Nano-silica, fumed

Collepardi M, Collepardi S, Skarp U, Troli R. Optimization of silica fume, fly ash and amorphous nano-silica in super plasticized high performance concrete. Am Conor Inst 2004 495-506. 

Nanocomposite membranes based on poly(4-methyl-2-pentyne) (PMP) and nano-sized fumed silica fillers have been put forward as a possible alternative to the less chemically resistant PTMSP for the removal ofC hydrocarbons (He et al, 2002). Specifically, an n-butane/methane separation factor of 26 and n-butane permeability of 19 000 Barrer were estimated when 30% hydrophilic silica was added to PMP, resulting in a simultaneous increase in n-butane/methane selectivity and n-butane permeability, in contrast to the more conventional trade-off relationships between selectivity and permeability in polymers. The addition of fumed silica in PMP enables this polymer to challenge PTMSP in terms of both efficiency and productivity, as it disrupts the molecular packing by fillers, which in turn causes a redistribution of the free volume (Merkel et al, 2002). 

Qzm and A50 have different affinities for BSA. Since the experiment was done at constant pH and ionic strength, the observed differences in the amount of BSA adsorbed, and the different conformation of BSA on the two silica dusts, is ascribed to the intrinsic properties of the two silica forms such as size and morphology (down to a micro- and nano level), surface hydrophilicity, impurities at the surface, and surface charge. Qzm and A50 particles are, in fact, very different entities they differ in particle dimensions (Qzm mean diameter 1600 nm, A50 40 nm) and bulk structure, which involves different surface features such as silanol population, (quartz exhibits around 5 SiOH/nm2, A50 2-3 SiOH/nm2), hydrophilicity, micromorphology (quartz particles exhibit steps and edges due to the grinding processes, fumed silica is made up by roundish particles) and the presence of metal ion impurities. 

Stress strain curves for silica nano fibre, CNF and systems formulated with more refined single and multi walled nano tubes are shown in Figure 12. The further simplification of the stress strain response over the PDMS formulated with fumed silica is apparent. There is no Mullins effect, in any of the tubular carbon modified systems, they all have a non complex modulas and a highly linear stress strain response. 

Rheological and Electrokinetic Behavior of Nano Fumed Silica Particle for ILD CMP... 

In fhe ILD CMP process, the most important factor is the characteristics of nano fumed silica slurry. The chemical interactions and physical properties of nano ceramic particulates must be considered to planarize the surface of wafer successfully. The dispersion stability of nano fumed silica slurry is direcfly related to the polishing rate (removal rate), the surface scrafch, and fhe uniformify (wifhin-wafer non-uniformify) of wafer surface across fhe whole wafer. Confrolling the dispersion stability of nano fumed silica slurry is a key parameter in the ILD CMP process. 

The Unique Behavior of Concentrated Nano Fumed Silica Hydrosols... 

Mixed matrix membranes based on fluorinated high free volume matrices loaded with fumed silica nanoparticles show attractive features, especially if compared to unloaded polymeric membranes. The addition of filler changes the FFV of the glassy polymeric matrix, thus positively affecting both solubility and diffnsivity. A simple procedure has been proposed to calculate the relevant properties of the MMM, which is based on limited experimental data represented by the solubility isotherm of a test penetrant and few values of diffusion coefficients. The nnexpected behaviour shown by the MMM obtained by using nano-filler loadings can be properly described by the method developed. The... 

The 0-D case is readily produced with traditional (nano)fillers such as carbon black and fumed silica e have been in use for over 50 years at the time of writing, this case will not be described here. 

Sekhon, S.S., Sharma, J.P., and Park, J.S. (2007) Conductivity behavior of nano-composite polymer electrolytes role of fumed silica and plasticizer. Macromol. Symp., 249/250, 209-215. 

The most commonly met regular nano-fillers are silicas and titanias. These are generally made by controlled precipitation in the presence of surfactants, to prevent agglomeration and fusion of particles. Sol-gel processes starting from metal alkoxides are often utilised. Some very fine particles produced by more conventional gas phase processes are just within the definition used for this discussion. For example, fumed silicas, with diameters of under 10 nm are available. 

Chrissafis et al. [302] compared four different nanopartides to produce nanobiocomposites based on PLA two layered silicates (Cloisite Na and Qoisite 20A MMTs), spherical nanopartides (fumed silica Si02) and MWCNTs. AH nanopartides induced a substantial enhancement of Young s modulus and TS compared to neat PCL. From TGA analysis it was also observed that modified MMT and fumed silica accelerate the decomposition of PCL owing to respective aminolysis and hydrolytic reactions. On the other hand, carbon nano tubes and unmodified MMT slowed the thermal degradation of PCL due to a shielding effect. 

Fillers magnetite (Fe304) with micro- and nano- size and carbonyl iron powder CIP were obtained from Sigma Aldrich, gamma iron oxide (y-Fe203) was supplied from ABCR, fumed silica AEROSIL A380 was purchased from Evonik Degussa. 

Flow stress is neither much affected by the incorporation of nano-particles. A low decrease of this flow stress is observed for sepiolite, silicates and hydrophobic fumed silica at a level of 1 weight percent and an increase is observed for these particles at a level of 3 wt.% (Figure 15). For the SEBS-g-MA compatibilized materials, the flow stress increase above 0.2 MPa probably because of the increase of toughness created by addition of SEBS-g-MA. 

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