Investigating optimal region for thermal and electrical properties of epoxy nanocomposites under high frequencies and temperatures

This research investigates the optimal region to achieve balanced thermal and electrical insulation properties of epoxy (EP) under high frequency (HF) and high temperature (HT) via integration of surface-modified hexagonal boron nitride (h-BN) nanoparticles. The effects of nanoparticle content and high temperature on various electrical (DC, AC, and high frequency) and thermal properties of EP are investigated. It is found that the nano h-BN addition enhances thermal performance and weakens electrical insulation properties. On the other side, under HF and HT stress, the presence of h-BN nanoparticles significantly improves the electrical performance of BN/EP nanocomposites. The EP has superior insulation properties at low temperature and low frequency, whereas the BN/EP nanocomposites exhibit better insulation performance than EP under HF and HT. The factors such as homogeneous nanoparticle dispersion in EP, enhanced thermal conductivity, nanoparticle surface modification, weight percent of nanoparticles, the mismatch between the relative permittivity of EP and nano h-BN, and the presence of voids in nanocomposites play the crucial role. The optimal nanoparticle content and homogenous dispersion can produce suitable EP composites for the high frequency and high temperature environment, particularly solid-state transformer applications.

Premade Nanoparticle Films for the Synthesis of Vertically Aligned Carbon Nanotubes

Carbon nanotubes (CNTs) offer unique properties that have the potential to address multiple issues in industry and material sciences. Although many synthesis methods have been developed, it remains difficult to control CNT characteristics. Here, with the goal of achieving such control, we report a bottom-up process for CNT synthesis in which monolayers of premade aluminum oxide (Al2O3) and iron oxide (Fe3O4) nanoparticles were anchored on a flat silicon oxide (SiO2) substrate. The nanoparticle dispersion and monolayer assembly of the oleic-acid-stabilized Al2O3 nanoparticles were achieved using 11-phosphonoundecanoic acid as a bifunctional linker, with the phosphonate group binding to the SiO2 substrate and the terminal carboxylate group binding to the nanoparticles. Subsequently, an Fe3O4 monolayer was formed over the Al2O3 layer using the same approach. The assembled Al2O3 and Fe3O4 nanoparticle monolayers acted as a catalyst support and catalyst, respectively, for the growth of vertically aligned CNTs. The CNTs were successfully synthesized using a conventional atmospheric pressure-chemical vapor deposition method with acetylene as the carbon precursor. Thus, these nanoparticle films provide a facile and inexpensive approach for producing homogenous CNTs.

Entropy Generation and Thermal Analysis of Nanofluid Flow Inside the Evacuated Tube Solar Collector

In the current investigation, the thermal and thermodynamic behavior of a buoyancy-driven evacuated tube solar collector has undergone precise evaluation, and the efficacy of nanoparticle dispersion in the base fluid has been scrutinized using computational fluid dynamics based on the finite volume method. The natural convection process was analyzed in different vertical sections of the absorber tube. The temperature and velocity distributions of water as the conventional working fluid and the nanofluid were compared at various cutting planes along the tube during the simulation time. In this problem, CuO nanoparticles with optimum thermal properties were suspended in the base fluid. According to the surveyed results, the temperature distribution analysis illustrates that the mean temperature of the tank experiences more enhancement when the nanofluid is used. The comparison of the heat transfer coefficient between two simulated cases shows the competency of utilizing CuO/water nanofluid in the thermal performance improvement of the collector. The results related to entropy generation assessment show that the irreversibility owing to fluid friction rises when the nanofluid is applied during the flow time. In contrast, the entropy generation of pure water owing to heat transfer surpasses the case with nanofluid.

Application of Copper Iodide Nanoparticle-doped Film and Fabric to Inactivate SARS-CoV-2 via the Virucidal Activity of Cuprous Ion (Cu + )

As a result of the novel coronavirus disease 2019 pandemic, strengthening control measures against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become an urgent global issue. In addition to antiviral therapy and vaccination strategies, applying available virucidal substances for SARS-CoV-2 inactivation is also a target of research to prevent the spread of infection. Here, we evaluated the SARS-CoV-2 inactivation activity of a copper iodide (CuI) nanoparticle dispersion, which provides Cu + ions having high virucidal activity, and its mode of actions. In addition, the utility of CuI-doped film and fabric for SARS-CoV-2 inactivation was evaluated. The CuI dispersion exhibited time-dependent rapid virucidal activity. Analyses of the modes of action of CuI performed by western blotting and real-time reverse transcription polymerase chain reaction targeting viral proteins and the genome revealed that CuI treatment induced the destruction of these viral components. In this setting, the indirect action of CuI-derived reactive oxygen species contributed to the destruction of viral protein. Moreover, the CuI-doped film and fabric demonstrated rapid inactivation of the SARS-CoV-2 solution in which the viral titer was high. These findings indicated the utility of the CuI-doped film and fabric as anti-SARS-CoV-2 materials for the protection of high-touch environmental surfaces and surgical masks/protective clothes. Throughout this study, we demonstrated the effectiveness of CuI nanoparticles for inactivating SARS-CoV-2 and revealed a part of its virucidal mechanism of action. IMPORTANCE The COVID-19 pandemic has caused an unprecedented number of infections and deaths. As the spread of the disease is rapid and the risk of infection severe, hand and environmental hygiene may contribute to suppressing contact transmission of SARS-CoV-2. Here, we evaluated the SARS-CoV-2-inactivation activity of CuI nanoparticles, which provide the Cu + ion, as an antiviral agent, and provided advanced findings of the virucidal mechanisms of action of Cu + . Our results showed that the CuI dispersion as well as CuI-doped film and fabric rapidly inactivated SARS-CoV-2 with a high viral titer. We also demonstrated the CuI’s virucidal mechanisms of action, specifically, the destruction of viral proteins and the genome by CuI treatment. Protein destruction largely depended on CuI-derived reactive oxygen species. This study provides novel information about the utility and mechanisms of action of promising virucidal material against SARS-CoV-2.

Production and modification of hydrochar from anaerobically digested cattail for adsorbing ammonium and phosphorous in wastewater

Water contamination by nitrogen and phosphorus ions has direct consequence of eutrophication to the ecosystem. The objective of this study is to investigate the production of hydrochars by acetic acid or sodium hydroxide assisted hydrothermal carbonization (HTC), various activation methods, and the potential of hydrochar as an adsorbent to remove NH4+-N and PO43−-P from wastewater. The results showed that acetic acid or sodium hydroxide assisted HTC and activation with magnesium chloride or air could improve the surface properties of hydrochar. Acetic acid modification generated extensive oxygenated functional groups, while sodium hydroxide modification produced hydrochar with a high N/C ratio and surface aromaticity. Treating hydrochar with magnesium chloride could impregnate nano-magnesium particles on the hydrochar, thereby improving the ability to remove N and P. Air activation of hydrochar resulted in more oxygen containing functional groups. The NH4+-N and PO43−-P adsorption capacities of these hydrochars ranged from 92.6 to 122.4mg/g and 1.6 to 15.8mg/g, respectively. The adsorption capacity of hydrochars in swine wastewater is similar to the results of artificial wastewater. The results suggested that Mg-nanoparticle dispersion and oxygen containing functional groups played a major role in adsorption than ion exchange and physisorption.

Role of Adsorbed Polymers on Nanoparticle Dispersion in Drying Polymer Nanocomposite Films

Polymers adsorbed on nanoparticles (NPs) are important elements that determine the dispersion of NPs in polymer nanocomposite (PNC) films. While previous studies have shown that increasing the number of adsorbed polymers on NPs can improve their dispersion during the drying process, the exact mechanism remained unclear. In this study, we investigated the role of adsorbed polymers in determining the microstructure and dispersion of NPs during the drying process. Investigation of the structural development of NPs using the synchrotron vertical-small-angle X-ray scattering technique revealed that increasing polymer adsorption suppresses bonding between the NPs at later stages of drying, when they approach each other and come in contact. On the particle length scale, NPs with large amounts of adsorbed polymers form loose clusters, whereas those with smaller amounts of adsorbed polymers form dense clusters. On the cluster length scale, loose clusters of NPs with large amounts of adsorbed polymers build densely packed aggregates, while dense clusters of NPs with small amounts of adsorbed polymers become organized into loose aggregates. The potential for the quantitative control of NP dispersion in PNC films via modification of polymer adsorption was established in this study.

Photocatalytic Decomposition of Organic Dyes Using a Rotating Cylinder System

In this study, a rotating cylinder system was used in the photocatalytic decomposition of organic dyes in aqueous medium for water purification. To this end, the titania nanoparticle dispersion was mixed with an organic dye solution under a rotating inner cylinder at controlled speed. The rate constant was adjusted by changing the speed of rotation to determine the optimal circulating velocity. Since nanoparticle dispersion is a secondary contaminant after wastewater treatment, the titania paste was deposited on the inner surface of the stationary outer cylinder to form a photocatalytic film. During repeated batch-mode operation, the deactivation of the deposited film was analyzed by measuring the rate constant as a function of time. Continuous operation was also used to remove organic dye in the water to study factors affecting the removal efficiency of methylene blue. Higher rotating velocity and slow feed rate facilitated the removal of contaminants via desorption of adsorbed dyes with adequate retention time.

Reaction Mechanism and Mechanical Property Improvement of Poly(Lactic Acid) Reactive Blending with Epoxy Resin

Polylactic acid (PLA) was melt-blended with epoxy resin to study the effects of the reaction on the mechanical and thermal properties of the PLA. The addition of 0.5% (wt/wt) epoxy to PLA increased the maximum tensile strength of PLA (57.5 MPa) to 67 MPa, whereas the 20% epoxy improved the elongation at break to 12%, due to crosslinking caused by the epoxy reaction. The morphology of the PLA/epoxy blends showed epoxy nanoparticle dispersion in the PLA matrix that presented a smooth fracture surface with a high epoxy content. The glass transition temperature of PLA decreased with an increasing epoxy content owing to the partial miscibility between PLA and the epoxy resin. The Vicat softening temperature of the PLA was 59 °C and increased to 64.6 °C for 0.5% epoxy. NMR confirmed the reaction between the -COOH groups of PLA and the epoxy groups of the epoxy resin. This reaction, and partial miscibility of the PLA/epoxy blend, improved the interfacial crosslinking, morphology, thermal properties, and mechanical properties of the blends.