High-purity calcium aluminate refractory cement and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to high-purity calcium aluminate refractory cement and a preparation method thereof, and the high-purity calcium aluminate refractory cement is prepared from the following components in parts by mass: 60-80 parts of high-purity calcium aluminate; 5 to 15 parts of nano zirconium oxide; 5 to 10 parts of hexaaluminate; 3-8 parts of modified silicon carbide whiskers; 0.5 to 2 parts of an organic water reducing agent; 1-3 parts of an inorganic binder; 0.1 to 1 part of an auxiliary agent; 1 to 3 parts of gypsum; and 15 to 30 parts of deionized water. The high-purity calcium aluminate serves as a base material to provide high fire resistance, the nano-zirconia enhances high-temperature stability and thermal shock resistance, and the hexaaluminate and the modified silicon carbide whiskers synergistically improve the compactness and mechanical strength of the material. All the components achieve synergistic interaction through gradient matching, and the final product has high refractoriness, excellent thermal shock resistance, good constructability and long-term stability and is suitable for high-temperature industrial scenes.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, in particular to high-purity calcium aluminate refractory cement and a preparation method thereof. Background Art

[0002] High-purity calcium aluminate refractory cement is primarily used in high-temperature industrial applications such as metallurgical furnaces, chemical reactors, electric furnace tapping troughs, and petrochemical equipment linings. It must withstand sustained high temperatures to prevent softening or collapse, maintain structural integrity under frequent temperature fluctuations, and possess moderate slurry fluidity for easy casting and controllable setting time to accommodate complex construction conditions. These performance requirements directly determine the material's service life and safety under high-temperature conditions and represent a core technical challenge in current refractory research and development.

[0003] To meet the above requirements, the following technical solutions are currently available:

[0004] Traditional aluminate bonding system: calcium aluminate cement is used as the main binder, and its high-temperature performance is enhanced by adjusting its ratio;

[0005] Metal fiber reinforcement technology: adding metal fibers (such as stainless steel fibers) to the base material to improve thermal shock resistance and crack growth resistance through fiber bridging effect;

[0006] Rapid sintering process: Rapid temperature rise sintering technology is used to shorten the production cycle, while controlling the sintering temperature to reduce impurity generation.

[0007] Although the above solutions have improved material performance to a certain extent, they still have the following limitations:

[0008] Limited binder performance: Traditional aluminate cement is prone to phase change and shrinkage at high temperatures, causing microcracks within the material and reducing overall strength;

[0009] Poor adaptability of reinforcing materials: The interface bonding strength between metal fibers and substrates is insufficient, making them prone to falling off during high-temperature cycles, thus weakening the thermal shock resistance effect;

[0010] The contradiction between sintering energy consumption and quality: Although rapid sintering can save energy, improper control of temperature gradient can easily cause local overheating, resulting in reduced product uniformity. Summary of the Invention

[0011] In view of the deficiencies in the prior art, the present invention provides a high-purity calcium aluminate refractory cement and a preparation method thereof, which solves the problems of the above-mentioned background technology.

[0012] According to a first aspect of the present invention, there is provided a high-purity calcium aluminate refractory cement, comprising the following components in parts by mass:

[0013] High-purity calcium aluminate: 60-80 parts;

[0014] Nano zirconium oxide: 5-15 parts;

[0015] Hexaaluminate: 5-10 parts;

[0016] Modified silicon carbide whiskers: 3-8 parts;

[0017] Organic water reducer: 0.5-2 parts;

[0018] Inorganic binder: 1 to 3 parts;

[0019] Additives: 0.1-1 parts;

[0020] Gypsum: 1-3 parts;

[0021] Deionized water: 15-30 parts.

[0022] High-purity calcium aluminate (HPCA) is used as a matrix material to provide excellent high-temperature stability and refractory performance. It can maintain structural integrity in high-temperature environments and is the core component that determines the refractory limit of high-purity calcium aluminate refractory cement.

[0023] Nano-zirconium oxide (Nano-ZrO2) is used to enhance the thermal shock resistance and high-temperature toughness of materials. Nano-zirconium oxide exhibits phase-transformation toughening properties, absorbing crack propagation energy during temperature changes, thereby improving overall mechanical properties.

[0024] Organic Water-reducing Agent (OWA): A composite system of sodium polyacrylate and polyethylene glycol is used to reduce slurry viscosity and improve fluidity. It achieves efficient dispersion through the dual mechanisms of steric hindrance and electrostatic repulsion, making construction operations more convenient.

[0025] Additive Mixture (AM) is used to improve the material's burst resistance and wear resistance. Polyethylene explosion-proof fiber melts and evaporates when heated, forming tiny channels to release internal vapor pressure. Nano-alumina fills these pores, improving density and surface finish.

[0026] Gypsum Modifier (GM): Calcium sulfate dihydrate as the main component, supplemented with retarding components, is used to adjust the setting time of cement. Adding an appropriate amount can delay early hydration reactions, avoid rapid setting or cracking during construction, and ensure quality of the finished product.

[0027] Deionized water (DIW): Serves as a dispersion medium, providing the liquid environment necessary for uniform mixing of the components. Deionized water contains no impurities, preventing unwanted chemical reactions and ensuring the stability and consistency of the final product.

[0028] According to the embodiments of the present invention, high-purity calcium aluminate serves as the matrix material, providing excellent high-temperature stability and refractory properties. Furthermore, nano-zirconia absorbs thermal stress and inhibits crack propagation through a phase transformation toughening mechanism, effectively improving the material's structural integrity under conditions of sudden temperature changes. Furthermore, the layered crystal structure of the hexaaluminate maintains volume stability at high temperatures, further enhancing its shrinkage resistance. These three factors work together to provide the material with excellent thermal shock resistance and high-temperature strength.

[0029] According to an embodiment of the present invention, modified silicon carbide whiskers are surface-treated to form a three-dimensional reinforced skeleton, exerting a bridging and pull-out effect, preventing crack propagation and improving fracture toughness. Nano-zirconia absorbs crack energy through phase change at the microscale, delaying crack initiation and enhancing thermal shock resistance. The two work together to build a cross-scale reinforcement network, achieving a superimposed improvement in flexural strength, impact resistance, and wear resistance through phase change toughening, structural inhibition, and skeleton load-bearing effects at the nano, submicron, micron, and millimeter scales, thereby extending the service life of the material under complex working conditions.

[0030] According to an embodiment of the present invention, the modified silicon carbide whiskers are silicon carbide whiskers surface-treated with a silane coupling agent, and the mass ratio of the silane coupling agent to the silicon carbide whiskers is 1:10-1:20.

[0031] Surface modified silicon carbide whiskers (SM-SCW): Surface treatment enhances interfacial bonding with the substrate, enhancing toughness. Silicon carbide whiskers inherently possess high strength and modulus. After treatment with a coupling agent, they can be evenly dispersed in the system, effectively preventing crack propagation.

[0032] According to embodiments of the present invention, silicon carbide whiskers treated with a silane coupling agent can more evenly bear external forces when subjected to stress, dissipating crack propagation energy through crack bridging, crack deflection, and whisker extraction. The introduction of the silane coupling agent creates a tighter interface between the whiskers and the substrate, delaying crack initiation and inhibiting rapid crack propagation, thereby improving the material's impact and thermal shock resistance.

[0033] According to an embodiment of the present invention, the hexaaluminate is a spinel phase composite formed by mixing magnesia alumina spinel and alumina through high-temperature calcination, and the mass ratio of the magnesia alumina spinel to the alumina is 1:1-1:3.

[0034] Hexaaluminate Compound (HA) has a layered crystal structure that effectively inhibits shrinkage and deformation in high-temperature environments, maintaining matrix density and structural strength. Its layered arrangement fills the gaps within the matrix and forms a staggered stacking structure, enhancing the material's overall compressive and oxidation resistance. It also promotes intergranular bonding during high-temperature sintering, enhancing the refractory cement's volume stability and mechanical properties.

[0035] According to the embodiments of the present invention, magnesium-aluminum spinel provides excellent thermal shock and oxidation resistance, while alumina enhances the material's high-temperature resistance through its high melting point and stable crystal structure. The two together form a layered composite structure at high temperatures. Through lattice matching and interfacial synergy, this significantly suppresses the material's volume shrinkage and abnormal grain growth at high temperatures, while simultaneously improving the matrix's density and mechanical strength.

[0036] According to an embodiment of the present invention, the organic water reducer is a homogeneous liquid mixture composed of sodium polyacrylate and polyethylene glycol; the inorganic binder is magnesium phosphate cement powder prepared by calcining magnesium oxide and ammonium dihydrogen phosphate; the additive is a solid mixture composed of polyethylene explosion-proof fiber and nano-alumina; and the gypsum is a homogeneous powder mixture composed of calcium sulfate dihydrate and sodium citrate.

[0037] Wherein, the mass ratio of the sodium polyacrylate to the polyethylene glycol is 1:0.5-1:1;

[0038] The mass ratio of the magnesium oxide to the ammonium dihydrogen phosphate is 1:0.8-1:1.2;

[0039] The mass ratio of the polyethylene explosion-proof fiber to the nano-alumina is 1:0.1-1:0.5;

[0040] The mass ratio of the calcium sulfate dihydrate to the sodium citrate is 95:5-98:2.

[0041] Inorganic Binder (IB): A magnesium phosphate cement system is used to provide early strength and promote densification during high-temperature sintering. Magnesium phosphate cement cures rapidly at room temperature and forms a stable mineral phase during subsequent heating, enhancing the overall strength of the material.

[0042] According to the embodiments of the present invention, the strong dispersing ability of sodium polyacrylate and the lubricating properties of polyethylene glycol complement each other, enabling the slurry to achieve excellent workability while maintaining stability. This synergistic effect not only optimizes the slurry's rheological properties but also reduces porosity through uniform dispersion, improving material densification and providing a uniform structural foundation for subsequent high-temperature sintering.

[0043] According to a second aspect of the present invention, a method for preparing high-purity calcium aluminate refractory cement is provided, such as Figure 1 As shown, the following steps are included:

[0044] S1: uniformly mixing the high-purity calcium aluminate, nano zirconium oxide, hexaaluminate and modified silicon carbide whiskers to prepare a composite matrix mixture;

[0045] S2: adding the organic water reducing agent, inorganic binder and additives to the composite matrix mixture, stirring and mixing at high speed to prepare a premix;

[0046] S3: adding the deionized water to the premix and continuously stirring until the slurry is uniform to obtain a casting slurry, and forming the casting slurry by high-pressure pressing to prepare a dense green body;

[0047] S4: placing the dense green body in a high-temperature furnace for sintering to prepare clinker;

[0048] S5: After naturally cooling to room temperature, the clinker is crushed and ground to prepare a primary powder;

[0049] S6: After mixing the primary powder with the gypsum, performing secondary grinding to prepare high-purity calcium aluminate refractory cement.

[0050] According to an embodiment of the present invention, the step of uniformly mixing the high-purity calcium aluminate, nano-zirconium oxide, hexaaluminate, and modified silicon carbide whiskers to prepare a composite matrix mixture comprises:

[0051] The high-purity calcium aluminate, nano zirconium oxide and hexaaluminate were mixed and dry-milled in a planetary ball mill for 2 hours at a rotation speed of 300 rpm to obtain a primary mixture;

[0052] The modified silicon carbide whiskers were added to the primary mixture at a mass ratio of 3%, ultrasonically dispersed in an ethanol medium for 20 minutes, and then dried at 80° C. for 2 hours to obtain the composite matrix mixture.

[0053] The silicon carbide whisker is immersed in a silane coupling agent solution with a mass concentration of 2%-5%, and refluxed at 60°C-80°C for 2-4 hours to obtain a reaction product. The surface of the reaction product is washed with deionized water and vacuum dried to obtain the modified silicon carbide whisker.

[0054] According to an embodiment of the present invention, the mass ratio of the high-purity calcium aluminate, nano zirconium oxide and hexaaluminate is 60:5:5-80:15:10.

[0055] According to an embodiment of the present invention, the step of adding the deionized water to the premix and continuously stirring until the slurry is uniform to obtain a casting slurry, and subjecting the casting slurry to high-pressure pressing to form a dense green body comprises:

[0056] The premix was transferred to a planetary mixer, and the deionized water was slowly added. The stirring speed was controlled to 300 rpm and the stirring time was 20 minutes to obtain a uniform casting slurry.

[0057] The casting slurry was injected into a metal mold and a pressure of 40 MPa was applied on a hydraulic press for 3 minutes. After demoulding, the density was ≥ 2.8 g / cm 3 The dense green body;

[0058] Wherein, the mass ratio of the deionized water to the premix is 0.25:1-0.5:1.25.

[0059] According to an embodiment of the present invention, the pressure of high-pressure pressing on the hydraulic press is 40 MPa, and the holding time is 3 minutes.

[0060] According to an embodiment of the present invention, the step of placing the dense green body in a high-temperature furnace for sintering to prepare clinker comprises:

[0061] The dense green body is placed in the high-temperature furnace and sintered by a three-stage gradient temperature increase method, a nitrogen protective atmosphere is introduced during the sintering process, and the oxygen content is controlled at ≤50ppm to prepare the clinker;

[0062] Wherein: the specific steps of the three-stage gradient temperature increase method include:

[0063] The first stage: heating to 800℃ at 5℃ / min and keeping at this temperature for 1 hour;

[0064] The second stage: heating to 1450℃ at 3℃ / min and keeping at this temperature for 3 hours;

[0065] The third stage: Cool naturally to room temperature.

[0066] According to an embodiment of the present invention, the particle size of the clinker is less than 40 μm and the density is 2.8-3.2 g / cm 3 .

[0067] According to an embodiment of the present invention, after naturally cooling to room temperature, crushing and grinding the clinker to prepare the primary powder includes:

[0068] The clinker is preliminarily crushed in a jaw crusher to a particle size of ≤10 mm to obtain primary ground clinker;

[0069] The primary ground clinker was added into a continuous ball mill and ground at a speed of 350 rpm for 2.5 hours, and the primary powder with a particle size of ≤8 μm was obtained after sieving;

[0070] The feed port size of the jaw crusher is 50 mm, and the discharge particle size is controlled by a screen; the continuous ball mill uses zirconium oxide as the grinding medium.

[0071] According to an embodiment of the present invention, during the clinker crushing, grinding and screening steps, the workshop ambient humidity needs to be controlled to less than 50% by an industrial dehumidifier or air conditioning system.

[0072] According to an embodiment of the present invention, the mixing of the primary powder and the gypsum and then secondary grinding to prepare high-purity calcium aluminate refractory cement includes:

[0073] The primary powder and the gypsum were mixed in a mass ratio of 98:2-103:7, placed in a horizontal sand mill, and ground at a speed of 450 rpm for 1.5 hours to obtain a secondary ground mixture;

[0074] After the secondary grinding mixture is separated by a cyclone classifier, the high-purity calcium aluminate refractory cement with a particle size D90≤5 μm is collected.

[0075] According to embodiments of the present invention, high-purity calcium aluminate refractory cement, produced through cyclone classification technology to achieve ultrafine particle size distribution, exhibits excellent high-temperature stability, alkali corrosion resistance, and stable thermal shock resistance, effectively resisting chemical erosion and thermal stress damage in high-temperature environments. This material is suitable for use in the metallurgical industry as linings for ladles and hot metal ladle linings, high-temperature structural components for ceramic kiln furniture, and the production of high-temperature refractory castables.

[0076] The present invention has the following beneficial effects:

[0077] This invention significantly enhances the high-temperature stability and thermal shock resistance of refractory materials through a composite design combining high-purity calcium aluminate with nano-zirconia and hexaaluminate. High-purity calcium aluminate, as the core matrix, provides excellent fire resistance and structural integrity, while its stable crystal structure effectively resists chemical attack and thermal stress damage at high temperatures. The synergistic effect of these three elements creates a multi-layered protection system, enabling the material to maintain excellent mechanical properties and volume stability even in extremely high-temperature environments, providing reliable protection for high-temperature industrial applications.

[0078] The present invention utilizes a cross-scale reinforcement system of modified silicon carbide whiskers and nano-zirconia, significantly optimizing the material's fracture toughness and wear resistance. Nano-zirconia delays crack initiation at the microscale through phase transformation toughening, complementing the macroscopic reinforcement of modified silicon carbide whiskers to construct a synergistic toughening network from the nanometer to the millimeter scale. This multi-scale reinforcement mechanism not only improves the material's flexural strength and wear resistance, but also effectively extends its service life under complex operating conditions. It is particularly suitable for critical locations in high-temperature dynamic load environments, such as metallurgical equipment linings and ceramic kiln furniture structures.

[0079] The present invention significantly improves the rheological properties and construction adaptability of the slurry through the synergistic optimization of organic water-reducing agents and inorganic binders. Magnesium phosphate cement, as an inorganic binder, rapidly solidifies at room temperature and provides early strength. At the same time, it forms a stable mineral phase during high-temperature sintering, promoting the densification process. The combination of the two not only improves the uniformity of material molding, but also enhances the structural density after high-temperature sintering by reducing porosity, laying the foundation for the material's ultimate performance and meeting the high-temperature industry's demand for high strength and high stability.

[0080] The additive system of this invention optimizes the material's anti-blasting properties and surface properties through the synergistic effect of explosion-proof fibers and nano-alumina. The polyethylene explosion-proof fibers melt and volatilize upon heating, forming microchannels that release internal vapor pressure and effectively prevent explosions. Nano-alumina fills pores, increasing density and improving surface finish. The addition of gypsum further regulates setting time, preventing premature setting or cracking, and ensuring construction quality.

[0081] The high-purity calcium aluminate refractory cement of the present invention has significant advantages in the fields of metallurgy, ceramics and high-temperature industries. Its ultrafine particle size distribution and high activity enable the material to react rapidly at high temperatures and form a dense structure, significantly improving its resistance to alkali corrosion and thermal shock stability. In high-temperature equipment such as ladles and molten iron tank linings, the material can effectively resist slag erosion and thermal stress shock. In ceramic kiln furniture and refractory castables, its excellent anti-burst and wear resistance can extend service life and reduce maintenance costs. Through precise proportioning and multi-scale enhanced design, the material exhibits excellent comprehensive performance under complex working conditions, providing efficient and reliable refractory solutions for high-temperature industries and promoting green manufacturing and sustainable development.

[0082] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 Flow chart of the preparation method of an embodiment of the present invention. DETAILED DESCRIPTION

[0084] The embodiments of the present application provide a high-purity calcium aluminate refractory cement and a preparation method thereof.

[0085] Example 1: Standard formula high purity calcium aluminate refractory cement

[0086] High purity calcium aluminate: 70 parts;

[0087] Nano zirconium oxide: 10 parts;

[0088] Hexaaluminate: 7.5 parts;

[0089] Modified silicon carbide whiskers: 5.5 parts;

[0090] Organic water reducer: 1.2 parts;

[0091] Inorganic binder: 2 parts;

[0092] Additives: 0.55 parts;

[0093] Gypsum: 2 parts;

[0094] Deionized water: 22.5 parts.

[0095] Example 2: Increasing the content of high-purity calcium aluminate

[0096] High purity calcium aluminate: 80 parts;

[0097] Nano zirconium oxide: 10 parts;

[0098] Hexaaluminate: 7.5 parts;

[0099] Modified silicon carbide whiskers: 5.5 parts;

[0100] Organic water reducer: 1.2 parts;

[0101] Inorganic binder: 2 parts;

[0102] Additives: 0.55 parts;

[0103] Gypsum: 2 parts;

[0104] Deionized water: 22.5 parts.

[0105] Example 3: Reducing Hexaaluminate Content

[0106] High purity calcium aluminate: 70 parts;

[0107] Nano zirconium oxide: 10 parts;

[0108] Hexaaluminate: 5 parts;

[0109] Modified silicon carbide whiskers: 5.5 parts;

[0110] Organic water reducer: 1.2 parts;

[0111] Inorganic binder: 2 parts;

[0112] Additives: 0.55 parts;

[0113] Gypsum: 2 parts;

[0114] Deionized water: 22.5 parts.

[0115] Example 4: Enhanced high temperature anti-burst performance High purity calcium aluminate: 70 parts;

[0116] Nano zirconium oxide: 12 parts;

[0117] Hexaaluminate: 9 parts;

[0118] Modified silicon carbide whiskers: 6 parts;

[0119] Organic water reducer: 1.2 parts;

[0120] Inorganic binder: 2.5 parts;

[0121] Additives: 0.7 parts;

[0122] Gypsum: 1.8 parts;

[0123] Deionized water: 22.5 parts.

[0124] Example 5: Optimizing Alkali Corrosion Resistance High-purity Calcium Aluminate: 70 parts;

[0125] Nano zirconium oxide: 10 parts;

[0126] Hexaaluminate: 7.5 parts;

[0127] Modified silicon carbide whiskers: 5.5 parts;

[0128] Organic water reducer: 1.3 parts;

[0129] Inorganic binder: 2.2 parts;

[0130] Additives: 0.6 parts;

[0131] Gypsum: 2.2 parts;

[0132] Deionized water: 22.5 parts.

[0133] Example 6: Improving mechanical strength High-purity calcium aluminate: 70 parts;

[0134] Nano zirconium oxide: 10 parts;

[0135] Hexaaluminate: 7.5 parts;

[0136] Modified silicon carbide whiskers: 7 parts;

[0137] Organic water reducer: 1.2 parts;

[0138] Inorganic binder: 3 parts;

[0139] Additives: 0.6 parts;

[0140] Gypsum: 2 parts;

[0141] Deionized water: 22.5 parts.

[0142] Comparative Example 1: No high-purity calcium aluminate nano-zirconium oxide: 10 parts;

[0143] Hexaaluminate: 7.5 parts;

[0144] Modified silicon carbide whiskers: 5.5 parts; organic water reducer: 1.2 parts;

[0145] Inorganic binder: 2 parts;

[0146] Additives: 0.55 parts;

[0147] Gypsum: 2 parts;

[0148] Deionized water: 22.5 parts.

[0149] Comparative Example 2: High-purity calcium aluminate without hexaaluminate: 70 parts;

[0150] Nano zirconium oxide: 10 parts;

[0151] Modified silicon carbide whiskers: 5.5 parts; organic water reducer: 1.2 parts;

[0152] Inorganic binder: 2 parts;

[0153] Additives: 0.55 parts;

[0154] Gypsum: 2 parts;

[0155] Deionized water: 22.5 parts.

[0156] Comparative Example 3: Unmodified silicon carbide whiskers

[0157] High purity calcium aluminate: 70 parts;

[0158] Nano zirconium oxide: 10 parts;

[0159] Hexaaluminate: 7.5 parts;

[0160] Organic water reducer: 1.2 parts;

[0161] Inorganic binder: 2 parts;

[0162] Additives: 0.55 parts;

[0163] Gypsum: 2 parts;

[0164] Deionized water: 22.5 parts.

[0165] Comparative Example 4: No gypsum

[0166] High purity calcium aluminate: 70 parts;

[0167] Nano zirconium oxide: 10 parts;

[0168] Hexaaluminate: 7.5 parts;

[0169] Modified silicon carbide whiskers: 5.5 parts;

[0170] Organic water reducer: 1.2 parts;

[0171] Inorganic binder: 2 parts;

[0172] Additives: 0.55 parts;

[0173] Deionized water: 22.5 parts.

[0174] Experimental example:

[0175] The performance of the above examples 1-6 and comparative examples 1-4 was measured, and the results are shown in Table 1.

[0176] 1. Fire resistance temperature test

[0177] Using the high-temperature sintering method, the sample was placed in a high-temperature furnace and heated to 1600°C. After keeping warm for 2 hours, it was naturally cooled. Its structural integrity and surface melting were observed, and the highest temperature at which the intact structure was maintained was recorded.

[0178] 2. Thermal shock resistance test

[0179] Through the rapid cooling and heating cycle test, the sample was heated in a high temperature environment of 1500℃ for 30 minutes, then quickly cooled to room temperature, and the cycle was repeated 20 times to observe whether the sample showed cracking, peeling or powdering, and the number of cycles and damage status were recorded.

[0180] 3. Compressive strength test

[0181] The samples were subjected to compression tests using a universal material testing machine at a loading speed of 2 mm / min. The maximum pressure that the samples could withstand before failure was recorded and the compressive strength was calculated.

[0182] 4. Alkali corrosion resistance test

[0183] The samples were immersed in 10% sodium hydroxide solution, kept at a constant temperature of 80°C for 24 hours, taken out, rinsed with distilled water and dried, and the mass loss rate and surface erosion degree of the samples before and after immersion were compared.

[0184] 5. Anti-burst performance test

[0185] To simulate a high-temperature rapid cooling environment, heat the sample to 1400°C and then rapidly cool it to observe whether cracking occurs due to uneven release of internal steam pressure. Record the crack incidence rate and crack extension range.

[0186] 6. Mechanical strength test

[0187] The flexural strength of the sample was tested by a three-point bending tester. The span was set to three times the sample length, the loading speed was 1 mm / min, and the maximum flexural force was recorded.

[0188] Table 1. Experimental data of Examples 1-6 and Comparative Examples 1-4 of the present invention

[0189]

[0190]

[0191] As shown in Table 1, the fire resistance performance is:

[0192] Increasing the content of high-purity calcium aluminate (Example 2) significantly improves the fire resistance limit to 1650°C, indicating its decisive role as a matrix material in high-temperature stability.

[0193] The refractory temperature of the sample without high-purity calcium aluminate (Comparative Example 1) is only 1400°C, and the structural integrity is seriously deteriorated, verifying its core status.

[0194] Thermal shock resistance:

[0195] Examples 1-6 all passed 20 rapid cooling and heating cycle tests, while comparative examples 1-4 all passed less than 18 cycles, indicating that the multi-component collaborative design (such as nano-zirconia phase transformation toughening) effectively inhibited crack propagation.

[0196] Mechanical strength:

[0197] The compressive strength of Example 6 with improved mechanical strength reaches 95 MPa and the flexural strength is 22 MPa, which are better than those of other examples; the compressive strength of the comparative examples lacking key components is generally lower than 75 MPa.

[0198] Alkali corrosion resistance:

[0199] The mass loss rate of Example 5 optimized for alkali corrosion resistance is only 0.5%, which is significantly better than other examples and comparative examples, indicating that the optimization of the ratio of inorganic binder to gypsum can enhance chemical stability.

[0200] Anti-burst performance:

[0201] Examples 1-6 showed no bursting phenomenon, while comparative examples 1-4 had a bursting rate as high as 8%-20%, indicating that the layered structure of the modified silicon carbide whiskers and hexaaluminate effectively released steam pressure and prevented bursting.

[0202] The above-integrated experimental data demonstrates that the high-purity calcium aluminate refractory cement proposed in this invention exhibits significant advantages in terms of refractory properties, thermal shock resistance, mechanical strength, and alkali corrosion resistance. Due to its excellent high-temperature stability and chemical inertness, this material is widely used in the metallurgical industry (such as linings for ladles and hot metal ladle), ceramic kiln furniture, high-temperature castables, and nuclear power equipment.

[0203] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0204] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A high-purity calcium aluminate refractory cement, characterized in that: The composition is as follows in parts by mass: High-purity calcium aluminate: 60-80 parts; Nano zirconium oxide: 5-15 parts; Hexaaluminate: 5-10 parts; Modified silicon carbide whiskers: 3-8 parts; Organic water reducer: 0.5-2 parts; Inorganic binder: 1-3 parts; Additives: 0.1-1 parts; Gypsum: 1-3 parts; Deionized water: 15-30 parts.

2. The high-purity calcium aluminate refractory cement according to claim 1, characterized in that: The modified silicon carbide whiskers are silicon carbide whiskers that have been surface-treated with a silane coupling agent; Wherein, the mass ratio of the silane coupling agent to the silicon carbide whiskers is 1:10-1:

20.

3. The high-purity calcium aluminate refractory cement according to claim 1, characterized in that: The hexaaluminate is a spinel phase composite formed by mixing magnesium aluminum spinel and aluminum oxide through high temperature calcination; Wherein, the mass ratio of the magnesia-alumina spinel to the alumina is 1:1-1:

3.

4. The high-purity calcium aluminate refractory cement according to claim 1, characterized in that: The organic water reducer is a homogeneous liquid mixture of sodium polyacrylate and polyethylene glycol; the inorganic binder is magnesium phosphate cement powder obtained by calcining magnesium oxide and ammonium dihydrogen phosphate; the additive is a solid mixture of polyethylene explosion-proof fiber and nano-alumina; and the gypsum is a homogeneous powder mixture of calcium sulfate dihydrate and sodium citrate. Wherein, the mass ratio of the sodium polyacrylate to the polyethylene glycol is 1:0.5-1:1; The mass ratio of the magnesium oxide to the ammonium dihydrogen phosphate is 1:0.8-1:1.2; The mass ratio of the polyethylene explosion-proof fiber to the nano-alumina is 1:0.1-1:0.5; The mass ratio of the calcium sulfate dihydrate to the sodium citrate is 95:5-98:

2.

5. A method for preparing the high-purity calcium aluminate refractory cement according to any one of claims 1 to 4, characterized in that: The steps include: uniformly mixing the high-purity calcium aluminate, nano zirconium oxide, hexaaluminate and modified silicon carbide whiskers to prepare a composite matrix mixture; Adding the organic water reducing agent, inorganic binder and additives to the composite matrix mixture, stirring and mixing at high speed to prepare a premix; Adding the deionized water to the premix and continuously stirring until the slurry is uniform to obtain a casting slurry, and subjecting the casting slurry to high-pressure pressing to prepare a dense green body; placing the dense green body in a high-temperature furnace for sintering to prepare clinker; After naturally cooling to room temperature, the clinker is crushed and ground to prepare primary powder; The primary powder is mixed with the gypsum and then subjected to secondary grinding to prepare high-purity calcium aluminate refractory cement.

6. The preparation method according to claim 5, characterized in that: The step of uniformly mixing the high-purity calcium aluminate, nano zirconium oxide, hexaaluminate and modified silicon carbide whiskers to prepare a composite matrix mixture comprises: The high-purity calcium aluminate, nano zirconium oxide and hexaaluminate were mixed and dry-milled in a planetary ball mill for 2 hours at a rotation speed of 300 rpm to obtain a primary mixture; The modified silicon carbide whiskers were added to the primary mixture at a mass ratio of 3%, ultrasonically dispersed in an ethanol medium for 20 minutes, and then dried at 80° C. for 2 hours to obtain the composite matrix mixture. The silicon carbide whisker is immersed in a silane coupling agent solution with a mass concentration of 2%-5%, and refluxed at 60°C-80°C for 2-4 hours to obtain a reaction product. The surface of the reaction product is washed with deionized water and vacuum dried to obtain the modified silicon carbide whisker.

7. The preparation method according to claim 5, characterized in that: The step of adding the deionized water to the premix and continuously stirring until the slurry is uniform to obtain a casting slurry, and subjecting the casting slurry to high-pressure pressing to form a dense green body comprises: The premix was transferred to a planetary mixer, and the deionized water was slowly added. The stirring speed was controlled to 300 rpm and the stirring time was 20 minutes to obtain a uniform casting slurry. The casting slurry was injected into a metal mold and a pressure of 40 MPa was applied on a hydraulic press for 3 minutes. After demoulding, the density was ≥ 2.8 g / cm 3 The dense green body; Wherein, the mass ratio of the deionized water to the premix is 0.25:1-0.5:1.

25.

8. The preparation method according to claim 5, characterized in that: The step of placing the dense green body in a high temperature furnace for sintering to prepare clinker comprises: The dense green body is placed in the high-temperature furnace and sintered by a three-stage gradient temperature increase method, a nitrogen protective atmosphere is introduced during the sintering process, and the oxygen content is controlled at ≤50ppm to prepare the clinker; Wherein: the specific steps of the three-stage gradient temperature increase method include: The first stage: heating to 800℃ at 5℃ / min and keeping at this temperature for 1 hour; The second stage: heating to 1450℃ at 3℃ / min and keeping at this temperature for 3 hours; The third stage: Cool naturally to room temperature.

9. The preparation method according to claim 5, characterized in that After naturally cooling to room temperature, the clinker is crushed and ground to prepare the primary powder, which includes: The clinker is preliminarily crushed in a jaw crusher to a particle size of ≤10 mm to obtain primary ground clinker; The primary ground clinker was added into a continuous ball mill and ground at a speed of 350 rpm for 2.5 hours, and the primary powder with a particle size of ≤8 μm was obtained after sieving; The feed port size of the jaw crusher is 50 mm, and the discharge particle size is controlled by a screen; the continuous ball mill uses zirconium oxide as the grinding medium.

10. The preparation method according to claim 5, characterized in that: The method of mixing the primary powder with the gypsum and then performing secondary grinding to prepare high-purity calcium aluminate refractory cement comprises: The primary powder and the gypsum were mixed in a mass ratio of 98:2-103:7, placed in a horizontal sand mill, and ground at a speed of 450 rpm for 1.5 hours to obtain a secondary ground mixture; After the secondary grinding mixture is separated by a cyclone classifier, the high-purity calcium aluminate refractory cement with a particle size D90≤5 μm is collected.

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