Three dimensionally ordered porous

Three-dimensionally ordered porous materials have been applied to electrochemical energy conversion systems, such as Uthium battery, fuel cell, and electrochanical double layer capacitor. Based on this technique, functional materials for other applications can be produced. The advantages of three-dimensionally ordered materials are based on micro or nano size ordered pores. 

Such a structure provides highly uniform porous nature. This is the most important point. For example, the uniform reaction may occur in all the pores. A higher mechanical strength may be realized from ordered stmcture. Especially, two-dimensional electrochemical reactions are strongly enhanced by using three-dimensionally ordered porous materials, as mentioned above. In other words, two-dimensional electrochemical reactions are converted to pseudo three-dimensional ones. This procedure is useful for practical applications. Presently, preparation of three-dimensionally ordered macroporous materials is not so easy due to low mechanical strength and the presence of minor defects. More extensive research will be carried out in the near future. 

The porous membrane templates described above do exhibit three-dimensionality, but with limited interconnectedness between the discrete tubelike structures. Porous structures with more integrated pore—solid architectures can be designed using templates assembled from discrete solid objects or su-pramolecular structures. One class of such structures are three-dimensionally ordered macroporous (or 3-DOM) solids, which are a class of inverse opal structures. The design of 3-DOM structures is based on the initial formation of a colloidal crystal composed of monodisperse polymer or silica spheres assembled in a close-packed arrangement. The interconnected void spaces of the template, 26 vol % for a face-centered-cubic array, are subsequently infiltrated with the desired material. 

Ordered macroporous materials (OMMs) are a new family of porous materials that can be synthesized by using colloidal microspheies as the template. - The most unique characteristics of OMMs are their uniformly sized macropores arranged at micrometer length scale in three dimensions. Colloidal microspheres (latex polymer or silica) can self assemble into ordered arrays (synthetic opals) with a three-dimensional crystalline structure. The interstices in the colloidal crystals are infiltrated with a precursor material such as metal alkoxide. Upon removal of the template, a skeleton of the infiltrated material with a three-dimensionally ordered macroporous structure (inverse opals) is obtained. Because of the 30 periodicity of the materials, these structures have been extensively studied for photonic applications. In this paper, the synthesis and characterization of highly ordered macroporous materials with various compositions and functionalities (silica, organosilica, titana, titanosilicate, alumina) are presented. The application potential of OMMS in adsorption/separation is analyzed and discussed. 

Sen T, Tiddy GJT, Casci JL, Anderson MW (2004) Synthesis and characterization of hierarchically ordered porous silica materials. Chem Mater 16 2044 Deng Y, Liu C, Yu T, Liu F, Zhang F, Wan Y, Zhang L, Wang C, Tu B, Webley PA, Wang H, Zhao D (2007) Facile synthesis of hierarchically porous carbons from dual colloidal crystal/block copolymer template approach. Chem Mater 19 3271 Luo Q, Li L, Yang B, Zhao D (2000) Three-dimensional ordered macroporous structures with mesoporous silica walls. Chem Lett 29 378... 

In order to produce a three-dimensionally ordered macroporous structure, the metal precursor solution should fulfil the following criteria (1) Sufficient metal should be present in the voids to form a macroporous wall, and the metal concentration should therefore be high. (2) Reactivity of the metal precursor should be mild so that it can infiltrate the voids. If the metal precursor reacts with a functional group on the surface of the template or moisture in the air before it infiltrates the voids, an ordered porous structure cannot be obtained. (3) The metal precursor should be solidified in the voids before the template is removed and the produced... 

Figure 4.16 SEM images of porous carbons prepared using hard template consisting of large polymer colloids (450 nm diameter) and small silica colloids. The particle size of silica colloids used as template for the small spherical pores is (a) 70-100 nm and (b) 40-50 nm. 1 Reprinted with permission from S.W. Woo, K. Dokko, K. Sasajima, T. Takei and K. Kanamura, Three-dimensionally ordered macroporous carbons having walls composed of hollow mesosized spheres. Chem. Commun., 4099—4101. Copyright (2006) Royal Society of Chemistry...

Macroporous materials with highly ordered and three-dimensional (3D) porous structures are technologically important for many appHcations such as catalysis. 

Three-Dimensionally Ordered Macro porous (3DOM) Perovskite Mixed Metal Oxides... 

Because of the attractive physicochemical properties and potential applications in catalysis, biotechnology, adsorption, and separation, fabrication of hierarchically porous (macro/mesoporous) materials, especially for the three-dimensional ordered macro/ mesoporous (3DOM) materials, has been a focus in the research on materials science and engineering in recent years [99,199,200], By using close-packed arrays of monodisperse spheres, such as polystyrene (PS), poly(methyl methacrylate) (PMMA), and silica as template, metals [201,202], metal oxides [203-208], metal chalcogenides [209], silica [204,210,211], carbon [212,213], polymers [214,215], and hydroxyapatite [216] with 3DOM structures have been generated. 

The advantage of this strategy is that the synthesis of the porous materials takes place in a confined space formed by the porosity of the template. Thus-synthesized perovskite has a high surface area with three-dimensional ordered mesoporous channels, which can not be achieved by conventional methods. Moreover, template-based growth is commonly a solution or colloidal dispersion based process. It is less expensive and readily scalable to mass production. It also offers the advantages of less contamination and is environmentally benign. [34]... 

MC simulations and semianalytical theories for diffusion of flexible polymers in random porous media, which have been summarized [35], indicate that the diffusion coefficient in random three-dimensional media follows the Rouse behavior (D N dependence) at short times, and approaches the reptation limit (D dependence) for long times. By contrast, the diffusion coefficient follows the reptation limit for a highly ordered media made from infinitely long rectangular rods connected at right angles in three-dimensional space (Uke a 3D grid). 

Compared to rivers and lakes, transport in porous media is generally slow, three-dimensional, and spatially variable due to heterogeneities in the medium. The velocity of transport differs by orders of magnitude among the phases of air, water, colloids, and solids. Due to the small size of the pores, transport is seldom turbulent. Molecular diffusion and dispersion along the flow are the main producers of randomness in the mass flux of chemical compounds. 

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