Fabrication of vertical-structured GaN-based light-emitting diodes using auto-split laser lift-off technique

Vertical-structured GaN-based light-emitting diodes (V-LEDs) were successfully fabricated using auto-split laser lift-off (LLO) technique. Compared to regular sapphire-substrate LED, the forward voltage of the V-LED at 20 mA is about 5% lower, while the light output power is about 43% higher. For V-LED, the saturation behavior of the light output power (Lop) is not observed when the injection current is increased to 480 mA, while the Lop of regular LED starts to decrease at around 110 mA. These improved results can be attributed to the total effect of less current crowding, surface roughening on n-GaN layer, highly reflective Ag mirror and good thermal conductivity of the electroplated Ni. Finally, mechanisms of the auto-split LLO technique are discussed based on one-dimensional heat equation. It is shown that the auto-split LLO process is determined by the vapor pressure of N2 gas, which is strongly dependent on the density of the laser energy. 漏 2012 The Electrochemical Society. All rights reserved

Distribution Characteristics and Accumulation Model for the Coal‐formed Gas Generated from Permo‐Carboniferous Coal Measures in Bohai Bay Basin, China: A Review

Coal‐formed gas generated from the Permo‐Carboniferous coal measures has become one of the most important targets for deep hydrocarbon exploration in the Bohai Bay Basin, offshore eastern China. However, the proven gas reserves from this source rock are remain low to date, and the distribution characteristics and accumulation model for the coal‐formed gas are not clear. Here we review the coal‐formed gas deposits formed from the Permo‐Carboniferous coal measures in the Bohai Bay Basin. The accumulations are scattered, and dominated by middle‐small sized gas fields, of which the proven reserves ranging from 0.002 to 149.4×108m3 with an average of 44.30×108m3 and a mid‐point of 8.16×108m3. The commercially valuable gas fields are mainly found in the central and southern parts of the basin. Vertically, the coal‐formed gas is accumulated at multiple stratigraphic levels from Paleogene to Archaeozoic, among which the Paleogene and Permo‐Carboniferous are the main reservoir strata. According to the transporting pathway, filling mechanism and the relationship between source rocks and reservoir, the coal‐formed gas accumulation model can be defined into three types: “Upward migrated, fault transported gas” accumulation model, “Laterally migrated, sandbody transported gas” accumulation model, and “Downward migrated, sub‐source, fracture transported gas” accumulation model. Source rock distribution, thermal evolution and hydrocarbon generation capacity are the fundamental controlling factors for the macro distribution and enrichment of the coal‐formed gas. The fault activity and the configuration of fault and caprock control the vertical enrichment pattern

The use of pyrite as a source of lixiviant in the bioleaching of electronic waste

Electronic waste (e-waste) contains a wide range of elements, many of which are highly toxic to environmental and human health. On the other hand e-waste represents a significant potential source of valuable metals. This study used microbial oxidation of pyrite to generate a biolixiviant. Its efficiency in the dissolution of metals from printed circuit boards (PCBs) was evaluated as well as the effects of metals and PCB concentrations on microbial activity. The addition of elemental metals (Cu, Cr, Ni, Sn, Zn) had an immediate inhibitory effect on pyrite oxidation, though leaching recovered after a period of adaptation. Bioleaching was inhibited initially by the addition of 1 % (w/v) ground PCB, but recovered rapidly, whereas pulp densities of =5 % had sustained negative impacts on culture activity and viability. The loss of culture viability meant that only abiotic copper dissolution occurred at=5 % PCB. Final copper recoveries declinedwith increasing PCB pulp density. The relatively high content of elemental iron caused a lag period in copper solubilisation possibly due to displacement reactions. Leptospirillum ferriphilum was primarily responsible for pyrite oxidation, and most affected by both the pure metals (particularly Ni and Cu) and PCB