以含有弱介面之韌化相韌化脆性陶瓷之研究

Abstract

為了改善陶瓷材料先天的脆性，在過往二、三十年陶瓷基複合材料研究當中，起初添加金屬強化相作為研究，但因金屬材料的熔點較低而限制了其應用面。在陶瓷韌化材方面，一般添加強度、硬度較高的顆粒、鬚晶及板晶等，但韌性的提升效果有限。本研究主要為提供一個新的陶瓷韌化概念，以強度相較於基地相較低，但含有弱介面之層狀陶瓷韌化材作為第二相，利用其層間弱介面的特性，使得脆性的陶瓷材料在破壞時破壞能量由此韌化材的層間弱介面吸收而產生韌化。 本研究使用三種材料系統，分別以氧化鋁與硼矽酸鹽玻璃基低溫共燒陶瓷（LTCC）作為基材，添加積層陶瓷電容（MLCC）以及碳化鈦矽（Ti3SiC2）層狀陶瓷作為韌化相進行無壓或熱壓燒結成試樣，進行強度與韌性的量測，確立強韌化機制，並輔以理論計算。此外，也以X光與奈米壓痕技術分析試樣內部的應力對於強度韌性之影響。有別於一般陶瓷基複合材料在基地相與第二相間的裂縫轉折或架橋，此一特殊的韌化機制的設計使得裂縫在含有弱介面的第二相內部產生轉折而吸收破壞能，可更進一步的改善陶瓷材料的韌性。

Since ceramic materials have various advantages to demonstrate their functions, they can be applied in many areas. However, ceramics are brittle and show catastrophic failure. The objective of many researches on structural ceramics is the development of materials with high reliability. Low-cost ceramic composite materials that exhibit excellent mechanical properties have attracted considerable interest for advanced engineering applications. For such materials, toughening remains one of the most important issues in enhancing the reliability. In the present study, three different kinds of ceramic-matrix composites are used as model systems to demonstrate the feasibility of using toughening agents with weak interfaces as a new approach. The reinforcements, such as BaTiO3 platelet containing weak interfaces and Ti3SiC2 compound can be incorporated to toughen the composite. The material selection is based on the higher thermal expansion coefficient and the lower elastic modulus of the reinforcement than those of the matrix. The toughening mechanism and the energy dissipation during crack propagation are investigated via different skills, such as residual stress analysis and nano-indentation. The role of the shape of the reinforcement and the effect of pullout during toughening is also discussed with theoretical calculation.