University of Science and Technology Beijing

About: University of Science and Technology Beijing is a education organization based out in Beijing, China. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 41558 authors who have published 44473 publications receiving 623229 citations. The organization is also known as: Beijing Steel and Iron Institute.

Influence of prior austenite grain size on martensite–austenite constituent and toughness in the heat affected zone of 700MPa high strength linepipe steel

Abstract: Structure–mechanical property relationship studies were carried out on Gleeble simulated intercritically reheated coarse-grained heat affected zone (ICCGHAZ) of 700 MPa linepipe steel microalloyed with Nb. The design of experiments was aimed at varying reheat temperature in the first pass to obtain different coarse grain size in the HAZ. This enabled the study of the effect of prior austenite grain size on martensite–austenite (M–A) constituent during the second pass reheating and its consequent influence on impact toughness. We elucidate here the role of phase transformation and the fraction, size, shape, distribution, and carbon content of M–A constituent on impact toughness. The data suggests that the fraction of M–A constituent is not influenced by grain size, but the size of M–A constituent is influenced by the prior austenite grain size, which consequently governs toughness. Coarse austenite grain size increases the size of M–A constituent and lowers the HAZ toughness. Coarse austenite grain associated with coarse M–A constituent along grain boundary is the dominant factor in promoting brittle fracture. The combination of fine prior austenite grain size and smaller M–A constituent is favorable in obtaining high toughness. Good toughness is obtained on refining the prior austenite grain size in the CGHAZ during first pass and hence ICCGHAZ in the second pass.

Li substituent tuning of LED phosphors with enhanced efficiency, tunable photoluminescence, and improved thermal stability.

Abstract: Solid-state phosphor-converted white light-emitting diodes (pc-WLEDs) are currently revolutionizing the lighting industry. To advance the technology, phosphors with high efficiency, tunable photoluminescence, and high thermal stability are required. Here, we demonstrate that a simple lithium incorporation in NaAlSiO4:Eu system enables the simultaneous fulfillment of the three criteria. The Li substitution at Al sites beside Na sites in NaAlSiO4:Eu leads to an enhanced emission intensity/efficiency owing to an effective Eu3+ to Eu2+ reduction, an emission color tuning from yellow to green by tuning the occupation of different Eu sites, and an improvement of luminescence thermal stability as a result of the interplay with Li-related defects. A pc-WLED using the Li-codoped NaAlSiO4:Eu as a green component exhibits improved performance. The phosphors with multiple activator sites can facilitate the positive synergistic effect on luminescence properties.

The giant electrocaloric effect and high effective cooling power near room temperature for BaTiO₃ thick film

Abstract: The electrocaloric effect (ECE) of BaTiO3multilayer thick film was investigated by direct calorimetric measurement. The ECE increases monotonically with the enhancement of applied field. The maximum ECE occurs above T c and shifts to higher temperature with increasing applied field. Under an ultrahigh field of 800 kV/cm, it exhibits a giant ECE of ΔT = 7.1 K and ΔS = 10.1 J/kg · K at 80 °C. The ECE heat follows a general power-law relation with the varying rate of applied field within a certain range. A high cooling power (∼50 W/kg) is achieved based on the net-cooling resulting from the different varying rates of rising and falling fields.

Microfluidic Chip-Based Wearable Colorimetric Sensor for Simple and Facile Detection of Sweat Glucose.

Abstract: This study reports a microfluidic chip-based wearable colorimetric sensor for detecting sweat glucose. The device consisted of five microfluidic channels branching out from the center and connected to the detection microchambers. The microchannels could route the sweat excreted from the epidermis to the microchambers, and each of them was integrated with a check valve to avoid the risk of the backflow of the chemical reagents from the microchamber. The microchambers contained the pre-embedded glucose oxidase (GOD)-peroxidase-o-dianisidine reagents for sensing the glucose in sweat. It was found that the color change caused by the enzymatic oxidation of o-dianisidine could show a more sensitive response to the glucose than that of the conventional GOD-peroxidase-KI system. This sensor could perform five parallel detections at one time. The obtained linear range for sweat glucose was 0.1-0.5 mM with a limit of detection of 0.03 mM. The sensor was also used to detect the glucose in sweat samples from a group of subjects engaged in both fasting and postprandial trials. The results showed that our wearable colorimetric sensor can reveal the subtle differences existing in the sweat glucose concentration after the fasting and the oral glucose uptake.