摘要:目前市場現有的陶瓷韌化材(ceramic reinforcement): 如碳化矽、氧化鋁等鬚晶及板晶陶瓷韌化材有如下缺點:1.單價高;2.添加陶瓷韌化材後,製程成本增加;3.可供選擇的韌化材非常有限。 但從韌化機構來看, 陶瓷韌化材的強度要高,但它與脆性的基材間的界面卻必須很弱。也正因為此種認知, 當陶瓷基材會與這些韌化材作用或燒結而產生強界面時,則這些韌化材即完全不能使用。
申請人以為要求高強度陶瓷韌化材,卻同時要求弱界面, 是相互矛盾的。但也正因為這個矛盾, 限制這些高強度陶瓷韌化材只能用在少數不會作用或燒結的陶瓷基地材中. 本研究擬設計一種創新的陶瓷韌化材, 此陶瓷韌化材除可韌化脆性陶瓷等外, 還必須不受限於任何特定基材材質,且成本要比市場現存的陶瓷韌化材要低。
而基本觀念為模仿魚鱗的設計, 我們在五年前執行國科會計畫: [生態陶瓷韌化材料的研發] (計畫編號: NSC91-2216-E-002 -030), 以魚鱗為研究對象, 觀察出魚鱗是一種層狀結構, 若施以適當熱處理, 可製作出具孔隙梯度分佈的多層板材. 且每層間存在一層多孔的介層. 近三年我們的初步可行性評估結果顯示此種內含弱界面的多晶板材可韌化玻璃,氫氧基磷灰石, 樹脂等, 因魚鱗可能較不適用在精密陶瓷中, 而本研究即以仿生為設計理念, 設計一種創新的陶瓷韌化材, 並探討其在韌化陶瓷的學術方面及產業方面的應用價值.
這種創新陶瓷韌化材內部須有弱界面, 這種內含弱界面的陶瓷韌化材可加入任何脆性材料中, 此陶瓷韌化材可與脆性基材作用或燒結而產生強界面, 當裂縫在脆性基材中產生後, 裂縫會直接進入內含弱界面的陶瓷韌化材, 然後在此韌化材中的弱界面轉折, 而產生韌化效應.
本研究第一年將集中在製程開發, 將內含弱界面的陶瓷韌化材加入氧化鋁基地中,量測含弱界面的韌化材對氧化鋁的機械性質及電性的影響. 而第二年將以氧化鋯及鈦酸鋇為基地材, 驗證含弱界面的韌化材對氧化鋯及鈦酸鋇的機械性質及電性的影響。
本研究將以兩年的時間, 證明以仿生學為基礎, 可撤底顛覆傳統陶瓷韌化材的設計, 並有可能大幅改善所有陶瓷材料的韌性, 突破目前陶瓷材料應用上的瓶頸. 本研究在學術上具創新性, 在產業上則具極高的應用價值。
Abstract: There are three dis-advantages for the nowadays ceramic reinforcements:
1. the cost is very high,
2. the processing fee to prepare the composites containing such reinforcements is also high;
3. there are only several reinforcements, such as SiC, Al2O3 whiskers and platelets, are available.
The most critical drawback of using such reinforcement is its possibility to react and sinter with the brittle matrix. Once the reaction or sintering is taken place between the reinforcement and matrix, a relatively strong interface is resulted. The ceramic reinforcement is then forbidden to be used for such brittle matrix.
The basic toughening requirement: strong reinforcement and weak interface, is controversy to the opinion to the present author. Such requirement limits the ceramic systems to be toughened by adding ceramic reinforcement. A new concept on designing of a new ceramic reinforcement is suggested in the present proposal. This new concept involves the ceramic reinforcement with internal weak interface.
We have carried out a NSC funded project 4 years ago. The project allowed us to look into the structure of fish scale with great detail. The structure of fish scale is a layered structure. By burning away the protein within the fish scale, a gradient materials with different amount of pores is formed. Furthermore, a weak interphase with large amount of pores is present between each layer. To verify the feasibility of using such structure for reinforcement, we have carried out the feasibility study on using fish scale to toughen glass hydroxyapatite, and resin. The results are encouraging, toughness enhancement is observed. However, the fish scale may not be used for advanced ceramics. By mimic the structure of fish scale, the new ceramic reinforcement with internal weak interface is proposed.
Such reinforcement with embedded weak interface can virtually add into any brittle matrix. The reinforcement can either react or sinter with the brittle matrix to form strong interface. The crack can penetrate into the reinforcement, then deflect from the internal weak interface. A toughness enhancement is expected.
The proposed work for the first year involves the process development and the preparation of a model system. The ceramic reinforcement with internal weak interface will be added into alumina matrix. The resulting mechanical and electrical properties of the composites will be measured. For the work of second year, the ceramic reinforcement with internal weak internal interface will be added into zirconia and barium titanate matrices. The properties of the composites will then be measured.
The present proposed study is aiming to design a new and promising ceramic reinforcement. Such reinforcement will be proved applicable to any brittle materials. The present study is proposing a breakthrough for the ceramic science. The potential of using such reinforcement for industry applications is also high.