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
Porous Si_(3)N_(4) ceramics were prepared by aqueous gelcasting using Si_(3)N_(4) poly-hollow microspheres(PHMs)as pore-forming agent.The effects of solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content on t...Porous Si_(3)N_(4) ceramics were prepared by aqueous gelcasting using Si_(3)N_(4) poly-hollow microspheres(PHMs)as pore-forming agent.The effects of solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content on the properties of porous Si_(3)N_(4) ceramics were investigated.Onlyβ-Si_(3)N_(4) phase is observed in porous Si_(3)N_(4) ceramics,and Si_(3)N_(4) PHMs distribute uniformly both in Si_(3)N_(4) green samples and porous Si_(3)N_(4) ceramics.Results show that solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content could considerably influence the properties of porous Si_(3)N_(4) ceramics.With the increase of solid loading of Si_(3)N_(4) slurry(decrease of Si_(3)N_(4) PHM content),the distributing state of Si_(3)N_(4) PHMs changes from contacting with each other to just embedding in the matrix,thus their porosity decreases,while their shrinkage,flexural strength,and fracture toughness increase.展开更多
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supported by China Postdoctoral Science Foundation(Nos.2013M530618 and 2015M572136)National Natural Science Foundation of China(Nos.51172120 and 51372093)+2 种基金Fundamental Research Funds for the Central Universities(HUST:2015J07)Open Fund of State Key Laboratory of New Ceramic and Fine Processing(Tsinghua University)(No.KF201518)the 02 Important and Special Project for the State Science and Technology(No.2013ZX2104-001-002).
文摘Porous Si_(3)N_(4) ceramics were prepared by aqueous gelcasting using Si_(3)N_(4) poly-hollow microspheres(PHMs)as pore-forming agent.The effects of solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content on the properties of porous Si_(3)N_(4) ceramics were investigated.Onlyβ-Si_(3)N_(4) phase is observed in porous Si_(3)N_(4) ceramics,and Si_(3)N_(4) PHMs distribute uniformly both in Si_(3)N_(4) green samples and porous Si_(3)N_(4) ceramics.Results show that solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content could considerably influence the properties of porous Si_(3)N_(4) ceramics.With the increase of solid loading of Si_(3)N_(4) slurry(decrease of Si_(3)N_(4) PHM content),the distributing state of Si_(3)N_(4) PHMs changes from contacting with each other to just embedding in the matrix,thus their porosity decreases,while their shrinkage,flexural strength,and fracture toughness increase.
