Preparation method of high-density ZTA ceramic granulation powder

Abstract

The invention provides a preparation method of high-density ZTA ceramic granulation powder, which comprises the following steps: mixing aluminum oxide powder, nano zirconium oxide and calcium titanate powder according to a certain proportion, dispersing in deionized water, carrying out ball milling, and adding a binder, a dispersant, a release agent and a defoaming agent during ball milling; and finally, sieving the ball-milled slurry by using a 90-mesh sieve, performing spray granulation by using centrifugal spray granulation equipment, and screening granulation powder under a 100-mesh sieve to obtain the ZTA ceramic powder. By introducing calcium titanate as a sintering aid, the sintering temperature of the ZTA ceramic is successfully reduced to 1500 DEG C from 1600 DEG C or above, a glass phase generated by a traditional aid is avoided during sintering, flaky calcium hexaluminate is generated in situ, grains can be refined, crack deflection can be induced, and high density of 98.4% or above is realized, so that the toughness and strength of the material are synergistically improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic materials, and relates to a preparation method of ZTA ceramic granulation powder. BACKGROUND

[0002] Zirconia toughened alumina ceramic, referred to as ZTA ceramic, is an important high-performance structural ceramic. As an important high-performance structural ceramic, ZTA ceramic is widely used in the fields of machinery, chemical industry, electronics, medical treatment and the like due to its excellent mechanical properties, wear resistance, corrosion resistance and high hardness. ZTA ceramic introduces zirconia as a toughening phase, and utilizes the phase transformation toughening mechanism (transition from tetragonal phase to monoclinic phase) to overcome the inherent high brittleness of alumina ceramic, thereby significantly improving the fracture toughness and bending strength of the material. The bending strength of traditional ZTA ceramic can reach 200-600 MPa, the fracture toughness is 2-5 MPa·m 1 / 2 , and the Vickers hardness is 1200-2000 HV.

[0003] However, the preparation of ZTA ceramic faces a key technical bottleneck: the sintering temperature is too high. The sintering temperature of conventional ZTA ceramic usually needs to reach 1600℃ or above, which significantly increases the production cost. High-temperature sintering also easily causes abnormal grain growth, forming micro defects such as pores and micro cracks, thereby reducing the reliability and mechanical properties of the material. Especially in the sintering process, if the zirconia is not uniformly dispersed or the phase transformation is not properly controlled, micro cracks will rapidly expand, thereby weakening the strength of the material. In addition, common additives for the preparation of ZTA ceramic include oxides or composite oxides such as MgO, TiO2, CuO and Nb2O5, glass phase additives such as borate and silicate systems; these additives produce liquid phase or promote diffusion mass transfer through atomic replacement in the sintering process, thereby reducing the densification temperature of the preparation, for example, CuO-TiO2-Nb2O5 composite additives can reduce the sintering temperature of ZTA ceramic to 1050℃, and achieve high thermal conductivity (18.7 W / m·K) and high bending strength (405 MPa); however, most of the additives for the preparation of ZTA ceramic will introduce glass phase, resulting in the decrease of the grain boundary strength of ZTA ceramic and the deterioration of high-temperature performance. SUMMARY

[0004] To solve the problems of high sintering temperature, abnormal grain growth, micro defects and glass phase introduced by preparation additives in the background art, the application provides a preparation method of high-density ZTA ceramic granulation powder, which realizes the synergistic enhancement of low-temperature sintering and microstructure optimization by introducing a small amount of calcium titanate to generate calcium hexaluminate in situ in the sintering process.

[0005] The method of the application comprises the following steps: S1, mixing alumina powder, nano zirconia and calcium titanate powder in a certain proportion to obtain ceramic powder; S2, disperse the ceramic powder in deionized water to obtain a ceramic slurry, and put the ceramic slurry into a ball mill to perform ball milling by using zirconium oxide ball milling medium; S3, add a binder, a dispersant, a release agent and a defoaming agent to the slurry ball-milled in step S2, and continue ball milling; S4, sieve the slurry ball-milled in step S3 through a 90-mesh sieve, and use a centrifugal spray granulation device to perform spray granulation, and sieve and take the granulated powder under a 100-mesh sieve to obtain a ZTA ceramic powder.

[0006] Preferably, in the step S1, the amount of calcium titanate added is 0.5-3% of the total mass of the ceramic powder, and the particle size of the calcium titanate is 0.5-4.5 microns.

[0007] Preferably, in the step S1, the amount of zirconium oxide added is 15% of the total mass of the ceramic powder.

[0008] Preferably, in the step S2, the solid content of the ceramic slurry is above 60%, the rotation speed of the ball mill is 220-240 r / min, and the ball milling time is 1-4 h.

[0009] Preferably, in the step S3, the binder includes polyvinyl alcohol, and the amount of the binder added is 0.5-1% of the total mass of the ceramic powder. The addition of the binder enables the powder particles to be bonded into microspheres during the spray granulation process, and the microspheres have good flowability, which facilitates subsequent mold pressing.

[0010] Preferably, in the step S3, the dispersant includes ammonium polyacrylate, and the amount of the dispersant added is 2 g per 1000 m 2 The addition of the ammonium polyacrylate enables the slurry to have good flowability.

[0011] Preferably, in the step S3, the release agent includes emulsified paraffin, and the amount of the release agent added is 1-2% of the total mass of the ceramic powder. The addition of the emulsified paraffin enables the granulated powder to have good release performance.

[0012] Preferably, the defoaming agent includes tributyl phosphate, and the amount of the defoaming agent added is 0.1% of the total mass of the ceramic powder.

[0013] Preferably, in the step S4, the parameters of the centrifugal spray granulation device are set as follows: the flow rate of the slurry is 20-40 ml / min; the rotation speed of the centrifugal atomizer is 6000-12000 r / min; the temperature of the upper air outlet is 240℃; and the temperature of the lower air outlet is 140℃. The parameter setting of the centrifugal spray granulation device ensures the morphology and completeness of the granulated powder, so as to obtain a granulated powder with low water content and a certain size distribution of the particle diameter.

[0014] Preferably, the granulation powder obtained in step S4 has a rest angle of 23-25°, a water content of ≤0.2%, and a loose bulk density of 1.10-1.14 g / cm 3 , and a tap density of 1.28-1.35 g / cm 3 .

[0015] Compared with the prior art, the present application has the following beneficial effects: (1) Significantly reducing the sintering temperature: The sintering temperature of traditional ZTA ceramics usually needs to be above 1600℃, while the present application successfully reduces the sintering temperature to 1500℃ by introducing calcium titanate as a sintering aid, utilizing its liquid-phase sintering effect and the lattice distortion caused by Ti 4+ solid solution, thereby effectively reducing energy consumption and production cost; (2) Achieving high density and avoiding the formation of glass phase: The addition of calcium titanate in the present application promotes the densification process of the material, so that the density of the finally prepared ZTA ceramic reaches more than 98.4%. The key lies in that, unlike traditional glass-phase sintering aids such as borate and silicate, calcium titanate avoids the formation of low-strength glass phase at the grain boundary, thereby being beneficial to maintaining or even improving the high-temperature performance and grain boundary strength of the material; (3) Optimizing the microstructure and refining the grain: During the sintering process, calcium titanate can react in situ with alumina to form calcium hexaluminate, and the calcium hexaluminate grains are usually in the form of plates or rods. These second-phase particles can produce a “pinning effect” on the alumina matrix grains, effectively inhibiting grain boundary migration and abnormal grain growth, thereby refining the overall microstructure of the ceramic; (4) Synergistically enhancing the toughness of the material: The in-situ generated plate-like or rod-like calcium hexaluminate grains, as well as the possible calcium titanate / calcium hexaluminate composite structure, can consume the energy of crack propagation through various toughening mechanisms such as crack deflection, branching, crack pinning, and grain pull-out; this forms a synergistic effect with the phase transformation toughening mechanism of zirconia, and together improves the fracture toughness of the material; (5) Improving the performance of the powder for the convenience of forming: By optimizing the slurry formulation (binder, dispersant, etc.) and the spray granulation process parameters, the finally obtained ZTA ceramic granulation powder has low water content, appropriate particle size distribution, low rest angle, and excellent flow performance; these characteristics provide convenience for the subsequent die forming process, ensure the uniformity and density of the green body, and lay a foundation for the uniformity and reliability of the final sintered body performance.

[0016] In summary, the application successfully reduces the sintering temperature of ZTA ceramic from above 1600 DEG C to 1500 DEG C by introducing calcium titanate as a sintering aid, avoids the glass phase generated by traditional aids in sintering, and generates calcium hexaluminate in situ in the form of flakes, which can refine the grain, induce crack deflection, and achieve a high density of more than 98.4%, thereby synergistically improving the toughness and strength of the material. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The production process flow chart of the application.

[0018] Figure 2 The XRD graph of the product after sintering of Example 1.

[0019] Figure 3 The micro-morphology graph of calcium hexaluminate grains in the ZTA ceramic of Example 1 Figure 4 The EDS scanning graph of calcium hexaluminate grains in the ZTA ceramic of Example 1, showing the superimposed graph of ZTA ceramic morphology and Ca element distribution.

[0020] Figure 5 The EDS scanning graph of calcium hexaluminate grains in the ZTA ceramic of Example 1, showing the single distribution graph of Ca element.

[0021] Figure 6 The micro-morphology of the ceramic using Al-Si-Ca based sintering aid of Comparative Example 1. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0023] A preparation method of high-density ZTA ceramic granulation powder, the production process flow chart is as shown in Figure 1 The specific steps are described as follows.

[0024] S1, mix alumina powder, nano zirconium oxide and calcium titanate powder in a certain proportion to obtain ceramic powder.

[0025] Specifically, the amount of calcium titanate added is 0.5-3% of the total mass of the ceramic powder, and the particle size of the calcium titanate is 0.5-4.5 microns; the amount of zirconium oxide added is 15% of the total mass of the ceramic powder; and the rest is alumina powder.

[0026] S2, disperse the ceramic powder in deionized water to obtain a ceramic slurry, and put the ceramic slurry into a ball mill for ball milling with zirconium oxide ball milling medium.

[0027] Specifically, the solid content of the ceramic slurry is above 60%, the rotation speed of the ball mill is 220-240 r / min, and the ball milling time is 1-4 h.

[0028] S3, adding a binder, a dispersant, a release agent, and an antifoaming agent to the slurry ball-milled in step S2, and continuing to ball mill.

[0029] Specifically, the binder is polyvinyl alcohol, and the amount of the binder added is 0.5-1% of the total mass of the ceramic powder. The dispersant is ammonium polyacrylate, and the amount of the dispersant added is 2 g per 1000 m 2 The amount of the dispersant added is 2 g per 1000 m

[0030] S4, sieving the slurry ball-milled in step S3 through a 90-mesh sieve, and using a centrifugal spray granulation device to spray granulate, and sieving the granulated powder under a 100-mesh sieve to obtain the ZTA ceramic powder.

[0031] Specifically, the parameters of the centrifugal spray granulation device are set as follows: the slurry flow rate is 20-40 ml / min; the rotation speed of the centrifugal atomizer is 6000-12000 r / min; the temperature at the upper air outlet is 240℃; and the temperature at the lower air outlet is 140℃.

[0032] Specifically, the angle of repose of the obtained granulated powder is 23-25°, the water content is ≤0.2%, the loose bulk density is 1.10-1.14 g / cm 3 , and the tap density is 1.28-1.35 g / cm 3 .

[0033] The technical solutions and technical effects of the present application are further illustrated by the following examples and comparative examples.

[0034] Example 1 820 g of alumina powder, 150 g of nano-zirconia powder, and 30 g of calcium titanate powder were uniformly mixed to obtain a ceramic powder.

[0035] The ceramic powder was dispersed in 500 g of deionized water, and was put into a ball mill to be ball-milled using zirconia ball milling media. The rotation speed of the ball mill was 220 r / min, and the ball milling time was 2 h.

[0036] Subsequently, 0.7% of polyvinyl alcohol based on the mass of the ceramic powder, 0.1% of tributyl phosphate based on the mass of the ceramic powder, 1% of emulsified paraffin wax based on the total mass of the ceramic powder, and 2 g of ammonium polyacrylate per 1000 m 2 of the surface area of the ceramic powder were added to the slurry. The ball milling was continued for 1 h, and then the slurry was discharged. The slurry was sieved through a 90-mesh sieve.

[0037] The slurry was pumped into a centrifugal spray granulation tower by using a peristaltic pump at a pumping speed of 35 ml / min. The centrifugal speed of the centrifugal spray granulation tower was 12000 r / min, the air inlet temperature was 240℃, and the air outlet temperature was 140℃.

[0038] The granulated powder was screened through a 100-mesh sieve, and the granulated powder had a water content of 0.17%, a rest angle of 24°, and a loose bulk density of 1.13 g / cm 3 , and a tap density of 1.32 g / cm 3 .

[0039] The granulated powder was pressure-formed by using a tablet press at a pressure of 125 Mpa, and then was pressure-kept for 10 min by using an isostatic press at a cylinder pressure of 150 Mpa, so as to obtain a green body density of 2.4 g / cm 3 .

[0040] The material was sintered by using a high-temperature electric furnace, was first excluded of organic matter at 500℃ for 2 h, and then was heated to 1500℃ for 1 h.

[0041] The sintered ZTA ceramic had a density of 4.108 g / cm 3 , a hardness of 1423 Hv, and a fracture toughness of about 6.15 MPa*m 1 / 2 .

[0042] Figure 2 The XRD pattern of the sintered product of Example 1 is shown in the figure, and the characteristic peaks correspond to four phases: Al2O3 (alumina) marked by black dots: it is the matrix phase of the ZTA ceramic; t-ZrO2 (tetragonal zirconia) marked by black rhombuses: as a toughening phase, it is the core component for realizing phase transformation toughening; CA6 (calcium hexaluminate) marked by stars: it is generated in situ from calcium titanate and alumina, and is the second phase formed after the calcium titanate is introduced in the application; m-ZrO2 (monoclinic zirconia) marked by triangles: it exists in a small amount, and is the product after part of the tetragonal zirconia is phase-transformed. Figure 1 The characteristic peaks of CA6 appear in the figure, which verifies the design of the application that “calcium titanate and alumina generate calcium hexaluminate in situ”, and this phase can refine the grains through “pinning effect”; a large amount of t-ZrO2 exists in the sintered product, which indicates that the tetragonal phase of zirconia has good stability and can play a phase transformation toughening role; and the sintered product does not have characteristic peaks of a glass phase, which verifies the advantage of the application that “avoiding introduction of a glass phase by traditional additives”.

[0043] Figure 3For the micro-morphology of calcium hexaluminate grains in the ZTA ceramic of Example 1, the light-colored, flaky or short rod-shaped particles in the figure correspond to calcium hexaluminate (CA6) grains, which are dispersed in the dark alumina matrix, verifying that the invention "calcium titanate and alumina in situ generate flaky or rod-shaped CA6". The flaky CA6 plays a "pinning effect" on the alumina matrix grains, which can inhibit the abnormal growth of the matrix grains, and the ZTA ceramic has a high fracture toughness. Figure 2 It can be seen that the matrix grain size is uniform and there is no obvious coarse grain, which reflects the effect of microstructure optimization; at the same time, the flaky or short rod-shaped CA6 morphology can consume crack propagation energy through mechanisms such as "crack deflection and crack pinning", and has a synergistic effect with the phase transformation toughening of zirconia to improve the toughness of the material. This morphology verifies the design goal of "in-situ generation of CA6 to optimize the microstructure and enhance the toughness" in the invention, and also explains the micro reasons for the improvement of the fracture toughness of the ZTA ceramic in Example 1.

[0044] Figure 4 The EDS scanning diagram of the calcium hexaluminate grains in the ZTA ceramic of Example 1 shows the superposition of the morphology of the ZTA ceramic and the distribution of Ca element; Figure 4 The light and dark areas in the figure correspond to the micro-morphology of the matrix (Al2O3) and grains of the ZTA ceramic; the green bright spots are the distribution positions of Ca element, and in the invention "calcium titanate and Al2O3 in situ generate CA6 (containing Ca)", so the area where the green bright spots are concentrated is the calcium hexaluminate (CA6) grains, which directly verifies the morphology of CA6, which is consistent with Figure 3 The CA6 area in the figure is flaky or short rod-shaped.

[0045] Figure 5 The EDS scanning diagram of the calcium hexaluminate grains in the ZTA ceramic of Example 1 shows the single distribution of Ca element; the aggregation area of green bright spots corresponds to the position of CA6, and it can be clearly seen that Ca element is concentrated in a specific area rather than uniformly dispersed, which confirms that CA6 is "a second phase generated in situ", which is consistent with the product characteristics of "calcium titanate and Al2O3 reacting to generate CA6" in the invention.

[0046] Figure 4 and Figure 5 together prove that Ca element (from calcium titanate) is not randomly dispersed, but is concentrated to form CA6 phase, verifying the technical route of "introducing calcium titanate → in-situ generating CA6 → achieving grain pinning and toughness synergism" in the invention, and also showing that the reaction process of calcium titanate is controllable and the distribution of the product (CA6) meets the design expectation of the invention.

[0047] Example 2 830g of alumina powder, 150g of nano-zirconia powder, 5g of magnesium oxide and 15g of calcium titanate powder were uniformly mixed to obtain ceramic powder.

[0048] The ceramic powder was dispersed in 500 g of deionized water and placed in a ball mill with zirconia ball milling media. The ball mill was rotated at 220 r / min for 2 h.

[0049] Subsequently, 0.7% of polyvinyl alcohol based on the mass of the ceramic powder, 0.1% of tributyl phosphate based on the mass of the ceramic powder, and 1% of emulsified paraffin wax based on the total mass of the ceramic powder were added to the slurry. 2 g of ammonium polyacrylate was added per 1000 m 2 of the surface area of the ceramic powder. The ball milling was continued for 1 h, and then the slurry was discharged. The slurry was sieved through a 90-mesh sieve.

[0050] The slurry was pumped into a centrifugal spray granulation tower using a peristaltic pump at a pumping speed of 35 ml / min. The centrifugal speed of the centrifugal spray granulation tower was 12000 r / min, the inlet air temperature was 240℃, and the outlet air temperature was 140℃.

[0051] The granulated powder was sieved through a 100-mesh sieve, and the water content of the granulated powder was 0.19%, the rest angle was 23°, the loose bulk density was 1.14 g / cm 3 , and the tap density was 1.31 g / cm 3 .

[0052] The granulated powder was pressure-formed using a tablet press at a pressure of 125 Mpa. Then, the isostatic press was used to maintain the pressure for 10 min, and the oil cylinder pressure was 150 Mpa. The green body density obtained was 2.4 g / cm 3 .

[0053] A high-temperature electric furnace was used to sinter the material. First, the organic matter was removed at 500℃ for 2 h. Then, the temperature was raised to 1500℃ for 1 h.

[0054] The sintered ZTA ceramic had a density of 4.091 g / cm 3 , a hardness of 1483 Hv, and a fracture toughness of about 5.88 MPa*m 1 / 2 .

[0055] Example 3 840 g of alumina powder, 150 g of nano-zirconia powder, and 10 g of calcium titanate powder were mixed uniformly to obtain a ceramic powder.

[0056] The ceramic powder was dispersed in 500 g of deionized water and placed in a ball mill with zirconia ball milling media. The ball mill was rotated at 220 r / min for 2 h.

[0057] Subsequently, 0.7% polyvinyl alcohol by mass of the ceramic powder, 0.1% tributyl phosphate by mass of the ceramic powder, 1% emulsified paraffin wax by mass of the total ceramic powder, 2g ammonium polyacrylate per 1000m 2 of the surface area of the ceramic powder were added to the slurry; the ball milling was continued for 1h, and then the slurry was discharged. The slurry was sieved through a 90-mesh sieve.

[0058] The slurry was pumped into a centrifugal spray granulation tower using a peristaltic pump at a pumping speed of 35ml / min. The centrifugal speed of the centrifugal spray granulation tower was 12000r / min, the air inlet temperature was 240℃, and the air outlet temperature was 140℃.

[0059] The granulated powder was sieved through a 100-mesh sieve, and the granulated powder had a moisture content of 0.2%, an angle of repose of 24.5°, a loose bulk density of 1.10g / cm 3 , and a tapped density of 1.33g / cm 3 .

[0060] The granulated powder was pressure-formed using a tablet press at a pressure of 125Mpa; then, the pressure was maintained for 10min using an isostatic press at a cylinder pressure of 150Mpa, and the green density of the obtained green body was 2.4g / cm 3 .

[0061] The material was sintered using a high-temperature electric furnace. First, the organic matter was removed by maintaining the temperature at 500℃ for 2h. Then, the temperature was raised to 1500℃ and maintained for 1h.

[0062] The sintered ZTA ceramic had a density of 4.081g / cm 3 , a hardness of 1446Hv, and a fracture toughness of about 5.82MPa*m 1 / 2 .

[0063] Comparative Example 1 An Al-Si-Ca sintering aid was used as a control.

[0064] 783.6g of alumina powder, 150g of nano-zirconia powder, and 62g of an Al-Si-Ca sintering aid were uniformly mixed to obtain a ceramic powder.

[0065] The ceramic powder was dispersed in 500g of deionized water and ball-milled in a ball mill for 2h. Subsequently, 0.7% polyvinyl alcohol by mass of the ceramic powder, 2g of ammonium polyacrylate per 1000m 2 of the surface area of the ceramic powder, and 0.1% tributyl phosphate by mass of the ceramic powder were added to the slurry, and the ball milling was continued for 1h. Then, the slurry was discharged and sieved through a 90-mesh sieve.

[0066] The slurry is pumped into the centrifugal spray granulation tower using a peristaltic pump at a pumping rate of 35 ml / min. The centrifuge in the centrifugal spray granulation tower operates at a speed of 12000 r / min, with an inlet air temperature of 240℃ and an outlet air temperature of 140℃.

[0067] The granulated powder passing through a 100-mesh sieve was collected. The moisture content of the granulated powder was 0.20%, the angle of repose was 25°, and the bulk density was 1.10 g / cm³. 3 The tap density is 1.29 g / cm³. 3 .

[0068] The granulated powder was pressurized using a tablet press at a pressure of 125 MPa; subsequently, it was held under pressure for 10 minutes using an isostatic press at a hydraulic cylinder pressure of 150 MPa, resulting in a green body density of 2.2 g / cm³. 3 .

[0069] The material was sintered using a high-temperature electric furnace, first held at 500℃ for 2 hours to remove organic matter. Then the temperature was raised to 1600℃ and held for 1 hour.

[0070] The sintered ceramic has a density of 3.956 g / cm³, a hardness of 1456 Hv, and a fracture toughness of approximately 4.87 MPa*m. 1 / 2 .

[0071] The microstructure of the ceramics in Comparative Example 1 using Al-Si-Ca sintering aids is as follows: Figure 6 As shown. Figure 6 The grains are coarse and uneven, with obvious large-sized alumina matrix grains. Some grains are much larger than the matrix grains in Example 1. This is because the Al-Si-Ca additive does not have the "calcium hexaaluminate (CA6) pinning effect" and cannot inhibit abnormal grain growth. Therefore, it requires a higher sintering temperature, reaching 1600℃. Figure 6 The sample contains pores and a glassy phase at grain boundaries. Small pores, such as those in the central region, are visible, and the grain boundaries exhibit a "blurred / adhesive" appearance. This corresponds to the glassy phase introduced by Al-Si-Ca additives, which reduces the density (the actual density of Comparative Example 1 is 3.956 g / cm³). 3 This is lower than the 4.108 g / cm³ of Example 1. 3 ), while weakening grain boundary strength; Figure 6 There is no plate-like or rod-like CA6 phase, unlike in Example 1. Figure 3 contrast, Figure 6 The lack of lamellar or rod-shaped second-phase particles prevents toughening through mechanisms such as crack deflection and pinning, which explains its fracture toughness (4.87 MPa*m). 1 / 2 (Lower than Example 1 (6.15 MPa*m)) 1 / 2 The reason is... Figure 6The micro-morphology of the ceramic directly reflects the defects of the traditional Al-Si-Ca series sintering aids: high-temperature sintering leads to coarse grains, the introduction of glass phase reduces the density and grain boundary strength, and the lack of a second phase structure for synergistic toughening, which exactly proves the technical advantages of the application of "introducing calcium titanate to generate CA6" in "low-temperature sintering, grain refinement, avoiding glass phase, and synergistic toughening".

[0072] From the above, the application has the following technical effects: I. Achieving low-temperature high-density sintering: In Example 1, calcium titanate is used as an additive, and the sintering temperature is reduced from 1600℃ of the traditional Al-Si-Ca series additive to 1500℃, while the sintered body density reaches 4.108g / cm 3 (>98.4%), which is higher than 3.956g / cm 3 of Comparative Example 1; combined with the results of Examples 2 and 3 (calcium titanate addition amount 0.5-3%), it is proved that calcium titanate promotes mass transfer through "liquid phase sintering + Ti 4+ lattice distortion", which can achieve high densification at 1500℃, and it is proved that it can achieve higher density at a lower temperature, solving the problem of "high sintering cost and low density"; II. Significantly improving the fracture toughness: the fracture toughness of the ZTA ceramic prepared in Example 1 reaches 6.15 MPa*m 1 / 2 , which is much higher than 4.87 MPa*m 1 / 2 of the comparative sample, about 26% higher; this is the synergistic effect of "crack deflection / pinning of flaky CA6" and "t-ZrO2 phase transformation toughening", which verifies that the in-situ generation of calcium hexaluminate by calcium titanate can effectively induce crack deflection and branching, thereby synergistically transforming zirconia, greatly improving the toughness of the material; the toughness of Examples 2 and 3 (5.88 MPa*m 1 / 2 , 5.82 MPa*m 1 / 2 ) is slightly lower, which side-by-side verifies the influence of the addition amount of calcium titanate (about 3%) on the generation of CA6, and further illustrates the controllability of the method of the application; III. Optimizing the performance of the powder and green body: the granulated powder obtained in Example 1 has better flowability and filling property (rest angle 24°, tap density 1.32 g / cm 3 , both better than the comparative example), and the green body density (2.4 g / cm 3 ) is also higher than that of the comparative example (2.2 g / cm 3 ), which reflects the continuous optimization of "powder flowability → green body uniformity → sintered body density", and reflects the matching of process parameters (spray granulation, ball milling, etc.) and additive selection, providing support for mass production stability and laying a solid foundation for obtaining high-density sintered body. Four, avoid glass phase and maintain performance: although the hardness (1423 Hv) of example 1 is slightly lower than that of the comparative example (1456 Hv), but example 1 avoids the glass phase inevitably produced by introducing Al-Si-Ca based additives, which is verified from the microscopic morphology (no grain boundary adhesion zone) and phase (XRD no glass phase peak); This means that the grain boundary strength and thermal shock resistance of the material under high temperature working condition are more stable, which makes up for the defects of traditional additives "high temperature performance degradation", and the product prepared by the embodiment of the application still has high density and high toughness, which is of great significance to maintain the high temperature performance and reliability of the material.

[0073] In summary, the application uses calcium titanate as a sintering aid, promotes the sintering mass transfer process by using liquid phase and element solid solution caused lattice distortion, and avoids the low strength glass phase introduced by traditional aluminum-silicon based sintering aids. Not only does the sintering temperature of ZTA decrease from 1600℃ to 1500℃, but also the density reaches more than 98.4%. The generated calcium hexaluminate plays a role in pinning alumina grains, inhibiting grain boundary diffusion and abnormal growth, refining the grain structure, and the flaky calcium aluminate grains will deflect and branch the cracks, which synergistically improves the fracture toughness of the material. The application improves the density of ZTA ceramic and optimizes the microstructure of ZTA ceramic without increasing additional processes.

[0074] The preferred embodiments of the application are described in detail above in combination with the drawings and specific examples, but the application is not limited to the specific details in the above embodiments, and various simple modifications can be made to the technical solutions of the application within the technical concept of the application, and these simple modifications all belong to the protection scope of the application.

Claims

1. A method for preparing a high-density ZTA ceramic granulation powder, characterized by, The application relates to a ZTA ceramic powder preparation method. S1, mixing alumina powder, nano zirconium oxide and calcium titanate powder according to a certain proportion to obtain ceramic powder; S2, dispersing the ceramic powder in deionized water to obtain ceramic slurry, and putting the ceramic slurry into a ball mill to perform ball milling by using zirconium oxide ball milling medium; S3, adding a binder, a dispersing agent, a release agent and a defoaming agent into the slurry ball-milled in the step S2, and continuing to perform ball milling; S4, spraying and granulating the slurry ball-milled in the step S3 by using a centrifugal spraying and granulating device, screening and taking the granulated powder below a 100-mesh screen to obtain ZTA ceramic powder.

2. The method according to claim 1, wherein the method is characterized by: In the step S1, the adding amount of calcium titanate is 0.5-3% of the total mass of the ceramic powder, and the particle size of the calcium titanate is 0.5-4.5 microns.

3. The method according to claim 2, wherein the method is characterized by: In the step S1, the adding amount of zirconium oxide is 15% of the total mass of the ceramic powder.

4. The method according to claim 3, wherein the method is characterized by: In the step S2, the solid content of the ceramic slurry is above 60%, the rotating speed of the ball mill is 220-240 r / min, and the ball milling time is 1-4 h.

5. The method according to claim 1, wherein the method is characterized by: In the step S3, the binder includes polyvinyl alcohol, and the adding amount of the binder is 0.5-1% of the total mass of the ceramic powder.

6. The method according to claim 5, wherein the method is characterized by: The dispersant in step S3 includes polyacrylate ammonium, 2g per 1000m 2 The dispersant added to the surface area of the ceramic powder is 2g.

7. The method according to claim 6, wherein the method is characterized by: In the step S3, the release agent includes emulsified paraffin, and the adding amount of the release agent is 1-2% of the total mass of the ceramic powder.

8. The method according to claim 7, wherein the method is characterized by: In the step S3, the defoaming agent includes tributyl phosphate, and the adding amount of the defoaming agent is 0.1% of the total mass of the ceramic powder.

9. The method according to claim 1, wherein the method is characterized by: In the step S4, the parameters of the centrifugal spraying and granulating device are set as follows: the slurry flow rate is 20-40 ml / min; the rotating speed of the centrifugal atomizer is 6000-12000 r / min; the temperature of the upper air outlet is 240 DEG C; and the temperature of the lower air outlet is 140 DEG C.

10. The method according to claim 9, wherein the method is characterized by: The granulation powder obtained in the step S4 has a rest angle of 23-25°, a moisture content of ≤0.2%, a loose bulk density of 1.10-1.14 g / cm 3 , and a tap density of 1.28-1.35 g / cm 3 .

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