Efficiency of Nanoscaled Flow Regulators

Abstract

In dry powders the particle flow is mainly determined by van der Waals forces. It was proved in systematic studies that in addition to the hydrophilic silica Aerosil® 200 also hydrophobic silicas, various types of carbon black, or precipitated silicas are able to act as flow regulators if these highly aggregated nanomaterials can be broken down into smaller fragments comprising only a few primary particles. To characterize the ability of a given nanomaterial to act as flow regulator, the two terms effectiveness and efficiency were introduced. Effectiveness describes the maximum achievable reduction of the tensile strength by a given concentration of the nanomaterial. The parameter efficiency expresses the mixing time required to achieve the maximum reduction of tensile strength. The efficiency, however, is strongly dependent on the energy brought up by the mixing procedure. This energy is needed to desagglomerate the highly aggregated nanomaterials. Since up to now there is no method to measure these forces directly and methods allowing their indirect determination were looked for.

Manufacturing, Properties, and Application of Nanosized Superhydrophobic Spherical Silicon Dioxide Particles as a Functional Additive to Fire Extinguishing Powders

“…The surface of the fire extinguishing component particles can be uniformly coated with the added hydrophobic particles. − Thus, there is no need in any procedure for agglomerate destruction, such as high-speed mechanical mixing. At the same time, it should be taken into account that as reported in refs , , , the mechanical destruction of strong agglomerates of ultradispersed additives often has an undesirable effect on the fire extinguishing: the particle size distribution is changed and can drop out of the required range.…”

Silica Nanoparticles as Glidants for Industrial Processing: A Statistical Approach

“…Thus, efficiency may depend on the strength of the aggregates, which is expected to be lower in hydrophobic NPs due to their lack of hydrogen bonds. 16,18,54 The surface coverage results presented in Figure 3 corroborate these previous reports. However, the differences in coverage between hydrophobic and hydrophilic NPs may not be solely due to the mixing conditions.…”

Hydrophobic nano SiO2 as flow-enhancing additives and flame retardant synergizes with CaCO3 to suppress gas explosion

“…The powder is liable to take up moisture during storage (because of the hygroscopic nature of the powder components), and therefore functional additives aid in making the powders more hydrophobic, which is essential to preventing clumping and increasing owability throughout the life cycle of the powders. 17,18 The owability of powders with ame retardant or explosive suppression characteristics is inuenced by factors including particle size, specic surface area, water content, hydrophobicity, and interparticle forces. These parameters play a positive or negative role in re and explosion protection.…”