Comparative Analyses of the Influence of TEOS Additives on the Sintering Kinetics of Nd: YAG Transparent Ceramics

In this work, the sintering kinetics of Nd: YAG transparent ceramics under the vacuum environment was studied by the high-temperature solid phase method. The effects of different sintering temperatures and TEOS content on the densification process of Nd: YAG ceramics were studied. Meanwhile, the crystal structure of Nd: YAG transparent ceramics doped with different contents of TEOS was studied by X-ray diffractometer (XRD) and differential thermal analysis (DTA). The micrographs of ceramics samples were analyzed by scanning electron microscope (SEM). The green sample is heated to 1450~1650°C for 0~2 h at a heating rate of 20°C/min in a vacuum environment (P T ≤ 10 -6 Pa), and the shrinkage of ceramic samples was analyzed in the vacuum atmosphere by the Johnson sintering model. The sintering activation energy of Nd: YAG transparent ceramics doped with different contents of TEOS was obtained. The results indicated that the addition of TEOS promoted the densification of ceramic samples. The grain size and relative density of ceramic samples increased, and the sintering activation energy decreased with the increase of TEOS content.

Plasma Treatment and TEOS Modification on Wood Flour Applied to Composite of Polyvinyl Chloride/Wood Flour

In this work, the effects of wood flour and tetraethyl orthosilicate (TEOS) content on the fusion time, fusion torque, fusion temperature, and fusion energy of polyvinyl chloride/wood flour (PVC/WF) composites were studied. Plasma-assisted surface treatment of WF before modifying with TEOS to form the silica nanoparticles on the surface of wood flour plays a role as a reinforcement of the phase interaction. This modification was confirmed by X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM) techniques. Moreover, BET data showed that specific surface area and volume of plasma treated WF and TEOS modified WF (WS) were considerably improved in comparison with original WF. By increasing WF, a remarkable increase in time, temperature, and energy of mixing process led to the enhancement of fusion torque. In the case of composite using WS, the increase of TEOS content resulted in shorter fusion time, whereas the other fusion characteristics of composites increased. The investigation of mechanical and rheological properties such as Young’s modulus and dynamic storage modulus G′ showed the stiffness of the PVC/WF composites has been significantly improved with increasing wood flour and modifier contents. The research showed an application of nanoparticles in the industrial production of polymer composite materials.

Formation of Zn- and Si-Based Oxide Systems: Analysis of Temperature Dependence of the Energy State

This article presents the results of the thermal analysis of dried colloidal solutions based on zinc nitrate with changes in tetraethoxysilane (TEOS) content. The main stages of the thermal decomposition of the dried sols were established and the activation energies of each stage were determined based on the results of thermogravimetric measurements using the Erofeev-Kolmogorov approach. For each stage, the products of thermal destruction in the gas phase were determined by mass-spectrometry. It was shown that the chemical decomposition in all samples started at a temperature above 200°C, and the temperature of zinc hydroxonitrate decomposition increased with increasing TEOS content in the ash, while the activation energy of that process decreased. X-ray diffraction analysis revealed that the thermal decomposition of dried sols at 600°C resulted in the formation of mixtures of ZnO in hexagonal syngony with amorphous SiO2 in amounts from 10 to 50 wt%.

Production of Light Olefins Through Catalytic Cracking of C5 Raffinate Over Surface-Modified ZSM-5 Catalyst

Surface modification of phosphorous-containing porous ZSM-5 catalyst (P/C-ZSM5-Sil.(X)) was carried out by a chemical liquid deposition (CLD) method using tetraethyl orthosilicate (TEOS) as a silylation agent. Different amount of TEOS (X = 5, 10, 20, and 30 wt%) was introduced into P/C-ZSM5il.(X) catalysts for surface modification. The catalysts were used for the production of light olefins (ethylene and propylene) through catalytic cracking of C5 raffinate. It was found that external surface acidity of P/C-ZSM5-Sil.(X) catalysts significantly decreased with increasing TEOS content. In the catalytic reaction, both conversion of C5 raffinate and yield for light olefins showed volcano-shaped curves with respect to TEOS content. Among the catalysts tested, P/C-ZSM5- Sil.(20) catalyst exhibited the best catalytic performance in terms of conversion of C5 raffinate and yield for light olefins. Thus, an optimal TEOS content was required for CLD treatment to maximize light olefin production in the catalytic cracking of C5 raffinate over P/C-ZSM5-Sil.(X) catalysts.

Preparation of SiO2/PMMA Organic-Inorganic Hybrid Membrane via Microemulsion Situ Polymerization Technology

SiO2 nanoparticles was synthesized by F127/MMA/(NH3+H2O)/TEOS inverse microemulsion, the formation and morphology of nanoparticles were analyzed by Ultraviolet-visible spectrum and transmission electron microscopy, and scanning electron microscope. The results showed that SiO2 nanoparticles were spherical structure and its average particle size was about 25 nanometers. The number of SiO2 nanoparticles in the microemulsion and hybrid membrane was increased slightly with the increase of TEOS content. However, agglomeration of SiO2 nanoparticles appeared in the hybrid membranes at high TEOS content.

Removal of cadmium and copper ions by Trichosporon cutaneum R57 cells immobilized onto polyvinyl alcohol/tetraethoxysilane hybrid matrices

Polyvinyl alcohol (PVA) and tetraethoxysilane (TEOS) hybrid materials were prepared by sol-gel methods and tested as matrices for immobilization of Trichosporon cutaneum R57, capable of removing cadmium and copper ions from aqueous solutions. A kinetic model was applied and the effects of matrix TEOS content on the copper and cadmium uptake equilibria and rate constants were investigated.

Fabrication of the Monolithic Silica Aerogels Using Sodium Silicate and its Network Strengthening

Silica wet gels were prepared from water glass (29 wt.% SiO2) by using Amberlite as a ion exchange resin. After washing in distilled water, the wet gels were further aged in a solution of TEOS/EtOH to strengthen the 3-dimensional network structure. With the increasing TEOS content in aging solution, BET surface area and porosity of the ambient dried silica aerogel were decreased, and the average pore diameter was decreased from 30nm to 10nm. Also, higher density and compressive strength were obtained in case of higher TEOS content. This is due to the precipitation of SiO2 nano particle by TEOS. Hence, TEOS addition plays an important role in both strengthening and increasing stiffness of silica wet gel network. By adding 30 vol.% TEOS, a crack-free monolithic silica aerogel tiles were obtained and its density, compressive strength, and thermal conductivity were shown 0.232 g/cm3, 7.3 MPa, and 0.029 W/mK, respectively.

Strengthening of Water Glass Based Aerogel by TEOS

In order to prevent the irreversible collapse of the silica aerogel backbone upon the drying of the liquid phase of silica wet gel derived from water glass based silicic acid, we tried to strengthen the aerogel back bone by aging silica wet gels in water and TEOS/ethanol solutions. Although aging of silica wet gels in water has been shown to grow the neck between silica particles of the aerogel backbone, it is hard to obtain a crack-free aerogel monolith. On the other hand, the mechanical stability of silica aerogels was improved significantly by aging the wet gel in TEOS/ethanol solutions with different TEOS content.

Effect of Silica Content in the PMMA/Silica Nano-Composite on the Mechanical Properties and Growth Behavior of Calcium Phosphate Crystals during Cell Culture

The effect of silica content in the PMMA/silica nano-composite on the mechanical properties and the growth behavior of apatite crystals were investigated. The PMMA/silica nano-composites with different silica content were synthesized through the sol-gel reaction with triethoxysilane end-capped PMMA and tetraethyl orthosilicate (TEOS). The compressive strength showed its maximum value when the content of TEOS was 20 wt% while the elastic modulus showed its maximum value when the content of TEOS was 60 wt%. The growth behavior of the apatite crystals following the cell culture showed different response according to the silica content. As increasing the TEOS content, the shape of the apatite crystals changed from globule-like structure to fiber-like one.