A method for designing particle size distribution of low-shrinkage ceramic green bodies and its application in the preparation of quartz ceramics

Abstract

The present invention discloses a method for designing particle size gradation for low-shrinkage ceramic green bodies and its application in the preparation of quartz ceramics, belonging to the field of ceramic materials technology. By optimizing the particle size gradation of quartz, the present invention promotes cristobalite crystallization during the preparation process of the quartz ceramics, improves sintering densification, and significantly enhances the mechanical properties and dimensional stability of the quartz ceramics, particularly their flexural strength under high-temperature conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic materials, and particularly relates to a method for designing particle size gradation of a low-shrinkage ceramic green body and an application thereof in the preparation of quartz ceramics. Background Art

[0002] Currently, there are two main types of ceramic cores commonly used for casting high-temperature alloy blades. One is an aluminum-based core with special alumina as the main component, and the other is a quartz ceramic core with fused quartz as the main matrix material. The main performance requirements of the core are to be able to withstand the thermal shock of the molten metal during high-temperature alloy casting, have excellent mechanical properties and dimensional stability at high temperatures, and quickly remove chemical substances after casting.

[0003] Quartz ceramic cores are a key material in hollow blade manufacturing, with their mechanical properties and dimensional stability directly impacting the production yield of hollow blades. While existing quartz ceramic cores offer the advantage of rapid chemical removal, they suffer from insufficient high-temperature mechanical properties. Therefore, particle size gradation plays a significant role in the production of quartz ceramic cores, yet systematic research and optimization methods are currently lacking. Summary of the Invention

[0004] To address the issue of insufficient high-temperature performance of quartz ceramics, this paper proposes a method for designing particle size distribution for low-shrinkage ceramic green bodies and its application in quartz ceramic production. By optimizing the particle size distribution of quartz, the dimensional stability and high-temperature mechanical properties of quartz ceramic cores are improved.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a method for designing particle size distribution of low shrinkage ceramic green bodies, comprising the following steps:

[0007] The particles are sorted by size, and different particle sizes are considered to be different diameters of spheres of equal diameter. Four particle sizes are selected for grading, and the θ value at which two adjacent spherical particles are tangent to each other is determined. The θ value is used to query the spherical code table to determine how many small spherical particles can surround a large spherical particle. The mass distribution ratio of two adjacent spherical particles of the same size is derived based on the mass calculation formula and the sphere volume calculation formula to obtain the optimal grading solution.

[0008] Among them, the particle sizes of the four particles are R1, R2, R3 and R4 from large to small, R2 = 0.633R1, R3 = 0.633R1 × 0.414, R4 = 0.633R1 × 0.225;

[0009] Without considering intermolecular forces, the particle size selection is based on the relationship between the particle radius ratio and the coordination number. If the most probable stacking method is selected to determine the number of small-sized spheres in the gaps between large-sized spheres and the polyhedron structure they form, the four particle sizes mentioned above can be derived.

[0010] The θ value of the tangent of spherical particles of two particle sizes R1 and R2 is calculated by formula (1) and formula (2);

[0011] sin01=R1 / (R1+R2)(1)

[0012] 0=2arcsin01(2)

[0013] The calculation method of the θ value of the tangent point between spherical particles of two particle sizes R2 and R3, and the θ value of the tangent point between spherical particles of two particle sizes R3 and R4 is the same as above;

[0014] Then, the mass distribution ratio of spherical particles of two adjacent particle sizes is calculated according to formula (3):

[0015]

[0016] In formula (3), m t is the mass of the t-level particle; m z is the mass of the z-level particle; k is the number of layers of the t-level particle encapsulating the z-level particle; R t is the radius of the t-level particle; R z is the radius of the z-level particle; Xt z is the number of z-level particles encapsulated by t-level particles;

[0017] The source of the spherical code table is SLOANE NJ A. Nice arrangements of points on asphere in various dimensions: Tables of Spherical Codes[R / OL].(2012-1-15)[2024-03-20].http: / / neilsloane.com / packings / dim3 / .

[0018] The schematic diagram of the large-sized spherical particles surrounded by small-sized spherical particles is shown in Figure 1 .

[0019] Preferably, k=1 or 2.

[0020] In the present invention, R1, R2, R3, and R4 satisfy R2 = 0.633R1, R3 = 0.633R1 × 0.414, and R4 = 0.633R1 × 0.225. This is primarily due to the fact that, without considering intermolecular forces, particle size selection is based on the relationship between the particle radius ratio and the coordination number. By selecting the most probable stacking method, the number of small-sized spheres in the gaps between the large-sized spheres and the resulting polyhedral structure are determined. The aforementioned four particle sizes can be derived based on this approach.

[0021] The second technical solution of the present invention is a process for preparing quartz ceramics, comprising the following steps:

[0022] The mass ratio of quartz particles of different particle sizes is calculated according to the above-mentioned low-shrinkage ceramic green body particle size gradation design method. The quartz particles are melted, a basic mineralizer is added, and then a molten plasticizer is added to obtain a mixed slurry. The mixed slurry is injected into a mold, sintered, and cooled to obtain a quartz ceramic.

[0023] Preferably, the basic mineralizer is a combination of one or more of cerium oxide, zirconium oxide, and titanium oxide.

[0024] More preferably, the particle size range of the quartz particles is 100-1000 mesh; the particle size of the cerium oxide is 300-500 mesh; the particle size of the zirconium oxide is 300-500 mesh; and the particle size of the titanium oxide is 600-800 mesh.

[0025] More preferably, the basic mineralizer is cerium oxide, zirconium oxide and titanium oxide.

[0026] More preferably, in parts by mass, the quartz particles account for 70 to 100 parts, the cerium oxide accounts for 1 to 5 parts, the zirconium oxide accounts for 10 to 20 parts, the titanium oxide accounts for 10 to 20 parts and the plasticizer accounts for 15 to 20 parts.

[0027] Preferably, the plasticizer is composed of paraffin wax, beeswax and polyethylene in a mass ratio of 88-92:5-8:1-5.

[0028] Preferably, when the mixed slurry is injected into the mold, the injection pressure is 3 to 6 MPa.

[0029] The beneficial technical effects of the present invention are as follows:

[0030] The present invention promotes cristobalite crystallization during the preparation of the quartz ceramic core by optimizing the particle size gradation of quartz, improves sintering densification, and significantly increases the mechanical properties and dimensional stability of the quartz ceramic core, especially the bending strength under high temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1This is a schematic diagram of the spherical particles with large particle size being surrounded by spherical particles with small particle size in the present invention. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0033] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0034] 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 the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] Example 1

[0037] A low-shrinkage ceramic green body particle size distribution design scheme and its application in quartz ceramic preparation, the steps are as follows:

[0038] Step 1, select R1 = 100 μm, select the mass ratio range of k = 2, and the calculation results are: primary particles: 9.63%, secondary particles: 30.32%, tertiary particles: 40.21%, and quaternary particles: 19.84%.

[0039] The specific mass ratio used is: first-level particles: 10%, second-level particles: 30%, third-level particles: 40%, and fourth-level particles: 20%.

[0040] Step 2: Weigh 4 kg of fused quartz, cerium oxide, zirconium oxide, and titanium oxide as solid powders in proportion (the mass percentages of fused quartz, cerium oxide, zirconium oxide, and titanium oxide in the solid powders are 70%, 2%, 14%, and 14%, respectively); weigh 800 g of paraffin wax, beeswax, and polyethylene in a mass ratio of 91:7:2 and mix them. Heat and melt to obtain a mixed solution, pour the evenly mixed solid powder into the mixed solution, and stir for 20 hours to obtain a uniform ceramic slurry.

[0041] Step 3: Place the slurry in a die-casting machine, inject the slurry into a core mold at a pressure of 4 MPa, and then sinter to obtain a quartz ceramic core.

[0042] Example 2

[0043] A low-shrinkage ceramic green body particle size distribution design scheme and its application in quartz ceramic preparation, the steps are as follows:

[0044] Step 1, select R1 = 60 μm, select the mass ratio range of k = 2, and the calculation results are: primary particles: 9.63%, secondary particles: 30.32%, tertiary particles: 40.21%, and quaternary particles: 19.84%.

[0045] The specific mass ratio used is: first-level particles: 10%, second-level particles: 30%, third-level particles: 40%, and fourth-level particles: 20%.

[0046] Step 2: Weigh 4 kg of fused quartz, cerium oxide, zirconium oxide, and titanium oxide as solid powders in proportion (the mass percentages of fused quartz, cerium oxide, zirconium oxide, and titanium oxide in the solid powders are 70%, 2%, 14%, and 14%, respectively); weigh 800 g of paraffin wax, beeswax, and polyethylene in a mass ratio of 91:7:2 and mix them. Heat and melt to obtain a mixed solution, pour the evenly mixed solid powder into the mixed solution, and stir for 20 hours to obtain a uniform ceramic slurry.

[0047] Step 3: Place the slurry in a die-casting machine, inject the slurry into a core mold at a pressure of 4 MPa, and then sinter to obtain a quartz ceramic core.

[0048] Example 3

[0049] A low-shrinkage ceramic green body particle size distribution design scheme and its application in quartz ceramic preparation, the steps are as follows:

[0050] Step 1, select R1 = 40 μm, select the mass ratio range of k = 2, and the calculation results are: primary particles: 9.63%, secondary particles: 30.32%, tertiary particles: 40.21%, and quaternary particles: 19.84%.

[0051] The specific mass ratio used is: first-level particles: 10%, second-level particles: 30%, third-level particles: 40%, and fourth-level particles: 20%.

[0052] Step 2: Weigh 4 kg of fused quartz, cerium oxide, zirconium oxide, and titanium oxide as solid powders in proportion (the mass percentages of fused quartz, cerium oxide, zirconium oxide, and titanium oxide in the solid powders are 70%, 2%, 14%, and 14%, respectively); weigh 800 g of paraffin wax, beeswax, and polyethylene in a mass ratio of 91:7:2 and mix them. Heat and melt to obtain a mixed solution, pour the evenly mixed solid powder into the mixed solution, and stir for 20 hours to obtain a uniform ceramic slurry.

[0053] Step 3: Place the slurry in a die-casting machine, inject the slurry into a core mold at a pressure of 4 MPa, and then sinter to obtain a quartz ceramic core.

[0054] Comparative Example 1

[0055] A low-shrinkage ceramic green body particle size distribution design scheme and its application in quartz ceramic preparation:

[0056] The only difference between this comparative example and Example 1 is the mass ratio of the first to fourth grade fused quartz particles in step 1. The remaining raw materials and steps are the same as those in Example 1. The specific mass ratio of the first to fourth grade fused quartz particles is: first grade particles: 5%, second grade particles: 20%, third grade particles: 40%, and fourth grade particles: 35%.

[0057] Comparative Example 2

[0058] A low-shrinkage ceramic green body particle size distribution design scheme and its application in quartz ceramic preparation:

[0059] The only difference between this comparative example and Example 1 is the different mass ratio of the first to fourth grade fused quartz particles in step 1. The remaining raw materials and steps are the same as those in Example 1. The specific mass ratio of the first to fourth grade fused quartz particles is: first grade particles: 35%, second grade particles: 35%, third grade particles: 20%, and fourth grade particles: 10%.

[0060] Comparative Example 3

[0061] A low-shrinkage ceramic green body particle size distribution design scheme and its application in quartz ceramic preparation:

[0062] The only difference between this comparative example and Example 2 is the different mass ratio of the first to fourth grade fused quartz particles in step 1. The remaining raw materials and steps are the same as those in Example 1. The specific mass ratio of the first to fourth grade fused quartz particles is: first grade particles: 5%, second grade particles: 20%, third grade particles: 40%, and fourth grade particles: 35%.

[0063] Comparative Example 4

[0064] A low-shrinkage ceramic green body particle size distribution design scheme and its application in quartz ceramic preparation:

[0065] The only difference between this comparative example and Example 2 is the mass ratio of the first to fourth grade fused quartz particles in step 1. The remaining raw materials and steps are the same as those in Example 1. The specific mass ratio of the first to fourth grade fused quartz particles is: first grade particles: 35%, second grade particles: 35%, third grade particles: 20%, and fourth grade particles: 10%.

[0066] Comparative Example 5

[0067] A low-shrinkage ceramic green body particle size distribution design scheme and its application in quartz ceramic preparation:

[0068] The only difference between this comparative example and Example 3 is the different mass ratio of the first to fourth grade fused quartz particles in step 1. The remaining raw materials and steps are the same as those in Example 1. The specific mass ratio of the first to fourth grade fused quartz particles is: first grade particles: 5%, second grade particles: 20%, third grade particles: 40%, and fourth grade particles: 35%.

[0069] Comparative Example 6

[0070] A low-shrinkage ceramic green body particle size distribution design scheme and its application in quartz ceramic preparation:

[0071] The only difference between this comparative example and Example 3 is the mass ratio of the first to fourth grade fused quartz particles in step 1. The remaining raw materials and steps are the same as those in Example 1. The specific mass ratio of the first to fourth grade fused quartz particles is: first grade particles: 35%, second grade particles: 35%, third grade particles: 20%, and fourth grade particles: 10%.

[0072] The properties of the quartz ceramic cores prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were tested. The testing methods are shown in Table 1, and the test results are shown in Table 2.

[0073] Table 1

[0074]

[0075] Table 2

[0076] Core number Shrinkage / % Room temperature strength / MPa High temperature strength / MPa Open porosity / % <![CDATA[Apparent density / (g / cm 3 )]]> Example 1 1.78 10.902 28.55 31.23 1.68 Example 2 1.67 12.222 33.48 32.94 1.63 Example 3 1.98 14.065 37.87 31.31 1.66 Comparative Example 1 2.03 9.087 25.82 33.22 1.60 Comparative Example 2 1.95 9.110 26.20 32.13 1.62 Comparative Example 3 2.33 11.202 30.97 34.72 1.57 Comparative Example 4 2.06 11.401 31.82 33.50 1.59 Comparative Example 5 2.21 13.620 34.20 32.14 1.60 Comparative Example 6 1.99 13.025 34.98 32.50 1.62

[0077] As can be seen from Table 1, by designing a four-level particle gradation and applying it to quartz ceramic cores prepared in three different particle size ranges, it was successfully achieved that the quartz ceramic core can still maintain stable mechanical properties after being kept at 1550°C for 0.5h. The high-temperature flexural strength of the core ranges from 28MPa to 38MPa.

[0078] The quartz ceramic core prepared according to the quartz particle grading design scheme of the present invention can significantly improve the high-temperature strength of the quartz ceramic core while controlling the shrinkage rate to less than 2%, thereby solving the problem of insufficient high-temperature strength of the quartz ceramic core that has long plagued the engine blade casting field.

[0079] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for designing particle size gradation of low shrinkage ceramic green bodies, characterized in that: The following steps are involved: The particles are sorted by size, and different particle sizes are considered to be different diameters of spheres of equal diameter. Four particle sizes are selected for grading, and the θ value at which two adjacent spherical particles are tangent to each other is determined. The θ value is used to query the spherical code table to determine how many small spherical particles can surround a large spherical particle. The mass distribution ratio of two adjacent spherical particles of the same size is derived based on the mass calculation formula and the sphere volume calculation formula to obtain the optimal grading solution. Among them, the particle sizes of the four particles are R1, R2, R3 and R4 from large to small, R2 = 0.633R1, R3 = 0.633R1 × 0.414, R4 = 0.633R1 × 0.225; The θ value of the tangent of spherical particles of two particle sizes R1 and R2 is calculated by formula (1) and formula (2); sinθ1=R1 / (R1+R2) (1) θ=2arcsinθ1 (2) The calculation method of the θ value of the tangent point between spherical particles of two particle sizes R2 and R3, and the θ value of the tangent point between spherical particles of two particle sizes R3 and R4 is the same as above; Then, the mass distribution ratio of spherical particles of two adjacent particle sizes is calculated according to formula (3): In formula (3), m t is the mass of the t-level particle; m z is the mass of the z-level particle; k is the number of layers of the t-level particle encapsulating the z-level particle; R t is the radius of the t-level particle; R z is the radius of the z-level particle; X tz is the number of z-level particles encapsulated by t-level particles; The source of the spherical code table is SLOANE NJ A. Nice arrangements of points on a sphere in various dimensions: Tables of Spherical Codes [R / OL]. (2012-1-15) [2024-03-20].

2. The method for designing particle size distribution of low shrinkage ceramic green bodies according to claim 1, wherein: k=1 or 2.

3. A process for preparing quartz ceramics, characterized in that: The following steps are involved: The low-shrinkage ceramic green body particle size gradation design method according to claim 1 or 2 calculates the mass ratio of quartz particles of different particle sizes, melts the quartz particles, adds a basic mineralizer, and then adds a molten plasticizer to obtain a mixed slurry, injects the mixed slurry into a mold, sinters, and cools to obtain a quartz ceramic.

4. The process for preparing quartz ceramics according to claim 3, wherein: The basic mineralizer is a combination of one or more of cerium oxide, zirconium oxide, and titanium oxide.

5. The process for preparing quartz ceramics according to claim 4, wherein: The particle size range of the quartz particles is 100-1000 meshes; the particle size of the cerium oxide is 300-500 meshes; the particle size of the zirconium oxide is 300-500 meshes; and the particle size of the titanium oxide is 600-800 meshes.

6. The process for preparing quartz ceramics according to claim 4, wherein: The basic mineralizers are cerium oxide, zirconium oxide and titanium oxide.

7. The process for preparing quartz ceramics according to claim 6, wherein: In terms of mass, the quartz particles account for 70 to 100 parts, the cerium oxide accounts for 1 to 5 parts, the zirconium oxide accounts for 10 to 20 parts, the titanium oxide accounts for 10 to 20 parts and the plasticizer accounts for 15 to 20 parts.

8. The process for preparing quartz ceramics according to claim 3, wherein: The plasticizer consists of paraffin, beeswax and polyethylene in a mass ratio of 88-92:5-8:1-5.

9. The process for preparing quartz ceramics according to claim 3, wherein: When the mixed slurry is injected into the mold, the injection pressure is 3-6 MPa.

Images