Although glass is usually considered as a very stable archaeological material, it can undergo severe degradation. Soda-lime glass, the most common glass throughout ancient times, is particularly sensitive to this problem. The glass surface absorbs moisture from its environment and the contact with CO2 causes Na2O and NaOH to convert to Na2CO3, which is extremely hygroscopic. The subsequent unst...

We use molecular-dynamics computer simulations to study the dynamics of amorphous (Na2O)2(SiO2). We find that the Na ions move in channels embedded in a SiO2 matrix. The characteristic distance between these channels gives rise to a prepeak in the structure factor at q approximately equal to 0.95 A(-1). The dynamics of sodium is given by a fast process which can be seen in the incoherent scatte...

We present the results of large scale computer simulations in which we investigate the structural and dynamic properties of silicate melts with the compositions (Na2O)2(SiO2) and (Al2O3)2(SiO2). In order to treat such systems on a time scale of several nanoseconds and for system sizes of several thousand atoms it is necessary to use parallel supercomputers like the CRAY T3E. We show that the si...

ransparent glass-ceramics have been prepared by heat-treating oxyfluoride glasses in the Na2O–Al2O3–SiO2–LaF3 system. The nanocrystallisation f LaF3 was achieved by controlling time and temperature parameters. Glasses and glass-ceramics were characterised by dilatometry, DTA, XRD nd TEM. The mean crystal size (<20 nm) and the crystal fraction increase with the temperature of heat treatment, whi...

We obtained Ba3Yb(BO3)3 single crystals by the flux method with solutions of the BaB2O4–Na2O–Yb2O3 system. The evolution of the cell parameters with temperature shows a slope change at temperatures near 873 K, which may indicate a phase transition that is not observed by changes appearing in the x-ray powder patterns or by differential thermal analysis (DTA). The evolution of the diffraction pa...

Sedimentary rocks are composed of detrital grains derived from source rocks, which are altered by chemical weathering, sorted during transport, and cemented during diagenesis. Fluvio-lacustrine sedimentary rocks of the Bradbury group, observed on the floor of Gale crater by the Curiosity rover during its first 860 sols, show trends in bulk chemistry that are consistent with sorting of mineral g...