Method for enhancing the compressive strength of cenospheres

Abstract

The application discloses a method for enhancing the compressive strength of hollow microspheres and relates to the technical field of hollow microsphere processing. Traditional hollow microspheres have internal unevenness during the manufacturing process, especially the voids gather due to thermal diffusion, form a gap, and then form a crack nucleus under the action of stress. The crack nucleus diffuses to the glass surface and develops into a microcrack. In addition, the structure of the glass surface also affects the generation of the microcrack. Under the condition of ultrahigh pressure, these small microcracks directly limit the upper limit of the strength of the hollow microspheres. The application utilizes a water-isostatic pressure resistant equipment to remove the hollow microspheres with small microcracks and other hollow microspheres with low compressive strength, such as eccentricity and multiple cavities, generated in the production process, so as to improve the strength of the remaining whole hollow microsphere products.

Description

Technical Field

[0001] This invention relates to the field of hollow microsphere processing technology, specifically to a method for enhancing the compressive strength of hollow microspheres. Background Technology

[0002] Hollow microspheres are tiny spherical materials that are hollow and contain an inert gas. Their density is generally between 0.1 and 0.7 g / cm³. 3 Hollow microspheres, typically ranging in size from 5 to 200 μm, are unique and stable hollow microparticles widely used in military, civilian, and other high-tech fields due to their low density, low thermal conductivity, low dielectric constant, and resistance to chemical corrosion. These microspheres are found in solid buoyancy materials, petrochemicals, emulsion explosives, heat insulation and fireproofing materials, stealth and sound-absorbing materials, advanced insulating materials, chemical additives, and low-density ablation materials. However, with continuous technological advancements and the development of new application areas, the performance requirements for hollow microspheres are becoming increasingly stringent, especially in terms of compressive strength. For example, when added to polymer materials to prepare low-density materials, particularly solid buoyancy materials, the relatively low compressive strength and susceptibility to breakage of hollow microspheres result in insignificant additive effects. Currently, commercially available hollow microspheres struggle to meet the requirements for ultra-high pressure and low density applications. Therefore, developing ultra-high pressure hollow microspheres would not only help expand their application areas but also improve the overall performance of composite materials using hollow microspheres as additives. Studies have found that the internal inhomogeneity of glass microspheres, especially the aggregation of vacancies due to thermal diffusion, forms voids, which then become crack nuclei under stress. These crack nuclei diffuse to the glass surface, aggregate, and develop into microcracks. Furthermore, the structure of the glass surface also influences microcrack formation. The interaction between Si-O-R+ ions on the glass surface and H2O in the air generates SiOH clusters.

[0003] Si-O-R++H2O=SiOH+ROH

[0004] Due to H + The size ratio of R + Due to their small size, glass microspheres are prone to surface microcracks caused by tensile stress. These microcracks are extremely small and, to date, cannot be directly observed. Glass is a typical brittle material with high brittleness, making it highly sensitive to even minute defects. The strength of glass microspheres depends on the presence of surface microcracks and the stress-induced propagation of these small cracks.

[0005] Under ultra-high pressure, these tiny microcracks directly limit the upper limit of the strength of hollow microspheres. Therefore, it is feasible to use a water-resistant isostatic pressure device to remove hollow glass microspheres with microcracks and other low compressive strengths such as eccentricity and multi-cavity defects generated during the production process in advance, thereby improving the strength of the remaining overall hollow microsphere products. Summary of the Invention

[0006] The purpose of this invention is to provide a method for enhancing the compressive strength of hollow microspheres, aiming to improve the strength of existing hollow microspheres.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for enhancing the compressive strength of hollow microspheres involves using a hydrostatic pressure testing device to pre-remove hollow microspheres with microcracks and other defects such as eccentricity and multi-cavity defects generated during the production process, resulting in ultra-high pressure hollow microspheres.

[0009] Specifically, it includes the following steps:

[0010] 1. Before pressurization, soak the hollow microsphere powder in a filter bag with water to prevent it from exploding under pressure.

[0011] 2. Use a water-resistant isostatic pressurization device to increase the pressure at a rate of 1-30 Psi / second. Hold the pressure for 2 minutes every 100-1500 Psi and observe for any problems. Continue increasing the pressure until the maximum pressure is reached. Hold the pressure for 30-60 minutes and then release the pressure.

[0012] 3. After being pressed, the hollow microspheres are subjected to gravity separation to remove broken glass microspheres and select the hollow microspheres that float on the water surface.

[0013] 4. The re-obtained hollow microspheres are tested using pressure testing equipment to determine their compressive strength, thus obtaining an ultra-high pressure hollow microsphere.

[0014] Furthermore, the filter bag in step 1 has a mesh size of 200-1000.

[0015] Furthermore, the soaking time in step 1 is 12-24 hours.

[0016] Furthermore, since the different densities of hollow microspheres represent different standard compressive strengths, the maximum pressure in step 2 is determined based on the density of the hollow microspheres.

[0017] It should be further noted that the above method is also applicable to the processing of hollow ceramic spheres, inorganic hollow spheres, and other similar products.

[0018] The beneficial effects of this invention are:

[0019] This invention utilizes a water-resistant isostatic pressing device to pre-remove hollow microspheres with low compressive strength caused by micro-cracks and other defects such as eccentricity and multi-cavity defects generated during the production process from the original hollow microsphere powder, thereby improving the strength of the remaining overall hollow microsphere product. Attached Figure Description

[0020] The invention will now be further described with reference to the accompanying drawings.

[0021] Figure 1 This is a flowchart of the present invention.

[0022] Figure 2 Comparison images of hollow microspheres before and after water isostatic pressure resistance: (a) eccentric hollow microspheres; (b) microcracked and broken hollow microspheres; (c) hollow microspheres with uneven wall thickness; (d) electron microscope image of hollow microspheres before pressure; (e) electron microscope image of hollow microspheres after pressure; (f) electron microscope image of hollow microspheres after gravity drift separation. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] The following embodiments are all in accordance with... Figure 1 The process shown is implemented.

[0025] Example 1: H-series hollow glass microspheres with a density of 0.120 g / cm3 and a standard compressive strength of 200 Psi (20% breakage rate) were selected. They were placed in an 800-mesh filter bag and soaked in water for 24 hours. After being drained, the water-containing filter bag was placed in a water-resistant isostatic pressure device. The pressure increase rate was set to 1 Psi / second, and the pressure was maintained for 2 minutes at every 100 Psi. Finally, the pressure was increased to the maximum pressure of 300 Psi and maintained for 30 minutes. After the pressure was increased, the hollow microspheres that floated on the surface were selected by gravity buoyancy and dried. The compressive strength was tested by a hollow glass microsphere (air) pressure tester and found to reach 400 Psi (20% breakage rate).

[0026] Example 2: Similar to the above case, the density of the M-series hollow glass microsphere raw powder was selected as 0.406 g / cm3, and the standard compressive strength was 6,000 Psi (20% breakage rate). Using the above method, the pressure was increased at a rate of 5 Psi / second, and the pressure was maintained at 1500 Psi for 2 minutes to reach the maximum pressure of 8,800 Psi. After pressing, the material was re-gravity bleached and dried. The compressive strength was tested by a hollow glass microsphere (air) pressure tester and found to reach 10,500 Psi (20% breakage rate).

[0027] Example 3: H-series hollow glass microspheres with a density of 0.650 g / cm3 and a standard compressive strength of 8,000 Psi (20% breakage rate) were selected. Using the above method, the pressure was increased at a rate of 10 Psi / second, and the pressure was maintained at 1500 Psi for 2 minutes to reach the maximum pressure of 10,000 Psi. After pressing, the microspheres were re-gravity-blended and dried. The compressive strength was tested by a hollow glass microsphere (air) pressure tester and found to reach 12,000 Psi (20% breakage rate).

[0028] like Figure 2 As shown in the figure, the hollow microspheres are compared before and after water isostatic pressure resistance in the above embodiment. It can be clearly seen from the figure that after the operation, the uniformity and integrity of the hollow microspheres are greatly improved, thereby improving the strength.

[0029] The above detailed embodiments provide a specific description of the analytical methods involved in this invention. It should be noted that the above description is only intended to help those skilled in the art better understand the methods and ideas of this invention, and is not intended to limit the scope of the invention. Without departing from the principles of this invention, those skilled in the art can make appropriate adjustments or modifications to this invention, and such adjustments and modifications should also fall within the protection scope of this invention.

Claims

1. A method of enhancing the compressive strength of hollow microspheres, characterized by, It comprises the following steps: (1) Before pressing, the original powder of hollow microsphere is put in filter cloth bag and soaked in water; the specification of the filter cloth bag is 200-1000 mesh; (2) The filter cloth bag containing water is placed in a water-isostatic pressure equipment, and the water-isostatic pressure equipment is used to increase the pressure at a rate of 1-30 psi / s; after each preset interval, the pressure is maintained for 2 minutes before the pressure is increased again; the preset interval ranges from 100 to 1500 psi; after the pressure is increased to the highest pressure, the pressure is maintained for 30-60 minutes before the pressure is released; the highest pressure is determined according to the density of the hollow microsphere; (3) The hollow microsphere after pressing is subjected to gravity elutriation to remove broken glass microspheres, and the hollow microspheres floating on the water surface are selected; (4) The reobtained hollow microspheres are detected by a pressure detection equipment to detect the compression strength value, thereby obtaining a superhigh-pressure hollow microsphere.

2. The method of claim 1, wherein the hollow microsphere has a diameter of 0.1 to 10 mm. The soaking time in step (1) is 12-24 hours.

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