Method for manufacturing aluminum-based nano / micro protrusions

Abstract

To provide aluminum-based nano-micro protrusions on an aluminum or aluminum-based alloy on which nano-micro protrusions were difficult to be formed by conventional irradiation of Ar ions, and a method for producing the protrusions.SOLUTION: Aluminum-based nano-micro protrusions are formed in a conical or truncated conical shape in an irradiation direction of Ga ions on a surface of an aluminum or aluminum-based alloy by irradiation of Ga ions. A method for producing aluminum-based nano-micro protrusions in which Ga ions are irradiated on a surface of an aluminum or aluminum-based alloy to allow aluminum-based nano-micro protrusions to grow in a conical or truncated conical shape in an irradiation direction of Ga ions.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention can be used for active catalysts, point contacts, electron emitters, lubricating surfaces, battery electrodes, optical filters, etc. Method for manufacturing aluminum-based nano / micro protrusions It relates to.

Background Art

[0002] Since 2005, the inventors have reported that nano- and micro-protrusions are created in the excitation field of Ar ion irradiation. That is, in the Cu plate, Cu, CuO, Cu2O (2005 - 2008, 2018, Patent Document 1), in Zn, Zn(O)ZnO (2008 - 2009, 2018), in the Cu-Zn alloy, α and β Cu-Zn (2009 - 2010), in the Cu-Fe alloy, Cu phase and Fe phase separators (2010 - 2012), and in Ag, Ag (2011, 2016) nano- and micro-protrusions are formed. All grow based on the Bottom-Up mechanism in which surface atoms activated by kV-class Ar ion irradiation diffuse on the surface in the direction of the ion irradiation source, and in many cases, they become conical nano- and micro-protrusions.

[0003] The formation of nano- and micro-protrusions in the Ar ion excitation reaction field depends on the activation energy of surface diffusion and the Ar ion sputtering threshold energy, as shown in FIG. 9 of Non-Patent Document 1. FIG. 9 of Non-Patent Document 1 is cited and shown as FIG. 13 in this specification. As is also clear from this FIG. 13, the lower the activation energy of surface diffusion and the Ar ion sputtering threshold energy of a metal, the easier it is to form nano- and micro-protrusions, and the higher these energies of a metal, the more difficult it is to form nano- and micro-protrusions. Therefore, until now, nano- and micro-protrusions have only been formed in metals such as Cu and Zn with relatively low energies of both, and in aluminum with a high Ar ion sputtering threshold energy, sufficient growth of nano- and micro-protrusions, that is, conical or frustum-shaped ones, has not been observed by Ar ion irradiation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Non-Patent Document

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In view of the above-described conventional problems, the present invention provides an aluminum having a particularly high Ar ion sputtering threshold energy compared to Cu and Zn and in which nano / micro protrusions are difficult to form, Method for manufacturing aluminum-based nano / micro protrusions and aims to provide

Means for Solving the Problems

[0007] As a result of intensive research to solve the above problems, the inventors have succeeded in growing aluminum-based nano / micro protrusions by irradiating Ga ions having an atomic weight larger than that of Ar ions (Ga atomic weight 69.7, Ar atomic weight 39.95).

[0008] Delete

[0009] Delete

[0010] Method for manufacturing aluminum-based nano / micro protrusions of the present invention is characterized by irradiating the surface of aluminum or an aluminum-based alloy with Ga ions and growing them in a conical or frustum-shaped manner in the irradiation direction of the Ga ions.

[0011] In the method for manufacturing the above-described aluminum-based nano / micro protrusions, it is desirable to apply compressive residual stress by mechanical polishing, peening, etc. to the surface of aluminum or an aluminum-based alloy before irradiating with Ga ions, so as to promote the growth of the aluminum-based nano / micro protrusions.

Advantages of the Invention

[0012] Delete

[0013] Delete

[0014] In the method for manufacturing the aluminum-based nano / micro protrusions of the present invention, since aluminum or an aluminum-based alloy is sputtered using Ga ions having both a larger atomic number and atomic weight than Ar ions, it is possible to grow aluminum-based nano / micro protrusions that could not be achieved with conventional lightweight Ar ions.

[0015] And by applying compressive residual stress to the surface of aluminum or an aluminum-based alloy by mechanical polishing, peening, etc., the growth of the aluminum-based nano / micro protrusions can be promoted.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the present invention will be described in detail according to examples. In the present invention, pure aluminum, aluminum alloys A5052 and A6063 were used as samples. Pure aluminum is 99.9 mass% Al. A5052 is an Al-Mg alloy containing 2.5 mass% Mg. Also, A6063 is an Al-Mg-Si alloy containing 0.48 mass% Mg and 0.48 mass% Si. The shapes are Φ20×1 mm, 12×12×3 mm, and 10×20×10 mm respectively, and A6063 is an extruded material.

[0018] As the Ga ion source, monovalent Ga ions (Ga + ) of FIB / SEM DualBeam, Halios600i manufactured by FEI (currently ThermoFisher) were used, and the irradiation was performed in Rectangular Mode. The irradiation voltage was basically 30 kV, and the current was changed from 9.4 to 65 nA. The irradiation time was up to 2000 sec. The irradiation angles were perpendicular to the surface and 30 deg. The irradiation surface was observed for sequential changes in SEM mode, and the time change of the maximum height of the nano / micro protrusions was obtained. Also, the generated nano / micro protrusions were subjected to composition analysis by EDS and FE-EPMA, and individual composition changes were also measured.

[0019] FIG. 15 shows an explanatory diagram of the growth status of nano-micro protrusions by Ga ion irradiation. It is considered that the surface aluminum (Al) atoms sputtered by Ga ion irradiation move in the irradiation direction of Ga ions by surface diffusion, and nano-micro protrusions grow. FIG. 16 shows the results of calculating the sputtering rates of aluminum by Ar ions and Ga ions according to Yamamura's formula (see Patent Document 2, paragraph number 0012). The sputtering rate at the peak by Ga ions is about twice that of the sputtering rate at the peak by Ar ions, indicating that Ga ions are sputtered more easily than Ar ions.

[0020] First, the results of irradiating pure aluminum with Ga ions will be described. As a pretreatment, surface smoothing was performed by surface diamond abrasive polishing + Al2O3 polishing + colloidal silica polishing, and a compressive residual stress of 80 MPa was applied. The Ga ion irradiation was at a voltage of 30 kV, a current of 45 nA, an irradiation angle of 30°, and in rectangular mode.

[0021] FIG. 1 shows aluminum-based nano-micro protrusions formed when the irradiation time was 240 seconds to 900 seconds using an aluminum substrate as a sample, and FIG. 2 shows those formed when the irradiation time was 1200 seconds. It can be seen that when the irradiation time is short, nano-micro protrusions in the shape of a conical body with a sharp tip are formed, and when the irradiation time is long, nano-micro protrusions in the shape of a truncated cone (frustum of a cone) with a chipped tip are formed. As shown in FIG. 3, the nano-micro protrusions grow smoothly with time.

[0022] FIG. 4 shows examples of locations where components were analyzed by EDS. FIG. 4(a) shows the analysis results of the matrix at point 001 (left central part) in FIG. 3, and FIG. 4(b) shows the analysis results of the nano-micro protrusion at point 003 (central lower part) in FIG. 3. The analysis values in FIG. 4(a) were C: 2.21 mass%, O: 2.41 mass%, Al: 94.99 mass%, Ga: 0.40 mass%, and the analysis values in FIG. 4(b) were O: 5.55 mass%, Al: 90.79 mass%, Ga: 1.71 mass%.

[0023] Next, the results of irradiating A5052 (Al-Mg alloy) with Ga ions will be described. The pretreatment is not significantly different from that described above. The irradiation of Ga ions is carried out at 30 kV, 9.4 nA, an irradiation angle of 30°, and in rectangular mode.

[0024] Figure 6 shows aluminum-based nano / micro protrusions formed when the irradiation time is 180 to 720 seconds using A5052 as a sample, and Figure 7 shows those formed when the irradiation time is 900 to 1800 seconds. Even when the irradiation time is 1200 seconds, conical nano / micro protrusions with sharp tips are formed, and when it reaches 1800 seconds, frustum-shaped nano / micro protrusions with chipped tips can be sporadically seen. As shown in Figure 8, these aluminum-based nano / micro protrusions grow almost linearly with time.

[0025] Figure 9 shows an example of the location where the components were analyzed by EDS. Figure 10(a) shows the analysis results of the matrix of the unillustrated part of the A5052 substrate, and Figure 10(b) shows the analysis results of the nano / micro protrusion at point 006 (upper right part) in Figure 9. The analysis values in Figure 10(a) are C: 3.42 mass%, O: 7.11 mass%, Mg: 2.53 mass%, and Al: 86.93 mass%, and the analysis values in Figure 10(b) are C: 2.82 mass%, O: 1.87 mass%, Mg: 2.51 mass%, Al: 91.81 mass%, and Ga: 0.99 mass%. There is no significant difference in the Mg content between the matrix and the nano / micro protrusions.

[0026] Next, the results of irradiating A6063 (Al-Mg-Si alloy) with Ga ions will be described. The pretreatment is the same as that described above. The irradiation of Ga ions is carried out at 30 kV, 2.5 to 45 nA, an irradiation angle of 30°, and in rectangular mode.

[0027] Figure 11 shows aluminum-based nano / micro protrusions formed when A6063 was used as a sample and irradiated with a current of 9.4 nA for irradiation times ranging from 180 seconds to 720 seconds. Figure 12 shows aluminum-based nano / micro protrusions formed when the irradiation time was 1200 seconds. Even when the irradiation time was 1200 seconds, conical nano / micro protrusions were formed in a relatively sparse state. The height of the nano / micro protrusions at 1200 seconds was 2 - 3 μm, which was considerably lower compared to those described above.

[0028] Figure 13 shows an SEM image indicating the analysis location in a state where the irradiation time was 1200 seconds with a current of 45 nA. Figure 14(a) shows the matrix at point 001 (left central part) of Figure 13, Figure 14(b) shows the nano / micro protrusions at point 007 (right central part), and Figure 14(c) shows the analysis results of the nano / micro protrusions at point 006 (lower right part). The analysis results at each point are as shown in Table 1.

[0029]

Table 1

[0030] As shown in Table 1, the Mg content of the nano / micro protrusions is lower compared to the matrix. Also, the Fe content in the nano / micro protrusions at point 006 is extremely high at 17.8 mass%. Generally, the Fe content of A6063 is specified to be 0.7 mass% or less. Thus, due to the variation in the alloy element content of the nano / micro protrusions, there is a possibility of imparting new properties such as strength, corrosion resistance, and electromagnetic characteristics.

[0031] It was also found that in A6063, the generation density of nano / micro protrusions varies significantly depending on the crystal plane. As a result of the IPF (Inverse Pole Figure) analysis of EBSD (Electron Backscatter Diffraction), it was found that the (111) plane, that is, the denser plane, is more likely to be generated, and the sparser plane is less likely to be generated. That is, there is a possibility of efficiently generating nano / micro protrusions by selectively irradiating the crystal plane with Ga ions.

[0032] Table 2 summarizes the morphological characteristics of the aluminum-based nano / micro protrusions obtained in the implementation of the present invention. In the case of the cone, an aspect ratio of 2.5 to 5 for pure aluminum, 3 to 5 for A5052, and 2.5 to 6 for A6063 was preferably obtained. Therefore, in the aluminum-based nano / micro protrusions of the present invention, the aspect ratio is desirably 2.5 to 6. If the aspect ratio is less than 2.5, it cannot be said to be a sufficiently sharp nano / micro protrusion, and the performance as an electron emitter or the like cannot be fully exhibited. If it exceeds 6, the strength is insufficient and it is liable to break. Similarly, in the case of the truncated cone, those with an aspect ratio within the above-mentioned range are desirable.

[0033]

Table 2

[0034] Strictly speaking, the tip of the cone is not a point but slightly circular. The tip radius was between 0.01 and 0.2 μm for all samples. Also, the apex angle was between 12 and 30° when the three types of samples were combined. Here, the apex angle refers to the angle at which the straight lines of the left and right sides intersect in a side view.

[0035] Table 2 also shows the height of the nano / micro protrusions where truncated cones appear. The truncated cones appeared at a height of 1.5 μm or more for pure aluminum, 3 μm or more for A5052, and 1.5 μm or more for A6063. This truncated cone is formed when the tip of the nano / micro protrusion is blown off by Ga ions due to the low strength of the sample used. In the samples used, the strength weakens in the order of A5052 > A6063 > pure aluminum.

[0036] Also, in the implementation of the present invention, in the case of long-time irradiation with Ga ions, the average density of the nano / micro protrusions was achieved at 17 per 100 μm for pure aluminum 2 , 23 per 100 μm for A5052 2 , and 6.5 per 100 μm for A6063 2 . Therefore, the average density is 6.5 per 100 μm 2The above is desirable. It can be said that the density is sufficient to exhibit the performance of the active catalyst or the like. There is no particular upper limit.

Industrial Applicability

[0037] The present invention is expected to be used in a wide variety of applications such as active catalysts, point contacts, electron emitters, lubricated surfaces, battery electrodes, and optical filters.

Claims

1. A method for manufacturing an aluminum-based nano / micro protrusion, characterized in that Ga ions are irradiated onto the surface of aluminum or an aluminum-based alloy to grow in a conical or frustum shape in the irradiation direction of the Ga ions.

2. The method for manufacturing an aluminum-based nano / micro protrusion according to Claim 1, characterized in that compressive residual stress is applied to the surface of aluminum or an aluminum-based alloy before irradiation with Ga ions to promote the growth of the aluminum-based nano / micro protrusion.

Images