柔性有机硅气凝胶的制备及其高温无机化转变研究

doi:10.15541/jim20220129

摘要/Abstract

摘要：

二氧化硅气凝胶以其低密度、高孔隙率等特性在高温隔热领域显示出广阔的应用前景, 但其脆性和高成本的超临界干燥方式限制了其应用。本研究以乙烯基三甲氧基硅烷(VTMS)和乙烯基甲基二甲氧基硅烷(VMDMS)为前驱体, 通过溶胶凝胶、常压干燥制备了具有高柔性的海绵状有机硅气凝胶, 并研究了前驱体摩尔比对气凝胶微观结构和压缩回弹性能的影响, 以及气凝胶分别在高温有氧和无氧环境中的无机化转变过程。结果表明, 随着前驱体中VTMS/VMDMS比例增加, 气凝胶颗粒变小且堆积更紧密, 其压缩回弹性能也随之降低; 在800 ℃空气氛围中, 气凝胶通过侧基的氧化和主链Si-O-Si的断裂、重排转化为无机SiO₂; 在800 ℃ N₂氛围中, 气凝胶通过裂解反应转化为无机SiO₂和游离碳的混合体, 1000~1400 ℃进一步处理后SiO₂和游离碳经碳热还原反应生成SiO₄、SiCO₃、SiC₂O₂和SiC₃O等无定形的Si-O-C结构和少量β-SiC纳米线; 经1200 ℃碳热还原反应生成的Si-O-C结构具有最优的耐高温氧化性能, 可为制备耐高温氧化Si-O-C气凝胶提供参考。

关键词: 有机硅气凝胶, 柔性, 隔热, 高温氧化, 高温裂解

Abstract:

Silica aerogels have wide application prospect in high temperature heat insulation due to their low density and high porosity. However, the brittleness and high cost of supercritical drying restrict their application. In this study, spongy silicone aerogels with high flexibility were prepared via Sol-Gel polymerization and atmospheric pressure drying using vinyltrimethoxysilane (VTMS) and vinylmethyldimethoxysilane (VMDMS) as precursors. The effects of precursor molar ratio on the microstructure and compressive resilience of aerogels, as well as the inorganic transformation process of aerogels in high temperature aerobic and anaerobic environments were studied. The results show that with the increase of VTMS/VMDMS ratio in the precursor, the aerogel particles become smaller and more tightly packed, and the compression resilience of aerogels also decreased. In air at 800 ℃, aerogels were transformed into inorganic SiO₂ by oxidation of organic side groups, fracture and rearrangement of main chain Si-O-Si. In N₂ at 800 ℃, aerogels were transformed into the mixture of inorganic SiO₂ and free carbon by pyrolysis reaction, and after further treatment at 1000-1400 ℃, SiO₂ and free carbon were subjected to carbothermal reduction reaction to form amorphous Si-O-C structures such as SiO₄, SiCO₃, SiC₂O₂, and SiC₃O, and a small amount of β-SiC nanowires. The Si-O-C structure formed by carbothermal reduction reaction at 1200 ℃ has optimal high temperature oxidation resistance, which can provide reference for the preparation of pyro-oxidation resistant Si-O-C aerogels.

Key words: silicone aerogel, flexibility, heat insulation, high-temperature oxidation, pyrolysis

中图分类号:

O648

罗艺, 夏书海, 牛波, 张亚运, 龙东辉. 柔性有机硅气凝胶的制备及其高温无机化转变研究[J]. 无机材料学报, 2022, 37(12): 1281-1288.

LUO Yi, XIA Shuhai, NIU Bo, ZHANG Yayun, LONG Donghui. Preparation and High Temperature Inorganic Transformation of Flexible Silicone Aerogels[J]. Journal of Inorganic Materials, 2022, 37(12): 1281-1288.

图/表 8

图1 溶胶-凝胶过程示意图(a), 气凝胶样品的红外谱图(b)、核磁谱图(c)和SEM照片(d~g)

Fig. 1 Schematic diagram of Sol-Gel process (a), IR spectra (b), NMR spectra (c) and SEM images (d-g) of aerogel samples Molar ratios of VTMS/VMDMS for aerogels (d-g) are 1, 2, 3, 4, respectively

图2 气凝胶样品的循环压缩应力-应变曲线

Fig. 2 Cyclic compression stress-strain curves of aerogels (a) Stress-strain curves after 10-cycle compression; (b) Cyclic compression stress-strain curves of sample V/VM-3 Colorful figures are available on website

图3 样品V/VM-3在空气氛围下的TG-IR谱图(a, b), 经不同温度处理后的实物图(c)和在800 ℃处理后的SEM照片(d)

Fig. 3 (a, b) TG-IR spectra of sample V/VM-3 tested in air; (c) Photographs of sample V/VM-3 after heat-treated at different temperatures; (d) SEM image of sample V/VM-3 after heat-treated at 800 ℃

图4 样品V/VM-3在N2氛围下的TG-IR谱图(a, b), 在不同温度处理后的XRD谱图(c)、核磁谱图(d)和SEM照片(e~h)

Fig. 4 (a, b) TG-IR spectra of sample V/VM-3 under N2 atmosphere; (c) XRD patterns, (d) NMR spectra and (e-h) SEM image of sample V/VM-3 after heat-treated at different temperatures (e) 800 ℃; (f) 1000 ℃; (g) 1200 ℃; (h) 1400 ℃

图5 碳化前后样品V/VM-3的照片

Fig. 5 Pictures of sample V/VM-3 before and after carbonization

图6 无机Si-O-C气凝胶的TG曲线

Fig. 6 TG curves of inorganic Si-O-C aerogels

图7 无机Si-O-C气凝胶在800 ℃氧化处理后的XRD谱图

Fig. 7 XRD patterns of inorganic Si-O-C aerogels after oxidized at 800 ℃

图8 样品T1400经800 ℃氧化处理后的SEM照片

Fig. 8 SEM image of sample T1400 after oxidized at 800 ℃

参考文献 31

[1]	SONG J W, CHEN C J, YANG Z, et al. Highly compressible, anisotropic aerogel with aligned cellulose nanofibers. ACS Nano, 2018, 12(1): 140. DOI PMID
[2]	HAN X, HASSAN K T, HARVEY A, et al. Bioinspired synthesis of monolithic and layered aerogels. Advanced Materials, 2018, 30(23): 1706294. DOI URL
[3]	OU H H, YANG P J, LIN L H, et al. Carbon nitride aerogels for the photoredox conversion of water. Angewandte Chemie International Edition, 2017, 56(36): 10905-10910. DOI URL
[4]	CAI B, SAYEVICH V, GAPONIK N, et al. Emerging hierarchical aerogels: self-assembly of metal and semiconductor nanocrystals. Advanced Materials, 2018, 30(33): 1707518. DOI URL
[5]	KHALILY M A, EREN H, AKBAYRAK S, et al. Facile synthesis of three-dimensional Pt-TiO₂ nano-networks: a highly active catalyst for the hydrolytic dehydrogenation of ammonia-borane. Angewandte Chemie International Edition, 2016, 55(40): 12257-12261. DOI URL
[6]	HAGEDORN K, LI W, LIANG Q J, et al. Catalytically doped semiconductors for chemical gas sensing: aerogel-like aluminum- containing zinc oxide materials prepared in the gas phase. Advanced Functional Materials, 2016, 26(20): 3424-3437. DOI URL
[7]	NICOLA H, ULRICH S. Aerogels-airy materials: chemistry, structure, and properties. Angewandte Chemie International Edition, 1998, 37(1/2): 22-45. DOI URL
[8]	BEAMISH J, HERMAN T. Adsorption and desorption of helium in aerogels. Physica B Condensed Matter, 2003, 329: 340-341.
[9]	BELLUNATO T, BRAEM A, BUZYKAEV A R, et al. Aerogel as cherenkov radiator for rich detectors. Nuclear Inst & Methods in Physics Research A, 2003, 502(1): 227-230.
[10]	KISTLER S S. Coherent expanded aerogel jellies. Nature, 1931, 127(3211): 741.
[11]	DU A, ZHOU B, ZHANG Z, et al. A special material or new state of matter: a review and reconsideration of the aerogel. Materials, 2013, 6(3): 941-968. DOI URL
[12]	HE F, YU W J, FANG M H, et al. An overview on silica aerogels synthesized by siloxane co-precursors. Journal of Inorganic Materials, 2015, 30(12): 1243-1253. DOI
[13]	NADARGI D Y, LATTHE S S, HIRASHIMA H, et al. Studies on rheological properties of methyltriethoxysilane (MTES) based flexible superhydrophobic silica aerogels. Microporous & Mesoporous Materials, 2009, 117(3): 617-626.
[14]	KANAMORI K, AIZAWA M, NAKANISHI K, et al. New transparent methylsilsesquioxane aerogels and xerogels with improved mechanical properties. Advanced Materials, 2007, 19(12): 1589-1593. DOI URL
[15]	RAO A V, BHAGAT S D, HIRASHIMA H, et al. Synthesis of flexible silica aerogels using methyltrimethoxysilane (MTMS) precursor. Journal of Colloid & Interface Science, 2006, 300(1): 279-285.
[16]	ZU G Q, SHIMIZU T, KANAMORI K, et al. Transparent, superflexible doubly cross-linked polyvinylpolymethylsiloxane aerogel superinsulators via ambient pressure drying. ACS Nano, 2018, 12(1): 521-532. DOI URL
[17]	ZU G Q, SHEN J, ZOU L P, et al. Preparation, mechanical properties and thermal properties of elastic aerogels. Journal of Inorganic Materials, 2014, 29(4): 417-422.
[18]	HONG J Y, BAK B M, WIE J J, et al. Reversibly compressible, highly elastic, and durable graphene aerogels for energy storage devices under limiting conditions. Advanced Functional Materials, 2015, 25(7): 1053-1062. DOI URL
[19]	HAYASE G, KANAMORI K, HASEGAWA G, et al. A superamphiphobic macroporous silicone monolith with marshmallow- like flexibility. Angewandte Chemie International Edition, 2013, 52(41): 10788-10791. DOI URL
[20]	QIU F X, ZHOU Y M, LIU J Z, et al. Study of ²⁹Si MAS NMR spectroscopy and electro-optic property based on polyimide/SiO₂. Photographic Science and Photochemistry, 2006, 24(1): 55-60.
[21]	SHIMIZU T, KANAMORI K, MAENO A, et al. Transparent ethylene-bridged polymethylsiloxane aerogels and xerogels with improved bending flexibility. Langmuir, 2016, 32(50): 13427-13434. PMID
[22]	ZHANG Z, WANG X D, SHEN J. Effect of organic-inorganic crosslinking degree on the mechanical and thermal properties of aerogels. Journal of Inorganic Materials, 2020, 35(4): 454-460. DOI
[23]	ZU G Q, KANAMORI K, WANG X D, et al. Superelastic triple-network polyorganosiloxane-based aerogels as transparent thermal superinsulators and efficient separators. Chemistry of Materials, 2020, 32(4): 1595-1604. DOI URL
[24]	NAZERAN N, MOGHADDAS J. Synthesis and characterization of silica aerogel reinforced rigid polyurethane foam for thermal insulation application. Journal of Non-Crystalline Solids, 2017, 461: 1-11. DOI URL
[25]	ZHANG Z, WANG X D, ZU G Q, et al. Resilient, fire-retardant and mechanically strong polyimide-polyvinylpolymethylsiloxane composite aerogel prepared via stepwise chemical liquid deposition. Materials & Design, 2019, 183: 108096.
[26]	CHEN Z Q, CHEN Y F, LIU H B. Pyrolysis of phenolic resin by TG-MS and FTIR analysis. Advanced Materials Research, 2013, 631-632: 104-109. DOI URL
[27]	金晶, 徐晓秋, 杨雄发, 等. 聚硅氧烷热稳定性研究进展. 化工新型材料, 2010, 38(1): 17-19.
[28]	HUANG D M, GUO C N, ZHANG M Z, et al. Characteristics of nanoporous silica aerogel under high temperature from 950 ℃ to 1200 ℃. Materials & Design, 2017, 129: 82-90.
[29]	YANG G X, BISWAS P. Computer simulation of the aggregation and sintering restructuring of fractal-like clusters containing limited numbers of primary particles. Journal of Colloid & Interface Science, 1999, 211(1): 142-150.
[30]	LI X K, LIU L, ZHANG Y X, et al. Synthesis of nanometre silicon carbide whiskers from binary carbonaceous silica aerogels. Carbon, 2001, 39(2): 159-165. DOI URL
[31]	MA J, YE F, LIN S J, et al. Large size and low density SiOC aerogel monolith prepared from triethoxyvinylsilane/tetraethoxysilane. Ceramics International, 2017, 43(7): 5774-5780. DOI URL