Crystallization kinetics phenomena assessment in a glass-ceramic material, by non-destructive
spectroscopic methods
D. Moudir, N.Kamel, Y. Mouheb, S.Kamariz, F.Aouchiche
Nuclear Research Center of Algiers, Nuclear Technology Division, 2. Bd Frantz Fanon, BP 399, RP-Algiers.
A. Benmounah, A.Djeridi
Unit, Process Materials and Environment, University M' Hamed Bouguerra, Boumerdes, 35000, Algeria.
Abstract—Non destructive tests are very useful to follow crystallization kinetics phenomena during the synthesis of aluminosilicate glass-ceramic materials. These composite matrices are dedicated for nuclear waste storage. In this study, we assessed the crystallization kinetics dependence, by many non- destructive tests, on the structure of an aluminosilicate glass- ceramic ceramized by a nucleation –crystallization treatment at 790°C during 2 h, and 900°C, for different periods of time ranging from 6 to 12 h. These tests are X-ray diffraction;
scanning electron microscopy and Fourier transform Infra-red spectroscopy.
For the whole of materials, Archimedes density is between 2530-2578 kg/m3. Both X-ray diffraction and scanning electron microscopy analyses reveal two main crystalline phases for the whole of heating treatments, namely spodumen and leucite. These phases grow regularly with the crystallization time. FTIR analysis shows Si-O-Si vibrations (680 cm-1and 457-467 cm-1), which shift toward lower values indicating Si-O-Me bonds formation (Me = metal), which are abundant for high ceramization times. The metals incorporated in the materials structure are well binded in the structure, conferring it durable properties. These non-destructive spectroscopic techniques allow following crystallization progress in the materials without altering the materials bulk, and are recommended for such studies.
Keywords—glass-ceramic; alluminosilicate glass;FTIR; SEM ; XRD.
I. INTRODUCTION
Glass-ceramics are considered as specific confinement matrices for radioactive waste. They contain crystals which can embed toxic radioisotopes.
They show potential interest to the confinement of radioactive waste by presenting a double shell protection, the first envelope is the crystalline phase which traps radionuclides and the second one is the glass as second barrier surrounding the crystal.
Adding to that, glass-ceramics structure allows accommodating impurities or other elements present in the waste, due to their flexibility [1]. In this work, we investigate the use of non -destructive techniques to assess physical,
microstructural and spectroscopic properties of a glass- ceramic (noted: GC) in the system: Si-Al-Li-Na. The GC is synthesized by a double melting followed by a crystallization treatment.
II. EXPERIMENTAL
The GC chemical composition is given in Table 1. The following commercial reagents are used for the synthesis:
Al2O3 (FLUKA), Fe2O3 (MERCK, Purity 99%), Na2O (Merck, purity99.5%), K2O (MERCK, Purity99%), Li2O (MERCK, Purity 99%), MgO (FLUKA, Purity 97%), MoO3 (MERCK, Purity99.5%), SiO2 (Prolabo), ZrO2
(Aldrich, Purity99%) and Y2O3(MERCK, Purity99%). The rare earth oxides are dried at 1000 °C, and the other oxides at 400 °C overnight. This step is important to ensure homogeneity of synthetic products, and obtain materials with isotropic properties.
La2O3is prepared by calcination at 450 °C from La (NO3)3
6 H2O (Fluka, purity99.99%). All reagents are finely ground in a manual agate mortar, to obtain a particle size of about 20 µm, before the preparation of the mixtures. Maintaining the Integrity of the Specifications
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TABLE I. CHEMICAL COMPOSITION(IN MOLE%.)OF THE BASED GLASS PER100G OF MIXTURE
Oxides Mole %
ZrO2 4.50
Al3O3 15.0
MgO 5.00
Na2O 6.00
Fe2O3 2.00
K2O 2.90
Li2O 12.0
La2O3 0.50
Y2O3 0.50
MoO3 0.50
SiO2 48.6
Total 100.0
The powder mixtures are homogenized in an Automatic Sieve Shaker D403 shaker for 6 h, to ensure good dispersion of the mixture. Both nucleation and crystallization temperatures are deducted from trace DTA (differential thermal analysis) analysis of the parent glass. Nucleation is carried out in the same furnace as that used for the glass melting of the oxide mixture at a nucleation temperature (Tn) such as: Tn = Tg + 20, thus 790 °C, for 2 h. Grain growth can be performed at a temperature close to the crystallization temperature of the base glass, Tc, which is 900 °C. The crystallization time is optimized as following: 6, 9 and 12 h.
The GCs are cooled in open air to room temperature. The powders densities (ρA) are measured by the Archimedes method. XRD analysis of the materials is performed by a Philips X'Pert Pro diffractometer, with Cu Kα1 ray (= 1.5418 Å), using Philips X'Pert High Score software for phase identification [2].
A scanning electron microscope (SEM) Philips XL30 allowed micrographic observations. FTIR analyses were performed using Nicolet 380 equipment. All these techniques are non-destructive because they allow us to recover the material, and lower the characterization process cost, by saving the materials for further technical characterizations.
III. RESULTS ANDDISCUSSIONS A. Physical characterization:
A.1. Density
The density of the obtained GCs with different crystallization times is measured by the Archimedes method. The results are given in Table 2.
TABLE II. VARIATION OF THEGCDENSITIES(KG/M3)ACCORDING TO CRYSTALLIZATION TIME(H).
Cristallisation time (h) 6 9 12
densityρA(kg/m3) 2509 2532 2573
The GC density increases with the crystallization time. It is between 2509 and 2573 kg/m3 for all the materials. This density rise can be attributed to the gradual germination and continuous heavy crystalline phases as a function of crystallization time. However, this hypothesis must be confirmed by further investigations of the GCs.
B. Microstructural characterization B.1. XRD phases identification
The GC XRD analysis gave the diffractogramms depicted in Figure 1. The results of phase’s identification are shown in Table 3.
Fig. 1. Diffractograms of the GCs for different crystallization times TABLE III. VARIATION OF THE GC DENSITIES (KG/M3) ACCORDING TO CRYSTALLIZATION TIME (H)
Cristallisation time
(h) Chemical composition JCPDS data [2]
6
79 % LiAlSi2O6 (01-074-1106) 19% Pr2Zr3(MoO4)9 (00-051-1851) 92% Zr0.935Y0.065O1.968 (01-080-2187)
9
82 % KAlSi2O6 (01-081-2221) 11% (K2.5Na0.5)Na(MoO4)2 (01-088-0302) 7 % Mg1.55Fe1.6O4 (01-080-0073)
12
60 % Mg0.6Al1.2Si1.8O6 (01-075-1568) 32 % NaAlSi2O6 (01-071-1504) 5 % NaLa(MoO4)2 (00-024-1103)
20 40 60 80 100 120
0 400 800 1200 1600
counts
2 Théta
(T=6h) (T=9h) (T=12h)
Cristallisation time
(h) Chemical composition JCPDS data [2]
3 % Gd3Fe2Fe3O12 (01-072-0141)
We note that for the lowest crystallization time, Tc=6 h, a main spodumene phase (LiAlSi2O6) is formed, and a secondary molybdate phase in the squeleton Pr2Zr3(MoO4)9.
At Tc = 9h, a main aluminosilicate phase of leucite (KAlSi2O6) is assigned to the crystallized GC. The highest aluminosilicate content, but doped in two different ways, is obtained for the maximum crystallization temperature (Tc = 12h). It exceeds 92% (60 % Mg 0.6Al1.2Si1.8O6 and 32 % NaAlSi2O6).
B.2. SEM microscopic observations
Observation of the microstructure of the studied GCs is carried out by scanning electron microscopy (SEM). The microscope used in this study is Philips ESEM XL 30 equipment. The micrographs are shown in Figures 2.a, 2.b, and 2.c. These micrographs allowed us observing both types of phases: the crystalline and glassy ones, and thus confirm the presence of the main crystalline phases, identified by XRD analysis in the ceramic.
2.a. Tc=6 h
2.b. Tc=9 h
2.c. Tc=12 h
Fig.2 Example of aSEM micrographs of the GCs for different Tc values B.3. FTIR analysis
FTIR analysis of the synthesized materials shows the vibrations of Si-O-Si. These low absorption vibrations are around 680 cm-1 and between (457 and 467) cm-1 [3]. The absorptions between 440 and 530 cm-1 are connected to the stretching vibration of Si-O-Si-O and Si-O-bridging oxygen [4]. The shift of these bands towards lower values indicates the formation of Si-O-Me (Me = Mg or Al metals) in a crystallized structure [5]. The vibrations of the bonds Al-O and Mg-O in Si-O-M appear at 720 cm-1. The bands located in the range of 950-1100 cm-1are due to Si-O-M (where M = Si, Al, Na) [5].
C. Conclusion
In this work, a GC is synthesized and many technical non- destructive techniques have been used to characterize the different GCs as a function of crystallysation temperature. The Archimedes density grows with the crystallization time. X-ray diffraction confirmed the formation of both aluminosilicate and molybdate phases in the material bulks. FTIR analysis confirmed the molecular structure of the as prepared GCs. The materials are safe and can be re-used for further characterizations.
References
[1] D. Caurant, Glasses, Glass-Ceramics And Ceramics For Immobilization Of Highly Radioactive Nuclear Wastes, In: Glasses, Glass-Ceramics and Ceramics, Editor: D. Caurant, Nova Science Publishers, 2009, Inc.pp.2- 437.
[2] JCPDS data Philips X’Pert High Score Package, Diffraction data CD- ROM. International Center for Diffraction Data, Newtown Square PA.
2004.
[3] R. Palanivel and G. Velraj, “FTIR and FT-Raman spectroscopic studies of fired clay artifacts recently excavated in Tamilnadu, India,” Indian J.
Pure Appl. Phys. vol.45, June 2007, pp. 501-508.
Cristallisation time
(h) Chemical composition JCPDS data [2]
3 % Gd3Fe2Fe3O12 (01-072-0141)
We note that for the lowest crystallization time, Tc=6 h, a main spodumene phase (LiAlSi2O6) is formed, and a secondary molybdate phase in the squeleton Pr2Zr3(MoO4)9.
At Tc = 9h, a main aluminosilicate phase of leucite (KAlSi2O6) is assigned to the crystallized GC. The highest aluminosilicate content, but doped in two different ways, is obtained for the maximum crystallization temperature (Tc = 12h). It exceeds 92% (60 % Mg 0.6Al1.2Si1.8O6 and 32 % NaAlSi2O6).
B.2. SEM microscopic observations
Observation of the microstructure of the studied GCs is carried out by scanning electron microscopy (SEM). The microscope used in this study is Philips ESEM XL 30 equipment. The micrographs are shown in Figures 2.a, 2.b, and 2.c. These micrographs allowed us observing both types of phases: the crystalline and glassy ones, and thus confirm the presence of the main crystalline phases, identified by XRD analysis in the ceramic.
2.a. Tc=6 h
2.b. Tc=9 h
2.c. Tc=12 h
Fig.2 Example of aSEM micrographs of the GCs for different Tc values B.3. FTIR analysis
FTIR analysis of the synthesized materials shows the vibrations of Si-O-Si. These low absorption vibrations are around 680 cm-1 and between (457 and 467) cm-1 [3]. The absorptions between 440 and 530 cm-1are connected to the stretching vibration of Si-O-Si-O and Si-O-bridging oxygen [4]. The shift of these bands towards lower values indicates the formation of Si-O-Me (Me = Mg or Al metals) in a crystallized structure [5]. The vibrations of the bonds Al-O and Mg-O in Si-O-M appear at 720 cm-1. The bands located in the range of 950-1100 cm-1are due to Si-O-M (where M = Si, Al, Na) [5].
C. Conclusion
In this work, a GC is synthesized and many technical non- destructive techniques have been used to characterize the different GCs as a function of crystallysation temperature. The Archimedes density grows with the crystallization time. X-ray diffraction confirmed the formation of both aluminosilicate and molybdate phases in the material bulks. FTIR analysis confirmed the molecular structure of the as prepared GCs. The materials are safe and can be re-used for further characterizations.
References
[1] D. Caurant, Glasses, Glass-Ceramics And Ceramics For Immobilization Of Highly Radioactive Nuclear Wastes, In: Glasses, Glass-Ceramics and Ceramics, Editor: D. Caurant, Nova Science Publishers, 2009, Inc.pp.2- 437.
[2] JCPDS data Philips X’Pert High Score Package, Diffraction data CD- ROM. International Center for Diffraction Data, Newtown Square PA.
2004.
[3] R. Palanivel and G. Velraj, “FTIR and FT-Raman spectroscopic studies of fired clay artifacts recently excavated in Tamilnadu, India,” Indian J.
Pure Appl. Phys. vol.45, June 2007, pp. 501-508.
Cristallisation time
(h) Chemical composition JCPDS data [2]
3 % Gd3Fe2Fe3O12 (01-072-0141)
We note that for the lowest crystallization time, Tc=6 h, a main spodumene phase (LiAlSi2O6) is formed, and a secondary molybdate phase in the squeleton Pr2Zr3(MoO4)9.
At Tc = 9h, a main aluminosilicate phase of leucite (KAlSi2O6) is assigned to the crystallized GC. The highest aluminosilicate content, but doped in two different ways, is obtained for the maximum crystallization temperature (Tc = 12h). It exceeds 92% (60 % Mg 0.6Al1.2Si1.8O6 and 32 % NaAlSi2O6).
B.2. SEM microscopic observations
Observation of the microstructure of the studied GCs is carried out by scanning electron microscopy (SEM). The microscope used in this study is Philips ESEM XL 30 equipment. The micrographs are shown in Figures 2.a, 2.b, and 2.c. These micrographs allowed us observing both types of phases: the crystalline and glassy ones, and thus confirm the presence of the main crystalline phases, identified by XRD analysis in the ceramic.
2.a. Tc=6 h
2.b. Tc=9 h
2.c. Tc=12 h
Fig.2 Example of aSEM micrographs of the GCs for different Tc values B.3. FTIR analysis
FTIR analysis of the synthesized materials shows the vibrations of Si-O-Si. These low absorption vibrations are around 680 cm-1 and between (457 and 467) cm-1 [3]. The absorptions between 440 and 530 cm-1are connected to the stretching vibration of Si-O-Si-O and Si-O-bridging oxygen [4]. The shift of these bands towards lower values indicates the formation of Si-O-Me (Me = Mg or Al metals) in a crystallized structure [5]. The vibrations of the bonds Al-O and Mg-O in Si-O-M appear at 720 cm-1. The bands located in the range of 950-1100 cm-1are due to Si-O-M (where M = Si, Al, Na) [5].
C. Conclusion
In this work, a GC is synthesized and many technical non- destructive techniques have been used to characterize the different GCs as a function of crystallysation temperature. The Archimedes density grows with the crystallization time. X-ray diffraction confirmed the formation of both aluminosilicate and molybdate phases in the material bulks. FTIR analysis confirmed the molecular structure of the as prepared GCs. The materials are safe and can be re-used for further characterizations.
References
[1] D. Caurant, Glasses, Glass-Ceramics And Ceramics For Immobilization Of Highly Radioactive Nuclear Wastes, In: Glasses, Glass-Ceramics and Ceramics, Editor: D. Caurant, Nova Science Publishers, 2009, Inc.pp.2- 437.
[2] JCPDS data Philips X’Pert High Score Package, Diffraction data CD- ROM. International Center for Diffraction Data, Newtown Square PA.
2004.
[3] R. Palanivel and G. Velraj, “FTIR and FT-Raman spectroscopic studies of fired clay artifacts recently excavated in Tamilnadu, India,” Indian J.
Pure Appl. Phys. vol.45, June 2007, pp. 501-508.
[4] R. Kaur, S. Singh, O.P. Pandey, “FTIR structural investigation of gamma irradiated BaO-Na2O-B2O3-SiO2 glasses,” Physica B, vol.
407,pp.4765-4769, December 2012.
[5] R.Petrovic,D.Janackovic,S.Zec,S.Drmanic,L.J.Kostic-
Gvozdenovic, “Crystallization behavior of alkoxy-derivrd cordierite gels ,” J. Sol-Gel Sci. Technol.vol. 28, pp111-118, August 2003.
