Analysis of ceramic fiber properties and composition
Ceramic fiber is a set of traditional insulation materials, refractory materials, excellent performance in one of the fibrous lightweight refractory materials. Its products cover various fields and are widely used in various industrial sectors. It is the basic material to improve the thermal performance of thermal equipment such as industrial furnaces and heating devices, and to realize the structure of light weight and energy saving.
Main chemical composition: SiO2: 45% -55% AL2O3: 40% -50% Fe2O3: 0.8% -1.0% Na2O + K2O: 0.2-0.5%
Features and Uses:
With low thermal conductivity, excellent thermal stability, chemical stability, non-corrosive. The brake linings produced with this fiber have good high temperature resistance and dispersibility, suitable for all kinds of mixer mixing.
Suitable for brake linings with high temperature resistance, good heat recovery performance and small brake noise Ceramic fiber is a kind of fibrous light refractory material with light weight, high temperature resistance, good thermal stability, low thermal conductivity, Small heat, and mechanical shock resistance. Therefore, it has been widely used in the fields of machinery, metallurgy, chemical engineering, petroleum, transportation, shipping, electronics and light industry, and has been applied more and more in cutting-edge science and technology departments such as aerospace and atomic energy The development prospects are very good. Ceramic fiber started late in our country, but has maintained the momentum of sustainable development, production capacity continues to increase, and the realization of a series of products, our country has become the world's ceramic fiber producer.
The Current Situation and Development Trend of Ceramic Fiber
As early as 1941, the United States Babcock Wilcox Corporation on the use of natural kaolin after melting by the electric arc furnace into a ceramic fiber. In the late 1940s, two companies in the United States produced aluminum silicate fibers and, for the first time, used them in the aviation industry. Into the 50's, ceramic fibers have been formally put into industrial production, to the 60's, has developed a variety of ceramic fiber products, and began to be used in industrial furnace wall lining. After the global energy crisis in 1973, the ceramic fiber gained rapid development. Among them, the aluminum silicate fiber was the fastest growing with an annual growth rate of 10% to 15%. The United States and Canada are major producers of ceramic fibers with an annual output of 100,000 tons or so, accounting for about 1/3 of the world's total annual production of refractory fibers. Europe's ceramic fiber production is located in the third, annual output reached 60,000 t or so. In the ceramic fiber with an annual output of 300,000 t, the proportions of various products are roughly: 45% for blankets and fiber modules; 25% for vacuum forming panels, felt and profiled products; and 15% for bulk fiber cotton: 6%; fiber amorphous material 6%: fiber paper 3%.
Ceramic fiber products are mainly used in the processing industry and heat treatment industry (industrial furnaces, heat treatment equipment and other thermal equipment), which consumes about 40%, followed by the steel industry, which consumes about 25%. Abroad, while increasing ceramic fiber production, pay attention to research and development of new varieties, in addition to the typical ceramic fiber products such as 1000, 1260, 1400, 1600 and mixed fibers, in recent years, the chemical composition of the melt added ZrO2 , Cr2O3 and other ingredients, so that the highest temperature ceramic fiber products to 1300 ℃. In addition, some manufacturers are still adding CaO, MgO and other ingredients in the chemical composition of the melt, successfully developed a variety of new products. Such as soluble ceramic fiber containing 62% ~ 75% Al2O3 high-strength ceramic fibers and high temperature ceramic textile fibers. Therefore, the current application of ceramic fibers in foreign countries has brought a very significant economic benefits, leading to the growing scope of the application of ceramic fibers, ceramic fiber production in some major industrialized countries continue to maintain the momentum of continued growth, especially glassy silicon Acrylic fiber is the most rapid development. At the same time, with the continuous expansion of the scope of application of ceramic fibers, the production structure of ceramic fiber products will be greatly changed, for example, the output of ceramic fiber blankets (including fiber blocks) has dropped from 70% of the production of ceramic fibers to 45% Ceramic fiber deep processing of products (such as fiber rope, cloth and other fiber products), fiber paper, fiber castables, plastic materials, spreads and other non-staple material fiber production increased substantially, close to 15% of ceramic fiber production. The development, production and application of new varieties of ceramic fibers have greatly promoted the application of ceramic fibers and the development of construction methods.
China's ceramic fiber production started later, in the early 1970s, it has successively in Beijing refractories plant and Shanghai plant successfully developed and put into mass production. In the following 10 years, ceramic fiber products were mainly produced by the process of "electric arc furnace melting, one-time air blowing and fiberizing, wet handmade felt", with backward technology and single product. Since 1984, Shougang refractory plant from the United States CE company introduced the resistance of spinning silk fiber ceramic fiber acupuncture blanket production line to 1987, different fiber-forming ceramic fiber acupuncture blanket production line and vacuum forming technology, from the change China's ceramic fiber production technology, backward production equipment and the appearance of a single product.
Since 1986, our country through the introduction of the ceramic fiber production equipment and technology digestion and absorption, combined with the development of the country, designed and built a different type of resistance method of spinning (or blowing) fiber dry acupuncture blanket production line 82 , Installed in 45 companies. Annual output has reached more than 100,000 t, becoming the world's largest producer. In addition to mass production of low-temperature, standard, high-purity, high-aluminum and other ceramic fiber Acupuncture blanket and ultra-light resin dry felts (boards), but also produce 14% to 17% ZrO2 zirconium fiber blanket. Its use temperature up to 1300 ℃ above.
The 20th century, the late 80s, Japan's direct drilling weaving company, Chevrolet and Intrinsic and other textile companies have invested in Beijing built a ceramic fiber textile products manufacturing enterprises, and mass production of ceramic fiber cloth, tape, twisted rope, casing, Fang Pangen and other ceramic fiber textiles, fiber fabric for the production of bulk fiber cotton and technology and equipment have been achieved localization. In the early 1990s, Beijing, Shanghai, Anshan, Shandong, Sanmenxia, ??Henan and other places successively introduced the spraying technology and equipment of ceramic fiber from the United States, France, Japan and other countries. In the industrial furnace of metallurgy and petrochemical industry, ceramic fiber Spray lining, saving energy consumption and achieved good economic benefits, has now been widely promoted, and in the metallurgical, petrochemical and machinery sectors such as industrial furnaces and heating devices have gained successful experience. Ceramic fibers and ceramic fiber coating technology simultaneously developed ceramic fiber castables, plastics, coating materials such as amorphous fiber materials, not only has a domestic manufacturing enterprises, but also in all types of industrial furnaces, heating devices and high-temperature pipe on the promotion and application.
Therefore, at present, China's ceramic fiber has been in the stage of continuous adjustment and development. The production technology and equipment of ceramic fiber, especially the dry-pressed acupuncture blanket, have the world advanced level. The chromium- and zirconium-containing aluminum silicate fiberboard New types of ceramic fibers and products, such as crystalline alumina fiber, polycrystalline mordenite fiber and mixed fiber products, have been successfully developed and industrialized production has been put into operation to make the fiber-type lightweight refractory material a complete series of products. The continuous expansion of the range of ceramic fibers, resulting in high strength, wind erosion hard fiber wall lining applications increasingly popular. At the same time, the development of ceramic fiber production technology, but also greatly promoted the application of ceramic fiber technology and construction methods.
Chemical Composition and Structure Properties of Ceramic Fiber
1 ceramic fiber chemical composition
The chemical composition of ceramic fiber is shown in Table 1.
Table 1 ceramic fiber chemical composition
2 ceramic fiber structural properties
Ceramic fiber diameter is generally 2μm ~ 5μm, the length of more than 30mm ~ 250mm, the fiber surface is smooth cylindrical, the cross-section is usually circular. Its structure is characterized by high porosity (usually more than 90%), and stomatal aperture and specific surface area. Due to the good thermal insulation of the air in the pores, the size of the pores in the fibers and the properties of the pores (open pores or closed pores) have a decisive influence on the thermal conductivity. In fact, the internal structure of ceramic fiber is a mixed structure composed of solid fiber and air, the microstructure characteristics of the solid phase and the gas phase are in the form of continuous phase, therefore, in this structure, the solid The material exists in a fibrous form and forms a continuous phase framework, while the gas phase is continuously present in the interstices of the fibrous material. It is because of the ceramic fiber has such a structure, so that the higher porosity, pore diameter and specific surface area larger, so that the ceramic fiber has excellent thermal insulation properties and smaller bulk density.
Mechanical and physical properties of ceramic fibers
There are many varieties of ceramic fiber, its chemical composition is not the same, so its mechanical and physical properties are also quite different, now choose a representative of the four kinds of the main ceramic fibers typical properties are shown in Table 2.
Table 2 4 kinds of ceramic fiber typical performance
Porcelain fiber manufacturing methods
1 chemical vapor reaction
Chemical vapor-phase reaction (CVR) method is based on B2O3 as raw material, the melt-spun B2O3 fiber, and then placed in a lower temperature and ammonia heating, B2O3 and ammonia to produce boron-ammonia intermediate compound, and then this Crystalline unstabilized fibers are further heated to 1800 ° C in ammonia or a mixture of ammonia and nitrogen under tension to convert them to BN fibers with a strength of up to 2.1 GPa and a modulus of up to 345 GPa.
2 chemical vapor deposition method
Chemical vapor deposition (CVD) method by the tungsten nitride boron fiber made. During manufacture, the boron fiber is first heated to 560 DEG C for oxidation, then the oxidized fiber is heated in ammonia to 1000 DEG C to 1400 DEG C, and the BN fiber can be obtained after reacting for about 6 hours.
3 polymer precursor method
Polymer precursor method is made of polyborazine melt spinning fiber made of cross-linked to produce non-melted fibers, and then cracked into fibers.
Si3N4 fiber has two manufacturing methods: First, chlorosilane and hexamethyldisilazane as the starting material, the first synthesis of stable hydrogenated polysilazane, made by melt spinning fibers, and after not melting and burning System to obtain Si3N4 fiber; the second is pyridine and silica as raw materials, under inert gas to form a white solid adduct reaction, and then carried out in a nitrogen solution ammonia obtained perhydropolysilazane, and then placed in nitrogen In the ammonia solution to obtain perhydropolysilazane.And then placed in a hydrocarbon solvent deep solution configured spinning solution, by dry spinning fibers, and then in inert gas or ammonia at 1100 ℃ ~ 1200 ℃ temperature heat treatment to obtain silicon nitride fibers.
SiBN3C fiber is also produced by the polymer precursor method, is a latest ceramic fiber, the starting material for the polysilazane, after melt spinning, crosslinking, not melting and cracking fiber.
The SiO2 fiber is made by the same process as the preparation of the high silica glass fiber, which is made into a glass frit and then secondarily melted by melt spinning in a platinum crucible drawing furnace at a temperature of about 1150 DEG C. A fiber or Further processed into fabrics and other finished products with hot hydrochloric acid, remove B2O3HNa2O composition, and then sintered so that the mass fraction of SiO2 in the fiber reaches 95% to 100%. In addition, there are SiO2 as raw material, formulated into a high viscosity sol after spinning, the precursor fiber obtained, and then heated to 1000 ℃, can be obtained with a purity of 99.999% quartz fiber. In addition, it is also possible to use a quartz rod or tube to melt and fuse the crude fibers with an oxyhydrogen flame, and then pull the continuous filaments with a diameter of 4 μm to 10 μm at a constant speed through an oxyhydrogen flame or a gas flame at a high speed with an SiO2 content of 99.9%.
Ceramic fiber applications
Ceramic fiber is a new type of fibrous lightweight refractory materials, a wide range of applications, mainly for metal-based and ceramic matrix composites and thermal insulation materials, such as used in aviation, aerospace and other demanding high temperature and good mechanical properties Components, including ablative materials such as the heatsink of the spacecraft returning to the atmosphere, the rocket cone, nozzles, exhaust vents and bulkheads. In addition, the filter can also be applied to molten metal or high temperature gas and liquid materials and extreme high temperature insulation materials.
The current trend of ceramic fiber development
A variety of ceramic fiber products and production continued development
Since the 90s of the 20th century, some large ceramic fiber manufacturers have set up their own groups and adjusted their internal structures in order to enhance their anti-risk capabilities. Some of the outdated processes, equipment, and production lines were eliminated and the product structure was compared The big adjustment has greatly reduced the ordinary aluminum silicate fiber products which are less competitive in the international market and expanded the production of high purity aluminum silicate fibers, chromium-containing fibers, zirconium-containing fibers, polycrystalline alumina fibers and polycrystalline耒 stone fiber and other products production capacity. At the same time, some large ceramic fiber enterprises have successfully developed and mass-produced new products such as polycrystalline zirconia fiber, silicon nitride fiber, silicon carbide fiber and boride fiber used for special applications such as DuPont Polycrystalline alumina long fibers (trade name FP fiber), containing 99.9% polycrystalline α-Al 2 O 3 with a fiber diameter of 20 μm, are mainly used in the manufacture of textiles. With the development of science and technology, advanced composite materials have been successfully developed. The reinforcements are mainly continuous long fibers and whiskers. Among them, silicon carbide fibers and whiskers are the most widely used in composites. The metal reinforced by silicon carbide fibers Base (titanium-based) composites, ceramic matrix composites have been used in the manufacture of spacecraft components, high-performance engine and other high temperature structural materials, is the 21st century, new materials in the field of aerospace and high technology.
2 ceramic fiber manufacturing technology, methods and technology rapid development
At present, two typical process technologies of ceramic fiber production in the world are still "resistance method blowing into fiber, dry acupuncture blanket" and "resistance method spinning silk into fiber, dry acupuncture blanket". As ceramic fibers are used more and more widely, and with the development of new and high technology, ceramic fiber products are required to develop in functional direction to meet the specific functional products needed in specific fields, such as making products with excellent high temperature resistance Performance, mechanical properties, flexibility and spinnability and so on.
In the manufacturing method, melt method and chemical method (colloidal method) co-exist simultaneously and simultaneously, to meet the needs of different varieties of applications. Melting method commonly used in the production of amorphous (glassy) fiber, its low-tech, low-cost production, the application of a wide range of products, mainly used in industrial furnaces, heating equipment, fire-resistant, insulation applications in the basic materials . Chemical method