著者

西山 宣正 若井 史博

出版者

日本高圧力学会

雑誌

高圧力の科学と技術 (ISSN:0917639X)

巻号頁・発行日

vol.28, no.3, pp.170-176, 2018 (Released:2018-10-04)

参考文献数

17

---

Nanopolycrystalline stishovite was fabricated under high pressure and temperature using Kawai-type apparatus. This material is the hardest oxide as well as one of the toughest ceramics with fracture toughness of about 12 MPa m1/2. We performed X-ray absorption spectroscopy using synchrotron radiation, bending tests using micro-cantilever specimens fabricated by focused ion beam technique, and first-principles calculations for this material. Using the obtained results, we demonstrated that this material is toughened by transformation toughening mechanism by fracture-induced amorphization of stishovite. This toughening mechanism can be a platform to produce new structural materials.

著者

御崎 智之 福留 寛隆 篠田 豊 赤津 隆 若井 史博

出版者

公益社団法人 日本セラミックス協会

雑誌

日本セラミックス協会 年会・秋季シンポジウム 講演予稿集 第24回秋季シンポジウム

巻号頁・発行日

pp.342, 2011 (Released:2011-09-30)

---

セラミックス製品の作製において焼結現象の理解は非常に重要である。焼結は原料粒子の収縮と粒界形成の過程であるが、多数の粒子が関係する焼結現象も本質は2粒子間の粒子界面で起こるミクロな相互運動の集合と考えることができる。そこで焼結力を定義することにより、このような2粒子間のミクロな相互運動の運動方程式を理論式に構築し、さらにシミュレーションにより収縮挙動を予測することができる。一方でこうした理論的な結果の信頼性を保証するには、実験的に現実で起こる現象を観測する必要がある。そこで本研究では、焼結理論と現実に起こる現象の橋渡しのために、ミクロ領域での粒界の相互運動を直接計測するためのミクロ試験片を開発した。

著者

大熊 学 渡辺 修平 篠部 寛 西山 宣正 竹内 晃久 上杉 健太郎 田中 諭 若井 史博

出版者

一般社団法人 粉体粉末冶金協会

雑誌

粉体および粉末冶金 (ISSN:05328799)

巻号頁・発行日

vol.66, no.12, pp.604-610, 2019-12-15 (Released:2019-12-15)

参考文献数

40

---

The characterization of the processing-induced defects is a significant step for developing defect-free processing, which is important to the assurance of the mechanical reliability of brittle ceramics. Recent advances in multiscale X-ray computed tomography which consists of micro-CT and nano-CT enables us to observe the three-dimensional (3D) internal structure non-destructively. Micro-CT reveals the distribution of defects in the entire body of a sample, while nano-CT reveals the shape of the identified defect. This powerful imaging tool was used to reveal the complicated 3D morphology of defects evolved during sintering of alumina. The hierarchical packing structure of granules was the origin of several types of strength-limiting defects, which could not be eliminated due to the differential sintering of heterogeneous microstructures. This imaging technique of internal defects provides a link between the processing and the fracture strength for the development of structural materials.

著者

日吉 英司 篠田 豊 赤津 隆 若井 史博

出版者

公益社団法人日本セラミックス協会

雑誌

日本セラミックス協会学術論文誌 : Nippon Seramikkusu Kyokai gakujutsu ronbunshi (ISSN:18821022)

巻号頁・発行日

vol.112, no.1312, pp.661-664, 2004-12-01

---

The distribution and the morphology of glass phase in polycrystals are affected by the dihedral angle and the volume fraction of the glass phase. The effects of temperature and chemical composition of intergranular glass on dihedral angle of glass-doped 3-mol%-yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) were studied by transmission electron microscopy (TEM). The intergranular glass was either SiO_2 (melting point of 1700℃) or Y_2O_3-Al_2O_3-SiO_2 eutectic glass (YAS glass: melting point of 1350℃). The average dihedral angles of SiO2-doped and YAS-doped 3Y-TZP, which were sintered at 1300℃, were found to be 70℃ and 50℃, respectively. The dihedral angle in YAS-doped 3Y-TZP decreased to 25℃ after annealing at 1500℃, whereas that in SiO_2-doped 3Y-TZP remained constant. From the relationship between the dihedral angle and the ratio of grain boundary energy to solid/glass interface energy (γSS/γSL) > it was suggested that XSS/^SL increased at elevated temperatures higher than the melting point of glass.