Effect of pre-oxidation and Al amount on the oxidation behavior of healing agents in YSZ-Mo(Si1-x,Alx)2 composite

Efficient and easy to produce self-healing agents have significant role on the development of self-healing composites. Herein, we report preoxidized Self-propagating high-temperature synthesis (SHS) synthesized Al-alloyed MoSi₂ for self-healing agent in thermal barrier coating system. The raw materials of Mo, Si and Al with molar aspect ratio of (1:1.6:0.4) and (1:1.2:0.8) were used to produce Mo(Si_1-x,Al_x) via SHS method. The healing agents were used to produce YSZ- Mo(Si_1-x,Al_x) composite by spark plasma sintering (SPS) method. Effect of peroxidation and Aluminum amount were studied after iso-thermal oxidation at 1050 °C with FE-SEM, EDX and XPS analysis. Oxide shell were grown on the surface of healing agent powders after preoxidizing. Oxide form of aluminum, silicon and molybdenum are available in oxide shell after preoxidation. Selective oxidation of Aluminum led to produce firm and continues Alumina oxide film on the surface of healing agents. Peroxidation is effective way to reserve the healing agent with molar aspect ratio of (1:1.2:0.8) by decreasing oxidation rates of them at working temperature and has not significant effect on healing agent with (1:1.6:0.4) molar aspect ratio. There is much prospect that this research will led to producing novel self-healing thermal barrier coatings by modification of healing agents composition in order to have the most appropriate properties at working condition.     

Assessing glass-ceramic homogeneity and nucleation self-correlation by crystallization statistics

In this work, we implemented and tested a statistical method to evaluate the microstructural uniformity of partially crystallized glasses employing the aggregation index (R-index), a parameter derived from the Poisson distribution function, which has mainly been used in Ecology studies. Since the crystal nucleation rate strongly depends on the chemical composition, the spatial crystal distribution in glass-ceramics can be used to infer their chemical homogeneity. We also tested the hypothesis, advanced by some authors, of preferential secondary nucleation close to preexisting crystals (even in chemically homogeneous samples). To this end, we conducted a nearest-neighbor statistical analysis of the spatial crystal distribution in partially crystallized Li₂Si₂O₅ and Ba₅Si₈O₂₁ glasses, used as model materials, by inspecting optical micrographs obtained at different magnifications. The resultant R-indexes indicate a very high degree of homogeneity of the crystal number distribution, reflecting the uniform distribution of the chemical elements in the parent glasses. Moreover, the results for both glasses refute the suggestion that crystal nucleation is self-correlated. These outcomes allow us to suggest the R-index as a valuable and easily implemented tool to evaluate the chemical homogeneity of glasses that undergo internal nucleation, such as those used for glass-ceramics.     

The shortest path in a simply-connected domain having a curved boundary

Given two distinct points S and E on a closed parametric curve forming the boundary of a simply-connected domain (without holes), this paper provides an algorithm to find the shortest interior path (SIP) between the two points in the domain. The SIP consists of portions of curves along with straight line segments that are tangential to the curve. The algorithm initially computes point-curve tangents and bitangents using their respective constraints. They are then analyzed further to identify potential tangents. A region check is performed to determine the tangent that will form part of the SIP. Portions of the curve that belong to the SIP are also identified during the process. The SIP is identified without explicitly computing the length of the curves/tangents. The curve is represented using non-uniform rational B-splines (NURBS). Results of the implementation are provided.     

A secured image steganography method based on ballot transform and genetic algorithm

Multimedia Tools and Applications - Rapid advances in digital technology have facilitated us to transfer a huge amount of electronic files over the internet. But in the presence of malicious...