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Sumiya H.,Industrial Materials and Process Technology R and D Laboratories
SEI Technical Review | Year: 2012

We have succeeded in synthesizing a single-phase (binderless) ultra-hard nano-polycrystalline diamond (NPD) by direct conversion sintering from graphite under ultra-high pressure and high temperature. The hardness of NPD is considerably high, far surpassing that of single-crystal diamonds even at high temperature. In addition, NPD shows outstanding strength, possessing no cleavage features and no anisotropy of mechanical properties. The NPD consists of very fine grains of several tens nanometers without containing any secondary phases and binder materials which greatly affect the mechanical properties and thermal stability. These characteristics of NPD suggest potential applications of this novel material to innovative cutting tools and wear resistance tools. This report reviews our systematic studies concerning NPD in terms of its synthesis mechanism, characteristics and applications.


Ueno T.,Industrial Materials and Process Technology R and D Laboratories | Matsunuma K.,Industrial Materials and Process Technology R and D Laboratories | Nishioka T.,Industrial Materials and Process Technology R and D Laboratories
SEI Technical Review | Year: 2012

Soft magnetic powder cores (SMPCs) are used for electromagnetic conversion coils which are essential parts in automotive, home appliance, and electronics industries. These cores, manufactured by compacting pure iron powder covered with an insulation layer, are distinguished by the high electromagnetic conversion efficiency. However, their electromagnetic conversion efficiency drastically decreases when they are subjected to conventional finishing processes. This is directly attributable to conductive layers formed on the finished surfaces, which significantly reduce the electrical resistance of material surfaces. As a solution to this problem, we developed an electrolytic re-insulation grinding method that finishes materials while applying a current between the material and the grinding wheel. This method regenerates the insulation properties of SMPCs through the electrolytic removal of conductive layers formed during finishing, thereby improving electrical resistance. This development enables the finishing of SMPCs without compromising their electromagnetic conversion efficiency.

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