Study on the Influencing Factors in the Process of Surface Strippable Decontaminant

One effective measure of radioactive material purification is the use of strippable decontaminants, which effectively coat the pollutant, capture suspended particles in the air, and deposit them onto the surfaces of objects. However, there are some shortcomings in terms of film formation and peelability, such as a brittle coating and poor peelability. Therefore, in order to meet future military and emergency needs, this research investigated the influencing factors in the process of surface strippable decontamination. Experiments included tests for wettability, potential, particle size, strippable performance, tensile performance, ultraviolet transmittance reflectance, and film formation as well as image analysis of photomicrographs from an optical microscope system. These experiments indicate that the strippable decontaminant is a viable means of contamination removal.

Crack channelling mechanisms in brittle coating systems under moisture or temperature gradients

Crack channelling is predicted in a brittle coating-substrate system that is subjected to a moisture or temperature gradient in the thickness direction. Competing failure scenarios are identified, and are distinguished by the degree to which the coating-substrate interface delaminates, and whether this delamination is finite or unlimited in nature. Failure mechanism maps are constructed, and illustrate the sensitivity of the active crack channelling mechanism and associated channelling stress to the ratio of coating toughness to interfacial toughness, to the mismatch in elastic modulus and to the mismatch in coefficient of hygral or thermal expansion. The effect of the ratio of coating to substrate thickness upon the failure mechanism and channelling stress is also explored. Closed-form expressions for the steady-state delamination stress are derived, and are used to determine the transition value of moisture state that leads to unlimited delamination. Although the results are applicable to coating-substrate systems in a wide range of applications, the study focusses on the prediction of cracking in historical paintings due to indoor climate fluctuations, with the objective of helping museums developing strategies for the preservation of art objects. For this specific application, crack channelling with delamination needs to be avoided under all circumstances, as it may induce flaking of paint material. In historical paintings, the substrate thickness is typically more than ten times larger than the thickness of the paint layer; for such a system, the failure maps constructed from the numerical simulations indicate that paint delamination is absent if the delamination toughness is larger than approximately half of the mode I toughness of the paint layer. Further, the transition between crack channelling with and without delamination appears to be relatively insensitive to the mismatch in the elastic modulus of the substrate and paint layer. The failure maps developed in this work may provide a useful tool for museum conservators to identify the allowable indoor humidity and temperature fluctuations for which crack channelling with delamination is prevented in historical paintings.

Optimization of Rice Husk Ash-Based Geopolymers Coating Composite for Enhancement in Flexural Properties and Microstructure Using Response Surface Methodology

If the coating is sufficiently flexible, no tears, cracks, or debond will occur. Although geopolymers have a great potential as a coating material, research on the flexural properties is very limited. In this study, a three-point bending test and scanning electron microscope were used to investigate the flexural properties and microstructure of the geopolymer composite coating (GCC), respectively. Response Surface Methodology (RSM) consists of a combination of mathematical and statistical techniques, which is useful in modelling, analyzing, and optimizing responses that are influenced by several factors. It was used in determining the relationship between each factor and determining the best composition for the composite coating. Several factors were considered including ratio of activated alkaline (AA) solution (V1), RHA/AA ratio (V2), and curing temperature (V3). Results showed that the RHA/AA ratio mostly influenced the response, followed by curing temperature while the ratio of AA was not significant. Lower V2 and V3 values provided the highest flexural strength and modulus. The optimum composition which provided the best coating of flexural properties were V1 = 3.5, V2 = 0.39, and V3 = 45.7 °C. Microscopic images showed that coating with high flexural properties (ductile coating) exhibited minor and rough cracks as compared to that of coating with low flexural properties (brittle coating) which displayed a crack with a clean linear cut. Brittle coating was highly agglomerated and has a significant negative effect on the flexural properties. By developing the optimum composition, the GCC may potentially be a good alternative as a building construction coating material.

Performance of Strain Gauge in Strain Measurement and Brittle Coating Technique

The strain gauge system consists of a metallic foil supported in a carrier and bonded to the specimen by a suitable adhesive. Previous chapters discussed the construction, configuration, and the material of the strain gauge. The strain gauge has advantages over the other methods. A strain gauge can give directly the strain value as output. However, in optical methods, it is required to interpret the results. It is also required to be aware that the strain gauge technology is majorly used, and it can also be easily wrongly used. Hence, it is required to obtain the proper knowledge of the strain gauge to get the full benefit of the technology. This chapter covers the majorly on the performance of the strain gauge, its temperature effects, and strain selection. Further, this chapter also covers the brittle coating technique that is used to decide the position of the strain gauge in the applications.

THE CHARACTERISTICS OF Al-Si COATING ON STEEL 22MnB5 DEPENDING ON THE HEAT TREATMENT

The coating on the 22MnB5 steel is intended to protect it against oxidation during the forming process. This steel is hot-pressed. A preheating before the pressing and subsequent hardening in the tool affects the properties of the AlSi coating. This study summarizes the results of investigating the effect of heat treatment parameters on the formation of intermetallics in the AlSi coating. The chemical analysis of the coating was performed by the EDX and EBSD method and the mechanical properties were determined by the Hysitron TI 950 TriboIndenter™ system. The result of this study is that, due to a diffusion during the heat treatment, the brittle coating was transformed into a tougher phase.