CN1060094C - Process for preparing metal-ceramic composite film by chemical plating - Google Patents

Abstract

A kind of electroless plating method for preparing metal-ceramic composite film is to use the ceramic composite film modified with metal active components obtained by the in-situ modification method on the surface of sol colloidal particles as the bottom film, and directly add the bottom film to the electroless plating solution electroless plating. Since the active component particles on the bottom film can be used as the catalytic active center and the crystal nucleus for the growth of metal particles in the electroless plating process, the necessary sensitization and activation steps in the conventional electroless plating process are omitted, and the metal deposition This increases speed while also avoiding metal deposition on non-target surfaces of the base film.

Description

An electroless plating method for preparing metal-ceramic composite film

The present invention relates to the preparation of inorganic membranes, specifically to provide a ceramic composite membrane modified with metal active components first prepared by in-situ modification of the surface of colloidal sol particles, and then use the composite membrane as the bottom membrane to directly A new method for preparing metal-ceramic composite films by electroless plating.

Due to its excellent thermal stability, mechanical and structural stability, the ability to resist chemical reagents and microbial erosion, the performance of easy purification and regeneration, and its greater surface modification potential than organic membranes, on the one hand it is As a membrane separation material, it has an attractive prospect to replace traditional organic membrane materials. On the other hand, there is a realistic possibility of obtaining a new chemical material (catalytic membrane) with dual functions of reaction and separation from inorganic membranes. Therefore, the research on inorganic membranes has attracted more and more attention. However, when inorganic membranes are applied to gases and catalytic reactions, their separation efficiency is low. Therefore, how to improve the gas separation efficiency of inorganic membranes is one of the focuses of people's attention. Due to the high gas permeability of porous inorganic membranes, attempts have been made to improve the selectivity of porous membranes to gases through membrane surface modification. This method is to modify the surface of the membrane by introducing a certain substance, because this substance can preferentially interact with a certain gas to improve the permeation and diffusion ability of the membrane surface, thereby improving the separation efficiency of the membrane. However, although a certain active substance is introduced into the porous ceramic composite membrane, this substance has a strong interaction with certain gases, thereby improving the selectivity of the membrane to these gases. However, in many fields such as electronics, metallurgy and petrochemical industries, a large amount of high-purity hydrogen or even ultra-pure hydrogen is required. The separation coefficient of the ceramic composite membrane modified with active materials obviously cannot meet the needs of high-purity and ultra-pure hydrogen production. In order to To further improve the selectivity of membranes for hydrogen separation to meet the needs of high-purity ultra-pure hydrogen and high-efficiency hydrogen separation, people have focused their attention on dense metal membranes, especially palladium and palladium alloy membranes. The early palladium and palladium alloy films were unsupported. Due to the limitation of mechanical strength and other factors, the thickness of these palladium and palladium alloy films was generally greater than 150 μm. Since the rate of hydrogen permeation through palladium and palladium alloy membranes is inversely proportional to the membrane thickness, an increase in the membrane thickness means a decrease in the membrane’s hydrogen permeation rate, and an increase in the membrane thickness will lead to an increase in the amount of metal used, thereby causing an increase in cost. The metal composite membrane developed in recent years successfully overcomes these shortcomings. This composite membrane is supported by a thin metal top membrane with high permeability and high selectivity on a porous inorganic bottom membrane with high thermal and mechanical stability. These porous inorganic bottom membranes, such as stainless steel, porous glass, ceramics, porous silver, etc., ensure that the metal composite membrane has both good mechanical stability and high permeability. There are also many methods for preparing the metal composite film, and the one close to the present invention is the electroless plating method. This method has become a commonly used preparation method for metal composite films because of its simple equipment, low cost and the ability to deposit a complete top film on any shape and hardness of the bottom film. The so-called electroless plating, for example, for palladium, is actually a metastable complex of palladium that is reduced by the reducing agent hydrazine hydrate on the target surface of the substrate to decompose to generate metallic palladium nuclei, and these palladium nuclei are exactly the reduction reaction The catalyst, so that the reduction reaction with self-catalysis characteristics continues, and the palladium nuclei are continuously generated and grown on the surface of the substrate to form a dense layer. However, some substrates such as porous glass, ceramics and even stainless steel do not have sufficient catalytic activity for the above-mentioned reduction reaction, so the reduction reaction cannot be started quickly, and a long induction period is required for the reduction reaction to proceed. In order to eliminate this induction period, before electroless plating, enough palladium nuclei must be formed on the target surface of the substrate as active centers to catalyze the above-mentioned reduction reaction. The general method is obtained through a pre-sensitization activation process, but the pre-treatment process of this sensitization activation has a long period and also introduces some impurities.

The object of the present invention is to provide a kind of electroless plating method of preparing metal-ceramic composite membrane, this method can save the necessary sensitization activation step in conventional electroless plating process, and metal deposition speed is accelerated, also avoided simultaneously Deposition of metals on non-target surfaces of base films.

The electroless plating method for preparing metal-ceramic composite film provided by the present invention is characterized in that ① the bottom film of the metal-ceramic composite film before electroless plating is to make metal Pd, Rh or Ag ions are adsorbed to the surface of sol particles to prepare oxide sol containing metal component modification, and then use the sol to impregnate porous ceramics with casting technology, and obtain a ceramic composite membrane pre-modified by metal active components through drying-roasting-reduction As the base film; ② use the ceramic base film containing the metal composite film directly in the plating solution for electroless plating, and make the metal-ceramic composite film. The preparation of its electroless plating solution and the electroless plating process can be carried out according to conventional methods. Specifically the electroless plating method of preparing metal-ceramic composite film of the present invention follows the steps:

1. Preparation of oxide hydrosol containing metal components: using the in-situ modification method, firstly make γ-AlOOH sol with aluminum water as raw material, and take metal ions for modification, such as nitrate or nitrate containing Pd, Rh or Ag ions Chloride solution is added to the sol to prepare an oxide hydrosol containing metal components;

2. Dip-coating porous ceramic base film: using casting technology, using the above-mentioned prepared water sol as dip-coating sol, dip-coating porous ceramic base film, and drying-roasting to obtain a composite film; the above dip-coating, drying, and roasting processes can be repeated many times, Until the required thickness is reached, a porous ceramic composite membrane modified by metal oxides is obtained;

3. Reducing the composite membrane with hydrogen: Reducing the above composite membrane with hydrogen to reduce the metal ions to a metal state;

4. Electroless plating: Prepare the electroless plating solution according to the conventional technology, and then put the composite film treated in 3 directly in the plating solution for electroless plating to complete the preparation of the metal-ceramic composite film.

In the above preparation method, in the preparation process of the aqueous sol containing metal components, in order to make most of the metal ions adsorb on the surface of the colloidal sol, a complexing agent can be added to the metal-containing solution, and the complexing agent and metal Ion complexation can change the charging state of the complexed metal ions, so that the metal ions are almost completely adsorbed on the surface of the sol colloid within the range where the oxide hydrosol is stable. Compounds that can be used as the above-mentioned complexing agent are HN ₃ or carboxylic acids containing tetracarboxylic groups and their ammonium, sodium or potassium salts, such as EDTA or EGTA and their ammonium, sodium or potassium salts. The ratio of the complexing agent to the metal ion is 5-0.1 molar ratio. The content of the metal component in the oxide hydrosol containing the metal component is 0.1-20% (weight) of the oxide.

In the process of dip-coating the porous ceramic base film, an appropriate amount of polyvinyl alcohol (PVA) or polyethylene glycol (PEG) can be added to the oxide hydrosol containing metal components to adjust the viscosity of the hydrosol to facilitate dip coating. . Adding PVA or PEG can be done in a conventional way, and in accordance with a conventional casting technique, to complete the dip-coating of the porous ceramic base film. The dip-coated ceramic base film is fired at 400-800° C. for 1-5 hours.

The hydrogen reduction process can use hydrogen to reduce the porous ceramic composite membrane containing metal components under the condition of 200-600 ° C. The reduction time should not be less than 30 minutes, so that the metal ions can be fully reduced into metals, generally 0.5-4 hours. The metal-ceramic composite film after the above treatment can be electroless plated according to the conventional chemical plating method to prepare a metal-ceramic composite film.

The present invention will be described in detail below by way of examples.

Example 1

1 mol/l γ-AlOOH sol was prepared from SB powder (a kind of industrial use - diaspore produced by Condea in Germany) as raw material, and EDTA and Pd(NO ₃ ) ₂ were prepared at a molar ratio of 1:1 to form 0 .01mol/l solution, take a certain amount of solution and add it to the above-mentioned γ-AlOOH sol, the amount of added pd is 3% (the weight percentage of pd/γ-Al ₂ O ₃ ), use acid or alkali to adjust the pH, after stirring, 100% pd(II) was exchanged on the surface of the micelle, and 0.8mol/l 3% pd modified γ-AlOOH sol (weight, pd/γ-Al ₂ O ₃ ) was prepared.

Example 2

Starting from SB powder, prepare 0.8mol/l 1% pd modified γ-AlOOH sol (weight, pd/γ-Al ₂ O ₃ ) by a method similar to Example 1 without adding EDTA, add 1% PVA and 2 %PRG adjusts the viscosity of the sol, and the final concentration of the sol is 0.5mol/l. Use this sol as a dip coating sol to dip coat a porous ceramic bottom film, which is a flat film whose main component is α-Al ₂ O ₃ , with a diameter of 3 cm and an average pore size of 0.1 to 0.3 μm. , dried at room temperature for two days, then baked in a muffle furnace at 550°C for 3 hours, after six cycles of dipping-drying-baking, and reduced in a hydrogen atmosphere at 500°C for 4 hours, the top film on the bottom film side has turned black, while the other side has no color change, indicating that there is no distribution of palladium on the base film.

Example 3

Using the composite film prepared in Example 2, the composite film was directly placed in the plating solution for electroless plating. The composition of the plating solution is shown in Table 3, and the relationship between the amount of metal deposition and time is shown in Table 4. The advantage of this method is that the sensitization and activation process is omitted, and after electroless plating, there is no metal deposition on the other side of the bottom film.

table 3. Electroless plating solution composition Pd(NH ₃ ) ₄ Cl ₂ 4g/1EDTA. 2Na 67.2g/lNH ₃ . H ₂ O (28%) 350ml/lN ₂ H ₄ (0.1M) 50ml/l PH 11.2 Temperature 50℃

Table 4. The relationship between the deposition amount of metal and the deposition time in the electroless plating process Deposition time (hr) 0.2 0.5 1 2 3 4 Deposit amount (mg/cm ² ) 0.45 0.83 1.62 3.41 5.12 6.03

Example 4

Utilize the hydrosol containing the metal component prepared in Example 1, and make peritoneal membrane according to the method of Example 2, wherein the content of palladium is 3% (Wt, Pd/γ-Al ₂ O ₃ ), then use this The sol was dip-coated on the base film twice, dried, and baked to obtain a Pd-modified γ-Al ₂ O ₃ composite film. After the composite film was reduced with hydrogen at 500°C for 2 hours, the γ-Al ₂ O ₃ film was The palladium is just reduced to the palladium core of metallic state (Pd°), then the composite membrane is directly placed in the electroless silver plating solution for electroless plating, the composition of the plating solution is as the composition of embodiment 3 electroless plating solution, but wherein Ag ions replace pd ions, and the relationship between the amount of metal deposition and time is shown in Table 5. Metal silver forms a complete top film on the surface of the production bottom film, thereby obtaining a silver/ceramic composite film.

table 5. The relationship between the deposition amount of metal and the deposition time in the electroless plating process Deposition time (hr) 0.5 1 1.5 2 2.5 3 Deposit amount (mg/cm ² ) 0.89 1.84 2.67 3.46 4.26 5.37

Example 5

Application of the palladium/ceramic composite membrane prepared by the method of Example 3, wherein the average thickness of the top palladium is about 5 μm, this palladium/ceramic composite membrane is used for hydrogen permeation experiments, wherein the hydrogen pressure at the high pressure side of the membrane is 3 atmospheres (absolute pressure), The low pressure side is 1 atmosphere, at 500℃, the hydrogen permeation rate of palladium/ceramic composite membrane is 21.7m ³ (STP)/m ² . hr, when using nitrogen-hydrogen mixed gas for gas separation experiments, the result was that the presence of nitrogen was not detected by the low-pressure side of the gas chromatography (ie, the permeation side), indicating that the palladium/ceramic composite membrane only permeates hydrogen and does not permeate nitrogen, and also shows that palladium The top layer is complete and dense, so the hydrogen selectivity of the palladium/ceramic composite membrane prepared by this method can reach 100%.

Show by above-mentioned example, adopt the technology of the present invention to have saved the sensitization and activation step of step multifarious and time-consuming that must be carried out in the conventional electroless plating process, and metal deposition speed is accelerated, also avoided metal at the non-target surface of base film simultaneously deposition on.

Claims (6)

1. chemical plating method for preparing the metal-ceramic composite membrane, it is characterized in that 1) counterdie that carries out the metal-ceramic composite membrane before the chemical plating prepares by following method: at first, utilize colloidal sol surface in situ method of modifying, make metal pd, Rh or silver ion are adsorbed onto the colloidal sol surface, obtain containing the oxide sol of metal component; Use this colloidal sol again, adopt casting technique dip-coating porous ceramics counterdie, drying-roasting-reduction and the pottery that obtains the pre-modification of containing metal active constituent is protected the counterdie of film again; 2) utilize prepared counterdie, directly put into chemical plating bath and carry out chemical plating.

2. according to the described chemical plating method of claim 1, when it is characterized in that preparing the oxide hydrosol of containing metal component, complexing agent is added containing metal pd, and in the nitrate or oxide solution of Rh or silver ion, the metal ion aqueous solution that will contain complexing agent again adds in the diaspore AlOOH colloidal sol.

3. according to the described chemical plating method of claim 2, it is characterized in that complexing agent is NH ₃, EDTA, EDGA or EDTA and EDGA ammonium, sodium or sylvite, complexing agent and metal ion add by 5～0.1 mol ratios.

4. according to the described chemical plating method of claim 1, it is characterized in that containing in the oxide sol of metal component tenor and oxide Al ₂O ₃Weight ratio be 0.1～20%.

5. according to the described chemical plating method of claim 1, it is characterized in that adopting the porous ceramics counterdie of casting technique dip-coating, under 400～800 ℃, carried out roasting 1～5 hour.

6. according to the described chemical plating method of claim 1, it is characterized in that adopting the porous of casting technique dip-coating to make pottery after the money counterdie carries out roasting, under 200～600 ℃, reduced 0.5～4 hour with hydrogen.