Особенности фотолюминесценции и наносекундная релаксация фототока в кристаллах CuIn-=SUB=-5-=/SUB=-S-=SUB=-8-=/SUB=- при высоком уровне оптического возбуждения

In CuIn5S8 crystals grown by the method of slow cooling of the melt at a constant temperature gradient, intense luminescence and nanosecond relaxation of the photocurrent are observed at a high level of optical excitation. Three emission bands with energies of 1.52, 1.48, and 1.465 eV are distinguished in the photoluminescence spectra. The photoactivation of the crystal in the range 300-600 K is explained by an increase in the hole mobility in the valence band with increasing temperature.

Solid-liquid interface morphology of white carbide eutectic during directional solidification

In this paper the analysis of solid-liquid interface morphology in white carbide eutectic was made. In a vacuum Bridgman-type furnace, under an argon atmosphere, directionally solidified sample of Fe - C alloy was produced. The pulling rate was v = 125 μm/s (450 mm/h) and constant temperature gradient G = 33.5 K/mm. The microstructure of the sample was frozen. The microstructure of the sample was examined on the longitudinal section using an light microscope and scanning electron microscope.

Snowbreeder 5: a Micro-CT device for measuring the snow-microstructure evolution under the simultaneous influence of a temperature gradient and compaction

ABSTRACTThe instrumented sample holder Snowbreeder 5 is used to investigate the simultaneous influence of settlement on temperature-gradient snow metamorphism in time-lapse micro-computed tomography experiments. So far, experiments have only been done on temperature-gradient snow metamorphism without settlement or settlement under isothermal conditions. With the new device we can impose a constant temperature gradient on a snow sample and induce settlement by placing a passive load on top of the snow sample. The weight of the load can be varied, simulating various snow heights on top of the snow sample. Snow-temperature measurements on the passive load are possible due to wireless data transfer via Bluetooth. The temperature gradient is set by controlling the air temperature inside the computer tomograph and by a Peltier element at the bottom of the snow sample. First experiments under isothermal conditions and a constant temperature gradient of 43 K m−1 showed that the settlement was reduced to almost half as soon as a temperature gradient was applied under otherwise almost equal snow conditions. The compactive viscosity in the isothermal experiment was in the range of literature values.

X-ray Diffraction Study of Directional Solidification Ledeburite

Directionally solidified sample of Fe-Fe3C eutectic alloy were produced under an argon atmosphere in a vacuum Bridgman-type furnace to study the eutectic growth with ν = 167 μm/s pulling rate and constant temperature gradient G = 33.5 K/mm. Since how the growth texture of eutectic cementite is related to its growth morphology remains unclear, the current study aims to examine this relationship. The technique such as X-ray diffraction, have been used for the crystallographic analysis of carbide particles in white cast irons.

Influence of Growth Rate on the Solute Distribution of Directionally Solidified Cu-Ag-Zr Alloy

Cu-2wt.Ag-2wt.%Zr alloy was directionally solidified with different growth rates(V=10-200 um/s) at a constant temperature gradient(G=3.1 K/mm) in a modified Bridgman furnace. The influence of growth rate was investigated by observing the microstructure and measuring the solutes’ compositions within the Cu-matrix and dendrite boundaries. The experimental results show that increasing the growth rate, decreased both the primary and secondary arm spacing and increased micro-Vickers hardness. The solutes’ concentration also increased as a result of the back diffusion caused by a decreasing growth rate. The electrical conductivity depends on the solutes’ distribution.

Microstructure Formation during Unidirectionally Solidified Pb-Bi-Sn Tenary Quasi-Peritectic Alloy

In order to investigate the microstructure formation resulted from quasi-peritectic reaction in Pb-Bi-Sn ternary alloy, specimens were directionally solidified with a constant temperature gradient (G=18 K/mm) and the growth velocities ranging from 0.5 μm/s to 10 μm/s. Experimental results indicated that a microstructure, which is composed of the residual primary α phase (Pb-rich solid solution), peritectic β-(Pb7Bi3) phase and Sn-rich solid solution phase was observed. Transition from primary α-cell to primary α-dendrite took place with the increasing growth velocity. The rod-like eutectic was observed in the inter-cellular region under low growth velocity. Detail analyses were adopted to identify the phases and determine the phase compositions, respectively.

Microstructural Response to Growth Rate and Mg Additions during Directional Growth of Al-Cu-Mg Alloys

Al-rich Al-Cu-Mg alloys have wide range of applications for automotive and aerospace where the control of the original solidification microstructure is important to achieve desired properties. Under constant temperature gradient G (4.84±0.13 K.mm-1), a series of directional solidification experiments were performed at 6 different growth rates V (16.7 – 166.7 µm/s) and 6 different Mg contents C0-Mg (0 – 5 wt.% Mg) of Al – 5wt.% Cu – (0-5)wt.% Mg alloys. The solid-liquid interface was investigated in as-quenched specimens. Primary dendrite arm spacing λ1 was measured on longitudinal and transverse sections of the specimens. The variations of λ1 with respect to V and C0-Mg were determined and the results were compared to the related theoretical models and the published data.