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Effect of gamma irradiation on the FTIR of cement kiln dust–bismuth borate glasses
Journal of Non-Crystalline Solids 419 (2015) 110–117
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Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol
Effect of gamma irradiation on the FTIR of cement kiln dust–bismuth borate glasses Yasser B. Saddeek a,⁎, Gehan Y. Mohamed b, H. Shokry Hassan c, A.M.A. Mostafa a, G. Abd elfadeel a a b c
Physics Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt Experimental Nuclear Physics Department, Nuclear Research Center, Atomic Energy Authority, Post Office No. 13759 Cairo, Egypt Advanced Technology and New Materials Research Institute, City of Scientific Research and Technology Applications, New Borg El-Arab City, Alexandria 21934, Egypt
a r t i c l e
i n f o
Article history: Received 23 October 2014 Received in revised form 5 February 2015 Accepted 18 March 2015 Available online 11 April 2015 Keywords: Bismuth borate glasses; Cement kiln dust; FTIR; γ-Radiation
a b s t r a c t Glasses from cement kiln dust and lead barium bismuth borate were prepared by the melt quenching method and studied by using FTIR and ultrasonic techniques before and after exposure to gamma irradiation at doses up to 120 kGy. The FTIR results indicated a deformation of the lead borate based glasses with the replacement of PbO by Bi2O3 which was attributed to the appearance of Bi–O stretching vibrations in [BiO6] structural units and generated excess of non-bridging oxygens. This deformation affected the [BO3] units which are indicated from the lower decreasing rate of N4 as a function of Bi2O3. The high covalency of Pb–O and B–O bonds compared with that of Bi–O or Si–O attracts the excess of non-bridging oxygens and resulted in a relaxation of the glass network. The relaxation decreased the ultrasonic velocities and the bulk modulus and hence the rigidity of the glass despite the increase of the density which was attributed to the replacement of Bi2O3 instead of PbO. The structural and rigidity changes due to composition variations showed a decreasing manner to the effects of radiation. The density of the glass increased while the ultrasonic velocities decreased. This behavior modulated the compositional behavior of the elastic moduli on Bi2O3 content. © 2015 Elsevier B.V. All rights reserved.
1. Introduction The structure of lead borate glasses had attracted scientific and industrial interests because the network of these remarkable glasses is capable of involving different mixed former/modifier oxides such as SiO2, Bi2O3, CaO, … [1]. Synthesis of these glasses revealed large glass forming regions and their vitreous network showed a significant variation with concentration depending on the composition of former/modifier oxides [2]. It was reported that heavy metal borate based glasses (HMG) such as PbO and Bi2O3 (HMO) are comparable and behaved as conditional glass network formers. Moreover, the glasses have a relatively large vitreous formation range and the forming property of Bi2O3 was greater than that of PbO. Moreover, incorporation of PbO or Bi2O3 with empty d orbital into borate based glasses colored these with colors that ranged from faint- to dark-yellow or brown, respectively [3,4]. The ions of these elements in vitreous network have a lone pair electron configuration and several stable coordinations with oxygens which enable more than one type of structural unit in the vitreous matrix to be created [5, 6]. It was reported that addition of Bi2O3 to lead borate glasses gave high stability against devitrification and chemical inertness due to the dual role of HMO [7,8]. These glasses have high refractive index, high infrared transparency, enhanced optical nonlinearity, and wide ⁎ Corresponding author. E-mail address: [email protected] (Y.B. Saddeek).
http://dx.doi.org/10.1016/j.jnoncrysol.2015.03.021 0022-3093/© 2015 Elsevier B.V. All rights reserved.
transmission window, are functional for generation of photo-induced second harmonic and can exhibit zero stress optic properties [9]. Moreover, it could be used as laser medium for broadband fiber amplifier since they exhibit very broad luminescence, radiation sensitive dosimeters and calorimeter medium for the superconducting of super collider or as shielding candidates due to its high absorption cross-section for radiation [10]. A category of structural studies has been appointed to explore the influence of modifier/former oxides in lead borate glasses including spectroscopic studies, such as FTIR [1,11], Raman [12] and NMR [13], in addition to neutron diffraction, X-ray diffraction [14] and molecular dynamics simulation [15]. The convenience of spectroscopic studies of these glasses was due to the significant difference between the masses of Pb or Bi and B atoms. This difference allowed for a separation of vibrational modes of HMO polyhedra and the borate structural units [2]. On the other hand, modifier/former oxides can be acquired from cement kiln dust (CKD) which is a pollution problem. This polluter of the environment is a by-product during the normal production of cement industry. Recently, much research has been focused on utilization CKD as the raw material to produce glass and glass–ceramics because vitrification seems to be one of the most promising technological options for establishment of this industrial waste. CKD consists mainly from CaO and SiO2. Thus, the use of this waste material for glass industry is of great economic technological and scientific importance with proper modulation of the chemical composition [16–19].
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In this work, waste cement kiln dust was used in the manufacture of glassy materials. This type of glass can be considered as a candidate for the production of novel glass resisted radiation when incorporated with oxides such as BaO, PbO and Bi2O3 that have high ability to absorb gamma radiation. It was also suggested that a dramatic improvement in reducing toxicity of lead borate based glasses was associated with the substitution of PbO by Bi2O3 into the borate network [3]. The use of Bi2O3 together with B2O3 increases the vitrification of the glasses. Therefore, the present work has been investigating the structural and rigidity properties of lead borate glasses containing CKD and different compositions of Bi2O3, by using ultrasonic and FTIR techniques before and after exposure to different doses of gamma irradiation.
2. Experimental procedures
Table 1 The glass compositions for BaO–B2O3–Bi2O3–PbO–CKD glasses (mol.%). Sample
G0 G1 G2 G3 G4 G5
Fig. 1. X-ray diffraction pattern of the investigated x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%).
At room temperature, a 60Co gamma cell (5Ci) as a gamma ray source with a dose rate of 1.15 kGy/h was used. Samples were subjected to six radiation doses in the range of 10–120 kGy. The investigated glass samples were exposed to the same gamma dose every time. Using a Fricke dosimeter, the absorbed dose in glass is expressed in terms of absorbed dose in water, rather than in terms of dose in glass. No cavity theory correction was made. Each glass sample was subjected to a total dose of 10, 20, 30, 60, 90 and 120 kGy according to previous work [22, 23]. FT-IR spectra of all the powdered samples after irradiation were recorded using the same conditions as before irradiation.
3. Results The FTIR spectra of the studied glass system in the range 4000– 400 cm−1 as shown in Fig. 2 revealed the characteristic broad absorption bands of borates and some small absorption band at ~3443 cm−1 brought by air moisture during the preparation of KBr pellets of the samples [21] and attributed to the fundamental stretching of hydroxyl groups. The FTIR spectral features of the base glass as shown in Fig. 2 have exhibited two intense absorption envelopes in the region 1515–1163 cm−1 and 1163–758 cm−1 and two peaks with lower intensity at 700 cm−1 and 466 cm−1. Absorption of the FTIR spectra in these regions was related to vibrations of specific structural groups in the borate network. According 25 Bi 2O3
20 Bi 2O3
15 Bi 2O3
Absorbance (a.u.)
The nominal glass compositions (the starting mixture [Table 1]) were prepared by the conventional melt-quenching method from powders of reagent grades of H3BO3, Bi2O3, PbO, BaO and cement kiln dust (CKD) according to the chemical formula x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) in an amount sufficient to produce 50 g glass. The details of the preparation of the studied glasses were mentioned in a previous work [20]. The amorphous state of the glasses was checked using X-ray diffraction. Philips X-ray diffractometer PW/1710 with Ni-filtered Cu-Kα radiation (λ = 1.542 Å) powered at 40 kV and 30 mA was used. The XRD patterns as shown in Fig. 1 revealed the characteristic broad humps of the vitreous materials and did not reveal discrete or any sharp peaks. Fourier transformation infrared (FT-IR) spectra for the glass powder were obtained using a spectrophotometer type JASCO, FT/IR-430 (Japan). For this purpose, each sample was mixed with KBr in the proportion of 1:100 (by weight) for 20 min and pressed into a pellet using a hand press. At least two spectra for each sample were recorded in the wavenumber range of 4000–400 cm−1 at a resolution of ±1 cm−1 by taking 256 scans. The spectra were corrected for dark-current noise, normalized and curve fitted to get quantitative values for the band areas of heavily overlapped bands. The details of curve-fitting procedure were mentioned elsewhere [21]. The density of each sample was measured by Archimedes' principle by using toluene as the immersion fluid. Four samples of each glass were used to determine the density (ρ). A random error in the density values was found as ±25 kg m−3. The ultrasonic velocities, longitudinal (vL) and shear (vT), at room temperature (~300 K) were obtained using the pulse-echo method. In this method, x-cut and y-cut transducers (KARL DEUTSCH) operated at a fundamental frequency of 4 MHz along with a digital ultrasonic flaw detector (KARL DEUTSCH Echograph model 1085) were used. The uncertainty in the measurement of the ultrasonic velocity is ± 10 m/s. The two velocities besides the density were utilized to determine two independent second-order elastic constants, L and G. For pure longitudinal waves L = ρv2L Z, and for pure transverse waves G = ρv2T Z. The elastic bulk modulus (Ke), and Young's modulus (Y) can be determined using the standard relations adopted in previous work [20]. The uncertainty in the measurement of the elastic moduli is ±0.15 GPa.
10 Bi 2O3
5 Bi 2O3
0 Bi 2O3
Composition (mol.%) BaO
B2O3
Bi2O3
PbO
CKD
3 3 3 3 3 3
40 40 40 40 40 40
0 5 10 15 20 25
25 20 15 10 5 0
32 32 32 32 32 32
4000
3600
3200
2800
2400
2000
1600
1200
800
400
-1
Wavenumber ( cm ) Fig. 2. FTIR spectra of the investigated x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%). Numbers at the plots represent Al2O3 content in mol%.
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Absorbance ( a.u. )
to the performed curve-fitting procedure for these intense overlapped bands, each individual band has two characteristic parameters; the center (C), which is related to some type of vibrations of a specific structural group and the relative area (A), which is proportional to the concentration of this structural group [21]. The characteristic parameters of each band of the FTIR spectra are given in Table 2. Fig. 3 illustrated the curve fitting spectra of the glasses 0 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 25 PbO, as an example. The values of the FTIR of the base glass agreed well with that reported for borate-based glasses [21,1]. Therefore, the absorption in the region of 1832–1163 cm− 1 was related to the conventional stretching vibrations of B–O bond of the trigonal BO3 units which were shared in various borate groups containing nonbridging oxygens (NBO) such as metaborate, pyroborate and orthoborate groups [1]. The second intense absorption envelop in the region of 1163– 758 cm−1 was attributed to B–O stretching vibration of BO4 units which were shared in various borate groups, like pentaborate, triborate and diborate groups [8]. The vibrations of borates in this region were overlapped with the vibrations of stretching vibrations of [SiO4] [20,21] and vibrations of symmetrical stretching from different structural units of Pb–O [3]. The first small peak band at 700 cm−1 is attributed to bending vibration of B–O–B in symmetric BO3 triangles [1] and the vibrations of the second peak at around 541–410 cm−1 were due to PbO6 structural units [3] overlapped with the vibrations of SiO2 [21]. As reported elsewhere [24,25], CaO or Fe2O3 (low concentrations) played a modifier role and the vibrations of the different cations such as Ca, Fe, Pb and Si may appear below 300 cm−1. The different assignments of the vibrations of the several structural units enabled the calculation of the concentration of structural units via the parameter N4 which is the ratio of the concentration of four coordinated boron atoms to the total concentration of boron atoms in the glass, i.e., N4 = [(area under the envelope between 758 and 1163 cm−1)/(area under the envelopes between 1832 and 758 cm−1 + area under the component band centered at ~700 cm−1)] [1]. The different areas can be obtained from the deconvolution technique described elsewhere [21]. The general characteristics of the FTIR spectra of these glasses can be summarized with the increase of Bi2O3 content as follows;
1800
1600
1400
1200
1000
800
600
400
-1
Wavenumber ( cm ) Fig. 3. Curve-fitting of FTIR spectra of the glasses 0 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 25 PbO.
(d) Due to the moderate Bi2O3 content in the studied glasses, vibrations from BiO3 units can be excluded and only stretching vibrations from distorted [BiO6] octahedron throughout the composition range can be detected. Bi3+ ions can be settled into the glass network interstitially to form ionic bonds between Bi3+ and individually bonded oxygen atoms resulted from the rupture of borate network. Thus, the appeared band at ~481 cm−1 can be attributed to vibrations of Bi–O bond in BiO6, while the band at ~542 cm−1 may be attributed to the vibrations of [PbO6] structural units [3,9]. The frequency and the area of this band decreased as the Bi2O3 content increased.
(a) There is a shift in the center of the band of the trigonal BO3 units with non-bridging oxygens to lower wavenumbers. (b) According to the deconvolution parameters of the FTIR spectra of the studied glasses [Table 2], the area of the bands attributed to BO4 increased slowly in the range 0 ≤ x ≤ 10 mol% of Bi2O3 content and decreased beyond this limit while the area of the bands of BO3 decreased slowly in the same range and increased beyond this limit. The center of the band of the bending vibration of symmetric BO3 triangles decreased in the range 0 ≤ x ≤ 10 mol% of Bi2O3 content, increased at x = 15 mol% of Bi2O3 and retaining its position beyond this limit. (c) Accordingly, N4 as a function of Bi2O3 content can be determined and as shown in Fig. 4, this parameter increased slowly as the Bi2O3 content increased.
Based on the FTIR spectra obtained for the studied glasses, the structure of these glasses therefore, can be assumed to be built up by [BO3], [BO4], [BiO6], [PbO6], and [SiO4] structural units. Therefore, as the Bi2O3 content increases, the concentration of [PbO6] structural units decreases until disappeared while the concentration of [BiO6] and [SiO4] increases. The values of density (ρ), ultrasonic velocities (vl and vs) and elastic moduli (bulk modulus: K, Young's modulus: E) of all the glass samples are listed in Table 3. The compositional dependence of longitudinal and transverse sound velocities is shown in Fig. 5 while the effect of Bi2O3 content on the elastic moduli is shown in Fig. 6. It is obvious that the ultrasonic velocities (vl and vs) decrease with increasing of Bi2O3 mol %, while Young's modulus (E) show a decrease with low
Table 2 The curve fitting parameters (the band centers C and the relative area A%) for the glasses. G0 G1 G2 G3 G4 G5
C A C A C A C A C A C A
– – 481 2.18 485 2.69 487 2.96 488 3.83 488 4.76
542 3.3 520 2.52 509 2.34 508 0.92 507 0.53 507 0.16
697 5.91 692 5.78 686 5.2 699 5.39 697 4.84 699 4.21
849 11.6 851 11.2 845 11.6 846 10.4 852 11.4 835 12.1
970 14.7 962 14.9 947 15.3 945 16.7 957 15.3 950 16.47
1086 12.9 1053 14.7 1039 15.6 1058 16.4 1036 16.4 1046 15.02
1229 12.4 1251 14.9 1245 16.4 1247 16.9 1223 15.7 1227 16.4
1349 18.4 1359 18.5 1351 18.5 1382 18.5 1337 19.6 1339 17.49
1473 16.7 1467 15.3 1481 12.4 1477 11.83 1470 12.4 1460 13.4
1619 4.09 – – – – – – – – – –
N4
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0.48
detected by several techniques such FTIR technique for example. Accordingly, the FTIR spectra of the exposed studied glasses to doses of γirradiation as shown in Figs. 7–9 revealed the following variations:
0.46
(a) The intensity of all the bands is lower to some extent than the corresponding FTIR spectra before irradiation. (b) The bands were rounded, smoothed and sharpened especially when the dose of radiation exceeds 20 kGy. (c) The frequency of the vibrations of Bi–O bond in BiO6 was increased as the dose increased. The position of the band of this frequency was not affected by radiation beyond the sample that had 20 mol% of Bi2O3 content. (d) As listed in Table 3, the density (ρ) increases with a lower rate with the successive doses of γ-irradiation and with small values lower than before irradiation as shown in Fig. (10). The ultrasonic velocities (vl and vs) showed a dissimilar behavior. For each sample, the longitudinal velocity decreases as the dose of γirradiation increases as shown in Fig. (11), while the transverse velocity increases firstly at 30 kGy and decreases beyond this dose. The behavior of the ultrasonic velocities and the density after irradiation with different doses affect the compositional dependence of the elastic moduli on Bi 2 O 3 content as shown in Fig. (12). For each sample, the bulk modulus decreases and Young's modulus increases as the dose of γ-irradiation increases.
0.44
0.42
0.40 0
5
10
15
20
25
Bi2O3 content (mol%) Fig. 4. Change of the fraction of four-coordinated boron N4 with Bi2O3 content in x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses. Lines are fitting plots of the data. The fitting was given from Y = 0.41 ± 0.007 ∗ X ± 3.98 ∗ 10−4 ∗ X2 ± 8.15 ∗ 10−6 ∗ X3. Error limit for N4 values is estimated as ±5%.
rate and the bulk modulus (K) increases with increasing of Bi2O3 mol %. The errors of the physical parameters were estimated by another work elsewhere [26]. On the other hand, glass is an amorphous material and had large free volume compared with the crystalline analogues. When a glass was subjected to a dose of gamma radiation, part of this energy was imparted to the structural units, and the impurities constitute the glass. The effect of radiation manifested itself in compaction the amorphous network, displacement their atoms from their equilibrium positions, changing the valence state of the structural units, or modified the bonds between the different anions and cations in the glassy network. These features can be Table 3 The density, ultrasonic velocities (vl and vs) and the elastic moduli (Young's modulus (E) and bulk modulus (K)) at difference doses of γ-irradiation for each sample. Dose (kGy)
ρ
vT
vL −3
−1
−1
Y
Ke
ms
ms
GPa
GPa
0 mol% of Bi2O3 concentration 0 4099 30 4141 120 4157
5007 4895 4875
2341 2322 2485
61.11 60.54 67.99
72.81 68.84 64.57
5 mol% of Bi2O3 concentration 0 4264 30 4309 120 4319
4956 4866 4849
2202 2225 2382
56.67 58.44 65.73
76.80 73.04 68.88
10 mol% of Bi2O3 concentration 0 4576 30 4621 120 4630
4858 4845 4777
2099 2118 2243
55.86 57.23 63.29
81.11 77.96 74.60
15 mol% of Bi2O3 concentration 0 4755 30 4802 120 4812
4793 4783 4752
2048 2071 2140
55.35 57.08 60.39
82.19 81.14 77.46
20 mol% of Bi2O3 concentration 0 4958 30 5006 120 5015
4761 4719 4624
2004 2034 2113
55.43 57.27 60.79
85.36 83.56 78.12
25 mol% of Bi2O3 concentration 0 5111 30 5148 120 5168
4588 4468 4447
1931 1976 2084
53.07 56.12 59.97
87.18 85.64 80.14
kg m
4. Discussion Generally, the center of the FTIR bands is affected by the different atomic masses of the constituents of a glass network. Atoms that had high atomic mass shifted the frequency of the vibrations towards lower wave numbers and vice versa with atoms that had low atomic masses. Thus, incorporation of a glass network modifier such as BaO with a relatively higher atomic mass [27] in a lead borate glass network [11] may reduce the frequency of the vibrations of its atoms and shift the FTIR bands to lower wave numbers. On the other hand, a recent study on a comparable structure of borate based glasses with cement kiln dust (CKD) [20] showed two effective regions of increasing CKD. In the first region, from 0 ≤ CKD ≤ 21 mol%, there is a coordination change of BO3 into BO4 rather than producing NBO, CaO4 and SiO4 structural units were created, the number of bridging oxygens, crosslink density and connectivity within the glass network increase which increase the elastic moduli of the network. The tendency to form BO4 structural units increases with the increase in ion field strength of Si4+. Beyond 21 mol% of CKD content, the silicon–oxygen network manifests itself by the destruction of BO4 into asymmetric BO3 with NBO that reduces the stability of the glasses. Thus, the rate of increase of the elastic moduli decreases which may be attributed to the conversion of BO4 into BO3 and creating NBO. Moreover, the preference to attract the oxygen ions for compensation of electric charge can be decided by the electronegativity theory. The electronegativity of the cations; boron, lead and silicon is 2.04, 2.33 and 1.9 respectively while that of oxygen is 3.44 [28]. As reported elsewhere, the covalency of a bond became stronger when the difference between the electronegativity of cation and anion ions decreased [4]. So, the covalency of Pb–O and B–O is stronger than that of Si–O in the network of the base glass. On the other hand, dibismuth trioxide is able to participate in the glass matrix as a network former or as a network modifier based on its concentration. It was reported that quite distorted [BiO6] octahedral structural units and the highest valence state of Bi cation manifested their self in borate based glasses have intermediate Bi2O3 content [27]. The analysis of the FTIR spectra of the studied vitreous system showed that the addition of Bi2O3 (the electronegativity of Bi is 2.02 [28]) content rearranged the internal structure of cement kiln dust
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2400 vl
5000
vs
2300 4900
4800
2100 4700
vs (m/s)
vl (m/s)
2200
2000
4600
1900 0
5
10
15
20
25
Bi2O3 content (mol %)
Fig. 5. Dependence of the longitudinal and shear ultrasonic velocities vL and vT in x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses, on the Bi2O3 content. Lines are fitting plots of the data. The fitting was given from Y = 5005 − 10.6 ∗ X − 0.2 ∗ X2, Y = 2330 − 25 ∗ X + 0.4 ∗ X2. The uncertainty in the measurement is ±15 m/s.
lead borate glass network by creating two regions; one in the range of 0 ≤ x ≤ 10 and the second in the range 10 ≤ x ≤ 25 mol% of Bi2O3. As shown in Fig. 4, the lower values of N4 than one indicated some type of majority of BO3 units in these glass structures. The values of N4 agree well with the reported values of HMO borate based glasses and borosilicate glasses [24–27]. The slightly increased values of N4 (0.41– 0.46), revealed a type of equilibrium in the BO4/BO3 ratio which means that BO3 units might decreased slowly while BO4 units increased 0 ≤ x ≤ 10 and beyond this limit its concentration seemed to be un affected with the increase of Bi2O3 content. This means that the Bi2O3 will affect mostly on the [BO3] units by decreasing with a lower rate the N4 as a function of Bi2O3. This suggestion is in good accordance with the electronegativity assumptions. This behavior may be attributed to the occupation of CaO by SiO2 for forming calcium silicate network in the structure of HMO borate based glasses. The increase of Bi2O3 content may destroy the associate of the silicon and/or boron with oxygen contributing in a relaxation process by creating non-bridging oxygens. This result along with the heavier mass of bismuth atom compared with the masses of the other constituents may be affected by the increase of the peak height of the bands of bending vibrations of borates on 700 cm−1 [29].
The shift of the vibrations of the bands of O–Bi to lower frequencies can be attributed to the lower stretching force constant of Bi–O compared with that of Pb–O. The area of the bands of the vibrations of [BiO6] structural units increases as the Bi2O3 content increases. This behavior suggested that Bi2O3 deformed the FTIR of the two intense envelopes of borate bands by the appearance of Bi–O stretching vibrations in [BiO6] structural units. This deformation generated excess of Bi3+ that may be attached to BO3 structural units to contribute in creating [BO4] structural units and splitting O–B–O, Pb–O–Pb and Pb–O–B bonds to form new bridging bonds of Bi–O–Bi, Bi–O–B and Bi–O–Pb. In this manner, the Si–O bonds are conserved without the creation of new non-bridging oxygens. These bands accumulate the contributions of the B–O and B–O–B stretching vibrations in the [BO3] structural units. The new bonds were formed due to the inducement of the electrostatic field of the strongly polarizing Bi3+ ions and the high covalency of Bi–O compared with that of Pb–O. Also, the excess of these ions resulted in a relaxation of the glass network and a progressive transformation of the lead–CKD–borate network into bismuth–CKD–borate network. As a consequence, the degree of connectivity of the glass network decreased with increasing number of [BiO6] polyhedra, i.e., it is suggested that Bi2O3 plays a network modifier role in the studied glasses [28].
90 K Y
80
120 kGy
75
90 kGy 60 kGy
Absorbance ( a.u. )
Elastic moduli (GPa)
85
70 65 60
30 kGy 20 kGy 10 kGy 0 kGy
55 50 0
5
10 15 Bi2O3 content (mol %)
20
25
Fig. 6. Composition dependence of the Young's modulus (E) and bulk modulus (K) on the Bi2O3 content of x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses. The line is a fitting plot of all presented data. The fitting was given from Y = 72 + 0.85 ∗ X − 0.01 ∗ X2 for (K), Y = 60 − 0.5 ∗ X + 0.001 ∗ X2 for (E). The error limit is estimated as ±0.15%.
1800
1600
1400
1200
1000
800
600
400
-1
Wavenumber ( cm ) Fig. 7. FTIR spectra of the glasses 0 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 25 PbO before and after different doses of gamma irradiation.
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115
120 kGy 90 kGy
Absorbance ( a.u. )
60 kGy 30 kGy
20 kGy 10 kGy 0 kGy
1600
1400
1200
1000
800
600
400
-1
Wavenumber ( cm ) Fig. 8. FTIR spectra of the glasses 15 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 10 PbO before and after different doses of gamma irradiation.
From Table 3 and as shown in Fig. 10, it can be seen that the density of the studied glasses increase with the increase of Bi2O3 content. This increase may be attributed to the replacement of PbO (molecular weight is 223.199 g mol−1) with Bi2O3 (molecular weight is 465.957 g mol−1) or to the high density of the formed [BiO6] compared with [PbO6] structural units. Thus, the increase of the density besides and the difference between Bi3+ (117 pm) [26] and Pb6+ (133 pm) [11] leading to a compacted structure. The relaxation of the glass structure due to the substitution of PbO by Bi2O3 as deduced from FTIR analysis indicated a breakdown of the ring type structure of the studied glasses through the generation of non-bridging oxygens and the depolymerisation of the glass matrix. The reorganization of the glass network manifested itself in the change
Fig. 10. Composition dependence of the density on the Bi2O3 content of x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses before and after different doses of gamma irradiation. The line is a fitting plot of all presented data. The fitting was given from Y = 4132 − 50 ∗ X − 0.34 ∗ X2. The error limit is estimated as ±25 kg m−3.
in co-ordination number, cross-link density and the decrease in the connectivity of the glass network. Moreover, the heavier atomic mass of Bi2O3 compared with that of PbO besides the lower bond strength of Bi–O [24] compared with that of Pb–O [11] leads to the decrease of the ultrasonic wave velocities as the Bi2O3 content increases. Thus, the ultrasonic velocity can be considered as a tool in revealing the degree of change in structure with composition of glasses. Basically there are some parameters that are competing with each other to control the behavior of the elastic moduli, such as the density, ultrasonic velocities, number of bridging oxygens, bond strength, cross-link density and coordination number [11,24]. The behavior of bulk modulus was controlled by the change in the cross-link density and coordination of the glass network [11,24]. Therefore, as the Bi2O3 content increases, the cross-link density and coordination of oxygens in the glass matrix increases, so the bulk modulus increases. On the other hand, the decrease of Young's modulus may be attributed to the
120 kGy
60 kGy 30 kGy 20 kGy 10 kGy 0 kGy
Ultrasonic longitudinal velocity, vl (m/s)
90 kGy
Absorbance ( a.u. )
(0 kGy) (30 kGy) (120 kGy)
5000
4900
4800
4700
4600
4500
4400 0
5
10
15
20
25
Bi2O3 content (mol %) 1400
1200
1000
800
600
400
-1
Wavenumber ( cm ) Fig. 9. FTIR spectra of the glasses 25 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 0 PbO before and after different doses of gamma irradiation.
Fig. 11. Composition dependence of the longitudinal ultrasonic velocity on the Bi2O3 content of x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses before and after different doses of gamma irradiation. The line is a fitting plot of all presented data. The fitting was given from Y = 5002 − 9.5 ∗ X − 0.2 ∗ X2. The error limit is estimated as ±10 ms−1.
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95 K (0 kGy) Y (0 kGy)
90
K (30 kGy) Y (30 kGy)
5. Conclusion
K (120 kGy) Y (120 kGy)
85
Elastic moduli (GPa)
80 75 70 65 60 55 50 0
5
10
15
20
25
Bi2O3 content (mol %) Fig. 12. Composition dependence of the Young's modulus (E) and bulk modulus (K) on the Bi2O3 content of x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses before and after different doses of gamma irradiation. The line is a fitting plot of all presented data. The fitting was given from Y = 68.7 + 1.1 ∗ X − 0.01 ∗ X2 for (K), Y = 64 + 1.2 ∗ X − 0.02 ∗ X2 for (E). The error limit is estimated as ±0.15%.
increase in the formation of NBO and the lower bond strength of Bi–O than Pb–O. The results were supported by the almost constant value of Young's modulus in terms of change in cross-link density and coordination of the glass network when Bi2O3 is increased. Vitreous materials lack long range order so it contained vacancies, non-bridging oxygens and impurities, which were affected directly with the energy of gamma irradiation. This effect may decrease the intensities of the FTIR absorption spectra or relax the vitreous network by creating defects or more disorder in the non-periodic arrangement of the structural units. High dense structural units such as [BiOn], [PbOn] or [BaOn] are less affected with the irradiation causing shielding behavior, while the interstitial components have a pronounced irradiation effect. Moreover, compacted glass structure or a network has strong covalent bonds such as Si–O–Si which shows less effects for irradiation [29–34]. Thus, the increase in the irradiation dose affected the studied glasses from 10 kGy to 120 kGy which revealed the following features; (a) The insensitivity of the bands at ~ 481, ~ 700, ~ 970 or at ~1354 cm−1 for increasing gamma radiation may be attributed to no configuration of BO3 structural units and the insensitivity increases at the glass had 25 mol% of Bi2O3 content. (b) The slow rate of increase of N4 was referred to the equilibrium between the structural units in a specific glass composition and the exposed energy of gamma irradiation created with slow rate NBO. In addition to the created NBO due to the relaxation of the structure, irradiation may generate some defects in the network of the glass. These defects may fill slightly the voids in the network of the glass which increase the density with different doses of γ-irradiation. These defects also can modify the cross-link density and coordination number which decrease the ultrasonic velocities and the bulk modulus [35,36]. (c) The trend of Young's modulus after a dose of 30 kGy of γirradiation is similar with the before irradiation which indicates that irradiation effects on the modulus at this stage weakly depend on composition. Beyond this dose, the boron–oxygen bond is more likely to be affected by irradiation and the damage can break the bonds between triagonal elements, allowing the formation of some [BO4] structural units which may increase the Young's modulus [37,38].
The center of the FTIR bands is affected by the heavy atomic masses of the constituents of a glass network such as Ba, Pb and Bi. Also, the presence of a CKD in a glass network provided high dense and strong cross-linked bonds. On this basis, the barium lead borate has 32 mol% of CKD modified with Bi2O3 that had four types of cations of glass formers (boron, lead, bismuth and silicon). The covalency Pb–O and B–O are stronger than Bi–O and Si–O according to the electronegativity theory. The width of the bands of the vibrations of [BiO6] structural units increases as the Bi2O3 content increases. This behavior suggested that Bi2O3 deformed the FTIR of the two intense envelopes of borate bands by the appearance of Bi–O stretching vibrations in [BiO6] structural units. This deformation generated excess of Bi3+ attached to BO3 structural units and coordinate with lead ions to contribute in creating [BO4] and [PbO6] structural units. These ions resulted in a relaxation of the glass network and the degree of connectivity of the glass network decreased with increasing number of [BiO6] polyhedra. Accordingly, new bonds were formed due to the inducement of the electrostatic field of the strongly polarizing Bi3+ ions and the high covalency of Pb–O and B–O bonds. The slightly increased values of N4 revealed a type of equilibrium in the BO4/BO3 ratio which means that BO3 units might decrease while BO4 units increased slowly with the increase of Bi2O3 content in accordance with electronegativity assumptions. The FTIR bands at ~700, ~ 970 or at ~1354 cm−1 are insensitive for increasing gamma radiation from 10 kGy to 120 kGy which may be attributed to no configuration of BO3 structural units and the insensitivity increases at the glass had 25 mol% of Bi2O3 content. In other words, the covalent bonds such as Si–O–Si provided by CKD compacted and interlinked the glass structure and the high dense structural units such as [BiOn], [PbOn] or [BaO4] seemed to resist the radiation effects at the former doses of gamma rays. The observed changes in ultrasonic velocity and elastic moduli are related to change in the structure of the glass matrix due to the increase of the amount of heavier atomic mass Bi2O3 content as well as to the irradiation effect. The density of the glass was increased and both the ultrasonic velocities (vl and vs) and the bulk modulus were decreased with the increasing Bi2O3 concentration. The decrease of the ultrasonic parameters was attributed to the relaxation of the network structure. As the different doses of γ-irradiation increases, the density of the glass increases and the ultrasonic along with the bulk modulus decrease. Such a process was attributed to the generation of defects which fill the voids of the network slightly and decrease the coordination number and cross-link density. Acknowledgments The authors wish to thank Al-Azhar University-Egypt for the financial support. References [1] H. Doweidar, G. El-Damrawi, E.F. El Agammy, Vib. Spectrosc. 73 (2014) 90. [2] A. Mohajerani, V. Martin, D. Boyd, J.W. Zwanziger, J. Non-Cryst. Solids 381 (2013) 29. [3] Y. Zhou, Y. Yang, F. Huang, J. Ren, S. Yuan, G. Chen, J. Non-Cryst. Solids 386 (2014) 90. [4] S. Abo-Naf, R. Elwan, G. Elkomy, J. Non-Cryst. Solids 358 (2012) 964. [5] E. Culea, J. Non-Cryst. Solids 357 (2011) 50. [6] M. Rada, L. Rus, S. Rada, E. Culea, T. Rusu, Spectrochim. Acta A Mol. Biomol. Spectrosc. 132 (2014) 533. [7] P. Venkateswara Rao, T. Satyanarayana, M. Srinivasa Reddy, Y. Gandhi, N. Veeraiah, Physica B 403 (2008) 3751. [8] G. Sharma, K. Singh, Manupriya, S. Mohan, H. Singh, S. Bindra, Radiat. Phys. Chem. 75 (2006) 959. [9] F. ElBatal, A. Abdelghany, H. ElBatal, Spectrochim. Acta A Mol. Biomol. Spectrosc. 122 (2014) 461. [10] K. Knoblochova, H. Ticha, J. Schwarz, L. Tichy, Opt. Mater. 31 (2009) 895. [11] Y. Saddeek, J. Alloys Compd. 467 (1–2) (2009) 14.
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Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol
Effect of gamma irradiation on the FTIR of cement kiln dust–bismuth borate glasses Yasser B. Saddeek a,⁎, Gehan Y. Mohamed b, H. Shokry Hassan c, A.M.A. Mostafa a, G. Abd elfadeel a a b c
Physics Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt Experimental Nuclear Physics Department, Nuclear Research Center, Atomic Energy Authority, Post Office No. 13759 Cairo, Egypt Advanced Technology and New Materials Research Institute, City of Scientific Research and Technology Applications, New Borg El-Arab City, Alexandria 21934, Egypt
a r t i c l e
i n f o
Article history: Received 23 October 2014 Received in revised form 5 February 2015 Accepted 18 March 2015 Available online 11 April 2015 Keywords: Bismuth borate glasses; Cement kiln dust; FTIR; γ-Radiation
a b s t r a c t Glasses from cement kiln dust and lead barium bismuth borate were prepared by the melt quenching method and studied by using FTIR and ultrasonic techniques before and after exposure to gamma irradiation at doses up to 120 kGy. The FTIR results indicated a deformation of the lead borate based glasses with the replacement of PbO by Bi2O3 which was attributed to the appearance of Bi–O stretching vibrations in [BiO6] structural units and generated excess of non-bridging oxygens. This deformation affected the [BO3] units which are indicated from the lower decreasing rate of N4 as a function of Bi2O3. The high covalency of Pb–O and B–O bonds compared with that of Bi–O or Si–O attracts the excess of non-bridging oxygens and resulted in a relaxation of the glass network. The relaxation decreased the ultrasonic velocities and the bulk modulus and hence the rigidity of the glass despite the increase of the density which was attributed to the replacement of Bi2O3 instead of PbO. The structural and rigidity changes due to composition variations showed a decreasing manner to the effects of radiation. The density of the glass increased while the ultrasonic velocities decreased. This behavior modulated the compositional behavior of the elastic moduli on Bi2O3 content. © 2015 Elsevier B.V. All rights reserved.
1. Introduction The structure of lead borate glasses had attracted scientific and industrial interests because the network of these remarkable glasses is capable of involving different mixed former/modifier oxides such as SiO2, Bi2O3, CaO, … [1]. Synthesis of these glasses revealed large glass forming regions and their vitreous network showed a significant variation with concentration depending on the composition of former/modifier oxides [2]. It was reported that heavy metal borate based glasses (HMG) such as PbO and Bi2O3 (HMO) are comparable and behaved as conditional glass network formers. Moreover, the glasses have a relatively large vitreous formation range and the forming property of Bi2O3 was greater than that of PbO. Moreover, incorporation of PbO or Bi2O3 with empty d orbital into borate based glasses colored these with colors that ranged from faint- to dark-yellow or brown, respectively [3,4]. The ions of these elements in vitreous network have a lone pair electron configuration and several stable coordinations with oxygens which enable more than one type of structural unit in the vitreous matrix to be created [5, 6]. It was reported that addition of Bi2O3 to lead borate glasses gave high stability against devitrification and chemical inertness due to the dual role of HMO [7,8]. These glasses have high refractive index, high infrared transparency, enhanced optical nonlinearity, and wide ⁎ Corresponding author. E-mail address: [email protected] (Y.B. Saddeek).
http://dx.doi.org/10.1016/j.jnoncrysol.2015.03.021 0022-3093/© 2015 Elsevier B.V. All rights reserved.
transmission window, are functional for generation of photo-induced second harmonic and can exhibit zero stress optic properties [9]. Moreover, it could be used as laser medium for broadband fiber amplifier since they exhibit very broad luminescence, radiation sensitive dosimeters and calorimeter medium for the superconducting of super collider or as shielding candidates due to its high absorption cross-section for radiation [10]. A category of structural studies has been appointed to explore the influence of modifier/former oxides in lead borate glasses including spectroscopic studies, such as FTIR [1,11], Raman [12] and NMR [13], in addition to neutron diffraction, X-ray diffraction [14] and molecular dynamics simulation [15]. The convenience of spectroscopic studies of these glasses was due to the significant difference between the masses of Pb or Bi and B atoms. This difference allowed for a separation of vibrational modes of HMO polyhedra and the borate structural units [2]. On the other hand, modifier/former oxides can be acquired from cement kiln dust (CKD) which is a pollution problem. This polluter of the environment is a by-product during the normal production of cement industry. Recently, much research has been focused on utilization CKD as the raw material to produce glass and glass–ceramics because vitrification seems to be one of the most promising technological options for establishment of this industrial waste. CKD consists mainly from CaO and SiO2. Thus, the use of this waste material for glass industry is of great economic technological and scientific importance with proper modulation of the chemical composition [16–19].
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In this work, waste cement kiln dust was used in the manufacture of glassy materials. This type of glass can be considered as a candidate for the production of novel glass resisted radiation when incorporated with oxides such as BaO, PbO and Bi2O3 that have high ability to absorb gamma radiation. It was also suggested that a dramatic improvement in reducing toxicity of lead borate based glasses was associated with the substitution of PbO by Bi2O3 into the borate network [3]. The use of Bi2O3 together with B2O3 increases the vitrification of the glasses. Therefore, the present work has been investigating the structural and rigidity properties of lead borate glasses containing CKD and different compositions of Bi2O3, by using ultrasonic and FTIR techniques before and after exposure to different doses of gamma irradiation.
2. Experimental procedures
Table 1 The glass compositions for BaO–B2O3–Bi2O3–PbO–CKD glasses (mol.%). Sample
G0 G1 G2 G3 G4 G5
Fig. 1. X-ray diffraction pattern of the investigated x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%).
At room temperature, a 60Co gamma cell (5Ci) as a gamma ray source with a dose rate of 1.15 kGy/h was used. Samples were subjected to six radiation doses in the range of 10–120 kGy. The investigated glass samples were exposed to the same gamma dose every time. Using a Fricke dosimeter, the absorbed dose in glass is expressed in terms of absorbed dose in water, rather than in terms of dose in glass. No cavity theory correction was made. Each glass sample was subjected to a total dose of 10, 20, 30, 60, 90 and 120 kGy according to previous work [22, 23]. FT-IR spectra of all the powdered samples after irradiation were recorded using the same conditions as before irradiation.
3. Results The FTIR spectra of the studied glass system in the range 4000– 400 cm−1 as shown in Fig. 2 revealed the characteristic broad absorption bands of borates and some small absorption band at ~3443 cm−1 brought by air moisture during the preparation of KBr pellets of the samples [21] and attributed to the fundamental stretching of hydroxyl groups. The FTIR spectral features of the base glass as shown in Fig. 2 have exhibited two intense absorption envelopes in the region 1515–1163 cm−1 and 1163–758 cm−1 and two peaks with lower intensity at 700 cm−1 and 466 cm−1. Absorption of the FTIR spectra in these regions was related to vibrations of specific structural groups in the borate network. According 25 Bi 2O3
20 Bi 2O3
15 Bi 2O3
Absorbance (a.u.)
The nominal glass compositions (the starting mixture [Table 1]) were prepared by the conventional melt-quenching method from powders of reagent grades of H3BO3, Bi2O3, PbO, BaO and cement kiln dust (CKD) according to the chemical formula x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) in an amount sufficient to produce 50 g glass. The details of the preparation of the studied glasses were mentioned in a previous work [20]. The amorphous state of the glasses was checked using X-ray diffraction. Philips X-ray diffractometer PW/1710 with Ni-filtered Cu-Kα radiation (λ = 1.542 Å) powered at 40 kV and 30 mA was used. The XRD patterns as shown in Fig. 1 revealed the characteristic broad humps of the vitreous materials and did not reveal discrete or any sharp peaks. Fourier transformation infrared (FT-IR) spectra for the glass powder were obtained using a spectrophotometer type JASCO, FT/IR-430 (Japan). For this purpose, each sample was mixed with KBr in the proportion of 1:100 (by weight) for 20 min and pressed into a pellet using a hand press. At least two spectra for each sample were recorded in the wavenumber range of 4000–400 cm−1 at a resolution of ±1 cm−1 by taking 256 scans. The spectra were corrected for dark-current noise, normalized and curve fitted to get quantitative values for the band areas of heavily overlapped bands. The details of curve-fitting procedure were mentioned elsewhere [21]. The density of each sample was measured by Archimedes' principle by using toluene as the immersion fluid. Four samples of each glass were used to determine the density (ρ). A random error in the density values was found as ±25 kg m−3. The ultrasonic velocities, longitudinal (vL) and shear (vT), at room temperature (~300 K) were obtained using the pulse-echo method. In this method, x-cut and y-cut transducers (KARL DEUTSCH) operated at a fundamental frequency of 4 MHz along with a digital ultrasonic flaw detector (KARL DEUTSCH Echograph model 1085) were used. The uncertainty in the measurement of the ultrasonic velocity is ± 10 m/s. The two velocities besides the density were utilized to determine two independent second-order elastic constants, L and G. For pure longitudinal waves L = ρv2L Z, and for pure transverse waves G = ρv2T Z. The elastic bulk modulus (Ke), and Young's modulus (Y) can be determined using the standard relations adopted in previous work [20]. The uncertainty in the measurement of the elastic moduli is ±0.15 GPa.
10 Bi 2O3
5 Bi 2O3
0 Bi 2O3
Composition (mol.%) BaO
B2O3
Bi2O3
PbO
CKD
3 3 3 3 3 3
40 40 40 40 40 40
0 5 10 15 20 25
25 20 15 10 5 0
32 32 32 32 32 32
4000
3600
3200
2800
2400
2000
1600
1200
800
400
-1
Wavenumber ( cm ) Fig. 2. FTIR spectra of the investigated x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%). Numbers at the plots represent Al2O3 content in mol%.
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Absorbance ( a.u. )
to the performed curve-fitting procedure for these intense overlapped bands, each individual band has two characteristic parameters; the center (C), which is related to some type of vibrations of a specific structural group and the relative area (A), which is proportional to the concentration of this structural group [21]. The characteristic parameters of each band of the FTIR spectra are given in Table 2. Fig. 3 illustrated the curve fitting spectra of the glasses 0 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 25 PbO, as an example. The values of the FTIR of the base glass agreed well with that reported for borate-based glasses [21,1]. Therefore, the absorption in the region of 1832–1163 cm− 1 was related to the conventional stretching vibrations of B–O bond of the trigonal BO3 units which were shared in various borate groups containing nonbridging oxygens (NBO) such as metaborate, pyroborate and orthoborate groups [1]. The second intense absorption envelop in the region of 1163– 758 cm−1 was attributed to B–O stretching vibration of BO4 units which were shared in various borate groups, like pentaborate, triborate and diborate groups [8]. The vibrations of borates in this region were overlapped with the vibrations of stretching vibrations of [SiO4] [20,21] and vibrations of symmetrical stretching from different structural units of Pb–O [3]. The first small peak band at 700 cm−1 is attributed to bending vibration of B–O–B in symmetric BO3 triangles [1] and the vibrations of the second peak at around 541–410 cm−1 were due to PbO6 structural units [3] overlapped with the vibrations of SiO2 [21]. As reported elsewhere [24,25], CaO or Fe2O3 (low concentrations) played a modifier role and the vibrations of the different cations such as Ca, Fe, Pb and Si may appear below 300 cm−1. The different assignments of the vibrations of the several structural units enabled the calculation of the concentration of structural units via the parameter N4 which is the ratio of the concentration of four coordinated boron atoms to the total concentration of boron atoms in the glass, i.e., N4 = [(area under the envelope between 758 and 1163 cm−1)/(area under the envelopes between 1832 and 758 cm−1 + area under the component band centered at ~700 cm−1)] [1]. The different areas can be obtained from the deconvolution technique described elsewhere [21]. The general characteristics of the FTIR spectra of these glasses can be summarized with the increase of Bi2O3 content as follows;
1800
1600
1400
1200
1000
800
600
400
-1
Wavenumber ( cm ) Fig. 3. Curve-fitting of FTIR spectra of the glasses 0 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 25 PbO.
(d) Due to the moderate Bi2O3 content in the studied glasses, vibrations from BiO3 units can be excluded and only stretching vibrations from distorted [BiO6] octahedron throughout the composition range can be detected. Bi3+ ions can be settled into the glass network interstitially to form ionic bonds between Bi3+ and individually bonded oxygen atoms resulted from the rupture of borate network. Thus, the appeared band at ~481 cm−1 can be attributed to vibrations of Bi–O bond in BiO6, while the band at ~542 cm−1 may be attributed to the vibrations of [PbO6] structural units [3,9]. The frequency and the area of this band decreased as the Bi2O3 content increased.
(a) There is a shift in the center of the band of the trigonal BO3 units with non-bridging oxygens to lower wavenumbers. (b) According to the deconvolution parameters of the FTIR spectra of the studied glasses [Table 2], the area of the bands attributed to BO4 increased slowly in the range 0 ≤ x ≤ 10 mol% of Bi2O3 content and decreased beyond this limit while the area of the bands of BO3 decreased slowly in the same range and increased beyond this limit. The center of the band of the bending vibration of symmetric BO3 triangles decreased in the range 0 ≤ x ≤ 10 mol% of Bi2O3 content, increased at x = 15 mol% of Bi2O3 and retaining its position beyond this limit. (c) Accordingly, N4 as a function of Bi2O3 content can be determined and as shown in Fig. 4, this parameter increased slowly as the Bi2O3 content increased.
Based on the FTIR spectra obtained for the studied glasses, the structure of these glasses therefore, can be assumed to be built up by [BO3], [BO4], [BiO6], [PbO6], and [SiO4] structural units. Therefore, as the Bi2O3 content increases, the concentration of [PbO6] structural units decreases until disappeared while the concentration of [BiO6] and [SiO4] increases. The values of density (ρ), ultrasonic velocities (vl and vs) and elastic moduli (bulk modulus: K, Young's modulus: E) of all the glass samples are listed in Table 3. The compositional dependence of longitudinal and transverse sound velocities is shown in Fig. 5 while the effect of Bi2O3 content on the elastic moduli is shown in Fig. 6. It is obvious that the ultrasonic velocities (vl and vs) decrease with increasing of Bi2O3 mol %, while Young's modulus (E) show a decrease with low
Table 2 The curve fitting parameters (the band centers C and the relative area A%) for the glasses. G0 G1 G2 G3 G4 G5
C A C A C A C A C A C A
– – 481 2.18 485 2.69 487 2.96 488 3.83 488 4.76
542 3.3 520 2.52 509 2.34 508 0.92 507 0.53 507 0.16
697 5.91 692 5.78 686 5.2 699 5.39 697 4.84 699 4.21
849 11.6 851 11.2 845 11.6 846 10.4 852 11.4 835 12.1
970 14.7 962 14.9 947 15.3 945 16.7 957 15.3 950 16.47
1086 12.9 1053 14.7 1039 15.6 1058 16.4 1036 16.4 1046 15.02
1229 12.4 1251 14.9 1245 16.4 1247 16.9 1223 15.7 1227 16.4
1349 18.4 1359 18.5 1351 18.5 1382 18.5 1337 19.6 1339 17.49
1473 16.7 1467 15.3 1481 12.4 1477 11.83 1470 12.4 1460 13.4
1619 4.09 – – – – – – – – – –
N4
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0.48
detected by several techniques such FTIR technique for example. Accordingly, the FTIR spectra of the exposed studied glasses to doses of γirradiation as shown in Figs. 7–9 revealed the following variations:
0.46
(a) The intensity of all the bands is lower to some extent than the corresponding FTIR spectra before irradiation. (b) The bands were rounded, smoothed and sharpened especially when the dose of radiation exceeds 20 kGy. (c) The frequency of the vibrations of Bi–O bond in BiO6 was increased as the dose increased. The position of the band of this frequency was not affected by radiation beyond the sample that had 20 mol% of Bi2O3 content. (d) As listed in Table 3, the density (ρ) increases with a lower rate with the successive doses of γ-irradiation and with small values lower than before irradiation as shown in Fig. (10). The ultrasonic velocities (vl and vs) showed a dissimilar behavior. For each sample, the longitudinal velocity decreases as the dose of γirradiation increases as shown in Fig. (11), while the transverse velocity increases firstly at 30 kGy and decreases beyond this dose. The behavior of the ultrasonic velocities and the density after irradiation with different doses affect the compositional dependence of the elastic moduli on Bi 2 O 3 content as shown in Fig. (12). For each sample, the bulk modulus decreases and Young's modulus increases as the dose of γ-irradiation increases.
0.44
0.42
0.40 0
5
10
15
20
25
Bi2O3 content (mol%) Fig. 4. Change of the fraction of four-coordinated boron N4 with Bi2O3 content in x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses. Lines are fitting plots of the data. The fitting was given from Y = 0.41 ± 0.007 ∗ X ± 3.98 ∗ 10−4 ∗ X2 ± 8.15 ∗ 10−6 ∗ X3. Error limit for N4 values is estimated as ±5%.
rate and the bulk modulus (K) increases with increasing of Bi2O3 mol %. The errors of the physical parameters were estimated by another work elsewhere [26]. On the other hand, glass is an amorphous material and had large free volume compared with the crystalline analogues. When a glass was subjected to a dose of gamma radiation, part of this energy was imparted to the structural units, and the impurities constitute the glass. The effect of radiation manifested itself in compaction the amorphous network, displacement their atoms from their equilibrium positions, changing the valence state of the structural units, or modified the bonds between the different anions and cations in the glassy network. These features can be Table 3 The density, ultrasonic velocities (vl and vs) and the elastic moduli (Young's modulus (E) and bulk modulus (K)) at difference doses of γ-irradiation for each sample. Dose (kGy)
ρ
vT
vL −3
−1
−1
Y
Ke
ms
ms
GPa
GPa
0 mol% of Bi2O3 concentration 0 4099 30 4141 120 4157
5007 4895 4875
2341 2322 2485
61.11 60.54 67.99
72.81 68.84 64.57
5 mol% of Bi2O3 concentration 0 4264 30 4309 120 4319
4956 4866 4849
2202 2225 2382
56.67 58.44 65.73
76.80 73.04 68.88
10 mol% of Bi2O3 concentration 0 4576 30 4621 120 4630
4858 4845 4777
2099 2118 2243
55.86 57.23 63.29
81.11 77.96 74.60
15 mol% of Bi2O3 concentration 0 4755 30 4802 120 4812
4793 4783 4752
2048 2071 2140
55.35 57.08 60.39
82.19 81.14 77.46
20 mol% of Bi2O3 concentration 0 4958 30 5006 120 5015
4761 4719 4624
2004 2034 2113
55.43 57.27 60.79
85.36 83.56 78.12
25 mol% of Bi2O3 concentration 0 5111 30 5148 120 5168
4588 4468 4447
1931 1976 2084
53.07 56.12 59.97
87.18 85.64 80.14
kg m
4. Discussion Generally, the center of the FTIR bands is affected by the different atomic masses of the constituents of a glass network. Atoms that had high atomic mass shifted the frequency of the vibrations towards lower wave numbers and vice versa with atoms that had low atomic masses. Thus, incorporation of a glass network modifier such as BaO with a relatively higher atomic mass [27] in a lead borate glass network [11] may reduce the frequency of the vibrations of its atoms and shift the FTIR bands to lower wave numbers. On the other hand, a recent study on a comparable structure of borate based glasses with cement kiln dust (CKD) [20] showed two effective regions of increasing CKD. In the first region, from 0 ≤ CKD ≤ 21 mol%, there is a coordination change of BO3 into BO4 rather than producing NBO, CaO4 and SiO4 structural units were created, the number of bridging oxygens, crosslink density and connectivity within the glass network increase which increase the elastic moduli of the network. The tendency to form BO4 structural units increases with the increase in ion field strength of Si4+. Beyond 21 mol% of CKD content, the silicon–oxygen network manifests itself by the destruction of BO4 into asymmetric BO3 with NBO that reduces the stability of the glasses. Thus, the rate of increase of the elastic moduli decreases which may be attributed to the conversion of BO4 into BO3 and creating NBO. Moreover, the preference to attract the oxygen ions for compensation of electric charge can be decided by the electronegativity theory. The electronegativity of the cations; boron, lead and silicon is 2.04, 2.33 and 1.9 respectively while that of oxygen is 3.44 [28]. As reported elsewhere, the covalency of a bond became stronger when the difference between the electronegativity of cation and anion ions decreased [4]. So, the covalency of Pb–O and B–O is stronger than that of Si–O in the network of the base glass. On the other hand, dibismuth trioxide is able to participate in the glass matrix as a network former or as a network modifier based on its concentration. It was reported that quite distorted [BiO6] octahedral structural units and the highest valence state of Bi cation manifested their self in borate based glasses have intermediate Bi2O3 content [27]. The analysis of the FTIR spectra of the studied vitreous system showed that the addition of Bi2O3 (the electronegativity of Bi is 2.02 [28]) content rearranged the internal structure of cement kiln dust
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2400 vl
5000
vs
2300 4900
4800
2100 4700
vs (m/s)
vl (m/s)
2200
2000
4600
1900 0
5
10
15
20
25
Bi2O3 content (mol %)
Fig. 5. Dependence of the longitudinal and shear ultrasonic velocities vL and vT in x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses, on the Bi2O3 content. Lines are fitting plots of the data. The fitting was given from Y = 5005 − 10.6 ∗ X − 0.2 ∗ X2, Y = 2330 − 25 ∗ X + 0.4 ∗ X2. The uncertainty in the measurement is ±15 m/s.
lead borate glass network by creating two regions; one in the range of 0 ≤ x ≤ 10 and the second in the range 10 ≤ x ≤ 25 mol% of Bi2O3. As shown in Fig. 4, the lower values of N4 than one indicated some type of majority of BO3 units in these glass structures. The values of N4 agree well with the reported values of HMO borate based glasses and borosilicate glasses [24–27]. The slightly increased values of N4 (0.41– 0.46), revealed a type of equilibrium in the BO4/BO3 ratio which means that BO3 units might decreased slowly while BO4 units increased 0 ≤ x ≤ 10 and beyond this limit its concentration seemed to be un affected with the increase of Bi2O3 content. This means that the Bi2O3 will affect mostly on the [BO3] units by decreasing with a lower rate the N4 as a function of Bi2O3. This suggestion is in good accordance with the electronegativity assumptions. This behavior may be attributed to the occupation of CaO by SiO2 for forming calcium silicate network in the structure of HMO borate based glasses. The increase of Bi2O3 content may destroy the associate of the silicon and/or boron with oxygen contributing in a relaxation process by creating non-bridging oxygens. This result along with the heavier mass of bismuth atom compared with the masses of the other constituents may be affected by the increase of the peak height of the bands of bending vibrations of borates on 700 cm−1 [29].
The shift of the vibrations of the bands of O–Bi to lower frequencies can be attributed to the lower stretching force constant of Bi–O compared with that of Pb–O. The area of the bands of the vibrations of [BiO6] structural units increases as the Bi2O3 content increases. This behavior suggested that Bi2O3 deformed the FTIR of the two intense envelopes of borate bands by the appearance of Bi–O stretching vibrations in [BiO6] structural units. This deformation generated excess of Bi3+ that may be attached to BO3 structural units to contribute in creating [BO4] structural units and splitting O–B–O, Pb–O–Pb and Pb–O–B bonds to form new bridging bonds of Bi–O–Bi, Bi–O–B and Bi–O–Pb. In this manner, the Si–O bonds are conserved without the creation of new non-bridging oxygens. These bands accumulate the contributions of the B–O and B–O–B stretching vibrations in the [BO3] structural units. The new bonds were formed due to the inducement of the electrostatic field of the strongly polarizing Bi3+ ions and the high covalency of Bi–O compared with that of Pb–O. Also, the excess of these ions resulted in a relaxation of the glass network and a progressive transformation of the lead–CKD–borate network into bismuth–CKD–borate network. As a consequence, the degree of connectivity of the glass network decreased with increasing number of [BiO6] polyhedra, i.e., it is suggested that Bi2O3 plays a network modifier role in the studied glasses [28].
90 K Y
80
120 kGy
75
90 kGy 60 kGy
Absorbance ( a.u. )
Elastic moduli (GPa)
85
70 65 60
30 kGy 20 kGy 10 kGy 0 kGy
55 50 0
5
10 15 Bi2O3 content (mol %)
20
25
Fig. 6. Composition dependence of the Young's modulus (E) and bulk modulus (K) on the Bi2O3 content of x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses. The line is a fitting plot of all presented data. The fitting was given from Y = 72 + 0.85 ∗ X − 0.01 ∗ X2 for (K), Y = 60 − 0.5 ∗ X + 0.001 ∗ X2 for (E). The error limit is estimated as ±0.15%.
1800
1600
1400
1200
1000
800
600
400
-1
Wavenumber ( cm ) Fig. 7. FTIR spectra of the glasses 0 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 25 PbO before and after different doses of gamma irradiation.
Y.B. Saddeek et al. / Journal of Non-Crystalline Solids 419 (2015) 110–117
115
120 kGy 90 kGy
Absorbance ( a.u. )
60 kGy 30 kGy
20 kGy 10 kGy 0 kGy
1600
1400
1200
1000
800
600
400
-1
Wavenumber ( cm ) Fig. 8. FTIR spectra of the glasses 15 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 10 PbO before and after different doses of gamma irradiation.
From Table 3 and as shown in Fig. 10, it can be seen that the density of the studied glasses increase with the increase of Bi2O3 content. This increase may be attributed to the replacement of PbO (molecular weight is 223.199 g mol−1) with Bi2O3 (molecular weight is 465.957 g mol−1) or to the high density of the formed [BiO6] compared with [PbO6] structural units. Thus, the increase of the density besides and the difference between Bi3+ (117 pm) [26] and Pb6+ (133 pm) [11] leading to a compacted structure. The relaxation of the glass structure due to the substitution of PbO by Bi2O3 as deduced from FTIR analysis indicated a breakdown of the ring type structure of the studied glasses through the generation of non-bridging oxygens and the depolymerisation of the glass matrix. The reorganization of the glass network manifested itself in the change
Fig. 10. Composition dependence of the density on the Bi2O3 content of x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses before and after different doses of gamma irradiation. The line is a fitting plot of all presented data. The fitting was given from Y = 4132 − 50 ∗ X − 0.34 ∗ X2. The error limit is estimated as ±25 kg m−3.
in co-ordination number, cross-link density and the decrease in the connectivity of the glass network. Moreover, the heavier atomic mass of Bi2O3 compared with that of PbO besides the lower bond strength of Bi–O [24] compared with that of Pb–O [11] leads to the decrease of the ultrasonic wave velocities as the Bi2O3 content increases. Thus, the ultrasonic velocity can be considered as a tool in revealing the degree of change in structure with composition of glasses. Basically there are some parameters that are competing with each other to control the behavior of the elastic moduli, such as the density, ultrasonic velocities, number of bridging oxygens, bond strength, cross-link density and coordination number [11,24]. The behavior of bulk modulus was controlled by the change in the cross-link density and coordination of the glass network [11,24]. Therefore, as the Bi2O3 content increases, the cross-link density and coordination of oxygens in the glass matrix increases, so the bulk modulus increases. On the other hand, the decrease of Young's modulus may be attributed to the
120 kGy
60 kGy 30 kGy 20 kGy 10 kGy 0 kGy
Ultrasonic longitudinal velocity, vl (m/s)
90 kGy
Absorbance ( a.u. )
(0 kGy) (30 kGy) (120 kGy)
5000
4900
4800
4700
4600
4500
4400 0
5
10
15
20
25
Bi2O3 content (mol %) 1400
1200
1000
800
600
400
-1
Wavenumber ( cm ) Fig. 9. FTIR spectra of the glasses 25 Bi2O3 − (40 B2O3–32 CKD–3 BaO) − 0 PbO before and after different doses of gamma irradiation.
Fig. 11. Composition dependence of the longitudinal ultrasonic velocity on the Bi2O3 content of x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses before and after different doses of gamma irradiation. The line is a fitting plot of all presented data. The fitting was given from Y = 5002 − 9.5 ∗ X − 0.2 ∗ X2. The error limit is estimated as ±10 ms−1.
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95 K (0 kGy) Y (0 kGy)
90
K (30 kGy) Y (30 kGy)
5. Conclusion
K (120 kGy) Y (120 kGy)
85
Elastic moduli (GPa)
80 75 70 65 60 55 50 0
5
10
15
20
25
Bi2O3 content (mol %) Fig. 12. Composition dependence of the Young's modulus (E) and bulk modulus (K) on the Bi2O3 content of x Bi2O3 − (40 B2O3–32 CKD–3 BaO) − (25 − x) PbO, (0 ≤ x ≤ 25 mol%) glasses before and after different doses of gamma irradiation. The line is a fitting plot of all presented data. The fitting was given from Y = 68.7 + 1.1 ∗ X − 0.01 ∗ X2 for (K), Y = 64 + 1.2 ∗ X − 0.02 ∗ X2 for (E). The error limit is estimated as ±0.15%.
increase in the formation of NBO and the lower bond strength of Bi–O than Pb–O. The results were supported by the almost constant value of Young's modulus in terms of change in cross-link density and coordination of the glass network when Bi2O3 is increased. Vitreous materials lack long range order so it contained vacancies, non-bridging oxygens and impurities, which were affected directly with the energy of gamma irradiation. This effect may decrease the intensities of the FTIR absorption spectra or relax the vitreous network by creating defects or more disorder in the non-periodic arrangement of the structural units. High dense structural units such as [BiOn], [PbOn] or [BaOn] are less affected with the irradiation causing shielding behavior, while the interstitial components have a pronounced irradiation effect. Moreover, compacted glass structure or a network has strong covalent bonds such as Si–O–Si which shows less effects for irradiation [29–34]. Thus, the increase in the irradiation dose affected the studied glasses from 10 kGy to 120 kGy which revealed the following features; (a) The insensitivity of the bands at ~ 481, ~ 700, ~ 970 or at ~1354 cm−1 for increasing gamma radiation may be attributed to no configuration of BO3 structural units and the insensitivity increases at the glass had 25 mol% of Bi2O3 content. (b) The slow rate of increase of N4 was referred to the equilibrium between the structural units in a specific glass composition and the exposed energy of gamma irradiation created with slow rate NBO. In addition to the created NBO due to the relaxation of the structure, irradiation may generate some defects in the network of the glass. These defects may fill slightly the voids in the network of the glass which increase the density with different doses of γ-irradiation. These defects also can modify the cross-link density and coordination number which decrease the ultrasonic velocities and the bulk modulus [35,36]. (c) The trend of Young's modulus after a dose of 30 kGy of γirradiation is similar with the before irradiation which indicates that irradiation effects on the modulus at this stage weakly depend on composition. Beyond this dose, the boron–oxygen bond is more likely to be affected by irradiation and the damage can break the bonds between triagonal elements, allowing the formation of some [BO4] structural units which may increase the Young's modulus [37,38].
The center of the FTIR bands is affected by the heavy atomic masses of the constituents of a glass network such as Ba, Pb and Bi. Also, the presence of a CKD in a glass network provided high dense and strong cross-linked bonds. On this basis, the barium lead borate has 32 mol% of CKD modified with Bi2O3 that had four types of cations of glass formers (boron, lead, bismuth and silicon). The covalency Pb–O and B–O are stronger than Bi–O and Si–O according to the electronegativity theory. The width of the bands of the vibrations of [BiO6] structural units increases as the Bi2O3 content increases. This behavior suggested that Bi2O3 deformed the FTIR of the two intense envelopes of borate bands by the appearance of Bi–O stretching vibrations in [BiO6] structural units. This deformation generated excess of Bi3+ attached to BO3 structural units and coordinate with lead ions to contribute in creating [BO4] and [PbO6] structural units. These ions resulted in a relaxation of the glass network and the degree of connectivity of the glass network decreased with increasing number of [BiO6] polyhedra. Accordingly, new bonds were formed due to the inducement of the electrostatic field of the strongly polarizing Bi3+ ions and the high covalency of Pb–O and B–O bonds. The slightly increased values of N4 revealed a type of equilibrium in the BO4/BO3 ratio which means that BO3 units might decrease while BO4 units increased slowly with the increase of Bi2O3 content in accordance with electronegativity assumptions. The FTIR bands at ~700, ~ 970 or at ~1354 cm−1 are insensitive for increasing gamma radiation from 10 kGy to 120 kGy which may be attributed to no configuration of BO3 structural units and the insensitivity increases at the glass had 25 mol% of Bi2O3 content. In other words, the covalent bonds such as Si–O–Si provided by CKD compacted and interlinked the glass structure and the high dense structural units such as [BiOn], [PbOn] or [BaO4] seemed to resist the radiation effects at the former doses of gamma rays. The observed changes in ultrasonic velocity and elastic moduli are related to change in the structure of the glass matrix due to the increase of the amount of heavier atomic mass Bi2O3 content as well as to the irradiation effect. The density of the glass was increased and both the ultrasonic velocities (vl and vs) and the bulk modulus were decreased with the increasing Bi2O3 concentration. The decrease of the ultrasonic parameters was attributed to the relaxation of the network structure. As the different doses of γ-irradiation increases, the density of the glass increases and the ultrasonic along with the bulk modulus decrease. Such a process was attributed to the generation of defects which fill the voids of the network slightly and decrease the coordination number and cross-link density. Acknowledgments The authors wish to thank Al-Azhar University-Egypt for the financial support. References [1] H. Doweidar, G. El-Damrawi, E.F. El Agammy, Vib. Spectrosc. 73 (2014) 90. [2] A. Mohajerani, V. Martin, D. Boyd, J.W. Zwanziger, J. Non-Cryst. Solids 381 (2013) 29. [3] Y. Zhou, Y. Yang, F. Huang, J. Ren, S. Yuan, G. Chen, J. Non-Cryst. Solids 386 (2014) 90. [4] S. Abo-Naf, R. Elwan, G. Elkomy, J. Non-Cryst. Solids 358 (2012) 964. [5] E. Culea, J. Non-Cryst. Solids 357 (2011) 50. [6] M. Rada, L. Rus, S. Rada, E. Culea, T. Rusu, Spectrochim. Acta A Mol. Biomol. Spectrosc. 132 (2014) 533. [7] P. Venkateswara Rao, T. Satyanarayana, M. Srinivasa Reddy, Y. Gandhi, N. Veeraiah, Physica B 403 (2008) 3751. [8] G. Sharma, K. Singh, Manupriya, S. Mohan, H. Singh, S. Bindra, Radiat. Phys. Chem. 75 (2006) 959. [9] F. ElBatal, A. Abdelghany, H. ElBatal, Spectrochim. Acta A Mol. Biomol. Spectrosc. 122 (2014) 461. [10] K. Knoblochova, H. Ticha, J. Schwarz, L. Tichy, Opt. Mater. 31 (2009) 895. [11] Y. Saddeek, J. Alloys Compd. 467 (1–2) (2009) 14.
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