Calcium silicate board with enhanced thermal stability and method for producing the same

Abstract

The application relates to the technical field of building materials, in particular to a calcium silicate board with enhanced thermal stability and a preparation method thereof. The calcium silicate board is prepared from 300-400 parts of calcined quicklime, 450-750 parts of dry quartz powder, 50-150 parts of modified alumina short fibers and 160-260 parts of deionized water. The modified alumina short fibers are grafted with polymers on the surface and introduced with zinc borate, so that the initiation and expansion of microcracks are effectively inhibited. The calcium silicate board exhibits excellent crack resistance and thermal stability under a high-temperature thermal shock environment, and is suitable for the development and application of building materials under high-temperature working conditions.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a calcium silicate board with enhanced thermal stability and its preparation method. Background Technology

[0002] Calcium silicate board, as an important inorganic non-metallic material, is widely used in building construction, industrial equipment, and high-temperature environments for thermal insulation and protection due to its excellent fire resistance, thermal insulation, and mechanical properties. However, with the increasing demands of modern industry on material performance, the limitations of traditional calcium silicate board in high-temperature thermal shock environments are becoming increasingly apparent. Especially under extreme temperature alternation conditions, calcium silicate board is prone to microcracks due to thermal stress concentration, leading to a decline in mechanical properties and structural instability, severely impacting its service life and safety.

[0003] In existing technologies, researchers have attempted to optimize the material structure of calcium silicate boards by introducing methods such as fiber reinforcement, ceramic phase modification, and polymer composites to improve the thermal stability and mechanical properties. For example, fiber reinforcement technology introduces inorganic fibers (such as glass fibers, carbon fibers, or alumina fibers) into the calcium silicate matrix to improve the tensile strength and crack resistance of the material. However, due to insufficient interfacial bonding between the fibers and the matrix, the fiber reinforcement effect is often difficult to maintain at high temperatures. Furthermore, the difference in the coefficients of thermal expansion between the fibers and the matrix leads to interfacial thermal stress concentration, further exacerbating the initiation and propagation of microcracks.

[0004] Ceramic phase modification is another common reinforcement method, which involves introducing oxide ceramic particles (such as alumina, zirconium oxide, or silicon carbide) into a calcium silicate matrix to improve the high-temperature strength and thermal shock resistance of the material. However, while the introduction of ceramic particles can suppress crack propagation to some extent, their rigidity may lead to a decrease in the overall toughness of the material, making it difficult to meet the performance requirements under complex thermal shock environments. Furthermore, the uniformity of ceramic particle dispersion in the matrix and the quality of interfacial bonding also directly affect the reinforcement effect. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a calcium silicate board with enhanced thermal stability and its preparation method, so as to solve the problem that existing calcium silicate boards are prone to microcrack propagation under high temperature thermal shock environment, resulting in mechanical property degradation and structural instability.

[0006] To achieve the above objectives, the present invention provides a calcium silicate board with enhanced thermal stability, which is prepared by weight from the following raw materials: 300-400 parts of calcined quicklime, 450-750 parts of dried quartz powder, 50-150 parts of modified alumina short fibers, and 160-260 parts of deionized water.

[0007] Furthermore, the preparation steps of the modified alumina short fibers are as follows:

[0008] S1: Add alumina short fibers to a mixture of deionized water and ethanol, ultrasonically stir for 20-40 min, then add vinyltrimethoxysilane, heat to 50-60℃, stir for 5-7 h, centrifuge, wash, and dry to obtain alkenylated alumina short fibers.

[0009] S2: Add butyl acrylate, methacrylic acid, 2-hydroxyethyl acrylate and Span 80 to a mixed solution of deionized water and anhydrous ethanol, stir for 20-40 min and adjust the pH to 3.8-4.2 with hydrochloric acid to form a pre-emulsion;

[0010] S3: Add zinc nitrate to deionized water and stir for 8-12 minutes. Add ammonium persulfate and continue stirring for 20-40 minutes to obtain the initiation solution.

[0011] S4: Under a nitrogen atmosphere, alkenylated alumina short fibers are added to the initiating solution and heated to 60-70℃. During stirring, a pre-emulsion is added dropwise. After the addition is complete, the mixture is stirred for 2.5-3.5 hours. Then, an 8-12 wt% boric acid aqueous solution is added, and stirring is continued for 20-40 minutes. The mixture is then centrifuged, washed, and dried to obtain modified alumina short fibers.

[0012] Preferably, the alumina short fibers in step S1 are composed of 85wt% alumina and 15wt% silicon dioxide, with an average diameter of 10-15μm and an average length of 40-60mm.

[0013] Preferably, in step S1, the weight ratio of alumina short fibers, deionized water, ethanol and vinyltrimethoxysilane is 50-150:250-750:500-1500:5-20.

[0014] Preferably, in step S2, the weight ratio of butyl acrylate, methacrylic acid, 2-hydroxyethyl acrylate, Span 80, deionized water and anhydrous ethanol is 25-75:15-45:10-35:1.5-4.5:250-750:150-450.

[0015] Preferably, in step S3, the weight ratio of zinc nitrate, deionized water, and ammonium persulfate is 6-18:50-150:0.8-2.4.

[0016] Preferably, in step S4, the weight ratio of alkenylated alumina short fibers, initiating solution, preemulsion and boric acid aqueous solution is 50-150:50-150:450-1300:60-100.

[0017] Preferably, the calcined quicklime is obtained by calcining quicklime at 960-1000℃ for 2-3 hours and grinding it through a 250-300 mesh sieve.

[0018] Preferably, the dried quartz powder is obtained by drying quartz powder at 100-110℃ for 10-15 hours and then grinding it through a 250-350 mesh sieve.

[0019] Furthermore, the present invention provides a method for preparing a calcium silicate board with enhanced thermal stability, comprising the following steps:

[0020] (1) Mix calcined quicklime, dried quartz powder, modified alumina short fibers and deionized water, and stir at 250-350 rpm for 12-18 min to obtain a slurry;

[0021] (2) The slurry is formed by flow forming machine to obtain the blank;

[0022] (3) Place the green blank in an autoclave and autoclave to obtain the plate;

[0023] (4) The steam-cured board is placed in a muffle furnace and calcined under a nitrogen atmosphere. After cooling, a calcium silicate board with enhanced thermal stability is obtained.

[0024] Preferably, the temperature of the slurry forming in step (2) is 38-42℃ and the vacuum degree is -0.07±0.01MPa.

[0025] Preferably, the steam pressing step in step (3) is as follows: heating to 155-165°C at 1-10°C / min under saturated steam pressure of 0.6-1MPa, holding for 6-10h, and then heating to 190-200°C at 1-1.5°C / min under saturated steam pressure of 1.4-1.6MPa, holding for 5-7h.

[0026] Preferably, the calcination step in step (4) is as follows: heating to 580-620℃ at a rate of 4-6℃ / min and holding at that temperature for 1.5-2.5 hours.

[0027] The beneficial effects of this invention are:

[0028] This invention achieves a synergistic improvement in the mechanical properties and thermal stability of materials by constructing a fiber-polymer-ceramic multiphase synergistic reinforcement system. The polymer grafted onto the fiber surface forms a gradient transition structure between a nano-carbon layer and the ceramic phase during pyrolysis, effectively filling micro-defects in the matrix and enhancing interfacial stress transfer efficiency. The in-situ generated borosilicate glass phase repairs thermal cycling damage through viscous flow, forming a dynamic self-healing protective layer. This multi-scale reinforcement mechanism enables the material to effectively disperse mechanical loads and thermal stresses during thermal shock, inhibiting the initiation and propagation of microcracks.

[0029] This invention utilizes the synergistic effect of flexible polymer segments and rigid ceramic phases to enable the reinforced system to possess both stress buffering and load-bearing functions. The gradient carbonization structure forms a transition layer with a high coefficient of thermal expansion, significantly reducing interfacial thermal stress between the fiber and the matrix. Zinc borate formed on the fiber surface effectively induces microcrack deflection, extending the crack propagation path and consuming fracture energy. Furthermore, the catalytically formed graphitized carbon network improves the material's thermal conductivity, accelerating heat diffusion and preventing localized overheating.

[0030] The calcium silicate board with enhanced thermal stability provided by this invention can maintain a stable microstructure and excellent mechanical properties even under extreme temperature alternation environments, providing an innovative solution for the development of building materials for high-temperature conditions. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] In the specific embodiment of this invention, the alumina short fibers were purchased from Suzhou Baird New Material Technology Co., Ltd., model Nextel720, with a composition of 85wt% alumina and 15wt% silicon oxide, an average diameter of 11.4μm, and an average length of 51.6mm.

[0033] Example

[0034] (1) Add 50g of alumina short fibers to a mixture of 250g of deionized water and 500g of ethanol, stir ultrasonically for 20min, then add 5g of vinyltrimethoxysilane, heat to 50℃, stir for 5h, centrifuge, wash, and dry to obtain alkenylated alumina short fibers.

[0035] (2) Add 25g butyl acrylate, 15g methacrylic acid, 10g 2-hydroxyethyl acrylate and 1.5g Span 80 to a mixed solution of 250g deionized water and 150g anhydrous ethanol, stir for 20min and adjust the pH to 3.8 with hydrochloric acid to form a pre-emulsion; add 6g zinc nitrate to 50g deionized water, stir for 8min, add 0.8g ammonium persulfate, and continue stirring for 20min to obtain an initiating solution; under a nitrogen atmosphere, add 50g alkenylated alumina short fibers to 50g initiating solution, heat to 60℃, add 450g pre-emulsion dropwise during stirring, stir for 2.5h after the addition is complete, add 60g of 8wt% boric acid aqueous solution, continue stirring for 20min, centrifuge, wash and dry to obtain modified alumina short fibers;

[0036] (3) Dry the quartz powder at 100℃ for 10h, grind it through a 250-mesh sieve to obtain dried quartz powder, then calcine the quicklime at 960℃ for 2h, grind it through a 250-mesh sieve to obtain calcined quicklime;

[0037] (4) Mix 300g of calcined quicklime, 450g of dry quartz powder, 50g of modified alumina short fiber and 160g of deionized water, and stir at 250rpm for 12min to obtain a slurry;

[0038] (5) The slurry is formed by flow forming machine at a temperature of 38℃ and a vacuum degree of -0.06MPa to obtain a blank;

[0039] (6) Place the green blank in an autoclave, heat it to 155°C at 1°C / min under 0.6MPa saturated steam pressure, hold it for 6 hours, then heat it to 190°C at 1°C / min under 1.4MPa saturated steam pressure, hold it for 5 hours, and obtain the board.

[0040] (7) The steam-cured board is placed in a muffle furnace and heated to 580°C at 4°C / min under a nitrogen atmosphere. The temperature is held for 1.5 hours and then cooled to obtain a calcium silicate board with enhanced thermal stability.

[0041] Example

[0042] (1) Add 100g of alumina short fibers to a mixture of 500g of deionized water and 1000g of ethanol, stir ultrasonically for 30min, then add 10g of vinyltrimethoxysilane, heat to 55℃, stir for 6h, centrifuge, wash, and dry to obtain alkenylated alumina short fibers.

[0043] (2) Add 58g butyl acrylate, 32g methacrylic acid, 25g 2-hydroxyethyl acrylate and 3g Span 80 to a mixed solution of 500g deionized water and 300g anhydrous ethanol, stir for 30min and adjust the pH to 4.0 with hydrochloric acid to form a pre-emulsion; add 12.5g zinc nitrate to 100g deionized water, stir for 10min, add 1.7g ammonium persulfate, and continue stirring for 30min to obtain an initiating solution; under a nitrogen atmosphere, add 100g alkenylated alumina short fibers to 100g initiating solution, heat to 65℃, add 900g pre-emulsion dropwise during stirring, stir and react for 3h after the addition is complete, add 80g of 10wt% boric acid aqueous solution, continue stirring for 30min, centrifuge, wash and dry to obtain modified alumina short fibers;

[0044] (3) Dry the quartz powder at 105℃ for 12 hours, grind it through a 300-mesh sieve to obtain dried quartz powder, then calcine the quicklime at 980℃ for 2.5 hours, grind it through a 300-mesh sieve to obtain calcined quicklime;

[0045] (4) Mix 350g of calcined quicklime, 600g of dry quartz powder, 100g of modified alumina short fiber and 210g of deionized water, and stir at 300rpm for 15min to obtain a slurry;

[0046] (5) The slurry is formed by flow forming machine at a temperature of 40℃ and a vacuum degree of -0.07MPa to obtain a blank;

[0047] (6) Place the green blank in an autoclave, heat it to 160°C at 5°C / min under 0.8MPa saturated steam pressure, hold it for 8h, then heat it to 195°C at 1.2°C / min under 1.5MPa saturated steam pressure, hold it for 6h, and obtain the board.

[0048] (7) Place the steam-cured board in a muffle furnace, heat it to 600°C at 5°C / min under a nitrogen atmosphere, keep it at the temperature for 2 hours, and then cool it to obtain a calcium silicate board with enhanced thermal stability.

[0049] Example

[0050] (1) Add 150g of alumina short fibers to a mixture of 750g of deionized water and 1500g of ethanol, stir ultrasonically for 40min, then add 20g of vinyltrimethoxysilane, heat to 60℃, stir for 7h, centrifuge, wash, and dry to obtain alkenylated alumina short fibers.

[0051] (2) 75g butyl acrylate, 45g methacrylic acid, 35g 2-hydroxyethyl acrylate and 4.5g Span 80 were added to a mixed solution of 750g deionized water and 450g anhydrous ethanol. The mixture was stirred for 40min and the pH was adjusted to 4.2 with hydrochloric acid to form a pre-emulsion. 18g zinc nitrate was added to 150g deionized water and stirred for 12min. 2.4g ammonium persulfate was added and stirred for another 40min to obtain an initiating solution. Under a nitrogen atmosphere, 150g alkenylated alumina short fibers were added to 150g of the initiating solution and heated to 70℃. 1300g of the pre-emulsion was added dropwise during stirring. After the addition was complete, the mixture was stirred for 3.5h. Then 100g of 12wt% boric acid aqueous solution was added and stirred for another 40min. The mixture was centrifuged, washed and dried to obtain modified alumina short fibers.

[0052] (3) Dry the quartz powder at 110℃ for 15 hours, grind it through a 350-mesh sieve to obtain dried quartz powder, then calcine the quicklime at 1000℃ for 3 hours, grind it through a 300-mesh sieve to obtain calcined quicklime;

[0053] (4) Mix 400g of calcined quicklime, 450-750g of dry quartz powder, 50-150g of modified alumina short fibers and 160-260g of deionized water, and stir at 350rpm for 18min to obtain a slurry;

[0054] (5) The slurry is formed by flow forming machine at a temperature of 40℃ and a vacuum degree of -0.08MPa to obtain a blank;

[0055] (6) Place the green blank in an autoclave, heat it to 165°C at 10°C / min under 1MPa saturated steam pressure, hold it for 10h, then heat it to 200°C at 1.5°C / min under 1.6MPa saturated steam pressure, hold it for 7h, and obtain the board.

[0056] (7) The steam-cured board is placed in a muffle furnace and heated to 620°C at 6°C / min under a nitrogen atmosphere. The temperature is maintained for 2.5 hours and then cooled to obtain a calcium silicate board with enhanced thermal stability.

[0057] Comparative Example 1:

[0058] The difference between Comparative Example 1 and Example 2 is that the alkenylated alumina short fibers in (2) are replaced with alumina short fibers;

[0059] The specific steps are as follows:

[0060] (1) Add 58g butyl acrylate, 32g methacrylic acid, 25g 2-hydroxyethyl acrylate and 3g Span 80 to a mixed solution of 500g deionized water and 300g anhydrous ethanol, stir for 30min and adjust the pH to 4.0 with hydrochloric acid to form a pre-emulsion; add 12.5g zinc nitrate to 100g deionized water, stir for 10min, add 1.7g ammonium persulfate, and continue stirring for 30min to obtain an initiating solution; under a nitrogen atmosphere, add 100g alumina short fibers to 100g initiating solution, heat to 65℃, add 900g pre-emulsion dropwise during stirring, stir and react for 3h after the addition is complete, add 80g of 10wt% boric acid aqueous solution, continue stirring for 30min, centrifuge, wash and dry to obtain modified alumina short fibers;

[0061] (2) Dry the quartz powder at 105℃ for 12 hours, grind it through a 300-mesh sieve to obtain dried quartz powder, then calcine the quicklime at 980℃ for 2.5 hours, grind it through a 300-mesh sieve to obtain calcined quicklime;

[0062] (3) Mix 350g of calcined quicklime, 600g of dry quartz powder, 100g of modified alumina short fiber and 210g of deionized water, and stir at 300rpm for 15min to obtain a slurry;

[0063] (4) The slurry is formed by flow forming machine at a temperature of 40℃ and a vacuum degree of -0.07MPa to obtain a green blank;

[0064] (5) Place the green blank in an autoclave, heat it to 160°C at 5°C / min under 0.8MPa saturated steam pressure, hold it for 8 hours, then heat it to 195°C at 1.2°C / min under 1.5MPa saturated steam pressure, hold it for 6 hours to obtain the board;

[0065] (6) Place the steam-cured board in a muffle furnace, heat it to 600°C at 5°C / min under a nitrogen atmosphere, keep it at the temperature for 2 hours, and then cool it to obtain calcium silicate board.

[0066] Comparative Example 2:

[0067] The difference between Comparative Example 2 and Example 2 is that butyl acrylate was not added in step (2);

[0068] The specific steps are as follows:

[0069] (1) Add 100g of alumina short fibers to a mixture of 500g of deionized water and 1000g of ethanol, stir ultrasonically for 30min, then add 10g of vinyltrimethoxysilane, heat to 55℃, stir for 6h, centrifuge, wash, and dry to obtain alkenylated alumina short fibers.

[0070] (2) Add 32g of methacrylic acid, 25g of 2-hydroxyethyl acrylate and 3g of Span 80 to a mixed solution of 500g of deionized water and 300g of anhydrous ethanol, stir for 30min and adjust the pH to 4.0 with hydrochloric acid to form a pre-emulsion; add 12.5g of zinc nitrate to 100g of deionized water, stir for 10min, add 1.7g of ammonium persulfate, and continue stirring for 30min to obtain an initiating solution; under a nitrogen atmosphere, add 100g of alkenylated alumina short fibers to 100g of initiating solution, heat to 65℃, add 900g of pre-emulsion dropwise during stirring, stir and react for 3h after the addition is complete, add 80g of 10wt% boric acid aqueous solution, continue stirring for 30min, centrifuge, wash and dry to obtain modified alumina short fibers;

[0071] (3) Dry the quartz powder at 105℃ for 12 hours, grind it through a 300-mesh sieve to obtain dried quartz powder, then calcine the quicklime at 980℃ for 2.5 hours, grind it through a 300-mesh sieve to obtain calcined quicklime;

[0072] (4) Mix 350g of calcined quicklime, 600g of dry quartz powder, 100g of modified alumina short fiber and 210g of deionized water, and stir at 300rpm for 15min to obtain a slurry;

[0073] (5) The slurry is formed by flow forming machine at a temperature of 40℃ and a vacuum degree of -0.07MPa to obtain a blank;

[0074] (6) Place the green blank in an autoclave, heat it to 160°C at 5°C / min under 0.8MPa saturated steam pressure, hold it for 8h, then heat it to 195°C at 1.2°C / min under 1.5MPa saturated steam pressure, hold it for 6h, and obtain the board.

[0075] (7) Place the steam-cured board in a muffle furnace, heat it to 600°C at 5°C / min under a nitrogen atmosphere, keep it at the temperature for 2 hours, and then cool it to obtain calcium silicate board.

[0076] Comparative Example 3:

[0077] The difference between Comparative Example 3 and Example 2 is that methacrylic acid was not added in step (2);

[0078] The specific steps are as follows:

[0079] (1) Add 100g of alumina short fibers to a mixture of 500g of deionized water and 1000g of ethanol, stir ultrasonically for 30min, then add 10g of vinyltrimethoxysilane, heat to 55℃, stir for 6h, centrifuge, wash, and dry to obtain alkenylated alumina short fibers.

[0080] (2) Add 58g of butyl acrylate, 25g of 2-hydroxyethyl acrylate and 3g of Span 80 to a mixed solution of 500g of deionized water and 300g of anhydrous ethanol, stir for 30min and adjust the pH to 4.0 with hydrochloric acid to form a pre-emulsion; add 12.5g of zinc nitrate to 100g of deionized water, stir for 10min, add 1.7g of ammonium persulfate, and continue stirring for 30min to obtain an initiating solution; under a nitrogen atmosphere, add 100g of alkenylated alumina short fibers to 100g of initiating solution, heat to 65℃, add 900g of pre-emulsion dropwise during stirring, stir and react for 3h after the addition is complete, add 80g of 10wt% boric acid aqueous solution, continue stirring for 30min, centrifuge, wash and dry to obtain modified alumina short fibers;

[0081] (3) Dry the quartz powder at 105℃ for 12 hours, grind it through a 300-mesh sieve to obtain dried quartz powder, then calcine the quicklime at 980℃ for 2.5 hours, grind it through a 300-mesh sieve to obtain calcined quicklime;

[0082] (4) Mix 350g of calcined quicklime, 600g of dry quartz powder, 100g of modified alumina short fiber and 210g of deionized water, and stir at 300rpm for 15min to obtain a slurry;

[0083] (5) The slurry is formed by flow forming machine at a temperature of 40℃ and a vacuum degree of -0.07MPa to obtain a blank;

[0084] (6) Place the green blank in an autoclave, heat it to 160°C at 5°C / min under 0.8MPa saturated steam pressure, hold it for 8h, then heat it to 195°C at 1.2°C / min under 1.5MPa saturated steam pressure, hold it for 6h, and obtain the board.

[0085] (7) Place the steam-cured board in a muffle furnace, heat it to 600°C at 5°C / min under a nitrogen atmosphere, keep it at the temperature for 2 hours, and then cool it to obtain calcium silicate board.

[0086] Comparative Example 4:

[0087] The difference between Comparative Example 4 and Example 2 is that 2-hydroxyethyl acrylate was not added in step (2);

[0088] The specific steps are as follows:

[0089] (1) Add 100g of alumina short fibers to a mixture of 500g of deionized water and 1000g of ethanol, stir ultrasonically for 30min, then add 10g of vinyltrimethoxysilane, heat to 55℃, stir for 6h, centrifuge, wash, and dry to obtain alkenylated alumina short fibers.

[0090] (2) Add 58g butyl acrylate, 32g methacrylic acid and 3g Span 80 to a mixed solution of 500g deionized water and 300g anhydrous ethanol, stir for 30min and adjust the pH to 4.0 with hydrochloric acid to form a pre-emulsion; add 12.5g zinc nitrate to 100g deionized water, stir for 10min, add 1.7g ammonium persulfate, and continue stirring for 30min to obtain an initiating solution; under a nitrogen atmosphere, add 100g alkenylated alumina short fibers to 100g initiating solution, heat to 65℃, add 900g pre-emulsion dropwise during stirring, stir and react for 3h after the addition is complete, add 80g of 10wt% boric acid aqueous solution, continue stirring for 30min, centrifuge, wash and dry to obtain modified alumina short fibers;

[0091] (3) Dry the quartz powder at 105℃ for 12 hours, grind it through a 300-mesh sieve to obtain dried quartz powder, then calcine the quicklime at 980℃ for 2.5 hours, grind it through a 300-mesh sieve to obtain calcined quicklime;

[0092] (4) Mix 350g of calcined quicklime, 600g of dry quartz powder, 100g of modified alumina short fiber and 210g of deionized water, and stir at 300rpm for 15min to obtain a slurry;

[0093] (5) The slurry is formed by flow forming machine at a temperature of 40℃ and a vacuum degree of -0.07MPa to obtain a blank;

[0094] (6) Place the green blank in an autoclave, heat it to 160°C at 5°C / min under 0.8MPa saturated steam pressure, hold it for 8h, then heat it to 195°C at 1.2°C / min under 1.5MPa saturated steam pressure, hold it for 6h, and obtain the board.

[0095] (7) Place the steam-cured board in a muffle furnace, heat it to 600°C at 5°C / min under a nitrogen atmosphere, keep it at the temperature for 2 hours, and then cool it to obtain calcium silicate board.

[0096] Comparative Example 5:

[0097] The difference between Comparative Example 5 and Example 2 is that zinc nitrate and boric acid were not added in step (2);

[0098] The specific steps are as follows:

[0099] (1) Add 100g of alumina short fibers to a mixture of 500g of deionized water and 1000g of ethanol, stir ultrasonically for 30min, then add 10g of vinyltrimethoxysilane, heat to 55℃, stir for 6h, centrifuge, wash, and dry to obtain alkenylated alumina short fibers.

[0100] (2) Add 58g butyl acrylate, 32g methacrylic acid, 25g 2-hydroxyethyl acrylate and 3g Span 80 to a mixed solution of 500g deionized water and 300g anhydrous ethanol, stir for 30min and adjust the pH to 4.0 with hydrochloric acid to form a pre-emulsion; add 1.7g ammonium persulfate to 100g deionized water and stir for 10min to obtain 100g initiating solution; under a nitrogen atmosphere, add 100g alkenylated alumina short fibers to the initiating solution, heat to 65℃, and add 900g pre-emulsion dropwise while stirring. After the addition is complete, stir the reaction for 3h, centrifuge, wash and dry to obtain modified alumina short fibers;

[0101] (3) Dry the quartz powder at 105℃ for 12 hours, grind it through a 300-mesh sieve to obtain dried quartz powder, then calcine the quicklime at 980℃ for 2.5 hours, grind it through a 300-mesh sieve to obtain calcined quicklime;

[0102] (4) Mix 350g of calcined quicklime, 600g of dry quartz powder, 100g of modified alumina short fiber and 210g of deionized water, and stir at 300rpm for 15min to obtain a slurry;

[0103] (5) The slurry is formed by flow forming machine at a temperature of 40℃ and a vacuum degree of -0.07MPa to obtain a blank;

[0104] (6) Place the green blank in an autoclave, heat it to 160°C at 5°C / min under 0.8MPa saturated steam pressure, hold it for 8h, then heat it to 195°C at 1.2°C / min under 1.5MPa saturated steam pressure, hold it for 6h, and obtain the board.

[0105] (7) Place the steam-cured board in a muffle furnace, heat it to 600°C at 5°C / min under a nitrogen atmosphere, keep it at the temperature for 2 hours, and then cool it to obtain calcium silicate board.

[0106] Performance testing:

[0107] Flexural strength: In accordance with Clause 6.3 of JC / T 564.1-2018, a WAW-1000C microcomputer-controlled electro-hydraulic servo universal testing machine was used, with a span of 200 mm and a loading rate of 5 mm / min. The results are shown in Table 1.

[0108] Compressive strength: According to GB / T 17617-2013, the loading rate is set to 2400 N / s until the specimen fails, and the maximum pressure value is recorded. The calculation formula is: C=P / A, where C is the compressive strength (MPa), P is the failure load (N), and A is the pressure-bearing area (mm²). 2 The results are shown in Table 1.

[0109] Thermal shock stability: The specimens were cut into 100mm×100mm×10mm sizes and dried in an oven at 105℃ until constant weight. The specimens were then tested in a high-temperature box-type resistance furnace with an initial temperature of 600℃. The specimens were placed vertically into the central area of ​​the furnace chamber preheated to 600℃ and kept at that temperature for 30 minutes. The specimens were then quickly removed and immediately immersed in deionized water at 25±2℃ for rapid cooling for 10 minutes. The specimens were then removed and dried with compressed air. The thermal shock cycle was repeated 20 times. The flexural strength was tested and the strength retention rate was calculated. The results are shown in Table 1.

[0110] Table 1 Performance Test Results

[0111]

[0112] Data Analysis:

[0113] As can be seen from the data in Examples 1-3 of Table 1, the enhanced thermal stability calcium silicate board prepared by this invention exhibits high flexural and compressive strength, and maintains a stable internal structure and mechanical strength even under alternating high-temperature and rapid-cooling conditions. This may be due to the acrylate copolymer grafted onto the surface of the alumina short fibers forming an interpenetrating network with the calcium silicate hydration products through molecular chains during the autoclaving stage. The nano-carbon layer formed by polymer carbonization during high-temperature pyrolysis synergistically interacts with the zinc borate generated in situ on the fiber surface, filling micro-defects in the matrix and enhancing the fiber-matrix interface bonding. This multi-scale reinforcement mechanism enables the material to effectively disperse stress when subjected to mechanical loads, while the high-temperature stability of zinc borate provides thermal barrier protection, inhibiting the propagation of microcracks caused by thermal stress.

[0114] As can be seen from the data in Table 1 for Example 2 and Comparative Example 1, surface alkenylation modification of alumina short fibers in Example 2 significantly improved the flexural strength, compressive strength, and post-thermal shock strength retention of the calcium silicate board. This is mainly because the alkenylation treatment constructs active grafting sites on the fiber surface through chemical bonding, enabling the subsequent polymer coating to achieve covalent bond anchoring. This strong interfacial bonding can more effectively transfer stress compared to physical adsorption, avoiding early failure caused by interfacial delamination. Simultaneously, the molecular chains on the fiber surface, after carbonization, can alleviate the interfacial stress caused by the difference in thermal expansion coefficients between the fiber and the matrix, maintaining structural integrity during thermal shock.

[0115] As can be seen from the data in Table 1 for Example 2 and Comparative Example 2, the addition of butyl acrylate in Example 2 significantly improved the mechanical properties and thermal shock stability of the calcium silicate board. The addition of butyl acrylate may have improved the adhesion between the fiber and the matrix, thereby increasing the uniformity and density of the matrix, enabling the material to maintain a high strength retention rate even after multiple thermal shock cycles.

[0116] As can be seen from the data in Table 1 for Example 2 and Comparative Example 3, the addition of methacrylic acid in Example 2 significantly enhanced the flexural strength, compressive strength, and thermal shock resistance retention of the calcium silicate board. This may be because the carboxylic acid groups on the methacrylic acid promote the formation of zinc nitrate and boric acid on the fiber surface.

[0117] As can be seen from the data in Table 1 for Example 2 and Comparative Example 4, the addition of 2-hydroxyethyl acrylate in Example 2 significantly improved the overall performance of the calcium silicate board. This may be because the hydroxyl functional groups of 2-hydroxyethyl acrylate form a hydrogen bond network with the hydration products of calcium silicate, promoting the fusion of the organic-inorganic phase interface during the autoclaving stage. The flexibility of the ethoxy segments allows the polymer layer to form a gradient carbonization structure during pyrolysis, and this gradual interface can effectively alleviate thermal stress concentration. The thermal decomposition products of hydroxyl groups may also participate in the formation of silicate lattice defects, enhancing the toughness of the matrix.

[0118] As can be seen from the data in Table 1 for Example 2 and Comparative Example 5, the introduction of zinc nitrate and boric acid in Example 2 significantly enhanced the mechanical properties and thermal shock stability of the calcium silicate board. This may be because zinc borate, formed by the reaction of zinc nitrate and boric acid, forms a nanofiber structure on the fiber surface, and its anisotropic thermal expansion characteristics can induce microcrack deflection. During high-temperature pyrolysis, B2O3 produced by the decomposition of zinc borate forms a borosilicate glass phase with a low expansion coefficient with SiO2. This in-situ generated interfacial phase not only improves the chemical compatibility between the fiber and the matrix, but also repairs micro-defects generated by thermal cycling through viscous flow. The catalytic effect of zinc ions may promote the graphitization of carbonization products, forming a high thermal conductivity network to accelerate heat diffusion, thereby significantly improving the thermal shock stability of the material.

[0119] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A calcium silicate board with enhanced thermal stability, characterized in that, The preparation is made from the following raw materials: calcined lime 300-400 parts, dry quartz powder 450-750 parts, modified alumina short fiber 50-150 parts and deionized water 160-260 parts by weight; The preparation steps of the modified alumina short fiber are as follows: S1: alumina short fiber is added into a mixture of deionized water and ethanol, and ultrasonic stirring is performed for 20-40 min, then vinyltrimethoxysilane is added, the temperature is raised to 50-60℃, stirring treatment is performed for 5-7 h, centrifugation, washing and drying are performed to obtain alkenylated alumina short fiber; S2: butyl acrylate, methacrylic acid, 2-hydroxyethyl acrylate and Span 80 are added into a mixed solution of deionized water and anhydrous ethanol, stirring is performed for 20-40 min, and hydrochloric acid is used to adjust the pH to 3.8-4.2 to form a pre-emulsion; S3: zinc nitrate is added into deionized water, stirring is performed for 8-12 min, ammonium persulfate is added, and stirring is continued for 20-40 min to obtain an initiation solution; S4: under a nitrogen atmosphere, alkenylated alumina short fiber is added into the initiation solution, the temperature is raised to 60-70℃, the pre-emulsion is added dropwise during stirring, after the dropwise addition is completed, stirring reaction is performed for 2.5-3.5 h, an 8-12 wt% boric acid aqueous solution is further added, stirring is continued for 20-40 min, centrifugation, washing and drying are performed to obtain modified alumina short fiber; The weight ratio of alumina short fiber, deionized water, ethanol and vinyltrimethoxysilane in step S1 is 50-150:250-750:500-1500:5-20; The weight ratio of butyl acrylate, methacrylic acid, 2-hydroxyethyl acrylate, Span 80, deionized water and anhydrous ethanol in step S2 is 25-75:15-45:10-35:1.5-4.5:250-750:150-450; The weight ratio of zinc nitrate, deionized water and ammonium persulfate in step S3 is 6-18:50-150:0.8-2.4; The weight ratio of alkenylated alumina short fiber, initiation solution, pre-emulsion and boric acid aqueous solution in step S4 is 50-150:50-150:450-1300:60-100.

2. The calcium silicate board for enhancing heat stability according to claim 1, characterized by, The calcined lime is obtained by calcining lime at 960-1000℃ for 2-3 h, and grinding through a 250-300 mesh sieve.

3. The calcium silicate board for enhancing thermal stability according to claim 1, characterized by, The dry quartz powder is obtained by drying quartz powder at 100-110℃ for 10-15 h, and grinding through a 250-350 mesh sieve.

4. The calcium silicate board for enhancing thermal stability according to claim 1, characterized by, The alumina short fiber in step S1 has a composition of 85 wt% alumina and 15 wt% silicon oxide, an average diameter of 10-15 μm and an average length of 40-60 mm.

5. A method for producing a calcium silicate board having enhanced thermal stability according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: (1) mixing calcined lime, dry quartz powder, modified alumina short fiber and deionized water, and stirring at 250-350 rpm for 12-18 min to obtain a slurry; (2) forming the slurry into a green body by a flow casting machine; (3) placing the green body in a steam autoclave, and steam pressing to obtain a plate. (4) The board after steaming is placed in a muffle furnace, calcined under nitrogen atmosphere, and cooled to obtain a calcium silicate board with enhanced thermal stability.

6. The method of producing a calcium silicate board with enhanced thermal stability according to claim 5, characterized in that, The temperature of the step (2) is 38-42℃, and the vacuum degree is -0.07±0.01MPa.

7. The method of producing a calcium silicate board having enhanced thermal stability according to claim 5, characterized by, The step (3) is steaming under saturated steam pressure of 0.6-1MPa, with temperature rising at 1-10℃ / min to 155-165℃, holding for 6-10h, then under saturated steam pressure of 1.4-1.6MPa, with temperature rising at 1-1.5℃ / min to 190-200℃, holding for 5-7h.

8. The method of producing a calcium silicate board having enhanced thermal stability according to claim 5, characterized by, The step (4) is calcining with temperature rising at 4-6℃ / min to 580-620℃, holding for 1.5-2.5h.

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