Role of Sulfur as a Reducing Agent for the Transition Metals Incorporated into Lithium Silicate Glass

Li2O·0.25Fe2O3·0.25NiO·1.5SiO2 glass was prepared with and without 5 wt % sulfur (S) while melting the mixture of the starting materials at 1350 °C for 1 h in air. A part of the as-prepared glass was heat treated for 1 h near its crystallization temperature (Tc) as determined from differential thermal analysis. Each glass was also investigated by means of Mössbauer spectroscopy, X-ray diffraction, FTIR, and DC conductivity. The Mössbauer spectra showed ionic Fe2+ and Fe3+ species in the glass as well as in the precipitated phase obtained after heat treatment. XRD patterns demonstrated the glassy phase formation in the as-quenched samples irrespective of the presence of sulfur. The heat treated samples showed different precipitated phases containing iron particles of nanometer size. The electric conductivity measurements showed that sulfur-doped samples had high values of (σ) probably because of small polaron hopping between Fe2+ and Fe3+

The relationship between local structure and photo-Fenton catalytic ability of glasses and glass-ceramics prepared from Japanese slag

Local structure and the photo-Fenton reactivity of iron-containing glasses and glass-ceramics prepared from Japanese domestic waste slag were investigated. The largest rate constant (k) of (2.8 ± 0.08) × 10−2 min−1 was recorded for the methylene blue degradation test by using H2O2 with a heat-treated ‘model slag’. The 57Fe Mössbauer spectrum was composed of a paramagnetic doublet with isomer shift of 0.18 ± 0.01 mm s−1 attributed to distorted FeIIIO4 tetrahedra. These results indicate that the paramagnetic Fe3+ provided strong photo-Fenton catalytic ability, and that waste slag can thus be recycled as an effective visible-light activated photocatalyst

Mössbauer and photocatalytic studies of CaFe2O4 nanoparticle-containing aluminosilicate prepared from domestic waste simulated slag

The relationship between local structure and visible-light activated photocatalytic effect of simulated domestic waste slag glass–ceramics (R-NaWSFe) was investigated. The largest pseudo-first-order rate constant of 9.75 × 10−3 min−1 was estimated for methylene blue decomposition test under the visible-light irradiation using R-NaWSFe with additional 30 mass% of Fe2O3 heat-treated at 900 °C for 100 min. The reason for the high photoactivity of this sample was mainly due to nanoparticles of CaFe2O4 and α-Fe2O3 confirmed by the Mössbauer spectrum measured at 77 K. It is concluded that the nanoparticles of magnetic components in silica are essential for exhibiting visible-light activated catalytic effect

Mössbauer and photocatalytic studies of CaFe2O4 nanoparticle-containing aluminosilicate prepared from domestic waste simulated slag

The relationship between local structure and visible-light activated photocatalytic effect of simulated domestic waste slag glass–ceramics (R-NaWSFe) was investigated. The largest pseudo-first-order rate constant of 9.75 × 10−3 min−1 was estimated for methylene blue decomposition test under the visible-light irradiation using R-NaWSFe with additional 30 mass% of Fe2O3 heat-treated at 900 °C for 100 min. The reason for the high photoactivity of this sample was mainly due to nanoparticles of CaFe2O4 and α-Fe2O3 confirmed by the Mössbauer spectrum measured at 77 K. It is concluded that the nanoparticles of magnetic components in silica are essential for exhibiting visible-light activated catalytic effect

Mössbauer study of FINEMET with different permeability

Stress field and magnetic field annealed FINEMET ribbons were investigated by 57Fe Mössbauer spectroscopy, magnetic and XRD methods. The change in relative areas of the 2nd and 5th lines in the Mössbauer spectra indicated significant variation in magnetic anisotropy due to the different annealing. High velocity resolution Mössbauer spectroscopy was also used to control the model applied for the evaluation of Mössbauer spectra. A correlation was found between the permeability and the magnetic anisotropy of the annealed FINEMET samples. This can be applied to predict production parameters of FINEMET ribbons with more favorable soft magnetic properties for technological applications. © 2012 Springer Science+Business Media Dordrecht

Application of the IR transmission method and the Mossbauer effect to the crystallization of calcium gallate glass

Crystallization of infrared-light transmitting 40CaO·60Ga2O3 glass caused by heat treatment, Full-size image (<1 K)γ-ray irradiation and YAG laser irradiation was investigated. The X-ray diffraction (XRD) data revealed that a CaGa4O7 phase was precipitated by heat treatment. The Avrami index (n) of 1.7±0.2 obtained from `the Fourier transform infrared (FT-IR) transmission method' combined with the Johnson–Mehl–Avrami (JMA) equation indicated that the crystallization proceeded three dimensionally. The activation energy (Ea) of 7.2±0.3 eV obtained from the JMA plot was equal to that obtained from the Kissinger plot in the differential thermal analysis: Ea=7.1±0.2 eV. Mössbauer spectra of 40CaO·59Ga2O3·Full-size image (<1 K)2O3 samples showed the oxidation of iron from Fe2+ to Fe3+. Mössbauer spectra of the 40CaO·59Ga2O3·Full-size image (<1 K)2O3 samples irradiated with the YAG laser also showed an oxidation of Fe2+ to Fe3+. In case of Full-size image (<1 K)γ-ray irradiated samples, however, a reduction of the iron from Fe3+ to Fe2+ was observed. This result indicates that Fe3+ occupies substitutional sites of Ga3+ in the gallate glass

Structural Characterization of Gel-Derived Calcium Silicate Systems

The main aim of this study is to synthesize calcium silicate ceramics that exhibit suitable properties to be used for biomedical applications. In the present work, attention was paid to the understanding of processing-structure relationships. A particular effort was made to clarify the identification of Ca-O-Si bonds by means of spectroscopy. The calcium silicate systems were prepared via a sol-gel route, varying the chemical compositions, the catalyst concentration, and the temperature and time of aging and heat treatment. The processes and the phases evolved during the sol-gel procedure were determined. The bond systems were investigated by Fourier transform infrared (FTIR) and (29)Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and the aggregate structures by scanning electron microscopy (SEM), small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and X-ray diffraction (XRD) measurements