Showing papers on "Thermogravimetric analysis published in 2013"
TL;DR: In this paper, the effects of Ni content on the electrochemical properties and the structural and thermal stabilities of Li[Ni x Co y Mn z ]O 2 ( x ǫ = 1/3, 0.6, 07, 08 and 0.85) synthesized via a coprecipitation method were reported.
1,524 citations
TL;DR: Thermogravimetric analyses reveal that P-CNCs exhibit a much higher thermal stability than partially sulfated CNCs (S-C NCs), which are frequently employed, but suffer from limited thermal stability.
517 citations
TL;DR: In this paper, the interaction between NiO nanoparticles and glucose has been studied using UV-vis absorption and fluorescence spectroscopy, and the zeta-potential of NiO nano-articles was used to gain insight about the interaction mode.
458 citations
TL;DR: The as-prepared 3D porous materials show an excellent adsorption capacity for acidic dyes on the basis of the pore-rich and amine-rich graphene structure, which is superior to other carbon materials.
Abstract: We report a facile method for the fabrication of three-dimensional (3D) porous materials via the interaction between graphene oxide (GO) sheets and polyethylenimine (PEI) with high amine density at room temperature under atmospheric pressure without stirring. The structural and physical properties of GO–PEI porous materials (GEPMs) are investigated by scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and nitrogen adsorption–desorption measurement and their chemical properties are analyzed by X-ray photoelectron spectroscopy, infrared spectroscopy, and Raman spectroscopy. GEPMs possess low density and hierarchical morphology with large specific surface area, and big pore volume. Furthermore, the as-prepared 3D porous materials show an excellent adsorption capacity for acidic dyes on the basis of the pore-rich and amine-rich graphene structure. GEPMs exhibit an extremely high adsorption capacity for amaranth (800 mg g–1), which are superior to other carbon materials. In addition, ...
367 citations
TL;DR: The photocatalytic activity for hydrogen evolution from aqueous triethanolamine solution was investigated and the highest activity can be attributed to the pure composition, the higher dye adsorption amount and the lowest defect concentration.
Abstract: Graphitic carbon nitride (g-C3N4) was prepared by pyrolysis of urea at different temperatures (450–650 °C), and characterized by thermogravimetric and differential thermal analysis (TG-DTA), elemental analysis (C/H/N), X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), Brunauer–Emmett–Teller (BET) analysis, Fourier transform-infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The samples prepared at low temperatures (450 and 500 °C) are a mixture of g-C3N4 and impurities, whereas the samples prepared at high temperatures (550, 600 and 650 °C) should be g-C3N4 (polymeric carbon nitride). The polymerization degree of g-C3N4 for the prepared samples increases to a maximum at 600 °C with increasing pyrolysis temperature and then decreases, whereas the defect concentration changes conversely, that is, g-C3N4 prepared at 600 °C has the lowest defect concentration. Using Eosin Y (EY) and the prepared sample as the sensitizer and the matrix, respectively, the photocatalytic activity for hydrogen evolution from aqueous triethanolamine solution was investigated. The g-C3N4 prepared at 600 °C exhibits the highest sensitization activity. Under optimum conditions (1.25 × 10−5 mol L−1 EY and 7.0 wt% Pt), the maximal apparent quantum yield of EY-sensitized g-C3N4 prepared at 600 °C for hydrogen evolution is 18.8%. The highest activity can be attributed to the pure composition, the higher dye adsorption amount and the lowest defect concentration.
314 citations
TL;DR: In this paper, the influence of particle size, time and temperature on the kinetics of the selective extraction of Al from the ternary layered transition metal carbide, Ti3AlC2, when powders of the latter are immersed in hydrofluoric acid.
282 citations
TL;DR: In this paper, the effect of drying method on selected material properties of nanocellulose was investigated using thermogravimetric analysis (TGA) and X-ray diffraction.
Abstract: The effect of drying method on selected material properties of nanocellulose was investigated. Samples of nanofibrillated cellulose (NFC) and cellulose nanocrystals (CNC) were each subjected to four separate drying methods: air-drying, freeze-drying, spray-drying, and supercritical-drying. The thermal stability and crystallinity of the dried nanocellulose were evaluated using thermogravimetric analysis (TGA) and X-ray diffraction. Supercritical-drying produced NFCs with the least thermal stability and the lowest crystallinity index. Air-drying or spray-drying produced NFCs which were more thermally stable compared with freeze-dried NFCs. The CNCs dried by the three methods (air-drying, freeze-drying, and spray-drying) have similar onset temperature of thermal degradation. The different drying methods resulted in various char weight percentages at 600 °C for the dried NFCs or CNCs from TGA measurements. The dried NFCs are pure cellulose I while the dried CNCs consist of cellulose I and II. The calculated crystallinity indices differ with each drying method. The cellulose II content in CNCs changes as a function of drying method. For the application of nanocellulose in non polar thermoplastics, spray-dried products are recommended according to their higher thermal stability and higher crystallinity index.
281 citations
TL;DR: In this paper, a two-stage crosslinking reaction process was correlated to differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA).
Abstract: Melamine formaldehyde (MF) resin was synthesized by the reaction between melamine and formaldehyde under alkaline condition in tetrohydrofuran medium with 1:3 melamine to formaldehyde molar ratio. The synthesized resins were characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). Curing and reaction mechanism was studied by thermal and spectroscopic analysis. Two exothermic peaks were observed in the DSC analysis indicating a two-step crosslinking reaction process was correlated to TGA analysis. FTIR studies at different temperatures explained the two-stage curing mechanism which is concurring with the DSC data. At a temperature range of 140–160 °C, reversible demethylolation is dominating to the crosslinking reaction. At temperature >160 °C, the crosslinking reaction dominates. On the basis of DSC and FTIR data, a possible crosslinking reaction route was derived and explained. The first stage of curing is the conversion of methylol groups to primary amine and the second stage is the crosslinking of methylol groups to the final product, methylene bridges. The thermal stability of the methylol groups, methylene bridges and the triazine ring, as well as the evaporation of effluents at different stages of curing, are also discussed based on combined TGA and DSC results. Curing studies and reaction mechanism of MF resin was studied by thermal and spectroscopic tools comparing DSC and FTIR studies explains the two-stage thermal curing mechanism. The first step of thermal curing at temperature range of 140–160 °C is the reverse reaction of methylol groups to melamine and second step occurring at temperature >160 °C is the crosslinking of methylol groups to the final product, methylene bridge. Hence, by the mutual agreement of DSC and FTIR studies, a possible reaction route was derived for the thermal curing process. The DSC–TGA thermogram supports the two-step process of the cure reaction by exhibiting two peaks in the same temperature region.
277 citations
TL;DR: Results indicated that the substitution of transition metals influences strongly the microstructure, crystal structure and antibacterial property of the cobalt ferrite nanoparticles.
275 citations
TL;DR: F Fourier transform infrared (FT-IR) spectroscopy indicates that there are no significant changes in the peak positions, suggesting that incorporation of MCC in PLA did not result in any significant change in chemical structure of PLA.
237 citations
TL;DR: In this paper, the shape stability and thermal conductivity of composite phase change material (PCM) with GPNs were investigated for thermal energy storage applications, where the maximum mass percentage of PA absorbed by GNPs was 91.94% without leakage of PA in molten state as proven by dropping point test.
TL;DR: In this paper, the co-pyrolysis characteristics and kinetics of biomass-plastic blends were investigated, and the structural differences between biomass and plastics directly affect their thermal decomposition behaviors.
TL;DR: The low thermal stability of 1-ethyl-3-methylimidazolium acetate has important implications for biomass experiments employing this ionic liquid, and the activation barriers for the S(N)2 nucleophilic substitution mechanisms are in good agreement with the experimentally determined values.
Abstract: The thermal stability of a series of dialkylimidazolium carboxylate ionic liquids has been investigated using a broad range of experimental and computational techniques. Ionic liquids incorporating fluoroalkyl carboxylate anions were found to have profoundly differing thermal stabilities and decomposition mechanisms compared with their non-fluorinated analogues. 1-Ethyl-3-methylimidazolium acetate was observed to largely decompose via an SN2 nucleophilic substitution reaction when under inert gas conditions, predominantly at the imidazolium methyl substituent. The Arrhenius equations for thermal decomposition of 1-ethyl-3-methylimidazolium acetate, and the C2-methylated analogue 1-ethyl-2,3-dimethylimidazolium acetate, were determined from isothermal Thermogravimetric Analysis experiments. The low thermal stability of 1-ethyl-3-methylimidazolium acetate has important implications for biomass experiments employing this ionic liquid. For these two ionic liquids, ion pair and transition state structures were optimised using Density Functional Theory. The activation barriers for the SN2 nucleophilic substitution mechanisms are in good agreement with the experimentally determined values.
TL;DR: Higher thermal stability and crystallinity of nano-cellulose were observed compared to that of precursor from TGA/DSC study, as well as particle size analysis and XRD study.
TL;DR: In this article, the solubility of carbon dioxide in a eutectic mixture containing choline chloride and ethylene glycol was determined for temperatures 303.15-343.15 K and pressures up to 6 MPa using a thermogravimetric microbalance.
TL;DR: The grafted cellulosic polymers were subsequently subjected to the evaluation of different physico-chemical properties in order to access their application in everyday life, in a direction toward green environment.
TL;DR: In this paper, carboxyl and amino groups have been introduced onto the surface of the multi-walled carbon nanotubes (MWCNTs) by the mixed acid treatment and the diazonium reaction, respectively.
01 Jul 2013
TL;DR: The results indicate that superhydrophobic graphene films can be produced by thermal treatment of hexadecylamine- and octadecyluine-grafted GO films, which will provide valuable guidance for the design and manufacture of graphene-based biomaterials, medical instruments, structural composites, electronics, and renewable energy devices.
Abstract: Surface functionalization of graphene oxide (GO) an important graphene precursor using alkylamines of varying chain lengths followed by thermal treatment resulted in the formation of superhydrophobic surfaces. Alkylamines consisting of hydrophobic long chain alkyl groups and hydrophilic amine groups were chemically reacted to the GO surface via two types of reactions viz. (i) amidation reaction between amine groups and carboxylic acid sites of GO and (ii) nucleophilic substitution reactions between amine and epoxy groups on GO surface. Successful grafting of alkylamines was confirmed using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H NMR), and thermogravimetric analysis (TGA). Alkylamine-modified GO surfaces showed enhanced roughness, and this effect was more pronounced with increasing amine chain length. Water contact angle measurements revealed that the hydrophobic nature of graphene depended on the chain length of the grafted alkylamines, and this fact may be corroborated to the decrease in the surface energy values. Our results indicate that superhydrophobic graphene films can be produced by thermal treatment of hexadecylamine- and octadecylamine-grafted GO films. These results will provide valuable guidance for the design and manufacture of graphene-based biomaterials, medical instruments, structural composites, electronics, and renewable energy devices.
TL;DR: Anatase titanium dioxide nanoparticles (TNPs) are synthesized by a simple and cost-effective process with and without freshly water-soluble egg white proteins (albumin) via sol-gel method.
Abstract: Anatase titanium dioxide nanoparticles (TNPs) are synthesized by a simple and cost-effective process with and without freshly water-soluble egg white proteins (albumin) via sol-gel method. The main advantage of using egg white proteins as a gelling agent is that it can provide long-term stability for nanoparticles by preventing particles agglomeration. The X-ray diffraction and FTIR results indicate that the synthesized nanoparticles have only the anatase structure without the presence of any other phase impurities. Additionally, the TNPs are characterized by a number of techniques such as thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet visible spectra (UV-vis). The sizes of titanium dioxide nanoparticles with and without using egg white solution are nm and nm, respectively. The results indicate that egg white solution is a reliable and cheap green gelling agent that can be used as a matrix in the sol-gel method to synthesis tiny size TNPs.
TL;DR: In this article, the hierarchical cell structure of the sansevieria ehrenbergii plant and fibers were analyzed using scanning electron microscope, optical microscope, Fourier transforms infrared, and X-ray diffraction.
Abstract: Natural cellulose fibers were newly identified from the sources of sansevieria ehrenbergii plant. These fibers were extracted using the mechanical decortication process. The hierarchical cell structure of the plant and fibers was analyzed using scanning electron microscope, optical microscope, Fourier transforms infrared, and X-ray diffraction. The density and diameter of the fibers were found to be approximately 0.887 g/cm3 and 10–250 μm, respectively. The various chemical compositions were analyzed and compared with other natural fibers. The thermal stability of the fiber was examined through thermogravimetric analysis/differential thermogravimetric analysis (DTG). The maximum peak temperature was obtained at 333.02 °C in DTG curve. The raw fibers exhibited a tensile strength of 50–585 MPa, an elongation at break of 2.8–21.7%, a Young’s modulus of 2.5–7.5 GPa, and a corrected compliances Young’s modulus of 2.5–7.8 GPa.
TL;DR: The effect of cellulose crystallinity on the formation of a liquid intermediate and on its thermal degradation was studied thermogravimetrically and by Py-GC/MS using a control cellulose (Avicel, crystallinity at 60.5%) and ball-milled Avicel (low cellulose, 6.5%).
TL;DR: In this article, a broad frequency (10−1−106 Hz) and temperature range (178−423 K) was used to probe the polymer/silica interface and two relaxation processes were identified for the composites: one corresponding to the bulklike polymer and a second one related to polymer chains close to the silica surface.
Abstract: Samples with different amounts of poly(vinyl acetate) adsorbed on silica particles were prepared in order to study their interfacial interactions and dynamics. The interface of adsorbed polymers to a substrate plays an important role in many applications such as polymer nanocomposites, thin films, and coatings. Characterization of such interfaces is thus of high importance since they were found to differ from bulk properties. Thermogravimetric analysis (TGA) is applied to analyze the amounts of polymer adsorbed on silica particles. Broadband dielectric spectroscopy (BDS) is employed in a broad frequency (10–1–106 Hz) and temperature range (178–423 K) in order to probe the polymer/silica interface. Two relaxation processes can be identified for the composites: one corresponding to the bulklike polymer and a second one related to polymer chains close to the silica surface. For the latter the dynamic glass transition is shifted to higher temperature due to reduced mobility. This effect is investigated in dep...
TL;DR: This report reports on the adsorption performance of calcium alginate and Ca-Alg2 with encapsulated graphene oxide (Ca- Alg2/GO) gel bead adsorbents for the successful removal of Cu(2+) ions from aqueous solution.
TL;DR: In this article, the surface morphology and structure of the Mn3O4-reduced graphene oxide (rGO) hybrid were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), powder Xray diffraction (XRD), Raman spectroscope, XPS, and thermogravimetric analysis.
Abstract: Mn3O4–reduced graphene oxide (rGO) hybrids were synthesized, and their catalytic performance in heterogeneous activation of peroxymonosulfate (PMS) to oxidize a target pollutant, Orange II, in aqueous solutions was investigated. The surface morphology and structure of the Mn3O4–rGO hybrids were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). Through an in situ chemical deposition and reduction, Mn3O4–rGO hybrids with Mn3O4 nanoparticles at an average size of 29.2 nm were produced. The catalytic activity in Orange II oxidative decomposition was evaluated in view of the effects of various processes, pH, PMS concentration, Orange II concentration, and temperature. The combination of Mn3O4 nanoparticles with graphene sheets leads to a much higher catalytic activity than that of...
TL;DR: In this paper, a stable solid base catalyst was used for the transesterification of soybean oil with methanol, to produce biodiesel, was carried out under batch conditions at refluxed methanoline over the CaO-SnO2 catalysts.
TL;DR: The mechanism of structural transformation during combustion of nickel nitrate (oxidizer)-glycine (fuel) system is investigated by using different in situ techniques, including time-resolved X-ray diffraction (TRXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) with dynamic mass spectrometry (MS), and high-speed infrared thermal imaging as mentioned in this paper.
Abstract: The mechanism of structural transformation during combustion of nickel nitrate (oxidizer)–glycine (fuel) system is investigated by using different in situ techniques, including time-resolved X-ray diffraction (TRXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) with dynamic mass spectrometry (MS), and high-speed infrared thermal imaging. It is shown that for initial compositions with a relatively large fuel-to-oxidizer ratio (φ), pure Ni phase forms directly in the combustion front. For fuel-lean conditions, only NiO phase can be detected. Analysis of the obtained data, including transmission and scanning electron microscopy (TEM–SEM) studies of the quenched reaction fronts, allows us to suggest the intrinsic mechanism of pure metal formation in the investigated system. It is shown that the combustion front propagates because of the reaction between N2O and NH3, which are the products of decomposition of the oxidizer and fuel. The excess of NH3 gas produced in fuel-rich condi...
TL;DR: In this paper, an adsorbent of magnetic polymer multi-wall carbon nanotube (MPMWCNT) was synthesized, which was composed of poly(1-glycidyl-3-methylimidazolium chloride) (ionic liquid-based polyether) and ferroferric oxide.
TL;DR: It is shown by FTIR, TGA that IL partly complexes with the polymer PVdF-HFP and partly remains dispersed in the matrix, and the variation of ionic conductivity with temperature of these gel polymeric membranes follows Arrhenius type thermally activated behavior.
Abstract: PVdF-HFP + IL(1-butyl-3-methylimidazolium tetrafluoroborate; [BMIM][BF4]) polymeric gel membranes containing different amounts of ionic liquid have been synthesized and characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared (FTIR), differential scanning calorimetry, thermogravimetric analysis (TGA), and complex impedance spectroscopic techniques. Incorporation of IL in PVdF-HFP polymer changes different physicochemical properties such as melting temperature (Tm), thermal stability, structural morphology, amorphicity, and ionic transport. It is shown by FTIR, TGA (also first derivative of TGA, “DTGA”) that IL partly complexes with the polymer PVdF-HFP and partly remains dispersed in the matrix. The ionic conductivity of polymeric gel membranes has been found to increase with increasing concentration of IL and attains a maximum value of 1.6 × 10–2 S·cm–1 for polymer gel membrane containing 90 wt % IL at room temperature. Interestingly, the values of conductivity of memb...
TL;DR: In this paper, the surface modification and functionalization of carbon nanotubes (CNTs) were investigated and two functional groups, dodecylamine (DDA) and 3-aminopropyl triethoxysilane (3-APTES), were successfully covalently attached to CNTs.
Abstract: In this work the surface modification and functionalization of carbon nanotubes (CNTs) were investigated. CNTs were firstly treated by acid mixture H2SO4/HNO3 to introduce the carboxylic group onto the surface of CNTs. This carboxylic group was used as reaction precursor in the functionalization. Two functional groups, dodecylamine (DDA) and 3-aminopropyl triethoxysilane (3-APTES), were successfully covalently attached to CNTs. The functionalized CNTs were characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, differential scanning calorimetry and thermal gravimetric analysis (DSC/TGA) and transmission electron microscopy (TEM) methods. The CNTs attached to the organofunctional moieties have greater versatility for further utilization in different application fields such as biology, nanocomposites, solar energy, etc.
TL;DR: Three new functionalized UiO-66-X frameworks incorporating BDC-X (BDC: 1,4-benzenedicarboxylate) linkers have been synthesized by a solvothermal method using conventional electric heating.
Abstract: Three new functionalized UiO-66-X (X = –SO3H, 1; –CO2H, 2; –I; 3) frameworks incorporating BDC-X (BDC: 1,4-benzenedicarboxylate) linkers have been synthesized by a solvothermal method using conventional electric heating. The as-synthesized (AS) as well as the thermally activated compounds were characterized by X-ray powder diffraction (XRPD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, thermogravimetric (TG), and elemental analysis. The occluded H2BDC-X molecules can be removed by exchange with polar solvent molecules followed by thermal treatment under vacuum leading to the empty-pore forms of the title compounds. Thermogravimetric analysis (TGA) and temperature-dependent XRPD (TDXRPD) experiments indicate that 1, 2 and 3 are stable up to 260, 340 and 360 °C, respectively. The compounds maintain their structural integrity in water, acetic acid and 1 M HCl, as verified by XRPD analysis of the samples recovered after suspending them in the respective liquids. As confirmed by N2, CO2 and CH4 sorption analyses, all of the thermally activated compounds exhibit significant microporosity (SLangmuir: 769–842 m2 g−1), which are comparable to that of the parent UiO-66 compound. Compared to the unfunctionalized UiO-66 compound, all the three functionalized solids possess higher ideal selectivity in adsorption of CO2 over CH4 at 33 °C.