Micron-sized Cu powder and preparation method thereof

Abstract

The invention discloses micron-sized Cu powder and a preparation method thereof.The method comprises the steps that raw materials are placed in a heating chamber, the heating chamber is vacuumized so that the vacuum degree can reach 80-150 KPa, and inert gas is introduced; the raw materials are subjected to heating treatment, the heating treatment temperature ranges from 1300 DEG C to 1700 DEG C, and the heat preservation time ranges from 10 min to 20 min; and cooling treatment is conducted on the Cu steam, the cooling treatment comprises the steps that the Cu steam and inert gas are mixed and then supplied into a closed space with a condenser, the flowing speed of the Cu steam and the inert gas supplied into the closed space is not lower than 500 ml / s, and the temperature difference of a cooling medium in the condenser before and after cooling treatment is not larger than 30 DEG C. According to the method, the micron-sized Cu powder which is uniform in size distribution and good in roundness can be obtained through simple operation.

Description

Technical Field

[0001] The present application relates to the field of materials, and in particular to micron-sized Cu powder and a preparation method thereof. Background Art

[0002] Micron-sized copper powder is widely used in various conductive adhesives, conductive coatings, conductive electrode materials and solar slurries due to its excellent electrical properties and relatively low cost (compared to silver powder, palladium powder, etc.), such as high conductivity. With the development of the electronics industry and the solar energy industry, ultra-fine thick film slurries prepared from micron-sized copper powder will play an important role in application scenarios such as large-scale integrated circuits and solar silicon wafers.

[0003] The condensation evaporation method is often used to prepare high-quality Cu powder because it is conducive to obtaining powders with clean interfaces. However, the current condensation evaporation method generally has high equipment costs, slow production speeds, and requires complex operations to control the uniformity of the produced powders. In addition, due to the complex operation of the current preparation process, it is difficult to maintain good consistency in the uniformity and roundness of the prepared powders in different production batches. Therefore, the current micron-level Cu powder and its preparation method still need to be improved. Summary of the invention

[0004] In view of the above problems, the present application provides a micron-sized Cu powder and a preparation method thereof.

[0005] In one aspect of the present application, the present application proposes a method for preparing micron-sized Cu powder. The method includes a heating treatment and a cooling treatment. Before the heating treatment is heated, an inert gas is introduced and the vacuum degree is increased, which can reduce the temperature of the molten Cu raw material and reduce the impurity content, and the Cu vapor and the inert gas are mixed to assist in the dispersion of the crystal nuclei and increase the flow rate of the raw material into the cooling space. At the same time, a condenser arranged in parallel is used to control the flow rate of the condensing medium, so that the material can form particles more evenly and quickly in the condensing unit. The above conditions work together to obtain micron-sized Cu powder with a relatively uniform size distribution and good roundness through simple operations.

[0006] In one aspect of the present application, the present application proposes a method for preparing micron-sized Cu powder. The method comprises: placing a raw material in a heating chamber, evacuating the heating chamber to make the vacuum degree reach 80-150KPa, and introducing an inert gas for atmosphere replacement; heating the raw material, the temperature of the heating treatment is 1300-1700 degrees Celsius, and the insulation time is 10-20min to form Cu vapor; cooling the Cu vapor, the cooling treatment comprises mixing the Cu vapor and the inert gas, and supplying them to a closed space with a condenser, the flow rate of the Cu vapor and the inert gas supplied to the inside of the closed space is not less than 500ml / s, and the temperature difference of the cooling medium in the condenser before and after the cooling treatment is not more than 30°C. Thus, nano Cu powder with low impurity content and good roundness can be easily formed.

[0007] According to an embodiment of the present application, the heating treatment further includes: heating at a heating rate of 20-50°C / min, and the temperature of the heating treatment is 1500-1680 degrees Celsius.

[0008] According to an embodiment of the present application, the vacuum degree is 100-150 KPa.

[0009] According to an embodiment of the present application, the flow rate of the Cu-containing mixture is 500-800 ml / s, the inert gas is He gas, and the mixing of the inert gas and Cu vapor is carried out at the entrance of the closed space.

[0010] According to an embodiment of the present application, the enclosed space includes a plurality of condensers, the plurality of condensers are plate condensers, the plurality of condensers are arranged at intervals, and the cooling medium inlets of the plurality of condensers are arranged in parallel.

[0011] According to an embodiment of the present application, the plate condenser is provided with regularly arranged spoiler columns, the plate condenser has the cooling medium inlet and the cooling medium outlet, and temperature sensors are provided at the cooling medium inlet and the cooling medium outlet. The method further includes: based on the temperature measured by the temperature sensor, adjusting the flow rate of the condensate so that the temperature difference between the cooling medium outlet and the cooling medium inlet is not higher than 30°C.

[0012] According to an embodiment of the present application, the Dv50 of the micron-sized Cu powder is 1-2 μm, and the sphericity is greater than 90%.

[0013] In another aspect of the present application, the present application proposes a micron-sized Cu powder. The micron-sized Cu powder contains 0.005-0.05wt% carbon, 0.08-2.0wt% oxygen, 1-2μm Dv50, and sphericity>90%. The micron-sized Cu powder has low impurity content and good roundness, and can meet the needs of various conductive pastes.

[0014] According to an embodiment of the present application, the iron content in the micron-sized Cu powder is less than 0.01wt%, the aluminum content is less than 0.01wt%, the silicon content is less than 0.01wt%, the calcium content is less than 0.01wt%, the magnesium content is less than 0.01wt%, and the zirconium content is less than 0.01wt%.

[0015] According to an embodiment of the present application, the micron-sized Cu powder is obtained by using the method described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0017] Figure 1 A flowchart of the preparation method of some embodiments of the present application; Figure 2 This is a scanning electron microscope image of the Cu powder prepared in Example 1 of the present application; Figure 3 This is the thermogravimetric analysis curve of the Cu powder prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0018] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the description and claims of this application and any variations thereof are intended to cover non-exclusive inclusions.

[0020] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0021] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0022] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0023] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0024] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "upper", "lower", "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present application and simplifying the description. They do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0025] In the first aspect of the present application, the present application proposes a method for preparing micron-sized Cu powder, by introducing an inert gas, reducing the temperature of the molten Cu raw material, reducing the impurity content, and increasing the vacuum degree, thereby increasing the particle size of the obtained Cu powder. In the cooling treatment step, the flow rate of the Cu raw material is increased, and multiple condensers are used in parallel for cooling, which improves the yield while allowing the material to form micron particles more evenly. The above conditions work together to obtain micron-sized Cu powder with a relatively uniform size distribution and good roundness through simple operations.

[0026] In one aspect of the present application, the present application provides a method for preparing micron-sized Cu powder. Figure 1The method comprises: controlling the vacuum degree in the heating unit to be 80-150KPa and introducing inert gas, heating the Cu-containing raw material, the temperature of the heating treatment is 1200-1500 degrees Celsius, and forming a Cu-containing mixture; supplying the Cu-containing mixture to a condensing unit for cooling treatment to obtain the micron-sized Cu powder, the condensing unit has a plurality of condensers inside, the plurality of condensers are arranged at intervals inside the condensing unit, and the condenser has a flowable cooling medium, and the cooling treatment comprises: controlling the flow rate of the Cu-containing mixture so that the residence time of the material inside the condensing unit is not less than 5 minutes; and / or controlling the flow rate of the cooling medium so that the temperature difference of the cooling medium at the cooling medium outlet and the cooling medium inlet of the condenser is not higher than 45°C. Thus, nano Cu powder with low impurity content and good roundness can be easily formed.

[0027] For ease of understanding, the following briefly describes the principle by which the present application can achieve the above beneficial effects: The method proposed in the present application can reduce the evaporation temperature and inhibit some impurity atoms from mixing into the Cu-containing mixture by controlling the evaporation conditions, improving the vacuum degree and passing an inert gas. Secondly, an inert gas with a certain flow rate is used to increase the rate at which the material enters the condensation unit, so that on the one hand, the Cu in the Cu-containing mixture can be distributed more evenly, preventing the nucleation rate from forming large particles too quickly, and on the other hand, the yield of the method can be improved. At the same time, by synchronously controlling the flow rate of the Cu-containing mixture in the condensation unit and the flow rate of the cooling medium, the cooling rate can be optimized, thereby regulating the roundness and uniformity of the Cu powder. Thus, the above parameters work together to obtain Cu powder of better quality under relatively simple operating conditions. The Cu powder obtained by the method proposed in the present application has a good roundness and a low impurity content.

[0028] According to an embodiment of the present application, the heating treatment may be performed in a sealed heating chamber, for example, in a heating chamber of a heating unit. The specific structure and material of the heating unit are not particularly limited, as long as they can withstand the aforementioned heating temperature. In order to facilitate the control of the pressure in the heating chamber of the heating unit, in some examples, the heating chamber may be a closed structure so as to remain relatively sealed during the stage of heating the Cu-containing mixture, thereby reducing the equipment cost required to maintain the vacuum degree.

[0029] Specifically, the heat treatment can be to place the raw material in a heating chamber, evacuate the heating chamber to make the vacuum degree reach 80-150KPa, and introduce an inert gas for atmosphere. The inert gas can be He gas. The introduction of inert gas can replace the air remaining in the chamber, avoid oxidation of the Cu-containing raw material in the subsequent heating process, and at the same time reduce the temperature at which the Cu raw material forms steam. On the other hand, it can also reduce the residual air in the subsequent high-temperature heating process. Reaction with Cu, resulting in an increase in the content of impurity elements in the product. Specifically, the flow rate of the inert gas can be controlled to maintain the vacuum degree, and for a period of time to achieve the replacement of the atmosphere in the chamber. Subsequently, the heat treatment can be started.

[0030] According to an embodiment of the present application, controlling the vacuum degree of the heat treatment to reach 80-150KPa and the temperature to 1300-1700 degrees Celsius is conducive to obtaining micron-grade Cu powder with good roundness and uniformity. Since the heating temperature needs to be maintained at a relatively high temperature to obtain Cu vapor, the preparation of Cu metal powder by the heating-condensation process usually requires precise temperature control, which involves precise monitoring of the temperature and more complex operations. In addition, when the parameter control of the heating and cooling treatments deviates, the particle size distribution of different batches also varies greatly, which in turn affects the stability of the conductive paste prepared using the Cu powder. The temperature required to form Cu vapor can be reduced by first evacuating the vacuum and then performing atmosphere replacement. In addition, when performing atmosphere replacement, the value change of the vacuum degree can also be maintained at no more than 10% of the preset value, thereby obtaining a stable evaporation environment.

[0031] Higher temperature and lower vacuum are conducive to obtaining relatively large crystal nuclei and forming micron-sized particles, but the continuous increase in vacuum and heating temperature will significantly increase the production cost. Therefore, in some embodiments, the temperature can be increased at a heating rate of 20-50°C / min, the temperature of the heating treatment is 1500-1680 degrees Celsius, and the temperature is kept for 10-20 minutes to obtain Cu vapor. The above process is conducive to obtaining Cu vapor that can form micron-sized particles. The evaporation rate is greatly affected by the vacuum and temperature, so by controlling the vacuum and temperature of the heating treatment, a more appropriate evaporation rate can be obtained, and finally a micron-sized Cu powder with a particle size that meets the requirements is obtained. In addition, the pressure in the heating treatment stage has a greater influence on the morphology of the formed Cu powder. When the vacuum is higher, it is more conducive to obtaining Cu powder with better roundness. Therefore, appropriately increasing the vacuum is conducive to obtaining micron-sized copper powder with better roundness. However, the increase in vacuum will lead to a significant increase in equipment cost, and under the condition of continuous inert gas, maintaining the vacuum also requires more complicated operations, that is, the vacuum needs to be monitored in real time. Therefore, the present application chooses to further increase the temperature of the heating treatment to obtain micron-sized particles with uniform particle size. In some specific embodiments, the heating temperature can be above 1600 degrees Celsius, and the vacuum degree can be not less than 100KPa. As mentioned above, the particle size of Cu powder is affected by the nucleation rate and the crystal nucleus growth rate. The decrease in temperature during the formation process will increase the supercooling, thereby increasing the nucleation rate, but the decrease in temperature will also reduce the diffusion rate. Diffusion is an important step in the crystallization process, and the decrease in diffusion rate is not conducive to increasing the nucleation rate. Therefore, the nucleation rate is greatly affected by temperature. Usually, with the increase of supercooling, the nucleation rate first increases and then decreases. The increase in nucleation rate will lead to the generation of more new crystal nuclei, so the nucleation rate and the crystal growth rate jointly affect the size and uniformity of the final nanoparticles.

[0032] The inventors have found that by controlling the vacuum degree and heating temperature of the heating treatment and carrying out a period of heat preservation treatment, it is beneficial to fully gasify the Cu-containing raw material and control the rate of the formed Cu vapor to be more appropriate. In continuous production, the above conditions are conducive to making the obtained Cu powder particle size more uniform in the subsequent condensation treatment, and extending the heat preservation time is also conducive to obtaining particles with larger particle size. In some embodiments, the heat preservation time can be 10-20 minutes, and the Dv50 of the obtained particles can be about 1.5μm.

[0033] According to an embodiment of the present application, the raw material may be a metal raw material such as a Cu rod. In order to improve the purity of the obtained powder, the Cu-containing raw material may be subjected to operations including but not limited to water washing, degreasing, ultrasonic treatment, etc. before treatment. The Cu-containing raw material is vaporized after the heating treatment to form Cu vapor for subsequent cooling treatment.

[0034] Cu vapor can be supplied to a closed space such as a condensing unit for cooling. In order to ensure that the Cu vapor evenly contacts the condenser when entering the condensing unit and improve production efficiency, an inert gas can be mixed with the Cu vapor and then supplied to the condensing unit. Specifically, after a certain period of heat preservation, a nozzle can be used to mix the Cu vapor and the inert gas and supply them to the condensing unit.

[0035] As mentioned above, during the heating treatment stage, the heating unit can be in a relatively closed state. In particular, at the beginning of production, the heating unit can be quickly made to reach the required vacuum degree and temperature by closing the passage between the heating unit and the condensing unit. When it is necessary to supply the material to the condensing unit, the passage between the two can be opened, such as opening a nozzle, and adding a second gas such as an inert gas through the nozzle.

[0036] For example, in some embodiments, the amount of the mixture supplied to the condensation unit can be controlled by adjusting the flow rate of the inert gas at the nozzle. By coordinating the flow rate of the cooling medium in the condenser, it is possible to prevent the crystal nuclei from agglomerating to produce oversized particles, obtain particles with a narrow particle size distribution, and improve the roundness of the formed Cu powder.

[0037] In some specific embodiments, the Cu-containing gas can be adjusted to be supplied to the condensation unit at a speed of not less than 500 ml / s. In some embodiments, the speed can be controlled by the flow rate of the second gas. In the related art, the preparation of micron-grade Cu powder generally has the problem of wide particle size distribution and poor particle roundness, so the obtained Cu powder varies greatly in different production batches. As mentioned above, due to the high melting point of Cu, a certain temperature and vacuum degree are required for heating treatment. Therefore, by regulating the cooling treatment step, on the one hand, the particle size and roundness of the obtained powder can be improved, and on the other hand, the difficulty of operation can be reduced: the cooling treatment part can better adjust the morphology of the obtained particles by controlling the flow rate of the second gas and the condensing medium, and relative to the regulation of the vacuum degree, the flow rate control of the airflow and the cooling medium is relatively easier.

[0038] In some embodiments, the nozzle may have a second gas inlet to mix the second gas with the Cu-containing mixture. In some embodiments, the flow rate of the material entering the condensation unit can be controlled by adjusting the flow rate of the second gas. This helps to maintain a relatively stable atmosphere in the heating process. This helps to more easily optimize the cooling rate and maintain the stability of the heating process.

[0039] According to an embodiment of the present application, in order to achieve condensation more effectively and reduce the accumulation of Cu powder on the surface of the condenser, which causes the particle size of the prepared Cu powder to be uncontrolled, the arrangement direction of the plate condenser can be the same as the direction of movement of the material in the condensation unit. Thus, a material with a certain speed can be used to impact the surface of the plate condenser to improve the heat exchange efficiency and prevent the accumulation of the material on the surface of the condenser to form particles with excessive particle size. For example, the material can be sprayed into the condensation unit through a nozzle in a vertical direction, and the plate condenser can also be arranged at intervals in the vertical direction. Compared with the inclined arrangement or the horizontal staggered arrangement, the vertical distribution is more conducive to reducing the temperature difference between multiple condensers, and it is also convenient to provide cooling medium for multiple condensers in parallel. Multiple parallel condensers can reduce the temperature difference between two adjacent condensers and obtain a more uniform cooling environment.

[0040] According to an embodiment of the present application, a plate condenser may be provided with regularly arranged spoiler columns to improve heat exchange efficiency. In some embodiments, the height of the spoiler columns may be consistent with the height of the cooling medium channel inside the condenser, or may be slightly lower than the height of the cooling medium channel. The specific structure inside the plate condenser may be designed according to the size of the condensing unit.

[0041] The inventors have found that if the material stays in the condensation unit for too short a time, the material cannot be fully cooled and grown in the condensation unit, which is not conducive to obtaining particles with a particle size of micrometers or uniformly distributed powders. If the temperature difference of the condensation medium before and after condensation is large, the material will also experience a large temperature difference when in contact with the condenser, which is also not conducive to obtaining particles with a narrow particle size distribution. When the flow rate of Cu vapor and the second gas supplied to the interior of the space is not less than 500 ml / s, and the temperature difference of the cooling medium in the condenser before and after the cooling treatment is not greater than 30°C, the roundness of the obtained particles can reach more than 90%, and the particle size distribution is also relatively narrow.

[0042] In order to conveniently control the flow rate of the cooling medium, temperature sensors can be provided at both the cooling medium inlet and the cooling medium outlet of the plate-type condenser. Based on the temperature measured by the temperature sensor, the flow rate of the condensate is adjusted so that the Cu-containing mixture forms micron-sized powders at a better cooling rate on the condenser surface. In some specific embodiments, the temperature difference between the cooling medium outlet and the cooling medium inlet can be made no higher than 30°C.

[0043] According to the embodiment of the present application, the Dv50 of the formed micron-sized Cu powder can be 1-2 μm, and the sphericity is greater than 90%. The impurity content of the micron-sized copper powder is low, for example, the micron-sized Cu powder contains 0.005-0.05wt% carbon and 0.08-2.0wt% oxygen.

[0044] In some embodiments, the surface of the micron-sized Cu powder may have a thin oxide layer. The thickness of the oxide layer is more than ten microns, and the main components of the oxide layer may be CuO, Cu (OH) 2, etc. An appropriate oxide layer can improve the anti-oxidation performance of the micron-sized Cu powder. Moreover, without affecting the main performance parameters of the Cu powder, an oxide layer of appropriate thickness can also reduce the requirements for the equipment and method for preparing the Cu powder, which is conducive to reducing production costs.

[0045] In another aspect of the present application, the present application proposes a micron-sized Cu powder. The micron-sized Cu powder contains 0.005-0.05wt% carbon, 0.08-2.0wt% oxygen, 1-2μm Dv50, and sphericity>90%. The micron-sized Cu powder has low impurity content and good roundness, and can meet the needs of various conductive pastes.

[0046] According to an embodiment of the present application, the Cu powder has an iron content of less than 0.01wt%, an aluminum content of less than 0.01wt%, a silicon content of less than 0.01wt%, a calcium content of less than 0.01wt%, a magnesium content of less than 0.01wt%, and a zirconium content of less than 0.01wt%.

[0047] According to an embodiment of the present application, the micron-sized Cu powder is obtained by using the method described above.

[0048] Therefore, the micron-sized Cu powder has all the characteristics and advantages of the Cu powder obtained by the aforementioned method, which will not be described in detail here.

[0049] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0050] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0051] Example 1 Heating treatment: close the nozzle, control the vacuum degree in the heating unit to 100 KPa and introduce inert gas He. After introducing inert gas for 15 minutes, start programmed temperature increase to 1550 degrees Celsius and keep it warm for 15 minutes.

[0052] Condensation treatment: Open the nozzle and introduce He gas from the nozzle at the same time, control the flow rate of the gas-liquid mixture into the condensation unit at 550ml / s, the condensate flow rate is 600ml / s, maintain the inlet and outlet temperature difference of the condenser at 25±2℃, and condensation treatment for 10min.

[0053] Example 2 Heating treatment: close the nozzle, control the vacuum degree in the heating unit to 85KPa and introduce inert gas He. After introducing inert gas for 15 minutes, start programmed temperature increase to 1700 degrees Celsius and keep it warm for 15 minutes.

[0054] Condensation treatment: open the nozzle and introduce He gas from the nozzle at the same time, control the flow rate of the gas-liquid mixture into the condensation unit at 600ml / s, the condensate flow rate is 800ml / s, maintain the inlet and outlet temperature difference of the condenser at 20±2℃, and condensation treatment for 10min.

[0055] Example 3 Heating treatment: close the nozzle, control the vacuum degree in the heating unit to 150 KPa and introduce inert gas He. After introducing inert gas for 15 minutes, start programmed temperature increase to 1500 degrees Celsius and keep it warm for 10 minutes.

[0056] Condensation treatment: Open the nozzle and introduce He gas from the nozzle at the same time, control the flow rate of the gas-liquid mixture into the condensation unit at 450ml / s, the condensate flow rate is 400ml / s, maintain the inlet and outlet temperature difference of the condenser at 30±2℃, and condensation treatment for 15min.

[0057] Example 4 Heating treatment: close the nozzle, control the vacuum degree in the heating unit to 120KPa and introduce inert gas He. After introducing inert gas for 15 minutes, start programmed temperature increase to 1500 degrees Celsius and keep it warm for 10 minutes.

[0058] Condensation treatment: Open the nozzle and introduce He gas from the nozzle at the same time, control the flow rate of the gas-liquid mixture into the condensation unit at 450ml / s, the condensate flow rate is 600ml / s, maintain the inlet and outlet temperature difference of the condenser at 28±2℃, and condensation treatment for 10min.

[0059] Comparative Example 1 The remaining operations are the same as those in Example 1, except that no inert gas is introduced into the heating unit and the heating temperature is 1600 degrees Celsius.

[0060] Comparative Example 2 The remaining operations were the same as in Example 1, except that the condensate flow rate was 200 ml / s, the condenser inlet and outlet temperature difference was 50 ± 2 °C, and the condensation treatment was 10 min. Comparative Example 3 The remaining operations are the same as those in Example 1, except that He gas is not introduced into the nozzle, and the Cu-containing mixture is allowed to enter the condensation unit at a flow rate of 100 ml / s.

[0061] The properties of the Cu powder prepared in the above examples and comparative examples were tested. The particle size was tested using a laser particle size analyzer to obtain the Dv10, Dv50 and Dv90 of the sample. The C content was measured using a carbon-sulfur analyzer, and the O content was measured using an oxygen analyzer.

[0062] The roundness is measured by conventional methods in the art, the ratio of the particle surface area to the surface area of ​​a sphere of equal volume to the particle. The roundness of a perfect sphere is 1, i.e. 100%, and the roundness of a particle that is approximately spherical is approximately 100%. The calculation formula of roundness I is as follows: Where Vp is the volume of the particle and Sp is the surface area of ​​the particle.

[0063] The roundness described in this application is the average value of the particle roundness.

[0064] Thermogravimetric analysis was performed on the Cu powder prepared in Example 1. The test results are as follows: Figure 2 shown.

[0065] Some test results of the above examples and comparative examples are shown in Table 1 below: Table 1 As shown in Table 1, a higher heating treatment temperature is conducive to obtaining micron-sized Cu powder with better roundness and narrower particle size distribution, and a higher flow rate of the material sprayed into the condensation unit and cooling water is conducive to improving the uniformity of the Cu powder. In addition, the inert atmosphere of the heating treatment is also conducive to reducing the content of impurity elements.

[0066] refer to Figure 2 as well as Figure 3 The Cu powder prepared in Example 1 has a relatively uniform particle size and a high roundness. Thermogravimetric analysis shows that the DTA curve of the Cu powder has a relatively obvious exothermic peak at around 217°C, and the TGA curve also has an inflection point near 217°C, which may be related to the oxidation of the Cu powder. A broad peak appears in the DTA curve at around 365°C, which may be related to the oxidation of impurity elements in the Cu powder. The peak appears at a higher temperature and has a wider peak width, which may be related to the oxidation of multiple impurities.

[0067] It can be seen from the data of Comparative Examples 1-3 and the embodiment that the key factors affecting the acquisition of micron-sized Cu powder with good roundness are to introduce inert gas into the heating unit, to keep the material sprayed into the cooling unit at a certain rate, and to maintain a small condensed water temperature difference.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing micron-sized Cu powder, characterized in that: include: The raw materials are placed in a heating chamber, and the heating chamber is evacuated to a vacuum degree of 80-150 KPa, and an inert gas is introduced to replace the atmosphere; The raw material is subjected to a heating treatment at a temperature of 1300-1700 degrees Celsius and a holding time of 10-20 minutes to form Cu vapor; The Cu vapor is subjected to a cooling treatment, wherein the cooling treatment comprises mixing the Cu vapor and the second gas and supplying the mixture to a closed space having a condenser, wherein the flow rate of the Cu vapor and the second gas supplied to the space is not less than 500 ml / s, and the temperature difference of the cooling medium in the condenser before and after the cooling treatment is not greater than 30°C.

2. The method according to claim 1, characterized in that The heating treatment further includes: heating at a heating rate of 20-50°C / min, and the temperature of the heating treatment is 1500-1680 degrees Celsius.

3. The method according to claim 1, characterized in that The vacuum degree is 100-150KPa.

4. The method according to claim 1, characterized in that The flow rate of the Cu-containing mixture is 500-800 ml / s, the inert gas is He gas, and the mixing of the inert gas and Cu vapor is carried out at the entrance of the closed space.

5. The method according to claim 4, characterized in that The enclosed space includes a plurality of condensers, wherein the plurality of condensers are plate-type condensers, the plurality of condensers are arranged at intervals, and the cooling medium inlets of the plurality of condensers are arranged in parallel.

6. The method according to claim 5, characterized in that The plate condenser is provided with regularly arranged spoiler columns, the plate condenser has the cooling medium inlet and the cooling medium outlet, the cooling medium inlet and the cooling medium outlet are both provided with temperature sensors, and the method further comprises: Based on the temperature measured by the temperature sensor, the flow rate of the condensate is adjusted so that the temperature difference between the cooling medium outlet and the cooling medium inlet is not higher than 30°C.

7. The method according to any one of claims 1 to 6, characterized in that: The Dv50 of the micron-sized Cu powder is 1-2 μm, and the sphericity is greater than 90%.

8. A micron-sized Cu powder, characterized in that: The micron-sized Cu powder contains 0.005-0.05wt% carbon, 0.08-2.0wt% oxygen content, 1-2μm Dv50, and sphericity>90%.

9. The micron-sized Cu powder according to claim 8, characterized in that: The micron-sized Cu powder has an iron content of less than 0.01 wt%, an aluminum content of less than 0.01 wt%, a silicon content of less than 0.01 wt%, a calcium content of less than 0.01 wt%, a magnesium content of less than 0.01 wt%, and a zirconium content of less than 0.01 wt%.

10. The micron-sized Cu powder according to claim 8 or 9, characterized in that: The micron-sized Cu powder is obtained by the method according to any one of claims 1 to 7.

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