Influence Of Silica Content Research Articles

Effect of hydrophobic nano-silica content on the surface properties of corn-starch films

Starch-based films can be used for applications such as single-use packaging for food with a short shelf life. Hence, starch-based films could be a green alternative to some plastic packaging. This study analyzes the influence of hydrophobic silica content on mechanical properties, surface free energy, surface roughness, and morphology of corn starch-based films. For this purpose, commercially available amorphous hydrophobic nano-silica, Aerosil® R972, was used. The lowest value of surface free energy was observed for the starch films with the lowest glycerol and silica content (57 ± 1 mJ·m–2 for CG40S2.5), while the highest value was with the highest glycerol and silica content (73 ± 2 mJ·m–2 for CG80S5.0). The influence of silica content on the tensile strength decreases and elongation at break was investigated. The results showed that the surface roughness increases when the silica content increases. The SEM and EDS observation confirmed the homogeneity of the developed materials. This study shows that the commercially available Areosil® type of silica can be successfully used to change the performance of starch films.

Analysis of the influence of excess cement paste content on the compression strength of UHPC

This research aimed to propose a rational method for dosing ultra-high performance concretes based on the association of three approaches: the definition of the ideal silica content, the use of the minimum paste volume, and the incorporation of fine basalt artificial sand. Through the combination of experimental methods and granular packing models, a robust experimental program consisting of eight steps was developed, aiming to obtain different compositions of ultra-high performance concretes, with self-compacting characteristics and compressive strength greater than 150 MPa at 28 days, after heat water treatment at 90°C. In addition, the influence of silica content, additional paste volume, different types of cure, test ages, and the addition of metallic fibers on the fluidity and strength of the composites were evaluated. Through the proposed method, the average strength of 186 MPa was achieved in the mix containing the minimum volume of paste, 484 kg∕m³ of cement, and 25% silica fume. The results obtained indicate that the proposed method tends to have the best proportion among the component materials, giving rise to traits that fit the international parameters that define the UHPC, but with reduced paste volumes and consumption of binders lower than those identified in the related literature. Through a rational, economic, and sustainable approach, which aims to optimize the use of higher-cost materials and minimize the use of scarce natural resources, the method contributes positively to the technological development of the sector.

Influence of Silica as an Abrasive on Friction Performance of Polyimide-Matrix Composites

This study investigated the friction performance of polyimide-matrix composites with various silica powder contents of different sizes. The friction tests were performed on a pin-on-disk tester at various velocities, ranging from 30 to 160 km/h. The experimental results indicate a silica powder size of 0.25±0.05 mm, a sample of 4 wt.% SiO2 demonstrated a high friction coefficient and better wear performance as compared to a sample without silica. The influence of silica content and powder size on the friction coefficient is directly related to the friction velocity. At low friction velocity (30–90 km/h), the friction coefficient increases as the SiO2 content increases, but decreases with increasing SiO2 particle size. At high friction velocity (90–160 km/h), the content and particle size of SiO2 have little influence on the friction coefficient. Experimental results indicate that large SiO2 particles can effectively hinder the motion of third body, which is advantageous to the formation of a compact third body and to the protection of the friction surface.

Polybenzoxazine/SiO2 nanocomposite coatings for corrosion protection of mild steel

A series of nanocomposite coatings (PBS) consisting of silane functional polybenzoxazine (PB-TMOS) and SiO2 nanoparticles were developed for corrosion protection of mild steel. The influence of silica content on corrosion resistance of PBS coatings was investigated by electrochemical measurements. The surface chemistry of nanoparticles and its effect on morphology of the PBS coating was also studied utilizing Fourier Transforms Infrared Spectroscopy, 29Si Nuclear Magnetic Resonance and Scanning Electron Microscopy analyses. The results indicate that the presence of the covalent bond between nanoparticles and PB-TMOS, greatly improves the interfacial interactions at the polymer/filler interfaces resulting in a better corrosion performance.

Crystallization of monosodium aluminate hydrate from a concentrated aluminate solution containing silica

The influence of silica content in concentrated aluminate solution on the crystallization of monosodium aluminate hydrate (MAH) has been investigated systematically. The resultant crystals were found to be round flakes, with a high silica concentration significantly inhibiting the crystallization. The conversion ratio and the average particle size of MAH crystals decreased with increasing SiO2 concentration in solution. The silicate impurity phases which crystallized simultaneously with MAH were identified as NaAlSiO4 and Na2SiO3 from low silica solution, Ca3Al2Si3O12, Ca3Al2(SiO4)2(OH)4, and Na4Ca4(Si6O18) we obtained when there was a high silica concentration. These phases have a much higher silica content than the more common desilication product Ca3Al2(SiO4)n(OH)12–4n from the Bayer process for alumina production where n is usually below 0.8.

Mechanical and microstructural properties of polystyrene based composites: positron lifetime spectroscopic and DSC studies

Abstract Polystyrene (PS) based composites respectively with cenosphere (CS) and calcium aluminosilicate (CAS) as fillers were studied using the positron lifetime technique to reveal the correlation between free volume, a microstructural property, and mechanical properties of the composites (tensile strength and tensile modulus). The thermal stability of the composites was determined using differential scanning calorimetry. The results showed that addition of CAS filler lead to a significant improvement in the mechanical properties of the composite, whereas addition of CS resulted in improvement in tensile modulus only. Both PS/CAS and PS/CS composites showed enhancement in thermal stability compared with that of the pure PS matrix. The positron results showed that the average free volume size for the PS/CAS composite (at 40 phr CAS) was reduced significantly compared with that of the pure PS. These results are understood in terms of the influence of silica content, filler-matrix interaction, and particle size.

Design simulation and fabrication process of polyimide and polyimide/silica hybrid materials for Rib-type arrayed waveguide grating

This study demonstrated the designed and fabricated results of rib-type polyimide and polyimide–silica hybrid material array waveguide grating (AWG) devices, with refractive indexes of 1.522/1.546/1.522 and 1.4907/1.53/1.4907 as top cladding/core/bottom cladding layers, respectively. Optical measurements indicated that the extinction coefficients of all samples were approximately zero at a 1550 nm wavelength. The coupling losses were−0.74 dB and − 3.28 dB, and the propagation losses were−0.5 4 dB/cm and − 0.21 dB/cm for rib-type polyimide and polyimide/silica hybrid waveguides, respectively. In the micro-compositional and chemical bonding analyses it appeared that the influence of silica content was larger than the Si―N bonds, and silica content played a key role in determining the refractive indexes in polyimide–silica hybrid. It was found that the greater the content of silica the less the refractive index and the less propagation loss when allowing the incorporation of organic polymer networks for reducing light absorption. Meanwhile, the greater nitrogen percentage could contribute to a larger refractive index in polyimide materials.

Influence of silica content in sulfonated polysulfone/ phosphotungstic acid hybrid membranes on properties for fuel cell application

AbstractThe sulfonated polysulfone (SPSU)/phosphotungstic acid (PWA)/silica (SiO2) hybrid membranes were researched for proton exchange membranes. The influence of silica content on the properties of composite membranes was studied in detail. The study displays that inorganic silica particles have a great influence on membrane properties, such as membrane durability, PWA extraction, proton and methanol transport behavior, thermal stability and water uptake. Interestingly, the hybrid membrane with 2 wt.% silica content showed the best results: low PWA extraction, long membrane life time under oxidative condition, high proton conductivity, and low methanol permeability. However, excessive silica content caused a large aggregation of SiO2 particles, leading to the deterioration of membrane properties.

Preparation and characterization of polyimide/silica/silver composite films

Polyimide/silica/silver hybrid films were prepared by the sol-gel method combined with in situ single-stage self-metallization technique. The structure of polyimide films in the thermal curing process and the influence of silica content on the migration and aggregation of silver particles to the surface of hybrid films were investigated. The hybrid films were characterized by transmission electron microscopy, dynamic mechanical thermal analysis, Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy and mechanical measurements. The results indicated that there was no degradation of the polyimide matrix after the formation of silica and silver particles. Silica acted as the nucleus for the silver particles. With increasing silica content, more and more silver particles were kept in the hybrid films instead of being migrated onto the surface of the hybrid films and the reflections of hybrid films decreased gradually.

Fabrication and characterization of plasma-sprayed HA / SiO 2 coatings for biomedical application

Fused silica powder has been mixed with hydroxyapatite (HA) powder and plasma sprayed by using gas tunnel-type plasma jet. The influence of silica content (10 wt% and 20 wt%) on the microstructure and mechanical properties of HA–silica coatings was investigated. For investigating the microstructure and mechanical properties of HA–silica coatings, SUS 304 stainless steel was used as substrate material. The spraying was carried out on roughened substrate in an atmospheric chamber. Scanning electron microscope micrographs of cross-sectioned HA/SiO 2 coatings showed that the sprayed HA coatings with 10 and 20 wt% SiO 2 have dense structure with low porosity compared to the pure HA coatings. On the other hand, as the amount of silica was increased the coatings became denser, harder and exhibited high abrasive wear resistance. The presence of silica significantly improved the adhesive strength of HA/SiO 2 coatings mainly due to the increase in bonding strength of the coating at the interface.

Characterization of thermo-optical and mechanical properties of calcium aluminosilicate glasses

In this work several different compositions of CaO:Al2O3:SiO2 were prepared under vacuum atmosphere to study the glass forming ability of this system as a function of the SiO2 content. Samples containing 25–45wt% of Al2O3, 31–44wt% of CaO, 14–39wt% of SiO2 and 4.1wt% of MgO were prepared in graphite crucibles, for approximately 2h at ∼1600°C. The influence of silica content is discussed in terms of the mechanical properties, glass transition temperature, crystallization temperature, transmittance spectrum, refractive index, mass density, specific heat, thermal diffusivity, thermal conductivity and the temperature coefficient of optical path length change. The results reinforce the idea that these glasses are strong materials, having useful working-temperature range, good combination of thermal, mechanical and optical properties that could be exploited in many optical applications, in particular, as glass laser materials.

Influence of silica content on migration of antidegradants to the surface in NR vulcanizates

Influence of silica content on migration of antidegradants to the surface in NR vulcanizates

Influence of silica content on migration of antidegradants to the surface in NR vulcanizates

Migration of antidegradants to the surface in silica-filled natural rubber (NR) vulcanizates was studied with migration-generating equipment using a vacuum technique. 2,6-Di-t-butyl-4-methyl phenol (BHT), N-phenyl-N′-isopropyl-p-phenylenediamine (IPPD), N-phenyl-N′-(1,3-dimethylbutyl-p-phenylenediamine (HPPD), and wax (n-C23H48, n-C24H50, n-C25H52, and n-C26H54) were employed as antidegradants. The migration rate was found to be dependent on the content of silica in the vulcanizates. IPPD migrates faster than BHT and HPPD irrespective of the content of silica. BHT migrates faster than HPPD at 60 and 80°C, but slower than HPPD at 100°C. The migration rates of BHT, IPPD, and HPPD decrease with increase of the silica content from 30 to 70 phr. Wax with a low molecular weight migrates faster than that with a high molecular weight. The migration rate of n-C23H48, irrespective of migration temperature, decreases with increase of the silica content, similar to BHT, IPPD, and HPPD, but those of n-C25H52 and n-C26H54 have a local maximum at 50 phr silica content. The activation energies for migration to the surface in the vulcanizate containing 50 phr of silica are 19.3, 28.7, 40.1, 42.2, 51.6, 58.8, and 65.5 kJ/mol for BHT, IPPD, HPPD, n-C23H48, n-C24H50, n-C25H52, and n-C26H54, respectively. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1821–1828, 1998

Influence of Silica Content on Liquid Phase Sintering of Silicon Carbide with Yttrium-Aluminum Garnet

Densification of SiC with oxide additives is affected mainly by the amounts of free C and SiO2 contained in the starting powders. In this study, the influence of oxidation of starting powders on densification was investigated. Oxidation of SiC powders, prior to liquid phase sintering, increased the oxygen content and decreased the carbon content remarkably, and led to higher sintered density for both α- and β-SiC. Higher sintered density was attributed to the formation of liquid at lower temperatures and the suppression of reactions between the free C and oxide additives.

DC Electrical Conductivity in Sodium and Potassium Galliosilicate Glasses

The dc electrical conductivity of several series of sodium and potassium galliosilicate glasses was measured. The property/composition relations observed in the present study are similar to those found for alkali aluminosilicate glasses, thus suggesting a similarity in the structural roles of aluminum and gallium ions. The present data are discussed in terms of this role. In addition, the influence of silica content, alkali content, and alkali identity on the electrical properties of these glasses is discussed.

Viscosity and Thermal Expansion of Sodium and Potassium Galliosilicate Glasses

The transformation‐range viscosity and thermal expansion behavior of several series of sodium and potassium galliosilicate glasses were studied. The trends observed in the results are similar to those found for alkali aluminosilicate glasses. This result suggests a similarity in the structural roles of aluminum and gallium ions. The present data are discussed in terms of this structural role. In addition, the influence of silica content, alkali content, and alkali identity on the thermal properties of these glasses is discussed.

Influence of Silica Content on the Surface Charge Characteristics of Allophanic Clays

AbstractThe surface and charge characteristics of 6 allophanic clays originating from a climatosequence of Andisols have been studied by titration, ion retention, surface area, and reactivity measurements. Several properties of these clays, such as the pH of zero charge, the magnitude of the surface area, and the reactivity of structural hydroxyl groups, appear to be governed by their chemical composition, especially by their silica content. A similar relationship between the above properties and silica content also exists for synthetic aluminosilicate gels (often quoted in the literature as possible models of allophanes), despite their different structure to the natural clays. An explanation is that as desilication proceeds, octahedral polymeric units of aluminum progressively individualize in both the synthetic and natural samples. The surface areas of the aUophanic clays, based on the slope of the titration curve at pH 7, are closely related to the amounts of structural hydroxyl that can react with fluoride at about the same pH. The permanent negative charges are always very low, even for silica-rich, allophane-bearing samples. It is therefore suggested that all of these clays should be virtually free of tetrahedral aluminum.