▎ 摘　　要

NOVELTY - Preparing shell-type composite material having sandwich structure, comprises e.g. dropping sodium hydroxide-aqueous ammonia mixture to aluminum chloride solution, stirring, transferring to high-temperature reaction kettle and reacting, removing the solution, washing with ethanol and deionized water, ultrasonically dispersing the obtained product into deionized water and freeze-drying, calcining γ-alumina oxyhydroxide nanowires, adding alumina nanowires into graphene oxide solution, stirring, mixing the alumina nanowires and graphene oxide, adsorbing nanowires on the surface of graphene oxide, ultrasonically processing, adding polyvinyl alcohol and glutaraldehyde, stirring, ultrasonically processing, and vacuum assistant filtering to obtain the final product. USE - The shell-type composite material is useful in engineering and material fields (claimed). ADVANTAGE - The method has a simple process; the composite material has high strength, high toughness, maintains excellent morphology and mechanical properties even when soaked in acid, alkali, organic solvent or ultrasonically, and maintains excellent self-support and structural stability in a humid environment. DETAILED DESCRIPTION - Preparing shell-type composite material having sandwich structure, comprises (i) taking 0.1-2 mol/ml aluminum chloride hexahydrate preferably 0.9-1.1 mol/ml and sodium hydroxide-aqueous ammonia mixture as precipitating agent, where the concentration of aqueous ammonia is 0.5-3.5 mol/ml, and the concentration of sodium hydroxide solution is 0.5-3.5 mol/ml, preferably concentration of these two alkaline solutions is 2.5-2.6 mol/ml, and mixing equal volumes of aqueous ammonia and sodium hydroxide solution for precipitating aluminum salts in aluminum chloride solutions, (ii) dropping 17.5 ml sodium hydroxide-aqueous ammonia mixture to 17.5 ml aluminum chloride solution, stirring for 5-60 minutes, transferring to high-temperature reaction kettle and reacting at 140-240 ℃ for 12-48 hours, where the volume of addition is regulated according to the size of the reaction kettle and the amount of samples to be prepared in equal proportions, preferably if 100 ml reaction kettle is selected, adding ≯ 40 ml sodium hydroxide-aqueous ammonia mixture and an equal volume of aluminum chloride solution, (iii) removing the solution in the sample obtain in step (ii) (common solid-liquid separation methods including filtration and centrifugation), washing with ethanol and deionized water for 3 times, ultrasonically dispersing the obtained product into deionized water and freeze-drying to obtain clean white γ-alumina oxyhydroxide nanowires, (iv) placing the γ-alumina oxyhydroxide nanowires in high-temperature furnace, calcining at 500 ℃ for 1-10 seconds to obtain amorphous alumina nanowires, calcining γ-alumina oxyhydroxide nanowires at 500 ℃ for 1-120 minutes to obtain dual-phase alumina nanowires with different degrees of crystallization and its crystallization ratio increases with the prolongation of time, and calcining γ-alumina oxyhydroxide nanowires for more than 360 minutes to obtain fully crystallized γ-alumina nanowires, where the calcination processes is carried out in air, oxygen or inert gas, (v) ultrasonically stirring and dispersing dried graphene oxide in deionized water to obtain a graphene oxide solution with a concentration of 2-10 mg/ml, preferably 5 mg/ml, heating and dispersing the solid polyvinyl alcohol in deionized water, heating at 60-90 ℃ and stirring vigorously for 4 hours until the polyvinyl alcohol is completely dissolved, cooling to room temperature while stirring to obtain a concentration of 0.5-4 mg/ml, preferably 2.5 mg/ml, and taking 50 wt.% glutaraldehyde and dispersing in deionized water to obtain glutaraldehyde dilution with a concentration of 0.5 mg/ml, and (vi) adding 2-20 mg alumina nanowires (preferably 7 mg) into 5 ml of 2-10 mg/ml (preferably 4 mg/ml) graphene oxide solution, stirring for 12-36 hours (preferably 36 hours), mixing the alumina nanowires and graphene oxide, adsorbing nanowires on the surface of graphene oxide, ultrasonically processing for 20-30 minutes, adding 4ml of 2.5 mg/ml polyvinyl alcohol, 0.2 ml of 0.5mg/ml glutaraldehyde, stirring for 12-18 hours, ultrasonically processing for 20-30 minutes, and vacuum assistant filtering to obtain the shell-type composite material reinforced by alumina nanowires.