CN105586581B - A kind of method in cement base piezoelectric composite material chemical nickel plating on surface - Google Patents

Abstract

The invention discloses a kind of method in cement base piezoelectric composite material chemical nickel plating on surface, including being roughened, reducing, activating, nickel plating the step of, roughening is carried out in alkaline coarsening solution, reducing solution used is the methanol or ethanol water of sodium borohydride, activating solution used is the aqueous solution of the nickel acetate containing additive or nickel sulfate, and nickel-plating liquid is：The 22g/L of nickel sulfate 18, the 16g/L of trisodium citrate 8, the 32g/L of sodium hypophosphite 26, the g/L of sodium acetate 8 14, borax 6 10g/L, pH are 6.5 7.5.The present invention is suitable for the various cement base piezoelectric composite materials using piezoelectric ceramics as functive, using cement and epoxy resin as matrix, cost is relatively low, the feature of environmental protection is more preferable, gained coating surface is smooth, uniformity, and corrosion resistance is good, good conductivity, solderability are strong, it is tightly combined with cement base piezoelectric composite material, difficult for drop-off, adhesion is good, has good application prospect.

Description

A method of electroless nickel plating on the surface of cement-based piezoelectric composite material

technical field

The invention relates to a method for plating nickel on the surface of a cement-based piezoelectric composite material, in particular to a method for palladium-salt-free activated electroless nickel plating on the surface of a cement-based piezoelectric composite material, and belongs to the technical field of non-metallic electroless plating.

Background technique

Piezoelectric materials are widely used in health monitoring of large-scale civil engineering because of their special electromechanical conversion characteristics. Piezoelectric materials mainly include piezoelectric ceramics and piezoelectric composite materials. The electromechanical coupling effect of piezoelectric ceramics is strong, and the piezoelectric strain constant is high, but the dielectric constant is high, so the piezoelectric voltage constant is generally low. Moreover, they have poor toughness and are prone to brittle cracking, resulting in low reliability and poor durability of devices made from them. Piezoelectric composite material is a new type of piezoelectric material that began to be studied in the 1980s. It is a composite material formed by using polymers such as epoxy resin, rubber or PVDF as a matrix and piezoelectric ceramics as a functional body. It combines the characteristics of piezoelectric ceramics and polymers, and has the characteristics of small dielectric constant, low density, and good toughness. However, polymer-based piezoelectric composites still have some defects, such as difficult polarization and low piezoelectric performance. It cannot be well applied to the health monitoring of large civil engineering.

The cement-based piezoelectric composite material is a mixture of cement and polymer as the matrix material, and piezoelectric ceramics as the functional body material. Cement-based piezoelectric composite materials have the characteristics of good compatibility with concrete, high strength, good durability, high sensitivity and low cost. The development of structures towards intelligence has extensive engineering application significance, so people pay more and more attention to them in the field of civil engineering. However, since the cement-based piezoelectric composite material is composed of three different materials: cement, polymer, and piezoelectric ceramics, cement is a cementitious material, polymer is a high molecular polymer, and piezoelectric ceramics is a typical Inorganic non-metallic materials, the components, process, formation mechanism, mechanical properties, surface state and other material properties of the three materials are different. If the metal coating has good properties on the three materials at the same time It is very difficult to adhere to the strength and achieve uniformity, which limits the application range of this type of cement-based piezoelectric composites. Therefore, it is of great significance for the popularization and application of cement-based piezoelectric composite materials to study the preparation method suitable for this type of cement-based piezoelectric composite material electrode, so that the cement-based piezoelectric composite material can exert excellent piezoelectric properties.

Electroless nickel plating has become an effective means of metallizing the surface of non-metallic materials because of its good hardness, corrosion resistance, electrical conductivity and weldability. The traditional electroless nickel plating process for non-metallic materials uses PdCl ₂ for _acid roughening-acid sensitization-acid activation-nickel plating process. During the plating process, it is inevitable that palladium particles fall into the plating solution, which affects the stability of the plating solution. In addition, the palladium salt activation method needs to be carried out under acidic conditions, and the acid has a strong corrosive effect on cement, so the palladium salt activation method of nickel plating is not suitable for cement-based piezoelectric composite materials.

At present, there is no literature report on the method of palladium-salt-free activated electroless nickel plating on the surface of cement-based piezoelectric composite materials. The electroless nickel plating process of sensitization and activation to avoid the erosion of cement-based piezoelectric composites by acidic media is of great significance for the application and development of cement-based piezoelectric composites and the improvement of the electroless nickel plating process. In addition, it is also of great significance to save the use of precious metals and reduce process costs.

Contents of the invention

The object of the present invention is to provide a kind of method on the surface electroless nickel plating of cement-based piezoelectric composite material, this method improves and optimizes electroless nickel-plating method and process parameter according to the characteristic of cement-based piezoelectric composite material, gained The nickel plating is of good quality and combines well with cement-based piezoelectric composites.

Prior to this, the inventor has successfully developed a nickel-plating process on the surface of polymer-based piezoelectric composite materials, and applied for a patent with the application number: 201110271920.3. However, because the properties of cement and polymer are very different, it has been verified by experiments that this method is only suitable for composite materials composed of polymer and piezoelectric ceramics, and is not suitable for cement-based piezoelectric composite materials. Moreover, this method needs to use acid in the process of coarsening, sensitization, and activation, which has a great corrosion effect on cement, and is not suitable for cement-based piezoelectric composite materials. Therefore, aiming at the characteristics of cement-based piezoelectric composite materials, the inventor obtained an electroless nickel plating method suitable for cement-based piezoelectric composite materials through a large number of studies and experiments. The process flow is: roughening-reduction-activation-nickel plating, the whole process All are carried out under neutral or alkaline conditions, which not only effectively avoids the erosion of cement-based piezoelectric composite materials by acidic conditions, but also can obtain a coating with good performance on the surface of cement-based piezoelectric composite materials.

The cement-based piezoelectric composite material mentioned in the present invention refers to a piezoelectric composite material formed with a piezoelectric ceramic as a functional body and a mixture of a polymer and cement as a matrix. The piezoelectric ceramics can be various disclosed piezoelectric ceramics, such as PMN-ZT, PZT piezoelectric ceramics; the cement can be various cements disclosed in the prior art that can be used as a piezoelectric composite matrix, such as Ordinary Portland cement; the polymer can be various polymers disclosed in the prior art that can be mixed with cement as a matrix, and the polymer of the present invention especially refers to epoxy resin. The cement-based piezoelectric composite material of the present invention can be of 1-3 type, 0-3 type, 1-1 type and the like. In the preparation process, in order to make the piezoelectric composite material form well, in addition to piezoelectric ceramics, cement and polymer, there are inevitably some auxiliary forming agents, such as curing agent, diluent and so on. When nickel-plated on its surface, nickel needs to form a firm bond with piezoelectric ceramics, cement, and polymer at the same time, so that the nickel electrode obtained can combine well with cement-based piezoelectric composite materials, which greatly increases the difficulty of nickel plating.

The present invention has researched and obtained a method suitable for electroless nickel plating on the surface of the cement-based piezoelectric composite material. The method includes the steps of roughening, reducing, activating, and nickel-plating the surface of the cement-based piezoelectric composite material. It is carried out in alkaline roughening solution, the reduction solution used for reduction is methanol aqueous solution of sodium borohydride or ethanol aqueous solution of sodium borohydride, the activation solution used for activation is aqueous solution of nickel acetate or nickel sulfate containing additives, and the plating solution used for nickel plating The nickel solution is composed of: nickel sulfate 18-22g/L, trisodium citrate 8-16g/L, sodium hypophosphite 26-32g/L, sodium acetate 8-14 g/L, borax 6-10g/L, pH It is 6.5-7.5.

Furthermore, the method of the present invention also includes the steps of surface grinding and degreasing the surface of the cement-based piezoelectric composite material before roughening.

Further, in the method of the present invention, the roughening liquid used for roughening is an aqueous solution, and the preparation method of the roughening liquid is: sodium hydroxide and sodium carbonate are mixed with a mass ratio of 5:1 to form sodium carbonate and sodium hydroxide The total mass fraction is 35wt% aqueous solution, and then potassium permanganate and ethylenediamine are added to the solution so that the concentration of potassium permanganate is 5g/L and the concentration of ethylenediamine is 30mL/L, and the roughened solution is obtained.

Further, roughening is carried out at about 30°C. Generally, the time required for roughening is about 30 minutes.

Further, the reducing solution of the present invention is methanol aqueous solution or ethanol aqueous solution of sodium borohydride, and the composition of activation solution is nickel acetate or nickel sulfate, additive and water, and described additive is potassium iodide, sodium lauryl sulfate, ethylenediamine or polyethylene glycol. The present invention adopts the combination of sodium borohydride and nickel salt to prepare active nickel (i.e., activation points) by reduction with sodium borohydride. The activation points obtained by this method can be evenly distributed on the surface of cement-based piezoelectric composite materials, so that the subsequent nickel plating During the process, the nickel layer can be evenly distributed on the piezoelectric ceramics, cement and polymer, without causing delamination, shedding, etc., which provides a solid foundation for the smooth progress of subsequent nickel plating. Nickel activation replaces the traditional palladium salt activation method, which has lower cost and better environmental protection, and overcomes the disadvantage that palladium salt activation must use acid to cause adverse effects on cement. During the reduction process, the effect is better when the content of sodium borohydride in the reducing solution is 65-75 g/L. During the activation process, when the content of nickel acetate or nickel sulfate in the activation solution is 5-55 g/L, the effect is better. It has been verified by experiments that when the concentration of nickel salt in the activation solution is 25-35 g/L, the nickel plating speed is faster And the corrosion resistance of the coating is better, so the preferred concentration of nickel salt is 25-35g/L, and the most preferred concentration is 25g/L.

In the present invention, methanol aqueous solution or ethanol aqueous solution is selected as the solvent for the reduction solution, and water is selected as the solvent for the activation solution. The choice of solvent has a great influence on the uniformity of the activation point and the firmness of the activation point, and also has an important influence on the uniformity of the nickel layer and the firmness of the bond with the cement-based piezoelectric composite material. According to the characteristics of the cement-based piezoelectric composite material, the present invention obtains the required solvent through a large number of experimental studies. When the sodium borohydride is dissolved in the alcohol aqueous solution, the quality of the obtained coating is good. Preferably, when the volume ratio of methanol or ethanol to water is 1:1, the effect is the best.

In the method of the present invention, sodium borohydride reduction and nickel salt activation are selected. The reduction can be carried out at room temperature, and the activation can be carried out at 25°C-40°C, preferably at about 35°C, and the temperature is relatively low. Reduction and activation can be completed in a relatively short period of time. Generally, the time required for reduction and activation is about 10 minutes.

Further, in the activation solution, the content of the additive is 20-30 mg/L, and the additive is potassium iodide, sodium lauryl sulfate, ethylenediamine or polyethylene glycol, preferably polyethylene glycol. Experiments have proved that the addition of additives can make the distribution of activation points more uniform, make the coating and cement-based piezoelectric composite materials better bonded, which is conducive to improving the plating speed, and the formed coating has good crystal growth, good metallic luster, and surface morphology. More preferably, the corrosion resistance of the coating can also be improved. In addition, after the addition of additives, the active points are more firmly adsorbed on the surface of the cement-based piezoelectric composite material, and are not easy to fall off during the nickel plating process, and will not pollute the nickel plating solution, so that the nickel plating solution can be reused many times, improving The stability and service life of the nickel plating solution are improved, the number of post-treatments of the nickel plating solution is reduced, the environmental pollution of the nickel plating solution is reduced, and the cost is also greatly reduced. In addition, after adding additives, the phosphorus content of the coating is increased. According to literature reports, the phosphorus content is related to the corrosion resistance of the coating. The higher the phosphorus content, the better the corrosion resistance of the coating. It can be seen that the addition of additives also increases the corrosion resistance of the coating.

After activation treatment to form activation points, cement-based piezoelectric composites can be nickel-plated. The nickel plating solution used in the present invention is an aqueous solution of nickel sulfate. The nickel plating solution needs to be matched with the reducing solution and the activation solution, and needs to meet the characteristics of the cement-based piezoelectric composite material itself. After a lot of research, the inventor has obtained the present invention A suitable nickel plating solution, wherein the nickel plating solution has the best effect when the following content is selected: nickel sulfate 20g/L, trisodium citrate 12g/L, sodium hypophosphite 30g/L, sodium acetate 12 g/L, borax 8g /L, the pH is 6.5-7.5. The pH of the nickel plating solution of the present invention is nearly neutral, good in stability, difficult to decompose, and can be stored for a long time, and the nearly neutral nickel plating solution overcomes the corrosion and nickel plating of cement-based piezoelectric composite materials caused by the partial acidity of the nickel plating solution. The quality of the nickel layer obtained by the alkaline solution is reduced, and the plating solution is unstable. In addition, through the coordination and cooperation of various components, the obtained coating can achieve the advantages of uniformity, corrosion resistance, and good bonding force.

Further, the pH of the nickel plating solution can be adjusted with ammonia water.

Further, nickel plating is performed at about 45°C, for example, 45-50°C. The nickel plating time is related to the thickness of the obtained nickel layer. When the nickel plating time is about 15-20min, the thickness of the nickel layer can reach about 2µm, and the appropriate thickness can be obtained by adjusting the time as needed. According to the report of prior art, in partial neutral nickel plating liquid, need at higher temperature, for example 60-70 ℃ could carry out nickel plating better, and the nickel plating temperature of the present invention only needs about 45 ℃, Defects such as reduced energy consumption and instability of the plating solution brought by high temperature have a greater relationship with the present invention's early stage treatment, uniform distribution of activated points and many distributions. Under this nickel plating condition, the obtained coating is dense, uniform, with good bonding force and excellent quality.

The method for nickel plating of the present invention specifically comprises the following steps:

(1) Grinding and degreasing the surface of the cement-based piezoelectric composite material;

(2) Put the degreased cement-based piezoelectric composite material in the roughening solution for roughening treatment, and rinse with water after treatment;

(3) Put the coarsened cement-based piezoelectric composite material into the reducing solution for reduction treatment, and then put the reduced cement-based piezoelectric composite material into the activation solution for activation treatment;

(4) After activation, the cement-based piezoelectric composite material is taken out, rinsed with water, added to the nickel plating solution for electroless nickel plating, and the nickel plating is stopped when the plating layer reaches the required thickness to obtain the nickel plating layer.

Aiming at the particularity of the cement-based piezoelectric composite material not being resistant to acid, the present invention provides an electroless nickel plating method without palladium salt activation on the surface of the cement-based piezoelectric composite material. , activation and other pretreatments to form self-catalytic active centers on the surface, and then electroless nickel plating. The entire nickel plating process does not involve acidic reagents and will not cause damage to cement-based piezoelectric composite materials. The present invention has the following advantages:

1. The present invention uses sodium borohydride reduction to prepare active nickel at normal temperature, and replaces palladium salt activation with nickel activation, which is scientific and reasonable, with lower cost and better environmental protection.

2. The nickel plating solution of the present invention is nearly neutral, has good stability, is not easy to decompose, and can be stored for a long time.

3. The nickel plating method of the present invention is suitable for various cement-based piezoelectric composite materials with piezoelectric ceramics as the functional body and cement and epoxy resin as the matrix. Nickel plating is carried out under low temperature conditions, with low energy consumption and high repetition rate. Through the cooperation of various process conditions, a metal nickel layer can be plated on piezoelectric ceramics and cement substrates at the same time, which provides a great opportunity for the subsequent application of cement-based piezoelectric composite materials. convenience.

4. The coating of the present invention is a nickel-phosphorus alloy, the surface of the coating is smooth, the crystal grains are tightly combined and evenly distributed, the coating is uniform, has good corrosion resistance, good conductivity, strong weldability, and is tightly combined with cement-based piezoelectric composite materials. It is not easy to fall off, has good binding force, and has a good application prospect.

Description of drawings

Figure 1 Effect of nickel acetate concentration on plating speed.

Figure 2 SEM image (3000 times) of the coating obtained by using methanol-water as solvent.

Figure 3 SEM image (3000 times) of the coating obtained by using ethanol-water as solvent.

Figure 4 Tafel curves of the coatings activated by nickel acetate and nickel sulfate.

Figure 5 SEM image (3000 times) of the coating obtained when the additive is potassium iodide.

Figure 6 SEM image (3000 times) of the coating obtained when the additive is sodium dodecyl sulfate.

Figure 7 SEM image (3000 times) of the coating obtained when the additive is ethylenediamine.

Figure 8 SEM image (3000 times) of the coating obtained when the additive is polyethylene glycol.

Figure 9 SEM image (3000 times) of the coating obtained when the additive is cetyltrimethylammonium bromide.

Figure 10 Effect of different additives on the phosphorus content of the coating.

Figure 11 shows the SEM+EDS image of the coating surface obtained by the palladium activation method.

Figure 12 Tafel curves of coatings with and without palladium activation.

Figure 13 SEM image (3000 times) of the coating obtained in Comparative Example 2.

Figure 14 SEM image (3000 times) of the coating obtained in Comparative Example 3.

detailed description

The present invention will be further elaborated below through specific examples, and the following description is only for explaining the present invention, and does not limit its content.

In the inventive method, utilize electrochemical workstation to measure the corrosion resistance of coating, concrete method is to be corrosion solution with 3.5% sodium chloride solution, is reference electrode with saturated calomel electrode, and platinum electrode is auxiliary electrode, and corrosion area is 1.5% cm ² , scanning speed 0.1 V/s, waiting time 2 s.

In the inventive method, utilize weighing method to measure the plating speed of coating:

In the formula: v is the plating speed (g·dm ^-2 ·h ^-1 ); Δ m is the weight gain of the plated piece before and after plating (g); S is the coating area (dm ² ); t is the plating time (h ).

In the method of the invention, a scanning electron microscope is used to analyze the morphology of the nickel plating layer.

In the method of the invention, an energy spectrum analyzer is used to analyze the composition of the coating.

In the following examples, taking Type 1-3 cement-based piezoelectric composite materials as an example, the nickel plating process and the influence of various process parameters on the nickel plating effect are introduced in detail. The cement-based piezoelectric composite material used is made of PZT-5 piezoelectric ceramics as the functional body, a mixture of ordinary Portland cement, epoxy resin and curing agent as the matrix, and is prepared by cutting-casting method. The epoxy resin can be Various epoxy resins that can be used in piezoelectric composites, such as glycidylamine-based or linear aliphatic-based epoxy resins, such as AB-grout resins. The preparation method is as follows: along the direction of the polarization of the piezoelectric ceramics, according to the volume fraction of the ceramic phase, the cutting machine is used to accurately cut out the piezoelectric ceramic columns of the required size; Ultrasonic cleaning is carried out to remove the residual impurities, and then the cleaned piezoelectric ceramic block is dried and placed in the mold; the matrix material is prepared according to the mass ratio of cement, epoxy resin and curing agent 4:4:1, After fully stirring, perform vacuum treatment, pour the treated matrix into the mold, and perform vacuum treatment again; cut and polish the sample until the piezoelectric ceramic columns are completely exposed on both surfaces of the sample; finally prepare a cement-based piezoelectric composites. The size of the obtained cement-based piezoelectric composite material was 8×8 mm ² , and the thickness was 2 mm.

Example 1

Nickel plating is carried out on the surface of the cement-based piezoelectric composite material of 8×8mm ² and thickness of 2mm, and the steps are as follows:

Step 1: Grinding and degreasing the surface of the cement-based piezoelectric composite material to be plated:

Grind the cement-based piezoelectric composite material to be plated with 600# and 1000# sandpaper in sequence, and then finely polish it with metallographic sandpaper. After ultrasonic cleaning for 10 minutes, immerse it in a degreasing solution containing acetone and ultrasonically clean it for 20 minutes.

Step 2: Surface roughening of the cement-based piezoelectric composite material to be plated:

Put the degreased cement-based piezoelectric composite material in the roughening solution for roughening, treat it at 30°C for 30 minutes, and then rinse it with water to remove the roughening solution. The preparation method of the coarsening solution is: mix sodium hydroxide and sodium carbonate with a mass ratio of 5:1 to form a solution with a mass fraction of 35wt% (the total concentration of sodium carbonate and sodium hydroxide is 35%), and then add it to the solution Add potassium permanganate and ethylenediamine, the concentration of potassium permanganate is 5g/L, and the concentration of ethylenediamine is 30mL/L.

Step 3: Reduction treatment of the cement-based piezoelectric composite material to be plated:

Put the roughened cement-based piezoelectric composite into the reducing solution and soak for 10 min at room temperature. The reducing solution is: a mixture of sodium borohydride, methanol and water, wherein the content of sodium borohydride is 70 g/L, and the volume ratio of methanol and water is 1:1.

Step 4: Activation treatment of the cement-based piezoelectric composite material to be plated:

Take out the reduced cement-based piezoelectric composite material and immerse it directly in the activation solution for 10 minutes at 35°C, so that the nickel ions can be reduced to simple nickel and adsorbed on the surface of the substrate. After activation, rinse with water.

Step 5: Electroless nickel plating on the surface of the cement-based piezoelectric composite after activation:

The activated cement-based piezoelectric composite material was immersed in the nickel plating solution for electroless nickel plating, and the plating was performed for 20 minutes. The nickel plating solution is: nickel sulfate 20g/L, trisodium citrate 12g/L, sodium hypophosphite 30g/L, sodium acetate 12 g/L, borax 8g/L, adjust the pH to 6.5-7.5 with ammonia water, and The temperature was 45°C.

In the above-mentioned step 4, the activation solution is an aqueous solution of nickel acetate, and multiple parallel tests are carried out so that the content of nickel acetate in the activation solution is 5 g/L, 15 g/L, 25 g/L, 35 g/L, 45 g/L, respectively. g/L, 55 g/L, to test the effect of nickel acetate content on the coating.

The properties of the coatings obtained under different activation solution concentrations were tested respectively. The coatings obtained at each concentration have a bright appearance and good solderability. The surface of the coating is relatively smooth and compact. The surface of the electrode is pasted with 3M adhesive tape for many times. After pasting, the coating is very complete without obvious damage and peeling. The bonding between the coating layer and the surface of the piezoelectric composite material is good, and no boundary line between the cement matrix and the ceramic matrix can be seen on the surface of each coating layer macroscopically.

The influence of nickel acetate concentration on plating speed is shown in Figure 1. It can be seen from the figure that the nickel plating speed increases with the increase of the concentration of nickel acetate in the main activated salt. It is more obvious that it increases almost linearly. In the range of 25-55 g/L, although the plating speed also increases with the increase of nickel acetate concentration, the increase rate slows down.

The concentration of nickel acetate has a certain influence on the corrosion resistance of the coating. The self-corrosion potential of the coating obtained under different nickel acetate concentrations is shown in Table 1. The more positive the self-corrosion potential, the better the corrosion resistance of the coating. It can be seen from Table 1 : As the concentration of nickel acetate increases, the self-corrosion potential shifts positively. When the concentration of nickel acetate is 25-35g/L, the positive shift in this range is the largest, and the corrosion resistance is the best. Beyond this range, the positive shift decreases. Corrosion resistance deteriorates.

Table 1 Self-corrosion potentials of coatings obtained at different concentrations of nickel acetate

Nickel acetate concentration/mg·L ^-1 5 15 25 35 45 55 E _corr / V -0.6572 -0.5949 -0.5344 -0.5243 -0.5445 -0.6033

Based on the above various properties, a better coating can be obtained when the nickel acetate content is 5-55g/L, preferably 25-35g/L, most preferably 25g/L.

Example 2

Nickel plating is carried out on the surface of the cement-based piezoelectric composite material of 8×8mm ² and thickness of 2mm, and the steps are as follows:

Step 1: Same as Example 1.

Step 2: Same as Example 1.

Step 3: Reduction treatment of the cement-based piezoelectric composite material substrate to be plated:

Put the roughened cement-based piezoelectric composite into the reducing solution and soak for 10 min at room temperature.

Step 4: Activation treatment of the cement-based piezoelectric composite material substrate to be plated:

The reduced cement-based piezoelectric composite material was taken out and immersed in the activation solution, soaked at 35°C for 10 minutes, so that nickel ions could be reduced to elemental nickel and adsorbed on the surface of the substrate, and rinsed with water. The activation solution is an aqueous solution of nickel acetate, and the content of nickel acetate is 25 g/L.

Step 5: Same as Example 1.

In the above step 3, the reduction solution is methanol aqueous solution or ethanol aqueous solution of sodium borohydride respectively, the content of sodium borohydride is 65 g/L, and the volume ratio of methanol or ethanol to water is 1:1.

The scanning electron microscope image of the coating obtained by using methanol aqueous solution is shown in Figure 2. The surface of the coating is bright, the coating is smooth, the grains are densely bonded, and the bonding force is good. Use 3M adhesive tape to repeatedly paste the surface of the coating, and the result is no obvious damage on the surface of the coating, which shows that the bonding force of the coating is excellent. The composition of the coating was analyzed by an energy spectrum analyzer. The phosphorus content of the cement matrix part reached 6.03wt%, and the phosphorus content of the ceramic matrix part reached 6.76wt%. The coating has a high phosphorus content and has good corrosion resistance.

The scanning electron microscope image of the coating obtained by using ethanol aqueous solution is shown in Figure 3. The surface of the coating is bright, the coating is smooth, the grains are densely bonded, and the bonding force is good. Use 3M adhesive tape to repeatedly paste the surface of the coating, and the result is no obvious damage on the surface of the coating, which shows that the bonding force of the coating is excellent. The composition of the coating was analyzed by an energy spectrum analyzer. The phosphorus content of the cement matrix part reached 4.93wt%, and the phosphorus content of the ceramic matrix part reached 4.39wt%.

It can be seen from Figure 2 and Figure 3 that the microscopic morphology of the coating obtained by using different reducing solvents is different. The surface unit cell of the coating obtained by using methanol aqueous solution is smaller, and the boundary line of the coating on the cement matrix and the ceramic matrix is not obvious. The surface unit cell of the coating obtained by using ethanol aqueous solution is larger, and the boundary line of the coating on the cement matrix and the ceramic matrix is relatively obvious.

In summary, sodium borohydride can obtain better coatings by using methanol-water mixture or ethanol-water mixture as solvent. The water mixture is less toxic and more environmentally friendly.

Example 3

Nickel plating is carried out on the surface of the cement-based piezoelectric composite material of 8×8mm ² and thickness of 2mm, and the steps are as follows:

Step 1: Same as Example 1.

Step 2: Same as Example 1.

Step 3: Same as Example 1.

Step 4: Activation treatment of the cement-based piezoelectric composite material substrate to be plated:

Take out the reduced cement-based piezoelectric composite material and immerse it in the activation solution, and soak it at 35°C for 10 minutes, so that nickel ions can be reduced to simple nickel and adsorbed on the surface of the substrate, and rinsed with water after activation.

Step 5: Same as Example 1.

In the above step 4, the activation solution is an aqueous solution of nickel acetate or nickel sulfate, and the content of nickel acetate or nickel sulfate is 25g/L.

The coatings obtained by nickel acetate and nickel sulfate have bright and smooth surfaces, and the intergranular bonding is dense. The surface of the coating was pasted repeatedly with 3M adhesive tape, and there was no obvious damage on the surface of the coating, which indicated that the bonding force of the coating was excellent. The Tafel curve of nickel acetate and nickel sulfate obtained coating is shown in Figure 4, as can be seen from Figure 4, the corrosion resistance of nickel sulfate activated coating is slightly inferior to the corrosion resistance of nickel acetate activated coating, so nickel acetate is preferred.

Example 4

Nickel plating is carried out on the surface of the cement-based piezoelectric composite material of 8×8mm ² and thickness of 2mm, and the steps are as follows:

Step 1: Grinding and degreasing the surface of the cement-based piezoelectric composite material to be plated:

Grind the cement-based piezoelectric composite material to be plated with 600# and 1000# sandpaper in sequence, and then finely polish it with metallographic sandpaper. After ultrasonic cleaning for 10 minutes, immerse it in a degreasing solution containing acetone and ultrasonically clean it for 20 minutes.

Step 2: Surface roughening of the cement-based piezoelectric composite material to be plated:

Put the degreased cement-based piezoelectric composite material in the roughening solution for roughening, treat it at 30°C for 30 minutes, and then rinse it with water to remove the roughening solution. The preparation method of the coarsening solution is: mix sodium hydroxide and sodium carbonate with a mass ratio of 5:1 to form a solution with a mass fraction of 35wt% (the total concentration of sodium carbonate and sodium hydroxide is 35%), and then add it to the solution Add potassium permanganate and ethylenediamine, the concentration of potassium permanganate is 5g/L, and the concentration of ethylenediamine is 30mL/L.

Step 3: Reduction treatment of the cement-based piezoelectric composite material to be plated:

Put the roughened cement-based piezoelectric composite into the reducing solution and soak for 10 min at room temperature. The reduction solution is: a mixture of sodium borohydride, methanol and water, wherein the content of sodium borohydride is 75g/L, and the volume ratio of methanol and water is 1:1.

Step 4: Activation treatment of the cement-based piezoelectric composite material to be plated:

Take out the reduced cement-based piezoelectric composite material and immerse it directly in the activation solution for 10 minutes at 35°C, so that the nickel ions can be reduced to simple nickel and adsorbed on the surface of the substrate. After activation, rinse with water. The activation solution is an aqueous solution of nickel acetate, and the content of nickel acetate is 25 g/L.

Step 5: Same as Example 1.

The resulting coating has a bright surface and good weldability. The coating surface is relatively smooth and dense. There is no boundary line or crack between the piezoelectric ceramic base and the cement base. The electrode surface is pasted with 3M adhesive tape many times. After pasting, the coating is still very complete. , no obvious damage and peeling off, the coating is well combined with the base material. The composition of the coating was analyzed with an energy spectrum analyzer. The phosphorus content of the cement matrix part reached 5.01wt%, and the phosphorus content of the ceramic matrix part reached 5.59wt%.

Example 5

Nickel was plated on the surface of the cement-based piezoelectric composite material according to the method of Example 4, except that the activation temperature was 25°C and 40°C.

The coatings obtained at the activation temperatures of 25°C and 40°C all have bright and smooth surfaces, and the bonding between grains is dense. The surface of the coating was pasted repeatedly with 3M adhesive tape, and there was no obvious damage on the surface of the coating, which indicated that the bonding force of the coating was excellent. The composition of the coating was analyzed with an energy spectrum analyzer. The phosphorus content of the cement matrix part of the coating obtained at 25 ° C reached 4.35wt%, and the phosphorus content of the ceramic matrix part reached 4.87wt%. The phosphorus content of the cement matrix part of the coating obtained at 40 ° C reached 4.98wt%, and the phosphorus content of the ceramic matrix part reached 5.64wt%.

Example 6

Nickel plating is carried out on the surface of the cement-based piezoelectric composite material of 8×8mm ² and thickness of 2mm, and the steps are as follows:

Step 1: Same as Example 1.

Step 2: Same as Example 1.

Step 3: Same as Example 1.

Step 4: Activation treatment of the cement-based piezoelectric composite material to be plated:

The reduced cement-based piezoelectric composite material was taken out and immersed in different activation solutions, soaked at 35°C for 10 minutes, so that nickel ions could be reduced to simple nickel and adsorbed on the surface of the substrate, and rinsed with water.

Step 5: Same as Example 1.

In the above step 4, the activation solution is an aqueous solution of nickel acetate mixed with different additives, and the additives used are respectively potassium iodide, sodium lauryl sulfate, ethylenediamine, polyethylene glycol, and cetyltrimethylammonium bromide. The content of nickel acetate in the activation solution is 25g/L, and the content of additives is 30mg/L. At the same time, the coating obtained from the activation solution without additives is used as a blank control.

After adding different additives, the resulting coating has no obvious boundary between the cement base and the piezoelectric ceramic base, and the coating is a whole. Figures 5 to 9 are SEM images of the coating when potassium iodide, sodium lauryl sulfate, ethylenediamine, polyethylene glycol, and cetyltrimethylammonium bromide are added to the activation solution, as can be seen from the figure , The coatings obtained by adding different additives all have bright and smooth surfaces, and the intergranular bonding is dense. The surface of the coating was pasted repeatedly with 3M adhesive tape, and there was no obvious damage on the surface of the coating, which indicated that the bonding force of the coating was excellent.

Figure 10 is a comparison of the phosphorus content of the coatings obtained by adding different additives in the activation solution. It can be seen from the figure that after adding potassium iodide, sodium lauryl sulfate, ethylenediamine, and polyethylene glycol, the phosphorus content of the coatings is different. The improvement of the degree shows that the addition of additives increases the corrosion resistance of the coating. Among them, after adding polyethylene glycol, the phosphorus content of the cement matrix part reaches 9.97wt%, and the phosphorus content of the ceramic matrix part reaches 10.45wt%. The synergistic effect is the most obvious. After adding cetyltrimethylammonium bromide, the phosphorus content of the coating decreases and the corrosion resistance decreases. It can be seen that after adding potassium iodide, sodium lauryl sulfate, ethylenediamine, and polyethylene glycol, the grains of the coating are tightly bonded, and the morphology of the coating is significantly improved, and the morphology of the coating is improved after adding polyethylene glycol. Most notably, while the addition of cetyltrimethylammonium bromide had little effect.

Example 7

Nickel plating is carried out on the surface of the cement-based piezoelectric composite material of 8×8mm ² and thickness of 2mm, and the steps are as follows:

Step 1: Same as Example 4.

Step 2: Same as Example 4.

Step 3: Same as Example 4.

Step 4: Same as Example 4.

Step 5: Electroless nickel plating on the surface of the cement-based piezoelectric composite after activation:

The activated cement-based piezoelectric composite material was immersed in the nickel plating solution for electroless nickel plating, and the plating was performed for 20 minutes. The nickel plating solution is: nickel sulfate 18g/L, trisodium citrate 8g/L, sodium hypophosphite 26g/L, sodium acetate 8 g/L, borax 6g/L, adjust the pH to 6.5-7.5 with ammonia water, and apply the plating The temperature is 45°C.

The surface of the obtained coating is bright and has good solderability. The surface of the coating is relatively smooth and compact. The surface of the coating is pasted with 3M adhesive tape many times. After pasting, the coating is still very complete without obvious damage or peeling off. The composition of the coating was analyzed by an energy spectrum analyzer. The phosphorus content of the cement matrix part reached 4.84wt%, and the phosphorus content of the ceramic matrix part reached 5.31wt%.

Comparative example 1

Nickel plating is carried out on the surface of the cement-based piezoelectric composite material of 8×8mm ² and thickness of 2mm, and the steps are as follows:

Step 1: Same as Example 1.

Step 2: Same as Example 1.

Step 3: Sensitization treatment of the cement-based piezoelectric composite material to be plated:

Put the roughened cement-based piezoelectric composite into the sensitization solution and soak at room temperature for 7 minutes. Sensitizing solution formula: stannous chloride: 30g/L, 37% concentrated hydrochloric acid: 50mL/L.

Step 4: Activation treatment of the cement-based piezoelectric composite material to be plated:

The sensitized cement-based piezoelectric composite material was put into the activation solution and soaked at room temperature for 8 minutes. The activation solution formula: palladium chloride: 0.4 g/L, 37% concentrated hydrochloric acid: 9.9 mL/L.

Step 5: Same as Example 1.

The surface of the coating obtained by the acidic palladium activation method is darker, incomplete, with obvious defects visible to the naked eye, and the plating speed is relatively small. Figure 11 is a scanning electron microscope and an energy spectrum diagram of the obtained coating surface. It can be seen from the scanning diagram that the coating surface is uneven. There are larger grains agglomerated. It can be seen from the energy spectrum that the coating contains Si, C, O and other impurities, and the phosphorus content is low, only 1.54wt%. When it comes to corrosion, it reacts with acid, so the performance of the coating obtained by the palladium activation method is poor.

Fig. 12 is the Tafel curve contrast figure of palladium activation and the coating obtained without palladium activation, as can be seen from the figure, the self-corrosion potential of the coating obtained by the palladium activation method is obviously greater than the self-corrosion potential of the coating obtained by the palladium activation method, indicating that there is no The palladium activation method is more suitable for electroless nickel plating on the surface of cement-based piezoelectric composites.

Comparative example 2

Nickel plating is carried out on the surface of the cement-based piezoelectric composite material of 8×8mm ² and thickness of 2mm, and the steps are as follows:

Step 1: Same as Example 1.

Step 2: Same as Example 1.

Step 3: Reduction treatment of the cement-based piezoelectric composite material to be plated:

The roughened cement-based piezoelectric composite material was put into the reducing solution and soaked at room temperature for 10 min. The reducing solution was pure methanol solution of sodium borohydride, and the content of sodium borohydride was 70 g/L.

Step 4: Same as Example 1.

Step 5: Same as Example 1.

The use of pure methanol as a sodium borohydride solvent is easy to volatilize and difficult to operate, and the resulting coating has poor bonding with the substrate. This may be due to the high activity of sodium borohydride in pure methanol and the formation of more activation centers on the surface of the substrate to speed up the plating process. Caused by too large, from the naked eye, the surface of the coating is uneven, and there are cracks in the cement matrix and the ceramic matrix. Figure 13 is the topography of the coating surface. , The cracks in the cement matrix and the ceramic matrix are large and are not covered by the coating, so using pure methanol as the sodium borohydride solvent cannot obtain a coating with good performance.

Comparative example 3

Nickel plating is carried out on the surface of the cement-based piezoelectric composite material of 8×8mm ² and thickness of 2mm, and the steps are as follows:

Step 1: Same as Example 1.

Step 2: Same as Example 1.

Step 3: Same as Example 1.

Step 4: Same as Example 1.

Step 5: Electroless nickel plating on the surface of the cement-based piezoelectric composite after activation:

The activated cement-based piezoelectric composite material was immersed in the nickel plating solution for electroless nickel plating, and the plating was performed for 20 minutes. The nickel plating solution is: nickel sulfate 30g/L, trisodium citrate 20g/L, sodium hypophosphite 20g/L, sodium acetate 12 g/L, borax 8g/L, adjust the pH to 6.5-7.5 with ammonia water, and apply the plating The temperature was 45°C.

The surface morphology of the obtained coating is shown in Figure 14. It can be seen from the figure that the surface of the coating is uneven and uneven, and there are large grain accumulation and agglomeration at the junction of the cement matrix and the ceramic matrix. In addition, the binding force of the coating is also poor, and the surface of the coating is pasted with 3M adhesive tape many times, and the surface of the coating is damaged and peeled off after pasting. Therefore, the choice of nickel plating solution has a great influence on the performance of the coating.

The embodiments of the present invention cannot be exhaustive. The above examples only enumerate and illustrate some of the embodiments of the present invention. On the basis of the above examples, change the types of piezoelectric ceramics, epoxy resin and cement, change The type of material can also give good plating results.

Claims (13)

1. a kind of method in cement base piezoelectric composite material chemical nickel plating on surface, including to cement base piezoelectric composite material surface Be roughened, reduced, being activated, Nickel Plating Treatment the step of, it is characterized in that：Roughening is carried out in alkaline coarsening solution, is reduced used Reducing solution is the methanol aqueous solution of sodium borohydride or the ethanol water of sodium borohydride, and it is containing adding to activate activating solution used Add the nickel acetate aqueous solution or nickel sulfate solution of agent, the additive is KI, lauryl sodium sulfate, ethylenediamine or poly- Ethylene glycol, the nickel-plating liquid composition used in nickel plating are：Nickel sulfate 18-22g/L, trisodium citrate 8-16g/L, sodium hypophosphite 26- 32g/L, sodium acetate 8-14 g/L, borax 6-10g/L, pH 6.5-7.5.

2. the method according to claim 11, it is characterized in that：The cement base piezoelectric composite material refer to using piezoelectric ceramics as Functive, the piezo-electricity composite material formed using the mixture of epoxy resin and cement as matrix.

3. method according to claim 1 or 2, it is characterized in that：The compound method of coarsening solution is：By sodium hydroxide and carbonic acid Sodium is with 5:1 mass ratio mixing, the aqueous solution of sodium carbonate and sodium hydroxide total mass fraction for 35wt% is made into, it is then molten to this Potassium permanganate and ethylenediamine are added in liquid, makes potassium permanganate concentration be 5g/L, ethylenediamine concentration is 30mL/L, produces coarsening solution.

4. the method according to claim 11, it is characterized in that：In reducing solution, the content of sodium borohydride is 65-75 g/L.

5. the method according to claim 11, it is characterized in that：In reducing solution, methanol or the volume ratio of ethanol and water are 1: 1。

6. the method according to claim 11, it is characterized in that：The composition of activating solution be nickel acetate or nickel sulfate, additive and Water, the additive are polyethylene glycol.

7. the method according to claim 1 or 6, it is characterized in that：In activating solution, the content of nickel acetate or nickel sulfate is 5-55 g/L；The content of additive is 20-30mg/L.

8. the method according to claim 11, it is characterized in that：In activating solution, the content of nickel acetate or nickel sulfate is 25-35g/ L。

9. the method according to claim 11, it is characterized in that：In activating solution, the content of nickel acetate or nickel sulfate is 25g/L.

10. the method according to claim 11, it is characterized in that：Roughening is carried out at 30 DEG C；Reduction is carried out at room temperature；It is living Change is carried out at 25 DEG C -40 DEG C；Nickel plating is carried out at 45-50 DEG C.

11. the method according to claim 11, it is characterized in that：Activation is carried out at 35 DEG C；Nickel plating is carried out at 45 DEG C.

12. according to the method described in claim 1,10 or 11, it is characterized in that：Coarsening time is 30min, reduction and activation when Between be 10min.

13. according to the method for claim 1, it is characterized in that, comprise the following steps：

（1）Cement base piezoelectric composite material surface is polished and oil removing；

（2）Cement base piezoelectric composite material after oil removing is placed in coarsening solution and carries out roughening treatment, water rinses after processing；

（3）Cement base piezoelectric composite material after roughening is put into reducing solution and carries out reduction treatment, the cement base after reduction Piezo-electricity composite material, which places into, carries out activation process in activating solution；

（4）After activation, cement base piezoelectric composite material is taken out, water rinses, and adds in nickel-plating liquid and carries out chemical nickel plating, coating reaches Stop nickel plating during to required thickness, produce nickel coating.