High-strength silver-copper alloy and preparation method

Abstract

The invention relates to the technical field of alloys, and discloses a high-strength silver-copper alloy and a preparation method thereof. The acidified carbon nanotubes are subjected to functional modification, methylbenzene-2, 4-diisocyanate reacts with surface active groups of the methylbenzene-2, 4-diisocyanate to introduce-NCO groups, then through hydroxyl reaction of-NCO and 4-hydroxyphthalic acid, a plurality of carboxyl groups are grafted on the surfaces of the carbon nanotubes, the carboxyl groups can firmly adsorb lanthanum nitrate through a coordination effect, and meanwhile, the carboxyl groups can also adsorb lanthanum nitrate through a coordination effect. The rare earth elements are prevented from being separated from the raw materials in the ball milling process, uniform distribution is ensured, the agglomeration tendency of the carbon nanotubes can be reduced, and the dispersity of the carbon nanotubes in the silver-copper alloy is improved; the carbon nanotubes have extremely high axial strength and excellent conductivity, the mechanical and electrical properties of the alloy material can be enhanced through load transfer and a conductive network effect, rare earth lanthanum is segregated at a grain boundary to form a pinning effect to refine grains, the alloy strength is further improved, and finally collaborative improvement of the strength and the conductivity of the silver-copper alloy is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of alloys, in particular to a high-strength silver-copper alloy and a preparation method thereof. Background Art

[0002] For high-end applications requiring high strength, conductivity, heat resistance, and ductility, such as industrial robot arms, drones, and motor rotors, existing high-strength and high-conductivity materials fail to meet these requirements. Silver-copper alloy, a binary alloy, exhibits excellent conductivity, fluidity, wettability, superior mechanical properties, high hardness, wear resistance, and resistance to welding.

[0003] Carbon nanotubes (CNTs), as quasi-one-dimensional nanomaterials, possess extremely high strength and excellent electrical conductivity, making them considered one of the most ideal reinforcements in metal-matrix composites. Therefore, combining CNTs with copper (Cu) is expected to further enhance mechanical properties while retaining or even improving Cu's inherent excellent thermal and electrical conductivity, thereby promoting the integrated development of materials in terms of structure and functionality. Due to their excellent mechanical, thermal, and electrical properties, CNT-reinforced copper-based composites have attracted widespread attention and are being applied in fields such as new energy transportation, defense, and electronic information. However, poor interfacial wettability and the tendency of CNTs to agglomerate result in weak interfacial bonding, which reduces the reinforcement efficiency of CNTs and limits the full utilization of their inherent excellent properties, severely restricting the practical application of such composites. Therefore, designing and regulating the interface of CNTs / Cu composites is an important means to achieve synergistic improvements in their overall performance. The patent with authorization announcement number CN109126822B discloses a carbon nanotube-gold-copper alloy composite material and its preparation method and application. Carbon nanotubes, gold and copper are melted and blended to obtain an alloy material. However, this patent only improves the alloy's anti-ablation performance, but does not improve the alloy's tensile strength, conductivity and other properties.

[0004] Rare earth elements (such as lanthanum) further enhance the alloy's performance through their unique electronic structure and chemical activity. They segregate at grain boundaries, creating a pinning effect that refines the grains, increasing alloy strength and improving toughness. They form stable compounds with impurities, raising the recrystallization temperature and enhancing the alloy's heat resistance to adapt to high-temperature operating conditions. They also serve as heterogeneous nucleation sites for precipitated phases, promoting their uniform distribution and minimizing adverse effects on the alloy's electrical conductivity. This silver-copper-rare earth alloy significantly improves its adaptability in applications, but practical applications still face challenges such as cost control for both silver and rare earths, and uniform rare earth addition. Summary of the Invention

[0005] In response to the deficiencies in the prior art, the present invention provides a high-strength silver-copper alloy and a preparation method, which solves the problem of insufficient strength of traditional silver-copper alloys.

[0006] In one aspect, the present invention provides a method for preparing a high-strength silver-copper alloy, comprising the following steps: Step (1): add toluene and acidified carbon nanotubes into a flask, perform ultrasonic dispersion, add toluene-2,4-diisocyanate and dibutyltin dilaurate, stir and react at 60-75° C. for 7-10 hours, then add 4-hydroxyphthalic acid, stir and react for 4-8 hours, filter, wash with ethanol, and dry to obtain phthalic acid-modified carbon nanotubes.

[0007] Step (2): adding phthalic acid-modified carbon nanotubes and lanthanum nitrate to water, stirring at 20-35° C. for 4-6 hours, filtering, washing the product with water, placing it in a muffle furnace, calcining it at 250-300° C. for 1-2 hours, and cooling it to obtain carbon nanotube-loaded lanthanum oxide.

[0008] Step (3): placing carbon nanotube-loaded lanthanum oxide, elemental silver, and elemental copper in a planetary ball mill, ball-milling and mixing in an argon atmosphere, placing them in a hot-type horizontal continuous casting device, and covering them with a layer of calcined charcoal. Argon is introduced, and they are melted at 1100-1250° C. and cooled to form a high-strength silver-copper alloy.

[0009] Furthermore, in step (1), the amount of acidified carbon nanotubes used is 100 parts by weight, the amount of toluene-2,4-diisocyanate used is 800-1500 parts by weight, the amount of dibutyltin dilaurate used is 6-12 parts by weight, and the amount of 4-hydroxyphthalic acid used is 850-1800 parts by weight.

[0010] Furthermore, in step (2), the amount of phthalic acid-modified carbon nanotubes used is 100 parts by weight, and the amount of lanthanum nitrate used is 20-60 parts by weight.

[0011] Furthermore, in step (3), the amount of carbon nanotube-loaded lanthanum oxide is 0.3-1 parts by weight, the amount of elemental copper is 100 parts by weight, and the amount of elemental silver is 3-4 parts by weight.

[0012] Another aspect of the present invention provides a high-strength silver-copper alloy obtained by the above-mentioned preparation method.

[0013] Beneficial technical effects: The present invention functionalizes acidified carbon nanotubes, introduces -NCO groups by reacting toluene-2,4-diisocyanate with its surface active groups, and then grafts multiple carboxyl groups on the surface of the carbon nanotubes through the reaction of -NCO with the hydroxyl group of 4-hydroxyphthalic acid; on the one hand, these carboxyl groups can firmly adsorb lanthanum nitrate through strong polarity or coordination, avoiding the separation of rare earth elements during the ball milling process of the raw materials and ensuring uniform distribution; on the other hand, they can reduce the tendency of carbon nanotubes to agglomerate and improve their dispersibility in silver-copper alloys. Carbon nanotubes have extremely high axial strength and excellent electrical conductivity, and can enhance the mechanical and electrical properties of alloy materials through load transfer and conductive network effects, which is beneficial to improving the mechanical strength and conductivity of the alloy; rare earth lanthanum segregates at the grain boundaries to form a pinning effect to refine the grains, further enhance the strength of the alloy and improve the toughness, ultimately achieving a synergistic improvement in the strength, toughness and conductivity of the silver-copper alloy. DETAILED DESCRIPTION

[0014] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0015] 2 g of carbon nanotubes were placed in a mixed solution of 120 mL of concentrated sulfuric acid and 40 mL of concentrated nitric acid HNO3, heated to 70°C, stirred and refluxed for 8 h, filtered, washed with pure water, and dried to obtain acidified carbon nanotubes.

[0016] Example 1: A method for preparing a high-strength silver-copper alloy, comprising the following steps: (1) Add 300 mL of toluene and 5 g of acidified carbon nanotubes into a flask, disperse by ultrasonication, add 75 g of toluene-2,4-diisocyanate and 0.3 g of dibutyltin dilaurate, stir and react at 75 ° C for 7 h, then add 42.5 g of 4-hydroxyphthalic acid, stir and react for 8 h, filter, wash with ethanol, and dry to obtain phthalic acid-modified carbon nanotubes; (2) Add 10 g of phthalic acid-modified carbon nanotubes and 5 g of lanthanum nitrate to 3 L of water, stir at 30 ° C for 6 h, filter, wash with water, place the product in a muffle furnace, calcine at 260 ° C for 1 h, and cool to obtain carbon nanotube-loaded lanthanum oxide; (3) Place 6g of carbon nanotube-loaded lanthanum oxide, 2kg of elemental copper, and 60g of elemental silver in a planetary ball mill, mill and mix them in an argon atmosphere, place them in a hot-type horizontal continuous casting device, cover them with a layer of calcined charcoal, introduce argon, melt them at 1250℃, cool and shape them, and obtain a high-strength silver-copper alloy.

[0017] Example 2: A method for preparing a high-strength silver-copper alloy, comprising the following steps: (1) Add 350 mL of toluene and 5 g of acidified carbon nanotubes into a flask, disperse them by ultrasonication, add 40 g of toluene-2,4-diisocyanate and 0.6 g of dibutyltin dilaurate, stir and react at 60 ° C for 10 h, then add 80 g of 4-hydroxyphthalic acid, stir and react for 4 h, filter, wash with ethanol, and dry to obtain phthalic acid-modified carbon nanotubes; (2) Add 10 g of phthalic acid-modified carbon nanotubes and 4 g of lanthanum nitrate to 4 L of water, stir at 25 ° C for 5 h, filter, wash with water, place the product in a muffle furnace, calcine at 275 ° C for 2 h, and cool to obtain carbon nanotube-loaded lanthanum oxide; (3) Place 10g of carbon nanotube-loaded lanthanum oxide, 2kg of elemental copper, and 80g of elemental silver in a planetary ball mill, mill and mix them in an argon atmosphere, place them in a hot-type horizontal continuous casting device, cover them with a layer of calcined charcoal, introduce argon, melt them at 1100℃, cool and shape them, and obtain a high-strength silver-copper alloy.

[0018] Example 3: A method for preparing a high-strength silver-copper alloy, comprising the following steps: (1) Add 320 mL of toluene and 5 g of acidified carbon nanotubes into a flask, disperse them by ultrasonication, add 50 g of toluene-2,4-diisocyanate and 0.4 g of dibutyltin dilaurate, stir and react at 65 °C for 8 h, then add 60 g of 4-hydroxyphthalic acid, stir and react for 5 h, filter, wash with ethanol, and dry to obtain phthalic acid-modified carbon nanotubes; (2) Add 10 g of phthalic acid-modified carbon nanotubes and 2 g of lanthanum nitrate to 4 L of water, stir at 20 ° C for 6 h, filter, wash with water, put the product into a muffle furnace, calcine at 250 ° C for 2 h, and cool to obtain carbon nanotube-loaded lanthanum oxide; (3) Place 15g of carbon nanotube-loaded lanthanum oxide, 2kg of elemental copper, and 100g of elemental silver in a planetary ball mill, ball-mill and mix them in an argon atmosphere, place them in a hot-type horizontal continuous casting device, cover them with a layer of calcined charcoal, introduce argon, melt them at 1150°C, cool and shape them, and obtain a high-strength silver-copper alloy.

[0019] Example 4: A method for preparing a high-strength silver-copper alloy, comprising the following steps: (1) Add 330 mL of toluene and 5 g of acidified carbon nanotubes into a flask, disperse by ultrasonication, add 65 g of toluene-2,4-diisocyanate and 0.5 g of dibutyltin dilaurate, stir and react at 70 ° C for 9 h, then add 75 g of 4-hydroxyphthalic acid, stir and react for 7 h, filter, wash with ethanol, and dry to obtain phthalic acid-modified carbon nanotubes; (2) Add 10 g of phthalic acid-modified carbon nanotubes and 6 g of lanthanum nitrate to 3 L of water, stir at 35 ° C for 4 h, filter, wash with water, put the product into a muffle furnace, calcine at 300 ° C for 1 h, and cool to obtain carbon nanotube-loaded lanthanum oxide; (3) Place 20g of carbon nanotube-loaded lanthanum oxide, 2kg of elemental copper, and 200g of elemental silver in a planetary ball mill, ball-mill and mix them in an argon atmosphere, place them in a hot-type horizontal continuous casting device, cover them with a layer of calcined charcoal, introduce argon, melt them at 1200℃, cool and shape them, and obtain a high-strength silver-copper alloy.

[0020] Comparative Example 1: A method for preparing a silver-copper alloy, comprising the following steps: (1) Place 2 kg of copper and 60 g of silver in a planetary ball mill, mill and mix them in an argon atmosphere, place them in a hot-type horizontal continuous casting device, cover them with a layer of calcined charcoal, introduce argon, melt them at 1250 ° C, cool and shape them, and obtain a silver-copper alloy.

[0021] Comparative Example 2: A method for preparing a silver-copper alloy, comprising the following steps: (1) 6 g of acidified carbon nanotubes, 2 kg of elemental copper, and 60 g of elemental silver were placed in a planetary ball mill, ball-milled and mixed in an argon atmosphere, placed in a hot-type horizontal continuous casting device, covered with a layer of calcined charcoal, introduced with argon, and melted at 1250 ° C. The mixture was cooled and formed to obtain a silver-copper alloy.

[0022] Comparative Example 3: A method for preparing a silver-copper alloy, comprising the following steps: (1) Add 10 g of acidified carbon nanotubes and 5 g of lanthanum nitrate to 3 L of water, stir at 30 ° C for 6 h, filter, wash the product with water, put it into a muffle furnace, calcine at 260 ° C for 1 h, and cool to obtain carbon nanotube-loaded lanthanum oxide; (2) Place 6g of carbon nanotube-loaded lanthanum oxide, 2kg of elemental copper, and 60g of elemental silver in a planetary ball mill, mill and mix them in an argon atmosphere, place them in a hot-type horizontal continuous casting device, cover them with a layer of calcined charcoal, introduce argon, melt them at 1250℃, cool and shape them, and obtain a silver-copper alloy.

[0023] Comparative Example 4: A method for preparing a silver-copper alloy, comprising the following steps: (1) Add 300 mL of toluene and 5 g of acidified carbon nanotubes into a flask, disperse by ultrasonication, add 75 g of toluene-2,4-diisocyanate and 0.3 g of dibutyltin dilaurate, stir and react at 75 °C for 7 h, then add 42.5 g of p-hydroxybenzoic acid, stir and react for 8 h, filter, wash with ethanol, and dry to obtain p-benzoic acid-modified carbon nanotubes; (2) Add 10 g of benzoic acid-modified carbon nanotubes and 5 g of lanthanum nitrate to 3 L of water, stir at 30 ° C for 6 h, filter, wash with water, put the product into a muffle furnace, calcine at 260 ° C for 1 h, and cool to obtain carbon nanotube-loaded lanthanum oxide; (3) Place 6g of carbon nanotube-loaded lanthanum oxide, 2kg of elemental copper, and 60g of elemental silver in a planetary ball mill, mill and mix them in an argon atmosphere, place them in a hot-type horizontal continuous casting device, cover them with a layer of calcined charcoal, introduce argon, melt them at 1250℃, cool and shape them, and obtain a silver-copper alloy.

[0024] Alloy conductivity test: Tested in accordance with the national standard GB / T 32791-2016 "Eddy Current Test Method for Electrical Conductivity of Copper and Copper Alloys".

[0025] Tensile strength and elongation tests: Tests are carried out in accordance with the national standard GB / T 228.1-2021 "Tensile tests on metallic materials - Part 1: Room temperature test methods".

[0026] The test results of the embodiments and comparative examples obtained by the above test methods are shown in Table 1 below: Table 1: Performance test results of silver-copper alloys prepared in various embodiments and comparative examples

[0027] As can be seen from Table 1, Examples 1 to 4 functionalize the acidified carbon nanotubes, introducing -NCO groups by reacting toluene-2,4-diisocyanate with its surface active groups, and then grafting multiple carboxyl groups on the surface of the carbon nanotubes through the reaction of -NCO with the hydroxyl group of 4-hydroxyphthalic acid. On the one hand, these carboxyl groups can firmly adsorb lanthanum nitrate through strong polarity or coordination, thereby avoiding the separation of rare earth elements during the ball milling process of the raw materials and ensuring uniform distribution. On the other hand, they can reduce the tendency of carbon nanotubes to agglomerate and improve their dispersibility in the silver-copper alloy. As a quasi-one-dimensional nanomaterial, carbon nanotubes can enhance the mechanical and electrical properties of the composite material through load transfer and conductive network effects by virtue of their extremely high axial strength and excellent electrical conductivity. Rare earth lanthanum segregates at the grain boundaries to form a pinning effect to refine the grains, further enhancing the strength of the alloy and improving the toughness, ultimately achieving a synergistic improvement in the strength, toughness and conductivity of the silver-copper alloy.

[0028] Compared with the examples, in Comparative Example 1, no carbon nanotube-loaded lanthanum oxide was added, and the resulting silver-copper alloy had insufficient strength and was difficult to meet the needs of large-scale applications; in Comparative Example 2, only acidified carbon nanotubes were added, and their reinforcing effect was far inferior to that of the carbon nanotube-loaded lanthanum oxide system, and the improvement effect on the performance of the silver-copper alloy was limited; in Comparative Example 3, the acidified carbon nanotubes were not modified, resulting in weak adsorption capacity for lanthanum nitrate, which was easily separated during subsequent ball milling, thereby affecting the dispersion of the carbon nanotubes in the alloy and ultimately reducing the strength of the alloy; in Comparative Example 4, toluene-2,4-diisocyanate and p-hydroxybenzoic acid were used to modify the acidified carbon nanotubes. Compared with the 4-hydroxyphthalic acid modification system, the number of carboxyl groups introduced on the surface of the carbon nanotubes was less, and the adsorption capacity for lanthanum nitrate was reduced, but because the carboxyl structure was still retained, the adverse effect on the strength of the alloy was relatively reduced.

[0029] The above embodiments are only used to illustrate the technical method of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A method for preparing a high-strength silver-copper alloy, characterized in that: The following steps are involved: Step (1), adding toluene and acidified carbon nanotubes into a flask, ultrasonically dispersing, adding toluene-2,4-diisocyanate and dibutyltin dilaurate, stirring to react, then adding 4-hydroxyphthalic acid, stirring to react, filtering, washing with ethanol, and drying to obtain phthalic acid-modified carbon nanotubes; Step (2), adding phthalic acid-modified carbon nanotubes and lanthanum nitrate to water, stirring and filtering, washing the product with water, placing it in a muffle furnace, calcining it at 250-300° C. for 1-2 hours, and cooling it to obtain carbon nanotube-loaded lanthanum oxide; Step (3): placing carbon nanotube-loaded lanthanum oxide, elemental silver, and elemental copper in a planetary ball mill, ball-milling and mixing in an argon atmosphere, placing the mixture in a hot-type horizontal continuous casting device, and covering it with a layer of calcined charcoal. Then, introducing argon, melting the mixture, and cooling the mixture to obtain a high-strength silver-copper alloy.

2. The method for preparing a high-strength silver-copper alloy according to claim 1, wherein: In the step (1), the amount of acidified carbon nanotubes used is 100 parts by weight, the amount of toluene-2,4-diisocyanate used is 800-1500 parts by weight, the amount of dibutyltin dilaurate used is 6-12 parts by weight, and the amount of 4-hydroxyphthalic acid used is 850-1800 parts by weight.

3. The method for preparing a high-strength silver-copper alloy according to claim 1, wherein: In step (1), the temperature of the first reaction is 60-75° C. and the time is 7-10 h; the time of the second reaction is 4-8 h.

4. The method for preparing a high-strength silver-copper alloy according to claim 1, wherein: In the step (2), the amount of phthalic acid-modified carbon nanotubes used is 100 parts by weight, and the amount of lanthanum nitrate used is 20-60 parts by weight.

5. The method for preparing a high-strength silver-copper alloy according to claim 1, wherein: The stirring temperature in step (2) is 20-35° C. and the stirring time is 4-6 h.

6. The method for preparing a high-strength silver-copper alloy according to claim 1, wherein: In the step (3), the amount of carbon nanotube-loaded lanthanum oxide is 0.3-1 parts by weight, the amount of elemental copper is 100 parts by weight, and the amount of elemental silver is 3-4 parts by weight.

7. The method for preparing a high-strength silver-copper alloy according to claim 1, wherein: The smelting temperature in step (3) is 1100-1250°C.

8. A high-strength silver-copper alloy obtained by the preparation method according to any one of claims 1 to 7.

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