JOURNAL OF LUMINESCENCE
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2019
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IF 2.961
Leipeng Li,Feng Qin,Lu Li,Hong Gao,Qin Deng,Zhiguo Zhang
Here a strategy was proposed to realize the thermal enhancement of the green luminescence of Tb 3+ ion through ground state thermal population. The 5 D 4 - 7 F 5 emission line of Tb 3+ ion was observed under the excitation of a commonly used 405 nm laser diode for the first time, to the best of our knowledge. Its intensity was found to increase by ten times upon increasing the temperature from 343 to 783 K. Moreover, this change law was in good accordance with the Boltzmann distribution . It was confirmed that the thermal population of the 7 F 5 state at the expense of the depopulation of the 7 F 6 ground state, namely the ground state thermal equilibrium, should be responsible for this uncommon phenomenon. For comparison, the Xe lamp was also used to directly excite the 7 F 6 - 5 D 3 absorption line of Tb 3+ ion. In this case, the 5 D 4 - 7 F 5 emission line of Tb 3+ ion was also observed. Different from the former case, this line decreased monotonously upon increasing the temperature over the experimental range. The reason for this change law was also discussed.
研究领域:
材料科学
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光学
✓ 已验证
产品关联
DOI
高影响因子
ACS Photonics
·
2021
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IF 7.529
Zhen Fang,Liyun Ding,Lintao Li,Kun Shuai,Boyu Cao,Yetao Zhong,Zhenghua Meng,Zhilin Xia
Thermal homeostasis can maintain body temperature of warm-blooded organisms in a narrow range to avoid hypothermia, ensuring the normal operation of life activities. Thermal homeostasis can make the internal temperature of target relatively insensitive to temperature changes of surrounding environment, which is of great significance to the efficient operation of equipment and the service life of material. The current systems that maintain thermal homeostasis need to consume electricity, which is very detrimental to energy consumption and global warming. Here, we propose a novel thermal homeostasis program by means of tunable sunlight-scattering behaviors of thermochromic hydrogel, without external energy input such as electrical energy and mechanical energy. A sandwich structure thermal homeostasiser (SSTH) generated by the thermal homeostasis program consists of three parts: the radiative cooling part at the top, the thermochromic part in the middle and the solar heating part at the bottom. The feasibility of thermal homeostasis based on SSTH has been verified theoretically and experimentally. With the ambient air temperature difference of more than 6 °C, SSTH can maintain its own temperature difference within 1.2 °C. The SSTH is a simple-feasible paradigm for achieving thermal homeostasis. This new thermal homeostasis method we proposed can fill the vacancy of the current thermal homeostasis control means and show great potential as a complementary mean of the existing building environment control system to go a step further toward zero-energy building.
研究领域:
材料科学
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能源科学
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环境科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF PHYSICAL CHEMISTRY B
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2024
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IF 2.8
Xingyu Wen,Wenshuai Bai,Dayu Zhang
The sulfuric–acid-catalyzed esterification reaction of 2-butanol and propionic anhydride is a vital industrial process. In this paper, several experiments are conducted via reaction calorimetry to validate that both sulfuric and propionic acids have discernible catalytic effects on the reaction. This finding complicates the accurate description of the reaction kinetics through traditional methods. So this paper turns to a kinetic-free black-box model, Gaussian process regression (GPR) model via 24 experiments, as a more adaptable approach. Besides, the best GPR model is combined with traditional heat balance model to generate a hybrid gray-box model, which can give complete knowledge of reaction process. The hybrid gray-box model finally achieves maximum root-mean-square error (RMSE) of 0.0069 for conversion, 0.6535 for temperature, and 10.6087 for heat flow rate, underscoring its pretty good predictive ability.
研究领域:
化学工程
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机器学习
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反应动力学建模
✓ 已验证
产品关联
DOI
PubMed
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2022
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IF 4.326
Yunhe Bai,Zhenxing Zhu,Qiuxiang Yin,Chuang Xie
Sweating is an important purification process involved in the layer melt crystallization technique. Modeling of the sweating process remains difficult due to the complicated association of mass balance, heat balance, and fluid flow through a dynamic crystal layer. A model of sweating was proposed in this work, attempting to give a facile prediction of the dynamic sweat mass and concentration based on the initial crystal layer structure other than empirical correlations. Heat balance equations were taken as the governing equations to calculate the crystal layer temperature and residual melt concentration. A curved capillary bundle model that obeys fractal distribution was adapted to describe the dynamic porous crystal layer. By combining mass balance, the nonlinear variation of melted mass with sweating time was estimated. Subsequently, para-xylene was used as the model material to validate the sweating model. A quasiequilibrium between solid and liquid was found at a slow sweating rate range in this work, which verified the model assumption and greatly simplify the calculation. It revealed that the melting amount of the crystal layer and the imbibition melt increased nonlinearly with the increase of temperature. The curved capillary bundle model was found to be able to give an accurate estimation of sweat mass according to the experimental data. The model has accurate predictions on the S-shaped curve of sweat mass and sweat concentration compared to the experimental sweating results.
研究领域:
化学工程
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材料科学
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热力学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING SCIENCE
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2022
·
IF 4.889
Li Chen,Jinyi Chen,Zhu Sun,Baiheng Wu,Fangfu Ye,Chun-Xia Zhao,Dong Chen
Nanoprecipitation is a flexible method to prepare biocompatible nanoparticles (NPs) for drug delivery and so on. However, it is generally hard to co-precipitate multiple polymers due to their different solvent solubility. Here, shellac/PLA/PS trimer NPs are prepared for the first time via one-step co-precipitation upon rapid solvent exchange and controlled phase separation. The morphology of shellac/PLA/PS NPs strongly depends on the interfacial tensions between different phases and could be tuned by the molecular surfactant added in the continuous aqueous phase. Since co-precipitation is a fast process, a high temperature is preferred for the system to reach the thermal equilibrium state; otherwise, the system may kinetically be locked in an intermediate state. The influences of polymer molecular weight and interfacial tension are also investigated in detail to reveal the underlying mechanisms of preparing shellac/PLA/PS trimer NPs with linear or triangular structures. This study will shield new light on the design and preparation of NPs with more diverse compositions and more complex structures via one-step co-precipitation and controlled phase separation and further expand the potential applications of NPs.
研究领域:
材料科学
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纳米技术
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药学
✓ 已验证
DOI
高影响因子
DRYING TECHNOLOGY
·
2023
·
IF 3.3
Wei Wang,Shuo Zhang,Yanqiu Pan,Yijia Ji,Xin Li,Guohua Chen,Xuewu Liu
A multiphase transport model was formulated to explore the adaptability of local thermal and mass equilibrium/non-equilibrium (LTE/LTNE and LME/LMNE) assumptions in simulating freeze-drying of porous media. Saturated and unsaturated samples with the same initial mass and moisture content but different initial saturations were used in freeze-drying experiments and numerical simulations. Four pairwise combinations between LTE/LTNE and LME/LMNE were tested using the commercial software of COMSOL Multiphysics based on the finite element method. Results showed that the LTE-LMNE assumption achieved excellent agreements between numerical and experimental drying curves with RMSEs being 1.81% for the saturated sample and all less than 1.00% for the unsaturated samples. Based on distributions of saturation and temperature, and variations of effective mass diffusivity and thermal conductivity, the rate-controlling factor was determined to be mass transfer for the saturated material and heat transfer for the unsaturated one. Convective heat transfer played an unimportant role in freeze-drying. The LTE-LMNE based model provided satisfactory predictive capabilities under different conditions. Appropriately increasing the operating temperature could boost the drying rate. Changing the chamber pressure had insignificant effects with drying time differences only below 3%. The smaller the initial saturation, the shorter the drying time. The initially unsaturated frozen material with preformed pores significantly enhanced the freeze-drying process and improved the process economy.
研究领域:
化学工程
·
热能工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）