corundum
Corundum is a gemstone formed by the crystallization of aluminum oxide (Al2O3), with an extremely high aluminum content. Corundum mixed with metallic chromium has a bright red color and is generally referred to as ruby; Blue or colorless corundum is generally classified as sapphire. Corundum ranks 9th in the Mohs hardness table. The specific gravity is 4.00, with a lattice structure of hexagonal columns. Due to the hardness of corundum and its relatively lower price than diamonds, it has become a good material for sandpaper and grinding tools.
Development trend
- the penetration rate of domestic honeycomb ceramics in the high-end market will increase -
Domestic honeycomb ceramics have achieved a localization penetration rate of over 90% in the field of energy conservation and purification of low-end industrial waste gases. It is expected that in the next five years, Chinese honeycomb ceramic production enterprises will continuously break through the technical barriers in the high-end market, and are expected to increase the penetration rate of high-end market products. For a long time, the core technology and product market of automobile exhaust purification treatment have been monopolized by foreign giants, and Corning in the United States and NGK in Japan have both enjoyed the dividend period of high-speed development in the automobile industry. With the upgrading of China's sixth national standard, domestic honeycomb ceramics in China will enter a development window period.
In addition to being used in automotive exhaust treatment systems, honeycomb ceramics can also be used in fields such as precision filtration and separation, noise reduction and insulation, gas separation and purification, and dehydration. The application scope has also expanded from traditional metallurgy, chemical engineering, and building materials to many aspects such as biochemistry, electronic engineering, food and beverage industry, aerospace, etc., with broad market application prospects. With the optimization and improvement of new processes and materials, the application fields of honeycomb ceramics will be further expanded, greatly highlighting their economic value and social benefits.
