Nickel shapes

Bamboo-shaped tubes. A carbon tube with a peculiar shape looking like bamboo, produced by the arc evaporation of nickel-loaded graphite, is shown in Fig. 8. The tube consists of a linear chain of hollow compartments that are spaced at nearly equal separation from 50 to 100 nm. The outer diameter of the bamboo tubes is about 40 nm, and the length typically several /im. One end of the tube is capped with a needle-shaped nickel particle which is in the normal fee phase, and the other end is empty. Walls of each compartment are made up by about 20 graphitic layers[34]. The shape of each compartment is quite similar to the needle-shape of the Ni particle at the tip, suggesting that the Ni particle was once at the cavities. 

Explosively clad metals, of which Deta-Clad4 is an example, are used mostly for small items such as tube sheets and heads for small heat exchangers or vessels. It is usually not economical for large surfaces or complex shapes. Nickel-chromium-molybdenum alloys and some other expensive metals can be applied to carbon steel by explosive bonding. 

LMe, Pr2XiCI 2 has been used as a precursor to a nickel(II) amido complex, and to an unusual T-shaped nickel(I)-carbonyl complex.4 The analogous bromide complex has been used as an ethylene polymerization catalyst,5 and as a source of nickel(I) for group-transfer and bond activation reactions (described in more detail in Section 12). 

Carbon formation on steam reforming catalysts takes place in three different forms whisker-like carbon, encapsulated carbon, and pyrolytic carbon as described in Table 2.2 [1]. Whisker-like carbon grows as a fiber from the catalyst surface with a pear-shaped nickel crystal on the end. Strong fibers can even break down catalyst particles increasing the pressure drop across the reformer tubes [4], The carbon for whisker formation is formed by the reaction of hydrocarbons as well as CO over transition metal catalysts [1], The whisker growth is a result of diffusion through the catalyst and nucleation to form a long carbonaceous fiber. 

In Germany, early AE experiments were performed by F. Forster in Fig. 2.3 (Forster Scheil 1936). Measuring extremely small voltage changes due to resistance variations, AE phenomena caused by martensite transformations could be detected in a wire-shaped nickel-steel specimen. This was because they had built an electro-dynamic transmitter/receiver system to transform mechanical vibrations into electrical voltages. 

These molds are usually made from aluminum, often with engraving. For high production rates and intricate surface configuration, electrodeposited shapes (nickel/ copper) backed with cast aluminum are used. 

Using a ball-shaped nickel working electrode, Guindet et al. plotted current-voltage curves, each point being characterized by impedance spectroscopy. All the measurements... 

This paper deals with the control of weld depth penetration for cylinders in gold-nickel alloy and tantalum. After introducing the experimental set-up and the samples description, the study and the optimization of the testing are presented for single-sided measurements either in a pulse-echo configuration or when the pump and the probe laser beams are shifted (influence of a thermal phenomenon), and for different kind of laser impact (a line or a circular spot). First, the ultrasonic system is used to detect and to size a flat bottom hole in an aluminium plate. Indeed, when the width of the hole is reduced, its shape is nearly similar to the one of a slot. Then, the optimization is accomplished for... 

Then, the weld depths penetration are controlled in a pulse-echo configuration because the weld bead (of width 2 mm) disturbs the detection when the pump and the probe beams are shifted of 2.2 mm. The results are presented in figure 8 (identical experimental parameters as in figure 7). The slow propagation velocities for gold-nickel alloy involve that the thermal component does not overlap the ultrasonic components, in particular for the echo due to the interaction with a lack of weld penetration. The acoustic response (V shape) is still well observed both for the slot of height 1.7 mm and for a weld depth penetration of 0.8 mm (lack of weld penetration of 1.7 mm), even with the weld bead. This is hopeful with regard to the difficulties encountered by conventional ultrasound in the case of the weld depths penetration. 

This signal is nearly square shaped because nickel exists from the front to the back surface. The depth scales are detennined from energy loss values, which are given in tabular fomi as a fiinction of energy [1, 2]. It is... 

Uses. The sinter oxide form is used as charge nickel in the manufacture of alloy steels and stainless steels (see Steel). The oxide furnishes oxygen to the melt for decarburization and slagging. In 1993, >100, 000 metric tons of nickel contained in sinter oxide was shipped to the world s steel industry. Nickel oxide sinter is charged as a granular material to an electric furnace with steel scrap and ferrochrome the mixture is melted and blown with air to remove carbon as CO2. The melt is slagged, pouted into a ladle, the composition is adjusted, and the melt is cast into appropriate shapes. A modification of the use of sinter oxide is its injection directiy into the molten metal (33). 

Tubular Fixed-Bed Reactors. Bundles of downflow reactor tubes filled with catalyst and surrounded by heat-transfer media are tubular fixed-bed reactors. Such reactors are used most notably in steam reforming and phthaUc anhydride manufacture. Steam reforming is the reaction of light hydrocarbons, preferably natural gas or naphthas, with steam over a nickel-supported catalyst to form synthesis gas, which is primarily and CO with some CO2 and CH. Additional conversion to the primary products can be obtained by iron oxide-catalyzed water gas shift reactions, but these are carried out ia large-diameter, fixed-bed reactors rather than ia small-diameter tubes (65). The physical arrangement of a multitubular steam reformer ia a box-shaped furnace has been described (1). 

The cubic BN crystals may also be bonded into strong bodies that make excellent cutting tools for hard iron and nickel-based alloys. Such tools produce red-hot chips and permit the wider use of tough, high temperature alloys which would otherwise be prohibitively difficult to shape (12,20,21) (see... 

The advantages of electroless nickel over hard chromium include safety of use, ease of waste treatment, plating rates of as much as 40 p.m/h, low porosity films, and the ability to uniformly coat any geometric shape without burning or using special anodes. Increased chemical safety is another... 

Electroforrning is the production or reproduction of articles by electro deposition upon a mandrel or mold that is subsequendy separated from the deposit. The separated electro deposit becomes the manufactured article. Of all the metals, copper and nickel are most widely used in electroforming. Mandrels are of two types permanent or expendable. Permanent mandrels are treated in a variety of ways to passivate the surface so that the deposit has very Httie or no adhesion to the mandrel, and separation is easily accompHshed without damaging the mandrel. Expendable mandrels are used where the shape of the electroform would prohibit removal of the mandrel without damage. Low melting alloys, metals that can be chemically dissolved without attack on the electroform, plastics that can be dissolved in solvents, ate typical examples. 

Stainless Steel There are more than 70 standard types of stainless steel and many special alloys. These steels are produced in the wrought form (AISI types) and as cast alloys [Alloy Casting Institute (ACI) types]. Gener y, all are iron-based, with 12 to 30 percent chromium, 0 to 22 percent nickel, and minor amounts of carbon, niobium (columbium), copper, molybdenum, selenium, tantalum, and titanium. These alloys are veiy popular in the process industries. They are heat- and corrosion-resistant, noncontaminating, and easily fabricated into complex shapes. 

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... 

Figure 5 Comparison of spectral profiles measured from a specimen of NiO using EDS and EELS. Shown are the oxygen K- and nickel L-shell signals. Note the difference in the spectral shape and peak positions, as well as the energy resolution of the two spectroscopies.

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