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High-temperature corrosion of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho)environmental barrier coating materials by volcanic ash

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1628-1638页

作者： Ayahisa Okawa Son Thanh Nguyen Tadachika Nakayama Thi-Mai-Dung Do Hisayuki Suematsu Shu Yin Takuya Hasegawa Tsuneo Suzuki Takashi Goto koichi niihara Institute of Multidisciplinary Research for Advanced Materials Tohoku UniversitySendai 980-8577Japan Department of Creative Engineering National Institute of TechnologyKushiro 084-0916Japan Extreme Energy-Density Research Institute Nagaoka University of TechnologyNagaoka 940-2188Japan Advanced Institute for Materials Research(WPI-AIMR) Tohoku UniversitySendai 980-8577Japan

Rare-earth silicates are promising environmental barrier coatings(EBCs)that can protect SiC_(f)/Si C_(m)substrates in next-genera tion gas turbine ***,RE_(2)Si_(2)O_(7)(RE=Yb and Ho)shows potential as an EBC due to its coefficient of thermal expansion(CTE)compatible with substrates and high resistance to water vapor *** target operating temperature for next-generation tur bine blades is 1400°*** is inevitable during adhesion to molten volcanic ash,and thus,understanding the corrosion behavior o the material is crucial to its *** study investigates the high-temperature corrosion behavior of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho).Samples were prepared using a solid-state reaction and hot-press *** were then exposed to volcanic ash at 1400°C for 224,and 48 *** 48 h of exposure,volcanic ash did not react with Yb_(2)Si_(2)O_(7)but penetrated its interior,causing *** Ho_(2)Si_(2)O_(7)was partially dissolved in the molten volcanic ash,forming a reaction zone that prevented volcanic ash melts from penetrating the *** increasing heat treatment time,the reaction zone expanded,and the thickness of the acicular apatite grains increased The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb_(2)Si_(2)O_(7)but decreased considerably over time for Ho_(2)Si_(2)O_(7).Th Ca in volcanic ash was consumed and formed apatite,indicating that RE^(3+)ions with large ionic radii(Ho>Yb)easily precipitated apatit from the volcanic ash.

关键词： environmental barrier coating volcanic ash rare-earth disilicate corrosion

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Microstructure and properties of alumina-silicon carbide nanocomposites fabricated by pressureless sintering and post hot-isostatic pressing

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 1-6页

作者： Young-Keun JEONG koichi niihara National Core Research Center for Hybrid Materials Solution Pusan National University Nagaoka University of Technology

A1203/5%SIC nanocomposites were fabricated by pressureless sintering using MgO as a sintering aid and then post hot-isostatic pressed （HIP）, which can subsequently break through the disadvantage of hot-pressing process. The MgO additive was able to promote the densification of the composites, but could not induce the grain growth of A1203 matrix due to the grain growth inhibition by nano-sized SiC particles. After HIP treatment, A12OJSiC nanocomposites achieved full densification and homogeneous distribution of nano-sized SiC particles. Moreover, the fracture morphology of HIP treated specimens was identical with that of the hot-pressed A1203/SiC nanocomposites showing complete transgranular fracture. Consequently, high fracture strength of 1 GPa was achieved for the A1203/5%SIC nanocomposites by pressureless sintering and post HIP process.

关键词： nanocomposite pressureless sintering fracture strength

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Measurement of metal vapor cooling speed during nanoparticle formation by pulsed wire discharge

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中国有色金属学会会刊：英文版 2009年第B9期19卷 183-188页

作者： Yuu SHIKODA Yoshinori TOKOI Koji SUWA Satoru ISHIHARA Tsuneo SUZUKI Tadachika NAKAYAMA Hisayuki SUEMATSU koichi niihara Extreme Energy-Density Research Institute Nagaoka University of Technology Department of Electrical and Electronic Engineering Niigata University Inovertion Satellite Niigata Japan Science and Technology Agency

Pulsed wire discharge(PWD) is one of nano-sized powder production methods. The object of this work is to study influence of the plasma/vapor/particle density using computer simulation and to establish temperature measurement method using a high-speed infrared thermometer in the PWD process. The temperature correction coefficient was obtained from geometric computer simulation results. Obtained correction coefficient was applied to the temperature measuring results. It was found from this result that obtained correction coefficient was appropriate. A temperature measurement method was established by using the high-speed infrared thermometer in PWD.

关键词：测量方法金属蒸气形成速度放电脉冲纳米导线红外线温度计计算机模拟冷却

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Microstructural evolution and mechanism of grain growth in magnesia ceramics prepared by high pressure and temperature with ultra-high heating rate

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Science China(Technological Sciences) 2014年第6期57卷 1085-1092页

作者： LIU JiangHao FU ZhengYi WANG WeiMin ZHANG JinYong WANG Hao WANG YuCheng LEE SooWohn niihara koichi State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Department of Environmental Engineering Sun Moon University Extreme Energy-Density Research Institute Nagaoka University of Technology1603-1 KamitomiokaNagaokaNiigata 940-2188Japan

The fast densification method of combustion reaction plus quick pressing was adopted to prepare nanocrystalline *** densification process of magnesia compact with a particle size of 100 nm was investigated,under the applied pressure of up to 170 MPa,and the temperature range of 1740–2080 K with ultra-high heating rate(above 1700 K/min).High-purity magnesia ceramics with a relative density of 98.8%and an average grain size of 120 nm was obtained at 1740 K,and the grain growth during the densification process was effectively *** characteristic morphology of evaporation-condensation was observed in the compact prepared at 2080 K,which revealed the actual process of mass transfer by gas ***,the investigation on the microstructure evolution and mechanism of grain growth was carried out,on the basis of as-preserved nanocrystalline *** result indicated that the grain growth of the nanocrystalline MgO was controlled by the mechanism of evaporation-condensation rather than surface ***,the pressure had an influence of restraining the grain growth based on solid diffusion and strengthening the effect of gas diffusion with the increasing *** the particular conditions,there existed an appropriate temperature for the densification of nanocrystalline magnesia,while the excessive temperature would exaggerate grain growth and impede densification.

关键词： grain growth densification heating rate evaporation-condensation surface diffusion nanocrystalline ceramics

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共沉淀法制备Al_2O_3-YAG复相陶瓷及其显微结构研究

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无机材料学报 2001年第1期16卷 169-172页

作者：王宏志高濂李炜群 Hirokazu Kawaoka koichi niihara 中国科学院上海硅酸盐研究所高性能陶瓷和超微结构国家重点实验室上海200050 日本大阪大学产业科学研究所

用共沉淀法制备了Ａｌ２Ｏ３－ＹＡＧ复合粉体，ＹＡＧ的结晶温度在１０００℃左右．共沉淀法制备的Ａｌ２Ｏ３－ＹＡＧ复合粉体经１５５０℃热压烧结，获得致密烧结体，ＹＡＧ的加入量对烧结温度的影响不大．Ａｌ２Ｏ３－５ｖｏｌ... 详细信息

用共沉淀法制备了Ａｌ２Ｏ３－ＹＡＧ复合粉体，ＹＡＧ的结晶温度在１０００℃左右．共沉淀法制备的Ａｌ２Ｏ３－ＹＡＧ复合粉体经１５５０℃热压烧结，获得致密烧结体，ＹＡＧ的加入量对烧结温度的影响不大．Ａｌ２Ｏ３－５ｖｏｌ％ＹＡＧ复合材料的抗弯强度为６０４ＭＰａ，断裂韧性为５．０ＭＰａｍ１／２；Ａｌ２Ｏ３－２５ｖｏｌ％ＹＡＧ复合材料的抗弯强度为６１１ＭＰａ，断裂韧性为４５ＭＰａｍ１／２．所有这些数据都高于单相Ａｌ２Ｏ３陶瓷的力学性能，说明ＹＡＧ的加入有利于Ａ１２Ｏ３陶瓷力学性能的提高．通过显微结构观察发现：大的ＹＡＧ颗粒位于Ａｌ２Ｏ３晶界上，小的ＹＡＧ颗粒位于Ａｌ２Ｏ３晶粒内．在Ａｌ２Ｏ３－５ｖｏｌ％ＹＡＧ复合材料中，许多小的白色区域存在于Ａｌ２Ｏ３晶粒内，这可能和较低的Ｙ２Ｏ３含量有关．

关键词：共沉淀法显微结构氧化铝 YAG复相陶瓷

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单一纳米复合材料的制备工艺和性质(英文)

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硅酸盐学报 2005年第7期33卷 876-881页

作者：新原晧一中山忠親長岡技術科学大学極限能量密度工学研究所

作者在12年前提出了一种新型材料设计概念———“单一纳米尺寸复合材料技术”。单一纳米尺寸指小于10nm,其目的是为了大幅度提高陶瓷材料的电磁及催化性能。过去10余年,作者致力于开发这类多功能高性能陶瓷材料和进行有关的基础研究工... 详细信息

作者在12年前提出了一种新型材料设计概念———“单一纳米尺寸复合材料技术”。单一纳米尺寸指小于10nm,其目的是为了大幅度提高陶瓷材料的电磁及催化性能。过去10余年,作者致力于开发这类多功能高性能陶瓷材料和进行有关的基础研究工作。文中介绍了Ge/GeO2,γFe2O3,CuO/CeO2,FeAg等单一纳米复合材料的制备方法和性质。釆用气相冷凝法或控制氧化法制备单一纳米粉体。由脉冲电流烧结法制备复合材料。讨论了复合材料微观结构与制备工艺的关系。介绍了CeCuO单一纳米催化剂对一氧化碳的纯化催化特性。

关键词：单一纳米复合材料同时蒸发亚稳态微结构控制纯化催化

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Material Design of Transition Metal Nitride for Hard Coating by Metal and Nonmetal Atom Substitution

Material Design of Transition Metal Nitride for Hard Coating...

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Fifth International Conference on Surface Engineering

作者： Tsuneo Suzuki Jun Inoue Hiroki Asami Tomoya Ibi Tadachika Nakayama Hisayuki Suematsu koichi niihara Extreme Energy-Density Research Institute Nagaoka University of Technology1603-1 KamitomiokaNagaokaNiigata 940-2188Japan

CrN thin films,which have been used as hard coating materials for cutting tools,plastic metal molds and friction parts,exhibit high hardness,excellent oxidation resistance and chemical ***,multi-component Cr-Me-N coatings,Me is metal elements such as Al,Si,have been explored in order to improve the properties of CrN *** only metal addition but also nonmetal addition to CrN coatings,the hardness and oxidation resistance improved by substitution of oxygen atoms for nitrogen atoms in CrN has been reported [1].Cr（N,O） is thought to be a material with O atoms substituted for some of the N atoms of CrN,in other words,it is believed to be a solid solution of CrN and CrO,although CrO is an unstable material at standard state and its existence has not been *** anticipate that it is possible to synthesis Cr-Me-N-O（Me;Mg,Cu,Mn,Ni and Cu） phase,which are dissolving the MeO into CrN in order to stabilize the chemical bonding of Cr-O,and the hardness of Cr-Me-N-O coatings is harder than Cr-Me-N and Cr-N-O *** films were deposited by the irradiation of Nd:YAG（λ = 355 nm） laser beam onto a *** disk with a diameter of 50 mm of 99 % pure Cr2N and sectored sheets of metal Me were used as the ***-crystal（100）-oriented silicon was used for *** substrate temperature was controlled at 500°*** the deposition,the chamber was evacuated to 2x10-6 Torr using rotary and *** were carried o0u.2t Taot r trh.e ammonia pressure（pNH3） of Figure 1 shows XRD patterns of the Cr-Mg-N-O thin films *** structure of main phase of all thin films was found to be B1（NaCl type） structure.

关键词： Chromium oxynitride Hard Coating substitution

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多晶YAG陶瓷的制备及力学性能

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硅酸盐学报 2001年第1期29卷 35-38页

作者：王宏志高濂 HirokazuKawaoka TohruSekino koichiniihara 中国科学院上海硅酸盐研究所高性能陶瓷和超微结构开放实验室上海200050 TheInstituteofScientificandIndustrialResearch

本实验采用共沉淀方法制备YAG微粉 ,Al和Y元素分布均匀 ,在 90 0℃煅烧 2h即可全部转变为YAG粉体 ,无过渡相 .15 0 0℃热压 1h可获得致密烧结体 ,其抗弯强度为 2 45MPa ,断裂韧性为 2 .0MPa·m1 /2 ,晶粒大小为 3～ 6μm ;14 0 0℃放电... 详细信息

本实验采用共沉淀方法制备YAG微粉 ,Al和Y元素分布均匀 ,在 90 0℃煅烧 2h即可全部转变为YAG粉体 ,无过渡相 .15 0 0℃热压 1h可获得致密烧结体 ,其抗弯强度为 2 45MPa ,断裂韧性为 2 .0MPa·m1 /2 ,晶粒大小为 3～ 6μm ;14 0 0℃放电等离子烧结 5min可获得相对密度为 93 %的烧结体 ,其抗弯强度为 3 4 8MPa,断裂韧性为 2 .1MPa·m1 /2 ,晶粒大小为 1～ 2 μm .

关键词：钇铝石榴石陶瓷放电等离子烧结粉体制备力学性能

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