Abstract
Diamond/silicon carbide (Diamond/SiC) composites, leveraging the ultra-high thermal conductivity and ultra-high hardness of diamond, along with the excellent chemical stability, mechanical strength, and thermal expansion matching characteristics of silicon carbide, have emerged as core candidate materials for next-generation structural components operating under extreme conditions and for high-end electronic thermal management. This paper provides a systematic review of the fundamental properties, mainstream fabrication methods, key application scenarios, and remaining challenges of these composites, aiming to serve as a reference for both research and engineering practice in related fields.
1. Introduction
With the rapid development of fifth-generation mobile communications, artificial intelligence, high-performance computing, and aerospace technologies, electronic devices are evolving toward higher power, higher integration density, and smaller form factors, imposing unprecedented stringent requirements on thermal management materials. At the same time, structural components used in extreme environments-such as deep‑sea equipment and chemical pump valves-urgently demand materials that combine high hardness, corrosion resistance, and long service life.
Diamond possesses an ultra‑high thermal conductivity of approximately 2000 W/(m·K) at room temperature and an extremely low coefficient of thermal expansion, making it an ideal reinforcement phase. Silicon carbide, in turn, offers high thermal conductivity (about 490 W/m·K at 300 K), excellent thermal expansion compatibility, and good interfacial wettability with diamond. The synergistic combination of these two phases endows diamond/SiC composites with outstanding overall performance in thermal, mechanical, and chemical stability.
2. Material Properties and Advantages
The core advantages of diamond/silicon carbide composites are reflected in the following aspects:
Thermal properties. The composites combine an exceptionally high thermal conductivity with a very low coefficient of thermal expansion. Studies have shown that the thermal conductivity of composites prepared by different processes can reach 300–700 W/(m·K) or even higher, far exceeding that of conventional heat‑spreading materials such as copper (≈400 W/m·K) and aluminum (≈200 W/m·K). Coherent Corporation's proprietary diamond‑loaded SiC ceramic composite has achieved an isotropic thermal conductivity exceeding 800 W/m·K. In terms of thermal expansion, the composite can attain values as low as 2.49–2.73×10⁻⁶ K⁻¹, closely matching that of the silicon chip substrate (≈2.5 ppm/°C).
Mechanical properties. The ultra‑high hardness of the diamond phase imparts excellent wear resistance to the composite. After liquid‑phase silicon infiltration and sintering, the material hardness can reach 48 GPa (HK2). The flexural strength can reach 420.2 MPa, and the elastic modulus 578.6 GPa, representing increases of 84.5% and 34.0%, respectively, over reaction‑bonded silicon carbide. The fracture toughness can reach 4.5–5 MPa·m¹/².
Chemical stability. Both diamond and silicon carbide exhibit excellent corrosion resistance, enabling the composite to maintain high corrosion resistance even in alkaline media and hydrothermal conditions, with residual silicon content controllable below 5 vol%.
3. Fabrication Technologies
The core of diamond/SiC composite fabrication lies in achieving effective bonding between diamond and the SiC matrix, as well as the densification and controlled construction of the composite structure. Based on the origin of the silicon carbide, fabrication methods can be divided into two major categories: one in which SiC is formed in situ through reaction processes, and the other in which a prefabricated SiC phase is directly introduced.
3.1 High‑Pressure High‑Temperature Sintering
In the high‑pressure high‑temperature (HPHT) sintering method, diamond micropowder is mixed with silicon powder and densified under high pressure and high temperature (typically 1–5 GPa, 1450–1600°C), allowing silicon to react with carbon on the diamond surface to form a silicon carbide matrix. The advantages of this method include low residual silicon content, high density, and strong interfacial bonding; however, it requires sophisticated equipment, entails high processing costs, and limits sample dimensions. Heat‑spreader materials prepared under pressures above 5.1 GPa and temperatures of 800–1650°C can achieve thermal conductivities of up to 650 W/m·K.
3.2 Reactive Melt Infiltration
Reactive melt infiltration (RMI) is one of the most widely adopted fabrication strategies. The basic process includes powder mixing, preforming, debinding, and infiltration steps-silicon is melted by heating and infiltrates into a pre‑prepared porous diamond preform under capillary action or applied pressure, where it reacts with carbon on the diamond surface to form a SiC bonding phase. This method yields high density, good interfacial bonding, and suitability for large‑scale fabrication, but it is prone to residual free silicon and challenges in precise control of the interfacial reaction. The combination of gelcasting and silicon infiltration enables the production of high‑performance composites at solid loadings as high as 65 vol%.
3.3 Precursor Conversion
In the precursor conversion method, diamond particles are mixed with silicon‑containing organic precursors (e.g., polycarbosilane) and then heated in vacuum or an inert atmosphere to pyrolyze the precursor and in situ form a SiC matrix. Its advantages include lower processing temperatures and the ability to construct complex or large structures, but the density is often insufficient and residual impurities are more likely.
3.4 Chemical Vapor Infiltration
Chemical vapor infiltration (CVI) introduces silicon‑containing gaseous precursors (e.g., methyltrichlorosilane) into the porous diamond preform at elevated temperatures, depositing SiC in situ on the diamond particle surfaces through gas‑phase reactions. This technique can produce composite structures with high purity and uniformity, but it is costly and slow.
3.5 Graded Forming Process
For structural component applications, the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) has developed a graded forming process-forming a diamond‑composite layer only on the functional surface subjected to high stress (with a diamond volume fraction of about 50%), while the substrate remains conventional machinable silicon carbide. The specific routes include double‑press forming and slurry coating; after liquid‑phase silicon infiltration, the surface hardness reaches 48 GPa and residual silicon is below 5%. This design significantly reduces processing costs while ensuring the performance of the critical service surface.
3.6 Additive Manufacturing
3D printing combined with liquid‑phase silicon infiltration has opened a new pathway for fabricating diamond/SiC components with complex geometries. Studies have shown that using a bimodal powder mixture with 75 vol% diamond, followed by liquid‑phase silicon infiltration at 1600°C, yields composites with a thermal conductivity of 300.5 W/m·K and a flexural strength of 270.7 MPa. This technological route is particularly suitable for manufacturing components with complex internal flow channels, such as liquid‑cooled devices.
4. Application Fields
4.1 Semiconductor Thermal Management
Thermal management represents the most promising application direction for diamond/SiC composites. As AI chip power consumption approaches the kilowatt level, conventional heat‑dissipation materials can no longer meet the requirements. The composite's thermal conductivity exceeds 700 W/(m·K) and its coefficient of thermal expansion is as low as 2.6 ppm/°C, closely matching the silicon chip substrate (2.5 ppm/°C), effectively solving the problems of interfacial cracking and heat dissipation failure caused by thermal expansion mismatch in high‑computing‑power chips. Coherent has already applied this material in scenarios such as direct chip heat dissipation, microchannel cold plates, and semiconductor device substrates. In February 2026, China's first 8‑inch diamond heat‑spreader production line was officially put into operation, marking the material's transition from laboratory to large‑scale production.
4.2 Extreme‑Environment Structural Components
In deep‑sea equipment and chemical engineering, pump bearings and seals are often subjected to the combined attack of strongly corrosive media and abrasive particles. Relying on the high hardness of the diamond phase and the excellent chemical stability of both constituents, diamond/SiC composites exhibit outstanding wear and corrosion resistance under severe operating conditions. In the SubSeaSlide project funded by the German Federal Ministry of Education and Research (BMBF), Fraunhofer IKTS has delivered bearing and seal prototypes made of this material to companies such as EagleBurgmann, Miba Industrial Bearings, and Sulzer, with industrial test results proving excellent.
4.3 Synchrotron Radiation Optics
Diamond/SiC composites are also being explored as substrate materials for X‑ray mirrors in high‑brightness synchrotron radiation sources. Their combination of high thermal conductivity and low thermal expansion helps maintain the surface figure accuracy of optical elements under high‑heat‑flux irradiation.
5. Interfacial Engineering and Performance Optimization
The quality of interfacial bonding is a key factor determining the overall performance of the composite. The close match in coefficients of thermal expansion between diamond and SiC endows them with good interfacial compatibility; however, interfacial phonon mismatch remains a significant factor limiting heat transport efficiency.
Studies have shown that introducing a TiC intermediate layer between diamond and SiC can form a quasi‑coherent interface, effectively reducing acoustic mismatch and interfacial dislocation density, and significantly improving interfacial performance. In addition, depositing a silicon pre‑layer on diamond surfaces by magnetron sputtering followed by vacuum annealing can gradually convert silicon into SiC (amorphous Si → crystalline Si → crystalline Si + SiC → SiC). Composites prepared using sub‑micron diamond powder as the carbon source can achieve residual silicon content as low as 7.41 vol% and a Young's modulus of 572±22 GPa.
6. Challenges and Outlook
Although diamond/silicon carbide composites exhibit outstanding performance potential, their large‑scale application still faces several challenges:
Fabrication cost. Processes such as HPHT sintering and CVI require expensive equipment and long processing cycles, limiting mass production and cost‑effectiveness. Although cost‑reduction approaches such as graded design and additive manufacturing have made progress, they are still far from large‑scale industrial application.
Complex shape forming. Many application scenarios (e.g., cold plates with internal flow channels, aspherical optical lenses, etc.) require complex geometries. Conventional molding processes are inadequate, and emerging technologies such as 3D printing still have room for improvement in terms of solid loading and densification.
Interface optimization. How to achieve uniform, low‑thermal‑resistance interfacial structures on a large scale remains a core issue in materials design. The mechanisms by which the thickness, composition, and microstructure of the interfacial transition layer affect heat transport performance need further elucidation.
Standardization and reliability. As an emerging material system, data on long‑term service reliability, performance evaluation standards, and testing methodologies are not yet fully established, requiring joint efforts from both academia and industry to advance.
7. Concluding Remarks
Diamond/silicon carbide composites integrate the ultra‑high thermal conductivity of diamond with the excellent overall properties of silicon carbide, showing broad application prospects in semiconductor thermal management, extreme‑environment structural components, high‑power optical elements, and more. With continued advances in fabrication technologies, deeper understanding of interfacial engineering, and accelerating industrialization, this material system is poised to become an indispensable key material for next‑generation high‑end equipment and electronic devices. From deep‑sea equipment to AI data centers, diamond/SiC composites are steadily moving from the laboratory to a broader engineering stage.