Harbin Engineering University

About: Harbin Engineering University is a education organization based out in Harbin, Heilongjiang, China. It is known for research contribution in the topics: Control theory & Computer science. The organization has 31149 authors who have published 27940 publications receiving 276787 citations. The organization is also known as: HEU.

Lightweight, Fire-Retardant, and Anti-Compressed Honeycombed-Like Carbon Aerogels for Thermal Management and High-Efficiency Electromagnetic Absorbing Properties.

Abstract: Ordered porous carbon materials (PCMs) have potential applications in various fields due to their low mass densities and porous features. However, it yet remains extremely challenging to construct PCMs with multifunctionalization for electromagnetic wave absorption. Herein, the honeycombed-like carbon aerogels with embedded Co@C nanoparticles are fabricated by a directionally freeze-casting and carbonization method. The optimized aerogel possesses low density (0.017 g cm-3 ), fire-retardant, robust mechanical performance (compression moduli reach 1411 and 420 kPa in the longitudinal and transverse directions at 80% strain, respectively), and high thermal management (high thermal insulation capability and high-efficiency electrothermal conversion ability). Notably, the optimized aerogel exhibits the excellent electromagnetic wave absorption properties with broad effective absorption bandwidth (13.12-17.14 GHz) and strong absorption (-45.02 dB) at a thickness of only 1.5 mm. Density functional theory calculations and the experimental results demonstrate that the excellent electromagnetic wave absorption properties stem from the synergetic effects among high electrical conductivity, numerous interfaces and dipoles and unique ordered porous structure. Meanwhile, the computer simulation technology (CST) simulation confirms that the multifunctional aerogel can attenuate more electromagnetic energy in a practical environment. This work paves the way for rational design and fabrication of the next-generation electromagnetic wave absorbing materials.

Effect of Sn content on strain hardening behavior of as-extruded Mg-Sn alloys

Abstract: The effects of Sn content on strain hardening behavior of as-extruded Mg-xSn (x = 1.3, 2.4, 3.6 and 4.7 wt%) binary alloys were investigated by uniaxial tensile tests at room temperature. Strain hardening rate, strain hardening exponent and hardening capacity were obtained from the true plastic stress-strain curves. After hot extrusion, the as-extruded Mg-Sn alloys are mainly composed of α-Mg matrix and second phase Mg2Sn, which only exists in Mg-3Sn and Mg-4Sn. Average grain size decreases from 15.6 μm to 3.6 µm with Sn content increases from 1.3 to 4.7 wt%. The experimental results show that Sn content decreases strain hardening ability of as-extruded Mg-Sn alloys, but gives rise to an obvious elevation in tensile strength, yield strength and elongation of them. With increasing Sn content, strain hardening rate decreases from 3527 MPa to 1211 MPa at (σ-σ0.2) = 50 MPa, strain hardening exponent decreases from 0.21 to 0.13 and hardening capacity decreases from 1.66 to 0.63. The variation in strain hardening behavior of Mg-Sn alloys with Sn content is discussed in terms of the influences of grain size and distribution of grain orientation.

Fine structural and morphological control of rare earth fluorides REF3 (RE = La–Lu, Y) nano/microcrystals: microwave-assisted ionic liquid synthesis, magnetic and luminescent properties

Abstract: Via a fast, facile and environmentally-friendly microwave-assisted ionic liquid method, binary rare earth fluoride REF3 (RE = La–Lu, Y) nano/microcrystals with multiform crystal structures (hexagonal and orthorhombic) and morphologies (nanodisks, secondary aggregates constructed from nanoparticles, and elongated nanoparticles) have been successfully fabricated. The experimental results indicate that the use of microwave irradiation and ionic liquid [BIBM][BF4] are responsible for the products. Microwave irradiation accelerates dramatically the reaction rate and shortens the reaction time. [BIBM][BF4] plays multiple roles as solvent, reactant and template. The possible formation mechanisms for REF3 nano/microcrystals with diverse well-defined morphologies have been presented in detail. Additionally, we systematically investigate the magnetic and luminescent properties of the GdF3 : Ce3+/Ln3+ (Ln = Eu, Tb and Dy). They show paramagnetic property with mass magnetic susceptibility value of 1.10 × 10−4 emu g−1 Oe at 300 K, and red (Eu3+), green (Tb3+) and blue (Dy3+) emissions due to the Ce3+ → Ln3+ (Ln = Tb, Eu, and Dy) energy transfer. This energy transfer occurs through the energy migration process like Ce3+ → Gd3+→ (Gd3+)n → Ln3+ and the Gd3+ ions plays an intermediate role in the process.