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3 results on '"Hehe Dong"'

1. Nanocrystalline Yb:YAG-Doped Silica Glass with Good Transmittance and Significant Spectral Performance Enhancements

Author

Hehe Dong, Yinggang Chen, Yan Jiao, Qinling Zhou, Yue Cheng, Hui Zhang, Yujie Lu, Shikai Wang, Chunlei Yu, and Lili Hu

Subjects
Yb:YAG nanocrystals, silica glass, microstructure, spectral properties, Chemistry, QD1-999
Abstract

In this study, Yb:YAG-nanocrystal-doped silica glass with high transmission and excellent spectral properties was successfully prepared using a modified sol–gel method. The X-ray diffraction (XRD), micro-Raman spectroscopy, electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), and high-resolution TEM (HR-TEM) analyses confirmed that the Yb:YAG nanocrystals, with their low content, homogeneous distribution, and small crystal size, directly crystallized into the silica glass network without annealing treatment. In contrast with conventional microcrystalline glass having large particles (>0.1 μm) and a large particle content, nanocrystalline glass with a homogeneous distribution and sizes of ~22 nm had higher optical transmittance and better spectral properties. Compared with Yb3+ doped silica glass without nanocrystals, the Yb:YAG-nanocrystal-doped silica glass had a 28% increase in absorption cross-section at 975 nm and a 172% enhanced emission cross-section at 1030 nm without any changes in the spectral pattern of the Yb3+ ions in the silica glass. Meanwhile, the Yb:YAG-doped silica glass with large size and high optical quality was easily prepared. Therefore, the Yb:YAG-nanocrystal-doped silica glass is expected to be a promising near-infrared laser material.

Published
2022
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2. Effect of modified hydrotalcites on flame retardancy and physical properties of paper

Author

Hehe Dong, Zongjia Song, Xuxu Yang, Cui Luqing, Songlin Wang, and Fei Wang

Subjects
Thermogravimetric analysis, Environmental Engineering, Materials science, Hydrotalcite, Layered double hydroxides, Bioengineering, engineering.material, Titanate, Limiting oxygen index, chemistry.chemical_compound, chemistry, Chemical engineering, engineering, Thermal stability, Itaconic acid, Waste Management and Disposal, Fire retardant
Abstract

Functionalized layered double hydroxides (LDHs) based on a multi-modifier system composed of itaconic acid (ITA) and titanate coupling agent (NDZ-201) were designed and fabricated in this paper with the aim to develop high-performance fire retardant paper. The structure of LDHs were characterized using Fourier transform infrared spectroscopic analysis, X-ray diffraction analysis, thermogravimetric analysis (TGA), scanning electron microscopic analysis, cone calorimetry, and laser particle size analysis. The results showed that carbonate anions were partially replaced by ITA, whereas the titanate coupling agent was attached to the surfaces of the hydrotalcites. The limiting oxygen index (LOI), TGA curves, total heat release rate (THR), and heat release rate (HRR) indicated that as the addition of hydrotalcites increased, the modified LDHs’ LOI value and thermal stability noticeably increased compared to the unmodified hydrotalcites, and the HRR and THR of the material decreased. When the addition amount was 25%, the LOI of ITA-LDHs was 26.9%. However, the Mg-Al hydrotalcites adversely affected the strength index of flame-retardant paper; the modified hydrotalcites clearly reduced this effect, and the whiteness of paper increased and reached 83%.

Published
2019

3. Preparation and characterization of chitosan membranes

Author

Shitao Yu, Huang Lianqing, Song Xiaoming, Shanshan Gao, Liu Jinling, Hehe Dong, Chen Fushan, and Cui Luqing

Subjects
Materials science, General Chemical Engineering, macromolecular substances, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Chitosan, chemistry.chemical_compound, Ultimate tensile strength, medicine, Dissolution, Aqueous solution, technology, industry, and agriculture, Plasticizer, General Chemistry, equipment and supplies, 021001 nanoscience & nanotechnology, Casting, 0104 chemical sciences, carbohydrates (lipids), chemistry, Chemical engineering, Tartaric acid, Swelling, medicine.symptom, 0210 nano-technology
Abstract

The present study investigates a new solvent system for the dissolution of chitosan and a new method for preparing chitosan membranes. First, aqueous tartaric acid was used to pretreat chitosan. Then, the chitosan was precipitated with ethanol or other regenerating agents, and 1.5 mL of 1-ethyl-3-methylimidazolium acetate ([EMIM]AC) was added to obtain translucent suspensions. The chitosan membranes were prepared by casting the suspensions on glass plates and allowing solvent evaporation. The structure and properties of the films were investigated by SEM, FT-IR, XRD and TGA. Also, the mechanical properties, as well as physical and chemical characteristics, of the chitosan films were evaluated. The results indicated that the optimum dissolution time was 10 min and the most suitable drying temperature was 60 °C. The thus-prepared film was moderately thick (about 0.02 mm) and had a smooth surface, without curling. The chitosan film prepared by ethanol regeneration had a tensile strength of up to 24 MPa, a minimum swelling degree of 78%, and a water vapor transmission rate of 270 g m−2 d−1 without the addition of plasticizer.

Published
2018

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