Dharmendra Pal

Structural and EPR studies of Lithium inserted layered Potassium tetra titanate K2Ti4O9 as material for K ions battery

AbstractLithium mixed Potassium tetra titanates with 0.2, 0.4, 0.6, 0.8 and 1.0 molar percentage of Li2CO3 (general formula K2−XLiXTi4O9) have prepared by a high temperature solid-state reaction route. The XRD results indicate that Lithium ions enter the unit cell maintaining the layered structure of solid solution. The crystals are monoclinic for xxa0=xa00.2, 0.4 and 0.6 while crystals are orthorhombic for xxa0=xa00.8 and 1.0 with a smalln change in ratio c/a in both cases. EPR analysis, The Lithium ions are accommodated with the Potassium ions in the interlayer space. The EPR spectra of Lithium mixed Potassium tetra titanates confirm the partial reduction of Ti4+ ions to Ti3+.

Autonomous Underwater Vehicle for 150m Depth–Development Phases and Hurdles Faced

This paper describes the various development phases and the associated hurdles faced during the design, fabrication, sub-system level testing, assembly, integration and overall system testing of an Autonomous Underwater Vehicle (AUV). This AUV has been designed for a depth of 150 m with multi-thruster actuation for shallow water applications. The AUV is having onboard power, electronics and advanced control module, navigation and payload sensors and modular software architecture. During the development of AUV various hurdles like how to power on AUV from outside, loose connections, isolation and grounding, water leakage, battery tripping, etc. have been faced and resolved. The present paper describes the complete development aspects in brief and highlights the various hurdles with remedies throughout the development. The AUV has been tested successfully for various missions at Idukki Lake, Cochin, India up-to a depth of 5m.

Influence of copper doping on structural and dielectric response on sodium lithium tri titanates (Na1.9Li0.1)Ti3O7:X Cu (0.0 ≤ X ≤ 0.1)

Pure and Cu-doped [(Na1.9Li0.1) Ti3O7XCu (0.01xa0≤xa0Xxa0≤xa01.0)] layered ceramics are prepared via the conventional solid state reaction method. The microstructure, dielectric properties and ac conductivity of copper doped (Na1.9Li0.1) Ti3O7 have been investigated. The XRD results indicate that copper ions enter the unit cell maintaining the layered structure of solid solution. The dependence of loss tangent (tanδ) and relative permittivity (εr) on temperature range (373–573xa0K) and frequency ranges (100xa0kHz–1xa0MHz) have been repeated for [(Na1.9Li0.1) Ti3O7]XCu (0.01xa0≤xa0Xxa0≤xa01.0)]. The dielectric losses in copper doped derivatives of layered (Na2-xLixTi3O7) (where Xxa0=xa00.1) ceramic are the cooperative contribution of electrical conductions, dipole orientation and space change polarization. The peaks of relative permittivity at high temperature indicate a possible ferroelectric phase transition. It is observed that low doping of paramagnetic ions (Cu2+) enhances electron hopping (polaron) conduction and impedes the interlayer ionic conduction. However, electron hopping conduction is dominant over lower temperature region, but as temperature raises interlayer ionic conduction begins to prevail.

Control Architecture for AUV-150: A Systems Approach

The aim of this paper remains to introduce the various design and runtime aspects of a state-of-the-art control architecture adopted for the development of an autonomous underwater vehicle (AUV-150), capable of operating up to a depth of 150 meters to perform sea-bed mapping and collecting oceanographic data. The system control architecture has been presented as an ensemble of both hardware and software modules organized in a well-connected framework for effective operation. Various specifications, harnessing layout and design issues have been discussed in this paper.

Effect of heavy mixing lithium with doping of manganese on structural, EPR and dielectric spectroscopic properties of Layered Na2Ti3O7

Sintered ceramic samples of Na2Ti3O7 with 50xa0% (1.0 Molar Percentage of Li2CO3 i. e. 50xa0% Lithium) with different doping molar percentages MnO2 (0.0xa0<xa0X<0.1) have been prepared through solid state reaction route. The microstructure, EPR, dielectric properties and ac conductivity of (NaLi)Ti3O7 with Mn [0.0xa0≤xa0X≤0.1] have been investigated. The X-ray diffraction patterns of pure and doped layered ceramics suggest the crystals are orthorhombic in phase. The room temperature electron paramagnetic resonance spectra reveal that that for lower percentage of doping manganese ions occupies Ti 4+ site with oxidation state Mn3+, while higher percentage of manganese ions doping leads to oxidation state Mn2+ in interlayer mixed (Na Li) site. In both cases the charge compensation mechanism should operate to maintain the overall charge neutrality of the lattice. For all pure and doped layered ceramics, ferroelectric transition having high transition temperature has been identifying at 648xa0K. Manganese ion doping decreases dielectric loss and increases dielectric constant due to inhibition of domain wall motion. It is apparent that ionic conduction becomes difficult due to presence of more lithium ions with sodium ions in interlayer space which shrinking the wide space of interlayer channels.

EPR AND MIXED IONIC-ELECTRONIC CONDUCTIVITY STUDIES OF PURE AND COPPER DOPED LAYERED LITHIUM SODIUM TITANATE (LiNa)Ti3O7

Sodium (50%) mixed layered Li2Ti3O7 and its 0.01, 0.05 & 1.0 molar percentage CuO doped derivatives have been prepared through high temperature solid state reaction and characterized through X- ray diffractometer, d.c. conductivity in the temperature range 373–700K and room temperature EPR investigation. Room temperature X-ray diffratograms confirm the phase evolution. Room temperature electron paramagnetic resonance (EPR) data show that Cu2+ occupies Ti4+ lattice sites giving rise to electric dipoles which increases electric permittivity. The absorption peak in EPR spectra gets broadened due to increased exchange interaction in heavily doped derivatives. Four distinct regions have been identified in the Ln(σT) versus 1000/T plots. Various electrical conduction mechanisms have involved during the whole temperature range of study