Enhanced thermoelectric properties in Ge-doped and single-filled skutterudites prepared by unique melt-spinning method

In this paper, we determined an effective substitution of Ge at Sb sites in Nd-filled p-type skutterudites, a series of Nd_.9Fe₂Co₂Sb_12-xGe_x compounds with compositions of x?=?0, 0.1, 0.2, 0.3 and 0.4 were synthesized by home-made induction melting, assembled inside the glove box and followed by spark plasma sintering process (SPS). The thermoelectric properties are investigated as a function of Ge doping content with fixed Nd-filler at 0.9 and the formation of skutterudite phase is characterized by X-ray diffraction. All samples possess positive Seebeck coefficients, representing effective p-type doping. It is observed that the electrical conductivity decreases with decreasing Ge doping concentrations while increased with temperature due to bipolar effect. The lightly doped samples (x?=?0.1 and 0.2) have lower lattice thermal conductivity over the entire temperature range, in which x?=?0.2 sample shows the highest ZT value of 0.82 at 700?K, which is 30% higher than that of the Ge-free sample. The improvement in ZT can be attributed to the optimized carrier concentration and reduced thermal conductivity. The enhancement of ZT through Ge doping, coupled with drastically reduced processing time, shows that these compounds may have great potential in application as p-type segments of the thermoelectric devices.     

Degradation of waste High-density polyethylene into fuel oil using basic catalyst

High-density polyethylene (HDPE) has been degraded thermally and catalytically using MgCO₃ at 450 °C into liquid fraction in a batch reactor. Different conditions like temperature, time and catalyst ratio were optimized for the maximum conversion of HDPE into liquid fraction. Catalytic degradation yielded 92% liquid fraction whereas 90% wax was obtained with thermal degradation. The composition of the liquid fraction was characterized by physicochemical properties of petroleum fuel tests. The catalytic liquid fraction consisted of high concentration of C₈-C₉, C₁₃-C₁₄ and C₁₇-C₁₈ hydrocarbons. The distillation data showed that ∼50% of the fraction has boiling point in the range of gasoline and ∼50% in the range of diesel oil.     

Using NMR displacement measurements to probe CO2 entrapment in porous media

Carbon dioxide sequestration in aquifers is seen as a potential climate change mitigation technique. One physical mechanism by which this could occur is capillary trapping of discrete pore‐scale CO₂ bubbles (referred to as ganglia) in the pore space. Nuclear magnetic resonance (NMR) techniques were used to quantify the spatial distribution and pore environment of such CO₂ entrapment in a model porous medium (random glass bead packing). 3D images revealed a relatively macroscopically homogeneous CO₂ entrapment, even though the image resolution is insufficient to resolve individual CO₂ ganglia. Quantification of the pore environment of the CO₂ ganglia was achieved using NMR displacement propagators (displacement probability distributions), acquired both before and after CO₂ entrapment. Lattice Boltzmann (LB) simulations were used to facilitate interpretation of the propagator statistics by considering various pore environments in which CO₂ could become trapped. Comparison with the experimental data suggests that CO₂ is preferentially entrapped in comparatively larger pores. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Exogenous Silicon Modulates Growth,Physio-Chemicals and Antioxidants in Barley (Hordeum vulgare L.) Exposed to Different Temperature Regimes

Silicon - The exogenous application of silicon (Si) is reported to enhance tolerance of plants against various environmental stresses. Therefore, the present study was carried out to examine the...     

Polyethylene glycol assisted facile sol-gel synthesis of lanthanum oxide nanoparticles: Structural characterizations and photoluminescence studies

In this study, lanthanum oxide nanoparticles (La₂O₃ NPs) synthesised via the facile sol-gel method, using a solution of micro-sized lanthanum oxide powders containing 20% nitric acid and high molecular weight polyethylene glycol (PEG). The as synthesised La₂O₃ NPs were then characterized using X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), energy-dispersive X-ray (EDS) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and photoluminescence (PL) spectroscopy. Our findings indicated that the concentration of PEG strongly influences the particle size and the lattice strain of the La₂O₃ NPs. A single phase hexagonal crystal structure was confirmed via XRD studies with lattice constants, a =?b =?0.3973?nm and c =?0.6129?nm. The average crystallite size and lattice strains estimated were in the range of approximately 25–28?nm and 0.0050–0.0055 respectively. The incremental nature of the crystallinity and lattice strains of the NPs was observed with the subsequent enhancement of PEG-contents, while the average particle size was reduced. The average particle size of La₂O₃ NPs estimated from ESEM imaging was consistent with that obtained from the XRD data. The photoluminescence spectra revealed a strong emission band located at a wavelength of 365?nm (typical green band) for all La₂O₃NPsamples. This is ascribed to the recombination of delocalized electrons around the conduction band with a single charged state of a surface oxygen vacancy.