A Nano Capacitor Including Graphene Layers Composed with Doped Boron and Nitr...CrimsonPublishersRDMS
A Nano Capacitor Including Graphene Layers Composed with Doped Boron and Nitrogen by Majid Monajjemi* in Crimson Publishers: Peer Reviewed Material Science Journals
Study of Microstructural, Electrical and Dielectric Properties of La0.9Pb0.1M...Scientific Review SR
The present work studies the microstructural and electrical properties of La0.9Pb0.1MnO3 and La0.8Y0.1Pb0.1MnO3 ceramics synthesized by solid-state route method. Microstructure and elemental analysis of both samples were carried out by field emission scanning electron microscope (FESEM) and energy dispersive spectroscopy (EDS) method, respectively. Phase analysis by X-ray diffraction (XRD) indicated formation of single phase distorted structure. The XRD data were further analyzed by Rietveld refinement technique. Raman analysis reveals that Y atom substitutes La site into the LPMO with shifting of phonon modes. The temperature variation of resistivity of undoped and Y-doped La0.9Pb0.1MnO3 samples have been investigated. The electrical resistivity as a function of temperature showed that all samples undergo an metal-insulator (M-I) transition having a peak at transition temperature TMI. Y-doping increases the resistivity and the metal-insulator transition temperature (TMI) shifts to lower temperature. The temperature-dependent resistivity for temperatures less than metal-insulator transition is explained in terms the quadratic temperature dependence and for T > TMI, thermally activated conduction (TAC) is appropriate. Variation of frequency dispersion in permittivity and loss pattern due to La-site substitution in LPMO was observed in the dielectric response curve.
A Nano Capacitor Including Graphene Layers Composed with Doped Boron and Nitr...CrimsonPublishersRDMS
A Nano Capacitor Including Graphene Layers Composed with Doped Boron and Nitrogen by Majid Monajjemi* in Crimson Publishers: Peer Reviewed Material Science Journals
Study of Microstructural, Electrical and Dielectric Properties of La0.9Pb0.1M...Scientific Review SR
The present work studies the microstructural and electrical properties of La0.9Pb0.1MnO3 and La0.8Y0.1Pb0.1MnO3 ceramics synthesized by solid-state route method. Microstructure and elemental analysis of both samples were carried out by field emission scanning electron microscope (FESEM) and energy dispersive spectroscopy (EDS) method, respectively. Phase analysis by X-ray diffraction (XRD) indicated formation of single phase distorted structure. The XRD data were further analyzed by Rietveld refinement technique. Raman analysis reveals that Y atom substitutes La site into the LPMO with shifting of phonon modes. The temperature variation of resistivity of undoped and Y-doped La0.9Pb0.1MnO3 samples have been investigated. The electrical resistivity as a function of temperature showed that all samples undergo an metal-insulator (M-I) transition having a peak at transition temperature TMI. Y-doping increases the resistivity and the metal-insulator transition temperature (TMI) shifts to lower temperature. The temperature-dependent resistivity for temperatures less than metal-insulator transition is explained in terms the quadratic temperature dependence and for T > TMI, thermally activated conduction (TAC) is appropriate. Variation of frequency dispersion in permittivity and loss pattern due to La-site substitution in LPMO was observed in the dielectric response curve.
Modulus spectroscopy study on Ferroelectric Lithium and Titanium modified Lea...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Effect of morphology on the photoelectrochemical performance of nanostructure...Pawan Kumar
Cu2O is a promising earth-abundant semiconductor photocathode for sunlight-driven water splitting. Characterization results are presented to show how the photocurrent density (Jph), onset potential (Eonset), band edges, carrier density (NA), and interfacial charge transfer resistance (Rct) are affected by the morphology and method used to deposit Cu2O on a copper foil. Mesoscopic and planar morphologies exhibit large differences in the values of NA and Rct. However, these differences are not observed to translate to other photocatalytic properties of Cu2O. Mesoscopic and planar morphologies exhibit similar bandgap (e.g.) and flat band potential (Efb) values of 1.93 ± 0.04 eV and 0.48 ± 0.06 eV respectively. Eonset of 0.48 ± 0.04 eV obtained for these systems is close to the Efb indicating negligible water reduction overpotential. Electrochemically deposited planar Cu2O provides the highest photocurrent density of 5.0 mA cm−2 at 0 V vs reversible hydrogen electrode (RHE) of all the morphologies studied. The photocurrent densities observed in this study are among the highest reported values for bare Cu2O photocathodes.
The single crystal of MoSe2 grown by
chemical vapour transport (CVT)technique are used for the
fabrication of Photoelectro chemical (PEC) solar cells. The
effect of the illumination intensity on the conversion efficiency
of the fabricated PEC solar cell is studied.
Comprehensive identification of sensitive and stable ISFET sensing layer high...IJECEIAES
The ISFET sensing membrane is in direct contact with the electrolyte solution, determining the starting sensitivity of these devices. A SiO2 gate dielectric shows a low response sensitivity and poor stability. This paper proposes a comprehensive identification of different high-k materials which can be used for this purpose, rather than SiO2. The Gouy-Chapman and Gouy-Chapman-Stern models were combined with the Site-binding model, based on surface potential sensitivity, to achieve the work objectives. Five materials, namely Al2O3, Ta2O5, Hfo2, Zro2 and SN2O3, which are commonly considered for micro-electronic applications, were compared. This study has identified that Ta2O5 have a high surface potential response at around 59mV/pH, and also exhibits high stability in different electrolyte concentrations. The models used have been validated with real experimental data, which achieved excellent agreement. The insights gained from this study may be of assistance to determine the suitability of different materials before progressing to expensive real ISFET fabrication.
Synthesis and structural characterization of cd s nanocrystals added with pb2+eSAT Journals
Abstract
For the past few years, the prepration and characterization of nanocrystals of materials have become an interesting area in the
research activity. CdS (Cadmium Sulphide) is a well known semi conducting material which finds applications in optical devices.
In the present study, we have made an attempt to investigate the effect of Pb2+ as impurity on the properties of CdS nanocrystals.
The samples were prepared by using simple domestic microwave assisted solvothermal method with ethylene glycol as solvant.
The samples prepared were annealed to have good ordering. X-ray diffraction measurements were carried out for all the smples.
The grain size, lattice parameter and yield were determined. The colour before and after annealing was noted. EDX and SEM
analyses were also done. The prepared samples were electrically characterized by making dielectric measurements on the
prepared pellets. The present study indicates that the polarization mechanism in the nano crystals considered is mainly
contributed by the space charge polarization.
Keywords: Semiconducting II –IV materieals, Cadmium sulphide, XRD patterns, solvothermal method, electrical
measurements
Study the effect of Mn2+ ions on the ac electrical properties of some iron do...IJRES Journal
Oxide glasses doped with transition metal ions are of high interest because of their variant applications in both science and technology fields. However, the normal melt quench method have used to prepared some iron doped phosphate glasses according the following molecular formula: (65-x) mol% P2O5 - 20 mol% Na2O - 15 mol% Fe2O3 - x mol% MnO, Where x= 0, 5,10, 20, 25. The room temperature Mössbauer Effect ME Spectra used to characterized the glassy state homogeneity of these glasses. ME spectra show, for all glasses, no magnetic field participate which mean good glassy state formation. The ac electrical transport properties were also measured, as function of temperature up to 500k. It was found that the ac conductivity increased with the gradual increase of Mn2+ cations, while the electrical activation energy decreased.
"Si chiamava Zaher Rezai. Il suo nome dirà qualcosa a qualcuno. Aveva 13 anni, o forse un pò di più. Era partito ancora bambino da Mazar-i Sharif. Aveva viaggiato avventurosamente fino a Venezia, l'ultimo tratto nascosto in un traghetto"
Modulus spectroscopy study on Ferroelectric Lithium and Titanium modified Lea...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Effect of morphology on the photoelectrochemical performance of nanostructure...Pawan Kumar
Cu2O is a promising earth-abundant semiconductor photocathode for sunlight-driven water splitting. Characterization results are presented to show how the photocurrent density (Jph), onset potential (Eonset), band edges, carrier density (NA), and interfacial charge transfer resistance (Rct) are affected by the morphology and method used to deposit Cu2O on a copper foil. Mesoscopic and planar morphologies exhibit large differences in the values of NA and Rct. However, these differences are not observed to translate to other photocatalytic properties of Cu2O. Mesoscopic and planar morphologies exhibit similar bandgap (e.g.) and flat band potential (Efb) values of 1.93 ± 0.04 eV and 0.48 ± 0.06 eV respectively. Eonset of 0.48 ± 0.04 eV obtained for these systems is close to the Efb indicating negligible water reduction overpotential. Electrochemically deposited planar Cu2O provides the highest photocurrent density of 5.0 mA cm−2 at 0 V vs reversible hydrogen electrode (RHE) of all the morphologies studied. The photocurrent densities observed in this study are among the highest reported values for bare Cu2O photocathodes.
The single crystal of MoSe2 grown by
chemical vapour transport (CVT)technique are used for the
fabrication of Photoelectro chemical (PEC) solar cells. The
effect of the illumination intensity on the conversion efficiency
of the fabricated PEC solar cell is studied.
Comprehensive identification of sensitive and stable ISFET sensing layer high...IJECEIAES
The ISFET sensing membrane is in direct contact with the electrolyte solution, determining the starting sensitivity of these devices. A SiO2 gate dielectric shows a low response sensitivity and poor stability. This paper proposes a comprehensive identification of different high-k materials which can be used for this purpose, rather than SiO2. The Gouy-Chapman and Gouy-Chapman-Stern models were combined with the Site-binding model, based on surface potential sensitivity, to achieve the work objectives. Five materials, namely Al2O3, Ta2O5, Hfo2, Zro2 and SN2O3, which are commonly considered for micro-electronic applications, were compared. This study has identified that Ta2O5 have a high surface potential response at around 59mV/pH, and also exhibits high stability in different electrolyte concentrations. The models used have been validated with real experimental data, which achieved excellent agreement. The insights gained from this study may be of assistance to determine the suitability of different materials before progressing to expensive real ISFET fabrication.
Synthesis and structural characterization of cd s nanocrystals added with pb2+eSAT Journals
Abstract
For the past few years, the prepration and characterization of nanocrystals of materials have become an interesting area in the
research activity. CdS (Cadmium Sulphide) is a well known semi conducting material which finds applications in optical devices.
In the present study, we have made an attempt to investigate the effect of Pb2+ as impurity on the properties of CdS nanocrystals.
The samples were prepared by using simple domestic microwave assisted solvothermal method with ethylene glycol as solvant.
The samples prepared were annealed to have good ordering. X-ray diffraction measurements were carried out for all the smples.
The grain size, lattice parameter and yield were determined. The colour before and after annealing was noted. EDX and SEM
analyses were also done. The prepared samples were electrically characterized by making dielectric measurements on the
prepared pellets. The present study indicates that the polarization mechanism in the nano crystals considered is mainly
contributed by the space charge polarization.
Keywords: Semiconducting II –IV materieals, Cadmium sulphide, XRD patterns, solvothermal method, electrical
measurements
Study the effect of Mn2+ ions on the ac electrical properties of some iron do...IJRES Journal
Oxide glasses doped with transition metal ions are of high interest because of their variant applications in both science and technology fields. However, the normal melt quench method have used to prepared some iron doped phosphate glasses according the following molecular formula: (65-x) mol% P2O5 - 20 mol% Na2O - 15 mol% Fe2O3 - x mol% MnO, Where x= 0, 5,10, 20, 25. The room temperature Mössbauer Effect ME Spectra used to characterized the glassy state homogeneity of these glasses. ME spectra show, for all glasses, no magnetic field participate which mean good glassy state formation. The ac electrical transport properties were also measured, as function of temperature up to 500k. It was found that the ac conductivity increased with the gradual increase of Mn2+ cations, while the electrical activation energy decreased.
"Si chiamava Zaher Rezai. Il suo nome dirà qualcosa a qualcuno. Aveva 13 anni, o forse un pò di più. Era partito ancora bambino da Mazar-i Sharif. Aveva viaggiato avventurosamente fino a Venezia, l'ultimo tratto nascosto in un traghetto"
L'opuscolo informativo è stato realizzato a cura del servizio tecnico boschi per dare una completa informazione dei boschi che stanno nascendo nel comprensorio di Mestre. Una pubblicazione sintetica e chiara che viene accompagnata da immagini e dati tecnici dei boschi.
A cura del servizio tecnico dell'Istituzione Bosco e Grandi Parchi è stato realizzato un percorso didattico illustrativo visibile sui totem collocati nel bosco. I visitatori che vogliono approfondire la conoscenza della flora e fauna presente nel Bosco dell'Osellino possono scaricare o visualizzare la guida riportata integralmente.
Disegni :Daniela Gerometta
A cura del servizio tecnico dell'Istituzione Bosco e Grandi Parchi è stato realizzato un percorso didattico illustrativo visibile sui totem collocati allinterno del parco San Giuliano. I visitatori che vogliono approfondire la conoscenza degli alberi presenti al parco San Giuliano possono scaricare o visualizzare integralmente la pubblicazione
Come è tradizione dal 2003, l'Associazione per il Bosco di Mestre, Istituzione Bosco e Grandi Parchi e gli Itinerari Educativi del Comune di Venezia, in primavera, organizzazno la manifestazione "un albero per ogni bambino"presso le aree del Bosco a Favaro Veneto: Sono invitati tutti i bambini e tutte le bambine della prima classe elementare dei plessi scolastici di Mestre e Venezia e partecipano alla messa a dimora di giovani piante, futuri alberi del bosco di Mestre.
Durante la manifestazione i giovani invitati assistono ad uno spettacolo di animazione legato al tema del bosco, partecipano all'impianto dei nuovi alberi, uno per classe, e gustano una merenda distribuita dai volontari della Protezione Civile che allestiscono un gazego e si rendono utili affinchè la festa si svolga al meglio.
Grazie all'ACTV, che mette a disposizione gratuitamente i suoi mezzi, i bambini ed i loro insegnanti raggiungono il bosco per trascorrere la mattina tra gioco e natura.
L'obiettivo principale di questa manifestazione è di sensibilizzare le nuove generazioni, per diventare nel prossimo futuro cittadini più consapevoli e rispettosi dell'ambiente in cui cresciamo e viviamo
International Journal of Engineering and Science Invention (IJESI)inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Fabrication and studying the dielectric properties of (polystyrene-copper oxi...journalBEEI
The preparation of (polystyrene-copper oxide) nanocomposites have been investigated for piezoelectric application. The copper oxide nanoparticles were added to polystyrene by different concentrations are (0, 4, 8 and 12) wt.%. The structural and A.C electrical properties of (PS-CuO) nanocomposites were studied. The results showed that the dielectric constant and dielectric loss of (PS-CuO) nanocomposites decrease with increase in frequency. The A.C electrical conductivity increases with increase in frequency. The dielectric constant, dielectric loss and A.C electrical conductivity of polystyrene increase with increase in copper oxide nanoparticles concentrations. The results of piezoelectric application showed that the electrical resistance of (PS-CuO) nanocomposites decreases with increase in pressure.
Microstructural and Dielectric Characterization of Sr doped Ba(Fe0.5Ta0.5)O3 ...theijes
Solid state reaction method was used to synthesize Ba1-xSrx(Fe0.5Ta0.5)O3 ceramic(x=0, 0.1, 0.2, 0.3, 0.4 and 0.5). The raw materials of making Sr doped Ba(Fe0.5Ta0.5)O3 were BaCO3, SrCO3, Fe2O3, Ta2O5 (purity better than 99%). Pellet and ring shaped samples prepared from each composition were sintered at 1400 and 1450ºC for 5 hour. The phase formation of Ba1-xSrx(Fe0.5Ta0.5)O3 was checked using X-ray diffraction (XRD) technique and observed a cubic perovskite crystal structure in space group Pm3m (221). Microstructure of the individual compound was examined by the field emission scanning electron micrograph (FESEM). Grain size was found to be varied with Sr content. The lattice parameter decreased with increasing Sr content. Dielectric spectroscopy was applied to investigate the electrical properties of BSFT at room temperature and in a frequency range of 100Hz–100 MHz. An analysis of the dielectric constant εʹ and loss tangent tan with frequency was performed assuming a distribution of relaxation times. The low frequency dielectric dispersion corresponds to the DC electrical conductivity.
Ultra-optical characterization of thin film solar cells materials using core...IJECEIAES
This paper investigates on new design of heterojunction quantum dot (HJQD) photovoltaics solar cells CdS/PbS that is based on quantum dot metallics PbS core/shell absorber layer and quantum dot window layer. It has been enhanced the performance of traditional HJQD thin film solar cells model based on quantum dot absorber layer and bulk window layer. The new design has been used sub-micro absorber layer thickness to achieve high efficiency with material reduction, low cost, and time. Metallicssemiconductor core/shell absorber layer has been succeeded for improving the optical characteristics such energy band gap and the absorption of absorber layer materials, also enhancing the performance of HJQD ITO/CdS/QDPbS/Au, sub micro thin film solar cells. Finally, it has been formulating the quantum dot (QD) metallic cores concentration effect on the absorption, energy band gap and electron-hole generation rate in absorber layers, external quantum efficiency, energy conversion efficiency, fill factor of the innovative design of HJQD cells.
Electrical transport properties of nanocrystalline and bulk nickel.pdfProximaCentauri15
In this work, the comparative study on the electrical transport properties of nanocrystalline nickel
ferrite (NiFe2O4) and its bulk counterpart has been carried out in detail by using complex impedance
spectroscopy in a wide range of frequencies (100 Hz–1 MHz) and temperatures (40 °C–320 °C). The
dispersive nature of the dielectric constant and loss factor is explained by the Maxwell-Wagner model
and Koop’s phenomenological theory. The value of the dielectric constant for nanocrystalline nickel
ferrite is found to be more as compared to its bulk counterpart. The frequency variation dielectric
permittivity is well fitted with the modified Debye formula, which suggests the presence of multiple
relaxation processes. The temperature dependent ac conductivity follows Jonscher’s universal power
law and reveals the presence of multiple transport mechanisms from small polaron hopping (SPH) to
correlated barrier hopping (CBH) mechanism near 200 °C. The estimated values of Mott parameters
are found to be satisfactory. Thermally activated relaxation phenomena have been confirmed by
scaling curves of imaginary impedance (Z) andmodulus (M). The comparison between the Z and
M spectra indicates that both long-range and short-rangemovement of charge carriers contribute to
dielectric relaxation with short-range charge carriers predominating at low temperatures while longrange
charge carriers are dominating at high temperatures. Analysis of the semicircular arcs of Nyquist
plot indicates the presence of grain boundary contribution to the electrical conduction process for the
nanocrystalline sample at high temperatures. The non-Debye type of relaxation has been examined by
stretching exponential factor (β) which has been estimated by fitting the modifiedKWW
(Kohlrausch-Williams-Watts) equation to the imaginary electric modulus curve. The value of β is
found to be strongly temperature dependent and its value for the nanocrystalline sample is less than
that of the bulk system which is explained on the basis of dipole-dipole interaction.
and Heat. The smoke sensors function by
detecting the presence of smoke particles either in a
photoelectric chamber or in an ionization chamber.
These sensors being placed on the ceiling Fire is seldom
detected in the incipient stage.
Loss due to fire damage not only accounts for
equipment and property destruction, but also loss of
data, interruption of service, cleanup and recovery cost.
On an average about $250,000 per incident.
The key to control these damages are not only
to detect fire as early as possible but also identify
exactly the origin of incident. All over the world the
latest technologies are being tested upon and
implemented to detect the fire at early stage. However
these require expensive proprietary solutions and may
not be easily deployable in existing infrastructure.
Technologies do exist today to detect fire at an
early stage but are expensive in nature and requires
pre-engineered planed deployment.
This paper demonstrates means to detect the
fire instantly and extinguished at initial stage. An
autonomous robot equipped with advanced fire
detection technology detect fire at initial stage,
extinguished by small conceived extinguisher, sound
hooter and also send message to pre assigned number
through GSM modem. A novel approach using color
sensor TCS3200 and simple LDR (Light Dependent
Register) makes the system highly cost effective. It is
effectively a fire surveillance system that continuously
read sensor values and received data are processed by
various complex algorithms to ensure fire detection
with highly reduced false alarm and immediate action.
It also covers a large area and thus the system costs are
minimized. It is highly useful for domestics as well as
industrial environment. The total system cost is less
than $200.
It is important to note that electrical supplies
must be cut down in case of a fire incident and thus also
takes the fire detection system offline. This system being
self-sufficient and battery powered can still function.
Amorphous-nano-crystalline silicon composite thin films (a-nc-Si:H) samples were synthesized by
Plasma Enhanced Chemical Vapor Deposition technique. The measurement of DC conductivities was
accomplished using Dielectric spectroscopy (Impedance Spectroscopy) in wide frequency and temperature range.
In analysis of impedance data, two approaches were tested: the Debye type equivalent circuit with two parallel R
and CPEs (constant phase elements) and modified one, with tree parallel R and CPEs including crystal grain
boundary effects. It was found that the later better fits to experimental results properly describes crystal grains
dielectric effect and hydrogen concentration indicating presence of strain. The amorphous matrix showed larger
resistance and lower capacity than nano-crystal phase. Also it was found that composite silicon thin film cannot
be properly described by equivalent circuit only with resistors and constant phase elements in serial relation
Effect of mesh grid structure in reducing hot carrier effect of nmos device s...ijcsa
This paper presents the critical effect of mesh grid that should be considered during process and device
simulation using modern TCAD tools in order to develop and optimize their accurate electrical
characteristics. Here, the computational modelling process of developing the NMOS device structure is
performed in Athena and Atlas. The effect of Mesh grid on net doping profile, n++, and LDD sheet
resistance that could link to unwanted “Hot Carrier Effect” were investigated by varying the device grid
resolution in both directions. It is found that y-grid give more profound effect in the doping concentration,
the junction depth formation and the value of threshold voltage during simulation. Optimized mesh grid is
obtained and tested for more accurate and faster simulation. Process parameter (such as oxide thicknesses
and Sheet resistance) as well as Device Parameter (such as linear gain “beta” and SPICE level 3 mobility
roll-off parameter “ Theta”) are extracted and investigated for further different applications.
Electrochemical Supercapacitive Performance of Sprayed Co3O4 ElectrodesIJERA Editor
Nanocrystalline cobalt oxide (Co3O4) thin film electrodes were fabricated by spray pyrolysis method on conducting fluorine doped tin oxide (FTO) substrates using ammonia complexed with cobalt chloride (CoCl2. 6H2O) solution. The structural and morphological properties of Co3O4electrodes were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM).The surface morphology study showed the film formation of porous surface with clusters. The electrochemical supercapacitive properties ofCo3O4 electrodes were evaluated using cyclic voltammetry and galvanostatic charge-discharge method. The Co3O4electrodes showed maximum specific capacitance of 168 F/g in 1 M aqueous KOH electrolyte at the scan rate of 20 mV/s. The maximum specific energy and specific power of the cell are 2.2Wh/kg and 0.23 kW/kg, respectively.
1. Short Communication
Effect of zirconium oxide nanoparticles on surface
morphology and energy storage of electrochemical capacitors
Mahdi Nasibi a,b,n
, Mahdi R. Sarpoushi a
, Rouhallah Hesan c
,
Mohammad Ali Golozar d
, Masoud Moshrefifar c
a
Technical Inspection Engineering Department, Petroleum University of Technology, Abadan, Iran
b
Health and Safety Engineering (HSE) Office, NIOPDC, Yazd Region, Yazd, Iran
c
Materials and Mining Engineering Department, Yazd University, Yazd, Iran
d
Materials Science and Engineering Department, Isfahan University of Technology, Isfahan, Iran
a r t i c l e i n f o
Keywords:
Supercapacitors
Nanomaterials
Morphology
ZrO2
a b s t r a c t
In this study, the effect of mixing zirconium oxide nanoparticles and carbon black particles
on surface morphology and electrochemical performance of prepared electrodes were
investigated. Scanning electron microscopy was used to characterize microstructure and
nature of nanocomposites. Charge stored (q) on different nanoparticle containing
electrodes was calculated and the effect of surface morphology on charge storage was
discussed. It is concluded that charge stored on the electrode shows an n-like change by
increasing nanoparticle content of electrodes. Addition of nanoparticle increases qn
O/qn
T
(from 0.05 to 0.18) which confirms the higher current response and higher voltage
reversal at the end potentials.
Crown Copyright & 2014 Published by Elsevier Ltd. All rights reserved.
1. Introduction
Electrochemical capacitors (ECs), with a combination of
high power density and high energy density, can be used
as a complementary energy-storage device along with a
primary power source, such as a battery or a fuel cell, for
power enhancement in short pulse applications [1]. High
cycle life, high energy efficiency and high self-discharge
rate are some of the supercapacitors characteristics [2,3].
Today, many laboratories are actively engaged in develop-
ment of well-known type of supercapacitors, viz., electro-
chemical double-layer, pseudo and hybrid supercapacitors,
and most research has been focused on development of
different electrode materials [4,5]. For practical applica-
tions, an EC must fulfill the following technical require-
ments: high specific capacitance, long cycle life and
high charge/discharge rate. Today, using nanoparticles is
of interest in order to improve these parameters. So,
nanoparticles distribution quality on the electrode surface
is of most important parameters [6]. In our previous work,
we investigated the effect of different mixing processes of
electrode material on dispersion quality of nanoparticles
which change their electrochemical performance. In this
work, we investigate the effect of nanoparticle contents of
the electrode material on microstructure and nature of
prepared electrodes using scanning electron microscopy,
and potentiodynamic polarization techniques. At the
end, quantitative measurements were reported for further
investigations.
2. Experimental
2.1. Materials
High purity (499%) nano-sized zirconium oxide (ZrO2)
particles (o100 nm), nickel foil (99.99% with 0.125 mm
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/mssp
Materials Science in Semiconductor Processing
http://dx.doi.org/10.1016/j.mssp.2014.03.037
1369-8001/Crown Copyright & 2014 Published by Elsevier Ltd. All rights reserved.
n
Corresponding author. Tel.: þ98 9113708480; fax: þ98 6314423520.
E-mail address: mahdi.nasibi@gmail.com (M. Nasibi).
Materials Science in Semiconductor Processing 24 (2014) 260–264
2. thickness) and polytetrafluoroethylene (o2 μm) were
purchased from Aldrich, USA. All other chemicals used in
this study were purchased from Merck, Germany. Carbon
black particles (o2 μm) were purchased from Degussa,
Germany. In order to prepare electrodes, the mixture
containing different wt% ZrO2 and carbon black (CB) and
10 wt% polytetrafluoroethylene (PTFE) was well mixed in
ethanol to form a paste and then was pressed onto the
nickel foil (25 MPa), which served as a current collector
(surface was 0.785 cm2
). The typical mass weight of
electrode material was 30 mg. The used electrolyte was
2 M KCl.
2.2. Characterization
The electrochemical measurements were performed
using an Autolab (Netherlands) potentiostat Model
PGSTAT 302N. CV tests were conducted at various scan
rates (s) with recording of potential response currents, I,
which is related by C¼I/s where C is the capacitance of the
electrode interface. The specific capacitance C (FgÀ1
) of the
active material was determined by integrating either the
oxidative or reductive parts of the cyclic voltammogram
curve to obtain voltammetric charge Q (C). This charge was
divided by mass of active material m (g) in the electrode
and width of the potential window of the cyclic voltam-
mogram ΔE (V), i.e., C¼Q/(ΔEm) [7]. The morphology and
nature of the prepared electrodes were studied using
scanning electron microscopy (TESCAN, USA).
3. Results and discussion
Nanoparticles distribution quality on the electrode
surface is one of the key parameters which controls the
electrical performance of nanoparticle containing electro-
des for supercapacitors. Using macroparticles like used
carbon black particles which store electrical energy
through the double layer mechanism, will make macro-
pores and macrogrooves with deep and hollow shapes on
surface of the electrode. Using the nanoparticles will make
nanopores with shallow shapes. Therefore, mixing the
nanoparticles with macroparticles will have a significant
effect on the morphology and nature of the prepared
electrodes. One of the thinkable morphology changes
by mixing of the nanoparticles with macroparticles is
schematically illustrated in Fig. 1. In the absence of the
nanoparticles, macrogrooves produced between CB parti-
cles and these grooves are exposed to the electrolyte for
charge storage (Fig. 1(a)). As the nanoparticle content of
Fig. 1. (a–d) Schematic illustration of the surface changes by addition of
nanoparticles into the electrode material and, (e) SEM image obtained
from 30:60:10 electrode. (For interpretation of the references to color in
this figure, the reader is referred to the web version of this article.)
Fig. 2. Nyquist diagrams of different ZrO2-content electrodes in 2 M KCl
electrolyte.
M. Nasibi et al. / Materials Science in Semiconductor Processing 24 (2014) 260–264 261
3. the electrodes increases the macropores are filled with
nanoparticles and the depth of the macrogrooves are
decreased (Fig. 1(b) and (c)). Then, all grooves are filled
and the CB particles on the surface of the electrode are
covered with a thin layer of ZrO2 nanoparticles and finally,
macrogrooves are replaced with the nanoporous structure
prepared by the nanoparticles (Fig. 1(d)). Therefore, active
surface used for charge storage on the surface of the
electrode is replaced and this increases the specific surface
area of the prepared electrodes. SEM images obtained from
30:60:10 (CB:ZrO2:PTFE) electrodes (Fig. 1(e)) confirm the
presence of macrogrooves made between the CB particles
(were shown by red lines) which nearly filled with ZrO2
nanoparticles. In these electrodes, CB particles can provide
a conductive channel due to their excellent conductivity.
Unlike the CB particles, metal oxides like ZrO2 are low
conductive materials but, have a pseudo capacitive char-
acteristic which can take place in redox reactions and
improve the energy storage capability of the electrodes.
This low conductivity decreases the charge stored on the
electrodes, especially at high sweep rates. Therefore, as the
nanoparticle content of the electrode increases, it is
proposed that the total charge stored on the electrode
surface increases, at first, due to increasing the specific
surface area and changing the charge storage mechanism
from double layer to pseudo, and then decreases due to
increasing the electrical resistance of the electrode.
The principle reaction involved in the charging and
discharging processes of zirconium dioxide in an aqueous
electrolyte can be described by reaction (1)
ZrIV
O2 þλþ
þeÀ
2ZrIII
OOλ ð1Þ
where λ denotes Kþ
, Hþ
.
Additionally, two mechanisms can be proposed for
supercapacitive charge storage in ZrO2. The first mechan-
ism is based on the intercalation/extraction of protons or
Fig. 3. Capacitance vs. potential curves obtained from (a) 90:00:10, (b) 50:40:10, (c) 30:60:10, (d) 20:70:10 and (e) 10:80:10 electrodes in 2 M KCl electrolyte.
M. Nasibi et al. / Materials Science in Semiconductor Processing 24 (2014) 260–264262
4. alkali cations into the oxide particles (denoted as reaction
(2)), whereas the second mechanism involves the surface
adsorption/desorption of proton or alkali cations probably
(denoted as reaction (3)):
ZrO2 þMþ
þeÀ
¼ ZrOOM ð2Þ
and
ðZrO2Þsurface þMþ
þeÀ
¼ ðZrOOMÞsurface ð3Þ
where Mþ
denotes Kþ
or H3Oþ
.
In order to gain a quantitative information on the effect of
surface changes on charge storage mechanism of the ZrO2/CB
electrodes by increasing the nanoparticle content of the
electrodes, the voltammograms obtained from different
nanoparticle containing electrodes were analyzed as a func-
tion of scan rate, according to the procedure reported by
Ardizzone et al. [8]. Then, the total charge and charge related
to the most accessible surface area were calculated.
Four prominent characteristics can be reported by chan-
ging the nanoparticle content of the electrodes from
obtained CV curves (Fig. 3): changing the shape of the CV
curves, changing the specific capacitance, deviation of the CV
curves from the classical square waveform expected for a
pure capacitor by increasing the sweep rate and, increasing
the voltage reversal at end potentials. As the nanoparticle
content of the electrodes increases electrical resistance of the
electrode increases (Fig. 2) and, up to 60%, the energy stored
on the electrode increases at first and then decreases due to
the electrical resistance and specific surface area changes of
the electrodes. Additionally, scan rate dependence of the
capacitance can be related to the less accessible surface area
(pores, cracks, etc) which become excluded as the rate
reaction is enhanced [9,10]. Ion diffusion ability of the
electrolyte into the surface of the electrode will have a
significant effect on the voltage reversal of the electrodes.
Improvement of the voltage reversal of the high nanoparticle
containing electrodes may be related to surface morphology
changes which change the active energy storage sites from
down the deep macropores to shallow nanopores. Calculat-
ing the total charge stored on electrodes and the charge
stored on less and more accessible surface area of the
electrodes are efficient indicators which indicate the charge
distribution on the electrode. In charge and discharge cycles,
the total charge can be written as a sum of an inner charge
from the less accessible reaction sites and an outer charge
from the more accessible reaction sites, i.e., q*
T¼q*
I þq*
O,
where q*
T, q*
I and q*
O are the total charge and charges related
to the inner and the outer surfaces, respectively [11]. The
extrapolation of q*
to v¼0 from 1/q*
vs. v1/2
plots obtained
from different nanoparticle containing electrodes (Fig. 4(a))
give the total charge qT which is the charge related to the
entire active surface of the electrode. In addition, extrapola-
tion of q*
to v¼1 (vÀ1/2
¼0) from the q*
vs. vÀ1/2
plots (Fig.
4(b)) give the outer charge q*
O, which is the charge due to
redox process on the most accessible active surface [8,11].
Total and outer charges vs. nanoparticle content of the
electrode obtained from different nanoparticle electrodes
were plotted in Fig. 4(c). Total and outer charge plots confirm
that the addition of nanoparticles increases and then
decreases the charge stored on the electrode surface, as
expected and explained above. Although, electrodes which
contain higher nanoparticle contents show higher ratio of the
outer charge to total charge (q*
O/q*
T) (increases from 0.05 to
0.18) which confirms the higher current response on voltage
reversal of high nanoparticle containing electrodes. Finally, it
is concluded that the 40:50:10 (CB:ZrO2:PTFE) electrodes
show better charge storage capability ($57C gÀ1
cmÀ2
)
(Fig. 4(c)). It may be due to the synergistic effect of the double
layer characteristic of the CB particles and the pseudo
characteristic of the ZrO2 nanoparticles. Changing the surface
morphology from macrogrooves to nanoporous structure
makes the 10:80:10 electrode to show the high outer charge
to total charge (q*
O/q*
T) ratio of as-high-as 0.18 which confirms
its high current response on voltage reversal.
4. Conclusions
In this study, effect of nanoparticle content of the ZrO2/
carbon black nanocomposite electrodes on the microstruc-
ture, nature and the electrochemical performance of the
prepared electrode were investigated. SEM images confirm
Fig. 4. (a) Extrapolation of q to v¼0 from the qÀ1
vs. v0.5
plot given the
total charge and (b) extrapolation of q to v¼1 from the q vs. vÀ0.5
plot
given the outer charge for CB electrodes. (c) Total and outer charge stored
on the different nanoparticle containing electrodes.
M. Nasibi et al. / Materials Science in Semiconductor Processing 24 (2014) 260–264 263
5. the surface changes from hallow macrogrooves to shallow
nanoporous structure by increasing the nanoparticle content
of the electrodes. Charge stored on the electrode surface
increases ($57C gÀ1
cmÀ2
obtained from 40:50:10 elec-
trode) at first, due to the synergistic effect of the carbon
black and ZrO2 nanoparticles, and then decreases by increas-
ing the nanoparticle content due to the electrical resistance
of the electrode. Finally, it is concluded that the current
response of the electrodes (q*
O/q*
T ratio of 0.18 obtained from
10:80:10 electrode) increases by addition of the nanoparti-
cles due to the surface changes from hollow macrogrooves to
the nanoporous structure.
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