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Author

Sampat Raj Vadera

Other affiliations: Andhra University
Bio: Sampat Raj Vadera is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Nanoparticle & Ferrite (magnet). The author has an hindex of 26, co-authored 63 publications receiving 2242 citations. Previous affiliations of Sampat Raj Vadera include Andhra University.


Papers
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TL;DR: In this article , the effect of the filler material characteristics on percolation threshold and resultant electromagnetic (EM) properties of composites has been investigated, and the composites are prepared by loading different filler fractions (wt. %) of three nano size carbon black (CB) as fillers to achieve broadband microwave absorption properties and electromagnetic interference (EMI) shielding over the 8-18 GHz frequency range.
Abstract: Silicone rubber based lightweight composites have been prepared using nano carbon black (CB) as fillers to achieve broadband microwave absorption properties and electromagnetic interference (EMI) shielding over the 8–18 GHz frequency range. The effect of the filler material characteristics on percolation threshold and resultant electromagnetic (EM) properties of composites has been investigated. The composites are prepared by loading different filler fractions (wt. %) of three nano size CB having different characteristics, viz., CB1 (∼5–10 nm), CB2 (∼15–20 nm), and CB3 (∼30–40 nm) in a silicone rubber matrix. The volume resistivity measurements suggest low value of percolation threshold, i.e., 2 wt. % for CB1-rubber composite, 3 wt. % for CB2-rubber composites, as compared to 15 wt. % for CB3-rubber composite. Filler concentration dependent EM properties, i.e., dielectric constant and dielectric loss tangent (tan δe), are evaluated for all the CB-rubber composites. Furthermore, calculated reflection loss (RL) values for these composites indicate that 3 wt. % CB1-rubber, 5 wt. % CB2-rubber, and 18 wt. % CB3-rubber composites can provide more than 90% microwave absorption (RL > −10 dB) in X (8–12 GHz) and Ku (12–18 GHz) bands with thickness ∼2.7 and ∼1.9 mm, respectively. Interestingly, the composites with higher loading (15 wt. %) of CB1 in the rubber matrix are found to give EMI shielding effectiveness values of ∼ 42 dB over the 8–18 GHz frequency range. In conclusion, CB1-silicone rubber composites have been found to give the best performance among the three studied composites. This composite provides >90% microwave absorption over the X band with 2.7 mm thickness and over the Ku band with thickness 1.9 mm with lowest concentration of fillers, i.e., 3 wt. % CB1 in the rubber matrix, and hence found potential for development of lightweight microwave absorbers for stealth applications.

7 citations

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TL;DR: In this paper, the phase pure rhombohedral structure of prepared powder was confirmed by X-ray diffraction and Fourier transform infrared studies, which confirmed that the ferroelectric properties of multiferroic BiFeO3 are contributing significantly for the observed MW absorption with respect to the magnetic contribution.
Abstract: Nanostructured multiferroic BiFeO3 powder has been synthesized using sol–gel route followed by optimized post-annealing treatment. The phase pure rhombohedral structure of prepared powder was confirmed by X-ray diffraction and Fourier transform infrared studies. The room temperature weak ferromagnetic nature (~ 0.15 emu/g) exhibited by the nanocrystalline BiFeO3 sample (~ 50 nm) is attributed to the canted spin ordering in the sample. The BiFeO3/NBR rubber composites, with 50–80 wt% filler loading fractions, show the dual band resonating microwave (MW) absorption behavior. The reflection loss (R.L.) values enhanced and required absorber thickness reduced simultaneously with increasing BiFeO3 loading fraction in composite samples. These results confirm that the ferroelectric properties of multiferroic BiFeO3 are contributing significantly for the observed MW absorption with respect to the magnetic contribution.

5 citations

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TL;DR: In this article, meso-scale self-assembly of doped semiconductor nanocrystals leading to the formation of monocrystalline nanorods showing enhanced photo-and electro-luminescence properties are reported.

5 citations

Journal Article
TL;DR: In this paper, high-resolution TEM image shows formation of hexagonal shape particles having lattice fringes along the (001) plane of wurzite phase, which is consistent with the energy calculated by using effective mass approximation model of Brus.
Abstract: Highly stable and optically transparent colloidal ZnO QDs have been synthesized at room temperature without using any surface capping agent. The as synthesized QDs show phase singularity of ZnO particles having wurzite (hexagonal) structure. TEM as well as AFM studies indicate that the average crystalline size of QDs is ∼ 7nm. Further, high resolution TEM image shows formation of hexagonal shape particles having lattice fringes along (001) plane of wurzite phase. Photoluminescence (PL) studies show bright luminescence with peak maximum at 530nm due to oxygen vacancy centers (V o ) present in QDs. The optical transmission spectrum of colloidal QDs of ZnO shows sharp absorption at 3.48eV which is blue shifted as compared to bulk ZnO (3.36eV) due to the quantum confinement effect. The band gap energy observed in QDs of ZnO is consistent with the energy calculated by using effective mass approximation model of Brus.

5 citations


Cited by
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18 Jul 2011-Small
TL;DR: The synthesis, characterization, properties, and applications of graphene-based materials are discussed and the promising properties together with the ease of processibility and functionalization make graphene- based materials ideal candidates for incorporation into a variety of functional materials.
Abstract: Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.

2,246 citations

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1,682 citations

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TL;DR: The broadband and tunable high-performance microwave absorption properties of an ultralight and highly compressible graphene foam (GF) are investigated and it is shown that via physical compression, the microwave absorption performance can be tuned.
Abstract: The broadband and tunable high-performance microwave absorption properties of an ultralight and highly compressible graphene foam (GF) are investigated. Simply via physical compression, the microwave absorption performance can be tuned. The qualified bandwidth coverage of 93.8% (60.5 GHz/64.5 GHz) is achieved for the GF under 90% compressive strain (1.0 mm thickness). This mainly because of the 3D conductive network.

1,533 citations

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TL;DR: This review focuses on the recent development and various strategies in the preparation, microstructure, and magnetic properties of bare and surface functionalized iron oxide nanoparticles (IONPs); their corresponding biological application was also discussed.

1,143 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive review of the state-of-the-art research activities related to ZnS nanostructures is provided, with the focus on the critical experiments determining the electrical, chemical and physical parameters of the nanostructure, and the interplay between synthetic conditions and nanoscale morphologies.

1,090 citations