Five Key Quality Indicators for Graphitization of Carbon Materials
"&"The quality of graphitization cannot be judged by intuition; it must be based on data. The following are five key indicators for evaluating the quality of graphitization:
1. Degree of Graphitization
The degre"&"e of graphitization is an indicator that measures the extent to which carbon materials are transformed into a graphite structure. It is usually determined by measuring the **d002 interplanar spacing** using X-ray diffraction (XRD). The d002 of ideal graph"&"ite is 3.354 ?, and the d002 of amorphous carbon is approximately 3.44 ?.
The higher the degree of graphitization, the closer d002 is to 3.354 ?. General requirements:- High-purity graphite: Graphitization degree >90%
- Ordinary graph"&"ite: Graphitization degree >80%
2. Stability
The higher the degree of graphitization, the lower the stability of the material. Measured using the **four-probe method**, the unit is μΩ·m. The stability of h"&"igh-quality graphite can be as low as 5-10 μΩ·m. Stability is a direct reflection of the product's conductivity and is one of the indicators most concerned by customers.
3. Flexural Strength
The mechanical propert"&"ies of graphite materials are determined using the **three-point bending test**.
If the temperature is not properly controlled or the material is rapidly cooled during graphitization, microcracks will form inside the material, leading to a decrease in"&" flexural strength. A balance needs to be found between flexural strength and the degree of graphitization—excessive graphitization, while improving electrical conductivity, may reduce strength. 4. Ash Content/Purity The content of inorganic impurities "&"in the material is determined using chemical analysis methods. High-purity graphite requires an ash content of <50 ppm, and ultra-high-purity graphite requires <5 ppm. Excessively high ash content indicates an impure protective atmosphere or contamination"&" within the furnace environment. 5. Microstructure The microstructure of the material—the size, orientation, and defect distribution of graphite lamellars—is observed using a scanning electron microscope (SEM) or a transmission electron microscope (TEM)"&". Microstructure determines the degree of anisotropy and final performance of a material.Evaluation Principles: All five indicators need to be evaluated comprehe"&"nsively; one cannot be considered alone. For example, if the degree of graphitization is very high but the flexural strength is very low, it indicates a problem with the manufacturing process (possibly rapid cooling leading to cracking). Only when all fiv"&"e indicators meet the standards can it be considered a truly high-quality product.