An environmental particulate spherical powder and a preparation method thereof

Abstract

The application discloses an environmental particulate spherical powder and a preparation method thereof, and belongs to the technical field of materials science. The environmental particulate spherical powder is prepared from artificial synthetic CMAS powder or natural solid particles as raw materials. The CMAS powder is sequentially subjected to ball milling, high-temperature melting, quenching and solid-phase sintering to obtain a crystalline CMAS bulk body. The natural solid particles or the crystalline CMAS bulk body is subjected to ball milling to obtain fine particulate powder, and a high-temperature melting characteristic curve of the fine particulate powder is obtained. The fine particulate powder is made into slurry and then sprayed and granulated to obtain powder particles with a target size. The powder particles are subjected to low-temperature sintering to remove a binder, and then subjected to high-temperature sintering densification treatment to obtain the environmental particulate spherical powder. The temperature of the densification treatment is determined based on the high-temperature melting characteristic curve. The prepared powder has excellent fluidity and compactness, the particle size of the powder is controlled in a range of 20-500 microns, and the spherical powder with concentrated particle size distribution can be obtained after screening. The prepared powder can provide high-quality and standardized materials for the research on the related thermal protection technology of an aero-engine.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine technology, and particularly relates to a spherical powder for environmental particulate matter and its preparation method. Background Technology

[0002] With the rapid development of my country's aerospace industry, the demand for high-performance aero engines is increasing. As the inlet temperature of high-pressure turbines in aero engines gradually rises, serious environmental deposits cause high-temperature corrosion of the thermal protection coating.

[0003] During takeoff, landing, and flight, especially in deserts or areas prone to sandstorms, aircraft inevitably inhale environmental dust (including sand, ash, and volcanic ash, collectively referred to as particulate matter). This dust enters the core of the aero-engine, where it undergoes repeated compression and impact to form fine particles. These particles then melt in the high-temperature environment and adhere to heat-sensitive components such as nozzles, guide vanes, and turbine blades, forming deposits. These deposits can clog cooling vents or corrode blade surface coatings in high-temperature environments, severely impacting their service performance and lifespan. Currently, the corrosive damage of environmental particulate matter to the surfaces of hot-end components of aero-engines has become one of the main factors affecting the lifespan of high-temperature protective coatings.

[0004] To study the motion and deposition behavior of environmental particulate matter within aero-engines and the high-temperature resistance of thermal protective coatings to thermal erosion from environmental particulate matter, it is necessary to prepare fine-grained environmental particulate matter powder and simulate the high-temperature erosion behavior of fine environmental particulate matter using an aero-engine environmental particulate matter service damage platform. To ensure a continuous supply of environmental particulate matter powder within the damage platform, the fed powder must possess excellent flowability to ensure its smooth entry into the high-temperature, high-speed flame for melting and ultimately adhesion to the high-temperature protective coating.

[0005] However, the irregular shape of existing particulate matter powders leads to poor flowability, making them prone to blockage or intermittent supply during transport, hindering the continuous and stable supply of powder to the high-temperature flame zone. Furthermore, the non-uniform particle size makes it impossible to quantitatively describe the powder supply during thermal shock experiments, severely limiting the reliability and accuracy of these experiments and impeding the accurate evaluation of coating erosion resistance and the research and development of related thermal protection technologies for aero-engines. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a spherical powder of environmental particulate matter and a method for preparing the same, so as to solve the problem that the existing environmental particulate matter powders are irregular in shape and have poor flowability, which makes it impossible to supply them continuously and stably during the transportation process, and at the same time overcome the defect that the uneven particle size makes it difficult to quantitatively describe the powder supply.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The first aspect of this invention provides a method for preparing spherical powder of environmental particulate matter, comprising the following steps:

[0009] Step S1: Select artificially synthesized CMAS powder or natural solid particles as raw materials for preparation;

[0010] Step S2: When the raw material is artificially synthesized CMAS powder, the raw material is sequentially ball-milled, high-temperature melted, and quenched to obtain glassy CMAS blocks, and then crystalline CMAS blocks are obtained by solid-state sintering.

[0011] Step S3: Ball mill the natural solid particles from step S1 or the crystalline CMAS block from step S2 to obtain fine particle powder; perform high-temperature melting test on the fine particle powder to obtain its high-temperature melting characteristic curve.

[0012] Step S4: After preparing the fine powder particles into a slurry with deionized water and binder, spray granulation is performed to obtain powder particles of the target size.

[0013] Step S5 involves low-temperature sintering to remove the binder from the powder particles, followed by high-temperature sintering to densify them, resulting in spherical powder particles of the target environment. The temperature of the high-temperature sintering densification process is determined based on the high-temperature melting characteristic curve obtained in step S3.

[0014] Preferably, the preparation method further includes step S6, which involves sieving the environmental particulate matter spherical powder from step S5 to obtain powders with different particle size distributions to meet the needs of different experiments.

[0015] Preferably, the artificially synthesized CMAS powder in step S1 comprises 33 mol.% CaO, 9 mol.% MgO, and 13 mol.% AlO. 1.5 , 45 mol.% SiO2.

[0016] Preferably, the natural solid particles in step S1 are selected from one or more combinations of naturally collected sand, dust, and volcanic ash.

[0017] Preferably, the high-temperature melting temperature in step S2 is 1300-1500℃, and the holding time is 1-5h; the solid-phase sintering temperature of the glassy CMAS block is the temperature at which its disordered state transforms into an ordered state, as determined by thermal analysis, and the holding time is 1-5h.

[0018] Preferably, the thermal analysis method is DSC.

[0019] Preferably, in the ball milling process of steps S2 and S3, anhydrous ethanol is used as the dispersant, the ball-to-material ratio is 5:1-3:1, the ball milling speed is 200-300 r / min, and the ball milling time is 10-20 h.

[0020] Preferably, the particle size of the fine powder obtained after ball milling in step S3 is ≤10 μm.

[0021] Preferably, the process parameters for spray granulation in step S4 include a slurry solid content of 30-40%, a binder content of 8-10%, an inlet temperature of 250-300℃, an outlet temperature of 90-110℃, an atomizer frequency of 100-500HZ, and a feed rate of 40-70 rpm.

[0022] Preferably, the adhesive is PVA.

[0023] Preferably, the temperature of the low-temperature sintering in step S5 is 400-600℃, and the holding time is 1-5h.

[0024] Preferably, the temperature of the high-temperature sintering densification treatment in step S5 is determined based on the high-temperature melting characteristic curve of step S3, including setting the temperature at which the projected area of ​​the sample shrinks by 5% in the curve as the temperature of the high-temperature sintering densification treatment; and then holding at this temperature for 3-10 hours.

[0025] Preferably, in step S6, the spherical powder of environmental particulate matter is sieved to obtain powder of three particle size levels, including 20-40 μm, 60-80 μm, and 100-120 μm.

[0026] The second aspect of the present invention provides a method for preparing spherical environmental particulate matter powder as described above, wherein the spherical environmental particulate matter powder has a particle size of 20 to 500 μm.

[0027] Preferably, the flowability index of the environmental particulate matter spherical powder is greater than 70, and the jetting index is greater than 80.

[0028] The third aspect of this invention proposes the application of the environmental particulate spherical powder prepared by the above-mentioned method, or the above-mentioned environmental particulate spherical powder, in simulating the high-temperature thermal protection service environment of hot-end components of aero-engines, and in simulating thermal erosion or thermal corrosion experiments on the surface of hot-end components.

[0029] The beneficial effects of this invention are as follows:

[0030] (1) The preparation method of the present invention can use artificially synthesized CMAS powder or natural solid particles as raw materials to prepare spherical powder of environmental particulate matter, which overcomes the challenges brought by the complex composition of raw materials from different sources and the large differences in intrinsic properties at high temperatures to the preparation process, and significantly broadens the source range and application scenarios of environmental particulate matter simulation powder.

[0031] (2) The preparation method of the present invention innovatively formulates the key high-temperature densification temperature parameters based on the high-temperature melting characteristic curve of the material itself, avoiding the coarseness of the previous empirical temperature range, and breaking through the limitations of the traditional empirical method for specific materials, ensuring the scientific nature, specificity and generalization of the densification process in temperature selection, and can significantly improve the density and stability of the powder.

[0032] (3) The spherical powder of environmental particulate matter prepared by the present invention has excellent flowability and density. The particle size range of the powder is controlled within 20 to 500 μm. After sieving, the particle size is classified to obtain spherical powder with concentrated particle size distribution. It can be applied to the thermal shock corrosion test of environmental particulate matter in thermal spraying or high temperature thermal protective coating. It can ensure the continuous and stable delivery of environmental particulate matter powder during the experiment and can quantitatively describe the supplied powder, thereby improving the reliability and accuracy of the experiment and significantly improving the experimental effect and application value of high temperature thermal protective coating.

[0033] (4) The spherical powder of environmental particulate matter prepared by the present invention can be obtained by particle size classification, and various powders with different particle sizes and distributions can be obtained. In addition to being used in thermal spraying or high-temperature thermal protection coating environmental particulate matter thermal shock corrosion experiments, it can also be used to simulate the deposition and corrosion process of environmental particulate matter in aero engines, which helps to promote the research and development of high-temperature thermal protection coating materials and improve the service performance and life of aero engines. Attached Figure Description

[0034] Figure 1 A schematic flowchart illustrating a method for preparing spherical powder of environmental particulate matter according to an embodiment of the present invention;

[0035] Figure 2 This is a DSC curve obtained by differential scanning calorimetry analysis of glassy CMAS powder in Example 1 of the present invention.

[0036] Figure 3 This is a high-temperature melting characteristic curve of the crystalline CMAS powder after ball milling in Example 1 of the present invention;

[0037] Figure 4 The images show the particle size distribution and morphology of the spherical powder of environmental particulate matter prepared in Example 1 of this invention, where a is the particle size distribution image and b is the morphology image.

[0038] Figure 5The images show the particle size distribution and corresponding morphology of the environmental particulate matter spherical powder obtained in Example 1 of this invention after sieving. Specifically, d and a are the particle size distribution and corresponding morphology of the 100-120 μm level, respectively; e and b are the particle size distribution and corresponding morphology of the 60-80 μm level, respectively; and f and c are the particle size distribution and corresponding morphology of the 20-40 μm level, respectively.

[0039] Figure 6 This is a high-temperature melting characteristic curve of the natural sand and gravel powder after ball milling in Example 2 of the present invention;

[0040] Figure 7 The images show the particle size distribution and morphology of the spherical powder of environmental particulate matter prepared in Example 2 of this invention, where a is the particle size distribution image and b is the morphology image.

[0041] Figure 8 This is a morphology diagram of the original natural sand and gravel powder of Comparative Example 1 of the present invention. Detailed Implementation

[0042] To make the objectives and technical solutions of this invention clearer and more complete, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the technical solutions of this invention, are all within the scope of protection of this invention.

[0043] Unless otherwise specified, all reagents and materials involved in the embodiments of this invention are commercially available products and can be purchased through commercial channels.

[0044] Terminology Explanation:

[0045] Flowability index: refers to a set of values ​​obtained by weighted summation of indices such as angle of repose, compressibility, angle of flatness, homogeneity or coagulation, used to comprehensively evaluate the flowability of powder. It mainly describes the strength of the natural flow characteristics of powder under the action of gravity. The index ranges from 0 to 100; the higher the index, the stronger the flowability of powder under the action of gravity.

[0046] Spray flow index: It is a set of values ​​obtained by weighted summation of flowability index, collapse angle, difference angle, dispersion and other indices. It is used to comprehensively evaluate the spray flowability of powder. It mainly describes the strength of the powder's ability to overcome gravity and splash in space. The index range is 0-100. The higher the index, the stronger the powder's ability to splash and disperse in space.

[0047] See Figure 1This invention provides a method for preparing spherical powder of environmental particulate matter, specifically including the following steps:

[0048] Step S1: Select artificially synthesized CMAS powder or natural solid particles as raw materials for preparation.

[0049] Specifically, the artificially synthesized CMAS powder includes a mixture of CaO, MgO, and AlO in a specific ratio. 1.5 The CMAS powder comprises four raw powders: CaO, SiO2, and CaO. Preferably, the CMAS powder, by molar weight, includes 33 mol.% CaO, 9 mol.% MgO, and 13 mol.% AlO2. 1.5 45 mol.% SiO2. Natural solid particles include naturally collected sand, dust, volcanic ash, or other natural environmental sediments.

[0050] Step S2: When the raw material is artificially synthesized CMAS powder, the raw material is sequentially ball-milled, high-temperature melted, and quenched to obtain glassy CMAS blocks, and then crystalline CMAS blocks are obtained through solid-state sintering.

[0051] Specifically, to homogenize the composition of CMAS, the four original powders constituting the CMAS powder were mixed evenly in a ball mill jar using anhydrous ethanol as a dispersant. The jar was then ball-milled in a ball mill at a ball-to-powder ratio of 5:1 to 3:1, a milling speed of 200-300 r / min, and a milling time of 10-20 h. Afterward, the ball-milled powder mixture was dried in a tray to ensure complete evaporation of the ethanol. The dried powder mixture was then placed in a crucible and held at 1300-1500℃ for 1-5 h to ensure complete melting of the four powders. The molten fluid was then rapidly introduced into deionized water for quenching to obtain glassy CMAS blocks.

[0052] To transform the glassy, ​​disordered amorphous CMAS into an ordered crystalline compound, making it hard and preventing the subsequent production of spherical powders for environmental particulate matter from easily breaking, the glassy CMAS bulk must undergo high-temperature solid-state sintering. Specifically, the temperature at which the bulk transitions from a disordered to an ordered state is determined using thermal analysis, thus establishing the high-temperature solid-state sintering temperature. The glassy CMAS bulk is heated to the sintering temperature and held at this temperature for 1-5 hours to allow sufficient diffusion and rearrangement of internal atoms to form a regular crystalline structure. After holding at this temperature, the bulk is slowly cooled in the furnace, ultimately yielding a highly crystalline ordered crystalline bulk. It should be noted that the temperature of the transition from a disordered to an ordered state can be measured using various thermal analysis methods, including differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and dynamic thermomechanical analysis (DMA). For example, when using DSC analysis, the temperature of the transition from a disordered to an ordered state is the starting temperature of the exothermic crystallization peak in the DSC curve.

[0053] Step S3: Ball mill the natural solid particles from step S1 or the crystalline CMAS block from step S2 to obtain fine particle powder; perform high-temperature melting test on the fine particle powder to obtain its high-temperature melting characteristic curve.

[0054] It should be understood that natural solid particles are crystalline materials, therefore high-temperature solid-state sintering is unnecessary. Specifically, natural solid particles or crystalline CMAS blocks are mechanically crushed using a planetary ball mill or other ball milling equipment. Through the high-frequency collision and friction of the grinding balls, the material is broken into fine powder particles no larger than 10 μm. Smaller particle sizes result in larger specific surface areas and higher surface energy, making them more prone to agglomeration into large, regular spherical powder particles during subsequent spray granulation. The crushed powder can be precisely controlled to have a particle size ≤10 μm through sieving or centrifugal separation. The ball milling process and parameters are the same as in step S2.

[0055] Furthermore, in order to determine the temperature of the subsequent high-temperature sintering densification treatment, a portion of fine powder particles was taken and subjected to high-temperature melting tests using instruments such as a high-temperature microscope and differential scanning calorimeter according to standard operating procedures to obtain its high-temperature melting characteristic curve.

[0056] Step S4: The fine powder particles are mixed with deionized water and binder to form a slurry, which is then spray-granulated to obtain powder particles of the target size.

[0057] Specifically, fine particulate powder is mixed with deionized water and a binder to form a uniform suspension slurry with a solid content of 30-40% and a binder content of 8-10%. The binder is preferably PVA (polyvinyl alcohol). The slurry is then fed into a spray drying system, where evaporation and agglomeration produce powder particles containing a solid binder. The particle size of the powder particles can be adjusted by controlling the atomizer speed and slurry supply rate in the spray drying system. A higher atomizer speed and slower feed rate result in smaller particle sizes; conversely, a lower atomizer speed and faster feed rate result in larger particle sizes. In this embodiment, the atomizer frequency is set to 100-500 Hz, the feed rate to 40-70 rpm, the inlet temperature to 250-300°C, and the outlet temperature to 90-110°C, ultimately yielding powder particles with a particle size range controlled between 20-500 μm.

[0058] Step S5 involves low-temperature sintering to remove the binder from the powder particles, followed by high-temperature sintering to densify them, resulting in spherical powder particles of the target environment. The temperature of the high-temperature sintering densification process is determined based on the high-temperature melting characteristic curve obtained in step S3.

[0059] Specifically, the powder containing solid binder is placed in a crucible and then in a muffle furnace. It is heated to 400-600℃ and held at that temperature for 1-5 hours for low-temperature sintering to remove the binder from the powder. The binder (such as PVA) decomposes into volatile substances such as CO2 and H2O at 400-600℃, thus detaching from the powder and preventing residual organic matter from affecting the powder's composition. This low-temperature sintering process ensures the complete removal of binders such as PVA.

[0060] Furthermore, the binder-removed powder particles are further heated in a muffle furnace for high-temperature sintering and densification treatment to obtain the final spherical powder of environmental particulate matter. It should be noted that the binder-removed powder particles are only bound by physical adsorption, resulting in low bonding strength between fine particles, making them easily broken and dispersed. Therefore, high-temperature sintering and densification treatment is necessary to ensure that the fine particles within the agglomerated spherical powder adhere to each other, guaranteeing the sphericity of the powder. The selection of the sintering temperature is crucial to this process. If the temperature is too high, the sintering deformation of the spherical powder will increase, causing different spherical particles to stick together, severely affecting the flowability of the powder. If the temperature is too low, the spherical powder will not undergo sintering, and the agglomerated fine particles will easily break and disperse during sieving. Therefore, the temperature of the high-temperature sintering and densification treatment must be strictly controlled to ensure the independence of the spherical powder particles, thereby ensuring the flowability of the powder.

[0061] In this embodiment of the invention, based on the high-temperature melting characteristic curve obtained in step S3, the shrinkage temperature (ST) at which the projected area of ​​the sample shrinks by approximately 5% in the curve, i.e., when the collected real-time area accounts for 95% of the initial area, is set as the temperature for high-temperature sintering densification treatment, and the sample is held at this temperature for 3-10 hours. When the projected area shrinks by 5%, a stable "necking" can form between the powder particles, but no significant deformation occurs. The sintering temperature determined by this method depends on the intrinsic high-temperature characteristics of various materials. Compared with the existing technology that only provides a fixed temperature range, this method is more targeted and universal, avoids the coarseness of previous empirical ranges, and breaks through the limitations of traditional empirical methods for specific materials. This makes the selection of sintering temperature more in line with thermodynamic and kinetic laws, significantly improving the scientific nature of temperature selection in this process.

[0062] Step S6: Use a standard sieve to sieve the spherical environmental particulate matter powder obtained in step S5 to obtain powders with different particle size distributions to meet the needs of different test conditions.

[0063] The spherical powder of environmental particulate matter prepared by the above steps has a wide particle size distribution. To obtain micron-sized powder with a concentrated particle size distribution suitable for different experimental conditions, the spherical powder can be sieved using a standard sieve. Preferably, the sieved powder has particle sizes in the range of 20-40 μm, 60-80 μm, and 100-120 μm, for application in simulating the high-temperature thermal protection service environment of hot-end components of aero-engines, as well as in simulating thermal erosion and thermal corrosion experiments on the surface of hot-end components.

[0064] Example 1

[0065] In this embodiment, the environmental particulate matter spherical powder is prepared from artificially synthesized CMAS powder containing the following molar percentages as raw materials: 33 mol.% CaO, 9 mol.% MgO, and 13 mol.% AlO. 1.5 45 mol.% SiO2. The specific steps include:

[0066] (1) Using anhydrous ethanol as a dispersant, four original powders of CMAS powder were mixed in proportion and placed into a ball mill jar with a ball-to-powder ratio of 3:1. The ball mill jar was placed in a planetary ball mill and ball milled at a speed of 240 r / min for 20 h. The mixture of the four original powders after ball milling was placed in a tray and dried to ensure that the ethanol was completely evaporated.

[0067] (2) The dried powder was placed in a platinum crucible and kept at 1400℃ for 3 hours to melt it completely. Then the molten fluid was quickly introduced into deionized water and quenched to obtain glassy CMAS blocks.

[0068] (3) Take a portion of the glassy CMAS block for DSC analysis, such as Figure 2 As shown, a significant endothermic and exothermic phenomenon occurs near 1200℃, indicating that this temperature is the point at which the glassy CMAS bulk transitions from disorder to order. Therefore, 1200℃ was chosen as the temperature for high-temperature solid-state sintering.

[0069] (4) The glassy CMAS block is placed back into the platinum crucible and heated to 1200℃ for 3 hours for high-temperature solid-state sintering, which promotes the glassy CMAS to change from a disordered amorphous structure to an ordered crystalline structure.

[0070] (5) Following the same procedure as in step (1), place the crystalline CMAS into a ball mill jar with a ball-to-material ratio of 3:1 and use anhydrous ethanol as a dispersant. Place the ball mill jar into a planetary ball mill and ball mill at a speed of 240 r / min for 20 h to obtain fine powder particles with a particle size of less than 10 μm. Dry the fine powder particles in the ball mill jar to ensure that the ethanol evaporates completely.

[0071] (6) Take a portion of the fine powder particles and perform a high-temperature melting test using a high-temperature microscope to obtain the following results: Figure 3 The high-temperature melting characteristic curve is shown. From the relationship between the sample projected area and temperature in the figure, it can be seen that the sample projected area decreases significantly near 800℃, and shrinks by about 5% at 750℃. Based on this, the temperature for subsequent high-temperature sintering densification treatment of the powder is set to 750℃.

[0072] (7) Prepare the spray granulation slurry according to the following proportions: 1000g of fine powder, 209g of PVA, and 1355g of deionized water. Mix the slurry thoroughly in a ball mill jar at a speed of 240 r / min for 5 h. This slurry will be used for spray granulation. 20-500 μm powder particles were prepared by spray drying. Specific parameters are shown in Table 1.

[0073]

[0074] (8) The powder particles were placed in a muffle furnace and sintered at 600℃ for 2 hours to remove PVA. Then the temperature was raised to 750℃ and held for 5 hours, causing the powder to shrink by about 5%. This ensured that the spherical powder particles were independent of each other and that the powder would not break under external force, ultimately obtaining dense environmental particulate spherical powder. Its particle size distribution and morphology are as follows: Figure 4 As shown, where, Figure 4 'a' in D shows D 10 Approximately 14.9 μm, indicating that 10% of the powder particles have a diameter less than or equal to 14.9 μm, D 50 Approximately 51.9 μm, indicating that 50% of the powder particles have a diameter of less than or equal to 51.9 μm, D 90 The particle size is approximately 232.9 μm, indicating that 90% of the powder particles have a diameter of less than or equal to 232.9 μm. Figure 4 b in the figure shows that the powder is approximately spherical.

[0075] (9) The prepared spherical environmental particulate matter powder was sieved using a standard sieve to obtain powders with relatively concentrated distributions of different particle sizes, in order to meet the needs of different experiments. The particle size distribution and morphology of the sieved spherical environmental particulate matter powder are as follows: Figure 5 As shown. In this embodiment, three levels of environmental particulate matter spherical powder with different particle sizes were obtained through sieving: 20-40 μm particle size class powder (…). Figure 5 c and f), 60-80μm particle size level powder ( Figure 5 (b and e), 100-120μm particle size level powder ( Figure 5 (a and d in the text).

[0076] Testing showed that the spherical powder of environmental particulate matter prepared in this embodiment had good flowability, with a flowability index of 76.50 and a jetting index of 82.50.

[0077] Example 2

[0078] In this embodiment, the spherical powder of environmental particulate matter is prepared from natural sand and gravel as raw material. The natural sand and gravel are sand and gravel particles collected from the desert, which vary in size and have irregular shapes. The specific steps include:

[0079] (1) Using anhydrous ethanol as a dispersant, natural sand and gravel were placed in a ball mill jar with a ball-to-material ratio of 3:1. The ball mill jar was then placed in a planetary ball mill and ball milled at a speed of 240 r / min for 20 h to obtain fine powder particles with a particle size of less than 10 μm. The fine powder particles in the ball mill jar were then dried to ensure complete evaporation of the ethanol.

[0080] (2) Take a portion of the fine powder particles and perform a high-temperature melting test using a high-temperature microscope. The high-temperature melting characteristic curve is shown below. Figure 6 As shown in the figure, the relationship between the projected area of ​​the sample and temperature reveals that the projected area of ​​natural sand and gravel shrinks by about 5% at around 1050℃. To obtain spherical powder of environmental particles that are independent and not easily broken, the temperature of the subsequent high-temperature sintering densification treatment is set to 1000℃ to ensure the density and flowability of the powder.

[0081] (3) Prepare the spray granulation slurry according to the following proportions: 1000g of fine powder, 209g of PVA, and 1355g of deionized water. Mix the slurry thoroughly in a ball mill jar at a speed of 240 r / min for 5 h. This slurry will be used for spray granulation. 20-500 μm powder particles were prepared by spray drying. Specific parameters are shown in Table 2.

[0082]

[0083] (4) The powder particles are placed in a muffle furnace and sintered at 600℃ for 2 hours to remove PVA. Then, the temperature is raised to 1000℃ and held for 5 hours, causing the powder to shrink by about 5%. This ensures that the spherical powder particles are independent of each other and that the powder will not break under external force, ultimately obtaining dense environmental particulate spherical powder. Its particle size distribution and morphology are as follows: Figure 7 As shown, where, Figure 7 'a' in D shows D 10 Approximately 33.7 μm, indicating that 10% of the powder particles have a diameter less than or equal to 33.7 μm, D 50 Approximately 71.6 μm, indicating that 50% of the powder particles have a diameter of 71.6 μm or less, D 90The particle size is approximately 121.9 μm, indicating that 90% of the powder particles have a diameter of less than or equal to 121.9 μm. Figure 7 b in the figure shows that the powder is approximately spherical.

[0084] (5) Use a standard sieve to sieve the prepared environmental particulate matter spherical powder to obtain powder with relatively concentrated distribution of different particle size levels, so as to meet the needs of different experiments.

[0085] Comparative Example 1

[0086] The morphology of natural sand and gravel raw powder is as follows Figure 8 As shown, the powders are mostly irregular polyhedral particles with poor flowability, making it impossible to guarantee continuous feeding. Furthermore, the original natural sand and gravel powders have a wide particle size distribution; large particles easily clog the nozzle, while small particles tend to splash during feeding, hindering the normal conduct of the experiment.

[0087] The test results showed that the flowability index of the original natural sand and gravel powder was 31.00, and the jetting index was 71.50. Its flowability index is much lower than that of the spherical environmental particulate matter powder prepared in Example 1 (76.50), and its jetting index is also lower than that of the spherical environmental particulate matter powder (82.50).

Claims

1. A method for preparing spherical powder of environmental particulate matter, characterized in that, Includes the following steps: Step S1: Select artificially synthesized CMAS powder or natural solid particles as raw materials for preparation; Step S2: When the raw material is artificially synthesized CMAS powder, the raw material is sequentially ball-milled, high-temperature melted, and quenched to obtain glassy CMAS blocks, and then crystalline CMAS blocks are obtained by solid-state sintering. Step S3: Ball mill the natural solid particles from step S1 or the crystalline CMAS block from step S2 to obtain fine particle powder; perform high-temperature melting test on the fine particle powder to obtain its high-temperature melting characteristic curve. Step S4: The fine powder particles are mixed with deionized water and binder to form a slurry, which is then spray-granulated to obtain powder particles with a particle size of 20-500 μm. Step S5 involves low-temperature sintering to remove the binder from the powder particles, followed by high-temperature sintering to densify them, resulting in spherical powder particles of the target environment. The temperature of the high-temperature sintering densification process is determined based on the high-temperature melting characteristic curve obtained in step S3.

2. The method for preparing spherical powder of environmental particulate matter according to claim 1, characterized in that, Also includes: Step S6 involves sieving the spherical particulate matter from step S5 to obtain powders with different particle size distributions to meet the needs of different experiments.

3. The method for preparing spherical powder of environmental particulate matter according to claim 1, characterized in that, In step S1, the natural solid particles are selected from one or more combinations of naturally collected sand, dust, and volcanic ash.

4. The method for preparing spherical powder of environmental particulate matter according to claim 1, characterized in that, In step S2, the high-temperature melting temperature is 1300-1500℃, and the holding time is 1-5h; the solid-phase sintering temperature of the glassy CMAS block is the temperature at which its disordered state transforms into an ordered state, determined by thermal analysis, and the holding time is 1-5h.

5. The method for preparing spherical powder of environmental particulate matter according to claim 1, characterized in that, In the ball milling process of steps S2 and S3, anhydrous ethanol is used as the dispersant, the ball-to-material ratio is 5:1-3:1, the ball milling speed is 200-300 r / min, and the ball milling time is 10-20 h.

6. The method for preparing spherical powder of environmental particulate matter according to claim 1, characterized in that, The process parameters for spray granulation in step S4 include a slurry solid content of 30-40%, a binder content of 8-10%, an inlet temperature of 250-300℃, an outlet temperature of 90-110℃, an atomizer frequency of 100-500Hz, and a feed rate of 40-70 rpm.

7. The method for preparing spherical powder of environmental particulate matter according to claim 1, characterized in that, In step S5, the low-temperature sintering temperature is 400-600℃, and the holding time is 1-5h.

8. The method for preparing spherical powder of environmental particulate matter according to claim 1, characterized in that, The temperature of the high-temperature sintering densification treatment in step S5 is determined based on the high-temperature melting characteristic curve of step S3, including setting the temperature at which the projected area of ​​the sample shrinks by 5% in the curve as the temperature of the high-temperature sintering densification treatment; and then holding at this temperature for 3-10 hours.

9. The environmental particulate matter spherical powder prepared by the method for preparing environmental particulate matter spherical powder according to any one of claims 1-8, characterized in that, The particle size of the environmental particulate matter spherical powder is 20–500 μm.

10. The environmental particulate spherical powder prepared by the method of any one of claims 1-8, or the environmental particulate spherical powder of claim 9, is used in simulating the high-temperature thermal protection service environment of hot-end components of aero-engines and in simulating thermal erosion or thermal corrosion experiments on the surface of hot-end components.

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