UNS: Rapid synthesis of ordered mesoporous materials through microwave processing of cooperatively assembled composites

1510612伏特介孔(孔径2-50 nm)材料被广泛应用于从催化到药物输送到能量存储和产生的许多应用。在大多数情况下，这些毛孔的连通性和大小对它们的性能至关重要。模板化的合成方法提供了一条控制这两种性质的途径。这些材料的典型直接合成方案包括将嵌段共聚物或表面活性剂与功能前体如溶胶-凝胶纳米颗粒(NPs)或晶态NPs组装在一起。在许多情况下，这些材料的有效制造仍然具有挑战性，特别是对于复杂的过渡金属氧化物。即使是合成普通硅酸盐SBA-15，标准工艺也需要48小时的水热合成，并在550℃下焙烧5小时(另外还需要3小时的加热和冷却时间)。这些漫长的制造过程和高耗能的焙烧过程严重限制了材料的多样性和商业创新。使用微波反应器可以将介孔硅酸盐的合成时间从几天缩短到几个小时。随着控制功率输出的微波技术的进步，包括模板降解在内的有序介孔二氧化硅的完全合成可以在几个小时内完成，而不是几天。但是，关于如何合理地选择用于微波反应的前驱体和模板以实现一步直接制备高功能有序介孔材料的信息有限。在这里，PI旨在研究微波方法在包括金属碳酸盐和氧化物在内的各种介孔材料的合成中的应用。智力价值本项目将阐明模板和前体的选择对自组装有序介孔材料的形貌的影响，并展示微波处理如何使混合金属氧化物纳米颗粒的形成是传统方法所不可能的。PI假设(1)嵌段共聚模板的热稳定性对介孔材料的最终结构至关重要，(2)高通量筛选将能够识别不能(不)获得有序介孔结构的组合物，(3)微波处理将能够合成常规途径无法获得的组合物，以及(4)卷对卷处理提供了快速和可扩展制造这些材料的连续路线。为了验证这些假设，PI将利用一系列嵌段共聚物和金属硝酸盐-柠檬酸盐(铁、钴、镍和锰)化学作为金属氧化物的前体。将使用傅里叶变换红外光谱(FTIR)和椭偏仪研究金属硝酸盐到金属氧化物的转化和聚合物模板的降解。反应动力学将作为微波功率的函数进行考察，并与传统的热法进行对比。化学转变将与小角x射线散射、原子力显微镜和x射线衍射所阐明的结构相关联，以提供关于原子晶体结构和自组装纳米结构的信息。最后，我们将研究这些材料的电化学性质，以了解这些自组装材料的结构如何影响电池和超级电容器的性能。通过对形貌、孔隙率和界面修饰进行控制，可以显著提高发电(太阳能电池)和存储(电池和超级电容器)的性能。通过该项目获得的理解可以为改善这些材料的性能提供指导方针，这些材料可以用于这些应用，这可能有助于美国实现能源独立。更广泛的教育影响将涉及未被充分代表的本科生的参与。与阿克伦全球聚合物学院和圣文森特圣玛丽高中的合作伙伴关系将包括教师和高中生参与研究，并向广泛的K-12学生受众传播，参与研究的高中生将通过参加科学博览会比赛向其他K-12学生和家长传播。外展工作将包括研究生，他们将有机会以较少的技术水平介绍提高整体科学素养所需的水平。

1510612-VogtMesoporous (2-50 nm pore size) materials are widely used in numerous applications from catalysis to drug delivery to energy storage and generation. In most of these cases, the connectivity and size of these pores are critical to their performance. Templated synthetic methods provide one route to control both of these properties. The typical direct synthesis scheme for these materials involves the assembly of block copolymers or surfactants with functional precursors such as sol gel nanoparticles (NPs) or crystalline NPs. The efficient fabrication of these materials remains challenging in many cases, especially with regards to complex transition metal oxides. Even for the synthesis of a common silicate, SBA-15, the standard process involves 48 hours of hydrothermal synthesis and calcination at 550 °C for 5 hours (with an additional 3 hours for heating and cooling). These lengthy fabrication processes and energy intensive calcination processes are significant limitations to material diversity and commercial innovations. Using microwave reactors can reduce the synthesis time for mesoporous silicates from days to hours. With the advances in microwave technology for controlling power output, the full synthesis of ordered mesoporous silicas, including template degradation, can be performed in a single step in a few hours instead of days. But there is limited information on how to rationally select precursors and templates for use in microwave reactions that enable the direct fabrication of highly functional ordered mesoporous materials in a single step. Here the PI aims to investigate the utility of microwave methods for the synthesis of a diverse class of mesoporous materials including metal carbonates and oxides.Intellectual MeritThis project will elucidate how the morphology of self-assembled ordered mesoporous materials is impacted by the template and precursor selection and show how microwave processing enables the formation of mixed metal oxide nanoparticles that are not possible using conventional methods. The PI hypothesizes that (1) the thermal stability of the block copolymer template is critical to the final structure of the mesoporous material, (2) high throughput screening will enable identification of compositions where ordered mesoporous structure can(not) be obtained, (3) microwave processing will enable synthesis of compositions not accessible by conventional paths, and (4) roll-to-roll processing provides a continuous route to the rapid and scalable fabrication of these materials. To test these hypotheses, the PI will utilize a systematic series of block copolymers and metal nitrate-citrate (Fe, Co, Ni, and Mn) chemistry for precursors to the metal oxides. The conversion of the metal nitrate to metal oxide and the degradation of the polymer template will be examined using Fourier transform infrared spectroscopy (FTIR) and ellipsometry. The reaction kinetics will be examined as a function of microwave power and contrasted against conventional thermal methods. The chemical transformations will be correlated with the structure as elucidated by small angle x-ray scattering, atomic force microscopy, and x-ray diffraction to provide information on both the atomic crystal structure and the self-assembled nanostructure. Finally the electrochemical properties of these materials will be examined to understand how the structure impacts performance for batteries and supercapacitors based on these self-assembled materials.Broader ImpactSustainable, cheap energy is a significant challenge. Energy generation (solar cells) and storage (batteries and supercapacitors) properties can be significantly enhanced by exercising control over morphology, porosity, and interfacial modifications. The understanding garnered through this project could provide guidelines for improving the properties of these materials that could be utilized in these applications, which could help the US toward energy independence. The broader educational impact will involve participation of underrepresented undergraduate students. Partnerships with the Akron Global Polymer Academy and St. Vincent St. Mary's high school will include teachers and high school students in both research and dissemination to a broad audience of K-12 students, whereby high school students involved in the research will disseminate to other K-12 students and parents through participation in Science Fair competitions. The outreach efforts will include graduate students who will thus have an opportunity to present at less technical levels necessary for improving overall science literacy.