Beijing University of Technology

About: Beijing University of Technology is a education organization based out in Beijing, Beijing, China. It is known for research contribution in the topics: Microstructure & Computer science. The organization has 31929 authors who have published 31987 publications receiving 352112 citations. The organization is also known as: Běijīng Gōngyè Dàxué & Beijing Polytechnic University.

Titanium alkoxide induced BiOBr–Bi2WO6 mesoporous nanosheet composites with much enhanced photocatalytic activity

Abstract: Here we report a facile hydrothermal route for the preparation of BiOBr–Bi2WO6 mesoporous nanosheet composites (MNCs) in the presence of titanium isopropoxide, Ti(OiPr)4. High resolution transmission electron microscopy, X-ray diffraction, nitrogen adsorption/desorption analysis and X-ray photoelectron spectroscopy were employed for structural and composition analyses of the MNCs. The photogenerated charge transfer and photocatalytic activity of BiOBr–Bi2WO6 MNCs were investigated by Kelvin probe force microscopy and UV-vis spectroscopy. We propose mechanisms to illustrate how titanium alkoxide induces the formation of mesoporous nanosheet heterostructures and the enhanced photodecomposition efficiency of the dye under low light intensity illumination. Overall, our results suggest that titanium alkoxide is not only strongly involved in the growth of BiOBr (001) facets, but also plays a critical role in the pore evolution of the product. Kelvin probe force microscopy analysis allows us to conclude that the resulting nanocomposites demonstrate high photogenerated charge mobility and a long lifetime. Dye molecules can be rapidly and thoroughly decomposed with the photocatalyst under very low light intensity illumination. The enhanced photocatalytic activity is attributed to well matched band edge positions of BiOBr and Bi2WO6 and the large specific surface area of the MNCs in view of the incorporation of mesopores and the highly exposed BiOBr (001) facet due to the use of Ti(OiPr)4 during the synthesis. The results presented here are expected to make a contribution toward the development of delicate nanocomposites for photocatalytic water purification and solar energy utilization.

Boosting the thermoelectric performance of p-type heavily Cu-doped polycrystalline SnSe via inducing intensive crystal imperfections and defect phonon scattering

Abstract: In this study, we, for the first time, report a high Cu solubility of 11.8% in single crystal SnSe microbelts synthesized via a facile solvothermal route. The pellets sintered from these heavily Cu-doped microbelts show a high power factor of 5.57 μW cm−1 K−2 and low thermal conductivity of 0.32 W m−1 K−1 at 823 K, contributing to a high peak ZT of ∼1.41. Through a combination of detailed structural and chemical characterizations, we found that with increasing the Cu doping level, the morphology of the synthesized Sn1−xCuxSe (x is from 0 to 0.118) transfers from rectangular microplate to microbelt. The high electrical transport performance comes from the obtained Cu+ doped state, and the intensive crystal imperfections such as dislocations, lattice distortions, and strains, play key roles in keeping low thermal conductivity. This study fills in the gaps of the existing knowledge concerning the doping mechanisms of Cu in SnSe systems, and provides a new strategy to achieve high thermoelectric performance in SnSe-based thermoelectric materials.

Prevention and treatment technologies of railway tunnel water inrush and mud gushing in China

Abstract: Water inrush and mud gushing are one of the biggest hazards in tunnel construction. Unfavorable geological sections can be observed in almost all railway tunnels under construction or to be constructed, and vary in extent. Furthermore, due to the different heights of mountains and the lengths of tunnels, the locations of the unfavorable geological sections cannot be fully determined before construction, which increases the risk of water inrush and mud gushing. Based on numerous cases of water inrush and mud gushing in railway tunnels, the paper tries to classify water inrush and mud gushing in railway tunnels in view of the conditions of the surrounding rocks and meteorological factors associated with tunnel excavation. In addition, the causes of water inrush and mud gushing in combination of macro- and micro-mechanisms are summarized, and site-specific treatment method is put forward. The treatment methods include choosing a method of advance geological forecast according to risk degrees of different sections in the tunnel, determining the items of predictions, and choosing the appropriate methods, i.e. draining-oriented method, blocking-oriented method or draining-and-blocking method. The treatment technologies of railway water inrush and mud gushing are also summarized, including energy relief and pressure relief technology, advance grouting technology, and advance jet grouting technology associated with their key technical features and applicable conditions. The results in terms of treatment methods can provide reference to the prevention and treatment of tunnel water inrush and mud gushing.