Ceramic welding methods and systems and high temperature ceramic materials made thereby

Abstract

Methods, systems and ceramic materials made thereby are provided whereby a refractory ceramic material is formed by separately entraining a particulate noncombustible ceramic oxide material and a particulate combustible exothermic metal fuel component in an oxygen-rich gas stream and a substantially inert gas stream, respectively. The oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible exothermic metal fuel component can then be mixed (e.g., within a ceramic welding lance having a distal end positioned close to the target site for ceramic formation) to form a combustible refractory mixture. The combustible refractory mixture may then be exposed to a high temperature environment (e.g., an ignition flame or the inherent operational temperature of a refractory structure to which the refractory material is being applied) sufficient to combust the combustible exothermic metal fuel component in the combustible refractory mixture and form a coherent mass of refractory ceramic material therefrom.

Description

CERAMIC WELDING METHODS AND SYSTEMS AND HIGH TEMPERATURE CERAMIC MATERIALS MADE THEREBYCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based on and claims priority to U.S. Provisional Application Serial No. 63 / 666,961 filed on July 2, 2024, the entire content of which is expressly incorporated hereinto by reference.FIELD

[0002] The embodiments disclosed herein relate generally to methods, systems and ceramic materials formed thereby. According to preferred embodiments, high temperature ceramic welding by the fusion of oxide ceramics is provided thereby forming a coherent mass of a high temperature ceramic oxide material, e.g., a ceramic oxide coating on a substrate.BACKGROUND

[0003] Ceramic welding processes are known which rely on the fusing (melting) of oxide ceramics with the energy derived from the ignition of exothermic combustible metals in a typically oxygen rich environment. (See in this regard, U.S. Patent Nos. 3684560, 4489022, 4792468, 5242639 and 5700309 as well as GB 402,203, the entire contents of each such patent being expressly incorporated hereinto by reference).

[0004] Exothermic metals are substances that release more energy than the energy required to ignite the metal initially. To date the conventional ceramic welding processes have used a single pressure vessel or venturi to convey a ceramic material and combustible metal fuel (predominantly exothermic metal) in a pressurized oxygen or oxygen rich gaseous stream. This stream is conveyed as a mixture in a series offlexible hoses and ultimately to an elongate welding lance that is placed into the heating vessel to be repaired. (See U.S. patents 5378493, 6186410 and 71 14663 as well as GB 2237803, the entire contents of each such patent being expressly incorporated hereinto by reference.) In such conventional systems all of the required material to have a sustained reaction are present as a mixture in the material stream and any source of ignition could thereby deleteriously cause that reaction to occur at any point in the pressure vessel, conveyance hoses, and the like rather than at the distal combustion zone of the lance. Because of this potential to have a sustained reaction, the choice of metal fuel(s) and the amount (percentage) of metal fuel(s), especially those metal fuels having exothermic properties, in the material mixture has been limited.Moreover, material compositions that can safely be produced in single material ceramic welding systems are typically predominantly silicious and thus do not possess sufficient refractory properties to withstand the corrosive and erosive environment that is typically encountered in some refractory structures, e.g., a refractory structure employed in glass manufacturing where the refractory is submerged below molten glass having temperatures above about 2,800°F (approximately 1538°C).

[0005] It would therefore be highly desirable if processes and systems could be provided which allow the formation of ceramic materials that can be formed in situ at high temperatures on substrate surfaces of refractory structures while such structures are in service, e.g., refractory structures employed in glass production. It is towards providing such processes and systems that the embodiments disclosed herein are directed.SUMMARY

[0006] Contrary to the conventional ceramic welding processes, the ceramic welding technology of the embodiments disclosed herein employs at least two separate and segregated subsystems, i.e., one subsystem toconvey the particulate noncombustible ceramic oxide material and another to convey the particulate combustible metal fuel component. In general, the first ceramic subsystem is adapted to convey the noncombustible ceramic oxides entrained in an oxygen gas stream. A combustible reaction is therefore not possible in the first subsystem due to the absence of a fuel, i.e., since the oxygen gas stream entrains predominantly only the noncombustible ceramic oxides and not the particulate combustible metal fuel component. The second subsystem conveys the particulate metal fuel component entrained in an inert gas stream. A reaction is also not possible in the second subsystem because of the lack of sufficient oxygen or a source of oxygen that would sustain combustion of the metal fuel if ignited.

[0007] These two streams from the first and second subsystems are directed to a conventional ceramic welding lance having a substantially uniform cross-sectional diameter and no internal obstructions. The two streams are thus mixed within and discharged from the distal (discharge) end of the lance as a combustible refractory mixture. The exothermic metal in the combustible refractory mixture is thereby ignited upon discharge from the lance by virtue of the high temperature environment into which the mixture is discharged and / or by virtue of a source of ignition (e.g., a flame). The lance is also preferably electrically grounded to ensure no static discharge. The use of the two subsystems together in accordance with the embodiments disclosed herein thereby allows for the use of metal fuels having a higher energy content and a higher percent of the total amount of refractory material being ceramically welded to the substrate than would be possible with a single pressure vessel or venturi as employed in the conventional ceramic welding processes.

[0008] Broadly, therefore, the embodiments disclosed herein are directed towards methods and systems for forming a refractory ceramicmaterial by separately entraining a particulate noncombustible ceramic oxide material and a particulate combustible metal fuel component in an oxygen-rich gas stream and a substantially inert gas stream, respectively. The oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metal fuel component can then be mixed together (e.g., within a ceramic welding lance and having a distal (discharge) end positioned close to the target site for ceramic formation) to form a combustible refractory mixture as the streams are conveyed through the lance. When discharged from the lance, the combustible refractory mixture will possess a minimum ignition temperature (MIT) such that upon exposure to a high temperature environment (e.g., the inherent operational temperature of a refractory structure to which the refractory material is being applied or an ignition flame) sufficient to combust the combustible metal fuel component in the combustible refractory mixture and form a coherent mass of refractory ceramic material therefrom. The resulting ceramic material that is formed may therefore safely contain relatively higher amounts of metal oxide formed by combustion of the metal fuel component as compared to conventional ceramic welding techniques.

[0009] According to some particularly preferred embodiments, methods and systems are provided for forming a refractory ceramic material using a ceramic welding lance, whereby first and second pressure vessels respectively containing a particulate noncombustible ceramic oxide material and a particulate combustible metal fuel component are provided so that the particulate noncombustible ceramic oxide material may be entrained in an oxygen-rich gas stream while the particulate combustible metal fuel component may separately be entrained in a substantially inert gas stream. The oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metalfuel component are then separately directed to the ceramic welding lance whereby the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material may be mixed with the substantially inert gas stream with the entrained combustible metal fuel component to form a combustible refractory mixture as it travels the length of the lance. The combustible refractory mixture is then expelled from the distal (discharge) end of the ceramic welding lance, e.g., toward a substrate surface of a refractory structure in a high temperature environment sufficient to combust the combustible metal fuel component in the combustible refractory mixture and form on the surface of the refractory structure a coherent mass of refractory ceramic material therefrom.

[0010] The oxygen-rich gas stream may comprise 80-100 vol.% of oxygen, while the substantially inert gas stream may comprise 70-100 vol.% of an inert gas (e.g., nitrogen, argon, carbon dioxide and the like)

[0011] By separately directing the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible exothermic metal fuel component to the welding lance, the weight percent of the combustible exothermic metal fuel component can be increased while the weight percent of the noncombustible ceramic oxide material may be substantially decreased. Of course, if desired, the amount of the noncombustible ceramic oxide could be increased while the amount of the combustible metal fuel component can be decreased depending on the environment in which the method and system are employed.

[0012] These and other aspects and advantages of the present invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

[0013] The disclosed embodiments of the present invention will be better and more completely understood by referring to the following detailed description of exemplary non-limiting illustrative embodiments in conjunction with the drawings of which:

[0014] FIG. 1 is a schematic representation of a ceramic welding system in accordance with an embodiment of the invention; and

[0015] FIG. 2 is a phase diagrapm showing the refractory properties of conventional ceramic materials formed by processes of the prior art vs. the ceramic materials that may be produced by the embodiments of the invention disclosed herein.DETAILED DESCRIPTION

[0016] Accompanying FIG. 1 schematically depicts an exemplary embodiment of a ceramic welding system 10 in accordance with the invention. As shown, the system 10 is provided with first and second subsystems 20, 40, for providing the oxygen entrained noncombustible ceramic oxide material and the inert gas entrained combustible metal fuel component, respectively, to a conventional water-cooled welding lance 12. The welding lance 12 is of sufficient length to allow operators to stand off from the extreme heat of the refractory structure (a representative part thereof shown by reference 14 in FIG. 1 ) while it is in operation.

[0017] The welding lance 12 will include respective separate internal passageways or conduits (not shown) for each of the oxygen entrained noncombustible ceramic oxide material (introduced to the lance 12 via line 45) and the inert gas entrained combustible metal fuel component (introduced to the lance 12 via line 25). The lance 12 however allows the oxygen entrained noncombustible ceramic oxide material andthe inert gas entrained combustible metal fuel component to be mixed with one another within the lance 12 so as to be expelled as a combustible mixture from the distal tip 12a thereof as a particulate spray 16 onto a surface of the refractory structure 14. The heat of the refractory structure 14 will thus ignite the combustible metal fuel component due to the presence of oxygen provided by the oxygen entrained noncombustible ceramic oxide material admixed therewith to result in a coherent layer 14a of refractory material on the surface of the refractory structure 14 which solidifies to form a refractory ceramic that is compatible with the ceramic substrate forming the refractory structure 14 on which the layer 14a is applied.

[0018] The first subsystem 20 includes a first closed pressure vessel 22 that predominantly comprises the noncombustible ceramic oxide material. Oxygen gas is supplied via line 23 from a pressurized source thereof (e.g., oxygen cylinders 24) to the vessel 22 so as to entrain the noncombustible ceramic oxide material therein and deliver it via line 25 to the proximal end of the welding lance 12. The first vessel 22 may, however, optionally contain some combustible metal fuel in an amount that would not in and of itself support a combustion reaction if ignited.

[0019] While the oxygen gas supplied via the cylinders 24 may be 100 vol.% oxygen, the embodiments disclosed herein may if desired also employ an oxygen-rich gas. By “oxygen-rich” gas is meant an oxygencontaining gas having 80 vol.% oxygen gas or greater. Thus, the oxygenrich gas which entrains the noncombustible ceramic oxide material contained in the vessel 22 may be 80-100 vol.%, e.g., 80 vol%, 85 vol.%, 90 vol.%, 95 vol.% or greater, for example up to and including 100 vol.%, of oxygen gas.

[0020] The second subsystem 40 includes a second closed pressure vessel 42 that predominantly contains the particulate combustible metal fuel component. An inert gas, e.g., nitrogen, argon,carbon dioxide and the like, is supplied via line 43 from a pressurized source thereof (e.g., inert gas (nitrogen) cylinders 44) to the vessel 42 so as to entrain the particulate combustible metal fuel component and deliver it via line 45 to the proximal end of the welding lance 12. The second vessel 42 may, however, optionally contain noncombustible ceramic oxide material in an amount that would not preclude combustion of the combustible fuel in the resulting combustible mixture discharged from the lance 12.

[0021] Although the streams in lines 25 and 45 are depicted in FIG. 1 as being delivered to the proximal end of the lance 12, they may alternatively be delivered to the distal end of the lance 12 or at any location between the proximal and distal ends of the lance 12 sufficient to achieve adequate mixture and combustion of the streams when discharged.

[0022] While the gas supplied via the cylinders 44 may be 100 vol.% inert gas, e.g., 100 vol.% nitrogen, there may be some relatively small amount of oxygen-containing gas present, e.g., oxygen or ambient (process) air, that is insufficient to promote combustion of the particulate combustible exothermic metal fuel component. Thus, the gas stream which is provided to entrain the particulate combustible metal fuel component may be a substantially inert gas stream. By “substantially inert gas” is meant that the gas stream contains mostly inert gas but could contain a relatively small amount of oxygen or oxygen-containing gas (e.g., oxygen or air), such as a substantially inert gas stream having 70 vol.% inert gas or greater. Thus, the substantially inert gas which entrains the particulate combustible exothermic metal fuel component contained in the vessel 42 may be 70-100 vol.%, e.g., 70 vol.%, 75 vol.%, 80 vol%, 85 vol.%, 90 vol.% or 95 vol.% or greater, for example up to and including 100 vol.% of inert gas.

[0023] The particulate noncombustible ceramic oxide material entrained in the oxygen-rich gas stream is most preferably delivered to the proximal (inlet) end of the welding lance 12 via line 25 at a flow rate of between about 20 to 30 SCFM, such as at about 25 SCFM and at a pressure of between about 10 to about 20 psi. The particulate combustible metal fuel component entrained in the substantially inert gas stream is preferably delivered to the proximal end of the welding lance 12 via line 45 at a flow rate between about 1 to about 5 SCFM, such as between about 2 to 3 SCFM. According to preferred embodiments, the flow rates of the particulate noncombustible ceramic oxide material entrained in the oxygen-rich gas stream and the combustible metal fuel component entrained in the substantially inert gas stream are such that a combustible mixture of the two streams is formed as they travel within the lance 12. The pressure and flow rates of the combustible mixture formed in and discharged from the lance 12 are therefore selected so as to be in the range of about 70 fps to about 140 fps, for example, between about 80 fps and 130 fps, ideally about 1 10 fps.

[0024] The differential flow rate between the lines 25 and 45 as noted above ensures that a combustible refractory mixture of the particulate noncombustible ceramic oxide material and the particulate combustible metal fuel component that is expelled from the distal (discharge) end of the lance 12 will be oxygen-rich thereby promoting ignition and combustion when the mixture is discharged as the spray 16 towards the surface of the refractory structure 14 as it enters the high temperature environment thereof. Preferably, the combustible refractory mixture formed in and discharged from the lance 12 will have an oxygen content of at least 70 vol.% or greater, such as at least 80 vol.% to 95 vol.% or greater, for example about 85 vol. % to about 93 vol.%. By “high temperature” is meant a temperature of 1200°F (about 650°C) or greater, such as for example a temperature of about 1470°F to about 1650°F (about 800-900°C) or greater. By way of example, a high temperature ofup to about 2,800°F (approximately 1540°C) is encountered when the refractory structure 14 is employed for glass production.

[0025] The weight ratio of the particulate noncombustible ceramic oxide material to the particulate combustible exothermic metal (fuel) component delivered to the lance 12 via the lines 25 and 45, respectively, is most preferably between about 94:6 to about 80:20, such as about 88:12. As noted previously, the processes of the embodiments disclosed herein enable the formation of a ceramic material containing substantially greater amounts of AI2O3 and thus substantially lower amounts of SiO2 as compared to conventional processes. As shown in FIG. 2, for example, the weight percent of AI2O3 in the ceramic materials of the invention may be between about 75 wt.% to about 85 wt%, for example, between about 79 wt.% to about 83 wt.%, while the amount of SiO2 can be correspondingly reduced to between about 15 wt.% to about 25 wt.%, for example between about 17 wt.% to about 21 wt.% (see FIG. 2).

[0026] In order to prevent backflow of oxygen gas into the line 25, the particulate combustible exothermic metal (fuel) component entrained in the inert gas stream is delivered by the line 45 at a pressure which is no less than 5 psi greater than the pressure in the line 25 (for example between 5 psi to 10 psi greater than the pressure in the line 25).

[0027] The particulate combustible metal fuel component may comprise particulate aluminum, magnesium, calcium, silicon, zirconium, chromium, vanadium and alloys and mixtures thereof. Such metal fuel particles will typically possess a volume particle size distribution (D50) (i.e., a volume distribution where 50% of the particles are greater than the stated size and 50% of the particles are less than the stated size) of about 50 pm or less, advantageously 10 pm or less, such as between 2 pm to about 40 pm or between about 3 pm to about 35 pm.

[0028] The particulate noncombustible ceramic oxide material is preferably one or more conventional particulate refractory oxide compounds, such as oxides of aluminum, magnesium, silicon, chromium and mixtures thereof.. Such noncombustible ceramic oxide particles will typically possess a particle size having an ASTM E11 mesh size of -10+140, such as about -30+80 mesh or -20+80 mesh.

[0029] Depending on the process conditions, a portion of the inert gas from the cylinders 44 could optionally also be supplied via line 28 to the line 23 and / or line 25 so that a mixture of inert gas and oxygen gas from the cylinders 44 and 24, respectively, may be supplied to the vessel 22 and entrain the particulate noncombustible ceramic oxide material therein which is supplied to the welding lance 12. Further, at the end of a welding cycle, the line 23 may be closed so as to allow only inert gas to flow from the cylinders 44 into the vessel 22 and then through the line 25 and the lance 25 thereby purging such components of oxygen.

[0030] As noted previously, the embodiments disclosed herein are capable of forming a ceramic material having a relatively high amount of between about 75 wt.% to about 85 wt%, for example, between about 79 wt.% to about 83 wt.%, of the combustible metal fuel component, e.g., AI2O3, and a relatively low amount of between about 15 wt.% to about 25 wt.%, for example between about 17 wt.% to about 21 wt.%, of the noncombustible ceramic oxide material, e.g., SiC>2.

[0031] The embodiments disclosed herein will be better understood by reference to the following non-limiting examples.EXAMPLES

[0032] One particularly preferred ceramic material that is conventionally used in the melting portion of a glass melting tank associated with glass manufacturing is an alumina, zirconia and silica(AZS) material. These AZS materials are conventionally produced using a fused cast method, in a capital intensive fused cast manufacturing facility. The finished blocks are then sent to the glass tank location for installation.

[0033] The system 10 schematically shown in FIG. 1 has however been employed to apply a material having a chemistry similar to AZS in an in situ basis. This material is applied with the system shown in FIG. 1 and is formed by fusing the constituent materials within the glass tank. The particulate material used in the pressure vessel subsystem 20 includes aluminum, silicon and nitrogen while the particulate material used in the subsystem 40 are zircon, fused white alumina and oxygen. Chemical analysis of the fused cast refractory and the welded materials (Inventive Ex. 1 and Inventive Ex. 2) of the system in accordance with the present invention in comparison to a conventional fused cast AZS material (CS-3) that is typically employed in glass manufacturing refractory structures (and which provides an especially well suited substrate to which the ceramic materials of the embodiments disclosed herein can be welded) appear in the table below:

[0034] The system 10 in accordance with the embodiments disclosed herein has been employed successfully to fuse a conventional fused cast AZS substrate material and a 95% and greater alumina ceramic material. Optionally, a high magnesia material may be employed. Materials of alumina and magnesia chemistries which possess relative high refractory properties are not able to be fused safely using a conventional single stream ceramic welding system as was previously described above. The three materials above are thus quite useful in a variety of glass, metal and mineral processing vessels to repair in situ and perhaps as primary relining material.

[0035] Preferably, the ceramic AZS materials formed by the methods described herein can have the following composition:AI2O3: 42 wt.% to 53 wt.%, preferably about 46 wt.% to about 50 wt.%ZrC : 28 wt.% to 42 wt.%, preferably about 33 wt.% to about 40 wt.%SiO2: 12 wt.% to 18 wt.%, preferably about 13 wt.% to 15 wt.%MgO: 0 wt.% to 4 wt.%, preferably about 2 wt.% to about 3 wt.%

[0036] The system 10 in accordance with the embodiments of this invention produces a ceramic material that, at glass making temperatures, does not contain liquid phases. The lack of liquid phase in the material at the service temperature of glass is fundamental to long refractory life and increased refractory properties. The relative phases in the ceramic materials formed by the system 10 of the embodiments disclosed herein versus traditional ceramic welding systems is shown in the phase diagram of FIG. 2.**********************

[0037] While the system 10 in accordance with the invention has been described in connection with the thermal welding of a ceramic refractory to a surface of an operational high temperature refractory structure, it will be understood that such a disclosure is directed to an especially preferred embodiment thereof. Thus, the system 10 could be employed to apply a ceramic welding material to an already pre-formed ceramic refractory block or body that could then be installed as needed within an existing refractory structure or used to construct a refractory structure. Alternatively or additionally, a conventional fuse-cast AZS refractory block could be configured to have one or more pockets or recesses that would then allow the refractory material of the embodiments disclosed herein to be welded thereto either in-situ on site or off site. It can also be envisioned that ceramic components could be pre-formed off site using the system 10 as described herein which are then adapted to being transported to a facility and adhered (e.g., via welding or mortaring) to the conformably shaped pockets or recesses in the existing refractory block.

[0038] It will therefore be understood that the description provided herein is presently considered to be the most practical and preferred embodiments of the invention. Thus, the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope thereof.

Claims

WHAT IS CLAIMED IS:1 . A method for forming a refractory ceramic material comprising:(a) separately entraining a particulate noncombustible ceramic oxide material and a particulate combustible metal fuel component in an oxygen-rich gas stream and a substantially inert gas stream, respectively;(b) mixing the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metal fuel component to form a combustible refractory mixture; and(c) exposing the combustible refractory mixture to a minimum ignition temperature sufficient to combust the combustible metal fuel component in the combustible refractory mixture and form a coherent mass of refractory ceramic material therefrom.

2. The method according to claim 1 , wherein step (a) comprises:(a1 ) providing first and second vessels respectively containing the particulate noncombustible ceramic oxide material and the particulate combustible metal fuel component;(a2) entraining the particulate noncombustible ceramic oxide material from the first vessel in the oxygen-rich gas stream and entraining the particulate combustible metal fuel component in the second vessel in a substantially inert gas stream.

3. The method according to claim 1 or 2, wherein step (b) further comprises:(b1 ) separately directing the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metal fuel component to the ceramic welding lance; and(b2) mixing the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metal fuel component within the ceramic welding lance to form the combustible refractory mixture4. The method according to claim 3, wherein step (c) comprises expelling the combustible refractory mixture from a distal end of the ceramic welding lance into a high temperature environment which is at least at the minimum ignition temperature of the combustible refractory mixture.

5. A method for forming a refractory ceramic material layer on a surface of an operational high temperature refractory structure, the process comprising:(a) providing a ceramic welding lance;(b) providing first and second vessels respectively containing a particulate noncombustible ceramic oxide material and a particulate combustible metal fuel component,(c) entraining the particulate noncombustible ceramic oxide material in an oxygen-rich gas stream and entraining theparticulate combustible metal fuel component in a substantially inert gas stream;(d) separately directing the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metal fuel component to the ceramic welding lance;(e) mixing the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metal fuel component to form a combustible refractory mixture; and(f) expelling the combustible refractory mixture from a distal end of the ceramic welding lance to expose the combustible refractory mixture to a high temperature environment at least at a minimum ignition temperature of the combustible refractory mixture sufficient to combust the combustible metal fuel component in the combustible refractory mixture and form a coherent mass of refractory ceramic material therefrom.

6. The method of claim 5, wherein step (d) is practiced by expelling and mixing the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metal fuel component from the distal end of the ceramic welding lance toward a surface of a refractory structure in the presence of the high temperature environment to form the refractory mass in situ on the surface of the refractory structure.

7. The method according to claim 5, wherein the substantially inert gas stream with the entrained combustible metal fuel component has a pressure that is 5 psi or greater as compared to the pressure of the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material.

8. The method according to claim 5, wherein the oxygen-rich gas comprises 80-100 vol.% of oxygen.

9. The method according to claim 5, wherein the substantially inert gas comprises 70-100 vol.% of an inert gas.

10. The method according to claim 9, wherein the inert gas is selected from the group consisting of nitrogen, argon and carbon dioxide.1 1 . The method according to claim 5, wherein the combustible mixture has an oxygen content of at least about 70 vol.% or greater.

12. The method according to claim 5, wherein a weight ratio of the particulate noncombustible ceramic oxide material to the particulate combustible exothermic metal fuel component supplied separately to the ceramic welding lance is between about 94 : 6 to about 80 : 20.

13. The method according to claim 5, wherein the particulate combustible exothermic metal fuel component comprises particulate selected from the group consisting of aluminum, magnesium, calcium, silicon, zirconium and alloys and mixtures thereof.

14. The method according to claim 13, wherein the particulate combustible exothermic metal fuel component has a volume particle size distribution (D50) of 50 pm or less.

15. The method according to claim 5, wherein the particulate noncombustible ceramic oxide material is an oxide of a metal selected from the group consisting of aluminum, magnesium, silicon, chromium and mixtures thereof.

16. The method according to claim 15, wherein the noncombustible ceramic oxide particles have a volume particle size distribution (D50) about 840 pm or less.

17. A system for forming a refractory ceramic material comprising: a ceramic welding lance; first and second vessels respectively containing a particulate noncombustible ceramic oxide material and a particulate combustible metal fuel component, sources of pressurized oxygen-rich gas and a substantially inert gas stream that are connected to the first and second vessels respectively and adapted to separately entrain the particulate noncombustible ceramic oxide material in the oxygen-rich gas stream and the particulate combustible metal fuel component in the substantially inert gas stream; first and second supply lines separately directing the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metal fuel component to the ceramic welding lance; whereinthe ceramic welding lance mixes and expels a combustible refractory mixture formed of the oxygen-rich gas stream with the entrained particulate noncombustible ceramic oxide material and the substantially inert gas stream with the entrained combustible metal fuel component from the distal discharge end of the ceramic welding lance into a high temperature environment at least at a minimum ignition temperature for the combustible refractory mixture sufficient to combust the combustible metal fuel component and form a coherent mass of the refractory ceramic material therefrom with the particulate noncombustible ceramic oxide material.

18. The system according to claim 17, wherein the oxygen-rich gas comprises 80-100 vol.% of oxygen.

19. The system according to claim 17, wherein the substantially inert gas comprises 70-100 vol.% of an inert gas.

20. The system according to claim 19, wherein the inert gas is selected from the group consisting of nitrogen, argon and carbon dioxide.21 . The system according to claim 17, wherein a weight ratio of the particulate noncombustible ceramic oxide material to the particulate combustible exothermic metal fuel component supplied separately to the ceramic welding lance is between about 94 : 6 to about 80 : 20.

22. The system according to claim 17, wherein the particulate combustible exothermic metal fuel component comprises metal particulates selected from the group consisting of aluminum,magnesium, calcium, silicon, zirconium and alloys and mixtures thereof.

23. The system according to claim 22, wherein the particulate combustible exothermic metal fuel component has an average particle size of 50 pm or less.

24. The system according to claim 17, wherein the particulate noncombustible ceramic oxide material is an oxide of a metal selected from the group consisting of aluminum, magnesium, silicon, chromium and mixtures thereof.

25. The system according to claim 25, wherein the noncombustible ceramic oxide particles have an average particle size of about 500 pm or less.

26. A coherent solid mass of ceramic refractory material made by the process of claim 1 .

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