An ultraviolet phosphor from submicrometer-sized particles of gadolonium-doped yttrium oxide prepared by heating of precursors in a polymer solution

Gadolonium-doped yttrium oxide (Y₂O₃:Gd) was synthesized by simple heating of precursors in a polymer solution. This material is potentially useful as an ultraviolet source, since ultraviolet light is emitted when electron transition between energy states in Gd ions occurs. The grain sizes of the particles were found to be sub-micron down to several tens of nanometers. Optimum conditions for producing highly crystalline material with small grain and crystal sizes was investigated by varying the parameters for the synthesis, such as heating temperature, heating time, and dopant concentration. A heating temperature at 800 °C and a heating time of 30 min was optimum, i.e., appreciably high crystallinity and small grain sizes were produced. The particles produce ultraviolet light, peaking at 315 nm, and the intensity of the light depends on the dopant concentration. The maximum intensity was achieved at a dopant concentration of 5 to 10% at./at.     

Simulation study of steels corrosion phenomenon in liquid lead–bismuth cooled reactors using molecular dynamics methods

Corrosion phenomena of stainless steel in liquid lead–bismuth as a coolant in nuclear fast breeder reactor are a field which is intensively investigated by the researchers in the recent year. We try to study this corrosion phenomena by computer simulation using molecular dynamics methods. The initial positions of the system were taken from the crystal structure data including the cell parameters and the types of the crystal. In this simulation, interatomic potential between Fe–Fe, Pb–Pb, Bi–Bi, Ni–Ni and Cr–Cr was assumed to follow Lennard–Jones potential. The Lennard–Jones potential parameters have been derived by fitting the data available in the literature. Nickel and chromium atoms were substituted into Fe crystal with the percentage of 10% and 16% to construct systems like SS 316. Molecular dynamics simulation has been done by interfacing iron and steel with liquid lead and liquid lead–bismuth in several temperatures. The result of this simulation showed that lead atoms can diffuse into Fe–10%Ni–16%Cr about 1.18 Å at 773 K while in Fe–10%Ni and Fe–16%Cr about 7.25 Å and 11.08 Å, respectively.     

Stability of granular tunnel

We demonstrated that the stability of tunnels made of granular matter is strongly dependent on the grain size, tunnel diameter, and water content inside the granules. Larger tunnel radius, larger grain size, and too much water content tend to destabilize the tunnel. We also developed a model to describe such findings. We identified a phase diagram of stability which is significantly controlled by the granular bond order. For granular bond order of above unity, we always able to build a stable tunnel. For granular bond order of less than unity, we obtained a general expression for estimating the maximum thickness of the stable tunnel. The phenomena related to granular tunnel stability have occurred in human activities (such as a collapse of the sand hole made on the beach) as well as in living animals (such as burrows dug by crabs, antlions, mongoose, beetles, turtles, or some species of rats). To the best of our knowledge, this work is the first exploration regarding the stability of the granular tunnel.