Ceramic Fiber: Opening A New Era For Refractories

Ceramic fiber is a lightweight, fiber-like refractory material, mainly from metal oxides (such as alumina, silicon oxide, zirconium oxide, magnesium oxide, etc.), binder and additives (such as colloidal silicon dioxide, polyvinyl alcohol, silicone resins) prepared from the fiber length of 100-250 mm, fiber diameter of 2-5 μm. ceramic fiber products have the advantages of lightweight (lighter than the refractory brick 75%, lighter than the castables 90% -95%), high temperature resistance, small heat capacity, heat preservation and high temperature insulation properties, and so widely used in aviation, petrochemical and other fields. Ceramic fiber products have the advantages of light weight (75% lighter than refractory bricks, 90%-95% lighter than castables), high temperature resistance, small heat capacity, good heat preservation and high-temperature insulation, etc. Therefore, they are widely used in the fields of aerospace, petrochemical industry and so on.

Low bulk density:

Ceramic fiber is more than 75% lighter than lightweight insulating brick lining and 90%-95% lighter than lightweight castable lining. The use of ceramic fiber lining can greatly reduce the load on the steel structure of the furnace and extend the service life of the furnace.

Low thermal capacity:

The heat capacity of ceramic fiber is only about 1/10 of that of lightweight heat-resistant lining and lightweight castable lining, while the heat capacity of furnace lining material is directly proportional to the weight of the lining. Low heat capacity means that the furnace in the reciprocating operation absorbs less heat, while the speed of warming up, greatly reducing the furnace temperature operation control in the amount of energy loss, especially for the heating furnace startup and shutdown to play a very significant energy-saving effect.

Low thermal conductivity:

Ceramic fiber furnace lining when the average temperature at 400 ℃ ℃, the thermal conductivity is less than 0.11Whm.K, when the average temperature at 600 ℃ ℃, the thermal conductivity is less than 0.2Whm.K; when the average temperature at 1000 ℃ ℃, the thermal conductivity is less than 0.28Whm.K. Thermal conductivity of lightweight clay bricks, about 1/8, for the lightweight heat-resistant lining (castable material) 1/10, the thermal insulation effect is very significant. The effect is very significant.

Simple construction:

There is no need to leave expansion joints during the construction process, and the influence of construction technology factors on the insulation effect of the furnace lining is small.

Excellent resistance to thermal and mechanical shock:

Fiber blankets and modules are flexible and elastic and have particularly good resistance to severe temperature fluctuations and mechanical vibrations. As long as the body to be heated can withstand, fiber folded module furnace lining can be heated or cooled faster and is not easily broken.

No baking required:

The furnace can be put into operation after the lining has been constructed, without the need for a baking process.

Good soundproofing performance:

Ceramic fiber can reduce the frequency less than 1000Hz of high-frequency noise, less than 3000Hz of sound waves, sound insulation ability is better than commonly used sound insulation materials, can significantly reduce noise pollution.

High thermal sensitivity:

Ceramic fiber furnace lining heat sensitivity is far better than conventional refractory lining, the current heating furnace is generally used in microcomputer control, fiber lining of the high heat sensitivity is more adapted to the automation of industrial furnace control.

Stable chemical properties:

Ceramic fiber is a neutral acidic material, in addition to reacting with strong acids and alkalis, it is not eroded by other weak acids, alkalis and water oil, steam, and lead, aluminum, copper does not infiltrate.

Wide range of uses:

In the use of temperature, can meet from 600 ℃ to 1600 ℃ the use of different temperature grades; in the form, has gradually formed from the traditional cotton, carpet, felt products to fiber modules, boards, shaped parts, paper, fiber textiles; from fiber cotton to fiber spray, plastic, castables, and other forms of secondary processing or deep-processing of the product, to fully meet the different industries of the industrial furnace on the use of refractory ceramic fiber products. The products can fully meet the requirements of different industrial furnaces in various industries for the use of refractory ceramic fiber products.

1,According to the chemical composition

SiO2 Ceramic Fiber, Al2O3 Ceramic Fiber, SiC Ceramic Fiber, Si3N4 Ceramic Fiber

2,According to product type

Ceramic Fiber Blanket, Ceramic Fiber Board, Ceramic Fiber Cotton, Unshaped Ceramic Fiber

Dumping Method

Process: Ceramic raw materials (such as alumina, SiO2, etc.) are mixed in a certain proportion and added to the melting furnace to be heated to a molten state, the molten ceramic liquid enters into the gluing hopper, and then through the high-speed rotating flinging wheel (usually up to a rotational speed of 10,000-15,000 r/min), it stretches into a fine filament under the action of centrifugal force. The flung fibers are further cooled and cured in a high temperature air stream to form ceramic fibers. Finally, the fibers are collected and processed into product forms such as felts and blankets.

Advantages: suitable for large-scale industrial production, large output, low cost; fiber diameter uniformity, length can be controlled, excellent performance; compared with other high-temperature process, energy consumption is relatively low.

Disadvantages: high equipment requirements, need to accurately control the melting temperature, dumping wheel speed and airflow speed and other parameters; due to the rapid cooling of the fiber at high temperatures, which may lead to greater internal stress, the strength of the fiber is slightly inferior to some of the special process preparation.

Spraying Method

Process: Ceramic raw materials (e.g. kaolin, quartz sand, etc.) are mixed and fed into a melting furnace, heated to a molten state, and then sprayed through a nozzle while being blown into fibers with a high-speed airflow (e.g. compressed air or steam). The fibers are cured during the cooling process and are eventually collected and processed into products such as felts and blankets.

Advantages: fast fiber forming speed, suitable for mass production, adjustable fiber length and diameter, relatively simple equipment, low investment costs.

Disadvantages: the diameter and strength of the fiber is not uniformly distributed, the production process will produce more dust and waste residue, affecting the environment, the need for high-temperature melting and high-speed airflow, energy consumption.

Sol-gel Method

Process: dissolve metal alcohol salts (such as aluminum alcohol salts, silanol salts) or inorganic salts in a solvent, add a catalyst (such as acid or alkali) to carry out hydrolysis and condensation reactions to form a uniform sol, which will be aged under certain conditions to form a gel. The gel is made into fiber preform through spinning process, and then calcined at high temperature to remove the organic components, and finally get the ceramic fiber.

Advantages: the chemical composition and microstructure of the fiber is uniform, stable performance, can be adjusted through the sol composition and process parameters, the preparation of different properties of the fiber.

Disadvantages: difficult to large-scale industrialized production, suitable for small batch, high-performance products.

Polymer in-situ Conversion Method

Process: Ceramic precursors (such as organosiloxanes) and polymers (such as polyacrylonitrile) are mixed to make the spinning liquid, and the mixture is made into fiber precursor through wet or dry spinning process, and then heat-treated at high temperatures, the polymer decomposes and the ceramic phase precipitates, and the ceramic fibers are obtained finally.

Advantages: ceramic fiber with complex structure can be prepared, the internal structure of the product is more dense, high strength.

Disadvantages: the heat treatment process requires strict control of temperature and atmosphere, suitable for laboratory research and small-scale production, difficult to large-scale industrialization.

Electrospinning Method

Process: Ceramic precursors (e.g. polymer solution or sol) are injected into an electrospinning device, and under the action of a high-voltage electric field (thousands of volts), the precursor solution is stretched into ultrafine fibers. After the fibers are cured on a collection plate, they are calcined at high temperature to remove the organic components, and finally ceramic fibers are obtained.

Advantages: nanoscale ultrafine fibers can be prepared with higher specific surface area and activity.

Disadvantages: slow electrospinning speed, difficult to mass production.

Formwork Method

Process flow: Select a suitable template material (e.g. carbon fiber or polymer fiber) as the precursor. Impregnate the ceramic precursor solution into the template to fill it fully, dry the impregnated preform and remove the solvent. Calcination at high temperature removes the template material, the ceramic phase precipitates and the ceramic fiber is finally obtained.

Advantages: the process is flexible, choose different template materials, can regulate the structure and performance of the fiber.

Disadvantages: template materials and process complexity, high production costs.

Ceramic fiber is an important refractory material, the upstream mainly includes alumina, silica, zircon and other minerals. These raw materials are processed by high temperature melting, blowing or centrifugation to make fibrous materials with excellent high temperature resistance, corrosion resistance and insulating properties. Ceramic fiber downstream is widely used in a variety of high temperature, high pressure and corrosive environment, such as aerospace, military, electronics, chemical, metallurgical and other industries

Downstream - Application Scenarios

Ceramic fiber raw cotton is usually processed into a variety of styles of ceramic fiber products for various industries to choose. The most important use of ceramic fiber products is thermal insulation in high temperature environments, the scope of application covers metallurgy, machinery, electronics, ceramics, glass, chemical industry, automotive, building materials, light industry, military, shipping, aerospace and other fields.

1,Adiabatic insulation materials

Ceramic fiber is a material with high temperature resistance and good thermal insulation performance, which can withstand a high temperature of 1500 ℃, and the thermal insulation performance is mainly determined by the hybrid structure of ceramic fiber (solid fiber and air composition). These characteristics make ceramic fiber can effectively solve the problem of poor toughness of refractory materials, and is widely used in industrial furnace walls and building materials.

Ceramic fiber as a high-quality refractory insulation materials, in line with the downstream industry on the "more energy efficient, more environmentally friendly, safer" demand. At present, the annual output of domestic ceramic fiber products of about 700,000 tons, accounting for about 2.9% of the proportion of refractory materials, the base is small, the future expansion in various niche applications will bring high growth potential. As ceramic fiber products are not completely standardized products, applied to different areas need to adjust the ingredients, processes and technical support, so its non-standard aspects of the application of the development of the entire industrial system and continue to expand.

Ceramic fiber not only has the characteristics of general fibers, but also has the high temperature resistance, corrosion resistance and oxidation resistance that ordinary fibers do not have, and to avoid the brittleness of the general refractory materials, thus replacing the traditional heavy refractory bricks to a certain extent, be used as industrial kiln wall lining materials. The biggest advantage of using ceramic fiber masonry made of industrial furnace in use is energy saving. For example, polycrystalline mullite fiber products can be used for a long time in high-temperature thermal equipment below 1600 ℃ as an insulating material, such as silicon carbide furnace, molybdenum silicide furnace, all kinds of iron and steel heating furnace, mechanical forging furnace, etc., can significantly improve the thermal efficiency of the equipment, substantial energy savings, improve productivity, improve product quality. Its application areas include various high-temperature industrial kiln insulation, ceramic furnaces, machinery and metallurgical heating furnaces, heat treatment furnaces and other industrial kilns, hot surface lining, high-temperature flame retardant, kiln door, kiln car, expansion joints and other insulation materials and glass kiln insulation

2,High temperature filter material

Ceramic fiber is the ideal choice for high temperature filtration material because of its high temperature resistance, good thermal insulation and chemical stability. It can withstand high temperatures up to 1600°C and is suitable for high temperature environments such as industrial kilns and high temperature flue gas filtration. Its internal structure consists of solid fiber and air, high porosity, low thermal conductivity, can effectively reduce energy loss. At the same time, ceramic fiber is a neutral acidic material, in addition to reacting with strong acids and alkalis, it is not eroded by other weak bases, weak acids, and water, oil and steam, and it is not infiltrated with lead, aluminum and copper, which ensures the stability of the filtration process and the reliability of the filtration effect. In addition, it has high strength and thermal shock resistance, not easy to break, long service life, and large specific surface area, high filtration purity, and can meet the requirements of filtration precision in high temperature environment.

In terms of application scenarios, ceramic fiber

In the industrial production field of iron and steel, cement, electric power and other industries for high temperature flue gas filtration, removing dust and harmful substances, reducing environmental pollution and improving production efficiency;

In metal smelting to remove impurities, improve metal purity and quality;

Filtering harmful substances in chemical production to protect equipment and the environment.

In the field of transportation, it is used in diesel engine exhaust microfiltration capture to reduce exhaust emission pollution.

In the field of environmental protection, ceramic fiber plays an important role in waste gas treatment, sewage treatment, etc., removing harmful substances, reducing the risk of environmental pollution and improving environmental quality.

3,Sound-absorbing And Sound-proofing Materials

Ceramic fiber material has a good sound absorption and sound insulation effect, mainly due to when the sound wave to the internal material, the sound wave and fiber pores within the presence of air to produce viscous effect, while the sound wave will also produce friction resistance with the fibers, and thus the loss of some of the acoustic energy into the formation of thermal energy. In addition, the air within the fiber pores in the compression of heat conduction, heat conduction will also make the sound energy loss, so that the incoming sound waves will be absorbed. Therefore, ceramic fiber material has good sound absorption and sound insulation effect, so that it is widely used in construction, transportation and other fields.

4,Catalyst carrier materials

Ceramic fibers have the advantages of large specific surface area, high porosity and good catalytic effect, etc. When the catalyst-loaded ceramic fibers are used in the controlled diffusion reaction, good catalytic effect is obtained due to the small diffusion resistance, so there is a great potential for the application of ceramic fibers as catalysts in the field of catalysis.

5,Reinforced and toughened materials

The disadvantage of poor toughness of ceramic materials is well known, and thus ceramic fiber is the most effective way to toughen ceramic materials. More applications of ceramic fibers are: Al2O3 long fibers, SiC long fibers and so on. At the same time, ceramic fibers can also be used in the toughening of metal materials. New functional materials: ceramic fiber has many advantages, so in the new high-temperature superconducting materials, new functional materials, such as far-infrared fibers, conductive fibers and other directions have been widely used.

6,Application of advanced ceramic fiber materials

Advanced ceramic fiber in the application of different from the traditional ceramic fiber, the focus is based on the characteristics of the fiber itself, in addition to the use of its high temperature resistance, heat insulation and fire-resistant features, but also amplify the play of its own other functional characteristics, such as its own wave-absorbing, corrosion-resistant, weather-resistant and so on.

Ceramic fiber itself is a semiconductor, is an important material for radar wave absorption, at the same time with lightweight, high strength, high temperature resistance, oxidation resistance and other ideal structural material properties. Through the preparation process to change the crystal structure, the resistivity of the fiber can be adjusted, and then multidirectional multilayer stacking so as to achieve the purpose of wave absorption and wave transmission. Ceramic fiber reinforced composite material can be directly prepared stealth structural parts, compared with the stealth coating has a higher strength and high temperature resistance. f-22 in the tail nozzle near the application of ceramic-based stealth structural materials; France's APTGD missile tail by the hexagonal small pieces of ceramic wave-absorbing materials, with good wave-absorbing effect; the U.S. Air Force developed a Si3N4 broadband wave-transparent radome.

(1) Zirconia fiber: as ultra-high-temperature insulation composite materials, protective materials, ablative materials, and satellite battery diaphragm materials, etc., used in aerospace, military, atomic energy and other fields; as a 1600 ~ 2000 ℃ ultra-high-temperature industrial furnaces, ultra-high-temperature gas furnace, ultra-high-temperature laboratory furnaces and other ultra-high-temperature heating device lining materials; and a lot of metals, alloys, glass composite to do a wide range of temperature Metal matrix composite materials used; can be used as ultra-high-temperature filtration materials, high-temperature reaction catalyst carrier, ultra-high-temperature liquid or gas filtration materials.

(2) Quartz fiber: It can be used as reinforcement material for high-temperature ablative materials, high-temperature adiabatic sealing material, resin reinforcement material, high-temperature insulation, bundling and wrapping material, etc. It can be used as industrial heat insulation, cable insulation wrapping, exhaust pipe heat insulation wrapping, high-temperature furnace door curtain and high-temperature friction reinforcement material for machinery, fireproof shell and other insulating protective layer, insulation of marine equipment, transformer, transformer, motor and other insulating materials for electronic products, as well as the reinforcement and insulation bundling material for electronic products. Enhanced insulation binding materials for electronic products, etc.

(1) high-performance and multi-functional materials innovation accelerated

Ceramic fiber to higher temperature resistance (≥ 1600 ℃), lower thermal conductivity (≤ 0.02 W / (m-K)) and multifunctional composite development. New material systems such as SiC@BN core-shell fibers, gradient ZrO₂-Al₂O₃ fibers continue to emerge, taking into account mechanical and thermal insulation properties. Driven by policy, in 2023, there are rare earth-containing toughened fibers to achieve 2000 thermal shock cycle zero failure, to meet the needs of aerospace extreme environments.

(2) Intelligent and precision preparation technology breakthroughs

Continuous, low defects preparation has become the core direction. 2022, the first fully automated electrostatic spinning line to achieve batch production of nanofibers (capacity of 1 ton / day), 3D printing composite molding technology so that the complex prefabricated body porosity controllable precision of ± 2%. AI process optimization system will shorten the research and development cycle by 50%, the yield is increased to more than 90%.

(3) Deep penetration of application scenarios to high-end manufacturing

Breaking through the limitations of traditional industrial furnaces and kilns, expanding to hydrogen energy storage and transportation (hydrogen brittle fiber liner), semiconductor heat field (high purity fiber crucible), nuclear energy shielding (neutron absorbing fiber composites) and other emerging fields. As of 2023, the annual growth rate of ceramic fiber usage in new energy equipment is over 40%, and the market share of spacecraft thermal protection has reached 35%.

(4) green recycling manufacturing system to build a comprehensive

Driven by environmental protection policies, low-carbon preparation processes (such as supercritical CO₂ spinning) coverage increased to 60%, the utilization rate of waste fiber recycling reached 85%. 2025 target to achieve the industry's energy consumption reduced by 30%, chromium-free environmentally friendly fiber products mandatory substitution of traditional materials containing toxicity, and to promote the industry's ESG ratings comprehensively improved.

Zinfon Refractory Technology Co.,Ltd

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