Study On The Formation And Performance Of Large-size B₄C/Al Composite Sheets

With the development of human space activity, the number of space debris is everincreasing, which runs around the earth as high speed. It greatly threatens an orbitingspace vehicle. In order to protect against the impact of the space debris and combine withthe shield structure which is widely used now, we have to prepare a kind of materials inlarge size. The B₄C/Al composite has the properties of low density, high strength and hightoughness, and it can be used to protect against the impact effectively. We prepared thelarge-size composite plates by the tape casting and pressureless infiltration in this paper.The materials have the excellent mechanical properties. Besides, we also tried to preparethe materials with the B₄C/Al composite powders by tape casting, and then it was sinteredby laminated. In this way we reduced the sintering temperature successfully.Firstly, we researched the optimum content of various components, scattered mecha-nism and rheological properties in the non-aqueous and aqueous slurries through thesedimentation test, Zeta potential and apparent viscosity test. Then the slurries were usedto tape cast, the results showed that the surface condition, density, fracture strength andfracture elongation of the green tape which prepared by the non-aqueous slurries werebetter than the green tape which prepared by the aqueous slurries. So, we chose thenon-aqueous slurries to do the next tests finally.The properties of the ceramic skeletons which were prepared by different green tapeswere studies. The results showed that the ceramic skeleton which prepared by the greentapes, in which binder content was4.5wt%, had high apparent porosity rate and enoughstrength. And then the ceramic skeletons were composited by pressureless infiltration in1000℃,1100℃,1200℃respectively. The results showed that the mechanical propertiesof the composite materials which were infiltrated in1200℃were best, and the Bendstrength, Fracture toughness, Elastic modulus and Vickers hardness was468MPa,9.86MPa·m1/2,214GPa and15.21GPa respectively. But the mechanical properties of the com- composites by this method were a bit worse than that prepared by the compressionmolding.Besides, we tried to use the B₄C/60wt%Al composite powders to tape casting.. Andthen the green tapes were laminar sintered by the composite powers in the air furnace. Theresults of the mechanical tests showed that the porosity rate of the materials sintered in720℃was1.7%which was the lowest, and the Bend strength, Fracture toughness,Elasticmodulus and Vickers hardness was412MPa,10.58MPa·m1/2,211GPa,13.73GParespectively. Besides, the results of EDX showed that the oxygen content of the systemwas6.98%. It proved that the Oxidation degree of B₄C and Al was not much high.