▎ 摘　　要

NOVELTY - Toughened alumina ceramic mobile phone backboard comprises 12-25 wt.% doped toughening component, 1.25-4.25 wt.% doped color changing composition, 0.25-1wt.% graphene and high purity aluminum oxide (balance). The doped toughening component is zirconium dioxide. The doped color changing component is high purity ferric oxide, high purity cobalt monoxide, high purity manganese(IV) oxide and/or high purity nickel(II) oxide, where the purity of the high purity components are 99.9%. USE - Used as toughened alumina ceramic mobile phone backboard. ADVANTAGE - The method can increase the fracture toughness of the aluminum oxide-based ceramics to 4.75 MPa.m1/2, the fracture toughness of traditional aluminum oxide-based ceramics up to 35% and wave transmission rate to 80-87%. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing backboard comprising (i) preparing a composite powder by preparing a high-purity alumina-doped toughening component mixed powder by adding doped color changing component and high-purity graphene, placing into a planetary ball mill and mixing at 80-120 revolutions/minute for 12-24hours; (ii) preparing crude powder by (a) adding a combustion improver to the organic carrier and mixing composite powder and the solution at 100?C for 1-2 hours, spraying granulation to obtain the granular material required for injection molding, injecting the obtained material into an injection molding machine to obtain a plate blank of the back sheet, where the injection molding machine has injection pressure of 45-55 MPa, temperature at 120-145 degrees C and time of 30-60 minutes, and components of organic carrier is 45-55 wt.% paraffin wax, 7.5-20 wt.% polyethylene, 15-25 wt.% ethylene ethyl acrylate, 4-19 wt.% polystyrene, 2-8 wt.% polymethacrylate and 1-4 wt.% dibutyl phthalate and the combustion improver accounts for 0.1-1 wt.% of the mass of the composite powder, then mixing diethanolamine and polysilazane in a ratio of 1:1 to obtain a mixed solution, where the mass ratio of organic carrier, composite powder and mixed solution is 35-45:100:10, or (b) adding the composite powder, ammonium polyacrylate dispersant and polyvinyl butyral (PVB) binder to the mixed solvent, ball milling in a ball mill jar at a speed of 80-120 revolutions/minute for 8-12 hours to obtain a uniformly dispersed casting slurry, filtering, vacuum defoaming and casting into a film strip having a thickness of 0.8-2 mm, drying the cast film into a dry box for 2-4 hours at 80-90 degrees C, placing the slice into a steel mold, vacuum packaging, placing into a warm isostatic pressure for warm isostatic pressing, heating at 80-90 degrees C, subjecting the product to vacuum packaging and sealing for 5-15 minutes under pressure of 150 MPa for 20-30 minutes and reliving pressure to obtain a plate blank having a 2D shape, where the mixed solvent is obtained by mixing toluene and isopropyl alcohol having a mass ratio of 1:1 and the mixed solvent is a composite powder having a mass ratio of 70%, ammonium polyacrylate is a composite powder having a mass ratio of 2% and PVB is a composite powder having a mass ratio of 3.1%; and (iii) drying the plate blank of back sheet obtained in the step (ii) at 90-110 degrees C for 1-3 hours to obtain a dried blank and placing into a thermal degreasing equipment at 400-550 degrees C for 35-45 hours, pre-sintering in an inert gas atmosphere for 2-3 hours at 800-1000 degrees C and heating up to 1450-1550 degrees C at a rate of 200 degrees C/hour, sintering for 2-3 hours, cooling the material at 950 degrees C at a rate of temperature change of 30-50 degrees C/hour, warming up to 1050 degrees C at the same rate, cooling down to 950 degrees C again, repeating the cycle of 950-1050 degrees C and then cooling to 950 degrees C for 5-10 times, maintaining the temperature at 1000 degrees C, warming for 72-90 hours and cooling with the furnace.