16 research outputs found
AlSi10Mg/AlN Interface Grain Structure after Laser Powder Bed Fusion
Details and features of the grain structure near the interface region between the AlN ceramic phase and AlSi10Mg matrix after the laser powder bed fusion (LPBF) were investigated. Aluminum nitride particles were obtained through self-propagating high-temperature synthesis and mechanically mixed with aluminum matrix powder. Optimization of the LPBF process parameters resulted in synthesized material free of pores and other defects. Optical microscopy analysis of etched cross-section and more detailed EBSD analysis revealed regions with relatively coarse grains at melting pool boundaries and fine grains in the melt pool core and near the AlN particles. Moreover, a pronounced orientation of fine elongated matrix grains towards the center of the ceramic particle was obtained. The such formed microstructure is attributed to directional heat sink during crystallization due to the higher thermal conductivity of aluminum nitride compared to the AlSi10Mg matrix. On the contrary, poor wettability of AlN by melt partly prevented the formation of such features, thus a combination of these factors determines the final microstructure of the interface in the resulting material
AlSi10Mg/AlN Interface Grain Structure after Laser Powder Bed Fusion
Details and features of the grain structure near the interface region between the AlN ceramic phase and AlSi10Mg matrix after the laser powder bed fusion (LPBF) were investigated. Aluminum nitride particles were obtained through self-propagating high-temperature synthesis and mechanically mixed with aluminum matrix powder. Optimization of the LPBF process parameters resulted in synthesized material free of pores and other defects. Optical microscopy analysis of etched cross-section and more detailed EBSD analysis revealed regions with relatively coarse grains at melting pool boundaries and fine grains in the melt pool core and near the AlN particles. Moreover, a pronounced orientation of fine elongated matrix grains towards the center of the ceramic particle was obtained. The such formed microstructure is attributed to directional heat sink during crystallization due to the higher thermal conductivity of aluminum nitride compared to the AlSi10Mg matrix. On the contrary, poor wettability of AlN by melt partly prevented the formation of such features, thus a combination of these factors determines the final microstructure of the interface in the resulting material
Influence of electron-hole and donor-acceptor interactions on the distribution coefficients of impurities in multiply doped semiconductors
New profiling and mooring records help to assess variability of Lake Issyk-Kul and reveal unknown features of its thermohaline structure
This article reports the results of three field campaigns conducted in
Lake Issyk-Kul in 2015, 2016, and 2017. During the campaigns, CTD profiling
and water sampling were performed at 34 locations all over the lake. A
total of 75 CTD profiles were obtained. Some biogeochemical and thermohaline
parameters at the lake surface were also mapped at high horizontal resolution
along the ship's track. In addition, thermistor chains were deployed at three
mooring stations in the eastern littoral region of the lake, yielding
147-day-long records of temperature data. The measurements revealed that – while
the thermal state of the active layer, as well as some biogeochemical
characteristics, were subject to significant interannual variability mediated
by atmospheric forcing – the haline structure of the entire lake was
remarkably stable at the interannual scale. Our data do not confirm the
reports of progressive warming of the deep Issyk-Kul waters as suggested in
some previous publications. However, they do indicate a positive trend of
salinity in the lake's interior over the last 3 decades. A noteworthy newly
found feature is a weak but persistent salinity maximum below the thermocline
at a depth of 70–120 m, from where salinity slightly decreased downwards.
The data from the moored thermistor chains support the previously published
hypothesis about the significant role of the submerged ancient riverbeds on the
eastern shelf in advecting littoral waters into the deep portion of the lake
during differential cooling period. We hypothesize that the less saline
littoral water penetrating into the deep layers due to this mechanism is
responsible for the abovementioned features of salinity profile, and we
substantiate this hypothesis by estimates based on simple model assumptions.</p