Luoyang, China
Luoyang, China

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Wang J.,University of Science and Technology Beijing | Li Y.,University of Science and Technology Beijing | Zhu X.,University of Science and Technology Beijing | Bo J.,Sinosteel Refractory Co. | And 2 more authors.
Advanced Materials Research | Year: 2011

The reaction between SiC and AlF3 has been investigated in CO atmosphere at high temperature. Experimental results are shown that the reaction intensity between SiC and AlF3 is accelerated with the rise of temperature. At the temperature of 950°C (aluminum electrolytic operation temperature is 935±15 °C), the reaction intensity of SiC and AlF 3 is not high and the major reaction products are SiF4 gas and Al4C3; Al4C3 occur severe hydration at room temperature which leads to the pulverization of specimens. The unexpected cells stop should try to be avoided or reduced during the usage of Si3N4-bonded SiC sidewall brick in aluminum electrolysis cells because of Al4C3 existents possibly. © (2011) Trans Tech Publications, Switzerland.


Zhu X.,University of Science and Technology Beijing | Li Y.,University of Science and Technology Beijing | Wang J.,University of Science and Technology Beijing | Zhai Y.,China Nuclear Power Engineering Co. | And 2 more authors.
Key Engineering Materials | Year: 2012

α-Si 3N 4 possesses excellent sintering activity. Si 3N 4 powder is always synthesized by silicon nitridation, the intensive reaction heat is difficult to diffuse, which leads to high reaction temperature and conversion of α-Si 3N 4 to β-Si 3N 4, thus α-Si 3N 4 is difficult to be obtained. While flame-isolation nitridation shuttle kiln has much larger furnace volume to conduct reaction heat (effective volume: 11500×4190×1684mm), and it owns homogeneous temperature field and stable heat conduction which benefits the preparation of α-Si 3N 4. Thermodynamic analysis of Si-N system is shown that Si 3N 4 can be formed by two formats: direct nitridation of Si(s) and indirect nitridation of SiO(g); to ensure completely nitridation, the particle size of silicon powder should be less than 88μm. With polysilicon cutting waste as starting materials, both reactive α-Si 3N 4 and SiC mixed powder were successfully prepared in flame-isolation nitridation shuttle kiln. Because of the gas-gas reaction between SiO(g) and N 2(g), α-Si 3N 4 is fiber-like and in favor of processing high quality Si 3N 4-based materials. © (2012) Trans Tech Publications.


Ren F.,Henan University of Science and Technology | Ren F.,Sinosteel Refractory Co. | Ren F.,University of South Florida | Ma Z.,Henan University of Science and Technology | Tian B.,Henan University of Science and Technology
Journal of Ceramic Processing Research | Year: 2014

Polyurethane foam was used as a precursor for fabricating SiC-based ceramic foam filters. Two recoating slurry processes were adopted to enhance the strength of ceramic foam. One was the recoating slurry of stoved green body and another was the recoating slurry of pre-sintered green body. The differences in weight increase and thermal shock resistance of ceramic foams fabricated by the two recoating slurry processes were investigated. The effects of pre-sintering temperature on weight increase and thermal shock resistance are discussed. Thermal shock resistance of ceramic foams fabricated by two recoating slurry processes is lower than that by the single coating slurry process. Compared with recoating slurry of pre-sintered green bodies, with the same slurry, the weight increase of ceramic foams fabricated by recoating slurry of the stoved green bodies is less, but the number of thermal cycles to failure is much higher. For ceramic foams fabricated by recoating slurry of presintered green bodies with the same slurry, the weight increase and the number of thermal cycles to failure decreased with the pre-sintering temperature. © 2004 Hanyang University. All right reserved.


Yu R.,Henan University of Science and Technology | Du P.,Henan University of Science and Technology | Zhou N.,Henan University of Science and Technology | Li C.,Sinosteel Refractory Co.
China's Refractories | Year: 2013

In order to enhance performance of pre-cast shapes of alumina based castables, the present work explored the approach of forming in-situ bonding phases by incorporating Si powders and then heating in carbon embedded atmosphere. Using tabular alumina as aggregates, tabular alumina, SiC powders, Si powders, calcium aluminate cement, microsilica and ultrafine a-Al 2O3 powders as matrix, alumina based ultra low cement (ULC) castables were prepared. Influences of Si powder addition at 0, 4%, 6%, 8% and 10% (in mass) on regular properties, cold modulus of rupture (CMOR), hot modulus of rupture (HMOR), thermal shock resistance (TSR) and microstructure of the castables after carbonization were investigated. After incorporation of Si powders and carbon embedded heating, the in-situ mullite and nonoxide phases such as SiAlON and SiC can be formed by oxidation, nitridation or carbonization reaction. HMOR and TSR of the castables with in-situ nonoxides bonding are obviously improved. After carbon embedded heating, the HMOR at 1 400 °C increases from 1. 6 MPa to 8. 3 MPa, and the residual CMOR ratio after thermal shock increases from 64. 9% to 137. 9% when Si addition increases from 0 to 10%.


Wang J.,University of Science and Technology Beijing | Li Y.,University of Science and Technology Beijing | Zhu X.,University of Science and Technology Beijing | Zhai Y.,University of Science and Technology Beijing | And 2 more authors.
Advanced Materials Research | Year: 2011

The reaction between Si3N4 and AlF3 had been investigated in CO atmosphere at high temperature. Experimental results are shown that the reaction between Si3N4 and AlF3 is accelerated with the rise of temperature. At the temperature of 950 °(aluminum electrolytic operation temperature is 935±15 °), there is obvious reaction between Si3N4 and AlF3; under this experiment condition, Si3N4 converted into Si2N2O partly, Si2N2O can also react with AlF3. The reaction products of Si3N4 with AlF3 are SiF4 (g) and AlN, while the reaction products of Si2N2O with AlF3 are SiF4 (g) and Al8O3N6. So, during the usage of Si 3N4-bonded SiC sidewall brick in aluminum electrolysis cells, the content of Si3N4 in Si3N 4-SiC block are reduced which can bring down the corrosion of aluminum electrolyte to the sidewall materials. © (2011) Trans Tech Publications, Switzerland.


Zhang D.,Xi'an University of Architecture and Technology | Zhang D.,Sinosteel Refractory Co. | Jiang M.,Xi'an University of Architecture and Technology | Xiao G.,Xi'an University of Architecture and Technology | Huang S.,Xi'an University of Architecture and Technology
China's Refractories | Year: 2012

Magnesia chrome bricks were prepared with fused MgO - Cr2 O3 synthesized material, fused magnesite and chrome ore as main starting materials. Nano-Al203 was added into refractories (2%, 4% and 6% in mass) substituting for A12O3 micropowder. After mixing and shaping, the bricks were fired at 1 550 ° C, 1 600° C, 1 650 t and 1 750 t, respectively. The microstruc-ture, sintering property, mechanical properties, thermal shock resistance and slag resistance of the specimens with the addition of nano-Al203 were investigated. The results indicate that the performance of brick with 4 mass% of nano-Al203 is greatly improved after firing at 1 650° C.


Wang L.,Xi'an University of Architecture and Technology | Wang L.,Sinosteel Refractory Co. | Jiang M.,Xi'an University of Architecture and Technology
China's Refractories | Year: 2012

High temperature oxidation behavior of two kinds of nitride bonded SiC based refractories was investigated at 1100-31500 °C by means of X-ray diffractometer, scanning electronic microscopy and thermogravimetry. The results show that: (1) with the temperature increasng, the oxidation mass increment rate of the specimen ncreases first and then decreases, and oxidation passivation occurs; (2) the oxidation resistance of SiAlON bonded SiC refractories is superior to that of Si 3N 4 bonded SiC refractries; (3) high temperature oxidation results in the increase of compressive strength at room temperature of SiC based refractories compared with specimen before oxidation; the compressive strength of SiAlON bonded SiC specimens oxidized at high temperatures decreases with the increase of the temperature as a result of formation and burst of surface bubble, while the decrease of compressive strength of Si 3N 4 bonded StC specimens oxidized at high temperatures is owing to the increase of the consistency of net-like crack associated with cristob-alite transformation during cooling.


Jia T.,Luoyang Institute of Science and Technology | Jia T.,Henan Polytechnic University | Min Z.,Luoyang Institute of Science and Technology | Cao J.,Henan Polytechnic University | And 4 more authors.
Journal Wuhan University of Technology, Materials Science Edition | Year: 2015

SnS2 nanoflakes were successfully synthesized via a simple hydrothermal process. The as-prepared SnS2 samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherms, and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activities of the as-prepared SnS2 nanoflakes under visible light irradiation (λ>420 nm) were evaluated by the degradation of rhodamine B (RhB). The effect of hydrothermal temperatures on the photocatalytic efficiency of as-prepared SnS2 nanoflakes was investigated. The experimental result showed that SnS2 nanoflakes synthesized at the temprature of 160° had higher photocatalytic efficiency and good photocatalytic stability. © 2015, Wuhan University of Technology and Springer-Verlag Berlin Heidelberg.


Xu D.,Zhengzhou University | Ye G.,Zhengzhou University | Zhu L.,Zhengzhou University | Liu L.,Sinosteel Refractory Co. | Huang Y.,Zhengzhou University
Proceedings UNITECR 2011 Congress: 12th Biennial Worldwide Conference on Refractories - Refractories-Technology to Sustain the Global Environment | Year: 2011

Mullite was prepared with mechanical activation using gibbsite-amorphous silica (white carbon black), boehmite-amorphous silica and alumina-amorphous silica as starting materials respectively. The influence of high-energy milling on crystalline change of the starting materials, and inception and complete temperatures of mullite formation was investigated using XRD. The mechanisms of mechanical activation for enhancing formation of mullite were briefly discussed. Different starting materials were compared in amorphization behavior during mechanical activation and mullite formation during heat treatment.

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