The Polishing By Micron Diamond

Diamond micron powder is mainly used in polishing of various industrial materials, although there are also other applications such

Figure 5.6. Fast pulverization can form shard, plates, and other irregular shapes of micron diamonds (GE Superabrasives' brochure).

as using micron diamond as feedstock for sintering polycrystalline diamond (PCD).

Because single crystal micron diamonds are formed by pulverizing larger diamonds of poor quality, so their shapes resemble broken glass. If the breaking force is too concentrated, very irregular shapes may form (Fig. 5.6). Such shapes contain ample sharp protrusions, so they can easily scratch work surface.

The shape of a micron diamond can be defined by aspect ratio or other projected features. Such features can be measured automatically by laser optical means.

For most applications, the requirements for micron diamond are the same, which is the particle should be as blocky as possible. The blocky shape can assure tighter size distribution. In this way, sharply protruded particles and oversized particles can be avoided, so is the possibility to scratch work surface, the nightmare for all precision polishing workers (Fig. 5.7). Moreover, tight grading may

Applied Force

Applied Force

Figure 5.7. Larger micron diamonds will receive higher force for polishing and hence they are likely to scratch work surface (top). More uniform size distribution of micron diamonds can assure more even force distribution and the less chance to scratch processed material. Source: GE Superabrasives brochure.

Figure 5.7. Larger micron diamonds will receive higher force for polishing and hence they are likely to scratch work surface (top). More uniform size distribution of micron diamonds can assure more even force distribution and the less chance to scratch processed material. Source: GE Superabrasives brochure.

The Heat Treatment of Mono Diamond Fines 103

20 - ■

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\ Irregular Shape \

A

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Blocky Shape \

0.01

0.10 1.00 Average Size (um)

10.00

Figure 5.8. The specific surface area for micron diamond of various sizes. Note that the irregular shaped micron diamonds have a much larger surface area than blocky ones (GE Superabrasives brochure).

also prevent under sized particles that can do no work, and hence they are wasted.

In addition, blocky shape can minimize surface areas and it is easy to clean, hence, micron diamond with blocky shape can be made very clean (Fig. 5.8). Surface cleanliness is an important attribute to avoid overgrowth of nickel during electro deposition for making plated diamond tools, or to prevent defects after sintering for making polycrystalline diamond (PCD). The surface contaminants can slow or stop the cobalt sweep across the grain boundaries, an essential requirement to form diamond bridges among individual diamond grains at high pressure and high temperature.

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