Fabricação de um cadinho pelo método de colagem de barbotina

Abstract

This work has as objective a ceramic crucible confection with complete functionality for use in Industrial Processes Laboratory at UFJF and also for a confection method study in order to provide future copies if necessary. The adopted confection method is Slip Casting method, which uses a porous cast and a slip. The porous cast is obtained through a mixture containing plaster and water, while the slip is obtained through a mixture of water, kaolin and a deflocculant agent. The porous cast was obtained through a mixture of approximately 40% water and 60% plaster (in weight), while the suspension was obtained through a mixture of 400ml water, 100ml kaolin and 4 drops of deflocculant agent. The Slip Casting method consists of filling a porous cast with a slip mixture, in which the liquid part from the slip is absorbed by the casts’ pores, forming a clay layer near the cast’s walls with varying thickness according to the casting’ duration. After the clay wall is formed, the slip’s excess must be removed. The absorbing time was 1min for the smaller casts and 2min for the bigger casts. The cast and clay coating must go through a drying period until the clay coating can be properly taken off. After dried the clay coating has the final product’s dimensions. After the casting process the product must go through sintering in a furnace at approximately 1300 C, but the rapid temperature increase during sintering could lead to structural defects causing deformations and possible cracks. In order to avoid said problems, a programmable temperature ramp furnace was used, initially heating until 400 C at a 5 C/min rate and remaining at the final temperature for 30min, then heating at a 12 C/min rate until 1000 C, remaining there for 2h. Even without cautious air removal from the slip, the casting slip process was efficient for small sized crucibles. However, for bigger crucible dimensions the structural failures caused by air bubbles made the sintering process impossible.