Preparation and application of an o-MAB phase Ti4CrSiB2 ceramic material

Abstract

This invention discloses a o The preparation and application of -MAB phase Ti4CrSiB2 ceramic material involves the following steps: Titanium powder, chromium powder, silicon powder, and boron powder are used as raw materials. Ball milling media are added to the raw materials, and the mixture is wet-mixed in a ball mill at a predetermined speed and time to obtain a homogeneous mixture. The mixture is then dried at a predetermined temperature and time to obtain a dried mixture. The dried mixture is pre-pressed, and subsequently heated and pressurized under vacuum at predetermined heating and pressurization rates until a predetermined sintering temperature and pressure are reached, at which point the Ti4CrSiB2 ceramic material is obtained. The above process uses relatively economical and cost-effective initial materials. The raw materials are simple, readily available, and inexpensive, facilitating the implementation of the process. The resulting Ti4CrSiB2 ceramic material exhibits high purity.

Description

Technical Field

[0001] This invention relates to a novel ceramic material, specifically a... o -MAB phase Ti4CrSiB2 ceramic material. Background Technology

[0002] Layered transition metal boride (MAB) ceramics have become a research hotspot in recent years due to their excellent physical and mechanical properties. MAB ceramics are a class of non-van der Waals layered materials with orthorhombic and hexagonal (space group P63 / mmc) crystal structures, where M is an early transition metal element, A is mainly composed of Group 3 and 4 elements represented by Al and Si, and B is boron. Their crystal structure is characterized by strong covalent bonds between MB and BB atoms, while weaker metallic and covalent bonds are formed between MA and BA atoms. Therefore, the MAB phase can be viewed as a layered structure formed by tightly connected MB structural units separated by weak MA and BA bonds, and the topology can be controlled using the weaker interlayer forces of MA. In currently reported MAB borides, M and A atoms are alternately stacked along orthorhombic directions. M atoms coordinated with boron form non-equilateral triangular prisms, and nearest-neighbor boron atoms also form one-dimensional zigzag chains perpendicular to the A layer. The edge along the x-direction determines the lattice constant 'a' perpendicular to the A layer. As a recently emerging layered material, layered transition metal borides (MABs) have become a research hotspot in recent years due to their excellent physical and chemical properties. Benefiting from their unique elemental composition and crystal structure, these compounds combine the superior mechanical properties of ceramics and metals, while also exhibiting high damage tolerance and fracture toughness, making them highly valuable for engineering applications. Currently, over a hundred MAB materials have been predicted, but only about 60 have been publicly synthesized, including bulk materials, powder materials, thin film materials, and single-crystal materials. To accelerate the engineering application of these materials, developing and expanding the MAB phase family of new members is of great value to serve national high-end equipment and national economic development. Selective solid solution of binary metal elements at the M-site of the MAB phase can yield a series of in-plane chemically ordered phase structures (…). i -MAB) and out-of-plane chemically ordered phase structures ( o -MAB).

[0003] Currently reported out-of-plane chemical order o MAB phase materials are relatively few, and research on their development and properties is not comprehensive enough. Therefore, exploring the preparation of novel out-of-plane chemically ordered ceramic materials is a prerequisite for their application. The diversity of chemical composition and structure of MAB phases and their solid solutions provides a wide range of options for further performance adjustment and practical applications. Summary of the Invention

[0004] The purpose of this invention is to disclose a o -MAB phase Ti4CrSiB2 ceramic materials and their preparation methods: Through a simple and green preparation process, ceramic materials with excellent mechanical properties, high damage tolerance and high temperature and low friction characteristics are obtained to meet the safe and reliable service requirements of mechanical components under harsh working conditions.

[0005] one, o Preparation of MAB phase Ti4CrSiB2 ceramic materials

[0006] o The preparation method of MAB phase Ti4CrSiB2 ceramic material (powder) includes the following steps:

[0007] (1) Weigh Ti powder, Cr powder, Si powder and B powder in a molar ratio of 4.0~4.3:1.0~1.3:1.0~1.3:2.0~2.3. The purity of the raw materials Cr powder, Ti powder, Si powder and B powder is ≥99.5% and the particle size is 1~3μm.

[0008] (2) Place the powder obtained in step (1) into an agate mortar and grind for 20-30 minutes to mix evenly. The grinding medium is anhydrous ethanol.

[0009] (3) Place the powder mixed in step (2) into a vacuum drying oven and dry it at 60~80℃ for 2~5 hours to obtain the desired target mixed powder;

[0010] (4) The target mixed powder obtained in step (3) is heated at 1500~1700℃ with a vacuum degree of less than 10. -1 The reaction was carried out under Pa conditions for 1 to 4 hours. After cooling in the furnace, the material was ground and sieved to obtain Ti4CrSiB2 ceramic material.

[0011] o The preparation method of MAB phase Ti4CrSiB2 ceramic material (bulk) includes the following steps:

[0012] (1) Weigh Ti powder, Cr powder, Si powder and B powder in a molar ratio of 4.0~4.3:1.0~1.3:1.0~1.3:2.0~2.3. The purity of the raw materials Cr powder, Ti powder, Si powder and B powder is ≥99.5% and the particle size is 1~3μm.

[0013] (2) Place the powder obtained in step (1) into an agate mortar and grind for 20-30 minutes to mix evenly. The grinding medium is anhydrous ethanol.

[0014] (3) Place the powder mixed in step (2) into a vacuum drying oven and dry it at 60~80℃ for 2~5 hours to obtain the desired target mixed powder;

[0015] (4) Press the target mixed powder obtained in step (3) into a green body, then perform vacuum hot pressing sintering on the green body, and cool it after sintering to obtain the target product Ti4CrSiB2 bulk ceramic.

[0016] Hot pressing sintering: The heating rate during sintering is 1~10℃ / min, the sintering temperature is 1500~1700℃, and the sintering time is 2~5 h. Vacuum is applied during sintering at a pressure of 10~40 MPa, with a vacuum degree <10. -1 Pa.

[0017] This invention o The synthesis mechanism of MAB phase Ti4CrSiB2 ceramic material: Using Ti powder, Cr powder, Si powder, and B powder as raw materials, based on the reaction Ti + Cr + Si + B → Ti4CrSiB2, a ceramic material with uniform microstructure is synthesized in situ through mechanical grinding and hot pressing sintering techniques. Temperature plays a crucial role in the synthesis... o The sintering temperature has a significant impact on MAB ceramic materials. It directly affects the diffusion rate of the original powder and grain growth. Too low a temperature will result in incomplete sintering and failure to synthesize a single phase, while too high a temperature will cause melting and molten metal to flow out. If the ball milling does not reach the predetermined speed and time, it will also lead to insufficient powder mixing, resulting in uneven elemental distribution in the later synthesized sample and affecting its performance.

[0018] two, o Structural characterization of MAB phase Ti4CrSiB2 ceramic materials

[0019] Tripartite phase M 5 AB 2 It has I4 / mcm A symmetrical orthorhombic crystal structure in which the M element occupies two Wyckoff sites, 16l and 4c. M 5 AB 2 Phase transformation into out-of-plane chemical order M 4 AB 2 ( o The MAB phase causes Ti and Cr to occupy Wyckoff sites 16l and 4c, respectively, while Si is intercalated between the 16l and 4c sites. The crystal structure of Ti4CrSiB2 ceramic material is as follows: Figure 1As shown, the first layer consists of Ti and B, the second layer consists only of Cr, the third layer can be considered as a periodic structure composed of Si atoms, and the fourth layer is composed of Cr. The coordination number of the Cr atom layer is 14, with Si atoms connected to it vertically. The coordination number of the Ti atom is 9, with two Cr atoms and two B atoms on adjacent planes. The bonding between Ti and Cr in the Ti4CrSiB2 phase is similar to the chemical bonds in their respective metals and alloys. A weaker covalent bond is formed between Ti / Cr and Si. In the Ti4CrSiB2 phase, covalent bonds within a triangular region formed by Ti / Cr atoms and one Si atom alternate with covalent bonds within an octahedron formed by four Ti / Cr atoms and two B atoms. This alternating arrangement of covalent bonds results in a low number of independent slip systems in the Ti4CrSiB2 phase, thus giving it extremely high melting point, strength, hardness, oxidation resistance, and thermal shock resistance. The nanolayered structure of the Ti4CrSiB2 phase determines its excellent thermal and electrical conductivity. These superior properties make it a promising candidate for applications in high-temperature structural components, heating elements, conductive ceramics, and damage-tolerant ceramics.

[0020] Figure 2 The X-ray diffraction pattern of the Ti4CrSiB2 ceramic powder prepared in Example 1 of this invention shows that the prepared Ti4CrSiB2 powder is a pure phase with only a small amount of impurity phase (Ti5Si3). Figure 3 The image shows the EDS energy spectrum of the Ti4CrSiB2 ceramic powder prepared in Example 1 of this invention. It can be seen that the elemental ratio of the Ti4CrSiB2 powder synthesized under these conditions is consistent with the raw material ratio.

[0021] three, o Performance evaluation of MAB phase Ti4CrSiB2 ceramic materials

[0022] 1. The density and compactness of the material were measured using a fully automated true density analyzer and the Archimedes' displacement method. The test results showed that the density of the prepared bulk material was 3.8668 g / cm³. 3 Its density reaches 98%.

[0023] 2. The hardness of the Ti4CrSiB2 ceramic block was tested using a Vickers hardness tester. Loads of 300 gf, 500 gf, and 1000 gf were applied for 10 seconds each. Three points were randomly selected at each load for testing, and the average value was calculated as the hardness of the Ti4CrSiB2 ceramic. Test results: Hardness at 300 gf was 13.412 GPa; hardness at 500 gf was 13.604 GPa; hardness at 1000 gf was 13.156 GPa. The hardness of the Ti4CrSiB2 ceramic is approximately 13 GPa.

[0024] 3. The fracture toughness of the ceramic material was evaluated using an electronic universal testing machine, employing the three-point bending single-sided notched beam (SENB) method, in accordance with GB / T 23906-2009 standard. Standard specimens of 2mm × 4mm × 25mm were machined using a diamond precision cutter. A single-sided notch, 2mm deep and 0.2mm wide, was then machined parallel to the height direction in the middle of the specimen. The dried specimen was placed on the three-point bending test stage of the testing machine with the notch facing downwards, at a loading rate of 0.05mm / min and a span of 20mm. Five specimens were tested in each group, and the average value was taken as the fracture toughness value of the material at different temperatures. The obtained load-displacement curves are shown below. Figure 5 As shown in the figure. Finally, the fracture toughness of the Ti4CrSiB2 ceramic was calculated to be 6.414 MPa·m. 1 / 2 .

[0025] 4. The tribological properties of Ti4CrSiB2 ceramics were tested using a reciprocating high-temperature friction tester. The test temperature was 800℃. The test atmosphere was atmospheric. A nickel-based single-crystal alloy (DD5) was selected as the friction pair. The applied load was 5 N, the frequency was 5 Hz, the reciprocating length was 5 mm, and the friction time was 1800 s. To ensure the accuracy of the experiment, the friction test was repeated three times at each temperature point. Figure 6 The friction coefficient curve is shown at 800℃. The average friction coefficient between Ti4CrSiB2 ceramic and DD5 is 0.36.

[0026] Based on the above-mentioned excellent high-temperature friction resistance, o MAB phase ceramics can be applied to high-temperature thermal protection materials and high-temperature friction structural components, and have great application potential in wear-resistant and friction-reducing structural components used in aerospace and marine engines under extreme operating conditions.

[0027] In summary, this invention uses titanium powder, chromium powder, silicon powder, and boron powder as raw materials to form a raw material mixture. Ball milling media are added to the raw material mixture, and the mixture is wet-mixed in a ball mill at a predetermined speed and time to obtain a final mixture. The final mixture is dried at a predetermined temperature and time to obtain a dried mixture. The dried mixture is pre-pressed, and then heated and pressurized under a vacuum or protective atmosphere at predetermined heating and pressurization rates until a predetermined sintering temperature and pressure are reached. Sintering is then performed at a predetermined sintering time, and the final temperature is lowered to room temperature at a predetermined cooling rate to obtain the Ti4CrSiB2 ceramic material. The initial materials used in this process are economical and cost-effective. The raw materials are simple, readily available, and inexpensive, facilitating the implementation of the process. The resulting Ti4CrSiB2 ceramic material has high purity. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the crystal structure of Ti4CrSiB2 prepared in this invention.

[0029] Figure 2 The image shows the X-ray diffraction pattern of the Ti4CrSiB2 ceramic powder prepared in Example 1 of this invention.

[0030] Figure 3 This is the EDS energy spectrum of the Ti4CrSiB2 ceramic powder prepared in Example 1 of the present invention.

[0031] Figure 4 This is a cross-sectional SEM image of the Ti4CrSiB2 ceramic block prepared in Example 3 of the present invention.

[0032] Figure 5 The load-displacement curves are for the Ti4CrSiB2 ceramic bulk material prepared in Example 3 of this invention.

[0033] Figure 6 The friction coefficient curve of the Ti4CrSiB2 ceramic bulk prepared in Example 3 of the present invention at 800℃. Detailed Implementation

[0034] The present invention will be further explained below with reference to specific embodiments.

[0035] Example 1

[0036] (1) The raw materials, Ti powder, Cr powder, Si powder and B powder, were mixed in a ratio of 4.0:1.0:1.0:2.0, and the total mass of the raw materials was about 20g. The raw materials were placed in an agate mortar, a small amount of alcohol was added as a ball milling medium, and the mixture was manually ground for 0.5h to obtain the mixture.

[0037] (2) Place the mixture obtained in step (1) into a drying oven and dry it at 60°C for 1 hour. Then, sieve the dried mixture through a sieve with a mesh size of 200.

[0038] (3) Place the dried mixed powder obtained in step (2) into an alumina crucible, and then place the alumina crucible into a vacuum carbon tube furnace for sintering. The vacuum reading should be <10. -1 Pa, the furnace temperature was raised from room temperature to 1500℃ at a heating rate of 5℃ / min and held for 2 hours; then the temperature was lowered from 1500℃ to 700℃ at a cooling rate of 5℃ / min, and then the heating switch was turned off and the furnace was allowed to cool naturally to room temperature, thus obtaining Ti4CrSiB2 powder.

[0039] The XRD pattern of Ti4CrSiB2 powder is shown below. Figure 2The spectrum indicates that the prepared Ti4CrSiB2 powder is a pure phase, containing only a small amount of impurity phase (Ti5Si3). The energy dispersive spectroscopy (EDS) spectrum and elemental distribution diagram of the Ti4CrSiB2 powder are shown below. Figure 3 ,Depend on Figure 3 It can be seen that the elemental ratio of the Ti4CrSiB2 powder synthesized under these conditions is consistent with the raw material ratio.

[0040] Example 2

[0041] (1) The raw materials, Ti powder, Cr powder, Si powder and B powder, were mixed in a ratio of 4.3:1.3:1.3:2.3, and the total mass of the raw materials was about 20g. The raw materials were placed in an agate mortar, a small amount of alcohol was added as a ball milling medium, and the mixture was manually ground for 0.5h to obtain the mixture.

[0042] (2) Place the mixture obtained in step (1) into a drying oven and dry it at 60°C for 1 hour. Then, sieve the dried mixture through a sieve with a mesh size of 200.

[0043] (3) Place the dried mixed powder obtained in step (2) into an alumina crucible, and then place the alumina crucible into a vacuum carbon tube furnace for sintering. The vacuum reading should be <10. -1 Pa, the furnace temperature was raised from room temperature to 1600℃ at a heating rate of 10℃ / min and held for 1 hour; then the temperature was lowered from 1600℃ to 700℃ at a cooling rate of 10℃ / min, and then the heating switch was turned off and the furnace was allowed to cool naturally to room temperature, thus obtaining Ti4CrSiB2 powder.

[0044] Example 3

[0045] (1) Ti powder, Cr powder, Si powder and B powder were mixed in a ratio of 4.0:1.0:1.0:2.0, with a total mass of approximately 20g. A small amount of alcohol was added as the ball milling medium and placed in a polytetrafluoroethylene ball milling jar with an alumina ball:mixed powder ratio of 5:1. The ball milling jar was placed in a planetary ball mill and ball milled at 200 r / min for 8 h under argon protection to obtain the mixed powder.

[0046] (2) After drying and sieving the mixed powder obtained in step (1), it is pressed into a green body, then vacuum hot pressing and sintering is performed, and the atmosphere furnace is evacuated for 10 min until the vacuum reading is <10. -1 The material was heated at a heating rate of 10℃ / min and pressurized at a predetermined pressurization rate of 0.5 MPa / min. Sintering was then carried out at a sintering temperature of 1500℃ and a pressure of 30 MPa for 2 hours. After the holding period, the temperature was lowered to 800℃ at a cooling rate of 10℃ / min and then cooled to room temperature in the furnace to obtain the Ti4CrSiB2 ceramic bulk.

[0047] The density of the prepared Ti4CrSiB2 ceramic bulk was tested to be 3.8668 g / cm³. 3 The hardness is 12±2.5 GPa, the density can reach 99.8%, and the flexural strength is 417.76±25.3 MPa. SEM images of the cross-section of the Ti4CrSiB2 ceramic bulk are shown below. Figure 4 As shown, the partial texture and layered structure of Ti4CrSiB2 grains make its main fracture mode a step-like crack that penetrates through the grain lamellae. The layered transgranular fracture requires overcoming the strong covalent bonds within the Ti4CrSiB2 grain lamellae, which is the reason for its high strength.

[0048] Example 4

[0049] (1) Ti powder, Cr powder, Si powder and B powder were mixed in a ratio of 4.3:1.3:1.3:2.3, with a total mass of approximately 20g. A small amount of alcohol was added as the ball milling medium and placed in a polytetrafluoroethylene ball milling jar with an alumina ball:mixed powder ratio of 5:1. The ball milling jar was placed in a planetary ball mill and ball milled at 200 r / min for 8 h under argon protection to obtain the mixed powder.

[0050] (2) After drying and sieving the mixed powder obtained in step (1), it is pressed into a green body, then vacuum hot pressing and sintering is performed, and the atmosphere furnace is evacuated for 10 min until the vacuum reading is <10. -1 The material was heated at a heating rate of 5℃ / min and pressurized at a predetermined pressure rate of 0.5 MPa / min. Sintering was then carried out at a temperature of 1600℃ and a pressure of 30 MPa for 2 hours. After the holding period, the temperature was lowered to 800℃ at a cooling rate of 5℃ / min and then cooled to room temperature in the furnace to obtain Ti4CrSiB2 ceramic.

[0051] The density of the prepared Ti4CrSiB2 ceramic was measured to be 3.9224 g / cm³. 3 The hardness is 13±3.5GPa, the density can reach 99.5%, and the flexural strength is 447.74±26.3 MPa.

Claims

1. A o - MAB phase Ti4CrSiB2 ceramic material, characterized in that, The ceramic material is a ternary boride having I4 / mcm The ternary boride has an orthorhombic crystal structure, wherein Ti and Cr occupy Wyckoff sites 161 and 4c, respectively, and the Si element is intercalated between the 161 and 4c sites.

2. A o A method for producing a MAB phase Ti4CrSiB2 ceramic material, characterized by, comprising the following steps: (1) Ti powder, Cr powder, Si powder and B powder are weighed according to the molar ratio of 4.0-4.3:1.0-1.3:1.0-1.3:2.0-2.3, the purity of the raw materials Cr powder, Ti powder, Si powder and B powder is all ≥99.5%, and the particle size is all 1-3 μm; (2) the powder obtained in step (1) is put into an agate mortar and ground for 20-30 min to mix uniformly, and the grinding medium is anhydrous ethanol; (3) the mixed powder of step (2) is put into a vacuum drying oven and dried at 60-80℃ for 2-5 hours, and the target mixed powder is obtained after drying; (4) the target mixed powder obtained in step (3) is heated at 1500-1700°C under a vacuum degree of less than 10 -1 for 1-4 hours under a P a condition, and then cooled in the furnace to obtain a Ti4CrSiB2 ceramic material.

3. A method as claimed in claim 1 o - Use of MAB phase Ti4CrSiB2 ceramic material in high-temperature resistant friction structures.

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