Neutron diffraction of calcium aluminosilicate glasses and melts

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. AbstractThe combination of neutron diffraction with aerodynamic levitation and laser heating, pioneered by Neville Greaves and co-workers about 15 years ago, is an important tool for studying the structure of liquid melts. Since the first work on liquid Al2O3 published in 2001, the technique has been largely improved and experiments are now routinely performed at neutron sources, providing interesting structural information on various materials.In this paper, the structure of glass-forming compounds in the system CaO-Al2O3-SiO2 was measured by applying neutron diffraction with aerodynamic levitation. Results obtained in the liquid state above the melting point and from the glass at room temperatures are presented. Various compositions were studied by increasing the silica content and by changing the ratio CaO/Al2O3. As observed using other methods, the main structural changes relate to modification of the Al-O short range order.

Structure of liquid tricalcium aluminate

“…In this work three structurally identical samples of Ca 3 Al 2 O 6 were prepared by using either Ca in its natural isotopic abundance, predominantly 44 Ca, and a 50 : 50 mixture of the two. Due to the contrast in scattering lengths of the different calcium isotopes, the S αβ (Q) functions containing Ca receive different weightings and give rise to observably different total structure factors denoted nat F (Q), mix F (Q), and 44 F (Q).…”

“…Three samples corresponding to nat F (Q), mix F (Q), and 44 F (Q) were prepared by weighing powders, in the correct proportions, of Al 2 O 3 ( 99.9%) and nat CaCO 3 or 44 CaCO 3 (97% enrichment) mixed with 44 CaAl 2 O 4 glass (99.2% enrichment) prepared for a previous experiment [3]. Each sample was melted in a platinum crucible by using the method described in Ref.…”

“…The resulting polycrystalline ceramics were levitated on a stream of 96.5% Ar + 3.5% O 2 (Arcal 22, Air Liquide) gas and melted by CO 2 laser heating. After rapid cooling, by switching off the laser power, spherical glasses were formed with diameters of 2.64(1) mm for the nat Ca sample and 2.40(1) mm for the 44 Ca and mix Ca samples. Sample reproducibility was checked by unpolarized Raman spectra measured for the glass samples at room temperature by using a T64000 Jobin Yvon confocal micro-Raman spectrometer equipped with a CCD detector with the 514.532 nm line of a Coherent Ar + laser as the excitation source.…”

“…NDIS has previously been used to measure the full set of partial structure factors of levitated liquid and supercooled Ni 36 Zr 64 [15] and Ni-Si alloys [16], although these measurements benefit from the large scattering length contrast of 23.1 fm between the 58 Ni and 62 Ni isotopes. Natural calcium is composed mainly of 40 Ca (96.941% abundance) and 44 Ca (2.086% abundance) that have coherent neutron-scattering lengths of 4.80(2) fm and 1.42(6) fm, respectively [17]. Although 43 Ca has a favorable negative scattering length [−1.56(9) fm], its low abundance (0.135%) means that it is generally impractical to use it for NDIS experiments.…”

“…Although 43 Ca has a favorable negative scattering length [−1.56(9) fm], its low abundance (0.135%) means that it is generally impractical to use it for NDIS experiments. Hence, mixtures of calcium in its natural abundance and 44 Ca are commonly used in NDIS experiments providing a modest scattering length contrast of 3.28(4) fm. NDIS with Ca isotopes was used previously to determine S CaCa (Q) in (CaO) 0.48 (SiO 2 ) 0.49 (Al 2 O 3 ) 0.03 glass [18,19], and has been combined with aerodynamic levitation and laser heating to investigate the structure of liquid and glassy CaSiO 3 [20] and CaAl 2 O 4 [3].…”