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Amechanism of local formation of crystals of random orientation in growth of single-crystal billets of refractory nickel alloys for blades of gas turbine engines is suggested. Aturn of the lattice is initiated at the place of contact between the initial melt and the surface of hard particles of NbC carbide and/or TiN nitride. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the influence of grain orientation on electrochemical behavior and semiconductor properties, such as donor density, flat-band potential, and diffusivity of point defects (D 0 ), of the passive films were studied on Nb single crystals with orientations of (100), (110), and (111) in phosphate buffered saline (PBS) and 1M NaOH solution by cyclic voltammetry, electrochemical impedance spectroscopy, Mott-Schottky analysis, and point defect model. The results shown that the (100) crystal face of Nb exhibits the lowest corrosion rate in both PBS and 1M NaOH solutions. The Mott-Schottky analysis revealed that the passive film formed on the (100) face has the lowest donor density and the flat-band potential was almost independent of the grain orientations, but decreased with an increase of pH. A different relationship between steady-state current density (j ss ) and film formation potential was observed in these two solutions and the possible causes were discussed. The diffusivity was calculated based on the point defect model. D 0 , of the passive films in PBS solution is in the range of 10–21 to 10–19cm2/s, depends on the grain orientation and film formation potential. In 1M NaOH solution, D 0 is close to 10–18cm2/s independent of the film formation potential. [Copyright &y& Elsevier]

Fabrication of high‐quality organic single‐crystalline semiconductors and their deterministic patterning are core opportunities as well as challenges for large‐scale integration of functional devices with high efficiency and boosted performance. Previous approaches on solution patterning of organic semiconductors have achieved efficient and versatile control of the position, alignment, and size of organic structures. However, the poorly controllable dewetting dynamics of organic solution gives rise to low crystallinity and disordered crystallographic orientation of generated organic architectures that limit their device performance. Here, 1D organic single‐crystal arrays with high crystallinity, strict crystallographic alignment, precise position, tunable, and homogeneous size are fabricated by exploiting an asymmetric‐wettability topographical template. Periodically arranged micropillars with lyophobic sidewalls and lyophilic tops permit the generation of capillary bridges, which enable unidirectional dewetting of organic solution and ordered packing of molecules. The 1D arrays present pure (100) crystallographic orientation with π–π stacking of molecules in the optimal direction of carrier transport, leading to high carrier mobility of 8.7 cm2 V−1 s−1 in the field‐effect transistor measurements. A facile pressure sensor based on the patterned belt arrays is fabricated, exhibiting high sensitivity and long‐term stability. Organic single crystals with high alignment and pure crystallographic orientation are patterned by exploiting an asymmetric‐wettability topographical template. The high carrier mobility reaches 8.7 cm2 V−1 s−1 in field‐effect transistor measurements. Pressure sensors based on it exhibit high sensitivity and durability. [ABSTRACT FROM AUTHOR]