Lei J.,Shanghai University |
Lei J.,Shanghai FRP Research Institute Co. |
Ma F.,Shanghai University |
Shi Y.,Shanghai University |
And 3 more authors.
Science China Technological Sciences | Year: 2012
The synthesis of polycrystalline aluminum oxynitride (AlON) powders was investigated by the carbothermal reduction and nitridation (CRN) of amorphous precursor obtained by wet chemical processing. Co-precipitation processing was employed to achieve amorphous precursor from Al(NO 3) 3 solution dispersed by nanosized carbon particles, which was composed of Al(OH) 3 and C particles homogeneously. The effects of the content of carbon black, pH value, and calcination temperature on formation of AlON phase were investigated by means of XRD, SEM and TEM, respectively. It was found that single phase AlON powder could be synthesized when the resultant precursors were calcined at 1750°C for 2 hours under flowing N2. Under optimal additional content of C (5.6wt%), the resultant AlON powders exhibited the primary particle size of about 1-3 μm with a specific surface area of 3.2 m 2/g, which were superior to that of carbothermal reduction of immediate mixture of γ-Al 2O 3/C powders. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.
Lei J.-X.,Shanghai University |
Lei J.-X.,Shanghai FRP Research Institute Co. |
Shi Y.,Shanghai University |
Shi J.-B.,Shanghai FRP Research Institute Co. |
Li X.,Shanghai University
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2015
AlON powders were synthesized by carbothermal reduction method using nano-sized Al2O3 and micron carbon powder as raw materials, and transparent AlON ceramics were densified by pressureless sintering under the condition of 1875 ℃×24 h. The mechanical, thermal and optical properties of the transparent AlON ceramic, as well as its microstructure were also characterized. The results show that the obtained transparent AlON ceramic has an average grain size of 110-120 μm. Its bending strength is (275±25) MPa at room temperature, and its specific heat capacity and thermal conductivity at room temperature reach 0.781 J/(g·K) and 12.3 W/(m·K), respectively. The in-line transmittance of the AlON ceramic sample(1 mm-thick) in wavelength range between 1000-5000 nm is around 80%, with the maximum transmittance of 83.7% at 3.93 μm. ©, 2015, Chinese Ceramic Society. All right reserved.
Wu H.,Shanghai FRP Research Institute Co. |
Liu B.-Y.,Shanghai Maritime University
Gongneng Cailiao/Journal of Functional Materials | Year: 2012
A polyol synthesis method was developed for preparation of amorphous carbon nanoparticles with high specific surface area under ambient atmosphere by the reaction of ferrocene and ammonium bromide in triethylene glycol (TREG) at 200°C. Samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N 2 adsorption-desorption isotherms. It was found that the nanoparticles were complete amorphous and agglomerate together due to the strong surface tension. The amorphous carbon nanoparticles with a diameter of 30-70 nm have a wide size distribution of mesopores with a brunauer-emmett-teller (BET) surface area of 578.68 m 2/g. It was proposed that the dissolved reactants uniformly dispersing in the TREG could react at a molecular level to form uniform carbon nanoparticles.
Zhang J.-X.,Xi'an Jiaotong University |
Xu Z.-Y.,Xi'an Jiaotong University |
Wang B.,Xi'an Jiaotong University |
Qin Y.,Xi'an Jiaotong University |
And 4 more authors.
Wuji Cailiao Xuebao/Journal of Inorganic Materials | Year: 2014
Porous silicon nitride ceramic was fabricated by using α-Si3N4 as raw material and Y2O3 as a sintering additive, with nitrogen pressure of 0.12 MPa, 0.32 MPa and 0.52 MPa. Effects of the nitrogen pressure on grain morphology and mechanical properties of the resultant porous Si3N4 ceramics were characterized by SEM, XRD and flexural strength. With the increasing of nitrogen pressure, sintering shrinkage decreased, with a corresponding increased porosity. Due to the increase of nitrogen pressure, the viscosity of liquid phase increased due to increased N solubility, leading to the low densification in the sintering. Fibrous β-Si3N4 grains were developed in the porous microstructure and the grain morphology and aspect ratio were greatly affected by the nitrogen pressures. The high viscosity of the liquid phase in nitrogen at high pressure led to restraining of the β-Si3N4 nucleation, and preferential growth of β-Si3N4. Due to the formation of elongated β-Si3N4, flexural strength of the porous Si3N4 ceramic was improved by the increase of nitrogen pressure, while decreased with the increase of porosity. The porous Si3N4 ceramics with porosity of 58% and flexural strength of 140 MPa were obtained at the nitrogen pressure of 0.52 MPa.
Xu Z.,Xi'an Jiaotong University |
Wang B.,Xi'an Jiaotong University |
Yang J.,Xi'an Jiaotong University |
Zhao Z.,Shanghai FRP Research Institute Co.
Journal of the American Ceramic Society | Year: 2014
Porous silicon nitride ceramics with various porosities were fabricated by liquid phase sintering of mixtures containing fibrous and equiaxed α-Si3N4 powder with a various content ratios. The effects of the contents of the fibrous α-Si3N4 powder (0%-100%) on the microstructure and mechanical properties of porous Si3N4 ceramics were studied. As the increase of the fibrous α-Si3N4 powder content, both the density of green bodies and the linear shrinkage decreased, resulting in increased porosity due to the inhibited densification by the fibrous Si3N4 particle. XRD analysis proved the complete formation of single β-Si3N4 phase. SEM analysis revealed that the microstructure of the low content of fibrous α-Si3N4 porous ceramics was almost composed of fine elongated β-Si3N4 grains with high aspect ratio while numerous coarse elongated β-Si3N4 grains with low aspect ratio surrounding fine grains were formed as the content of the fibrous α-Si3N4 powder increased. With the increase in content of the fibrous α-Si3N4 powder from 0% to 100%, the porosity changed from 47.8% to 56.6%, and the flexural strength decreased from 146 to 62 MPa correspondingly, indicating a flexural adjustment of the porosity and mechanical properties. © 2014 The American Ceramic Society.
Hu W.,Shanghai FRP Research Institute Co.
Key Engineering Materials | Year: 2014
A rapid sintering densification treatment was performed on the surface of silica ceramic by using hydrogen-oxygen flame. The effects of surface densification processing on the phase composition, microstructure and bending strength of the silica ceramic were studied. Results showed that, after the densification processing, there was no obvious change in the phase composition of the silica ceramic but gradual transition structure happened. The transition structure not only prevents the abrupt structural change from the densification layer to porous layer of the silica ceramic but also guarantees the strong interface bonding between adjacent layers, leading to the improved bending strength. The present densification processing could realize the integrated fabrication of silica material with different density. © (2015) Trans Tech Publications, Switzerland.
Tang S.,Nanjing Research Institute of Electronics Technology |
Shen L.,Shanghai FRP Research Institute Co. |
He B.,Nanjing Research Institute of Electronics Technology |
Li Y.,Nanjing Research Institute of Electronics Technology
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2016
By applying the impedance matching technique and using metallic wire grid electrical tunable unit, the optimization design of electrical tunable was performed for plate joints (or reinforcing rib) in large partitioning dielectric radome. On the premise of guaranteeing mechanical performance of joint structure, the transmission efficiency of optimized mixed dielectric structure containing metallic wire grids improves by about 20% compared with plate joints. In addition, by loading different metallic wire grids, the frequency range of best transmission for mixed structure can be adjusted, thus can be used to develop radomes of various frequency. This provides a novel technological pathway to design high-performance large dielectric radomes. © 2016, BUAA Culture Media Group Ltd. All right reserved.
Shen L.X.,Shanghai FRP Research Institute Co.
Materials Science Forum | Year: 2015
With the process optimizing, electromagnetic performance designing, structural strength/stiffness checking and testing, a cost-effective and environment-friendly approach to manufacturing a submarine radome and its related products at low cost is introduced in this article: The submarine radome is made of an epoxy-matrix composite reinforced with E-glass fabric through the vacuum infusion and heating cure processing. © (2015) Trans Tech Publications, Switzerland.