Ageing ferrites

The inductance of adjustable coils with a ferrite core and the capacity of trim capacitors are strongly influenced by metal screwdrivers. It is important for trim capacitors and coils in oscillator circuits to be adjusted in the precise centre of the resonance area. Should this occur at the side, then oscillators sometimes fail to REACT when there is question of a change in temperature or ageing of components. Thus more situations can be mentioned in which you can benefit from the advantages of ceramic screwdrivers. 

The ferrite phase makes up 5 15% of normal Portland cement clinkers. It is tetracalcium aluminoferrile (CajAIFeOj) substantially modified in composition by variation in Al/Fe ratio and incorporation of foreign ions. The rale at which it reacts with water appears to be somewhat variable, perhaps due to differences in composition or other characteristics, but in general is high initially and intermediate between those of alite and belite at later ages. 

In Ciment Fondu, the ferrite phase seems to play no significant part in early hydration at 20 C, but at 30-38 C over 80% was found to have reacted by 2 months (C47). The melilite and pleochroite seem to be unreactive. When belite is present, silicate ions can be detected in the solution within a few minutes, but then disappear it seems that precipitation occurs and further dissolution is inhibited. Among the minor oxide components. TiO, and MgO mainly occur in the unreactive phases. Na,0 and K,0 scarcely affect the solution equilibria at early ages, as their concentrations are very low (M88). 

Soler MAG, Lima ECD, da Silva SW, Melo TFO, Pimenta ACM, Sinnecker JP, Azevedo RB, Garg VK, Oliveira AC, Novak MA, Morais PC (2007) Aging investigation of cobalt ferrite nanoparticles in low pH magnetic fluid. Langmuir 23 9611-9617... 

The materials behavior (austenitic, austeno-ferritic, and ferritic steels - base metal, welds, heat affected zones) in terms of thermal aging and its effect on mechanical properties, embrittlement, sensitiveness to corrosion (in normal and incidental environment), and radiation effect on the potentially exposed structures. 

Dynamic and thermal ageing phenomena may embrittle either ferritic and austenitic steels. 

The orientation relationship 100 b// 2110 Hand 011 b// 0001 h between hexagonal M02C precipitates (H) in ferrite (B) Fe - 4.0 mass% Mo - 0.20 mass% C steel homogenized in an argon atmosphere at 1300°C for about 1 h, brine quenched, and aged at 710°C forupto 10 h have been determined by [2002Shi]. 

A detailed electron microscopic examination has been made on high purity C-Fe-V alloys with particular reference to the aging behavior prior to the hardness peak in the temperature range of 500-600°C [1966Ray]. Precipitation of vanadium carbide on aging has been studied in a ferritic iron-vanadium alloy containing a small amount of carbon by [1973Hei]. 

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