Structure and defect interaction mediated transport mechanism of mixed di-tri valent cation containing ceria-based Ionic conductors

The aim of this study is to investigate structure and electrical response of mixed di-tri valent cation containing Ce_1-xHo_0.1Sr_xO_2-δ (x = 0.02–0.1) ionic conductor. The Rietveld analysis of X-ray diffraction profiles confirms the solubility limit of Sr²⁺ ions into ceria lattice upto x = 0.06 and the co-existence of secondary phase SrCeO₃ afterwards. With the increase of Sr²⁺ ions into ceria, formation of defect cluster increases and concentration of free oxygen vacancies decreases. The composition x = 0.06 shows lowest conductivity due the highest association energy of defect clusters. The dielectric constant plays a crucial role for the formation of defect clusters and conductivities of the compositions. The presence of SrCeO₃ and depletion of oxygen vacancies at grain boundary region enhance the grain boundary resistances. The dielectric constant of grain boundary region affects the grain boundary conductivity.     

On Predictability of Groundwater Level in Shallow Wells Using Satellite Observations

Management of groundwater resources needs continuous and efficient monitoring networks. Sparsity of in situ measurements both spatially and temporally creates hindrance in framing groundwater management policies. Remotely sensed data can be a possible alternative. GRACE satellites can trace groundwater changes globally. Moreover, gridded rainfall (RF) and soil moisture (SM) data can shed some light on the hydrologic system. The present study attempts to use GRACE, RF and SM data at a local scale to predict groundwater level. Ground referencing of satellite data were done by using three machine learning techniques- Support Vector Regression (SVR), Random Forest Method (RFM) and Gradient Boosting Mechanism (GBM). The performance of the developed methodology was tested on a part of the Indo-Gangetic basin. The analyses were carried out for nine GRACE pixels to identify relationship between individual well measurements and satellite-derived data. These nine pixels are classified on the basis of presence or absence of hydrological features. Pixels with the presence of perennial streams showed reasonably good results. However, pixels with wells located mostly near the stream gave relatively poorer predictions. These results help in identifying wells which can reasonably represent the regional shallow groundwater dynamics.     

Eu3+-doped transparent potassium lanthanum silicate (KLaSiO4) glass-ceramic nanocomposites: Synthesis,properties and application

The preparation of Eu³⁺-doped novel K₂O-La₂O₃-Al₂O₃-SiO₂ (KLAS)-based glass and transparent KLS (KLaSiO₄) glass–ceramic (GC) nanocomposites is reported. Nanostructures of the transparent GCs were analyzed by FE-SEM, H(R)-TEM and SAED techniques. The average size of the crystallites is calculated using XRD data and found to be in the range 13–19?nm which is matched well with the average particle size observed from TEM images in the range 5–18?nm. Photoluminescence spectra of Eu³⁺ ions exhibit emission transitions of ⁵D₀?→?⁷F_j (j?=?0 and 1–4) under the excitation at 394?nm. The emission spectra reveals up to 3-fold enhancement of luminescence performance of the KLS GC nanocomposites compared to as-prepared glass. This enhancement is caused due to entering of Eu³⁺ ions into the KLS crystal sites by replacing the La³⁺ ions. Such luminescence properties of KLS glass-ceramic nanocomposites could be a promising candidate as laser host for many laser devices.     

Predicting chemical reaction equilibria in molten carbonate fuel cells via molecular simulations

It has been recently suggested that hydroxide ions can be formed in the electrolyte of molten carbonate fuel cells when water vapor is present. The hydroxide can replace carbonate in transporting electrons across the electrolyte, thereby reducing the CO₂ separation efficiency of the fuel cell although still producing electricity. In this work, we obtain the equilibrium concentration of hydroxide in five molten alkali carbonate salts from molecular simulations. The results reveal that there can be a substantial amount of hydroxide in the electrolyte at low partial pressures of CO₂ . In addition, we find that the equilibrium concentration of molecular water dissolved in the electrolyte is over two orders of magnitude higher than that of CO₂ . Increasing the size and polarizability (or in other words reducing the “hardness”) of the cations present in the electrolyte can reduce the hydroxide fraction, but at the cost of lowering ionic conductivity.     

Initial biocompatibility and enhanced osteoblast response of Si doping in a porous BCP bone graft substitute

Granular shape biphasic calcium phosphate (BCP) bone grafts with and without doping of silicon cations were evaluated in regards to biocompatibility and MG-63 cellular response. To do this we studied Cellular cytotoxicity, cellular adhesion and spreading behavior and cellular differentiation with alizarin red S staining. Gene expression in MG-63 cells on the implanted bone substitutes was also examined at different time points using RT-PCR. In comparison, the Si-doped BCP granule showed more cellular viability than the BCP granule without doping in MTT assay. Moreover, cell proliferation was much higher when Si doping was employed. The cells grown on the silicon-doped BCP substitutes had more active filopodial growth with cytoplasmic webbing that proceeded to the flattening stage, which was indicative of well cellular adhesion. When these cells were exposed to Si-doped BCP granules for 14 days, well differentiated MG-63 cells were observed. Osteonectin and osteopontin genes were highly expressed in the late stage of differentiation (14 days), whereas collagen type I mRNA were found to be highly expressed during the early stage (day 3). These combined results of this study demonstrate that silicon-doped BCP enhanced osteoblast attachment/spreading, proliferation, differentiation and gene expression.     

Nanostructured cigarette wrapper encapsulated PDMS-RGO sandwiched composite for high performance EMI shielding applications

Here, we report a unique hybrid sandwich-type composite structure consisting of waste cigarette wrapper (CW) inserted in polydimethylsiloxane (PDMS) and reduced graphene oxide (RGO) composite matrix that displays a high EMI shielding effectiveness (SE) of ~50.79 dB in the extended Ku-band. The function of the inserted CW is to facilitate the multiple reflections and heat dissipation as it contains an Al coating. The interior of CW in the composite as well as the three-dimensional conductive networks of RGO throughout the PDMS matrix facilitates the microwave absorption through conductive dissipation and heat dissipation. Thus, an absorption-multiple reflection-absorption pathway is followed due to the combination of three sandwiched layers, that is, PDMS-RGO, CW, and PDMS-RGO. The sandwich architecture of the hybrid PDMS nanocomposite containing both CW and RGO displays a superior EMI SE over the nanocomposite that only contains RGO as filler in PDMS matrix. Moreover, the fabricated composite displays a high thermal conductivity which helps to dissipate the radiated microwave energy via a Joule heating effect. Thus, the fabricated lightweight and flexible hybrid composite structure could be an efficient microwave absorber which offers an attractive and cost-effective alternative approach to metal based conventional EMI shielding materials.     

Synthesis and characterization of l-tyrosine based novel polyphosphates for potential biomaterial applications

Starting from the natural amino-acid l-tyrosine, a diphenolic monomeric molecule was developed using carbodiimide mediated solid-phase synthesis techniques. This monomeric molecule was polymerized by reacting it in equimolar proportions with suitable dihalophosphates to yield novel biodegradable polyphosphates containing peptide linkages and phosphoester linkages alternating in the polymer backbone. The biodegradability of such a polymer is expected to arise from the hydrolytic degradability of the phosphoester linkages and the enzymatic degradability of the peptide linkages in the polymer backbone. Design of such a polymer is expected to make a significant contribution to biomaterials research, regarding drug delivery device and tissue engineering scaffold applications. The monomer was obtained by a novel solid phase carbodiimide-mediated amide coupling process. The subsequent polymers were obtained by solution-phase dehydrochlorination polycondensation reactions in the presence of a suitable acid acceptor. The synthesized polymers were characterized by ¹³C NMR, ³¹P NMR and FTIR for their chemical structure, by GPC for their molecular weight distribution, and by DSC and TGA for their thermal transition characteristics.