Estimation of thermodynamic stability of isoperiodic epitaxial structures whith GaInSbAs and GaInAsP solid solutions

The work studied the thermodynamic stability of GaInSbAs, GaInAsP heterosystems on different substrates. The isotherms of spinodal decomposition caused by chemical changes in the internal energy of the alloy and by elastic stresses at the layer-substrate interface are obtained with the model of quasiregular solutions. It has been found that elastic stresses lead to an expansion of the region of thermodynamic stability of isoperiodic solid solutions for GaSb substrates and a decrease in the critical temperature. The developed model can be using to selection of the technological modes and parameters of epitaxial growth.

Resonant Precession of Magnetization and Precession - Induced DC voltages in FeGaB Thin Films

Measurements of frequency dependent ferromagnetic resonance (FMR) and spin pumping driven dc voltage (Vdc) are reported for amorphous films of Fe78Ga13B9 (FeGaB) alloy to address the phenomenon of self-induced inverse spin Hall effect (ISHE) in plain films of metallic ferromagnets. The Vdc signal, which is antisymmetric on field reversal, comprises of symmetric and asymmetric Lorentzians centered around the resonance field. Dominant role of thin film size effects is seen in setting the magnitude of static magnetization, Vdc and dynamics of magnetization precession in thinner films (≤ 8 nm). The film thickness dependence of magnetization parameters indicates the presence of a magnetically disordered region at the film – substrate interface, which may promote preferential flow of spins generated by the precessing magnetization towards the substrate. However, the Vdc signal also draws contributions from rectification effects of a ≈ 0.4 % anisotropic magnetoresistance and a large (≈ 54 nΩ.m) anomalous Hall resistivity (AHR) of these films which ride over the effect of spin – orbit coupling driven spin-to-charge conversion near the film – substrate interface. We have addressed these data in the framework of the existing theories of electrodynamics of a ferromagnetic film subjected to radio-frequency field in a coplanar waveguide geometry. Our estimation of the self-induced ISHE for the sample with 54 nΩ.m AHR shows that it may contribute significantly (≈ 90%) to the measured symmetric voltage. This study is expected to be very useful for fully understanding the spin pumping induced dc voltages in metallic ferromagnets with disordered interfaces and large anomalous Hall effect.

Effects of interface conditions on heat and mass transfer during modeling of laser dissimilar welding

An improved 3 D heat and mass transfer model was developed to study the effects of interface conditions during modelling of laser dissimilar welding. In detail, the interface conditions consist of the physical processes at gas/liquid surface (e.g. free surface deformation and optical absorptance), substrate interface (e.g. mixture properties in liquid phase and thermal contact condition) and solid/liquid interface (e.g. fusion line). Their effects on heat and mass transfer are numerically and experimentally analyzed, which are all non-negligible in the welding modelling. In conclusion, free surface deformation influences convection flow and should be considered in the situation of micro-welding and high energy-input welding. Besides, the energy transfer between laser and substrate is more reasonably described by the optical absorptance expressed in polynomial function. The mass transfer induced variation of mixture properties is well described by the method based on time-dependent mixture fraction. Thermal resistance between clamp and substrate should be considered in the modelling of temperature field on macroscale. The joint conductance at substrate interface could be neglected when modelling heat and mass transfer inside the melt pool, while it should be calculated in the simulation of temperature distribution based on the mechanism of heat conduction. The obtained results in this paper provide a vital insight into the interface conditions in laser dissimilar welding process.

Responses of Leaf Celery to Floating Culture System with Different Depths of Water-substrate Interface and NPK-fertilizer Application

Wetland areas in Indonesia cover more than 33,3 million hectares, and slightly less than 40 % is inland swamp. During the rainy season, for up to 9 months annually, the wetlands are flooded, and no conventional agricultural activities can be done by local farmers. However, this condition can be seen as an opportunity to employ floating culture system. The objective of this research was to evaluate responses of leaf celery to floating culture system with different depths of water-substrate interface and NPK-fertilizer application. The results of this study indicated that the depth of water-substrate interface (WSI) should be maintained between 1 to 3 cm. At less than 1 cm, continuous contact between the water surface and the bottom part of the substrate cannot be ensured; meanwhile, aerobic substrate volume was reduced and caused significant effects on growth and yield in celery plants if WSI was deeper than 3 cm. Moreover, the effectiveness of NPK-fertilizer application was weakened if the depth of WSI was at 6 cm. Fresh leaf yield in celery plants harvested at 45 days after transplanting (DAT) can be predicted as early as 3 weeks earlier using the midrib length of the largest leaf or plant height as a predictor measured at 26 DAT. HIGHLIGHTS Depth of water-substrate interface (WSI) should be maintained between 1 to 3 cm for better growth and higher yield in floating culture system Effects of NPK fertilizer application diminished if WSI deeper than 3 cm Yield of celery harvested at 45 days after transplanting can be predicted as earlier as 3 weeks using midrib length of the largest leaf or plant height as predictor GRAPHICAL ABSTRACT

Using Amorphous CoB Alloy as Transducer to Detect Acoustic Propagation and Heat Transport at Interface

Acoustic oscillation provides useful information regarding the interfacial coupling between metal transducer layers and substrate materials. The interfacial coupling can be significantly reduced by a mechanically soft layer between the transducer and substrate. However, preserving a thin, soft layer at the interface during fabrication is often challenging. In this study, we demonstrate that an amorphous CoB alloy on top of a sapphire substrate can substantially amplify acoustic oscillations. By analyzing the attenuation of acoustic oscillations, we show that a thin, soft layer with a thickness of >2 ± 1 Å exists at the interface. The intermediate layer at the interface is further verified by investigating heat transport. By analyzing the slow decrease of the temperature of the transducer layer, we determine a thermal conductance of 35 ± 5 MW m−2 K−1 at the transducer/substrate interface. This low value supports the existence of a thin, soft layer at the interface. Our results demonstrate that an amorphous metal with B alloying effectively preserves the soft nature at the interface and detects the acoustic propagation and heat transport across it.