Convergence of the Finite Difference Scheme for a Fast Diffusion Equation in Porous Media

We are concerned with an implicit scheme for the finite difference solution to a nonlinear parabolic equation with a multivalued coefficient that describes the fast diffusion in a porous medium. The boundary conditions contain the multivalued function as well. We prove the stability and the convergence of the scheme, emphasizing the precise nature of convergence in this specific case, and compute the error level of the approximating solution. The method is aimed to simplify the numerical computations for the solutions to equations of this type, without performing an approximation of the multivalued function. The theory is illustrated by numerical results.     

The Prospect of Dimensionality in Porous Semiconductors

With the advent of silicon-based semiconductors, a plethora of previously unknown technologies became possible. The development of lightweight low-dimensional organic semiconductors followed soon after. However, the efficient charge/electron transfers enabled by the non-porous 3D structure of silicon is rather challenging to be realized by their (metal-)organic counterparts. Nevertheless, the demand for lighter, more efficient semiconductors is steadily increasing resulting in a growing interest in (metal-)organic semiconductors. These novel materials are faced with a variety of challenges originating from their chemical design, their packing and crystallinity. Although the effect of molecular design is quite well understood, the influence of dimensionality and the associated change in properties (porosity, packing, conjugation) is still an uncharted area in (metal-)organic semiconductors, yet highly important for their practical utilization. In this Minireview, an overview on the design and synthesis of porous semiconductors, with a particular emphasis on organic semiconductors, is presented and the influence of dimensionality is discussed.     

Efficient production of nanoporous silicon carbide from rice husk at relatively low temperature

Nanoporous silicon carbide with a specific surface area of up to 186.45 m² g⁻¹ has been efficiently synthesized from waste rice husk using a magnesiothermic reduction at 950 °C as a key step. Throughout the entire process, the recovery rates of silicon, potassium and phosphorus from rice husk can reach 88.46, 91.5 and 65.5%, respectively. Turning rice husk waste into a real treasure, this promising method for producing porous SiC protects the environment and brings economic benefits.     

Modern Inorganic Aerogels

Essentially, the term aerogel describes a special geometric structure of matter. It is neither limited to any material nor to any synthesis procedure. Hence, the possible variety of materials and therefore the multitude of their applications are almost unbounded. In fact, the same applies for nanoparticles. These are also just defined by their geometrical properties. In the past few decades nano‐sized materials have been intensively studied and possible applications appeared in nearly all areas of natural sciences. To date a large variety of metal, semiconductor, oxide, and other nanoparticles are available from colloidal synthesis. However, for many applications of these materials an assembly into macroscopic structures is needed. Here we present a comprehensive picture of the developments that enabled the fusion of the colloidal nanoparticle and the aerogel world. This became possible by the controlled destabilization of pre‐formed nanoparticles, which leads to their assembly into three‐dimensional macroscopic networks. This revolutionary approach makes it possible to use precisely controlled nanoparticles as building blocks for macroscopic porous structures with programmable properties.     

高比能高功率全石墨烯锂离子电容器

石墨烯由于拥有超高比表面积和超高电导率而被作为电化学电容器材料广泛研究.本文采用树脂为碳源，通过一种方便快捷的树脂交换法制备一种具有高比表面积的多级孔三维石墨烯（3DG）.经过此种方法的催化、造孔、热处理等主要工艺步骤后，可显著增加石墨烯材料的小、介孔数量，从而提高材料的电化学性能.通过BET测试表明，3DG的比表面积可达2400 m²/g，孔体积达到2.0 cm³/g.以3DG作为正负极材料制备高比能量高功率型锂离子电容器（3DG-LIC），可使3DG-LIC的工作电压从传统超级电容器的2.5 V扩展到4.0 V，能量密度也从20 Wh/kg提高到105 Wh/kg.另外，相同的化学和微观结构能很好地平衡正负极的容量及速率，使高比能量高功率的3DG-LIC具有更宽阔的应用领域.     

A Carbocationic Triarylmethane-Based Porous Covalent Organic Network

A thermally stable carbocationic covalent organic network (CON), named RIO-70 was prepared from pararosaniline hydrochloride, an inexpensive dye, and triformylphloroglucinol in solvothermal conditions. This nanoporous organic material has shown a specific surface area of 990 m² g⁻¹ and pore size of 10.3 Å. The material has CO₂ uptake of 2.14 mmol g⁻¹ (0.5 bar), 2.7 mmol g⁻¹ (1 bar), and 6.8 mmol g⁻¹ (20 bar), the latter corresponding to 3 CO₂ molecules adsorbed per pore per sheet. It is shown to be a semiconductor, with electrical conductivity (σ) of 3.17×10⁻⁷ S cm⁻¹, which increases to 5.26×10⁻⁴ S cm⁻¹ upon exposure to I₂ vapor. DFT calculations using periodic conditions support the findings.