Search results for "silica"

Investigation on the Properties and on the Photo-Oxidation Behaviour of Polypropylene/Fumed Silica Nanocomposites

2021

This work investigates the effects of very small amounts of fumed silica on the morphology and on the rheological and mechanical behaviour of polypropylene nanocomposites and on their photo-oxidation behaviour. Polypropylene nanocomposites were prepared using a twin-screw corotating extruder with 0, 1 and 2 wt/wt% of SiO2. Morphological, mechanical, thermomechanical and rheological properties were examined. It was found that the viscosity of the matrix is reduced by the presence of the silica nanoparticles, suggesting a poor adhesion between the two phases and probably some lubricating effect. On the contrary, the mechanical and, in particular, the thermomechanical properties of the matrix …

Accelerated laboratory weathering of polypropylene composites filled with synthetic silicon-based compounds

2019

Abstract Non-functionalized and n-alkyl functionalized polyhedral oligomeric silsesquioxanes (POSS), siloxane-silsesquioxane resins and the sol-gel silicas were for the first time examined as possible UV-stabilizers and/or antioxidants in polypropylene (PP). The obtained composites were subjected to the accelerated laboratory weathering tests. The influence of the weathering conditions on the structure and properties of the PP materials was evaluated on the basis of the results from Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) studies. It was found that weathering resistance of the PP materials was strongly de…

Proton conductivity through polybenzimidazole composite membranes containing silica nanofiber mats

2019

The quest for sustainable and more efficient energy-converting devices has been the focus of researchers&prime

Luminescence of phosphorus doped silica glass

2017

This work is supported by Material Science program IMIS2 of Latvia.

Atomistic modeling of crystal structure of Ca1.67SiHx

2015

The atomic structure of calcium-silicate-hydrate (C-1.67-S-H-x) has been investigated by theoretical methods in order to establish a better insight into its structure. Three models for C-S-H all derived from tobermorite are proposed and a large number of structures were created within each model by making a random distribution of silica oligomers of different size within each structure. These structures were subjected to structural relaxation by geometry optimization and molecular dynamics steps. That resulted in a set of energies within each model. Despite an energy distribution between individual structures within each model, significant energy differences are observed between the three m…

Fe3O4@Au@mSiO2 as an enhancing nanoplatform for Rose Bengal photodynamic activity

2017

A novel nanoplatform composed of three types of materials with different functionalities, specifically core-shell Fe3O4@Au nanoparticles encapsulated near the outer surface of mesoporous silica (mSiO2) nanoparticles, has been successfully synthesised and used to enhance the efficiency of a photosensitiser, namely Rose Bengal, in singlet oxygen generation. Fe3O4 is responsible for the unusual location of the Fe3O4@Au nanoparticle, while the plasmonic shell acts as an optical antenna. In addition, the mesoporous silica matrix firmly encapsulates Rose Bengal by chemical bonding inside the pores, thus guaranteeing its photostability, and in turn making the nanosystem biocompatible. Moreover, th…

The Importance of Intermediate Range Order in Silicates: Molecular Dynamics Simulation Studies

2003

We present the results of large scale computer simulations in which we investigate the structural and dynamic properties of silicate melts with the compositions (Na2O)2(SiO2) and (Al2O3)2(Si02). In order to treat such systems on a time scale of several nanoseconds and for system sizes of several thousand atoms it is necessary to use parallel supercomputers like the CRAY T3E. We show that the silicates under consideration exhibit additional intermediate range order as compared to silica (SiO2) where the characteristic intermediate length scales stem from the tetrahedral network structure. For the sodium silicate system it is demonstrated that the latter structural features are intimately con…

Behaviour of advanced tritium breeder pebbles under simultaneous action of accelerated electrons and high temperature

2017

The authors greatly acknowledge the technical and experimen-tal support of O. Valtenbergs and L. Avotina (Institute of Chemical Physics, University of Latvia). The work is performed in the frames of the University of Latvia financed project No. Y9-B044-ZF-N-300, “Nano, Quantum Technologies, and Innovative Materials for Eco-nomics”.

The synthesis of micrometer- and submicrometer-size spheres of ordered mesoporous oxide MCM-41

1997

Study of silica-based intrinsically emitting nanoparticles produced by an excimer laser

2019

International audience; We report an experimental study demonstrating the feasibility to produce both pure and Ge-doped silica nanoparticles (size ranging from tens up to hundreds of nanometers) using nanosecond pulsed KrF laser ablation of bulk glass. In particular, pure silica nanoparticles were produced using a laser pulse energy of 400 mJ on pure silica, whereas Ge-doped nanoparticles were obtained using 33 and 165 mJ per pulse on germanosilicate glass. The difference in the required energy is attributed to the Ge doping, which modifies the optical properties of the silica by facilitating energy absorption processes such as multiphoton absorption or by introducing absorbing point defect…