Here, High Energy Ball Milling (HEBM) is used to prepare Cr doped ZnO (Zn 1-x Cr x O, x = 0-0.04)... more Here, High Energy Ball Milling (HEBM) is used to prepare Cr doped ZnO (Zn 1-x Cr x O, x = 0-0.04) nanoceramics and their electrical behaviour is studied in detail. The X-ray diffraction suggests a hexagonal wurtzite structure. The Rietveld refinement XRD pattern of the sample calcined at 900 • C suggests that up to 4 at% of Cr can be doped into the ZnO structure. After sintering, the growth in the particle size was observed for Cr doped ZnO samples. The complex impedance behaviour of samples suggests a decrease in resistance with temperature. This shows the Negative Temperature Coefficient of Resistance (NTCR) characteristic of the Cr doped ZnO sample in the studied temperature range (300-500 • C). At higher temperature, the electrical relaxation behaviour is of the non-Debye type as observed from the relaxation time distribution. The equivalent electrical circuit of ZnO and Cr doped ZnO ceramic samples are a parallel arrangement of bulk capacitance (C b) and bulk resistance (R b).
In this study, monoclinic LiFeBO 3 was carbon-coated and iodine doped via a solid-state reaction ... more In this study, monoclinic LiFeBO 3 was carbon-coated and iodine doped via a solid-state reaction to improve the electrochemical performance of pristine LiFeBO 3 as cathode material in lithium-ion batteries. In order to enhance the electrical conductivity of LiFeBO 3 , the highly electronegative iodide anion was doped in a limited amount (x = 0.005) at the oxygen site of the borate to produce LiFeBO 3Àx I 2x. A thin carbon layer was then deposited in situ on the LiFe-BO 2.995 I 0.01 particles (to produce "LFBI/C") to protect them from air and moisture. Field-emission scanning electron microscopy (FE-SEM) data indicated the aggregated morphology of the synthesized samples. Powder X-ray diffraction (XRD) and 7 Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) measurements revealed that both the doped and undoped LiFeBO 3based samples had mainly monoclinic structures, although a small amount of a vonsenite-type phase was formed upon iodine doping. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) data confirmed the successful insertion of iodine in the cathode material. The specific discharge capacity of LFBI/C at 0.05 C rate (144.68 mAh g À1) was higher than that of carbon-coated LiFeBO 3 (122.46 mAh g À1). The increased capacity of LFBI/C was also evident in long charge-discharge cycles conducted at 1 C rate and in the overall rate performance. Interestingly, the iodine-doped sample exhibited significantly high specific discharge capacity even at 10 C rate.
Globular amorphous carbonaceous materials embedded with graphite encapsulated metallic Co-nanopar... more Globular amorphous carbonaceous materials embedded with graphite encapsulated metallic Co-nanoparticles with a high degree of crystallinity are synthesized by pyrolysis and demonstrated as excellent candidates for optical limiters.
Physical chemistry chemical physics : PCCP, Jan 21, 2017
Homogenously dispersed nanoparticles having a magnetic core and graphitic-carbon shells in amorph... more Homogenously dispersed nanoparticles having a magnetic core and graphitic-carbon shells in amorphous carbon globules are prepared using a low-cost pyrolysis technique. Synergetic microwave absorption in carbon globules embedded with nanoscale iron/iron-carbide graphite (FeC) particles via dielectric, magnetic and Ohmic losses is emphasized in this work. The electromagnetic interference (EMI) shielding properties of the FeC nanoparticles dispersed in polyvinylidene fluoride (PVDF) are studied in the 8-18 GHz frequency range and compared with those of PVDF composites containing similar weight fractions of conducting/magnetic phase micro-particles such as carbonyl iron (CI) or electrolytic iron (EI) or a similar amount of amorphous carbon phase such as amorphous carbon (a-C) globules. The PVDF/FeC composite shows a maximum SET value of -23.9 dB at 18 GHz, as compared to the SET for the other composites. The enhanced EMI shielding in the PVDF/FeC composite is attributed to the increased...
Here, High Energy Ball Milling (HEBM) is used to prepare Cr doped ZnO (Zn 1-x Cr x O, x = 0-0.04)... more Here, High Energy Ball Milling (HEBM) is used to prepare Cr doped ZnO (Zn 1-x Cr x O, x = 0-0.04) nanoceramics and their electrical behaviour is studied in detail. The X-ray diffraction suggests a hexagonal wurtzite structure. The Rietveld refinement XRD pattern of the sample calcined at 900 • C suggests that up to 4 at% of Cr can be doped into the ZnO structure. After sintering, the growth in the particle size was observed for Cr doped ZnO samples. The complex impedance behaviour of samples suggests a decrease in resistance with temperature. This shows the Negative Temperature Coefficient of Resistance (NTCR) characteristic of the Cr doped ZnO sample in the studied temperature range (300-500 • C). At higher temperature, the electrical relaxation behaviour is of the non-Debye type as observed from the relaxation time distribution. The equivalent electrical circuit of ZnO and Cr doped ZnO ceramic samples are a parallel arrangement of bulk capacitance (C b) and bulk resistance (R b).
In this study, monoclinic LiFeBO 3 was carbon-coated and iodine doped via a solid-state reaction ... more In this study, monoclinic LiFeBO 3 was carbon-coated and iodine doped via a solid-state reaction to improve the electrochemical performance of pristine LiFeBO 3 as cathode material in lithium-ion batteries. In order to enhance the electrical conductivity of LiFeBO 3 , the highly electronegative iodide anion was doped in a limited amount (x = 0.005) at the oxygen site of the borate to produce LiFeBO 3Àx I 2x. A thin carbon layer was then deposited in situ on the LiFe-BO 2.995 I 0.01 particles (to produce "LFBI/C") to protect them from air and moisture. Field-emission scanning electron microscopy (FE-SEM) data indicated the aggregated morphology of the synthesized samples. Powder X-ray diffraction (XRD) and 7 Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) measurements revealed that both the doped and undoped LiFeBO 3based samples had mainly monoclinic structures, although a small amount of a vonsenite-type phase was formed upon iodine doping. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) data confirmed the successful insertion of iodine in the cathode material. The specific discharge capacity of LFBI/C at 0.05 C rate (144.68 mAh g À1) was higher than that of carbon-coated LiFeBO 3 (122.46 mAh g À1). The increased capacity of LFBI/C was also evident in long charge-discharge cycles conducted at 1 C rate and in the overall rate performance. Interestingly, the iodine-doped sample exhibited significantly high specific discharge capacity even at 10 C rate.
Globular amorphous carbonaceous materials embedded with graphite encapsulated metallic Co-nanopar... more Globular amorphous carbonaceous materials embedded with graphite encapsulated metallic Co-nanoparticles with a high degree of crystallinity are synthesized by pyrolysis and demonstrated as excellent candidates for optical limiters.
Physical chemistry chemical physics : PCCP, Jan 21, 2017
Homogenously dispersed nanoparticles having a magnetic core and graphitic-carbon shells in amorph... more Homogenously dispersed nanoparticles having a magnetic core and graphitic-carbon shells in amorphous carbon globules are prepared using a low-cost pyrolysis technique. Synergetic microwave absorption in carbon globules embedded with nanoscale iron/iron-carbide graphite (FeC) particles via dielectric, magnetic and Ohmic losses is emphasized in this work. The electromagnetic interference (EMI) shielding properties of the FeC nanoparticles dispersed in polyvinylidene fluoride (PVDF) are studied in the 8-18 GHz frequency range and compared with those of PVDF composites containing similar weight fractions of conducting/magnetic phase micro-particles such as carbonyl iron (CI) or electrolytic iron (EI) or a similar amount of amorphous carbon phase such as amorphous carbon (a-C) globules. The PVDF/FeC composite shows a maximum SET value of -23.9 dB at 18 GHz, as compared to the SET for the other composites. The enhanced EMI shielding in the PVDF/FeC composite is attributed to the increased...
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