Some fibrous ceramic products may have an organic binder that burns-off during in the furnace or end-use application. Other products may have a ceramic or high-temperature binder that forms or remains after exposure to high temperatures. Loose or bulk fibrous and other fibrous insulation products may not have any binders.
Bulk chopped fibers are used in composite reinforcement applications, flowable insulation, or as the key components in woven fabrics, braids, knits, rope, roving, or other specialty fabrics. This category includes thin, continuous-fiber filaments used for similar purposes.
Continuous fibers are processed into a knitted structure of either two or three dimensions. Knitting provides a more conformable structure than weaving, which is valuable for contoured surfaces.
Nonwoven materials are textile- or fiber-based products shaped into mats of randomly-oriented fibers, felt, needlepunched cloth, spun bound, or meltblown structures.
Roving is made of tows, untwisted bundles of continuous filaments. Yarn is made of continuous, often plied strands of natural or man-made fibers or filaments.
Threads are thin, continuous strands or filaments used for stitching or reinforcement. Monofilaments are used in reinforcement applications. Multi-fiber threads are used in sewing or stitching.
Products are twisted or braided rope or cordage. Heat-insulating rope or braid is used to provide a thermal seal around doors or other openings in furnace walls.
Woven products are used for composite tooling and the formation of structures. Continuous fibers are processed into two- or three-dimensional structures by weaving fibers on a loom.
Other unlisted, specialized, or proprietary product types or forms.
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Precast refractory shapes are formed prior to exposure to a furnace, or other high-temperature application. Pouring tubes, ladle impact pads, dams and weirs, impact runners, troughs, covers, furnace roofs, and skimmer paddles are some examples applications for precast shapes.
Stock products are available in the form of a solid bar or rod, usually with a square cross-section. Stock forms can be processed in rectangular, oval, hexagonal or other shapes.
Blocks are building materials or masonry units consisting of fired ceramic or cement materials with a regular shape. Blocks usually have a rectangular shape; however, specialized shapes are used for paving, refractory, decorative, and other specialized applications. Refractory or fireclay blocks are manufactured from temperature-resistant materials. Refractory blocks are stacked to form an insulating furnace, boiler, or other thermal process vessel wall. The refractory blocks are usually cemented together with a refractory mortar. Blocks are similar to bricks, but typically smaller in overall dimensions.
Brick are building materials or masonry units consisting of fired ceramic or cement materials with a rectangular shape. Red bricks have higher iron content and are used to build walls in structural or load-bearing applications. Firebricks, refractory bricks, or fireclay bricks are stacked to form an insulating furnace, boiler, chimney, or other thermal-process vessel wall. Usually, the bricks are cemented together with a refractory mortar.
Crucibles include alumina, copper, or refractory vessels as well as tools used to melt, contain, handle, and/or process metals, glass, and other materials at high temperatures. They are fabricated from ceramics, refractory metals, or water-cooled copper. Crucibles may be large vessels or build-in place liners for industrial iron or aluminum melting in primary production plants or metal casting foundries. Thermal source crucibles or evaporation boats are small specialized crucibles used in thin-film deposition for optical, optoelectronic, nanotechnology and semiconductor applications. Labware or analytical crucible products are small in size and fabricated from high-purity materials for laboratory applications such as fusion, reaction or incineration of samples for chemical analysis or material synthesis.
Spargers or diffusers are porous ceramics used to blow fine bubbles of a gas into a metal melt to remove impurities, particulates or other detrimental melt gases. They are also used to de-oxidize melts and enable chemical reactions. Filters are porous ceramics that are used to remove impurities by passing the molten materials through the filter.
Foundry or plunger tools are designed to be immersed in molten metal and aid in the processing and casting of metal melts. Foundry and plunger tools include stirring rods, mixing paddles, dippers, skimmers, degasser tubes, degassing rotors, riser stalks, and stopper rods. Plunger mixers or stirring rods are dipped into molten materials to agitate, mix or sample the metal or glass melt to assure consistent homogeneity. Stopper rods are used to control the flow and mixing or molten material in a crucible, ladle, pot or furnace. Stoppers are used to stop or control flow of a melt by plugging up a hole in the bottom of a furnace crucible or melting pot. Dippers or skimmers are used to remove molten metal.
Kiln furniture includes beams, posts, setters, supports, rollers, baffles, kiln cars, boats, shelves, and other components for supporting, moving, and processing products or raw materials in furnaces or kilns.
Modular or sectional lining systems consist of a series of interlocking components that fit or stack together to form a protective furnace lining. Induction furnaces often use a modular furnace lining system fabricated from ceramics that do not interfere with the inductive heating process. Liners may use a backup of ramming cement behind the liner, but not within the interlocking grooves. The removal of refractory cement between the ceramic sections improves lining life and quality of the melt. Tongue and groove crucibles are a modular crucible system consisting of a series of interlocking components that stack together to form a furnace lining or crucible.
Tubes or hollow beams have a round or rectangular cross-section and are designed for use in a furnace. The tube forms a barrier between the furnace's heating elements and heated parts. Radiant heater or furnace tubes contain the combustion heat source or the heating elements in order to provide infrared heating without contamination from combusted gases or attack of heating elements.
Rolls or rollers are tubes or hollow, shaped components used in bearing, rolling and material handling applications. Ceramic rollers are a key component in hybrid ceramic roller bearings. Ceramic or fused silica rolls are used in furnaces to handle or move hot glass sheets or other thermally-processed materials.
Pouring nozzles or orifices are used to direct or meter the flow of molten metal or other melted materials. Atomization nozzles are a critical component in the gas atomization process used to produce metal powders. Ceramic nozzles are also used to shield other components of a system from arcs or abrasive jet/blast streams. Pouring cups, pouring tubes, tundish nozzles, and continuous casting tips also belong in this category. A launder or spout is used delivery molten metal or molten glass from a furnace to ladle or crucible, from furnace to furnace, or from a furnace or crucible to a mold or forming equipment.
Tile is a flat, thin ceramic shape, usually with beveled edges for lining or covering a surface. Tile is available in square, rectangular, hexagonal, triangular, round, or custom shapes. Tiles often have a protective glaze to create a waterproof or water-resistant surface. Tile can be smooth and glossy for wall applications, or anti-slip textured with a matt finish for floor applications.
Tubes are designed to protect a thermocouple from molten metals, glass or materials, and corrosive atmospheres.
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Refractory cements and raw materials consist of castables, rams, aggregates and binders that are resistant to high temperatures. Monolithic refractories are liners for furnace walls or other thermal process equipment fabricated without joints by ramming, gunning, pouring or casting the refractory cements or raw materials in place.
Clinkers, refractory aggregates, or grogs are coarse granules with high refractoriness that are bonded together to form a refractory product or cement. Grog is fired clay that has been crushed. Clinker is a fused mineral or mineral mixture, such as alumina or bauxite and lime, which is crushed into a powder to manufacture cements. Aggregates are materials that are added to mortar, grout or cement at time of mixing to impart special properties such as refractoriness, erosion resistance, or oxidation resistance. Synthetic aggregates are fused mineral or mineral mixtures crushed to a coarse granular size range rather than a fine, powdered clinker. Mineral aggregates consist of mined and crushed rock, stone or sand. Mineral aggregates usually require thermal processing (calcining, roasting, burning or fusing) to achieve the desired refractory properties. Refractory aggregates are also used to build up a shell in the investment casting process.
Ceramic adhesives usually consist of a mixture of an inorganic, high-temperature binder and fine aggregate or ceramic filler. The binder and aggregate form a ceramic bond at high temperatures. Ceramic adhesives are used to bond together ceramic or metal components for use in high-temperature applications. Ceramic adhesives usually have a finer consistency, higher purity and lower viscosity compared to typical refractory cements.
Stock products are available as coatings, sealants or in forms that can be brushed or sprayed onto a surface such as a furnace wall, mold, or gas turbine blades. Surfaces may be constructed of ceramic, metal or polymer, or other materials.
Granular fill is a loose, insulating material such as vermiculite that is loaded into a cavity to provide insulation and remains in a loose, unbonded condition. Bed media is a loose, granular ceramic used in a catalytic oxidizer, fluid-bed heater or other thermal process unit to hold, filter or carry chemicals or particles during the heating or burning operation. Ceramic bed media and granular fill typically have a high degree of porosity.
Gunning mixes are refractory cements or powdered products that are loaded with a gun into a form or onto a furnace wall to fashion an insulating layer. Wet and dry gunning mixes are available.
Investment may consist of a refractory powder with a plaster or phosphate binder that is cast around a lost wax pattern. Investment may also consist of a ceramic slurry and powder that is coated onto a hanging lost wax, plastic, or foam pattern. Permanent molds are made from refractory, ceramic, or ceramic-coated metal molds. Plastic refractory cement is rammed around a reusable pattern to form a permanent ceramic mold. Refractory aggregates are also used to build up a shell in the investment casting process.
Patching, repair, or finishing cements consist of mixtures designed for repairing cracks or filling holes in refractory linings. Some patching or repair cements may be pumpable for caulking of cracks. Other patching cements have good troweling, plastering or palming characteristics to allow cracks to be applied by hand. Finishing cements are used to make a harder finishing refractory layer on the surface of an existing refractory.
Ceramic potting compounds usually consist of a mixture of a binder and a ceramic filler or aggregate. They are used to electrically insulate conductors and resistance-heating elements for use under elevated temperature conditions where a polymer potting compound would burn up or degrade. The fillers and binders must have low resistivity and high dielectric strength.
Refractory cements or products have a sufficiently low viscosity to allow pumping of the refractory into joints or hot spots to make hot or cold repairs of a refractory body or component. Some castable areas are also pumpable. Patching or finishing cements consist of mixtures that have good troweling, plastering or palming characteristics to allow cracks to be caulked, or a harder finishing refractory layer to be applied by hand.
Wet rams are refractory cements with enough plasticity to allow the wet mix to be rammed or formed into place in a furnace or in a form. Ramming materials have a clay-to-putty-like consistency. Rams generally have a lower water content and less plasticity than moldables. Both dry rams (vibratables) and wet mix rams are available.
Refractory mortars usually consist of a mixture of a binder or clinker and a fine aggregate. They are used to bond together brick and join components for use in high-temperature applications. Clinker is a fused mineral or mineral mixture, such as alumina or bauxite and lime, which is crushed into a fine powder to manufacture cements. Aggregates are coarser, granular materials that are added to mortar, grout or cement at time of mixing to impart special properties such as refractoriness, erosion resistance, or oxidation resistance. Synthetic aggregates are fused mineral or mineral mixtures crushed to a coarse granular size range rather than a fine, powdered clinker.
Rigidizers are used to stiffen fibrous refractory products such as tapes, papers, fabrics or wraps. Rigidizers are liquid coatings consisting of a fine refractory powder dispersed in a liquid binder.
Troweling cements have good plastering or palming characteristics to allow the refractory to be applied by hand or rammed into place. Moldable cements usually have more water and a higher degree of plasticity than rams. Moldables or plastic cements are used to patch or form precast shapes.
Other unlisted, specialized, or proprietary refractory cement or monolithic refractory products.
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Alumina or aluminum oxide (Al2O3) is a compound that consists of aluminum and oxygen. Typically, it used in the alpha alumina structural form. In its pure form, alumina is a white ceramic material with high hardness. Fully-dense alumina can be translucent.
Alumina is used widely because of its versatility and relatively low cost. Depending on its purity and density, alumina is used to make refractory tubes, industrial crucibles, analytical labware, dielectric substrates, wear components, refractory cements and abrasives. Alumina’s main drawback, its relatively poor thermal shock resistance, is due to its higher coefficients of thermal expansion and lower thermal conductivity compared to other pure ceramic materials, such as silicon carbide (SiC).
Ceramics contain or are based upon natural or synthetic aluminosilicate minerals such as sillimanite, fibrolite, or mica. Sillimanite, fibrolite, and mica are aluminum silicate (Al2SiO5) compounds that consist of silicon, aluminum and oxygen. Sillimanite is also a naturally-occurring mineral that is calcined through processing. Mica also contains potassium, and is characterized by its layer structure. Mica is fire-proof and non-fusing, and can resist temperatures of up to 900° C - depending on the type of mica. Mica also has low heat conductivity, excellent thermal stability, and good dielectric or electrical insulation properties. The major types of mica are muscovite, biotite, and phlogopite.
Carbon (C) is a non-metallic element with an extremely high sublimation temperature, and a wide variety of crystalline structure forms (polymorphism). Diamond and diamond-like carbon (DLC) materials have high hardness and excellent wear resistance. Graphite is a crystalline form of carbon available as pyrolytic graphite, hexagonal graphite, or diamond.
Carbon is available as amorphous / vitreous carbon, pyrolytic graphite, hexagonal graphite, and diamond or diamond-like carbon. Carbon without a protective coating must be used in reducing or vacuum atmospheres to prevent oxidation at elevated temperatures.
Depending on the purity, density, and crystal structure, carbon is used for refractory linings, industrial crucibles, EDM electrodes, arc furnace electrodes, analytical labware, composites, refractory cements, and super abrasives.
Calcium aluminate (CaAlO3) refractories are usually derived from calcium aluminate, calcium, or alumina bearing minerals. Calcium aluminate is used in refractory cements and shapes as well as synthetic slag additions for metallurgical operations.
Carbides and carbide materials include silicon carbide, tungsten carbide and titanium carbide as well as other compounds of a metal (Ti, W, Cr, Zr) or metalloid (B, Si) and carbon. Carbides have excellent wear resistance and high hot hardness.
Kaolin-based refractories or ceramics use natural kaolin or a mixture of clay and other ceramics such as alumina, calcium aluminate or silicon carbide. Kaolin acts as a binder and provides plasticity. It is a hydrous, mineral clay that is based on aluminum silicate [Al2(Si205)(0H)4]. Kaolin is also referred to as clay, anhydrous aluminum silicate, aluminum silicate dihydrate, nacrite, dickite, kaolinite, calcined, kaolinite, china clay, bolus alba, porcelain clay, aluminum, silicate hydroxide, or aluminum silicate (hydrated). Kaolin’s plate-like structure allows particles in a wet clay mass to slide across each other and maintain plasticity. Kaolin is a white, soft plastic clay composed primarily of well-ordered kaolinite mineral [Al2Si2O5(OH)4] with minor amounts of quartz, feldspar, and sheet silicate minerals (mica, illite, smectite, and chlorite).
Geologically, there are two types of kaolin deposits, i.e., primary and secondary kaolin. Primary kaolin is formed through the alteration, or kaolinization, of in-situ minerals of feldspar and other aluminum silicates to kaolinite. Secondary kaolin is laid down as sediments, usually in fresh water, far from the place of origin. Various types of secondary kaolin are ball clay, fireclay, or flint clay depending on kaolinite content and their properties.
Magnesia ceramics or refractories are based on compounds that consist of magnesium and oxygen. Magnesite or magnesia refractories or minerals are also known as magnesium oxide, magnesium carbonate, dead burned magnesite, calcined magnesite, periclase or magnesia clinker. Depending on the origin and processing, magnesia is divided into caustic, dead-burnt, fused, precipitated, sintered or calcined and synthetic magnesia forms.
The high melting point (2800° C) and heat resistance (1700°C in the reducing and 2300° C in oxidizing atmosphere) of magnesium oxide make it suitable for the production of refractories. Magnesite is the naturally occurring mineral or ore used to produce magnesium oxide based refractories. Magnesite often contains iron, manganese or other activator elements. Magnesium oxide refractories with a carbon bond are frequently used in the steel industry. Magnesite refractories have good resistance to molten iron and steel.
Boride ceramics are compounds of a metal and boron such as zirconium boride (ZrB2) or titanium boride (TiB2). Titanium borides show an increase in ductility with an increase in temperature.
Mineral wool is an aggregate of fine filaments produced by blowing air or steam through molten blast-furnace slag (slag wool), through molten rock (rock wool), or through molten glass (glass wool).
Mullite (3Al2O3-2Si02 or Al6Si2O13) is a compound of aluminum, silicon and oxygen. Mullite can also be viewed as a phase in the alumina-silica binary system. Mullite is a synthetic, fused or calcined crystalline aluminum silicate produced in electric arc furnaces from alumina and silica. Mullite usually has an off-white or tan color. Depending on the purity and density, mullite can have superior dielectric and thermal shock properties and resistance to slag and silicate refractory bonds. Mullite is used for refractory tubes, industrial crucibles, analytical labware, dielectric substrates, wear components and in refractory cements. Calcining kyanite minerals often derive refractory grade mullite or alumina-mullite mixtures.
Nitride ceramic materials include boron nitride, aluminum nitride and silicon nitride. Nitrides generally have good thermal conductivity, so dense forms are not as useful for insulation purposes. Nitride provides good dielectric or electrical insulating properties. Nitrides also have useful wear properties. Boron nitride (BN) ceramics are based on compounds of boron and nitrogen. Boron nitride is relatively inert and has good thermal conductivity combined with good electrical insulation, making this material useful in fabricating substrates and insulators in microelectronics applications. BN is polymorphic, meaning that it occurs in a wide variety of crystalline structure forms. BN is available as amorphous or vitreous, pyrolytic, hexagonal and cubic crystal structures. Cubic boron nitride (CBN) is a super abrasive that is second only to diamond in hardness. BN is more resistant to oxidation than carbon. Depending on the purity, density and crystal structure, boron nitride is used for refractory linings, industrial crucibles, arc furnace electrodes, analytical labware, composites, refractory cements and super abrasives. Hexagonal BN is structurally weak and used as a high temperature lubricant, coating or release agent. Aluminum nitride (AlN) ceramics are compounds of aluminum metal and nitrogen. Aluminum nitride is relatively inert and its good thermal conductivity combined with high electrical insulation ability makes these materials useful as substrates, insulators and barrier layers in microelectronics applications. Silicon nitride (Si3N4) is a compound that consists of silicon and nitrogen. It has superior mechanical properties and forms a protective SiO2 skin at high temperatures. Silicon nitride ceramics are difficult to sinter by conventional means because the material dissociates above 1800o C.
Porcelain materials are used for both industrial and ornamental applications. Traditional porcelain is made from a mixture of feldspar, clay (kaolin) and flint. Steatite or cordierite porcelains are commonly used in electrical insulator applications. Many porcelain compositions are based on the K20-Al203-SiO2 or Mg0-Al203-SiO2 ternary systems.
Refractory materials are based on a silicate system such as fused silica, calcium silicate (CaSiO3), aluminum silicate, magnesium silicate, or quartz. Fused silica is a compound of silicon and oxygen. High purity amorphous fused silica is a high performance ceramic with very low expansion, remarkable thermal shock resistance, low thermal conductivity, excellent electrical insulation up to 1000°C and excellent resistance to corrosion from molten metal and glass.
Silicon carbide (SiC) is a compound of silicon metalloid and oxygen. Typically, SiC is used in the alpha silicon carbide structural form. SiC is a black, high hardness ceramic that is usually harder than alumina. Depending on the addition of impurities, SiC may be green or black in color. Fully dense SiC can be transparent (moissanite). SiC is used widely due to its versatility and a relatively low cost. Depending on its purity and density, SiC is used in refractory tubes, industrial crucibles, wafer semi-insulating substrates, wear components, refractory cements and abrasives. SiC forms a protective SiO2 skin that prevents further oxidation at very high temperatures in non-reducing atmospheres. Because of its low coefficient of thermal expansion and high thermal conductivity, SiC has a relatively high thermal shock resistance compared to other ceramic materials.
Zirconia or zirconium oxide (ZrO2) is an extremely refractory compound of zirconium and oxygen. Zirconia may have additions of calcia, magnesia or yttria to stabilize the structure into a cubic structure. Zirconia stabilized in the cubic crystal structure avoids cracking and mechanical weakening during heating and cooling. Certain zirconia materials have the ability to transformation toughen (tetragonal to monoclinic phase change) under applied stress. They are often used in wear applications that require improved fracture toughness and stiffness over alumina. Zirconia ceramics possess excellent chemical inertness and corrosion resistance at temperatures well above the melting point of alumina. Zirconia is more costly than alumina, so it is only used where alumina will fail. Zirconia has low thermal conductivity and is an electrical conductor above 800° C. Zirconia is used to fabricate oxygen sensors or fuel cell membranes because zirconia possesses the unique ability to allow oxygen ions to move freely through the crystal structure above 600° C. Zirconia products should not be used in contact with alumina above 1600°C. Depending on the purity and density, zirconia is used in refractory tubes or cylinders, industrial crucibles, analytical labware, sensors, wear components, refractory cements, thermocouple protection tubes, furnace muffles, liners and high temperature heating element supports.
Other unlisted, specialized, or proprietary materials such as yttria (Y2O3), hafnia (HfO2,), ceria (CeO2) and other rare earth oxide (REO) ceramics.
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The maximum temperature that the refractory or ceramic material can be used continuously without the degradation of structural or other required end-use properties.
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Thermal conductivity is the linear heat transfer per unit area through a material for a given applied temperature gradient. Heat flux (h) = [thermal conductivity (k) ] x [temperature gradient (Δ T)]
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Modulus of rupture (MOR), cross-break strength or flexural strength (3-point or 4-point) is the maximum flexural stress a bar can withstand before failure or fracture occurs. The bar is supported by two points beneath the bar and the load is applied by one or two points above the bar. Cross break strength is used to evaluate the strength of ceramics or other materials that do not provide sufficient plastic deformation to reliably tensile test.
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Composite materials consist of a matrix material reinforced with a stronger or higher modulus second phase. The second phase may be in the form of particulates, chopped fibers or continuous fibers. The matrix may consist of a ceramic (CRC, ceramic matrix composite), a metal (MMC or metal matrix composite) or a polymer material. Ceramic or glass fibers are commonly utilized as the reinforcement due to their high strength and/or modulus.
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Products use or are available with a glaze (fused glass enamel), metallized coating, plastic coating, or other protective coatings. The coating may seal porosity, improve water or chemical resistance or enhance joining to metals or other materials.
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Polycrystalline ceramic material where individual grains or crystal are bonded to each of a pure ceramic body without the introduction of a foreign material (binder) beyond small traces of dopants or sintering aids. The materials are formed and/or densified through:
Pressing and sintering or firing
Hot pressing or hipping
Extrusion
Fusing and casting or crystal growth
Deposition process - CVD or PVD
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Products are suitable for chemical processing applications due to their high-temperature and/or corrosion resistance. They include ceramics or refractories with resistance to molten glass, ceramics, metals, plastics or other materials during milling, firing, calcination, fusion or other processes.
Products are used in foundries for melting and casting aluminum, steel, copper alloys or other metals. They include ceramic and refractory crucibles, tubes, stoppers, liners, spouts, permanent molds, thermocouple protection tubes, combustion gas heater tubes, submersible heater tubes, die casting stalks / sleeves, and other furnace components
Products are heat-resistant ceramic materials specialized for use in containing or holding semiconductor or optical components during processing. They include crucibles, furnace components, wafer chucks, wafer furnace boats and thin film chamber liners. These materials or refractory component must meet higher cleanliness or particulate-level standards.
Other unlisted, specialized or proprietary applications.
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