Papers by Dr. Erum Pervaiz
The promising frontier for next-generation energy storage and clean energy production: A review on synthesis and applications of MXenes
Materials Science for Energy Technologies
Influence of Rare Earth (Gd<sup>3+</sup>) on Structural, Gigahertz Dielectric and Magnetic Studies of Cobalt ferrite
Journal of physics, Jun 10, 2013
ABSTRACT A series of Gd3+ doped nanocrystalline Co-ferrites CoGdxFe2-xO4 (x = 0.0 to 0.1) has bee... more ABSTRACT A series of Gd3+ doped nanocrystalline Co-ferrites CoGdxFe2-xO4 (x = 0.0 to 0.1) has been prepared by sol-gel auto combustion technique. Structural and morphology studies were performed using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Indexed XRD patterns confirm the formation of pure cubic spinel phase. Average crystallite sizes ranges from 16 nm to 25 nm ±2, were calculated from Sherrer&#39;s formula and Williamson Hall plots. Crystal strain increases with increase in doping amount of trivalent Gd ion. Lattice constant (a) and crystallite size D (311) increases with increase in Gd3+ concentration due to large ionic radii (0.94nm) of Gd3+ replacing Fe3+ (0.64nm). SEM images show the spherical morphology and uniform size distribution. Room temperature DC electrical resistivity decreases (~106) for x=0.025 then increases up to x=0.1 ~ (4.5×107). Dielectric properties have been studied using RF Impedance/material analyzer in the frequency range of 1 MHz to 1GHz. All the studied samples show a semi-conducting behavior as Permittivity and tangent loss (tanδ) decreases with the substitution of Gd3+ in parent crystal structure and have values of 4.92 and 0.016 at 1 GHz respectively. Complex impedance and Complex electric modulus plots were further studied for complete contribution of grains and grain boundary resistances to conduction and resonance frequencies respectively. Magnetic studies by Vibrating Sample Magnetometer (VSM) shows that magnetization (Ms) decreases with increase in Gd3+ concentration from 63 emu/gm to 27.26 emu/gm. Coercivity (Hc) first decreases for x=0.025, after which it increases to 2308 Oe for x=0.1.
Journal of Magnetism and Magnetic Materials, Oct 1, 2013
coexistence region of two phases called morphotropic phase boundary (MPB). Therefore, the formati... more coexistence region of two phases called morphotropic phase boundary (MPB). Therefore, the formation of MPB becomes one of the most important issues in PZT ceramics regarding excellent performance for practical applications [3]. Pb(Ni 1/3 Nb 2/3)O 3 (PNN) and Pb(Zn 1/3 Nb 2/3)O 3 (PZN) are two typical materials with relaxor ferroelectric behaviors, which are frequently combined with PZT to form new MPB and to improve further the electrical properties [4-7]. According to the previous studies, 0.5Pb(Ni 1/3 Nb 2/3) O 3-0.5Pb(Zr 1/2 Ti 1/2)O 3 ceramics with high dielectric permittivities of ε r = 4000 at room temperature (25 °C) and ε r = 22,000 at Curie temperature (125 °C) were prepared by a columbite precursor method [8]. A large piezoelectric coefficient (d 33) of 800 pC/N was achieved in the 0.1PZN-0.1PNN-0.8PZT (10 mol% Sr 2+ doped) prepared by the conventional solid-state reaction method [9]. Unfortunately, a high sintering temperature, approximately 1300 °C, is usually required to prepare those PZTbased ceramics, which limits drastically their use due to the evaporation of PbO and the compositional fluctuation. Hence, some sintering aids, such as ZnO/Li 2 O, CuO, LiBiO 2 and Li 2 CO 3 were added to decrease the sintering temperature as well as to improve the electrical properties of PMN-PNN-PZT (Note that PMN means Pb(Mg,Nb) O 3), PMN-PZT and PZT-PZN [10-14]. Until now, however, synthesis of high performance PZN-PNN-PZT ceramics with the addition of sintering aids has been rarely reported. In this work, the effects of Li 2 CO 3 addition on the sintering activity, structure, phase transition and electrical properties of PZN-PNN-PZT ceramics are systematically investigated. We focus on a low temperature synthesis and a significant enhancement of the piezoelectric coefficient as well as dielectric permittivity for top-level applications.
Frontiers in Materials, Nov 16, 2020
Energy storage devices are the ultimate flexible solution to overcome energy deficiency. Thre is ... more Energy storage devices are the ultimate flexible solution to overcome energy deficiency. Thre is a need is to find innovative nanomaterials to overcome the delays in efficiency and sustainability. Herein, we report the synthesis of hierarchical MoS 2 /rGO nanohybrids as electrode material for supercapacitors. Pure phase and flower-shaped molybdenum disulfide (MoS 2) nanosheets have been synthesized using a meek hydrothermal method followed by the preparation of MoS 2 /rGO nanohybrids. The physicochemical aspects and electrochemical properties have been carefully analyzed using cyclic voltammetry and galvanostatic charge-discharge method in the 1 M KCL electrolyte. The capacitance of MoS 2 and MoS 2 /rGO were found to be 297 F/g (66 mAh/g or 238 C/g) and 850 F/g (153.5 mAh/g or 552.5 C/g) at 1 A/g respectively, with 95.3% retention in capacitance after 10,000 cycles at 2 A/g. The improved electrochemical performance of the MoS 2 /rGO electrode could be ascribed to rapid diffusion pathways delivered by rGO and improved redox reactions of hierarchical MoS 2 nanosheets owing to the high surface area (391 m 2 /g). This feature enables a decrease in the entire impedance of electrodes which agrees with the findings obtained from electrochemical impedance spectroscopy.
Synthesis of carbon nanomaterials from different pyrolysis techniques: a review
Materials research express, May 16, 2018
High frequency AC response, DC resistivity and magnetic studies of holmium substituted Ni-ferrite: A novel electromagnetic material
Journal of Magnetism and Magnetic Materials, 2014
ABSTRACT Nanoparticles of holmium substituted nickel ferrites (NiHoxFe2-xO4) with x ranging from ... more ABSTRACT Nanoparticles of holmium substituted nickel ferrites (NiHoxFe2-xO4) with x ranging from 0.0 to 0.15 have been prepared by the sol-gel auto-combustion method. Structural and morphology studies have been performed by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). XRD patterns revealed the formation of pure spinel phase ferrites without any impurity phase. Lattice parameter increases along with a decrease in crystallite size with increasing the concentration of Ho3+ in the parent nickel ferrite due to large ionic radius of Ho3+ (0.901 Å) as compared to Fe3+ (0.67 Å). SEM shows the spherical, uniformly distributed homogenous nanoparticles grown by controlled reaction parameters of the sol-gel method. Complex permittivity (ɛ*) and complex electric modulus (M*) have been studied for the present nanoferrites in the frequency ranges of 1 MHz-1 GHz. Frequency dependent dielectric parameters (relative permittivity (ɛ‧), dielectric loss (ɛ″), dielectric loss tangent (tan δ)) decreases due to holmium substitution in nickel ferrites, showing the electrical conduction is decreasing in the nickel holmium ferrites with increase in the concentration of holmium. Complex modulus plots shows the poorly resolved semi circles and relaxation of nanoferrite is studied in the high frequency region. Also the relaxation time increases due to increase in x (0.0-0.15). DC electrical resistivity increases (107 Ω-cm-1010 Ω-cm) due to holmium ions substitution in nickel ferrites. Magnetic behavior was also characterized using a Vibrating Sample Magnetometer (VSM) under an applied magnetic field of 10 kOe and shows that magnetization decreases with increase in composition of holmium in nickel ferrites. High frequency behavior, low losses and very high DC electrical resistivity made the material a novel one for electromagnetic devices.
Gd 3+ doped nanocrystalline Co-ferrites CoGd x Fe 2-x O 4 (x =0.0 to 0.1) has been prepared by so... more Gd 3+ doped nanocrystalline Co-ferrites CoGd x Fe 2-x O 4 (x =0.0 to 0.1) has been prepared by sol-gel auto combustion technique. Structural and morphology studies were performed using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Indexed XRD patterns confirm the formation of pure cubic spinel phase. Average crystallite sizes ranges from 16 nm to 25 nm ±2. Lattice constant (a) and crystallite size D (311) increases with increase in Gd 3+ concentration due to large ionic radii (0.94nm) of Gd 3+ replacing Fe 3+ (0.64nm). FT-IR analysis shows the presence of two expected bands attributed to tetrahedral and octahedral metal oxygen vibrations. SEM images show the spherical morphology and uniform size distribution. Room temperature DC electrical resistivity decreases (~10 6) for x=0.025 then increases up to x=0.1 ~ (2.67x10 8) Ω-cm. Dielectric properties have been studied in the frequency range of 1 kHz to 5 MHz. Permittivity and tangent loss (tanδ) decreases with the substitution of Gd 3+ in parent crystal structure and have values of 12.4 and 0.0160 at 5 MHz respectively. Complex impedance plots were further studied for complete contribution of grains and grain boundary resistances. Magnetic studies shows that magnetization (Ms) de creases with increase in Gd 3+ concentration from 63 emu/gm to 27.26 emu/gm, thus the material is becoming low loss dielectric, highly resistive and soft magnetic due to Gd 3+ doping.
Experimental investigation of polysulfone modified cellulose acetate membrane for CO2/H2 gas separation
Korean Journal of Chemical Engineering, 2022
Processed gas streams from the water gas shift reactor (WGSR) are enriched with CO 2 and H 2 . Pu... more Processed gas streams from the water gas shift reactor (WGSR) are enriched with CO 2 and H 2 . Purification of H 2 from CO 2 for different applications is required because of its environmental and economic benefits. Among different separation technologies, membrane technology gets much attention due to its various advantages. In this work, cellulose acetate/polysulfone blended membranes were fabricated via solution casting method for CO 2 /H 2 separation. The separation performance of pure CA membrane was enhanced by addition of PSF. The fabricated membranes were analyzed through various characterization techniques, such as FTIR, SEM, DSC, and XRD. Gas permeation results show that permeability of CO 2 increased with increasing concentration of PSF. Notable permeability (P=80.51 Barrer) of CO 2 and selectivity of CO 2 /H 2 =1.83 of CA/PSF 2 wt% were achieved at 25 °C and 2.5 bar compared to pure CA membrane. To the best of our knowledge, this blend has been studied for the first time for gas separation, prepared through the solution casting method.
Energy & Environment, Jul 31, 2019
The most important environmental challenge that the world is facing today is the control of the q... more The most important environmental challenge that the world is facing today is the control of the quantity of CO 2 in the atmosphere, because it causes global warming. Increase in the global temperature results in greenhouse gas emission, interruption of the volcanic activity, and climatic changes. The alarming rise of the CO 2 level impels to take some serious action to control these climatic changes. Various techniques are being utilized to capture CO 2. However, chemical absorption and adsorption are supposed to be the most suitable techniques for postcombustion CO 2 capture, but the main focus is on adsorption. The aim of this study is to provide a brief overview on the CO 2 adsorption by a novel class of adsorbents called the metal-organic framework. The metal-organic framework is a porous material having high surface area with high CO 2 adsorption capacity. The metal-organic frameworks possess dynamic structure and have large capacity to adsorb CO 2 at either low pressure or high pressure due to its cavity size and surface area. Adsorption of CO 2 in the metal-organic framework at various pressures depends upon pore volume and heat of adsorption correspondingly. In this review, different synthesis methods of the metal-organic framework such as slow evaporation, solvo thermal, mechanochemical, electrochemical, sonochemical, and microwave-assisted synthesis are briefly described as the structure of the metal-organic frameworks are mostly dependent upon synthesis techniques. In addition to this, different strategies are discussed to increase the CO 2 adsorption capacity in the metal organic-framework.
Journal of Magnetism and Magnetic Materials, Nov 1, 2012
Nanocrystalline cobalt ferrites with nominal composition CoCr x Fe 2 À x O 4 ranging from x ¼0.0 ... more Nanocrystalline cobalt ferrites with nominal composition CoCr x Fe 2 À x O 4 ranging from x ¼0.0 to 0.5 with step increment of 0.25 were prepared by sol-gel auto combustion and chemical co-precipitation techniques. A comparative study of structural, electrical and magnetic properties of these ferrites has been measured using different characterization techniques. Structural and micro-structural studies were measured using X-ray diffraction, Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy and atomic force microscopy. Crystallite sizes of the series are within the range of 12-29 7 2 nm. Lattice parameters decrease by increasing Cr 3 þ concentration. FTIR confirms the presence of two lattice absorption bands. DC electrical resistivity increases to a value of $ 10 10 O-cm with increase in Cr 3 þ concentration, but the most significant increase is in samples prepared by sol-gel combustion. Dielectric properties have been measured as a function of frequency at room temperature. Dielectric loss decreases to 0.1037 and 0.0108 at 5 MHz for chemical co-precipitation and sol-gel combustion, respectively. Impedance measurements further helped in analyzing the electrical properties and to separate the grain and grain boundary resistance effects using a complex impedance analysis. Magnetic parameters were studied using a vibrating sample magnetometer in the applied field of 10 kOe. The saturation magnetization decreased from 63 to 10.8 emu/gm with increase in Cr 3 þ concentration.
WS2 nanosheets rooted in polyethylene terephthalate membrane for gas barrier properties improvement
Journal of Materials Science, Mar 6, 2023
Materials Research Bulletin, Jun 1, 2012
A series of aluminum substituted Ni-ferrite nanoparticles have been synthesized by chemical copre... more A series of aluminum substituted Ni-ferrite nanoparticles have been synthesized by chemical coprecipitation and sol-gel techniques. The samples were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscope (AFM), Fourier Transform Infrared Spectroscopy (FTIR), DC electrical resistivity and dielectric properties. Analysis of the Xray diffraction pattern of all the samples confirmed the formation of single phase face centered cubic (FCC) spinel structure. The crystallite sizes (D 311) have been calculated from most intense peak using the Scherrer formula. The particle size remains within the range 25-41 nm. The unit cell parameters decrease with the increase in Al 3+ concentration (x) in both techniques. FTIR measurements show two fundamental absorption bands, assigned to the vibration of tetrahedral (Asites) and octahedral (B-sites), which were slightly changed with increasing Al 3+ concentration (x). DC electrical resistivity increases from 6.60×10 7 to 6.9×10 10 -cm as the Al 3+ concentration (x) increases from 0.00 to 0.50. The results of DC electrical resistivity have been explained on the basis of polaron conduction mechanism. Activation energy calculated from the DC electrical resistivity versus temperature for all the samples ranges from 0.441 to 0.66 eV. The dielectric properties are studied as a function of frequency in the range 100Hz to 5 MHz at room temperature. The dielectric constant and loss tangent decreases with increasing Al 3+ concentration from 22 to 14, 0.354 to 0.27 respectively at 5MHz for all the samples. Impedance measurements as a function of frequency (1 KHz-5MHz) at room temperature further helped in analyzing the electrical properties of the prepared samples. Resistance of the grain boundary and grains can be separated using complex impedance analysis. Hence low values of dielectric constant increase the penetration depth of electromagnetic radiation which warrants their application at high frequencies.
Catalytic Activity and Kinetic Studies of Core@Shell Nanostructure NiFe2O4@TiO2 for Photocatalytic Degradation of Methyl Orange Dye
Journal of the Chemical Society of Pakistan, 2020
Current research focuses on synthesis and characterization of magnetically separable core@shell (... more Current research focuses on synthesis and characterization of magnetically separable core@shell (NiFe2O4@TiO2) nanostructured photocatalyst with different weight percent (10, 20, 30, and 40) TiO2 using simple wet chemical techniques. Magnetic core with TiO2 shell was synthesized by the hydrolysis of TTIP precursor with NiFe2O4 nanoparticles. NiFe2O4 nanoparticles were synthesized by the sol-gel auto combustion method. The synthesized nanostructures were characterized for structural, morphological and magnetic behavior using XRD, TEM, SEM and VSM while the surface area was calculated using Brunauer-Emmett-Teller analyzer. Pure nickel ferrite was indexed as spinel FCC crystal structure while anatase titania was confirmed from the characteristic peaks in the indexed XRD patterns. SEM images show the uniform particle size and spherical morphology with average size of 18.85 nmand#177;2nm. The Surface area of prepared core@shell nanostructures was found as 258 m2/g for 10 wt. % TiO2 photocatalyst. A decrease in surface area has been observed with the increase in TiO2 percentage. The photo-catalytic degradation of MO was studied using UV-Visible spectroscopy under NiFe2O4-TiO2 catalyst. UV-spectra revealed degradation of methyl orange by the decrease in the characteristic peak at 460 nm. Kinetics of degradation reaction were studied by the integral method of analysis using UV absorbance data at 460 nm. The photo-catalytic activity of as synthesized catalyst was enhanced many folds as compared to the pure nickel ferrite. M-H curves obtained from VSM revealed a decrease in the magnetization of nickel ferrite with a coating of non-magnetic TiO2.
NiFe2O4/SiO2 nanostructures as a potential electrode material for high rated supercapacitors
Ceramics International, May 1, 2021
Abstract Engineered materials are crucial for the higher efficiency of supercapacitors. Current w... more Abstract Engineered materials are crucial for the higher efficiency of supercapacitors. Current work presents roughly shaped spherical NiFe2O4 nanoparticles dispersed in the SiO2 matrix NiFe2O4/SiO2 as a newfangled electrode material for supercapacitors with remarkable performance. Designing the NiFe2O4/SiO2 nanostructure with a sol-gel method followed by the Stober method to grow silica has instigated NiFe2O4/SiO2 as dynamic material with higher electrochemical activity. Physicochemical aspects of NiFe2O4/SiO2 nanostructures are evaluated using Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analysis. The electrochemical activity is evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) representing the comparable efficiency and reversibility of the electrode materials. The prepared electrode shows a capacitance of 925 F/g (154.1 mAh/g or 555 C/g) at 1 A/g, with 95.5% capacitance retention after 5000 cycles at 20 mA/cm2. The improved electrochemical performance of the NiFe2O4/SiO2 electrode can be subjected to prompt diffusion process provided by NiFe2O4/SiO2 and enhanced redox reactions owing to the high surface area. The mentioned features decrease the total impedance of the electrodes as suggested by electrochemical impedance spectroscopy (EIS).
Journal of Superconductivity and Novel Magnetism, Sep 8, 2012
In this paper, flowerlike MoS 2 hollow microspheres were synthesized by a facile hydrothermal sol... more In this paper, flowerlike MoS 2 hollow microspheres were synthesized by a facile hydrothermal solution route with the assistance of Pluronic F-127. The as-prepared products were characterized by X-ray powder diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental results indicated reaction time and surfactant have significant effects on the morphology of the as-prepared products. A possible formation mechanism has also been investigated on the basis of a series of transmission electron microscopy (TEM) studies of the product obtained at different durations. This well-controlled synthesis approach may be extended to fabricate complex hollow structures of other transition metal sulfide materials.
Antimony (Sb 3+) doped nickel ferrites (NiSb x Fe 2-x O 4) with x=0.0, 0.035, 0.065 and 0.1, have... more Antimony (Sb 3+) doped nickel ferrites (NiSb x Fe 2-x O 4) with x=0.0, 0.035, 0.065 and 0.1, have been synthesized by hydrothermal route using an autoclave at 160 0 C for 12 hrs. AC conductivities for all the samples have been observed in the frequency range of 1MHz to 3 GHz, where AC conductivity increases due to the addition of antimony in nanocrystalline nickel ferrites. Electromagnetic properties were studied by measuring complex dielectric permittivity (ɛ*), complex magnetic permeability (μ*) in the frequency range of 1 MHz to 3 GHz at room temperature using RF/impedance analyzer. Reflection losses (RL) were calculated for all the samples using permittivity and permeability measurements according to the transmission line theory. Maximum RL of-54dB was obtained for antimony doped nickel ferrite x=0.065 at 2.4 GHz with a band width of 1.2 GHz and decreases for high antimony concentration x=0.1 (-49dB). Low dielectric permittivity, high permeability and conductivity made this material a compatible option for single layered and multilayered chip inductors. While low RL values suggest nickel ferrite a possible candidate for electromagnetic absorption devices and radar absorbing material.
Engineering, Technology & Applied Science Research, Apr 19, 2018
V 2 O 5 /TiO 2 is an important catalyst used in many industrial reactions like selective oxidatio... more V 2 O 5 /TiO 2 is an important catalyst used in many industrial reactions like selective oxidation of o-xylene to phthalic anhydride, selective catalytic reduction of NO x , selective oxidation of alkanes, etc. The partial oxidation of o-xylene to synthesize phthalic anhydride is an exothermic reaction and leaves hot spots on the catalyst's surface. The yield of phthalic anhydride strongly depends on the activity and stability of the catalyst. In this work, a computational fluid dynamics (CFD) analysis has been conducted to compare the yield of lab prepared catalyst with the commercially used catalyst. This work is first attempt to simulate V 2 O 5 /TiO 2 catalyst for cracking heavy hydrocarbons in the petrochemical industry using k-ε turbulence and species transport models in CFD. The results obtained are in the form of scaled residuals, area-weighted average, and contours of pressure and temperature. Simulation results of lab synthesized and commercially used catalysts, applying finite volume method (FVM) are compared, which emphasize the scope of CFD modeling in the catalytic cracking process of petrochemical industry.
Blending of ZnO Nanorods in Cellulose Acetate Mixed Matrix Membrane for Enhancement of CO2 Permeability
Journal of Polymers and The Environment, Jan 2, 2023
Materials research express, Feb 21, 2014
Pure phase aluminum doped nickel ferrite nanoparticles [NiAl x Fe 2−x O 4 ] with x = 0.0, 0.25 an... more Pure phase aluminum doped nickel ferrite nanoparticles [NiAl x Fe 2−x O 4 ] with x = 0.0, 0.25 and 0.5 have been investigated for magnetic and electromagnetic absorbing properties in S band and influence of Al 3+ ions has been studied. Nickel aluminum ferrites have been synthesized by co-precipitation and sol-gel auto combustion routes. Magneto-dielectric properties were measured in terms of complex permeability (μ*) and complex permittivity (ε*) at 300 K in the frequency range of 1 MHz to 3 GHz using RF material/impedance analyzer. Dielectric permittivity (ε′ and ε″) has been observed to decrease with the increase in applied frequency and concentration of aluminum ions (x = 0.0-0.5). Magnetic permeability (μ′ and μ″) has been found to decrease with the increase in aluminum ions concentration. Electromagnetic absorbing properties were studied for all the samples by calculating the reflection losses (RL) in the frequency range of 1 MHz-3 GHz using the permittivity and permeability measurements in accordance with the transmission line theory. RL (dB) values lie in the range of −42 dB to −57 dB. RL values (> −10 dB) confirm more than 90% absorption of electromagnetic waves incident normal to the material surface. Aluminum doping has increased the RL values from −45 dB to −57 dB along with the shift of RL dip towards the higher frequency side for the samples prepared by sol-gel auto combustion technique. Magnetic properties have been studied by vibrating samples magnetometer (VSM) at room temperature and a decrease in magnetic properties has been observed due to increase in x from 0.0-0.5.
Facile and efficient synthesis of carboxylic terminated Ti3C2Tx nanosheets using citric acid
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Papers by Dr. Erum Pervaiz