Fumed Silica Nanoparticles Research Articles

On the Complex Flow Dynamics of Shear Thickening Fluids Entry Flows

Due to their nature, using shear thickening fluids (STFs) in engineering applications has sparked an interest in developing energy-dissipating systems, such as damping devices or shock absorbers. The Rheinforce technology allows the design of customized energy dissipative composites by embedding microfluidic channels filled with STFs in a scaffold material. One of the reasons for using microfluidic channels is that their shape can be numerically optimized to control pressure drop (also known as rectifiers); thus, by controlling the pressure drop, it is possible to control the energy dissipated by the viscous effect. Upon impact, the fluid is forced to flow through the microchannel, experiencing the typical entry flow until it reaches the fully developed flow. It is well-known for Newtonian fluid that the entrance flow is responsible for a non-negligible percentage of the total pressure drop in the fluid; therefore, an analysis of the fluid flow at the entry region for STFs is of paramount importance for an accurate design of the Rheinforce composites. This analysis has been numerically performed before for shear-thickening fluids modeled by a power-law model; however, as this constitutive model represents a continuously growing viscosity between end-viscosity plateau values, it is not representative of the characteristic viscosity curve of shear-thickening fluids, which typically exhibit a three-region shape (thinning-thickening-thinning). For the first time, the influence of these three regions on the entry flow on an axisymmetric pipe is analyzed. Two-dimensional numerical simulations have been performed for four STFs consisting of four dispersions of fumed silica nanoparticles in polypropylene glycol varying concentrations (7.5–20 wt%).

Fumed-Si-Pr-Ald-Barb as a Fluorescent Chemosensor for the Hg2+ Detection and Cr2O72- Ions: A Combined Experimental and Computational Perspective.

The surface of fumed silica nanoparticles was modified by pyridine carbaldehyde and barbituric acid to provide fumed-Si-Pr-Ald-Barb. The structure was identified and investigated through diverse techniques, such as FT-IR, EDX, Mapping, BET, XRD, SEM, and TGA. This nanocomposite was used to detect different cations and anions in a mixture of H2O:EtOH. The results showed that fumed-Si-Pr-Ald-Barb can selectively detect Hg2+ and Cr2O72- ions. The detection limits were calculated at about 5.4 × 10-3 M for Hg2+ and 3.3 × 10-3 M for Cr2O72- ions. A computational method (DFT) was applied to determine the active sites on the Pr-Ald-Barb for electrophilic and nucleophilic attacks. The HOMO-LUMO molecular orbital was calculated by B3LYP/6-311G(d,p)/LANL2DZ theoretical methods. The energy gap for the Pr-Ald-Barb and Pr-Ald-Barb+ion complexes was predicted by the EHOMO and ELUMO values. The DFT calculation confirms the suggested experimental mechanism for interacting the Pr-Ald-Barb with ions.

Rheological and adhesive improvements of terminal blend rubberized asphalt via fumed silica nanoparticle modification

Due to the high degree of desulfurization and depolymerization of crumb rubber (CR) particles in terminal blend rubberized asphalt (TBRA), their elasticity and adhesive performance are insufficient. To address this, the study utilized low-cost fume silica nanoparticles (FSNPs) to enhance the elasticity and adhesive properties. TBRA binders with varying CR contents (30 %, 40 %, 50 %) were modified using different dosages of FSNPs (2 %, 4 %, 6 %). The microstructure of FSNPs was examined through TEM and SEM. Using a dynamic shear rheometer (DSR) test, contact angle test, and atomic force microscope (AFM) test, the effects of FSNPs on the rheological properties, surface energy, and adhesive properties of TBRA binders were evaluated. The results showed significant improvements in the deformation resistance and elasticity of the TBRA binders modified with FSNPs. This is attributed to the branched network structure of FSNPs, which notably enhances the binder's cohesion, thereby strengthening its resistance to shear deformation and improving elasticity. FSNPs effectively reduce the moisture sensitivity of TBRA, due to the hydrophilic hydroxyl groups on FSNPs being replaced by hydrophobic methyl groups (-CH3). The inadequate bonding performance of TBRA can be attributed to the high levels of extensively depolymerized and desulfurized CR particles, which reduce the cohesiveness of the binder. The addition of FSNPs, although it lowers the surface energy of TBRA binders, significantly enhances their cohesiveness due to the branched network structure, thereby improving their bond performance. AFM results indicate that FSNPs enhance the adhesive strength of the TBRA binder surface due to their high specific surface area, which provides more van der Waals forces and electrostatic interactions. For economic efficiency, an addition of 4 % is recommended for TB30, and 2 % for TB40 and TB50. At these specified concentrations, the bond strength of the TBRA binder can be increased by 45–55 %.

Mechanical and thermal properties of fumed silica‐incorporated silane‐terminated urethane/epoxy‐interpenetrating polymer network nanocomposites

AbstractIn this study, it was aimed to improve the mechanical and thermal properties of epoxy materials based on diglycidyl ether of bisphenol‐A‐based. For this purpose, three different nanocomposite materials were prepared at various ratios including a fumed silica nanoparticle‐reinforced epoxy nanocomposite (FSN), an epoxy/silane‐terminated urethane (STU) hybrid interpenetrating polymer network (IPN) nanocomposite (SHIN), and a fumed silica‐reinforced epoxy/STU hybrid IPN nanocomposite (FSHIN). While synthesizing SHIN, 3‐isocyanato propyl trimethoxy silane (ICPTMS) and poly (hexamethylene carbonate) diol were used. The synthesized STU polymer chains were crosslinked by reacting them with TEOS via the sol–gel process. Therefore, hybrid networks were obtained. Moreover, fumed silica nanoparticles were incorporated into the hybrid networks via the sol–gel process for FSHINs. The three different nanocomposite materials exhibited much more improved properties than the neat epoxy. The most prominent nanocomposite was FSHIN. In comparison with the neat epoxy, Young's modulus, ultimate tensile strength, and Izod impact resistance values increased at ratios of 53%, 50%, and 223%, respectively. Glass transition temperature values and char yield values increased substantially in all nanocomposites. However, thermal decomposition temperatures increased only for FSNs. Moreover, these values for FSHINs that were very close to those of the neat epoxy were considerably higher than those of SHINs.Highlights Fumed silica‐incorporated silane‐terminated urethane/epoxy IPN nanocomposites. Substantially improved mechanical properties and impact resistance. Improved thermal stability.

Desalination setup coated by silicone epoxy nanocomposite: A study on hydrophobic characteristics and condensation mechanisms

The formation of tortuous filmwise condensation in desalination setup alongside with reduction in thermal conductivity is a challenge accompanied by efficiency loss. This issue is directly influenced by hydrophobicity, which is a function of surface roughness, as well as surface chemistry. In this sense, the hydrophobicity of variant silicone epoxy based nanocomposites was evaluated to identify the optimum proportion composite for surface condensation of desalination setup. To this end, three types of fumed silica with distinct surface chemistry were utilized in a matrix at the weight percentage of 0.5, 1, 1.5, and 2. To investigate the hydrophobicity, roughness, and distribution of reinforcement, a series of characterization techniques, including contact angle, AFM, and FESEM were used. It was found that, in comparison to pure matrix, the nanocomposite modified with 5 wt % of hydrophobic additive and 0.5 wt % of hydrophilic fumed silica nanoparticles (SE/5B/0.5R200) has the highest contact angle (about 35%) and roughness (13 times), due to the migration of nanoparticle onto the surface. Also, coating the condensation surface of the desalination setup with optimum thickness, i.e. 60 × 10−6 m, resulted in the efficiency improvement by about 33 % compared to the uncoated setup, even after 168 hrs. Indeed, dropwise condensation, straight path movement of droplets, besides thermal conductivity adjust the efficiency.

Cost-effective enhancement of high viscosity modified bitumen anti-aging properties using organic layered double hydroxide/fume silica nanoparticles composite nanomaterials

High-viscosity modified bitumen (HVMB) is prone to thermal-oxidative and photooxidative aging, resulting in pavement diseases. The use of conventional Nano-modifiers to enhance the aging resistance of bitumen is often hindered by high costs, limiting their adoption in widespread applications. This study aims to evaluate the impact of a cost-effective Multi-Dimensional Nano-Composite (MDNC) modifier on the durability of HVMB, which includes organically modified Layered Double Hydroxides (OLDHs) and Fumed Silica Nanoparticles (FSNPs). Additionally, Zero-Dimensional Nanomaterials (ZDNs) such as FSNPs, Nano-SiO2, or Nano-TiO2, in combination with various MDNC modifiers consisting of OLDHs and ZDNs, were also utilized as comparative anti-aging modifiers for HVMB binders. FTIR, XRD, and contact angle tests indicate that LDHs modified with KH560 (OLDHs) exhibit improved hydrophobicity and increased interlayer distance. The temperature sweep test of the unaged binders and the FESEM test of the Nano-modifier indicate that the branched network structure of the FSNPs significantly enhances the high-temperature elasticity of the HVMB binders. Rheological test results have shown that both ZDNs and MDNC modifiers can delay the changes in rheological parameters after aging. Combining FTIR and SARA (Saturates, Aromatics, Resins, Asphaltenes) results, it was found that the combination of OLDHs/FSNPs synergistically inhibited the increase in the content of heavy components in bitumen during thermal oxygen and ultraviolet aging. The enhancement of the HVMB's thermal oxidation aging resistance by OLDHs/FSNPs composite modifiers is primarily due to the multidimensional structure of the composite nanomaterial, which effectively prevents the penetration of oxygen molecules. Meanwhile, the improvement in resistance to ultraviolet aging is mainly due to the absorption and scattering characteristics of FSNPs. Therefore, OLDHs/FSNPs are demonstrated to be a cost-effective multidimensional nano-modifier.

Effect of temperature on electrical resistivity of EVA-LDPE nanocomposites for photovoltaic encapsulating application: An activation energy method

This article evaluates the effect of mixing strategy on thermo-electrical resistance of ethylene vinyl acetate (EVA), low-density polyethylene (LDPE) and fumed silica nanoparticles (FSN) based composite encapsulating materials. The nanocomposites were synthesized by solution compounding method with various sequence of ingredients addition. The quantity of ingredients is same for all nanocomposites where the ratio of EVA, LDPE and FSN addition is 10:1:0.11. The structural morphology of the samples prepared by different mixing sequence was studied under Transmission Electron Microscopy (TEM). DC volume resistivity (VR) were evaluated at 25 °C, 50 °C and 75 °C for all the compositions to check the insulation behaviour at extreme service temperature as VR is an assessing parameter for photovoltaic (PV) encapsulating materials. For obvious reason, the magnitude of VR decreases with increasing temperature. Activation energy (Ea ) was estimated from Arrhenius equation and the value evaluated was very much dependent on the ingredients mixing strategy. Good electrical resistance with desired activation energy were obtained for the nanocomposites; prepared with a particular mixing strategy where percolation threshold achieved. Finally, the TEM structure and insulation property relationship has been addressed against the experimental findings.

Unique Crystallization Characteristics of Pickering High Internal Phase Emulsion Templated Porous Constructs.

To study the crystallization behavior of polymeric chains under the influence of porosity, the thermal properties of various nonporous and porous poly(ε-caprolactone) (PCL) based constructs were investigated. Porous cross-linked PCL nanocomposite constructs were fabricated utilizing in situ polymerization of CL-based surfactant-free Pickering high internal phase emulsions (HIPEs), stabilized using modified fumed silica nanoparticles (mSiNP) at a minimal concentration of 0.6 wt %. The corresponding nanocomposite constructs exhibited polyhedral pore morphology with significant pore roughness due to the presence of mSiNP. DSC thermograms of nonporous constructs illustrated diminished crystallization temperature and kinetics upon cross-linking and inclusion of mSiNP which confirmed suppressed mobility of polymer chains. Further introduction of porosity led to substantial supercooling, resulting in crystallization temperatures as low as -24 °C. Changes in the crystal structure of various nonporous and porous constructs were also studied using XRD. The crystallization behavior of porous constructs was finally evaluated using Jeziorny, Ozawa, and Mo theories under nonisothermal conditions. Significant deviation from the theoretical model, as observed in the case of porous constructs, implied a complex crystallization mechanism that eventually was not only controlled by the chain immobility due to cross-linking but also heterogeneity present in the wall thickness of the constructs. The unique melting-crystallization phenomenon observed in such constructs may further be expanded to other systems of high heat capacity for utilization as energy storage materials.

Enhanced mechanical and thermal properties of phenolic-type phthalonitrile nanocomposites with fumed silica nanoparticles

Enhancing the mechanical properties and thermal stability of phthalonitrile polymers by hybrid modification holds significant importance in broadening their thermal-structural applications within high-temperature environments. Herein, fumed silica nanoparticles were considered as modifiers for a class of phenolic-type phthalonitrile resin, i.e., PN75, and their effects on mechanical properties and thermal stability were explored. First, contact angle tests (CA) were employed to show that the PN75 melt had good wettability on hydrophilic fumed silica (FS) and poor wettability on hydrophobic fumed silica (RFS). FS had a relatively satisfactory dispersion within PN75, which was indicated by scanning electron microscope (SEM), followed by FS/PN75 nanocomposites were prepared by melt blending under vacuum, with maximum FS addition 3 wt% of PN75. Second, the flexural strength and modulus of nanocomposites were increased by 23.5% and 11.9%. Finally, thermal stability of the FS/PN75 was promoted from 21.6% to 25.6% in char residue at 800 °C in the air atmosphere by the thermogravimetric analysis (TGA), which was contributed by the high heat-resistance and the shielding effect of FS. This work would inspire in-depth studies on modification and design of phthalonitrile-based hybrid composites for extreme thermal environment.

Super-tough poly(lactic acid)/silicone rubber thermoplastic vulcanizates: The organic and inorganic synergistic interfacial compatibilization

Polymer modification using silicone rubber represents a promising avenue for enhancing physico-mechanical properties. However, achieving optimal performance through direct blending is hindered by the poor interface compatibility between silicone rubber and the matrix. In this study, we prepared super-tough thermoplastic vulcanizates (TPVs) of polylactic acid/silicone rubber through dynamic vulcanization with PLA, methyl vinyl silicone rubber (MVQ), glycidyl methacrylate grafted MVQ (MVQ-g-GMA), and fumed silica nanoparticles (SiO2). The impact of the SiO2 addition in MVQ on the morphology, mechanical properties, crystallization, and thermal properties of the TPVs was investigated. The results showed that MVQ-g-GMA and SiO2 exhibited a synergistic compatibilization effect significantly improving the interfacial adhesion between PLA and MVQ. Therefore, the impact and tensile strength of the TPVs increased from 8.0 kJ/m2 and 22.2 MPa to 62.6 kJ/m2 and 36.7 MPa, respectively. Moreover, the TPVs also presented good low-temperature toughness with a maximum impact strength of 40.4 kJ/m2 at −20 °C. Additionally, improvements in thermal stability and crystallization rate were also observed. Overall, combining organic and inorganic synergistic compatibilization is a feasible and effective method to fabricate outstanding low-temperature toughness to PLA.

Performance and Mechanism of Using Low-Cost Fumed Silica Nanoparticles in Enhancing High Viscosity Modified Asphalt

Fumed silica nanoparticles (FSNPs) have shown significant potential in polymer modification due to their economic viability. This study aims to explore the impact of FSNPs on the performance of high viscosity modified asphalt (HVMA). For a comprehensive view, we also introduced Nano-SiO2 and Nano-TiO2, common nano-modifiers, for comparison with the results achieved by FSNPs. The morphology of these nano-modifiers was observed with Field Emission Scanning Electron Microscopy (FESEM). The changes in rheological, chemical, and thermal properties of HVMA before and after modification were evaluated using techniques such as Dynamic Shear Rheometer (DSR), Fluorescence Microscope, Fourier Transform Infrared Spectroscopy (FTIR), and Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC). The FESEM results revealed that FSNPs form a branchlike network while Nano-SiO2 and Nano-TiO2 lack specific structures or clear interconnections. Further rheological testing reveals that, when compared to Nano-SiO2 and Nano-TiO2, FSNPs improve the high-temperature performance of HVMA by 2–3 times and bolster its fatigue resistance by 1.2–3 times, while reducing temperature sensitivity. These enhancements are attributed to the synergistic strengthening between the FSNP's branchlike network and the SBS polymer network structure, underlining the significance of FSNPs' shape and connectivity in HVMA rheological property improvement.

Fumed-Si-Pr-Pi a new Ag+ ion chemosensor in aqueous media

The surface of fumed silica nanoparticles can react with various organic groups. Fumed-silica can be functionalized by the reaction of (3-Chloropropyl)trimethoxysilane (CPTMS) to yield Fumed-Si-Pr-Cl, followed by the treatment with piperazine to obtain Fumed-Si-Pr-Pi, which was applied to detect metal ions. The optical activity of Fumed-Si-Pr-Pi was studied by fluorescence spectroscopy. It was demonstrated that among all different cations, the Ag+ ions quenched the PL of the Fumed-Si-Pr-Pi more strongly than other heavy metals, with LOD 5.43 × 10−7 M.

Pickering phase change slurries

HypothesisPhase change slurries (PCS) have emerged as a promising class of oil-in-water emulsions for energy applications, but stability remains an issue. Pickering phase change slurries (PPCS) stabilized solely by nanoparticles could offer enhanced stability. We hypothesize that stability in PPCS can be achieved by tuning environmental variables of salinity and temperature. ExperimentsA paraffin-based PPCS stabilized using fumed silica nanoparticles was developed and assessed under varying NaCl concentrations (up to 150 mM) and temperatures (up to 70 °C). Extended-DLVO modeling, confocal, and cryogenic electron microscopy analyzed the silica-paraffin interactions. Rheological experiments examined the impact of effective volume fraction, thermal expansion, and salinity on the viscosity and shear stability of PPCS. The stability of the resulting formulation was assessed under high pressure and temperature conditions. FindingsIncreased salinity did not change the packing density of the silica at the oil–water interface (82% ± 6%) but did increase the adsorbed layer thickness and network formation, enhancing the formulation's resistance to shear-induced instability. A critical volume fraction of 0.51 ± 0.01 was identified, beyond which viscosity increased significantly. The resulting formulations remained stable under high pressures and temperatures, regardless of salinity. These findings offer insights into the variables affecting PPCS properties, assisting in designing stable PPCS formulations for diverse applications.

Influence of fumed silica nanoparticles on the rheological and anti-aging properties of bitumen

Inorganic nanofillers such as nano silica (nano-SiO2) modifiers can enhance the rheological and anti-aging performance of bitumen. However, nanoparticles are susceptible to aggregation and are considered costly for modifying a bituminous pavement. In this study, fumed silica nanoparticles (FSNs) are proposed as a novel bitumen modifier, which is only 1/10 the price of conventional nano-SiO2. The properties of FSNs are compared with those of organically modified nano-SiO2 (MNS) and ordinary SiO2 (OS) particles. Firstly, the surface morphology of OS, MNS, and FSNs is examined through field emission scanning electron microscopy (FESEM). The rheological, chemical, and thermal properties of base and silica-modified bitumen are investigated before and after different aging methods. The results reveal that FSNs readily form a network structure in the bitumen matrix, which effectively enhances the bitumen's elasticity and deformation resistance at high temperatures. Furthermore, regardless of the aging method used, FSNs dramatically reduce the complex modulus aging index of bitumen, demonstrating their resistance to thermo-oxidative degradation and ultraviolet radiation aging. The Fourier transform infrared (FTIR) spectra indicate that FSNs effectively reduce the carbonyl index of bitumen due to their chemical stability and barrier properties. The differential scanning calorimetry (DSC) results show that the glass transition temperature (Tg) of FSN-modified bitumen does not change much after aging, which is due to the inhibition of the conversion of light components into asphaltene during the aging process. Therefore, the FSNs can be considered as a cost-effective and promising modifier for increasing the durability of bitumen.

Drycells: Cell-suspension micro liquid marbles for single-cell picking.

Cell-picking technology is essential for cell culturing. Although the recently developed tools enable single-cell-level with a >95% aqueous culture medium, thereby acting as a powerful cell-picking tool, is reported. The proposed "drycells" are formed by spraying a cell suspension onto a powder bed of hydrophobic fumed silica nanoparticles. The particles adsorb to the droplet surface and form a superhydrophobic shell, which prevents the drycells from coalescence. The number of encapsulated cells per drycell can be controlled by adjusting the drycell size and cell-suspension concentration. Moreover, it is possible to encapsulate a pair of normal or cancerous cells and create several cell colonies within a single drycell. A sieving process can be used to sort the drycells according to size. The size of the droplet can range from one to hundreds of micrometers. The drycells are sufficiently stiff to be collected using a tweezer; however, centrifugation separates them into nanoparticles and cell-suspension layers, with the separated particles being recyclable. Various handling techniques, such as splitting coalescence and inner liquid replacement, can be used. We believe that the application of the proposed drycells will greatly improve the accessibility and productivity of single-cell analysis. This article is protected by copyright. All rights reserved.

Molecular Layer Deposition of Polyurea on Silica Nanoparticles and Its Application in Dielectric Nanocomposites.

Polymer nanocomposites (NCs) offer outstanding potential for dielectric applications including insulation materials. The large interfacial area introduced by the nanoscale fillers plays a major role in improving the dielectric properties of NCs. Therefore, an effort to tailor the properties of these interfaces can lead to substantial improvement of the material's macroscopic dielectric response. Grafting electrically active functional groups to the surface of nanoparticles (NPs) in a controlled manner can yield reproducible alterations in charge trapping and transport as well as space charge phenomena in nanodielectrics. In the present study, fumed silica NPs are surface modified with polyurea from phenyl diisocyanate (PDIC) and ethylenediamine (ED) via molecular layer deposition (MLD) in a fluidized bed. The modified NPs are then incorporated into a polymer blend based on polypropylene (PP)/ethylene-octene-copolymer (EOC), and their morphological and dielectric properties are investigated. We demonstrate the alterations in the electronic structure of silica upon depositing urea units using density functional theory (DFT) calculations. Subsequently, the effect of urea functionalization on the dielectric properties of NCs is studied using thermally stimulated depolarization current (TSDC) and broadband dielectric spectroscopy (BDS) methods. The DFT calculations reveal the contribution of both shallow and deep traps upon deposition of urea units onto the NPs. It could be concluded that the deposition of polyurea on NPs results in a bi-modal distribution of trap depths that are related to each monomer in the urea units and can lead to a reduction of space charge formation at filler-polymer interfaces. MLD offers a promising tool for tailoring the interfacial interactions in dielectric NCs.

Poly(lactic acid)/Plasticizer/Nano-Silica Ternary Systems: Properties Evolution and Effects on Degradation Rate.

Plasticized nanocomposites based on poly(lactic acid) have been prepared by melt mixing following a two-step approach, adding two different oligomeric esters of lactic acid (OLAs) as plasticizers and fumed silica nanoparticles. The nanocomposites maintained a remarkable elongation at break in the presence of the nanoparticles, with no strong effects on modulus and strength. Measuring thermo-mechanical properties as a function of aging time revealed a progressive deterioration of properties, with the buildup of phase separation, related to the nature of the plasticizer. Materials containing hydroxyl-terminated OLA showed a higher stability of properties upon aging. On the contrary, a synergistic effect of the acid-terminated plasticizer and silica nanoparticles was pointed out, inducing an accelerated hydrolytic degradation of PLA: materials at high silica content exhibited a marked brittleness and a dramatic decrease of molecular weight after 16 weeks of aging.

Evaluation and prediction of rise velocity and drag coefficient of an ascending bubble affected by the impurity in continuous and discrete phases, distinctly and concurrently

Obtaining a deep knowledge about the bubbly flow systems, which are widely applied in various chemical and industrial processes, is crucial for scholars and engineers to achieve more accurate equipment design and processes control. This paper is dedicated to experimentally investigate the distinctly and concurrently effects of fumed silica nanoparticles (NPs) and hexane vapor molecules as impurities in continuous and discrete phases, respectively, on the terminal velocity and drag coefficient of a single rising bubble in aqueous solutions. The obtained experimental data were compared to the calculated data by derived correlations in literatures. As a result, none of those can predict the experimental data and a new correlation for considering the SiO2 NPs as an impurity in liquid is required. As a novelty, this work proposed two new correlations for prediction of terminal velocity and drag coefficient of a rising bubble in NPs solutions as a function of NPs concentration in aqueous solutions. The proposed correlations of terminal velocity and drag coefficient are in excellent agreements with the experimental data over the range of Re <310 and We <1.8, and with the maximum average relative errors of about 0.5% and 1.3%, respectively. Moreover, an interesting synergistic effect at the bubble interface was shown, due to creation of hexane oily layer at the interface and its interaction with rotational and vibrational effects of NPs in 200 ppm solution, where the exerted drag force on the rising bubble was reduced by 12.5% in comparison to the pure water (Air) case.

Effect of graphene oxide–iron oxide hybrid nanocomposite on the high-velocity impact performance of Kevlar fabrics impregnated with nanosilica/polyethylene glycol shear thickening fluid

In this paper, the influence of graphene oxide (GO) and GO–Fe3O4 hybrid nanocomposite (GFHN) as additives for nanosilica/polyethylene glycol shear thickening fluid (STF) was investigated on the fiber pull-out response and high-velocity impact performance of Kevlar fabrics. To fabricate GFHN nanofillers, the Fe3O4 nanoparticles were linked onto the graphene oxide surfaces using the electrostatic self-assembly method. The GO sheets and GFHN nanofillers were separately incorporated into STF containing fumed silica nanoparticles and the Kevlar fabrics were impregnated with the obtained STF-GO and STF-GFHN nano-mixtures. The pull-out test results of the impregnated Kevlar fabric indicated that the STF-GO nano-mixture decreased while the STF-GFHN nano-mixture increased the friction between the yarns of the impregnated fabric. This was in correlation with the high-velocity impact test results in which the STF-GO nano-mixture deteriorated while the STF-GFHN nano-mixture considerably improved the high-velocity impact resistance of the impregnated Kevlar fabric. The Kevlar fabric impregnated with STF-GFHN nano-mixture containing 0.4 wt% GFHN nanofillers experienced the maximum pull-out force and impact energy absorption with 163% and 73% improvements, respectively, compared to the neat fabric.

Dielectric properties of low-temperature sintered forsterite (Mg2SiO4) using high-dispersion and nanoparticle-based solid-state reaction process

Dielectric materials with low dielectric constant and low loss are in high demand due to the rapid development of telecommunication systems toward 5G and 6G. In this work, a modified solid-state reaction method is reported for the synthesis of low dielectric constant forsterite (Mg2SiO4) at low calcination temperatures by using MgO and fumed silica nanoparticles (NPs). The forsterite phase was obtained at 1000 °C, where the sintering temperature was reduced from 1500 °C to 1200 °C. As-synthesized forsterite has a low dielectric constant of 3.9 with low tan δ = 0.00047 at 1 GHz. Low-temperature sintered forsterite is suitable for microelectronics applications.