Advances and Discoveries in Non-equilibrium Driven Nanomaterials and Thin Films: Non-equilibrium Nanostructures
Sponsored by: TMS Functional Materials Division, TMS: Energy Conversion and Storage Committee
Program Organizers: Ritesh Sachan, Oklahoma State University; Srinivasa Rao Singamaneni, University of Texas at El Paso; Amit Pandey, Lockheed Martin Space; Nuggehalli Ravindra, New Jersey Institute of Technology
Monday 8:00 AM
February 24, 2020
Room: Solana
Location: Marriott Marquis Hotel
Session Chair: Ritesh Sachan, Oklahoma State University; Amit Pandey, Ansys
8:00 AM Keynote
Discoveries of Q-carbon and Q-BN and Direct Conversion of Carbon into Diamond and h-BN into c-BN: Jagdish Narayan1; Ritesh Sachan2; 1North Carolina State University; 2Oklahoma State University
From Stone Age to Bronze Age to Iron Age to Semiconductors and Nanomaterials, materials through their properties have played a critical role in improving the quality of human life and taking us to a next level. Recent discovery of Q-Materials may take us to a higher level yet in view of their unprecedented superior properties. Among its many unique and unprecedented properties, Q-carbon is harder (as much as 70%) than diamond, it is ferromagnetic and electrochromic in pure form and it can be made superconducting upon doping with boron with transition temperature over 57K (highest for BCS superconductors). This record superconducting temperature is expected to go still higher with increasing B-concentration in Q-carbon. Carbon can be also converted into diamond in the form of single-crystal nanodots (NV nanodiamons), microdots, nanoneedles, microneedles, and large-area single-crystal films, which can be doped with both n- and p-type dopants for a variety of applications.
8:40 AM Invited
Quasi-one-dimensional Mo Chains for Efficient Hydrogen Evolution Reaction: Yong Pei1; Bingan Lu2; Rao Apparao3; 1Xiangtan University; 2Hunan University; 3Clemson University
Structural modulation of catalytic nanostructures and fundamental understanding of their active sites at the atomic scale are important for predicting and improving the catalytic properties of nanostructures. We prepared quasi-one-dimensional (1D) metal molybdenum (Mo) chains confined in atom-thick molybdenum disulfide (MoS2), referred henceforth as Mo/MoS2 nanosheets, and evaluated their hydrogen evolution reaction (HER) properties. The unsaturated Mo sites in the chains increase the carrier density and facilitate the diffusion of hydrogen along the chains, mimicking an atomic scale reactor which leads to an experimentally observed enhanced catalytic performance. Within the framework of Volmer-Tafel model, the calculated kinetic barrier for H2 evolution is only 0.48 eV for Mo/MoS2, which is significantly lower than that for the Pt (111) surface (∼0.8 eV). In particular, Mo/MoS2 nanosheets supported on reduced graphene oxide outperformed commercial Pt on glassy carbon in the practically meaningful high-current region.
9:10 AM Invited
Laser Processing in the Transmission Electron Microscope: Gerd Duscher1; Chenze Liu1; Yu-Chuan Lin2; Yueying Wu3; Philip Rack1; Mathew Chisholm2; Alexander Pureztky2; David Geohegan2; 1University of Tennesse; 2Oak Ridge National Laboratory; 3University of Tennessee
Laser processing in a transmission electron microscope (TEM) enables the continuous observation of crystallization of amorphous or nano-crystalline precursors from nucleation to materials far from equilibrium. The prototype system by Waviks, Inc. consists of laser diodes coupled to single mode optic fibers which function as a micromanipulator. Here we will report the growth of 2D materials on different substrates and synthesis of phase-separated bi-metallic nanoparticles. The beauty of the system is that synthesis can be observed in-situ with atomic resolution imaging, diffraction and/or EELS. This setup can also be used as a pump-probe system in which the photons excite states that then can be probed with the electron beam through monochromated EELS. In the case of a photonic nano-crystalline system the evanescent light field enhanced by a plasmon can then create stimulated emission and stimulated absorption of electrons, and thus allows to discriminate optical bright from dark plasmon modes.
9:40 AM Break
10:00 AM Invited
Emergence of Shallow Energy Levels in B-doped Q-carbon: A high- temperature Superconductor: Ritesh Sachan1; Jagdish Narayan2; Jordan Hachtel3; Juan Idrobo3; 1Oklahoma State University; 2North Carolina State University; 3Oak Ridge National Laboratory
We report the spectroscopic demonstration of the shallow-level energy states in the recently discovered B-doped Q-carbon Bardeen-Cooper-Schrieffer (BCS) high-temperature superconductor. The Q-carbon is synthesized by ultrafast melting and quenching, allowing for high B-doping concentrations which in- crease the superconducting transition temperature (Tc) to 36 K (compared to 4 K for B-doped diamond). The increase in Tc is attributed to the increased density of energy states near the Fermi level in B-doped Q-carbon, which give rise to superconducting states via strong electron-phonon coupling below Tc. These shallow-level energy states, however, are challenging to map due to limited spatial and energy resolu- tion. Here, we use ultrahigh energy resolution monochromated electron energy-loss spectroscopy (EELS), to detect and visualize the newly formed shallow-level energy states (vibrational modes) near the Fermi level (ranging 30e100 meV) of the B-doped Q-carbon.
10:30 AM
Controlling Nanoscale Eutectic Microstructures in Directionally Laser Melted Al-Cu Alloyed Thin Films: Eli Sullivan1; John Tomko1; Jonathan Skelton1; Patrick Hopkins1; James Fitz-Gerald1; Jerrold Floro1; 1University of Virginia
Eutectic solidification by scanning laser melting readily creates nanostructuring in thin films. Sputter deposited Al-Cu eutectic thin films on fused silica, 500 and 200 nm thick, produced highly-regular lamellae whose spacing is controlled by the laser scan speed, where interlamellar spacing < 50 nm was achieved. Hypoeutectic films exhibit unusual structure, wherein regions of equiaxed dendrites compete with a chaotic lamellar structure. Thin films offer a unique opportunity to impose deliberate geometric modification of solidification that may offer new control over carrier transport. Shadow masking during film growth produces external shapes in the film such as strips, arcs, or circles, which modify solidification nanostructures via the boundary conditions on thermal diffusion. Even more interesting is the ability to selectively perturb the solidification front using focused-ion-beam milling of nano-hole arrays, which can create long-range, super-periodic modulation of the structure. Support of the NSF under grant DMR-1663085 is gratefully acknowledged.
10:55 AM
Fabrication of Nanodiamond and Q-carbon by Ultrafast Quenching of Carbon Structures for Electron Field Emission Devices: Ariful Haque1; Ritesh Sachan1; Jagdish Narayan1; 1North Carolina State University
In this study, we report on the direct conversion of sp2 rich carbon nanotube (CNT) and amorphous carbon structures into nanostructured diamond and Q-carbon by nanosecond pulsed laser annealing for electron field emission applications. The characteristic Raman peak at 1332 cm−1 downshifts to 1324 cm−1 for diamond nanostructures due to the phonon confinement effect. The high-resolution electron-energy-loss spectroscopy of the laser irradiated CNTs shows a characteristic peak at 292 eV for σ* for sp3 bonding of diamond. The laser irradiated CNT structures with nanodiamond seeds were used to grow large diamond crystals in hot-wire chemical vapor deposition. Furthermore, nanosecond pulsed laser annealing technique was used to convert the amorphous carbon film (grown by pulsed laser deposition) into large area quenched carbon(Q-carbon) film for field emission applications. Overall, this work shows that the PLA technique can be used efficiently for the controlled fabrication of nanodiamond and Q-carbon based high-performance field emitters.
11:20 AM
Microstructure Morphology and Concentration Modulation of Bicontinuous Nanocomposite Thin-films during Physical Vapor Deposition: James Stewart1; Remi Dingreville1; 1Sandia National Laboratories
Metallic nanocomposite thin-films with intertwined bicontinuous morphologies can be synthesized using physical vapor deposition of two immiscible metals. Understanding the phase ordering kinetics controlling the way the microstructure and concentration develop is crucial to obtaining reliable functionalities in these nanostructured thin films. We elucidated the complex relationship between the vapor deposition conditions and the resulting spontaneous self-assembled nanoscale morphologies by using three-dimensional phase field simulations. Our simulations account for both the deposition of the incident vapor phase of a binary alloy onto a substrate, surface interdiffusion and the subsequent spinodal decomposition in the resulting elastically inhomogeneous binary thin-film. Using the simulation results, we constructed a structure-zone diagram that establishes the various types of achievable spontaneous self-assembled microstructure morphologies and concentration modulations during physical vapor deposition. This work provides guidance on the choice of alloy chemistry and deposition conditions to obtain specific nanostructured morphologies and concentration modulations for bicontinuous nanocomposite thin-films.
11:40 AM
Synthesis and Densification of Functional Metal-oxide Nano Bulk Composite with Far from Equilibrium State: Yasuhiro Kodera1; A Volodchenkov1; Kyle Chan1; Takahito Imai2; Javier Garay1; 1University of California, San Diego; 2Ryukoku University
The material with far from equilibrium (FFE) state may exhibit extraordinaire functional properties. Obtaining FFE bulk materials through powder consolidation approaches requires the specifically designed powder synthesis method for the particular consolidation method. This is because an appropriate energy balance (heat) is required to obtain bulk form while maintaining FFE state. In other word, FFE materials can be obtained only within the specific processing condition (processing window). When FFE materials are overheated, it will convert to an equilibrium state with conventional properties. Here we will present results on the chemical synthesis of metastable material/phases, and the integration into a consolidated nanocomposite via Current Activated Pressure Assisted Densification (CAPAD). We will show the processing of metastable iron oxide/silica hard bulk magnets with coercive fields comparable to typical rare-earth magnets. And an increase in energy product of ferrite magnet by forming nano-composite with 3d transition metal will be presented.