Fumihiro Wakai

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Plasma electrolytic oxidation (PEO) was used to make a multifunctional porous titanium oxide (TiO2) coating on a titanium substrate. The key finding of this study is that a highly crystalline TiO2 coating can be made by performing the PEO in an ammonium acetate (CH3COONH4) solution; the PEO coating was formed by alternating between rapid heating by spark(More)
Silicon dioxide has eight stable crystalline phases at conditions of the Earth's rocky parts. Many metastable phases including amorphous phases have been known, which indicates the presence of large kinetic barriers. As a consequence, some crystalline silica phases transform to amorphous phases by bypassing the liquid via two different pathways. Here we(More)
The development of strong, tough, and damage-tolerant ceramics requires nano/microstructure design to utilize toughening mechanisms operating at different length scales. The toughening mechanisms so far known are effective in micro-scale, then, they require the crack extension of more than a few micrometers to increase the fracture resistance. Here, we(More)
Sintering is a common process during which nanoparticles and microparticles are bonded, leading to the shrinkage of interstitial pore space. Understanding morphological evolution during sintering is a challenge, because pore structures are elusive and very complex. A topological model of sintering is presented here, providing insight for understanding 3-D(More)
It is extremely difficult to realize two conflicting properties-high hardness and toughness-in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations(More)
The rearrangement process during liquid phase sintering has been generally accepted that driven by the capillary forces between solid grains embedded in liquid. This paper outlines a computer-based method for three-dimensional computer simulation of rearrangement during liquid phase sintering. The theoretical models dealing with the fundamental interaction(More)
Fine-grained tungsten carbide copper (WC-Cu) cemented carbide was sintered via spark plasma sintering at 1773K using a fine WC powder with a mean particle size of 0.11 mm. The mechanical properties were compared with tungsten carbide cobalt (WC-Co) cemented carbide and a binderless WC-sintered material. The Vickers hardness and fracture toughness obtained(More)