Giuseppe Cocito

Determination of rare earth elements by ion chromatography. Separation procedure optimization

In the development of research on materials for optical fibres production, the use of pure lanthanum compounds is very important for the manufacture of glasses, since they can play an important role for signal enhancement by fluorescence emission. For this purpose, an ion exchange chromatographic method for rare earth determination has been studied and optimized. The analytical column involved was a multimode ion exchange type and the effectiveness of ligands (namely oxalic and diglycolic acids) on lanthanides elution was investigated. Elutions were performed for ligand concentrations ranging from 0 to 80 mM and pH ranges from 3.0 to 5.5 coupled with a post-column spectrophotometric detection with 4-(2-pyridylazo)resorcinol (PAR) at 520 nm. After optimization, gradient elution enabled the determination of lanthanides with in a total analysis time of 25 min. The method developed has been applied to the analysis of YbF3 (after acidic microwave digestion) for the determination of impurities due to other rare earth elements.

Crystallization behaviour of fluorozirconate glasses

Abstract Results are reported on crystallization modes in undoped ZBLAN and praseodymium doped ZBLAN glasses. The transformation usually proceeds from the surface with growth of oriented crystals. Activation energies of 154 and 216 kJ/mol were found for different crystallization stages at temperatures around 600 K.

Different processes for the preparation of fluorozirconate glasses

Abstract Different processes for the preparation of fluorozirconate glasses (ZBLAN) have been investigated by infrared spectroscopy (IR) and x-ray diffraction (XRD) on fluoride powders, during the reaction. Glasses have been prepared with 20-10-5-0 (% weight) ammonium bifluoride (NH4F·HF) or with nitrogen trifluoride (NF3) as fluorinating agent. In order to improve the quality of the glasses, small percentages (about 5%) of NH4F·HF are a good compromise between fluorination and hydration of starting products; NF3 is very effective during the fluorination step of the preparation: our electron spin resonance measurements (ESR) on these last glasses after γ-irradiation (20 Mrad), do not detect any O2 signal.

Environmental effects on surface devitrification of fluorozirconate glasses

Abstract Surface devitrification of fluorozirconate glasses has a dominant role in preform drawing and highly depends on environmental conditions. The effects of different atmospheres (N 2 , SF 6 , CF 4 , CHF 3 , CHCIF 2 , CHCl 2 F, CCl 2 F 2 , CBrF 3 , C 2 F 6 , C 2 ClF 5 , C 2 Cl 2 F 4 , C 3 F 8 , air) and different materials (platinum, gold, graphite, Teflon ® PTFE, aluminum) normally used in glass processing were analysed. The devitrification phenomenon, occuring on the surface and into the bulk after sample reheating at drawing temperature, was checked by several analysis techniques and the kinetic parameters were calculated by DSC analysis to evaluate effects induced by different materials. Surface devitrification of glasses treated under CF 4 atmosphere is less evident than for samples treated under other gases. Moreover it was found that platinum should be avoided for glass processing equipments, because of its tendency to induce crystallization.

Process analysis in the preparation of fluorozirconate glasses

Different preparation processes for fluorozirconate glasses (ZBLAN) have been investigated by infrared spectroscopy (IR) and x-ray diffraction (XRD). Glasses have been prepared with different NH4 F.HF amount (20–10–5–0% weight) or with NF 3 0 as fluorinating agent. The presence of NF 3 in the fluorination step of the preparation is useful to improve the glass quality in terms of oxide and hydroxil content: electron spin resonance (ESR) on these glasses (γ-irradiated, 20 Mrad) does not detect any signal.

Determination of trace amounts of copper and iron in zirconium oxychloride by inductively coupled plasma atomic emission spectrometry using the standard additions method

Inductively coupled plasma atomic emission spectrometry has been used in order to evaluate the concentrations of iron and copper impurities in zirconium oxychloride. After suitable wavelength selection an analytical procedure has been developed in order to take account of the heavy matrix effects in the spectroscopic determination of both species, using the standard additions method.

Concentration Profile On Binary Silica Glasses Through Molecular Electronic Polarizability

A method to derive the concentration profile directly by the refractive index profile measurements was developed for binary silica glasses. Using the Lorenz-Lorentz relation, it is possible to derive the molecular electronic polarizability values at 632.8 nm from the RNF measurements on fibres and EDS concentration measurements on preform discs. Substituting these values a direct relation between the refractive index and the molar fraction can be obtained. A good agreement between the concentration profile derived with our method and the EDS results was observed.

PL measurements on fluorozirconate glasses

Several fluoro-zirconate glasses, ZBLA type, have been prepared in CSELT. Fluorides, as raw materials and the technique of melting in Pt crucible were initially adopted.