Papers by Keyword: Temperature Gradient

Abstract: Large temperature gradient was introduced to improve the removal rate of metal impurity in silicon ingot during direction solidification. The concentration of metal impurities in the silicon ingot with a large temperature gradient is 0.96 ppmw. The solidification time is reduced by 20% due to the fast speed of crystal growth improved; meanwhile the purity is increased by 64%.

Abstract: International Maritime Organization (IMO) has revised MARPOL Annex VI to accelerate the reduction of exhaust emission. MARPOL already reduce the maximum sulfur content to 0.1% inside emission control area (ECA) since January 2015. To fulfill that requirement, the ship operator should switch the fuel to marine gas oil (MGO) before entering ECA. The change-over operation could induce several potential problems because of many differences between two fuel’s properties. The potential problems can be avoided by considering both fuel specification, fuel and sulfur concentration, as well as temperature gradient of mixed fuel using Ubbelohde diagram.

Abstract: The off-axis solution growth of 4H-SiC was studied focusing on the morphological instabilities by using conventional TSSG technique. The morphology depends strongly on the crystalline polarity, and that on Si surface can be characterized by wandering while that on C surface is characterized by strong step-bunching. By raising the temperature gradient, step bunching on Si surface is considerably suppressed which can be consistent to the constitutional super cooling scheme. However, C surface exhibits strong step bunching as the temperature gradient increase. These behaviors can be explained by the difference in Ehrlich-Schwoebel barrier and diffusion behavior of adatoms.

Abstract: Temperature and moisture substantially affect the water elimination procedure, occurring in the drying stage, of ceramic blocks used in building construction. In the present work, a modeling of the thermal gradients and moisture content during the drying process of red clayey ceramic blocks was analyzed using computer simulation by means of Mathematica^® software program. Results of two-dimensional thermal gradients and variation of moisture content were predicted. This revealed that regions next to the vertices of prismatic ceramic blocks are more susceptible to structural damage due to development of cracks and deformations.

Abstract: In order to gain control over hard X-ray (over 30 keV), we have considered the X-ray diffraction in Laue geometry (over 30 keV) from a single crystal of quartz influenced by the temperature gradient. It was experimentally proved that the intensity of the reflected beam can be increased up to 35 times if the X-ray energies are 30 keV and keV for reflecting atomic planes () depending on the value of the temperature gradient. As the temperature gradient increases, the focus moves closer to the crystal and the focal spot shrinks in the diffraction plane.

Abstract: The behavior of the interference absorption coefficient of X-rays in Laue geometry depending upon the disposition of diffraction vector and temperature gradient vector in the perpendicular direction to the reflecting atomic planes family was experimentally studied. The study was carried out for the different thicknesses of quartz single crystal for atomic planes. It was shown that in the case of anti-parallel disposition of the diffraction vector and temperature gradient vector the absorption coefficient of X-rays sharply decreases with the increase of temperature gradient and in the case of the parallel disposition of the diffraction vector and the temperature gradient vector the absorption coefficient firstly increases and then decreases. The theoretical calculation corresponding to the experiment conditions have been done. The physical explanation of the obtained experimental results has been made. The obtained results are in good correspondence with the experiment.

Abstract: A three-dimensional model of CMSX-6 superalloy coupons was built in the paper, temperature field was calculated with software ProCAST. The temperature values of coupons were indicated from the measurement at the rate of 3 mm min^-1 withdrawal velocity during directional solidification process, and the temperature gradient of different location of the coupons were calculated. It turned out that: the simulated results and the measured results are in good agreement; due to the different medial and lateral affected by radiation, isotherms showed sloped distributions in the process of the withdrawal; the temperature gradient of the measured positions in the coupons which are 10 mm, 50 mm, 100 mm, 150 mm far from the copper chill, are 8.0 Kmm^-1, 3.0 Kmm^-1, 2.5 Kmm^-1, 1.8 Kmm^-1 respectively.

Abstract: Fused cast Zirconia-Alumina-Silica material (AZS) is the key refractory to glass furnace. In order to reduce production cost and optimize production process, the influences of riser position and riser size on temperature gradient, solidification time, residual melt modulus, solidification fraction, and cooling rate of cast system were studied by the finite element simulation method according to the brick size of 600 mm × 400 mm × 300 mm. It turned out that it would be more efficient in feeding when riser located at the center of maximum surface of a brick or when the height of riser is 250 mm-270 mm, while the volume ratio of brick to riser is 2.95-2.74, on condition that the size of riser upper surface is 450 mm × 450 mm and the bottom 150 mm×150 mm.

Abstract: This paper deals with the experimental measurements and computer analysis of the development of heat of hydratation and shrinkage in a large-scale model of a reinforced concrete slab. A large-scale model was built in situ to experimentally verify the design of the reinforcement, with the aim of preventing the formation of cracks in slab. The model represents a four times four meters cut of a slab structure of a thickness of 1.6 m. Bars in the horizontal direction of the slab were extended behind the concrete body and welded to a steel frame, which simulated the anchorage of horizontal reinforcement of a continuous slab. Before casting, the reinforcement bars were fitted with vibrating wire strain gauges and with resistance gauges for monitoring the strain, as well as with temperature sensors for determining the temperature field caused by heat of hydration. According to the needs of the experiment, the structure was modelled in GiD 11.0 software and calculated in the AtenaWin program. The experimental results and the results obtained by a numerical analysis were compared.

Abstract: This paper deals with the experimental measurements and computer analysis of the development of heat of hydration and shrinkage in a large-scale model of a reinforced concrete wall with a base slab. A large-scale model was built in situ to experimentally verify the design of the reinforcement, with the aim of preventing the formation of cracks in a long massive wall located on a base slab. The model represents a four meter cut of a long wall structure (thickness of 1.6 m) together with its base slab (thickness of 1 m). Bars in the longitudinal direction of the wall and of the base slab were extended behind the concrete body and welded to a steel frame, which simulated an anchorage of longitudinal reinforcement of a continuous wall with a base slab. Before casting, the reinforcement bars were equipped with vibrating wire strain gauges and resistance gauges for monitoring the strain, as well as with temperature sensors for determining the temperature field caused by heat of hydration. According to the needs of the experiment, the structure was modelled in GiD 11.0 software and calculated in the AtenaWin program. The results of the experiment and the numerical analysis were mutually compared.