Ceramic fiber / metal composite for liquefied gas storage tank and manufacturing method thereof

Abstract

The present invention relates to a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank and a method for manufacturing the same. The ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank can maintain its physical properties under low temperature and cryogenic environments, such as for the storage and transportation of liquefied gases like liquefied natural gas (LNG) or liquefied hydrogen. In addition, due to the excellent adhesion between the ceramic fiber / metal heterogeneous composite, delamination does not occur at room temperature and cryogenic temperatures, and the physical properties are excellent. Since it is produced through a simple process, it has excellent price competitiveness and can replace barrier materials for storage tanks used in low-temperature and cryogenic environments, such as conventional liquefied gas storage and transportation.

Description

Technology Field

[0001] The present invention relates to a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank and a method for manufacturing the same. Background Technology

[0002] Fossil fuels such as oil and coal, which have been used as energy sources, are finite resources that will eventually be depleted and have the disadvantage of being a major cause of climate change due to the emission of carbon compounds during combustion. As climate change accelerates, the world is engaging in various discussions regarding reducing carbon emissions and limiting global temperature rise in order to lower dependence on oil and move away from an oil-based economy.

[0003] Liquefied natural gas (LNG), which is natural gas with a main component of methane that is cooled to minus 162 degrees to liquefy it, is considered an energy source for preventing global warming due to its low carbon dioxide emissions.

[0004] The storage and transportation of liquefied gases, such as liquefied hydrogen or liquefied natural gas (LNG), are carried out through storage tanks and vessels, and since cryogenic conditions of minus 253 degrees or minus 162 degrees must be maintained, strict structures are required for storage.

[0005] Liquefied gas storage tanks currently used on ships can be broadly classified into membrane and independent tank types depending on the cargo tank configuration of the vessel. The independent tank type involves the cargo tank being manufactured independently and mounted on the hull, designed so that the tank itself can handle ultra-low temperature LNG. The membrane type is an integrated design where the hull and the cargo tank are combined; it improves upon the shortcomings of older independent tanks by allowing the cargo tank and the hull to support the internal LNG pressure and weight together.

[0006] The membrane system consists of two layers of insulation surrounding the cargo tank, for example, comprising a lower insulation panel, a secondary barrier, an upper insulation panel, and a primary barrier. The secondary barrier primarily serves as a preliminary protective layer to prevent the leakage of low-temperature and cryogenic materials inside the storage tank. In other words, if a leakage of stored material occurs due to a crack in the primary barrier, the secondary barrier prevents the leaked material from penetrating through the lower insulation panel. The secondary barrier is mainly used in two forms: a flexible secondary barrier (FSB) and a rigid secondary barrier (RSB); the flexible form can be utilized in automated process equipment for securing membrane storage vessels.

[0007] Referring to prior art, it is disclosed that the secondary barrier may be composed of multiple membranes made of any one of stainless steel, aluminum, brass, zinc, or high-manganese steel, or may be made of metals such as Invar alloy, stainless steel, or aluminum alloy, or may be composed of Triplex, which is an aluminum sheet with glass fibers attached.

[0008] However, in the case of conventional metals such as stainless steel, additional structural technologies, such as adding corrugations, are required to ensure sufficient performance as a barrier. Furthermore, in the case of composites in which glass fibers are attached to metal sheets, there is a problem in that the glass fibers do not exhibit excellent low-temperature and cryogenic properties, which affect the mechanical properties of the composite and fail to properly demonstrate thermal conductivity.

[0009] Meanwhile, in the case of secondary barriers equipped with Triplex, the structure consists of layers stacked in the order of secondary insulation panels, RSB (Rigid Secondary Barrier), FSB (Flexible Secondary Barrier), and primary insulation panels. Since the secondary insulation panels undergo repeated expansion and contraction due to thermal loads and stresses generated during the loading and unloading of liquefied natural gas, they are constructed with a gap of approximately 30 mm rather than being continuous. Most secondary barriers are composed of RSBs, which are positioned between the secondary and primary insulation panels and thus bear the bending stress and localized loads that may occur in the cargo tank during operation. Therefore, if the RSB is damaged, the primary and secondary insulation panels will come into direct contact, causing the collapse of the entire cargo tank system. Furthermore, damage to secondary barriers has been reported several times recently.

[0010] Accordingly, there is a demand for more effective materials with excellent physical properties and eco-friendly characteristics that can be used as barriers for storage tanks utilized in low-temperature and cryogenic environments, such as for the storage and transportation of liquefied gases. Prior art literature

[0011] (Patent Document 0001) KR 10-2019-0049192 A1 The problem to be solved

[0012] The object of the present invention is to provide a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank and a method for manufacturing the same.

[0013] Another objective of the present invention is to provide a ceramic fiber / metal heterogeneous composite capable of maintaining physical properties under low and cryogenic environments, such as the storage and transportation of liquefied gases like liquefied natural gas (LNG) or liquefied hydrogen.

[0014] Another objective of the present invention is to provide a method for manufacturing a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank that can replace barrier materials for storage tanks used in low-temperature and cryogenic environments, such as conventional liquefied gas storage and transportation, by having excellent adhesion properties between the ceramic fiber / metal heterogeneous composite, preventing delamination at room temperature and cryogenic temperatures, having excellent physical properties, and having excellent price competitiveness as it is produced by a simple process. means of solving the problem

[0015] To achieve the above objective, the present invention relates to a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank comprising: a first ceramic fiber layer; a first metal sheet layer laminated to the first ceramic fiber layer; and a second ceramic fiber layer laminated to the metal sheet layer, wherein the first ceramic fiber layer, the first metal sheet layer, and the second ceramic fiber layer are bonded by an adhesive layer.

[0016] In addition, the first ceramic fiber layer and the second ceramic fiber layer may be selected from the group consisting of basalt fibers, silicon carbide fibers, carbon fibers, and mixtures thereof.

[0017] In addition, the first metal sheet layer may be selected from the group consisting of aluminum sheets, stainless steel sheets, and copper sheets.

[0018] In addition, the adhesive layer may include a polymer resin selected from the group consisting of epoxy resin, acrylic resin, polyurethane resin, polyamide resin, polyimide resin, polyethylene resin, polypropylene resin, ethylene vinyl acetate copolymer, and mixtures thereof.

[0019] In addition, the metal sheet layer may be surface-treated to increase the adhesion efficiency with the first ceramic fiber layer and the second ceramic fiber layer by means of an adhesive layer.

[0020] In addition, the metal sheet layer may have an arithmetic mean roughness (Ra) of 0.1 μm to 10 μm due to surface treatment.

[0021] In addition, the metal sheet layer may be surface-treated by scratching or by using an acidic solution.

[0022] Additionally, the ceramic fiber / metal heterogeneous composite further comprises a second metal sheet layer laminated to the second ceramic fiber layer and a third ceramic fiber layer laminated to the second metal sheet layer, wherein the second ceramic fiber layer, the second metal sheet layer, and the third ceramic fiber layer can be bonded by an adhesive layer.

[0023] In addition, the ceramic fiber / metal heterogeneous composite can be used as a Flexible Secondary Barrier (FSB) or a Rigid Secondary Barrier (RSB).

[0024] A method for manufacturing a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank according to another embodiment of the present invention may include the step of manufacturing a laminate comprising a first ceramic fiber layer, a first polymer resin layer, a first metal sheet layer, a second polymer resin layer, and a second ceramic fiber layer; and the step of bonding the laminate by applying heat and pressure.

[0025] In addition, the first metal sheet layer may further include a step of performing a pretreatment process on the metal sheet layer, consisting of washing with a solvent or ultrasonic cleaning and drying, before the step of forming the laminate.

[0026] In addition, the first metal sheet layer may further include a step of controlling surface roughness by surface treatment after performing the pretreatment process.

[0027] In addition, the bonding step may be carried out under a temperature range of 100°C to 250°C and a pressure range of 6 bar to 20 bar.

[0028] In addition, the step of manufacturing the above laminate may involve laminating a first ceramic fiber layer, a first polymer resin layer, a first metal sheet layer, a second polymer resin layer, a second ceramic fiber layer, a third polymer resin layer, a second metal sheet layer, a fourth polymer resin layer, and a third ceramic fiber layer.

[0029] A barrier for a liquefied gas storage tank according to another embodiment of the present invention may include a ceramic fiber / metal heterogeneous composite for the liquefied gas storage tank. Effects of the invention

[0030] The present invention is a novel ceramic fiber / metal heterogeneous composite that can maintain physical properties under low and cryogenic environments, such as the storage and transportation of liquefied gases like liquefied natural gas (LNG) or liquefied hydrogen.

[0031] In addition, due to the excellent adhesion between the ceramic fiber / metal heterogeneous composite, delamination does not occur at room temperature and cryogenic temperatures, and the physical properties are excellent. Since it is produced through a simple process, it has excellent price competitiveness and can replace barrier materials for storage tanks used in low-temperature and cryogenic environments, such as conventional liquefied gas storage and transportation. Specific details for implementing the invention

[0032] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0033] The storage and transportation of liquefied gases, such as liquefied hydrogen or liquefied natural gas (LNG), are carried out through storage tanks and vessels, and must maintain cryogenic conditions of minus 253 degrees or below, or minus 162 degrees or below.

[0034] Liquefied gas storage tanks currently used on ships can be broadly classified into membrane and independent tank types depending on the cargo tank configuration of the vessel. The independent tank type involves the cargo tank being manufactured independently and mounted on the hull, designed so that the tank itself can handle ultra-low temperature LNG. The membrane type is an integrated design where the hull and the cargo tank are combined; it improves upon the shortcomings of older independent tanks by allowing the cargo tank and the hull to support the internal LNG pressure and weight together.

[0035] As described above, the storage tank for storing and transporting the liquid hydrogen or liquid natural gas is composed of two layers of insulation in the case of a membrane type, and among the elements constituting the insulation, the secondary barrier mainly serves as a preliminary protective barrier to prevent the leakage of low-temperature and cryogenic substances inside the storage tank. The present invention relates to a ceramic fiber / metal heterogeneous composite for a liquid gas storage tank that can be used as a material for the secondary barrier.

[0036] Conventionally, Triplex, which is made by bonding glass fiber sheets to both sides of an aluminum sheet, is mainly used as a secondary barrier material. Since glass fiber sheets possess properties such as strength, insulation, and corrosion resistance, bonding glass fiber sheets to both sides of an aluminum sheet results in excellent mechanical performance and physical properties when used as a secondary barrier. However, because the glass fiber sheets themselves are expensive, there is a need to develop a composite material with excellent mechanical properties that can secure price competitiveness and solve problems arising in cryogenic environments.

[0037] In the present invention, a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank to replace a glass fiber sheet comprises: a first ceramic fiber layer; a first metal sheet layer laminated to the first ceramic fiber layer; and a second ceramic fiber layer laminated to the metal sheet layer, wherein the first ceramic fiber layer, the first metal sheet layer, and the second ceramic fiber layer can be bonded by an adhesive layer.

[0038] The ceramic fiber layer may be a ceramic fiber fabric formed by, for example, a plain weave, a twill weave, or a satin weave, and preferably a ceramic fiber fabric formed by a plain weave, but is not limited to the above examples.

[0039] The thickness of the ceramic fiber fabric included in the ceramic fiber layer may vary depending on the weaving method, for example, it may be 0.1 mm to 0.4 mm. In addition, the weight may be in the range of 200 g / m2 to 400 g / m2. When used within the above range, the tensile value for a secondary barrier can be satisfied.

[0040] Ceramic fibers can exhibit excellent strength, corrosion resistance, heat resistance, and cold resistance, making them suitable and efficient for use as components in storage tanks operating in low and cryogenic environments.

[0041] Specifically, the first ceramic fiber layer and the second ceramic fiber layer may be selected from the group consisting of basalt fibers, silicon carbide fibers, carbon fibers, and mixtures thereof, but preferably may be basalt fibers. The basalt fibers not only have superior price competitiveness compared to carbon fibers, but also, as described above, when bonded to both sides of the first metal sheet layer by an adhesive layer, exhibit excellent mechanical performance, and in particular, excellent tensile, shear, and environmental resistance characteristics even in cryogenic environments.

[0042] Basalt fibers can be manufactured by melt-spinning basalt, a type of volcanic rock, at a high temperature of 1400°C to 1500°C. Basalt fibers possess high strength compared to metal materials, exhibit corrosion resistance superior to that of alloys, and can demonstrate excellent heat and cold resistance over a wide temperature range of -260°C to 650°C. Therefore, they can be efficiently applied to components such as barriers of storage tanks in low-temperature and cryogenic environments, such as for the storage and transportation of liquefied gases like liquefied natural gas (LNG) or liquefied hydrogen, and exhibit excellent physical properties.

[0043] The first metal sheet layer above may be selected from the group consisting of aluminum sheets, stainless steel sheets, and copper sheets, but preferably aluminum sheets; however, any metal sheet capable of being used as a secondary barrier material for liquefied gas storage tanks in low and cryogenic environments with ceramic fiber layers bonded to both sides as described above may be used without limitation.

[0044] The metal sheet layer may have an arithmetic mean roughness (Ra) of 0.1 μm to 10 μm, 0.1 μm to 5 μm, 0.1 μm to 2 μm, or 0.5 μm to 1.5 μm due to surface treatment. Additionally, the 10-point average roughness (Rz) may be 1 μm to 20 μm, 2 μm to 15 μm, or 5 μm to 13 μm. As described above, the metal sheet layer having a surface roughness within the above range can improve adhesion with the ceramic fiber layer, thereby exhibiting superior physical properties.

[0045] Specifically, in the case of an aluminum sheet, the Ra of the untreated aluminum sheet may be 0.18 μm in the grain direction and 0.30 μm in the direction perpendicular to the grain, and the Rz may be 0.89 μm in the grain direction and 1.90 μm in the direction perpendicular to the grain. In the case of an aluminum sheet having such surface roughness, the metal sheet layer having such an average roughness value can improve adhesion with the ceramic fiber layer, thereby exhibiting superior physical properties.

[0046] The above metal sheet layer may be surface-treated by scratching or by using an acidic solution.

[0047] Surface treatment using the above acidic solution can be performed at an appropriate temperature using an acid, for example, nitric acid, hydrochloric acid, sulfuric acid, or a combination thereof, as an etching solution.

[0048] In addition, surface treatment through scratching can be performed by forming surface roughness using sandpaper, specifically by treating the surface of a metal sheet layer in horizontal and vertical directions with sandpaper of 100 mesh to 3000 mesh, 100 mesh to 2000 mesh, or 100 mesh to 1000 mesh to have a specific surface roughness value.

[0049] The adhesive layer may include a polymer resin selected from the group consisting of epoxy resin, acrylic resin, polyurethane resin, polyamide resin, polyimide resin, polyethylene resin, polypropylene resin, ethylene vinyl acetate copolymer, and mixtures thereof. The polymer resin included in the adhesive layer may be selected depending on whether it is applied to the triplex structure or pentaflex structure described later, and whether it can exhibit suitable physical properties for use as a barrier material.

[0050] The adhesive layer described above differs depending on whether the composite is manufactured as an FSB (Flexible Secondary Barrier) or an RSB (Rigid Secondary Barrier). For use as an FSB, a polymer film may be used to form the adhesive layer, and for use as an RSB, a liquid adhesive composition may be used to form the adhesive layer.

[0051] At this time, the liquid adhesive composition for manufacturing RSB can be manufactured by applying the liquid adhesive composition to one surface of the ceramic fiber layer described above and bonding it to a metal sheet layer, or by applying the liquid adhesive composition to one surface of the ceramic fiber layer and curing it to produce a prepreg, and then laminating the manufactured prepreg onto a metal sheet layer to produce a composite.

[0052] When manufacturing RSB as described above, the degree of application of the liquid adhesive composition may be 14% to 25%, i.e., the resin content (resin content in prepreg, Resin contents), in the content of the adhesive composition included in the ceramic fiber layer, and may be 16% to 21%. When the adhesive composition is included in the ceramic fiber layer within the above range, the best adhesive properties can be exhibited, and excellent tensile, vertical tensile, and shear tensile properties can be exhibited under room temperature and cryogenic conditions.

[0053] The adhesive layer is intended to bond the metal sheet layer and the ceramic fiber layer as described above, and the first ceramic fiber layer and the first metal sheet layer are bonded by the adhesive layer, and the first metal sheet layer and the second ceramic fiber layer can also be bonded by the adhesive layer.

[0054] Specifically, depending on the shape of the laminate, it may have a triplex structure or a pentaplex structure.

[0055] The above triplex structure may be in the form of a first ceramic fiber layer, a first adhesive layer, a first metal sheet layer, a second adhesive layer, and a second ceramic fiber layer stacked and bonded in that order.

[0056] The above Pentaflex structure is a Tripleflex structure, and the ceramic fiber / metal heterogeneous composite further comprises a second metal sheet layer laminated to the second ceramic fiber layer and a third ceramic fiber layer laminated to the second metal sheet layer, wherein the second ceramic fiber layer, the second metal sheet layer, and the third ceramic fiber layer may be bonded by an adhesive layer.

[0057] More specifically, the above-described Pentaflex structure may be in the form of being laminated and bonded in the order of a first ceramic fiber layer, a first adhesive layer, a first metal sheet layer, a second adhesive layer, a second ceramic fiber layer, a third adhesive layer, a second metal sheet layer, a fourth adhesive layer, and a third ceramic fiber layer.

[0058] The first ceramic fiber layer, the second ceramic fiber layer, and the third ceramic fiber layer described above are identical to the description of the ceramic fiber layer described above, and may be made of the same material or different materials, and may have the same thickness or different thicknesses.

[0059] The first adhesive layer, the second adhesive layer, and the third adhesive layer described above are identical to the description of the adhesive layer described above, and may be made of the same material or different materials, and may have the same thickness or different thicknesses.

[0060] The first metal sheet layer and the second metal sheet layer described above are identical to the description of the metal sheet layer described above, and may be made of the same material or different materials, and may have the same thickness or different thicknesses.

[0061] The above ceramic fiber / metal heterogeneous composite can be used as a Flexible Secondary Barrier (FSB) or a Rigid Secondary Barrier (RSB).

[0062] The above FSB has flexible properties and can serve to connect primary barriers to each other, while the RSB has slightly rigid properties and can serve as a secondary barrier and support structure. Depending on the type of polymer resin constituting the adhesive layer of the ceramic fiber / metal heterogeneous composite (100), it can be formed flexibly or rigidly, and thus can be applied as an FSB or an RSB.

[0063] A method for manufacturing a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank according to another embodiment of the present invention may include the step of manufacturing a laminate comprising a first ceramic fiber layer, a first polymer resin layer, a first metal sheet layer, a second polymer resin layer, and a second ceramic fiber layer; and the step of bonding the laminate by applying heat and pressure.

[0064] The first metal sheet layer may further include a step of performing a pretreatment process on the metal sheet layer, consisting of washing with a solvent or ultrasonic cleaning and drying, before the step of forming the laminate.

[0065] The above pretreatment process is intended to remove oil present in the metal sheet layer to further enhance the adhesion effect with the ceramic fiber layer described later, and examples of solvents used for washing may be selected from the group consisting of acetone, ethanol, isopropanol, methanol, and mixtures thereof. In the above pretreatment process, the washing and drying processes may be performed once or two or more times, for example, three to five times, as needed.

[0066] After performing the aforementioned pretreatment process, a step of controlling surface roughness by surface treatment may be further included. The step of controlling surface roughness may be intended to improve adhesion with the ceramic fiber layer, thereby improving the formation efficiency and physical properties of the heterogeneous composite.

[0067] The step of controlling the surface roughness may involve surface treatment of the metal sheet layer through scratching or surface treatment using an acidic solution.

[0068] Surface treatment using the above acidic solution can be performed at an appropriate temperature using an acid, for example, nitric acid, hydrochloric acid, sulfuric acid, or a combination thereof, as an etching solution.

[0069] In addition, surface treatment through scratching can be performed by forming surface roughness using sandpaper, specifically by treating the surface of a metal sheet layer in horizontal and vertical directions with sandpaper of 100 mesh to 3000 mesh, 100 mesh to 2000 mesh, or 100 mesh to 1000 mesh to have a specific surface roughness value.

[0070] A laminate can be manufactured by performing a pretreatment process and a process for controlling surface roughness on the aforementioned metal sheet layer, and stacking in the order of a first ceramic fiber layer, a first polymer resin layer, a first metal sheet layer, a second polymer resin layer, and a second ceramic fiber layer.

[0071] In addition, the step of manufacturing the above laminate may be to manufacture the laminate by laminating a first ceramic fiber layer, a first polymer resin layer, a first metal sheet layer, a second polymer resin layer, a second ceramic fiber layer, a third polymer resin layer, a second metal sheet layer, a fourth polymer resin layer, and a third ceramic fiber layer.

[0072] A laminate formed by stacking the above-described first ceramic fiber layer, first polymer resin layer, first metal sheet layer, second polymer resin layer, and second ceramic fiber layer in that order is intended to form a triplex structure, and a laminate formed by stacking the first ceramic fiber layer, first polymer resin layer, first metal sheet layer, second polymer resin layer, second ceramic fiber layer, third polymer resin layer, second metal sheet layer, fourth polymer resin layer, and third ceramic fiber layer may be intended to form a pentaflex structure.

[0073] In addition, the structure of the laminate may be a triplex structure or a pentaplex structure, and is not limited to the above examples; the laminate may be manufactured by adding a polymer resin layer, a metal sheet layer, and a ceramic fiber layer in addition to the third ceramic fiber layer. That is, the structure of the laminate described above is not limited, and any structure for use as a material for a secondary barrier can be manufactured without limitation.

[0074] After the step of manufacturing the above laminate, a step of bonding by applying heat and pressure may be included.

[0075] The bonding step may be carried out under a temperature range of 100°C to 250°C and a pressure range of 5 bar to 20 bar, under a temperature range of 150°C to 250°C and a pressure range of 6 bar to 15 bar, and heat and pressure may be applied for 3 to 10 minutes under a temperature range of 200°C to 250°C and a pressure range of 6 bar to 13 bar. In the bonding step, as heat and pressure are applied, the polymer resin layer melts, and the effect of bonding the ceramic fiber layer and the metal sheet layer can be achieved.

[0076] The bonding step described above can be performed on the laminated structure using a composite prepreg equipment within the temperature and pressure ranges described above. By applying heat and pressure to the laminated structure within the temperature and pressure ranges, the polymer resin can be melted and appropriately absorbed into the ceramic fiber layer, thereby not only exhibiting an excellent bonding effect but also, when used as a material for a secondary barrier, exhibiting excellent mechanical properties even in low and cryogenic environments.

[0077] Accordingly, as described above, the polymer resin is melted and absorbed into the ceramic fiber layer to strengthen adhesion and physical properties, so the thickness of the polymer resin layer may be 10 μm to 50 μm. If the thickness of the polymer resin layer is too thin, even if the polymer resin is melted under the heat and pressure conditions described above, it may not be sufficiently absorbed into the ceramic fiber layer, resulting in a decrease in adhesion effect, peeling, or a decrease in mechanical properties.

[0078] In addition, if a polymer resin layer with a thickness exceeding the above range is used, the polymer resin may completely penetrate the ceramic fiber layer during the process of melting and absorption, which may result in a decrease in marketability.

[0079] According to a method for manufacturing a ceramic fiber / metal heterogeneous composite of one embodiment of the present invention, a ceramic fiber layer having excellent physical properties is used, a resin layer corresponding to the specific ceramic fiber layer used is applied, and a pretreatment process and a surface roughness generation process are performed on the metal sheet layer before forming the laminate to primarily improve adhesion, and at the same time, temperature and pressure conditions during the molding stage are optimized to exhibit ideal adhesion to secondarily improve adhesion, thereby increasing the adhesion between heterogeneous materials constituting the heterogeneous composite and further improving the physical properties of the heterogeneous composite. Accordingly, the ceramic fiber / metal heterogeneous composite manufactured according to one embodiment of the present invention possesses excellent low-temperature and cryogenic properties and mechanical properties that can be used as a barrier for storage tanks in low-temperature and cryogenic environments, such as for the storage and transportation of liquefied gases like liquefied natural gas (LNG) or liquefied hydrogen, and can exhibit excellent eco-friendliness.

[0080] Preparation Example 1

[0081] (1) Provide a metal sheet layer

[0082] An aluminum sheet (thickness 30 μm) was prepared as a metal sheet layer, washed three times with acetone, and dried to remove oil from the surface. Subsequently, the metal sheet layer was surface-treated.

[0083] (2) Ceramic fiber layer and resin layer provided

[0084] A fabric made of basalt fibers was prepared as the ceramic fiber layer, and an EVA film or PA6 film was prepared as the polymer resin layer.

[0085] (3) Complex formation

[0086] Laminate basalt fiber fabric, polymer resin film, surface-treated aluminum sheet, polymer resin film and basalt fiber fabric (Triplex), or laminate basalt fiber fabric, polymer resin film, aluminum sheet, polymer resin film, basalt fiber fabric, polymer resin film, aluminum sheet, polymer resin film and basalt fiber fabric (Pentaflex),

[0087] The above laminate was subjected to a bonding process using equipment for about 6 minutes at a temperature of 200°C to 250°C and a pressure of 6 bar to 13 bar. Afterward, it was cooled with an air pressure for 3 minutes to produce a ceramic fiber / metal heterogeneous composite.

[0088] Test Example 1

[0089] Tensile test results by basalt fiber type

[0090] Triplex structured composites were prepared according to the type of basalt fiber, and tensile tests were conducted under room temperature conditions and cryogenic environments. The specimens for the above tests were prepared and tested in accordance with ISO 1421 standards.

[0091] division form name thickness density fiber Basalt plain weave Plain weave 0 0.25mm 27*31 Plain weave 1 0.13mm 15*15 Plain weave 2 0.22mm 8*8 Plain weave 3 0.13mm 12*12 Plain weave 4 0.13mm 10*10 Basalt pitcher Jujajik 1 0.22mm 12*12

[0092] For basalt fiber fabrics formed by plain weave and basalt fiber fabrics formed by satin weave, a tensile test was conducted under the above specifications under room temperature (15℃ to 25℃) conditions.

[0093] The tensile measurement results for plain weave 0 and satin weave 1 in triplex structured composites, according to the polymer resin constituting the adhesive layer, are as shown in Table 3 below:

[0094] LLDPE PE_30 B_5 7320H HDPE_25 HDPE_10 LDPE_70 LDPE_50 LDPE_30 Required strength 200MPa Plain weave 0 285.992 168.529 177.286 186.077 Fail Fail 185.766 228.572 260.428 Jujajik 1 262.462 171.356 - - 192.726 168.798 186.3386 214.249 256.379

[0095] It was confirmed that exceeding the required strength of 200 MPa within the above range is affected not only by whether the basalt fiber is plain weave or satin weave, but also by the type of polymer resin.

[0096] Additionally, triplex structured composites were prepared for plain weaves 1 to 4, and tensile tests were conducted under room temperature conditions; the results are shown in Table 4 below:

[0097] Plain weave 1 Plain weave 2 Plain weave 3 Plain weave 4 Required strength 200MPa LLDPE 261 250.5 246.4 257.7 LDPE_30 253.4 275.8 252.8 300

[0098] According to the above test results, it was confirmed that all plain weaves 1 to 4 exhibited excellent tensile strength characteristics.

[0099] In addition, tensile tests were conducted under cryogenic conditions, using plain weave 2 and plain weave 4 basalt fibers as representative examples, and LLDPE and LDPE_30 as polymer resins.

[0100] To conduct the cryogenic tensile test, specimens were fabricated and tested in accordance with ISO 1421 standards, and the results of the tensile test conducted under -170℃ conditions are as shown in Table 5 below:

[0101] Plain weave 2 Plain weave 4 Required strength 250MPa LLDPE 402.47 488.78 LDPE_30 450.3 504.6

[0102] (Unit MPa)

[0103] According to the above test results, it was confirmed that the composite specimen of the present invention exhibits excellent tensile properties even under cryogenic conditions.

[0104] Additionally, a vertical tensile test was performed. Specimen fabrication and testing were carried out in reference to ASTM D2095, and the room temperature and cryogenic temperature conditions were tested under the same temperature conditions as the tensile test described above.

[0105] The test results are as shown in Tables 6 and 7 below:

[0106] Plain weave 2 Plain weave 4 Required strength 3MPa LLDPE 3.834 7.787 LDPE_30 3.261 4.776

[0107] Plain weave 2 Plain weave 4 Required strength 7MPa LLDPE 7.31 11.70 LDPE_30 10.654 11.59

[0108] (Unit MPa)

[0109] According to the above test results, excellent vertical tensile properties exceeding the required strength were exhibited even in the vertical tensile test under room temperature conditions (Table 6), and excellent vertical tensile properties exceeding the required strength were exhibited even in the vertical tensile test under cryogenic conditions (Table 7).

[0110] Additionally, a shear tensile test was performed. Specimen fabrication and testing were carried out in accordance with ISO 11003-2 standards, and the room temperature and cryogenic temperature conditions were tested under the same temperature conditions as the tensile test described above.

[0111] The test results are as shown in Tables 8 and 9 below:

[0112] Plain weave 2 Plain weave 4 Required strength 4MPa LLDPE 9.92 8.387 LDPE_30 8.075 9.287

[0113] Plain weave 2 Plain weave 4 Required strength 7MPa LLDPE 19.94 29.66 LDPE_30 24.01 34.49

[0114] (Unit MPa)

[0115] According to the above test results, excellent shear tensile characteristics exceeding the required strength were exhibited even in the shear tensile test under room temperature conditions (Table 8), and excellent shear tensile characteristics exceeding the required strength were exhibited even in the vertical tensile test under cryogenic conditions (Table 9).

[0117] Comparison of tensile strength according to surface treatment of metal sheet layers

[0118] The tensile strength characteristics of the composite were verified based on the presence or absence of surface treatment of the metal sheet layer.

[0119] For surface treatment, the surface of the aluminum sheet was polished in a horizontal and vertical cross pattern using 100 mesh, 400 mesh, and 800 mesh sandpaper under the following conditions, and then the surface roughness was measured using a surface roughness meter (SE3500, Kosaka).

[0120] sandpaper roughness number of polishing cycles Average parameters Ra (㎛) Rz (㎛) - - grain direction 0.18 0.89 Vertical direction 0.30 1.90 #100 8 horizontal and 8 vertical intersections each 1.38 12.70 #400 1 horizontal and 1 vertical intersection each 0.42 5.36 8 horizontal and 8 vertical intersections each 0.90 10.14 #800 8 horizontal and 8 vertical intersections each 0.60 6.81

[0121] A composite of the manufacturing example was prepared using the surface-treated aluminum sheet described above, and tensile tests, vertical tensile tests, and shear tensile tests were conducted under the same conditions as the previous experiment.

[0122] For the surface-treated aluminum sheets, average values ​​were calculated and recorded in the table below. The above tensile test, vertical tensile test, and shear tensile test were conducted under room temperature conditions, plain weave 4 basalt fibers were used, and the resins were classified by thickness.

[0123] The test results are as shown in Table 11 below:

[0124] division seal perpendicular shear Scratch surface treatment present / absent X O X O X O LDPE_30 257 285 7.7 8.2 8.3 9.2 LDPE_50 275 295 2.4 6.7 4.3 11.3

[0125] (Unit MPa)

[0126] According to the above test results, it was confirmed that differences in tensile properties, vertical tensile properties, and shear tensile properties occurred depending on the difference in surface roughness.

[0128] In addition, when aluminum sheets surface-treated with sulfuric acid were subjected to plain weave 4 basalt fibers and EVA as the polymer resin under room temperature conditions as described above, the tensile strength measurement results are as shown in Table 12 below:

[0129] Basalt plain weave 4 Chemical treatment X O tensile strength 257 250~260

[0130] (Unit MPa)

[0131] According to the above test results, it was confirmed that when using aluminum sheets surface-treated with sulfuric acid, there was no significant difference in tensile properties compared to aluminum sheets that were not surface-treated.

[0133] Preparation Example 2

[0134] (1) Provide a metal sheet layer

[0135] An aluminum sheet (thickness 30 μm) was prepared as a metal sheet layer, washed three times with acetone, and dried to remove oil from the surface. Subsequently, the metal sheet layer was surface-treated.

[0136] (2) Ceramic fiber layer and resin layer provided

[0137] A fabric made of basalt fibers was prepared as a ceramic fiber layer, and an adhesive composition was prepared by mixing a curing agent (Kukdo Chemical D76609) with two types of liquid epoxy resins (Kukdo Chemical YD128 and YD011a80 mixed in a weight ratio of 9:1 to 8:2) as a polymer resin layer, and the composition was applied to the basalt fibers by hand layup and cured at 100°C for 5 minutes to produce a prepreg.

[0138] Instead of manufacturing with the prepreg described above, an adhesive composition may be applied to basalt fibers and used directly to form the composite described below.

[0139] The above adhesive composition was prepared by mixing an epoxy resin and a curing agent in a weight ratio of 9:1.

[0140] (3) Complex formation

[0141] Laminates a prepreg containing basalt fiber fabric, a surface-treated aluminum sheet, and a prepreg containing basalt fiber fabric (Triplex), or laminates a prepreg containing basalt fiber fabric, an aluminum sheet, a prepreg containing basalt fiber fabric, an aluminum sheet, and a prepreg containing basalt fiber fabric (Pentaflex).

[0142] The above laminate was subjected to a bonding process using equipment for about 6 minutes at a temperature of 200°C to 250°C and a pressure of 6 bar to 13 bar. Afterward, it was cooled with an air pressure for 3 minutes to produce a ceramic fiber / metal heterogeneous composite.

[0143] Instead of the prepreg mentioned above, a composite can also be manufactured by applying an adhesive composition to a basalt fiber fabric using a hand layup method and laminating it directly onto a surface-treated aluminum sheet.

[0145] Test Example 2

[0146] Evaluation of adhesion degree according to the type of adhesive layer

[0147] To manufacture the composite of Manufacturing Example 2 described above, a polymer film containing an epoxy resin was used instead of a liquid epoxy resin to prepare the composite in the same triplex structure, and a room temperature vertical tensile test and a shear test were performed.

[0148] The specimens for the vertical tensile test were prepared and tested in accordance with ASTM D2095, and the specimens for the shear test were prepared and tested in accordance with ISO 11003-2.

[0149] The test results are as shown in Tables 13 and 14 below:

[0150] A type Type B C type Required strength 3 MPa Plain weave C 0.165 0.69 4.228

[0151] A type Type B C type Required strength 4 MPa Plain weave C 1.172 1.042 2.035

[0152] According to the above test results, Type A and Type B utilized commercially available epoxy resins for adhesion, and although they could be manufactured into composites, it was confirmed that values ​​fell short of the standard under room temperature conditions. Type C utilized the adhesive composition of the above-described manufacturing example and was confirmed to exhibit excellent vertical tensile strength and shear strength under room temperature conditions.

[0153] Additionally, a tensile test was conducted on the C type under room temperature conditions. For the tensile test, specimens were prepared and tested in accordance with ISO 1421 standards. As a result of the test, it was required to exhibit a tensile strength of 200 MPa or higher, but it was confirmed that the composite using the adhesive composition of Preparation Example 2 described above exhibited excellent tensile strength characteristics of 293.203 MPa.

[0154] Evaluation of properties based on the content of the adhesive composition in prepreg

[0155] When applying an adhesive composition to a basalt fiber fabric by hand layup, prepregs were prepared such that the resin content absorbed by the adhesive composition into the basalt fiber fabric was 14% and 16%, and after preparing composites, characteristic evaluations were conducted under room temperature conditions and cryogenic conditions (-170℃).

[0156] The evaluation method for tensile properties, vertical tensile properties, and shear resistance properties was conducted in the same manner as the experimental method described above.

[0157] The test results are as shown in Tables 15 through 20:

[0158] Resine Contents Resin C type 14% Suji C type 16% Required strength 200MPa Plain weave C 309 295

[0159] Table 15 above shows the results of evaluating tensile properties under room temperature conditions.

[0160] Resine Contents Resin C type 14% Suji C type 16% Required strength 3.0 MPa Plain weave C 6.8 6.7

[0161] Table 16 above shows the results of evaluating vertical tensile properties under room temperature conditions.

[0162] Resine Contents Resin C type 14% Suji C type 16% Required strength 4.0 MPa Plain weave C 9.1 11.3

[0163] Table 17 above shows the results of evaluating shear tensile properties under room temperature conditions.

[0164] Resine Contents Resin C type 14% Suji C type 16% Required strength 250MPa Plain weave C 430 380

[0165] Table 18 above shows the results of evaluating tensile properties under cryogenic conditions.

[0166] Resine Contents Resin C type 14% Suji C type 16% Required strength 3.0 MPa Plain weave C 10.51 17.8

[0167] Table 19 above shows the results of evaluating vertical tensile properties under cryogenic conditions.

[0169] Resine Contents Resin C type 14% Suji C type 16% Required strength 4.0 MPa Plain weave C 20.2 30.2

[0170] Table 20 above shows the results of evaluating shear tensile properties under cryogenic conditions.

[0171] Based on the above test results, it was confirmed that under cryogenic conditions, the best effects in tensile, vertical tensile, and shear tensile properties were observed when the resin content absorbed by the basalt fiber fabric exceeded 14%, that is, when it was 16% or more, or 16% to 19%, as in the present invention.

[0172] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

Claim 1 A ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank comprising: a first ceramic fiber layer; a first metal sheet layer laminated to the first ceramic fiber layer; and a second ceramic fiber layer laminated to the first metal sheet layer, wherein the first ceramic fiber layer and the second ceramic fiber layer are in the form of a plain weave including basalt fibers, and the first ceramic fiber layer, the first metal sheet layer and the second ceramic fiber layer are bonded by an adhesive layer selected from epoxy resin or polyethylene resin, and the first metal sheet layer has an arithmetic mean roughness (Ra) of 0.1 μm to 10 μm by surface treatment through scratching. Claim 2 delete Claim 3 In claim 1, the first metal sheet layer is a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank selected from the group consisting of aluminum sheets, stainless steel sheets, and copper sheets. Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 A ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank according to claim 1, wherein the ceramic fiber / metal heterogeneous composite further comprises a second metal sheet layer laminated to the second ceramic fiber layer and a third ceramic fiber layer laminated to the second metal sheet layer, and wherein the second ceramic fiber layer, the second metal sheet layer, and the third ceramic fiber layer are bonded by an adhesive layer. Claim 9 In claim 1, the ceramic fiber / metal heterogeneous composite is a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank used as a Flexible Secondary Barrier (FSB) or Rigid Secondary Barrier (RSB). Claim 10 A method for manufacturing a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank, comprising: a step of manufacturing a laminate including a first ceramic fiber layer, a first polymer resin layer, a first metal sheet layer, a second polymer resin layer, and a second ceramic fiber layer; and a step of bonding the laminate by applying heat and pressure, wherein the first ceramic fiber layer and the second ceramic fiber layer are in the form of a plain weave including basalt fibers, the first polymer resin layer and the second polymer resin layer include epoxy resin or polyethylene resin, and the first metal sheet layer is subjected to a pretreatment process consisting of washing with a solvent or ultrasonic cleaning and drying on the first metal sheet layer before the step of forming the laminate, and after performing the pretreatment process, the surface roughness is controlled by surface treatment through scratching so that the arithmetic mean roughness (Ra) is 0.1 μm to 10 μm. Claim 11 delete Claim 12 delete Claim 13 A method for manufacturing a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank, wherein the bonding step is carried out in a temperature range of 100°C to 250°C and a pressure range of 6 bar to 20 bar. Claim 14 A method for manufacturing a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank, wherein the step of manufacturing the laminate is to laminate a first ceramic fiber layer, a first polymer resin layer, a first metal sheet layer, a second polymer resin layer, a second ceramic fiber layer, a third polymer resin layer, a second metal sheet layer, a fourth polymer resin layer, and a third ceramic fiber layer. Claim 15 A barrier for a liquefied gas storage tank comprising a ceramic fiber / metal heterogeneous composite for a liquefied gas storage tank according to claim 1.

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