• Applied Chemistry for Engineering
• /
• v.21 no.5
• /
• pp.514-521
• /
• 2010

A new one-shot process was employed to fabricate proton exchange membranes (PEMs) over conventional solvent-casting process. Here, PEMs containing nano-dispersed silica nanoparticles were fabricated using one-shot process similar to the bulk-molding compounds (BMC). Different components such as reactive dispersant, urethane acrylate nonionmer (UAN), styrene, styrene sulfuric acid and silica nano particles were dissolved in a single solvent dimethyl sulfoxide (DMSO) followed by copolymerization within a mold in the presence of radical initiator. We have successfully studied the water-swelling and proton conductivity of obtained nanocomposite membranes which are strongly depended on the surface property of dispersed silica nano particles. In case of dispersion of hydrophilic silica nanoparticles, the nanocomposite membranes exhibited an increase in water-swelling and a decrease in methanol permeability with almost unchanged proton conductivity compared to neat polymeric membrane. The reverse observations were achieved for hydrophobic silica nanoparticles. Hence, hydrophilic and hydrophobic silica nanoparticles were effectively dispersed in hydrophilic and hydrophobic medium respectively. Hydrophobic silica nanoparticles dispersed in hydrophobic domains of PEMs largely suppressed swelling of hydrophilic domains by absorbing water without interrupting proton conduction occurred in hydrophilic membrane. Consequently, proton conductivity and water-swelling could be freely controlled by simply dispersing silica nanopartilces within the membrane.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.31 no.1
• /
• pp.47-56
• /
• 2023

This study describes the successful synthesize strategy for the silica nanoparticles utilizing various water sources, including tap, industrial, and stream waters without using deionized water. Also, as-synthesized silica nanoparticles are employed as dispersive materials for the electro-responsive smart fluid application. Specifically, homogeneous silica nanoparticles with sizes of 500-700nm are successfully prepared in large scale at once (ca. 12.0 g) with the described experimental method and showing similar structural and chemical characteristics with silica nanoparticles synthesized using the deionized water. The size of silica nanoparticles are varied according to the ion conductivity differences of tap, industrial, stream water, and deionized water. The size of silica nanoparticles decresed with the increased ion conductivity, indicating the ion suppression of growth of silica nanoparticles. Moreover, as-synthesized silica nanoparticles from various water sources of electro-responsive characteristic are investigated by the smart fluid application. The smart fluids containing silica nanoparticles synthesized by tap, industrial, and stream water exhibited higher shear stress compared to the deionized water, owing to the more rigid fibril-like structures formed by the smaller silica nanoparticles. Conclusively, uniform silica nanoparticles from various water sources without any purification are able to successfully prepared without usage of deionized water and resulting silica nanoparticles manifested higher electro-responsive performance.

• Journal of Powder Materials
• /
• v.25 no.5
• /
• pp.420-425
• /
• 2018

Core-shell structured nanoparticles are garnering attention because these nanoparticles are expected to have a wide range of applications. The objective of the present study is to improve the coating efficiency of gold shell formed on the surface of silica nanoparticles for $SiO_2@Au$ core-shell structure. For the efficient coating of gold shell, we attempt an in-situ synthesis method such that the nuclei of the gold nanoparticles are generated and grown on the surface of silica nanoparticles. This method can effectively form a gold shell as compared to the conventional method of attaching gold nanoparticles to silica particles. It is considered possible to form a dense gold shell because the problems caused by electrostatic repulsion between the gold nanoparticles in the conventional method are eliminated.

• Advances in nano research
• /
• v.16 no.1
• /
• pp.71-79
• /
• 2024

Nanotechnology is the latest technology developed by humanity, trying to use the molecular properties of materials found in nature to create devices that solve the problems plaguing humanity and their efficiency. Man is also trying to change the meaning of molecules to nano so that a body made up of these particles has all the properties of these particles. Nanotechnology is not a new field but a new approach in all areas. A new perspective in concrete technology has been created by the use of nanoparticles in recent years. Adding silica nanoparticles to concrete mixes improves its properties and increases its strength. However, different results and reported mechanisms explain the behavior of nanoparticles in the mixture; Therefore, it took much work to generalize the results and predict the behavior of nano concretes. This article is about the construction simulation technology of civil engineering based on artificial intelligence, which deals with the effect of nanoparticles on improving concrete properties. This was demonstrated by analyzing laboratory samples in various mixture configurations and observing how silica nanoparticles affected their microstructure with scanning electron microscopy (SEM). Based on SEM measurements, silica nanoparticles have a powerful effect because of their specific surface area. Their increase and decrease must be sought in interacting with the filling and nucleation mechanism and the pozzolanic activity. Each of these mechanisms dominates at different ages of hydration and affects the microstructure and mechanical properties of concrete.

• Advances in nano research
• /
• v.14 no.2
• /
• pp.117-126
• /
• 2023

This experimental study investigated friction stir welding (FSW) of the acrylonitrile-butadiene-styrene (ABS) T-joint in the presence of various nano-silica levels. This study aim to handle the drawbacks of the friction stir welding (FSW) of an ABS T-joint with various quantity of nanoparticles and assess the performance of nanoparticles in the welded joint. Moreover, the relationship between the nanoparticle quantity and FSW was analyzed using response surface methodology (RSM) Box-Behnken design. The input parameters were the tool rotation speed (400, 600, 800 rpm), the transverse speed (20, 30, 40 mm/min), and the nano-silica level (0.8, 1.6, 2.4 g). The tensile strength of the prepared specimens was determined by the universal testing machine. Silica nanoparticles were used to improve the mechanical properties (the tensile strength) of ABS and investigate the effect of various FSW parameters on the ABS T-joint. The results of Box-Behnken RSM revealed that sound joints with desired characteristics and efficiency are fabricated at tool rotation speed 755 rpm, transverse speed 20 mm/min, and nano-silica level 2.4 g. The scanning electron microscope (SEM) images revealed the crucial role of silica nanoparticles in reinforcing the ABS T-joint. The SEM images also indicated a decrease in the nanoparticle size by the tool rotation, leading to the filling and improvement of seams formed during FSW of the ABS T-joint.

• Polymer(Korea)
• /
• v.36 no.6
• /
• pp.721-726
• /
• 2012

Thermoplastic polyurethane (TPU) elastomer is used as an encapsulant in undersea sonar devices. A new material for sonar encapsulant exhibiting better mechanical strength than TPU along with a lower swelling ratio for seawater and oil is required to prolong its application. TPU grafted silica nanoparticles (TPU-g-silica) were prepared and then they were melt mixed with TPU to fabricate desirable composites for underwater applications. The composite containing silica nanoparticles exhibited better tensile strength and lower swelling ratios in the seawater and oil than TPU regardless of the surface treatment of the silica particles. At fixed silica content in the composite, the TPU/TPU-g-silica composite exhibited better tensile strength and lower swelling ratio than the TPU composite with the pristine silica particles. Furthermore, the TPU/TPU-g-silica composite exhibited enhanced tensile strength as compared to TPU after being impregnated with oil.

• Macromolecular Research
• /
• v.17 no.11
• /
• pp.907-911
• /
• 2009

To improve the moisture stability of the $CaS:Eu^{2+}$ red phosphor, surface coatings with silica nanoparticles were performed using five different methods, i.e., $P_1$, $P_2$, $P_3$, $P_4$, and $P_5$. The phosphors were coated with silica nanoparticles using a dip coating method ($P_1$) and sol-gel method ($P_2$). The phosphors were coated using a solution containing silica nanoparticles and poly(1-vinyl-2-pyrrolidone), PVP, $(P_3$). The phosphors were also coated with silica nanoparticles by reacting with the 1-vinyl-2-pyrrolidone (VP) monomer ($P_4$) or by reacting with mixtures containing VP and tetraethylorthosilicate ($P_5$). A decrease in the photoluminescence (PL) intensity was observed regardless of the coating methods. However, the moisture stability of the phosphors was enhanced by the coating when aged in a temperature-controlled humidity chamber. Among these methods, the $P_4$ (or $P_5$) method exhibited the greatest increase in moisture stability of the phosphors. The coated phosphors showed a relatively constant intensity with aging time, whereas the uncoated phosphor showed a decrease.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.96-96
• /
• 2010

Monodispersed spherical silica-coated ceria nanoparticles were prepared through a sol-gel process using tetraethylorthosilicate (TEOS) and ceria fine particles. In this process, ceria fine particles were also prepared from cerium nitrate. The mean size of ceria particles was 300nm. Silica nanoparticles with narrow particle size distribution were prepared by controlled hydrolysis of TEOS solution. The silica sols were obtained by peptization, the process of redispersing a coagulated colloid, and were coated on ceria particles by the control of the weight ratio of silica/ceria and the pH of the mixture in aqueous solution. The morphologies of particles were characterized with scaning electron microscopy(SEM), transmission electron microscopy(TEM) and atomic force microscopy(AFM). The coating thickness of silica particles obtained by using this method was controlled in the range of 30 - 70nm.

• Journal of Environmental Science International
• /
• v.17 no.7
• /
• pp.711-717
• /
• 2008

The use of support materials on the nanoparticle synthesis and applications has advantages in many aspects; resisting the aggregation and gelation of nanoparticles, providing more active sites by dispersing over the supports, and facilitating a filtering process. In order to elucidate the influence of the supports on the nitrate reduction reactivity, the supported iron nanoparticles were prepared by borohydride reduction of an aqueous iron salt in the presence of supports such as activated carbon, silica and polyethylene. The reactivity for nitrate reduction decreased in the order of unsupported Fe(0) > activated carbon(AC) supported Fe(0) > polyethylene(PE) supported Fe(0) ${\ge}$ silica supported Fe(0). Rate constants decrease with increasing initial nitrate concentration implying that the reaction is limited by the surface reaction kinetics.

• Advances in concrete construction
• /
• v.7 no.1
• /
• pp.51-63
• /
• 2019

The project focuses on the dynamic analysis of concrete beams reinforced with silica-nanoparticles under blast loading. The structure is located at two boundary conditions. The equivalent composite properties are determined using Mori-Tanak model. The structure is simulated with sinusoidal shear deformation theory. Employing nonlinear strains-displacements, stress-strain, the energy equations of beam were obtained and using Hamilton's principal, the governing equations were derived. Using differential quadrature methods (DQM) and Newmark method, the dynamic deflection of the structure is obtained. The influences of volume percent and agglomeration of silica nanoparticles, geometrical parameters of beam, boundary condition and blast load on the dynamic deflection were investigated. Results showed that with increasing volume percent of silica nanoparticles, the dynamic deflection decreases.