Lowering Sintering Temperature

Reducing Crystallite Size and Modifying Particle Morphology 

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It was also found [8] that the sintering conditions have significant effects on the resistivity of the Smo.iCeo.gOi.g material. As shown in Fig. 4, the overall resistivity decreases with lower sintering temperature and attains a minimum at the sintering temperature of 1100-1200 °C, which is about 31 ohm-cm at 700 °C measurement. This makes the Smo.2Ceo.801,9 material capable of working as SOFC s electrolyte at temperatures lower than 700 C to avoid possible reduction of cerium (4+) and thus suitable for intermediate-temperature SOFC. 

Unfortunately, it appears that this method cannot be applied to the fabrication of Cu cermets due to the low melting temperatures of CuO and CU2O. For lower sintering temperatures, it is likely that the electrolyte powder within the electrode does not become connected, either to itself or to the electrolyte. 

Mizutani et al ° carried out a review of some of the problems of metal-lubricant composites, and in particular the difficulty caused by the fact that sintering temperatures are limited by the thermal stability of the lubricant. The result of this is that either softer metals must be used, or lower sintering temperatures which result in lower structural strength due to brittleness. This led them to investigate metal-lubricant composites in which the lubricant is synthesised in situ. The result was the ternary alloy of iron, molybdenum and sulphur which was described in Chapter 9, and which had the characteristics of a slightly sulphur-depleted molybdenum disulphide composite. 

Present development trends focus on the use of nano-scaled powders to produce, at lower sintering temperature, bioceramic with densities close to the... 

It is clear that the optical transmittance of the samples sintered for 120 min(T=70-75%) are better than those sintered for 60(T=55-65%) or 90(T=65-70%) min. Therefore, a longer soaking results in a higher optical transmittance. But for the same soaking lime, lower sintering temperature leads to a better transmittance, which can be confirmed by the samples sintered at 1600 °C for 60 or 90 min, not including the case of 120 min. 

Further work in this direction is connected with lowering the sintering temperature of electrolyte ceramics accompanied by simultaneous increase of the isothermal exposure time. Lower sintering temperature can result in smaller grain sizes at the same high density of ceramics that could improve such characteristics of membranes as current density and thermal stability. 

By using hot isostatic pressing (HIP) techniques, we can to achieve densification at much lower temperatures (900°C vs. 1300°C). The use of lower sintering temperatures not only saves on energy costs but prevents the formation of other calcium phosphate phases, such as TCP, which usually form when HA is sintered at T > 900°C. 

HlPing is a technique we encountered earlier, but not in the context of forming films. If a metal implant is coated with HA particles then HlPing can be used to form a dense adherent coating. To achieve a uniform application of pressure on the HA particles an encapsulation material (e.g., a noble metal foil) is necessary. As mentioned earlier, HlPing allows the use of lower sintering temperatures than pressureless techniques as a result there is less chance of altering the microstructure or mechanical properties of the metal substrate. 

In order to achieve lower sintering temperatures, also many other metallic additives such as Ni, Co, and Cr, or borides of these elements have been used at higher concentrations to allow liquid phase sintering of TiB2- These transition metals... 

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