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XPS spectra, centered on the O1s level of the PP samples : aged during 80 days (c), 60 days (b), and non treated (a).
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In the present work we are concerned in the study, by means of the X-ray Photoelectron Spectroscopy (XPS), of the solar radiation impact (atmospheric environment), on the natural aging of the polypropylene (PP). The study has focused on two periods of aging, 60 and 80 days. Results of the quantitative analysis show an important degradation of the a...
Contexts in source publication
Context 1
... (C1s, peak at 285 eV) is the main constituent on the surface of the non- treated sample (Fig. 1a). The intensity of the corresponding peak decreases during aging (Figures 3b and 3c), but it remains however the dominant constituent in comparison to the other species. Oxygen, whose peak O1s is located at 532 eV, in very weak concentration on the surface of the new PP (Table 1), increases during the aging process to the detriment of C1s, its intensity becomes comparable to that of C1s. ...
Context 2
... effect of the duration of the aging gives rise to an evolution of the peaks intensity associated with all these bonds (Fig.2). Figure 3 shows the results of this decomposition. For the new sample (Fig. 3a), the O1s can be decomposed in four elementary peaks located at 530.1, 531.9, 532.4 and 534.0 eV associated respectively with the charge effect in the polymer surface, and to C=O, C-OH and O=C-O bonds. ...
Context 3
... of these radicals occurs after the extremely rapid combination with oxygen [20,21] followed by a release of hydrogen from the polymer chain. The effect of the duration of the aging gives rise to an evolution of the peaks intensity associated with all these bonds (Fig.2). Figure 3 shows the results of this decomposition. For the new sample (Fig. 3a), the O1s can be decomposed in four elementary peaks located at 530.1, 531.9, 532.4 and 534.0 eV associated respectively with the charge effect in the polymer surface, and to C=O, C-OH and O=C-O bonds. During aging, the intensity of the peaks associated with C-OH and O=C-O bonds decreases at the expense of that corresponding to the C=O ...
Context 4
... diagram following illustrates a such mechanism [4,5]. Taking account of a such diagram and of the relative intensities of the peaks coming from the decomposition of C1s and O1s peaks (Figures 2 and 3), several reactional mechanisms, which may stabilize the polymer structure, can take place. The first, and the most probable, comes from the neutralization of a state occupied by a proton, leading to the formation of the C-OH bond. ...
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The article presents a kinetic study of the thermal decomposition of three compounds derived from pyran that have not been reported in the literature. These compounds are widely used in pharmacology to obtain important products of technological and industrial interest. The compound (2,6-dietoxitetrahydro-2H-pyran; 2-etoxi-6-propoxytetrahydro-2H-pyr...
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Citations
... eV (-NH + -) [51] for GO/CoFe/Pani-Ce and the peaks at 398.4 eV (=N-) [51,54], 399.33 eV(-NH-) [51,55,56] and 402.27 eV (-NH + -) [51,55,57] for GO/Pani-Ce/CoFe can be understood from the XPS results. The peaks at 394.43 eV (for GO/CoFe/Pani-Ce) and 393.42 eV (for GO/Pani-Ce/CoFe) are probably due to the Ce-N bonding which shows the connection between cerium oxide and polyaniline chain[58,59]. Interestingly, the peak in the region of 400.49 ...
... Interestingly, the peak in the region of 400.49 eV was shifted to a high field at 402.27 eV, which is probably due to the bonding of cerium oxide from the oxygen side too -NH + -of Pani(-N-O-)[59].Fig. 7shows the XPS spectra of O 1s in GO/Pani-Ce/CoFe and GO/CoFe/Pani-Ce respectively. ...
... The C1s and O1s peaks deconvolution of all the selected materials was conducted to examine the later behavior of the nanocomposites further. [53,54], respectively. In the case of the PEF nanocomposites, an extra peak is found at 292 eV attributed to the π-π* transition of the GNPs' and CNTs' graphitic layers [55]. ...
... deconvolution of neat PEF, PEF/ 1 GNPs, PEF/1 CNTs, and PEF/0.25 GNPs/1 CNTs, re-spectively, while the corresponding binding energies and areas of each deconvoluted peak are reported in Tables 5 and 6, for the C1s and O1s core levels. The deconvoluted carbon peaks found in all the PEF samples at binding energies of 284.6, 285.2, 286, 286.8, and 289 eV (±0,2 eV error values) are attributed to the C=C sp 2 and C-C sp 3 carbon hybridization, and the C-OH, C-O, and C=O/O=C-O bonds [53,54], respectively. In the case of the PEF nanocomposites, an extra peak is found at 292 eV attributed to the π-π* transition of the GNPs' and CNTs' graphitic layers [55]. ...
... Accordingly, the deconvoluted oxygen peaks were found near 531.4, 532, and 533.6 eV for all the PEF materials and correspond to the O-C=O, C-OH, and O-C=O bonds, respectively [53,54]. The sp 2 to sp 3 ratio for neat PEF is close to 3, confirming the 6 C-C bonds with sp 2 and 2 C-C bonds with sp 3 hybridization on the PEF monomer; incorporating any of the carbon nanofillers, the corresponding ratio increases due to the sp 2 carbon hybridization of the graphitic layers of the GNPs and CNTs. ...
Poly(ethylene 2,5-furandicarboxylate) (PEF) nanocomposites reinforced with Graphene nanoplatelets (GNPs) and Carbon nanotubes (CNTs) were in situ synthesized in this work. PEF is a biobased polyester with physical properties and is the sustainable counterpart of Polyethylene Terephthalate (PET). Its low crystallizability affects the processing of the material, limiting its use to packaging, films, and textile applications. The crystallization promotion and the reinforcement of PEF can lead to broadening its potential applications. Therefore, PEF nanocomposites reinforced with various loadings of GNPs, CNTs, and hybrids containing both fillers were prepared, and the effect of each filler on their structural characteristics was investigated by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy—attenuated total reflectance (FTIR–ATR), and X-Ray Photoelectron Spectroscopy (XPS). The morphology and structural properties of a hybrid PEF nanocomposite were evaluated by Transmission Electron Microscopy (TEM). The thermo-oxidative degradation, as well as lifetime predictions of PEF nanocomposites, in an ambient atmosphere, were studied using Thermogravimetric Analysis (TGA). Results showed that the fillers’ incorporation in the PEF matrix induced changes in the lamellar thickness and increased crystallinity up to 27%. TEM analysis indicated the formation of large CNTs aggregates in the case of the hybrid PEF nanocomposite as a result of the ultrasonication process. Finally, the presence of CNTs caused the retardation of PEF’s carbonization process. This led to a slightly longer lifetime under isothermal conditions at higher temperatures, while at ambient temperature the PEF nanocomposites’ lifetime is shorter, compared to neat PEF.
High‐performance thermoplastic composites of polyketones [poly‐aryl‐ether‐ketone (PAEK), poly‐ether‐ether‐ketone (PEEK), poly‐ether‐ketone‐ketone (PEKK)] reinforced with continuous carbon fiber (CF) were consolidated using towpreg produced by multi‐scale aqueous dispersion coating technique. An intra‐matrix trend of composite strength and void fraction was studied to identify the composite with maximum strength free of voids for each polyketone matrix. The CF/PAEK composite with a flexural strength of ~2047 MPa and ILSS of ~99 MPa with a fiber volume fraction of ~67% had the maximum strength free of voids among CF/PAEK composite and all polyketone composites studied. The highest crystallinity (34.5%), and the highest amount of hydrogen bonding and bonds formed between CF, PI nanoparticle, and PAEK explained the origin of strength in CF/PAEK composite. The maximum strength among CF/PEEK and CF/PEKK composite free of voids had a flexural strength of ~1861 MPa, ~1981 MPa; ILSS of ~74 MPa, ~60 MPa; fiber volume fraction of ~61% and ~ 65%, respectively. The polyimide (PI) nanoparticles layer on CF formed the fiber matrix interface, supported hydrogen bonding in all polyketone composites, and formed bonds with CF and matrices of PAEK and PEEK establishing a synergistic effect.
Highlights
Intra‐matrix trend of strength and voids in polyketone composites studied.
Void‐free, high‐performance, high fiber volume fraction composites developed.
CF/PAEK composite had maximum strength among polyketone composites studied.
PI nanoparticles formed bonds with CF and matrices of PAEK and PEEK.
CF/PAEK composite strength originates from crystallinity, H bond, and bonding.
In this work, nano-sized niobium oxides with different crystal structures can be produced by thermal treatment of nonstoichiometric nanocrystalline niobium carbide (NbCy) and serve as effective sorbents and photocatalytic materials. Differential thermal analysis of initial NbCy powder was carried out, and temperatures of thermal treatment for the were chosen. The nanopowders were studied using powder X-ray diffraction, scanning electron microscopy, low-temperature N2 adsorption-desorption, X-ray photoelectron spectroscopy and diffuse reflectance electron spectroscopy methods. The specific surface area of samples annealed at 100, 200, 300, 400, 500 °C was about 224, 255, 273, 224 and 47 m²/g, respectively. The photocatalytic activity of the obtained nanopowders was analyzed during the oxidation of an aqueous solution of methyl orange on exposure to visible light. The photocatalytic activity of nanopowders grows with the annealing temperature increasing from 100 to 500 °C and reaches the maximum value for the higher niobium oxide Nb2O5. The time of complete decoloration of dye was 165 min. The tests performed to establish the sorption equilibrium between catalyst and dye in the dark revealed that the nanopowder produced during annealing at 300 °C possesses a high sorption capacity of 76.5%, which allows it to be considered as an effective sorbent.
Two chromite spinel-based composite materials, MnIICrIII2O4/MnIIMnIII2O4/C and CoCr2O4/C are successfully synthesized by a solid-state conversion process via annealing Mn–Cr-coordination compound and Co–Cr-coordination compound at 350 °C in air for 1 h, respectively. The two composite materials both show the morphology of nanoparticles, in which the spinels are embedded in carbon matrix into a continuous phase. The as-prepared composite materials are used as supercapacitor electrodes in basic electrolyte. The MnIICrIII2O4/MnIIMnIII2O4/C composite material possesses a high specific capacity of 184.0 mAh g⁻¹ at a current density of 0.5 A g⁻¹ with a superior rate capability of 138.3 mAh g⁻¹ (75.2% retention) at 20 A g⁻¹. Meanwhile, CoCr2O4/C nanoparticles also deliver a high specific capacity of 158.8 mAh g⁻¹ at a current density of 0.5 A g⁻¹ with a superior rate capability of 125.0 mAh g⁻¹ (78.7% retention) at 20 A g⁻¹. The good supercapacitive behaviors of the two composite materials are probably attributed to the characteristics of bimetallic compound and the presence of multiple valence states in the samples, giving rise to obvious redox responses. And the MnIICrIII2O4/MnIIMnIII2O4/C and CoCr2O4/C composites possess reversible electrochromism.
NiV2O6/C composites are prepared via a solid-state conversion process by low temperature (150 °C) annealing nickel‑vanadium-based coordination polymer, [Ni(phen)H2O][V2O6]. The obtained NiV2O6/C nanoribbons are interconnected to form a sponge-like morphology, when the composites are first used as supercapacitor electrode, it exhibits a specific capacitance of 745.6 F g⁻¹ at 0.5 A g⁻¹ with a good rate capability of 520.0 F g⁻¹ (69.7% retention) at 10 A g⁻¹ (20-folds). The NiV2O6/C composite exhibits good cycling performance, the capacitance retentions at 6000th and 12000th charging/discharging cycles at 2 A g⁻¹ are 81.5% and 77.8% relative to the original capacitances, respectively. The morphological and compositional changes of the NiV2O6/C composite electrode before and after 12,000 GCD cycles (two-electrode system) are carefully elaborated through a series of characterization (SEM, EDS, and XPS). Furthermore, the NiV2O6/C nanoribbons possess reversible electrochromism, which is probably related to the intervalence charge transfer (IVCT, VIV → VV).
Control and mechanism analysis of a Ge quantum dot (QD) formation on a Si(100) substrate by using carbon (C)-mediated c(4×4) surface reconstruction (SR) and solid-phase epitaxy (SPE) methods were demonstrated. The Si surface was reconstructed via the formation of C-Si bonds before Ge deposition in the SR method, while the QDs were formed by annealing of an amorphous Ge/C/Si heterostructure in the SPE method. In the SR method, the QDs grew in the Volmer-Wever (VW) mode at C=0.25 and 0.50 ML, and in the Stranski-Krastanov (SK) mode at C=0.75 ML. The VW-mode QDs were formed owing to the c(4×4) surface reconstruction which acted like a virtual partition for Ge nucleation. At C=0.5 and 0.75 ML, it was confirmed that the C-Ge bonds were formed near the Ge/Si interface because the unreacted excessive C atoms remained at the Ge/Si interface. The formation of C-Ge bonds induced the strain relief of the Ge layer and acted to change the growth mode to the SK mode at C=0.75ML. On the other hand, in the SPE method, the QDs grew in the VW mode at C=0.1 and 0.25 ML due to the Ge aggregation, and in the SK mode at C ≥ 0.4 ML. It was found that a large number of C-Ge bonds owing to the C incorporation into the Ge layer during the SPE induced to form a wetting layer. Therefore, the reduction of the strain energy in the Ge layer occurred at the low C coverage and induced the transition to the SK mode. These results suggest that the growth modes of the QDs via C mediation are controllable in both methods by changing the amount of C used as the mediation layer owing to the change in the C binding states at the Ge/Si interface or in the Ge layer.
