Crack-free coatings

The crack-free coated alumina specimens were subjected to a diffusion bonding (DB) procedure, described above. The parameters of the process were same as for non-graded specimens. After the bonding to IN-738 superalloy the joints were examined by their appearance and microstructure. For some specimens it was found that good, crack-free microstructure does not guaranteed high mechanical properties, in particular at elevated temperatures under external mechanical load. 

Much lower voltages between 30 and 90 V were used by Javidi et al. (2008) to deposit EPD coatings on 316L stainless steel between 1 and 5 min deposition time. Samples coated at 60 V and 3 min yielded continuous, well adherent and crack-free coatings. With increasing deposition time, the deposition rate as well as the current density decreased and maintained a saturation value at constant voltage. 

Once the membrane was successfully produced, it was analysed for characterisation and scanning. The sol-gel technique was successfully used to obtain a crack-free unsupported membrane, which was expected to have pore size of 1-2 nm. The development of the crack-free membrane may not have the same strength without strong, solid support. The next stage of this work was to characterise the fabricated membrane. Hie objectives of this study were to develop a zirconia-coated 7-alumina membrane with inorganic porous support by the sol-gel method and to characterise the surface morphology of the membrane and ceramic support. 

Figure 16.23 presents the alumina-coated ceramic membrane. There were opportunities to fabricate a crack-free ceramic membrane coated with y-alumina. The supported zirconia-alumina membrane on the ceramic support shows an irregular surface. The non-uniform surface of ceramic support causes the irregular surface on the top layer of the membrane. Some of the membrane sol was trapped in the porous ceramic support during coating, and caused the irregularity of the membrane surface. 

The technical demands for a cheese coating are very comprehensive since it has to fulfill a large number of functions [132,135]. First of all, it has to offer both mechanical and hygienic protection over a long period of time. Therefore, the coating should be homogeneous and crack free and adhere well to the wet... 

Figure 1b), showing that the ordered microstructure was retained even after the removal of surfactants. The d value of the calcined film was 4.1 nm. The SEM image of the film surface (data not shown) also indicates that the film is continuous and crack free. These observations are well consistent with those reported in the previous paper[2], showing the formation of silica-surfactant mesostructured material and the successful transformation of the as coated film into a nanoporous silica film. 

Abstract. Liquid phase deposition methods are a useful way to create mineral oxide films from aqueous solution under near-ambient conditions. These approaches have been applied to the creation of ceramic coatings on polymers and on polymer-matrix composites. Control has been achieved over the adherence and crystallinity of the solution-deposited thin films based on controlling the composition of both the deposition solution and the substrate surface. The challenge of depositing such films from water, while minimizing film cracking has also been addressed. Crack-free ceramic films of up to 200 nm thickness have been achieved on a variety of polymer substrates. 

The thermal stress of graded cemented carbide near the interfece is smaller than non- graded cemented carbide, and it was confirmed to achieve a crack- and peel- free coated product by a graded structure. 

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