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Zhou B.-Y.,University Of Science And Technology Liaoning | Li Z.-J.,University Of Science And Technology Liaoning | Wu F.,University Of Science And Technology Liaoning | Qu D.-L.,University Of Science And Technology Liaoning | And 2 more authors.
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2014

Thermal decomposition of cubic magnesite blocks with the side length of 20 mm, 30 mm, 40 mm and 50 mm were investigated by TG. The results indicate that under the same conversation ratio, decomposition activation energy increases with size of block magnesite increasing. The relation between block size (L=20-50 mm) and activation energy meets the formula: E=4.795×L+34.070(kJ/mol). Thermal decomposition of magnesite block is controlled by different mechanism functions at different decomposing stages: At earlier stage, 3D mould with n=2 controlled by Anti-Jander's formula is the most probable mechanism function. Decomposition equation is dα/dT=6.111×1010×β-1exp [(4.098-0.577×L)×T-1](1+α)2/3 [(1+α)1/3-1]-1; In the middle stage, random nucleation and subsequent growth models with n=3(Code: AE3) controlled by Avrami-Erofeev formula is the most probable mechanism function. Decomposition equation is dα/dT=1.422×109×β-1exp [(4.098-0.577×L)×T-1](1-α) [-ln(1-α)]-2; in the later stage, random nucleation and subsequent growth models with n=3/2 controlled by Avrami-Erofeev formula is the most probable mechanism function. Decomposition equation is dα/dT=2.477×109×β-1exp [(4.098-0.577L)×T-1](1-α) [-ln(1-α)]-2. The study provides a theoretical basis for the planning of block magnesite production MgO process. Source


Zhou B.-Y.,University Of Science And Technology Liaoning | Li Z.-J.,University Of Science And Technology Liaoning | Wu F.,University Of Science And Technology Liaoning | Qu D.-L.,University Of Science And Technology Liaoning | And 2 more authors.
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2014

Block magnesite were calcined by the way of hot press sintering, the crystallinity of the samples calcined under 1400 ℃×2 h at 1 MPa, 5 MPa and 9 MPa were studied. The results show that at P=1 MPa, the particle clearance is larger, the liquid phase distribution is inhomogeneous and the migration rate of grain boundary in all directions are inhomogeneous and most of periclase grains are subhedral crystals and have inferior degree of crystallinity. At P=5 MPa, periclase grains in samples are arranged closely, the liquid phase distribution is uniform, periclase grains have the highest degree of crystallinity and the grains growth are best. At P=9 MPa, because of the sample structure producing stress and strain, grains bring out deformation, damage and fracture phenomenon and periclase grains have inferior degree of crystallinity with the worst growth of grains. ©, 2014, Chinese Ceramic Society. All right reserved. Source


Zhou B.-Y.,University Of Science And Technology Liaoning | Li Z.-J.,University Of Science And Technology Liaoning | Wu F.,University Of Science And Technology Liaoning | Qu D.-L.,University Of Science And Technology Liaoning | And 2 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2015

Using a high temperature furnace to calcining block magnesite, periclase particles densification behaviour was studied in the process of block magnesite sintering. The results show that the periclase particles densification process at the early stage of block magnesite sintering includes four stages: positive ions and negative ions polarization and gravitation increasing at particle surface, so that the spacing of the particles decreased; Occuring of point contact among particles and particles agglomeration; Formation of surface contact among particles causes the decreasing of the clearance among particles; Forming sintering neck and the densification degree increasing. The volume of the pseudomorph of magnesite has important effects on the densification behaviour of the particles. When the temperature is in the range of 1150-1200℃, the volume of the pseudomorph particles contracts, leading the decrease of the coordination numbers and the specific surface area of the particles. Sintering densification is impeded and appears slowing phenomenon of the densification process, which is a significant difference between block magnesite and powder magnesite sintering. In uniform heating sintering process, sintering activation energy is different in different temperature range. When the temperature is in the range of 1000-1110℃, Q=412.368 kJ/mol, and for the temperature range of 1110-1230℃, Q=473.990 kJ/mol. When the temperature is within 1230-1300℃, Q=385.266 kJ/mol. As the temperature increases, The sintering densification rate of periclase particles is increased and then decreased. ©, 2015, Editorial Office of Transactions of Materials and Heat Treatment. All right reserved. Source


Wu F.,University Of Science And Technology Liaoning | Zhou B.,University Of Science And Technology Liaoning | Li Z.,University Of Science And Technology Liaoning | Qu D.,University Of Science And Technology Liaoning | And 2 more authors.
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2014

The sintering process of block magnesite at a deadweight pressure was simulated in a hot-pressing sintering process to reveal the densification behavior of magnesite under a hot-pressing condition,. The results show that the periclase particles are densified promptly during the heating process at a certain heating rate, and the rearrangement rate of periclase particles increases with increasing the deadweight pressure, thus reducing the duration and the temperature for the densification. In the heat preservation stage, the samples are densified due to the plastic flow and diffusion, respectively. In the plastic flow stage, the rate of densification increases with increasing P/η, leading to the decrease of the duration of plastic flow. In the diffusion stage, the porosity of the sample decreases but the grain size increases gradually with increasing the duration of preservating temperature. The elastic modulus/deformation caused by stress relief and the decreasing rate of the relative density of the samples increase with the increase of the deadweight pressure during the cooling process. The optimum density and degree of crystallinity in periclase phase can be obtained at the deadweight pressure of 5 MPa. ©, 2014, Chinese Ceramic Society. All right reserved. Source


Luan X.,University Of Science And Technology Liaoning | Zhou B.-Y.,University Of Science And Technology Liaoning | Li Z.-J.,University Of Science And Technology Liaoning | Wu F.,University Of Science And Technology Liaoning | And 2 more authors.
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2015

The block magnesite was calcined using high temperature electric furnace. The grains growth and densification behavior of periclase at last sintering stage of block magnesite (1600-1800℃) were investigated. The results show that with the temperature increasing, the grain boundary moves rapidly, the rate of pore "convergence-exclusion" and the moving speed of the grain boundaries to the curvature center increase, which cause particles densification rapidly and periclase grains grow significantly. During 1600-1700℃, grain boundary diffusion is the dominant mechanism of controlling densification, the activation energy of grain growth is 1.382×103 kJ·mol-1 and crystallization is the main way of grains growth; At the period of 1700-1800℃, volume diffusion is the dominant mechanism of controlling densification, the activation energy of grain growth is 1.164×103 kJ·mol-1 and glomerocryst grow is the main way of grains growth. Accompanying temperature increases, the activation energy of grain growth decreases, and the rate of grain growth increases. ©, 2015, Rengong Jingti Xuebao/Journal of Synthetic Crystals. All right reserved. Source

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