Clean soft magnetic alloy with SiC ceramic foam filters for - ceramic foam filter - filtration and separation industry

Preparation of a soft magnetic alloy used in the production process of foam ceramic filters. The filter with silicon carbide, clay, alumina powder as raw material, preparation of organic foam impregnation process. Were analyzed with SEM and XRD section microstructure and crystalline phase. The results showed dense microstructure section uniform, crystalline phase composition of silicon carbide, mullite and cristobalite phase. The kind of heat-resistant ceramic foam filter vibration of up to 8 . field applications show that oxygen, nitrogen, aluminum content of the removal rates reached 33.15%, 22.79% and 41.62%, a good filtering effect.

Purified using ceramic foam filter technology to achieve high-quality metal melt metal casting is a relatively mature technology, widely used in the production process of various metals. Soft magnetic alloy of purification can be applied ceramic foam filters carried out. According to the casting temperature of soft magnetic alloy 1300 ~ 1350 , identified as matrix material with silicon carbide ceramic foam filter to filter. Silicon carbide is a kind of integrated high performance ceramic materials. but silicon carbide is covalently materials, sintering is difficult, needed the combination of the second method to prepare silicon carbide foam ceramic. a certain proportion of clay and alumina at high temperatures can be transformed into mullite, mullite and silicon carbide which has a similar thermal expansion coefficient and excellent chemical compatibility is a great potential of refractories [1]. so can be used alumina, clay as a sintering aid, but need to determine the appropriate dosage and the sintering temperature to obtain good high temperature properties of foam ceramic filter.

1 Preparation of ceramic filters 1.1 preparation of raw materials Using foam as the precursor poly acid, purity> 95% of SiC powder (over 320 mesh) as the substrate material; purity of more than 97% of the industrial -Al2O3 powder (over 320 mesh) and clay (over 320 mesh) as sintering additive; CMC and PVA as binder.

1.2 Preparation of blank In the beaker, add sintering agent -Al2O3 powder, clay; adding carboxymethyl cellulose, 2% polyvinyl alcohol (PVA) solution as a binder; adding polyethylene glycol as a surfactant ; adding SiC powder; last a certain amount of water, stirring with a mechanical stirring 15min, and then put it aside for 2 h, and then stir the paste are required.

Will handle a good polyurethane foam immersed in slurry, repeatedly rubbing fully removed after infiltration, removal of excess slurry by extrusion, while also making pulp by squeezing even fully attached to the pore size of polyurethane foam on. then naturally dried blank. such as a dip, the slurry can not be fully attached to the polyurethane foam, it can be repeated numerous times until you get the hang plasma process suitable SiC porous ceramic filter quality green body.

1.3 sintered blank Sintered blank can be divided into low, medium temperature, heat three stages.

Low temperature stage of drying the green body, in order to free water can be discharged, to avoid the large amount of gas produced in a short time, causing cracking green body, the natural dried biscuit placed in drying oven, 120 for drying 2h. in the volatile temperature stage of the bubble period, the stage of mainly polyurethane foam and other organic volatile stage, the heating rate must be at that stage too fast, to avoid the volatile organic compounds caused severe cracking of green bodies. billet will be dried body to no more than 100 / h heating rate to 600 (polyurethane foam ignited above) insulation 1h, to ensure the full bubble evaporates.

Into high-temperature ceramic glass on stage, a relatively high speed (an average of 8 / min) heated to sintering temperature, the furnace heat 2h, so that fully sintered ceramic body, and then cooled with the furnace, which was good preparation ceramic filter. Preparation by the ceramic filters shown in Figure 1.

2 SiC and sintering aids and sintering temperature to determine the performance of ceramic filters Silicon carbide crystals are mainly -SiC, is a hexagonal system, is heat stable. Si and C atoms with covalent bonds between, each atomic sphere are closely arranged to each other and hold each other tetrahedral gap to form a solid compact structure, is difficult to sinter pure silicon carbide crystals, the sintering mechanism is evaporation - condensation mass transfer. This is because the silicon lattice can be great, great at a high temperature vapor pressure, since the combination of silicon carbide sintering temperature above 2000 . which must be added to promote sintering agent to lower the sintering temperature [1]. In selecting suitable oxide additives need to be considered, in order to fully dense silicon carbide, sintering process requires not only To produce liquid, but also to prevent the oxide additives or reaction with the silicon carbide to be weak. high temperature, metal oxide and silicon carbide in the reaction may be:

Junction temperature will generate a combination of glass, silicon carbide particles will be wrapped in one glass of phases during the cooling process because of the contraction, would form a decentralized, discrete state, the splitting will occur in their holes; if too much sintering aids, the main phase silicon carbide is relatively decreased, there will be local glass coated with silicon carbide phase is too small, or even only the glass phase and no carbonation the phenomenon of silicon particles, while relatively low strength of glass phase, will result in lower overall strength; if sintering aid is too small, the content of glass phase will be reduced, the role of the SiC coating will be weakened, will make part of the silicon carbide particles are not effectively connected and exposed to the outside, can also cause decreased strength.

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