- Email: [email protected]
Positron Annihilation Spectroscopy study of minerals commonly found in shale
Nuclear Instruments and Methods in Physics Research B xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Positron Annihilation Spectroscopy study of minerals commonly found in shale q Helge Alsleben a, Fnu Ameena b, James Bufkin c, Joah Chun d, C.A. Quarles b,⇑ a
Texas Christian University, School of Geology, Energy, and the Environment, Fort Worth, TX 76129, USA Texas Christian University, Department of Physics and Astronomy, Fort Worth, TX 76129, USA c Angelo State University, San Angelo, TX 76909, USA d Colorado College, Colorado Springs, CO 80903, USA b
a r t i c l e
i n f o
Article history: Received 20 June 2017 Accepted 29 June 2017 Available online xxxx Keywords: Positron Positronium Lifetime Doppler Broadening S parameter Clay Minerals
a b s t r a c t Positron Annihilation Lifetime and Doppler Broadening spectroscopies are used to investigate twentythree different rock-forming minerals that are commonly found in shale. Doppler Broadening provides information about the positron and positronium (Ps) trapping sites for comparison among the various minerals. Correlations of positron lifetime and Doppler Broadening are observed for different groups of minerals. Finally, Ps formation, or lack thereof, in the various minerals has been determined. Ó 2017 Elsevier B.V. All rights reserved.
1. Introduction Positron Annihilation Spectroscopy (PAS) has been very effectively used to characterize diverse properties of many materials such as defects in metals and semiconductors and free volume in polymers [9,13,16]. What distinguished these materials where PAS has been most successful is that they are typically uniform and homogeneous. PAS has been much less frequently applied to the study of natural materials such as rocks and minerals. The most detailed study of sandstone and limestone rocks is still the work of Urban-Klaehn [18], Urban-Klaehn et al. [19,20], Quarles et al. [14]. Opals, a variety of hydrated silica, have been studied by several groups because of the long positronium lifetimes observed in the cage structure of the opals [19,20,21,2,5]. Montmorillonites have been studied by several authors because of their interesting layered structure [15,17,6,10]. There have also been a few studies of specific types of minerals [4,7]. But, there has not been up to now a systematic investigation of minerals, perhaps because of the great variety of minerals that occur naturally.
q Conference on the Application of Accelerators in Research and Industry, CAARI 2016, 30 October – 4 November 2016, Ft. Worth, TX, USA. ⇑ Corresponding author. E-mail address: [email protected] (C.A. Quarles).
The present work has been motivated by recent investigation of positron lifetime and Doppler Broadening in Barnett Shale samples which have shown a small intensity of positronium Ps) formation. [1]. The samples studied had XRF information on 35 elements, XRD information on mineral constituents, and chemical information on total organic carbon TOC) [3,11]. While the positron annihilation lifetime parameters were not observed to be significantly correlated with elemental composition or mineral composition, the S parameter from the Doppler Broadening experiments was found to improve the prediction of TOC when coupled with certain elements known to be weakly correlated with TOC such as Cu, Ni or Zn concentration. The S parameter had also been observed to be somewhat correlated with TOC in another previous study of a shale core [12]. However, it has not been known where Ps is formed in the shale. Previous research has shown that Ps is not formed in quartzrich sandstone, calcite-rich limestone or dolomite-rich rocks, which contain minerals that also constitute a significant part of most shale samples [19,20]. No information about Ps formation in clay minerals, which are often dominant in shale, has been available. The purpose of the present study is to determine which clay minerals form Ps and to provide new information to help determine the nature of possible Ps trapping sites in shale and minerals samples. Twenty-five different common rock-forming minerals have been studied. Hydration of some of the minerals has also been
http://dx.doi.org/10.1016/j.nimb.2017.06.027 0168-583X/Ó 2017 Elsevier B.V. All rights reserved.
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027
2
H. Alsleben et al. / Nuclear Instruments and Methods in Physics Research B xxx (2017) xxx–xxx
Nomenclature DB LT PAS Ps S
Doppler Broadening Lifetime Positron Annihilation Spectroscopy Positronium S parameter
studied. As a result of this work, a better understanding of where Ps can be trapped in the shale samples is obtained. 2. Experimental details 2.1. Positron Annihilation Spectroscopy (PAS) Doppler Broadening (DB) is a type of PAS that measures the shape of the spectrum of the 511 keV annihilation gamma ray line. The line is broadened by the annihilation electron’s momentum and is sensitive to the sample’s electron momentum density. Broadening is characterized by the S and W parameters, which depend on annihilation with valence or core electrons respectively. S and W are strongly anti-correlated and depend on chemical composition and structure. S is larger (and W is smaller) when: (1) the probability of annihilation with valence electrons is higher, (2) positron trapping sites are larger, and (3) more Ps is formed. Positron lifetime spectroscopy measures the positron lifetime and intensity. The average positron lifetime is due to both direct annihilation and positron trapping, which are not resolved in this experiment. The positron lifetime is longer when there are larger trapping sites. So in some cases there is a correlation between the positron lifetime and the S parameter. Ps is also formed in some materials and the Ps lifetime and intensity are then measured as well. The details of the experimental setup have been previously given [1]. The source-sample arrangement used was, in some cases, the conventional one with the source sandwiched between two samples. This was when the material was powdered and two equivalent samples could be prepared in polyethylene holders covered with 12 mm Kapton film. In other cases, such as some minerals and solid or crystalline materials, only one sample was available. So the source was sandwiched between the one sample and a 1.3 mm Ti foil of sufficient thickness to stop all the positrons. The Na-22 positron source manufactured by Isotope Products Lab was initially 50 micro Ci carrier-free NaCl sealed between two 12.5 mm Ti foils. The active width of the NaCl spot was about 2 mm. Correction was made in the lifetime analysis for the positron annihilation in the source and in the Ti foil, if used. In either case of one or two samples, the percent of positrons that stopped in the sample, the source or the Ti foil was modeled using MCNPX [22], and private communication). The lifetime was measured for Ti foil alone and used with the MCNPX results to correct for the source and the Ti foil. In the single sample setup, 34% of the positrons stopped in the sample. The experimental technique of using only one sample in the lifetime measurement has been more fully described and validated in Jacobson et al. [8].
TOC W XRF XRD
Total Organic Carbon W parameter X-ray Fluorescence X-ray Diffraction
Table 1 Summary of Mineral samples studied. Mineral
Formula
Illite – Smectite Montmorillonite Nontronite Kaolinite Ripidolite (chlorite group) Chlorite (chlorite group) Apatite K-feldspar (Orthoclase) Albite (Plagioclase) Anorthite (Plagioclase) Marcasite Pyrite Siderite Limonite Calcite Dolomite Quartz
(K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] (Ca or Na)0.33(Al,Mg)2Si4O10(OH)2nH2O Ca0.5(Si7Al0.8Fe0.2)(Fe3.5Al0.4Mg0.1)O20(OH)4 Al2Si2O5(OH)4 (Mg,Fe,Al)6(Al,Si)4O10(OH)8 (Mg,Fe)3(Si,Al)4O10(OH)2(Mg,Fe)3(OH)6 Ca10(PO4)6(OH, F, Cl)2 KAlSi3O8 NaAlSi3O8 CaAl2Si2O8 FeS2 FeS2 FeCO3 FeO(OH)nH2O CaCO3 CaMg(CO3)2 SiO2
Phyllosilicate samples are Fe-rich. The two FeS2 samples differ in crystal structure. Marcasite is orthorhombic compared to Pyrite, which is cubic. Forty different samples were studied. The minerals and clays come from the Clay Mineral Society, Wards Natural Science Establishment and the TCU Dept. of Geology collection. Several samples were in crystal form: Albite, Apatite, Siderite, Calcite, Quartz, Pyrite, Chlorite, Anorthite and Orthoclase. The other samples were powdered. 3. Results and discussion Fig. 1 shows that the W and S parameters for the various mineral samples are negatively correlated, as would be expected. In W
2.2. Samples studied The mineral samples studied are summarized in Table 1. Phyllosilicates, layered silicate minerals, include the Illite-Smectites, Nontronites, Montmorillonites, Kaolinites, and Ripidolite and Chlorite. Tectosilicates are cage structures and include Orthoclase or KFeldspar and the Plagioclases Albite and Anorthite. Several of the
Fig. 1. W parameter versus S parameter for Clay minerals. The errors are smaller than the point size. The lines are fits to the data in the two regions.
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027
H. Alsleben et al. / Nuclear Instruments and Methods in Physics Research B xxx (2017) xxx–xxx
versus S plots, samples where a similar type of trapping site is dominant are expected to lie along the same line. The two lines shown in the figure are the least square fits to two sections of the data: S > 0.46 and S < 0.44. The samples with higher W, or more annihilation with core electrons, suggest that trapping is important, the samples with lower W suggest that positron annihilation with the bulk is dominant. Thus, the Montmorillonites, Chlorite, Kaolinite, Orthoclase and Apatite tend to share one type of trapping site predominantly. While the Fe minerals, Illite-smectite samples, Plagioclase, Ripidolite and Nontronite, which is an iron rich smectite group clay, may be dominated by annihilation with the bulk. One Fe mineral and one or two illite samples could lie on a third line of intermediate slope and so be somewhat influenced by positron trapping as well as bulk annihilation. In Fig. 2 the various Fe, Mg, Mn and Ca Carbonate samples are seen to lie along a common line suggesting a common type of positron trapping site probably associated with the CO3 radical. The structure for the carbonate minerals is the same. In Fig. 3, the relation between positron lifetime and the S parameter is shown. The minerals fall into three distinct groups of positron lifetime. The Phyllosilicates (Montmorillonites and Illites) and the Tectosilicate (Orthoclase) have positron lifetimes from 0.3 to 0.35 ns suggesting larger trapping sites or multiple vacancy sites. The Kaolinites, Chlorite and other Tectosilicates (Pla-
Fig. 2. S parameter versus W parameter for the Carbonate samples. The errors are smaller than the point size.
3
gioclase) fall into the 0.2–0.26 ns region. This suggests smaller trapping sites than the higher lifetime group. Finally, the iron bearing minerals (Pyrite, Marcasite, Limonite) and Ripidolite and Apatite have low positron lifetimes 0.15 ns, suggesting dominance by bulk annihilation similar to common oxides (ZnO, etc.). The trend in the Tectosilicates is shown by the dashed line. Orthoclase is found to have a higher lifetime, whereas the two Plagioclase samples have lower lifetimes. Orthoclase is monoclinic with a = b – c, whereas Plagioclase is triclinic a – b – c (least symmetry). So, in this case, the structure rather than composition may determine positron trapping and lifetime. The difference in Chlorite and Ripidolite, both members of the chlorite group, is also interesting. In this case, the difference in lifetime could be due more to composition of the sample rather than structure. In Fig. 4, the Ps intensity for the minerals studied is shown. The largest Ps intensity is found in the Ca-Montmorillonite samples. Na-Montmorillonite, on the other hand, shows very little Ps formation. Orthoclase, Kaolinite, Marcasite and Limonite also have a significant Ps intensity. There is significant difference in Ps formation for the various Illite-Smectite samples. The Nontronite B sample is Al-poor and Fe-rich and shows very little Ps formation, while the Al-rich Nontronite G sample has significant Ps formation. The Smectite sample SWA-1 is Ferruginous Smectite and also has no Ps formation. So generally we find Ps formation is reduced or suppressed in Fe-rich clay samples and increased in the more hydrated samples, like Limonite. There is no Ps formed in Quartz, Pyrite, Albite (Plagioclase), Chlorite or Apatite. The dashed line is shown at the 1% level. So, in addition to the Na-Montmorillonite, Siderite, Anorthhite (Plagioclase), Ripidolite and some Smectite samples show very little Ps formation. The small increase in Ps formation between crystalline Siderite and Siderite powder illustrate a common feature seen with powdered samples that have not been dried. In a few cases, an attempt was made to dehydrate the clay sample by heating under vacuum. In the case of CaMontmorillonite a 2% reduction in Ps formation was observed. However, no significant change was observed in the other clay samples, so variation in hydration is likely to be a small effect in Ps formation. Fig. 5 shows Ps lifetime vs Ps Intensity. The samples with intensity less than 1% are not very well determined. These are the points to the left of the dotted line. One point (Orthoclase) has a very large uncertainty in intensity and a low lifetime. The average lifetime for those 10 samples that are well determined is consistent with that expected for water trapping sites. This is similar to what was seen for Ps lifetime in the shale samples [1].
Fig. 3. Positron lifetime versus S parameter.
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027
4
H. Alsleben et al. / Nuclear Instruments and Methods in Physics Research B xxx (2017) xxx–xxx
Fig. 4. Summary of the Positronium Intensity for the mineral samples studied.
Fig. 6. Average positron lifetime versus Positronium lifetime. Fig. 5. Positronium Lifetime versus Positronium Intensity.
4. Conclusions Fig. 6 shows the average positron lifetime versus the Ps lifetime. These results can be compared to Fig. 3. Here it is clear that the Phyllosilicates, except for the Kaolinites, have a positron lifetime in the 0.3–0.35 ns range rather independent of the Ps lifetime. Again the Orthoclase falls in this positron lifetime range at the low end of the Ps lifetime. In this case the Orthoclase connects well with the other tectosilicates and the Fe-bearing minerals (unless they are also plyllosilicates) and have a trend of decreasing positron lifetime with Ps lifetime.
Urban-Klaehn et al. [19,20] has shown there is no Ps formation in sandstone, calcite or dolomite. Ameena et al. [1] found that the Ps intensity of 14 well-characterized Barnett Shale samples ranged from 0.9% to 2.2%. The present results on common mineral constituents of shale support the conclusion that most Ps formation in shale is associated with water in the clay components such as Ca-Montmorillonite, Kaolinite, Limonite and Illite-Smectite. The average positron lifetime decreases from sandstone 0.34 ns) to calcite 0.28 ns) to dolomite 0.26 ns) [19,20]. The average
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027
H. Alsleben et al. / Nuclear Instruments and Methods in Physics Research B xxx (2017) xxx–xxx
positron lifetime in 14 Barnett Shale samples ranges from 0.23 to 0.28 ns [1]. In the variety of clay minerals studied here, the positron lifetimes tend to fall into three groups Montmorillonites, Orthoclase and Illites (0.29–0.36 ns), Kaolinites, Chlorite and Plagioclase (0.21–0.29 ns) and Apatite and Fe minerals (0.14– 0.17 ns). Thus, shale lifetimes can be understood, at least qualitatively, as a mix of the various clay components and Silica and Carbonate. For example, a shale sample with a lifetime in the 0.23 ns range would be expected to have a low Silica and Illite-Smectite component. Acknowledgements The REU Physics and Astronomy program at TCU is funded by the National Science Foundation under grant PHY-1358770. Joah Chun and James Bufkin were both participants in the TCU REU program during the Summer of 2014. References [1] Ameena, F., Alsleben, H., Quarles, C. A., 2015, Positron annihilation spectroscopy study of Barnett Shale core, C 23rd Conference on Application of Accelerators in Research and Industry, CAARI 2014, www.sciencedirect.com. Physics Procedia 66, 416 – 424. [2] I.I. Bardyshev, A.D. Mokrushin, A.A. Pribylov, et al., Porous structure of synthetic opals, Colloid J. 68 (2006) 20–25. [3] Bunting, Philip John, 2007, Petrographic analysis of the Barnett Shale in the Fort Worth Basin, Masters Thesis in Geology, Texas Christian University. [4] J. Chojcan, M. Sachanbin´ski, Positron annihilation in Tektite and Hyalite, Acta Phys. Pol., A 83 (1993) 267–271. [5] J. Chojcan, M. Sachanbin´ski, R. Idczak, R. Konieczny, Positron annihilation in precious and common opals, NUKLEONIKA 58 (1) (2013) 225–228. [6] G. Consolati, I. Natali-Sora, R. Pelosato, F. Quasso, Investigation of cationexchanged montmorillonites by combined x-ray diffraction and positron annihilation lifetime spectroscopy, J. Appl. Phys. 91 (1928), http://dx.doi.org/ 10.1063/1.1432472. [7] Y. Honda, Y. Yoshida, Y. Akiyama, S. Nishijima, Feasibility of classification of clay minerals by using PAS, 11th International Workshop on Positron and Positronium Chemistry (PPC-11) IOP Publishing, J. Phys: Conf. Ser. 618 (2015) 012037, http://dx.doi.org/10.1088/1742-6596/618/1/012037.
5
[8] L.G. Jacobsohn, K. Serivalsatit, C.A. Quarles, J. Ballato, Investigation of Er-doped Sc2O3 transparent ceramics by positron annihilation spectroscopy, J. Mater. Sci. 50 (2015) 3183–3188, http://dx.doi.org/10.1007/s10853-015-8881-8. [9] Jean, Y.C., Mallon, P.E., Schrader, D.M., eds., 2003, Principles and Applications of Positron and Positronium Chemistry, (World Scientific) NJ. [10] J.M. Joshi, H.S. Sodaye, P.K. Pujari, S. Srisaila, M.B. Bajpai, Positron annihilation spectroscopic investigation of Al-pillared montmorillonites, Catal. Lett. 51 (1) (1998) 109–112, http://dx.doi.org/10.1023/A:1019093202950. [11] Kiesel, Meredith Ann, 2013, Chemostratigraphy and elemental analysis of the Mississippian Barnett shale formation using energy-dispersive x-ray fluorescence spectrometry, Fort Worth Basin, Johnson County, Texas, Masters Thesis in Geology, Texas Christian University. [12] C.D. Patterson, C.A. Quarles, J.A. Breyer, Possible new well-logging tool using positron Doppler broadening to detect total organic carbon (TOC) in hydrocarbon source rocks, Radiat. Phys. Chem. 68 (2003) 523–526. [13] Prochazka, I., 2001, Positron Annihilation Spectroscopy, Material Structure, vol. 8, num.2, pp. 55-62. [14] Quarles, C. A., Chin-yu Hsueh, Urban, J. M., Salaita, G.N., 1994, Application of positron annihilation spectroscopy to the study of lithology and porosity of well-characterized rocks: Doppler broadening of annihilation radiation and lifetime measurements, SPLWA 35th Annual Logging Symposium, June 19-22, 1994. [15] Sano, M., Murakami, H., Ichimura, K., 2006, Positronium in a layered-structure material: Montmorillonite, Journal of Radioanalytical and Nuclear Chemistry, Volume 239, Issue 2, DOI: 10.1007/BF02349505. [16] V.P. Shantarovich, Positronium atom in solids- peculiarities of formation and interconnections with free volume nanostructure, J. Nucl. Radiochem. Sci. 7 (1) (2006) R37–R52. [17] B. Sláviková, M. Iskrová, V. Majerník, O. Šauša, J. Krištiak, K. Jesenák, Water in Montmorillonites, Mater. Sci. Forum 666 (2011) 119–122. [18] Urban-Klaehn, J.M., 1998, Application of Positron Annihilation Spectroscopy to the Characterization of Rocks, Doctoral Dissertation in Physics, Texas Christian University. [19] J. Urban-Klaehn, C.A. Quarles, Positron annihilation spectroscopy of sandstone and carbonate rocks, J. Appl. Phys. 86 (1999) 355. [20] Urban-Klaehn, J.M., Quarles, C. A., 1999, Positron annihilation in opals: evidence of positronium formation, CP474, Applications of accelerators in research and Industry, edited by J.L. Duggan and I. L. Morgan, The American Institute of Physics 1-56396-825-8/99/, pp. 345-348. [21] J. Urban-Klaehn, A.W. Hunt, M. Ford, et al., Studies of superlattice structure of opals as compared to other rocks by use of positron annihilation, X-ray powder diffraction and scanning electron microscopy methods, J. Idaho Acad. Sci. 41 (2) (2005) 1–19. [22] M. Urban-Klaehn, R. Spaulding, A.W. Hunt, E.S. Peterson, Applicability of the MCNPX particle transport code for determination of the source correction effect in positron lifetime measurements on thin polymer films, Phys Stat Sol C 4 (2007) 3732–3734.
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Positron Annihilation Spectroscopy study of minerals commonly found in shale q Helge Alsleben a, Fnu Ameena b, James Bufkin c, Joah Chun d, C.A. Quarles b,⇑ a
Texas Christian University, School of Geology, Energy, and the Environment, Fort Worth, TX 76129, USA Texas Christian University, Department of Physics and Astronomy, Fort Worth, TX 76129, USA c Angelo State University, San Angelo, TX 76909, USA d Colorado College, Colorado Springs, CO 80903, USA b
a r t i c l e
i n f o
Article history: Received 20 June 2017 Accepted 29 June 2017 Available online xxxx Keywords: Positron Positronium Lifetime Doppler Broadening S parameter Clay Minerals
a b s t r a c t Positron Annihilation Lifetime and Doppler Broadening spectroscopies are used to investigate twentythree different rock-forming minerals that are commonly found in shale. Doppler Broadening provides information about the positron and positronium (Ps) trapping sites for comparison among the various minerals. Correlations of positron lifetime and Doppler Broadening are observed for different groups of minerals. Finally, Ps formation, or lack thereof, in the various minerals has been determined. Ó 2017 Elsevier B.V. All rights reserved.
1. Introduction Positron Annihilation Spectroscopy (PAS) has been very effectively used to characterize diverse properties of many materials such as defects in metals and semiconductors and free volume in polymers [9,13,16]. What distinguished these materials where PAS has been most successful is that they are typically uniform and homogeneous. PAS has been much less frequently applied to the study of natural materials such as rocks and minerals. The most detailed study of sandstone and limestone rocks is still the work of Urban-Klaehn [18], Urban-Klaehn et al. [19,20], Quarles et al. [14]. Opals, a variety of hydrated silica, have been studied by several groups because of the long positronium lifetimes observed in the cage structure of the opals [19,20,21,2,5]. Montmorillonites have been studied by several authors because of their interesting layered structure [15,17,6,10]. There have also been a few studies of specific types of minerals [4,7]. But, there has not been up to now a systematic investigation of minerals, perhaps because of the great variety of minerals that occur naturally.
q Conference on the Application of Accelerators in Research and Industry, CAARI 2016, 30 October – 4 November 2016, Ft. Worth, TX, USA. ⇑ Corresponding author. E-mail address: [email protected] (C.A. Quarles).
The present work has been motivated by recent investigation of positron lifetime and Doppler Broadening in Barnett Shale samples which have shown a small intensity of positronium Ps) formation. [1]. The samples studied had XRF information on 35 elements, XRD information on mineral constituents, and chemical information on total organic carbon TOC) [3,11]. While the positron annihilation lifetime parameters were not observed to be significantly correlated with elemental composition or mineral composition, the S parameter from the Doppler Broadening experiments was found to improve the prediction of TOC when coupled with certain elements known to be weakly correlated with TOC such as Cu, Ni or Zn concentration. The S parameter had also been observed to be somewhat correlated with TOC in another previous study of a shale core [12]. However, it has not been known where Ps is formed in the shale. Previous research has shown that Ps is not formed in quartzrich sandstone, calcite-rich limestone or dolomite-rich rocks, which contain minerals that also constitute a significant part of most shale samples [19,20]. No information about Ps formation in clay minerals, which are often dominant in shale, has been available. The purpose of the present study is to determine which clay minerals form Ps and to provide new information to help determine the nature of possible Ps trapping sites in shale and minerals samples. Twenty-five different common rock-forming minerals have been studied. Hydration of some of the minerals has also been
http://dx.doi.org/10.1016/j.nimb.2017.06.027 0168-583X/Ó 2017 Elsevier B.V. All rights reserved.
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027
2
H. Alsleben et al. / Nuclear Instruments and Methods in Physics Research B xxx (2017) xxx–xxx
Nomenclature DB LT PAS Ps S
Doppler Broadening Lifetime Positron Annihilation Spectroscopy Positronium S parameter
studied. As a result of this work, a better understanding of where Ps can be trapped in the shale samples is obtained. 2. Experimental details 2.1. Positron Annihilation Spectroscopy (PAS) Doppler Broadening (DB) is a type of PAS that measures the shape of the spectrum of the 511 keV annihilation gamma ray line. The line is broadened by the annihilation electron’s momentum and is sensitive to the sample’s electron momentum density. Broadening is characterized by the S and W parameters, which depend on annihilation with valence or core electrons respectively. S and W are strongly anti-correlated and depend on chemical composition and structure. S is larger (and W is smaller) when: (1) the probability of annihilation with valence electrons is higher, (2) positron trapping sites are larger, and (3) more Ps is formed. Positron lifetime spectroscopy measures the positron lifetime and intensity. The average positron lifetime is due to both direct annihilation and positron trapping, which are not resolved in this experiment. The positron lifetime is longer when there are larger trapping sites. So in some cases there is a correlation between the positron lifetime and the S parameter. Ps is also formed in some materials and the Ps lifetime and intensity are then measured as well. The details of the experimental setup have been previously given [1]. The source-sample arrangement used was, in some cases, the conventional one with the source sandwiched between two samples. This was when the material was powdered and two equivalent samples could be prepared in polyethylene holders covered with 12 mm Kapton film. In other cases, such as some minerals and solid or crystalline materials, only one sample was available. So the source was sandwiched between the one sample and a 1.3 mm Ti foil of sufficient thickness to stop all the positrons. The Na-22 positron source manufactured by Isotope Products Lab was initially 50 micro Ci carrier-free NaCl sealed between two 12.5 mm Ti foils. The active width of the NaCl spot was about 2 mm. Correction was made in the lifetime analysis for the positron annihilation in the source and in the Ti foil, if used. In either case of one or two samples, the percent of positrons that stopped in the sample, the source or the Ti foil was modeled using MCNPX [22], and private communication). The lifetime was measured for Ti foil alone and used with the MCNPX results to correct for the source and the Ti foil. In the single sample setup, 34% of the positrons stopped in the sample. The experimental technique of using only one sample in the lifetime measurement has been more fully described and validated in Jacobson et al. [8].
TOC W XRF XRD
Total Organic Carbon W parameter X-ray Fluorescence X-ray Diffraction
Table 1 Summary of Mineral samples studied. Mineral
Formula
Illite – Smectite Montmorillonite Nontronite Kaolinite Ripidolite (chlorite group) Chlorite (chlorite group) Apatite K-feldspar (Orthoclase) Albite (Plagioclase) Anorthite (Plagioclase) Marcasite Pyrite Siderite Limonite Calcite Dolomite Quartz
(K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] (Ca or Na)0.33(Al,Mg)2Si4O10(OH)2nH2O Ca0.5(Si7Al0.8Fe0.2)(Fe3.5Al0.4Mg0.1)O20(OH)4 Al2Si2O5(OH)4 (Mg,Fe,Al)6(Al,Si)4O10(OH)8 (Mg,Fe)3(Si,Al)4O10(OH)2(Mg,Fe)3(OH)6 Ca10(PO4)6(OH, F, Cl)2 KAlSi3O8 NaAlSi3O8 CaAl2Si2O8 FeS2 FeS2 FeCO3 FeO(OH)nH2O CaCO3 CaMg(CO3)2 SiO2
Phyllosilicate samples are Fe-rich. The two FeS2 samples differ in crystal structure. Marcasite is orthorhombic compared to Pyrite, which is cubic. Forty different samples were studied. The minerals and clays come from the Clay Mineral Society, Wards Natural Science Establishment and the TCU Dept. of Geology collection. Several samples were in crystal form: Albite, Apatite, Siderite, Calcite, Quartz, Pyrite, Chlorite, Anorthite and Orthoclase. The other samples were powdered. 3. Results and discussion Fig. 1 shows that the W and S parameters for the various mineral samples are negatively correlated, as would be expected. In W
2.2. Samples studied The mineral samples studied are summarized in Table 1. Phyllosilicates, layered silicate minerals, include the Illite-Smectites, Nontronites, Montmorillonites, Kaolinites, and Ripidolite and Chlorite. Tectosilicates are cage structures and include Orthoclase or KFeldspar and the Plagioclases Albite and Anorthite. Several of the
Fig. 1. W parameter versus S parameter for Clay minerals. The errors are smaller than the point size. The lines are fits to the data in the two regions.
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027
H. Alsleben et al. / Nuclear Instruments and Methods in Physics Research B xxx (2017) xxx–xxx
versus S plots, samples where a similar type of trapping site is dominant are expected to lie along the same line. The two lines shown in the figure are the least square fits to two sections of the data: S > 0.46 and S < 0.44. The samples with higher W, or more annihilation with core electrons, suggest that trapping is important, the samples with lower W suggest that positron annihilation with the bulk is dominant. Thus, the Montmorillonites, Chlorite, Kaolinite, Orthoclase and Apatite tend to share one type of trapping site predominantly. While the Fe minerals, Illite-smectite samples, Plagioclase, Ripidolite and Nontronite, which is an iron rich smectite group clay, may be dominated by annihilation with the bulk. One Fe mineral and one or two illite samples could lie on a third line of intermediate slope and so be somewhat influenced by positron trapping as well as bulk annihilation. In Fig. 2 the various Fe, Mg, Mn and Ca Carbonate samples are seen to lie along a common line suggesting a common type of positron trapping site probably associated with the CO3 radical. The structure for the carbonate minerals is the same. In Fig. 3, the relation between positron lifetime and the S parameter is shown. The minerals fall into three distinct groups of positron lifetime. The Phyllosilicates (Montmorillonites and Illites) and the Tectosilicate (Orthoclase) have positron lifetimes from 0.3 to 0.35 ns suggesting larger trapping sites or multiple vacancy sites. The Kaolinites, Chlorite and other Tectosilicates (Pla-
Fig. 2. S parameter versus W parameter for the Carbonate samples. The errors are smaller than the point size.
3
gioclase) fall into the 0.2–0.26 ns region. This suggests smaller trapping sites than the higher lifetime group. Finally, the iron bearing minerals (Pyrite, Marcasite, Limonite) and Ripidolite and Apatite have low positron lifetimes 0.15 ns, suggesting dominance by bulk annihilation similar to common oxides (ZnO, etc.). The trend in the Tectosilicates is shown by the dashed line. Orthoclase is found to have a higher lifetime, whereas the two Plagioclase samples have lower lifetimes. Orthoclase is monoclinic with a = b – c, whereas Plagioclase is triclinic a – b – c (least symmetry). So, in this case, the structure rather than composition may determine positron trapping and lifetime. The difference in Chlorite and Ripidolite, both members of the chlorite group, is also interesting. In this case, the difference in lifetime could be due more to composition of the sample rather than structure. In Fig. 4, the Ps intensity for the minerals studied is shown. The largest Ps intensity is found in the Ca-Montmorillonite samples. Na-Montmorillonite, on the other hand, shows very little Ps formation. Orthoclase, Kaolinite, Marcasite and Limonite also have a significant Ps intensity. There is significant difference in Ps formation for the various Illite-Smectite samples. The Nontronite B sample is Al-poor and Fe-rich and shows very little Ps formation, while the Al-rich Nontronite G sample has significant Ps formation. The Smectite sample SWA-1 is Ferruginous Smectite and also has no Ps formation. So generally we find Ps formation is reduced or suppressed in Fe-rich clay samples and increased in the more hydrated samples, like Limonite. There is no Ps formed in Quartz, Pyrite, Albite (Plagioclase), Chlorite or Apatite. The dashed line is shown at the 1% level. So, in addition to the Na-Montmorillonite, Siderite, Anorthhite (Plagioclase), Ripidolite and some Smectite samples show very little Ps formation. The small increase in Ps formation between crystalline Siderite and Siderite powder illustrate a common feature seen with powdered samples that have not been dried. In a few cases, an attempt was made to dehydrate the clay sample by heating under vacuum. In the case of CaMontmorillonite a 2% reduction in Ps formation was observed. However, no significant change was observed in the other clay samples, so variation in hydration is likely to be a small effect in Ps formation. Fig. 5 shows Ps lifetime vs Ps Intensity. The samples with intensity less than 1% are not very well determined. These are the points to the left of the dotted line. One point (Orthoclase) has a very large uncertainty in intensity and a low lifetime. The average lifetime for those 10 samples that are well determined is consistent with that expected for water trapping sites. This is similar to what was seen for Ps lifetime in the shale samples [1].
Fig. 3. Positron lifetime versus S parameter.
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027
4
H. Alsleben et al. / Nuclear Instruments and Methods in Physics Research B xxx (2017) xxx–xxx
Fig. 4. Summary of the Positronium Intensity for the mineral samples studied.
Fig. 6. Average positron lifetime versus Positronium lifetime. Fig. 5. Positronium Lifetime versus Positronium Intensity.
4. Conclusions Fig. 6 shows the average positron lifetime versus the Ps lifetime. These results can be compared to Fig. 3. Here it is clear that the Phyllosilicates, except for the Kaolinites, have a positron lifetime in the 0.3–0.35 ns range rather independent of the Ps lifetime. Again the Orthoclase falls in this positron lifetime range at the low end of the Ps lifetime. In this case the Orthoclase connects well with the other tectosilicates and the Fe-bearing minerals (unless they are also plyllosilicates) and have a trend of decreasing positron lifetime with Ps lifetime.
Urban-Klaehn et al. [19,20] has shown there is no Ps formation in sandstone, calcite or dolomite. Ameena et al. [1] found that the Ps intensity of 14 well-characterized Barnett Shale samples ranged from 0.9% to 2.2%. The present results on common mineral constituents of shale support the conclusion that most Ps formation in shale is associated with water in the clay components such as Ca-Montmorillonite, Kaolinite, Limonite and Illite-Smectite. The average positron lifetime decreases from sandstone 0.34 ns) to calcite 0.28 ns) to dolomite 0.26 ns) [19,20]. The average
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027
H. Alsleben et al. / Nuclear Instruments and Methods in Physics Research B xxx (2017) xxx–xxx
positron lifetime in 14 Barnett Shale samples ranges from 0.23 to 0.28 ns [1]. In the variety of clay minerals studied here, the positron lifetimes tend to fall into three groups Montmorillonites, Orthoclase and Illites (0.29–0.36 ns), Kaolinites, Chlorite and Plagioclase (0.21–0.29 ns) and Apatite and Fe minerals (0.14– 0.17 ns). Thus, shale lifetimes can be understood, at least qualitatively, as a mix of the various clay components and Silica and Carbonate. For example, a shale sample with a lifetime in the 0.23 ns range would be expected to have a low Silica and Illite-Smectite component. Acknowledgements The REU Physics and Astronomy program at TCU is funded by the National Science Foundation under grant PHY-1358770. Joah Chun and James Bufkin were both participants in the TCU REU program during the Summer of 2014. References [1] Ameena, F., Alsleben, H., Quarles, C. A., 2015, Positron annihilation spectroscopy study of Barnett Shale core, C 23rd Conference on Application of Accelerators in Research and Industry, CAARI 2014, www.sciencedirect.com. Physics Procedia 66, 416 – 424. [2] I.I. Bardyshev, A.D. Mokrushin, A.A. Pribylov, et al., Porous structure of synthetic opals, Colloid J. 68 (2006) 20–25. [3] Bunting, Philip John, 2007, Petrographic analysis of the Barnett Shale in the Fort Worth Basin, Masters Thesis in Geology, Texas Christian University. [4] J. Chojcan, M. Sachanbin´ski, Positron annihilation in Tektite and Hyalite, Acta Phys. Pol., A 83 (1993) 267–271. [5] J. Chojcan, M. Sachanbin´ski, R. Idczak, R. Konieczny, Positron annihilation in precious and common opals, NUKLEONIKA 58 (1) (2013) 225–228. [6] G. Consolati, I. Natali-Sora, R. Pelosato, F. Quasso, Investigation of cationexchanged montmorillonites by combined x-ray diffraction and positron annihilation lifetime spectroscopy, J. Appl. Phys. 91 (1928), http://dx.doi.org/ 10.1063/1.1432472. [7] Y. Honda, Y. Yoshida, Y. Akiyama, S. Nishijima, Feasibility of classification of clay minerals by using PAS, 11th International Workshop on Positron and Positronium Chemistry (PPC-11) IOP Publishing, J. Phys: Conf. Ser. 618 (2015) 012037, http://dx.doi.org/10.1088/1742-6596/618/1/012037.
5
[8] L.G. Jacobsohn, K. Serivalsatit, C.A. Quarles, J. Ballato, Investigation of Er-doped Sc2O3 transparent ceramics by positron annihilation spectroscopy, J. Mater. Sci. 50 (2015) 3183–3188, http://dx.doi.org/10.1007/s10853-015-8881-8. [9] Jean, Y.C., Mallon, P.E., Schrader, D.M., eds., 2003, Principles and Applications of Positron and Positronium Chemistry, (World Scientific) NJ. [10] J.M. Joshi, H.S. Sodaye, P.K. Pujari, S. Srisaila, M.B. Bajpai, Positron annihilation spectroscopic investigation of Al-pillared montmorillonites, Catal. Lett. 51 (1) (1998) 109–112, http://dx.doi.org/10.1023/A:1019093202950. [11] Kiesel, Meredith Ann, 2013, Chemostratigraphy and elemental analysis of the Mississippian Barnett shale formation using energy-dispersive x-ray fluorescence spectrometry, Fort Worth Basin, Johnson County, Texas, Masters Thesis in Geology, Texas Christian University. [12] C.D. Patterson, C.A. Quarles, J.A. Breyer, Possible new well-logging tool using positron Doppler broadening to detect total organic carbon (TOC) in hydrocarbon source rocks, Radiat. Phys. Chem. 68 (2003) 523–526. [13] Prochazka, I., 2001, Positron Annihilation Spectroscopy, Material Structure, vol. 8, num.2, pp. 55-62. [14] Quarles, C. A., Chin-yu Hsueh, Urban, J. M., Salaita, G.N., 1994, Application of positron annihilation spectroscopy to the study of lithology and porosity of well-characterized rocks: Doppler broadening of annihilation radiation and lifetime measurements, SPLWA 35th Annual Logging Symposium, June 19-22, 1994. [15] Sano, M., Murakami, H., Ichimura, K., 2006, Positronium in a layered-structure material: Montmorillonite, Journal of Radioanalytical and Nuclear Chemistry, Volume 239, Issue 2, DOI: 10.1007/BF02349505. [16] V.P. Shantarovich, Positronium atom in solids- peculiarities of formation and interconnections with free volume nanostructure, J. Nucl. Radiochem. Sci. 7 (1) (2006) R37–R52. [17] B. Sláviková, M. Iskrová, V. Majerník, O. Šauša, J. Krištiak, K. Jesenák, Water in Montmorillonites, Mater. Sci. Forum 666 (2011) 119–122. [18] Urban-Klaehn, J.M., 1998, Application of Positron Annihilation Spectroscopy to the Characterization of Rocks, Doctoral Dissertation in Physics, Texas Christian University. [19] J. Urban-Klaehn, C.A. Quarles, Positron annihilation spectroscopy of sandstone and carbonate rocks, J. Appl. Phys. 86 (1999) 355. [20] Urban-Klaehn, J.M., Quarles, C. A., 1999, Positron annihilation in opals: evidence of positronium formation, CP474, Applications of accelerators in research and Industry, edited by J.L. Duggan and I. L. Morgan, The American Institute of Physics 1-56396-825-8/99/, pp. 345-348. [21] J. Urban-Klaehn, A.W. Hunt, M. Ford, et al., Studies of superlattice structure of opals as compared to other rocks by use of positron annihilation, X-ray powder diffraction and scanning electron microscopy methods, J. Idaho Acad. Sci. 41 (2) (2005) 1–19. [22] M. Urban-Klaehn, R. Spaulding, A.W. Hunt, E.S. Peterson, Applicability of the MCNPX particle transport code for determination of the source correction effect in positron lifetime measurements on thin polymer films, Phys Stat Sol C 4 (2007) 3732–3734.
Please cite this article in press as: H. Alsleben et al., Positron Annihilation Spectroscopy study of minerals commonly found in shale, Nucl. Instr. Meth. B (2017), http://dx.doi.org/10.1016/j.nimb.2017.06.027