Synthesis of substituted β-styrylmalonates by sequential isomerization of 2-arylcyclopropane-1,1-dicarboxylates and (2-arylethylidene)malonates

A method has been developed for the synthesis of substituted β-styrylmalonates by conversion of 2-arylcyclopropane-1,1-dicarboxylates (ACDC) in the presence of gallium trichloride into the corresponding 1,2-zwitterionic intermediates or (2-arylethylidene)malonates, followed by treatment with pyridine at rt leading to an isomerization of the emerging double bond. This method allows one to expand these reactions to include ACDC with acceptor substituents at the aromatic ring.

Recovery of Gallium from Simulated GaAs Waste Etching Solutions by Solvent Extraction

Gallium arsenide is used in semiconductor industries worldwide. Numerous waste etching solutions are produced during the processes of GaAs wafer production. Therefore, a complete and eco-friendly technology should be established to recover gallium as a gallium chloride solution and remove arsenic ion from waste GaAs etching solution. In this study, the gallium trichloride and arsenic trisulfide powders were dissolved in ammonia solutions to prepare the simulated solutions, and the pH value was adjusted to pH 2 by nitric acid. In the extraction step, the GaAs etching solutions were extracted using 0.5 M Cyanex 272 solutions in kerosene at pH 2 and 0.1 O/A ratio for 5 min. The extraction efficiency attained 77.4%, which had an optimal ratio of concentration, and the four steps extraction efficiency attained 99.5%. After extraction, iron sulfate heptahydrates were added into the raffinate, and the arsenic ions were precipitated. The removed rate attained 99.9% when the Fe/As ratio was 10. In the stripping step, the organic phase was stripped with 0.5 M hydrochloric acid at 1 O/A ratio for 3 min, and 97.5% gallium was stripped. Finally, the purity of gallium chloride solution was 99.95% and the gallium was seven times the concentration of the etching solutions.

Investigations into the Growth of GaN Nanowires by MOCVD Using Azidotrimethylsilane as Nitrogen Source

Gallium trichloride (GaCl3) and azidotrimethylsilane (CH3)3SiN3were employed as alternatives gallium and nitrogen precursors respectively in the growth of GaN nanowires via a metal-organic chemical vapor deposition (MOCVD) system. Au pre-deposition on Si (100) substrate was using as catalysis seed to grown of GaN nanowires. X-Ray, FE-SEM and AFM analyses reveal that nanowires grown at temperature 1050 C present morphology characteristic to model VLS. Scanning electron microscopy reveal a surface morphology made up of wurzite that suggests that wires growth involve a melting process. A nucleation and growth mechanism, involving the congruent melting clusters of precursor molecules on the hot substrate surface, is therefore invoked to explain these observations. We attributed the improved growth behavior to the nearer-to-equilibrium growth and may be close to local thermodynamic equilibrium.