Scientific paper
Characterization of the Radiation Effect in A Binder by X-Ray Diffraction
Vjera Novosel - Radovi},a,* Nikol Radovi},b Milka Balena
and Franjo [afara
a @eljezara Sisak, 44000 Sisak, Croatia b Faculty of Geodesy, University of Zagreb, 10000 Zagreb, Croatia * Corresponding author: E-mail: nradovic@geof.hr Received: 03-04-2008 Dedicated to the memory of Professor Ljubo Gotte
Abstract
The influence of x - ray radiation on samples of binder (LÌ2CO3, H3BO3, Na2B4O7 ■ IOH2O) was examined. The components were ground and placed as thin film on the Mylar foil and exposed to beam of primary x - ray on semi - automatic x - ray spectrometer (Au - anode, 20 mA/ 45 KV) successively for period 1 to 8 hours. Comparative results were observed for x - ray diffraction analysis, scanning electron microscope analysis and sieve analysis.
Keywords: Radiation effect, briquetting conditions, structural changes
1. Introduction
For analysis by X-ray emission spectrometry powder samples are prepared using the melting technique or the briquetting technique.1-4 In the case of briquetting a binder is added to the sample. The amount of binder will depend on the nature of the sample and on its phase composition. For each type of powder sample the briquetting conditions are determined in advance5. The briquetted samples should have a compact, smooth surface as well as good handling resistance6. Only samples having positive handling resistance values are measured. Certain samples, however, may exhibit reduced handling resistance values during measurement. In this work handling resistance was measured with a VDM apparatus of own manufacture.7,8 Our examination of standard samples of iron ore, sinters, mixture for sinters, and high furnace slag pressed into briquettes with a binder and exposed to X-rays demonstrated diminished wear resistance as well as the appearance of surface cracking and edge sprinkling (Figure 1).
A
B
Figure 1. The sample of standard sinters A - before and B - after irradiation 4 hours in the Philips semiautomatic X-ray spectrometer (Au - anode, 20 mA/ 45 KV)
2. Experimental
The effect of exposure to X-rays in briquetted sinter samples was investigated on model samples. The model
samples were prepared with the binders Li2CO3 Merck, and H3BO3 and Na2B4O7 ■ 10H2O Kemika. They were ground in a WC attachment of a Spex mixer mill for 30 minutes and placed, as a thin film, on a mylar foil in the sample holder PW 1427/40. Then they were irradiated in a Philips semi - automatic X-ray spectrometer PW 1410/10 (Au anode, 20 mA/ 45 KV) for the duration of one to eight hours.
The irradiated samples were examined by means of X-ray diffraction and scanning electron microscopy, and by sieve analysis. Diffraction patterns were collected at room temperature using a Philips counter diffractometer with monochromatized CoKa radiation. From those patterns the maximum shift (lmax) and full width at half maximum intensity (FWHM) were assessed. The lmax values were determined from the diffraction lines corresponding to dk interplanar spacing as follows: 1.39 À for the Li2CO3 binder, 1.60 À for H3BO3, and 1.56 À for Na2B4O7 ■ 10H2O. The respective FWHM values were 2.83 À for Li2C03, 3.17 À for H3BO3 and 4.83 À for Na2B4O7 ■ 10H2O. Micrographs of the nonirradiated samples were taken with a scanning electron microscope and microa-nalyser, a Joel JXA - 50A. Both the irradiated and nonir-radiated H3BO3 samples were examined by sieve analysis (DlN system). Samples of the fractions resulting from sieve analysis of the nonirradiated H3BO3 were subsequently irradiated for two hours. After irradiation each fraction was once again subjected to sieve analysis.
3. Results
Results of investigation are presented in figures and in tables. Figures 2 show characteristic sections of diffraction patterns of the Li2CO3, H3BO3, and Na2B4O7 ■ 10H2O samples, before and after irradiation: H3BO3 was irradiated for two hours, Li2CO3 and Na2B4O7 ■ 10^2O for eight hours.
The number, relative intensity, and shape of diffraction lines changed with the irradiation time. Concurrently, as a result of radiation exposure, changes in the lmax (Figure 3) and FWHM (Figure 4) values were observed.
There was a shift in the lmax values with respect to the initial values: to 0.017 foi" Li2CO3, to 0.036 for H3BO3, and to 0.137 °2e for Na2^4O7 ■ 10H2O. The FWVHIM value for Li2CO3 was 0.017, for H3BO3 0.036, and for Na2B4O7 ■ 10^2O 0.047 °2e. According to litera-ture9 those changes were due to grain fragmentation or enlargement, and/or to microstrain. They produced a direct effect on the mechanical properties and microstruc-ture of the material, which in our case was briquette with a binder. Table 1 shows changes in the grain size of the irradiated H3BO3 sample.
After two hours of irradiation the percentage of the 125-90 Mm fraction rose from 2.32 to 19.54%, and of the 90-63 Mm fraction from 0.56 to 7%. At the same time the 125 Mm fraction percentage diminished from 94.95 to 71.97%, and the 63 Mm fraction percentage from 2.12 to
Ml
85°	80°
OX»-)ir.nK
2)
1.60
1.40 ,44 . 1 Al
1.56 1 SJ 1-481.51, „
80 76° 72° 68° 64
2CS) / CoK

3)
1.41
1.79
1.60
1.76
1.56 j
75°	70° 65° 60"
2(H) / Cnk'
Figure 2. Characteristic part of the X-ray diffraction patterns 1 - Li2CO3 recorded at 25 °C: A - before and B - after irradiation 8 hours, 2 - H3BO3 recorded at 25°C: A - before and B - after irradiation 2 hours, 3 - Na,B4O7 ■ 10H,O recorded at 25°C: A - before andB - after irradiation 8 hours.
Figure 3. Shift values L.. for different binder samoles
E TIME, h
Figure 4. FWHM values for different binder samnles
1)
Table 1. Distribution of grain size fraction of boric acid irradiated by X-rays in function of exposure time
Exposure	Percentage of fractions
time (h)	grain size ranges of fractions (^m)*
	> 125	125-90	90-63	< 63
0	94.95	2.32	0.56	2.12
1	65.48	29.43	1.57	3.46
2	71.97	19.54	7.00	1.41
mean values of no less than three measurements.
Figure 5. Distribution of grain size fractions determined in fractions separated from H3BO3 sample and irradiated by X-rays after that for 2 h. Irradiation condiations: Au - anode, 20 mA/ 45 KV.
1.41%. Similar effects were observed in other fractions as well,10 Figure 5.
Sieve analysis of each of the sample fractions irradiated after separation from the total H3BO3 sample, gives better information about the changes taking place inside the fractions. In addition to the grain sizes apperataining
Figure 7. Scanning electron micrographs of H3BO3 recorded at 25 °C: before and after irradiation: 1 - 0, 2 - 1, 3 - 2 hours. Magnifications 15000 X.
to the basic fraction, other sizes appear in each fraction after irradiation. Scanning electron micrographs of Li2CO3 (Figure 6), H3BO3 (Figure 7), and Na2B4O7 ■ 10H20 (Figure 8) after two, four or eight hours of irradiation show grain fragmentation of different size and shape.
Increase in the number of smaller size fractions can be accounted for by breaking of the larger grain as a result of irradiation. Formation of sharply edged particles can be seen in Figure 6, interruption of the initially regular lamellar structure in Figure 7, and appearance of cracks on the grain surface in Figure 8. These radiolytic changes led to structural changes which, in turn, were responsible for diminished handling resistance of standard samples11 as regards their analytical use in X-ray emission spectrometry, as well as for the limited period of use.
Figure 6. Scanning electron micrographs of Li2CO3 recorded at 25 °C: before and after irradiation: 1 - 0, 2 - 1, 3 - 4 and 4 - 8 hours. Magnifications 1500 X.
Figure 8. Scanning electron micrographs of Na2B4O7 ■ 10H2O recorded at 25 °C: before and after irradiation: 1 - 0, 2 - 1, 3 - 4 and 4 - 8 hours. Magnifications 15000 X.
4. Conclusions
5. References
Results show that standard samples preset into briquettes with Li2CO3, H3B03, andNa2B4O7 ■ 10H20 binders exhibited diminished handling resistance following exposure to X-rays. Depending on duration of exposure X-ray diffraction patterns demonstrated changes in the number, relative intensity, and shape of diffraction lines, as well as a broadening and shift in position, Imax °20. Examination of samples of the fraction resulting from sieve analysis of the nonirradiated H3BO3 which were first irradiated for one or two hours and then resubjected to sieve analysis, showed a different radiation effect. As a result of irradiation, in addition to the grain size pertaining to basic fraction, other grain sizes were also present. Grain fragmentation due to irradiation is visible on the micrographs. The amount of large grains increased as did the number of smaller grain sizes. Formation of sharply edged particles, interruption of initial lamellar structure, and appearance of cracks on the grain surface were observed. These radiolytic changes led to structural changes which, in turn, were responsible for diminished handling resistance of standard samples as regards their analytical use in X-ray emission spectrometry, as well as for the limited period of use.
1.	F. Claisse, Quebec Dept. Mines. P. R. 1956, 327, 3-19.
2.	K. Norrish, J. T. Hutton, CSIRO Aust. Div. Soils 1964, 3, 1-10.
3.	R. Jenkins, Bull. Anal. Equip Philips, 17.7000.38.029.4.21 Eindhoven, 1970.
4.	R. V. Grieken, A. A. Markowicz, Handbook X-Ray Spectrometry, Sample Preparation for X-Ray Fluorescence, Marcel Dekker, Inc. New York, 2002, pp. 936-976.
5.	Vj. Novosel - Radovic, Ph. D. Thesis, Tehnološki fakultet Sveučilišta u Zagrebu, Zagreb, 1983.
6.	J. Jacobs, Nat. Inst. Mat. Repub. J. Afr. Rep. 1975, 1742, 4-10.
7.	Vj. Novosel - Radovic, Da. Maljkovic, CHIMA, 1998, 7-8, 215.
8.	Vj. Novosel - Radovic, Da. Maljkovic, Metalurgija, 1999, 38, 47.
9.	B. N. Sineh, J. Noel. Mater. Oct. 1998, 258-261.
10.	Vj. Novosel - Radovic, Da. Maljkovic, M. Nenadic, Spec-trochemica Acta, 1985, 40B, 701-704.
11.	Vj. Novosel - Radovic, N. Radovic, F. Safar, Book of Abstract Denver X-Ray Conference, 2006, 7-11 August 2006, Denver, Colorado, U.S.A., pp. 80.
Povzetek
Briketi narejeni z Li2CO3, H3BO3 in Na2B4O7 ■ 10H20 kot vezivom so po obsevanju z rentgenskimi žarki izkazovali zmanjšano zmožnost splošne uporabe. Rentgenski posnetki izkazujejo spremembe v številu, relativni intenziteti in obliki difrakcijskih maksimumov. Te radiološke spremembe so predvidoma vplivale na strukturne spremembe in tako posredno vplivale na uporabnost briketov v rentgenski emisijski spektrometriji.