română C.R. IORDĂNESCU (ȘTEFAN), M. ELIȘA, G. EPURESCU, M. FILIPESCU, M. ENCULESCU, R.C.C. MONTEIRO, L. CONSTANTIN
Abstract
In the present work we study the optical, structural and morphological properties of CdS-doped glass films, deposited by Pulsed Laser Deposition (PLD) method. The glass target used for ablation was prepared by conventional melt-quenching technique and the semiconductor dopant, CdS powder, was embedded in the borosilicate melt glass host by continuous stirring. In order to improve the properties of the films, the laser wavelength was modified. Photoluminescence emission (PL) of CdS-doped glass films revealed a broad band located in the visible range. The structural analysis was carried out by micro-Raman spectroscopy, pointing out specific vibration modes for Si-O-Si bonds as well as for CdS dopant. The morphology and the chemical characterization of the films were investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and Atomic Force Microscopy (AFM).
Keywords
borosilicate glass, thin film, pulsed laser deposition, luminescence, CdS-doped glass
HAN XUECAI, TONG YILIN
Abstract
Chalcogenide glasses have many potential applications as a result of their particular optical and electrical properties, which are considered to be strongly determined by the elementary network-forming structural units and their mutual interconnection. The aim of our work is the investigation and modeling of As-rich chalcogenide glasses with possible basic structure units. Ab initio quantum chemical calculation with DFT/B3LYP method is performed to investigate the cage-like AsxSySez. The calculated total energy reveals that the total energy at the stationary point with the As4SnSe3-n (n=0,1,2,3) and As4SnSe4-n n(n=0,1,2,3,4)clusters decrease corresponding to the fall of S and Se content in the As4SnSe3-n and As4SnSe4-n clusters, respectively. The calculated fundamental frequencies were utilized to predict the assignment of unknown peaks in As-S-Se Raman spectra, which is considered to have good accordance between experimental and calculated data, it is concluded that the cage-like AsxSySez clusters play an important role in the structure of As-S-Se amorphous system.
Keywords
ab initio, DFT, chalcogenide glass, vibration analysis
A. EL HAT, A. HADRI, F.Z. CHAFI, B. FARES, N. HASSANAIN , A. MZERD
Abstract
Zn1-xCuxO thin films with different Cu concentration x= (0; 2; 5; 7 at %) are deposited by spray pyrolysis technique on heated glass substrate at 350°C. The physical properties of the films are characterized by several techniques in order to study their structural, surface roughness, optical and electrical properties. It is observed from X-ray diffraction (XRD) analysis that the Cu doped ZnO films are polycrystalline and exhibit a preferential orientation along (002) plane. The Atomic force microscopy (AFM) measurements revealed that the surface roughness of the films is decreased from 0 to 5 at % Cu then increased strongly for 7 at % Cu. From optical measurements, a significant decrease in average optical transmission is observed for all doped samples and the band gap value is decreased from 3.3 to 3.07 eV with increase in Cu concentration. The Hall Effect electrical measurements show that all samples are n-type and the best value of the electrical resistivity 1.35x10-1(Ω.cm) is obtained for 5 at % Cu.
Keywords
spray pyrolysis, ZnO thin films, Cu-doped ZnO, Hall Effect, Band gap, AFM, Refractive index, extinction coefficient
M.A. IONESCU, I. CIUCĂ
Abstract
Surface roughness measurements by AFM and SEM were performed on thin films of Parylene-N and Parylene-C deposited via Chemical Vapour Deposition of polymers also known as Polymer Vapour Depostion (PVD) on Si(111). AFM revealed a smoother surface for Parylene–C, while the Parylene–N showed a dimpled surface with isolated valleys. SEM on Parylene–C showed a smooth surface, with debris, while the Parylene–N revealed a dimpled surface with fibrils bundled together. Angles measured on AFM profile lines are larger when compared to angles measured on SEM images because of the broadening effect in AFM due to tip size. Global features are kept similar. The Parylene-C coating appears with a convex shape, the edges being thicker with a gradient towards the center. Parylene – N appears uniform in thickness with the dimpled aspect observed on the smaller observed surface.
At least at this scale, by surface morphology, we could infer that Parylene – N was deposited homogeneous or that the Parylene – C coating was warped. If this is so we think that Parylene-N’s higher level molecular activity during deposition generates greater penetration into crevices than that observed in Parylene-C, making it superior for coating complex topographies specially for medical instrumentation.
Keywords
Atomic Force Microscopy, Scanning Electron Microscopy, Parylene-N, Parylene-C
ANDREI-DAN BUSUIOC, RAMONA ENUŢĂ, ŞTEFANIA STOLERIU, OVIDIU OPREA, TEODOR VIŞAN
Abstract
La3+ or V5+ doped SnO2 powders were synthesized by the precipitation method, the crystalline phases being obtained after a thermal treatment at 400 °C. The calcined samples were characterized in terms of crystalline structure, morphology and optical properties by employing X-ray diffraction, scanning electron microscopy and UV-Vis spectroscopy. The results indicate that both doping cations modify the average crystallite size and bandgap of SnO2 based materials, while their concentration permits a fine tuning of the functional features.
Keywords
Semiconductor Oxides; Precipitation Method; Dopants; Bandgap; Gas Sensors
OUIDETTE SLIMI, LAID HAMMICHE, DJAMEL DJOUADI, AZEDDINE CHELOUCHE, MALAAZ MEDDOURI
Abstract
Nanocomposite films formed by direct inclusion of ZnO aerogel nanoparticles in liquid state silica matrix and deposited by dip and spin-coating techniques on glass substrates were elaborated. The ZnO aerogel particles were synthesized in supercritical methanol using a modified sol-gel process. The elaborated particles and the coated composite films were characterized by XRD, FTIR spectroscopy and by optical absorption. XRD patterns show a broadening of diffraction peaks of ZnO crystallites and a significant reduction in the intensity after their dispersion in silica. A reduction in lattice parameters was observed after the introduction of ZnO aerogel particles in silica. The Zn-O vibration bond strongly shifts to lower wavenumbers in composite films compared to the aerogel due to the formation of silica layerand successfully grafted over the ZnO nanoparticles. A strong Zn-O-Zn vibration bond is observed only in the spin-coated film. The blue shift observed in the absorption spectra indicates an enhancement in the optical band gap due to quantum confinement effect of ZnO nanoparticles when they are dispersed in silica matrix.
Keywords
supercritical drying, ZnO aerogel, composite films, spin-coating, dip-coating
ANDRADA PASCU, ALIDA TIMAR-GABOR, AHMED KADARI, VIORICA SIMON
Abstract
Structural characteristics of undoped and gadolinium doped melt-derived samples of SiO2-B2O3 oxide system, as well as thermoluminescence (TL) properties and kinetic parameters of the sample with 40SiO2∙59.5B2O3∙0.5Gd2O3 composition were investigated in the present study. The gadolinium doped sample showed bright TL signal following irradiation with 6 Gy, good repeatability (under 10% deviation from the unit), linear dose dependence for the tested dose range (0.75 Gy – 9 Gy) and a minimum detectable dose of 34 mGy for instantaneous measurements. The kinetic parameters associated with the glow curves of 40SiO2∙59.5B2O3∙0.5Gd2O3 sample followed second order kinetics, while the value of the average activation energy was 0.88 eV. Both undoped and gadolinium doped samples were characterized by similar structural features.
Keywords
TGA, XRD, FTIR, thermoluminescence (TL), kinetic parameters, borosilicates
C.VIVEKANANDHAN, P.S.SAMPATH, SURESH SAGADEVAN
Abstract
Composite materials are being widely employed in numerous modern applications. Fabrication of new composite materials has been holding the consideration of scientists worldwide and attempts are being made to improve the applicability of these materials. In perspective of this advancement in the research field, the present work attempts to concentrate the impact of nanoclay content on the structural and morphological behavior of epoxy composites. Epoxy materials were reinforced with various particulate portions of chosen nanoclay and the specimens were investigated. The structural examination of the polymer composite with X-ray diffraction showed that the nanoclay was distributed as an intercalated structure in the polymer matrix, and the d-spacing of layers decreased with increasing nanoclay content. SEM images analysis revealed that 2% nanoclay reinforced samples exhibited less number of but more uniform pores compared with 10% nanoclay reinforced samples.
Keywords
Composite materials, Nanoclay, Scanning electron microscopy, X-ray diffraction.
C. RAMESH, C. MANICKAM, T. MARIDURAI, V.R. ARUN PRAKASH
Abstract
In this present work particulate epoxy composite was prepared with thermo assisted surface treated Fe2O3 fine particles. The principal aim of this work is to improve wear resistance of epoxy resin by reinforcing iron oxide particles. Particle size of 800nm and 200nm were used to fabricate particular composites. Particles were heat treated from 30º C to 900º C in a muffle furnace to relive induced stresses which are gained in pre processes and getting magnetite phase. The resultant phase change in iron oxide particles were confirmed by X-ray diffraction. The heat treated particles were again surface treated with a silane coupling agent 3-Aminopropyletriethoxysilane (APTMS). The composites were prepared with reinforcement of 1wt%, 3wt% and 5wt% of iron oxide filler into epoxy resin. All proportions of composites were cured by an aliphatic hardener triethylenetetramine (TETA). Wear characters of epoxy-iron(III)oxide system was studied with pin-on-disc setup. Wear resistance was improved significantly for particle loaded composite in which heat treated siliconized iron oxide-epoxy system gave better result. Scanning electron microscopic images revealed filler dispersion on epoxy matrix.
Keywords
Particulate composite; APTMS; SEM; Optical microscopy; Pin-on-disc
ANDREI-DAN BUSUIOC, RAMONA ENUŢĂ, ŞTEFANIA STOLERIU, TEODOR VIŞAN
Abstract
Pure and La3+ or V5+ doped SnO2 based ceramics were obtained by shaping and sintering of nanosized powders, previously synthesized by the precipitation method. The thermal treatment temperature was in the 1300 - 1500°C range. The resulted ceramic bodies were characterized through X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The ceramic properties and sensitivity towards methane and isopropyl alcohol vapours were also determined. It was demonstrated that dopants use has a beneficial effect on the gas detection capability, especially at low concentrations.
Keywords
Tin Oxide; Semiconductor; Ceramics; Dopants; Gas Sensitivity.
ENIKÖ VOLCEANOV, ADRIAN VOLCEANOV, SIMONA MARIA SANDU
Abstract
The purpose of this work is to examine the possibility of developing a new way to use abundant ash waste from coal burning through a rapid thermal treatment of ceramic composite bodies. The formulation of ceramic bodies was realized with clay and 10-50% (by weight) fly ash (class F) originated from bituminous coal burning and followed by rapid sintering at 950°C, 1000°C and 1050°C in microwave field at varying intervals of time ranging from 5 to 20 minutes. The ceramic properties in conjunction with morphological-structural characteristics after microwave field roasting were investigated. The results show that the development of lightweight ceramic starting from clay and coal ash can be effective in appropriate heat treatment conditions in microwave field at 2.45 GHz frequency. The effectiveness of the sintering process was evaluated as a function of the sintering time and specimen composition. The mineralogical phase analysis of samples cured at 1050°C for 20 minute showed the major crystalline mineral compounds as: quartz, mullite and hematite. The ceramic properties recommend them as lightweight aggregates for application in building materials area.
Keywords
Coal ash, Lightweight ceramic, Microwaves
COSMIN VANCEA, MARIUS GHEJU, GIANNIN MOȘOARCĂ
Abstract
The present paper proposes an innovative way to harness the exhausted reactive mixtures resulted from the removal of Cr(VI) with Fe0 in continuous-flow system (column experiments), by vitrification using two types of common waste glasses: window panes and cathode ray tubes (CRT). The melting of the two types of wastes (glass and the reactive mixture containing chromium), conducted in economically advantageous conditions at 1000°C for 180 minutes generates very viscous melts that were difficult to process. Therefore it was considered necessary to use borax as a flux in order to improve the fluidity of the melted glasses. The RX diffraction was used to confirm the vitreous character of the samples, validating the purposed melting conditions. The hydrolytically stability, determined according to the ISO 719/1985, classify all the investigated glasses in the most stable class of glasses HGB1. The chemical stability and chromium and iron ions leachability were determined and American Extraction Procedure Toxicity Test respectively. The chemical stability of the glasses expressed by measuring their dissolution rate show two different behaviors: one for acidic and neutral mediums and another for alkaline medium, corresponding to two different attack mechanisms on the glass matrix. At pH = 5.5 and pH = 7.0 the glasses dissolution rates are very low, between 0.013-0.059 g/h, while at pH = 8.5 the values rise to 0.143-0.492 g/h. The amounts of chromium and iron ions leached from all the investigated glasses regardless the environment’s pH and the considered time are very low, between 0-0.0104 % of the total chromium and between 0-0.0042 % of the total iron brought by the exhausted reactive mixtures. The obtained results confirm the viability of the suggested solution for immobilizing the exhausted reactive mixtures containing chromium together with common waste glasses in order to obtain glasses having very high chemical stability with multiple economic advantages.
Keywords
wastes vitrification, waste glasses, glass recycling, chromium wastes.
A. DJERIDI, N. KAMEL, A. BENMOUNAH, D. MOUDIR, S. KAMARIZ, Y. MOUHEB
Abstract
An iron phosphate glass in the system 25 wt.% Fe2O3- 57 wt.% P2O5 - 8 wt.% B2O3 - 8 wt.% Na2O - 2 wt.% As2O3 was synthesized by a double melting /casting method at 1100°C. Fe/P is atomic weight ratio is fixed to 0.67. 20 wt.% of simulated nuclear wastes were successfully immobilized in the glass bulk. Both density and molar volume, measured for both pure and waste loaded glasses, are representative values of phosphate glasses. X-ray diffraction analysis confirmed the amorphous feature of both glasses, and scanning electron microscopy allows the microstructure observations. The glass transition temperature (Tg), the crystallization (Tc) and melting (Tm) temperatures are measured by DTA analysis. Tg = 623 and 580°C; Tc= 766 and 679 °C and Tm=933 and 929 °C; for the pure and RW loaded glasses, respectively. Hruby (KH =(Tc - Tg)/(Tm - Tc), Weinberg (KW =(Tc - Tg)/Tm) and Lu/Liu (KLL = Tc/(Tg + Tm)) criteria were used for the evaluation of glass stability of both pure and radioactive waste loaded glasses. Although the values are lower for the radioactive waste loaded glass compared to those for the pure glass, and thus, the no loaded glass is more stable than the radioactive waste loaded one. The calculated criteria remain in an acceptable interval between 0.11-0.86, suggesting that the glass stability is not altered by the addition of 20 wt.% of simulated radioactive waste. The glass forming ability (GFA) is assessed by ΔTxg =(Tx – Tg), ω2, α, β, γm, and ε criteria. The calculated criteria allow valuable conclusions on the good thermal behavior of the radioactive waste loaded phosphate glass.
Keywords
Iron phosphate glass, Thermal stability, Glass forming ability, Radioactive waste, DTA, XRD, SEM.