Silicon nitride composite is joined to itself by heating interlayer of Y2 O3 -AL2O3 -SiO2 mixtures above their liquidus temperatures in flowing nitrogen. The joined specimens are tested in four point flexure from room...Silicon nitride composite is joined to itself by heating interlayer of Y2 O3 -AL2O3 -SiO2 mixtures above their liquidus temperatures in flowing nitrogen. The joined specimens are tested in four point flexure from room temperature to 1373 K. The interface microstruclure and fractured surfaces after testing are observed and analyzed by SEM, EPMA and XRD respectively. The results show that F2 O3 -A12 O3 -SiO2 glass reacts with Si3 N4 at interface, forming the Si3 N4/Si2 N2 O( Y-AlrSi-O-N glass/ Y-Al- Si-O glass gradient interface. With the increase of bonding temperature and holding time, the joint strength first increases, reaching a peak, and then decreases . According to interfacial analyses , the bonding strength depends on joint thickness .展开更多
Si3N4 ceramics were prepared by pressureless sintering at 1 650 ℃ in nitrogen atmosphere using Si3N4 powder as main starting material and adding nano Al203 powder （3%, 6%, 9%, 12%, and 15% in mass, the same hereinaf...Si3N4 ceramics were prepared by pressureless sintering at 1 650 ℃ in nitrogen atmosphere using Si3N4 powder as main starting material and adding nano Al203 powder （3%, 6%, 9%, 12%, and 15% in mass, the same hereinafter）. The bending strength and fracture toughness （KIC） of the specimens were detected.The microstructure and phase compositions of the specimens were analyzed. The results show that SigN4 ceramics can be prepared by pressureless sintering when adding 9% -12% nano-A1203 as active reactant, which dissolves in Si3N4, in-situ forming non-oxide SiAION. The obtained Si3N4 ceramics have the maximum bending strength of 710. 86 MPa and KIC of 8. 61 MPa · m1/2 The exceUent properties come from many interwoven structures distributed uniformly in the ceramics matrix, u,hich is composed of big and firm plate-like β-Si3N., hexagonal SiAION and sheet Si2N2 0.展开更多
氮化硅陶瓷具有优异的物理机械性能和化学性能,被广泛应用于高温、化工、冶金、航空航天等领域.在结构陶瓷中氮化硅陶瓷虽具有相对较高的断裂韧性,但为了进一步拓宽氮化硅陶瓷的运用领域和提高其使用可靠性,改善其断裂韧性一直是该材料...氮化硅陶瓷具有优异的物理机械性能和化学性能,被广泛应用于高温、化工、冶金、航空航天等领域.在结构陶瓷中氮化硅陶瓷虽具有相对较高的断裂韧性,但为了进一步拓宽氮化硅陶瓷的运用领域和提高其使用可靠性,改善其断裂韧性一直是该材料研究的重要课题.笔者通过利用氮化硅陶瓷的自增韧技术,使用复合烧结助剂和在氮化硅基体中添加长柱状β-Si3 N4晶种,制备高断裂韧性的氮化硅陶瓷.采用X射线衍射、扫描电镜、阿基米德法、三点抗弯曲强度、单边切口梁法等测试方法对陶瓷的组成、显微结构、显气孔率以及抗弯强度和断裂韧性等进行了分析与表征.首先研究了无压烧结制备氮化硅陶瓷过程中,烧结助剂(Y2 O 3和Al2 O 3)对其烧结性能和力学性能的影响,当Y2 O 3含量为8wt%,Al2 O 3含量为4wt%时,氮化硅陶瓷的相对密度达95%以上,抗弯强度为674 MPa,断裂韧性为6.34 MPa·m1/2.再通过引入La2 O 3提高氮化硅晶粒的长径比,使氮化硅陶瓷的抗弯强度和断裂韧性达到686 MPa和7.42 MPa·m1/2.笔者通过无压烧结工艺,在1750℃制备了长柱状的β-Si3 N4晶种,晶种的平均长度为2.82μm,平均粒径为0.6μm,平均长径比为4.7,着重研究了晶种对氮化硅陶瓷烧结性能和力学性能的影响.氮化硅陶瓷中加入晶种后,其烧结性能和抗弯强度略有降低,但断裂韧性得到了很大的提高;且随着晶种添加量的增加,断裂韧性先升高再降低,掺杂量为2wt%时,断裂韧性达到最大(7.68 MPa·m1/2),提高了20%以上.展开更多
文摘Silicon nitride composite is joined to itself by heating interlayer of Y2 O3 -AL2O3 -SiO2 mixtures above their liquidus temperatures in flowing nitrogen. The joined specimens are tested in four point flexure from room temperature to 1373 K. The interface microstruclure and fractured surfaces after testing are observed and analyzed by SEM, EPMA and XRD respectively. The results show that F2 O3 -A12 O3 -SiO2 glass reacts with Si3 N4 at interface, forming the Si3 N4/Si2 N2 O( Y-AlrSi-O-N glass/ Y-Al- Si-O glass gradient interface. With the increase of bonding temperature and holding time, the joint strength first increases, reaching a peak, and then decreases . According to interfacial analyses , the bonding strength depends on joint thickness .
文摘Si3N4 ceramics were prepared by pressureless sintering at 1 650 ℃ in nitrogen atmosphere using Si3N4 powder as main starting material and adding nano Al203 powder （3%, 6%, 9%, 12%, and 15% in mass, the same hereinafter）. The bending strength and fracture toughness （KIC） of the specimens were detected.The microstructure and phase compositions of the specimens were analyzed. The results show that SigN4 ceramics can be prepared by pressureless sintering when adding 9% -12% nano-A1203 as active reactant, which dissolves in Si3N4, in-situ forming non-oxide SiAION. The obtained Si3N4 ceramics have the maximum bending strength of 710. 86 MPa and KIC of 8. 61 MPa · m1/2 The exceUent properties come from many interwoven structures distributed uniformly in the ceramics matrix, u,hich is composed of big and firm plate-like β-Si3N., hexagonal SiAION and sheet Si2N2 0.
文摘氮化硅陶瓷具有优异的物理机械性能和化学性能,被广泛应用于高温、化工、冶金、航空航天等领域.在结构陶瓷中氮化硅陶瓷虽具有相对较高的断裂韧性,但为了进一步拓宽氮化硅陶瓷的运用领域和提高其使用可靠性,改善其断裂韧性一直是该材料研究的重要课题.笔者通过利用氮化硅陶瓷的自增韧技术,使用复合烧结助剂和在氮化硅基体中添加长柱状β-Si3 N4晶种,制备高断裂韧性的氮化硅陶瓷.采用X射线衍射、扫描电镜、阿基米德法、三点抗弯曲强度、单边切口梁法等测试方法对陶瓷的组成、显微结构、显气孔率以及抗弯强度和断裂韧性等进行了分析与表征.首先研究了无压烧结制备氮化硅陶瓷过程中,烧结助剂(Y2 O 3和Al2 O 3)对其烧结性能和力学性能的影响,当Y2 O 3含量为8wt%,Al2 O 3含量为4wt%时,氮化硅陶瓷的相对密度达95%以上,抗弯强度为674 MPa,断裂韧性为6.34 MPa·m1/2.再通过引入La2 O 3提高氮化硅晶粒的长径比,使氮化硅陶瓷的抗弯强度和断裂韧性达到686 MPa和7.42 MPa·m1/2.笔者通过无压烧结工艺,在1750℃制备了长柱状的β-Si3 N4晶种,晶种的平均长度为2.82μm,平均粒径为0.6μm,平均长径比为4.7,着重研究了晶种对氮化硅陶瓷烧结性能和力学性能的影响.氮化硅陶瓷中加入晶种后,其烧结性能和抗弯强度略有降低,但断裂韧性得到了很大的提高;且随着晶种添加量的增加,断裂韧性先升高再降低,掺杂量为2wt%时,断裂韧性达到最大(7.68 MPa·m1/2),提高了20%以上.
