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Abstract  

We have used molecular simulations to study the properties of nanocomposites formed by the chemical incorporation of polyhedral oligomeric silsesquioxane (POSS) particles in the cross-linked epoxy network. The particular POSS molecule chosen—glycidyloxypropyl-heptaphenyl POSS—can form only one bond with the cross-linker and thus was present as a dangling unit in the network. Four epoxy-POSS nanocomposites containing different fractions (up to 30 mass/%) of POSS particles were studied in this work. Well-relaxed atomistic model structures of the nanocomposites were created and then molecular dynamics simulations were used to characterize the density, glass transition temperature (T g), and the coefficient of volume thermal expansion (CVTE) of the systems. In addition to the effect of nanoparticle loading, the effect of nanoparticle chemistry on the nanocomposite properties was also characterized by comparing these results with our previous results (Lin and Khare, Macromolecules 42:4319–4327, 2009) on neat cross-linked epoxy and a nanocomposite containing a POSS nanoparticle that formed eight bonds with the cross-linked network. Our results showed that incorporation of these monofunctional POSS particles into cross-linked epoxy does not cause a measurable change in its density, glass transition temperature, or the CVTE. Furthermore, simulation results were used to characterize the aggregation of POSS particles in the system. The nanofiller particles in systems containing 11, 20, and 30 mass/% POSS were found to form small clusters. The cluster-size distribution of nanoparticles was also characterized for these systems.

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Summary  

The thermal decomposition of manganese tris(malonato)ferrate(III) hexahydrate, Mn3[Fe(CH2C2O4)3]2 . 6H2O has been investigated from ambient temperature to 600 °C in static air atmosphere using various physico-chemical techniques, i.e., simultaneous TG-DTG-DSC, XRD, Mössbauer and IR spectroscopic techniques. Nano-particles of manganese ferrite, MnFe2O4, have been obtained as a result of solid-state reaction between a-Fe2O3 and MnO (intermediate species formed during thermolysis) at a temperature much lower than that for ceramic method. SEM analysis of final thermolysis product reveals the formation of monodisperse manganese ferrite nanoparticles with an average particle size of 35 nm. Magnetic studies show that these particles have a saturation magnetization of 1861G and Curie temperature of 300 °C. Lower magnitude of these parameters as compared to the bulk values is attributed to their smaller particle size.

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Abstract  

The transformation mechanism of Fe cations in natural olivine after thermal treatments in air has been studied using mainly57Fe Mössbauer spectroscopy. -Fe2O3 nanoparticles appear as the primary Fe3+ phase in Mössbauer spectra of olivine samples heated at 600-900 °C. These nanoparticles are thermally unstable and they are transformed to -Fe2O3 with the increase of heating time. Another transformation mechanism of iron related with the complete decomposition of olivine structure has been observed at temperatures of 1000 °C and higher. The mixed oxide MgFe2O4 with the spinel structure and enstatite MgSiO3 were identified as iron-bearing decomposition products.

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Abstract  

Thermolysis of double complex salt [Pd(NH3)4][AuCl4]2 has been studied in helium atmosphere from ambient to 350 °C. The XAFS of Pd K and Au L3 edges and thermogravimetry measurements have been carried out to characterize the intermediates and the final product. In the temperature range 115–160 °C the complex is decomposed to form Pd(NH3)2Cl2 and AuCl4−xNx species with x ranging from 2 to 3. Subsequent heating of the intermediate up to 300 °C leads to the total loss of NH3. The Au–Cl and Au–Au bonds form the local environment of Au at the stage of decomposition while only four chlorine atoms are around Pd. At the temperature of 330 °C the Au and Pd nanoparticles as well as residues of palladium chloride are detected. The final product consists of separated Au and Pd nanoparticles.

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Abstract  

Phase change nanocomposites were prepared by dispersing γ-Al2O3 nanoparticles into melting paraffin wax (PW). Intensive sonication was used to make well dispersed and homogeneous composites. Differential scanning calorimetric (DSC) and transient short-hot-wire (SHW) method were employed to measure the thermal properties of the composites. The composites decreased the latent heat thermal energy storage capacity, L s, and melting point, T m, compared with those of the PW. Interestingly, the composites with low mass fraction of the nanoparticles, have higher latent heat capacity than the calculated latent heat capacity value. The thermal conductivity of the nanocomposites was enhanced and increased with the mass fraction of Al2O3 in both liquid state and solid state.

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Abstract  

Meso-2,3-dimercaptosuccinic acid (DMSA) forms stable complexes with a remarkable wide range of metal ions. This relatively small molecule has attracted increasing attention in the field of radiopharmacy, treatment of heavy metal intoxications and nanoparticles preparation. In this review detailed summary of all physical, chemical and biological properties of DMSA and its complex compounds with 99mTc, 186/188Re, 166Ho, 177Lu and 90Y is provided. The clinical utilisation of DMSA complexes in the nuclear medicine and its use for treatment of heavy metal intoxication is briefly summarised. The aspects of its application in the field of nanoparticles preparation is behind the scope of this review, therefore it is only shortly described.

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Abstract  

A simple method for preparing F-doped anatase TiO2 nanoparticles with high visible light photocatalytic activity was developed using TiCl4 and HF as TiO2 and fluorine precursors in HCl solution by a one-step hydrothermal treatment without any organic species. The presence of HF plays an important role in the formation of the F-doped shuttle-like anatase TiO2 nanostructures. XRD analysis showed that the F could prevent the transformation of anatase to rutile in HCl solution. Compared with ordinary TiO2, the F-doped TiO2 nanoparticles synthesized at 180 °C exhibited better photocatalytic activity for the degradation of rhodamine B under visible light irradiation. Possible formation mechanism of F-doped anatase TiO2 under hydrothermal conditions was discussed.

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Abstract  

Heat capacity is one of the most characteristic and important properties when the peculiarities of magnetic nanosystems are studied. In these systems the magnetic ordering becomes obvious due to the thermal effects such as heat capacity anomalies. It was considered earlier that heat capacity change under magnetic fields applied is slight and it cannot be taken into account in thermodynamic calculations. However the experimental heat capacity data for ferrofluids under magnetic fields applied show that field and temperature heat capacity dependences have a complicated behavior and in magnetic fields an essential heat capacity change takes place. On the other hand in the literature the contradictory data about heat capacity of nanoparticles appear. According to some papers nanoparticles heat capacity can exceed heat capacity of a bulk material a few times.

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Abstract  

The advantages of the capillary electrophoresis method, known to be highly selective, have been tested on some standard latex colloids and nanoparticles of thorium phosphate, investigated separately or in mixtures. The results have been compared to those obtained by laser Doppler velocimetry. Both methods appear as complementary: capillary electrophoresis is more efficient to point out very fine particles among others, but is more restricting about the supporting medium.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Wenbin Cao, Xingfa Gao, Li Qu, Zhenlin Chen, Genmei Xing, Jun Tang, Huan Meng, Zhen Chen, and Yuliang Zhao

Abstract  

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.

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