分析了Ba Ti1-xNbxO3(0≤x≤0.04)陶瓷样品中存在的补偿机制及其结构与介电性能的变化。结果表明:Nb5+的掺入没有引起第二相的生成,并能减小陶瓷晶粒尺寸;Nb5+离子的加入有利于Ba Ti O3陶瓷从正常铁电体向弛豫铁电体转变,降低介电常数...分析了Ba Ti1-xNbxO3(0≤x≤0.04)陶瓷样品中存在的补偿机制及其结构与介电性能的变化。结果表明:Nb5+的掺入没有引起第二相的生成,并能减小陶瓷晶粒尺寸;Nb5+离子的加入有利于Ba Ti O3陶瓷从正常铁电体向弛豫铁电体转变,降低介电常数峰值温度(Tm),提高室温介电常数,减小剩余极化强度(Pr)和矫顽场(Ec)。通过Gulp模拟并分析得出当Nb5+掺入后,主要以空位进行补偿,且以钡空位补偿为主,形成缺陷簇。展开更多
Computational energy minimization techniques have been used to study the structure and crystal properties of kaolinite. The full elastic tensors of the sheet silicates of clay have been derived with first-principles c...Computational energy minimization techniques have been used to study the structure and crystal properties of kaolinite. The full elastic tensors of the sheet silicates of clay have been derived with first-principles calculations based on density functional theory. All calculations were performed using GULP program.展开更多
The experimental prediction of the mechanical properties of minerals remains difficult because of their small particle size (typically < 2 micrometers). This work aims at examining, the effect of an applied mechani...The experimental prediction of the mechanical properties of minerals remains difficult because of their small particle size (typically < 2 micrometers). This work aims at examining, the effect of an applied mechanical constraint on the hydration behaviour in the case of Na rich-montmorillonite and its relation with the elastic properties. The mechanical constraint is created, at the laboratory scale, by applying a monoaxial pressure for unstressed host material (i.e. Na rich montmorillonite). The structural analysis before and after stress is achieved using an XRD profile modeling approach. This investigation allowed us to determine several structural parameters related to the nature, abundance, size, position and organization of exchangeable cation and water molecule in the interlamellar space along the c* axis. In order to evaluate the affected elastic properties, the GULP code have been used to study the structure and the interlamellar organization. Indeed, the bulk modulus and elastic constants of montmorilonite have been calculated from first principles within density functional theory (DFT). The obtained Young’s modulus for Na-montmorillonite interlayer varies from 5 GPa to 16 GPa. According to the interlamellar space configuration the calculated elastic constant tensors indicate that the a direction is slightly more flexible than the b direction. The calculated elastic constant tensor along c is much lower than the constants calculated along a and b.展开更多
文摘分析了Ba Ti1-xNbxO3(0≤x≤0.04)陶瓷样品中存在的补偿机制及其结构与介电性能的变化。结果表明:Nb5+的掺入没有引起第二相的生成,并能减小陶瓷晶粒尺寸;Nb5+离子的加入有利于Ba Ti O3陶瓷从正常铁电体向弛豫铁电体转变,降低介电常数峰值温度(Tm),提高室温介电常数,减小剩余极化强度(Pr)和矫顽场(Ec)。通过Gulp模拟并分析得出当Nb5+掺入后,主要以空位进行补偿,且以钡空位补偿为主,形成缺陷簇。
文摘Computational energy minimization techniques have been used to study the structure and crystal properties of kaolinite. The full elastic tensors of the sheet silicates of clay have been derived with first-principles calculations based on density functional theory. All calculations were performed using GULP program.
文摘The experimental prediction of the mechanical properties of minerals remains difficult because of their small particle size (typically < 2 micrometers). This work aims at examining, the effect of an applied mechanical constraint on the hydration behaviour in the case of Na rich-montmorillonite and its relation with the elastic properties. The mechanical constraint is created, at the laboratory scale, by applying a monoaxial pressure for unstressed host material (i.e. Na rich montmorillonite). The structural analysis before and after stress is achieved using an XRD profile modeling approach. This investigation allowed us to determine several structural parameters related to the nature, abundance, size, position and organization of exchangeable cation and water molecule in the interlamellar space along the c* axis. In order to evaluate the affected elastic properties, the GULP code have been used to study the structure and the interlamellar organization. Indeed, the bulk modulus and elastic constants of montmorilonite have been calculated from first principles within density functional theory (DFT). The obtained Young’s modulus for Na-montmorillonite interlayer varies from 5 GPa to 16 GPa. According to the interlamellar space configuration the calculated elastic constant tensors indicate that the a direction is slightly more flexible than the b direction. The calculated elastic constant tensor along c is much lower than the constants calculated along a and b.
