Synthesis of three-dimensional ordered mesoporous MnO_2 and its catalytic performance in formaldehyde oxidation

Three-dimensional（3D）ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template.The material was used for catalytic oxidation of HCHO.The material has high surface areas and the mesoporous characteristics of the template,with cubic symmetry（ia3d）.It consists of a β-MnO2 crystalline phase corresponding to pyrolusite,with a rutile structure.Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the 3D-MnO2 catalyst has a large number of exposed Mn4＋ ions on the（110）crystal plane surfaces,with a lattice spacing of 0.311 nm; this enhances oxidation of HCHO.Complete conversion of HCHO to CO2 and H2O was achieved at 130 °C on 3D-MnO2; the same conversions on α-MnO2 and β-MnO2 nanorods were obtained at 140 and 180 °C,respectively,under the same conditions.The specific mesoporous structure,high specific surface area,and large number of surface Mn4＋ ions are responsible for the catalytic activity of 3D-MnO2 in HCHO oxidation.

Second-order two-scale computational method for ageing linear viscoelastic problem in composite materials with periodic structure

The correspondence principle is an important mathematical technique to compute the non-ageing linear viscoelastic problem as it allows to take advantage of the computational methods originally developed for the elastic case. However, the correspon- dence principle becomes invalid when the materials exhibit ageing. To deal with this problem, a second-order two-scale （SOTS） computational method in the time domain is presented to predict the ageing linear viscoelastic performance of composite materials with a periodic structure. First, in the time domain, the SOTS formulation for calcu- lating the effective relaxation modulus and displacement approximate solutions of the ageing viscoelastic problem is formally derived. Error estimates of the displacement ap- proximate solutions for SOTS method are then given. Numerical results obtained by the SOTS method are shown and compared with those by the finite element method in a very fine mesh. Both the analytical and numerical results show that the SOTS computational method is feasible and efficient to predict the ageing linear viscoelastic performance of composite materials with a periodic structure.

Second-order two-scale computations for conductive radiative heat transfer problem in periodic porous materials

In this paper, a kind of second-order two-scale （SOTS） computation is developed for conductive-radiative heat trans- fer problem in periodic porous materials. First of all, by the asymptotic expansion of the temperature field, the cell problem, homogenization problem, and second-order correctors are obtained successively. Then, the corresponding finite element al- gorithms are proposed. Finally, some numerical results are presented and compared with theoretical results. The numerical results of the proposed algorithm conform with those of the FE algorithm well, demonstrating the accuracy of the present method and its potential applications in thermal engineering of porous materials.

Three-dimensional ordered macroporous perovskite-type La_(1-x)K_xNiO_3 catalysts with enhanced catalytic activity for soot combustion: the Effect of K-substitution

Three-dimensional ordered macroporous (3DOM) La1?xKxNiO3 perovskite-type catalysts were successfully prepared by a colloidal crystal template method and characterized by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray scattering elemental mapping, X-ray diffraction, Raman and X-ray photoelectron spectroscopy, and temperature-programmed reduction of H2. Further, their catalytic activity in soot combustion was determined by temperature-programmed oxidation reaction. K substitution into the LaNiO3 lattice led to remarkably improved catalytic activity of this catalyst in soot combustion. Amongst various catalysts, La0.95K0.05NiO3 exhibited the highest activity in soot combustion (with its T50 and CO2 S values being 338 °C and 98.2%, respectively), which is comparable to the catalytic activities of Pt-based catalysts under the condition of poor contact between the soot and the catalyst. K-substitution improves the valence state of Ni and increases the number of oxygen vacancies, thereby leading to increased density of surface-active oxygen species. The active oxygen species play a vital role in catalyzing the elimination of soot. The perovskite-type La1?xKxNiO3 nanocatalysts with 3DOM structure without noble metals have potential for practical applications in the catalytic combustion of diesel soot particles.

Advances in microwave assisted synthesis of ordered mesoporous materials

Mesoporous materials with uniform pores and high specific areas are used in many fields including catalysts, separation and adsorbents, etc. In order to find faster and more economical synthesis routes, the use of microwave heating was deeply studied. Compared to the hydrothermal method, microwave energy can heat the samples to crystallization temperature rapidly and uniformly result in homogeneous nucleation and shorten crystallization time. The basic principles of microwave assisted synthesis and advantages of microwave heating, and the obtained progress concerning ordered mesoporous materials through microwave synthesis were summarized.

Efficient aerobic oxidative desulfurization via three-dimensional ordered macroporous tungsten-titanium oxides

A series of three-dimensional ordered macroporous(3 DOM)W-TiO_(2)catalysts have been prepared through a facile colloidal crystal template method.The prepared materials characterized in detail exhibited enhanced catalytic activity in aerobic oxidative desulfurization process.The experimental results indicated that the as-prepared materials possessed excellent 3 DOM structure,which is beneficial for the catalytic activity.The sample 3 DOM W-TiO_(2)-20 exhibited the highest activity in ODS process,and the sulfur removal can reach 98%in 6 h.Furthermore,the oxidative product was also analyzed in the reaction process.

Pore-filling Three-dimensionally Ordered Macroporous Polyimide Composite Proton Conducting Membranes

The silica opal templates were prepared from three silica colloids of different diameters of 230 nm, 500 nm and 1.5 mm by a filtration route. The large-scale stable opal template membranes after sintering the deposited SiO2 opal template can be successfully obtained by optimizing the pH value and NaCl concentration in silica colloidal solutions. The three-dimensionally ordered macroporous（3DOM） polyimide membranes without crack were fabricated by reproducing the structure of silica opal template. We prepared the pore-filling composite proton exchange membranes by filling the 3DOM structure with proton conducting organosilane sol. The result indicates that the composite membranes exhibit higher water uptake than pure filling organosilane gel. The proton conductivity increased with the increasing of pore cell in composite membranes.

Color tunable upconversion emission in CeO_2:Yb,Er three-dimensional ordered macroporous materials

The three-dimensional ordered macroporous CeO2：Yb,Er materials were prepared, and the influence of doping concentra- tion of Yb3＋ or Er3＋ ions on upconversion property was investigated. Green and red upconversion emissions were observed under the excitation of 980 nm at room temperature. It was found that the ratio of red to green upconversion emission intensity increased with increasing of concentration of the Yb3＋ or Er3＋ ions in the three-dimensional ordered macroporous CeO2：Yb,Er materials. When the concentration of Yb3＋ was 10 mol%, pure red upconversion emission was obtained. The varied mechanism of ratio of red to green upconversion emission intensity was discussed with the concentration of Yb3＋ or Er3＋ ions.

TiB-Ti周期序构复合材料设计、制备及性能研究

高性能结构材料部件在航空航天、交通汽车、电子信息、冶金等领域具有重要的应用价值,得到了广泛研究。增强结构材料部件整体性能的方法主要包括材料本征性能提升和结构复合设计优化,但提高单一结构材料的本征力学性能的研究已接近极限。本研究旨在提出周期序构结构材料的理念,并采用一体化烧结制备出整体性能更好的结构复合材料,从而探索高性能结构复合材料发展的新范式。通过周期序构化的设计,构建了兼具陶瓷高硬度和金属强韧性的TiB-Ti功能单元,设计制备了不同周期序构模式的TiB-Ti高性能结构复合材料。在此基础上,对这些结构进行了力学性能研究,并通过分析其断裂模式来探究不同序构模式对材料整体性能的影响。结果表明,周期序构化可以通过改变材料宏观断裂模式和应力分散特性来提高材料的整体性能。这一研究新范式对其他结构复合材料的结构设计和性能突破具有指导和借鉴意义。对周期序构模式的复杂化探索,对周期序构结构材料的应用场景探索和其他性能测试研究也将是未来需要重点关注的问题。

单分散胶粒、胶态晶体和三维有序周期性材料的研究进展

单分散胶粒是食品、印染、陶瓷、光学胶片和电磁流变体等材料的主要成分,其三维有序组装结构被通称为胶态晶体。具有三维周期性结构的胶态晶体在光电研究领域具有特殊意义。以胶态晶体为模板可复制获得结构上与其三维周期性结构反相的新型功能性介孔材料。后者兼具固体材料本身和长程周期有序结构两种特性,是当前光电领域急需的光子晶体的最佳候选。本文综合阐述了单分散胶粒、胶态晶体以及具有三维周期性有序结构的材料的制备、性质和初步及潜在应用。

Effects of Au-Ce strong interactions on catalytic activity of Au/CeO_2/3DOM Al_2O_3 catalyst for soot combustion under loose contact conditions

Au/3DOM（three-dimensionally ordered macroporous） Al2O3 and Au/CeO2/3DOM Al2O3 were prepared using a reduction-deposition method and characterized using scanning electron microscopy,N2 adsorption-desorption,X-ray diffraction,transmission electron microscopy,ultraviolet-visible spectroscopy,temperature-programmed hydrogen reduction,and X-ray photoelectron spectroscopy.Au nanoparticles of similar sizes were well dispersed and supported on the inner walls of uniform macropores.The norminal Au loading is 2%.Al-Ce-O solid solution in CeO2/3DOM Al2O3 catalysts can be formed due to the incorporation of Al^3＋ ions into the ceria lattice,which causes the creation of extrinsic oxygen vacancies.The extrinsic oxygen vacancies improved the oxygen-transport properties.The strong metal-support interactions between Au and CeO2 increased the amount of active oxygen on the Au nanoparticle surfaces,and this promoted soot oxidation.The activities of the Au-based catalysts were higher than those of the supports（Al2O3 or CeO2/3DOM Al2O3） at low temperature.Au/CeO2/3DOM Al2O3 had the highest catalytic activity for soot combustion,with T（10）,T（50）,and T（90） values of 273,364,and 412℃,respectively.

Synthesis of 3D ordered macroporous indium tin oxide using polymer colloidal crystal template

Three-dimensional (3D) ordered macroporous indium tin oxide (ITO) is pre- pared using a polymer colloidal crystal template that is formed by self-assembly of the monodisperse poly(methyl methacrylate) (PMMA) microspheres. The morphologies and BET surface area of the macroporous material is examined by scanning electron micro- scope, transmission electron microscopy and N2 adsorption/desorption. Results indicate that the macroporous material has highly ordered arrays of the uniform pores replicated from the PMMA colloidal crystal template when the polymer colloidal crystal template is removed by calcinations at 500℃. The pore diameter (about 450 nm) of macroporous ITO slightly shrank to the PMMA microspheres. The BET surface area and pore volume of the macroporous material are 389 m2·g-1 and 0.36 cm3·g-1, respectively. Moreover, the macroporous ITO, containing 5 mol% Sn and after annealing under vacuum, shows the minimum resistivity of ρ = 8.2×10-3 Ω· cm. The conductive mechanism of macroporous ITO is discussed, and it is believed that the oxygen vacancies are the major factor for excellent electrical properties.

Immobilization of Glucose Oxidase on Ordered Macroporous Silicas Functionalized with Amino Group

A novel glucose oxidase immobilized on three-dimensionally ordered macroporous （3DOM） material has been prepared by firstly preparation of hybrid 3DOM SiO2-NH2 materials using colloidal crystal method, and following covalent immobilization of glucose oxidase on the pore walls of the 3DOM materials. The materials were characterized by SEM, FTIR, DSC and BET techniques. SEM observation shows that the macropores are highly ordered and are interconnected by small windows. FTIR measurement shows that there are amino and organic groups in the pore walls. The surface area of the 3DOM SiO2-NH2 material is about 10.2 m2/g. The loaded amount of enzyme is increased with amino content in the materials. The immobilized enzyme has high activity, thermal stability and can be reused.

Preparation and characterization of 3-dimensionally ordered macroporous SiC

Three-dimensionally (3D) long range ordered macroporous SiC ceramics were prepared through infiltrating polymethylsilane (PMS) into the 3D ordered sacrificial silica template, pyrolysis and the template removal. It was found that the pore size (84―658 nm), BET surface area (299.44―584.64 m2/g) and micropore volume (0.25―0.64 cm3/g) of the achieved porous SiC can be tailored by utilizing different sizes silica sphere templates. There exist three kinds of pores in the porous ceramics: sphere inversed pores, windows and mesopores (2―5 nm). The sphere inversed pores were packed as hcp structure and three dimensionally penetrated through the windows, and the mesopores endowed the porous ceramics surprising high BET surface areas and micropore volumes.

长周期结构Mg_(94)Cu_4Y_2储氢合金的吸放氢动力学和组织转变

设计并制备含有长周期堆垛有序结构(LPSO)的Mg_(94)Cu_4Y_2储氢合金,研究了合金在吸放氢过程中组织的转变机制以及吸放氢动力学性能。结果表明,Mg_(94)Cu_4Y_2合金主要由Mg、Mg2Cu和高度固溶Cu、Y元素的含18R及14H型的LPSO组成。LPSO在首次吸氢过程中分解,并原位生成均匀的(MgH_2+MgCu_2+YH_3)纳米复合组织。在随后的脱氢和吸放氢循环中,合金主要通过Mg/MgH_2反应实现吸放氢。细小均匀分布的Mg2Cu和YH_2对Mg/MgH_2的催化作用,使该合金表现出较优良的吸放氢动力学特性。

Mg-13Gd-1Zn合金的组织与力学性能

研究了铸态、退火态、挤压态和T5时效态Mg-13Gd-1Zn三元合金的显微组织和力学性能。结果表明,合金的铸态组织由α-Mg、(Mg,Zn)3Gd和14H-LPSO长周期相组成。合金在均匀化退火和热挤压后的直接时效(T5)过程中都发生了晶内14H-LPSO相的沉淀析出,表明合金中14H-LPSO的沉淀相变发生在一个很宽的温度范围(200~510℃)。在挤压后合金的直接时效(T5)过程中发生了β’及β1相的沉淀析出。在沉淀强化和LPSO强化的共同作用下,合金的屈服强度、抗拉强度和伸长率分别为197 MPa、397 MPa和2.56%。在200℃/80 MPa和200℃/120 MPa两种实验条件下,Mg-13Gd-1Zn合金的抗蠕变性能均优于WE54合金。

一类存贮模型及其最优存贮策略

当工厂仓库容量有限时,常常需要租借仓库来进行存贮.但是,由于租借仓库的存贮单价通常比自己仓库的存贮单价高,所以不能用经典的经济批量公式来计算,有必要重新进行研究.本文研究了原料仓库和产品仓库容量均有限条件下的定料生产销售存贮问题,建立了相应的存贮模型,给出了最优定料生产存贮策略.

论国际秩序规则供给的路径选择——基于人类命运共同体理念

在当前国际格局发生重大变动的背景下,国外学界有人提出了守成大国为规则和秩序维护者而新兴大国为国际秩序破坏者的观点,这显然是受了'修昔底德陷阱'理论的影响,并为中美两国掉入'修昔底德陷阱'刻意制造依据。当前,处于大变革下的国际格局越来越容易出现规则衰减而混乱增加的现象,中国如何确定自身在这一剧烈变动过程中的地位,已引起国内外国际关系和国际法学者的广泛关注。作为负责任的复兴大国,中国已经提出了'一带一路'倡议和推动构建人类命运共同体的理念,并积极采取措施维护国际秩序的稳定。本文认为,中国应当通过加大规则供给力度的方式来加固国际秩序稳定的基础作用,尤其是要在规则供给的核心领域、优先储备领域以及长远领域,积极参与未来国际规则的塑形和供给。通过调整自我定位和在不同规则领域里重视多边路径,综合利用区域和一定程度的单边实践路径,以及强化利用主导或主要参与的国际组织等平台,重新实现国际秩序的稳定,为实现中华民族伟大复兴的中国梦创造良好的国际环境。