Combustion cermets

M. Marinsek, K. Zupan, J. Maeek, Ni-YSZ cermet anodes prepared by citrate/nitrate combustion synthesis , Journal of Power Sources 106,178-188 (2002). 

Combinations of ceramic and metal systems - sometimes referred to as "cermets" have excellent resistance to mechanical damage (one of the limitations associated with the use of vitreous enamel for process plant). The combination of ceramic and metal in surface coatings also provides oxidation and corrosion resistance to the underlying metal substrate. The technique is particularly applicable to regions of low temperature in air preheaters in combustion plant, i.e. near or below the acid dew point. Page [1980] reports some extensive tests. Over a five year period some 40 corrosion resisting steels, alloy steels and organic and... 

Key words Combustion Synthesis/Strontium Titanate/Cermet/Electrode Fuel Cell... 

This paper tries to link different properties of a Sr(Ti,Fe)03 perovkite with PtRu metal catalyst for high and low temperature applications. The ceramic/metal (SrTio.85Feo.i503.d)o.5(PtRu)o.5 cermet is prepared by combustion synthesis, as well as the material achieved are studied and characterised as electrocatalyst. 

These materials are normally prepared by mechanical mixing of oxides, but the combustion method is also used to produce impurity-free materials with high specific surface area. A perovskite (SrTiFe03.5)-alloy (PtRu) cermet is obtained directly by combustion synthesis (fig.l). It presents a low crystallinity, low Pt crystal size ( 15nm) and a specific surface area of 48.5 mVg. 

The combustion as-prepared powders are a two compatible phases on alloy/ceramic cermet, with a small particle size, low crystallinity and a good PtRu alloy dispersion. 

The simplest form of densification, uniaxial pressing, has been used to densify a variety of materials such as TiC -I- NiAl, TiC -i- Ni3Al [41], TiC + Ni, TiC -1- Fe [42], and others [43,44]. Two parameters play an important role in this type of postreaction densification the magnitude of the applied pressure and the time of its application relative to the completion of the combustion process. Figure 30 shows the dependence of the residual porosity in TiC-Ni/Al cermets on the applied pressure. As the figure shows, the relative density increases from about 50 to 99% as the pressure is increased from ambient (0.1 MPa) to about 28 MPa [41]. The timing of the application of the pressure relative to the synthesis reaction has also... 

Another example of synthesis of TiC-based compact cermets is reported by Xing et al. [90]. These authors describe the synthesis of dense NiAl-20 vol-% TiC composites through a reaction of a mixture of Ni, Al, Ti, and C powders in a hot press. The reaction was performed using the volume combustion mode heating the green mixture until a reaction is observed in the entire sample. The samples were heated up to 1500°C under the influence of an applied pressure. The products were 98.9% dense but the TiC particles (0.2-1 pm) were not uniformly dispersed in the matrix. The combustion process had similar ignition characteristics to the... 

U. Anselmi-Tamburini, F. Maglia, G. Spinolo, and Z. A. Munir, Ni/YSZ cermets from combustion synthesis effect of process parameter on product microstructure, J. Am. Ceram. Soc. 1998, 81, 1765-1772. 

S. Adachi, T. Wada, T. Mihara, Y. Miyamoto, M. Koizumi, and O. Yamada, Fabrication of titanium carbide cermets by high-pressure self-combustion sintering of titanium powder and carbon fiber, J. Am. Ceram. Soc. 1989,72, 805-809. 

Gas Turbine. A device for the conversion of the energy of hot gases, derived from internal combustion, into rotary motion of a machine element. The efficiency increases with operating temperature and is at present limited by the safe temperature at which heat-resisting alloys can be used. There has been much research on the possible use of cermets and other special ceramics in these turbines, particularly in the blades. Gassy Surface. See fuzzy texture. Gate. See stopper. 

---