Vol.2 No.2 2009

57/98

Research paper : A strategy to reduce energy usage in ceramic fabrication (K. Watari et al.)−137−Synthesiology - English edition Vol.2 No.2 (2009) surfaces of the ceramic particle and the inorganic binder.AFM detects the interactive force generated between the sample and the probe as the displacement of cantilever (a plate spring for force detection). Conventionally, it is used as a “microscope” to obtain morphological information of the sample surface, but it can be used to actually measure the interactive force between the particle sample and planar sample by attaching the desired particle onto the tip of the cantilever to be used as a probe (colloid probe method) (Fig. 6). The force in vertical direction (attraction and repulsion) against the planar sample can be estimated from the deflection of the cantilever, and the force in parallel direction (lateral direction) against the planar sample can be estimated from the torsion of the cantilever. We attached the hydraulic alumina particle to the tip of the cantilever, and measured the interactive force with the alumina single crystal substrate set as a model substance of ceramic particle. This was the first attempt to assess the interactive force that the inorganic binder may exert on the ceramic surface.As a result of measurements, a repulsion that could not be explained by general electrostatic interaction or van der Waals force was detected between the inorganic binder particle and the alumina substrate. It was concluded that this was an interactive force called the hydration repulsion. When a substance with high hydrophilic property is placed in water, a thin layer (hydration layer) where the water molecules are bound and structured by hydrogen bonds is formed on the surface. The repulsion force generated when a foreign surface approaches is hydration repulsion. Also, from the measurement of interactive force in the lateral direction, it was found that a more “slippery” condition occurred when hydration repulsion was observed between the surfaces compared to when there was no hydration repulsion (no hydration layer)[14].The existence of the water film that was hypothesized in the development of the inorganic binder was confirmed as a hydration layer that caused hydration repulsion. Also it was indicated that the fluidity was expressed since the hydration layer increased the lubricity between the inorganic binder and the ceramic particle.6 DiscussionThe flow of our research is summarized in Fig. 7. Many researchers including us worked on the elemental technologies to realize the energy-saving process, and arrived at various findings. This corresponds to Type 1 Basic Research, and some elemental technologies are shown on the left of Fig. 7. However, many of the elemental technologies developed fell into the “valley of death” due to poor compatibility with the existing manufacturing process or increased costs. In this research, we first narrowed down the conditions assuming that the result will be used at the site of production. As a result, the technological and economic issues that may lead to the “valley of death” were clarified. The R&D to solve these issues corresponds to Type 2 Basic Research.The development of low-temperature sintering technology is an attractive area in material process research. There are diverse approaches to low-temperature sintering, and an effective energy-saving process seems to be possible by combining various methods. However, all of the elemental technologies for low-temperature sintering accompany great material transfer for ceramics, and greatly alter the conditions of the existing manufacturing process. On the other hand, the newly developed binder technology has the characteristics of: (1) not greatly changing the property of the raw powder, and (2) not enforcing great material transfer for ceramics. Since we thought we should construct an energy-saving process without requiring great changes to the existing manufacturing process, the research topic became clear. Considering the positioning of this research, it corresponds to the definition of the research theme. However, this definition is “to find simplicity in complexity,” and is based on the knowledge and experience gained over the years.Since binder function changes significantly due to the type and amount of the raw powder, solvent, and binder, there is an extremely small number of systematic research publication. Also, since several binders are combined to obtain an optimal forming function, the roles of each binder are intricately intertwined. Therefore, although positioned as an extremely important element of ceramics R&D, there was hardly any scientific investigation of binders. Therefore, we decided to aim for reduction or elimination of the organic binder while maintaining the same function as the existing organic binder. We worked on the organic and inorganic binder technologies under these conditions. This is an extraction of technologies to develop a novel binder technology.Fig. 6 Measurement of inter-surface interactive force.Detect attractionAlumina single crystal substratePlanar samplePlanar samplePlanar samplePlanar sampleSlipperyDoes not slipTorsion of cantilever: LargeTorsion of cantilever: SmallInorganic binder particleDetect repulsionCantilever

※このページを正しく表示するにはFlashPlayer9以上が必要です