Delta-iron

Soft white, ductile metal high-purity metal is very ductile at ordinary temperatures occurs in three allotropic forms (i) body-centered cubic form, alpha iron stable up to 910°C, (ii) face-centered cubic form, gamma iron occurring between 910 to 1,390°C, and (iii) body-centered delta iron allotrope forming above 1,390°C. Density 7.873 g/cm at 20°C melting point 1,538°C vaporizes at 2,861°C hardness (Brinell) 60 electrical resistivity 4.71 microhm-cm at 0°C tensile strength 30,000 psi Poisson s ratio 0.29 modulus of elasticity 28.5 X 10 psi thermal neutron absorption cross-section 2.62 bams velocity of sound 5,130 m/s at 20°C. 

The allotropy of elemental iron plays an important role in the formation of iron alloys. Upon solidification from the melt, iron undergoes two allotropic transformations (see Figure 2.9). At 1539°C, iron assumes a BCC structure, called delta-iron (5-Fe). Upon further cooling, this structure transforms to the FCC structure at 1400°C, resulting in gamma-iron (y-Fe). The FCC structure is stable down to 910°C, where it transforms back into a low-temperature BCC structure, alpha-iron (a-Fe). Thus, 5-Fe and a-Fe are actually the same form of iron, but are treated as distinct forms due to their two different temperature ranges of stability. 

When cooled, pure iron solidities at about 1.5.1b C as delta iron, having a body-centered cubic lattice structure. This form changes allmropically to... 

Delta-iron (8-Fe). At 1392 C, a third transformation occurs and the face-centered cubic lattice reverts to a body-centered cubic form (a = 293.22 pm) with a density of 7357 kg.rn , which again becomes ferromagnetic. Finally, at a melting point of 1535"C, iron absorbs the latent heat required for fusion and becomes Hquid (i.e., molten iron) ... 

Delta-ferrite (8-ferrite, bcc). Like alpha-ferrite, delta-ferrite consists of a solid solution of any element in body-centered cubic delta iron. In the case of carbon, its maximum solubility in delta-iron is only 0.1 wt.% at 1487°C. 

Pure iron is a fairly soft silver/white ductile and malleable moderately dense (7.87 gcm ) metal melting at 1,535 °C. It exists in three allotropic forms body-centered cubic (alpha), face-centered cubic (gamma), and a high temperature body-centered cubic (delta). The average value for the lattice constant at 20 °C is 2.86638(19)A. The physical properties of iron markedly depend on the presence of low levels of carbon or silicon. The magnetic properties are sensitive to the presence of low levels of these elements, and at room temperature pure iron is ferromagnetic, but above the Curie point (768 °C), it is paramagnetic. 

Kaplan, D., Knox, A. Coffey, C. 2002. Reduction of Contaminant Mobility at the TNX Outfall Delta Through the Use of Apatite and Zero-Valent Iron as Soil Amendments. Westinghouse Savannah River Company, Savannah River, Georgia, WSRC-TR-2002-00370. 

Alpha tocopherol Beta, delta, and gamma are considered to be more effective antioxidants Incompatible with peroxides and metal ions, especially iron, and copper. May be absorbed into plastic. Protect from light, and oxygen during storage... 

Three allotropic forms of iron are known (I) alpha irott. which is present below 769 C t2) grimnitr iron, which exists between 906 and 1.4(14 0, uid (3) delta imn, which occurs between 1,404 and l,536"C, On slow cooling, die reverse changes occur, but may be slowed or partly or entirely prevented in the presence ol alloying elemenls. 

The nature of the film formed by y-APS on steel is strongly dependent on the pretreatment of the steel surface. This in itself is not surprising and has been documented in the literature. However, the TOFSIMS delta indicate that methanol-cleaned, mechanically polished steel is passivated because it has formed iron soaps by reaction with fatty acids in the polishing process. 

The described enhancement of carbamazepine photodegradation by Fe(III) oxide colloids could take place in deltas and estuaries, and our laboratory data suggest that the photochemical consequences of the chloride build-up could more than compensate the decrease of iron, due to colloid coagulation and sedimentation, which is usually observed in these environments. Interestingly, carbamazepine photodegradation on interaction between Fe(III) oxide colloids and chloride was more important than DOM-sensitized photolysis or direct photolysis, which are usually major photodegradation pathways for organic pollutants in surface waters [93]. 

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