This paper reveals the synergic effect of fly ash (FA) and calcium aluminate cement (CAC) on the properties of pumice-based geopolymer mortars. Geopolymer mortar samples produced by replacing 0, 10, 20, and 30% of the...
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This paper reveals the synergic effect of fly ash (FA) and calcium aluminate cement (CAC) on the properties of pumice-based geopolymer mortars. Geopolymer mortar samples produced by replacing 0, 10, 20, and 30% of the pumice with FA and/or CAC are cured at ambient temperature, and 60C degrees. Physical properties, compressive strength (7, 28, and 90-days), durability, and microstructure of these samples are investigated in this study. While CAC and heat curing greatly reduce the setting time, FA has a limited effect on the setting time. However, both FA and CAC significantly increase the workability of the mortar mix. By replacing the optimum amount of the pumice with FA and CAC, the 7-day compressive strength of heat-cured geopolymer mortars can achieve 68.0 MPa. On the other hand, CAC significantly increases the compressive strength of the geopolymer mortars and their resistance to the wetting-drying and seawater. In addition, the FA has a limited effect on the enhancement of the mechanical properties and durability of the geopolymer mortars. Efflorescence is slightly reduced by FA and CAC additives, however, is greatly reduced by heat curing. The SEM/EDS show that CAC creates C-A-S-H gel and together with FA they reduce cracks and voids in the geopolymer matrix. The findings reveal that the properties of both fresh and hardened geopolymer mortars can be improved by replacing pumice with a suitable amount of FA and CAC.
In this paper, the timing-offset differential signal is proposed to reduce the common-mode and differential-mode noises induced by the right-angled differential transmission line. The right-angled differential transmi...
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In this paper, the timing-offset differential signal is proposed to reduce the common-mode and differential-mode noises induced by the right-angled differential transmission line. The right-angled differential transmission line using the timing-offset differential signal can greatly reduce the time-domain transmission common-mode noise from 0.065 to 0.019 V and the time-domain reflection differential-mode noise from 0.033 to 0.023 V as compared with the right-angled differential transmission line using a zero offset time differential signal. Besides, the differential-to-common-mode conversion is reduced from -6.3 to -12.4 dB. Moreover, the differential-mode transmission is larger than -1.25 dB and the differential-mode reflections are smaller than -17 dB from dc to 6 GHz. In order to verify the simulation results, a real circuit is fabricated and measured where the measurement results are in good agreement with the simulation results.
A novel one-step strategy has been developed to prepare boronic acid functional group modified silica particles, SiO2@GOPS-APBA, which contained large amount of immobilized boronic acid groups and demonstrated high af...
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A novel one-step strategy has been developed to prepare boronic acid functional group modified silica particles, SiO2@GOPS-APBA, which contained large amount of immobilized boronic acid groups and demonstrated high affinity towards diol-containing compounds. Solid state NMR and FT-IR spectrum proved that the boronic acid groups were successfully introduced on the surface of silica. TGA and element analysis demonstrated that the amount of boronic acid groups immobilized on the silica was about 1.0 mmol/g. The morphology and structure were studied by SEM and nitrogen adsorption-desorption measurements. The adsorption amount of catechol on SiO2@GOPS-APBA was determined to be 162 mu mol/g, which was higher than the samples prepared by the previously published approaches. This one-step approach represented an environment-friendly conception and a promising surface functionlization method. (C) 2015 Elsevier B.V. All rights reserved.
In this study, 6061-based metal matrix composites containing upto 15 weight percent of SiC particulates were successfully synthesized using casting route. The microstructural characteristics of the cast composites wer...
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In this study, 6061-based metal matrix composites containing upto 15 weight percent of SiC particulates were successfully synthesized using casting route. The microstructural characteristics of the cast composites were investigated with particular emphasis on the retention of SiC particulates as a function of the processing parameters. The results of the interfacial characterization studies revealed higher dynamic ultra microhardness of the matrix in the immediate vicinity of the SiC particulates. This was rationalized in terms of segregation related microstructural changes in the SiC/6061 interfacial region. Results of the ambient temperature mechanical testing demonstrate that an increase in the weight percent of ceramic reinforcement increases the strength and modulus and degrades the ductility of the matrix material. These results are correlated with the strengthening models and the microstructural characteristics of the cast composites investigated in the present study.
We have examined the electronic structure of ScH2, YH2, and YH2 using optical absorptivity and thermoreflectance techniques in the photon energy range from 0.2 to 5 eV between 4.2 and 340 K. The measured quantities we...
We have examined the electronic structure of ScH2, YH2, and YH2 using optical absorptivity and thermoreflectance techniques in the photon energy range from 0.2 to 5 eV between 4.2 and 340 K. The measured quantities were used to determine the frequency-dependent dielectric functions and the dependence of the dielectric functions on temperature modulation. The results show that the low-energy properties (hν≲1.5 eV) are dominated by intraband absorption and a plasmon falling near 1.5-1.8 eV. Interband absorption is observed to be strong and structured above the interband onsets of ∼ 1.25, ∼ 1.6, and ∼ 1.9 eV for ScH2, YH2, and LuH2, respectively. The observed interband features can be interpreted in terms of the self-consistent band calculations of ScH2 and YH2 presented in the companion paper, and experimental features can be related to specific bands in particular parts of the Brillouin zone. The systematics observed in these three trivalent metal dihydrides can be correlated well to theory. Extensive studies with samples of varying hydrogen to metal ratio (x) within the dihydride phase were carried out to examine the influence of hydrogen sublattice disorder on the optical properties and electronic structure. It was observed that, for x approaching 2, interband features which could be related to d-band absorption were broadened by increasing lattice disorder, and new features in the interband absorption spectra were observed which could not be interpreted without postulating the hydrogen occupancy of significant numbers of octahedral sites. The strong x dependence of the optical features emphasizes the importance of studying well-characterized samples.
In this work, thick nanocrystalline mesoporous titania layers are synthesized via chemical Solution deposition using a water based citratoperoxo-Ti(IV)-precursor solution. The aqueous citratoperoxo-Ti(IV)-precursor So...
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In this work, thick nanocrystalline mesoporous titania layers are synthesized via chemical Solution deposition using a water based citratoperoxo-Ti(IV)-precursor solution. The aqueous citratoperoxo-Ti(IV)-precursor Solution is modified by the addition of polyvinyl alcohol (PVA), which acts as a thickener and pore forming agent. Layers are tape casted onto ITO-coated glass substrates and are thermally processed. The influence of process parameters like Ti(IV)-concentration, blade thickness, crystallization temperature and time on the film's phase composition, morphology and thickness are investigated by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), variable angle spectroscopic ellipsometry (VASE), atomic force microscopy (AFM) and profilometry. It is shown that the Ti(IV)-concentration and heat treatment influence the size and shape of the grains of which the films are composed, the film morphology (porosity, surface roughness) and the layer thickness, but no influence on the phase formation is observed. In all cases phase pure anatase layers are obtained. (C) 2007 Elsevier Ltd. All rights reserved.
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