JOURNAL OF POROUS MATERIALS
·
2020
·Vol. 27
·期 4
·1241-1251
·
IF 2.183
Huang Siqi,Wu Xiaoxu,Li Zhi,Shi Long,Zhang Yan,Liu Qiong
In this work, monolithic silica aerogels were prepared in pure water within 4 h by using MTMS as the precursor under ambient pressure drying (APD). The effects of the volume ratio of H 2 O/MTMS, CTAB content and NH 3 ·H 2 O concentration on the properties of MTMS-based aerogels (MSA) were investigated experimentally. The realization of the rapid synthesis of MSA under APD is attributed to getting rid of the aging process, solvent exchange and surface modification. It demonstrates that the microstructure of MSA is comprised of coralloid branches. Furthermore, the greater volume ratio of H 2 O /MTMS, larger CTAB content and smaller NH 3 ·H 2 O concentration cause relatively slimmer coralloid branches, smaller pores and weakened connectivity of skeletons. It also finds that the MSA with a greater volume ratio of H 2 O/MTMS presents larger Young’s modulus and smaller compressive stress, which is because of the correspondingly different microstructures. The as-prepared MSA shows a low density of 0.064 g/cm 3 and a contact angle as high as 143.4°, which provides their potentials for some engineering applications.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
Materials
·
2024
·Vol. 17
·期 11
·2641
·
IF 3.1
Jinjing Guo,Kaiqiang Luo,Wenqi Zou,Jun Xu,Baohua Guo
Ambient pressure drying (APD) of silica aerogels has emerged as an attractive method adapting to large-scale production. Spring-back is a unique phenomenon during APD of silica aerogels with volume expansion after its shrinkage under capillary force. We attribute the intense spring-back at elevated drying temperatures to a dense structure formed on the surface and the formation of positive internal pressure. Furthermore, an APD-assisted foaming method with an in situ introduction of NH4HCO3was proposed. NH4HCO3decomposing at drying temperatures hastened the emergence of positive pressure, thereby increasing the expansion volume. Compared to the previous method, the porosity of silica aerogel increased from 82.2% to 92.6%, and mesopore volume from 1.79 cm3g−1to 4.54 cm3g−1. By adjusting the amount of the silicon source, silica aerogels prepared by the APD-assisted foaming method generated higher volume expansion and lower thermal conductivity. After calcination to remove undecomposed ammonium salts, the hydrophobic silica aerogel with a density of 0.112 g cm−3reached a mesopore volume of 5.07 cm3g−1and a thermal conductivity of 18.9 mW m−1·K−1. This strategy not only improves the thermal insulation properties, but also offers a significant advancement in tailoring silica aerogels with specific porosity and mesopore volume for various applications.
研究领域:
材料科学
·
隔热材料
✓ 已验证
产品关联
DOI
PubMed
高影响因子
COMPOSITES COMMUNICATIONS
·
2022
·
IF 7.685
Xin Li,Hao He,Qiang Liu,Chunxia Zhao,Hongbing Chen
Preparation of inexpensive aerogel via ambient-drying is an important goal in aerogel field. In this study, the sol-gel transformation of polyvinyl alcohol (PVOH)/clay was achieved by γ-ray irradiation, followed by solvent exchanging, 1H, 1H, 2H, 2H-Perfluorodecyltrimethoxysilane (FAS) grafting and ambient-drying to obtain a hydrophobic aerogel. Compared with the freeze-drying method, the specific surface area and pore size distribution of the aerogels prepared by ambient-drying obviously increased, which is more favorable for the grafting of FAS. The water contact angle of the resulting aerogel increased to 139.5° after grafting, while the flammability slightly decreased. The compressive modulus, density and specific modulus of aerogels also increased gradually with the increase of irradiation. When the absorbed dose arrived 100 kGy, the compressive modulus, density and specific modulus reached 25.8 MPa, 0.213 g/cm 3 and 118 MPa·cm 3 /g, respectively. This novel method offers an easy and inexpensive way for fabricating hydrophobic aerogel using water soluble raw materials.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
ADVANCED FUNCTIONAL MATERIALS
·
2024
·
IF 18.5
Yu-Chuan Zhang,Rong Ding,Peng-Gang Su,Fu-Rong Zeng,Xu-Xu Jia,Zai-Yin Hu,Yu-Zhong Wang,Hai-Bo Zhao
Oriented aerogels, emerging as a new generation of lightweight electromagnetic interference (EMI) materials, often face complex synthesis processes. While creating an orderly oriented microstructure for EMI aerogels through ambient pressure drying (APD) shows promise, it remains a significant challenge. Here, inspired by the directional grown structure of the plant, a new strategy that employs rapid precursor orientation followed by slow cross-linking to achieve the APD of directional EMI aerogels is proposed. This approach demonstrates that low-temperature oriented polymerization of polyaniline enables strong cross-linking with poly(3,4-ethylenedioxythiophene) and alginate, forming a robust conductive directional skeleton and mitigating surface tension issues during mild drying. The resulting aerogel features high conductivity (48.84 S m −1 ), excellent flame retardancy, and impressive compressive strength. Notably, its sturdy frame allows for further enhancement with other functional materials, such as Mxene, through re-processing and re-drying. The tree-branch-like aerogel achieves a significantly improved EMI shielding effectiveness of 50.3 dB across an ultrawideband range of 8.2–40 GHz. This strategy offers a new idea for the straightforward preparation of functional aerogels with programmability and oriented microstructures using ambient drying.
研究领域:
材料科学
·
仿生学
·
电磁学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF NON-CRYSTALLINE SOLIDS
·
2018
·
IF 2.488
Ting Zhou,Lunlun Gong,Xudong Cheng,Yuelei Pan,Congcong Li,Heping Zhang
The by-product silicon tetrachloride (SiCl 4 ) was usually obtained from polysilicon industry and was a cheaper alternative precursor. An economic method to produce silica aerogel using silicon tetrachloride under ambient pressure drying was presented in this work, which can also solve the pollution problem during the by-product silicon tetrachloride treatment process. The prepared aerogel samples were characterized by scanning electron microscopy, Brunauer-Emmett-Teller analysis, thermal conductivity analysis, contact angle test, Fourier transform infrared spectroscopy and thermogravimetric analysis . It was found that the molar ratio of H 2 O/SiCl 4 could affect the properties of aerogels seriously. The density and thermal conductivity first decreased and then increased as the molar ratio increased from 13 to 32. The porosity showed an opposite trend with the density. Silica aerogel with high specific surface area (856.7 m 2 /g), low density (0.077 m 3 /g) and low thermal conductivity (0.0213 W/m·k) were obtained at the optimal conditions when the molar ratio was 25. The resulting aerogel is also mesoporous material with super hydrophobicity and have a huge application in thermal insulation field.
研究领域:
材料科学
·
环境科学
✓ 已验证
DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE
·
2025
·
IF 3.9
Jiang Shaoqi,Jiang Shan,Chen Sikui,Liu Li,Yan Jiatong,Xiang Cheng,Guo Ronghui
Cellulose aerogel fibers with their unique combination of high porosity, low density, and robust mechanical properties, show great promise as candidates for thermal insulation materials and flexible devices. However, their mechanical performance is inherently limited, and conventional drying techniques such as freeze-drying (FD) and supercritical drying (SCD) are both time-consuming and energy-intensive, posing significant challenges for large-scale industrial applications. Atmospheric pressure drying (APD) has emerged as a simple and cost-effective alternative, demonstrating considerable potential in the fabrication of aerogel fibers. In this study, chitosan was incorporated during the dissolution stage to reinforce the cellulose framework. Following solvent exchange, the material was subjected to APD in an oven, resulting in the fabrication of low-shrinkage chitosan-reinforced cellulose aerogel fibers (CKAF). The porosity of CKAF can be controlled between 38 and 75% by selecting solvents with different surface tensions for solvent exchange and adjusting the affinity between the solvent and the CKAF framework during APD. The shrinkage of atmospheric pressure drying chitosan-reinforced cellulose aerogel fibers (APD-CKAF) with a chitosan content of 10% to cellulose was 11%, which was only 1.9% higher than that of FD (9.1%). However, the pore structure of the APD-CKAF is compact and uniform, with a pore size distribution ranging from 0 to 48 nm, primarily centered around 20 nm, and a porosity of approximately 75%. The APD-CKAF exhibits superior mechanical strength (22.1 MPa, a 16.3% improvement over the FD samples) and elongation at break (55.1%, a 111.5% increase compared with the FD samples). The APD-CKAF exhibits excellent thermal insulation properties over a wide temperature range. This study presents a low-cost and high-efficiency strategy for the fabrication of cellulose aerogel fibers, advancing their potential for thermal insulation applications.
研究领域:
材料科学
·
生物材料
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Materials & Interfaces
·
2024
·
IF 8.3
Xin Zhang,Lei Han,Haijun Zhang,Weijie Cai,Xinyue Wang,Shuang Wang,Yabo Gao,Xuefeng Liu,Yage Li,Shaowei Zhang
Cellulose foams are considered an effective alternative to plastic foam, because of their advantages of low density, high porosity, low thermal conductivity, and renewable nature. However, they still suffer from complex processing, poor mechanical properties, and flammability. As an agricultural waste, bagasse is rich in cellulose, which has attracted much attention. Inspired by the fact that borate ions can effectively enhance the strength of plant tissue by their cross-linking with polysaccharides, the present work designs and fabricates a series of multifunctional bagasse foams with robust strength and improved thermal insulation and flame retardancy via a unique borax-induced self-assembly and atmospheric pressure drying route using bagasse as a raw material, borate as a cross-linking agent, and chitosan as an additive. As a result, the optimized foam exhibits a high porosity (93.5%), a high hydrophobic water contact angle (150.4°), a low thermal conductivity (63.4 mW/(m·K) at 25 °C), and an outstanding flame retardancy. The present study provides a novel and inspiring idea for large-scale production of cellulose foams through an environmentally friendly and cost-effective approach.
研究领域:
材料科学
·
生物质资源利用
✓ 已验证
产品关联
DOI
PubMed
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2015
·
IF 3.453
Jin Wang,Yulu Zhang,Yong Wei,Xuetong Zhang
A very fast (less than 2 h) and one-pot synthetic strategy was developed for the synthesis of silica aerogels . Organic silica gel was first formed under basic condition by adding a predetermined amount of hexane to a freshly prepared silica sol. After aging at elevated temperature for several minutes, the organogel was mechanically crushed and vigorously stirred in a mixture of trimethylchlorosilane and hexane . Finally, silica aerogel was produced by drying the hydrophobized organogel at temperatures higher than 180 °C. The effects of gelation conditions, amount of modification agents, and drying temperatures on the physical properties of the silica aerogels were investigated. The N 2 adsorption and desorption measurements indicated that high BET surface areas (up to 725.8 m 2 /g) could be obtained for the aerogels sintering at 350 °C, while that of the silica aerogels dried at 180 °C were relative lower (from 379.4 to 564.8 m 2 /g based on the modification conditions). Similar trend was also found in the thermal conductivities of the aerogels, e.g., lower values of thermal conductivity (∼0.025 W/mK) were obtained for the sintering samples, while that of the samples without sintering were relative higher (∼0.034 W/mK). In summary, a fast ambient pressure drying method has been developed, which show a great potential to synthesize silica aerogels in the industrial scale.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF POROUS MATERIALS
·
2021
·Vol. 28
·期 3
·651-659
·
IF 2.496
Yue Sheng,Li Xiaolei,Yu Huijun,Tong Zongwei,Liu Zhengdao
High-strength silica aerogels were prepared successfully by a new two-step surface modification (TSSM) method via ambient pressure drying (APD). Methyltrimethoxysilane (MTMS) and Trimethylchlorosilane (TMCS) were used as silylating agents in TSSM. First, MTMS is used to consume the residual pore water in the gel, and bridge the links between the secondary particles, further improving the structure of the Si–O–Si network. And then, TMCS is used in the second surface modification due to its smaller steric hindrance, higher reactivity, and more –CH 3 groups, so that the –OH in the gel can be completely replaced by –CH 3 , thereby reducing the shrinkage and improving the hydrophobicity of aerogels during APD. On the basis of keeping the low density (0.1616 g/cm 3 ), low thermal conductivity (0.0226 W m −1 K −1 )) and high hydrophobicity, the prepared samples also have high compressive strength (~ 0.6 MPa) which is far greater than other silica aerogels at present, making it possible to prepare high-strength aerogel blocks via APD. Possible mechanism of the improvement of mechanical properties by TSSM is discussed.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF NON-CRYSTALLINE SOLIDS
·
2016
·
IF 1.825
Ming Li,Hongyi Jiang,Dong Xu,Ou Hai,Wei Zheng
Hydrophobic silica aerogels were prepared by a fast co-precursor method based on sol-gel process under ambient pressure drying. Organic tetraethoxysilane (TEOS) and inorganic aqueous alkaline silica sol were simultaneously used as starting materials, while trimethylchlorosilane (TMCS) was chosen as surface modification agent. Alkaline silica sol plays a double role of increasing pH value for condensation reactions and as co-precursor. The porosity and hydrophobicity of silica aerogels were in close correlation with the synthesis parameters. The monolithic and crack-free sample with a low density of 0.130 g ∙ cm − 3 and high water contact angle of 142.8° was obtained by optimized the synthesis conditions (silica sol/TEOS molar ratio, ethanol/silica sol molar ratio, H 2 O/silica sol molar ratio and TMCS/n-Hexane volume ratio were 0.58, 1.32, 5.34 and 1:7, respectively).
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
MATERIALS & DESIGN
·
2016
·
IF 3.997
Xiaobing Tang,Aihua Sun,Chengyi Chu,Mingli Yu,Si Ma,Yuchuan Cheng,Jianjun Guo,Gaojie Xu
A novel silica nanowire-silica composite aerogels with excellent thermal insulation and mechanical properties was prepared by adding SiO 2 nanowires as a secondary phase into the silica matrix and drying at ambient pressure . The SiO 2 nanowires and silica aerogel matrix have outstanding compatibility and dispersibility because the components of nanowire and aerogel matrix all are silica, which contributes to the improvement of the mechanical property of the silica composite aerogels. The physical, mechanical and thermal properties of the SiO 2 nanowires based composite silica aerogel are investigated and discussed in detail. The results indicate that the monolithic aerogels with high specific surface area, porosity and large pore volume . The thermal conductivity of the composite silica aerogels only increases gently (0.006 W·m − 1 K − 1 ) as the addition of SiO 2 nanowires rises from 0 wt% to 14 wt%, while their mechanical properties have been improved greatly. The SiO 2 nanowires based composite silica aerogel would be widely used in the thermal insulation application because of its outstanding thermal insulation property.
研究领域:
材料科学
·
热力学工程
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Xiaodong Hu,Shanshan Zhang,Bo Yang,Ming Hao,Zhijun Chen,Yanbo Liu,Xiaoxiao Wang,Jinbo Yao
Ambient drying is currently the cheapest and most efficient way to prepare aerogels, but it is invisible for the preparation of cellulose aerogels. In this paper, we describe a method of preparing cellulose aerogels that can be dried under atmospheric pressure by freeze-linking technique. The amino silane coupling agent forms an amino-rich polymer layer on the bacterial cellulose surface during the freezing process. And, the cross-linked network constructed by Schiff base reaction can strengthen the fiber skeleton in the process of solvent exchange. Due to the double cross-linked network structures, the cellulose ethanol gel can be dried directly under atmospheric pressure at 60 °C and the volume shrinkage can be as low as 3.3 %±1.4 %. In the process of solvent exchange, the loss of some polysiloxane causes defects in the aerogel, which not only reduces its thermal conductivity but also increases its specific surface area. And the water resistance, thermal performance, and dye adsorption performance of the aerogel are also significantly improved. This study provides a low-cost and high-efficiency solution for the manufacture of cellulose aerogels and promotes their wide applications.
研究领域:
材料科学
·
化学工程
✓ 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）