Calculations based on the fractal geometry in the estimation of surface
heterogeneity are superior compared with conventional calculation methods
(e.g. from the data of gas adsorption or X-ray radiation scattering) as they
can be applied without limitation as far as the range of surface sizes of
the studied structures is concerned. This paper presents structural characteristics
of carbon and carbon- free nanomaterials based on the determined surface and
volumetric fractal coefficients. Fractal coefficients were determined from
the data obtained by means of two independent methods: sorptometry and atomic
force microscopy (AFM). Correlation between porosity parameters and fractal
coefficients is presented.
It was found that Sc2@C84 or Sc2O3 could be “kicked” into the cavities of single wall carbon nanotubes (SWNTs) by reactor neutrons. Neutron irradiation also
efficiently induces coalescing reactions between two fullerene cages with an atom-spacer, forming a C2m=C=C2n type of carbon nanomaterials. This process provides a new subject of studying interactions (and their consequences) of neutrons
with nanoparticles, which may put new insights for neutron sciences.
Synthesis of silver nanoparticles (NPs) in an impinging jet reactor (IJR) was investigated due to its unique properties of efficient mixing and lack of channel walls which avoid fouling. Silver NPs were formed at room temperature by reducing silver nitrate with sodium borohydride in the presence of sodium hydroxide. Two types of ligand were used to stabilize the NPs, trisodium citrate, and polyvinyl alcohol (PVA). Weber number, the ratio between inertial forces and surface tension forces, is used to characterize flow in impinging jets. Flow regimes were investigated forWeber numbers in the range of 13–176. A liquid sheet/chain regime was identified at lowerWeber numbers (<90), and an unstable rim structure was identified at higherWeber numbers (>90). Mixing time was found to be in the range 1–7ms, using theVillermaux—Dushman reaction system and interaction by exchange with the mean mixing (IEM) model. Fastest mixing occurred at Weber number ca. 90. Using trisodium citrate as a ligand, NP size decreased from 7.9 ± 5.8 nm to 3.4 ± 1.4 nm when flow rate was increased from 32 mL/min to 72 mL/min using 0.5 mm jets, and from 6.4 ± 3.4 nm to 5.1 ± 4.6 nm when flow rate was increased from 20 mL/min to 32 mL/min using 0.25 mm jets. Using PVA as a ligand, NP size decreased from 5.4 ± 1.6 nm to 4.2 ± 1.1 nm using 0.5 mm jets and stayed relatively constant between 4.3 ± 1 nm and 4.7 ± 1.3 nm using 0.25 mm jets. In general, the size of the NPs decreased when mixing was faster.
S=SO3) and gehlenite (C2AS),
synthesized by sol–gel method was investigated by means of isothermal
heat flow calorimeter at different temperatures. These phases were obtained
by crystallization processing at different temperatures from their xerogels
(nano-crystalline) prepared by the sol–gel method at ambient temperature.
The crystallization of C2S begins below 600C and
it is well crystallized at 900C. X-ray diffraction patterns reveal that
β-C2S is formed and it remains stable since after
slow cooling. The crystallization of C2AS xerogels
starts with the formation of C2S, then it reacts with
alumina to form mineral C2AS at 1100C. The effect
of hydration temperature upon the hydration reaction of C2S
obtained at 600 and 900C and C2AS annealed at
600 and 1100C was investigated by means of isothermal calorimeter. An
increase in the temperature of hydration brought about initial acceleration
of all samples, as indicated by the increased magnitude of peak of calorimetric
curves. The microstructure of the samples cured at hydrothermal condition
after 1 and 7 days has been examined by means of scanning electron microscopy
(SEM). Fine crystals of calcium silicate hydrate (C–S–H) were
developed in C2S samples, while C2AS
has been hydrated to form gehlenite hydrate supplemented by C–S–H.
Nanosized Pd doped and supported on Mn2O3 catalysts were prepared and tested for CO oxidation. The introduction of Pd in Mn2O3 enhances the activity for CO oxidation due to a synergistic effect. The supported samples showed total CO conversion at lower temperature as compared to doped samples, whereas pristine Mn2O3 showed total CO conversion at a much higher temperature. The presence of Pd greatly improved the catalytic activity for CO oxidation. The presence of moisture in the feed gas does not deactivate the catalysts for CO oxidation. XRD pattern substantiates the formation of Mn2O3 phase, SEM images show that the particles are in the nanosized range and roughly spherical in appearance. From TEM images, the average particle size was found to be around 50 nm. Thermal analysis data indicates the phase change from Mn2O3 to Mn3O4 beyond 900 °C and also gives information regarding the thermal stability of Mn2O3 after the incorporation of Pd in the lattice.
The liquid-phase benzylation of aromatic compounds with benzyl chloride (BC) has been investigated over a series of iron-FSM-16
materials with different Si/Fe ratios (Si/Fe = 90, 60, and 10) synthesized by a microwave-hydrothermal (M-H) process and characterized
by several spectroscopic techniques such as N2 adsorption measurements, X-ray diffraction, electron spin resonance (ESR) and Mössbauer spectroscopy. Catalytic data in the
benzylation of aromatic compounds such as benzene and toluene with BC show that Fe-FSM-16 samples synthesized by the M-H process
are very active and recyclable catalysts. The kinetics of benzene benzylation over this catalyst has been thoroughly investigated.
A solvothermal continuous-flow method for the scalable and shape tunable synthesis of rod-like/spherical TiO2 nanocrystals (NCs) has been developed. The as-prepared colloidal NCs show photocatalytic activity in an addition–cyclization cascade under continuous-flow conditions.
Introduction Graphene is a carbon-based nanomaterial build solely of sp 2 C atoms organized in a hexagonal crystalline structure. To obtain graphene, different approaches have been employed in the last years [ 1 ]. In colloidal form graphene was