A Study on the Quantitative Analysis of Portable XRF for the Components Analysis of Metal Cultural Heritage

In this study we conducted component analyses of portable XRF detectors using four Au-Cu alloy standard samples to improve their accuracy by drawing up a calibration curve based on ICP-OES standard values. The portable XRF analysis found absolute errors of 0.3 to 3.7 wt% for Au and 0.2 to 8.2 wt% for Cu, confirming that the error range and standard deviation differed from one detector to another. Furthermore, the calibration curve improved their accuracy, such that the relative error rates of Au and Cu decreased from 9.8% and 14% to 3.5% and 3.7%, respectively. Accordingly, an experiment to confirm the calibration curve was conducted using unknown samples, finding that the measured values of the unknown samples fell on the calibration curve. Therefore, to accurately analyze the components of metal cultural heritage items, it is necessary to prepare a calibration curve for each element after checking whether the detector is suitable for the artifact.

Quantitative Determination of Low Contents of Manganese in Steels by EPMA

The fluorescence effect induced by Kβ photons is usually so small that it can be neglected. However, in the Fe–Mn system, omitting Kβ fluorescence correction will lead to the overestimation of the Mn content especially when Mn is the minor alloy element. In this study, the error in the Mn concentration induced by Kβ fluorescence was investigated by both Monte Carlo simulation, using the pyPENELOPE program, and systematic electron probe measurements on the Fe–0.53% Mn alloy standard by the aid of CalcZAF software. It is shown that the error caused by Kβ fluorescence exceeds 4% for the Fe–0.53% Mn alloy. The problem can be overcome by utilizing CalcZAF in which β-line fluorescence has been included, or by employing a similar standard Fe–0.85% Mn for Mn in the absence of β-line fluorescence correction. In addition, a modified calibration curve method, using k-values instead of X-ray intensity as a variable, is presented and used to measure the Mn concentration. The accuracy of this method is as good as or better than that of the conventional matrix correction method. Compared with conventional calibration curve methods, it is time-saving because the k-value is not sensitive to instrument fluctuations and the established curve remains valid for a long period.

Detecting Temporal Changes of Self-Absorption in a Laser-Induced Copper Plasma from Time-Resolved Photomultiplier Signal Emission Profiles

This work reports an investigation on the feasibility of using a photomultiplier tube (PMT) to follow the time evolution of self-absorption of copper resonance transitions at 324.7 nm and 327.4 nm. The plasma was obtained by focusing a Nd:YAG laser, operated at 1064 nm, on a series of aluminum alloy standard disks containing different copper concentrations. The results described have been obtained at different times and with different set-ups. These set-ups consisted of a Paschen–Runge polychromator, a LIBS 2000 spectrometer, and a spectrometer equipped with both an intensified charge-coupled device (ICCD) and PMT. Both PMT signals and time-resolved spectra were obtained and the ratio of the two Cu resonant lines was calculated, compared, and discussed. By selecting different delay times and integration gates of the PMT signals, the self-absorption effect of the Cu resonant lines was found to be changing, implying that, by careful selection of the integration window of PMT signals, the self-absorption may be minimized, thus improving the calibration linearity of the technique.

Surface Recrystallization and Twin Formation in a Single Crystal Superalloy

The samples of single crystal superalloy DD6 were grit blasted and then heat treated in the temperature range of 1100-1250°C for 4h and the DD6 alloy ‘standard heat treatment’ in vacuum furnace, respectively. The results showed that cellular recrystallization occurred in the surface layer after heating at 1100°C for 4 hours. While equiaxed recrystallization grains occurred near the surface of the samples annealed at 1200°C for 4 hours, meanwhile, cellular recrystallization located between equiaxed recrystallization grains and the original region. With the improvement of the heating temperature, the size of cellular recrystallization decreased, while the size of equiaxed recrystallization grains increased, and the shape of the coarse γ′ phase in the cellular recrystallization changed from lamellar to equiaxial. Fully equiaxed recrystallization grains nucleated after standard heat treatment. Furthermore, the twins occurred in fully equiaxed recrystallization grains, and that the γ′ phase of the twin plane appeared different from that of the equiaxed recrystallization boundary. On the contrary, the twin formation was not observed in the cellular recrystallization grains. Therefore, the differences in twin behavior between the fully equiaxed recrystallization and cellular recrystallization grains were discussed.