Short-range structure of alkaline-earth borate glasses by pulsed neutron diffraction and molecular dynamics simulation

Ohtori, Norikazu; Takase, Keiichi; Akiyama, Isao; Suzuki, Yushi; Handa, Keita; Sakai, Ichiro; Iwadate, Yasuhiko; Fukunaga, Toshiharu; Umesaki, Norimasa

doi:10.1016/s0022-3093(01)00662-7

Cited by 31 publications

(19 citation statements)

References 18 publications

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“…The calculated dependences agree with the available NMR data to within the scatter of the results obtained by different authors [23,24] and is in excellent agreement with the theoretical curve x / (1x) in the range from 16 to 33 mol % BaO. In the range from 33 to 50 mol % BaO, the other (IR, neutron diffraction, molecular dynamics [25,26]) data fit well the curve constructed under the assumption that each third atom in the metaborate groupings has a fourfold coordination (z = 0.33). If the predicted value N 4 = 0.33 for the metaborate glass will be subsequently con- ), + firmed by NMR spectroscopy, the correspondence between the structures of BaO · B 2 O 3 stoichiometric groupings and the high-temperature crystalline modifications of barium metaborate should be revised.…”

Section: Discussionsupporting

confidence: 85%

“…Mg series decreases by a factor of approximately two, whereas the glass transition temperature T g increases considerably [15,[22][23][24][25][26][27][28][29]. In order to resolve this contradiction, Yiannopoulos et al [15] and Kamitsos [25] proposed to take into account not only the fraction of fourfold-coordinated boron atoms but also strong bonds that are formed between the modifier alkalineearth cations and the oxygen environment.…”

Section: Discussionmentioning

confidence: 99%

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Structure-Property Relations in Barium Borate Glasses from Raman Scattering Data

Markova¹,

Yanush²,

Polyakova

et al. 2005

Glass Phys Chem

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Glasses in the x BaO-(100x )B 2 O 3 system ( x = 16-50 mol %) are investigated by Raman spectroscopy. The spectral forms of stoichiometric groupings are separated from the experimental Raman spectra. The diagram of the content of these groupings in glasses is constructed. The diagram obtained makes it possible to calculate the densities, refractive indices, temperature coefficients of linear expansion, and fractions of fourfold-coordinated boron atoms with the use of the experimentally determined partial properties of the groupings. It is revealed that the dependences of the boson peak intensity, the boson peak frequency, and the glass transition temperature on the composition of glasses in the barium borate system correlate with each other.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Structure-Property Relations in Barium Borate Glasses from Raman Scattering Data

Markova¹,

Yanush²,

Polyakova

et al. 2005

Glass Phys Chem

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“…Taking into consideration the low resolution of the present ND experiment, the agreement is reasonable reported for alkali diborate glasses [20][21][22][23]. RMC calculations have revealed that for all studied glassy compositions the B atoms are 3-fold and 4-fold coordinated by O atoms, as it is illustrated in Fig.…”

Section: Reverse Monte Carlo Modelling and Resultssupporting

confidence: 87%

Development of Glass Matrix for Radioactive Waste Conditioning

Fábián

Araczki

2017

MSF

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Abstract. Understanding of the incorporation of actinides in borosilicate matrix used for nuclear waste storage is of a great importance for radioactive waste immobilization. This study carried out on matrix glasses doped respectively with 30wt% UO3 and CeO2, Nd2O3 used for chemical modelling of the actinides. Neutron and X-ray diffraction measurements and Reverse Monte Carlo (RMC) simulations were performed. For several glasses, it was found that the basic network structure consists of tetrahedral SiO4 units and of mixed trigonal BO3 and tetrahedral BO4. The BO3 and BO4 units are linked to SiO4, forming mixed [4] Si-O- [3] B and [4] Si-O- [4] B bond-linkages. From significant second neighbour atomic pair correlations have been revealed that U, Ce, Nd accommodates in both silicate and borate site. IntroductionThe final and safe storage of radioactive waste materials is nowadays an existing and urgently to be solved problem. The most feasible and accepted way for storage of high-level radioactive waste (HLW) is the vitrification process, where the active elements are melted and poured into glass form, and thereafter deposited in the deep geological formation, where the objective is to retain the radionuclides in the host rocks, and to block access to the biosphere [1,2]. Borosilicate glass is a preferred and accepted waste form [3][4][5][6]. Vitrification plants are expected to be operational for the next 50 years, and a great number of relevant research to further enhance effectiveness and reduce cost being conducted in this area [7,8]. Future plans should reflect the best application of processing technologies and a knowledge of waste forms that reduces risk to the public and the environment while also avoiding unnecessary cost and delay. Essentially the most important task in this area is to find a simple and well controllable process where we can immobilize the HLW's. The main problems are the high number of components, high melting temperature, crystallization, unknown basic processes and a high preparation costs.Step by step we have made successful attempt to prepare borosilicate matrix glasses with the general composition of SiO2-B2O3-Na2O-BaO-ZrO2. In this study we intend to explore basic network structure on the glasses by performing neutron-and X-ray diffraction experiments, which are complementary each other, X-ray diffraction data are dominated by contributions from heavier elements, while neutron diffraction gives information mainly on the light elements. Our aim is to develop, optimize and compare the basic network structure of this glasses especially regarding the matrix glass with that of the uranium and lanthanides containing glassy network. In order to do this, simultaneous RMC simulation of the two data sets is applied to generate reliable 3-dimensional atomic configurations and to calculate the atomic parameters.

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“…For this reason, the structure of the quenched glass sample examined in this case does not exactly match the structure of the molten oxide at 1573 K. However, assuming that the effect of the quenching rate on the borate structure is similar for all compositions, a qualitative evaluation of the molten borate structure can be obtained by investigating the structure of the corresponding quenched glass. Ohtori et al, 35 who studied the structure of the CaO-B 2 O 3 system using IR spectroscopy and MD simulations, found approximately constant relative fractions of 4-coordinated boron in a similar composition range. According to Du and Stebbins,33 the peaks centered at 12 and 0 ppm correspond to 3-and 4-coordinated boron in the Na 2 O-B 2 O 3 -SiO 2 glass system, respectively.…”

Section: Effect Of Borate Structure On Thermal Conductivitymentioning

confidence: 98%

Influence of structure and temperature on the thermal conductivity of molten CaO–B₂O₃

2017

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The effect of the temperature and borate structure on the thermal conductivity of the molten CaO–B2O3 binary system was investigated. The thermal conductivity was measured from 1573 K to approximately the liquidus temperature using a transient hot‐wire method, and was found to decrease with increasing temperature. The temperature dependence of the thermal conductivity in the molten oxide system was interpreted in terms of the lifetime of phonon‐like excitations and Maxwell relaxation times. The short‐range order borate structure was investigated through magic angle spinning (MAS) and triple‐quantum MAS (3Q‐MAS) NMR. Although the content of 4‐coordinated boron was not significantly affected by the addition of CaO, structural changes associated with the fraction of 3‐coordinated boron in ring and non‐ring sites were observed. The Raman spectra showed that the intermediate range order borate structure was changed from boroxyl rings to chain‐type metaborate units at higher CaO concentrations. The thermal conductivity decreased with decreasing BO1.5/CaO ratio, owing to the depolymerization of the borate network.

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Short-range structure of alkaline-earth borate glasses by pulsed neutron diffraction and molecular dynamics simulation

Cited by 31 publications

References 18 publications

Structure-Property Relations in Barium Borate Glasses from Raman Scattering Data

Structure-Property Relations in Barium Borate Glasses from Raman Scattering Data

Development of Glass Matrix for Radioactive Waste Conditioning

Influence of structure and temperature on the thermal conductivity of molten CaO–B₂O₃

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Short-range structure of alkaline-earth borate glasses by pulsed neutron diffraction and molecular dynamics simulation

Cited by 31 publications

References 18 publications

Structure-Property Relations in Barium Borate Glasses from Raman Scattering Data

Structure-Property Relations in Barium Borate Glasses from Raman Scattering Data

Development of Glass Matrix for Radioactive Waste Conditioning

Influence of structure and temperature on the thermal conductivity of molten CaO–B2O3

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Product

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Influence of structure and temperature on the thermal conductivity of molten CaO–B₂O₃