Research on precision-calibration techniques for selected area electron diffraction patterns of pyrocarbon.

Area of Science:

• Materials Science
• Crystallography
• Electron Microscopy

Background:

• Accurate characterization of pyrocarbon's structural properties, specifically orientation angle (OA) and interlayer spacing (d002), is crucial for its application in advanced composites.
• Selected Area Electron Diffraction (SAED) is a powerful technique for analyzing crystalline materials, but precise quantitative analysis of pyrocarbon SAED patterns presents challenges.

Purpose of the Study:

• To develop and validate novel algorithms for the precise determination of orientation angle (OA) and interlayer spacing (d002) from SAED patterns of pyrocarbon.
• To assess the effectiveness of these algorithms for analyzing pyrocarbon in Carbon/Carbon (C/C) composites produced via chemical vapor infiltration.

Main Methods:

• Development of a suite of algorithms including a five-point center-determined technique, ellipse detection with an integral factor, background subtraction, and Gaussian multipeak fitting.
• Implementation of algorithms for intensity sampling, data correction, and data fitting, considering the contribution ratio of reflection intensity to average d002.
• Application and evaluation of programmed algorithms on SAED patterns of pyrocarbon, with and without beam stop images.

Main Results:

• The proposed algorithms effectively measure various SAED patterns of pyrocarbon, accommodating the presence or absence of beam stop images.
• Azimuthal intensities along the (002) diffraction arcs generally follow a Gaussian distribution, particularly evident in highly textured pyrocarbon.
• The Gaussian multipeak fitting algorithm is essential for achieving accurate orientation angle (OA) measurements.

Conclusions:

• The developed algorithmic approach provides a robust and effective method for quantitative analysis of pyrocarbon SAED patterns.
• Accurate determination of pyrocarbon's structural parameters (OA and d002) is achievable with the implemented computational techniques.
• The findings highlight the importance of Gaussian multipeak fitting for precise orientation angle determination in pyrocarbon characterization.