12008-40-1Relevant academic research and scientific papers
Structural Role of PbO in Li2O-PbO-B2O3 Glasses
Ganguli, Munia,Rao
, p. 65 - 76 (1999)
Thermal and spectroscopic studies have been carried out on a number of glasses with wide ranging compositions in the pseudoternary glass system Li2O-PbO-B2O3 in order to understand the structural role of PbO in these glasses. Infrared, Raman, and 11B MAS-NMR results indicate that PbO behaves as a network former in these glasses and is possibly incorporated in the network as [PbO4/2]2- units. The formation of [PbO4/2]2- units leads to the creation of neutral three-coordinated boron (B03) which, in turn, leads to the reformation of four-coordinated boron (B-4) in the structure at the expense of two-coordinated (B-2) and singly coordinated (B2-1) boron atoms. The variations of glass transition temperatures (Tg) and molar volumes also support this model.
Critical analysis of glass stability parameters and application to lithium borate glasses
Ferreira, Eduardo B.,Zanotto, Edgar D.,Feller, Steve,Lodden, Grant,Banerjee, Joy,Edwards, Trent,Affatigato, Mario
, p. 3833 - 3841 (2011)
We reevaluated nine parameters of glass stability (GS) against crystallization determined from differential scanning calorimetry (DSC) experiments to predict the glass-forming ability (GFA) of oxide liquids on cooling. Then, borate glasses were prepared and tested, covering the Li 2O-B2O3 system with 20.0-66.7 mol% lithia. The glasses were prepared from both commercial chemical and powders, obtained by a solution method. The GS parameters were calculated using characteristic glass transition, crystallization, and melting peaks of DSC thermograms. We found that seven stability parameters give similar trends for compositions up to 33.3 mol% lithia, where, as we expected, GS significantly decreases with lithia content. Thereafter, up to 66.7 mol% lithia, GS shows a broad shallow maximum, but is approximately constant indicating that, surprisingly, composition does not significantly affect the GFA in this wide compositional range. This result qualitatively agrees with our successful experience of preparing glasses with compositions up to 74 mol% lithia and corroborates the adequacy of simple DSC tests to comparatively gauge the GS and GFA of glass-forming liquids.
Borate glass structure by Raman and infrared spectroscopies
Kamitsos, E. I.,Chryssikos, G. D.
, p. 1 - 16 (2007/10/02)
Raman and infrared spectroscopies have been employed to probe the continuous evolution of borate glass structures as a function of the nature and concentration of alkali oxide modifiers.At relatively low alkali contents, the glasses contain covalent networks consisting of interconnected units bearing BO4- tetrahedra.Further addition of alkali oxide causes the progressive depolymerization of the network as a result of the formation of non-bridging oxygen atoms.Eventually, complete network disruption into small and highly charged borate units results in ionic glasses.The nature of the alkali cation determines the structure of these glasses by affecting several high-temperature isomerization or disproportionation equilibria.
Comparison of Experimental and Theoretical Data on the Structure of the LiBO Molecule
Ermilov, A. Yu.,Nemukhin, A. V.,Stepanov, N. E.
, p. 108 - 109 (2007/10/02)
The results of experimental mass spectrometric studies of the Li(g) + BO(g) = LiBO(g) reaction are compared with those of quantum-mechanical calculations of the energy of the LiBO molecule.It is shown that the relative stabilities of the LiOB and LiBO isomers cannot be established from experimental data of the type examined here.The results of the calculation by molecular statistics are shown to be critically dependent on the parameters of the model.Both theoretical and experimental results suggest the presence of both LiBO isomers over a wide temperature range.
Cation-Network Interactions in Binary Alkali Metal Borate Glasses. A Far-Infrared Study
Kamitsos, E. I.,Karakassides, M. A.,Chryssikos, G. D.
, p. 5807 - 5813 (2007/10/02)
The far-infrared spectra of compositions probing the glass-forming regions of all five binary alkali metal borate systems χM2O.(1-χ)B2O3 (00.25.One distribution of cation sites has been observed for the lower alkali metal content Rb and Cs glasses.The fractions of cations in the two different network sites have also been evaluated.The squares of the frequencies of the cation-motion bands were found to vary linearly with composition, and exhibit kinks at χ ca. 0.20, for all but the Cs glasses.This behavior was explained on the basis of the network structural changes known to occur at this composition.
