CN106757239B - A kind of method of silicon carbide fibre electroplating nickel on surface - Google Patents

Abstract

The invention discloses a method for electroplating nickel on the surface of silicon carbide fibers, which relates to the surface treatment of silicon carbide fibers. The continuous SiC fiber is cut to obtain the continuous SiC fiber, and then heat-treated to degumming to obtain the degummed SiC fiber; the degummed SiC fiber is boiled in NaOH solution, and after rinsing, the degreasing SiC fiber is obtained; the degreasing SiC fiber is obtained Soak the SiC fibers in nitric acid aqueous solution for acid corrosion to roughen the surface to increase the surface energy and enhance the bonding force between the coating and the fiber. After taking it out of the nitric acid aqueous solution, rinse it again to obtain SiC with a roughened surface. fiber; dry the SiC fiber after surface roughening to obtain pretreated dry SiC fiber; prepare the electroplating solution, use the obtained pretreated dry SiC fiber as the cathode, and the metal nickel plate as the anode, place it in the electroplating solution, and pretreat A layer of bright and dense nickel metal coating is formed on the surface of the dry SiC fiber, and the surface of the silicon carbide fiber is electroplated with nickel.

Description

A method for electroplating nickel on the surface of silicon carbide fiber

technical field

The invention relates to surface treatment of silicon carbide (SiC) fibers, in particular to a method for electroplating nickel on the surface of silicon carbide fibers.

Background technique

Continuous fiber reinforced metal matrix composites are a new type of composite materials. It is composed of continuous fiber with excellent mechanical properties as reinforcement and composited with metal matrix. Reinforcing fibers are generally low-density, high-strength, high-temperature-resistant ceramic fibers. Due to the addition of fibers, the composite material has excellent comprehensive properties such as low density, high specific strength, high specific modulus, high temperature resistance, high electrical conductivity, and high thermal conductivity. It has great potential in advanced weapons, aerospace, nuclear energy, and electrical fields. Broad application prospects. For example, continuous fiber-reinforced titanium alloy composite materials have been used abroad for important parts such as jet engine blades and drive shafts; continuous fiber-reinforced aluminum-based composite materials have been used abroad for jet fighter vertical tail balance and tail beams, and automotive air conditioner boxes , small pressure vessels and nuclear fusion reactors; continuous fiber-reinforced nickel-based composites are also being developed (Wang Tao, Zhao Yuxin, et al. Progress and key issues in the development of continuous fiber-reinforced metal-based composites [J]. Journal of Aeronautical Materials, 2013 ,33(2):87-96; Yu Huashun. Metal matrix composites and their preparation technology [M]. Beijing: Chemical Industry Press, 2006,50).

Continuous fiber-reinforced metal matrix composites are generally prepared by liquid casting, that is, the metal needs to be melted at high temperature, and then (under pressure) flow through a fixed mold filled with fiber fabrics, and the composite material in the desired shape can be obtained after cooling. Most of the continuous reinforcing fibers used in this method are inorganic fibers, such as carbon fibers, quartz fibers, SiC fibers, boron fibers, etc. These fibers have limited wettability with the liquid metal, resulting in poor bonding between the fiber and the matrix interface in the composite material, and poor mechanical properties of the composite material; in addition, some fibers and the matrix alloy may undergo violent chemical reactions at high temperatures, resulting in fiber breakdown. damage, thereby losing the performance of the composite material.

Pre-preparing metal coating on the fiber surface is an effective way to solve the above problems. The fiber surface metallization treatment can not only effectively improve the wettability and compatibility between the fiber and the metal matrix, but also prevent the subsequent composite treatment from damaging the fiber, thereby improving the performance of the composite material. Metallic nickel is currently a relatively mature coating material, mainly because it has good thermal stability and physical and chemical stability, and it has good wettability with various metal substrates. The methods of nickel plating on the surface of continuous fiber mainly include electroplating, electroless plating, magnetron sputtering and so on. Among them, the electroplating method has the advantages of simple equipment, low cost, high efficiency, easy control and continuous production, and is favored by the application industry.

At present, the fibers used for metal nickel plating are mainly organic fibers, quartz fibers and carbon fibers. Both organic fibers and quartz fibers are insulating materials with poor electrical conductivity and cannot be directly electroplated. Usually, electroless plating is used to prepare metal coatings, or a composite process of first electroless plating and then electroplating is used. For example, Fang Dongsheng and others have achieved nickel plating on the surface of aramid fiber by using electroless plating technology (Fang Dongsheng, Sun Yong, et al. Research on electroless nickel plating on the surface of aramid fiber [J]. New Chemical Materials, 2013, 41(2) :60-62); Bai Lixiao and others first electroless Ni-P plating on the surface of quartz fiber, and then electroplating Ni, successfully realized the surface metallization of quartz fiber (Bai Lixiao, research on the joint process of electroless Ni-P plating and electroplating Ni on the surface of quartz fiber .Master's degree thesis of Nanchang University, 2007.). The characteristic of the electroless plating process is that it needs to roughen, sensitize and activate the plating surface (activation treatment requires precious metal reagents). Compared with electroplating, the process is complicated and the cost is high, which is not conducive to large-scale production. Carbon fiber is a fiber material that can be directly electroplated, mainly because carbon fiber has a low resistivity (less than 10 ^-2 Ω·cm). At present, there have been many studies on the surface metallization of carbon fibers (Wan Liying, Yao Zhangfu. Research on continuous nickel plating on the surface of carbon fibers [J]. Journal of Nanchang Hangkong University, 2015,29(2):57-61; Lu Xiaoxuan, Lu Chunxiang, et al. Research on electroplating nickel on the surface of carbon fiber[J]. New Chemical Materials, 2011,39(8):89-91; Han Xiao, Zhou Yuxi, et al. Effect of electroplating time on electroplating nickel on carbon fiber surface[J].Electroplating and Finishing, 2014,33(9):363-365; Xu Xianfeng, Hong Longlong, et al. Research on Electroless Nickel Plating and Electroless Nickel Plating on Carbon Fiber Surface[J]. Functional Materials, 2013, Supplement (Ⅱ)(44):264-267 ; Lv Xiaoxuan, Lv Chunxiang, et al. Effect of anodic oxidation on carbon fiber nickel plating [J]. New Carbon Materials, 2010,25(6):454-459). Although carbon fiber is suitable as a substrate for direct electroplating, the subsequent preparation of metal matrix composites is carried out at the melting temperature of the metal. Carbon fiber is easy to react with the metal coating at high temperature, and its high temperature oxidation resistance is poor, which will lead to mechanical damage. Severe loss of properties, which ultimately degrades the performance of metal matrix composites. Therefore, seeking reinforcements with better thermophysical and chemical stability is an urgent need for the preparation of metal matrix composites.

Silicon carbide (SiC) fibers prepared by the precursor conversion method have excellent properties such as light weight, high strength, high modulus, high temperature resistance, and oxidation resistance. Compared with carbon fibers, its diameter is slightly larger (about 14 μm), and it has better compatibility with metals at high temperatures, and is less prone to surface reactions, so it is an ideal reinforcing fiber for high-performance metal matrix composites. The fiber preparation technology was invented by Professor Yajima of Tohoku University in 1975 (S.Yajima, J.Hayashi, M.Omori.Continuous Silicon Carbide fiber of tensile strength[J].Chemical Letters,1975(9):931) . Its main technical route is: first synthesize polycarbosilane precursor; polycarbosilane is melt-spun to prepare fibrils; fibrils are cross-linked by hot air for non-melting treatment; finally, high-temperature treatment under protective atmosphere (Ar or N ₂ ) Obtain SiC fiber. The resistivity of SiC fibers prepared by this technical route can vary in a wide range, which is much higher than that of carbon fibers, so that there is still a significant difference between its electrical conductivity and carbon fibers. In addition, the surface morphology and electrochemical state of SiC fibers are also different from those of carbon fibers, making them difficult to plate. Therefore, the principle and specific process of SiC fiber and carbon fiber electroplating are different.

So far, there has been no report on the direct electroplating of nickel on the surface of SiC fibers.

Contents of the invention

The purpose of the present invention is to provide a method for electroplating nickel on the surface of silicon carbide fibers.

The present invention comprises the following steps:

1) Cutting the continuous SiC fiber to obtain a fixed-length continuous SiC fiber;

In step 1), the continuous SiC fiber can be prepared by the precursor conversion method; the cutting can be cut according to the required length.

2) heat-treating and degumming the continuous SiC fibers to obtain degummed SiC fibers;

In step 2), the heat treatment degumming can place the continuous SiC fiber in a porous graphite crucible, then put the crucible into a tube furnace for heat treatment and degumming, and raise the temperature to 500-700°C at a rate of 5°C/min, And keep warm for 0.5h, then cool with the furnace.

3) Boiling the degummed SiC fibers in NaOH solution, and rinsing to obtain degreased SiC fibers;

In step 3), the molar concentration of the NaOH solution can be 1mol/L; the boiling time can be 10-30min; the washing can be washed at least 3 times with distilled water,

4) Soak the degreasing SiC fibers in aqueous nitric acid solution for acid corrosion to roughen the surface to increase the surface energy and strengthen the bonding force between the coating and the fibers. After taking it out from the aqueous nitric acid solution, rinse it again to obtain SiC fiber after surface roughening;

In step 4), the mass fraction of the nitric acid aqueous solution may be 65%, the soaking time may be 15-45 minutes, and the rinsing may be at least 3 times with distilled water.

5) drying the SiC fibers after surface roughening to obtain pretreated dry SiC fibers;

In step 5), the drying may be performed by putting the roughened SiC fiber into a vacuum drying oven, and drying at 50-70° C. for 10-30 minutes.

6) Prepare the electroplating solution, use the pretreated dry SiC fiber obtained in step 5) as the cathode, and the metal nickel plate as the anode, put them in the electroplating solution, and under the action of a constant direct current of 100-200mA, energize for 1-10 minutes, A layer of bright and dense nickel metal coating is formed on the surface of the pretreated dry SiC fiber to realize nickel plating on the surface of the silicon carbide fiber.

In step 6), the composition of the electroplating solution can be: nickel sulfate 100～350g/L, nickel chloride 50～80g/L, boric acid 30～45g/L, sodium lauryl sulfate 0.05～0.2g/L L, wherein, nickel sulfate provides a nickel source for electrodeposition, nickel chloride is an anode activator, boric acid is a pH buffer, and sodium lauryl sulfate is an anti-pinhole agent; the pH of the electroplating solution can be 3 to 4 , the temperature can be 25-60°C; the pH adjustment of the electroplating solution can be adjusted by dripping ammonia water and HCl solution; the pH adjustment of the electroplating solution is one of the key steps to implement electroplating, changing the pH value of the solution The surface charge state of the substrate can be changed, thereby changing its adsorption capacity for metal nickel ions. Due to the particularity of the structure, SiC fibers have a special isoelectric point (pHiep=2~3), and the pH value needs to be limited to a narrow range. It is one of the main differences between SiC fiber and other fiber materials; adjusting the temperature of the electroplating solution to 25-60°C is the precise control of the plating temperature, and it is also one of the key steps for electroplating SiC fiber , there are two main reasons: first, the temperature has a significant impact on the electroplating speed, and adjusting the temperature can control the electroplating speed; second, the resistivity of SiC fiber is much higher than that of carbon fiber, under the same plating current, the SiC fiber The real-time power is higher and the heat release is more significant. Therefore, it is necessary to adjust the heat release of SiC fibers by controlling the solution temperature to avoid excessive plating speed. For SiC fibers with high resistivity, it is necessary to reduce the temperature of the plating solution to control the plating speed; under the action of a constant DC current of 100-200mA, the nickel ions in the plating solution (H) are generated on the surface of the pretreated dry SiC fiber (E) Reduction reaction, after energizing for 1-10 minutes, a layer of bright and dense nickel metal coating can be formed on the surface of the pretreated dry SiC fiber. Regulating the current is another key step in electroplating the SiC fiber. The resistivity of the SiC fiber is between 100 and Between 107Ω·cm, different resistivities correspond to different plating currents. The higher the resistivity, the greater the plating current required. Current control needs to be implemented for SiC fibers with different resistivities.

The invention utilizes the principle of electrolysis, uses the metal nickel plate as the anode, and the SiC fiber as the cathode, directly deposits a fine, compact, small porosity, uniform and controllable metal nickel coating on the surface of the SiC fiber. The process route of the method is simple and the cost is low, and the prepared nickel-plated SiC fiber can be used as a reinforcing body of a metal wire and a metal-matrix composite material.

In the present invention, the continuous SiC fiber prepared by the precursor conversion method is used as the substrate, and a layer of dense, fine-grained, uniform and controllable nickel metal coating is deposited on the surface of the SiC fiber by using the principle of electrolysis.

The beneficial effects of the present invention are:

(1) Electroplating technology is used to obtain nickel metal coating on the surface of continuous SiC fiber. The process route has the advantages of simple equipment, low cost, high efficiency and easy industrial production;

(2) Under the process conditions specified in the present invention, the SiC fiber has a suitable surface roughness and electrochemical state, and the metallic nickel coating obtained on the SiC fiber has fine grain, compactness, small porosity, uniform thickness and is compatible with the coating Combining good features;

(3) The thickness of the nickel-plated layer prepared by the present invention is controllable, and there is no bridging between the fibers, so that the strength and weaving performance of the SiC fiber after nickel-plating will not be significantly reduced, and it is expected to be used as a reinforcement for metal wires and high-performance metal matrix composites Body use.

Description of drawings

Figure 1 is the surface morphology of nickel-plated SiC fibers obtained after electroplating for 10 min.

Figure 2 is the cross-sectional morphology of nickel-plated SiC fibers obtained after electroplating for 10 min.

Detailed ways

The present invention is described in further detail below in conjunction with embodiment.

(1) Cut the continuous SiC fiber with a resistivity of 10Ω·cm according to the required length to obtain a fixed-length continuous SiC fiber (A);

(2) Place the continuous SiC fiber (A) in a porous graphite crucible, and then put the crucible into a tube furnace for heat treatment and degumming: heat up to 600°C at a rate of 5°C/min, and keep it at 600°C for 0.5h , and then cooled with the furnace to obtain degummed SiC fibers (B);

(3) Boil the degummed SiC fiber (B) in 1mol/L NaOH solution for 15min to remove the organic and inorganic attachments on the surface, and then rinse it with distilled water for more than 3 times to obtain the degreased SiC fiber (C);

(4) Put the degreased SiC fiber (C) into an aqueous solution of nitric acid with a mass fraction of 65% for acid corrosion to roughen its surface to increase its surface energy and enhance the bonding between the coating and the fiber. After soaking for 30 min, it was taken out from the nitric acid solution, and then rinsed with distilled water for more than 3 times to obtain the SiC fiber (D) with a roughened surface.

(5) Put the roughened SiC fiber (D) into a vacuum drying oven, and dry at 60° C. for 15 minutes to obtain a pretreated dry SiC fiber (E).

(6) Prepare electroplating solution (F), the concentration of each substance in the electroplating solution is respectively: nickel sulfate 160g/L, nickel chloride 80g/L, boric acid 30g/L, sodium lauryl sulfate 0.1g/L.

(7) The measured isoelectric point of the SiC fiber to be plated is pH _iep =2.5. Adjust the pH value of the electroplating solution to 3.5 to obtain the electroplating solution (G).

(8) Adjust the temperature of the electroplating solution (G) to 50° C. to obtain the electroplating solution (H).

(9) The pretreated dry SiC fiber (E) is used as the cathode, and the metal nickel plate is used as the anode. Under the action of a constant direct current of 150mA, the nickel ions in the electroplating solution (H) are deposited on the pretreated dry SiC fiber (E) A reduction reaction occurs on the surface, and a layer of bright and dense nickel metal coating can be formed on the surface of the pretreated dry SiC fiber (E) after electrification for 10 minutes.

See Figures 1 and 2 for the surface and cross-sectional topography of the nickel-plated SiC fiber obtained after electroplating for 10 minutes. It can be seen from Figures 1 and 2 that the plating has been successful, the coating particles are fine, and the coating thickness is uniform. After testing, the tensile strength of the nickel-plated SiC fiber (the thickness of the coating is 700nm) is 2GPa, and the resistivity is 1.5×10 ^-3 Ω·cm.

Claims (9)

1. a method for electroplating nickel on the surface of silicon carbide fibers, characterized in that it may further comprise the steps: 1) Cutting the continuous SiC fiber to obtain a fixed-length continuous SiC fiber; the continuous SiC fiber is a continuous SiC fiber prepared by a precursor conversion method; 2) heat-treating and degumming the continuous SiC fibers to obtain degummed SiC fibers; 3) Boiling the degummed SiC fibers in NaOH solution, and rinsing to obtain degreased SiC fibers; 4) Soak the degreasing SiC fibers in aqueous nitric acid solution for acid corrosion to roughen the surface to increase the surface energy and strengthen the bonding force between the coating and the fibers. After taking it out from the aqueous nitric acid solution, rinse it again to obtain SiC fiber after surface roughening; 5) drying the SiC fibers after surface roughening to obtain pretreated dry SiC fibers; 6) Prepare the electroplating solution, use the pretreated dry SiC fiber obtained in step 5) as the cathode, and the metal nickel plate as the anode, put them in the electroplating solution, and under the action of a constant direct current of 100-200mA, energize for 1-10 minutes, A layer of bright and dense nickel metal coating is formed on the surface of the pretreated dry SiC fiber to realize nickel plating on the surface of the silicon carbide fiber. 2. The method for electroplating nickel on the surface of a silicon carbide fiber as claimed in claim 1 is characterized in that in step 2), the degumming of the heat treatment is to place the continuous SiC fiber in a porous graphite crucible, and then put the crucible into Carry out heat treatment and degumming in a tube furnace, raise the temperature to 500-700°C at a rate of 5°C/min, keep it warm for 0.5h, and then cool with the furnace. 3. The method for electroplating nickel on the surface of a silicon carbide fiber as claimed in claim 1, characterized in that in step 3), the molar concentration of the NaOH solution is 1mol/L. 4. A method for electroplating nickel on the surface of silicon carbide fibers according to claim 1, characterized in that in step 3), the boiling time is 10 to 30 minutes. 5. The method for electroplating nickel on the surface of a silicon carbide fiber according to claim 1, characterized in that in steps 3) and 4), the flushing is at least 3 times with distilled water. 6. The method for electroplating nickel on the surface of a silicon carbide fiber according to claim 1, characterized in that in step 4), the mass fraction of the nitric acid aqueous solution is 65%, and the soaking time is 15 to 45 minutes. 7. The method for electroplating nickel on the surface of a silicon carbide fiber according to claim 1 is characterized in that in step 5), the drying is to put the roughened SiC fiber into a vacuum drying oven for 50 to 70 ℃ drying 10 ~ 30min. 8. The method for electroplating nickel on the surface of a silicon carbide fiber according to claim 1, characterized in that in step 6), the electroplating solution consists of: nickel sulfate 100～350g/L, nickel chloride 50～80g /L, boric acid 30～45g/L, sodium lauryl sulfate 0.05～0.2g/L, wherein, nickel sulfate provides nickel source for electrodeposition, nickel chloride is anode activator, boric acid is pH buffer agent, twelve Sodium Alkyl Sulfate is an anti-pinhole agent. 9. A method for electroplating nickel on the surface of silicon carbide fibers according to claim 1, characterized in that in step 6), the pH of the electroplating solution is 3-4, and the temperature is 25-60°C.