Carbon fibers and graphite fibers are often confused, in fact, there are distinct hierarchical and performance differences between the two kind of fibers. Graphite fibers are a special category of carbon fibers processed through high-temperature graphitization. The core differences lie in aspects such as carbon content, crystalline structure, performance, and application scenarios, with detailed analysis as follows:

1. Core Definitions and Inherent Relationship Between Carbon Fibers and Graphite Fibers
Carbon fibers refer to fibrous carbon materials with a carbon content of ≥90%. They are made from precursor fibers (such as polyacrylonitrile (PAN), pitch, and viscose) through processes like pre-oxidation and carbonization, and are a general term. Graphite fibers, on the other hand, are the "advanced version" of carbon fibers. They require high-temperature graphitization treatment at over 2000°C based on carbon fibers to increase the carbon content to ≥99%, forming a highly graphitized crystalline structure. Thus, graphite fibers are a specialized sub-type of carbon fibers with unique performance. In simple terms: Graphite fibers are always carbon fibers, but not all carbon fibers are graphite fibers.

2. Comparison of Key Performance Differences
The performance differences between the two stem from the regularity of their crystalline structures, specifically reflected in the following 5 core dimensions:

Carbon Content: Carbon fibers have a carbon content of 90%-99%, which increases with the rise of carbonization temperature. Graphite fibers have a carbon content of ≥99%; the high-temperature graphitization process largely removes impurities such as hydrogen and oxygen, making their carbon purity close to the theoretical value.

Crystalline Structure: Carbon fibers have a low degree of graphitization (usually <60%), with carbon atoms forming a graphite-like structure in random stacking. Their lamellae have disordered orientations and contain numerous pores. Graphite fibers have a degree of graphitization of ≥90%, with carbon atoms forming highly regular hexagonal graphite crystals. Their lamellae are arranged along the fiber axis direction, with very few pores and a denser structure.

Mechanical Performance: Carbon fibers are characterized by "high strength", with a tensile strength of 3-7GPa and an elongation at break of 1.5%-2.5%, but their elastic modulus is relatively low (200-400GPa). Graphite fibers have an extremely high elastic modulus (400-1000GPa), but their tensile strength is slightly lower (2-5GPa). They also have higher brittleness, with an elongation at break of only 0.5%-1.5%.

Thermal and Electrical Performance: Due to their highly regular crystal structure, graphite fibers have much higher thermal conductivity (1000-2000W/(m·K)) and electrical conductivity than ordinary carbon fibers (with a thermal conductivity of 10-100W/(m·K)). They also have an extremely low thermal expansion coefficient (close to zero or even negative expansion) and excellent thermal stability. Ordinary carbon fibers have moderate thermal and electrical conductivity, and their thermal expansion coefficient is slightly higher than that of graphite fibers.

Chemical Stability: Both have good corrosion resistance. However, due to their dense structure and extremely low impurity content, graphite fibers have better stability than ordinary carbon fibers in high-temperature (>1000°C) oxidizing environments and are less prone to oxidative weight loss。

3. Main Differences in Preparation Processes
The key difference in the preparation processes of the two lies in the "graphitization step", with specific process comparisons as follows:

Carbon Fiber Preparation: Precursor fibers (e.g., PAN) → Pre-oxidation (200-300°C, to prevent melting) → Carbonization (1000-1800°C, to remove non-carbon elements and form a graphite-like structure) → Surface treatment → Sizing → Finished product. The core process is "carbonization".

Graphite Fiber Preparation: Semi-finished carbon fibers → Graphitization (2000-3000°C, to rearrange carbon atoms at high temperature and form regular graphite crystals) → Purification (to remove residual impurities and improve carbon purity) → Surface treatment → Sizing → Finished product. Compared with carbon fiber preparation, it has two additional key steps: "high-temperature graphitization" and "purification". Moreover, the graphitization process consumes high energy, leading to a significant increase in cost.

4. Differentiation of Application Scenarios
Performance differences determine that the two have different focuses in application fields, showing the characteristic of "cost-performance adaptation":

Carbon Fiber Applications: Focus on scenarios requiring "high strength + cost-effectiveness", such as sports equipment (badminton rackets, tennis rackets, bicycle frames), automotive lightweight components (car bodies, drive shafts), wind turbine blades, building reinforcement materials, and conventional aerospace structural parts (e.g., secondary load-bearing structures of aircraft). These applications balance strength while controlling costs.

Graphite Fiber Applications: Focus on scenarios requiring "high modulus + high thermal conductivity + extreme environment adaptation", such as high-end aerospace fields (rocket engine nozzles, satellite antenna supports, and spacecraft load-bearing structures, which need to withstand extreme temperature differences and high pressure), electronic information fields (chip heat dissipation substrates, high thermal conductivity composite materials), and high-end medical equipment (e.g., components of nuclear magnetic resonance equipment). These scenarios have extremely high performance requirements and low cost sensitivity.

5. Summary: Core Differences in One Sentence
Carbon fibers are "basic-type" high-carbon fibers, featuring high strength and high cost-effectiveness, with wide applications. Graphite fibers are "high-end-type" graphitized carbon fibers, characterized by high modulus, high thermal conductivity, and high purity. They are designed specifically for extreme environments and high-end scenarios, with higher costs.

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