X-Ray Fluorescence Lab Report

Transcription

1 X-Ray Fluorescence Lab Report Arena Holguin, Sylvia Navidad, Gabriel Gonzalez MME5401/MASE /14/11

2 1. Introduction X-Ray fluorescence (XRF) is a popular, nondestructive analytical method for elemental compositon analysis of materials. Qualitative analysis with XRF is concerned with answering questions regarding the composition of unknown substances in a given sample. X-ray Fluorescence was performed on two samples of clay pottery obtained from the Pueblo Indian community. Both sides of the sample labeled (designated a and b) were analyzed along with one side of sample A portable, handheld XRF spectrometer was used to analyze the samples. 2. Physics of XRF X-ray Fluoresence is an elemental analysis technique that uses an external x-ray source, such as silver, to obtain information from a sample. The process begins with the external x-ray causing the photoejection of a core electron. The ejected electron leaves behind a vacancy and another electron at a higher energy level falls down to fill it. A characteristic x-ray photon is produced by the electron that falls. This process can be seen in Figure 1. In Energy Dispersive X-ray Fluoresence (EDXRF), the characteristic x-ray is then collected in a semiconductor detector and analyzed to determine the element present in the sample. The detector converts the energy of the incident X-ray into a voltage pulse whose amplitude is proportional to that energy. A multichannel analyzer is used to accumulate a histogram of the pulse amplitude spectrum. Thus, XRF can perform simultaneous multiple element analysis for material samples. (1) The nomenclature of XRF transitions is based on the levels from which the first electron is ejected and from where the second electron falls. For example, if an electron is ejected from the K level and an electron falls from the L sublevel 3, the transition is called Kα1. This can be seen in Figure 2 along with other examples of transitions. Furthermore, the energy of the XRF process can be measured by subtracting the energy of the lower level from the higher level energy. X-ray Fluorescence measures wavelengths, λ, between nm which can also be translated to energies between KeV. (2) Figure 1. X-Ray Fluorescence Process (3) 1. The sample is excited with X-ray light 2. An inner electron is ejected 3. A characteristic x-ray is emitted by an electron that falls to fill in the vacancy from the initially ejected atom. 2

3 Figure 2. Energy level transitions for XRF nomenclature (2) 3. Experimental Methods An X-MET 3000TX handheld XRF spectrometer (Fig. 3) with a silver element producing the incident x-ray was used in this experiment. The two samples analyzed were clay pottery fragments obtained from the Pueblo Indians. Both sides of the sample were analyzed and labeled as a and b (Fig. 4 a-b). Only one side of the sample, which had bands, was analyzed (Fig.4 c). The samples were carefully placed on the XRF and analyzed for 300 seconds. Figure 3. X-MET 3000TX handheld XRF spectrometer 3

4 (a) (b) (c) Figure 4. (a) Sample a (b) Sample b (c) Sample Experimental data and results Figure 5 shows the calibrated peak for each of the three samples. The black line is the spectra, the red line is the peak fit, and the yellow line represents the background. Figure 6 shows the mass fraction calculations for each element detected in the samples based on the peak fit area. Nickel was detected on both sides of sample while none of it was detected in sample The last two figures (Fig. 7 and 8) are the data graphs for some of the elements with the highest mass fractions. The mass fraction plots in Figure 7 demonstrate a similar composition for Fe along with a similar concentration of Ti and possibly Zn between both sides of sample and sample The graphs in Figure 8 show a very similar concentration of Cu for both sides of sample 14273, however, that of sample is significantly different. Both sides of sample demonstrate similar compositions except for the concentration Co which has a higher mass fraction on side a. 4

5 Figure 5. XRF Spectra (a) Sample a (b) Sample b (c) Sample

6 14273-a Element Group Fit Area Sigma Mass Fraction S K 1.82E E E-04 Cl K 6.46E E E-04 K K 1.79E E E-02 Ca K 4.38E E E-02 Ti K 2.16E E E-02 V K 1.91E E E-03 Cr K 3.50E E E-03 Mn K 2.98E E E-03 Fe K 7.04E E E-01 Co K 2.25E E E-02 Ni K 2.88E E E-04 Cu K 5.63E E E-03 Zn K 2.30E E E-02 Ga K 2.15E E E-03 As K 3.10E E E-03 Se K 8.02E E E-03 Br K 6.82E E E-03 Rb K 7.41E E E-02 Sr K 1.56E E E-01 Y K 5.02E E E-02 Zr K 1.51E E E-02 Nb K 5.22E E E-02 Nb L 1.90E E E-03 Mo K 5.10E E E-02 Pd L 1.39E E E-05 Ag L 1.25E E E-04 Cd L 1.43E E E-04 Sn L 5.15E E E-03 Sb L 9.71E E E-03 Te L 2.77E E E-03 W L 2.46E E E-03 Pt L 3.75E E E-03 Au L 7.70E E E-02 Bi L 1.01E E E b Element Group Fit Area Sigma Mass Fraction S K 3.32E E E-04 Cl K 2.79E E E-04 K K 1.42E E E-03 Ca K 1.13E E E-02 Ti K 1.65E E E-02 V K 1.69E E E-03 Cr K 3.76E E E-03 Mn K 3.94E E E-03 Fe K 6.69E E E-01 Co K 2.24E E E-02 Ni K 9.60E E E-04 Cu K 4.88E E E-03 Zn K 2.04E E E-02 Ga K 2.01E E E-03 As K 3.31E E E-03 Se K 9.20E E E-03 Br K 8.68E E E-03 Rb K 7.78E E E-02 Sr K 1.51E E E-02 Y K 5.11E E E-02 Zr K 1.53E E E-02 Nb K 5.53E E E-02 Mo K 5.53E E E-02 Pd L 5.51E E E-04 Ag L 1.09E E E-04 Sn L 2.50E E E-03 Sb L 2.90E E E-02 Te L 6.79E E E-03 W L 9.77E E E-04 Pt L 2.01E E E-03 Au L 7.72E E E-02 Bi L 1.01E E E Element Group Fit Area Sigma Mass Fraction S K 5.70E E E-04 Cl K 5.83E E E-04 K K 1.36E E E-03 Ca K 1.65E E E-03 Ti K 3.25E E E-02 V K 3.83E E E-03 Cr K 4.60E E E-03 Mn K 2.24E E E-04 Fe K 1.50E E E-01 Co K 3.59E E E-02 Cu K 4.04E E E-03 Zn K 2.43E E E-03 Ga K 2.19E E E-04 As K 5.73E E E-03 Se K 8.10E E E-03 Br K 8.32E E E-03 Rb K 6.81E E E-02 Sr K 2.36E E E-02 Y K 4.91E E E-02 Zr K 1.86E E E-02 Zr L 1.27E E E-04 Nb K 6.05E E E-02 Mo K 5.76E E E-02 Pd L 1.01E E E-04 Ag L 1.01E E E-04 Cd L 8.33E E E-04 Sn L 5.80E E E-03 Sb L 3.36E E E-03 Te L 3.44E E E-03 W L 3.42E E E-03 Pt L 2.97E E E-03 Au L 7.71E E E-02 Bi L 1.12E E E-03 Figure 6. Peak Data and Mass Fraction for (a) Sample a (b) Sample b (c) Sample

7 Figure 7. Data plots comparing elements with highest mass fractions in each sample (Fe held constant) 7

8 Figure 8. Data plots comparing elements with highest mass fractions in each sample (Cu held constant) 8

9 References 1. Whan, R.E. ASM Materials Characterization (Vol. 10). Metals Park : American Society for Metals. 2. Lopez, Jorge. X-Ray Fluorescence. [lecture]. s.l. : The University of Texas at El Paso, November Rigaku (EDXRF). [Online] 11 1,