Determination of impurities in graphite using synchrotron radiation based X-ray fluorescence spectrometry.
Determination of impurities namely Ca, Mn, Fe, Ni, Zn, Sr and Pb in graphite by energy dispersive X-ray fluorescence spectrometry is described using microfocused synchrotron radiation. The internal standard and standard addition methodologies were adopted for quantification and the results were compared with tube-based X-ray fluorescence spectrometry. Analysis of the results by the F and t-tests revealed their statistical equivalence. Synchrotron measurements improved the detection limits by an order of magnitude compared to the tube based technique. Cr and Zr, which were below the quantification limit in tube based technique, were also quantified by synchrotron based technique.
Chemical characterization of graphite by instrumental neutron activation analysis
Nuclear and commercial grade graphite samples were analysed by instrumental neutron activation analysis (INAA) using high flux reactor neutrons. Eleven elements (Na, K, As, Sc, Fe, Cr, Co, Zn, La, Ce, and Sm) were determined in eight samples of graphite (two nuclear grade and six commercial grade) by irradiating at a neutron flux of 3 × 1013 cm−2 s−1 in CIRUS reactor and assaying the activity by high-resolution gamma ray spectrometry using 40% relative efficiency HPGe detector coupled to an MCA. Concentrations of elements were determined by relative method of INAA. Results of both types of graphites as well as detection limits achieved by INAA method are discussed in the paper.
The effect of pressure and fast neutron irradiation on the thermal expansion coefficients of graphite crystals
Abstract Large changes in the interlayer spacing of a graphite crystal can be obtained by the application of pressure or by fast neutron irradiation. In the latter case, it is well known that the thermal expansion coefficient parallel to the hexagonal axis ( α c ) decreases substantially, while the expansion coefficient parallel to the basal planes α c changes (at ambient) from a small negative to a small positive value. No measurements of the effects of pressure have been reported. A simple model of the interlayer forces which agrees well with experiment is used to calculate the effect of interlayer contraction (pressure) and expansion (irradiation) on the expansion coefficient α c and the latter compared with experiment. Consideration is given to changes in α a