Pang Yan,Li Lin,Ru Jiahe,Zhou Qiang,Wang Xiang,Liu Zhaomiao
The application performance of droplets, including the size and core-shell volumetric ratio of a double emulsion droplet, is investigated under various geometric sizes and flow rates in a flow-focusing capillary device. This study uses three-dimensional (3D) printing to create a novel substrate to assemble capillaries and make the inner dimension of the device tunable. Droplet generation is separated into two regions (uniform or non-uniform) based on the interface coupling shapes, where different generation modes are classified based on the rupture form of the multilayer interfaces. A map of the generation modes is established based on geometric size and flow conditions. In the dripping mode, interface coupling and its effect on generation are analyzed by the interface necking process for the two generation sub-modes (with/without a ball). The local capillary number of the double emulsion droplet is established for these sub-modes to analyze variations in the inner droplet volume, which helps propose the volume predictive model of inner and outer droplets.
E Cheng,Yeming Zhu,Qibo Deng,Zhengyan Zhang,Xintao Tian
The electrode is an important part of a micro-ultrasonic phased array, commonly fabricated by magnetron sputtering technology. However, with the expansion of the application field, the structures of the phased arrays are becoming more complex, making the traditional magnetron sputtering method no longer applicable, and the realization of micro-scale phased array electrodes by direct printing technology still faces great challenges. Herein, an electric field-driven direct printing method was proposed to fabricate micro-ultrasonic phased array electrodes. The influence of sintering parameters on the resistivity and the effect of printing parameters on the geometric size and surface morphology of the electrode were comprehensively explored, and the mathematical model between the electrode line width and the printing parameters was established. The final printed electrodes exhibit superior properties with a resistivity of 2.4 × 10−7\Omega\cdot m, a surface roughness range of 460–550 nm, and a line width range of 125–480 µm. Additionally, a micro-scale electrode was printed on the piezoelectric ceramic with PZT-5 as the material, and after polarization treatment, the piezoelectric coefficient can reach 405 pC N−1, which proves that this method can be applied in the field of fabricating phased array electrodes.
Xiaolu Zhuo,Xingzhong Zhu,Qian Li,Zhi Yang,Jianfang Wang
We report on a method for the preparation of uniform and length-variable Ag nanorods through anisotropic Ag overgrowth on high-purity Au nanobipyramids. The rod diameters can be roughly tailored from ∼20 nm to ∼50 nm by judicious selection of differently sized Au nanobipyramids. The rod lengths can be tuned from ∼150 nm to ∼550 nm by varying the Ag precursor amount during the overgrowth process and/or by anisotropic shortening through mild oxidation. The controllable aspect ratios, high purity, and high dimensional uniformity of these Ag nanorods enable the observation of Fabry–Pérot-like multipolar plasmon resonance modes in the colloidal suspensions at the ensemble level, which has so far been demonstrated only on Au nanorods prepared electrochemically with anodic aluminum oxide templates. Depending on the mode order and geometry of the Ag nanorods, the multipolar plasmon wavelengths can be readily tailored over a wide spectral range from the visible to near-infrared region. We have further elucidated the relationships between the multipolar plasmon wavelengths and the geometric dimensions of the Ag nanorods at both the ensemble and single-particle levels. Our results indicate that the Au nanobipyramid-directed, dimensionally controllable Ag nanorods will be an attractive and promising candidate for developing multipolar plasmon-based devices and applications.
Jian Peng,Da-Wei Wang,Zheng-You Cheng,Ming-Feng Yang,Jiang-Tao Liu,Ming Wang
In this study, the microwave absorption performance of carbonyl iron powder (CIP) was enhanced by tuning the geometric dimensions and electromagnetic-dielectric synergism. The ball-shaped CIP was firstly milled into different flattened CIP (FCIP) via a ball milling process with different milling time. The electromagnetic-dielectric synergism of CIP can be regulated by surface coating with silicon dioxide (SiO 2 ) and mixing with multi-walled carbon nanotubes (MWCNT). The minimum reflection loss (RL min ) and effective absorption bandwidth (EAB) values has been greatly improved. Specifically, the maximum EAB and RL min of the FCIP with thick SiO 2 nanoparticle layer are 7.9 GHz at a thickness of 1.9 mm and −40.6 dB at a thickness of 1.7 mm, respectively. For the SiO 2 @FCIP + MWCNT samples, the effective absorption frequency range covers from 3.0 to 18.0 GHz via changing the sample thickness from 1.5 to 5.0 mm. Therefore, this study provide effective strategies to regulate microwave absorption performance of CIP.
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