In-situ preparation method of nickel silicide nanowires and obtained nickel silicide nanowires

Abstract

The present invention discloses an in-situ preparation method of nickel silicide nanowires and the obtained nickel silicide nanowires, belonging to the technical field of nanomaterials. The in-situ preparation method of the present invention comprises the following steps: adding nickel salt to SiC w The dispersion is dissolved, and then NH4HCO3 aqueous solution is added, stirred for reaction, and the solid product obtained after the reaction is washed and dried, and then heated to 550-650℃ and calcined under H2 atmosphere to obtain the product. w ) as the silicon source, and SiC was prepared by heterogeneous precipitation method. w @Ni(CO3)2·2Ni(OH)2·2H2O precipitation, followed by H2 calcination, yields nickel silicide nanowires. The overall preparation process is simple, does not require multiple high-temperature treatments, and has low equipment requirements. The resulting nickel silicide nanowires are high in purity and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to an in-situ preparation method of nickel silicide nanowires and the obtained nickel silicide nanowires. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and is not necessarily regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Metal silicides are widely used in the semiconductor field due to their low resistivity and high thermal stability. Typical applications include electrical components, gate electrodes, photovoltaic and thermoelectric devices. With the continuous miniaturization of microelectronic devices, the development of nanoscale silicide structures has become an urgent need for technological development.

[0004] Nickel silicide nanowires have a low silicidation temperature, consume little silicon during the reaction process, and can be transported in one dimension, making them a research hotspot in recent years. Currently, the synthesis method for nickel silicide primarily relies on chemical vapor deposition. For example, patent publication number CN101555016A discloses a method for preparing nickel silicide nanowires. This involves forming a silicon dioxide layer on the surface of a silicon substrate, then depositing a titanium layer. The silicon substrate with the titanium layer is placed in a reaction chamber and heated to 500-1000°C. Nickel clusters are sputtered and deposited onto the silicon substrate surface, growing the nickel silicide nanowires. However, this method involves complex preparation steps, high heating temperatures, and demanding equipment. Furthermore, it is difficult to ensure efficient production of nickel silicide nanowires.

[0005] The paper "Formation and evolution of nickel silicide in silicon nanowires" (IEEE Transactions on Electron Devices, 2014, 61(10): 3363-3371) provides a method for preparing nickel silicide nanowires. Using silane as a silicon precursor and gold as a catalyst, the nanowires are grown using a vapor-liquid-solid growth technique in an ultra-high vacuum chemical vapor deposition chamber. Annealing then produces the resulting nickel silicide nanowires. This method requires a harsh high vacuum environment, resulting in a complex and tedious preparation process.

[0006] The paper "Growth of single-crystalline nickel silicide nanowires with excellent physical properties" (CrystEngComm, 2015, 17(9): 1911-1916) provides a method for preparing nickel silicide nanowires. The method involves ultrasonically cleaning a silicon substrate in acetone and isopropyl alcohol, removing native oxides with dilute hydrofluoric acid, and then rinsing with deionized water. A nickel film is then deposited. In a chemical vapor deposition chamber, the nickel silicide nanowire material is synthesized on the Ni film using electron beam evaporation of SiH4 / H2 gas. The toxicity of the SiH4 used in this method limits its large-scale production.

[0007] Patent publication number CN106558474B discloses a method for preparing nickel silicide nanowires. Silicon-containing nanowires are formed by chemical vapor deposition (CVD), followed by a nickel layer deposited on their surface by CVD. A confining layer is then deposited by CVD, followed by annealing. This method requires multiple CVD steps, which are demanding on equipment, complex and costly, and results in low production efficiency.

[0008] Therefore, it is necessary to provide a simple, efficient and low-cost method for preparing nickel silicide nanowire materials. Summary of the Invention

[0009] In view of this, the present invention provides an in-situ preparation method of nickel silicide nanowires and the obtained nickel silicide nanowires, which solves the problems of high energy consumption, complicated steps and low production efficiency caused by the multilayer vapor deposition method in the prior art.

[0010] In a first aspect, the present invention provides an in-situ preparation method of nickel silicide nanowires, comprising the following steps:

[0011] Adding nickel salt to SiC w The nickel salt is dissolved in the dispersion and the SiC w The mass ratio of is (1.4~1.8) : (0.9~1.1); then add NH4HCO3 aqueous solution, stir to react, wash and dry the solid product obtained after the reaction, and then heat to 550~650℃ and calcine under H2 atmosphere to obtain.

[0012] In a second aspect, the present invention provides nickel silicide nanowires prepared by the above-mentioned in-situ preparation method.

[0013] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0014] The present invention uses silicon carbide whiskers (SiCw ) as the silicon source, and SiC was prepared by heterogeneous precipitation method. w @Ni(CO3)2·2Ni(OH)2·2H2O precipitation, followed by H2 calcination, yields nickel silicide nanowires. The overall preparation process is simple, does not require multiple high-temperature treatments, and has low equipment requirements. The resulting nickel silicide nanowires are high in purity and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0016] Figure 1 1 is a transmission electron microscope image and an energy dispersive spectrometer elemental analysis diagram of the nickel silicide nanowire of Example 1 of the present invention, wherein a is the microscopic morphology of the nickel silicide nanowire, b is a partial magnified view of the morphology of a, c is the Ni element distribution diagram, and d is the Si element distribution diagram;

[0017] Figure 2 is an X-ray diffraction pattern of nickel silicide nanowires according to Example 1 of the present invention;

[0018] Figure 3 It is the X-ray diffraction pattern of the product of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0020] The present invention provides an in-situ preparation method of nickel silicide nanowires, comprising the following steps:

[0021] Adding nickel salt to SiC w The solid product obtained after the reaction is washed and dried, and then heated to 550-650 ° C in a H2 atmosphere and calcined to obtain the product.

[0022] In the present invention, silicon carbide whiskers (SiC w ) is a silicon-containing precursor, and a heterogeneous precipitation method is used to react nickel salt with NH4HCO3 in solution. w The outer layer is coated with Ni(CO3)2·2Ni(OH)2·2H2O precipitate to obtain SiC w@Ni(CO3)2·2Ni(OH)2·2H2O precipitation (precursor) is in a layered state. The water-soluble ammonium salt is removed by washing to purify the precursor. After drying, it is calcined in a H2 atmosphere to avoid the influence of oxygen on the synthesis of nickel silicide nanowires. At the same time, the excess CO3 is removed under the reduction effect of hydrogen. 2- and OH - ; Ni has strong reducing properties and will react with silicon carbide whiskers to produce nickel silicide nanowires.

[0023] In the present invention, the SiC w The length is 2~10μm, SiC w The diameter is 20~80nm.

[0024] In the present invention, the nickel salt is selected from nickel nitrate hexahydrate or nickel sulfate hexahydrate; the specific reaction of the heterogeneous precipitation process is as follows:

[0025] SiC w +Ni(NO3)2·6H2O+NH4HCO3→SiC w @Ni(CO3)2·2Ni(OH)2·2H2O↓+NH4NO3+CO2↑;

[0026] SiC w +NiSO4·6H2O+NH4HCO3→SiC w @Ni(CO3)2·2Ni(OH)2·2H2O↓+(NH4)2SO4+CO2↑.

[0027] In the present invention, the nickel salt and SiC w The mass ratio of SiC is (1.4~1.8): (0.9~1.1). w Too much mass can result in uncoated silicon carbide whiskers, which do not participate in the reduction process and thus affect purity. Too much nickel salt can lead to residual nickel salt during the reduction process, also reducing purity. An appropriate mass ratio is beneficial for synthesizing high-purity nickel silicide nanowires.

[0028] In the present invention, the SiC w The dispersion includes SiC w , water and dispersant; the SiC w The mass ratio of SiC to dispersant is 1: (1~5). w It has a large aspect ratio and is very easy to agglomerate, so it needs to be evenly dispersed in the solution with the help of a dispersant. w The preparation method of the dispersion is not particularly limited and conventional preparation methods in the art may be used. For example, dispersion may be promoted by ultrasound, stirring, heating, etc.

[0029] In the present invention, the dispersant is selected from one or both of polyethylene glycol and polyvinyl pyrrolidone. These agents can increase the viscosity of the aqueous solution while exhibiting good water solubility and being easily removed through subsequent washing steps. When the dispersant is polyethylene glycol (PEG), the molecular weight of the polyethylene glycol is 2,000 to 10,000, with PEG 6000 being most preferred. Furthermore, the concentration of the dispersant is 1 to 20 g / L, which can be selected based on the specific dispersion conditions.

[0030] In the present invention, the concentration of the NH4HCO3 aqueous solution is 40-100 g / L, and the NH4HCO3 aqueous solution is added at a set flow rate. Furthermore, the stirring reaction is specifically performed as follows: when stirring reaches a pH of 7.2-7.8, the addition of the NH4HCO3 aqueous solution is stopped, and stirring is continued for 40-80 minutes. The stirring reaction can be carried out at room temperature (10-40°C) without the need for an additional heat source. The flow rate of the NH4HCO3 aqueous solution is 0.001-0.01 L / min.

[0031] In the present invention, in the step of washing and drying the solid product obtained after the reaction, the solid product is obtained by standing, filtering or centrifuging. The present invention preferably adopts centrifugation to obtain the solid product. The washing is carried out by washing with water and ethanol in sequence, and the number of washings is 2 to 5 times to remove water-soluble impurities and obtain a high-purity silicon nickel precursor. The present invention does not impose any special restrictions on the drying method, and can adopt the drying methods commonly used in the art, such as ordinary drying, vacuum drying, freeze drying, supercritical CO2 drying, etc. The present invention preferably adopts vacuum drying. After the drying is completed, the present invention also includes a step of sieving the obtained powder to give it a larger reaction area.

[0032] In the present invention, the calcination time is 1 to 5 hours, more preferably 1.5 to 2.5 hours; the flow rate of H2 is 0.3 to 0.8 L / min; and the heating rate to the calcination temperature is 2 to 8°C / min.

[0033] The present invention also provides nickel silicide nanowires prepared by the above in-situ preparation method. The obtained nickel silicide nanowires mainly have the following compound forms: Ni3Si, Ni2Si and Ni 31 Si 12 wait.

[0034] The technical solution of the present invention is further described below in conjunction with specific examples. Unless otherwise specified, the present invention has no special restrictions on the sources of the reagents used in the following examples, and commercially available products known to those skilled in the art can be used. w The average length is 4 μm and the average diameter is 50 nm.

[0035] Example 1

[0036] This embodiment provides an in-situ preparation method for nickel silicide nanowires.

[0037] (1) Place distilled water in a beaker, weigh and add polyethylene glycol 6000 (PEG6000), place the beaker in a water bath, and stir with magnetic stirring at a constant temperature of 55°C for 15 minutes until PEG6000 is completely dissolved. Cool to room temperature to obtain a PEG aqueous solution with a concentration of 7.5 g / L.

[0038] (2) 1g SiC w The powder was added to the PEG aqueous solution (containing 2.3 g PEG6000) obtained in step (1), ultrasonically dispersed and mechanically stirred for 30 min to obtain SiC w dispersion.

[0039] (3) Add 1.4g Ni(NO3)2·6H2O to the SiC w The dispersion was stirred until completely dissolved to obtain a mixed solution.

[0040] (4) Dissolve NH4HCO3 in distilled water to prepare an NH4HCO3 aqueous solution with a concentration of 79 g / L.

[0041] (5) The 79 g / L NH4HCO3 aqueous solution prepared in step (4) was slowly added dropwise to the mixed solution prepared in step (3) at a rate of 0.003 L / min, with continuous stirring and monitoring the pH until the pH reached 7.5; then, the addition of NH4HCO3 was stopped to obtain a reaction mixture.

[0042] (6) The reaction mixture obtained in step (5) was stirred for 60 min and then allowed to stand for 24 h.

[0043] (7) Pour out the supernatant liquid, continue to add distilled water and let it stand, pour out the supernatant liquid after stratification, and repeat the distilled water washing step for a total of 3 times; then wash with anhydrous ethanol, the washing times are 3 times, and the steps are the same as washing with distilled water; after washing, vacuum dry at 100 ° C for 24 hours, and then sieve (the sieve is 50 mesh) to obtain the silicon nickel precursor.

[0044] (8) The silicon nickel precursor prepared in step (7) was heated to 600°C at a heating rate of 5°C / min in a H2 atmosphere (the H2 flow rate was controlled to be 0.6 L / min), and calcined at this temperature for 2 h to obtain nickel silicide nanowires.

[0045] The transmission electron microscope image and energy dispersive spectroscopy (EDS) elemental analysis of the nickel silicide nanowires in this embodiment are shown in Figure 2. Figure 1As shown, a is the microscopic morphology of nickel silicide nanowires, and b is a local magnified view of the morphology of a. It can be seen that the nickel silicide material is a nanowire structure. Figure 1 Figures c and d are the scanning element distribution diagrams of b. It can be seen that the element distribution of the nanowire shows that the inner layer is Ni and the outer layer is Si.

[0046] The X-ray diffraction pattern of the nickel silicide nanowires in this embodiment is as follows: Figure 2 As shown, it can be seen that no other impurity peaks appear, indicating that high-purity nickel silicide material is in situ prepared on the surface of the material. There are three forms of nickel silicide compounds, namely Ni3Si, Ni2Si and Ni 31 Si 12 .

[0047] Example 2

[0048] This embodiment provides an in-situ preparation method for nickel silicide nanowires.

[0049] (1) Place distilled water in a beaker, weigh and add polyvinylpyrrolidone (PVP), place the beaker in a water bath, and stir magnetically at a constant temperature of 55°C for 15 minutes until the PVP is completely dissolved. Cool to room temperature to obtain a PVP aqueous solution with a concentration of 7.5 g / L.

[0050] (2) 1g SiC w The powder was added to the PVP aqueous solution (containing 2.3 g PVP) obtained in step (1), ultrasonically dispersed and mechanically stirred for 30 min to obtain SiC w dispersion.

[0051] (3) Add 1.4g NiSO4·6H2O to the SiC w The dispersion was stirred until completely dissolved to obtain a mixed solution.

[0052] (4) Dissolve NH4HCO3 in distilled water to prepare an NH4HCO3 aqueous solution with a concentration of 79 g / L.

[0053] (5) The 79 g / L NH4HCO3 aqueous solution prepared in step (4) was slowly added dropwise to the mixed solution prepared in step (3) at a rate of 0.003 L / min, with continuous stirring and monitoring the pH until the pH reached 7.5; then, the addition of NH4HCO3 was stopped to obtain a reaction mixture.

[0054] (6) The reaction mixture obtained in step (5) was stirred for 60 min and then allowed to stand for 24 h.

[0055] (7) Pour out the supernatant liquid, continue to add distilled water and let it stand, pour out the supernatant liquid after stratification, and repeat the distilled water washing step for a total of 3 times; then wash with anhydrous ethanol, the washing times are 3 times, and the steps are the same as washing with distilled water; after washing, vacuum dry at 100 ° C for 24 hours, and then sieve (the sieve is 50 mesh) to obtain the silicon nickel precursor.

[0056] (8) The silicon nickel precursor prepared in step (7) was heated to 580°C at a heating rate of 5°C / min in a H2 atmosphere (the H2 flow rate was controlled to be 0.6 L / min), and calcined at this temperature for 2 h to obtain nickel silicide nanowires.

[0057] X-ray diffraction analysis showed that the compound forms of the nickel silicide nanowires prepared in this embodiment were Ni3Si, Ni2Si and Ni 31 Si 12 .

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 1 is that the SiC w The mass of the powder was 1.4 g.

[0060] The X-ray diffraction pattern of the reduced powder is as follows Figure 3 As shown, it can be seen that there are nickel silicide nanowires and excess silicon carbide whiskers, and the purity is reduced.

[0061] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An in-situ preparation method of nickel silicide nanowires, characterized in that: The steps include: Adding nickel salt to SiC w Dissolved in the dispersion; the nickel salt and SiC w The mass ratio of is (1.4-1.8): (0.9-1.1); then, an NH4HCO3 aqueous solution is added, the reaction is stirred, and the solid product obtained after the reaction is washed and dried, and then heated to 550-650°C under a H2 atmosphere and calcined for 1-5 hours to obtain; The obtained nickel silicide nanowires include Ni3Si, Ni2Si and Ni 31 Si 12 .

2. The in-situ preparation method according to claim 1, wherein The SiC w The length is 2~10μm, SiC w The diameter is 20~80nm.

3. The in-situ preparation method according to claim 1, wherein The nickel salt is nickel nitrate hexahydrate or nickel sulfate hexahydrate.

4. The in-situ preparation method according to claim 1, wherein The SiC w The dispersion includes SiC w , water and dispersant; the SiC w The mass ratio of the dispersant to the surfactant is 1:(1~5).

5. The in-situ preparation method according to claim 4, wherein: The dispersant is selected from one or both of polyethylene glycol and polyvinyl pyrrolidone.

6. The in-situ preparation method according to claim 4, wherein: The concentration of the dispersant is 1-20 g / L.

7. The in-situ preparation method according to claim 1, wherein The concentration of the NH4HCO3 aqueous solution is 40-100 g / L, and the NH4HCO3 aqueous solution is added at a set flow rate.

8. The in-situ preparation method according to claim 7, wherein: The stirring reaction is specifically as follows: when the pH is 7.2-7.8, the addition of the NH4HCO3 aqueous solution is stopped, and then stirring is continued for 40-80 minutes; and the washing is performed by washing with water and ethanol in sequence.

9. The in-situ preparation method according to claim 1, wherein: The flow rate of H2 is 0.3~0.8L / min.

10. Nickel silicide nanowires prepared by the in-situ preparation method according to any one of claims 1 to 9.

Images