With the advent of amorphous oxide semiconductors (AOS) like amorphous indium gallium zinc oxide (a-IGZO), the analysis and prediction of amorphous structures has regained importance, more so, since first principles based studies are being increasingly employed to explain device behavior. Negative bias illumination stress in a-IGZO thin film transistors is one such example. However, the amorphous atomic structure is complex and defect or dopant studies require each site to be modeled independently and this leads to significant computational costs. Therefore, a simplification in the representation of the amorphous oxide network is effected so that it may lead to identifying similar atomic sites. The amorphous network is visualized as a network of polyhedra. The polyhedra has at its center a cation with the bonded oxygen atoms at the vertices and it comprises the short range interactions characterized by bond lengths and bond angles. Based on a first principles study of 10 a-IGZO models containing 36 cations each, it was found that the 360 polyhedra of the a-IGZO models can actually be described with only ten polyhedral motifs. These polyhedra are then connected to each other via a shared vertex or an edge; face-sharing was not observed in these models. Graph theory is used to map this network using either a graph of cationic polyhedra as the nodes or a bipartite graph (composed of cations and anions as individual nodes), each of which is described using the respective adjacency matrix. The second nearest interactions are characterized by the degree of each vertex and each atomic site is now characterized by a polyhedron and network metrics; and hence, can be compared with same-element sites. The changes in network itself, are quantified as the composition changes, when varying the ratio of In:Ga:Zn in a-IGZO. For example, the average vertex connectivity of a pair of indium sites reflects on the continuity of overlap between the In-5s orbitals which compose the conduction band minimum in a-IGZO, which, in turn, affects the transport properties of the semiconductor. Thus, the long range interactions of the physical amorphous network are described by the graph metrics. Moreover, evolutionary algorithm in conjunction with this graph theoretic representation can be used to generate new amorphous models. Two parent graph are chosen and then spliced and then bred. The new graph is then reverse-engineered to form an amorphous model which then undergoes ionic and volume relaxation in the framework of density functional theory. The resulting graph is the child and the new amorphous model, with the energy as the fitness criteria.

For heat-assisted magnetic recording (HAMR) heads, a major reliability limiter is the peak near-field transducer (NFT) temperature. Since the NFT is nanoscale, heat sinking is controlled by materials and interfaces within a few 100 nm of the NFT. Heat sinks can be metallic to take advantage of the 10x-100x higher thermal boundary conductance (TBC) of metal/metal interfaces, versus nonmetal interfaces. Oxide formation at these interfaces can greatly decrease the TBC and contribute to NFT failure. Likewise, the thermal resistance of material between the NFT and media recording layer greatly influences the NFT operating temperature. Here we use pump-probe thermoreflectance techniques (FDTR, TDTR) to study metal-metal interfaces and detect partial oxidation of a buried metallic thin film, as well as evaluate the interface thermal conductance of amorphous-amorphous interfaces in a film stack representative of a HAMR head-media interface.

We fabricated a novel open-air channel with high efficient capillary-driven system inspired by a coastal animal “wharf roach”. The animal has open-air channels on its legs to transport water spontaneously using by capillary force. We abstracted principles controlling this phenomenon and applied it to artificial open-air channels, aiming at manipulating liquids without external energies. After surface modification for high surface free energy, the inspired open-air channels were able to transport water against gravity as well as the open-air channels of wharf roach by capillary effect of surface microstructures and chemistries. Topographical variation in micrometer-scaled patterns induced transport velocities improvement due to the enhancement of spreading intervals between the microstructure and wettability. Considering topography of micropatterned surfaces, the open-air channels with controllable transport velocity are applicable to capillary-driven microfluidics and lab-on-a-chips.

Determining what external stimuli influence cell differentiation, morphology, and growth continues to be a focus on many research groups to meet the healthcare Grand Challenges. While prior work has shown the influence of stiffness, surface chemistry and topography, these parameters often change in tandem, making it difficult to delineate the role of an individual component. This study examined the possible incorporation of microelectronic processing to produce reusable substrates for cell guidance studies. Subsequent plating of substrates cleaned with methods common in a microelectronic fabrication process showed complex responses including migration. Optical characterization of surfaces after cleaning showed remaining cellular debris that could be removed through the incorporation of a piranha solution. The micro patterned substrates did allow controlled comparison between dental pulp stem cells and osteoblast cells. The dental pulp cells did not show any cell alignment or cell proliferation (as indicated by cell density) with the isotropic or anisotropic micropatterns on the initial plating. The osteoblast cells (control) only aligned with the lines and not any of the other patterns (dots, holes or hexagons).

Lanthanum zirconate (La2Zr2O7) nano-crystalline films with cubic structure have been successfully prepared by a facile synthesis approach called reactive spray deposition technology (RSDT). La2Zr2O7 nanoparticles are produced by combusting a precursor solution of lanthanum acetylacetonate hydrate and zirconium acetylacetonate dissolved in an organic solvent mixture. The nanoparticles formed during the combustion process are directly deposited onto the substrate. The composition and microstructure of the as-deposited films are extensively characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The thermal diffusivities of the films are investigated by the means of laser flash method.

A virtual X-Ray Laboratory for Materials Science and Engineering has been developed and used as a flexible and powerful tool to help undergraduate and graduate students become familiar with the design and operation of the X-ray equipment in visual and interactive ways in order to learn fundamental principles underlying X-ray analytical methods. The virtual equipment and lab assignments have been used for: (i) authentic online experimentation, (ii) homework and control assignments with traditional and blended courses, (iii) preparing students for hands-on work in physical X-ray labs, (iv) lecture demonstrations, and (v) performance-based assessment of students’ ability to apply gained theoretical knowledge for operating actual equipment and solving practical problems. Students have also used the virtual diffractometer linked and synchronized with an actual powder diffractometer for blended experimentation. Using the associated learning and content management system (LCMS) and authoring tools, instructors kept track of students’ performance and designed new virtual experiments and more personalized learning assignments for students. The lab has also been integrated with the MITx course available on the massive open online course edX platform for Massachusetts Institute of Technology for undergraduate students.

The synthesis of Y2Ti2O7-Al2O3 compositional (multiphase) ceramics from powder mixtures Al2O3-Y2O3-TiO2 was carried out in two stages: 1) under the traditional sintering and then 2) in regime of directed laser heating. It was established that the sintering of mixtures with different content of components and the ratio of TiO2/Y2O3 = 2.34 in ceramic specimens the main phases are Y2Ti2O7 and α-Al2O3. The content of the main phases in ceramic materials also depends upon the oxide content in the initial mixtures. In ceramics the Y3Al5O12 is formed only at sufficiently high content of titanium and yttrium oxides in initial mixtures. In laser remelting, the phase composition is substantially different from that obtained at the traditional sintering, and depends on the mode of laser heating: irradiation power and the moving speed of the laser beam (i.e., heating temperature). Under certain conditions of laser remelting can be obtained superficial ceramic layer with crystallographic directional crystallization of Y2Ti2O7 and Al2O3 crystallites. The size of crystallites and the coefficient texturing also depend on the mode of laser treatment.

Fully atomistic molecular dynamics simulations were carried out to investigate how a liquid-like water droplet behaves when into contact with a nanopore formed by carbon nanotube arrays. We have considered different tube arrays, varying the spacing between them, as well as, different chemical functionalizations on the uncapped nanotubes. Our results show that simple functionalizations (for instance, hydrogen ones) allow tuning up the wetting surface properties increasing the permeation of liquid inside the nanopore. For functionalizations that increase the surface hydrophilicity, even when the pore size is significantly increased the droplet remains at the surface without tube permeation.

It is known that microstructure of metallic polycrystalline materials irradiated with neutrons is often characterized by a high degree of heterogeneity in distribution of radiation-induced defects. Depleted zones are located along grain boundaries and their width is not only determined by irradiation temperature and damage dose, but also by migration of point defects and dislocations integrity, that makes it more difficult to interpret experimental results of this phenomenon. At present, denuded zones are still objects for investigation as they influence both operation characteristics of reactor materials and their safe long-term storage. In this work, denuded zones in hexagonal ducts of spent fuel assemblies constructed from 0.08C-16Cr-11Ni-3Mo and 0.12C-18Cr-10Ni-Ti stainless steels from BN-350 fast nuclear reactor were investigated by TEM. There were determined some irradiation parameters affecting the development of denuded zones and their width; void size distributions in near-grain boundary regions are presented. There was shown redistribution of alloying elements at grain boundaries using Energy-dispersive X-ray spectroscopy (EDS).