Progress in domestic high-purity graphite breakthrough: From import dependence to self-controlled technical path

Progress in domestic high-purity graphite breakthrough: From import dependence to self-controlled technical path

High-purity graphite, as a strategic basic material, is widely used in semiconductor single crystal furnaces for heating elements, neutron moderator in nuclear reactors, thermal field systems for photovoltaic direct pulling single crystal silicon (CZ method), and high-end electrodes, among other fields. Its purity requirements are extremely strict - the boron content must be lower than 0.1 ppm, the total amount of metal impurities should be controlled within 1 ppm, and it must have excellent structural density and high-temperature dimensional stability. For a long time, this field has been highly dependent on international giants such as German SGL Carbon, Japanese Toyo Tanso, and American GrafTech for supply, with the domesticization rate remaining consistently below 30%. Since 2023, under the continuous promotion of the national new materials industry's 'Strategic Foundation Project' and key core technology breakthrough special projects, China's high-purity graphite industry has achieved a systematic breakthrough and gradually established an independent technical system covering raw material purification, forming process, high-temperature heat treatment, and the entire process quality control.

In the isostatic pressing process, traditional domestic graphite often fails to meet the strict requirements for structural consistency of the thermal field of large-sized single-crystal furnaces (over 8 inches) due to poor powder dispersion and uneven pressure transmission, resulting in a large density gradient and a relatively high microscopic porosity. Zhongfu Industry, leveraging its technical expertise in high-purity cathode carbon blocks for aluminum electrolysis, completed the construction of the first fully automated graphite powder surface modification - cold isostatic pressing integrated production line in China in 2024. Through nanoscale Al2O3 coating and gradient pressure control technology, the density dispersion of Φ600 mm isostatic pressing blocks was reduced from ±0.03 g/cm³ to ±0.008 g/cm³. After being graphitized at 2800°C, the product density reached 1.82 g/cm³. It has been verified by leading photovoltaic enterprises such as Zhonghuan Co., Ltd. and TCL Zhonghuan for the installation of thermal field components.

High-temperature purification is the core process for achieving ultra-low impurity content. Fangda Carbonite completed the independent research and development and industrial application of the 'Dual-Temperature Zone Gradient Vacuum High-Temperature Purification Furnace' in 2023. It broke through the bottleneck of insufficient temperature uniformity (±15℃) in traditional single-temperature zone furnaces, achieving precise temperature control within the range of 2700–2900℃ with an accuracy of ±3℃. It also integrated a dynamic halogen gas sweeping system and a multi-level condensation capture system, increasing the boron element removal efficiency to 99.99%. The final product's boron content was stably controlled at 0.06–0.08 ppm, and the total amount of metal impurities such as iron, nickel, and calcium was ≤0.8 ppm. This technological achievement has supported its provision of high-purity graphite crucible components for 12-inch integrated circuit silicon wafer growth furnaces for Shanghai Microelectronics Equipment (SMEE), and it entered the small-scale supply stage in 2025.

Kaijin Energy focuses on controlling the source of precursors and establishing a process quality control system. The company collaborates with the Shanxi Institute of Coal Chemicals of the Chinese Academy of Sciences to establish a full-chain impurity traceability model for 'graphitized coke - needle coke - high-purity graphite', and has developed an impurity migration database based on ICP-MS online monitoring. This enables dynamic early warning and closed-loop regulation of key impurities such as boron, vanadium, and titanium during each process from calcination to impregnation. In 2024, its mass-produced nuclear power neutron reflection layer graphite modules were tested by a third-party organization, China Nuclear Power Research and Design Institute. The size change rate before and after irradiation was less than 0.08%, and the thermal neutron absorption cross-section reached 1.42×10−24 cm², meeting the requirements of the CAP1400 demonstration engineering technical specifications. It became the first high-purity graphite supplier in China to obtain the HAF601 certification from the Nuclear Safety Bureau.

Currently, the substitution rate of domestic high-purity graphite in the thermal field of photovoltaic single-crystal furnaces has reached 76% (according to the statistics of the China Nonferrous Metals Industry Association in January 2025). However, in the core components of semiconductor equipment (such as crystal growth crucibles, insulation tubes) and the key structural components of the fourth-generation nuclear energy system (molten salt reactors, high-temperature gas-cooled reactors), there are still practical challenges such as long verification cycles for long-term service reliability, high user introduction barriers, and an incomplete standard system. Especially in the modeling of creep behavior under continuous operation at temperatures above 2800°C and the research on the irradiation-oxidation coupling damage mechanism, the accumulation of basic data is still relatively weak. In the future, it is necessary to further strengthen the collaboration among industry, academia, research institutions, and enterprises, accelerate the formulation of national standards such as 'General Technical Conditions for High-Purity Graphite Materials' and 'Evaluation Methods for Graphite Components for Semiconductor Applications', and simultaneously build a national database for the service performance of high-purity graphite materials and an accelerated aging test platform to systematically enhance the credibility and adaptability of domestic materials.

In summary, during the period from 2023 to 2026, key enterprises such as Zhongfu Industry, Fangda Carbon, and Kaijin Energy have achieved significant breakthroughs in dimensions such as isostatic pressing forming accuracy, stability of purification at temperatures above 2800℃, and full-process control of low boron and low metal impurities. Domestic high-purity graphite is moving from being 'usable' to 'easy to use' and 'long-lasting', providing a solid foundation for ensuring the security of supply chains for strategic industries such as semiconductors, advanced nuclear energy, and new energy in China.

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