New Phases in the Mg-Al-Sr System

This work presents experimental investigation of 14 different alloys with differential scanning calorimetery (DSC), scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) analysis, quantitative electron probe micro-analysis (EPMA) and X-ray diffraction (XRD) techniques to identify the phases in the Mg-Al-Sr system and to determine their compositions. DSC has permitted real time measurement of the phase changes involved in these systems. The temperature ranges for the phase transformations and enthalpy of melting and enthalpy of formation of the compounds are reported. Comparison between these results and the thermodynamic findings has been discussed. The microstructure of the Mg-Al-Sr-based alloys is primarily dominated by (Mg) and (Al4Sr). The plate-like structure has been identified as Al4Sr. A new ternary intermetallic with chemical composition of 69.9 ± 1.5 at.% magnesium, 19.3 ± 2.0 at.% aluminum and 8.7 ± 0.6 at.% strontium has been identified in three different alloys. This phase was characterized as a large precipitate. Three ternary solid solutions have been observed. The solubility ranges of Al in Mg38Sr9 and Mg17Sr2 are 12.5 and 8.5 at.%, respectively, whereas the solubility of Mg in Al4Sr compound is found to be 23 at.% in the investigated samples. Further, Mg was found to dissolve 11.4 at.% Al at room temperature.

Oxygen Precipitation in Nitrogen Doped CZ Silicon

Nitrogen doping of CZ silicon results in an early formation of large precipitate nuclei during crystal cooling, which are stable at 900°C. These are prone to develop stacking faults and high densities of defects inside defect denuded zones of CZ silicon wafers. Simultaneous doping of FZ silicon with nitrogen and oxygen results in two main stages of precipitate nucleation during crystal cooling, an enhanced nucleation around 800°C, which is nitrogen induced, and a second enhancement around 600°C, which depends on the concentration of residual oxygen on interstitial sites. A combined technique of ramping with 1K/min from 500-1000°C with a final anneal at 1000°C for 2h and lateral BMD measurement by SIRM provides a possibility to delineate v/G on nitrogen-doped silicon wafers. Surface segregation of nitrogen and oxygen during out-diffusion can explain the enhanced BMD formation in about 105m depth and the suppressed BMD formation in about 405m depth below the surface. The precipitate growth is enhanced in regions where nitrogen is filled up again after a preceding out-diffusion.

Dephenolization from aqueous solution by treatment with peroxidase and a coagulant

To develop a new enzymatic method for removal of phenols from wastewater, the reaction of phenols with horseradish peroxidase was investigated in the presence or absence of a coagulant. Phenols are effectively removed by treatment with peroxidase and a cationic polymer coagulant. The coagulant precipitated enzymatic products of phenol, and reduced the inactivation of peroxidase caused by reaction of products from phenol with the enzyme. This stabilization of peroxidase lessened the amount of enzyme required for phenol removal. Reaction of the coagulant with products from phenol resulted in a large precipitate and only simple filtration was required for separation.