Coated honeycomb ceramic regenerator

Abstract

The heat accumulator takes mullite composite ceramic with nano zirconium oxide as a crystal boundary pinning phase as a matrix, fundamentally improves the phase stability and microstructure integrity of the matrix at the sintering temperature of the coating, and solves the early failure problems of the traditional heat accumulator caused by degradation of the matrix, uneven coating, weak adhesion and poor slag resistance by compounding the ceramic coating with zirconium oxide powder, magnesium oxide, silicon dioxide, aluminum oxide as the main body and introducing a synergistic additive system of hydroxypropyl methyl cellulose and pentaerythritol. Through the synergistic design of the material and structure of the matrix and the coating, the heat accumulator has high specific surface area, excellent thermal stability, structural strength, thermal shock resistance and excellent slag erosion resistance, and significantly improves the service life and reliability under high temperature severe working conditions.

Description

Technical Field

[0001] This invention relates to the field of high-performance ceramic matrix composite materials technology, and in particular to a coated honeycomb ceramic heat storage body. Background Technology

[0002] Honeycomb ceramic regenerators are widely used in high-temperature heat exchange fields such as industrial furnaces and waste gas treatment. Through the periodic heat storage and release process, they can significantly improve the thermal efficiency of the system. However, in practical applications, ordinary honeycomb ceramic regenerators face the following prominent problems: (1) Pore blockage: Impurities and gaseous corrosion products such as Fe2O3 in blast furnace gas are easily deposited on the inner wall of the pores. In particular, silicon oxide crystals grow at high temperatures and form an affinity bond with the surface of the regenerator, which leads to rapid blockage of the gas channels and a sharp drop in heat exchange efficiency; (2) Insufficient thermal shock resistance and corrosion resistance: Under the combined action of high-temperature thermal cycling and chemical corrosion, the matrix material is prone to microcracks, deformation, and even structural damage; the widely used cordierite or ordinary mullite honeycomb ceramics, when their surface is used to improve performance When applying functional coatings, the high sintering temperature required for the coating (usually above 1250℃) can easily lead to unstable matrix phase, abnormal grain growth or over-sintering, resulting in a decrease in matrix strength and thermal shock stability, which in turn becomes a weak link in the entire composite material product; (3) Poor performance of surface functional layer: Existing surface modification technologies, such as coating ceramic glaze or microcrystalline glass layer, can improve temperature resistance to a certain extent, but their composition is poorly matched with the matrix, and the coating is prone to macroscopic inhomogeneity, microscopic cracking, weak bonding with the matrix, etc. Moreover, it is not resistant to erosion in slag-containing environments and it is difficult to achieve long-term protection of the matrix.

[0003] Therefore, there is an urgent need to develop a honeycomb ceramic heat storage body with a complete and stable matrix structure, a uniform and firm coating, and excellent resistance to thermal shock and slag erosion, in order to meet the increasingly demanding requirements of high-temperature industrial applications. Summary of the Invention

[0004] This application provides a coated honeycomb ceramic heat storage body that addresses the performance deficiencies of traditional products through synergistic innovation in material systems and structures. The heat storage body utilizes a highly stable composite ceramic matrix made of mullite with nano-zirconia as a grain boundary pinning phase, suppressing abnormal grain growth and performance degradation at the coating sintering temperature. Furthermore, a functional coating composed of ceramic components such as zirconia micropowder, along with a synergistic additive system of hydroxypropyl methylcellulose and pentaerythritol, is applied to the matrix surface, achieving uniform coverage, stress dissipation, and strong bonding. The resulting heat storage body exhibits excellent thermal stability, structural integrity, thermal shock resistance, and superior slag erosion resistance, improving its service life and reliability under harsh high-temperature conditions.

[0005] This application provides a coated honeycomb ceramic heat storage body, comprising: a honeycomb ceramic substrate, wherein the substrate is a composite ceramic body composed of mullite and nano-zirconia as a grain boundary pinning phase, wherein the weight of the nano-zirconia is 10-20 parts of the total weight of the substrate raw materials; and a composite ceramic coating, wherein the coating is formed on the inner and outer surfaces and the inner walls of the pores of the honeycomb ceramic substrate by coating and sintering.

[0006] Furthermore, the nano-zirconia is yttrium oxide-stabilized tetragonal zirconia with a particle size D50 of no more than 100 nanometers.

[0007] Furthermore, the coating is formed from a slurry comprising the following components in parts by weight: zirconia micro powder: 92-98 parts; magnesium oxide: 2-4 parts; silica: 1-2.5 parts; alumina: 0.2-0.5 parts; hydroxypropyl methylcellulose: 0.3-1.0 parts; pentaerythritol: 0.5-3.0 parts; dispersant: 0.5-1.0 parts; binder: 0.5-4.0 parts; defoamer: 0.1-0.5 parts; deionized water: 150-250 parts.

[0008] Furthermore, the hydroxypropyl methylcellulose comprises a combination of two hydroxypropyl methylcelluloses with different degrees of substitution. The first hydroxypropyl methylcellulose has a methoxy substitution degree of 28.0%-30.0% and a hydroxypropoxy substitution degree of 7.0%-12.0%, while the second hydroxypropyl methylcellulose has a methoxy substitution degree of 19.0%-24.0% and a hydroxypropoxy substitution degree of 4.0%-7.5%. The mass ratio of the two hydroxypropyl methylcelluloses ranges from 1:2 to 2:1.

[0009] Furthermore, the coating has a coating slurry application rate of 15-20 wt%.

[0010] Furthermore, in the method for preparing the coating, the drying process is a staged drying process, including: a. Initial stage: Place the coated blank in an environment with a temperature of 25-30℃ and a relative humidity of more than 85% to air dry for 3-4 hours; b. Intermediate stage: Transfer the green body to a forced-air drying oven and dry at 60-80℃ for 3-4 hours; c. Later stage: Raise the temperature of the drying oven to 100-120℃ and continue drying for 1-2 hours.

[0011] Furthermore, the preparation of the slurry includes a ball milling step, and the fineness D50 of the slurry after ball milling is not greater than 0.3 micrometers.

[0012] Furthermore, the dispersant is polyacrylamide, the binder is sodium tripolyphosphate, and the defoamer is a polyether defoamer.

[0013] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: The coating of this invention primarily employs a silica-repellent oxide ceramic material, which has a different crystallization temperature than silicon dioxide. This makes it less prone to interdiffusion of elements within the operating temperature range of the honeycomb ceramic, thus improving the problem of silicon dioxide crystal adhesion, deposition, and blockage on the honeycomb ceramic surface. The coating prepared by this invention has a dense structure and strong interfacial bonding, exhibiting excellent resistance to slag erosion and significantly improving the durability of the heat storage body in high-temperature environments containing slag.

[0014] By introducing HPMC and PE and utilizing their synergistic effect, the macroscopic rheological behavior of the slurry and the microscopic mechanical response of the coating are combined and improved, which solves the technical contradiction of the difficulty in achieving both coating uniformity and crack resistance, and obtains a coating product with significantly optimized comprehensive performance.

[0015] By introducing HPMC combinations with different degrees of substitution and generating multi-level synergy with PE, the rheological behavior, wetting process, network structure and stress dissipation mechanism of the slurry were optimized at the molecular scale. This solved the technical problem of simultaneously improving coating uniformity, crack resistance and high interfacial strength at the macro scale.

[0016] By constructing a staged drying regime that matches the material's functional evolution dynamics, the orderly and synergistic effects of interface anchoring, stress dissipation, and network reinforcement were achieved at the micro level. At the macro level, problems such as weak adhesion, cracking, and insufficient strength that easily occur in coatings during the drying process were solved. Ultimately, a high-performance coating with strong interface bonding, complete and dense structure, and excellent slag resistance was obtained. Detailed Implementation

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0018] Example 1: A coated honeycomb ceramic heat storage body, the preparation method of the coated honeycomb ceramic heat storage body specifically includes the following steps: Step 1: Prepare composite ceramic coating slurry; 1.1 Weigh each raw material according to the following parts by weight: Zirconia micro powder: 92-98 parts; Magnesium oxide: 2-4 parts; Silica: 1-2.5 parts; Alumina: 0.2-0.5 parts; Hydroxypropyl methylcellulose: 0.3 - 1.0 parts (its viscosity at 20°C and 2% aqueous solution is 4000 - 20000 mPa·s); Pentaerythritol: 0.5 - 3.0 parts (with particle size D50 controlled at 1-10 micrometers); Dispersant polyacrylamide: 0.5-1.0 parts; Sodium tripolyphosphate binder: 0.5-4.0 parts; Defoamer (polyether type): 0.1-0.5 parts; Deionized water: 150-250 parts.

[0019] 1.2 The specific steps for slurry preparation are as follows: a. Pre-dissolving hydroxypropyl methylcellulose: Take approximately one-third of the total amount of deionized water and heat it to 60-80℃. While mechanically stirring at 400-600 rpm, slowly and evenly sprinkle the weighed hydroxypropyl methylcellulose powder onto the surface of the hot water. Continue stirring for 20-40 minutes until it is completely dissolved to form a transparent liquid, then allow it to cool to room temperature for later use.

[0020] b. Pentaerythritol pre-dispersion: Add the weighed pentaerythritol powder to the cooled hydroxypropyl methylcellulose gel above, and stir at 400-600 rpm for 15-30 minutes to fully wet and disperse it, forming a uniform composite mother liquor.

[0021] c. Preparation of the main mixture: Add the remaining deionized water to the main reactor, and add the dispersant and binder in sequence while stirring at 300-500 rpm, stirring until completely dissolved.

[0022] d. Mixing and ball milling: Add the composite mother liquor prepared in step b to the main reactor and stir it evenly with the main mixture. Then, add all the ceramic functional powders and defoamer in sequence. Transfer the mixed slurry to a ball mill, add grinding stones at a ratio of material:ball:water = 1:2:1.5, and ball mill for 6-12 hours until the slurry fineness reaches D50 of no more than 0.3 microns.

[0023] e. Aging: After ball milling, discharge the slurry and let it stand at room temperature for 12-24 hours before use.

[0024] Step 2: Pretreatment of the honeycomb ceramic substrate; 2.1 Preparation of pinned phase composite ceramic matrix: Raw material ratio (parts by weight): Mullite powder (D50 = 1.0 μm): 85 parts Nano-sized yttrium oxide stabilized zirconia (3Y-TZP, D50 = 50 nm): 15 parts Sintering aid (MgO-Y2O3 composite): 1.5 parts Organic binder (methylcellulose): 5.0 parts Plasticizer (glycerin): 3.0 parts Lubricant (polyethylene glycol): 2.0 parts Deionized water: appropriate amount (adjust to a viscosity suitable for extrusion). Mixing and kneading: Mullite powder, nano-zirconia powder, and sintering aids were placed in a planetary ball mill and mixed for 6 hours using zirconia balls as the medium to ensure that the nano-zirconia particles were uniformly dispersed around the mullite particles.

[0025] The uniformly mixed powder is thoroughly mixed with organic binder, plasticizer, lubricant and appropriate amount of deionized water in a vacuum ply mill until a billet with uniform composition and good plasticity is obtained.

[0026] Extrusion molding and drying: The blank is loaded into a honeycomb ceramic extruder and extruded through a specific mold to form a green body with a regular honeycomb-shaped pore structure.

[0027] The green blanks were air-dried at room temperature for 24 hours, and then transferred to an 80°C forced-air drying oven for 48 hours to completely remove moisture.

[0028] High-temperature sintering: The dried green body is placed in a high-temperature kiln.

[0029] Sintering is performed according to the following procedure: the temperature is increased to 600°C at 2°C / min and held for 2 hours to completely remove organic components; then the temperature is increased to 1650°C at 3°C / min and held at this temperature for 4 hours, followed by furnace cooling to room temperature.

[0030] 2.2 Matrix Pretreatment: Cleaning: The pinned phase composite honeycomb ceramic matrix prepared by the above method was carefully cleaned with dry compressed air to remove any dust that may have adhered during transportation and storage.

[0031] Drying: Place the cleaned substrate in an oven at 110°C for 3 hours to ensure that the substrate is completely dry before coating to avoid moisture affecting the properties of the slurry.

[0032] Reserved: The treated substrate is placed in a desiccator for later use in impregnation coating.

[0033] Step 3: Impregnation coating; The pretreated honeycomb ceramic substrate is completely immersed in the prepared slurry for 2-5 minutes. Remove the substrate and let it stand vertically for 30-60 seconds. Then, gently blow it from one side with low-pressure compressed air to remove excess slurry from the channels. Control the slurry coating rate at 15-20 wt% by weighing. This impregnation-discharge process can be repeated 2-3 times.

[0034] Step 4: Drying and sintering; Step drying: First, place the coated substrate in the shade at room temperature for 2-4 hours, then transfer it to a forced-air drying oven at 80-100℃ and dry for 2-4 hours; High-temperature sintering: The dried green body is placed in a kiln and sintered according to the following procedure: the temperature is raised to 1250-1350℃ at a rate of 2-3℃ / minute, and held at this temperature for 2-4 hours. Then it is cooled to room temperature with the furnace to obtain the final product.

[0035] Experiments were conducted for this embodiment to verify the effects of adding HPMC and PE alone and in combination in the basic slurry formulation on the coating uniformity, resistance to drying cracking, and resistance to chemical corrosion.

[0036] I. Experimental Parameters 1. Basic formula (parts by weight); Zirconia micro powder: 95 parts; Magnesium oxide: 3 parts; Silica: 1.8 parts; Alumina: 0.3 parts; Dispersant (polyacrylamide): 0.8 parts; Binder (sodium tripolyphosphate): 2.0 parts; Defoamer (polyether type): 0.3 parts; Deionized water: 200 parts (fixed total amount, used for pre-dissolution and main mixing); 2. Experimental group design; All the following additions are based on the total weight of the above base formulation, and the experimental groups are shown in Table 1 below; Table 1

[0037] 3. Preparation steps and parameters; Slurry preparation: HPMC pre-dissolution: Take 70 parts (about 1 / 3) of the total 200 parts of water, heat to 70±5℃, slowly add HPMC (if required for this group) while stirring at 500 rpm, stir for 30 minutes, and cool for later use.

[0038] PE pre-dispersion: If PE needs to be added to this group, add PE to the cooled HPMC adhesive (or an equal amount of water) and stir at 500 rpm for 20 minutes.

[0039] Ball milling: Mix the premixed liquid with the remaining raw materials and ball mill for 8 hours. The fineness of the slurry is controlled to be D50 ≤ 0.3μm.

[0040] Aging: The slurry is left to stand at room temperature for 16 hours.

[0041] Coating and sintering: Substrate: Mullite-nanozirconia composite honeycomb ceramic substrate with a specification of 100 mesh (approximately 1.5 mm pore size) was uniformly used according to the method in step 2: honeycomb ceramic substrate pretreatment.

[0042] Coating: Immerse for 3 minutes, let stand for 45 seconds, and then purge with compressed air at 0.15 MPa for 5 seconds. The target coating rate is controlled at (18±0.5) wt%, which is achieved by precisely controlling the immersion and lifting speed to ensure that the weight of each coating group is consistent and to eliminate thickness variables.

[0043] Drying: After air drying at room temperature for 3 hours, dry in a forced-air environment at 90℃ for 3 hours.

[0044] Sintering: Heat to 1300℃ at 3℃ / min, hold for 3 hours, and then cool with the furnace.

[0045] II. Performance testing methods and standards; 1. Assessment of slurry uniformity: Methods: Visual observation combined with touch test. After sintering, five samples were randomly selected, and the smoothness of the inner wall of the pores was felt by touch.

[0046] Rating criteria: Advantages: The holes are clear and the inner walls are smooth and uniform, without any roughness.

[0047] Good: The orifice is clear, and there is a slight granular feel on the inner wall, but no blockage.

[0048] Poor: There are obvious lumps or blockages in the duct, and the inner wall is rough.

[0049] 2. Assessment of resistance to drying cracking: Method: After drying and before sintering, the coating surface was observed using a 10x magnifying glass.

[0050] Rating criteria: Advantages: Smooth surface, without any visible cracks.

[0051] Good: There are slight, discontinuous, fine hair cracks in some areas.

[0052] Poor: Pervasive "mud crack"-like network cracks appear.

[0053] 3. Ion dissolution rate test: This is achieved by measuring the ion dissolution rate of specific metal ions (zirconium ions, Zr) in the corrosive solution. 4+ The concentration of the coating was used to test its density.

[0054] Method: The sintered samples (uniform size 20mm × 20mm × 10mm) were completely immersed in a polytetrafluoroethylene container containing 50mL of 20wt% sulfuric acid solution.

[0055] After sealing the container, place it in a constant temperature water bath at 80℃ to accelerate corrosion for 24 hours.

[0056] After the etching process was completed, the sample was removed and the concentration of zirconium (Zr) in the etching solution was determined using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0057] Calculation: Zr ion leaching concentration (μg / cm²) = (total mass of Zr ions measured) / (sample surface area). The lower this value, the better the coating density and the stronger the acid resistance.

[0058] 4. Slag resistance test; Method: The sintered sample was processed into a block of 60mm×60mm×20mm. A groove with a diameter of 30mm and a depth of 10mm was prepared in the center of its surface to simulate a crucible. 5.0g of standard blast furnace slag powder (chemical composition: SiO2 35%, CaO 40%, Al2O3 10%, Fe2O3 5%, MgO 10%) was filled into the groove. The sample was placed in a high-temperature furnace and heated to 1350℃ at a rate of 5℃ / min, and held at this temperature for 3 hours. It was then cooled to room temperature with the furnace.

[0059] Evaluation criteria: Advantages: When the sample is cut open and the cross-section is observed, the coating shows no erosion or peeling, and the slag penetration depth is < 0.1 mm; Good: The coating shows slight corrosion, with slag penetration depth of 0.1-0.3 mm; Poor: The coating is obviously eroded or peeled off, and the depth of slag penetration is > 0.3 mm.

[0060] The test results are shown in Table 2 below; Table 2

[0061] The experimental results of this embodiment show that hydroxypropyl methylcellulose (HPMC) and pentaerythritol (PE) have a synergistic effect in terms of function: HPMC mainly improves the rheological properties of the slurry, ensuring the macroscopic uniformity of the coating; while PE, by inducing microplastic deformation, mainly controls stress dissipation, giving the coating excellent resistance to drying cracking. Both are indispensable, and their performance is limited when used alone. However, when they are added in combination (experimental group 5), the synergistic effect is optimal, successfully preparing a uniform, crack-free, dense, and corrosion-resistant coating with the best overall performance.

[0062] The technical solutions described in the embodiments of this application above have at least the following technical effects or advantages: When high-silicon-content organic waste gas is incinerated in a regenerative thermal oxidizer (RTO), the operating temperature of the RTO is 700-1100℃. Silicon in the waste gas begins to crystallize at 900℃. Since ordinary honeycomb ceramic heat exchangers, ceramic glaze coatings, and microcrystalline glass coatings are also primarily composed of silicon dioxide, they have a strong affinity for the generated silicon dioxide crystals, quickly clogging the gas channels. The coating of this invention primarily uses silicon-repellent oxide ceramic materials, which have a different crystallization temperature than silicon dioxide. This makes interdiffusion of elements less likely to occur within the operating temperature range of the honeycomb ceramic, thus improving the problem of silicon dioxide crystal adhesion, deposition, and clogging on the honeycomb ceramic surface.

[0063] By introducing nano-zirconia as a grain boundary pinning phase and utilizing the Zener pinning effect, the grain boundary migration and grain growth of the main crystalline phase (mullite) of the matrix are significantly suppressed during the high-temperature sintering of the matrix and subsequent coating. This ensures that the microstructure (grain size, phase composition) of the matrix remains stable after the coating sintering process at 1250-1350℃, without any strength attenuation or degradation.

[0064] By introducing hydroxypropyl methylcellulose (HPMC) and pentaerythritol (PE), the technical challenges of poor macroscopic coating uniformity and microscopic drying stress cracking in the preparation process of existing honeycomb ceramic heat storage body coatings are synergistically solved.

[0065] Hydroxypropyl methylcellulose (HPMC), as a rheology modifier, exhibits pseudoplastic fluid properties in its polymer chains upon hydration and expansion in the aqueous phase, forming a three-dimensional network structure. This property manifests macroscopically as follows: under shear forces during the coating process, the slurry viscosity instantaneously decreases, enhancing fluidity and ensuring full penetration and uniform coverage of the entire inner surface of the complex porous matrix. Once the shear force is removed, the slurry viscosity rapidly recovers, effectively resisting gravity-induced sagging and precisely maintaining the wet coating morphology. This ensures the uniformity and integrity of the coating thickness on a macroscopic scale.

[0066] Pentaerythritol (PE), as a plastic crystal and structural toughening agent, has uniformly dispersed micron-sized rigid particles that are bonded to the flexible HPMC network through intermolecular forces such as hydrogen bonds. During the drying process, when the coating experiences shrinkage stress due to water loss, the PE particles act as stress concentration points, inducing micro-plastic deformation within themselves and simultaneously causing local shear yielding in the surrounding HPMC matrix. This process actively dissipates a large amount of shrinkage strain energy, transforming the concentrated stress that could potentially lead to macroscopic penetrating cracks into a large amount of dispersed, harmless micro-plastic deformation, thereby significantly improving the fracture toughness of the coating and its resistance to drying cracking at the microscale.

[0067] Through the synergistic effect of HPMC and PE, a stress management system combining a flexible network and rigid particles is constructed. The continuous phase composed of HPMC provides overall structural support and morphological retention, while the dispersed phase of PE acts as a built-in, numerous micro-stress modulator. This synergy achieves optimization of the entire process, from rheological control (macroscopic uniformity) in the slurry coating stage to stress dissipation (microscopic crack resistance) in the drying and curing stage. The resulting technical effect overcomes the performance limitations of single components, producing a coating with extremely high uniformity, density, defect-free characteristics, and strong adhesion to the substrate. Ultimately, this improves the impermeability, durability, and service life of the coated honeycomb ceramic heat storage body under harsh operating conditions.

[0068] Example 2: Example 1, by introducing HPMC and PE and utilizing their synergistic effect, combined and improved the macroscopic rheological behavior of the slurry with the microscopic mechanical response of the coating, resolving the technical contradiction of simultaneously achieving coating uniformity and crack resistance, and obtaining a coating product with optimized overall performance. To further improve the overall performance of the coating, further improvements were made based on Example 1.

[0069] The HPMC comprises a combination of two hydroxypropyl methylcelluloses with different degrees of substitution. The first HPMC has a methoxy substitution degree of 28.0%-30.0% and a hydroxypropoxy substitution degree of 7.0%-12.0%, which is a high degree of substitution group. The second type of HPMC has a methoxy substitution degree of 19.0%-24.0% and a hydroxypropoxy substitution degree of 4.0%-7.5%, which is the low substitution degree group; The mass ratio of the two HPMCs ranges from 1:2 to 2:1.

[0070] In the slurry preparation step, the two types of HPMC mentioned above are pre-dissolved. Specifically, take approximately one-third of the total mass of deionized water from the formulation and heat it to 60-80℃. While mechanically stirring at 400-600 rpm, pre-mix the weighed first and second HPMC powders and slowly and evenly sprinkle the mixture onto the surface of the hot water. Continue stirring for 30-40 minutes until completely dissolved to form a homogeneous and transparent composite slurry. Then allow it to cool to room temperature for later use.

[0071] Based on Example 1, this embodiment conducts experiments to verify the effect of using two HPMC combinations with different degrees of substitution on improving the adhesion between the coating and the substrate and the uniformity of wetting compared to using a single HPMC.

[0072] I. Experimental parameters; 1. Basic formula (parts by weight) Zirconia micro powder: 95 parts; Magnesium oxide: 3 parts; Silica: 1.8 parts; Alumina: 0.3 parts; Pentaerythritol: 1.5 parts; Dispersant (polyacrylamide): 0.8 parts; Binder (sodium tripolyphosphate): 2.0 parts; Defoamer (polyether type): 0.3 parts; Deionized water: 200 parts; The amount of HPMC added is shown in Table 3 below; Table 3

[0073] 3. Preparation steps and parameters; Slurry preparation: The steps of Example 2 were followed, including the pre-dissolution step of composite HPMC to ensure that the two types of HPMC were fully co-dissolved.

[0074] Coating and sintering: The process parameters are the same as in Example 1, and the slurry coating rate is controlled at (18±0.5)wt%.

[0075] II. Performance testing methods and standards; 1. Evaluation of wetting and spreading effect: Method: Before coating, use a pipette to take 0.1 mL of slurry and drop it onto different flat parts of the same substrate, and measure its contact angle (using a contact angle meter or by image analysis software). Measure 5 points for each sample.

[0076] Standard: Calculate the average and standard deviation of the contact angle. The smaller the average and standard deviation, the better and more uniform the wettability.

[0077] 2. Thermal shock bonding strength test; Method: Weigh the sintered sample (M3); Place the sample in a box furnace preheated to 800°C and keep it at that temperature for 15 minutes. Remove the sample quickly and immediately immerse it in running cold water at 25°C for 5 minutes to cool it rapidly. Remove the sample and dry it thoroughly at 110℃ for 2 hours; Gently brush away any loose coating debris from the surface with a soft brush, then weigh it (M4). Calculation: Coating quality loss rate = [(M3 - M4) / M3] × 100% 3. Adhesion cross-cut test; Method: Refer to the national standard GB / T 9286-1998 "Cross-cut test of paint and varnish film" and use a hard cutting tool to cut a grid of squares with a spacing of 1 mm or 2 mm on the coating surface, cutting through the coating to the substrate.

[0078] Use a soft-bristled brush to gently brush 5 times along the diagonal direction.

[0079] Apply the special tape, press it firmly, and then quickly peel it off at a 60-degree angle.

[0080] Rating criteria: Grade 0: The cut edges are completely smooth, with no chips falling off.

[0081] Grade 1: Slight peeling at the intersection of the incisions, with a peeling area ≤5%.

[0082] Grade 2: Peeling at the incision edges and / or intersections, with a peeling area >5% to ≤15%. The test results are shown in Table 4 below; Table 4

[0083] This experiment shows that using HPMC with two different degrees of substitution (high and low) (experimental group C) produces a synergistic enhancement effect on the wetting and spreading properties, interfacial bonding strength and adhesion of the coating compared with using HPMC with a single degree of substitution (comparative examples A and B).

[0084] The technical solutions described in the embodiments of this application above have at least the following technical effects or advantages: By introducing hydroxypropyl methylcellulose (HPMC) with different degrees of substitution, the shortcomings of single HPMC in balancing slurry wettability, network strength and interfacial bonding with the matrix are solved, thereby further improving the macroscopic uniformity of the coating and the microscopic interfacial bonding strength.

[0085] High-substituted HPMC (methoxy 28.0%-30.0%, hydroxypropoxy 7.0%-12.0%) has relatively strong hydrophobicity, enabling it to form a three-dimensional network with high structural strength in the aqueous phase, providing a solid skeletal support for the slurry. Macroscopically, this manifests as the slurry exhibiting high yield stress and excellent anti-sagging properties. Low-substituted HPMC (methoxy 19.0%-24.0%, hydroxypropoxy 4.0%-7.5%) has stronger hydrophilicity and is more flexible, effectively reducing the surface tension of the slurry and enhancing its penetration and spreading ability. Macroscopically, this manifests as the slurry exhibiting better wettability to the matrix, especially in low surface energy regions.

[0086] Through pre-dissolution, two HPMC molecular chains with different degrees of substitution intertwine and bond in water, forming a heterogeneous composite network structure that combines high strength and high flexibility. At the microscopic level, the low-substitution HPMC molecular chains in this composite network preferentially wet and anchor to the substrate surface, laying the foundation for subsequent film formation; while the high-substitution HPMC molecular chains enhance the cohesive energy density of the entire network. The macroscopic effect of this synergistic effect is that the slurry achieves better and more stable wetting and spreading ability, while the coating formed after drying and curing has a stronger interfacial bonding layer with the substrate, improving its resistance to peeling caused by environmental stress.

[0087] Furthermore, this composite HPMC system exhibits a multi-level synergistic effect with pentaerythritol (PE). Microscopically, this composite network combines high strength and high flexibility, not only anchoring PE particles more stably and preventing agglomeration, but also providing a superior mechanical environment for PE-induced microplastic deformation: its high-strength portion is sufficient to support and transfer stress to the PE particles, while its flexible portion better adapts to and cooperates with this plastic deformation, thereby dissipating shrinkage stress throughout the entire coating volume more efficiently and uniformly. Macroscopically, this multi-level synergistic mechanism results in the coating achieving extreme uniformity while further enhancing interfacial bonding strength and overall structural integrity, with thermal shock resistance and bonding strength surpassing systems using a single HPMC.

[0088] Example 3: Example 2, by introducing HPMC combinations with different degrees of substitution and achieving multi-level synergy with PE, optimized the rheological behavior, wetting process, network structure, and stress dissipation mechanism of the slurry at the molecular scale. This solved the technical problem of simultaneously improving coating uniformity, crack resistance, and high interfacial adhesion at the macroscopic scale, resulting in a coating product with further improved overall performance. Further improvements were made based on Example 2 to further enhance its overall performance.

[0089] In step 4, the drying and sintering process is carried out in stages. The specific steps of the staged drying are as follows: a. Initial HPMC interface wetting stage: Place the green body in an environment with a temperature of 25-30℃ and a relative humidity of more than 85% for air drying for 3-4 hours; b. Mid-term PE stress dissipation stage: Transfer the green body to a forced-air drying oven and keep it at 60-80℃ for 3-4 hours; c. Later HPMC network enhancement stage: Raise the temperature of the drying oven to 100-120℃ and continue drying for 1-2 hours.

[0090] Based on experimental group C in embodiment 2, the technical solution of this embodiment is tested and experimental group D is used. The difference between experimental group D and experimental group C is that a staged drying method is used. The mass loss rate (%) of experimental group D after thermal shock was tested to be 0.01-0.02, the adhesion grade of cross-cut test was 0, and the slag resistance performance was excellent.

[0091] The technical solutions described in the embodiments of this application above have at least the following technical effects or advantages: By introducing a staged drying regime, problems such as stress concentration in the coating, weakened interfacial bonding, and microscopic defects caused by the mismatch between the moisture evaporation rate and the material's functional response during traditional isothermal or simple step drying processes are solved. By precisely controlling the temperature and humidity of different drying stages to match the functional activation kinetics of the composite HPMC system and pentaerythritol (PE), the temporal regulation of the functions of each component can be achieved.

[0092] Initially, under low temperature (25-30℃) and high humidity (>85% RH) conditions, the driving force for water molecule evaporation is significantly reduced. This environment delays the curing of the slurry surface, providing ample time for the more hydrophilic, low-substituted HPMC molecular chains to migrate and expand, achieving full and uniform adsorption and anchoring to the substrate surface through intermolecular forces such as hydrogen bonds. This stage promotes the formation of a continuous and robust initial interface layer, macroscopically manifested as enhanced initial adhesion between the coating and the substrate. This lays the foundation for withstanding drying stress in subsequent stages and effectively avoids the problem of weakened adhesion caused by uneven wetting in the early stages.

[0093] During the mid-stage stress dissipation, when the temperature rises to the activation window of PE's plastic deformation (60-80℃), significant shrinkage stress begins to form within the coating due to the large-scale evaporation of free water. At this specific temperature, PE particles dispersed in the HPMC network act as stress concentration points, and their crystal structure can undergo microscopic plastic deformation such as slip or twinning, while simultaneously inducing local shear bands in the surrounding HPMC matrix. This process actively and efficiently converts concentrated elastic strain energy into plastic work and surface energy, thereby dissipating stress. This mechanism avoids excessive accumulation of shrinkage stress at fragile interfaces or within the coating itself, macroscopically manifesting as the suppression of the initiation and propagation of macroscopic and microscopic cracks during drying, fundamentally ensuring the integrity of the coating.

[0094] During the later structural stabilization stage, at higher temperatures (100-120℃), the rate of bound water removal accelerates. At this point, the highly substituted HPMC molecular chains, with their increased hydrophobicity and chain rigidity, exhibit enhanced mobility, deeper intermolecular entanglement, and further strengthened hydrogen bond networks. This allows the three-dimensional network structure constructed from HPMC to achieve final curing and reinforcement. This stage endows the dried coating with sufficient mechanical strength and rigidity, enabling it to withstand the mechanical and thermal stresses during subsequent handling, storage, and sintering processes, thus preventing damage during later treatments.

[0095] This phased drying process forms a synergistic system that is tightly linked in time and mutually supportive in function. The robust interface formed in the initial stage is the foundation for the effective transfer and distribution of stress in the intermediate stage; the efficient stress dissipation in the intermediate stage protects the initially formed interface and the entire coating structure from damage, and provides a defect-free preform for the later stage; the later stage, through network reinforcement, fixes the complete, low-stress coating structure formed in the first two stages. This time-based functional coupling enables precise control of the entire process, from interface optimization to bulk toughening and then to overall strengthening.

[0096] By constructing a staged drying regime that matches the material's functional evolution dynamics, the orderly and synergistic effects of interface anchoring, stress dissipation, and network reinforcement were achieved at the micro level. At the macro level, problems such as weak adhesion, cracking, and insufficient strength that easily occur in coatings during the drying process were solved, ultimately resulting in a high-performance coating with strong interface bonding and complete structure.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A coated honeycomb ceramic heat storage body, characterized in that, include: A honeycomb ceramic matrix, wherein the matrix is ​​a composite ceramic body composed of mullite and nano-zirconia as a grain boundary pinning phase, wherein the nano-zirconia is 10-20 parts by weight of the total weight of the matrix raw materials. A composite ceramic coating, wherein the coating is formed on the inner and outer surfaces and the inner walls of the pores of the honeycomb ceramic substrate by coating and sintering; The coating is formed from a slurry comprising the following components in parts by weight: zirconia micro powder: 92-98 parts; Magnesium oxide: 2-4 parts; Silicon dioxide: 1-2.5 parts; Alumina: 0.2-0.5 parts; Hydroxypropyl methylcellulose: 0.3-1.0 parts; Pentaerythritol: 0.5-3.0 parts; Dispersant: 0.5-1.0 parts; Binder: 0.5-4.0 parts; Defoamer: 0.1-0.5 parts; Deionized water: 150-250 parts.

2. The coated honeycomb ceramic heat storage body as described in claim 1, characterized in that, The nano-zirconia is yttrium oxide-stabilized tetragonal zirconia with a particle size D50 of no more than 100 nanometers.

3. The coated honeycomb ceramic heat storage body as described in claim 1, characterized in that, The hydroxypropyl methylcellulose comprises a combination of two hydroxypropyl methylcelluloses with different degrees of substitution. The first hydroxypropyl methylcellulose has a methoxy substitution degree of 28.0%-30.0% and a hydroxypropoxy substitution degree of 7.0%-12.0%. The second hydroxypropyl methylcellulose has a methoxy substitution degree of 19.0%-24.0% and a hydroxypropoxy substitution degree of 4.0%-7.5%. The mass ratio of the two hydroxypropyl methylcelluloses ranges from 1:2 to 2:

1.

4. The coated honeycomb ceramic heat storage body as described in claim 1, characterized in that, The coating has a coating rate of 15-20 wt%.

5. The coated honeycomb ceramic heat storage body as described in claim 1, characterized in that, In the method for preparing the coating, the drying process is a staged drying process, including: a. Initial stage: Place the coated blank in an environment with a temperature of 25-30℃ and a relative humidity of more than 85% to air dry for 3-4 hours; b. Intermediate stage: Transfer the green body to a forced-air drying oven and dry at 60-80℃ for 3-4 hours; c. Later stage: Raise the temperature of the drying oven to 100-120℃ and continue drying for 1-2 hours.

6. The coated honeycomb ceramic heat storage body as described in claim 1, characterized in that, The preparation of the slurry includes a ball milling step, and the fineness D50 of the slurry after ball milling is not greater than 0.3 micrometers.

7. The coated honeycomb ceramic heat storage body as described in claim 1, characterized in that, The dispersant is polyacrylamide, the binder is sodium tripolyphosphate, and the defoamer is a polyether defoamer.

Images