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162 results on '"Ren, Haishen"'

21. Effect of binary ion substitution on the crystal structure and microwave dielectric properties of MgTa2O6 ceramics.

Author

Gao, Yang, Chen, Junjie, Fang, Weishuang, Peng, Haiyi, Xie, Tianyi, Ren, Haishen, Yao, Xiaogang, and Lin, Huixing

Subjects
PERMITTIVITY, COMPLEX ions, LARGE deviations (Mathematics), DIELECTRIC properties, CRYSTAL structure, CERAMICS, MICROWAVES
Abstract

Mg1/3A11/3A21/3Ta2O6 ceramics (where A1 and A2 represent Co, Ni, or Zn) were prepared using the solid‐phase reaction route. The results of X‐ray diffraction and Raman tests showed that (Co1/2Ni1/2)2+, (Co1/ 2Zn1/2)2+, and (Ni1/2Zn1/2)2+ ions replaced Mg2+ ions in the lattice of MgTa2O6, resulting in the formation of a pure tri‐rutile structure. All three complex ions could significantly reduce the sintering temperature of the ceramics (by 150°C–200°C) and could broaden the sintering window. The large deviation (48.8%–69.2%) between the porosity corrected relative permittivity εr‐corr. and the theoretical relative permittivity εr‐theo. might be due to the overestimation of the ionic polarizability of Ta5+ by Shannon. (Co1/2Ni1/2)2+ has the most significant effect of increasing the bond energy of ceramic A–O bonds, reducing the τf value from 51 to 36 ppm/°C. In addition, the mechanisms affecting their dielectric properties are discussed based on bond ionicity (fi), full width at half maximum (FWHM) of Raman peak, and bond energy (E). Mg1/3Co1/3Ni1/3Ta2O6 ceramic sintered at 1350°C have the most excellent microwave dielectric properties: εr = 26.8, Q × f = 86,000 GHz, and τf = 36 ppm/°C. [ABSTRACT FROM AUTHOR]

Published
2025
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22. Enhancement of 4T2 → 4A2 with temperature via energy transfer of the optical thermometer Mg5Al7O16:Cr3+.

Author

Wei, Yang, Jin, Ye, Chen, Yifei, Hu, Weixin, Wang, Chongzhou, Zhang, Zhihui, Meng, Fancheng, Huang, Fuxiang, Ma, Li, Wang, Xiao-jun, and Ren, Haishen

Abstract

The luminescence properties and temperature sensing performances of Mg5Al7O16:Cr3+ are systematically studied in this paper, synthesized using the solid-state sintering method. Based on X-ray diffraction and first-principles calculations, Cr3+ is verified to occupy the octahedral Mg2+ and Al3+ sites in the host Mg5Al7O16. From the Tanable–Sugano diagram, Cr3+ is in a strong crystal environment to induce sharp line emissions of Cr3+ around 700 nm. As the temperature rises, the excitation and emission ranging from 303 to 543 K are recorded, and overlapping of emissions from 2E → 4A2 and 4T2 → 4A2 is observed. The emissions in the 303–543 K range are separated using deconvolution. The emission from 2E → 4A2 decreases with increasing temperature, which is a normal thermal quenching behavior. However, the emission from 4T2 → 4A2 increases with temperature until 523 K. Energy transfer through phonon assistance from 2E to 4T2 is verified using temperature-dependent excitation and decay curves. It is used for the temperature-reading method based on the luminescence intensity ratio (LIR). The highest relative sensitivity is 1.80% K−1 at 303 K and is retained at above 1.00% K−1 in the 303–403 K range. [ABSTRACT FROM AUTHOR]

Published
2024
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23. Low thermal stress and excellent gas tightness in BaO‒CaO‒Al2O3‒B2O3‒SiO2 glass‐ceramic for long‐term ITSOFC application.

Author

Ren, Haishen, Ge, Wenjie, Chen, Le, Peng, Haiyi, Meng, Fancheng, Lin, Huixing, and Jin, Ye

Subjects
*SOLID oxide fuel cells, *ELASTIC modulus, *THERMAL batteries, *DISPERSION strengthening, *THERMOCYCLING
Abstract

The increased coefficient of thermal expansion (CTE) mismatch and mechanical performance degradation of glass‐based sealant‐induced thermal stress are critical issues for long‐term application of solid oxide fuel cell (SOFC). In this work, the double effect of MgO particle on dispersion strengthening, inhibition low‐CTE phase transformation, thermal stress, and leakage rate in BaO‒CaO‒Al2O3‒B2O3‒SiO2 (BCABS) glass‐ceramic were investigated and analyzed. The low‐CTE mono‐BaAl2Si2O8 phase was suppressed by the MgO particle reacting with BCABS glass‐ceramic. Consequently, the CTE for BCABS glass‐ceramic without MgO decreases from 11.47 at 1 h to 10.18 ×10−6/°C at 1000 h and reduction rate is higher than 10%, bring about the thermal stress of sealant itself and interface had tripled (200 MPa) and leakage rate was high than 0.06 sccm/cm after 250 h. However, the CTE of 20 wt% MgO‐reinforced BCABS glass‐ceramic sealant only declined about 4.0% for 1000 h, resulting in slow increase or even decrease in the thermal stress (low than 60 MPa) and maintaining stable leakage rate below 0.04 sccm/cm for 1000 h with three thermal cycles. This study was useful for identifying optimal CTE matching and elastic modulus of glass‐based sealant for efficient and stable long‐term operation of SOFC. [ABSTRACT FROM AUTHOR]

Published
2025
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