Papers by Keyword: Transition Metal Oxide

Abstract: Spinel ferrite nanoparticles are potential candidates for multiple biomedical applications. Spinel ferrite nanoparticles have been studied extensively for understanding physical, chemical, electro-optical as well as magnetic properties which are fascinating due to cationic distributions corresponding to tetrahedral sites and octahedral sites in a cubic phase. Biocompatibility and large magnetic moment are basic requirements in spinel ferrite nanoparticles for efficient functioning in specific application purpose. Fe₃O₄ (magnetite) is an important member of spinel ferrite group with high chemical stability and ferrimagetic material property at nanodimension. Superparamagnetic state and biocompatibility of magnetite (Fe₃O₄) spinel ferrite nanoparticle has already been proven. Spinel ferrite magnetite nanoparticles have been developed based on precipitation of iron oxide using ferric and ferrous ions at the ratio 2:1 in alkaline media at and above 100°C. The experimental parameters have been set to synthesize pure and uniformly sized magnetite nanoparticles. No other phases of iron oxides were detected other than magnetite spinel phase in the XRD result. The average crystal size has been determined from XRD peak broadening. Absorption spectra were investigated using UV-Vis Spectrometer and FTIR. Thermal and magnetic measurements were carried out Digital Scanning Calorimeter and SQUID Magnetometer. One sample of the prepared nanoparticles with polymer coating of polyvinyl alcohol has been studied for superparamagnetic nature. Superparamagnetic particles show saturation value of magnetization 51.26 emu/g at 100 K. ZFC-FC curves for two samples with polymer coating of polyvinyl alcohol and hydroxy-propyl methyl cellulose have also been studied. Keywords: Spinel Ferrite, Magnetite, Ferrimagnetism, Transition metal oxide, Superparamagnetism. Statements and declarations Competing Interests: The authors declare that there is no competing financial interest that are related directly or indirectly to the reported work in this paper. Conflict of interest: There is no conflict of interest. Acknowledgements The Authors are grateful to IISER Bhopal, CRF facility for providing instrumentation facility to characterize magnetic properties. We acknowledge thanks to Lovely Professional University for providing us necessary characterization technique for the XRD analysis and thermal analysis.

Abstract: High energy and power density, good life cycle are highly sought in fabricating supercapacitors. In this study, Co₃O₄ was successfully deposited on nickel foam via electrochemical route. The nucleation of cobalt hydroxide and its transformation to oxide were monitored using chronoamperometry and cyclic voltammetry. Changes in current density and detected redox peaks suggest the electrochemical activity of Co₃O₄ in an alkaline media. A specific capacitance 1291 F/g at current density of 2.5 mA/cm was achieved showing the supercapacitive property of the synthesized Co₃O₄. EDX results confirms the incorporation of samarium to cobalt oxide. Furthermore, scanning electron microscopy (SEM) reveals the evolution of nanosheets to nanoflowers as the electrochemical synthesis parameters were varied. The effect of morphology on the electrochemical activity and performance of Co₃O₄ with Samarium could pave way in developing high energy and power density electrode for supercapacitors.

Abstract: Cobalt oxide (Co₃O₄) nanosheets were successfully synthesized and deposited onto the nickel foam substrate via electrochemical route. The chronoamperograms during the deposition revealed electrochemical activity resulting to the nucleation of the cobalt ions forming cobalt hydroxide and transformation to cobalt oxide. Energy dispersive xray (EDX) results elucidates the presence of samarium, cobalt and oxygen in the sample. The formation of nanosheets was confirmed by scanning electron microscopy. It was found that adding more samarium in the electrochemical bath changes the morphology of the final product from nanosheets to nanoflowers. The evolution of nanosheets to nanoflowers of the synthesized material could pave way for its potential application in the field of electrochemical energy storage devices and electrochemical sensors.

Abstract: We report the use of nanostructured metal oxides as cathode interfacial layers for improved performance hybrid polymer electronic devices such as light-emitting diodes (PLEDs) and solar cells. In particular, we employ a stoichiometric (WO3) and a partially reduced tungsten metal oxide (WOx) (x<3), both deposited as very thin layers between an aluminum (Al) cathode and the active polymer layer in hybrid PLEDs and achieve improved PLED device performance reflected as an increase in the current density and luminance and a reduction of the operating voltage. On the other hand, we investigate the use of a stoichiometric tungsten oxide layer as a thin cathode interfacial layer in hybrid polymer photovoltaic cells (Hy-PVs). We demonstrate improved photovoltaic cell performance, primarily as a result of the substantial increase in the short-circuit photocurrent. The improved PLED device characteristics are attributed to enhanced electron injection that primarily results from the lowering of the effective interfacial barrier, as evidenced by photovoltaic open circuit voltage measurements, and improved electron transfer. On the other hand, the observed improvement in the hybrid solar cell performance is primarily attributed to its enhanced internal quantum efficiency, most likely due to the improved electron transport and extraction at the active layer/WO3/Al interface and the reduction of the corresponding contact series resistance. Correlation between the metal oxide surface morphology and the device performance is also investigated and will be discussed.

Abstract: We report on photoemission studies of SrTiO3, Pr0.55(Ca1-ySry)0.45MnO3 (PCSMO, y=0.25,0.40), and Ti1-xCoxO2-δ (x=0.05, 0.10) under laser illumination and discuss the origins of the unusual electronic structure changes induced by optical excitation at the surfaces of these transition-metal oxides. The present study shows that photoemission spectroscopy is a powerful tool to explore novel photo-induced electronic states which can open up possibilities of new optical devices.

Abstract: Nanoscale particle size of metal oxides and hydroxides showed enhanced various physical properties and performance. We established a simple, cost-effective, room-temperature (RT) precipitation method for the preparation of the magnetic, first-raw transition metal (TM) hydrated oxide and hydroxide nanoparticles. This method is based on the use of the TM nitrate, as the metal source, and cyclohexylamine (CHA), as a precipitating agent, either in the water (H2O) or ethanol (EtOH) medium. We found that the precipitation medium and the identity of precipitated TM strongly affect the morphology, particle size, and magnetism of the product. The morphology varies from spherical, to rectangular, to rod shape; while the size varies in the range of 5-30 nm. All samples showed paramagnetic behavior with Curie temperatures span over a wide range (20-150K). Huge hysteresis looses has been observed for manganese (Mn) sample, prepared in H2O. The coercively (Hc) at 4.2K for this sample is about 1.5T, which is comparable to the strongest permanent magnets (Nd-based magnets) available at room temperature. The energy product (Hc*MR) is about 4.5*105 (emu/g)Oe.

Abstract: The most attractive way to storage hydrogen safely and economically is in metal hydrides. In particular, magnesium has attracted much interest since their hydrogen capacity exceeds that of known metal hydrides. One of the approaches to improve the kinetic is addition of metal oxide. In this paper, we tried to improve the hydrogen absorption properties of Mg. The effect of transition oxides, such as Nb2O5 on the kinetics of the Mg hydrogen absorption reaction was investigated. MgHx-Nb2O5 composites have been synthesized by hydrogen induced mechanical alloying. The powder synthesized was characterized by XRD, SEM, EDX, BET and simultaneous TG/DSC analysis. The hydrogenation behaviors were evaluated by using an automatic Sievert’s type PCT apparatus. Absorption/desorption kinetics and PCI of MgHx catalyzed with 5wt.%Nb2O5(as-received), 5wt.%Nb2O5(30min. milled) are determined at 423, 473, 523, 573, 623K.

Abstract: Using mesoporous silicas as hard templates and facilitating crystal growth of transition metal oxides inside the pores, some mesoporous crystals can be produced after removing the templates. This paper gives a brief review of the research of mesoporous crystals of transition metal oxides in the last five years, including the technical development and potential applications of the new form of oxides.

Abstract: The electrical and structural properties of the mixture of Co3O4 and In2O3 were studied. All the samples were added with 2% nanocrystalline SiO2 and sintered at 1000°C for 2 hours. The sintered bodies of the samples were of high density and the average particle size was ~2μm. The materials showed the NTC behavior in a wide temperature range (100-350°C). The resistivity of the materials at room temperature decreased with increase the content of the In2O3 from 0% to 10%. The thermistor constant (B) values and activation energy(E) were 7835, 6637, 5903K, and 0.675, 0.572, and 0.509 eV as the content of In2O3 were 0%, 5% and 10%, respectively.

Abstract: This work reports the effect of doping aluminium in the Li[Li(1/3-x/3)Crx-0.05M0.05Mn(2/3- 2x/3)]O2 (x= 0.2; M= Al), layered cathode material. The cathode material was prepared by citric acid assisted sol-gel process. The sample is characterized by TG/DTA, XRD and FESEM measurements. The Al- doped cathode has delivered an initial discharge capacity of 250 mAh/g with a current density of 0.12 mA/cm2.