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Six flow modes are distinguished in the flow-focusing experiments of a liquid jet forced by a high-speed air stream. The domains of the modes are identified on the parameter space of the liquid flow rateQland the gas pressure drop Δpg. The disturbance wavelength λ and breakup lengthLof the jet are also measured. A theoretical model considering axisymmetric disturbances is proposed, and a basic velocity profile of hyperbolic-tangent function is utilized. The linear temporal and spatio-temporal instability analyses are carried out using the Chebyshev collocation method. The effects of the flow parameters and the velocity profile on the flow instability are discussed. The temporal instability analysis demonstrates that the interfacial shear causes the instability of short waves and retards the instability of long waves. Moreover, the spatio-temporal instability analysis gives the transition boundary between the absolute and convective instability (AI/CI). The most unstable wavelength predicted by the temporal instability analysis and the AI/CI boundary predicted by the spatio-temporal instability analysis are in good agreement with the experimental results.

Semiconductor heterostructures composed of 2D transition metal dichalcogenides (TMDCs) are of considerable interest for fundamental studies and potential applications in atomically thin electronic and optoelectronic devices. [1][2][3][4][5][6][7][8][9] The studies to date have been largely limited to mechanical exfoliation and restacking approach, [10][11][12][13][14][15] with limited yield and scalability for practical device development. To move the field to the next level and enable scalable device integration, much effort has been devoted to developing robust synthetic strategies for scalable synthesis of 2D heterostructures with tailored configuration. In particular, considerable success has been achieved in the synthesis of complex 2D lateral heterostructures and superlattices. [16][17][18][19][20] On the other hand, although a number of TMDCs vertical heterostructures have been reported, [21][22][23][24][25][26][27][28][29][30] the general synthesis of high-quality vertical heterostructures remains a significant challenge due to the difficulties in initiating and controlling nucleation of a new atomic layer on the dangling bond free basal plane of 2D TMDCs. The current synthetic approach generally relies on incidental nucleation or the high-temperature-induced defects in the basal plane, which is difficult to control, only applicable to specific material combinations, and usually produces heterostructures with rich defects, interlayer diffusion/alloying, and a poor control of layer thickness and heterostructure interface, due to the unavoidable atomic substitution [30][31][32][33] and thermal decomposition of the existing TMDCs templates. [10] To our knowledge, the rational growth mechanism and universal growth strategy have never been proposed to be widely applied in the family of 2D TMDCs heterostructures.With density functional theory (DFT) calculations, we provide an in-depth understanding toward the growth mechanism of TMDCs vertical heterostructures in the aspect of nucleation and kinetics. It reveals that active clusters with high diffusion barrier will induce the nucleation on top of TMDC templates to realize vertical heterostructure. In our experiment, through rational control of the metal/chalcogenide ratio in vapor precursors, we realize the effective manipulation of the diffusion The rational control of the nucleation and growth kinetics to enable the growth of 2D vertical heterostructure remains a great challenge. Here, an in-depth study is provided toward understanding the growth mechanism of transition metal dichalcogenides (TMDCs) vertical heterostructures in terms of the nucleation and kinetics, where active clusters with a high diffusion barrier will induce the nucleation on top of the TMDC templates to realize vertical heterostructures. Based on this mechanism, in the experiment, through rational control of the metal/chalcogenide ratio in the vapor precursors, effective manipulation of the diffusion barrier of the active clusters and precise control of the heteroepitaxy direction are rea...

Transparent Ag and Eu(3+) co-doped oxyfluoride glasses with composition 50SiO(2)-20Al(2)O(3)-30CaF(2) were prepared by melt-quenching technique. The structural and luminescent properties of glasses, energy transfer mechanism between luminescent centers were systematically investigated. The missing nanoparticles signals in absorption spectra, XRD patterns and TEM images, the additional broad excitation band at 325-375 nm indicate that the broad emission band at 400-700 nm is originated from very small molecule-like, non-plasmonic Ag particles (ML-Ag-particles). A perfect white light emission was realized by combining intense red emission of Eu(3+) with broad band emission of ML-Ag-particles. These results suggest that Ag and Eu(3+) co-doped oxyfluoride glasses could be potentially applied as white light-emitting phosphors for ultra-violet LED chips.

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