Processing of ceramic-metal interpenetrating composites

Abstract

Interpenetrating composites consist of 3-dimensionally interpenetrating matrices of two different phases; in the present work they were alumina and aluminium-magnesium alloys and were produced by infiltrating ceramic foams with molten alloys. The foams were made by mechanically agitating ceramic suspensions to entrain gases and then setting the structure via the in-situ polymerisation of organic monomers, a process known as gel casting. This resulted in the foams having a very open and interconnected structure that could be easily infiltrated by the molten metals. Previous composites have been produced at Loughborough University using squeeze casting; however, whilst infiltration was usually accomplished in a matter of seconds, the resulting size and shape of the composite was limited. Hence the present work has focused on investigating the potential for using gravity-fed infiltration. Whilst this was much slower, often taking several minutes, when optimised it is believed it will offer the potential for the production of large and complex-shaped pieces.The composites were produced at atmospheric pressure by infiltrating 2-10 wt.% magnesium content Al-Mg alloys into 20% dense Al 2 O 3 foams with highly interconnected porosity. The processing parameters of temperature, ≥ 900°C, and atmosphere, flowing N 2 -Ar, were investigated to determine the processing window and infiltration kinetics. In-situ observation of the process shows that infiltration is faster at higher temperatures, Mg contents and N 2 partial pressures. Both optical and scanning electron microscopy (SEM) have been used to characterize the composites. p2

Reproducibility of ZrO2-based freeze casting for biomaterials

“…water) is prepared, (2) the slurry is directionally frozen in a controlled manner, causing the liquid freezing agent to template the solid loading, (3) the frozen scaffold is freeze dried in order to remove the freezing agent and create a green body, and (4) the green body is sintered in order to form a final, porous scaffold where the ice crystals have been converted into aligned pores [1,3,4,8]. Once these porous scaffolds have been fabricated, they can be infiltrated with polymers or metals in order to create two-phase interpenetrating composites [5,[10][11][12].…”

Centrifugal Infiltration of Porous Ceramic Preforms by the Liquid Al Alloy – Theoretical Background and Experimental Verification

“…In the vast majority of cases, they concern metal infiltration into granular [6,25] or fibrous preforms [14][15][16]. As it results from the review of literature, there are few works on modelling [20] as well as designing the structure and properties of composites obtained as a result of metal infiltration into porous ceramic foam [26][27][28][29].…”

Preliminary Tests of Cellular SiC/Iron Alloy Composite Produced by a Pressureless Infiltration Technique

“…Contrary to composites with a dispersed ceramic phase, in this type of materials the properties of the matrix and reinforcement complement each other in a better way [4][5][6][7][8]. One of the methods which allows obtaining this kind of composites is infiltration of previously prepared ceramic materials having a porous, open structure -so called preforms -by molten metal.…”