CN101974770A - Aqueous solution for electrodepositing iridium layer and method for preparing iridium layer in aqueous solution by way of electrodeposition - Google Patents

Abstract

The invention discloses an aqueous solution of an electrodeposited iridium layer and a method for preparing an iridium layer by electrodeposition in the solution. 100ml of the aqueous solution is prepared to contain an iridium compound with a concentration of 0.3-8g in terms of iridium and a stress reducer of 0.002 ~0.09mol, conductive salt 0.002~0.12mol, pH buffer 0.002~0.06mol. When electrodepositing the iridium layer, the pH value of the aqueous solution is 2.0-5.0, the cathode current density is 0.01-4.00A/dm ² , and the stirring speed is 60-1500r/min, the temperature is 70-90°C, after 1.0-50 hours of electrodeposition Take it out, wash it with deionized water, and then dry it at a temperature of 35-55° C. for 5-30 minutes, and then form an iridium layer with a particle size of 0.1-1.5 μm on the surface of the cathode plate. The prepared iridium layer is flat, dense, uniform in grains and free of cracks.

Description

Aqueous solution for electrodepositing iridium layer and method for preparing iridium layer by electrodeposition in the solution

technical field

The invention relates to an aqueous solution used for preparing an iridium layer by electrodeposition, and also relates to using a constant current method in the aqueous solution to prepare an iridium layer by electrodeposition.

Background technique

Many high-temperature materials such as C/C, ceramics and refractory metals such as molybdenum Mo, rhenium Re, tungsten W, etc., can be used as missile cruiser turbine engines, rocket combustion chamber walls, gas turbine engines, thermal power generators, and automobile industries due to their high melting points. And other base materials that require high temperature, but these materials are difficult to exert their characteristics because they cannot withstand ultra-high temperature oxidation corrosion above 1500 °C. In order to maintain the properties of these materials at ultra-high temperatures, it is necessary to prepare dense coatings that can resist ultra-high temperature oxidation on their surfaces. The materials of anti-oxidation coating mainly include silicide, noble metal, Ni-Cr alloy and so on. The noble metal iridium Ir is favored as an anti-oxidation coating for its series of excellent properties. Iridium Ir is currently the only refractory metal that satisfies high strength, high melting point, and excellent oxidation resistance at ultra-high temperatures. Therefore, the iridium layer can be used as an ultra-high temperature anti-oxidation coating for high-temperature materials and refractory metal components in extreme environments. Conventional oxidation coatings have a higher service temperature and longer service life.

At present, the methods for obtaining the iridium layer mainly include: chemical vapor deposition, magnetron sputtering, plasma spraying method, double glow plasma method, electrodeposition in high temperature molten salt system, etc. The equipment required for preparing the iridium layer by chemical vapor deposition is expensive and the cost is high. The magnetron sputtering method can produce high-purity iridium coatings, but the deposition rate is slow and it is not suitable for deposition on complex shapes. The iridium layer obtained by plasma spraying has a high porosity and cannot be used as a protective coating, especially in an ultra-high temperature environment. The iridium coating prepared by the double-glow plasma method produces high residual stress inside the coating due to the high-density ion bombardment of the iridium coating during the preparation process. The preparation of iridium layer by high-temperature molten salt electrodeposition has problems such as high operating temperature, high energy consumption, and strong corrosion.

Contents of the invention

One of purpose of the present invention is to propose a kind of aqueous solution that adopts when preparing iridium layer by electrodeposition, the concentration that contains iridium compound (calculated by iridium) in the described aqueous solution of preparation 100ml is 0.3～8g, stress reducing agent 0.002～0.09mol , conductive salt 0.002-0.12mol, pH value buffer agent 0.002-0.06mol.

The iridium compound is water-soluble iridium trichloride IrCl ₃ , iridium tetrachloride IrCl ₄ , iridium tribromide IrBr ₃ , iridium triiodide IrI ₃ , sodium hexachloroiridite Na ₃ IrCl ₆ , Potassium chloroiridite K ₃ IrCl ₆ , ammonium hexachloroiridite (NH ₄ ) ₃ IrCl ₆ , sodium hexabromoiridite Na ₃ IrBr ₆ , potassium hexabromoiridite K ₃ IrBr ₆ , hexachloroiridate One of sodium Na ₂ IrCl ₆ , potassium hexachloroiridate K ₂ IrCl ₆ and ammonium hexachloroiridate (NH ₄ ) ₂ IrCl ₆ .

The stress reducing agent is one of saccharin, sulfamic acid, sodium sulfamate, potassium sulfamate, 1,5-naphthalenesulfonic acid, 1,3,6-naphthalenetrisulfonic acid, and thiourea.

The conductive salt is one of potassium nitrate, sodium sulfate, sodium nitrate and sodium chloride.

The pH buffering agent is one of citric acid, ammonium citrate, sodium citrate, potassium citrate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate and disodium hydrogen phosphate.

The pH value of the aqueous solution may range from 2.0 to 5.0.

Another object of the present invention is to propose a method for preparing an iridium layer by electrodeposition in an aqueous solution using a constant current method. The iridium layer prepared by electrodeposition in aqueous solution by the method has the advantages of convenient operation, smooth, dense, uniform particles, no cracks, and suitable for deposition on components with complex shapes.

A kind of method for preparing iridium layer in the aqueous solution of electrodeposited iridium layer of the present invention is to carry out the step of preparing iridium layer by electrodeposition on the cathode under the condition of constant current mode:

(A) Preparation of electrolyzer solution

First, a certain amount of stress reducing agent, conductive salt and pH value buffer are dissolved in deionized water in turn, and then a certain amount of iridium compound is added while stirring under heating, and the volume is constant to a certain volume. Finally, adjust the pH value of the aqueous solution with 2.0 mol/L NaOH solution or 2.0 mol/L HCl solution.

Described iridium compound is water-soluble iridium trichloride, iridium tetrachloride, iridium tribromide, iridium triiodide, sodium hexachloroiridite (III), potassium hexachloroiridite (III), Ammonium(III) hexachloroiridite, sodium(III) hexabromoiridite, potassium(III) hexachloroiridate, sodium(IV) hexachloroiridate, potassium(IV) hexachloroiridate and hexachloroiridate One of ammonium iridate (IV).

The stress reducer may be one of saccharin, sulfamic acid, sodium sulfamate, potassium sulfamate, 1,5-naphthalenesulfonic acid, 1,3,6-naphthalenetrisulfonic acid, and thiourea.

The conductive salt can be one of potassium nitrate, sodium sulfate, sodium nitrate and sodium chloride.

The pH buffering agent can be one of citric acid, ammonium citrate, sodium citrate, potassium citrate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and disodium hydrogen phosphate.

(B) Electrode selection

Anode: one of graphite, platinum or iridium;

Cathode: The cathode can be made of a plate with conductivity on the surface, such as C fiber, Ni ₃ Al alloy of engine base material, Mo, W, Pt, Re or Nb refractory metal.

(C) Electrodeposition under constant current conditions

When electrodepositing the iridium layer, the pH value of the aqueous solution is adjusted to the range of 2.0 to 5.0, the cathode current density is 0.01 to 4.00A/dm ² , the stirring speed is 60 to 1500r/min, and the temperature is 70 to 90°C. After 50 hours, it is taken out, rinsed with deionized water, and then dried at a temperature of 35-55°C for 5-30 minutes, and an iridium layer is formed on the surface of the cathode plate. The prepared iridium layer is flat, dense, uniform in grains and free of cracks.

Description of drawings

FIG. 1 is an SEM picture of an iridium layer prepared in Example 1 of the present invention.

FIG. 1A is an enlarged SEM picture of the iridium layer prepared in Example 1 of the present invention.

Figure 2 is an EDS image of an iridium layer obtained on the surface of a Pt electrode.

Detailed ways

The present invention will be described in further detail below in conjunction with examples.

A kind of aqueous solution (electrolyzer liquid) that adopts when electrodeposition prepares iridium layer of the present invention, this aqueous solution is made up of iridium compound, stress reducer, conductive salt and pH buffering agent;

Dosage: Prepare 100ml of electrodeposited iridium layer aqueous solution containing 0.3-8g of iridium compound (the iridium compound is measured as iridium element), 0.002-0.09mol of stress reducer, 0.002-0.12mol of conductive Salt, 0.002-0.06mol pH buffer.

In the present invention, the iridium compound is water-soluble iridium trichloride IrCl ₃ , iridium tetrachloride IrCl ₄ , iridium tribromide IrBr ₃ , iridium triiodide IrI ₃ , sodium hexachloroiridite Na ₃ IrCl ₆ , potassium hexachloroiridite K ₃ IrCl ₆ , ammonium hexachloroiridite (NH ₄ ) ₃ IrCl ₆ , sodium hexabromoiridite Na ₃ IrBr ₆ , potassium hexabromoiridite K ₃ IrBr _6. One of sodium hexachloroiridate Na ₂ IrCl ₆ , potassium hexachloroiridate K ₂ IrCl ₆ and ammonium hexachloroiridate (NH ₄ ) ₂ IrCl ₆ .

In the present invention, the stress reducer can be saccharin, sulfamic acid, sodium sulfamate, potassium sulfamate, 1,5-naphthalenesulfonic acid, 1,3,6-naphthalenetrisulfonic acid, thiourea One of.

In the present invention, the conductive salt may be one of potassium nitrate, sodium sulfate, sodium nitrate and sodium chloride.

In the present invention, the pH buffering agent can be citric acid, ammonium citrate, sodium citrate, potassium citrate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate A sort of.

In the present invention, the pH value of the aqueous solution during electrodeposition of the iridium layer may range from 2.0 to 5.0, the cathode current density may be from 0.01 to 4.00A/dm ² , and the temperature of the electrodeposited solution may be from 70 to 90°C. Applying the present invention, under the condition of constant current mode, the steps of preparing iridium layer by electrodeposition on the cathode include:

(A) Preparation of electrolyzer solution

First, a certain amount of stress reducing agent, conductive salt and pH value buffer are dissolved in deionized water in turn, and then a certain amount of iridium compound is added while stirring under heating, and the volume is constant to a certain volume. Finally, adjust the pH value of the aqueous solution (electrolytic bath) with 2.0 mol/L NaOH solution or 2.0 mol/L HCl solution.

Described iridium compound can be easily water-soluble iridium trichloride, iridium tetrachloride, iridium tribromide, iridium triiodide, sodium hexachloroiridite (III), potassium hexachloroiridite (III ), ammonium (III) hexachloroiridite, sodium (III) hexabromoiridite, potassium (III) hexabromoiridate, sodium (IV) hexachloroiridate, potassium (IV) hexachloroiridate and One of ammonium hexachloroiridate (IV).

The stress reducer may be one of saccharin, sulfamic acid, sodium sulfamate, potassium sulfamate, 1,5-naphthalenesulfonic acid, 1,3,6-naphthalenetrisulfonic acid, and thiourea.

The conductive salt can be one of potassium nitrate, sodium sulfate, sodium nitrate and sodium chloride.

The pH buffering agent can be one of citric acid, ammonium citrate, sodium citrate, potassium citrate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and disodium hydrogen phosphate.

(B) Electrode selection

Anode: one of graphite, platinum or iridium;

Cathode: The cathode can be made of a plate with conductivity on the surface, such as C fiber, Ni ₃ Al alloy of engine base material, Mo, W, Pt, Re or Nb refractory metal.

(C) Electrodeposition under constant current conditions

When electrodepositing the iridium layer, the pH value of the aqueous solution is adjusted to the range of 2.0 to 5.0, the cathode current density is 0.01 to 4.00A/dm ² , the stirring speed is 60 to 1500r/min, and the temperature is 70 to 90°C. Take it out after 50 hours, wash it with deionized water, and then dry it at a temperature of 35-55° C. for 5-30 minutes, and then an iridium layer is formed on the surface of the cathode plate. The prepared iridium layer is flat, dense, uniform in grains and free of cracks.

Example 1:

In the electrodeposition tank, respectively dissolve 0.04mol sulfamic acid, 0.05mol sodium nitrate, and 0.03mol citric acid in 50ml of deionized water; 3.8g of iridium trichloride (IrCl ₃ ), heated up to 80°C±2°C to fully dissolve the iridium trichloride, add deionized water to 100ml of the solution, and finally adjust the pH value to 3.5 with 2.0mol/L NaOH solution ±0.2.

Use a graphite plate (the size of the graphite plate is 3.0cm × 2.0cm × 0.1cm, with a purity of 99.9%) as the anode, and a Pt gold plate (the size of the Pt gold plate is 3.0cm × 2.0cm × 0.1cm) as the cathode, and the surface of the anode and the cathode The surfaces are arranged parallel to each other, and the distance between the anode and the cathode is about 20mm;

Electrodeposition is carried out by direct current, and the constant current method is adopted, and the cathode current density is 0.50A/dm ² ;

After electrodeposition in the electrodeposition solution at 80°C±2°C for 20 hours, the cathode base material was taken out, rinsed with deionized water, and then dried at 35°C for 10 minutes to form an iridium layer on the Pt surface.

The iridium layer obtained on the Pt surface was observed with a scanning electron microscope (SEM), and its morphology is shown in FIG. 1 . It can be seen from Figure 1 that there is a flat and dense covering layer on the surface of the Pt substrate; it can be seen from Figure 1A that the particles of the covering layer on the Pt substrate are relatively uniform, and the particles are about 0.3 μm.

The EDS test was performed on the coating layer obtained on the Pt surface, as shown in Figure 2. It can be seen from Figure 2 that the composition of the covering layer obtained on the Pt surface is metal iridium Ir.

Example 2:

In the electrodeposition tank, respectively dissolve 0.01mol potassium sulfamate, 0.01mol potassium nitrate, and 0.004mol potassium dihydrogen phosphate in 50ml of deionized water; then add iridium while stirring at a stirring speed of 1000r/min. Sodium hexachloroiridite (III) with an elemental measurement of 1.0g was heated up to 70°C±2°C to fully dissolve sodium hexachloroiridite (III), and deionized water was added to make the solution 100ml, and finally 2.0mol/ L of HCl solution to adjust the pH to 2.5 ± 0.2.

Use a graphite plate (the size of the graphite plate is 3.0cm×2.0cm×0.1cm, and the purity is 99.9%) as the anode, and use the engine base material Ni ₃ Al alloy plate (the size of the Ni ₃ Al alloy plate is 3.0cm×2.0cm×0.1cm) As a cathode, the surface of the anode and the surface of the cathode are arranged parallel to each other, and the distance between the anode and the cathode is about 20mm;

Electrodeposition is carried out by direct current, and the constant current method is adopted, and the cathode current density is 3A/dm ² ;

After electrodeposition in the electrodeposition solution at 70°C±2°C for 5 hours, the cathode base material was taken out, rinsed with deionized water, and then dried at a temperature of 50°C for 5 minutes to form an iridium layer on the Pt surface.

Observing the iridium layer obtained on the surface of the Ni ₃ Al alloy plate with a scanning electron microscope (SEM), there is a smooth and dense covering layer on the surface of the Ni ₃ Al alloy plate substrate; the particles of the covering layer on the Ni ₃ Al alloy plate substrate Relatively uniform, and the particles are about 1.1μm.

The EDS test was carried out on the covering layer obtained on the surface of the Ni ₃ Al alloy plate, and the composition of the covering layer obtained on the surface of the Ni ₃ Al alloy plate was metallic iridium Ir.

Example 3:

In the electrodeposition tank, respectively dissolve 0.08mol thiourea, 0.10mol sodium chloride, and 0.05mol potassium citrate in 50ml of deionized water; For 7.0g of ammonium hexachloroiridate (IV), heat up to 85°C±2°C to fully dissolve the ammonium hexachloroiridate (IV), add deionized water to a solution of 100ml, and finally use 2.0mol/L HCl solution Adjust the pH to 4.5 ± 0.2.

Use a graphite plate (the size of the graphite plate is 3.0cm × 2.0cm × 0.1cm, and the purity is 99.9%) as the anode, and use a Re metal plate (the size of the Re metal plate is 3.0cm × 2.0cm × 0.1cm) as the cathode, and the surface of the anode and the cathode The surfaces are arranged parallel to each other, and the distance between the anode and the cathode is about 20mm;

Electrodeposition is carried out by direct current, and the constant current method is adopted, and the cathode current density is 1.50A/dm ² ;

After electrodeposition in the electrodeposition solution at 85°C±2°C for 10 hours, the cathode base material was taken out, rinsed with deionized water, and then dried at a temperature of 35°C for 10 minutes to form an iridium layer on the Pt surface.

The iridium layer obtained on the surface of the Re metal plate is observed with a scanning electron microscope (SEM), and there is a smooth and dense covering layer on the surface of the Re metal plate; the particles of the covering layer on the Re metal plate are relatively uniform, and the particles are about 0.5 μm.

The EDS test was carried out on the covering layer obtained on the surface of the Re metal plate, and the composition of the covering layer obtained on the surface of the Re metal plate was metal iridium Ir.

Electrodeposition is carried out by direct current in Example 1, and the constant current method is adopted, and the cathode current density is 0.50A/dm ² ; after 20 hours of electrodeposition in the electrodeposition solution at 80°C ± 2°C, the cathode base material is taken out, and deionized water After rinsing and drying at a temperature of 35° C. for 10 minutes, an iridium layer was formed on the Pt surface. Prepare the required aqueous solution composition of iridium layer like this:

The preparation of the iridium layer by electrodeposition in the aqueous solution prepared by the present invention can be operated at a lower temperature (70-90° C.), and the process conditions such as solution composition, solution pH value, and current density are easy to control. It is suitable for deposition in various Shaped substrate surface, low equipment investment, relatively simple process, and easy operation. Therefore, the preparation of iridium layer by electrodeposition in aqueous solution has broad application prospects.

Claims (7)

1. An aqueous solution of an electrodeposited iridium layer, characterized in that: the concentration of an iridium compound in iridium is 0.3～8g, stress reducer 0.002～0.09mol, conductive salt 0.002～0.12mol in the described aqueous solution of preparation 100ml, pH value buffer agent 0.002～0.06mol. 2. the aqueous solution of a kind of electrodeposition iridium layer according to claim 1, it is characterized in that: described iridium compound is iridium trichloride IrCl ₃ soluble in water, iridium tetrachloride IrCl ₄ , iridium tribromide IrBr ₃ , iridium triiodide IrI ₃ , sodium hexachloroiridite Na ₃ IrCl ₆ , potassium hexachloroiridite K ₃ IrCl ₆ , ammonium hexachloroiridite (NH ₄ ) ₃ IrCl ₆ , hexabromoiridite Na ₃ IrBr ₆ , potassium hexabromoiridate K ₃ IrBr ₆ , sodium hexachloroiridate Na ₂ IrCl ₆ , potassium hexachloroiridate K ₂ IrCl ₆ and ammonium hexachloroiridate (NH ₄ ) ₂ IrCl ₆ One of. 3. the aqueous solution of a kind of electrodeposition iridium layer according to claim 1, is characterized in that: described stress reducer is saccharin, sulfamic acid, sodium sulfamate, potassium sulfamate, 1,5-naphthalene One of sulfonic acid, 1,3,6-naphthalenetrisulfonic acid, and thiourea. 4. the aqueous solution of a kind of electrodeposition iridium layer according to claim 1, is characterized in that: described conductive salt is the one in potassium nitrate, sodium sulfate, sodium nitrate and sodium chloride. 5. the aqueous solution of a kind of electrodeposition iridium layer according to claim 1, is characterized in that: described pH value buffering agent is citric acid, ammonium citrate, sodium citrate, potassium citrate, sodium dihydrogen phosphate, One of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and disodium hydrogen phosphate. 6 . The aqueous solution for electrodepositing an iridium layer according to claim 1 , wherein the pH value of the aqueous solution can range from 2.0 to 5.0. 7. a kind of method that adopts the aqueous solution of electrodeposition iridium layer as claimed in claim 1 to prepare the method for iridium layer, it is characterized in that: under constant current mode condition, carry out electrodeposition on negative electrode and prepare the step of iridium layer to have: (A) Preparation of electrolyzer solution First, a certain amount of stress reducing agent, conductive salt and pH value buffer are dissolved in deionized water in turn, and then a certain amount of iridium compound is added while stirring under heating, and the volume is constant to a certain volume. Finally, adjust the pH value of the aqueous solution with 2.0 mol/L NaOH solution or 2.0 mol/L HCl solution. Described iridium compound is water-soluble iridium trichloride, iridium tetrachloride, iridium tribromide, iridium triiodide, sodium hexachloroiridite (III), potassium hexachloroiridite (III), Ammonium(III) hexachloroiridite, sodium(III) hexabromoiridite, potassium(III) hexachloroiridate, sodium(IV) hexachloroiridate, potassium(IV) hexachloroiridate and hexachloroiridate One of ammonium iridate (IV). The stress reducer may be one of saccharin, sulfamic acid, sodium sulfamate, potassium sulfamate, 1,5-naphthalenesulfonic acid, 1,3,6-naphthalenetrisulfonic acid, and thiourea. The conductive salt can be one of potassium nitrate, sodium sulfate, sodium nitrate and sodium chloride. The pH buffering agent can be one of citric acid, ammonium citrate, sodium citrate, potassium citrate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and disodium hydrogen phosphate. (B) Electrode selection Anode: one of graphite, platinum or iridium; Cathode: The cathode can be made of a plate with conductivity on the surface, such as C fiber, Ni ₃ Al alloy of engine base material, Mo, W, Pt, Re or Nb refractory metal. (C) Electrodeposition under constant current conditions When electrodepositing the iridium layer, the pH value of the aqueous solution is adjusted to the range of 2.0 to 5.0, the cathode current density is 0.01 to 4.00A/dm ² , the stirring speed is 60 to 1500r/min, and the temperature is 70 to 90°C. Take it out after 50 hours, wash it with deionized water, and then dry it at a temperature of 35-55° C. for 5-30 minutes, and then an iridium layer is formed on the surface of the cathode plate. The prepared iridium layer is flat, dense, uniform in grains and free of cracks.

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