Grain alteration

The has found wide use in studying presolar grains, IDPs, and Stardust samples, and in analyzing the fine-grained alteration minerals in carbonaceous chondrites. 

Schellmann (1966) goethite grains altered in Recent shallow-marine environment, Guinea coastal sands corrected for 24% goethite and... 

Both the anhydrous, porous IDPs and Tempel 1 appear to have a higher crystalline to amorphous silicate ratio than is inferred from infrared spectroscopy of interstellar or most circumstellar grains. This could simply be a result of grain alteration in interstellar space, with radiation processing converting crystalline silicates to amorphous silicates. 

The temporal distribution of Mn sources is apparently more complicated. Mn is relatively enriched in the early precipitates, depleted in some of the later ones, and enriched in others (e.g. the Ranzano and Antognola). This trend hints at the possiblity of multiple sources for Mn, some mobilized relatively early, whereas others were possibly affiliated with grain alteration later in diagenesis. 

The main component of sandstone reservoirs ( siliciclastic reservoirs ) is quartz (Si02). Chemically it is a fairly stable mineral which is not easily altered by changes in pressure, temperature or acidity of pore fluids. Sandstone reservoirs form after the sand grains have been transported over large distances and have deposited in particular environments of deposition. 

In order to dry the crystals, the Buchner funnel is inverted over two or three thicknesses of drying paper (i.e., coarse-grained, smooth surfaced Alter paper) resting upon a pad of newspaper, and the crystalline cake is removed with the aid of a clean spatula several sheets of drying paper are placed on top and the crystals are pressed flrmly. If the sheets become too soiled by the mother liquor absorbed, the crystals should be transferred to fresh paper. The disadvantage of this method of rapid drying is that the recrystallised product is liable to become contaminated with the Alter paper flbre. 

For a coarse-grained (particle containing) graphite, the system depicted in Figure 1 is typical. The nin-of-kiln coke is brought in on railroad cars and emptied into pits where the coke is conveyed to an elevator. The elevator feeds a second conveyor that empties the coke into any one of a number of storage silos where the coke is kept dry. The manufacturer usually specifies a maximum moisture content in the incoming coke at about 0.1—0.2% to ensure that mix compositions are not altered by fluctuations in moisture content. 

Since the rate of formation of cementite is determined by nucleation, and therefore proceeds more rapidly in fine-grained steels, it follows that the T-T-T diagram will show a more rapid onset of austenite decomposition than in steels of the same composition, but a coarser grain size. The shape of the T-T-T curve is also a function of the steel composition, and is altered by the presence of alloying elements at a low concenuation. This is because the common alloying elements such as manganese, nickel and clrromium decrease... 

In addition to the alloy compositions being of importance with regard to susceptibility to stress-corrosion cracking, the resistance of the alloy can be altered by microstructural factors. Hanninen has reviewed the available literature quite thoroughly and has concluded that a fine grain size is likely to be beneficial. Strain imposed prior to use tends to be deleterious because deformed material usually acts anodic with respect to unstrained material and because the introduction of plastic deformation may also... 

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