The application of ultrasound radiation to the synthesis of nanocrystalline metal oxide in a non-aqueous solvent

Highly crystalline metal oxide nanoparticles of TiO₂, WO₃, and V₂O₅ were synthesized in just a few minutes by reacting transition metal chloride with benzyl alcohol using ultrasonic irradiation under argon atmosphere in a non-aqueous solvent. The sonochemical process was conducted at a relatively low temperature, 363 K. A unique crystallization process of these nanoparticles has been observed and characterized by powder X-ray diffraction (PXRD), high resolution scanning electron microscopy (HRSEM), and BET. The particles’ size and shape measured from HRSEM reveal “quasi” zero-dimensional, spherical TiO₂ particles in the range of 3–7 nm. The V₂O₅ particles have a “quasi” one-dimensional ellipsoidal morphology, with lengths in the range of 150–200 nm and widths varying between 40 and 60 nm. The WO₃ particles were obtained as “quasi” two-dimensional platelets with square shapes having facets ranging from 30 to 50 nm. The thickness of these platelets was between 2 and 7 nm. The mechanism of the reactions leading to these three metal oxide nanoparticles in a non-aqueous system is substantiated by Nuclear Magnetic Resonance (NMR), and Electron Spin Resonance (ESR).     

Synthesis of glycoluril catalyzed by potassium hydroxide under ultrasound irradiation

Synthesis of the glycolurils catalyzed by potassium hydroxide was carried out in 17–75% yield at 40 °C in EtOH under ultrasound irradiation. Compared to the method using stirring, the main advantage of the present procedure is milder conditions and shorter reaction time.     

Tritium isotope separation by CO2-laser irradiation at low temperatures

Tritium isotope separation by CO₂-laser induced multiphoton dissociation of CTF₃ is investigated. For the optimization of the performance of this working substance, trifluoromethane, the conditions to yield high-selectivity at high-operating pressure and low-critical fluence for complete dissociation are studied using our deconvolution procedure. The irradiation conditions are varied over the following ranges; wavenumber: 1052–1087 cm^–1, gas temperature: 25°C to –78°C, CHF₃ pressure: 5–205 Torr. The selectivities exceeding 10⁴ are observed for 85–205 Torr CHF₃ at –78°C by the irradiation at 1057 cm^–1.     

Ultrasound effects on restricted silica gelation during silica extraction from Pyro-Metallurgical copper slag under acidifying conditions

Pyro-metallurgical copper slag (CS) waste was used as the source material for ultrasound (US) silica extraction under acidification processes with 26 kHz with HCl, HNO₃, and H₂SO₄ at different concentrations at 100, 300, and 600 W. During acidifying extraction processes, US irradiation inhibited silica gel formation under acidic conditions, especially at lower acid concentrations of less than 6 M, whereas a lack of US irradiation led to enhanced gelation. When US stopped, gelation occurred to a considerable degree, suggesting that the gel particle size distribution was aggregated in the 3–400 µm size range. However, with US, the size was mainly in the 1–10 µm range. Results of elemental analysis indicated that US treatment decreased the co-precipitation of other metal ions such as Fe, Cu, and Al sourced from CS for lower acidic medium, whereas the higher concentration medium accelerated silica gelation and the co-precipitation of other metals. With acids of HCl and HNO₃, and H₂SO₄, the gelations were less likely to occur at 6 M and 3 M during US irradiation, but acidic extraction without US was efficient for silica gelation and co-precipitation of other metals in the purified silica. The silica extraction yield with H₂SO₄ concentration of 3 M was 80% with 0.04% of Fe, whereas the silica product from HCl 6 M had a 90% extraction yield with only 0.08% of Fe impurity. In contrast, even though the non-US system of HCl 6 M had a higher yield at 96%, the final product had 0.5% Fe impurity, which was much higher than the US system. Consequently, the US extraction process was quite noticeable for silica recovery from CS waste.     

Ultrasound assisted co-precipitation of nanostructured CuO–ZnO–Al2O3 over HZSM-5: Effect of precursor and irradiation power on nanocatalyst properties and catalytic performance for direct syngas to DME

Nanostructured CuO–ZnO–Al₂O₃/HZSM-5 was synthesized from nitrate and acetate precursors using ultrasound assisted co-precipitation method under different irradiation powers. The CuO–ZnO–Al₂O₃/HZSM-5 nanocatalysts were characterized using XRD, FESEM, BET, FTIR and EDX Dot-mapping analyses. The results indicated precursor type and irradiation power have significant influences on phase structure, morphology, surface area and functional groups. It was observed that the acetate formulated CuO–ZnO–Al₂O₃/HZSM-5 nanocatalyst have smaller CuO crystals with better dispersion and stronger interaction between components in comparison to nitrate based nanocatalysts. Ultrasound assisted co-precipitation synthesis method resulted in nanocatalyst with more uniform morphology compared to conventional method and increasing irradiation power yields smaller particles with better dispersion and higher surface area. Additionally the crystallinity of CuO is lower at high irradiation powers leading to stronger interaction between metal oxides. The nanocatalysts performance were tested at 200–300 °C, 10–40 bar and space velocity of 18,000–36,000 cm³/g h with the inlet gas composition of H₂/CO = 2/1 in a stainless steel autoclave reactor. The acetate based nanocatalysts irradiated with higher levels of power exhibited better reactivity in terms of CO conversion and DME yield. While there is an optimal temperature for CO conversion and DME yield in direct synthesis of DME, CO conversion and DME yield both increase with the pressure increase. Furthermore ultrasound assisted co-precipitation method yields more stable CuO–ZnO–Al₂O₃/HZSM-5 nanocatalyst while conventional precipitated nanocatalyst lost their activity ca. 18% and 58% in terms of CO conversion and DME yield respectively in 24 h time on stream test.     

Effect of pH values on surface modification and solubility of phosphate bioglass-ceramics in the CaO–P2O5–Na2O–SrO–ZnO system

The bioactive glass-ceramics in the CaO–P₂O₅–Na₂O–SrO–ZnO system were synthesized by the sol–gel technique, and then chemically treated at different pH values to study the solubility and surface modification. Samples sintered at 650 °C for 4 h consisted of the crystalline phase β-Ca₂P₂O₇ and the glass matrix. After soaking in the solution at pH 1.0, the residual glass matrix on the surface appeared entirely dissolved and no new phase could be detected. Whereas at pH 3.0, web-like layer exhibiting peaks corresponding to CaP₂O₆ was formed and covered the entire surface of the sample. When conducted at pH 10.0, only part of the glass matrix was dissolved and a new phase Ca₄P₆O₁₉ was precipitated, forming the petaline layer. The chemical treatment can easily change the surface morphologies and phase composition of this bioactive glass-ceramics. The higher level of surface roughness resulting from the new-formed layer would improve the interface bonding and benefit for cell adhesion.     

The influence of polychromic light on the surface of MDI based polyurethane elastomer

A polyurethane elastomer was synthesized starting from 4,4′ diphenylmethane diisocyanate and poly(ethyleneadipate)diol. Butylene glycol was used as chain extender. Surface properties after photo-degradation of the elastomer under the action of the radiation with λ > 300 nm was monitored by FT-IR spectroscopy and contact angle measurements. The quality of polymer surface was observed under optical microscope. The formation of photo-Fries rearrangement and Norrish II reaction products during irradiation was associated with the gloss loss (from 100% for non-irradiated sample to 27% after 200 h irradiation time) and modification of wettability. There were also found significant modifications with irradiation time of both the glass transition temperature (T_g decreases from 64 °C for non-irradiated sample to 53 °C after 200 h irradiation) and the swelling coefficient (an increase from 1.2% up to 2.5% is observed after 200 h irradiation).     

Rapid esterification of fatty acid using dicationic acidic ionic liquid catalyst via ultrasonic-assisted method

Biodiesel production via esterification/transesterification reactions can be catalyzed by homogenous or heterogeneous catalysts. Development of heterogeneous catalysts for biodiesel production is highly advantageous due to the ease of product purification and of catalyst recyclability. In this current work, a novel acidic [DABCODBS][CF₃SO₃]₂ dicationic ionic liquid (DIL) was used as heterogeneous catalyst to produce biodiesel using oleic acid as model oil. The esterification was conducted under ultrasonic irradiation (20 kHz) using a 14 mm ultrasonic horn transducer operated at various duty cycles. It was observed that the duty cycle, amplitude, methanol to oil molar ratio, catalyst amount and reaction temperature were the major factors that greatly impact the necessary reaction time to lead to a high yield of biodiesel. The reaction conditions were optimized with the aid of Response Surface Methodology (RSM) designed according to the Quadratic model of the Box Behnken method. The optimum conditions were found to be at catalyst amount of 0.64 mol%, methanol to oil ratio of 14.3:1, temperature of 59 °C, reaction time of 83 min and amplitude of 60% in continuous mode. The results showed that the oleic acid was successfully converted into esters with conversion value of 93.20% together with significant reduction of reaction time from 7 h (using mechanical stirring) to 83 min (using ultrasonication). The results also showed that the acidic DIL catalyst we designed purposely was efficient to catalyze the ultrasonic-assisted esterification yielding high conversion of oleic acid to methyl oleate on short times. The DIL was also recycled and reused for at least five times without significant reduction in performance. Overall, the procedure offers advantages including short reaction time, good yield, operational simplicity and environmentally benign characteristics.     

The sonochemical decolourisation of textile azo dye Orange II: Effects of Fenton type reagents and UV light

The removal of Orange II (O-II) from aqueous solution under irradiation at 850 kHz has been studied. The effects of both homogeneous (with FeSO₄/H₂O₂)_, and heterogeneous (Fe containing ZSM-5 zeolite/H₂O₂) Fenton type reagents are reported together with the effect of UV irradiation in combination with ultrasound both alone and with homogeneous Fenton-type reagent.Degrees of decolourisation of 6.5% and 28.9% were observed using UV radiation and ultrasound, respectively, whereas under the simultaneous irradiation of ultrasound and UV light, the decolourisation degree reached 47.8%, indicating a synergetic effect of ultrasound and UV light. The decolourisation was increased with the addition of Fenton’s reagent with an optimal Fenton molar reagent ratio, Fe²⁺:H₂O₂ of 1:50. In the combined process of ultrasound and UV light with the homogeneous Fenton system 80.8% decolourisation could be achieved after 2 h indicating that UV improves this type of Orange II degradation. The degree of decolourisation obtained using the heterogeneous sono-Fenton system (Fe containing ZSM-5 zeolite catalysts + H₂O₂ + ultrasound) were consistently lower than the traditional homogeneous ultrasound Fenton system. This can be attributed to the greater difficulty of the reaction between Fe ions and hydrogen peroxide.In all cases the Orange II ultrasonic decolourisation was found to follow first order kinetics.     

Computer simulation of shock waves in the completely asymmetric simple exclusion process

We study the evolution of the completely asymmetric simple exclusion process in one dimension, with particles moving only to the right, for initial configurations corresponding to average density _– ( ₊) left (right) of the origin, _{– +}. The microscopic shock position is identified by introducing a second-class particle. Results indicate that the shock profile is stable, and that the distribution as seen from the shock positionN(t) tends, as time increases, to a limiting distribution, which is locally close to an equilibrium distribution far from the shock. Moreover , withV=1– _–– ₊, as predicted, and the dispersion ofN(t), ²(t), behaves linearly, for not too small values of ₊– _–, i.e., , whereS is equal, up to a scaling factor, to the valueS _WA predicted in the weakly asymmetric case. For ₊= _– we find agreement with the conjecture .Dedicated to the memory of Paola Calderoni.     

Lithium ion conductive glass–ceramics with Li3Fe2(PO4)3 and YAG laser-induced local crystallization in lithium iron phosphate glasses

The glasses with the composition of 37.5Li₂O–(25 − x)Fe₂O₃–xNb₂O₅–37.5P₂O₅ (mol%) (x = 5,10,15) are prepared, and it is found that the addition of Nb₂O₅ is effective for the glass formation in the lithium iron phosphate system. The glass–ceramics consisting of Nasicon-type Li₃Fe₂(PO₄)₃ crystals with an orthorhombic structure are developed through conventional crystallization in an electric furnace, showing electrical conductivities of 3 × 10^− 6 Scm^− 1 at room temperature and the activation energies of 0.48 eV (x = 5) and 0.51 eV (x = 10) for Li⁺ ion conduction in the temperature range of 30–200 °C. A continuous wave Nd:YAG laser (wavelength: 1064 nm) with powers of 0.14–0.30 W and a scanning speed of 10 μm/s is irradiated onto the surface of the glasses, and the formation of Li₃Fe₂(PO₄)₃ crystals is confirmed from XRD analyses and micro-Raman scattering spectra. The crystallization of the precursor glasses is considered as new route for the fabrication of Li₃Fe₂(PO₄)₃ crystals being candidates for use as electrolyte materials in lithium ion secondary batteries.     

Nonlinear Optical Characteristics of BSO and BGO Photorefractive Crystals in Visible and Infrared Ranges

Nonlinear refraction, nonlinear absorption and optical limiting in photorefractive crystals Bi₁₂SiO₂₀(BSO) and Bi₁₂GeO₂₀(BGO) at the wavelengths of 1064 and 532 nm were investigated. It was shown that both BSO and BGO crystals possess by positive nonlinear refraction in two investigated spectral ranges (n ₂ ^BSO=(2.5 ± 0.5)× 10^–12 esu, n ₂ ^BGO=(6.3 ± 1.3)× 10^–12 esu at equals 1064 nm; n ₂ ^BSO=(4.4 plusmn; 0.9)× 10^–12 esu, n ₂ ^BGO=(7.4 ± 1.5)× 10^–12 esu at = 532 nm). The nonlinear absorption was due to three-photon absorption at the wavelength of 1064 nm ( ⁽³⁾ _BSO=(2.5 ± 0.8)× 10^–20cm³W^–2, ⁽³⁾ _BSO=(4.4 ± 1.3)× 10^–20cm³W^–2) and two-photon absorption at the wavelength of 532 nm ( ⁽²⁾ _BSO=(2 ± 0.4)× 10^–9cm W^–1, ⁽²⁾ _BGO=(3.7 ± 0.7)× 10^–9cm W^–1).     

Microstructural characterization and optical polarization of glass with needle-like micro–nano silver oriented arrangement

Homogeneous glasses in the Na₂O–B₂O₃–Al₂O₃–SiO₂ system doped with proper amount of AgCl were obtained by melting at a temperature of 1450 °C. Then, with several steps of treatment, including crystallization, elongation and reduction, the glass with oriented arrangement of needle-like micro–nano silver particles was produced. The microstructure and the optical properties of the glass samples in different stages were studied by SEM-EDAX, FE-SEM and UV–Vis spectrum. The results showed that the glass after elongation and reduction exhibits excellent polarization performance in the wavelength range from 600 nm to 900 nm, with an extinction ratio larger than 45 dB. The glass only elongated shows also slight polarizing performance, which may result from the formation of filament structure of Ag during elongation processing.     

Dielectric constant and current transport for HfO2 thin films on ITO

The dielectric constant and leakage current mechanisms for HfO₂ thin films deposited on indium–tin–oxide using reactive rf sputtering deposition were examined. Indium–tin–oxide was selected as the bottom metal as it is of interest as an electrode in transparent field-effect transistor development. The dielectric constant of HfO₂ films was approximately 20 and did not vary significantly with deposition conditions. Temperature-dependent leakage current measurements indicate that Schottky emission is the dominant transport mechanism in films deposited at low temperature and/or low oxygen pressure. The HfO₂/indium–tin–oxide barrier height was extracted to be 1.1±0.2 eV. Films deposited at high temperature and/or oxygen pressure deviate from the Schottky emission model, presumably due to the formation of polycrystalline material with grain boundary conduction. PACS  73.61.Ng; 73.50.Lw; 77.55.+f     

13C-selective infrared multiple-photon decomposition study of CBrClF2

The infrared multiple-photon single-frequency decomposition (IRMPD) of CBrClF₂ was examined as functions of laser wavenumber, laser fluence, and partial pressure of CBrClF₂. The initial step was the scission of a C-Br bond. In the presence of O₂ the carbon-containing product was CF₂O and its subsequent hydrolysis gave CO₂. The initial dissociation was highly ¹³C selective at wavenumbers below 1014 cm^–1. CBrClF₂ decomposed at relatively low fluences as compared to CHClF₂. However, the decomposition yield rapidly decreased with increasing pressure. In the large-scale irradiation experiment using about 8 J pulse at 1 Hz, we obtained a carbon yield of 0.41 mol per pulse at a ¹³C-atom fraction of 17% for a mixture of 10 Torr CBrClF₂ and 10 Torr O₂, and a carbon yield of 0.17 mol per pulse at a fraction of 29% for a mixture of 20 Torr CBrClF₂ and 20 Torr O₂. The IRMPD of CHClF₂ gave a carbon yield of 0.18 mol per pulse at 48% for 10 Torr neat CHClF₂ and yield of 0.25 mol at 52% for 20 Torr CHClF₂. The large-scale irradiation experiment was also carried out for mixtures of CBr₂F₂ and O₂. CHClF₂ is the most productive of ¹³C.     

NO dissociation and N2 production in the presence of co-adsorbed SO2 and D2 on Pt(3 3 2)

NO dissociation and subsequent N₂ production in the presence of co-adsorbed S¹⁸O₂ and D₂ on the surface of stepped Pt(3 3 2) were studied using Fourier transform infra red reflection–absorption spectroscopy (FTIR-RAS) combined with thermal desorption spectroscopy (TDS). Reduction of NO by D (D₂ is adsorbed dissociatively on Pt surfaces) proceeds to a limited extent, because this reaction is rate-controlled by NO dissociation and the supply of D atoms at the higher surface temperatures at which NO dissociation becomes significant (350 K and higher). NO–D reaction is suppressed in the presence of S¹⁸O₂, depending significantly on the S¹⁸O₂ coverage and the competition between the reactions NO–D and S¹⁸O₂–D. When the supply of D₂ is limited, e.g., 0.1 L in this study, the presence of S¹⁸O₂ suppresses the NO–D reaction. With a sufficient supply of D₂, e.g., 0.4 L and higher, D-atom competing reactions do not play a role any more because the reactions of both NO and S¹⁸O₂ with D proceed only to a very limited extent. As such, generation of O atoms from S¹⁸O₂ dissociation is the main reaction that leads to the suppression in NO dissociation and consequently, N₂ production.It is also concluded that the presence of S¹⁸O₂ does not seriously poison the active sites on the Pt surface, providing that there is a sufficient D supply to remove O atoms from both NO dissociation and S¹⁸O₂ dissociation.     

A convenient and efficient protocol for the synthesis of 5-aryl-1,3-diphenylpyrazole catalyzed by hydrochloric acid under ultrasound irradiation

The synthesis of 5-aryl-1,3-diphenylpyrazole via the reactions of 3-aryl-2,3-epoxy-1-phenyl-1-propanone with phenylhydrazine was carried out in 69–99% yields at room temperature under ultrasound irradiation. This method provides several advantages such as operational simplicity, higher yield and environment friendly.     

Effect of annealing temperature on the photocatalytic activity of WO3 for O2 evolution

Commercial WO₃ powder was annealed in air at four different temperatures and characterized by XRD and BET. The samples were used for the photooxidation of H₂O to O₂ under visible light irradiation (λ > 420 nm) in the presence of IO₃⁻ and the evolved gases were analyzed by gas chromatography. The results showed that the WO₃ photocatalyst of monoclinic phase, which was obtained by annealing at 750 °C for 4 h, displayed the best activity in terms of O₂ evolution among all the samples. Moreover, the activity was also found to be slightly affected by the grain size of the WO₃ samples.     

Scintillation and optical stimulated luminescence of Ce-doped CaF2

Scintillation and optical stimulated luminescence of Ce 0.1–20% doped CaF₂ crystals prepared by Tokuyama Corp. were investigated. In X-ray induced scintillation spectra, luminescence due to Ce³⁺ 5d–4f transition appeared around 320 nm with typically 40 ns decay time. By ²⁴¹Am 5.5 MeV α-ray irradiation, 0.1% doped one showed the highest scintillation light yield and the light yield monotonically decreased with Ce concentrations. Optically stimulated luminescence after X-ray irradiation was observed around 320 nm under 550 or 830 nm stimulation in all samples. As a result, intensities of optically stimulated luminescence were proportional to Ce concentrations. Consequently, scintillation and optically stimulated luminescence resulted to have a complementary relation in Ce-doped CaF₂ system.     

Thermodynamics and phase stabilities of the ternary system Li-In-Sb

Electrochemical investigations of the phase equilibria of the ternary system Li-In-Sb show the existence of two new ternary phases, Li₃InSb₂ and nominally Li₆InSb₃ which has a wide range of stoichiometry along the quasi-binary cut InSb-Li₃Sb. Both compounds are stable in equilibrium with elemental indium and antimony. The lithium activities are limited to ranges from 6.6×10^–8 to 3.6×10^–7 and 9.3×10^–8 to 1.1 ×10^–5, respectively, at 400 °C. The standard Gibbs energies of formation of Li₃InSb₂ and Li₆InSb₃ are –296.2 and –568.8 kJ/mol, respectively, at 400 °C and ideal stoichiometry. The activity ranges of Li, In and Sb are given for the stability of all phases of the ternary system.On leave from Institut für Physikalische und Theoretische Chemie, Technische Universität Graz, Austria