The Fabrication Of Al₂O₃ Rod Structures By Lyophilization At Ambient Pressure

The fabrication of nano-ceramic materials has been an important focus for some time in materials science and technology, as the nano-ceramic materials outweigh other traditional materials in numerous respects. A well-known family of nano-ceramic materials is alumina(Al2O3). In this paper, we first explored three lyophilization methods to prepare dry loose Al2(SO4)3 powder, and then we invented a fast well drill of using wear-resistant materials. We have applied for patents of lyophilization at ambient pressure and the fast well drill. In addition, this paper introduced three methods of freeze-dried: ice sublimation, variable pressure lyopholization and lyophilization at ambient pressure. After the heat treatment, loose Al2(SO4)3 powder turned into Al2O3 with nanorod structures by these methods.The method of ice-subliming is that to froze the aluminium solutions of 0.01 mol/L,0.005 mol/L and 0.0005 mol/L into ice by being immersed into liquid nitrogen and then placed it with a vacuum chamber. After 24 hours, we got three dry white fluff Al2(SO4)3 samples. Then placed three samples in a high temperature furnace at 1300℃, being calcined for 2 hours, resulting Al2O3 nanometer powder. Reducing the concentration, is helpful to reduce the width of Al2O3 nanowires, and to increase nanorods content gradually, with the finest one reaching 50 nm. After calcination, Al2O3 nanorods content is gradually increased. We observed the diameter of the finest Al2O3 nanorods is about 60 nm.The second method, lyophilizer of transforming pressure, is to improve the equipment based on vacuum ice-subliming. By adding an intelligent negative pressure controller to the vacuum chamber, which can effectively regulate the value of the pressure in vacuum chamber, we can explore the effect of transforming pressure. In this experiment, the main manner of refrigeration is chilling plate. We produced a temperature difference by making upper and lower surfaces. Formulated a concentration of 0.5 mol/L of Al2(SO4)3 solution was placed in a vacuum chamber and then we began lyophilizing. Adjusted the pressure to be 10 k Pa, 20 k Pa, 60 k Pa, and adjusted the temperature of the solution obtained to be-15℃, respectively. We got three Al2(SO4)3 dry samples by lyophilization. These lyophilized samples morphology are lamellar body structure mostly, and there is a second nuclear generated on the surface of the sheet. As the pressure increasing, the number of second nuclear increases, and the size becomes smaller. Adjusting pressure can change the migration distance of the ice sublimation precipitated solute. Therefore, we got Al2O3 nanorods with diameter of about 200 nm after calcination.The third method refers to lyophilizing the sample at ambient pressure. This part is the content of issued patents. The same principle that use two cold surfaces to induce the difference of temperature, is also adopted here, in order to sublimate water out. Formulated concentrations of 0.5 mol/L, 0.1 mol/L, 0.01 mol/L of Al2(SO4)3 solutions were placed inside the lyophilization at ambient pressure and lyophilized to get dry Al2(SO4)3 powder, respectively. Freeze-drying thickness of about 1mm every day. Then these samples were placed in a high temperature furnace, after calcination, we got Al2O3 nanorods with diameter of about 200-300 nm.After introducing three types of lyophilizations, we turned to do other different solutions lyophilized. I considered that K, Al, O presence of diverse products. So I tried to dope certain proportion of K2SO4 solution(10%, 20%, 30%, 40%, 50% by volume) into Al2(SO4)3 solution. I used the method of ice-submiling to obtain some different dry samples. Then placed them in a high temperature furnace, after reaching 1300℃ continue to calcine 2h,we got some mixed samples. When the addition is greater than 20%,we got nanorod structures of mixed KAl5O8 and KAl11O17.The last part is about a new well drill. It has already been authorized for utility model patents. The current well drills work under a certain speed and drilling pressure, the resistance of cutters withstand sustained pressure into the rock, easily damaged. Therefore, the drill only can work on a low-speed at high pressure or on a high speed at low pressure. Otherwise, we invented a new drill whose drilling speed is proportional to the speed under a suitable drilling pressure. The cutting teeth uses the cylinder of diamond enhancing alloy, under the 5 t drilling pressure and 150 r/min speed to achieve 8 m/h drilling speed,which is about 5 times than that got from the wear shoes drill.