Showing papers on "Thermogravimetric analysis published in 2009"

Preparation and characterization of graphitic carbon nitride through pyrolysis of melamine

Abstract: Graphitic carbon nitride (g-C3N4) has been synthesized via a two-step pyrolysis of melamine (C3H6N6) at 800°C for 2 h under vacuum conditions. X-ray diffraction (XRD) patterns strongly indicate that the synthesized sample is g-C3N4. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) morphologies indicate that the product is mainly composed of graphitic carbon nitride. The stoichiometric ratio of C:N is determined to be 0.72 by elemental analysis (EA). Chemical bonding of the sample has been investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Electron energy loss spectroscopy (EELS) verifies the bonding state between carbon and nitrogen atoms. Optical properties of the g-C3N4 were investigated by PL (photoluminescence) measurements and UV–Vis (ultraviolet–visible) absorption spectra. We suppose its luminescent properties may have potential application as component of optical nanoscale devices. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were also performed.

Synthesis and Characterization of Titania-Graphene Nanocomposites.

Abstract: In this work, the synthesis and physiochemical characterization of titanium oxide nanoparticle−graphene oxide (TiO2−GO) and titanium oxide nanoparticle−reduced graphene oxide (TiO2−RGO) composites was undertaken. TiO2−GO materials were prepared via the hydrolysis of TiF4 at 60 °C for 24 h in the presence of an aqueous dispersion of graphene oxide (GO). The reaction proceeded to yield an insoluble material that is composed of TiO2 and GO. Composites were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy, N2 adsorption−desorption, and thermal gravimetric analysis/differential thermal analysis (TGA/DTA). This approach yielded highly faceted anatase nanocrystals with petal-like morphologies on and embedded between the graphene sheets. At higher GO concentrations with no stirring of the reaction media, a long-range ordered assembly for TiO2−GO sheets was observed due to self-assembly. GO−TiO2 compo...

Plasma Induced Grafting Carboxymethyl Cellulose on Multiwalled Carbon Nanotubes for the Removal of UO22+ from Aqueous Solution

Abstract: Carboxymethyl cellulose (CMC) is grafted on multiwalled carbon nanotubes (MWCNT) by using plasma techniques. The CMC grafted MWCNT (MWCNT-g-CMC) is characterized by using Fourier transform infrared spectra (FT-IR), Raman spectra, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA)−differential thermal analysis (DTA), scanning electron microscopy (SEM), and N2-BET methods in detail. The application of MWCNT-g-CMC in the removal of UO22+ from aqueous solution is investigated. MWCNT-g-CMC has much higher sorption ability in the removal of UO22+ than raw MWCNT. The MWCNT-g-CMC is a suitable material in the preconcentration and solidification of heavy metal ions from large volume of aqueous solutions.

Nanostructured α-Fe2O3 Thin Films for Photoelectrochemical Hydrogen Generation

Abstract: α-Fe2O3 thin film photoelectrodes were fabricated by aerosol-assisted chemical vapor deposition (AACVD) using a new hexanuclear iron precursor [Fe6(PhCOO)10(acac)2(O)2(OH)2]·3C7H8 (1) (where PhCOO = benzoate and acac = 2,4-pentanedionate). The precursor (1) designed for AACVD has a low decomposition temperature and sufficient solubility in organic solvents and was synthesized by simple chemical techniques in high yield. It was characterized by melting point, FT-IR, X-ray crystallography, and thermogravimetry (TGA). The TGA analysis proved that complex (1) undergoes facile thermal decomposition at 475 °C to give iron oxide residue. In-house designed AACVD equipment was used to deposit highly crystalline thin films of α-Fe2O3 on fluorine-doped SnO2 coated glass substrates at 475 °C in a single step. The material properties were characterized by XRD, XPS, and Raman spectroscopy, and the results confirmed that films were highly crystalline α-Fe2O3 and free from other phases of iron oxide. Further analysis of ...

Nanocellulose reinforced PVA composite films: Effects of acid treatment and filler loading

Abstract: Nanocellulose was prepared by acid hydrolysis of microcrystalline cellulose (MCC) at different hydrobromic acid (HBr) concentrations. Polyvinyl alcohol (PVA) composite films were prepared by the reinforcement of nanocellulose into a PVA matrix at different filler loading levels and subsequent film casting. Chemical characterization of nanocelluloses was performed for the analysis of crystallinity (Xc), degree of polymerization (DP), and molecular weight (Mw). The mechanical and thermal properties of the nanocellulose reinforced PVA films were also measured for tensile strength and thermogravimetric analysis (TGA). The acid hydrolysis decreased steadily the DP and Mw of MCC. The crystallinity of MCC with 1.5 M and 2.5 M HBr showed a significant increase due to the degradation of amorphous domains in cellulose. Higher crystalline cellulose showed the higher thermal stability than MCC. From X-ray diffraction (XRD) analysis, nanocellulose samples showed the higher peak intensity than MCC cases. Reduction of MCC particle by acid hydrolysis was clearly observed from scanning electron microscope (SEM) images. The tensile and thermal properties of PVA composite films were significantly improved with the increase of the nanocellulose loading.

Synthesis of Flower-Like NiO and Effects of Morphology on Its Catalytic Properties

Abstract: NiO with novel flower-like morphology was prepared by using a two-step, template- and surfactant-free, environmentally friendly method. Flower-like NiO was composed of many irregular nanosheets that were assembled together by weak interactions. The as-prepared materials were characterized by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy with selected area electron diffraction patterns, N2 sorption, temperature-programmed reduction with CO, X-ray photoelectron spectroscopy (XPS), and in situ Fourier transform infrared (FT-IR) for CO adsorption. The catalytic behaviors for CO oxidation were studied by using a fixed bed microreactor. Compared to NiO nanoparticles, we found the flower-like NiO possessed a larger surface area, bimodal pore size distribution, higher reducibility, and superior catalytic activity for CO oxidation. The XPS and CO in situ FT-IR results showed that its catalytic property was morphology...

High-Performance Carboxylated Polymers of Intrinsic Microporosity (PIMs) with Tunable Gas Transport Properties†

Abstract: Carboxylated polymers of intrinsic microporosity (carboxylated PIMs) are reported as potential high-performance materials for membrane-based gas separation Carboxylated PIM membranes were prepared by in situ hydrolysis of the nitrile groups of PIM-1 films Structural characterization was performed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) The degree of hydrolysis was determined by carbon elemental analysis The thermal properties were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) Compared with PIM-1, carboxylated PIMs with different degrees of hydrolysis have similar thermal and mechanical properties but show higher selectivity for gas pairs such as O2/N2, CO2/N2, He/N2, and H2/N2 with a corresponding decrease in permeability Selectivity coupled to high permeability combines to exceed the Robeson upper-bound line for the O2/N2 gas pair This work demonstrates that significant improvements in gas separati

Reinforcing Poly(ε-caprolactone) Nanofibers with Cellulose Nanocrystals

Abstract: We studied the use of cellulose nanocrystals (CNXs) obtained after acid hydrolysis of ramie cellulose fibers to reinforce poly(e-caprolactone) (PCL) nanofibers. Chemical grafting with low-molecular-weight PCL diol onto the CNXs was carried out in an attempt to improve the interfacial adhesion with the fiber matrix. Grafting was confirmed via infrared spectroscopy and thermogravimetric analyses. The polymer matrix consisted of electrospun nanofibers that were collected as nonwoven webs. The morphology as well as thermal and mechanical properties of filled and unfilled nanofibers were elucidated by scanning electron microscopy, differential scanning calorimetry, and dynamic mechanical analysis, respectively. The addition of CNXs into PCL produced minimal changes in the thermal behavior of the electrospun fibers. However, a significant improvement in the mechanical properties of the nanofibers after reinforcement with unmodified CNXs was confirmed. Fiber webs from PCL reinforced with 2.5% unmodified CNXs sho...

CFRP-Recycling Following a Pyrolysis Route: Process Optimization and Potentials

Abstract: Pyrolysis is a well known method to recover carbon fibers from composite waste. In order to bring these recycled carbon fibers back into new composites, and to provide a 'closed loop' for this material, their properties have to be investigated and proved suitable for new products. In a former study a strong influence of the pyrolysis process on the surface of the recovered fibers was found. This in turn influenced other properties like fiber strength, electrical properties and fiber―matrixadhesion. These results offer the possibility to control individual properties of recycled carbon fibers and their composites, but on the other hand they indicate a necessity for process optimization in order to provide a high quality of the recycled fibers. In this study different process parameters during pyrolysis were investigated and optimized in order to provide the reclaimed carbon fibers with properties close to new fibers. The optimization was done by labscale pyrolysis experiments performed in a thermogravimetric analyzer (TGA), with variation of pyrolysis temperature, isothermal dwell time and oven atmosphere, respectively. The recovered fibers were analyzed by scanning electron microscopy and Raman spectroscopy. Finally a pyrolysis test on a semi-industrial-scale was successfully performed to demonstrate the technical viability of the optimized process parameters.

Hydrogen production by steam gasification of polypropylene with various nickel catalysts

Abstract: Several nickel-based catalysts (Ni/Al2O3, Ni/MgO, Ni/CeO2, Ni/ZSM-5, Ni-Al, Ni-Mg-Al and Ni/CeO2/Al2O3) have been prepared and investigated for their suitability for the production of hydrogen from the two-stage pyrolysis–gasification of polypropylene. Experiments were conducted at a pyrolysis temperature of 500 °C and gasification temperature was kept constant at 800 °C with a catalyst/polypropylene ratio of 0.5. Fresh and reacted catalysts were characterized using a variety of methods, including, thermogravimetric analysis, scanning electron microscopy with energy dispersive X-ray spectrometry and transmission electron microscopy. The results showed that Ni/Al2O3 was deactivated by two types of carbons (monoatomic carbons and filamentous carbons) with a total coke deposition of 11.2 wt.% after reaction, although it showed to be an effective catalyst for the production of hydrogen with a production of 26.7 wt.% of the theoretical yield of hydrogen from that available in the polypropylene. The Ni/MgO catalyst showed low catalytic activity for H2 production, which might be due to the formation of monoatomic carbons on the surface of the catalyst, blocking the access of gaseous products to the catalyst. Ni-Al (1:2) and Ni-Mg-Al (1:1:2) catalysts prepared by co-precipitation showed good catalytic abilities in terms of both H2 production and prevention of coke formation. The ZSM-5 zeolite with higher surface area was also shown to be a good support for the nickel-based catalyst, since, the Ni/ZSM-5 catalyst showed a high rate of hydrogen production (44.3 wt.% of theoretical) from the pyrolysis–gasification of polypropylene.

Facile preparation and thermal degradation studies of graphite nanoplatelets (GNPs) filled thermoplastic polyurethane (TPU) nanocomposites

Abstract: A facile method with the advantage of using only one single solvent throughout the whole processing was introduced to prepare graphite nanoplatelet (GNP) filled thermoplastic polyurethane (TPU) nanocomposites. Morphological studies showed that the employed method could provide the uniform dispersion of GNPs in the TPU matrix. Storage modulus of the nanocomposites was increased with increasing GNP content, and the improvement was more obvious at temperatures below the glass transition temperature (Tg) of TPU. For the nanocomposite that contains 3.9 vol% (the maximum loading employed in this study) of GNP, it still showed a long elongation at break of over 600%. Thermogravimetric analysis (TGA) showed that the incorporation of GNPs could improve the thermal stability of the nanocomposites. In addition, cone calorimetry results showed that the GNPs could act as intumescent flame retardant and significantly reduced the heat release rate (HRR), thus improved the flame retardancy of the TPU matrix.

Study of Carbon Dioxide Adsorption on Mesoporous Aminopropylsilane-Functionalized Silica and Titania Combining Microcalorimetry and in Situ Infrared Spectroscopy

Abstract: Two calcined mesoporous supports, silica and titania, were functionalized with aminopropylsilane (APS). The samples were characterized using ATR (attenuated total reflectance), nitrogen sorption at 77 K, and thermogravimetric analysis. The functionalized silica and titania are mesoporous and were grafted with 1.4 and 1.6 molecules of APS per nm2, respectively. Infrared measurements propose that the properties of the amine sites are affected by the chemical properties of the support. For example, the NH2 bending vibration δ(NH) was shifted to lower wavenumbers from 1597 to 1575 cm−1 from the silica to the titania grafted sample, respectively. This could be explained by different interactions with the surface hydroxyl groups of silica and titania. The grafted samples were investigated for carbon dioxide adsorption by combining microcalorimetry and in situ FTIR spectroscopy. Their CO2 adsorption properties are presented in comparison to the nongrafted support materials. Microcalorimetric measurements show im...

Polypyrrole-Coated SnO2 Hollow Spheres and Their Application for Ammonia Sensor

Abstract: Polypyrrole-coated SnO2 hollow spheres hybrid materials have been synthesized through an in situ polymerization of pyrrole monomers in the presence of preprepared SnO2 hollow spheres. The hybrids were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), and thermogravimetric analysis (TG). Experimental data showed certain synergetic interaction existed in the hybrids, probably resulting in the enhanced thermal stability of polypyrrole coatings. Gas sensing tests showed that the hybrids possessed very fast response and high sensitivity to ammonia gas at room temperature, implying its potential application for gas sensors.

Facile synthesis and unique physicochemical properties of three-dimensionally ordered macroporous magnesium oxide, gamma-alumina, and ceria-zirconia solid solutions with crystalline mesoporous walls.

Abstract: Three-dimensionally (3D) ordered macroporous (3DOM) MgO, gamma-Al(2)O(3), Ce(0.6)Zr(0.4)O(2), and Ce(0.7)Zr(0.3)O(2) with polycrystalline mesoporous walls have been successfully fabricated with the triblock copolymer EO(106)PO(70)EO(106) (Pluronic F127) and regularly packed monodispersive polymethyl methacrylate (PMMA) microspheres as the template and magnesium, aluminum, cerium and zirconium nitrate(s), or aluminum isopropoxide as the metal source. The as-synthesized metal oxides were characterized by means of techniques such as X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), Fourier transform infrared (FT-IR), high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy/selected area electron diffraction (HRTEM/SAED), BET, carbon dioxide temperature-programmed desorption (CO(2)-TPD), and hydrogen temperature-programmed reduction (H(2)-TPR). It is shown that the as-fabricated MgO, gamma-Al(2)O(3), Ce(0.6)Zr(0.4)O(2), and Ce(0.7)Zr(0.3)O(2) samples possessed single-phase polycrystalline structures and displayed a 3DOM architecture; the MgO, Ce(0.6)Zr(0.4)O(2), and Ce(0.7)Zr(0.3)O(2) samples exhibited worm-hole-like mesoporous walls, whereas the gamma-Al(2)O(3) samples exhibited 3D ordered mesoporous walls. The solvent (ethanol or water) nature and concentration, metal precursor, surfactant, and drying condition have an important impact on the pore structure and surface area of the final product. The introduction of surfactant F127 to the synthesis system could significantly enhance the surface areas of the 3DOM metal oxides. With PMMA and F127 in a 40% ethanol solution, one can generate well-arrayed 3DOM MgO with a surface area of 243 m(2)/g and 3DOM Ce(0.6)Zr(0.4)O(2) with a surface area of 100 m(2)/g; with PMMA and F127 in an ethanol-HNO(3) solution, one can obtain 3DOM gamma-Al(2)O(3)with a surface area of 145 m(2)/g. The 3DOM MgO and 3DOM gamma-Al(2)O(3) samples showed excellent CO(2) adsorption behaviors, whereas the 3DOM Ce(0.6)Zr(0.4)O(2) sample exhibited exceptional low-temperature reducibility. The unique physicochemical properties associated with the copresence of 3DOM and mesoporous walls make these porous materials ideal candidates for applications in heterogeneous catalysis and CO(2) adsorption.