Water-based Suspensions Research Articles

Water-based 8YSZ electrolyte suspension optimised by design of experiments

Solid oxide cells are approaching commercial viability, with most of the currently used materials representing state-of-the-art advancements. However, widespread market adoption hinges on reducing costs. In this context, manufacturing improvements – particularly those that minimise material waste during production – can play a crucial role in lowering the capital expenditure (CAPEX) of solid oxide cells, ultimately influencing the levelised cost of fuel for end users.This study presents an optimisation of electrolyte slurry formulation for tape casting. By controlling variables such as solid loading, binder content, milling parameters, and casting conditions, we achieved reproducible results in electrolyte thickness, porosity, and electrical conductivity.The slurries were prepared by ball milling, employing a range of compositions that included both low and high solid and binder contents. The resulting rheological profiles, tape quality, thickness, and porosity were carefully evaluated. The experimental design culminated in an optimised composition, for which electrical conductivity was measured using electrochemical impedance spectroscopy. The impedance data were deconvoluted into grain bulk and grain boundary contributions, enabling further refinement of the sintering temperature and subsequent microstructure.

Study of square-wave AC electrophoretic deposition of lithium titanate anodes for Li-ion batteries

Electrophoretic deposition (EPD), while being a scientifically interesting technique due to its inherent versatility, has only limited success in industrial applications. This is partly due to the need to employ expensive and potentially hazardous organic solvents in traditional suspensions. Recently, a significant effort has been focused on the use of aqueous systems and AC-EPD approaches. In this article we present a study and characterization of square-wave electrophoretic deposition at different frequencies of the lithium titanate water-based suspension for application in lithium-ion batteries. We have found that the mass of the deposit linearly increases with time. This reveals that depletion zones are less prone to form in an alternating field, hence enabling formation of homogeneous films and diminishing a growth in bath resistance as compared to DC mode. The EPD performed at critical frequency of 40kHz results in higher content of carbon co-deposited with LTO, improved capacity and power capability and of Li/LTO cells.

Fabrication of Water-Based Alcoholized Poly(butylene succinate-co-adipate) Submicron Particles as Green Coating Agents for Sustainable Paper Packaging.

This work aims to fabricate the water-based suspension of poly(butylene succinate-co-adipate) (PBSA) particles by an oil-in-water emulsion technique for use as coating agents to enhance paper-based packaging performances and sustainability. A commercial PBSA resin is functionalized by sizing down an approach via microwave-assisted alcoholysis using propylene glycol (PG). The effect of PBSA/PG feed ratio on the structures, properties, and particle formability of the alcoholized (aPBSA) products is examined. 1H NMR results reveal that the average molecular weight of the aPBSA product decreases to half that of neat PBSA when using a ratio of 24:1 and further decreases to a quarter at 6:1. By using small-size aPBSA, the obtained water-based particles show high stability due to high hydroxyl content and poly(vinyl alcohol) assistance. The suspension is then sprayed on a kraft paper substrate and heated at 60 and 100 °C. SEM results reveal that the submicron aPBSA particles penetrate the paper matrix, filling the paper's pores and forming a protective, smooth layer on the paper surfaces. The coated paper shows high water resistance (Cobb60 value of 19.6 g/m2) and water vapor transmission rate (1160 g/(m2 day)). In addition, the aPBSA-coated layers do not impede the paper's repulping and recycling processes, making it a promising solution for improving the sustainability of paper-based packaging.

Coupling APS/SPS Techniques for Cu-TiO2 Antibacterial Coating Deposition: Application to Water Treatment

Since the COVID-19 pandemic, efforts in the field of surface decontamination have been redoubled. Finding innovative self-cleaning devices has become a challenge, and several solutions have been proposed in the market in recent years. In this work, an optimized powder/suspension plasma spray process at atmospheric pressure, using a Triplex Pro 210TM torch, is implemented to produce Cu-TiO2 surface coatings on stainless steel. The purpose is to investigate the potential improvement of antibacterial efficacy by the reactive surface species generated from TiO2 photoactivity under irradiation. A water-based suspension, prepared with AnalaR NORMAPURTM TiO2, is used as a precursor to incorporate the photocatalyst into an antibacterial copper matrix. Surface antibacterial tests according to ASTM 2180 standards were performed, and experiments were performed in treated contaminated water. Sub-stoichiometric blue TiO2 coatings showed complete bacterial elimination after 90 min of visible light irradiation, and Cu-TiO2 surface coatings were even able to disinfect the surfaces under white light, making the application interesting for bacterial destruction under natural illumination. These materials are also intended for application in water treatment, including both pathogens and chemical micropollutants, which is a pressing issue facing many countries today.

Influence of nanoparticle concentration on the flow regimes of crude oil – Nanosuspension in a microchannel

This paper presents the results of an investigation into the effect of silica nanoparticles on two-phase flow regimes in a Y-shaped microchannel. The following fluids were subjected to investigation: oil, water, and a water-based suspension containing SiO2 nanoparticles at a weight concentration of 1 ≤ φ ≤ 10 %. A systematic investigation of the flow regimes revealed the following: slug, parallel, and droplet regimes. The ranges of existence of the obtained flow regimes were determined and flow regime maps were constructed as a function of fluid flow rates and dimensionless numbers. The results of the study demonstrated that the slug length and frequency of slug formation are influenced by varying silica concentrations. Furthermore, the correlation between slug length and nanoparticle concentration remains consistent as the suspension flow rate increases. The dependence of the ratio of oil layer width to channel width for suspensions with varying nanoparticle concentrations was quantified. A mathematical simulation of two-phase flow of immiscible fluids was conducted. The results of the numerical simulation demonstrated the existence of the flow regimes that had been previously identified through experimentation. The aforementioned methodology may therefore be employed for the investigation of the two-phase immiscible flow of oil and nanosuspension.

Conductive water-based graphene suspension for electromagnetic interference shielding via spray coating on SiP module

Conductive inks have been widely used to develop electronic devices, such as sensors, RFID antennas, and transistors. Electronic utilization is a coating that forms conductive films for electromagnetic interference shielding (EMI Shielding). This process also can be employed to cover electronic modules called System in Package (SiP). A technology known as conformal shielding utilizes spray coating with metallic inks to form a conductive layer over the SiP. Traditionally, copper or silver inks have been the primary materials employed due to their high electrical conductivity. Conversely, these metallic inks are associated with significant costs, environmental impacts, and complex production methods. In this context, water-based graphene dispersion could be an alternative to EMI Shielding for electronic chips. Graphene is attractive due to its excellent electrical and thermal properties, reduced cost, and being an environmentally friendly material. In this study, a water-based graphene suspension was developed and applied via spray coating to form films for electromagnetic shielding. The graphene dispersion in water utilized Carboxymethyl cellulose (CMC). Characterizations of the graphene suspension, including morphology, particle size distribution, and chemical analysis, were conducted. The resistivity of the resulting films and their shielding effectiveness (SE) were measured. Electronic chip modules were painted to assess coverage. The study demonstrated the successful formulation of a stable water-graphene suspension exhibiting favorable electrical resistivity (2.8 × 10−2 Ω.cm) after drying at 300 °C for 1 h. The resulting film achieved a shielding effectiveness of −9 dB at 1.0 GHz. Graphene film completely covered the electronic chips, indicating an alternative conformal shielding.

Enhancing thermal performance in enclosures filled with nanofluids subjected to sinusoidal heating: a numerical study

ABSTRACT This study conducts a comprehensive numerical investigation into enhancing thermal transfer within square enclosures filled with water-based oxide nanoparticle suspensions, subjected to central sinusoidal heating. Further flow configuration, influenced by an inclined magnetic field, is designed with a focus on enhancing thermal efficiency for engineering applications. Key innovations include the application of sinusoidal heating elements to enhance thermal performance significantly. Computational analysis supported by finite element analysis, quantifies the impact of these parameters on flow dynamics and thermal transmission, presenting a substantial advance in the understanding of nanofluid-filled enclosure thermal management. The study reveals that the undulation of the heating element plays a crucial role in the heat transfer rate, with improvements observed as undulation increases. The introduction of magnetic fields further controls flow distribution and buoyancy effects, as demonstrated by our findings that an increase in the Rayleigh number correlates with enhanced convection, dominating the cavity's thermal dynamics. Additionally, the report outlines the conditions under which the Nusselt number increases, indicating enhanced thermal performance. These insights are pivotal for designing optimized heat transfer systems and energy-efficient applications, setting a new benchmark for thermal management strategies in practical engineering contexts.

Microstructure of Deposits Sprayed by a High Power Torch with Flash Boiling Atomization of High-Concentration Suspensions.

The main objective of this study was to use flash boiling atomization as a new method to inject suspensions with high solid content into the high-power plasma flow. The water-based suspension was prepared with submicron titanium oxide particles with an average size of 500 nm. The investigated solid concentrations were 20, 40, 55 and 70 wt%. Two plasma torches operated at 33, 70 and 110 kW were used to investigate the effect of increasing power on the deposited microstructure and deposition efficiency. At low torch power, the deposition efficiency decreased with increasing solid concentration, and deposits with a high number of unmelted particles were obtained with 70 wt% suspensions. At high torch power, the deposition efficiency increased with increasing solid concentration, and dense deposits were obtained with 70 wt% suspensions. XRD analysis was performed on all deposits to determine the distribution of rutile and anatase phases. The percentage of the anatase phase varied from 35.7% to 66.9%, depending on the power input and solid concentration.

Efficient composite dispersants for high solid content, low viscosity nano-zirconia slurries: An experimental and molecular dynamics simulation study

An effective dispersant is essential for creating a high-quality water-based ceramic suspension. When the solid content of the slurry is high, a single dispersant proves inadequate. This study proposes a strategy for producing nano-YSZ (yttria-stabilized zirconia) ceramic slurries with high solid content and low viscosity using compound dispersants ammonium polyacrylate (PAANH4) and fructose. The efficacy of dispersion is evaluated through rheological experiments and zeta potential analysis. The optimal dispersant effect is achieved when the compound dispersants are added in the following proportions: PAANH4 = 0.5 wt% and fructose = 5 wt%. Consequently, the viscosity of the nano-YSZ slurry, with a solid content of 50 vol%, is reduced to 696 mPa·s at a shear rate of 100 s−1. Both PAANH4 and fructose effectively lower the slurry’s viscosity via two separate mechanisms: electrostatic-steric stabilization and increasement of free water content. Molecular dynamics (MD) simulation was utilized to examine the nanoparticle dispersion process. The results show that after adding dispersants, the distance between two equilibrium particles is 4 nm, and the potential mean force curve displays a clear energy barrier. This provides a new method for investigating the dispersion effects of dispersants.

On-Chip Micro-Supercapacitor with High Areal Energy Density Based on Dielectrophoretic Assembly of Nanoporous Metal Microwire Electrodes.

Advances in the Internet of Things (IoT) technology have driven the demand for miniaturized electronic devices, prompting research on small-scale energy-storage systems. Micro-supercapacitors (MSCs) stand out in this regard because of their compact size, high power density, high charge-discharge rate, and extended cycle life. However, their limited energy density impedes commercialization. To resolve this issue, a simple and innovative approach is reported herein for fabricating highly efficient on-chip MSCs integrated with nanoporous metal microwires formed by dielectrophoresis (DEP)-driven gold nanoparticle (AuNP) assembly. Placing a water-based AuNP suspension onto interdigitated electrodes and applying an alternating voltage induces in-plane porous microwire formation in the electrode gap. The DEP-induced AuNP assembly and the gold microwire (AuMW) growth rate can be adjusted by controlling the applied alternating voltage and frequency. The microwire-integrated MSC (AuMW-MSC) electrically outperforms its unmodified counterpart and exhibits a 30% larger electrode area, along with 72% and 78% higher specific and areal capacitances, respectively, than a microwire-free MSC. Additionally, AuMW-MSC achieves maximum energy and power densities of 3.33 µWh cm-2 and 2629 µW cm-2, respectively, with a gel electrolyte. These findings can help upgrade MSCs to function as potent energy-storage devices for small electronics.

Application of ultra-low-volume spray for the control of vegetable disease in greenhouse: Investigation of formulation performance and potential dermal exposure.

The use of pesticides in greenhouse vegetable cultivation is necessary and significant. However, traditional pesticide application methods such as the use of backpack sprayers with water-diluted pesticides have certain drawbacks, e.g., uneven distribution, high labor intensity, and safety risks. In this work, fluazinam ultra-low-volume liquids (Flu-ULVs) were prepared using oily solvents as carriers. The effects of different oils on the physical properties of the preparations were investigated. The Flu-ULV can be sprayed directly using a hand-held ultra-low-volume (ULV) sprayer without dilution with water. Compared with commercial water-based suspension concentrates of fluazinam, the Flu-ULV samples showed better wetting of tomato leaves, better atomization, and more uniform droplet distribution. At a dosage of 300 mL/ha, the coverage rate of tomato leaves ranged from 32.47% to 79.3%, with a droplet deposition density of 556 to 2017 droplets/cm2. Application of Flu-ULVs provided 70.86% control efficacy against gray mold in tomatoes, which was higher than those achieved with reference products. Dermal exposure to Flu-ULVs was also evaluated in greenhouse experiments. The coverage rates for all parts of the operator's body ranged from 0.02% to 0.07%, with deposition volumes of 2.23 to 12.26 μg/cm2. Ground ULV spraying of fluazinam was proved to be an effective and safe management option for the control of tomato gray mold in greenhouses. This study laid a foundation for the use of ultra-low volume spray to control vegetable diseases in greenhouse, especially those induced by high humidity environment. © 2024 Society of Chemical Industry.

Turbulent Heat Transfer of Hybrid Nanofluid with Nano-Encapsulated Phase Change Material in a Square Channel

Investigation of turbulent mixed convection of different working fluids, namely, pure water, CuO/water nanofluid, n-octadecane/water nanofluid (or slurry), and a hybrid water-based suspension of CuO and n-octadecane nanoparticles in a uniformly heated vertical square channel is carried out. The shear stress transport/kappa-omega model is applied to simulate the turbulent flow. Eulerian–Lagrangian two phase model and homogeneous model are employed to simulate the nanofluid flow. It is shown that Eulerian–Lagrangian two-phase model predicts higher Nusselt number and friction factor than single-phase model and the results of two-phase model are closer to experimental data. It is found that a new hybrid nanofluid with dispersed nano-encapsulated phase change material particles provides better thermal and hydrodynamic performances compared to other nanofluids. Slurry containing 5% n-octadecane provides an improvement of nearly 37.2%, while hybrid nanofluid (1% CuO + 5% n-octadecane) offers added convective heat transfer enhancement of almost 60%. With increasing volume fraction, friction factor becomes slightly larger than that of pure water. For 5% n-octadecane/water and 1% CuO + 5% n-octadecane/water nanofluids, friction factor increases by 2.5% and 1.7%, respectively. Due to dominance of thermal entropy generation, total entropy generation reduces by increasing Reynolds number and volume fraction.

Tailoring the porosity level of the suspension plasma sprayed coatings using a dual suspension injection system

This study investigated the feasibility of tailoring the porosity in suspension plasma sprayed (SPS) coatings using a dual suspension injection system. Two titanium dioxide water-based suspensions with different particle sizes were injected into the plasma jet through two injectors located at different radial distances from the exit of the plasma torch. By varying the spray parameters, the fraction of unmelted particles in the coatings coming from the injector located farther from the torch changed. The total porosity was evaluated to range from approximately 16 % to 36 %, and the variation was related principally to the gaps between the unmelted particles. Among the selected spray parameters, the suspension feed rate and distance between the injectors were found to have the most significant effect on increasing the porosity. The samples were analyzed using SEM, XRD, and Raman spectroscopy.

Novel Surface Treatment to Mitigate Fouling in Heat Exchangers and Process Equipment

The global impact of climate changes due to greenhouse gas emissions cannot be overemphasized. To combat this, engineers are striving to develop innovative enhancements for heat transfer and fouling reduction in process equipment as a pathway to reduce CO2 emissions. A novel surface application of Minimox® treatment, a water-based suspension of rare-earth oxides, is a promising solution. The self-protective alloy treatment, unlike a traditional continuous coating, has no measurable thickness, does not impose any operating temperature limits, protects from high temperature oxidation, and decreases surface energy and polarity that leads to low fouling and coking rates. Minimox can be applied by dipping or spraying to both external and internal surfaces, including non-conventional tubing shapes. A post-application curing at 400 °C for 1 h is needed to ensure maximum fouling mitigation efficacy. Laboratory tests conducted to simulate operating conditions in a Coker furnace show that the Minimox-treated tubes reduce coke formation by about 80% as compared to untreated tubes. In addition, adhesion of coke to the Minimox treated tubes was significantly lower than for the untreated tubes. Field data collected in refinery applications involving Coker furnace tubes and a vacuum column wash bed are promising, lending support the laboratory results.

Study of thermal convection in chemically reactive carbon nanotube suspension saturated in anisotropic porous enclosure

This study aims to investigate the influence of chemical reactions and anisotropic porous material on the convective instability, heat and mass transfer rate of water-based carbon nanotube suspension. Flow governing dynamics are modeled using the modified Brinkman–Buongiorno model. The effects of pertinent flow characterizing parameters such as chemical reaction parameter, porosity parameter, mechanical anisotropy parameter and thermal anisotropy parameter on the threshold of convection, heat and mass transport rate are discussed and compared for three types of enclosures: shallow, square and tall. The study concludes that nanoliquid suspended with single-walled carbon nanotubes has higher heat and mass transfer capability than the multi-walled carbon nanotubes when saturated in a tall porous enclosure and also tall enclosure allows the convection to set in earlier. Anisotropic effect and destructive chemical reaction delay the starting of convection. Further, it is observed that the heat transfer rate decreases with the chemical reaction parameter.

On the Applicability of Modified Water-Based Yttria-Stabilized Zirconia Suspensions to Produce Plasma-Sprayed Columnar Coatings

In this paper, the applicability of the modified water-based yttria-stabilized zirconia (YSZ) suspensions, including different dispersants, to produce plasma-sprayed coatings with a “columnar microstructure” is investigated. The effects of processing parameters, like the suspension liquid-phase ethanol content, change in substrate roughness, and spray distance on the resulting coating morphologies, are investigated. The results showed that increasing the ethanol concentration, substrate surface roughness, and spray distance promotes the formation of coatings with a columnar structure. Moreover, the application of modified water-based suspensions, including the α-Terpineol dispersant, has led to the deposition of columnar coatings with comparable morphologies of coatings deposited from ethanol-based suspensions.

Singlet oxygen lifetime changes in dying glioblastoma cells.

Time-resolved phosphorescence detection was employed to determine the lifetime of singlet oxygen in live cells. Using hypericin as a photosensitizer, singlet oxygen was generated in U87MG glioblastoma cells. The phosphorescence of singlet oxygen was detected in aqueous cell suspensions following pulsed laser excitation. Our goal was to eliminate or reduce the problems associated with lifetime measurements in water-based cell suspensions. The apparatus enabled simultaneous singlet oxygen phosphorescence and transient absorption measurements, reducing uncertainty in lifetime estimation. The changes in singlet oxygen lifetime were observed during early and late apoptosis induced by photodynamic action. Our findings show that the effective lifetime of singlet oxygen in the intracellular space of the studied glioblastoma cells is 0.4 μs and increases to 1.5 μs as apoptosis progresses. Another group of hypericin, presumably located in the membrane blebs and the plasma membrane of apoptotic cells, generates singlet oxygen with a lifetime of 1.9 μs.

Effect of diamond seeds size on the adhesion of CVD diamond coatings on WC-Co instrument

In this study, we investigated the effect of the size of diamond seeds on the adhesion of multilayered polycrystalline diamond (PCD) films, grown by microwave plasma-assisted chemical vapor deposition (MPCVD). For that, identical WC-Co substrates were separately seeded by a set of diamond powders with various average particle sizes from water-based suspensions using similar seeding procedures. This investigation included powders with a difference in particle sizes of nearly 3 orders of magnitude: from 5 nm up to 2-4 μm. Seeded substrates were used to grow 8-10 μm thick multilayered PCD films using MPCVD with time-limited cycling injections of N2 gas. The Raman spectra and scanning electron microscopy (SEM) studies showed the similarity of microstructure and phase composition of all grown films, which confirmed that all films were grown in similar conditions. The performed scratch tests revealed sufficient differences in the adhesion of the films seeded with different diamond particles. The PCD film grown on 250-500 nm particles delaminated even before any mechanical investigations. The substrates seeded with 50 nm particles allowed the formation of the stable PCD film, but it started flaking under a load as small as 15 N. The 2-4 μm powder allowed the formation of PCD film with decent adhesion, which had local flaking under scratch test, which can be explained by the inhomogeneity of seeds distribution. Detonation nanodiamond (DND) powders allowed the formation of continuous diamond films with decent adhesion, however, powders with positive zeta potential were superior due to a much lower agglomeration of separate particles.

Superhydrophobic ceramic coatings with lotus leaf-like hierarchical surface structures deposited via suspension plasma spray process

In this work, superhydrophobic yttria-stabilized zirconia coatings were deposited via the suspension plasma spray process using a new water-based suspension. The new water-based suspension was prepared with the addition of surfactant, which showed a much lower surface tension than the conventional water-based suspension, and meanwhile was much cheaper and safer, and more environmentally friendly than the ethanol-based suspension. The coatings exhibited lotus leaf-like hierarchical surface structures of micron-sized protuberances with superimposed nanometer-sized splats/particles. After chemical modification, the coatings showed excellent water repellency with a water contact angle of ∼157°, a roll-off angle of ∼5°, and complete droplet rebound behaviors. The ethanol-based suspension and conventional water-based suspension were also prepared and used for coating deposition. Comprehensive characterizations of the suspension properties (surface tension, viscosity, atomization behaviors), surface structures, and wetting behaviors of different coatings were conducted for comparative investigation. The formation mechanism of different surface structures was elaborated by investigating the properties of suspensions and plasma gas flow, the aerodynamic breakup behaviors of suspensions, and the motion of impinging particles. The different wetting behaviors of coatings were correlated with the surface structures and wetting states. The study provides a rapid and cost-effective way to deposit hierarchically-structured superhydrophobic ceramic coatings via the water-based suspension plasma spray process.

Effect of water-based nanoclay and ambient temperature on rheological properties of UHPC pastes

Rheological properties of ultra-high-performance concrete (UHPC) pastes significantly impact the flowability and segregation resistance of UHPC, thus are of great importance to investigate. This study investigated the coupled effect of the water-based nanoclay suspension and ambient temperatures on rheological properties of UHPC pastes. Firstly, the water-based nanoclay was proved to show good compatibility with used PCE-based HRWR. Besides, the nanoclay content varied from 0 to 0.20% and the evaluated ambient temperatures were 10 °C, 25 °C, and 35 °C. Results showed that the addition of nanoclay and elevation of ambient temperatures significantly increased plastic viscosity and dynamic yield stress of UHPC pastes. The thixotropy of UHPC pastes was also enhanced, which was quantified by a bi-linear model including initial fluctuations of static yield stress (τfloc) and thixotropy index (IA). The enhancement of rheological properties are closely related to the evolution of internal microstructure, including physical and chemical effects. The physical effects refer to the flocculation between particles: (1) the addition of nanoclay accelerated the flocculation by the electrostatic attraction forces; (2) the elevation of ambient temperatures accelerated the flocculation by promoting Brownian motions of particles. The chemical effects refer to the increased hydration reaction: (1) the nanoclay addition increased aluminates contents, thus promoting the hydration of C3A to generate ettringite; (2) the elevation of ambient temperatures increased the dissolution of C3A then promoted the hydration. More importantly, ettringite is the main hydration product to affect the rheological properties of UHPC pastes. This study revealed the coupled effect of water-based nanoclay and ambient temperature on rheology of UHPC pastes and will advance the large-scale application of the water-based nanoclay suspension.