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Kaptay G.,Applied NanoMaterials | Kaptay G.,University of Miskolc
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2014

In this paper the performance of the linear, exponential and combined models to describe the temperature dependence of the excess Gibbs energy of solutions in the framework of the Redlich-Kister model is discussed. The models are not compared to existing Calphad optimized databases, rather they are tested against the 209 binary solid and liquid metallic alloys, for which reliable experimental data exist on the heat of mixing and Gibbs energy of mixing in the handbook of Predel. It was found that the linear model often leads to high-T artifact (artificial inverted miscibility gaps) and the excess Gibbs energy approaches infinity at high temperatures, which seems unreasonable. It was also found that although both the exponential and combined models can in principle lead to low-T artifact (liquid re-stabilization), in real systems it probably does not take place, at least for the "normal" systems (a system is "normal", if the heat of mixing, excess entropy of mixing and excess Gibbs energy of mixing have the same sign at the temperature of measurement; 86% of all systems are found "normal"). The problem with the exponential model is that it is unable to describe the "exceptional" systems (14% of all systems). It is shown that the combined model is able to describe also these "exceptional" systems, as well. An algorithm is worked out to ensure that the combined model does not run into any high-T or low-T artifact, even when it is used to describe the "exceptional" systems. It is concluded that the T-dependence of the interaction energies for all solution phases described by the Redlich-Kister polynomials should be described by the combined model. In this way an improved databank on excess Gibbs energies of solution phases can be gradually built, not leading to any artifact. © 2013 Elsevier Ltd.


Hjiri M.,Applied NanoMaterials | El Mir L.,Applied NanoMaterials | El Mir L.,Islamic University | Leonardi S.G.,Messina University | And 3 more authors.
Sensors and Actuators, B: Chemical | Year: 2014

Al-doped ZnO (AZO) nanoparticles have been prepared using a modified sol-gel technique. The as-prepared AZO nanoparticles were annealed at 400 C, and their morphologies and microstructural characteristics were investigated using transmission electron microscopy (TEM) and x-ray powder diffraction (XRD) analyses. Crystallites with an average size of approximately 60-70 nm and ZnO as a primary phase were observed in all samples. In addition, smaller nanoparticles (less than 5 nm) with an Al-rich structure covering the surface of larger ZnO crystallites were also noted on the Al-doped samples. Chemoresistive devices consisting of a thick layer of AZO nanoparticles on interdigitated alumina substrates have been fabricated, and their electrical and sensing characteristics for carbon monoxide were investigated. Al-doping provided a remarkable decrease in the electrical resistance of the sensing layer at the working temperature of the sensors (250-300 C). The sensors based on Al-doped ZnO exhibited a higher response than the pure ZnO sample, allowing the detection of CO at sub-ppm concentrations in air. The enhancement in sensing properties was discussed in terms of the characterization and electrical data. © 2014 Elsevier B.V. All rights reserved.


Larbi A.,National Engineering School of Tunis | Dahman H.,Applied NanoMaterials | Kanzari M.,National Engineering School of Tunis | Kanzari M.,University of Tunis
Vacuum | Year: 2014

In this paper we present the influence of substrate temperature on structural and optical characteristics of the ternary Sn3Sb 2S6. The samples were deposited by vacuum thermal evaporation onto glass substrates at various substrate temperatures (30-60-100-140-160) °C. The films were analyzed by X-ray diffraction, atomic force microscopy (AFM) and spectrophotometric measurements. The XRD analysis showed the presence of only homogenous Sn3Sb2S6 phase. The surface roughness of the deposited films varied between 3.6 and 16 nm with decreasing the substrate temperature from 160 to 30°C. We found that by increasing the substrate temperature from 30 to 160°C, the optical band gap decreased from 1.47 to 1.18 eV. The absorption coefficients of the films are in the range of 105-106 cm-1. The refractive index n has been analyzed according to the Wemple-Di Domenico single oscillator model and the values of E0 and Ed were determined. © 2014 Elsevier Ltd. All rights reserved.


Azam A.,King Abdulaziz University | Azam A.,Applied NanoMaterials | Ahmed A.S.,Applied NanoMaterials | Oves M.,Aligarh Muslim University | And 2 more authors.
International Journal of Nanomedicine | Year: 2012

Background: CuO is one of the most important transition metal oxides due to its captivating properties. It is used in various technological applications such as high critical temperature superconductors, gas sensors, in photoconductive applications, and so on. Recently, it has been used as an antimicrobial agent against various bacterial species. Here we synthesized different sized CuO nanoparticles and explored the size-dependent antibacterial activity of each CuO nanoparticles preparation. Methods: CuO nanoparticles were synthesized using a gel combustion method. In this approach, cupric nitrate trihydrate and citric acid were dissolved in distilled water with a molar ratio of 1:1. The resulting solution was stirred at 100°C, until gel was formed. The gel was allowed to burn at 200°C to obtain amorphous powder, which was further annealed at different temperatures to obtain different size CuO nanoparticles. We then tested the antibacterial properties using well diffusion, minimum inhibitory concentration, and minimum bactericidal concentration methods. Results: XRD spectra confirmed the formation of single phase CuO nanoparticles. Crystallite size was found to increase with an increase in annealing temperature due to atomic diffusion. A minimum crystallite size of 20 nm was observed in the case of CuO nanoparticles annealed at 400°C. Transmission electron microscopy results corroborate well with XRD results. All CuO nanoparticles exhibited inhibitory effects against both Gram-positive and -negative bacteria. The size of the particles was correlated with its antibacterial activity. Conclusion: The antibacterial activity of CuO nanoparticles was found to be size-dependent. In addition, the highly stable minimum-sized monodispersed copper oxide nanoparticles synthesized during this study demonstrated a significant increase in antibacterial activities against both Gram-positive and -negative bacterial strains. © 2012 Azam et al, publisher and licensee Dove Medical Press Ltd.


Dahman H.,Applied NanoMaterials | Rabaoui S.,Applied NanoMaterials | Alyamani A.,King Abdulaziz City for Science and Technology | El Mir L.,Applied NanoMaterials | El Mir L.,Islamic University
Vacuum | Year: 2014

In this paper, Cu2SnS3 film with about 600 nm thickness was successfully prepared, for the first time, by one step sol-gel spin coating route on glass substrate. The sample was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-vis spectroscopy. The X-ray diffraction result showed that the obtained layer was composed by Cu2SnS3 phase and has a tetragonal (I-42m) structure with (112) preferential orientation. The grain size calculated with Scherrer's formula was about 5 nm. The AFM and SEM studies reveal that the synthesized film is rough and compact without any visible cracks or pores. The film has high absorbance in the visible range (α > 5104 cm-1 at 2.88 eV) and direct band gap energy of 1.34 eV. This makes the material as a good candidate for low cost and friendly environment thin film solar cells. © 2013 Elsevier Ltd. All rights reserved.


Ramadoss A.,Applied NanoMaterials | Saravanakumar B.,Jeju National University | Lee S.W.,Georgia Institute of Technology | Kim Y.-S.,Georgia Institute of Technology | And 4 more authors.
ACS Nano | Year: 2015

In this work, we have fabricated a piezoelectric-driven self-charging supercapacitor power cell (SCSPC) using MnO2 nanowires as positive and negative electrodes and a polyvinylidene difluoride (PVDF)-ZnO film as a separator (as well as a piezoelectric), which directly converts mechanical energy into electrochemical energy. Such a SCSPC consists of a nanogenerator, a supercapacitor, and a power-management system, which can be directly used as a power source. The self-charging capability of SCSPC was demonstrated by mechanical deformation under human palm impact. The SCSPC can be charged to 110 mV (aluminum foil) in 300 s under palm impact. In addition, the green light-emitting diode glowed using serially connected SCSPC as the power source. This finding opens up the possibility of making self-powered flexible hybrid electronic devices. © 2015 American Chemical Society.


Nakate U.T.,Applied NanoMaterials | Kale S.N.,Applied NanoMaterials
Materials Today: Proceedings | Year: 2016

The surfactant-free nanocrystalline NiCo2O4 nanoplates were synthesized using microwave irradiation method using metal chloride salts as precursors. Synthesized NiCo2O4nanoplateswere characterized using X-ray diffraction (XRD), fiel emission scanning electron microscope (FE-SEM), Energy dispersive spectrometer (EDS) for their structural and morphological and elemental analysis. Brunauer-Emmett-Teller (BET) surface area measurements show the surface area to be 11.60 m2/g and the crystallite size to be ~14.74 nm. The optical studies show two Co3+ spin states contributions to band gap with values as 1.90 eV and 3.3 eV. The samples show high hydrophobicity, with good magnetic properties and conductivity. © 2016 Elsevier Ltd.


Kaptay G.,Applied NanoMaterials | Kaptay G.,University of Miskolc
Journal of Materials Science | Year: 2012

The abbreviation "nano-Calphad" stands for "Calculation of Phase Diagrams for nano-systems." Nanosystems contain at least one phase or at least one interface layer (film, complexion) with at least one of its dimensions being below 100 nm. The essential task of nano-Calphad is to introduce correctly the surface term into the equation for the Gibbs energy. In view of the controversy between the Kelvin and Gibbs equations, even this task does not have an obvious solution (in the present paper, the Gibbs method is preferred). However, there are many further questions to be addressed when the Calphad method is converted into the nano-Calphad method. This paper attempts to give an as full as possible list of all those problems, such as: (i) the definition of a new, independent thermodynamic variable, (ii) the extended phase rule, (iii) the curvature dependence of the interfacial energies, (iv) the dependence of interfacial energies on the separation between interfaces (including the problem of surface melting), (v) the role of the shapes and relative arrangement of phases, (vi) the role of the substrate (if such exists), and (vii) the role of segregation, taking into account its effect on the mass balance within multi-component nano-phases and its surface phase transition and complexion. It is also shown that the well-known meaning of the tie line in binary two-phase fields is lost in nanosystems. The issues related to the size limits of materials thermodynamics and the need for a more complete databanks on molar volumes and interfacial energies are discussed. © Springer Science+Business Media, LLC 2012.


Budai I.,Applied NanoMaterials | Budai I.,Debrecen University
Materialwissenschaft und Werkstofftechnik | Year: 2012

Aluminum matrix monotectic alloys with a homogeneous distribution of the second phase droplets can be obtained in large ingots, if the droplets are stabilized by solid particles of optimized wettability at the interface of the two, immiscible liquid metals. In this paper, Al-matrix emulsions with Cd-rich droplets, stabilized by Al 4Sr intermetallic particles are prepared, based on our previous paper. The new information in the present paper is the development of a new type of a mixer, allowing increased rotational speed, and hence, more efficient emulsification without the danger of mixing the liquid metals out of the crucible. As the comparative experiments proved, the ratio of emulsified Cd-rich liquid was found to increase considerably when the old mixer was replaced by the new one. Particularly, there is no 1-phase Cd-rich sedimentation found at the bottom of the crucible when the mixer of the new design is applied. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


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