[001] The invention relates to a carbon-containing article comprising a carbon-containing material and having a surface preparation comprising a fiber that reduces oxidation of the carbon-containing composition, including, but not limited to, carbon-fiber reinforced refractory compositions and articles for use in metallurgy.

BACKGROUND OF THE INVENTION

[002] Compositions and articles containing carbon are often used in industrial applications. Carbon has low density and thermal expansion, can have high tensile strength, but can oxidize at temperatures as low as 400°C. Carbon-fiber can both improve the physical properties of articles and permit the production of new light-weight products. For example, carbon-fiber can increase product service life and, considerably reduce raw material consumption. Carbon-fiber can also reduce the risk of thermal shock, particularly in refractory applications. Applying carbon-fiber under tension around refractory articles, such as oxide- or carbon-bonded refractory bodies, can greatly increase the thermal shock resistance of the articles. Unfortunately, carbon-fiber can also oxidize at temperatures above 400 °C, which reduces the effectiveness of the carbon-fiber in high-temperature refractory applications.

[003] Thermal shock resistance can be a problem for refractory components. In addition to improving thermal shock resistance, carbon-fiber can also simplify the refractory handling procedures (e.g., reduce pre-heating time), increase the service life, and reduce the probability of catastrophic failure. The use of carbon-fiber filament winding under tension can also increase the safety of refractory components and reduce inherent operational hazards. [004] Carbon-fiber reinforced ceramic composites (CFRCs) represent a novel class of materials, which can be characterized by exceptional mechanical properties at elevated temperatures. Carbon-fibers have extremely low thermal expansion and high mechanical strength even under tension. CFRCs can, therefore, produce lightweight components that reduce both material costs and energy consumption. Unfortunately, the benefits of carbon-fiber can be lost if the carbon oxidizes.

[005] Oxidation of refractories that contain carbon, including, but not limited to, carbon-fiber, graphite, and pyrolytic carbon, can impair the properties of these refractories. Refractory felts or glazes are commonly used to reduce oxidation by restricting the contact of carbon-containing refractories with oxygen, including oxygen from contact with air. Both, however, are not completely satisfactory. Refractory felts can create a physical barrier that limits oxygen diffusion to the carbon, but such felts are porous and so do not provide complete protection. Further wrapping an article in refractory felt can greatly increase cost and production time. Glazes often poorly wet carbon-containing refractories, particularly when the surface of the refractory comprises a major portion of carbon such as carbon-fiber. The contact angle between glazes and carbon-containing surfaces can be greater than 90°; therefore, the glaze does not effectively wet-out the material surface upon the application of a glaze film, and does not produce a uniform coating. Thus, the anti-oxidation effectiveness of glazes can be poor. Poor wetting can also cause pinholes in the protective glaze and delamination during preheating. Pinhole and delamination expose the carbon-containing article to the atmosphere and potential oxidation.

[006] Metal phosphate paints have also been used to reduce oxidation of CFRCs. Metal phosphate coatings do not completely suppress carbon oxidation and are only suitable for a limited duration of only a few hours. More effective is the formation of a thin film of silicon carbide for the anchoring of high temperature and ultra-high temperature oxygen coating. The cost of the material and the process for this type of coating are relatively expensive and therefore incompatible with the price of refractories.

[007] A need exists to reduce oxidation of carbon-containing refractories at elevated temperatures and at a reasonable cost. Reducing carbon oxidation during the pre-heat or use of a carbon-containing refractory article can better preserve the mechanical properties of the article. SUMMARY OF THE INVENTION

[008] The object of this invention is to reduce oxidation of carbon-containing articles, in particular articles with outer surfaces comprising carbon, such as, for example, carbon-fiber. A carbon-containing article includes any article comprising oxidizable carbon. Examples of a carbon-containing article include, but are not limited to, carbon-bonded compositions, carbon- fiber reinforced compositions, pyrolytic carbon compositions, graphite compositions, carbon- carbon composites, preceramic polymer-infiltrated carbon-fiber ceramics (PIP), or liquid-silicon- infiltrated carbon-fiber ceramics (LSI), or combinations of any thereof.

[009] A surface of an article comprising a carbon-containing composition that is exposed to air can be protected from oxidation by an oxidation-resistant layer that may be a fiber layer. The fiber layer can include any composition that resists oxidation and can be made into a filament or fabric or a combination thereof. Filament means a single filament or a bundle of filaments, also known as a tow. The fiber layer can comprise, but is not limited to, basalt, quartz, glass, silicon carbide, boron nitride, alumina, mullite, or zirconia, or a combination of any thereof. The filament or fabric is typically wound around the carbon-containing article, and can be wound as one or more fiber layers. Optionally, a layer comprising a resin can be applied to the surface of the carbon-containing article to improve adhesion of the fiber layer to the underlying carbon- containing composition. The resin can comprise pre-ceramic polymers, phenolic resins, acrylic resins, epoxy resins, polyurethane resins, silicone resins, pitches, or starches, or a combination of any thereof. The fiber layer can be coated with a resin so that adhesion to the carbon-containing composition and cohesion among the filaments or other fibers is improved. Advantageously, this may also reduce porosity of the fiber layer thereby restricting oxygen diffusion to the underlying carbon-containing compositions.

[010] The fiber layer can include an exterior surface and the exterior surface of the fiber layer can be coated with a coating layer, such as, for example, a resin or a glaze. The coating layer can be applied by any suitable process including, but not limited to, spraying, dipping, brushing, cold-spraying, or thermal-spraying. The resin or glaze can be applied either before or after application of the fiber layer to the carbon-containing composition. If applied before, the fiber layer and glaze or resin can be applied in a single step to the carbon-containing composition. If applied after, the resin or glaze can be applied to an external surface of the fiber layer. Glaze means any inorganic coating capable of forming a substantially continuous layer. Glazes can include, for example, silica, silicate, borosilicate glass, aluminosilicate glass, barium

aluminosilicate, or strontium aluminosilicate, or a combination of any thereof. As either a filament or fabric, the fiber layer tends to improve wettability of the carbon-containing article, vis-a-vis, a glaze or a resin. Better wettability improves the continuity of the resultant coating so that oxidation of the carbon-containing composition can be further reduced.

[011] The fiber layer can be applied to the carbon-containing composition as a wrap. The wrap can be single-layer or multi-layer. Application of the wrap can be accomplished by several methods, including, without limitation, filament winding with or without applied tension, hand lay-up, resin transfer molding, or vacuum bagging, or a combination of any thereof, for the oxidation protection on novel fiber reinforced refectory composites. Advantageously, the fiber layer can provide mechanical protection to the carbon-containing article. The fabric can comprise a woven or non-woven felt, blanket, or mat.

[012] The glaze can include an anti-oxidant. Suitable anti-oxidants include, for example, molybdenum metal, silicon, aluminum metal, boron carbide, silicon carbide, or aluminum carbide, or a combination of any thereof. A glaze can produce an oxygen barrier coating and can wet the fiber. Glazes are commonly applied as a slurry and may comprise a frit and/or antioxidant that vitrifies at elevated temperatures, thereby mechanically preventing oxygen from contacting the carbon-containing composition and reducing oxidation.

BRIEF DESCRIPTION OF THE DRAWINGS

[013] Figure 1 shows a cross-section of an article of the present invention.

[014] Figure 2 shows the article of Figure 1 with the addition of a glaze.

[015] Figure 3 shows a cross-section of a carbon-containing article surrounded by a glaze- impregnated fiber.

[016] Figure 4 shows a cross section of an article of the present invention.

[017] Figure 5 shows a cross section of a nozzle of the present invention.

[018] Figure 6 shows a cross section of a nozzle of the present invention.

[019] Figure 7 shows a cross section of a nozzle of the present invention.

[020] Figure 8 shows a cross section of a nozzle of the present invention.

[021] Figure 9 shows a cross section of a nozzle of the present invention.

[022] Figure 10 shows a cross section of a nozzle of the present invention.

[023] Figure 11 shows a cross section of a nozzle of the present invention. [024] Figure 12 shows a cross section of a nozzle of the present invention,

[025] Figure 13 shows a cross section of a nozzle of the present invention,

[026] Figure 14 shows a cross section of a nozzle of the present invention,

[027] Figure 15 shows a cross section of a nozzle of the present invention,

[028] Figure 16 shows a cross section of a nozzle of the present invention,

[029] Figure 17 shows a cross section of a nozzle of the present invention,

[030] Figure 18 shows a cross section of a nozzle of the present invention,

[031] Figure 19 shows a cross section of a nozzle of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[032] The invention comprises an article comprising a carbon-containing composition covered, at least in part, by an oxidation-resistant layer such as an oxidation-resistant fiber layer. Carbon- containing compositions can include, but are not limited to, articles in the fields of aerospace, automotive, metallurgy, chemical processing, materials handling, high temperature composites, and CFRCs. Metallurgical articles include, for example, nozzles, shrouds, tubes, crucibles, lances, degassers, plugs, tundish furniture, stopper rods, and slide plates. The carbon-containing composition includes oxidizable carbon. The fiber layer includes an oxidation-resistant filament or fabric. The fiber layer should be more resistant to oxidation than the carbon in the article. The fiber layer can comprise compositions including, but not limited to, basalt, quartz, glass, silicon carbide, boron nitride, alumina, mullite, or zirconia, or a combination of any thereof. Basalt means any composition comprising a majority of alumina-silicate. A suitable basalt composition comprises 35-56 wt.% silica and 10-20 wt.% alumina. Other suitable basalt compositions can include, by weight, 42-56% silica, 11-18%) alumina, 5-12% iron(III) oxide, 7- 12% calcium oxide, 4-11% magnesium oxide, and less than 5% of each of sodium oxide, titanium oxide, and potassium oxide. Another suitable basalt composition can include, by weight, 35-45% Si0 ₂ , 10-20 % A1 ₂ 0 ₃ , 4-8% MgO, 20-40% CaO, less than 3% Fe ₂ 0 ₃ , and less than 1% MnO.

[033] The fiber layer can mechanically adhere to the surface of the article comprising the carbon-containing composition. The fiber layer can be applied to the surface of the carbon- containing composition by a method selected from the group consisting of fiber or filament winding with an applied tension, fiber or filament winding without an applied tension, hand lay- up, resin transfer molding, vacuum bagging, and a combination of any thereof. A filament can be wound around the carbon-containing composition, for example. Various fiber winding techniques are known in the art and may be used in this invention, including cylindrical winding, helical winding, and combinations thereof. The filament can be wound continuously around the carbon-containing composition, and can be wound either with or without tension. The fiber layer can be secured to the carbon-containing composition by any suitable means, such as, for example, using mechanical fasteners. The fiber layer can include a woven basalt fabric, for example.

[034] The fiber layer can wrap around the carbon-containing composition's surface. The fiber layer can be mechanically anchored to the refractory body of an article comprising the carbon- containing composition by being wound under tension or with the use of a resin that adheres to the carbon-containing composition. The mechanical properties of the fiber layer can be comparable to carbon-fiber in terms of tensile strength, elastic modulus, elongation at break, and/or density. These properties can be very beneficial in CFRCs. Advantageously, the fiber layer can form a physical barrier layer that can protect the article from accidental mishandling. A plurality of fiber layers can be used to improve oxidation-resistance and mechanical strength. The fiber layer or layers can be coated with organometallic compounds, polycarbosilane polymer, polysiloxane polymer, polysilazane polymer, ethylsilicate, silica, silicate, borosilicate glass, aluminosilicate glass, barium aluminosilicate, or strontium aluminosilicate, or a combination of any thereof. These are particularly useful when applied to a filament prior to winding on or otherwise being applied on a carbon-containing composition.

[035] Figure 1 shows a carbon-containing article 10. The article 10 comprises a carbon- containing composition and an oxidation-resistant fiber layer 24. The carbon-containing composition (20 and 22) comprises an object 20 surrounded by carbon-fiber 22. The oxidation- resistant fiber layer 24 surrounds the carbon-containing composition, thereby reducing oxygen diffusion to the carbon-containing composition. The object 20 can comprise either an oxide- bonded or a carbon-bonded composition, for example. Carbon-fiber 22 restricts the thermal expansion of the object 20, thereby placing the object 20 in compression. The oxidation-resistant fiber layer 24 protects the carbon-fiber 22 from oxidizing so that the carbon-fiber 22 maintains its mechanical strength and can continue to maintain compression on the object 20.

[036] Figure 2 shows an article 10 comprising an object 20, which may comprise a carbon- containing composition (20), surrounded by an oxidation-resistant fiber layer 24. the oxidation- resistant fiber layer 24 is covered by a coating layer of oxidation-resistant glaze or resin 26. The object 20 can include, for example, a carbon-bonded article, a carbon-reinforced article, or a combination thereof.

[037] Figure 3 shows an object 20, which may comprise a carbon-containing composition (20), covered in part by an oxidation-resistant fiber layer 24, which may be resin or glaze coated. The oxidation-resistant fiber layer 24 may be applied to the object 20 in a single step. Advantageously, this reduces the number of manufacturing steps and can reduce oxygen diffusion to the carbon-containing composition. A resin or glaze can be applied to a fiber (e.g., a filament or fabric) before the fiber is applied to the carbon-containing composition to form an oxidation-resistant fiber layer. The fiber can be dipped into a liquid resin or glaze, and the coated fiber can be applied to the carbon-containing composition. Alternatively, a resin or glaze can be applied to a fiber by brushing and the fiber layer can be secured to the carbon- composition by hand lay-up, resin transfer molding, or vacuum bagging, for example. The resin or glaze may include an anti-oxidant, as described above.

[038] Figure 4 depicts, in cross-section, a tube 42 according to the invention. A bore 44 is surrounded radially by an oxide bonded refractory 46, which is surrounded by a concentric layer of carbon fiber 22, which is surrounded by an oxidation protection layer 48, which may comprise an oxidation-resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof.

[039] Figure 5 depicts, in cross section, a cylindrical nozzle 50 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having a radial interior surface and a radial exterior surface. A layer of oxide bonded refractory 46 having a radial exterior surface is embedded annularly in the exterior surface of the carbon- containing composition 53 between the upper end and the lower end of the nozzle 50. A layer of carbon fiber 22 having a radial exterior surface is disposed on the radial exterior surface of the oxide-bonded refractory 46. An oxidation-resistant layer 54, which may comprise an oxidation- resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the radial exterior surface of the carbon fiber 22. [040] Figure 6 depicts, in cross section, a flared nozzle 56 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 53 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having a radial interior surface and a radial exterior surface. A layer of oxide bonded refractory 46 having a radial exterior surface is embedded annularly in the exterior surface of the carbon-containing composition 53 between the upper end and the lower end of the nozzle 56. A layer of carbon fiber 22 having a radial exterior surface is disposed on the radial exterior surface of the oxide- bonded refractory 46. An oxidation-resistant layer 54, which may comprise an oxidation- resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination thereof, is disposed on the radial exterior surface of the carbon fiber 22.

[041] Figure 7 depicts, in cross-section, a tapered nozzle 58 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having a radial interior surface and a radial exterior surface. A layer of oxide bonded refractory 46 having a radial exterior surface is embedded annularly in the exterior surface of the carbon-containing composition 53 between the upper end and the lower end of the nozzle 58. A layer of carbon fiber 22 having a radial exterior surface is disposed on the radial exterior surface of the oxide- bonded refractory 46. An oxidation-resistant layer 54, which may comprise an oxidation- resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the radial exterior surface of the carbon fiber 22.

[042] Figure 8 depicts, in cross-section, a flared nozzle 56 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having a radial interior surface and a radial exterior surface. An annular layer of carbon fiber 22 having a radial exterior surface is disposed on the radial exterior surface of the carbon-containing composition 53 between the upper end and the lower end of the nozzle 56. An oxidation-resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the radial exterior surface of the carbon fiber 22.

[043] Figure 9 depicts, in cross section, a tapered nozzle 58 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having a radial interior surface and a radial exterior surface. An annular layer of carbon fiber 22 having a radial exterior surface is disposed on the radial exterior surface of the carbon-containing composition 53 between the upper end and the lower end of the nozzle 58. An oxidation-resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the radial exterior surface of the carbon fiber 22.

[044] Figure 10 depicts, in cross-section, a cylindrical nozzle 50 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having a radial interior surface and a radial exterior surface. An annular layer of carbon fiber 22 having a radial exterior surface is disposed on the radial exterior surface of the carbon-containing composition 53 between the upper end and the lower end of the nozzle 50. An oxidation-resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the radial exterior surface of the carbon fiber 22.

[045] Figure 11 depicts, in cross-section, a flared nozzle 56 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having an interior surface proximal to the bore and an exterior surface distal to the bore. A layer of carbon fiber 22 having an exterior surface is disposed on the exterior surface of the carbon-containing composition 53. An oxidation-resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the exterior surface of the carbon fiber 22.

[046] Figure 12 depicts, in cross-section, a tapered nozzle 58 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having an interior surface proximal to the bore and an exterior surface distal to the bore. A layer of carbon fiber 22 having an exterior surface is disposed on the exterior surface of the carbon- containing composition 53. An oxidation-resistant layer 54, which may comprise an oxidation- resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the exterior surface of the carbon fiber 22.

[047] Figure 13 depicts, in cross-section, a cylindrical nozzle 50 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having an interior surface proximal to the bore and an exterior surface distal to the bore. A layer of carbon fiber 22 having an exterior surface is disposed on the exterior surface of the carbon- containing composition 53. An oxidation-resistant layer 54, which may comprise an oxidation- resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the exterior surface of the carbon fiber 22.

[048] Figure 14 depicts, in cross-section, a flared nozzle 56 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having an interior surface proximal to the bore and an exterior surface distal to the bore. An annular oxidation-resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the radial exterior surface of the carbon-containing composition 53 between the upper end and the lower end of the nozzle 56.

[049] Figure 15 depicts, in cross-section, a tapered nozzle 58 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having an interior surface proximal to the bore and an exterior surface distal to the bore. An annular oxidation-resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the radial exterior surface of the carbon-containing composition 53 between the upper end and the lower end of the nozzle 58.

[050] Figure 16 depicts, in cross-section, a cylindrical nozzle 50 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having an interior surface proximal to the bore and an exterior surface distal to the bore. An annular oxidation-resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the radial exterior surface of the carbon-containing composition 53 between the upper end and the lower end of the nozzle 50.

[051] Figure 17 depicts, in cross-section, a flared nozzle 56 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having an interior surface proximal to the bore and an exterior surface distal to the bore. An oxidation- resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the exterior surface of the carbon-containing composition 53.

[052] Figure 18 depicts, in cross-section, a tapered nozzle 58 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by carbon-containing composition 53 having an interior surface proximal to the bore and an exterior surface distal to the bore. An oxidation- resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the exterior surface of the carbon-containing composition 53.

[053] Figure 19 depicts, in cross-section, a cylindrical nozzle 50 according to the invention. A bore 44 comprises an entry port 51 at its upper end and terminates in at least one exit port 52 at its lower end. The bore 44 is surrounded radially by a carbon-containing composition 53 having an interior surface proximal to the bore and an exterior surface distal to the bore. An oxidation- resistant layer 54, which may comprise an oxidation-resistant fiber layer, an oxidation-resistant resin, or an oxidation-resistant glaze, or a combination of any thereof, is disposed on the exterior surface of the carbon-containing composition 52.

[054] In an example of the invention, the fiber layer comprises a basalt composition comprising at least 50% by weight alumina-silicate. Basalt normally melts at around 1000 °C, and mixtures can soften at around 700 °C. For this reason, basalt compositions are not typically used in refractory applications such as metallurgy. Steel casting occurs at temperatures above 1550 °C and basalt would liquefy and cease to be an effective oxidation barrier. The present invention, however, does not depend on the mechanical strength of the fiber layer, but rather on the strength of the carbon-containing composition. The fiber layer need be present only for so long as is necessary to impede oxidation of the carbon-containing composition for a particular use. Again, in steel casting applications, this would be during pre-heat before an article comes in contact with the steel. Pre-heating often occurs at temperatures below the melting point of basalt compositions.

[055] The fiber layer can also be coated with a glaze to further improve oxidation resistance. The fiber layer functions as both an oxygen barrier and as a wetting agent for a glaze coating and, unlike metal phosphate or silicon carbide coatings, the fiber layer provides an exterior surface onto which glazes can be easily applied. The chemical composition of the fiber layer can be quite similar to the composition of the fusible frit that comprises many glazes, so that the glaze readily wets the fiber layer, and the thermal expansion of the fiber layer is comparable to that of the glaze. The similarity of the mechanical and chemical properties of the fiber layer and the glaze can reduce the chance of pin-holing, delamination, peeling, and ultimately oxidation of the underlying carbon-containing article. For example, basalt fibers comprise alumina and silica, which are common components in many glazes. [056] The application of the fiber layer can depend on the article to be protected. For substantially cylindrical articles or articles having lateral surfaces, such as, metallurgical ladle shrouds and submerged entry nozzles, the fiber layer can be applied by winding a filament under tension. The fiber layer can be a continuous filament or can be a fabric. The fiber layer can be wrapped upon a previously wound carbon-fiber or fiber layer, thereby improving the thermal shock resistance, mechanical strength, service life, and safety. Additionally, a glaze can be coated onto the fiber layer to further improve the oxidation resistance. The fiber layer can comprise a composition that improves wetting of the glaze. As described above, an example of such a fiber composition includes basalt, which is chemically similar to many glazes thereby assuring chemical adherence of the glaze on basalt fiber.

[057] The fiber layer can be applied to an interior surface, exterior surface, or both, of an article. Crucibles, for example, can have a fiber layer placed on the exterior surface and on the interior surface. The interior surface defines the volume of the crucible. For example, a filament can be wound around the exterior surface of the crucible and a fabric can be adhered to the interior surface.

[058] Other examples of carbon-containing articles include CFRCs, which can be produced by, for example, winding of pre-preg carbon filament, hand lay-up of pre-preg carbon-fiber fabric layers, and hand lay-up of pre-preg carbon-fiber fabric layers and vacuum bagging; and resin transfer molding (RTM). Additionally, processes such as PIP or LSI may be used to create a carbon-fiber composite. According to the invention, a fiber layer is applied to the surface of the described CFRCs. Oxidation resistance can be further improved by applying a glaze onto the fiber layer. [059] The invention encompasses the use of resins or glazes with or without an anti -oxidant additive. Pre-ceramic resins can seal any porosity that is present before or generated during pyrolysis. Pre-ceramic resins can be used in place of or in conjunction with a fiber coated with a resin.

[060] Example 1

[061] A first carbon-containing article was produced comprising a carbon-bonded refractory tube with a carbon-fiber wound under tension around the tube. Tension secured the carbon-fiber to the refractory tube. A second carbon-containing article was produced comprising a carbon- bonded refractory tube with a carbon-fiber wound under tension around the tube and also having a basalt fiber wound under tension around the carbon-fiber. Tension secured the carbon-fiber to the refractory tube and also the basalt fiber to the carbon-fiber. The two carbon-containing articles were subjected to pre-heating. After only 1 hour at 900°C the carbon-fiber of the first article had completely oxidized. The second article resisted oxidation for 3 hours at 1200°C after which the test was terminated. The basalt fiber significantly reduced oxidation of the carbon- fiber thereby preserving the performance of such articles.

[062] Example 2

[063] A first CFRC article was coated only with a traditional oxidation-resistant glaze. A second CFRC article was wrapped in basalt fiber and then coated with the same traditional oxidation-resistant glaze. Both articles were placed in a refractory lined container and heated using a natural gas/air burner. After 1 hour at 900°C, the carbon-fiber on the first CFRC article had oxidized, so that the expected benefit of using carbon-fiber would be vitiated. The second CFRC article was preheated for 3 hours at 1200°C. The second CFC showed no evidence of oxidation The integrity of the carbon-fiber and its function were maintained. [064] Various features and characteristics are described in this specification and illustrated in the drawings to provide an overall understanding of the invention. It is understood that the various features and characteristics described in this specification and illustrated in the drawings can be combined in any operable manner regardless of whether such features and characteristics are expressly described or illustrated in combination in this specification. The Inventors and the Applicant expressly intend such combinations of features and characteristics to be included within the scope of the invention, and further intend the claiming of such combinations of features and characteristics to not add matter to the application. The invention can comprise, consist of, or consist essentially of the various features and characteristics described in this specification.

[065] Elements

10. Article

20. Object

22. Carbon fiber

24. Oxidation-resistant fiber layer

26. Coating layer

42. Tube

44. Bore

46. Oxide bonded refractory

48. Oxidation protection layer

50. Cylindrical nozzle

51. Entry port

52. Exit port

53. Carbon-containing composition

54. Oxidation-resistant layer Flared nozle Tapered nozzle