Aerosil Fumed Silica

MWNT are produced in form of black powder with bulk density of 15-40 g/dm3. Experiments carried out by us have shown that low bulk density MWNT samples are preferable for application in composite materials, particularly for PTFE-MWNT composites. So, we tried to produce MWNT with the bulk density as low as possible. This was achieved by use of co-precipitated Fe203Mo03-Al303 catalysts containing aerosil (fumed silica) as a pseudo-liquid diluent of growing nanotubes [11, 12],... 

Anon (n.d.). Basic characteristics of aerosil fumed silica. Frankfurt, Degussa AG. 

Nitrogen adsorption was performed at -196 °C in a Micromeritics ASAP 2010 volumetric instrument. The samples were outgassed at 80 °C prior to the adsorption measurement until a 3.10 3 Torr static vacuum was reached. The surface area was calculated by the Brunauer-Emmett-Teller (BET) method. Micropore volume and external surface area were evaluated by the alpha-S method using a standard isotherm measured on Aerosil 200 fumed silica [8]. Powder X-ray diffraction (XRD) patterns of samples dried at 80 °C were collected at room temperature on a Broker AXS D-8 diffractometer with Cu Ka radiation. Thermogravimetric analysis was carried out in air flow with heating rate 10 °C min"1 up to 900 °C in a Netzsch TG 209 C thermal balance. SEM micrographs were recorded on a Hitachi S4500 microscope. 

In this way fumed silicas are formed. This process was developed by Degussa and the thus formed silicas were marketed as Aerosil. A flow-chart of the production process is displayed in figure 1.1. 

The pyrogenic silicas are formed at high temperatures. The most common type of fume silica , which is produced by the flame hydrolysis of silicon tetrachloride, is widely known as Aerosil. This term has become generic for the fume silicas, although strictly Aerosil is the trade mark of Degussa (Fetch, 1994). Other pyrogenic silicas are made by the high-temperature fusion or vaporization of sand in an arc or plasma. 

SYNS ACTICEL AEROSIL AMORPHOUS SILICA DUST AQUAFIL CAB-O-GRIP II CAB-O-SIL CAB-O-SPERSE CATALOID COLLOIDAL SIUCA COLLOIDAL SILICON DIOXIDE DAVISON SG-67 DICALITE DRI-DIE PESTICIDE 67 ENT 25,550 FOSSIL FLOUR FUMFX) SILICA FUMED SILICON DIOXIDE O LUDOX NALCOAG NYACOL NA ACOL 830 NYACOL 1430 SANTOCEL SG-67 SIUCA, AMORPHOUS SILICIC ANHYDRIDE SIUCON DIOXIDE (FCQ SIUKILL VULKASIL... 

Figure 6.40 Storage modulus ver-sus frequency for suspension of fumed silica (Aerosil R972 surface area = 108 m /g aggregate size 200 nm) at a concentration of = 0.085 in PDMS Mw = 118,000). The modulus for the unfilled PDMS is also shown, as is the modulus for the suspension treated in two differ-ent ways (MSI, MS2) to remove the active silanol groups from the silica particle surface. (From Aranguren et al. 1992, with permission from the Journal of Rheology.)...

Aerosil Cab-O-Sil Cab-O-Sil MSP-, colloidal silica fumed silica light anhydrous silicic acid silicic anhydride silicon dioxide fumed Wacker HDK. 

Fig. 1 shows the variation of 7( measured at 100°C by IGC, when treating a pyrogenic or fumed silica (Aerosil from Degussa, Germany) at 100 - 700°C. The same figure presents... 

Figure 5. Variation of 7 with the number of -CH2- groups grafted on the surface of a fumed silica (Aerosil 130, Degussa) using n-alcohols as reactants.

Silica powders in the form of precipitated silica, pyrogenic or fumed silicas (aerosils), and silica gels are the largest volume specialty silicas. Silica gel is the term commonly used to refer to the xerogels obtained by drying silica hydrosols. 

As shown in Fig. 10, the PZR 1 of a cordierite suspension is consistent with the lEP of a fumed silica (Aerosil 200 Degussa Co., Belgium) suspension. This indicates that the interfacial properties of an aqueous cordierite suspension in an acid region are governed by the surface silanol sites ( SiOH) and therefore suggests that the PZR 1 corresponds to the inherent lEP of an aqueous cordierite suspension. The anomalous increase in the potential above pH 3.5 leads to a second potential reversal (PZR 2) at a higher pH value. This was attributed to the readsorption of dissolved aluminum hydroxy species via the surface-induced hydrolysis [44], for example. 

Figure 5 Textural properties (pore volume and pore diameter) of dried xerogels containing different amounts of fumed silica (aerosil 0X50). (From Toki et al. [59].)...

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