CN107815677A - A kind of method that metal bonding intensity is significantly improved using metal complex - Google Patents

Abstract

The invention relates to a method for improving the bonding strength of metals by utilizing metal complexes. In particular, it concerns the effect of Schiff base metal complexes on the strength of metal bonds. The design method is to construct the micro-nano structure on a clean metal plate; hydroxylation on the surface of the metal plate; preparation of the double salicylaldehyde Schiff base ligand and its metal complexes; self-assembly of the Schiff base metal complexes on the surface of the metal plate; A single-lap shear sample was pressed to explore its effect on the metal/resin bond strength. The invention improves the interface strength between the metal and the resin through the effects of mechanical meshing force, chemical bond, molecular winding and the like. Combining anodic oxidation with Schiff base titanium complex process, the single-lap shear strength of TC4/PEEK reaches 47.5MPa, which is 54.2% higher than that of pure anodic oxidation (30.8MPa). It is beneficial to solve the problems of interface delamination, damp heat aging and the like in the fiber metal laminate, and the preparation process is simple, the reaction conditions are controllable, and large-scale production and application can be realized.

Description

A Method for Significantly Improving Metal Bonding Strength Using Metal Complexes

technical field

The invention belongs to the field of metal surface modification, and relates to a method for improving metal bonding strength by using metal complexes, in particular to the influence of Schiff base metal complexes on metal bonding strength.

Background technique

Fiber metal laminates, which were developed for high fatigue crack areas of civil aircraft in the early days, are super-hybrid laminates formed by alternate lamination of fiber composite materials and metal sheets and hot pressing. Hyper-hybrid laminates combine the excellent toughness of metals with the high strength, high modulus, and fatigue resistance of fiber composites to meet higher requirements in the aerospace field.

There are multi-layer interfaces in the middle of fiber metal laminates. If the interface bonding performance is poor, the advantages of metal laminates such as excellent fatigue resistance, high damage tolerance, and high strength cannot be exerted. Therefore, the adhesive performance between metal and resin directly leads to its application in aerospace, automobile and construction industries.

At present, there are mechanical methods (physical methods) and chemical methods to improve the interface bonding performance. The main purpose is to improve (1) the roughness of the surface, increase the contact area, and increase the bonding force through mechanical engagement; (2) change the surface structure, and make the metal and resin bonded through chemical bonds as much as possible. Because chemical bonds have stronger bond energy and stability than various physical interactions, optimizing their interface properties through chemical bonds has become a key research direction.

After searching the existing literature, it is found that the Chinese application publication number: CN103540934A, the patent titled "a surface-modified medical titanium metal material and its preparation method" proposes to graft more than one generation of titanium metal with terminal on the surface of titanium metal. Amino dendritic macromolecules, in order to improve not only the mechanical chimerism between the implant and the bone tissue, but also a strong chemical osseointegration. However, this method of improving the surface activity of metals through organic substances is only used in medicine, and this organic substance is only suitable for the human body environment and cannot withstand high temperatures. However, the present invention attempts to improve the interfacial properties of structural materials through high-temperature-resistant metal-organic complexes.

Contents of the invention

The invention relates to a method for improving the bonding strength of metals by using metal complexes, aiming at overcoming the phenomenon that the metal-resin interface is easy to delaminate.

The invention utilizes the strong chemical bond between the metal complex and the hydroxyl group on the metal surface to improve the interface performance between the metal and the resin. After the surface of the metal plate is treated by anodic oxidation and hydroxylation, a Schiff base metal complex is grafted on the surface. The Schiff base metal complex is connected to the metal end through a chemical bond, and the other end has molecular entanglement and adsorption with the resin. Force, thus playing the role of bridging. And, the present invention does significantly improve the interfacial bonding performance.

The invention provides a method for improving metal bonding strength by utilizing metal complexes:

Include the following steps:

S1. Remove the oil stain and oxide film of the metal plate;

Wherein, the specific steps of cleaning the metal plate are: preparing a mixed acid solution of nitric acid and hydrofluoric acid, and the mass fraction of nitric acid is 350g/L, and the mass fraction of hydrofluoric acid is 60g/L. Put the metal plate cleaned with acetone and water in the mixed acid solution for about 40 seconds, take it out quickly, rinse with a large amount of water, and wash away the acid solution.

Further, a micro-nano rough structure can be constructed on the surface of the metal plate, the method is anodic oxidation, and its specific operation steps are: prepare electrolyte: sodium hydroxide 300g/L, sodium tartrate 65g/L, ethylenediaminetetraacetic acid 30g /L, sodium silicate 6g/L. A titanium plate is used as the anode, and a stainless steel of the same size is used as the cathode, and the distance between the cathode and the anode is fixed at 3 cm. The voltage of the DC power supply during anodizing is 10V-15V, and the time is 10min-20min.

S2. Hydroxylation of the metal plate surface; using Piranha solution, wherein the volume ratio of H ₂ SO ₄ to H ₂ O ₂ solution is 7:3. Immerse the treated metal plate in the above solution, treat it at a high temperature of 90°C for about 5 minutes, take out the metal plate, rinse it with distilled water several times, dry it, and set it aside.

S3, preparing the Schiff base metal complex.

Further, the preparation method of the Schiff base ligand is as follows: weigh 3,5-di-tert-butyl salicylaldehyde in absolute ethanol, magnetically stir and reflux to dissolve, and quickly drop ethylenediamine into the reaction flask under stirring, Rapidly produced a large amount of yellow precipitate, filtered, washed with hot anhydrous ethanol for 3 times, and dried in vacuum until constant weight to obtain a yellow solid powder, which was stored in vacuum for later use.

Further, the preparation method of the Schiff base metal complex is: dissolve the Schiff base ligand in dehydrated toluene, add Ti(OCH ₂ CH ₃ ) ₄ or Al(CH ₃ ) ₃ and other organometallic solutions under magnetic stirring, and react at room temperature 2h, suction filtration, the resulting solid was dried.

S4. Grafting a Schiff base complex on the surface of the metal plate by means of self-assembly. Dissolve the Schiff base metal complex in DMF (dimethylformamide) or NMP (N-methylpyrrolidone), then immerse the metal plate, and take out the metal plate at a constant speed after 1-2 hours.

The beneficial effects of the present invention are:

1) Use metal complexes to change the interface properties. Metal complexes belong to metal-organic compounds, and are mostly used in the fields of medicine and functional materials. It is a useful exploration to change metal-resin bonding.

2) The Schiff base metal complex and the metal end are connected by chemical bonds, and the other end and the resin generate molecular entanglement, adsorption and other forces, thereby playing a bridging role and significantly improving the interface bonding performance.

3) Combining anodic oxidation with Schiff base titanium complex process, the single lap shear strength of TC4/PEEK reaches 47.5MPa, which is 54.2% higher than that of pure anodized sample (30.8MPa).

4) The whole preparation process is simple, the reaction conditions are controllable, and large-scale production and application can be realized.

Description of drawings

Fig. 1 is a schematic diagram of metal surface treatment of the present invention, wherein (1) 1 is a metal plate, (2) 2 is the nano-rough structure of the metal plate surface; (3) 3 is the hydroxyl group on the metal plate surface; (4) 4 is the Schiff base complex grafted on the surface of the metal plate.

Fig. 2 is the FTIR test of the surface after the metal TC4 surface treatment of the present invention.

Fig. 3 is the TG-DSC curve of the Schiff base complex prepared in the present invention.

Fig. 4 is the contact angle test and surface energy after various TC4 surface treatments of the present invention.

Fig. 5 is a surface topography diagram after various TC4 surface treatments of the present invention.

Fig. 6 is a comparison diagram of the single lap shear strength of the TC4/PEEK interface of the present invention.

Detailed ways

The method of using metal complexes to improve metal bonding strength will be described in detail below through specific examples:

Example 1:

The first step is metal pretreatment. Cut a TC4 titanium plate of appropriate size, wash it with distilled water, and put the sample into acetone to clean it to remove oil; Rinse the sample with clean water and then transfer it to acid solution for cleaning for about 40 seconds to remove the oxide film on the surface of the TC4 titanium plate.

The second step is metal anodizing. Preparation of electrolyte: sodium hydroxide 300g/L, sodium tartrate 65g/L, ethylenediaminetetraacetic acid 30g/L, sodium silicate 6g/L. A TC4 titanium plate is used as the anode, and a stainless steel of the same size is used as the cathode, and the distance between the cathode and the anode is fixed at 3 cm. The voltage of the DC power supply during anodizing is 10V-15V, and the time is 10min-20min.

The third step is the hydroxylation of the metal surface. Prepare _Piranha solution in which the volume ratio of _H2SO4 to H2O2 solution is ₇ : ₃ . Immerse the treated TC4 in the above solution, treat it at a high temperature of 90°C for about 5 minutes, take out the metal plate, rinse it with distilled water several times, dry it, and set it aside.

The fourth step is to prepare Schiff base complexes and Schiff base titanium complexes. Weigh 9.4g (0.04mol) of 3,5-di-tert-butyl salicylaldehyde in 60mL of absolute ethanol, dissolve under magnetic stirring under reflux, and quickly drop 1.2ml (0.02mol) of ethylenediamine into the reaction flask under stirring , quickly produced a large amount of yellow precipitate, filtered, washed with hot anhydrous ethanol for 3 times, and dried in vacuum to constant weight to obtain a yellow solid powder, which was stored in vacuum for later use. Weigh 2.9564g (0.006mol) of 3,5-di-tert-butyl salicylaldehyde ethylenediamine ligand and dissolve it in 40mL of toluene, add 0.8mL (slightly less than 1.10mL) of Ti(OCH ₂ CH ₃ ) under magnetic stirring _4. React at room temperature for 2 hours, then add 0.108ml of distilled water, and stir for 3 hours. The reaction liquid crystallized at room temperature to obtain yellow blocky crystals, which were filtered, dissolved in dehydrated toluene and recrystallized twice, filtered, and vacuum-dried to constant weight to obtain a yellow solid, which was stored in vacuum for future use.

The fifth step is self-assembly of Schiff base metal complexes. Dissolve the above Schiff base complex in 50 mL of DMF, immerse the above-treated TC4 plate in the solution, lift it out at a uniform speed after 2 hours of self-assembly, and put it in an oven at 70°C to dry and evaporate the solution. Record the metal plate after this treatment as A+C.

Fig. 2 is the surface FTIR test of the TC4 board after Example 1. In the infrared spectrum, the broad peak at about 3432.10cm-1 is the -OH group. Part of this hydroxyl group may come from water molecules, and most of them should belong to the hydroxyl group obtained after Piranha treatment on the metal surface; the peaks at 2959.71cm-1 and 2869.71cm-1 The peak is the hydrocarbon group introduced by the raw material 3,5-di-tert-butyl salicylaldehyde; the peak at 1628.54cm-1 belongs to the absorption peak of the imine group (-CH=N-); the expansion and contraction of the phenolic hydroxyl group (Ar-O) The vibration peak appears at 1276.84cm-1. The peak at about 528cm-1 belongs to the absorption peak of O-Ti, indicating that the O on the phenolic hydroxyl group is coordinated with metal Ti, while the peak at about 550cm-1 belongs to the Ti-N bond, indicating that the N atom and Ti Atoms form coordination bonds. It shows that the Schiff base titanium complex self-assembles successfully on the metal plate.

Fig. 3 is a TG-DSC analysis diagram of the Schiff base titanium complex prepared in the present invention. It can be seen from the figure that the sample begins to decompose at about 358°C to 528°C, and the mass changes slightly at 390°C, which basically meets the temperature of hot pressing.

Example 2:

The first step is metal pretreatment. Cut a TC4 titanium plate of appropriate size, wash it with distilled water, and then put the sample into an acetone solution to clean it to remove oil stains; Rinse the sample with clean water and then transfer it to acid solution for cleaning for about 40s to remove the oxide film on the surface of the TC4 titanium plate.

In the second step, the metal surface is hydroxylated. Prepare _Piranha solution in which the volume ratio of _H2SO4 to H2O2 solution is ₇ : ₃ . Immerse the treated TC4 in the above solution, treat it at a high temperature of 90°C for about 5 minutes, take out the metal plate, rinse it with distilled water several times, dry it, and set it aside.

The third step is to prepare Schiff base complexes and Schiff base titanium complexes. Weigh 9.4g (0.04mol) of 3,5-di-tert-butylsalicylaldehyde in 60mL of absolute ethanol, dissolve under magnetic stirring under reflux, and quickly drop 1.2mL (0.02mol) of ethylenediamine into the reaction flask under stirring , quickly produced a large amount of yellow precipitate, filtered, washed with hot anhydrous ethanol for 3 times, and dried in vacuum to constant weight to obtain a yellow solid powder, which was stored in vacuum for later use. Weigh 2.9564g (0.006mol) of 3,5-di-tert-butyl salicylaldehyde ethylenediamine ligand and dissolve it in 40ml of toluene, add 0.8mL (slightly less than 1.10mL) of Ti(OCH ₂ CH ₃ ) under magnetic stirring _4. React at room temperature for 2 hours, then add 0.108 mL of distilled water, and stir for 3 hours. The reaction liquid crystallized at room temperature to obtain yellow blocky crystals, which were filtered, dissolved in dehydrated toluene and recrystallized twice, filtered, and vacuum-dried to constant weight to obtain a yellow solid, which was stored in vacuum for future use.

The fourth step is self-assembly of Schiff base metal complexes. Dissolve the above Schiff base complex in 50 mL of DMF, immerse the above-treated TC4 plate in the solution, lift it out at a uniform speed after 2 hours of self-assembly, and put it in an oven at 70°C to dry and evaporate the solution. Record the metal plate after this treatment as P+C.

Comparative example 1:

The first step is metal pretreatment. Cut a TC4 titanium plate of appropriate size, wash it with distilled water, and then put the sample into an acetone solution to clean it to remove oil stains; Rinse the sample with clean water and then transfer it to acid solution for cleaning for about 40s to remove the oxide film on the surface of the TC4 titanium plate.

The second step is metal anodizing. Preparation of electrolyte: sodium hydroxide 300g/L, sodium tartrate 65g/L, ethylenediaminetetraacetic acid 30g/L, sodium silicate 6g/L. A TC4 titanium plate is used as the anode, and a stainless steel of the same size is used as the cathode, and the distance between the cathode and the anode is fixed at 3 cm. The voltage of the DC power supply during anodizing is 10V-15V, and the time is 10min-20min. Record the metal plate after this treatment as A.

Comparative example 2:

Metal pretreatment. Cut a TC4 titanium plate of appropriate size, wash it with distilled water, and then put the sample into an acetone solution to clean it to remove oil stains; Rinse the sample with clean water and then transfer it to acid solution for cleaning for about 40s to remove the oxide film on the surface of the TC4 titanium plate. Record the metal plate after this treatment as P.

Fig. 4 shows the surface wettability of the metal plate TC4 after Example 1, Example 2, Comparative Example 1, and Comparative Example 2. Where (a) is P; (b) is P+C; (c) is A; (d) is A+C. It can be seen from the figure that since the Schiff base metal complexes belong to organic matter, the self-assembled Schiff base titanium complexes will increase the wetting angle of P and A samples and reduce the surface energy. However, strong chemical bonds play a dominant role in the results of Schiff base titanium complexes enhancing metal bonding properties.

Fig. 5 is a surface topography diagram of the metal plate TC4 after Example 1, Example 2, Comparative Example 1, and Comparative Example 2. Where (a) is P; (b) is A; (c) is P+C, A+C. It can be seen from the figure that, compared with the P sample, the surface of the A sample has uniform spheres, forming nano-protrusions and pits on the surface of the metal TC4, which increases the bonding area with the resin and forms a mechanical bite to improve the interface. strength. The surface of the P+C and A+C samples presents a flower shape, and it is similar to growing out of the collective, further indicating that the Schiff base titanium complex interacts with the metal plate through a certain bond.

Figure 6 shows the effects of different treatment methods of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 on the bonding performance of TC4/PEEK. The size of the cut metal plate is 100*25, and the single-lap joint is 12.5*25. Lay the metal plate/resin/metal plate in sequence, and perform hot pressing on a flat vulcanizing machine. First, put the laminate into the mold and heat it from room temperature to 390°C, and hold at this temperature for 20 minutes, then pressurize at 0.6MPa and hold for 20 minutes, and finally, carry out natural cooling, when the temperature is lower than 340°C, start to release the pressure, and take out the sample when it cools to room temperature. The shear tensile test was carried out on the single sample by electronic universal testing machine. It can be seen from the figure that the self-assembled Schiff base titanium complex significantly improves the shear strength of the interface, and among the four samples, the anodized and self-assembled Schiff base titanium complex samples (A+C) have higher shear strength , reaching 47.5MPa, which is 54.2% higher than that of pure anodized sample (30.8MPa).

Claims (9)

1. A kind of 1. method that metal bonding intensity is improved using metal complex, it is characterised in that comprise the following steps：

   S1, the greasy dirt and oxide-film for going metallic plate；

   S2, metal sheet surface hydroxylating；

   S3, prepare Schiff base metal complexes；

   S4, Schiff base metal complexes are grafted in metal sheet surface by the method for self assembly.
2. 2. the method as described in claim 1, it is characterised in that：In step S1, the metallic plate is titanium alloy or aluminium alloy；Go The method of the oxide-film of metallic plate is after phosphoric acid solution, aqueous slkali or hydrofluoric acid/nitric acid mixed acid solution clean, to be washed with clear water Only.
3. 3. the method as described in claim 1, it is characterised in that：Also have between step S1 and step S2 and construct metal sheet surface The step of coarse structure of micro-nano；The building method of the coarse structure of described micro-nano is sandblasting, photoetching or anodic oxygen Change.
4. 4. the method as described in claim 1, it is characterised in that：In step S2, the hydroxylated solution of described metal sheet surface For Piranha solution, wherein H₂SO₄With H₂O₂The volume ratio of solution is 7:3.
5. 5. the method as described in claim 1, it is characterised in that：Schiff base metal complexes are matched somebody with somebody for schiff bases described in step S3 Body and the product of organometallic solutions reaction；Described Schiff base ligand is the multidentate ligand containing N, O.
6. 6. method as claimed in claim 3, it is characterised in that：The method of the anodic oxidation is using titanium plate as anode, with phase Stainless steel with size is negative electrode, and the fixed anode-cathode distance of negative and positive two is 3cm, and anodic oxidation electrolyte is sodium hydroxide, tartaric acid The mixed solution of sodium, ethylenediamine tetra-acetic acid and sodium metasilicate, the voltage of dc source are 10V~15V, the time be 10min~ 20min；

   The sodium hydroxide, sodium tartrate, ethylenediamine tetra-acetic acid and sodium metasilicate mixed solution in sodium hydroxide 300g/L, winestone Sour sodium 65g/L, ethylenediamine tetra-acetic acid 30g/L, sodium metasilicate 6g/L.
7. 7. method as claimed in claim 4, it is characterised in that：The metal sheet surface hydroxyl, which turns to, immerses metallic plate Piranha solution, 5min or so is handled under 90 celsius temperatures, metallic plate takes out, and distilled water flushing is multiple, and drying is standby.
8. 8. method as claimed in claim 5, it is characterised in that：The preparation method of the Schiff base metal complexes is by bigcatkin willow Aldehyde is dissolved in absolute ethyl alcohol, heating, stirring, and fast drop ethylenediamine is in reaction bulb under agitation, a large amount of precipitations to be generated, Filter, hot absolute ethyl alcohol washs 3 times, and it is the multidentate ligand containing N, O to be dried under vacuum to constant weight and obtain yellow solid powder；Then will The multidentate ligand containing N, O, which is dissolved in water-toluene, stirs lower addition Ti (OCH₂CH₃)₄Or Al (CH₃)₃Organometallic solutions, 2h is reacted at room temperature, is filtered, it is Schiff base metal complexes that gained solid, which is dried,.
9. 9. the method as described in claim 1, it is characterised in that：In step S4, the method for described self assembly is by step (3) Described in Schiff base metal complexes dissolve in DMF or NMP, then immerse metallic plate, metallic plate at the uniform velocity taken out after a few hours.