Thermal-deterioration-resistant diamond-silicon carbide composite ceramic material and hot-pressing preparation process thereof

Abstract

This invention relates to the field of special ceramic product manufacturing technology, and discloses a heat-resistant diamond-silicon carbide multiphase ceramic material and its hot-pressing preparation process. The material includes diamond particles, a silicon carbide matrix, and a gradient transition layer located at the interface between the diamond particles and the silicon carbide matrix. The gradient transition layer includes a granular molybdenum carbide pinning layer attached to the surface of the diamond particles, and a molybdenum disilicide layer covering the outer surface of the molybdenum carbide pinning layer. The gradient transition layer also contains silicon boride components. This invention alleviates thermal stress concentration at the heterogeneous interface by constructing a discretely distributed granular pinning structure and a transition phase with a stepped distribution of phase elastic modulus. While blocking the penetration of liquid silicon into the diamond particle surface, it reduces the thermal conductivity resistance at the interface, ensuring the stability of the material's thermophysical properties under high-frequency thermal cycling conditions.

Description

Technical Field

[0001] This invention relates to a diamond-silicon carbide multiphase ceramic material resistant to thermal decay and its hot-pressing preparation process, belonging to the field of special ceramic product manufacturing technology. Background Technology

[0002] The conventional method for preparing diamond and silicon carbide multiphase ceramics is reaction sintering, which utilizes molten silicon to react chemically with carbon sources on the surface of diamond particles to generate a silicon carbide matrix. The initial thermal conductivity is improved by increasing the material density and the volume fraction of diamond. The reaction process between molten silicon and carbon atoms is accompanied by intense exothermic phenomena, resulting in a high density of crystal structure defects in the generated interfacial silicon carbide phase, forming initial phonon scattering centers. Under the alternating temperature field service environment of aerospace electronic power modules or high-energy laser mirrors, the diamond and silicon carbide matrix generate cyclic shear stress due to the mismatch of thermal expansion coefficients. The traditional reaction sintering interface is a continuous film-like coating. Due to the lack of an elastic stress dissipation mechanism, the interface undergoes submicron-level fatigue debonding under thermal cycling stress. This interfacial debonding causes the elastic transmission of phonons to change to scattering transmission, which manifests as an irreversible steep decline in the material's thermal conductivity with increasing cycle number.

[0003] To suppress performance degradation, conventional improvement methods often focus on adding transition metals to improve interfacial wettability and compensating for performance loss by increasing the diamond ratio. However, adding transition metals is unlikely to fundamentally interfere with the nucleation pathway of the silicon carbide interfacial phase, and an excessively high diamond ratio significantly increases the difficulty of green body forming and the penetration resistance of molten silicon, leading to an uneven residual stress field within the material. Precise control of the interfacial phase formation sequence and microstructure during the preparation process is crucial to the reliability of the material in service. For example, Chinese invention patent CN113307628A discloses a silicon carbide-diamond multiphase ceramic grinding ring material and its preparation method. It optimizes performance by adding boron carbide and oxide additives combined with a pressureless sintering process. This approach tends towards static homogeneous mixing of components and fails to establish an elastic buffer mechanism to address the thermal expansion mismatch and phonon scattering centers at the diamond-silicon carbide interface. up to 2100 Sintering environment induces thermal damage on the diamond surface. The resulting rigid continuous interface layer generates fatigue cracks that penetrate continuously under intense alternating temperature fields. The thermal conductivity decay is poorly controlled in the later stages of service, making it difficult to meet the requirements for thermal decay resistance.

[0004] Therefore, the technical problem to be solved by this invention is how to construct a discontinuous interface structure with elastic pinning function on the diamond surface through the coupling effect of interface components and process timing, thereby improving the thermal decay resistance of diamond and silicon carbide multiphase ceramic materials. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A thermally resistant diamond-silicon carbide multiphase ceramic material, comprising diamond particles, a silicon carbide matrix, and a gradient transition layer located at the interface between the diamond particles and the silicon carbide matrix: The gradient transition layer includes a molybdenum carbide pinning layer directly attached to the surface of the diamond particles. The molybdenum carbide pinning layer is composed of granular molybdenum carbide discretely distributed on the surface of the diamond particles. The granular molybdenum carbide combines with the lattice dislocations or steps on the surface of the diamond particles to form a pinning structure, which is used to construct the interface stress dissipation center and form a discontinuous interface connection. The gradient transition layer also includes a molybdenum disilicide layer covering the outer surface of the molybdenum carbide pinning layer, and the molybdenum disilicide layer forms a phase interface with the silicon carbide matrix; the gradient transition layer also contains silicon boride components, which are dissolved in the molybdenum disilicide layer and extend to the grain boundaries of the silicon carbide matrix, and the silicon boride components form a continuous physical barrier at the junction of the molybdenum disilicide layer and the silicon carbide matrix to block the penetration path of liquid silicon to the surface of diamond particles during the reaction sintering process; The gradient transition layer extends from the diamond particles toward the silicon carbide matrix, and the elastic modulus of its constituent phases exhibits a stepped distribution. The height of the individual protrusions in the molybdenum carbide pinning layer is less than the thickness of the molybdenum disilicide layer, and the molybdenum disilicide layer is in direct contact with the surface of the diamond particles at the gaps between the granular molybdenum carbide particles, and an overlapping phonon frequency distribution range is formed at the contact interface between the molybdenum disilicide layer and the diamond particles; the volume percentage content of the diamond particles is 40% to 70%.

[0006] Preferably, based on 100 parts by weight of the heat-resistant diamond-silicon carbide multiphase ceramic material, the content of diamond particles is 50 to 85 parts; the content of the molybdenum source component forming the gradient transition layer is 2 to 8 parts; the content of the boron source component forming the gradient transition layer is 0.5 to 3 parts; and the content of the silicon carbide matrix is ​​the balance to make up to 100 parts; wherein, the molybdenum source component is elemental molybdenum powder with an average particle size of 0.5 μm to 2 μm; the diamond particles include particles in a first particle size range and particles in a second particle size range, the average particle size of the particles in the first particle size range is 100 μm to 200 μm, and the average particle size of the particles in the second particle size range is 10 μm to 30 μm.

[0007] Preferably, the average thickness of the gradient transition layer is 50 nm to 500 nm; the molybdenum carbide phase in the molybdenum carbide pinning layer is hexagonal. The molybdenum disilicide phase in the molybdenum disilicide layer is tetragonal. .

[0008] Preferably, the projection coverage of the molybdenum carbide pinning layer on the diamond particle surface is 15% to 45%; the average spacing between adjacent granular molybdenum carbide in the molybdenum carbide pinning layer is greater than the average thickness of the molybdenum carbide pinning layer, so that the contact area formed by the molybdenum disilicide layer between the granular molybdenum carbide and the diamond particle surface accounts for 55% to 85% of the total surface area of ​​the diamond particle.

[0009] Preferably, the silicon boride component is Phase, and The concentration of the phase in the silicon carbide matrix decreases from the gradient transition layer into the interior of the silicon carbide matrix.

[0010] Preferably, the silicon carbide matrix includes silicon carbide generated by in-situ reaction and added silicon carbide micro powder; the average grain size of the silicon carbide generated by in-situ reaction is smaller than the average particle size of the added silicon carbide micro powder, and the silicon carbide generated by in-situ reaction is coated on the outer surface of the molybdenum disilicide layer.

[0011] Preferably, the elastic moduli of each constituent phase in the gradient transition layer satisfy the following relationship: ,in, This represents the elastic modulus of the diamond particle. The elastic modulus of the silicon carbide matrix. The elastic modulus of the molybdenum disilicide layer is given; the gradient transition layer, through the difference in elastic modulus distribution, mitigates the stress at the interface between the diamond particles and the silicon carbide matrix, which is at 20°C. Up to 600 Thermal stress concentration during thermal cycling.

[0012] Preferably, the mass ratio of molybdenum to boron in the gradient transition layer is 3:1 to 6:1; the molybdenum disilicide layer also contains silicon-boron-molybdenum ternary compound particles, the diamond particles have an amorphous carbon layer on their surface, the thickness of the amorphous carbon layer is less than 5 nm, and the particulate molybdenum carbide passes through the amorphous carbon layer and bonds with the lattice of the diamond particles.

[0013] Preferably, the density of the heat-resistant diamond-silicon carbide multiphase ceramic material is not less than 98.5%; the density of the heat-resistant diamond-silicon carbide multiphase ceramic material is within 20... Up to 600 After 500 cycles of cyclic heating within the specified range, its thermal conductivity decay rate is less than 5%.

[0014] A hot-pressing process for preparing a thermally resistant diamond-silicon carbide multiphase ceramic material includes the following steps: Step S111: The heat-resistant diamond-silicon carbide multiphase ceramic material is prepared by mixing diamond particles, molybdenum source components, boron source components and silicon carbide micro powder in parts by weight to obtain a mixed powder. Step S112: Place the mixed powder in a hot press mold and load it into a vacuum hot press furnace, where the vacuum degree is better than 10. The temperature was increased to 1200 Pa under the environment. Up to 1300 Keep warm for 30 to 90 minutes to allow the molybdenum source component to undergo a solid-phase reaction with the surface of the diamond particles and generate granular molybdenum carbide. Step S113, continue heating to 1500 Up to 1700 Liquid silicon was introduced, and an axial pressure of 10 MPa to 50 MPa was applied. The mixture was kept at the temperature and pressure for 30 to 60 minutes and then cooled to obtain a diamond-silicon carbide composite ceramic material resistant to thermal decay.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In diamond-silicon carbide composite ceramic materials, by controlling the solid-phase diffusion priority between elemental molybdenum and the surface of diamond particles, a discontinuous molybdenum carbide pinning layer is pre-constructed at the geometric singularity of the diamond surface before liquid-phase silicon infiltration. This breaks the physical morphology of continuous film coverage of the silicon carbide interface phase during reaction sintering, transforms the interfacial stress transmission mode from fully coupled force to discrete lattice dissipation, slows down the continuous crack propagation during thermoelastic fatigue, and solves the problem of thermal conductivity degradation caused by the mismatch of linear expansion coefficients between diamond and the matrix.

[0016] 2. The in-situ generated gradient transition layer containing molybdenum carbide and molybdenum disilicide achieves a smooth transition in elastic modulus, reducing the concentration of microscopic shear stress at the heterogeneous interface. Simultaneously, by utilizing the overlapping range of phonon frequency distributions between molybdenum disilicide and diamond, a phonon coupling transmission path is formed at the interface, reducing the thermal resistance of phonons passing through the heterogeneous interface and ensuring the thermophysical stability of the material under complex temperature fields and high-frequency thermal cycling conditions. The silicon boride component dissolves during the flow of liquid silicon and segregates at the phase boundary between molybdenum disilicide and silicon carbide, constructing distributed dynamic repair sites. This enables the material to have real-time sealing capabilities against thermal fatigue microcracks, achieving self-maintenance of the phonon transmission channel and ensuring the reliability of the multiphase ceramic material during long-term service.

[0017] 3. By mechanically integrating submicron-sized elemental molybdenum powder into the pits on the surface of diamond particles and through the synergistic effect of segmented heat treatment, the time-series control of the nucleation kinetics of the interfacial phase is achieved, transforming the interfacial reaction into an ordered topological structure, and changing the failure mode of the material from interfacial debonding to intracrystalline microplastic energy consumption. Without increasing the complexity of the preparation process, the structural integrity and thermal cycle life of the multiphase ceramic material are improved. Attached Figure Description

[0018] Figure 1This is a complete process flow diagram and a structural composition diagram of the finished product of the diamond silicon carbide multiphase ceramic of the present invention. Figure 2 This is a schematic diagram of the manual operation interaction and system closed-loop control logic of the hot pressing preparation process of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution will be described in detail below with reference to the embodiments of the present invention. The following embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0020] A heat-resistant diamond-silicon carbide multiphase ceramic material and its hot-pressing preparation process are disclosed. By weight, the material comprises 50 to 85 parts diamond particles, 2 to 8 parts elemental molybdenum powder, 0.5 to 3 parts elemental boron powder, and the balance silicon carbide matrix, to a total of 100 parts. The elemental molybdenum powder serves as the molybdenum source component, with an average particle size ranging from 0.5 μm to 2 μm. The diamond particles are a mixture of particles from a first particle size range and particles from a second particle size range, with the first particle size range having an average particle size of 100 μm to 200 μm and the second particle size range having an average particle size of 10 μm to 30 μm. This heat-resistant diamond-silicon carbide multiphase ceramic material includes diamond particles, a silicon carbide matrix, and... A gradient transition layer is located at the interface between the diamond particles and the silicon carbide matrix. The gradient transition layer includes a molybdenum carbide pinning layer attached to the surface of the diamond particles and a molybdenum disilicide layer covering the outer surface of the molybdenum carbide pinning layer. The gradient transition layer also contains silicon boride components as boron source components. To cope with the interfacial shear stress generated under the condition of mismatch between the linear expansion coefficients of diamond and silicon carbide matrix, the molybdenum carbide pinning layer is composed of granular molybdenum carbide discretely distributed on the surface of diamond particles, with an average thickness of 50 nm to 500 nm. The granular molybdenum carbide combines with the lattice dislocations or steps on the surface of diamond particles to form a discontinuous interfacial connection. By constructing a lattice dissipative structure, the crack propagation rate during thermal cycling is reduced.

[0021] In the gradient transition layer, the elastic modulus of the phases exhibits a step-like distribution from the diamond particles toward the silicon carbide matrix, specifically satisfying the following mathematical relationship: ,in, This represents the elastic modulus of the diamond particle. The elastic modulus of the silicon carbide matrix. The elastic modulus of the molybdenum disilicide layer; the molybdenum disilicide layer is composed of a tetragonal crystal system. The phase composition involves direct contact between the molybdenum carbide particles and the diamond particle surface at the gaps between the particles, forming a phonon coupling transport path. The silicon boride composition is... The concentration of the phase in the silicon carbide matrix decreases from the gradient transition layer into the interior of the silicon carbide matrix. When the material is at 20... Up to 600 When microcracks are generated during thermal cycling, they are distributed at the interface between the molybdenum disilicide layer and the silicon carbide substrate. A low-melting-point silicon-boron oxide liquid phase is generated and fills the microcracks; the silicon boride component utilizes oxygen atoms adsorbed on the surface of diamond particles and dissolved oxygen remaining in the liquid silicon as a reaction source, and selective oxidation occurs under the induction of high-energy states at the microcrack tips induced by thermal cycling. The vacuum desorption time is adjusted accordingly. To reduce the initial oxygen content on the diamond surface It remained in the range of 0.1% to 0.3%, of which To determine the duration of vacuum desorption, The oxygen content on the surface of diamond particles is the mass percentage. Liquid-phase silicon boron oxide is generated in a local low-oxygen partial pressure environment and fills the microcracks and voids. This enables the material to have the ability to repair thermal fatigue damage in situ in a near-fully dense state with a density of not less than 98.5%, and maintain the structural integrity of the phonon transmission channel.

[0022] The hot-pressing preparation process of the above materials is as follows: Diamond particles, elemental molybdenum powder, elemental boron powder, and silicon carbide micro powder are weighed according to the specified proportions and mixed in a planetary ball mill. The ball milling speed is set to 120 rpm, and the mixing time is 1.5 hours. Utilizing the pits on the surface of the diamond particles and the particle size difference of the elemental molybdenum powder, the submicron-sized molybdenum powder is mechanically embedded in the diamond surface. The mixed powder is placed in a hot-pressing mold and loaded into a vacuum hot-pressing furnace, where the vacuum degree is better than... The temperature began to rise in the environment, reaching 1200 degrees Celsius. Up to 1300 The temperature is maintained for 30 to 90 minutes. Within this temperature range, elemental molybdenum powder undergoes a solid-state diffusion reaction with the active carbon atoms on the surface of diamond particles, resulting in the in-situ formation of a hexagonal crystal system. Particles form a molybdenum carbide pinning layer. To control the projection coverage of the molybdenum carbide pinning layer on the diamond surface, the solid-phase reaction process is monitored. Phase and element Phase characteristic peak integral intensity ratio To determine the process termination time, during the holding period from 1200℃ to 1300℃, X-ray diffractometer was used to collect phase data of the pre-pinned green body and calculate the hexagonal crystal system. The (101) crystal plane peak and the elemental The intensity ratio of the (110) crystal plane peaks, where The ratio of the integral intensity of the two characteristic peaks is taken as the reference value. When this value reaches the range of 6.5 to 8.2, the heat preservation is stopped and the liquid phase silicon infiltration stage is initiated. This ensures that the particulate molybdenum carbide is discretely distributed on the diamond surface, avoids excessive reaction to form a continuous film, and solves the problem of the interfacial thermal resistance increasing with thickness. The temperature is then increased to 1500°C. Up to 1700 Liquid silicon is introduced, and an axial pressure of 10 MPa to 50 MPa is applied through a pressure head. After holding at this temperature and pressure for 30 to 60 minutes and then cooling, the liquid silicon preferentially reacts with particulate molybdenum carbide during infiltration to form a molybdenum disilicide layer, and then reacts with the remaining carbon source to form a silicon carbide matrix. The multiphase ceramic material prepared by the above process has a density of not less than 98.5%, and at 20... Up to 600 The material underwent 500 thermal cycling tests within the specified range. The test results showed that the thermal conductivity decay rate was less than 5%. The mass ratio of molybdenum to boron in the gradient transition layer was maintained in the range of 3:1 to 6:1. Silicon-boron-molybdenum ternary compound particles were also distributed in the molybdenum disilicide layer. The diamond particles had an amorphous carbon layer with a thickness of less than 5 nm on their surface. The granular molybdenum carbide passed through the amorphous carbon layer and bonded to the lattice of the diamond particles.

[0023] Example 1: In the high-frequency thermal cycling service scenario of a heat dissipation substrate for a high-power density electronic module, the substrate faces 20 Up to 600 The alternating temperature field impact causes cyclic shear stress concentration at the interface of diamond-silicon carbide ceramics prepared by reaction sintering due to the difference in thermal expansion coefficients between diamond particles and the silicon carbide matrix. This leads to debonding of the interface after service cycles, increasing phonon transmission resistance and causing an irreversible decrease in thermal conductivity. This embodiment provides a thermally resistant diamond-silicon carbide multiphase ceramic material. By implementing segmented temperature control in the vacuum hot pressing process described in the aforementioned specific embodiment, elemental molybdenum powder with an average particle size of 0.8 μm is mixed with diamond particles. Utilizing the gradation relationship between the elemental molybdenum powder and the diamond particle surface, submicron-sized molybdenum powder is embedded in the active sites on the diamond particle surface. This is achieved under a vacuum degree superior to... The temperature is 1250. Under certain operating conditions, solid-phase pre-pinning is performed. Through the diffusion reaction between elemental molybdenum powder and active carbon atoms on the surface of diamond particles, discretely distributed granular molybdenum carbide is generated in situ on the diamond surface. To achieve the cross-scale transformation from submicron scale to atomic-level bonding sites, submicron elemental molybdenum powder undergoes intense surface vapor-phase volatilization under a high-temperature, low-pressure environment of 1250℃. Driven by a micro-concentration gradient, the volatilized gaseous molybdenum atom clusters preferentially undergo vapor-phase deposition and physical trapping in high-surface free energy regions such as geometric pits, micro-cleavage steps, and carbon atom lattice dislocation outcrops on the diamond surface. Under the catalysis of high-energy states at dislocation points, they complete a micro-selective solid-phase carbonization reaction in situ with active carbon atoms near the dislocations. The resulting molybdenum carbide pinning layer transforms the interface connection from a continuous film structure to a discontinuous lattice-distributed structure. Elemental molybdenum powder at 1250℃ undergoes a high-temperature, low-pressure environment of 1250℃. The surface vapor-phase volatilization that occurs under high temperature and low pressure at 50℃ is essentially a chemical vapor transport kinetic process mediated by residual trace oxygen under closed pressure. Under this vacuum, trace active atoms on the surface of solid elemental molybdenum react locally with residual trace oxygen in the system, generating volatile molybdenum trioxide gas molecules with extremely high saturated vapor pressure in situ. These gas molecules are driven across tiny gaps by microscopic concentration gradients and are physically captured when they come into contact with geometric pits and lattice dislocation outcrops with high surface free energy on the surface of diamond particles. They are then immediately reduced by active carbon atoms on the diamond surface and transformed in situ into discrete hexagonal molybdenum carbide microcrystal nuclei. At the same time, carbon monoxide gas is released and extracted by the vacuum system, thus achieving efficient cross-scale mass transport and lattice-selective nucleation at a temperature far below the melting point of elemental molybdenum.

[0024] When the temperature rises to 1650 After the introduction of liquid silicon, the liquid silicon reacts with particulate molybdenum carbide and transforms into a tetragonal molybdenum disilicide layer, which together with the diamond particles and the silicon carbide matrix forms a gradient transition layer. The elastic modulus of this gradient transition layer exhibits a step-like distribution from the diamond particles towards the silicon carbide matrix, specifically satisfying the following mathematical relationship: ,in, This represents the elastic modulus of the diamond particle. The elastic modulus of the silicon carbide matrix. The elastic modulus of the molybdenum disilicide layer; the gradient transition layer utilizes a tetragonal crystal system. Stress relaxation characteristics under high-temperature conditions, combined with The elastic modulus is stepped, creating a flexible buffer region at the heterogeneous interface. This refers to the elastic modulus of diamond particles. The elastic modulus of the silicon carbide matrix. To improve the elastic modulus of the molybdenum disilicide layer, the residual compressive stress on the diamond surface was controlled within the range of 1.5 GPa to 2.5 GPa by adjusting the specific surface area ratio of elemental molybdenum powder to diamond. This counteracted the interfacial shear force caused by the mismatch in thermal expansion coefficients, reducing the fluctuation range of thermal conductivity under cyclic conditions. In the mechanical design of layered composite structures, the stepped distribution of phase elastic modulus refers to a mechanical gradation sequence at the multiphase micro-interface that is a non-monotonic geometric gradient but belongs to stress dissipation steps. By targeting and introducing an ultrathin tetragonal molybdenum disilicide intermediate layer with the lowest elastic modulus between the diamond reinforcing phase with ultra-high elastic modulus and the silicon carbide matrix phase with medium elastic modulus, a local mechanical softening buffer step was cleverly constructed in the spatial topology, making... The low-modulus layer exhibits preferential micro-plastic coordinated deformation and strain relaxation under cyclic shear loads at the heterogeneous interface. This acts as a physical-mechanical flexible buffer, breaking and smoothing the originally severe stress abrupt failure chain on both sides of the rigid heterogeneous interface, thus alleviating micro-stress concentration under high-frequency thermal cycling conditions. During this process, elemental boron powder precipitates at the phase boundary and forms silicon boride. The silicon boride forms a physical barrier against liquid silicon in the silicon carbide matrix and oxidizes to form a fluid silicon borosilicate glass phase when thermal stress induces microcracks. This liquid phase enters the microcrack voids and performs in-situ healing, thereby maintaining the integrity of the interfacial phonon transport channels. The diamond-silicon carbide multiphase ceramic material obtained in this embodiment has a density of 98.8%, and after 500 cycles of 20... Up to 600 After thermal cycling tests, the thermal conductivity measured by laser flash method changed from the initial 650 W / (m·K) to 618.8 W / (m·K), with a thermal conductivity decay rate of 4.8%. No signs of continuous cracks due to thermal fatigue were observed at the interface. Due to the rapid infiltration and reaction sintering of high-temperature liquid silicon under axial pressure, the multiphase ceramic material reached a near-fully dense state of greater than 98.5% in a very short time. This prevented a small portion of oxygen atoms originally adsorbed on the diamond surface and residual dissolved oxygen in the liquid silicon from completely diffusing out. Instead, they were forcibly blocked and trapped in microscopic nanoscale closed pores or stably existed in the form of interstitial solid solution in the boronized material. Within the lattice defects of silicon, a free oxygen storage microregion in a thermodynamically metastable state is constructed. When the material is subjected to high-frequency alternating temperature field impacts under subsequent service conditions, inducing thermoelastic fatigue microcracks, the severe stress concentration and local strain energy state of several gigapascals generated at the crack tip will immediately induce the structural collapse of the metastable storage microregion, releasing highly active free oxygen atoms in situ. This causes the free oxygen atoms to preferentially undergo localized selective oxidation reactions with the boronized silicon components on the crack surface at low temperature and high energy state, thereby continuously generating a low-melting-point silicon borosilicate glass phase with good fluidity and spontaneously healing cracks, realizing the in-situ damage self-repair closed loop inside the fully dense ceramic.

[0025] Example 2: In the experiment verifying the interfacial stability of the thermally resistant diamond-silicon carbide multiphase ceramic material under varying temperature conditions, the effects of the discrete molybdenum carbide pinning layer and the distributed silicon boride composition on phonon transport stability and crack repair mechanism were analyzed. The vacuum pressure of the vacuum autoclave used in the physical experimental platform was at a vacuum level of [missing information]. to The temperature control accuracy is better than [specific range]. The pressure application accuracy is The thermal conductivity meter used is based on the laser flash method, and its measurement range covers 100 to 1000. The resolution is 0.01. In the parameter setting procedure, the determination of the amount of elemental molybdenum powder added balances the density of interfacial pinning points and the increase in matrix thermal resistance. The setting method is to increase the amount of elemental molybdenum powder as the specific surface area of ​​diamond particles increases to maintain the coverage of surface active sites. During signal acquisition, system measurement noise with a root mean square value of 0.5% is superimposed, and the test sample is pre-set to 20... / min of temperature fluctuation disturbance source; This experiment constructed a control system consisting of the sample group of the present invention, control group A, control group B, control group C and control group D, wherein the sample group of the present invention uses a ratio of 65 parts diamond particles, 5.0 parts elemental molybdenum powder, 1.2 parts elemental boron powder and the balance silicon carbide matrix; control group A removes elemental molybdenum powder characteristics to verify the inhibitory effect of pinning layer on interface debonding; control group B removes elemental boron powder characteristics to verify crack in situ healing ability; control group C sets the elemental molybdenum powder content to 1.0 parts, which is lower than the lower limit; control group D sets the elemental molybdenum powder content to 10.0 parts, which is higher than the upper limit of molybdenum source component content of the present invention.

[0026] Table 1: Performance Verification Data for Each Sample Group

[0027] Referring to Table 1, under the initial input state, after undergoing solid-phase pre-pinning at 1250℃, the sample group of the present invention showed the formation of discretely distributed granular particles on the diamond surface. The measured surface density of its nailing points is After 500 thermal cycles, the thermal conductivity of the sample group of this invention decreased from the initial 655.2. It dropped to 624.1 The attenuation rate was 4.75%; control group A, lacking a discrete pinning layer, experienced shear stress concentration at the interface due to thermal expansion coefficient mismatch, leading to interfacial debonding and a thermal conductivity attenuation rate of 18.32%; control group D showed deterioration, with the interfacial thermal resistance increasing with the interfacial phase layer thickness when the elemental molybdenum powder content exceeded the upper limit to 10.0 parts, resulting in a decrease in initial thermal conductivity to 485.6. Control group B lacked the physical barrier provided by the silicon boride component, and excessive infiltration of liquid silicon led to damage to the diamond structure, with a thermal conductivity decrease rate of 9.24%. Experimental results confirmed that the particulate matter produced by the solid-phase pre-pinning reaction triggered by segmented temperature control... The molybdenum disilicide gradient transition layer generated by the liquid-solid displacement reaction, in Under the distribution of elastic modulus, the continuity of thermal stress transmission at the heterogeneous interface is reduced, in which This refers to the elastic modulus of diamond particles. The elastic modulus of the silicon carbide matrix. The elastic modulus of the molybdenum disilicide layer is [value missing]. When thermal fatigue microcracks are generated, the distributed silicon boride components are oxidized to form a fluid silicon boron oxide liquid phase, which performs in-situ filling and maintains the integrity of the phonon transport channels.

[0028] Example 3: This example combines Figures 1 to 2 This document describes a heat-resistant diamond-silicon carbide multiphase ceramic material and its hot-pressing preparation process. Figure 1 As shown, the process begins with the initial solid raw material feeding and mixing stage, where the raw materials include 50 to 85 parts of diamond particles, 2 to 8 parts of elemental molybdenum powder, 0.5 to 3 parts of elemental boron powder, and silicon carbide micro powder as one of the matrix components. After the above raw materials are mixed and ball-milled in step S111 to form a mixed powder, they enter the solid-phase reaction step S112 of vacuum hot pressing at 1200°C. Up to 1300 Under certain conditions, molybdenum powder is converted into molybdenum carbide to form a pre-pinned green blank. Liquid silicon (Si) is introduced as one of the matrix components through high-temperature melt infiltration, followed by a vacuum hot-pressing liquid-phase sintering step S113 at 1500°C. Up to 1700 Densification was completed under the conditions of generating molybdenum disilicide and silicon boride. Finally, after cooling and demolding, a diamond silicon carbide multiphase ceramic with a total weight of 100 parts was obtained. The finished product structure includes diamond particles as a reinforcing phase, a gradient transition layer containing molybdenum disilicide and molybdenum carbide pinning, a physical barrier component containing silicon boride, and a silicon carbide matrix composed of in-situ generated initial micro powder, with a material density greater than 98.5%.

[0029] like Figure 2 As shown, the process engineer, as the main executor, is involved in the entire process flow. Their operations cover raw material proportioning and molding, as well as the raw material pretreatment stage, which involves vacuum desorption for high oxygen content. After a mechanical ball milling process, the process is connected to the hot press furnace automatic control system at 1200°C. Up to 1300 The solid-state pre-pinning sintering stage and 1500 Up to 1700 The liquid phase infiltration densification stage is monitored in a closed loop. During this stage, an axial pressure of 10 MPa to 50 MPa is applied. At the same time, the hot press furnace automatic control system performs densification rate monitoring and temperature field thermal hysteresis compensation based on real-time feedback data, thereby ensuring the accurate execution of process parameters.

[0030] Example 4: In transient thermal shock scenarios of heat dissipation components for high-power-density avionics modules, ceramic materials need to... The internal heat flux density is from to The intense fluctuations in temperature necessitate extremely high thermomechanical stability and phonon transport efficiency at the diamond-silicon carbide heterostructure interface. This embodiment provides a thermally degrade-resistant diamond-silicon carbide multiphase ceramic material and its hot-pressing preparation process. Control parameters for the segmented heating stage are determined using an interface kinetic calibration procedure, and the average particle size of the selected elemental molybdenum powder is measured. The depth is 1.2 μm. Based on the solid-state diffusion coefficient of molybdenum atoms at diamond grain boundaries, the holding time for the solid-state pre-pinning stage is determined by establishing a monotonically increasing functional relationship between diffusion depth and reaction time. Under this working condition, the heat preservation time will be... The time was set to 55 minutes to ensure that the granules generated in situ were of good quality. The molybdenum powder penetrates a 3nm thick amorphous carbon layer on the diamond surface and anchors at diamond lattice dislocations. To establish the spatial layout of the discrete pinning structure, the amount of elemental molybdenum powder added is determined based on the total specific surface area of ​​the diamond particles. The control logic is to set the mass fraction of elemental molybdenum powder so that the projected area coverage of granular molybdenum carbide on the diamond surface is between 15% and 25%. When the projected area coverage is less than 15%, the density of interfacial pinning points is insufficient to block the propagation of microcracks caused by thermal stress. When the projected area coverage is greater than 25%, the molybdenum carbide particles become interconnected and tend to form a continuous film, resulting in an increase in phonon scattering cross section and an increase in interfacial thermal resistance. The cumulative specific surface area of ​​the diamond particles is measured by a laser particle size analyzer. Based on the above ratio, the amount of elemental molybdenum powder is determined to be 4.5 parts, and finally, discrete pinning sites with an average spacing of 800nm ​​are constructed on the diamond surface.

[0031] In the stage of introducing liquid silicon, the mass ratio of elemental molybdenum powder to elemental boron powder was set at 4:1. This ratio was determined based on the segregation effect of boron atoms in molten silicon. Simultaneously with the formation of the molybdenum disilicide layer, the boron component forms a solute accumulation zone at the liquid silicon front, thereby increasing the kinetic damping of the liquid silicon flow and preventing it from dissolving and damaging the diamond lattice. The penetration rate of liquid silicon in the silicon carbide preform was measured. When the molybdenum-boron ratio was in the range of 3:1 to 6:1, the penetration rate at the interface between the molybdenum disilicide layer and the silicon carbide matrix was measured. With a phase concentration reaching 2% by mass, a physical barrier against excessive silicon infiltration is constructed. The material prepared in this embodiment maintains stable phonon transport efficiency at the interface after 500 thermal shock cycles. Microstructural analysis of the gradient transition layer confirms that the heterogeneous interface formed by the 320nm thick molybdenum disilicide layer and granular molybdenum carbide satisfies… The elastic modulus gradient of the relationship effectively alleviates stress concentration at the edges of diamond particles, among which... This represents the elastic modulus of the diamond particle. The elastic modulus of the silicon carbide matrix. The elastic modulus of the molybdenum disilicide layer was measured at 600. The transient thermal conductivity at that time was 585. Compared to the initial thermal conductivity, the decay rate was only 4.2%, and no continuous thermal fatigue cracks were observed at the interface. The heat dissipation component maintained the stability of thermal conductivity under complex temperature fields. In the microstructure control, the overlap of phonon frequency distribution in the direct contact area between the molybdenum disilicide layer and the diamond particle surface between the granular molybdenum carbide particles was achieved by strictly controlling its average thickness within the nanometer-scale fluctuation range of 50 nm to 500 nm. Due to the impedance difference between the intrinsic phonon elastic transport impedance of molybdenum disilicide and diamond, the atomic-level clamping effect of this ultrathin heterojunction interface can significantly change the local lattice vibration modes on both sides of the contact surface, causing the phonon density of states on the molybdenum disilicide side to shift towards higher frequencies, while simultaneously lowering the high-frequency lattice vibration cutoff frequency on the diamond surface. This forces the control and drives the core heat-carrying phonon spectrum of the two phases to generate large-area physical resonance and overlap in the vibration frequency range of 10 terahertz to 15 terahertz, greatly expanding the effective phonon elastic transport cross section and reducing the interface phonon scattering probability and intrinsic thermal resistance from the bottom layer.

[0032] Example 5: For cases where different batches of elemental molybdenum powder or silicon carbide micro powder are used, in order to maintain the consistency of the distribution of interface pinning points, a calibration procedure based on quantitative phase abundance analysis is adopted. This is achieved by collecting data at different holding times. The sample was examined and its phase composition was determined using an X-ray diffractometer. - Rays in The measurement of hexagonal crystal systems was performed by scanning within the range of 30 to 80 degrees. Phase and element The ratio of the integral intensity of the characteristic peaks of the phases, and the relationship between this ratio and the holding time. The change pattern determines the termination time of the solid-phase diffusion stage. of Crystalline peaks and elemental properties of When the crystal plane peak intensity ratio reaches 8:1, it is determined that the elemental molybdenum powder on the surface of the diamond particles has been transformed into discretely distributed granular molybdenum carbide. In the actual mass production vacuum hot pressing closed-loop control, it is not necessary to place the diffractometer directly into the high-temperature furnace cavity. Instead, a numerical mapping dictionary is established in advance between the aforementioned offline diffraction-measured micro-phase transformation intensity ratio and the macroscopic mold displacement expansion amount of the same material batch within the corresponding holding time. The hot pressing automatic control system only needs to collect the macroscopic displacement electrical signal of the mold in real time and compare it with the mapping dictionary to indirectly and accurately determine whether the internal micro-phase transformation intensity ratio has reached the aforementioned process termination threshold of 8:1. The numerical mapping dictionary between the micro-phase transformation intensity ratio and the macroscopic mold displacement expansion amount is a deterministic lookup table composed of calibration test data from the pre-production stage. In the pre-conducted solid-phase reaction process calibration, high precision is used to determine whether the micro-phase transformation intensity ratio has reached the aforementioned process termination threshold of 8:1. The displacement sensor records the absolute axial extension of the hot press mold in real time under different holding times. When offline quantitative phase analysis confirms that the ratio of the integral intensity of the two characteristic peaks of hexagonal molybdenum carbide and elemental molybdenum reaches the precise 8:1 process control point, the system automatically stores the corresponding macroscopic cumulative thermal expansion displacement of the mold as the target control threshold in the corresponding retrieval matrix. During the closed-loop control operation of actual mass production, the hot press furnace automatic control system only needs to read the output electrical signal of the pressure head displacement sensor in real time with a sampling period of 20 milliseconds and convert it into the actual axial displacement. It directly performs scalar value comparison in the retrieval table. Once the real-time displacement reaches or exceeds the target control threshold corresponding to the batch of materials, it is determined that the microscopic phase transformation intensity ratio has reached the process endpoint, thereby automatically terminating the current holding stage and switching to the next process.

[0033] Before the hot pressing process for heat dissipation components in a vacuum hot press furnace, a temperature field uniformity and pressure feedback calibration procedure is performed by pre-placing thermocouples at the center and edge of the hot pressing mold, and the thermal hysteresis parameters at different heating rates are measured. And establish temperature compensation formula ,in Set the temperature for the heating controller. To measure the actual temperature inside the mold, This is a temperature correction bias, used to correct the delay effect of thermal radiation conduction in a vacuum environment, at 1500. During the liquid-solid displacement stage up to 1700℃, the penetration depth of liquid silicon was determined by real-time monitoring of the pressure head displacement rate. When the displacement rate approached zero and the axial pressure fluctuation was less than 0.5 MPa, the reaction sintering process was considered complete. This maintained the residual stress gradient within the diamond-silicon carbide multiphase ceramic material at a level less than 50 MPa / mm, ensuring the material's stability at 20℃. Up to 600 The structure is stable under thermal cycling conditions.

[0034] Example 6: In a scenario where surface activity consistency is adjusted for diamond particles from different storage batches, the initial oxygen content on the surface of the diamond particles is measured. Determining the vacuum pretreatment time using a method based on energy dispersive spectroscopy analysis. When the concentration is greater than 0.1%, the operating temperature is 400°C before mixing in the planetary ball mill. The vacuum desorption process maintains a furnace cavity vacuum level superior to And the duration depends on the relation. Confirmed, among which The desorption time is expressed in minutes. This is a time correction factor with a value of 500. This time correction factor, representing a mass percentage, is obtained through incremental step calibration: at 400... In a vacuum heating environment, with an observation cycle of ten minutes, the cumulative step time required for the vacuum level to recover from negative square Pascal to the initial static vacuum level was monitored. It was found that for every 0.1% increase in oxygen content on the diamond particle surface, the corresponding desorption step time increased by five minutes. The time correction coefficient determined through this calibration relationship can compensate for the differences in specific surface area adsorption caused by changes in diamond particle size distribution. This pre-calibration procedure removes adsorbed gases from the diamond surface and exposes active sites, ensuring the subsequent formation of granular... Anchoring with the diamond lattice; to eliminate the apparent numerical difference between the global time calculation result and the actual local operation step count, the five minutes recorded in the process refers to the single step observation time increment executed by the system to confirm that the static vacuum degree has reached a steady state within a single verification cycle. In the complete step-by-step dynamic desorption process control, the entire pre-calibration and execution procedure contains 10 completely continuous independent detection step stages. Therefore, when the mass percentage of oxygen on the surface of diamond particles increases by 0.1%, the step observation time needs to be extended by five minutes in each independent detection step stage, so that the net increment of the actual total process time after the sum of all 10 step stages accurately reaches 50 minutes. This is completely self-consistent and closed-loop with the macroscopic desorption total time increment obtained by the global calculation formula, thereby achieving accurate dynamic compensation for the adsorption differences of materials with different gradations while ensuring the complete unity of the underlying operation logic of the control system.

[0035] When the vacuum hot press furnace is operating at 1500 Up to 1700 During the liquid-solid displacement reaction, the axial shrinkage allowance under constant radial dimension inside the mold is collected in real time by a displacement sensor configured at the end of the hot press mold head. Calculate the densification rate per unit time. ,in For densification rate, The change in displacement The time interval is the critical threshold at which the reaction is determined to end. The setting is 0.05 mm / min. Once the densification rate is detected over a continuous 5-minute period... Below And axial pressure Fluctuation in During the cooling phase, the system automatically switches to the cooling stage. This process control logic eliminates the risk of excessive dissolution of diamond by liquid silicon, ensuring that the diamond-silicon carbide composite ceramic material reaches a density standard of no less than 98.5% under different furnace room temperature field distributions.

[0036] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A diamond-silicon carbide multiphase ceramic material resistant to thermal decay, characterized in that, It includes diamond particles, a silicon carbide matrix, and a gradient transition layer located at the interface between the diamond particles and the silicon carbide matrix: The gradient transition layer includes a molybdenum carbide pinning layer directly attached to the surface of the diamond particles. The molybdenum carbide pinning layer is composed of granular molybdenum carbide discretely distributed on the surface of the diamond particles. The granular molybdenum carbide combines with the lattice dislocations or steps on the surface of the diamond particles to form a pinning structure, which is used to construct the interface stress dissipation center and form a discontinuous interface connection. The gradient transition layer also includes a molybdenum disilicide layer covering the outer surface of the molybdenum carbide pinning layer, and the molybdenum disilicide layer forms a phase interface with the silicon carbide matrix; the gradient transition layer also contains silicon boride components, which are dissolved in the molybdenum disilicide layer and extend to the grain boundaries of the silicon carbide matrix, and the silicon boride components form a continuous physical barrier at the junction of the molybdenum disilicide layer and the silicon carbide matrix to block the penetration path of liquid silicon to the surface of diamond particles during the reaction sintering process; The gradient transition layer extends from the diamond particles toward the silicon carbide matrix, and the elastic modulus of its constituent phases exhibits a stepped distribution. The height of the individual protrusions in the molybdenum carbide pinning layer is less than the thickness of the molybdenum disilicide layer, and the molybdenum disilicide layer is in direct contact with the surface of the diamond particles at the gaps between the granular molybdenum carbide particles, and an overlapping phonon frequency distribution range is formed at the contact interface between the molybdenum disilicide layer and the diamond particles; the volume percentage content of the diamond particles is 40% to 70%.

2. The thermally resistant diamond-silicon carbide multiphase ceramic material according to claim 1, characterized in that, Based on a total weight of 100 parts for the heat-resistant diamond-silicon carbide multiphase ceramic material, the content of diamond particles is 50 to 85 parts; the content of the molybdenum source component forming the gradient transition layer is 2 to 8 parts; the content of the boron source component forming the gradient transition layer is 0.5 to 3 parts; and the content of the silicon carbide matrix is ​​the balance to make up to 100 parts. Among them, the molybdenum source component is elemental molybdenum powder with an average particle size of 0.5 μm to 2 μm; the diamond particles include particles in a first particle size range and particles in a second particle size range, the average particle size of the particles in the first particle size range is 100 μm to 200 μm, and the average particle size of the particles in the second particle size range is 10 μm to 30 μm.

3. The thermally resistant diamond-silicon carbide multiphase ceramic material according to claim 1, characterized in that, The average thickness of the gradient transition layer ranges from 50 nm to 500 nm; the molybdenum carbide phase in the molybdenum carbide pinning layer is hexagonal. The molybdenum disilicide phase in the molybdenum disilicide layer is tetragonal. .

4. The thermally resistant diamond-silicon carbide multiphase ceramic material according to claim 1, characterized in that, The projection coverage of the molybdenum carbide pinning layer on the diamond particle surface is 15% to 45%; the average spacing between adjacent granular molybdenum carbide in the molybdenum carbide pinning layer is greater than the average thickness of the molybdenum carbide pinning layer, so that the contact area formed by the molybdenum disilicide layer between the granular molybdenum carbide and the diamond particle surface accounts for 55% to 85% of the total surface area of ​​the diamond particle.

5. The thermally resistant diamond-silicon carbide multiphase ceramic material according to claim 1, characterized in that, Silicon boride composition is Phase, and The concentration of the phase in the silicon carbide matrix decreases from the gradient transition layer into the interior of the silicon carbide matrix.

6. The thermally resistant diamond-silicon carbide multiphase ceramic material according to claim 1, characterized in that, The silicon carbide matrix includes silicon carbide generated by in-situ reaction and added silicon carbide micro powder; the average grain size of the silicon carbide generated by in-situ reaction is smaller than the average particle size of the added silicon carbide micro powder, and the silicon carbide generated by in-situ reaction is coated on the outer surface of the molybdenum disilicide layer.

7. The thermally resistant diamond-silicon carbide multiphase ceramic material according to claim 1, characterized in that, The elastic moduli of each constituent phase in the gradient transition layer satisfy the following relationship: ,in, This represents the elastic modulus of the diamond particle. The elastic modulus of the silicon carbide matrix. The elastic modulus of the molybdenum disilicide layer is given; the gradient transition layer, through the difference in elastic modulus distribution, mitigates the stress at the interface between the diamond particles and the silicon carbide matrix at 20°C. Up to 600 Thermal stress concentration during thermal cycling.

8. The thermally resistant diamond-silicon carbide multiphase ceramic material according to claim 1, characterized in that, The mass ratio of molybdenum to boron in the gradient transition layer is 3:1 to 6:1; silicon-boron-molybdenum ternary compound particles are also distributed in the molybdenum disilicide layer, and the diamond particles have an amorphous carbon layer on their surface. The thickness of the amorphous carbon layer is less than 5 nm. The particulate molybdenum carbide passes through the amorphous carbon layer and combines with the lattice of the diamond particles.

9. The thermally resistant diamond-silicon carbide multiphase ceramic material according to claim 1, characterized in that, The density of the heat-resistant diamond-silicon carbide multiphase ceramic material is not less than 98.5%; the density of the heat-resistant diamond-silicon carbide multiphase ceramic material is within 20... Up to 600 After 500 cycles of cyclic heating within the specified range, its thermal conductivity decay rate is less than 5%.

10. A hot-pressing preparation process for a thermally resistant diamond-silicon carbide multiphase ceramic material, used to achieve the thermally resistant diamond-silicon carbide multiphase ceramic material as described in claim 1, characterized in that, Includes the following steps: Step S111: The heat-resistant diamond-silicon carbide multiphase ceramic material is prepared by mixing diamond particles, molybdenum source components, boron source components and silicon carbide micro powder in parts by weight to obtain a mixed powder. Step S112: Place the mixed powder in a hot press mold and load it into a vacuum hot press furnace, where the vacuum degree is better than 10. The temperature was increased to 1200 Pa under the environment. Up to 1300 Keep warm for 30 to 90 minutes to allow the molybdenum source component to undergo a solid-phase reaction with the surface of the diamond particles and generate granular molybdenum carbide. Step S113, continue heating to 1500 Up to 1700 Liquid silicon was introduced, and an axial pressure of 10 MPa to 50 MPa was applied. The mixture was kept at the temperature and pressure for 30 to 60 minutes and then cooled to obtain a diamond-silicon carbide composite ceramic material resistant to thermal decay.

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