Papers by Author: Yu Cheng Yin

Abstract: Calcium aluminate cement (CAC) and hydratable alumina (HA) are the most widely used binders for refractory castables. Nevertheless, CAC as the binder for refractory castable generates some low melting point phases when coupled with SiO₂, which deteriorate the high temperature performance of refractory castables. Although hydratable alumina (HA) bonded castables overcome the drawbacks of CAC bonded ones, they demand a longer mixing time and higher water contents due to HA's high specific surface area, as well as increasing the shear stress and viscosity of HA bonded castables. Therefore, in this paper, CAC combined with HA was used as the binder for corundum- spinel castables to obtain better performance. Sodium tripolyphosphate (STPP), dispersing alumina (ADS) and polycarboxylate ether dispersant (FS60) were used as dispersants, and their effects on the rheological behaviors of CAC-HA bonded corundum-spinel castables suspensions had been investigated. According to the viscosity-shear rate and stress-shear rate curves of suspensions with different dispersants, it was suggested that STPP, ADS, FS60 were all helpful for rheological performance of suspensions. Suspensions achieved much better rheological behavior with 0.3 wt.% of STPP, 1.0wt.% of ADS and 0.1wt.% of FS60, respectively. Suspensions with ADS and FS60 presented to be pseudo plastic fluid, which was helpful for the installation process of CAC-HA bonded corundum-spinel castables. And FS60 could simultaneously impart electrostatic and steric stabilization to the given suspension. Considering the actual rheological performance of CAC-HA bonded corundum-spinel castables, FS60 was much better than ADS.

Abstract: The hydrolysis process of a silane coupling agent KH-570 in deionized water, ethanol, and their mixed medium was characterized by continuous online conductivity testing, respectively. In addition, hydration products of KH-570 in different mediums were analyzed by Fourier transform infrared spectroscopy (FTIR) to correlate with its hydration process. Results indicate that the KH-570 hydrates fast and to a large degree in deionized water, but at the same time, its hydrolysis products condensate together with increasing rate during the hydration process. However, the introduction of ethanol could significantly reduce the degree of the condensation. The hydrolysis degree of KH-570 was relatively large in a mix medium of deionized water and ethanol with the mass ratio of 5:1, and condensation degree of hydrolysis products was also small. KH-570 would hydrate quickly in a hydration medium of colloidal silica, and subsequently, its hydration products would directly react with colloidal silica, which could accelerate the formation of Si-O-Si three-dimensional network structure, and thus promoting the setting of colloidal silica. The hydration of 0.9wt% KH-570 in colloidal silica could be sufficient, and correspondingly, its effect on the coagulation of colloidal silica was better.

Abstract: In order to make sure whether the Cr₂O₃ would change to Cr⁶⁺ during the service, 4wt % Cr₂O₃ was added to the calcium aluminate cement bonded Al₂O₃-SiC-C castables for blast furnace main trough, then the phase evolution was analyzed through thermodynamic calculation done by Factsage 6.1 under air atmosphere, which is close to its real work conditions. Calculations results show that Cr₂O₃ was reduced to Cr₃C₂ with low air amount, with amount of air increase, Cr₃C₂ transformed to Cr₄C and Cr₅Si₃ successively, and turned to Cr₂O₃ at last with much more air, and no compound including Cr⁶⁺ was founded.

Abstract: In order to determine the torsion strength of non-metal materials at ambient and high temperature, a kind of equipment with inductive heating, infrared thermometer and torque loading by mechanical electrical rider was development. This equipment has advantages such as quick heating, accurate temperature test and controlling, easy controlling and continues of torque loading and test atmosphere can be controlled. The torsion strength of fireclay bricks with sample size of 40 mm × 40 mm × 230 mm, were tested separately at room temperature, 800°C, 1000°C, 1100°C and 1200°C, using this equipment. Results indicated that for the same batch of samples, the torsion strength determined by this equipment has good consistency, and mean while, it was found that the torsion strength decreased with the increase of test temperature obviously. In additional, developed equipment could be used for the determination of torsion creep at high temperature, the highest temperature of fracture under certain torque during the heating process, torque cycle fatigue failure of materials and so on.

Abstract: In order to overcome the disadvantages of thermal expansion measurements using small samples, such as 10mm×50mm, for refractories with aggregates larger than 20mm, a new apparatus and method were developed by Wuhan University of Science and Technology for the thermal expansion determination of refractories using large samples. Thermal expansion determination of large refractory samples, such as 40mm×40mm×160mm, can be finished by this new apparatus up to 1600°C. During the process of thermal expansion measurement by this new apparatus, the temperature difference along the length of large refractory sample with large aggregates can be observed by three thermocouples, which were inserted into sample. Determination was done when the whole sample is the same temperature or in the permissible temperature range. Results comparison between this new apparatus and calibrated model 1161V dilatometer produced by ANTER Corporation show that developed apparatus has good accuracy.