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In the present work, the nature of the electrical mechanism for carrier transport in Alq3 is studied by current-voltage measurements and broadband dielectric spectroscopy. The d.c. currentvoltage characteristics at low applied electrical field exhibits a classical “N” shape due to interfacial states located at metal-organic interface, but tend to disappear when successive higher forward bias is applied. Using dielectric spectroscopy it is possible to observe that the main relaxation peak shifts to a higher frequency with the increase of the applied d.c. voltage (from approximately 100 Hz with 0 V d.c. bias to approximately 400 Hz with 6 V d.c. bias) indicating a semiconductor structure change. The logarithmic Z’’ vs. Z’ plot has a slope about 0.7 that decreases to 0.5 with the increasing applied d.c. voltage, reaching a classic Debye relaxation. An attempt to correlate with some structural changes is made.

Machining of cemented carbide pre-sintered forms is a strong abrasive operation, leading to significant expenses on tool consumption. To overcome this problem, the industry often uses very hard polycrystalline diamond (PCD) inserts. However, the presence of a soft binder in the PCD diamond layer weakens its abrasion resistance. An alternative to PCD is the use of cobalt-free CVD diamond films as cutting tools. In this work, CVD diamond films brazed to metal holders were used as cutting tips in machining of green WC forms and the performance compared to PCD. Diamond films of thickness ~0.4mm were grown by microwave plasma assisted CVD (MPCVD) on silicon substrates. The wafers so obtained were processed into small triangles (tips), through laser cutting and subsequent removal of the silicon substrate using chemical etching. The tips were then brazed to steel holders with reactive Ag/Cu/Ti filler metal. Abrasion resistance was tested in rough turning conditions on pre-sintered and isostatic pressed cemented carbide bars at 10ms -1 of cutting speed. The worn surfaces were observed by SEM. The onset of flank wear on PCD inserts was detected at about 30 hours of working time, while the cutting edge of the CVD diamond tool kept its sharpness even after almost 40 hours. Micro-cracking and crystal pullouts at the cutting edge were identified as the main wear mechanisms of the PCD tool.