Aerospace gas turbine engines are now designed such that the heat resistant super alloys operate at temperature very close to their melting, so current strategies for performance improvement are centered on thermal barrier coatings. Lower thermal conductivities lead to temperature reductions at the substrate/bond coat interface which slows the rate of the thermally induced failure mechanisms. Alternatively, lower thermal conductivity of thermal barrier coating (TBC) layers might allow designers to reduce the TBC

thickness there by decreasing the significant centrifugal load that the mass of the TBC imposes on the rotating turbine engine components. One approach to improve TBC system is to optimize the pore morphologies in order to reduce the thermal conductivity while still retaining high in-plane compliance. The second approach to improve TBC system performance is to optimize the surface microstructure, surface

densification, phase structures mechanical characteristic, chemical structure, and thermo-physical properties. The main focus of this work is to study the influence of Al PO4 (and laser)-sealed ZrO2-MgO coatings on thermal barrier coating system comprised of zirconia stabilized with magnesia top coat to predict the best improvement of TBC system and to optimize the surface microstructure, surface densification, phase structures, mechanical characteristic, chemical structure, and thermo-physical properties as well as their properties with those obtained using reference techniques. Thermal expansion studies were used to study the high temperature stability of the different coatings (reference and modified coatings) structures. As low thermal conductivity is one of the most important features of TBC, thermal diffusivity and specific heat measurements were carried out. Also the mechanical measurements (e.g.

micro-hardness, tensile bond strength, young’s modulus), phase analyses using XRD and chemical analysis using electron dispersive X-ray (EDX) for elemental analysis in scanning microscopy studies

An experimental study was conducted at University of Gondar from November 2015 to April 2016. The objective of this study was to evaluate the pathogenicity, gross and histopathological lesion of coccidiosis in broiler chickens.One hundred commercial one day old broiler chicks, unvaccinated against coccidiosis, was used during this experiment. At day 14, chickens of G1 (n=25), G2 (n=25) andG3 (n=25) were infected with 2 x 104 sporulated oocysts of E. tenella,E. acervulina and mixed Eimeria spp. respectively; G4 (n=25) served as the uninfected control group. Fifteen birds were sacrificed in each group with seven days after infection. The prepatent period for E. tenella (G1) and mixed Eimeria spp(G3) was five days, however, E.acervulina (G2) had prepatent period of four days. The observed pathological lesion score ranged from +1 to +4 were recorded in infected chickens. Chickens infected in E.tenella showed sever lesion score when compared to other infected groups. The histopathological findings infected chickens were showed different stages of parasite, villous atrophy, severe inflammation, mononuclear inflammatory cell infiltrated, sever haemorrhagic areas.