Enhanced compactness of oriented MFI zeolite films by heat treatment of seed layer

The achievement of compact and defect-free film structure is crucial for the application of b-oriented MFI zeolite film. In this work, a novel heat treatment technique was used to treat zeolite seeded substrates prior to secondary growth. The influence of the heat treatment parameters such as treat temperature and time on the final film morphology were systematically investigated. The relationship between film compactness and the parameters was established. Under the optimized treat temperature of 120?°C and treat time of 1?h, compact and uniform b-oriented MFI zeolite film was achieved. The applicability of the optimum heat treatment condition was validated by employing various film substrates.     

Large increase of Curie temperature in (110)-oriented La0.7Sr0.3MnO3 films

From the perspectives of scientific researches and practical applications, it is desirable to explore high operating temperature ferromagnetic films. The effect of biaxial strain on magnetic properties of (110)-oriented La_0.7Sr_0.3MnO₃ films was studied. High quality La_0.7Sr_0.3MnO₃ films were grown on (110)-oriented perovskite single crystal substrates using pulsed laser deposition, varying substrate-induced misfit strains from ??2.27–0.75%. A remarkable enhancement of Curie temperature has been achieved for (110)-oriented La_0.7Sr_0.3MnO₃ films clamped with small misfit strains (i.e., grown on LAST (110)). The enhanced Curie temperature of (110)-oriented La_0.7Sr_0.3MnO₃ films could be attributed to the misfit strain between the films and the underlying substrates and may have technological implication for applications at high temperature environments.     

Effect of donor W and acceptor Ni codoping at Ti site on the structure and electrical properties of Na0.5Bi0.5TiO3 thin film

Pure Na_0.5Bi_0.5TiO₃ (NBT), donor W⁶⁺ doped NBT (NBTW), acceptor Ni²⁺ doped NBT (NBTNi), as well as donor W⁶⁺ and acceptor Ni²⁺ codoped NBT (NBTWNi) polycrystalline films are fabricated on indium tin oxide (ITO)/glass substrates via a chemical solution deposition method. The roles of aliovalent-ion substitution on the crystallinity, ferroelectric and dielectric properties of NBT film are mainly investigated. With the introduction of aliovalent-ion, the surface of the doped film becomes more uniform and the leakage current is reduced. Well saturated polarization-electric field (P-E) loops can be observed in W⁶⁺ and Ni²⁺ codoped NBT film due to its lowest leakage currents compared to those of other films. Also, the effect of voltage and frequency on the capacitance-voltage (C-V) curve and the dielectric tunability for the NBTWNi film is discussed. The ferroelectric and dielectric properties are largely improved in NBTWNi film, which can be ascribed to the synergetic effect of high-valence W⁶⁺ and low-valence Ni²⁺ ions. The cooperation between the acceptor and donor cations can effectively eliminate the mobile oxygen vacancies in NBT films.     

Enhancement of piezoelectric and ferroelectric performances in (Na0.85K0.15)0.5Bi0.5TiO3 films with BaTiO3 interlayers

In this work, in order to optimize the electrical performance of (Na_0.85K_0.15)_0.5Bi_0.5TiO₃ (NKBT) thin films, 20 nm-thick BaTiO₃ (BTO) layer was utilized by deliberately coating in the NKBT film-substrate interface or in the NKBT film, i.e., BTO layers coated in sequence with NBKT layers. The BTO layer, especial coated in the NKBT film, was beneficial for crystallization process and more preferable to form a denser film morphology. The BTO-coated NKBT composite films exhibited much enhancement in electrical properties compared to the films without BTO layer. Accordingly, a high effective piezoelectric coefficient d₃₃^* of 75 pm/V and remnant polarization P_r of 22.1 μC/cm², as well as a low leakage current density of 1.2 × 10^?5 A/cm² were obtained in the 460 nm-thick composite film with BTO layers coated in the NBKT film. It meant that this kind of BTO-coated NKBT composite film could perform as a potential candidate for the lead-free piezoelectric applications. The observed enhancement in the electrical properties with the introduction of BTO layer could be mainly explained by the weakened influence of domain pinning in the film-electrode interface and grain boundaries due to the decreased strain in the film-electrode interface and better crystallinity in the highly (110)-oriented NKBT films, thereby enhancing motion of domain-walls.     

透明红外硫系薄膜非均匀性检测及影响因素

薄膜非均匀性的无损检测对于制备大面积高质量的红外透明薄膜尤为重要。针对红外薄膜光学均匀性难以获取的困难,提出了一种同时获得单层透明红外薄膜厚度和折射率均匀性的无损检测方法。实验上,通过磁控溅射法在二氧化硅衬底上制备了厚度约1.4μm红外透明Ge-Sb-Se硫系薄膜,然后在该薄膜上标定出36个80μm×80μm区域,利用显微傅里叶红外光谱仪测得该36个区域的透射谱,通过分段滤波的方法滤除背景噪声,运用改进的Swanepoel方法计算得到了薄膜每一个区域的厚度和折射率,进而精确获得该薄膜的厚度和折射率均匀性,结果表明精度优于0.5%。     

柱塞副微观表面对间隙油膜压力的影响

根据分形理论中的W-M函数建立柱塞与缸体孔表面三维形貌数学模型,并利用MATLAB软件编写程序,分析分形维数对表面微观形貌的影响。将柱塞副间隙油膜沿轴向展成平面,建立油膜厚度及压力分布计算模型,采用有限体积法求解二维雷诺方程,分析粗糙度对柱塞副间隙油膜压力分布的影响。结果表明:随着分形维数的增加,柱塞表面粗糙度呈增加趋势,且表面粗糙度越大,压力峰值越大。     

表面形貌对粗糙接触界面流体润滑特性的影响

为探究不同表面形貌对粗糙接触界面液体润滑特性的影响，基于有限差分法结合雷诺方程和膜厚方程，研究阶梯形貌、波纹形貌、随机形貌和峡谷形貌4种不同粗糙接触界面液体润滑时的载荷分布及规律。研究发现：4种粗糙表面的三维载荷分布规律都与其表面形貌相对应，在波“峰”处载荷大，摩擦力随载荷的增大而增大，在波“谷”载荷小，摩擦力随载荷减小而减小；4种粗糙表面的载荷随表面展开面积比的变化趋势却有所不同；随表面展开面积比的增大，阶梯形貌表面的载荷呈线性增大，波纹形貌表面的载荷基本不变，随机分布形貌表面的载荷呈增大趋势，峡谷形貌表面的载荷呈先增大后减小的变化趋势。研究结果可以进一步补充现有表面形貌表征和流体润滑等相关研究理论。     

纳米银-聚合物薄膜的制备及力电性能测试

聚合物基底上纳米银颗粒薄膜的制备工艺相对简单,成本较低,且该薄膜具有成为高敏感性压阻应力/应变传感材料的潜力。本文采用银镜制备法在聚酰亚胺(PI)和聚乙烯(PE)上合成了纳米银颗粒薄膜,系统研究了该薄膜制备工艺、结构特性、材料性能之间的关系。实验考察了材料“浸泡”时间及聚合物材料前处理等因素对材料表面吸附纳米颗粒含量的影响,研究了 “浸泡”时间对纳米银颗粒粒径大小、颗粒含量及分布的影响,并探讨了不同聚合物基体的颗粒特性对薄膜二维导电渗滤,压阻特性及拉伸性能的影响。研究表明,增加“浸泡”时间能够增加纳米银颗粒粒径大小,提高银颗粒的含量及分布均匀性；在相同的制备条件下,PI基底较PE基底对纳米银颗粒具有更加优异的吸附效果；在PI 和PE基底上的纳米银颗粒薄膜均表现出显著的压阻性能,且电阻对应变的敏感性随应变的增大及银颗粒含量的减少而显著提高。