Ball planetary

Ball, planetary-centrifugal, vibratory or ultrasonic mills are used for milling TiB2 and ZrBj powders. The milling elements are balls of cemented carbide (WC-Co) or ball-bearing steel. 

K-absorption spectrum of yttrium in YH3, which was mechanically treated in a ball planetary mill during 20 min. with angular rate of 1630 rot./min. is shown in Fig. 6 (c). This absorption spectrum, as seen from the picture, is shifted relatively to the spectrum of untreated YH3 hydride to the side of lower energies, which in accordance with the found out correlation has to testify to thermal stability of reduction of treated yttrium hydride. Actually, we determined by the method of hydrogen thermal desorption, that as a result of mechanic dispersing of this hydride its temperature of decomposition decreased more than on 300 °C (Fig. 7), i.e. the... 

Powders of MgH2, TiHi s and YH3 hydrides, obtained from the gas phase, were mechanically grinded. Grinding was carried out in a ball planetary mill in argon medium at rotation speed of 1630 rot/min. Grinding balls and hydride bulk were in ratio of 20 1. 

Planetary Ball Milling This is a method of increasing the gravitational force acting on balls in a ball mill. For example, refractoiy metals and carbides can be ground to 1 to 2.6 [Lm in 5 to 20 min in an apparatus capable of applying a centrifugal force of 10 to 50 G. [Dobrovol sldi, Poroshk. MetalL, 7(6), 1-7 (1967)]. 

Pulverit planetaiy mills are available from Geoscience Inc. Highspeed planetary-baU mills can be used to perform rapid tests to sinmlate ball milhng of materials [Vock, DECHEMA-Monogr, 69, HI-8 (1972)]. The size of high-speed mills will be much smaller than the size of same-capacity ball mills [Bradley, S. Afr Mech. Eng., 22, 129 (1972)]. 

The S-form can be obtained by treating Copper Phthalocyanine Blue in benzene or toluene with aqueous sulfuric acid in the presence of a surfactant [21], The e-phase is produced by comminution of the a-, 7-, or 8-modification, for instance in a planetary ball mill. The mill base is then aftertreated in an organic solvent at elevated temperature. It is important to realize that the temperature, depending on the solvent, must be kept below the transition temperature at which the e-phase converts to the (3-modification (30 to 160°C). The e-modification is made best from the 7-phase, and the most preferred solvents are alcohols [22], For the industrially hitherto insignificant tt, X, and R-forms of Copper Phthalocyanine Blue (see [1], Vol. II, 34-35). 

A serious limitation of the ball or tube mill is that it operates effectively only below its critical speed, as given by equation 2.10. In the planetary mill, described by Bradley et alS2y>, this constraint is obviated by rotating the mill simultaneously about its own axis and about an axis of gyration, as shown in Figure 2.32. In practice, several cylinders are incorporated in the machine, all rotating about the same axis of gyration. 

Tumbler, jar, drum, or cannon ball mills Szegvari attritor vertical mills and other vertical stirred ball mills Planetary Fritsch and Retsch model mills Shaker (vibratory) SPEX model mills... 

At this frequency of impacts the energy transferred to the powder would be comparable with that achieved in a planetary ball mill. The milling cylinder suitable for reactive milling is shown in Fig. 1.8. 

There are other advantages of employing magnetic ball mills besides the control of mechanical milling modes. Since the centrifugal force becomes a secondary factor in milling, and the reactor shell rotates at low RPM, contamination from balls and shell wear is lower than in a vibrational or a planetary mill there is less ball wear involved and contaminations with Fe from steel become less of the problem. Also lower rotations and uniaxial movement of reactors paced on horizontal axle allow... 

Jones S.K. Rees R.M. Skiba U.M. and Ball B.C. (2005). Greenhouse gas emissions from a managed grassland. Global and Planetary Change, 47(2-4), 201-211. 

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