氧化對碳化矽/氧化鋯/莫來石複合材料之機械性質的影響

Abstract

氧化對碳化矽╱氧化鋯╱莫來石複合材料 之機械性質的影響

研究生：劉易家 指導教授：林健正博士

國立交通大學 材料科學與工程學系 中文摘要

本研究以熱壓法製備碳化矽╱氧化鋯╱莫來石之複合材料，在1000 ℃及1200℃進行25小時的氧化處理，分別測量試片氧化後之抗折強 度及破裂韌性值與未氧化試片作一比較。實驗的主要目的是要探討試片在不同的氧化條件及氧化鋯含量中對複合材料機械性質的影響。研究結果顯示，SiC/ZrO2/mullite複合材料經由1000℃之氧化後並不會有任何結晶相或zircon相生成。而在1200℃氧化後，MZY20及MZY30開始有結晶相cristobalite 產生以及微量的zircon相生成；同時MZY50及MZY80不僅產生cristobalite結晶相而且會有較多之zircon相生成。除此之外，未經氧化的試片中會有較多之t-ZrO2及較少量之m-ZrO2；一旦經由氧化之後，試片開始產生較多之m-ZrO2，相對的使 t-ZrO2逐漸減少。在未經氧化材料的抗折強度值，與材料本身的緻 密性有一定程度的關係，即材料之緻密性愈佳則抗折強度值會上 升。經1000℃氧化後，0vol％∼50vol％ZrO2試片之強度改變率會 增加，而1200℃時，除了0vol％∼10vol％ZrO2片之強度改變率 有增加外，其餘皆為下降之情形。未氧化材料破裂韌性值隨氧化鋯 含量之增加而增加。在0vol％∼50vol％ZrO2試片中經1000℃ 及1200℃氧化後其破裂韌性改變率皆有增加，且隨ZrO2vol％之增 加有依次遞減之趨勢。除了80vol％∼100vol％ZrO2試片外，其餘 試片經氧化後會使破裂韌值增加之主要原因為氧化鋯正方晶相至單斜晶相(t→m)的相變化能力增強所致。

Effect of Oxidation on Mechanical Properties of SIC/ZrO2/Mullite Composites

Student:Yi-Jia-Liu Advisor:Chien-Cheng Lin

National Chiao Tung UniversityInstitute of Materials Science and Engineering

Abstract

Sic / zirconia / mullite composites with various zirconia contents, fabricated by hot pressing , were exposed in air isothermally for 25 hours at 1000 and 1200℃, respectively. Then the bending Strenath and fracture toughness of the oxidation samples as well as as-hot pressed samples were measured. This study aimed at the effect of oxidation and various zirconia contents on mechanical properties of Sic / zirconia / mullite composites. The result showed that the crystallization product or zircon(ZrSio4)phase from the composite after exposed. at 1000℃ would not occur. It was found the oxidation product cristobalite and some zircon phase from the composits with 20vol%&30vol%ZrO2 after exposed at1200℃ Meanwhile, the crystallization product of cristobalite and more zircon phase were presented in the case of the composites containing 50vol%&80vol%ZrO2.In addition, more t-ZrO2 and less m-ZrO2 were obtained in Samples before oxidation , while more m-ZrO2 and less t-ZrO2 were acquired in samples after oxidation. The bending strength of unoxidized samples was on the increase along with growth of consolidation. The strength change(%) from the composites with 0vol%&50vol%ZrO2 after exposed at 1000℃ ould increase and the composites with 20vol%~100volZrO2 at 1200℃ would decrease. The higher zirconia content the higher fracture toughness of unoxidized samples.The fracture toughness change(%) from the composites containing 0vol%~5vol%ZrO2 after oxidation was increased and the fracture toughness change(%)was on the decrease in pace with the increase of zirconia content. After Sic/ zirconia / mullite composites with 0vol%~50vol%ZrO2 was oxidized, the improvement of fracture toughness was mainly attributed to the enhancement of (t)→(m) phase transformation.