Cast iron with a silicon carbide foam ceramic filters Preparation and Properties - Filtration and Separation Industry

Cast iron with a silicon carbide foam ceramic filters Preparation and Properties Zhe Wang 1, Feng Ren Zhang 1, Feng-Jun Li 2,3, LIU Ping 1, MA combat red one, ice stone book 1

(1. Henan University of Science and Technology of Materials Science and Engineering, Luoyang 471003, China; 2. Tsinghua University Mechanical University, Beijing 100084, China; 3. China First Tractor Group Co., Ltd., Luoyang 471004)

Abstract: Fabrication of organic foam impregnated with silicon carbide foam ceramic filter, the ratio of the composite binder, sintering additives (Al2O3) content and the addition of sintering. Compressive strength of samples with Al2O3 content of the best match between the relationship between the formation of mullite phase is the material strength is an important contributor to improve. To adopt the best formula was obtained at 1400 SiC foam ceramic filter compressive strength 1.9 MPa, the sample heated to 1100 , 15 water into the quench thermal shock up to 15 times.

Keywords: ceramic foam; SiC; binder; CMC CLC number: TG221 Document code: A Article ID :1001-4977 (2006) 11-1137-03 Ceramic foam filters have been around for many years, ceramic filters may effectively reduce or eliminate non-metallic inclusions in castings, cleaning liquid cast alloy, with good economic and social benefits. Ceramic foam is a foam-like shape, as is porous ceramics, it is the ordinary porous ceramic, porous ceramic honeycomb, the recently developed third-generation porous ceramic product [1-2]. Preparation of foam ceramics currently the most commonly used organic foam impregnation process [3], which is based on organic foam for the skeleton, dip, dried, and then high temperature sintering, the sintering process, combustion of volatile organic compounds, leaving the network structure ceramic. I prepared by using a composite adhesive high-performance silicon carbide ceramic foam filter, and the ratio of the composite binder, the quantity of sintering additives and firing temperature on the material phase composition, microstructure , mechanical properties and thermal shock performance.

1 Test materials and methods Order to determine the proportion of composite binder, the quantity of sintering additives, sintering temperature and obtain good slurry properties, the raw materials used in this experiment are: purity of greater than 95% of SiC powder (320 mesh) as the base material, the purity of more than 97% of the industrial -Al2O3 powder (320 mesh) as sintering additive, SiO2 concentration of 50% of the silica sol and the CMC as a binder. Foam impregnation with a silicon carbide foam ceramic filter, the sintering process consists of drying, evaporation, high temperature roasting and other components. L (933) orthogonal three factors were complex binder (carboxymethyl cellulose + silica) ratio (mass ratio), sintering additives Al2O3 content (mass fraction) and the firing temperature ( ).

Orthogonal test fired on 9 group filters into the chip sampling to measure the volume, weight, bulk density was measured by using the drainage method of porosity, thermal shock resistance of the sample is heated by electric furnace to the sample to 1100 , add 15 water quench, remove and put in electric furnace, the heat rose to 1 100 10min before quenching; if the surface of macro-cracks, the sample is completely thermal shock damage, note the number of cycles. Using Shimadzu (Shimadzu) AG-I250KN Precision universal testing machine testing compressive strength, with PhilipsX'pert MPDpro X-ray diffraction to study the phase composition and Nissan JSM-5610LV scanning electron microscope fractography.

2 Test Results and Analysis Orthogonal test results in Table 1, according to the size of the table by mid-level difference between the R factor impact on the performance indicators: composite binder> firing temperature> content of sintering aids, preparation of silicon carbide foam ceramic the use of composite filters carboxymethyl cellulose binder (CMC) and the best ratio of 1:2 silica, alumina 20%, sintering temperature 1400 .

2.1 composite binder of (C6H9O4-O-CH2COONa) n as the CMC formula, white or slightly yellow, the floc or powder, granular or fibrous solids, it is dissolved in water, low viscosity liquid Well, more in line with the nature of Newtonian fluid, indicating a strong adhesive, bonding with the formation of water-soluble cellulose film materials and the basic properties of inorganic materials bond. Carboxymethyl cellulose in the role of ceramics in the bonding of polymer molecules or macromolecules depend on the formation of strong hydrogen bonding and van der Waals force the network structure shown, it is organic, high temperature, together with the volatile foam, will not Pollution ceramics; but volatile organic foam made gas phase is not severe and the ceramic sintering, at this time of volatile organic binder reduces the bonding effect, make ceramic body cracks, so to add silica to the high temperature binder .

High temperature inorganic binder generally used in the binder, silica sol was in the SiO2 network structure, strong adhesion, water loss after the sol has a high activity is beneficial to sintering, but it reduce the high temperature performance of the filter, so slurry need to use the best ratio in the binder. Table 1, when the CMC and the silica ratio of 1:1, the ceramic green body after drying mesh strength is not high, and collapse after sintering, the maximum compressive strength is only 0.7MPa. The CMC and the silica ratio was 1:3, the incorporation of the excess of silica, SiO2 excess heat generated at low temperature when the great expansion of cristobalite phase, which greatly reduce the high temperature performance of the filter, when the CMC and the sol was 1:2 when used as a binder have an average compressive strength of 1.43MPa and an average of 12 times the thermal shock.

2.2 Sintering temperature Higher sintering temperature, resulting in more liquid, lower the viscosity of the liquid phase. Thus, more liquid penetration hole, making a more dense sintered body. However, in Table 1, the sample does not appear in the highest maximum intensity of the sintering temperature of 1450 , but in 1400 , this phenomenon is due to the high sintering temperature resulted in materials with oxidation of SiC is higher than the lower sintering temperature, thereby generating more cristobalite phase in Figure 1, while cristobalite during the cooling process will occur about 3% of the volume change, this transformation will bring certain materials, micro-cracks [4], micro-cracks strength of the material there will cause some damage, resulting in the samples sintered under 1450 lower than the 1 400 under the strength of the samples sintered at 1400 mullite formation is the strength of the material is an important contributor to improve, mullite is also high temperature strengthening phase, refractoriness to improve the material has a very good role.

2.3 Selection liquid phase sintering additives

Silicon carbide ceramic due to its high covalent bonding characteristic of sintering diffusion rate is very low, and the grain boundary energy and surface energy ratio is high, the formation of grain boundary energy are not readily available, it is difficult to pure silicon carbide normal pressure sintering approach to production of high density materials

I am China Metal Products writer, reports some information about coke vending machine , bubblegum machine.