Suspension stability efficient evaluation method based on temperature control-full spectrum

Abstract

A suspension stability efficient evaluation method based on temperature control-full spectrum relates to the field of suspension stability evaluation, and comprises the following steps: S1, determining a standard detection temperature; s2, configuring a to-be-tested suspension group loaded with interference factors; s3, placing the to-be-detected suspension group in an ultraviolet-visible spectrophotometer, heating to a standard detection temperature, setting a scanning wavelength range, scanning to obtain a to-be-detected extinction degree change curve, and evaluating the stability of the to-be-detected suspension based on the dispersion degree of the to-be-detected extinction degree change curve along with time; or, raising the temperature to a standard detection temperature, constructing an extinction degree-time curve, and extracting characteristic parameters in the extinction degree-time curve to evaluate the stability of the suspension. According to the method, the sedimentation, aggregation and layering processes of a suspension system are accelerated under the condition of controlled temperature rise, and the differential expression of different systems in the aspect of stability is remarkably amplified, so that the tiny sedimentation trend is shown in limited time, the detection period is shortened, and the detection efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of suspension stability evaluation, specifically a high-efficiency method for evaluating suspension stability based on temperature control and full spectrum. Background Technology

[0002] Suspensions (including nanofluids, colloidal dispersions, and pharmaceutical formulations) have wide applications in materials science, energy, biomedicine, coatings, and food. The stability of suspensions has a decisive impact on their performance and practical application value. For example, in the field of nanofluid thermal conduction, particle sedimentation will significantly reduce its thermal conductivity; in formulations and coatings, unstable suspensions will lead to a decline in product performance or even failure.

[0003] Suspensions of the same type refer to suspensions with the same dispersed components. Adding different interfering factors to the same type of suspension can form different suspension systems. Evaluating the stability of different suspension systems helps to theoretically reveal the mechanism by which interfering factors affect the stability of the dispersion system, establishing an "interference-stability" correlation model to improve the theoretical foundation of fields such as colloid chemistry. Furthermore, it can guide industrial production in practical applications, ensuring product quality, optimizing processes, and reducing costs by clarifying key control parameters, thus meeting the application needs of multiple fields such as coatings, pharmaceuticals, mineral processing, and biomedicine.

[0004] Currently, common methods for evaluating the stability of suspensions include visual inspection, centrifugation, zeta potential measurement, and spectrophotometry (single wavelength).

[0005] Visual methods record the sedimentation behavior of suspensions during settling by observing the naked eye or using optical imaging techniques, such as changes in surface clarity and sediment height. While simple, this method has a long detection cycle (often several hours to several days) and is susceptible to interference from subjective human judgment, making it difficult to achieve high-throughput or quantitative analysis.

[0006] Centrifugation accelerates particle sedimentation through high-speed centrifugation. The equivalent natural sedimentation time is often calculated using centrifugation speed and time, thus indirectly evaluating dispersion stability. While this method speeds up the evaluation process, it has two key problems: the centrifugal force is much greater than in actual operating environments, failing to reflect natural sedimentation behavior; and high-speed rotation may lead to redistribution of the dispersant and particles, interfering with the accurate evaluation results.

[0007] The zeta potential method indirectly determines the electrostatic stability of a suspension by measuring the repulsive force between surface charges of particles. It is simple to operate and provides quantifiable data. However, it cannot reflect the differences in suspension stability caused by steric hindrance, has poor applicability to large particles or non-electrostatically stable systems, and cannot directly assess sedimentation behavior. Spectrophotometry (single wavelength) determines the sedimentation process of particles by measuring absorbance or absorbance changes at a specific wavelength. This method is simple, efficient, and sensitive, but it is also time-consuming.

[0008] Therefore, there is an urgent need for a simple, rapid, and universally applicable method for evaluating the stability of suspensions, which can distinguish the stability levels of different suspension systems based on the same type of suspension in a short time. Summary of the Invention

[0009] This invention provides a highly efficient method for evaluating the stability of suspensions based on temperature control and full spectrum, which can distinguish the stability levels of different suspension systems based on the same type of suspension in a short time.

[0010] To achieve the above objectives, the specific solution adopted by the present invention is as follows: a highly efficient method for evaluating the stability of suspensions based on temperature control and full spectrum, comprising the following steps:

[0011] S1. Place the standard suspension in a UV-Vis spectrophotometer, using the blank sample as a reference, set the scanning wavelength range and temperature gradient, and start interval scanning when the temperature is raised to the specific temperature in the temperature gradient to obtain the standard extinction change curve. Determine the standard detection temperature based on the dispersion of the standard extinction change curves at different specific temperatures.

[0012] S2. Configure the test suspension group with added interference factors;

[0013] S3. Place the suspension to be tested in a UV-Vis spectrophotometer, set the scanning wavelength range and heat to the standard detection temperature, scan to obtain the extinction change curve, and evaluate the stability of the suspension to be tested based on the degree of dispersion of the extinction change curve over time.

[0014] Alternatively, the suspension to be tested can be placed in a UV-Vis spectrophotometer, heated to the standard detection temperature, the target scanning wavelength can be set, and the extinction of the suspension to be tested can be monitored in real time. An extinction-time curve can be constructed, and characteristic parameters in the extinction-time curve can be extracted to evaluate the stability of the suspension.

[0015] As a further optimization of the above technical solution, the scanning wavelength range includes, but is not limited to, 200–800 nm.

[0016] As a further optimization of the above technical solution, the target scanning wavelength is one of the wavelengths in the extinction change curve where the extinction changes significantly with time.

[0017] As a further optimization of the above technical solution, the interval scanning is performed once every 5 minutes, and the continuous scanning time is more than 20 minutes.

[0018] As a further optimization of the above technical solution, the temperature gradient includes, but is not limited to, 40℃, 60℃, 80℃, 100℃, and 120℃.

[0019] As a further optimization of the above technical solution, the method for determining the separation degree of the standard extinction change curve is as follows: the specific temperature corresponding to the standard extinction change curve with obvious dispersion is taken as the standard detection temperature, wherein the obvious dispersion is indicated by an extinction change rate greater than or equal to 0.1.

[0020] As a further optimization of the above technical solution, the interfering factors include, but are not limited to, at least one of the following: dispersion concentration, pH value, dispersant type and dispersant concentration. For each interfering factor, a test suspension group is set up, and each test suspension group contains multiple test suspensions.

[0021] As a further optimization of the above technical solution, the stability of the suspension to be tested is evaluated based on the degree of separation of the extinction change curve over time. Specifically, the more dispersed the extinction change curve is, the worse the stability.

[0022] As a further optimization of the above technical solution, the characteristic parameters in the extinction-time curve include the initial extinction E0 and the half-life T. 1 / 2 The rate of decrease per unit time, k, and the change in extinction intensity, ΔE, over a given time period; where T 1 / 2 The longer the length, the more stable the suspension under test; the smaller the k, the more stable the suspension under test; the smaller the ΔE, the more stable the suspension under test.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention proposes a novel evaluation approach that combines appropriate high-temperature acceleration with full-spectrum dynamic monitoring. By accelerating the sedimentation, aggregation, and stratification processes of suspension systems under controlled temperature elevation, the differences in stability among different systems are significantly amplified, allowing minute sedimentation trends to emerge within a limited time. The detection cycle is reduced from several hours to 20–60 minutes, greatly improving detection efficiency. This approach is particularly suitable for comparing and evaluating multiple formulation samples or for rapid initial screening of multiple dispersion systems.

[0025] Unlike traditional methods that rely on manual visual inspection or single-point measurements, this invention also achieves continuous and quantitative assessment of suspension stability. Its core lies in: using a UV-Vis spectrophotometer to monitor extinction changes across the entire wavelength range in real time and non-contactly at a standard detection temperature, automatically generating extinction-time curves, and extracting quantitative parameters such as half-life and rate of change from them. This method also ensures the consistency and objectivity of the results, avoiding interference from human factors. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the ultraviolet-visible spectrophotometer with temperature control function used in this invention.

[0027] Figure 2 This is a schematic diagram of the overall process of the embodiments and comparative examples of the present invention;

[0028] Figure 3 The temperature correction data is from Example 1;

[0029] Figure 4 The extinction variation curves of a 0.1 wt% alumina suspension at different set temperatures (and actual temperatures);

[0030] Figure 5 The graph shows the change in average particle size of alumina suspensions over time under different pH conditions.

[0031] Figure 6 Zeta potential data for alumina suspensions under different pH conditions;

[0032] Figure 7 Visual views of suspensions at different time points under a series of pH conditions (pH values ​​from left to right are 2, 4, 6, 8, 10, and 12).

[0033] Figure 8 The extinction curves of alumina suspensions at different pH values ​​within 1 hour under room temperature conditions (without heating) are shown.

[0034] Figure 9 The extinction change curves of alumina suspensions at different pH values ​​within 1 hour under standard test temperature conditions are shown. 120℃ is the temperature set by the temperature controller, and the temperature in parentheses is the actual temperature of the suspension.

[0035] Figure 10 The extinction-time curves of alumina suspensions at different pH values ​​under standard testing temperature conditions at a specific wavelength;

[0036] Figure 11Visual views of alumina suspensions containing a series of different PVP dispersant concentrations at different time points (from left to right, PVP concentrations are 0, 0.01wt%, 0.02wt%, 0.05wt%, 0.1wt%, 0.2wt%, and 0.4wt%).

[0037] Figure 12 The extinction curves of alumina suspensions containing different PVP dispersant concentrations within 1 hour under room temperature conditions (without heating) are shown.

[0038] Figure 13 The extinction change curves of alumina suspensions containing different PVP dispersant concentrations within 1 hour under standard test temperature conditions;

[0039] Figure 14 Extinction-time curves of alumina suspensions containing different PVP dispersant concentrations at a specific wavelength under standard testing temperature conditions;

[0040] Figure 15 Figure 1 shows the extinction curves of a 0.025 wt% TiO2 suspension at different temperatures: (a) 40℃, (b) 60℃, (c) 80℃, (d) 100℃, and (e) 120℃.

[0041] Figure 16 Visual views of suspensions at different time points under a series of pH conditions (pH values ​​from left to right are 2, 4, 6, 8, 10, and 12).

[0042] Figure 17 The extinction curves of titanium dioxide suspensions at different pH conditions over 1 hour are shown.

[0043] Figure 18 The extinction curves of titanium dioxide suspensions under different pH conditions for 1 hour under standard detection temperature (120℃) are shown.

[0044] Figure 19 Extinction-time curves of titanium dioxide suspensions at specific wavelengths under different pH conditions;

[0045] Figure 20 This is a graph showing the particle size of nano-titanium dioxide under different pH conditions. Detailed Implementation

[0046] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Parts not described or disclosed in detail in the following embodiments of the present invention should be understood as prior art known or should be known by those skilled in the art.

[0047] This invention discloses a highly efficient method for evaluating the stability of suspensions based on temperature control and full spectrum, comprising the following steps:

[0048] S1. Determine the standard test temperature

[0049] The standard suspension was placed in a UV-Vis spectrophotometer, with a blank sample as a reference. The scanning wavelength range and temperature gradient were set. The scanning wavelength range was 200–800 nm, and the temperature gradients set on the temperature controller were 40℃, 60℃, 80℃, 100℃, 120℃, and 130℃.

[0050] When the temperature is raised to a specific temperature in the temperature gradient, interval scanning begins to obtain the standard extinction change curve; the interval scanning is performed once every 5 minutes, and the scanning continues for about 1 hour at each specific temperature in the temperature gradient.

[0051] The standard test temperature is determined based on the degree of dispersion of the standard extinction change curves at different specific temperatures. Specifically, the specific temperature corresponding to the standard extinction change curve with a significant degree of dispersion is taken as the standard test temperature.

[0052] S2. Configure the test suspension group with added interference factors;

[0053] Interference factors include at least one of particle concentration, pH value, dispersant type and dispersant concentration. For each interference factor, a test suspension group is set up, and each test suspension group contains multiple test suspensions.

[0054] When the interfering factors are particle concentration and pH value, the dispersed component in the standard suspension is the dispersed particles, such as alumina in alumina suspension and titanium dioxide in titanium dioxide suspension.

[0055] When the interfering factor is the concentration of the dispersant, the dispersed component in the suspension is a mixture of dispersed particles and dispersant. For example, if the interfering factor is the concentration of the dispersant PVP, the dispersed component in the suspension is a mixture of alumina and PVP.

[0056] S3. Place the suspension to be tested in a UV-Vis spectrophotometer, set the scanning wavelength range and heat it to the standard detection temperature, and scan to obtain the extinction change curve to be tested. The scanning wavelength range, which is the scanning wavelength range of step S1, is 200 to 800 nm.

[0057] The stability of the suspension under test is evaluated based on the degree of dispersion of the extinction change curve over time. The more dispersed the extinction change curve is, the worse the stability.

[0058] This invention also discloses another method for evaluating the stability of a test suspension. After determining the standard detection temperature and configuring the test suspension group with added interference factors, the test suspension group is placed in a UV-Vis spectrophotometer, heated to the standard detection temperature, and the target scanning wavelength is set. Real-time extinction monitoring of the test suspension is performed. The target scanning wavelength is any wavelength with a large extinction change rate within the range of 200–800 nm. An extinction-time curve is constructed, and characteristic parameters from the extinction-time curve are extracted to evaluate the stability of the suspension. The characteristic parameters in the extinction-time curve include the initial extinction E0 and the half-life T. 1 / 2 The rate of decrease per unit time k and the change in extinction ΔE over a certain period of time; where T 1 / 2 The longer the length, the more stable the suspension under test; the smaller the k, the more stable the suspension under test; the smaller the ΔE, the more stable the suspension under test.

[0059] Example 1

[0060] A method for evaluating the stability of suspensions based on temperature control and full spectrum is presented. In this embodiment, the suspension is an alumina suspension.

[0061] First, the experimental apparatus (i.e., ultraviolet-visible spectrophotometer) used in the efficient evaluation method for suspension stability of the present invention is briefly described below:

[0062] like Figure 1 As shown, the UV-Vis spectrophotometer is equipped with a temperature control device, which includes a heating ceramic element 3, a Pt100 temperature probe 4, and a temperature controller 5. A cuvette 2 is placed inside the sample cell 1. The heating ceramic element 3 and the Pt100 temperature probe 4 are fixed to the bottom of the sample cell 1. The heating ceramic element 3 heats the bottom of the cuvette 2, and the Pt100 temperature probe 4 measures the temperature of the heating ceramic element 3. The heating ceramic element 3 and the Pt100 temperature probe 4 are connected to the external temperature controller 5 via wires. The temperature controller 5 also functions as a temperature measuring and temperature control device.

[0063] It should be noted that other commercially available UV-Vis spectrophotometers can also be used, as long as they can heat the sample to be tested and control the heating temperature in real time.

[0064] The specific evaluation method includes the following steps:

[0065] S1. Place the standard suspension in a UV-Vis spectrophotometer, using the blank sample as a reference, set the scanning wavelength range and temperature gradient, and start interval scanning when the temperature is raised to the specific temperature in the temperature gradient to obtain the standard extinction change curve. Determine the standard detection temperature based on the dispersion of the standard extinction change curves at different specific temperatures.

[0066] S101, Prepare standard suspension

[0067] Accurately weigh 0.05g of alumina powder using an analytical balance and add it to a 150mL Erlenmeyer flask containing deionized water. After thorough stirring with a glass rod to initially disperse the powder, place the Erlenmeyer flask in a 500W ultrasonic cleaner for ultrasonic vibration for 10 minutes, stirring once every 5 minutes during the ultrasonic process, to prepare a suspension with an Al2O3 concentration of 0.1wt%, which is the Al2O3 standard suspension.

[0068] S102, Detection of standard suspensions

[0069] First, the temperature control device is calibrated. The temperature calibration data is as follows: Figure 3 As shown.

[0070] The scanning wavelength range of the UV-Vis spectrophotometer was then set to 200–800 nm, using a blank sample as a reference. The temperature control device was activated, and temperature gradients of 40°C, 60°C, 80°C, 100°C, 120°C, and 130°C were set. Measurements were started after the temperature reached the set values ​​(i.e., the specific temperatures within the temperature gradient). At each temperature, a scan was performed every 5 minutes, and measurements were continued for 1 hour to obtain the standard extinction change curve at each specific temperature. In this embodiment, six Al2O3 standard suspensions were used, and each Al2O3 standard suspension was measured at a specific temperature within a temperature gradient.

[0071] S103. Determine the standard test temperature.

[0072] like Figure 4 As shown, the effect of temperature on the stability of the suspension was studied under different temperature conditions. When the temperature controller was set between 40 and 100℃, the standard extinction curve was relatively compact with small changes, indicating that the stability of the nano-alumina suspension was relatively good at this temperature, and the temperature-accelerated alumina sedimentation rate was not significant. When the temperature controller temperature was increased to 120℃, the extinction change began to increase significantly, indicating that the stability of the nano-alumina suspension decreased significantly at 120℃. After continuing to raise the temperature to 130℃, the actual temperature of the suspension exceeded 100℃, and it began to boil, with disordered spectral changes. Therefore, 120℃ was selected as the standard detection temperature for subsequent experiments, at which point the actual temperature of the suspension was approximately 95℃.

[0073] S2. Configure the test suspension group with the interference factor, which is pH value;

[0074] Specifically, multiple standard suspensions were taken and their pH was adjusted with 0.1M HCl and 0.1M NaOH solutions to obtain a test suspension group containing 5 test suspensions with pH values ​​of 2, 4, 6, 10 and 12.

[0075] S3. Place the suspension to be tested in a UV-Vis spectrophotometer, set the scanning wavelength range and heat to the standard detection temperature, scan to obtain the extinction change curve, and evaluate the stability of the suspension to be tested based on the degree of dispersion of the extinction change curve over time.

[0076] Figure 9 The extinction curves of suspensions at different pH values ​​from 400 to 800 nm are presented under standard detection temperature (120℃). Each suspension corresponds to one extinction curve. The results show that, when the temperature is controlled at the standard detection temperature, the extinction curves of each system show significant differences. The spectral intensity of suspensions at pH 10 and 6 decreases significantly, indicating that particle aggregation is intensified and the system stability is poor under these two pH conditions. The decrease in spectral intensity is smaller at pH 12. At pH 2 and 4, the extinction curves show the smallest changes, indicating that the system has good stability. Figure 10 The graph shows the change in extinction over time for suspensions at different pH values ​​at a specific wavelength. It can be seen from the graph that the extinction changes are minimal at pH = 2 and 4, indicating good system stability under these conditions. The extinction change is also relatively small at pH = 12, indicating relatively good suspension stability. However, at pH = 6 and 10, the extinction changes significantly over time, indicating faster particle sedimentation and poorer system stability under these conditions. Therefore, it can be concluded that the stability of alumina suspensions under different pH conditions is in the order: pH = 2 > pH = 4 > pH = 12 > pH = 6 > pH = 10.

[0077] Example 2

[0078] The overall steps in this embodiment are the same as those in Embodiment 1, except that step S3 is different.

[0079] S3 in this embodiment is: placing multiple samples of the suspension to be tested in a UV-Vis spectrophotometer, heating to the standard detection temperature, setting the target scanning wavelength and monitoring the extinction of the suspension to be tested in real time, constructing an extinction-time curve, and extracting characteristic parameters from the extinction-time curve to evaluate the stability of the suspension.

[0080] By monitoring the extinction of the suspension in real time at any wavelength with a large rate of change in extinction, an extinction-time curve is constructed. Based on this curve, characteristic parameters including initial extinction (E0), half-life (T1 / 2), rate of decrease per unit time (k), and change in extinction over a certain time (ΔE) can be extracted to quantitatively characterize the stability of the suspension. 1 / 2A longer ΔE indicates slower sedimentation and a more stable system; a smaller k indicates a lower particle sedimentation rate and better stability; a smaller ΔE indicates a lower final sedimentation degree and a relatively more stable system. The obtained data is processed to calculate parameters such as the spectral change rate or extinction half-life.

[0081] The specific extraction parameters are shown in Table 1:

[0082] Figure 10 The extinction-time curves shown illustrate the change in extinction of the test suspensions at different pH values ​​at a specific wavelength (700 nm) over time. The graphs reveal that the suspensions at pH = 2 and 4 exhibited the smallest changes in extinction, indicating good system stability under these conditions. The extinction change was also relatively small at pH = 12, suggesting relatively good suspension stability. However, at pH = 6 and 10, the extinction changed significantly over time, indicating faster particle sedimentation and poorer system stability under these conditions.

[0083] right Figure 10 The parameter extraction results are shown in Table 2. The longer the half-life, the smaller the rate of change and the better the stability.

[0084] Table 2

[0085] Table 2 shows that the stability under different pH conditions is as follows: pH=2>pH=4>pH=12>pH=6>pH=10.

[0086] Example 3

[0087] A method for efficient evaluation of suspension stability based on temperature control and full spectrum is presented in this embodiment, in which the alumina suspension is supplemented with dispersant PVP.

[0088] The specific evaluation method includes the following steps:

[0089] S1. Determine the standard test temperature

[0090] This study still focuses on the alumina system, so 120℃ was used as the standard test temperature. At this temperature, the actual measured suspension temperature was about 95℃.

[0091] S2. Configure the test suspension group with interference factors, the interference factor being the dispersant concentration.

[0092] Specifically, a test suspension group was prepared with a pH value of 8 and containing 0.1 wt% nano-alumina with different dispersant concentrations (0 wt%, 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.4 wt%, 1 wt%). This test suspension group included Al2O3+PVP test suspensions with different dispersant concentrations.

[0093] S3. Place the suspension to be tested in a UV-Vis spectrophotometer, set the scanning wavelength range to 400-800nm ​​and heat it to the standard detection temperature, scan to obtain multiple extinction change curves, and evaluate the stability of the suspension to be tested based on the degree of dispersion of the extinction change curves over time.

[0094] Figure 13 The extinction curves of suspensions with different dispersant concentrations at the standard detection temperature (120℃) are shown across the entire wavelength range. After heating to 120℃, the extinction curves of suspensions with different dispersant concentrations showed significant differentiation within 1 hour. Suspensions with dispersant concentrations of 0.01wt%–0.05wt% exhibited a larger decrease in extinction curves, indicating poor stability of the nano-alumina suspensions under low dispersant concentration conditions. Under other dispersant concentration conditions, the changes in extinction curves were relatively small, indicating that the suspensions exhibited better stability at these concentrations.

[0095] Example 4

[0096] The overall steps in this embodiment are the same as those in Embodiment 3, except that step S3 is different.

[0097] In this embodiment, step S3 specifically includes:

[0098] The suspension to be tested is placed in a UV-Vis spectrophotometer, heated to the standard detection temperature, the target scanning wavelength is set, and the extinction of the suspension to be tested is monitored in real time. An extinction-time curve is constructed, and characteristic parameters in the extinction-time curve are extracted to evaluate the stability of the suspension.

[0099] By monitoring the extinction of the suspension in real time at any wavelength with a large rate of change in extinction, an extinction-time curve is constructed. Based on this curve, characteristic parameters such as initial extinction (E0), half-life (T1 / 2), rate of decrease per unit time (k), and change in extinction over a certain time (ΔE) can be extracted to qualitatively and quantitatively characterize the stability of the suspension. The obtained data are then processed to calculate parameters such as the spectral change rate or extinction half-life.

[0100] The test results are as follows Figure 14As shown in the figure, the alumina suspension with a dispersant concentration of 0.01wt% to 0.05wt% exhibits a large change in extinction, indicating that the system has poor stability under these conditions and the concentration of dispersant is insufficient to maintain the stability of the suspension. Under other dispersant concentrations, the change in extinction is smaller, and the stability of the suspension is relatively better.

[0101] right Figure 16 The parameters were extracted, as shown in Table 3:

[0102] Table 3

[0103] The data in Table 3 show that the stability of alumina suspensions with dispersant (PVP) concentrations of 0.01 wt% to 0.2 wt% gradually increases with increasing dispersant concentration. The stability of alumina suspensions with concentrations of 0.4 wt% and 1 wt% tends to be stable. PVP effectively prevents nanoparticle aggregation by forming a steric hindrance layer on the particle surface through adsorption. Compared with traditional methods, the efficient suspension stability evaluation method of this invention can more quickly and effectively reflect the stability differences of nano-alumina suspensions under different dispersant concentrations. Under appropriate high-temperature auxiliary conditions, minute stability differences in the suspension groups are amplified and visually displayed through extinction change curves, providing a more powerful means for rapid and accurate evaluation of suspension stability.

[0104] Example 5

[0105] A method for evaluating the stability of suspensions based on temperature control and full spectrum is proposed. In this embodiment, the suspension is a titanium dioxide suspension.

[0106] The specific evaluation method includes the following steps:

[0107] S1. Place the standard suspension in a UV-Vis spectrophotometer, using the blank sample as a reference, set the scanning wavelength range and temperature gradient, and start interval scanning when the temperature is raised to the specific temperature in the temperature gradient to obtain the standard extinction change curve. Determine the standard detection temperature based on the dispersion of the standard extinction change curves at different specific temperatures.

[0108] S101, Prepare standard suspension

[0109] Accurately weigh 0.0125 g of titanium dioxide powder using an analytical balance and add it to a 150 mL Erlenmeyer flask containing deionized water. After thorough stirring with a glass rod to initially disperse the powder, place the Erlenmeyer flask in a 500 W ultrasonic cleaner for ultrasonic vibration for 10 min. This prepares a titanium dioxide suspension with a concentration of 0.025 wt%, which is the standard titanium dioxide suspension.

[0110] S102, Detection of standard suspensions

[0111] The scanning wavelength range of the UV-Vis spectrophotometer was set to 500–800 nm, with a blank sample as a reference. The temperature control device was turned on, and the temperature was set to 40℃, 60℃, 80℃, 100℃, and 120℃ respectively. After the temperature rose to the set value, the measurement began. At each temperature, a scan was performed every 5 minutes, and the measurement was continued for 1 hour to obtain the standard extinction change curve at each temperature.

[0112] S103. Determine the standard test temperature.

[0113] like Figure 15 As shown, by comparing the extinction variation patterns and trends at different temperatures, it was found that the standard extinction variation curve is relatively compact and the change is small when the temperature is between 40 and 100℃, indicating that the stability of the nano-titanium dioxide suspension is relatively good at this temperature, and the temperature-accelerated sedimentation rate of titanium dioxide is not significant. When the temperature rises to 120℃, the change in extinction begins to increase significantly, indicating that the stability of the nano-alumina suspension decreases significantly at 120℃. The absorbance change is the largest and follows a normal pattern at 120℃, therefore 120℃ was selected as the standard detection temperature thereafter.

[0114] S2. Configure the test suspension group with the interference factor loaded; the interference factor is pH value;

[0115] Specifically, multiple standard suspensions were taken and their pH was adjusted with 0.1M HCl and 0.1M NaOH solutions to obtain a test suspension group containing 5 test suspensions with pH values ​​of 2, 4, 6, 10 and 12.

[0116] S3. Place the suspension to be tested in a UV-Vis spectrophotometer, set the scanning wavelength range and heat to the standard detection temperature, scan to obtain the extinction change curve, and evaluate the stability of the suspension to be tested based on the degree of dispersion of the extinction change curve over time.

[0117] like Figure 18 As shown, under 120℃ conditions, the spectra of titanium dioxide suspensions at pH 4 and 6 showed a greater degree of spectral separation within 1 hour, indicating poor stability of the suspensions at these pH values. The spectra of suspensions at pH 2 and 10 showed a smaller degree of spectral separation, but the solutions also exhibited some instability. The spectra of silica suspension at pH 10 showed the smallest degree of spectral separation, indicating good stability of the suspensions under these conditions.

[0118] Example 6

[0119] The overall steps in this embodiment are the same as those in Embodiment 5, except for step S3:

[0120] The suspension to be tested is placed in a UV-Vis spectrophotometer, heated to the standard detection temperature, the target scanning wavelength is set, and the extinction of the suspension to be tested is monitored in real time. An extinction-time curve is constructed, and characteristic parameters in the extinction-time curve are extracted to evaluate the stability of the suspension.

[0121] By monitoring the extinction of the suspension in real time at any wavelength with a large rate of change in extinction, an extinction-time curve is constructed. Based on this curve, characteristic parameters such as initial extinction (E0), half-life (T1 / 2), rate of decrease per unit time (k), and change in extinction over a certain time (ΔE) can be extracted to qualitatively and quantitatively characterize the stability of the suspension. The obtained data are then processed to calculate parameters such as the spectral change rate or extinction half-life.

[0122] like Figure 19 The figure shows the change in extinction of silica suspensions with different concentrations over time at a specific wavelength (700 nm). It can be seen from the figure that the higher the titanium dioxide concentration, the smaller the change in extinction, and the better the stability of the suspension. Figure 19 The parameters were extracted, and the results are shown in Table 4: Table 4 Evaluation parameters of titanium dioxide suspension under different pH conditions Table 4 shows that the stability under different pH conditions is as follows: pH = 10 > pH = 2 > pH = 12 > pH = 4 > pH = 6.

[0125] The specific procedures for evaluating the stability of suspensions in the embodiments and comparative examples of this invention are as follows: Figure 2 As shown.

[0126] Comparative Example 1

[0127] Measurement of zeta potential and particle size: A certain amount of alumina powder was weighed and added directly to deionized water to prepare a suspension with an alumina concentration of 0.05 wt%. The pH of the suspension was adjusted with 0.1 M HCl and 0.1 M NaOH solutions. The pH values ​​of the suspension were 2, 4, 6, 8, 10 and 12. After ultrasonic dispersion for 10 min, the zeta potential of the suspension and the change in particle size within 20 min were measured.

[0128] Data on particle size changes of alumina suspension over 20 minutes under different pH conditions are as follows: Figure 5As shown in the figure, the average particle size of the alumina nanoparticle suspension at pH 8 is above 1000 nm, and it varies significantly within 20 minutes. The average particle size of the alumina suspension at other pH values ​​is below 350 nm, and the particle size variation within 20 minutes is smaller. This indicates that changes in pH affect the aggregation behavior of alumina nanoparticles, leading to changes in particle size. At pH 8, the particle size variation of the alumina nanoparticles is large, and the suspension stability is poor; while under acidic or alkaline conditions, the particle size variation is small, and the suspension stability is good. Figure 6 The zeta potentials shown exhibit similar results. Around pH 8, the zeta potential of the alumina suspension is close to zero, i.e., the isoelectric point, indicating poor suspension stability. Suspensions further from the isoelectric point have larger absolute zeta potentials, indicating better suspension stability. These results are consistent with those obtained using the temperature-controlled full-spectrum method, but they cannot further distinguish the differences in suspension stability under acidic or alkaline pH conditions.

[0129] Comparative Example 2

[0130] Extinction degree determination and visual sedimentation experiment at room temperature: 0.05 g of nano-Al2O3 powder was weighed and dispersed in 50 mL of deionized water to prepare an Al2O3 suspension with a concentration of 0.1 wt%. After adjusting the pH of the suspension with 0.1 M HCl and 0.1 M NaOH, it was ultrasonically dispersed for 10 min using a 500 W ultrasonic instrument. The suspension was then quickly transferred to a sedimentation tube for free sedimentation. The sedimentation in the test tube was observed and photographed at regular intervals. In addition, the change in extinction degree of the suspension over one hour was measured using a UV-Vis spectrophotometer at room temperature to characterize the stability of the suspension.

[0131] Visual observation of the settling of nano-alumina suspensions at different pH values ​​(2, 4, 6, 8, 10, 12) after one day of static settling was performed. Figure 7 As shown, at pH 8, the suspension exhibited significant precipitation after 1 hour, and the alumina suspension completely precipitated after 10 hours, indicating that the nano-alumina suspension had poor stability at pH 8. While slight precipitation occurred at pH values ​​of 2, 4, 6, 10, and 12 after 4 hours, the stability under these pH conditions could not be further distinguished visually. Even after observing for one day, the difference in stability could not be visually differentiated.

[0132] Figure 8 The figures show the extinction variation curves across all wavelengths at room temperature. Within 1 hour, only the extinction variation curve for the suspension at pH 8 showed a decrease; the extinction variation curves for the other suspensions did not show significant changes. This indicates that at room temperature, only the suspension at pH 8 showed significant sedimentation within 1 hour, while sedimentation was not significant at other pH levels, making it impossible to distinguish differences in stability.

[0133] Comparative Example 3

[0134] Following the method for preparing the test suspension group in Example 3, an Al2O3+PVP test suspension with a pH value of 8 and containing 0.1wt% nano-alumina and different dispersant concentrations (0wt%, 0.01wt%, 0.02wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.4wt%) was prepared.

[0135] The Al2O3+PVP suspension was subjected to one day of natural settling and visual observation. Figure 11 As shown, without a dispersant, due to the suspension being at its isoelectric point of pH=8, significant precipitation occurs within 1 hour, with a thick layer of nano-alumina precipitate quickly forming at the bottom, while the upper layer remains relatively clear. After adding a dispersant, the precipitation phenomenon is significantly reduced, and almost no precipitation is observed. The suspension maintains a relatively stable dispersion state until about 5 hours later, when a relatively large proportion of the clear upper layer is observed in suspensions with dispersant concentrations of 0.01wt% and 0.02wt%, indicating relatively poor stability.

[0136] Figure 12 The extinction curves of the Al2O3+PVP suspension under room temperature are shown. Within 1 hour, the extinction curves of all suspensions containing different dispersant concentrations did not change significantly, indicating that the stability differences of suspensions after adding different concentrations of dispersant cannot be effectively distinguished under non-heating conditions.

[0137] Comparative Example 4

[0138] Following the method of preparing the test suspension in Example 5, the pH value of the suspension was adjusted to obtain titanium dioxide test suspensions with pH values ​​of 2, 4, 6, 8, 10, and 12.

[0139] like Figure 16 As shown, visual observation of the sedimentation of titanium dioxide suspensions at different pH values ​​(2, 4, 6, 8, 10, 12) over one day revealed that at pH 8, significant precipitation occurred after 4 hours, and complete sedimentation occurred after 8 hours, indicating poor stability of the titanium dioxide suspension at pH 8. While slight sedimentation was observed at pH values ​​of 2, 4, 6, 10, and 12 after 8 hours, visual observation was insufficient to differentiate the stability under these pH conditions; even after one day of observation, the differences in stability could not be distinguished visually.

[0140] like Figure 17 The results show the extinction changes at room temperature. The titanium dioxide suspension at pH 8 showed the greatest change in extinction within 1 hour, while no changes were observed at other pH levels. Only the suspension at pH 8 showed significant sedimentation within 1 hour; sedimentation was not significant at other pH levels, making it impossible to distinguish differences in stability.

[0141] The relationship between titanium dioxide suspension particle size and pH value is as follows: Figure 20 As shown, the particle size of titanium dioxide is largest at pH=8 and smallest at pH=10.

[0142] Results analysis:

[0143] Compared with Comparative Examples 1 and 2, Example 2 demonstrates that the efficient method for evaluating the stability of suspensions of the present invention can amplify stability differences under high temperature, making minute aggregation behaviors more apparent in spectral changes. It can accurately distinguish the stability differences of alumina suspensions under acidic and alkaline conditions, thus providing a rapid and precise stability evaluation method that is helpful for the screening and optimization of nano-suspension systems.

[0144] The test results of Example 3 were compared with those of Comparative Example 3: the results of Example 3 using the efficient evaluation method for suspension stability of the present invention within 1 hour were consistent with the results of Comparative Example 3 using the visual sedimentation method over one day, indicating that the present invention is an efficient evaluation method.

[0145] The experimental results of Example 5 were compared with those of Comparative Example 4: The results of Example 5 using the efficient evaluation method for suspension stability of the present invention within 1 hour were consistent with the results of the particle size analysis method of Comparative Example 4.

[0146] In summary, compared with the traditional evaluation methods used in Comparative Examples 1-3, the efficient suspension stability evaluation method of this invention effectively accelerates the sedimentation rate of particles by increasing the temperature of the suspension system, thereby amplifying the differences in stability between similar systems in a short time. This method utilizes the effects of enhanced Brownian motion induced by heating and reduced solution viscosity to make minute sedimentation trends apparent in a short time. The detection cycle is reduced from the traditional several hours or even days to 20-60 minutes, significantly improving detection efficiency. It is particularly suitable for comparing and evaluating multiple similar formulation samples or for rapid initial screening of dispersed systems.

[0147] This method establishes an extinction-time curve by real-time acquisition of the extinction change of suspensions at a specific wavelength, and further extracts characteristic parameters such as half-life and extinction change rate to achieve qualitative and quantitative characterization of stability. The entire process requires no contact with the sample, avoiding human interference and subjective judgment, and the test results have good reproducibility. The method proposed in this invention has the advantages of continuous monitoring, quantitative analysis, and strong adaptability, and is suitable for assessing the stability of suspensions under various parameter conditions, including particle type, concentration, and different dispersant systems.

[0148] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A highly efficient method for evaluating the stability of suspensions based on temperature control and full spectrum, characterized in that, Includes the following steps: S1. Place the standard suspension in a UV-Vis spectrophotometer, using the blank sample as a reference, set the scanning wavelength range and temperature gradient, and start interval scanning when the temperature is raised to the specific temperature in the temperature gradient to obtain the standard extinction change curve. Determine the standard detection temperature based on the dispersion of the standard extinction change curves at different specific temperatures. S2. Configure the test suspension group with added interference factors; S3. Place the suspension to be tested in a UV-Vis spectrophotometer, set the scanning wavelength range and heat to the standard detection temperature, scan to obtain the extinction change curve, and evaluate the stability of the suspension to be tested based on the degree of dispersion of the extinction change curve over time. Alternatively, the suspension to be tested can be placed in a UV-Vis spectrophotometer, heated to the standard detection temperature, the target scanning wavelength can be set, and the extinction of the suspension to be tested can be monitored in real time. An extinction-time curve can be constructed, and characteristic parameters in the extinction-time curve can be extracted to evaluate the stability of the suspension.

2. The efficient evaluation method for suspension stability based on temperature control and full spectrum as described in claim 1, characterized in that, The scanning wavelength range includes, but is not limited to, 200–800 nm.

3. The efficient evaluation method for suspension stability based on temperature control and full spectrum as described in claim 1, characterized in that, The target scanning wavelength is one of the wavelengths in the extinction variation curve where the extinction changes significantly over time.

4. The efficient evaluation method for suspension stability based on temperature control and full spectrum according to claim 1, characterized in that, Interval scanning is performed every 5 minutes, and continuous scanning time is more than 20 minutes.

5. The efficient evaluation method for suspension stability based on temperature control and full spectrum according to claim 1, characterized in that, Temperature gradients include, but are not limited to, 40℃, 60℃, 80℃, 100℃, and 120℃.

6. The efficient evaluation method for suspension stability based on temperature control and full spectrum according to claim 1, characterized in that, The method for determining the degree of separation of the standard extinction change curve is as follows: the specific temperature corresponding to the standard extinction change curve with obvious dispersion is taken as the standard detection temperature, and the obvious dispersion is indicated by an extinction change rate greater than or equal to 0.

1.

7. The efficient evaluation method for suspension stability based on temperature control and full spectrum according to claim 1, characterized in that, Interference factors include, but are not limited to, at least one of the following: dispersion concentration, pH value, dispersant type and dispersant concentration. For each interference factor, a test suspension group is set up, and each test suspension group contains multiple test suspensions.

8. The efficient evaluation method for suspension stability based on temperature control and full spectrum according to claim 1, characterized in that, The stability of a suspension is evaluated based on the degree of separation of the extinction change curve over time. Specifically, the more dispersed the extinction change curve is, the worse the stability.

9. The efficient evaluation method for suspension stability based on temperature control and full spectrum according to claim 1, characterized in that, The characteristic parameters in the extinction-time curve include the initial extinction E0 and the half-life T. 1 / 2 The rate of decrease per unit time, k, and the change in extinction intensity, ΔE, over a given time period; where T 1 / 2 The longer the length, the more stable the suspension to be tested; the smaller the k, the more stable the suspension to be tested; the smaller the ΔE, the more stable the suspension to be tested.

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