Vertically Aligned Nanocomposite Thin Films

Vertically aligned nanocomposite (VAN) thin films have recently stimulated significant research interest to achieve better material functionality or multifunctionalities. In VAN thin films, both phases grow epitaxially in parallel on given substrates and form a unique nano-checkerboard structure. Multiple strains, including the vertical strain which along the vertical interface and the substrate induced strain which along the film and substrate interface, exist in VAN thin films. The competition of these strains gives a promise to tune the material lattice structure and future more the nanocomposite film physical properties. Those two phases in the VAN thin films are selected based on their growth kinetics, thermodynamic stability and epitaxial growth ability on given substrates. In the present work, we investigated unique epitaxial two-phase VAN (BiFeO3)x:(Sm2O3)1-x and (La0.7Sr0.3MnO3)x:(Mn3O4)1-x thin film systems by pulsed laser deposition. These VAN thin films exhibit a highly ordered vertical columnar structure with good epitaxial quality. The strain of the two phases can be tuned by deposition parameters, e.g. deposition frequency and film composition. Their strain tunability is found to be related directly to the systematic variation of the column widths and domain structures. Their physical properties, such as dielectric loss and ferromagnetisms can be tuned systematically by this variation. The growth morphology, microstructure and material functionalities of VAN thin films can be varied by modifying the phase ratio, substrate orientation or deposition conditions. Systematic study has been done on growing (SrTiO3)0.5:(MgO)0.5 VAN thin films on SrTiO3 and MgO substrates, respectively. The variation of column width demonstrates the substrate induced strain plays another important role in the VAN thin film growth. The VAN thin films also hold promise in achieving porous thin films with ordered nanopores by thermal treatment. We selected (BiFeO3)0.5:(Sm2O3)0.5 VAN thin films as a template and get uniformly distributed bi-layered nanopores. Controllable porosity can be achieved by adjusting the microstructure of VAN (BiFeO3):(Sm2O3) thin films and the annealing parameters. In situ heating experiments within a transmission electron microscope column provide direct observations into the phases transformation, evaporation and structure reconstruction during the annealing. Systematic study in this dissertation demonstrate that the vertically aligned nanocomposite microstructure is a brand new architecture in thin films and an exciting approach that promises tunable material functionalities as well as novel nanostructures

Evolution of microstructure, strain and physical properties in oxide nanocomposite films

We, using LSMO:ZnO nanocomposite films as a model system, have studied the effect of film thickness on the physical properties of nanocomposites. It shows that strain, microstructure, as well as magnetoresistance strongly rely on film thickness. The magnetotransport properties have been fitted by a modified parallel connection channel model, which is in agreement with the microstructure evolution as a function of film thickness in nanocomposite films on sapphire substrates. The strain analysis indicates that the variation of physical properties in nanocomposite films on LAO is dominated by strain effect. These results confirm the critical role of film thickness on microstructures, strain states, and functionalities. It further shows that one can use film thickness as a key parameter to design nanocomposites with optimum functionalities

Room Temperature Ferrimagnetism and Ferroelectricity in Strained, Thin Films of BiFe0.5Mn0.5O3.

Highly strained films of BiFe0.5Mn0.5O3 (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (TC ∼ 600K), with a room temperature saturation moment (MS ) of up to 90 emu/cc (∼ 0.58 μB /f.u) on high quality (001) SrTiO3. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe3+ and Mn3+. While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.This is the final published version. It's also available from Advanced Functional Materials: http://onlinelibrary.wiley.com/doi/10.1002/adfm.201401464/full

Defect Distributions and Transport in Nanocomposites: A Theoretical Perspective

Nanomaterials are attracting great interest for many applications, including radiation tolerance. Most work on radiation effects in nanomaterials has focused on the interfaces. Here, we examine the other aspect of nanocomposites, the dual phase nature. Solving a reaction–diffusion model of irradiated composites, we identify three regimes of steady-state behavior that depend on the defect properties in the two phases. We conclude that defect evolution in one phase depends on the defect properties in the other phase, offering a route to controlling defect evolution in these materials. These results have broad implications for nanomaterials more generally

Microstructure and Texture of 2205 Duplex Stainless Steel Additive Parts Fabricated by the Cold Metal Transfer (CMT) Wire and Arc Additive Manufacturing (WAAM)

Additive parts made of 2205 duplex stainless steel were fabricated by cold metal transfer (CMT) wire and arc additive manufacturing (WAAM), and their microstructure and properties were systematically studied. The X-ray diffraction results show that austenite phase and ferrite phase were formed in the additive parts. Due to the low heat input characteristics of CMT-WAAM, no σ phase was observed. The microstructure in the additive parts was different from the bottom to the top, with the content of austenite phase gradually increasing and that of ferrite gradually decreasing. The EBSD results indicate that the ferrite phase in the bottom part grew parallel to the normal direction of {100}. However, the ferrite phase in the middle part grew parallel to the plane composed of the build direction and normal direction, and along {100} and {111}. The effect of the ferrite and austenite contents on the mechanical performance of the additive parts was simulated using the LAMMPS software. The simulation results exhibit a common characteristic in that the dislocations move mainly along the 1/6 crystallographic direction families. The simulated maximum tensile stress values of the bottom, middle, and top parts were 23.3 GPa, 22.3 Gpa, and 22.5 Gpa, respectively. The data from the bottom tensile strength simulation were consistent with the actual data, and the bottom tensile strength was the largest in the actual tensile process

Microstructure and Texture of 2205 Duplex Stainless Steel Additive Parts Fabricated by the Cold Metal Transfer (CMT) Wire and Arc Additive Manufacturing (WAAM)

Additive parts made of 2205 duplex stainless steel were fabricated by cold metal transfer (CMT) wire and arc additive manufacturing (WAAM), and their microstructure and properties were systematically studied. The X-ray diffraction results show that austenite phase and ferrite phase were formed in the additive parts. Due to the low heat input characteristics of CMT-WAAM, no σ phase was observed. The microstructure in the additive parts was different from the bottom to the top, with the content of austenite phase gradually increasing and that of ferrite gradually decreasing. The EBSD results indicate that the ferrite phase in the bottom part grew parallel to the normal direction of {100}. However, the ferrite phase in the middle part grew parallel to the plane composed of the build direction and normal direction, and along {100} and {111}. The effect of the ferrite and austenite contents on the mechanical performance of the additive parts was simulated using the LAMMPS software. The simulation results exhibit a common characteristic in that the dislocations move mainly along the 1/6<112> crystallographic direction families. The simulated maximum tensile stress values of the bottom, middle, and top parts were 23.3 GPa, 22.3 Gpa, and 22.5 Gpa, respectively. The data from the bottom tensile strength simulation were consistent with the actual data, and the bottom tensile strength was the largest in the actual tensile process

Regression of mature corneal lymphatic vessels by intracorneal ranibizumab injection

Objective: Ranibizumab is a Fab fragment of a recombinant, humanized, monoclonal anti-vascular endothelial growth factor (VEGF) antibody. This study analyzes the possibility of regressing lymphangiogenesis and hemangiogenesis by intracorneal ranibizumab injection. In addition, the effect of ranibizumab on corneal endothelial cells (CECs) of mice is also studied. Methods: Hemangiogenesis and lymphangiogenesis were induced in female BALB/c mice using the murine model of suture-induced inflammatory neovascularisation. The treatment group received an intracorneal injection of ranibizumab (controls: phosphate buffered saline (PBS)). Corneas were excised at different time points (1 day, 5 days, and 10 days) after the injection, and corneal whole mounts were stained with CD31, LYVE-1, and alizarin red S to quantify hemangiogenesis, lymphangiogenesis, and corneal endothelium. The morphology was analyzed by using the image analysing programme Cell boolean AND F and Image J image analysis programme, respectively. Results: In accordance with our previous findings, lymphatic vessels and blood vessels could be reduced after an intracorneal ranibizumab injection: One day after the injection, lymphatic vessels were reduced by 18% (P = 0.4), blood vessels were reduced by 22% (P = 0.083); after 5 days and 10 days, lymphatic vessels were reduced by 50% (P = 0.002) and 63% (P 0.05). Conclusions: This study is the first to demonstrate that the intracorneal ranibizumab injection is a novel technique to specifically induce regression of corneal lymphatics and blood vessels without affecting corneal endothelial cells

Effect of Co2N impurity on the superconducting properties of δ-MoN thin films grown by polymer assisted deposition

We report the effect of Co2N impurity on the superconducting properties of δ-MoN thin films grown by polymer-assisted deposition on c-cut sapphire (Al2O3). The films show a superconducting transition temperature of 10.4 K and an upper critical field Hc2(0) perpendicular to the film surface around 3 T. The latter corresponds to a relatively large coherence length ξ, which enhances the two-dimensional limit when the magnetic field is applied parallel to the film surface. In comparison with pure δ-MoN films, the inclusion of Co2N impurity in the δ-MoN films could significantly modify the critical current density at the vortex-free state. The ability to tune the superconducting properties of metal-nitride superconductors by introducing chemically and structurally compatible impurity may find potential applications for superconducting single-photon detectors.Fil: Haberkorn, Nestor Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Zhang, Yingying. Tsinghua University; ChinaFil: Bi, Zhenxing. Ibm Research; Estados UnidosFil: Park, Bae Ho. Konkuk University; Corea del SurFil: Civale, Leonardo. Los Alamos National Laboratory; Estados UnidosFil: Jia, Quanxi. Konkuk University; Corea del Sur. University at Buffalo; Estados Unidos. State University of New York; Estados Unido