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Abstract Effective lubrication under extreme conditions such as high temperature is of considerable importance to ensure the reliability of a mechanical system. New lubricants that can endure high temperatures should be studied and employed as alternatives to traditional oil-based lubricant. In this paper, a thermocapillary model of a silicone-oil droplet is developed by solving the Navier–Stokes and energy equations to obtain the flow, pressure, and temperature fields. This is accomplished using a conservative microfluidic two-phase flow level set method designed to track the interface between two immiscible fluids. The numerical simulation accuracy is examined by comparing the numerical results with experimental results obtained for a silicone-oil droplet. Hence, the movement and deformation of molten silicon droplets on graphite and corundum are numerically simulated. The results show that a temperature gradient causes a tension gradient on the droplet surface, which in turn creates a thermocapillary vortex. As the vortex develops, the droplet migrates to the low-temperature zone. In the initial stage, the molten silicon droplet on the corundum substrate forms two opposite vortex cells, whereas two pairs of opposite vortices are formed in the silicone fluid on the graphite substrate. Multiple vortex cells gradually develop into a single vortex cell, and the migration velocity tends to be stable. The greater the basal temperature gradient, the stronger the internal thermocapillary convection of the molten silicon droplet has, which yields higher speeds.

In this paper, we present a solidification growth model that primarily describes the principal components of horizontal ribbon growth process, but also discusses the interaction between fluid flow and heat transfer, crystallization dynamics, and the effects of oxygen impurity distribution in melts, particularly with respect to the morphology of the interface. The effects of the jet cooling rate, pulling speed, and transfer coefficient on solute transport were studied. The results showed that a higher jet velocity produces a sharper temperature gradient at the interface and a stronger Marangoni effect, facilitates solute transport in the silicon melt, and promotes higher oxygen concentration in crystal. The stronger Marangoni convection causes more rapid oxygen transfer in the silicon melt and a higher oxygen concentration. Solidification front increases the downward flow velocity of the eddy current as the pulling speed is increased; this leads to a decrease in solute concentration at the interface. An increase in the downward flow of the vortex confluence facilitates the reduction of solute concentration in the crystal. An increase in the upward flow of the vortex confluence will increase the concentration in the crystal. The oxygen concentration is concentrated at the top and bottom of the silicon ribbon.

Polycrystalline silicon is the dominant material in solar cells and plays an important role in photovoltaic industry. It is important for not only the conventional production of silicon ingots but also the direct growth of silicon wafers to control crystallization for obtaining the desired polycrystalline silicon. To the best of our knowledge, few studies have systematically reported about the effects of crystalline planes on the solidification behavior of liquid silicon and the analysis of the microstructural features of the polysilicon structure. In this study, molecular dynamics simulations were employed to investigate the solidification and microstructure evolution of polysilicon, with focus on the effects of the seed distribution and cooling rate on the growth of polycrystalline silicon. The (110), (111), and (112) planes were extruded by the (100) plane and formed the inclusion shape. The crystallization of silicon consisted of diamond-type structures is relatively high at a low cooling rate. The simulations provide substantial information regarding microstructures and serve as guidance for the growth of polycrystalline silicon.

Effective lubrication under extreme conditions such as high temperature is of considerable importance to ensure the reliability of a mechanical system. New lubricants that can endure high temperatures should be studied and employed as alternatives to traditional oil-based lubricant. In this paper, a thermocapillary model of a silicone-oil droplet is developed by solving the Navier-Stokes and energy equations to obtain the flow, pressure, and temperature fields. This is accomplished using a conservative microfluidic two-phase flow level set method designed to track the interface between two immiscible fluids. The numerical simulation accuracy is examined by comparing the numerical results with experimental results obtained for a silicone-oil droplet. Hence, the movement and deformation of molten silicon droplets on graphite and corundum are numerically simulated. The results show that a temperature gradient causes a tension gradient on the droplet surface, which in turn creates a thermocapillary vortex. As the vortex develops, the droplet migrates to the low-temperature zone. In the initial stage, the molten silicon droplet on the corundum substrate forms two opposite vortex cells, whereas two pairs of opposite vortices are formed in the silicone fluid on the graphite substrate. Multiple vortex cells gradually develop into a single vortex cell, and the migration velocity tends to be stable. The greater the basal temperature gradient, the stronger the internal thermocapillary convection of the molten silicon droplet has, which yields higher speeds. [ABSTRACT FROM AUTHOR]