Cu(II) and Gd(III) doped boehmite nanostructures: a comparative study of electrical property and thermal stability

The present article reports the effect of transition (Cu2+) and rare earth metal (Gd3+) ion doping on structural, microstructural and electrical properties of boehmite nanoparticles. Rietveld refinement is adopted here to refine the x-ray diffractograms for further analyzing the microstructural details and their alteration due to the incorporation of foreign cations. This is probably the first time when dielectric properties of these doped boehmite samples having been reported herein. These samples show remarkably high dielectric constant values which corroborate that doping enhances the microstrain values inside the orthorhombic structure and results in higher crystallographic defects. Enhancement in defect sites causes the augmentation of relative permittivity and ac conductivity. Temperature stability has also been enhanced significantly in our Cu-doped sample. The present study enables us to determine a relationship between crystalline deformation and electrical properties of nanomaterials which may be highly beneficial in fabricating cost-effective energy harvesting devices

An insight into the structure, composition and hardness of a biological material: the shell of freshwater mussels

The shell of the freshwater mussel (Mollusca: Bivalvia) is a composite biological material linked with multifunctional roles in sustaining ecosystem services. Apart from providing mechanical strength and support, the shell is an important site for adherence and growth of multiple types of algae and periphyton. Variations in the shell architecture are observed in the mussels both within a species and among different species. Considering the prospective utility of the shell of the freshwater mussels as a biological material, an assessment of the shell characteristics was accomplished usingCorbicula bensoniandLamellidens marginalisas model species. The calcium carbonate (CaCO3) content of the shells, physical features and mechanical strength were assessed along with the morphometric analysis. The CaCO(3)content of the shell (upto 95% to 96% of the shell weight) of both the mussels was positively correlated with the shell length, suggesting increased deposition of CaCO(3)in shells with the growth of the species. The cross sectioned views of FE-SEM images of the shells exhibited distinct layered structure with external periostracum and inner nacreous layer varying distinctly. In the growing region, the growth line was prominent in the mussel shells revealed through the FESEM images. In addition XRD, FTIR and EDS studies on the mussel shells confirmed the existence of both aragonite and calcite forms of the calcium carbonate crystals with the incidence of various functional groups. The mechanical strength of the mussel shells was explored through nanoindentation experiments, revealed significant strength at the nanoparticle level of the shells. It was apparent from the results that the shell of the freshwater musselL. marginalisandC. bensoniqualify as a biological material with prospective multiple applications for human well-being and sustaining environmental quality

Nanoflower, nanoplatelet and nanocapsule Mg(OH)(2) powders for adsorption of CO2 gas

The soft chemical synthesis of self-assembled magnesium hydroxide (Mg(OH)(2)) nanoplatelets with surface area as high as about 300 m(2) g(-1) was achieved in the present work. The nanopowders such as MHN, MHCl, MHBr were synthesized at similar to 30 A degrees C without using any catalyst or surfactant using, respectively, precursor solutions of Mg(NO3)(2), MgCl2, MgBr2 and characterized by XRD, BET surface area, BJH pore size analysis, FTIR, FE-SEM, TEM and EDX techniques. It was found that the MHN and MHCl nanopowders comprised of nanoflowers formed by self-assembly of nanoplatelets and porous nanoplatelets, while the MHBr nanopowders comprised of a random assembly of nanocapsules. The powders possessed the technologically important quality of reproducible CO2 adsorption at room temperature and its desorption at a relatively lower temperature of 75 A degrees C. Based on the experimental evidences, the mechanisms of various microstructure formations and CO2 adsorption mechanism were also proposed

Novel Growth Mechanisms of Self-assembled Mg(OH)2 Nanoplatelets

Here we report for the first time the time-dependent mechanisms of self assembly and growth of Mg(OH)2 nanoparticles. For this purpose, the nanopowders are obtained by a simple chemical precipitation route. To understand the route map of the growth process; the nanopowders are subsequently characterized by XRD, FTIR, BET, pore size distribution, FESEM and TEM analysis techniques. Based on the results obtained from aforesaid characterizations the mechanisms of self-assembly and nanoplatelets growth process as a function of reaction time are explained

Development of a Cu(I) doped boehmite based multifunctional sensor for detection and removal of Cr(VI) from wastewater and conversion of Cr(VI) into an energy harvesting source

This article reports a copper doped boehmite (CBH) based nano-material which is capable of detecting and removing hexavalent chromium simultaneously. Basic characterization has been performed to determine its phase purity, particle size (similar to 20 nm), morphology and surface properties (surface area 15.29 m(2) g(-1) and pore diameter 3.9 nm) by using some basic characterization tools. The Rietveld refinement method has been adopted to analyze the microstructural details of the synthesized nanostructure. Photoinduced electron transfer (PET) based quenching of fluorescence is mainly responsible for chromium sensing in this case. This nanosensor is exceptionally sensitive (limit of detection similar to 6.24 mu M) and merely selective towards hexavalent chromium ions. Industrial wastewater samples have also been used here to demonstrate the real life applicability of this material, which shows the same trend. This fluoro-sensor gains its multi-functionality when it comes to the adsorption based removal of Cr(VI) from wastewater. The synthesized material shows a remarkably high adsorption rate (similar to 85% in just 5 minutes) due to its sponge-like porous structure. Adsorption of hexavalent chromium from wastewater enhances the dielectric constant of this material significantly (similar to 7.93 times). Ionic polarization-dependent enhancement of the dielectric constant resulting from industrial wastewater treatment is a quite unmarked approach. Very low tangent loss with augmented dielectric permittivity makes this nano-material desirable for energy harvesting applications. Previously many articles have reported the sensing and removal of various industrial effluents. Keeping this in mind, this work has been designed and, apart from sensing and removal, it provides a new insight into energy harvesting from wastewater

Effects of various morphologies on the optical and electrical properties of boehmite nanostructures

The present article reports three different grain morphologies of boehmite nanoparticles: spherical (EBH), needle-shaped (UBH) and flower-like (HBH). EBH possesses the highest surface area, whereas HBH has the lowest. A novel synthesis route for spherical (EBH) boehmite nanostructures using ethylenediamine has been reported here. Moreover, we have compared the growth mechanisms and morphology-dependent changes in the optical and electrical properties of the three samples. The band gap energies were evaluated to be 5.30 eV, 5.44 and 5.87 eV for EBH, UBH and HBH, respectively. Strong photoluminescence (PL) emission for all the nanostructures, the highest for HBH, was noted. The lowest surface area of HBH provides a surface with fewer defects; this seals the possibility of energy loss via non-radiative recombination of electrons and holes, which enhances the PL intensity. The dielectric constants for EBH, UBH and HBH are 1.49 x 10(6), 1.14 x 10(5), and 7.14 x 10(4), respectively. Variations in the dielectric loss tangents and temperature-dependent electrical properties of the three morphologies were evaluated in support. Also, the ac conductivity and impedance analyses are in good accordance with our dielectric analysis. The present investigation may be highly beneficial in developing biosensors, bio-imaging, and fabricating cost-effective energy storage devices

Intelligently designed fly-ash based hybrid composites with very high hardness and Young's modulus

Currently, India generates annually about 112 million tones of fly ash (FA), as an industrial waste from thermal power plants. As part of the global journey to convert waste to wealth here we report the intelligent design based synthesis of FA based hybrid composites with spectacular improvement in Young's modulus and nanohardness. The novel design approach utilized alkali activation as well as simultaneous reinforcements of the porous FA matrix with a layered white china clay (WCC) and chopped E glass fiber. The developed materials were subsequently characterized by nanoindentation technique, pH measurement, alkali dissolution, FESEM, etc. techniques to evolve the structure-property correlation. The optimized design and optimal alkali activation lead to achievements of about 233% and 545% enhancements in Young's modulus and hardness, respectively. These results are rationalized in terms of chemical analysis, Si:Al ratio, presence of silicate network modifiers e.g., Na2O and CaO, microstructure, density, extent of polymerization due to alkali activation, processing condition and elastic recovery as well as the ratio of energy spent in elastic and plastic deformations during the nanoindentation processes. Finally, a schematic model is proposed to explain the experimental observations. (C) 2017 Elsevier Ltd. All rights reserved

Synthesis of mixed calcite-calcium oxide nanojasmine flowers

Here we report for the very first time a simple, inexpensive, room temperature synthesis method of formation of mixed calcite calcium oxide nanojasmines (CTCaONJs). The method involves chemical precipitation in aqueous medium at room temperature in open atmosphere in order to allow natural carbonation to occur. Aqueous solutions of calcium nitrate dihydrate (Ca(NO3)(2)center dot 2H(2)O) and sodium hydroxide are used as precursors. The nanopowder is characterized by the Fourier transform infrared (FTIR) spectrometry, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDAX), BET (Brunauer-Emmett-Teller), BJH (Barrett-Joyner-Halenda) techniques. Optical properties of nanojasmines (NJs) were investigated by UV-vis spectroscopy. The powder has calcite as the major phase and calcium oxide as the minor phase. The crystallite size of calcite along (104) crystallographic direction is about 18 nm with a size strain of about 1.03%. The high (e.g., 8.8 m(2)g(-1)) surface area powder exhibits a mesoporous microstructure with 5-15 nm pore size. Further, it possesses a relatively higher optical band gap of 5.87 eV. The FESEM and TEM based evidences show that the CTCaONJ flowers mainly comprise of nanoplatelets made up of irregular nanorods and nanowires consisting of amorphous spherical nanoparticles. Based on these experimental evidences a qualitative model is proposed to explain the growth mechanism of the CTCaONJ flowers. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Failure and deformation mechanisms at macro- and nano-scales of alkali activated clay

Here we report two qualitative models on failure and deformation mechanisms at macro- and nano-scales of alkali activated clay (AACL), a material of extraordinary importance as a low cost building material. The models were based on experimental data of compressive failure and nanoindentation response of the AACL materials. A 420% improvement in compressive strength (sigma(c)) of the AACL was achieved after 28 days (d) of curing at room temperature and it correlated well with the decrements in the residual alkali and pH concentrations with the increase in curing time. Based on extensive post-mortem FE-SEM examinations, a schematic model for the compressive failure mechanism of AACL was proposed. In addition, the nanoindentation results of AACL provided the first ever experimental evidence of the presence of nano-scale plasticity and a nano-scale contact deformation resistance that increased with the applied load. These results meant the development of a unique strain tolerant microstructure in the AACL of Indian origin. The implications of these new observations were discussed in terms of a qualitative model based on the deformation of layered clay structure

Catalyst free growth of MgO nanoribbons

Here, we report for the first time ever the catalyst free growth of magnesium oxide (MgO) nanoribbons on soda lime silica glass substrates by a green and inexpensive chemical route. The MgO nanoribbons were grown when the precursor magnesium hydroxide (Mg(OH)(2)) thin films were converted to MgO after 2 h of heat treatment in air at 450 degrees C. The MgO thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and the related energy dispersive X-ray spectroscopy (EDAX) techniques. Finally, a plausible mechanism is suggested for growth of the MgO nanoribbons. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved