Vol.11 No.2 2018

報告:Additive manufacturing of ceramic components (大司)−88−Synthesiology Vol.11 No.2(2018)made when the body is trailed by powder being re-coated on it and is more likely to occur typically in the following cases: (1) the binder is still heated and adhesive, (2) the squeegee moves too fast, or (3) the mixed powder is too owable. Thus, it can be resolved by cooling the binder suciently, lowering the squeegee movement speed, or lowering the powder flowability. Figure 7 (c) shows an example of successful formation of a green bogy without the above issues (embedded in powder). In the post process, first the binder is removed from the obtained green body by burning it out. The heating schedule, pressure, atmosphere, etc. for this process should be carefully selected so that undesired deformation and distortion would be minimized while the binder is melted and burnt out. Infiltration is often employed for densification. A typical example is siliconized silicon carbides (SiSiC), where melted Si is infiltrated through porous SiC-C green bodies produced by PLM, followed by reaction between Si and C for formation of secondary SiC and densification.[23] Free carbon produced during burning the polymer binder can be used for this reaction. Slurry infiltration into green bodies also can increase green and sinter densities as already stated.[19] In post-sintering, selection of conditions including heating schedule, pressure, atmosphere, etc. is crucial for obtaining sound sintered bodies, and knowledge and experiences so far on sintering of conventional green bodies are of great use for it. The green and sintered bodies are evaluated in terms of appearance (cracks, delamination, distortion, etc.), green/sinter densities, strength, and others.As seen so far, many of the technical processing items are closely connected and correlated to each other; such close relations are expressed by solid lines in Fig. 5. It can be said that particularly powder preparation substantially affects many of the subsequent processes of lamination and post process. For example, the properties of the binder are critically important for the powder supply, pre-heating and laser irradiation of the lamination (melting point, cohesiveness, adhesiveness, wettability, etc.), while they are also crucial to the debinding and infiltration (where burnt binder is often used for reaction with inltrated ones) of the post process (melting point, burnability, etc.). Thus, powder preparation is the most essential process in PLM, similarly to the cases of conventional ceramic processing. Sound products can be obtained only after all the technical items are properly selected and performed. It should be noted that the approach for examining and integrating the technical items into optimal AM technology described in this chapter is employed similarly in SLM and CLS. 5 Prototype models produced by AMTaking advantage of the developed AM technologies, the HCMT project has manufactured several types of unique prototypes aimed at various target applications, some of which are described in this chapter. The rst are stage models produced by PLM, which are anticipated as basic structures for ceramic exposure stages used in future semiconductor industries; some examples are shown in Fig. 8, in comparison with a conventional structure.[1][24]-[26] A light and stiff exposure stage of large scale and complex shape is critically needed for next generation IC chip production where more accurate positioning and higher throughput will be strongly required. While the conventional rib structure produced by molding consists of simple walls (a), AM can make that having windows in the walls (b), and furthermore truss structures of light weight/high stiffness (c-e), which were not obtainable until now. The models of (b-e) are siliconized silicon carbides (SiSiC) which are obtained by Si inltration into SiC-C green bodies followed by reaction-sintering, as described above. Their feature is high specific stiffness (Young’s modulus/bulk density) and very little sintering-shrinkage, both of which are advantageous for application to large-sized exposure stage products. In order to fully recognize AM as industrial manufacturing technologies, it is crucially important for products produced by AM to have properties equivalent to those of conventional ones. Table 2 compares bulk density, Young’s modulus, specic stiness, Table 2. Bulk density, Young’s modulus, specific stiffness (Young’s modulus/bulk density) and flexural strength of PLM-produced SiSiC and conventional one (molding approach). 320290Flexural strength (MPa)113113Specic stiness340340Young’s modulus (GPa)3.03.0Bulk densityConventionalPLM

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