Controlled synthesis of Co₂C nanochains using cobalt laurate as precursor: Structure, growth mechanism and magnetic properties

Zhang, Yajing,Zhu, Yuan,Wang, Kangjun,Li, Da,Wang, Dongping,Ding, Fu,Meng, Dan,Wang, Xiaolei,Choi, Chuljin,Zhang, Zhidong Elsevier 2018 Journal of magnetism and magnetic materials Vol.456 No.-

<P><B>Abstract</B></P> <P>Cobalt carbides (Co<SUB>2</SUB>C and Co<SUB>3</SUB>C) nanocomposites exhibit interesting hard magnetic property, controlled synthesis of individual phase facilitates to clarify the magnetism of each, but it is difficult to obtain the single phase. We present a new approach to address this issue via a polyol refluxing process, using cobalt laurate as the precursor. The single phase Co<SUB>2</SUB>C magnetic nanochains self-assembled by nanoparticles are synthesized. The precursor is the key factor for controlling the growth kinetics of the Co<SUB>2</SUB>C nanochains. Cobalt, instead of cobalt carbides, is produced if cobalt chloride, acetate and acetylacetonate replace cobalt laurate as the precursor, respectively. The evolution of the growth process has been studied. In the formation of Co<SUB>2</SUB>C, first fcc-Co produces, then it transforms into Co<SUB>2</SUB>C by carbon diffusion process, and the produced carbon first exists in disordered state and then a small amount of them transforms into graphite. Saturation magnetization (<I>Ms</I>) of Co<SUB>2</SUB>C nanochains obtained at 300 °C for 20, 60, and 180 min are 27.1, 18.9, and 10.9 emu g<SUP>−1</SUP>, respectively. The decrease of <I>Ms</I> caused by increasing carbon content, and the carbon content are much larger than the stoichiometric ratio value of Co<SUB>2</SUB>C (9.2 wt%). The Co<SUB>2</SUB>C nanochains have mesoporous pore of 3.8 nm and the specific surface area of 48.6 m<SUP>2</SUP> g<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Co<SUB>2</SUB>C magnetic nanochains are synthesized using cobalt laurate as the precursor in TEG. </LI> <LI> The precursor of cobalt laurate is the key factor for controlling the growth kinetics of Co<SUB>2</SUB>C nanochains. </LI> <LI> Ms of Co<SUB>2</SUB>C nanochains obtained at 300 °C for 20, 60, and 180 min are 27.1, 18.9, and 10.9 emu g<SUP>−1</SUP>, respectively. </LI> <LI> The decrease of Ms is caused by increasing carbon content with increasing reaction time. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>We present a new approach to obtain single phase Co<SUB>2</SUB>C nanochains by using cobalt laurate as the precursor.</P> <P>[DISPLAY OMISSION]</P>

Analytical investigation on lateral load responses of self-centering walls with distributed vertical dampers

Xiaogang Huang,Zhen Zhou,Dongping Zhu 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.3

Self-centering wall (SCW) is a resilient and sustainable structural system which incorporates unbonded posttensioning (PT) tendons to provide self-centering (SC) capacity along with supplementary dissipators to dissipate seismic energy. Hysteretic energy dissipators are usually placed at two sides of SCWs to facilitate ease of postearthquake examination and convenient replacement. To achieve a good prediction for the skeleton curve of the wall, this paper firstly developed an analytical investigation on lateral load responses of self-centering walls with distributed vertical dampers (VD-SCWs) using the concept of elastic theory. A simplified method for the calculation of limit state points is developed and validated by experimental results and can be used in the design of the system. Based on the analytical results, parametric analysis is conducted to investigate the influence of damper and tendon parameters on the performance of VD-SCWs. The results show that the proposed approach has a better prediction accuracy with less computational effects than the Perez method. As compared with previous experimental results, the proposed method achieves up to 60.1% additional accuracy at the effective linear limit (DLL) of SCWs. The base shear at point DLL is increased by 62.5% when the damper force is increased from 0kN to 80kN. The wall stiffness after point ELL is reduced by 69.5% when the tendon stiffness is reduced by 75.0%. The roof deformation at point LLP is reduced by 74.1% when the initial tendon stress is increased from 0.45fpu to 0.65fpu.

Preparation of Al2O3/AZ91D Mg Interpenetrating Composites Using Lost Foam Casting Combined with Layered Extrusion Forming

Wenming Jiang,Guangyu Li,Feng Guan,Junwen Zhu,Dongping Zhang,Zitian Fan 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4

A novel method named lost foam casting (LFC) process combined with layered extrusion forming (LEF) technology wasproposed to prepare the Al2O3/AZ91D Mg interpenetrating composites, and the microstructural characteristics, thermalexpansion performance and wear resistance of the Al2O3/AZ91D interpenetrating composites were investigated in this work. The results indicated that a superior bonding between AZ91D magnesium alloy and Al2O3porous ceramic was achieved. The Al2O3/AZ91D interpenetrating composites exhibited obvious improvements in the thermal expansion performance andthe wear resistance compared to the AZ91D alloy. Therefore, the LFC process combined with the LEF technology providesa promising method for the preparation of the Al2O3/AZ91D interpenetrating composites.

RNAi‐mediated knockdown of juvenile hormone esterase causes mortality and malformation in Tribolium castaneum

Xu Zhanyi,Yan Ru,Qian Jiali,Chen Dongping,Guo Yirong,Zhu Guonian,Wu Huiming,Chen Mengli 한국곤충학회 2022 Entomological Research Vol.52 No.11

RNA interference is an efficient approach for gene function identification and a potential novel strategy for selectively controlling pests. The red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae), is a major global storage pest, which causes great economic loss. Juvenile hormone esterase (JHE), a carboxylesterase, is responsible for the degradation of juvenile hormone. However, the knockdown effect of jhe on metamorphosis of pupae or adult in T. castaneum is unknown. In this study, we analyzed the expression profiles of Tc j h e in the larval stage, we found that Tc j h e was expressed throughout the whole larval instars and the expression levels were relatively high right after molting. Furthermore, we knocked down the expression of Tcjhe by injecting dsTc j h e , which significantly increased the mortality of adults and decreased the eclosion rate. In addition, abnormal developmental phenotypes, including wing deformitity, pupal–adult monsters and shrunken adults, were observed. Our finding indicates that JHE plays an important role in the metamorphosis and development in T. castaneum, suggesting that Tc j h e could be used as a potential target for the development of RNAi-based control strategies in T. castaneum.

Tension–Shear Experimental Analysis and Fracture Models Calibration on Q235 Steel

Xiaogang Huang,Zhen Zhou,Yazhi Zhu,Dongping Zhu,Lu Lu 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.5

Tension–shear loading is a common loading condition in steel structures during the earthquake shaking. To study ductile fracture in structural steel under multiple stress states, experimental investigations on the diff erent fracture mechanisms in Chinese Q235 steel were conducted. Diff erent tension–shear loading conditions achieved by using six groups of inclined notch butterfl y confi gurations covering pure shear, tension–shear and pure tension cases. Numerical simulations were carried out for all the specimens to determine the stress and strain fi elds within the critical sections. Two tension–shear fracture models were calibrated based on the hybrid experimental–numerical procedure. The equivalent fracture strain obtained from the round bar under tensile loading was used for evaluating these two models. The results indicated that the tension–shear criterion as a function of the shear fracture parameter had better performance in predicting the fracture initiation of structural steel under diff erent loading conditions.