scholarly journals Facile Synthesis of Methylsilsesquioxane Aerogels with Uniform Mesopores by Microwave Drying

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 375 ◽  
Author(s):  
Xingzhong Guo ◽  
Jiaqi Shan ◽  
Wei Lei ◽  
Ronghua Ding ◽  
Yun Zhang ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Production Efficiency ◽  
Sol Gel ◽  
Microwave Drying ◽  
Remarkable Effect ◽  
Good Thermal Stability ◽  
Pore Structures ◽  
Sol Gel Process ◽  
20 Nm ◽  
Uniform Mesopores

Methylsilsesquioxane (MSQ) aerogels with uniform mesopores were facilely prepared via a sol–gel process followed by microwave drying with methyltrimethoxysilane (MTMS) as a precursor, hydrochloric acid (HCl) as a catalyst, water and methanol as solvents, hexadecyltrimethylammonium chloride (CTAC) as a surfactant and template, and propylene oxide (PO) as a gelation agent. The microstructure, chemical composition, and pore structures of the resultant MSQ aerogels were investigated in detail to achieve controllable preparation of MSQ aerogels, and the thermal stability of MSQ aerogels was also analyzed. The gelation agent, catalyst, solvent, and microwave power have important roles related to the pore structures of MSQ aerogels. Meanwhile, the microwave drying method was found to not only have a remarkable effect on improving production efficiency, but also to be conducive to avoiding the collapse of pore structure (especially micropores) during drying. The resulting MSQ aerogel microwave-dried at 500 W possessed a specific surface area up to 821 m2/g and a mesopore size of 20 nm, and displayed good thermal stability.

scholarly journals Facile Synthesis of Methylsilsesquioxane Aerogels with Uniform Mesopores by Microwave Drying

2019 ◽  
Author(s):  
Xingzhong Guo ◽  
Jiaqi Shan ◽  
Wei Lei ◽  
Ronghua Ding ◽  
Yun Zhang ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Production Efficiency ◽  
Sol Gel ◽  
Microwave Drying ◽  
Remarkable Effect ◽  
Good Thermal Stability ◽  
Pore Structures ◽  
Sol Gel Process ◽  
20 Nm ◽  
Uniform Mesopores

Methylsilsesquioxane aerogels with uniform mesopores have been facilely prepared via a sol–gel process followed by microwave drying with methyltrimethoxysilane (MTMS) as precursor, hydrochloric acid (HCl) as catalyst, water and methanol as solvents, hexadecyltrimethylammonium chloride (CTAC) as surfactant and template and propylene oxide (PO) as gelation agent. The microstructure, chemical composition and pore structures of the resultant MSQ aerogels were investigated in detail to achieve controllable preparation of MSQ aerogels, and the thermal stability of MSQ aerogels was also analyzed. The gelation agent, catalyst, solvent and microwave power have important roles on pore structures of MSQ aerogels. Meanwhile, microwave drying method is found to not only have a remarkable effect on improving production efficiency, but also be conducive to avoid the collapse of pore structure especially micropores during drying. The resulting MSQ aerogel microwave-dried at 500 W possesses a specific surface area up to 821 m2/g and a mesopore size of 20 nm, and displays good thermal stability.

scholarly journals Preparation and Characterization of Transparent Polyimide–Silica Composite Films Using Polyimide with Carboxylic Acid Groups

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 489 ◽  
Author(s):  
Kwan Moon ◽  
Boknam Chae ◽  
Ki Kim ◽  
Seung Lee ◽  
Young Jung
Keyword(s):  
Thermal Stability ◽  
Carboxylic Acid ◽  
Coefficient Of Thermal Expansion ◽  
Condensation Reaction ◽  
Sol Gel ◽  
Composite Films ◽  
Amic Acid ◽  
Good Thermal Stability ◽  
Silica Composite ◽  
Sol Gel Process

Polyimide (PI) composite films with thicknesses of approximately 100 µm were prepared via a sol–gel reaction of 3-aminopropyltrimethoxysilane (APTMS) with poly(amic acid) (PAA) composite solutions using a thermal imidization process. PAA was synthesized by a conventional condensation reaction of two diamines, 3,5-diaminobenzoic acid (DABA), which has a carboxylic acid side group, and 2,2′-bis(trifluoromethyl)benzidine (TFMB), with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) in N,N-dimethylacetamide (DMAc). The PAA–silica composite solutions were prepared by mixing PAA with carboxylic acid side groups and various amounts of APTMS in a sol–gel process in DMAc using hydrochloric acid as a catalyst. The obtained PI–silica composite films showed relatively good thermal stability, and the thermal stability increased with increasing APTMS content. The optical properties and in-plane coefficient of thermal expansion (CTE) values of the PI–silica composite films were investigated. The CTE of the PI–silica composite films changed from 52.0 to 42.1 ppm/°C as the initial content of APTMS varied. The haze values and yellowness indices of the composite films increased as a function of the APTMS content.

Synthesis and Thermal Stability of Nontransformable Tetragonal (ZrO2)0.96(REO1.5)0.04 (Re=Sc3+, Y3+) Nanocrystals

2013 ◽  
Vol 334-335 ◽  
pp. 60-64 ◽  
Author(s):  
Mohammad Reza Loghman-Estark ◽  
Reza Shoja Razavi ◽  
Hossein Edris
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Scanning Electron Microscopy ◽  
Sol Gel ◽  
Average Diameter ◽  
X Ray ◽  
Transmission Electron ◽  
20 Nm ◽  
Thermal Stability Of ◽  
Scanning Electron

Scandia, yttria doped zirconia ((ZrO2)0.96(REO1.5)0.04(RE=Sc3+, Y3+)) nanoparticles were prepared by the modified sol-gel method. The microstructure of the products was characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Thermal stabillity of SYSZ nanocrystals were also investigated. The SYSZ nanocrystals synthesized with EGM:Zr+4mole ratio 4:1, calcined at 700°C, have average diameter of ~20 nm.

Studies on Preparation and Property of 2.5D SiO2f/ SiO2 Composites

2009 ◽  
Vol 79-82 ◽  
pp. 1767-1770 ◽  
Author(s):  
Shu Ang Han ◽  
Kai Hui Jiang ◽  
Jun Wu Tang
Keyword(s):  
Dielectric Properties ◽  
Flexural Strength ◽  
Process Parameters ◽  
Sol Gel ◽  
Microwave Drying ◽  
Optimal Parameters ◽  
Optimal Process ◽  
The Real ◽  
Sol Gel Process ◽  
5 Ghz

In this paper, 2.5D SiO2f/SiO2 composites were fabricated via sol-gel process employing 2.5D braided silica fiber fabrics as reinforcements and high pure silicasol as slurry. The process parameters are optimized and the optimal parameters are as follows: the silicasol of 30.8 wt. % as slurry, microwave drying, and sintering at 900 °C. Utilizing the optimal process parameters, the density and the flexural strength of the composites can reach 1.65 g•cm-3 and 80.68 MPa respectively. Dielectric properties of the 2.5D SiO2f/SiO2 composites were also measured, and the real part of the permittivity is 3.40 at 5 GHz. The excellent mechanical and dielectric properties of the 2.5D SiO2f/SiO2 composites can well meet the requirements of radome materials.

Effect of Cores on Photoluminescence of Hybrid SiO2-Coated CdTe Quantum Dots

2020 ◽  
Vol 20 (9) ◽  
pp. 5478-5485
Author(s):  
Cong Xie ◽  
Yubin Zhao ◽  
Yuxiang Song ◽  
Yingjie Liu ◽  
Yaya Wang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Stability ◽  
Sol Gel ◽  
Quantum Yields ◽  
Core Shell ◽  
Aqueous Synthesis ◽  
Pl Spectra ◽  
Cdte Qds ◽  
Sol Gel Process ◽  
20 Nm

Compared with conventional semiconductor quantum dots, hybrid SiO2 coated CdTe QDs exhibited high stability, long fluorescent lifetime, high photoluminescence quantum yields, and well biocompatibility. In this paper, CdTe QDs with tunable PL from green to red emitting were prepared by an aqueous synthesis. A sol–gel process resulted in CdTe QDs coated with a hybrid SiO2 shell contained CdS-like clusters to obtain red-shifted PL spectra, increased PL efficiency and high stability. The clusters were formed by the reaction of Cd2+ and S2− ions generated via the decomposition of thioglycolic acid. The clusters around CdTe cores created a core–shell structure which is very similar with traditional semiconductor core–shell QDs. After being coated with a hybrid SiO2 shell, the PL of green-emitting naked CdTe QDs was red-shifted largely (~30 nm) while the PL of yellowemitting CdTe QDs revealed a small red-shifted (~20 nm). Furthermore, The PL of red-emitting naked CdTe QDs was red-shifted much small (less than 10 nm). This phenomenon is ascribed to the change of band gap of CdTe cores with sizes. The red-shift of PL spectra is attributed to the CdS-like clusters around the core rather than the thickness of the hybrid SiO2 shell.

Pd/SiO2 Organic-Inorganic Hybrid Materials by Sol-Gel Method: Preparation and Thermal Stability under H2 Atmosphere

2015 ◽  
Vol 1118 ◽  
pp. 20-27
Author(s):  
Jing Yang ◽  
Bao Song Li ◽  
Xiang Huo ◽  
Hao Xu ◽  
Hai Yun Hou
Keyword(s):  
Thermal Stability ◽  
Calcination Temperature ◽  
Hybrid Materials ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Inorganic Hybrid ◽  
X Ray ◽  
Good Thermal Stability ◽  
Pd Doping

Pd/SiO2 organic-inorganic hybrid materials were prepared by adding PdCl2 into methyl-modified silica sol. The Pd/SiO2 hybrid materials were characterized by X-ray diffraction (XRD), fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The effects of calcination temperature and Pd-doping on the phase transition of Pd element and the thermal stability of CH3 group in the Pd/SiO2 organic-inorganic hybrid materials were investigated. The results showed that the reduced metallic Pd0 exhibits good thermal stability under H2 atmosphere in the calcination process. Pd element in noncalcined Pd/SiO2 materials exists in PdCl2 form, calcination at 200 °C in a H2 atmosphere produces some metallic Pd0 and calcinations at 350 °C results in the complete transformation of Pd2+ to metallic Pd0. With the increase of calcination temperature, the Pd0 particle sizes increase and the hydrophobic Si−CH3 bands decrease in intensity. As the calcination temperature is greater than or equal to 350 °C, the loading of metallic Pd0 nearly has no influence on the chemical structure but, with the increase of Pd content, the formed Pd0 particle size increases. To keep the hydrophobicity of Pd/SiO2 membrane materials, the optimal calcination temperature is about 350 °C under H2 atmosphere.

Synthesis and Second-Order Optical Nonlinearity of Inorganic-Organic Hybrid Films Bearing Y-Type NLO Active Chromophore

2007 ◽  
Vol 336-338 ◽  
pp. 552-554
Author(s):  
Xiao Nan Mei ◽  
Hai Yao Lin ◽  
Yuan Jing Cui ◽  
Ping Lv ◽  
Guo Dong Qian
Keyword(s):  
Thermal Stability ◽  
Sol Gel ◽  
Optical Nonlinearity ◽  
Second Order ◽  
Inorganic Materials ◽  
Hybrid Films ◽  
Organic Hybrid ◽  
Type Silicon ◽  
Sol Gel Process ◽  
Organic Chromophore

In order to achieve a large hyperpolarizability (β) value and thermal stability, a novel Y-type silicon precursor ICTES-DBPNPI was synthesized. By the sol-gel process, the new organic-inorganic materials having organic chromophore were prepared.

Preparation and Characterization of Silica-Coated ZnSe Nanowires with Thermal Stability and Photoluminescence

2007 ◽  
Vol 7 (12) ◽  
pp. 4494-4500 ◽  
Author(s):  
Shenglin Xiong ◽  
Baojuan Xi ◽  
Weizhi Wang ◽  
Hongyang Zhou ◽  
Shuyuan Zhang ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Volume Ratio ◽  
Silica Coating ◽  
Sol Gel Process ◽  
High Resolution Tem ◽  
Potential Applications ◽  
Znse Nanowires

Silica-coated ZnSe nanowires with well-controlled the thickness of sheath in the range of 10–60 nm have been synthesized through a simple sol–gel process. The thickness of silica coating could be controlled through altering reaction parameters such as volume ratio of TEOS and ammonia. XRD, high-resolution TEM, X-ray photoelectron spectroscopy (XPS), Raman spectra, thermogravimetric analysis (TGA), and photoluminescence (PL) spectra were used to characterize the core/sheath nanostructures. Room-temperature PL measurements indicate these silica-coated ZnSe nanowires remarkably improve the PL intensity. Meanwhile, the thermal stability has been enhanced greatly, which is useful for their potential applications in advanced semiconductor devices.

scholarly journals Insulating Thermal and Water-Resistant Hybrid Coating for Fabrics

Coatings ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 72 ◽  
Author(s):  
Simona Ortelli ◽  
Anna Luisa Costa
Keyword(s):  
Thermal Stability ◽  
Sol Gel ◽  
Hybrid Coating ◽  
Inorganic Hybrid ◽  
Tio2 Nps ◽  
Nonwoven Fabrics ◽  
Burn Out ◽  
Sol Gel Process ◽  
Coated Fabrics

Organic–inorganic hybrid (ceramer) coatings were synthesized and deposited on the polyester nonwoven fabrics through the sol–gel process. This promoted the formation of an insulating barrier that was able to enhance the thermal stability and the hydrophobicity of fabrics. The hybrid phase is made of an organic network arising from different alkoxysilane precursors (trimethoxymethylalkoxysilane (TMEOS), 3-aminopropyl-trimethoxyalkoxysilane (APTMS), and tetraethylorthosilicate (TEOS)) and inorganic phase made of titanium dioxide TiO2 nanoparticles (NPs) and, in some cases, coated by P-based compound. The characterization of hybrid phase at liquid (size distribution and zeta potential of dispersed nanoparticles), dried state (crystalline phase, thermogravimetric (TGA), and Fourier transform infrared spectroscopic (FTIR) analyses), and on deposited coatings (contact angle, burn-out tests) aimed to find a correlation between the physicochemical properties of ceramer and functional performances of coated fabrics (thermal stability and hydrophobicity). The results showed that all ceramer formulations were able to improve the char formation after burn-out, in particular the highest thermal stability was obtained in the presence of TMEOS precursor and TiO2 NPs coated by P-based compound, which also provided the highest hydrophobicity. In conclusion, we presented an environmentally friendly and easily scalable process for the preparation of ceramer formulations capable of being formed into transparent, thermal-resistant, and hydrophobic fabric coatings, whose functions are extremely challenging for the textile market.

Hybrid Nanocomposite Coatings for Application in Construction Materials: Tribological Study

2009 ◽  
Vol 151 ◽  
pp. 234-239 ◽  
Author(s):  
Celia Silvestre ◽  
M.J. López-Tendero ◽  
Manuel Cruz-Yusta ◽  
Noelia Baeza ◽  
Celia Guillem ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Sol Gel ◽  
Construction Materials ◽  
Hybrid Coatings ◽  
Nanocomposite Coatings ◽  
Hybrid Nanocomposite ◽  
Simultaneous Formation ◽  
Inorganic Hybrid ◽  
Good Thermal Stability ◽  
Construction Products

The Nanocomposite group of AIDICO and the Nanomaterials Group of University of Valencia collaborate in the research of new organic-inorganic hybrid materials with application in construction products. Tribological properties and good thermal stability are some of the required specifications for such applications. Some hybrid coatings based on simultaneous formation of epoxy and silica networks are introduced in this work. Elastic modulus and hardness obtained from TDMA analyses and indentation techniques, together with thermal stability by TGA, are the main properties analysed in order to fulfil the requirements for construction coating applications. New routes for obtaining these coatings based on sol-gel have been explored.

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