Probing the Use of Silane-Grafted Fumed Silica Nanoparticles to Produce Stable Transformer Oil-Based Nanofluids

In this experimental investigation, hydrophobic silane-grafted fumed nano-silica was employed in transformer oil to formulate nanofluids (NFs). A cold-air atmosphere-pressure plasma reactor working on the principle of dielectric barrier discharge was designed and utilized to functionalize the surface of these nanoparticles. A field emission scanning electron microscope (FE-SEM) coupled with energy-dispersive X-ray (EDX) module and Fourier transform infrared (FTIR) spectroscopy were used to scan surface features of new and plasma-treated nanoparticles. The study revealed considerable changes in the surface chemistry of nanoparticles, which led to good dispersibility and stability of nanofluids. The measurements of AC breakdown voltages (AC-BDV) of nanofluids so prepared were conducted according to IEC-Std 60156, and a significant improvement in the dielectric strength was achieved. A statistical analysis of these results was performed using Weibull probabilistic law. At a 5% probability of failure, modified nanofluid remarkably exhibited a 60% increase in breakdown voltage. The dielectric properties such as variation of εr and tan δ in temperature of up to 70 °C were measured and compared with untreated fluid. Results exhibit an increase in tan δ and a slight decrease in permittivity of nanofluids. The analysis also revealed that while unpolar silane coating of NPs increased the breakdown strength, the polar-amino-silane-coated NPs in oil resulted in a drastic reduction. Details of this antagonistic trend are elaborated in this paper.

Thermal and Rheological Properties of Hydrophobic Nanosilica in Sunflower Oil Suspensions at High Pressures

Nowadays, the reduction of the environmental impact associated with the operation of the oil industry is a primary concern. A growing trend is to develop low-toxicity formulations based on biodegradable components. In this sense, vegetable oils structured with nanomaterials could be an alternative to mineral or synthetic oils for sustainable fluid formulations. Hydrophobic fumed silica nanoparticles have the capability to change the rheological behavior of oil in suspensions, providing a large variety of non-Newtonian behaviors over a wide range of temperatures, from shear-thinning to gel-like, depending on the concentration and the nanosilica’s hydrophobicity, that permits the design of fluids with selected characteristic and applications. This work explores the microstructure and the rheological behavior of hydrophobic fumed silica dispersed in a sunflower oil as a function of temperature and pressure. The results suggest that the suspensions of hydrophobic silica in sunflower oil reveals appropriate rheological and thermal properties over a wide range of temperatures and pressures to serve as components of sustainable drilling fluids.

3D Liquid Marble Microbioreactors Support In Vitro Maturation of Prepubertal Ovine Oocytes and Affect Expression of Oocyte-Specific Factors

In vitro oocyte maturation (IVM) is a well-established technique. Despite the high IVM rates obtained in most mammalian species, the developmental competence of IVM oocytes is suboptimal. The aim of this work was to evaluate the potential beneficial effects of a liquid marble microbioreactor (LM) as a 3D culture system to mature in vitro prepubertal ovine oocytes, as models of oocytes with intrinsic low competence. Cumulus–oocyte complexes of prepubertal sheep ovaries were in vitro matured in a LM system with hydrophobic fumed-silica-nanoparticles (LM group) or in standard conditions (4W control group). We evaluated: (a) maturation and (b) developmental rates following in vitro fertilization (IVF) and embryo culture; (c) expression of a panel of genes. LM and 4W groups showed similar IVM and IVF rates, while in vitro development to blastocyst stage approached significance (4W: 14.1% vs. LM: 28.3%; p = 0.066). The expression of GDF9, of enzymes involved in DNA methylation reprogramming and of the subcortical maternal complex was affected by the IVM system, while no difference was observed in terms of cell-stress-response. LM microbioreactors provide a suitable microenvironment to induce prepubertal sheep oocyte IVM and should be considered to enhance the developmental competence of oocytes with reduced potential also in other species, including humans.

Enhanced Oil Recovery with Size-Dependent Interactions of Nanoparticles Surface-Modified by Zwitterionic Surfactants

This study reports the size-dependent interactions of silica nanoparticle (NP) dispersions with oil, which facilitate oil recovery from sandstone rock. Herein, we studied various 7–22 nm sized colloidal silica NPs (CSNPs; the colloidal state when dispersed in aqueous solutions) and fumed silica nanoparticles (FSNPs; the dry powder state). Interfacial tension at the oil-nanofluids interface declined with decreasing NP size in a range from 7 to 22 nm. This is because NP spatial density at the interface increased with smaller particle size, thereby, the interface area per NP decreased to approximately 1/30, and interfacial energy had reduced enough. In addition, smaller NPs more strongly were adsorbed to the rock because of improved diffusion in suspension and increased adsorption density. This caused creating a wedge film between oil and rock, which changed the oil contact angle. Due to this effect, core flooding experiments indicated that oil recovery increased with decreasing particle size. However, FSNP dispersions exhibited low recovery factor because of particle aggregation. This phenomenon may facilitate massive permeability reduction, thus causing oil trapping inside rock pore. We found that both the sizes and types of CSNPs and FSNP affected the Interfacial tension at oil-water interface and rock surface wettability, which influenced ultimate oil recovery.

Rheological, physicochemical, and microstructural properties of asphalt binder modified by fumed silica nanoparticles

Warm mix asphalt (WMA) is gaining increased attention in the asphalt paving industry as an eco-friendly and sustainable technology. WMA technologies are favorable in producing asphalt mixtures at temperatures 20–60 °C lower in comparison to conventional hot mix asphalt. This saves non-renewable fossil fuels, reduces energy consumption, and minimizes vapors and greenhouse gas emissions in the production, placement and conservation processes of asphalt mixtures. At the same time, this temperature reduction must not reduce the performance of asphalt pavements in-field. Low aging resistance, high moisture susceptibility, and low durability are generally seen as substantial drawbacks of WMA, which can lead to inferior pavement performance, and increased maintenance costs. This is partly due to the fact that low production temperature may increase the amount of water molecules trapped in the asphalt mixture. As a potential remedy, here we use fumed silica nanoparticles (FSN) have shown excellent potential in enhancing moisture and aging susceptibility of asphalt binders. In this study, asphalt binder modification by means of FSN was investigated, considering the effects of short-term and long-term aging on the rheological, thermal, and microstructural binder properties. This research paves the way for optimizing WMA by nanoparticles to present enhanced green asphalt technology.

Effect of Fumed Silica Nanoparticles on Ultraviolet Aging Resistance of Bitumen

In this study, bitumen modified by fumed silica nanoparticles was characterized through dynamic shear rheometer tests, scanning electron microscopy, and Fourier transform infrared spectroscopy. The fumed silica nanoparticles were used in three different ratios, i.e., 0.1, 0.2 and 0.3 wt.-% of bitumen. Specifically, the modified bitumen characteristics were studied after laboratory aging by analyzing the chemical composition and rheological properties. From the determination of oxidation degree and carbonyl index it was found that the resistance of the modified bitumen to ultraviolet aging was improved with the increasing nanoparticle content. In bitumen modified by fumed silica nanoparticles, the nanoparticles were well dispersed. Moreover, the results illustrated that the bitumen properties were improved, and the improvement effect of 0.1 wt.-% fumed silica nanoparticles was more distinct than the higher concentrations.