Aurel Pui

Thermal decomposition of ammonia. N2H4-an intermediate reaction product

The paper reports the thermal decomposition of ammonia under dynamic conditions at 800°C in a quartz reactor. Its purpose is to confirm the homogeneous-heterogeneous degenerated branched chain mechanism established in previous studies, which assume the formation of N2H4 as a molecular intermediate; this paper identifies hydrazine as a product of thermal decomposition using FT-IR and UV-VIS spectroscopies.

Studies on adsorption capacity of cationic dyes on several magnetic nanoparticles

Abstract In this study the dyes used are Basic fuchsin and Methylene blue. The adsorption was studied in relation to the metal in the ferrite, time of exposure and dye concentration. The highest adsorbtion capacity was observed for MgFe2O4 at a dye concentration of 0.06 mM, adsorption percent of 88% in 3 hours. Desorption was also studied by redispersion in ethanol. The main adsorption mechanism is thought to be through electrostatic interaction, mainly due to surfactant groups present on the nanoparticles. The nanoparticles have ferromagnetic behavior under magnetic field which allows for effective separation.

Synthesis and hydrophilic properties of Mo doped TiO2 thin films

Amorphous undoped TiO2 and Mo-doped TiO2 thin films were obtained by spray pyrolysis. By heat treatment, they became polycrystalline consisting in anatase, or mixed anatase/rutile phases, if deposited on glass or silicon, respectively. Mo enters in the TiO2 matrix as Mo5+, determining a slight red shift of the absorption edge. Based on Fourier transmission infrared analysis, performed on the studied films, before and after irradiation, providing information on the relationship between hydrophilicity and the amount of the adsorbed hydroxyl groups, we certify once again that the anatase phase (present in proportion of 100% in the films deposited on glass) is superior concerning the hydrophilic properties. Mo enhances wettability for the films deposited on silicon, compared to the undoped one, even if determines a rise in the rutile weight percentage, as a combined effect with the substrate nature. The decomposition of the oleic acid confirms that titania films with higher hydrophilic performances are also g...

Electrochemical and spectroscopic characterization and catalytic activity of Co(II) complexes of tetra-chloro-R-Salen ([tClSalen= bis (3,5-di-chloro-α-R salicylidene)ethylenediamine]) and tetra-chloro-R-Salophen ([tClSalophen= bis (3,5-di-chloro-α-R salicylidene)-1,2-phenylenediamine]), R=H, CH3, CH2-CH3

A series of 3,5-tetra-chloro-R-Salen and 3,5-tetra-chloro-R-Salophen Co(II) complexes, (where Ru2009=u2009H, CH3, and CH2-CH3; Salen is bis(salicylaldehyde)ethylenediimine; and Salophen is bis(salicylaldehyde) N,N′-o-phenylendiimine) have been obtained. The synthesis and characterization of the free ligands and Co(II) complexes and also catalytic activity of the complexes are reported in this article. The characterization of the complexes was performed by elemental analyses, cyclic voltammetry, UV-Vis, FT-IR and EPR spectroscopy, and by elemental analyses, UV-Vis and FT-IR spectroscopy for the free ligands. The catalytic oxygenation of 2,6-di-tert-butylphenol, with these complexes, leads to the formation of two products, benzoquinone and diphenoquinone. In this process the Co(II) complexes form reversible adducts with molecular oxygen.

Synthesis and characterization of zinc oxide nanoparticles

The research is aimed at synthesis and characterization of nanoscaled zinc oxide particles and their application on linen fibrous supports, for thermal properties. To impart thermal activity to the fibrous nanocomposites, nanoparticles as well as fibrous nanocomposites were produced in different hydrothermal conditions of temperature (90xa0°C). To characterize the nanoparticles composition, their shape, size, and crystallinity, investigations technique, such as Fourier transformed infrared spectroscopy, scanning electron microscopy, and X-ray powder diffractometry were used. Differential scanning calorimetry analysis profiles were also revealed. The thermal treatment of linen fabrics with nanosized ZnO does not modify significantly their thermal stability.

Synthesis and Characterization of Co-Substituted Ferrite Nanocomposites

We report the synthesis of CoxNi1-xFe2O4 (where x is 0, 0.25, 0.50, 0.75, 1) nanoparticles (NPs) by a wet chemical method using carboxymethyl cellulose (CMC) solution as surfactant. Their structure and magnetic properties were evaluated by X-ray diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The gas and humidity sensing properties of the samples were also investigated. Powder X-ray diffraction analysis demonstrated the formation of face-centered cubic structure for all the samples. The average crystallite size and lattice parameters have been calculated by Rietveld refinement. The FTIR spectra of NPs confirm the presence of CMC functional groups and stretching bands attributed to the intrinsic vibrations of tetrahedral and octahedral sites of spinel ferrite. The magnetization curves of the nanocomposites at room temperature demonstrated saturation magnetizations from 21 emu/g to 58 emu/g and coercivity values between 130 Oe and 835 Oe. As not many studies have been published on this topic, the gas sensing properties of Ni-substituted Co ferrites have been evaluated. The measurements revealed that Co0.25Ni0.75Fe2O4 is the most sensitive to acetone vapors.

Zinc oxide-linen fibrous composites: morphological, structural, chemical and humidity adsorptive attributes:

The main result and characterizing aspect of the research consists of the effectiveness of novel ZnO-linen fibrous composites synthesized by means of hydrothermal deposition of zinc oxide onto linen fibers, with the assistance of two surfactants. This has a direct implication on the relationship between the morphological, structural and chemical attributes and water vapor sorption-desorption behavior. Methodology consists of the hydrothermal synthesis of zinc oxide onto linen fibrous substrates previously grafted with MCT-β-CD (MonoChloroTriazinyl–β-CycloDextrin) via a hydrothermal process. The morphological, structural and chemical properties of the samples were examined, in terms of a co-assisted investigation system: SEM images for the morphology, EDX analysis for surface composition, FTIR spectroscopy and X-ray diffractometry for structural samples features. Dynamic vapor sorption (DVS) analysis will complete this study. According to the results provided by the characterization technique, the uniformity of the fabric coated with ZnO powder hydrothermally synthesized with assistance of CTAB (Cetyl TrimethylAmmonium Bromide) is better than that of ZnO powder hydrothermally synthesized in the presence of Pluronic P123 and possesses good washing fastness. X-ray diffraction results have indicated that the composites exhibited a more ordered structure and higher water vapor sorption-desorption capacity (obtained by DVS analysis) compared with those of the reference fibrous linen supports.

Letter: Study on the mechanism of ferrite-induced dinitrophenol photodegradation

We report here the effectiveness of gas chromatography mass spectrometry techniques in establishing the ferrite-associated photocatalytic degradation mechanism of pesticide 2,4-dinitrophenol (2,4-DNP). Unlike the previously discussed DNP-degradation mechanisms that involve either oxidation or reduction reactions, ferrite-based ultraviolet (UV) photodegradation of DNP affords the nontoxic 6-hydroxy-3,5-dinitrohexa-2,4-dienal by an unusual water addition to the benzene core. We searched for and demonstrated the presence of an epoxide of DNP within the photodegradation process, which may unambiguously explain the novel photochemical mechanism. During the 15 min UV photoinduced process, DNP degradation efficiency on the zinc ferrite catalyst was calculated to be 82%, whereas the first-order kinetic rate constant k was as high as 3.4 × 10−2 min−1.

Zinc Oxide — Linen Fibrous Composites: Morphological, Structural, Chemical, Humidity Adsorptive and Thermal Barrier Attributes

Nanoparticles are extremely reactive, due to their high surface energy, and most systems undergo aggregation without protection of their surfaces. To eliminate or minimize generated waste and implement sustainable processes, recently green chemistry and chemical processes have been emphasized for the preparation of nanoparticles [2]. Much attention is now being focused on polysaccharides used as the protecting agents of nanoparticles. As stabilizing agent soluble starch has been selected and as the reducing agent in aqueous solution of AgNO3 for silver nanoparticle growth, and a-D-glucose, has been elected. To maintain noble metal (platinum, palladium and silver) nanoparticles in colloid suspension, Arabinogalactan has been used as a novel protecting agent for [3]. Synthesized platinum, palladium and silver nanoparticles with narrow size distribution have been achieved by using porous cellulose

Correlation Between Size of CoFe 2 O 4 Nanoparticles Determined from Experimental and Calculated Data by Different Mathematical Models

This study reports the synthesis of CoFe2O4 nanoparticles by coprecipitation method in the presence of Linseed Oil as surfactant. The capping agent was used to stabilize the particles and prevent their agglomeration. The characteriza- tion studies were conducted by in situ X-ray diffraction, transmission electron microscopy, thermal analysis (TG-DTA) and FTIR spectroscopy. The average particle sizes obtained by XRD data were used to obtain a correlation with size of CoFe2O4 nanoparticles determined, using mathematical equations based on different models. The statistical studies show that the cubic model gives a good correlation within the whole temperature range (100 - 850 °C). The result of these in- vestigations was very useful for establishing the optimal calcination temperature. FT-IR spectroscopy and thermogra- vimetric analysis (TG) showed that the core-shell structure type of CoFe2O4 nanoparticles is stable below this annealing temperature. TEM analysis indicates that the CoFe2O4 samples during the calcinations treatment were spherical in shape and uniform in morphology and particles size.