氧化鋁/氧化鋯雙相複合材料之製程及其機械性質研究

Abstract

本研究主要是以混煉方式，製備具有塑性之複合陶瓷胚料 (Al2O3/3Y-TZP)，探討不同添加劑及混練順序對胚體流變行為、微結 構均勻度與燒結體機械性質之影響。利用扭矩流變儀及毛隙流變儀觀 察胚體之流變性質，後續燒結體微結構由掃描式電子顯微鏡觀察，並 對雙相微結構之均勻度定量化分析。實驗結果顯示複合添加劑 (Darvan C+Glycerol)能提升關鍵胚體固含量到57.4 vol%，且在A3 混 練順序下，胚料能吸收較多捏煉能量，打散胚體內聚結，使雙相複合 材料顯示較佳結構分布，且具有較窄的粒徑分佈。在胚料含有2 wt% 黏結劑以上，降伏強度即大於0.24 MPa，另添加乾燥控制劑之甲醯 胺及高比表面積之γ-Al2O3 後，能降低胚料流動指數低於0.3，單位時 間面積內水分散失率低於0.02 g/h*cm2，提升塑性指標達3.7%。 K-A3(A70Z)胚體以1600OC，持溫1 小時燒結，結果顯示燒結相對密 度為98.2%，平均破壞強度382 MPa，韋伯模數7.2，主要缺陷為大 型氣泡及氧化鋁聚結。 研究第二部份是採用膠粒製程，用以提升雙相燒結體微結構均勻 度及移除內部缺陷。實驗結果顯示，C-A70Z 以1550OC，持溫1 小時 燒結達相對密度99.9%，其四點彎曲破壞強度為551 MPa，韋伯模數 為14.5。但在氧化鋯添加量較少之C-A85Z，其四點彎曲破壞強度656 及韋伯模數15.1 皆高於C-A70Z。 在兩種不同氧化鋯添加量下，複合材料之磨耗機制由原本脆性破 壞轉為部份延性破壞，在荷重42 N 及磨耗速率0.63 m/s 下，C-A70Z 具有最佳磨耗率7.2×10-8 cm3/Nm。

In this research, the ceramic feedstocks (Al2O3/3Y-TZP) were prepared by kneading of plastic formations. The effects of different additives and kneading sequences to rheological behavior, degree of homogeneity and mechanical properties of the feedstocks were investigated. The rheological properties of the feedstock were analyzed by the torque rheomerty, capillary rheometer. After sintering at suit temperatures of ≦1600OC, the two-phase microstructure was quantitatively analyzed by optical and scanning electron microscopy. The results showed that the component additives (Darvan C+Glycerol) could increase critical solid loading of feedstock to 57.4 vol%. The kneading sequence (A3) could input more shear-energy to break-up agglomeration in the feedstocks. The particles with narrow size distribution and good dispersion were optimized in the A3 kneading sequence. The yield stress of feedstock was greater than 0.24 MPa with 2 wt% PVA binder. The addition of the dry agent (formamide) and γ-Al2O3 with high surface area could control the water evaporation rate lower than 0.02 g/h*cm2, lower the flow exponent than 0.3, and increase the plastic index to 3.7%. The relative sintered density of K-A3 (A70Z) reached 98.2% T.D. as sintered at 1600OC for 1 hr. The four-point bending strength of K-A3 was 382 MPa with lower Weibull modulus 7.2. The major fracture origins are large air bubbles and Al2O3 agglomerates. The second part of this research was adopted colloidal process to increase the degree of homogeneity of composite microstructure and control the flaw size distribution. The results showed the relative sintereddensity of C-A70Z reached 99.9% T.D. as sintered at lower temperature 1550OC for 1 hr. The four-point bending strength of C-A70Z was 551 MPa and Weibull modulus 14.5. For C-A85Z with a lower ZrO2 content (15 vol%), the average bending strength 656 MPa and Weibull modulus 15.1 were obtained. At different volume ratio of ZrO2 content, the wear mechanism of the composite will changed from severe brittle fracture (15 vol%) to plastic deformation (30 vol%) at an applied normal load of 42N and a sliding velocity of 0.63 m/s. The best wear resistance rate of 7.2×10-8 cm3/Nm was noted in C-A70Z.