Preparation method of copper-based composite powder with high infrared laser absorptivity and reaction device

Abstract

The invention discloses a preparation method of copper-based composite powder with high infrared laser absorptivity and a reaction device of the copper-based composite powder, and belongs to the technical field of metal additive manufacturing. The preparation method of the copper-based composite powder comprises the following steps that copper powder is subjected to acid pickling pretreatment, Cu2O-coated Cu powder is prepared through air suspension dynamic etching, the Cu2O-coated Cu powder is purified, and the prepared composite powder is of a core-shell structure and comprises a copper core and a cuprous oxide modified shell wrapping the surface of the copper core; by means of the structure, the absorptivity of the copper powder to near-infrared laser of 1064 nm and the like can be remarkably improved to 30% or above, and therefore the problems that pure copper is poor in melting and multiple in forming defect due to high reflectivity in laser additive manufacturing are effectively solved. The composite powder can be directly used for existing selective laser melting or directional energy deposition equipment, has great significance in achieving high-density copper part forming under medium power, and is convenient to prepare, low in cost and high in practicability.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing technology, specifically relating to a copper-based composite powder suitable for selective laser melting (SLM) or laser directional energy deposition (DED) processes, and particularly a method for preparing copper-based composite powder with high infrared laser absorption rate and its reaction apparatus. Background Technology

[0002] Pure copper and most copper alloys exhibit extremely high reflectivity (>90%) and extremely low absorptivity (<10%) to commonly used near-infrared lasers (such as 1064 nm wavelength), resulting in low energy input efficiency during laser additive manufacturing. Insufficient energy input easily leads to incomplete powder melting, producing defects such as porosity, spheroidization, and lack of interlayer bonding, resulting in poor sample density and overall performance. To overcome this problem, existing technologies often require a significant increase in laser power (typically requiring kilowatt-level high-power lasers), which not only increases equipment costs, energy consumption, and process control difficulty, but may also cause problems such as overheating and spattering.

[0003] To overcome the aforementioned bottlenecks, surface modification of copper powder to enhance its laser absorption rate has become a key research direction. Currently, the main technical approach is to prepare a cuprous oxide (Cu₂O) layer with high infrared light absorption on the surface of copper powder. However, existing methods all have technical limitations in achieving effective, uniform, and robust Cu₂O coating. For example, the disproportionation reaction method utilizes Cu-containing... 2+ The solution reacts with a reducing agent under alkaline conditions to generate Cu2O particles, which are then physically mixed or adsorbed onto the surface of copper powder. The Cu2O particles obtained by this method have weak interfacial bonding with the copper matrix, and the Cu2O coating layer is easily peeled off. Patent CN106041120A uses a similar liquid-phase reduction method to prepare nanoscale copper / cuprous oxide (Cu / Cu2O) core-shell structures. However, laser additive manufacturing (SLM / DED) processes require the use of micron-sized (typically 15-150 μm) spherical metal powders to ensure good flowability. Mixing nanomaterials as a reinforcing phase with micron-sized matrix powder easily leads to severe component segregation and uneven dispersion. For low-temperature oxidation methods, the main approach is to control the heat treatment of copper powder in a low-temperature oxygen-containing environment to oxidize its surface and generate Cu2O. This method is extremely sensitive to temperature, oxygen partial pressure, and time, has poor reproducibility, and the resulting oxide layer often has varying thickness and uneven distribution, frequently exhibiting obvious "layering" or "regional" unevenness along the powder stacking direction.

[0004] Therefore, developing a novel technology that can construct a uniform, dense, and firmly bonded Cu2O coating layer on the surface of copper powder, while also being process-controllable and suitable for large-scale preparation, has become an urgent need to promote the mature application of laser additive manufacturing of copper and copper alloys. Summary of the Invention

[0005] Based on the aforementioned research background, the purpose of this invention is to provide a copper-based composite powder that is simple in structure, easy to prepare, and low in cost. A uniform, dense Cu2O layer, tightly bonded to the copper substrate, is generated in situ on the surface of the copper powder using a chemical etching method. The prepared composite powder significantly improves the absorption rate of 1064 nm near-infrared laser, thereby enabling high-quality forming of copper-based components on conventional power laser additive manufacturing equipment, overcoming the forming difficulties caused by the low infrared laser absorption rate of copper powder in existing technologies. This invention also provides a reaction apparatus for achieving dynamic etching in air suspension to prepare the aforementioned copper-based composite powder with high infrared laser absorption rate.

[0006] The first objective of this invention is to provide a method for preparing copper-based composite powder with high infrared laser absorption rate, comprising the following steps: (1) Copper powder pickling pretreatment Weigh 30.0 g to 100.0 g of copper powder and add it to 200 mL of 0.1 mol / L to 0.3 mol / L acidic solution. Sonicate the solution at room temperature for 5 to 15 minutes, then gently agitate to remove the CuO or Cu2O oxide layer from the surface of the copper powder. Immediately filter the solution and wash it 3 to 5 times with deionized water until the filtrate is neutral. Wash twice with anhydrous ethanol to replace the water. Vacuum dry the powder to obtain clean, active copper powder.

[0007] (2) Preparation of Cu2O@Cu powder by air suspension dynamic etching • Add the pretreated copper powder from step (1) to a gas washing bottle containing 200 mL of deionized water. Place the gas washing bottle in a constant temperature water bath, and set the water bath temperature to 40℃~80℃. Use the prepared FeCl3 solution as an etching agent and load it into an atomizing device. Introduce mixed gas into the gas washing bottle and adjust the gas flow rate to ensure that the copper powder is uniformly tumbling in the bottle without violent impact. Start the atomizing device and spray the FeCl3 solution uniformly into the gas washing bottle at a rate of 2.0 mL / min~5.0 mL / min for 5min~15min. After the FeCl3 solution is added, continue the reaction for 30min~60min, then turn off the reaction device and stop heating and gas introduction. During this process, the solution color gradually changes from the initial light yellow to orange or brownish-red, indicating that a Cu2O layer is formed on the surface of the copper powder. The reaction principle is shown in reaction (1-6): 2Fe 3+ (aq) + Cu(s) → 2Fe 2+ (aq) + Cu + (aq)(1) Cu + (aq) + 2Cl −(aq) → [CuCl2] − (aq)(2) 2[CuCl2] − (aq) + H2O(aq) → Cu2O(s)↓ + 4Cl − (aq) + 2H + (aq)(3) 2Cu + (aq) + 2OH − (aq) → Cu2O(s)↓ + H2O(aq) (4) Cu + (aq) + Cl − (aq) → CuCl(s)↓(5) 2Cu(s) + 4Cl − (aq) +O2(g)↑ → 2CuCl2(s)↓ + 2H2O(aq) (6) (3) Purification of Cu2O@Cu powder After the chemical etching reaction in step (2) is completed, the powder is filtered and transferred to 200 mL of dilute HCl with a concentration of 0.1 mol / L to 0.3 mol / L. The solution is then sonicated at room temperature for 5 to 15 minutes to dissolve any CuCl or CuCl2 (yellow-green) that may be generated. The powder is then filtered and washed 3 to 5 times with deionized water or anhydrous ethanol. Finally, the purified Cu2O@Cu composite powder is obtained by vacuum drying.

[0008] Preferably, in step (1), the raw material copper powder used is spherical or near-spherical gas-atomized pure copper powder with a purity of ≥99.9% and a particle size range of 10 μm~50 μm (suitable for selective laser melting (SLM) process) or 50 μm~100 μm (suitable for laser directional energy deposition (DED) process).

[0009] Preferably, in step (1) copper powder pickling, the acidic solution is one of dilute nitric acid (HNO3), dilute hydrochloric acid (HCl), or acetic acid (CH3COOH), with a concentration of 0.1 mol / L to 0.3 mol / L.

[0010] Preferably, in step (2), the mixed gas is compressed air and oxygen, the flow rate of the mixed gas is 0.5 L / min to 1.5 L / min, and the volume percentage of O2 in the mixed gas is 5 vol% to 15 vol%.

[0011] Preferably, in step (2), the etching solution is a FeCl3 solution with a concentration of 0.01 mol / L to 0.05 mol / L, and the spray flow rate is set to 2.0 mL / min to 5.0 mL / min. 100 mL of a 0.01 mol / L to 0.05 mol / L FeCl3 solution is placed in an atomizing device, and the atomizing device is started. The FeCl3 solution is sprayed into the reaction system at a rate of 2.0 mL / min to 5.0 mL / min for 5 min to 15 min to achieve dynamic etching via air suspension.

[0012] Preferably, in step (3), the composite powder has a core-shell structure, including a copper core and a cuprous oxide (Cu2O) modified layer coated on the surface of the copper core; the Cu2O has a cubic block particle microstructure, and the mass of the Cu2O modified layer accounts for 0.5 wt% to 5 wt% of the total mass of the composite powder.

[0013] Preferably, in steps (1) and (3), the vacuum drying temperature of the washed powder is controlled at 60℃~80℃, and the time is 2 h~4 h.

[0014] Preferably, in steps (1), (2), and (3), HNO3, FeCl3, HCl, and NaOH are all analytical grade (AR≥99%).

[0015] Preferably, the Cu2O modified layer is generated in situ on the surface of spherical or near-spherical copper particles by chemical etching, with a particle sphericity ≥90%, which meets the requirements of laser additive manufacturing.

[0016] Another objective of this invention is to provide a reaction apparatus for implementing the gas suspension dynamic etching described in step (2) above, comprising a gas flow meter, an atomizing device, a gas washing bottle, a water bath, and a tail gas absorption bottle. The gas washing bottle is placed in the water bath. The gas flow meter is connected to the gas washing bottle through a gas pipe. The tail gas absorption bottle is connected to the gas washing bottle through a gas pipe. The top of the atomizing device is provided with an atomizer inlet, a signal cable, and an atomizer outlet. The atomizer inlet is connected to air to provide a stable airflow. The atomizer outlet is connected to the upper part of the gas washing bottle through a gas pipe. The signal cable is connected to a water level sensor located inside the atomizer and the atomizer.

[0017] Preferably, the gas mixing cylinder contains a mixture of compressed air and oxygen, and a gas flow meter is installed on the gas pipe connecting to the gas mixing cylinder.

[0018] Preferably, the atomizer contains an etching solution, which is 100 mL of FeCl3 solution with a concentration of 0.01 mol / L to 0.05 mol / L, and the tail gas absorption bottle 9 contains a dilute NaOH solution.

[0019] The beneficial effects of this invention are: (1) The present invention achieves a uniform and dense cuprous oxide (Cu2O) layer coating on the surface of copper powder, which is tightly bonded to the copper substrate. The surface Cu2O layer can effectively capture infrared laser energy, and the copper powder can be fully melted using conventional power equipment, which greatly reduces the dependence on high-power lasers.

[0020] (2) The composite powder prepared by the method of the present invention has a core-shell structure, including a copper core and a cuprous oxide (Cu2O) modified shell covering its surface. This structure can significantly improve the absorption rate of copper powder to near-infrared lasers such as 1064 nm to more than 30%, thereby effectively solving the problem of poor melting and many forming defects caused by the high reflectivity of pure copper in laser additive manufacturing.

[0021] (3) The micron-scale core-shell structure design of the composite powder improves the infrared light absorption capability while maintaining the sphericity and fluidity of the original copper powder, ensuring stable operation in the existing powder spreading / feeding system, and finally achieving full melting and dense stacking of the powder to form high-density (>95%), low porosity and very few unfused defects of high-quality copper components.

[0022] (4) The present invention can achieve copper powder surface modification by one-step wet dynamic chemical etching process. The method is simple and mild, does not require complex equipment, and is conducive to large-scale production.

[0023] (5) The reaction device of the present invention can realize gas suspension dynamic etching to prepare composite powder with high efficiency. The device uses controllable airflow to make copper powder uniformly suspended and tumble in the liquid phase, so as to achieve full contact between the powder and the atomized etching agent, avoid the peeling of the modified layer caused by traditional mechanical stirring, and ensure the uniformity and integrity of the Cu2O coating layer. Attached Figure Description

[0024] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the embodiments and comparative examples will be briefly described below.

[0025] Figure 1 The images show the SEM morphology of copper powder after chemical etching in Example 1 and Comparative Example 1. Figure 2 The powder laser absorption rate of Example 1 and Comparative Example 1 measured at wavelengths of 600 nm to 1200 nm is shown in the graph. Figure 3 The images show the SEM morphology of copper powder after chemical etching in Example 2 and Comparative Example 2. Figure 4 The powder laser absorption rate of Example 2 and Comparative Example 2 measured at wavelengths of 600 nm to 1200 nm is shown in the graph. Figure 5The images show the SEM morphology of copper powder after chemical etching in Examples 3 and 3. Figure 6 The powder laser absorption rate of Example 3 and Comparative Example 3 measured at wavelengths of 600 nm to 1200 nm is shown in the graph. Figure 7 The components are: 1. Gas flow meter; 2. Atomizing device; 3. Atomizer inlet; 4. Signal cable; 5. Atomizer outlet; 6. Water level sensor; 7. Atomizer; 8. Gas washing bottle; 9. Water bath; 10. Tail gas absorption bottle. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the methods described are conventional methods, and the raw materials described are obtainable from publicly available commercial sources.

[0027] In the following embodiments: Cu powder purity ≥99.9%, particle size 10 μm~100 μm, morphology spherical or near-spherical, Shanghai Naio Nanotechnology Co., Ltd. HNO3, FeCl3, HCl, and NaOH were all analytical grade (AR≥99%), Shanghai Aladdin Biochemical Technology Co., Ltd. Laser absorption rate testing of the composite powders prepared in the examples and comparative examples: The experiments were conducted using a UV-Vis spectrophotometer (UV-3600plus). The wavelength was set to 600 nm to 1200 nm, and the slit width was 5 nm.

[0028] This invention provides a reaction apparatus for preparing Cu2O@Cu powder through dynamic etching in air suspension. The apparatus includes a gas flow meter 1, an atomizing device 2, a gas washing bottle 8, a water bath 9, and a tail gas absorption bottle 10. The gas washing bottle 8 is placed in the water bath 9, enabling constant-temperature water bath heating for the etching reaction. The gas flow meter 1 contains a mixture of compressed air and oxygen. The gas flow meter 1 is connected to the gas washing bottle 8 via a gas pipe that extends into the lower part of the gas washing bottle 8, contacting the liquid inside. By controlling the gas flow meter 1, the flow rate and velocity of the mixed gas can be controlled. The tail gas absorption bottle 10 is connected to the gas washing bottle 8 via a gas pipe. One end of the gas pipe is located at the top of the gas washing bottle without contacting the liquid inside, while the other end is located in the tail gas absorption bottle 10, contacting the dilute NaOH solution inside, thereby collecting the tail gas. The atomizing device 2 is equipped with an atomizer inlet 3, a signal cable 4, and an atomizer outlet 5 at its top. The atomizer inlet 3 is connected to air to provide a stable airflow. The atomizer outlet 5 is connected to the upper part of the gas washing bottle 8 via an air pipe. The signal cable 4 is connected to a water level sensor 6 and an atomizer 7 located inside the atomizing device 2. The atomizing device 2 contains an etching solution, which is 100 mL of FeCl3 solution with a concentration of 0.01 mol / L to 0.05 mol / L. The water level sensor 6 is used to monitor the remaining amount of FeCl3 solution in the atomizing device 2. The atomizer 7 atomizes the FeCl3 solution and sprays it into the gas washing bottle 8 in the form of micron-sized droplets, thereby achieving air-suspension dynamic etching to prepare Cu2O@Cu powder. Example 1 (1) Copper powder pickling pretreatment Weigh 30.0 g of copper powder and add it to 200 mL of 0.1 mol / L dilute HNO3 solution. Sonicate the powder for 5 min at room temperature, then gently agitate. Filter immediately and wash with deionized water 3–5 times until the filtrate is neutral. Then, wash the powder twice with anhydrous ethanol to replace the water and dry it in a vacuum drying oven at 60 °C for 2 h to obtain surface-pretreated copper powder.

[0029] (2) Preparation of Cu2O@Cu powder by air suspension dynamic etching Add the dried copper powder from step (1) to a gas washing bottle containing 200 mL of deionized water. Simultaneously, set the water bath temperature to 40℃ and add 100 mL of 0.01 mol / L FeCl3 solution to the nebulizer. Turn on the mixed gas and adjust the gas flow rate to 0.5 L / min. Start the nebulizer and spray the FeCl3 solution into the reaction system at a rate of 2.0 mL / min for 5 min. After the FeCl3 solution has been added, continue to ventilate for another 30 min, then turn off the experimental apparatus and stop heating and ventilation.

[0030] (3) Purification of Cu2O@Cu powder After the reaction in step (2) is complete, filter the powder and transfer it to 200 mL of 0.1 mol / L dilute HCl solution. Sonicate at room temperature for 5 min. After filtering, wash the powder 3-5 times with deionized water or anhydrous ethanol. Finally, dry in a vacuum drying oven at 60℃ for 2 h to obtain purified Cu2O@Cu composite powder.

[0031] Comparative Example 1 This comparative example aims to investigate the effect of the gas atmosphere on the chemical etching process. Its preparation process is basically the same as in Example 1, with the key difference being: the gasification process in step (2) is omitted, and the etching reaction is carried out in a completely static liquid environment. The specific process is as follows: (1) Copper powder pickling pretreatment This step is exactly the same as step (1) in Example 1. Weigh 30.0 g of copper powder and add it to 200 mL of 0.1 mol / L dilute HNO3 solution. After sonication for 5 min at room temperature, gently shake. Filter immediately and wash with deionized water 3-5 times until the filtrate is neutral. Then, wash the powder twice with anhydrous ethanol to replace the water and dry it in a vacuum drying oven at 60℃ for 2 h to obtain surface-pretreated copper powder.

[0032] (2) Preparation of Cu2O@Cu powder by static etching Add the dried copper powder from step (1) to a static reaction vessel (such as a beaker or flask) containing 200 mL of deionized water. Set the water bath temperature to 40°C and turn off the introduction of the mixed gas. Add 100 mL of 0.01 mol / L FeCl3 solution (non-atomized addition) to the reaction system at once. React for 35 min under static conditions in a 40°C water bath. After the reaction is complete, turn off the heating.

[0033] (3) Purification of Cu2O@Cu powder This step is exactly the same as step (3) in Example 1. After the reaction in step (2) is completed, the powder is filtered and transferred to 200 mL of 0.1 mol / L dilute HCl solution, and sonicated at room temperature for 5 min. After filtering, the powder is washed 3-5 times with deionized water or anhydrous ethanol. Finally, it is dried in a vacuum drying oven at 60℃ for 2 h to obtain the purified composite powder.

[0034] like Figure 1As shown in (a), in Example 1, a large number of uniform (nanoscale) cubic Cu2O particles (indicated by white arrows) were grown in situ on the surface of copper powder, indicating that Cu2O nucleation and growth could be achieved under these experimental conditions. However, due to the low FeCl3 solution concentration (0.01 mol / L) and low gas flow rate (0.5 L / min), the Cu2O nucleation conditions were insufficient, resulting in small particle size (Cu2O nuclei) and weak bonding between them, with obvious gaps, leading to a discontinuous coating structure. In contrast, in Comparative Example 1, only slight corrosion marks were observed on the surface of the copper powder ( Figure 1 (b) As indicated by the white arrow, no Cu2O particle formation was detected. This result indicates that, in the absence of a carrier gas-provided dynamic etching environment, the slow diffusion and participation of dissolved oxygen in the solution alone are insufficient to drive and sustain Cu2O nucleation and growth. Therefore, a dynamic air-suspension environment plays a crucial role in achieving in-situ, uniform growth of Cu2O.

[0035] The composite powders prepared in Example 1 and Comparative Example 1 were subjected to ultraviolet-visible-near-infrared spectroscopy to evaluate their optical absorption characteristics in commonly used wavelengths of laser additive manufacturing. The results are as follows: Figure 2 As shown in Example 1, the composite powder coated with Cu2O particles exhibits an absorption rate of 0.161 for near-infrared light (1064 nm). Within the 600-1200 nm spectral range, its absorption rate monotonically increases with decreasing wavelength. In contrast, in Comparative Example 1, due to slight corrosion of the powder surface and the absence of Cu2O particle coating, the absorption rate at 1064 nm is only 0.110. This indicates that simple surface roughening does not effectively enhance light absorption in the near-infrared band; instead, the destruction of surface morphology leads to increased scattering.

[0036] Example 2 (1) Copper powder pickling pretreatment Weigh 50 g of copper powder and add it to 200 mL of 0.2 mol / L dilute HNO3 solution. Sonicate the powder at room temperature for 10 min, then gently agitate. Filter immediately and wash with deionized water 3-5 times until the filtrate is neutral. Then, wash the powder twice with anhydrous ethanol to replace the water, and dry it in a vacuum drying oven at 70℃ for 3 h to obtain surface-pretreated copper powder.

[0037] (2) Preparation of Cu2O@Cu powder by air suspension dynamic etching Add the dried copper powder from step (1) to a gas washing bottle containing 200 mL of deionized water. Simultaneously, set the water bath temperature to 60℃ and add 100 mL of 0.03 mol / L FeCl3 solution to the nebulizer. Turn on the mixed gas and adjust the gas flow rate to 1.0 L / min. Start the nebulizer and spray the FeCl3 solution into the reaction system at a rate of 3 mL / min for 10 min. After the FeCl3 solution has been added, continue to ventilate for another 45 min, then turn off the experimental apparatus and stop heating and ventilation.

[0038] (3) Purification of Cu2O@Cu powder After the reaction in step (2) is complete, filter the powder and transfer it to 200 mL of 0.2 mol / L dilute HCl solution. Sonicate at room temperature for 10 min. After filtering, wash the powder 3-5 times with deionized water or anhydrous ethanol. Finally, dry in a vacuum drying oven at 70℃ for 3 h to obtain purified Cu2O@Cu composite powder.

[0039] Comparative Example 2 This comparative example aims to investigate the effect of an alkaline reaction environment on the dynamic etching process of air suspension. Its preparation process is basically the same as in Example 2, with the key difference being: before the etching reaction begins in step (2), NaOH solution is added to the reaction system to adjust the initial pH to 10.0, in order to study the retardation effect of alkaline conditions on etching kinetics and its influence on product formation. The specific process is as follows: (1) Copper powder pickling pretreatment This step is exactly the same as step (1) in Example 2. Weigh 50 g of copper powder and add it to 200 mL of 0.2 mol / L dilute HNO3 solution. After sonicating at room temperature for 10 min, gently shake. Filter immediately and wash with deionized water 3-5 times until the filtrate is neutral. Then, wash the powder twice with anhydrous ethanol to replace the water and dry it in a vacuum drying oven at 70℃ for 3 h to obtain surface-pretreated copper powder.

[0040] (2) Preparation of Cu2O@Cu powder by air suspension dynamic etching Add the dried copper powder from step (1) to a gas washing bottle containing 200 mL of deionized water, and adjust the pH of the mixture in the gas washing bottle to 10.0 using 0.1 mol / L NaOH solution. Set the water bath temperature to 60℃ and add 100 mL of 0.03 mol / L FeCl3 solution to the nebulizer. Turn on the mixed gas and adjust the gas flow rate to 1.0 L / min. Start the nebulizer and spray the FeCl3 solution into the reaction system at a rate of 3.0 mL / min for 10 min. After the FeCl3 solution has been added, continue to ventilate for another 45 min, then turn off the experimental apparatus and stop heating and ventilation.

[0041] (3) Purification of Cu2O@Cu powder This step is exactly the same as step (3) in Example 2. After the reaction in step (2) is completed, the powder is filtered and transferred to 200 mL of 0.2 mol / L dilute HCl solution, and sonicated at room temperature for 10 min. After filtering, the powder is washed 3-5 times with deionized water or anhydrous ethanol. Finally, it is dried in a vacuum drying oven at 70℃ for 3 h to obtain the purified composite powder.

[0042] like Figure 3 As shown in (a), Example 2, based on Example 1, appropriately increased the FeCl3 concentration, gas flow rate, reaction temperature, and time to obtain a composite powder with a more complete structure. Clearly, the copper powder surface was completely coated with larger, denser, and tightly bonded cubic Cu2O particles, forming a typical core-shell structure (Cu2O@Cu). The results indicate that the optimized process conditions further promoted the nucleation and growth of Cu2O. In contrast, Comparative Example 2 added NaOH solution to the reaction system before the etching reaction to adjust the pH to 10.0, to alleviate etching over-concentration caused by excessive concentration; the morphology was as shown. Figure 3 As shown in (b). Under alkaline conditions, OH... - The significantly increased concentration altered the thermodynamic equilibrium of the reaction pathway. On one hand, Fe... 3+ Under alkaline conditions, Fe(OH)3 precipitate or complex is easily formed, leading to a decrease in oxidation potential. On the other hand, a high pH value is not conducive to the stable existence of Cu⁺, inhibiting the precipitation of Cu₂O. Therefore, the etching reaction is suppressed, and slight etching marks are observed on the surface of the copper powder, with no Cu₂O formation observed.

[0043] The composite powders prepared in Example 2 and Comparative Example 2 were subjected to ultraviolet-visible-near-infrared spectroscopy tests, and the results are as follows: Figure 4As shown. Thanks to the dense Cu2O coating layer formed on the surface of the copper powder, the sample of Example 2 exhibited excellent light absorption characteristics, with an absorptivity of 0.359 at a wavelength of 1064 nm. The results indicate that a continuous Cu2O shell can more effectively capture photon energy in the near-infrared band. In contrast, the powder in Comparative Example 2 failed to achieve effective surface modification under alkaline conditions, with an absorptivity of only 0.089 at 1064 nm. This further confirms that simply extending the reaction time or adjusting the gas flow rate and temperature, without a suitable Cl... - Etching at a certain concentration cannot induce the formation of a Cu2O functional layer, and therefore cannot improve the laser absorption performance.

[0044] Example 3 (1) Copper powder pickling pretreatment Weigh 100 g of copper powder and add it to 200 mL of 0.3 mol / L dilute HNO3 solution. Sonicate the powder at room temperature for 15 min, then gently agitate. Filter immediately and wash with deionized water 3-5 times until the filtrate is neutral. Then, wash the powder twice with anhydrous ethanol to replace the water, and dry it in a vacuum drying oven at 80℃ for 4 h to obtain surface-pretreated copper powder.

[0045] (2) Preparation of Cu2O@Cu powder by air suspension dynamic etching Add the dried copper powder from step (1) to a gas washing bottle containing 200 mL of deionized water. Simultaneously, set the water bath temperature to 80℃ and add 100 mL of 0.05 mol / L FeCl3 solution to the nebulizer. Turn on the mixed gas and adjust the gas flow rate to 1.5 L / min. Start the nebulizer and spray the FeCl3 solution into the reaction system at a rate of 5 mL / min for 15 min. After the FeCl3 solution has been added, continue to ventilate for another 60 min, then turn off the experimental apparatus and stop heating and ventilation.

[0046] (3) Purification of Cu2O@Cu powder After the reaction in step (2) is complete, filter the powder and transfer it to 200 mL of 0.3 mol / L dilute HCl solution. Sonicate at room temperature for 15 min. After filtering, wash the powder 3-5 times with deionized water or anhydrous ethanol. Finally, dry in a vacuum drying oven at 80℃ for 4 h to obtain purified Cu2O@Cu composite powder.

[0047] Comparative Example 3 This comparative example aims to investigate the effect of an acidic reaction environment on the dynamic etching process of air suspension. Its preparation process is basically the same as in Example 3, with the key difference being: before the etching reaction begins in step (2), dilute HCl is added to the reaction system to adjust the initial pH to 5.0, aiming to study the accelerating effect of enhanced acidity on etching kinetics. The specific process is as follows: (1) Copper powder pickling pretreatment This step is exactly the same as step (1) in Example 3. Weigh 100 g of copper powder and add it to 200 mL of 0.3 mol / L dilute HNO3 solution. After sonicating at room temperature for 15 min, gently shake. Filter immediately and wash with deionized water 3-5 times until the filtrate is neutral. Then, wash the powder twice with anhydrous ethanol to replace the water and dry it in a vacuum drying oven at 80℃ for 4 h to obtain surface-pretreated copper powder.

[0048] (2) Preparation of Cu2O@Cu powder by air suspension dynamic etching Add the dried copper powder from step (1) to a gas washing bottle containing 200 mL of deionized water. Adjust the pH of the mixture in the gas washing bottle to 5.0 using 0.1 mol / L dilute HCl solution. Set the water bath temperature to 80℃ and add 100 mL of 0.05 mol / L FeCl3 solution to the nebulizer. Turn on the mixed gas and adjust the gas flow rate to 1.5 L / min. Start the nebulizer and spray the FeCl3 solution into the reaction system at a rate of 5.0 mL / min for 15 min. After the FeCl3 solution is added, continue to ventilate for another 60 min, then turn off the experimental apparatus and stop heating and ventilation.

[0049] (3) Purification of Cu2O@Cu powder This step is exactly the same as step (3) in Example 3. After the reaction in step (2) is completed, the powder is filtered and transferred to 200 mL of 0.3 mol / L dilute HCl solution, and sonicated at room temperature for 15 min. After filtering, the powder is washed 3-5 times with deionized water or anhydrous ethanol. Finally, it is dried in a vacuum drying oven at 80℃ for 4 h to obtain the purified composite powder.

[0050] like Figure 5As shown in (a), in Example 3, the microstructure of the composite powder changed significantly when the FeCl3 concentration, gas flow rate, reaction temperature, and time were further increased compared to Example 2. The surface coating structure of the copper powder was destroyed, and some Cu2O particles detached from the surface, existing as independent blocky particles. This phenomenon indicates that excessively strong oxidation etching conditions triggered a non-uniform and violent reaction, weakening the interfacial bond between the Cu2O shell and the copper core, leading to peeling and disrupting the continuity of the core-shell structure. In contrast, in Comparative Example 3, the pH was adjusted to 5.0 with HCl, introducing a high concentration of Cl... - This inhibited the precipitation of Cu2O. For example... Figure 5 As shown in (b), the copper powder surface was over-etched, forming pits and grooves of varying depths, which severely damaged the integrity of the powder, and no Cu2O particles were observed to form.

[0051] The composite powders prepared in Example 3 and Comparative Example 3 were subjected to ultraviolet-visible-near-infrared spectroscopy tests, and the results are as follows: Figure 6 As shown. The improved absorptivity (0.226) at 1064 nm in Example 3 is mainly due to the individual Cu2O particles, but the increased exposed copper surface increases laser reflection, resulting in a less effective strengthening effect than in Example 2 (0.359). In contrast, Comparative Example 3 showed no significant improvement in absorptivity at 1064 nm, only 0.083, due to severe etching of the copper powder surface. The results of Example 3 and Comparative Example 3 together reveal that precise control of reaction conditions and the medium environment is crucial for achieving controllable oxidation of the copper powder surface during the process of optimizing Cu2O coating: excessive conditions can cause coating peeling or severe etching, which is not conducive to obtaining composite powder with stable high laser absorptivity.

[0052] In summary, this invention provides an infrared absorption-enhanced composite powder for copper laser additive manufacturing and a simple preparation method thereof. This composite powder utilizes a dynamic chemical etching method to construct a cuprous oxide (Cu2O) coating layer in situ on the surface of copper powder, forming a Cu2O@Cu core-shell structure. The preparation method is simple, mild, low-cost, and easily scalable.

[0053] The core of this invention lies in the innovative control of FeCl3 concentration, gas flow rate, reaction temperature, and time to induce a controlled oxidation reaction on the surface of copper powder, generating a Cu2O modified layer that is firmly bonded to the copper substrate. This structural design effectively solves the industry bottleneck of extremely low absorption rate (<10%) of pure copper for near-infrared lasers (such as 1064 nm). The laser absorption rate of the treated composite powder can be significantly increased to over 30%, making it possible to form high-quality pure copper components on commercial laser additive manufacturing equipment with conventional power. This provides a key material foundation for promoting the application of copper in additive manufacturing technologies such as selective laser melting (SLM) and laser-directed energy deposition (DED), and is particularly suitable for fields with stringent requirements for conductivity, thermal conductivity, and complex structures, such as the direct digital manufacturing of aerospace heat sinks, electronic packaging heat sinks, and customized radio frequency components.

[0054] The embodiments described above are merely preferred examples of the present invention, and not all possible implementations. Based on the core concept of the Cu2O@Cu core-shell structure disclosed in this invention, all technical solutions obtained by those skilled in the art without creative effort, through any modifications, substitutions, and improvements such as adjusting process parameters, using copper powders of different particle sizes or grades, or performing subsequent processing on the composite powder, should fall within the protection scope of the claims of this invention.

Claims

1. A method for preparing copper-based composite powder with high infrared laser absorption rate, characterized in that, Includes the following steps: (1) Copper powder pickling pretreatment Weigh 30.0 g to 100.0 g of copper powder and add it to 200 mL of acidic solution. After sonicating at room temperature for 5 min to 15 min, gently shake and filter. Wash with deionized water 3 to 5 times until the filtrate is neutral. Then wash twice with anhydrous ethanol to replace the water. Finally, dry in a vacuum drying oven. (2) Preparation of Cu2O@Cu powder by air suspension dynamic etching After drying the copper powder in step (1), add it to a gas washing bottle containing 200 mL of deionized water. Place the gas washing bottle in a constant temperature water bath with a water bath temperature of 40℃~80℃. Introduce mixed gas into the gas washing bottle and spray the etching solution into the gas washing bottle in the form of micron-sized droplets through an atomizing device. After the etching solution is added, continue to ventilate and react for 30 min~60 min. Then turn off the reaction device and stop heating and ventilating. (3) Purification of Cu2O@Cu powder After the reaction in step (2) is completed, filter the powder and transfer it to 200 mL of 0.1 mol / L to 0.3 mol / L dilute HCl solution. Sonicate the powder at room temperature for 5 min to 15 min. After filtering the powder, wash it 3 to 5 times with deionized water or anhydrous ethanol. Finally, dry it under vacuum to obtain the purified copper-based composite powder.

2. The method for preparing copper-based composite powder with high infrared laser absorption rate according to claim 1, characterized in that, In step (1), the copper powder is spherical or near-spherical gas-atomized copper powder with a purity of ≥99.9% and a particle size range of 10μm~100μm.

3. The method for preparing copper-based composite powder with high infrared laser absorption rate according to claim 1, characterized in that, In step (1), the acidic solution is one of dilute HNO3, dilute HCl, or acetic acid (CH3COOH), with a concentration of 0.1 mol / L to 0.3 mol / L.

4. The method for preparing a copper-based composite powder with high infrared laser absorption rate according to claim 1, characterized in that, In step (2), the mixed gas is compressed air and oxygen, the flow rate of the mixed gas is 0.5 L / min to 1.5 L / min, and the volume percentage of O2 in the mixed gas is 5 vol% to 15 vol%.

5. The method for preparing copper-based composite powder with high infrared laser absorption rate according to claim 1, characterized in that, In step (2), the etching solution is FeCl3 solution. 100 mL of FeCl3 solution with a concentration of 0.01 mol / L to 0.05 mol / L is placed in the atomizing device. The atomizing device is started and the FeCl3 solution is sprayed into the gas washing bottle at a rate of 2.0 mL / min to 5.0 mL / min for 5 min to 15 min to achieve gas suspension dynamic etching.

6. The method for preparing a copper-based composite powder with high infrared laser absorption rate according to claim 1, characterized in that, In step (3), the composite powder has a core-shell structure, including a copper core and a cuprous oxide (Cu2O) modified layer coated on the surface of the copper core; Cu2O has a cubic block particle micromorphology, and the mass of the Cu2O modified layer accounts for 0.5 wt%~5 wt% of the total mass of the composite powder.

7. The method for preparing a copper-based composite powder with high infrared laser absorption rate according to claim 1, characterized in that, In steps (1) and (3), the vacuum drying temperature is 60℃~80℃ and the time is 2 h~4 h.

8. A reaction apparatus for performing the gas-suspended dynamic etching as described in claim 1, characterized in that, The device includes a gas flow meter (1), an atomizing device (2), a gas washing bottle (8), a water bath (9), and a tail gas absorption bottle (10). The gas washing bottle (8) is placed in the water bath (9). The gas flow meter (1) is connected to the gas washing bottle (8) through a gas pipe. The tail gas absorption bottle (10) is connected to the gas washing bottle (8) through a gas pipe. The top of the atomizing device (2) is provided with an atomizer inlet (3), a signal cable (4), and an atomizer outlet (5). The atomizer inlet (3) is connected to the air to provide a stable airflow. The atomizer outlet (5) is connected to the upper part of the gas washing bottle through a gas pipe. The signal cable (4) is connected to the water level sensor (6) and the atomizer (7) located inside the atomizing device (2).

9. The reaction apparatus for gas suspension dynamic etching according to claim 8, characterized in that, The gas flow meter (1) contains a mixture of compressed air and oxygen.

10. The reaction apparatus for gas-suspended dynamic etching according to claim 8, characterized in that, The atomizing device (2) contains an etching solution, which is 100 mL of FeCl3 solution with a concentration of 0.01 mol / L to 0.05 mol / L; the tail gas absorption bottle (10) contains a dilute NaOH solution.

Images