High toughness zirconia-based ceramic having a grain boundary monoclinic phase structure and method of making the same
By forming a monoclinic phase layer of controllable thickness at the grain boundaries of zirconia-based ceramics, and combining it with interface regulation additives, the problem of insufficient strain coordination at the grain boundaries of traditional Y-TZP ceramics has been solved, realizing zirconia-based ceramic materials with high toughness and high strength, which are suitable for high-reliability structures and thermal protection components.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TSINGHUA UNIVERSITY
- Filing Date
- 2026-02-04
- Publication Date
- 2026-06-05
AI Technical Summary
Traditional Y-TZP ceramics have difficulty controlling the thickness, orientation, and distribution continuity of the monoclinic phase layer at the grain boundaries, resulting in insufficient strain coordination ability. Under long-term service or thermal cycling, local phase transformation runaway and crack initiation are prone to occur.
By forming a monoclinic phase layer with controllable thickness at the grain boundaries of zirconia-based ceramics, and combining interface control agent A and defect control agent B, the thickness of the monoclinic phase layer is controlled to be 1-10 nm, with a continuous distribution ratio of 30-80%, and it has an orientation relationship with adjacent grains, forming a tetragonal/monoclinic/cubic phase interface structure, thereby achieving grain boundary mismatch strain coordination, crack deflection, and dislocation slip energy absorption.
It significantly improves the fracture toughness and bending strength of the material, increases the crack deflection angle to 45-60°, increases toughness by ≥60%, enhances resistance to low-temperature degradation, stabilizes the phase at high temperatures, and achieves an interface-dominated toughening mechanism.
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Figure CN122145163A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of structural ceramics and interface engineering, and particularly relates to a high-toughness zirconia-based ceramic with a monoclinic phase structure at grain boundaries and its preparation method. Background Technology
[0002] Traditional Y-TZP (Yttria-Stabilized Tetragonal Zirconia Polycrystals) achieves toughening through a stress-induced transformation from the tetragonal to the monoclinic phase. However, grain boundaries are often brittle and lack strain-coordinating capabilities. Long-term service or thermal cycling can lead to uncontrolled local phase transformation and crack initiation. If a stable and controllable monoclinic layer can be constructed at the grain boundaries, this layer will become a local strain-coordinating zone, significantly improving energy dissipation and crack deflection. However, current technologies struggle to control its thickness, orientation, and distribution continuity, and the underlying mechanisms are not uniformly understood. Summary of the Invention
[0003] The present invention aims to at least partially solve one of the technical problems in the related art.
[0004] Therefore, the purpose of this invention is to propose a high-toughness zirconia ceramic with a monoclinic phase structure at grain boundaries and its preparation method, analyze and elucidate its toughening mechanism, achieve strain coordination and energy dissipation at the interface level, and significantly improve the fracture toughness of the material.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] The first aspect of this invention provides a high-toughness zirconia-based ceramic with a monoclinic grain boundary structure, wherein the matrix phase is... , A monoclinic phase with controllable thickness exists at the grain boundaries. Layers form an interface structure of tetragonal / monoclinic / cubic phases, or tetragonal / monoclinic / cubic phases; the monoclinic phase The layer has an orientation relationship with the adjacent grains and is accompanied by misfit dislocation bands or strain regions.
[0007] In some embodiments, the monoclinic phase The thickness of the layer is 1-10 nm.
[0008] In some embodiments, the monoclinic phase The layer thickness is 2–5 nm, and the continuous distribution ratio is 30–80%.
[0009] In some embodiments, the atomic percentage concentration of Y element at the grain boundary is reduced by 10–50% compared to that in the grain, and the atomic percentage concentration of oxygen vacancies at the grain boundary is increased by 5–20% compared to that in the grain.
[0010] In some embodiments, the monoclinic phase The orientation relationship between the layer and adjacent grains includes at least the following: .
[0011] In some embodiments, the fracture toughness of the zirconia-based ceramic material Flexural strength .
[0012] In some embodiments, the toughening mechanism of the zirconia-based ceramic material includes grain boundary mismatch strain coordination, crack deflection, dislocation slip energy absorption, and monoclinic reversible phase transformation energy absorption.
[0013] In some embodiments, the zirconia-based ceramic material contains 0.3–3.0 wt% of interface modifier A, wherein interface modifier A is selected from... , , Cosol, and A mixture of any one or more of them.
[0014] In some embodiments, the zirconia-based ceramic material further contains 0.02–2.0 wt% of defect-modifying agent B, wherein the defect-modifying agent B is selected from... , and A mixture of any one or more of them.
[0015] The second aspect of this invention provides a method for preparing the high-toughness zirconia-based ceramic described in any embodiment of the first aspect of this invention, comprising:
[0016] Will The powder is mixed with interface control agent A, wherein the interface control agent A accounts for 0.3–3.0 wt% of the total weight of oxides in the ceramic material, and the interface control agent A is selected from... , , Cosol, and A mixture of any one or more of the following;
[0017] Drying and shaping yields a green body;
[0018] The green body is sintered at 1400–1500 °C for 1–2 h in a low-oxygen partial pressure inert atmosphere or a carbothermic reducing atmosphere, with a cooling rate of 2–5 °C / min, to form a monoclinic phase with controllable thickness at the grain boundaries. layer.
[0019] Compared with ordinary Y-TZP, the present invention has the following beneficial effects:
[0020] The thickness and orientation of the monoclinic layer at the grain boundary are controllable;
[0021] The crack deflection angle is increased to 45–60°;
[0022] Toughness increased by ≥ 60%, and resistance to low-temperature degradation enhanced;
[0023] The phase is stable at high temperatures (1000 °C);
[0024] Mechanistically, the monoclinic phase layer acts as a strain coordination zone, where dislocation slip and micro-phase transformation work together to dissipate energy, which is a “interface-dominated toughening mechanism”. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the T / M / T grain boundary structure and lattice orientation of the zirconia-based ceramic prepared in Example 1 of the present invention. ;
[0026] Figure 2 This is a TEM image of the zirconia-based ceramic prepared in Example 1 of the present invention at the crack. Detailed Implementation
[0027] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.
[0028] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.
[0029] The endpoints and any values of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this application.
[0030] The first aspect of this invention provides a high-toughness zirconia-based ceramic with a monoclinic grain boundary structure, wherein the matrix phase is... , A monoclinic phase with a thickness of 1–10 nm exists at the grain boundaries. layer( Layers), forming a tetragonal / monoclinic / cubic phasor interface structure, or a tetragonal / monoclinic / cubic phasor interface structure; monoclinic phasor The layer has an orientation relationship with the adjacent grains, such as This is accompanied by mismatched dislocation zones or strain zones, which induce crack deflection and energy dissipation under external loads.
[0031] Furthermore, monoclinic phase The layer thickness is preferably 2–5 nm, with a continuous distribution ratio of 30–80%. A 2–5 nm thick monoclinic phase... The layer is concentrated in the middle section of the grain boundary region of the ceramic material in the embodiments of the present invention, and occupies a large proportion, which is considered to play a major role in improving the fracture toughness of ceramics.
[0032] Furthermore, the atomic percentage concentration of Y element at the grain boundary is 10–50% lower than that in the grain, and the atomic percentage concentration of oxygen vacancies at the grain boundary is 5–20% higher than that in the grain.
[0033] Furthermore, the fracture toughness of the zirconia-based ceramic provided in the first aspect embodiment of the present invention... Specifically, it can achieve Flexural strength .
[0034] Optionally, in the zirconia-based ceramic provided in the first aspect of the present invention, an interface control agent A is added. The interface control agent will enhance the reactivity of carbon through catalysis, generate ZrC, and eventually transform it into a monoclinic zirconia layer during the cooling process.
[0035] Furthermore, interface regulation agent A is selected from... , , Cosol, and The mixture of one or more of the above, with the added interface modifier A accounting for 0.3–3.0 wt% of the total weight of oxides in the ceramic material. If this range is exceeded, the ceramic properties will decrease or significant second phase precipitation will occur.
[0036] Optionally, the zirconia-based ceramic provided in the first aspect of the present invention also contains a defect-regulating agent B, which regulates oxygen defects by introducing cations with a set valence state, thereby optimizing phase composition, sintering performance, regulating microstructure and improving overall mechanical properties.
[0037] Furthermore, defect-modifying agent B is selected from... , , One or more of the defect-modifying agents B are added, accounting for 0.2–2.0 wt% of the total weight of oxides in the ceramic material.
[0038] The zirconia-based ceramics provided in the first aspect of this invention have toughening mechanisms including grain boundary mismatch strain compatibility, crack deflection, dislocation slip energy absorption, and monoclinic phase. Layers can absorb energy through reversible phase transitions.
[0039] The method for preparing the above-mentioned high-toughness zirconia-based ceramic provided in the second aspect embodiment of the present invention includes the following steps:
[0040] Step S1, The powder and interface control agent A are mixed in a set ratio;
[0041] Step S2: Dry and shape the mixture from step S1 to obtain a blank;
[0042] Step S3: Place the above-mentioned green body in an inert atmosphere with a low oxygen partial pressure (not exceeding 0.1 atm) or a carbothermic reducing atmosphere and sinter at 1400–1500 °C for 1–2 h with a cooling rate of 2–5 °C / min to form a monoclinic phase with a thickness of 1–10 nm at the grain boundaries. layer.
[0043] Furthermore, the carbon source C is selected from phenolic resin, polyvinyl alcohol, sucrose, carbon black, etc., and is used to form the precursor of monoclinic zirconium dioxide: zirconium carbide, based on a C equivalent of 0.2–2.0 wt%.
[0044] The following describes specific embodiments of the present invention:
[0045] Example 1 ( system)
[0046] 3 mol% Powder (average particle size 200 nm) with 2 wt% The sol is mixed evenly.
[0047] The above mixture is dried into a blank to obtain a green body.
[0048] The above-mentioned blank was subjected to Ar and ( Zhan Ar and High-toughness zirconia-based ceramic materials were obtained by sintering at 1460 °C for 1 h in a mixed atmosphere (5% of the total volume) and a cooling rate of 3 °C / min.
[0049] See Figure 1 The high-toughness zirconia-based ceramic material was observed using high-resolution transmission electron microscopy (HRTEM), revealing the formation of approximately 5 nm thick strata at the grain boundaries. layer. Figure 1 The grain boundary between T(101) and T(100) is shown. The phase has a thickness of about 3 nm and a continuity of about 70%.
[0050] The Y element content in the prepared high-toughness zirconia-based ceramic material was detected using energy-dispersive X-ray spectroscopy (EDS). According to the EDS results, the Y element content decreased by about 40% from the grain to the interface. The decrease in Y element content indirectly proves that the monoclinic phase exists at the grain boundaries, because the Y content of monoclinic zirconia is generally very low.
[0051] The high-toughness zirconia-based ceramic material prepared in this embodiment was tested according to GB / T 23806—2009 "Test Method for Fracture Toughness of Fine Ceramics - Single-sided Pre-cracked Beam (SEPB) Method". The measured fracture toughness was [value missing]. Flexural strength .
[0052] See Figure 2 TEM images observed at the crack revealed that the original tetragonal and cubic phases transformed into the M phase during crack formation, and the crack deflection angle was measured. .
[0053] Example 2 ( Sol-gel system
[0054] 4 mol% Powder (average particle size 200 nm) + 1 wt% The sol is mixed evenly.
[0055] The above mixture is dried into a blank to obtain a green body.
[0056] The above-mentioned blank is in Sintering was carried out at 1480 °C for 2 h under a specific atmosphere, with a cooling rate of 2 °C / min.
[0057] A 1–3 nm M layer was formed, and the crack deflection angle was measured based on TEM images of the crack location. Fracture toughness is .
[0058] Example 3 ( Cosol+ Doped systems)
[0059] 3.5 mol% 1 wt% Cosol and 0.2 wt% Mix thoroughly.
[0060] The above mixture is dried into a blank to obtain a green body.
[0061] The above-mentioned blank is in Sintering was carried out at 1450 °C for 1.5 h under a specific atmosphere, with a cooling rate of 3 °C / min.
[0062] TEM observation of layer M Interface continuity > 70%, toughness Its thermal shock resistance is superior to that of Example 1.
[0063] Comparative Example 1 (as a comparative example of Example 1, without additives)
[0064] The difference between this comparative example and Example 1 is that no interface-modifying agent A was added to the ceramic material. Sol. The rest of the preparation process is the same as in Example 1.
[0065] HRTEM observations revealed no M-layer formation at the grain boundaries, and the fracture toughness of the resulting ceramic was only [missing information]. .
[0066] Comparative Example 2 (as a comparative example of Example 1, using high...) (its content is > 5.5 mol%)
[0067] 6 mol% Sintering was performed under the same conditions as in Example 1, resulting in complete cubication without the formation of the M layer, and the fracture toughness was approximately [missing value]. .
[0068] These results demonstrate that the composition and atmosphere window (primarily referring to the oxygen partial pressure) of this invention are crucial for achieving the grain boundary M-layer and high toughness. Under oxygen-free conditions, zirconium carbide cannot be oxidized to monoclinic zirconium oxide, while excessive oxygen introduces numerous defects, reducing mechanical properties. Therefore, the oxygen partial pressure should be controlled within a small range.
[0069] It is understood that the interface regulation aid A added in the embodiments of the present invention segregates at grain boundaries during sintering, providing the local chemical and defect conditions required for the nucleation of monoclinic phase layers at grain boundaries; it controls the oxygen partial pressure in the furnace within a preset window in the critical temperature range of sintering and cooling, promoting the nucleation and stable maintenance of monoclinic phase layers at grain boundaries; at the same time, by controlling the time-temperature history of sintering holding and cooling through the sensitive temperature range of phase stability, it restricts the element redistribution and growth kinetics of phase transformation layers at grain boundaries, thereby ensuring that the thickness of the monoclinic phase layer at grain boundaries is stably limited to the nanoscale range, such as 1–10 nm. The ceramic material prepared in the embodiments of the present invention can induce crack deflection, bifurcation, and passivation under loading, and is accompanied by phase transformation phenomena at the cracks, achieving interface-dominated energy dissipation and improving fracture toughness. Its bending strength exceeds 1200 MPa.
[0070] In summary, this invention provides a ceramic material with high toughness that can be achieved through grain boundary engineering and its preparation method, which is suitable for high-reliability structures, thermal protection, and microwave absorbing ceramic components.
[0071] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.
Claims
1. A high-toughness zirconia-based ceramic with a monoclinic phase structure at grain boundaries, characterized in that, Its matrix phase is , A monoclinic phase with controllable thickness exists at the grain boundaries. Layers form an interface structure of tetragonal / monoclinic / cubic phases, or tetragonal / monoclinic / cubic phases; the monoclinic phase The layer has an orientation relationship with the adjacent grains and is accompanied by misfit dislocation bands or strain regions.
2. The high-toughness zirconia-based ceramic according to claim 1, characterized in that, The monoclinic phase The thickness of the layer is 1-10 nm.
3. The high-toughness zirconia-based ceramic according to claim 1, characterized in that, The monoclinic phase The layer thickness is 2–5 nm, and the continuous distribution ratio is 30–80%.
4. The high-toughness zirconia-based ceramic according to claim 1, characterized in that, The atomic percentage concentration of Y at the grain boundaries is 10–50% lower than that in the grains, while the atomic percentage concentration of oxygen vacancies at the grain boundaries is 5–20% higher than that in the grains.
5. The high-toughness zirconia-based ceramic according to claim 1, characterized in that, The monoclinic phase The orientation relationship between the layer and adjacent grains includes at least the following: .
6. The high-toughness zirconia-based ceramic according to claim 1, characterized in that, fracture toughness of the zirconia-based ceramic material Flexural strength .
7. The high-toughness zirconia-based ceramic according to claim 1, characterized in that, The toughening mechanism of the zirconia-based ceramic material includes grain boundary mismatch strain coordination, crack deflection, dislocation slip energy absorption, and monoclinic reversible phase transformation energy absorption.
8. The high-toughness zirconia-based ceramic according to claim 1, characterized in that, The zirconia-based ceramic material contains 0.3–3.0 wt% of interface modifier A, wherein interface modifier A is selected from... , , Cosol, and A mixture of any one or more of them.
9. The high-toughness zirconia-based ceramic according to claim 8, characterized in that, The zirconia-based ceramic material also contains 0.02–2.0 wt% of defect-modifying agent B, which is selected from... , and A mixture of any one or more of them.
10. A method for preparing the high-toughness zirconia-based ceramic according to any one of claims 1 to 7, characterized in that, include: Will The powder is mixed with interface control agent A, wherein the interface control agent A accounts for 0.3–3.0 wt% of the total weight of oxides in the ceramic material, and the interface control agent A is selected from... , , Cosol, and A mixture of any one or more of the following; Drying and shaping yields a green body; The green body is sintered at 1400–1500 °C for 1–2 h in a low-oxygen partial pressure inert atmosphere or a carbothermic reducing atmosphere, with a cooling rate of 2–5 °C / min, to form a monoclinic phase with controllable thickness at the grain boundaries. layer.