An impact-resistant boron carbide ceramic composite material and a method for preparing the same

Abstract

The application provides an impact-resistant boron carbide ceramic composite material and a preparation method thereof, and belongs to the technical field of ceramic composite materials. TiB2@carbon nanometer pinning agents are introduced, the carbon shells of which can not only prevent nano-particle agglomeration, but also purify the particle surfaces, so that the TiB2 cores can effectively pin grain boundaries and refine grains to improve the hardness and strength of the material; the high-activity precursors are used to form a silicon carbide-boron nitride composite whisker network in a sintering process, which can improve the fracture toughness of the material through crack deflection and bridging mechanisms; the introduced amorphous precursors form a liquid phase at high temperatures to promote densification, and are solidified into a tough amorphous interface phase after cooling to passivate micro-cracks; the three components cooperatively build an energy absorption chain, so that the composite material is endowed with excellent impact resistance, and through the inhibition of abnormal grain growth in the high-temperature sintering stage, the strengthening of grain boundary bonding and the construction of a continuous reinforcing framework, the stability of the material under high-temperature conditions is improved.

Description

Technical Field

[0001] This invention belongs to the field of ceramic composite materials technology, and relates to an impact-resistant boron carbide ceramic composite material and its preparation method. Background Technology

[0002] Boron carbide ceramics, due to their low density, ultra-high hardness, high neutron absorption cross section, and excellent chemical stability, have shown broad application prospects in high-tech fields such as national defense, nuclear industry, and wear-resistant components. However, their strong covalent bond structure and intrinsic brittleness result in extremely low fracture toughness, making them highly susceptible to catastrophic brittle fracture under impact loads. This severely limits their reliability and application range as structural protection materials. Furthermore, the high temperature required for densification sintering of boron carbide and the tendency for abnormal grain growth during sintering further degrade their mechanical properties.

[0003] In metallurgical, thermal equipment, and high-temperature wear conditions, boron carbide ceramics, in addition to impact and crack resistance, must maintain stable microstructure and interface bonding at high temperatures to prevent grain boundary weakening and defect evolution from leading to a decrease in load-bearing capacity. On the other hand, high-temperature, long-term sintering results in higher energy consumption and a narrower process window, which is also detrimental to green manufacturing.

[0004] Existing technologies typically employ physical blending to introduce second-phase reinforcements such as silicon carbide and titanium diboride, along with sintering aids to reduce densification difficulties. However, the added reinforcing phase powder is prone to agglomeration during mixing, resulting in uneven distribution within the matrix and hindering the achievement of ideal reinforcement and toughening effects. It may even become a new source of defects. Secondly, impurities such as oxides on the surface of boron carbide and reinforcing phase particles weaken the bonding strength at the phase interface, making the interface a weak point for crack propagation. Furthermore, in high-temperature applications, the low-melting-point / non-ideal interface layer formed by the additives at grain boundaries may introduce new weak points, thus affecting the integrity and long-term stability of the heat-resistant structure. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an impact-resistant boron carbide ceramic composite material and its preparation method. This application constructs a synergistically toughened impact-resistant boron carbide ceramic system by introducing three functionalized additives: The introduction of a core-shell structured titanium boride@carbon nanoparticle pinning agent effectively prevents nanoparticle aggregation, ensuring uniform dispersion and pinning at grain boundaries, thereby inhibiting grain growth and refining grains to improve the material's hardness and strength. Furthermore, the outer carbon shell can purify oxides on the particle surface in situ during sintering, laying the foundation for a strong bond between phases. Utilizing a carbon support loaded with a highly active precursor, a silicon carbide-boron nitride composite whisker network is generated in situ during sintering. These whiskers, acting as a three-dimensional skeleton, absorb a large amount of fracture energy through crack deflection, bridging, and other mechanisms, endowing the material with excellent fracture toughness. Simultaneously, the introduced amorphous precursor melts at high temperatures to form a liquid phase, greatly promoting material densification and forming a tough amorphous phase at the grain boundaries after rapid cooling, passivating microcracks. These three elements work together to form a close synergy, ultimately creating an energy absorption chain within the material: the refined grains provide initial resistance, the amorphous phase at the interface absorbs microcrack energy, and the whisker network hinders the propagation of macrocracks. This synergistic effect endows the composite material with excellent comprehensive impact resistance.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing an impact-resistant boron carbide ceramic composite material, the method comprising:

[0008] S1: Prepare a toluene solution of polycarbosilane; add boric acid and melamine to anhydrous ethanol to obtain solution A, mix solution A with the toluene solution of polycarbosilane to obtain a mixed impregnation solution, add mesoporous carbon powder to the mixed impregnation solution and stir to impregnate, rotary evaporate to obtain coarse powder, and heat treat the coarse powder under an argon atmosphere to obtain an in-situ silicon carbide-boron nitride composite whisker precursor;

[0009] S2: Prepare a titanium boride deionized water suspension, add glucose to obtain reaction solution B, transfer reaction solution B to a reaction vessel, react, centrifuge, wash and dry to obtain titanium boride@polymer precursor powder; treat the titanium boride@polymer precursor powder under an argon atmosphere, cool naturally and grind to obtain titanium boride@carbon nanoparticle pinning agent.

[0010] S3: Under argon protection, aluminum powder, nickel powder, yttrium powder and cobalt powder are weighed and mixed to obtain mixed metal powder, which is then ball-milled in a planetary ball mill to obtain an amorphous precursor;

[0011] S4: Boron carbide matrix powder, in-situ silicon carbide-boron nitride composite whisker precursor, titanium boride@carbon nanoparticle pinning agent and amorphous precursor are mixed by wet ball milling to obtain a mixed slurry. The mixed slurry is dried and sieved to obtain composite powder. It is loaded into a graphite mold and sintered by spark plasma sintering. After furnace cooling, impact-resistant boron carbide ceramic composite material is obtained.

[0012] As a preferred technical solution of the present invention, in step S1, the mass fraction of the polycarbosilane toluene solution is 10-20 wt.%, for example, it can be 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, or 20 wt.%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] In some optional embodiments, the molar ratio of boric acid to melamine is (2-3):1, for example, it can be 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3.0:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0014] In some optional embodiments, the boric acid in solution A has a mass fraction of 4-6 wt.%, for example, 4.0 wt.%, 4.2 wt.%, 4.4 wt.%, 4.6 wt.%, 4.8 wt.%, 5.0 wt.%, 5.2 wt.%, 5.4 wt.%, 5.6 wt.%, 5.8 wt.%, or 6.0 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0015] In some optional embodiments, the molar ratio of silicon atoms derived from polycarbosilane to boron atoms derived from boric acid in the mixed impregnation solution is (8-12):1, for example, it can be 8.0:1, 8.4:1, 8.8:1, 9.2:1, 9.6:1, 10.0:1, 10.4:1, 10.8:1, 11.2:1, 11.6:1 or 12.0:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0016] In some optional embodiments, the stirring and impregnation time is 2-4 hours, for example, it can be 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0017] In some optional embodiments, the total mass ratio of the mesoporous carbon powder to the polycarbosilane, boric acid and melamine in the mixed impregnation solution is 1:(1-2), for example, it can be 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.0, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0018] In some optional embodiments, the coarse powder is heat-treated in an argon atmosphere at a temperature of 600-700°C, for example, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, or 700°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0019] In some optional embodiments, the coarse powder is heat-treated in an argon atmosphere for 1-2 hours, for example, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0020] As a preferred embodiment of the present invention, in step S2, the mass fraction of titanium boride in the titanium boride suspension is 3-5 wt.%, for example, it can be 3.0 wt.%, 3.2 wt.%, 3.4 wt.%, 3.6 wt.%, 3.8 wt.%, 4.0 wt.%, 4.2 wt.%, 4.4 wt.%, 4.6 wt.%, 4.8 wt.%, or 5.0 wt.%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] In some alternative embodiments, the mass ratio of glucose to titanium boride is 1:(2-4), for example, it can be 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3.0, 1:3.2, 1:3.4, 1:3.6, 1:3.8 or 1:4.0, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0022] In some optional embodiments, the hydrothermal reaction temperature of the reaction solution B is 160-190°C, for example, it can be 160°C, 163°C, 166°C, 169°C, 172°C, 175°C, 178°C, 181°C, 184°C, 187°C or 190°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0023] In some optional embodiments, the hydrothermal reaction time of the reaction solution B is 6-12 hours, for example, 6.0 hours, 6.6 hours, 7.2 hours, 7.8 hours, 8.4 hours, 9.0 hours, 9.6 hours, 10.2 hours, 10.8 hours, 11.4 hours, or 12.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the titanium boride@polymer precursor powder is treated in an argon atmosphere at a temperature of 700-900°C, for example, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C, or 900°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the titanium boride@polymer precursor powder is treated in an argon atmosphere for 1-2 hours, for example, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0026] In a preferred embodiment of the present invention, in step S3, the mass ratio of aluminum powder, nickel powder, yttrium powder, and cobalt powder is (70-72):(13-15):(10-12):(3-4), for example, it can be (70.0, 70.2, 70.4, 70.6, 70.8, 71.0, 71.2, 71.4, 71.6, 71.8, or 72.0):(13.0, 13.2, 13.4, 13.6, 13.8, 14.0). 14.2, 14.4, 14.6, 14.8 or 15.0: (10.0, 10.2, 10.4, 10.6, 10.8, 11.0, 11.2, 11.4, 11.6, 11.8 or 12.0): (3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 or 4.0), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0027] In some optional embodiments, the ball-to-material mass ratio during the ball milling of the mixed metal powder is (10-20):1, for example, it can be 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 or 20:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0028] In some optional embodiments, the rotational speed of the ball mill for mixing metal powder is 200-400 rpm, for example, 200 rpm, 220 rpm, 240 rpm, 260 rpm, 280 rpm, 300 rpm, 320 rpm, 340 rpm, 360 rpm, 380 rpm or 400 rpm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the ball milling time of the mixed metal powder is 20-40 hours, for example, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours or 40 hours, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0030] As a preferred embodiment of the present invention, in step S4, the mass ratio of the boron carbide matrix powder, the in-situ silicon carbide-boron nitride composite whisker precursor, the titanium boride@carbon nanoparticle pinning agent, and the amorphous precursor is (75-85):(5-12):(2-5):(3-8), for example, it can be (75, 76, 77, 78, 79, 80, 81, 82, 83, 84 or 85):(5.0, 5.7, 6.4, 7.1, 7. 8, 8.5, 9.2, 9.9, 10.6, 11.3 or 12.0: (2.0, 2.3, 2.6, 2.9, 3.2, 3.5, 3.8, 4.1, 4.4, 4.7 or 5.0): (3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5 or 8.0), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0031] In some optional embodiments, the first heating rate during sintering of the composite powder is 50-80℃ / min, for example, it can be 50℃ / min, 53℃ / min, 56℃ / min, 59℃ / min, 62℃ / min, 65℃ / min, 68℃ / min, 71℃ / min, 74℃ / min, 77℃ / min or 80℃ / min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the first temperature for sintering the composite powder is 1450-1550°C, for example, it can be 1450°C, 1460°C, 1470°C, 1480°C, 1490°C, 1500°C, 1510°C, 1520°C, 1530°C, 1540°C or 1550°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the axial pressure during the sintering of the composite powder to the first temperature is 10-15 MPa, for example, it can be 10.0 MPa, 10.5 MPa, 11.0 MPa, 11.5 MPa, 12.0 MPa, 12.5 MPa, 13.0 MPa, 13.5 MPa, 14.0 MPa, 14.5 MPa or 15.0 MPa, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] In some optional embodiments, the holding time at the first temperature during sintering of the composite powder is 5-10 min, for example, it can be 5.0 min, 5.5 min, 6.0 min, 6.5 min, 7.0 min, 7.5 min, 8.0 min, 8.5 min, 9.0 min, 9.5 min or 10.0 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the axial pressure during the holding stage at the first temperature when the composite powder is sintered is 40-60 MPa, for example, it can be 40 MPa, 42 MPa, 44 MPa, 46 MPa, 48 MPa, 50 MPa, 52 MPa, 54 MPa, 56 MPa, 58 MPa or 60 MPa, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the second heating rate during sintering of the composite powder is 90-100℃ / min, for example, it can be 90℃ / min, 91℃ / min, 92℃ / min, 93℃ / min, 94℃ / min, 95℃ / min, 96℃ / min, 97℃ / min, 98℃ / min, 99℃ / min or 100℃ / min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0037] In some optional embodiments, the second temperature for sintering the composite powder is 1750-1850°C, for example, it can be 1750°C, 1760°C, 1770°C, 1780°C, 1790°C, 1800°C, 1810°C, 1820°C, 1830°C, 1840°C or 1850°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0038] In some optional embodiments, the holding time at the second temperature during sintering of the composite powder is 3-5 min, for example, it can be 3.0 min, 3.2 min, 3.4 min, 3.6 min, 3.8 min, 4.0 min, 4.2 min, 4.4 min, 4.6 min, 4.8 min or 5.0 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] Secondly, the present invention provides an impact-resistant boron carbide ceramic composite material.

[0040] This application introduces three functionalized additives to construct a multi-scale, in-situ self-generated reinforcement and toughening system to improve the impact resistance of boron carbide ceramics. A composite structure consisting of a micron-sized whisker framework, nanoparticle-pinned grain boundaries, and an amorphous interface layer is formed through sintering.

[0041] First, an in-situ silicon carbide-boron nitride composite whisker precursor is introduced to construct a three-dimensional reinforcing network. By uniformly impregnating polycarbosilane and boric acid / melamine into a high-specific-surface-area mesoporous carbon support, a highly active precursor dominated by the Si–C–B–N amorphous phase is formed during a low-temperature pretreatment stage at 600-700℃, and fixed within the pores and surface of the mesoporous carbon support. During the subsequent high-temperature sintering stage, this amorphous network decomposes, releasing silicon-containing gaseous substances. These gaseous substances, catalyzed by the liquid phase formed by the melting of the amorphous precursor, in-situ grow silicon carbide whiskers with large aspect ratios in the interparticle spaces. Simultaneously, boron nitride components form on or near the whisker surface, constituting a unique silicon carbide-boron nitride composite structure. When cracks propagate, these whiskers can consume fracture energy through mechanisms such as crack deflection, thereby improving the fracture toughness of the material.

[0042] Secondly, titanium boride@carbon nanoparticle pinning agents are introduced to strengthen grain boundaries and purify interfaces at the nanoscale. A core-shell structure is formed by uniformly coating the surface of titanium boride nanoparticles with a carbon shell using a hydrothermal method. This carbon shell acts as a steric hindrance during mixing and the initial heating phase, effectively preventing the hard agglomeration of titanium boride nanoparticles and ensuring their uniform dispersion at the boron carbide grain boundaries after sintering. During sintering, the carbon shell also undergoes a carbothermic reduction reaction with the unavoidable oxides on the surface of the boron carbide particles, generating a cleaner and stronger ceramic-ceramic interface. Ultimately, these uniformly distributed ultra-hard titanium boride nanoparticles at the grain boundaries effectively suppress abnormal growth of boron carbide grains during sintering through the grain boundary pinning effect. The refined grains improve the hardness and strength of the material, providing a higher threshold for resisting impact loads.

[0043] Furthermore, the introduction of amorphous precursors enables the construction of tough amorphous interface phases. This multi-element alloy has a low eutectic point and is pre-amorphized under high-energy ball milling to enhance its activity. At the first holding plateau of sintering (1450-1550℃), the precursor melts to form a small amount of liquid phase. The presence of the liquid phase promotes the densification process: on the one hand, it facilitates rapid particle rearrangement through capillary forces; on the other hand, it provides a high-speed channel for mass migration, accelerating the formation of sintering necks. The temperature is then programmed to a higher second plateau (1750-1850℃) to eliminate the last remaining porosity by activating atomic diffusion and to promote strong interfacial bonding between phases, thereby achieving final densification and structural strengthening of the material. After furnace cooling, a composite interface layer dominated by amorphous phases forms at the grain boundaries, making the grain boundary bonding more continuous and stable. This reduces the risk of interface weakening and crack propagation at high temperatures to some extent, helping to maintain structural integrity. During the rapid cooling stage after sintering, the molten multi-element alloy preferentially forms a composite interface layer dominated by amorphous phase and locally accompanied by nanoscale intermetallic compounds / borides / carbides due to its complex composition and high cooling rate. This interface layer has higher fracture energy and certain plasticity than the brittle ceramic interface, which helps to passivate crack tips and absorb impact energy.

[0044] Meanwhile, these three additives exhibit a synergistic effect. The liquid phase formed by the amorphous precursor not only promotes its own densification but also provides an ideal catalytic environment and mass transfer medium for the in-situ growth of silicon carbide whiskers. Simultaneously, the interface-cleansing effect of titanium boride@carbon nanoparticle pinning agent creates favorable conditions for good wetting and strong bonding between the liquid phase and the boron carbide matrix. When resisting impact loads, this synergistic effect manifests as a multi-scale, progressive energy absorption chain: impact stress is first resisted by the refined grains and high-hardness matrix; when microcracks initiate, their propagation is hindered and passivated by the tough amorphous phase at the grain boundaries; and for macroscopic cracks penetrating the first two lines of defense, they are effectively deflected and bridged by the micron-scale silicon carbide-boron nitride whisker network, ultimately exhausting their energy. It is this synergistic toughening mechanism that enables the final boron carbide ceramic composite material to achieve excellent impact resistance.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] This application describes the in-situ generation of a micron-sized silicon carbide-boron nitride composite whisker reinforcement network within a boron carbide ceramic matrix during the high-temperature sintering stage. This is achieved by first preparing a highly active amorphous intermediate product on a carbon support, and then, during high-temperature sintering, utilizing liquid-phase catalysis to decompose this intermediate product. This allows for the growth of silicon carbide-boron nitride composite whiskers within the interparticle gaps. The resulting whisker network effectively hinders crack propagation and absorbs significant amounts of fracture energy through crack deflection, bridging, and pull-out mechanisms, thereby enhancing the fracture toughness of the composite material. Simultaneously, this in-situ self-generated ceramic whisker reinforcement framework is less prone to softening failure under high-temperature conditions, helping to maintain the continuity of the reinforcement network and the stability of the load-bearing path, thus improving the integrity of the heat-resistant structure.

[0047] The boronized titanium@carbon nanoparticle pinning agent introduced in this application achieves dual functions of grain boundary strengthening and interface purification at the nanoscale through its core-shell structure. The outer carbon shell prevents the internal boronized titanium nanoparticles from agglomerating during mixing and heating, and also acts as a reducing agent to remove oxides from the surface of boron carbide during sintering, thus ensuring a clean and strong interfacial bond. This allows the internal boronized titanium core to be uniformly dispersed and effectively "pinned" at the grain boundaries, refining the grains by inhibiting boron carbide grain growth, ultimately improving the hardness and strength of the composite material and enhancing its impact resistance. Furthermore, the clean and strong ceramic-ceramic interface bond can reduce the possibility of interface degradation at high temperatures to a certain extent, helping the material maintain structural integrity and stability under high-temperature conditions.

[0048] This application introduces an amorphous precursor to construct a tough amorphous interface phase. This amorphous precursor plays a dual role: during sintering, it first melts to form a liquid phase, significantly accelerating material densification by promoting particle rearrangement and mass migration; in subsequent rapid cooling, this liquid phase solidifies into a tough amorphous interface phase. This amorphous phase can absorb a large amount of energy through a unique deformation mechanism when the material is subjected to impact, effectively passivating and inhibiting crack propagation; furthermore, the presence of this continuous grain boundary phase helps to mitigate interfacial stress concentration under high-temperature conditions and reduce the tendency for microcracks to rapidly propagate along grain boundaries, thereby improving the integrity of the heat-resistant structure.

[0049] There is a synergistic effect among these three additives. During sintering, the liquid phase formed by the amorphous precursor not only promotes overall densification but also provides a catalytic environment and mass transfer medium for the in-situ growth of silicon carbide whiskers, while the interface purification effect of titanium boride@carbon pinning agent ensures good bonding between the phases. This synergistic effect ultimately constructs an impact energy absorption system: first, grain refinement provides high initial resistance; second, the tough amorphous phase at the interface is responsible for hindering and passivating microcracks; finally, the whisker network dissipates the energy of macrocracks through deflection and bridging. It is this integrated synergistic toughening mechanism that endows the composite material with excellent impact resistance. Attached Figure Description

[0050] Figure 1 : A physical image of the in-situ silicon carbide-boron nitride composite whisker precursor prepared in Example 1 of this application;

[0051] Figure 2 : A physical image of the titanium boride@carbon nanoparticle pinning agent prepared in Example 1 of this application. Detailed Implementation

[0052] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that employ any obvious substitutions and modifications made to the embodiments described herein.

[0053] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0054] Example 1

[0055] This embodiment provides an impact-resistant boron carbide ceramic composite material and its preparation method. The preparation method of the impact-resistant boron carbide ceramic composite material specifically includes the following steps:

[0056] S1: Prepare a toluene solution of polycarbosilane with a mass fraction of 18 wt.%; add boric acid and melamine to anhydrous ethanol to obtain solution A, wherein the molar ratio of boric acid to melamine is 2.8:1, and the mass fraction of boric acid in solution A is 5.5 wt.%; mix solution A with the toluene solution of polycarbosilane to obtain a mixed impregnation solution, wherein the molar ratio of silicon atoms derived from polycarbosilane to boron atoms derived from boric acid in the mixed impregnation solution is 9:1; add mesoporous carbon powder to the mixed impregnation solution and stir and impregnate for 3.5 h, wherein the total mass ratio of mesoporous carbon powder to polycarbosilane, boric acid and melamine in the mixed impregnation solution is 1:1.8; rotary evaporation to obtain coarse powder, which is heat-treated at 620℃ for 1.2 h under argon atmosphere to obtain in-situ silicon carbide-boron nitride composite whisker precursor; Figure 1 The image shows an in-situ silicon carbide-boron nitride composite whisker precursor. It can be observed that the whole is a gray-black powder, mainly composed of fine particles, with a small number of small particle agglomerates visible in some areas. After the powder is piled up, it forms a natural cone / mound shape, with scattered fine powder particles visible at the edges, showing a certain degree of flowability and dispersibility.

[0057] S2: Prepare a titanium boride deionized water suspension with a titanium boride mass fraction of 4.5 wt.% and add glucose to obtain reaction solution B, wherein the mass ratio of glucose to titanium boride is 1:3.5. Transfer reaction solution B to a reaction vessel and react at 170℃ for 8 h. Centrifuge, wash, and dry to obtain titanium boride@polymer precursor powder. Treat it at 750℃ for 1.3 h under an argon atmosphere, and then allow it to cool naturally and grind to obtain titanium boride@carbon nanoparticle pinning agent. Figure 2 The image shows a titanium boride@carbon nanoparticle pinning agent. It is a blackish-gray powder. After the powder is spread, the surface is relatively flat, the particles are fine, and there are no obvious large lumps, indicating a good degree of fine powdering.

[0058] S3: Under argon protection, aluminum powder, nickel powder, yttrium powder and cobalt powder are weighed and mixed to obtain a mixed metal powder, wherein the mass ratio of aluminum powder, nickel powder, yttrium powder and cobalt powder is 71:14:11:3.5. The mixture is then placed in a planetary ball mill and ball-milled to obtain an amorphous precursor; wherein the ball-to-material mass ratio is 18:1, the ball milling speed is 250 rpm, and the ball milling time is 25 h.

[0059] S4: Boron carbide matrix powder, in-situ silicon carbide-boron nitride composite whisker precursor, titanium boride@carbon nanoparticle pinning agent, and amorphous precursor are wet-milled to obtain a mixed slurry, wherein the mass ratio of boron carbide matrix powder, silicon carbide-boron nitride nanocomposite whisker precursor, titanium boride@carbon nanoparticle pinning agent, and amorphous precursor is 80:8:3:5; the mixed slurry is dried and sieved to obtain composite powder, which is then placed in a graphite mold and sintered using spark plasma sintering, followed by furnace cooling to obtain impact-resistant boron carbide ceramic composite material. The sintering procedure is as follows: heating to a first temperature of 1480℃ at a first heating rate of 60℃ / min, with an axial pressure of 11MPa during the heating process, followed by holding at the first temperature for 6min, with an axial pressure of 45MPa during the holding stage; heating to a second temperature of 1780℃ at a second heating rate of 92℃ / min and holding for 3.5min.

[0060] Example 2

[0061] This embodiment provides an impact-resistant boron carbide ceramic composite material and its preparation method. The preparation method of the impact-resistant boron carbide ceramic composite material specifically includes the following steps:

[0062] S1: Prepare a toluene solution of polycarbosilane with a mass fraction of 10 wt.%; add boric acid and melamine to anhydrous ethanol to obtain solution A, wherein the molar ratio of boric acid to melamine is 2:1, and the mass fraction of boric acid in solution A is 4 wt.%; mix solution A with the toluene solution of polycarbosilane to obtain a mixed impregnation solution, wherein the molar ratio of silicon atoms derived from polycarbosilane to boron atoms derived from boric acid in the mixed impregnation solution is 12:1; add mesoporous carbon powder to the mixed impregnation solution and stir and impregnate for 2 hours, wherein the total mass ratio of mesoporous carbon powder to polycarbosilane, boric acid and melamine in the mixed impregnation solution is 1:1; rotary evaporation to obtain coarse powder, which is heat-treated at 700℃ for 2 hours under argon atmosphere to obtain an in-situ silicon carbide-boron nitride composite whisker precursor.

[0063] S2: Prepare a titanium boride deionized water suspension with a titanium boride mass fraction of 3 wt.%, add glucose to obtain reaction solution B, wherein the mass ratio of glucose to titanium boride is 1:2. Transfer reaction solution B to a reaction vessel and react at 190℃ for 12 h. Centrifuge, wash and dry to obtain titanium boride@polymer precursor powder. Treat it at 900℃ for 2 h under argon atmosphere, cool naturally and grind to obtain titanium boride@carbon nanoparticle pinning agent.

[0064] S3: Under argon protection, aluminum powder, nickel powder, yttrium powder and cobalt powder are weighed and mixed to obtain mixed metal powder, wherein the mass ratio of aluminum powder, nickel powder, yttrium powder and cobalt powder is 72:13:10:4. The mixture is then placed in a planetary ball mill and ball-milled to obtain an amorphous precursor; wherein the ball-to-material mass ratio is 10:1, the ball milling speed is 400 rpm, and the ball milling time is 40 h.

[0065] S4: Boron carbide matrix powder, in-situ silicon carbide-boron nitride composite whisker precursor, titanium boride@carbon nanoparticle pinning agent, and amorphous precursor are wet-milled to obtain a mixed slurry, wherein the mass ratio of boron carbide matrix powder, silicon carbide-boron nitride nanocomposite whisker precursor, titanium boride@carbon nanoparticle pinning agent, and amorphous precursor is 85:5:5:3; the mixed slurry is dried and sieved to obtain composite powder, which is then placed in a graphite mold and sintered using spark plasma sintering. The powder is then cooled in the furnace to obtain an impact-resistant boron carbide ceramic composite material. The sintering procedure is as follows: the temperature is increased to a first temperature of 1550℃ at a first heating rate of 80℃ / min, with an axial pressure of 15MPa during the heating process; then the temperature is held at the first temperature for 10min, with an axial pressure of 60MPa during the holding stage; finally, the temperature is increased to a second temperature of 1850℃ at a second heating rate of 100℃ / min and held for 5min.

[0066] Example 3

[0067] This embodiment provides an impact-resistant boron carbide ceramic composite material and its preparation method. The preparation method of the impact-resistant boron carbide ceramic composite material specifically includes the following steps:

[0068] S1: Prepare a toluene solution of polycarbosilane with a mass fraction of 12 wt.%; add boric acid and melamine to anhydrous ethanol to obtain solution A, wherein the molar ratio of boric acid to melamine is 2.2:1, and the mass fraction of boric acid in solution A is 4.5 wt.%; mix solution A with the toluene solution of polycarbosilane to obtain a mixed impregnation solution, wherein the molar ratio of silicon atoms derived from polycarbosilane to boron atoms derived from boric acid in the mixed impregnation solution is 11:1; add mesoporous carbon powder to the mixed impregnation solution and stir and impregnate for 2.5 h, wherein the mass ratio of mesoporous carbon powder to the total solid solutes of polycarbosilane, boric acid and melamine in the mixed impregnation solution is 1:1.2; rotary evaporation to obtain coarse powder, which is heat-treated at 680 °C for 1.8 h under argon atmosphere to obtain in-situ silicon carbide-boron nitride composite whisker precursor.

[0069] S2: Prepare a titanium boride deionized water suspension with a titanium boride mass fraction of 3.5 wt.% and add glucose to obtain reaction solution B, wherein the mass ratio of glucose to titanium boride is 1:2.5. Transfer reaction solution B to a reaction vessel and react at 180℃ for 10 h. Centrifuge, wash, and dry to obtain titanium boride@polymer precursor powder. Treat it at 850℃ for 1.7 h under an argon atmosphere, and then allow it to cool naturally and grind to obtain titanium boride@carbon nanoparticle pinning agent.

[0070] S3: Under argon protection, aluminum powder, nickel powder, yttrium powder and cobalt powder are weighed and mixed to obtain a mixed metal powder, wherein the mass ratio of aluminum powder, nickel powder, yttrium powder and cobalt powder is 70:15:12:3. The mixture is then placed in a planetary ball mill and ball-milled to obtain an amorphous precursor; wherein the ball-to-material mass ratio is 12:1, the ball milling speed is 350 rpm, and the ball milling time is 35 h.

[0071] S4: Boron carbide matrix powder, in-situ silicon carbide-boron nitride composite whisker precursor, titanium boride@carbon nanoparticle pinning agent, and amorphous precursor are wet-milled to obtain a mixed slurry, wherein the mass ratio of boron carbide matrix powder, silicon carbide-boron nitride nanocomposite whisker precursor, titanium boride@carbon nanoparticle pinning agent, and amorphous precursor is 75:12:2:8; the mixed slurry is dried and sieved to obtain composite powder, which is then placed in a graphite mold and sintered using spark plasma sintering, followed by furnace cooling to obtain impact-resistant boron carbide ceramic composite material. The sintering procedure is as follows: heating to a first temperature of 1520℃ at a first heating rate of 70℃ / min, with an axial pressure of 14MPa during the heating process, followed by holding at the first temperature for 9min, with an axial pressure of 55MPa during the holding stage; heating to a second temperature of 1820℃ at a second heating rate of 98℃ / min and holding for 4.5min.

[0072] Example 4

[0073] This embodiment provides an impact-resistant boron carbide ceramic composite material and its preparation method. The preparation method of the impact-resistant boron carbide ceramic composite material specifically includes the following steps:

[0074] S1: Prepare a toluene solution of polycarbosilane with a mass fraction of 20 wt.%; add boric acid and melamine to anhydrous ethanol to obtain solution A, wherein the molar ratio of boric acid to melamine is 3:1 and the mass fraction of boric acid in solution A is 6 wt.%; mix solution A with the toluene solution of polycarbosilane to obtain a mixed impregnation solution, wherein the molar ratio of silicon atoms derived from polycarbosilane to boron atoms derived from boric acid in the mixed impregnation solution is 8:1; add mesoporous carbon powder to the mixed impregnation solution and stir and impregnate for 4 hours, wherein the total mass ratio of mesoporous carbon powder to the total solid solutes of polycarbosilane, boric acid and melamine in the mixed impregnation solution is 1:2; rotary evaporation to obtain coarse powder, which is then heat-treated at 600℃ for 1 hour under an argon atmosphere to obtain an in-situ silicon carbide-boron nitride composite whisker precursor.

[0075] S2: Prepare a titanium boride deionized water suspension with a titanium boride mass fraction of 5 wt.%, add glucose to obtain reaction solution B, wherein the mass ratio of glucose to titanium boride is 1:4. Transfer reaction solution B to a reaction vessel and react at 160℃ for 6 h. Centrifuge, wash and dry to obtain titanium boride@polymer precursor powder. Treat it at 700℃ for 1 h under argon atmosphere, cool naturally and grind to obtain titanium boride@carbon nanoparticle pinning agent.

[0076] S3: Under argon protection, aluminum powder, nickel powder, yttrium powder and cobalt powder are weighed and mixed to obtain a mixed metal powder, wherein the mass ratio of aluminum powder, nickel powder, yttrium powder and cobalt powder is 71.5:13.5:10.5:3.2. The mixture is then placed in a planetary ball mill and ball-milled to obtain an amorphous precursor; wherein the ball-to-material mass ratio is 20:1, the ball milling speed is 200 rpm, and the ball milling time is 20 h.

[0077] S4: Boron carbide matrix powder, in-situ silicon carbide-boron nitride composite whisker precursor, titanium boride@carbon nanoparticle pinning agent, and amorphous precursor are wet-milled to obtain a mixed slurry, wherein the mass ratio of boron carbide matrix powder, silicon carbide-boron nitride nanocomposite whisker precursor, titanium boride@carbon nanoparticle pinning agent, and amorphous precursor is 82:10:4:6; the mixed slurry is dried and sieved to obtain composite powder, which is then placed in a graphite mold and sintered using spark plasma sintering, followed by furnace cooling to obtain impact-resistant boron carbide ceramic composite material. The sintering procedure is as follows: heating to a first temperature of 1450℃ at a first heating rate of 50℃ / min, with an axial pressure of 10MPa during the heating process, followed by holding at the first temperature for 5min, with an axial pressure of 40MPa during the holding stage; heating to a second temperature of 1750℃ at a second heating rate of 90℃ / min and holding for 3min.

[0078] Comparative Example 1

[0079] This comparative example provides an impact-resistant boron carbide ceramic composite material. The difference from Example 1 is that uncoated titanium boride is used directly to replace the titanium boride@carbon nanoparticle pinning agent. Other operating steps and process parameters are exactly the same as in Example 1.

[0080] Comparative Example 2

[0081] This comparative example provides an impact-resistant boron carbide ceramic composite material. The difference from Example 1 is that a mixture of silicon carbide whiskers and boron nitride powder is used to directly replace the in-situ silicon carbide-boron nitride composite whisker precursor. Other operating steps and process parameters are exactly the same as in Example 1.

[0082] Comparative Example 3

[0083] This comparative example provides an impact-resistant boron carbide ceramic composite material. The difference between this example and Example 1 is that no amorphous precursor is added, while the other operating steps and process parameters are exactly the same as in Example 1.

[0084] Comparative Example 4

[0085] This comparative example provides an impact-resistant boron carbide ceramic composite material. The difference between this example and Example 1 is that titanium boride@carbon nanopinning agent is not added, while other operating steps and process parameters are exactly the same as in Example 1.

[0086] Comparative Example 5

[0087] This comparative example provides an impact-resistant boron carbide ceramic composite material. The difference between this example and Example 1 is that no in-situ silicon carbide-boron nitride composite whisker precursor is added. All other operating steps and process parameters are exactly the same as in Example 1.

[0088] The impact-resistant boron carbide ceramic composite materials prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to performance testing, and the specific process is as follows:

[0089] The fracture toughness of the test samples was determined according to GB / T23806-2009;

[0090] The flexural strength of the test sample was determined according to GB / T6569-2006.

[0091] The high-temperature flexural strength (1000℃) of the sample was tested according to GB / T 14390-2008.

[0092] The actual density of the sample is measured according to Archimedes' principle; the theoretical density of the sample is calculated; and the compactness of the sample can then be calculated.

[0093] Density = (actual density / theoretical density) × 100%.

[0094] The test results are shown in Table 1.

[0095] Table 1. Performance test results of the impact-resistant boron carbide ceramic composite materials prepared in Examples 1-4 and Comparative Examples 1-5

[0096] Density (%) <![CDATA[Fracture toughness (MPa·m 1 / 2 )]]>< Flexural strength (MPa) High-temperature flexural strength (MPa) Example 1 98.8 7.5 940 750 Example 2 98.2 7.2 932 743 Example 3 98.9 7.4 920 732 Example 4 98.5 7.6 915 729 Comparative Example 1 92.1 6.0 700 425 Comparative Example 2 90.0 4.5 550 382 Comparative Example 3 81.4 3.0 350 154 Comparative Example 4 95.1 6.7 753 446 Comparative Example 5 96.2 5.3 880 527

[0097] As shown in Table 1, the test results of Example 1 and Comparative Example 1 reveal that replacing titanium boride@carbon nanoparticle pinning agent with uncoated exposed titanium boride nanoparticles results in the loss of the synergistic protection and purification function unique to the core-shell structure. The exposed nanoparticles, due to their high surface energy, are prone to agglomeration and cannot be uniformly dispersed at grain boundaries, significantly reducing their inhibitory effect on grain growth, leading to coarsening of the material grains and a decrease in flexural strength. Furthermore, the lack of in-situ reduction and purification by the carbon shell at high temperatures weakens the interfacial bonding strength due to impurities such as oxides on the particle surface, making cracks more likely to propagate along weak interfaces, thus reducing fracture toughness. Simultaneously, these nanoclusters may form micropores during sintering, reducing density. The exposed nanoparticles are more prone to agglomeration, and the weakened interfacial purification / protection effect makes it more difficult to maintain grain boundary pinning and interfacial bonding at high temperatures, resulting in a decrease in high-temperature flexural strength.

[0098] As shown in Table 1, the test results of Example 1 and Comparative Example 2 indicate that directly replacing the in-situ silicon carbide-boron nitride composite whisker precursor with a mixture of silicon carbide whiskers and boron nitride powder results in the inability of the physically blended components to form a synergistic structure synthesized in situ. High aspect ratio silicon carbide whiskers are prone to entanglement and agglomeration during the mixing process. These agglomerates not only fail to form a uniform three-dimensional reinforcing network but also become defect and porosity sources, leading to a decrease in material density and flexural strength. The whisker network, which serves as the core toughening mechanism, fails due to uneven distribution, and the physical interface bonding force is far weaker than that of the in-situ grown chemical interface, preventing crack bridging and pull-out mechanisms from functioning effectively, resulting in a decrease in the material's fracture toughness. Whisker entanglement and agglomeration, along with the formation of defects / porosity, make it easier for cracks to initiate and propagate from defects under high-temperature loads, leading to a decrease in high-temperature flexural strength.

[0099] As shown in Table 1, the test results of Example 1 and Comparative Example 3 reveal that the absence of the liquid phase formed by the amorphous precursor at high temperatures transforms the entire sintering process from liquid-phase sintering to solid-phase sintering. Under the same process conditions, material migration between particles becomes difficult, resulting in a large number of residual pores within the material and a decrease in density. High porosity reduces flexural strength and fracture toughness; the lack of a liquid phase promotes densification, leading to even higher residual pores, which reduces the effectiveness of the load-bearing section at high temperatures and decreases high-temperature flexural strength.

[0100] As shown in Table 1, the test results of Example 1 and Comparative Example 4 indicate that without the addition of titanium boride@carbon nanoparticle pinning agent, the density change is minimal due to the continued existence of the liquid-phase sintering mechanism. However, the absence of the pinning effect of nanoparticles at grain boundaries leads to boron carbide grain growth at high temperatures. This coarsened microstructure results in decreased flexural strength; simultaneously, the coarsened grains make crack propagation paths straighter, reducing the material's fracture toughness; and without grain boundary pinning, grains are more prone to coarsening at high temperatures, further reducing high-temperature flexural strength.

[0101] As shown in Table 1, the test results of Example 1 and Comparative Example 5 indicate that without the addition of the silicon carbide-boron nitride composite whisker precursor, the density and flexural strength do not change significantly because the grain refinement strengthening and liquid phase sintering mechanisms function normally. However, the fracture toughness of the material decreases because it loses the crack bridging and pull-out effect of the whisker network that resists macroscopic crack propagation. Densification and grain refinement strengthening are still present, but the energy-consuming effects of the whisker network on crack bridging / deflection are missing, resulting in insufficient resistance to macroscopic crack propagation at high temperatures and a decrease in high-temperature flexural strength.

[0102] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method of making an impact resistant boron carbide ceramic composite material, characterized by, The preparation method includes: S1: Prepare a toluene solution of polycarbosilane; add boric acid and melamine to anhydrous ethanol to obtain solution A, mix solution A with the toluene solution of polycarbosilane to obtain a mixed impregnation solution, add mesoporous carbon powder to the mixed impregnation solution and stir to impregnate, rotary evaporate to obtain coarse powder, and heat treat the coarse powder under an argon atmosphere to obtain an in-situ silicon carbide-boron nitride composite whisker precursor; S2: Prepare a titanium boride deionized water suspension, add glucose to obtain reaction solution B, transfer reaction solution B to a reaction vessel, react, centrifuge, wash and dry to obtain titanium boride@polymer precursor powder; treat the titanium boride@polymer precursor powder under an argon atmosphere, cool naturally and grind to obtain titanium boride@carbon nanoparticle pinning agent. S3: Under argon protection, aluminum powder, nickel powder, yttrium powder and cobalt powder are weighed and mixed to obtain mixed metal powder, which is then ball-milled in a planetary ball mill to obtain an amorphous precursor; S4: Boron carbide matrix powder, in-situ silicon carbide-boron nitride composite whisker precursor, titanium boride@carbon nanoparticle pinning agent and amorphous precursor are mixed by wet ball milling to obtain a mixed slurry. The mixed slurry is dried and sieved to obtain composite powder. It is loaded into a graphite mold and sintered by spark plasma sintering. After furnace cooling, impact-resistant boron carbide ceramic composite material is obtained.

2. The method of claim 1, wherein the method further comprises the step of: In S1: ​ The molar ratio of boric acid to melamine is (2-3):1; The boric acid has a mass fraction of 4-6 wt.% in solution A.

3. The method of claim 1, wherein the method further comprises the step of: In S1: ​ The molar ratio of silicon atoms derived from polycarbosilane to boron atoms derived from boric acid in the mixed impregnation solution is (8-12):1; The total mass ratio of the mesoporous carbon powder to the polycarbosilane, boric acid and melamine in the mixed impregnation solution is 1:(1-2).

4. The method for preparing an impact-resistant boron carbide ceramic composite material according to claim 1, characterized in that, In S2: The mass ratio of glucose to titanium boride is 1:(2-4).

5. The method for preparing an impact-resistant boron carbide ceramic composite material according to claim 1, characterized in that, In S2: The titanium boride@polymer precursor powder is treated at a temperature of 700-900℃ under an argon atmosphere. The titanium boride@polymer precursor powder is treated under an argon atmosphere for 1-2 hours.

6. The method for preparing an impact-resistant boron carbide ceramic composite material according to claim 1, characterized in that, In S3: The mass ratio of aluminum powder, nickel powder, yttrium powder and cobalt powder is (70-72):(13-15):(10-12):(3-4).

7. The method for preparing an impact-resistant boron carbide ceramic composite material according to claim 1, characterized in that, In S4: The mass ratio of the boron carbide matrix powder, the in-situ silicon carbide-boron nitride composite whisker precursor, the titanium boride@carbon nanopinning agent, and the amorphous precursor is (75-85):(5-12):(2-5):(3-8).

8. The method for preparing an impact-resistant boron carbide ceramic composite material according to claim 1, characterized in that, In S4: The first temperature during the sintering of the composite powder is 1450-1550℃; The composite powder is sintered at the first temperature for 5-10 minutes.

9. The method for preparing an impact-resistant boron carbide ceramic composite material according to claim 1, characterized in that, In S4: The second temperature during the sintering of the composite powder is 1750-1850℃; The holding time at the second temperature during the sintering of the composite powder is 3-5 minutes.

10. An impact-resistant boron carbide ceramic composite material prepared by the preparation method according to any one of claims 1-9.

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