Structural and Morphological Properties of Zn1−xZrxO with Room-Temperature Ferromagnetism and Fabricated by Using the Co-Precipitation Technique

M. Hassan,R. Irfan,S. Riaz,S. Naseem,S. S. Hussain,G. Murtaza 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.5

In this study, ZnO was doped with various concentrations of zirconium (xZr = 0 - 5 mole%), by using the co-precipitation method so as to achieve successful formation of a single-phase diluted magnetic semiconductor. X-Ray diffraction results showed that the crystal structure of Zn1−xZrxO was that of hexagonal wurtzite. The structural properties showed no additional phases at low impurity contents (xZr < 3%); however, impurity peaks belonging to ZrO2 appeared at high impurity contents (xZr 3%). The calculated ZnO lattice constants ‘a’ and ‘c’ were found to be 3.256 °A and 5.203 °A, respectively, which are in close match to the values found in the literature. For undoped ZnO, the average calculated particle size was 75.35 nm, and calculated bond length was 1.98 °A. The residual strains and the secondary phases of ZrO2 were found to affect the lattice parameters and the bond lengths. The scanning electron microscopy images showed a porous structure with non-uniform surface morphology. However, a few nano-scale dendrite-type structures were also present, indicating the potential applications of Zr-doped ZnO in nano-devices. Vibrating sample magnetometry (VSM) was employed to measure the magnetic properties, and the measurements showed undoped ZnO to be diamagnetic; however, doping with Zr induced a small ferromagnetic character at small magnetic fields. On the otherhand, a paramagnetic behavior was evident at higher magnetic fields. The magnetization at 1T was observed to degrade with increasing Zr content in the ZnO host lattice, which was due to the residual strains and the secondary phases.

Experimental investigation of aerosols removal efficiency through self-priming venturi scrubber

Suhail Ali,Khalid Waheed,Kamran Qureshi,Naseem Irfan,Masroor Ahmed,Waseem Siddique,Amjad Farooq 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.10

Self-priming venturi scrubber is one of the most effective devices used to collect aerosols and soluble gas pollutants from gaseous stream during severe accident in a nuclear power plant. The present study focuses on investigation of dust particle removal efficiency of the venturi scrubber both experimentally and theoretically. Venturi scrubber captures the dust particles in tiny water droplets flowing into it. Inertial impaction is the main mechanism of particles collection in venturi scrubber. The water injected into venturi throat is in the form of jets through multiple holes present at venturi throat. In this study, aerosols removal efficiency of self-priming venturi scrubber was experimentally measured for different operating conditions. Alumina (Al2O3) particles with 0.4-μm diameter and 3950 kg/m3 density were treated as aerosols. Removal efficiency was calculated for different gas flow rates i.e. 3-6 m3/h and liquid flow rates i.e. 0.009–0.025 m3/h. Experimental results depict that aerosols removal efficiency increases with the increase in throat velocity and liquid head. While at lower air flow rate of 3 m3/h, removal efficiency decreases with the increase in liquid head. A theoretical model of venturi scrubber was also employed and experimental results were compared with mathematical model. Experimental results are found to be in good agreement with theoretical results.

Study of an improved and novel venturi scrubber configuration for removal of radioactive gases from NPP containment air during severe accident

Farooq Mujahid,Ahmed Ammar,Qureshi Kamran,Shah Ajmal,Waheed Khalid,Siddique Waseem,Irfan Naseem,Ahmad Masroor,Farooq Amjad 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.9

Owing to the rising concerns about the safety of nuclear power plants (NPP), it is essential to study the venturi scrubber in detail, which is a key component of the filtered containment venting system (FCVS). FCVS alleviates the pressurein containment byfiltering and venting out the contaminated air. Themain objective of this research was to perform a CFD investigation of different configurations of a circular, non-submerged, selfpriming venturi scrubber to estimate and improve the performance in the removal of elemental iodine from the air. For benchmarking, a mass transfer model which is based on two-film theory was selected and validated by experimental data where an alkaline solution was considered as the scrubbing solution. This mass transfer model was modified and implemented on a unique formation of two self-priming venturi scrubbers in series. Euler-Euler method was used for two-phase modeling and the realizable K ε model was used for capturing the turbulence. The obtained results showed a remarkable improvement in the removal of radioactive iodine from the air using a series combination of venturi scrubbers. The removal efficiency was improved at every single data point.

Investigation of dust particle removal effi ciency of self-priming venturi scrubber using computational fl uid dynamics

Sarim Ahmed,Hassan Mohsin,Kamran Qureshi,Ajmal Shah,Waseem Siddique,Khalid Waheed,Naseem Irfan,Masroor Ahmad,Amjad Farooq 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.5

A venturi scrubber is an important element of Filtered Containment Venting System (FCVS) for theremoval of aerosols in contaminated air. The present work involves computational fluid dynamics(CFD) study of dust particle removal efficiency of a venturi scrubber operating in self-priming mode usingANSYS CFX. Titanium oxide (TiO2) particles having sizes of 1 micron have been taken as dust particles. CFD methodology to simulate the venturi scrubber has been first developed. The cascade atomizationand breakup (CAB) model has been used to predict deformation of water droplets, whereas the EulerianeLagrangian approach has been used to handle multiphase flow involving air, dust, and water. Thedeveloped methodology has been applied to simulate venturi scrubber geometry taken from the literature. Dust particle removal efficiency has been calculated for forced feed operation of venturi scrubberand found to be in good agreement with the results available in the literature. In the second part, venturiscrubber along with a tank has been modeled in CFX, and transient simulations have been performed tostudy self-priming phenomenon. Self-priming has been observed by plotting the velocity vector fields ofwater. Suction of water in the venturi scrubber occurred due to the difference between static pressure inthe venturi scrubber and the hydrostatic pressure of water inside the tank. Dust particle removal efficiencyhas been calculated for inlet air velocities of 1 m/s and 3 m/s. It has been observed that removalefficiency is higher in case of higher inlet air velocity.

Designed synthesis of silver nanoparticles in responsive polymeric system for their thermally tailored catalytic activity towards hydrogenation reaction

Muhammad Shahid,Zahoor Hussain Farooqi,Robina Begum,Khalida Naseem,Muhammad Ajmal,Ahmad Irfan 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.5

Poly(N-isopropylacrylamide-acrylamide-methacrylic acid) [p(NIPa-AAm-Ma)] polymer microgels were prepared by free radical precipitation polymerization method. AgNPs were fabricated in the sieves of polymer network by chemical reduction using AgNO3 salt as a precursor of silver ions. Various techniques like dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared microscopy (FTIR), and UV-Visible spectroscopy were used for characterization of pure and composite microgels. The diameter of AgNPs fabricated in polymeric network was found to be in the range of 10-15 nm. Stimuli responsive behavior of hybrid microgels was same as that of pure microgels. Catalytic efficiency of the hybrid microgels was investigated by reducing 4-Nitroaniline (4-NA) into 4-Aminoaniline (4-AA) using NaBH4 as reducing agent under different conditions of temperature of the medium, concentration of reducing agent, 4-Nitroaniline and hybrid microgels to explore the catalysis process. Kinetic and thermodynamic aspects of reduction of 4-Nitroaniline in the presence of catalyst were also discussed on the basis of values of Arrhenius and Eyring parameters like pre-exponential factor, activation energy, enthalpy of activation and entropy of activation. Catalytic activity of the hybrid microgels was found to be thermally tunable in the temperature range of 25- 70 oC. The value of rate constant (kapp) for reduction of 4-NA was minimum at 55 oC, which can be attributed to volume phase transition of the hybrid microgels.

Study of hydrodynamics and iodine removal by self-priming venturi scrubber

Ahad Jawaria,Rizwan Talha,Farooq Amjad,Waheed Khalid,Ahmad Masroor,Qureshi Kamran Rasheed,Siddique Waseem,Irfan Naseem 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.1

Filtered containment system is a passive safety system that controls the over-pressurization of containment in case of a design-based accidents by venting high pressure gaseous mixture, consisting of air, steam and radioactive particulate and gases like iodine, via a scrubbing system. An indigenous lab scale facility was developed for research on iodine removal by venturi scrubber by simulating the accidental scenario. A mixture of 0.2 % sodium thiosulphate and 0.5 % sodium hydroxide, was used in scrubbing column. A modified mathematical model was presented for iodine removal in venturi scrubber. Improvement in model was made by addition of important parameters like jet penetration length, bubble rise velocity and gas holdup which were not considered previously. Experiments were performed by varying hydrodynamic parameters like liquid level height and gas flow rates to see their effect on removal efficiency of iodine. Gas holdup was also measured for various liquid level heights and gas flowrates. Removal efficiency increased with increase in liquid level height and gas flowrate up to an optimum point beyond that efficiency was decreased. Experimental results of removal efficiency were compared with the predicted results, and they were found to be in good agreement. Maximum removal efficiency of 99.8% was obtained.