A method for preparing microcrystalline foam glass and its application

Abstract

This disclosure relates to the field of microcrystalline glass technology, specifically to a method for preparing microcrystalline foam glass and its application. The preparation method includes: uniformly mixing base glass powder, a first foaming agent, a second foaming agent, and a first nucleating agent to obtain a batch material; wherein the first foaming agent is a carbonate foaming agent; the second foaming agent is a layered bimetallic hydroxide foaming agent; and the first nucleating agent is an oxide nucleating agent; then pressing the batch material into shape; then heating to the foaming temperature; holding at this temperature for 1-2 hours; then cooling to the nucleation temperature; holding at this temperature for 0.5-1 hour; finally heating to the crystallization temperature; holding at this temperature for 1-1.5 hours; to obtain microcrystalline foam glass.

Description

Technical Field

[0001] This disclosure relates to the field of microcrystalline glass technology, specifically to a method for preparing microcrystalline foam glass and its application. Background Technology

[0002] Microcrystalline foam glass is a porous inorganic material that combines the structural characteristics of a glass matrix and a microcrystalline phase. Due to its excellent thermal insulation, sound absorption, high-temperature resistance, and chemical stability, it is widely used in building insulation, industrial kiln linings, and high-temperature filtration. Currently, microcrystalline foam glass is typically prepared using waste glass or basic glass powder as raw materials, incorporating carbonate foaming agents and nucleating agents such as zirconium oxide and titanium dioxide, through processes including high-temperature melting and foaming, cooling nucleation, and reheating crystallization.

[0003] However, existing technologies still have significant shortcomings: on the one hand, conventional carbonate foaming agents decompose rapidly and in a concentrated manner at high temperatures, which can easily lead to excessively high local gas pressure, bubble bursting or merging, resulting in uneven pore size distribution; on the other hand, existing nucleating agents mostly use commercially available dense spherical zirconium dioxide or titanium dioxide, which have limited specific surface area and low surface defect density, and cannot effectively induce microcrystals to precipitate oriented along the bubble wall. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for preparing microcrystalline foam glass and its application, so as to overcome the shortcomings in related technologies.

[0005] According to a first aspect of the present disclosure, a method for preparing microcrystalline foam glass is provided, the method comprising: Step 1: Mix the base glass powder, the first foaming agent, the second foaming agent, and the first nucleating agent evenly to obtain the batch material; Wherein, the first foaming agent is a carbonate foaming agent; the second foaming agent is selected from layered bimetallic hydroxide foaming agents; and the first nucleating agent is selected from oxide nucleating agents. Step 2: Press the compound into shape; then heat to the foaming temperature; keep warm for 1-2 hours; Step 3: Cool to nucleation temperature; hold at this temperature for 0.5-1 hour; Step 4: Heat to the crystallization temperature; keep warm for 1-1.5 hours; obtain the microcrystalline foam glass.

[0006] In one aspect of this disclosure, the carbonate foaming agent is selected from one or more of calcium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, barium carbonate, strontium carbonate, and lithium carbonate. Preferably, the carbonate foaming agent is selected from one or more of calcium carbonate, sodium carbonate, potassium carbonate, and magnesium carbonate. More preferably, the carbonate foaming agent is a mixture of calcium carbonate and sodium carbonate.

[0007] In one aspect of this disclosure, the carbonate foaming agent is a mixture of calcium carbonate and sodium carbonate in a mass ratio of (3-5):1.

[0008] In one aspect of the embodiments of this disclosure, the layered bimetallic hydroxide foaming agent is selected from layered bimetallic hydroxides of intercalated organic acids or organic acid radicals.

[0009] In one aspect of the embodiments of this disclosure, the intercalated organic acid or layered bimetallic hydroxide of organic acid radicals is selected from lactate-intercalated hydrotalcite, cinnamate-intercalated hydrotalcite, citrate-intercalated hydrotalcite, sorbic acid-intercalated hydrotalcite, or ethylenediaminetetraacetic acid-intercalated hydrotalcite.

[0010] In one aspect of this disclosure, the second foaming agent is citrate-intercalated magnesium aluminum hydrotalcite; the citrate-intercalated magnesium aluminum hydrotalcite is prepared through the following steps: Step 1-a: Dissolve sodium citrate in water to obtain a sodium citrate solution; Step 2-a: Dissolve magnesium nitrate hexahydrate and aluminum nitrate nonahydrate in water to obtain a mixed salt solution; Step 3-a: Dissolve sodium hydroxide in water to obtain an alkaline solution; Step 4-a: Under nitrogen protection, the alkaline solution and the mixed salt solution are simultaneously added dropwise to the sodium citrate solution; during the addition process, the dropping rate is controlled so that the pH value of the reaction system is controlled within the range of 10±0.5; after the addition is completed, crystallize at reflux temperature for 5-8 hours. Step 5-a: After the reaction is completed, the citrate-intercalated magnesium aluminum hydrotalcite is obtained by separation, washing and drying.

[0011] In one aspect of the embodiments of this disclosure, preferably, the citrate-intercalated magnesium aluminum hydrotalcite is prepared by the following steps: Step 1-a: Dissolve sodium citrate dihydrate in deionized water to prepare a sodium citrate solution with a concentration of 0.5-1.5 mol / L; Step 2-a: Add magnesium nitrate hexahydrate and aluminum nitrate nonahydrate to deionized water in a molar ratio of Mg:Al = (2-4):1 to prepare a mixed salt solution with a total metal ion concentration of 0.5-2.0 mol / L; Step 3-a: Dissolve sodium hydroxide in deionized water to prepare an alkaline solution with a concentration of 1-3 mol / L; Step 4-a: Under nitrogen protection, the alkaline solution and the mixed salt solution are simultaneously added dropwise to the sodium citrate solution at a dropping rate of 5-20 mL / min; during the addition, the relative dropping rate of the two solutions is controlled so that the pH value of the reaction system is controlled within the range of 10±0.5; after the addition is completed, crystallization is carried out at a reflux temperature of 80°C-100°C for 6-8 hours. Step 5-a: After the reaction is completed, the mixture is separated by centrifugation or filtration, washed with deionized water until the pH of the filtrate is less than 8, and then dried at 60°C for 12-16 hours to obtain the citrate-intercalated magnesium aluminum hydrotalcite.

[0012] In one aspect of the embodiments of this disclosure, the mass ratio of the first foaming agent and the second foaming agent is selected from (2-20):1; preferably (5-10):1.

[0013] In one aspect of this disclosure, the first nucleating agent is selected from one or more of zirconium dioxide, titanium dioxide, phosphorus pentoxide, chromium trioxide, ferric oxide, nickel oxide, cerium dioxide, and vanadium pentoxide. Preferably, the first nucleating agent is selected from one or more of zirconium dioxide, titanium dioxide, and cerium dioxide. More preferably, the first nucleating agent is zirconium dioxide.

[0014] In one aspect of the embodiments of this disclosure, specifically, the first nucleating agent is zirconium dioxide prepared by using chitosan as a template.

[0015] In one aspect of this disclosure, the zirconium dioxide prepared using chitosan as a template is obtained through the following steps: Step 1-b: Add chitosan to an aqueous acetic acid solution and stir for 1-2 hours to obtain a chitosan solution; Step 2-b: Dissolve zirconium oxynitrate in water to obtain a salt solution; Step 3-b: Add the salt solution to the chitosan solution and stir vigorously for 2-4 hours to obtain a mixed solution; Step 4-b: Add the mixed solution dropwise to the ammonia solution while stirring. After the addition is complete, continue stirring for 1-3 hours, and then let it stand for 4-8 hours. Step 5-b: Then filter, wash, and dry to obtain a solid; the solid is then heat-treated to obtain the zirconium dioxide prepared by using chitosan as a template.

[0016] In one aspect of the embodiments of this disclosure, in step 5-b, the heat treatment is as follows: heating to 400℃-600℃ at a heating rate of 2-5℃ / min, holding at that temperature for 2-5 hours; and then naturally cooling to room temperature.

[0017] In one aspect of this disclosure, preferably, the zirconium dioxide prepared using chitosan as a template is obtained through the following steps: Step 1-b: Add chitosan with a degree of deacetylation ≥90% and a molecular weight of 100,000-200,000 to an aqueous solution of acetic acid with a volume fraction of 1%-3%, and stir for 1-2 hours until completely dissolved to obtain a chitosan solution; Step 2-b: Dissolve zirconium oxynitrate in deionized water to prepare a salt solution with a zirconium ion concentration of 0.25-1.75 mol / L; Step 3-b: Add the salt solution to the chitosan solution at a mass ratio of chitosan to zirconium of (1-3):1, and mix vigorously for 2-4 hours to obtain a mixed solution; Step 4-b: Add the mixed solution dropwise to an ammonia solution that is being stirred, wherein the mass fraction of the ammonia solution is 25%-28%; after the addition is complete, continue stirring for 1-3 hours, and then let it stand for 4-8 hours to age. Step 5-b: Filtration, washing with deionized water until the filtrate is neutral, then drying the filtered solid at 60°C-80°C for 12-24 hours to obtain the precursor solid; heating the precursor solid to 475°C-525°C at a heating rate of 2-3°C / min, holding at that temperature for 2-4 hours, and then naturally cooling to room temperature to obtain the zirconium dioxide prepared by using chitosan as a template.

[0018] In one aspect of this disclosure, the base glass powder is a sodium-calcium silicate system glass powder, comprising, by mass percentage: 50%-75% SiO2, 10%-18% (Na2O + K2O), 5%-15% (CaO + MgO), and 1%-8% Al2O3; the balance being unavoidable impurities. Preferably, the base glass powder comprises, by mass percentage: 60%-75% SiO2, 12%-18% (Na2O + K2O), 8%-15% (CaO + MgO), and 1%-5% Al2O3; the balance being unavoidable impurities. More preferably, the base glass powder comprises, by mass percentage: 65%-72% SiO2, 13%-16% (Na2O + K2O), 9%-12% (CaO + MgO), and 1%-3% Al2O3; the balance being unavoidable impurities.

[0019] In one aspect of the embodiments of this disclosure, specifically, the base glass powder comprises, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance being unavoidable impurities.

[0020] In one aspect of the embodiments of this disclosure, the foaming temperature is selected from 1000℃-1100℃; the nucleation temperature is selected from 700℃-750℃; and the crystallization temperature is selected from 850℃-900℃.

[0021] According to a second aspect of the present disclosure, a microcrystalline foam glass is provided, which is prepared by the aforementioned preparation method.

[0022] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects: As can be seen from the above embodiments, the present invention achieves a more uniform pore size distribution and improved compressive strength of microcrystalline foam glass through the interaction of a dual foaming system and a chitosan template zirconium dioxide nucleating agent.

[0023] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0024] Figure 1 This is a SEM image of the zirconium dioxide prepared in Example 1 of this disclosure. Detailed Implementation

[0025] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0027] For the sake of brevity, this article only discloses a few specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0028] In this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0029] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0030] Unless otherwise stated, the terms used in this disclosure have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this disclosure can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this disclosure).

[0031] The term "about" is used to describe and indicate small variations. When used in conjunction with an event or situation, the term may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format herein. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0032] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0033] The present disclosure will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present disclosure are obtained through conventional commercial means. Unless otherwise specified, all contents mentioned below are mass contents. Unless otherwise specified, it is understood that the process is carried out at room temperature.

[0034] Example Example 1: Example 1 includes the following steps: 1. Preparation of citrate-intercalated magnesium aluminum hydrotalcite: Dissolve 18.4 g of sodium citrate dihydrate in 100 mL of deionized water to obtain a sodium citrate solution. Dissolve 20.0 g of magnesium nitrate hexahydrate and 15.0 g of aluminum nitrate nonahydrate in 100 mL of deionized water to obtain a mixed salt solution. Dissolve 8.0 g of sodium hydroxide in 100 mL of deionized water to obtain an alkaline solution.

[0035] Under nitrogen protection, an alkaline solution and a mixed salt solution were simultaneously added dropwise to a sodium citrate solution. The addition was monitored using a pH meter, and the dropping rate was controlled to maintain the pH of the reaction system within the range of 10 ± 0.5. After the addition was complete, the mixture was crystallized at 92°C for 6 hours. After the reaction was finished, the mixture was centrifuged, washed thoroughly with deionized water until the pH of the filtrate was < 8, and then dried at 60°C for 14 hours to obtain citrate-intercalated magnesium aluminum hydrotalcite.

[0036] 2. Preparation of chitosan-template zirconium dioxide: 2.0 g of chitosan with a degree of deacetylation ≥90% and a molecular weight of 100,000-200,000 was added to 100 mL of a 2% (v / v) aqueous acetic acid solution and stirred for 1.5 h until completely dissolved to obtain a chitosan solution. 3.5 g of zirconium oxynitrate was dissolved in 20 mL of deionized water to prepare a salt solution. The salt solution was added to the chitosan solution and stirred vigorously for 3 h (magnetic stirring at 800 rpm) to obtain a mixed solution. This mixed solution was added dropwise to 200 mL of a 25% (w / w) aqueous ammonia solution, and stirring was continued for 2 h after the addition was complete, followed by aging for 6 h. The solution was filtered, washed with deionized water until the filtrate was neutral, and the resulting solid was dried at 60°C for 18 h to obtain the precursor solid.

[0037] The precursor solid was heated to 500°C at a heating rate of 2°C / min and held at that temperature for 3 hours, then naturally cooled to room temperature to obtain zirconium dioxide prepared using chitosan as a template; its SEM image is shown below. Figure 1 As shown.

[0038] 3. Preparation of microcrystalline foam glass: Prepare the raw materials according to the following mass proportions: 100g of basic glass powder, 2.4g of calcium carbonate, 0.6g of sodium carbonate, 0.3g of the aforementioned citrate-intercalated magnesium aluminum hydrotalcite, and 0.5g of the aforementioned chitosan template zirconium dioxide.

[0039] The base glass powder contains, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance is unavoidable impurities.

[0040] The above raw materials were placed in a ball mill and dry-mixed for 2 hours to obtain a batch. The batch was then loaded into a mold and pressed into a 50mm×50mm×30mm blank under a pressure of 15MPa.

[0041] The molded preform is placed in a high-temperature furnace and heat-treated according to the following process: foaming stage: heated to 1050°C at a heating rate of 4°C / min and held for 1.5h; nucleation stage: cooled to 720°C at a cooling rate of 12°C / min and held for 0.5h; crystallization stage: heated to 880°C at a heating rate of 8°C / min and held for 1.0h; finally cooled to room temperature with the furnace to obtain the microcrystalline foam glass of this embodiment.

[0042] Example 2: Example 2 includes the following steps: 1. Preparation of citrate-intercalated magnesium aluminum hydrotalcite: Dissolve 18.4 g of sodium citrate dihydrate in 100 mL of deionized water to obtain a sodium citrate solution. Dissolve 20.0 g of magnesium nitrate hexahydrate and 15.0 g of aluminum nitrate nonahydrate in 100 mL of deionized water to obtain a mixed salt solution. Dissolve 8.0 g of sodium hydroxide in 100 mL of deionized water to obtain an alkaline solution.

[0043] Under nitrogen protection, an alkaline solution and a mixed salt solution were simultaneously added dropwise to a sodium citrate solution. The addition was monitored using a pH meter, and the dropping rate was controlled to maintain the pH of the reaction system within the range of 10 ± 0.5. After the addition was complete, the mixture was crystallized at 92°C for 6 hours. After the reaction was finished, the mixture was centrifuged, washed thoroughly with deionized water until the pH of the filtrate was < 8, and then dried at 60°C for 14 hours to obtain citrate-intercalated magnesium aluminum hydrotalcite.

[0044] 2. Preparation of microcrystalline foam glass: Prepare the raw materials according to the following mass proportions: 100g of basic glass powder, 2.4g of calcium carbonate, 0.6g of sodium carbonate, 0.3g of the aforementioned citrate-intercalated magnesium aluminum hydrotalcite, and 0.5g of zirconium dioxide (commercially available, with a D50 particle size of 5μm, and a monoclinic / tetragonal mixed crystal form).

[0045] The base glass powder contains, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance is unavoidable impurities.

[0046] The above raw materials were placed in a ball mill and dry-mixed for 2 hours to obtain a batch. The batch was then loaded into a mold and pressed into a 50mm×50mm×30mm blank under a pressure of 15MPa.

[0047] The molded preform is placed in a high-temperature furnace and heat-treated according to the following process: foaming stage: heated to 1050°C at a heating rate of 4°C / min and held for 1.5h; nucleation stage: cooled to 720°C at a cooling rate of 12°C / min and held for 0.5h; crystallization stage: heated to 880°C at a heating rate of 8°C / min and held for 1.0h; finally cooled to room temperature with the furnace to obtain the microcrystalline foam glass of this embodiment.

[0048] Example 3: Example 3 includes the following steps: 1. Preparation of citrate-intercalated magnesium aluminum hydrotalcite: Dissolve 18.4 g of sodium citrate dihydrate in 100 mL of deionized water to obtain a sodium citrate solution. Dissolve 20.0 g of magnesium nitrate hexahydrate and 15.0 g of aluminum nitrate nonahydrate in 100 mL of deionized water to obtain a mixed salt solution. Dissolve 8.0 g of sodium hydroxide in 100 mL of deionized water to obtain an alkaline solution.

[0049] Under nitrogen protection, an alkaline solution and a mixed salt solution were simultaneously added dropwise to a sodium citrate solution. The addition was monitored using a pH meter, and the dropping rate was controlled to maintain the pH of the reaction system within the range of 10 ± 0.5. After the addition was complete, the mixture was crystallized at 92°C for 6 hours. After the reaction was finished, the mixture was centrifuged, washed thoroughly with deionized water until the pH of the filtrate was < 8, and then dried at 60°C for 14 hours to obtain citrate-intercalated magnesium aluminum hydrotalcite.

[0050] 2. Preparation of microcrystalline foam glass: Prepare the raw materials according to the following mass proportions: 100g of basic glass powder, 2.4g of calcium carbonate, 0.6g of sodium carbonate, 0.3g of the aforementioned citrate-intercalated magnesium aluminum hydrotalcite, and 0.5g of zirconium dioxide (commercially available, with a D50 particle size of 1μm, and a monoclinic / tetragonal mixed crystal form).

[0051] The base glass powder contains, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance is unavoidable impurities.

[0052] The above raw materials were placed in a ball mill and dry-mixed for 2 hours to obtain a batch. The batch was then loaded into a mold and pressed into a 50mm×50mm×30mm blank under a pressure of 15MPa.

[0053] The molded preform is placed in a high-temperature furnace and heat-treated according to the following process: foaming stage: heated to 1050°C at a heating rate of 4°C / min and held for 1.5h; nucleation stage: cooled to 720°C at a cooling rate of 12°C / min and held for 0.5h; crystallization stage: heated to 880°C at a heating rate of 8°C / min and held for 1.0h; finally cooled to room temperature with the furnace to obtain the microcrystalline foam glass of this embodiment.

[0054] Comparative Example 1: Comparative Example 1 includes the following steps: Prepare the raw materials according to the following mass proportions: 100g basic glass powder, 2.6g calcium carbonate, 0.7g sodium carbonate, and 0.5g zirconium dioxide (commercially available, with a D50 particle size of 1μm, monoclinic / tetragonal mixed crystal form).

[0055] The base glass powder contains, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance is unavoidable impurities.

[0056] The above raw materials were placed in a ball mill and dry-mixed for 2 hours to obtain a batch. The batch was then loaded into a mold and pressed into a 50mm×50mm×30mm blank under a pressure of 15MPa.

[0057] The preform was placed in a high-temperature furnace and heat-treated according to the following process: foaming stage: heated to 1050°C at a heating rate of 4°C / min and held for 1.5h; nucleation stage: cooled to 720°C at a cooling rate of 12°C / min and held for 0.5h; crystallization stage: heated to 880°C at a heating rate of 8°C / min and held for 1.0h; finally cooled to room temperature with the furnace to obtain the microcrystalline foam glass of this comparative example.

[0058] Comparative Example 2: Comparative Example 2 includes the following steps: 1. Preparation of chitosan-template zirconium dioxide: 2.0 g of chitosan with a degree of deacetylation ≥90% and a molecular weight of 100,000-200,000 was added to 100 mL of a 2% (v / v) aqueous acetic acid solution and stirred for 1.5 h until completely dissolved to obtain a chitosan solution. 3.5 g of zirconium oxynitrate was dissolved in 20 mL of deionized water to prepare a salt solution. The salt solution was added to the chitosan solution and stirred vigorously for 3 h (magnetic stirring at 800 rpm) to obtain a mixed solution. This mixed solution was added dropwise to 200 mL of a 25% (w / w) aqueous ammonia solution, and stirring was continued for 2 h after the addition was complete, followed by aging for 6 h. The solution was filtered, washed with deionized water until the filtrate was neutral, and the resulting solid was dried at 60°C for 18 h to obtain the precursor solid.

[0059] The precursor solid was heated to 500°C at a heating rate of 2°C / min, held at that temperature for 3 hours, and then naturally cooled to room temperature to obtain zirconium dioxide prepared by using chitosan as a template.

[0060] 2. Preparation of microcrystalline foam glass: Prepare the raw materials according to the following mass proportions: 100g of basic glass powder, 2.6g of calcium carbonate, 0.7g of sodium carbonate, and 0.5g of the chitosan template zirconium dioxide prepared above.

[0061] The base glass powder contains, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance is unavoidable impurities.

[0062] The above raw materials were placed in a ball mill and dry-mixed for 2 hours to obtain a batch. The batch was then loaded into a mold and pressed into a 50mm×50mm×30mm blank under a pressure of 15MPa.

[0063] The preform was placed in a high-temperature furnace and heat-treated according to the following process: foaming stage: heated to 1050°C at a heating rate of 4°C / min and held for 1.5h; nucleation stage: cooled to 720°C at a cooling rate of 12°C / min and held for 0.5h; crystallization stage: heated to 880°C at a heating rate of 8°C / min and held for 1.0h; finally cooled to room temperature with the furnace to obtain the microcrystalline foam glass of this comparative example.

[0064] Example 4: Example 4 includes the following steps: 1. Preparation of lactate-intercalated magnesium aluminum hydrotalcite: 20.0 g magnesium nitrate hexahydrate and 15.0 g aluminum nitrate nonahydrate were dissolved in 100 mL of deionized water to obtain a mixed salt solution; 5.0 g sodium hydroxide and 5.3 g anhydrous sodium carbonate were dissolved in 100 mL of deionized water to obtain a mixed alkali solution; the mixed salt solution was placed in a three-necked flask, and the mixed alkali solution was added under rapid stirring with a magnetic stirrer, and stirring was continued for 10 min; then the mixture was refluxed at 100°C for 8 h for crystallization; after the reaction was completed, the mixture was filtered, washed with water, soaked in ethanol, and then dried at 60°C for 12 h, and then ground to obtain carbonate-type hydrotalcite precursor powder.

[0065] Weigh 5.6g of carbonate-type hydrotalcite precursor powder and add it to ethylene glycol; dissolve 3.74g of 60% sodium lactate aqueous solution in 40mL of deionized water, then pour it into ethylene glycol, adjust the pH of the system to 4.5 with dilute nitric acid, pour the mixture into a three-necked flask, and reflux and stir at 120°C for 3h; after the reaction is completed, filter, wash with water, dry at 100°C for 12h, and grind to obtain lactate-intercalated magnesium aluminum hydrotalcite.

[0066] 2. Preparation of chitosan-template zirconium dioxide: The steps here are the same as in Example 1.

[0067] 3. Preparation of microcrystalline foam glass: Prepare the raw materials according to the following mass proportions: 100g of basic glass powder, 2.4g of calcium carbonate, 0.6g of sodium carbonate, 0.3g of the lactate-intercalated magnesium aluminum hydrotalcite prepared above, and 0.5g of the chitosan template zirconium dioxide prepared above.

[0068] The base glass powder contains, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance is unavoidable impurities.

[0069] The above raw materials were placed in a ball mill and dry-mixed for 2 hours to obtain a batch. The batch was then loaded into a mold and pressed into a 50mm×50mm×30mm blank under a pressure of 15MPa.

[0070] The molded preform is placed in a high-temperature furnace and heat-treated according to the following process: foaming stage: heated to 1050°C at a heating rate of 4°C / min and held for 1.5h; nucleation stage: cooled to 720°C at a cooling rate of 12°C / min and held for 0.5h; crystallization stage: heated to 880°C at a heating rate of 8°C / min and held for 1.0h; finally cooled to room temperature with the furnace to obtain the microcrystalline foam glass of this embodiment.

[0071] Example 5: Example 5 includes the following steps: 1. Preparation of cinnamate-intercalated magnesium aluminum hydrotalcite: 11.0 g of magnesium nitrate hexahydrate and 9.9 g of aluminum nitrate nonahydrate were dissolved in 100 mL of deionized water to obtain a mixed salt solution; 6.2 g of cinnamic acid was dissolved in ethanol to obtain a cinnamic acid ethanol solution; 6 g of sodium hydroxide was dissolved in 100 mL of deionized water to obtain an alkaline solution; the mixed salt solution was placed in a three-necked flask, and the cinnamic acid ethanol solution was slowly added under stirring, followed by the alkaline solution, and the temperature was controlled at 70°C with stirring and reflux for 3 h; after the reaction was completed, the mixture was filtered, washed with water, soaked in ethanol, and then dried at 60°C for 12 h, and ground to obtain cinnamate-intercalated magnesium aluminum hydrotalcite.

[0072] 2. Preparation of chitosan-template zirconium dioxide: The steps here are the same as in Example 1.

[0073] 3. Preparation of microcrystalline foam glass: Prepare the raw materials according to the following mass proportions: 100g of basic glass powder, 2.4g of calcium carbonate, 0.6g of sodium carbonate, 0.3g of the aforementioned cinnamate-intercalated magnesium aluminum hydrotalcite, and 0.5g of the aforementioned chitosan template zirconium dioxide.

[0074] The base glass powder contains, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance is unavoidable impurities.

[0075] The above raw materials were placed in a ball mill and dry-mixed for 2 hours to obtain a batch. The batch was then loaded into a mold and pressed into a 50mm×50mm×30mm blank under a pressure of 15MPa.

[0076] The molded preform is placed in a high-temperature furnace and heat-treated according to the following process: foaming stage: heated to 1050°C at a heating rate of 4°C / min and held for 1.5h; nucleation stage: cooled to 720°C at a cooling rate of 12°C / min and held for 0.5h; crystallization stage: heated to 880°C at a heating rate of 8°C / min and held for 1.0h; finally cooled to room temperature with the furnace to obtain the microcrystalline foam glass of this embodiment.

[0077] Example 6: Example 6 includes the following steps: 1. Preparation of borate-intercalated magnesium aluminum hydrotalcite: 20.0 g magnesium nitrate hexahydrate and 15.0 g aluminum nitrate nonahydrate were dissolved in 100 mL of deionized water to obtain a mixed salt solution; 5.0 g sodium hydroxide and 5.3 g anhydrous sodium carbonate were dissolved in 100 mL of deionized water to obtain a mixed alkali solution; the mixed salt solution was placed in a three-necked flask, and the mixed alkali solution was added under rapid stirring with a magnetic stirrer, and stirring was continued for 10 min; then the mixture was refluxed at 100°C for 8 h for crystallization; after the reaction was completed, the mixture was filtered, washed with water, soaked in ethanol, and then dried at 60°C for 12 h, and then ground to obtain carbonate-type hydrotalcite precursor powder.

[0078] Weigh 5.0g of the above-mentioned carbonate-type magnesium aluminum hydrotalcite precursor powder, add it to 100mL of hot water, stir well, and pour it into a three-necked flask. Heat and stir. Weigh 3.0g of boric acid, dissolve it in 50mL of hot water, and add it dropwise to the three-necked flask using a burette. At the same time, use a pH meter to test the pH value of the mixture and adjust it with dilute nitric acid to maintain it at around 3.5. After the addition is complete, start heating and stirring, and reflux the reaction at 85°C for 2 hours. After the reaction is complete, filter it with hot water until neutral, and then dry it at 60°C for 12 hours. Grind it to obtain borate-intercalated magnesium aluminum hydrotalcite.

[0079] 2. Preparation of chitosan-template zirconium dioxide: The steps here are the same as in Example 1.

[0080] 3. Preparation of microcrystalline foam glass: Prepare the raw materials according to the following mass proportions: 100g of basic glass powder, 2.4g of calcium carbonate, 0.6g of sodium carbonate, 0.3g of the aforementioned borate-intercalated magnesium aluminum hydrotalcite, and 0.5g of the aforementioned chitosan-template zirconium dioxide.

[0081] The base glass powder contains, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance is unavoidable impurities.

[0082] The above raw materials were placed in a ball mill and dry-mixed for 2 hours to obtain a batch. The batch was then loaded into a mold and pressed into a 50mm×50mm×30mm blank under a pressure of 15MPa.

[0083] The molded preform is placed in a high-temperature furnace and heat-treated according to the following process: foaming stage: heated to 1050°C at a heating rate of 4°C / min and held for 1.5h; nucleation stage: cooled to 720°C at a cooling rate of 12°C / min and held for 0.5h; crystallization stage: heated to 880°C at a heating rate of 8°C / min and held for 1.0h; finally cooled to room temperature with the furnace to obtain the microcrystalline foam glass of this embodiment.

[0084] Example 7: Example 7 includes the following steps: 1. Preparation of magnesium aluminum hydrotalcite: 20.0 g of magnesium nitrate hexahydrate and 15.0 g of aluminum nitrate nonahydrate were dissolved in 100 mL of deionized water and stirred until completely dissolved to obtain a mixed salt solution. 9.6 g of NaOH and 3.2 g of Na₂CO₃ were weighed and dissolved in 100 mL of deionized water and stirred until dissolved. The mixed salt solution was placed in a 70°C water bath, and the above-mentioned alkaline solution was slowly added dropwise under vigorous stirring, controlling the adding rate to maintain the pH of the reaction system at 10 ± 0.5; a white precipitate appeared during the addition. After the addition was complete, the mixture was kept at this temperature and stirred for 3 hours to age. After the reaction solution cooled to room temperature, the precipitate was separated by filtration, washed with deionized water, and then dried at 60°C for 12 hours. The resulting product, magnesium aluminum hydrotalcite, was obtained by grinding.

[0085] 2. Preparation of chitosan-template zirconium dioxide: The steps here are the same as in Example 1.

[0086] 3. Preparation of microcrystalline foam glass: Prepare the raw materials according to the following mass proportions: 100g of basic glass powder, 2.4g of calcium carbonate, 0.6g of sodium carbonate, 0.3g of the aforementioned prepared magnesium aluminum hydrotalcite, and 0.5g of the aforementioned prepared chitosan template zirconium dioxide.

[0087] The base glass powder contains, by mass percentage: 70.5% SiO2, 13.0% Na2O, 1.0% K2O, 9.0% CaO, 2.0% MgO, and 1.5% Al2O3; the balance is unavoidable impurities.

[0088] The above raw materials were placed in a ball mill and dry-mixed for 2 hours to obtain a batch. The batch was then loaded into a mold and pressed into a 50mm×50mm×30mm blank under a pressure of 15MPa.

[0089] The molded preform is placed in a high-temperature furnace and heat-treated according to the following process: foaming stage: heated to 1050°C at a heating rate of 4°C / min and held for 1.5h; nucleation stage: cooled to 720°C at a cooling rate of 12°C / min and held for 0.5h; crystallization stage: heated to 880°C at a heating rate of 8°C / min and held for 1.0h; finally cooled to room temperature with the furnace to obtain the microcrystalline foam glass of this embodiment.

[0090] The standard deviation of pore size distribution and the values ​​of compressive strength for Examples 1-7 and Comparative Examples 1-2 are shown in Table 1 below. The test procedure for the standard deviation of pore size distribution is as follows: diamond wire cutting of the sample, cleaning with anhydrous ethanol, vacuum drying and then gold sputtering treatment; then taking SEM images of the sample cross-section, using image analysis to count the equivalent circle diameter of no less than 200 pores, and calculating the standard deviation σ; the smaller σ is, the more uniform the pore size distribution.

[0091] Table 1

[0092] Comparing Example 3 and Comparative Example 1, it can be seen that the introduction of citrate-intercalated hydrotalcite significantly reduces the standard deviation of pore size, proving that the interlayer citrate in the intercalated hydrotalcite pre-decomposes during the foaming stage, forming a primary microporous network, reducing the local gas pressure in the main carbonate foaming process, and improving pore size uniformity. Comparing Examples 1 and Examples 4-7, it can be seen that lactate-intercalated hydrotalcite (Example 4) is more effective than pure hydrotalcite (Example 7), but citrate-intercalated hydrotalcite (Example 1) is significantly the best; while borate-intercalated hydrotalcite (Example 6) and cinnamate-intercalated hydrotalcite (Example 5) show a decline in compressive strength and pore size uniformity compared to Example 7, indicating that not all intercalations can produce a positive effect.

[0093] Depend on Figure 1 As can be seen, the zirconium dioxide prepared by the chitosan template method exhibits a porous and rough morphology. Its interconnected sharp edges and rough surfaces, compared to ordinary spherical particles, expose more active sites for heterogeneous nucleation in the glass melt, which can induce the precipitation of microcrystals along the bubble walls, thereby enhancing compressive strength. Furthermore, the pre-decomposition of citrate ions during heating forms a uniform microporous network among the glass powder particles before the carbonate main blowing agent. This primary pore structure provides diffusion channels for the CO2 released subsequently by the carbonate, preventing gas accumulation in localized melts that could lead to bubble bursting or merging. Therefore, Example 1 exhibits a more uniform pore size distribution.

[0094] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A method for preparing microcrystalline foam glass, characterized in that, The preparation method includes: Step 1: Mix the base glass powder, the first foaming agent, the second foaming agent, and the first nucleating agent evenly to obtain the batch material; Wherein, the first foaming agent is a carbonate foaming agent; the second foaming agent is selected from layered bimetallic hydroxide foaming agents; and the first nucleating agent is selected from oxide nucleating agents. Step 2: Press the compound into shape; then heat to the foaming temperature; keep warm for 1-2 hours; Step 3: Cool to nucleation temperature; hold at this temperature for 0.5-1 hour; Step 4: Heat to the crystallization temperature; keep warm for 1-1.5 hours; obtain the microcrystalline foam glass.

2. The method for preparing microcrystalline foam glass according to claim 1, characterized in that, The carbonate foaming agent is selected from one or more of calcium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, barium carbonate, strontium carbonate, and lithium carbonate.

3. The method for preparing microcrystalline foam glass according to claim 1, characterized in that, The layered bimetallic hydroxide foaming agent is selected from layered bimetallic hydroxides with intercalated organic acids or organic acid radicals.

4. The method for preparing microcrystalline foam glass according to claim 3, characterized in that, The intercalated organic acids or layered bimetallic hydroxides of organic acid radicals are selected from lactate-intercalated hydrotalcite, cinnamate-intercalated hydrotalcite, citrate-intercalated hydrotalcite, sorbic acid-intercalated hydrotalcite, or ethylenediaminetetraacetic acid-intercalated hydrotalcite.

5. The method for preparing microcrystalline foam glass according to claim 1, 3, or 4, characterized in that, The second foaming agent is citrate-intercalated magnesium aluminum hydrotalcite; the citrate-intercalated magnesium aluminum hydrotalcite is prepared through the following steps: Step 1-a: Dissolve sodium citrate in water to obtain a sodium citrate solution; Step 2-a: Dissolve magnesium nitrate hexahydrate and aluminum nitrate nonahydrate in water to obtain a mixed salt solution; Step 3-a: Dissolve sodium hydroxide in water to obtain an alkaline solution; Step 4-a: Under nitrogen protection, the alkaline solution and the mixed salt solution are simultaneously added dropwise to the sodium citrate solution; During the dropping process, the dropping rate was controlled to keep the pH of the reaction system within the range of 10±0.5; after the dropping was completed, the system was crystallized at reflux temperature for 5-8 hours. Step 5-a: After the reaction is completed, the citrate-intercalated magnesium aluminum hydrotalcite is obtained by separation, washing and drying.

6. The method for preparing microcrystalline foam glass according to claim 1, characterized in that, The first nucleating agent is selected from one or more of zirconium dioxide, titanium dioxide, phosphorus pentoxide, chromium trioxide, ferric oxide, nickel oxide, cerium dioxide, and vanadium pentoxide.

7. The method for preparing microcrystalline foam glass according to claim 6, characterized in that, The first nucleating agent is zirconium dioxide prepared using chitosan as a template; the zirconium dioxide prepared using chitosan as a template is obtained through the following steps: Step 1-b: Add chitosan to an aqueous acetic acid solution and stir for 1-2 hours to obtain a chitosan solution; Step 2-b: Dissolve zirconium oxynitrate in water to obtain a salt solution; Step 3-b: Add the salt solution to the chitosan solution and stir vigorously for 2-4 hours to obtain a mixed solution; Step 4-b: Add the mixed solution dropwise to the ammonia solution while stirring. After the addition is complete, continue stirring for 1-3 hours, and then let it stand for 4-8 hours. Step 5-b: Then filter, wash, and dry to obtain a solid; the solid is then heat-treated to obtain the zirconium dioxide prepared by using chitosan as a template.

8. The method for preparing microcrystalline foam glass according to claim 1, characterized in that, The base glass powder is a sodium-calcium silicate system glass powder, which contains, by mass percentage: 50%-75% SiO2, 10%-18% (Na2O + K2O), 5%-15% (CaO + MgO), and 1%-8% Al2O3; the balance is unavoidable impurities.

9. The method for preparing microcrystalline foam glass according to claim 1, characterized in that, The foaming temperature is selected from 1000℃-1100℃; the nucleation temperature is selected from 700℃-750℃; and the crystallization temperature is selected from 850℃-900℃.

10. A microcrystalline foam glass, characterized in that, The microcrystalline foam glass is prepared by the preparation method according to any one of claims 1-9.

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