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The main aim of this work is to comparatively reveal the effect of fibre type, length and content on compressive strength and microstructure of structural geopolymer concrete (GPC) produced under constant mixture and curing parameters in order to address the significant gap in present literature. Firstly, GPCs with different NaOH concentrations (i.e., 6, 9, 12 and 15 M) and activator solution/binder (a/b) ratios (i.e., 0.45 and 0.55) were produced in ambient curing condition, and optimum production parameters were determined based on the preliminary evaluations. Then, glass and polypropylene fibres in 6‐mm length (GS6 and PP6) and polyamide and polypropylene fibres in 12‐mm length (PY12 and PP12) were included in GPCs at ratio of 0.4%, 0.8% and 1.2% (by volume). Compressive strength, apparent porosity, bulk density, ultrasonic pulse velocity (UPV), X‐ray diffraction (XRD) and scanning electron microscope (SEM) analysis of GPC samples were carried out comparatively. The inclusion of GS6 fibre enhanced the compressive strength thanks to fibre surface being covered by geopolymer gel and the strong adhesion between GS fibre and geopolymer matrix. SEM images of fibre reinforced GPC (FRGPC) also confirmed the experimental findings, which were attributed to improvement in compressive strength. Regardless of the fibre type, the maximum compressive value strength was obtained from GPC specimens with 0.4% fibre and then decreased. Higher fibre inclusions led to poor compaction, workability issues and inhomogeneous fibre dispersions. A very good relation (R2 = 0.98) was acquired between UPV and compressive strength values of GPC/FRGPC samples. [ABSTRACT FROM AUTHOR]

This study is aimed to synthesize zinc oxide nanoparticles (ZnO NPs) from Aloe barbadensis Miller leaf extract using the green synthesis method at room temperature. The biosynthesized NPs are characterized by X‐ray diffraction (XRD), UV–vis spectroscopy (UV–vis), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscope (SEM). The XRD pattern has revealed the hexagonal wurtzite structure with a crystallite size of 16 nm for synthesized ZnO NPs. The FTIR results display the formation of ZnO NPs and the presence of other functional groups. The UV–vis absorption spectrum shows an absorption band at 347 nm and the value of the bandgap is found to be 3.75 eV. The surface morphology of synthesized NPs is visualized by SEM images, it is observed that most of the NPs are needle in shape. Further, these NPs will find applications in biosensing and photocatalytic activity. [ABSTRACT FROM AUTHOR]

The paper reports the results of the analyses performed on a Roman quadrans dating back to the first century ad, belonging to a group of more than 8.000 coins found in the bed of river Tiber during an archaeological research in 1987–1988. The quadrans was examined by means of X‐ray diffraction, scanning electron microscopy, energy dispersion spectroscopy, and X‐ray photoelectron spectroscopy. Energy dispersion spectroscopy analytical results confirmed that the coin is made of pure copper. The compounds present in the patina have been identified through X‐ray diffraction. The spectrum is the overlapping of several peaks, and the results show that the patina substantially consists of malachite Cu2CO3(OH)2, cupric chloride CuCl2, and nantokite CuCl. X‐ray photoelectron spectroscopy only evidences nantokite because of the different analysis depths of the two techniques. This means that nantokite forms a thin outer layer in the concretion covering the quadrans. [ABSTRACT FROM AUTHOR]

Copper-containing thin films were synthesized by a citrate sol-gel method using ethylene glycol. The evolution of the shape and local atomic structure of the copper-containing fractal crystallites at different stages of growth was investigated by the combination of experimental and theoretical techniques. A surface morphological study of the deposited film samples was carried out using SEM. It revealed the evolution of the crystallite structures as a function of annealing temperature. To describe this mechanism diffusion-limiting aggregation and cluster-cluster models were used. X-ray absorption spectroscopy (XANES) was applied to show the dynamics of the local atomic structure of Cu ion and the copper oxidation state at different stages of crystallites formation. It was found that at temperatures up to 250 °C the Cu2Cl(OH)3 (atacamite phase) and chelate complex are formed. With temperature increases changes in the local atomic structure as well as in morphology take place and at 500 °C CuO formed. As a result of these processes, the fractal organization of the other level was observed. [ABSTRACT FROM AUTHOR]

We report a multi-instrument characterization of the carbon particles in carbon/polymer/nanodiamond core-shell materials used for high-performance liquid chromatography. These particles are prepared by the carbonization/pyrolysis of poly(divinylbenzene) (PDVB) microspheres. Scanning electron microscopy showed that the particles (4.9 µm initially) decreased in size after air oxidation (to 4.4 µm) and again after carbonization (down to 3.5 µm) but remained highly spherical. Brunauer-Emmett-Teller measurements showed low surface areas initially (as received: 1.6 m2/g, after air oxidation: 2.6 m2/g) but high values after carbonization (445 m2/g). Fourier transform infrared spectroscopy revealed the changes in the functional groups after air oxidation (C = O and C-O stretches appear), carbonization (carbon-oxygen containing moieties disappear), and acid treatment (reintroduction of carbon-oxygen containing moieties). X-ray photoelectron spectroscopy (XPS) and elemental analysis revealed the surface and bulk oxygen contents before and after treatments. By XPS, the atom percent oxygen for the as received, air oxidized, carbonized, and acid treated particles are 8.7, 16.6, 3.7, and 13.8, respectively, and by elemental analysis, the percent oxygen in the materials is 0.6, 8.1, 0.9, 16.9, respectively. A principal components analysis of time-of-flight secondary ion mass spectrometry data identified ions that were enhanced in the different materials, where almost 90% of the variation in the analyzed peak areas was captured by two principle components. X-ray diffraction and Raman spectroscopy suggested that the carbonized PDVB was disordered. Thermogravimetric analysis showed significant differences between the differently treated PDVB microspheres. This work applies directly to a commercial product and the process for preparing it. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The influences of the nature and the extent of M(III) ion substitution on the structure, morphology and surface properties of layered double hydroxides, LDHs [Mg1− x M(III) x(OH)2](CO3) x/ n· mH2O, M(III) being Al or/and Fe and x= M(III)/[(Mg+M(III)], and derived mixed oxides were investigated. Three series: Mg−Al, Mg−Al−Fe and Mg−Fe were synthesized using low supersaturation co-precipitation method at constant pH, with different Mg : Al : Fe ratio and x in the wide range from 0.15 to 0.7 in order to obtain complex, multi-phase systems with disordered structure, developed surface area, acid–base and redox properties favourable for catalytic application. The morphology of LDHs and their derived mixed oxides did not change considerably although pronounced changes in structural and surface properties occur by thermal decomposition. The increase in Al amount, as well as the deviation of M(III) content from the optimal range for the single LDH phase synthesis, causes the formation of smaller particles and decrease of mixed oxide crystallite size. The nature and amount of M(III) influence the development of surface area, after thermal treatment, depending mainly on the presence of smaller mesopores, not visible by scanning electron microscope. Although the particle size has no considerable influence on the value of the surface area, it was observed that the samples with smaller particles (Mg–Al and Mg–Al–Fe series) have also higher surface area compared with the samples with larger particles (Mg–Fe series). [ABSTRACT FROM AUTHOR]