1,721,032 research outputs found
Enhanced morphology and mechanical characteristics of clay/styrene butadiene rubber nanocomposites
No full textAchieving complete exfoliation of clay in their polymer nanocomposite is a matter of interest as it can significantly affect the material properties. Herein, an efficient way of enhancing the interlayer spaces of organically modified clays (OC) containing two types of surfactants, benzyl methyl hydrogenated tallow (Cloisite 10A) and dimethyl dihydrogenated tallow (Cloisite 20A) while mixing with the styrene butadiene rubber (SBR) is reported. The prolonged swelling of the OC in toluene helped the rubber chains to disentangle in the interlayer spaces identifiable from the morphology and the change of the d-value. The small angle X-ray scattering traces for all the Cloisite 20A/SBR composites indicated a very extensive dispersion of the OC and using the Guinier equation from SAXS, radius of gyration was calculated. An optimal size of 6–7 nm for the dispersed clay particles was found for maximizing resistance to abrasion as well as mechanical properties. Finally the enhanced tensile properties were correlated with the vulcanization behavior as well as the filler/polymer interfacial interaction from rheology through the completely exfoliated morphology observed for the swollen clay filled samples. Moreover an exclusive mechanism for curing of the composites was also derived
Effects of date palm and green tea polyphenol extracts on the thermal stability and mechanical properties of poly lactic acid
No full textPoly (lactic acid) (PLA) is a biodegradable polymer whose thermal and mechanical performance can be enhanced through natural additives such as polyphenols. In this study, polyphenols extracted from green tea (Camellia sinensis L.) and date palm (Phoenix dactylifera L., Arecaceae) were incorporated into PLA at concentrations of 1, 5, and 10 wt.% using an internal mixer. The oxidative thermal stability of the blends was examined by thermogravimetric analysis and differential scanning calorimetry, while their morphology and mechanical properties were also characterized. Both polyphenols improved the thermal stability of PLA, with green tea polyphenols showing a greater effect, likely due to their broader range of active compounds. However, increasing polyphenol content reduced the glass transition temperature, tensile strength, and Young’s modulus, while enhancing elongation at break and ductility. These findings indicate that plant-derived polyphenols act as both thermal stabilizers and plasticizers within the PLA matrix
Microtron Irradiation Induced Tuning of Band Gap and Photoresponse of Al-ZnO Thin Films Synthesized by mSILAR
No full textAl-doped polycrystalline nano ZnO (Al-ZnO) thin films with different doping concentrations were successfully prepared by the microwave-assisted successive ionic layer adsorption and reaction (mSILAR) technique. The structural analysis along with the orientation of the prepared films was examined by powder x-ray diffraction (PXRD) patterns. The deposited film is polycrystalline and the (002) orientation enhanced upon doping. Additional investigations were carried out to study the effect of electron beam irradiation (e−-irradiation) on the band gap and photoconductivity of both irradiated and unirradiated samples. Both the Al doping and e−-irradiation led to the enhancement of the photoconductivity of prepared materials. This property enables us to tune the properties of materials for various applications by controlling dopant concentrations and e−-irradiation. The dependence of photocurrent on e−-irradiation of Al-ZnO thin films was not reported previously. Therefore, Al-doped polycrystalline nano-ZnO thin film is a promising material for band gap engineering and for the development of solar cells
MoS2-Based Hybrid Piezoelectric Materials
No full textThe utilization of renewable energy is the primary focus of the scientific world today. However, the large initial cost, space requirements, and low technological upgrades fade its merits, and lead to difficulty in its establishment. Therefore, energy harvesting is a viable option that operates by the piezoelectric effect. The piezoelectric effect is the property of a material that creates voltage when it undergoes deformation. Recently, two-dimensional (2D) transition-metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2), have demonstrated piezoelectric capabilities because of their non-centrosymmetric crystal structure, which enables the formation of a dipole moment when the material is stressed. In contrast, the application of an external electric field develops deformation in the MoS2 structure known as the inverse piezoelectric effect. Furthermore, the piezoelectric output depends on various factors of the MoS2 material, such as the number of atomic layers, crystal orientation, and the point of application of strain. The present chapter aims to cover the background of the working mechanism, various preparation methods, and piezoelectric energy harvesting of MoS2-based materials.Scopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Author Correction: Stretchable Electrospun PVDF-HFP/Co-ZnO Nanofibers as Piezoelectric Nanogenerators (Scientific Reports, (2018), 8, 1, (754), 10.1038/s41598-017-19082-3)
No full textIn Figure 5, Co-ZnO was incorrectly given as Ni-ZnO. In addition, the line on the graph for PVDF-HFP was omitted. The correct Figure 5 appears below as Figure 1. (Figure presented.).Scopu
Effect of Zn-Fe2O3 nanomaterials on the phase separated morphologies of polyvinylidene fluoride piezoelectric nanogenerators
No full textSelf-powered devices based on piezoelectric nanogenerators (PENGs) are becoming crucial in the upcoming smart societies as they can integrate multifunctional applications, especially sensing, energy storage, etc. In this work, we explore the piezoelectric voltage generation happening in polyvinylidene fluoride (PVDF) nanocomposites developed by phase separation. The simple method adopted for the nanocomposite synthesis rules out the high voltage required for the normal electrospun PENGs and adds to their cost-effectiveness. Zinc-doped iron oxide (Zn-Fe2O3) nanomaterials influence the piezoelectric properties by enhancing the crystallinity and structural properties of the polymer. The phase separation process causes structural rearrangements within the PVDF by inducing the directional alignment of -CH2- and -CF2-chains and is the major reason for electroactive phase enhancement. Layers of Zn-Fe2O3 were uniformly distributed in the phase-separated PVDF without being negatively influenced by the solvent-non-solvent interactions during phase separation. At 3 wt%, the Zn-Fe2O3 induced an open circuit voltage of 0.41 volts, about 12 times greater than that of the neat PVDF film. Nanoparticles affected the thermal degradation and crystallinity of the polymer composites most effectively, and the dielectric properties of the PVDF/Zn-Fe2O3 composite microfilms were also pronounced. The proposed simple and cost-effective approach to flexible microfilm fabrication suggests significant applications in wearable electronics.This work was supported by the Qatar University Student Grant under QUST-1-CAS-2023-944 and the Qatar National Research Fund under UREP29-069-2-022. The statements made herein are solely the responsibility of the authors. The TEM, SEM, and EDX were accomplished in the Central Laboratories Unit at Qatar University.Scopu
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