Compaction experiments on ice-silica particle mixtures: Implication for residual porosity of small icy bodies

Ultrafiltration of three laboratory made silica and two commercial silica sols was studied using Amicon YC membrane in a 200 ml capacity batch-cell. The effect of silica particle size, stirring conditions, pressure, pH and silica contents on ultrafiltration was investigated. The results obtained indicate that the smaller particles have, disregarding the stirring conditions, lower filtration flux. The differences observed in filtration flux are more pronounced in the conditions without stirring. The obtained value of the membrane resistance is independent of the conditions investigated (stirring, pressure, pH, silica contents and particle size). The values of the resistance of polarized solids, specific resistance, and the mass of gel per membrane surface unit were calculated for all experimental conditions.

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An Update on The Problem of Small Comets

Highlights of Astronomy ◽

10.1017/s1539299600020657 ◽

1998 ◽

Vol 11 (1) ◽

pp. 237-238

Author(s):

J.C. Brandt ◽

M.F. A’Hearn

Keyword(s):

Recent Work ◽

Terrestrial Planets ◽

Indirect Methods ◽

Earth’S Atmosphere ◽

Direct Observations ◽

Icy Bodies ◽

Earth's Atmosphere ◽

Search Program ◽

Volatile Materials

The evidence for a major population of small comets (SCs) is summarized in two steps. First, we briefly summarize our previous work. Second, we describe recent work that continues to find SCs. When new capabilities become available that can detect SCs, we expect to find them and this is occurring. At present, their detection is a haphazard process and we advocate a dedicated, optimized search program. We define SCs as those icy bodies (i.e., sublimating bodies) with radius less than 1000 meters. Often the existence of SCs is inferred from effects ascribed to them. These “effects” include: lunar cratering; cratering on Ganymede; excess interplanetary hydrogen; delivery of volatile materials to the terrestrial planets; and a source of fragile bodies entering the Earth’s atmosphere. While some of these indirect methods support the existence of SCs, direct observations are clearly preferred.

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Spherical silica particle production by combined biomimetic-Stöber synthesis using renewable sodium caseinate without petrochemical agents

Applied Nanoscience ◽

10.1007/s13204-021-01762-2 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1151-1167

Author(s):

Ricky Curley ◽

Russell A. Banta ◽

Shane Garvey ◽

Justin D. Holmes ◽

Eoin J. Flynn

Keyword(s):

Silica Particle ◽

Particle Production ◽

Sodium Caseinate ◽

Spherical Silica ◽

Spherical Silica Particle

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Acoustic characterization of silica nanoparticle-impregnated Kevlar fabric

Textile Research Journal ◽

10.1177/00405175211023812 ◽

2021 ◽

pp. 004051752110238

Author(s):

Oluwafemi P Akinmolayan ◽

James M Manimala

Keyword(s):

Transmission Loss ◽

Silica Nanoparticle ◽

Air Gap ◽

Thin Plates ◽

Residual Porosity ◽

Ballistic Performance ◽

Number Of Layers ◽

Structural Applications ◽

Acoustic Characterization

Silica nanoparticle-impregnated Kevlar (SNK) fabric has better specific ballistic performance in comparison to its neat counterparts. For multifunctional structural applications using lightweight composites, combining this improved ballistic functionality with an acoustic functionality is desirable. In this study, acoustic characterization of neat and SNK samples is conducted using the normal-incidence impedance tube method. Both the absorption coefficient and transmission loss (TL) are measured in the 60–6000 Hz frequency range. The influence of parameters such as number of layers of neat or treated fabric, percentage by weight of nanoparticle addition, spacing between fabric layers, and residual porosity is examined. It is found that while absorption decreases with an increase in nanoparticle addition for frequencies above about 2500 Hz, increasing the number of layers shifts peak absorption to lower frequencies. By introducing an air-gap behind the fabric layer, dominant low-frequency (1000–3000 Hz) absorption peaks are obtained that correlate well with natural modes of mass-equivalent thin plates. Examining the influence of residual porosity by laminating the SNK samples reveals that it contributes to about 30–50% of the total absorption. Above about 1500 Hz, 3–5 dB of TL increase is obtained for SNK samples vis-à-vis the neat samples. TL is found to increase beyond that of the neat sample above a threshold frequency when an air-gap is introduced between two SNK layers. With an increase in the weight of nanoparticle addition, measured TL tends to be closer to mass law predictions. This study demonstrates that SNK fabric could provide improved acoustic performance in addition to its ballistic capabilities, making it suitable for multifunctional applications and could form the basis for the development of simplified models to predict the structural acoustic response of such nanoparticle–fabric composites.

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