Surface Analysis of one Pound from the Egyptian Coins

Transcription

1 Surface Analysis of one Pound from the Egyptian Coins S. A. Abd El Aal 1, N.Dawood 2, and A. I. Helal 1 1-Central Lab. for Elemental & Isotopic Analysis, NRC, AEA. 2-Taiba University Saudi Arabia. ABSTRACT Two different analytical techniques namely, X-Ray Fluorescence and Energy Dispersive x-ray are used in the present work to investigate the surface elemental analysis of one pound Egyptian coins produced at the years 2005, and. Every coin has a yellow disk and white ring. Laser ablation technique is used to produce small particles form the surface of the pound. Key Words: X-ray Fluorescence/ Energy Dispersive x-ray. 1-INTRODUCTION X-ray fluorescence (XRF) technique is among other elemental analytical compositions techniques, which are used to study the ancient coins of countries ( 1, 2). It can analyze the coins and can give additional insight in some cases about the economic status at different nations (3, 4). It is nondestructive, fast, sensitive, and multi-elemental analytical technique. Scanning Electron Microscope attached with Energy Dispersive X-ray fluorescence (SEM -EDX) technique is regarded as a microprobe technique. It can analyses a specific area of the coin which can reach the dimension of 1mm 1mm or less to give the elemental composition in that specific place (5). In the present work, multi-elemental composition of elemental analysis of one pound from the Egyptian coins that produced at the years 2005, and by using XRF and EDX techniques was performed. The major and minor elements in the Egyptian coins alloy are discussed for more investigation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is used to ablate the surface of the coins. 2-EXPERIMENTAL The coins are washed by distilled water and nitric acid 2.5% placed in an ultrasonic cleaner for 10 minutes and then dried with air streaming for 5 minutes. Elemental analysis studies were made on three groups of coins, which were released at the years 2005, and. The shape of the three coins of the pound is similar and shown in Fig. (1). Fig. (1): One-pound Egyptian coins released at the years 2005, and

2 The X-ray Fluorescence (XRF) spectrometer is used to analyze the coins. Figure (2) represents the schematic diagram of the XRF system used for the study. The system consists of a low power aircooled X-ray tube as an excitation source. The operating voltage and the current of the X-ray tube were 30 kv and 0.6 ma, respectively. The X-rays from the tube was exposed on a molybdenum secondary exciter and the generated characteristic X-rays of molybdenum were used to excite the elements present in the studied coins samples. The measurement time for the determination of the main components was 300 seconds. The characteristic X-rays emitted from the elements present in each sample were collected using a Si (Li)detector and a PC-based multi-channel analyzer (6). The unit can detect elements from sodium to uranium Fig. (2): Schematic diagram of the XRF system. Fig. (3): Schematic cross-section of an electron microprobe column with the energy dispercive analyzer (EDX). On the other hand, microprobe EDX analysis is a non-destructive technique used for solid surfaces elemental analysis. The range of detection is from majors to minors down to 100 part per million per -264-

3 gram (ppm). The analysis can detect elements from carbon to uranium. Quantitative elemental analysis was done by using ZAF correction calculations. EDX was done for three coins on the surface of the coins to detect the elemental changes. Firstly the coins were analyzed by XRF and then by EDX on the surface of the coins (7, 8). One-Pound Coin 3-RESULTS AND DISCUSSION At the years 2005 to 2010, the geometrical round shape of the Egyptian pound coin was the same. The mean weight of the 2005, and were 8.42gm, 8.39 gm and 8.43gm, respectively. Elemental Composition of the three Coins by XRF technique The elemental composition and concentrations expressed as percentages of 2005, and one-pound Egyptian s coin on the surface by XRF technique are given in Table (1). Inspection of Table (1) shows that the disk of 2005 one-pound coin was mainly copper and aluminum. Other elements such as Ni, Fe, S and Si were observed with minor concentrations less than (1 %). The copper concentration was high and reached (92 %) with low concentration of aluminum that reached (8 %). For the same coin the ring surface analysis gives different data, it is Cu and Ni alloy. The copper concentration was reached to (74 %), while the concentration of nickel reached to (25 %). The disk of coin became copper and zinc alloy. The concentration of copper decreased to (71%) and the concentration of zinc was nearly (28%). The ring surface analysis for the ring of coin became mainly nickel with concentration of nearly (99%). Other elements such as Ni, Fe and S were observed with minor concentrations less than (1 %). Table (1): Concentration (in mass %) of various elements in one pound Egyptian s coin by XRF technique. Year Cu Ni Fe S Si Al Zn Elemental Composition of three Coins by Microprobe EDX technique. Finally, for the disk of coin, the concentration of copper was nearly (74%) and the concentration of zinc was increased to (24%). Other elements such as Ni, Fe and S were observed with minor -265-

4 concentrations less than (2 %). The ring surface analysis for the coin meanly nickel with concentration of nearly (95%). Other elements such as Ni, Fe and S were observed with minor concentrations less than (5 %). Microprobe EDX technique gives the possibility to analyze the elemental composition of a small and fine area of the surface of the disk and ring. The elemental composition and concentrations expressed in the percentages of 2005, and one-pound Egyptian s coin on the surface of the disk and the ring by microprobe EDX technique is given in Table (2). Inspection of table 2 shows that the surface of the disk of 2005 one-pound coin is copper and aluminum. Other elements such as O, Fe, and Si were observed with minor concentrations (3%). Oxygen element can be observed by EDX technique, which cannot be detected by XRF technique. By comparing results of XRF and EDX techniques, there is an agreement between the two techniques for detection of Cu, Fe, Si and Al elements on surface of the disk of 2005 one-pound coin. Concerning the bulk of the coin, table 2 shows that the surface of the disk of 2005 one pound s coin it was copper and aluminum. Other elements O, Fe, Si and Zn were observed with minor concentrations (3%). Microprobe EDX technique was used to complete the whole figure of the elemental composition of the coin because it showed that outer ring of 2005 one pound s coin contained Ni element with concentration of (25%) in the surface of ring of the coin. Table 2 shows that on surface of the disk of one pound s coin it was copper and zinc. Oxygen was observed with minor concentration of (3%). The elemental composition on the surface of the ring was nickel with low concentration of Fe less than (1%). Microprobe EDX analysis on surface of the disk of one pound s coin showed that the alloy was copper and zinc with minor concentration (5%) of oxygen. The elemental composition on surface of the ring was nickel with low concentration of Fe less than (0.5%). Table (2): Concentration (in mass %) of various elements in one pound Egyptian s coin microprobe EDX technique. Year Cu Ni Fe S Si Al Zn O The Egyptian pound is consisting of two alloy surfaces (disk and ring). Pulsed laser ablation shots of every part of the coin and the ablation plume components can deposit on a glass substrate and form thin metallic layers ( 9,10). These layers were characterized by XRF, EDX and SEM to study the deposited structure of the coin. The laser shots are used in the raster mode as shown in Fig (3)

5 Fig. (4): SEM micrograph for LA in the raster mode When the Laser irradiance was 1.5x109 w/cm2 and laser repetition was 10 Hz the formed structure was irregular and the particle size was around 1µm as shown in Fig. (4). 2μm Fig. (5): SEM micrograph of metallic structure on glass substrate. After changing the laser repetition rate to 20 Hz, with the same laser parameters the particle size distribution tend to be homogenous as shown in Fig.(5). The particle size distribution was measured and the high distribution of particle sizes was around 200 nm

6 2μm Fig.(6): SEM photomicrograph of Nanostructure material on glass substrate by using LA. Fig.(6): The cross-section of one pound. When raster mode is used, the composition of small particles is the same for the surface alloy of the pound as in Table (2). When the drilling mode is used, the composition of the small particles is the same of the surface alloy of the pound but the concentration of the iron element (Fe) increased -268-

7 because of the core of the pound has iron as a major element. This fact discovered after the cutting of the pound and analyzed the bulk cross-section as in Table (3). Table (3): Concentration (in mass %) of various elements in one pound Egyptian s coin (bulk cross-section) by microprobe EDX technique. Egyptian pound Cu Ni Fe Si Al Mn Zn surface cross sec surface cross sec REFERENCES (1) R.Tapash Rautray, S. Suman Nayak, B.Bipin Tripathy, Saubhagyalaxmi Das, Manas R. Das, Satya R Das, Pranab K. Chattopadhyay; Applied Radiation and Isotopes; 69, 1385 (2011). (2) M. Hajivaliei, M.L. Garg, D.K. Handa, K.L. Govil, T.Kakavand, V.Vijayan, K.P. Singh and I.M. Govil; Nucl. Instr. and Meth. B; 150, 645 (1999). (3) M. M. Al- Kofahi and K. F. Tarawneh; X-Ray Spectrom.; 29, 39(2000). (4) Z. Sándor, S. Tölgyesi, I. Gresits,, M. Káplán-Juhász ; Journal of Radioanalytical and Nuclear Chemistry; 246, 385 (2000). (5) DeLorey, Tom; "Certified 74 Aluminum Cent", COINage Magazine. p. 34,(Nov. 2005). (6) Y. Chen, G. Luo, J. Diao, O. Chornoguz, M. Reeves and A. Vertes ; J. Phys.,Conf. Ser; 59,548 (). (7) K. Vijay, Nanosilicon edited by Hardbound, Elsevier Ltd.(). (8) A. Pitarch, I. Queralt, A. Alvarez-Perez, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms; 269, 308 (2011). (9) A. Pitarch, I. Queralt Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms; 268, 1682 ( 2010). (10) B. Constantinescu, R. Bugoi, E. Oberlander Tarnoeanu, K. Parvan; Romanian Reports in Physics; 57, 1021( 2005)