32 research outputs found
Determination of structural changes and phase transformations in boron carbide by static and dynamic studies
No full textRecent transmission electron microscopy results demonstrate that the failure of B4C is commensurate with the segregation of boron icosahedra embedded in amorphous carbon in 2–3 nm wide amorphous bands along the (113) lattice direction, in good agreement with our recent theoretical results. Boron carbide is generally composed of multiple polytypes of B4C which have the same primitive lattice parameters but differ from each other by the location of the boron and carbon atoms in the unit cells. The unit cells are formed by a 12-atom B12-nCn icosahedron and a 3-atom (C3-nBn) chain. Our theoretical results indicate that one polytype, B12(C3), whose formation is responsible for
the failure of the entire material. This anomalous and poorly understood glass-like behavior in boron carbide has been the subject of research since its discovery over 70 years ago. The characterization of disorder in hot pressed and powder boron carbide samples
is therefore of primary interest. The research work has focused on characterization techniques which can be used at a micrometric sampling size so that individual powder grains of the material can be utilized. Specifically, micro-Raman and electrical
conductivity measurements can be used with micrometric gap cells to understand the disorder in B4C.The results also demonstrate that it is possible to induce transformations in boron carbide using electric fields that are comparable with those obtained under shock and nanoindentation. Our calculations present a hypothesis which can provide a solution to prevent the
premature failure of B4C. A route to achieve suppression of the B12(CCC) polytype without significantly affecting the elastic constants is via low concentration Silicon (Si) doping of B4C. Suppression of B12(CCC) by Si doping has implications towards
development of boron carbide armor with improved properties for protection against high velocity threats. In order to achieve this, nanostructures (nanowires, nanorods, etc.) of Sidoped boron carbide have been synthesized using a Solid-Liquid-Solid (SLS) growth
mechanism. The resulting structures have been characterized by SEM, TEM and Raman
spectroscopy and consolidated to evaluate their mechanical properties. In addition, the application of nanowires in a transparent and thermally conducting nanocomposite is demonstrated.Ph.D.Includes abstractVitaIncludes bibliographical referencesby Varun Gupt
A compact ultra‐wide band planar antenna with corrugated ladder ground plane for multiple applications
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Parasitic Rectangular Patch Antenna with Variable Shape Ground Plane for Satellite and Defence Communication
No full textU-Shaped Microstrip Patch Antenna with Partial Ground Plane for Mobile Satellite Services (MSS)
No full textDumbbell Shaped Microstrip Broadband Antenna
No full textAbstract In this article, a dumbbell shaped microstrip broadband microstrip antenna with partial ground plane is presented, The overall dimension of the proposed antenna is 20 × 15 × 1.5 mm3 and is fabricated on FR4 substrate which has electrical permittivity of 4.3 and loss tangent of 0.025. FR4 is a low cost and easily available. The thickness of the substrate is 1.5 mm. The impedance bandwidth of the proposed antenna is 151.11 % (3.48 GHz to 25 GHz). The peak gain and radiation efficiency of the proposed antenna are 4.5 dB and 68 % respectively in the operating frequency band. Due to introduction of rings on the edges of the octagon and cutting of circular slots with the rectangular slits in the ground plane the antenna starts resonating from 3.48 GHz to 25 GHz. Simulated results are in good agreement with the measured results. The proposed antenna covers partial frequency range for ultra-wide band applications, 3.5/5.5 GHz WiMAX band, 5.2/5.8 GHz WLAN band, 8/12 GHz X-band, 12/18 GHz Ku -band. It can be used in space and satellite communications etc. Curves of radiation pattern and S-parameter of both simulated and measured results are shown. The impedance curves, surface current, radiation efficiency, simulated return losses, gain, and radiation patterns of the proposed antenna are described in the paper
A Novel Approach For Compact Antenna With Parasitic Elements Aimed At Ultra-Wideband Applications
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Multi-band high-frequency antenna for satellite, automotive radar, and 6G communication
No full textAbstract This paper presents the design and development of a compact multi-band high-frequency antenna tailored for millimeter-wave applications, particularly within the 6G frequency range. The antenna features a small footprint of 10 × 12 × 1.5 mm2 and is designed using advanced electromagnetic simulations in CST Microwave Studio. Fabrication was carried out on an FR4 substrate, selected for its favorable properties at high frequencies. The antenna demonstrates an exceptionally wide impedance bandwidth of approximately 166%, covering a broad frequency range from 9.1 GHz to 100 GHz with a central frequency near 45.45 GHz. It exhibits stable radiation characteristics across the operating band, achieving a peak gain of 7.95dBi and an overall efficiency of 85%. Its miniaturized form factor and broad operational range make it a strong candidate for a wide spectrum of applications, including X-band radar, Ku-band satellite communications, K-band sensing, Ka-band 5G systems, V-band short-range wireless, W-band automotive radar, and future technologies such as 6G and security imaging systems
