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Anwar M.S.,Koo Bon Heun 한국물리학회 2022 Current Applied Physics Vol.39 No.-
We report the detail investigation on the magnetic and magnetocaloric behaviour of polycrystalline Mn1-xZnxFe2O4 (0.0 ≤ x ≤ 0.7) ferrite. The magnetization analysis shows that the increase of Zn concentration in the samples results in decrease of saturation magnetization. The maximum magnetic entropy change, |ΔSmMax| is evaluated through M-H isotherms measurements and takes values of 1.25, 1.11, 1.07, and 0.64 Jkg-1K-1 for x = 0.0, 0.3, 0.5, and 0.7, respectively under a maximum applied magnetic field of 2.5 T. The corresponding relative cooling power (RCP) for these samples were found to be 102, 162, 96, and 89 Jkg-1 for x = 0.0, 0.3, 0.5, and 0.7, respectively. After the comparison of the obtained values of |ΔSmax M| and RCP with those reported earlier for the other compounds, recommend to explore such common soft ferrites based materials for magnetic refrigeration.
Hussain, I.,Anwar, M. S.,Lee, S. R.,Koo, B. H. Springer Science + Business Media 2015 Journal of superconductivity and novel magnetism Vol.28 No.11
<P>We report the structural, magnetic, and magnetocaloric properties of (0.95)La0.7Ca0.3MnO3/(0.05)Mn1-x Zn (x) Fe2O4 (x = 0.0, 0.1, 0.3, 0.5) composites. Polycrystalline samples of the composite material were prepared using the solid-state reaction method. The phase purity and structure of the samples were confirmed using the X-ray powder diffraction (XRD) method. Scanning electron microscope (SEM) studies of the samples reveal that Mn1-x Zn (x) Fe2O4 is mainly distributed at the surface and grain boundaries of the perovskite matrix La0.7Ca0.3MnO3. The variation of magnetization (M) as a function of temperature and applied magnetic field was investigated. The M-T data plots indicate a paramagnetic to ferromagnetic transition upon cooling in all samples. The magnetic entropy change was also studied through the examination of measured magnetic isotherms, M (H, T) near Curie temperature T (C) . A magnetocaloric effect has been estimated in terms of isothermal magnetic entropy change. A maximum entropy change value of 1.72 J/kg K was recorded for a magnetic field change of 3 T with a relative cooling power (RCP) value of 177 J/kg for the (0.95)La0.7Ca0.3MnO3/(0.05)MnFe2O4 composite sample.</P>
Ahmed, F.,Arshi, N.,Anwar, M.S.,Lee, S.H.,Byon, E.S.,Lyu, N.J.,Koo, B.H. Elsevier 2012 CURRENT APPLIED PHYSICS Vol.12 No.suppl2
We report the preparation of Zn<SUB>1-x</SUB>Ni<SUB>x</SUB>O nanorods through a chemical route using microwave irradiation. The obtained Zn<SUB>1-x</SUB>Ni<SUB>x</SUB>O nanorods were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy and magnetization measurements. XRD and TEM results showed that the Zn<SUB>1-x</SUB>Ni<SUB>x</SUB>O nanorods have single phase nature with wurtzite structure and Ni was successfully incorporated at Zn site into the ZnO. The shape of the nanorods changed from hexagon (length ~1.5 μm, diameter ~200 nm) to pencil like tip (length ~1 μm, diameter ~80 nm) by only changing the Ni content from 1% to 3% in ZnO. Concerning the Raman scattering spectra, the modification in the intensity of E<SUB>2</SUB><SUP>high</SUP> mode and sub-band edge emissions provides enough evidence for the existence of intrinsic defects associated with the O atoms. Magnetic measurement results revealed that Zn<SUB>1-x</SUB>Ni<SUB>x</SUB>O nanorods show the well-defined ferromagnetic features at room temperature and the value of M<SUB>s</SUB> increased with the increase of Ni concentration.
Eun-Kyung Jang,정병권,Gun-Seok Park,Abdur Rahim Khan,Sung-Jun Hong,박영준,WON-CHAN KIM,JAE-HO SHIN,Khalid M S Al-Ghamdi,Bassam Oudh Al-Johny,Yasir Anwar,Muhammad Faisal Siddiqui,Ihsan Ullah 한국응용곤충학회 2020 Journal of Asia-Pacific Entomology Vol.23 No.1
Photorhabdus spp. has a high molecular weight Tc toxin with insecticidal activity. These toxins have been suggested as an alternative to BT toxin from Bacillus thuringiensis. Herein, we constructed a cosmid library with the genome of M1021 and screened the Escherichia coli clones showing insect toxicity by injecting each clone into Galleria mellonella larvae. In a total of 1020 clones, one clone with high insecticidal activity was selected and the nucleotide sequence of the cosmid of the clone was determined. In cosmid PtC28, a gene with 87% homology to the tccB gene of Photorhabdus temperata was found. Consequently, we have isolated the tccB gene cassette from the M1021 and expressed in E. coli expression vectors. The toxin was produced in the form of inclusion bodies but the denatured and refolded recombinant TccB showed strong mortality to the G. mellonella larvae.
Anwar, M.S.,Danish, Rehan,Park, Keun Young,Koo, Bon Heun Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.5
The effect of precursor concentration on the structural, morphological, and optical properties of $TiO_2$nano-flowers was investigated in this study. An increase in crystallite size was observed with an increase in the concentration of the precursor (titanium butoxide). The FE-SEM micrographs of the as-prepared samples show a three-dimensional flower-like morphology. The flowers consist of several nanorods coming out of a single core and have very sharp edges. Also, the variation in the aspect ratio of the nanostructure was observed with the concentration of the precursor. The photocatalytic properties of the samples show that the sample that has a high aspect ratio (AR~9) has a much better photocatalytic activity compared to the nano-crystal with a low aspect ratio (AR~6.1). It is believed that the excellent photocatalytic performance and short time synthesis of $TiO_2$nano-flowers using the microwave hydrothermal method can have potential applications in the field of photocatalysis.
Behaviour of volcanic pumice based thin walled composite filled columns under eccentric loading
Anwar Hossain, Khandaker M. Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.16 No.1
This paper describes experimental and theoretical investigations on the behaviour of thin walled composite (TWC) filled columns under eccentric loading conditions. Details of the experimental investigation including description of the test columns, testing arrangements, failure modes, strain characteristics, load-deformation responses and effects of various geometric and material parameters are presented. The current paper also introduces the use and effect of lightweight Volcanic Pumice Concrete (VPC) in TWC columns. Analytical models for the design of columns under eccentric loading conditions have been developed taking into consideration the effect of confined concrete. The performance of design equations is validated through experimental results. The proposed design models are found to produce better results compared with available design procedures and Code based formulations. A computer program is developed to generate the interaction diagrams based on the proposed design equations that can be used for design purposes.
Study of nanocrystalline ceria thin films deposited by e-beam technique
Anwar, M.S.,Kumar, Shalendra,Ahmed, Faheem,Arshi, Nishat,Seo, Yong Jun,Lee, Chan Gyu,Koo, Bon Heun Elsevier 2011 CURRENT APPLIED PHYSICS Vol.11 No.1
<P><B>Abstract</B></P><P>We have studied the effect of electron gun power and substrate temperature on the properties of nanocrystalline ceria thin films using electron beam evaporation method. The ceria films were grown on the glass substrate and characterized using different techniques such as: X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy and UV-visible spectroscopy measurements. It was observed that electron gun power has influence on the crystallite size which increases (from 5 to 11 nm) as the gun power increases. Also, the crystallite size increases from 8 to 22 nm by increasing substrate temperature from room temperature (RT) to 400 °C. The FE-SEM images show that all the films have nanocrystalline growth. From the Raman spectra, we have observed two peaks at 466 and 565 cm<SUP>−1</SUP>. The peak at 466 cm<SUP>−1</SUP> is assigned to the presence of the F<SUB>2g</SUB> mode of CeO<SUB>2</SUB> whereas the peak at 565 cm<SUP>−1</SUP> is due to the presence of the oxygen vacancies. UV-visible measurements reflect that all the films have high transparency, more than 80% in the visible region.</P>
Above room temperature magnetic transition and magnetocaloric effect in La_0.66_Sr_0.34_MnO₃
M. S. Anwar,샤런드라쿠마르,Faheem Ahmed,Nishat Arshi,김근우,구본흔 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.10
In this study, the magnetic and the magnetocaloric properties of the La0.66Sr0.34MnO3 (LSMO) compound were investigated. The X-ray diffraction result indicates that the LSMO sample has a single phase of rhombohedral symmetry without any impurity phase. The magnetic study reveals that the specimen La0.66Sr0.34MnO3 exhibits a ferromagnetic-paramagnetic transition at TC ∼ 376 K. Using Arrott plots, the phase transition from ferromagnetic to paramagnetic is found to be of second order. A maximum magnetic entropy change of 1.25 J/kgK has been observed for a low applied magnetic field of 1T. The relative cooling power values exhibit a nearly linear dependence on the applied magnetic field. Moreover, the analysis of the magnetocaloric effect (MCE) using the Landau theory o f phase transitions shows good agreement with the experimental results, confirming the importance of magnetoelastic coupling and electron interactions in the magnetocaloric properties of perovskite manganites. This investigation suggests that La0.66Sr0.34MnO3 can be used as a potential magnetic refrigeration material.
M. S. ANWAR,FAHEEM AHMED,G. W. Kim,허시내,구본흔 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12
A detailed investigation of the magnetic and the magnetocaloric properties of La0.7Sr0.3MnO3,La0.7Ca0.3MnO3 and La0.7Ca0.1Sr0.2MnO3 for possible application in magnetic refrigeration is presented. The adiabatic magnetic entropy change was determined for a magnetic field change from0 to 2.5 T by using magnetization data. A broad table-like entropy change with a relative coolingpower of 111 J/kg in an applied magnetic field of 2.5 T with an operating temperature range of54 K was observed in the La0.7Ca0.1Sr0.2MnO3 sample. The broadening in the magnetic entropychange in La0.7Ca0.1Sr0.2MnO3 is discussed in light of the tricritical mean-field theory. The tricriticalexponent () was calculated for the La0.7Ca0.1Sr0.2MnO3 sample and found to be 4.76± 0.03, which is very close to the proposed value = 5 for the tricitical exponent. The studiedsamples can be considered as giant magnetocaloric materials for room-temperature refrigeration.