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R. Nirmala

Bio: R. Nirmala is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Magnetization & Magnetic refrigeration. The author has an hindex of 26, co-authored 219 publications receiving 2482 citations. Previous affiliations of R. Nirmala include Chonbuk National University & Tata Institute of Fundamental Research.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors demonstrate that successive electrospinning can change the fiber morphology in the electrospun mat of the polymer at the same electro-spinning parameters and demonstrate that the formation of spider-net structures with high aspect ratio was responsible to increase the mechanical strength of nylon-6 mat.

115 citations

Journal ArticleDOI
TL;DR: This work was focused on preparation and characterizations of chitosan blended polyamide-6 nanofibers by a new single solvent system via electrospinning process for human osteoblastic (HOB) cell culture applications.

99 citations

Journal ArticleDOI
TL;DR: It is demonstrated that the electrospun polyurethane containing CaCl2 composite nanofibers enhanced the in vitro bioactivity and supports the growth of apatite-like materials.
Abstract: Polyurethane nanofibers containing calcium chloride (CaCl2) were prepared via an electrospinning technique for the biomedical applications. Polyurethane nanofibers with different concentration of CaCl2 were electrospun, and their bioactivity evaluation was conducted by incubating in biomimetic simulated body fluid (SBF) solution. The morphology, structure and thermal properties of the polyurethane/CaCl2 composite nanofibers were characterized by means of scanning electron microscopy (SEM), field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetry. SEM images revealed that the CaCl2 salt incorporated homogeneously to form well-oriented nanofibers with smooth surface and uniform diameters along their lengths. The SBF incubation test confirmed the formation of apatite-like materials, exhibiting enhanced bioactive behavior of the polyurethane/CaCl2 composite nanofibers. This study demonstrated that the electrospun polyurethane containing CaCl2 composite nanofibers enhanced the in vitro bioactivity and supports the growth of apatite-like materials.

96 citations

Journal ArticleDOI
TL;DR: The magnetic, magnetocaloric, and magnetoresistive properties of the polycrystalline compound HoNiAl have been studied in this article, showing that the compound undergoes two magnetic transitions, one at 14k and the other at 5k, due to the onset of an antiferromagnetic ordering, as the temperature is lowered.
Abstract: The magnetic, magnetocaloric, and magnetoresistive properties of the polycrystalline compound HoNiAl have been studied The temperature variations of magnetization and heat capacity show that the compound undergoes two magnetic transitions, one at 14K and the other at 5K The former is due to the paramagnetic-ferromagnetic transition, while the latter is attributed to the onset of an antiferromagnetic ordering, as the temperature is lowered The M-H isotherm obtained at 2K shows a metamagnetic transition with a critical filed of about 13kOe The maximum values of isothermal magnetic entropy change and adiabatic temperature change, for a field change of 50kOe, are estimated to be 236J∕kgK and 87K, respectively The relative cooling power is found to be about 500J∕kg for a field change of 50kOe A large magnetoresistance of about 16%, near the ordering temperature of 14K, is observed for a field of 50kOe The magnetic, magnetocaloric, and magnetoresistance data seem to suggest the presence of magnetic pol

68 citations

Journal ArticleDOI
TL;DR: In this article, the magnetocaloric effect in polycrystalline samples of Laves phase compounds was found to be maximum near the ordering temperature with values of $7\phantom{\rule{0.3em}{0ex}}\mathrm{J}\phantom{ 0.2em}{ 0ex}}{mol}}^{\ensuremath{-}1}1}, 0.05, and 0.1
Abstract: Magnetic, magnetocaloric, and magnetoresistance studies have been carried out on polycrystalline samples of Laves phase compounds $\mathrm{Ho}{({\mathrm{Ni}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x})}_{2}$ [$x=0$, 0.05, and 0.1]. The magnetocaloric effect in $\mathrm{Ho}{\mathrm{Ni}}_{2}$ is found to be maximum near the ordering temperature with values of $7\phantom{\rule{0.3em}{0ex}}\mathrm{J}\phantom{\rule{0.2em}{0ex}}{\mathrm{mol}}^{\ensuremath{-}1}\phantom{\rule{0.2em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ and $10.1\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for the isothermal magnetic entropy change and the adiabatic temperature change, respectively, for a field of $50\phantom{\rule{0.3em}{0ex}}\mathrm{kOe}$. With Fe substitution, the temperature variation of magnetocaloric effect shows an additional peak at low temperatures, which is much more pronounced than the peak at the ordering temperature. The origin of the low temperature peak is attributed to the field-induced metamagnetic transition. The magnetoresistance data also seem to support the occurrence of the metamagnetic transition.

66 citations


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01 Sep 1955
TL;DR: In this paper, the authors restrict their attention to the ferrites and a few other closely related materials, which are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present.
Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

2,659 citations

Journal ArticleDOI
TL;DR: This work aims to provide a comprehensive overview of electrospun nanofibers, including the principle, methods, materials, and applications, and highlights the most relevant and recent advances related to the applications by focusing on the most representative examples.
Abstract: Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

2,289 citations

Journal ArticleDOI
TL;DR: The magnetocaloric effect and its most straightforward application, magnetic refrigeration, are topics of current interest due to the potential improvement of energy efficiency of cooling and temperature control systems, in combination with other environmental benefits associated to a technology that does not rely on the compression/expansion of harmful gases.

941 citations

Journal ArticleDOI
TL;DR: A survey of the literature for ca. one thousand B-site substituted perovskite oxides can be found in this article, together with their electronic and magnetic properties and properties.

815 citations