Mo-Cu composite powder and preparation method thereof
By forming a molybdenum-copper heteropolyacid ammonium complex precursor in an organic amine solution and combining it with a stepwise reduction process, the problems of uniform mixing and phase separation of Mo and Cu were solved, and ultrafine Mo-Cu composite powder with uniform composition and good interfacial bonding was prepared, thus improving the overall performance of the material.
Patent Information
- Application Number
- CN202511968027.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-03-06
AI Technical Summary
Existing technologies make it difficult to achieve uniform mixing of Mo and Cu and precise control of phase separation, resulting in problems with the compositional uniformity, interfacial bonding, and grain size of molybdenum-copper composites.
By forming a molybdenum-copper heteropolyacid ammonium complex precursor in an organic amine solution, and utilizing polyethyleneimine to competitively complex molybdate and copper ions, combined with a stepwise reduction process, molecular-level mixing and controllable phase separation are constructed to form a tight interfacial structure.
Ultrafine Mo-Cu composite powder with uniform composition and good interfacial bonding was obtained, which improved the overall performance of the material, especially its thermal conductivity and adjustable coefficient of thermal expansion.
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Figure CN121607640A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of powder metallurgy, specifically relating to a Mo-Cu composite powder and its preparation method. Background Technology
[0002] Molybdenum-copper composites possess the properties of both Mo and Cu, exhibiting excellent thermal, electrical, and mechanical properties, as well as a low and controllable coefficient of thermal expansion. They are widely used in heat sink materials, electronic packaging materials, and aerospace high-temperature materials.
[0003] However, since Mo and Cu are immiscible and cannot form intermetallic compounds, currently available molybdenum-copper composites are merely pseudo-alloys composed of two phases, Mo and Cu. Because it is difficult to obtain highly dense molybdenum-copper composites using traditional powder metallurgy methods, there are problems in meeting requirements regarding alloy properties, microstructure, and density.
[0004] There are four currently known methods for preparing nano-molybdenum-copper composite powders: mechanical alloying, sol-gel method, oxidation-co-reduction method, sol-spray drying-co-reduction method, and chemical co-precipitation method.
[0005] Mechanical alloying relies on the rotation or vibration of a ball mill to subject the powder to intense impact, grinding, and stirring, breaking the powder into nanoscale particles. Simultaneously, inter-diffusion occurs between different elements, resulting in the formation of uniformly distributed nanocrystalline Mo-Cu composite powder from a mixture of Mo and Cu powders under high-energy ball milling. Although this method can refine the grains, it also has problems such as poor powder flowability, cold welding agglomeration, and the unavoidable introduction of impurities that affect the material's performance.
[0006] The sol-gel method uses inorganic substances or metal alkoxides as precursors. After mixing and reaction, a transparent and stable sol system is formed. After aging, the sol particles slowly polymerize to form a three-dimensional network structure gel. The gel is then dried, sintered, and solidified to obtain a nanostructured alloy powder. This method yields powders with higher purity and uniformity, lower sintering temperatures, and easier control of the reaction, greatly avoiding side reactions. However, it suffers from problems such as complex gel preparation processes, making it unsuitable for large-scale production.
[0007] The oxide co-reduction method involves mixing molybdate with Cu₂O or CuO, oxidizing it at temperatures above 250 °C, and then reducing it to obtain molybdenum-copper composite powder. While this method can achieve near-100% theoretical density alloys through sintering at relatively low temperatures, the significant difference in reduction temperatures between molybdenum and copper oxides leads to premature powder agglomeration and Cu segregation, resulting in uneven composition of the Mo-Cu composite powder. The sol-spray drying-co-reduction method involves preparing a solution of molybdenum and copper salts using acid and alkali reagents, spray drying it to obtain a precursor, and then calcining and reducing it to obtain nano-molybdenum-copper composite powder. However, this method suffers from complex processes, difficulty in precisely controlling process parameters, and high production costs.
[0008] The chemical coprecipitation method uses molybdenum and copper salts as raw materials, which are sequentially dissolved in an appropriate amount of deionized water. A precipitant is then added dropwise under continuous stirring to form a precipitate. After drying, calcination, and reduction, the precipitate is finally transformed into Mo-Cu composite powder. Ammonia is commonly used as a precipitant, but its high volatility can easily lead to fluctuations in the ammonia concentration in the solution, thus affecting the stability of the ammonium molybdate complex. This fluctuation makes it difficult to precisely control the pH and reaction rate during the precipitation process, resulting in quality differences between different batches.
[0009] In summary, the existing technologies suffer from several problems: how to achieve uniform mixing of Mo and Cu at the atomic / molecular scale to overcome their thermodynamic immiscibility, and how to precisely control the separation and growth kinetics of the two phases during subsequent heat treatment to obtain composite powders with uniform composition, good interfacial bonding, nanoscale grain size, and good dispersibility. Mechanical alloying introduces defects and impurities; the sol-gel method is complex; and traditional co-precipitation methods (if simply mixing metal salts) are prone to component segregation due to differences in pH and hydrolysis rates of Mo and Cu ion precipitation, making true "molecular-level" mixing impossible.
[0010] Therefore, developing a new method that can ensure molecular-level mixing from the source and guide subsequent phase separation processes through ingenious process design is the key to breaking through existing technological bottlenecks. Summary of the Invention
[0011] The first objective of this invention is to provide a method for preparing Mo-Cu composite powder by mixing molybdenum and copper at the molecular level.
[0012] A second objective of this invention is to provide a Mo-Cu composite powder prepared by the method for preparing the Mo-Cu composite powder.
[0013] A third objective of this invention is to provide an application of the Mo-Cu composite powder.
[0014] This invention is achieved through the following technical solution: A method for preparing Mo-Cu composite powder includes the following steps: S1. Molybdate and copper salt are mixed in an aqueous solution of organic amine, so that molybdate ions and copper ions complex with the amine groups in the organic amine to form a precursor solution. S2 Then, polyethyleneimine is added to the precursor solution at 40-60℃, so that polyethyleneimine competitively complexes the molybdate ions and copper ions that are complexed with the amine group in the precursor solution. S3 Add acid to lower the pH of the precursor solution to disrupt the stability of the complex of polyethyleneimine with molybdate and copper ions, and induce the simultaneous and uniform precipitation of molybdate and copper ions to generate the Mo-Cu-O composite oxide precursor. S4 calcined the Mo-Cu-O composite oxide precursor at 350~450℃ in an inert or weakly oxidizing atmosphere to obtain the composite oxide; S5 reduces the composite oxide to obtain Mo-Cu composite powder.
[0015] The molybdate includes ammonium molybdate; The copper salts include copper chloride, copper sulfate, or copper nitrate.
[0016] The organic amine includes at least one of dimethylamine, trimethylamine, ethylenediamine, or triethylamine.
[0017] The molecular weight (MW) of the polyethyleneimine is 25000 g / mol.
[0018] The acid includes nitric acid or hydrochloric acid.
[0019] The reduction includes the steps of low-temperature reduction using a reducing gas at 300~350℃ and then high-temperature reduction at 650~850℃.
[0020] The reducing gas includes hydrogen.
[0021] The concentration of molybdate in the precursor solution is 0.1~0.2 mol / L; The concentration of copper salt in the precursor solution is 0.5~1.0 mol / L; The concentration of polyethyleneimine in the precursor solution is 3.99 × 10⁻⁶. -4 mol / L; The concentration of organic amine in the precursor solution is 0.6~1.0 mol / L. A Mo-Cu composite powder prepared by the aforementioned method.
[0022] The aforementioned Mo-Cu composite powder is used in the preparation of molybdenum-copper alloys.
[0023] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing ultrafine Mo-Cu composite powder based on molecular-level uniform doping and controllable phase separation through thermodynamic and kinetic regulation. This method not only yields ultrafine composite powder with narrow particle size distribution and precise compositional control, but more importantly, it constructs numerous dense heterogeneous interfaces between the Mo and Cu phases, enhancing the interfacial bonding strength between the two phases and thus significantly improving the overall performance of the final sintered material.
[0024] The method for preparing ultrafine Mo-Cu composite powder provided by this invention includes the following steps: (1) Precise design and preparation of molecular-level precursor solutions: Selecting specific molybdates (such as ammonium heptamolybdate, (NH4)6Mo7O) 24 ) and copper salts (such as copper nitrate, Cu(NO3)2), can form ammonium molybdate complex anions in organic amines using a Mo source, while Cu² + The ability of molybdenum and copper to form stable copper-ammonia complex cations with organic amines allows for the mixing of molybdenum and copper. Specifically, they are mixed in a solution of organic amines (such as dimethylamine, trimethylamine, ethylenediamine, triethylamine, etc.) to form a molybdenum-copper heteropolyacid ammonium complex precursor solution. Compared to commonly used ammonia, organic amines are more stable at room temperature and pressure, less prone to decomposition or volatilization, and therefore provide a more stable alkaline environment, enabling precise pH control. Furthermore, organic amines can form stable complexes with metal ions; by adjusting the type of organic amine, the selectivity and rate of the reaction can be modulated, thus obtaining an adjustable alkaline environment. In this solution, Mo and Cu elements are not simply mixed ions, but rather form molecular-level binding units through coordination bonds, ensuring a high degree of atomic-scale homogeneity of the two elements from the source.
[0025] (2) Induced coprecipitation and interface modification: Polyethyleneimine is added to the homogeneous precursor solution to competitively complex with molybdate and copper ions, causing these ions to simultaneously complex onto the same polyethyleneimine molecule, thus achieving molecular-level mixing. Next, a non-precipitating acidic substance (such as dilute nitric acid or dilute hydrochloric acid) is slowly added dropwise under vigorous stirring to gradually lower the pH of the system, thereby disrupting the stability of molybdate and copper ions and inducing their synchronous and uniform precipitation to generate a Mo-Cu-O composite oxide precursor. Simultaneously, the molecular chains of polyethyleneimine can be adsorbed onto the surface of the newly formed nuclei, inhibiting Ostwald ripening and hard agglomeration of particles through steric hindrance, achieving refinement of the precipitate particle size and control of monodispersity.
[0026] (3) Controlled thermal decomposition and phase reconstruction of the precursor: The obtained precipitate was washed and dried, and then calcined at a controlled temperature in an inert or weakly oxidizing atmosphere at 350-450℃. The purpose of this step is not only to remove water of crystallization and some organic amines, but more importantly, to promote the transformation of the amorphous Mo-Cu-O precursor into crystalline oxides (such as MoO3 and CuO). Due to the initial molecular-level mixing, molybdenum ions and copper ions will form a stacking pattern similar to that of organic amine molecules. Therefore, the resulting MoO3 and CuO grains are extremely small, and the two phases exhibit a highly dispersed "interpenetrating network" structure, laying the foundation for the mutual restraint growth in the subsequent reduction process.
[0027] (4) Stepwise controllable reduction and interface construction: The calcined composite oxide powder is reduced in a hydrogen atmosphere in two steps with programmed temperature rise.
[0028] 1) First step: low-temperature reduction (300~350℃): At this temperature, CuO, which is thermodynamically easier to reduce, is preferentially reduced to ultrafine metallic Cu particles. These nascent Cu particles are highly dispersed in the unreacted MoO3 matrix.
[0029] 2) Second step: High-temperature reduction (650~850℃): As the temperature rises, MoO3 begins to be reduced to Mo. The innovation of this process lies in utilizing the "volatilization-deposition" mechanism (chemical vapor transport, CVT) of MoO3 reduction: intermediate products such as MoO2(OH)2(g) are transported in the gas phase and reduced and deposited on the surface of existing Cu particles. Simultaneously, solid-phase reduced Mo nuclei also begin to grow. Crucially, the dispersed Cu and Mo phases mutually pin and restrict each other during growth: Cu particles effectively hinder the migration and growth of Mo grains, and conversely, the Mo phase network also limits the coarsening of Cu particles. This kinetic mutual inhibition leads to the final ultrafine Mo-Cu composite structure, in which the two phases have a clear interface and are tightly bound.
[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Fundamental component uniformity: By constructing a molybdenum-copper heteropolyacid ammonium complex precursor, this invention achieves uniform mixing of Mo and Cu at the molecular scale, fundamentally solving the component segregation problem caused by differences in ion precipitation behavior in traditional coprecipitation methods, and ensuring the accuracy and high uniformity of the final product composition.
[0031] (2) Innovative in-situ interface construction mechanism: This invention utilizes the chemical vapor transport mechanism of MoO3 during the reduction process and the mutual kinetic constraint effect of two-phase growth to construct a large number of tightly bonded Mo-Cu heterostructures in situ. This unique microstructure gives the powder extremely high sintering activity, and the final material can simultaneously possess high thermal conductivity and an adjustable low coefficient of thermal expansion.
[0032] (3) Precise control at multiple scales: This invention achieves precise control of the entire process from the molecular scale (precursor design), the nanoscale (precipitated particle control) to the micrometer scale (morphology of particles after reduction). By controlling parameters such as precursor solution chemistry, precipitation pH, calcination and reduction regime, the chemical composition, particle size, morphology and phase distribution of the final composite powder can be designed, which is incomparable to simple mixing processes.
[0033] (4) Ingenuity and universality of the process: The process equipment of this method is relatively simple. Its core ideas—"molecular-level mixing" and "controllable phase separation"—have important reference significance and universality for the preparation of ultrafine composite powders of other metal systems that are difficult to miscible (such as W-Cu, Ag-Ni, etc.), and show strong scalability. Attached Figure Description
[0034] Figure 1 The Mo-30Cu composite powders prepared in Examples 1 and 2 are shown, wherein, Figure 1 (a) shows the Mo-30Cu composite powder prepared in Example 1; Figure 1 (b) shows a SEM image of the Mo-40Cu composite powder prepared in Example 2; Figure 2 The XRD pattern of the Mo-30Cu composite powder prepared in Example 1 is shown. Detailed Implementation
[0035] Example 1 Preparation of ultrafine Mo-30Cu composite powder (1) Preparation of molecular-level precursor solution: Accurately weigh 0.147 mol ammonium heptamolybdate and 0.704 mol copper nitrate trihydrate and place them in a 2000 mL beaker. First, add about 800 mL of deionized water, 61.5 mL of dimethyl ethylamine (density 0.675 g / mL) and 39.8 mL of diethylamine (density 0.71 g / mL), and stir magnetically until the solids are completely dissolved, forming a deep blue transparent solution (this color indicates the formation of a copper ammonium complex ion, which coexists with molybdate ions). Among them, dimethyl ethylamine and diethylamine coordinate with molybdate ions and copper ions, respectively. Then, add deionized water to a total volume of 1200 mL and continue stirring for 30 minutes to ensure the formation of a homogeneous molybdenum-copper ammonium complex precursor solution.
[0036] (2) Induced coprecipitation and interface modification: Add 11.4 mL of polyethyleneimine (1.05 g / mL) to the above solution and stir for 5 minutes to mix thoroughly. Place the beaker in a 40℃ water bath and, with vigorous stirring at 600 rpm, slowly add 2 mol / L dilute nitric acid solution dropwise at a rate of 1-2 drops per second using a constant pressure dropping funnel. This process gently removes ammonia and neutralizes the solution, causing the pH value of the system to slowly and uniformly decrease from alkaline to 5.5. At this point, the solution can be observed to change from dark blue to a suspension, and a light blue precipitate is formed. Continue stirring for 1 hour to allow for complete aging.
[0037] (3) Solid-liquid separation and drying: The obtained suspension was filtered, and the precipitate was washed three times alternately with deionized water and anhydrous ethanol to remove residual organic amines and nitrate ions. The filter cake was placed in a vacuum drying oven and dried at 100°C for 180 minutes to obtain a loose blue precursor powder.
[0038] (4) Controlled thermal decomposition of the precursor: The dried precursor powder was placed in an alumina crucible and then placed in a muffle furnace. It was heated to 400°C in static air at a heating rate of 2°C / min and calcined at this temperature for 120 minutes. After cooling in the furnace, a gray-black Mo-Cu composite oxide mixed powder was obtained.
[0039] (5) Stepwise Controllable Reduction and Interface Construction: A suitable amount of the above oxide powder was placed in the corundum boat of the tube reduction furnace. High-purity nitrogen (99.999%) was first introduced to purge the air, and then hydrogen was switched (flow rate of 100 ml / min). The temperature was increased to 320℃ at a rate of 5℃ / min and held for 150 minutes to complete the first step of CuO→Cu reduction. Subsequently, the temperature was increased to 700℃ at the same rate and held for 150 minutes to fully reduce MoO3 to Mo. After the reduction was completed, the powder was cooled to room temperature under a hydrogen atmosphere to obtain ultrafine Mo-30Cu composite powder.
[0040] Performance characterization: X-ray diffraction analysis revealed that the final powder contained only Mo and Cu phases, with no other impurities. Scanning electron microscopy showed that the powder formed uniform, coral-like porous aggregates with an aggregate size of approximately 100-200 nanometers. High-resolution electron microscopy and energy dispersive spectroscopy confirmed that the Mo and Cu phases were interwoven and uniformly distributed at a scale of 50-100 nanometers, with clear interfaces.
[0041] Example 2 Preparation of ultrafine Mo-40Cu composite powder (1) Preparation of molecular-level precursor solution: Weigh 0.222 mol ammonium tetramolybdate and 0.939 mol copper nitrate trihydrate, and dissolve them in deionized water, 79.1 mL triethylamine (density 0.726 g / mL), and 24.6 mL dimethylamine (density 1.042 g / mL) according to the method in Example 1, to finally prepare a uniform blue transparent solution with a total mass of 1200 mL. Triethylamine and dimethylamine are coordinated with molybdate ions and copper ions, respectively.
[0042] (2) Induced coprecipitation and interface modification: After adding 0.48 mmol of polyethyleneimine, the mixture was stirred vigorously at room temperature, and the pH value was precisely adjusted to 4.5 by adding 2 mol / L dilute nitric acid dropwise. The subsequent precipitation, washing, and drying steps were the same as in Example 1.
[0043] (3) Controllable thermal decomposition of precursor: The dry precursor powder was heated to 350°C in air at 3°C / min and calcined for 90 minutes to obtain composite oxide powder.
[0044] (4) Stepwise controllable reduction and interface construction: Under a hydrogen atmosphere, the first step reduction condition was set at 350℃ / 120 minutes to more thoroughly reduce CuO to fine Cu crystal nuclei. The second step reduction temperature was set at 780℃ / 120 minutes to promote the full reduction of Mo and the optimization of the two-phase structure. Finally, ultrafine Mo-40Cu composite powder was obtained.
[0045] Performance Characterization: Due to the high Cu content and precipitation at a low pH, the powder obtained in this embodiment exhibits extremely high sintering activity. Subsequent discharge plasma sintering at a low temperature of 950°C yields a bulk material with a relative density exceeding 98.5% and excellent thermal conductivity.
[0046] Example 3 Preparation of ultrafine Mo-20Cu composite powder (1) Preparation of molecular-level precursor solution: Weigh 0.185 mol ammonium octamolate and 0.469 mol copper nitrate trihydrate, and prepare a homogeneous precursor solution according to the method in Example 1.
[0047] (2) Induced coprecipitation and interface modification: After adding 0.48 mmol of polyethyleneimine, the pH value was adjusted to 6.0 by adding dilute nitric acid dropwise in a 35°C water bath. This higher final pH value is conducive to the formation of a denser precursor precipitate. Subsequent treatment was the same as in Example 1.
[0048] (3) Controllable thermal decomposition of precursor: The dry precursor powder is heated to 450°C in air at 2°C / min and calcined for 150 minutes to fully convert the precursor into MoO3 and CuO with appropriate crystallinity.
[0049] (4) Stepwise controllable reduction and interface construction: The first step of reduction was carried out at 300℃ for 180 minutes. The second step of reduction was carried out at 800℃ and held for 180 minutes. The higher reduction temperature and longer holding time were intended to utilize a more significant "volatilization-deposition" effect to allow the Mo phase to be deposited more fully on the Cu phase surface, resulting in a composite powder with stronger interfacial bonding between the two phases. Finally, ultrafine Mo-20Cu composite powder was obtained.
[0050] Performance characterization: The powdered Mo obtained under these conditions exhibits better phase continuity, making it suitable for electronic packaging applications requiring higher strength and high-temperature stability. The grain size remains within the nanometer range, effectively suppressing abnormal Mo grain growth at low Cu content.
[0051] Example 4 (1) Preparation of molecular-level precursor solution: Weigh 0.147 mol ammonium heptamolybdate and 0.971 mol copper chloride, and prepare the solution according to the method in Example 1.
[0052] (2) Induced coprecipitation and interface modification: 0.48 mmol of polyethyleneimine was added. The precipitation process was carried out at room temperature and the pH was controlled at 5.0.
[0053] (3) Subsequent steps: The drying, calcination (400℃ / 120min) and reduction (320℃ / 150min, 700℃ / 150min) conditions are exactly the same as those in Example 1.
[0054] Performance characterization: Compared with Example 1, the powder obtained in this example has better primary ultrafine particle dispersibility, significantly reduced hard agglomeration, and higher specific surface area, demonstrating the controllability of different dispersants on the final powder morphology.
[0055] The above embodiments fully demonstrate the effectiveness and controllability of the present invention. By precisely controlling the precursor solution chemistry, precipitation pH, heat treatment, and reduction process, the chemical composition, particle size, morphology, and phase distribution of ultrafine Mo-Cu composite powder can be effectively controlled, thereby meeting the specific requirements of different application scenarios for material performance. The process of the present invention has good repeatability, stable product quality, and high industrial application value.
Claims
1.A method for preparing Mo-Cu composite powder, comprising the following steps: S1 mixing a molybdate and a copper salt in an aqueous solution of an organic amine to form a precursor solution by complexing molybdate ions and copper ions with amine groups in the organic amine; S2 then adding polyethyleneimine to the precursor solution at 40-60℃ to competitively complex the molybdate ions and copper ions in the precursor solution with the amine groups; S3 adding an acid to reduce the pH of the precursor solution to destroy the stability of the complex of polyethyleneimine with molybdate and copper ions, and induce synchronous and uniform precipitation of the molybdate and copper ions to form a Mo-Cu-O composite oxide precursor; S4 calcining the Mo-Cu-O composite oxide precursor in an inert or weakly oxidizing atmosphere at 350-450℃ to obtain a composite oxide; and S5 reducing the composite oxide to obtain the Mo-Cu composite powder. 2.The method for preparing Mo-Cu composite powder according to claim 1, wherein: the molybdate comprises ammonium molybdate; and the copper salt comprises copper chloride, copper sulfate or copper nitrate. 3.The method for preparing Mo-Cu composite powder according to claim 1, wherein: the organic amine comprises at least one of dimethylamine, trimethylamine, ethylenediamine or triethylamine. 4.The method for preparing Mo-Cu composite powder according to claim 1, wherein: the polyethyleneimine has a MW of 25000 g / mol. 5.The method for preparing Mo-Cu composite powder according to claim 1, wherein: the acid comprises nitric acid or hydrochloric acid. 6.The method for preparing Mo-Cu composite powder according to claim 1, wherein: the reduction comprises the steps of low-temperature reduction at 300-350℃ using a reducing gas and then high-temperature reduction at 650-850℃. 7.The method for preparing Mo-Cu composite powder according to claim 6, wherein: the reducing gas comprises hydrogen. 8.The method for preparing Mo-Cu composite powder according to claim 1, wherein: in the precursor solution, the concentration of the molybdate is 0.1-0.2 mol / L; in the precursor solution, the concentration of the copper salt is 0.5-1.0 mol / L; and in the precursor solution, the concentration of the organic amine is 0.6-1.0 mol / L. 9.A Mo-Cu composite powder prepared by the method according to any one of claims 1-8. 10.The Mo-Cu composite powder according to claim 9, wherein: the Mo-Cu composite powder is used to prepare a molybdenum-copper alloy. The concentration of polyethyleneimine in the precursor solution is 3.99 x 10-3 mol / L. mol / L.