Borate glasses are the technologically important class of glasses and play a significant role in various applications. Borate glasses contain planar BO3 groups as structural units, rather than tetrahedral SiO4 groups. The oxygen atoms are, as in SiO2, again connected to two network-forming atoms, in case of boron. The radial distribution analysis describes the B2O3 glass structure as consisting of boroxol rings, that is, planar rings containing three boron atoms and three oxygen atoms. The network forming of the B2O3 and the SiO4 is affected with the addition of some metal cation additives Pb, Zn, Cd, and so forth. These additives also work as a network modifier and a nucleating agent for crystallization of glass. Therefore, the optical properties of the borate glasses have been changed significantly.

https://downloads.hindawi.com/archive/2012/428497.pdf

A Review on Infrared Spectroscopy of Borate Glasses with Effects of Different Additives

A self-ordered, crystalline-glass, mesoporous nanocomposite for use as a lithium-based storage device with both high power and high energy densities.

Novel Ag3PO4 photocatalyst possesses high visible-light photocatalytic activity, but the large crystallite size and the photocorrosion severely limit its practical application. It is highly desirable to develop new Ag3PO4 photocatalytic systems with nanosized structure and good photocatalytic stability. In this work, we prepare new graphene-modified nanosized Ag3PO4 photocatalyst by in situ growth strategy in an organic solvent. The as-prepared nanosized Ag3PO4 particles–graphene composite exhibits enhanced visible-light photocatalytic activity and stability toward the degradation of methylene blue (MB) in aqueous solution compared with bare nanosized Ag3PO4 particles and conventional large-sized Ag3PO4 particles–graphene composite. This enhanced photocatalytic activity and stability arise from the positive synergetic effects of the nanosized Ag3PO4 particles and graphene sheets including an increase in the number of active adsorption sites, suppression of charge recombination, reducing the formation of Ag nanoparticles. This work shows a great potential of nanosized Ag3PO4 particles–graphene composite for environmental purification of organic pollutants.

Graphene-modified nanosized Ag3PO4 photocatalysts for enhanced visible-light photocatalytic activity and stability

La2(MoO4)3 phosphors with various Eu3+ concentrations were prepared via a facile co-precipitation process. The crystal structure and morphology of the phosphors were characterized by means of XRD and field emission scanning electron microscope. The crystal unit cell parameters a, b, and c for the monoclinic phase La2(MoO4)3 were calculated to be 16.989, 11.927, and 16.086 A, respectively. The average size of the phosphor particles was estimated to be around 88.5 nm. The Huang–Rhys factor was derived from the phonon sideband spectra to be 0.073. The self-generated quenching process of Eu3+ was explained based on Auzel’s model, and the intrinsic radiative transition lifetime for 5D0 level was confirmed to be 0.99 ms. A new approach for calculating the Judd–Ofelt parameters was developed, meanwhile the Judd–Ofelt parameters Ωλ (λ = 2, 4, 6) of Eu3+ in La2(MoO4)3 phosphors were confirmed to be 10.70 × 10−20, 1.07 × 10−20, and 0.56 × 10−20 cm2, respectively. Finally, the optimal doping concentration for achiev...

Optical transition, electron-phonon coupling and fluorescent quenching of La2(MoO4)3:Eu3+ phosphor

Modified iron phosphate glasses have been prepared with nominal molar compositions [(1−x)·(0.6P2O5–0.4Fe2O3)]·xRySO4, where x = 0–0.5 in increments of 0.1 and R = Li, Na, K, Mg, Ca, Ba, or Pb and y = 1 or 2. In most cases the vast majority or all of the sulfate volatalizes and quarternary P2O5–Fe2O3–FeO–RyOz glasses or partially crystalline materials are formed. Here we have characterized the structure, thermal properties, chemical durability and redox state of these materials. Raman spectroscopy indicates that increasing modifier oxide additions result in depolymerization of the phosphate network such that the average value of i, the number of bridging oxygens per –(PO4)– tetrahedron, and expressed as Qi, decreases. Differences have been observed between the structural effects of different modifier types but these are secondary to the amount of modifier added. Alkali additions have little effect on density; slightly increasing Tg and Td; increasing α and Tliq; and promoting bulk crystallization at temperatures of 600–700 °C. Additions of divalent cations increase density, α, Tg, Td, Tliq and promote bulk crystallization at temperatures of 700–800 °C. Overall the addition of divalent cations has a less deleterious effect on glass stability than alkali additions. 57Fe Mossbauer spectroscopy confirms that iron is present as Fe2+ and Fe3+ ions which primarily occupy distorted octahedral sites. This is consistent with accepted structural models for iron phosphate glasses. The iron redox ratio, Fe2+/ΣFe, has a value of 0.13–0.29 for the glasses studied. The base glass exhibits a very low aqueous leach rate when measured by Product Consistency Test B, a standard durability test for nuclear waste glasses. The addition of high quantities of alkali oxide (30–40 mol% R2O) to the base glass increases leach rates, but only to levels comparable with those measured for a commercial soda-lime-silica glass and for a surrogate nuclear waste-loaded borosilicate glass. Divalent cation additions decrease aqueous leach rates and large additions (30–50 mol% RO) provide exceptionally low leach rates that are 2–3 orders of magnitude lower than have been measured for the surrogate waste-loaded borosilicate glass. The P2O5–Fe2O3–FeO–BaO glasses reported here show particular promise as they are ultra-durable, thermally stable, low-melting glasses with a large glass-forming compositional range.

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Effects of modifier additions on the thermal properties, chemical durability, oxidation state and structure of iron phosphate glasses

Ternary phosphates are found to vitrify within large domains of compositions inside the phase diagrams P 2 O 5 -WO 3 -A 2 O (A = Li, Na). Structural approach of the highly modified glasses P 2 O 5 -A 2 MoO 4 -A 2 O (M = Mo,W) was investigated using various spectroscopic techniques such as infrared, Raman, and electron spin resonance (ESR). These glasses were found to contain MO 6 octahedra, MO 4 tetrahedra, M 2 O 7 dimers, PO 4 tetrahedra, and also P 2 O 7 or metaphosphate chains, depending on the composition considered. As shown in earlier studies, the glass network is progressively depolymerized as the content of A 2 O increases. ESR experiments were conducted on both X-ray irradiated and unirradiated samples. Unirradiated glasses exhibit two ESR signals attributed to W 5+ and Mo 5+ centers that are octahedrally coordinated. Irradiation of these glasses induces new paramagnetic centers ascribed to the phosphorus-oxygen-hole-center and peroxy radicals. The M 5+ concentration depends strongly on the sample composition and temperature. ESR parameters are determined using a computer simulation approach adapted for vitreous materials.

Infrared, Raman, and Electron Spin Resonance Studies of Vitreous Alkaline Tungsten Phosphates and Related Glasses

Electronic and ionic conductivity of glasses inside the Li2O–MoO3–P2O5 system

Electrical properties of glasses in the Na2O–MoO3–P2O5 system

Raman spectroscopic study of the phase transitions sequence in Li3Fe2(PO4)(3) and Na3Fe2(PO4)(3) at high temperature

This study investigated the power of hydroxyapatite adsorbent prepared by a combined precipitation-microwave method, for removing a cationic dye methylene blue in aqueous media. The used adsorbent was characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR). The adsorption tests were conducted in batch mode. The effect of temperature, the pH of the solution and the mass of the adsorbent on the adsorption were determined. It is found that the adsorption was pH and temperature dependent. The kinetic study showed that the second-order model gives a better description of the kinetics of the adsorption reaction than the first-order model. Analysis of adsorption isotherms using different classical models showed that adsorption may be governed by the isotherms of Langmuir. The thermodynamic parameters were determined from the values of the maximum adsorption capacity and equilibrium constants.

/pdf/removal-of-methylene-blue-from-water-using-hydroxyapatite-1l0ihl6dpz.pdf

Lahcen Bih

Papers

Infrared, Raman, and Electron Spin Resonance Studies of Vitreous Alkaline Tungsten Phosphates and Related Glasses

Electronic and ionic conductivity of glasses inside the Li2O–MoO3–P2O5 system

Electrical properties of glasses in the Na2O–MoO3–P2O5 system

Raman spectroscopic study of the phase transitions sequence in Li3Fe2(PO4)(3) and Na3Fe2(PO4)(3) at high temperature

Removal of Methylene Blue from Water Using Hydroxyapatite Submitted to Microwave Irradiation