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CN-121974704-A - High-stability rubidium boron silicon superhard compound and preparation method thereof

CN121974704ACN 121974704 ACN121974704 ACN 121974704ACN-121974704-A

Abstract

The invention discloses a high-stability rubidium boron silicon superhard compound and a preparation method thereof, belonging to the technical field of superhard materials, wherein the superhard compound is a composite structure block material formed by taking rubidium-boron-silicon as a basic skeleton and introducing an alkali metal regulator; the composite structure comprises a high-entropy ceramic matrix and nano twin crystals distributed in the matrix, wherein the high-entropy ceramic matrix is a solid solution composed of rubidium, boron, silicon and alkali metal cations introduced by the alkali metal regulator, the nano twin crystals are lamellar crystal structures with coherent twin crystal boundaries, and the ultra-hard rubidium-boron-silicon compound with ultra-high hardness and excellent thermal stability is developed through the collaborative innovation of a material system and a preparation process, so that a brand new solution is provided for ultra-hard materials serving in extremely high temperature environments.

Inventors

  • LU MINGCHUN

Assignees

  • 吉林化工大学

Dates

Publication Date
20260505
Application Date
20260206

Claims (10)

  1. 1. The high-stability rubidium boron silicon superhard compound is a composite structure block material formed by taking rubidium-boron-silicon as a basic framework and introducing an alkali metal regulator, wherein the composite structure comprises a high-entropy ceramic matrix and nano twin crystals distributed in the matrix, the high-entropy ceramic matrix is a solid solution composed of rubidium, boron, silicon and alkali metal cations introduced by the alkali metal regulator, and the nano twin crystals are lamellar crystal structures with coherent twin crystal boundaries.
  2. 2. A superhard compound according to claim 1, wherein the alkali metal cation is any one of potassium, caesium or calcium.
  3. 3. A superhard compound according to claim 1, having a vickers hardness of 62.8-68.2 gpa and a hardness retention of 93.2-95.0% after heat treatment in an atmospheric environment at 1100 ℃ for 10 hours.
  4. 4. A method of preparing a superhard compound according to any one of claims 1 to 3, comprising the steps of: S1, preparing precursor powder, namely mechanically alloying rubidium-containing compounds, alkali metal regulators, boron powder and silicon powder serving as raw materials through a high-energy ball milling process, and enabling the rubidium-containing compounds, the alkali metal regulators and the boron powder to undergo a solid phase reaction to form the precursor with the lamellar crystal structure of the coherent twin crystal boundary, so as to obtain composite precursor powder; S2, performing sectional spark plasma sintering on the composite precursor powder, performing first-step sintering at 800-900 ℃ and 30-60 MPa to realize diffusion and pre-densification of components, and performing second-step sintering at 1200-1400 ℃ and 4-6 GPa to completely form and refine the coherent twin boundary lamellar structure to obtain the superhard compound.
  5. 5. The method according to claim 4, wherein in step S1, the rubidium-containing compound is rubidium oxide or rubidium carbonate, and the alkali metal regulator is any one of potassium carbonate, cesium carbonate and calcium oxide.
  6. 6. The preparation method of the high-energy ball milling machine according to claim 4, wherein in the step S1, the high-energy ball milling process is performed under the protection of argon, the ball mass ratio is (15-25): 1, the rotating speed is 350-450 r/min, and the ball milling time is 20-40 h.
  7. 7. The method according to claim 4, wherein in step S1, the molar ratio of the rubidium element to the alkali metal element in the rubidium-containing compound and the alkali metal regulator is 1 (0.5-2), and the molar ratio of the total number of moles of the rubidium element and the alkali metal element to the boron element is 1 (8-15).
  8. 8. The method according to claim 4, wherein in the step S1, the molar ratio of boron element to silicon element is 1.5 to 4:1.
  9. 9. The preparation method of the ceramic powder according to claim 4, wherein in the step S2, the heat preservation time of the first sintering is 3-8 min, and the heat preservation time of the second sintering is 8-15 min.
  10. 10. The method according to claim 4, wherein in the step S2, the temperature rising rate from the first sintering to the second sintering is 80-150 ℃ per minute, and the second sintering is cooled to 400-600 ℃ at a rate of 50-70 ℃ per minute after the second sintering is completed.

Description

High-stability rubidium boron silicon superhard compound and preparation method thereof Technical Field The invention relates to the technical field of superhard materials, in particular to a high-stability rubidium boron silicon superhard compound and a preparation method thereof. Background Superhard materials are critical materials indispensable to the modern industry, and the upper performance limits directly determine the technical level of tip fabrication and equipment. With the development of the fields of aerospace, high-end numerical control machine tools and the like towards the fields of high efficiency, high precision, dry cutting and the like, more stringent requirements are put forward on the performance of superhard materials under the extreme thermal-force coupling working condition. Specifically, for applications such as high-speed cutting and superalloy processing, not only is the material required to have extremely high hardness at normal temperature to resist plastic deformation and wear, but also it is required to maintain stability of microstructure and non-attenuation of hardness for a long period of time in a continuous high-temperature environment. Conventional superhard material systems, represented by diamond and cubic boron nitride (cBN), do not fully meet the challenges of this application requirement. This is because diamond, although the hardest material in nature, starts to oxidize in air at temperatures exceeding 450 ℃ and reacts readily with iron group elements at high temperatures, which severely limits its wide application in the processing of steel materials. cBN has thermal stability and chemical inertness superior to diamond, but its absolute hardness is difficult to meet the requirements for limited hardness, and its performance is still significantly degraded after prolonged ultra-high temperature exposure. In order to break through the bottleneck of the thermal stability of the traditional superhard material, the high-entropy ceramic is developed as an emerging material design strategy, and the material provides a new possibility for cooperatively improving the hardness and thermal stability of the material through the high-entropy effect, the lattice distortion effect and the delayed diffusion effect induced by multi-principal element alloying. However, the existing super-hard ceramics such as high-entropy boride, carbide and the like still face two technical difficulties. Firstly, the initial hardness of the material after preparation is still available, but after long-term high-temperature service, the hardness retention rate is greatly reduced due to reasons such as grain boundary migration, phase decomposition or element segregation, namely the long-term thermal stability is insufficient, secondly, the existing sintering driving force of a high-entropy boride system is insufficient, the densification degree of the existing high-entropy boride system is seriously dependent on extremely high sintering temperature and external pressure which are far higher than the melting point of the components of the high-entropy boride system, so that not only is the serious challenge for equipment and energy consumption provided, but also the abnormal growth of crystal grains is inevitably caused by long-term exposure at high temperature, and the mechanical property of the material is damaged. Therefore, the contradiction between the hardness and the thermal stability of the existing high-entropy material is broken through, the high-stability strengthening phase such as nano twin crystals is intrinsically constructed in the high-entropy material through innovative microstructure design, and the preparation method which is relatively mild and accurately controllable is assisted, so that the high-stability strengthening phase becomes a key science and technical problem for realizing the performance crossing of the next-generation super-hard material. Disclosure of Invention The invention aims to provide a high-stability rubidium boron silicon superhard compound and a preparation method thereof, so as to solve the technical problem that the hardness of the existing superhard material is remarkably attenuated and the microstructure is instable in an extremely high-temperature environment. In order to achieve the above object, the present invention provides the following solutions: The super hard compound is a composite structure block material formed by taking rubidium-boron-silicon as a basic skeleton and introducing an alkali metal regulator, wherein the composite structure comprises a high-entropy ceramic matrix and nano twin crystals distributed in the matrix, the high-entropy ceramic matrix is a solid solution composed of rubidium, boron, silicon and alkali metal cations introduced by the alkali metal regulator, and the nano twin crystals are lamellar crystal structures with coherent twin crystal boundaries. Specifically, the alkali metal cation is any one of potassium ion,