Layered structures adhesion quality

The quality of this method is improved by the use of an inert atmosphere under reduced pressure. Individual alloying elements are not burnt off, oxide and nitride formation is suppressed, and adhesion and layer structure is improved. 

At ambient conditions usually a biaxial compressive stress is present in the brittle top layer of the substrate. At high biaxial stresses a characteristic delamination pattern, the telephone cord structure is frequently observed. Figure 4 shows an AFM image of this structure, observed for an ITO layer on a polymer substrate. From the characteristic sizes an estimate for the adhesion quality can be obtained. 

The second reason for this could be the adhesion quality on the interphase boundary. One can expect much better interaction between LDPE and PP as compared to the PP and PET. For example, the authors [75] demonstrated an intensive presence of transcrystalline layers of LDPE on the PP nanofibrils, which considerably contribute to the improvement of the matrix-reinforcement adhesion and thus enhance the final mechanical properties. Using TEM, the same phenomenon was obsei-ved in an earlier study [80,81] on stained thin slices of injection molded samples of LDPE/PET with MFC structure. What is more, the transciystallization phenomenon is less typical for MFC based on PP/PET [82]. This observation indicates that LDPE is much more inclined to form transcrystalline layei-s on the same type of fibrils (PET) than PP is. 

In the future, pre-coated metal sheets could probably be used, but then the spot weld bonding would be no more possible. In addition, one has to keep in mind that the adhesive strength on such coatings is lower than that of high strength structural adhesives. Even the adhesion quality of a hot dip galvanized steel coating has to be tested since with some structural adhesive the zinc layer debonds from the metal surface. 

The barrier quality is determined by the surface properties of the polymer substrate and the properties of the metal layer [12]. The most crucial factor is the surface quality of the substrate. If there is an adsorbate on the surface, it may be desorbed during the evaporation process, which leads to pinholes and poor adhesion of the metal layer. If the adsorbate is water, A1 may react with the water and lead to the formation of A1 oxide which has barrier properties substantially inferior to those of metallic Al. Also the lack of functional groups on the polymer surface causes poor adhesion and thus a change in the structure of the layer. 

Volatile tungsten(IV) 0x0 alkoxide//3-diketonate complexes of structural type W(0)(/1-diketonate)(OR)3 (R = t-Pr, f-Bu /3-diketonate = acac, 32, hfac, 33) are excellent precursors for the low-pressure CVD of electrochromic tungsten oxide films, as shown by Chisholm and coworkers. While with 32b and 33b the produced films were transparent and blue, 32a and 33a led to pale yellow layers which darkened to pale green-blue when exposed to air for several days. With the exception of 33a, all other tungsten complexes formed good-quality films with respect to adhesion and surface coverage however, no surface selectivity for quartz, pyrex or ITO was observed. 

Thin coatings not only are used for mechanical protection and lubrication, but are widely applied to protect against corrosion and chemical reaction [47-49]. The steel body of a car is first covered by a zinc layer, which is further treated in a phosphate bath, to promote the adhesion of the paint. Damaging this sandwich structure, by breaking one of these layers, results in quick corrosion of the car body rust. The improvement in the quality of this protective coating during the last 20 years is shown by the increase of the duration of the corrosion warranty proposed by car manufacturers (from 2 years less than 15 years ago, to 8 years at the present time). 

The erosion resistance of the soil may be increased by raising the cohesion of the soil aggregates this may be done by treating the soil with binding substances [507]. Such substances include cellulose and its derivatives (lignin, humic acid), bitumen, peat cement, and various structure-forming substances from plant residues. The adhesive substances envelop the soil particles. The layer so formed, a few microns thick, imparts the quality of tacki-... 

In most cases, after cleaning a further surface pretreatment, which may involve metallic and/or nonmetallic layers, is necessary in order to obtain good adhesion and thus protective properties. Also, the quality of the application procedures determines the final protective properties [3-18]. Of course, the structure of the polymeric network, the chemical composition, flaws, and the ease with which the coating is damaged on mechanical impact are also relevant for the final effectiveness of the protection. In fact, we have to take into account the properties of the whole system. 

For a more economical fabrication of microtubular SOFC with more reliability and flexibility in quality control, an advanced dry-jet wet extrusion technique, that is, a phase inversion-based co-extrusion process, followed by co-sintering and reduction processes was employed to fabricate a novel electroly te/anode dual-layer hollow fiber. Using the co-extrusion technique, one of the layers has to be thick in order to provide mechanical strength to the fiber, and in this design, the anode is chosen to be the thick layer due to the much lower ohmic losses (as shown in Figure 11.16). Use of co-extrusion has many advantages over conventional dry-jet wet extrusion methods such as simplified fabrication and better control over the manbrane structure. Furthermore, the risk of defects formation can be reduced and at the same time greater adhesion between the layers can be achieved. 

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