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39 results on '"Luo, Yinfu"'

20. Lightweight, Robust, and Multifunctional Polyimide-Based Carbon Foams for Electromagnetic Interference Shielding and Thermal Insulation

Author

Wang, Fenglin, Zhou, Cuiqing, Ni, Long, Meng, Haichao, Zou, Huawei, Liang, Mei, Luo, Yinfu, and Zhou, Shengtai

Abstract

Polyimide (PI)-based carbon foams (CFs) with excellent compressive strength, thermal insulation, and electromagnetic interference (EMI) shielding properties were fabricated through microsphere foaming and carbonization processes. The cell size of CFs ranged from 207.8 to 563.9 μm and could be regulated by adjusting the size of polyester ammonium salts (PEASs), and the chemical structure depended on the carbonization temperature. The compressive strength of C1100-PIF-1 was 0.74 MPa with a density of 119.9 kg·m–3. The thermal conductivities of C800-PIF-1 at room temperature, 500, and 1000 °C were 0.126, 0.202, and 0.252 W·m–1K–1, respectively. Furthermore, CFs exhibited excellent EMI shielding properties, with C1100-PIF-2 and C1100-PIF-3 reaching 56.4 and 42.1 dB at 8.2–12.4 GHz. The electrical conductivity fell in the range of 5.5–38.5 S·m–1. The CFs fabricated in this work, which combined exceptional mechanical strength, thermal insulation, and EMI shielding properties, had potential applications in aerospace, high-temperature insulation, and chemical catalysis.

Published
2024
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25. Lightweight polyimide-derived carbon foams with anisotropic porous structures prepared by microwave-assisted foaming and carbonization for thermal insulation and EMI shielding applications.

Author

Ni, Long, Kang, Zhenling, Luo, Yinfu, Yan, Liwei, Lu, Junyu, Wang, Guanchun, Qiu, Shaoyu, Liang, Mei, Zhou, Shengtai, and Zou, Huawei

Abstract

Lightweight and anisotropic porous carbon materials have promising applications in thermal insulation and electromagnetic interference (EMI) shielding fields. Herein, lightweight polyimide foams (PIFs) with anisotropic pore structures were prepared by adopting a microwave-assisted foaming method and the obtained PIFs were employed as derivatives to fabricate carbon foams, i.e., PICFs. The PICFs with aligned ellipsoidal strip-like pore structures presented low volumetric shrinkage (44.87–50.24%) and weight loss (36.33–48.17%), along with favorable compressive strength (102.96 kPa), and high temperature thermal resistance. In addition, the anisotropic pore structure imparted efficient thermal insulation and infrared thermal stealth properties to PICFs, with thermal conductivity as low as 0.0356 W (m K)−1 along the horizontal direction (perpendicular to the pore growth direction). When carbonized at 1400 °C, PICF1400 with a low density (22.9 kg m−3) and thin thickness (1.9 mm) exhibited a high electrical conductivity of 23.91 S m−1 in the horizontal direction. The EMI shielding effectiveness (SE) and specific EMI SE reached as high as 53.2 dB and 12216 dB (g cm−2), respectively. Moreover, PICF800 exhibited a high absorption coefficient of 0.91. Therefore, a facile strategy was proposed for fabricating lightweight PICFs which possess multifunctional properties enabling potential applications in high-end engineering sectors. [ABSTRACT FROM AUTHOR]

Published
2023
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36. Preparation and mechanism study of intrinsic hard segment flame‐retardant polyurethane foam.

Author

Luo, Yinfu, Miao, Zongnan, Sun, Tong, Zou, Huawei, Liang, Mei, Zhou, Shengtai, and Chen, Yang

Subjects
HEAT release rates, ENTHALPY, URETHANE foam, CONDENSED matter, CARBONIZATION, COMPRESSIVE strength
Abstract

The hard segment of polyurethane foam (PUF) plays a special role in degradation and carbonization. In this work, flame‐retardant hard segment (HSFR) used to promote fire resistance was synthesized successfully. The limiting oxygen index (LOI), vertical combustion, and micro‐combustion calorimetry tests indicated the flame retardancy of the foam was elevated by introducing HSFR. When HSFR with an addition of 60 phr, the LOI value was increased from 17.0 to 25.5%, UL‐94 reached V‐0 rating, the peak heat release rate (p‐HRR) and total heat release (THR) decreased by 63.9% and 10.0%, respectively. In addition, the compressive strength of HSFR‐60 increased by five times. Further, the flame‐retardant mechanism of HSFR was proposed. In vapor phase, HSFR could generate PO and PO2, which combine with flammable free radical and hinder segment decomposition. In condensed phase, HSFR could promote the dehydration and carbonization of chain and the formation of dense and graphitized char. This article provides a practical method for the preparation of green, highly effective, and durable flame‐retardant PUF. [ABSTRACT FROM AUTHOR]

Published
2021
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