Determination of the crystallite size of graphite in calcined petroleum coke using ARL X’TRA Companion XRD

Importance of the Topic

Calcined Petroleum Coke is a carbon-rich material crucial in aluminum production and metallurgy. Its electrical performance depends on graphite crystallite size, making reliable measurement methods essential for quality control and research. X-ray diffraction provides a standardized approach to determine crystallite size in compliance with ASTM protocols.

Goals and Overview of the Study

The study demonstrates the application of a benchtop X-ray diffraction instrument to assess the crystallite size of graphite in calcined petroleum coke. It aims to validate measured values against certified references and confirm compliance with industry standards.

Methodology

Experimental steps included reflection mode analysis of a graphite reference sample using copper K alpha radiation. A zero-background holder and sample spinning minimized errors. Peak broadening was characterized by fitting the graphite 002 reflection with a Pseudo-Voigt function and applying the Scherrer equation to extract the domain length.

Used Instrumentation

• Thermo Scientific ARL X’TRA Companion benchtop X-ray diffraction system
• Theta–theta goniometer in Bragg–Brentano geometry with a 160 mm radius
• 600 W Cu or Co X-ray source with radial and axial collimation
• Variable beam knife and optional water chiller reducing air scattering
• Solid-state pixel detector enabling rapid data acquisition
• Integrated software for one-click Rietveld refinement and LIMS connectivity

Key Results and Discussion

The measured FWHM of the graphite 002 reflection yielded a crystallite size of 28.0 Å, matching the certified value of 28.5 Å within uncertainty. Profile fitting provided accurate peak widths. No strain effects were observed, rendering more complex deconvolution methods unnecessary for this sample.

Benefits and Practical Applications

Reliable and rapid determination of crystallite size supports quality control in electrode production and metallurgical processes. The benchtop system simplifies routine analysis, meets ASTM D5187, and integrates with laboratory information systems for streamlined workflows.

Future Trends and Possibilities

• Expansion to strain analysis and texture quantification using Williamson–Hall methods
• Automation and remote monitoring through enhanced LIMS integration
• Application to diverse carbonaceous materials and composite electrodes
• Advancements in detector technology for higher resolution and speed

Conclusion

The ARL X’TRA Companion provides a robust, standardized solution for crystallite size measurement of graphite in calcined petroleum coke. Its accuracy, speed, and compliance with ASTM standards make it well suited for industrial and research laboratories.

References

• P. Scherrer, Göttinger Nachrichten Gesell. 1918, 2, 98–100
• G. K. Williamson and W. H. Hall, Acta Metall. 1953, 1, 22–31