Micron Diamond Applications

Because of the poor diamond yield and the excessive steps required to recover and purify diamond, shock wave compressed micron diamonds are intrinsically expensive (e.g. four times more than pulverized micron diamond of the same size), hence, their market size is limited. The annual production of shock wave compressed micron diamonds is less than 1 ton with the sales value of about $10 million that is less than 1/10 of conventional micron diamond. Hence, they are mainly used in premium applications, such as for the texture grinding of hard drives (Fig. 5.22) and super smooth polishing of gemstones.

Shock wave compressed micron diamond has a specific surface area that is about three times higher than pulverized single crystals. Although the abundance of surface area may be the source of contamination, it may actually eliminate the sharp protrusion of corners. Sharp protrusion has been the single most troublesome problem associated with pulverized single crystal micron diamond. The sharp protrusion can easily scratch the work surface

Figure 5.22. Shock wave compressed micron diamond used to carve out concentric marks of a hard drive (left) and super smooth polishing of read head ferrite (right).

that needs to be polished by using micron diamonds (Figs. 5.23 and 5.24).

In addition, during the polishing of a heterogeneous material that contains two or more phases with different hardness such as hard particles embedded in a soft matrix (e.g. cobalt cemented WC), the polycrystalline nature of shock wave compressed micron diamond can moderate the hardness difference and sweep through without causing too much variation in height. In contrast, the pulverized single crystal can easily gouge up soft spots and leave pits behind (Fig. 5.25).

Another advantage of polishing with polycrystalline micron diamond is that it can form microchips along weak interfaces between constituent grains. In essence, the polycrystals can constantly sharpen itself for continual polishing. On the other

Figure 5.23. Texturing comparison of various diamond types.

Figure 5.24. The potato shaped shocked wave compressed micron diamond particle does not possess sharp corners so it will not damage the work surface much (left). On the other hand, the conventional pulverized single crystal micron diamond particle resemble the shape of broken glass. It has many sharp corners so the scratching of the work surface is inevitable (right).

Figure 5.24. The potato shaped shocked wave compressed micron diamond particle does not possess sharp corners so it will not damage the work surface much (left). On the other hand, the conventional pulverized single crystal micron diamond particle resemble the shape of broken glass. It has many sharp corners so the scratching of the work surface is inevitable (right).

Figure 5.25. Single crystal micron diamond can easily pick up soft spots from work surface and leave many scars behind (top). Polycrystalline micron diamond can polish composite materials evenly without causing depressed regions (bottom).

hand, single crystal micron diamond may either break in half or move away without micro chipping (Fig. 5.26).

The ability to self-sharpen has allowed polycrystals to maintain the aggressive polishing speed (Fig. 5.27). Hence, large poly-crystals can polish fast without scratching work piece.

Although shock wave compressed polygrits of nanodiamond have replaced micron diamond as the preferred texturing diamond

Figure 5.26. The integral single crystal will break in large chunks along cleavage planes and lose the polishing ability (left). The homogeneous polycrystal may chip off individual grains and retain much of its original size for subsequent work (right).

0.40

0.20

0 15 30 60 90 120

Polishing Time (sec)

Figure 5.27. Micron diamond polycrystals can polish at a much faster speed than monocrystals.

0 15 30 60 90 120

Figure 5.27. Micron diamond polycrystals can polish at a much faster speed than monocrystals.

when hard drives became Gb per disk in storing density. However, as the storage medium approaches 100 Gb per disk, even the polygrits were too abrasive as to cause scratches. The dynamite nanodiamond is used instead. Due to the increased number of particles per carat with the downsizing of the nanodiamond, the weight used for dynamite diamond was actually reduced. For

Figure 5.28. Specific surface area (ordinate) as a function of the average grain size (abscissa). Note that pulverized diamond fines are much more contamination prong than euhedral diamond fines produced in this research. Explosive (shock wave) and dynamite diamond fines are even worse as they can never be maintained clean.

Figure 5.28. Specific surface area (ordinate) as a function of the average grain size (abscissa). Note that pulverized diamond fines are much more contamination prong than euhedral diamond fines produced in this research. Explosive (shock wave) and dynamite diamond fines are even worse as they can never be maintained clean.

example, when the hard drives were still in Mb densities, typical slurry for texturing may contain 10 carats per liter of micron diamond. This loading was reduced to 1 carat per liter when shock wave nanodiamond was used. The loading was further reduced by using dynamite nanodiamonds that have thousands of times more particles per carat.

Surface areas of explosive nano and micron diamonds are much higher than conventional micron diamonds that are produced by pulverizing unwanted diamond scraps (e.g. diamond grits with irregular shapes and high levels of inclusion, also natural diamond boarts) (Fig. 5.28).

Chapter Six

How To Reduce Acne Scarring

How To Reduce Acne Scarring

Acne is a name that is famous in its own right, but for all of the wrong reasons. Most teenagers know, and dread, the very word, as it so prevalently wrecks havoc on their faces throughout their adolescent years.

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