Powder and particle accumulation heterogeneity characterization method, data acquisition device and use method

Abstract

The present invention discloses a method for characterizing the heterogeneity of powder and granular accumulation, which includes the following steps: S1, collecting the absorption height and corresponding absorption time of the powder and granular accumulation structure in each direction, taking the square root of the absorption time as the X axis and the absorption height of the powder and granular body as the Y axis, performing linear fitting to obtain the liquid absorption slope value in each direction; S2, calculating the average value of the liquid absorption slope value, and then calculating the standard deviation of the liquid absorption slope value in each direction; S3, calculating the coefficient of variation of the liquid absorption slope based on the standard deviation of the liquid absorption slope value in each direction, and the coefficient of variation is an index for characterizing the heterogeneity of the powder and granular accumulation structure. Based on the analysis of the capillary liquid absorption movement law of the fluid in the powder and granular accumulation structure, the slope of the linear relationship of the absorption movement is tested, the powder and granular accumulation structure is inverted, the powder and granular accumulation structure to be tested is divided into several regions, the coefficient of variation of the linear relationship slope of the absorption movement of all regions is calculated, and the heterogeneity index of the powder and granular accumulation structure is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder and particle characterization. More specifically, the present invention relates to a method for characterizing the heterogeneity of powder and particle accumulation, a data acquisition device, and a method of use. Background Art

[0002] Powders and particles are the raw materials for the chemical manufacturing of numerous materials. Their packing structure serves as the foundation or carrier for the chemical reaction microstructures of these materials. Quantitative characterization of this packing structure is fundamental to the chemical manufacturing and engineering applications of powders and particles. However, this structure is susceptible to multiple factors, including particle size, morphology, charge, chemical composition, and the "arch bridge" effect of the powder. Consequently, progress in quantitative characterization of this structure has been slow.

[0003] Currently, the research related to the quantitative characterization of powder-particle stacking focuses on the characterization of powder-particle mixing uniformity and the characterization of powder-particle packing density. The latter only captures the dispersion of the components within the powder, while the latter captures the bulk density of a given amount of powder under deadweight or pressure. Neither approach considers the influence of various factors on the stacking structure of the components. Summary of the Invention

[0004] The present invention provides a method for characterizing the heterogeneity of powder and particle accumulation, which uses the coefficient of variation of the slope of the linear relationship of absorption movement in various directions to characterize the heterogeneity of the powder and particle accumulation structure.

[0005] The present invention is achieved by providing a method for characterizing the heterogeneity of powder and particle accumulation, the method specifically comprising the following steps:

[0006] S1. Collect the fluid absorption height and corresponding absorption time of the powder and granular accumulation structure in each direction, use the square root of the absorption time as the X-axis and the fluid absorption height as the Y-axis, perform linear fitting, and obtain the liquid absorption slope value in each direction of the fitting line;

[0007] S2, calculating the average of the liquid absorption slope values, and then calculating the standard deviation of the liquid absorption slope values ​​in each direction;

[0008] S3. Calculate the coefficient of variation of the liquid absorption slope based on the standard deviation of the liquid absorption slope values ​​in each direction. The coefficient of variation is an indicator that characterizes the heterogeneity of the powder and particle stacking structure.

[0009] Furthermore, the coefficient of variation Y of the liquid absorption slope is equal to the percentage of the ratio of the standard deviation δ of the water absorption slope value to the average value X of the water absorption slope, that is, Y=100*δ / X.

[0010] Furthermore, the powder and granules are dry powder and granules or powder and granules formed by wet molding and then rapid evaporation.

[0011] The present invention is achieved by providing a data acquisition device for characterizing the heterogeneity of powder and particle accumulation, the data acquisition device comprising:

[0012] A bottom plate for holding fluid, wherein a hard porous sponge is arranged in the middle of the bottom plate, and the height of the hard porous sponge is the same as the side wall of the bottom plate;

[0013] The test mold used to place powder and particle accumulation samples is made of transparent material. Multiple digital scales for characterizing fluid absorption height are evenly distributed on the outer surface. The inlet at the end of the test mold is sealed by cutting filter paper. The sealed test mold is placed in the middle position of the hard porous sponge, with the inlet of the test mold facing the chassis.

[0014] Furthermore, the test mold material is polymethyl methacrylate, polypropylene or polycarbonate.

[0015] Furthermore, the fluid is water or ethanol.

[0016] The present invention is implemented as follows: a method for using a data acquisition device, the method of using is as follows:

[0017] Prepare the powder and granular accumulation sample, start adding fluid into the bottom plate, and make the fluid level equal to the side wall height. After the porous sponge is saturated with liquid, place the test mold with the powder and granular accumulation sample in the middle of the hard porous sponge, and start counting and timing, collecting the time when the absorption liquid level line reaches the set height of each digital scale, or collecting the height when the absorption liquid level line reaches each digital scale at each set time.

[0018] Furthermore, the preparation method of the powder and particle stacking sample is as follows:

[0019] Weigh a certain amount of powder and coarse and fine particle mixture, and fill it into the test mold layer by layer or all at once. Apply a pressure of 5 to 10 MPa during the filling process. Seal the inlet at the end of the test mold with filter paper to complete the preparation of the powder and particle accumulation sample.

[0020] Furthermore, the preparation method of the powder and particle stacking sample is as follows:

[0021] Weigh a certain amount of powder and coarse and fine particle mixture, add water or ethanol, stir to form a slurry, and pour it into the test mold; after molding, put it into a 30-60℃ forced air drying oven for heating, take it out after 1-5 hours, disassemble the test mold, put the formed test block into a 100-150℃ forced air drying oven for heating, take it out after 1-8 hours, seal it with transparent tape on all sides after cooling, place it in the test mold, and seal the inlet at the end of the test mold with filter paper to complete the preparation of the powder and particle accumulation sample.

[0022] Based on the analysis of the capillary absorption movement law of fluid in the powder and particle accumulation structure, the slope of the linear relationship of absorption movement is tested, the powder and particle accumulation structure is inverted, the powder and particle accumulation structure to be tested is divided into several areas, and the coefficient of variation of the slope of the linear relationship of absorption movement in all areas is calculated to obtain the heterogeneity index of the powder and particle accumulation structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flow chart of a method for characterizing the heterogeneity of powder and particle stacking provided in an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of the structure of a data acquisition device for characterizing the heterogeneity of powder and particle accumulation provided by an embodiment of the present invention;

[0025] 1. Chassis, 2. Fluid, 3. Porous sponge, 4. Cut-off filter paper, 5. Absorption level line, 6. Digital ruler, 7. Powder and particle accumulation sample, 8. Test mold. DETAILED DESCRIPTION

[0026] The specific implementation methods of the present invention will be further explained in detail below by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0027] The present invention relates to two types of powder and particle stacking structures, one is dry powder and particles, which are naturally stacked or pressurized, and the other is powder and particles formed by wet molding and then quickly evaporated; the powder and particles have almost no time to react with the wet stirring liquid, and rely on capillary forces to condense together, belonging to a stacking structure. Both types of powder and particle stacking structures will produce capillary phenomena, namely capillary action, when they come into contact with the wetting liquid. This refers to the phenomenon that the fluid rises in the stacking structure due to the capillary force overcoming the fluid's own gravity and the liquid's viscous resistance. The various pores in the powder and particle stacking structure can be abstracted into capillary pores, and the surface of the pores can absorb the fluid in contact with it to reduce the surface energy of the pores. Washburn and Lucas carried out research on the absorption movement of fluids in the capillaries of powder and particle stacking, and Chatterjee, after summarizing the work of his predecessors, obtained the equation reflecting the movement of fluids in long capillary structures:

[0028]

[0029] Where l is the absorption height of the fluid in the capillary, t is the time corresponding to the fluid absorption height, r is the capillary radius, ρ and μ represent the density and viscosity of the fluid, respectively, and σ and θ represent the surface tension and contact angle of the fluid, respectively. In actual use, formula (1) is usually simplified to formula (2), as follows:

[0030]

[0031] The constant C reflects the parameters of the absorbing fluid and the powder-particle stacking structure. Generally, the same fluid is used in the capillary absorption process, and the value of the constant C depends solely on the stacking structure of the powder. When the powder is uniformly stacked, formula (2) indicates that the absorption height of the stacking structure is proportional to the square root of the absorption time. The constant C reflects the parameters of the uniform stacking structure of the powder. This paper proposes a method for quantifying the heterogeneity of the stacking structure of powders with different components and particle sizes, which can be used to characterize the heterogeneity of the stacking structure of powders with different components and particle sizes.

[0032] Based on the analysis of the capillary water absorption movement law of the fluid in the powder and granular accumulation structure, the slope of the linear relationship of the absorption movement is tested and the accumulation structure of the powder and granular body is inverted. The accumulation structure of the powder and granular body includes the components of the accumulated particles and the accumulation pores of the particles. Different accumulation structures include differences in the accumulation components and differences in the accumulation capillary pores. In theory, as long as one parameter of the accumulation components and the accumulation pores changes, the movement state of the fluid will change. Current technology cannot analyze the impact of a particle and the pores surrounded by several particles on the movement state of the fluid. However, for a certain number of particles and the accumulation area surrounded by them, the analysis of the fluid movement state and the slope of the linear relationship of the fluid absorption movement can be tested to invert the accumulation of the area. The powder and granular body accumulation structure to be tested is divided into several areas, and the coefficient of variation of the slope of the linear relationship of the absorption movement in all areas is calculated to obtain the heterogeneity index of the powder and granular body accumulation structure.

[0033] Figure 1 A flow chart of a method for characterizing the heterogeneity of powder and particle stacking provided in an embodiment of the present invention, wherein the method specifically comprises the following steps:

[0034] S1. Collect the absorption height and corresponding absorption time of the powder and granular accumulation structure in each direction, and use the square root of the absorption time (t 1 / 2 ) is the X-axis, the absorption height of the powder (L) is the Y-axis, and a linear fit is performed to obtain the liquid absorption slope value in each direction;

[0035] S2. Calculate the average value (X) of the liquid absorption slope value, and then calculate the standard deviation (δ) of the liquid absorption slope value in each direction;

[0036] S3. Calculate the coefficient of variation of the liquid absorption slope based on the standard deviation of the liquid absorption slope values ​​in each direction. The coefficient of variation is an indicator of the heterogeneity of the powder and particle accumulation structure. The larger the coefficient of variation of the liquid absorption slope, the higher the heterogeneity of the powder and particle accumulation structure.

[0037] The coefficient of variation (Y) of the liquid absorption slope is calculated as the percentage of the ratio of the standard deviation (δ) of the liquid absorption slope value to the average value (X) of the liquid absorption slope, that is, Y = 100*δ / X.

[0038] Figure 2The schematic diagram of the structure of the data acquisition device for characterizing the heterogeneity of powder and particle accumulation provided by the embodiment of the present invention only shows the part related to the embodiment of the present invention for the convenience of explanation.

[0039] The data acquisition device includes:

[0040] A bottom plate for holding fluid, wherein a hard porous sponge is arranged in the middle of the bottom plate, and the height of the hard porous sponge is the same as the side wall of the bottom plate;

[0041] The test mold used to place powder and particle accumulation samples is made of transparent material. Multiple digital scales for characterizing fluid absorption height are evenly distributed on the outer surface. The inlet at the end of the test mold is sealed by cutting filter paper. The sealed test mold is placed in the middle position of the hard porous sponge, with the inlet of the test mold facing the chassis.

[0042] The rigid porous sponge supports the weight of the powder and particles while also utilizing its porous channels to absorb the fluid. This prevents the fluid from being lost due to capillary absorption caused by the accumulated structure of the powder and particles when replenishment is needed. The sealing filter paper seals the powder and particles within the test mold while also utilizing qualitative filter paper, which is thin and has a large pore size, to prevent it from interfering with the absorption of the liquid.

[0043] The test mold material is a transparent material such as polymethyl methacrylate, polypropylene, polyethylene, polycarbonate, polyamide or ABS, preferably polymethyl methacrylate, polypropylene, polyethylene terephthalate or polycarbonate, more preferably polymethyl methacrylate, polypropylene or polycarbonate;

[0044] The test mold is a hollow square column or rolled into a hollow cylinder. Technical parameters to consider include transparency, mechanical properties, surface hardness, and resistance to alkaline solution corrosion. The test mold uses sheet material or coiled material. The warpage error in any direction must be less than or equal to ±5μm / 1cm. The sheet material or coiled material must have a light transmittance greater than or equal to 75%, a surface hardness of 5H or higher, and a light transmittance greater than or equal to 70% after immersion in an alkaline solution at room temperature for 24 hours. For dry-loading and pressing of powders and granules, the test mold plate must have a compressive strength greater than or equal to 10MPa. For wet-casting and drying of powders and granules, the compressive strength of the test mold must be greater than or equal to 5MPa.

[0045] The test mold can be designed in a cylindrical, rectangular, or cube shape, with rectangular and cylindrical shapes being preferred. The empirical relationship between the maximum particle size (D) of the loaded powder and the mold width or diameter (W) is W = 6-1200*D, with the height being 1-3 times the width or diameter. The corresponding relationship between the thickness (T) of the plate and the mold width or diameter (W) is T = 0.01-0.20*W.

[0046] The outer surface of the test mold is laser engraved with a data scale with a minimum scale of 1 to 10 mm. There is at least one data scale in the center every 3 to 10 cm of the width of the plate outer surface, and there is at least one data scale in the center every 3 to 10 cm of the circular outer surface arc. Each data scale can obtain the slope of the linear relationship between the powder and particle accumulation structure and the fluid capillary absorption belonging to its own area.

[0047] The method of using the data acquisition device is as follows:

[0048] Prepare the powder and granular accumulation sample, start adding fluid (usually water or ethanol) into the bottom plate, and the fluid liquid level should be at the same height as the side wall. After the porous sponge is saturated with water, place the test mold with the powder and granular accumulation sample in the middle of the hard porous sponge, and start counting and timing, collecting the time when the absorption liquid level line reaches the set height of each digital scale, or collecting the height of the absorption liquid level line in each digital scale at each set time.

[0049] Preparation method of dry powder and granular bulk test sample: weigh appropriate amount of powder and coarse and fine particle mixture, load them into the test mold layer by layer or all at once, apply a pressure of 5 to 10 MPa layer by layer or all at once, and seal the inlet with filter paper to prepare the dry powder bulk test sample.

[0050] Preparation method of powder and particle accumulation specimen based on wet powder and particle: weigh appropriate amount of powder and coarse and fine particle mixture, add water or ethanol and stir to form slurry, and pour into test mold; after forming, put it into 30-60℃ forced air drying oven for heating, take it out after 1-5 hours, disassemble the mold, put the test block into 100-150℃ forced air drying oven for heating, take it out after 1-8 hours, seal it with transparent tape on all sides after cooling, place it at the entrance of the test mold and seal it with filter paper to prepare the wet evaporation test specimen.

[0051] Compared with the wet slurry, the dried slurry will have a slight shrinkage in macroscopic volume. The use of transparent tape for sealing compensates for the shrinkage of the wet sample during the drying process, so that the dried sample can fully fill the original wet-prepared mold and prevent improper inhalation of the fluid when the test block absorbs the fluid by capillary force.

[0052] The following Examples 1 to 4 test the heterogeneity of the stacking structure of powders with different components and particle sizes; Specific embodiment 1

[0054] The test mold material is polymethyl methacrylate (PMMA) sheet, 5mm thick, 10cm long (high), and 5cm wide. It has a light transmittance of 90%, a compressive strength of 15MPa, a surface hardness of 8H, a warpage error of ±4μm / 1cm in any direction, and a light transmittance of 85% after immersion in an alkaline solution at room temperature for 24 hours. Each PMMA sheet is laser-engraved with a data scale with a minimum graduation of 1mm along its length. The four sheets are bonded together into a hollow rectangular block using acrylic structural adhesive. The block is placed vertically and sealed at the bottom with qualitative filter paper.

[0055] A total of 290 g of dry powder particles with a maximum particle size of 5 mm were poured into the hollow test mold in five layers, and the layered compaction pressure was 6 MPa.

[0056] Use a flat tray with a surface area 200 times that of the test specimen. The bottom plate should be 2 cm thick, and the height, including the side walls, should be 4 cm. Place a rigid, porous sponge measuring 10 cm x 10 cm x 2 cm in length, width, and height within the tray. Fill the tray with pure water until the water level is at the same height as the side walls. Place the test specimen in the center of the saturated sponge. Start a stopwatch and record the time (10 seconds, 19 seconds, 34 seconds, 48 ​​seconds, 67 seconds, 85 seconds, 109 seconds, 126 seconds, 154 seconds, and 186 seconds) required for the water level in each direction of the transparent test mold to reach the specified scale (1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, and 10 cm).

[0057] The water absorption height and the corresponding water absorption time data in four directions were processed and the square root of the water absorption time (t 1 / 2 ) as the X-axis and the water absorption height (L) as the Y-axis, and linear fitting is performed to obtain L~t 1 / 2 The water absorption slope values ​​of the linear relationship are 0.8701, 0.9881, 0.9504 and 0.9232, respectively. The calculated average value of the water absorption slope is 0.9330, the calculated standard deviation of the water absorption slope values ​​in the four directions is 0.0500, the coefficient of variation of the water absorption slope is 5.3%, and the heterogeneity index of the powder and particle stacking structure is 5.3%. Specific embodiment 2

[0059] The test mold is made of transparent polypropylene coil, bonded into a hollow cylindrical shape with structural adhesive. The coil is 8mm thick and 12cm high, with a hollow inner diameter of 6cm, a light transmittance of 76%, a compressive strength of 6MPa, and a surface hardness of 6H. After 24 hours of immersion in a room-temperature alkaline solution, the light transmittance of the sheet is 82%. Six laser-engraved scales with a minimum graduation of 1mm are evenly spaced along the height of the transparent polypropylene hollow cylinder. The transparent polypropylene hollow cylinder (test mold) is placed along its height and sealed at the bottom with qualitative filter paper.

[0060] Pour 860g of slurry with a maximum particle size of 3mm into the test mold all at once. After smoothing the surface, heat the sample in a 50°C forced air drying oven for 1 hour. Remove the sample after disassembling the test mold and heat the sample in a 120°C forced air drying oven for 1 hour. After cooling, seal the sample with scotch tape on all sides, place it in the test mold prepared with the slurry, and glue it into a cylindrical shape with structural adhesive. This completes the test specimen.

[0061] Use a flat tray with a surface area 250 times the cross-sectional surface area of ​​the test specimen. The bottom plate should be 1 cm thick, and the sidewalls, including the bottom plate, should be 4 cm high. Place a rigid, porous sponge measuring 12 cm x 12 cm x 3 cm in length, width, and height within the tray. Fill the tray with pure water until the water level is at the same height as the sidewalls. Place the test specimen in the center of the saturated sponge. Start a stopwatch and record the time (18 seconds, 30 seconds, 38 seconds, 52 seconds, 65 seconds, 81 seconds, 99 seconds, 117 seconds, 137 seconds, 161 seconds, 179 seconds, and 205 seconds) for the water level in each direction of the transparent mold to reach the specified scale (1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 11 cm, and 12 cm).

[0062] The water absorption height in 6 directions and the corresponding water absorption time data were input into the processing software and the square root of the water absorption time (t 1 / 2 ) as the X-axis and the water absorption height (L) as the Y-axis, and linear fitting is performed to obtain L~t 1 / 2 The water absorption slope values ​​of the linear relationship were 1.1020, 1.2174, 1.0685, 1.3063, 1.4425, and 0.9582, respectively. The average water absorption slope was 1.1825, the standard deviation of the water absorption slope values ​​in the six directions was 0.1755, and the coefficient of variation of the water absorption slope was 14.8%. The heterogeneity index of the powder and particle stacking structure was 14.8%. Specific embodiment 3

[0064] The test mold material is polyethylene terephthalate (PET) sheets, 2mm thick, 9cm long, and 4cm wide. They have a light transmittance of 95%, a compressive strength of 17MPa, a surface hardness of 9H, and a warpage tolerance of ±3μm / 1cm in any direction. After immersion in an alkaline solution at room temperature for 24 hours, the light transmittance is 89%. Each PET sheet is laser-engraved with a data scale with 1mm increments at even intervals along its length. The four sheets are then glued together using acrylic structural adhesive to form a hollow rectangular block. The block is placed vertically and sealed at the bottom with qualitative filter paper.

[0065] Prepare 300g of dry powder particles with a maximum particle size of 0.1mm and 150g of styrene-acrylic resin emulsion with a content of 20%. Mix the dry powder particles and the resin emulsion, stir them evenly, and pour them into a hollow rectangular plate (i.e., test mold) at one time. After smoothing the surface, heat it in a 60℃ forced air drying oven. Take it out after 5 hours. Disassemble the test mold, heat the test block in a 110℃ forced air drying oven, and take it out after 7 hours. After cooling, seal it with transparent tape on all sides, place it in the test mold prepared with the slurry, and then use structural adhesive to glue it into a square column to prepare the test sample.

[0066] Use a flat tray with a surface area 180 times that of the test specimen. The bottom plate should be 2 cm thick, and the sidewalls of the container, including the bottom plate, should be 3 cm high. Place a rigid, porous sponge measuring 8 cm long, 8 cm wide, and 1 cm high inside the tray. Fill the tray with pure water until the water level is at the same height as the sidewalls. Place the test specimen in the center of the saturated sponge. Start a stopwatch and record the time it takes for the water level in each direction of the transparent mold to reach the set scale (1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm) (9 seconds, 17 seconds, 24 seconds, 34 seconds, 49 seconds, 61 seconds, 75 seconds, 92 seconds, and 113 seconds).

[0067] The water absorption height in four directions and the corresponding water absorption time data were input into the processing software, and the square root of the water absorption time (t 1 / 2 ) as the X-axis and the water absorption height (L) as the Y-axis, and linear fitting is performed to obtain L~t 1 / 2 The water absorption slope values ​​of the linear relationship are 1.0621, 0.8906, 0.9688 and 0.7912, respectively. The calculated average value of the water absorption slope is 0.9282, the calculated standard deviation of the water absorption slope values ​​in the four directions is 0.1151, the coefficient of variation of the water absorption slope is 12.4%, and the heterogeneity index of the powder and particle stacking structure is 12.4%. Specific embodiment 4

[0069] The test mold is made of transparent polycarbonate coil, bonded into a hollow cylindrical shape with structural adhesive. The coil is 15mm thick and 50cm high, with an inner diameter of 24cm and a light transmittance of 80%. The coil also has a compressive strength of 7MPa and a surface hardness of 7H. After immersion in a room-temperature alkaline solution for 24 hours, the light transmittance of the sheet is 83%. Eight laser-engraved scales with a minimum graduation of 10mm are evenly spaced along the surface of the transparent polycarbonate hollow cylinder. The transparent polycarbonate hollow cylinder (test mold) is placed along its height and sealed at the bottom with qualitative filter paper.

[0070] 69 kg of slurry with a maximum particle size of 15 mm was poured into the test mold all at once. After smoothing the surface, the sample was placed in a 45°C forced air drying oven and heated for 2 hours. The sample was then removed from the mold and placed in a 110°C forced air drying oven and heated for 3 hours. After cooling, the sample was sealed with scotch tape on all sides, placed in the test mold prepared with the slurry, and then glued into a cylindrical shape with structural adhesive. This completed the test specimen.

[0071] Use a flat tray with a surface area 280 times the cross-sectional surface area of ​​the test specimen. The bottom plate should be 5 cm thick, and the sidewalls of the container, including the bottom plate, should be 10 cm high. Place a rigid, porous sponge measuring 30 cm x 30 cm x 10 cm in length, width, and height within the tray. Fill the tray with pure water until the water level is at the same height as the sidewalls. Place the test specimen in the center of the saturated sponge. Start a stopwatch and record the time (33 seconds, 45 seconds, 65 seconds, 81 seconds, 99 seconds, 123 seconds, 147 seconds, 169 seconds, 190 seconds, and 221 seconds) for the water level in each direction of the transparent mold to reach the specified scale (5 cm, 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, 35 cm, 40 cm, 45 cm, and 50 cm).

[0072] The water absorption height in 8 directions and the corresponding water absorption time data were input into the processing software and the square root of the water absorption time (t 1 / 2 ) as the X-axis and the water absorption height (L) as the Y-axis, and linear fitting is performed to obtain L~t 1 / 2 The water absorption slope values ​​for the linear relationship were 4.9341, 4.3751, 5.0637, 6.0652, 5.6589, 4.6910, 4.6066, and 4.9886, respectively. The average water absorption slope was 5.0479, the standard deviation of the water absorption slope values ​​in eight directions was 0.5606, and the coefficient of variation of the water absorption slope was 11.1%. The heterogeneity index of the powder and particle stacking structure was 11.1%.

[0073] The present invention has been described exemplarily. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A method for characterizing the heterogeneity of powder and particle stacking, characterized in that: The method specifically comprises the following steps: S1. Collect the fluid absorption height and corresponding absorption time of the powder and granular accumulation structure in each direction, perform linear fitting with the square root of the absorption time as the X-axis and the fluid absorption height as the Y-axis, and obtain the liquid absorption slope value in each direction of the fitting line; S2, calculating the average of the liquid absorption slope values, and then calculating the standard deviation of the liquid absorption slope values ​​in each direction; S3. Calculate the coefficient of variation of the liquid absorption slope based on the standard deviation of the liquid absorption slope values ​​in each direction. The coefficient of variation is an indicator of the heterogeneity of the powder and particle stacking structure. The coefficient of variation Y of the liquid absorption slope is equal to the percentage of the ratio of the standard deviation δ of the water absorption slope value to the average value X of the water absorption slope, that is, Y=100*δ / X.

2. The method for characterizing the accumulation heterogeneity of powders and particles according to claim 1, wherein: The powder and granules are dry powder and granules or powder and granules formed by wet molding and then rapid evaporation.

3. The method for characterizing the accumulation heterogeneity of powders and particles according to claim 1 or 2, wherein: The data acquisition device used for characterization of powder and particle accumulation heterogeneity includes: A bottom tray for holding fluid, wherein a hard porous sponge is arranged in the middle of the bottom tray, and the height of the hard porous sponge is the same as the side wall of the bottom tray; The test mold used to place powder and particle accumulation samples is made of transparent material. Multiple digital scales for characterizing fluid absorption height are evenly distributed on the outer surface. The inlet at the end of the test mold is sealed by cutting filter paper. The sealed test mold is placed in the middle position of the hard porous sponge, with the inlet of the test mold facing the chassis.

4. The method for characterizing the accumulation heterogeneity of powders and particles according to claim 3, wherein: The test mold materials are polymethyl methacrylate, polypropylene or polycarbonate.

5. The method for characterizing the accumulation heterogeneity of powders and particles according to claim 3, wherein: The fluid is water or ethanol.

6. The method for characterizing the accumulation heterogeneity of powders and particles according to claim 4 or 5, wherein: The method of using the data acquisition device is as follows: Prepare the powder and granular accumulation sample, start adding fluid into the bottom plate, and make the fluid level equal to the side wall height. After the porous sponge is saturated with water, place the test mold with the powder and granular accumulation sample in the middle of the hard porous sponge, and start counting and timing, collecting the time when the absorption liquid level line reaches the set height of each digital scale, or collecting the height of the absorption liquid level line in each digital scale at each set time.

7. The method for characterizing the accumulation heterogeneity of powders and particles according to claim 6, wherein: The preparation method of powder and particle stacking sample is as follows: Weigh a certain amount of powder and coarse and fine particle mixtures, and fill them into the test mold layer by layer or all at once. Apply a pressure of 5-10 MPa during the filling process. Seal the inlet at the end of the test mold with filter paper to complete the preparation of the powder and particle accumulation sample.

8. The method for characterizing the accumulation heterogeneity of powders and particles according to claim 6, wherein: The preparation method of powder and particle stacking sample is as follows: Weigh a certain amount of powder and coarse and fine particle mixture, add water or ethanol, stir to form a slurry, and pour it into the test mold; after molding, put it into a 30-60℃ forced air drying oven for heating, take it out after 1-5 hours, disassemble the test mold, and place the formed test block into a 100-150℃ forced air drying oven for heating, take it out after 1-8 hours, seal it with transparent tape on all sides after cooling, and place it in the test mold. The inlet at the end of the test mold is sealed with filter paper to complete the preparation of the powder and particle accumulation sample.

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