CRYSTALLINE SIZE OF CALCINED PETROLEUM COKE BY X-RAY DIFFRACTION: ASTM D5187
EXPLANATION
Crystallinity of petroleum coke is a general measure of quality affecting suitability for end use and is a function of the heat treatment. The crystallite thickness is used to determine the extent of such heat treatment, for example, during calcinations. The value of Lc determined is not affected by coke microporosity or the presence of foreign, noncrystalline material such as dedust oil.
An X-ray diffraction pattern of a representative, pulverized sample of calcined petroleum coke is obtained using conventional X-ray scanning techniques. Calcined petroleum coke contains crystallites of different thickness of all crystallites in the sample by empirical interpretation of the X-ray diffraction pattern. The crystallite diameter La is not determined by this method.
TEST SUMMARY
A packed sample pulverized to less than 75 m is subjected to a monochromatic X-ray beam and rotated to produce a diffraction pattern under specific conditions. The location and the shape of the peak with hkl = (002) at d = 3.35 A0 is used to calculate the Lc by manual interpretation of the peak or by computer simulation.
TEST PRECISION
Repeatability: 0.021 X
Reproducibility: 0.11 X
Where X is the average of two results in angstroms.
The bias of this test method has not been determined since there is no accepted reference material for this analysis.
This test method has no bias.
