9th Forum on New Materials
F:P01 Production of Magnetically Soft Components from FeSi6.5 Alloy with Selective Laser Melting Technology - Optimisation, Prototyping and Post-processing
B. JóZwik, A. Kolano-Burian, P. Zackiewicz, A. PilSniak, M. Polak, A. Brudny, A. RadoN, Łukasiewicz Research Network, Institute of Non-Ferrous Metals, Gliwice, Poland; A. Wójcik, Institute of Metallurgy and Materials Science, Polish Academy of Sciences, Krakow, Poland
Selective Laser Melting is a dynamically developing branch of Additive Manufacturing which utilises numerically controlled laser beam to precisely melt metallic powder bed in order to acquire complex, near net shape geometry often difficult or impossible to obtain elsewhere. It was decided to capitalise on the aforementioned advantages provided by the SLM technology in printing with the FeSi6.5 alloy – a magnetically soft yet extraordinarily brittle material, unavailable to conventional methods of production through rolling and binding, which could supersede the more accessible alloys with lower Si content due to superior magnetic properties. The aim of this work was to establish a complete set of printing parameters suitable for creation of dense, crack-free specimens, investigation of heat treatment possibilities and optimisation for low power losses. The acquired data allowed for the manufacturing of a thin-walled transformer prototype based on the Hillbert’s curve intersection. The assembled device exhibited not only lowered power losses but also improved values of remanence and coercivity in comparison to solid toroidal specimens printed with the same optimised strategy.
F:P02 Soft Magnetic Amorphous and Nanocrystalline Ribbons for Energy Conversion and Storage
T. WARSKI1, 2, L. Hawelek1, A. Radon1, A. Pilsniak1, A. Kolano-Burian1, M. Polak1, A. Wojcik3, 1Lukasiewicz Research Network - Institute of Non-Ferrous Metals, Gliwice, Slaskie, Poland; 2Silesian University of Technology, Gliwice, Slaskie, Poland; 3Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Malopolskie, Poland
Nowadays, soft magnetic alloys in the form of amorphous and nanocrystalline ribbons are a promising class of materials for application in miniaturized energy conversion and storage systems. They bridge the gap between heavy and highly-loss silicon steels and low-induction and brittle ferrites. Moreover, amorphous ribbons are flexible and durable, which enables their special use in electronics. Magnetic, magnetoelastic, mechanical and anti-corrosion properties can be controlled by changing the chemical composition and appropriate annealing. In this work, the crystallization process, crystal structure and magnetic properties for two high induction series of alloys: Fe81Ni5CuxB14 (x = 0, 0.6, 1) and Fe76-xNi10CuxB14 (x = 0, 0.7, 1) in the form of ribbons were investigated. Their chemical compositions were determined on the basis of thermodynamic calculations. The obtained flexible amorphous ribbons were characterized by 1.35-1.55 T and 21-32 A/m2, and then improved by annealing process (conventional and ultra rapid) up to 1.55-1.73T and 14.2-29.2 A / m2. The optimally annealed materials can be successfully applicated in energy conversion and storage systems.
F:P03 Morpho-structural Characterization of Polymer Embedded BaTiO2 and y-Fe2O3 Nano-structures
L. Mihai1, A. Marcu1, A. Rotaru2, G. Caruntu2, 3, D. Caruntu2, 3, F. Dumitrache1, A. Criveanu1, L. Gavrila-Florescu1, M. Zamfirescu1, 1National Institute for Laser Plasma and Radiation Physics, Magurele, Ilfov, Romania; 2Department of Electrical Engineering and Computer Science & MANSiD Research Center, “Stefan Cel Mare” University, Suceava, Romania; 3Department of Chemistry and Biochemistry, Central Michigan University, Mount Pleasant, MI, USA
BaTiO3 nanomaterials possess a high dielectric constant values which vary in a wide range usually controlable by a Sr content. They have attractive applications in highly capacitive films for energy storage and transistor due to their large band gap (>3 eV) which can limit the leakage current and a high optical transparency. On the other hand, γ-Fe2O3 nano-structures are biocompatible and have a superparamagnetic behavior. In the present studies we investigated electric and magnetic properties of polymer embedded particles and mixtures for nano-devices application. While BaTiO3 nanoparticles were produced in few sizes by the wet chemistry approach, γ-Fe2O3 nano-structures were produced by laser pirolysis in 3 dimension of 2.5, 5 and 10 nm. Their were embedded in variable ratios in polymer for a nano-lithography based device fabrication. Their optic, electric and magnetic properties were further investigated. Nanodevices fabrication using such nanoparticles were further tested and morpho-structural investigations as well as some nano-device fabrication preliminary results are presented in this paper.
F:P04 Modelling a Combined Electrostatic – Triboelectric Flexible Generator
S.E. HAIM, Univ. Grenoble Alpes, CNRS, Grenoble INP, G2Elab, Grenoble, France; C. Jean-Mistral, Univ. Lyon, INSA-Lyon, CNRS UMR 5259, LaMCoS, Villeurbanne, France; A. Sylvestre, Univ. Grenoble Alpes, CNRS, Grenoble INP, G2Elab, Grenoble, France
Soft electrostatic generators (SEG), generally made of electroactive polymers, represent an efficient way to power up devices widely used in the IoT, including smart clothes, biomechanical energy harvesters or sensors. The working principle of these generators is to use the variation of capacitance to convert mechanical energy into electrical one. Our team demonstrated that an electret can be used to replace the needed external voltage supply of these SEGs leading to an energy self-sufficient soft generator. The goal of our work is to improve the volume density of energy of our electrostatic generator by replacing the electret with a sliding-mode triboelectric function. An experimental study was conducted to better understand how this phenomenon works. This enabled to carry out a finite element modeling of the electrical power generated during the mechanical deformation (50% of strain) of our centimeter-scale generator coupling these electrostatic and triboelectric modes. A thorough optimization regarding the shape, size and materials used for this triboelectric function, has been done to achieve a targeted output power of 100uW.
F:P05 Microstructure Analysis of Metal Thin Film on Polyimide Substrate under Tensile Stress for Flexible Display
Hongwon Choi, Changwan Seo, Insun Yoon, Keumhwan Park, Chan-Jae Lee, Korea Electronics Technology Institute, Seongnam, South Korea
Recently, electronic devices that can change the shape of a display, such as rollable or foldable, have been interested. As the display device repeatedly undergoes deformation such as rolling or folding, the stress generated at this time affects a plurality of components inside the display. Because a polymer substrate and a metal line having a large difference in the coefficient of Young's modulus, a large stress and failure are generated between them according to the deformation of the panel. In this study, the change in the microstructure of the metal was analyzed when the metal was stretched according to the degree of deformation. As the metal used, Mo, Al, etc., which are widely applied in displays, were used. In order to create an elongated deformation of the metal, a tensile test was performed to generate displacement. Then, the microstructure change and resistance change that occurred in the metal layer were analyzed. As a result of the tensile test using UTM, microcracks in thin Mo layer with 100 nm on PI film occurred as expanding by 1%. However, due to the recovery force of the substrate, the grains of metal were kept attached to each other, so there was no change in resistance. As it exceeds 5%, buckling that the metal thin film is completely broken occurs.
F:P06 Zr-based Super Elastic Alloy and its Piezoresistive Response for Strain Sensor
YoungEun Kim1, JaeSang Cho2, DongHwan Wang2, Chan-Jae Lee1, KeumHwan Park1, 1Korea Electronics Technology Institute, 2School of Integrative Engineering, Chung-Ang University, South Korea
Amorphous alloys, also known as metallic glass, are metallic materials with disordered atomic-scale structure. Due to their unique structural characteristic, the metallic amorphous alloys exhibit excellent properties such as corrosion resistance and high elastic strain limit. In this study, the unique characteristics of MG is considered for fabrication of long-term stable thin film strain sensors. The absence of sharp Bragg peaks in XRD spectrum of Zr-MG thin film confirms the absence of long-range ordered crystalline structure and the grain boundaries. Grain boundaries that exist on polycrystalline metal thin films contribute to the small elastic limit of the films, which often cause irreversible plastic deformation and crack formation. Thus, absence of grain boundary in Zr-MG film should contribute to a higher elastic limit than that of conventional polycrystalline metals.
F:P07 Ti:sapphire Crystalline Core and Clad Fiber for Broadband NIR Emission
T.I Yang, S.L. Huang, National Taiwan University, Taipei, Taiwan; P.S. Yeh, National Taiwan University of Science and Technology, Taipei, Taiwan
Broadband and high-brightness light sources are essential for high-speed optical coherence tomography (OCT) with ultrahigh spatial resolution. Using Ti:sapphire crystalline fiber (CF) as the gain medium, the heat dissipation efficiency and pump/signal mode matching are significantly enhanced as compared with bulk material. Using the same clad material as the core, single-mode Ti:sapphire CF with crystalline core and clad was developed using dip coating process and high temperature sintering at 1750 oC. Solid-state single crystal growth was observed, and single-crystalline cladding was formed, as evidenced by the examination of electron backscattered diffraction and SEM. The growth speed along (11 ̅0) is about 2.7 times that of the (001) direction. From preliminary optical transmission measurement at 1550 nm, the measured 0.053-radian far-field angle of the transmitted light matches well with that of the fundamental mode. At a core size of 30 μm, the measured refractive index difference between core and clad was 1.0x10-4. Because of the solid-state growth, very limited amount of the Ti3+ ions in core were diffused into the clad. This makes Ti:sapphire CF based broadband emissions be advantageous for various full-field and frequency-domain OCT applications with cellular resolution.
F:P08 The Broadband Emission from Cr3+ Ion in Near-Infrared Phosphors for Light-emitting Diodes
N. Majewska1, T. Lesniewski1, S. Mahlik1, V. Rajendran2, Mu-Huai Fang2, Wen-Tse Huang2, G. Leniec3, S.M. Kaczmarek3, Ru-Shi Liu2, 1Institute of Experimental Physics, Faculty of Mathematic, Physics, and Informatics, Gdansk University, Gdansk, Poland; 2Department of Chemistry, National Taiwan University, Taipei, Taiwan; 3Institute of Physics, Department of Mechanical Engineering and Mechatronics, West Pomeranian University of Technology Szczecin, Szczecin, Poland
Hotspot worldwide due to potential biological applications. Recently, Cr3+-activated luminescent materials have become a promising candidate in pc-IR LEDs. One promising material for NIR sources is magentoplumbites activated by Cr3+ ions. These materials are characterized by efficient NIR luminescence. The emission spectra show two different emission types, a narrow line emission around 690 nm and a broad emission in longer wavelengths, coming from two different crystallographic sites denoted by Cr1 and Cr2. The time resolve spectroscopy shows that the decay time of Cr2 emission is surprisingly in ms range at RT, which shows that this luminescence certainly is not the spin-allowed 4T2→4A2 transition. Additionally, the high-pressure induced shift of Cr2 emission towards lower energies with the rate around -1.5 cm-1/kbar, is a strong indicator that Cr2 emission cannot be accounted to the 4T2→4A2, which would shift towards shorter wavelengths, typically at a much stronger rate. The direction and magnitude of the pressure shift is in good agreement with the typical pressure shift rate of the 2E→4A2 transition, which suggests that we deal with spin forbidden 2E→4A2 transition of Cr3+ or Cr3+ pairs.
F:P09 High Pressure Study of AlN Doped with Eu2+ and Ce3+
M. KAMINSKI, S. Mahlik, A. Lazarowska, T. Lesniewski, Institute of Experimental Physics, Faculty of Mathematic, Physics, and Informatics, University of Gdansk, Gdansk, Poland; Ru-Shi Liu, Department of Chemistry, National Taiwan University, Taipei, Taiwan
With the growing need of finding a way to produce an energetically efficient light source that is a white light emitting diode (WLED), also called solid-state lighting, nitride phosphors have again taken on significance. Among them, AlN with its wide band gap, high thermal conductivity, and high stability, when doped with lanthanide ions is a suitable candidate. Appropriate spectroscopy measurements had been performed. High-pressure spectroscopy measurements show an unusual difference in results between AlN:Ce3+ and AlN:Eu2+. Both ions exhibit emission caused by d-f transitions (5d1→4f7 for AlN:Eu2+ and 5d1→2F5/2 for AlN:Ce3+). The emission and excitation spectra measurements under pressure allowed for a calculation of the pressure induced shift rate: dS\hbar\omega/dP is 1.36 cm-1/kbar for AlN:Eu2+ and -5.49 cm-1/kbar for AlN:Ce3+. This allowed for a calculation of the KQ parameter . Additionally, temperature dependent emission spectra were measured. It showed familiar PL intensity and FWHM trends for AlN:Eu2+, when the ones for AlN:Ce3+ were rather unusual. Finally, kinetic luminescence measurements were performed where AlN:Eu2+ decay times exhibited single-exponentional decay, when AlN:Ce3+ decay times showed it as double-exponentional.
F:P10 Resistive Switching in V-doped Cr2O3 Thin Films Mott Insulator for Memory Applications
M. RODRIGUEZ FANO, J. Tranchant, E. Janod, B. Corraze, P.-Y. Jouan, L. Cario, M.-P. Besland, Université de Nantes, CNRS, Institut des Matériaux Jean Rouxel, Nantes, France
The performances of Flash memories approach their limits as the most advanced technology nodes encounter unwanted physical effects due to miniaturization and short economical payback. Among studied alternatives, Mott Insulators (MI) are promising candidates for the next generation of memory devices. It was observed both on crystals and thin films that the Insulator-to-Metal transition (IMT), characteristic of canonical MI such as (V0.95 Cr0.05)2O3, Ni(S,Se)2 or chalcogenides AM4Q8 can be triggered by electric pulses. A MI can thus reproduce the memory writing-erasing process by a reversible non-volatile IMT, and previous studies have demonstrated competitive memory performances based on this IMT. In this work, we investigate the resistive switching in thin films of (Cr1-xVx)2O3 (0 < x < 1). Thin films of the solid solution were deposited and annealed to reach the expected stoichiometry and good crystalline quality. All deposited films share the same crystalline phase. The Mott-Hubbard gap evolves within this solid solution and modifies the resistive switching characteristics in MIM structures. The electrical behavior has been investigated on Metal-Insulator-Metal structures for some selected chemical compositions and will be presented and discussed.
F:P11 Integration of Memristive Switching with Sensing in Ag Alloy Nanoparticle based Memsensors
R. GUPTA1, N. Carstens1, M. Terasa2, T. Strunskus1, F. Faupel1, R. Adelung2, A. Vahl1, 1Institute for Materials Science - Chair for Multicomponent Materials, Faculty of Engineering, Kiel University, Kiel, Germany; 2Institute for Materials Science - Functional Nanomaterials, Faculty of Engineering, Kiel University, Kiel, Germany
The advancement of neuromorphic engineering offers great potential to create novel electronics inspired by brain functionalities. One of the bottlenecks in achieving this is the combined data detection and processing in single devices. Memsensor is one such two terminal device combining the functionalities of memristive and sensor devices. It is highly promising in the field of neuromorphic engineering and has the capability to mimic aspects of neurons and synapses in future electronics. In this work, a system of SiOxNy/Ag/SiOxNy is considered. Tailored Ag alloy nanoparticles (NPs) embedded in a SiOxNy dielectric matrix are used in a multi-stack set-up fabricated by Gas Aggregation Source (GAS) to realize a broad range of filamentary type of switching (diffusive and bipolar) characteristics. To incorporate memsensor activities into the device, wide-bandgap semiconductor TiO2 and ZnO are used as the matrix materials that are sensitive towards UV light. The test system consists of Ag alloy NPs embedded into both the matrices. It is analysed how the switching performance of the memsensor device is modulated under the application of UV light. Such an approach will help in understanding and implementing memsensor functionalities with filamentary switching processes in detail.
F:P12 Towards Photocatalytically Generated Long-range Connections for Artificial Neural Networks
B. ADEJUBE1, M. Paulsen2, J. Schardt2, T. Strunskus1, F. Faupel1, M. Gerken2, A. Vahl1, 1Institute for Materials Science - Chair for Multicomponent Materials, Faculty of Engineering, Kiel University, Kiel, Germany; 2Institute of Electrical Engineering and Information Engineering - Chair for Integrated Systems and Photonics, Faculty of Engineering, Kiel University, Kiel, Germany
Neural networks combine a high number of local short-range synaptic connections between neurons with long-range axonal connections to maximize efficiency in network communication. While most attention is focused on memristive devices which could be a representation of the local synaptic connection, the long-range global plasticity has received relatively lesser attention. To optimize the performance of artificial neural devices, a deeper consideration on how to derive long-range global plasticity is a necessity. This study focuses on creating a structure with qualities that are essential for long-range connections such that it would maximize efficient network connection and allow for sufficient stability in the network. In this work, by photocatalytic reduction from a precursor solution, using TiO2 as photocatalyst, localized growth of metallic gold lines with well-defined geometry under optical stimulus is demonstrated. Results show that the growth of the metallic lines is influenced by catalytic activity of the substrate, UV light intensity and precursor solution. The electrical properties and optimal coverage needed to obtain a connecting path between the nanoparticles are investigated.
F:P13 Structural Transformation and Phase Change Properties of Se Substituted GeTe
R. Shekhawat, H. Pamuluri, V. Erkkara Madhavan, K. Ramesh, Indian Institute of Science-Bangalore, Bangalore, India
GeTe1−xSex (0 ≤ x ≤ 1.0) alloys have been prepared both in bulk and thin film forms to study the effect of selenium (Se) substitution for tellurium (Te) on the phase change properties. It is observed that with increasing Se substitution in GeTe, the structure transforms from rhombohdral structure to orthorhombic structure. Rietveld Refinement analysis support the phase transformation and show that the short and long bond lengths in crystalline GeTe decrease with increasing Se substitution but the rate of reduction of shorter bond length is more than the longer bond length. The GeTe1−xSex thin films undergo amorphous to crystalline phase change when annealed at high temperatures. The transition temperature shows an increasing trend with the Se substitution. The contrast in electrical resistivity between the amorphous and crystalline states is 104 for GeTe, and with the Se substitution, the contrast increases considerably to 106 for GeTe0.5Se0.5. Devices fabricated with thin films show that the threshold current decreases with the Se substitution indicating a reduction in the power required for WRITE operation. The present study shows that the crystalline structure, resistance, bandgap, transition temperature and threshold voltage of GeTe can be effectively controlled.
F:P14 Multiple Magnetization Switching and Magnetic Glass Signature in Gd doped Distorted Antiferromagnetic Perovskite SmCrO3
S. DAS, R.K. Dokala, S. Thota, Department of Physics, Indian Institute of Technology Guwahati, Assam, India
SmCrO_3 and GdCrO_3 exhibits consist of multiferroic behavior, giant magnetic entropy change, and magnetization reversal, considered vital phenomena for the development of thermo-magnetic switches and non-volatile magnetic storage devices. The current system deals with the temperature and field dependence of magnetization of the bulk polycrystalline Sm_0.9Gd_0.1CrO_3 which demonstrates the robust magnetization reversal in the ZFCW case (maximum -35.6 emu/mol) with the change in polarity in all the ZFCW, FCC, and FCW cases, that has not been observed before in the similar system making it quite fascinating in the field of magnetic memory storage. For T = 38 K, the Sm3+ spins get completely polarized and orient from Γ_4 (G_x,A_y,F_z) to Γ_1 (A_x,G_y,C_z) configuration. At lower temperature, the Gd_3+ spins get activated and trigger the upraise of the moment (T_N^Gd ~ 7 K) with Γ_2 (F_x,C_y,G_z) with the C-configuration along the y-axis. Upraise in the magnetic moment at low temperature is due to the higher magnetic moment of Gd_3+ (7.94 µB/f.u.) than that of Sm_3+ (0.84 µB/f.u.). The magnetic glassy signature (T_G ~ 27 K) is easy to distinguish from the huge bifurcation between the FCC and FCW M-T plots. For T < T_G, Gd spins experience a spin-flip transition.
F:P15 Degenerate Spin-states Widening the Metamagnetic Phase in Twinned Antiferromagnetic Charge-Ordered Pr_0.35Yb_0.10Sr_0.55MnO_3
R.K. DOKALA, S. DAS, S. Thota, Department of Physics, Indian Institute of Technology Guwahati, Assam, India
Multiferroic o-Pr_1-xSr_xMnO_3 exhibits a giant charge ordering phenomena with ΔT(T_C – T_N) = 80 K, giving rise to a metamagnetic region. The h-YbMnO_3 orders antiferromagnetically at 85 K driven by the superexchange interaction along Mn^(3+)-O^(2-)-Mn^(3+) which is due to the in-plane AFM alignment Mn^3+ spins. Current work demonstrates the average cationic radius of Pr_0.35Yb_0.1Sr_0.55MnO_3 is 1.3276 Å which is greater than YbMnO_3 (1.1549 Å) and lesser than the PSMO (1.3327 Å). The substitution of Yb^3+ (μ_eff = 4.54 μ_B) magnetic ion at the A-site of PSMO gives another AFM transition, T_N^*=83 K below the AFM transition of CO region T_N^CO=158 K along with the FM transition of CO region T_C^CO=283 K as shown in the given figure. The metamagnetic region where the double exchange interaction among Mn^(4+)-O^(2-)-Mn^(3+) moments is active with the FM coupling and drastically spanned to a broad range, ΔT = 125 K. The correlation among manganite ions switch to higher values of magnetization with the magnetic field dependence in a wide range as compared to the Nd, Gd, and Eu substituted PSMO systems. The active Yb^3+ magnetic moments at the lower temperatures below T_N^* lift the overall magnetic moment.
F:P16 Signature of Dirac Fermions in Type-II Dirac Semimetal NiTe2
M.T. JAMES, S. Mandal, N.K Sebastian, R. Ganesan, P.S. Anil Kumar, Indian Institute of Science, Bangalore, India
Dirac semimetal (DSM) is a type of topological material with fourfold degenerate linear band crossing in the bulk, exhibiting nontrivial spin-momentum locking mediated by spin-orbit coupling (SOC). This is due to the preservation of both inversion symmetry and time-reversal symmetry. NiTe2, a potential candidate of type-II DSM, in addition to the Fermi arcs, has topologically nontrivial surface states below the Fermi level due to nontrivial Z2 topological gap. DFT calculations on NiTe2 have implied weak topological superconducting property with two Dirac points located at k = (0, 0, ±0.35)(2π/c) on both sides of the Γ point along the  direction. Since the two bulk Dirac points project to the same point in the (001) surface, the surface Fermi arcs occur on the side surfaces (i.e. parallel to the kz axis). The topological nature of bulk NiTe2 was addressed through Angle-resolved Photoemission spectroscopy (ARPES), revealing the existence of Dirac nodes. Theoretical calculations further speculate that NiTe2 is a promising candidate for exploring topological superconductivity, topological Dirac fermions, and other emergent phenomena for the development of spintronics or topological devices. The chiral magnetic effect is a macroscopic manifestation of the quantum anomaly in the relativistic field theory of chiral fermions which is a phenomenon arising from a collective motion of particles and antiparticles in the Dirac sea. No signature of Dirac fermions has been obtained till now in electrical transport measurements in bulk NiTe2.However, on thinning down to the nanoscale, we observe negative magnetoresistance (MR) when the magnetic field is parallel to the current direction at low temperatures up to 10K. The observed phenomenon is a strong evidence of the chiral magnetic effect. It stems from the effective transformation of the Dirac point to Landau levels (LL) with n=0 chiral LL playing a crucial role in the phenomenon. This effect occurs only when a component of the electric field is parallel to the magnetic field and represents a topologically non-trivial gauge field background. Thickness-dependent resistivity with temperature depicts the shifting of chemical potential away from the Dirac point and the presence of topological surface states (TSS). Hall Effect shows the transition from two types of carriers to single type carriers on thinning down the flake and holes being the majority carriers for thinner flakes. We observed weak anti localization from bulk Dirac point which competes with the chiral anomaly.
F:P17 Low temperature electrical transport of nanoflakes of strong topological insulator BiSbTe1.25Te1.75
n.k. sebastian, P.S. Anil Kumar, Indian Institute of Science, Bangalore, India
We report the electrical transport properties of exfoliated nano flake of a 3-dimensional strong topological insulator BiSbTe1.25Se1.75.Here, we demonstrate the role of the bulk insulating states as well as the surface 2-D metallic states in transport.This substitution of Sb and Te on Bi2Te3 leads to placing the Fermi level on the surface Dirac cone within the bulk bandgap. Insulator like behaviour (bulk contribution) was observed above 50K, whereas surface dominated metallic behaviour was observed below 50K, evident from resistance versus temperature measurements. Magneto-transport measurements reveal the existence of Dirac fermions and a nontrivial Berry phase of π as evident from the observed 2-D weak antilocalization(WAL) effect.WAL was fitted using Hikami-Larkin Nagaoka equation and the variation of phase coherence length with temperature indicated 2-D Nyquist dephasing,involving electron-electron interaction.Hall measurements upto 50K gave linear n-type metallic behaviour.At higher temperatures,it starts becoming nonlinear and from 100K onwards, it shows that the 3-D bulk is p-type semiconductor.It indicates that the Fermi level is in the bulk bandgap,above the surface Dirac cone,but below the intrinsic level. We also observed universal conductance fluctuations in our sample.
F:P18 Ultrahigh Specific Surface Area 2D-Nanostructured Carbon Electrodes and Coatings by Electrospinning
Qi Li, Feng Yan, J. Texter, Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, China; Coating Research Institute, School of Engineering, Eastern Michigan University, Ypsilanti, MI, USA; Strider Research Corporation, Rochester, NY, USA
Aqueous thermodynamically-stable dispersions of carbon nanotubes and graphene, respectively, at 6-17% by weight, are prepared by multiphase fluid processing using polymerized ionic liquid stabilizers. These dispersions provide ultra-high thermal conductivity and heterostructured and high specific surface area coatings. Such advanced coatings enable development of a platform for catalytic membranes and electrocatalytic electrodes derived by electrospinning (ES) and further extend the utility and potential of 2D materials and advanced composites based on 2D materials. We demonstrate how networks made by ES can be grown beyond inherent 1D fibers to provide 2D-heterostructured networks as supports and electrodes. Two classes of such networks are presented: (1) randomly oriented graphene flakes connected by nanofibers; (2) 2D-microscale membranes composing mesoscale networks of MWCNTs connected by nanofibers. Morphology tuning and densification, and modulation of ionic and electrical conductivities by chemical doping, chemical deposition, and anion exchange are described. Directions for future developments and applications are articulated.
F:P19 Influence of Oxygen in Ti3AlC2 MAX Precursor on the Physical Characteristics of Ti3C2Tx MXene Nanosheet
Subin Choi, Keum Hwan Park, Chan-Jae Lee, Jong-Woong Kim, Jeonbuk National University, Jeonju, South Korea
Ti3C2TX-based MXene nanosheet has attracted significant attention due to its high conductivity, hydrophilic surface, rich chemistry, and large surface area. Ti3C2TX MXene is typically prepared by selective etching of Al layers from Ti3AlC2 MAX precursor. The characteristic of MAX is one of the factors that determine the shape, electrical conductivity and surface termination of MXene, and we have focused on the effect of the oxygen content in MAX phases on the MXene nanosheet. In this study, two types of MXene monolayers were prepared by etching from MAX precursors with different oxygen concentrations. A large number of particles that appeared to be impurities in MXene originated from MAX with higher oxygen content (HO-MXene), and as a result, MXene nanosheets were coated with wrinkles. In contrast, the surface of MXene developed from MAX with lower oxygen content (LO-MXene) was smooth and wrinkles-free. From the result of energy dispersive X-ray spectroscopy (EDS) mapping, some particles were shown noticeably, and the peak corresponding to Al2O3 also appeared in the O1s spectrum of X-ray photoelectron spectroscopy (XPS). The electrical conductivity of the HO-MXene and LO-MXene were measured 7,800 S/cm and 10,540 S/cm, respectively.
F:P20 Effect of Synthesis Route on the Structural, Compositional, and Electrochemical Properties of g-C3N4/Ce-MOF Nanocomposites
Z. DURMUS, A.W. Maijenburg, Centre for Innovation Competence (ZIK) SiLi-nano, Martin Luther University Halle-Wittenberg, Halle (Salle), Germany; R. Köferstein, Institut für Chemie Festkörperchemie, Martin Luther University Halle-Wittenberg, Halle (Salle), Germany
In this study, nitrogen-vacancy modified graphitic carbon nitrides (g-C3N4) were synthesized via different thermopolymerization routes using different precursors. Then Ce(III)-based metal-organic frameworks (Ce-MOF) were in-situ synthesized onto g-C3N4 sheets via a low-temperature solvothermal method to obtain g-C3N4/Ce-MOF nanocomposites. Structural, physical, and morphological features of components and nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), surface area measurement (BET and BJH), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) methods. Electrochemical properties of nanocomposites will be studied and discussed for their potential application as photo(electro)chemical (P(E)C) catalysts.
F:P21 Improving the Longevity of Triboelectric Charge
L. GERMANE1, L. Lapčinskis1, 2, M. Knite1, A. Šutka2, 1Institute of Technical Physics, Faculty of Materials Science and Applied Chemistry, Riga Technical University, Riga, Latvia; 2Institute of Materials and Surface Engineering, Faculty of Materials Science and Applied Chemistry, Riga Technical University, Riga, Latvia
Triboelectrification is a phenomenon when charge is created on the surface by contacting and separating two materials. On a daily basis these charges can be observed on surfaces of insulators, therefore uncontrolled friction can lead to serious safety threat as an accidental discharge may cause emergence of sparks. However, triboelectric charges can be also used for energy harvesting, as demonstrated by triboelectric nanogenerators. Triboelectric charge in polymers forms as a result of mechanical action when the covalent bond of polymer chain is cleaved and mechanoions are created. This charge can be observed for several hours after the bond cleavage, however the largest it is in the first seconds. As reported, stabilization is obtained through interaction with radical fragments that also form after bond cleavage. To stabilize charge on polymers and, therefore, increase both the magnitude and longevity of the measured charge, polymer systems incorporating additives that provide stable radicals can be made. For example, addition of PMMA polymer on the surface of elastomer yields increase in the observed charge density by an order of magnitude. In that way it is possible to create materials with potential to use in high-performance triboelectric nanogenerators.
F:P22 Multi-responsive Hydrogel Microspheres for the Controlled Release of Ozoile
g. ciarleglio1, 2, S. Vella2, E. Toto1, M.G. Santonicola1, 1Department of Chemical Engineering Materials Environment (DICMA) Sapienza University of Rome, Rome, Italy; 2 Erbagil s.r.l., Telese Terme (BN), Italy
Natural and biodegradable polymers with pH-responsive properties, such as alginate and chitosan, are widely exploited for drug delivery applications, most notably in the form of biocompatible microspheres. In addition, thermo-responsive poly(N-isopropyl-acrylamide) (PNIPAM) is often added to biomedical delivery systems due to its lower critical solution temperature close to human physiological conditions. In this work, multi-responsive microspheres (MRMs) made of alginate/chitosan/PNIPAM hydrogels were developed and applied as carriers of Ozoile, a stable ozonide derived from olive oil in a patented process. Ozoile acts as a biological inducer, regulating the main metabolic pathways and stimulating the endogenous defense system. The MRMs were prepared from an alginate/NIPAM emulsion containing different concentrations of Ozoile. The extrusion-dripping technique combined with ion gelation crosslinking was used, and the MRMs were further optimized by a chitosan coating to improve the stability. The chemical composition and microstructure of the MRMs were evaluated using FTIR spectroscopy and optical and electron microscopy. Differential scanning calorimetry was used to investigate the thermo-responsive properties of the MRMs and optimize their critical transition temperature.
F:P23 Landau-energy Landscape Reconstruction for a Ni-Fe-Ga(Co) Shape Memory Alloy
K. ZOUBKOVA, P. Sedlák, H. Seiner, Institute of Thermomechanics, Czech Academy of Sciences, Prague, Czech Republic; E. Villa, CNR ICMATE Sede di Lecco, Lecco, Italy; M. Tahara, H. Hosoda, Institute of Innovative Research (IIR), Tokyo Institute of Technology, Yokohama, Japan; V. Chernenko, BCMaterials & University of Basque Country (UPV/EHU), Bilbao, Spain
Shape memory alloys (SMAs) and ferroelastic materials in general are solids which exhibit diffusionless transformation between two or more crystal structures induced by stress or temperature. Therefore, the Gibbs energy of a ferroelastic crystal lattice should exhibit a non-convex shape with multiple minima, each minimum corresponding to one crystal structure stable under the given conditions. This talk presents a detailed reconstruction of the Gibbs energy landscape evolution of the Ni-Fe-Ga(Co) shape memory alloy with temperature and strain. An energy function ansatz is suggested based on the Landau theory approximation and its appropriateness is confirmed by results from resonant ultrasound spectroscopy (RUS) measurements in a broad temperature range. The RUS methodology is described in great detail. To find the temperature-dependent parameters of the energy function, the evolution of stress-strain curves with temperature was recorded. The best fit under the ansatz was sought for the segments of the curves corresponding to pure elastic strain. An explicit formula for the Landau energy landscape is provided and the dependence of the parameters on temperatures is expressed using linear and quadratic approximations.
F:P24 Static and Dynamic Characterization of Flexinol Wires in a Biomimetic Perspective
B. Tondu, Université Fédérale de Toulouse, and LAAS-CNRS, Toulouse, France
Flexinol wires are a low-priced, and easy to implement, commercial version of shape-memory alloy NiTinol wires. If technical data, like maximum force corresponding to given current, are easy to obtain, the scientific literature about static and dynamic characterization of such wires is still limited. In order to get such results, we developed an original experimentally set-up where the contraction of a Flexinol wire, with given embedded loads, can be recorded by means of a laser pointing on a rubber patch on which a suitable strain gauge has been glued. As a consequence, both current force and displacement contraction may be obtained. Two sets of results can be deduced and are reported for three different wire diameters: - a classic identification of contraction displacement versus time, with and without load; in our case, we highlight the relevance of a nonlinear over-damped model which could further be used for open-loop and closed-loop control, - a comparison of static and dynamic contraction of Flexinol wire with skeletal muscle in order to determine its biomimetic nature with respect to the so-called physiological Tension-Length curve and Hill’s curve.
F:P25 Investigation of Thermally Induced Intermartensitic Transformations in Ni-Mn-Ga-Fe Alloy
M. VINOGRADOVA1, O. Sozinov1, L. Straka2, P. VeRtát2, E. Lähderanta1, K. Ullakko1, 1Department of Physics, LUT-University, Lappeenranta, Finland; 2FZU - Institute of Physics of the Czech Academy of Sciences, Czech Republic
In Ni-Mn-Ga alloys many fascinating features have been reported, such as magnetic field induced strain of 6-12%, extremely low twinning stress of 0.02-1 MPa, large magnetocaloric effect, and others. Alloy properties depend on crystal structure and are sensitive to temperature. Despite numerous investigations, the crystal structure of modulated martensitic phases 10M and 14M in Ni-Mn-Ga alloys is still under discussion. We suggest that traditional structure determination methods could have been impacted by hierarchical twin microstructure ranging from micro- to nanoscale in the Ni-Mn-Ga system originating from high-mobility and low-energy twin boundaries. The present study examined martensites in a Ni-Mn-Ga-Fe single crystal with simplified variant microstructures at various temperatures. It allowed us to compare lattice parameters of nonmodulated (NM) and modulated phases 10M and 14M at the same temperature range due to the large thermal hysteresis of intermartensitic transformations. Here we specially focused on the temperature dependence of monoclinic distortion in 10M and 14M, as well as its jump during structure transformations. Analysis of the results is based on nano-twinning model of 10M and 14M structures widely used for first-principles electronic structure calculations.
F:P26 Full Variation of Site Substitution in Ni-Mn-Ga by Ferromagnetic Transition Metals
V. KOPECKY, M. Rames, M. Veis, O. Heczko, FZU - Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
Simple alloying of Ni-Mn-Ga may not lead to desirable increase of transition temperatures, martensitic (Tm) and Curie (Tc), keeping preserved its extraordinary performance like highly mobile twin boundaries. Therefore, many attempts were put on finding an element which would substitute part of the compound and successfully increase both temperatures. We chose ferromagnetic transition metals Fe, Co or Ni at the level of 5~at. %. We prepared nine Ni-Mn-Ga-X compounds varying in substitution for each original element at the time. Such systematic production allows comparison of both effect of the new element and deficiency of the original element. We found contradictory trends of Tm and Tc for most of the compounds. The highest Tm (571~K) was found for Ni50.0Mn25.4Ga20.3Ni4.3 (at. %) compound exhibiting concurrently the second lowest Tc (325~K). Compound Ni44.9Co5.1Mn25.1Ga24.9 exhibits the lowest Tm detected (77~K) and the highest Tc (444~K). One of the compounds, Ni45.3Fe5.3Mn23.8Ga25.6, exhibited no martensitic transition which is not predicted by broadly used e/a parameter but well-predicted by Ne/a criterion. Moreover, the nonoccurrence of Tm was studied by MOKE which revealed correlation with a missing interband transition identified from the off-diagonal spectra.
F:P28 Preparation and Spectroscopic Investigations of Oxide Glasses with High Iron Concentrations
T. TASHEVA1, R. Harizanova1, I. Mihailova1, I. Avramova2, Z. Cherkezova-Zheleva3, D. Paneva3, C. Rüssel4, 1University of Chemical Technology and Metallurgy, Sofia, Bulgaria; 2Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria; 3Institute of Catalysis, Bulgarian Academy of Sciences, Sofia, Bulgaria; 4Otto Schott Institute for Materials Research, Jena University, Jena, Germany
Oxide glasses with high 3d-transition metal concentrations and based on them magnetic glass-ceramics find application in microelectronics, sensors and in medicine. The synthesis of glass-ceramics with pre-determined phase compositions, controlled crystal sizes and volume fractions requires knowledge on the structure, valency and coordination in which constituting elements are present in glass.
The synthesis of glasses with mol% composition (100-x)(0.16Na2O/0.10CaO/0.74SiO2)/xFe2O3, x = 5, 10, 15 and 20 was performed by traditional melt-quenching technique. The densities of the prepared materials are determined pycnometrically. Based on the experimental results for the density, the molar volume Vm and the oxygen packing density (OPD) are evaluated. The valence states of the ions in the prepared glasses are studied by X-ray photoelectron spectroscopy. The presence of Fe ions both as Fe3+ and Fe2+ and the occurrence of bonds from the type Si-O-Fe is observed. Depending on the Fe-oxide concentration, the number of bridging and non-bridging oxygens varies. The valence states and the coordinations of Fe-ions in the glasses are investigated by Mössbauer spectroscopy which detects Fe3+ ions in both tetrahedral and octahedral coordination in the glass. Fe2+ is also found to be octahedrally coordinated in all glasses. For the sample with x= 20 mol%, also the occurrence of Fe2O3 and Fe3O4 is detected.
Acknowledgements: Authors express gratitude to BNSF, contract КП-06-Н48/4 for the financial support.
F:P29 Prelaminar Characterization of Advanced Alloys as Structural Material for LFR
A. MELI, ESSENTIAL Group, DENERG, Politecnico di Torino, Torino, Italy; M. Tarantino, S. Bassini, A. Fiore, C. Ciantelli, M. Angiolini, D. Martelli, ENEA - Department for Fusion and Technology for Nuclear Safety and Security C. R. Brasimone, Camugnano (Bologna), Italy
The Lead cooled Fast Reactors are one of most promising Gen. IV nuclear systems, currently under development in Europe, China and USA. They can ensure enhanced performances, minimal waste production thanks to a closed fuel-cycle, but they also have some issues to be addressed. One of the most critical is the long-term degradation processes initiated in structural materials in contact with liquid lead. Corrosion in liquid lead is originated from physical-chemical phenomena involving the dissolution of the constituent elements, their transport, and chemical reactions with non-metallic impurities (e.g. oxidation by the dissolved oxygen). The alloy’s microstructure, thermal and fluid-dynamic effects have also relevant importance on the corrosion resistance of the components. In this framework, an experimental campaign has been run at the research center ENEA of Brasimone exploiting LECOR loop facility, with the aim of characterizing the behavior of a set of alloys with and without coating in the following condition: 550°C, in fluent lead at 1m/s, for 2600h, with oxygen dissolved 10-5 wt. %. The alloys investigated are: AISI 316L, 15-15Ti AIM1, ceramic alumina coatings by PLD and D-Gun, Al-base coating by pack cementation. Results will be presented and discussed in this work.
F:P30 W/Steel Composites as a Potential Interlayer for the Joining of W and Steel for the First Wall of a Fusion Reactor
V. GANESH1, 2, D. Dorow-Gerspach1, S. Heuer1, L. Leich2, J. Matejicek3, M. Vilemova3, M. Bram2, 4, J. Willem Coenen1, 5, M. Wirtz1, G. Pintsuk1, W. Theisen2, C. Linsmeier1, 1Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung - Plasmaphysik, Jülich, Germany; 2Institut für Werkstoffe, Lehrstuhl Werkstofftechnik, Ruhr Universität Bochum, Bochum, Germany; 3Institute of Plasma Physics of the Czech Academy of Sciences, Prague, Czech Republic; 4Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung - Werkstoffsynthese und Herstellungsverfahren, Jülich, Germany; 5Department of Engineering Physics, University of Wisconsin Madison, Madison, USA
For the first wall of a future fusion reactor, a joint between tungsten (W) and steel is required. But the large difference in the coefficient of thermal expansion (CTE) between them leads to thermal stresses at its interface, when joined directly. An interlayer of a functionally graded material which gradually varies the CTE from W to steel, could redistribute this thermal stress. In this work W/steel composites were successfully manufactured employing three different techniques each with optimized process parameters: atmospheric plasma spraying (APS), electro-discharge sintering (EDS) and spark plasma sintering (SPS). Three concentration levels were taken: 25 vol% W, 50 vol% W and 75 vol% W. The study involves the comparative analysis of their microstructures and their residual porosity. The SPS-composites show the lowest porosity followed by EDS-composites and then followed by APS-composites. The APS-composites have a flat-cake like microstructure with alternating W- and steel-splats whereas the SPS- and EDS-composites have a metal matrix composites like microstructure with spherical embedded W particles inside the inside the steel matrix. Dilatometry measurements confirmed the basic principle of the approach, as the measured CTE were in good agreement with the expected values.
F:P31 Nanostructured Mo Mirrors Behavior under He Irradiation
L. CiupiNski1, A.T. KrawczyNska1, M. Gloc1, D. Setman2, M. Spychalski1, P. Petersson3, 1Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw, Poland; 2University of Vienna, Faculty of Physics, Vienna, Austria; 3KTH Physics Royal Institute of Technology, Stockholm, Sweden
The main candidate for diagnostic mirrors in future fusion reactors is single crystal molybdenum. However, this candidate material is not very economically efficient, therefore in this study nanostructured molybdenum is investigated as potential competitive solution. The microstructure of molybdenum mirrors was refined by high pressure torsion which led to the average grain size of 110 nm. Its thermal stability was verified up to 300°C. Subsequently, refined mirrors and a reference micrograined one were irradiated by 2 keV He ions with the dose of 5x1016/cm 2 and 8x1016/cm 2. Reflectivity measurements in the 300-2400 nm range were performed. Surface observations using scanning, scanning transmission and transmission electron microscopes were carried out. The total reflectivity of undeformed and deformed mirrors irradiated with He ions dose of 5x1016cm-2 decreases comparably. Dose increase up to 8x1016cm-2 causes a further slight decrease in reflectivity. However, the reflectivity of deformed mirrors decreases noticeably more. The detailed observation of cross sections enabled to understand and explain the different behavior of nanostructured samples in comparison with micrograined ones while irradiated with a higher dose.
F:P32 Selection of Inboard Materials for Optimal Radial Build of a Tokamak Fusion Reactor
BONG GUEN HONG, Chonbuk National University, Jeonju-si, South Korea
Selection of inboard materials is important in determination of the optimal radial build of a tokamak fusion reactor. The optimal radial build and system parameters of the reactor are determined through a tokamak systems analysis coupled with a neutron transport analysis. In a configuration with an inboard blanket, the shielding performance was the best for a tungsten carbide (WC) as s shield material, which showed smaller reactor size than cases with other shield materials. Shield materials such as WC, ferritic/martensite steel (FMS), and borated steel (BS) showed large neutron flux for tritium breeding in the blanket which is attributed to reflected neutron by tungsten (W) and steel (Fe). In a configuration with only an outboard breeding blanket, it was shown that the tritium self-sufficiency could be satisfied with neutron multiplier and/or reflector materials which replaced an inboard blanket. Titanium carbide (TiC) was the best regarding the neutron reflecting performance. With lead (Pb) as a neutron multiplier, neutron spectrum softening by Pb enhanced the reflector performance and increased tritium breeding at the outboard blanket. A proper combination of the multiplier and reflector materials can result in smaller reactor size than the reactor with an inboard blanket.
F:P33 Potentiodynamic Electrochemical Impedance Spectroscopy of CuGaSe2 Photocathode for Photoelectrochemical Water Splitting
B. Mahmoudi, R. Singh, F. Caddeo, T. Lindenberg, T. Schneider, T. Hölscher, R. Scheer, A.W. Maijenburg, Center for Innovation Competence (ZIK) “SiLi-nano”, Martin Luther University Halle Wittenberg, Halle, Germany
Electrochemical impedance spectroscopy (EIS) has emerged as an indispensable and precise technique in research fields related to electrochemistry such as semiconductor electrochemistry, corrosion, and liquid batteries. Therefore, a full Potentiodynamic-EIS has been carried out on polycrystalline CuGaSe2 semiconductor thin film at 27 different potentials in dark as well as AM1.5G (400 Watt/m2) conditions, with all crucial steps including the analysis of Nyquist plots and fitting of the data employing a realistic equivalent circuit, which allowed to extract all relevant parameters for CuGaSe2 such as back contact Schottky barrier (Bc), space charge region (Scr), surface states (SS), surface oxide (ox), and Helmholtz double layer (HDL) capacitances.
F:P34 CuBi2O4 Nanofibers for photoelectrochemical water splitting
D. EBERHART, A.W. MAIJENBURG, Martin-Luther-University Halle-Wittenberg, Halle, Germany
For the synthesis of the CuBi2O4 nanofiber photocathodes, we choose the highly efficient, scalable, and cost-effective electrospinning technique. This process can be easily combined with sol-gel-chemistry, which is a well-known low-cost solution-processing method for the preparation of photocatalytic materials. An interesting advantage of electrospinning, is that there are a lot of parameters that can be varied for optimum water splitting efficiency, e.g. solution properties, processing parameters and the setup design. The main solution parameters which can be optimized are the viscosity, conductivity, surface tension and the solvent volatility. For this, the optimal precursors and concentrations need to be found. The processing parameters that influence the properties of the formed nanofibers are the flow rate, the electric field strength, humidity and the thermal annealing conditions after the electrospinning process. The flow rate as well as the electrical field strength have influence on the fiber diameter and the thermal annealing process influences the morphology of the fibers.
F:P35 Carbon Encapsulated Core-shell Nickel@nickel Sulfide as High-capacity Battery-type Cathode for High-capacity Hybrid Supercapacitors
M.R. PALLAVOLU, R.R. NALLAPUREDDY, SANG W. JOO, School of Mechanical Engineering, Yeungnam University, Gyeongsan, Republic of Korea
The development of green and clean synthetic technologies has exceeded energy requirements, which has prompted researchers to use sustainable biomass. The low-cost and high-performance electrode materials are essential for energy storage development and applications. Herein, the cost-effective and easily synthesized bio-inspired hierarchical NiS-Ni@PC hybrid material is presented for supercapacitor application. The hierarchical nanostructure of carbon encapsulated core-shell Ni was derived using wheat snacks as the source material and the hierarchical core-shell growth of carbon encapsulated Ni@NiS flower formation is optimized by the different thiourea concentrations. The hierarchical nanostructures enable rapid diffusion and easy transfer of ions to the active material. The battery type NiS-Ni@PC material exhibited excellent electrochemical properties such as a specific capacity of 430 C g-1 at 1 A g-1 current density and a high capacity retention of 97%. Asymmetric supercapacitor device (NiS-Ni@PC//PC) exhibited superior energy and power densities as well as capacitance retention (95%) over 5000 cycles. This research looks promising and made at a simple approach for further processing on fabricating efficient anode and cathodic materials for battery-type supercapacitors.