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Ma S.,Beijing Materials University | Ma S.,Beijing Tongda Refractory Technologies Co. | Huang Z.,Beijing Materials University | Gao C.,Beijing Tongda Refractory Technologies Co. | And 2 more authors.
Key Engineering Materials | Year: 2014

Super-grade bauxite, pure silicon carbide, andalusite and metal silicon were used as the raw materials to produce plastic phase mullite-SiC bricks. By analysis of the microstructure, physical and chemical properties, it proves that the introduction of metal plastic phase can improve the properties of bricks, such as lower porosity, higher cold crush strength, and wearing resistance. It also can improve the toughness, and effectively relieve the thermal and mechanical stress when using in cement kilns. By analysis of the comparison with MA spinel bricks and ordinary mullite-SiC bricks, the plastic phase mullite-SiC bricks have good thermal shock resistance and lower thermal conductivity. The result shows that the bricks can replace MA spinel bricks using in the transition zone of cement kilns and realizes the aim of saving energy and a long service life. © (2015) Trans Tech Publications, Switzerland.


Cao S.,University of Science and Technology Beijing | Li Y.,University of Science and Technology Beijing | Sun J.,University of Science and Technology Beijing | Zhang H.,University of Science and Technology Beijing | And 5 more authors.
Key Engineering Materials | Year: 2016

In this article, we study the high temperature creep properties of Al2O3∼78% high-alumina bauxite (the mass fraction of Al2O3 in the raw ore is about 78%). The results indicate that the Al2O3∼78% high-alumina bauxite at 1100°C/50h, 1200°C/50h and 1300°C/50h creep ratio is -0.266%, -1.589% and -4.088% respectively. X-ray diffraction shows that the main crystal phase of Al2O3∼78% high-alumina bauxite is corundum phase after high temperature sintered. At 1100°C and 1200°C, TiO2 is an independent existence as the rutile phase, the aluminum titanate phase is formed by the reaction of rutile and corundum at 1300°C. SEM analysis results indicate that with the increase of temperature, more corundum particles covered by liquid phase, the direct connections between corundum particles are broken and the creep resistance is greatly reduced. The creep curve fitting after 25 hours indicate that the samples enter the steady-state creep stage and the creep property shows linear relations at three different temperatures. The results of steady-state creep stage reflect the high-temperature creep properties of Al2O3∼78% high-alumina is poor. The poor performance of creep resistance unable to satisfy the industrial demand and is inadequacy for being the low creep refractories. © 2016 Trans Tech Publications, Switzerland.


Sun G.S.,Wuhan University of Science and Technology | Gu H.Z.,Wuhan University of Science and Technology | Fang Y.N.,Wuhan University of Science and Technology | Feng Y.S.,Beijing Tongda Refractory Technologies Co.
Advanced Materials Research | Year: 2014

The lightweight of refractory is propitious for energy-saving and emission-reduction of the high temperature refractories industry and sustainable development of the refractories resource. This paper researches on properties of the lightweight mullite aggregate which is prepared by two kinds of bauxites and aluminum dross and fired at 1400°C, 1450°C, 1500°C, 1600°C for 1h. The result shows that, (1) The minimum density of grade I bauxite is 2.11g/cm3 which is prepared by adding 50wt% aluminum dross and fired at 1600°C; (2) The minimum density of grade III bauxite is 1.54g/cm3 which is prepared by adding 50wt% aluminum dross and fired at 1450°C. © (2014) Trans Tech Publications, Switzerland.


Li Y.,University of Science and Technology Beijing | Zhang J.,University of Science and Technology Beijing | Zhang J.,Beijing Tongda Refractory Technologies Co. | Li J.,University of Science and Technology Beijing | And 4 more authors.
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2013

The Al-Al2O3 composite sliding gate with a transient phase (Cr2O3) was prepared with tabular alumina, fused white corundum, fine powder of Cr2O3, metal Al as starting materials and phenolic resin as a binder. The results show that Cr2O3 is unstable when sintered under carbon burial at 1450°C for 6 h. It can transform to Cr3C2, Cr7C3 or Al8Cr5 intermetallic compound, and its existing state depends on the Cr2O3 quantities. The composite sliding gate contains (Al2OC)1-x(AlN)x, Al4O4C, Cr3C and Cr7C3 as reinforcement phases and Al8Cr5 as a plastic phase. It is indicated that the main composition of sliding gate is Al-Al4O4C-Al2O3 at Cr2O3 of 3% (in mass, the same below); the main composition of sliding gate is Al8Cr5-(Al2OC)1-x (AlN)x-Al2O3 at Cr2O3 of 6%, 9% and 12%, respectively; and the main composition sliding gate is Al8Cr5-Al2O3 at Cr2O3 of 15%. Al8Cr5-(Al2OC)1-x (AlN)x-Al2O3 system has the superior physical properties at Cr2O3 of 6%.


Ma S.,University of Science and Technology Beijing | Li Y.,University of Science and Technology Beijing | Sun J.,University of Science and Technology Beijing | Xia W.,Beijing Tongda Refractory Technologies Co.
Advanced Materials Research | Year: 2011

Sintered magnesia with different particle sizes, fused MgAl 2O4 and FeAl2O4 were used as the raw materials. FeAl2O4 is added in MgO-MgAl2O4 bricks at different ratios to gradually replace MgAl2O4. After the raw materials were molded and sintered at the tunnel furnace with the temperature 1 530°C for 10 hours, the MgO-MgAl2O 4-FeAl2O4 bricks could be made. After the analysis of the phase composition, microstructure and routine performance of the specimens, the influence by adding FeAl2O4 to the samples on the properties such as thermal shock resistance, adhesion strength of kiln crust are discussed as the key point. The result shows that the addition of FeAl2O4 has no evidently influence on the apparent porosity and volume density. The cold compressive strength of the samples reduces gradually with the addition of FeAl2O4, and it decreases obviously when the amount of FeAl2O4 is more than 8%. When the addition of FeAl2O4 is 5% FeAl 2O4 in the MgO-MgAl2O4-FeAl 2O4 bricks, MgAl2O4 and FeAl 2O4 can combine each other's advantages. The thermal shock resistance not only decreased obviously but the adhesion strength to kiln crust is increased. © (2011) Trans Tech Publications, Switzerland.


Tong L.,Beijing Tongda Refractory Technologies Co. | Luo H.,Beijing Tongda Refractory Technologies Co. | Zhang L.,Beijing Tongda Refractory Technologies Co. | Zhan H.,Beijing Tongda Refractory Technologies Co.
China's Refractories | Year: 2014

A single phase Na - X zeolite was synthesized from pretreated oil shale ash by alkaline fusion and hydrothermal treatment. Effects of the NaOH concentration, crystallization time and temperature on the formation of Na - X zeolite were studied in detail. The single phase Na - X zeolite powders can be prepared by alkaline fusion of pretreated oil shale ash at 600 °C for 1 h , and crystallization at 80 -100 °C for 8 - 10 h with NaOH concentration of 3 - 3. 5 mol • L-1. Na - A zeolite appears when decreasing NaOH concentration , crystallization time or temperatuzre , and an unnamed zeolite emerges when prolonging crystallization time or raising crystallization temperature. SEM micrographs suggest that the aggregates of Na-X zeolite particles have perfect dispersity and uniform granular with about 1. 5 μm in size , and most of the Na - X zeolite crystals display a regular octahedral structure with the size of about 500 nm. The specific surface area of the powders with single Na - X zeolite phase reaches the maximum value of 488. 163 2 m2g-1, larger than that of multiple zeolite powders.


Yang H.,University of Science and Technology Beijing | Li Y.,University of Science and Technology Beijing | Xia W.,Beijing Tongda Refractory Technologies Co. | Li Y.,Beijing Tongda Refractory Technologies Co.
Advanced Materials Research | Year: 2012

The composite samples using flint clay, andalusite and silicon carbide as starting material are made from the proportion of 35:60:5, 45:50:5, 55:40:5, 65:30:5 respectively. The samples are sintered at 1200°C, 1300°C, 1400°C, 1450°C and 1500°C holding 4hrs separately. Both microstructure and mechanism of oxidation were analyzed by XRD and SEM. The results show that the samples have good resistance against oxidization below 1500°C, only the sample of fourth formula perform excellent and have the thinnest oxidation layer between all the formulas at 1500°C. © (2012) Trans Tech Publications.


Sun Y.,University of Science and Technology Beijing | Li Y.,University of Science and Technology Beijing | Cao S.,University of Science and Technology Beijing | Zhang H.,University of Science and Technology Beijing | And 3 more authors.
Key Engineering Materials | Year: 2016

High temperature creep properties of Al2O3-SiO2 ore (65% Al2O3 by mass percentage, abbreviation for Al2O3∼65) was studied. The results show that the creep rates at 1300°C × 50h, 1400°C × 50h and 1500°C × 50h were -0.89%,- 1.75%, - 5.76%, respectively. At 1300°C, ore has good creep resistance. As the temperature increases, the high temperature creep resistance of Al2O3 ∼ 65 bauxite ore is significantly reduced. Creep process can be divided into two stages: when the time t < 30h, the sample are in the densification process; after 30 hours, the creep properties show that the relationship between time and the creep rate is linear. At 1300°C, the absolute value which is the slope of the linear relationship is smaller, exhibited an excellent high-temperature creep resistance. The loading softening-temperature of Al2O3 ∼ 65 bauxite ore is 1343°C. The Sample phase and microstructure are characterized by X-ray diffraction and scanning electron microscopy (SEM). The results show that mullite reticular is formed in sample at 1300°C; at this point, TiO2 mostly exist as Rutile. At 1400°C and 1500°C, TiO2 mostly exist as Aluminum titanate, Corundum phase portion into mullite. © 2016 Trans Tech Publications, Switzerland.


Zhang H.,University of Science and Technology Beijing | Li Y.,University of Science and Technology Beijing | Sun J.,University of Science and Technology Beijing | Cao S.,University of Science and Technology Beijing | And 5 more authors.
Key Engineering Materials | Year: 2016

Specimens were prepared by using iron-rich magnesia and high-pure magnesia as the main starting materials, and introducing fused corundum of 3%(in mass), 6%, 9%, 12%, 15% respectively and sintered at 1420°C. The samples were characterized by XRD and SEM. The results show that in-situ synthesized composite spinel solid solution were formed in the reaction between iron-rich magnesia and fused corundum. Iron oxides play a key role on the formation of spinel solid solution. When fused corundum was added in a certain particle size, the material showed core-shell structure. Outer layer of core-shell structure were spinel solid solution and the inside were corundum. These core-shell structure make the synthesis of spinel solid solution bonded periclase material at low temperature happen. © 2016 Trans Tech Publications, Switzerland.


Chen J.H.,University of Science and Technology Beijing | Li B.,Beijing Tongda Refractory technologies Co. | Zhan H.S.,Beijing Tongda Refractory technologies Co. | Su J.D.,Beijing Tongda Refractory technologies Co. | And 2 more authors.
Applied Mechanics and Materials | Year: 2014

In this paper, we added silicon nitride in the samples of common bauxite and the bauxite with high potassium and sodium oxide content, treated them at the high temperature of 1,400°C and 1,500°C, and then conducted analysis with XRD, SEM and EDS. The results are as follows: After adding β-Si3N4 in sintered bauxite, the partial pressure of oxygen in the composite materials will be reduced, the decomposition and volatilization of compounds with high partial pressure of oxygen (such as potassium oxide and sodium oxide) will be promoted, the content of these compounds in the bauxite will be lowered, and the hazards of the compounds with low melting point will be weakened; meanwhile, with the reduction of potassium, sodium and iron oxide, the lattice of alumina will be activated, the β-Sialon phase will be easily formed and the high temperature properties of sintered bauxite materials will be strengthened. © (2014) Trans Tech Publications, Switzerland.

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