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

A Framework for Controversial Issue Gatekeeping within Social Studies Education: The Case of Japan

This article addresses how social studies teachers in Japan might employ a framework for addressing controversial issues. This framework recognizes multiple and overlapping contexts for curriculum and instruction decision making, including the classroom, community, and society. It also categorizes the state of topics among five levels, ranging from deeply taboo, silenced and unknown to student, taboo, controversial, free discussion and deliberation, and settled with little or no disagreement. Finally, we submit recommendations for pre- and in- service teachers, teacher education departments, and educational policy makers to reconceptualize how they think about controversial issues in light of the essential democratic normative mandate to teach them

Safety and Effectiveness of Perospirone in Comparison to Risperidone for Treatment of Delirium in Patients with Advanced Cancer: A Multicenter Prospective Observational Study in Real-World Psycho-Oncology Settings

The clinical benefit of perospirone for treatment of delirium in patients with advanced cancer is not sufficiently clear. The objective of this study was to compare the safety and effectiveness of perospirone to those of risperidone for the treatment of delirium in patients with advanced cancer. This is a secondary analysis of a multicenter prospective observational study in nine psycho-oncology consultation services in Japan. The study used the Delirium Rating Scale (DRS) Revised-98 to measure effectiveness and the CTCAE (Common Terminology Criteria for Adverse Events) version 4 to assess safety. Data from 16 patients who received perospirone and 53 patients who received risperidone were analyzed. The mean age was 70 years in the perospirone group and 73 years in the risperidone group. Both groups showed a significant decrease in the total score of DRS-R-98 after three days of treatment (perospirone: 11.7 (7.9-15.4) to 7.0 (3.3-10.7), difference −4.7, effect size=0.72, p=0.003; risperidone: 15.5 (13.6-17.4) to 12.2 (10.1-14.2), difference −3.3, effect size=0.55, p=0.00). The risperidone group showed significant improvements in sleep-wake cycle disturbance, orientation, attention, and visuospatial ability. In the perospirone group, there was a significant improvement of sleep-wake cycle disturbance. The median daily dose of perospirone was 4 mg/day. There were fewer episodes of somnolence as an adverse event in the perospirone group. Low-dose perospirone was thus found to be effective for the treatment of delirium in patients with advanced cancer and may be associated with fewer episodes of over-sedation as an adverse event

ヘム鉄とイソフラボンの新しい作用メカニズムの解明による保健機能食品の開発

食品としても広く摂取されているヘム(鉄)は我々の生命維持に必須の物質であるが、過剰の遊離ヘムはラジカル発生源で毒性が強く、ヘムオキシゲナーゼ(HO)により分解されて抗酸化物質ビリルビンを生じる。HOには、基質ヘムなどで発現が増加する誘導型HO-1と、発現量が変化しにくい構成型HO-2があり、HO-1誘導が生体防御に重要であることや、HO抑制が癌を抑制する可能性が示されている。本研究では将来的な応用も視野に入れ、ヘム鉄やイソフラボンなど食品化合物によるヘム分解系調節とその作用機序を、ヒト由来細胞を用いて解析した。低酸素はHO-1だけでなくHO-2の発現も減少させたが、これには複数の調節機構が含まれていた。siRNAによりHO-2の発現を抑制するとHO-1が誘導され、ヘム負荷条件下でのHO-2発現抑制は細胞内ヘム濃度を上昇させたことから、HO-2がヘム濃度調節とHO-1制御に重要であることが強く示唆された。イソフラボン化合物の作用としては、ゲニステインはヘムなどによるHO-1誘導を抑制したが、ダイゼインは誘導物質や細胞によってはHO-1誘導を抑制しなかった。ヘム鉄とイソフラボンは食品として併用される可能性も高いことから、食品成分としてはHO-1誘導を抑制しにくいダイゼインが好ましい場合もあると考えられる。またエストラジオールはHO-1誘導を抑制しなかったことなどから、イソフラボンによるHO-1誘導抑制は、エストロジェン受容体を介する既知の機序とは異なるものによる可能性が示唆された。学術論文や学会発表に加え、特許出願や国際食品素材/添加物会議、所属機関公開講座などでも発表・広報活動を積極的に行ってきた。本研究による成果を更に発展させて、より効率的なHO誘導法・抑制法を見出し、生体防御機能食品や抗癌薬などへの実用化へつなげたい。Heme is widely used as a food chemical for iron supplementation. Heme is an essential molecule for us as prosthetic groups for hemoglobin and many other hemoproteins. Excess free heme is a pro-oxidant and toxic, and is degraded by heme oxygenase (HO) to iron, CO and biliverdin, which is rapidly converted to bilirubin, an antroxidant. There are two isozymes of HO, namely inducible HO-1 and constitutive 110-2. Induction of HO-1 is an important defense mechanism against oxidative stress, and some HO inhibitors have antitumor activity. In this project, I have been evalutated the effects and analyzed the mechanisms of action of food chemicals such as heme iron and soy isoflavones on heme catabolism, using various types of human cells.Prolonged hypoxia decreased the expression level of HO-2 as well as that of HO-1, and these down-regulations of HOs were caused at both transcriptional and post-transcriptional levels. Down-regulation of 110-2 by siRNA induced the HO-1 expression, and HO-2 knock-down 1 under some conditions increased the intracellular heme content, suggesting the significance of HO-2 in the maintenance of cellular heme levels and in the regulation of HO-1 expression. Genistein, a soy isoflavone, inhibited the induction of HO-1 by heme and other chemicals, while daidzein, another soy isoflavone, did not inhibited the induction of HO-1 in some cases. Together with results of our other experiments, these inhibitory effects of isoflavones on HO-1 induction were suggested to be mediated by estrogen receptor-independent mechanism.研究課題/領域番号:16500503, 研究期間(年度):2004-2005出典：「ヘム鉄とイソフラボンの新しい作用メカニズムの解明による保健機能食品の開発」研究成果報告書　課題番号16500503 (KAKEN：科学研究費助成事業データベース（国立情報学研究所）)　　　本文データは著者版報告書より作