Nano-Fibrillar Ceramics by Gas Phase Reduction

在这个项目中，将研究一种新发现的廉价的气体/固体还原工艺，以在致密的半导体二氧化钛表面创建具有有序纳米孔通道的纳米纤维结构。利用扫描和透射电子显微镜仔细研究初始二氧化钛结构(如无定形、锐钛矿型或金红石型)、晶体取向(即具有不同取向的金红石单晶体)和固溶体添加剂对所得纳米纤维的取向和形貌的影响。通过考察时间、温度、气体流量和气体气氛对还原程度的影响(通过热重分析和横截面的电子显微镜确定)，对纳米纤维氧化物的稳态气相还原的速率限制步骤(S)进行评估。最后，基于交流电学数据的集总参数复平面分析(LP/CPA)，对纳米纤维结构的电学性质进行了研究和建模。还将测试纳米纤维结构的传感和催化反应活性。所提出的方法是一种非常廉价的制备纳米结构陶瓷平台的方法，可用于各种应用，特别是在化学传感和催化方面。为了能够更广泛地使用这种方法，需要对纤维形成的机理有一个基本的了解，以便能够识别关键的工艺变量。提出的方法整合了陶瓷加工、显微镜、传感和催化性能的建模和测试方面的尖端资源。这类平台的其他潜在应用包括光子晶体和光光学设备。此外，该工艺还可能为陶瓷的微/纳米加工开辟一条新的途径，这是一项艰巨的任务。

In this project, a newly-discovered, inexpensive gas/solid reduction process will be examined for creating nanofibrillar structures with organized nanopore channels on surfaces of dense, semiconducting titanium dioxide. The influence of the starting titanium dioxide structure (e.g., amorphous, anatase, or rutile forms), the crystallographic orientation (i.e., single crystals of rutile with varied orientations), and solid-solution additives, on the orientation and morphology of the resulting nanofibers will be carefully examined with the use of scanning and transmission electron microscopy. The rate-limiting step(s) for the steady-state, gas-phase reduction of nanofibrillar oxide will be evaluated by examining the influence of time, temperature, gas flow rates, and gas atmospheres on the extent of reduction (as determined by thermogravimetric analyses and electron microscopy of cross-sections). Finally, electrical properties of the nanofibrillar structures will be investigated and modeled based on the so-called lumped parameter complex plane analysis (LP/CPA) of the ac electrical data. Sensing and catalytic reactivity of the nanofibrrillar structures will also be tested.The proposed approach is a very inexpensive method for fabrication of nano-structured ceramic platform for various applications, particularly for chemical sensing and catalysis. To enable more widespread use of the method, a fundamental understanding of the mechanism of fiber formation is needed so that critical process variables can be identified. The proposed approach integrates cutting-edge resources in ceramic processing, microscopy, modeling and testing of sensing and catalytic properties. Other potential applications of such platforms include photonic crystals and photo-optical devices. Moreover, the proposed process may also open a new avenue for micro-/nano-machining of ceramics, which is a non-trivial task.