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A core-envelope model for a spherical superdense distribution of matter is reported, with a core consisting of anisotropic
fluid engulfed by an envelope containing fluid with isotropic pressure is reported. The background space-time of the whole
configuration is characterized by a two-parameter parabolic geometry. The physical plausibility of the model is examined both
analytically and numerically, and suitability of the model for describing space-times of superdense stars containing strange
matter, such as Her-X1 and SAX, is also discussed. 相似文献
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Kaur Harsimrat Marwaha Anupma Singh Charanjeet Narang Sukhleen Bindra Jotania Rajshree Bai Yang Mishra Sanjay R. Singh Dharmendra Sombra A.S.B. Ghimire Madhav Dhruv Preksha 《Journal of Electronic Materials》2020,49(3):1646-1653
Journal of Electronic Materials - Microwave absorbers are an important topic of interest to mitigate electromagnetic interference. Here, we have investigated electromagnetic absorption properties... 相似文献
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Mohd. Hashim Alimuddin Sagar E. Shirsath S.S. Meena R.K. Kotnala Shalendra Kumar Pramod Bhatt R.B. Jotania Ravi Kumar 《Materials Chemistry and Physics》2013
The nanocomposites of the polyaniline and Co1−xCuxFe2O4 (PANI/CoCuFe) were prepared by in-situ oxidative polymerization of aniline. Prepared nanocomposites samples were characterized by using various experimental techniques like X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), vibrating sample magnetometer (VSM), Mössbauer spectroscopy and ultraviolet–visible spectrophotometry (UV–VIS). The elemental analysis as obtained from the energy dispersive X-ray spectroscopy (EDAX) measurement is in close agreement with the expected composition from the stoichiometry of the reactant solutions. XRD result confirms that all the samples have the single phase cubic spinel structure. Unit cell parameter ‘a’ is found to decrease with the increase in copper ion substitution. The crystallite size was investigated by using the Debye–Scherer formula and it was found in the range of ∼28–37 nm. FE-SEM confirmed the homogeneous and well defined surface morphology of the synthesized samples. FT-IR study showed the main absorption bands corresponding to the spinel structure those arose due to the tetrahedral and octahedral stretching vibrations. Cation distribution was estimated using XRD data. Hysteresis measurements revealed that the saturation magnetization decreased with increase in Cu2+ substitution. Magnetic environment of 57Fe in Cu-doped cobalt ferrite was investigated by using Mössbauer spectroscopy. Mössbauer study evidenced the ferrimagnetic behavior of the synthesized samples. 相似文献
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Chetna C. Chauhan Amrin R. Kagdi Rajshree B. Jotania Anupama Upadhyay Charanjeet Singh Sandhu Sagar E. Shirsath Sher Singh Meena 《Ceramics International》2018,44(15):17812-17823
Polycrystalline nanoparticles of M-type Ca(ZrCo)xFe12?2xO19 (0.0?≤?x?≤?1.0) hexaferrites were prepared using a simple heat treatment method at a low heating temperature of 650?°C. Effect of cobalt-zirconium substitution on the structural, microstructural, magnetic and dielectric properties was investigated. XRD analysis indicates that all the samples possess a hexagonal structure with anti-ferromagnetic α-Fe2O3 phase. The values of lattice parameters and cell volume found to be increased with increasing the cobalt-zirconium substitution along with the amount of α-Fe2O3 phase. Crystal symmetry has not affected by Zr–Co substitution in prepared calcium hexaferrite samples but the position of diffraction peak [108] is found to shift towards a lower angle as an increase in the substitution of Zr–Co. The crystallite size found to vary between 12 and 17?nm. SEM images show agglomerated grains and surface morphology has changed with Zr–Co substitution. EDX analysis of typical samples revealed the presence of Ca, Fe, Co, Zr. The magnetic analysis revealed the formation of multi-domain structure. Room temperature Mössbauer spectra of prepared samples show that all five sextets are merged together with a paramagnetic doublet and it confirmed that the size of particles is very small in the nano range. Single and double semicircle arcs were observed in Cole-Cole plots, due to the contributions of grain and grain boundaries resistance. 相似文献
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R B Jotania S M Joshi G J Baldha H H Joshi R G Kulkarni 《Bulletin of Materials Science》1991,14(4):903-906
The real and imaginary (lossy) components of a.c. susceptibility of high-T
c
superconductor YBa1·5Ca0·5Cu3O7−δ were measured as a function of temperature for different a.c. fields and frequencies. From the lossy component of the a.c.
susceptibility the transport critical current density and its temperature dependence have been computed on the basis of Kim’s
critical state model. 相似文献
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A systematic study of the Co1.4Ge0.4Fe1.2O4 system by X-ray, magnetization, and AC-susceptibility techniques is presented. The present system exhibits para-ferri-cluster spin glass transition for x ⩽0.2, while x ⩾0.3 it exhibits only a cluster spin glass transition. The AC susceptibility and DC magnetization data support the cluster spin glass ordering in the system. The system exhibits local spin canting behavior 相似文献
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