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Mn/C-codoped GaN nanostructures are prepared by carbothermal nitridation with active charcoal as the carbon source. The studies have shown that carbon doping in the GaN matrix has favored the N sites over the Ga sites, Mn/C-codoping in the GaN matrix is energetically favorable, and the C-codoping has enhanced the preference of the ferromagnetic coupling to the antiferromagnetic coupling between the two doped Mn sites.

Density functional theory is used to study the structural, electronic and optical properties of oxygen-defective [Zn.sub.3][N.sub.2]. The results have shown that [Zn.sub.3][N.sub.2] with nitrogen replaced by oxygen is more stable than that with interstitial oxygen and substitutional oxygen for nitrogen in defective [Zn.sub.3][N.sub.2] is responsible for the n-type conduction character.

Density functional theory (DFT) calculations are used to study the N-doping effects on the electronic and optical properties of Ti[O.sub.2] rutile crystal. The results have shown that substitutional N to Ti structure has a bandgap narrowing in the rutile crystal because N impurity introduces some energy states in the bottom of the conduction band.

Performance of wastewater treatement sludge-carbon (SC) can be evidently improved by removing the inorganic fractions. A novel investigation for recovery of Al from acid leaching of SC and synthesis of nano-Al(OH)3 has been conducted. Results show that the sodium aluminates with high purity can be obtained by effectively dissolving the inorganic fractions from SC and by further removing the impurities (Fe3+, Ca2+, Mg2+, S4+, and P3+). Highly dispersed Al(OH)3 with high SBET is obtained at pH = 6. The peaks of -CH2- vibration and the C1s peaks (binding energies of 284.6 eV) imply that polyethylene glycol 1000 (PEG-1000) is chemically adsorbed on the surface of Al(OH)3 samples, which is propitious to reduce the hydrogen bonds between water molecules and surface -OH groups to prevent hard agglomeration. The stretching vibration peaks of [AlO2]- and the Na1s peaks confirm that a trace of sodium aluminate (NaAl(OH)4, Na+(H2O)4[Al(OH)4-], or the dehydrated monomers) is retained in the prepared Al(OH)3. The main phase transformation for calcination (=800 °C) of the SC-derived Al(OH)3 is from amorphous Al(OH)3 to amorphous A12O3. Here we highlight that production of Al(OH)3 and SC from sludge provides the potential application in significant quantities that can revolutionize the handling of such kinds of harmful waste. [ABSTRACT FROM AUTHOR]

The N-doping effects on the electronic and optical properties of TiO2rutile crystal have been studied using density functional theory (DFT). The calculations of several possible N-doped structures show that band gaps have little reduction but some N 2p states lie within the band gap in the substitutional N to O structure and interstitial N-doped rutile supercell, which results in the reduction of the photon-transition energy and absorption of visible light. In contrast, substitutional N to Ti doped model has a significant band-gap narrowing. The results maybe clarify confusions in nitrogen-doped TiO2rutile crystal. [ABSTRACT FROM AUTHOR]