Fabrication of lanthanum doped BaTiO3 fine-grained ceramics with a high dielectric constant and temperature-stable dielectric properties using hydro-phase method at atmospheric pressure

Lanthanum doped BaTiO₃ powders were synthesized by the hydro-phase method at atmospheric pressure, which controls the uniformity and particle size of the ceramic powders. The effects of La³⁺ ions concentration on the microstructure and dielectric properties of BaTiO₃ ceramics were studied. The results suggested that both the average grain size and dielectric constants (ε_r and ε_max) of the ceramics decreased as the concentration of La³⁺ increased. The ceramic met the X8R specifications: La³⁺ ions concentration of 3 mol%, a permittivity of 2322, low dielectric loss of less than 0.6% at room temperature, and average grain size of about 260 nm.     

Exceptional thermal interface properties of a three-dimensional graphene foam

We have uncovered some unusual thermal interface properties of a three-dimensional, flexible and interconnected graphene foam (GF). The thermal interfacial resistance of GF at Si–Al interface is as low as 0.04 cm²K W⁻¹, which is one order of magnitude lower than conventional thermal grease and thermal paste-based thermal interfacial material (TIM). The thermal contact resistance was found to dominate the overall interfacial resistance of GF-based TIM, in as much as the bulk thermal conductivity of GF is rather high. The contact pressure-dependent thermal interfacial resistance of GF exhibits an asymptotic behavior, which converges into a plateau value at an ultralow contact pressure (∼0.1 MPa). Significantly, the GF-based TIM has shown a superior performance to vertically aligned carbon nanotubes currently held as the gold standard (at least ∼75% improvement in thermal interfacial resistance at Si–Al interface), thus providing a strong candidate for the next generation of high-performance carbon-based TIM.     

Thickness effect on the crystallization characteristic of RF sputtered Sb thin films

Journal of Materials Science: Materials in Electronics - The monobasic Sb thin films with different thicknesses were prepared by radio frequency magnetron sputtering. The evolutions of Sb thin film...     

Optimization for etching shallow ridge and trench profiles on silicon based on continuous etching process in ICPRIE system

Microsystem Technologies - In order to directly characterize sidewall roughnesses of shallow microstructures with etching depth less than 10 μm using a conventional atomic force...     

Synthesis and failure behavior of super-aligned carbon nanotube film wrapped graphene fibers

Significant progress has been made in recent years in research on wet spinning and hydrothermal synthesis of graphene fibers. In this paper, we report the relationship between the mechanical performance of graphene oxide (GO) fibers and their processing parameters in wet spinning. With super-aligned carbon nanotube (CNT) film wrapping, the specific strength and electrical conductivity of reduced GO (rGO) fibers were simultaneously enhanced by 22% and 49%, respectively. Thicker CNT film wrapping of the rGO fiber induces a core–sheath structure; the resulting interfacial debonding and slippage under fiber axial loading were examined. The findings of this study provide guidelines for optimization of high-performance graphene/CNT hybrid fibers.     

Influence of the surface treatment of PEDOT:PSS layer with high boiling point solvent on the performance of inverted planar perovskite solar cells

Since perovskite precursor solution is typically prepared from high boiling point solvents, understanding the effect of high boiling point solvent treatment of the PEDOT:PSS layer on the performance of perovskite solar cells is important for device processing optimization. In this paper, influence of the surface treatment of the PEDOT:PSS layer with high boiling point solvent, including N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and ethylene glycol (EG), on the device performance of the perovskite solar cells was investigated. Increased conductivity was measured for the PEDOT:PSS film after solvent treatments, which was ascribed to the partial removal of PSS component from the PEDOT:PSS layer, as evidenced by the UV–vis absorption spectroscopy and XPS spectroscopy. In comparison with the reference cell, poorer device performance was obtained for the perovskite solar cells directly deposited on the solvent washed PEDOT:PSS film, which was ascribed to the increased pin hole density of the perovskite films. However, insertion of a thin PSSNa layer between the PEDOT:PSS layer and the perovskite layer greatly improved device performance, demonstrating that PSS-rich surface is favorite for the crystal growth of the perovskite film. Increased external quantum efficiency over 600–750 nm was measured for the cells based on solvent treated PEDOT:PSS layer, leading to a short circuit current and the consequent performance enhancement.     

Probing graphene interfaces with secondary electrons

The empty states of graphene and graphene adsorbed on nickel (1 1 1) are studied using a plane-wave pseudo-potential method based on local density functional theory. The analysis is used to assign spectroscopic features observed in secondary electron emission experiments either to the graphene sheet or to the nickel substrate. The calculations provide insights into the key role of the graphene–substrate interaction, through the hybridization between carbon and nickel states, and indicate secondary electron emission as an efficient probe for interfaces made of two dimensional crystals.     

钴/氧化镁催化体系升温速率对单壁碳纳米管管径的调节作用

以钴(Co)、氧化镁(MgO)作催化剂和催化剂载体,采用化学气相沉积(CVD)法催化裂解甲烷气体制备单壁碳纳米管(SWNTs)。利用拉曼光谱、紫外-红外-近红外吸收光谱、透射电子显微镜、X射线衍射、扫描电子显微镜等手段对样品进行表征。结果表明,在Co/MgO催化体系下,通过改变升温速率可以调节产物中粗细管径(0.8～1.4nm)SWNTs的相对含量;同时还证实了在不同的升温速率下所得到MgO基体的晶体结构是相同的。