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Structural and Magnetic Properties of Gd-Ni-co-doped BiFeO₃ Nanoparticles
Sandeep Kumar Singh Patel,Jae-Hyeok Lee,Min-Kwan Kim,Sang-Koog Kim 한국자기학회 2019 Journal of Magnetics Vol.24 No.3
Single-phase (GdNi)x(BiFe)1-x O₃ (x = 0, 0.025, and 0.05) nanoparticles of 30-40 nm particle size on average were fabricated using a sol-gel method. Transmission electron microscopy, X-ray diffraction as well as Raman spectral measurements and analyses revealed that the (GdNi)x(BiFe)1-xO₃ nanoparticles undergo a structural transformation from the rhombohedral R3c structure (for x = 0 and 0.025) to the triclinic P1 (for x = 0.05). X-ray photoemission spectroscopy served to confirm that co-doping of Gd<SUP>3+</SUP> and Ni<SUP>2+</SUP> ions decreases oxygen-vacancy concentration, reflecting less Fe<SUP>2+</SUP> content in the co-doped samples compared with pure BiFeO₃. Magnetization hysteresis loops showed that the magnetization value for x = 0.05 at 50 kOe increases significantly to M = 5.32 emu/g at 300 K and to 14.47 emu/g at 5 K, representing 760 and 690 % enhancements relative to those for x = 0. Fitting of the Curie-Weiss law to the observed magnetization-versus-temperature curves indicated the presence of weak ferromagnetic coupling in the samples. We also noted the exchange bias effect in the nano-size particles, possibly originating from exchange coupling between surface spins of an uncompensated ferromagnetic nature and core spins of an antiferromagnetic nature. We ascribed these significant improvements in the Gd-Ni-co-doped BiFeO₃ nanoparticles’ magnetic properties to the rhombohedral R3c to triclinic P1 structural transformation, due to the samples’ particle size being smaller than the modulation length of the canted antiferromagnetic ordering of the Fe<SUP>3+</SUP> spins. These enhanced magnetic properties, notably, might prove useful for a variety of spintronic applications.
Patel, Sandeep Kumar Singh,Lee, Jae-Hyeok,Bhoi, Biswanath,Lim, Jung Tae,Kim, Chul Sung,Kim, Sang-Koog Elsevier 2018 Journal of magnetism and magnetic materials Vol.452 No.-
<P><B>Abstract</B></P> <P>We fabricated Gd-doped Y<SUB>3</SUB>Fe<SUB>5</SUB>O<SUB>12</SUB> (YIG) nanoparticles by a modified sol–gel method. We investigated the effects of isovalent Gd<SUP>3+</SUP>-ion substitution on the structural and magnetic properties of Y<SUB>3−x</SUB>Gd<SUB>x</SUB>Fe<SUB>5</SUB>O<SUB>12</SUB> (0 ≤ x ≤ 3) nanoparticles. Isovalent Gd<SUP>3+</SUP>-ion substitution for Y<SUP>3+</SUP> leads to lattice expansion and change in the Fe(<I>a</I>)–O–Fe(<I>d</I>) bond angle. The X-ray photoemission spectroscopy and Mössbauer measurements revealed a high-spin state of Fe<SUP>3+</SUP>. The Mössbauer analysis showed an increase in the Fe<SUB>(d)</SUB> <SUP>3+</SUP>/Fe<SUB>(a)</SUB> <SUP>3+</SUP> ratio, indicating a relocation of Y<SUP>3+</SUP> ions at the dodecahedral sites and Fe<SUP>3+</SUP> ions at the octahedral sites. The magnetic properties could be explained in terms of magnetic-structural evolution with increasing Gd<SUP>3+</SUP> content. The field dependence of magnetization indicated a clear decrease of the magnetization while the magnetic anisotropy first decreases and then increases with the increase of Gd<SUP>3+</SUP> content. These Gd<SUP>3+</SUP>-ion-substituted nanocrystalline garnet ferrites are suitable for use in a variety of magneto-optical applications.</P>
Sandeep Chaudhary, Kashyap Arvindbhai Patel, 김두기(Dookie Kim),조성국(Sung Gook Cho),Ahmer Ali 한국구조물진단유지관리학회 2011 한국구조물진단학회 학술발표회논문집 Vol.15 No.1
Studies are presented for the dynamic behaviour of steel-concrete composite floors. A typical two spans composite floor is considered for this study and assumed to be subjected to a typical earthquake. The deflection and stresses are obtained at different time instants for the composite floor with rigid connection and flexible connection. The FE model developed, in ABAQUS, for the study accounts for the nonlinear material behaviour. The flexibility of shear connectors between steel girder and concrete slab is found to significantly affect the dynamic behaviour of steel-concrete composite floors.
Patel, Sandeep Kumar Singh,Lee, Jae-Hyeok,Kim, Min-Kwan,Bhoi, Biswanath,Kim, Sang-Koog The Royal Society of Chemistry 2018 Journal of Materials Chemistry C Vol.6 No.3
<P>We fabricated single-crystalline, Gd-doped BiFeO3 (BFO) nanowires using a hydrothermal technique. X-ray diffraction (XRD) data combined with their Rietveld refinements and high-resolution transmission electron microscopy (HRTEM) revealed pure single-phase crystalline Bi1−xGdxFeO3 (<I>x</I> = 0, 0.05, 0.10) nanowires of 40-60 nm diameter and their structural transformation from the rhombohedral <I>R</I>3<I>c</I> (for <I>x</I> = 0 and 0.05) to the orthorhombic <I>Pn</I>21<I>a</I> crystal structure (for <I>x</I> = 0.10). The addition of Gd<SUP>3+</SUP> ions to the pure-phase BFO leads to remarkable changes in the structural and magnetic properties, and these effects are caused by differences in the ionic-radii and magnetic moment between the Bi<SUP>3+</SUP> and Gd<SUP>3+</SUP> ions. According to the observed magnetization-field (<I>M-H</I>) and magnetization-temperature (<I>M</I>-<I>T</I>) curves, with increasing Gd<SUP>3+</SUP> concentration, the saturation magnetization (<I>M</I>S), squareness (<I>M</I>r/<I>M</I>S), coercivity (<I>H</I>C), exchange-bias field (<I>H</I>EB) and magnetocrystalline anisotropy (<I>K</I>) increased markedly, by <I>M</I>S = 1.26 emu g<SUP>−1</SUP> (640%), <I>M</I>r/<I>M</I>S = 0.19 (20.5%), <I>H</I>C = 7788 Oe (4560%), <I>H</I>EB = 501 Oe (880%) and <I>K</I> = 1.62 × 10<SUP>5</SUP> erg cm<SUP>−3</SUP> (3500%), for <I>x</I> = 0.10 relative to the data for <I>x</I> = 0. In such Gd-doped BFO nanowire samples, spin-canted Dzyaloshinskii-Moriya interaction, remarkable enhancements in the magnetocrystalline anisotropy as well as uncompensated surface ferromagnetic spin states in the antiferromagnetic core regions were also found. Such remarkable enhancements in Gd-doped BFO nanowires might offer a variety of spintronic applications.</P>
Vishnu Baburaj,Sandeep Patel,Vishal Kumar,Siddhartha Sharma,Mandeep Singh Dhillon 대한견주관절의학회 2024 대한견주관절의학회지 Vol.27 No.1
Background: Clinical outcomes after fixation of distal humerus intraarticular fractures are directly related to the quality of reduction. The use of three-dimensional (3D)-printed fracture models can benefit preoperative planning to ensure good reduction. This review aims to determine if surgery performed with 3D printing assistance are faster and result in fewer complications and improved clinical outcomes than conventional methods. We also outline the benefits and drawbacks of this novel technique in surgical management of distal humerus fractures. Methods: A systematic literature search was carried out in various electronic databases. Search results were screened based on title and abstract. Data from eligible studies were extracted into spreadsheets. Meta-analysis was performed using appropriate computer software. Results: Three randomized controlled trials with 144 cases were included in the final analysis. The 3D-printed group had significantly shorter mean operating time (mean difference, 16.25 minutes; 95% confidence interval [CI], 12.74–19.76 minutes; P<0.001) and mean intraoperative blood loss (30.40 mL; 95% CI, 10.45–60.36 mL; P=0.005) compared with the conventional group. The 3D-printed group also tended to have fewer complications and a better likelihood of good or excellent outcomes as per the Mayo elbow performance score, but this did not reach statistical significance. Conclusions: Three-dimensional-printing-assisted surgery in distal humerus fractures has several benefits in reduced operating time and lower blood loss, indirectly decreasing other complications such as infection and anemia-related issues. Future good-quality studies are required to conclusively demonstrate the benefits of 3D printing in improving clinical outcomes.
Rapid prediction of long-term deflections in composite frames
Umesh Pendharkar,Sandeep Chaudhary,K. A. Patel,A.K. Nagpal 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.3
Deflection in a beam of a composite frame is a serviceability design criterion. This paper presents a methodology for rapid prediction of long-term mid-span deflections of beams in composite frames subjected to service load. Neural networks have been developed to predict the inelastic mid-span deflections in beams of frames (typically for 20 years, considering cracking, and time effects, i.e., creep and shrinkage in concrete) from the elastic moments and elastic mid-span deflections (neglecting cracking, and time effects). These models can be used for frames with any number of bays and stories. The training, validating, and testing data sets for the neural networks are generated using a hybrid analytical-numerical procedure of analysis. Multilayered feed-forward networks have been developed using sigmoid function as an activation function and the back propagation-learning algorithm for training. The proposed neural networks are validated for an example frame of different number of spans and stories and the errors are shown to be small. Sensitivity studies are carried out using the developed neural networks. These studies show the influence of variations of input parameters on the output parameter. The neural networks can be used in every day design as they enable rapid prediction of inelastic mid-span deflections with reasonable accuracy for practical purposes and require computational effort which is a fraction of that required for the available methods.