Paper porosity measurement and aperture analysis method based on microscopic CT (Computed Tomography)

Abstract

The invention discloses a paper porosity measurement and aperture analysis method based on microscopic CT, which comprises the following steps: carrying out a scanning experiment on paper through an X-CT scanning system, carrying out contrast adjustment, filtering noise reduction and image segmentation on a sequence two-dimensional slice obtained by X-CT scanning by adopting Avizo software, separating a paper fiber phase from a paper pore phase to obtain a paper pore model, and carrying out micro-CT analysis on the paper pore model; calculating the porosity; on the basis of the pore model, a pore throat model is generated, and tortuosity, fractal dimension and pore size distribution structure parameters are further extracted.

Description

Technical Field

[0001] This invention belongs to the field of paper performance characterization and evaluation technology, specifically involving a paper porosity measurement and pore size analysis method based on micro-CT, which is used for the development and evaluation of paper-based materials. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Paper is a porous, thin-layered material formed by interwoven plant fibers. The pore structure of the paper base material is a key factor affecting the mechanical properties of paper, and is of great significance to the strength of paper and guiding improvements in papermaking processes. Traditional experimental measurement methods (scanning electron microscopy, transmission electron microscopy) can only obtain the surface structure of paper, failing to reveal its internal characteristics and lacking Z-axis structural features. This makes it difficult to establish the pore structure and conduct in-depth analysis of its relationship with paper mechanical properties. In contrast, X-ray computed tomography (X-CT) has significant advantages. It is a non-destructive technique that can non-destructively detect the internal structure of objects, directly providing three-dimensional features of the material's interior. Summary of the Invention

[0004] In order to overcome the shortcomings of existing technologies where the paper porosity measured by calculation and experimental methods is not accurate enough and cannot reflect the specific distribution of pores, the purpose of this invention is to provide a paper porosity measurement and pore size analysis method based on micro-CT.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: The invention provides a method for analyzing and characterizing the pore structure of paper based on micro-CT, including the following steps: characterizing the microscopic three-dimensional structure of paper using X-CT, and using Avizo software to perform contrast adjustment, filtering and noise reduction, and image segmentation on the sequence of two-dimensional slices obtained by X-CT scanning, thereby constructing a three-dimensional pore model of paper and extracting relevant pore structure parameters. The simulation results and experimental results corroborate each other, indicating the reliability of extracting structural parameters from images.

[0006] (1) The paper was scanned using an X-CT scanning system to obtain and reconstruct the sequence of two-dimensional slices of the paper structure; (2) Import the reconstructed sequence image into Avizo software, and perform binarization and threshold segmentation based on the grayscale image to separate the paper fiber phase and pore phase; (3) Fill the paper fiber phase to obtain the overall paper structure model; (4) Calculate the porosity; (5) Extract the connected pores and generate a pore throat model based on the connected pore model. Based on this pore throat model, tortuosity, fractal dimension and pore size distribution structural parameters can be extracted.

[0007] The binarization and threshold segmentation are as follows: Binarization converts a grayscale image into a binary image, and then interactive thresholding is used to segment the image.

[0008] Interactive threshold selection is used when relevant information in a grayscale image corresponds to a specific grayscale range. By default, the current selection is displayed in blue on an orthogonal image with grayscale data as the background.

[0009] Pressing Apply creates a binary output image, which will create a new field where each value within the threshold range is 1, and all other field values ​​are 0.

[0010] The beneficial effects of this invention are: This invention proposes using micro-CT scanning to obtain two-dimensional sections of paper, modeling and segmenting the porous phase using Avizo software, calculating the paper's porosity, tortuosity, and fractal dimension, and obtaining a ball-and-stick model of the paper pores. Data is then compared with BET measurement experiments. This pore structure analysis using modeling software allows for proactive design of paper porosity, guiding the selection of experimental and process parameters, and saving significant sample consumption and time in actual experiments. Attached Figure Description

[0011] Figure 1 This is the ball-and-stick model obtained by the present invention.

[0012] Figure 2 This refers to the layer-by-layer porosity of the sample obtained by this invention. Detailed Implementation

[0013] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0014] It should be noted that the accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting this patent. To better illustrate embodiments of the invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the dimensions of the actual product. The following detailed descriptions are illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0015] This invention does not impose any special restrictions on the type or source of paper. Example 1

[0016] (1) Product properties: printing paper (2) The printing paper was scanned using an X-CT scanning system to obtain and reconstruct the sequence slices; (3) Import the reconstructed sequence image into Avizo software, adjust the image contrast to [35023, 65535] using Colormap, and then use the Interactive Thresholding module to perform threshold segmentation on the image by adjusting the Intensity Range to [0, 28495] to obtain the paper pore phase. Then use the Volume Rendering command to obtain the pore model. (4) Use the Interactive Thresholding module to perform threshold segmentation on the image by adjusting the Intensity Range to [28945,65536] to obtain the paper fiber phase, and then use the Volume Rendering command to obtain the model of the fiber phase; (5) Use the Fill Holes command to fill the paper fiber phase to obtain the overall paper model; (6) Select the pore model and use the Volume Fraction command to calculate the paper porosity; (7) Use the Axis Connectivity module to extract the connected pores. Based on the connected pore model, use the Separate Object and Generate Pore Network Model modules to generate a pore throat model. Based on this throat model, tortuosity, fractal dimension, and pore size distribution structural parameters can be extracted; Example 2

[0017] (1) Product properties: filter paper (2) The printing paper was scanned using an X-CT scanning system to obtain and reconstruct the sequence slices; (3) Import the reconstructed sequence image into Avizo software, adjust the image contrast to [32035, 65535] using Colormap, and then use the Interactive Thresholding module to perform threshold segmentation on the image by adjusting the Intensity Range to [0, 27650] to obtain the paper pore phase. Then use the Volume Rendering command to obtain the pore model. (4) Use the Interactive Thresholding module to perform threshold segmentation on the image by adjusting the Intensity Range to [27650, 65536] to obtain the paper fiber phase, and then use the Volume Rendering command to obtain the model of the fiber phase; (5) Use the Fill Holes command to fill the paper fiber phase to obtain the overall paper model; (6) Select the pore model and use the Volume Fraction command to calculate the paper porosity; (7) Use the Axis Connectivity module to extract the connected pores. Based on the connected pore model, use the Separate Object and Generate Pore Network Model modules to generate a pore throat model. Based on this throat model, tortuosity, fractal dimension, and pore size distribution structural parameters can be extracted; Example 3

[0018] (1) Product properties: Pulp board (2) The printing paper was scanned using an X-CT scanning system to obtain and reconstruct the sequence slices; (3) Import the reconstructed sequence image into Avizo software, adjust the image contrast to [32550, 65535] using Colormap, and then use the Interactive Thresholding module to perform threshold segmentation on the image by adjusting the Intensity Range to [0, 29450] to obtain the paper pore phase. Then use the Volume Rendering command to obtain the pore model. (4) Use the Interactive Thresholding module to perform threshold segmentation on the image by adjusting the Intensity Range to [29450, 65536] to obtain the paper fiber phase, and then use the Volume Rendering command to obtain the model of the fiber phase; (5) Use the Fill Holes command to fill the paper fiber phase to obtain the overall paper model; (6) Select the pore model and use the Volume Fraction command to calculate the paper porosity; (7) Use the Axis Connectivity module to extract the connected pores. Based on the connected pore model, use the Separate Object and Generate Pore Network Model modules to generate a pore throat model. Based on this throat model, tortuosity, fractal dimension, and pore size distribution structural parameters can be extracted; Example 4

[0019] (1) Product properties: Handmade cotton pulp paper, beating degree 20°SR (2) The printing paper was scanned using an X-CT scanning system to obtain and reconstruct the sequence slices; (3) Import the reconstructed sequence image into Avizo software, adjust the image contrast to [32660, 65535] using Colormap, and then use the Interactive Thresholding module to perform threshold segmentation on the image by adjusting the Intensity Range to [0, 26780] to obtain the paper pore phase. Then use the Volume Rendering command to obtain the pore model. (4) Use the Interactive Thresholding module to perform threshold segmentation on the image by adjusting the Intensity Range to [26780, 65536] to obtain the paper fiber phase, and then use the Volume Rendering command to obtain the model of the fiber phase; (5) Use the Fill Holes command to fill the paper fiber phase to obtain the overall paper model; (6) Select the pore model and use the Volume Fraction command to calculate the paper porosity; (7) Use the Axis Connectivity module to extract the connected pores. Based on the connected pore model, use the Separate Object and Generate Pore Network Model modules to generate a pore throat model. Based on this throat model, tortuosity, fractal dimension, and pore size distribution structural parameters can be extracted; The results are output in tabular and graphical form. The first column of the table indicates the data source, and the second, third, and fourth columns show the porosity, tortuosity, and fractal dimension of the paper, respectively. Figure 1 A ball-and-stick model with pores. Figure 2 The porosity is the layer-by-layer porosity of the sample.

[0020] Table 1 Pore structure parameters of the samples Data source Porosity Tortuosity fractal dimension BET experimental data 0.2013 1.103 2.543 3D CT image extraction 0.2325 1.137 2.5201 This method uses different types of paper for experimental research, and the BET method is used to measure porosity and pore size distribution to verify the reliability of the data. The porosity extracted from 3D CT images is higher than that obtained by the experimental method. This is because the experimental method can only measure pores that are connected to the outside world, and cannot measure the closed pores inside the paper or the pores of the plant fibers themselves, while the pores measured by 3D micro-CT include the above-mentioned pores, so the porosity will be higher than the experimental value. The tortuosity and fractal dimension extracted from the micro-CT images are in good agreement with the experimental values. The porosity and pore size distribution obtained by both the experimental method and this method show objective consistency, indicating that this method has a certain degree of reliability in measuring the porosity and analyzing the pore size distribution of paper, and has significant role and meaning in guiding the selection of process parameters and the changing trends of paper structural properties.

[0021] It should be stated that the above-described specific embodiments are merely preferred embodiments of the present invention and the technical principles applied thereto. However, the implementation of this method is not limited to the embodiments described. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this method should be considered equivalent substitutions and are included within the protection scope of this method. Furthermore, some terminology used in this specification and claims is not limiting but merely for ease of description.

Claims

1. A method for analyzing and characterizing the pore structure of paper based on micro-CT, comprising the following steps: Step 1: Scan the paper using an X-CT scanning system to obtain and reconstruct the sequential slice images of the paper structure; Step 2: Import the reconstructed sequence image into Avizo software, and perform threshold segmentation based on the grayscale image to separate the paper fiber phase and the pore phase. Step 3: Fill in the paper fiber phase to obtain the overall paper structure model; Step 4: Calculate the porosity; Step 5: Extract the connected pores. Based on the connected pore model, generate a pore throat model. Based on this pore throat model, tortuosity, fractal dimension, and pore size distribution structural parameters can be extracted.

2. The method for measuring paper porosity and analyzing pore size according to claim 1, characterized in that, In step 2, thresholding is performed by adjusting the image contrast using a colormap until the fiber phase and pore phase can be distinguished by the naked eye, and then using the InteractiveThresholding module to perform thresholding on the image by adjusting the Intensity Range.

3. The method for measuring paper porosity and analyzing pore size according to claim 1, characterized in that, Step 3 specifically involves using the Fill Holes command to fill the paper fiber phase to obtain the overall paper model.

4. The method for measuring paper porosity and analyzing pore size according to claim 1, characterized in that, The porosity calculation in step 4 is as follows: using the Volume Fraction command, select the pore phase data as Input Image, the filling fiber phase as Input Image Mask, select 3D Interpretation to obtain the total porosity, and select XY planes to obtain the layer-by-layer porosity.

5. The method for measuring paper porosity and analyzing pore size according to claim 1, characterized in that, The specific steps for generating the pore throat model in step 5 are as follows: the Axis Connectivity module is used to extract the connected pores, and based on the connected pore model, the Separate Object and Generate Pore Network Model modules are used to generate the pore throat model.

Images