Roger England, Cummins, Inc.
Ke Han, Floriday State University
Yugang Sun, Argonne National Laboratory
Wenge Yang, Center for High Pressure Science and Technology Advanced Research (HPSTAR)
Symposium Support Carnegie Institution of Washington, Efree
Center of High Pressure Science and Technology Advanced Research (HPSTAR)
W2: High Pressure and Materials II
Monday PM, November 30, 2015
Hynes, Level 1, Room 101
2:30 AM - *W2.01
Melting of Hydrogen above 200 GPa
Eugene Gregoryanz 1
1The University of Edinburgh Edinburgh United KingdomShow Abstract
It was theorized, that at high compressions, the increased zero-point oscillations in hydrogen would destabilize the lattice and form a ground fluid state at 0 K1. Theory also predicts this fluid would have very unusual properties governed by quantum effects2,3. By combining Raman spectroscopy and in-situ high temperature techniques at high pressures, we have investigated the behavior of dense hydrogen above 200 GPa and above 300K, P-T conditions previously inaccessible in experiments. The novel data lead to a significant revision of the phase diagram of hydrogen above 200 GPa and suggest unusual physics in the molecular liquid and solid phases.
1.E. Brovman, Y. Kagan, A.Kholas, Soviet Physics JETP. 35, 783 (1972).
2.E. Babaev, A. Sudbo, N.W. Ashcroft, Nature. 431, 666 (2004).
3.E. Babaev, A. Sudbo, N.W. Ashcroft, Phys. Rev. Lett. 95, 105301 (2005).
3:00 AM - *W2.02
Dramatic Enhancement in Superconducting Properties of New BiS2 Based ReO/FBiS2 Superconductors (Re = La, Pr, Nd, Sm) and Bi4O4S3 under Hydrostatic Pressure
S. Arumugam 1
1Bharathidasan University Tamil Nadu IndiaShow Abstract
Layered superconducting compounds have been the focus of immense interest due to the discovery of superconductivity in cuprate and iron-based systems. Discovery of Fe based pnictide superconductors viz. REFeAsO/F (RE=rare earths) with superconductivity in more than 55K has attracted a lot of attention. Primarily, because this is the only class of superconductors besides infamous high Tc cuprates (HTSc), which falls outside the popular BCS (Bardeen Cooper Schrieffer) theoretical limit of 40K. Moreover both Fe pnictides and Cuprates superconductors do have striking similarities viz. the semimetallic/insulating magnetic ground states, very high upper critical fields and the layered structures. Seemingly the role of CuO2 planes in cuprates is played by the FeAs superconducting layers in pnictides. Within the same structure of REFeAsO, when FeAs layer is replaced by BiS2 a new superconductor REOBiS2 emerged very recently, though with lower Tc of around 5K. The similar layered structure and existence of superconductivity in BiS2 layer mimicking the FeAs superconducting block of REFeAsO system has been a recent point of debate and it will be addressed in the presentation and comment on the fact about how the new FeAs and BiS2 based superconductors are thought provoking for both experimentalists and theoreticians outside the HTSc cuprates mystery of more than two decades by now.
Discovery of superconductivity in BiS2 layers of Bi4O4S3 and ReO/FBiS2 systems has attracted tremendous interest of both experimentalists and theoreticians from condensed matter physics community. Comparing the role of various Re in ReO/FFeAs and ReO/FBiS2, one finds that though Tc of (La/Pr/Nd)O0.5F0.5BiS2 is around 2.1K/3.5K/5K respectively, the same for (La/Pr/Nd)O0.8F0.2FeAs is 26K/43K/50K. It appears that chemical pressure plays an important role in superconductivity of these layered BiS2 and FeAs superconductors. We review our efforts on synthesis and physical properties of title compounds from very beginning and present the new results related to impact of hydrostatic pressure on their superconductivity. The Tc of ReO/FBiS2 compounds is enhanced to fivefold for just above 1GPa external pressure, accompanied with normal state semi-metallic to metallic transition in normal state, which is thought provoking for solid state physics community.
3:45 AM - W2.04
Studies of Uranyl Peroxides at Elevated Pressures
Katlyn Turner 1 Wendy Mao 1 Rodney C. Ewing 1
1Stanford University Stanford United StatesShow Abstract
Uranyl peroxides are a diverse family of compounds that form in environmentally relevant conditions. They are of great importance due to the prevalence of the uranyl (UO22+) cation in nuclear waste. This oxidized form of uranium is a common constituent of nuclear waste, and peroxide forms in waste from the alpha-radiolysis of water. Understanding the properties of uranyl peroxides is considered an important piece of the nuclear waste management pie. Uranyl peroxides assemble into diverse nano-cages. These clusters consist of 20 to -68 uranyl units in various cage topologies. Their properties have been characterized extensively in ambient P-T conditions; uranyl peroxides form spontaneously in wide pH ranges, and can form a multitude of structures due to the uranyl cation's ability to incorporate a variety of ligands in its equatorial bonding positions. Much study has been devoted to characterizing their crystal structures and properties in solution. These structures often crystallize readily and persist for extended time periods in situ. Here, several uranyl peroxides have been studied in the solid-state at elevated pressures to determine their strengths, bulk moduli, and structures at high pressures. The aforementioned properties have been found to depend heavily on the compositions of the uranyl peroxides in question, and their ambient structures. Two uranyl peroxides in particular have been fully characterized: U60 and U24Py12. U60 clusters are of special interest because they are topologically identical to carbon fullerenes, forming isometric crystals with the formula: Li68K12(OH)20[UO2(O2)(OH)]60(H2O)310. In diamond anvil cell experiments, the fullerene U60 topology is stable up to pressures of 10 GPa, above which the structure collapses irreversibly. A pressure-induced tetragonal structure (a = 36.6764(2), c = 35.1672(4) Å) forms in the range of 4 to 10 GPa, as determined by in situ synchrotron XRD and Raman spectroscopy. Above 10 GPa, the U60 decomposes into smaller uranyl peroxides, as confirmed by ESI-MS. U24Py12 clusters form tetragonal crystals at ambient pressures with the formula: Na8[(UO2)24(O2)24(P2O7)12]. Single crystals of U24Py12 undergo reversible pressure-induced amorphization at 17 GPa. Based on Raman spectroscopy, the uranyl units persist to 50 GPa, at which point the Raman signal is imperceptible. Following pressure quenching, the original tetragonal structure of U24Py12 recovers, as evidenced by in situ XRD and Raman spectroscopy. In contrast to the topologically-identical C60, which collapses at pressures above 30 GPa, but retains its hexagonal structure, U60 loses its long-range periodicity at much lower pressures and ultimately forms smaller clusters. U24Py12 retains its chemical and structural integrity upon pressure quenching. The persistence of uranyl peroxide nano-cage structures during pressure experiments is a unique result, showing the strength of these compounds in extreme conditions.
4:30 AM - *W2.05
Theoretical Design, Synthesis, and Properties Study of Typical Transition Metal Nitrides under Pressure
Tian Cui 1 Kuo Bao 1
1Jilin University Changchun ChinaShow Abstract
The combination of transition metal and light elements such as B, C, N, and O is an effective approach to developing novel superhard multifunction materials. With this philosophy, compounds such as OsB2, ReB2, FeB4, PrN2, IrN2, OsN2, Re3N, and Re2N were successfully designed for the past decade. TM nitrides play a special role within these materials, for their high melting point, high chemical stability, corrosion resistance, high hardness, semiconductor property, and superconductivity with relatively high transition temperature. Thus we systematically studied several kinds TM nitrides theoretically and experimentally.
The structure, stoichiometry, phase transition, mechanical properties, hardness, and electronic structure of typical transition metal - nitrogen systems, such as Re-N, Tc-N, W-N, Nb-N, and FeN are investigated extensively by means of first-principles density functional theory. And some of them were synthesized by high pressure and high temperature technique and the high pressure characters of them were also studied. More than a dozen of new nitrides such as Re3N2, ReN3, ReN4, TcN, Tc2N3, TcN2, TcN3, TcN4, W3N2, NbO-WN, W5N6, Nb2N, NbN2, NbN3, and NbN4 with high hardness have been theoretically designed. The polycrystalline ε-NbN sample has been synthesized, and the incompressibility and rigidity have been measured for the first time. Our works on typical transition nitrides established the relations among their physical properties such as the N concentration, bonding, and hardness. New approaches for designing novel superhard multifunctional materials are therefore covered throughout the research.
5:00 AM - *W2.06
Theory of Transitions between Metallic and Insulating States in Simple Metals
Ivan I. Naumov 1 Russell J Hemley 1
1Carnegie Institution of Washington Washington United StatesShow Abstract
As experimentally established, all the alkali metals and heavy alkaline earth metals (Ca, Sr and Ba) become progressively less conductive on compression, at least up to some critical limit over a broad pressure range. Of these metals, Li and Na clearly undergo pressure-induced metal-insulator transitions, which may also be called reverse Mott transitions. Here, using group theory arguments and first-principles calculations, we show that such transitions are controlled by symmetry principles not previously recognized. The valence bands in the insulating states are described by simple and composite band representations constructed from localized Wannier functions centered on points unoccupied by atoms, and which are not necessarily all symmetrical. The character of the Wannier functions is closely related to the degree of s-p(-d) hybridization and reflects multi-center chemical bonding in these insulating states. The conditions under which an insulating state is allowed for structures having an integer number of atoms per primitive unit cell as well as re-entrant (i.e., metal-insulator-metal) transition sequences are detailed, resulting in predictions of semimetallic phases with flat surface states. The general principles developed are tested and applied to the alkali and alkaline earth metals, including elements where high-pressure insulating phases have been identified or reported (e.g., Li, Na, and Ca).
5:30 AM - W2.07
Steels and Intermetallics under Extreme Conditions
Klaus-Dieter Liss 1 4 7 Ayumi Shiro 2 Ken-ichi Funakoshi 3 Mark Reid 7 1 Hiroshi Suzuki 4 Takahisa Shobu 2 Yuji Higo 5 Hiroyuki Saitoh 2 Shuoyuan Zhang 2 3 Yo Tomota 6 Koichi Akita 4
1ANSTO Kirrawee DC Australia2Japan Atomic Energy Agency Kouto Japan3CROSS-Tokai Tokai Japan4Japan Atomic Energy Agency Tokai Japan5Japan Synchrotron Radiation Research Institute Kouto Japan6Ibaraki University Hitachi Japan7University of Wollongong Wollongong AustraliaShow Abstract
Materials are being designed and engineered for ever superior mechanical and operational properties, such as steels for lighter cars and energy-absorbing behavior in an accident, and titanium aluminides for lighter airplane turbine blades. The manufacturing of such materials may involve processes at extreme conditions, under high pressure or high temperature. Examples are high-pressure torsion and near net-shape forging. Therefore, it becomes eminently important to know and understand the phase diagrams of such materials at extreme conditions. Structural changes may open processing windows, while elevated mechanical properties are conserved under less extreme conditions. Here, we present first phase diagram studies on high-manganese steels and on titanium aluminides by in-situ synchrotron X-ray diffraction in a large-volume cell.
5:45 AM - W2.08
The 2.5 Power Law: A General Rule of Metallic Glasses
Qiaoshi Charles Zeng 1 2 3
1Carnegie Institution of Washington Argonne United States2Stanford University Stanford United States3Center for High Pressure Science and Technology Advanced Research Shanghai ChinaShow Abstract
Metallic glass (MG) is an important new category of materials with many unique properties, but very few rigorous laws are known to define its ‘disordered&’ structure. Recently we found that under simple compression, the volume (V) of a MG changes precisely with the 2.5 power of its principle diffraction peak position (1/q1). In the present study, we determine the V and q1 of a Ce68Al10Cu20Co2 MG by in-situ high-pressure x-ray microscopy and diffraction, and find that the 2.5 power law holds even through and during its polyamorphic transition. The transition is, in effect, equivalent of a continuous compositional change of 4f-electron-localized Ce (γ-like) to 4f-electron-itinerant Ce (α-like), indicating the 2.5 power law is general for tuning with composition and pressure. We further reexamine the previously reported compositional power law exponent of 2.3 on seven different MGs, and find indeed the more precise determination also yields the exponent of 2.5. The exactness and universality of the 2.5 power law imply that the structural change in various MGs may strictly follow a general rule of packing which is imposed by efficient filling of the space without identifiable symmetry.
W1: High Pressure and Materials I
Monday AM, November 30, 2015
Hynes, Level 1, Room 101
9:00 AM - *W1.01
Recent Breakthroughs in High-Pressure Materials Science
Ho-kwang Mao 1
1Center for High Pressure Science and Technology Advanced Research Shanghai ChinaShow Abstract
Pressure categorically and profoundly alters all materials. With the recent experimental breakthroughs after the turn of century, especially the new synchrotron facilities and nanotechnology coupled with diamond-anvil cell, sweeping changes of structural, electronic, magnetic and bonding properties have been uncovered and often come as a total surprise. Fundamental breakthroughs have been observed across the board in simple elements, organic compounds, stoichiometry of compounds, free electron metals, strongly correlated systems, superhard materials, materials, metallic glasses, nanomaterials, and deep-Earth minerals. We are witnessing a new era of materials science and applications with the added pressure dimension.
W3: Poster Session I: High Pressure and Materials
Monday PM, November 30, 2015
Hynes, Level 1, Hall B
9:00 AM - W3.01
High Pressure Calorimetry as a Tool or Process Optimization
Kristina Lilova 1 Link Brown 1
1Setaram Inc. Hillsborough United StatesShow Abstract
The thermal behaviour of materials exposed to high pressure process during manufacturing or transformation cannot be understood and/or predicted if their physicochemical properties are determined under atmospheric pressure conditions. The high pressure calorimetry is used to simulate the actual condition thus providing critical data on the materials&’ behaviour.
Based on the MicroDSC technology, Setaram Instrumentation has designed a calorimeter operating up to 1 000 bars and between -45°C and 120°C. A dedicated high pressure panel is attached to the HP MicroDSC to cover the pressure range either under controlled pressure scanning or isobaric conditions. A review of recent work perfroemd with this technique will be presented to illustrate the effectiveness of directly acquiring calorimetric data at high pressure.
For example polymers are often processed at elevated temperatures and pressures (ex: high pressure injection molding, extrusion) and under different gases (foaming) with significant effects on their melting points or glass transition temperatures. High pressure calorimetry can be also applied in the food industry for the investigation of the oxidative stability of oils; the modification of glass transition temperature of carbohydrates; to polymorphic changes in fatty compounds, etc.. Pressure-induced solid-solid transitions are also of key interest in the pharmaceutical industry. Gas hydrates or clathrate formation and dissociation, and wax appearance temperature in crude or diesel oils represent another pressure dependant phenomena which has been successfully studies using high pressure calorimetry as well
9:00 AM - W3.02
Guest Dependent Brillouin and Raman Spectroscopic Studies to Probe the Flexibility of ZIF-8 at High Pressures and Low Temperatures
Dhanya Radhakrishnan 1 Chandrabhas Narayana 1
1Jawaharlal Nehru Centre for Advanced Scientific Research Bangalore IndiaShow Abstract
Metal organic frameworks (MOFs) are microporous materials consisting of metal ions and organic linkers which have a huge variety of applications like gas storage, separation, catalysis, drug delivery etc. Zeolitic imidazolate frameworks (ZIF) are a class of MOFs where the metal atoms (Mn+=Zn2+, Co2+) are tetrahedrally coordinated to the N atoms of imidazolate derived linkers (IM=C3N2H3-) subtending an angle of 1450 at M-IM-M centre analogous to Si-O-Si angle in zeolites to form porous architecture. ZIF-8, a prototypical ZIF has been widely studied due to its exceptional chemical, thermal stability and its gas adsorption properties which makes it a potential candidate for many practical applications. ZIF-8 posses exceptionally low shear modulus (< 1 GPa) which results in pressure induced mechanical failure upon application of shear stresses when used in practical applications. We have used Brillouin spectroscopy to study the pressure dependence of the acoustic modes (or elastic properties) of ZIF-8 in different pressure transmitting mediums (guests) and under non-hydrostatic conditions. Our study shows the pressure induced flexibility and dynamics of ZIF-8 as well as a huge increase in the acoustic velocities on applying pressure, illustrating the role of guest in enhancing the elastic properties. On applying pressure the size of windows connecting the pores of ZIF-8 increases (gate opens) letting more guests to enter the pores. The pressure transmitting medium plays an important role in this gate opening behaviour. The interaction between the framework and guest which results in different pressure dependent behaviour in different mediums is investigated using high pressure Raman spectroscopy. We have also studied the temperature dependent elastic properties of ZIF-8 on adsorption of various gases.
9:00 AM - W3.03
Pressure- and Temperature-Induced Phase Transitions in [(CH2)3NH2][Zn(HCOO)3]: Raman Scattering Study
Nathalia Leal Costa 1 Tercio Almeida da Silva 1 Waldeci Paraguassu 1 Miroslaw Maczka 2 Maciej Ptak 2 Krzysztof Hermanowicz 2
1Universidade Federal do Paraacute; Beleacute;m Brazil2Polish Academy of Sciences Wroclaw PolandShow Abstract
Metal-organic frameworks (MOFs) of the general formula [cat][M(HCOO3)], with M = divalent cation and cat = amine cation, have received a lot of attention in recent years because of their CO2 sorption capacity, magnetic, ferroelectric and multiferroic properties, and glassy behavior.[1-4] In this respect, the first report on the discovery of multiferroic properties in dimethylammonium (DMA) MOFs of the formula [(CH3)2NH2][M(HCOO)3] (M = Mn, Ni, Fe, Co) was published in 2009.5 This discovery promoted broad interest in the properties and phase transition mechanism in these compounds, as well as led to many efforts to synthesize novel amine-templated metal formate frameworks. Raman scattering and IR spectra have been performed on azetidinium zinc formate, [(CH2)3NH2][Zn(HCOO)3] under the Temperature- and pressure variation. Raman spectra reveal distinct anomalies in mode frequencies and bandwidths near 250 and 300 K. These anomalies were attributed to structural phase transitions associated with the gradual freezing of ring-puckering motions of the azetidinium cation. Pressure-dependent studies revealed a pressure-induced transition near 0.4 GPa. Raman spectra indicate that the structure of the room-temperature intermediate phase observed near 0.4 GPa is the same as the monoclinic structure observed at ambient pressure below 250 K. The second phase transition was found near 2.4 GPa. This transition has strong first-order character and is associated with strong distortion of both the zinc formate framework and azetidinium cations. The last phase transition was found near 7.0 GPa. This transition leads to lowering of the symmetry and further distortion of the zinc formate framework, whereas the azetidinium cation structure is weakly affected.
(1) Rossin, A.; Chierotti, M. R.; Giambiastiani, G.; Gobetto, R.; Peruzzini, M. CrystEngComm 2012, 14, 4454minus;4460.
(2) Zhang, W.; Xiong, R. G. Chem. Rev. 2012, 112, 1163minus;1195.
(3) Wang, Z.; Zhang, B.; Otsuka, T.; Inoue, K.; Kobayashi, H.; Kurmoo, M. Dalton Trans. 2004, 2209minus;2216.
(4) Jain, P.; Dalal, N. S.; Toby, B. H.; Kroto, H. W.; Cheetham, A. K. J. Am. Chem. Soc. 2008, 130, 10450minus;10451.
9:00 AM - W3.04
Pressure-Induced Structural Transformations in In2-xYx(MoO4)3 Systems
Waldeci Paraguassu 1 Raffael Mendonca 2 Bojan A Marinkovic 4 Miroslaw Maczka 3 Josue Mendes Filho 2
1Universidade Federal do Paraacute; Belem Brazil2Universidade Federal do Cearaacute; Fortaleza Brazil3Polish Academy of Sciences Wroclaw Poland4Pontifiacute;cia Universidade Catoacute;lica do Rio de Janeiro Rio de Janeiro BrazilShow Abstract
Molybdates and tungstates systems with A2(XO4)3 formula (A = a trivalent ion from Al to Ho; X = Mo6+, W6+) have been investigated due to their optical, ferroelastic, ferroelectric and negative thermal expansion (NTE) properties.1,2,3 Particularly, NTE systems are widely studied as potential fillers in order to control thermal expansion in composites. The Sc2(WO4)3/ZrO2 and Sc2(WO4)3/Cu composites, for example, show almost zero thermal expansion when the volume fraction of Sc2(WO4)3 is as high as 25 and 70%, respectively.4 In general, the easy of XO4 rotation in open framework systems is at the origin of its specific properties. In particular, the relation of these rotations with the low/negative thermal expansion of such structure is well established (see e.g. the NASICON and LAS frameworks, see e.g. J. Mol. Struct. 270 (1992) 407-416, Solid State Ionics 9&10 (1983) 845-850, 73 (1994) 209-220, etc. and refs herein) , i.e., NTE properties in framework structures are intrinsically related to the existence of low energy Rigid Unit Modes (RUMs) or transverse anharmonic vibrations of the two-fold coordinated oxygen atoms. In this work we report results of high-pressure Raman experiments (P < 8 GPa) on In2-xYxMo3O12 for x = 0.0 and 0.5. A crystalline to crystalline structural phase transition and pressure-induced amorphization (PIA) have been identified. The structural phase transition takes place at 1.5 and 1.0 GPa for In2(MoO4)3 and In1.5Y0.5(MoO4)3, respectively, resulting in the change of structure from monoclinic P21/a to a more denser structure. The pressure-induced amorphization started at 5 GPa and 3.4 GPa for In2Mo3O12 and In1.5Y0.5Mo3O12, respectively. The amorphization process takes place in two stages in the case of In1.5Y0.5Mo3O12 phase, while for In2Mo3O12 it is not complete until the pressures as high as 7 GPa. Our results also suggest that with increase of ionic size of the A3+ ions, the octahedral distortion increases and consequently larger local structural disorder is introduced in the A2(MoO4)3 system.
 E. T. Keve, S. C. Abrahams and J. L. Bernstei, Journal of Chemical Physics. 1971, 54, 3185-&.
 Y. Wang, T. Honma and T. Komatsu, Materials Chemistry and Physics. 2012, 133, 118.
 J. S. O. Evans, T. A. Mary and A. W. Sleight, Journal of Solid State Chemistry. 1997, 133, 580.
 Q. Q. Liu, X. N. Cheng and J. Yang, Materials Technology. 2012, 27, 388.
9:00 AM - W3.05
Pressure-Induced Crystal-Amorphous Transformation in Y2Mo3O12
Katiane Pereira da Silva 2 Cleanio Luz Lima 3 Paulo T. C. Freire 1 Antonio G. Souza Filho 1 B. A. Marinkovic 4 Kimberly J. Miller 5 Mary Anne White 5 J. Mendes Filho 1 Waldeci Paraguassu 2 Abraao C. T. Dias 1
1Universidade Federal do Cearaacute; Fortaleza Brazil2Universidade Federal do Paraacute; Beleacute;m Brazil3Universidade Federal do Piauiacute; Teresina Brazil4PUC-Rio Rio de Janeiro Brazil5Dalhousie University Halifax CanadaShow Abstract
The discovery in ZrW2O8  of strong and isotropic negative thermal expansion (NTE), also known as thermomiotic behavior , has raised interest in searching for materials with similar NTE properties. The NTE phenomenon has been the subject of manystudies with the aim to find suitable materials for applications that require controllable, low, or zero thermal expansion coefficients .
Among the NTE materials, the family of A2M3 O12 (A = trivalent cation, M = W/Mo) compounds has been widely investigated, since many members exhibit such a phenomenon . The NTE behavior in Y2Mo3O12 is known but the mechanism is not yet satisfactorily understood . The importance of understanding the pressure-induced amorphization in these materials comes from the fact that this phenomenon is related to NTE .
In this work we investigate the vibrational properties a high-pressure Raman spectroscopic study of Y2Mo3O12 and Y2Mo3O12middot;xH2O (x < 3). Our goal is to achieveinsight concerning the role of MoO4 units and O-O bonds on the structural packing and related NTE phenomenon. An analysis of vibrational modes suggests that the anhydrous material experiences a phase transformation from orthorhombic to a lower symmetry phase (probably monoclinic) about 0.3 GPa, and to a highly disordered phase above 2.4 GPa. The structural transformation to the high-pressure disordered phase is not reversible and suggests the onset of a pressure-induced amorphization process. The vibrational mode dependence on pressure is discussed considering lattice dynamics calculations.
 J. Evans, Z. Hu, J. Jorgensen, D. Argyriou, S. Short, A. Sleight, Science 275 (1997) 61.
 C.P. Romao, K.J. Miller, C.A. Whitman, M.A. White, B.A. Marinkovic, in: Jan Reed-ijk, K. Poeppelmeier (Eds.) Comprehen. Inorg. Chem. 4 (2013) 127.
 J. Evans, T. Mary, A. Sleight, Physica B 241 (1997) 311.
 B.A. Marinkovic, P.M. Jardim, R.R. de Avillez, F. Rizzo, Solid State Sci. 7 (2005)1377.
 S. Sikka, J. Phys. Condens. Matter 16 (2004) S1033.
9:00 AM - W3.06
Synthesis, Compression, and Equation of State of Perovskites and Post-Perovskites in the (MgxFe1-x)GeO3 System
Camelia Veronica Stan 1 4 Jason Krizan 1 4 Robert Cava 1 Vitali Prakapenka 2 Thomas Duffy 3
1Princeton University Princeton United States2University of Chicago Chicago United States3Princeton University Princeton United States4Princeton University Princeton United StatesShow Abstract
Germanates have wide applications as structural analogs in the study of silicate crystals and glasses, particularly in the field of high-pressure research. At high pressures and temperatures, (Mg,Fe)(Si,Ge)O3 undergoes a sequence of transitions from a pyroxene (px) to a perovskite (pv), followed ultimately by a transition to a CaIrO3-type post-perovskite (ppv) structure. In silicates, this sequence of transitions is crucial for understanding the structure and dynamics of planetary interiors, but the transition pressures and temperatures are difficult to achieve (e.g. ~125 GPa and 2500 K pv agrave; ppv in MgSiO3). Magnesium iron germanates are useful analogs because they undergo these phase transitions at much lower pressures and temperatures than in the silicates (e.g. ~63 GPa and 1800 K pv agrave; ppv in MgGeO3), enabling improved characterization of the nature and properties of the transitions. In order to investigate the effect of Fe2+ on the pv agrave; ppv phase boundary, and on the compressibilities of pv and ppv, polycrystalline px with compositions of (MgxFe1-x)2Ge2O6 (x = 1, 0.9, 0.8, 0.6, 0.5) were synthesized and characterized using x-ray diffraction, Raman, Mössbauer, and microprobe analysis. The px samples were found to exhibit a linear increase in lattice parameters with iron content. Raman peaks became broader, and shifted linearly to lower frequency with increasing iron. Mössbauer data for (Mg0.5Fe0.5)GeO3 and (Mg0.8Fe0.2)GeO3 px showed that the iron is high-spin Fe2+ that is concentrated primarily in the M1 site. Laser heated x-ray diffraction diamond anvil cell compression experiments were performed at beamline 13-ID-D of the Advanced Photon Source. Pv and ppv were synthesized from all px compositions upon compression and heating. The pressure-volume equations of state of MgGeO3 and (Mg0.8Fe0.2)GeO3 pv and ppv were determined, showing a change in volume between the compositions but negligible effect of Fe2+ on compressibility. Future work will focus equation of state measurements of other compositions in order to further determine the effect of Fe on the compressibility of the pv and ppv phases, on the exact temperature and pressure range for the pv agrave; ppv phase transition in each composition, and on the nature of the two phase loop as a function of composition, pressure and temperature.
9:00 AM - W3.07
HPHT Synthesis of Rocksalt Mn0.5Zn0.5O: A Potential New Visible-Light Photocatalyst
Venkata Srinu Bhadram 1 Timothy Strobel 1 Russell J Hemley 1
1Carnegie Institution of Washington Washington United StatesShow Abstract
Discovery of efficient and inexpensive photocatalytic materials is required for the practical implementation of solar based H2 production through water splitting. The challenge here lies in designing new semiconductor materials which can absorb solar light and can also have the band-edge positions matching with water redox couple. One possible material design strategy is to tune the properties of existing inexpensive transition metal oxide catalysts to improve solar energy absorption while preserving the redox reactivity. Based on this strategy, some theoretical predictions suggest that the bandgap of photocatalyst MnO can be tuned for visible light activity by doping Zn in place of Mn. However, the required doping concentrations are as high as 50 at% which would be possible only through high pressure and high temperature (HPHT) synthetic techniques. Here, we synthesize rocksalt Mn0.5Zn0.5O using HPHT technique in multi-anvil apparatus starting with 1:1 mixture of rocksalt MnO, wurtzite ZnO. As synthesized material exhibits narrower bandgap compared to its parent oxides and can be a potential visible light photocatalyst for water splitting applications.
9:00 AM - W3.08
Enhanced Stress Corrosion Resistance of Fine-Grained Mg-Al-Zn Alloys Produced by ECAP Plus Aging Treatment
LiJuan Zhuang 1 Aibin Ma 1 2 Jinghua Jiang 1 Dan Song 1 Mingshan Qiang 1
1Hohai University Nanjing China2Hohai University Suqian ChinaShow Abstract
Microstructure of commercial pure Mg, AZ31 and AZ91D Mg alloys were remarkably changed by multi-pass equal-channel angular pressing (ECAP) plus aging treatment, to investigate the effect of various substrate states on stress corrosion cracking(SCC) of the fine-grained Mg alloys with better mechanical properties. The slow-stain-rate tensile results in distilled water showed that pure Mg was not susceptible to SCC and the susceptibility increased with Al content. The more high-angle grain boundaries after ECAP seriously hampered the crack initiation of SCC of the fine-grained Mg alloys, and the uniform distribution of broken second phases changed localized corrosion to general corrosion. After combining ECAP with pre-solution and post-aging, the smaller and even-distributed precipitation particles in the Mg matrix can effectively inhibit the anodic dissolution process and prevent the cracks from propagating. Moreover, the fine precipitates in the grain boundary can act as trapping sites for atomic hydrogen to nucleate hydrogen bubbles, thereby reducing hydrogen concentration below a critical value to retard hydrogen embrittlement. Therefore, the post-ECAP aging Mg alloys have the higher stress corrosion resistance than that processed by ECAP.
W4: Poster Session II: High Magnetic Field, High Strain Rates and Other Extreme Environment on Materials
Monday PM, November 30, 2015
Hynes, Level 1, Hall B
9:00 AM - W4.01
High Performance Aluminum Carbon Nanotube Composites
Shawn Lichvar 3 Alexander Savadilis 3 Shelby Stigers 4 Kofi Wi Adu 2 1
1Pennsylvania State University University Park United States2Pennsylvania State University, Altoona Altoona United States3Pennsylvania State University University Park United States4Pennsylvania State University, Altoona Altoona United StatesShow Abstract
Carbon nanotubes (CNTs) have been recognized as potential candidate for reinforcements in lightweight metals. A composite consisting of CNTs embedded in an Al-matrix might work as an ultra-low-resistive material with the potential of having a room-temperature resistivity far below Al, Cu and Ag. While several advances have been made in developing Al-CNT composites, three major challenges: (1) interfacial bond strength between CNT and the Al matrix, (2) homogeneous dispersion of the CNTs in the Al matrix and impurity (CNTs) scattering centers, continue to limit progress in Al-CNT composites. Several conventional methods including powder metallurgy, melting and solidification, thermal spray and electrochemical deposition have been used to process Al and CNT to form composites. We present preliminary results that address these challenges and demonstrate the fabrication of ductile high strength Al-CNT composite wires of 1.0mm diameter with ~12% ± 2% reduction in the electrical resistivity of Al-CNT composite using CNT-hybrid as reinforcement and an inductive melting technique that takes advantage of the induced eddy current in the melt to provide in-situ stirring.
9:00 AM - W4.02
Multilayer Optical Structures for Spatial and Temporal Probing of the Shock Compression Response of Heterogeneous Materials
David A. Scripka 1 Gyuhyon Lee 1 Garret LeCroy 1 Changyan Sun 1 Zhitao Kang 1 Christopher J. Summers 1 Naresh N. Thadhani 1
1Georgia Institute of Technology Atlanta United StatesShow Abstract
Multilayer optical structures are photonic devices that have unique spectral properties determined by the thickness and composition of the individual layers. These spectral properties are also driven by time-resolved material states in the multilayer, and due to this intrinsic sensitivity the spectral response of these structures can be altered by external perturbations. With nanometer to micrometer dimensions, near instantaneous optical response, and potential micron level spatial sensitivity, these structures have significant potential to form the basis for mesoscale time-resolved experimental diagnostics. Such tools are needed to effectively probe the dynamic behavior of heterogeneous materials, to correlate the influence of mesoscale structural characteristics with observed shock-compressed states.
Initial computational and experimental results have shown that the magnitude of dynamic loading can be directly correlated to the altered spectral response of the multilayer structures. A coupled computational-experimental study is being performed to fully characterize the optical and mechanical behavior of multilayer optical structures, applied to both homogeneous and heterogeneous material systems. A mechanistic analysis of the spectral response of the structures to dynamic loading will be presented, along with computational simulations illustrating the observable spectral effects of 1D shock loading. Results from fabrication of specific multilayer designs and laser-driven 1D shock loading experiments will be shown and compared to the simulation results. Simulations of heterogeneous loading in mesoscale materials will also be presented, illustrating the potential spatial sensitivity of the multilayer structures in various applications. Additional applications and challenges associated with spatially resolved data collection methodology will be discussed.
9:00 AM - W4.03
Simulation and Fabrication of Various Optical Structures as Tools for Meso-Scale Shock Studies
Gyu Hyon Lee 1 David A. Scripka 1 Changyan Sun 1 Zhitao Kang 2 1 Christopher J. Summers 1 Naresh N. Thadhani 1
1Georgia Inst of Technology Atlanta United States2Georgia Tech Research Institute Atlanta United StatesShow Abstract
Measuring and understanding the mechanical, physical, and chemical changes induced during dynamic loading ofheterogeneous systemswithmeso-scale variations,is critically important for designing impact resistant material systems.The dynamic loading response ofheterogeneous systemsis difficult to acquire and differs significantly from the continuum behavior. Furthermore, the information obtained is oftenlimited. Understanding the shock behavior ofheterogeneous systems with meso-scale variations supports a variety of engineering applications, such as high impact collisions and thedetonation of heterogeneous explosives.
In this study, we investigated the use of various optical structures such asmultilayers (Bragg reflectors) and optical mirror cavities (OMC)asmeso-scale in-situ diagnostic tools for measuring compression and stress in real time under dynamic loading. Their optical properties such as reflectance and transmission were simulated using OpenFilters software and the design criteria were determined. Poly(9-vinylcarbazole) (PVK) and poly vinyl alcohol (PVA) dissolved in their respective solvents were spin-coated sequentially to form multilayers witha tunable reflectance peak from 300-900nm. Inorganic SiO2/Al2O3 multilayers or cavity structuresmay also be fabricated using ion-assisted deposition (IAD). Various OMC structures such as Ag/SiO2/Ag, and Ag/Al2O3/Agwere fabricated with a sharptransmission peak of FWHM less than 10 nm, a critical requirement for sensor applications. The mechanical responses of fabricated optical structures under dynamic loading were recorded by using a streak system to measuretheirtime-resolved spectral response.The generated shock impacts the optical structures with a pressure pulse width of 25 nanoseconds at pressures of 1-10 GPa. Theoretical predictions show a well-defined shift to shorter wavelengths that is proportional to the impact velocity and which for the OMC structure has been substantiated experimentally. The results of these studies are being used to design sensor couponscapable of measuring the dynamic response of heterogeneous systems at themeso-scale. Additionally, the collected results increase the understanding and differentiation between thermal and strain effects onthe system
9:00 AM - W4.04
Erosion-Resistant Electrode Coatings of Vacuum and Gas-Discharge Switching Devices
Sergey M. Karabanov 1 Dmitriy Suvorov 1 Gennadiy Gololobov 1 Victor Gurov 1 Evgeny V. Slivkin 1 Dmitriy Y. Tarabrin 1
1Ryazan State Radio Engr Univ Ryazan Russian FederationShow Abstract
High-current electrodes of vacuum and gas-discharge switching devices (pseudospark switches, high power thyratrons, reed switches) are made of refractory materials: Mo, Ta, W alloys, etc. having high fusion temperature in order to increase their life time. The prospective direction of erosion resistance increase is the use of multilayer coatings, meeting the requirements of local heat resistance, high heat conductivity and electroconductivity, generally consisting of refractory metal layers, a high heat conductivity layer and an intermediate layer equalizing thermomechanical stresses. For maximization of erosion resistance it is necessary to calculate thermal field and mechanical stresses inside the multilayer coating structure for conditions of local thermal effect on the film structure.
The paper presents the results of numerical calculation of characteristics of electrodes erosion-resistant coatings of vacuum and gas-discharge switching devices with W-Ti-Cu and W-Mo-Cu structures at local thermal effect equivalent to the influence of the channel form discharge. The calculation of thermal effect on W-Ti-Cu and W-Mo-Cu film structures is carried out in axially symmetrical approximation taking into account temperature change of materials characteristics using COMSOL Multiphysics.
The calculations show that in W-Ti-Cu structure the greatest temperatures gradient is located in Ti layer that is caused by its small heat conductivity, and the maximum thermomechanical stresses - on border of W-Ti layers. In W-Mo-Cu structure the temperatures gradients in W and Mo layers are approximately identical that is caused by similar heat conductivity factors, and the maximum thermomechanical stresses are concentrated on border of Mo-Cu layers. Comparison of W-Ti-Cu and W-Cu structures shows that Ti layer reduces more than 2 times the arising thermomechanical stresses.
The dependence calculation of the maximum value of interlaminar mechanical stresses at various layers thickness of W-Ti-Cu, W-Mo-Cu coatings shows that:
- in W-Ti-Cu structure the increase in W layer thickness within 5-50 microns results in more than 10 times decrease of thermomechanical stresses on W-Ti border. The dependences of mechanical stresses between W-Ti and Ti-Cu layers on titan layer thickness have minima the sum of which corresponds to Ti layer thickness of 50 mu;m.
- in W-Mo-Cu structure the increase of W layer thickness within 5-100 mu;m leads to insignificant decrease (less than 1.5 times) of thermomechanical stresses on Mo-Cu border and to stresses decrease on W-Mo border approximately by 5 times. The growth of Mo layer thickness within 5-100 microns leads to insignificant decrease (less than 1.5 times) of thermomechanical stresses on W-Mo border and to stresses decrease on Mo-Cu border approximately twice.
In general, W-Ti-Cu structures provide approximately two times smaller level of mechanical stresses in comparison with W-Mo-Cu structure at similar coatings thickness.
9:00 AM - W4.05
High Temperature Nanoindentation of Hard Coatings
Marcello Conte 1 2 Jakob Schwiedrzik 2 Gaurav Mohanty 2 Dario Ciani 1 Bertrand Bellaton 1 Philippe Kempe 1 Nicholas Randall 1 Johann Michler 2
1Anton Paar TriTec SA Peseux Switzerland2Empa Thun SwitzerlandShow Abstract
Hard coatings endure extreme temperature and wear during their usage lifetime. Gaining fundamental insights into their mechanical deformation at service temperatures is essential to develop better, more wear resistant coatings and to evaluate their performance. Nanoindentation is well suited to probe the mechanical properties of hard coatings in service conditions, particularly high temperatures. However, till date, this versatile technique has mostly been limited to ambient conditions. Determining the mechanical properties of hard coatings and thin films, particularly at low depths penetration depths (less than 100nm) and high temperatures requires high measurement stability and low compliance of the system so that the artifacts of measurements are kept to a minimum.
This poster will present test results of a novel vacuum high temperature nanoindentation system that enables mechanical property measurements of thin films and hard coatings up to 700 °C. The system, based on the Ultra Nanoindentation Tester (UNHT), utilizes active surface referencing consisting of two independent indentation axes: one for surface referencing and the other for indentation. This design minimizes thermal drift and results in almost zero compliance that makes it attractive for such challenging measurements. Independent indenter, reference and sample heating coupled with tip-sample surface temperature tuning results in drift rates of less than 5nm/min at 700 °C. High temperature indentation test results on nitride hard coating will be presented as a case study.
9:00 AM - W4.06
Kinetic Monte Carlo Simulation of Oxygen Diffusion in Ytterbium Disilicate
Brian S. Good 1
1NASA Glenn Research Ctr Cleveland United StatesShow Abstract
Ytterbium disilicate is of interest as a potential environmental barrier coating for aerospace applications, notably for use in next generation jet turbine engines. In such an extreme environment, the transport of oxygen and water vapor through these coatings is undesirable if high temperature corrosion is to be avoided. In an effort to understand the diffusion process in these materials, we have performed kinetic Monte Carlo simulations of vacancy-mediated and interstitial oxygen diffusion in Ytterbium disilicate. Oxygen vacancy site energies, vacancy formation energies, heats of solution and migration barrier energies were computed using Density Functional Theory. We have found that, in the case of vacancy-mediated diffusion, many potential diffusion paths involve large barrier energies, but some paths have barrier energies smaller than one electron volt. However, computed vacancy formation energies suggest that the intrinsic vacancy concentration is small. In the case of interstitial diffusion, migration barrier energies are typically smaller, but the heat of solution is positive, indicating that the concentration of interstitial oxygen is likely to be small. It is therefore expected that the material is unlikely to exhibit significant oxygen permeability.
9:00 AM - W4.07
Premature Degradation of Aerospace Coatings in Extreme Environments
Nickolaus K Weise 1 Ann Mera 2 Dennis Bellevou 2 James Wynne 1
1Naval Research Laboratory Washington United States2Naval Air Warfare Center Patuxent River United StatesShow Abstract
High performance coatings that are utilized in aerospace environments are designed to withstand extreme temperature changes as well as harsh operational environments. Due to the high cost of these coatings, they are expected to have a lifespan of at least 15 years. This increased lifecycle is intended to reduce maintenance cost and downtime. However, many of these high performance coatings are failing long before the manufacturer&’s stated life span, triggering expensive and time-intensive reworks and repainting. Results from past engineering investigations have suggested that urea linkages from over-indexing with excess isocyante contribute to coating accelerated degradation. Coatings are typically over indexed to ensure complete reaction with the incorporated polyol and thus form more durable coatings. In this study, we have synthesized control analogous coatings that were overindexed from 1.1 to 2 -NCO:-OH. These coatings were then subjected to accelerated weathering and analyzed with both bulk thermal and surface characterization techniques. Thermal and surface analysis of weathered coatings illustrated changes not only in the mechanical integrity, but also in the chemical makeup that were correlated with the index value of the coating. The effects excess urea linkages had on coating degradation will be discussed in detail.
9:00 AM - W4.08
Time-Resolved Studies of Carbon Nanotube Network Formation during Laser Pulse Heating
Stephen Bartolucci 1 Michael J Miller 1 Jeffrey M. Warrender 1
1ARDEC-RDECOM Watervliet United StatesShow Abstract
Carbon nanotube/polymer composites have been studied extensively for applications in which increased thermal stability or increased flammability is desired. However, the behavior of such materials under more extreme environments has not been studied. In our work, we have examined carbon nanotube composite behavior when subjected to laser pulse heating (LPH) with a 1064 nm variable pulse laser. The heating rates in these studies are five orders of magnitude higher than traditional thermal stability studies. In previous work, we have shown that the carbon nanotube composites form a protective nanotube network on the surface of the composite, which reduces heat input to the underlying polymer and slows mass loss. We have recently studied the interaction of the laser beam with the plume formed above the nanotube composites and correlated this interaction to time-resolved mass loss data. In addition, we have performed time-resolved studies on the formation of the protective nanotube network during the millisecond time domain of the laser pulse. The formation and subsequent behavior of the network layer was studied as a function of laser power and nanotube content in the composites.
Stephen F. Bartolucci, Karen E. Supan, Jeffrey M. Warrender, Christopher E. Davis, Lawrence La Beaud, Kyler Knowles, Jeffrey S. Wiggins, “Laser-Induced thermo-oxidative degradation of carbon nanotube/polypropylene nanocomposites”, Composites Science and Technology, 105 (2014) 166-173.
9:00 AM - W4.09
Microstructure, Resistivity and Hardness of Directionally Solidified Cu-6wt.%Ag Alloy with a Magnetic Field
Xiaowei Zuo 1 Rui Guo 1 Lin Zhang 1 Engang Wang 1 Ke Han 2
1Northeastern University Shenyang China2National High Magnetic Field Laboratory, Florida State University Tallahassee United StatesShow Abstract
Cu-Ag alloy with high strength and high conductivity is widely used as coil material for high-field AC pulsed and DC resistant magnets. The property of Cu-Ag material is closely related to microstructure during solidification and heat treatment. In this study, a static magnetic field was superimposed to directional solidification of Cu-6wt.%Ag alloy. Applying magnetic field during solidification increased both primary dendrite arm spacing and length of proeutectic Cu, increased solubility of Ag in proeutectic Cu, but decreased volume fraction of eutectic colony. These increased the resistivity and the hardness of alloy. The modeling of resistivity showed that the changes were as a result of changes in the solubility of Ag in proeutectic Cu. The solidified samples were cold rolled. By comparison with the sample without the magnetic field, the sample solidified with magnetic field had lower volume fraction of off-eutectics, lower hardness at lower reduction, but had higher hardness at higher reduction. It was thought to be from the role of more precipitates of Ag induced during rolling. Ageing at 300°C promoted the Ag atoms to precipitate from proeutectic Cu matrix. This optimized the combination of strength and conductivity of alloys.
9:00 AM - W4.10
Low Temperature Work Hardening Behavior of FeMnNiCoCr
Alexander Kauffmann 1 Hans Chen 1 Klaus-Peter Weiss 2 Jens Freudenberger 3 Martin Heilmaier 1
1Karlsruhe Institute of Technology (KIT) Karlsruhe Germany2Karlsruhe Institute of Technology (KIT) Karlsruhe Germany3IFW Dresden Dresden GermanyShow Abstract
Equiatomic FeMnNiCoCr which crystallizes as a face-centered cubic solid solution is one of the few examples of high-entropy alloys which can be tailored by means of classical metallurgical processes like cold-working and subsequent recrystallization as well as hot-working. Thus, regarding this new class of materials, FeMnNiCoCr has been the most investigated high-entropy alloy, so far. Recently, Otto et al. [Acta Materialia 61 (2013) 5743-5755] revealed an increasing mechanical strength together with an increase of elongation to failure by decreasing test temperature down to 77 K. The observed change of mechanical properties was accompanied with planar slip in the entire temperature range during the initial stages of deformation as well as the activation of deformation twinning at 77 K in later stages beyond a tensile strain of 20 %.
We present quasistatic tensile and compressive tests at low temperatures down to 9 K of this FeMnNiCoCr alloy which was produced by arc-melting, homogenization and recrystallization subsequent to a cold-deformation process. Work hardening rate as a function of flow stress of FeMnNiCoCr at low temperature is compared to well-understood materials like single-phase copper alloys or TWIP steels exhibiting different amounts of deformation by twinning. In contrast to the aforementioned classical materials, an outstanding ability for work hardening at low temperature must be noted for FeMnNiCoCr. The appearance of twinning induced plasticity, which plays an important role for the work hardening behavior during low temperature deformation, is evaluated by means of orientation imaging microscopy. The orientation dependence of deformation under compression and tensile loading is stressed.
9:00 AM - W4.11
Effects of Combustion Gas Species on Y2O3 Film Produced from Metal-EDTA Complex by Flame-Spraying Technique
Keiji Komatsu 1 Tetsuo Sekiya 1 Hasebe Yasuhiro 1 Ayumu Toyama 1 Atsushi Nakamura 2 1 Masahiro Noguchi 3 Yu Li 3 Shigeo Ohshio 1 Hiroki Akasaka 1 Hidetoshi Saitoh 1
1Nagaoka University of Technology Nagaoka Japan2Chubu Chelest Yokkaichi Japan3Nippon Steel amp; Sumikin Hardfacing Kamedio-Ethou-ku JapanShow Abstract
In the thermal spray, temperature and velocity of the in-flight particles can be controlled by selecting thermal spray parameter such as the appropriate combustion gases. For example, theoretical studies indicated that the combustion gas species and their ratios in a high-velocity oxygen fuel (HVOF) affect the temperature and velocity of the in-flight particles, which in turn determine the collision energy when they impinge on the substrate. Therefore, the choice of combustion gases is very important and it determines the particle collision energy.
Metal-EDTA complexes have low decomposition temperatures and various metal oxides with different morphologies can be obtained by pyrogenic decomposition of the metal EDTA complexes. Spray drying and laser deposition were used to synthesize metal oxides with metal-EDTA complexes in previous studies. Recently, we developed a technique for synthesizing a thick metal oxide layer from a metal-EDTA complex using commercial flame-spraying apparatus. High-rate deposition of metal oxides from the metal-EDTA complexes was accomplished with the assistance of combustion gas mixtures of C2H2-O2 or H2-O2. In particular, the metal-EDTA complexes&’ species and their diameters affected the crystal structures and morphologies. For example, a Er2O3 film with 9% cross-sectional porosity was synthesized on a stainless steel (SUS) substrate from a EDTAbull;Erbull;H complex. A Y2O3 layer with 15% porosity was also formed on a SUS substrate under similar conditions. In this study, the combustion gas species selected were C2H2-O2 and H2-O2 mixtures. With the assistance of these combustion gases, we synthesized Y2O3 films on stainless steel substrates from the EDTAbull;Ybull;H using the flame thermal spray technique and investigated the effects of the combustion gas species. We measured the temperature and velocity of the in-flight particles for each kind of combustion gas. The crystal structure, surface, cross-sectional morphology, and elemental distribution of the films were then analyzed.
In this study, yttria (Y2O3) films were deposited on stainless steel substrates from yttriumbull;hydrogenbull;ethylenediaminetetraaceate (EDTAbull;Ybull;H) complex by flame spraying. The gas mixtures of acetylene-oxygen (C2H2-O2) or hydrogen-oxygen (H2-O2) were used for the combustion flame and the effects of the combustion gas species on Y2O3 films were investigated. Experiments revealed that the particles propelled in the H2-O2 flame had lower temperature and higher velocity compared with the particles in the C2H2-O2 flame. The existence of Y2O3 crystalline phases and complete decomposition of the Y-EDTA complexes were confirmed. The porosity of the film was 25% when the H2-O2 flame was used and 32% when the C2H2-O2 flame was used. In addition, the Y2O3 films showed excellent adherability in tape tests. The H2-O2 flame is thus considered suitable for fabricating dense Y2O3 films.
9:00 AM - W4.12
Thermal Conductivity and Thermal Shock Behaviour of CYSZ/GZ Thermal Barrier Coatings
Mustafa Guven Gok 1 Gultekin Goller 1
1Istanbul Technical University (ITU) Istanbul TurkeyShow Abstract
Among the alternative thermal barrier coating materials, gadolinium zirconate (Gd2Zr2O7, GZ) seems to be the most efficient one in terms of its low thermal conductivity (0.65 Wm-1K-1), high phase stability (above 1200°C) and better resistant to hot corrosion than YSZ. But, thermal shock behaviour of the GZ is poor due to its low coefficient of thermal expansion (10.4x10-6 K-1) and high tendency to react with TGO layer. In this study, CYSZ/GZ multilayered and functionally graded thermal barrier coatings were produced by high-velocity oxy-fuel (HVOF) and atmospheric plasma spraying (APS) processes in 2, 4 and 8 layered. Microstructure, thermal conductivity and thermal shock behaviour of the coatings were evaluated. The results indicated that the lowest thermal conductivity value and higher thermal shock resistance were achieved with functionally graded thermal barrier coatings.
9:00 AM - W4.13
Effect of B4C Addition on Densification, Microstructure and Mechanical Properties of TZM Alloys
Baris Yavas 1 Onuralp Yucel 1 Filiz Sahin 1 Gultekin Goller 1
1Istanbul Technical University Chemical and Metallurgical Faculty Istanbul TurkeyShow Abstract
Pure molybdenum is one of the most important refractory metal and its alloys are used for high temperature applications in a variety of industries. However, application temperature is limited by the beginning of recrystallization, which can be inhibited by addition of fine grained structure and the formation of TiC and ZrC in the grain boundaries of molybdenum in TZM alloys (molybdenum alloy containing 0.5-0.8 wt% titanium, 0.08-0.1 wt% zirconium and 0.016-0.02 wt% carbon). In this study, B4C-TZM composites having 0-30 vol% B4C were sintered by spark plasma sintering (SPS). The prepared composites were then characterized in terms of their densification, microstructure and mechanical properties.
9:00 AM - W4.14
Microstructural Characterization of Molybdenum-Molybdenum Carbide Structures Produced by Spark Plasma Sintering (SPS)
Can Cekli 1 Onuralp Yucel 1 Filiz Sahin 1 Gultekin Goller 1
1Istanbul Technical University Chemical and Metallurgical Faculty Istanbul TurkeyShow Abstract
Pure molybdenum (Mo) is an important refractory metal, having high wear and heat resistance properties, electrical (5.5 × 10#8209;8 Omega; m) and thermal (139 W m#8209;1 K#8209;1) conductivity. In this study, pure molybdenum powders were sintered by spark plasma sintering (SPS) technique. Sintering process was conducted under various temperatures and periods (1650°C, 1700°C, 1725°C and 3 min, 6 min, 9 min) in order to investigate the effect of sintering parameters on sintering behavior, microstructure and mechanical properties.
The linear shrinkage of the specimens depending on temperature and time were recorded during sintering process. Dense molybdenum metals with a relative density of more than 97.5% were obtained at temperature of 1650°C with a holding time of 3 minutes. Relative density values decreased with increasing sintering temperature and period. Microstructure analysis revealed that, during sintering process molybdenum carbide layers are formed on the surfaces of the specimens as a result of carbon diffusion from the graphite sheets. Molybdenum carbide layers have thickness of more than 500µ at 1725°C. Microhardness results of surfaces were ~14-15GPa while the results of the substance metals were ~2-2.1GPa. These results proved that during sintering process a substance layer of molybdenum metal and a carbon rich layer of molybdenum carbide is formed.
W1: High Pressure and Materials I
Monday AM, November 30, 2015
Hynes, Level 1, Room 101
9:30 AM - *W1.02
High Pressure Induced Superconductivity in ZrTe5
Zhaorong Yang 1 Yonghui Zhou 1 Xianggang Wan 3 Wenge Yang 2 Hongwei Gu 4 Mingliang Tian 1
1High Magnetic Field Laboratory Hefei China2Center for High Pressure Science and Technology Advanced Research Shanghai China3Nanjing University Nanjing China4CAS Beijing ChinaShow Abstract
As a new topological material, ZrTe5 exhibits novel properties. Pressure is believed to be effective for studying the topological phase transitions experimentally. In this work, we have performed resistance and ac magnetic susceptibility measurements for ZrTe5 single crystal at various pressures up to 68.5 GPa. We show that, accompanied by complete suppression of the high temperature resistance anomaly near 120 K, superconductivity is induced at a critical pressure of 6.2 GPa. The superconducting transition temperature Tc initially increases with pressure then decreases slightly with a maximum of 4.0 K at 14.6 GPa. At pressures above 21.2 GPa, a second superconducting phase with the maximum Tc of about 6.0 K manifests and coexists with the original one. We also performed the theoretical calculations of pressure-induced variations of both crystal and electronic band strucrues to explore the origin of superconductivity in the pressurized ZrTe5.
10:00 AM - W1.03
Calculations and Experimental Studies of Bis-Triaminoguanidium Azotetrazolate (TAGzT) under High Pressure
Iskander G Batyrev 1 Rosario C Sausa 1
1US ARL Aberdeen United StatesShow Abstract
Nitrogen-rich organic compounds may offer distinct advantages over conventional energetic materials for applications relating to gas generators, low-signature propellants, and additives to pyrotechnics and explosives. We have performed plane-wave, density functional theory calculations of TAGzT, an energetic, nitrogen-rich salt, up to 40 GPa, and report the pressure dependences of polarizability, x-ray diffraction patterns, and dipole moments. These results are compared to those we obtain experimentally from Raman Spectroscopy,1 and x-ray diffraction analysis and infrared spectroscopy. Our results suggest TAGzT does not undergo any phase transitions within this pressure range. Mulliken and Hirshfeld population analysis of TAGzT at ambient and high pressure yields the change of charge distribution with an increase in pressure. We report and discuss this trend at the meeting. Also, we report trends in the pressure-induced modifications of both bond lengths and angles of TAGzT, and reveal how hydrogen bonding contributes to the stability of TAGzT under pressure.
1K.D. Behler, J.A. Ciezak-Jenkins, R.C. Sausa, J. Phys. Chem A. 117(8), 1737 (2013)
10:15 AM - W1.04
New 1212-Molybdo-Cuprate Phases Using High Pressure and High Temperature Synthesis
Miguel Angel Alario-Franco 1
1Univ Complutense Madrid SpainShow Abstract
New Molybdo- Cuprates of 1212 type with composition Mo0.5Cu0.5Sr2RECu2O7.5 (RE = Rare Earth) have been prepared by High Pressure and High Temperature (HPHT) synthesis. Their crystal structures were characterized by combining the X-Ray/neutron powder diffraction and electron diffraction techniques. All the materials show tetragonal symmetry, crystallizing in the P4/mmm space group (S.G.). Structural analysis using the joint refinement of RT NPD and RT XRD showed that the chain oxygens are randomly distributed in the two different oxygen site, which are not completely filled and the defect induced by oxygen vacancies in fact makes the chain fragmented and disordered. A remarkable microdomain texture has been identified using the electron microscopy. The microstructure of these compounds is interpreted by a well-known diagonal cell radic;2ap × radic;2ap × 3ap, distributed in three dimensional domains, as confirmed by the SEAD and HRTEM. X-ray photoelectron spectroscopy (XPS) studies show the predominance of the non magnetic MoVI state over the MoV one. At the same time oxidation state of copper is found to be dominated by CuII. The presence of higher amount of nonmagnetic MoVI is found to be a reason for the absence of the magnetic interaction in these materials. Specific heat studies indicate the magnetic ordering at 2.13 K for Mo0.5Cu0.5Sr2GdCu2O7.5 material is due to the 3-dimentional AFM ordering of the Gd ion. The heat capacity of the Mo0.5Cu0.5Sr2HoCu2O7.5 material shows a flat maximum at 5 K due to the separation of the two lowest-lying singlet levels of HoIII ions at that temperature.
10:30 AM - W1.05
High Pressure Phase Relations in the Lanthanoid Mononitrides
Morten Bormann Nielsen 1 Martin Bremholm 1 Davide Ceresoli 2
1Aarhus University Aarhus C Denmark2University of Milan Milan ItalyShow Abstract
The rare-earth nitrides with formula LnN (Ln rare-earth element) constitute a series of compounds all crystallizing in the rock-salt (B1 type) structure. While transition metal nitrides have been studied widely at high pressure, the corresponding series using lanthanoids have not. They have high hardness and mechanical strength and are also of interest owing to their magnetic, electronic and optical properties[1-3]. The systematic change in lanthanoid properties as the 4f shell is filled also makes these systems ideal for comparison with theory and many such DFT studies already exist in literature[4-8].
In this work, we present the result of high pressure exploration of the phase behavior of the LnN with Ln = Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er. Powders of all phases have been measured up to at least 80 GPa, using synchrotron x-ray diffraction. In the whole series, only La, Pr, Ce and Tb have previously been explored experimentally[7,9-11]. The findings are compared to our own theoretical calculations and trends throughout the series are highlighted.
 C.-G. Duan,et al, J. Phys.: Condens. Matter. 19 315220, 2007
 P. Larson, et al, Phys. Rev. B, 75 045114, 2007
 C.M. Aerts,et al, Phys. Rev. B 69 045115, 2004
 A. Svane, et al, J. Phys.: Condens. Matter 10 5309-5325, 1998
 Hao A. et al. J. Phys. Chem. Solids 74 1504-1508, 2013
 Shabara et al. Results Phys. 1 30-35, 2011
 Jakobsen et al. Solid State Commun. 121 447-452, 2002
 Gupta D.C. et al. J. Mol. Model. 19 5343-5354, 2013
 Schneider et al. J. Appl. Phys. 111 093503, 2012
 Cynn et al. J. Phys.: Conf. Ser. 215 012010, 2010
 Olsen et al. J. Alloys Compd. 533 29-32, 2012
10:45 AM - W1.06
Transition Mechanism of Coesite under High Pressure and Room Temerature
Qingyang Hu 1 2 3 Howard Sheng 2 3
1Carnegie Institution of Washington Washington United States2George Mason University Fairfax United States3HPSTAR Shanghai ChinaShow Abstract
Polymorphs of SiO2 and their transitions have long been a focus of great interest and intense theoretical and experimental pursuits. Compressing single-crystal coesite SiO2 under hydrostatic pressures of 26~53 gigapascal at room temperature, we discover a new polymorphic phase transition mechanism of coesiteto post-stishovite, by means of single-crystal synchrotron X-ray diffraction experiment and first-principles computational modeling. The transition features formation of multiple previously unknown triclinic phases of SiO2 on the transition pathway as structural intermediates.The metastable phases are similar in volume and degenerate in free-energy, but distinct in structures and x-ray diffraction patterns. Coexistence of the low-symmetry phases results in extensive splitting of the original coesite X-ray diffraction peaks that appear as a dramatic peak broadening and weakening, thus resembling an amorphous material. This work