Mg-2B powder mixtures

Fig. 3.19 XRD patterns of Mg-2B powder mixtures made with non-oxidized boron after milling for (a) 50 h and (b) 200 h...

Fig. 3.21 XRD pattern of the 200 h milled Mg-2B powder mixture made with oxide-free amorphous B after DSC test. For comparison the XRD pattern after 200 h milling is also shown...

Figure 1. Backscattered electron (BSE) images of the morphology of powders processed under shearing mode by reactive mechanical alloying under hydrogen, a) 2Mg-Co mixture milled for 30h using WD=10 mm and BPWR=10 1 and b) Mg-2B (crystalline (c) boron) mixture milled for 5h using WD=5 mm and BPWR=44 1. RPM=60 applied during milling.

In the Mg-2B system both crystalline (c) and amorphous (a) boron (B) powders were used for the processing by CRMA (Fig.4, 5). In the XRD pattern of the mixture of Mg and crystalline (c) boron shown in Fig. 6 besides peaks from p-MgH2 and Mg some peaks labeled by x are also observed. 

The solid-state reactions were carried out by taking approximately 100-500 mg of the powdered phenylpropiolic acids 2a-c in round-bottomed flasks. The flasks were lightly plugged with cotton and kept in oil baths at appropriate temperatures between 70-110 °C. Within 27 days, the samples became discolored and some sublimed acid and phenylacetylene could be seen coated at the top of the flask. The mixtures were stirred occasionally, and after 46 weeks, the reaction mixtures were separated by column chromatography. The following reaction details were noted for acids 2a-c (acid, percent conversion to Diels-Alder anhydride, percent unreacted plus sublimed acid, time of reaction, temperature of reaction) 2a, 25%, 32%, 5 weeks, 95°C 2b, 30%, 25%, 6 weeks, 90°C 2c, 20%, 30%, 3 weeks, 90 °C. 

Methoxybenzaldehyde lb (136 mg, 1 mmole) and NH2OHHCl (84 mg, 1.2 mmole) were mixed thoroughly with NH4OAC (108 mg, 1.4 mmole). The resulting powder was taken in a test tube, kept in an alumina bath inside a micro-wave oven and irradiated for 1 min. The mixture was removed from the oven, cooled and shaken with CHC13 (15 mL). After filtration, the filtrate was concentrated and the residue was subjected to column chromatography over silica gel using hexane-EtOAc (7 3) as eluent to afford 4-methoxybenzonitrile 2b (119 mg, 90%). 

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