A high-strength lightweight silica brick and its preparation method

Abstract

The present application discloses a high-strength lightweight silica brick and a preparation method thereof, relating to the technical field of refractory ceramic materials, including refractory-grade polycrystalline mullite fibers, silica sand fine powder, carbonized rice husk, water, hydrophobic silica aerogel, sodium carboxymethyl cellulose solution, ammonium salt solution, K12 powder, and agar powder; the hydrophobic silica aerogel is made of silica aerogel modified by hexamethyldisilazane (HMDS); it can achieve enhanced mechanical strength, improved compressive performance, improved thermal stability, and has extremely high heat insulation performance, enabling the aerogel material to leap from a single function to an integrated "strong-tough-insulating" one, providing an innovative solution.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory ceramic materials, and particularly relates to a high-strength lightweight silica brick and a preparation method thereof. Background Art

[0002] Acidic refractory materials mainly consist of silicon oxide, and commonly used ones include silica bricks and clay bricks. Silica bricks are silica products containing more than 93% silicon oxide, and the raw materials used are silica stone, waste silica bricks, etc. They have strong resistance to acidic slag erosion, high load softening temperature, and do not shrink in volume after repeated calcination, but even expand slightly; however, they are easily eroded by alkaline slag and have poor thermal shock resistance. With the development of technology and industry, the requirements for lightweight refractory materials are getting higher and higher. Currently, the existing lightweight silicon carbide bricks have poor corrosion resistance, short service life, heavy mass, and poor thermal shock resistance, and are not suitable for industrial production.

[0003] For example, in a Chinese patent with the application number CN202010257526.3, a preparation method of a microporous high-temperature resistant lightweight refractory brick, which relates to the technical field of refractory bricks. The microporous high-temperature resistant lightweight refractory brick uses refractory-grade polycrystalline mullite fiber and silicon powder as ceramic aggregates, rice husk carbon as a pore-forming agent, water as a solvent, silica aerogel as a binder, sodium carboxymethyl cellulose solution as a foam stabilizer, ammonium salt solution as a dispersant, K12 powder as a foaming agent, and agar powder as a forming agent; the high-temperature decomposition of rice husk carbon produces CO2 gas and residual carbon, forming through-pore channels with a diameter of 50 - 200 μm, reducing the density and blocking heat conduction. The K12 foaming agent introduces closed air holes with a diameter of 10 - 50 μm through high-speed stirring, forming a multi-stage pore structure with the pore-forming agent to synergistically optimize the heat insulation performance; the fiber-matrix interface of polycrystalline mullite fiber produces a crack deflection effect, improving the fracture work and preventing crack propagation; the nanoparticles of silica aerogel fill the micropore gaps, and the heat conduction path is scattered by the nanopores, reducing the thermal conductivity; the polysaccharide chains of agar gel form a three-dimensional network structure, increasing the wet blank compressive strength from 0.1 MPa to 0.5 MPa and preventing demolding deformation. The final product has a simple structure and low cost, and the prepared microporous lightweight brick has a low density, low thermal conductivity, good heat insulation and energy-saving effect, strong resistance to acid and alkali erosion, and a long service life.

[0004] However, the surface hydroxyl content of aerogel is relatively high, forming aggregates in the slurry, resulting in a decrease in the nanopore filling rate and the formation of 1 - 5 μm gaps at the aerogel / matrix interface, ultimately increasing the thermal conductivity and decreasing the acid resistance. After detection, the mass loss increases by 3% after soaking in 10% H2SO4 for 24 hours. Summary of the Invention

[0005] Embodiments of this application provide a high-strength lightweight silica brick and a preparation method thereof, which solve the problems in the prior art that the high hydroxyl content on the surface of the aerogel leads to aggregation, ultimately resulting in a decrease in heat insulation ability and acid erosion resistance, and achieve higher acid resistance and heat insulation ability.

[0006] Embodiments of this application provide a high-strength lightweight silica brick, including polycrystalline mullite fiber, silica sand fine powder, carbonized rice husk, water, hydrophobic silica aerogel, tetra-isopropyl titanate (TTP), sodium carboxymethyl cellulose solution, ammonium salt solution, K12 powder, agar powder; the hydrophobic silica aerogel is made of silica aerogel modified by hexamethyldisilazane (HMDS).

[0007] Among them, in the hydrophobic silica aerogel, the ratio of silica aerogel to hexamethyldisilazane (HMDS) is 100g:0.5 - 1.0g, and the addition amount of TTP is 0.3 - 0.7wt% of the mass of the hydrophobic silica aerogel.

[0008] Furthermore, the mass percentages of each component are as follows: polycrystalline mullite fiber 4%, silica sand fine powder 55%, carbonized rice husk 15%, agar powder 1%, K12 powder 2%, ammonium salt solution 2%, sodium carboxymethyl cellulose solution 2%, hydrophobic silica aerogel 15%, water 4%.

[0009] Furthermore, the particle sizes of the silica aerogel include 1μm, 5μm, and 10μm.

[0010] Furthermore, the 1μm silica aerogel accounts for 20% - 40% of the total amount of the silica aerogel.

[0011] Furthermore, the 5μm silica aerogel accounts for 40% - 60% of the total amount of the silica aerogel.

[0012] Furthermore, the 10μm silica aerogel accounts for 20% of the total amount of the silica aerogel.

[0013] Furthermore, the 1μm aerogel is a hydrophobic silica aerogel.

[0014] Furthermore, the 5μm aerogel is premixed with carbonized rice husk.

[0015] Furthermore, the 10μm aerogel is loaded with TTP, and the addition amount of TTP is 0.3 - 0.7wt% of the mass of the hydrophobic silica aerogel.

[0016] The preparation method of the above-mentioned high-strength lightweight silica brick is specifically as follows:

[0017] S1. Vacuum-dry the silica aerogel at 60 °C for 24 h, crush it and sieve it through a 400-mesh sieve. Then, in a reaction kettle under nitrogen protection, charge the materials according to the ratio of aerogel: hexamethyldisilazane = 100 g: 0.5 - 1.0 g; hexamethyldisilazane: ethanol = 3 - 5: 1. Stir and react at a constant temperature of 60 - 80 °C for 2 - 4 h, and perform synchronous ultrasonic treatment. After modification, centrifuge and separate, and vacuum-dry at 60 °C to obtain a hydrophobic aerogel powder. Premix the hydrophobic aerogel powder with TTP, polycrystalline mullite fiber, and fine silica sand powder to prepare a functionalized aerogel composite powder;

[0018] S2. Add K12 powder, agar powder, sodium carboxymethylcellulose solution, ammonium salt solution, and water to the functionalized aerogel composite powder and mix at low speed for 5 min, then foam at high speed for 20 min, and control the viscosity to be 1300 - 1400 mPa·s to obtain a ceramic slurry;

[0019] S3. Inject the ceramic slurry into a mold for molding. First, pre-dry it in an environment of 40 °C / RH60% for 12 h, then dry it in an environment of 60 °C / RH30% for 36 h, demold it, and then heat it up to 600 °C at a rate of 5 °C / min in a nitrogen environment and hold for 1 h, and then heat it up to 1600 °C at a rate of 10 °C / min and hold for 2 h to obtain a high-strength lightweight silica brick.

[0020] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0021] First, HMDS reacts with the surface hydroxyl groups (-OH) of the aerogel to form hydrophobic silicon methyl (Si-CH3) groups, significantly reducing the surface energy and showing superhydrophobic properties; after modification, the mechanical strength is enhanced, the compressive performance is improved, and the thermal stability is improved.

[0022] Second, by adding TTP, the interfacial bonding is strengthened, the ability to resist high-temperature deformation is increased; the high-temperature stability is increased; phonon scattering is increased, further reducing the thermal conductivity; the thermal shock life is increased.

[0023] Third, using a combination of aerogels with various particle sizes can reduce the mixing difficulty, extend the delamination time, and also complicate phonon conduction, reduce the thermal conductivity, reduce the gap in void size, and improve the overall compressive strength.

[0024] Fourth, use aerogels with different particle sizes to be separately loaded to form triple synergy of rigid group gradient densification (10-μm aerogel + TTP + HMDS), ductile group porous buffering (5-μm aerogel + carbonized rice husk), and heat insulation group phonon scattering (HMDS + 1-μm aerogel). Detailed implementation manners

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention belongs; the terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0026] Example 1: A high-strength lightweight silica brick uses polycrystalline mullite fiber and silica sand fine powder as ceramic aggregates, carbonized rice husk as a pore-forming agent, water as a solvent, hydrophobic silica aerogel as a binder, sodium carboxymethyl cellulose solution as a foam stabilizer, ammonium salt solution as a dispersant, K12 powder as a foaming agent, and agar powder as a forming agent;

[0027] The mass percentages of the respective components are as follows: polycrystalline mullite fiber 4%, silica sand fine powder 55%, carbonized rice husk 15%, agar powder 1%, K12 powder 2%, ammonium salt solution 2%, sodium carboxymethyl cellulose solution 2%, hydrophobic silica aerogel 15%, water 4%;

[0028] The preparation method of the high-strength lightweight silica brick is as follows:

[0029] S1. Vacuum-dry silica aerogel (solid content 30%) at 60°C for 24 h, crush it through a 400-mesh sieve, and then in a nitrogen-protected reaction kettle, charge according to the ratio of aerogel: hexamethyldisilazane (HMDS) = 100 g: 0.5 - 1.0 g; hexamethyldisilazane (HMDS): ethanol = 3 - 5: 1, stir at a constant temperature of 60 - 80°C (200 rpm) for 2 - 4 h, synchronously perform ultrasonic treatment (40 kHz, 300 W), after modification, centrifuge and separate (5000 rpm × 10 min), and vacuum-dry at 60°C to obtain hydrophobic aerogel powder. Premix the hydrophobic aerogel powder, polycrystalline mullite fiber, silica sand fine powder, and carbonized rice husk to prepare a functionalized aerogel composite powder.

[0030] S2. Add K12 powder, agar powder, sodium carboxymethyl cellulose solution, ammonium salt solution, and water to the functionalized aerogel composite powder, mix at a low speed (100 rpm) for 5 min, and then foam at a high speed (800 rpm) for 20 min, controlling the viscosity to be 1300 - 1400 mPa·s to obtain a ceramic slurry.

[0031] S3. Inject the ceramic slurry into a mold for molding, first pre-dry it in an environment of 40°C / RH60% for 12 h, then dry it in an environment of 60°C / RH30% for 36 h, demold, and then heat it to 600°C at a rate of 5°C / min in a nitrogen environment and hold for 1 h, and then heat it to 1600°C at a rate of 10°C / min and hold for 2 h to obtain the high-strength lightweight silica brick.

[0032] The technical solutions in the embodiments of the present application at least have the following technical effects or advantages:

[0033] HMDS reacts with the surface hydroxyl groups (-OH) of the aerogel to form hydrophobic silicon methyl (Si-CH3) groups, significantly reducing the surface energy and exhibiting superhydrophobic properties; after modification, the mechanical strength is enhanced, the compressive performance is improved, and the thermal stability is increased;

[0034] The hydrophobic aerogel is used as a binder to reduce the capillary pressure of water during drying and sintering, avoid structural collapse, and improve the yield; the low density of the aerogel and the pore former act synergistically to increase the porosity and reduce the density of the silica brick while maintaining the strength; because the hydrophobic surface reduces water adsorption, microcracks caused by drying stress are avoided; the enhanced skeleton (polycrystalline mullite fiber) of the modified aerogel and the hydrophobic binder act synergistically to improve the overall compressive and flexural strengths.

[0035] Combined with the void structure on the premise of the low thermal conductivity of the hydrophobic aerogel, the overall thermal conductivity of the silica brick can be significantly reduced, and the heat insulation performance can be improved; moreover, the hydrophobic surface prevents water penetration, reduces freeze-thaw cycles and structural damage in high-temperature environments, and extends the service life; sintered to 1600 °C under nitrogen protection, the hydrophobic groups may be partially decomposed, but the remaining Si-CH3 still provides hydrophobicity and high-temperature stability, while promoting the formation of the ceramic phase (mullite), enhancing the high-temperature strength, and preventing deterioration caused by the oxidation of the aerogel.

[0036] To verify the properties of the modified silica aerogel, a group experiment was carried out on the silica aerogel, and the specific grouping is shown in Table 1;

[0037] Table 1 Experimental grouping of modified aerogel

[0038]

[0039] To verify the microscopic mechanism of the hydrophobized aerogel, the contact angle was measured by the sessile drop method (Krüss DSA100), the crystallinity of mullite was detected by XRD quantitative analysis (Bruker D8 Advance, Cu-Kα radiation), the agglomeration size was detected by SEM-EDS analysis (FEI Quanta FEG250, acceleration voltage 20 kV), and the number of hydroxyl groups was detected by chemical titration (sodium hydroxide titration), and the results are shown in Table 2;

[0040] Table 2 Verification of the microscopic mechanism of modified aerogel

[0041]

[0042] For further verification of the particle size optimization of silica aerogel, the specific surface area was detected by BET specific surface area test (Micromeritics ASAP2460), and the proportion of mesopores was detected by mercury intrusion porosimetry (AutoPore IV9500). The results are shown in Table 3;

[0043] Table 3 Verification of the particle size of modified aerogel

[0044]

[0045] The comprehensive performance of high-strength lightweight silica bricks added with hydrophobic aerogel was verified by detecting the density (GB / T2997-2015), compressive strength (GB / T5072-2023), thermal conductivity (GB / T10294-2008), and number of thermal shock cycles (GB / T10294-2008, flaw detection method, 1100 °C Water cooling at 25 °C until cracks >1 mm appear), and the results are shown in Table 4;

[0046] Table 4 Performance test of high-strength lightweight silica bricks containing modified aerogel

[0047]

[0048] Example 2: The above example solved the problems of nano-dispersion and high-temperature stability through HMDS surface modification and protective sintering process. However, HMDS in the raw materials is prone to hydrolysis into hexamethyldisiloxane (HMDSO) in a humid environment, resulting in its inability to react with aerogel and a decrease in the stability of the slurry. To optimize its stability and further improve its performance, it was further improved on the basis of Example 1.

[0049] During the preparation of high-strength lightweight silica bricks, tetra-isopropyl titanate (TTP) was also added simultaneously when hydrophobic silica aerogel was blended and foamed at high speed with other components. The addition amount of TTP was 0.3-0.7 wt% of the mass of hydrophobic silica aerogel.

[0050] The technical solutions in the embodiments of the present application at least have the following technical effects or advantages:

[0051] By adding TTP, the interfacial bonding is strengthened, the ability to resist high-temperature deformation is increased; the high-temperature stability is increased; phonon scattering is increased, and the thermal conductivity is further reduced; the thermal shock life is increased.

[0052] The ground state electron configuration of Ti atoms (Z = 22) in TTP is [Ar]3d 2 4s 2 , and the vacant 3d orbitals (0-4 eV) can accept lone pair electrons to form coordination bonds. The lone pair electrons of oxygen in isopropoxy (-OCH(CH3)2) (2p4 It fills the 3d orbitals of Ti to form a σ coordination bond (bond energy ~250 kJ / mol).

[0053] When TTP encounters water, the Ti-O-C bond breaks: Ti-O-C3H7 + H2O → Ti-OH + HO-C3H7

[0054] After hydrolysis, highly reactive Ti-OH groups (pKa ≈ 5.2) are formed, which are more acidic than Si-OH (pKa ≈ 8.5). They preferentially react with HMDS to form Ti-O-Si (bond energy 523 kJ / mol) and replace Si-O-Si (bond energy 443 kJ / mol); also, due to the relatively fast hydrolysis reaction rate of TTP, it competes in the hydrolysis reaction and reduces the possibility of HMDS getting damp;

[0055] Formation of Ti-O-Si: Ti-OH + Si-OH → Ti-O-Si + H2O

[0056] The steric hindrance effect of the isopropoxy groups in TTP inhibits side reactions: The C-O-Ti bond angle of 112° hinders the self-condensation of HMDS molecules, instead increasing the formation of Ti-O-Si and improving the reaction selectivity;

[0057] The Ti-O-Si network serves as a crystal nucleus template, inducing the preferential growth of mullite crystals along the

[001] direction; reducing the mullite grain size from 200 nm to 50 nm; and the Ti-O-Si network forms a coherent interface with the Al2O3 lattice, reducing the thermal reaction force at high temperatures and further reducing the oxidation degree of the hydrophobic silica aerogel at high temperatures.

[0058] Ti 4+ 's d 0 electronic structure forms an electron defect center, capturing the O 2- holes in Al2O3, inhibiting the diffusion of oxygen ions at high temperatures, significantly reducing the oxidation rate, and catalyzing the condensation of silanol groups. The reaction activation energy decreases from 85 kJ / mol to 62 kJ / mol, also promoting the reaction to be more complete.

[0059] The Ti-O-Si interface forms atomic-level lattice distortion, resulting in increased phonon scattering, interfering with the directional movement of phonons, randomizing their propagation directions, thereby reducing the heat transfer efficiency and improving the heat insulation performance.

[0060] Group experiments were carried out on Example 2. Experiments were conducted on the basis of Case B to detect the results produced by TTP, as shown in Table 5;

[0061] Table 5 Performance Test of High-Strength Lightweight Silica Bricks Containing TTP

[0062]

[0063] Note: The decrease in the proportion of Ti-O-Si bonds in Case F is due to side reactions (self-condensation) caused by excessive TTP.

[0064] Microscopic mechanism experiments were carried out on the ceramic slurry and high-strength lightweight bricks after adding TTP, and the results are shown in Table 6;

[0065] Table 6 Verification of the Microscopic Mechanism of TTP

[0066]

[0067] Example 3: In Example 2, by adding TTP, the various properties of the lightweight bricks were greatly enhanced. However, during the mixing process of the slurry, due to the density difference of each component, the slurry stratified, the pore distribution was large, and the compressive strength decreased. A great deal of energy was required to strengthen the mixing. Therefore, further improvements were made on the basis of Example 2.

[0068] The silica aerogel includes a combination of multiple particle sizes, and the particle sizes include 1 μm (20%-40%), 5 μm (40%-60%), and 10 μm (20%);

[0069] The technical solutions in the embodiments of the present application at least have the following technical effects or advantages:

[0070] Using a combination of aerogels with multiple particle sizes can reduce the mixing difficulty, extend the stratification time, and also complex phonon conduction, reduce the thermal conductivity, reduce the gap in the void size, and improve the overall compressive strength.

[0071] The sedimentation rate of 1-μm particles is 0.08 mm / h, the sedimentation rate of 5-μm particles is 0.5 mm / h, and the sedimentation rate of 10-μm particles is 2.0 mm / h. Using a combination of multiple particle sizes makes it more difficult to stratify in the slurry. Based on the original slurry that stratifies after standing for 2 h, using a combination of multiple particle sizes can extend it to a maximum of 72 h without obvious stratification;

[0072] The voids are mainly generated by the reaction of carbonized rice husks. When carbonized rice husks decompose alone, the gas escape path is single, forming macropores larger than 100 μm; the adjacent rice husk pyrolysis zones will overlap, resulting in the merger of voids into millimeter-scale defects. Small particles (1 μm) penetrate into the gaps between carbonized rice husks to form a nanoscale framework, delaying the initial pyrolysis temperature, inhibiting the gas diffusion rate, and preventing the voids from being too large. Medium particles (5 μm) connect multiple carbonized rice husk particles, dividing the pyrolysis gas channels to reduce the standard deviation of the void size; large particles (10 μm) form a mechanical support framework around the carbonized rice husks to prevent the voids from collapsing, making the pore size distribution concentrated (80% of the voids are in the range of 80-120 μm);

[0073] The binding energies of silica aerogels with different particle sizes to HMDS and TTP can better highlight their functions. The 1-μm aerogel has a high specific surface area and high activity. It preferentially adsorbs HMDS to form a complete monolayer, shielding the hydroxyl groups and reducing the viscosity of the slurry. TTP penetrates into the particle gaps to form Ti-O-Si, enhancing the compressive strength. The larger the particle size, the lower the coverage rate of HMDS adsorption. The 10-μm aerogel forms a hydrophobic belt, enhancing the flexural strength. At the interface, Ti-O-Al-Si ternary bonds (bond energy 650 kJ / mol) are generated with TTP, bridging the aerogel and the matrix. The 5-μm aerogel can act as a joint structure, connecting the skeleton structures formed by large- and small-particle-size aerogels. The formed hydrophilic-hydrophobic alternating interface can improve the fiber bonding strength. Mullite whiskers are in-situ generated on the surface of TTP, and Ti-O-Al bonds are formed with Al2O3, enabling the connection between aerogels with different particle sizes and ultimately forming a complex skeleton structure. Under this complex structure, the voids in the silica brick are numerous and complex, further increasing the phonon mean free path.

[0074] Experiments were carried out on different combinations of Example 3 based on Case D, and the experimental results are shown in Table 7.

[0075] Table 7 Performance verification of high-strength lightweight bricks manufactured with different combinations

[0076]

[0077] The key properties of the ceramic slurry and the high-strength lightweight bricks manufactured therefrom were tested, and the results are shown in Table 8.

[0078] Table 8 Key property verification of ceramic slurries prepared with different combinations and the high-strength lightweight bricks manufactured therefrom

[0079]

[0080] Example 4: In Example 3, the phonon conduction was further complicated by the combined use of large and small particle sizes, reducing the thermal conductivity and increasing the thermal shock cycle life. To further optimize its practical application ability, it was further improved based on Example 3.

[0081] The aerogels with different particle sizes were separately loaded. The 10-μm aerogel was loaded with TTP, and the addition amount of TTP was 0.3 - 0.7 wt% of the mass of the hydrophobic silica aerogel. The 5-μm aerogel was premixed with carbonized rice husk, and the 1-μm aerogel was the hydrophobic silica aerogel.

[0082] The technical solutions in the embodiments of the present application at least have the following technical effects or advantages:

[0083] Separate loading of aerogels with different particle sizes is used to form triple synergy of rigid group gradient densification (10μm aerogel + TTP + HMDS), tough group porous buffering (5μm aerogel + carbonized rice husk), and heat insulation group phonon scattering (HMDS + 1μm aerogel);

[0084] For the rigid group gradient densification (10μm aerogel + TTP + HMDS), tetrapropyl orthotitanate (TTP) reacts with the surface hydroxyl groups of the 10μm aerogel to form Ti-O-Si bonds, forming a ceramicized interface layer; hexamethyldisilazane (HMDS) coats the unreacted hydroxyl groups (coverage rate ≥ 95%), the contact angle is increased to 125°, blocking the water penetration path, maintaining structural stability at high temperatures (>1200°C), preventing softening; forming a gradient modulus interface to inhibit the concentration of thermal stress;

[0085] For the tough group porous buffering (5μm aerogel + carbonized rice husk), rice husk pyrolyzes at 300 - 600°C to generate CO2 / H2O gas, forming controllable pores of 50 - 200μm; the 5μm aerogel fills the gaps between rice husks, dividing the macropores into nano-micron scale multi-level pores, absorbing impact energy through pore collapse (energy absorption efficiency 28MJ / m3); the crack propagation path is tortuous, improving the fracture toughness;

[0086] For the heat insulation group phonon scattering (HMDS + 1μm aerogel), the 1μm aerogel forms mesopores of 2 - 5nm, scattering high-frequency phonons (>10THz); the hydrophobic coating reduces the van der Waals force between particles, inhibits nano-agglomeration, maintains the porosity to block the heat conduction path, and has a low thermal conductivity; the hydrophobic layer is stable at high temperatures, avoiding the increase in thermal conductivity caused by the intrusion of water vapor;

[0087] The rigid group bears the mechanical load, the tough group absorbs the impact energy, and the heat insulation group blocks the heat flow, achieving: a breakthrough in the contradictory properties of compressive strength and thermal conductivity; the high-temperature strength retention rate reaches 91% (1600°C), the ceramic bonding (TTP) of the rigid group resists compression, the pore collapse of the tough group consumes energy, and the nano-pores of the heat insulation group inhibit crack initiation: the HMDS hydrophobic layer prevents the performance degradation in a humid environment, and at the same time realizes high strength, high toughness, and ultra-low thermal conductivity, breaking through the shackles of traditional materials "strong but brittle, heat-insulating but weak"; it has stable performance under extreme conditions such as 1600°C high temperature, water quenching thermal shock, and high humidity. Through the triple synergy of "chemical bonding strengthening (TTP) + physical pore formation buffering (carbonized rice husk) + nano-scattering heat insulation (HMDS)", this solution realizes the leap of aerogel materials from a single function to "strong-tough-heat-insulating" integration, providing an innovative solution for high-end fields such as aerospace and new energy.

[0088] Perform performance testing on Example 4, and the grouping is shown in Table 9;

[0089] Table 9 Experimental grouping of Example 4

[0090]

[0091] The performance of the fourth embodiment was detected in groups, and the results are shown in Table 10;

[0092] Table 10 Performance verification of the high-strength and lightweight bricks prepared in the fourth embodiment

[0093]

[0094] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-strength lightweight silica brick, characterized in that, It includes polycrystalline mullite fiber, fine silica sand powder, carbonized rice husk, water, hydrophobic silica aerogel, tetra-isopropyl titanate, sodium carboxymethyl cellulose solution, ammonium salt solution, K12 powder, and agar powder; the hydrophobic silica aerogel is made of silica aerogel modified by hexamethyldisilazane; Among them, the ratio of silica aerogel to hexamethyldisilazane in the hydrophobic silica aerogel is 100g:0.5 - 1.0g, and the addition amount of tetra-isopropyl titanate is 0.3 - 0.7wt% of the mass of the hydrophobic silica aerogel; the particle sizes of the silica aerogel include 1μm, 5μm, and 10μm.

2. The high-strength and lightweight silica brick according to claim 1, characterized in that, The mass percentages of each component are as follows: polycrystalline mullite fiber 4%, fine silica sand powder 55%, carbonized rice husk 15%, agar powder 1%, K12 powder 2%, ammonium salt solution 2%, sodium carboxymethyl cellulose solution 2%, hydrophobic silica aerogel 15%, and water 4%.

3. A high-strength and lightweight silica brick according to claim 1, characterized in that, The 1μm silica aerogel accounts for 20% - 40% of the total amount of silica aerogel.

4. A high-strength and lightweight silica brick according to claim 1, characterized in that, The 5μm silica aerogel accounts for 40% - 60% of the total amount of silica aerogel.

5. A high-strength and lightweight silica brick as claimed in claim 1, wherein, The 10μm silica aerogel accounts for 20% of the total amount of silica aerogel.

6. A preparation method of a high-strength lightweight silica brick according to any one of claims 1-5, characterized in that, The preparation method of the high-strength lightweight silica brick is as follows: S1. Vacuum-dry the silica aerogel at 60°C for 24h, crush it through a 400-mesh sieve, and then in a nitrogen-protected reaction kettle, feed materials according to the ratio of aerogel: hexamethyldisilazane = 100g:0.5 - 1.0g; hexamethyldisilazane: ethanol = 3 - 5:1, stir and react at a constant temperature of 60 - 80°C for 2 - 4h, synchronously perform ultrasonic treatment, after modification, centrifuge and separate, vacuum-dry at 60°C to obtain hydrophobic aerogel powder, and premix the hydrophobic aerogel powder with polycrystalline mullite fiber, fine silica sand powder, and carbonized rice husk to make a functionalized aerogel composite powder; S2. Add K12 powder, agar powder, sodium carboxymethyl cellulose solution, ammonium salt solution, and water to the functionalized aerogel composite powder, mix at low speed for 5min, and then foam at high speed for 20min, control the viscosity to be 1300 - 1400mPa·s to obtain a ceramic slurry; During the preparation of the high-strength lightweight silica brick, tetra-isopropyl titanate is also added simultaneously when the hydrophobic silica aerogel is mixed and foamed at high speed with other components, and the addition amount of tetra-isopropyl titanate is 0.3 - 0.7wt% of the mass of the hydrophobic silica aerogel; S3. Inject the ceramic slurry into a mold for molding, pre-dry it in an environment of 40°C / RH60% for 12h, then dry it in an environment of 60°C / RH30% for 36h, demold, and then heat it to 600°C at a rate of 5°C / min in a nitrogen environment and hold for 1h, and then heat it to 1600°C at a rate of 10°C / min and hold for 2h to obtain the high-strength lightweight silica brick.

Images