Development of thermal barrier coatings with excellent delamination resistant property by extreme internal oxidation

In Japan, the proportion of thermal power generation has increased since after the Great East Japan Earthquake in 2011, accounting for approximately 85% in 2015. Compared to other power generations, thermal power plants have a large amount of carbon dioxide emissions relative to the amount of power generation. Therefore, it is an urgent task to reduce carbon dioxide emissions by improving the efficiency of thermal power plants. Increasing the turbine inlet gas temperature improves the efficiency of the gas turbine thermal power plants. However, high-temperature components, such as rotating blades, are close to their maximum service temperature. Therefore, application of the thermal barrier coating (TBC) on the turbine blade substrate is needed to protect a structure. The TBC system usually consists of ceramic top-coating (TC) and intermediate metallic bond-coating (BC) on a Ni-based superalloy substrate. To reduce the effect of the heat flux on the structure, heat resistant material, such as Yttria-Stabilized Zirconia (YSZ), is commonly used for TC layer. While, for BC, MCrAlY (M: Co and/or Ni) alloy is commonly used to protect the substrate from oxidation and corrosion, as well as to improve the bonding strength between the TC and the BC layers. However, delamination of the TBC can occur, because of significant thermal stresses generated when the coating cools down from high to room temperature. Therefore, improvement of TBC delamination resistance is indispensable. Delamination of the TBC is caused by the Thermally Grown Oxide (TGO) formed at the interface between TC and BC, because of the discrepancy in the thermal expansion coefficient between TGO and TC or BC. Therefore, the TBC formation control is important to improve the delamination resistance of TBC. Previously, authors have succeeded in improving the delamination resistance of TBC by adding cerium (Ce) to the CoNiCrAlY alloy as a BC which assist the formation of the inward TGO. The inward TGO reduces the thermal stress experienced by TBC through the formation of vertical cracks initiated by the inward TGO. However, the inward TGO only forms when the temperature is over 1100°C, which is higher than the substrate temperature during the gas turbine thermal power plants operation temperature. As a result of further research, authors have succeeded in reducing the inward TGO formation temperature to 1000ºC close to the actual use environment by adding ceria (CeO2) instead of Ce to the BC materials. In our studies, it was improved that the TBC delamination resistance thanks to the introduction of internal oxidation during BC formation using High Velocity Oxy-Fuel (HVOF) technique. It was showed that internal oxidation introduced during the film formation proceeded sufficient inward oxide at high-temperature exposure (900°C) and exhibited high delamination resistance. Thus, adding CeO2 to the CoNiCrAlY alloy and introducing internal oxidation during BC formation is efficient to reduce the inward oxide formation temperature. However, when the inward oxide is introduced to BC, the internal oxidation might reduce the oxidation resistance of TBC system. In addition, oxidation and corrosion of the substrate can occur due to direct exposure to the combustion environment through vertical cracks. Therefore, it is needed to develop a new BC combining oxidation resistance and delamination resistance. Two-layer BC is considered. The first layer of the BC, located on the substrate side, has less internal oxidation and helps in the protection of the substrate. The second layer of the BC, located on the TC side, has a lot of internal oxides and improves the coating delamination resistance. Thus, it possible to develop TBC compatible with delamination resistance properties and substrate protection properties. The aim of our study is to improve the delamination resistance of TBC and develop TBC with reduced inward TGO formation temperature. For this purpose, TBC with CeO2 and ZrO2 added to the BC material were prepared. To perform TBC specimens with internal oxide in the BC, BC materials with several particle sizes and several BC spraying methods were used. The internal oxide amount and delamination resistant property of these TBC specimens were evaluated with SEM observation and four-point bending test. And also, the high-temperature oxidation behavior and the delamination resistance of TBC with two layers of BC, aiming to achieve both delamination resistance and substrate protection, were evaluated

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内容の要約広島大学(Hiroshima University)博士(文学)Doctor of Philosophydoctora

Current Insights into Mesenchymal Signatures in Glioblastoma

Glioblastoma (GBM) is a fatal primary malignant brain tumor in adults. Despite decades of research, the prognosis for GBM patients is still disappointing. One major reason for the intense therapeutic resistance of GBM is inter- and intra-tumor heterogeneity. GBM-intrinsic transcriptional profiling has suggested the presence of at least three subtypes of GBM: the proneural, classic, and mesenchymal subtypes. The mesenchymal subtype is the most aggressive, and patients with the mesenchymal subtype of primary and recurrent tumors tend to have a worse prognosis compared with patients with the other subtypes. Furthermore, GBM can shift from other subtypes to the mesenchymal subtype over the course of disease progression or recurrence. This phenotypic transition is driven by diverse tumor-intrinsic molecular mechanisms or microenvironmental factors. Thus, better understanding of the plastic nature of mesenchymal transition in GBM is pivotal to developing new therapeutic strategies. In this review, we provide a comprehensive overview of the current understanding of the elements involved in the mesenchymal transition of GBM and discuss future perspectives

Empirical analysis on the normative reasoning of media policy in Europe: Focusing on the presence of a public service broadcaster and entry barriers by a licensing system in the broadcasting market

This study attempts to verify the functions of the main part of the media policy in European society, especially through the establishment of a public service broadcaster (PSB) and the creating of entry barriers by a licensing system in the terrestrial broadcasting market through developments in social psychology and communication theory. Thus far, media policy has been examined normatively and theoretically, but less rigorous proofs were provided. Our analysis integrates patch-worked and multidimensional past researches and clarifies the causal relationships in the overall picture through a structural equation model (SEM) using data from various social surveys. This reveals that these policies have a positive effect on people's acquisition of the basic requirements for democracy, the development of social capital and people's quality of life, happiness

Bofutsushosan, an Oriental Herbal Medicine, Attenuates the Weight Gain of White Adipose Tissue and the Increased Size of Adipocytes Associated with the Increase in Their Expression of Uncoupling Protein 1 in High-Fat Diet-Fed Male KK/Ta mice

Bofutsushosan (BOF), an oriental herbal medicine, has been used as an anti-obesity drug in overweight patients. In the present study, to evaluate the anti-obesity and anti-diabetic effects of BOF, we investigated the effects of BOF on the white adipose tissue (WAT) weight, the size of adipocytes, adiponectin expression, and oral glucose tolerance test results in high-fat diet-fed male KK/Ta mice. In addition, the mRNA expression levels of uncoupling protein 1 (UCP1) and UCP2 mRNA in WAT and brown adipose tissue (BAT) were measured. 6-week-old KK/Ta mice were divided into four groups and fed a purified powdered basal diet (the BD group), a purified high-fat (HF) powdered diet containing suet powder at 37.5 g/100 g diet (the HF group), a high-fat diet plus 1.0% bofutsushosan (BOF) treatment (the HF + BOF group), or a high-fat diet plus 1.0% daisaikoto (DAI) treatment (the HF + DAI group) for 4 weeks. The weight of WAT and the size of adipocytes were increased in the HF group compared with those in the BD group, and these increases in the HF group were significantly inhibited in the HF + BOF group, but not affected in the HF + DAI group. There were no statistically significant differences in plasma levels and tissue mRNA levels of adiponectin among the four groups. There were no significant differences in UCP1 mRNA expression of BAT among the four groups. The expression of UCP1 mRNA in WAT was found in the HF + BOF group, but little expression was seen in the WAT of the BD, HF, or HF + DAI groups. The elevated plasma glucose levels and responses after the glucose loading in the HF group tended to decrease in the HF + BOF group. These results suggest that BOF decreases the weight and size gains of WAT along with up-regulating UCP1 mRNA in WAT in high-fat diet-fed mice

The Association of Triglyceride to High-Density Lipoprotein Cholesterol Ratio with High-Risk Coronary Plaque Characteristics Determined by CT Angiography and Its Risk of Coronary Heart Disease

The triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio is an independent risk index for cardiovascular events. This study aimed to evaluate the association between TG/HDL-C ratio and coronary plaque characteristics as seen on coronary computed tomography angiography (CCTA) and the corresponding increase in the likelihood of cardiovascular events. A total of 935 patients who underwent CCTA for suspected coronary artery disease (CAD) were included. High-risk plaques (HRP) were defined based on three characteristics: positive remodeling, low-density plaques, and spotty calcification. Significant stenosis was defined as luminal narrowing of >70%. Patients with a higher TG/HDL-C ratio showed significantly greater prevalence of HRP and significant stenosis than patients with low TG/HDL-C ratios (p < 0.01). Multivariate logistic analysis demonstrated that the TG/HDL-C ratio was significantly associated with the presence of HRP (p < 0.01) but not with significant coronary stenosis (p = 0.24). During the median follow-up period of 4.1 years, 26 cardiovascular events including cardiovascular death and acute coronary syndrome occurred. The highest TG/HDL-C tertile was associated with cardiovascular events, with the lowest TG/HDL-C tertile as the reference (hazard ratio, 3.75; 95% confidence interval, 1.04-13.50). A high TG/HDL-C ratio is associated with the presence of CCTA-verified HRP, which can lead to cardiovascular events in patients with suspected CAD