The conditions of ZnO-Al2O3 aqueous suspensions and slip casting were optimized to obtain dense green compacts and further to obtain high density ZnO-Al2O3 ceramic composites.The Zeta potential of raw powders was meas...The conditions of ZnO-Al2O3 aqueous suspensions and slip casting were optimized to obtain dense green compacts and further to obtain high density ZnO-Al2O3 ceramic composites.The Zeta potential of raw powders was measured.ZnO and Al2O3 powders have lower Zeta potential than-45 mV commonly at pH 8-10.3 with polyacrylic acid(PAA)added.The influence of pH and the mass fraction of the additives on the stability and fluidity of the suspensions added with PAA and polyethylene glycol(PEG) was investigated by experiments of viscosity and sedimentation.The suspensions have the lowest viscosity and the best stability at pH 9 with 0.2%PAA(mass fraction).The maximum density of green compacts is 66.6%of theoretical density(TD)with compacting and homogeneous green particles.An ultrahigh density sintered compact(>99.6%TD)could be obtained after pressureless sintering at 1 400℃for 2 h.展开更多
Fully stabilized YSZ solid electrolyte was prepared by slip casting. The density was measured according to the Archimedes principle and the linear shrinkage was calculated from measuring the sizes of samples before an...Fully stabilized YSZ solid electrolyte was prepared by slip casting. The density was measured according to the Archimedes principle and the linear shrinkage was calculated from measuring the sizes of samples before and after sintering. XRD analysis was conducted to verify the phase structure of both the starting YSZ powder and the prepared YSZ electrolyte. The microstructure of fracture surface and the electrical properties of the samples sintered at different temperatures were investigated via SEM and a complex impedance method, respectively. By comparison of the properties and features among the samples, a slip casting method was established to be a simple way to manufacture high-quality YSZ electrolyte at the sintering temperature of 1550℃ for 3 h, which provides a new approach for YSZ electrolyte with complex shapes and mass production.展开更多
mole fraction) yttria-stabilized zirconia electrolyte thin wall tubes were p repared by i mproved slip casting method. The length and wall thickness of the tubes are 266 mm and 0.4～0.9 mm, respectively and the relat...mole fraction) yttria-stabilized zirconia electrolyte thin wall tubes were p repared by i mproved slip casting method. The length and wall thickness of the tubes are 266 mm and 0.4～0.9 mm, respectively and the relative density is 96.7%. The microstr ucture and electrical properties of samples sintered at different temperatures w ere studied using SEM and ac impedance spectroscopy. The effect of sintered dens ity, grain and grain boundary on the electrical properties of the samples was analyzed. The research results show that the density of the samples increase s gradually with increasing sintering temperatures. The microstructure of sample s strongly influences its electrical properties, and the electrical properti es of samples enhance with the increase of sintered density. The ionic conductiv ity of grain and grain boundary is increased as the sintering temperature incre ases. Better sinterability of the samples was obtained at the sintering temperat ure of 1650 ℃. The maximum open circuit voltage and short circuit current for s ingle cell is 0.946 V and 1.84 A, respectively. The maximum output power of sing le cell is 0.46 W at the temperature of 850 ℃.展开更多
Centrifugal slip casting in prefabricated template was used to prepare open-cell Al2O3 foams. Aqueous α- Al2O3 slurries with up to 50% solid contents (volume fraction) were prepared. The sedimentation of slurries dur...Centrifugal slip casting in prefabricated template was used to prepare open-cell Al2O3 foams. Aqueous α- Al2O3 slurries with up to 50% solid contents (volume fraction) were prepared. The sedimentation of slurries during centrifugation was discussed with respect to the hydronamic conditions at large particle concentrations. The effect of solid contents on mass segregation was observed. Segregation phenomena were hindered for slurries with high solid loadings exceeding 50% (volume fraction). The dried and sintered behaviors of samples were analyzed. The cell struts in green bodies had good particles packing and showed high green density (63.4% theory density). After sintered at 1500 ℃, the cell struts of final products had high sintered density (98.8% theory density) and homogeneous microstructure. The porosity of final products is 75.6%展开更多
The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to...The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to obtain cell struts with gradient distribution of Al 2 O 3 and ZrO 2 particles and high packing density.Aqueous Al 2 O 3-20vol.% ZrO 2 slurries with 20vol.% solid contents were prepared and the dispersion and rheological characteristics of the slurries were investigated.The settling velocity and mass segregation of Al 2 O 3 and ZrO 2 particles at different centrifugal accelerations were calculated and studied.The drying behavior,macrostructure,microstructure,compressive property and resistance to thermal shock of the sintered products were also investigated.The results show that the difference of settling velocity of Al 2 O 3 and ZrO 2 particles increases and mass segregation becomes acute with an increase in centrifugal acceleration.The cell struts prepared at a centrifugal acceleration of 1,690 g have high sintered density(99.0% TD) and continuous gradient distribution of Al 2 O 3 and ZrO 2 particles.When sintered at 1,550 o C for 2 h,the cell size of gradient Al 2 O 3-ZrO 2 foam is approximately uniform,about 1.1 mm.With the porosity of gradient Al 2 O 3-ZrO 2 ceramic foams increasing from 75.3% to 83.0%,the compressive strength decreases from 4.4 to 2.4 MPa,and the ceramic foams can resist 8-11 repeated thermal shock from 1,100 o C to room temperature.展开更多
Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the...Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.展开更多
Based on the heat transfer analysis of Air-Slip DC mold, a numerical model was presented to study the quantitative relationships between critical solidification layer and casting rate, pouring temperature and mold coo...Based on the heat transfer analysis of Air-Slip DC mold, a numerical model was presented to study the quantitative relationships between critical solidification layer and casting rate, pouring temperature and mold cooling ability etc. The analytical results show that the Air-Slip mold heat transfer condition plays important roles on choices of a casting rate and the pouring temperature, and that the product of billet diameter and casting rate is a certain constant under a certain condition of the mold.展开更多
Slip casting and subsequent pressureless sintering(PLS)allow the preparation of complex-shaped and large-sized Ti3AlC2 components for many potential applications.The behaviors of the suspensions,green compacts,and sin...Slip casting and subsequent pressureless sintering(PLS)allow the preparation of complex-shaped and large-sized Ti3AlC2 components for many potential applications.The behaviors of the suspensions,green compacts,and sintered samples of Ti3AlC2 were studied in this paper.The optimized condition of 1 wt%of arabic gum as dispersant at pH=10 results in a Ti3AlC2 suspension for slip casting Ti3AlC2 green compacts without macro defects or cracks.The sintering temperature and Al4C3 embedding powder are found to dominate the properties of the sintered Ti3AlC2 samples.The Ti3AlC2 sample sintered at 1450℃for 1.5 h with Al4C3 embedding powder reaches the best properties,namely 95.3%relative density,hardness of 4.18 GPa,thermal conductivity of 29.11W·m-1·K-1,and electrical resistivity of 0.39μΩ·m.The findings in this work may pave the way for the application of MAX phases with large size and complex shape.展开更多
A cone-shaped gadolinium doped ceria（Ce0.9Gd0.1O1.95,GDC） electrolyte cylinder with a thin wall was fabricated using slip cast-ing technique.The diameter of the larger open end of the cone-shaped cylinder was 0.85 c...A cone-shaped gadolinium doped ceria（Ce0.9Gd0.1O1.95,GDC） electrolyte cylinder with a thin wall was fabricated using slip cast-ing technique.The diameter of the larger open end of the cone-shaped cylinder was 0.85 cm,the length was 1.0 cm,and the thickness of the wall was 0.026 cm after sintering.Both the electrolyte and electrode powders were fabricated by using a glycine-nitrate process.A single solid oxide fuel cell（SOFC） was prepared with the cone-shaped electrolyte,NiO-GDC（70：30 wt.%） anode and Sm0.5Sr0.5CoO3（SSC） cathode.Its electrochemical performance（I-V curve） and electrochemical impedance spectroscopy（EIS） were studied with humidified hydrogen as the fuel and air as the oxidant.The maximum output power density was about 300 ？mW/cm2 at 700 oC.The EIS results showed that the dominant loss of the SOFC was from the ohmic resistance of the electrolyte.展开更多
In the present work transparent Y2O3 ceramics were made by slip casting and vacuum sintering of nanopowders with sodium poly-acrylic acid（PAA-Na） as dispersant.The rheological properties of Y2O3 nanopowder slurry we...In the present work transparent Y2O3 ceramics were made by slip casting and vacuum sintering of nanopowders with sodium poly-acrylic acid（PAA-Na） as dispersant.The rheological properties of Y2O3 nanopowder slurry were investigated using different amounts of dis-persant and solid contents.The microstructures and transmittance of the sintered ceramics were also studied by means of scanning electron microscopy（SEM） and ultra-violet visible spectrometry.The results showed that rheological behaviors of the Y2O3 nanopowder slurry were effectively promoted by sodium polyacrylic acid.Highly dispersive and stable slurries were obtained as the dispersant was added over 1.0 dwb% under the fixed conditions of pH 11 and 45 wt.% solid content.All the slip cast green bodies were sintered into highly dense ceramics after sintering at 1700 oC for 5 h in vacuum,wherein the sample added with 1.1% sodium polyacrylic acid exhibited the highest relative den-sity of 99.36% and transmission of 30% at 800 nm wavelength.展开更多
基金Project(50477044)supported by the National Natural Science Foundation of China
文摘The conditions of ZnO-Al2O3 aqueous suspensions and slip casting were optimized to obtain dense green compacts and further to obtain high density ZnO-Al2O3 ceramic composites.The Zeta potential of raw powders was measured.ZnO and Al2O3 powders have lower Zeta potential than-45 mV commonly at pH 8-10.3 with polyacrylic acid(PAA)added.The influence of pH and the mass fraction of the additives on the stability and fluidity of the suspensions added with PAA and polyethylene glycol(PEG) was investigated by experiments of viscosity and sedimentation.The suspensions have the lowest viscosity and the best stability at pH 9 with 0.2%PAA(mass fraction).The maximum density of green compacts is 66.6%of theoretical density(TD)with compacting and homogeneous green particles.An ultrahigh density sintered compact(>99.6%TD)could be obtained after pressureless sintering at 1 400℃for 2 h.
基金supported by the National High-Tech Research and Development Program of China (No. 2006AA09Z205)the National Natural Science Foundation of China (No. 40573046)the Science and Technology Foundation of Guizhou Province of China (No. (2006)2105)
文摘Fully stabilized YSZ solid electrolyte was prepared by slip casting. The density was measured according to the Archimedes principle and the linear shrinkage was calculated from measuring the sizes of samples before and after sintering. XRD analysis was conducted to verify the phase structure of both the starting YSZ powder and the prepared YSZ electrolyte. The microstructure of fracture surface and the electrical properties of the samples sintered at different temperatures were investigated via SEM and a complex impedance method, respectively. By comparison of the properties and features among the samples, a slip casting method was established to be a simple way to manufacture high-quality YSZ electrolyte at the sintering temperature of 1550℃ for 3 h, which provides a new approach for YSZ electrolyte with complex shapes and mass production.
文摘mole fraction) yttria-stabilized zirconia electrolyte thin wall tubes were p repared by i mproved slip casting method. The length and wall thickness of the tubes are 266 mm and 0.4～0.9 mm, respectively and the relative density is 96.7%. The microstr ucture and electrical properties of samples sintered at different temperatures w ere studied using SEM and ac impedance spectroscopy. The effect of sintered dens ity, grain and grain boundary on the electrical properties of the samples was analyzed. The research results show that the density of the samples increase s gradually with increasing sintering temperatures. The microstructure of sample s strongly influences its electrical properties, and the electrical properti es of samples enhance with the increase of sintered density. The ionic conductiv ity of grain and grain boundary is increased as the sintering temperature incre ases. Better sinterability of the samples was obtained at the sintering temperat ure of 1650 ℃. The maximum open circuit voltage and short circuit current for s ingle cell is 0.946 V and 1.84 A, respectively. The maximum output power of sing le cell is 0.46 W at the temperature of 850 ℃.
文摘Centrifugal slip casting in prefabricated template was used to prepare open-cell Al2O3 foams. Aqueous α- Al2O3 slurries with up to 50% solid contents (volume fraction) were prepared. The sedimentation of slurries during centrifugation was discussed with respect to the hydronamic conditions at large particle concentrations. The effect of solid contents on mass segregation was observed. Segregation phenomena were hindered for slurries with high solid loadings exceeding 50% (volume fraction). The dried and sintered behaviors of samples were analyzed. The cell struts in green bodies had good particles packing and showed high green density (63.4% theory density). After sintered at 1500 ℃, the cell struts of final products had high sintered density (98.8% theory density) and homogeneous microstructure. The porosity of final products is 75.6%
基金financially supported by the Natural Science Foundation of Liaoning Province(No.:201102090)the Doctoral Initiating Project of Liaoning Province Foundation for Natural Sciences,China(No.:20111068)+2 种基金the High School Development Plan for Distinguished Young Scholars of Liaoning Province Education Committee(No.:LJQ2012056)the National High-Tech Research and Development Program of China("863"Program,No.:2011AA060102)the International Science and Technology Cooperation Program of China,(No.:2011DFR50270)
文摘The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to obtain cell struts with gradient distribution of Al 2 O 3 and ZrO 2 particles and high packing density.Aqueous Al 2 O 3-20vol.% ZrO 2 slurries with 20vol.% solid contents were prepared and the dispersion and rheological characteristics of the slurries were investigated.The settling velocity and mass segregation of Al 2 O 3 and ZrO 2 particles at different centrifugal accelerations were calculated and studied.The drying behavior,macrostructure,microstructure,compressive property and resistance to thermal shock of the sintered products were also investigated.The results show that the difference of settling velocity of Al 2 O 3 and ZrO 2 particles increases and mass segregation becomes acute with an increase in centrifugal acceleration.The cell struts prepared at a centrifugal acceleration of 1,690 g have high sintered density(99.0% TD) and continuous gradient distribution of Al 2 O 3 and ZrO 2 particles.When sintered at 1,550 o C for 2 h,the cell size of gradient Al 2 O 3-ZrO 2 foam is approximately uniform,about 1.1 mm.With the porosity of gradient Al 2 O 3-ZrO 2 ceramic foams increasing from 75.3% to 83.0%,the compressive strength decreases from 4.4 to 2.4 MPa,and the ceramic foams can resist 8-11 repeated thermal shock from 1,100 o C to room temperature.
文摘Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.
文摘Based on the heat transfer analysis of Air-Slip DC mold, a numerical model was presented to study the quantitative relationships between critical solidification layer and casting rate, pouring temperature and mold cooling ability etc. The analytical results show that the Air-Slip mold heat transfer condition plays important roles on choices of a casting rate and the pouring temperature, and that the product of billet diameter and casting rate is a certain constant under a certain condition of the mold.
基金financially supported by National Natural Science Foundation of China (51731004, 51671054, 51501038)Natural Science Foundation of Jiangsu Province (BK20181285)“the Fundamental Research Funds for the Central Universities” in China (2242018K40108, 2242018K40109)
文摘Slip casting and subsequent pressureless sintering(PLS)allow the preparation of complex-shaped and large-sized Ti3AlC2 components for many potential applications.The behaviors of the suspensions,green compacts,and sintered samples of Ti3AlC2 were studied in this paper.The optimized condition of 1 wt%of arabic gum as dispersant at pH=10 results in a Ti3AlC2 suspension for slip casting Ti3AlC2 green compacts without macro defects or cracks.The sintering temperature and Al4C3 embedding powder are found to dominate the properties of the sintered Ti3AlC2 samples.The Ti3AlC2 sample sintered at 1450℃for 1.5 h with Al4C3 embedding powder reaches the best properties,namely 95.3%relative density,hardness of 4.18 GPa,thermal conductivity of 29.11W·m-1·K-1,and electrical resistivity of 0.39μΩ·m.The findings in this work may pave the way for the application of MAX phases with large size and complex shape.
基金Project supported by the National "863" Program of China (2007AA05Z136)the National Natural Science Foundation of China (51172113)+1 种基金the Taishan Scholar Overseas Distinguished Professorship Program from the Shandong Province Government,the Shandong Natural Science Foundation for Distinguished Young Scholars (JQ201118)the Research Foundation for Talented Scholars of Qingdao University of Science and Technology (400-0022374)
文摘A cone-shaped gadolinium doped ceria（Ce0.9Gd0.1O1.95,GDC） electrolyte cylinder with a thin wall was fabricated using slip cast-ing technique.The diameter of the larger open end of the cone-shaped cylinder was 0.85 cm,the length was 1.0 cm,and the thickness of the wall was 0.026 cm after sintering.Both the electrolyte and electrode powders were fabricated by using a glycine-nitrate process.A single solid oxide fuel cell（SOFC） was prepared with the cone-shaped electrolyte,NiO-GDC（70：30 wt.%） anode and Sm0.5Sr0.5CoO3（SSC） cathode.Its electrochemical performance（I-V curve） and electrochemical impedance spectroscopy（EIS） were studied with humidified hydrogen as the fuel and air as the oxidant.The maximum output power density was about 300 ？mW/cm2 at 700 oC.The EIS results showed that the dominant loss of the SOFC was from the ohmic resistance of the electrolyte.
基金Project supported by Liaoning Provincial Natural Science Foundation (a20062019)National Natural Science Foundation of China (50990303,51072030)
文摘In the present work transparent Y2O3 ceramics were made by slip casting and vacuum sintering of nanopowders with sodium poly-acrylic acid（PAA-Na） as dispersant.The rheological properties of Y2O3 nanopowder slurry were investigated using different amounts of dis-persant and solid contents.The microstructures and transmittance of the sintered ceramics were also studied by means of scanning electron microscopy（SEM） and ultra-violet visible spectrometry.The results showed that rheological behaviors of the Y2O3 nanopowder slurry were effectively promoted by sodium polyacrylic acid.Highly dispersive and stable slurries were obtained as the dispersant was added over 1.0 dwb% under the fixed conditions of pH 11 and 45 wt.% solid content.All the slip cast green bodies were sintered into highly dense ceramics after sintering at 1700 oC for 5 h in vacuum,wherein the sample added with 1.1% sodium polyacrylic acid exhibited the highest relative den-sity of 99.36% and transmission of 30% at 800 nm wavelength.
