Electric Double Layer Repulsion Research Articles

Carbon aerogels by pyrolysis of TEMPO-oxidized cellulose

Although carbon aerogels derived from naturally occurring materials have been developed extensively, a reasonable synthetic approach using cellulose-resource remains unclear. Here, we report a strategy to prepare carbon aerogels originated from cellulose position-selectively oxidized by TEMPO-oxidized process. Contrary to non-TEMPO-oxidized cellulose-derived carbon aerogels (NCCA) with relative loose structure, TEMPO-oxidized cellulose-derived carbon aerogels (TCCA) with tight fibrillar-continuous network are monitored, suggesting the importance of TEMPO-oxidized modification towards creating the architecture of subsequently produced carbon aerogels. TCCA endows a higher BET area despite owning slightly dense bulk density comparing with that of NCCA. The structural texture of TCCA could be maintained in a way in comparison to TEMPO-oxidized cellulose-derived aerogel, due to the integration and aggregation effect by losing the electric double layer repulsion via ionization of the surface carboxyl groups. FTIR and XPS analyses signify the evidence of non-functionalized carbon-skeleton network formation in terms of TCCA. Further, the mechanism concerning the creation of carbon aerogels is also established. These findings not only provide new insights into the production of carbon aerogels but also open up a new opportunity in the field of functional carbon materials.

Characterization of Platinum Electrode Surfaces by Electrochemical Surface Forces Measurement

The surface forces between platinum, Pt, electrodes and those between the Pt electrode and mica in aqueous HClO4 were measured at various potentials (E) applied to the electrodes using an electrochemical surface forces apparatus (EC-SFA). This apparatus uses the twin-path surface forces apparatus, recently developed for opaque samples. The influence of the proton adsorption on the surface interactions was studied. The Pt electrodes were prepared by the template-stripping procedure using glass templates. The electrode surfaces were smooth (RMS roughness: 0.26 nm for a 5 μm × 5 μm area) and polycrystalline based on the atomic force microscopy and cyclic voltammetry results, respectively. When the applied potential E was decreased from 0.5 to 0.2 V (vs Ag/AgCl), the electric double layer (EDL) repulsion between the Pt electrodes decreased. The absolute values of the surface potentials, |ψ0|, calculated using the EDL theory were 58 and 43 mV at E = 0.5 and 0.2 V, respectively. The EDL force at E = 0.2 V was t...

Different transport behaviors of Bacillus subtilis cells and spores in saturated porous media: Implications for contamination risks associated with bacterial sporulation in aquifer

In this study, we compared the transport characteristics of Bacillus subtilis cells and their spores in saturated porous media. Both the bacteria cells and spores were readily transported under lower ionic strengths (IS) (1mM), featuring high mass recovery rates (>75%). The bacteria cells recovery rate declined to 58.05% when the IS increased to 100mM; but the spores recovery rate remained at 74.54%. Spores appear to be more mobile than bacterial cells over wide range of IS. Surface properties and breakthrough curves analysis of the two bio-particles (cells and spores) indicated that attachment, straining and blocking mechanisms contribute differently to deposition processes. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory further indicated that the particles attachment may primarily occurred at the secondary energy minimum. More important, XDLVO calculations showed that the dominant forces changed with IS, altering the efficiency of particles attachment. The electric double layer repulsion mainly controlled particle deposition at 1mM. In contrast, the van der Waals attraction and Lewis acid-base interactions dominated particle deposition at 100mM. This study showed that spores are more mobile than bacteria cells in subsurface environment. Given that spores form under harsh environmental conditions, we must consider spore formation and transport when groundwater microbial contamination occurs.

Probing the Interaction Mechanism between Air Bubbles and Bitumen Surfaces in Aqueous Media Using Bubble Probe Atomic Force Microscopy.

Surface interactions involving deformable air bubbles have attracted tremendous interest in a wide range of engineering applications, such as mineral flotation and bitumen extraction. In this work, for the first time, the interaction forces between air bubbles and bitumen surfaces in complex aqueous media of varying pH, salinity, and salts were directly measured using a bubble probe atomic force microscope (AFM) technique. The AFM topographic imaging reveals that bitumen surface tends to be rougher and form distinct domains at high NaCl concentration or under strongly alkaline environment. The force measurements demonstrate the critical role of ionic strength and solution pH in bubble-bitumen interaction and attachment, which could be well described by a theoretical model based on Reynolds lubrication theory and augmented Young-Laplace equation by including the effect of disjoining pressure. In 1 mM NaCl, the electrical double layer (EDL) repulsion inhibited bubble-bitumen attachment, and such a repulsive effect could be further strengthened with increasing solution pH. In 500 mM NaCl, the hydrophobic attraction could lead to bubble-bitumen attachment, while a high solution pH could weaken the hydrophobic interaction. The addition of calcium ion in 500 mM NaCl could enhance the hydrophobic interaction and facilitate the bubble-bitumen attachment, most likely attributed to the bridging effect between calcium ions and the functional groups (e.g., carboxyl group) of interface-active molecules on bitumen surfaces, thus leading to higher surface roughness and hydrophobic moieties/aggregates on bitumen as confirmed by AFM imaging. Our results provide quantitative information on the interaction mechanism between air bubbles and bitumen surfaces in complex aqueous solutions at the nanoscale, which has useful implications to many related interfacial interactions in industrial processes such as oil production, oil-water separation, and wastewater treatment.

DEM modelling of particle-bubble capture through extended DLVO theory

This work presents a computational study based on Discrete Element Method (DEM) to investigate the capture of particles by bubbles in the presence of electrical double layer repulsion. In the DEM model a fully mobile boundary condition was assumed for the gas-liquid (bubble) interface. The forces acting on the particle were gravitational, buoyancy, hydrodynamic, as well as elastic and damping forces if/when the particle penetrated inside the bubble. Surface forces were considered and were evaluated through the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. A preliminary theoretical analysis of the surface forces was carried out in order to determine the possibility of particle capture. This analysis included the determination of the interaction potential energy. Five different types of interaction energy curves were found. They were characterised by (1) a monotonic increase with distance; (2) the presence of a primary minimum; (3) the presence of an energy barrier and a primary minimum, (4) the presence of an energy barrier and a primary and a secondary minimum, and (5) a monotonic decrease with distance. DEM modelling was conducted to investigate the induction time for a single particle-bubble system. It was found that the induction time decreased with increasing contact angle and decreasing height of the energy barrier. In contrast, the primary minimum had very limited impact on induction time. Additionally, modelling of a more complex system consisting of a single bubble and multiple particles was also carried out. The multiple particle-single bubble simulation results showed that a decrease in induction time considerably enhanced collection efficiency. Finally, the concept of “contactless” flotation, which occurs in the case in which only a primary minimum exists, was also demonstrated through the use of DEM modelling.

Probing the Effect of Salinity and pH on Surface Interactions between Air Bubbles and Hydrophobic Solids: Implications for Colloidal Assembly at Air/Water Interfaces.

In this work, a bubble probe atomic force microscope (AFM) was employed to quantify the interactions between two air bubbles and between an air bubble and an octadecyltrichlorosilane (OTS)-hydrophobized mica under various aqueous conditions. The key parameters (e.g., surface potentials, decay length of hydrophobic attraction) were obtained by analyzing the measured forces through a theoretical model based on Reynolds lubrication theory and an augmented Young-Laplace equation by including effect of disjoining pressure. The bubble-OTS hydrophobic attraction with a decay length of 1.0 nm was found to be independent of solution pH and salinity. These parameters were further used to predict the attachment of OTS-hydrophobized particles onto the air/water interface, demonstrating that particle attachment driven by hydrophobic attraction could be facilitated by suppressing electrical double-layer repulsion at low pH or high salinity condition. This facile methodology can be readily extended to quantify interactions of many other colloidal particles with gas/water and oil/water interfaces, with implications for colloidal assembly at different interfaces in many engineering applications.

Design of latex-layered double hydroxide composites by tuning the aggregation in suspensions.

Colloidal stability of polymeric latex particles was studied in the presence of oppositely charged layered double hydroxide (LDH) platelets of different interlayer anions. Adsorption of the LDH particles led to charge neutralization and to overcharging of the latex at appropriate concentrations. Mixing stable colloidal suspensions of individual particles results in rapid aggregation once the LDH adsorption neutralizes the negative charges of the polymer spheres, while stable suspensions were observed at high and low LDH doses. The governing interparticle interactions included repulsive electrical double layer forces as well as van der Waals and patch-charge attractions, whose strength depended on the amount of LDH particles adsorbed on the latex surface. The type of the LDH interlayer anions did not affect the colloidal stability of the samples. Structural investigation of the obtained latex-LDH composites revealed that the polymer spheres were completely coated with the inorganic platelets once their concentration was sufficiently high. These results are especially important for designing synthetic routes for hybrid systems in suspensions, where stable colloids are required for uniform film-formation and for the homogeneous distribution of the inorganic filler within the composite materials.

Implementation of diffusion and electrostatic forces to produce a new slip velocity in the multiphase approach to nanofluids

Due to the improvement of heat transfer by nanofluids, an understanding of the interactions between nanoparticles and the base fluid is essential for simulation. The relative or slip velocity between nanoparticles and the base fluid is one of the main factors in choosing the multiphase mixture model approach. In this paper, a new slip velocity is proposed and used to compare the simulation result to the experimental results of natural convective flow in a cavity filled with an alumina nanofluid. Therefore, the ANSYS-Fluent 15.0 software is employed and the new slip velocity is applied as a user-defined function. The new slip velocity is a result of the combination of Brownian and thermophoretic diffusions, lift, buoyancy and centrifugal forces, virtual mass, pressure gradient, Van der Waals attraction and electric double layer repulsion forces. The comparison between these forces and induced drag force will provide the corresponding slip velocity. The simulation results were in good agreement with the flow pattern and heat transfer features of the experimental studies in the literature. It was found that thermophoretic and electrostatic slip mechanisms should essentially be considered in simulations, as well as buoyancy force. The major effects of electrostatic slip velocity are mainly seen in concentration higher than 1vol.%, while thermophoresis could not be ignored in any concentration. Therefore, the implemented slip velocity reveals some critical aspects of nanoparticle and base fluid interactions compared to an algebraic velocity.

A new combination of nanoparticles mass diffusion flux and slip mechanism approaches with electrostatic forces in a natural convective cavity flow

Understanding of the phenomena involved in the mixture of nanoparticles and fluid requires more investigation in terms of many aspects. Both diffusion process and slip mechanisms are studied here with a new approach applied in the governing equations in Mixture model. The new approach tested for laminar natural convective flow inside a cavity (with two differentially heated walls) by using ANSYS FLUENT 15.0 with the presence of Alumina and Zinc Oxide nanofluids. The new slip mechanism covers the effects of virtual mass, pressure gradient, lift, buoyancy, centrifugal, van der Waals attraction and electrical double layer repulsion forces. All the slip mechanism and source terms in the governing equations are implemented as User Define Functions in ANSYS FLUENT 15.0. The numerical results provided good agreement with experiments performed in this study. Depending on the volume fraction, heat transfer may improve or deteriorate, as reported by others. The comparison indicates that the ability of the proposed method is mainly associated to the concentration distribution, and of course in the ranges of volume fraction studied here. It is also found that the diffusion fluxes change the concentration profile near the diabatic walls, while the slip mechanism will be dominant in adiabatic walls.

Evaluation of the particle sizes of four clay minerals

The particle size distributions (PSD) of four clay minerals from the US Clay Minerals Society, kaolinite, illite, Ca2+-montmorillonite, and Na+-montmorillonite, were analyzed using different dispersion techniques to evaluate their PSD variability and intrinsic particle sizes. Both dry dispersion in pressurized air and wet dispersion in water and ethyl alcohol with and without an interlayer expanding agent, glycerol, were employed, along with mechanical ultrasound disaggregation and chemical dispersion. Results show that all four clay minerals exhibit multimodal PSD consisting of superimposed subordinate lognormal distributions from submicron and 1–2μm primary particles, 10–20μm flocculi (and trace impurities). Microflocs of 50–500μm occur only in the dry dispersion mode. Owing to the presence of relatively strong flocculi that are not prone to breakdown to smaller primary particles, the intrinsic PSD of these clay minerals cannot be readily obtained by the adopted dispersion methods. The two swelling clay minerals, Na+-montmorillonite and Ca2+-montmorillonite, are more sensitive than the non-swelling ones, kaolinite and illite, to different dispersion solvents. The variability of these clay minerals' PSD is further discussed in terms of the complex interactions among clay mineral particles, polar or less polar solvent, and dispersant, such as swelling, cation exchange, exfoliation, and electrical double layer repulsion. A significant practical implication is that most existing dispersion methods for PSD analysis tend to overestimate the silt-sized fraction but underestimate the clay-sized fraction, which may yield misleading classification for clay mineral-rich soils. For expansive clay minerals, appropriate dispersants should be selected to avoid cation exchange between the sample and dispersants, which can change their intrinsic PSD.

Hollow graphene oxide spheres: facile synthesis and formation mechanism

In this work, we introduced a facile approach for preparing hollow graphene oxide spheres (HGOSs). By electrostatic self-assembly polystyrene (PS)/graphene oxide (GO), core/shell microspheres were synthesized. After removal of the sacrificial PS colloidal spheres by toluene solution treatment, HGOSs were prepared successfully. Based on the DLVO theory, van der Waals force and electric double layer repulsion were proposed to quantitatively analyze the self-assembly of the composite structure. The theoretical formulation for the resultant interaction force F versus separation between the surfaces d showed a significant low energy barrier for the aggregation of the GO and PS, which predicted the favorable HGOSs formation.

Improved flotation performance of hematite fines using citric acid as a dispersant

In this study, citric acid was used as a dispersant to improve the flotation performance of hematite fines. The effect and mechanism of citric acid on the reverse flotation of hematite fines were investigated by flotation tests, sedimentation experiments, scanning electron microscopy (SEM), zeta-potential measurements, and X-ray photoelectron spectroscopy (XPS). The results of SEM analysis and flotation tests reveal that a strong heterocoagulation in the form of slime coating or coagulation in hematite fine slurry affects the beneficiation of hematite ores by froth flotation. The addition of a small amount of citric acid (less than 300 g/t) favorably affects the reverse flotation of hematite fines by improving particle dispersion. The results of sedimentation experiments, zeta-potential measurements, and XPS measurements demonstrate that citric acid adsorbs onto hematite and quartz surfaces via hydrogen bonding, thereby reducing the zeta potentials of mineral surfaces, strengthening the electrical double-layer repulsion between mineral particles, and dispersing the pulp particles.

Probing Interactions between Air Bubble and Hydrophobic Polymer Surface: Impact of Solution Salinity and Interfacial Nanobubbles.

The interactions between air bubbles and hydrophobic polymer surfaces in aqueous media play important roles in many industrial and engineering processes. In this work, the interaction forces between air bubble and a model hydrophobic polymer-polystyrene (PS) in NaCl solutions (1 mM to 1000 mM) were directly measured using a bubble probe atomic force microscope (AFM) technique, and the measured forces were analyzed by a theoretical model based on Reynolds lubrication theory and augmented Young-Laplace equation including the influence of disjoining pressure. It was found that the theoretical analysis, by assuming that the PS surface was a pristine and bare polymer surface in aqueous solutions, could not fully agree with the experimental force measurements at intermedium salinity condition (i.e., 100 mM NaCl), and the discrepancy could not be described by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory even including the effects of non-DLVO interactions such as hydrophobic interaction. Atomic force microscope (AFM) imaging demonstrated that the above discrepancy was caused by the presence of interfacial nanobubbles (INBs) on the hydrophobic PS surface. The solution salinity was found to significantly affect the size and surface coverage of INBs on the PS surface, thereby influencing the surface forces. At high NaCl concentration (e.g., 500 and 1000 mM), the INB formation (and its impact on the surface interactions) and electric double layer repulsion were highly suppressed, and the bubble-PS attachment was observed attributing to their hydrophobic attraction with a decay length of ∼0.75 ± 0.05 nm. The results agree with our previous surface force measurements between two PS surfaces using a surface forces apparatus. This work provides useful insights into the interaction mechanism between air bubbles and hydrophobic polymer surfaces, as well as the influence of solution salinity and interfacial nanobubbles on the bubble-polymer interaction.

Ultrafiltration of charge-stabilized dispersions at low salinity.

We present a comprehensive study of cross-flow ultrafiltration (UF) of charge-stabilized suspensions, under low-salinity conditions of electrostatically strongly repelling colloidal particles. The axially varying permeate flux, near-membrane concentration-polarization (CP) layer and osmotic pressure profiles are calculated using a macroscopic diffusion-advection boundary layer method, and are compared with filtration experiments on aqueous suspensions of charge-stabilized silica particles. The theoretical description based on the one-component macroion fluid model (OCM) accounts for the strong influence of surface-released counterions on the renormalized colloid charge and suspension osmotic compressibility, and for the influence of the colloidal hydrodynamic interactions and electric double layer repulsion on the concentration-dependent suspension viscosity η, and collective diffusion coefficient Dc. A strong electro-hydrodynamic enhancement of Dc and η, and likewise of the osmotic pressure, is predicted theoretically, as compared with their values for a hard-sphere suspension. We also point to the failure of generalized Stokes-Einstein relations describing reciprocal relations between Dc and η. According to our filtration model, Dc is of dominant influence, giving rise to an only weakly developed CP layer having practically no effect on the permeate flux. This prediction is quantitatively confirmed by our UF measurements of the permeate flux using an aqueous suspension of charged silica spheres as the feed system. The experimentally detected fouling for the largest considered transmembrane pressure values is shown not to be due to filter cake formation by crystallization or vitrification.

Hydrophobic nano-asperities in control of energy barrier during particle–surface interactions

To explain differences in colloidal interactions for spherical hydrophobic particles, a theoretical analysis of the interaction potential was carried out for a model rough particle interacting with a smooth and flat surface in an electrolyte solution. The attractive hydrophobic interaction potential was added to repulsive retarded van der Waals and repulsive electrical double layer interaction potentials. The rough microscopic particles were modeled as spheres decorated with nano-sized hemispherical asperities. Parameters that reflect common flotation separation systems were selected for testing this theoretical model and computation of the energy barrier applicable to particle–surface interactions. It was found that hydrophobic asperities with the radius of only a few nanometers reduced the energy required for particle attachment to a hydrophobic surface by several times. The value of this energy barrier was reduced by as much as two orders of magnitude when the radius of nano-sized asperities increased to a few tens of nanometers. Theoretical analysis also revealed that surface coverage of microscopic particles by nano-sized asperities was not as important as the size of the asperities.

Orthokinetic aggregation of charged colloidal particles in the presence of repulsive double layer force: A trajectory analysis with the solution of non-linear Poisson–Boltzmann equation

Abstract We studied turbulent coagulation rates of well-characterized carboxyl-terminated latex particles as a function of pH at different KCl concentrations. The negative charge of the studied particles increases and thus develops the electrical double layer repulsion with increasing pH. The pH-dependent coagulation rate was analyzed on the basis of the trajectory analysis with the Derjaguin, Landau, Verwey, and Overbeek theory using the solution of non-linear Poisson–Boltzmann (PB) equation under the charge regulation boundary condition, in which the electrostatic boundary conditions such as surface potential depends on surface separation distance. It should be noted that this is the first attempt to compare the calculated results with the experimental data of the effect of surface charge on turbulent coagulation rates. The calculation using the trajectory analysis can well describe the experimental data. However, to obtain the good agreement between the experimental data and the calculation, we need to decrease the Hamaker constant A H with increasing KCl concentration. The dependence of A H on salt concentration is probably ascribed to the fact that the origin of the van der Waals attraction is essentially electrostatic dipole–dipole interaction between molecules. That is, we consider that the van der Waals attraction is increasingly screened by the charge of ions with increasing salt concentration.

Floc flotation of jamesonite fines in aqueous suspensions induced by ammonium dibutyl dithiophosphate

The hydrophobic flocculation of jamesonite fines in aqueous suspensions induced by ammonium dibutyl dithiophosphate was investigated using laser particle size analysis, microscope analysis, electrophoretic light scattering and infrared spectroscopy. Single minerals of 4.607 μm for the 50% volumetric diameters were researched by varying several parameters, including pH, ammonium dibutyl dithiophosphate concentration, stirring strength and kerosene addition. It is found that the maximal floatability of jamesonite fines is induced by ammonium dibutyl dithiophosphate at pH 6, and the floc flotation increases with increasing ammonium dibutyl dithiophosphate concentration despite a simultaneous increase in the negative ζ potential of jamesonite, meaning that hydrophobic interaction between the particles increases much more strongly than electric double layer repulsion from the adsorption of ammonium dibutyl dithiophosphate. It is also found that the floc flotation is closely correlated with the size of flocs, which is strongly influenced by the stirring strength and enhanced by the addition of a small amount of kerosene. The results of FTIR spectra indicate that adsorption of ammonium dibutyl dithiophosphate onto jamesonite is chemical adsorption and the adsorption product is lead dibutyl dithiophosphate.

Effect of ionic strength and permeate flux on membrane fouling: Analysis of forces acting on particle deposit and cake formation

In Cross-Flow Microfiltration (CFMF), suspended particles deposit to form a cake layer on the membrane surface, which provides a resistance to permeate flow. The cake resistance, which plays an important role on the performance of CFMF, is mainly determined by the packing porosity of the cake and, the physical and chemical properties of particles. This study aimed at understanding the porosity and the specific filtration resistance of the cake for a given condition. These properties have been studied using experiments under a constant permeate flux. Factors such as permeate flux and ionic strength were investigated in terms of the particles deposition and cake formation. This study also adopted a force balance model to predict the deposit rate of particles and then compare with the experimental results. Inter-particle forces (electric double layer repulsion force and Van der Waals attraction force) were incorporated into the calculation of cake structure (cake porosity and specific resistance) together with the equilibrium condition of hydrodynamic forces. The experimental results showed that the higher the permeate flux led to the greater amount of particles deposit and the denser structure of cake. The porosity of cake decreased with the increase in ionic strength (0∼0.01M) and then increased sharply afterwards (0.01∼0.1M). The hydrodynamic force balance model estimated well the tendency of variation in cake structure depending on the ionic strength.

Coverage and disruption of phospholipid membranes by oxide nanoparticles.

We studied the interactions of silica and titanium dioxide nanoparticles with phospholipid membranes and show how electrostatics plays an important role. For this, we systematically varied the charge density of both the membranes by changing their lipid composition and the oxide particles by changing the pH. For the silica nanoparticles, results from our recently presented fluorescence vesicle leakage assay are combined with data on particle adsorption onto supported lipid bilayers obtained by optical reflectometry. Because of the strong tendency of the TiO2 nanoparticles to aggregate, the interaction of these particles with the bilayer was studied only in the leakage assay. Self-consistent field (SCF) modeling was applied to interpret the results on a molecular level. At low charge densities of either the silica nanoparticles or the lipid bilayers, no electrostatic barrier to adsorption exists. However, the adsorption rate and adsorbed amounts drop with increasing (negative) charge densities on particles and membranes because of electric double-layer repulsion, which is confirmed by the effect of the ionic strength. SCF calculations show that charged particles change the structure of lipid bilayers by a reorientation of a fraction of the zwitterionic phosphatidylcholine (PC) headgroups. This explains the affinity of the silica particles for pure PC lipid layers, even at relatively high particle charge densities. Particle adsorption does not always lead to the disruption of the membrane integrity, as is clear from a comparison of the leakage and adsorption data for the silica particles. The attraction should be strong enough, and in line with this, we found that for positively charged TiO2 particles vesicle disruption increases with increasing negative charge density on the membranes. Our results may be extrapolated to a broader range of oxide nanoparticles and ultimately may be used for establishing more accurate nanoparticle toxicity assessments and drug-delivery systems.

Aqueous and Nonaqueous Colloidal Processing of Difficult‐to‐Densify Ceramics: Suspension Rheology and Particle Packing

Aqueous and nonaqueous colloidal processing of zirconium diboride (ZrB2) and boron carbide (B4C) has been investigated. The aqueous and nonaqueous ZrB2 and B4C suspension formulations have been optimized. The suspensions were cast into green bodies using slip casting. The correlation between the state of dispersion with the rheological properties of the suspensions and the resulting packing density was observed in both aqueous and nonaqueous processing. The attractive interactions between powder particles in water were difficult to overcome with electrical double layer or electrosteric repulsion. Reasonably low viscosity aqueous ZrB2 suspensions up to 45 vol% solids could be prepared. It was not possible to produce low viscosity (viscosity below 1 Pa·s at shear rate of 100 s−1) aqueous B4C suspensions with solid content above 30 vol%. Slip casting of the weakly aggregated ZrB2 suspensions resulted in low packing densities (~55% relative density) of the green bodies. On the other hand, dispersion of powder particles in nonaqueous media (cyclohexane and dodecane) enabled suspensions with lower viscosities and a higher maximum solid concentration (up to 50 vol%) to be prepared. The well‐dispersed nonaqueous suspensions promoted an efficient particle packing, resulting in higher green densities (64% and 62% relative density for ZrB2 and B4C, respectively) compared to aqueous processing. The significantly high green densities are promising to allow densification of the materials at lower sintering temperature.