Facile Synthesis of Amine-Functionalized CdTe Quantum Dots Dependence on Chain Length of Amines.

Amine-terminated CdTe quantum dots were fabricated by a non-toxic, facile, one-pot method via a non-dimethylcadmium precursor and non-injection-based synthesis. To enhance the quantum yield of the CdTe quantum dots, sufficient passivation of the surface was accomplished with alkyl amines, and their structure, optical properties, and photoluminescence efficiency were investigated. For amine-terminated CdTe quantum dots, the position of the absorption peak was red-shifted at timelapse, which implies an increase in the size of the nanocrystals. In particular, the shorter the alkyl chain length, the higher the growth rate. Photoluminescence quantum yield for oleylamine-CdTe quantum dots, determined using rhodamine 6G as a standard, showed an improvement of 41% compared to that of non-functionalized CdTe quantum dots. These results could be described by the kinetics of nucleation and growth and the effects of steric hindrance with regard to alkyl chain length on quantum dots.

Electrochemical Performances of Li2MnSiO4 Cathodes Synthesized by Mechanical Alloying Process.

We report the fabrication and electrochemical properties of Li2MnSiO4 powders produced by various solid-state reactions, such as ball-, attrition-, and bead-milling. Li2MnSiO4 powders prepared by bead-milling had the smallest particle sizes (~100 nm) and the largest amount of surface carbon (~20 wt%), which were produced by adding sucrose during milling process. The surface carbon layer can improve electronic/ionic conductivity of Li2MnSiO4 as cathode material for lithium ion battery. As expected, the bead-milled Li2MnSiO4 powder electrode showed the best electrochemical performance of the electrode materials obtained by the various solid-state reactions. This is attributed to the small particle size and facile electronic transport through the conductive carbon layer on each Li2MnSiO4 particle.

Materials flow analysis of neodymium, status of rare earth metal in the Republic of Korea.

Materials flow analysis of neodymium, status of rare earth elements (REEs) in the Republic of Korea has been investigated. Information from various resources like the Korean Ministry of Environment, Korea international trade association, United Nations Commodity Trade Statistics Database and from individual industry were collected and analyzed for materials flow analysis of neodymium. Demand of neodymium in the Republic of Korea for the year 2010 was 409.5 tons out of which the majority of neodymium, i.e., 68.41% was consumed by domestic electronics industry followed by medical appliances manufacturing (13.36%). The Republic Korea is one of the biggest consumer and leading exporter of these industrial products, absolutely depends on import of neodymium, as the country is lacking natural resources. The Republic of Korea has imported 325.9 tons of neodymium permanent magnet and 79.5 tons of neodymium containing equipment parts mainly for electronics, medical appliances, and heavy/light vehicles manufacturing industry. Out of which 95.4 tons of neodymium permanent magnet get exported as an intermediate product and 140.6 tons of neodymium in the form of consumable products get exported. Worldwide the neodymium is at the high end of supply chain critical metal because of increasing demand, scarcity and irreplaceable for technological application. To bring back the neodymium to supply stream the recycling of end of life neodymium-bearing waste can be a feasible option. Out of total domestic consumption, only 21.9 tons of neodymium have been collected and subsequently recycled. From material flow analysis, the requirement for an efficient recycling system and element-wise material flow management for these REEs in the Republic of Korea were realized and recommended.

Recycling process for recovery of gallium from GaN an e-waste of LED industry through ball milling, annealing and leaching.

Waste dust generated during manufacturing of LED contains significant amounts of gallium and indium, needs suitable treatment and can be an important resource for recovery. The LED industry waste dust contains primarily gallium as GaN. Leaching followed by purification technology is the green and clean technology. To develop treatment and recycling technology of these GaN bearing e-waste, leaching is the primary stage. In our current investigation possible process for treatment and quantitative leaching of gallium and indium from the GaN bearing e-waste or waste of LED industry dust has been developed. To recycle the waste and quantitative leaching of gallium, two different process flow sheets have been proposed. In one, process first the GaN of the waste the LED industry dust was leached at the optimum condition. Subsequently, the leach residue was mixed with Na2CO3, ball milled followed by annealing, again leached to recover gallium. In the second process, the waste LED industry dust was mixed with Na2CO3, after ball milling and annealing, followed acidic leaching. Without pretreatment, the gallium leaching was only 4.91 w/w % using 4M HCl, 100°C and pulp density of 20g/L. After mechano-chemical processing, both these processes achieved 73.68 w/w % of gallium leaching at their optimum condition. The developed process can treat and recycle any e-waste containing GaN through ball milling, annealing and leaching.

Enhanced low-temperature power density of solid oxide fuel cell by nickel nanoparticle infiltration into pre-fired Ni/yttria-stabilized zirconia anode.

The Ni/yttria-stabilized zirconia (YSZ) anode morphology of an anode-supported solid oxide fuel cell (SOFC) unit cell was improved by nickel nanoparticle infiltration. A colloidal route was selected for efficient fabrication of nickel metal nanoparticles and subsequent infiltration into the Ni/YSZ anode of a pre-fired SOFC unit cell. The power density of the anode-supported SOFC unit cell was measured by the potentiostatic method to investigate the effect of nickel nanoparticle infiltration. The increase in the power density of the Ni/YSZ anode with nickel nanoparticle infiltration became gradually less significant as the SOFC operating temperature increased from 700 to 800 degrees C. The improved performance of the Ni/YSZ anode with nickel nanoparticle infiltration compared to that of an anode without nickel nanoparticles is tentatively attributed to two factors: The discretely distributed nanoparticles on the nanostructured electrodes exhibited significant catalytic effects on the electrochemical performance of the electrodes, in addition to substantially increasing the triple phase boundary lengths.

Optical study of Mn-doped Bi4Ti3O,12 thin films by spectroscopic ellipsometry.

Mn-doped Bi4Ti3O12(B4T3) thin films grown at 400 degrees C on a Pt/Ti/SiO2/Si substrate through pulsed laser deposition (PLD) were analyzed via spectroscopic ellipsometry (SE). The PLD targets were produced through the conventional solid-state sintering method, and the film samples were annealed at 600 degrees C. The SE spectra of B4T3 films were measured using a rotating analyzer type ellipsometer within the 1.12 to 6.52 eV energy range, with the various incidence angles. The optical properties of the B4T3 films with increasing Mn-mol concentration were extracted using a multilayer model for the whole structure and the Tauc-Lorentz (TL) dispersion relation for the B4T3 film layer. The analysis results clearly showed that the significant changes in optical properties of B4T3 films are caused by thermal annealing procedure and the Mn-mol concentrations. X-ray diffraction (XRD) measurement was also performed to confirm the results of SE analysis.