Gravimetric Curves Research Articles

Decoupling of water and oxygen diffusion phenomena in order to prove the occurrence of thermo-oxidation during hygrothermal aging of thermosetting resins for RTM composite applications

A novel experimental/numerical method is set up in order to decouple water and oxygen diffusion phenomena and to prove the occurrence of thermo-oxidation during hygrothermal aging of thermosetting resins for RTM composite applications. The method consists of creating artificial environmental conditions under pure water, pure oxygen and a water/oxygen mixture and in following the mass uptake of polymer samples during aging. Global and local (ultra-microindentation) mechanical properties of samples are then measured during and after aging, for each environmental conditioning. By analyzing the gravimetric curves with the aid of diffusion–reaction models and the results of mechanical tests, it is shown that water and oxygen diffusion phenomena are coupled in a complex way and that diffusion/reaction phenomena between water and oxygen take place during hygrothermal aging.

Effect of acetone–butanol–ethanol addition to diesel on the soot reactivity

The ability of acetone–butanol–ethanol (ABE) to reduce pollutant emissions has been validated in recent studies. In this study, the effect of addition of ABE (up to 30% by volume) to diesel on the soot oxidation reactivity was investigated to further evaluate the feasibility of increasing the particulate filter regeneration rate. The oxidation activities of soot samples were compared using the average activation energies calculated from the thermal gravimetric curves. It was found that the average activation energies of the ABE-diesel-blends-derived soot are lower than that of diesel-derived soot. The variations in the physical and chemical properties of the soot samples were investigated to determine the parameters that improve the soot oxidation reactivity. Several experimental diagnostic techniques, such as Fourier transform infrared spectroscopy, elemental analysis, X-ray diffraction, and high-resolution transmission electron microscopy, were used to investigate the changes in the functional groups, atomic O/C and H/C ratios, nanocrystallite parameters, and soot nanostructures. With increasing concentration of ABE in diesel, the size of the primary particles, nanocrystallite length, and amount of aromatic CC functional groups in the soot decrease, while the nanocrystallites tortuosity, amount of oxygenated functional groups, and atomic O/C and H/C ratios increase. The changes of these parameters prove the higher reactivity of ABE-diesel-blends-derived soot.

Localized analysis of paint-coat drying using dynamic speckle interferometry

The paint-coating is part of several industrial processes, including the automotive industry, architectural coatings, machinery and appliances. These paint-coatings must comply with high quality standards, for this reason evaluation techniques from paint-coatings are in constant development. One important factor from the paint-coating process is the drying, as it has influence on the quality of final results. In this work we present an assessment technique based on the optical dynamic speckle interferometry, this technique allows for the temporal activity evaluation of the paint-coating drying process, providing localized information from drying. This localized information is relevant in order to address the drying homogeneity, optimal drying, and quality control. The technique relies in the definition of a new temporal history of the speckle patterns to obtain the local activity; this information is then clustered to provide a convenient indicative of different drying process stages. The experimental results presented were validated using the gravimetric drying curves

Influence of pigment and internal stresses on water uptake in model epoxy: a thermodynamic approach

This study focused on the influence of a pigment (titanium dioxide at rates of 10 and 20 wt%) on the hygrothermal ageing of a model epoxy polymer resin (DGEBA–DAMP). An ageing cycle composed of sorption and desorption steps was applied at different temperatures. Gravimetric study was carried out on free films. Results of pigmented samples were compared with those of the resin alone to better understand impact of the titanium dioxide. TiO2 had no major influence on gravimetric curves: water content curves exhibited a pseudo-Fickian behaviour during sorption and Fickian one during desorption. Moreover, results pointed out that pigment did not absorb water. Curve treatment allowed to obtain diffusion coefficient and water content at equilibrium for each step of ageing. Values of diffusion coefficients indicated that titanium dioxide did not have major influence on the beginning of diffusion, whereas it slowed down the end of water uptake. During sorption, water content at equilibrium was dependent on TiO2 amount. After desorption, pigmented systems contained residual water for ageing cycles at high temperature. Finally, results of diffusion coefficients showed that diffusion phenomena were heat dependent. A thermodynamic approach was then used to have access to enthalpy of diffusion ΔH and pre-exponential factor D 0. These parameters were impacted by the presence of titanium dioxide. This was mainly due to the presence of additional internal stresses of Type II.

Preparation, characterization and featuring of an inclusion complex of nerol with β-cyclodextrin

Nerol is an acyclic type monoterpene with important biological activities. However, the low solubility in aqueous media is a limiting factor for its user. Cyclodextrins have been widely used in order to improve the solubility, stability and bioavailability of nonpolar molecules through the formation of inclusion complexes. Thus, the present study consists in the development of nerol inclusion complex in combination with the β-cyclodextrin (β-CD) followed by characterizing by thermal analysis and spectrophotometric absorption in the infrared (FTIR). The results suggest a complexation of nerol with β-CD having detours and changed the intensity of various bands. The thermo gravimetric curve of CI found to indicate an output of solvating water molecules from the complex cavity formed for replacement of drug molecules probably included. Thus, it is concluded a possibility to obtain inclusion complexes of nerol monoterpene with β-CD, which will increase its solubility and facilitate delivery process.

Preparation and characterization of a copper@polyimide core–shell structure via an in situ induction/imidization route

Based on the combination of an in situ induction and imidization method for improving the interface bonding of an inorganic material and a polymer, copper@polyimide (Cu@PI) core–shell composite particles have been successfully prepared from poly(amic acid) ammonium salts (PAAS) and a Cu complex via a simple solvothermal process. The structures and the morphologies of the samples were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM), respectively. It was found that PAAS formed PI via a thermal imidization and subsequently precipitated in the solvent. Through crystallization induction, it then successfully coated on the surface of the formed Cu particles. Based on thermo gravimetric analyses curves and due to no Cu oxidation reactions taking place in the core coated with high-temperature-resistant PI, the weight increase was determined to be 106.4%, instead of up to 124.0% in samples consisting of pure Cu.

Synthesis, spectroscopic, and antimicrobial study of Ca(II), Fe(III), Pd(II), and Au(III) complexes of amoxicillin antibiotic drug

Synthesis, spectroscopic characterization, theoretical and antimicrobial studies of Ca(II), Fe(III), Pd(II), and Au(III) complexes of amoxicillin (amox) antibiotic drug are presented in the current paper. Structure of 1: 1 (metal: amox) complexes were elucidated on the basis of elemental analyses, and IR, Raman, 1H NMR, and electronic spectral data. According to molar conductance measurements the complexes had electrolyte nature. Amoxicillin reacted with metal ions as a tridentate ligand coordinated with metal ions via–NH2,–NH, and β-lactam carbonyl groups. The complexes were formulated as [Ca(amox-Na)(H2O)]·Cl2·4H2O (1), [Fe(amox-Na)(H2O)3]·Cl3·3H2O (2), [Pd(amox-Na)(H2O)]·Cl2 (3), and [Au(amox-Na)(H2O)]·Cl3 (4). Kinetic thermodynamic parameters (E*, ΔS*, ΔH*, and ΔG*) were calculated based on the Coats–Redfern and Horowitz–Metzger methods using thermo gravimetric curves of TG and DTG. Nanosize particles of amoxicillin complexes have been studied by XRD, SEM, and TEM methods. Theoretical studies of the synthesized complexes have been performed.

(NH4)2WS4 precursor as a hole-injection layer in organic optoelectronic devices

This paper presents a facile method to fabricate the hole injection layer (HIL) for organic photovoltaic cells (OPVs) and organic light-emitting diodes (OLEDs) using a thermally annealed (NH4)2WS4 precursor under air ambient. The thermal gravimetric analysis curve shows that WS3, WS2, and WOx are formed by the thermal decomposition of (NH4)2WS4 above 160°C. The disappearance of the S 2p peak in the photoemission spectra and of the W–S peak in the Raman spectra as well as the decrease in the water contact angle after annealing at 250°C suggest that (NH4)2WS4 decomposed into WOx. The power conversion efficiency (PCE) of the OPV improved from 1.51% to 3.14% after the insertion of 250°C-annealed (NH4)2WS4 as the HIL, which is comparable to the PCE of the OPV based on poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) HIL (3.23%). Furthermore, the luminance efficiency of the OLED with 250°C-annealed (NH4)2WS4 (15.76cd/A) was higher than that of the device based on PEDOT:PSS (12.34cd/A). The results of the in situ deposition experiments revealed that the improved device performance originates from the energy level alignment and electron–hole balance. These data demonstrate that 250°C-annealed (NH4)2WS4 is a promising candidate for fabrication of the HIL in optoelectronic devices using a facile solution process under air ambient.

Ligational behavior of clioquinol antifungal drug towards Ag(I), Hg(II), Cr(III) and Fe(III) metal ions: Synthesis, spectroscopic, thermal, morphological and antimicrobial studies

This article presents a synthesis, characterization, theoretical and biological (anti-bacterial, and anti-fugal) evaluation studies of Ag(I), Hg(II), Cr(III) and Fe(III) complexes of clioquinol (CQ) drug ligand. Structures of the titled complexes cited herein were discussed using elemental analyses and spectral measurements e.g., IR, 1H NMR, and electronic studies. The results confirmed the formation of the clioquinol complexes by three molar ratios (1:1) for Ag(I), (1:2) for Hg(II) and (1:3) for both Cr(III) and Fe(III) metal ions. The clioquinol reacts as a bidentate chelate bound to all respected metal ions through the oxygen and nitrogen of quinoline-8-ol. The metal(II) ions coordinated to clioquinol ligand through deprotonation of OH terminal group. Infrared and 1H NMR spectral data confirm that coordination is via the oxygen of phenolic group and nitrogen atom of quinoline moiety. The molar conductance measurements of the CQ complexes in DMSO correspond to be non-electrolyte nature. Thus, these complexes may be formulated as [Ag(CQ)(H2O)2] H2O, [Hg(CQ)2]⋅2H2O, [Cr(CQ)3] and [Fe(CQ)3]H2O. The Coats–Redfern method, the kinetic thermodynamic parameters like activation energies (E∗), entropies (ΔS∗), enthalpies (ΔH∗), and Gibbs free energies (ΔG∗) of the thermal decomposition reactions have been deduced from thermogravimetric curves (TG) with helpful of differential thermo gravimetric (DTG) curves. The narrow size distribution in nano-scale range for the clioquinol complexes have been discussed using X-ray powder diffraction (XRD), scanning electron microscope (SEM), and X-ray energy dispersive spectrometer (EDX) analyzer.

Optical, Thermal and Nonlinear Properties of Tristhiourea Lanthanum Nitrate

The single crystals of tristhiourea lanthanum nitrate (TTLaN) have been grown by solution growth using slow evaporation technique. The optical study revealed that the crystal has high transmission with lower cut-off wavelength of 235.78 nm. The EDAX analysis confirmed the grown compound elements. The presence of functional groups was identified through Fourier transform-infrared technique. The thermal stability of the crystal was determined from thermo gravimetric and differential thermal analysis curve. The second harmonic generation behavior of TTLaN crystal was tested by Kurtz-Perry powder technique. This single novel semiorganic crystal of TTLaN showed very good optical transmission property, high thermal stability and large non-linearity nature.

Interaction of vanadium (IV) solvates (L) with second-generation fluoroquinolone antibacterial drug ciprofloxacin: Spectroscopic, structure, thermal analyses, kinetics and biological evaluation (L = An, DMF, Py and Et3N)

The preparation and characterization of the new solid complexes [VO(CIP)2L]SO4⋅nH2O, where L=aniline (An), dimethylformamide (DMF), pyridine (Py) and triethylamine (Et3N) in the reaction of ciprofloxacin (CIP) with VO(SO4)2·2H2O in ethanol. The isolated complexes have been characterized with their melting points, elemental analysis, IR spectroscopy, magnetic properties, conductance measurements, UV–Vis. and 1H NMR spectroscopic methods and thermal analyses. The results supported the formation of the complexes and indicated that ciprofloxacin reacts as a bidentate ligand bound to the vanadium ion through the pyridone oxygen and one carboxylato oxygen. The activation energies, E*; entropies, ΔS*; enthalpies, ΔH*; Gibbs free energies, ΔG*, of the thermal decomposition reactions have been derived from thermo gravimetric (TGA) and differential thermo gravimetric (DTG) curves, using Coats–Redfern and Horowitz–Metzeger methods. The lowest energy model structure of each complex has been proposed by using the density functional theory (DFT) at the B3LYP/CEP-31G level of theory. The ligand and their metal complexes were also evaluated for their antibacterial activity against several bacterial species, such as Bacillus Subtilis (B. Subtilis), Staphylococcus aureus (S. aureus), Nesseria Gonorrhoeae (N. Gonorrhoeae), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli).

Thermogravimetric Investigation of Calcium Oxalate

The thermal properties of calcium oxalate were studied by means of TG analyzer. The factors such as heating rate, filling amounts of specimens and filling atmosphere etc., which may affect thermo gravimetric (TG) curves in TG analysis test were investigated. The results showed that, with the improving of heating rate, filling amounts of specimens and close packing, the starting reaction temperature was postponed more obviously and the width of reaction temperature range rises. The flow of the nitrogen gas enhanced heat transmission, caused the starting reaction temperature to shift to the low temperature zone, and it could also affect the response course. But the factors above didnt obviously influence the weightlessness of specimens.

Variation of optimum yttrium doping concentrations of perovskite type proton conductors BaZr1−xYxO3−α (0≤x≤0.3) with temperature

A solid state reaction method was used to prepare the perovskite-structured compounds BaZr1−xYxO3−α (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3). The X-ray diffraction (XRD) pattern indicated that the target perovskite phases were obtained. With increasing Y concentration the unit cell parameters of BaZr1−xYxO3−α samples were expanded, and Y doping became more difficult. However, high synthesis temperature is helpful to promote Y doping. The SEM results showed that the samples exhibited poor sinterability with increasing Y-doping content. Thermal gravimetric (TG) curves analysis showed the more mass decreasing of BaZr1−xYxO3−α (0≤x≤0.3) samples at high temperature with more Y doping and more proton introducing. The electrochemical impedance spectra (EIS) of specimens showed that conductivities of BaZr1−xYxO3−α (0≤x≤0.3) increased with increasing temperature from 300 to 900 °C in wet air. At 900 °C, the conductivity of BaZr1−xYxO3−α (0≤x≤0.3) first increased with increasing doped amount of Y, and reached the highest value of 1.07×10−3 S/cm when x was 0.2, then decreased gradually with further increasing Y content. At 600 °C, BaZr0.75Y0.25O3−α displayed the highest conductivity, while the conductivity of BaZr0.7Y0.3O3−α was the highest at 300 °C. The results indicated that there should be an optimum Y doping concentration yielding the highest conductivity at a constant temperature, and the optimum Y doping concentration should increase in the humidity atmosphere as the temperature decreases. So increasing the Y-doping concentration is helpful to improve the conductivities of BaZr1−xYxO3−α materials at low temperature.

Synthesis, optical and thermal studies on novel semi organic nonlinear optical Urea Zinc Acetate crystals by solution growth technique for the applications of optoelectronic devices

Abstract Urea Zinc Acetate (UZA), a novel semi organic nonlinear optical crystal having dimensions 30×28×10 mm3 has been synthesized using slow evaporation technique. The lattice parameters for the grown crystals were determined using single crystal XRD. The presence of functional groups for the grown crystals was confirmed using Fourier Transform Infrared (FT-IR) spectroscopy. The optical absorption studies show that the material has wide optical transparency in the entire visible region. The thermal stability of the crystal was determined from thermo gravimetric and differential thermal analysis curve. The second harmonic generation was confirmed by Kurtz powder method and it is found to be 3 times than that of KDP crystal.

Effect of Sn doping on structural, optical, electrical and wettability properties of oriented ZnO nanorod arrays

Herein we present a modified sol gel route for the one step fabrication of oriented ZnO nanorod arrays. The method is seed layer free, and nanorods directly attach to a substrate. We also present the effect of tin (Sn) content on the crystallinity, microstructural, optical and electrical properties of the ZnO nanorod arrays. Thermo gravimetric (TG) curves of gel precursors showed that most of the organic groups and other volatiles were removed at about 450 °C. X-ray diffraction patterns confirmed that the films were polycrystalline in nature with (002) preferred orientation. The texture coefficient, grain size, dislocation density and lattice parameters of the ZnO arrays were determined. The SEM micrographs revealed that the undoped and 1 at.%Sn doped films were composed of nanorods and the concentration of 2 at.%Sn doping hindered the rod like structure growth and modulated into granular nature. UV-visible transmission spectroscopy indicated that the transparency of the films increased with Sn content. On Sn doping, the films also exhibited a red shift and slight shrinkage of band gap. The electrical studies revealed that 1 at.% of Sn doping enhanced electrical conduction in ZnO films and beyond that the distortion caused in the lattice reduced the conductivity. The contact angle of the ZnO nanostructures varied between 91° and 115° depending upon the Sn content. Therefore, 1 at.%Sn doping into ZnO nanorods improves the crystallinity, electrical conductivity and water contact angle.

Electrochemical synthesis of a double‐layer film of ZnO nanosheets/nanoparticles and its application for dye‐sensitized solar cells

ABSTRACTA double‐layer film, consisting of an upper layer of ZnO nanosheets and a lower layer of ZnO nanoparticles (designated as ZnONS/NP), was synthesized for the photoanode of a dye‐sensitized solar cell (DSSC) by a one‐step potentiostatic electrodeposition on a conducting fluorine‐doped tin oxide substrate at 70 °C in a solution containing zinc nitrate and sodium acetate, followed by the pyrolysis of the film at 300 °C. The growth mechanism of the double‐layer nanostructure was studied by monitoring the morphological changes at various periods of electrodeposition. The effects of the concentration of acetate anion on the morphology of the double‐layer structure were also studied. The double‐layer film of ZnONS/NP showed a better self‐established light scattering property, compared with that of a thin film of ZnO nanoparticles, prepared without acetate anion. The concentration of an acetate anion in the electrolyte for the electrodeposition of the double‐layer film, the electrodeposition period, and the period for dye adsorption were optimized for obtaining the best performance for a DSSC with a photoanode consisting of the double layer. A metal‐free dye, coded as D149, was used in this research. A conversion efficiency of 4.65% was achieved for a DSSC (0.2376 cm2) with the photoanode, consisting of the double‐layer film, under 100 mW/cm2 illumination in the wavelength range of 400–800 nm. X‐ray diffraction patterns, thermo gravimetric curves, elemental analysis, scanning electron microscopic images, transmission electron microscopic image, transmission spectra, and electrochemical impedance spectra were used to explain observations. Copyright © 2012 John Wiley & Sons, Ltd.

Spectral study of HCl plasma etching of gallium arsenide

Chlorine-containing gases are widely used in etching series of materials. In this field, hydrogen chloride is one of the most promising plasma reagents. In this paper, emission spectroscopy techniques have been applied to study an etching of gallium arsenide in HCl plasma. The gas emission spectrum consists only of atomic components. The excitation of atoms is carried out with an electron impact, while their collapse is accompanied by emission deactivation. The control of the etching process can be performed spectrally using the intensities of the gallium monochloride and gallium resonant lines. The induction period of about 1 min is observed in the spectral and gravimetric kinetic curves of etch gallium arsenide, but it is absent in samples previously subjected to etching.

Preparation and characterization of a chemically sulfated cashew gum polysaccharide

Cashew gum (CG) was sulfated in pyridine:formamide using chlorosulfonic acid as the reagent. Confirmation of sulfation was obtained by Fourier transform infrared (FTIR) spectroscopy through the presence of an asymmetrical S=O stretching vibration at 1259 cm-1. The degrees of substitution were 0.02, 0.24 and 0.88 determined from the sulfur percentage. 1D and 2D nuclear magnetic resonance (NMR) data showed that the sulfation occurred at primary carbons. An increase of at least 4% of the solution viscosity was observed due to sulfation. The thermal gravimetric curves (TGA) indicate that the derivatives are stable up to ca. 200ºC. The sulfated CG is compared to carboxymethylated CG in order to verify the possibility of the use of the former in the preparation of polyelectrolyte complexes; the latter is already being used for this application.

Mineralogical and Geochemical Characteristics and Genesis of Hydrothermal Kaolinite Deposits within Neogene Volcanites, Kütahya (Western Anatolia), Turkey

AbstractThe Kütahya kaolinite deposits are the most important source of raw materials for the ceramics industry in Turkey. To date, no detailed mineralogical or geochemical characterizations of these materials have been carried out; the present study aims to fill that gap. The Kütahya kaolinite deposits formed by alteration of dacite and andesite tuffs related to Neogene volcanism whichwas associated withe xtensional tectonics. The kaolinite deposits contain silica and Fe- and Ti-bearing phases (pyrite, goethite, and rutile) in vertical and subvertical veins that diminish and then disappear upward. Mineralogical zonation outward from the main kaolinite deposit is as follows: kaolinite ± smectite + illite + opal-CT + feldspar; feldspar + kaolinite + quartz + smectite + illite; quartz + feldspar + volcanic glass. The veins and mineral distributions demonstrate that hydrothermal alteration was the main process in the development of the kaolinite deposits of the area. The very sharp, intense, diagnostic basal reflections at 7.2 and 3.57 Å, as well as non-basal reflections, well defined pseudohexagonal to hexagonal crystallinity with regular outlines, ideal differential thermal analysis-thermal gravimetric curves, and ideal, sharp, infrared spectral bands indicate well crystallized kaolinite. Micromorphologically, the development of kaolinite plates at the edges of altered feldspar and devitrified volcanic glass indicates an authigenic origin. Lateral increase in (SiO2+Fe2O3+MgO+Na2O+CaO+K2O)/(Al2O3+TiO2) from the center of the kaolinite deposit outward also indicates hydrothermal zonation. Enrichment of Sr in altered and partially altered rocks relative to freshvolca nic-rock samples demonstrates retention of Sr and depletion of Rb, Ba, Ca, and K during hydrothermal alteration of sanidine and plagioclase within the volcanic units. In addition, depletion of heavy rare earth elements (HREE) relative to light rare earth elements (LREE) in the kaolinized materials may be attributed to the alteration of hornblende. The negative Eu anomaly suggests the alteration of feldspar by hydrothermal fluids. The isotopic data from kaolinite and smectite indicate that hydrothermalalteration processes developed at 119.1–186.9°C and 61.8–84.5°C, respectively. Thus, the kaolinite deposits formed by hydrothermal alteration of volcanic glass, feldspar, and hornblende by a dissolutionprecipitation mechanism which operated under acidic conditions within Neogene dacite, andesite, and tuffs.

Reaction of C60 with Hydrogen Gas: In Situ Monitoring and Pathways

Kinetics and pathways of C60 reaction with hydrogen gas were studied in a broad temperature interval and over extended periods of time. Specifically, hydrogenation was monitored in situ at high temperature and high hydrogen pressure conditions using the gravimetric method. The shape of gravimetric curve was found to depend on hydrogenation temperature: at 350–400 °C saturation of the sample weight was achieved, whereas at 420–440 °C the sample weight reached the maximum and decreased upon prolonged hydrogenation. The weight decrease is due to fullerene cage fragmentation with formation of light hydrocarbons evaporating from the sample. Hydrogenation products were studied by X-ray diffraction, MALDI TOF and APPI FT-ICR mass spectrometry, liquid chromatography, and elemental analysis. Hydrogenation pathways (from C60H18 up to C60H56) and possible mechanisms of hydrogenation-induced fragmentation of fulleranes are discussed.