, such as fumed silica nanoparticles. Due to its fractal structure and its high specific area, fumed silica is prone to self-aggregation and can consequently form a network of connected or interacting particles in polymer matrices [ 29 ]. It has been
Authors:Giancarlo Angelini, Ornella Ursini, and Franco Cataldo
Fullerene/silica hybrid materials were obtained by radiation grafting on silica surface of toluene or decalin solutions of
C60. As determined by thermogravimetric analysis, the amount of C60 grafted on silica surface was dependent from the radiation dose administered and independent from the C60 concentration and the nature of the organic solvent. In absence of air, a dose of 48 kGy was sufficient to ensure a grafting
level of 30% by weight of C60 in the hybrid material. The fullerene/silica hybrid material shows a remarkable thermal stability, since the early decomposition
starts above 300 °C as measured by DTG and DTA. The chemical structure of the fullerene/silica hybrid material was determined
by FT-IR spectroscopy and with solid state 13C CP-MAS NMR. The potential application of such materials has been outlined.
Authors:Marcela Stoia, Mircea Stefanescu, Mirela Barbu, Paul Barvinschi, and Lucian Barbu-Tudoran
systems NiM 2 III O 4 , where M III = Fe III and Cr III , inside a silica matrix. In order to obtain 50% NiFe 2 O 4 /50% SiO 2 and 50% NiCr 2 O 4 /50% SiO 2 nanocomposites, we have used a versatile route based on the thermal decomposition inside the
Authors:Quan Wan, Christopher Ramsey, and George Baran
Three different silica filler materials were thermally treated in order to effect dehydration, dehydroxylation, and rehydroxylation.
Samples were characterized by thermogravimetry (TG), pycnometry, elemental analysis, and scanning electron microscopy (SEM).
For all fillers, our results indicate incremental removal of silanol groups at higher heating temperatures and irreversible
dehydroxylation at over 673 K. To remove the organic content and maintain adequate silanol density for subsequent silanization
on Stöber-type silica, we suggest heating at 673 K followed by overnight boiling in water.
Authors:Jinho Hong, Jeongwoo Lee, Chang Hong, and Sang Shim
In order to enhance the thermal conductivity of MWCNT filled poly(dimethyl siloxane) (PDMS) composites, the MWCNT was coated
with silica layer by three step reactions. The composites filled with raw and silica-coated MWCNTs were prepared and the properties
were investigated in terms of the curing characteristics, mechanical properties, and thermal conductivity. Due to the poor
compatibility between raw MWCNT and PDMS, raw MWCNT showed poor dispersion uniformity and wettability in PDMS. On the other
hand, due to the chemical affinity between silica/MWCNT and PDMS throughout the hydrogen bonding, the silica-coated MWCNT
filled PDMS showed improved mechanical properties in terms of tensile strength and 100% modulus, and good interfacial compatibility
than raw MWCNT incorporated PDMS. Finally, the good wettability of silica/MWCNT in PDMS resulted in higher thermal conductivity
caused from the facile phonon movement at the interface even with the smaller MWCNT contents.
Authors:K. Katok, V. Tertykh, V. Yanishpolskii, A. Ragulya, V. Klimenko, and D. Klymchuk
Matrix isolation of ferroelectric BaTiO3 nanoparticles was executed by formation of protective silica shell (via hydrolysis and polycondensation of tetraethyl orthosilicate)
on particles of precursor—barium titanyl oxalate. Synthesized BaTiO3–SiO2 composites have been characterized by IR spectroscopy, XRD, TEM, DTA/DTG methods.
The temperature influence on the adsorption mechanism of anionic polyacrylic acid (PAA) macromolecules on the silica surface
was studied. For this purpose, the following techniques were applied: spectrophotometry, thermogravimetry, potentiometric
titration and microelectrophoresis. This method allowed to determine the adsorbed amounts of polymer, changes in thermal characteristic
of silica surface with adsorbed PAA, surface charge density of the solid as well as zeta potential of SiO2 particles in the presence and absence of polyacrylic acid. All measurements were carried out in the temperature range 15-35 °C.
The free energies of adsorption were calculated from the adsorption data fitted by the Langmuir model. The obtained results
of increase of PAA adsorption and its adsorption free energies with the rising temperature suggest that adsorbed polymer conformation
changes from the coiled structure to more stretched one. Moreover, the polymer adsorption on the silica surface at 25 °C leads
to changes in the course of thermogravimetric curves as a result of surface properties modification of the solid by bonded
Authors:Hernane T. Barcelos, Luclecia D. Nunes, Guilherme W. Tavares, Edesio F. C. Alcantara, and Alexandre G. S. Prado
demand as well as time, and chemical consumption [ 3 – 6 ]. In order to solve these problems, metal ion extraction has been extensively applied to modified surfaces. In this way, solid modified silica with organofunctional groups is the immobilization of
Authors:Przemysław Rybiński, Grażyna Janowska, and Ludomir Ślusarski
The article presents the results of testing thermal properties and combustibility of butadieneacrylonitrile
rubber with 18% contents of bounded acrylonitrile, NBR 18. Two types of silica, Zeosil 175C and Ultrasil VN-3, with different
specific surfaces were used as filler.
Zeosil 175C and Ultrasil VN-3 were modified via cryogenic dezaggregation method. The activity of
unmodified and cryogenic modified silica toward butadiene-acrylonitrile rubber were investigated.
The sulphur and peroxide vulcanizates contained 20, 30, 40, and 50 phr. of the filler were studied.
The article discusses also the test results of thermal stability and flammability of NBR 18 containing
silica prepared "in situ" from alkoxysilane precursor.
The test results were obtained with the use of derivatograph, measurements of flammability by the
method of oxygen index, and in air.
The effect of the silica modification on the SEM and AFM was also examined.
The method of cryogenic modification enables to achieve increase of mineral fillers activity towards
elastomer and reduction in the flammability of NBR 18 vulcanizates.
It has been found that the modification of the vulcanizates of NBR 18 with tetraethoxysilane that
makes it possible to form silica "in situ" reduces the flammability of cross-linked rubbers.
Authors:Anna Petruczynik, Monika Waksmundzka-Hajnos, and Michał Hajnos
Alkaloid standards have been chromatographed on silica layers with a variety of aqueous and nonaqueous mobile phases. The effect on retention, efficiency, and peak symmetry of pH, anionic ionpairs, DEA, and ammonia in aqueous mobile phases was examined. The effect of the concentration of ion-suppressing reagent — diethylamine — on retention, separation efficiency, and peak shape in normal-phase systems was also studied. Systems with the best selectivity and efficiency were used to separate alkaloid standards mixtures and plant extracts by 2D TLC.