The green specimens of nano-size Y-TZP are formed by gelcasting method. Using polymer electrolytes NaPAA and NH_4PAA, we have studied the rheological properties of slurry.The optimum pH range is between 8 to 10. The p...The green specimens of nano-size Y-TZP are formed by gelcasting method. Using polymer electrolytes NaPAA and NH_4PAA, we have studied the rheological properties of slurry.The optimum pH range is between 8 to 10. The proper amount of dispersant changes with the solid content.The rheological measurements of suspension containing NH_4PAA show lower viscosity.The theoretical green density has been calculated.展开更多
A novel near-net process, gelcasting, was successfully used to prepare larger size 316L stainless steel parts with complex shape. In this study, the effects of process parameters on the viscosity of the slurry and the...A novel near-net process, gelcasting, was successfully used to prepare larger size 316L stainless steel parts with complex shape. In this study, the effects of process parameters on the viscosity of the slurry and the dry green strength were investigated. The results show that gas atomization （GA） powder is more suitable for gelcasting compared with water atomization （WA） powder. The maximum solid loading is 55vo1% for ball-milled slurry with GA powders. And the optimum amounts of monomers （acrylamide （AM）＋methylenebisacrylamide （MBAM）; the mass ratio, 30：1） and initiator in the AM system are 1.8% （based on the weight of metal powder） and 0.8%-1.4% （based on the weight of monomers）, respectively, at which, the maximum green strength obtained is 33.7 MPa. The mechanical properties of the sintered specimen are as follows： ultimate tensile strength, 493 MPa; yield strength, 162 MPa; and HRB, 72.展开更多
Spherical Ti-45A1-8.5Nb-（W,B,Y） alloy powder prepared by an argon plasma process was near-net shape by gelcasting. In the non-aqueous system, methaerylate-2-hydroxy ethyl, toluene, benzoyl peroxide, and N,N-dimethyl...Spherical Ti-45A1-8.5Nb-（W,B,Y） alloy powder prepared by an argon plasma process was near-net shape by gelcasting. In the non-aqueous system, methaerylate-2-hydroxy ethyl, toluene, benzoyl peroxide, and N,N-dimethylaniline were used as the monomer, solvent, initiator, and catalyst, respectively. To improve sintering and forming behaviors, many additives were included in the suspension. The concentrated suspension with a solid loading of 70vo1% was prepared. The high Nb-TiA1 powder was analyzed by electron microscopy and X-ray diffraction. It was found that the green bodies had a smooth surface and homogeneous microstructure, exhibiting a bending strength as high as 50 MPa. After sintering at 1480℃ for 2 h in vacuum, uniform complex-shaped high Nb-TiA1 parts were successfully produced.展开更多
The raw materials of Al, Si, SiO2, and SiC were used to prepare Sialon-SiC suspeusion for gelcasting by adjuting the pH value and content of SiC particle and controlling the milling time. The result shows that the sta...The raw materials of Al, Si, SiO2, and SiC were used to prepare Sialon-SiC suspeusion for gelcasting by adjuting the pH value and content of SiC particle and controlling the milling time. The result shows that the stable suspension for gelcasting coald be got by adding 40wt% SiC particle at pH = 8. Al would eusily hydralyze to deteriorate the suspension when the milling time was too long, so the optimum milling time should be less than 100 minutes. At last, a well-dispersed suspension with a viseosity of less than 0.32Pa· s was obtained and the solid looming was 54vol% .展开更多
Sintering additives to gelcasting Sialon-SiC were decided by the optimizing experiments. The results show that Sialon-SiC can be sintered under 1450℃ and sintering temperature decreases by 100℃, when 2%～3% TiO 2 o...Sintering additives to gelcasting Sialon-SiC were decided by the optimizing experiments. The results show that Sialon-SiC can be sintered under 1450℃ and sintering temperature decreases by 100℃, when 2%～3% TiO 2 or Guangxi clay is used as sintering additive.展开更多
An approach to fabricate sintered copper with high green strength and high sintered density using nonaqueous gelcasting technol- ogy is presented in this study. The effects of various gelcasting processing parameters ...An approach to fabricate sintered copper with high green strength and high sintered density using nonaqueous gelcasting technol- ogy is presented in this study. The effects of various gelcasting processing parameters such as monomer content, monomer/crosslinker ratio, initiator content, dispersant dosage, and temperature on the flexural strength of dried green bodies and the relative density of sintered bodies were studied to obtain better microstructures and properties. The appropriate process parameters obtained for copper gelcasting are as follows monomer content, 20vol%-30vol% （based on the total volume of reagents）; monomer/crosslinker ratio, 10：1 to 20：1; initiator content, 3vol%-4vol% （based on the volume of the monomer）; dispersant dosage, 1.5wt%-2.5wt% （based on the mass of the copper powder）; and reaction temperature, 65-75℃.展开更多
The rheological behavior and gelcasting of composite suspensions of SiC and synthesized Al 2O 3-Y 2O 3-La 2O 3 powder as sintering aid were investigated. It was found that the rheological behavior of SiC particles cou...The rheological behavior and gelcasting of composite suspensions of SiC and synthesized Al 2O 3-Y 2O 3-La 2O 3 powder as sintering aid were investigated. It was found that the rheological behavior of SiC particles could be modified with a slightly oxidized surface that was similar to silica in colloidal behavior. The smaller the particles were, the more similar to silica the SiC powder was. The pH value of Al 2O 3-Y 2O 3-La 2O 3 synthesized powder slurry at isoelectric points (IEP) is higher than that of SiC powder. The dispersant PAA-NH 4 changes the IEP of both SiC and Al 2O 3-Y 2O 3-La 2O 3 powder slurry to higher pH values. The experimental results indicate that the composite suspension could possess satisfactory stability and lower viscosity at pH =10.1 and PAA-NH 4 as dispersant. The optimum solid loading was 550 0 in volume. Machinable green bodies with uniform complex shape are gained after molding.展开更多
Titanium carbide ceramics with high porosity were fabricated by gelcasting process with methacrylamide as a chain forming monomer,methylenebisacrylamide as a cross-linker monomer and tetramethylammonium hydroxide as a...Titanium carbide ceramics with high porosity were fabricated by gelcasting process with methacrylamide as a chain forming monomer,methylenebisacrylamide as a cross-linker monomer and tetramethylammonium hydroxide as a dispersant.The stability of suspension,mechanical properties,phase composition and micro structure were investigated by zeta potential,bending and compressive strengths,X-ray diffraction and scanning electron microscopy(TEM) analyses,respectively.The results show that the optimal concentration of dispersant for the best homogeneous unagglomerated microstructures is 0.4 wt%at pH 9.The highest green strength of 33 MPa is obtained from the suspension with 40 vol% solid loading and25 wt% monomer.The porosity increases with the increase in monomer content and the decrease in solid loading.Also,the strength of porous TiC ceramic decreases with the content of pores increasing in the sintered ceramics.展开更多
Porous silicon nitride ceramics have attracted a considerable attention due to their excellent overall performance,but poor porosity homogeneity and structural shrinkage induced by prolonged high temperature sintering...Porous silicon nitride ceramics have attracted a considerable attention due to their excellent overall performance,but poor porosity homogeneity and structural shrinkage induced by prolonged high temperature sintering limit its further application.Herein,as a three-in-one solution for the above issues,for the first time we develop a novel approach that integrates the merits of gelcasting-SHS(self-propagating high-temperature synthesis)to prepare porous Si_(3)N_(4)ceramics to simultaneously achieve high porosity,high strength,high toughness,and low thermal conductivity across a wide temperature range.By regulating the solid content,porous Si_(3)N_(4)ceramics with homogeneous pore structure are obtained,where the pore size falls inbetween 1.61 and 4.41 pm,and the elongated grains are interlaced and interlocked to form micron-sized coherent interconnected pores.At the same time,porous Si_(3)N_(4)ceramics with porosity of 67.83%to 78.03%are obtained,where the compressive strength reaches 11.79 to 47.75 MPa and fracture toughness reaches 1.20 to 6.71 MPa-m1/2.展开更多
In this work, low-cost titanium was fabricated by gelcasting of titanium hydride powder. The effects of morphology and grain composition of powder raw material and solid loading on the rheological behavior of gelcasti...In this work, low-cost titanium was fabricated by gelcasting of titanium hydride powder. The effects of morphology and grain composition of powder raw material and solid loading on the rheological behavior of gelcasting slurry were studied. The degreasing, dehydriding and sintering behaviors of gelcasted green body were investigated by differential thermal analysis （DTA） and dilatometer. The results show that the solid loading of titanium hydride slurry reaches 50 vol%. Combination of dehydriding and sintering in one process accelerates the densification, and the relative sintered density of the final part achieves 96.5 %. In order to test the ability of gelcasting process for fabricating structural materials, a resin handle produced by 3D printing technology was used as a model and a titanium handle was successfully fabricated. Higher solid loading and better sinterability of titanium hydride powder promote manufacture of bulk titanium with high relative density, complex shape and well-defined microstructure.展开更多
Porous Si3N4 self-reinforce ceramics were prepared by gelcasting using agarose solutions. By changing the agarose content in the slurries, the porous silicon nitride ceramics with different porosities, α→β-Si3N4 ph...Porous Si3N4 self-reinforce ceramics were prepared by gelcasting using agarose solutions. By changing the agarose content in the slurries, the porous silicon nitride ceramics with different porosities, α→β-Si3N4 phase transformation, and mechanical properties were obtained. When the agarose content changed from 0.2% to 0.8% (w/w, based on powder), the porosities increased from 10.3% to 21.4%, while the fracture strength decreased from 455 to 316 MPa and the fracture toughness decreased from 6.6 to 5.5 MPa·m1/2. Many fibrous β-Si3N4 grains grown from the internal wall of the round pores is the typical microstructure of the gelcasting porous silicon nitride ceramic. Both elongated β-Si3N4 grains and suitable interfacial bonding strength contributes to high fracture toughness by favoring crack deflection and bridging. The growth mechanisms of fibrous grains resulted from the synergy of solution-diffusion-reprecipitation and vapor-liquid-solid (VLS).展开更多
文摘The green specimens of nano-size Y-TZP are formed by gelcasting method. Using polymer electrolytes NaPAA and NH_4PAA, we have studied the rheological properties of slurry.The optimum pH range is between 8 to 10. The proper amount of dispersant changes with the solid content.The rheological measurements of suspension containing NH_4PAA show lower viscosity.The theoretical green density has been calculated.
文摘A novel near-net process, gelcasting, was successfully used to prepare larger size 316L stainless steel parts with complex shape. In this study, the effects of process parameters on the viscosity of the slurry and the dry green strength were investigated. The results show that gas atomization （GA） powder is more suitable for gelcasting compared with water atomization （WA） powder. The maximum solid loading is 55vo1% for ball-milled slurry with GA powders. And the optimum amounts of monomers （acrylamide （AM）＋methylenebisacrylamide （MBAM）; the mass ratio, 30：1） and initiator in the AM system are 1.8% （based on the weight of metal powder） and 0.8%-1.4% （based on the weight of monomers）, respectively, at which, the maximum green strength obtained is 33.7 MPa. The mechanical properties of the sintered specimen are as follows： ultimate tensile strength, 493 MPa; yield strength, 162 MPa; and HRB, 72.
基金the National Natural Science Foundation of China(No.51274039)the Guangdong Industry-University-Research Foundation(No.2011A090200091)
文摘Spherical Ti-45A1-8.5Nb-（W,B,Y） alloy powder prepared by an argon plasma process was near-net shape by gelcasting. In the non-aqueous system, methaerylate-2-hydroxy ethyl, toluene, benzoyl peroxide, and N,N-dimethylaniline were used as the monomer, solvent, initiator, and catalyst, respectively. To improve sintering and forming behaviors, many additives were included in the suspension. The concentrated suspension with a solid loading of 70vo1% was prepared. The high Nb-TiA1 powder was analyzed by electron microscopy and X-ray diffraction. It was found that the green bodies had a smooth surface and homogeneous microstructure, exhibiting a bending strength as high as 50 MPa. After sintering at 1480℃ for 2 h in vacuum, uniform complex-shaped high Nb-TiA1 parts were successfully produced.
文摘The raw materials of Al, Si, SiO2, and SiC were used to prepare Sialon-SiC suspeusion for gelcasting by adjuting the pH value and content of SiC particle and controlling the milling time. The result shows that the stable suspension for gelcasting coald be got by adding 40wt% SiC particle at pH = 8. Al would eusily hydralyze to deteriorate the suspension when the milling time was too long, so the optimum milling time should be less than 100 minutes. At last, a well-dispersed suspension with a viseosity of less than 0.32Pa· s was obtained and the solid looming was 54vol% .
文摘Sintering additives to gelcasting Sialon-SiC were decided by the optimizing experiments. The results show that Sialon-SiC can be sintered under 1450℃ and sintering temperature decreases by 100℃, when 2%～3% TiO 2 or Guangxi clay is used as sintering additive.
基金financially supported by the National Science Foundation of China (Grant No. 51274041)
文摘An approach to fabricate sintered copper with high green strength and high sintered density using nonaqueous gelcasting technol- ogy is presented in this study. The effects of various gelcasting processing parameters such as monomer content, monomer/crosslinker ratio, initiator content, dispersant dosage, and temperature on the flexural strength of dried green bodies and the relative density of sintered bodies were studied to obtain better microstructures and properties. The appropriate process parameters obtained for copper gelcasting are as follows monomer content, 20vol%-30vol% （based on the total volume of reagents）; monomer/crosslinker ratio, 10：1 to 20：1; initiator content, 3vol%-4vol% （based on the volume of the monomer）; dispersant dosage, 1.5wt%-2.5wt% （based on the mass of the copper powder）; and reaction temperature, 65-75℃.
文摘The rheological behavior and gelcasting of composite suspensions of SiC and synthesized Al 2O 3-Y 2O 3-La 2O 3 powder as sintering aid were investigated. It was found that the rheological behavior of SiC particles could be modified with a slightly oxidized surface that was similar to silica in colloidal behavior. The smaller the particles were, the more similar to silica the SiC powder was. The pH value of Al 2O 3-Y 2O 3-La 2O 3 synthesized powder slurry at isoelectric points (IEP) is higher than that of SiC powder. The dispersant PAA-NH 4 changes the IEP of both SiC and Al 2O 3-Y 2O 3-La 2O 3 powder slurry to higher pH values. The experimental results indicate that the composite suspension could possess satisfactory stability and lower viscosity at pH =10.1 and PAA-NH 4 as dispersant. The optimum solid loading was 550 0 in volume. Machinable green bodies with uniform complex shape are gained after molding.
文摘Titanium carbide ceramics with high porosity were fabricated by gelcasting process with methacrylamide as a chain forming monomer,methylenebisacrylamide as a cross-linker monomer and tetramethylammonium hydroxide as a dispersant.The stability of suspension,mechanical properties,phase composition and micro structure were investigated by zeta potential,bending and compressive strengths,X-ray diffraction and scanning electron microscopy(TEM) analyses,respectively.The results show that the optimal concentration of dispersant for the best homogeneous unagglomerated microstructures is 0.4 wt%at pH 9.The highest green strength of 33 MPa is obtained from the suspension with 40 vol% solid loading and25 wt% monomer.The porosity increases with the increase in monomer content and the decrease in solid loading.Also,the strength of porous TiC ceramic decreases with the content of pores increasing in the sintered ceramics.
基金supports from the National Natural Science Foundation of China(NSFC,Nos.51872159 and 52072381).
文摘Porous silicon nitride ceramics have attracted a considerable attention due to their excellent overall performance,but poor porosity homogeneity and structural shrinkage induced by prolonged high temperature sintering limit its further application.Herein,as a three-in-one solution for the above issues,for the first time we develop a novel approach that integrates the merits of gelcasting-SHS(self-propagating high-temperature synthesis)to prepare porous Si_(3)N_(4)ceramics to simultaneously achieve high porosity,high strength,high toughness,and low thermal conductivity across a wide temperature range.By regulating the solid content,porous Si_(3)N_(4)ceramics with homogeneous pore structure are obtained,where the pore size falls inbetween 1.61 and 4.41 pm,and the elongated grains are interlaced and interlocked to form micron-sized coherent interconnected pores.At the same time,porous Si_(3)N_(4)ceramics with porosity of 67.83%to 78.03%are obtained,where the compressive strength reaches 11.79 to 47.75 MPa and fracture toughness reaches 1.20 to 6.71 MPa-m1/2.
基金financially supported by the National Natural Science Foundation of China(No.51274039)the State Key Laboratory of Advanced Metals and Materials(No.2012-ZD04)
文摘In this work, low-cost titanium was fabricated by gelcasting of titanium hydride powder. The effects of morphology and grain composition of powder raw material and solid loading on the rheological behavior of gelcasting slurry were studied. The degreasing, dehydriding and sintering behaviors of gelcasted green body were investigated by differential thermal analysis （DTA） and dilatometer. The results show that the solid loading of titanium hydride slurry reaches 50 vol%. Combination of dehydriding and sintering in one process accelerates the densification, and the relative sintered density of the final part achieves 96.5 %. In order to test the ability of gelcasting process for fabricating structural materials, a resin handle produced by 3D printing technology was used as a model and a titanium handle was successfully fabricated. Higher solid loading and better sinterability of titanium hydride powder promote manufacture of bulk titanium with high relative density, complex shape and well-defined microstructure.
基金Project supported by the National Natural Science Foundation of China (No 90716022)the Science Fund for Distinguished Young Scholars of Heilongjiang Province (No JC200603),China
文摘Porous Si3N4 self-reinforce ceramics were prepared by gelcasting using agarose solutions. By changing the agarose content in the slurries, the porous silicon nitride ceramics with different porosities, α→β-Si3N4 phase transformation, and mechanical properties were obtained. When the agarose content changed from 0.2% to 0.8% (w/w, based on powder), the porosities increased from 10.3% to 21.4%, while the fracture strength decreased from 455 to 316 MPa and the fracture toughness decreased from 6.6 to 5.5 MPa·m1/2. Many fibrous β-Si3N4 grains grown from the internal wall of the round pores is the typical microstructure of the gelcasting porous silicon nitride ceramic. Both elongated β-Si3N4 grains and suitable interfacial bonding strength contributes to high fracture toughness by favoring crack deflection and bridging. The growth mechanisms of fibrous grains resulted from the synergy of solution-diffusion-reprecipitation and vapor-liquid-solid (VLS).
