During thermal debinding in ceramic injection molding, the inhomogeneity of green body is a key origin of cracks. In this study, the impact of low molecular weight binders on the homogeneity of the green body was inve...During thermal debinding in ceramic injection molding, the inhomogeneity of green body is a key origin of cracks. In this study, the impact of low molecular weight binders on the homogeneity of the green body was investigated. Incidence of cracks during thermal debinding indicated that the volume ratio of wax to stearic acid should be out of high viscosity and incompletely wetting region. In these two formulation regions, typical inhomogeneous microstructures were observed. By mercury intrusion method, it was shown that pore size distribution of the debinded compacts was determined by thermal degradation of low molecular weight binders. A particle-rich region model was established to predict the nucleation of cracks caused by solid loading fluctuation. The criterion of cracks nucleation was that local capillary force from solid loading fluctuation was larger than the suction force from the surroundings.展开更多
Binder system is critical to the success of metal injection molding(MIM). A novel PEG based binder for MIM was developed, which was made of high density polyethylene (HDPE), polyethylene glycol (PEG), polymer W, stear...Binder system is critical to the success of metal injection molding(MIM). A novel PEG based binder for MIM was developed, which was made of high density polyethylene (HDPE), polyethylene glycol (PEG), polymer W, stearic acid(SA) and dioctyl phthalate (DOP). The components of binder have interactions with each other, so the binder have good compatibility. The thermal decomposition process of binder exhibits three stages during debinding. The binder could be debound by pyrolysis or solvent, and could easily be removed in a short time in ethanol without defects and evironmental concern. A lot of interconnected pores formed after solvent debinding, which is helpful to the escape of pyrolysis gases during subsequent thermal debinding or presintering. [展开更多
Pore opening and binder flow during the initial stage of thermal debinding in metal injection molded parts was investigated. Scaning electron microscopy(SEM) pictures of 316 L stainless steel parts using wax based bin...Pore opening and binder flow during the initial stage of thermal debinding in metal injection molded parts was investigated. Scaning electron microscopy(SEM) pictures of 316 L stainless steel parts using wax based binder show that small particles will move to the surface with the process of debinding. SEM pictures of different mass loss rate specimens indicate that initial pores will emerge when as little as 4% binder removes. During the initial stage of thermal debinding, vapor tension varies in different place due to the difference of curvature. Thus more binders will be removed in places with smaller cavity between metal powders, and in these places small openings emerge.展开更多
In this work,various backbone binders were used in wax-based binder system to formulate zirconia parts by ceramic injection molding (CIM).The effect of different backbone binders on the molding,debinding,and sintering...In this work,various backbone binders were used in wax-based binder system to formulate zirconia parts by ceramic injection molding (CIM).The effect of different backbone binders on the molding,debinding,and sintering behaviors was investigated.After blending process,the feedstock using multi-polymer components exhibited more homogeneous structure compared with that using the mono-polymer ones due to the synergistic effect of multi-polymers.During solvent debinding,some defects such as 'slumping' and 'peeling' appeared in the parts containing ethylene-vinyl acetate copolymer (EVA),but they were not found in the parts with other thermal polymers.Also,as for the parts after sintering,the one using low density polyethylene (LDPE) and high density polyethylene (HDPE) as backbone binders presented a more uniform microstructure with finer zirconia grains among all the investigated compositions,and thus obtained the highest flexural strength (～949 MPa) and relative density (～98.9％).展开更多
The thermal degradation behaviors of AlN green specimens were studied by thermogravimetry analysis during the ceramic powder injection molding debinding process. The optimum binder composition and the debinding cycle ...The thermal degradation behaviors of AlN green specimens were studied by thermogravimetry analysis during the ceramic powder injection molding debinding process. The optimum binder composition and the debinding cycle were demonstrated by observing the TGA and DTA plots of AlN green specimens and analyzing the microstructure at different temperatures. By adding HDPE into the PW EVA binder used in powder injection molding AlN can effectively reduce the mass lose rate in debinding process and improve the shape retention ability. At last, aluminum nitride ceramic with high room temperature thermal conductivity of 162.5?W·m -1 ·K -1 was produced. [展开更多
基金supported by the National Nature Science Foundation of China (NSFC) under grantNo. 50572049 the National High Technology Researchand Development Program of China ("863 Program") un-der grant No. 2007AA03Z522.
文摘During thermal debinding in ceramic injection molding, the inhomogeneity of green body is a key origin of cracks. In this study, the impact of low molecular weight binders on the homogeneity of the green body was investigated. Incidence of cracks during thermal debinding indicated that the volume ratio of wax to stearic acid should be out of high viscosity and incompletely wetting region. In these two formulation regions, typical inhomogeneous microstructures were observed. By mercury intrusion method, it was shown that pore size distribution of the debinded compacts was determined by thermal degradation of low molecular weight binders. A particle-rich region model was established to predict the nucleation of cracks caused by solid loading fluctuation. The criterion of cracks nucleation was that local capillary force from solid loading fluctuation was larger than the suction force from the surroundings.
文摘Binder system is critical to the success of metal injection molding(MIM). A novel PEG based binder for MIM was developed, which was made of high density polyethylene (HDPE), polyethylene glycol (PEG), polymer W, stearic acid(SA) and dioctyl phthalate (DOP). The components of binder have interactions with each other, so the binder have good compatibility. The thermal decomposition process of binder exhibits three stages during debinding. The binder could be debound by pyrolysis or solvent, and could easily be removed in a short time in ethanol without defects and evironmental concern. A lot of interconnected pores formed after solvent debinding, which is helpful to the escape of pyrolysis gases during subsequent thermal debinding or presintering. [
文摘Pore opening and binder flow during the initial stage of thermal debinding in metal injection molded parts was investigated. Scaning electron microscopy(SEM) pictures of 316 L stainless steel parts using wax based binder show that small particles will move to the surface with the process of debinding. SEM pictures of different mass loss rate specimens indicate that initial pores will emerge when as little as 4% binder removes. During the initial stage of thermal debinding, vapor tension varies in different place due to the difference of curvature. Thus more binders will be removed in places with smaller cavity between metal powders, and in these places small openings emerge.
基金This work was financially supported by National Natural Science Foundation of China
文摘In this work,various backbone binders were used in wax-based binder system to formulate zirconia parts by ceramic injection molding (CIM).The effect of different backbone binders on the molding,debinding,and sintering behaviors was investigated.After blending process,the feedstock using multi-polymer components exhibited more homogeneous structure compared with that using the mono-polymer ones due to the synergistic effect of multi-polymers.During solvent debinding,some defects such as 'slumping' and 'peeling' appeared in the parts containing ethylene-vinyl acetate copolymer (EVA),but they were not found in the parts with other thermal polymers.Also,as for the parts after sintering,the one using low density polyethylene (LDPE) and high density polyethylene (HDPE) as backbone binders presented a more uniform microstructure with finer zirconia grains among all the investigated compositions,and thus obtained the highest flexural strength (～949 MPa) and relative density (～98.9％).
文摘The thermal degradation behaviors of AlN green specimens were studied by thermogravimetry analysis during the ceramic powder injection molding debinding process. The optimum binder composition and the debinding cycle were demonstrated by observing the TGA and DTA plots of AlN green specimens and analyzing the microstructure at different temperatures. By adding HDPE into the PW EVA binder used in powder injection molding AlN can effectively reduce the mass lose rate in debinding process and improve the shape retention ability. At last, aluminum nitride ceramic with high room temperature thermal conductivity of 162.5?W·m -1 ·K -1 was produced. [
