A method for preparing magnetic nickel tapered nanowires

Abstract

The present invention relates to a method for preparing magnetic nickel tapered nanowires, comprising the following steps: (1) irradiating and sensitizing a polymer template with a latent track by a fast heavy ion beam; (2) sputtering a gold conductive layer on one side of the polymer template with the latent track, and then depositing a copper conductive layer on the surface of the gold conductive layer by electrochemical deposition; (3) etching the side of the polymer template with the latent track without the gold-copper conductive layer using an etching solution to obtain a polymer template with tapered linear channels; (4) electrochemically depositing magnetic nickel tapered nanowires on the side of the polymer template with the tapered linear channels without the gold-copper conductive layer; and (5) stripping the gold-copper conductive layer to obtain the magnetic nickel tapered nanowires. The present invention is simple and efficient, and for the first time achieves the controllable preparation of magnetic nickel tapered nanowire arrays, successfully preparing small-sized magnetic nickel tapered nanowire arrays with excellent microwave absorption performance.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic nanomaterials, and in particular to a method for preparing magnetic metal nickel tapered nanowires. Background Art

[0002] While scientific and technological progress continues to advance industrialization and intelligence, it also leads to serious electromagnetic wave pollution, which significantly impacts human health, the ecological environment, and national security. Microwave absorbing materials are an effective solution to various problems, including electromagnetic pollution and interference. Among the many electromagnetic functional materials, high-frequency soft magnetic materials, with their inherent advantages such as good magnetic loss, dielectric loss, and high snooker limit, are ideal absorbers and have therefore attracted extensive attention and research.

[0003] Many scholars have conducted extensive research in the field of absorbing materials, revealing the relationship between the performance of absorbing materials and novel structures, such as core-shell structures, hollow / porous structures, flower-like structures, foam structures and one-dimensional (1D) structures. These results show that structure is crucial to regulating the performance of absorbing materials.

[0004] One-dimensional magnetic nanomaterials, due to their strong shape anisotropy and parallel orientation distribution in arrays, can significantly improve electromagnetic wave absorption performance and are considered to have great potential in the field of electromagnetic wave absorption. Low-symmetry tapered nanowires, in particular, are particularly promising. The simultaneous reduction in geometric size and symmetry within magnetic nanostructures is bound to produce novel magnetic phenomena and even enhance application performance.

[0005] There are numerous methods for preparing one-dimensional magnetic nanostructures, including chemical vapor deposition, sol-gel, electrospinning, arc discharge, molecular beam epitaxy, and template-assisted electrochemical deposition. However, these methods often exhibit shortcomings such as easy clustering, oxidation, geometrical uncertainty, and the inability to fabricate them on a large scale. Consequently, a simple and efficient method for preparing tapered magnetic metal nanowires remains lacking. The complexity and limited controllability of preparing ideal low-symmetry tapered nanowire structures have hindered the application of magnetic nickel tapered nanowire arrays for high-frequency microwave absorption. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a simple and efficient method for preparing magnetic metal nickel tapered nanowires.

[0007] To solve the above problems, the present invention provides a method for preparing magnetic nickel tapered nanowires, comprising the following steps:

[0008] (1) After the polymer template is irradiated and sensitized by a fast heavy ion beam, a polymer template with a latent track is obtained;

[0009] (2) sputtering a gold conductive layer on one side of the polymer template of the latent track, and then using electrochemical deposition, with a copper electrode as the anode and the conductive gold layer as the cathode, depositing a copper conductive layer on the surface of the gold conductive layer;

[0010] (3) etching the side of the polymer template of the latent track without the gold-copper conductive layer using an etching solution to obtain a polymer template with tapered linear channels;

[0011] (4) Electrochemically depositing magnetic nickel tapering nanowires on the side of the polymer template with the tapering linear channels without the gold-copper conductive layer using a Ni electrode as an anode and a conductive gold layer as a cathode;

[0012] ⑸ Peel off the gold-copper conductive layer to obtain magnetic metal nickel gradually thinning nanowires.

[0013] The material of the polymer template in step (1) is polycarbonate, and its thickness is 12 μm.

[0014] The conditions for the fast heavy ion beam irradiation in step (1) are that the heavy ions are xenon ions or tantalum ions, and the irradiation dose is 1×10 8 ions / cm 2 .

[0015] The sensitization conditions in step (1) are to sensitize the front and back sides under the ultraviolet sensitization lamp for 10 minutes each, and the sensitization power is 50 mW / cm 2 .

[0016] The duration of sputtering the gold conductive layer in step (2) is 134 s.

[0017] The electrochemical deposition conditions in step (2) are to use a mixed electrolyte of 75 g / l CuSO4·5H2O and 30 g / l H2SO4 and apply a constant voltage of 0.7 V at room temperature.

[0018] The etching solution in step (3) is a mixed solution of methanol and 9 M sodium hydroxide solution in a volume ratio of 1:9; the etching temperature is room temperature and the etching time is 12±3 min.

[0019] The electrochemical deposition conditions in step (4) are to use a mixed electrolyte of 250 g / l NiSO4·6H2O, 50 g / l NiCl2·6H2O and 30 g / l H3BO3, and apply a constant voltage of 1.35 V at room temperature.

[0020] A magnetic nickel tapered nanowire is prepared by the method described above.

[0021] The magnetic nickel tapered nanowires are characterized in that the average length of the magnetic nickel tapered nanowires is 10.7±0.4 μm, the minimum diameter is 20 nm, and the tapering angle is θ It is 0.58±0.09°.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The present invention prepares magnetic nickel tapered nanowires by combining asymmetric etching and electrochemical deposition with a fast heavy ion track template. The diameter of the obtained nanowires changes gradiently along the axial direction, and the minimum characteristic size can reach 20 nm.

[0024] 2. The preparation method of the present invention is clean, efficient, does not require post-processing, and can be prepared on a large scale.

[0025] 3. The present invention utilizes a fast heavy ion track template method for fabrication. The magnetic nickel nanowire arrays stored within the template are protected from air and are therefore resistant to oxidation. The fast heavy ion irradiation fluence determines the spacing of the magnetic nickel nanowires within the template. By regulating the irradiation fluence, the spacing of the magnetic nickel nanowires can be controlled, resulting in a fabricated array that is less likely to cluster.

[0026] 4. The template track irradiated by fast heavy ions in the present invention is uniform and continuous. Combined with asymmetric etching, uniform tapering linear channels can be etched inside the template. The geometric morphology of the magnetic nickel tapering nanowires is limited by the channel size inside the template. The etching solution composed of methanol and 9 M sodium hydroxide solution can react with the polymer in the track damage area in the fast heavy ion track template. Among them, methanol can perform horizontal body etching on the polymer, and sodium hydroxide solution can perform vertical track etching on the polymer. Therefore, by controlling the ratio of methanol and sodium hydroxide solution in the etching solution, nanoscale channels with specific geometry can be accurately etched in the polymer template. By selecting templates of different thicknesses, the length parameters of the magnetic nickel tapering nanowires can be effectively controlled. Therefore, based on the advantage of being able to strictly control the geometric dimensions of the nanostructure, the controllable preparation of magnetic nickel tapering nanowires has been achieved for the first time, and the resulting tapering nanowires have a smooth surface.

[0027] 5. Compared with other current methods for preparing magnetic nanostructures, the magnetic metal nickel tapered nanowires prepared by the method of the present invention have excellent microwave absorption performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0029] Figure 1 It is a preparation flow chart of the present invention.

[0030] Figure 2 The gold conductive layer of the tapered magnetic nickel nanowires of the present invention. (a) A polymer template with a gold spraying time of 134 seconds; (b) A polymer template with a gold spraying time of 268 seconds; (c) An SEM image of the residual gold layer on the cone tip after a gold spraying time of 268 seconds (scale: 2 μm); (d) An SEM image of the residual gold layer on the cone tip after a gold spraying time of 268 seconds (scale: 15 μm).

[0031] Figure 3 The SEM images of the magnetic nickel tapered nanowires of the present invention are shown in Figure 1. a represents a single magnetic nickel tapered nanowire; b represents an array of magnetic nickel tapered nanowires.

[0032] Figure 4 Figure 1 shows the SEM geometric dimensions of a single magnetic nickel tapered nanowire and the length parameters of the tapered nanowire. (a) shows the SEM geometric dimensions of a single wire; (b) shows the definition of the tapering angle; and (c) shows the length of the magnetic nickel tapered nanowire (scale: 5 μm).

[0033] Figure 5 This is a statistical characterization of the SEM morphology of a single magnetic nickel tapered nanowire of the present invention. TNW-a is the first single magnetic nickel tapered nanowire; TNW-b is the second single magnetic nickel tapered nanowire; and TNW-c is the third single magnetic nickel tapered nanowire.

[0034] Figure 6 TEM characterization images of the magnetic nickel tapered nanowires of the present invention. a is the diffraction ring at the tip of the magnetic nickel tapered nanowire; b is the TEM image of the tip of the magnetic nickel tapered nanowire (minimum diameter up to 20 nm).

[0035] Figure 7 The electromagnetic parameters of the magnetic nickel nanowires of the present invention are as follows: a is the dielectric constant of the magnetic nickel nanowires; b is the magnetic permeability of the magnetic nickel nanowires.

[0036] Figure 8 This is a graph of microwave reflection loss RL (Reflection Loss) of the magnetic nickel tapered nanowires of the present invention.

[0037] Figure 9This is a performance diagram of the magnetic metal nickel tapered nanowires of the present invention. Among them: Ref.1 is Li Y, Wei H, ChenL, et al. Regulating the Electronic Structure of MAX Phases Based on Rare EarthElement Sc to Enhance Electromagnetic Wave Absorption[J]. ACS Nano, 2024, 18(14): 10019~10030; Ref.2 is Zhang Y, Zhang L, Tang L, et al. S-NiSe / HGNanocomposites with Balanced Dielectric Loss Encapsulatedin Room-TemperatureSelf-Healing Polyurethane for Microwave Absorption and Corrosion Protection[J]. ACS Nano, 2024, 18(11): 8411~8422; Ref.3 is Cheng J, Li Y, Raza H, et al. Cross-Scale Synergistic Manipulation of Dielectric Genes in PolymetallicSulfides from Micropolarization to MacroconductanceToward Wide-Band MicrowaveAbsorption[J]. Advanced Functional Materials, 2024,n / a(n / a): 2405643; Ref.4 is Wu P, Kong X, Feng Y, etc. Phase Engineering on Amorphous / Crystalline γ‐Fe2O3 Nanosheets for Boosting Dielectric Loss and High‐Performance Microwave Absorption[J]. Adv Funct Materials, 2023: 2311983; Ref.5 is Qian Y, Wu Z, Lv X, etc. Fixed-Point Atomic Regulation Engineered Low-Thickness Wideband Microwave Absorption[J]. Small, 2024, n / a(n / a): 2401878; Ref.6 is Tang Z, Xu L, Xie C, etc. Synthesis of CuCo2S4@Expanded Graphite with crystal / amorphous heterointerface and defects for electromagnetic wave absorption[J]. Nat Commun, 2023, 14(1): 5951; Ref.7 is Wen C, Li X, Zhang R, etc. High-Density Anisotropy Magnetism Enhanced Microwave Absorption Performance in Ti3C2T x MXene@Ni Microspheres[J]. ACS Nano, 2022, 16(1): 1150~1159; Ref.8 is Liu P, Gao S, Wang Y, etc. Carbon nanocages with N-doped carbon inner shell and Co / N-doped carbon outer shell as electromagnetic wave absorption materials[J]. Chemical Engineering Journal, 2020, 381: 122653; Ref.9 is Liang L, Li Q, Yan X, etc. Multifunctional Magnetic Ti3C2T xMXene / Graphene Aerogel with Superior Electromagnetic Wave Absorption Performance[J]. ACS Nano, 2021, 15(4): 6622~6632; Ref.10 is Wang Y, Qu Z, Wang W, et al. Multidimensional nanomaterialssynergistic polyimide nanofiber / MXene / NiFe2O4hybrid aerogel for high-performance microwave absorption[J]. Chemical Engineering Journal, 2023, 470:144435. DETAILED DESCRIPTION

[0038] like Figure 1 As shown, a method for preparing magnetic nickel tapered nanowires comprises the following steps:

[0039] (1) The polymer template is first irradiated with a fast heavy ion beam, where the heavy ions are xenon ions or tantalum ions, and the irradiation dose is 1×10 8 ions / cm 2 Then sensitize the front and back sides under UV sensitization lamp for 10 minutes each, with a sensitization power of 50 mW / cm 2 After the sensitization is completed, a polymer template with latent tracks is obtained.

[0040] Wherein: the material of the polymer template is polycarbonate, and its thickness is 12 μm.

[0041] (2) A gold conductive layer was sputtered onto the polymer template side of the latent track for 134 s. A copper conductive layer was then deposited onto the gold conductive layer using electrochemical deposition, using a copper electrode as the anode and the conductive gold layer as the cathode. A mixed electrolyte of 75 g / l CuSO₄·5H₂O and 30 g / l H₂SO₄ was used, and a constant voltage of 0.7 V was applied at room temperature.

[0042] (3) Etch the side of the latent track polymer template without the gold-copper conductive layer using an etchant consisting of a 1:9 volume ratio (ml / ml) of methanol and 9 M sodium hydroxide solution. Etch at room temperature for 12 ± 3 minutes. Upon completion, a polymer template with tapering linear channels is obtained.

[0043] (4) On the side of the polymer template with tapering linear channels without the gold-copper conductive layer, a Ni electrode was used as the anode and the conductive gold layer was used as the cathode. A mixed electrolyte of 250 g / l NiSO4·6H2O, 50 g / l NiCl2·6H2O and 30 g / l H3BO3 was used, and a constant voltage of 1.35 V was applied at room temperature to electrochemically deposit magnetic metal nickel tapering nanowires.

[0044] ⑸ Peel off the gold-copper conductive layer to obtain the magnetic metal nickel tapering nanowires preserved in the polymer template.

[0045] The average length of the magnetic nickel tapered nanowires is 10.7±0.4 μm, the minimum wire diameter is 20 nm, and the tapering angle is θ It is 0.58±0.09°.

[0046] The fast heavy ion track template in the present invention refers to a polymer film having tapering linear nanopores obtained by etching with specific chemical reagents after fast heavy ion irradiation.

[0047] The following description will be made using PC film as an example.

[0048] A method for preparing magnetic nickel tapered nanowires includes the following steps:

[0049] (1) The fast heavy ion beam accelerated by the accelerator carries high energy and bombards the polymer surface, breaking a large number of chemical bonds in the polymer to form a highly damaged area. From this area, the polymer chains undergo cross-linking reactions or break and recombine to form track structures. The fast heavy ions are xenon ions or tantalum ions, and the irradiation dose is 1×10 8 ions / cm 2 .

[0050] During the UV-sensitization of the ion track template, the track core region inside the PC template undergoes photooxidation and photodegradation, the polymer chains are cut and release gas, and the polymer fragments are broken into tiny pieces. Therefore, UV-sensitization can improve the etching efficiency of the etching solution on the track region. The latent track template was UV-sensitized on both sides for 10 minutes each, with a sensitization power of 50 mW / cm 2 .

[0051] ⑵ Use a magnetron sputtering device to sputter a gold conductive layer for 134 s on one side of the latent track polymer template.

[0052] Research has shown that a smaller diameter at the tip of a tapered magnetic nickel nanowire facilitates electromagnetic wave penetration, ultimately leading to strong electromagnetic wave absorption by the nanowire. The thickness of the sputtered gold layer plays a crucial role in controlling the tip diameter of the nanowire. By controlling the sputtering time and thus the thickness of the gold conductive layer, the optimal sputtering time parameters were achieved, enabling the tip diameter of the magnetic nickel nanowire to be as small as 20 nm, laying the foundation for strong electromagnetic wave absorption by the nanowire.

[0053] Figure 2 (a-b) are comparison images of polymer templates with gold spraying time of 134 s and 268 s. Figure 2 (c,d) are SEM images of tapered magnetic nickel nanowires at a sputtering time of 268 s. As can be seen, the excessively thick gold layer is difficult to remove, remaining on the tip of the tapered nanowire. The residual gold layer at the tip negatively impacts electromagnetic wave absorption. After a series of comparative experiments, a sputtering time of 134 s was determined to be the optimal parameter for preparing tapered magnetic nickel nanowires.

[0054] Using copper as electrodes, a copper conductive layer was electrochemically deposited on the gold layer. The copper conductive layer provided auxiliary support for the PC template. A mixed solution of 75 g / l CuSO₄·5H₂O and 30 g / l H₂SO₄ served as the electrolyte. A copper rod was placed as the electrode, and a DC voltage of 0.7 V was applied. The deposition time was approximately 17 minutes.

[0055] (3) Using an etching solution to etch the side of the latent track polymer template without the gold-copper conductive layer, a polymer template with tapered linear channels is obtained.

[0056] The etching solution is a mixture of methanol and 9 M sodium hydroxide solution in a volume ratio of 1:9, which is then allowed to stand for more than one day. The etching temperature is room temperature, and the etching time is 12 ± 3 min.

[0057] A gold rod was inserted into the etching solution as an electrode, and a 0.2 V DC voltage was applied. The positive and negative electrodes were connected to a Model 6482 picoammeter (Keithley, USA). The stencil current was measured in real time. The etching progress of the tapered channels was determined based on the current curve, and the stencil was removed promptly. After etching was completed, the remaining etching solution in the sedimentation tank was aspirated with a rubber-tipped dropper and replaced with deionized water. The deionized water was allowed to remain in the sedimentation tank for five minutes to ensure that no etching solution or etching residue remained in the stencil channels.

[0058] (4) Electrochemically depositing magnetic nickel tapering nanowires on one side of the gold-free copper conductive layer of the tapering linear nanochannel template.

[0059] A mixed deposition solution of 250 g / l NiSO4·6H2O, 50 g / l NiCl2·6H2O, and 30 g / l H3BO3 was used. A Ni electrode was used as the anode. A constant voltage of 1.35 V was applied at room temperature, and the deposition current was monitored by a 6482 picoammeter.

[0060] (5) Peeling off the gold-copper conductive layer yields magnetic nickel tapered nanowires. The strong bonding between copper and gold forms the gold-copper conductive layer, while the weaker bonding between the gold conductive layer and the polymer template allows the layer to be removed by mechanically peeling off the copper substrate. This leaves only the tapered nanowire array and the polycarbonate template, which is unresponsive and undisturbed by electromagnetic fields, in subsequent magnetic measurements.

[0061] The average length of the magnetic nickel tapered nanowires prepared by the above method is 10.7±0.4 μm, the minimum wire diameter is 20 nm, and the tapering angle is θ The SEM morphology of a single nanowire and its array is shown in Figure 2. Figure 3 As shown in Figure 2, the Ni nanocone array is oriented perpendicular to the substrate and arranged in parallel. Figure 4 As shown, the length L of the sample is measured. Three tapering nanowires are randomly selected and divided into three sections, namely "upper, middle and lower". The diameter D of the tapering nanowires is measured by taking regions of the same length ( Figure 5 ), through the formula , calculate the tapering angle of the tapering nanowire θ , the results are shown in Table 1.

[0062] Table 1 Geometrical dimensions of magnetic nickel tapered nanowires

[0063]

[0064] The statistical results show that the average value of the three-segment tapering angle of a single tapering nanowire is 0.58±0.09°, with a very small error value, indicating that the tapering angle of the magnetic metal nickel nanowire prepared by the template method combined with asymmetric etching and electrochemical deposition can be approximately constant. As the tapering nanowire grows, its diameter increases linearly, and the surface of the tapering nanowire is smooth and has no abrupt changes. TEM characterization of the tapering nanowire (such as Figure 6 The results show that the tapering nanowires are polycrystalline and have a minimum diameter of 20 nm.

[0065] The electromagnetic parameters of the sample were tested using a vector network analyzer to obtain the magnetic permeability, dielectric constant and reflection loss (RL) data of the tapered nanowires at 2-18 GHz, which were used to evaluate the microwave absorption capacity of the sample.

[0066] Figure 7a and Figure 7 b characterizes the dielectric constant and permeability of the tapered nanowires. The real part represents energy storage, while the imaginary part represents energy loss. The real and imaginary parts of the dielectric constant of the tapered nanowires show no distinct peaks, and the imaginary part fluctuates between 0 and 1. The imaginary part of the permeability of the tapered nanowires is relatively flat in the frequency range of 2-8 GHz. From 8-18 GHz, it shows a clear trend of first rising and then falling, reaching a peak at 16 GHz. The resonant peak of the imaginary part of the permeability represents resonant loss. Magnetic materials typically lose electromagnetic waves through mechanisms such as hysteresis loss, eddy current loss, natural resonance, and exchange resonance. Hysteresis loss is primarily concentrated in the low-frequency band, making its contribution negligible. The nanometer-scale diameter of the tapered nanowires minimizes eddy current loss. Therefore, it is inferred that natural resonance and exchange resonance are the primary magnetic loss mechanisms for microwave absorption in the tapered nanowire array. Electromagnetic waves entering the magnetic nickel tapered nanowires are significantly lost through magnetic resonance, achieving excellent microwave absorption performance.

[0067] Using the obtained electromagnetic parameters and based on the transmission line theory, we calculated the reflection loss RL of the magnetic nickel tapered nanowires ( Figure 8 ), the electromagnetic absorption performance of tapered magnetic nickel nanowires was evaluated. An RL value below -10 dB indicates 90% absorption of electromagnetic waves, corresponding to the effective absorption band (EAB). A three-dimensional reflection loss plot shows that the sample with tapered nanostructures exhibits excellent RL loss strength, achieving strong microwave absorption (-50.11 dB / mm) at a low matching thickness. At a matching thickness of 1.58 mm, the absorption intensity reached -79.18 dB, and the absorption bandwidth reached 6.6 GHz.

[0068] Figure 9 The microwave absorption performance of tapered magnetic nickel nanowires with a 1° taper angle was compared with that of other advanced microwave absorbing materials. The results show that the microwave absorption performance of tapered magnetic nickel nanowires far exceeds that of comparable metal-based microwave absorbing materials, as well as that of most other carbon materials, dielectric materials, and composite materials. This superior microwave absorption performance stems from the low dielectric loss due to the array structure, the inherent advantages of the natural resonance loss of magnetic materials, and the strong exchange resonance loss due to size modulation. These factors lay the foundation for the application of tapered magnetic nickel nanowires in microwave absorption.

Claims

1. A method for preparing magnetic nickel tapered nanowires, comprising the following steps: (1) After the polymer template is irradiated and sensitized by a fast heavy ion beam, a polymer template with a latent track is obtained; the conditions for the fast heavy ion beam irradiation are that the heavy ions are xenon ions or tantalum ions, and the irradiation dose is 1×10 8 ions / cm 2 ; (2) sputtering a gold conductive layer on one side of the polymer template of the latent track, and then using electrochemical deposition, with a copper electrode as the anode and the conductive gold layer as the cathode, depositing a copper conductive layer on the surface of the gold conductive layer at room temperature; (3) etching the side of the polymer template of the latent track without the gold-copper conductive layer using an etching solution at room temperature to obtain a polymer template with tapered linear channels; (4) Electrochemically depositing magnetic nickel tapering nanowires at room temperature using a Ni electrode as an anode and a conductive gold layer as a cathode on the side of the polymer template with tapering linear channels without the gold-copper conductive layer; ⑸ The gold-copper conductive layer was peeled off to obtain magnetic nickel tapered nanowires. The average length of the magnetic nickel tapered nanowires was 10.7±0.4 μm, the minimum diameter was 20 nm, and the tapering angle was θ It is 0.58±0.09°.

2. The method for preparing magnetic nickel tapered nanowires according to claim 1, wherein: The material of the polymer template in step (1) is polycarbonate, and its thickness is 12 μm.

3. The method for preparing magnetic nickel tapered nanowires according to claim 1, wherein: The sensitization conditions in step (1) are to sensitize the front and back sides under the ultraviolet sensitization lamp for 10 minutes each, and the sensitization power is 50 mW / cm 2 .

4. The method for preparing magnetic nickel tapered nanowires according to claim 1, wherein: The duration of sputtering the gold conductive layer in step (2) is 134 s.

5. The method for preparing magnetic nickel tapered nanowires according to claim 1, wherein: The electrochemical deposition conditions in step (2) are to use a mixed electrolyte of 75 g / l CuSO4·5H2O and 30 g / l H2SO4 and apply a constant voltage of 0.7 V at room temperature.

6. The method for preparing magnetic nickel tapered nanowires according to claim 1, wherein: The etching solution in step (3) is a mixed solution of methanol and 9 M sodium hydroxide solution in a volume ratio of 1:9; the etching temperature is room temperature and the etching time is 12±3 min.

7. The method for preparing magnetic nickel tapered nanowires according to claim 1, wherein: The electrochemical deposition conditions in step (4) are to use a mixed electrolyte of 250 g / l NiSO4·6H2O, 50 g / l NiCl2·6H2O and 30 g / l H3BO3, and apply a constant voltage of 1.35 V at room temperature.

Images