Search results for "thermogravimetric analysis"
showing 10 items of 212 documents
High-nuclearity Ni-substituted polyoxometalates: a series of poly(polyoxotungstate)s containing 20–22 nickel centers.
2011
Three high-nuclearity Ni-substituted polyoxotungstates (POTs)--[Ni(enMe)2(H2O)2]2[Ni(H2O)6]2[Ni(enMe)2][Ni(H2O)2]1.5[HNi20X4W34(OH)4O136(H2O)6(enMe)8]·11 H2O (3), [Ni(en)2(H2O)]2[H8Ni21X4W34(OH)4O136(en)10(H2O)5]·22 H2O (4), and [Ni(enMe)2]2[H6Ni22X4W34(OH)4O136(H2O)6(enMe)10]·18 H2O (5), in which en = ethylenediamine, enMe = 1,2-diaminopropane, X = 0.5 P+0.5 Ge--were made under hydrothermal conditions and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The structures of 3–5 can be viewed as novel derivatives of [H6Ni20P4W34(OH)4O136(enMe)8(H2O)6]·12 H 2O (1) and [Ni(en)2(H2O)]2[H8Ni20P4W34(OH)…
Sepiolite-reinforced epoxy nanocomposites: Thermal, mechanical, and morphological behavior
2010
A bisphenol A-based epoxy resin was modified with pristine sepiolite and an organically surface-modified sepiolite and thermally cured using two different curing agents: an aliphatic and a cycloaromatic diamine. The nanocomposites were characterized by dynamic mechanical analysis (DMA), rheology, thermogravimetric analysis (TGA), and electron microscopy. The initial sepiolite–epoxy mixtures show a better dispersion for the sepiolite-modified system that forms a percolation network structure. Mechanical properties have also been determined. The flexural modulus of the epoxy matrix slightly increases by the incorporation of the organophilic sepiolite. The flexural strength of the sepiolite-mo…
Modification of polyoxymethylene for increased thermal resistance
2017
Ternary nanocomposites, composed of polyoxymethylene (POM), ethylene octene copolymer and zinc oxide (ZnO), are prepared by melt compounding. The effects of two types of ethylene-octene copolymers, differing with α-octene content (38% for EOC38 and 17% for EOC17), as well as nanostructured ZnO on thermal behavior of POM are investigated. The content of EOC in the POM based composites is varied between 10 and 50 wt%, while the content of ZnO is 2 wt%. Thermal behavior of POM based systems are studied by using differential scanning calorimetry and thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. Results of thermogravimetric analysis show that, by rising either …
Low Temperature H2S Removal with Metal-Doped Nanostructure ZnO Sorbents: Study of the Origin of Enhanced Reactivity in Cu-Containing Materials
2011
Sulfidation of pure and metal-doped ZnO nanostructure sorbents (M0.03Zn0.97O, M = Fe, Co, Ni, Cu) was studied in order to clarify the effect of metal on the transformation kinetics at 200−350 °C. The solids were prepared by coprecipitation from metal nitrate solution followed by calcination at 400 °C. Reaction with H2S was studied by thermal gravimetric analysis (TGA) using a gas mixture containing 0.2 vol % H2S in equimolar H2−N2. It was found that at 350 °C the TGA sulfidation profiles of all studied samples are similar, with the interface reaction being the main rate-determining step. After lowering the temperature to 250 °C the transformation of Cu0.03Zn0.97O continues to be controlled …
Facile Fabrication of Natural Polyelectrolyte-Nanoclay Composites: Halloysite Nanotubes, Nucleotides and DNA Study
2020
Complexation of biopolymers with halloysite nanotubes (HNTs) can greatly affect their applicability as materials building blocks. Here we have performed a systematic investigation of fabrication of halloysite nanotubes complexes with nucleotides and genomic DNA. The binding of DNA and various nucleotide species (polyAU, UMP Na2, ADP Na3, dATP Na, AMP, uridine, ATP Mg) by halloysite nanotubes was tested using UV-spectroscopy. The study revealed that binding of different nucleotides to the nanoclay varied but was low both in the presence and absence of MgCl2, while MgCl2 facilitated significantly the binding of longer molecules such as DNA and polyAU. Modification of the nanotubes with DNA an…
Straightforward preparation of highly loaded MWCNT-polyamine hybrids and their application in catalysis
2020
Multiwalled carbon nanotubes (MWCNTs) were easily and efficiently functionalised with highly cross-linked polyamines. The radical polymerisation of two bis-vinylimidazolium salts in the presence of pristine MWCNTs and azobisisobutyronitrile (AIBN) as a radical initiator led to the formation of materials with a high functionalisation degree. The subsequent treatment with sodium borohydride gave rise to the reduction of imidazolium moieties with the concomitant formation of secondary and tertiary amino groups. The obtained materials were characterised by thermogravimetric analysis (TGA), elemental analysis, solid state 13C-NMR, Fourier-transform infrared spectroscopy (FT-IR), transmission ele…
Comparative study of historical woods from XIX century by thermogravimetry coupled with FTIR spectroscopy
2019
Thermal and structural properties of historical woods from apparatuses of the Historical Collection of the Physics Instruments of the University of Palermo have been investigated by FTIR spectroscopy coupled with thermogravimetric analysis. Specifically, the wooden portions of apparatuses from XIX century have been studied. The investigated woods belong to different taxa (Swietenia mahagoni, Picea abies and Juglans regia). The thermal behavior of the wooden materials has been successfully interpreted on the basis of specific indexes determined by the quantitative analysis of the FTIR spectra. The kinetics of the wood pyrolysis have been investigated by using a non-isothermal approach based …
Synthesis and characterization of chiral azobenzene dye functionalized Janus dendrimers
2008
Abstract Eight bischromophoric bisMPA based polyester Janus dendrimers emanating from a pentaerythritol core were synthesized and their properties evaluated. 4-((4-(Ethyl(2-(2-(6-methoxynaphthalen-2-yl)propanoyloxy)ethyl)amino)-phenyl)diazenyl)-benzoic acid and 4-((4-(ethyl(2-(2-(6-methoxynaphthalen-2-yl)propanoyloxy)-ethyl)-amino)phenyl)diazenyl)-3-nitrobenzoic acid were attached to the dendritic polyester skeleton to make chiral dendrimers up to the second generation. The structures and the purity of the molecules were verified with 1H NMR, 13C NMR, ESI TOF mass spectrometry, and elemental analysis. Spectral properties were evaluated with UV–vis and CD spectrometer. The compounds displaye…
Structural, mechanical and thermal behavior assessments of PCL/PHB blends reactively compatibilized with organic peroxides
2018
Abstract The efficiency of two commercially available organic peroxides, dicumyl peroxide (DCP) and di-(2-tert-butyl-peroxyisopropyl)-benzene (BIB), during reactive processing of poly(e-caprolactone)/poly(3-hydroxybutyrate) (PCL/PHB) blends was investigated. The changes in chemical structure of PCL/PHB blends, as a function of organic peroxide type (DCP/BIB) and content (in range: 0–1.0 parts by weight - pbw), were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis combined with infrared spectroscopy, and headspace analysis combined with gas chromatography with flame ionization detector. Performance properties of PCL/PHB blends were evaluated based on diffe…
Synthesis and Comparative Catalytic Study of Zirconia-MnCO3or -Mn2O3for the Oxidation of Benzylic Alcohols
2016
Abstract We report on the synthesis of the zirconia–manganese carbonate ZrO x (x %)–MnCO3 catalyst (where x=1–7) that, upon calcination at 500 °C, is converted to zirconia–manganese oxide ZrO x (x %)–Mn2O3. We also present a comparative study of the catalytic performance of the both catalysts for the oxidation of benzylic alcohol to corresponding aldehydes by using molecular oxygen as the oxidizing agent. ZrO x (x %)–MnCO3 was prepared through co‐precipitation by varying the amounts of Zr(NO3)4 (w/w %) in Mn(NO3)2. The morphology, composition, and crystallinity of the as‐synthesized product and the catalysts prepared upon calcination were studied by using scanning electron microscopy, tr…