Cost-Effective Preparation of Hydrophobic and Thermal-Insulating Silica Aerogels

The aim of this study is to reduce the manufacturing cost of a hydrophobic and heat-insulating silica aerogel and promote its industrial application in the field of thermal insulation. Silica aerogels with hydrophobicity and thermal-insulation capabilities were synthesized by using water-glass as the silicon source and supercritical drying. The effectiveness of acid and alkali catalysis is compared in the formation of the sol. The introduction of sodium methyl silicate for the copolymerization enhances the hydrophobicity of the aerogel. The resultant silica aerogel has high hydrophobicity and a mesoporous structure with a pore volume exceeding 4.0 cm3·g-1 and a specific surface area exceeding 950 m2·g-1. The obtained silica aerogel/fiber-glass-mat composite has high thermal insulation, with a thermal conductivity of less than 0.020 W·m-1·K-1. The cost-effective process is promising for applications in the industrial preparation of silica aerogel thermal-insulating material.

The Influence of Surface Modified Silica Nanoparticles: Properties of Epoxy Nanocomposites

The influence of the surface-modified (CCS) and un-modified (UCS) silica nanoparticles on epoxy nanocomposites were studied. Two different nanocomposites systems were synthesized using tetraethylorthosilicate (TEOS) and 3-(triethoxysilyl) propylamine APTES as a precursor and coupling agent, respectively. In the uncoupled composite system (UCS) the silica particles were solely generated using TEOS as a precursor. The APTES was used as a coupling agent to chemically link the silica (SiO2) particles to the matrix in the coupled composite system (CCS). Both composite systems were fabricated as thin films. The SiO2 epoxy nanocomposites thin films were characterized by Differential Scanning Calorimetry (DSC), RAMAN, Fourier Transform Infra-Red (FT-IR), Scanning Electron Microscopy (SEM) and Thermal Gravimetric (TGA) analysis. RAMAN and FT-IR analysis confirmed the curing of epoxy resin and the generation of the inorganic structural network formation. SEM analysis of these nanocomposites revealed that silica particles were uniformly dispersed in the epoxy matrix. DSC analysis of the nano-composites revealed an increase in glass transition (T g) temperature with the addition of nanofiller. TGA analysis shows enhanced thermal stability of the coupled composite system in comparison to the neat and uncoupled epoxy composite system.

Phytochemical Synthesis of Silver Nanoparticles Using Anthemis Nobilis Extract and Its Antibacterial Activity

In this work, green synthesis of silver nanoparticles is described by phytochemical reducing silver nitrate aqueous solution using Anthemis nobilis. For this purpose, Anthemis nobilis extract was used for the synthesis of silver nanoparticles as both surfactant and reducing agent. Green synthesis method is a good alternative to physical and chemical methods, since it is fast, simple, environmentally-friendly and economic. The produced nanoparticles are identified using FE-SEM, EDX, and FT-IR and Uv/Vis techniques. Formation of silver nanoparticles is verified in 430–420 nm range. Reduction of silver ions by hydroxyl functional group is also confirmed by FT-IR device. EDX device confirms the presence of a peak for Ag element without any impurity peak. Silver nanoparticles are identified by FE-SEM device and found to have average size between 17 and 42 nm. Also, the antibacterial activity of the synthesized nanoparticles is compared with that of staphyloccusaureus and pseudomonasa aeruginosa and the maximum inhibitory activity against the bacteria is obtained using 1 mM nitrate solution.

One-Pot Synthesis and Rheological Study of Cationic Poly (3-acrylamidopropyltrimethyl ammoniumchloride) P(APTMACl) Polymer Hydrogels

The main objective of this research work is to explore the complete and extensive rheological studies of cationic poly (3-acrylamidopropyl trimethyl ammonium chloride) P(APTMACl) hydrogel, prepared by free radical polymerization method at room temperature. Hydrogel was characterized by various techniques such as SEM, FTIR and TGA, whereas rheological properties of synthesized hydrogel were obtained using frequency sweep and frequency curve analysis in different temperature range. Storage modulus (G′) and loss modulus (G′′) were investigated as a function of angular frequencies and shear stress at various temperatures. Rheological models like Bingham plastic model, modified Bingham and Ostwald power law were applied to understand the rheological performance of the gels. Flow curves obtained at different temperatures indicate that P(APTMACl) hydrogel shows a non-Newtonian pseudo plastic behavior. All results concluded that rheology is a powerful tool to study the complete visco-elastic behavior of polymer hydrogel for multiple applications.