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Journal Details
Format
Journal
eISSN
2083-134X
ISSN
2083-1331
First Published
16 Apr 2011
Publication timeframe
4 times per year
Languages
English

Search

Volume 31 (2013): Issue 1 (January 2013)

Journal Details
Format
Journal
eISSN
2083-134X
ISSN
2083-1331
First Published
16 Apr 2011
Publication timeframe
4 times per year
Languages
English

Search

25 Articles
Open Access

The birefringence spectroscopic studies on ferroelectric glycine phosphite (GPI) single crystals

Published Online: 09 Feb 2013
Page range: 1 - 5

Abstract

Abstract

The ferroelectric glycine phosphite single crystals have been grown from aqueous solution by both conventional and Sankaranarayanan-Ramasamy methods. The modified channelled spectrum method has been adopted for spectral dependence of optical birefringence studies over the wavelength range of 480–620 nm, which show that both the crystals exhibit relatively high birefringence values. The photoluminescence excitation studies were carried out for the grown crystals in a wide wavelength range between 300 nm and 600 nm at 224 K. The crystals were also subjected to scanning electron microscopy analysis in order to determine the ferroelectric domain pattern configuration.

Keywords

  • crystal growth
  • birefringence
  • semi-organic materials
  • photoluminescence
  • SEM
Open Access

Tuning photocurrent response through size control of CdSe quantum dots sensitized solar cells

Published Online: 09 Feb 2013
Page range: 6 - 13

Abstract

Abstract

The photovoltaic characterization of CdSe quantum dots sensitized solar cells (QDSSCs) by tuning band gap of CdSe quantum dots (QDs) through size control has been investigated. Fluorine doped tin oxide (FTO) substrates were coated with 20 nm in diameter TiO2 nanoparticles (NPs). Pre-synthesized colloidal CdSe quantum dots of different sizes (from 4.0 to 5.4 nm) were deposited on the TiO2-coated substrates using direct adsorption (DA) method. The FTO counter electrodes were coated with platinum, while the electrolyte containing I−/I3− redox species was sandwiched between the two electrodes. The current density-voltage (J-V) characteristic curves of the assembled QDSSCs were measured for different dipping times, and AM 1.5 simulated sunlight. The maximum values of short circuit current density (Jsc) and conversion efficiency (η) are 1.62 mA/cm2 and 0.29 % respectively, corresponding to CdSe QDs of size 4.52 nm (542 nm absorption edge) and of 6 h dipping time. The variation of the CdSe QDs size mainly tunes the alignment of the conduction band minimum of CdSe with respect to that of TiO2 surface. Furthermore, the Jsc increases linearly with increasing intensity of the sun light, which indicates the sensitivity of the assembled cells.

Keywords

  • CdSe quantum dot
  • tuning band gap
  • direct adsorption
  • quantum dots sensitized solar cell
  • photovoltaic cells
Open Access

Electrical properties of hybrid planar diode based on palladium phthalocyanine and titanium dioxide

Published Online: 09 Feb 2013
Page range: 14 - 18

Abstract

Abstract

This work presents experimental studies of a planar diode made of the layers of indium tin oxide, titanium dioxide, palladium phthalocyanine and gold. The current rectification ratio was 105 at 1.5 V. The analysis of the electrical properties of the system was based on small signal complex capacitance spectra measured in the frequency range of 25 Hz — 1 MHz at different values of bias. No depletion region at the TiO2/PdPc interface was observed. Forward bias specifically affected both parts of the complex capacitance and the observed effect probably resulted from the rearrangement of charge carriers injected into the organic layer.

Keywords

  • organic diode
  • palladium phthalocyanine
  • titanium dioxide
Open Access

A high acid mesoporous USY zeolite prepared by alumination

Published Online: 09 Feb 2013
Page range: 19 - 24

Abstract

Abstract

A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of Brønsted acid sites and strong Lewis acid sites increased whereas weak Lewis acid sites decreased twice. The mesoporous structure composed of inter-and intra-crystalline pores in the aluminated HUSY increased the external surface area of the zeolite, improving accessibility of molecules to the active sites and enhancing its catalytic ability. The realuminated HUSY zeolite supported with Ru catalyst exhibited a higher catalytic activity for benzene hydrogenation than the parent HUSY zeolite; the reaction rate in comparison to the mesozeolite increased by 5.5 times.

Keywords

  • mesozeolite
  • alumination
  • HUSY
  • acid catalyst
  • catalytic hydrogenation
Open Access

Electronic properties of M2InV3O11 (M(II) = Zn(II) and Co(II)) compounds

Published Online: 09 Feb 2013
Page range: 25 - 28

Abstract

Abstract

The electronic properties of multicomponent vanadate oxides M2InV3O11 (M(II) = Zn(II) and Co(II)) were investigated by electrical resistivity and electron paramagnetic resonance (EPR) measurements. Replacement of non-magnetic Zn(II) cations with magnetic Co(II) ions resulted in a significant drop in the electrical conductivity and an increase in the activation energy. The EPR spectroscopy revealed the presence of VO2+ vanadyl ions in both compounds, while the presence of divalent cobalt ions was identified in the Co2InV3O11 oxide at low temperatures. The concentration of VO2+ vanadyl ions was found to be about one order higher for the vanadate oxide without magnetic ions. It is suggested that the increased concentration of VO2+ ions could be responsible for the enhanced conductivity of Zn2InV3O11.

Keywords

  • EPR
  • magnetic properties, conductivity
Open Access

Characterization of carbon deposit with controlled carburization degree

Published Online: 09 Feb 2013
Page range: 29 - 35

Abstract

Abstract

Promoted nanocrystalline iron was carburized in a differential tubular flow reactor with thermogravimetric measurement of mass changes. The carburization process was carried out in the presence of pure methane under atmospheric pressure at 650 °C to obtain different carburization degrees of the sample. The carburized iron samples were characterized by the X-ray diffraction, high-resolution transmission electron microscope in the energy-dispersive X-ray spectroscopy mode, thermoprogrammable oxidation, and Raman spectroscopy. As a result of the methane decomposition on the nanocrystalline iron the following nanocrystalline products were observed: iron carbide Fe3C, graphite, iron and nanotubes. The crystallinity of the samples increased with the carburization degree.

Keywords

  • nanocrystalline iron
  • carburization process
  • carburization degree
  • carbon deposit
  • iron carbide
Open Access

Influence of stearic acid on the structure and rheological behavior of injection-molded ZTA suspensions

Published Online: 09 Feb 2013
Page range: 36 - 42

Abstract

Abstract

The zirconia-toughened-alumina (ZTA) composite powder was exposed to a prior ball milling treatment with a small amount of stearic acid (SA) before the traditional blending process. The effect of different amounts of stearic acid on surface properties of the powder, the particle size distribution of the powder, and the rheological properties of the suspension were systematically studied within the design of experiments. Fourier transformation infrared spectroscopy (FTIR) analysis was used to prove the chemical interaction between the stearic acid and the ZTA powder. The effects of SA content on the particle sizes and their distribution were carefully examined. Rheological properties such as viscosity, yield stress, and power law exponent of the suspensions were determined within a temperature range of 140–170 °C. The optimal content of SA to improve the properties of the suspensions was found to be 3 wt.%.

Keywords

  • ZTA suspension
  • ceramic injection molding
  • rheological property
Open Access

Synthesis and characterization of new optically active poly(amide-imide)s derived from N,N′-(pyromellitoyl) bis-L-tyrosine and various diamines

Published Online: 09 Feb 2013
Page range: 43 - 51

Abstract

Abstract

Five new optically active poly(amide-imide)s(PAIs) 5a–e were prepared by direct polycondensation reaction of N,N′- (pyromellitoyl) bis-L-tyrosine 3 as chiral dicarboxylic acid with various aromatic diamines 4a–e. Triphenylphosphite(TPP)/pyridine(py) in the presence of calcium chloride (CaCl2) and N-methyl-2-pyrrolidone (NMP) were successfully applied to direct polycondensation reaction. The resulting new polymers were obtained in good yields with inherent viscosities ranging between 0.48 dL/g and 0.6 dL/g. They were analyzed with a C.H.N. elemental analyzer, FTIR, 1H-NMR, UV-VIS spectroscopy and polarimeter (specific rotation measurement, [α]D25). Thermogravimetric analysis (TGA) indicated that the residual weight percentage of polymers at 600 °C were between 48.66 % and 64.21 %, which showed their thermal stability. These polymers are attractive to be used as packing materials in chromatography columns for separation of enantiomers.

Keywords

  • polycondensation
  • poly(amide-imide)s
  • optical activity
Open Access

Extraction of edingtonite from a natural zeolite under hydrothermal conditions

Published Online: 09 Feb 2013
Page range: 52 - 58

Abstract

Abstract

In the present study, edingtonite has been extracted from natural zeolite clinoptilolite by simulating the natural hydrothermal conditions in the laboratory, under the influence of solutions with different concentrations of Ba+2 and Na+, varying from 0.5 to 2.8 mol/L, at 150 °C. In this work, the essential hydrothermal conditions have been provided by hydrothermal autoclaves. The natural and laboratory prepared samples were characterized by XRD, XRF and SEM methods.

Keywords

  • clinoptilolite
  • phase transformation
  • hydrothermal conditions
  • edingtonite
Open Access

One-step reduction, characterization and magnetic behaviour of exfoliated graphene oxide

Published Online: 09 Feb 2013
Page range: 59 - 64

Abstract

Abstract

The functionalized graphene (GO) was fabricated by a simple method of chemical reduction in a polar aprotic solvent. This paper therefore, describes a versatile and synthetic route for the preparation of reduced graphene oxide (RGO) and its behavior when exposed to magnetic field environment. The characterization results of transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy and the attenuated total reflectance-Fourier transform infra-red (ATR-FTIR) analysis indicate that graphite was exfoliated and reduced to graphene layers.

Keywords

  • chemical reduction
  • hydrazine hydrate
  • graphite oxide
  • reduced graphene oxide
  • exfoliate
Open Access

Synthesis of nanocrystalline nickel and iron carbides by decomposition of hydrocarbons

Published Online: 09 Feb 2013
Page range: 65 - 70

Abstract

Abstract

Decomposition of hydrocarbons was carried out on nickel and iron catalysts containing small amounts of calcium and aluminum oxides as structural promoters. Decomposition of methane, ethane and ethylene was studied under atmospheric pressure in the temperature range from 500 to 700 °C. The phase composition of the obtained samples was investigated using X-ray diffraction method. The role of nickel and iron carbides in the formation of carbon deposit was discussed.

Keywords

  • nanocrystalline nickel carbide
  • nanocrystalline iron carbide
  • decomposition of hydrocarbons
Open Access

Structural and surface properties of TiO2 thin films doped with neodymium deposited by reactive magnetron sputtering

Published Online: 09 Feb 2013
Page range: 71 - 79

Abstract

Abstract

Thin films were deposited using modified, high energy magnetron sputtering method from Ti-Nd mosaic targets. The amount of neodymium dopant incorporated into two sets of thin films was estimated to be 0.8 and 8.5 at.%, by means of energy dispersive spectroscopy. On the basis of x-ray diffraction method, the type of crystalline structure and crystallites size were evaluated directly after the deposition process and after additional post-process annealing at 800 °C temperature. The influence of annealing on the surface properties was evaluated with the aid of atomic force microscopy. Uniformity of the dopant distribution in titanium dioxide matrix was examined with the aid of secondary ion mass spectroscopy. Additionally, using atomic force microscope, diversification and roughness of the surface was determined. Chemical bonds energy at the surface of TiO2:Nd thin films was investigated by x-ray photoelectron spectroscopy method. Wettability measurements were performed to determine contact angles, critical surface tensions and surface free energy of prepared coatings. On the basis of performed investigations it was found, that both factors, the amount of neodymium dopant and the post-process annealing, fundamentally influenced the physicochemical properties of prepared thin films.

Keywords

  • TiO2
  • neodymium
  • physicochemical properties
  • magnetron sputtering
Open Access

Structural and dielectric properties of La substituted polycrystalline Ca(Ti0.5Fe0.5)O3

Published Online: 09 Feb 2013
Page range: 80 - 87

Abstract

Abstract

Polycrystalline Ca1−x Lax(Ti0.5Fe0.5)O3 were prepared by the standard solid state reaction technique. Pellet shaped samples prepared from each composition were sintered at 1573 K for 5 h. The X-ray diffraction analysis indicated the formation of a single-phase orthorhombic structure. The lattice parameters as well as densities increased but the average grain sizes decreased with the increase of La content. The dielectric measurements were carried out at room temperature as a function of frequency and composition. The experimental results revealed that dielectric constant (ɛ′) decreased but dielectric loss (tan δ) and ac electrical conductivity (σ ac) increased as frequency increased. The composition dependence of ɛ′ and tan δ indicated that they decreased with the increase of La content. The σ ac was derived from the dielectric measurements and it is concluded that the conduction in the present samples is due to mixed polarons hopping.

Keywords

  • ceramics
  • chemical synthesis
  • X-ray diffraction
  • dielectric properties
Open Access

Photodecomposition of Rhodamine B on TiO2/SiO2 thin films prepared by sol-gel method

Published Online: 09 Feb 2013
Page range: 88 - 94

Abstract

Abstract

Glasses showing catalytic effect have been of much interest recently because the catalytic layer is very effective in reducing of pollutants. The use of these glasses may bring reduction in cleaning costs. There are several methods of preparation of TiO2 with good catalytic properties, but sol-gel technique offers an opportunity to enhance catalytic effect by precise optimization of the composition and microstructure of the layer. This study concerns optimization of the composition and preparation technology of catalytic layers based on SiO2-TiO2 system. Catalytic effect was studied using Rhodamine B as a sensor. UV-VIS and photoelectron spectroscopy were the main research tools used in this study.

Keywords

  • photocatalytic effect
  • titanium layer
  • sol-gel
  • Rhodamine B
Open Access

An ammonia sensor based on in situ-synthesized polyaniline nanostructures

Published Online: 09 Feb 2013
Page range: 95 - 100

Abstract

Abstract

Nowadays, a good deal of research is focusing on the development of new analytical procedures for detection of hazardous agents, such as bacteria, harmful pollutants, toxic vapors, and many others. The majority of the research is aimed at developing new sensors and analytical equipment. This paper demonstrates a simple construction of an ammonia sensor based on commercially available electronic connectors with active elements from polyaniline. The main goal of this research is to present the simplicity of sensor manufacturing, without the need for advanced apparatus such as electropolymerization or electrospinning set-up. The active element of the proposed sensor is composed of polyaniline synthesized in situ on the surface of conductive glue. The layer of the conductive glue is a key element in this sensor as it protects the metallic pin against destruction during in situ synthesis of polyaniline (acidic and oxidizing conditions).

Keywords

  • ammonia sensor
  • polyaniline
  • nanostructures
Open Access

Research into the relationship between the surface topography, texture and mechanical properties of PVD-Cu/Ni multilayers

Published Online: 09 Feb 2013
Page range: 101 - 107

Abstract

Abstract

The paper presents the results of structural examinations and mechanical tests of Cu/Ni multilayers fabricated by the magnetron sputtering method. The investigated multilayers were differentiated by Ni sublayer thickness (1, 3 and 6 nm), while the retaining Cu sublayer thickness was unchanged (2 nm). Measurements demonstrated that the multilayers were strongly textured in the direction of their growth [111], with the thinnest multilayer (Cu/Ni = 2/1) showing a stronger texture. Stronger texturing was associated with greater surface roughness. Multilayers with the largest thickness had higher hardness and Young’s modulus. The properties of Cu/Ni multilayers depended both on the thickness of their sublayers, as well as on their total thickness.

Keywords

  • Cu/Ni multilayers
  • thermal stability
  • X-ray diffraction
  • texture
  • atomic force microscopy
Open Access

Luminescent homo- and hetero-metallic hybrid molecular materials constructed by covalent grafting

Published Online: 09 Feb 2013
Page range: 108 - 114

Abstract

Abstract

In this paper, 3-(triethoxysilyl)-propyl isocyanate (abbreviated as TESPIC) was modified by ethylparaben (EPB) to produce corresponding organic-inorganic monomers (EPB-TESPIC) with two components equipped with covalent bonds, which not only can coordinate to RE ions (Tb3+ and Eu3+) but also act as a sol-gel precursor. Luminescent hybrid materials consisting of terbium-europium complex, covalently bonded to silica-based network, have been obtained in situ via a sol-gel approach. Proton nuclear magnetic resonance spectroscopy (1HNMR) and Fourier transform infrared spectroscopy (FT-IR) were applied to characterize the structure of EPB-TESPIC. UV-visible, phosphorescence, and luminescence spectra were obtained to characterize the photophysical properties of the obtained hybrid material. Through co-hydrolysis and polycondensation, Tb3+ and Eu3+ can be introduced into the same organic-inorganic hybrid monomer, forming Si-O backbones. The experimental results show that the strong luminescence of rare-earth ions substantiates the optimum energy match and effective intramolecular energy transfer between the triplet state energy of coordination complex and the emissive energy level of the rare-earth ions. The hybrid material systems are expected to have potential applications in photophysical sensors.

Keywords

  • chemical modification
  • organic-inorganic hybrids
  • photoluminescence
  • sol-gel process
Open Access

Optical pH detector based on LTCC and sol-gel technologies

Published Online: 09 Feb 2013
Page range: 115 - 121

Abstract

Abstract

This paper presents an investigation on using sol-gel thin film as a material for sensors application in LTCC (Low Temperature Co-fired Ceramics) technology. This material gives the opportunity to make new, low-cost highly integrated optoelectronic devices. Sensors with optical detection are a significant part of these applications. They can be used for quick and safe diagnostics of some parameters. Authors present a pH detector with the optical detection system made of the LTCC material. The main part of the device is a flow channel with the chamber and sol-gel active material. The silica sol-gel with bromocresol green indicator was used. As the absorbance of sol-gel layer changes with the pH value of a measured medium, the transmitted light power was measured. The pH detector was integrated with the electronic components on the LTCC substrate.

Keywords

  • Low Temperature Cofired Ceramics LTCC
  • sol-gel
  • pH sensor
  • optical amonia detection
Open Access

CuO as sintering additive to Sr0.4Ca0.6La4Ti5O17 ceramics

Published Online: 09 Feb 2013
Page range: 122 - 125

Abstract

Abstract

The effects of CuO addition on the sintering behavior and microwave dielectric properties of Sr0.4Ca0.6La4Ti5O17 ceramics were investigated. CuO was selected as a liquid phase sintering aid to lower the sintering temperature of Sr0.4Ca0.6La4Ti5O17 ceramics. With CuO addition, the sintering temperature of Sr0.4Ca0.6La4Ti5O17 ceramics was effectively reduced from 1550 °C to 1475 °C. The crystalline phase exhibited no phase difference and no second phase was detected at all addition levels. The electric permittivity was not significantly affected by various amounts of CuO addition and ranged from 52 to 54. Small values (<+7 ppm/K) of the temperature coefficient of resonant frequency were obtained for Sr0.4Ca0.6La4Ti5O17 ceramics. However, the unloaded quality factor Q u was strongly dependent upon the CuO concentration. Q u f o ∼ 10500 GHz was obtained for Sr0.4Ca0.6La4Ti5O17 ceramics with 0.5 wt.% of CuO addition, sintered at 1475 °C.

Keywords

  • CuO
  • calcination
  • additive
Open Access

Improvement of supercapacitor parameters by nickel ion intercalation into activated carbon

Published Online: 09 Feb 2013
Page range: 126 - 132

Abstract

Abstract

The relation between the porous structure and the electron structure in carbon materials was investigated in order to optimize the efficiency of the physical-chemical processes in an electric double layer (EDL) formed at the boundary between the carbon material and the electrolyte (KOH 30 % aqueous solution). In particular, an Ni2+ intercalative modification of nanoporous carbon resulted in more than a triple increase in the specific capacitance and a significant improvement of the charge-discharge kinetics in the EDL.

Keywords

  • Ni-intercalative modification
  • small angle X-ray scattering
  • nanocluster
  • nanoporous carbon
  • supercapacitor
Open Access

Structural properties of Sb- and Te-based binary compounds: Spin-orbit effect

Published Online: 09 Feb 2013
Page range: 133 - 138

Abstract

Abstract

The band structure of AlSb, GaSb, ZnTe and CdTe is calculated using the empirical pseudopotential method (EPM) coupled with spin-orbit (SO) splitting. We applied our empirical model of bulk modulus with SO effect. It has been noticed that SO has a crucial effect on the band structure of these compounds but does not influence the structural phase transition. The calculated results are in good agreement with the experimental data.

Keywords

  • binary compounds
  • spin-orbit
  • structural properties
Open Access

Photo-induced changes in arsenic selenide films

Published Online: 09 Feb 2013
Page range: 139 - 145

Abstract

Abstract

The spectral dependence of the transmittance and reflectance of thermally-evaporated amorphous AsxSe100−x (where x = 20 and 40 at.%) films was measured in the wavelength range of 190–900 nm. A procedure was given for accurate determination of the film thickness using a standard method of numerical differences from the experimental data. The process of indirect electronic transitions was found to be responsible for the photon absorption. The variation of the energy band gap with the exposure time was investigated. Amorphous-crystalline transformations occurring as a result of photoexposure have been confirmed by the structural studies of the As20Se80 specimens using the scanning electron microscope and transmission electron microscope. Photodarkening relaxation under light exposure of the well annealed films was studied and the relaxation process has been described by the stretched exponential function (SEF).

Keywords

  • chalcogenides
  • arsenic selenide glasses
  • optical properties
  • photo-induced effects
  • photo-darkening relaxation
Open Access

Cyclic voltammetry and impedance studies of undoped diamond films

Published Online: 09 Feb 2013
Page range: 146 - 150

Abstract

Abstract

The undoped, polycrystalline diamond films were deposited on tungsten wire substrates by hot filament chemical vapor deposition (HF CVD), using a precursor gas mixture of methanol with excess of hydrogen. The morphology and quality of the as-deposited films were monitored by scanning electron microscopy (SEM) and Raman spectroscopy. The surface morphology analyzed by SEM resembles a continuous and well faceted diamond film. Raman results showed essential differences in qualities of diamond films grown at different hydrocarbon concentrations. The electrochemical properties of diamond electrodes were examined with cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS). The CV experiments revealed a large chemical window (>∼4.3 V) of undoped diamond. Analysis of the ferrocyanide-ferricyanide couple at a diamond electrode suggests some extent of electrochemical quasi-reversibility, but the rates of charge transfer across the diamond substrate interface vary with diamond quality.

Keywords

  • CVD diamond
  • Raman spectroscopy
  • cyclic voltammetry (CV)
  • electrochemical impedance spectroscopy (EIS)
Open Access

Optical, structural and electrical properties of pure and urea doped KDP crystals

Published Online: 09 Feb 2013
Page range: 151 - 157

Abstract

Abstract

Single crystals of good optical quality, made of potassium dihydrogen phosphate (KDP) doped with urea were grown by slow evaporation solution growth technique at a constant temperature of 35 °C. Optical absorption and dielectric properties were studied for pure and urea doped KDP crystals. Using powder XRD studies, crystalline nature of pure and urea doped KDP crystals was confirmed. AC conductivity was measured for the grown crystals. DC electrical conductivity and photoconductivity studies were carried out for pure and urea doped KDP crystals and the differences caused by the dopant were also discussed.

Keywords

  • absorption
  • powder XRD
  • dielectric
  • photoconductivity
  • potassium dihydrogen phosphate (KDP)
Open Access

Erratum to Preparation of crystal-controlled Y-TZP/Al2O3 nanocomposites

Published Online: 09 Feb 2013
Page range: 158 - 158

Abstract

25 Articles
Open Access

The birefringence spectroscopic studies on ferroelectric glycine phosphite (GPI) single crystals

Published Online: 09 Feb 2013
Page range: 1 - 5

Abstract

Abstract

The ferroelectric glycine phosphite single crystals have been grown from aqueous solution by both conventional and Sankaranarayanan-Ramasamy methods. The modified channelled spectrum method has been adopted for spectral dependence of optical birefringence studies over the wavelength range of 480–620 nm, which show that both the crystals exhibit relatively high birefringence values. The photoluminescence excitation studies were carried out for the grown crystals in a wide wavelength range between 300 nm and 600 nm at 224 K. The crystals were also subjected to scanning electron microscopy analysis in order to determine the ferroelectric domain pattern configuration.

Keywords

  • crystal growth
  • birefringence
  • semi-organic materials
  • photoluminescence
  • SEM
Open Access

Tuning photocurrent response through size control of CdSe quantum dots sensitized solar cells

Published Online: 09 Feb 2013
Page range: 6 - 13

Abstract

Abstract

The photovoltaic characterization of CdSe quantum dots sensitized solar cells (QDSSCs) by tuning band gap of CdSe quantum dots (QDs) through size control has been investigated. Fluorine doped tin oxide (FTO) substrates were coated with 20 nm in diameter TiO2 nanoparticles (NPs). Pre-synthesized colloidal CdSe quantum dots of different sizes (from 4.0 to 5.4 nm) were deposited on the TiO2-coated substrates using direct adsorption (DA) method. The FTO counter electrodes were coated with platinum, while the electrolyte containing I−/I3− redox species was sandwiched between the two electrodes. The current density-voltage (J-V) characteristic curves of the assembled QDSSCs were measured for different dipping times, and AM 1.5 simulated sunlight. The maximum values of short circuit current density (Jsc) and conversion efficiency (η) are 1.62 mA/cm2 and 0.29 % respectively, corresponding to CdSe QDs of size 4.52 nm (542 nm absorption edge) and of 6 h dipping time. The variation of the CdSe QDs size mainly tunes the alignment of the conduction band minimum of CdSe with respect to that of TiO2 surface. Furthermore, the Jsc increases linearly with increasing intensity of the sun light, which indicates the sensitivity of the assembled cells.

Keywords

  • CdSe quantum dot
  • tuning band gap
  • direct adsorption
  • quantum dots sensitized solar cell
  • photovoltaic cells
Open Access

Electrical properties of hybrid planar diode based on palladium phthalocyanine and titanium dioxide

Published Online: 09 Feb 2013
Page range: 14 - 18

Abstract

Abstract

This work presents experimental studies of a planar diode made of the layers of indium tin oxide, titanium dioxide, palladium phthalocyanine and gold. The current rectification ratio was 105 at 1.5 V. The analysis of the electrical properties of the system was based on small signal complex capacitance spectra measured in the frequency range of 25 Hz — 1 MHz at different values of bias. No depletion region at the TiO2/PdPc interface was observed. Forward bias specifically affected both parts of the complex capacitance and the observed effect probably resulted from the rearrangement of charge carriers injected into the organic layer.

Keywords

  • organic diode
  • palladium phthalocyanine
  • titanium dioxide
Open Access

A high acid mesoporous USY zeolite prepared by alumination

Published Online: 09 Feb 2013
Page range: 19 - 24

Abstract

Abstract

A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of Brønsted acid sites and strong Lewis acid sites increased whereas weak Lewis acid sites decreased twice. The mesoporous structure composed of inter-and intra-crystalline pores in the aluminated HUSY increased the external surface area of the zeolite, improving accessibility of molecules to the active sites and enhancing its catalytic ability. The realuminated HUSY zeolite supported with Ru catalyst exhibited a higher catalytic activity for benzene hydrogenation than the parent HUSY zeolite; the reaction rate in comparison to the mesozeolite increased by 5.5 times.

Keywords

  • mesozeolite
  • alumination
  • HUSY
  • acid catalyst
  • catalytic hydrogenation
Open Access

Electronic properties of M2InV3O11 (M(II) = Zn(II) and Co(II)) compounds

Published Online: 09 Feb 2013
Page range: 25 - 28

Abstract

Abstract

The electronic properties of multicomponent vanadate oxides M2InV3O11 (M(II) = Zn(II) and Co(II)) were investigated by electrical resistivity and electron paramagnetic resonance (EPR) measurements. Replacement of non-magnetic Zn(II) cations with magnetic Co(II) ions resulted in a significant drop in the electrical conductivity and an increase in the activation energy. The EPR spectroscopy revealed the presence of VO2+ vanadyl ions in both compounds, while the presence of divalent cobalt ions was identified in the Co2InV3O11 oxide at low temperatures. The concentration of VO2+ vanadyl ions was found to be about one order higher for the vanadate oxide without magnetic ions. It is suggested that the increased concentration of VO2+ ions could be responsible for the enhanced conductivity of Zn2InV3O11.

Keywords

  • EPR
  • magnetic properties, conductivity
Open Access

Characterization of carbon deposit with controlled carburization degree

Published Online: 09 Feb 2013
Page range: 29 - 35

Abstract

Abstract

Promoted nanocrystalline iron was carburized in a differential tubular flow reactor with thermogravimetric measurement of mass changes. The carburization process was carried out in the presence of pure methane under atmospheric pressure at 650 °C to obtain different carburization degrees of the sample. The carburized iron samples were characterized by the X-ray diffraction, high-resolution transmission electron microscope in the energy-dispersive X-ray spectroscopy mode, thermoprogrammable oxidation, and Raman spectroscopy. As a result of the methane decomposition on the nanocrystalline iron the following nanocrystalline products were observed: iron carbide Fe3C, graphite, iron and nanotubes. The crystallinity of the samples increased with the carburization degree.

Keywords

  • nanocrystalline iron
  • carburization process
  • carburization degree
  • carbon deposit
  • iron carbide
Open Access

Influence of stearic acid on the structure and rheological behavior of injection-molded ZTA suspensions

Published Online: 09 Feb 2013
Page range: 36 - 42

Abstract

Abstract

The zirconia-toughened-alumina (ZTA) composite powder was exposed to a prior ball milling treatment with a small amount of stearic acid (SA) before the traditional blending process. The effect of different amounts of stearic acid on surface properties of the powder, the particle size distribution of the powder, and the rheological properties of the suspension were systematically studied within the design of experiments. Fourier transformation infrared spectroscopy (FTIR) analysis was used to prove the chemical interaction between the stearic acid and the ZTA powder. The effects of SA content on the particle sizes and their distribution were carefully examined. Rheological properties such as viscosity, yield stress, and power law exponent of the suspensions were determined within a temperature range of 140–170 °C. The optimal content of SA to improve the properties of the suspensions was found to be 3 wt.%.

Keywords

  • ZTA suspension
  • ceramic injection molding
  • rheological property
Open Access

Synthesis and characterization of new optically active poly(amide-imide)s derived from N,N′-(pyromellitoyl) bis-L-tyrosine and various diamines

Published Online: 09 Feb 2013
Page range: 43 - 51

Abstract

Abstract

Five new optically active poly(amide-imide)s(PAIs) 5a–e were prepared by direct polycondensation reaction of N,N′- (pyromellitoyl) bis-L-tyrosine 3 as chiral dicarboxylic acid with various aromatic diamines 4a–e. Triphenylphosphite(TPP)/pyridine(py) in the presence of calcium chloride (CaCl2) and N-methyl-2-pyrrolidone (NMP) were successfully applied to direct polycondensation reaction. The resulting new polymers were obtained in good yields with inherent viscosities ranging between 0.48 dL/g and 0.6 dL/g. They were analyzed with a C.H.N. elemental analyzer, FTIR, 1H-NMR, UV-VIS spectroscopy and polarimeter (specific rotation measurement, [α]D25). Thermogravimetric analysis (TGA) indicated that the residual weight percentage of polymers at 600 °C were between 48.66 % and 64.21 %, which showed their thermal stability. These polymers are attractive to be used as packing materials in chromatography columns for separation of enantiomers.

Keywords

  • polycondensation
  • poly(amide-imide)s
  • optical activity
Open Access

Extraction of edingtonite from a natural zeolite under hydrothermal conditions

Published Online: 09 Feb 2013
Page range: 52 - 58

Abstract

Abstract

In the present study, edingtonite has been extracted from natural zeolite clinoptilolite by simulating the natural hydrothermal conditions in the laboratory, under the influence of solutions with different concentrations of Ba+2 and Na+, varying from 0.5 to 2.8 mol/L, at 150 °C. In this work, the essential hydrothermal conditions have been provided by hydrothermal autoclaves. The natural and laboratory prepared samples were characterized by XRD, XRF and SEM methods.

Keywords

  • clinoptilolite
  • phase transformation
  • hydrothermal conditions
  • edingtonite
Open Access

One-step reduction, characterization and magnetic behaviour of exfoliated graphene oxide

Published Online: 09 Feb 2013
Page range: 59 - 64

Abstract

Abstract

The functionalized graphene (GO) was fabricated by a simple method of chemical reduction in a polar aprotic solvent. This paper therefore, describes a versatile and synthetic route for the preparation of reduced graphene oxide (RGO) and its behavior when exposed to magnetic field environment. The characterization results of transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy and the attenuated total reflectance-Fourier transform infra-red (ATR-FTIR) analysis indicate that graphite was exfoliated and reduced to graphene layers.

Keywords

  • chemical reduction
  • hydrazine hydrate
  • graphite oxide
  • reduced graphene oxide
  • exfoliate
Open Access

Synthesis of nanocrystalline nickel and iron carbides by decomposition of hydrocarbons

Published Online: 09 Feb 2013
Page range: 65 - 70

Abstract

Abstract

Decomposition of hydrocarbons was carried out on nickel and iron catalysts containing small amounts of calcium and aluminum oxides as structural promoters. Decomposition of methane, ethane and ethylene was studied under atmospheric pressure in the temperature range from 500 to 700 °C. The phase composition of the obtained samples was investigated using X-ray diffraction method. The role of nickel and iron carbides in the formation of carbon deposit was discussed.

Keywords

  • nanocrystalline nickel carbide
  • nanocrystalline iron carbide
  • decomposition of hydrocarbons
Open Access

Structural and surface properties of TiO2 thin films doped with neodymium deposited by reactive magnetron sputtering

Published Online: 09 Feb 2013
Page range: 71 - 79

Abstract

Abstract

Thin films were deposited using modified, high energy magnetron sputtering method from Ti-Nd mosaic targets. The amount of neodymium dopant incorporated into two sets of thin films was estimated to be 0.8 and 8.5 at.%, by means of energy dispersive spectroscopy. On the basis of x-ray diffraction method, the type of crystalline structure and crystallites size were evaluated directly after the deposition process and after additional post-process annealing at 800 °C temperature. The influence of annealing on the surface properties was evaluated with the aid of atomic force microscopy. Uniformity of the dopant distribution in titanium dioxide matrix was examined with the aid of secondary ion mass spectroscopy. Additionally, using atomic force microscope, diversification and roughness of the surface was determined. Chemical bonds energy at the surface of TiO2:Nd thin films was investigated by x-ray photoelectron spectroscopy method. Wettability measurements were performed to determine contact angles, critical surface tensions and surface free energy of prepared coatings. On the basis of performed investigations it was found, that both factors, the amount of neodymium dopant and the post-process annealing, fundamentally influenced the physicochemical properties of prepared thin films.

Keywords

  • TiO2
  • neodymium
  • physicochemical properties
  • magnetron sputtering
Open Access

Structural and dielectric properties of La substituted polycrystalline Ca(Ti0.5Fe0.5)O3

Published Online: 09 Feb 2013
Page range: 80 - 87

Abstract

Abstract

Polycrystalline Ca1−x Lax(Ti0.5Fe0.5)O3 were prepared by the standard solid state reaction technique. Pellet shaped samples prepared from each composition were sintered at 1573 K for 5 h. The X-ray diffraction analysis indicated the formation of a single-phase orthorhombic structure. The lattice parameters as well as densities increased but the average grain sizes decreased with the increase of La content. The dielectric measurements were carried out at room temperature as a function of frequency and composition. The experimental results revealed that dielectric constant (ɛ′) decreased but dielectric loss (tan δ) and ac electrical conductivity (σ ac) increased as frequency increased. The composition dependence of ɛ′ and tan δ indicated that they decreased with the increase of La content. The σ ac was derived from the dielectric measurements and it is concluded that the conduction in the present samples is due to mixed polarons hopping.

Keywords

  • ceramics
  • chemical synthesis
  • X-ray diffraction
  • dielectric properties
Open Access

Photodecomposition of Rhodamine B on TiO2/SiO2 thin films prepared by sol-gel method

Published Online: 09 Feb 2013
Page range: 88 - 94

Abstract

Abstract

Glasses showing catalytic effect have been of much interest recently because the catalytic layer is very effective in reducing of pollutants. The use of these glasses may bring reduction in cleaning costs. There are several methods of preparation of TiO2 with good catalytic properties, but sol-gel technique offers an opportunity to enhance catalytic effect by precise optimization of the composition and microstructure of the layer. This study concerns optimization of the composition and preparation technology of catalytic layers based on SiO2-TiO2 system. Catalytic effect was studied using Rhodamine B as a sensor. UV-VIS and photoelectron spectroscopy were the main research tools used in this study.

Keywords

  • photocatalytic effect
  • titanium layer
  • sol-gel
  • Rhodamine B
Open Access

An ammonia sensor based on in situ-synthesized polyaniline nanostructures

Published Online: 09 Feb 2013
Page range: 95 - 100

Abstract

Abstract

Nowadays, a good deal of research is focusing on the development of new analytical procedures for detection of hazardous agents, such as bacteria, harmful pollutants, toxic vapors, and many others. The majority of the research is aimed at developing new sensors and analytical equipment. This paper demonstrates a simple construction of an ammonia sensor based on commercially available electronic connectors with active elements from polyaniline. The main goal of this research is to present the simplicity of sensor manufacturing, without the need for advanced apparatus such as electropolymerization or electrospinning set-up. The active element of the proposed sensor is composed of polyaniline synthesized in situ on the surface of conductive glue. The layer of the conductive glue is a key element in this sensor as it protects the metallic pin against destruction during in situ synthesis of polyaniline (acidic and oxidizing conditions).

Keywords

  • ammonia sensor
  • polyaniline
  • nanostructures
Open Access

Research into the relationship between the surface topography, texture and mechanical properties of PVD-Cu/Ni multilayers

Published Online: 09 Feb 2013
Page range: 101 - 107

Abstract

Abstract

The paper presents the results of structural examinations and mechanical tests of Cu/Ni multilayers fabricated by the magnetron sputtering method. The investigated multilayers were differentiated by Ni sublayer thickness (1, 3 and 6 nm), while the retaining Cu sublayer thickness was unchanged (2 nm). Measurements demonstrated that the multilayers were strongly textured in the direction of their growth [111], with the thinnest multilayer (Cu/Ni = 2/1) showing a stronger texture. Stronger texturing was associated with greater surface roughness. Multilayers with the largest thickness had higher hardness and Young’s modulus. The properties of Cu/Ni multilayers depended both on the thickness of their sublayers, as well as on their total thickness.

Keywords

  • Cu/Ni multilayers
  • thermal stability
  • X-ray diffraction
  • texture
  • atomic force microscopy
Open Access

Luminescent homo- and hetero-metallic hybrid molecular materials constructed by covalent grafting

Published Online: 09 Feb 2013
Page range: 108 - 114

Abstract

Abstract

In this paper, 3-(triethoxysilyl)-propyl isocyanate (abbreviated as TESPIC) was modified by ethylparaben (EPB) to produce corresponding organic-inorganic monomers (EPB-TESPIC) with two components equipped with covalent bonds, which not only can coordinate to RE ions (Tb3+ and Eu3+) but also act as a sol-gel precursor. Luminescent hybrid materials consisting of terbium-europium complex, covalently bonded to silica-based network, have been obtained in situ via a sol-gel approach. Proton nuclear magnetic resonance spectroscopy (1HNMR) and Fourier transform infrared spectroscopy (FT-IR) were applied to characterize the structure of EPB-TESPIC. UV-visible, phosphorescence, and luminescence spectra were obtained to characterize the photophysical properties of the obtained hybrid material. Through co-hydrolysis and polycondensation, Tb3+ and Eu3+ can be introduced into the same organic-inorganic hybrid monomer, forming Si-O backbones. The experimental results show that the strong luminescence of rare-earth ions substantiates the optimum energy match and effective intramolecular energy transfer between the triplet state energy of coordination complex and the emissive energy level of the rare-earth ions. The hybrid material systems are expected to have potential applications in photophysical sensors.

Keywords

  • chemical modification
  • organic-inorganic hybrids
  • photoluminescence
  • sol-gel process
Open Access

Optical pH detector based on LTCC and sol-gel technologies

Published Online: 09 Feb 2013
Page range: 115 - 121

Abstract

Abstract

This paper presents an investigation on using sol-gel thin film as a material for sensors application in LTCC (Low Temperature Co-fired Ceramics) technology. This material gives the opportunity to make new, low-cost highly integrated optoelectronic devices. Sensors with optical detection are a significant part of these applications. They can be used for quick and safe diagnostics of some parameters. Authors present a pH detector with the optical detection system made of the LTCC material. The main part of the device is a flow channel with the chamber and sol-gel active material. The silica sol-gel with bromocresol green indicator was used. As the absorbance of sol-gel layer changes with the pH value of a measured medium, the transmitted light power was measured. The pH detector was integrated with the electronic components on the LTCC substrate.

Keywords

  • Low Temperature Cofired Ceramics LTCC
  • sol-gel
  • pH sensor
  • optical amonia detection
Open Access

CuO as sintering additive to Sr0.4Ca0.6La4Ti5O17 ceramics

Published Online: 09 Feb 2013
Page range: 122 - 125

Abstract

Abstract

The effects of CuO addition on the sintering behavior and microwave dielectric properties of Sr0.4Ca0.6La4Ti5O17 ceramics were investigated. CuO was selected as a liquid phase sintering aid to lower the sintering temperature of Sr0.4Ca0.6La4Ti5O17 ceramics. With CuO addition, the sintering temperature of Sr0.4Ca0.6La4Ti5O17 ceramics was effectively reduced from 1550 °C to 1475 °C. The crystalline phase exhibited no phase difference and no second phase was detected at all addition levels. The electric permittivity was not significantly affected by various amounts of CuO addition and ranged from 52 to 54. Small values (<+7 ppm/K) of the temperature coefficient of resonant frequency were obtained for Sr0.4Ca0.6La4Ti5O17 ceramics. However, the unloaded quality factor Q u was strongly dependent upon the CuO concentration. Q u f o ∼ 10500 GHz was obtained for Sr0.4Ca0.6La4Ti5O17 ceramics with 0.5 wt.% of CuO addition, sintered at 1475 °C.

Keywords

  • CuO
  • calcination
  • additive
Open Access

Improvement of supercapacitor parameters by nickel ion intercalation into activated carbon

Published Online: 09 Feb 2013
Page range: 126 - 132

Abstract

Abstract

The relation between the porous structure and the electron structure in carbon materials was investigated in order to optimize the efficiency of the physical-chemical processes in an electric double layer (EDL) formed at the boundary between the carbon material and the electrolyte (KOH 30 % aqueous solution). In particular, an Ni2+ intercalative modification of nanoporous carbon resulted in more than a triple increase in the specific capacitance and a significant improvement of the charge-discharge kinetics in the EDL.

Keywords

  • Ni-intercalative modification
  • small angle X-ray scattering
  • nanocluster
  • nanoporous carbon
  • supercapacitor
Open Access

Structural properties of Sb- and Te-based binary compounds: Spin-orbit effect

Published Online: 09 Feb 2013
Page range: 133 - 138

Abstract

Abstract

The band structure of AlSb, GaSb, ZnTe and CdTe is calculated using the empirical pseudopotential method (EPM) coupled with spin-orbit (SO) splitting. We applied our empirical model of bulk modulus with SO effect. It has been noticed that SO has a crucial effect on the band structure of these compounds but does not influence the structural phase transition. The calculated results are in good agreement with the experimental data.

Keywords

  • binary compounds
  • spin-orbit
  • structural properties
Open Access

Photo-induced changes in arsenic selenide films

Published Online: 09 Feb 2013
Page range: 139 - 145

Abstract

Abstract

The spectral dependence of the transmittance and reflectance of thermally-evaporated amorphous AsxSe100−x (where x = 20 and 40 at.%) films was measured in the wavelength range of 190–900 nm. A procedure was given for accurate determination of the film thickness using a standard method of numerical differences from the experimental data. The process of indirect electronic transitions was found to be responsible for the photon absorption. The variation of the energy band gap with the exposure time was investigated. Amorphous-crystalline transformations occurring as a result of photoexposure have been confirmed by the structural studies of the As20Se80 specimens using the scanning electron microscope and transmission electron microscope. Photodarkening relaxation under light exposure of the well annealed films was studied and the relaxation process has been described by the stretched exponential function (SEF).

Keywords

  • chalcogenides
  • arsenic selenide glasses
  • optical properties
  • photo-induced effects
  • photo-darkening relaxation
Open Access

Cyclic voltammetry and impedance studies of undoped diamond films

Published Online: 09 Feb 2013
Page range: 146 - 150

Abstract

Abstract

The undoped, polycrystalline diamond films were deposited on tungsten wire substrates by hot filament chemical vapor deposition (HF CVD), using a precursor gas mixture of methanol with excess of hydrogen. The morphology and quality of the as-deposited films were monitored by scanning electron microscopy (SEM) and Raman spectroscopy. The surface morphology analyzed by SEM resembles a continuous and well faceted diamond film. Raman results showed essential differences in qualities of diamond films grown at different hydrocarbon concentrations. The electrochemical properties of diamond electrodes were examined with cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS). The CV experiments revealed a large chemical window (>∼4.3 V) of undoped diamond. Analysis of the ferrocyanide-ferricyanide couple at a diamond electrode suggests some extent of electrochemical quasi-reversibility, but the rates of charge transfer across the diamond substrate interface vary with diamond quality.

Keywords

  • CVD diamond
  • Raman spectroscopy
  • cyclic voltammetry (CV)
  • electrochemical impedance spectroscopy (EIS)
Open Access

Optical, structural and electrical properties of pure and urea doped KDP crystals

Published Online: 09 Feb 2013
Page range: 151 - 157

Abstract

Abstract

Single crystals of good optical quality, made of potassium dihydrogen phosphate (KDP) doped with urea were grown by slow evaporation solution growth technique at a constant temperature of 35 °C. Optical absorption and dielectric properties were studied for pure and urea doped KDP crystals. Using powder XRD studies, crystalline nature of pure and urea doped KDP crystals was confirmed. AC conductivity was measured for the grown crystals. DC electrical conductivity and photoconductivity studies were carried out for pure and urea doped KDP crystals and the differences caused by the dopant were also discussed.

Keywords

  • absorption
  • powder XRD
  • dielectric
  • photoconductivity
  • potassium dihydrogen phosphate (KDP)
Open Access

Erratum to Preparation of crystal-controlled Y-TZP/Al2O3 nanocomposites

Published Online: 09 Feb 2013
Page range: 158 - 158

Abstract

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