AIST Stories No1
14/36

From AIST to the Innovative World12walls. As a result, occurrences of mold and mites became more common. Not only are buildings damaged more easily by humidity: this humidity also started to affect health.”At the time, Maeda’s superior and Ceramic Applications Department Material Technology Section head Yasuo Shibasaki believed that the method for solving these problems lay in traditional construction methods for Japanese houses and materials; therefore, traditional technology was reconsidered. At exactly that time, related parties came to learn of a storehouse built during the Edo period that was to be dismantled. Further, during the dismantling process, a precious mud wall sample was obtained.“Storehouses have high thermal insulation properties and are superior in their humidity characteristics. In order to understand the reasons for this, the structure of a mud wall of thickness 10-plus cm was investigated: it was discovered that the wall had a multi-layer structure with several layers. The mechanisms of the surface and inner layers differ and this was related to the moisture-adsorption characteristics for adsorption of moisture in the air and the extent of moisture retention in the wall interior. In other words, it became clear that fine holes (pores) of differing sizes in the respective layers capture the moisture from the air, and this moisture accumulates in the interior. When it becomes dry, the moisture is released.“The mud wall was in fact respiring and controlling the humidity. It was the moment where lost ancient wisdom came to the rescue,” recalled Maeda with a grin on his face.In search of a material to make walls that can breathe!With the mud wall mechanism was elucidated, the next problem was exactly how to reproduce it using current technology. Even if it was to be reproduced, the solution was by no means to actually fabricate a mud wall: rather, it was to develop an all-new ceramic that could control humidity as if it were actually respiring itself.While humidity-controlling construction materials existed at the time, their applications were extremely limited, including such areas as storage facilities for cultural assets. Storage areas for cultural assets are closed spaces whose doors rarely open and close and as such, one only need consider restricting fluctuations in moisture levels over a long time span. However, the new approach being attempted was for general residential applications, which involved totally different conditions.“In the case of a residence, the door is opened several times per day and the amount of moisture indoors varies over short time spans. Humidity rises rapidly even when water is boiled or when other cooking takes place. For this reason, our first task was to search for what type of material to use ▲An automated measuring device for testing the moisture-adsorption characteristics of nanoporous ceramics. Without such a device, testing alone would take two to three months.*2 Zeolite: A typical porous crystalline material in which pores approximately a nanometer across are uniformly arranged. Many zeolites comprise porous structures formed by bonding of silicon, aluminum, oxygen or phosphorus. They are utilized in a wide variety of applications including separation, adsorbents, shape-selective solid catalysts, ion exchange agents, chromatography column packing, chemical reaction sites, humidity agents, and construction materials.*3 Diatomaceous earth: A porous substance formed by the sedimentation and fossilization of the frustules of diatoms, a type of phytoplankton. Currently they are widely used as construction materials

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