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Effects of TiO <sub/>2</sub> doping on microstructure and properties of directed laser deposition alumina/aluminum titanate composites
摘要： Al2O3-based composite ceramics have excellent high temperature performance and are ideal materials for preparing hot end components. However, poor fracture toughness and thermal shock resistance limit its applications. Based on the excellent low thermal expansion characteristics and thermal shock resistance of Al2TiO5 ceramic, different composition ratios of Al2O3/Al2TiO5 composite ceramics were prepared by directed laser deposition (DLD) technology. Effects of TiO2 doping amount on microstructure and properties of the composite ceramics were investigated. Results show that α-Al2O3 phase is discretely distributed in the continuous aluminum titanate matrix when TiO2 doping amount between 2 and 30 mol%. With the increase of TiO2 doping amount, content of Al2O3 gradually decreases and its morphology changes from cellular to dendritic. When TiO2 doping amount reaches 43.9 mol%, the microstructure transforms into fine Al2TiO5/Al6Ti2O13 eutectic structure. Property test results show that Al2O3/Al2TiO5 composite ceramics have good comprehensive mechanical properties when TiO2 doping amount between 2 and 6 mol%.
关键词： Al2O3/Al2TiO5,microstructure,Additive manufacturing,properties,composite ceramics
更新于2025-11-21 11:03:13
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In-situ synthesis of mullite-SiCw composite ceramics in Li2O-Al2O3-SiO2 ternary system for solar heat transmission pipeline
摘要： Nano-SiC whiskers (nano-SiCw) were in-situ synthesized in Li2O-Al2O3-SiO2 ternary system for preparing highly densified mullite-SiCw composite ceramics used for solar heat transmission pipeline. Mechanisms on the in-situ synthesis of nano-SiCw in the ternary system were investigated and the impact of nano-SiCw on the performances of the composites had been studied. Results showed that the growth processes of nano-SiC whiskers in Li2O-Al2O3-SiO2 ternary system were dominated by liquid-solid (LS) mechanism and the Li2CO3 additive could improve the SiCw yield through increasing the content of liquid phase and lowering the liquid viscosity. Sample BS3 (with 2.22 wt% Li2CO3 additive) sintered at 1440 °C obtained the highest SiC content of 47.9%. Nano-SiC whiskers with a diameter of 20e30 nm were interlocking with rod-like mullite crystals to improve the mechanical properties of the composites, and sample BS1 sintered at 1420 °C showed the highest bending strength of 115.4 MPa. The in-situ synthesized SiCw also shew significant effects on improving the thermophysical properties of the composites and sample BS1 exhibited a 3.6 times higher thermal conductivity than that of blank sample B1 without the introduction of nano-SiCw.
关键词： Li2O-Al2O3-SiO2 ternary system,Thermal conductivity,Mullite-SiCw composite ceramics,Solar heat transmission pipeline,SiC whiskers
更新于2025-09-23 15:23:52
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Influence of Sm and Nb on the structural, electric, magnetic and magneto-electric properties of BaTiO3-Li0.5Fe2.5O4 composite ceramics grown by the conventional solid state technique
摘要： The Sm and Nb doped BaTiO3-Li0.5Fe2.5O4 composite ceramics having chemical formulae (90)BaTi(1?2x)NbxSmxO3 + (10) Li0.5Fe2.5O4 (x = 0, 0.05 and 0.1) were synthesized using conventional solid state technique. The structural, morphological, magnetic, dielectric, ferroelectric and magneto-electric properties of composites have been studied. The XRD measurement reveals the absence of peaks pertaining to impurities and strongly confirms the high crystalline nature of all the composites. From FESEM images, the average grain size of composites increases with increase in the concentration of Nb and Sm. The VSM studies confirm the soft magnetic nature of all the composites. The dielectric measurements confirm the increase in the transition temperature (Tc) of the BTL composite with an increase in the concentration of Nb and Sm. The P–E studies confirm that the ferroelectric nature of the BTL composite softens after doping Nb and Sm in it. The ME voltage coefficient value confirms the uniform growth of grains in all the composites and reveals a strong interaction between ferroelectric and magnetic orders.
关键词： magneto-electric properties,BaTiO3-Li0.5Fe2.5O4,electric properties,magnetic properties,composite ceramics,Sm and Nb doping,structural properties
更新于2025-09-09 09:28:46