A high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material and its preparation method and application

Abstract

The present invention discloses a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material, as well as its preparation method and application. The method comprises the following steps: subjecting CNTs coated with a Cr(OH)3 coating on the surface to solution-assisted ball milling with Cu powder, then filtering and drying, and then dry-milling with different ball milling parameters for more than two times to mix, and vacuum sintering and hot-rolling the obtained composite powder to obtain a composite material. After sintering and hot rolling, the Cr(OH)3 on the surface of the CNTs will undergo in-situ decomposition in the Cu matrix to form Cr2O3, thereby forming a CNTs-Cr2O3-Cu composite interface with a Cr2O3 transition layer. The strength, hardness, and Young's modulus of the Cu-based composite material with this interface are significantly improved, and the strengthening efficiency of CNTs is also significantly improved. The composite material has broad application prospects in fields requiring high mechanical properties, high thermal conductivity, and high electrical conductivity.

Description

Technical Field

[0001] The present invention belongs to the field of new metal-based composite materials, and specifically provides a high-strength and toughness intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material, as well as a preparation method and application thereof. Background Art

[0002] Copper (Cu) has excellent thermal and electrical conductivity and is widely used in fields such as electricity, electrical equipment, and weapons. However, the low strength of pure Cu limits its direct application in industrial fields. To obtain mechanical properties that meet application requirements, adding reinforcements to the Cu matrix has been widely adopted. As a new generation of copper-based composites, carbon nanotube (CNT)-reinforced Cu-based composites have attracted widespread attention from materials researchers worldwide due to the remarkable mechanical properties and excellent thermoelectric properties of CNTs.

[0003] For CNT-reinforced metal matrix composites (MMCs), load transfer and Orowan reinforcement mechanisms have been shown to be the two dominant reinforcement mechanisms of the composites. Their reinforcement efficiency depends on the dispersion and location of the CNTs, as well as the interfacial bonding between the CNTs and the metal matrix. In other words, to fully realize the potential strengthening effect of CNTs on MMCs, the prerequisite is to achieve uniform dispersion of CNTs within the metal matrix grains and strengthen the interfacial bonding.

[0004] The mechanical properties of carbon nanotube-reinforced copper-based composites prepared in existing research still fall far short of the expected ideal values. During the actual composite preparation process, the carbon nanotubes (CNTs) exhibit severe agglomeration and poor interfacial bonding between the CNTs and the copper matrix, significantly weakening the load transfer effect. The reason why CNTs are so prone to agglomeration is that they have a high aspect ratio, resulting in strong van der Waals forces between the CNTs and making them difficult to disperse. This causes the agglomerated CNTs to form pores within themselves during their use as reinforcements, leading to early crack sources in the composite. In poor dispersion, the formation of agglomerated pores can even deteriorate the matrix properties due to the formation of agglomerated pores. It is also worth noting that CNTs are inherently hydrophobic and do not chemically react with the copper matrix. The poor wettability between the copper matrix and the CNTs (in the carbon-copper system, the wetting angle between carbon and copper is 145° at 1150°C) also significantly weakens the load transfer effect. Based on existing needs and problems, in order to achieve high-performance carbon nanotube-reinforced copper-based composites, it is necessary to solve the two key problems of difficult dispersion of carbon nanotubes and poor interface bonding ability with the copper matrix. Summary of the Invention

[0005] In order to overcome the difficulties in dispersing CNTs in a metal matrix due to the strong van der Waals forces between them and the high aspect ratio of CNTs, and to improve the interfacial bonding between CNTs and the metal matrix, the primary purpose of the present invention is to provide a method for preparing a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material.

[0006] Another object of the present invention is to provide a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material prepared by the above method.

[0007] Another object of the present invention is to provide an application of the above-mentioned high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material comprises the following steps:

[0010] (1) Preparation of composite powder: CNTs coated with Cr(OH)3 coating were subjected to solution-assisted ball milling with Cu powder, filtered and dried, and then dry-milled twice or more with different ball milling parameters to obtain composite powder;

[0011] (2) Sintering of composite materials: vacuum sintering the composite powder to obtain a bulk composite material;

[0012] (3) Thermal processing of composite materials: The bulk composite material obtained after sintering is plastically deformed under a hot rolling process, thereby completely eliminating the sintering residual pores and preparing a completely dense bulk composite material.

[0013] This invention proposes coating CNTs with a uniform and continuous Cr(OH)3 coating via a solution chemical reaction before preparing a Cu-based composite material via powder metallurgy. This coating reduces the density difference between the CNTs and Cu powder, promoting uniform dispersion of the CNTs within the mixed powder. Furthermore, by combining the advantages of wet and dry milling, the CNTs are distributed intragranularly within the Cu matrix. A thermal sintering process induces the in-situ conversion of the Cr(OH)3 coating on the CNTs to a Cr2O3 coating. Finally, a hot rolling process achieves full densification of the composite and allows for the re-regulation of the CNT distribution within the Cu matrix. Microstructural characterization of the material demonstrates that the Cr(OH)3 coating on the CNTs promotes CNT dispersion during the mixed powder manufacturing process. Furthermore, the compositional interaction between the Cr2O3 and Cu matrix, as well as the formation of chromium carbides between the Cr2O3 and CNTs, enhances the interfacial bonding of the CNT-reinforced Cu-matrix composite. Due to the intragranular distribution of the reinforcing phase and the novel composite interface structure, the mechanical properties of the composite are significantly improved.

[0014] The CNTs described in step (1) are multi-walled CNTs, and a Cr(OH)3 coating is coated on the surface of the CNTs by a solution direct reaction method to prepare CNTs with a surface coated with a Cr(OH)3 coating. The thickness of the Cr(OH)3 coating on the surface of the CNTs is 3nm to 30nm, and the volume percentage content of CNTs and Cu powder is Cu: 99.5~98vol.%, CNTs: 0.5~2vol%.

[0015] The CNTs with the surface coated with Cr(OH)3 coating in step (1) can be prepared by referring to the existing technology, such as CN114655945A.

[0016] The parameters of the solution-assisted ball milling process in step (1) are as follows: anhydrous ethanol as the ball milling medium, a ball mill speed of 100 to 400 rpm, a ball-to-material mass ratio of 2:1 to 10:1, and a ball milling time of 1 to 10 hours. The wet ball milling process is used to uniformly disperse the CNTs coated with the Cr(OH)3 coating in the Cu powder without destroying the Cr(OH)3 coating structure on the CNTs.

[0017] The process parameters for the two or more dry ball millings in step (1) are as follows: a ball mill speed of 100 to 500 rpm, a ball milling time of 1 to 20 hours, a ball-to-material mass ratio of 2:1 to 20:1, and a stearic acid content of 0.15 wt.% of the powder (referring to the CNTs and Cu powder coated with the Cr(OH)3 coating). The dry ball milling is preferably carried out under an argon protective atmosphere to enhance cold welding and adhesion of the Cu powder, thereby achieving embedding of the CNTs coated with the Cr(OH)3 coating into the Cu powder particles.

[0018] In the composite powder obtained in step (1), CNTs are embedded in the interior of the Cu powder particles rather than being adsorbed on the surface of the particles.

[0019] The sintering process parameters in step (2) are as follows: sintering temperature of 800-1050°C, sintering pressure of 30-50 MPa, sintering time of 20-60 minutes, and sintering atmosphere of vacuum, so as to convert the Cr(OH)3 coating into Cr2O3 and form a Cu-Cr2O3-CNTs composite interface.

[0020] The hot rolling process parameters of step (3) are as follows: hot rolling holding temperature of 700-900°C and downward pressing amount of 30-60% to eliminate pores and regulate the position of CNTs, so as to achieve complete densification of the composite material and distribution of the Cr2O3-CNTs composite phase inside the Cu matrix grains rather than at the grain boundaries.

[0021] A high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material is prepared by the above method.

[0022] The high-strength and toughness intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material described in the present invention can be applied to the fields of high-temperature wear-resistant conductive materials, optoelectronic and electromagnetic special functional materials, and can be widely used in complex functional applications such as integrated circuit lead frames, resistance welding electrodes, armatures, power tool commutators, and conductive equipment with special requirements such as high-temperature wear-resistant wires, cables, electrical switches, contact wires / pantographs, and specific devices such as condensers, radiators, and the inner walls of heat exchangers.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1) Pre-coating Cr(OH)3 coating on CNTs is easier to achieve continuous coating and uniform thickness than directly coating with oxide or carbide coating, and the process is very simple;

[0025] 2) The Cr(OH)3 coating can effectively eliminate the density difference between CNTs and Cu powder, thereby promoting the good and uniform dispersion of CNTs in the mixed powder manufacturing process;

[0026] 3) The combination of wet grinding and dry grinding can not only achieve uniform dispersion of CNTs within the Cu matrix crystal, but also effectively avoid the destruction of the Cr(OH)3 coating on the CNT surface, and achieve the distribution of CNTs within the Cu matrix grains;

[0027] 4) During the composite material preparation process, the Cr(OH)3 coating undergoes in-situ thermal decomposition and is converted into Cr2O3. The Cr2O3 converted by the in-situ reaction can produce a stronger interaction with the Cu matrix and react in-situ with CNTs to form chromium carbide. The resulting CNTs-Cr2O3-Cu matrix interface is well bonded.

[0028] 5) The composite material of the present invention has excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0030] Figure 1 These are the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization results of the CNTs with surface coated with Cr(OH)3 coating used in Example 1; (a) is the SEM image of the CNTs with surface coated with Cr(OH)3 coating, (b) is the TEM image of the CNTs with surface coated with Cr(OH)3 coating, and the inset is the corresponding HRTEM image.

[0031] Figure 2 These are the SEM characterization results of the composite powder obtained in step (2) of Example 1; wherein (a) is the SEM image of the composite powder, and (b) is the magnified SEM image of the composite powder.

[0032] Figure 3 These are the TEM characterization results of the intracrystalline distribution characteristics of the Cr2O3-CNTs composite phase in the Cu matrix of the composite material prepared in Example 1; (a) is a dark-field TEM image of the composite material, and (b) is an enlarged dark-field TEM image of the square area in (a).

[0033] Figure 4 TEM characterization results of the microstructural characteristics of the Cr2O3-CNTs composite phase in the Cu matrix of the composite material prepared in Example 1; wherein (a) is a bright field TEM image of the composite phase in the matrix, the inserted SAED pattern is from the circle 1 area in (a), (b) is an HRTEM image of the in-situ formed Cr2O3, (c) is an HRTEM image of the interface structure between Cr2O3 and CNTs, and the inserted FFT image is from the square area marked in (c), (d) is an HRTEM image of the interface structure between Cr3C2 and Cr2O3, and the inserted FFT image is from Cr3C2 in (d), (e) is an HRTEM image of Cr3C2 in (d), and (f) is the Cr recorded in the circle 2 area in (a). 23SAED image of C6, (g) is the enlarged dark field TEM image of the square g marked in (a), and (h) is the element line scan result along the marked oblique line in (g).

[0034] Figure 5 3 is a comparison chart of the mechanical properties of the composite material prepared in Example 1 and pure copper. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiment of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention. Obviously, the embodiment described is a part of the embodiment of the present invention, rather than all embodiments. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Reagents used in the embodiment can be purchased from the market routinely unless otherwise specified.

[0036] The ball-to-material ratios described in the following examples are by mass, g / g.

[0037] The CNTs used in the following examples are multi-walled CNTs with a diameter of about 10±1 nm and a length of about 2-6 μm.

[0038] Example 1:

[0039] The preparation of a Cu-based composite material with an intracrystalline Cr2O3-CNTs composite phase reinforced was carried out using 99.25 vol.% pure Cu powder and 0.75 vol.% CNTs powder as raw materials. The preparation steps are as follows:

[0040] (1) According to the process scheme of Example 2 described in CN114655945A, a Cr(OH)3 coating with a thickness of 3 to 10 nm was coated on the surface of CNTs using a solution direct reaction process (such as the attached Figure 1 As shown), CNTs with a surface coated with Cr(OH)3 were prepared;

[0041] (2) The CNTs coated with Cr(OH)3 coating on the surface were mixed with the Cu powder of the above ratio by solution-assisted ball milling and subsequent two-step dry ball milling to obtain a composite powder; the parameters of the solution-assisted ball milling process were: anhydrous ethanol as the ball milling medium, a ball mill speed of 350 rpm, a ball-to-material ratio of 8:1, and a ball milling time of 5 h; the dry ball milling mixing was carried out under argon protection, and the parameters of the first stage were: a ball mill speed of 350 rpm, a ball milling time of 5 h, and a ball-to-material ratio of 10:1; the ball milling medium stearic acid was 0.15 wt.% of the powder; the parameters of the second stage of dry ball milling mixing were: a ball mill speed of 500 rpm, a ball milling time of 5 h, and a ball-to-material ratio of 10:1; the obtained composite powder was as shown in the attached Figure 2 As shown, CNTs are embedded in the interior of Cu powder particles rather than adsorbed on the particle surface;

[0042] (3) The prepared composite powder was sintered at 1000°C for 30 min. During the sintering process, a mechanical pressure of 40 MPa was applied to the sample in a vacuum atmosphere.

[0043] (4) The sintered sample was hot rolled at 800°C with a reduction of 50% in multiple passes to obtain a Cr2O3-CNTs composite phase reinforced Cu-based composite material.

[0044] In the composite material prepared in this embodiment, the Cr2O3-CNTs composite phase is distributed within the crystal, as shown in the attached Figure 3 In addition, the in-situ formed Cr2O3 has a high degree of crystallinity and forms a tightly bonded interface with CNTs without any gaps. Cr carbides are also formed at the interface, which helps to improve the interface strength. Figure 4 The mechanical properties of the prepared composite material are significantly improved compared to pure copper, as shown in the attached Figure 5 As shown, its yield strength, Vickers hardness (HV0.2) and Young's modulus are 383.5 MPa, 117.3 and 112.5 GPa respectively, which are significantly higher than 120.9 MPa, 87.1 and 93.9 GPa of pure copper.

[0045] Example 2:

[0046] The preparation of a Cu-based composite material reinforced with a Cr2O3-CNTs composite phase distributed within the crystal was carried out using 99.0 vol.% pure Cu powder and 1.0 vol.% CNTs powder as raw materials. The preparation steps are as follows:

[0047] (1) According to the process scheme of Example 2 described in CN114655945A, a Cr(OH)3 coating with a thickness of 3 to 10 nm was coated on the surface of CNTs using a solution direct reaction process to prepare CNTs with a surface treated with a Cr(OH)3 coating;

[0048] (2) CNTs with a surface coated with Cr(OH)3 coating were mixed with the Cu powder of the aforementioned proportion by solution-assisted ball milling and subsequent two-step dry ball milling to obtain a composite powder; the parameters of the solution-assisted ball milling process were: anhydrous ethanol as the ball milling medium, a ball mill speed of 350 rpm, a ball-to-material ratio of 5:1, and a ball milling time of 5 h; the dry ball milling mixing was carried out under argon protection, and the parameters of the first stage were: a ball mill speed of 350 rpm, a ball milling time of 5 h, and a ball-to-material ratio of 10:1; the ball milling medium stearic acid was 0.15 wt.% of the powder; the parameters of the second stage of dry ball milling mixing were: a ball mill speed of 500 rpm, a ball milling time of 5 h, and a ball-to-material ratio of 10:1.

[0049] (3) The prepared composite powder was sintered at 1000°C for 30 min. During the sintering process, a mechanical pressure of 40 MPa was applied to the sample in a vacuum atmosphere.

[0050] (4) The sintered sample was hot rolled at 800°C with a reduction of 50% in multiple passes to obtain a Cu-based composite material reinforced with an intragranular Cr2O3-CNTs composite phase. The yield strength, Vickers hardness (HV0.2), and Young's modulus of the bulk composite prepared in this example were 410.3 MPa, 126.0 GPa, and 119.7 GPa, respectively.

[0051] Example 3:

[0052] The preparation of a Cu-based composite material reinforced with a Cr2O3-CNTs composite phase distributed within the crystal was carried out using 99.0 vol.% pure Cu powder and 1.0 vol.% CNTs powder as raw materials. The preparation steps are as follows:

[0053] (1) According to the process scheme of Example 4 described in CN114655945A, a Cr(OH)3 coating with a thickness of 10 to 30 nm was coated on the surface of CNTs using a solution direct reaction process to obtain CNTs with a surface treated with a Cr(OH)3 coating;

[0054] (2) CNTs with a surface coated with Cr(OH)3 coating were mixed with Cu powder of the aforementioned proportion by solution-assisted ball milling and subsequent two-step dry ball milling to obtain a composite powder; the parameters of the solution-assisted ball milling process were: anhydrous ethanol as the ball milling medium, a ball mill speed of 350 rpm, a ball-to-material ratio of 8:1, and a ball milling time of 5 h; the dry ball milling mixing was carried out under argon protection, and the parameters of the first stage were: a ball mill speed of 350 rpm, a ball milling time of 5 h, and a ball-to-material ratio of 10:1; the ball milling medium stearic acid was 0.15 wt.% of the powder; the parameters of the second stage of dry ball milling mixing were: a ball mill speed of 500 rpm, a ball milling time of 5 h, and a ball-to-material ratio of 10:1.

[0055] (3) The prepared composite powder was sintered at 1000°C for 30 min. During the sintering process, a mechanical pressure of 40 MPa was applied to the sample in a vacuum atmosphere.

[0056] (4) The sintered sample was hot rolled at 800°C with a reduction of 50% in multiple passes to obtain a Cu-based composite material reinforced with an intragranular Cr2O3-CNTs composite phase. The yield strength, Vickers hardness (HV0.2), and Young's modulus of the bulk composite material prepared in this example were 403.1 MPa, 139.4 GPa, and 124.5 GPa, respectively.

[0057] Example 4:

[0058] The preparation of the Cu-based composite material with a Cr2O3-CNTs composite phase distributed in the crystal was carried out using 98.5 vol.% pure Cu powder and 1.5 vol.% CNTs powder as the raw materials. The preparation steps are as follows:

[0059] (1) According to the process scheme of Example 4 described in CN114655945A, a Cr(OH)3 coating with a thickness of 10 to 30 nm was coated on the surface of CNTs using a solution direct reaction process to obtain CNTs with a surface treated with a Cr(OH)3 coating;

[0060] (2) CNTs with a surface coated with Cr(OH)3 coating were mixed with the Cu powder of the aforementioned proportion by solution-assisted ball milling and subsequent two-step dry ball milling to obtain a composite powder; the parameters of the solution-assisted ball milling process were: anhydrous ethanol as the ball milling medium, a ball mill speed of 350 rpm, a ball-to-material ratio of 8:1, and a ball milling time of 5 h; the dry ball milling mixing was carried out under argon protection, and the parameters of the first stage were: a ball mill speed of 400 rpm, a ball milling time of 5 h, and a ball-to-material ratio of 8:1; the ball milling medium stearic acid was 0.15 wt.% of the powder; the parameters of the second stage of dry ball milling mixing were: a ball mill speed of 500 rpm, a ball milling time of 5 h, and a ball-to-material ratio of 10:1.

[0061] (3) The prepared composite powder was sintered at 1000°C for 30 min. During the sintering process, a mechanical pressure of 40 MPa was applied to the sample in a vacuum atmosphere.

[0062] (4) The sintered sample was hot rolled at 800°C with a reduction of 50% in multiple passes to obtain a Cu-based composite material reinforced with an intragranular Cr2O3-CNTs composite phase. The yield strength, Vickers hardness (HV0.2), and Young's modulus of the bulk composite material prepared in this example were 432.7 MPa, 167.2 GPa, and 143.8 GPa, respectively.

[0063] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material, characterized in that: The following steps are involved: (1) CNTs coated with Cr(OH)3 coating and Cu powder were subjected to solution-assisted ball milling, filtered and dried, and then dry-milled for more than two times with different ball milling parameters to obtain composite powder; (2) vacuum sintering the composite powder to obtain a bulk composite material; the sintering process parameters are as follows: sintering temperature of 800-1050° C., sintering pressure of 30-50 MPa, sintering time of 20-60 min, and vacuum sintering atmosphere; (3) hot rolling the bulk composite material obtained after sintering to obtain the high-strength and toughness intragranular distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material; the hot rolling process parameters are as follows: hot rolling holding temperature 700-900°C, and downward pressing amount 30-60%.

2. The method for preparing a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material according to claim 1, characterized in that: The CNTs whose surfaces are coated with Cr(OH)3 coating in step (1) are prepared by coating the CNTs with Cr(OH)3 coating on the surface using a solution direct reaction method; the CNTs are multi-walled CNTs, and the thickness of the Cr(OH)3 coating on the surface of the CNTs is 3nm to 30nm.

3. The method for preparing a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material according to claim 1, characterized in that: The volume percentage content of the CNTs and Cu powder in step (1) is: Cu: 99.5-98 vol.%, CNTs: 0.5-2 vol%.

4. The method for preparing a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material according to claim 1, characterized in that: The parameters of the solution-assisted ball milling process in step (1) are: anhydrous ethanol is used as the ball milling medium, the ball mill speed is 100 to 400 rpm, the ball-to-material mass ratio is 2:1 to 10:1, and the ball milling time is 1 to 10 h.

5. The method for preparing a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material according to claim 1, characterized in that: The process parameters of the dry ball milling for more than two times in step (1) are as follows: a ball mill speed of 100 to 500 rpm, a ball milling time of 1 to 20 h, a ball-to-material mass ratio of 2:1 to 20:1; stearic acid as the ball milling medium, and stearic acid accounting for 0.15 wt.% of the powder; and dry ball milling is carried out under an argon protective atmosphere.

6. The method for preparing a high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material according to claim 1, characterized in that: In the composite powder obtained in step (1), the CNTs are embedded in the interior of the Cu powder particles rather than being adsorbed on the surface of the particles.

7. A high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material, characterized in that The invention discloses a novel nanostructured carbonyl phosphate ...

8. Application of the high-strength and tough intracrystalline distributed Cr2O3-CNTs composite phase reinforced Cu-based composite material according to claim 7 in the field of high-temperature wear-resistant conductive materials or opto-electromagnetic special functional materials.

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