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The effect of the addition of additives such as melamine (Mel), silica nanoparticles and a phosphorus-based compound, i.e. 3-(6-oxidodibenzo[c,e][1,2]oxaphosphinin-6-yl)propenamide (DA), on the fire and mechanical performance of a bisphenol A diglycidyl ether (DGEBA)-based epoxy resin cured with isophoronediamine has been investigated. A UL 94-V0 classification was achieved for epoxy resin containing DA at 2 wt% of phosphorus loading. However, addition of silica nano particles was necessary to avoid melt dripping. The incorporation of DA and Mel to the epoxy resin promoted a remarkable reduction (48% to 70%) in the heat release rate (HRR) values, a significant delay (up to 47%) in the ignition time in cone calorimetry experiments, and thus an increase (~75%) in the time to flashover. Evolved gas, thermal and fire analysis was used to propose the combined mode of action of DA, Mel and silica in the fire performance improvement of the epoxy system. Tensile and three-point bending flexural tests showed that the addition of DA increases the rigidity of the resin, resulting in a strong increase in the Young's modulus (up to 34%) and in a slight reduction in fracture strength, elongation break and toughness which is typical for non-reactive additives.

Amino functionalized PEGylated silica nanoparticles were prepared by one pot-procedure, based on ammonia catalysed hydrolysis and polycondensation of Tetraethoxysilane (TEOS) and 3-Aminopropyltriethoxysylane (APTS), in alcohol medium (ethanol) (Sather method), containing PEG 5000 monomethyl ether. Particles size was studied using Transmission Electron Spectroscopy (TEM). PEGylation and amino functionalization was investigated through FT-IR and Thermogravimetric analysis (TG). The structure of nanoparticles consists of nanosilica (a few nanometers in size) dispersed into a PEG matrix, produced by entanglement of PEG chains. The stability of the water colloidal suspension depends on the PEG/silica mass ratio, that changes with PEG concentration in the reaction batch. By properly selecting the PEG concentration, nanoparticles smaller than 150 nm were obtained, stable towards aggregation in water media up to 6 months. The observed need of an optimal PEG/silica mass ratio for long-term stability can be explained on the basis of particles structure and assuming that both steric and electrostatic effect concur to stabilisation. (C) 2010 Elsevier BM. All rights reserved.

Polyelectrolite hydrogels were submitted to the biomimetic method. The experimental results clearly show that the method has coated them with HA globular crystals of similar to 500 nm in diameter. Moreover, the method strongly influences the swelling of the hydrogels. The results strongly suggest that a biologically active HA layer forms also on the surface of the internal pores. Therefore, it is a powerful method for producing micro- and nano-patterned structures of biologically active apatite on the surface of hydrogels and of their pores. (C) 2002 Elsevier Science B.V. All rights reserved.

A new metallic glass alloy characterized by high amplitude of magnetoelastic waves was synthesized. X-ray spectra evidenced the amorphous structure in the as-cast material, while differential thermal analysis confirmed the metastable initial phase and the occurrence of several crystallization peaks. The alloy shows a high difference between the glass transition and crystallization temperatures. Several heat treatments were performed and the structural relaxation effects were shown by means of the behavior of magnetization, Curie temperature and the resonant magneto-elastic wave amplitude. The strong increase of the last parameter, induced by the occurrence of the amorphous structure, is the most important result for application. Magnetic and magneto-elastic properties deteriorate if crystallization occurs, but in the optimal condition a partial nanocrystallisation may be present.

2.5CaO . 2SiO(2) gel was synthesised by hydrolytic polycondensation of tetramethyl orthosilicate (TMOS) with calcium nitrate in alcoholic medium. Thermal treatments were carried out to convert the gel into the glass. However, a completely amorphous sample was not obtained. The gel-derived material structure was examined by FTIR spectroscopy. The IR spectra suggested that the gel-derived material has a different structure than the corresponding melt-quenched glass, for having a more uniform distribution of nonbridging oxygens among the SiO4 tetrahedra. Crystallisation of the gel-derived material, examined by differential thermal analysis is reported and discussed. The activation energy for crystal growth, E-c = 782 kJ/mol, and the Avrami parameter, n = 1, which indicates a surface nucleation mechanism, were evaluated by non-isothermal methods. The results were compared with those obtained for a conventionally prepared glass of the same composition. (C) 1998 Elsevier Science B.V.

Powdered samples (170-230 mesh) of a glass of composition 1.25 CaO . SiO2 were soaked in a simulated body fluid (SBF). The powders were submitted to Fourier transform infrared transmission spectroscopy as coarse powders (such as drawn out from the SBF) and as fine powders (soaked and subsequently ground). Soaked samples were submitted to differential thermal analysis (DTA) and the crystalline phases formed during heating in the DTA apparatus were identified by means of X-ray diffraction analysis. The method appears to be useful in studying the mechanism of deposition of the hydroxyapatite layer. It is documented, by using the same method, that the mechanism involves the reactions of hydrolysis and successive condensation and repolymerization of the silicate substrate. These reactions are very fast. Extensive Ca2+ cation depletion occurs, but appears to be slower. (C) 1996 Elsevier Science Limited.

Glasses of the series 0.65((1+x)Ag2OYB2O3 (1-Y)P2O5)0.35AgI (0 less-than-or-equal-to x less-than-or-equal-to 0.6 and 0 less-than-or-equal-to y less-than-or-equal-to 0.2) have been prepared. Their glass transformation temperature, T(g), electrical conductivity, sigma, and conduction activation energy, E(sigma) and preexponential factor, sigma0, have been evaluated. The substitution of B2O3 to P2O5 has been found to be useful in making both T(g) and sigma to increase. The results have been interpreted on the basis of a structure composed of AgI microdomains in a phosphate or borophosphate matrix and on the basis of the diffusion path model for ionic conduction.

Cordierite (Corning EX-66 100/25) catalyst support samples, contaminated by Na 2 O and CaO, have been studied in the temperature range 800–1200°C by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results suggest that in CaO-contaminated samples the behaviour is strongly influenced by the Ca 2+ ion diffusion rate; additional crystalline phases and microstructures develop at different temperatures. At 1200°C, anorthite, a tectosilicate, forms in the same way as the crystalline phases carnegieite and nepheline form in the case of Na 2 O contamination at 800–1000°C. All these phases have similar composition; their formulae are 2CaO2Al 2 O 3 4SiO 2 and 2Na 2 O2Al 2 O 3 4SiO 2 . For the Na 2 O-contaminated samples, the formation of a high-temperature liquid phase can explain the presence of the observed glassy phase. In earlier studies of CaO- and Na 2 O-contaminated samples, mechanical properties were obtained by four-point bending (modulus of rupture); these data can be correlated with the results obtained in the present investigation.

The surface and bulk crystallization of Li2O · 2 SiO2 glass has been studied by differential thermal analysis and the influence of the specific surface area of the sample and the nucleation heat treatment on the crystallization kinetics is pointed out. The kinetic parameters were also evaluated from the DTA curves and related to the crystallization mechanism. The results agree well with the isothermal data reported in the literature.

The influence of small substitutions of different cations for Na+ ions on the devitrification behaviour of Na2O·2 SiO2 glass has been investigated by differential thermal analysis. The stability of the glasses has been related to the glass transition temperature/liquidus temperature ratio and to the field strength of the cations.

In previous papers [1–3] methods for evaluating the kinetic parameters of crystal growth in inorganic glasses from DTA curves were proposed by the authors. These methods were used to study the devitrification kinetics of different glass systems and the results were in good agreement with those obtained by alternative methods. In this paper the non-isothermal devitrification of NaP0 3 glass has been studied in order to show that in some cases two different interpretations can be drawn from the experimental DTA results. It has been shown that the correct interpretation can be selected if SEM investigations are also carried out.