Lightweight composite porcelain clay and preparation method thereof

Abstract

The invention discloses lightweight composite porcelain clay and a preparation method thereof, and belongs to the technical field of building materials. The porcelain clay comprises kaolin and a magnesium oxide and titanium oxide composite nucleating agent in a specific mass ratio. During preparation, the raw materials are firstly smelted and quenched by water, and then two-stage gradient heat treatment is performed. Through the synergistic effect of the composite nucleating agent and a unique heat treatment process, a high-strength crystal skeleton and uniform pores are constructed in the material, the unification of light weight and high strength is realized, and the problem of low strength of the existing light ceramic is solved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a lightweight composite kaolin and its preparation method. Background Technology

[0002] Environmentally friendly ceramics made from kaolin are increasingly widely used in construction. These materials not only possess excellent wear resistance, corrosion resistance, low water absorption, and decorative properties, making them suitable for flooring and wall paving in various public places, but can also be further processed into high-performance ceramic curtain walls and other new exterior wall decoration materials. These materials exhibit superior high strength, high weather resistance, and corrosion resistance, significantly extending the service life of buildings.

[0003] In traditional architecture, ceramics have been used as important materials for structural masonry, sealing walls, cladding, and sanitary ware. Ceramic blocks possess high compressive strength, making them suitable for load-bearing or non-load-bearing walls in low- to mid-rise buildings. Ceramic cladding (such as wall tiles and floor tiles) combines functionality and decorative effects; glazing further enhances their waterproofness, wear resistance, and aesthetics. Porcelain clay, due to its fine texture, pure white color, and high plasticity, is a key raw material for producing various architectural ceramics (such as ceramic tiles, exterior wall tiles, and glazed tiles). Especially in the high-end decorative field, porcelain glazed tiles made from refined kaolin clay, with their dense, white body, high strength, and good durability, are chosen for their superior performance and decorative effect, despite their significantly higher cost compared to ordinary clay tiles.

[0004] However, despite the numerous applications of porcelain-based ceramics in construction, traditional porcelain materials generally suffer from high density and weight, which not only increases the load on building structures but also affects transportation and construction efficiency. To adapt to the development trend of lightweight and energy-saving buildings, the development of lightweight, high-strength porcelain-based materials has become an important research direction. While common lightweight ceramic preparation methods (such as adding pore-forming agents and foaming processes) can effectively reduce density, they often lead to a significant decrease in the material's mechanical strength, making it difficult to simultaneously meet the requirements of lightweighting and structural performance, thus limiting its application in load-bearing or high-strength building components. Therefore, how to achieve a balance between lightweighting and high strength while maintaining the excellent properties of porcelain materials through compositional and process innovation is a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a lightweight composite kaolin and its preparation method to solve the problems of low strength and difficulty in balancing lightweight and high strength in existing lightweight ceramic materials.

[0006] The present invention provides a lightweight composite kaolin, the raw materials of which include, by weight, 100 parts of kaolin and 1-10 parts of composite nucleating agent; the composite nucleating agent is composed of magnesium oxide and titanium oxide, wherein the mass ratio of magnesium oxide to titanium oxide is 1:1.

[0007] Furthermore, the kaolin is calcined kaolin with an average particle size of 1-10 μm.

[0008] Furthermore, the kaolin is selected from brand name Polestar 200R.

[0009] Furthermore, the average particle size of the magnesium oxide is approximately 1-5 μm.

[0010] Furthermore, the titanium oxide is a composite of micron-sized TiO2 and nano-sized TiO2 in a mass ratio of 1:(1-2).

[0011] Furthermore, the average particle size of the micron-sized TiO2 is 1-5 μm, and the average particle size of the nano-sized TiO2 is 20-30 nm.

[0012] This invention also provides a method for preparing lightweight composite kaolin, specifically including the following steps:

[0013] S1. Mix kaolin and the composite nucleating agent evenly, melt at 1400-1600℃ for 0.5-2 hours to form a homogeneous melt, and then cool rapidly to obtain the basic mixture;

[0014] S2. Perform gradient heat treatment on the basic mixture: first heat to 850-950℃ at a heating rate of 3℃ / min and hold for 2 hours; then continue heating to 1150-1250℃ at a heating rate of 5℃ / min and hold for 4 hours; after the heat treatment is completed, cool to room temperature under controlled temperature to obtain the lightweight composite kaolin.

[0015] Furthermore, in step S1, the rapid cooling method is water quenching or air quenching.

[0016] This invention utilizes magnesium oxide and micro-nano composite TiO2 as a composite nucleating agent, combined with a unique two-stage gradient heat treatment process, to successfully prepare a composite kaolin that combines lightweight and high mechanical strength. Its beneficial effects and principles are as follows:

[0017] The composite nucleating agent produced a significant synergistic effect. Magnesium oxide, acting as a network modifier and reinforcing phase precursor, reduced the high-temperature viscosity of the system, promoting mass transfer and sintering. Furthermore, it reacted with Al2O3 in kaolin to form high-hardness magnesium aluminum spinel (MgAl2O4), which dispersed throughout the matrix, providing reinforcement through pinning and crack deflection. Micron-sized TiO2 primarily acted as a "reaction promoter," with its Ti... 4 ⁺ The solid solution into the magnesium aluminum spinel (MgAl2O4) lattice generates cation vacancies, which greatly activates Mg 2+The diffusion of Al³⁺ and O²⁻ significantly lowers the spinelization temperature; nano-sized TiO₂ acts as a "highly efficient nucleating agent" and "pore stabilizer," its huge specific surface area providing a vast number of heterogeneous nucleation sites, ensuring the fine and uniform distribution of crystal nuclei. Simultaneously, the nanoparticles stabilize the bubble interfaces in the high-temperature melt, contributing to the formation of a uniform and fine pore structure. These three factors work synergistically to lower the nucleation energy barrier thermodynamically and kinetically, enabling low-temperature, high-efficiency sintering and the construction of pore structures.

[0018] Secondly, a specific "gradient heat treatment process" is employed: the first stage (lower temperature, sufficient holding time) focuses on maximizing uniform nucleation while strictly suppressing premature crystal growth; the second stage (higher temperature, longer holding time) focuses on providing a stable growth environment for the formed nuclei, allowing them to grow controllably into interwoven mullite crystals, which together with spinel particles form a robust ceramic framework. This method of separating and independently optimizing the two kinetic processes of "nucleation" and "growth" is key to obtaining a uniform, dense microstructure, thereby enabling the material framework itself to possess extremely high load-bearing capacity while retaining a large number of pores. Detailed Implementation

[0019] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0020] Example 1

[0021] A method for preparing lightweight composite kaolin includes the following steps:

[0022] S1. Weigh 100 parts by weight of calcined kaolin (Polestar 200R, average particle size 2 μm), 2.5 parts by weight of MgO (average particle size 3 μm), 1.25 parts by weight of micron-sized TiO2 (average particle size 3 μm), and 1.25 parts by weight of nano-sized TiO2 (average particle size 25 nm). Place the raw materials in a ball mill jar and ball mill them together with ethanol as the medium for 6 hours. After drying, pass the mixture through a 200-mesh sieve. Place the uniformly mixed powder in a corundum crucible and put it into a high-temperature furnace. Heat the furnace to 1500℃ at a rate of 5℃ / min and hold for 1 hour to fully melt and homogenize it. Then, quickly pour the melt into deionized water for quenching to obtain glassy slag. After drying the slag, process it with a crusher and pass it through a 100-mesh sieve to obtain the basic mixture.

[0023] S2. The basic mixture is loaded into a square graphite mold and lightly pressed into a green body under a pressure of 10 MPa. The green body is then placed in a programmable temperature controlled furnace for two-stage heat treatment. It is heated to 900°C at a heating rate of 3°C / min and held for 2 hours. Subsequently, it is heated to 1200°C at a heating rate of 5°C / min and held for 4 hours. After heat treatment, the furnace is slowly cooled to below 200°C at a controlled cooling rate (approximately 2°C / min), and then removed and cooled to room temperature in air to obtain the lightweight composite porcelain clay.

[0024] Example 2:

[0025] A method for preparing lightweight composite kaolin includes the following steps:

[0026] S1. Batching and Melting: Weigh 100 parts by weight of calcined kaolin, 1 part by weight of MgO, 0.5 parts by weight of micron-sized TiO2, and 0.5 parts by weight of nano-sized TiO2. The raw material processing is the same as in Example 1. Melt at 1480℃ for 1.5 hours, then quench with water to prepare the basic mixture.

[0027] S2. Gradient heat treatment: In the first stage, the temperature is increased to 850℃ at 3℃ / min and held for 2 hours; in the second stage, the temperature is increased to 1150℃ at 5℃ / min and held for 4 hours, followed by furnace cooling.

[0028] Example 3:

[0029] A method for preparing lightweight composite kaolin includes the following steps:

[0030] S1. Batching and Melting: Weigh 100 parts by weight of calcined kaolin, 5 parts by weight of MgO, 2.5 parts by weight of micron-sized TiO2, and 2.5 parts by weight of nano-sized TiO2. The raw material processing is the same as in Example 1. Melt at 1550℃ for 0.5 hours, then quench with water to prepare the basic mixture.

[0031] S2. Gradient heat treatment: In the first stage, the temperature is increased to 950℃ at 3℃ / min and held for 2 hours; in the second stage, the temperature is increased to 1250℃ at 5℃ / min and held for 4 hours, followed by furnace cooling.

[0032] Comparative Example 1

[0033] The preparation method differs from that of Example 1 only in that the composite nucleating agent is only 5 parts by weight of MgO, and no TiO2 is added. The other steps and process parameters are exactly the same as those in Example 1.

[0034] Comparative Example 2

[0035] The preparation method differs from Example 1 only in that all TiO2 in the composite nucleating agent is provided by 2.5 parts by weight of micron-sized TiO2, without the addition of nano-sized TiO2. The other steps and process parameters are exactly the same as in Example 1.

[0036] Comparative Example 3

[0037] The preparation method uses the same raw material formula as in Example 1, but the two-stage gradient heat treatment is cancelled. Instead, the basic mixture is pressed into a compact and then heated directly from room temperature to 1200°C at a single heating rate of 5°C / min, and held for 4 hours, followed by furnace cooling.

[0038] Comparative Example 4

[0039] The preparation method differs from Example 1 only in that the total amount of composite nucleating agent added is still 5 parts by weight, but the mass ratio of MgO to TiO2 is adjusted to 2:1, that is, 3.33 parts by weight of MgO and 1.67 parts by weight of micro-nano composite TiO2 are added (where the mass ratio of micron to nano TiO2 is maintained at 1:1). All other raw materials, steps and process parameters are exactly the same as in Example 1.

[0040] The samples prepared in the above embodiments and comparative examples were subjected to the following performance tests:

[0041] Bulk density test: The Archimedes displacement method was used for determination;

[0042] Compressive strength test: The test was conducted using a universal testing machine with a cubic specimen measuring 20mm×20mm×20mm and a loading rate of 0.5mm / min.

[0043] Table 1: Performance Test Results

[0044] <![CDATA[Volume density (g / cm 3 )]]> Compressive strength (MPa) Example 1 1.18 65 Example 2 0.95 48 Example 3 1.15 59 Comparative Example 1 1.32 22 Comparative Example 2 1.22 28 Comparative Example 3 1.20 20 Comparative Example 4 1.22 42

[0045] As shown in the table above, this invention (Examples 1-3) successfully constructed a robust framework in kaolin clay, consisting of a fine mullite crystal interwoven network and a dispersed spinel reinforcing phase, by using a specific mass ratio (1:1) of MgO and micro-nano composite TiO2 as a composite nucleating agent, combined with a two-stage gradient heat treatment process of low-temperature nucleation followed by high-temperature crystal growth, while maintaining a uniform pore structure. The absence of any key component (such as in Comparative Examples 1 and 2) or changes to the key process (such as in Comparative Example 3) would lead to microstructural degradation, making it impossible to simultaneously achieve both lightweight (high porosity) and high strength. This fully verifies the non-obviousness and synergistic necessity of the various elements in the technical solution of this invention. Furthermore, comparing the experimental results of Example 1 and Comparative Example 4 shows that a 1:1 mass ratio of MgO to TiO2 in the composite nucleating agent is one of the key methods of this invention. Even if the total amount of additives, the types of raw materials and the heat treatment process are kept the same as in the optimal example 1, simply changing the mass ratio to 2:1 results in a decrease of more than 35% in the compressive strength of the product (42 MPa) compared to example 1 (65 MPa).

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A lightweight composite kaolin, characterized in that, The raw materials include, by weight, 100 parts of kaolin and 1-10 parts of composite nucleating agent; the composite nucleating agent is composed of magnesium oxide and titanium oxide, wherein the mass ratio of magnesium oxide to titanium oxide is 1:

1.

2. The lightweight composite kaolin according to claim 1, characterized in that, The kaolin mentioned is calcined kaolin with an average particle size of 1-10 μm.

3. The lightweight composite kaolin according to claim 1, wherein the average particle size of the magnesium oxide is about 1-5 μm.

4. The lightweight composite porcelain clay according to claim 1, wherein the titanium oxide is composed of micron-sized TiO2 and nano-sized TiO2 in a mass ratio of 1:(1-2).

5. The lightweight composite kaolin according to claim 1, wherein the average particle size of the micron-sized TiO2 is 1-5 μm, and the average particle size of the nano-sized TiO2 is 20-30 nm.

6. A method for preparing lightweight composite kaolin as described in any one of claims 1-5, specifically comprising the following steps: S1. Mix kaolin and the composite nucleating agent evenly, melt at 1400-1600℃ for 0.5-2 hours to form a homogeneous melt, and then cool rapidly to obtain the basic mixture; S2. Perform gradient heat treatment on the basic mixture: first heat it to 850-950℃ at a heating rate of 3℃ / min and hold it for 2 hours; then continue heating it to 1150-1250℃ at a heating rate of 5℃ / min and hold it for 4 hours; after the heat treatment is completed, control the cooling to room temperature to obtain the lightweight composite porcelain clay.