A hollow bead heat resistance visual evaluation method based on a high temperature microscope

Abstract

The present application relates to a kind of hollow small ball heat resistance visualization evaluation method based on high temperature microscope technique.First, temperature calibration is carried out to high temperature metallographic microscope, second, 1-10mg hollow small ball is evenly sprinkled on glass slide using medicine spoon, and the glass slide is vibrated, so that the hollow small ball on it is single layer distribution, not mutually overlapping, shielding, in 600-1000 ℃ temperature interval, at least three grades of temperature increasing rate is used to heat, and the state of hollow small ball under each temperature increasing rate is recorded in real time using video image.Subsequently, according to the state continuous change spectrum of microsphere in heating process, the temperature T m1 、 m2 、 m3 of 50±5% proportion of hollow small ball in a certain field of view is determined, which softens and collapses.Finally, the softening temperature T m1 、 m2 、 m3 of hollow small ball under at least three grades of temperature increasing rate is linearly fitted, and the softening temperature T m of hollow small ball at heating speed of 0 ℃ / min, i.e., constant temperature, is obtained, which is the heat resistance characteristic temperature in equilibrium state.

Description

Technical Field

[0001] This project relates to a visualization evaluation technology for the heat resistance of hollow spheres, which belongs to the field of testing technology and is used for evaluating the heat resistance and softening temperature of hollow spheres. Background Technology

[0002] Hollow microspheres are a new type of energy-saving, clean, and lightweight filler. Due to their hollow structure, light weight, thermal insulation, high electrical insulation strength, wear resistance, corrosion resistance, radiation protection, sound insulation, low water absorption, and stable chemical properties, microspheres were mass-produced by 3M and PQ in the 1990s. Abroad, hollow microspheres are widely used as multifunctional fillers in composite materials, including rubber and plastics, coatings, fiberglass, emulsion explosives, and oil drilling. The main chemical component of hollow microspheres is soda-lime borosilicate glass, with a particle size of 2–120 μm, a wall thickness of 1–2 μm, and a bulk density of 0.08–0.16 g / cm³. 3 Compressive strength 3~120MPa, thermal conductivity 0.03~0.043W / m·K.

[0003] Common methods for testing softening temperature include the capillary method and the DSC method.

[0004] The capillary method is a classic method for determining the softening temperature of chemical substances. It is simple to operate, provides intuitive observations, and can be performed visually or using a photocell. The softening temperature is obtained by visually recording the temperatures at which the sample begins to collapse within the capillary (initial melting) and when the sample has completely become a clear liquid (full melting). This melting point is then repeated at a lower heating rate. However, visual methods are subject to observational errors. Therefore, photocell capillary methods are also used to test softening temperatures, utilizing the difference in photoelectric signals between the solid and liquid states to replace visual judgment. However, because glass microspheres range in size from 2 to 120 μm, are hollow, and easily broken, it is difficult to observe their state changes visually or using a photocell, making the capillary method unsuitable for this purpose.

[0005] The Direct Scaling (DSC) method is a technique for quantitatively assessing the phase changes and softening temperature of chemical substances by measuring the relationship curve between heat flux (J / g) and temperature (°C) under programmed temperatures. This method is effective for testing pure substances. However, due to the complex composition, varying size and wall thickness of hollow spheres, they lack a fixed softening temperature, resulting in chaotic and complex endothermic peaks during DSC testing. Therefore, it is difficult to evaluate the heat resistance of hollow spheres.

[0006] In the characterization of hollow spheres, there are currently problems such as inconsistencies in testing methods between research and application units, and outdated standards and methods, which seriously affect the accuracy of hollow sphere performance characterization. Currently, there are no practical methods for evaluating the heat resistance of hollow spheres or testing their softening temperature.

[0007] This project proposes a visual evaluation method for the heat resistance of hollow spheres based on high-temperature microscopy, which can solve the above-mentioned problems. Summary of the Invention

[0008] The purpose of this invention is to evaluate the heat resistance of hollow spheres based on high-temperature microscopy technology and to test their softening temperature using image observation and comparison methods.

[0009] The technical solution of this invention is: a method for visually evaluating the heat resistance of hollow spheres based on high-temperature microscopy, comprising:

[0010] Sprinkle 1-10 mg of hollow microspheres evenly on a glass slide and vibrate the slide to make the hollow microspheres distributed in a single layer without overlapping or obstructing each other. Heat the slide at at least three heating rates in the temperature range of 600-1000℃ and record the state of the hollow microspheres at each heating rate in real time using a high-temperature microscope with video images.

[0011] Based on the spectrum of continuous state changes during the heating process of hollow spheres, determine the temperature at which 50±5% of the hollow spheres soften and collapse at each heating rate in a field of view.

[0012] Linear fitting was performed on the softening temperature of the hollow spheres at each heating rate to obtain the softening temperature T of the hollow spheres when the heating rate is 0℃ / min, i.e., when the temperature is held at a constant temperature. m The above temperatures are the heat resistance characteristic temperatures under equilibrium conditions.

[0013] Preferably, the high-temperature microscope needs to be calibrated before use. Specifically, a pure Ag foil standard sample is used as the sample, and the temperature is increased according to the following procedure: from room temperature to 950°C at 50°C / min, and held for 1 min; from 950°C to 970°C at 1°C / min, and held for 1 min; from 970°C to 200°C at 50°C / min, and held for 1 min; from 200°C to 50°C at 20°C / min, and the procedure is ended. When the temperature continuously changes from 950°C to 970°C, the change in the state of the silver foil is observed in real time. The temperature value T1 at the moment when the silver foil changes from solid to liquid microspheres is recorded. The temperature value that needs to be calibrated is T1-962°C.

[0014] Preferably, the three heating rate levels include at least three heating rate levels: A, B, and C, where A is 20±10℃ / min, B is 5±2℃ / min, and C is 1~2℃ / min.

[0015] Preferably, the heating process within the temperature range of 600–1000℃, using three heating rates (A, B, and C), includes:

[0016] Heating was performed at rate A, and the temperature at which 50±5% of the hollow spheres within a field of view softened and collapsed was recorded as T. m1 ;

[0017] Replace the hollow ball at T m1 Within a temperature range of ±100℃, the temperature was increased at the B-level heating rate, and the state of the hollow spheres within this temperature range was observed. The temperature at which 50±5% of the hollow spheres softened and collapsed within a field of view was recorded and denoted as T. m2 ;

[0018] Replace the hollow ball at T m2 Within a temperature range of ±20℃, the temperature was increased at a heating rate of C, and the state of the hollow spheres within this temperature range was observed. The temperature at which 50±5% of the hollow spheres softened and collapsed within a field of view was recorded and denoted as T. m3 .

[0019] Preferably, for T respectively m1 T m2 T m3 Linear fitting was performed to obtain the heat resistance characteristic temperature T at which 50±5% of the hollow spheres softened and collapsed when the heating rate was 0℃ / min, i.e., when the temperature was held at a constant temperature. m .

[0020] Preferably, the heating process using the A-level heating rate is as follows: heating from room temperature to 600°C at a rate of 50-100°C / min; heating from 600°C to 1000°C at the A-level heating rate; and cooling from 1000°C back to room temperature.

[0021] Preferably, in T m1 Within a temperature range of ±100℃, the heating process using the B-level heating rate involves raising the temperature from room temperature to T at a rate of 50–100℃ / min. m1 -100℃, from T m1 -100℃, heated to T at temperature setting B. m1 +100℃; from T m1 The temperature dropped from +100℃ to room temperature.

[0022] Preferably, in T m2Within a temperature range of ±20℃, the heating process using the C-level heating rate involves raising the temperature from room temperature to T at a rate of 50–100℃ / min. m2 -20℃, from T m2 -20℃ is heated to T at a rate of C. m2 +20℃; from T m2 The temperature dropped from +20℃ to room temperature.

[0023] Preferably, the method for determining the softening and collapse temperature of hollow microspheres is as follows: for a single hollow microsphere, the softening temperature is the temperature at which the top of the microsphere breaks, at which point the image contrast at the top of the microsphere undergoes a significant abrupt change; for multiple adjacent hollow microspheres, the softening temperature is the temperature at which a significant bridging occurs between the microspheres, at which point the multiple hollow glass particles adhere to each other.

[0024] Preferably, the number of hollow spheres within a field of view is 300 to 600.

[0025] This invention employs a method based on high-temperature microscopy to determine the softening temperature of hollow spheres by observing continuous morphological changes, thereby evaluating their heat resistance. This method establishes a complete, scientific, and precise evaluation technique for the heat resistance of hollow spheres, filling a gap in this field. The measurement results are more reliable, the judgment criteria are more scientific, and the image observation is more intuitive, making it of significant value and importance. Attached Figure Description

[0026] Figure 1 For the project's technical solution;

[0027] Figure 2 A standard chart showing the continuous morphological transformation of a single hollow sphere under temperature.

[0028] Figure 3 The top fracture morphology of a single hollow sphere under temperature action;

[0029] Figure 4 A standard chart showing the continuous morphological transformation of multiple hollow spheres under temperature.

[0030] Figure 5 The morphology of multiple hollow spheres after fusion and shrinkage;

[0031] Figure 6 This is a schematic diagram of the collapse process of a hollow sphere;

[0032] Figure 7 The state of the hollow spheres changes with temperature at a heating rate of 20℃ / min. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and examples.

[0034] like Figure 1 As shown, a visual evaluation method for the heat resistance of hollow microspheres based on a high-temperature microscope is presented. First, the high-temperature metallurgical microscope is calibrated. During the calibration process, a 3mm section of pure Ag foil standard sample is used as the test sample. The temperature is increased according to a specific program, and the temperature value at the instant the silver foil changes from a solid to a liquid microsphere is recorded. Next, 1-10mg of hollow microspheres are evenly sprinkled onto a glass slide using a spatula, and the slide is vibrated to ensure that the hollow microspheres are distributed in a single layer without overlapping or obstruction. The temperature is increased in the range of 600-1000℃ at rates of 20℃ / min, 5℃ / min, and 1℃ / min, and the state of the hollow microspheres is recorded in real time using video images. Finally, based on the continuous change spectrum of the microspheres' state during heating, the temperature T at which 50% of the hollow microspheres in a specific field of view soften and collapse is determined. m1 T m2 T m3 Finally, the softening temperature T of the hollow spheres at speeds of 20℃ / min, 5℃ / min, and 1℃ / min were determined. m1 T m2 T m3 By performing optimal polynomial fitting, the softening temperature T of the hollow spheres when the heating rate is 0℃ / min, i.e., when held at a constant temperature, is obtained. m The above temperatures are the heat resistance characteristic temperatures under equilibrium conditions.

[0035] Example

[0036] First, a high-temperature microscope temperature calibration is performed. This high temperature generally requires the microscope to withstand temperatures up to 1200℃. A pure Ag foil standard sample of approximately 3 mm in diameter is used as the test sample. The following heating procedure is followed: from room temperature, increase to 950℃ at 50℃ / min and hold for 1 min; from 950℃, increase to 970℃ at 1℃ / min and hold for 1 min; from 970℃, decrease to 200℃ at 50℃ / min and hold for 1 min; from 200℃, decrease to 50℃ at 20℃ / min and end the procedure. As the temperature continuously changes from 950℃ to 970℃, the state change of the silver foil is observed in real time. The temperature value T1 at the instant the silver foil changes from solid to liquid microspheres is recorded. The temperature value requiring calibration is T1 - 962℃.

[0037] Next, using a spatula, 1-10 mg of hollow microspheres were evenly sprinkled onto a glass slide, and the slide was shaken to ensure that the hollow microspheres were distributed in a single layer without overlapping or obstruction. The slide was then placed in the stage of a high-temperature metallurgical microscope, and the temperature was increased according to the following procedure: from room temperature to 600℃ at 50℃ / min; from 600℃ to 1000℃ at 20℃ / min; and from 1000℃ to room temperature at 100℃ / min. The state of the hollow microspheres at 600℃-1000℃ was observed. Due to the influence of factors such as microsphere composition, size, wall thickness, and morphological integrity, the softening temperature of each microsphere was different. The standard spectrum of the continuous morphological transformation of a single hollow microsphere under temperature is shown below. Figure 2 As shown. Therefore, statistical methods were used to evaluate the heat resistance of the hollow microspheres. The temperature at which 50% of the microspheres softened and collapsed within a field of view was recorded and denoted as T. m1 . , Figure 6 A schematic diagram of the hollow sphere collapse process is given. For a single hollow sphere, the softening temperature is the temperature at which the top of the microsphere ruptures. At this point, the image contrast at the top of the microsphere undergoes a significant abrupt change, as shown in the diagram. Figure 3 As shown; for multiple adjacent hollow microspheres, the softening temperature is the temperature at which significant bridging occurs between the microspheres, at which point the multiple hollow glass particles adhere to each other, as shown. Figure 4 As shown. The morphology of multiple hollow spheres after fusion and shrinkage is as follows. Figure 5 As shown in the figure. The state of the hollow spheres changes with temperature at a heating rate of 20℃ / min. Figure 7 As shown.

[0038] Then, replace the hollow ball with a smaller one, and place it in T. m1 Within a temperature range of ±100℃, the temperature was increased at a rate of 5℃ / min, and the state of the hollow microspheres within this temperature range was observed. The temperature at which 50% of the microspheres softened and collapsed within a field of view was recorded and denoted as T. m2 ;

[0039] Replace the hollow ball at T m2 Within a temperature range of ±20℃, the temperature was increased at a rate of 1℃ / min, and the state of the hollow spheres within this temperature range was observed. The temperature at which 50% of the microspheres softened and collapsed within a field of view was recorded and denoted as T. m3 .

[0040] Finally, for T respectively m1 T m2 T m3 Linear fitting was performed to obtain the heat resistance characteristic temperature T at which 50% of the microspheres softened and collapsed when the heating rate was 0℃ / min, i.e., when the temperature was maintained at a constant temperature. m In the example provided in this invention, linear fitting is performed using the least squares method on T.m1 T m2 T m3 Linear fitting can be performed conveniently in software such as Excel or Origin.

[0041] The parts of this invention not described in detail are common knowledge to those skilled in the art.

Claims

1. A method for visually evaluating the heat resistance of hollow spheres based on high-temperature microscopy, characterized in that, include: Sprinkle 1-10 mg of hollow microspheres evenly on a glass slide and vibrate the slide to make the hollow microspheres distributed in a single layer without overlapping or obstructing each other. Heat the slide at at least three heating rates in the temperature range of 600-1000℃ and record the state of the hollow microspheres at each heating rate in real time using a high-temperature microscope with video images. For a single hollow microsphere, the softening temperature is defined as the temperature at which the top of the microsphere breaks. For multiple adjacent hollow microspheres, the softening temperature is defined as the temperature at which obvious bridging occurs between the microspheres, i.e., the temperature at which multiple hollow microspheres stick together. Based on the spectrum of continuous state change of hollow microspheres during heating and the definition method of hollow microsphere softening temperature, the softening temperature of hollow microspheres in an observed field of view is determined. Within a field of view, 300 to 600 hollow spheres were collected. Statistical methods were used to record the softening temperatures of 50 ± 5% of the hollow spheres at each heating rate. At least three heating rates (A, B, and C) were included, with A at 20 ± 10 °C / min, B at 5 ± 2 °C / min, and C at 1 to 2 °C / min. Linear fitting was performed on the softening temperatures of the hollow spheres at each heating rate to obtain the softening temperature T of the hollow spheres at a heating rate of 0 °C / min (i.e., constant temperature holding). m The above temperatures are the heat resistance characteristic temperatures under equilibrium conditions.

2. The method according to claim 1, characterized in that, The high-temperature microscope needs to be calibrated before use. Specifically, a pure Ag foil standard sample is used as the sample, and the temperature is increased according to the following procedure: from room temperature to 950°C at 50°C / min and held for 1 min; from 950°C to 970°C at 1°C / min and held for 1 min. Cool from 970℃ to 200℃ at a rate of 50℃ / min, and hold for 1 minute; The program is terminated when the temperature drops from 200℃ to 50℃ at a rate of 20℃ / min. When the temperature changes continuously from 950℃ to 970℃, the change in the state of the silver foil is observed in real time. The temperature value T1 at the instant when the silver foil changes from solid to liquid microspheres is recorded. The temperature value that needs to be calibrated is T1-962℃.

3. The method according to claim 1, characterized in that, Heating within the temperature range of 600–1000℃ using three heating rates (A, B, and C) includes: Heating was performed at rate A, and the temperature at which 50±5% of the hollow spheres within a field of view softened and collapsed was recorded as T. m1 ; Replace the hollow ball at T m1 Within a temperature range of ±100℃, the temperature was increased at the B-level heating rate, and the state of the hollow spheres within this temperature range was observed. The temperature at which 50±5% of the hollow spheres softened and collapsed within a field of view was recorded and denoted as T. m2 ; Replace the hollow ball at T m2 Within a temperature range of ±20℃, the temperature was increased at a heating rate of C, and the state of the hollow spheres within this temperature range was observed. The temperature at which 50±5% of the hollow spheres softened and collapsed within a field of view was recorded and denoted as T. m3 .

4. The method according to claim 3, characterized in that, For T respectively m1 T m2 T m3 Linear fitting was performed to obtain the heat resistance characteristic temperature T at which 50±5% of the hollow spheres softened and collapsed when the heating rate was 0℃ / min, i.e., when the temperature was held at a constant temperature. m .

5. The method according to claim 3, characterized in that, The specific process of heating at the A-level heating rate is as follows: from room temperature to 600℃ at a rate of 50-100℃ / min; from 600℃ to 1000℃ at the A-level heating rate; and from 1000℃ back to room temperature.

6. The method according to claim 3, characterized in that, In T m1 Within a temperature range of ±100℃, the heating process using the B-level heating rate involves raising the temperature from room temperature to T at a rate of 50–100℃ / min. m1 -100℃, from T m1 -100℃, heated to T at temperature setting B. m1 +100℃; from T m1 The temperature dropped from +100℃ to room temperature.

7. The method according to claim 3, characterized in that, In T m2 Within a temperature range of ±20℃, the heating process using the C-level heating rate involves raising the temperature from room temperature to T at a rate of 50–100℃ / min. m2 -20℃, from T m2 -20℃ is heated to T at a rate of C. m2 +20℃; from T m2 The temperature dropped from +20℃ to room temperature.

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