Reinforced geopolymer gun barrel

Abstract

A gun barrel can include a cylindrical layer defining an internal bore; and a geopolymer layer on the cylindrical layer; and a continuous fiber reinforced composite on the geopolymer layer. Advantageously, the geopolymer layer can include a thermally conductive material dispersed in a geopolymer matrix. Such a multilayered gun barrel can improve the heat transfer characteristics of the gun barrel relative to a gun barrel without such a geopolymer layer. The geopolymer layer additionally can include a density-reducing material dispersed through the geopolymer matrix to further improve heat transfer and / or weight of the gun barrel relative to a gun barrel composed entirely of metal.

Description

41384.04062REINFORCED GEOPOLYMER GUN BARRELCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and all benefit of U.S. Provisional Patent Application No. 63 / 689,702, filed on August 31, 2024, the entire disclosure of which is fully incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to a gun barrel and, in particular, to a multilayered gun barrel including a geopolymer layer that can improve heat transfer characteristics of the gun barrel.BACKGROUND

[0003] The materials of construction chosen for rifle barrels (e.g. all steel or all titanium) are chosen for their structural properties (strength and stiffness) to withstand the pressure created when a rifle cartridge is fired and to maintain uniform bullet trajectories (grouping). In some applications, in order to keep groupings as tight as possible, an even heavier bull barrel (nontapered cylinder) is used. These structures made and materials result in durable but heavy barrels. Some manufacturers have been able to combat the weight problem by reducing the amount of metal and replacing the metal with lightweight and high-strength carbon fiber-reinforced thermoset resin. This thermoset resin, however, is a very poor heat conductor and thus the heat retention in the rifle is increased over that of an all-metallic barrel. Moreover, the more heat a barrel maintains the less accurate it is, a common problem after multiple shots. This excess heat either reduces accuracy of the rifle or forces a reduction in the firing rate to maintain desired groupings. Also, carbon wrapped barrels that exist today still require a fully metallic chamber shank (the outside of the chamber). This is the thickest and heaviest part of the barrel. Some current carbon fiber modified steel barrel producers claim that harmonic tuning of the barrel is accomplished by adding compression to the lock nut at the muzzle.

[0004] Accordingly, there is an ongoing need for improved gun barrels, such as those that have improved heat transfer and / or reduced weight while maintaining sufficient strength.SUMMARY

[0005] Advantages of the present disclosure include a multilayered gun barrel having a cylindrical layer, and a geopolymer layer thereon. Such a gun barrel can have improved heat transfer characteristics and / or reduced weight compared to an all-metal gun barrel.41384.04062

[0006] In an implementation, a gun barrel can include a cylindrical layer defining an internal bore; and a geopolymer layer overlaying an outer surface of the cylindrical layer. Advantageously, the geopolymer layer can be composed of a geopolymer matrix, e.g., an metallosilicate polymer network with metal atoms linking silicate groups. The geopolymer layer further can comprise a thermally conductive material dispersed in a geopolymer matrix. Such thermally conductive materials can facilitate thermal transport through the geopolymer layer and can include one or more of a thermally conductive carbon, carbon fiber, carbon nanomaterial, silver, copper, aluminum, thermally conductive ceramic, or a combination thereof. The geopolymer layer can comprise a density-reducing material dispersed in a geopolymer matrix to reduce the density of the geopolymer matrix relative to the geopolymer matrix without the density-reducing material. Such density-reducing materials advantageously can improve thermal characteristics of the geopolymer layer. The density-reducing materials can include a porous aggregate, hollow beads, e.g., hollow glass beads, hollow ceramic beads, or a combination thereof. In some aspects, the density-reducing material can act as the thermally conductive material, e.g., thermally conductive hollow beads can act as a thermally conductive material and as a density-reducing material.

[0007] In some aspects, the geopolymer layer can include a plurality of continuous fibers therein, e.g. a plurality of continuous fibers embedded in a geopolymer matrix. Such a fiber reinforced geopolymer layer advantageously can allow for a thinner cylindrical layer. In addition to, or as an alternative to a fiber reinforced geopolymer layer, the gun barrel further can include a continuous fiber reinforced composite overlaying the geopolymer layer. Such a continuous fiber reinforced composite can include a plurality of continuous fibers therein.

[0008] Other implementations of the present disclosure include processes for preparing a gun barrel which include applying a geopolymer layer on an outer surface of a cylindrical layer defining an inner bore. The geopolymer layer can be applied by spraying, rolling and / or dip coating an aqueous formulation onto the outer surface of the cylindrical layer. The aqueous formulation can comprise geopolymer matrix forming components of (a) a metal silicate; (b) a metal oxide; (c) a water-soluble caustic agent; and (d) water. The aqueous formulation further can comprise a thermally conductive material; and / or a density-reducing material that has a bulk density which is less than a density of a geopolymer matrix formed from the geopolymer matrix forming components. The process further can include forming a continuous fiber reinforced composite on the geopolymer layer.41384.04062

[0009] A further implementation of the present disclosure includes a method of using a gun barrel such as by propelling a projectile through the gun barrel.

[0010] Implementations of the present disclosure include one or more of the following features individually or combined. For example, the cylindrical layer can comprise a metal, e.g., a steel, stainless steel, titanium, brass, red brass, iron, bronze, aluminum, or a combination thereof, or a ceramic, or a combination of metal and ceramic. In some aspects, the geopolymer layer can be formed from an aqueous formulation that comprises geopolymer matrix forming components of: (a) a metal silicate; (b) a metal oxide; (c) a water-soluble caustic agent; and (d) water. The aqueous formulation further can include a thermally conductive material; and / or a density-reducing material that has a bulk density which is less than a density of a geopolymer matrix formed from the geopolymer matrix forming components. In some aspects, the metal silicate can comprise one or more of: an alkali metal silicate, alkaline earth metal silicates, sodium silicate, sodium silicate, lithium silicate, potassium silicate, neosilicates, sorosilicates, cyclosilicates, inosilicates, phyllosilicates, tectosilcates, mullite, kaolinite, muscovite, or any combination thereof. In other aspects, the metal oxide can comprise one or more of: aluminum trihydrate (ATH), zinc oxide (ZnO), iron oxide, titanium dioxide (TiCh), copper oxide, tin oxide, zirconium oxide, manganese oxide, nickel oxide, silver oxide, vanadium oxide, bismuth oxide, or any combination thereof. In still further aspects, the water-soluble caustic agent can comprise one or more of: an alkali metal hydroxide, Na2O(SiO2), Li2O(SiO2), K2O(SiCh), or ammonium hydroxide, or a combination thereof.

[0011] Additional advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only certain aspects are shown and described, simply by way of illustration of carrying out certain subject matter. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the drawings, which are not necessarily drawn to scale, like numerals can describe similar components in different views. Like numerals having different letter suffixes can represent41384.04062 different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various aspects discussed in the present document. In the drawings:

[0013] FIG. 1 depicts a front cross-sectional view of an exemplary gun barrel as contemplated by the present disclosure. Exemplary layers of a gun barrel are shown.

[0014] FIG. 2 depicts a front cross-sectional view of another exemplary gun barrel as contemplated by the present disclosure. Exemplary layers of a gun barrel are shown.

[0015] FIG. 3 depicts a cut-off of a side cross-sectional view of the gun barrel of FIG. 2.

[0016] FIG. 4 depicts a side cross-sectional view of another exemplary gun barrel showing exemplary layers of the barrel encasing the bore region and extending to the shank encasing the body region.DETAILED DESCRIPTION OF THE DISCLOSURE

[0017] The present disclosure may be understood more readily by reference to the following detailed description of desired embodiments and the examples included therein.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

[0019] The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0020] As used in the specification and in the claims, the term "comprising" can include the embodiments "consisting of' and "consisting essentially of.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named ingredients / steps and permit the presence of other ingredients / steps. However, such description should be construed as also describing compositions or processes as "consisting of' and "consisting essentially of' the enumerated ingredients / steps, which allows the presence of only41384.04062 the named ingredients / steps, along with any impurities that might result therefrom, and excludes other ingredients / steps.

[0021] As used herein, the terms “about” and “at or about” mean that the amount or value in question can be the value designated some other value approximately or about the same. It is generally understood, as used herein, that it is the nominal value indicated ±10% variation unless otherwise indicated or inferred. The term is intended to convey that similar values promote equivalent results or effects recited in the claims. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but can be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. In general, an amount, size, formulation, parameter or other quantity or characteristic is “about” or “approximate” whether or not expressly stated to be such. It is understood that where “about” is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise.

[0022] Unless indicated to the contrary, the numerical values should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

[0023] All ranges disclosed herein are inclusive of the recited endpoint and independently of the endpoints. The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and / or values.

[0024] As used herein, approximating language can be applied to modify any quantitative representation that can vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially,” may not be limited to the precise value specified, in some cases. In at least some instances, the approximating language can correspond to the precision of an instrument for measuring the value. The modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4” also discloses the range “from 2 to 4.” The term “about” can refer to plus or minus 10% of the indicated number. For example, “about 10%” can indicate a range of 9% to 11%, and “about 1” can mean from 0.9-41384.040621.1. Other meanings of “about” can be apparent from the context, such as rounding off, so, for example “about 1” can also mean from 0.5 to 1.4. Further, the term “comprising” should be understood as having its open-ended meaning of “including,” but the term also includes the closed meaning of the term “consisting.” For example, a composition that comprises components A and B can be a composition that includes A, B, and other components, but can also be a composition made of A and B only. Any documents cited herein are incorporated by reference in their entireties for any and all purposes.

[0025] The term “continuous fiber,” as used herein, refers to a fiber that has a long aspect ratio (length-to-diameter ratio). Due to the long aspect ratio of the continuous fiber, the continuous fiber may be wrapped, woven, knitted, braided, arranged to be substantially parallel, or used in a nonwoven fabric. In embodiments, where the continuous fiber are arranged to be substantially parallel, the continuous fibers may span all or substantially all of a dimension of the continuous fiber reinforced polymeric composite. The term “substantially all of a dimension,” as used herein, refers to greater than 75% of a dimension of the continuous fiber reinforced polymeric composite.

[0026] The term “average diameter,” as used herein with respect to the continuous fibers, refers to an average of the diameters of each of the fibers in the plurality of continuous fibers.

[0027] The term “average diameter,” as used herein with respect to the thermally non-conductive hollow beads, refers to an average of the diameters of each bead of the thermally non-conductive hollow beads.

[0028] The term “average length,” as used herein, refers to an average of the lengths of the thermally conductive material.

[0029] The term “average geometrical dimension,” as used herein, refers to an average of the largest dimensions of the thermally conductive material.

[0030] The term “ambient temperature,” as used herein, refers to about 20 °C.

[0031] The term “thermal inertia,” as used herein, refers to the property of a material that expresses the degree of slowness with which its temperature reaches that of the environment. A relatively lower thermal inertia indicates a faster return to equilibrium with the environment. A relatively higher thermal inertia indicates a greater resistance of a material to return to ambient temperature. Thermal inertia is calculated as the square root of the product of volumetric heat41384.04062 capacity and thermal conductivity (i.e., thermal inertia = ^(volumetric heat capacity x thermal conductivity)).

[0032] The term “thermal conductivity,” as used herein, refers to a measure of a material’s ability to conduct heat. The defining equation for thermal conductivity is q = -kAT, where q is the heat flux, k is the thermal conductivity, and AT is the temperature gradient. An alternative is thermal conductivity calculated by multiplying heat capacity by density and by thermal diffusivity (i.e., thermal conductivity = (heat capacity x density) x thermal diffusivity).

[0033] The term “thermal diffusivity,” as used herein, refers to the rate of heat transfer through a medium.

[0034] The term “heat capacity,” as used herein, refers to the number of heat units needed to raise the temperature of the material by one degree.

[0035] The term “volumetric heat capacity,” as used herein, refers to the heat capacity of a material divided by the volume of the material.

[0036] The term “density” as used herein, refers to a material’s mass per unit of volume.

[0037] The term “bulk density” or “apparent density” as used herein, refers to the mass of the combination of particles in a material divided by the bulk volume of the material, where the bulk volume is the total volume occupied by the material including any particles included with or contained within or around the bulk material. The bulk volume includes void volume between the particles and any internal volume within any particles within the bulk material that have an internal volume, including for example hollow beads.

[0038] The term “heat transfer” may be classified as active (i.e., heat exchanges) or passive (i.e., heat sinks). Efficient movement of heat from one location to another may be critical to optimal operation of various equipment or instruments. The object of heat transfer may be to eliminate (i.e., remove) heat from the system and “dump” the heat into the environment. Greater efficiency may be derived by actively using the heat transferred, such as in waste heat recovery units or counter flow heat exchangers. Alternatively, system efficiency may be derived from creating a new equilibrium where at a higher temperature, heat energy is eliminated from the system at essentially the same rate as it is input. However, after heating, conventional materials may not return to ambient temperature at a desired cooling rate (i.e., relatively quickly).41384.04062

[0039] The present disclosure is directed to a multilayered gun barrel, which includes one or more geopolymer layers comprised of a geopolymer matrix, e.g., an metallosilicate polymer network, as well as methods for using and making such gun barrels. Advantageously, a layer including the geopolymer matrix can include a thermally conductive material dispersed in the geopolymer matrix to improve the thermal conductivity of the geopolymer layer. In addition, the geopolymer layer can include a density-reducing material with a bulk density less than a density of the geopolymer matrix. That is, the density-reducing material has a bulk density that is less than the density of the geopolymer matrix formed from geopolymer forming components and without the density-reducing material. In some aspects, the thermally conductive material can comprise a thermally conductive carbon, carbon fiber, carbon nanomaterial, silver, copper, aluminum, thermally conductive ceramic, or a combination thereof. In addition, the densityreducing material can comprise a porous aggregate, hollow beads (e.g., hollow glass beads, hollow ceramic beads, etc.), or a combination thereof. In a geopolymer layer configured with a geopolymer matrix together with a thermally conductive material and a density-reducing material, the thermally conductive material can act as a conduit to transfer heat that is channeled by the density-reducing material, e.g., thermally non-conductive hollow beads, through and out of the geopolymer layer thereby imparting a low thermal inertia to the geopolymer layer. Gun barrels of the present disclosure can be used with devices that fire projectiles including rifles, and aircraft and seacraft guns.

[0040] Advantageously, a gun barrel of the present disclosure can include: (1) a cylindrical layer defining the internal bore, and (2) a geopolymer layer overlaying an outer surface of the cylindrical layer. Optionally, a continuous fiber reinforced composite can be added overlaying the geopolymer layer. The cylindrical layer and geopolymer layer can improve heat characteristics of the gun barrel and an optional continuous fiber reinforced composite layer can allow for greater weight reduction of the barrel relative to a barrel composed of all metal or even carbon fiber barrels currently on the market. Further, and as described in more detail below, the geopolymer layer can translate (conduct) heat faster than steel or titanium. Moreover, the layers can be bonded together to make one cohesive part. In addition, the chamber and chamber shank can also be composed of a multilayered configuration including a cylindrical layer, a geopolymer layer overlaying an outer surface of the cylindrical layer, and optionally, a continuous fiber reinforced composite overlaying the geopolymer layer. Such a multilayered chamber can provide further light-weighting and can reduce the diameter of the shank as well.41384.04062

[0041] FIG. 1 illustrates a front cross-sectional view of a multilayered gun barrel of the present disclosure. As shown, gun barrel 100 includes cylindrical layer 102, which defines an internal bore 101 of the gun barrel. Cylindrical layer 102 includes an outer surface 102a and an inner surface 102b. In FIG. 1, geopolymer layer 104 is directly on and overlays outer surface 102a of cylindrical layer 102 (e.g., there are no intervening layers between the outer surface 102a and the geopolymer layer 104).

[0042] FIGS. 2 and 3 illustrate another multilayered gun barrel 200 of the present disclosure. FIG. 2 shows a front cross-sectional view and FIG. 3 shows a cut-off of a side cross-sectional view of the gun barrel. As illustrated for this example, gun barrel 200 includes a cylindrical layer 202 defining an internal bore 201. Cylindrical layer 102 includes an outer surface 102a and an inner surface 102b. In this example, the inner surface 202b is smooth. The figure further illustrates geopolymer layer 204 overlaying the outer surface 202a of the cylindrical layer 202. For this example, gun barrel 200 also includes a continuous fiber reinforced composite 206 overlaying geopolymer layer 204.

[0043] Gun barrels of the present disclosure can be configured for use with any size gun including firearms, stationary or mobile guns, military weapons, artillery, cannons, guns for aircraft and seacraft.

[0044] For example, in certain aspects, a gun barrel of the present disclosure can be configured for a rifle. FIG. 4 illustrates such an exemplary gun barrel configuration for a rifle 400 and includes cylindrical layer 402 defining internal bore 401 along a longitudinal axis of the barrel 400. The bore 401 is the hollow internal lumen of the barrel and takes up a vast majority portion of the barrel length 410. It is the part of the barrel where a projectile (bullet, shell, shot, slug, etc.) is located prior to firing the projectile. For this example, the bore 401 include grooves called rifling 403 machined into the bore wall (e.g., the cylindrical layer). As a result of the rifling and in contrast to the previous examples, the inner surface of the cylindrical layer 402 is not smooth. The gun barrel further includes a chamber 430 at a proximal end of the barrel and a shank 420 at a proximal end of the chamber, e.g., at one end of the barrel or the breech end of the barrel. The shank 430 can be used for removably mounting the gun barrel 400 to a receiver (not shown).

[0045] In addition to the cylindrical layer, gun barrel 400 includes a geopolymer layer 404 overlaying an outer surface of the cylindrical layer 402. For this example, gun barrel 400 further includes a continuous fiber reinforced composite 406 overlaying the geopolymer layer 404.41384.04062

[0046] In some implementations, the gun barrel can include a shank at one end of the barrel. The shank can include a geopolymer layer 404 that includes thermally conductive material dispersed in a geopolymer matrix. Such a geopolymer layer can further include a density-reducing material dispersed in the geopolymer matrix.

[0047] The gun barrel 400 can further include a gas tube port (not shown) to allow gas to exit the bore from inner surface of cylindrical layer through the geopolymer layer and the continuous fiber reinforced composite overlayer. Such gas ports can be used with semiautomatic and automatic rifles.

[0048] The various layers of a multilayered gun barrel of the present disclosure can have various compositions and structures. The following provides details of the various compositions and structures and can be used for a gun barrel of the present disclosure.Cylindrical Layer

[0049] The cylindrical layer can be constructed of any suitable material that has suitable hoop strength for withstanding the forces associated with firing a projectile along the longitudinal axis of the bore of a gun barrel. For example, the cylindrical layer can be constructed of one or more of a metal, a ceramic, or a combination thereof, including for example a bonded ceramic. Suitable metals that can comprise the cylindrical layer can include one or more of steel, stainless steel, titanium, brass, red brass, iron, bronze, aluminum, and the like, including one or more combinations thereof. The steel can include chrome-molybdenum alloy steel, such as grades AISI 4140, AISI 4150, AISI 4340, and AISI 4350. The stainless steel can include 17-4 PH or SAE steel grades 410, 416, or 416R. The ceramic can include one or more alumina ceramics.

[0050] The cylindrical layer can have a thickness (determined from its inner surface to its outer surface, e.g., from inner surface 102b to its outer surface 102a shown in FIG. 1) in the range of from about 0.1 mm to about 0.5 mm, from about 0.5 mm to about 1 mm, from about 1 mm to about 2 mm, from about 2 mm to about 3 mm, from about 3 mm to about 4 mm, from about 4 mm to about 5 mm, from about 5 mm to about 6 mm, from about 6 mm to about 7 mm, from about 7 mm to about 8 mm, from about 8 mm to about 9 mm, from about 9 mm to about 10 mm, including any and all increments therebetween. In some aspects, cylindrical layer 202 can have a thickness in the range of from about 10 mm to about 20 mm, from about 20 mm to about 40 mm, from about 40 mm to about 60 mm, from about 60 mm to about 80 mm, from about 80 mm to about 100 mm, including any and all increments therebetween.41384.04062

[0051] The cylindrical layer can define a suitable bore diameter. For example, the cylindrical layer 202 can have a miniature-bore. That is, internal bore can have a diameter of less than about 6 mm. In other examples, internal bore can have a diameter in the range of from about 1.0 mm to about 1.5 mm, from about 1.5 mm to about 2.0 mm, from about 2.0 mm to about 2.5 mm, from about 2.5 mm to about 3.0 mm, from about 3.0 mm to about 3.5 mm, from about 3.5 mm to about 4.0 mm, from about 4.0 mm to about 4.5 mm, from about 4.5 mm to about 5.0 mm, from about 5.0 mm to about 5.5 mm, from about 5.5 mm to about 6.0 mm, including any and all increments therebetween. The inner bore can have a small-bore with a diameter in the range of from about 5.6 mm to about 8.1 mm. For example the inner bore can have a diameter in the range of from about 5.6 mm to about 6.0 mm, from about 6.0 mm to about 6.2 mm, from about 6.2 mm to about6.4 mm, from about 6.4 mm to about 6.6 mm, from about 6.6 mm to about 6.8 mm, from about6.8 mm to about 7.0 mm, from about 7.0 mm to about 7.2 mm, from about 7.2 mm to about7.4 mm, from about 7.4 mm to about 7.6 mm, from about 7.6 mm to about 7.8 mm, from about7.8 mm to about 8.0 mm, from about 8.0 mm to about 8.2 mm, including any and all increments therebetween. Alternatively, inner bore can have a medium-bore with a diameter of from about8.4 mm to about 9.9 mm. For example, the inner bore can have an inner diameter in the range of from about 8.4 mm to about 8.6 mm, from about 8.6 mm to about 8.8 mm, from about 8.8 mm to about 9.0 mm, from about 9.0 mm to about 9.2 mm, from about 9.2 mm to about 9.4 mm, from about 9.4 mm to about 9.6 mm, from about 9.6 mm to about 9.8 mm, from about 9.8 mm to about 10.0 mm including any and all increments therebetween. The inner bore can have a large-bore with a diameter of about 10 mm or larger. For example, inner bore can have a diameter in the range of from about 10 mm to about 11 mm, from about 11 mm to about 12 mm, from about 12 mm to about 13 mm, from about 13 mm to about 14 mm, from about 14 mm to about 15 mm, from about 15 mm to about 20 mm, from about 20 mm to about 40 mm, from about 40 mm to about 60 mm, from about 60 mm to about 80 mm, from about 80 mm to about 100 mm, from about 100 mm to about 200 mm, from about 200 mm to about 400 mm, including any and all increments therebetween.Geopolymer Layer

[0052] As described above, the geopolymer layer overlays an outer surface of the cylindrical layer and can completely cover the outer layer of the cylindrical layer. Advantageously, the gun barrel can be composed of one or more geopolymer layers.41384.04062

[0053] The geopolymer layer can include a geopolymer matrix and can include further components. For example, to improve thermal conductivity, the geopolymer layer can include a thermally conductive material dispersed in a geopolymer matrix. The thermally conductive material included in the geopolymer layer can act as a conduit to transfer heat through and out of the geopolymer layer.

[0054] The thermally conductive material can include a thermally conductive carbon, carbon fiber, carbon nanomaterial, silver, copper, aluminum, thermally conductive ceramic blend, or one or more combinations thereof. The thermally conductive material can include milled carbon fiber, graphene, or a combination thereof. Thermally conductive ceramic blends can include any one or more of boron nitride, beryllium oxide, aluminum beryllium oxide, silicon carbide, copper aluminum oxide, or aluminum nitride. The thermally conductive material can have a regular shape, an irregular shape, or a combination thereof. The shapes can include plates, particles, acicular, fibrous, filamentous, tubular, or a combination thereof. The shapes can be of micron size, nano size, or a combination thereof. As an example, the thermally conductive material can be present in a range of about 3 wt% to 30 wt%, based on a total weight of the geopolymer matrix or geopolymer layer.

[0055] The thermally conductive material can have an average length of from about 10 microns to about 500 microns. For example, the thermally conductive material can have an average length of from about 10 microns to about 25 microns, from about 25 microns to about 50 microns, from about 50 microns to about 75 microns, from about 75 microns to about 100 microns, from about 100 microns to about 150 microns, from about 150 microns to about 200 microns, from about 200 microns to about 250 microns, from about 250 microns to about 300 microns, from about 300 microns to about 350 microns, from about 350 microns to about 400 microns, from about 400 microns to about 450 microns, from about 450 microns to about 500 microns including any and all increments therebetween.

[0056] In addition to a thermally conductive material dispersed in a geopolymer matrix, the geopolymer layer further can include a density-reducing material. Such a density-reducing material should have a bulk density that is less than a density of the geopolymer matrix without the density-reducing material. This can be determined by determining the bulk density of the density-reducing material and comparing that bulk density to the density of the geopolymer matrix form from geopolymer matrix forming materials and without the density-reducing41384.04062 material. The density-reducing material can be present in a range of about 5 wt% to 50 wt% of the geopolymer composition or geopolymer layer.

[0057] In some aspects, the density-reducing material can comprise a porous aggregate and / or hollow beads, which can be dispersed in the geopolymer matrix. The porous aggregate can include natural or artificial bulk stone material of porous structure with a density of not more than 1,200 kg / m3(1.2 g / cm3). There are many materials of this type available with a bulk density ranging from about 50 kg / m3to 1000 kg / m3(about 0.05 g / cm3- 1 g / cm3), including vermiculite, perlite, diatomaceous earth, and expanded clay aggregate. The hollow beads can include hollow glass beads, hollow ceramic beads, or one or more combinations thereof. The hollow beads can include thermally non-conductive hollow beads. The hollow beads can include thermally non-conductive hollow beads, which act as thermally non-conductive density-reducing material. The hollow beads can also be a thermally conductive material, e.g., thermally conductive hollow beads can act as a thermally conductive material and as a density -reducing material.

[0058] The hollow beads can have an average diameter from about 5 microns to 1000 microns. For example, the hollow beads can have an average diameter of from about 5 microns to about 10 microns, from about 10 microns to about 100 microns, form about 100 microns to about 200 microns, from about 200 microns to about 400 microns, from about 400 microns to about 600 microns, from about 600 microns to about 800 microns, from about 800 microns to about 1000 microns including any and all increments therebetween.

[0059] The thermally conductive material and / or the density-reducing material can be added to and continuously mixed into a homogenous solution of the geopolymer matrix forming components to form a geopolymer matrix having dispersed therein the thermally conductive material and / or the density-reducing material.

[0060] A geopolymer layer including thermally conductive material and a density-reducing material such as hollow beads can have the thermally conductive material act as a conduit to transfer heat that is channeled by the thermally non-conductive hollow beads through and out of the geopolymer layer, thereby imparting a low thermal inertia to the geopolymer layer.

[0061] Each geopolymer layer formed on the cylindrical layer can have a thickness of greater than or equal to about 0.1 mm, greater than or equal to about 0.5 mm, greater than or equal to about 1 mm, greater than or equal to about 3 mm, and / or greater than or equal to about 5 mm. The geopolymer layer can have a thickness of less than or equal to about 15 mm, less than or equal to41384.04062 about 13 mm, and / or less than or equal to about 10 mm. The geopolymer layer can have a thickness in the range of from about 0.1 mm to about 15 mm, from about 0.1 mm to about 13 mm, from about 0.1 mm to about 10 mm, from about 0.5 mm to about 15 mm, from about 0.5 mm to about 13 mm, from about 0.5 mm to about 10 mm, from about 1 mm to about 15 mm, from about 1 mm to about 13 mm, from about 1 mm to about 10 mm, from about 3 mm to about 15 mm, from about 3 mm to about 13 mm, from about 3 mm to about 10 mm, from about 5 mm to about 15 mm, from about 5 mm to about 13 mm, and / or from about 5 mm to about 10 mm, including any and all increments therebetween.

[0062] The geopolymer layer can be formed directly on an outer surface of a cylindrical layer defining an inner bore by applying, e.g., spraying, such as by an aerosol, rolling and / or dip coating, an aqueous formulation. The aqueous formulation includes geopolymer matrix forming components of a metal silicate, a metal oxide, a water-soluble caustic agent, and water. In addition to the geopolymer matrix forming components, the aqueous formulation can further comprise a thermally conductive material and a density-reducing material that has a bulk density which is less than a bulk density of a geopolymer matrix formed from the geopolymer matrix forming components. Further, the aqueous formulation of the present disclosure advantageously can have all of the components that react to form the geopolymer matrix (e.g., metal silicate, metal oxide, water-soluble caustic agent, and other reactive components) dissolved or substantially dissolved in the formulation to allow forming thin geopolymer coating layers from such a formulation.

[0063] In other implementations, the aqueous formulation of the present disclosure can include optional components such as: one or more catalysts or activators, e.g., carbonates or bicarbonates, phosphate acids and partial acids, or organic carboxylic acids to modify time of cure and / or reactivity of the formulation components; one or more rheology modifiers; one or more ceramic particles such as ceramic spheres, Zeeospheres, Carborundum (SiC), AI2O3, etc.; one or more fibers such as those composed of cellulose or cellulose derivatives, jute, coir, a polyamide, polyethylene terephthalate, acrylic, modacrylic, polyacrylonitrile, polyvinylalcohol, basalt, glass, quartz, carbon, etc.; one or more surfactants; or any combination thereof. Certain of these components may or may not be soluble in the formulation and may be solid components of the aqueous formulation.

[0064] The amounts of the components used to form the aqueous formulation can be adjusted for ease of application of the formulation to a surface of the cylindrical layer and the desired characteristics of the formed coating. For example, the aqueous formulation for forming a41384.04062 geopolymer layer can have a weight ratio of the metal silicate to metal oxide ranging from about 5:1 to 1 :5, e.g., from about 4.5:1, 4: 1, 3.5: 1, 3: 1, 2.5: 1, 2: 1, 1.5: 1, 1 :1 to 1 :1, 1 : 1.5, 1 :2, 1 :2.5, 1 :3, 1 :3.5, 1 :4, 1 :4.5, and any value thereof or therebetween. The aqueous formulation can have a weight ratio of the metal silicate to metal oxide ranging from about 1 : 1 to about 1 :3 for rapid curing formulations and from about 3:1 to about 1.5: 1 to form very thin coatings. In some implementations the aqueous formulation includes, based on the total weight of the aqueous formulation, 10 wt% to 45 wt% of the metal silicate, 5 wt% to 65 wt% of the metal oxide, 5 wt% to 30 wt% of the water-soluble caustic agent. In addition, the aqueous formulation can include, based on the total weight of the aqueous formulation, 25 wt% to 80 wt% of the water. For example, when used for dip-coating, the geopolymer layer can be formed from, on a weight basis, 10 wt% to 30 wt% of the metal silicate, 30 wt% to 40 wt% of the metal oxide, 5 wt% to 10 wt% of the water-soluble caustic agent, and 20 wt% to 50 wt% of the water, based on the total weight of the formulation. When applied with an atomized spray application, the aqueous formulation can be prepared from, on a weight basis, 15 wt% to 35 wt% of the metal silicate, 5 wt% to 30 wt% of the metal oxide, 10 wt% to 25 wt% of the water-soluble caustic agent, and 35 wt% to 70 wt% of the water, based on a total weight of the formulation. Although, the metal silicate and the metal oxide components are listed separately in the present disclosure, these components can be included in the aqueous formulation from a source that has both of these components together, such a kaolin, etc. and forming the aqueous formulation is not limited to using the metal silicate and the metal oxide as separate components.

[0065] Useful metal silicates that can be used to form the aqueous formulations of the present disclosure include one or more of: an alkali metal silicate, an alkaline earth metal silicate, sodium silicate, lithium silicate, potassium silicate, neosilicates, sorosilicates, cyclosilicates, inosilicates, phyllosilicates, tectosilcates, mullite, kaolinite, muscovite, etc. or one or more combinations thereof. The alkali metal silicate can include a sodium silicate, e.g., sodium metasilicate, Na2 Si^O2^ or (Na2O)v(SiO2)^, such as sodium metasilicate (Na2SiOs), sodium orthosilicate (Na4SiO4), sodium pyrosilicate (Na6Si2O?), etc. These sodium silicate compounds are generally colorless transparent solids or white powders, and soluble in water in various concentrations. In some aspects of the present disclosure, the formulations comprise sodium metasilicate as the majority of the metal silicate, e.g., the metal silicate comprises at least 50 wt% sodium metasilicate such as at least 60 wt% of sodium metasilicate. The alkaline earth metal silicate can include a calcium silicate (Ca2SiO4), 2CaO SiCh, larnite (3CaO SiCh), alite (2CaO 2SiO2), 2CaO 2SiO2, wollastonite (CaSiCh), a magnesium silicate, etc.41384.04062

[0066] Metal oxides that can be used to form the aqueous formulations of the present disclosure include one or more of aluminum trihydrate (ATH), zinc oxide (ZnO), iron oxide, titanium dioxide (TiCh), copper oxide, tin oxide, zirconium oxide, manganese oxide, nickel oxide, silver oxide, vanadium oxide, bismuth oxide or one or more combinations thereof. Further, it is understood that metal oxides in aqueous solutions can convert to their equivalent hydroxide, and thus the use of metal hydroxide is equivalent to use of the metal oxide (e.g., ZnO is equivalent to Zn(OH)2). Hence, a metal oxide in the present disclosure is understood to include or be substituted for its metal hydroxide. In some aspects of the present disclosure, the aqueous formulations are formed from aluminum trihydrate as the metal oxide in percent of the metal oxide of at least 20 wt% of the total metal oxide, e.g., 20 wt% to 100 wt%; 10 wt% to 50 wt%; or 75 wt% to 100 wt% of the total metal oxide. In some aspects of the present disclosure, the formulations are formed from zinc oxide as the metal oxide in percent of the metal oxide of at least 20 wt% of the total metal oxide, e.g., 20 wt% to 100 wt%; 10 wt% to 50 wt%; or 75 wt% to 100 wt% of the total metal oxide.

[0067] The water-soluble caustic agent of the aqueous formulation is designed to facilitate dissolution of the alkali metal silicate and metal oxide in water and any other component that can react with the alkali metal silicate and metal oxide in water. Examples of water-soluble caustic agents useful for the present disclosure include, without limitation one or more of: an alkali metal hydroxide (such as NaOH, KOH), alkali metal carbonates (such as Na2COs, K2CO3), alkali metal phosphates (such as NasPO4, K3PO4), Na2O(SiO2), ammonium hydroxide, or one or more combinations thereof. Sufficient amount of water-soluble caustic agent is combined with the alkali metal silicate and metal oxide to form an aqueous formulation with the desired level of solids and will increase the pH of the formulation to generate a pH of no less than 8, such as a pH no less than 8.5, 9, 9.5, 10, 10.5, 11, 12, 12.5, 13, 13.5, 14, , etc. Increasing the pH tends to increase the amount of alkali metal silicate and metal oxide dissolved in the formulation.

[0068] In some aspects, the aqueous formulations of the present disclosure have at least 95 wt% of the alkali silicate content as silicate ions in solution. This state can be determined, for example, when the solution can be passed through a 0.5 pm filter with no remaining visible particulate residue.

[0069] To facilitate spray application of the aqueous formulations of the present disclosure, the aqueous formulation can have a viscosity ranging from about 25 cP to about 1,000 cP as determined by cup and bob viscosity measurement at a temperature of 85°F (29.4 °C), e.g., a viscosity ranging from about 20 cP to about 200 cP for very thin, uniform coating layers and about41384.04062140 cP to about 700 cP for thicker, rougher coating layers. Viscosity of the system measured by rotational viscometry (cup and bob viscosity measurement) is performed as per ASTM D2196, D2556, D7867.

[0070] The aqueous formulations of the present disclosure can be prepared by combining geopolymer matrix forming components of a metal silicate, a metal oxide, a water-soluble caustic agent, and water to form the formulation. The metal silicate and the metal oxide can be from the same source material or separate source materials or a combination thereof. The aqueous formulations can further include combining other components that can react with the metal silicate and the metal oxide in the formulation to form the geopolymer matrix. The aqueous formulations can further include combining a thermally conductive material and a density-reducing material that has a bulk density which is less than a bulk density of a geopolymer matrix formed from the geopolymer matrix forming components. The thermally conductive material and density-reducing material are used to form the geopolymer layer.

[0071] The geopolymer layer described herein can have relatively low thermal inertia (e.g., less than or equal to about 2,500 J / m2K s1 / 2), e.g., from about 420 J / m2K s1 / 2to about 2,500 J / m2K s1 / 2. Such a low thermal inertia can facilitate the geopolymer layer, after heating, returning to ambient temperature at a desired cooling rate. Additionally, in embodiments, the relatively low thermal inertia of the geopolymer layer may reduce the maximum temperature of the gun barrel during heating.

[0072] The thermal conductivity of a material can be used to describe the heat transferability of a material. That is, the greater the thermal conductivity, the greater the degree of accepting heat from the environment. However, thermal conductivity is calculated by multiplying heat capacity by density and by thermal diffusivity. Thus, focusing on thermal conductivity may provide an advantage to high density and high heat capacity material and may not appreciate the potential effectiveness of lightweight materials on improved thermal characteristics. Thermal conductivity does not take into account the ability of a material to release heat from a volume. Accordingly, when considering materials for use in heat-exchange or heat-release applications, thermal conductivity may not give the user an advantage over alternative materials. As such, thermal inertia may be more prudent to evaluate for these applications.

[0073] In addition to low thermal inertia, the geopolymer layer can have a relatively low heat capacity (e.g., less than or equal to about 1.75 J / gK) such that one or more geopolymer layers have an overall reduced heat capacity.41384.04062

[0074] In some implementations, the geopolymer layer can have a geopolymer matrix with a density from about 1.8 g / cm3to about 2.9 g / cm3. The density of the geopolymer matrix will depend on the composition of the components used to form the matrix. In addition, the density of the geopolymer layer (as opposed to the geopolymer matrix) will depend on the composition of geopolymer matrix forming components and any added density -reducing material. In some implementations, the density of the geopolymer layer can be inversely proportional to the amount of density-reducing material, e.g., porous aggregate and / or hollow beads, added to form the geopolymer layer. In Some implementations, the density of the geopolymer layer is less than 1.8 g / cm3, such as less than 1.6 g / cm3, 1.4 g / cm3, 1.2 g / cm3, etc.

[0075] The geopolymer layer can include a volumetric heat capacity in the range of from about 1.2 J / gK g / cm3to about 2.0 J / gK g / cm3.Continuous fiber reinforced composite layer

[0076] In some implementations, the gun barrel of the present disclosure includes a continuous fiber reinforced composite layer. Such a layer can be the same as the geopolymer layer, e.g., the geopolymer layer can include a plurality of continuous fibers in a geopolymer matrix. Such a geopolymer layer with the plurality of continuous fibers can include other components such as the thermally conducive material and the density-reducing material. Alternatively or in addition, the multilayered gun barrel of the present disclosure can include more than one geopolymer layer overlaying the cylindrical layer in which one of the geopolymer layers includes the plurality of continuous fibers and one or more other geopolymer layers include other components. Alternatively or in addition, the multilayered gun barrel of the present disclosure can include more than one geopolymer layers with or without the plurality of continuous fibers and a separate continuous fiber reinforced composite layer that includes a matrix material prepared from other than a geopolymer. The addition of a plurality of continuous fibers in a layer can impart strength and stiffness to the gun barrel and thus can reduce the thickness of the cylindrical layer thereby reducing the weight of the gun barrel.

[0077] In some implementations, the plurality of continuous fibers can be configured substantially in parallel. The layer including the fibers, can comprise a plurality of continuous fibers in the form of a tow, yam, end, pic, roving, woven fabric, knitted fabric, braided fabric, or non-woven fabric.41384.04062

[0078] The plurality of continuous fibers can include carbon fibers, AR-glass fibers, aramid fibers, basalt fibers, metallic fibers, and / or one or more combinations thereof. The metallic fibers can include, for example, one or more metals such as boron, beryllium, aluminum, copper, tungsten, titanium, nickel, stainless steel, and / or one or more alloys thereof.

[0079] The plurality of continuous fibers can have an average diameter from 1 micron to 100 microns. The plurality of continuous fibers can have an average diameter greater than or equal to 1 micron, greater than or equal to 5 microns, or even greater than or equal to 7 microns. The plurality of continuous fibers can include an average diameter less than or equal to 100 microns, less than or equal to 50 microns, or even less than or equal to 35 microns. The plurality of continuous fibers can include an average diameter from 1 micron to 100 microns, from 1 micron to 50 microns, from 1 micron to 35 microns, from 5 microns to 100 microns, from 5 microns to 50 microns, from 5 microns to 35 microns, from 7 microns to 100 microns, from 7 microns to 50 microns, or even from 7 microns to 35 microns, or any and all increments therebetween.

[0080] In some aspects, the plurality of continuous fibers can comprise an average length greater than or equal to 5 cm, greater than or equal to 7 cm, greater than or equal to 10 cm, greater than or equal to 15 cm, or even greater than or equal to 20 cm. Those skilled in the art will appreciate that the maximum length of the continuous fibers may be determined by various considerations, including but not limited to, the orientation, use, and arrangement of the continuous fibers.

[0081] In some aspects, the plurality of continuous fibers can include a coating or a sizing composition. The sizing composition both protects the fiber during processing as well as promotes chemical or mechanical bonding between the thermoplastic matrix and the continuous fibers. For example, the sizing composition can comprise a film former, a lubricant, a coupling agent, or a combination thereof. Coatings may include metalized coatings. Metalized coatings may be applied to a fiber by submitting a metal to one or more of chemical vapor Deposition (CVD), physical vapor deposition (PVD), or electroless plating.

[0082] In some implementations a carbon fiber tow can be pulled through a liquid geopolymer bath and the wet filaments can be wound in helical fashion over a mandrel. This mandrel can be a removable or disposable form to pre-fabricated composite tubes or the mandrel can be comprised of a steel gun barrel or the mandrel can be comprised of a steel gun barrel which has been coated with a geopolymer layer. In these instances, once cured, a continuous fiber reinforcement with a geopolymer matrix has been formed.41384.04062

[0083] In other implementations a continuous carbon fiber fabric, mat, or knit can be preimpregnated with liquid geopolymer and fashioned into a desired geometry either in a form for a pre-fabricated composite tube or directly onto a steel gun barrel or directly onto a steel gun barrel that has been coated with a geopolymer layer. In these instances, once cured, a continuous fiber reinforcement with a geopolymer matrix has been formed.

[0084] The continuous fiber reinforced composite layer can have a thickness of from about 0.1 mm to about 100 mm. The continuous fiber reinforced composite layer can have a thickness in the range of from about 0.1 mm to about 0.5 mm, from about 0.5 mm to about 1 mm, from about 1 mm to about 2 mm, from about 2 mm to about 3 mm, from about 3 mm to about 4 mm, from about 4 mm to about 5 mm, from about 5 mm to about 6 mm, from about 6 mm to about 7 mm, from about 7 mm to about 8 mm, from about 8 mm to about 9 mm, from about 9 mm to about 10 mm, including any and all increments therebetween. In some embodiments, the continuous fiber reinforced composite 130 can have a thickness in the range of from about 10 mm to about 20 mm, from about 20 mm to about 40 mm, from about 40 mm to about 60 mm, from about 60 mm to about 80 mm, from about 80 mm to about 100 mm, including any and all increments therebetween.

[0085] The continuous fiber reinforced composite layer can include continuous fibers and a second thermally conductive material disposed in a matrix material such as a geopolymer matrix or epoxy thermoset polymer.

[0086] In some implementations the matrix material of the continuous fiber reinforced composite layer is a geopolymer matrix, which can be formed from geopolymer matrix forming components as described above. For example, in some implementations (including but not limited to the implementation shown in FIGS. 2-3), the polymeric material of the continuous fiber reinforced composite layer can be the same as the geopolymer matrix employed in the geopolymer layer of the gun barrel. The continuous fiber reinforced composite layer can include the thermally conductive material dispersed in the geopolymer matrix. The continuous fiber reinforced composite layer can include a density-reducing material, e.g., thermally non-conductive hollow beads dispersed in the geopolymer matrix. The continuous fiber reinforced composite layer can include both the thermally conductive material and the thermally non-conductive hollow beads dispersed in the geopolymer matrix. The continuous fiber reinforced composite layer can further include one or more additives comprising curing agents to form the geopolymer matrix.41384.04062

[0087] In other implementations, continuous fiber reinforced composite layer can include other polymeric materials. The polymeric material can include a thermoplastic polymer, thermoset polymer, or a combination thereof within which the continuous fibers are placed. The continuous fiber reinforced composite layer can include the thermoplastic polymer, the thermoplastic polymer comprising polyamides, polyphenylene sulfides, polyetherimides, polysulfones, polyethersulfones, polyetherketones, polyetheretherketones, or a combination thereof. The continuous fiber reinforced composite layer can include the thermoset polymer, the thermoset polymer comprising Bisphenol A epoxy, Bisphenol F epoxy, novolac epoxy, phenolic resin, bismaleimide, benzoxazine, cyanate resin, silicone resin, or a combination thereof. The continuous fiber reinforced composite layer 206 can further include one or more additives comprising curing agents of polyamine, anhydride, and polyphenolic.

[0088] Depending on the desired fiber arrangement of the continuous fiber reinforced composite layer (e.g., continuous fiber reinforced composite layer 206), various methods can be used to prepare the continuous fiber reinforced composite layer. In some implementations, a continuous fiber can be immersed and pulled through a bath of polymeric material and wrapped around a mandrel. The mandrel turns while the fiber is held in tension and moved from one end of the mandrel to the other and back and forth until a sufficient thickness of fiber reinforced polymer is added to the mandrel. The fiber, polymeric material, and mandrel are heated to consolidate and cure the resultant composite which is then pulled off the mandrel.

[0089] In some implementations, the present disclosure provides a method of using a gun barrel. The method can include propelling a projectile through the gun barrel. The projectile can be propelled by a firearm including a gun barrel of the present disclosure such as a rifle or other device configured with the gun barrel.

[0090] Gun barrels of the present disclosure can be readily formed by applying a geopolymer layer on an outer surface of a cylindrical layer. The process can include the step of forming a continuous fiber reinforced composite on the geopolymer layer. In some aspects, the process can include the step of removing an outer layer of the cylindrical layer prior to applying the geopolymer layer on the surface thereof.

[0091] The geopolymer layer can be formed by applying an aqueous formulation of the present disclosure on to the cylindrical layer and drying the applied formulation on the cylindrical layer to cure the formulation into the geopolymer layer on the cylindrical layer. The aqueous formulation41384.04062 includes geopolymer matrix forming components of a metal silicate, a metal oxide, a water-soluble caustic agent, and water. Such geopolymer forming components can form a geopolymer matrix such as an metallosilicate polymer network. The formulation can further include a thermally conductive material, and a density-reducing material that has a bulk density which is less than a bulk density of a geopolymer matrix formed from the geopolymer matrix forming components, e.g., the density-reducing material can comprise a porous aggregate and / or hollow beads.

[0092] In some implementations, a geopolymer layer can be formed by applying one or more aqueous formulations of the present disclosure to the cylindrical layer. The aqueous formulation can be applied in a variety of ways including spraying, brushing, rolling, dip coating, electrodeposition, etc. In one aspect, the coating composition is applied to the cylindrical layer by spraying the aqueous formulation onto the substrate as an aerosol, e.g., a suspension of fine liquid droplets in air or another gas. Aerosol sprays can be generated from aerosol spray dispensers, atomizers, etc.

[0093] Concurrent with or after applying one or more aqueous formulations to the cylindrical layer, the formulation dries or is dried. Drying the formulation causes it to cure and bond to the surface of the cylindrical layer. Upon drying, the geopolymer forming components form long- range, covalently bonded, non-crystalline (amorphous) networks such as a geopolymeric matrix material.

[0094] Drying can be carried out conveniently in air at ambient conditions. For example, the aqueous formulation can be dried in air from a temperature range of about 20 °C to about 80 °C. Drying can also be carried out by heating at a temperature of from about 50 °C to about 500 °C in air or another gas, such as heating from 50 °C to about 500 °C, 50 °C to about 200 °C, 50 °C to about 150 °C. Exposing an applied aqueous formulation of the present disclosure to heat can increase the hardness of the formed geopolymer layer.

[0095] In some implementation, continuous fiber reinforced composite can be wound on top of the geopolymer layer to form a multilayered gun barrel. In other implementations, a pre-fabricated continuous fiber reinforced composite can be pushed over the geopolymer layer. In either case, the continuous fiber reinforced composite can be applied on the geopolymer layer prior to the geopolymer layer being fully cured and the assembly fully cured to form a cohesive multilayered gun barrel.41384.04062

[0096] In some implementation a pre-fabricated continuous fiber reinforced composite can be pre-affixed over the cylindrical layer with a gap between the internal face of the pre-fabricated continuous fiber reinforced composite and the outer surface of the cylindrical layer. An aqueous formulation including geopolymer matrix forming components can be injected into the gap and then sealed. The system formed therein can be set to cure, effectively bonding the layers.

[0097] Only certain features and aspects of the present disclosure and examples of their versatility are shown and described in the present disclosure. It is to be understood that the technology disclosed herein is capable of use in various other combinations and environments and is capable of changes or modifications. Thus, for example, those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific substances, procedures and arrangements described herein. Such equivalents are considered to be within the scope of the invention and are covered by the following claims.

Claims

41384.04062What is claimed is:

1. A gun barrel comprising: a cylindrical layer defining an internal bore; and a geopolymer layer overlaying an outer surface of the cylindrical layer.

2. The gun barrel of claim 1, wherein the geopolymer layer comprises a geopolymer matrix; and wherein the geopolymer matrix comprises an metallosilicate polymer network.

3. The gun barrel of claim 1, wherein the geopolymer layer comprises a thermally conductive material dispersed in a geopolymer matrix.

4. The gun barrel of claim 3, wherein the thermally conductive material comprises a thermally conductive carbon, carbon fiber, carbon nanomaterial, silver, copper, aluminum, thermally conductive ceramic, or a combination thereof.

5. The gun barrel of claim 1, wherein the geopolymer layer comprises a density-reducing material dispersed in a geopolymer matrix, wherein the density-reducing material has a bulk density less than the density of the geopolymer matrix without the density-reducing material.

6. The gun barrel of claim 5, wherein the density-reducing material comprises porous aggregate and / or hollow beads dispersed in the geopolymer matrix.

7. The gun barrel of claim 5, wherein the density-reducing material comprises hollow glass beads, hollow ceramic beads, or a combination thereof.

8. The gun barrel of claim 7, wherein the hollow beads have an average diameter from 5 microns to 1000 microns.

9. The gun barrel of any one of claims 2-8, wherein the geopolymer layer comprises a geopolymer matrix together with the thermally conductive material, and the density-reducing material.

10. The gun barrel of any one of claims 1-9, wherein the geopolymer layer has a thickness of from about 0.1 mm to about 15 mm.

11. The gun barrel of any one of claims 1-10, wherein the geopolymer layer includes a plurality of continuous fibers therein.41384.0406212. The gun barrel of any one of claims 1-11, further comprising a continuous fiber reinforced composite overlaying the geopolymer layer, wherein the continuous fiber reinforced composite includes a plurality of continuous fibers therein.

13. The gun barrel of any one of the preceding claims, wherein the geopolymer layer is formed from an aqueous formulation that comprises geopolymer matrix forming components of: (a) a metal silicate; (b) a metal oxide; (c) a water-soluble caustic agent; and (d) water.

14. The gun barrel of claim 13, wherein the aqueous formulation further includes a thermally conductive material; and / or a density-reducing material that has a bulk density which is less than a density of a geopolymer matrix formed from the geopolymer matrix forming components.

15. The gun barrel of claim 13, wherein the ratio of metal silicate to metal oxide ranges from about 5 : 1 to about 1 :5.

16. The gun barrel of claim 13, wherein the metal silicate comprises at least 50 wt% sodium metasilicate.

17. The gun barrel of claim 14, wherein the aqueous formulation comprises, based on the total weight of the aqueous formulation, 10 wt% to 45 wt% of the metal silicate, 5 wt% to 65 wt% of the metal oxide, and 5 wt% to 25 wt% of the water-soluble caustic agent.

18. The gun barrel of claim 13, wherein the aqueous formulation comprises, based on the total weight of the aqueous formulation, 25 wt% to 80 wt% of the water.

19. The gun barrel of claim 13, wherein the aqueous formulation has a pH of no less than 9.

20. The gun barrel of claim 13, wherein the aqueous formulation has a viscosity ranging from about 25 cP to about 1,000 cP as measured by cup and bob viscosity measurement.

21. The gun barrel of claim 13, wherein the metal silicate comprises one or more of: an alkali metal silicate, alkaline earth metal silicate, or any combination thereof.

22. The gun barrel of claim 13, wherein the metal silicate comprises one or more of: sodium silicate, lithium silicate, potassium silicate, or any combination thereof.

23. The gun barrel of claim 13, wherein the metal silicate comprises one or more of: neosilicates, sorosilicates, cyclosilicates, inosilicates, phyllosilicates, tectosilcates, mullite, kaolinite, muscovite, or any combination thereof.41384.0406224. The gun barrel of claim 13, wherein the metal oxide comprises one or more of: aluminum trihydrate (ATH), zinc oxide (ZnO), iron oxide, titanium dioxide (TiCh), copper oxide, tin oxide, zirconium oxide, manganese oxide, nickel oxide, silver oxide, vanadium oxide, bismuth oxide, or any combination thereof.

25. The gun barrel of claim 13, wherein the water-soluble caustic agent comprises one or more of: an alkali metal hydroxide, Na2O(SiO2), Li2O(SiO2), K2O(SiO2), or ammonium hydroxide.

26. The gun barrel of claim 13, wherein the metal silicate comprises one or more of an alkali metal or alkaline earth silicate; the metal oxide comprises one or more of aluminum trihydrate (ATH), zinc oxide (ZnO), iron oxide, titanium dioxide (TiO2), copper oxide, zirconium oxide, manganese oxide, nickel oxide, silver oxide, vanadium oxide, bismuth oxide; and the water- soluble caustic agent comprises one or more of: NaOH, KOH, or Na2O(SiO2),Li2O(SiO2), K2O(SiO2), or ammonium hydroxide.

27. The gun barrel of claim 13, wherein the aqueous formulation further comprises one or more catalysts, activators, or rheology modifiers.

28. The gun barrel of any one of claims 1-27, wherein the cylindrical layer comprises a metal.

29. The gun barrel of any one of claims 1-27, wherein the cylindrical layer comprises a steel, stainless steel, titanium, brass, red brass, iron, bronze, aluminum, or a combination thereof.

30. The gun barrel of any one of claims 11 or 12, wherein the continuous fiber reinforced composite comprises a plurality of continuous fibers configured substantially in parallel.

31. The gun barrel of any one of claims 11 or 12, wherein the plurality of continuous fibers are in the form of a tow, yarn, end, pic, roving, woven fabric, knitted fabric, braided fabric, or non-woven fabric.

32. The gun barrel of claim 31, wherein the plurality of continuous fibers comprise carbon fibers, glass fibers, aramid fibers, basalt fibers, metallic fibers, or a combination thereof.

33. The gun barrel of claim 31, wherein the plurality of continuous fibers comprise metallic fibers, wherein the metallic fibers comprise boron, beryllium, aluminum, copper, tungsten, titanium, nickel, stainless steel, or an alloy thereof.41384.0406234. The gun barrel of any one of claims 30-33, wherein the plurality of continuous fibers have an average diameter from 1 micron to 100 microns.

35. The gun barrel of any one of claims 30-34, wherein the gun barrel includes the continuous fiber reinforced composite, which comprises the plurality of continuous fibers disposed in a geopolymer material.

36. The gun barrel of any one of claims 30-35, wherein the plurality of continuous fibers includes a coating or a sizing composition.

37. The gun barrel of any one of claims 30-35, wherein the plurality of continuous fibers includes a metallicized coating.

38. The gun barrel of any one of the previous claims, comprising a gas tube port to allow gas to exit the bore.

39. The gun barrel of any one of the previous claims, wherein the gun barrel includes a shank at one end of the barrel and wherein the shank comprises a geopolymer layer comprising thermally conductive material dispersed in a geopolymer matrix.

40. A method of using a gun barrel, comprising propelling a projectile through the gun barrel of any one of the previous claims.

41. A process of preparing a gun barrel, comprising: applying a geopolymer layer on an outer surface of a cylindrical layer defining an inner bore.

42. The process of claim 41, further comprising removing an outer layer of the cylindrical layer prior to applying the geopolymer layer on the surface thereof.

43. The process of claim 41, wherein applying the geopolymer layer comprises spraying, rolling and / or dip coating an aqueous formulation onto the outer surface of the cylindrical layer, wherein the aqueous formulation comprises geopolymer matrix forming components of: (a) a metal silicate; (b) a metal oxide; (c) a water-soluble caustic agent; and (d) water.

44. The process of claim 43, wherein the aqueous formulation further comprises a thermally conductive material; and / or a density-reducing material that has a bulk density which is less than a bulk density of a geopolymer matrix formed from the geopolymer matrix forming components.41384.0406245. The process of any one of claims 41-43, further comprising curing the applied aqueous formulation at a temperature of from about 5 °C to about 500 °C.

46. The process of any one of claims 41-43, comprising applying more than one layer of the geopolymer layer on the outer surface of the cylindrical layer, wherein each layer has a thickness in the range of from about 0.1 mm to about 15 mm.

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