Silica nanoparticles in high silica/alkali molar ratio solutions as fire-retardant impregnants for woods

2009 ◽  
pp. n/a-n/a ◽  
Author(s):  
Carlos A. Giudice ◽  
Andrea M. Pereyra
Keyword(s):  
Silica Nanoparticles ◽  
Fire Retardant ◽  
Molar Ratio ◽  
High Silica

scholarly journals Hierarchical Low Si/Al Ratio Ferrierite Zeolite by Sequential Postsynthesis Treatment: Catalytic Assessment in Dehydration Reaction of Methanol

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Enrico Catizzone ◽  
Massimo Migliori ◽  
Alfredo Aloise ◽  
Rossella Lamberti ◽  
Girolamo Giordano
Keyword(s):  
Textural Properties ◽  
Vapour Phase ◽  
Solution Concentration ◽  
Methanol Conversion ◽  
Molar Ratio ◽  
Light Hydrocarbons ◽  
Hierarchical Zeolites ◽  
Type Zeolite ◽  
High Silica ◽  
High Silica Zeolites

In contrast to high silica zeolites, it is difficult to obtain mesoporosity in zeolites with low Si/Al ratio (e.g., <20) via conventional NaOH-based treatment, making the obtainment of hierarchical zeolites with high acidity a challenging target. In this paper, we report the preparation of hierarchical FER-type zeolite at low Si/Al molar ratio (about 10) by postsynthesis etching involving a sequence of three treatments with NaAlO2, HCl, and NaOH solutions and investigate the effect of both NaAlO2 solution concentration and time of treatment on the textural properties. The obtained materials exhibit a mesoporous volume higher than the parent ferrierite with no significant effect on the sample acidity. The catalytic activity of some samples was investigated in vapour-phase methanol dehydration to dimethyl ether, revealing the superiority of hierarchical zeolites in terms of methanol conversion, although the presence of mesopores causes formation of light hydrocarbons at high temperatures.

Encapsulation of silica nanoparticles by poly(methyl methacrylate-co-styrene) via emulsion polymerization using dimethylaminoethyl methacrylate

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Mohammad Barari ◽  
Naser Sharifi-Sanjani
Keyword(s):  
Methyl Methacrylate ◽  
Silica Nanoparticles ◽  
Emulsion Polymerization ◽  
Monomer Concentration ◽  
Molar Ratio ◽  
Average Particle ◽  
Scanning Calorimetry ◽  
Potential Measurement ◽  
Emulsion Copolymerization ◽  
Dimethylaminoethyl Methacrylate

AbstractEncapsulation of silica nanoparticles was performed by emulsion copolymerization of methyl methacrylate (MMA) and styrene (St) using dimethylaminoethyl methacrylate (DM) as an auxiliary monomer. The emulsion polymerization was performed in the presence of silica nanoparticles as the seed to obtain encapsulated silica nanoparticles with polymer content and average particle sizes ranged from 35 wt. % to 85 wt. % and 114 to 272 nm respectively. Electrostatic attraction between anionic surface of silica beads and cationic amino groups of DM is the main driving force for the encapsulation of the silica nanoparticles. The influence of MMA, St and DM concentration on the coating of the silica nanoparticles was studied. It was demonstrated that DM has an important role in stabilizing the system. Transmission electron microscopy showed that coreshell structures with silica particles as core were coated with the polymer, of which the amount and morphology were influenced by the total monomer concentration and molar ratio of MMA to St. Zeta potential measurement confirmed the presence of DM on the surface of composite particles. Thermogravimetric analysis showed that the incorporation of silica in polymer matrix results in an enhancement of thermal stability in the encapsulated products. Differential scanning calorimetry studies indicated that the glass transition temperature of encapsulated particles can be either higher or lower than those of the pure terpolymer counterpart, depending on the DM content of the polymer shell. The products were also characterized by FT-IR spectroscopy.

scholarly journals SYNTHESIS OF In-CONTAINING HIGH-SILICA ZEOLITE OF ZSM-5 TYPE

2017 ◽  
Vol 60 (8) ◽  
pp. 84
Author(s):  
Khasay R. Samedov ◽  
Ulviya A. Mamedova ◽  
Kerim G. Ragimov ◽  
Zarema A. Jabbarova
Keyword(s):  
Degree Of Crystallinity ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Solid Product ◽  
X Ray ◽  
Type Zeolite ◽  
High Silica ◽  
Tetrabutylammonium Iodide ◽  
High Degree ◽  
Ratio Of Components

High silicate zeolite ZSM-5 on the basis of SiO2–In2O3–NaOH with an organic structure forming agent tetrabutylammonium iodide (TBAI) was synthesized in the temperature range of T = 150–220°C, pH = 9-12, τ = 48-240 h. As initial components, silica gel MSKO containing 86% SiO2, tetrabutylammonium iodide (TBAI), chemically pure NaOH and metallic indium (In) were used which mixed by hydrothermal synthesis. At the end of the synthesis, the solid product was separated from the mother liquor, washed on the filter with distilled water from an excess of alkali and dried at 120 °C, calcined at 550 °C (16 h). The products of hydrothermal crystallization were determined by X-ray (RFA – on the device D2-Phaser "Bruker"), differential thermal (DTA- STA-449 F3 Jupiter NETZSCH), by X-ray diffraction (XRD of brand SRM-18) and infrared spectroscopy (IR on FTIR spectroscopy, Nicolefisio VSA) analysis methods. During the synthesis, it was experimentally established that at T = 200 °C; τ = 240 h; pH≈9-10 molar ratio of components 5.78SiO2∙0.058In2O3∙0.625Na2O∙0.11H2O∙0.95 ((C4H9) 4NJ) – MFI-type zeolite is crystallized. When comparing XRF data with literature data, they were referred to a type zeolite of ZSM-5 differing in high degree of crystallinity. The following chemical composition of the synthesized zeolite (wt.%) was established by the X-ray diffraction (SRM-18) method: SiO2 – 94.01; In2O3 – 4.92; Na2O – 1.06 corresponding to the formula 0.96Na2O:In2O3:88SiO2:10H2O.Forcitation:Samedov Kh.R., Mamedova U.A., Ragimov K.G., Jabbarova Z.A. Synthesis of In-containing high-silica zeolite of ZSM-5 type.Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 8. P. 84-87.

Enhanced Specific Heat Capacity of Nanomaterials Synthesized by Dispersing Silica Nanoparticles in Eutectic Mixtures

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Donghyun Shin ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Capacity ◽  
Specific Heat ◽  
Silica Nanoparticles ◽  
Specific Heat Capacity ◽  
Solid Phase ◽  
Thermal Power ◽  
Lithium Carbonate ◽  
Molar Ratio ◽  
Heat Capacity Measurements ◽  
The Cost

Anomalous enhancements in the specific heat capacity values of nanomaterials were measured in this study. Silica nanoparticles (∼2–20 nm) were dispersed into eutectic of lithium carbonate and potassium carbonate (62:38 by molar ratio) at 1.5% mass concentration. The specific heat capacity measurements were performed using a differential scanning calorimeter (DSC). The specific heat capacity of the silica nanocomposite (solid phase) was enhanced by 38–54% and the specific heat of the silica nanofluid (liquid phase) was enhanced by 118–124% over that of the pure eutectic. Electron microscopy of the samples shows that the nanoparticles induce phase change (forms a higher density “compressed phase”) within the solvent material. Hence, a new model is proposed to account for the contribution of the compressed phase to the total specific heat capacity of the nanomaterials. The proposed model is found to be in good agreement with the experimental data. These results have wide ranging implications, such as for the development of efficient thermal storage systems that can enable significant reduction in the cost of solar thermal power.

Fabrication of Chitosan-coated Mesoporous Silica Nanoparticles Bearing Rosuvastatin as Drug Delivery System

2021 ◽  
Vol 18 ◽  
Author(s):  
Mojdeh Rahnama Ghahfarokhi ◽  
Ghasem Dini ◽  
Behrooz Movahedi
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Mesoporous Silica ◽  
Specific Surface ◽  
Silica Nanoparticles ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Mesoporous Silica Nanoparticles ◽  
Molar Ratio

Aim: In this work, to improve the solubility and bioavailability of the rosuvastatin (RSV) drug, chitosan-coated mesoporous silica nanoparticles (CS-MSNs) as drug delivery systems were fabricated. Methods: To do this, first MSNs with a maximum specific surface area were synthesized from sodium silicate as silica source and different molar ratios of cethyl trimethylammonium bromide (CTAB) and pluronics (P123, PEO20PPO17PEO20) as surfactants via the sol-gel process. Then, the synthesized MSNs were coated by CS polymer with the help of (3-glycidoxypropyl)methyldiethoxysilane (GPTMS) as a linker between MSNs and CS. Subsequently, the RSV drug was loaded into the synthesized CS-coated MSNs. The products were characterized by different techniques, including X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR). The in vitro drug release profile of the fabricated DDS was evaluated in a typical phosphate-buffered saline (PBS) solution at different pH values (i.e., 4, 6, and 7.4) for 48 h. To assess the cytotoxicity, the viability of the human fibroblast cells exposed to the fabricated DDS was also examined. Results: The results showed that at an optimal molar ratio of P123/CTAB, the amorphous MSNs with a specific surface area of about 1080 m2/g, a pore diameter of 4 nm, a pore volume of 1.1 cm3/g, and an average size of about 30 nm were synthesized. Also, the presence of all the components, including the CS coating and the RSV drug, was confirmed in the structure of the fabricated DDS by FTIR analysis. Due to the pH-responsive feature of the CS coating, the RSV drug release from the fabricated DDS showed a reasonable environmental response; as the pH value of the PBS solution decreased, the degree of drug release increased. Conclusion: The CS coating enhanced the cytotoxicity of the fabricated DDS and led to sustainable drug release behavior, which would provide a beneficial approach for drug delivery technology.

Sol-Gel Synthesis of Amorphous Silica Nanoparticles: Study of the Process Parameters Influence on Structure and Particle Size Distribution

2018 ◽  
Vol 912 ◽  
pp. 77-81
Author(s):  
Renata Deliberato Aspasio ◽  
Jairo Freitas da Silva Jr. ◽  
Roger Borges ◽  
Juliana Marchi
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Silica Nanoparticles ◽  
Size Distribution ◽  
Functional Groups ◽  
Process Parameters ◽  
Amorphous Silica ◽  
Sol Gel ◽  
Molar Ratio ◽  
Sol Gel Synthesis

The synthesis of silica particles at the nanoscale through the sol-gel method is of great interest due to their potential use in industrial applications. The Stöber method is the most used method for the silica nanoparticles production using ammonia as a catalyst. This work studied the sol-gel synthesis of amorphous silica nanoparticles described by Stöber, in order to evaluate the influence of the variation of the process parameters (molar ratio water/TEOS = 25 and 55, reagent feed rate = 0.6 mL/min and 18 mL/min, pH = 12 and 9 and reaction time of 0, 5, 30, 60 and 120 minutes) on the particle size distribution and structural functional groups. The particle size distribution was analyzed by dynamic light scattering (DLS) and the structural functional groups was analyzed by infrared spectroscopy through Fourier transform (FTIR). The molar ratio water/TEOS influenced the functional groups presents and the time influenced the particle diameter distribution. It was not possible to identify the influence of the feed rate and pH in the results. The particle diameters found were between 200-500nm. This result may be occurred due to mass diffusion and/or nanoparticles aggregation.

Synthesis and Characterization of Silica Nanoparticles

2007 ◽  
Vol 121-123 ◽  
pp. 49-52 ◽  
Author(s):  
R. Aghababazadeh ◽  
S. Tabatabae ◽  
Ali Shokuhfar ◽  
A.R. Mirhabibi
Keyword(s):  
Electron Microscopy ◽  
Silica Nanoparticles ◽  
Silica Particles ◽  
Alcoholic Solution ◽  
Chemical System ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Monodisperse Colloidal Silica

Currently there are several models discussed to describe the formation of monodispersed silica particles. Monodisperse colloidal silica was prepared from tetraethoxysilane in mixture of ammonia, water and ethanol. Chemical system reaction permits the controlled growth of silica nanoparticles and subsequent condition of silicic acid in alcoholic solution. The molar ratio of NH4OH, C2H5OH and H2O has a significant effect on particle size and specific surface area of silica particles. The nature of particles was evaluated using X-ray diffraction, energy dispersive spectroscopy (EDS) and BET. The morphology of particles were determined by scanning electron microscopy (SEM) and transmission electron microscopy(TEM).

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