Particle size measuring device based on combination of dynamic light scattering method and sedimentation method

Abstract

The utility model discloses a particle size measuring device based on combination of a dynamic light scattering method and a sedimentation method. The particle size measuring device comprises a laser, a light intensity adjusting unit, a sample pool, a thermostatic bath, a PD detector, an optical fiber head, an APD detector, a data acquisition unit, a PC and a control unit. The laser emits incident laser, the incident laser passes through the light intensity adjusting unit, penetrates through the sample cell and a sample and then enters the PD detector, and a transmission light signal is collected through the data acquisition unit and transmitted to software for calculating the particle size and concentration of settled large particles; scattered light is received by an optical fiber head with a fixed angle of 90 degrees or 160-175 degrees and is converted into a digital signal by an APD detector, and the digital signal enters a data acquisition unit and is transmitted to software for calculating the particle size of particles in a non-settling nanometer range. According to the technical scheme provided by the utility model, the particle size distribution information of the wide-distribution particle dispersion system in a nanometer-micron order range is measured in a testing process.

Description

Technical Field

[0001] This utility model relates to the field of particle size measurement, specifically a particle size measurement device based on a combination of dynamic light scattering and sedimentation methods. Background Technology

[0002] Particle size measurement technology has been widely used in materials, chemistry and chemical engineering, food and agriculture, semiconductors, biopharmaceuticals, energy and environmental protection, and other fields. It plays an important role in improving the performance and quality of materials, adjusting and optimizing processes, drug design and environmental monitoring.

[0003] Existing particle size measurement methods each have their advantages and limitations. The sedimentation method, based on Stokes' law, calculates particle size by measuring the settling velocity of particles in a liquid, and is suitable for measuring larger particles (micrometers in size). The dynamic light scattering method calculates particle size by measuring the scattered light fluctuations caused by the Brownian motion of particles in a liquid, and is suitable for small-diameter particles, offering high accuracy and speed.

[0004] Dynamic light scattering requires a homogeneous sample without sedimentation, while sedimentation methods cannot detect nanoscale particles suspended in liquids. Therefore, neither sedimentation nor dynamic light scattering can be used alone to measure the particle size distribution of samples covering the nanometer to micrometer range. This invention enables the measurement of particle size distribution information in a broad-distribution particle dispersion system within the nanometer to micrometer range in a single testing process. The sedimentation method has an effective detection range of 1 μm to 50 μm, and the dynamic light scattering method has an effective detection range of 1 nm to 1 μm particles. Utility Model Content

[0005] To address the problems of existing measurement methods, this invention provides a particle size measurement device that combines dynamic light scattering and sedimentation methods. This device offers advantages such as ease of operation, high-efficiency and high-precision temperature control, small sample requirements, wide measurement range, and high overall measurement accuracy.

[0006] The technical solution adopted in this utility model is:

[0007] A particle size measurement device based on a combination of dynamic light scattering and sedimentation methods includes a laser, an intensity adjustment unit, a sample cell, a constant temperature bath, a PD detector, an optical fiber head, an APD detector, a data acquisition unit, a PC, and a control unit.

[0008] The laser emits a laser beam that shines onto the sample in the sample cell;

[0009] The sample cell contains a suspension of large particles with sedimentation characteristics and small particles without sedimentation characteristics, and the refractive index and absorptivity of the large and small particles are the same.

[0010] The light intensity adjustment unit includes a set of attenuators mounted on a rotating wheel and driven by a motor for adjusting the intensity of incident light;

[0011] The sample cell is a container for holding the sample to be tested. The internal cross-section of the sample cell is a square of 10mm×10mm, the optical path L is 10mm, the sample cell volume is ≥4ml, and it is designed to be transparent from four sides. The material is quartz or K9 glass.

[0012] The constant temperature bath reaches the set temperature value by receiving commands from the control unit, with an accuracy of ±0.1℃ and a range of -15℃ to 120℃;

[0013] The PD detector is placed at a 0° angle to the laser incident direction. The incident light enters the PD detector after passing through the sample cell. The PD detector is used to detect the transmitted light energy.

[0014] The fiber optic head is placed at a fixed angle in the direction of laser incidence. The possible angles include: 90° in the direction of laser incidence, or 160° to 175° away from the direction of laser incidence. The scattered light enters the APD detector through the fiber optic cable. The APD detector is used to detect the energy of the scattered light.

[0015] The data acquisition unit is used to receive signals from the PD detector and APD detector, and transmit the signals to the PC for calculation;

[0016] The control unit is used to receive commands from the PC, output control signals to control the temperature of the constant temperature bath to control the temperature of the test sample, and output control signals to control the position of the light intensity adjustment unit and adjust the light intensity of the incident light.

[0017] This invention also provides a method for measuring particle size based on a combination of dynamic light scattering and sedimentation methods, comprising the following measurement steps:

[0018] 1) Input the required calculation parameters into the software: dynamic viscosity of the sample η, total height of the sample h, and particle density ρ. p Medium density ρ f The refractive index n of the particles p Particle absorption rate A p The refractive index n of the medium f The test is conducted using parameters such as sedimentation particle size analysis, dynamic light scattering analysis, and Mie theory calculations.

[0019] 2) Inject the blank sample into the sample cell. The blank sample is a liquid sample dispersion medium that does not contain particles. The liquid level of the sample is higher than the position of the incident light detection point. Then, place the sample cell into the constant temperature bath for constant temperature operation so that the blank sample reaches the set temperature.

[0020] 3) Control the light intensity adjustment unit to adjust the incident laser intensity so that the incident laser intensity is attenuated to the linear response range of the PD detector. If there are multiple attenuators corresponding to the linear response range of the PD detector, use the attenuator with the smallest attenuation of the incident laser intensity within the linear response range of the PD detector for testing.

[0021] 4) The PD detector collects the transmitted light intensity I0 of the blank sample;

[0022] 5) Remove the blank sample from the thermostatic bath;

[0023] 6) Inject the mixed suspension sample to be tested into the sample cell, with the sample liquid level higher than the incident light detection point, and then place the sample cell into the constant temperature bath for constant temperature operation;

[0024] 7) After the isothermal operation is completed, the sedimentation particle size test begins. The transmitted light intensity changes over time due to the sedimentation of large particles in the mixed suspension sample. The PD detector transmits the collected transmitted light intensity intensity over time to the PC software via the data acquisition unit, plotting the transmitted light intensity versus time curve. From this, the particle size distribution curve of the sedimented large particles is obtained, and the D particle size distribution is further calculated. 大 [3,2];

[0025] The typical characteristics of the transmitted light intensity versus time curve are as follows: the transmitted light intensity fluctuates within a small range from the start of the test to a certain time t0. This time period is defined as the initial test platform, and the average light intensity of this platform is used to obtain the initial transmitted light intensity I1; from t0 onwards, the transmitted light intensity increases with the increase of the test time, reaching a certain time t n Afterward, the intensity of the transmitted light begins to fluctuate within a small range, and then essentially stops changing. Let t be defined. n The test platform is a stable test platform until the end of the test. The average light intensity of the platform is taken to obtain the stable transmitted light intensity I2.

[0026] When the transmitted light signal reaches the stable test platform, the sedimentation test is completed. At this time, the large particles in the sample have all settled to the bottom of the sample cell, and the small particles that are still suspended in the sample are non-settled.

[0027] 8) The dynamic light scattering test begins. The APD detector starts collecting dynamic light scattering test signals. The intensity modulation unit adjusts the incident light intensity to ensure the scattered light signal is within the linear response range of the APD detector. The APD detector transmits the collected scattered light intensity over time to the PC software via the data acquisition unit. Correlation curves are obtained through relevant calculations, and the light intensity distribution curve of non-settling small particles is obtained through multi-exponential fitting. Further, the particle size and volume distribution curve are obtained, and D is calculated. 小 [3,2];

[0028] 9) Through

[0029]

[0030] φ can be derived 小 Where R is half the optical path length, Φ 小 Q represents the total volume fraction of non-settling small particles. e小 The extinction coefficient of non-settling small particles is calculated using Mie theory;

[0031] pass

[0032]

[0033] Then φ can be derived. 大 , Φ 大 Q represents the total volume fraction of settled large particles. e大 The extinction coefficient of the settled large particles is calculated using the Mie theory.

[0034] S is obtained by summing the peak areas of all the particle size distributions calculated by the sedimentation method. 大 S is obtained by summing the peak areas of all the particle size distributions calculated by the dynamic light scattering method. 小 , with S 大 :S 小 =φ 小 φ 大 The proportional relationship between the particle size distribution curves of settled large particles and non-settled small particles is obtained and integrated into a single particle size volume distribution curve.

[0035] Step 8) further includes the following calculation steps:

[0036] The dynamic light scattering method employs autocorrelation technology, and the light intensity distribution of the particle size can be obtained through a multi-exponential fitting method. The fitting formula is as follows:

[0037]

[0038] n represents the number of particle size fractions.

[0039] Given n p and A p In this case, combining Mie theory, the volume distribution can be derived from the light intensity distribution, thus obtaining D. 小 [3,2].

[0040] This invention can measure particle size distribution information in the nanometer to micrometer range of a wide-distribution particle dispersion system in a single test process. The effective detection range of sedimentation method is 1μm to 50μm, and the effective detection range of dynamic light scattering is 1nm to 1μm particles. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the electrical principle of the device of this utility model;

[0042] Figure 2 This is a schematic diagram of the structure of the device of this utility model;

[0043] Figure 3 This is a schematic diagram of the detection optical path of the sample cell of this utility model;

[0044] Figure 4 This is a schematic diagram illustrating the derivation of the sample volume distribution curve obtained during the testing process.

[0045] In this array, 1 is the laser, 2 is the attenuation plate group, 3 is the motor, 4 is the incident light, 5 is the sample cell, 6 is the constant temperature bath, 7 is the transmitted light, 8 is the PD detector, 9 is the scattered light, 10 is the fiber optic head, 11 is the APD detector, 12 is the data acquisition unit, 13 is the PC, and 14 is the control unit. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings.

[0047] like Figure 1-4 As shown, this utility model provides a particle size measurement device based on a combination of dynamic light scattering and sedimentation methods, including a laser 1, a light intensity adjustment unit, a sample cell 5, a constant temperature bath 6, a PD detector 8, an optical fiber head 10, an APD detector 11, a data acquisition unit 12, a PC 13, and a control unit 14.

[0048] The laser 1 emits a laser beam that illuminates the sample in the sample cell 5.

[0049] The sample cell 5 contains a suspension of liquid containing large particles with sedimentation characteristics and small particles without sedimentation characteristics.

[0050] The light intensity adjustment unit includes a set of attenuators 2 mounted on a rotating wheel and driven by a motor 3 for adjusting the intensity of incident light;

[0051] The sample cell 5 is a container for holding the sample to be tested. The internal cross-section of the sample cell is a square of 10mm×10mm, the optical path L is 10mm, the volume of the sample cell is ≥4ml, and it is designed to be transparent from all four sides. The material is quartz or K9 glass.

[0052] The constant temperature bath 6 receives commands from the control unit 14 to reach the set temperature value with an accuracy of ±0.1℃ and a range of -15℃ to 120℃.

[0053] The PD detector 8 is placed at a 0° angle to the laser incident direction. The incident light 4 enters the PD detector 8 after passing through the sample cell 5. The PD detector 8 is used to detect the energy of the transmitted light 7.

[0054] The fiber optic head 10 is placed at a fixed angle in the laser incident direction. The possible angles include: a 90° angle in the laser incident direction, or an angle of 160° to 175° away from the laser incident direction. The scattered light 9 enters the APD detector 11 through the fiber optic head 10. The APD detector 11 is used to detect the energy of the scattered light 9.

[0055] The data acquisition unit 12 is used to receive signals from the PD detector 8 and the APD detector 11, and transmit the signals to the PC 13 for calculation;

[0056] The control unit 14 is used to receive instructions from the PC terminal 13, output control signals to control the temperature of the constant temperature bath 6 to control the temperature of the test sample, and output control signals to control the position of the light intensity adjustment unit and adjust the light intensity of the incident light 4.

[0057] The test includes the following steps:

[0058] 1) Input the required calculation parameters into the software: dynamic viscosity of the sample η, total height of the sample h, and particle density ρ. p Medium density ρ f The refractive index n of the particles p Particle absorption rate A p The refractive index n of the medium f The test is conducted using parameters such as sedimentation particle size analysis, dynamic light scattering analysis, and Mie theory calculations.

[0059] 2) Inject the blank sample into the sample cell 5. The blank sample is a sample dispersion medium liquid that does not contain particles. The liquid level of the sample is higher than the detection point of the incident light 4. Then, place the sample cell 5 into the constant temperature bath 6 for constant temperature operation so that the blank sample reaches the set temperature.

[0060] 3) Control the intensity adjustment unit to adjust the intensity of the incident laser 4 so that the intensity of the incident laser 4 is attenuated to the linear response range of the PD detector 8. If there are multiple attenuators within the linear response range of the PD detector 8, use the attenuator with the smallest intensity attenuation of the incident laser 4 within the linear response range of the PD detector 8 for testing.

[0061] 4) The PD detector 8 collects the transmitted light intensity I0 of the blank sample;

[0062] 5) Remove the blank sample from the constant temperature bath 6;

[0063] 6) Inject the mixed suspension sample to be tested into the sample cell 5, with the sample liquid level higher than the detection point of the incident light 4, and then place the sample cell 5 into the constant temperature bath 6 for constant temperature operation.

[0064] 7) After the isothermal operation is completed, the sedimentation particle size test begins. The transmitted light intensity 7 caused by the sedimentation of large particles in the mixed suspension sample changes over time. The PD detector 8 transmits the collected transmitted light intensity intensity over time signal to the PC13 software through the data acquisition unit 12, plots the transmitted light intensity versus time curve, and obtains the particle size and volume distribution curve of the sedimented large particles, further calculating D. 大 [3,2];

[0065] The typical characteristics of the transmitted light intensity versus time curve are as follows: the transmitted light intensity fluctuates within a small range from the start of the test to a certain time t0. This time period is defined as the initial test platform, and the average light intensity of this platform is used to obtain the initial transmitted light intensity I1; from t0 onwards, the transmitted light intensity increases with the increase of the test time, reaching a certain time t n Afterward, the intensity of the transmitted light begins to fluctuate within a small range, and then essentially stops changing. Let t be defined. n The test platform is a stable test platform until the end of the test. The average light intensity of the platform is taken to obtain the stable transmitted light intensity I2.

[0066] When the transmitted light signal reaches the stable test platform, the sedimentation test is completed. At this time, the large particles in the sample have all settled to the bottom of the sample cell, and the small particles that are still suspended in the sample are non-settled.

[0067] 8) The dynamic light scattering test begins. The APD detector 11 starts collecting dynamic light scattering test signals. The intensity adjustment unit controls the light intensity of the incident light 4 to adjust the scattered light 9 signal within the linear response range of the APD detector 11. The APD detector 11 transmits the signal of the collected scattered light intensity changing with time to the PC13 software through the data acquisition unit 12. Correlation curves are obtained through relevant calculations, and the light intensity distribution curve of non-settling small particles is obtained through multi-exponential fitting. The particle size and volume distribution curve are further obtained, and D is calculated. 小 [3,2];

[0068] 9) Through

[0069]

[0070] φ can be derived 小 Where R is half the optical path length, Φ 小 Q represents the total volume fraction of non-settling small particles. e小 The extinction coefficient of non-settling small particles is calculated using Mie theory;

[0071] pass

[0072]

[0073] Then φ can be derived. 大 , Φ大 Q represents the total volume fraction of settled large particles. e大 The extinction coefficient of the settled large particles is calculated using the Mie theory.

[0074] S is obtained by summing the peak areas of all the particle size distributions calculated by the sedimentation method. 大 S is obtained by summing the peak areas of all the particle size distributions calculated by the dynamic light scattering method. 小 , with S 大 :S 小 =φ 小 φ 大 The proportional relationship between the particle size distribution curves of settled large particles and non-settled small particles is obtained and integrated into a single particle size volume distribution curve.

[0075] Step 8) also includes the following calculation steps:

[0076] The dynamic light scattering method employs autocorrelation technology, and the light intensity distribution of the particle size can be obtained through a multi-exponential fitting method. The fitting formula is as follows:

[0077]

[0078] n represents the number of particle size fractions.

[0079] Given n p and A p In this case, combining Mie theory, the volume distribution can be derived from the light intensity distribution, thus obtaining D. 小 [3,2].

[0080] This invention can measure particle size distribution information in the nanometer to micrometer range of a wide-distribution particle dispersion system in a single test process. The effective detection range of sedimentation method is 1μm to 50μm, and the effective detection range of dynamic light scattering is 1nm to 1μm particles.

Claims

1. A particle size measurement device based on a combination of dynamic light scattering and sedimentation methods, characterized in that: Includes laser, intensity modulation unit, sample cell, thermostat, PD detector, fiber optic connector, APD detector, data acquisition unit, PC, and control unit; The laser emits a laser beam that illuminates the sample in the sample cell; The sample cell contains a suspension of large particles with sedimentation characteristics and small particles without sedimentation characteristics, and the refractive index and absorptivity of the large and small particles are the same. The light intensity adjustment unit includes a set of attenuators mounted on a rotating wheel and driven by a motor for adjusting the intensity of incident light; The sample cell is a container for holding the sample to be tested; The constant temperature bath reaches the set temperature value by receiving commands from the control unit, with an accuracy of ±0.1℃ and a range of -15℃ to 120℃; The PD detector is placed at a 0° angle to the laser incident direction. The incident light enters the PD detector after passing through the sample cell. The PD detector is used to detect the transmitted light energy. The fiber optic head is placed at a fixed angle in the direction of laser incidence; The data acquisition unit is used to receive signals from the PD detector and the APD detector, and transmit the signals to the PC for calculation; The control unit is used to receive commands from the PC, output control signals to control the temperature of the constant temperature bath to control the temperature of the test sample, and output control signals to control the position of the light intensity adjustment unit and adjust the light intensity of the incident light.

2. The particle size measurement device based on a combination of dynamic light scattering and sedimentation methods according to claim 1, characterized in that: The sample cell has an internal cross-section of 10mm×10mm square, an optical path length L of 10mm, a sample cell volume ≥4ml, a four-sided light-transmitting design, and is made of quartz or K9 glass.

3. The particle size measurement device based on a combination of dynamic light scattering and sedimentation methods according to claim 1, characterized in that: The fixed angles that can be placed include: a 90° angle from the laser incident direction, or an angle of 160° to 175° away from the laser incident direction. The scattered light enters the APD detector through the optical fiber, and the APD detector is used to detect the energy of the scattered light.

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