Results 1 - 10 of 1816
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[en] The present study reports on facile deposition of single-phase BiVO4 thin films by nebulizer spray pyrolysis route for different spray volumes (5, 10, 15, and 20 ml). The main objective is to identify the optimum thickness and morphology of BiVO films for enhanced photocatalytic performance. The physical properties of the films were characterized using different analytical techniques. Highly compact and flake-like structures in BiVO film were resulted for higher spray volume without any aid of additive or template in the preparation procedure. Nanoflake BiVO film possessed high optical absorption, effective charge carrier transport properties, and high penetration depth, and exhibited maximum photodegradation efficiency for the treatment of rhodamine B and methyl orange dyes.
[en] CoCuFeO (CCFO) and BaSrTiO (BST) particles were respectively prepared by chemical coprecipitation and hydrothermal method, then CCFO/BST composite liquid was synthesized by distributing surface modified CCFO and BaSrTiO particles into insulating silicone oil. Effects of volume fraction (ϕ = 1%, 2%, 5% and 10%) on the microstructure, dielectric, ferroelectric and magnetoelectric coupling effect were comparatively investigated. XRD showed that the pure phase of CCFO and BST particles was successfully prepared. CCFO/BST composite particle shows ferromagnetic behavior due to the contribution of magnetic phase CCFO. The dielectric constant of CCFO/BST composite liquid is about 1/25 of the composite particles, and the dielectric constant value of the composite liquid decreases with increasing the volume fraction because the permittivity of silicone oil is far smaller than that of CCFO/BST composite particles. The relative change of dielectric constant of composite liquid under the action of external magnetic field is greater than that of composite particle due to its mobility of particles in liquid. The values of remnant polarization (P), coercive field (E) and leakage current of CCFO/BST composite liquid increase monotonically with increasing volume fraction, while excessive volume fraction may result in abnormal phenomenon because of the agglomeration of particles. Magnetic field-induced chain structure of the composite liquid has been observed under a light microscope at a magnification of 200. The maximal magnetoelectric (ME) coupling coefficient is about 89.78 V/(cm Oe), which is obtained in the CCFO/BST composite liquid when the volume fraction is 10%.
[en] Lithium tantalite (LiTaO) is an excellent single crystal, only a few studies focused on polycrystalline LiTaO ceramics, because it is difficult to sintering densification in fabrication process by common sintering. In this paper, LiTaO composite ceramics with added 3 wt% MnO were obtained by hot-pressing sintering at different temperatures from 1200 to 1350 °C. The sinterability, microstructure and dielectric properties of LiTaO ceramics fabricated at sintering temperatures were investigated. The relative density of the LiTaO ceramics was significantly enhanced as the sintering temperature increases first and then decreased. The LiTaO ceramics achieved the highest relative density (98.6%) and shown homogeneous microstructure when sintered at 1300 °C. The LiTaO and manganese oxide phases were observed in the MnO/LiTaO ceramics fabricated at different sintering temperatures. The dielectric properties of MnO/LiTaO ceramics were significantly influenced by the sintering temperatures. The study of dielectric properties revealed that the specimen had excellent dielectric properties when sintering temperature was 1300 °C and the dielectric constant was 78, as it tends to stay invariable at room temperature.
[en] The calcium-based lead borate glasses doped with 1 mol% Sm ions were prepared using melt quenching technique. The prepared glass samples were analyzed through an X-ray diffractometer, FT-IR, Optical absorption, Emission, and fluorescence decay analysis. Physical properties have been calculated for the prepared glasses. The absorption spectrum has been recorded for 1.0 mol% Sm ions doped calcium-based lead borate glasses. From the absorption spectrum, oscillatory strengths and JO intensity parameters have been calculated. The visible and near-infrared emission spectra were recorded with 402 nm excitation for 1.0 mol% Sm ions. The prepared glass shows that the highest emission intensity for G → H transition centered at 610 nm. Emission properties for the prepared glass were calculated. Decay profile has been analyzed and lifetime value for G exited level of Sm ion calculated for 1.0 mol% Sm ions doped Ca-based lead borate glass: decay profile was well fitted for exponential decay 2, and the lifetime of G excited level is 1.041 ms. The obtained results suggested that the present 1.0 mol% Sm ions doped calcium-based lead borate glass could be useful for the visible lasers and or photonic display devices applications.
[en] This paper presents the study of four gypsum mixtures, focusing on the role of both inorganic and organic additives and on the micro-structural features and mechanical properties. Additives have been chosen among those most reported in historical recipes, for example magnesia, lime putty, rabbit glue. The selected mixes refer to gypsum-based materials used in artworks manufacture, such as plasters, mouldings, stuccoworks, pastiglia. Blank reference materials were prepared on purpose according to the specific recipe, in order to verify the final composition and to highlight the hardening mechanisms and the formation of setting compounds. The chemical composition was related to workability properties and final mechanical resistance and the action of additives as retardants was studied with interesting results. For instance, MgO imparts good properties to the mechanical features, especially with regard to the compressive strength characteristics.
[es]En este artículo se han analizado cuatro mezclas basadas en yeso y se ha estudiado la influencia de los aditivos utilizados para su preparación, tanto orgánicos como inorgánicos, sobre las propiedades mecánicas y microestucturales de los materiales resultantes. Los aditivos utilizados se seleccionaron en base a aquellos que han sido principalmente publicados en recetas históricas, tales como magnesia, cal o cola de conejo. Por su parte, las mezclas basadas en yeso se eligieron en base aquellas principalmente utilizadas en obras de arte, incluyendo escayolas, molduras, estucados o pastiglia. También se prepararon materiales de referencia (control), de acuerdo a una mezcla específica, para verificar la composición química de las diferentes mezclas preparadas y comparar sus mecanismos de endurecimiento y formación. La composición química de los materiales preparados se ha correlacionado con su trabajabilidad y resistencia mecánica. Además, se estudió la acción retardante de los aditivos utilizados con interesantes resultados. Por ejemplo, el MgO confiere buenas propiedades mecánicas al material, especialmente en lo que se refiere a la resistencia a la compresión
[en] The phase transformation characteristics and isothermal oxidation behavior of ternary NiTiTa (at.%) and NiTiTa (at.%) alloys were investigated through differential scanning calorimetry and thermogravimetric analysis techniques in addition to surface morphology captured by scanning electron microscopy. It was found that the ambient temperature and chemical composition are important factors in the oxidation behavior of the alloys in oxygen atmosphere. The oxidation constants were linearly increased with oxidation temperatures ranging between 850 and 1150 °C. The activation energies were determined to be 283.54 kJ/mol and 249.38 kJ/mol for the NiTiTa (at.%) and NiTiTa (at.%) alloys, respectively.
[en] In this study, the optical properties and gamma-ray competence of barium–lead borate glasses with chemical form BaO–BO–PbO have been investigated. The optical features such as optical energy gap (E), linear refractive index (n), molar refraction (R), molar polarizability (αmolar), metallization criterion (M), dielectric constants (static and optical), reflection loss (R), optical transmission (T) and others for the investigated glasses were calculated. Results show that E measures in (eV) and E values were changed from 3.18 to 2.53 eV, while n increases from 2.350 to 2.536. Phy-X/PSD software has been applied to report the radiation attenuation factors of the tested glasses. The results implied that all samples have the high attenuation ability at lower energies and the maximum µ/ρ is reported at 15 keV and lies within the range of 29.398 and 68.228 cm/g. The minimum effective atomic number (Z) occurs at 1.5 MeV and equals to 10.90, 11.30, 12.41, 13.57, 16.79 and 20.55 for the tested glasses. At 0.2 MeV, the Z changes from 19.42 to 49.10 due to the increase of PbO from 0.5 to 30 wt%. The half value layer (HVL) results revealed that the current glasses have very low HVL values at the 15 keV (in the range of 0.00202 to 0.00671 cm). The HVL increases with the energy which indicates that the photon with high energy can penetrate the samples easily. The HVL results also showed that increasing the density of the samples leading to reduce the HVL and BBP30 has the thinner HVL, while BBP0.5 has the thicker HVL.
[en] This paper investigates the radiation shielding properties, such as linear and mass attenuation coefficients, half and tenth value layers, effective atomic number and electron density, and radiation protection efficiency as a function of photon energy, of a new composite, PbI-doped polyester. The mentioned polyester composite was prepared with different proportions of lead(II) iodide (5% increments between 5 and 20%) so that impact of the dopant amount on radiation shielding could be properly analyzed. The prepared composites were tested in 22 different energies in the energy range of 59.5–1408.0 keV with the use of HPGe detector and eight radioactive point sources. The obtained results were further validated by comparing the results of XCOM computer program, and negligible discrepancies were observed. It was observed that PbI (20%) composite is more effective gamma radiation shielding material than other produced composites. In light of this information, it can be said that the shielding efficiency increases with increasing lead(II) iodide amount.
[en] Biocomposites of waste polypropylene (wPP) with 20 phr (part per 100 parts of [wPP]) corn husk fibers (CHF) as bio-filler were prepared for environmental aspect. Maleic anhydride (MAH) was used, with 5, 10 phr concentration as compatabilizer was carried out. The obtained biocomposites were irradiated by γ radiation ranging from 5 to 25 kGy. Mechanical, physical and thermal properties of the biocomposites were studied to evaluate the effect of CHF addition on the properties of obtained composites. It has been found that there is deterioration in all properties. However, by the addition of MAH, the former properties were improved. The obtained results were confirmed by Fourier transform infrared (FTIR) and scanning electron microscopy (SEM).
[en] Peripherally metalated porphyrinoids are promising functional π-systems displaying characteristic optical, electronic, and catalytic properties. In this work, 5-(2-pyridyl)- and 5,10,15-tri(2-pyridyl)-B-subporphyrins were prepared and used to produce cyclometalated subporphyrins by reactions with [CpIrCl], which proceeded through an efficient C−H activation to give the corresponding mono- and tri-Ir complexes, respectively. While the mono-Ir complex was obtained as a diastereomeric mixture, a C-symmetric tri-Ir complex with the three Cp-units all at the concave side was predominantly obtained in a high yield of 90 %, which displays weak NIR phosphorescence even at room temperature in degassed CHCl, differently from the mono-Ir complexes. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)