Interdiffusion substrates

An inversion of these arguments indicates that release agents should exhibit several of the following features (/) act as a barrier to mechanical interlocking (2) prevent interdiffusion (J) exhibit poor adsorption and lack of reaction with at least one material at the interface (4) have low surface tension, resulting in poor wettabihty, ie, negative spreading coefficient, of the release substrate by the adhesive (5) low thermodynamic work of adhesion ... 

A multilayer-type structure probably due to cords in the molten zone between single arc sprayed (0.25 MPa) Ni droplets and steel substrate were found in AES point depth profiles [2.158]. That particular arc spraying condition turned out to yield the best adhesion. Plasma-sprayed AI2O3 layers separated from pre-oxidized Ni Substrate had a micrometer-thick NiO layer on the substrate-sided face and micrometer-deep oxide interdiffusion [2.159]. In this work also, AES point depth profiling substantiated technological assumptions about adhesion mechanisms. 

Similar to the primers developed for cyanoacrylate resins, the solvent carrier plays an important role in facilitating interdiffusion of the primer and the substrate. Fig. 12 shows a schematic view of the top few microns of an injection molded TPO surface. 

Diffusion theory involves the interdiffusion of macromolecules between the adhesive and the substrate across the interface. The original interface becomes an interphase composed of mixtures of the two polymer materials. The chemical composition of the interphase becomes complex due to the development of concentration gradients. Such a macromolecular interdiffusion process is only... 

The adhesion promotion of an organic matrix to an inorganic substrate using a silane has been studied to model the structure of the created interphase [64-66]. The polymer/silane interphase is influenced by the solubility parameter of both the silane coupling agent and the polymer. More interdiffusion occurs when the solubility parameters of the polymer and the silane closely match together. It is believed that this model can be applied to silicone adhesive/solid substrate system. 

Figure 3 Layer-resolved band energy contributions to the MAE for Cu/Fee/Cu (001) multilayers interdiffused at one of the Fe/Cu interfaces (shaded area), round symbols 30 %, cross 15 %, diamonds 0 % Only the Fe layers are numbered. For the interface layer of the Fe film (numbered by 1) only the contribution of the Fe component, whereas for the interface layer of the substrate (one layer to the left) only the contribution of the Cu component is displayed.

With tin coatings on brass, the interdiffusion of coating and substrate brings zinc to the surface of the tin the action can be rapid even with electrodeposited coatings. The effect of zinc in the surface layers is to reduce the resistance of the coating to dulling in humid atmospheres, and the layer of zinc corrosion product formed makes soldering more difficult. An intermediate layer of copper or nickel between brass and tin restrains this interdiffusion . 

Silver coatings may blister above 200°C because of oxygen diffusion. A nickel undercoat stops interdiffusion with a copper substrate above 150°C. Alloying with antimony, selenium, sulphur or rhenium increases hardness—the coefficient of friction is also much reduced in the last case. ... 

In order to achieve the enhanced strength, atomically sharp A IB interfaces are needed for the mechanism proposed by Koehler. The multilayer hlms should be deposited under a relative low temperature in order to avoid the interdiffusion between the layers. Thus, PVD techniques such as evaporation and sputtering deposition are the reasonable methods to fabricate multilayer hlms. There are several ways to achieve the alternate deposition of the composing layers A and hxed substrate position mode, repeated substrate po-... 

Hence, the decision to use a heated substrate with simultaneous evaporation of the component metals as an aid to homogenization requires consideration of whether or not it might have an adverse effect, i.e., causing preferential nucleation of one component, which interdiffusion may not be able to remedy. It was believed (60) that in preparing Pd-Rh alloys by simultaneous deposition on a substrate at 400°C, rhodium nucleated preferentially and that crystallites grew by the addition of palladium (and rhodium) atoms. The diffusion of palladium atoms into this kernel formed a phase with 88 =t 5% Rh (phase II). The outer shell of the crystallite, phase I, was in effect a solid solution deficient in rhodium compared with the overall film composition, and the Rh content of phase I therefore increased as the Rh flux was increased. 

Fig. 29. SIMS profiles of total deuterium density in two composite samples subjected to a one hour deuteration in the same plasma product environment at 300°C (Johnson, 1988). Both samples had a substrate containing 2 x 10IH Sb/cm3 this was covered with an epitaxial layer containing 3 x 1018 As/cm3 for the upper curve, and with one containing 5x 10 7 As/cm3 for the lower curve. There was in both cases a little interdiffusion. All sample surfaces were prepared for deuteration by removing the oxide with a dilute HF etch, rinsing with distilled water, and blowing dry with heated nitrogen.

The diffusion theory states that interpenetration and entanglement of polymer chains are additionally responsible for bioadhesion. The intimate contact of the two substrates is essential for diffusion to occur, that is, the driving force for the interdiffusion is the concentration gradient across the interface. The penetration of polymer chains into the mucus network, and vice versa, is dependent on concentration gradients and diffusion coefficients. It is believed that for an effective adhesion bond the interpenetration of the polymer chain should be in the range of 0.2-0.5 pm. It is possible to estimate the penetration depth (/) by Eq. (5),... 

Electrodeposition presents, in principle, several advantages for the investigation and production of layered alloys. Among these are the tendency of electrodeposited materials to grow epitaxial and thus to form materials with a texture influenced by the substrate. Electrodeposition can be used in systems that do not lend themselves to vacuum deposition. The electrodeposition process is inexpensive and can be upscaled with relative ease for use on large parts further, it is a room-temperature technology. This last point may be important for systems in which undesirable interdiffusion between the adjacent layers may readily occur. 

The local coordination of the majority specie (substrate material) in the new interface phases. The interdiffusion region is often heterogeneous from the point of view of the substrate material (different first nearest neighbour environments) than for the adsorbate, therefore considerations on the resolution of multiple phases also apply. 

The dentin-adhesive interface has been studied using a Raman microprobe technique [199], which shows the formation of resin-reinforced dentin and the penetration of resin into dentin substrate to a depth of 5-6 microns. Further study of the interface showed that only small molecules such as MMA, 4-MET (hydrolyzed 4-META) or oligomers infiltrated the dentin, and that all of the resin in the dentin originated from the monomer solution [200]. SEM and TEM studies of the ultrastructure of the resin-dentin interdiffusion zone showed a 2 micron zone with closely packed collagen fibrils running parallel to the interface [201]. 

The SNMS depth profile (ion intensity as a function of sputter time) for the matrix elements of a Ba07Sr03TiO3 layer on a silicon substrate with Pt/Ti02/Si02 buffer layers is illustrated in Figure 9.8. Inhomogeneity of the perovskite layer was detected especially for Sr. Furthermore, an interdiffusion of matrix elements of the Ba07Sr03TiO3 layer and of the Pt barrier layer was observed. 

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