Controlled Synthesis, Processing, and Applications of Structural and Functional Nanomaterials: Development of Nanomaterials and Nanostructures
Sponsored by: ACerS Basic Science Division, ACerS Electronics Division, ACerS Engineering Ceramics Division
Program Organizers: Haitao Zhang, University of North Carolina at Charlotte; Gurpreet Singh, Kansas State University; Kathy Lu, Virginia Tech; Edward Gorzkowski, Naval Research Laboratory ; Jian Shi, Rensselaer Polytechnic Institute; Kejie Zhao, Purdue University ; Michael Naguib , Tulane University; Sanjay Mathur, University of Cologne
Monday 8:00 AM
November 2, 2020
Room: Virtual Meeting Room 26
Location: MS&T Virtual
Session Chair: Kathy Lu, Virginia Tech; Haitao Zhang, UNC Charlotte
8:00 AM
Introductory Comments: Controlled Synthesis, Processing, and Applications of Structural and Functional Nanomaterials: Haitao Zhang1; 1University of North Carolina at Charlotte
Introductory Comments
8:05 AM Invited
The Formation Mechanism of TiO2 Polymorphs under Hydrothermal Conditions: Wenbin CAO1; Zefu Tan2; 1University of Science and Technology Beijing; 2Chongqing Three Gorges University
In a hydrothermal synthesis of TiO2, TiO2 polymorphs are formed via condensation reaction of [Ti(OH)h(H2O)6-h]4-h (h, the hydrolysis ratio) monomers. In this study, the formation mechanism was proposed that the hydrolysis ratio h determines the crystal structure of TiO2. The detailed nucleation process of TiO2 has been derived. The corresponding relationship between the hydrolysis ratio and the crystal structure has been investigated. When the h is in the intervals of h≤ 2, 2 < h < 3, 3 ≤ h < 5 and h ≥ 5, the predicted crystal structures of TiO2 are rutile, a mixed crystal (rutile, brookite and anatase), anatase and brookite, respectively. In addition, the hydrolysis ratio under different hydrothermal conditions was modified by introducing the ionic product correction. And, the dynamical change of the hydrolysis ratio during the hydrothermal crystallization has been investigated. The theoretical predictions of crystal structure of TiO2 has been experimentally verified.
8:35 AM Invited
Oxide Nucleation and Growth during In Situ Oxidation of Cu and Cu Alloys: Judith Yang1; 1University of Pittsburgh
Fundamental understanding of oxidation of metals and alloys is critical for corrosion protection, catalyst design and nano-oxide synthesis. However, the transient stages of oxidation - from the nucleation of the metal oxide to the formation of the thermodynamically stable oxide - represent a scientifically challenging and technologically important terra incognito. These issues can only be understood through detailed study of the relevant microscopic processes at the atomic scale in situ. We have previously demonstrated via in situ TEM that the formation of epitaxial Cu2O islands during the transient oxidation of Cu thin films bear a striking resemblance to heteroepitaxy, where the initial stages of growth are dominated by oxygen surface diffusion. We are now correlating in situ Environmental High-Resolution TEM (HREM) with atomistic simulations to understand the atomic-scale surface dynamics of oxide nucleation and growth. We will also investigate binary alloy, Cu-Ni, for essential insights into selective oxidation.
9:05 AM
Explore Different Roles of Catalysts in the Growth of Si-based Nanostructures: Shifat Us Sami1; Samuel Bultman1; Haitao Zhang1; 1University of North Carolina at Charlotte
Catalysts play an important role in the controlled growth of various nanostructures. In a conventional Vapor-liquid-solid process, catalyst particles are normally used to accommodate vapor precursors and induce the formation of one-dimensional nanostructures. However, from our recent studies, catalysts could have a new role to enhance the reactions at the solid surface and promote the formation of vapor precursors from solid sources, which is otherwise hard to be vaporized under certain experimental conditions. The different roles of different catalyst particles are sensitive to their stability and vapor pressures at different temperature. In this talk, the roles of different catalysts (e.g., Te, Cu, and Au) will be revealed on the growth of Si-based nanostructures, including SiOx nanowires and Si2Te3 2D nanolayers. The catalyst effects on the composition and morphology controls of nanostructures will be demonstrated. The mechanism could promote the nanomaterial growth under less critical conditions (e.g., lower growth temperature).
9:25 AM
Direct Synthesis of Nanoclusters from Cu Nanowires: Diego Santa Rosa Coradini1; Matheus Araujo Tunes1; Thomas Kremmer1; Peter Uggowitzer2; Stefan Pogastscher1; Claudio Geraldo Schön3; 1Montauniversty Leoben; 2ETH Zürich; 3Escola politécnica da Universidade de São Paulo
The synthesis of Cu-rich nanoclusters from single-crystal Cu nanowires via the application of Ar plasma etching will be reported. These clusters were synthesised at room temperature only in function of plasma exposure time. A detailed scanning transmission electron microscopy study was carried out in order to evaluate the effects of plasma exposure in Cu nanowires and the generated Cu-rich nanoclusters. Electron diffraction was used to assess possible phase transformations of the nanowires. Large surface-to-volume ratio induced chemisorption effects of residual active species in the plasma environment on the surface of Cu nanowires is considered to have a significant influence on their transformation to nanoclusters.
9:45 AM
Purification of Carbon Nanotube Yarns via Incandescent Annealing: Pouria Khanbolouki1; Mehran Tehrani1; 1The University of Texas at Austin
This study presents a systematic investigation of carbon nanotube (CNT) yarn purification from its catalytic constituents and byproducts via an incandescent current induced annealing process in high vacuum. It is concluded that incandescent annealing can provide a low-energy alternative for purification of CNT structures from their catalytic constituents in a matter of seconds compared to thermal annealing at high temperatures, which takes hours. The difference is due to different impurity removal mechanisms involved in the two processes. The structural and morphological changes within the CNT yarns were investigated via scanning/transmission electron microscopy, energy dispersive spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The morphological changes are correlated with the electrical property evolution of the CNT yarns. The impurity removal mechanisms, CNT doping mechanisms, and pros and cons of the current characterization methods for bulk CNT structures are discussed.
10:05 AM Invited
Multiscale Modeling of Radiation-induced Precipitation Hardening by Cu Nanoclusters in Fe-Cu Alloys: Xian-Ming Bai1; 1Virginia Polytechnic Institute and State University
Maintaining the long-term mechanical integrity of reactor pressure vessels (RPVs) is critical for the reactor safety of light water reactors. RPV steels typically contain low concentration of alloying elements such as Cu. Under neutron irradiation, many nano-size Cu clusters can precipitate as second phase particles. These Cu nanoclusters can block dislocation gliding and thus lead to precipitation hardening and embrittlement. In this work, cluster dynamics modeling is used to model the precipitation kinetics of Cu nanoclusters in Fe-Cu alloys of different compositions under neutron irradiation conditions. Molecular dynamics simulations are conducted to provide atomistic mechanisms of Cu precipitation process in the Fe matrix. Using the Cu precipitation kinetics from cluster dynamics modeling (e.g., Cu cluster number density and size), a barrier hardening model is used to predict Cu nanoclusters-induced precipitation hardening and embrittlement under different irradiation conditions.
10:35 AM Invited
Nanocomposites with Extremely High Fractions of Nanomaterials via Infiltration of Polymers into Nanoparticle Packings: Daeyeon Lee1; 1University of Pennsylvania
A common approach to imbue polymers with useful functionality is to add nanoparticles to produce nanocomposites. Despite decades of research, however, it remains a challenge to produce nanocomposites with very high concentrations (> 50 vol%) of nanoparticles using conventional methods. In this talk, I will describe a simple, potentially scalable method to manufacture nanocomposite films with extremely high fractions of nanoparticles. A bilayer of polymer and nanoparticles is heated above the glass transition temperature of the polymer to induce capillary rise infiltration (CaRI) of the polymer into the interstitial voids of the nanoparticle packing, producing a nanocomposite film with an extremely high filler fraction (> 60 vol%). I will describe the impact of nanoconfinement on the dynamics of polymer infiltration and also discuss how the composition of the CaRI nanocomposite affect their structure as well as their optical and mechanical properties.
11:05 AM
ZnO Nanoparticle-Poly(methyl methacrylate) Hybrid Ultraviolet Shielding Films: Kathy Lu1; Lingchen Kong1; Advaith Rau1; Ni Yang1; 1Virginia Polytechnic Institute and State University
Flexible hybrid films are finding increasing applications in functional devices. In this work, transparent ZnO nanoparticle (NP) and poly(methyl methacrylate) (PMMA) hybrid films are made for ultraviolet (UV) shielding. The tensile strength increases with the ZnO NP volume percent. The elongation at break also increases with the ZnO content increase until 10 vol%, after which the elongation at break stays constant. All the ZnO-PMMA films show UV absorption at ~365 nm wavelength, with an increasing degree for higher ZnO content samples and a corresponding light transmittance decrease at longer wavelengths. Long term UV irradiation leads to reduction in tensile strength and elongation at break, along with lower UV shielding performance. The optimal ZnO content is 5-10 vol% for the overall UV shielding performance.
11:25 AM
Towards Superhard Binderless Nanocrystalline Tungsten Carbide: Kevin Anderson1; James Wollmershauser1; Heonjune Ryou1; Edward Gorzkowski1; Boris Feigelson1; 1U.S. Naval Research Laboratory
Tungsten carbide, with a typical Vickers hardness ~26 GPa, is not generally considered a superhard material (Hv > 40 GPa). In this work, fully dense, binderless nanocrystalline tungsten carbide ceramics with a Vickers hardness as high as 39 GPa and indentation fracture resistance values of > 9 MPa√m were produced by Environmentally Controlled – Pressure Assisted Sintering (EC-PAS). EC-PAS utilizes applied pressure (2 GPa), low temperature (< 0.5 Tm), and creation and preservation of pristine nanoparticle surfaces throughout the sintering process to achieve densification with negligible grain growth. Tungsten carbide ceramics produced through this process had grain sizes as small as 26 nm and were characterized with XRD, SEM (including XEDS and EBSD), Vickers microindentation, and instrumented nanoindentation. The mechanical properties – microstructure relationship will be discussed with respect to the powder processing and sintering conditions, in addition to possible process improvements leading to further increases in hardness.