Zirconia-based ceramic foam process principle

Ceramic foam is a porosity of up to 70% to 90%. Only a bulk density of 0.3 ~ 0.6g /. Having a three-dimensional network skeleton and interconnected pore structure of porous ceramics. In addition to its high temperature resistance, corrosion resistance and other ceramics generally with the performance outside. Also it has a low density, high strength, high porosity, large surface area, strong interference of fluid from the filtration and adsorption characteristics of a good. Because of these advantages. Ceramic foam has been applied in many fields. And it has attracted the attention of the global materials sector. And it has seen rapid development.

Today, for better performance zirconia ceramic foam products. Only a handful of domestic companies to produce. And most of them is the introduction of foreign technology. The use of foreign good quality foam precursor. High production costs. Limited to small batch production. The major products for export. Therefore, to carry out low-cost high-performance zirconia ceramic foam research. Optimize the production process. So that domestic technology has reached the international advanced level. It has become the focus of attention of the industry. This zirconia ceramic foam future mass production and widely used. For the relevant domestic enterprises to participate in international competition in the production and in a good position. It has a very important significance.

The basic theory of ceramic foam

Ceramic foam structure theory hole

Ceramic foam material having a three-dimensional network skeleton and interconnected pore structure. Which is composed of a hole for a three-dimensional space-filling polyhedron. If the solid composition of the foam just hole edges (cavities connected through wall openings). It claimed that the foam is perforated; if those polyhedral wall is solid. So that each of the cavities are adjacent cavities closed mutually isolated. It claimed that the foam is a closed cell. Of course, some ceramic foam material containing a portion of the opening, also contains a portion of the obturator.

Geometry ceramic foam material has almost the same cellular material long history. In Plateau (1873) paper on solid geometry. I believe cavity shape is rhombic dodecahedron (garnet morphology Power 12 planes). The shape of this space into the cavity, which is certainly the arrangement can be achieved. But that is not the most effective way to achieve a three-dimensional porous solids. For over a century, the surface area per unit volume in the smallest space filling cavities. Is considered to be slightly curved surface Kelvin proposed ten tetrahedron. Recently, Weaire Phelan and computer software used to minimize the surface area of the processing. Proved surface area per unit volume in pores smaller units. This unit consists of six fourteen hole surface cavities (12 pentagons and two hexagons face surface) and two pentagonal dodecahedron constitution. They are all equal volume. The fourteen faces hole arranged manner three orthogonal axes. Twelve faces the hole in its pore portions. Resulting in an overall simple cubic lattice structure. Only hexagonal surface is planar, all the pentagonal faces are curved. However, the effective space-filling is not the only factor influence the shape of the cavity. When other factors predominate. The shape of the cavity may be associated with these two forms are very different. In the characterization of ceramic foam material characteristics and control over their performance. Composition edge solid volume fraction is an important parameter. Connecting factor closing hole edges and the hole wall is more difficult to determine, if the surface tension is the dominant factor in structure formation. The four edge vertices sentenced 109.4 ° intersect. The three edge surfaces at 120 ° impose intersect.

Ceramic foam formation mechanism

Mechanism of use of aggregate particles accumulate to form a foam ceramic bonding

In ceramic foam formation. The mass transfer process is not continuous. The connection between the aggregate particles. You can rely on the same components added thereto fine particles. Its easy-to-use sintering characteristics. At a temperature and large particles connected. You can also use some of the additives. Or they can generate expansion coefficient and chemical components and aggregates at high temperatures and can match the aggregate liquid phase infiltration. Or with the solid phase should occur between aggregate aggregate particles are bonded. Each one aggregate only on a few points mentioned above to form a large number of three-dimensional through channels with other particles.

In general, this type of material. The larger size of the aggregate particles, the greater the average pore diameter is formed, the narrower the particle size distribution of the aggregate. More uniform distribution of the resulting ceramic foam pores. Because of the possibility of additives and aggregates between solid phase reaction, diffusion, liquid infiltration, the interaction between the liquid phase reaction. The foam was a certain shrinkage during firing, so the additive type, quantity, baking temperature, time, atmosphere and other factors affect the pore structure of the material. Additive increase in volume for a long time. Porosity and average pore diameter will be reduced. Sintering or sintering temperature is too high for too long. Forming liquid fills the pores. Also reduce the porosity or the formation of closed pores.

Mechanism prepare organic foam ceramic foam impregnation method

By adsorptive ceramic slurry can burn organic foam carrier. Then burn the support material pore structure formed at high temperatures. If the use of polyurethane foam as the porous carrier. Pore structure can be made the same as the original foam ceramic foam. Can choose according to need support different pore structure. But the choice of the carrier should have sufficient elasticity and strength. It can support a wet material which is not adsorbed by the pores closed. After the slurry was dried at lower temperatures green plastic row. At this rate of temperature increase should be slow. Foam to prevent burnout too fast leaving the hole collapse. After burning the foam to be volatile. And then at a faster rate of warming. Ceramic material sintered at high temperatures. But still maintaining the original framework and to produce the desired ceramic foam. Porosity thus prepared porous ceramics up to 70% to 90%. This molding method for producing a foamed ceramic foam impregnation method referred to as organic. This method is suitable for the preparation of high porosity, open porosity porous ceramic. This experiment is the use of this preparation method.

Organic foam impregnation process is the preparation of a high porosity ceramic foam is an effective process. Such ceramic and having an open three dimensional network skeleton structure. This special structure to act as a filter material has the following significant advantages: ① through the fluid when the pressure loss. ② a large surface area of fluid contact efficiency. ③ light weight. Class ceramic foam filter is used for fluid, especially a molten metal filtration. Ceramic particles sintered body with the traditional use of glass fiber cloth, compared not only easy to operate, save energy, reduce costs, and high filtration efficiency. In addition to the molten metal and other fluid filtration outside. It also can be used as high-temperature flue gas treatment, catalyst supports, solid heat exchangers and electrode materials.

Certain burn additives mechanism or volatilized at high temperatures leaving voids in the ceramic body using

Porosity is usually formed by the accumulation of particles of porous ceramics actual range is 25% to 35%. Therefore, in cases where a high porosity. Often added toner and carbon black in the ingredients, these substances at a high temperature combustion of volatile leaving a void. Can be prepared by this method is higher than 60% porosity porous ceramic. Add a small amount of material will burn the material porosity, maximum pore impact and reduce the strength of the material.