Prestressed reinforcement coating slurry suitable for various building ceramics, preparation method and application thereof

Abstract

The present invention discloses a prestressed reinforcement coating slurry suitable for various architectural ceramics, as well as its preparation method and application, belonging to the technical field of ceramic reinforcement materials. The coating slurry is composed of a coating powder and a solvent, wherein the coating powder is composed of the following components by weight: 40-50% quartz; 10-12% alumina; 20-30% dolomite; 2-5% α-spodumene; 2-5% polyvinyl butyral; 0.5-0.8% dispersant; and 5-8% kyanite. The present invention prepares a coating slurry from quartz, alumina, dolomite, α-spodumene, and kyanite, capable of improving the damage tolerance of various architectural ceramic substrates.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic reinforcement materials, in particular to a coating slurry for prestressed reinforcement applicable to various building ceramics, and a preparation method and application thereof. Background Art

[0002] According to a preparation method for prestressed ceramics proposed by Bao et al., the difference in thermal expansion coefficients between the coating material and the base material is utilized so that during the cooling process after co-firing, the surface coating material forms compressive stress on the base due to its smaller thermal expansion coefficient. This residual compressive stress will offset the external tensile stress on the material and improve the bending strength of the material. For example, a layer of alumina is coated on the surface of zirconia ceramics. After sintering, the strength is increased by 45% compared with a single zirconia ceramic. The fracture toughness of ceramic materials is generally very low. The fundamental reason is that when cracks propagate, the energy dissipation is almost entirely concentrated in the formation of new surfaces, and there is a lack of a mechanism to significantly consume the crack propagation energy. Therefore, to improve the fracture toughness of ceramic materials, it is necessary to increase the energy dissipated during the crack propagation process, that is, to increase the crack propagation resistance of the material. The residual compressive stress in the prestressed composite can effectively hinder and inhibit the growth and propagation of surface microcracks.

[0003] The sizes and specifications of architectural ceramics are increasing, and the requirements for their service life and physical strength are becoming increasingly stringent. It is known that the mechanical properties of brittle ceramics are affected by their surface residual stresses. Properly designing the surface residual compressive stress can improve the flexural strength and surface crack resistance of ceramics. However, the mechanisms that influence other mechanical properties remain to be explored. For example, the damage tolerance of ceramic materials is an effective metric for quantifying the service safety index of brittle materials. It refers to the material's ability to resist failure due to defects, cracks, or other damage within a specified service life. Specifically, it refers to the ability of a brittle ceramic structure to maintain its residual strength over a specified service life after sustaining quantitative damage caused by fatigue, corrosion, or random impact. Studies of the damage tolerance of nano-layered granular ceramics have shown that damage tolerance is related to the material's intrinsic crack size, which in turn depends on the ratio of the material's fracture toughness to its flexural strength, while its energy dissipation capacity is determined by the ratio of its elastic modulus to its surface hardness. Therefore, the damage tolerance of ceramic materials can be calculated from four fundamental mechanical property theorems, effectively and quantitatively reflecting the structural reliability of ceramics.

[0004] At the same time, existing technologies have been proposed to construct prestressed coatings on the surfaces of architectural ceramics to improve their mechanical properties. However, the ability of the same prestressed coating to enhance mechanical properties varies depending on the composition of the architectural ceramic powder. The existing technology lacks a prestressed coating material that is universally applicable to a wide range of architectural ceramics. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention discloses a coating slurry for prestressed reinforcement suitable for a variety of building ceramics, as well as its preparation method and application. The coating slurry of the present invention can significantly improve the bending strength and fracture toughness of a variety of building ceramic substrates when applied on them, and has high damage tolerance and universality.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In one aspect, the present invention provides a coating slurry for prestressed reinforcement applicable to a variety of architectural ceramics, comprising a coating powder and a solvent, wherein the coating powder comprises the following components in percentage by mass:

[0008]

[0009] The solvent is ethanol, and the amount used is 2-3 times the mass of the coating powder.

[0010] Preferably, in the coating slurry for prestressed reinforcement applicable to various architectural ceramics, the coating powder is composed of the following components in weight percentage:

[0011]

[0012]

[0013] Preferably, the quartz particle size is 300 mesh; the alumina particle size is 500 mesh; the dolomite particle size is 250 mesh; the α-spodumene particle size is 200 mesh; the kyanite particle size is 325 mesh; the molecular weight of the polyvinyl butyral is 90,000-120,000, and the dispersant is castor oil.

[0014] On the other hand, the present invention provides a method for preparing the above-mentioned prestressed reinforcement coating slurry suitable for various architectural ceramics, comprising adding the coating powder and ethanol into a ball mill, ball milling and dispersing for more than 5 hours, and then discharging the slurry for later use;

[0015] During the ball milling process, the mass ratio of the coating powder to the ball milling balls is 1:10; and the rotation speed during the ball milling process is 300 r / min.

[0016] On the other hand, the present invention also provides an application of the above-mentioned prestressed reinforcement coating slurry suitable for a variety of building ceramics. The above-mentioned coating slurry is applied to the upper and lower surfaces of the building ceramic substrate, dried, sintered at high temperature, and then cooled to room temperature.

[0017] Furthermore, the building ceramic matrix is ​​prepared by the following method: placing the building ceramic powder in a 120mm×20mm dry pressing mold, pressurizing it to 96000N at a rate of 800N / s, maintaining the pressure for 1 minute, taking out the formed block after pressing, and pre-firing the formed block at a pre-firing temperature of 600°C, heating it at a rate of 5°C / min, keeping it at 600°C for 60 minutes, and then cooling it with the furnace. The pre-firing matrix is ​​chamfered to obtain the building ceramic matrix.

[0018] Furthermore, the prepared building ceramic substrate was placed flat on the experimental table, and the coating slurry was evenly coated on the upper and lower surfaces of the substrate. After the slurry was dried (50°C, 1h), it was placed in a high-temperature air furnace for pressureless sintering. During the sintering process, the temperature was raised to 650°C at a rate of 5°C / min, kept warm for 1h, then raised to 1190°C at a rate of 5°C / min and kept warm for 30min, and finally dropped to 700°C at a rate of 5°C / min, and then cooled with the furnace.

[0019] Preferably, the coating thickness on the surface of the architectural ceramic substrate is 50-100 μm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention mixes quartz, alumina, dolomite, α-spodumene and kyanite and then coats the mixture on a pre-fired building ceramic substrate. After pressureless co-firing, a prestressed composite is obtained. Due to the difference in thermal expansion coefficient, residual compressive stress is formed on the surface of the substrate, thereby achieving the effect of prestressing to enhance the bending strength and fracture toughness of various building ceramic substrates and improve the damage tolerance.

[0022] This study explores the effects of prestressed coatings on the flexural strength, fracture toughness, elastic modulus, and damage tolerance of architectural ceramics, and explains the mechanisms by which they influence the mechanical properties of the substrate and enhance its performance. By tightly sintering the prestressed coating onto the architectural ceramic substrate, the present invention exploits the difference in thermal expansion coefficients to form residual compressive stress after sintering, achieving prestressed strengthening and effectively improving a range of mechanical properties of the brittle ceramic material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an SEM image of a composite ceramic prepared using the coating slurry of an embodiment of the present invention and formula 1#. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0025] Unless otherwise specified, the materials and reagents used in this invention are commercially available. The quartz particle size is 300 mesh; the alumina particle size is 500 mesh; the dolomite particle size is 250 mesh; the α-spodumene particle size is 200 mesh; and the kyanite particle size is 325 mesh. The molecular weight of polyvinyl butyral is 90,000-120,000.

[0026] The present invention provides a coating slurry for prestressed reinforcement applicable to a variety of architectural ceramics, a preparation method thereof, and applications thereof. Specific embodiments are as follows.

[0027] Example 1

[0028] A coating slurry for prestressed reinforcement suitable for various architectural ceramics, comprising a coating powder and a solvent, wherein the coating powder comprises the following components in percentage by mass:

[0029]

[0030]

[0031] The solvent is ethanol, and the amount used is twice the mass of the coating powder.

[0032] The above-mentioned method for preparing the coating slurry for prestressed reinforcement suitable for various building ceramics is as follows: coating powder and ethanol are added to a ball mill and ball-milled for more than 5 hours, wherein the mass ratio of coating powder to ball milling balls is 1:10; the rotation speed during the ball milling process is 300r / min, and the slurry is discharged for later use.

[0033] Example 2

[0034] A coating slurry for prestressed reinforcement suitable for various architectural ceramics, comprising a coating powder and a solvent, wherein the coating powder comprises the following components in percentage by weight:

[0035]

[0036] The solvent is ethanol, and the amount used is 2.6 times the mass of the coating powder.

[0037] The preparation method is the same as that of Example 1.

[0038] Example 3

[0039] A coating slurry for prestressed reinforcement suitable for various architectural ceramics, comprising a coating powder and a solvent, wherein the coating powder comprises the following components in percentage by mass:

[0040]

[0041]

[0042] The solvent is ethanol, and the amount used is 3 times the mass of the coating powder.

[0043] The preparation method is the same as that of Example 1.

[0044] Example 4

[0045] A coating slurry for prestressed reinforcement suitable for various architectural ceramics, comprising a coating powder and a solvent, wherein the coating powder comprises the following components in percentage by mass:

[0046]

[0047] The solvent is ethanol, and the amount used is 2.6 times the mass of the coating powder.

[0048] The preparation method is the same as that of Example 1.

[0049] In order to further illustrate the beneficial effects of the present invention, a comparative example is constructed as follows.

[0050] Comparative Example 1

[0051] The kyanite was replaced with an equal amount of quartz, and the other conditions were the same as those in Example 2.

[0052] Comparative Example 2

[0053] Dolomite was replaced with an equal amount of quartz, and the remaining conditions were the same as in Example 2.

[0054] Comparative Example 3

[0055] Alumina was replaced with an equal amount of quartz, and the remaining conditions were the same as in Example 2.

[0056] Comparative Example 4

[0057] The quartz was replaced by an equal amount of alumina, and the other conditions were the same as those in Example 2.

[0058] Comparative Example 5

[0059] The kyanite was replaced by an equal amount of calcite, and the other conditions were the same as those in Example 2.

[0060] Comparative Example 6

[0061] The α-spodumene was replaced with an equal amount of quartz, and the other conditions were the same as those in Example 2.

[0062] Comparative Example 7

[0063] The dolomite was replaced with an equal amount of talc powder, and the other conditions were the same as those in Example 2.

[0064] Comparative Example 8

[0065] Kyanite was replaced by an equal amount of industrial zinc oxide, and the remaining conditions were the same as in Example 2.

[0066] The coating slurries prepared in the above examples and comparative examples were applied to the upper and lower surfaces of the architectural ceramic substrate, and their performance was tested as follows.

[0067] The formula of building ceramic powder is as follows:

[0068] Formulation #1: 60.25% SiO2, 12.31% CaO, 7.64% Al2O3, 2.55% Na2O, 1.87% K2O, 1.57% SrO, 1.32% BaO, 0.72% MgO, 0.62% ZnO, 0.17% Fe2O3, and 10.98% loss on ignition;

[0069] Formula 2#: potassium sodium feldspar 25%, high white sodium stone 15%, high white potassium sand 28%, high white lime mud 10%, A93 ball clay 20%, burned talc 2%.

[0070] Formula 3#: porcelain clay 62%, quartz powder 23%, kaolin 5%, alumina 5%, calcium silicate 2%, sodium silicate 1%, sodium sulfate 0.5%, sodium hydroxide 0.5%, ammonium sulfate 0.5%, sodium silicate 0.5%.

[0071] Formula 4#: 35% hot-stewed converter slag, 25% coke stone, 12% clay, 22% talc, and 6% feldspar.

[0072] The present invention provides an application of the above-mentioned prestressed reinforcement coating slurry applicable to various architectural ceramics. The prepared coating slurry is applied to the upper and lower surfaces of the architectural ceramic substrate, dried, sintered at high temperature, and then cooled to room temperature. Specifically:

[0073] (1) The building ceramic matrix is ​​prepared by the following method: the building ceramic powder is placed in a 120 mm × 20 mm dry pressing mold, pressurized at a rate of 800 N / s to 96000 N, and maintained at pressure for 1 min. After pressing, the molded block is taken out and pre-fired at a pre-fire temperature of 600 ° C. The temperature is increased at a rate of 5 ° C / min, kept at 600 ° C for 60 min, and then cooled with the furnace. The pre-fired matrix is ​​chamfered to obtain the building ceramic matrix.

[0074] (2) The prepared architectural ceramic substrate was placed flat on the experimental table, and the coating slurry was evenly coated on the upper and lower surfaces of the substrate. After drying at 50°C for 1 hour, it was placed in a high-temperature air furnace for pressureless sintering. During the sintering process, the temperature was raised to 650°C at a rate of 5°C / min, kept warm for 1 hour, then raised to 1190°C at a rate of 5°C / min and kept warm for 30 minutes, and finally lowered to 700°C at a rate of 5°C / min, and then cooled with the furnace.

[0075] Taking Examples 1-4 and Comparative Examples 1-8 as examples, the same amount of slurry was applied to a building ceramic substrate using the above method to prepare composite ceramics, and their properties were tested.

[0076] The flexural strength of architectural ceramic matrices and prestressed composite ceramics (GB / T 6569-2006) was tested using a microcomputer-controlled electronic universal testing machine (Model C45, MTS). The effective average value of the measured experimental data was calculated. Data that differed from the average value by 20% or more were considered invalid, and the effective average value was regarded as the flexural strength of the sample.

[0077] The fracture toughness of the matrix and composite ceramics was tested using the single-sided notched beam method (a testing method and device for the fracture toughness of a ceramic substrate CN202110773710.8). A cut with half the width was cut at 1 / 2 of the length of the sample. The cutting line width was 0.25 mm. Considering the vibration of the cutting line during the actual cutting process, the incision width was approximately 0.30 mm. The fracture toughness test span was 50 mm, and the beam displacement rate was 0.1 mm / min. The data collection method was the same as that of the bending strength test, and the effective average value was regarded as the fracture toughness value of the material.

[0078] The pulse excitation method (JC / T2172–2013) was used to test the elastic modulus of architectural ceramic matrix and prestressed composite ceramics at room temperature.

[0079] The surface hardness of the architectural ceramic matrix and prestressed composite was tested using a Vickers hardness tester. Before testing the hardness, the following preparatory experiments were performed: the test samples that were broken after the above strength test were mounted, and rough polished for 3 hours and fine polished for 3 hours using a polishing machine until a clear mirror gloss was observed on the sample surface. The polished samples were then subjected to a surface hardness test. The experimental conditions were: 500GF, holding load for 30 seconds, and 2 test points were evenly spaced on the sample surface. Ten hardness values ​​were measured at each test point. A thermal expansion coefficient of the matrix and composite was measured using a thermal dilatometer (DIL402C, Lindsay, Germany).

[0080] The cross-sectional morphology of the prestressed composite ceramics was observed by electron microscopy.

[0081] The uncontrolled expansion of cracks in a material is a key factor affecting its fracture toughness and bending strength. The presence of residual compressive stress can effectively counteract external tensile stress, so that when the sample is subjected to tension and cracks, it needs to be subjected to greater stress, thereby increasing the fracture strength of the material. The residual stress of the surface layer is related to the properties and structural shape of the inherent material. In the coated beam specimen, the stress in the coating can be regarded as thin film stress, that is, it is approximately uniformly distributed in the thickness direction. Therefore, the residual compressive stress of the coating can be determined by formula (1):

[0082]

[0083] Where: c is the coating participation stress; S s is the cross-sectional area of ​​the matrix; S c is the cross-sectional area of ​​the coating; E c is the elastic modulus of the coating; E s is the matrix elastic modulus; α c is the thermal expansion coefficient of the coating; α s is the thermal expansion coefficient of the substrate; △T is the difference between the brittle-ductile transition temperature and room temperature.

[0084] The residual compressive stress in the coating and the residual tensile stress in the substrate form a balanced system. Let S represent their respective cross-sectional areas, then:

[0085] σ c S c =σ s S c (2)

[0086] Where: s is the residual stress in the matrix.

[0087] According to fracture mechanics, the strength can be estimated by the crack size, and the fracture toughness K IC and intensity σ f The relationship between depends on the main crack size:

[0088] K IC =σ f ·Y·a 1 / 2 (3)

[0089] Among them: Y is the geometric factor; a is the crack length; the ratio of fracture toughness to strength reflects the material's ability to withstand crack size, while on the other hand, the ratio of elastic modulus to hardness reflects the material's ability to dissipate energy. Therefore, the damage tolerance of the material D t It can be expressed as the product of these two terms:

[0090]

[0091] As long as the fracture toughness K of the material is obtained IC , bending strength σ b , hardness H, and elastic modulus E, the damage tolerance of the material can be quantitatively calculated.

[0092] The present invention controls completely identical sintering preparation and performance testing conditions, respectively tests and compares the mechanical properties of the architectural ceramic matrix and the prestressed composite, and finally calculates the damage tolerance of the matrix and the composite based on the above mechanical properties.

[0093] The above-mentioned performance tests were performed on the prestressed composite ceramics prepared in the above-mentioned embodiments and comparative examples, and the results are shown in Tables 1-3.

[0094] Table 1

[0095]

[0096] As can be seen from Table 1, the coating slurry prepared by the present invention can significantly improve the fracture toughness and bending strength of the substrates of formulas 1#-4# after coating, so that they have a higher damage tolerance. The coating slurry prepared by the present invention is universally applicable to a variety of building ceramics.

[0097] Compared to the ceramic matrix of Formula 1, the prestressed architectural ceramics showed a 25.6-42.6% increase in flexural strength and a 35.6-66.4% increase in fracture toughness. The surface prestress had little effect on the overall elastic modulus and hardness. The damage tolerance of the prestressed architectural ceramics increased by 32.7%. The coating slurry also exhibited a significant strengthening effect on other architectural ceramics.

[0098] Table 2

[0099]

[0100]

[0101] Table 3

[0102]

[0103] As can be seen from Table 2-3, the coating slurry prepared by omitting or replacing any one of the kyanite, quartz, dolomite, alumina, and α-spodumene of the present invention may be able to improve the damage tolerance of a certain building ceramic substrate, but is not suitable for many building ceramic substrates.

[0104] In summary, the present invention mixes quartz, alumina, dolomite, α-spodumene and kyanite and then coats the mixture on a pre-fired building ceramic substrate. After pressureless co-firing, a prestressed composite is obtained, thereby achieving the effect of prestressing to enhance the bending strength and fracture toughness of various building ceramic matrices and improve their damage tolerance.

[0105] The above is a preferred embodiment of the present invention. For ordinary technicians in this technical field, making several improvements and modifications without departing from the principles of the present invention should also be considered as the scope of protection of the present invention.

Claims

1. An application of a prestressed reinforcement coating slurry suitable for various architectural ceramics, characterized in that: Apply the coating slurry on the upper and lower surfaces of the building ceramic substrate, dry it, sinter it at high temperature, and then cool it to room temperature; The coating slurry is composed of coating powder and solvent, wherein the coating powder is composed of the following components in mass percentage: The solvent is ethanol, and the amount used is 2-3 times the mass of the coating powder; The quartz particle size is 300 mesh; the alumina particle size is 500 mesh; the dolomite particle size is 250 mesh; the α-spodumene particle size is 200 mesh; the kyanite particle size is 325 mesh; the molecular weight of the polyvinyl butyral is 90,000-120,000; and the dispersant is castor oil; The formula of the architectural ceramic matrix is ​​as follows: Formula 1: 60.25% SiO2, 12.31% CaO, 7.64% Al2O3, 2.55% Na2O, 1.87% K2O, 1.57% SrO, 1.32% BaO, 0.72% MgO, 0.62% ZnO, 0.17% Fe2O3 and 10.98% loss on ignition; Formula 2#: potassium-sodium feldspar 25%, high white sodium stone 15%, high white potassium sand 28%, high white plaster 10%, A93 ball clay 20%, burned talc 2%; Formula 3#: China clay 62%, quartz powder 23%, kaolin 5%, alumina 5%, calcium silicate 2%, sodium silicate 1%, sodium sulfate 0.5%, sodium hydroxide 0.5%, ammonium sulfate 0.5%, sodium silicate 0.5%; Formula 4#: 35% hot-stewed converter slag, 25% coke stone, 12% clay, 22% talc, and 6% feldspar.

2. The use according to claim 1, characterized in that The coating powder is composed of the following components in weight percentage:

3. The use according to claim 1 or 2, characterized in that The coating slurry is prepared by the following method: adding the coating powder and the solvent into a ball mill, ball milling and dispersing for more than 5 hours, and then slurrying out for use; During the ball milling process, the mass ratio of the coating powder to the ball milling balls was 1:10; and the rotation speed during the ball milling process was 300 r / min.

4. The use according to claim 1, characterized in that The architectural ceramic matrix is ​​prepared by the following method: placing architectural ceramic powder in a 120 mm × 20 mm dry pressing mold, applying pressure at a rate of 800 N / s to 96,000 N, maintaining the pressure for 1 minute, taking out the formed block after pressing, pre-firing the formed block at a pre-firing temperature of 600° C., increasing the temperature at a rate of 5° C. / min, maintaining the temperature at 600° C. for 60 minutes, and then cooling with the furnace, and chamfering the pre-firing matrix to obtain the architectural ceramic matrix.

5. The use according to claim 4, characterized in that The prepared building ceramic substrate is placed flat on the laboratory table, and the coating slurry is evenly coated on the upper and lower surfaces of the substrate. After the slurry is dried, it is placed in a high-temperature air furnace for pressureless sintering. During the sintering process, the temperature is raised to 650°C at a rate of 5°C / min, kept warm for 1 hour, then raised to 1190°C at a rate of 5°C / min and kept warm for 30 minutes, and finally lowered to 700°C at a rate of 5°C / min, and then cooled with the furnace.

6. The use according to claim 4, characterized in that The coating thickness on the surface of the architectural ceramic substrate is 50-100 μm.

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