Functional Nanomaterials: Functional Low-Dimensional (0D, 1D, 2D) Materials 2022: Low-Dimensional Mechanics, Interfaces, Surfaces
Sponsored by: TMS Functional Materials Division, TMS: Nanomaterials Committee
Program Organizers: Michael Cai Wang, University of South Florida; Yong Lin Kong, University of Utah; Sarah Ying Zhong, University of South Florida; Surojit Gupta, University of North Dakota; Nasrin Hooshmand, Georgia Institute of Technology; Woochul Lee, University of Hawaii at Manoa; Min-Kyu Song, Washington State University; Simona Hunyadi Murph, Savannah River National Laboratory; Hagar Labouta, University of Manitoba; Max Anikovskiy, University of Calgary; Patrick Ward, Savannah River National Laboratory

Tuesday 8:00 AM
March 1, 2022
Room: 260B
Location: Anaheim Convention Center

Session Chair: Michael Cai Wang, University of South Florida; Surojit Gupta, University of North Dakota

8:00 AM  Invited
Nanoscale Effects on Intercalation-induced Phase Transitions in 2D Materials: Mengjing Wang1; Joshua Pondick1; Shiyu Xu1; Judy Cha1; 1Yale University
     Phase transitions in transition metal dichalcogenides (TMDCs) by lithium intercalation have enabled access to phases with novel properties attractive for energy storage, functional devices, and catalysis. Despite the extensive intercalation studies in MoS2, the effects of lithium intercalation in other 2D group VI TMDCs and heterostructures, as well as nanoscale effects on the thermodynamics of the phase transitions, are rarely reported. Moreover, nucleation pathways of the phase transitions remain underexplored experimentally, prohibiting effective engineering control of these phase transitions. We developed in situ multi-modal probes to monitor the real-time structure-property relationships of 2D TMDCs during intercalation. In this talk, I will highlight several examples that showcase the nanoscale effects and novel phases that emerge in lithium intercalated TMDCs, such as a semiconducting phase in lithiated WTe2, heterogeneous interface effects to delay the phase transition of MoS2 in MoS2/graphene heterostructures, and the thermodynamics of phase transitions in MoTe2.

8:20 AM  Invited
Freeze Casting of Graphene Aerogel Structures with Unidirectional Pores: Yu-Kai Weng1; Seungha Shin1; Kenneth Kihm1; Douglas Aaron1; Mohammad Bahzad1; Mian Umar Saeed1; 1University of Tennessee
    We studied the synthesis of directionally porous graphene aerogel (D-GA) structure, which is promising as an electrode material to overcome major technical barriers in organic electrochemical systems: poor ionic conductivity and mass transport. For the creation of unidirectional pores, we employed freeze casting under various synthesis conditions such as temperature gradient. Thermal, electrical, and physical properties (including pore size and alignment) of the synthesized graphene aerogels were evaluated. For more comprehensive understanding of graphene aerogel synthesis using freeze casting, water-ice phase change and graphene structuring processes were computationally investigated via atomistic molecular dynamics and macroscale finite volume method simulations. Through the computational study, we presented the control of water-ice freezing propagation, effects of graphene-water interaction on freezing, and Benard cell convection behavior during water-ice phase change for graphene structuring. Therefore, this research enhances fundamental understanding of freeze casting processes and suggests an effective synthesis process of 3D graphene electrode structure.

8:40 AM  Invited
Intrinsic Fatigue of Graphene and Molybdenum Disulfide: Tobin Filleter1; 1University of Toronto
     With the ever-increasing demand for the long-term reliability of devices and structures, the fatigue behavior of 2D materials necessitates careful investigation. Here we designed an intrinsic fatigue study of suspended two-dimensional (2D) materials based on a modified atomic force microscopy technique. Pristine graphene exhibited a remarkable fatigue life of more than one billion cycles at large stress levels, which is higher than any other materials reported to date [1]. Due to the defective nature of MoS2, its lifetime is highly scattered under the same stress conditions. Surprisingly, both pristine graphene and MoS2 did not reveal any obvious progressive damage during the fatigue loading process, as manifested by its non-changing morphology and non-degraded mechanical properties, as well as atomic structures examination by molecular dynamics simulations. [1] T. Cui et al., “Fatigue of graphene", Nature Materials, 19 (2020) 405-411

9:00 AM  Keynote
Mechanics Design in Cellulose-enabled High-performance Functional Materials: Teng Li1; 1University of Maryland, College Park
    The abundance of cellulose found in natural resources such as wood, and the wide spectrum of structural diversity of cellulose nanomaterials in the form of micro-nano-sized particles and fibers, have sparked a tremendous interest to utilize cellulose's intriguing mechanical properties in designing high-performance functional materials, where cellulose's structure–mechanics relationships are pivotal. In this talk, multiscale mechanics understanding of cellulose, including the key role of hydrogen bonding, the dependence of structural interfaces on the spatial hydrogen bond density, the effect of nanofiber size and orientation on the fracture toughness, will be discussed. Progress in these fronts renders cellulose a prospect of being effectuated in an array of emerging sustainable applications and being fabricated into high-performance structural materials that are both strong and tough.

9:45 AM Break

10:05 AM  
Effects of Graphene Surface Interaction on Water-ice Phase Change: Yu-Kai Weng1; Seungha Shin1; Kenneth Kihm1; Douglas Aaron1; 1University of Tennessee
    For fundamental understanding of water freezing propagation control, the effects of graphene surface interaction were investigated using molecular dynamics simulations. We measured the propagation speed under various freezing conditions and examined the water molecule mobility, thermodynamic driving force of phase change, and energetics near water/ice and water/graphene interfaces. Due to the competition between the mobility and thermodynamic driving force, the maximum speed of freezing propagation appeared at 252 K. Also, our study on water/ice interfacial energy for different water-contacting ice surface orientations showed that a higher interfacial energy led to a faster ice propagation. Due to the graphene-water interaction, ice crystal near graphene was aligned to have an ice surface with the lowest interfacial energy facing graphene. This leads to a faster freezing propagation along the graphene surface, suppressing ice formation perpendicular to graphene. These findings provide insights for the ice propagation control and the freeze casting of graphene.

10:25 AM  
Exciton Transport in Strained Two-dimensional Semiconductors: Jin Myung Kim1; Kwang-Yong Jeong2; Jaepil So2; Mike Wang3; Peter Snapp1; Hong-Gyu Park2; SungWoo Nam1; 1University of Illinois at Urbana-Champaign; 2Korea University; 3University of South Florida
    Exciton in two-dimensional (2D) van der Waals semiconductors has emerged as a prospective component for integrated optoelectronic circuits and interconnects working at room temperature. Strain is a key parameter that can guide exciton transport by creating lateral gradient of exciton energy. However, demonstration of this phenomenon has mostly been limited to spectroscopic interpretation within diffusion-limited length scale. Here, we report strain-induced exciton transport in monolayer WSe2 via pump-probe photoluminescence (PL) measurement. We employed wrinkle architecture to engineer reconfigurable local strain and optically resolvable strain gradient on WSe2. The pump-probe PL maps revealed that strain gradient can induce flux of high-energy excitons to the nearest energy minima up to 2.9 μm-away from pump point with high transport efficiency (>40%). We proposed exciton dynamics model in relation to local strain and strain gradient on WSe2. Our results provide a platform for strain-engineered 2D materials for mechanically reconfigurable optoelectronic circuits and straintronic devices.

10:45 AM  Keynote
Nanoscale Frictional Behavior of Two-dimensional Materials: Robert Carpick1; 1University of Pennsylvania
    I will discuss friction behavior of nanocontacts with 2D materials studied with atomic force microscopy (AFM) and molecular dynamics (MD) simulations. Graphite exhibits a nonmonotonic dependence of friction on humidity. From MD, we attribute this to adsorbed water molecules that, when sparse, act as pinning sites, but when plentiful, form a quasi-ordered, incommensurate, low-friction layer []. We also discuss 2D transition metal dichalcogenide (TMD) films, which exhibit intrinsically low friction, although not as low as graphene, attributable to the interfacial potential energy corrugation []. Friction is measured for sliding on MoS2 from cryogenic to elevated temperatures, with the paradoxical observation that sometimes friction decreases dramatically with temperature (thermolubricity), but other times is athermal. Finally, we compared MoS2, MoSe2, and MoTe2 in bulk and monolayer forms. AFM and MD show that MoS2 has the highest friction and MoTe2 the lowest. Simulations unlock the key to this dependence [].