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Cyclic Oxidation Behavior of an EB-PVD CoCrAlY Coating Influenced by substrate/coating Interdiffusion

Chinese Journal of Aeronautics 2012年第5期25卷 796-803页

作者： LIANG Tianquan GUO Hongbo PENG Hui GONG Shengkai School of Materials Science and Engineering Beihang University Beijing 100191 China School of Materials Science and Engineering Guangxi University Nanning 530004 China

To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superalloy DZ125 at 1 050℃ is investigated. The 40 μm thick CoCrA1Y coating has a cyclic oxidation life of around 160 h, and the oxidation constant is 1.915× 10^-7 ***^-8.s-1. However, severe spallation of the oxides containing Co, Cr, Ni, Ta and Ti occurs with longer cyclic oxidation. The degradation in oxidation resistance for the coating is related to the depletion of A1 due to the oxide spallation and interdiffu- sion. Severe interdiffusion between the coating and underlying substrate occurs at 1 050 ℃. The composition of the substrate has an important effect on the thermal cycling lifetime of the coating. The influencing mechanism is discussed.

关键词： CoCrA1Y coating cyclic oxidation degradation interdiffusion substrate composition

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Germination and Early Seedling Growth of Moringa oleifera Lam with Different Seeds Soaking Time and substrates at the Yongka Western Highlands Research Garden Park (YWHRGP) Nkwen-Bamenda, North-West Cameroon

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American Journal of Plant Sciences 2016年第15期7卷 2173-2185页

作者： Bernard Palmer Kfuban Yerima Grace Mbakpor Ayuk Roger Kogge Enang Nicole Guehjung Yanick Alphonse Tiamgne Department of Soil Science University of Dschang Dschang Cameroon Department of Crop Production University of Dschang Dschang Cameroon Ministry of Agriculture and Rural Development West Region Cameroon

Moringa oleifera is a multipurpose tree used to remedy problems related to food insecurity and soil fertility degradation. Proper husbandry of this crop is contingent on the use of seedlings of good quality. This study aimed at assessing the germination and early seedling growth with different soaking durations and substrates composition. The seeds were obtained from the Far North region of Cameroon. A randomized complete block design with three replications was used. Two factors were tested;soaking duration with 4 treatment levels of 0 day, 4 days, 8 days and 12 days and substrates with 8 treatment levels: 100% soil, 75% soil + 25% poultry manure (PM), 50% soil + 50% PM, 25% soil + 75% PM, 100% sand, 75% sand + 25% PM, 50% sand + 50% PM and 25% sand + 75% PM. Germinated seeds and growth parameters were collected after every 5 days. The results showed that soaking duration and substrate composition influence germination and initial development of M. oleifera (p ≤ 0.05). At 25 days after soaking (DAS), soaking durations of 0 day (68.7%) and 8 days (53.1%) showed the highest germination percentages while seeds soaked for 12 days occupied the least position with 37.5%. At the same time, 75% soil + 25% PM (68.7%), 100% sand (64.5%) and 100% soil (60.5%) with the unsoaked seeds showed the highest germination percentages. The least germination percentages were represented by 50% sand + 50% PM and 25% sand + 75% PM with 35.5% and 27%, respectively. Unsoaked seeds with the substrates of 50% soil + 50% PM are the best practice for M. oleifera seedling production in the nursery.

关键词： Soaking substrate composition Germination Initial Growth Western Highlands

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