A method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition

Abstract

This invention discloses a method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene (POM) decomposition, relating to the fields of powder metallurgy and metal powder surface modification technology. This method involves particle size classification, followed by pulsed weak oxidation and oxygen plasma doping treatments to passivate the catalytic activity of conventional tungsten copper powder. Nano-sized tungsten copper powder is then organically coated to form a formaldehyde-capturing layer. Finally, the two modified powders are compounded with a POM matrix, synergistically inhibiting POM decomposition through multiple mechanisms to obtain a stable feedstock suitable for injection molding. This invention reduces the catalytic activity of conventional tungsten copper powder through surface passivation and zirconium doping, and endows the nano-powder with formaldehyde-capturing capabilities through organic coating. The two work synergistically in the feedstock process, blocking the catalytic reaction pathway between the metal and the POM matrix while eliminating decomposition products, thus improving the processing stability of the feedstock and the product lifespan. This provides a new path for the development of high-performance tungsten copper feedstocks.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy and metal powder surface modification technology, specifically to a method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition. Background Technology

[0002] Tungsten-copper alloys combine the low thermal expansion of tungsten with the high thermal conductivity of copper, making them indispensable key packaging materials for high-end electronics fields such as next-generation high-power integrated circuits, optical communication devices, and semiconductor lasers. As electronic devices continue to evolve towards higher power densities, miniaturized integration, and more complex irregular structures, traditional machining methods, due to their low material utilization, high production costs, and inability to process complex internal structures, can no longer meet the development needs of the high-end electronics industry. Powder injection molding, as a near-net-shape forming technology, provides a highly promising solution for the high-performance, low-cost manufacturing of complex tungsten-copper parts, enabling large-scale, efficient production of components. In the powder injection molding technology system, the plastic-based binder with polyoxymethylene (POM) as the core component, combined with the process route of catalytic debinding, has outstanding advantages such as high green strength, small deformation of the green body during the debinding process, excellent dimensional accuracy and consistency, and short production cycle. It has achieved mature industrial application in injection molding of stainless steel, ceramic and other material systems. However, its application in tungsten copper material systems has always been limited by the core technology bottleneck. Tungsten copper powder has a strong catalytic effect on POM, which causes POM to decompose violently in the mixing and injection molding process, directly causing the failure of feed preparation. This problem has become a key obstacle restricting the large-scale production of high-performance tungsten copper injection molded parts.

[0003] Current research and industrial applications of tungsten copper powder injection molding (POM) largely utilize paraffin-based binder systems to circumvent POM decomposition issues. While this system enables basic molding processes, it has revealed numerous insurmountable drawbacks during industrial adoption. Green bodies prepared with paraffin-based binders exhibit low strength and are prone to irreversible deformation under tensile stress from complex structural parts during demolding and subsequent debinding processes. This results in significant dimensional inconsistencies and insufficient batch stability in the final product. Furthermore, the debinding process for paraffin-based binders is lengthy and inefficient. During debinding, the green body is also prone to swelling and flow deformation, further exacerbating the deformation of the molded product. This fails to meet the high-precision manufacturing requirements of high-end electronic packaging components. Existing research on POM decomposition... The solutions to this problem mostly focus on mitigation measures at the process level, such as delaying the decomposition reaction of POM through inert atmosphere protection and low-temperature, low-speed mixing. However, these methods cannot fundamentally block the chain reaction of catalytic decomposition and are difficult to control batch stability in large-scale production. Some technologies use a single coupling agent coating treatment, which only achieves a limited inhibition effect through physical isolation. However, they do not passivate the highly active catalytic sites on the surface of tungsten copper powder. The bonding force between the coating layer and the powder matrix is ​​insufficient, and it is prone to breakage and failure under the high shear of mixing. At the same time, they do not specifically control the self-accelerating characteristics of the decomposition process, and cannot completely solve the core problem of POM decomposition, making it difficult to support the stable preparation and industrial application of plastic-based tungsten copper feedstock. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for micro-oxidation and coating treatment of tungsten-copper powder surface to inhibit the decomposition of polyoxymethylene. This method involves classifying the tungsten-copper powder by particle size, performing pulsed weak oxidation treatment on conventional powder to construct a gradient micro-oxidation layer composed of tungsten and copper oxides on its surface; subsequently, oxygen plasma treatment is performed and trace amounts of zirconium doping are introduced to further improve interface stability; the nanoparticles are organically coated to form a formaldehyde-capturing resin layer; finally, the modified two types of powders are compounded and combined with a POM matrix to prepare a feedstock.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition, the specific steps of which are as follows: S100 Powder Classification: The tungsten copper raw material powder is classified by particle size to obtain conventional tungsten copper powder and nano tungsten copper powder. The two powders are set aside separately to provide basic raw materials for subsequent differentiated surface treatment. S200, conventional powder micro-oxidation: Conventional tungsten copper powder is treated with a pulse weak oxidation method that is controlled by both atmosphere and temperature, forming a uniform gradient micro-oxidation layer on the surface of the conventional tungsten copper powder, which is composed of tungsten trioxide, tungsten dioxide, copper oxide and cuprous oxide, so that the powder surface and core maintain a stable phase state. S300, Oxygen Plasma Treatment and Doping: Conventional tungsten copper powder that has undergone micro-oxidation is subjected to oxygen plasma treatment. Zirconium is introduced during the oxygen plasma treatment process, and then the lattice doping and stabilization of zirconium are completed through subsequent annealing. S400, fine powder organic coating: the surface of nano tungsten copper powder is coated to form a continuous formaldehyde-capturing organic coating layer composed of melamine-formaldehyde resin or urea-formaldehyde resin on the surface of the nano tungsten copper powder, so that the oxide layer maintains a stable interface state. S500, Powder Compounding and Composite: The conventional tungsten copper powder with surface treatment is thoroughly mixed with nano tungsten copper powder, and then the mixed powder is composited with a POM-based thermoplastic polymer matrix. This allows the conventional tungsten copper powder and nano tungsten copper powder to form a synergistic overall structure in the matrix, constituting a complete surface modification and composite system that is suitable for the feed preparation requirements of powder injection molding process.

[0006] Furthermore, the two-stage classification process involves: firstly, using an air classifier to perform primary classification of the tungsten-copper raw material powder, controlling the airflow velocity of the air classifier to be 8-12 m / s, to obtain conventional tungsten-copper powder with a particle size of 1-5 μm and fine-particle powder with a particle size <1 μm; then, using a sedimentation classification method to perform secondary classification of the fine-particle powder, to obtain nano-tungsten-copper powder with a particle size of 20-100 nm; the powder in the 100 nm-1 μm range after classification can be returned to the raw material powder for re-classification; the conventional tungsten-copper powder and the nano-tungsten-copper powder are respectively placed in sealed containers, the sealed containers are filled with dry nitrogen, and stored in a dry environment at room temperature, with the relative humidity of the storage environment controlled at 30-50%.

[0007] Furthermore, in the conventional powder micro-oxidation process, conventional tungsten copper powder is evenly spread in the furnace chamber of a controlled atmosphere furnace with a thickness of 2-5 mm. First, nitrogen gas with a purity of not less than 99.99% is introduced to completely replace the air in the furnace. The nitrogen gas introduction rate is 10-15 L / min, and the replacement time is 15-20 minutes. After the replacement is completed, a weak oxidation atmosphere is provided by alternating oxygen pulse and nitrogen purging. The oxygen pulse introduction time is 30-60 seconds, and the introduction rate is 5-8 L / min. The nitrogen purging time is 2-3 minutes, and the purging rate is 12-18 L / min. The alternation cycle is 8-12 times.

[0008] Furthermore, during the conventional powder micro-oxidation process, the temperature is increased sequentially in steps of 120℃, 200℃, and 280℃, with the heating rate controlled at 5-8℃ / min. When the temperature reaches 120℃, it is held for 10-15 minutes; when the temperature reaches 200℃, it is held for 15-25 minutes; and when the temperature reaches 280℃, it is held for 25-30 minutes. After the holding time is completed, the temperature is allowed to cool naturally to room temperature, forming a gradient micro-oxidation layer with a thickness of 15-20nm on the surface of the conventional tungsten copper powder.

[0009] Furthermore, the gradient micro-oxide layer is composed of tungsten oxide and copper oxide, wherein the tungsten oxide includes tungsten trioxide and tungsten dioxide, and the copper oxide includes copper oxide and cuprous oxide. Conventional tungsten copper powder remains in a metallic state and does not undergo overall oxidation. The thickness of the gradient micro-oxide layer gradually decreases from the outside to the inside.

[0010] Furthermore, the oxygen plasma treatment power is 100-150W, the treatment time is 10-15 minutes, the treatment gas pressure is 0.1-0.3MPa, and the oxygen flow rate is 3-5L / min. After the oxygen plasma treatment is completed, the conventional tungsten copper powder is placed in an annealing device for low-temperature annealing treatment. The annealing temperature is 120-180℃, the annealing time is 20-30 minutes, and an inert gas is introduced for protection during the annealing process. Argon is selected as the inert gas, and the introduction rate is 8-10L / min.

[0011] Furthermore, the doping treatment specifically involves adding a zirconium-containing precursor 5-8 minutes after the start of oxygen plasma treatment. The zirconium-containing precursor is selected from zirconium nitrate or zirconium oxychloride, and the amount added is 0.05-0.1% of the mass of conventional tungsten copper powder. The zirconium-containing precursor is uniformly sprayed onto the surface of conventional tungsten copper powder in the form of an aqueous solution at a spraying rate of 2-3 mL / min. After the oxygen plasma treatment is completed, in the subsequent annealing process, the annealing heating rate is controlled at 3-5 °C / min to ensure that the zirconium element is uniformly distributed in the micro oxide film. The zirconium element is stably present in the oxide film lattice through the heat preservation annealing treatment, thus completing the doping treatment.

[0012] Furthermore, the surface coating treatment first involves dispersing nano-tungsten copper powder in a solution containing formaldehyde-capturing organic components. The formaldehyde-capturing organic components are selected from melamine-formaldehyde resin or urea-formaldehyde resin. The mass concentration of the organic components in the solution is 5-10%. During the dispersion process, a combination of ultrasonic dispersion and mechanical stirring is used. The ultrasonic power is 80-120W, the dispersion time is 15-20 minutes, the mechanical stirring speed is 200-300 r / min, and the stirring time is 25-35 minutes, so that the organic components are uniformly adsorbed and bonded on the surface of the nano-tungsten copper powder.

[0013] Furthermore, the thickness of the organic coating layer is adjusted by controlling the mass concentration of the organic components in the solution, the reaction time, and the mechanical stirring speed. The reaction time is controlled at 30-40 minutes, and the mechanical stirring speed is stabilized at 250-300 r / min, so that the thickness of the organic coating layer on the surface of the nano-tungsten copper powder is strictly controlled at 3-5 nm. After coating, the nano-tungsten copper powder is collected by centrifugation at a speed of 3000-4000 r / min for 10-15 minutes.

[0014] Furthermore, the powder compounding and composite process involves first mixing conventional tungsten copper powder and nano-tungsten copper powder at a mass ratio of 2-3:1. A three-dimensional mixer is then used to uniformly mix the modified conventional tungsten copper powder and nano-tungsten copper powder. The speed of the three-dimensional mixer is 150-200 r / min, and the mixing time is 20-60 minutes. After mixing, the mixed powder and POM-based thermoplastic polymer matrix are added to a melt blending device at a mass ratio of 88-96:4-12. The polymer matrix is ​​composed of 80-90wt% POM and 10-20wt% auxiliary components. The auxiliary components include one or more of polypropylene, high-density polyethylene, lubricant EBS, and stearic acid. The melt blending temperature is controlled at 180-200℃, the stirring speed is 10-60r / min, and the blending time is 30-60 minutes. The mixed powder and POM-based thermoplastic polymer matrix are fully compounded by heating and melting and mechanical shearing to prepare a tungsten copper feedstock suitable for powder injection molding process.

[0015] Compared with existing technologies, this method for micro-oxidation and coating of tungsten copper powder surface to inhibit polyoxymethylene decomposition has the following beneficial effects: I. This invention addresses the core pain points of powder injection molding (POM) processes by performing graded treatment on PIM-specific tungsten copper powder. This achieves differentiated surface modification between conventional and nano-tungsten copper powders, thereby constructing a multi-layered interface control mechanism within the overall feed system. For conventional powders, pulsed weak oxidation and oxygen plasma are used in synergistic treatment to form a gradient-distributed micro-oxide layer on the surface. Trace amounts of zirconium are introduced for doping and stabilization, improving the structural density and thermal stability of the oxide layer and effectively blocking the catalytic reaction pathway between the tungsten copper powder and the POM matrix. For nano-powders, an organic coating layer enables formaldehyde capture, actively adsorbing and stabilizing the free formaldehyde generated throughout the entire process of feed mixing and injection molding, thus inhibiting POM decomposition at its source. This graded control strategy not only preserves the original metallic properties of the powder but also, through interface functionalization design, experimentally verified to increase the POM initiation decomposition temperature by more than 45°C and improve the stability of feed cycle reuse by more than 7 times. This enhances the processing stability of the feed and the service life of the final product, avoiding the problem of difficulty in balancing interface bonding and catalytic inhibition.

[0016] II. This invention achieves a synergistic improvement in the overall performance of the feedstock by constructing a synergistic mechanism between conventional powder and nanopowder in a POM-based feedstock system. The gradient oxide layer and trace zirconium doping structure on the surface of the conventional powder not only physically block direct contact between the metal and the matrix, but also chemically reduce interfacial reactivity and decrease the catalytic degradation of POM during thermal processing. The organic coating layer on the surface of the nanopowder plays a formaldehyde-capturing role, continuously removing decomposition products and forming a self-healing decomposition-inhibiting barrier. The uniform distribution and synergistic effect of the two in the matrix enable the feedstock to maintain excellent stability throughout the entire process of melt blending, granulation, and injection molding, improving the feedstock's flowability, molding stability, and the mechanical properties and aging resistance of the product. This invention breaks through the limitations of the single interface control method in traditional powder modification technology and proposes a composite modification concept that integrates structure and function, providing a new technical path for the development of high-performance tungsten copper feedstocks for powder injection molding.

[0017] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 A flowchart of a method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition; Figure 2 This is a data transmission diagram illustrating a method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition. Figure 3 This is a schematic diagram of data transmission during the oxygen plasma treatment and doping steps of the present invention. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0021] Example 1: This embodiment addresses the powder injection molding requirements of high-precision thin-walled tungsten-copper packaging shells for optical communication devices. It involves synergistic surface modification and feedstock preparation of tungsten-copper powder to adapt to the molding requirements of packaging shells with a wall thickness not exceeding 1 mm. Figure 1 As shown, the specific implementation process is as follows: A two-stage classification process was employed to classify the tungsten-copper raw material powder by particle size: First, an air classifier was used for primary classification, with the airflow velocity controlled at 10 m / s, yielding conventional tungsten-copper powder with a particle size of 1-5 μm and fine powder with a particle size <1 μm. Second, the fine powder was further classified using sedimentation classification to obtain nano-tungsten-copper powder with a particle size of 20-100 nm. The powder in the 100 nm-1 μm range was then recycled back to the raw material powder for reclassification. The conventional and nano-tungsten-copper powders were separately placed in sealed containers filled with dry nitrogen and stored in a dry environment at room temperature with a relative humidity controlled at 40%. This two-stage classification process yields two types of powder with concentrated particle size distributions, providing suitable basic raw materials for subsequent differentiated surface treatments, while ensuring high raw material utilization through powder recycling.

[0022] Conventional tungsten-copper powder was treated using a pulsed weak oxidation method with dual controllable atmosphere and temperature. The powder was evenly spread 3 mm thickly in the furnace chamber of a controlled atmosphere furnace. First, nitrogen gas with a purity of at least 99.99% was introduced to completely replace the air in the furnace at a rate of 12 L / min for 18 minutes. After replacement, a weak oxidation atmosphere was provided by alternating cycles of oxygen pulses and nitrogen purging. The oxygen pulse duration was 45 seconds, and the introduction rate was 6 L / min. The nitrogen purging time was 2.5 minutes, the purging rate was 15 L / min, and the cycle was repeated 10 times. Simultaneously, the temperature was increased sequentially in steps of 120℃, 200℃, and 280℃, with a heating rate controlled at 6℃ / min. At 120℃, the temperature was held for 12 minutes; at 200℃, for 20 minutes; and at 280℃, for 28 minutes. After the holding time, the temperature was allowed to cool naturally to room temperature, forming a gradient micro-oxide layer with a thickness of 15-20 nm on the surface of the conventional tungsten-copper powder. This gradient micro-oxide layer is composed of tungsten trioxide, tungsten dioxide, copper oxide, and cuprous oxide. The interior of the conventional tungsten-copper powder remains in a metallic state and does not undergo overall oxidation. The thickness of the gradient micro-oxide layer gradually decreases from the outside to the inside. The core objective of this step is to form a uniform gradient oxide layer on the powder surface, passivating the highly catalytically active sites on the powder surface while preserving the metallic properties and sintering activity of the powder core.

[0023] Conventional tungsten-copper powder that had undergone micro-oxidation was subjected to oxygen plasma treatment. The oxygen plasma power was controlled at 120W, the treatment time at 12 minutes, the treatment pressure at 0.2MPa, and the oxygen flow rate at 4L / min. Six minutes after the start of oxygen plasma treatment, zirconium nitrate was added as a zirconium-containing precursor at a concentration of 0.08% of the mass of the conventional tungsten-copper powder. The zirconium nitrate was uniformly sprayed onto the surface of the conventional tungsten-copper powder in the form of an aqueous solution at a spraying rate of 2.5mL / min. After oxygen plasma treatment, the conventional tungsten-copper powder was placed in an annealing apparatus for low-temperature annealing at 150℃ for 25 minutes. Argon gas was introduced as an inert gas for protection during annealing at a flow rate of 9L / min. The heating rate was controlled at 4℃ / min during annealing to ensure uniform distribution of zirconium in the micro-oxide film. The annealing process with a holding phase ensured that the zirconium was stably present in the oxide film lattice, completing the doping process. This step, through oxygen plasma activation and zirconium doping, further enhances the structural stability and chemical inertness of the oxide layer, and strengthens the passivation effect of catalytic sites. Figure 3 As shown.

[0024] Surface coating treatment was performed on nano-tungsten copper powder. First, the nano-tungsten copper powder was dispersed in a formaldehyde-capturing organic component solution containing melamine-formaldehyde resin, with a mass concentration of 8% for the organic component. During dispersion, a combination of ultrasonic dispersion and mechanical stirring was used. The ultrasonic power was controlled at 100W for 18 minutes, and the mechanical stirring speed was 250 r / min for 30 minutes, ensuring uniform adsorption and bonding of the organic component on the surface of the nano-tungsten copper powder. The thickness of the organic coating layer was adjusted by controlling the mass concentration of the organic component in the solution, the reaction time, and the mechanical stirring speed. The reaction time was controlled at 35 minutes, and the mechanical stirring speed was stabilized at 280 r / min, strictly controlling the thickness of the organic coating layer on the surface of the nano-tungsten copper powder to be 3-5 nm. After coating, the nano-tungsten copper powder was collected by centrifugation at 3500 r / min for 12 minutes. This step forms a formaldehyde-capturing layer on the surface of the nano-powder through organic coating, blocking direct contact between the nano-powder and the POM matrix, while simultaneously capturing the formaldehyde produced during decomposition and inhibiting the decomposition chain reaction.

[0025] First, the conventional tungsten copper powder and nano-tungsten copper powder were mixed at a mass ratio of 2.5:1. A three-dimensional mixer was used to thoroughly mix the modified conventional tungsten copper powder and nano-tungsten copper powder, controlling the mixer speed at 180 r / min and the mixing time at 40 minutes. After mixing, the mixed powder and POM-based thermoplastic polymer matrix were added to a melt blending device at a mass ratio of 94:6. The POM-based thermoplastic polymer matrix was composed of 85 wt% POM and 15 wt% auxiliary components, with polypropylene and EBS lubricant selected as the auxiliary components. The melt blending temperature was controlled at 190℃, the stirring speed at 35 r / min, and the blending time at 45 minutes. Through heating, melting, and mechanical shearing, the mixed powder and POM-based thermoplastic polymer matrix were fully compounded, preparing a tungsten copper feedstock suitable for powder injection molding. The solid content of the tungsten copper powder in the feedstock was 94 wt%, which falls within the design range of 88-96 wt%. This step involves powder compounding and melt blending to construct a feeding system that allows two types of modified powders to work synergistically, adapting to the requirements of powder injection molding process.

[0026] After the preparation in this embodiment was completed, the feed performance was systematically characterized, and a parallel comparative test was conducted with the control group feed prepared from unmodified tungsten copper powder. The core test data are as follows: Decomposition behavior test during the mixing process: During the mixing process at 190℃, the control group feed showed a distinct formaldehyde irritating odor after 10 minutes of mixing, and the feed appeared dry and lost its fluidity after 30 minutes of mixing; the feed prepared in this embodiment did not release a distinct formaldehyde odor during the entire 45-minute mixing process, and the feed remained in a uniform fluid state after the mixing was completed, without drying or clumping.

[0027] Thermal stability test: Thermogravimetric analysis results showed that the initial decomposition temperature of POM in the control group was 202℃, while the initial decomposition temperature of POM in this embodiment was 248℃, an increase of 46℃; after holding at a constant temperature of 200℃ for 30 minutes, the thermal weight loss rate of the control group was 18.7%, while the thermal weight loss rate of the embodiment was only 0.25%, which significantly inhibited the thermal decomposition of POM.

[0028] Injection molding cycle stability test: The allowable value for green body weight fluctuation was set to ±1.5%. In the control group, the injection pressure increased by 15% and the green body weight fluctuation exceeded ±2.5% during the second injection cycle. The feed prepared in this embodiment showed that after 8 consecutive injection cycles, the injection pressure fluctuation was ≤3% and the green body weight fluctuation was always ≤±0.8%, and the cycle stability was significantly improved.

[0029] Molding performance verification: The feed material was finally used to prepare the green blank of the thin-walled tungsten copper package shell on the powder injection molding machine. The green blank had a complete appearance and no molding defects such as cracking, swelling, or material shortage. The dimensional fluctuation was ≤±0.5%, which met the requirements of high-precision molding and subsequent mass production of package shells for optical communication devices.

[0030] In summary, this embodiment addresses the molding requirements of high-precision thin-walled tungsten copper packaging shells for optical communication. Through a complete process of powder classification, gradient micro-oxidation, oxygen plasma zirconium doping, organic coating, and powder compounding, it achieves synergistic surface modification of tungsten copper powder, preparing a high-performance tungsten copper feedstock suitable for powder injection molding. This effectively solves the problem of catalytic decomposition of POM during processing and is fully adapted to the mass production needs of high-end packaging parts in the field of optical communication.

[0031] Example 2: This embodiment addresses the powder injection molding requirements of irregularly shaped tungsten-copper heat sink parts with side holes and microchannel structures for high-power semiconductor lasers. It focuses on the synergistic surface modification and feedstock preparation of tungsten-copper powder to adapt to the molding requirements of complex irregularly shaped heat sink parts, such as... Figure 2 As shown, the specific implementation process is as follows: A two-stage classification process was employed to classify the tungsten-copper raw material powder by particle size: First, an air classifier was used for primary classification, with the airflow velocity controlled at 11 m / s, yielding conventional tungsten-copper powder with a particle size of 1-5 μm and fine powder with a particle size <1 μm. Then, the fine powder was further classified using a sedimentation method to obtain nano-tungsten-copper powder with a particle size of 20-100 nm. The powder in the 100 nm-1 μm range was then recycled back to the raw material powder for reclassification. The conventional and nano-tungsten-copper powders were separately placed in sealed containers filled with dry nitrogen and stored in a dry environment at room temperature with a relative humidity controlled at 35%. This two-stage classification process yields two types of powder with concentrated particle size distributions, providing suitable basic raw materials for subsequent differentiated surface treatments, while ensuring high raw material utilization through powder recycling.

[0032] Conventional tungsten-copper powder was treated using a pulsed weak oxidation method with dual controllable atmosphere and temperature. The powder was evenly spread 4 mm thickly in the furnace chamber of a controlled atmosphere furnace. First, nitrogen gas with a purity of at least 99.99% was introduced to completely replace the air in the furnace. The nitrogen introduction rate was 14 L / min, and the replacement time was 20 minutes. After replacement, a weak oxidation atmosphere was provided by alternating cycles of oxygen pulses and nitrogen purging. The oxygen pulse introduction time was 60 seconds, and the introduction rate was 7. The nitrogen purging process was carried out at a rate of 16 L / min for 3 minutes, with 12 alternating cycles. Simultaneously, the temperature was increased sequentially in steps of 120℃, 200℃, and 280℃ at a rate of 7℃ / min. At 120℃, the temperature was held for 15 minutes; at 200℃, for 25 minutes; and at 280℃, for 30 minutes. After these holding times, the temperature was allowed to cool naturally to room temperature, forming a gradient micro-oxide layer with a thickness of 15-20 nm on the surface of the conventional tungsten-copper powder. This gradient micro-oxide layer is composed of tungsten trioxide, tungsten dioxide, copper oxide, and cuprous oxide. The interior of the conventional tungsten-copper powder remains in a metallic state and does not undergo overall oxidation. The thickness of the gradient micro-oxide layer gradually decreases from the outside to the inside. The core objective of this step is to form a uniform gradient oxide layer on the powder surface, passivating the highly catalytically active sites on the powder surface while preserving the metallic properties and sintering activity of the powder core.

[0033] Conventional tungsten-copper powder that has undergone micro-oxidation treatment was subjected to oxygen plasma treatment. The power of the oxygen plasma treatment was controlled at 150W, the treatment time was 15 minutes, the treatment pressure was 0.3MPa, and the oxygen flow rate was 5L / min. Eight minutes after the start of the oxygen plasma treatment, zirconium oxychloride was added as a zirconium-containing precursor. The amount of zirconium oxychloride added was 0.1% of the mass of the conventional tungsten-copper powder. The zirconium oxychloride was uniformly sprayed onto the surface of the conventional tungsten-copper powder in the form of an aqueous solution at a spraying rate of 3mL / min. After the oxygen plasma treatment, the conventional tungsten-copper powder was placed in an annealing device for low-temperature annealing treatment at a temperature of 180℃ for 30 minutes. Argon gas was introduced as an inert gas for protection during the annealing process at a flow rate of 10L / min. The heating rate was controlled at 5℃ / min during the annealing process to ensure that the zirconium element was uniformly distributed in the micro-oxide film. The zirconium element was stably present in the oxide film lattice through the holding annealing treatment, thus completing the doping treatment. This step further enhances the structural stability and chemical inertness of the oxide layer and strengthens the passivation effect of catalytic sites through oxygen plasma activation and zirconium doping.

[0034] Surface coating treatment of nano-tungsten copper powder was performed by first dispersing the nano-tungsten copper powder in a formaldehyde-capturing organic component solution containing urea-formaldehyde resin, with a mass concentration of 10% organic component. During dispersion, a combination of ultrasonic dispersion and mechanical stirring was used, controlling the ultrasonic power at 120W for 20 minutes and the mechanical stirring speed at 300 rpm for 35 minutes, ensuring uniform adsorption and bonding of the organic component on the surface of the nano-tungsten copper powder. The thickness of the organic coating layer was adjusted by controlling the mass concentration of the organic component in the solution, the reaction time, and the mechanical stirring speed, with the reaction time controlled at 40 minutes and the mechanical stirring speed stabilized at 300 rpm, strictly controlling the thickness of the organic coating layer on the surface of the nano-tungsten copper powder to be 3-5 nm. After coating, the nano-tungsten copper powder was collected by centrifugation at 4000 rpm for 15 minutes. This step forms a formaldehyde-capturing layer on the surface of the nano-powder through organic coating, blocking direct contact between the nano-powder and the POM matrix, while simultaneously capturing the formaldehyde produced during decomposition and inhibiting the decomposition chain reaction.

[0035] First, the conventional tungsten copper powder and nano-tungsten copper powder were mixed at a mass ratio of 3:1. A three-dimensional mixer was used to thoroughly mix the modified conventional tungsten copper powder and nano-tungsten copper powder, with the mixer speed controlled at 200 r / min and the mixing time at 30 minutes. After mixing, the mixed powder and POM-based thermoplastic polymer matrix were added to a melt blending device at a mass ratio of 93:7. The POM-based thermoplastic polymer matrix was composed of 90 wt% POM and 10 wt% auxiliary components, with the auxiliary components being high-density polyethylene and stearic acid. The melt blending temperature was controlled at 200℃, the stirring speed at 50 r / min, and the blending time at 60 minutes. Through heating, melting, and mechanical shearing, the mixed powder and POM-based thermoplastic polymer matrix were fully compounded, resulting in a tungsten copper feedstock suitable for powder injection molding. The solid content of the tungsten copper powder in the feedstock was 93 wt%, which falls within the design range of 88-96 wt%. This step involves powder compounding and melt blending to construct a feeding system in which two types of modified powders work synergistically, adapting to the injection molding requirements of complex irregularly shaped parts.

[0036] After the preparation in this embodiment was completed, the feed performance was systematically characterized, and a parallel comparative test was conducted with the control group feed prepared from unmodified tungsten copper powder. The core test data are as follows: Decomposition behavior test during the mixing process: During the mixing process at 200℃, the control group feed showed a strong formaldehyde irritating odor after 8 minutes of mixing, and the feed completely lost its fluidity and became severely clumped after 30 minutes of mixing; the feed prepared in this embodiment did not release any obvious formaldehyde odor during the entire 60-minute mixing process, and the feed remained in a uniform and smooth fluid state after the mixing was completed, without drying or clumping.

[0037] Thermal stability test: Thermogravimetric analysis results showed that the initial decomposition temperature of POM in the control group was 201℃, while the initial decomposition temperature of POM in this embodiment was 251℃, an increase of 50℃; after holding at a constant temperature of 200℃ for 60 minutes, the thermal weight loss rate of the control group was 27.3%, while the thermal weight loss rate of the embodiment was only 0.38%, which significantly inhibited the thermal decomposition of POM.

[0038] Injection molding cycle stability test: The allowable value for green body weight fluctuation was set to ±1.5%. In the control group, the injection pressure increased by 12% and the green body weight fluctuation exceeded ±2.1% during the first cycle injection. The feed prepared in this embodiment showed that after 7 consecutive cycles injection, the injection pressure fluctuation was ≤4% and the green body weight fluctuation was always ≤±0.7%, which showed excellent cycle stability and could meet the needs of mass production.

[0039] Molding performance verification: Finally, the feed material was used to prepare the irregular tungsten copper heat sink green blank with side holes and microchannel structure on the powder injection molding machine. The green blank had a complete appearance and no molding defects such as cracking, swelling, or material shortage. The microchannel and side hole structure was completely filled and the dimensional fluctuation was ≤±0.5%, which fully met the high-precision molding and mass production requirements of heat sink parts for high-power semiconductor lasers.

[0040] In summary, this embodiment addresses the complex structural forming requirements of irregularly shaped tungsten-copper heat sink components for high-power semiconductor lasers. Through differentiated powder classification treatment, pulsed weak oxidation gradient modification, oxygen plasma zirconium doping, formaldehyde-capturing organic coating, and melt blending processes, it achieves synergistic modification and feedstock preparation of tungsten-copper powder. This effectively solves the problem of catalytic decomposition of POM during high-temperature processing. The prepared feedstock possesses excellent rheological properties and mold-filling ability, enabling stable forming of irregularly shaped heat sink green blanks with microchannels and side holes, meeting the high-precision forming and industrial application requirements of core components for high-power semiconductor lasers.

[0041] In summary, this embodiment addresses the complex structural requirements of irregularly shaped tungsten-copper heat sink components for high-power semiconductor lasers. Through differentiated powder classification treatment, pulsed weak oxidation gradient modification, oxygen plasma zirconium doping, formaldehyde-capturing organic coating, and melt blending processes, it achieves the synergistic modification and feedstock preparation of tungsten-copper powder. The entire process achieves precise passivation and long-term protection of the powder surface's catalytic activity, effectively solving the decomposition problem of polyoxymethylene during processing. The prepared feedstock possesses excellent rheological properties and molding capacity, enabling stable molding of irregularly shaped heat sink green blanks with microchannels and side holes, meeting the high-precision molding and industrial application requirements of core components for high-power semiconductor lasers.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition, characterized in that, The specific steps of this method are as follows: S100, Powder Classification: The tungsten copper raw material powder is subjected to particle size classification to obtain conventional tungsten copper powder and nano tungsten copper powder. S200, conventional powder micro-oxidation: Conventional tungsten copper powder is treated with a pulse weak oxidation method that is controlled by both atmosphere and temperature to form a uniform gradient micro-oxidation layer on the surface of the conventional tungsten copper powder. S300, Oxygen Plasma Treatment and Doping: Conventional tungsten copper powder that has undergone micro-oxidation is subjected to oxygen plasma treatment, and zirconium is introduced during the oxygen plasma treatment process. The zirconium is then lattice doped and stabilized through subsequent annealing. S400, Nanopowder Organic Coating: The surface of nano tungsten copper powder is coated to form a continuous formaldehyde-capturing organic coating layer on the surface of the nano tungsten copper powder. S500, Powder Compounding and Composite: The conventional tungsten copper powder with surface treatment is thoroughly mixed with nano tungsten copper powder, and then the mixed powder is composited with POM-based thermoplastic polymer matrix to form a complete surface modification and composite system, which is suitable for the feed preparation requirements of powder injection molding process.

2. The method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition according to claim 1, characterized in that, In step S100, the powder classification process employs a two-stage classification process: firstly, an air classifier is used to classify the tungsten copper raw material powder, controlling the airflow velocity of the air classifier to be 8-12 m / s, resulting in conventional tungsten copper powder with a particle size of 1-5 μm and fine-particle powder with a particle size <1 μm; then, the fine-particle powder is classified in a second stage using a sedimentation classification method to obtain nano-tungsten copper powder with a particle size of 20-100 nm; the powder in the 100 nm-1 μm range after classification is returned to the raw material powder for reclassification; the conventional tungsten copper powder and the nano-tungsten copper powder are respectively placed in sealed containers, the sealed containers are filled with dry nitrogen, and stored in a dry environment at room temperature, with the relative humidity of the storage environment controlled at 30-50%.

3. The method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition according to claim 1, characterized in that, In step S200, during the conventional powder micro-oxidation process, conventional tungsten copper powder is placed in a controlled atmosphere furnace. Nitrogen gas is first introduced to replace the air in the furnace, and then a weak oxidizing atmosphere is formed by alternating oxygen pulses and nitrogen purging.

4. The method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition according to claim 1, characterized in that, In step S200, during the conventional powder micro-oxidation process, the temperature is increased sequentially in steps of 120℃, 200℃, and 280℃, and each temperature range is held for 10-30 minutes to form a gradient micro-oxidation layer with a thickness of 15-20nm on the surface of the conventional tungsten copper powder.

5. The method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition according to claim 1, characterized in that, In step S200, the gradient micro-oxide layer is composed of tungsten oxide and copper oxide, wherein the tungsten oxide includes tungsten trioxide and tungsten dioxide, and the copper oxide includes copper oxide and cuprous oxide. The conventional tungsten copper powder remains in a metallic state and does not undergo overall oxidation. The thickness of the gradient micro-oxide layer gradually decreases from the outside to the inside.

6. The method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition according to claim 1, characterized in that, In step S300, the oxygen plasma treatment power is 100-150W, the treatment time is 10-15 minutes, the treatment gas pressure is 0.1-0.3MPa, and the oxygen flow rate is 3-5L / min. After the oxygen plasma treatment is completed, the conventional tungsten copper powder is placed in an annealing device for low-temperature annealing treatment. The annealing temperature is 120-180℃, the annealing time is 20-30 minutes, and an inert gas is introduced for protection during the annealing process. Argon is selected as the inert gas, and the introduction rate is 8-10L / min.

7. The method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition according to claim 1, characterized in that, In step S300, the specific steps for introducing and fixing zirconium are as follows: 5-8 minutes after the start of oxygen plasma treatment, a zirconium-containing precursor is added. The zirconium-containing precursor is selected from zirconium nitrate or zirconium oxychloride, and the amount added is 0.05-0.1% of the mass of conventional tungsten copper powder. The zirconium-containing precursor is uniformly sprayed onto the surface of conventional tungsten copper powder in the form of an aqueous solution at a spraying speed of 2-3 mL / min. After the oxygen plasma treatment is completed, in the subsequent annealing process, the annealing heating rate is controlled at 3-5℃ / min to make the zirconium element uniformly distributed in the micro oxide film. The zirconium element is stably present in the oxide film lattice through the annealing treatment in the heat holding stage, thus completing the doping treatment.

8. The method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition according to claim 1, characterized in that, In step S400, the surface coating treatment first disperses the nano-tungsten copper powder in a solution containing a formaldehyde-capturing organic component. The formaldehyde-capturing organic component is selected from melamine-formaldehyde resin or urea-formaldehyde resin. The mass concentration of the organic component in the solution is 5-10%. During the dispersion process, a combination of ultrasonic dispersion and mechanical stirring is used. The ultrasonic power is 80-120W, the dispersion time is 15-20 minutes, the mechanical stirring speed is 200-300r / min, and the stirring time is 25-35 minutes, so that the organic component is uniformly adsorbed and bonded on the surface of the nano-tungsten copper powder.

9. The method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition according to claim 1, characterized in that, In step S400, the thickness of the organic coating layer is adjusted by controlling the mass concentration of the organic components in the solution, the reaction time, and the mechanical stirring speed. The reaction time is controlled to be 30-40 minutes, and the mechanical stirring speed is stabilized at 250-300 r / min, so that the thickness of the organic coating layer on the surface of the nano-tungsten copper powder is strictly controlled to be 3-5 nm. After coating, the nano-tungsten copper powder is collected by centrifugation at a speed of 3000-4000 r / min for 10-15 minutes.

10. The method for micro-oxidation and coating treatment of tungsten copper powder surface to inhibit polyoxymethylene decomposition according to claim 1, characterized in that, In step S500, the powder compounding and composite are first prepared according to the mass ratio of conventional tungsten copper powder to nano tungsten copper powder of 2-3:

1. The modified conventional tungsten copper powder and nano tungsten copper powder are mixed evenly using a three-dimensional mixer. The speed of the three-dimensional mixer is 150-200 r / min and the mixing time is 20-30 minutes. After the mixing is completed, the mixed powder and POM-based thermoplastic polymer matrix are added to the melt blending equipment at a mass ratio of 88-96:4-12. The melt blending temperature is controlled at 180-200℃, the stirring speed is 10-60 r / min, and the blending time is 30-60 minutes. Through heating and melting and mechanical shearing, the mixed powder and POM-based thermoplastic polymer matrix are fully compounded to prepare a tungsten copper feedstock suitable for powder injection molding process.

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