Exfoliators

This study detects the defect of the void and the exfoliation in the solid phase diffusion bonding interface of ductile cast iron and stainless steel with a nickel insert metal using ultrrasonic testing method, and examine the influence of mutual interference of the reflectional wave both the defect and the interface. 

Ni used sheets of 0.1 and 0.3mm in thickness i as an insert metal ( The roughness of surface is the maximum height 0.5 n m). Moreover, SUS304 and FCD500 are processed with the lathe. And, the belted defect (width w=0.04 1.0mm) which the exfoliation defect in the bonding surface of SUS304, FCD500 and Ni sheet are assumed... 

None of the above methods is sufiBcient for neutrons, however. Neutrons penetrate mader so easily that the only effective approach is to use materials with a very high surface-to-vohuue ratio. This can be accomplished with small particles and exfoliated graphite, for instance, but the teclmique has essentially been abandoned in surface sdidies [7, 8]. 

Fig. 4.25 Adsorption isotherms showing low-pressure hysteresis, (a) Carbon tetrachloride at 20°C on unactivated polyacrylonitrile carbon Curves A and B are the desorption branches of the isotherms of the sample after heat treatment at 900°C and 2700°C respectively Curve C is the common adsorption branch (b) water at 22°C on stannic oxide gel heated to SOO C (c) krypton at 77-4 K on exfoliated graphite (d) ethyl chloride at 6°C on porous glass. (Redrawn from the diagrams in the original papers, with omission of experimental points.)...

Vcrmiculitc. A micaceous mineral is roasted to cause exfoliation for use as an insulating material. 

Any region where two surfaces are loosely joined or come into close proximity qualifies as a crevice site as long as water may enter. Partially exfoliated coatings may produce crevices. Surfaces may be metallic or nonmetallic. Usually, however, at least one surface is metallic. Crevices commonly are present at gaskets, flanges, washers, bolt holes, rolled tube ends, incompletely fused welds, contact points in plate-and-... 

Cooling tower Threaded pipe joints Bolts, nuts, washers Partially exfoliated coatings Lap joints in sheet metal Between bushings and shafts on pumps Pump gaskets... 

Figure 5.6 Rust layer on carbon steel mill water supply pipe. Note the partially exfoliated region at the bottom of the photo.

An irregular trough of metal loss is apparent along the circumference of the ring (Fig. 16.4). Metal loss is severe near the nozzle holes (Fig. 16.5). The corroded zone is covered with light and dark corrosion products and deposits. Analysis of these revealed substantial quantities of copper and zinc. Microscopic examinations revealed exfoliation of the aluminum ring in corroded regions. 

The more severe metal loss adjacent to the brass nozzles is apparently due to a direct galvanic interaction between the aluminum ring and the brass nozzles. The type of exfoliation observed microscopically in corroded areas is consistent with galvanic attack. 

Exfoliation corrosion is especially prevalent in aluminum alloys. The grain structure of the metal determines whether exfoliation corrosion will occur. In this form of corrosion, degradation propagates below the surface of the metal. Corrosion products in layers below the metal surface cause flaking of the metal. 

Exfoliation-also called lamination, refers to the falling away of metal in layers. 

Abblasehahn, m. blowoff cock, abblasen, v.t. blow away, blow off, blow blast (castings) distil off. — v.i. (of gases) expand. Abblaseventil, n. blowoff valve, abblassen, v.i. fade, lose color, grow pale, abblattem, v.r. i. scale off, exfoliate desquamate shed the leaves. — v.t. descale strip of leaves. 

Schieferung, /. scaling off, exfoliation schist-osity, foliated structure. 

Vermiculite is a naturally occurring group of hydrated aluminum-iron-magnesium silicates having a laminate structure. When subjected to direct heat in a furnace, the pulverized material exfoliates or expands in size, and then consists of a series of parallel plates with air spaces between. 

As seen above Moran et a ., has commented upon the exfoliation corrosion of Al-Li-Cu-Zr-Ge . The mechanism has been investigated by Reboul and Bouvaist and a mathematical model suggested by Robinson . The influence of alloy elements in Al-Zn-Mg has been reported by Reboul and it has been shown that exfoliation corrosion of Al-Mg-Si in irrigation water is also governed by alloy and impurity concentration . 

Electrodeposits of Pt can only be applied as relatively thin coatings that are porous. Although the porosity decreases with increase in deposit thickness, so does the internal stress and if the platinum adhesion is poor the coating may exfoliate. As a consequence, thicknesses of 2-5 to 1-5 fim Pt... 

Additional metal layers can create bimetallic corrosion cells if discontinuities appear in service. The layer of copper beneath cadmium plate on aluminium (using a zincate plus cuprocyanide deposit technique) can cause corrosion troubles. When aluminium is plated with nickel and chromium, rapid service corrosion in the zinc layer causes exfoliation. 

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