IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Effect of high strain rate deformation on the properties of SS304L and SS316LN alloys
No full textEffect of high strain rate deformation on the properties of SS304L and SS316LN alloys has been studied using Split Hopkinson Pressure Bar (SHPB) in the strain rate regime of 7 x 10(2)-3 x 10(3). The results indicate towards a higher rate of increase in flow stress for SS304L steel as compared to SS316LN with increasing the strain rates. The results corroborate well with the extent of strain induced volume fraction of martensite, as measured using Magnetic Barkhausen Emission (MBE) technique. The steep increase in strength of SS304L at low strain e.g., < 5% and strain rate up to similar to 1.8 x 10(3) s(-1) is attributed to strain induced martensitic transformation. Whereas, SS316LN remains mostly nonresponsive in the strain induced phase transformation process in the entire strain rate regime. Both the materials have shown a poor strain hardening behaviour. Up to the strain rate 1.8 x 10(3) s(-1) a growth of 23% and 18.5% of hardness value was observed in SS304L and SS316LN materials respectively. As the strain rate is further increased, hardness value in case of SS304L material has shown a decreasing trend, while that of SS316LN material has shown an increasing trend. The experimental observation has been tried to explain in terms of strain induced changes in their lattice structure that occur in the respective materials due to mechanical impact and their respective chemical composition
Origin of ferroelectricity in orthorhombic LuFeO3
No full textWe demonstrate that small but finite ferroelectric polarization (similar to 0.01 mu C cm(2)) emerges in orthorhombic LuFeO3 (Pnma) at T-N (similar to 600 K) because of commensurate (k = 0) and collinear magnetic structure. The synchrotron x-ray and neutron diffraction data suggest that the polarization could originate from enhanced bond covalency together with subtle contribution from the lattice. The theoretical calculations indicate enhancement of bond covalency as well as the possibility of structural transition to the polar Pna2(1) phase below T-N. The Pna2(1) phase, in fact, is found to be energetically favorable below T-N in orthorhombic LuFeO3 (albeit with very small energy difference) than in isostructural and nonferroelectric LaFeO3 or NdFeO3. Application of electric field induces finite piezostriction in LuFeO3 via electrostriction resulting in clear domain contrast in piezoresponse force microscopy images
In Situ Synthesis of Mesoporous TiO2 Nanofibers Surface-Decorated with AuAg Alloy Nanoparticles Anchored by Heterojunction Exhibiting Enhanced Solar Active Photocatalysis
No full textWe designed an electrospinning synthesis protocol to obtain in situ, the mesoporous TiO2 nanofibers, which are surface-decorated with plasmonic AuAg nanoparticles (AuAg-mTNF-H). Such alloy nanoparticles are found to be partially exposed on the surface of the nanofibers. Characterization by HRTEM and EDS confirmed the formation of 1:1 AuAg alloy nanoparticles on the surface of TiO2 nanofibers with heterojunction at the interfaces. On the basis of electron microscopic characterization, we proposed that, during the formation of the nanofibers, the incorporated metal ions with surface capping of negative charges migrated toward the outer surface of the nascent fibers under the influence of high positive voltage required for electrospinning. As a result, after the subsequent thermal treatment, the crystallization of TiO2 nanofibers and the formation of alloy nanoparticles took place, leading to the formation of a deep heterojunction through partial embedment of the nanoparticles. The formation of AuAg alloy also restricted the oxidation of Ag, thus making the nanoparticles highly stable in ambient condition. Accordingly, such unique AuAg-mTNF-H photocatalyst shows strong light absorption property covering the entire range of visible wavelengths with stability. The solar light harvesting property of AuAg-mTNF-H was verified by monitoring solar light induced H-2 evolution via water splitting and photodecomposition of MB. In both the cases AuAg-mTNF-H showed excellent H-2 evolution and photodecomposition of dye
Influence of fly ash and steam on microstructure, and mechanical properties of oxide bonded porous SiC ceramics
Get PDFCeramic filters specially SiC filters are used in advanced coal combustion and gasification processes to remove fine dust particles from the fuel gas at high temperatures and high pressure for protection of turbine blades and other downstream components from corrosion and erosion and to meet the environmental regulations. Processing of corrosion resistant porous SiC ceramics at low temperature using a simple technique is still challenging. In this study oxide bonded porous SiC ceramics were synthesized by cost effective method. The corrosion behaviour of SiC ceramic filter materials in presence of steam, coal ash and both coal ash and steam was investigated at 1000 degrees C for 96-240 h. The apparent changes in mass, porosity and density with corrosion duration and environment were recorded. Finally SEM, XRD and mechanical tests of the corroded samples were carried out. The corrosion test results indicated water vapour is the perpetrator for strength degradation. (C) 2019 SECV. Published by Elsevier Espana, S.L.U
Polarization Properties of Selectively Gold-filled Suspended Core Microstructured Optical Fibers
No full textWe study the polarization properties of suspended core microstructured optical fibers (SC-MOFs) with hexagonal lattice structure and high air-filling fraction having a single gold-filled hole along the horizontal axis. The interaction between the core-guided light and metal leads to surface plasmon resonance (SPR) at particular frequencies where the phase-matching condition is satisfied. We observe from the modal analysis that MOFs with high air-filling fraction offer the possibility of coupling of the fundamental mode with the first-order surface plasmon polariton (SPP) mode. With the increase in the suspension factor (SF), the fundamental mode couples with higher order SPP modes and the coupling strength also enhances. It also leads to an increase in modal birefringence. Reduction in beat length by an order of magnitude compared to the reported values is being reported for the first time to our knowledge. We have achieved the lowest beat length of 0.0105 mm at 1 μm wavelength for the structure having d/Λ = 0.85 and SF = 1.65. The results show that such plasmonic SC-MOFs may perform as efficient in-fiber polarizers and polarization filters
Influence of nanoparticle size on nucleation of electroactive phase and energy storage behaviour of zinc ferrite/ poly(vinylidene fluoride) nanocomposite
No full textThe incorporation of different size of nanoparticles in polymer matrix plays a dominating role in determining the overall structural, microstructural and electrical properties of the fabricated composites. In this paper, an investigation was done in order to establish the effect of incorporating different size of zinc ferrite (ZF) nanoparticles in poly(vinylidene fluoride) (PVDF) matrix. The incorporated spherical ZF nanoparticle induced nucleation of electroactive phases in PVDF matrix by means of electrostatic interaction between the surface charge of the filler and the dipoles of PVDF. The fraction of nucleated electroactive phases is strongly dependent on the size of the nanoparticles. There is a critical size of the nanoparticle, below which the nucleation efficiency of the filler diminishes as it may be swelled by the polymer macromolecules. On the other hand, if the filler size is too large, there is a possibility of formation of mixed conformation of polar and nonpolar phase. Further, this behaviour was correlated with the electrical response of composite where nanoparticle with the critical radius incorporated PVDF composite, exhibited maximum dielectric and ferroelectric property. Finally, a number of participating dipoles of polymer chain interact with ZF nanoparticle of different size were calculated by a model analysis and were represented schematically
A comparative study and experimental observations of optical fiber sagnac interferometric based strain sensor by using different fibers
No full textDesigning of strain monitoring system is a vibrant topic for the researchers. Strain monitoring systems are required in various fields such as mechanics, aeronautics, metallurgy and health monitoring of complex structures etc. Researchers designed different strain monitoring systems based on requirements. In this paper, we have reported a comparative study of Optical Fiber Sagnac Interferometer (OFSI) based strain sensors using three different types of fiber, i. e Polarization Maintaining Fiber (PMF), Standard Photonic Crystal Fiber (PCF) and High Birefringence Photonic Crystal Fiber (Hi-Bi PCF). The transmission spectrums of the sensors were recorded using Optical Spectrum Analyzer (OSA). We have experimentally analyzed the response and sensitivity of the sensors at different applied strains. The experimental results show that the optical interferometric strain sensor using PMF is having highest sensitivity in comparison to other sensors