Silicon mullite brick capable of being filled with thermal insulation material and production process of silicon mullite brick

Abstract

The invention discloses a silicon mullite brick capable of being filled with a thermal insulation material and a production process thereof, and belongs to the technical field of refractory material production. The silicon mullite brick comprises a surface layer, a middle layer and an inner layer from outside to inside, the surface layer contains tabular corundum and silicon carbide micro powder, the middle layer contains mullite hollow balls, pre-sintered kyanite and nano-zirconia, the inner layer contains aluminum oxide hollow balls, floating beads and silicon carbide whiskers, and three-dimensional through pore channels are formed inside the silicon mullite brick. The pore channels are filled with silicon dioxide aerogel and ceramic fiber composite heat insulation materials, and the filling rate is larger than or equal to 85%. The production process comprises the steps of gradient material distribution, composite forming, in-situ foaming, vacuum impregnation strengthening, fluctuation sintering strengthening and the like. Through gradient composite structure design and multi-process cooperation, a three-dimensional functional partition is constructed, high-density filling and structural stability of the heat insulation material are achieved, mechanical strength and heat insulation performance are balanced, thermal shock resistance is remarkably improved, the service life is remarkably prolonged, and a novel refractory material is provided for high-temperature industrial equipment.

Description

Technical Field

[0001] The invention relates to the technical field of refractory material production, in particular to a silica-molybdenum brick capable of being filled with thermal insulation material and a production process thereof. Background Art

[0002] Currently, the thermal insulation performance of silica-molybdenum bricks, as high-temperature refractory materials, mainly relies on reducing material density or introducing closed-cell structures. A structural and process system specifically designed for the filling function of thermal insulation materials has not yet been developed, resulting in fundamental defects in the existing products in achieving efficient thermal insulation: Structural flaws: Traditional silica-molybdenum bricks utilize a homogeneous, dense structure or isolated, closed-cell design, lacking a three-dimensional through-hole system suitable for the penetration of insulation materials. Insulation materials such as aerogel and ceramic fiber can only be applied via surface coating (filling ratio <15%) and cannot penetrate deeply into the matrix to form an effective insulation layer. Pore ​​size mismatch: The pore size generated by conventional pore-forming processes is randomly distributed (10μm-2mm), which is an order of magnitude different from that of nanoscale thermal insulation materials (such as aerogel powder D50 = 20-50nm). This results in loose filling of macropores and blockage of micropores, making it impossible to build a dense thermal insulation network. Process conflict: Insulation material filling must be carried out after the brick body is sintered. However, materials such as aerogel cannot withstand secondary high-temperature treatment (>300°C). If it is carried out simultaneously with the sintering process, the resin binder will carbonize and contaminate the matrix. Existing technologies cannot solve the compatibility conflict between filling timing and sintering temperature. Interface failure: The insulation material of a simple impregnation filling is bonded to the substrate only by physical adsorption. At high temperatures, the difference in thermal expansion coefficient (CTE of silica-molybdenum bricks ≈ 5.5×10-6 / ℃ vs. CTE of aerogel ≈ 0.5×10-6 / ℃) causes interface delamination, resulting in the insulation layer being completely detached from the pores of the substrate.

[0003] Existing technologies inherently lack specialized "fillable" structural designs and process adaptability, preventing silica-molybdenum bricks from achieving long-term thermal insulation as a thermal insulation material. This technological gap severely restricts their application in energy-saving upgrades in high-temperature equipment such as cement kilns and metallurgical furnaces. Summary of the Invention

[0004] The main purpose of the present invention is to provide a silica-molybdenum brick that can be filled with insulation material and a production process thereof, which can effectively solve the problems mentioned in the background technology.

[0005] To achieve the above object, the technical solution adopted by the present invention is: A silica-molybdenum brick capable of being filled with thermal insulation material and a production process thereof, comprising a surface layer, an intermediate layer and an inner layer which are sequentially composited from the outside to the inside; The surface layer comprises 70-80wt% of plate-shaped corundum and 20-30wt% of silicon carbide powder, wherein the plate-shaped corundum particle size is 0.5-1mm, and the silicon carbide powder D50 is ≤5μm; The intermediate layer comprises 60-70wt% of mullite hollow spheres, 20-30wt% of pre-calcined kyanite and 5-10wt% of nano-zirconia, and the particle size of the mullite hollow spheres is 0.3-0.8mm; The inner layer comprises 50-60wt% of hollow alumina balls, 30-40wt% of floating beads and 10-20wt% of silicon carbide whiskers, and the particle size of the hollow alumina balls is 1-2mm; The silica-molybdenum brick has three-dimensional through-holes inside, and the holes are filled with silica aerogel and ceramic fiber composite insulation material, with a filling rate of ≥85%.

[0006] By combining the surface plate-like corundum with silicon carbide powder (70-80wt% corundum provides wear resistance, 20-30wt% silicon carbide enhances oxidation resistance), the middle layer of mullite hollow balls and kyanite work together (60-70wt% hollow balls build the pore skeleton, 20-30wt% pre-burned kyanite buffers thermal expansion stress), and the inner layer of alumina hollow balls combined with silicon carbide whiskers (50-60wt% hollow balls reduce thermal conductivity, 10-20wt% whiskers improve toughness), a composite functional system of "external resistance and internal isolation" is formed. The three-dimensional through-channel design enables the insulation material filling rate to exceed 85%.

[0007] Preferably, the intermediate layer of mullite hollow spheres is surface coated, and the coating layer is composed of aluminum dihydrogen phosphate and nano zirconium oxide in a mass ratio of 3:1, and the coating layer thickness is 5-10 μm. During sintering, the aluminum dihydrogen phosphate-nano zirconium oxide coating layer (mass ratio 3:1) reacts with the surface of the mullite hollow spheres to form an AlPO4-ZrO2 composite interface layer, whose thermal expansion coefficient (4.8×10 -6 / ℃) between mullite (5.2×10 -6 / ℃) and aerogel filling layer (0.5×10 -6 / ℃), effectively relieving interlayer thermal stress and inhibiting the propagation of pore cracks through zirconia phase transformation toughening.

[0008] Preferably, the composite insulation material is composed of silica aerogel powder and Al2O3-SiO2 ceramic fibers in a 4:1 mass ratio. The ceramic fibers have an aspect ratio greater than 100, and the aerogel has a porosity of 95% or greater. In this 4:1 aerogel-ceramic fiber composite, the aerogel (porosity ≥ 95%) fills the micropores to achieve nanoscale insulation, while the Al2O3-SiO2 fibers (aspect ratio > 100) penetrate the macropores in a three-dimensional network structure. The fiber bridging effect increases the bonding strength between the matrix and the filler by more than 50%, and prevents high-temperature migration of aerogel particles.

[0009] Preferably, a production process of silica-molybdenum bricks that can be filled with insulation material comprises the following steps: S1. Gradient material distribution: Using a layered material distribution system with electromagnetic positioning function, the surface layer, middle layer and inner layer materials are placed into the mold according to the spatial coordinate positioning. The depth of the surface layer material is 10-15% of the total thickness of the brick body, the middle layer is 50-60%, and the inner layer is 25-35%; S2. Composite molding: S2.1, Pre-pressing stage: pre-pressing for 30-60s at a vibration frequency of 10-15Hz and a pressure of 0.5-1MPa; S2.2, Gradient pressurization: Increase the pressure step by step to 3-5 MPa at a rate of 0.2 MPa / s, and maintain each pressure level for 60-90 seconds; S2.3, pressure maintenance and exhaust: maintain the pressure at 5 MPa for 120-180 seconds, and simultaneously apply ultrasonic vibration at a frequency of 25-30 Hz; S3, in-situ foaming: Place the formed body in a nitrogen atmosphere kiln and sinter according to the following temperature program: S3.1. Raise the temperature to 800°C at 3°C / min to trigger the initial decomposition of the foaming agent; S3.2. Raise the temperature to 1350°C at a rate of 1.5°C / min until the foaming agent is completely decomposed to form pores. S3.3, heat at 1350°C for 30 min to complete the directional growth of the pores; S4, vacuum impregnation strengthening: S4.1. Cool the sintered body to 80-120°C and place it in a vacuum tank. Evacuate the vacuum to ≤0.01 MPa and maintain the pressure for 20-30 minutes. S4.2, step-by-step impregnation: S4.2.1. First, inject silica sol slurry containing nano-SiO2 aerogel with a slurry viscosity of 200-300 mPa·s and an injection pressure of 0.3-0.5 MPa; S4.2.2. Then inject Al2O3-SiO2 ceramic fiber suspension with a fiber mass concentration of 5-8% and an injection pressure of 0.1-0.2 MPa; S4.3, Microwave Gradient Curing: S4.3.1. Stage 1: Irradiate at 2.45 GHz, 3 kW for 5-8 minutes to allow the slurry to initially gel; S4.3.2. Second stage: 915MHz, 1kW continuous irradiation for 15-20 minutes to complete deep curing; S5. Wave sintering strengthening: S5.1. After heating to 1200°C at 5°C / min, switch to the fluctuating temperature control mode: S5.1.1. In the range of 1200-1450°C, perform temperature fluctuations of ±10°C every 10 minutes; S5.1.2. The number of fluctuation cycles is ≥ 24 times, with a total duration of 4-5 hours; S5.2. After sintering, cool rapidly to below 800°C at a rate of 10°C / min.

[0010] The electromagnetic positioning and distribution system uses magnetic field to regulate the crystal plane orientation of plate-shaped corundum (0.5-1mm), so that it is arranged parallel to the brick surface to form a dense anti-scour layer; it simultaneously controls the uniform distribution of mullite hollow balls (0.3-0.8mm) in the middle layer, laying the spatial topological foundation for the subsequent foaming to form directional channels.

[0011] Preferably, the layered fabric distribution system described in step S1 is equipped with a laser thickness measurement feedback device that monitors the thickness of each fabric layer in real time and automatically compensates for thickness deviations, with a control accuracy of ±0.1mm. The laser thickness measurement feedback device dynamically adjusts the fabric distribution by scanning the thickness of each layer in real time (with a control accuracy of ±0.1mm), ensuring a precise match between the densified surface layer (10-15% of the total thickness), the porous middle layer (50-60%), and the lightweight inner layer (25-35%), thereby avoiding interfacial stress concentration caused by layer thickness deviations.

[0012] Preferably, the foaming agent is added in step S3.1 by mixing magnesium carbonate and silicon nitride powder in a ratio of 2:1, and then using a fluidized bed coating process to form a 5-10 μm thick coating layer on the surface of the mullite hollow spheres, with the coating layer accounting for 3-5% of the mass of the hollow spheres. The fluidized bed coating process allows the magnesium carbonate-silicon nitride foaming agent (2:1) to be evenly attached to the surface of the mullite hollow spheres. During sintering, the CO2 and NH3 gases produced by the decomposition of the foaming agent are directedly released through the gaps between the spheres, forming radial through-holes (pore diameter 50-300 μm) with the hollow spheres as nodes. The channel tortuosity is reduced to 1.3-1.5 (conventional processes are >2.0), significantly improving the permeability efficiency of the thermal insulation material.

[0013] Preferably, the silica sol slurry in step S4.2.1 comprises the following components: Nano-SiO2 aerogel powder: 40-50wt%; Silica sol (SiO2 content 25%): 30-40wt%; Polyvinyl butyral binder: 5-8wt%; Glycerol leveling agent: 1-2wt%; The slurry undergoes high-speed shear emulsification treatment at a shear rate of ≥5000 rpm for 20-30 minutes. Polyvinyl butyral (5-8 wt%) and glycerol (1-2 wt%) in the silica sol slurry work synergistically under high-speed shear (≥5000 rpm) to form a stable dispersion of aerogel powder (40-50 wt%). The silica sol (30-40 wt%) gels in situ, forming Si-O-Si chemical bonds with the pore walls of the matrix, increasing the filler bonding strength to ≥2 MPa.

[0014] Preferably, the temperature fluctuation in step S5.1.1 adopts a sawtooth wave and square wave superposition mode, wherein: Sawtooth wave amplitude ±5°C, period 5min; Square wave amplitude ±5°C, period 15min; The phase difference between the two is 90°, and a composite temperature curve is generated through the Fourier superposition algorithm. The phase difference superposition temperature control mode of the sawtooth wave (±5℃ / 5min) and the square wave (±5℃ / 15min) generates an asymmetric temperature field through the Fourier algorithm, which promotes the preferential growth of grains along the (110) crystal plane, improving the material's high-temperature creep resistance by 40%. At the same time, the microstress field generated by the wave sintering can close the microcracks on the pore surface and reduce the porosity fluctuation to ±1.5%.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a gradient composite structure design and multi-process collaborative innovation to create a three-dimensional functional partitioning system within the silica-molybdenum brick: a surface layer with wear-resistant protection, a middle layer with directional channels, and an inner layer with enhanced thermal insulation. Combined with in-situ foaming, vacuum impregnation reinforcement, and dynamic temperature-controlled sintering, this technology achieves a high-density filling of the insulation material within the matrix while synergizing structural stability. This innovative process effectively balances the conflict between the mechanical strength and thermal insulation properties of the refractory material, significantly improving its thermal shock resistance and service life. Furthermore, by optimizing the sintering process, energy consumption is reduced, providing a new refractory material for high-temperature industrial equipment that combines structural strength with efficient thermal insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the production process of the present invention. DETAILED DESCRIPTION

[0017] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0018] like Figure 1 The production process flow diagram of silica-molybdenum bricks that can be filled with insulation materials is shown below, which is explained in conjunction with a detailed embodiment.

[0019] 1. Component design of silica-molybdenum bricks (taking 10kg bricks as an example) (1) Surface layer (thickness 12%, total mass 1.2 kg) Raw material ratio: Tabular corundum (particle size 0.5-1mm): 75wt% (0.9kg) Silicon carbide powder (D50=3μm): 25wt% (0.3kg) Features: Tabular corundum provides high-temperature wear resistance, while silicon carbide micropowder enhances oxidation resistance. The two form a dense erosion-resistant surface layer through particle grading.

[0020] (2) Middle layer (55% thickness, 5.5 kg total mass) Raw material ratio: Coated mullite hollow spheres (particle size 0.3-0.8mm): 65wt% (3.575kg) Pre-burned kyanite (calcined at 1500℃ for 2h, particle size 0.1-0.3mm): 25wt% (1.375kg) Nano-zirconia (average particle size 50nm): 10wt% (0.55kg) Hollow ball coating process: Magnesium carbonate and silicon nitride were mixed in a 2:1 mass ratio and coated on the surface of hollow mullite spheres using a fluidized bed coating system (inlet air temperature 120°C, fluidization velocity 1.5 m / s). The coating layer accounted for 4% of the sphere's mass. The coating layer consisted of aluminum dihydrogen phosphate and nano-zirconium oxide in a 3:1 mass ratio. After sintering, an AlPO4-ZrO2 interface layer was formed to relieve thermal stress.

[0021] (3) Inner layer (33% thickness, total mass 3.3kg) Raw material ratio: Alumina hollow spheres (particle size 1-2 mm): 55wt% (1.815kg) Floating beads (particle size 0.2-0.5mm): 35wt% (1.155kg) Silicon carbide whiskers (aspect ratio 200:1): 10% (0.33 kg) Structural design: Large-size hollow alumina balls build a low-density skeleton, floating beads fill the gaps, and cross-lap silicon carbide whiskers enhance toughness, forming a "lightweight-high-strength" inner layer.

[0022] (IV) Filling insulation material (filling rate 88%) Compound formula: Silica aerogel powder (porosity 96%, D50=30nm): 4kg Al2O3-SiO2 ceramic fiber (aspect ratio 150:1, diameter 5μm): 1kg Mixing process: A three-dimensional drum mixer (rotating speed 30 rpm, mixing time 60 min) was used to evenly disperse the fibers in the aerogel powder to form a three-dimensional network filling body.

[0023] 2. Production process implementation steps (1) S1 gradient fabric (mold size: 300mm×150mm×100mm) Equipment parameters: The layered material distribution system is equipped with an electromagnetic positioning device (magnetic field strength 0.2T) and a laser thickness gauge (accuracy ±0.1mm).

[0024] Clothing process: Surface layer: After mixing plate-shaped corundum and silicon carbide powder, evenly spread it along the bottom of the mold with a thickness of 12mm (accounting for 12% of the total thickness). Electromagnetic positioning is used to orient the corundum particles parallel to the brick surface.

[0025] Middle layer: A mixture of coated mullite hollow balls, pre-burned kyanite, and nano-zirconia is added, with a laying thickness of 55mm. Laser thickness measurement is used to compensate for deviations in real time (if the thickness of a certain area is less than 55mm, 0.5g of material will be automatically added).

[0026] Inner layer: Pour a mixture of hollow alumina balls, floating beads, and silicon carbide whiskers, laying a thickness of 33mm to ensure that the interfaces of each layer are flat.

[0027] (2) S2 composite molding S2.1 Pre-loading stage: The vibration table frequency is 12 Hz, and a pressure of 0.8 MPa is applied for 45 seconds to make the particles initially dense and expel the air between large particles.

[0028] S2.2 Gradient pressurization: The pressure is increased at a rate of 0.2 MPa / s, and each pressure level (1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa) is maintained for 90 seconds. For example, it takes 5 seconds to increase from 1 MPa to 2 MPa. During the pressure maintenance period, the particles are rearranged to form a uniform skeleton.

[0029] S2.3 Pressure maintaining exhaust: Maintaining a pressure of 5 MPa for 150 seconds, the 28 Hz ultrasonic vibration was simultaneously activated to break the tiny bubbles using the cavitation effect, resulting in a green body density of 2.2 g / cm 3 (75% of theoretical density).

[0030] (III) S3 in-situ foaming (nitrogen furnace volume 1m 3, nitrogen flow rate 5L / min) Heating program: Stage 1: The temperature is raised to 800 °C at 3 °C / min, and magnesium carbonate begins to decompose (MgCO3→MgO+CO2↑), forming initial micropores in the gaps between the hollow spheres.

[0031] Stage 2: The temperature is raised to 1350°C at 1.5°C / min. Silicon nitride reacts with the coating (Si3N4+3O2→3SiO2+2N2↑). The generated CO2 and N2 gases diffuse radially along the hollow sphere, forming through channels with a pore size of 50-300μm and a channel tortuosity of 1.4 (traditional process>2.0).

[0032] Stage 3: Keeping at 1350℃ for 30min, the pores grow in a directional manner to form a three-dimensional through-hole network with hollow spheres as nodes.

[0033] (4) S4 vacuum impregnation strengthening S4.1 Preprocessing: The sintered body was cooled to 100°C, placed in a vacuum tank (50 L capacity), and evacuated to 0.008 MPa for 25 min to ensure that the residual air rate in the pores was less than 0.5%.

[0034] S4.2 Step-by-step impregnation: Step 1: Aerogel silica sol slurry injection Slurry formula (10kg): nano-SiO2 aerogel powder 45wt% (4.5kg), silica sol (SiO2 content 25%) 35wt% (3.5kg), polyvinyl butyral 7wt% (0.7kg), glycerol 1.5wt% (0.15kg), and the remaining 11.5% is deionized water.

[0035] Preparation process: Process in a high-speed shear emulsifier (6000 rpm) for 25 minutes to form a stable slurry with a viscosity of 250 mPa·s. The slurry is then injected at a pressure of 0.4 MPa to penetrate into the micropores (<100 μm).

[0036] Step 2: Ceramic fiber suspension injection Suspension formula: Al2O3-SiO2 ceramic fibers (mass concentration 6%) are dispersed in deionized water, 0.5% sodium hexametaphosphate is added as a dispersant, and injected at a pressure of 0.15 MPa. The fibers fill the macropores (>100 μm) and form a bridging structure.

[0037] S4.3 Microwave Gradient Curing The first stage: 2.45 GHz, 3 kW irradiation for 6 min, rapid gelation of silica sol, and fixed position of aerogel particles.

[0038] The second stage: 915MHz, 1kW irradiation for 18 minutes, the deep ceramic fiber and the gel layer are chemically bonded (Si-O-Al bond), and the bonding strength reaches 2.2MPa.

[0039] (5) S5 wave sintering strengthening Heating and fluctuating temperature control: The temperature was raised to 1200°C at a rate of 5°C / min and then switched to a composite temperature fluctuation mode: a sawtooth wave (amplitude ±5°C, period 5 min) and a square wave (amplitude ±5°C, period 15 min) were superimposed with a 90° phase difference. A composite curve was generated through PLC programming, with a ±10°C fluctuation completed every 10 min for 24 cycles (a total of 4.8 h).

[0040] Principle: The asymmetric temperature field promotes the preferential growth of corundum grains along the (110) crystal plane, the grain size is refined from 50μm to 30μm, and the creep resistance is improved by 40%; the microstress field closes the microcracks on the pore surface, and the porosity fluctuation is controlled at ±1.2%.

[0041] Rapid cooling treatment: After sintering, the brick was rapidly cooled to 700°C at a rate of 10°C / min to avoid shrinkage cracks in the aerogel due to slow cooling. The final brick size deviation was <±0.3mm.

[0042] 3. Performance Test and Results Test items Test Method Measured value Technical indicators Bulk density GB / T2997-2015 1.85g / cm3 ≤2.0g / cm3 Thermal conductivity (800℃) GB / T3438-2015 0.35W / (m·K) ≤0.4W / (m·K) Thermal shock resistance (1100℃ water cooling) GB / T30873-2014 50 times without cracks ≥30 times Fill rate Micro-CT scan 88% ≥85% Interface bonding strength Pull-out test 2.1MPa ≥2MPa 4. Principle Description Gradient structure design: the surface layer is wear-resistant, the middle layer is porous, and the inner layer is heat-insulating. Functional zoning is achieved through layered distribution, solving the insulation defects of the traditional homogeneous structure of silica-molybdenum bricks.

[0043] In-situ foaming and directional pores: The magnesium carbonate-silicon nitride coating can controllably produce gas during the sintering process, forming through pores with hollow spheres as nodes. The pore size distribution matches the insulation material (50-300μm pores are suitable for 5-100μm fibers and nano-aerogels).

[0044] Vacuum impregnation and microwave curing: step-by-step impregnation achieves gradient filling of "micropore aerogel filling and macropore fiber framework", and microwave curing avoids high temperature damage to the aerogel while forming a chemical bonding interface.

[0045] Fluctuation sintering strengthening: Compound temperature fluctuation promotes preferential grain growth and pore structure stability, improves high-temperature mechanical properties, and solves the thermal expansion mismatch problem between the filling material and the matrix in traditional processes.

[0046] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A silica-molybdenum brick that can be filled with thermal insulation material and its production process, characterized by: It includes a surface layer, an intermediate layer and an inner layer which are compounded in sequence from the outside to the inside; The surface layer comprises 70-80wt% of plate-shaped corundum and 20-30wt% of silicon carbide powder, wherein the plate-shaped corundum particle size is 0.5-1mm, and the silicon carbide powder D50 is ≤5μm; The intermediate layer comprises 60-70wt% of mullite hollow spheres, 20-30wt% of pre-calcined kyanite and 5-10wt% of nano-zirconia, and the particle size of the mullite hollow spheres is 0.3-0.8mm; The inner layer comprises 50-60wt% of hollow alumina balls, 30-40wt% of floating beads and 10-20wt% of silicon carbide whiskers, and the particle size of the hollow alumina balls is 1-2mm; The silica-molybdenum brick has three-dimensional through-holes inside, and the holes are filled with silica aerogel and ceramic fiber composite insulation material, with a filling rate of ≥85%.

2. The silica-molybdenum brick capable of being filled with thermal insulation material and its production process according to claim 1, characterized in that: The hollow mullite balls in the middle layer are subjected to surface coating treatment, wherein the coating layer is composed of aluminum dihydrogen phosphate and nano zirconium oxide in a mass ratio of 3:1, and the thickness of the coating layer is 5-10 μm.

3. The silica-molybdenum brick capable of being filled with thermal insulation material and its production process according to claim 1, characterized in that: The composite thermal insulation material is formed by compounding silica aerogel powder and Al2O3-SiO2 ceramic fibers in a mass ratio of 4:1, the aspect ratio of the ceramic fibers is greater than 100, and the porosity of the aerogel is greater than or equal to 95%.

4. A process for producing a silica-molybdenum brick capable of being filled with a thermal insulation material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Gradient material distribution: Using a layered material distribution system with electromagnetic positioning function, the surface layer, middle layer and inner layer materials are placed into the mold according to the spatial coordinate positioning. The depth of the surface layer material is 10-15% of the total thickness of the brick body, the middle layer is 50-60%, and the inner layer is 25-35%; S2. Composite molding: S2.1, Pre-pressing stage: pre-pressing for 30-60s at a vibration frequency of 10-15Hz and a pressure of 0.5-1MPa; S2.2, Gradient pressurization: Increase the pressure step by step to 3-5 MPa at a rate of 0.2 MPa / s, and maintain each pressure level for 60-90 seconds; S2.3, pressure maintenance and exhaust: maintain the pressure at 5 MPa for 120-180 seconds, and simultaneously apply ultrasonic vibration at a frequency of 25-30 Hz; S3, in-situ foaming: Place the formed body in a nitrogen atmosphere kiln and sinter according to the following temperature program: S3.

1. Raise the temperature to 800°C at 3°C / min to trigger the initial decomposition of the foaming agent; S3.

2. Raise the temperature to 1350°C at a rate of 1.5°C / min until the foaming agent is completely decomposed to form pores. S3.3, heat at 1350°C for 30 min to complete the directional growth of the pores; S4, vacuum impregnation strengthening: S4.

1. Cool the sintered body to 80-120°C and place it in a vacuum tank. Evacuate the vacuum to ≤0.01 MPa and maintain the pressure for 20-30 minutes. S4.2, step-by-step impregnation: S4.2.

1. First, inject silica sol slurry containing nano-SiO2 aerogel with a slurry viscosity of 200-300 mPa·s and an injection pressure of 0.3-0.5 MPa; S4.2.

2. Then inject Al2O3-SiO2 ceramic fiber suspension with a fiber mass concentration of 5-8% and an injection pressure of 0.1-0.2 MPa; S4.3, Microwave Gradient Curing: S4.3.

1. Stage 1: Irradiate at 2.45 GHz, 3 kW for 5-8 minutes to allow the slurry to initially gel; S4.3.

2. Second stage: 915MHz, 1kW continuous irradiation for 15-20 minutes to complete deep curing; S5. Wave sintering strengthening: S5.

1. After heating to 1200°C at 5°C / min, switch to the fluctuating temperature control mode: S5.1.

1. In the range of 1200-1450°C, perform temperature fluctuations of ±10°C every 10 minutes; S5.1.

2. The number of fluctuation cycles is ≥ 24 times, with a total duration of 4-5 hours; S5.

2. After sintering, cool rapidly to below 800°C at a rate of 10°C / min.

5. The production process of a silica-molybdenum brick that can be filled with thermal insulation material according to claim 4, characterized in that: The layered fabric system in step S1 is equipped with a laser thickness measurement feedback device to monitor the thickness of each layer of fabric in real time and automatically compensate for thickness deviations with a control accuracy of ±0.1mm.

6. The production process of a silica-molybdenum brick that can be filled with thermal insulation material according to claim 4, characterized in that: The foaming agent is added in step S3.1 as follows: magnesium carbonate and silicon nitride powder are mixed in a ratio of 2:1, and a fluidized bed coating process is used to form a 5-10 μm thick coating layer on the surface of the mullite hollow sphere, and the coating layer accounts for 3-5% of the mass of the hollow sphere.

7. The process for producing a silica-molybdenum brick capable of being filled with thermal insulation material according to claim 4, characterized in that: The silica sol slurry in step S4.2.1 comprises the following components: Nano-SiO2 aerogel powder: 40-50wt%; Silica sol (SiO2 content 25%): 30-40wt%; Polyvinyl butyral binder: 5-8wt%; Glycerol leveling agent: 1-2wt%; The slurry is subjected to high-speed shear emulsification treatment, with a shear rate of ≥5000rpm and a treatment time of 20-30min.

8. The process for producing a silica-molybdenum brick capable of being filled with thermal insulation material according to claim 4, characterized in that: The temperature fluctuation in step S5.1.1 adopts a sawtooth wave and square wave superposition mode, wherein: Sawtooth wave amplitude ±5°C, period 5min; Square wave amplitude ±5°C, period 15min; The phase difference between the two is 90°, and a composite temperature curve is generated by Fourier superposition algorithm.

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