Attritor mills

Cemented carbides and nitrides are manufactured by a powder metallurgy process using liquid phase sintering (Figure 2.1). The cobalt or nickel binder metal, in the form of fine powder, is blended with the carbide or nitride powders in ball mills or attritor mills lined with carbide sleeves. 

In Fig. 19.8(a) and Fig. 19.8(c) the fine microstructures of hot-pressed reference samples resulting from ball and attritor milling and sintering are... 

Batch Composition (wt%) Carbon black/graphite added to batch (wt%) Ball milling (ethanol) at 360 rpm Attritor milling (ethanol) at 600 rpm Hot pressing 1800°C, 2 h nitrogen atm. (MPa)... 

The particle size of the precleaned coals was reduced to mean diameters near 10 jum by milling in a stirred-ball slurry attritor mill. Slurries containing 20% by weight coal dispersed in deionized water were milled for 2 minutes using 6.3 mm diameter stainless steel media (140 cc slurry/kg media) and an agitator shaft speed of 290 rpm (18). The slurries were then filtered and dried in a recirculating nitrogen atmosphere at 110°C for 3 hours. 

Fig. 1.2 Motions of balls in attritor mills the dotted vertical line represents the axis of rotation of a vertical shaft on which a number of horizontal shafts (arms) are mounted, which strike balls and agitate their motion in a very energetic manner powder particles trapped between the balls are subjected to high-rate deformation processes...

Other Mills. There are many types of mills that have been tried in industry. Two additional types worthy of mention are the Attritor mill and the SWMill. 

The Attritor mill (24) has bars that rotate, lift the grinding media, and drop it upon the paste to break up the agglomerates while at the same time the paste is circulated by a pump. The mill is designed for pigments that are difficult to disperse. It is claimed that this mill is more efficient than a ball mill. 

In organic solvents, GOD and POD enzymes become extremdy rigid and can be dispersed with ease. Dispersions were made by grinding GOD and POD in xylene/methoxy propanol with or without a surfactant using an Attritor mill (2—4 hi or a ball mill (24 h). Grinding was continued until dispersion of <1 /m were ootained. The composition of a typical dispersion is 1.876 g GOD, 4.298 g POD, 11.79 g sodium dodecyl sulfate, 41.06 g xylene and 41.06 g 1—methoxy—2—propanol. 

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