Vacuum apparatus ball mill

A colorless, colloidal precipitate was formed and stirred thoroughly for about 15 minutes, whereupon it was filtered by suction. The raw product thus obtained was washed with water until It contained only about Va% water-soluble salts. After drying for 12 hours In a vacuum apparatus at 60°C and under a pressure of 12 mm Hg, the product had the form of hard pieces. The pieces were comminuted to powder in a ball mill and the powder was passed through a sieve (3,600 meshes per cm ). The small residue on the sieve was again pulverized and passed through the same sieve. The yield was 870 g, or 99% of theoretical, calculated on the assumed formula... 

Imamura et al. [137] studied absorption of Mg ball-milled with graphite and benzene as milling additives. In a Sieverts-type apparatus, the mixture after 20 h milling was able to absorb at 180°C. This in itself is nothing outstanding because milled, activated, and cycled MgH can also absorb at 200°C (Fig. 2.22a). Bouaricha et al. [138] also studied absorption of a Mg -i- graphite mixture at 300°C, which showed much better kinetics than that of just milled Mg. A number of researchers studied both absorption and desorption [25, 139-141] but unfortunately, all desorption studies were conducted in vacuum. However, it must be pointed out that even under vacuum conditions, desorption kinetics were no better than those obtained with a number of other additives discussed earlier in the text. The lowest desorption temperature applied was 290°C. 

A mixture of 50 grams of well dried O acid and 100 grams of technical sodium hydroxide is ground in a ball mill for 24 hours. The mixture is then placed in a vacuum baking apparatus (Fig. 30, page 181) which is evacuated and heated, as uniformly as possible by means of an oil... 

Schematic diagrams of the apparatus, designed in our lab at< y, are shown in Fig. 1. Polymer flakes are placed, with a balls of about 5 mm dieter, in a glass an oule A about 4 cm in diameter and 7 cm in length. To the other end of the ampoule an ESR sample tube B is attached. Through connector C, the ampoule can be connected to a vacuum system and then evacuated to 10 mm Hg. After evacuation the connector is sealed off and the ampoule is removed from the vacuum system. The evacuated ampoule is now placed on a vibrator, wWch moves vertically at about 4 cycle per second. The procedure can be carried out in a Dewar flask containing coolant, such as liquid nitrogen, to fix the temperature. After some hours of this vibration, the crushed flakes are transferred to the ESR sample tube without raising the temperature of the sample. Ihen, sample tube containing the fractured flakes is placed in an ESR cavity at controlled temperature. The ball-mill apparatus permitted polymeric materials to be crushed in vacuum at low temperature and the ESR spectrum to be observed without contamination of oxygen.

Figure 1 Ball-milling apparatus (A) glass ampoule, (B) ESR sample tube, (C) arm for vacuum system, (D) milling balls, (N) belt, (M) motor, (P) pulley, (R) crank, (S) stand, (V) Dewer vessel containing a coolant...

The ESR spectrum observed from polypropylene (PP) milled by the ball-mill apparatus shown in Figure 1 is shown in Figure 6(a). The spectrum in Figure 6(b) is a simulation spectrum derived from a superposition with a one to one relative ratio of the two radicals, (8) and (9). Agreement between the observed spectrum and the simulated one is satisfactory. Thus, one can conclude that pair formations of the two radical species is induced by ball-milling in vacuum at 77 This result is... 

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