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C/SiO2 and C/SiC composite foam monoliths from rice husk for thermal insulation and EMI shielding
Chithra A.,Rajeev R.,Prabhakaran K. 한국탄소학회 2022 Carbon Letters Vol.32 No.2
Preparation of advanced functional materials from agricultural waste by eco-friendly processing route is inevitable for sustainable development. This work demonstrates the development of carbon/silica (C/SiO2) and carbon/silicon carbide (C/SiC) composite foam monoliths of low thermal conductivity, high EMI shielding performance and reasonable compressive strength from rice husk. The C/SiO2 and C/SiC composite foams are obtained by carbonization and subsequent carbothermal reduction, respectively, of rice husk–sucrose composites consolidated by filter-pressing rice husk powder dispersed in sucrose solutions of various concentrations (300–600 g L−1). The amorphous nature of silica in C/SiO2 and the presence of β-SiC in C/SiC are evidenced from XRD and TEM analysis. The compressive strength and thermal conductivity are depending on the foam density which is tailored by sucrose solution concentration. The compressive strength in the ranges of 0.32–1.67 and 0.19–1.19 MPa are observed for C/SiO2 and C/SiC foams, respectively, with density in the ranges of 0.26–0.37 and 0.18–0.29 g cm−3. The C/SiO2 and C/SiC exhibited thermal conductivity in the ranges of 0.150–0.205 W m−1 K−1 and 0.165–0.431 W m−1 K−1, respectively. The C/SiO2 and C/SiC composite foams show absorption dominated EMI shielding effectiveness in the ranges of 18–38.5 dB and 20–43.7 dB, respectively. The inherent pore channels and corrugated surface structure in rice husk, electrically conducting carbon and dielectric SiO2 and SiC contribute to the total EMI shielding.
Praveen Wilson,Sujith Vijayan,K. Prabhakaran 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.80 No.-
Microcellular SiC foams (MSiCFs) are produced by thermal setting of dispersions of silicon and NaClpowders in molten sucrose-glycerol solutions in a mould followed by carbonization, NaCl removal andreaction bonding at 1500 C. The acidic silica layer on silicon particle surface catalyses the setting of thepastes byOH condensation. The SiC nanowires grown in situ by a catalyst-free vapour–solid (VS)mechanism creates web-like architecture within the microcells (cell size2 to 22 mm) of the foams. TheMSiCFs with porosity in the range of 86.8–91.1 vol.% exhibit thermal conductivity and compressivestrength in the ranges of 0.334–0.758 W m 1 K 1 and 0.97–2.38 MPa, respectively. The MSiCFs showexcellent electromagnetic interference (EMI) shielding property in the X-band frequency regionenhanced by the in situ grown SiC nanowires within microcells. The EMI shielding effectiveness (45.6 dB)and specific shielding effectiveness (137 dB g-1 cm3) are the highest reported for SiC foams.
PV fed Hybrid Power Converter for rural home applications
Karthikeyan A,Praneeth C.V.S,Prabhakaran K. K. 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposes a standalone PV fed hybrid power converter for rural home applications. The aim of the proposed system is to simultaneously deliver the power extracted from PV panels to DC and AC home loads using the proposed hybrid converter topology. The system operates in either MPP or Non–MPP mode depending on the total power demanded by the loads. Modified Perturb and Observe (P&O) MPPT algorithm is used to extract maximum power from PV panels. SPWM based modified PWM technique is used for converter operation. In the MPP mode the power distribution to DC load and AC load is in accordance with the duty generated by modified MPPT. In Non MPP mode, power distribution is in accordance with the duty generated by the single loop voltage control for DC load. The simulation studies for the proposed system are carried out in MATLAB/SIMULINK environment.
P. G. Freeman,S. R. Giblin,K. Hradil,R. A. Mole,D. Prabhakaran 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.10
The magnetic excitation spectrums of charge stripe ordered La2−xSrxNiO4 x = 0.45 and x = 0.4were studied by inelastic neutron scattering. We found the magnetic excitation spectrum of x = 0.45from the ordered Ni2+ S = 1 spins to match that of checkerboard charge ordered La1.5Sr0.5NiO4. The distinctive asymmetry in the magnetic excitations above 40meV was observed for both doping levels, but an additional ferromagnetic mode was observed in x = 0.45 and not in the x = 0.4. We discuss the origin of crossover in the excitation spectrum between x = 0.45 and x = 0.4 with respect to discommensurations in the charge stripe structure.
Bilayer splitting and wave functions symmetry inSr3Ir2O7
Moreschini, L.,Moser, S.,Ebrahimi, A.,Dalla Piazza, B.,Kim, K. S.,Boseggia, S.,McMorrow, D. F.,Rønnow, H. M.,Chang, J.,Prabhakaran, D.,Boothroyd, A. T.,Rotenberg, E.,Bostwick, A.,Grioni, M. American Physical Society 2014 Physical review. B, Condensed matter and materials Vol.89 No.20
The influence of dimensionality on the electronic properties of layered perovskite materials remains an outstanding issue. We address it here for Sr3Ir2O7, the bilayer compound of the iridate Srn+1IrnO3n+1 series. By angle-resolved photoemission spectroscopy we show that in this material the interlayer coupling is large and that the intercell coupling is, conversely, negligible. From a detailed mapping of the bilayer splitting, and from the intensity modulation of the bonding and antibonding bands with photon energy, we establish differences and similarities with the prominent case of the bilayer superconducting cuprates.