Chromium multilayers

Figure 10.6. (a) Indentation nanohardness of silver/chromium multilayers and single films of the constituent metals, as a function of depth affected by plastic deformation, (b) Charpy impact energies, a measure of fracture toughness, of three materials, as a function of test temperature they are mild steel, ultrahigh-carbon steel and a composite of the two kinds of steel (courtesy Dr. J. Wadsworth) (Fig. 10.6(b) is from Kum et at. (1983)). 

AES sputter depth profile through an iron/copper/chromium multilayer structure. Each layer is 5 nm thick (Courtesy of Thermo Fisher Scientific)... 

The trend in CVD metallization is toward greater use of copper, and the refractory metals and their silicides in multilayered metallization designs, typically consisting of metal-silicide contacts, refractory-metal barriers, and copper or an aluminum alloy as the principal interconnect metal. Other metals deposited by CVD such as chromium, molybdenum, platinum, rhodium, and ruthenium are also actively considered for use as conductors. 

The adsorption of gases and vapors on mesoporous materials is generally characterized by multilayer adsorption followed by a distinct vertical step (capillary condensation) in the isotherm accompanied by a hysteresis loop. Studies of adsorption on MCM-41 have also demonstrated the absence of hysteresis for materials having pore size below a critical value. While this has been reported for silica gel and chromium oxide containing some mesopores, no consistent explanation has been offered [1], However, conventional porous materials, having interconnected pores with a broader size distribution, are generally known to display a hysteresis loop with a point of closure which is characteristic of the adsorptive. These materials have an independent method of estimating the pore size from XRD and TEM, that allows comparison with theoretical results. Consequently, we have chosen these materials to test the proposed model. 

The first material found to display GMR was a multilayer system consisting of 30-A layers of iron interspersed with chromium layers of between 9 and 18 A. This... 

Multilayered coatings are produced by plating different metals from the same solution at different potentials. A pulse train-shaped potential is enforced, resulting in the multilayer deposition. For example, multilayered coatings based on copper, nickle, chromium, in that order, can be applied to either metal or plastic components for visual appearance, corrosion and wear resistance, and weight saving. 

Let us assume that P is the fraction of available sites on the alumina surface that are occupied by chromium ions. Multilayer adsorption will be excluded, so that each site may be occupied only once. If there are N chromium atoms on the surface, then the number of atoms in single, double, triple, and quadruple clusters denoted by 8, D, T, and Q, respectively, are given by the expressions listed in Table VI. Note that there are several types of triple and quadruple clusters. Formulae are presented for both a plane triangular lattice and a plane square lattice. The original article should be consulted for the derivation of these expressions (202). The actual arrangement of the alumina sites depends upon the exposed surface plane, and for our purposes either the triangular or the square lattice is an adequate approximation to the surface. The quantities SjN, DjN, TjN, and QjN are shown graphically in Fig. 36 as a function of the fraction P of the occupied sites. 

Interesting electrical properties are to be expected with the stepwise extension of this TT-system. The preparation of multilayered cyclophanes proved to be laborious [6] nevertheless new synthetic methods in transition metal chemistry of arenes have opened up a promising alternative approach via preparation of multidecker sandwich complexes (structure type D in Fig. 3). First row transition metals like chromium, iron and cobalt [51] form strong coordinative bonds with arenes when their oxidation state is low [48a] whereas second and third row elements like ruthenium, rhodium and iridium are strongly bonded towards arenes in higher oxidation states [48a, 51]. Sandwich complexes of cyclophanes can be divided into two groups ... 

Optimization of growth parameters has permitted to create multilayer monolithic heterostructures (MMH) with buried nanocrystallites of iron and chromium disilicides. A new approach to study of optical properties of MMH-structures has been developed and tested. 

More effective are films with microcracks or micropores as obtained with modem chromium-plating electrolytes. Furthermore, double layer or multilayer chromium films provide very stable corrosion protection. 

Implantation and analysis were performed on two specimens during the first part of this report period (1) oxygen implanted into a chromium layer on sapphire, and (2) chromium implanted into a Ti.Oy/AlgOg multilayered structure on silicon. 

For (2), it is desired that the implanted chromium come to rest at a position far beyond the first four layers of the specimen (distance greater than 100 nm). A multilayer sample of crystalline Ti Oy and amorphous Alj,0., on a silicon sulbstrate was obtained for use. in this study. The sample was made up of 38 repetitions of alternating layers of crystalline Ti,Oy and amorphous Al,03. In the implanted area, the thickness of each layer was approximately 190 nm. The sample was implanted with 350 KeV Cr at room temperature, While RBS did not detect the presence of the multilayered structure either before or after implantation, TEM cross-section samples of the as lmp anteci specimen did show that a multilayer was Indeed present. From this sample, some evidence of Implantation damage could be discerned. 

Copper coatings are used both for decorative and for corrosion protection from the atmosphere. Copper coated steels are used as roofs, flashings, leaders, gutters, and architectural trim. Copper undercoats also improve the corrosion resistance of multilayered coatings, specifically in the plating of nickel and chromium. 

In contrast, 25 times as much dipicolinic acid is adsorbed per unit weight of chromium hydroxide, despite the larger particle size of the latter as compared to hematite. Since it is quite improbable that this acid would form multilayers, it must be concluded that its molecules can actually diffuse into the hydrated amorphous particles of chromium hydroxide, i.e. in this case absorption is taking place. The crystalline character of hematite allows only for surface interactions, resulting - at best - in a monolayer. 

Duplex coatings are superior to bright nickel coatings in many atmospheres. Since the chromium deposit is the topmost layer in a multilayer coating, the durability of the chromium deposit controls the corrosion behavior of the duplex nickel during the initial stage of exposure. Duplex nickel coatings provide excellent corrosion resistance in natural atmospheres. 

The pigment flakes can typically be manufactured sequentially in a series of specialized roll-coating machines. In the first machine a carrier film, the sorelease layer, is deposited on a moving polymer web (transfer foil). This release layer is soluble in organic solvents so that the later formed multilayer film can be removed from the web at the end of the process. After depositing this release layer, the transfer foil is placed in a vacuum deposition roll coater and the first metal layer (e.g., chromium) as the semitransparent absorber metal is deposited followed by the first dielectric layer (e.g., magnesium fluoride) and the opaque metal layer (e.g., chromium). The second dielectric layer and the second semitransparent absorber... 

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