scholarly journals Synthesis of sodium silicate-based silica aerogels with graphene oxide by ambient pressure drying

2021 ◽  
Author(s):  
Oznur Kaya Cakmak ◽  
Khalil T. Hassan ◽  
Jiabin Wang ◽  
Xiao Han ◽  
Lidija Šiller
Keyword(s):  
Graphene Oxide ◽  
Surface Area ◽  
Sodium Silicate ◽  
Ambient Pressure ◽  
Physical And Mechanical Properties ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Silica Matrix ◽  
X Ray Diffraction ◽  
Composite Aerogels

AbstractHere we study how graphene oxide affects silica aerogels and their physical and mechanical properties by examining volume shrinkage, pore volume, surface area and compressive strength of these composite aerogels. Composite aerogels were made through adding different amount of graphene oxide (GO) to sodium silicate precursor by using ambient pressure drying method. Additionally, the chemical composition of the composite aerogels was determined using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. A rougher structure was observed when the GO loading increased and the characteristic peak of GO in XRD disappeared due to the random distribution of GO within the silica matrix. FTIR spectrum of composite aerogels shows that the relative intensity of silanol groups on the silica matrix have downward tendency with the addition of GO. The specific surface area had maxima with the addition of 0.01 wt% GO surface area to 578 m2 /g. The mechanical strength of aerogels was increased, with the loading of GO from 0.0 wt% to 0.2 wt%, and the compressive modulus increased from 0.02 MPa to 0.22 MPa.

Cellulose nanofibril reinforced silica aerogels: optimization of the preparation process evaluated by a response surface methodology

RSC Advances ◽  
2016 ◽  
Vol 6 (102) ◽  
pp. 100326-100333 ◽  
Author(s):  
Jingjing Fu ◽  
Chunxia He ◽  
Jingda Huang ◽  
Zhilin Chen ◽  
Siqun Wang
Keyword(s):  
Mechanical Properties ◽  
Response Surface Methodology ◽  
Response Surface ◽  
Ambient Pressure ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Preparation Process ◽  
Cellulose Nanofibril ◽  
Drying Method ◽  
Composite Aerogels

CNF–silica composite aerogels with reinforced mechanical properties were prepared under an ambient pressure drying method and optimized by a response surface methodology.

Pore Structure Characterization of TiO2-SiO2 Composite Aerogel Prepared via Ambient Pressure Drying by Sol Pre-Modification Process

2012 ◽  
Vol 534 ◽  
pp. 101-105 ◽  
Author(s):  
Jing Xiao Liu ◽  
Lu Nan Bai ◽  
Fei Shi ◽  
Zhi Qiang Hu ◽  
Yan Yan Jiang ◽  
...  
Keyword(s):  
Specific Surface ◽  
Pore Structure ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Ambient Pressure ◽  
Volume Ratio ◽  
Ambient Pressure Drying ◽  
Composite Aerogel ◽  
Composite Aerogels

In this paper, TiO2-SiO2composite aerogels were prepared via ambient pressure drying by sol-gel and sol pre-modification method. The pre-modification solution consists of hexamethyldisiloxane (HMDSO) as buffering agent, trimethylchlorosilane (TMCS) as modifier and hexane as organic solvent. The pore structure of TiO2-SiO2composite aerogels was characterized by N2adsorption-desorption method. The effects of HMDSO/TMCS volume ratio on the pore structure and properties of TiO2-SiO2composite aerogel were studied. The results indicate that the pre-modification of TiO2-SiO2composite sol by adding HMDSO/TMCS/Hexane solution could shorten the preparation period. Increasing the amount of HMDSO is favorable for obtaining TiO2-SiO2composite aerogel with higher specific surface area and pore volume. The best volume ratio of HMDSO/TMCS/composite sol for preparing mesoporous TiO2-SiO2composite aerogels were 12:6:120 and 12:12:120, with which the specific surface area and pore volume of the obtained TiO2-SiO2composite aerogel are 425.2～645.4 m2/g and 0.80～2.85 m3/g, respectively.

Preparation and Properties of Hydrophobic Silica Aerogels by Ambient Pressure Drying Method

2011 ◽  
Vol 71-78 ◽  
pp. 1040-1043
Author(s):  
Hui Wang ◽  
Shi Ming Liu ◽  
Ling Ke Zeng
Keyword(s):  
Surface Area ◽  
Ambient Pressure ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Drying Method ◽  
Hydrophobic Properties ◽  
Large Pore Volume

Silica alcogels were prepared by hydrolysis with hydrochloric acid and condensation with NH4OH of ethanol diluted tetraethylorthosilicate (TEOS) precursor and trimethylchlorosilane and hexane as surface modifying agent. The physical properties such as density, appearance, hydrophobicity, surface area, pore size distribution and thermal stability were measured. It was found that the physical and hydrophobic properties of the silica aerogels depend on the TMCS/hexane (V) volume ratio. The density decreased with increase ofV, and the aerogels are more hydrophobic asV=3%. The aerogels were thermally stable up to a temperature of 350 °C, and the aerogel prepared has a high surface area and large pore volume.

Hydrophobic Silica Aerogels by Ambient Pressure Drying

2015 ◽  
Vol 830-831 ◽  
pp. 476-479
Author(s):  
Srinivasan Nagapriya ◽  
M.R. Ajith ◽  
H. Sreemoolanadhan ◽  
Mariamma Mathew ◽  
S.C. Sharma
Keyword(s):  
Surface Area ◽  
Atmospheric Pressure ◽  
Polar Solvent ◽  
Ambient Pressure ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Sol Gel Process

Silica aerogels have been prepared through sol-gel process by polymerization of TEOS in the presence of NH4F and NH4OH as catalysts. The solvent present in the gel is replaced by ethanol followed by a non-polar solvent such as n-hexane prior to solvent modification step. Gels are made hydrophobic by treating them with HMDZ to prevent rupture during drying, which has been confirmed by FTIR. Gels are then washed and dried carefully in a PID controlled oven at atmospheric pressure. The ageing duration and solvent exchange combinations are optimized to yield crack-free gels prior to drying. Aerogels are characterized for density, specific surface area, pore volume, pore size, thermal stability and contact angle. Hydrophobic, high surface area (570 m2/g), low density (0.07 g/cm3) silica aerogels are synthesized by using optimized mole ratio of precursors and catalysts. Silica aerogel granules (1-3 mm) as well as monoliths (Ф~35 mm) could be produced through ambient pressure drying of gels.

Preparation of Hydrophobic Silica Aerogels from Industrial Microsilica and its Oil Adsorption Properties

2012 ◽  
Vol 531-532 ◽  
pp. 103-107 ◽  
Author(s):  
Fei Shi ◽  
Jing Xiao Liu ◽  
Xiao Li Dong ◽  
Zhi Wei Zhang ◽  
Peng Cheng Du ◽  
...  
Keyword(s):  
Sodium Silicate ◽  
Hydrothermal Reaction ◽  
Ambient Pressure ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Mixed Solution ◽  
Hydrophobic Silica ◽  
Oil Adsorption

Hydrophobic silica aerogels were prepared from industrial microsilica via ambient pressure drying. The process consists of two stages, synthesis of sodium silicate solution from microsilica by hydrothermal reaction with sodium hydroxide, and preparation of silica aqueous gel and porous silica aerogels from the obtained sodium silicate solution. The mixed solution of hexane/ethanol/trimethylchlorosilane was used to modify the sol-gel derived silica aqueous gel so as to obtain porous structure by ambient pressure drying. The microstructure, pore properties of the silica aerogels were analyzed by FTIR and N2 adsorption-desorption methods, and the oil adsorption of the synthesized silica aerogels was investigated. The results indicate that the obtained silica aerogels are light-weight and hydrophobic porous materials, with the specific surface area of 767~828 m2•g-1, porosity of 91.5~95.1% and the average pore diameter of 5.22~8.02 nm. The synthesized silica aerogels have good oil adsorption capacity and the highest saturated oil adsorption rate can achieve 1105%.

scholarly journals Silica Aerogel Monoliths Derived from Silica Hydrosol with Various Surfactants

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3192 ◽  
Author(s):  
Dong Chen ◽  
Xiaodong Wang ◽  
Wenhui Ding ◽  
Wenbing Zou ◽  
Qiong Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Stability ◽  
Silica Aerogel ◽  
Low Cost ◽  
Ambient Pressure ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Low Thermal Conductivity ◽  
Silica Hydrosol ◽  
High Production Cost

Owing to their ultra-low thermal conductivity, silica aerogels are promising thermal insulators; however, their extensive application is limited by their high production cost. Thus, scientists have started to explore low-cost and easy preparation processes of silica aerogels. In this work, a low-cost method was proposed to prepare silica aerogels with industrial silica hydrosol and a subsequent ambient pressure drying (APD) process. Various surfactants (cationic, amphoteric, or anionic) were added to avoid solvent exchange and surface modification during the APD process. The effects of various surfactants on the microstructure, thermal conductivity, and thermal stability of the silica aerogels were studied. The results showed that the silica aerogels prepared with a cationic or anionic surfactant have better thermal stability than that prepared with an amphoteric surfactant. After being heated at 600 °C, the silica aerogel prepared with a cationic surfactant showed the highest specific surface area of 131 m2∙g−1 and the lowest thermal conductivity of 0.038 W∙m−1∙K−1. The obtained low-cost silica aerogel with low thermal conductivity could be widely applied as a thermal insulator for building and industrial energy-saving applications.

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