Method for determining slurry state using fractionation centrifugation

Abstract

This invention provides a method for determining the state of a slurry using graded centrifugation, comprising the following steps: S1: centrifuging the slurry to be tested at different speeds and then collecting the supernatant; S2: measuring the viscosity, conductivity, and transmittance of the supernatant; S3: comparing the viscosity data at different speeds to obtain particle size and stability data in the slurry; comparing the conductivity data at different speeds to obtain the adhesion data of ionomer resin on carbon particles in the slurry; comparing the transmittance data at different speeds to obtain the particle morphology data of solid particles in the slurry. This invention breaks through the constraints of traditional thinking and achieves the analysis of the slurry state by using graded centrifugation to determine the slurry state, solving the long-standing problem of difficulty in analyzing the state of catalyst slurries. The operation method is simple and highly practical.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more specifically, to a method for determining the state of a slurry using graded centrifugation. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) is a power generation device that uses hydrogen as fuel and effectively converts its chemical energy into electrical energy. Its high energy density, fast start-up speed, low operating temperature, and environmental friendliness make it ideal as a power source for electric vehicles, portable small power supplies, and underwater propulsion systems. Therefore, since the 1990s, it has received widespread attention from governments worldwide and various sectors including energy, automotive, home appliance, and military industries, leading to rapid technological development.

[0003] The state of the catalyst slurry is a key factor determining the performance of the fuel cell catalyst layer. It consists of the catalyst, solvent, ion exchange resin solution, and certain additives. By controlling the slurry state, the molding quality and microstructure of the catalyst layer can be adjusted, thereby improving battery performance.

[0004] Analyzing the state of slurries is fundamental to improving their performance, but the analysis is challenging due to the characteristics of the slurries themselves. First, slurries are black suspended particulate systems with extremely low transmittance, making them difficult to accurately identify using most optical analysis methods. Second, slurries are mixtures containing liquids, polymers, and solid particles, with complex functional groups and numerous interfering factors, making systematic analysis using traditional chemical methods difficult. Third, slurries are thermodynamically unstable systems, and their state changes over time. Fourth, the solid particles in slurries are extremely fine and mesoscopic colloidal particles, making it difficult to observe their state using simple methods. Currently, research on slurries, besides macroscopic viscosity and rheological characteristic tests, also involves diluting the slurry and using dynamic light scattering to study particle size; however, changes in the slurry state caused by dilution are unavoidable. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for determining the state of slurry using graded centrifugation.

[0006] A method for determining the state of a slurry using fractionation centrifugation according to the present invention includes the following steps:

[0007] S1: After centrifuging the slurry to be tested at different speeds, the supernatant of the slurry is collected.

[0008] S2: Measure the viscosity, conductivity, and transmittance of the supernatant;

[0009] S3: Compare viscosity data at different rotation speeds to obtain particle size and stability data in the slurry; compare conductivity data at different rotation speeds to obtain adhesion data of ion exchange resin on carbon particles in the slurry; compare transmittance data at different rotation speeds to obtain particle morphology data of solid particles in the slurry.

[0010] Preferably, the rotational speed range is 0 to 10,000 rpm.

[0011] Preferably, the base for the variation of different rotational speeds is 1000 revolutions per minute.

[0012] Preferably, the rotation speed is represented by R. By comparing the viscosity data at different rotation speeds, the particle size and stability data of the slurry are obtained. Specifically: if a sudden drop in viscosity occurs within the rotation speed range of 0 ≤ R ≤ 5000 rpm, there are many large-diameter particles in the slurry and the stability is low; if a sudden drop in viscosity occurs within the rotation speed range of 5000 < R ≤ 10000 rpm, there are many small-diameter particles in the slurry and the stability is high; if no sudden drop in viscosity occurs, the particle size distribution range of the slurry is wide.

[0013] Preferably, the slurry includes carbon particles and resin, wherein the carbon particles are large particles of varying sizes that are easy to settle, and the resin is a conductive polymer that can ionize and is not easy to settle.

[0014] By comparing conductivity data at different rotation speeds, the adhesion data of resin on carbon particles in the slurry was obtained. Specifically, when the conductivity changes little, the resin dispersion ability is strong, and the resin adhesion on the carbon particles is low. As the carbon particles settle, the resin is not easy to leave the dispersion system. When the viscosity drops suddenly, the conductivity drops suddenly, and the surface resin dispersion ability is weak, and the resin adhesion on the carbon particles is high.

[0015] Preferably, by comparing transmittance data at different rotation speeds, the particle morphology data of solid particles in the slurry can be obtained, specifically:

[0016] If less resin adheres to carbon particles, the resin is less likely to leave the dispersion system as the carbon particles settle, and the dispersion system has a stronger ability to disperse the resin. The more carbon particles that settle, the higher the transparency.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention breaks through the constraints of traditional thinking and achieves the analysis of slurry state by using a graded centrifugation method to determine the slurry state. By graded centrifugation, the composition of slurry in different states can be obtained. Through testing, the solid content size distribution of different slurries, the adhesion state of resin and catalyst in different slurries, the resin dissociation state of different slurries, the stability state of different slurries, and the surface energy of the system can be compared. This solves the long-standing problem of analyzing the state of catalyst slurries. The operation method is simple and highly practical. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0020] Basic Implementation Example:

[0021] This invention provides a method for determining the state of slurry using graded centrifugation, comprising the following steps:

[0022] S1: After centrifuging the slurry to be tested at different speeds, the supernatant of the slurry is collected. The speed range is 0 to 10,000 rpm, and the base value for the different speeds is 1,000 rpm.

[0023] S2: Measure the viscosity, conductivity, and transmittance of the supernatant;

[0024] S3: Compare viscosity data at different rotation speeds to obtain particle size and stability data in the slurry; compare conductivity data at different rotation speeds to obtain adhesion data of ion exchange resin on carbon particles in the slurry; compare transmittance data at different rotation speeds to obtain particle morphology data of solid particles in the slurry.

[0025] Because large particles settle at low rotational speeds and small particles settle at high rotational speeds, if the slurry contains only one type of particle size, all particles will settle together at a certain rotational speed, causing a sudden decrease in viscosity. If the slurry contains particles of various sizes, some particles will settle at each rotational speed, meaning the particles gradually settle from largest to smallest, thus gradually decreasing the viscosity. Specifically, by comparing viscosity data at different rotational speeds, we can obtain particle size and stability data for the slurry. Specifically: a sudden drop in viscosity within the rotational speed range of 0–5000 rpm indicates a high proportion of large-diameter particles and low stability; a sudden drop in viscosity within the rotational speed range of greater than 5000 rpm and less than 10000 rpm indicates a high proportion of small-diameter particles and high stability; no sudden drop in viscosity indicates a wide particle size distribution range in the surface slurry.

[0026] The slurry in this invention contains two materials: carbon particles and resin. The carbon particles are large particles of varying sizes, which easily settle; the resin is a conductive polymer, similar to sulfuric acid, which is ionizable and does not easily settle. The carbon particles are dispersed in the slurry, while the resin exists in two states: either directly dispersed in the slurry or attached to the surface of the carbon particles. The conductivity of the slurry mainly depends on the resin dispersed in it. This resin is not only ionized but also freely mobile, while the resin attached to the carbon surface is restricted in its movement and does not affect the conductivity. The viscosity of the slurry is affected by both the resin and the carbon particles, but the concentration of carbon particles is a decisive factor. Specifically, by comparing conductivity data at different rotation speeds, the adhesion data of the ion-exchange resin on the carbon particles in the slurry can be obtained, specifically:

[0027] A small change in conductivity indicates that the ion exchange resin has strong dispersing ability, with little adhesion to carbon particles, and is not easily removed from the dispersion system as the carbon particles settle. If the conductivity drops sharply along with the viscosity, it indicates that the ion exchange resin has weak dispersing ability and more resin adheres to the carbon particles.

[0028] Furthermore, by comparing transmittance data at different rotation speeds, we can obtain data on the particle morphology of solid particles in the slurry, specifically:

[0029] If the resin has less adhesion to the carbon particles, it is more difficult for it to leave the dispersion system as the carbon particles settle. The dispersion system has a stronger ability to disperse the resin. Since the resin is transparent, the carbon particles will block light. The more carbon particles settle, the higher the transparency.

[0030] Example 1:

[0031] Take a certain type of slurry. The slurry consists of 2g of platinum-carbon catalyst 1, 5g of resin solution 1, and 60g of a mixed solution of alcohol 1 (isopropanol), alcohol 2 (n-propanol), triol (glycerol), and water (1:0.5:0.1:2) (mass ratio). Measure its viscosity, conductivity, and transmittance.

[0032] Specifically, the slurry was centrifuged at speeds of 0 rpm, 2000 rpm, 5000 rpm, 8000 rpm, and 10000 rpm, respectively. The supernatant of the centrifuged slurry was collected, and its viscosity, conductivity, and transmittance were measured. The measured data are shown in Table 1.

[0033] Table 1: Experimental data of slurry after centrifugation in Example 1

[0034] Example 1 <![CDATA[Viscosity( mPa·s )]]> <![CDATA[Conductivity ( μS / cm)]]> Light transmittance (%) 0 75 70 0 2000 31 62 0 5000 20 60 50 8000 11 47 60 10000 4 42 65

[0035] In this embodiment, a sudden drop in viscosity occurred at a rotation speed of 2000 rpm, indicating that the particle size of the slurry dispersion system is larger, D = 0.786 μm, making it easy to settle and with low stability.

[0036] In this embodiment, the conductivity of the slurry changes relatively little, suggesting that the ionomer resin adheres less to the carbon particles and is less likely to leave the dispersion system as the carbon particles settle. This dispersion system, in turn, has a stronger dispersing ability for the resin. The higher conductivity in this embodiment indicates a higher degree of resin dissociation. Characterizing the state of ionomer resin on the carbon surface is a classic challenge in the industry; this invention can indirectly infer the adsorption state of the resin.

[0037] In this embodiment, the high light transmittance of the slurry indicates that the solid particles in the slurry mainly exist in the form of large particle sizes, which are easy to settle.

[0038] Example 2:

[0039] Take a certain type of slurry, the composition of which is 2g of platinum carbon catalyst 2, 5g of resin solution 1, and 60g of a mixed solution of alcohol 1 (isopropanol): alcohol 2 (n-propanol): triol (glycerol): water (1:0.5:0.1:2) (mass ratio), and measure its viscosity, conductivity and transmittance.

[0040] Specifically, the slurry was centrifuged at speeds of 0 rpm, 2000 rpm, 5000 rpm, 8000 rpm, and 10000 rpm, respectively. The supernatant of the centrifuged slurry was collected, and its viscosity, conductivity, and transmittance were measured. The measured data are shown in Table 2.

[0041] Table 2: Experimental data of slurry after centrifugation in Example 2

[0042] Example 2 <![CDATA[Viscosity( mPa·s )]]> <![CDATA[Conductivity ( μS / cm)]]> Light transmittance (%) 0 52 15 0 2000 47 12 0 5000 42 13 10 8000 23 12 31 10000 6 11 42

[0043] In this embodiment, a sudden drop in viscosity occurred at a rotation speed of 8000 rpm, indicating that the particle size of the slurry dispersion system is smaller, D = 0.235 μm, making it less prone to sedimentation and exhibiting high stability.

[0044] In this embodiment, the slurry exhibits minimal change in conductivity, indicating that the ionomer resin adheres less to the carbon particles and is less likely to leave the dispersion system as the carbon particles settle. This dispersion system, in turn, demonstrates stronger resin dispersibility. The lower conductivity in this embodiment indicates a lower degree of resin dissociation.

[0045] In this embodiment, the slurry has low light transmittance, indicating that the solid particles are highly dispersed in the slurry as small particles, making them difficult to settle.

[0046] Example 3:

[0047] Take a certain type of slurry, the composition of which is 2g of platinum carbon catalyst 3, 5g of resin solution 2, and 60g of a mixed solution of alcohol 1 (isopropanol): alcohol 2 (n-propanol): triol (glycerol): water (1:0.5:0.1:2) (mass ratio), and measure its viscosity, conductivity and transmittance.

[0048] Specifically, the slurry was centrifuged at speeds of 0 rpm, 2000 rpm, 5000 rpm, 8000 rpm, and 10000 rpm, respectively. The supernatant of the centrifuged slurry was collected, and its viscosity, conductivity, and transmittance were measured. The measured data are shown in Table 3.

[0049] Table 3: Experimental data of slurry after centrifugation in Example 3

[0050] Example 3 <![CDATA[Viscosity( mPa·s )]]> <![CDATA[Conductivity ( uS / cm)]]> Light transmittance (%) 0 21 55 0 2000 15 42 20 5000 12 41 52 8000 11 31 53 10000 4 24 71

[0051] The viscosity reduction in this embodiment is relatively stable, indicating that the particle distribution range of the slurry in this embodiment is relatively wide, with D ranging from 0.386 μm to 0.521 μm.

[0052] In this embodiment, the transmittance of the slurry changes steadily, similar to the viscosity change, indicating a wide particle distribution range. Simultaneously, the high final transmittance of the slurry in this embodiment also indicates a high surface energy of the system, making it difficult for solid particles to suspend.

[0053] In summary, comparing the various embodiments, Examples 1 and 2 exhibited sudden viscosity drops at 2000 rpm and 8000 rpm, respectively, indicating that the dispersion system in Example 1 had larger particle sizes, lower stability, and was more prone to sedimentation. In contrast, the slurry dispersion system in Example 2 had smaller particle sizes, higher stability, and was less prone to sedimentation. The viscosity decrease in Example 3 was relatively stable, indicating that Example 3 had a wider particle size distribution range.

[0054] Compared to Examples 1 and 3, the conductivity change in Example 2 was smaller, indicating that the ion exchange resin in Example 2 had less adhesion to the carbon particles and was less likely to leave the dispersion system as the carbon particles settled. This dispersion system, however, had a stronger dispersing ability for the resin. The resin is transparent, while the carbon particles block light; the more carbon particles that settle, the higher the transparency.

[0055] Compared to Examples 1 and 3, Example 2 exhibits lower conductivity, indicating a lower degree of resin dissociation. Example 2 actually uses a different resin than the other examples, with conductivity changing little with centrifugal speed, indicating less attached resin. Most of the resin did not settle with the carbon particles, maintaining conductivity within a small range. However, although less resin adheres, its low degree of dissociation results in low slurry conductivity.

[0056] Compared to Examples 1 and 3, Example 2 exhibits lower light transmittance, indicating that the solid particles are highly dispersed in the slurry as small particles, making them difficult to settle. Example 1 shows a stable change in light transmittance, similar to its viscosity change, indicating a higher proportion of large particles and a relatively smaller proportion of small particles. Meanwhile, Example 3 shows a higher final light transmittance, further indicating that the system has a higher surface energy, making it less prone to suspending solid particles.

[0057] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0058] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for determining the state of a slurry using fractional centrifugation, characterized in that, It comprises the following steps: S1: centrifuging the slurry to be tested at different rotating speeds, and taking the supernatant of the slurry; S2: measuring the viscosity, conductivity and transmittance of the supernatant; S3: comparing the viscosity data at different rotating speeds to obtain the particle size and stability data of the slurry; comparing the conductivity data at different rotating speeds to obtain the data of the attachment of the ionic resin on the carbon particles in the slurry; and comparing the transmittance data at different rotating speeds to obtain the data of the particle form of the solid particles in the slurry; The rotating speed ranges from 0 to 10000 rpm; The change base of different rotating speeds is 1000 rpm; The rotating speed is represented by R, and the comparison of the viscosity data at different rotating speeds obtains the particle size and stability data of the slurry, specifically: when the rotating speed is within 0≤R≤5000 rpm, the viscosity suddenly drops, the slurry contains many large-particle-size particles, and the stability is low; when the rotating speed is within 5000<R≤10000 rpm, the viscosity suddenly drops, the slurry contains many small-particle-size particles, and the stability is high; When the viscosity does not suddenly drop, the particle size distribution range of the slurry is wide; The slurry comprises carbon particles and resin, the carbon particles are large particles and are easy to settle, and the resin is a conductive polymer that can be ionized and is not easy to settle; The comparison of the conductivity data at different rotating speeds obtains the data of the attachment of the resin on the carbon particles in the slurry, specifically: when the conductivity changes little, the resin has strong dispersing ability, and the resin has less attachment on the carbon particles, so the resin is not easy to leave the dispersion system with the settlement of the carbon particles; when the viscosity suddenly drops, the conductivity suddenly drops, indicating that the surface resin has weak dispersing ability and the resin has more attachment on the carbon particles.

2. The method for determining the state of a slurry using fractional centrifugation according to claim 1, characterized in that, The comparison of the transmittance data at different rotating speeds can obtain the data of the particle form of the solid particles in the slurry, specifically: When the resin has less attachment on the carbon particles, the resin is not easy to leave the dispersion system with the settlement of the carbon particles, the dispersion system has stronger dispersing ability for the resin, and the more the settled carbon particles are, the higher the transparency is.