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Novel two-step processing route combining mechanical alloying and microwave hyb...

In this work, microwave hybrid sintering at 1300 and 1350 °C was carried out for densification of La9.33Si2Ge4O26 mechanically alloyed powder with apatite structure. The pellets sintered at these two temperatures present the same structure (apatite) with relative densities of 92 and 96%, respectively. Mechanical analysis performed on sintered materials revealed the following results: hardness of 7.1 and 8.0 GPa...

On the influence of silica type on the structural integrity of dense La9.33Si2G...

Apatite-type rare earth based oxides, such as R-doped lanthanum oxides of general formula La9.33(RO4)6O2 with R = Ge, Si, exhibit high ionic conductivity and low activation energy at moderate temperatures, when compared to the yttria-stabilized zirconia electrolyte making them potential materials to be used in the range 500–700 °C, for intermediate temperature solid oxide fuel cells (IT-SOFCs). In this study, d...

Fracture toughness of dense cordierite: sintering cycle effect

The aim of this work was to analyse the fracture behaviour of commercial dense cordierite bodies sintered in an electrical furnace in static air at 1250ºC, 1275ºC and 1300ºC for 30 min using different cycling schedules in order to obtain tougher materials at minimum energy costs. Using a stereomicroscope and a scanning electron microscope, fracture surfaces of as-sintered bars tested under four-point bending at...

Synthesising carbo-nitrides of some d-group transition metals using a solar fur...

Carbo-nitride synthesis was undertaken using a solar furnace at PSA in flowing N2/Ar gas mixture under total pressure 1 atm and processing temperature T = 1600ºC for some d-group transition elements (Ti; Zr, V, Nb, Mo, W) starting from 1.5G/M (graphite/metal powder mixture with mole ratio 1.5:1) compact to ensure co-presence of free carbon with the reaction product. Clear X-ray diffraction (XRD) evidence of for...

Effect of the sintering conditions on the morphology of La9.33Si2Ge4O26 oxyapat...

Solid oxide fuel cells (SOFCs) are devices that allow direct conversion of chemical to electrical energy through an electrochemical reaction in a cleaner and more efficient way than conventional processes (eg. gas turbines). They are characterized by the use of a solid oxide material as the electrolyte. Yttria-stabilised zirconia (YSZ) has traditionally been used in SOFCs electrolytes at temperatures in the ra...

Synthesizing higher nitride of molybdenum (Mo) and iron (Fe) in ammonia (NH3) g...

Flowing gaseous ammonia NH3 with suppressed extent of dissociation (un-cracked NH3) is acknowledged to function as a powerful nitriding medium to realize formation of metal nitride MNx with considerably high N/M ratio x that cannot be achieved through reaction of M with N2 gas. For example, mono-nitride d-MoN of Mo and e-FeNx phase of Fe with x = 0.33 ˜ 0.50 (i. e. hypo-stoichiometric sub-nitride e-Fe2N) were r...

Synthesis and thermal behavior of La9.33Si2Ge4O26 apatite for SOFCs

Powders of La2O3, GeO2 and SiO2 were dry milled in a planetary ball mill with different rotation speeds (150–350 rpm) and increasing milling times up to 35 h in order to obtain the La9.33Si2Ge4O26 apatite phase at room temperature. The results showed that the higher the rotation speed the lower the time required for the formation of the apatite phase. No reaction between the starting powders was observed at 150...

Mechanical properties of sintered La9.33Si2Ge4O26 oxyapatite materials for SOFC...

Mechanical properties of La9.33Si2Ge4O26 prepared by mechanical alloying and subsequent sintering at 1300–1400 °C for 1 h were evaluated. Hardness and Young's modulus values in the range 7.3–9.6 GPa and 106–135 GPa, respectively, were obtained from nanohardness tests. The fracture toughness values derived from the Palmqvist method varied between 3.5 and 3.9 MPa m1/2 from classical microindentation test with an ...

Heterogeneity along the Height in Disc Specimens of Graphite/Tungsten Powder Mi...

Compositional heterogeneity along the thickness of compacted disc specimens of graphite/tungsten powder mixtures with substoichiometric carbon atom ratios (0.35, 0.50 and 1.00) heated by concentrated solar beam to 1600 C was characterised by X-ray diffraction. Top surface of any examined test piece was consisted purely of mono-carbide WC while the bottom surface showed different constitution depending on the ne...

Structured metal-zeolite catalysts for the catalytic combustion of VOCs