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Wang J.,Shandong University | Zhao G.-Q.,Shandong University | Wang G.-C.,Shandong University | Yuan J.,Institute 53 of China North Industries Group Corporation
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2014

According to the numerical simulation model of the rolling process of powder sintered 93 tungsten alloy sheet and using the finite software DEFORM, the effect of roll convexity on head crack of the rolled sheet and the principal stress change in the crack point were analyzed. The results show that, with the increase of roll convexities, roll force and the rolled sheet width are on the rise, effective stress and effective strain change slightly, stress triaxiality and cracking tendency increase with the increasing of roll convexities absolute value, the selected range of roll convexities is -0.02-0.05 mm.

Li Y.,Central South University | Li Y.,Institute 53 of China North Industries Group Corporation | Chen G.,Central South University | Li Q.,Central South University | And 2 more authors.
Journal of Alloys and Compounds | Year: 2011

Fe3O4/polypyrrole (PPy) core/shell nanocomposite, with Fe3O4 nanoparticle as core and PPy as shell, could be facilely synthesized via in situ chemical oxidative polymerization of pyrrole monomers on the surface of Fe3O4 nanoparticles. The results indicate that core/shell nanocomposite consists of Fe3O 4 core with the mean diameter of 100 nm and adjacent PPy shell with a thickness of about 70 nm. The as-prepared Fe3O4/PPy core/shell nanocomposite exhibits a saturated magnetization of 20.1 emu/g and coercivity value of 368.3 Oe, respectively. The electromagnetic characteristics of Fe3O4/PPy core/shell nanocomposite were also investigated with a vector network analyzer in the 2-18 GHz range. The absorbing peak position moves to lower frequency with increasing the thicknesses of samples. The value of the minimum reflection loss is -22.4 dB at 12.9 GHz for Fe3O4/PPy core/shell nanocomposite with a thickness of 2.3 mm, and a broad peak with a bandwidth lower than -10 dB is about 5 GHz. Such strong absorption is attributed to better electromagnetic matching due to the existence of PPy and the special core/shell structure. © 2011 Elsevier B.V. All rights reserved.

Zhang X.-Y.,Shandong University | Zhang Y.-J.,Shandong University | Gong H.-Y.,Shandong University | Wang C.-L.,Shandong University | And 4 more authors.
Gongneng Cailiao/Journal of Functional Materials | Year: 2013

Nano black high near-infrared (NIR) reflectance ceramic pigments were prepared with ferric nitrate, chromium nitrate, citric acid, and ethylene glycol by sol-gel method. The effects of different molar ratio of Fe and Cr, hydrolysis temperature, the pH of the solution, concentration of metal ions and calcination temperature were investigated. The results show that the crystalline phase of the as-prepared pigments is Cr1.3Fe0.7O3 with average NIR reflectance about 77.58% in 700-2500 nm wavelength range when Fe/Cr molar ratio was 0.50, hydrolysis temperature was 70°C, pH value was 3-4, metal ion concentration was 2.5-3.5 mol/L, calcination temperature was 900°C.

Wang J.,Shandong University | Zhao G.,Shandong University | Chen L.,Shandong University | Li J.,Institute 53 of China North Industries Group Corporation
Materials and Design | Year: 2016

The isothermal hot compression tests for powder metallurgy pure tungsten were carried out by using Gleeble 3800 thermo mechanical simulator at deformation temperatures from 1523K to 1823K and strain rates from 0.001s-1 to 1s-1. The deformation behavior of powder metallurgy pure tungsten at elevated temperature were studied, and six constitutive equations were respectively established based on Arrhenius model, Johnson-Cook model, modified Johnson-Cook model, Zerilli-Armstrong model, modified Zerilli-Armstrong model, and KHL model. Moreover, the predictability of the derived constitutive equations was evaluated by using the correlation coefficient (Rc) and average absolute relative error (AARE). The results show that flow stress of pure tungsten is affected not only by strain rate and deformation temperature, but also by strain. The flow stress of pure tungsten at elevated temperature could be well described by Arrhenius model, modified JC model, modified Zerilli-Armstrong model, and KHL model. The present study can provide some important and basic data for the simulation of plastic deformation processes of powder metallurgy pure tungsten. © 2015 Elsevier Ltd.

Huang X.,Nanjing University of Information Science and Technology | Huang X.,Georgia Institute of Technology | Zhang J.,Nanjing Center | Liu Z.,Nanjing University of Information Science and Technology | And 4 more authors.
Journal of Alloys and Compounds | Year: 2015

Abstract The porous hollow BaFe12O19/CoFe2O4 microrods were prepared by an easy and reproducible in situ synthetic method. Cotton cellulose was used as the sacrificial bio-template. The as-prepared hard/soft ferrite composites were homogeneously distributed on the surface of the microrods. It was demonstrated that the porous hollow microrods-like structure and the exchange-coupled interaction between hard and soft ferrites were beneficial to improve the microwave absorption properties. The weight content of the hard/soft ferrite composites was low to 60 wt%, whereas reflection loss could reach to -10 dB in the frequency range of 8.2-16.3 GHz. The fabrication of porous hollow BaFe12O19/CoFe2O4 microrods was an efficient approach to solve the heavy mass problem of the conventional hard/soft ferrite matrix microwave absorption materials. © 2015 Elsevier B.V.

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