Controlling unconfined yield strength in a humid environment through surface modification of powders

Stevens, Nathanael; Tedeschi, S.; Powers, Kevin; Moudgil, Brij M.; El‐Shall, H.

doi:10.1016/j.powtec.2008.10.001

Cited by 24 publications

(8 citation statements)

References 12 publications

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“…The key factor affecting the movement of liquid droplets on hydrophobic or oleophobic surfaces may be considered to be the microscopic w ad on a rough surface. The expression of w ad , based on the Young-Dupre `equation is written as 22,23 Since the liquid droplet partially sits on the silica sphere stacking surfaces (as shown in Figure 4), the work of adhesion is a function of the wetted solid fraction ( f ). Thus, eq 2 can be rewritten as 11 For complete nonwetting (i.e, θ ) 180°and f ) 0), w ad is absolutely equal to 0 resulting in completely noninteracting solid and liquid phases, reflecting that the droplet is levitated.…”

Section: Resultsmentioning

confidence: 99%

Contact Angle Hysteresis and Work of Adhesion of Oil Droplets on Nanosphere Stacking Layers

Hsieh

Chen

2009

J. Phys. Chem. C

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Surface repellency of liquid droplets with different surface tensions (23.4-73.2 mN/m) on nanostructured surfaces built of one-and two-tier silica sphere stacking surfaces were investigated, and contact angle hysteresis (CAH) and work of adhesion were analyzed. It was shown that the binary nano-and sub-micrometer-scaled roughened surfaces exhibited better repellency toward oil drops with surface tension of 30 mN/m, and the CAH behavior strongly depended on both liquid types and density of three-phase contact line. This improvement of hysteresis from the two-tier texture is attributed to the facts that (i) the arrangement of submicrometer spheres generates a primary roughness that allows air cushion in the texture and (ii) the deposition of nanospheres creates a large number of point contact fashion to repel the oil penetration, reducing the length of the liquid-solid contact line (i.e., Cassie state). The existing air layer tends to impart the fraction of vapor-solid contact, which decreases the kinetic barrier of drop movement. Incorporated with the Young-Dupre `equation, it has shown a linear relationship between the difference between cosines of advancing and receding angles and the work of adhesion. Accordingly, it reveals that the adhesion of solid-oil contact interface is reduced due to the design of surface topography.

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Section: Resultsmentioning

confidence: 99%

Contact Angle Hysteresis and Work of Adhesion of Oil Droplets on Nanosphere Stacking Layers

Hsieh

Chen

2009

J. Phys. Chem. C

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“…A minimum amount is needed to, first, surpass the rough surface of grains, and, second, form a meniscus between non-touching neighbors, so the number of necks is critically affected at low liquid volumes. Thus, for increasing contents of wetting liquid, powders [171], granular materials [79][80][81]172,173] and capillary suspensions [30,31] show a rapid rise from vanishing yield stress to a stable value. This value corresponds to full pendular bridging (all particles contribute to the capillary network [31]) and remains constant along the pendular state, which indicates that further increase of the neck volume does not change the cohesion between the grains.…”

Section: Ensemble Cohesionmentioning

confidence: 98%

Colloidal crystals and water: Perspectives on liquid–solid nanoscale phenomena in wet particulate media

Gallego-Gómez

Morales‐Flórez

Morales

et al. 2016

Advances in Colloid and Interface Science

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Solid colloidal ensembles inherently contain water adsorbed from the ambient moisture. This water, confined in the porous network formed by the building submicron spheres, greatly affects the ensemble properties. Inversely, one can benefit from such influence on collective features to explore the water behavior in such nanoconfinements. Recently, novel approaches have been developed to investigate in-depth where and how water is placed in the nanometric pores of self-assembled colloidal crystals. Here we summarize these advances, along with new ones, that are linked to general interfacial water phenomena like adsorption, capillary forces and flow. Waterdependent structural properties of the colloidal crystal give clues to the interplay between nanoconfined water and solid fine particles that determines the behavior of ensembles. We elaborate on how the knowledge gained on water in colloidal crystals provides new opportunities for multidisciplinary study of interfacial and nanoconfined liquids and their essential role in the physics of utmost important systems such as particulate media.

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“…increasing the contact angle through surface modification or by increasing the dispersion force through the use of a volatile medium. Research on the use of surface modification to control the contact angle is reported in detail elsewhere 19) however only the relevant results will be discussed below. For this investigation, aluminum flakes were coated with a hydrophobic silane and the dispersion properties were examined using the FTIR Air Chamber.…”

Section: Figmentioning

confidence: 99%

“…This requires a systematic study of these factors and their effect on the dispersion of the resultant aerosol. In previous work, the efficacies of different dr ying methods were investigated and two novel CO2 based drying methods developed 18) as was the use of surface modification to control capillary adhesion 19) . During this research, the ef fect of humidity and hydrophobicity, flow aids and interparticle contact area, and dispersion methods have been studied and the results analyzed through the guidance of a statistical experimental design.…”

Section: Introductionmentioning

confidence: 99%

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Improving Aerosol Dispersion through Processing and Dissemination Techniques

Tedeschi

Powers

Ranade

et al. 2009

KONA

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The state of dispersion is a vital aspect of powder technology impacting both traditional and emerging technologies in many diverse areas of interest including health care, industry, the environment, and the military. In such applications, the properties and quality of the resultant product will be directly and noticeably affected by the degree to which the particles are dispersed. In any operation where satisfactory particle dispersion is imperative, a reduction in dispersion, or increased agglomeration, leads to poor efficiency and ultimately results in lower yields and increased cost. As powder technology moves into the nano-age, the challenges of maintaining and improving particle dispersion become increasingly important. Decreasing particle size into the submicron range can significantly increases the effect of surface forces leading to an increase in the cohesive forces of the powder, thus, making an understanding of dispersion even more essential. In order to develop the knowledge base to understand and control aerosol dispersion, a fundamental study into significant powder characteristics and environmental conditions that influence dispersion has been conducted. This paper discusses the results of testing various techniques employed to improve the dispersion of sub-micron aluminum flakes such as using a fumed silica spacer to reduce interparticle contact area and, in turn, attractive van der Waals forces, as well as examining the effect of dissemination pressure on the state of dispersion of the particles. This research was conducted using statistical experimental design in order to efficiently study significant factors.

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Controlling unconfined yield strength in a humid environment through surface modification of powders

Cited by 24 publications

References 12 publications

Contact Angle Hysteresis and Work of Adhesion of Oil Droplets on Nanosphere Stacking Layers

Contact Angle Hysteresis and Work of Adhesion of Oil Droplets on Nanosphere Stacking Layers

Colloidal crystals and water: Perspectives on liquid–solid nanoscale phenomena in wet particulate media

Improving Aerosol Dispersion through Processing and Dissemination Techniques

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