Adhesion zones structure

But in reality, failure occurs in most cases within the adhesion zone. This is the main reason that engineers have some doubts to use adhesives in structural applications. 

That other important cellular processes and events may be associated with these structures as well, is supported by our recent finding that capsular polysaccharides also seem to be produced over the adhesion zones, and by the observation of other laboratories that bacterial DNA adheres to those portions of envelope isolates that show connections between the inner and outer membrane. 

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. 

Step 3. The set of fracture properties G(t) are related to the interfaee structure H(t) through suitable deformation mechanisms deduced from the micromechanics of fracture. This is the most difficult part of the problem but the analysis of the fracture process in situ can lead to valuable information on the microscopic deformation mechanisms. SEM, optical and XPS analysis of the fractured interface usually determine the mode of fracture (cohesive, adhesive or mixed) and details of the fracture micromechanics. However, considerable modeling may be required with entanglement and chain fracture mechanisms to realize useful solutions since most of the important events occur within the deformation zone before new fracture surfaces are created. We then obtain a solution to the problem. 

PN-junctions 2 are formed in a substrate 1. An oxide is grown by anodic oxidation over the whole surface of the substrate. A metallic layer 4 is deposited on the anodic oxide. This layer may consist of a first layer which has a good adhesion to the oxide and a second layer which is opaque to infrared radiation. The metallic layer is shaped by photolithography in order to cover only zones surrounding the detector regions. A dielectric layer 5 is deposited covering the whole surface and the photodiodes are connected by metal connections 6. An embodiment with a planar structure is also shown. 

Transmission Electron Microscopy (TEM) has been used to characterize aluminum thin films thermally evaporated (vacuum around 10 4 Torr) on Polyethyleneterephtalate (Mylar) and to correlate the crystallographic structure of the system Al/Mylar and the adhesion of the aluminum films. The adhesion of these films has been measured by a Peel test technique. For the polymer, an amorphous layer (t=12 nm) followed by a crystalline film have been observed on a Corona treated film and the opposite configuration has been found on a bi-axially stretched film. Some spherical precipitation ana interdiffusion zones have also be observed in the Mylar for the films which have the lower coefficient of adhesion (100 g/inch). The main conclusion is the augmentation of the adhesion of the aluminum film as the size of the grains decreases and/or as the microroughness of the Al/Mylar interface increases. 

A more recent hypothesis is that the craze tip breaks up into a series of void fingers by the Taylor meniscus instability - . Such instabilities are commonly observed when two flat plates with a layer of liquid between them are forced apart or when adhesive tape is peeled from a solid substrate jjjg hypothesis in the case of a craze is that a wedge-shaped zone of plastically deformed and strain softened polymer is formed ahead of the craze tip (Fig. 3 a) this deformed polymer constitutes the fluid layer into which the craze tip meniscus propagates whereas the undeformed polymer outside the zone serves as the rigid plates which constrain the fluid. As the finger-like craze tip structure propagates, fibrils... 

The functions of the extracellular matrix are manifold (1.) stabilization of the tissue and organ structure, (2.) structural linkage of cells, (3.) transmission of information between the various types of cells within the tissue and the extracellular milieu, (4.) adhesion or migration of cells, and (5.) influence on the development and differentiation of cells and their polarity. In fibrogenesis, collagen fibres build the framework in which the other components of the extracellular matrix are embedded. In line with this wide scop>e of functions, the extracellular matrix is not only organ-sp>ecific as regards its architecture, but it also displays variations at different locations within the liver, e.g. in Disse s space, in the periportal fields and within the acinus zones. The extracellular matrix is a dynamic structure, i. e. there is a constant equilibrium between build-up (by matrix-metalloproteinases = MMP) and break-down (by tissue inhibitors of matrix metaUoproteinases = TIMP). 

---