The curing and adsorption behaviors of an epoxy/amidoamine system under the influence of iron, aluminum, and zinc oxides are studied by using differential scanning calorimetry (DSC) and diffuse reflectance infrared spectroscopy (DRIFT). From DRIFT, it is obtained that the amidoamine curing agent is preferentially adsorbed on the three metal oxide surfaces. The amount of amidoamine adsorbed is in the order of iron oxide>zinc oxide>aluminum oxide. Moreover, the iron and zinc oxides adsorb resins more firmly than the aluminum oxide. The results of DSC analyses indicate that more amine related exotherms are found in the specimen filled with the iron oxide but more amide related exotherms are found in the zinc oxide added specimens and they are related to the difference in the preferential adsorption found on three metal oxides. The curing characteristics are also changed in the presence of metallic fillers and the greatest change is obtained from the specimen containing the iron oxide.
Authors:Nashaat N. Nassar, Azfar Hassan and Pedro Pereira-Almao
effect of nanoparticles toward asphaltene cracking has to be determined. Our previous studies have provided information on the catalytic effect of transition metaloxide nanoparticles toward asphaltene gasification and oxidation [ 2 , 6 , 7 , 12
Authors:Y. Inoue, O. Tochiyama, H. Yamazaki and A. Sakurada
A model for treating the sorption of metal ions on hydrous metal oxides was established based on the assumptions that these materials are weakly acidic cation exchangers and have a discrete exchanger phase. The experimental results of the sorption of metal ions on the hydrous niobium(V) and tin(IV) oxides are found to be consistent with the formulas derived from the model by considering that the charge balance and the mass action law hold in the exchanger phase and cations are sorbed by the distribution between this phase and the bulk aqueous phase.
Simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) were applied to light crude oil combustion in the
presence and absence of metal oxide. In crude oil-limestone mixture, three main transitional stages are detected. These are
distillation, low-temperature oxidation (HTO) and high temperature oxidation (HTO) regions respectively. In the case of experiments
with Fe(III)-chloride at different amounts, the shape of TG-DTA curve is changed considerably. Kinetic parameters of the samples
are determined using ASTM method. Reduction in activation energy is considered to be an indication of the catalytic activity
of the additive.
Thermal degradation of poly(2,2′,-propane-bis-4-phenyl carbonate) or bisphenol A polycarbonate (PC) alone and in presence of metal oxide as additives have been discussed. Thermal degradation of PC in presence of metal oxide additives may be surface induced catalytic thermo-oxidative degradation. Some metal oxides retard thermo-oxidative degradation of PC.
The kinetic parameters for the thermal degradation of high impact polystyrene (HIPS) in presence of some metal oxides exhibit
reaction rate compensation effect. In thermal degradation of HIPS in presence of transition metal oxides different active
centers act simultaneously as reaction sites and macroradicals are formed through random chain scission, disproportion or
cyclization. Some oxides retard the polymer degradation through crosslinking and cyclization by the interaction of macroradicals
with the double bond in butadiene.
Authors:L. Zane Miller, James J. Rutowski, Jonathan A. Binns, Guillermo Orts-Gil, D. Tyler McQuade and Jeremy L. Steinbacher
We present a rapid approach for forming monodisperse silica microcapsules decorated with metal oxide nanoparticles; the silica–metal oxide composites have a hierarchical architecture and a range of compositions. The details of the method were defined using titania precursors. Silica capsules containing low concentrations of titania (<1 wt. %) were produced via an interfacial reaction using a simple mesofluidic T-junction droplet generator. Increasing the titania content of the capsules was achieved using two related, flow-based postsynthetic approaches. In the first approach, a precursor solution containing titanium alkoxides was flowed through a packed-bed of capsules. The second approach provided the highest concentration of titania (3.5 wt. %) and was achieved by evaporating titanium precursor solutions onto a capsule packed-bed using air flow to accelerate evaporation. Decorated capsules, regardless of the method, were annealed to improve the titania crystallinity and analyzed by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD), and Fourier transform infrared (FT-IR) spectroscopy. The photocatalytic properties were then compared to a commercial nanoparticulate titania, which the microcapsule-supported titania outperformed in terms of rate of degradation of an organic dye and recyclability. Finally, the generality of the flow-based surface decoration procedures was demonstrated by synthesizing several composite transition metal oxide–silica microparticle materials.
Authors:K. Muraleedharan, M. Kannan and T. Gangadevi
The effect of additives (CuO, MnO2 and TiO2) on the thermal decomposition kinetics of potassium metaperiodate (KIO4) to potassium iodate (KIO3) has been studied in air by thermogravimetry under isothermal conditions. Irrespective of whether p- or n-type, the metal
oxides show only a little or no influence on the rate of the decomposition except for the small decrease when the oxide concentration
is as high as 10 wt%. The rate law for the decomposition of KIO4 (Prout–Tompkins model) remained unaffected by the additives.
Kinetic methods for studying the transport properties of non-stoichiometric transition metal oxides and sulphides have been
described. It has been shown that modern microthermogravimetric techniques enable, in rather simple way, the determination
of the concentration and the mobility of point defects in these materials as a function of temperature and oxidant activity,
with an accuracy difficult to attain with other, much more complicated and time consuming methods. The advantages of the kinetic
methods described in this paper have been illustrated by the results obtained on Mn-MnS-S2 system which has been extensively studied in detail by different authors using various conventional techniques.
Authors:K. Rane, H. Uskaikar, R. Pednekar and R. Mhalsikar
The hydroxide, oxalate and citrate precursors of the metal oxides such as γ-Fe2O3, (MnZn)Fe2O4, Cu(K)Fe2O4, BaTiO3, La(Sr)MnO3, La(Sr)AlO3, La/Gd(Ca/Ba/Sr)CoO3, and anatase TiO2 on modifications with the hydrazine decompose at low temperatures give single phase oxides of superior properties, while
the complexes without such modification require higher temperatures for achieving the phases. The hydrazine released at lower
temperatures reacts with the oxygen in the atmosphere, N2H4+O2→N2+2H2O; ΔH=−625 kJ mol−1, and liberates enormous energy that is sufficient for the oxidative decomposition of the complexes now devoid of hydrazine.
Such extra energy is not available in the case of the precursors without such modifications. The reaction products of hydrazine
oxidation provide desired partial pressure of moisture needed for the stabilization of γ-Fe2O3. Also, the nitrogen that is formed in the reaction of hydrazine with oxygen gets trapped in the lattice of TiO2 giving yellow color nitrogen doped TiO2−xNx photocatalyst. Thus, hydrazine method of preparation has many advantages in the preparation of metal oxides of superior properties.