Sinter body, anode

Improvement of Thermal Conductivity of the Anode Sinter Body For the... 

The corrosion resistance of TiN can be presented by anodic polarization curves. The polarization result of TiNo.gr sintered body determined at room temperature is shown in Figure 11.3.1 [11]. Since its electrode potential directly after immersion in dilute sulfuric acid is positive (4-0.016 V), it is not soluble for the dilute sulfuric acid. The current density increases rapidly with increasing the voltage, and then decreases reversibly from 0.1 to 0.5 V, showing passivation of TiN. This behavior resembles to anodic polarization curve of titanium. This would be due to substoichiometric composition TiN with excess amount of titanium. Dissolution of TiN is possible in hot fluoric nitric acid solution alone. 

The anode bodies of tantalum, aluminum, and most recently niobium capacitors are made of highly porous metals. These bodies are obtained either by sintering fine metal powders or electrochemical etching of thin foils. A thin dielectric layer is then electrochemically grown on the metal surface. Due to the porous structure of the anode bodies, the cathode polymer must be able to penetrate deep into the pores and coat aU internal surfaces in order to utilize the full, potential capacitance of the anode. 

The side of the anode was shielded by a sintered alumina tube, and the top was covered with loose alumina (2-3 mm thick layer) in order to prevent any reaction between CO2 and the carbon anode body. The anode was 42 mm in diameter and had a threaded hole in the top to connect it to the threaded stainless steel tube (shielded with a sintered alumina tube) with a closed end, holding the anode and serving as current lead. A Pt-PtlORh thermocouple placed inside a sintered alumina tube was used to record the electrolysis temperature. 

Tantalum capacitors, as shown in Fig. 3.21, are formed by sintering Ta metal powder around a Ta lead wire to form a porous body that serves as the anode. The porous Ta is then coated with a semiconductive Mn02 layer, and coated with carbon and silver paints to form the cathode. A supporting T bar is then welded to the lead wire and the assembly is encapsulated. A wet electrolyte may be used in place of the Mn02. Tantalum capacitors are very stable over time and temperature. 

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