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1,469 results on '"ZHANG, Xian-ming"'

27. The normal force evolution of the substrate during the withdrawal process

Author

Zhang, Heng-Kuan, Yin, Ya-Ran, Pan, Xu-Qi, Zhang, Xian-Ming, Chen, Wen-Xing, and Hu, Guo-Hua

Subjects
Coating processes -- Methods, Viscosity -- Analysis, Engineering and manufacturing industries, Science and technology
Abstract

The evolution of normal force on the smooth plate immersed in Newtonian and yield stress fluids was investigated during the dip coating. The influences of withdrawal velocity, liquid rheological property, and plate roughness were elaborated. For all fluids, the variation of force versus the withdrawing height was divided into four stages. Importantly, the control forces for coating in each stage were determined, which are in turn viscous force-capillary, viscous force-gravity, capillary-viscous force, and gravity. The critical value of normal force controlled from capillary to viscous effect during drainage was adopted to calculate the surface tension. The possibility of measuring the surface tension was verified under the negligible interference of viscous effect and film instability through a detailed analysis on the evolution of force in a series of tests. Accordingly, the applicable conditions with the low withdrawal speed, high viscosity, and rough surface were finally achieved. This work can provide a theoretical basis for the film-formation mechanism and surface tension measurement in dip coating. KEYWORDS coatings, shear, tension, viscosity, yielding, 1 | INTRODUCTION Coating a layer of thin film on a solid surface is commonly encountered in industrial production and application, such as environmental protection, medicine, spinning, material protection, magnetization, [...]

Published
2022
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39. Promoting structural distortion to enhance the crystal field strength of Mn(II) in tetrahedral bromide for near-unity yellow emission.

Author

Qi, Zhikai, Zhang, Ke, Zhao, Xingxing, Zhang, Nan, Li, Shi-Li, and Zhang, Xian-Ming

Subjects
BOND angles, REDSHIFT, MANGANESE, BROMIDES, CRYSTALS
Abstract

Two zero-dimensional hybrid manganese bromide polymorphs ((DMAPH)2MnBr4) exhibit single-crystal to single-crystal phase transformation, accompanied by an increase in MnBr4 tetrahedral bond angle variance (σ2). This structural change leads to an emission redshift due to enhanced crystal field strength, achieving yellow emission with near-unity quantum yield, which highlights its potential for solid-state lighting applications. [ABSTRACT FROM AUTHOR]

Published
2024
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42. X‐ray‐ultraviolet–visible‐near‐infrared photoresponses realized in a lead‐free hybrid perovskite ferroelectric through light‐induced ferro‐pyro‐phototronic effect.

Author

Fu, Dongying, Ma, Yanli, Wu, Shufang, Pan, Lin, Wang, Qi, Zhao, Ruifang, Zhang, Xian‐Ming, and Luo, Junhua

Subjects
BAND gaps, FERROELECTRIC crystals, SINGLE crystals, LIGHT absorption, DETECTION limit
Abstract

Due to the built‐in electric field induced by spontaneous polarization in hybrid perovskite (HP) ferroelectrics, the devices based on them exhibit excellent performance in self‐powered photodetection. However, most of the self‐powered photodetector are made of lead‐based HP ferroelectrics and have a relatively narrow photoresponse waveband. Although lead‐free HPs solve the problem of lead toxicity, their optoelectronic performance is inferior to that of lead‐based HPs and photoresponse waveband is limited by its optical band gap, which hinders their further application. To solve this problem, herein, a lead‐free HP ferroelectric (HDA)BiI5 (HDA is hexane‐1,6‐diammonium) with large spontaneous polarization shows an enhanced photocurrent and achieves x‐ray‐ultraviolet–visible‐near‐infrared (x‐ray‐UV–Vis–NIR) photoresponse through the ferro‐pyro‐phototronic (FPP) effect. The ferroelectric, pyroelectric, and photovoltaic characteristics coupled together in a single‐phase (HDA)BiI5 ferroelectric is an effective way to improve the performance of the devices. What is particularly attractive is that the FPP effect not only improves the optoelectronic performance of (HDA)BiI5, but also achieves broadband photoresponses beyond its optical absorption range. Especially, the current boosting with an exceptional contrast of ~1100% and 2400% under 520 and 637 nm, respectively, which is associated with FPP effect. Meanwhile, single crystal self‐powered photodetector based on (HDA)BiI5 also exhibit significant FPP effects even under high‐energy x‐ray, which owns an outstanding sensitivity of 170.7 μC Gy−1 cm−2 and a lower detection limit of 266 nGy s−1 at 0 V bias. Therefore, it is of great significance to study the coupling of multiple physical effects and improve device performance based on lead‐free HP ferroelectrics. [ABSTRACT FROM AUTHOR]

Published
2024
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