Highly oriented and highly dense ceramic and method of making and use

Abstract

The application relates to a high-orientation high-density ceramic, a preparation method and application, and belongs to the technical field of functional ceramic material preparation. The preparation raw materials of the high-orientation high-density ceramic include any two or more than two kinds of raw materials of a bonding aid, small-particle-size high-orientation ceramic powder, large-particle-size high-orientation ceramic powder and an aqueous graphene oxide solution; the small-particle-size high-orientation ceramic powder and the large-particle-size high-orientation ceramic powder are selected from alpha-Al2O3, hBN, SiC, layered molybdate and SiO2; and the bonding aid is selected from yttrium oxide, magnesium oxide, aluminum oxide, silicon dioxide and mullite. The small-particle-size high-orientation ceramic powder and / or the large-particle-size high-orientation ceramic powder is mixed with the aqueous graphene oxide solution, and the bonding aid is used for strictly controlling the particle size and weight ratio of the high-orientation ceramic, the gaps among the large-particle-size high-orientation ceramic powders are filled by the small-particle-size high-orientation ceramic powder, and the mechanical property and functional property of the ceramic are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional ceramic material preparation, and particularly relates to a high-orientation high-density ceramic, a preparation method and application thereof. BACKGROUND

[0002] High-orientation structure ceramics have a wide range of applications in modern industry and technology. These ceramic materials usually exhibit superior mechanical properties in a certain direction, enabling them to perform well in cases where they need to withstand high stress in a specific direction or be applied to functional structural components.

[0003] Although ceramic materials with high-orientation structure have important applications in many fields, there are still some problems in the actual preparation and sintering process, which limit their practical application. High-orientation structure ceramic materials are usually sintered after being pressed into a green body from powders with high orientation (such as fibrous, columnar, and lamellar). However, during the sintering process, the high-orientation powder has problems such as uneven stacking structure, poor orientation, and low powder density, which leads to unstable performance, high porosity, and many residual defects (such as pores and cracks) in the final ceramic material, thereby affecting its mechanical properties and practicality. For example, the directional thermal conductivity of existing hexagonal boron nitride ceramics is much lower than the in-plane thermal conductivity of its single-layer structure. This is mainly because the hexagonal boron nitride powder has a unique multi-layer lamellar structure and extremely high hardness, which easily forms a "card house structure" with many pores between the interlocked layers during the ceramic green body forming and sintering process, affecting the structural orientation, sintering density, and mechanical and machining properties of the ceramic.

[0004] In order to improve the orientation and density of ceramic materials, existing methods usually use high temperature, high pressure, and discharge plasma sintering methods, combined with magnetic field, liquid phase sintering, and template grain growth to optimize the structural arrangement of the crystal grain size inside the ceramic during sintering. Although such methods can improve the structural orientation and mechanical, directional thermal and electrical conductivity of ceramic materials to some extent, they usually require complex and precise process control and have high requirements for sintering temperature, pressure, and atmosphere. For example, some ceramic materials with orientation structure require high sintering temperature, but high temperature may cause grain growth, phase transition, or oxidation of the material, thereby affecting its performance. For another example, hot-pressing sintering process can apply axial pressure to ceramic powder to improve the orientation of the material, but it cannot be used to prepare ceramic materials with complex morphological structures. Due to the poor uniformity and poor density of the ceramic green body structure, the ceramic green body structure is easily cracked under high pressure and high temperature sintering conditions, affecting the preparation efficiency and performance stability of the ceramic material. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a high-orientation high-density ceramic, a preparation method and an application, so as to solve the problem of poor performance of the existing ceramic materials.

[0006] In one aspect, the present application provides a high-orientation high-density ceramic, and the preparation raw materials include any two or more of small-particle-size high-orientation ceramic powder, large-particle-size high-orientation ceramic powder and graphene oxide aqueous solution, and a binding aid;

[0007] The small-particle-size high-orientation ceramic powder and the large-particle-size high-orientation ceramic powder are selected from a-Al2O3, hBN, SiC, layered molybdate and SiO2.

[0008] The binding aid is selected from yttrium oxide, magnesium oxide, aluminum oxide, silicon dioxide and mullite.

[0009] Further, the mass ratio of the small-particle-size high-orientation ceramic powder and / or the large-particle-size high-orientation ceramic powder to the binding aid is 100:(0-40).

[0010] Further, the mass ratio of the small-particle-size high-orientation ceramic powder and / or the large-particle-size high-orientation ceramic powder to the graphene oxide aqueous solution is 10:1-200:1.

[0011] Further, the mass ratio of the large-particle-size high-orientation ceramic powder to the small-particle-size high-orientation ceramic powder is 1:1-1:35.

[0012] Further, the average particle size of the large-particle-size high-orientation ceramic powder is 80-500 μm, and the average particle size of the large-particle-size high-orientation ceramic powder is 10-30 times the average particle size of the small-particle-size high-orientation ceramic powder.

[0013] Further, the particle size of the binding aid is less than or equal to the average particle size of the small-particle-size high-orientation ceramic powder.

[0014] In another aspect, the present application provides a preparation method of a high-orientation high-density ceramic, which includes the following steps:

[0015] S1: The large-particle-size high-orientation ceramic powder and the small-particle-size high-orientation ceramic powder are respectively mixed with a solvent in a proportion of 10 g:1 L;

[0016] Then, any two or more of the mixed large-particle-size high-orientation ceramic powder solution, the small-particle-size high-orientation ceramic powder solution and the graphene oxide aqueous solution are mixed;

[0017] S2: The binding aid is mixed with a solvent in a proportion of 10 g:1 L;

[0018] S3: mixing the mixed solution prepared in S1 and S2, stirring, and then vacuum filtering to obtain dry mixed powder blocks, and transferring the mixed powder blocks to a sintering mold;

[0019] S4: placing the mold in a heating furnace and drying at 100-600 DEG C for 0.5-2 hours to obtain a ceramic green body;

[0020] S5: sintering the obtained ceramic green body to obtain a high-orientation high-density ceramic.

[0021] Further, the size of the graphene oxide sheet in the graphene oxide aqueous solution is greater than or equal to 5 microns.

[0022] Further, the application provides an application of the high-orientation high-density ceramic in preparing a directional uniform heating composite honeycomb structure, and the directional uniform heating composite honeycomb structure comprises an outermost directional uniform heating layer, and the directional uniform heating layer is prepared from the high-orientation high-density ceramic.

[0023] Further, the application provides a directional uniform heating composite honeycomb structure, which comprises, from top to bottom, a directional uniform heating layer, an upper skin, a honeycomb core, a core filler and a lower skin, and the directional uniform heating layer is prepared from the high-orientation high-density ceramic.

[0024] Compared with the prior art, the application can achieve at least one of the following beneficial effects:

[0025] 1. The high-orientation high-density ceramic provided by the application is prepared from any two or more of small-particle-size high-orientation ceramic powder, large-particle-size high-orientation ceramic powder and graphene oxide aqueous solution, for example, a combination of small-particle-size high-orientation ceramic powder and large-particle-size high-orientation ceramic powder, a combination of small-particle-size high-orientation ceramic powder and graphene oxide aqueous solution, a combination of large-particle-size high-orientation ceramic powder and graphene oxide aqueous solution, or a combination of large-particle-size high-orientation ceramic powder, small-particle-size high-orientation ceramic powder and graphene oxide aqueous solution; finally, a binding aid is added, which can improve the orientation and density in the green body structure forming process, and improve the high-orientation and excellent performance of the finally obtained ceramic material.

[0026] 2. The application adopts a combination of small-particle-size high-orientation ceramic powder and large-particle-size high-orientation ceramic powder, controls the ratio of the two, and selects high-orientation ceramic powder with different orientation forms (such as fibrous, columnar and sheet-shaped) and different particle sizes, so that high-orientation high-density ceramic can be obtained, and the high-orientation high-density ceramic has high density and mechanical strength.

[0027] 3. The application mixes small-particle-size high-orientation ceramic powder or large-particle-size high-orientation ceramic powder with graphene oxide aqueous solution, which can optimize the orientation of the ceramic and the performance of the ceramic.

[0028] 4、The application adopts small particle size high orientation ceramic powder, large particle size high orientation ceramic powder, and mixing with graphene oxide aqueous solution, and the aid of bonding agent, strictly controls the particle size size and weight ratio of high orientation ceramic, fills the gap between large particle size high orientation ceramic powder with small particle size, improves the density of ceramic; the orientation preference of large particle size high orientation ceramic powder in the stacking process is used to optimize the orientation of ceramic, and the large particle size high orientation ceramic powder acts as a "structural bridge" between small particle size high orientation ceramic powder and bonding agent, greatly improving the mechanical strength of the ceramic.

[0029] 5、The preparation method of the ceramic of the application optimizes the orientation in the mixing powder drying process by designing the powder mixing method, introducing graphene oxide and vacuum filtration means. The high orientation ceramic prepared by this method has lower porosity than the ceramic prepared by the traditional method, and can still exhibit excellent material performance under the condition of pressureless sintering, such as ultra-high in-plane thermal conductivity, ultra-high bending strength, etc.

[0030] The above technical solutions can be combined with each other to realize more preferred combination solutions. Other features and advantages of the application will be described in the subsequent specification, and some advantages will become apparent from the specification, or will be understood by implementing the application. The purpose and other advantages of the application can be realized and obtained from the contents specifically pointed out in the specification and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0032] Figure 1 The ceramic fracture scanning electron microscope photo obtained in Example 11;

[0033] Figure 2 The ceramic fracture scanning electron microscope photo obtained in Example 10;

[0034] Figure 3 The ceramic fracture scanning electron microscope photo obtained in Example 9;

[0035] Figure 4 The ceramic fracture scanning electron microscope photo obtained in Example 12;

[0036] Figure 5 The ceramic fracture scanning electron microscope photo obtained in Example 15;

[0037] Figure 6 The ceramic fracture scanning electron microscope photo obtained in Example 16;

[0038] Figure 7A directional uniform heating composite honeycomb structure is provided.

[0039] Wherein 11 is an upper skin, 12 is a lower skin, 2 is a honeycomb core, 3 is a directional uniform heating layer, and 4 is a core filler. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of the present application and serve to explain the principles of the embodiments of the present application, but are not intended to limit the scope of the present application.

[0041] Highly oriented structure ceramics are increasingly favored due to their superior mechanical and functional properties. However, highly oriented structure ceramics are usually sintered from green bodies prepared by pressing powders with high orientation (such as fibrous, columnar, and lamellar) into green bodies. However, during the sintering process, the highly oriented powders have problems such as non-uniform stacking structure, poor orientation, and low powder density, which leads to unstable performance, high porosity, and many residual defects (such as pores and cracks) of the final ceramic material, thereby affecting the mechanical properties and practicality.

[0042] Therefore, the present application provides a highly oriented and highly dense ceramic, and the preparation raw materials include any two or more of small particle size highly oriented ceramic powder, large particle size highly oriented ceramic powder, and graphene oxide aqueous solution, and a bonding aid.

[0043] The small particle size highly oriented ceramic powder and the large particle size highly oriented ceramic powder are selected from alpha-Al2O3, hBN, SiC, layered molybdate, and SiO2.

[0044] The bonding aid is yttrium oxide, magnesium oxide, aluminum oxide, silicon dioxide, and mullite.

[0045] Compared with the prior art, the highly oriented and highly dense ceramic provided by the present application uses any two or more of small particle size highly oriented ceramic powder, large particle size highly oriented ceramic powder, and graphene oxide aqueous solution, such as a combination of small particle size highly oriented ceramic powder and large particle size highly oriented ceramic powder, a combination of small particle size highly oriented ceramic powder and graphene oxide aqueous solution, a combination of large particle size highly oriented ceramic powder and graphene oxide aqueous solution, or a combination of large particle size highly oriented ceramic powder, small particle size highly oriented ceramic powder, and graphene oxide aqueous solution. Finally, a bonding aid is added, which can improve the orientation and density during the structure forming process of the green body, thereby improving the high orientation and excellent performance of the final ceramic material.

[0046] It should be noted that the small particle size highly oriented ceramic powder and the large particle size highly oriented ceramic powder in the present application are selected from materials with orientation, such as one-dimensional fibrous or rod-shaped, and two-dimensional lamellar, such as lamellar alpha-Al2O3 and lamellar hexagonal boron nitride (hBN).

[0047] Specifically, the mass ratio of the small particle size high orientation ceramic powder and / or the large particle size high orientation ceramic powder to the binding aid is 100:(0-40), such as 100:1, 100:10, 100:20, 100:30 or 100:40.

[0048] It should be noted that the binding aid in the present application is used to prepare ceramics with the high orientation ceramic powder, and the type of the binding aid affects the performance of the obtained ceramics. When the binding aid is selected as alumina, the obtained ceramics have high thermal conductivity; when the binding aid is selected as mullite, the obtained ceramics have high hardness; when the binding aid is selected as a mixture of alumina, magnesium oxide and mullite, the obtained ceramics have both good thermal conductivity and high mechanical strength.

[0049] The present application can select different binding aids according to different use scenarios of ceramics, such as high demand for thermal conductivity performance and low demand for mechanical performance; or high demand for both thermal and mechanical performance; or high demand for mechanical performance and low demand for thermal performance, and the overall scheme is simple and flexible.

[0050] Further, the mass ratio of the small particle size high orientation ceramic powder and / or the large particle size high orientation ceramic powder to the graphene oxide aqueous solution is 10:1-200:1, such as 10:1, 20:1, 40:1, 50:1, 70:1, 80:1, 100:1, 120:1, 150:1, 180:1 or 200:1.

[0051] Specifically, the size of the graphene oxide sheet in the graphene oxide aqueous solution is greater than or equal to 5 microns.

[0052] Specifically, the concentration of the graphene oxide aqueous solution is 0.5 mg / ml-10 mg / ml, such as 0.5 mg / ml, 1.5 mg / ml, 2.5 mg / ml, 5 mg / ml, 7 mg / ml or 10 mg / ml.

[0053] It should be noted that in the preparation process of the ceramics, the addition of the graphene oxide aqueous solution (referred to as GO solution) can reduce the repulsive force between the small particle size high orientation ceramic powder caused by the cohesive force, optimize the arrangement structure, and make the high orientation ceramic powder and the binding aid more uniformly dispersed. In addition, the vacuum filtration can make the surface structure of the obtained ceramics more smooth, especially the boron nitride ceramics.

[0054] When the mass of the high orientation ceramic powder is less than 10 times the mass of the graphene oxide, the content of graphene is too high, which affects the temperature resistance of the material; when the mass of the high orientation ceramic powder is higher than 200 times the mass of the graphene oxide, the content of graphene is too low, which cannot play a role in adjusting the arrangement structure of the ceramics and optimizing the mechanical properties of the structure.

[0055] Specifically, the average particle size of the large particle size high orientation ceramic powder is 10-30 times of the average particle size of the small particle size high orientation ceramic powder.

[0056] Specifically, the average particle size of the large particle size high orientation ceramic powder is 80-500 μm.

[0057] It should be noted that in the present application, the large particle size high orientation ceramic powder and the small particle size high orientation ceramic powder can be compounded, and the particle size and weight ratio of the large particle size high orientation ceramic powder and the small particle size high orientation ceramic powder can be further controlled and optimized. The small particle size high orientation ceramic powder can fill the gaps between the large particle size high orientation ceramic powders, thereby improving the density of the ceramic. The orientation preference of the large particle size high orientation ceramic powder in the stacking process can optimize the orientation of the ceramic. The large particle size high orientation ceramic powder can act as a "structural bridge" between the small particle size high orientation ceramic powder and the bonding aid, thereby greatly improving the mechanical strength of the ceramic.

[0058] Specifically, the mass ratio of the large particle size high orientation ceramic powder and the small particle size high orientation ceramic powder is 1:1-1:35.

[0059] Preferably, the average particle size of the large particle size high orientation ceramic powder can be 80 μm, 120 μm, 200 μm, 350 μm or 500 μm.

[0060] Preferably, the average particle size of the small particle size high orientation ceramic powder can be 2 μm, 8 μm, 12 μm, 25 μm or 50 μm.

[0061] The present application needs to control the mass ratio of the large particle size high orientation ceramic powder and the small particle size high orientation ceramic powder. The mass of the small particle size high orientation ceramic powder is 1-35 times of the mass of the large particle size high orientation ceramic powder.

[0062] Preferably, the mass of the small particle size high orientation ceramic powder is 1 times, 2 times, 4 times, 6 times, 10 times, 15 times, 18 times, 22 times, 25 times, 30 times or 35 times of the mass of the large particle size high orientation ceramic powder.

[0063] Preferably, the mass of the small particle size high orientation ceramic powder is 1-10 times of the mass of the large particle size high orientation ceramic powder.

[0064] According to the simulation and experimental results, as the content of the large particle size high orientation ceramic powder decreases, the orientation gradually decreases, and the larger the absolute value of IOP is, the higher the orientation of the material is.

[0065] Specifically, the bonding aid is yttrium oxide, magnesium oxide, aluminum oxide, silicon dioxide and mullite.

[0066] Specifically, the particle size of the binding aid is less than or equal to the average particle size of the selected small particle size high orientation ceramic powder.

[0067] It should be noted that the large particle size high orientation ceramic powder in the application serves as a bridge connecting the small particle size high orientation ceramic powder and the binding aid, and the particle size of the binding aid is controlled to be less than or equal to the average particle size of the small particle size high orientation ceramic powder. When the particle size of the binding aid is small, it can fill the gaps and increase the density and strength of the final ceramic.

[0068] The application provides a preparation method of high orientation high density ceramic, which comprises the following steps:

[0069] S1: The large particle size high orientation ceramic powder and the small particle size high orientation ceramic powder are respectively mixed with a solvent in a proportion of 10g:1L;

[0070] Then, any two or more of the mixed large particle size high orientation ceramic powder solution, the small particle size high orientation ceramic powder solution and the graphene oxide aqueous solution are mixed;

[0071] S2: The binding aid is mixed with a solvent in a proportion of 10g:1L;

[0072] S3: The mixed solutions prepared in S1 and S2 are mixed, and after stirring, a dry mixed powder block is obtained by vacuum filtration, and the mixed powder block is transferred to a sintering mold;

[0073] S4: The mold is placed in a heating furnace and dried at 100-600 DEG C for 0.5-2 hours to obtain a ceramic green body;

[0074] S5: The obtained ceramic green body is sintered to obtain a high orientation high density ceramic.

[0075] Compared with the prior art, the application uses the large particle size high orientation ceramic powder and the small particle size high orientation ceramic powder to improve the orientation of the ceramic green body and the final ceramic; or the graphene oxide aqueous solution is added to the large particle size high orientation ceramic powder and / or the small particle size high orientation ceramic powder, and the vacuum filtration method is used to improve the orientation and performance of the ceramic green body and the final ceramic.

[0076] Before sintering, the mixed powder block needs to be dried at 100-600 DEG C, and when the graphene oxide aqueous solution is used, in order not to affect the content of the material, the drying is carried out at 100-500 DEG C. However, when the graphene oxide aqueous solution is left during the preparation process, the drying is carried out at 500-600 DEG C for 0.5-1h. The graphene will be oxidized in the presence of oxygen at 500 DEG C or above, and will be converted into carbon dioxide and removed.

[0077] The ceramic prepared by the preparation method of the ceramic has lower porosity than a ceramic green body prepared by a traditional method (pressing), and even under the condition of pressureless sintering, the ceramic still has excellent performance, such as super-high in-plane thermal conductivity and super-high bending strength, etc., for example, when the ceramic is prepared from alumina, the bending strength is above 190.67 MPa; when the ceramic is prepared from hexagonal boron nitride, the axial thermal conductivity is above 12.05 W / m·K, and the radial thermal conductivity is above 90.22 W / m·K.

[0078] Specifically, the solvent includes but is not limited to one or more of water, methanol, ethanol, ethylene glycol, isopropanol, butyl alcohol, dimethylformamide, acetone, and tetrahydrofuran.

[0079] It should be noted that adding the solvent to the large-particle-size high-orientation ceramic powder and / or the small-particle-size high-orientation ceramic powder in the application can make them better dispersed and not cause agglomeration problems, for example, hBN is better dispersed in isopropanol than in water.

[0080] Specifically, in step S6, sintering is performed by pressure sintering or pressureless sintering, and the sintering temperature is 1750-2000℃.

[0081] Specifically, when pressure sintering is performed, the pressure is 5-40 MPa.

[0082] The application further provides a ceramic application for preparing a directional uniform heating composite honeycomb structure, which comprises, from top to bottom, a directional uniform heating layer, an upper skin, a honeycomb core and core filler, and a lower skin, wherein the directional uniform heating layer is prepared from the ceramic.

[0083] It should be noted that on the basis of a single honeycomb structure, a directional uniform heating layer is added to the surface, which can conduct heat laterally to a low-temperature area, greatly avoiding the accumulation and accumulation of heat on the surface, reducing the input of effective heat per unit area in the heat concentration area on the surface, making the surface energy distribution more uniform, hindering the conduction of part of the heat to the inside of the honeycomb, effectively solving the problem of serious local heating caused by insufficient heat resistance of the honeycomb structure in actual application, thereby effectively improving the thermal stability of the honeycomb structure.

[0084] Specifically, the thickness of the directional uniform heating layer is 0.01-10 mm.

[0085] Specifically, the material of the upper skin and the lower skin is one of titanium-based and nickel-based alloys, and the thickness is 0.1-20 mm.

[0086] Specifically, the honeycomb core is a honeycomb-like grid structure, the thickness is 0.01-3 mm, the height is 1-50 mm, and the material is titanium alloy.

[0087] Specifically, the core filler has a density less than 1 g / cm 3 of the silicon-based fiber or the silicon-based aerogel or the graphene aerogel.

[0088] Specifically, the manufacturing method of the directional uniform heating composite honeycomb structure comprises the following steps:

[0089] S1, performing surface treatment to lay, spray or brush one or more layers of brazing filler metal layers on the lower skin;

[0090] S2, using vacuum brazing or gas protection brazing, first welding the honeycomb core and the lower skin together;

[0091] S3, filling the honeycomb core filler into the honeycomb core by mechanical and / or manual method;

[0092] S4, performing surface treatment to lay, spray or brush one or more layers of brazing filler metal layers on the upper skin;

[0093] S5, welding the upper skin and the honeycomb core together to obtain the honeycomb structure; the welding temperature is 450-1400℃, and the holding time is 20-60 min;

[0094] S6, using spraying, brazing or bonding to prepare the directional uniform heating layer on the outer surface of the upper skin of the honeycomb structure;

[0095] S7, after the final welding of the component is completed, the whole is subjected to stabilization heat treatment, and the heat treatment temperature is lower than the welding temperature by 20-100℃.

[0096] The directional uniform heating honeycomb structure can avoid the aggregation and accumulation of heat on the surface to the greatest extent, can conduct the heat to the low temperature area in the transverse direction, can reduce the effective heat input per unit area in the heat concentration area on the surface of the honeycomb, and can hinder the transmission of heat in the honeycomb through the conduction and radiation effect, thereby improving the heat capacity of the honeycomb structure, reducing the effective transmission amount of the heat of the honeycomb from the hot end to the cold end, and effectively realizing the secondary control of the imported heat, so that the overheating failure problem of the protected device due to too much imported heat can be avoided.

[0097] The directional uniform heating honeycomb structure can meet the current lightweight development trend, can effectively improve the heat resistance / heat insulation capacity of the honeycomb structure, can improve the safety of the protected device in the honeycomb, and has the advantages of light weight, heat resistance and high heat insulation capacity.

[0098] In order to more clearly describe the present application, the following examples and comparative examples are further illustrated.

[0099] Example 1

[0100] A method for preparing Al2O3 ceramic with high bending strength, comprising the following steps:

[0101] S1. 10 g of large-particle-size flaky α-Al2O3 ceramic powder (average particle size of 80 μm) and 10 g of small-particle-size flaky α-Al2O3 ceramic powder (average particle size of 6 μm) were weighed according to the proportion, mixed with a solvent, and added into 2 L of isopropyl alcohol for mechanical stirring for 1 hour;

[0102] S2. 20 ml of graphene oxide (GO) aqueous solution (5 mg / ml) was weighed and mixed with the solution prepared in S1, and mechanically stirred for 1 hour;

[0103] S3. 2 g of binder Al2O3 round powder (average particle size of 2.5 μm) was weighed according to the proportion and added into 200 ml of isopropyl alcohol solution for mechanical stirring for 1 hour,

[0104] S4. The mixed solution prepared in S2 and S3 was mixed, mechanically stirred for 2 hours, and then vacuum filtration was performed to obtain a dry mixed powder block, and the mixed powder block was transferred to a sintering mold;

[0105] S5. The mold was placed in a muffle furnace, dried at 550°C for 2 hours in an air atmosphere, and a ceramic green body was prepared;

[0106] S6. The obtained ceramic green body was sintered under pressureless conditions, the sintering temperature was 1850°C, and the sintering time was 12 h, and an alumina ceramic was prepared.

[0107] Examples 2-8, Comparative Examples 1-2

[0108] The differences between Examples 2-8 and Comparative Examples 1-2 are shown in Table 1, and the properties of the alumina ceramics obtained in Examples 1-8 and Comparative Examples 1-2 were detected, and the detection results are shown in Table 2.

[0109] Table 1: Difference parameters between examples and comparative examples

[0110] Group Large particle size / g Small particle size / g GO solution / ml Example 1 10 10 20 Example 2 6 14 20 Example 3 3 17 20 Example 4 0 20 20 Example 5 10 10 80 Example 6 10 10 200 Example 7 10 10 0 Example 8 20 0 20 Comparative Example 1 0 20 0 Comparative Example 2 20 0 0

[0111] Table 2: Detection results

[0112]

[0113] As can be seen from Examples 1-4 and in combination with Table 2, the large-particle-size high-orientation ceramic powder and the small-particle-size high-orientation ceramic powder are compounded, and then the graphene oxide aqueous solution is added, the absolute value of IOP and the bending strength of the obtained alumina ceramic are higher, and the apparent porosity is lower, which indicates that the obtained alumina ceramic has good orientation, strength and density.

[0114] It can be seen from Example 1 and Example 7, Example 4 and Comparative Example 1, and Example 8 and Comparative Example 2 in combination with Table 2 that when the graphene oxide aqueous solution is added in the large particle size high orientation ceramic powder and / or the small particle size high orientation ceramic powder, the IOP and the bending strength of the obtained aluminum oxide ceramic gradually increase, and the apparent porosity gradually decreases. It is indicated that under the action of the graphene oxide aqueous solution, the orientation, strength and density of the aluminum oxide ceramic can be improved.

[0115] Example 9

[0116] A preparation method of a high orientation arranged hexagonal boron nitride ceramic, comprising the following steps:

[0117] The large particle size flaky hexagonal boron nitride ceramic powder (average particle size of 250 μm) 8 g and the small particle size flaky hexagonal boron nitride ceramic powder (average particle size of 10 μm) 12 g are weighed according to the proportion; a total of 20 g of orientation ceramic powder is added into 2 L of ethanol and mechanically stirred for 1 hour;

[0118] 40 ml of graphene oxide (GO) aqueous solution (5 mg / ml) is added, and mechanical stirring is continued for 2 hours.

[0119] The above mixed solution is vacuum filtered to obtain a dry mixed powder block, which is transferred to a sintering mold. The mold is placed in a muffle furnace, dried at 550°C in an air atmosphere for 2 hours, and a boron nitride ceramic green body is prepared. Then, hot-pressing sintering (1900°C, 30 MPa, 1 h) is performed to obtain a hexagonal boron nitride ceramic.

[0120] Example 10-18, Comparative Example 3-4

[0121] The differences between Example 10-18 and Comparative Example 3-4 and Example 9 are shown in Table 3, and the hexagonal boron nitride ceramics obtained in Example 9-18 and Comparative Example 3-4 are detected for performance, and the detection results are shown in Table 4.

[0122] Table 3: Difference between examples and comparative examples

[0123] Group Large particle size / g Small particle size / g GO solution / ml Example 9 8 12 0 Example 10 4 16 0 Example 11 2 18 0 Example 12 8 12 40 Example 13 4 16 40 Example 14 2 18 40 Example 15 8 12 80 Example 16 8 12 200 Example 17 0 20 40 Example 18 20 0 40 Comparative Example 3 0 20 0 Comparative Example 4 20 0 0

[0124] Table 4: Detection results

[0125]

[0126]

[0127] As can be seen from Examples 9-14 and in combination with Table 4, when the graphene oxide aqueous solution is added in the large-particle-size high-orientation ceramic powder and / or the small-particle-size high-orientation ceramic powder, the IOP and thermal conductivity of the obtained hexagonal boron nitride ceramic increase, and the density gradually increases. It is indicated that under the action of the graphene oxide aqueous solution, the orientation, thermal conductivity and density of the hexagonal boron nitride ceramic can be improved.

[0128] As can be seen from Examples 9-11 and in combination with Figures 1-3 It can be seen that when the GO solution is not added, with the increase of the large flake content, the orientation arrangement structure of the hexagonal boron nitride ceramic is optimized.

[0129] As can be seen from Examples 9, 12, 15, 16 and in combination with Figures 3-6 It can be seen that when the weight of the large-particle-size high-orientation ceramic powder and the small-particle-size high-orientation ceramic powder is unchanged, with the increase of the GO solution content, the orientation arrangement structure of the hexagonal boron nitride ceramic is optimized.

[0130] Application Example

[0131] The above Example 12 is used to prepare a directional thermal uniform composite honeycomb structure, referring to Figure 7 from top to bottom, sequentially comprising a directional thermal uniform layer, an upper skin, a honeycomb core and a core filler, and a lower skin; wherein the directional thermal uniform layer is prepared from the hexagonal boron nitride ceramic obtained in Example 12 of the present application.

[0132] Application Example 1

[0133] The lower skin and one side of the honeycomb core are polished with 1000# sandpaper, and the roughness is controlled in the range of 0.4-0.6, then the brazing filler metal is laid flat between the two, the brazing filler metal is Ti-Zr-Cu-Ni, and the welding is completed under vacuum conditions, the welding process is selected as 920℃, the holding time is 20min, and then the stabilization heat treatment is carried out at 900℃ for 20min, and the adjusted density of 0.8g / cm 3 The silica fiber with the adjusted density of 0.8g / cm

[0134] The oriented heat uniform layer 3, the upper skin 11, the lower skin 12, the honeycomb core 2 and the core filler 4 are combined to form an oriented heat uniform composite honeycomb structure, wherein the thickness of the oriented heat uniform layer 3 is 0.1 mm, the thickness of the upper skin 11 and the lower skin 12 is 1 mm, the size of the honeycomb core 2 is 10 mm in height and 10 mm in inscribed circle diameter, and the core filler 4 is filled according to the specific density.

[0135] Back temperature test: one side of the honeycomb surface of the oriented heat uniform layer is heated to 700 DEG C, and the temperature of the other side is tested. The result shows that the measured cold surface temperature is lower than 60 DEG C, and the heat resistance is better.

[0136] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, and should be covered in the protection scope of the present application.

Claims

1. A highly oriented, highly dense ceramic, characterized in that, The preparation raw materials include small particle size high orientation ceramic powder, large particle size high orientation ceramic powder and graphene oxide aqueous solution, and a binding aid; the mass ratio of the small particle size high orientation ceramic powder and the large particle size high orientation ceramic powder to the graphene oxide in the graphene oxide aqueous solution is 10:1-200:1; the mass ratio of the large particle size high orientation ceramic powder to the small particle size high orientation ceramic powder is 1:1-1:35; the average particle size of the large particle size high orientation ceramic powder is 80-500 μm; the average particle size of the large particle size high orientation ceramic powder is 10-30 times of the average particle size of the small particle size high orientation ceramic powder; The small particle size high orientation ceramic powder and the large particle size high orientation ceramic powder are selected from α-Al2O3, hBN, SiC, layered molybdate and SiO2. The binding aid is selected from yttrium oxide, magnesium oxide, aluminum oxide, silicon dioxide and mullite. The preparation of the high orientation high density ceramic is mixing the small particle size high orientation ceramic powder and the large particle size high orientation ceramic powder with the graphene oxide aqueous solution, adding the binding aid and then performing vacuum filtration, drying and then performing pressureless or pressure sintering.

2. The highly oriented, highly dense ceramic of claim 1, wherein, The mass ratio of the small particle size high orientation ceramic powder and the large particle size high orientation ceramic powder to the binding aid is 100:(1-40).

3. The highly oriented, highly dense ceramic of claim 1, wherein, The particle size of the binding aid is less than or equal to the average particle size of the small particle size high orientation ceramic powder.

4. A method of producing a highly oriented and highly dense ceramic according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1: proportionally weighing the large particle size high orientation ceramic powder and the small particle size high orientation ceramic powder and mixing with solvent, the mixing ratio being 10 g:1 L; Then the mixed large particle size high orientation ceramic powder solution, the small particle size high orientation ceramic powder solution and the graphene oxide aqueous solution are mixed; S2: proportionally weighing the binding aid and mixing with solvent, the mixing ratio being 10 g:1 L; S3: mixing the mixed solutions prepared in S1 and S2, stirring, vacuum filtration to obtain dry mixed powder blocks, and transferring the mixed powder blocks to a sintering mold; S4: placing the mold in a heating furnace, drying at 100-600 ℃ for 0.5-2 hours to obtain a ceramic green body; S5: sintering the obtained ceramic green body to obtain a high orientation high density ceramic.

5. The method of claim 4, wherein the ceramic is a high-orientation high-density ceramic. The size of the graphene oxide in the graphene oxide aqueous solution is greater than or equal to 5 μm.

6. Use of a highly oriented, highly dense ceramic for the preparation of a directionally uniform heat composite honeycomb structure, characterized in that, The directional uniform heating composite honeycomb structure comprises an outermost directional uniform heating layer, and the directional uniform heating layer is prepared from the high orientation high density ceramic according to any one of claims 1-3 or the high orientation high density ceramic obtained in claim 4 or 5.

7. A directionally isostatically consolidated composite honeycomb structure characterized by, From top to bottom, there are a directional uniform heating layer, an upper skin, a honeycomb core, a core filler and a lower skin, and the directional uniform heating layer is prepared from the high orientation high density ceramic according to any one of claims 1-3 or the high orientation high density ceramic obtained in claim 4 or 5.

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