Facile and time-resolved chemical growth of nanoporous CaxCoO2 thin films for flexible and thermoelectric applications

CaxCoO2 thin films can be promising for widespread flexible thermoelectric applications in a wide temperature range from room-temperature self-powered wearable applications (by harvesting power from body heat) to energy harvesting from hot surfaces (e.g., hot pipes) if a cost-effective and facile growth technique is developed. Here, we demonstrate a time resolved, facile and ligand-free soft chemical method for the growth of nanoporous Ca0.35CoO2 thin films on sapphire and mica substrates from a water-based precursor ink, composed of in-situ prepared Ca2+-DMF and Co2+-DMF complexes. Mica serves as flexible substrate as well as sacrificial layer for film transfer. The grown films are oriented and can sustain bending stress until a bending radius of 15 mm. Despite the presence of nanopores, the power factor of Ca0.35CoO2 film is found to be as high as 0.50 x 10-4 Wm-1K-2 near room temperature. The present technique, being simple and fast to be potentially suitable for cost-effective industrial upscaling.Comment: 16 pages, 5 figure

Development and characterization of yttria stabilized zirconia and Al2O3 thin films by pulsed laser deposition:Special Issue

The present study concerns development of yttria stabilized zirconia (YSZ), Al2O3 and a multilayer of Al2O3-YSZ thin film deposition by pulsed laser deposition (PLD) technique for its application as thermal barrier coating (TBC). The detailed study included characterization (microstructure, composition, phase and surface topography) of the thin film. The phase analysis of the YSZ films deposited at room temperature showed amorphous feature, while the film deposited at high temperature showed the formation of tetragonal phase. Residual stress analysis of the coating showed the presence of compressive stress and was maximum at 573 K (sigma(11) = -8.1 GPa and sigma(22) = -6.4 GPa). Residual stress was found to decease with increase in substrate temperature and was found to be lowest at 973 K (sigma(11) = -3.0 GPa and sigma(22) = -1.7 GPa). The cross-sectional morphology of the YSZ and Al2O3 thin films deposited at room temperature showed presence of inter-columnar porosities which changed to a dense structure with increase in substrate temperature

Occurrence and diversity of microalgae in phytoplankton collected from freshwater community ponds of Hooghly District, West Bengal, India

A study on diversity, seasonal occurrence, distribution percentage of microalgal taxa and physico-chemical parameters of five community ponds, located in Chinsurah town, Hooghly district of West Bengal, has been carried out. Correlation between occurrence of microalgal genera and some parameters of environment, physico-chemical nature of natural water bodies were explored by Canonical Correspondence Analysis (CCA). Diversity indices have been calculated using PAST software program. A total of 23 microalgal taxa belonging to four algal classes were recorded and the study indicated that the microalgal diversity vary with variation in physico-chemical parameters of water and light intensity. Out of these genera, occurrence of Chodatella sp. in late summer and Tetrallantos sp. and Synechocystis sp. in winter season were specific. In CCA, multiple variables (dissolved oxygen, water temperature, electrical conductivity, pH, light intensity and inorganic phosphorous) played a significant role in occurrence of microalgal taxa. Observation concluded that the Chlorophycean members were dominant throughout the study period and the Shannon–Wiener diversity index was highest for a site with large number of Chlorophycean member. This study will help in future to assess water quality

Morphological variations in geographically isolated populations of Bryum coronatum Schwager (Bryaceae, Bryales)

Four populations of Bryum coronatum Schwager (Bryaceae, Bryales), collected from widely separated geographic regions - Sambalpur, Odisha; Lataguri, West Bengal; Gangtok and Changu, Sikkim; were studied with regard to variation in taxonomically significant morphological features as well as their dimension of both gametophytic and sporophytic features. In this study special emphasis has been put on spore dimension and spore ornamentation pattern as revealed by Scanning Electron Microscopy (SEM). Dimension of taxonomically significant morphological parameters were measured for four populations and were subjected to analysis of variance (One way ANOVA) and Principal component analysis (PCA). ANNOVA results showed significant variation for all features except leaf length and upper leaf cell breadth. PCA results corroborated ANNOVA result only for upper leaf cell breadth. Spore ornamentation as revealed through SEM, is found to be bacculate in all the populations. CCA graph revealed that summer, winter temperature and monsoon rainfall influence leaf size, lamina cell size, capsule size, peristome size and spore size. With the help of above mentioned observations and statistical analysis the morphological variations, due to phenotypic plasticity have been quantified to reach at a meaningful conclusion. Taxonomic significance of spore dimension and wall ornamentation is also discussed

Optical and electrical properties of undoped and doped Ge nanocrystals

Size-dependent photoluminescence characteristics from Ge nanocrystals embedded in different oxide matrices have been studied to demonstrate the light emission in the visible wavelength from quantum-confined charge carriers. On the other hand, the energy transfer mechanism between Er ions and Ge nanocrystals has been exploited to exhibit the emission in the optical fiber communication wavelength range. A broad visible electroluminescence, attributed to electron hole recombination of injected carriers in Ge nanocrystals, has been achieved. Nonvolatile flash-memory devices using Ge nanocrystal floating gates with different tunneling oxides including SiO2, Al2O3, HfO2, and variable oxide thickness [VARIOT] tunnel barrier have been fabricated. An improved charge storage characteristic with enhanced retention time has been achieved for the devices using VARIOT oxide floating gate

Improved infrared photoluminescence characteristics from circularly ordered self-assembled Ge islands

The formation of circularly ordered Ge-islands on Si(001) has been achieved because of nonuniform strain field around the periphery of the holes patterned by focused ion beam in combination with a self-assembled growth using molecular beam epitaxy. The photoluminescence (PL) spectra obtained from patterned areas (i.e., ordered islands) show a significant signal enhancement, which sustained till 200 K, without any vertical stacking of islands. The origin of two activation energies in temperature-dependent PL spectra of the ordered islands has been explained in detail

PEER Testbed Study on a Laboratory Building: Exercising Seismic Performance Assessment

From 2002 to 2004 (years five and six of a ten-year funding cycle), the PEER Center organized the majority of its research around six testbeds. Two buildings and two bridges, a campus, and a transportation network were selected as case studies to “exercise” the PEER performance-based earthquake engineering methodology. All projects involved interdisciplinary teams of researchers, each producing data to be used by other colleagues in their research. The testbeds demonstrated that it is possible to create the data necessary to populate the PEER performancebased framing equation, linking the hazard analysis, the structural analysis, the development of damage measures, loss analysis, and decision variables. This report describes one of the building testbeds—the UC Science Building. The project was chosen to focus attention on the consequences of losses of laboratory contents, particularly downtime. The UC Science testbed evaluated the earthquake hazard and the structural performance of a well-designed recently built reinforced concrete laboratory building using the OpenSees platform. Researchers conducted shake table tests on samples of critical laboratory contents in order to develop fragility curves used to analyze the probability of losses based on equipment failure. The UC Science testbed undertook an extreme case in performance assessment—linking performance of contents to operational failure. The research shows the interdependence of building structure, systems, and contents in performance assessment, and highlights where further research is needed. The Executive Summary provides a short description of the overall testbed research program, while the main body of the report includes summary chapters from individual researchers. More extensive research reports are cited in the reference section of each chapter