Slip casting mechanics

The process starts with contacting a porous support with the colloidal precursor solution in a dip-coating or a spin-coating process. Film formation starts either with a film-coating or a slip-casting mechanism as will be discussed below. 

The process is perfectly described by a rapid slip casting mechanism. After a few seconds the layer thickness after calcination is of the order of 4-7 pm. The... 

Common consolidation methods include variations on pressing powders, plastic forming, slip casting and tape casting. The choice of which method to use for a given application is very dependent upon the shape, size and required dimensional tolerances of the final product, available capital outlay and desired productivity. Each of these methods is examined in turn below, followed by sintering, which turns the consolidated powders into a monolithic body with mechanical integrity. 

Ceramic Ablators, Several types of subliming or melting ceramic ablators have been used or considered tor use in dielectric applications particulady with quartz or boron nitride [10043-11-5] fiber reinforcements to form a nonconductive char. Fused silica is available in both nonporous (optically transparent) and porous (slip cast) forms. Ford Aerospace manufactures a 3D silica- fiber-reinfo reed composite densified with colloidal silica (37). The material, designated AS-3DX, demonstrates improved mechanical toughness compared to monolithic ceramics. Other dielectric ceramic composites have been used with performance improvements over monolithic ceramics (see Composite materials, ceramic matrix). 

It is technically easier to manufacture a molded component from SiC-powder by slip casting or dry pressing, working it mechanically and then sintering pressureless at 1950 to 2000°C. Due to the low sintering activity of silicon carbides, such processes have only been recently successfully carried out with the advent of fine particulate SiC-powders (specific surface area > 5 m /g) with low oxygen-contents (< 0.2%). Boron or aluminum and free carbon or boron carbide are added as sintering aids. 

Two main groups of lyogel film formation mechanisms can be distinguished (i) film coating, and (ii) slip casting. In the film-coating process, capillary forces in pores do not play a role and this process can be used also on dense, non-porous substrates. The slip cast process is widespread in the production of bulk ceramics but has only been recently applied to the production of membranes [3,9]. In this process capillary forces play a dominant role. 

Adcock DS, McDowall IC (1957) The Mechanism of Filterpressing and Slip Casting. J Am Ceram Soc 40 355-362... 

Fennelly TJ, Reed JS (1972) Mechanics of pressure slip casting. J Am Ceram Soc 55 264-268... 

Ramavath P, Biswas P, Rajeswari K, Suresh MB, Johnson R, Padmanabham G et al (2014) Optical and mechanical properties of compaction and slip cast processed transparent polycrystalline spinel ceramics. Ceram Int 40 5575-5581... 

For the purpose of testing mechanical properties after sintering, it was decided to slip-cast bars using this slurry. The Plasta--of-Paris (PoP) powder used to make the molds was Khatri s Level Plaster of Paris , Mumbai. India. Based on results from prior work it was decided to use a w ater Plaster-of-Paris (PoP) powder ratio of 80ml/100gm. 

The mechanical as well as the high temperature properties of this material, have been studied in some detail. Bars fabricated using the slip-casting technique have shown good density. Young s modulus values and flexural strength, which corroborate the values reported in literature. Cyclic thermal shock quench tests have been performed on the bars, to study the effect on mechanical properties. These observations have been supported by microstructural analysis. 

In general the size of the pores depends, among other factors, on the particle size of the aggregate. Particle size is the most important parameter in the production of ceramic products it must be optimized to ensure that the desired mechanical and physical properties are achieved. The majority of ceramic products are manufactured by the process of slip casting in a mold. Maintenance of the desired PSD requires control of the dispersion stabUity of the ceramic shp. Like all ceramic materials and castables, in alumina refractories a proper PSD is of importance. 

Some of the early analyses incorrectly treated the mechanics of slip casting in terms of a diffusion process. The slip casting process involves the/low of liquid through a porous medium, which is described by Darcy s law. In one dimension, Darcy s law can be written as... 

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