Structural characterization of sulfoborate glasses containing magnesium oxide

Magnesium sulfoborate glasses of different compositions were prepared using melt quenching method with the purpose of using it for optical properties. The Fourier Transform Infra-red (FTIR) Spectroscopy, Nuclear Magnetic Resonance (NMR) and X-Ray Diffraction (XRD) have been carried out. Density and molar volume have been evaluated and analysed. From the results of XRD, the absent of discrete and continuous sharp peaks confirmed the amorphous nature of the glass compositions while the results from both FTIR and NMR revealed the existence of BO3, BO4 units. Addition of MgO to sulfoborate influenced the conversion of the dominant BO3 groups to BO4 groups. The BO4 groups are known for creating complex defects that transform into that stable trap good for optical phenomena. It was observed that the density of glass increases while the molar volume is decreases with respect to increase in concentration of alkaline earth oxide in the glass compositions

Optical properties of diamond like carbon films prepared by DC-PECVD

Diamond-like carbon (DLC) thin films were deposited at different substrate temperatures using methane and hydrogen gas in DC-PECVD at 2x10-1Torr. From the light transmission using UV-VIS spectroscopy it was found that the optical transition had changed from allowed indirect transition to allowed direct transition as the substrate temperature increased. The Optical gap increased with temperature, highest of 3.034 eV was observed at 573 K, beyond which it dropped. Colour of the film changed from light brownish to a colourless transparent film in the higher temperature. The Urbach energy decreased from 1.25 eV to 0.75 eV with increasing substrate temperature till 573 K and a slight increase after it. This trend is attributed to change in sp3/sp2 ratio or change in structure. The cluster size decreases with temperature, resulting in larger band gap and the structure more ordered. Similar pattern is also witnessed in the emission spectrum of the photoluminescence

Preparation of Titania Doped Argentum Photocatalyst and its Photoactivity Towards Palm Oil Mill Effluent Degradation

This paper reports on the photocatalytic degradation of pre-treated palm oil mill effluent (POME) over titania loaded with photocatalyst. The argentum loading on the titania was varied from 0.25 to 1.0 wt% via wet-impregnation technique. X-ray diffraction characterization of all the photocatalysts showed that the photo-active rutile phase was still intact after the photocatalyst synthesis. In addition, the UV–Vis diffuse reflectance measurements indicate an improved visible light energy absorption and that the band gap energy was significantly reduced (averaging 2.50 eV) when titania was loaded with argentum, compared to the pristine titania that recorded a reading of 3.20 eV. The 0.50 wt% argentum/titania photocatalyst offered the most effective degradation of pre-treated POME under the irradiation of 100 W of UV light (25.0%) and also visible light (16.0%), respectively, over a loading of 0.2 g/L. Significantly, the maximum photocatalyst loading determined from the current work was 1.0 g/L

Optical-fiber thermal-wave-cavity technique to study thermal properties of silver/clay nanofluids

Thermal properties enhancement of nanofluids have varied strongly with synthesis technique, particle size and type, concentration and agglomeration with time. This study explores the possibility of changing the thermal wave signal of Ag/clay nanofluids into a thermal diffusivity measurement at well dispersion or aggregation of nanoparticles in the base fluid. Optical-Fiber Thermal-Wave-Cavity (OF-TWC) technique was achieved by using a small amount of nanofluid (only 0.2 mL) between fiber optic tip and the Pyroelectric detector and the cavity-length scan was performed. We established the accuracy and precision of this technique by comparing the thermal diffusivity of distilled water to values reported in the literature. Assuming a linear Pyroelectric signal response, the results show that adding clay reduced the thermal diffusivity of water, while increasing the Ag concentration from 1 to 5 wt.% increased the thermal diffusivity of the Ag nanofluid from 1.524×10−3 to 1.789×10−3 cm2/s. However, in particular, nanoparticles show the tendency to form aggregates over time that correlated with the performance change of thermal properties of nanofluid. Our results confirm the high sensitivity of OF-TWC technique raises the potential to be applied to measuring the optical and thermal properties of nanofluids. Furthermore, this technique allows the extraction of information not obtained using other traditional techniques

Influence of Dy3+ in physical and optical behavior of calcium sulfate ultra-phosphate glasses

To examine the influence of trivalent dysprosium ion (Dy3+) on physical and optical properties prepared by melt quenching method. The samples composition of 20CaSO4 (80 - x) P2O5 - xDy2O3, where x = 0.1, 0.2, 0.3, 0.4 and 0.5mol% were prepared and analyzed. Materials were characterized by X-ray diffraction, UV visible and photoluminescence spectroscopy, amorphous nature of the samples was confirmed by X-ray diffraction technique, UV-Vis for optical measurement and luminescence for excited state dynamics. The UV absorption spectra of the glass sample correspond to 6H11/2 (1673 nm), 6H9/2 (1262 nm), 6F9/2(1087 nm), 6H5/2 (899 nm), 6F5/2 (796 nm), 6F3/2 (753 nm), 6G11/2 (422), 4I13/2 (384) and 6P7/2 (347).The physical properties comprise of glass density, molar average molar volume, ion concentration, dielectric constant and molar refractive index was determined. The band gap (Eopt), Urbach energies (ΔE) and refractive index lie in range and decreases with increase in Dy3+ concentration. Therefore, Dy3+ compositional changes were examined and indicate that dysprosium phosphor could serves as a potential candidate for optical application as laser is included

Towards an effective potential for the monomer, dimer, hexamer, solid and liquid forms of hydrogen fluoride

We present an attempt to build up a new two-body effective potential for hydrogen fluoride, fitted to theoretical and experimental data relevant not only to the gas and liquid phases, but also to the crystal. The model is simple enough to be used in Molecular Dynamics and Monte Carlo simulations. The potential consists of: a) an intra-molecular contribution, allowing for variations of the molecular length, plus b) an inter-molecular part, with three charged sites on each monomer and a Buckingham "exp-6" interaction between fluorines. The model is able to reproduce a significant number of observables on the monomer, dimer, hexamer, solid and liquid forms of HF. The shortcomings of the model are pointed out and possible improvements are finally discussed.Comment: LaTeX, 24 pages, 2 figures. For related papers see also http://www.chim.unifi.it:8080/~valle

Evaluation of the Photocatalytic Degradation of Pre-Treated Palm Oil Mill Effluent (POME) Over Pt-Loaded Titania

This paper reports the photocatalytic degradation of pre-treated palm oil mill effluent (POME) over a Pt-doped titania photocatalyst. Pt loading on the titania was varied from 0.25 to 1.0 wt% via alcohol reduction of chloroplatinic acid (H2PtCl6). XRD characterization of the photocatalysts showed that the photo-active anatase phase was still intact after the photocatalyst synthesis while the XPS spectrum confirmed that the deposited Pt was free from the Cl and existed as Pt0 and Pt4+. In addition, the UV–vis diffuse reflectance measurement indicated an improved light energy absorption in the visible light spectrum. Moreover, the band gap energy (3.16–3.17 eV) was reduced when titania was doped with Pt, compared to the pristine titania with 3.20 eV. The 0.5 wt% Pt/TiO2 photocatalyst offered the most effective degradation of pre-treated POME under the irradiation of 100 W of UV light (10%) and also visible light (11%), respectively, over a loading of 0.2 g/L. Significantly, the maximum 0.5 wt% Pt/TiO2 photocatalyst loading determined from the current work was 1.0 g/L

Eu and dy co-activated SrB2Si2O8 blue emitting phosphor: synthesis and luminescence characteristics

The main focus in this research was to understand the influence of Dy3+ and Eu3+ doping/co-doping and sintering atmosphere on the luminescence properties of SrB2Si2O8. Single phase Eu and Dy doped/co-doped SrB2Si2O8 ceramics were synthesized in different atmosphere through solid state reaction technique. An inexpensive method was occupied to provide reducing sintering atmosphere. Europium doped SrB2Si2O8 exhibit unusual reduction from trivalent to a divalent oxidation state even in an oxidizing atmosphere. We also discovered co-doping with Dy3+ ions produced further europium reduction in this phosphor. By manipulating the sintering condition and co-doping, a reddish-purple to blue tune-able phosphor under 390 nm excitations were produced and their Commission International del’Eclairage (CIE) color coordination were calculated and plotted in a CIE 1931 diagram. Photoluminescence spectra of the Eu2+/Eu3+ and Dy3+ co-doped SrB2Si2O8 phosphor showed energy transfer from Dy3+ to Eu3+ and Eu2+ which was observable in Dy3+ f-f excitation transitions and the Dy-O charge transfer bands. A weak 777 nm emission from 3p5P to 3s5S0 transition of O2- ions were observed in all the samples. The excitation and emission peaks of f - f transition from Dy3+ and Eu3+ as well as 4f - 5d transition of Eu2+ were also discussed. The long excitation band in ultraviolet (UV) region from these doped/co-doped SrB2Si2O8 ceramics produced phosphors with efficient UV excitation for solid state lighting