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 & Laser. 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.

Effect of Zn Content on the Microstructure and Properties of Super-High Strength Al-Zn-Mg-Cu Alloys

Abstract: The microstructure and properties of three different Al-Zn-Mg-Cu alloys with high Zn content (9 wt pct, 10 wt pct, and 11 wt pct, marked as 9Zn, 10Zn, and 11Zn, respectively) were investigated. The strength of alloys increases as the Zn content increases from 9 wt pct to 10 wt pct, while it does not increase any more as the Zn content increases continuously from 10 wt pct to 11 wt pct. The stress-corrosion cracking (SCC) resistance decreases as the Zn content increases from 9 wt pct to 10 wt pct, while it changes unobviously as the Zn content increases continuously from 10 wt pct to 11 wt pct. The elongation and fracture toughness of alloys decrease as the Zn content increases in these Al-Zn-Mg-Cu alloys. The Zn content has little effect on the precipitation reaction of Al-Zn-Mg-Cu alloys that contain the mixture of GP zones, and η′ are the main Matrix Precipitates (MPt) in the peak-aging state, and the mixture of η′ and η are the main MPt in the over-aging state. The amount of MPt and coarse T (AlZnMgCu) phases are shown to increase with the increasing Zn content in Al-Zn-Mg-Cu alloys. The coarse T phases hardly dissolve into the matrix and are the source for the crack initiation, which may be the responsibility for the negative effect on the properties of high Zn content Al-Zn-Mg-Cu alloys.

An unusual red carbon nitride to boost the photoelectrochemical performance of wide bandgap photoanodes

Abstract: Tuning the bandgap of a semiconductor to achieve strong band-to-band visible light absorption is highly desirable but challenging for photocatalysis. This work presents a facile molten-salt-assisted route to prepare red-colored polymerized carbon nitride (RPCN) nanosheets with a remarkable redshifted absorption and narrowed bandgap of 1.9 eV. Both experimental findings and theoretical calculations reveal that alkali heteroatoms are effective to tune the surface and electronic structures of carbon nitride, resulting in significantly reduced bandgap and excellent solubility. The RPCN-sensitized TiO nanorod-based photoanode generates an impressive photocurrent density of ≈2.33 mA cm at 1.23 V versus reversible hydrogen electrode under Air Mass 1.5 G illumination without any cocatalyst, which is 2.6 folds higher than that of the bare TiO photoanode. The new findings in this work could inspire the electronic structure engineering of semiconductor photocatalysts to greatly enhance the visible light absorption and provide a generic strategy to enhance the photoelectrochemical performance of wide-bandgap semiconductor photoelectrodes.

Spatial gradient distributions of thermal shock-induced damage to granite

Abstract: In this study, we attempted to investigate the spatial gradient distributions of thermal shock-induced damage to granite with respect to associated deterioration mechanisms. First, thermal shock experiments were conducted on granite specimens by slowly preheating the specimens to high temperatures, followed by rapid cooling in tap water. Then, the spatial gradient distributions of thermal shock-induced damage were investigated by computed tomography (CT) and image analysis techniques. Finally, the influence of the preheating temperature on the spatial gradients of the damage was discussed. The results show that the thermal shock induced by rapid cooling can cause more damage to granite than that induced by slow cooling. The thermal shock induced by rapid cooling can cause spatial gradient distributions of the damage to granite. The damage near the specimen surface was at a maximum, while the damage inside the specimen was at a minimum. In addition, the preheating temperature can significantly influence the spatial gradient distributions of the thermal shock-induced damage. The spatial gradient distribution of damage increased as the preheating temperature increased and then decreased significantly over 600 °C. When the preheating temperature was sufficiently high (e.g. 800 °C), the gradient can be ignored.