RU2724264C1 - Method of producing nickel-bearing nanorods with controlled aspect ratio - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: method involves making a track polymer matrix having through pore channels, on one side of which there is a layer of copper with subsequent build-up of the layer to thickness of 3–7 mcm in a galvanic bath with copper sulphate, preparation of a galvanic bath from a mixture of HBO– 25–35 g/l; CuSO×5HO – 4–8 g/l; NiSO×7HO – 160–220 g/l at ratio of nickel and copper salts in range from 20:1 to 30:1, pores filling of matrix with alternating layers of copper and nickel by means of metal deposition in galvanic bath from mixture, wherein voltage 0.7 V and 1.8 V is cyclically changed for deposition of copper and nickel layers separately, after filling of pores with layers of copper and nickel, track polymer matrix is dissolved in NaOH with concentration from 220 g/l to 260 g/l at temperature from 60 to 80 °C. Obtained nanowires are washed, and then dissolving substrate copper layer and simultaneously etching from nanowires layers of copper in solution of NHOH (150–200 g/l) and CuSO×5HO (1 g/l) at room temperature, obtained suspension from nickel layers forming nickel rods is transferred from the etching solution into water using a magnet.EFFECT: disclosed is a method of producing nickel nanorods of cylindrical shape with a given aspect ratio.1 cl, 1 dwg, 2 ex

Description

Nanorods are a new and promising object for use in various sectors of the national economy, for example, in electronics for creating transistors and nanosensors, nanovoltics, in medicine for creating portioned capsules of drugs and their activation in the right part of the body by dissolving the capsule.

The present invention is specifically directed to the creation of many separate (single) nickel nanorods of cylindrical shape with a given aspect ratio i.e. with the required ratio of the height of the nanorod to its width.

A method for producing combined copper-nickel nanorods is known from the literature, which includes the manufacture of a track polymer matrix having through pore channels, preparing an electrolyte from a mixture of aqueous solutions of nickel and copper salts, creating a copper layer on the matrix surface, filling the matrix pores with alternating layers of copper and nickel by galvanic metal deposition, separation of the obtained long rods from alternating layers of metals from the pores of the polymer matrix (Huijun Yao, Lu Xie, Yaxiong Cheng, Jinglai Duan, Yonghui Chen, Shuangbao Lyu, Youmei Sun, Jie Liu, Tuning the coercivity of Cu / Ni multilayer nanowire arrays by tailoring, Materials & Design, Volume 123, 5 June 2017, Pages 165-173).

In the known method, the obtained long rods (nanowires) from alternating layers of metals were transferred onto a silicon substrate, and then the copper layer was dissolved and the change in the coercive force of Cu / Ni nanorods was studied depending on various parameters.

The disadvantage of this method is that it is intended for use solely for the purpose of conducting individual experiments and does not allow to obtain individual arrays of nickel nanorods on an industrial scale.

The technical task of the proposed method is the development of a technologically simple and effective way to obtain an array of individual nickel nanorods in large quantities.

The technical result is the creation of a method for producing nickel nanorods on an industrial scale.

The stated technical problem is achieved as a result of the fact that in the method of producing nanorods, which includes the manufacture of a track polymer matrix having through channels, pores, the preparation of an electrolyte from a mixture of aqueous solutions of nickel and copper salts, the creation of a copper layer on the matrix surface, filling the matrix pores with alternating copper layers and nickel by means of galvanic deposition of metals, separation of the obtained long rods from alternating layers of metals forming nanowires from the pores of the polymer matrix, characterized in that a copper layer used as a substrate is deposited on one side of the matrix by preliminary vacuum thermal spraying followed by layer build-up copper to a thickness of 3-7 microns in a galvanic bath with copper sulfate, then a matrix, one of the sides of which is covered with a layer of copper, is immersed in a galvanic bath containing a mixture of electrolytes of salts of H ₃ BO ₃ - 25-35 g / l; CuSO ₄ * 5H ₂ O - 4-8 g / l; NiSO ₄ * 7H ₂ O - 160-220 g / l when the ratio of salts of Nickel and copper in the range of 20: 1 to 30: 1, cyclically change the voltage of 0.7 V and 1.8 V for the deposition of separately layers of copper and Nickel, the duration of each of the voltages is determined by the value of the leaking charge, which is established experimentally and depends on the area of the sample, the pore density of the polymer matrix, the deposited material and the thickness of the layer, after filling the pores with copper and nickel layers, the track polymer matrix is dissolved in a NaOH solution with a concentration of 220 g or more / l to 260 g / l at temperatures ranging from 60 to 80 ° C, the resulting nanowires consisting of alternating layers of copper and nickel on a copper substrate are washed, and then the copper layer of the substrate is dissolved and layers of copper in the NH ₄ solution are etched from the nanowires OH (150-200 g / l) and CuSO ₄ * 5H ₂ O (1 g / l) at room temperature, the suspension obtained from nickel layers forming nickel rods is transferred from the etching solution to water using a magnet.

The sequence of operations of the method is illustrated by the flowchart in the figure.

The ultimate goal of the invention is to obtain a large number of relatively long nanowires, consisting of alternating layers of copper and nickel, which are then divided by dissolving the copper layers into separate cylindrical nickel nanorods with a given aspect ratio.

The first step of the method is the preparation of a polymer matrix, in the pores of which the formation of nanowires is made, from which cylindrical nanorods are then obtained. In track membranes, all pores are “calibrated”, which is important for obtaining the same nanowires and then the same nanorods. The matrix is made by known methods - by bombarding polymer films with high-energy particles, piercing the film through.

After preparing the polymer matrix with predetermined pore parameters, an electrically conductive layer is created on one of its surfaces. The creation of such a layer is carried out in two stages. At the first stage, a thin layer of copper (up to 50 nm.) Is sprayed onto the matrix surface. Spraying is carried out by thermal spraying of metal in a vacuum, for example at the VUP-4 installation. At the second stage, the obtained thin layer of copper is strengthened by galvanic deposition of copper in a galvanic bath, which is conducted at a constant voltage. In this case, the thickness of the copper layer increases to 5 μm.

The third step of the method is the preparation of an electrolyte. The peculiarity is that two electrolytes are prepared, which are then drained together. The electrolyte is a mixture of electrolytes of salts of H ₃ BO ₃ - 25-35 g / l; CuSO ₄ * 5H ₂ O - 4-8 g / l; NiSO ₄ * 7H ₂ O - 160-220 g / l with a ratio of nickel and copper salts in the range of 20: 1 to 30: 1.

The fourth operation of the method is to conduct a galvanic process in a cell filled with electrolyte, which was obtained in the previous operation. In order to obtain successively alternating layers of copper and nickel of a given height, the deposition voltage in the plating bath is periodically changed. The voltages of 0.7 V and 1.8 V are cyclically changed to separately deposit copper and nickel layers, the duration of each of the voltages is determined by the amount of leaking charge, which is established experimentally. The duration of each of the stresses depends on the area of the sample, the pore density of the polymer matrix, the deposited material and the thickness of the layer. The deposition time of the copper layer and the nickel layer (in the cycle) differs, which is primarily due to the difference in the concentration of ions of these metals in the electrolyte, as well as the difference in the nature of the deposition of copper and nickel ions and the required amount of precipitate (layer thickness). Also, the deposition time of individual pairs of copper and nickel layers (cycle) varies with the growth of nanowires. This is due to a change in the deposition conditions of each of the metals as the pore channel is filled (by diffusion features of the deposition of a narrow pore channel). The total growth time can be determined by the formula

where t _total ^_ total growth time;

t _1i is the growth time of the copper layer;

t _2i is the growth time of the i-th nickel layer;

i is the physical number of the cycle,

N is the number of pairs of layers.

The fifth step of the method is to separate the resulting array of layered nanowires on a copper substrate from the polymer matrix. The operation is carried out by chemical dissolution of the polymer matrix or mechanical removal of the polymer matrix. When the matrix is chemically dissolved, it is dissolved in a NaOH solution with a concentration of 220 g / l to 260 g / l at temperatures in the range of 60 to 80 ° C, and then the obtained two-component nickel-copper nanowires on a copper substrate are washed.

The sixth step of the method is the etching of a copper substrate and copper layers from the obtained nanowires. The operation is carried out by dissolving copper in a solution of NH ₄ OH (150-200 g / l) and CuSO ₄ * 5H ₂ O (1 g / l) at room temperature.

The seventh step of the method is the transfer of the obtained suspension of nickel nanorods from the etching solution into water using a magnet.

Examples of the method.

Example 1

Obtaining cylindrical magnetic nanorods of nickel with a diameter of 100 nm and a length of 400 nm.

We used a matrix - a polymer film with the following characteristics: pore diameter - 100 nm; radiation density - 1.2 * 10 ⁹ cm ^-2 ; thickness - 12 microns. A sample with an area of 30 cm ^{2 was} coated on one side by thermal vacuum spraying with a thin layer of copper at VUP-4; layer thickness - 50 nm. The sprayed layer was then galvanically strengthened by additional electrodeposition of copper. Precipitation was performed in a solution of CuSO ₄ * 7H ₂ O - 200 g / l and H ₂ SO ₄ - 10 g / l. In this case, the sample was placed horizontally in a galvanic cell. The process was conducted at a constant current of 400 mA for 30 minutes. As a result, one side of the film was completely covered by a conductive layer with a thickness of 7.5 μm. The resulting film (matrix) was cut into individual fragments with an area of 5 cm ² .

Next, the matrix was fixed in a special galvanic cell, while the deposition area was 2.5 cm ² . The electrodeposition process was carried out using a programmable potentiostat - galvanostat Elins P - 2X. The device made it possible to measure electrodeposition parameters and switch the electrodeposition modes (potential) depending on time and / or fixed parameters. To obtain layered nanowires, which will be further divided into separate nanorods, an electrolyte of the following composition was used: H ₃ BO ₃ - 32.5 g / l; CuSO ₄ * 5H ₂ O - 6.2 g / l; NiSO ₄ * 7H ₂ O - 196.5 g / l. The deposition mode was set to obtain thin copper (sacrificial) layers and nickel (functional) 400 nm long. To obtain such structures, we used the pulsed mode -: the potential changed stepwise from 0.7 V (growth of copper layers) to 1.8 V (growth of nickel layers). Upon completion of the growth of the nickel layer, the cycle was repeated. The number of cycles is 5. The potential was switched when a certain charge was reached. For the copper layer, it was - 270 mC; for a nickel layer - 690 μl.

The resulting array of nanorods was separated from the track membrane. For this, the matrix (track membrane) was dissolved in a NaOH solution - 240 g / l at a temperature of 60 ° C for 2 hours. Then, the selected array of nanowires, consisting of individual heterostructured nanorods fixed on a common copper substrate, was washed in distilled water.

At the next stage, copper (the common substrate and the “sacrificial” layers of copper in each of the nanowires) was dissolved in a solution of NH ₄ OH - 200 g / l and CuSO ₄ * 5H ₂ O - 1 g / l, for 72 hours, at room temperature .

After copper removal in the etching solution, a suspension of individual cylindrical nanorods of the required size was formed. The pickling solution was drained, and the suspension was washed in distilled water and left in water for storage and subsequent use. At this stage, all manipulations with nanorods were carried out using a magnet wrapped in a polymer film.

Example 2

Obtaining cylindrical magnetic nanorods of nickel with a diameter of 70 nm and a length of 200 nm.

Used matrices with the following characteristics: pore diameter - 70 nm; radiation density - 7.8 * 10 cm ^-2 ; thickness - 12 microns.

The growth stresses of each layer were the same as in Example 1. The charge for the deposition of copper layers (100 nm) was 880 mC; for nickel layers (200 nm) - 1120 μl.

For electrodeposition, an electrolyte of the same composition was used. Preparation of the matrix, subsequent (after growing) removal of the track membrane and selective etching of copper occurred in the mode described in example 1.

The experiments on obtaining nickel nanorods with an adjustable aspect ratio show the industrial applicability of the proposed method.

Claims (1)

A method for producing nickel nanorods with an adjustable aspect ratio, including the manufacture of a track polymer matrix having through pore channels, preparing an electrolyte from a mixture of aqueous solutions of nickel and copper salts, creating a copper layer on the matrix surface, filling the matrix pores with alternating layers of copper and nickel by galvanic deposition, separation of the obtained long rods from alternating layers of nickel and copper forming nanowires from the pores of the polymer matrix, characterized in that a copper layer used as a substrate is deposited on one side of the matrix by preliminary vacuum thermal spraying followed by the growth of the copper layer to a thickness 3-7 microns in a galvanic bath with copper sulfate, then a matrix, one of the sides of which is coated with a layer of copper, is immersed in a galvanic bath containing a mixture of electrolytes of salts of H ₃ BO ₃ - 25-35 g / l; CuSO ₄ × 5H ₂ O - 4-8 g / l; NiSO ₄ × 7H ₂ O - 160-220 g / l with a ratio of nickel and copper salts in the range from 20: 1 to 30: 1; the voltages of 0.7 V and 1.8 V are cyclically changed to separately deposit copper and nickel layers in this case, the duration of each of the voltages is determined by the amount of leaking charge, which is determined experimentally depending on the area of the sample, the pore density of the polymer matrix, the deposited material and the thickness of the layer, after filling the pores with copper and nickel layers, the track polymer matrix is dissolved in a NaOH solution with a concentration from 220 g / l to 260 g / l at temperatures in the range from 60 to 80 ° C, the resulting nanowires consisting of alternating layers of copper and nickel on a copper substrate are washed, and then the copper layer of the substrate is dissolved and the copper layers are etched from the nanowires a solution of NH ₄ OH (150-200 g / l) and CuSO ₄ × 5H ₂ O (1 g / l) at room temperature, the suspension obtained from nickel layers forming nickel nanorods is transferred from the etching solution to water using new magnet.

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