A geopolymer material with multi-level pore coordinated regulation and its preparation method

Abstract

The present invention discloses a geopolymer material with multi-level pore coordinated control and a preparation method thereof, belonging to the technical field of inorganic porous materials. The material is composed of a geopolymer matrix, hollow glass microspheres, nano-oxide particles, a chemical foaming agent, and a surfactant. Through a three-level coordinated structure of millimeter-scale pores, micron-scale pores, and nano-scale pores, the material has a porosity greater than 85%, while achieving coordinated optimization of thermal conductivity (≤0.060 W / (m·K)) and compressive strength (≥0.3 MPa). The preparation method comprises: mixing water glass with alkaline solution to prepare an activator, mixing it with a metakaolin matrix, and then sequentially adding a surfactant, HGB, and nanoparticles, and finally introducing a foaming agent for injection molding and curing. By regulating the HGB particle size, the specific surface area of ​​the nanoparticles, and the amount of foaming agent, the pore distribution can be optimized to meet the differentiated requirements for material strength and thermal conductivity in fields such as building insulation and industrial thermal insulation.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic porous materials, and in particular to a geopolymer material with multi-level pore coordinated regulation and a preparation method thereof. Background Art

[0002] The construction industry is a key area of ​​energy consumption in my country. The energy consumption caused by heat transfer in its building envelope accounts for more than 70%. The development of high-efficiency and energy-saving insulation materials has become a key breakthrough in reducing building energy consumption. Among the mainstream insulation materials in the current market, organic materials (such as polystyrene and polyurethane) have low thermal conductivity (0.02-0.04W / (m·K)), but their flammability leads to significant fire hazards. The toxic smoke released during combustion seriously threatens life safety. Inorganic materials (such as rock wool and foam glass) have excellent fire resistance, but due to their high bulk density (≥150kg / m 3 ), the thermal conductivity is relatively high (0.04-0.07W / (m·K)), which makes it difficult to take into account both thermal insulation and lightweight structure requirements.

[0003] Geopolymers (geopolymers), as a new type of inorganic cementitious material, are considered a promising thermal insulation substrate due to their high mechanical strength (compressive strength ≥ 20 MPa), excellent fire resistance (fire resistance limit ≥ 2 hours), and low-carbon preparation process. However, due to their low porosity, traditional dense geopolymers often have a thermal conductivity exceeding 0.1 W / (m·K), which cannot meet the requirements of building insulation. In recent years, researchers have introduced porosity into geopolymers through methods such as chemical foaming and the addition of lightweight aggregates. However, simply manipulating a single pore structure is difficult to achieve the thermal conductivity required for use as a building insulation material. Furthermore, reducing thermal conductivity inevitably sacrifices strength, affecting the proper use of the insulation material.

[0004] These technical bottlenecks demonstrate significant limitations in the pore structure design of existing porous geopolymer materials: A single pore size makes it difficult to achieve a synergistic balance between thermal insulation and mechanical properties, while simply stacking multiple porous components can easily lead to interfacial defects and strength loss. Therefore, precisely controlling multiple levels of pore size to achieve a synergistic improvement in thermal conductivity and compressive strength while maintaining high porosity has become a key challenge in breaking through the application barriers of geopolymer insulation materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a geopolymer material with multi-level pore coordinated regulation and a preparation method thereof, so as to solve the problems raised in the above background technology, achieve low thermal conductivity while ensuring high porosity of the material, and also have good compressive resistance.

[0006] To achieve the above object, the present invention provides a geopolymer material with multi-level pore coordinated control, which comprises, by weight, 100 parts of a geopolymer matrix, 3-15 parts of hollow glass microspheres, 0.5-4 parts of nanoparticles, 1-6 parts of a chemical foaming agent, and 1-3 parts of a surfactant;

[0007] The geopolymer material has a three-level pore structure:

[0008] (a) The volume of millimeter-scale pores with a size of 100 μm to 3 mm accounts for 30-50%;

[0009] (b) The volume of micron-sized pores of 1-100 μm accounts for 20-40%;

[0010] (c) Nanopores <1 μm account for 10-30% of the volume.

[0011] Preferably, the geopolymer matrix is ​​one or both of metakaolin and fly ash.

[0012] Preferably, the hollow glass microspheres have a particle size of 10-100 μm and a true density of 0.28-0.51 g / cm 3 , the floating rate is ≥90%.

[0013] Preferably, the nanoparticles are one or both of fumed silica and aerogel silica powder; wherein the specific surface area of ​​fumed silica is ≥200m 2 / g, particle size is 10-50nm; the particle size of aerogel silica powder is ≤100nm.

[0014] Preferably, the nanoparticles are a mixture of fumed silica and aerogel silica powder, wherein the mass ratio of fumed silica to aerogel silica powder is 1:1-1:3.

[0015] Preferably, the chemical foaming agent is aluminum powder or hydrogen peroxide with a concentration of 30-35%.

[0016] Preferably, the surfactant is one of benzalkonium chloride, sodium lauryl sulfate or dioctyl sodium sulfosuccinate.

[0017] The present invention also provides a method for preparing the above-mentioned geopolymer material with multi-level pore coordinated regulation, which specifically comprises the following steps:

[0018] (1) Mix water glass and sodium hydroxide solution and let it stand for 12-24 hours to prepare an alkaline activator;

[0019] (2) Mix the geopolymer matrix and the alkali activator and stir for 10-20 minutes;

[0020] (3) Add surfactant, hollow glass microspheres, and nanoparticles in sequence and stir for 5-10 minutes;

[0021] (4) Add chemical foaming agent, stir rapidly for 30-60 seconds and then inject into the mold;

[0022] (5) Curing at 60±5℃ for 12-24h, and curing at room temperature for 7 days after demoulding.

[0023] Preferably, the modulus of water glass is 1.5-3.3, the concentration of the sodium hydroxide solution is 6-10 mol / L, and the mass ratio of water glass to sodium hydroxide is 7-8:1.

[0024] Preferably, the liquid-to-solid mass ratio of the geopolymer matrix to the alkali activator is 0.35-0.45.

[0025] The present invention incorporates different pore-forming materials into a geopolymer matrix to create pores of varying sizes within the geopolymer. The pore sizes vary significantly, ranging from 3 mm to 10 nm. Large pores help reduce density and decrease the solid-phase thermal conductivity of the framework, while medium pores act as a transitional mechanism, reducing thermal conductivity while maintaining a certain strength. Small pores effectively reduce convective heat transfer within the pores, thereby lowering thermal conductivity. This achieves a synergistic optimization of thermal conductivity and compressive strength, reducing thermal conductivity while increasing compressive strength.

[0026] Therefore, the present invention provides a geopolymer material with multi-level pore coordinated regulation and a preparation method thereof, which has the following beneficial effects:

[0027] (1) The geopolymer thermal insulation material prepared by the present invention has multi-level pores (porosity ≥ 85%) and a density ≤ 0.3 g / cm 3 While ensuring high porosity of the material, it achieves low thermal conductivity (thermal conductivity ≤ 0.060W / (m·K)), and also has good compressive strength (≥ 0.3MPa). The thermal conductivity is 30-40% lower than that of a single foaming process, and the compressive strength is 100-150% higher than that of a system without HGB / nanoparticles. It can meet the differentiated requirements for material strength and thermal conductivity in fields such as building insulation and industrial insulation.

[0028] (2) In addition, the preparation method of the present invention has simple process and low cost, and can also realize the effective utilization of industrial waste fly ash.

[0029] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1The following are structural comparison diagrams of the geopolymer matrix of Example 2 of the present invention and the multi-level porous geopolymer material obtained by doping different pore-forming materials into the geopolymer matrix, wherein (a) shows the millimeter-level pores of the geopolymer matrix; (b) shows the millimeter-level pores of the multi-level porous geopolymer material; (c) shows the micrometer-level pores of the geopolymer matrix; (d) shows the micrometer-level pores of the multi-level porous geopolymer material; (e) shows the nanometer-level pores of the geopolymer matrix; and (f) shows the micrometer-level pores of the multi-level porous geopolymer material. DETAILED DESCRIPTION

[0031] The present invention provides a multi-level porous geopolymer material, which is made of the following raw materials in parts by weight:

[0032] 100 parts of geopolymer matrix (selected from metakaolin or a mixture of metakaolin and fly ash, when a mixture of metakaolin and fly ash is selected, the amount of fly ash added is ≤50%, and preferably the mass ratio of metakaolin to fly ash is 1:1).

[0033] Hollow glass microspheres (HGB) 3-15 parts, particle size 10-100 μm, true density 0.28-0.51 g / cm 3 , floating rate ≥90%.

[0034] 0.5-4 parts of nanoparticles, selected from fumed silica (specific surface area ≥ 200m 2 / g, particle size 10-50nm) or aerogel silica powder (particle size ≤100nm), preferably the mixing mass ratio of fumed silica and aerogel silica powder is 1:1-1:3, more preferably, the mixing mass ratio of fumed silica and aerogel silica powder is 1:1.

[0035] 1-6 parts of chemical foaming agent, which is hydrogen peroxide (concentration 30-35%) or aluminum powder.

[0036] 1-3 parts of surfactant, selected from benzalkonium chloride (BAC), sodium lauryl sulfate or dioctyl sodium sulfosuccinate (OT).

[0037] The multi-level porous geopolymer material has a three-level pore structure:

[0038] (a) Millimeter-scale pores (100 μm-3 mm): generated by chemical foaming agents, accounting for 30-50% of the volume, reducing material density and blocking solid-phase heat transfer.

[0039] (b) Micron-sized pores (1-100 μm): formed by HGB filling, accounting for 20-40% of the volume, enhancing the skeleton strength and inhibiting gas convection.

[0040] (c) Nanoscale pores (<1 μm): They are composed of intrinsic pores and nanoparticle accumulation generated during the curing process of geopolymers, accounting for 10-30% of the volume, increasing the phonon scattering path to reduce radiation heat transfer.

[0041] The multi-level porous geopolymer material has a thermal conductivity of ≤0.055W / (m·K), a compressive strength of ≥0.3MPa, a porosity of ≥85%, and a density of ≤0.3g / cm³.

[0042] In the present invention, the wall thickness of the HGB is 2-5 μm, and when the amount of HGB is 3-8 parts and the amount of nanoparticles is 1-3 parts, the ratio of thermal conductivity to compressive strength is ≤0.15 (W / (m·K)) / MPa.

[0043] The present invention also provides a method for preparing the multi-level porous geopolymer material, comprising the following steps:

[0044] (1) Mix water glass with a modulus of 1.5-3.3 and sodium hydroxide solution (concentration 6-10 mol / L) in a mass ratio of 7-8:1 and let it stand for 12-24 hours to prepare an alkaline activator.

[0045] (2) Mix the geopolymer matrix and the alkali activator (liquid-to-solid ratio 0.35-0.45) and stir for 10-20 minutes.

[0046] (3) Add surfactant, HGB, and nanoparticles in sequence and stir for 5-10 minutes.

[0047] (4) Add chemical foaming agent, stir rapidly for 30-60 seconds and then inject into the mold.

[0048] (5) Curing at 60±5℃ for 12-24h, and curing at room temperature for 7 days after demoulding.

[0049] The technical solution of the present invention is further described below by means of the accompanying drawings and examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Any other changes, modifications, substitutions, combinations, and simplifications made without violating the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the protection scope of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application and belong to the scope of protection of the present invention.

[0050] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.

[0051] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.

[0052] Unless otherwise specified in the present invention, the reagents, instruments, and equipment used are those commonly used by those skilled in the art.

[0053] Example 1

[0054] This embodiment provides a method for preparing a geopolymer material with multi-level pore coordinated regulation, which specifically includes the following steps:

[0055] 1) Mix 12.8 g of sodium hydroxide, 100 g of water glass, and 5.7 g of water, stir for 30 minutes, and let stand for 24 hours to obtain an alkaline activator.

[0056] 2) The alkaline activator was mixed with 123 g of metakaolin and mechanically stirred at a speed of 1000 r / min for 15 minutes to obtain a geopolymer slurry.

[0057] 3) Add 5g of hollow glass microspheres and 2g of fumed silica to the geopolymer slurry, then continue stirring for 5 minutes. Then add 2.5g of 30% hydrogen peroxide, stir evenly, and quickly pour into the mold, then seal with plastic wrap.

[0058] 4) The slurry and the mold were transferred to a 60°C oven for curing for 2 hours. The mold was then removed and the oven was continued to cure at 60°C for 4 hours. The slurry was then removed from the oven and cured at room temperature for 7 days to obtain a porous geopolymer insulation material with multi-level porosity.

[0059] The surface morphology of the samples was captured using SEM, and the pore area percentages were calculated and the volume percentages were estimated. Combined with the pore size distribution results from mercury intrusion and BET tests, the three-level pore structure percentages of the multi-level porosity geopolymer insulation material were calculated. Among them, millimeter-scale pores (100μm-3mm) accounted for 35% of the volume; micron-scale pores (1-100μm) accounted for 35% of the volume; and nanoscale pores (<1μm) accounted for 30% of the volume.

[0060] The porosity of the obtained multi-level porous geopolymer insulation material is 84.9% and the density is 0.26g / cm 3 , thermal conductivity 0.060W / (m·K), compressive strength 0.40MPa.

[0061] Example 2

[0062] This embodiment provides a method for preparing a geopolymer material with multi-level pore coordinated regulation, which specifically includes the following steps:

[0063] 1) Mix 12.8 g of sodium hydroxide, 100 g of water glass, and 5.7 g of water, stir for 30 minutes, and let stand for 24 hours to obtain an alkaline activator.

[0064] 2) The alkaline activator was mixed with 123 g of metakaolin and mechanically stirred at a speed of 1000 r / min for 15 minutes to obtain a geopolymer slurry.

[0065] 3) Add 5g of hollow glass microspheres and 1g of fumed silica + 1g of aerogel powder to the geopolymer slurry, then continue stirring for 5 minutes. Then add 2.5g of 35% hydrogen peroxide, stir evenly, and quickly pour into the mold, then seal with plastic wrap.

[0066] 4) Place the slurry together with the mold in a 60°C oven for curing for 2 hours, then remove the mold and continue curing in a 60°C oven for 4 hours. Then take it out of the oven and cure it at room temperature for 7 days to obtain the following: Figure 1 The porous geopolymer insulation material with multi-level porosity is shown. The surface morphology of the sample was obtained by SEM, and the pore area ratio was calculated and the volume ratio was estimated. Combined with the pore size distribution results of the mercury intrusion method and the BET method, the three-level pore structure ratio of the multi-level porosity geopolymer insulation material was calculated. Among them, the volume of millimeter-level pores of 100μm-3mm accounts for 45%; the volume of micron-level pores of 1-100μm accounts for 35%; and the volume of nano-level pores <1μm accounts for 20%. Figure 1 It can be seen that by adding HGB and nanoparticles, the directional optimization of the three-level pore distribution can be achieved, meeting the differentiated requirements of material strength and thermal conductivity in the fields of building insulation, industrial insulation, etc.

[0067] The porosity of the obtained multi-level porous geopolymer insulation material is 88.9% and the bulk density is 0.25g / cm 3 , thermal conductivity is 0.053W / (m·K) and compressive strength is 0.36MPa.

[0068] Example 3

[0069] This embodiment provides a method for preparing a geopolymer material with multi-level pore coordinated regulation, which specifically includes the following steps:

[0070] 1) Mix 12.8 g of sodium hydroxide, 100 g of water glass, and 5.7 g of water, stir for 30 minutes, and let stand for 24 hours to obtain an alkaline activator.

[0071] 2) 70 g of metakaolin and 70 g of fly ash were mixed, added to the above-mentioned alkali activator, and mechanically stirred at a speed of 1000 r / min for 15 minutes to obtain a geopolymer slurry.

[0072] 3) Add 10g of hollow glass microspheres and 2g of fumed silica to the geopolymer slurry, then continue stirring for 5 minutes. Then add 2.5g of 30% hydrogen peroxide, stir evenly, and quickly pour into the mold, then seal with plastic wrap.

[0073] 4) The slurry and the mold were transferred to a 60°C oven for curing for 2 hours. The mold was then removed and the oven was continued to cure at 60°C for 4 hours. The slurry was then removed from the oven and cured at room temperature for 7 days to obtain a porous geopolymer insulation material with multi-level porosity.

[0074] The surface morphology of the samples was captured using SEM, and the pore area percentages were calculated and the volume percentages were estimated. Combined with the pore size distribution results from mercury intrusion and BET tests, the three-level pore structure percentages of the multi-level porosity geopolymer insulation material were calculated. Among them, millimeter-scale pores (100μm-3mm) accounted for 35% of the volume; micron-scale pores (1-100μm) accounted for 40% of the volume; and nanoscale pores (<1μm) accounted for 25% of the volume.

[0075] The porosity of the obtained multi-level porous geopolymer insulation material is 85.3% and the density is 0.27g / cm 3 , thermal conductivity 0.057W / (m·K), compressive strength 0.42MPa.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a geopolymer material with multi-level pore coordinated regulation, characterized by: The geopolymer material comprises, by weight, 100 parts of a geopolymer matrix, 3-15 parts of hollow glass microspheres, 0.5-4 parts of nanoparticles, 1-6 parts of a chemical foaming agent, and 1-3 parts of a surfactant; The geopolymer material has a three-level pore structure: (a) The volume of millimeter-scale pores with a size of 100 μm to 3 mm accounts for 30-50%; (b) The volume of micron-sized pores of 1-100 μm accounts for 20-40%; (c) Nanopores <1 μm account for 10-30% of the volume; The preparation specifically comprises the following steps: (1) Mix water glass and sodium hydroxide solution and let it stand for 12-24 hours to prepare an alkaline activator; (2) Mix the geopolymer matrix and the alkali activator and stir for 10-20 minutes; (3) Add surfactant, hollow glass microspheres, and nanoparticles in sequence and stir for 5-10 minutes; (4) Add chemical foaming agent, stir rapidly for 30-60 seconds and then inject into the mold; (5) Curing at 60±5℃ for 12-24h, and curing at room temperature for 7 days after demoulding.

2. The method for preparing a geopolymer material with multi-level pore coordinated regulation according to claim 1, characterized in that: The geopolymer matrix is ​​one or both of metakaolin and fly ash.

3. The method for preparing a geopolymer material with multi-level pore coordinated regulation according to claim 1, characterized in that: The hollow glass microspheres have a particle size of 10-100 μm and a true density of 0.28-0.51 g / cm 3 , the floating rate is ≥90%.

4. The method for preparing a geopolymer material with multi-level pore coordinated regulation according to claim 1, characterized in that: The nanoparticles are one or both of fumed silica and aerogel silica powder; wherein the specific surface area of ​​fumed silica is ≥200m 2 / g, particle size is 10-50nm; the particle size of aerogel silica powder is ≤100nm.

5. The method for preparing a geopolymer material with multi-level pore coordinated control according to claim 4, characterized in that: The nanoparticles are a mixture of fumed silica and aerogel silica powder, wherein the mass ratio of fumed silica to aerogel silica powder is 1:1-1:

3.

6. The method for preparing a geopolymer material with multi-level pore coordinated control according to claim 1, characterized in that: The chemical foaming agent is aluminum powder or hydrogen peroxide with a concentration of 30-35%.

7. The method for preparing a geopolymer material with multi-level pore coordinated control according to claim 1, characterized in that: The surfactant is one of benzalkonium chloride, sodium lauryl sulfate or dioctyl sodium sulfosuccinate.

8. The method for preparing a geopolymer material with multi-level pore coordinated control according to claim 1, characterized in that: The modulus of water glass is 1.5-3.3, the concentration of sodium hydroxide solution is 6-10 mol / L, and the mass ratio of water glass to sodium hydroxide is 7~8:

1.

9. The method for preparing a geopolymer material with multi-stage pore coordinated control according to claim 8, characterized in that: The liquid-solid mass ratio of the geopolymer matrix to the alkali activator is 0.35-0.45.

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