Preparation of Silica Aerogels Monoliths from Hydrophobic Silica Gels and Pluronic10R5 via Sol–Gel Process

Silica aerogel, the most common type of aerogels, comprised of 95% air in its structure which made the aerogel has a high surface area, high porosity, low density, and low thermal conductivity. Because of its structure and high porosity, one of its major weakness compared to other materials is being very brittle. This study aims at strengthening the connection points between silica nanoparticles using Pluronic10R5 (poly(propylene oxide)8–poly(ethylene oxide)22–poly(propylene oxide)8) where the Pluronic10R5 was used to reduce phase separation during the silica condensation reaction in the sol–gel process. Silica aerogel monoliths were prepared via a sol–gel process from hydrophobic silica gels and Pluronic10R5 with an ambient pressure drying (APD) process. Results from the compression test showed that the Pluronic10R5/silica aerogels have improved mechanical property by ten times that of unmodified silica aerogels. A thermogravimetric analysis (TGA) showed a mass loss at 300–400 °C that is attributed to the surface methyl group, while a mass loss at 200 °C refers to the loss of Pluronic10R5 which confirms the incorporation of Pluronic10R5 into the monolith. Moreover, infrared (IR) images revealed that the top surface temperature of Pluronic10R5/silica aerogels monolith is about 80 °C differs from the bottom heat source temperature of 160 °C.

Download Full-text

Preparation and Characterization of Ultralow Density Silica Aerogels by Acetonitrile Supercritical Drying

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.519.83 ◽

2012 ◽

Vol 519 ◽

pp. 83-86 ◽

Cited By ~ 6

Author(s):

Guang Wu Liu ◽

Xing Yuan Ni ◽

Bin Zhou ◽

Qiu Jie Yu

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Silica Aerogel ◽

Sol Gel ◽

Supercritical Drying ◽

Silica Aerogels ◽

High Specific Surface Area ◽

Molar Ratio ◽

Sol Gel Process

This paper deals with the synthesis of ultralow density silica aerogels using tetramethyl orthosilicate (TMOS) as the precursor via sol-gel process followed by supercritical drying using acetonitrile solvent extraction. Ultralow density silica aerogels with 6 mg/cc of density was made for the molar ratio by this method. The microstructure and morphology of the ultralow density silica aerogels was characterized by the specific surface area, SBET, SEM, and the pore size distribution techniques. The results show that the ultralow density silica aerogel has the high specific surface area of 812m2/g. Thermal conductivities at desired temperatures were analyzed by the transient plane heat source method. Thermal conductivity coefficients of silica aerogel monoliths changed from 0.024 to 0.043W/ (m K) as temperature increased to 400°C, revealed an excellent heat insulation effect during thermal process.

Download Full-text

Effects of Surfactants on the Synthesis of Silica Aerogels Prepared by Ambient Pressure Drying

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.512-515.1625 ◽

2012 ◽

Vol 512-515 ◽

pp. 1625-1630

Author(s):

Hua Zheng Sai ◽

Li Xing ◽

Jun Hui Xiang ◽

Fu Shi Zhang ◽

Li Jie Cui ◽

...

Keyword(s):

Ambient Pressure ◽

Sol Gel ◽

Drying Shrinkage ◽

Silica Aerogels ◽

Ambient Pressure Drying ◽

Ammonium Bromide ◽

High Porosity ◽

Free Silica ◽

Sol Gel Process ◽

Cetyltrimethyl Ammonium

In this research, aerogels were synthesized by a two-step sol-gel process without supercritical conditions. During the process, tetraethoxysilane (TEOS) was used as precursor, and different surfactants, i.e. cetyltrimethyl ammonium bromide (CTAB) and polyethylene glycol–600 (PEG–600), were used as dopants respectively. In order to minimize the drying shrinkage and preserve the high porosity structure, the surface of the gels was modified by trimethylchlorosilane (TMCS) before the ambient pressure drying (APD). The effect of surfactent on the structure of the resulting aerogels was investigated. The aerogels which involved surfactants exhibited resistance to cracking during the APD of the alcogels. The modification by TMCS has been confirmed using Infrared (IR) spectroscopy. The porous structure of aerogels was investigated by Brunauer-Emmett- Teller (BET) instrument, differential scanning calorimeter (DSC) and scanning electron micrograph (SEM). The results indicated that surfactants as dopants could significantly affect the structure and optical property of aerogels and be beneficial for obtaining crack-free silica aerogels via ambient pressure drying process.

Download Full-text

The Monolithic Silica Aerogel Derived from MTMS/TEOS

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.364.631 ◽

2013 ◽

Vol 364 ◽

pp. 631-634

Author(s):

Yu Xi Yu ◽

Yong Chen

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Silica Aerogel ◽

Sol Gel ◽

Supercritical Drying ◽

Silica Aerogels ◽

Synthesis And Characterization ◽

Sol Gel Process

The experimental results on the synthesis and characterization of tetraethoxysilane (TEOS)/ methyltrimethoxysilane (MTMS)-based silica aerogels using two step sol-gel process via supercritical drying, are described. The obtained TEOS/MTMS-based aerogel showed properties of 0.1g/cm3 density, 95.5% porosity and 1070 m2/g specific surface area.

Download Full-text

Preparation of Macroprous C12A7 Mayenite Monoliths via a Sol-Gel Process with Nitrates as Precursors

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.768.211 ◽

2018 ◽

Vol 768 ◽

pp. 211-217 ◽

Cited By ~ 1

Author(s):

Rui Wang ◽

Yu Kun Sun ◽

Bao Jia Qi Jiang ◽

Hui Yang ◽

Xing Zhong Guo

Keyword(s):

Heat Treatment ◽

Phase Separation ◽

Binary System ◽

Propylene Oxide ◽

Crystalline Phase ◽

Sol Gel ◽

Single Crystalline ◽

Sol Gel Process

Macroporous Ca12Al14O33(C12A7) mayenite monoliths have been successfully prepared via a sol-gel process in the presence of propylene oxide (PO) and poly (ethyleneoxide) (PEO). Gelation of CaO-Al2O3binary system with nitrates salts as additional precursors is accelerated by PO as an acid scavenger, while PEO works as a phase separation inducer to mediate the phase separation of the system. Appropriate PO and PEO amounts allow the formation of monolithic xerogel with interconnected macropores and co-continuous skeletons. The resultant dried gels are amorphous and the single crystalline phase Ca12Al14O33mayenite forms after heat-treatment at 1100 °C in air, while the macrostructure is preserved with a porosity as high as 78% and smoother and denser skeletons.

Download Full-text

Statistical approaching of sol-gel process in preparation of silica aerogel derived from geothermal silica by several acids

10.1063/1.5141682 ◽

2019 ◽

Author(s):

S. Silviana ◽

Ilham Nur Hakim Rambe ◽

Hendra Sudrajat ◽

Mochammad Abdillah Zidan

Keyword(s):

Silica Aerogel ◽

Sol Gel ◽

Sol Gel Process

Download Full-text

Characterization of porous silica gels prepared via the sol-gel process by29Si CP/MAS solid-state NMR spectroscopy

Molecular Physics ◽

10.1080/00268979000102101 ◽

1990 ◽

Vol 71 (4) ◽

pp. 769-780 ◽

Cited By ~ 23

Author(s):

K.L. Walther ◽

A. Wokaun ◽

A. Baiker

Keyword(s):

Solid State ◽

Nmr Spectroscopy ◽

Solid State Nmr ◽

Sol Gel ◽

Porous Silica ◽

Silica Gels ◽

Solid State Nmr Spectroscopy ◽

Sol Gel Process

Download Full-text

Mechanical Behavior of Bioactive Glass-Polyvinyl Alcohol Hybrid Foams Obtained by the Sol-Gel Process

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.284-286.757 ◽

2005 ◽

Vol 284-286 ◽

pp. 757-760 ◽

Cited By ~ 2

Author(s):

Marivalda Pereira ◽

Showan N. Nazhat ◽

Julian R. Jones ◽

Larry L. Hench

Keyword(s):

Polyvinyl Alcohol ◽

Bioactive Glass ◽

Mechanical Behavior ◽

Sol Gel ◽

Precursor Solution ◽

High Porosity ◽

Soft Tissue Regeneration ◽

Sol Gel Process ◽

Potential Applications ◽

Hybrid Foams

The possibility of enhancing mechanical properties by incorporation of polymeric components to sol-gel derived materials is extremely attractive to prepare macroporous scaffolds, leading to materials with potential applications in both hard and soft tissue regeneration. In this work bioactive glass-polyvinyl alcohol hybrids were developed and their mechanical behavior was evaluated. Hybrids were synthesized by adding polyvinyl alcohol to a sol-gel precursor solution, which was then foamed with the addition of a surfactant and vigorous agitation. The foams were cast, aged and dried at 40°C. A cleaning step to decrease the acidic character of the obtained hybrids was undertaken by immersion in a NH4OH solution. The mechanical behavior of the hybrids was evaluated in compression using both stress and strain control tests. Hybrid foams had a high porosity varying from 60-90% and the macropore diameter ranged from 10 to 600 µm. The modal macropore diameter varied with the inorganic phase composition and with the polymer content in the hybrid. The strain at fracture of the as prepared hybrid foams was substantially greater than pure gel-glass foams. The cleaned hybrids presented a slightly higher strength and lower deformation than the as prepared foams.

Download Full-text