Coating material-coated light metal that inhibits generation of space debris

Abstract

To provide a coating material-coated light metal with functions improved by coating, through using a coating material having excellent functions, even with the coating material having a Young's modulus and density different from those of a light metal.SOLUTION: A coating material-coated light metal 1 includes a coating material 3 and a light metal 2 with density of 5 g / cm3 or less and having a Young's modulus 40 times or larger than a Young's modulus of the coating material 3. At least part of the light metal 2 is coated by the coating material (layer) 3. Preferably, an acoustic impedance of the light metal 2 is 8 times or more of an acoustic impedance of the coating material 3.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a light metal, particularly in the form of a plate, coated with a coating material that suppresses the generation of space debris. [Background technology]

[0002] For example, in food manufacturing processes, tiny ejections can be a problem, but when we turn our attention to space, ejecta, which are ejected during high-speed collisions of space debris, become a problem. For the sustainable development of space, it is necessary to at least reduce ejections, but although there are researches and inventions to capture large space debris, it is difficult to capture tiny space debris. For example, cladding materials that can reduce and suppress ejecta are useful for protecting the space environment from environmental pollution caused by microspace debris and making space sustainable.

[0003] Patent document 1 describes that the multi-layer insulation covering the outer surface of the spacecraft structure comprises multiple layers stacked on top of each other, the multiple layers including an outermost layer film, a detection layer, an intermediate layer film, and an innermost layer film 21, and that the outermost layer film is formed, for example, by applying aluminum vapor deposition to at least one surface of a polyimide film. In Non-Patent Document 1, silsesquioxane (RSiO) is added to the outermost polyimide film of the multi-layer insulation material used on the outer surface of a spacecraft to make it resistant to atomic oxygen, etc. 1.5 ) n It is described that the coating is

[0004] Light metals, such as aluminum alloys, are promising materials that can reduce and suppress ejecta caused by space debris, but the use of coating materials to enhance their functionality may be effective. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-111936 A [Non-patent literature]

[0006] [Non-Patent Document 1] Toagosei Group Annual Research Report No. 16 (TREND 2013) 10-15 Yoshida, Naomasa et al. Summary of the Invention [Problem to be solved by the invention]

[0007] However, if the Young's modulus and acoustic impedance of the coating material and the light metal are significantly different, it is generally considered that peeling is likely to occur at the interface. Therefore, the present invention aims to provide a light metal whose function is improved by the coating (hereinafter, sometimes referred to as "coated light metal") by using a coating material that has excellent function even if the coating material has a Young's modulus and acoustic impedance significantly different from those of the light metal. [Means for solving the problem]

[0008] The present invention which solves the above problems is as follows. [1] A coating material and a gypsum lath having a Young's modulus 40 times or more that of the coating material and a density of 5 g / cm 3 The present invention relates to a coating material-coated light metal comprising the following light metal, and at least a portion of the light metal is coated with the coating material. [2] The coating material-coated light metal according to [1], wherein the acoustic impedance of the light metal is 8 times or more higher than the acoustic impedance of the coating material. [3] The coating material-coated light metal according to [1] or [2], characterized in that the coating material is an inorganic-organic composite material. [4] The coating material-coated light metal according to [3], wherein the inorganic-organic complex is a siloxane-based compound. [5] The light metal coated with the coating material according to [3], characterized in that the light metal is aluminum, magnesium or titanium. [6] The coating material-coated light metal according to [4], wherein the light metal is aluminum, magnesium or titanium. [7] A coating material-coated light metal according to [1] or [2], characterized in that the coating material-coated light metal is used to capture a flying object, and / or to reduce or suppress ejection material generated when the coating material-coated light metal is hit by a flying object, and / or to cushion the impact of the flying object. [8] The coating material-coated light metal described in [1] or [2] is characterized in that the flying object and / or the ejected object is space debris and is used as a space debris bumper. [9] A method for using the coating material-coated light metal described in [1] or [2] above to capture a flying object, and / or to reduce or suppress ejection material generated when the coating material-coated light metal is hit by a flying object, and / or to cushion the impact of the flying object. Effect of the Invention

[0009] According to the coated light metal of the present invention, the required coating thickness is 1 to 150 μm, which is very thin and has almost no effect on the overall mass, but the number of ejectors can be reduced by about half. [Brief description of the drawings]

[0010] [Figure 1] This figure shows the state of space debris based on the reliability evaluation method of the flux model of MASTER2009 / ORDEM3.0. [Diagram 2]1 is a schematic diagram showing a coating material-coated light metal according to one embodiment of the present invention, and a state in which a flying object collides with the coating material-coated light metal. FIG. [Diagram 3] (a) A diagram showing a high-speed impact test method using a flying object against a plate-shaped light metal covered with a coating material, and the state of the forward and backward ejection, (b) an example of an ejector, and (c) the dimensions (length a, width b) and projected area (Ae) of the ejector. [Figure 4] FIG. 1 shows the observation results of a projectile impact test on a test specimen, where the test specimen is (a) coated with Al 5 μm, (b) coated with Al 25 μm, and (c) uncoated Al. [Diagram 5] 5A to 5C are diagrams showing the observation results near the through-holes in FIGS. [Figure 6] FIG. 13 shows the ejecta size distribution for a test specimen. [Figure 7] FIG. 1 shows the observation results of a verification plate (copper plate) conforming to ISO, with the test specimens (a) coated with Al 5 μm, (b) coated with Al 25 μm, and (c) uncoated Al. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be made without departing from the scope of the invention.

[0012] From Figure 1, we can see that the amount of space debris is increasing year by year, and that the smaller the size of the debris, the more numerous it is, for example, when comparing 1 mm and 100 μm size space debris. To explain more specifically, it is as follows. Both the horizontal and vertical axes are logarithmic, and a one-digit change on the horizontal axis results in a two-digit change on the vertical axis, meaning a 100-fold increase.

[0013] As shown in FIG. 2, a coating material-coated light metal 1, which is one embodiment of the present invention, has a coating layer 3 of about 20 μm of coating material on a light metal 2. When a projectile 4 collides with the surface of the coating material-coated light metal 1, the surface is recessed during the collision to form a crater 5, and a crater lip 6 and an ejecta 7 are generated from the crater lip. If the coating material-coated light metal 1 is thin, a through hole will be created. The light metal used for the coating material 1 has a density of 5 or less, for example, aluminum (density 2.7 g / cm 3 ), magnesium (density 1.7 g / cm 3 ) or titanium (density 4.5 g / cm 3 ) is preferred.

[0014] The material for forming the coating layer 3 is preferably an inorganic-organic composite material, which is highly resistant to the space environment, and more preferably a siloxane-based compound. As the siloxane-based compound, for example, a silsesquioxane derivative or a siloxane-modified polyimide is even more preferable. Note that silsesquioxane (RSiO 1.5 ) n is a compound that exists intermediate between inorganic silica (SiO) and organic silicone (R2Si0).

[0015] The light metal 2 is preferably aluminum, magnesium, or titanium, and the coating material is silsesquioxane. The Young's modulus is compared as follows: the Young's modulus of aluminum is 70 GPa, that of magnesium is 45 GPa, and that of titanium is 116 GPa. On the other hand, the Young's modulus of the silsesquioxane derivative (density: 1 g / cm 3 The Young's modulus of the light metals (approximately 1 GPa) is approximately 1 GPa. Therefore, Young's modulus of aluminum / Young's modulus of silsesquioxane derivatives = 70 / 1 = 70, Young's modulus of magnesium / Young's modulus of silsesquioxane derivatives = 45 / 1 = 45, Young's modulus of titanium / Young's modulus of silsesquioxane derivatives = 116 / 1 = 116. Therefore, Young's modulus of light metals / Young's modulus of coating material is 40 or more.

[0016] Next, comparing them from the perspective of acoustic impedance, we see the following. This is because acoustic impedance has an effect when considering the reflection and transmission of wave propagation. Acoustic impedance = density x speed of sound, and since the speed of sound is √(Young's modulus / density), acoustic impedance = √(Young's modulus x density). Therefore, the acoustic impedance of a silsesquioxane derivative = √(1 x 1 = 1, the acoustic impedance of aluminum = √(70 x 2.7) = 13.7, the acoustic impedance of magnesium = √(45 x 1.7) = 8.75, and the acoustic impedance of titanium = √(116 x 4.5) = 22.8. For this reason, it is preferable for the acoustic impedance of light metals to the acoustic impedance of coating materials to be 8 times or more, and more preferably 10 times or more.

[0017] Then, the Young's modulus and acoustic impedance are significantly different at densities of 5 g / cm 3 It is generally believed that when coating the following light metals with a coating material, the two are likely to peel off. However, it has been found that, unexpectedly, peeling does not occur easily, and that inorganic-organic composites are preferable as coating materials for light metals, siloxane-based compounds are more preferable, and silsesquioxane derivatives (silsesquioxane-based) are particularly excellent.

[0018] The reasons for this are not yet fully clear, but the following hypothesis can be made. Coating material peeling off from coated light metal is related to 1) Young's modulus, which relates to elongation, and 2) acoustic impedance, which relates to wave reflection. In the case of 1), there is little deformation and it does not elongate that much, so differences in Young's modulus are not related. In the case of 2), the coating layer is thin, so it is thought that the waves do not reflect and transmit ideally, but rather interfere in a complex way and cancel each other out.

[0019] The thickness of the coating layer 3 is preferably 1 to 150 μm, more preferably 5 to 25 μm, and most preferably 10 to 20 μm, from the viewpoint of achieving a good balance between atomic oxygen resistance, high transparency, UV resistance, and low outgassing, and being lightweight. The fact that the coating material-covered light metal 1 is in a plate shape (plate shape) is effective for capturing space debris or simulated flying objects. Furthermore, when the light metal 2 is an aluminum alloy, the material is preferably JIS6061, JIS2219, JIS2024 or JIS1100 from the viewpoints of ease of production and rapid substitution for the aluminum alloys currently in widespread use.

[0020] Using the coating material-coated light metal 1 to capture a flying object 4 with the coating material-coated light metal 1, and / or to reduce ejecta generated when the coating material-coated light metal 1 is hit by the flying object 4, and / or to mitigate the impact from the flying object 4, is a useful method of using the coating material-coated light metal 1, and therefore the coating material-coated light metal 1 used for this purpose is useful. Furthermore, even if the space debris becomes another flying object 4, the same applies if there is a need to capture the flying object 4.

[0021] Therefore, in the case where a structure equipped with a coating material-coated light metal 1 is placed in space, a case where space debris (space junk) or a simulated flying object (hereinafter sometimes referred to as "flying object, etc.") 4 collides with the coating material-coated light metal 1 at high speed will be described with reference to Figure 2.

[0022] When a flying object or the like 4 collides with the coating material-coated light metal 1 at high speed, a through hole (not shown) or a crater 5 and a crater lip 6 are formed on the surface of the coating material-coated light metal 1 that has been hit. In general, the higher the impact speed, the larger the through hole diameter or the size of the crater 5, and the formation of the crater lip 6 is promoted. However, the through hole diameter or the size and shape of the crater 5 and the crater lip 6 change depending on the material properties (yield stress, fracture elongation, etc.), and further, the tendency changes depending on the combination of materials. From the surface of the coating material-coated light metal 1 that has been hit, an ejecta (ejected material) 8, which is a fragment of the coating material-coated light metal 1, is ejected. The ejecta (ejected material) 7, 8 remain in space as it is and become space debris. The larger the size of the crater 5, the larger the volume becomes the ejecta (ejected material), and becomes space debris. The larger the crater lip 6, the fewer the ejecta (ejected material) 7, 8.

[0023] The following is a description of high-speed collisions. Since the launch of Sputnik 1 in October 1957, the amount of space debris in low Earth orbit has been increasing. It is said that there are 20,000 objects over 100 mm, 500,000 to 700,000 objects over 10 mm, and over 100 million objects over 1 mm that can be tracked from the ground, and they are hindering space activities. The average impact speed is 10 km / s. In the future, development on the moon and lunar orbit is planned, and there is a possibility that space debris will increase outside of low Earth orbit. In high-speed collisions with an impact speed of 10 km / s, which is rarely seen on Earth, the flying object breaks up during the impact, and if the material that is impacted is thick, a crater is formed on its surface, and if it is thin, it penetrates and a through hole is formed. In either case, a crater lip is formed at the boundary surface.

[0024] The following describes through holes, craters, and crater lips. A through hole is a hole that penetrates the material that is impacted, and a crater is a depression that is formed on the surface of the material that is impacted. A crater lip is a protrusion that is formed near the boundary of the through hole or crater. The higher the impact speed, the larger the size of the through hole and crater, and the formation of the crater lip is promoted, but the size and shape of the through hole, crater, and crater lip change depending on the material properties (yield stress, breaking elongation, etc.), and further, the tendency changes depending on the combination of materials. In general, in the case of a homogeneous material, it is known that the larger the yield stress or hardness, the smaller the through hole or crater, and the larger the breaking elongation, the larger the crater lip (hereinafter sometimes simply referred to as "lip") that is formed. However, there are almost no materials that have both a high yield stress or hardness and a high breaking elongation, and furthermore, for use in space, it is preferable for the material to be lightweight. Since the debris bumpers of the space station are made of plates (approximately 1 mm) made of JIS6061, the aluminum alloy used in the examples and comparative examples was JIS6061 with a thickness of 1.0 mm. EXAMPLES

[0025] (Production of test specimens) Four sheets of JIS 6061 aluminum alloy in plate form (plate shape), measuring 5 cm x 15 cm and 1.0 mm thick, and a silsesquioxane derivative as a coating material were prepared. One of the four sheets was coated with a thickness of 5 μm (aluminum alloy coated with coating material 11, Example 1), the other was coated with a thickness of 25 μm (aluminum alloy coated with coating material 12, Example 2), and the remaining two sheets were not coated (aluminum alloy 13, Comparative Example 1). In other words, four test pieces were prepared.

[0026] (High-speed impact testing with flying objects) As shown in Fig. 3, a high-speed collision test using a flying object was carried out. Coating material-coated aluminum alloy 11 (Example 1), coating material-coated aluminum alloy 12 (Example 2), and aluminum alloy 13 (Comparative Example 1) were used as targets, and a flying object with a predetermined collision speed (high speed) that passed through a through hole of the verification plate was collided with the target, and an ejector (forward ejector 14) ejected from the target toward the verification plate was received by the verification plate, and an ejector (rearward ejector 14') ejected from the target toward the pressurized wall was received by the pressurized wall (rearward ejector 14' was not measured). The distance between the verification plate and the target was 50 mm so as to be within the range specified by ISO 11227, and the distance between the pressurized wall and the target was 100 mm so as to be within the range specified by ISO 11227.

[0027] The verification plate is as follows: For example, the material is in accordance with ISO 11227, a copper plate is used, the model number and hardness are C1100P-1 / 4H, and the recommended thickness is 2 mm.

[0028] Regarding the pressurized walls, the following is true: Aluminum alloy 2024 or 2017 is often used to simulate the pressurized walls of the actual space station (it is said that the real pressurized walls are made of 2219 material).

[0029] The projectile is as follows. For example, the ISO 11227 standard stipulates that the material should be aluminum alloy 2017 or 2024. The projectile is a sphere, and the diameter is 1 mm and the impact speed is 5 km / s according to ISO 11227, but we used a sphere with a diameter of 3.2 mm to account for the approximate kinetic energy. Moreover, from the viewpoint of ultra-high speed collisions, the predetermined speed of the flying object is preferably 2 km / s or more.

[0030] The dimensions of the ejector 24 shown in FIG. 3(b) were determined by measuring a projection view of the ejector 24' shown in FIG. 3(c) and determining its length a and width b.

[0031] In the following experimental example, a projectile impact test was conducted using copper plate C1100P-1 / 4H (thickness 2 mm) as the verification plate, aluminum alloy 2024 as the simulant material for the pressurized wall, and aluminum alloy 2017 (φ3.2 mm) as the projectile.

[0032] When a coated aluminum alloy 11 was used and the collision speed was 3.15 km / s from the coated side (Experimental Example 1), a through hole h11 and a lip h11A were observed on the coated side (collision surface side) as shown in Figures 4(a) and 5(a). When a coated aluminum alloy 12 was used and the collision speed was 3.29 km / s from the coated side (Experimental Example 2), a through hole h12 and a lip h12A were observed on the coated side (collision surface side) as shown in Figures 4(b) and 5(b). When a coated aluminum alloy 13 was used and the collision speed was 3.12 km / s from the coated side (Comparative Experimental Example 1), a through hole h13 and a lip h13A were observed on the coated side (collision surface side) as shown in Figures 4(c) and 5(c). As shown in Figures 5(a) to (c), there was no significant change in the size and shape of the lip depending on whether or not there was a coating near the through-hole.

[0033] Table 1 summarizes the coating material-coated aluminum alloys 11 and 12 (Examples 1 and 2), aluminum alloy 13 (Comparative Example 1), and Experimental Examples 1 and 2 and Comparative Experimental Examples 1 and 2 that used them. Comparing the area of ​​the through holes, for example, Example 1 / Example 2 = 11.2 / 11.7 = 0.957, Example 1 / Comparative Experimental Example 1 = 11.2 / 11.5 = 0.974, Example 1 / Comparative Experimental Example 2 = 11.2 / 11.3 = 0.991, and Example 2 / Comparative Experimental Example 1 = 11.7 / 11.5 = 1.02. That is, the area of ​​the through holes was almost the same depending on whether the coating was present or not. The collision speed was 3.15 km / s to 3.29 km / s, which was almost the same. (Table 1) JPEG2024170888000002.jpg44159

[0034] As shown in Figure 6, the relationship between the length a of the front ejector and the number of ejectors (the vertical axis is the cumulative number distribution) is as follows: The number (cumulative number) of ejectors larger than the length a of the front ejector for each length of the front ejector was as follows when the length a of the front ejector was, for example, about 1 mm: Coating material coated aluminum alloy 12 (aluminum coating 25 μm, Example 2) impact speed 3.29 km / s (Experimental Example 2) < Coating material coated aluminum alloy 11 (aluminum coating 5 μm, Example 1) impact speed 3.15 km / s (Experimental Example 1) < Aluminum alloy 13 (no aluminum coating, Comparative Example 1) impact speed 3.12 km / s (Comparative Experimental Example 1) < Aluminum alloy 13 (no aluminum coating, Comparative Example 1) impact speed 3.15 km / s (Comparative Experimental Example 2) From the above, it was found that the number of ejecta was reduced by coating with aluminum alloy, and the effect was seen even with a coating thickness of 5 μm.

[0035] Forward ejection was investigated using a verification plate (copper plate) conforming to ISO 11227, using the indirect method to evaluate forward ejection. The verification plate is placed in front of the target, and the ejecta flying forward collide with it, creating an indentation (crater) on the surface, which is used to evaluate the ejection. In addition, there are holes (h21, h22, h23) in the center for the projectile to pass through.

[0036] In Figure 7, copper plate 21 (Figure (a) Al 5 μm coating), copper plate 22 (Figure (b) Al 25 μm coating), and copper plate 23 (Figure (c) no Al coating) are photographs of the verification plates after the experiment, and in each case, a circular indentation area can be observed around the hole through which the projectile passes. In each case, the inner diameter was about 80 mm, and the outer diameter was about 100 mm. The inner and outer diameters became slightly larger by coating, but this did not make a big difference. There was also no big difference in the number, size, or density of the indentations. [Industrial Applicability]

[0037] As exploration of the Moon and Mars progresses in the future, the coating material-coated light metal of the present invention can be used to combat space debris on the Moon and Mars, in addition to the current problem of space debris around the Earth. [Explanation of symbols]

[0038] 1: Coating material coated light metal 2: Light metal 3: Coating layer (material) 4: Projectile 5: Crater 6, h11A, h12A, h13A: Crater lip 7: Ejecta from the crater lip 11, 12: Aluminum alloy coated with coating material 13: Aluminum alloy h11, h12, h13, h21, h22, h23: Through hole 21, 22, 23: Copper plate 8, 24, 24´: Ejector

Claims

1. A coating material and a coating material having a Young's modulus of 40 times or more that of the coating material and a density of 5 g / cm ３ A coating material-coated light metal comprising: a light metal as follows: and at least a portion of the light metal is coated with the coating material.

2. 2. The coating material-coated light metal according to claim 1, wherein the acoustic impedance of the light metal is at least eight times that of the coating material.

3. 3. The light metal coated with a coating material according to claim 1, wherein the coating material is an inorganic-organic composite material.

4. 4. The coating material-covered light metal according to claim 3, wherein said inorganic-organic complex is a siloxane-based compound.

5. 4. The coating material-coated light metal according to claim 3, wherein the light metal is aluminum, magnesium or titanium.

6. 5. The coating material-coated light metal according to claim 4, wherein the light metal is aluminum, magnesium or titanium.

7. The coating material-coated light metal according to claim 1 or 2, characterized in that the coating material-coated light metal is used to capture a flying object, and / or to reduce or suppress ejection material generated when the coating material-coated light metal is hit by a flying object, and / or to cushion the impact of the flying object.

8. 3. The coating material-coated light metal according to claim 1 or 2, wherein the flying object and / or the ejected object is space debris, and the coating material-coated light metal is used as a space debris bumper.

9. A method for using the coating material-coated light metal according to claim 1 or 2, characterized in that the coating material-coated light metal is used to capture a flying object, and / or to reduce or suppress the ejection material generated when the coating material-coated light metal is hit by a flying object, and / or to mitigate the impact of the flying object.

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