Bulk and Grain Boundary Diffusion of Titanium in High Purity Niobium
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Roles of niobium pentoxide, vanadium pentoxide and titanium dioxide in the grain growth and sintering of uranium dioxide
Pure uo2 sinters readily at temperatures below 1600°c when non-stoichiometric oxygen introduced during the presintering treatment is available for diffusion and subsequent densification. In the absence of excess oxygen sintering occurs at temperatures above 1600°C by self-diffusion of stoichiometric oxygen in uo2 • Grain growth occurs when open porosity has been eliminated and is controlled by ...
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Variable temperature transport between 1.4 and 300 K, structural imaging, and theoretical calculations were used to characterize the properties of electrically active 24 degrees and 36.8 degrees [001] tilt SrTiO3 grain boundaries with 0.1 at. % niobium doping. An anomaly in boundary resistance and capacitance characteristics typical of a positive temperature coefficient effect is observed. This...
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Austenite grain growth in microalloyed steels is governed by the coarsening of fine precipitates present at grain boundaries below the grain coarsening temperature. Zener model is widely used in metals to describe the pinning effect of second phase particles precipitated in the matrix. In this work it has been discussed whether grain boundary or volume diffusion is the rate controlling process ...
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Nickel-doped tungsten specimens were prepared with high purity chemicals and sintered. Although activated sintering starts more than 400 C below the bulk eutectic temperature, the nickel-rich crystalline secondary phase does not wet the tungsten grain boundaries in the solid state. These results contrast with the classical activated sintering model whereby the secondary crystalline phase was pr...
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Modern vehicle bodies make intensive use of high strength steel grades to meet the contradicting demand of lighter weight and simultaneously better mechanical performance. For many steel grades microalloying by niobium is the key to achieve their characteristic property profile. In HSLA steels niobium enhances the strength primarily by grain refinement. In interstitial free high strength steels...
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تاریخ انتشار 2002