MVC 7 Awards Gallery

“NaCl CRYSTALS WITH NOVEL ARCHITECTURES“

Nuerxida Pulati, Post Doctorate, Materials Science and Engineering

Scientific Process: Additives affect unique growth of NaCl crystals with unusual architectures.

FIRST PLACE

“THE BEAUTY OF WEATHERING“

Xin Gu, Graduate Student, Geosciences / Geochemistry

Scientific Process: At Shale Hills Critical Zone Observatory (SSHO), we find that pyrite and chlorite oxidation is the leading reaction that is capable of initiating deep weathering as deep as 15 m at ridge top. The
released irons during weathering are precipitated in pores/fractures as iron oxide particles. This thin section was from a rock chip gathered from 1.3 m below ground surface at SSHO. This uncoated thin section was
imaged by FEI NanoSEM 630 FESEM microscope with a vCD detector. The horizontal field width is 10.39 μm. Energy dispersive X-ray spectroscopy (EDS) was performed to identify minerals.

SECOND PLACE

“VERTICAL MOLYBDENUM-DISULFIDE FINS“

Rafael Vilá, Undergraduate Student, Materials Science and Engineering

Scientific Process: A scanning electron micrograph of molybdenum-disulfide (MoS2) “Fins” grown on a hexagonal silicon carbide (6H-SiC) substrate. The unique
vertical growth results from a combination of the high surface energy of the SiC and a high molybdenum to sulfur (Mo:S) ratio during synthesis.

THIRD PLACE

“2D LAYER MATERIAL, TAS2, GROWN BY CVD “

Xiaoxing Cheng, Graduate Student, Materials Science and Engineering

Scientific Process: Tantalum Disulfide (TaS2) is a 2D layer material, which belongs to the 2D Transition Metal Dichalcogenide family. The TaS2 shown, is grown by Chemical Vapor Disposition (CVD). The Tantalum powder and Sulfur powder are heated to their vapor phases and then react with each other to form TaS2, which then deposits onto the substrate and will grows larger in shape. During growth, atoms around the corners grow faster than those along the edges, which explains the yellow ‘branch’ shape. In the blue background, small black triangles correspond to small TaS2 domains which haven’t been able to melt into each other and grow larger sizes.

FIRST PLACE

“AERIAL, TUNGSTEN PLATEAUS AND NICKEL FORESTS“

Katherine Kragh-Buetow, Graduate Student, Materials Science and Engineering

Scientific Process: An aerial SEM view of tungsten-rich plateaus and towers amongst nickel-rich forests. Tungsten-nickel alloys are being investigated as electrical contacts to silicon carbide. After high temperature annealing, a distinctive surface morphology manifests on the surface. Tungsten-rich plates resembling different shapes form amongst more nickel-rich regions.

SECOND PLACE

“YFESEM OF SILICA OPAL INFILTRATED WITH SILICON“

Shih-Ying Yu, Graduate Student, Materials Science and Engineering

Scientific Process: FESEM showing a cross section of infiltration of silicon inside a silica opal template by high pressure chemical vapor deposition (HPCVD). Silicon is grown inside the voids of the opal template by means of HPCVD. The three-‐dimensional artificial solid is defined as silicon inverse opal metalattice providing a platform to study the fundamental electrical and thermal properties of semiconductors

THIRD PLACE

“OGALLIUM NITRIDE SHELL FORMATIONS“

Zakaria Al Balushi, Graduate Student, Materials Science and Engineering

Scientific Process: Field-emission scanning electron micrograph of the growth of gallium nitride at low-temperatures on CVD graphene that has been transferred onto float glass. This illustrates the formation of hallow
gallium nitride shell structures made from the competition between the nitridation of the surface of the gallium droplets and desorption of gallium atoms from the droplets during the growth process.

FIRST PLACE

“PYRIDINE MOLECULES IN A SILVER NANO-JUNCTION“

Dhabih V. Chulhai, Graduate Student, Department of Chemistry

Scientific Process: The strong electric fields created around plasmonic nanomaterials, like in the silver nano-junction simulated here, can enhance the Raman signals of nearby molecules by several orders of magnitude. The experimentally observed Raman spectrum is an ensemble measurement, with a majority of the signal originating from only a few molecules in the “hot spot”. The model, which combines molecular dynamics simulations and a classical coupling of the electric fields with the molecules’ polarizabilties, allows us to decompose the observed ensemble Raman spectrum into the contributions from individual molecules. In this image, we colorize this decomposition into the molecules that contribute very little (blue) and those that contribute most (red) of the observed Raman signal.

SECOND PLACE

“LITHIATION MECHANISMS AND MORPHOLOGY CHANGES OF SILICON NANOWIRE (SiNW) COATED WITH AMORPHOUS SiO2 (A-SiO2) LAYER“

Alireza Ostadhossein, Graduate Student, Engineering Science and Mechanics/Mechanical and Nuclear Engineering

Scientific Process: The use of high capacity Si based electrode has been hampered by its mechanical degradation due to the large volume expansion/ contraction during cycling. Coting layers to protect the Silicon anodes from electrochemical degradation. SiO2 is one of the most abundant materials on Earth. Silicon oxide with controlled morphology and crystallinity by Atomic Layer Deposition (ALD) onto SiNWs can be used to enhance the lithium storage. A modeling approach is designed based reactive molecular dynamics using ReaxFF to understand, design, and make coated Si anode structures with high current efficiency and stability. Lithiation of crystalline SiNW with a-SiO2 surface is studied here. The Li atoms are shown with purpel dots while the Si and O atoms are shown with yellow and red,
respectively. VMD software is used to visulaize the results. The lithiation is retarded by the oxide layer due to the constraining effect of oxide layer. The volume expansion of SiNW upon lithiation decreases significantly due to the constraining effects of oxide coating.

THIRD PLACE

“AFFECTING THE ELECTROCHEMICAL CYCLABILITY OF Li-ion BATTERIES“

Zhe Liu, Graduate Student, Materials Science and Engineering

Scientific Process: SEI, the passivation layer between anode and electrolyte, has been demonstrated to significantly affect the electrochemical cyclability of Li-ion batteries. This picture shows the interfacial structure of Li metal anode and lithium carbonate, the major SEI component, from first-principle simulation. The colorful solid balls represent the positions of the atoms and the golden contours depict the electronic clouds. In the picture, prominent atomic and electronic reconstruction can be observed at the Li/SEI interface.