Abstract: This review research aims to discuss the results obtained researches on cement containing pure cement, pulverised fly ash, and nanoparticles, in order for eliminating negative side effects underlie the substitution of by–products for pure Portland cement. Nanoparticles (NP) used in these researches are nanoTiO2, nanoSiO2, nanoCaCO3, fibers of carbon nano tube (CNT), nanolimestone (nanoCaCO3), nanoZrO2, nanoclays, and nanometakaolin (nMK) for improving properties of cement systems. Published manuscripts explains two methods regarding on the usage of nanoparticles for cement system: blending and ultrasonication for dispersion of nanoparticles. However, differences between blending and ultrasonication methods suggested by various researchers are also discussed. Experiments reported these papers include the water demand, the density, the setting–times, the heat of hydration, the fluidity, the compressive strength and the flexural strength. According to these results, nanoparticles increase the water demand and heat of hydration of cement; it decreases the density and fluidity for cement mortars, evidently. The most effective nanoparticles on early compressive and flexural strengths are fibers of carbon nano tube and nanoCaCO3. These papers also point effects of these nanoparticles on the strength gain of cement. This review paper inform us until Effect of nanomaterial on water demand and density section in this Part I. Second part of this review paper will explain Hydration properties of Portland pulverised fly ash cement section, Effect of nanomaterial on setting–time section, Effect of nanomaterial on heat of hydration section, Strength gain mechanisms for hardened Portland pulverised fly ash cement paste and mortar section, Effect of nanomaterial on compressive strength section, Effect of nanomaterial on flexural strength (Bending) section, and Conclusion section.
Abstract: The progress of nanotechnology resulted in the development of new instruments in the civil engineering and its applications. In particular, the use of carbon nanofillers into the matrix of construction materials can provide enhanced properties to the material in both of mechanical and electrical performance. In constructions, concrete is among the most used material. Due to the peculiarities of its components and its structure, it is suitable to modifications, at the nanometer level too. Moreover, to guarantee structural safety it is desirable to achieve a diffuse monitoring of structures in order to identify incipient situations of damages and possible risk for people. The ideal solution would be to realize structures able to identify easily and quickly their behavior modifications. This paper presents a research work about the characterization of the self-sensing abilities of novel cementitious composites with conductive carbon nanoinclusions and their application into a structural reinforced concrete beam. The self-sensing evidence is achieved through the correlation between the variation of strains and the variation of electrical resistance or resistivity. Nanomodified cement pastes with different carbon nanofillers has been tested. The experimental campaign shows the potentialities of this new types of sensors made of nanomodified concrete for diffuse Structural Health Monitoring.
Abstract: Carbonation governs the microstructure and the overall mechanical performance of mixes involving MgO cements as the main binder. Aggregate grading has a significant influence on the carbonation process due to the different particle arrangements that determine the porosity and permeability of the resulting formulations. This work investigates the effect of aggregate particle size distribution on the carbonation of blocks containing reactive MgO. Samples containing four different aggregate profiles were subjected to accelerated carbonation at 20% CO2 concentration for up to 28 days. While the influence of gap grading on strength development was not very pronounced, mixes with the lowest initial porosity indicated the greatest increase in density at the end of 28 days. This also translated into the highest strength results obtained due to the formation of hydrated magnesium carbonates, reaching 10 MPa only after 1 day of carbonation. The porosity values measured before carbonation were inversely correlated with the corresponding densities and final strengths of each mix. An inverse correlation between porosity and permeability values before carbonation led to the conclusion that the connectivity of pores rather than the total pore volume controls the carbonation reaction. Mixes with higher initial permeabilities achieved the highest strengths, proving that the extent of CO2 diffusivity is mainly dependent on pore connectivity.
Abstract: In this study nickel and boron doped sodium cobalt oxide NaCo2-xNixByO4 (0≤x≤0.3, 0≤y≤0.1) nanocrystalline thermoelectric ceramic powders were synthesized using electrospinning techniques and then consolidated into bulk ceramics. The differences in the microstructure and thermoelectric properties of the samples as a result of doping effect have been investigated. The crystalline structures of the powders and nanofibers were characterized using X-ray diffraction and scanning electron microscopy and BET Analysis before and after the calcination process at different temperatures. Nanofibers prepared by the use of electrospinning technique, have a diameter of approximately 300 nm, and the diameter of the grains of calcined powders was observed to range between 150 to 500 nanometers. Thermoelectric properties of the bulk ceramics were measured by physical properties measurement system (Lot-Oriel PPMS) in a temperature range of 15–300 K. The calculated values of dimensionless figure of merit at 300 K are 4.25×10-5, 5.3×10-6, 8.6×10-5 and 9×10-6 for sintered powders from undoped, Ni and B doped powders, respectively.
Abstract: Synthesis and characterization of Cr/Al2O3-bentonite nanocomposite as a hydrocracking catalyst of castor oil have been conducted. The catalyst was prepared according to the following method. At the first step, bentonite was activated using H2SO4 to obtain H-bentonite, after that the activated clay was pillarized by Al2O3, Next, a salt solution of Cr (NO3)3·9H2O was impregnated in the pillared bentonite sample, followed by calcination and reduction to obtain the final catalyst, i.e. Cr/Al2O3-bentonite. The catalysts including unpillared bentonite were characterized using infrared spectrometer (FT-IR), X-Ray diffractometer (XRD), X-ray Fluorescence spectrometer (XRF), Transmission Electron Microscope (TEM) and gas sorption analyzer. GC-MS analysis was conducted to characterize the hydrocracking product. The research results showed that pillarization of bentonite caused an increasing of the basal spacing of bentonite in an amount of 1.01 nm. Although Chrom was unevenly dispersed on the bentonite and it probably blocked the bentonite framework resulted in the decrease of catalyst specific surface area, Cr/Al2O3-bentonite catalyst gave the best conversion of 64.03%. The GC-MS analysis data showed that the hydrocracking products contained various kinds of organic compounds such as acetone, acetic acid, methyl benzene, octane, heptanal, 2-octene, 1-undecanoic acid, 9-octadecenal and 10-undecenoic acid.
Abstract: Quantum dots (QDs) are powerful luminescent probes for detecting single-molecules and imaging live cells. Despite several reports on bioimaging and biosensing applications of QDs, controlled and targeted detection of biomolecules using quantum dots is an ongoing challenge. When a QD is conjugated with an ideal chromophore, which can be a fluorescent or a non-fluorescent dye molecule, QD luminescence can be quenched by Förster resonance energy transfer (FRET) to the quencher dye. However, the photoluminescence of QD can be recovered upon on-demand release of the quencher. Our study focuses on quenching of QD photoluminescence after conjugation with a non-fluorescent dye molecule, black hole quencher 1 (BHQ-1), intermediated with a molecular sensing target peptide GPLG↓VRGK. Based on steady-state and time-resolved photoluminescence measurements of QD and the QD-peptide-BHQ-1 sensor assemblies, we attribute the quenching of photoluminescence intensity and lifetime to FRET from the QD to BHQ-1molecules. Here the intermediate peptide GPLG↓VRGK can be cleaved by matrix metalloproteinase-2 (MMP-2), an enzyme that is upregulated in cancer cells extra cellular matrix (ECM), at its Gly and Val region shown by the down headed arrow. Here the QD-pep-BHQ-1 conjugate detected the MMP-2 presence at the extra cellular matrix of H1299 cancer cells. Further the QD-pep-BHQ-1 molecules were conjugated at the surface of a mesoporous silica nanoparticle (MSN) scaffold to localize maximum target peptide in a nanospace volume for the future αvβ3 integrin receptor targeted detection of MMP-2. The luminescence quenching of MSN-QD-pep-BHQ-1 conjugates were analyzed with time resolved photoluminescence measurement.