Opportunities of striation-free crystal growth with ultrasound effect

The main condition for elimination of growth striations is the formation of standing waves in the melt for damping of convection. The formation of standing waves between the crucible bottom...

Solution Growth of SiC from the Crucible Bottom with Dipping under Unsaturation State of Carbon in Solvent

SiC crystals are grown using a Si-Cr-based solvent by a top-seeded solution growth (TSSG) method by changing the dipping time after when the growth temperature is reached. Step-flow-like curve morphologies were observed for a dipping time after 15 min, while polycrystallization occurred at the periphery for that after 120 min, which corresponded to the dipping under unsaturated and supersaturated carbon in the solvent, respectively. Furthermore, the solution growth of SiC with dipping under unsaturated carbon was easily realized by the growth from the crucible bottom, step-flow-like growth was achieved. Using this technique, dominant polytypes of SiC in various growth conditions after stable seed dipping under the unsaturation in the solvent can be demonstrated.

Numerical study on the effect of additional resistive heating and crystal rotation on sapphire single crystals (Al2O3) grown by the Kyropoulos method

Reduction of melt–crystal interface convexity during Kyropoulos growth of sapphire single crystals through rotation and crucible bottom heating.

Reagents Activity in a Copper Droplets / Post-Processing Slag Suspension

The suspension of the copper droplets in the post-processing slag taken directly from the KGHM-Polska Miedź S.A. Factory (from the direct-to-blister technology as performed in the flash furnace) was subjected to the special treatment with the use of the one of the typical industrial reagent and with the complex reagent newly patented by the authors. This treatment was performed in the BOLMET S.A. Company in the semi-industrial conditions. The result of the CaCO3, and Na2CO3 chemicals influence on the coagulation and subsequent sedimentation of copper droplets on the crucible bottom were subjected to comparison with the sedimentation forced by the mentioned complex reagent. The industrial chemicals promoted the agglomeration of copper droplets but the coagulation was arrested / blocked by the formation of the lead envelope. Therefore, buoyancy force forced the motion of the partially coagulated copper droplets towards the liquid slag surface rather than sedimentation on the crucible bottom. On the other hand, the complex reagent was able to influence the mechanical equilibrium between copper droplets and some particles of the liquid slag as well as improve the slag viscosity. Finally, the copper droplets coagulated successfully and generally, were subjected to a settlement on the crucible bottom as desired / requested.

Numerical Simulation of Temperature Field during Vacuum Sublimation Purification of Metal Tm

The thermo physical parameters of Tm vapor and the range of sublimation temperature have been determined by vapor pressure of metal Tm, and a 2-D axis-symmetric heat transfer model has been developed to investigate the temperature distribution in sublimation furnace. The simulation results show that, due to the heat loss at crucible bottom, the temperature of crucible, solid metal and Tm vapor increases with crucible height increasing, reaches the maximum value in the middle of crucible in height direction, and then decreases rapidly, and the maximum temperature is closer to the heating body temperature with its increasing; at the outside surface of condenser, the temperature decreases sharply, and the temperature curves with various heating body temperature are almost overlapped, the condensing region of Tm vapor is not affected by the heating body temperature; the temperature of upper surface of solid Tm is about 30°C lower than that of heating body, and the absolute and relatively temperature differences decrease correspondingly with increasing of heating body temperature.

Growth of Optical Crystals by the Micro-Pulling-Down Method

The micro-pulling-down technique is a crystal growth method that has been mostly developed since 1992. The general scheme of the growth system is relatively simple: the melt (oxide, fluoride, metal) residing in a crucible is transported in downward through microcapillary channel(s) made in the bottom of the crucible. Two driving forces (capillary action and gravity) support the delivery of the melt to the liquid/solid growth interface formed under the crucible due to a properly established temperature gradient. Appropriate configuration of the crucible bottom allows for controlling of the crystal shape (fibers, rods, tubes, plates) and the dimensions of the crystals' cross sections that range approximately from 0.1 to 10 mm. A great number of scientifically and industrially important optical crystal fibers have been successfully produced using this method.