Un ciment liquide doté de propriétés conductrices analogues à celle du métal liquide a été mis au point par des scientifiques américains. Ce résultat pourrait permettre de fabriquer un nouveau type de matériau, qui pourrait notamment entrer dans la fabrication des écrans qui équipent nos smartphones, téléviseurs et autres écrans plats.
Des scientifiques américains ont créé un ciment liquide doté de propriétés conductrices analogues à celle du métal liquide. Ces travaux pourraient permettre d'utiliser le ciment pour fabriquer une génération plus performante de verre métallique, un matériau aux propriétés très prisées des ingénieurs.
Le verre métallique ? Il s'agit en fait d'un alliage métallique liquide, qui a été refroidi brusquement afin de lui conférer une structure dite « amorphe », un état qui caractérise notamment le verre (d'où le nom de verre métallique) : cet état de la matière, généralement obtenu par refroidissement d'un liquide n'ayant pas eu le temps de cristalliser, s'oppose à la structure dite cristalline, qui est l'état naturel vers lequel tend un alliage métallique liquide lorsqu'il se refroidit.
Jusqu'ici, seul le métal permettait de créer du verre métallique. Ce nouveau résultat vient désormais montrer que le ciment peut, lui aussi, permettre de fabriquer du verre métallique.
Le verre métallique présente de nombreux avantages, parmi lesquels une résistance mécanique très supérieure à celle des alliages métalliques traditionnels. Le verre métallique est notamment utilisé pour fabriquer les écrans des téléphones tactiles, des téléviseurs et des ordinateurs portables.
Ces travaux ont fait l'objet d'un article publié le 27 mai dans la revue Proceeding of the National Academy of Sciences, sous le titre "Network topology for the formation of solvated electrons in binary CaO-Al2O3 composition glasses".
Network topology for the formation of solvated electrons in binary CaO–Al2O3 composition glasses
Glass formation in the CaO–Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO–Al2O3 glasses using combined density functional theory–reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O–Ca and O–Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al–O is stronger than that of Ca–O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71–74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass
Glass formation in the CaO–Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO–Al2O3 glasses using combined density functional theory–reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O–Ca and O–Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al–O is stronger than that of Ca–O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71–74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass
Le Journal de la Science
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