陶瓷材料在燒結(jié)過(guò)程中存在自發(fā)收縮，特別是高氣孔率泡沫陶瓷，其燒結(jié)收縮率高達(dá)40~80vol%。近日，清華大學(xué)材料學(xué)院楊金龍教授課題組和瑞士聯(lián)邦理工大學(xué)André Studart教授課題組發(fā)明了一種通過(guò)金屬顆粒自組裝制備超穩(wěn)定的泡沫漿料，首次基于金屬顆粒的柯肯達(dá)爾效應(yīng)制備了燒結(jié)無(wú)收縮且性能優(yōu)異的Al2O3陶瓷及Al2O3/Al復(fù)合材料，揭示了Al核/Al2O3殼層結(jié)構(gòu)在熱氧化過(guò)程中發(fā)生的空心化過(guò)程及機(jī)理，并進(jìn)一步利用亞微米級(jí)粉體原位空心化造成的膨脹與粉體燒結(jié)收縮相抵消，真正實(shí)現(xiàn)了陶瓷材料的燒結(jié)零收縮甚至是負(fù)收縮制備，是一種顛覆性的技術(shù)創(chuàng)新。

通過(guò)在亞微米級(jí)尺度構(gòu)建多級(jí)孔結(jié)構(gòu)，這種新型的空心球組裝材料具有超高的力學(xué)性能，氣孔率為90%的氧化鋁泡沫陶瓷抗壓強(qiáng)度高達(dá)14.8MPa，可見(jiàn)報(bào)道類似泡沫陶瓷的2~10倍，如圖1和表1所示。圖2為多級(jí)孔氧化鋁泡沫陶瓷顯微結(jié)構(gòu)。該研究工作還論證了該思路結(jié)合3D打印、冷凍注模工藝、凝膠注模成型工藝等不同方式構(gòu)建多級(jí)孔材料的普適性，為近凈尺寸制備輕質(zhì)高強(qiáng)陶瓷材料提供了新思路。

相關(guān)研究成果申請(qǐng)發(fā)明專利，并以“Ultra-strong hierarchical porous materials via colloidal assembly and oxidation of metal particles”為題發(fā)表在期刊Advanced Functional Materials (Impact Factor: 16.836)。主編和審稿人對(duì)該研究工作給予高度評(píng)價(jià)：“Should be published as a VIP paper. The paper constitutes a significant advance in both science and technology of materials. The novel process enables producing porous alumina ceramics with higher strengths than by other processes particularly in the very highly porous region (between 85 and 95%). The ability to produce such materials with near zero change in dimensions during sintering has significant advantages in economically manufacturing complex shaped components from these materials. There are several clever scientific advances as well. The use of the Kirkendall effect to create the "hollow" particles within a macroscopic green body is quite clever. The ability to control the shrinkage/expansion to near zero by considering the volume expansion during oxidation and sintering shrinkage is a significant contribution to the state of the art in ceramic processing. The demonstration that the approach can be used in combination with 3D printing, freeze casting and gelcasting provides confidence that the approach can be used to manufacture complex shaped components.”

圖1 空心微珠組裝多級(jí)孔陶瓷的力學(xué)性能

表1 燒結(jié)不收縮Al/Al2O3復(fù)合泡沫材料與傳統(tǒng)亞微米粉體制備的氧化鋁泡沫陶瓷對(duì)比

圖2 多級(jí)孔氧化鋁泡沫陶瓷顯微結(jié)構(gòu)

該論文通訊作者為清華大學(xué)材料學(xué)院楊金龍教授和瑞士聯(lián)邦理工大學(xué)材料系A(chǔ)ndré Studart教授，第一單位為清華大學(xué)材料學(xué)院，霍文龍博士與張笑妍博士為該文的共同第一作者。