Cladding of Mg alloy with Zr based BMG Alloy

NASA Astrophysics Data System (ADS)

Prasada Rao, A. K.; Oh, Y. S.; Faisal, M. K.; Kim, N. J.

2016-02-01

In the present work, an attempt has been made to clad AZ31 magnesium alloy with Zr-based bulk metallic glassy alloy (Vit-1), by casting method. The interface studies conducted using SEM-EDS line scan indicate that a good bond is formed at the clad interface of Zr and Mg. And the mechanism involved is discussed herein.

Porous Ceramic Composite ZrO2(MgO)-MgO for Osteoimplantology

NASA Astrophysics Data System (ADS)

Buyakov, A. S.; Kulkov, S. N.

2017-02-01

Pore and crystalline structure, biocompatibility of ceramic composite ZrO2(MgO)-MgO were studied. The main mechanical characteristics were determined and it has been shown that compression strength directly depends on microstresses obtained from X-ray data. In-vitro studies of mesenchymal stromal stem cells (MMSC), cultivated on material surface are shown that cell proliferation and differentiation of MMSC goes throw osteogenic type.

Proximity to a ferroelectric instability in Ba1-xCaxZrO3

NASA Astrophysics Data System (ADS)

Kim, H. S.; Christen, H. M.; Biegalski, M. D.; Singh, D. J.

2010-09-01

Ferroelectricity in ABO3 perovskites driven by A-site disorder is seen as a powerful approach toward lead-free piezoelectrics and ferroelectrics as well as to forming multiferroic compounds. Here we investigate the Ba1-xCaxZrO3 solid solution by structural and dielectric measurements on pulsed laser deposition grown films and by first principles calculations. Films on SrRuO3-coated SrTiO3 substrates are studied for x between 0 and 0.44. Despite the expectation that the Ca-ions assume off-center positions in the perovskite lattice, dielectric measurements show no evidence for ferroelectricity. This behavior is explained by first principles supercell calculations that show ferroelectricity at expanded volume but a rapid suppression thereof as the volume is reduced, thus indicating that our paraelectric Ba1-xCaxZrO3 films are close to a ferroelectric instability. These results demonstrate the important interplay between unit cell volume and ferroelectricity arising from off-centered ions.

Structure and Electrical-Transport Relations in Ba(Zr,Pr)O3-δ Perovskites.

PubMed

Antunes, Isabel; Amador, Ulises; Alves, Adriana; Correia, Maria Rosário; Ritter, Clemens; Frade, Jorge Ribeiro; Pérez-Coll, Domingo; Mather, Glenn C; Fagg, Duncan Paul

2017-08-07

Members of the perovskite solid solution BaZr 1-x Pr x O 3-δ (0.2 ≤ x ≤ 0.8) with potential high-temperature electrochemical applications were synthesized via mechanical activation and high-temperature annealing at 1250 °C. Structural properties were examined by Rietveld analysis of neutron powder diffraction and Raman spectroscopy at room temperature, indicating rhombohedral symmetry (space group R3̅c) for members x = 0.2 and 0.4 and orthorhombic symmetry (Imma) for x = 0.6 and 0.8. The sequence of phase transitions for the complete solid solution from BaZrO 3 to BaPrO 3 is Pm3̅m → R3̅c → Imma → Pnma. The structural data indicate that Pr principally exists as Pr 4+ on the B site and that oxygen content increases with higher Pr content. Electrical-conductivity measurements in the temperature range of 250-900 °C in dry and humidified (pH 2 O ≈ 0.03 atm) N 2 and O 2 atmospheres revealed an increase of total conductivity by over 2 orders of magnitude in dry conditions from x = 0.2 to x = 0.8 (σ ≈ 0.08 S cm -1 at 920 °C in dry O 2 for x = 0.8). The conductivity for Pr contents x > 0.2 is attributable to positively charged electronic carriers, whereas for x = 0.2 transport in dry conditions is n-type. The change in conduction mechanism with composition is proposed to arise from the compensation regime for minor amounts of BaO loss changing from predominantly partitioning of Pr on the A site to vacancy formation with increasing Pr content. Conductivity is lower in wet conditions for x > 0.2 indicating that the positive defects are, to a large extent, charge compensated by less mobile protonic species. In contrast, the transport mechanism of the Zr-rich composition (x = 0.2), with much lower electronic conductivity, is essentially independent of moisture content.

A-SITE-AND/OR B-SITE-MODIFIED PBZRTIO3 MATERIALS AND (PB, SR, CA, BA, MG) (ZR, TI,NB, TA)O3 FILMS HAVING UTILITY IN FERROELECTRIC RANDOM ACCESS MEMORIES AND HIGH PERFORMANCE THIN FILM MICROACTUATORS

NASA Technical Reports Server (NTRS)

Bilodeau, Steven (Inventor); Baum, Thomas H. (Inventor); Roeder, Jeffrey F. (Inventor); Chen, Ing-Shin (Inventor)

2004-01-01

A modified PbZrTiO.sub.3 perovskite crystal material thin film, wherein the PbZrTiO.sub.3 perovskite crystal material includes crystal lattice A-sites and B-sites at least one of which is modified by the presence of a substituent selected from the group consisting of (i) A-site substituents consisting of Sr, Ca, Ba and Mg, and (ii) B-site substituents selected from the group consisting of Nb and Ta. The perovskite crystal thin film material may be formed by liquid delivery MOCVD from metalorganic precursors of the metal components of the thin film, to form PZT and PSZT, and other piezoelectric and ferroelectric thin film materials. The thin films of the invention have utility in non-volatile ferroelectric memory devices (NV-FeRAMs), and in microelectromechanical systems (MEMS) as sensor and/or actuator elements, e.g., high speed digital system actuators requiring low input power levels.

Mechanical properties, in vitro corrosion and biocompatibility of newly developed biodegradable Mg-Zr-Sr-Ho alloys for biomedical applications

PubMed Central

Ding, Yunfei; Lin, Jixing; Wen, Cuie; Zhang, Dongmei; Li, Yuncang

2016-01-01

Our previous studies have demonstrated that Mg-Zr-Sr alloys can be anticipated as excellent biodegradable implant materials for load-bearing applications. In general, rare earth elements (REEs) are widely used in magnesium (Mg) alloys with the aim of enhancing the mechanical properties of Mg-based alloys. In this study, the REE holmium (Ho) was added to an Mg-1Zr-2Sr alloy at different concentrations of Mg1Zr2SrxHo alloys (x = 0, 1, 3, 5 wt. %) and the microstructure, mechanical properties, degradation behaviour and biocompatibility of the alloys were systematically investigated. The results indicate that the addition of Ho to Mg1Zr2Sr led to the formation of the intermetallic phases MgHo3, Mg2Ho and Mg17Sr2 which resulted in enhanced mechanical strength and decreased degradation rates of the Mg-Zr-Sr-Ho alloys. Furthermore, Ho addition (≤5 wt. %) to Mg-Zr-Sr alloys led to enhancement of cell adhesion and proliferation of osteoblast cells on the Mg-Zr-Sr-Ho alloys. The in vitro biodegradation and the biocompatibility of the Mg-Zr-Sr-Ho alloys were both influenced by the Ho concentration in the Mg alloys; Mg1Zr2Sr3Ho exhibited lower degradation rates than Mg1Zr2Sr and displayed the best biocompatibility compared with the other alloys. PMID:27553403

Characterization of ZrO2 buffer layers for sequentially evaporated Y-Ba-CuO on Si and Al2O3 substrates

NASA Technical Reports Server (NTRS)

Valco, George J.; Rohrer, Norman J.; Pouch, John J.; Warner, Joseph D.; Bhasin, Kul B.

1988-01-01

Thin film high temperature superconductors have the potential to change the microwave technology for space communications systems. For such applications it is desirable that the films be formed on substrates such as Al2O3 which have good microwave properties. The use of ZrO2 buffer layers between Y-Ba-Cu-O and the substrate has been investigated. These superconducting films have been formed by multilayer sequential electron beam evaporation of Cu, BaF2 and Y with subsequent annealing. The three layer sequence of Y/BaF2/Cu is repeated four times for a total of twelve layers. Such a multilayer film, approximately 1 micron thick, deposited directly on SrTiO3 and annealed at 900 C for 45 min produces a film with a superconducting onset of 93 K and critical temperature of 85 K. Auger electron spectroscopy in conjunction with argon ion sputtering was used to obtain the distribution of each element as a function of depth for an unannealed film, the annealed film on SrTiO3 and annealed films on ZrO2 buffer layers. The individual layers were apparent. After annealing, the bulk of the film on SrTiO3 is observed to be fairly uniform while films on the substrates with buffer layers are less uniform. The Y-Ba-Cu-O/ZrO2 interface is broad with a long Ba tail into the ZrO2, suggesting interaction between the film and the buffer layer. The underlying ZrO2/Si interface is sharper. The detailed Auger results are presented and compared with samples annealed at different temperatures and durations.

Improvement of the field-trapping capabilities of bulk Nd Ba Cu O superconductors using Ba Cu O substrates

NASA Astrophysics Data System (ADS)

Matsui, Motohide; Nariki, Shinya; Sakai, Naomichi; Iwafuchi, Kengo; Murakami, Masato

2006-07-01

We used Ba-Cu-O substrates to fabricate bulk Nd-Ba-Cu-O superconductors using a top-seeded melt-growth method. There were several advantages for the use of Ba-Cu-O substrate compared to conventional substrate materials such as MgO, ZrO2, Al2O3, RE123 and RE211 (RE = rare earth). The Ba-Cu-O did not react with the precursor and minimized liquid loss. Accordingly, the introduction of large-sized cracks was suppressed. We also found that Tc values were high at the bottom regions, which was ascribed to the beneficial effect of Ba-Cu-O in suppressing Nd/Ba substitution. As a result, we obtained bulk Nd-Ba-Cu-O superconductors that exhibited fairly good field-trapping capabilities, even at the bottom surfaces.

High temperature dielectrics and defect characteristic of (Nb, Mn, Zr) modified 0.4(Ba0.8Ca0.2)TiO3 - 0.6Bi(Mg0.5Ti0.5)O3 ceramics

NASA Astrophysics Data System (ADS)

Ren, Shaokai; Chen, Zhi; Yan, Tianxiang; Han, Feifei; Kuang, Xiaojun; Fang, Liang; Liu, Laijun

2018-07-01

Transition elements Nb, Mn and Zr were selected to substitute Ti of 0.4(Ba0.8Ca0.2)TiO3 -0.6Bi(Mg0.5Ti0.5)O3 (BCT-BMT) ceramic in order to extend its operation temperature and decrease its dielectric loss for the application of high-temperature capacitors. Nb and Mn play an opposite role on the defect compensation, decreasing and increasing the concentration of oxygen vacancies, respectively. The temperature of the maximum relative permittivity, Tm, decreases from 140 °C to 90 °C for the Nb and Zr modified BCT-BMT ceramics. The permittivity (εr) peak of the former exhibits a broad and stable relative permittivity ∼600 (±5% variation) from 50 °C to 520 °C with the dielectric loss ≤0.02 from 60 °C to 440 °C (1 kHz). The modified Curie-Weiss law indicates that the doping elements result in an enhancement of diffuse phase transition. Activation energies of relaxation frequency and conduction of the samples were characterized by the impedance spectroscopy. A clear relationship between the magnitude of activation energy and the concentration of oxygen vacancies was revealed.

High mobility La-doped BaSnO3 on non-perovskite MgO substrate

NASA Astrophysics Data System (ADS)

Kim, Youjung; Shin, Juyeon; Kim, Young Mo; Char, Kookrin

(Ba,La)SnO3 is a transparent perovskite oxide with high electron mobility and excellent oxygen stability. Field effect device with (Ba,La)SnO3 channel was reported to show good output characteristics on STO substrate. Here, we fabricated (Ba,La)SnO3\\ films and field effect devices with (Ba,La)SnO3 channel on non-perovskite MgO substrates, which are available in large size wafers. X-ray diffraction and transmission electron microscope (TEM) images of (Ba,La)SnO3\\ films on MgO substrates show that the films are epitaxial with many threading dislocations. (Ba,La)SnO3 exhibits the high mobility with 97.2 cm2/Vs at 2 % La doping on top of 150 nm thick BaSnO3 buffer layer. Excellent carrier modulation was observed in field effect devices. FET performances on MgO substrates are slightly better than those on SrTiO3 substrates in spite of the higher dislocation density on MgO than on SrTiO3 substrates. These high mobility BaSnO3 thin films and transistors on MgO substrates will accelerate development for applications in high temperature and high power electronics. Samsung Science and Technology Foundation.

Impedance spectroscopy studies on lead free Ba1-xMgx(Ti0.9Zr0.1)O3 ceramics

NASA Astrophysics Data System (ADS)

Ben Moumen, S.; Neqali, A.; Asbani, B.; Mezzane, D.; Amjoud, M.; Choukri, E.; Gagou, Y.; El Marssi, M.; Luk'yanchuk, Igor A.

2018-06-01

Ba1-xMgx(Ti0.9Zr0.1)O3 (x = 0.01 and 0.02) ceramics were prepared using the conventional solid state reaction. Rietveld refinement performed on X-ray diffraction patterns indicates that the samples are tetragonal crystal structure with P4mm space group. By increasing Mg content from 1 to 2% the unit cell volume decreased. Likewise, the grains size is greatly reduced from 10 μm to 4 μm. The temperature dependence of dielectric constants at different frequencies exhibited typical relaxor ferroelectric characteristic, with sensitive dependence in frequency and temperature for ac conductivity. The obtained activation energy values were correlated to the proposed conduction mechanisms.

Influence of in situ and ex situ ZrO2 addition on the properties of MgB2

NASA Astrophysics Data System (ADS)

Chen, S. K.; Glowacki, B. A.; MacManus-Driscoll, J. L.; Vickers, M. E.; Majoros, M.

2004-02-01

The effect of ZrO2 addition on the properties of MgB2 has been studied using in situ and ex situ processes. The in situ process was performed by introducing ZrO2 from the milling tools into MgB2 throughout the planetary ball milling, whereas the ex situ process was accomplished by mixing ZrO2 from the milling tools with MgB2 by hand grinding in a mortar. A detectable amount of ZrO2 was present in MgB2 after 4 h of milling during the in situ process and its content increased with milling time as expected. The 400 h milled powder was partially amorphized and showed the formation of a minority ZrB2 phase. For milling up to 100 h, diamagnetism of MgB2 was significantly reduced while Tc remained unchanged. Superconductivity was totally destroyed after 148 h of milling. The loss of superconductivity is attributed to the effect of disordering induced by mechanical milling. As a result of in situ ZrO2 addition, the initial Tc and crystal structure of MgB2 could not be restored upon annealing. With increasing milling time, the expansion of lattice parameters in both the a-axis and c-axis may be due to possible substitution of Mg or B by Zr. The result from the magnetic measurement shows that Jc of MgB2 is deteriorated by in situ ZrO2 addition. On the other hand, ex situ ZrO2 addition with annealing did not degrade the Tc of MgB2.

Diffusion of Zr, Ru, Ce, Y, La, Sr and Ba fission products in UO 2

DOE PAGES

Perriot, R.; Liu, X. -Y.; Stanek, C. R.; ...

2015-01-08

The diffusivity of the solid fission products (FP) Zr (Zr 4+), Ru (Ru 4+, Ru 3+), Ce (Ce 4+), Y (Y 3+), La (La 3+), Sr (Sr 2+) and Ba (Ba 2+) by a vacancy mechanism has been calculated, using a combination of density functional theory (DFT) and empirical potential (EP) calculations. The activation energies for the solid fission products are compared to the activation energy for Xe fission gas atoms calculated previously. Apart from Ru, the solid fission products all exhibit higher activation energy than Xe. Furthermore, for all solid FPs except Y 3+, the migration of the FPmore » has lower barrier than the migration of a neighboring U atom, making the latter the rate limiting step for direct migration. An indirect mechanism, consisting of two successive migrations around the FP, is also investigated. The calculated diffusivities show that most solid fission products diffuse with rates similar to U self-diffusion. But, Ru, Ba and Sr exhibit faster diffusion than the other solid FPs, with Ru 3+ and Ru 4+ diffusing even faster than Xe for T < 1200 K. The diffusivities correlate with the observed fission product solubility in UO 2, and the tendency to form metallic and oxide second phase inclusions.« less

Giant negative electrocaloric effect in PbZrO3/0.88BaTiO3-0.12Bi(Mg1/2,Ti1/2)O3 multilayered composite ferroelectric thin film for solid-state refrigeration

NASA Astrophysics Data System (ADS)

Huang, D.; Wang, J. B.; Zhong, X. L.; Li, B.; Zhang, Y.; Jin, C.; Zheng, D. F.; Meng, X. J.

2017-11-01

A giant negative electrocaloric (EC) effect in a PbZrO3/(0.88BaTiO3-0.12 Bi(Mg1/2,Ti1/2)O3) (PZ/(BT-BMT)) multilayered composite ferroelectric (MCFE) thin film which is grown on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel method is investigated in this work. The negative EC effect in the PZ/(BMT-BT) MCFE thin film is greatly higher than that in the PZ AFE thin film with an adiabatic temperature change (ATC) ΔT = 1.5 K. The ATC ΔT of the PZ/(BMT-BT) MCFE thin film is -32 K under the applied electric field change ΔE = 1151 kV/cm. The result is conducive to enhance the EC refrigeration efficiency greatly.

Fabrication and electrochemical performance of a stable, anode supported thin BaCe0.4Zr0.4Y0.2O3-δ electrolyte Protonic Ceramic Fuel Cell

NASA Astrophysics Data System (ADS)

Nasani, Narendar; Ramasamy, Devaraj; Mikhalev, Sergey; Kovalevsky, Andrei V.; Fagg, Duncan P.

2015-03-01

The present work deals with the fabrication and electrochemical characterisation of a potential protonic ceramic fuel cell based on a Ni-BaZr0.85Y0.15O3-δ anode supported thin film proton conducting BaCe0.4Zr0.4Y0.2O3-δ electrolyte with a Pr2NiO4+δ cathode. Anode and electrolyte materials were prepared by an acetate-H2O2 combustion method. A thin (∼5 μm), dense and crack free BaCe0.4Zr0.4Y0.2O3-δ electrolyte film was successfully obtained on a porous anode support by spin coating and firing at 1450 °C. Maximum power densities of 234, 158, 102 and 63 mW cm-2 at 700, 650, 600 and 550 °C, respectively were achieved for the Ni-BaZr0.85Y0.15O3-δ/BaCe0.4Zr0.4Y0.2O3-δ/Pr2NiO4+δ single cell under fuel cell testing conditions. Electrode polarisation resistance was assessed at open circuit conditions by use of electrochemical impedance spectroscopy (EIS) and is shown to dominate the area specific resistance at low temperatures. Postmortem analysis by scanning electron microscopy (SEM), reveals that no delamination occurs at anode/electrolyte or electrolyte/cathode interfaces upon cell operation.

Microstructure and Phase Evolution in Mg-Gd and Mg-Gd-Nd Alloys With Additions of Zn, Y and Zr

NASA Astrophysics Data System (ADS)

Khawaled, S.; Bamberger, M.; Katsman, A.

Microstructure and phase evolution in Mg-Gd and Mg-Gd-Nd based alloys with additions of Zn, Zr and Y were analyzed in the as-cast, solution treated and aged conditions. Alloys has been investigated after solution treatment at 540°C for 24hr followed by isothermal aging at 175°C up to 32 days by using of Vickers hardness, optical microscopy, scanning electron microscopy equipped with EDS, X-ray diffraction and transmission electron microscopy. It was found that the as-cast alloys contained primary α-Mg matrix, eutecticlike structures, cuboid-like phases and Zr-rich clusters. The homogenized and quenched alloys contained primary α-Mg solid solution, smaller amount of divorced eutectic compounds, enlarged cuboid-like particles and Zr-rich clusters. The eutectic phase was Mg5Gd prototype with the composition Mg5(GdxNd1-x, x≈0.2). The compositions of the cuboid shaped particles are characterized by enlarged amount of Gd and can be written as Mg2(Gd x Y1-x) with x≈0.85 in the Mg-5Gd based alloy, and Gd4(YxNd1-x) with x≈0.5 in the Mg-6Gd-3.7Nd based alloy. The cuboid shaped particles grew during aging and reached 3µm average size. Precipitation of ß″ and ß' phases during aging was observed. Mg-6Gd-3.7Nd based alloy reached a maximum value of microhardness after 16 days of aging; in Mg-Gd based alloy, microhardness increased more slowly and reached a maximum value after 32 days of aging.

Fatigue and retention in ferroelectric Y-Ba-Cu-O/Pb-Zr-Ti-O/Y-Ba-Cu-O heterostructures

NASA Astrophysics Data System (ADS)

Ramesh, R.; Chan, W. K.; Wilkens, B.; Gilchrist, H.; Sands, T.; Tarascon, J. M.; Keramidas, V. G.; Fork, D. K.; Lee, J.; Safari, A.

1992-09-01

Fatigue and retention characteristics of ferroelectric lead zirconate titanate thin films grown with Y-Ba-Cu-O(YBCO) thin-film top and bottom electrodes are found to be far superior to those obtained with conventional Pt top electrodes. The heterostructures reported here have been grown in situ by pulsed laser deposition on yttria-stabilized ZrO2 buffer [100] Si and on [001] LaAlO3. Both the a- and c-axis orientations of the YBCO lattice have been used as electrodes. They were prepared using suitable changes in growth conditions.

Effect of two-stage sintering on dielectric properties of BaTi0.9Zr0.1O3 ceramics

NASA Astrophysics Data System (ADS)

Rani, Rekha; Rani, Renu; Kumar, Parveen; Juneja, J. K.; Raina, K. K.; Prakash, Chandra

2011-09-01

The effect of two-stage sintering on the dielectric properties of BaTi0.9Zr0.1O3 ceramics prepared by solid state route was investigated and is presented here. It has been found that under suitable two-stage sintering conditions, dense BaTi0.9Zr0.1O3 ceramics with improved electrical properties can be synthesized. The density was found to have a value of 5.49 g cc-1 for normally sintered samples, whereas in the case of the two-stage sintered sample it was 5.85 g cc-1. Dielectric measurements were done as a function of frequency and temperature. A small decrease in the Curie temperature was observed with modification in dielectric loss for two-stage sintered ceramic samples.

Microemulsion and Sol-Gel Synthesized ZrO₂-MgO Catalysts for the Liquid-Phase Dehydration of Xylose to Furfural.

PubMed

Parejas, Almudena; Montes, Vicente; Hidalgo-Carrillo, Jesús; Sánchez-López, Elena; Marinas, Alberto; Urbano, Francisco J

2017-12-18

Two series of catalysts were prepared by sol-gel and microemulsion synthetic procedure (SG and ME, respectively). Each series includes both pure Mg and Zr solids as well as Mg-Zr mixed solids with 25%, 50% and 75% nominal Zr content. The whole set of catalysts was characterized from thermal, structural and surface chemical points of view and subsequently applied to the liquid-phase xylose dehydration to furfural. Reactions were carried out in either a high-pressure autoclave or in an atmospheric pressure multi-reactor under a biphasic (organic/water) reaction mixture. Butan-2-ol and toluene were essayed as organic solvents. Catalysts prepared by microemulsion retained part of the surfactant used in the synthetic procedure, mainly associated with the Zr part of the solid. The MgZr-SG solid presented the highest surface acidity while the Mg3Zr-SG one exhibited the highest surface basicity among mixed systems. Xylose dehydration in the high-pressure system and with toluene/water solvent mixture led to the highest furfural yield. Moreover, the yield of furfural increases with the Zr content of the catalyst. Therefore, the catalysts constituted of pure ZrO₂ (especially Zr-SG) are the most suitable to carry out the process under study although MgZr mixed solids could be also suitable for overall processes with additional reaction steps.

The hot deformation behavior and microstructure evolution of HA/Mg-3Zn-0.8Zr composites for biomedical application.

PubMed

Liu, Debao; Liu, Yichi; Zhao, Yue; Huang, Y; Chen, Minfang

2017-08-01

The hot deformation behavior of nano-sized hydroxylapatite (HA) reinforced Mg-3Zn-0.8Zr composites were performed by means of Gleeble-1500D thermal simulation machine in a temperature range of 523-673K and a strain rate range of 0.001-1s -1 , and the microstructure evolution during hot compression deformation were also investigated. The results show that the flow stress increases increasing strain rates at a constant temperature, and decreases with increasing deforming temperatures at a constant strain rate. Under the same processing conditions, the flow stresses of the 1HA/Mg-3Zn-0.8Zr specimens are higher than those of the Mg-3Zn-0.8Zr alloy specimens, and the difference is getting closer with increasing deformation temperature. The hot deformation behaviors of Mg-3Zn-0.8Zr and 1HA/Mg-3Zn-0.8Zr can be described by constitutive equation of hyperbolic sine function with the hot deformation activation energy being 124.6kJ/mol and 125.3kJ/mol, respectively. Comparing with Mg-3Zn-0.8Zr alloy, the instability region in the process map of 1HA/Mg-3Zn-0.8Zr expanded to a bigger extent at the same conditions. The optimum process conditions of 1HA/Mg-3Zn-0.8Zr composite is concluded as between the temperature window of 573-623K with a strain rate range of 0.001-0.1s -1 . A higher volume fraction and smaller grain size of dynamic recrystallization (DRX) grains was observed in 1HA/Mg-3Zn-0.8Zr specimens after the hot compression deformation compared with Mg-3Zn-0.8Zr alloy, which was ascribed to the presence of the HA particles that play an important role in particle-stimulated nucleation (PSN) mechanism and can effectively hinder the migration of interfaces. Copyright © 2017 Elsevier B.V. All rights reserved.

Self-assembled Co-BaZrO 3 nanocomposite thin films with ultra-fine vertically aligned Co nanopillars

DOE PAGES

Huang, Jijie; Li, Leigang; Lu, Ping; ...

2017-05-11

A simple one-step pulsed laser deposition (PLD) method has been applied to grow self-assembled metal-oxide nanocomposite thin films. The as-deposited Co-BaZrO 3 films show high epitaxial quality with ultra-fine vertically aligned Co nanopillars (diameter <5 nm) embeded in BZO matrix. The diameter of the nanopillars can be further tuned by varying the deposition frequency. The metal and oxide phases grow separately without inter-diffusion or mixing. Taking advantage of this unique structure, a high saturation magnetization of ~1375 emu/cm 3 in the Co- BaZrO 3 nanocomposites has been achieved and further confirmed by Lorentz microscopy imaging in TEM. Furthermore, the coercivitymore » values of this nanocomposite thin films range from 600 Oe (20 Hz) to 1020 Oe (2 Hz), which makes the nanocomposite an ideal candidate for high-density perpendicular recording media.« less

Effects of Al3(Sc,Zr) and Shear Band Formation on the Tensile Properties and Fracture Behavior of Al-Mg-Sc-Zr Alloy

NASA Astrophysics Data System (ADS)

Huang, Hongfeng; Jiang, Feng; Zhou, Jiang; Wei, Lili; Qu, Jiping; Liu, Lele

2015-11-01

The mechanical properties and microstructures of Al-6Mg-0.25Sc-0.1Zr alloy (wt.%) during annealing were investigated by means of uniaxial tensile testing, optical microscope, scanning electron microscope, transmission electron microscope, and high-resolution transmission electron microscope. The results show that a large number of micro and grain-scale shear bands form in this alloy after cold rolling. As the tensile-loading force rises, strain softening would generate in shear bands, resulting in the occurrence of shear banding fracture in cold-rolled Al-Mg-Sc-Zr alloys. Recrystallization takes place preferentially in shear bands during annealing. Due to the formation of coarse-grain bands constructed by new subgrains, recrystallization softening tends to occur in these regions. During low-temperature annealing, recrystallization is inhibited by nano-scale Al3(Sc,Zr) precipitates which exert significant coherency strengthening and modulus hardening. However, the strengthening effect of Al3(Sc,Zr) decreases with the increasing of particle diameter at elevated annealing temperature. The mechanical properties of the recrystallized Al-Mg-Sc-Zr alloy decrease to a minimum level, and the fracture plane exhibits pure ductile fracture characteristics.

Enhanced antibacterial properties, biocompatibility, and corrosion resistance of degradable Mg-Nd-Zn-Zr alloy.

PubMed

Qin, Hui; Zhao, Yaochao; An, Zhiquan; Cheng, Mengqi; Wang, Qi; Cheng, Tao; Wang, Qiaojie; Wang, Jiaxing; Jiang, Yao; Zhang, Xianlong; Yuan, Guangyin

2015-06-01

Magnesium (Mg), a potential biodegradable material, has recently received increasing attention due to its unique antibacterial property. However, rapid corrosion in the physiological environment and potential toxicity limit clinical applications. In order to improve the corrosion resistance meanwhile not compromise the antibacterial activity, a novel Mg alloy, Mg-Nd-Zn-Zr (Hereafter, denoted as JDBM), is fabricated by alloying with neodymium (Nd), zinc (Zn), zirconium (Zr). pH value, Mg ion concentration, corrosion rate and electrochemical test show that the corrosion resistance of JDBM is enhanced. A systematic investigation of the in vitro and in vivo antibacterial capability of JDBM is performed. The results of microbiological counting, CLSM, SEM in vitro, and microbiological cultures, histopathology in vivo consistently show JDBM enhanced the antibacterial activity. In addition, the significantly improved cytocompatibility is observed from JDBM. The results suggest that JDBM effectively enhances the corrosion resistance, biocompatibility and antimicrobial properties of Mg by alloying with the proper amount of Zn, Zr and Nd. Copyright © 2015 Elsevier Ltd. All rights reserved.

Large Energy Density, Excellent Thermal Stability, and High Cycling Endurance of Lead-Free BaZr0.2Ti0.8O3 Film Capacitors.

PubMed

Sun, Zixiong; Ma, Chunrui; Wang, Xi; Liu, Ming; Lu, Lu; Wu, Ming; Lou, Xiaojie; Wang, Hong; Jia, Chun-Lin

2017-05-24

A large energy storage density (ESD) of 30.4 J/cm 3 and high energy efficiency of 81.7% under an electrical field of 3 MV/cm was achieved at room temperature by the fabrication of environmentally friendly lead-free BaZr 0.2 Ti 0.8 O 3 epitaxial thin films on Nb-doped SrTiO 3 (001) substrates by using a radio-frequency magnetron sputtering system. Moreover, the BZT film capacitors exhibit great thermal stability of the ESD from 16.8 J/cm 3 to 14.0 J/cm 3 with efficiency of beyond 67.4% and high fatigue endurance (up to 10 6 cycles) in a wide temperature range from room temperature to 125 °C. Compared to other BaTiO 3 -based energy storage capacitor materials and even Pb-based systems, BaZr 0.2 Ti 0.8 O 3 thin film capacitors show either high ESD or great energy efficiency. All of these excellent results revealed that the BaZr 0.2 Ti 0.8 O 3 film capacitors have huge potential in the application of modern electronics, such as locomotive and pulse power, in harsh working environments.

Broad Temperature Pinning Study of 15 mol.% Zr-Added (Gd, Y)-Ba-Cu-O MOCVD Coated Conductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, AX; Khatri, N; Liu, YH

BaZrO3 (BZO) nanocolumns have long been shown to be very effective for raising the pinning force F-p of REBa2Cu3Ox (REBCO, where RE = rare earth) films at high temperatures and recently at low temperatures too. We have successfully incorporated a high density of BZO nanorods into metal organic chemical vapor deposited (MOCVD) REBCO coated conductors via Zr addition. We found that, compared to the 7.5% Zr-added coated conductor, dense BZO nanorod arrays in the 15% Zr-added conductor are effective over the whole temperature range from 77 K down to 4.2 K. We attribute the substantially enhanced J(c) at 30 Kmore » to the weak uncorrelated pinning as well as the strong correlated pinning. Meanwhile, by tripling the REBCO layer thickness to similar to 2.8 mu m, the engineering critical current density J(e) at 30 K exceeds J(e) of optimized Nb-Ti wires at 4.2 K.« less

Electronic structure and bonding interactions in Ba1- x Sr x Zr0.1Ti0.9O3 ceramics

NASA Astrophysics Data System (ADS)

Mangaiyarkkarasi, Jegannathan; Sasikumar, Subramanian; Saravanan, Olai Vasu; Saravanan, Ramachandran

2017-06-01

An investigation on the precise electronic structure and bonding interactions has been carried out on Ba1- x Sr x Zr0.1Ti0.9O3 (short for BSZT, x = 0, 0.05, 0.07 and 0.14) ceramic systems prepared via high-temperature solid state reaction technique. The influence of Sr doping on the BSZT structure has been examined by characterizing the prepared samples using PXRD, UV-visible spectrophotometry, SEM and EDS. Powder profile refinement of X-ray data confirms that all the synthesized samples have been crystallized in cubic perovskite structure with single phase. Charge density distribution of the BSZT systems has been completely analyzed by the maximum entropy method (MEM). Co-substitution of Sr at the Ba site and Zr at the Ti site into the BaTiO3 structure presents the ionic nature between Ba and O ions and the covalent nature between Ti and O ions, revealed from MEM calculations. Optical band gap values have been evaluated from UV-visible absorption spectra. Particles with irregular shapes and well defined grain boundaries are clearly visualized from SEM images. The phase purity of the prepared samples is further confirmed by EDS qualitative spectral analysis.

The depolarization performances of 0.97PbZrO3-0.03Ba(Mg1/3Nb2/3)O3 ceramics under hydrostatic pressure

NASA Astrophysics Data System (ADS)

Su, Rigu; Nie, Hengchang; Liu, Zhen; Peng, Ping; Cao, Fei; Dong, Xianlin; Wang, Genshui

2018-02-01

Several 0.97PbZrO3-0.03Ba(Mg1/3Nb2/3)O3 (0.97PZ-0.03BMN) ceramics were prepared via the columbite precursor method. Their microstructures and pressure-dependent ferroelectric and depolarization performances were then studied. The X-ray diffraction patterns of ground and fresh samples indicate that a main rhombohedral symmetry crystal structure is present in the bulk and that it sits alongside a trace quantity of an orthorhombic antiferroelectric phase that results from the effect of grinding on the surface. The remanent polarization (Pr) of the 0.97PZ-0.03BMN reached 32.4 μC/cm2 at 4.5 kV/mm and ambient pressure. In an in situ pressure-induced current measurement, more than 91% of the retained Pr of the pre-poled sample was released when the pressure was increased from 194 MPa to 238 MPa. That this pressure-driven depolarization should be attributed to the pressure-induced ferroelectric-antiferroelectric phase transition is supported by the emergence of double P-E loops at high hydrostatic pressures. Moreover, the 0.97PZ-0.03BMN ceramics exhibit no temperature-induced phase transitions and little related polarization loss up to 125 °C, which suggests that Pr has excellent thermal stability. The sharp depolarization behavior at low pressures and excellent temperature stability reveal that our 0.97PZ-0.03BMN ceramics exhibit superior performances in mechanical-electrical energy conversion applications.

A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect

PubMed Central

Naveed-Ul-Haq, M.; Shvartsman, Vladimir V.; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C.

2016-01-01

The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 − 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 −CoFe2O4 bulk composites with similar content of the ferrite phase. PMID:27555563

A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect

NASA Astrophysics Data System (ADS)

Naveed-Ul-Haq, M.; Shvartsman, Vladimir V.; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C.

2016-08-01

The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 - 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 -CoFe2O4 bulk composites with similar content of the ferrite phase.

Pair luminescence in Cr3+ -doped Ba2Mg(BO3)2

NASA Astrophysics Data System (ADS)

Bondzior, Bartosz; Miniajluk, Natalia; Dereń, Przemysław J.

2018-05-01

Cr3+ ions were introduced to the Ba2Mg(BO3)2 host to provide information about the site occupation, crystal field strength, and the site symmetry. The samples were synthesized by solid-state reaction. Emission observed under 440 nm excitation was characteristic for Cr3+ ions in strong octahedral ligand field with Dq/B parameter ratio 2.74 and sharp R line at 698 nm. The charge mismatch between Cr3+ dopant and Mg2+ host ion is compensated by the creation of Cr3+ pair in the vicinity of Ba or Mg vacancy. The emission decay curve is bi-exponential with decay times 1.2 and 13.3 ms.

Luminescence properties of long-lasting phosphor SrMg2(PO4)2:Eu2+, Ho3+, Zr4+

NASA Astrophysics Data System (ADS)

Tang, Wei; Wang, Mingwen; Lin, Wei; Ye, Yaping; Wu, Xue

2016-12-01

Novel long lasting phosphors SrMg2(PO4)2:Eu2+, SrMg2(PO4)2:Eu2+, Zr4+, SrMg2(PO4)2:Eu2+, Ho3+ and SrMg2(PO4)2:Eu2+, Ho3+, Zr4+ were synthesized by conventional solid-state reaction method. The luminescent properties were systematically characterized by X-ray diffraction, photoluminescent excitation and emission spectra, as well as thermoluminescence spectrum and decay curves. The XRD patterns indicated that the samples belonged to monoclinic phase and co-doping Eu2+, Ho3+ and Zr4+ ions had no effect on the basic crystal structure. These phosphors emitting purplish blue light is related to the characteristic emission of Eu2+. The afterglow time of Eu2+ activated SrMg2(PO4)2 can be greatly enhanced by the co-doping of Ho3+, Zr4+. After the 365 nm UV light excitation source switching off, the Sr0.92Mg1.95(PO4)2:Eu2+0.01, Zr4+0.05, Ho3+0.07 phosphorescence can be observed for more than 1013 s in the limit of light perception of dark-adapted human eyes (0.32 mcd/m2). Different kinds of TL peaks at 423, 448 and 473 K have appeared, and traps densities have increased compared with the Eu2+ single doped SrMg2(PO4)2 phosphor. By analyzing the TL curve the depths of traps were calculated to be 0.846, 0.896 and 0.946 eV, respectively, which suggested that the co-doping of Ho3+, Zr4+ improved the electron storage ability of material. Besides, the mechanism was discussed in this report.

Incorporation of Mg, Sr, Ba, U, and B in High-Mg Calcite Benthic Foraminifers Cultured Under Controlled pCO2

NASA Astrophysics Data System (ADS)

Not, C.; Thibodeau, B.; Yokoyama, Y.

2018-01-01

Measurement of elemental ratios (E/Ca) has been performed in two symbiont-bearing species of high-Mg calcite benthic foraminifers (hyaline, Baculogypsina sphaerulata and porcelaneous, Amphisorus hemprichii), cultured under five pCO2 levels, representing preindustrial, modern, and three predicted future values. E/Ca ratios were analyzed by Laser Ablation coupled with Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS). We measured several E/Ca, such as Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca simultaneously. We observed that high-Mg calcite benthic foraminifers possess higher E/Ca than low-Mg calcite foraminifers, irrespective of their calcification mode (hyaline or porcelaneous). In both modes of calcification, Mg, Sr, Ba, U, and B incorporation could be controlled by Rayleigh fractionation. However, more data are needed to validate and quantify the relative importance of this process and closely investigate the presence/absence of other mechanism. Therefore, it highlights the need for a multielemental approach when looking at trace element incorporation. Finally, no significant relationship was observed between the different ratios and the pCO2 of the water, suggesting that none of the Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca is sensitive to bottom water pCO2 or pH for these species.

Introduction of BaSnO3 and BaZrO3 artificial pinning centres into 2G HTS wires based on PLD-GdBCO films. Phase I of the industrial R&D programme at SuperOx

NASA Astrophysics Data System (ADS)

Chepikov, V.; Mineev, N.; Degtyarenko, P.; Lee, S.; Petrykin, V.; Ovcharov, A.; Vasiliev, A.; Kaul, A.; Amelichev, V.; Kamenev, A.; Molodyk, A.; Samoilenkov, S.

2017-12-01

An industrial R&D programme is ongoing at SuperOx, aimed at improving 2G HTS wire performance in magnetic field. We introduce perovskite artificial pinning centres (APC) into the HTS layer matrix. In contrast to most studies described in the literature, we use the high rate production processing parameters and PLD equipment at SuperOx. This paper reports the results of Phase I of this programme. We fabricated 2G HTS wires by pulsed laser deposition of GdBCO films doped with 6%, 12% and 18% (molar) of BaSnO3 and 6% (molar) of BaZrO3, and compared their performance with an undoped reference sample. The depositions were carried out at production growth rates of 375, 560 and 750 nm min-1 by varying laser pulse frequency. BaZrO3 and BaSnO3 formed columnar semi-coherent nanoinclusions in the GdBCO film matrix. The average transverse size of the nanocolumns was about 5 nm, and their volume density correlated with the dopant concentration. All doped samples exhibited much lower angular anisotropy of in-field critical current and higher lift-factors than the undoped sample. Samples containing 6% BaSnO3 and deposited at the lower growth rates, had higher I c than the undoped sample in the entire temperature range, in a wide range of magnetic field (B//c). The sample containing 6% BaZrO3 had higher I c than the undoped sample at 20 and 4.2 K. These results are an encouraging start of our programme, as they show a positive impact of APC introduced into 2G HTS wires fabricated at production throughput. Phase II work will be focussed on maximising the improvements in specific temperature and field conditions, as well as on the verification of reproducibility of the improvements in production wires.

Mechanochemical synthesis of MgF2 - MF2 composite systems (M = Ca, Sr, Ba)

NASA Astrophysics Data System (ADS)

Scholz, G.; Breitfeld, S.; Krahl, T.; Düvel, A.; Heitjans, P.; Kemnitz, E.

2015-12-01

The capability of mechanochemical synthesis for the formation of MgF2-MF2 (M: Ca, Sr, Ba) composites, solid solutions or well-defined compounds was tested applying a fluorination of different fluorine-free metal sources with NH4F directly at milling. No evidence was found for a substitution of Mg2+ with Ca2+ (Sr2+, Ba2+) ions, or vice versa, in rutile or fluorite structure. However, an equimolar ratio of Mg2+ to the second cation allows the mechanochemical synthesis of tetrafluoromagnesates, MMgF4, which is more and more hampered the smaller the radius of the cation M2+ is. BaMgF4 is formed even phase pure from the acetates, SrMgF4 can only be observed in a mixture accompanied by the binary fluorides. In addition, 19F MAS NMR spectra along with calculations of 19F isotropic chemical shift values according to the superposition model point to the formation of a metastable phase of CaMgF4, which disappears at thermal treatment and decomposes into the binary fluorides CaF2 and MgF2.

Influence of Sc on microstructure and mechanical properties of Al-Si-Mg-Cu-Zr alloy

NASA Astrophysics Data System (ADS)

Li, Yukun; Du, Xiaodong; Zhang, Ya; Zhang, Zhen; Fu, Junwei; Zhou, Shi'ang; Wu, Yucheng

2018-02-01

In the present study, the effects of Mg, Cu, Sc and Zr combined additions on the microstructure and mechanical properties of hypoeutectic Al-Si cast alloy were systematically investigated. Characterization techniques such as optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron back-scatter diffraction (EBSD), atomic force microscopy (AFM), transmission electron microscope (TEM), Brinell hardness tester and universal testing machine were employed to analyze the microstructure and mechanical properties. The results showed that Sc served as modifier on the microstructure of Al-3Si-0.45Mg-0.45Cu-0.2Zr alloys, including modification of eutectic Si and grains. Extraordinarily, grain refinement was found to be related to the primary particles, which exhibited a close orientation to matrix. After T6 heat treatment, the grain structures were composed of nano-scaled secondary Al3(Sc, Zr) precipitates and spherical eutectic Si. Combined with T6 heat treatment, the highest hardness, yield strength, ultimate tensile strength and elongation were achieved in 0.56 wt.% Sc-modified alloy. Interestingly, the strength and ductility had a similar tendency. This paper demonstrated that combined additions of Mg, Cu, Sc and Zr could significantly improve the microstructure and performance of the hypoeutectic Al-Si cast alloy.

Mechanical properties and corrosion behavior of Mg-Gd-Ca-Zr alloys for medical applications.

PubMed

Shi, Ling-Ling; Huang, Yuanding; Yang, Lei; Feyerabend, Frank; Mendis, Chamini; Willumeit, Regine; Ulrich Kainer, Karl; Hort, Norbert

2015-07-01

Magnesium alloys are promising candidates for biomedical applications. In this work, influences of composition and heat treatment on the microstructure, the mechanical properties and the corrosion behavior of Mg-Gd-Ca-Zr alloys as potential biomedical implant candidates were investigated. Mg5Gd phase was observed at the grain boundaries of Mg-10Gd-xCa-0.5Zr (x=0, 0.3, 1.2wt%) alloys. Increase in the Ca content led to the formation of additional Mg2Ca phase. The Ca additions increased both the compressive and the tensile yield strengths, but reduced the ductility and the corrosion resistance in cell culture medium. After solution heat treatment, the Mg5Gd particles dissolved in the Mg matrix. The compressive strength decreased, while the corrosion resistance improved in the solution treated alloys. After ageing at 200°C, metastable β' phase formed on prismatic planes and a new type of basal precipitates have been observed, which improved the compressive and tensile ultimate strength, but decreased the ductility. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of MgO modified β-TCP nanoparticles on the microstructure and properties of β-TCP/Mg-Zn-Zr composites.

PubMed

Zheng, H R; Li, Z; You, C; Liu, D B; Chen, M F

2017-03-01

The mechanical properties and corrosion resistance of magnesium alloy composites were improved by the addition of MgO surface modified tricalcium phosphate ceramic nanoparticles (m-β-TCP). Mg-3Zn-0.8Zr composites with unmodified (MZZT) and modified (MZZMT) nanoparticles were produced by high shear mixing technology. Effects of MgO m-β-TCP nanoparticles on the microstructure, mechanical properties, electrochemical corrosion properties and cytocompatibility of Mg-Zn-Zr/β-TCP composites were investigated. After hot extrusion deformation and dynamic recrystallization, the grain size of MZZMT was the half size of MZZT and the distribution of m-β-TCP particles in the matrix was more uniform than β-TCP particles. The yield tensile strength (YTS), ultimate tensile strength (UTS), and corrosion potential (Ecorr) of MZZMT were higher than MZZT; the corrosion current density (I corr ) of MZZMT was lower than MZZT. Cell proliferation of co-cultured MZZMT and MZZT composite samples were roughly the same and the cell number at each time point is higher for MZZMT than for MZZT samples.

Mechanical Properties and Microstructure of TIG and FSW Joints of a New Al-Mg-Mn-Sc-Zr Alloy

NASA Astrophysics Data System (ADS)

Xu, Guofu; Qian, Jian; Xiao, Dan; Deng, Ying; Lu, Liying; Yin, Zhimin

2016-04-01

A new Al-5.8%Mg-0.4%Mn-0.25%Sc-0.10%Zr (wt.%) alloy was successfully welded by tungsten inert gas (TIG) and friction stir welding (FSW) techniques, respectively. The mechanical properties and microstructure of the welded joints were investigated by microhardness measurements, tensile tests, and microscopy methods. The results show that the ultimate tensile strength, yield strength, and elongation to failure are 358, 234 MPa, and 27.6% for TIG welded joint, and 376, 245 MPa and 31.9% for FSW joint, respectively, showing high strength and superior ductility. The TIG welded joint fails in the heat-affected zone and the fracture of FSW joint is located in stirred zone. Al-Mg-Mn-Sc-Zr alloy is characterized by lots of dislocation tangles and secondary coherent Al3(Sc,Zr) particles. The superior mechanical properties of the TIG and FSW joints are mainly derived from the Orowan strengthening and grain boundary strengthening caused by secondary coherent Al3(Sc,Zr) nano-particles (20-40 nm). For new Al-Mg-Mn-Sc-Zr alloy, the positive effect from secondary Al3(Sc, Zr) particles in the base metal can be better preserved in FSW joint than in TIG welded joint.

Viscosity of the liquid Al-6Mg-1Mn-0.2Sc-0.1Zr alloy

NASA Astrophysics Data System (ADS)

Reznik, P. L.; Chikova, O. A.; Tsepelev, V. S.

2017-07-01

The microstructure and the phase composition of as-cast Al-Mg-Mn-Sc-Zr alloy samples are studied by electron microscopy and electron-probe microanalysis. The processes of solidification and melting of this alloy are described. The temperature dependence of the kinematic viscosity of the Al-Mg-Mn-Sc-Zr melts is studied during heating and subsequent cooling of the samples. The measurement results are used to determine the temperature at which inherited microheterogeneities in the melts are destroyed irreversibly.

Microstructural analysis of biodegradable Mg-0.9Ca-1.2Zr alloy

NASA Astrophysics Data System (ADS)

Istrate, B.; Munteanu, C.; Geanta, V.; Baltatu, S.; Focsaneanu, S.; Earar, K.

2016-08-01

Magnesium alloys have applications in aerospace and medical applications as biodegradable orthopedic implants. Alloying with biocompatible elements, such as calcium or zirconium contribute to refining the the microstructure and improves corrosion resistance with the formation of an eutectic compound - Mg2Ca at boundary alpha-Mg grains. The purpose of this paper is to present the microstructure throw optical and scanning electron methods and phase and constituents identification with X-ray analysis. The results showed the presence of alpha-Mg grains with formation of a mechanical compound - Mg2Ca and appearance of alpha- Zr phase relatively uniformly distributed in nests.

Characterization of oxygen vacancies and their migration in Ba-doped Pb(Zr0.52Ti0.48)O3 ferroelectrics

NASA Astrophysics Data System (ADS)

Zhang, M. F.; Wang, Y.; Wang, K. F.; Zhu, J. S.; Liu, J.-M.

2009-03-01

We investigate in detail the migration kinetics of oxygen vacancies (OVs) in Ba-doped Pb(Zr0.52Ti0.48)O3 (PZT) ferroelectrics by complex impedance spectroscopy. The temperature dependent dc-electrical conductivity σdc suggests that Ba doping into PZT can lower significantly the density of OVs, leading to the distinctly decreased σdc and slightly enhanced activation energy U for the migration of OVs, thus benefiting the polarization fatigue resistance. Furthermore, the polarization fluctuation induced by the relaxation of OVs is reduced by the Ba doping. The Cole-Cole fitting to the dielectric loss manifests strong correlation among OVs, and the migration of OVs appears to be a collective behavior.

On the Precipitation in an Ag-Containing Mg-Gd-Zr Alloy

NASA Astrophysics Data System (ADS)

Zhang, Yu; Zhu, Yuman; Rong, Wei; Wu, Yujuan; Peng, Liming; Nie, Jian-Feng; Birbilis, Nick

2018-02-01

The evolution of precipitates in a high-strength Mg-2.4Gd-0.4Ag-0.1Zr (at. pct) alloy was investigated using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The precipitation of Mg-2.4Gd-0.4Ag-0.1Zr includes β- and γ-type precipitates, the latter involving a hitherto unreported precipitation sequence that is the focus of the present study. The β-type precipitation sequence is described as follows: supersaturated solid solution (S.S.S.S.) → ordered solute clusters → zigzag GP zones → β' → βF' → β 1 → β. Compared with the precipitation sequence of the Mg-Gd system, the proposed β-type precipitation sequence includes ordered solute clusters, zigzag GP zones, and βF' , but excludes β″. The strain field around the coarsened β' phase is supposed to stimulate the formation of the β^'F phase. Furthermore, the βF' phase provides preferential nucleation site for the β 1 phase. The γ-type precipitation sequence is proposed as follows: S.S.S.S. → basal GP zones → γ''' → γ″ → γ. The crystal structures, morphologies, and orientations of the basal GP zone, γ''', γ″, γ phases were comprehensively examined and established herein. The results are described in the context of other, but similar, alloy systems. A holistic description of the precipitate evolution in Ag-containing Mg-Gd alloys is discussed and rationalized.

Electrical characterization of Mn doped-(Ba{sub 0.3}Sr{sub 0.7})Mn{sub x}(Ti{sub 0.9}Zr{sub 0.1}){sub 1-x}O{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahmood, A.; Materials Research Laboratory, Institute of Physics & Electronics, University of Peshawar, 25120; Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD

2015-12-15

Highlights: • Solid state processing of the (Ba{sub 0.3}Sr{sub 0.7})Mn{sub x}(Ti{sub 0.9}Zr{sub 0.1}){sub 1−x}O{sub 3} ceramics. • Mn incorporated on the Ti-site into the host lattice of (Ba{sub 0.3}Sr{sub 0.7})Mn{sub x}(Ti{sub 0.9}Zr{sub 0.1}){sub 1−x}O{sub 3}. • NTCR behavior was observed in the sintered samples. - Abstract: (Ba{sub 0.3}Sr{sub 0.7})Mn{sub x}(Ti{sub 0.9}Zr{sub 0.1}){sub 1-x}O{sub 3} (x = 0.00, 0.013, 0.015 and 0.05) ceramics were prepared by solid state sintering route at the 1500 °C for 6 h in air. Effect of Mn substitution on the structure of Ba{sub 0.3}Sr{sub 0.7}(Ti0{sub .9}Zr{sub 0.1}){sub 1−x}O{sub 3} perovskite was investigated systematically. Dielectric and impedancemore » spectroscopic studies were conducted to understand the electronic microstructure of the Ba{sub 0.3}Sr{sub 0.7}(Ti0{sub .9}Zr{sub 0.1}){sub 1−x}O{sub 3} ceramics. Sample with x = 0.05 showed the highest dielectric constant (ϵ{sub r} = 1826) and low dielectric loss (tanδ = 0.001) at 10 kHz, around the room temperature, while the sample with x = 0.00 showed good microwave (MW) dielectric properties (Qf{sub o} = 838 and ϵ{sub r} = 550). The impedance spectroscopic analysis confirmed the electrical homogeneity of the samples with x = 0.013, 0.015 and 0.05, where grain boundaries dominated the conduction mechanism. Similarly, the sample with x = 0.00 was found to possess both grain boundary and bulk resistive contributions.« less

Temperature dependences of the electromechanical and electrocaloric properties of Ba(Zr,Ti)O3 and (Ba,Sr)TiO3 ceramics

NASA Astrophysics Data System (ADS)

Maiwa, Hiroshi

2017-10-01

The electrocaloric properties of Ba(Zr,Ti)O3 and (Ba,Sr)TiO3 ceramics (BZT and BST, respectively) were investigated by the indirect estimation and direct measurement of temperature-electric field (T-E) hysteresis loops. The measured T-E loops had shapes similar to those of the strain-electric field (s-E) loops. The measured temperature changes (ΔTs) at around 30 °C of the BZT ceramics sintered at 1450 °C and BST ceramics sintered at 1600 °C upon the release of the electric field from 30 kV/cm to 0 were 0.34 and 0.57 K, respectively. The temperature dependences of the electromechanical and electrocaloric properties were investigated. The BZT ceramics sintered at 1450 °C exhibited the largest electromechanical and electrocaloric properties at around 30 °C, which corresponds to the phase transition temperature. BST is more temperature dependent than BZT. BST ceramics sintered at 1600 °C exhibited the largest electromechanical and electrocaloric properties at around 29 °C, which is about 10 °C higher than the phase transition temperature.

The effect of dopants on the microwave dielectric properties of Ba(Mg{sub 0.33}Ta{sub 0.67})O{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Surendran, Kuzhichalil P.; Sebastian, Mailadil T.; Mohanan, Pezholil

2005-11-01

The effect of dopants with different valencies and ionic radii on the densification, structural ordering, and microwave dielectric properties of Ba(Mg{sub 1/3}Ta{sub 2/3})O{sub 3} (BMT) is investigated. It is found that dopants such as Sb{sub 2}O{sub 5}, MnO, ZrO{sub 2}, WO{sub 3}, and ZnO improve the microwave dielectric properties of BMT. Addition of trivalent dopants is detrimental to the cation ordering and dielectric properties of BMT. A correlation between the microwave dielectric properties of BMT and ionic radii of the dopant has been established. The variation of the dielectric properties of pure and doped BMT at cryogenic temperatures is alsomore » discussed.« less

The influence of HF treatment on corrosion resistance and in vitro biocompatibility of Mg-Zn-Zr alloy

NASA Astrophysics Data System (ADS)

Ye, Xin-Yu; Chen, Min-Fang; You, Chen; Liu, De-Bao

2010-06-01

The samples made of a Mg-2.5wt.%Zn-0.5wt.%Zr alloy were immersed in the 20% hydrofluoric acid (HF) solution at room temperature for different time, with the aim of improving the properties of magnesium (Mg) alloy in applications as biomaterials. The corrosion resistance and in vitro biocompatibility of untreated and fluoride-coated samples were investigated. The results show that the optimum process is to immerse Mg alloys in the 20% HF solution for 6 h. After the immersion, a dense magnesium fluoride (MgF2) coating of 0.5 μm was synthesized on the surface of Mg-Zn-Zr alloy. Polarization tests recorded a reduction in the corrosion current density from 2.10 to 0.05 μA/cm2 due to the MgF2 protective coating. Immersion tests in the simulated body fluid (SBF) also reveal a much milder corrosion on the fluoride-coated samples, and its corrosion rate was calculated to be 0.05 mm/yr. Hemolysis test suggests that the conversion coated Mg alloy has no obvious hemolysis reaction. The hemolysis ratio (HR) of the samples decreases from 11.34% to 1.86% with the HF treatment, which meets the requirements of biomaterials (HR < 5%). The coculture of 3T3 fibroblasts with Mg alloy results in the adhesion and proliferation of cells on the surface of fluoride-coated samples. All the results show that the MgF2 conversion coating would markedly improve the corrosion resistance and in vitro biocompatibility of Mg-Zn-Zr alloy.

Luminescence properties of Eu2+ in M2MgSi2O7 (M=Ca, Sr, and Ba) phosphors

NASA Astrophysics Data System (ADS)

Kim, T.; Kim, Y.; Kang, S.

2012-03-01

The photoluminescence properties of alkali-earth magnesium silicates (M2MgSi2O7, M=Ca, Sr, and Ba) doped with Eu2+ were investigated. Solid solutions of Ba x Sr2- x Si2O7, Ca2MgSi2O7, and Sr2MgSi2O7 were prepared. Ba x Sr2- x Si2O7 retained a tetragonal crystal structure similar to the structure of the other compounds up to a stoichiometry of x=1.6, which enabled a systematic study of the common structure. Monoclinic Ba2MgSi2O7 was prepared, and the luminescence properties were compared with those of other samples. The emission and excitation spectra of tetragonal M2MgSi2O7 (M=Ca, Sr, and Ba) changed as a function of the covalency, site symmetry, and crystal field strength. The luminescence properties showed excellent agreement with theoretical predictions based on these factors. The Stokes shift differentiated the emission behaviors of the tetragonal and monoclinic structures.

Role of A-site Ca and B-site Zr substitution in BaTiO3 lead-free compounds: Combined experimental and first principles density functional theoretical studies

NASA Astrophysics Data System (ADS)

Keswani, Bhavna C.; Saraf, Deepashri; Patil, S. I.; Kshirsagar, Anjali; James, A. R.; Kolekar, Y. D.; Ramana, C. V.

2018-05-01

We report on the combined experimental and theoretical simulation results of lead-free ferroelectrics, Ba(1-x)CaxTiO3 (x = 0.0-0.3) and BaTi(1-y)ZryO3 (y = 0.0-0.2), synthesized by standard solid state reaction method. First principles density functional calculations are used to investigate the electronic structure, dynamical charges, and spontaneous polarization of these compounds. In addition, the structural, ferroelectric, piezoelectric, and dielectric properties are studied using extensive experiments. The X-ray diffraction and temperature dependent Raman spectroscopy studies indicate that the calcium (Ca) substituted compositions exhibit a single phase crystal structure, while zirconium (Zr) substituted compositions are biphasic. The scanning electron micrographs reveal the uniform and highly dense microstructure. The presence of polarization-electric field and strain-electric field hysteresis loops confirms the ferroelectric and piezoelectric nature of all the compositions. Our results demonstrate higher values for polarization, percentage strain, piezoelectric coefficients, and electrostrictive coefficient compared to those existing in the literature. For smaller substitutions of Ca and Zr in BaTiO3, a direct piezoelectric coefficient (d33) is enhanced, while the highest d33 value (˜300 pC/N) is observed for BaTi0.96Zr0.04O3 due to the biphasic ferroelectric behavior. Calculation of Born effective charges indicates that doping with Ca or Zr increases the dynamical charges on Ti as well as on O and decreases the dynamical charge on Ba. An increase in the dynamical charges on Ti and O is ascribed to the increase in covalency of Ti-O bond that reduces the polarizability of the crystal. A broader range of temperatures is demonstrated to realize the stable phase in the Ca substituted compounds. The results indicate enhancement in the temperature range of applicability of these compounds for device applications. The combined theoretical and experimental study is

Orthorhombic-tetragonal phase coexistence and enhanced piezo-response at room temperature in Zr, Sn, and Hf modified BaTiO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalyani, Ajay Kumar; Brajesh, Kumar; Ranjan, Rajeev, E-mail: rajeev@materials.iisc.ernet.in

2014-06-23

The effect of Zr, Hf, and Sn in BaTiO{sub 3} has been investigated at close composition intervals in the dilute concentration limit. Detailed structural analysis by x-ray and neutron powder diffraction revealed that merely 2 mol. % of Zr, Sn, and Hf stabilizes a coexistence of orthorhombic (Amm2) and tetragonal (P4mm) phases at room temperature. As a consequence, all the three systems show substantial enhancement in the longitudinal piezoelectric coefficient (d{sub 33}), with Sn modification exhibiting the highest value ∼425 pC/N.

Composition, response to pressure, and negative thermal expansion in M IIB IVF 6 (M = Ca, Mg; B = Zr, Nb) [Composition, response to pressure, and negative thermal expansion in A IIB IVF 6; A - Ca, Mg, B - Zr, Nb

DOE PAGES

Hester, Brett R.; Hancock, Justin C.; Lapidus, Saul H.; ...

2016-12-27

CaZrF 6 has recently been shown to combine strong negative thermal expansion (NTE) over a very wide temperature range (at least 10–1000 K) with optical transparency from mid-IR into the UV range. Variable-temperature and high-pressure diffraction has been used to determine how the replacement of calcium by magnesium and zirconium by niobium(IV) modifies the phase behavior and physical properties of the compound. Similar to CaZrF 6, CaNbF 6 retains a cubic ReO 3-type structure down to 10 K and displays NTE up until at least 900 K. It undergoes a reconstructive phase transition upon compression to ~400 MPa at room temperature and pressure-induced amorphization above ~4 GPa. Prior to the first transition, it displays very strong pressure-induced softening. MgZrF 6 adopts a cubic ( Fmmore » $$\\bar{3}$$m) structure at 300 K and undergoes a symmetry-lowering phase transition involving octahedral tilts at ~100 K. Immediately above this transition, it shows modest NTE. Its’ thermal expansion increases upon heating, crossing through zero at ~500 K. Unlike CaZrF 6 and CaNbF 6, it undergoes an octahedral tilting transition upon compression (~370 MPa) prior to a reconstructive transition at ~1 GPa. Cubic MgZrF 6 displays both pressure-induced softening and stiffening upon heating. MgNbF 6 is cubic ( Fm$$\\bar{3}$$m) at room temperature, but it undergoes a symmetry-lowering octahedral tilting transition at ~280 K. It does not display NTE within the investigated temperature range (100–950 K). Furthermore the replacement of Zr(IV) by Nb(IV) leads to minor changes in phase behavior and properties, the replacement of the calcium by the smaller and more polarizing magnesium leads to large changes in both phase behavior and thermal expansion.« less

Composition, response to pressure, and negative thermal expansion in M IIB IVF 6 (M = Ca, Mg; B = Zr, Nb) [Composition, response to pressure, and negative thermal expansion in A IIB IVF 6; A - Ca, Mg, B - Zr, Nb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hester, Brett R.; Hancock, Justin C.; Lapidus, Saul H.

CaZrF 6 has recently been shown to combine strong negative thermal expansion (NTE) over a very wide temperature range (at least 10–1000 K) with optical transparency from mid-IR into the UV range. Variable-temperature and high-pressure diffraction has been used to determine how the replacement of calcium by magnesium and zirconium by niobium(IV) modifies the phase behavior and physical properties of the compound. Similar to CaZrF 6, CaNbF 6 retains a cubic ReO 3-type structure down to 10 K and displays NTE up until at least 900 K. It undergoes a reconstructive phase transition upon compression to ~400 MPa at room temperature and pressure-induced amorphization above ~4 GPa. Prior to the first transition, it displays very strong pressure-induced softening. MgZrF 6 adopts a cubic ( Fmmore » $$\\bar{3}$$m) structure at 300 K and undergoes a symmetry-lowering phase transition involving octahedral tilts at ~100 K. Immediately above this transition, it shows modest NTE. Its’ thermal expansion increases upon heating, crossing through zero at ~500 K. Unlike CaZrF 6 and CaNbF 6, it undergoes an octahedral tilting transition upon compression (~370 MPa) prior to a reconstructive transition at ~1 GPa. Cubic MgZrF 6 displays both pressure-induced softening and stiffening upon heating. MgNbF 6 is cubic ( Fm$$\\bar{3}$$m) at room temperature, but it undergoes a symmetry-lowering octahedral tilting transition at ~280 K. It does not display NTE within the investigated temperature range (100–950 K). Furthermore the replacement of Zr(IV) by Nb(IV) leads to minor changes in phase behavior and properties, the replacement of the calcium by the smaller and more polarizing magnesium leads to large changes in both phase behavior and thermal expansion.« less

Electrodeposition of hydroxyapatite coating on Mg-4.0Zn-1.0Ca-0.6Zr alloy and in vitro evaluation of degradation, hemolysis, and cytotoxicity.

PubMed

Guan, Ren-Guo; Johnson, Ian; Cui, Tong; Zhao, Tong; Zhao, Zhan-Yong; Li, Xue; Liu, Huinan

2012-04-01

A novel biodegradable Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy was successfully produced using a series of metallurgical processes; including melting, casting, rolling, and heat treatment. The hardness and ultimate tensile strength of the alloy sheets increased to 71.2HV and 320 MPa after rolling and then aging for 12 h at 175°C. These mechanical properties were sufficient for load-bearing orthopedic implants. A hydroxyapatite (HA) coating was deposited on the Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy using a novel coating process combining alkali heat pretreatment, electrodeposition, and alkali heat posttreatment. The microstructure, composition, and phases of the Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy and HA coating were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The degradation, hemolysis, and cytocompatibility of the HA-coated and uncoated Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy were studied in vitro. The corrosion potential (E(corr)) of Mg-4.0Zn-1.0Ca-0.6Zr alloy (-1.72 V) was higher than Mg (-1.95 V), Mg-0.6Ca alloy (-1.91 V) and Mg-1.0Ca alloy (-1.97 V), indicating the Mg-Zn-Ca-Zr alloy would be more corrosion resistant. The initial corrosion potential of the HA-coated Mg alloy sample (-1.51 V) was higher than the uncoated sample (-1.72 V). The hemolysis rates of the HA-coated and uncoated Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy samples were both <5%, which met the requirements for implant materials. The HA-coated and uncoated Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy samples demonstrated the same cytotoxicity score as the negative control. The HA-coated samples showed a slightly greater relative growth rate (RGR%) of fibroblasts than the uncoated samples. Both the HA-coated and uncoated Mg-4.0Zn-1.0Ca-0.6Zr (wt %) alloy provided evidence of acceptable cytocompatibility for medical applications. Copyright © 2012 Wiley Periodicals, Inc.

Atomic layer deposited ZrO2 nanofilm on Mg-Sr alloy for enhanced corrosion resistance and biocompatibility.

PubMed

Yang, Qiuyue; Yuan, Wei; Liu, Xiangmei; Zheng, Yufeng; Cui, Zhenduo; Yang, Xianjin; Pan, Haobo; Wu, Shuilin

2017-08-01

The biodegradability and good mechanical property of magnesium alloys make them potential biomedical materials. However, their rapid corrosion rate in the human body's environment impairs these advantages and limits their clinical use. In this work, a compact zirconia (ZrO 2 ) nanofilm was fabricated on the surface of a magnesium-strontium (Mg-Sr) alloy by the atomic layer deposition (ALD) method, which can regulate the thickness of the film precisely and thus also control the corrosion rate. Corrosion tests reveal that the ZrO 2 film can effectively reduce the corrosion rate of Mg-Sr alloys that is closely related to the thickness of the film. The cell culture test shows that this kind of ZrO 2 film can also enhance the activity and adhesion of osteoblasts on the surfaces of Mg-Sr alloys. The significance of the current work is to develop a zirconia nanofilm on biomedical MgSr alloy with controllable thickness precisely through atomic layer deposition technique. By adjusting the thickness of nanofilm, the corrosion rate of Mg-Sr alloy can be modulated, thereafter, the degradation rate of Mg-based alloys can be controlled precisely according to actual clinical requirement. In addition, this zirconia nanofilm modified Mg-Sr alloys show excellent biocompatibility than the bare samples. Hence, this work provides a new surface strategy to control the degradation rate while improving the biocompatibility of substrates. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Microscopic origins of the large piezoelectricity of leadfree (Ba,Ca)(Zr,Ti)O3

NASA Astrophysics Data System (ADS)

Nahas, Yousra; Akbarzadeh, Alireza; Prokhorenko, Sergei; Prosandeev, Sergey; Walter, Raymond; Kornev, Igor; Íñiguez, Jorge; Bellaiche, L.

2017-06-01

In light of directives around the world to eliminate toxic materials in various technologies, finding lead-free materials with high piezoelectric responses constitutes an important current scientific goal. As such, the recent discovery of a large electromechanical conversion near room temperature in (1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 compounds has directed attention to understanding its origin. Here, we report the development of a large-scale atomistic scheme providing a microscopic insight into this technologically promising material. We find that its high piezoelectricity originates from the existence of large fluctuations of polarization in the orthorhombic state arising from the combination of a flat free-energy landscape, a fragmented local structure, and the narrow temperature window around room temperature at which this orthorhombic phase is the equilibrium state. In addition to deepening the current knowledge on piezoelectricity, these findings have the potential to guide the design of other lead-free materials with large electromechanical responses.

Effects of Sm addition on electromagnetic interference shielding property of Mg-Zn-Zr alloys

NASA Astrophysics Data System (ADS)

Yang, Chubin; Pan, Fusheng; Chen, Xianhua; Luo, Ning

2017-06-01

The electromagnetic interference (EMI) shielding of Sm-containing magnesium alloys in the 30-1500 MHz testing frequency range was investigated by coaxial cable method. The results demonstrated that Mg-3Zn alloys displayed the best electromagnetic shielding property. When 0.5 wt% of Zr was added for crystal grain refinement, the shielding effectiveness (SE) was apparently reduced. The addition of the rare earth element Sm in ZK magnesium alloys can improve the electromagnetic interference shielding of magnesium alloys. The main reason for the differences in electromagnetic interference shielding of magnesium alloys was the change in conductivity. The addition of Zr in Mg-Zn alloys can refine the grains and consequently improve the grain boundary area significantly. Therefore, the number of irregularly arranged atoms at the grain boundaries increased, decreasing the conductivity of magnesium alloys and leading to a decrease in the electromagnetic interference shielding. Following the Sm addition, the Mg-Zn-Sm phase was precipitated at the grain boundaries and in cores. The precipitation of Sm-containing rare earth phases could consume the solid-soluted Zn atoms within the Mg, resulting in an increase in electrical conductivity and electromagnetic interference shielding improvement.

Phase controlled synthesis of (Mg, Ca, Ba)-ferrite magnetic nanoparticles with high uniformity

NASA Astrophysics Data System (ADS)

Wang, S. F.; Li, Q.; Zu, X. T.; Xiang, X.; Liu, W.; Li, S.

2016-12-01

(Mg, Ca, Ba)-ferrite magnetic nanoparticles were successfully synthesized through modifying the atomic ratio of polysaccharide and chelating agent at an optimal sintering temperature. In the process, the polysaccharide plays an important role in drastically shrinking the precursor during the gel drying process. In the metal-complex structure, M2+ ion active sites were coordinated by -OH of the water molecules except for EDTA anions. The MFe2O4 magnetic nanoparticles exhibited enhanced magnetic properties when compared with nano-MFe2O4 of similar particle size synthesized by other synthesis route reported in the literature. In particular, the sintering temperature improves the crystallinity and increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles significantly.

Super-microporous solid base MgO-ZrO2 composite and their application in biodiesel production

NASA Astrophysics Data System (ADS)

Su, Jiaojiao; Li, Yongfeng; Wang, Huigang; Yan, Xiaoliang; Pan, Dahai; Fan, Binbin; Li, Ruifeng

2016-10-01

The super-microporous microcrystalline MgO-ZrO2 nanomaterials (pore size 1-2 nm) was prepared successfully via a facile one-pot evaporation-induced self-assembly (EISA) method and employed in the transesterification of soybean oil and methanol. X-ray diffraction, transmission electron microscope, temperature programmed desorption of CO2, and N2 adsorption porosimetry were employed to characterize the nanocomposites. Nitrogen sorption isotherms revealed that these materials had large surface areas of more than 200 m2/g. Moreover, the sample with a Mg/Zr molar ratio of 0.5 and calcined at 400 °C showed high biodiesel yield (around 99% at 150 °C).

Ba2Mg(BO3)2:Bi3+ - A new phosphor with ultraviolet light emission

NASA Astrophysics Data System (ADS)

Lakshminarasimhan, N.; Jayakiruba, S.; Prabhavathi, K.

2017-10-01

Ultraviolet light emission was observed in a new Ba2Mg(BO3)2:Bi3+ phosphor. Bi3+ substitution for Ba2+ in the lattice was supplemented with K+ to maintain the charge neutrality. The samples of the formula Ba2-2xBixKxMg(BO3)2 [x = 0, 0.001, 0.01, 0.02, and 0.05] synthesized by solid state reaction were characterized using powder X-ray diffraction for their phase formation. Raman and diffuse reflectance UV-Vis spectroscopic techniques were used to obtain information on the vibrational modes and optical properties, respectively. The room temperature photoluminescence measurements revealed an ultraviolet emission at 370 nm when excited using 304 nm wavelength and the Stokes shift is 5868 cm-1.

Anisotropy of the Irreversibility Field for Zr-doped (Y,Gd)Ba 2<\\sub>Cu3<\\sub>O<7-x<\\sub> Thin Films up to 45 T

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tarantini, C.; Jaroszynski, J.; Kametani, F.

2011-01-01

The anisotropic irreversibility fieldBIrr of twoYBa2Cu3O7 x thin films dopedwith additional rare earth (RE)= (Gd, Y) and Zr and containing strong correlated pins (splayed BaZrO3 nanorods and RE2O3 anoprecipitates) has been measured over a very broad range up to 45 T at temperatures 56 K < T < Tc. We found that the experimental angular dependence of BIrr ( ) does not follow the mass anisotropy scaling BIrr ( ) = BIrr (0)(cos2 + 2 sin2 ) 1/2, where = (mc/mab)1/2 = 5 6 for the RE-doped Ba2Cu3O7 x (REBCO) crystals, mab and mc are the effective masses along themore » ab plane and the c-axis, respectively, and is the angle between B and the c-axis. For B parallel to the ab planes and to the c-axis correlated pinning strongly enhances BIrr , while at intermediate angles, BIrr ( ) follows the scaling behavior BIrr ( ) (cos2 + 2 RP sin2 ) 1/2 with the effective anisotropy factor RP 3 significantly smaller than the ass anisotropy would suggest. In spite of the strong effects of c-axis BaZrO3 nanorods, we found even greater enhancements of BIrr for fields along the ab planes than for fields parallel to the c-axis, as well as different temperature dependences of the correlated pinning contributions to BIrr for B//ab and B//c. Our results show that the dense and strong pins, which can now be incorporated into REBCO thin films in a controlled way, exert major and diverse effects on the measured vortex pinning anisotropy and the irreversibility field over wide ranges of B and T . In particular, we show that the relative contribution of correlated pinning to BIrr for B//c increases as the temperature increases due to the suppression of thermal fluctuations of vortices by splayed distribution of BaZrO3 nanorods.« less

Relationship between fabrication method and chemical stability of Ni-BaZr0.8Y0.2O3-δ membrane

NASA Astrophysics Data System (ADS)

Fang, Shumin; Wang, Siwei; Brinkman, Kyle S.; Su, Qing; Wang, Haiyan; Chen, Fanglin

2015-03-01

NiO effectively promotes the sintering of highly refractory Y-doped BaZrO3 (BZY) through the formation of BaY2NiO5, providing a simple and cost-effective method for the fabrication of dense BZY electrolyte and Ni-BZY hydrogen separation membrane at ∼1400 °C. Unfortunately, insulating BaCO3 and Y2O3 phases formed on the surface of BZY and Ni-BZY prepared by solid state reaction method with NiO after annealing in wet CO2. Ni-BZY membranes prepared from different methods suffered different degree of performance loss in wet H2 at 900 °C. The chemical instability of Ni-BZY is attributed to the formation of a secondary phase (BaY2O4) generated from the reduction of BaY2NiO5 in H2 during the sintering process. Both BaY2O4 and BaY2NiO5 react with H2O, and CO2 at elevated temperatures, generating insulating Ba(OH)2 and BaCO3 phases, respectively. The less BaY2O4 is formed in the fabrication process, the better chemical stability the Ni-BZY membranes possess. Therefore, a new Ni-BZY membrane is prepared through a judicial combination of BZY powders prepared from combined EDTA-citric and solid state reaction methods, and demonstrates exceptional chemical stability in H2O and CO2, enabling stable and even improved hydrogen flux in wet 50% CO2 at 900 °C.

Electrical properties and phase transition of Ba(Zr{sub 0.05}Ti{sub 0.95}){sub 1−x}(Fe{sub 0.5}Ta{sub 0.5}){sub x}O{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruea-In, C.; Rujijanagul, G., E-mail: rujijanagul@yahoo.com

2015-09-15

Highlights: • Properties of of Ba(Zr{sub 0.05}Ti{sub 0.95}){sub 1−x}(Fe{sub 0.5}Ta{sub 0.5}){sub x}O{sub 3} ceramics were investigated. • Small amount of dopant produced a large change in dielectric and phase transition. • A phase diagram of Ba(Zr{sub 0.05}Ti{sub 0.95}){sub 1−x}(Fe{sub 0.5}Ta{sub 0.5}){sub x}O{sub 3} ceramics was proposed. • Dielectric tunability increased with increasing x concentration. - Abstract: In this work, properties of Ba(Zr{sub 0.05}Ti{sub 0.95}){sub 1−x}(Fe{sub 0.5}Ta{sub 0.5}){sub x}O{sub 3} ceramics with 0.00≤ x ≤0.07 were investigated. The ceramics were fabricated by a solid state reaction technique. X-ray diffraction analysis indicated that all samples exhibited single phase perovskite. Examination of themore » dielectric spectra revealed that the Fe and Ta additives promoted a diffuse phase transition, and the two phase transition temperatures, as observed in the dielectric curve of pure Ba(Zr{sub 0.05}Ti{sub 0.95})O{sub 3}, merged into a single phase transition temperature for higher x concentrations. The transformation was confirmed by ferroelectric measurements. In addition, the doped ceramics exhibited high relative dielectric tunability, especially for higher x concentration samples.« less

Microstructure and hot compression deformation of the as-cast Mg-5.0Sn-1.5Y-0.1Zr alloy

NASA Astrophysics Data System (ADS)

Luo, Xiaoping; Kang, Li; Li, Qiushu; Chai, Yuesheng

2015-08-01

The hot compression deformation behavior and microstructure of as-cast Mg-5.0Sn-1.5Y-0.1Zr alloy were investigated by performing isothermal hot compression tests. The tests were conducted using a thermal mechanical simulator at 250-450 °C and strain rates ranging from 0.002 to 2 s-1, with a maximum deformation strain of 50 %. The effects of the deformation parameters on the microstructure evolution of the Mg-5.0Sn-1.5Y-0.1Zr alloy were discussed. The study revealed the flow behavior and the deformation mechanism of the Mg-5.0Sn-1.5Y-0.1Zr alloy. The dependence of flow stress on temperature and strain rate was described by a hyperbolic sine constitutive equation. Through regression analysis, the activation energy of 223.26 kJ mol-1 for plastic deformation was determined by considering flow stress at a strain rate of 0.2. Microstructure observation showed that dynamic recrystallization occurred extensively along grain boundaries at temperatures higher than 300 °C and strain rates lower than 0.02 s-1. This observation provides a theoretical basis for the manufacture and application of the Mg-5.0Sn-1.5Y-0.1Zr alloy.

In vivo comparative property study of the bioactivity of coated Mg-3Zn-0.8Zr alloy.

PubMed

Sun, Jin'e; Wang, Jingbo; Jiang, Hongfeng; Chen, Minfang; Bi, Yanze; Liu, Debao

2013-08-01

In this in vivo study, degradable Mg-3Zn-0.8Zr cylinders were coated with a calcium phosphorus compound (Ca-P) layer or a magnesium fluoride (MgF2) layer; uncoated Mg-3Zn-0.8Zr alloy was used as a control. These were then implanted intramedullary into the femora of nine Japanese big-ear white rabbits for implantation periods of 1, 2 and 3 months. During the postoperative observation period with radiographic examination, the results showed that the MgF2-coated implants were tolerated well compared to the Ca-P-coated implants and uncoated implants. Moreover, large amounts of cells, rich fibrillar collagen and calcium and phosphorus products were found on the surface of the MgF2-coated implants using scanning electron microscopy. Micro-computed tomography further showed a slight decrease in volume (23.85%) and a greater increase in new bone mass (new bone volume fraction=11.56%, tissue mineral density=248.81 mg/cm(3)) for the MgF2-coated implants in comparison to uncoated and Ca-P compound-coated implants after 3 months of implantation. Copyright © 2013 Elsevier B.V. All rights reserved.

Fundamental Study of the Development and Evaluation of Biodegradable Mg-Y-Ca-Zr Alloys as Novel Implant Materials

NASA Astrophysics Data System (ADS)

Da-Tren Chou

Degradable metals hold considerable promise as materials which exhibit higher mechanical properties than degradable polymers while corroding over time to alleviate complications such as stress-shielding and infection that is inherent to permanent, bioinert metallic biomaterials. Specifically, degradable magnesium (Mg) alloys have emerged as a promising alternative for orthopedic and craniofacial applications due to their positive bone remodeling behavior, good biocompatibility, and relatively high strength compared to polymers while exhibiting similar stiffness to natural bone. Increasing the strength to maintain device integrity during degradation while simultaneously controlling the rapid corrosion of Mg to reduce the risk of hydrogen gas accumulation and toxicity are ongoing paramount goals for optimizing Mg alloys for musculoskeletal applications. In order to address these goals, novel Mg-Y-Ca-Zr based alloys were developed with alloying elements judiciously selected to impart favorable properties. Processing techniques including solution heat treatment combined with hot extrusion were employed to further enhance the desired properties of the material namely, controlled corrosion, high strength and ductility, and minimal toxic response. Increasing the Y content contributed to improved corrosion resistance yielding corrosion rates similar to commercial Mg alloys. Hot extrusion was employed to reduce the grain size, thereby improving mechanical properties through the Hall-Petch relation. Extrusion yielded extremely high strength relative to other Mg alloys, values approaching that of iron-based alloys, due to the presence of Mg12YZn, a long period stacking order phase that served to impede dislocation propagation. Both as-cast and extruded Mg-Y-Ca-Zr alloys demonstrated excellent in vitro cytocompatibility eliciting high viability and proliferation of MC3T3 pre-osteoblast cells and human mesenchymal stem cells. Alloying elements Y and Zr were specifically shown

Difference between resistance degradation of fixed valence acceptor (Mg) and variable valence acceptor (Mn)-doped BaTiO3 ceramics

NASA Astrophysics Data System (ADS)

Yoon, Seok-Hyun; Randall, Clive A.; Hur, Kang-Heon

2010-09-01

The difference in the resistance degradation behavior was investigated between fixed valence acceptor (Mg) and the variable valence acceptor (Mn)-doped BaTiO3 ceramics with an increase of each acceptor concentration. Coarse-grained specimens with uniform grain sizes and different acceptor concentrations were prepared. In the case of Mg-doped BaTiO3, the time to degradation systematically decreased with the increase in Mg concentration. In contrast, there is a systematically increased time to degradation with the increase in Mn concentration in Mn-doped BaTiO3. The fast degradation by the increase in Mg concentration directly corresponded to an increase in the Warburg impedance and ionic transference number (tion) associated with an increase in oxygen vacancy concentration ([VO••]). On the other hand, no distinct Warburg impedance or ionic conduction contribution could be observed with the increase in Mn concentration. It is supposed that the increase in [VO••] is negligible in spite of the increase in acceptor Mn concentration, when it is compared to Mg-doped BaTiO3. The much lower [VO••] and more dominant electron/hole trapping effect due to multivalence nature of Mn are supposed to cause such a contrary degradation behavior between Mg and Mn-doped BaTiO3. Reoxidation in a slightly reducing atmosphere (N2) showed better resistance to degradation behavior than in a oxidizing air atmosphere in both Mg and Mn-doped BaTiO3, which is anticipated to be an increase in the electron/hole trapping sites. All these behaviors could be explained by the low temperature defect chemical model that shows difference in the defect structure between Mg and Mn-doped BaTiO3, and its dependence on the oxygen partial pressure (pO2) during reoxidation and cooling. Not only the [VO••], but also the density of electron/hole trap sites, are believed to be crucial in controlling resistance degradation.

A study on microstructure and corrosion resistance of ZrO2-containing PEO coatings formed on AZ31 Mg alloy in phosphate-based electrolyte

NASA Astrophysics Data System (ADS)

Zhuang, J. J.; Guo, Y. Q.; Xiang, N.; Xiong, Y.; Hu, Q.; Song, R. G.

2015-12-01

ZrO2-containing ceramic coatings formed on the AZ31 Mg alloy were fabricated in an alkaline electrolyte containing sodium phosphate and potassium fluorozirconate (K2ZrF6) by plasma electrolytic oxidation (PEO). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) techniques were used to study the phase structure and composition of the coatings. It is indicated that the coatings formed in the K2ZrF6-containing electrolyte were composed of MgO, MgF2 and t-ZrO2. Morphological investigation carried out by scanning electron microscopy (SEM) and stereoscopic microscopy, revealed that the uniformity of coatings increased and roughness of coatings decreased after the addition of K2ZrF6. Electrochemical investigation was achieved by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) test. The results showed that the PEO coating formed in K2ZrF6-containing electrolyte exhibited an improved corrosion resistance than that of the coating formed in K2ZrF6-free electrolyte. In addition, the polarization and EIS tests results both showed that the suitable concentration (2.5 g/l) of K2ZrF6 is of significant ability to improve the corrosion resistance of coatings. However, 5 g/l and 10 g/l K2ZrF6 has a negative effect on improving the corrosion resistance of PEO coatings compared with the coating formed in 2.5 g/l K2ZrF6-containing electrolyte.

Phase transition, crystal water and low thermal expansion behavior of Al{sub 2−2x}(ZrMg){sub x}W{sub 3}O{sub 12}·n(H{sub 2}O)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Fang; Liu, Xiansheng; Song, Wenbo

2014-10-15

Al{sub 2−2x}(ZrMg){sub x}W{sub 3}O{sub 12} for 0≤x≤1.0 are synthesized to reduce the phase transition temperature of Al{sub 2}W{sub 3}O{sub 12}. It is found that the incorporation of (ZrMg){sup 6+} into the lattice of Al{sub 2}W{sub 3}O{sub 12} not only reduces its orthorhombic-to-monoclinic phase transition temperature but also elevates its softening temperature, broadening its applicable temperature range considerably. Al{sub 2−2x}(ZrMg){sub x}W{sub 3}O{sub 12} with x<0.5 exhibit low coefficients of thermal expansion (CTEs) and non-hygroscopicity, while those for x≥0.7 are obviously hygroscopic and the CETs decrease with increasing the content of (ZrMg){sup 6+} so that Al{sub 0.2}(ZrMg){sub 0.9}W{sub 3}O{sub 12} and ZrMgW{submore » 3}O{sub 12} exhibit negative thermal expansion. Temperature-dependent Raman spectroscopic study shows the hardening of W–O bonds above 373 K which is attributed to the release of crystal water. The effect of crystal water on the thermal expansion property is discussed based on the hydrogen bond between H in crystal water and electronegative O in Al(ZrMg)–O–W linkages. - Graphical abstract: (a and b) Temperature dependent Raman spectra of Al{sub 2−x}(ZrMg){sub x}W{sub 3}O{sub 12} (x=0.1, 0.2), (c and d) Building block of a unit cell of Al{sub 2−x}(ZrMg){sub x}W{sub 3}O{sub 12}·n(H{sub 2}O) and schematic showing the effect of crystal water on Al(Zr, Mg)–O–W linkages. - Highlights: • (ZrMg){sup 6+} reduces orthorhombic-to-monoclinic phase transition of Al{sub 2}W{sub 3}O{sub 12}. • The incorporation of (ZrMg){sup 6+} elevates the softening temperature of Al{sub 2}W{sub 3}O{sub 12}. • Al{sub 2−2x}(ZrMg){sub x}W{sub 3}O{sub 12} (x<0.5) exhibit low CTEs and non-hygroscopicity. • Al{sub 0.2}(ZrMg){sub 0.9}W{sub 3}O{sub 12}·0.8H{sub 2}O and ZrMgW{sub 3}O{sub 12}·2H{sub 2}O present NTE. • Hydrogen bond between H in H{sub 2}O and O in Al(ZrMg)–O–W affects thermal expansion.« less

Effect of europium ion concentration on the structural and photoluminescence properties of novel Li2BaZrO4: Eu3+ nanocrystals

NASA Astrophysics Data System (ADS)

Ahemen, I.; Dejene, F. B.; Kroon, R. E.; Swart, H. C.

2017-12-01

This work reports the influence of Eu3+ ion concentration on the structure and photoluminescence properties of Li2BaZrO4 nanocrystals including its intrinsic quantum efficiency (IQE). Chemical bath method was employed in the synthesis procedure. X-ray diffraction results showed tetragonal phase for Eu3+ ion concentration in the range 1 and 7 mol% and cubic phase at 8 mol%. The presence of barium oxide (BaO) was confirmed from selected area electron diffraction (SAED). The excitation spectra for these phosphors consisted of broad charge transfer (CT) bands due to the combination of Zr4+ - O2- and Eu3+-O2- charge transfer states. Superimposed on the CT band were direct excitation levels of Eu3+ and Ba2+ ions, in the range 320-450 nm. At high Eu3+ ions concentrations, the intensities of CT bands decreased because some of the ions were coordinated with Ba2+ ions. Photoluminescence emissions for all the doped samples at room temperature appeared to be entirely from intraconfigurational Eu3+ emissions and depended both on the site symmetry as well as the ion concentration. The quadrupole-quadrupole multipolar process was found to be solely responsible for the luminescence quenching. The intensity parameters (Ω2 ,Ω4), asymmetry ratio, R0 and the average decay lifetime of the nanocrystals showed dependence on concentration. High internal quantum efficiency (IQE) values were obtained at low Eu3+ ion concentrations, but efficiency decreased with increasing ion concentration. The CIE coordinates values were comparable to existing red phosphors and in combination with the high IQE make this phosphor a good candidate for red light emitting applications.

Strong green fluorescent hydrogels with Ba2 MgSi2 O7 :Eu2+ phosphor embedded in cellulose.

PubMed

Zhang, Xinguo; Qin, Xingzhen; Chen, Hailan

2017-06-01

Non-cytotoxic and green-emitting fluorescent hydrogels were constructed from a cellulose solution containing Ba 2 MgSi 2 O 7 :Eu 2 + green phosphor in a NaOH/urea aqueous system. The structure, optical properties and cytotoxicity of these hydrogels were studied. The Ba 2 MgSi 2 O 7 :Eu 2 + phosphor particles were dispersed evenly in the cellulose hydrogel matrix. Good luminescent properties of Ba 2 MgSi 2 O 7 :Eu 2 + phosphor were maintained in the hydrogels, leading to strong green emission under ultraviolet excitation. Fluorescent hydrogels have no obvious cytotoxicity in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) proliferation test, and have potential use in in vivo applications like optical imaging and drug delivery. Copyright © 2016 John Wiley & Sons, Ltd.

Structures, phase transitions and microwave dielectric properties of the 6H perovskites Ba 3BSb 2O 9, B=Mg, Ca, Sr, Ba

NASA Astrophysics Data System (ADS)

Ling, Chris D.; Rowda, Budwy; Avdeev, Maxim; Pullar, Robert

2009-03-01

We present a complete temperature-composition phase diagram for Ba 3BSb 2O 9, B=Mg, Ca, Sr, Ba, along with their electrical behavior as a function of B. These compounds have long been recognized as 6H-type perovskites, but (with the exception of B=Mg) their exact structures and properties were unknown due to their low symmetries, temperature-dependent phase transitions, and difficulties in synthesizing pure samples. The full range of possible space group symmetries is observed, from ideal hexagonal P6 3/ mmc to monoclinic C2/ c to triclinic P1¯. Direct second-order transitions between these phases are plausible according to group theory, and no evidence was seen for any further intermediate phases. The phase diagram with respect to temperature and the effective ionic radius of B is remarkably symmetrical for B=Mg, Ca, and Sr. For B=Ba, a first-order phase transition to a locally distorted phase allows a metastable hexagonal phase to persist to lower temperatures than expected before decomposing around 600 K. Electrical measurements revealed that dielectric permittivity corrected for porosity does not change significantly as a function of B and is in a good agreement with the values predicted by the Clausius-Mossotti equation.

ZrO2 Layer Thickness Dependent Electrical and Dielectric Properties of BST/ZrO2/BST Multilayer Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahoo, S. K.; Misra, D.; Agrawal, D. C.

2011-01-01

Recently, high K materials play an important role in microelectronic devices such as capacitors, memory devices, and microwave devices. Now a days ferroelectric barium strontium titanate [Ba{sub x}Sr{sub 1-x}TiO{sub 3}, (BST)] thin film is being actively investigated for applications in dynamic random access memories (DRAM), field effect transistor (FET), and tunable devices because of its properties such as high dielectric constant, low leakage current, low dielectric loss, and high dielectric breakdown strength. Several approaches have been used to optimize the dielectric and electrical properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found thatmore » inserting a ZrO{sub 2} layer in between two BST layers results in a significant reduction in dielectric constant, loss tangent, and leakage current in the multilayer thin films. Also it is shown that the properties of multilayer structure are found to depend strongly on the sublayer thicknesses. In this work the effect of ZrO{sub 2} layer thickness on the dielectric, ferroelectric as well as electrical properties of BST/ZrO{sub 2}/BST multilayer structure is studied. The multilayer Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3}/ZrO{sub 2}/Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} film is deposited by a sol-gel process on the platinized Si substrate. The thickness of the middle ZrO{sub 2} layer is varied while keeping the top and bottom BST layer thickness as fixed. It is observed that the dielectric constant, dielectric loss tangent, and leakage current of the multilayer films reduce with the increase of ZrO{sub 2} layer thickness and hence suitable for memory device applications. The ferroelectric properties of the multilayer film also decrease with the ZrO{sub 2} layer thickness.« less

Ferroelectric, elastic, piezoelectric, and dielectric properties of Ba(Ti0.7Zr0.3)O3-x(Ba0.82Ca0.18)TiO3 Pb-free ceramics

NASA Astrophysics Data System (ADS)

Yuan, Ruihao; Xue, Deqing; Zhou, Yumei; Ding, Xiangdong; Sun, Jun; Xue, Dezhen

2017-07-01

We designed and synthesized a pseudo-binary Pb-free system, Ba(Ti0.7Zr0.3)O3-x(Ba0.82Ca0.18)TiO3, by combining a rhombohedral end (with only cubic to rhombohedral ferroelectric phase transition) and a tetragonal end (with only cubic to tetragonal ferroelectric phase transition). The established composition-temperature phase diagram is characterized by a tricritical point type morphotropic phase boundary (MPB), and the MPB composition has better ferroelectric, piezoelectric, and dielectric properties than the compositions deviating from MPB. Moreover, a full set of material constants (including elastic stiffness constants, elastic compliance constants, piezoelectric constants, dielectric constants, and electromechanical coupling factors) of the MPB composition are determined using a resonance method. The good piezoelectric performance of the MPB composition can be ascribed to the high dielectric constants, elastic softening, and large electromechanical coupling factor.

Incorporation of ZrO2 particles in the oxide layer formed on Mg by anodizing: Influence of electrolyte concentration and current modes.

PubMed

Sankara Narayanan, T S N; Lee, Min Ho

2016-02-15

The objectives of the present study are to ascertain, particle incorporation during the initial stages of microarc oxidation (MAO), feasibility of increasing the level of particle incorporation through manipulation of process variables and, the use of MgO-ZrO2 composite coatings either as a pre-treatment or as a post-treatment for MAO coated Mg. Anodic oxide coatings were prepared using 0.3M NaOH+15g/l ZrO2 and 3M NaOH+15g/l ZrO2 at 10V under direct current, pulsed current (PC) unipolar and PC bipolar modes. MAO coatings were prepared using 5g/l NaOH+15g/l Na2SiO3 at 250V under direct current mode for 2min. The study reveals that it is possible to incorporate ZrO2 particles in the anodic oxide layer, suggesting such a possibility during the initial stages of MAO. When the MgO-ZrO2 composite coating is used as a pre-treatment, it helps to reduce the size and density of the pores of the MAO coatings and increased the corrosion resistance. When it is used as a post-treatment, lamellar shaped Mg(OH)2 with a very high surface area is formed on the surface, which would be beneficial to impart a better bioactivity and to facilitate immobilization of biomolecules. Copyright © 2015. Published by Elsevier Inc.

Photoluminescence and thermoluminescence properties of Eu2+ doped and Eu2+ ,Dy3+ co-doped Ba2 MgSi2 O7 phosphors.

PubMed

Sao, Sanjay Kumar; Brahme, Nameeta; Bisen, D P; Tiwari, Geetanjali

2016-11-01

In this work, we report the preparation, characterization, comparison and luminescence mechanisms of Eu 2 + -doped and Eu 2 + ,Dy 3 + -co-doped Ba 2 MgSi 2 O 7 (BMSO) phosphors. Prepared phosphors were synthesized via a high temperature solid-state reaction method. All prepared phosphors appeared white. The phase structure, particle size, and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) analysis. The luminescence properties of the phosphors were investigated by thermoluminescence (TL) and photoluminescence (PL). The PL excitation and emission spectra of Ba 2 MgSi 2 O 7 :Eu 2 + showed the peak to be around 381 nm and 490 nm respectively. The PL excitation spectrum of Ba 2 MgSi 2 O 7 :Eu 2 + Dy 3 + showed the peak to be around 341 nm and 388 nm, and the emission spectrum had a broad band around 488 nm. These emissions originated from the 4f 6 5d 1 to 4f 7 transition of Eu 2 + . TL analysis revealed that the maximum TL intensity was found at 5 mol% of Eu 2 + doping in Ba 2 MgSi 2 O 7 phosphors after 15 min of ultraviolet (UV) light exposure. TL intensity was increased when Dy 3 + ions were co-doped in Ba 2 MgSi 2 O 7 :Eu 2 + and maximum TL intensity was observed for 2 mol% of Dy 3 + . TL emission spectra of Ba 1.95 MgSi 2 O 7 :0.05Eu 2 + and Ba 1.93 MgSi 2 O 7 :0.05Eu 2 + ,0.02Dy 3 + phosphors were found at 500 nm. TL intensity increased with UV exposure time up to 15 min, then decreased for the higher UV radiation dose for both Eu doping and Eu,Dy co-doping. The trap depths were calculated to be 0.54 eV for Ba 1.95 MgSi 2 O 7 :0.05Eu 2 + and 0.54 eV and 0.75 eV for Ba 1.93 MgSi 2 O 7 :0.05Eu 2 + ,0.02Dy 3 + phosphors. It was observed that co-doping with small amounts of Dy 3 + enhanced the thermoluminescence properties of Ba 2 MgSi 2 O 7 phosphor. Copyright © 2016 John Wiley & Sons, Ltd. [Correction added on 5 April 2016, after first online publication: The

Energy transfer between Eu-Mn and photoluminescence properties of Ba0.75Al11O17.25-BaMgAl10O17:Eu2+,Mn2+ solid solution

NASA Astrophysics Data System (ADS)

Zhou, Jun; Wang, Yuhua; Liu, Bitao; Li, Feng

2010-08-01

In order to evaluate the energy transfer between Eu-Mn in Ba0.75Al11O17.25-BaMgAl10O17 solid solution, Ba0.75Al11O17.25-BaMgAl10O17:Eu2+,Mn2+ phosphors were prepared by flux method. The crystal structure and the morphology of the solid solution were demonstrated by x-ray dirrfactometer and scanning electron microscopy. The photoluminescence mechanisms were explained by the energy transfer of Eu2+ to Mn2+ and the Dexter theory. A redshift of green emission peak and a decrease in decay time with the increase in Mn2+ concentration were observed. These phenomena are attributed to the formation of Mn2+ paired centers after analysis by a method of Pade approximations.

Flexible tensile strain sensor based on lead-free 0.5Ba (Ti0.8Zr0.2) O3-0.5(Ba0.7Ca0.3) TiO3 piezoelectric nanofibers

NASA Astrophysics Data System (ADS)

Xing, Lindong; Zhu, Ruijian; Wang, Zengmei; Wang, Fengxia; Kimura, Hideo

2017-09-01

Here, we report our study results of a flexible piezoelectric tensile strain sensor which is fabricated by synthesizing 0.5Ba (Zr0.2Ti0.8) O3-0.5(Ba0.7Ca0.3) TiO3 (0.5BZT-0.5BCT) nanofibers via an electrospinning process. Our nanofibers show an ultrahigh d33 of 275 pm V-1. 0.5BZT-0.5BCT nanofibers and MW-CNTs are dispersed in polydimethylsiloxane (PDMS) to fabricate a highly stretchable and flexible tensile sensor, and the multiple roles of the MW-CNTs are probed and demonstrated. This nanofiber-based piezoelectric tensile strain sensor shows great resolution and sensitivity under external mechanical deformation. It is suitable for applications in complex environments.

Arsenic and fluoride removal from contaminated drinking water with Haix-Fe-Zr and Haix-Zr resin beads.

PubMed

Phillips, Debra H; Sen Gupta, Bhaskar; Mukhopadhyay, Soumyadeep; Sen Gupta, Arup K

2018-06-01

The objective of the study was to carry-out batch tests to examine the effectiveness of Haix-Fe-Zr and Haix-Zr resin beads in the removal of As(III), As(V) and F - from groundwater with a similar geochemistry to a site where a community-based drinking water plant has been installed in West Bengal, India. The groundwater was spiked separately with ∼200 μg/L As(III) and As(V) and 5 mg/L F - . Haix-Zr resin beads were more effective than Haix-Fe-Zr resin beads in removing As(III) and As(V). Haix-Zr resin beads showed higher removal of As(V) compared to As(III). Haix-Zr resin beads removed As(V) below the WHO (10 μg/L) drinking water standards at 8.79 μg/L after 4 h of shaking, while As(III) was reduced to 7.72 μg/L after 8 h of shaking. Haix-Fe-Zr resin beads were more effective in removing F - from the spiked groundwater compared to Haix-Zr resin beads. Concentrations of F - decreased from 6.27 mg/L to 1.26 mg/L, which is below the WHO drinking water standards (1.5 mg/L) for F - , after 15 min of shaking with Haix-Fe-Zr resin beads. After 20 min of shaking in groundwater treated with Haix-Zr resin beads, F - concentrations decreased from 6.27 mg/L to 1.43 mg/L. In the removal of As(III), As(V), and F - from the groundwater, Haix-Fe-Zr and Haix-Zr resin beads fit the parabolic diffusion equation (PDE) suggesting that adsorption of these contaminants was consistent with inter-particle diffusion. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effect of Cr, Ti, V, and Zr Micro-additions on Microstructure and Mechanical Properties of the Al-Si-Cu-Mg Cast Alloy

NASA Astrophysics Data System (ADS)

Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

2016-05-01

Uniaxial static and cyclic tests were used to assess the role of Cr, Ti, V, and Zr additions on properties of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in as-cast and T6 heat-treated conditions. The microstructure of the as-cast alloy consisted of α-Al, eutectic Si, and Cu-, Mg-, and Fe-rich phases Al2.1Cu, Al8.5Si2.4Cu, Al5.2CuMg4Si5.1, and Al14Si7.1FeMg3.3. In addition, the micro-sized Cr/Zr/Ti/V-rich phases Al10.7SiTi3.6, Al6.7Si1.2TiZr1.8, Al21.4Si3.4Ti4.7VZr1.8, Al18.5Si7.3Cr2.6V, Al7.9Si8.5Cr6.8V4.1Ti, Al6.3Si23.2FeCr9.2V1.6Ti1.3, Al92.2Si16.7Fe7.6Cr8.3V1.8, and Al8.2Si30.1Fe1.6Cr18.8V3.3Ti2.9Zr were present. During solution treatment, Cu-rich phases were completely dissolved, while the eutectic silicon, Fe-, and Cr/Zr/Ti/V-rich intermetallics experienced only partial dissolution. Micro-additions of Cr, Zr, Ti, and V positively affected the alloy strength. The modified alloy in the T6 temper during uniaxial tensile tests exhibited yield strength of 289 MPa and ultimate tensile strength of 342 MPa, being significantly higher than that for the Al-Si-Cu-Mg base. Besides, the cyclic yield stress of the modified alloy in the T6 state increased by 23 pct over that of the base alloy. The fatigue life of the modified alloy was substantially longer than that of the base alloy tested using the same parameters. The role of Cr, Ti, V, and Zr containing phases in controlling the alloy fracture during static and cyclic loading is discussed.

Improving High-Temperature Tensile and Low-Cycle Fatigue Behavior of Al-Si-Cu-Mg Alloys Through Micro-additions of Ti, V, and Zr

NASA Astrophysics Data System (ADS)

Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

2015-07-01

High-temperature tensile and low-cycle fatigue tests were performed to assess the influence of micro-additions of Ti, V, and Zr on the improvement of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in the as-cast condition. Addition of transition metals led to modification of microstructure where in addition to conventional phases present in the Al-7Si-1Cu-0.5Mg base, new thermally stable micro-sized Zr-Ti-V-rich phases Al21.4Si4.1Ti3.5VZr3.9, Al6.7Si1.2TiZr1.8, Al2.8Si3.8V1.6Zr, and Al5.1Si35.4Ti1.6Zr5.7Fe were formed. The tensile tests showed that with increasing test temperature from 298 K to 673 K (25 °C to 400 °C), the yield stress and tensile strength of the present studied alloy decreased from 161 to 84 MPa and from 261 to 102 MPa, respectively. Also, the studied alloy exhibited 18, 12, and 5 pct higher tensile strength than the alloy A356, 354 and existing Al-Si-Cu-Mg alloy modified with additions of Zr, Ti, and Ni, respectively. The fatigue life of the studied alloy was substantially longer than those of the reference alloys A356 and the same Al-7Si-1Cu-0.5Mg base with minor additions of V, Zr, and Ti in the T6 condition. Fractographic analysis after tensile tests revealed that at the lower temperature up to 473 K (200 °C), the cleavage-type brittle fracture for the precipitates and ductile fracture for the matrix were dominant while at higher temperature fully ductile-type fracture with debonding and pull-out of cracked particles was identified. It is believed that the intermetallic precipitates containing Zr, Ti, and V improve the alloy performance at increased temperatures.

Luminescence in microcrystalline green emitting Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor

NASA Astrophysics Data System (ADS)

Panse, V. R.; Kokode, N. S.; Shinde, K. N.; Dhoble, S. J.

2018-03-01

Green emitting Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor powders were synthesized via the wet chemical synthesis and the luminescent proprieties were studied when excited at 380 nm and present a dominant and strong green luminescence peak at 543 nm, due to D-F transition. The preparation of Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor powders were confirmed by X-ray diffraction (XRD) results without any secondary or impurity phases. The size and morphology of the Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor powders were further examined by scanning electron microscopy (SEM). Photoluminescence (PL) results have shown strongest green emission at 543 nm, which is originated due to 5D4-7F5 transition of Tb3+ ion, for the Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor. The addition of concentration Tb3+ was greatly improved the photoluminescence properties of present phosphors. The present study suggests that the Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor is a strong candidate as a green component for phosphor-converted white light-emitting diodes (LEDs).

Preparation and Characterization of BaTiO3-PbZrTiO3 Coating for Pyroelectric Energy Harvesting

NASA Astrophysics Data System (ADS)

Raghavendra, R. M.; Praneeth, K. P. S. S.; Dutta, Soma

2017-01-01

Harvesting energy from waste heat is a promising field of research as there are significant energy recovery opportunities from various waste thermal energy sources. The present study reports pyroelectric energy harvesting using thick film prepared from a (x)BaTiO3-(1 - x)PbZr0.52Ti0.48O3 (BT-PZT) solid solution. The developed BT-PZT system is engineered to tune the ferro to paraelectric phase transition temperature of it in-between the phase transition temperature of BaTiO3 (393 K) and PbZrTiO3 (573 K) with higher pyroelectric figure-of-merit (FOM). The temperature-dependent dielectric behavior of the material has revealed the ferro- to paraelectric phase transition at 427 K with a maximum dielectric constant of 755. The room-temperature (298 K) pyroelectric coefficient (Pi) of the material was obtained as 738.63 μC/m2K which has yielded a significantly high FOM of 1745.8 J m-3 K-2. The enhancement in pyroelectric property is attributed to the morphotopic phase transition between tetragonal and rhombohedral PZT phases in the BT-PZT system. The developed BT-PZT system is capable of generating a power output of 1.3 mW/m2 near the Curie temperature with a constant rate (0.11 K/s) of heating. A signal conditioning circuit has been developed to rectify the time-varying current and voltage signals obtained from the harvester during heating cycles. The output voltage generated by the pyroelectric harvester has been stored in a capacitor for powering wearable electronics.

The modification of BaCe{sub 0.5}Zr{sub 0.3}Y{sub 0.2}O{sub 3–δ} with copper oxide: Effect on the structural and transport properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyagaeva, Yu. G.; Vdovin, G. K.; Nikolaenko, I. V.

2016-06-15

The effect of the content of CuO additive on the sinterability, phase composition, microstructure, and electrical properties of BaCe{sub 0.5}Zr{sub 0.3}Y{sub 0.2}O{sub 3–δ} proton-conducting material is studied. Ceramic samples were produced by the citrate–nitrate synthesis method with the addition of 0, 0.25, 0.5, and 1% CuO. It is shown that the relative density of the samples containing 0.5 and 1% CuO is higher than 94% at a sintering temperature of 1450°C, whereas the relative density of the material is no higher than 85% at a lower content of the sintering additive. From the data of X-ray diffraction analysis and scanningmore » electron microscopy, it is established that the introduction of a small CuO content (0.25%) is inadequate for single-phase and high-dense ceramics to be formed. The conductivity and scanning electron microscopy data show that the sample with BaCe{sub 0.5}Zr{sub 0.3}Y{sub 0.2}O{sub 3–δ} + 0.5% CuO composition possesses high total and ionic conductivities as well as a high degree of microstructural stability after hydrogen reduction of the ceramics. The citrate–nitrate method modified by the introduction of a small CuO content can be recommended for the production of single-phase, gas-tight, and high-conductivity electrolytes based on both BaCeO{sub 3} and BaZrO{sub 3}.« less

Site Redistribution, Partial Frozen-in Defect Chemistry, and Electrical Properties of Ba1-x(Zr,Pr)O3-δ.

PubMed

Antunes, Isabel; Mikhalev, Sergey; Mather, Glenn Christopher; Kharton, Vladislav Vadimovich; Figueiras, Fábio Gabriel; Alves, Adriana; Rodrigues, Joana; Correia, Maria Rosário; Frade, Jorge Ribeiro; Fagg, Duncan Paul

2016-09-06

Changes in nominal composition of the perovskite (ABO3) solid solution Ba1-x(Zr,Pr)O3-δ and adjusted firing conditions at very high temperatures were used to induce structural changes involving site redistribution and frozen-in point defects, as revealed by Raman and photoluminescence spectroscopies. Complementary magnetic measurements allowed quantification of the reduced content of Pr. Weak dependence of oxygen stoichiometry with temperature was obtained by coulometric titration at temperatures below 1000 °C, consistent with a somewhat complex partial frozen-in defect chemistry. Electrical conductivity measurements combined with transport number and Seebeck coefficient measurements showed prevailing electronic transport and also indicated trends expected for partial frozen-in conditions. Nominal Ba deficiency and controlled firing at very high temperatures allows adjustment of structure and partial frozen-in defect chemistry, opening the way to engineer relevant properties for high-temperature electrochemical applications.

Enhanced bioactivity of Mg-Nd-Zn-Zr alloy achieved with nanoscale MgF2 surface for vascular stent application.

PubMed

Mao, Lin; Shen, Li; Chen, Jiahui; Wu, Yu; Kwak, Minsuk; Lu, Yao; Xue, Qiong; Pei, Jia; Zhang, Lei; Yuan, Guangyin; Fan, Rong; Ge, Junbo; Ding, Wenjiang

2015-03-11

Magnesium (Mg) alloys have revolutionized the application of temporary load-bearing implants as they meet both engineering and medical requirements. However, rapid degradation of Mg alloys under physiological conditions remains the major obstacle hindering the wider use of Mg-based implants. Here we developed a simple method of preparing a nanoscale MgF2 film on Mg-Nd-Zn-Zr (denoted as JDBM) alloy, aiming to reduce the corrosion rate as well as improve the biological response. The corrosion rate of JDBM alloy exposed to artificial plasma is reduced by ∼20% from 0.337 ± 0.021 to 0.269 ± 0.043 mm·y(-1) due to the protective effect of the MgF2 film with a uniform and dense physical structure. The in vitro cytocompatibility test of MgF2-coated JDBM using human umbilical vein endothelial cells indicates enhanced viability, growth, and proliferation as compared to the naked substrate, and the MgF2 film with a nanoscale flakelike feature of ∼200-300 nm presents a much more favorable environment for endothelial cell adhesion, proliferation, and alignment. Furthermore, the animal experiment via implantation of MgF2-coated JDBM stent to rabbit abdominal aorta confirms excellent tissue compatibility of the well re-endothelialized stent with no sign of thrombogenesis and restenosis in the stented vessel.

Density functional calculations of carbon substituting for Zr in barium zirconate

NASA Astrophysics Data System (ADS)

Al-Hadidi, Meaad; Goss, J. P.; Al-Ani, Oras A.; Briddon, P. R.; Rayson, M. J.

2017-06-01

Oxide perovskites such as BaZrO3 possess many significant properties which render them useful in many technological and scientific applications such as sensors, optoelectronics, laser frequency doubling and high capacity memory cells. Several methods are used to grow BaZrO3 crystal, and organic species that may be present during growth lead to carbon contamination. We have investigated, using density-functional theory, the role of carbon impurities on the structural, electrical and electronic properties of carbon substituting of Zr in cubic barium zirconate. The local vibrational modes of the defect centre has been calculated and we suggest it is a feasible route to experimental identification

Cryogenic and elevated temperature strengths of an Al-Zn-Mg-Cu alloy modified with Sc and Zr

NASA Astrophysics Data System (ADS)

Senkova, S. V.; Senkov, O. N.; Miracle, D. B.

2006-12-01

The effect of minor additions of Sc and Zr on tensile properties of two developmental Al-Zn-Mg-Cu alloys was studied in the temperature range -196°C to 300°C. Due to the presence of Sc and Zr in a fine dispersoid form, both low-temperature and elevated temperature strengths of these alloys are much higher than those of similar 7000 series alloys that do not contain these elements. After short holding times (up to 10 hours) at 205°C, the strength of these alloys is higher than those of high-temperature Al alloys 2219-T6 and 2618-T6; however, the latter alloys show better strength after longer holding times. It is suggested that additional alloying of the Sc-containing Al-Zn-Mg-Cu alloys with other dispersoid-forming elements, such as Ni, Fe, Mn, and Si, with a respective decrease in the amounts of Zn and Mg may further improve the elevated temperature strength and decrease the loss of strength with extended elevated temperature exposure.

Mechanical properties and biocorrosion resistance of the Mg-Gd-Nd-Zn-Zr alloy processed by equal channel angular pressing.

PubMed

Zhang, Junyi; Kang, Zhixin; Wang, Fen

2016-11-01

A Mg-Gd-Nd-Zn-Zr alloy was processed by equal channel angular pressing (ECAP) at 375°C. The grain size of Mg-Gd-Nd-Zn-Zr alloy was refined to ~2.5μm with the spherical precipitates (β1 phase) distributing in the matrix. The mechanical properties of ECAPed alloy were significantly improved as a result of the grain refinement and precipitation strengthening. The corrosion rate of the ECAPed magnesium alloy in simulated body fluid dramatically decreased from 0.236mm/a to 0.126mm/a due to the strong basal texture and refined microstructure. This wrought magnesium alloy shows potentials in biomedical application. Copyright © 2016 Elsevier B.V. All rights reserved.

Dielectric properties of PVDF/0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 composites

NASA Astrophysics Data System (ADS)

Pandey, Bablu K.; Chandra, K. P.; Kolte, Jayant; Kulkarni, A. R.; Jayaswal, S. K.; Prasad, K.

2018-05-01

Ceramic powder of 0.50(Ba0.7Ca0.3)TiO3-0.50Ba(Zr0.2Ti0.8)O3(BCZT50) at morphotropic phase boundary composition was prepared usingsolid-statesynthesis technique followed by extensive high energy ball milling. The crystal symmetry, space group and unit cell dimensions were determined from the X-raydiffraction data of BCZT50 using FullProf software andthe average crystallite size was estimated using Williamson-Hall approach. FTIR spectra confirmed the formation of perovskite type solid solutions. The prepared ceramic powder was utilized to prepare lead-free (1- x)PVDF/xBCZT50 ceramic-polymer composites with x = 0.025, 0.05, 0.10, 0.15, 0.20, 0.25 were prepared using melt- mixing technique. The distribution of BCZT50 particles in the PVDF matrix were examined using anoptical microscope. Filler concentration dependent real and imaginary parts of dielectric constant data followed exponential growth types of variation. The low value of tanδ(˜10-2) can be advantageous forsensing/detectionapplications.

Effects of Er3+ and Pr3+ Substitution on Structural, Dielectric, Ferroelectric and Photoluminescence Properties of the BaTi0.9Zr0.1O3 Ceramic

NASA Astrophysics Data System (ADS)

Zouari, I.; Sassi, Z.; Seveyrat, L.; Perrin, V.; Zghal, S.; Abdelmoula, N.; Lebrun, L.; Khemakhem, H.

2017-07-01

BaTi0.9Zr0.1O3 (BZT), Ba1- x Ln2 x/3□ x/3Ti0.9Zr0.1O3 (with x = 0.5% mol and Ln = Er3+) (BZT-Er) and Ba1- x Ln2 x/3□ x/3Ti0.9Zr0.1O3 (with x = 0.5% mol and Ln = Pr3+) (BZT-Pr) were prepared via the conventional solid-state reaction method. X-ray diffraction showed that all these ceramics were in the single perovskite phase at room temperature (RT). The temperature dependence of dielectric behavior was investigated in the temperature range 25-225°C and exhibited a classical ferroelectric behavior. A slight decrease of the Curie temperature ( T C) with Pr3+ and Er3+ substitution was observed in addition to an increase in the maximum dielectric permittivity ( \\varepsilon_{r {max} }^' }} ) of about 40% for the BZT-Er. At RT, the ferroelectric and piezoelectric coefficients were decreased for BZT-Pr, but were maintained for BZT-Er with a piezoelectric coefficient ( d 33) of 185 pC/N, a planar electromechanical coupling factor of 30%, and a remanent polarization of 11.6 μC/cm2. The Raman bands as a function of temperature confirmed the paraelectric-ferroelectric phase transition of all those ceramics. The photoluminescence spectra showed that strong red (615 nm and 645 nm) and bright green (523 nm and 545 nm) emission bands were obtained, under excitation by laser at 488 nm at RT, for BZT-Pr and BZT-Er, respectively. These multifunctional materials showed a significant technological promise in coupling device applications.

Electrocaloric effects in the lead-free Ba (Zr ,Ti )O3 relaxor ferroelectric from atomistic simulations

NASA Astrophysics Data System (ADS)

Jiang, Zhijun; Prokhorenko, Sergei; Prosandeev, Sergey; Nahas, Y.; Wang, D.; Íñiguez, Jorge; Defay, E.; Bellaiche, L.

2017-07-01

Atomistic effective Hamiltonian simulations are used to investigate electrocaloric (EC) effects in the lead-free Ba (Zr0.5Ti0.5)O3 (BZT) relaxor ferroelectric. We find that the EC coefficient varies nonmonotonically with the field at any temperature, presenting a maximum that can be traced back to the behavior of BZT's polar nanoregions. We also introduce a simple Landau-based model that reproduces the EC behavior of BZT as a function of field and temperature, and which is directly applicable to other compounds. Finally, we confirm that, for low temperatures (i.e., in nonergodic conditions), the usual indirect approach to measure the EC response provides an estimate that differs quantitatively from a direct evaluation of the field-induced temperature change.

Optical and vibrational spectroscopy of Ba0.85Ca0.15Zr0.1Ti0.9O3 modified lithium borate glass ceramics

NASA Astrophysics Data System (ADS)

Viswanath, Pamarti; Prashanth, Sadhu Sai Pavan; Molli, Muralikrishna; Wicram, Jaschin Prem; Sai Muthukumar, V.

2018-04-01

Glass ceramics are excellent replacement for single crystalline materials which are expensive and difficult to fabricate. In this context, we have attempted to fabricate glass nanocomposites comprising of Lithium Borate glass matrix embedded with lead free ferroelectric Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT). Both of these functional materials are known to exhibit excellent ferroelectric behavior and are currently explored for various device applications. We have prepared these novel glass nanocomposite using melt-quenching techniquein various chemical composition involving different molar ratio. x(Ba0.85Ca0.15Zr0.1Ti0.9O3)-(1-x)(Li2O.2B2O3) where (x=0.1,0.2,0.3,0.4). The as-quenched samples exhibited amorphous nature as revealed by X-ray Diffraction studies. With the increase in BCZT content we have observed significant alteration in optical bandgap and Urbach energy. The tailoring of optical properties by tuning the structure was probed by Raman vibrational spectroscopy which confirmed the dominant role played by BCZT as a network modifier in these borate glasses. Concomitantly, these glass nanocomposites were found to be excellent UV absorbers.

Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} and Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} (0{<=}x{<=}1): synthesis, structure and dielectric properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thirumal, M.; Jawahar, I.N.; Surendiran, K.P.

2002-11-20

Oxides belonging to the families Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} and Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} were synthesized by the solid state reaction route. Sintering temperatures of 1300 deg. C led to oxides with disordered (cubic) perovskite structure. However, on sintering at 1425 deg. C hexagonally ordered structures were obtained for Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} over the entire range (0{<=}x{<=}1) of composition, while for Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} the ordered structure exists in a limited range (0{<=}x{<=}0.5). The dielectric constant is close to 30 for the Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} family of oxides while the Mg analoguesmore » have lower dielectric constant of {approx}18 in the range 50 Hz to 500 kHz. At microwave frequencies (5-7 GHz) dielectric constant increases with increase in niobium concentration (22-26) for Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9}; for Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} it varies between 12 and 14. The 'Zn' compounds have much higher quality factors and lower temperature coefficient of resonant frequency compared to the 'Mg' analogues.« less

Domain structures and local switching in lead-free piezoceramics Ba0.85Ca0.15Ti0.90Zr0.10O3

NASA Astrophysics Data System (ADS)

Turygin, A. P.; Neradovskiy, M. M.; Naumova, N. A.; Zayats, D. V.; Coondoo, I.; Kholkin, A. L.; Shur, V. Ya.

2015-08-01

Lead-free piezoelectrics are becoming increasingly important in view of environmental problems of currently used lead-based perovskites such as lead zirconate titanate (PZT). One of the recent candidates for PZT replacement, solid solutions of BaZr0.2Ti0.8O3 and Ba0.7Ca0.3TiO3, are investigated in this work by piezoresponse force microscopy. Coexistence of the tetragonal and rhombohedral phases in this material is observed, which probably gives rise to easy polarization switching due to multiple domain states. The period of observed domain lamella scales with the grain size obeying well-known square root dependence characteristic of BaTiO3 ceramics. Domain switching and relaxation are investigated at the nanoscale as a function of the applied voltage and duration of the applied voltage pulses. The observed distortion of piezoresponse hysteresis loops near grain boundaries is attested to the increased concentration of defects. Nanoscale piezoelectric properties of these materials are discussed.

Characterization of Localized Filament Corrosion Products at the Anodic Head on a Model Mg-Zn-Zr Alloy Surface

DOE PAGES

Rossouw, David; Fu, Dong; Leonard, Donovan N.; ...

2017-02-15

In this study, localized filament corrosion products at the anodic head on a model Mg-1%Zn-0.4%Zr alloy surface were characterized by electron microscopy techniques of site-specific lamella prepared by focused ion beam milling. It is revealed that the anodic head propagates underneath a largely intact thin and dense MgO surface film and comprises dense aggregates of nano-crystalline MgO within a nano-porous Mg(OH) 2 network. In conclusion, the findings contribute new supportive direct imaging insight into the source of the enhanced H 2 evolution that accompanies anodic dissolution of Mg and its alloys.

Characterization of Localized Filament Corrosion Products at the Anodic Head on a Model Mg-Zn-Zr Alloy Surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rossouw, David; Fu, Dong; Leonard, Donovan N.

In this study, localized filament corrosion products at the anodic head on a model Mg-1%Zn-0.4%Zr alloy surface were characterized by electron microscopy techniques of site-specific lamella prepared by focused ion beam milling. It is revealed that the anodic head propagates underneath a largely intact thin and dense MgO surface film and comprises dense aggregates of nano-crystalline MgO within a nano-porous Mg(OH) 2 network. In conclusion, the findings contribute new supportive direct imaging insight into the source of the enhanced H 2 evolution that accompanies anodic dissolution of Mg and its alloys.

Capture of Hydrogen Using ZrNi

NASA Technical Reports Server (NTRS)

Patton, Lisa; Wales, Joshua; Lynch, David; Parrish, Clyde

2005-01-01

Water, as ice, is thought to reside in craters at the lunar poles along with CH4 and H2 . A proposed robotic mission for 2012 will utilize metal/metal hydrides for H2 recovery. Specifications are 99% capture of H2 initially at 5 bar and 100C (or greater), and degassing completely at 300C. Of 47-systems examined using the van't Hoff equation, 4 systems, Mg/MgH2, Mg2Ni/Mg2NiH4, ZrNi/ZrNiH2.8, and Pd/PdH0.77, were considered likely candidates for further examination. It is essential, when selecting a system, to also examine questions regarding activation, kinetics, cyclic stability, and gas impurity effects. After considering those issues, ZrN1 was selected as the most promising candidate, as it is easily activated and rapidly forms ZrNiH 2.8 . In addition, it resists oxide poisoning by CO2, and H2O, while some oxidation by O2 is recommended for improved activation . The presence of hydrogen in the as received Zr-Ni alloy from Alfa Aesar posed additional technical problems. X-ray diffraction of the Zr-Ni powder (-325 mesh), with a Zr:Ni wt% ratio of 70:30, was found to consist of ZrH2, ZrNiH2.8, and ZrNi. ZrH2 in the alloy presented the risk that after degassing that both Zr and ZrNi would be present, and thus lead to erroneous results regarding the reactivity of ZrNi with H2 . Fortunately, ZrH2 is a highly stable hydride that does not degas H2 to any significant extent at temperatures below 300C. Based on equilibrium calculations for the decomposition of ZrH2, only 1 millionth of the hydride decomposed at 300C under a N2 atmosphere flowing at 25 ccm for 64 hours, the longest time for pretreatment employed in the investigation. It was possible, from the X-ray results and knowledge of the Zr:Ni ratio, to compute the composition of a pretreated specimen as being 76 wt% ZrNi and the balance ZrH2.

Novel approach to Zr powder production by smooth ZrCl4 bubbling through molten salt

NASA Astrophysics Data System (ADS)

Bae, Hyun-Na; Choi, Mi-Seon; Lee, Go-Gi; Kim, Seon-Hyo

2016-01-01

A reduction process using ZrCl4 bubbles as a reactant was investigated to produce zirconium metals. ZrCl4 vapor was bubbled through the lance in the bath, in which Mg melt and MgCl2 salt were separated. Zr powder was formed by a reduction of ZrCl4 bubbles in magnesium layer. However, the lance was clogged by the aggregate of zirconium occurred during ZrCl4 vapor injecting leading to interruption of ZrCl4 supply into the bath. This phenomenon could be caused by the presence of magnesium at the lance tip, which passes through MgCl2 salt during bubbling, and then zirconium was formed in the forms of intermetallic compounds with aluminum. In this study, the effect of molten salt on the troubled phenomena was investigated and it was verified that CaCl2 with relatively low Weber number meaning relatively high surface tension as molten salt is effective in inhibiting the lance clogging phenomena. Then, a few micrometer-sized Zr powder with the high purity of 91.6 wt% was obtained smoothly without the formation of intermetallic compound.

Formation of metal nanoparticles in MgF2, CaF2 and BaF2 crystals under the electron beam irradiation

NASA Astrophysics Data System (ADS)

Bochkareva, Elizaveta S.; Sidorov, Alexander I.; Yurina, Uliana V.; Podsvirov, Oleg A.

2017-07-01

It is shown experimentally that electron beam action with electrons energies of 50 and 70 keV on MgF2, CaF2 and BaF2 crystals results in local formation in the crystal near-surface layer of Mg, Ca or Ba nanoparticles which possess plasmon resonance. In the case of MgF2 spheroidal nanoparticles are formed, in the cases of CaF2 and BaF2 - spherical. The formation of metal nanoparticles is confirmed by computer simulation in dipole quasistatic approximation. The dependence of absorption via electron irradiation dose is non-linear. It is caused by the increase of nanoparticles concentration and by the increase of nanoparticles sizes during irradiation. In the irradiated zones of MgF2 crystals, for irradiation doses less than 80 mC/cm2, the intense luminescence in a visible range appears. The practical application of fabricated composite materials for multilevel optical information recording is discussed.

Effect of the addition of MgF2 and NaF on the thermal, optical and magnetic properties of fluoride glasses for sensing applications

NASA Astrophysics Data System (ADS)

Wang, Yujie; Wang, Shuangbao; Deng, Saifu; Liu, Jianting; Zhang, Jiahui

2017-10-01

Optical glass was very important for the development of optical fiber sensor. In this paper, a new type fluoride glass of ZrF4-BaF2-AlF3-NaF-MgF2(ZBANM) was synthesized for sensing application which has low loss and high magneto-optical coefficient, and it was found that the glass system had at least 60% transmittance from 3.5 μm to 7 μm and smallest verdet constant of 4.628E-5/(rad A-1) at 632.8 nm. The relationship among the compositions of sample glass with its thermal property, optical absorptivity and magnetic-optical coefficients was respectively studied with Thermal Gravimetric-Differential Thermal Analyzer, Fourier Transform infrared spectroscopy and a home-made magneto optical bench. The study indicated that transmittance of fluoride glass structure had been obviously improved after moderate content of Mg2+ and Na+ was doped. Simultaneously, with the molar ratio of alkaline-earth ions Mg increased, the Verdet constant of fluoride glass was increased. And the glass structure with composition of 48%ZrF4-24%BaF2-6%AlF3-8%NaF-14%MgF2 exhibited a small molar absorptivity and the largest Verdet constant of 2.853E-4/(rad A-1).

Structural and mechanical properties of evaporated pure and mixed MgF2-BaF2 thin films

NASA Astrophysics Data System (ADS)

Thielsch, Roland; Pommies, Matthieu; Heber, Joerg; Kaiser, Norbert; Ullmann, Jens

1999-09-01

To grow dense and hard MgF2 films substrate temperatures of about 300 degrees C are required, which unfortunately leads to high tensile film stress and the ability of crack formation. Lowering tensile stress in MgF2 films can be achieved by admixture a second fluoride material of higher cation radius than Mg2+. While former investigation were performed with non-heated films the purpose of the present work was to verify the behavior of mixed films when deposited at elevated substrate temperatures. One of the promising add material is BaF2 which enables evaporation of appropriate pre-mixed materials from a single source. The BaF2 content in the mixed films was varied from 3 to 55 mol percent in the MgF2 host. Optical, mechanical, and structural properties of samples deposited at different substrate temperatures have been studied by spectral photometry, IR spectroscopy, ex situ measurement of mechanical stress, x-ray diffraction, and -reflectometry, RBS, as well as investigation of surface morphology.

New intermetallic MIrP (M=Ti, Zr, Nb, Mo) and MgRuP compounds related with MoM'P (M'=Ni and Ru) superconductor

NASA Astrophysics Data System (ADS)

Kito, Hijiri; Iyo, Akira; Wada, Toshimi

2011-01-01

Using a cubic-anvil high-pressure apparatus, ternary iridium phosphides MIrP (M=Ti, Zr, Nb, Mo) and MgRuP have been prepared by reaction of stoichiometric amounts of each metal and phosphide powders at around 2 Gpa and above 1523 K for the first time. The structure of these compounds prepared at high-pressure has been characterized by X-ray powder diffraction. Diffraction lines of these compounds are assigned by the index of the Co2Si-type structure. The electrical resistivity and the d.c magnetic susceptibility of MIrP (M=Ti, Zr, Nb, Mo) have measured at low temperatures. Unfortunately, no superconducting transition for MIrP (M=Ti, Zr, Nb, Mo) and MgRuP are observed down to 2 K.

Two-Step Reactive Aid Sintering of BaZr0.8Y0.2O3- δ Proton-Conducting Ceramics

NASA Astrophysics Data System (ADS)

Wang, Siwei; Chen, Yan; Zhang, Lingling; Ren, Cong; Chen, Fanglin; Brinkman, Kyle S.

2015-12-01

Ceramic-based proton conductors enable high-temperature hydrogen economy applications such as hydrogen separation membranes, fuel cells, and steam electrolyzers. BaZr0.8Y0.2O3- δ (BZY) proton-conducting oxide possesses the highest level of proton conductivity reported to date, but poor sinterability hinders its widespread utilization. In this paper, we report a two-step reactive aid sintering (TRAS) method involving the introduction of BaCO3 and B2O3-Li2O for the preparation of dense BZY ceramics sintered at 1500°C. The resulting BZY samples showed a pure perovskite structure with a dramatic increase in the relative density to 91.5%. In addition, the shrinkage during sintering was improved to 19.3% by a TRAS method as compared to 2.6% by the conventional solid date reaction method. The bulk conductivity was improved due to enhanced densification, while the grain boundary conductivity decreased due to the blocking behavior of the sintering aid resulting in a decrease in the total conductivity of the samples.

Two-Step Reactive Aid Sintering of BaZr 0.8Y 0.2O 3-δ Proton-Conducting Ceramics

DOE PAGES

Wang, Siwei; Chen, Yan; Zhang, Lingling; ...

2015-10-14

Ceramic-based proton conductors enable high-temperature hydrogen economy applications such as hydrogen separation membranes, fuel cells, and steam electrolyzers. BaZr 0.8Y 0.2O 3-δ (BZY) proton-conducting oxide possesses the highest level of proton conductivity reported to date, but poor sinterability hinders its widespread utilization. Here, we report a two-step reactive aid sintering (TRAS) method involving the introduction of BaCO 3 and B 2O 3-Li 2O for the preparation of dense BZY ceramics sintered at 1500°C. The resulting BZY samples showed a pure perovskite structure with a dramatic increase in the relative density to 91.5%. In addition, the shrinkage during sintering was improvedmore » to 19.3% by a TRAS method as compared to 2.6% by the conventional solid date reaction method. Moreover, the bulk conductivity was improved due to enhanced densification, while the grain boundary conductivity decreased due to the blocking behavior of the sintering aid resulting in a decrease in the total conductivity of the samples.« less

Contrasting the Role of Mg and Ba Doping on the Microstructure and Thermoelectric Properties of p-Type AgSbSe2.

PubMed

Liu, Zihang; Shuai, Jing; Geng, Huiyuan; Mao, Jun; Feng, Yan; Zhao, Xu; Meng, Xianfu; He, Ran; Cai, Wei; Sui, Jiehe

2015-10-21

Microstructure has a critical influence on the mechanical and functional properties. For thermoelectric materials, deep understanding of the relationship of microstructure and thermoelectric properties will enable the rational optimization of the ZT value and efficiency. Herein, taking AgSbSe2 as an example, we first report a different role of alkaline-earth metal ions (Mg(2+) and Ba(2+)) doping in the microstructure and thermoelectric properties of p-type AgSbSe2. For Mg doping, it monotonously increases the carrier concentration and then reduces the electrical resistivity, leading to a substantially enhanced power factor in comparison to those of other dopant elements (Bi(3+), Pb(2+), Zn(2+), Na(+), and Cd(2+)) in the AgSbSe2 system. Meanwhile, the lattice thermal conductivity is gradually suppressed by point defects scattering. In contrast, the electrical resistivity first decreases and then slightly rises with the increased Ba-doping concentrations due to the presence of BaSe3 nanoprecipitates, exhibiting a different variation tendency compared with the corresponding Mg-doped samples. More significantly, the total thermal conductivity is obviously reduced with the increased Ba-doping concentrations partially because of the strong scattering of medium and long wavelength phonons via the nanoprecipitates, consistent with the theoretical calculation and analysis. Collectively, ZT value ∼1 at 673 K and calculated leg efficiency ∼8.5% with Tc = 300 K and Th = 673 K are obtained for both AgSb0.98Mg0.02Se2 and AgSb0.98Ba0.02Se2 samples.

Sequentially evaporated thin Y-Ba-Co-O superconducting films on microwave substrates

NASA Technical Reports Server (NTRS)

Valco, G. J.; Rohrer, N. J.; Warner, J. D.; Bhasin, K. B.

1989-01-01

The development of high T sub c superconducting thin films on various microwave substrates is of major interest in space electronic systems. Thin films of YBa2Cu3O(7-Delta) were formed on SrTiO3, MgO, ZrO2 coated Al2O3, and LaAlO3 substrates by multi-layer sequential evaporation and subsequent annealing in oxygen. The technique allows controlled deposition of Cu, BaF2 and Y layers, as well as the ZrO buffer layers, to achieve reproducibility for microwave circuit fabrication. The three layer structure of Cu/BaF2/Y is repeated a minimum of four times. The films were annealed in an ambient of oxygen bubbled through water at temperatures between 850 C and 900 C followed by slow cooling (-2 C/minute) to 450 C, a low temperature anneal, and slow cooling to room temperature. Annealing times ranged from 15 minutes to 5 hrs. at high temperature and 0 to 6 hr. at 450 C. Silver contacts for four probe electrical measurements were formed by evaporation followed with an anneal at 500 C. The films were characterized by resistance-temperature measurements, energy dispersive X-ray spectroscopy, X-ray diffraction, and scanning electron microscopy. Critical transition temperatures ranged from 30 K to 87 K as a function of the substrate, composition of the film, thicknesses of the layers, and annealing conditions. Microwave ring resonator circuits were also patterned on these MgO and LaAlO3 substrates.

Influence of Applied Voltage and Film-Formation Time on Microstructure and Corrosion Resistance of Coatings Formed on Mg-Zn-Zr-Ca Bio-magnesium Alloy

NASA Astrophysics Data System (ADS)

Yandong, Yu; Shuzhen, Kuang; Jie, Li

2015-09-01

The influence of applied voltage and film-formation time on the microstructure and corrosion resistance of coatings formed on a Mg-Zn-Zr-Ca novel bio-magnesium alloy has been investigated by micro-arc oxidation (MAO) treatment. Phase composition and microstructure of as-coated samples were analyzed by the x-ray diffraction, energy dispersive x-ray spectroscopy and scanning electron microscopy. And the porosity and average of micro-pore aperture of the surface on ceramic coatings were analyzed by general image software. Corrosion microstructure of as-coated samples was caught by a microscope digital camera. The long-term corrosion resistance of as-coated samples was tested in simulated body fluid for 30 days. The results showed that the milky white smooth ceramic coating formed on the Mg-Zn-Zr-Ca novel bio-magnesium alloy was a compound of MgO, Mg2SiO4 and MgSiO3, and its corrosion resistance was significantly improved compared with that of the magnesium substrate. In addition, when the MAO applied voltage were 450 V and 500 V and film-formation time were 9 min and 11 min, the surface micro-morphology and the corrosion resistance of as-coated samples were relatively improved. The results provided a theoretical foundation for the application of the Mg-Zn-Zr-Ca novel bio-magnesium alloy in biomedicine.

Fine-grained BaZr0.2Ti0.8O3 thin films for tunable device applications

NASA Astrophysics Data System (ADS)

Ying, Z.; Yun, P.; Wang, D. Y.; Zhou, X. Y.; Song, Z. T.; Feng, S. L.; Wang, Y.; Chan, H. L. W.

2007-04-01

A study of the structure and in-plane dielectric properties of BaZr0.2Ti0.8O3 thin film epitaxially grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) single-crystal substrates through pulsed-laser deposition has been carried out. X-ray diffraction measurements revealed a good crystallinity and tensile in-plane stress in the film. Fine grains with an average size of ˜20 nm were observed using atomic force microscopy. Curie temperature of the film was found to be ˜120 °C, which is 100 °C higher than that of the ceramic. Butterfly-shaped C-V curve confirmed the in-plane ferroelectric state in the film. A large dielectric tunability of ˜50% was found in the film.

Structure and electrical properties of <001> textured (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 lead-free piezoelectric ceramics

NASA Astrophysics Data System (ADS)

Ye, S. K.; Fuh, J. Y. H.; Lu, L.

2012-06-01

<001> textured (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCTZ) lead-free piezoelectric ceramics were prepared by templated-grain growth method using BaTiO3 as template. The degree of orientation and the microstructure of the ceramics with different amount of template were investigated. The electrical properties of the textured-ceramics in the optimized condition were dramatically enhanced compared with randomly-oriented BCTZ ceramics. The textured BCTZ ceramics showed high piezoelectric constants d33 = 470 pC/N and d31 = -170 pC/N, and high electromechanical coupling factors kp = 44% and k31 = 22%. In addition, the Curie point of the textured ceramics revealed an increase with the template content.

Enhanced Proton Conductivity in Y-Doped BaZrO3 via Strain Engineering.

PubMed

Fluri, Aline; Marcolongo, Aris; Roddatis, Vladimir; Wokaun, Alexander; Pergolesi, Daniele; Marzari, Nicola; Lippert, Thomas

2017-12-01

The effects of stress-induced lattice distortions (strain) on the conductivity of Y-doped BaZrO 3 , a high-temperature proton conductor with key technological applications for sustainable electrochemical energy conversion, are studied. Highly ordered epitaxial thin films are grown in different strain states while monitoring the stress generation and evolution in situ. Enhanced proton conductivity due to lower activation energies is discovered under controlled conditions of tensile strain. In particular, a twofold increased conductivity is measured at 200 °C along a 0.7% tensile strained lattice. This is at variance with conclusions coming from force-field simulations or the static calculations of diffusion barriers. Here, extensive first-principles molecular dynamic simulations of proton diffusivity in the proton-trapping regime are therefore performed and found to agree with the experiments. The simulations highlight that compressive strain confines protons in planes parallel to the substrate, while tensile strain boosts diffusivity in the perpendicular direction, with the net result that the overall conductivity is enhanced. It is indeed the presence of the dopant and the proton-trapping effect that makes tensile strain favorable for proton conduction.

Effects of Al addition on atomic structure of Cu-Zr metallic glass

NASA Astrophysics Data System (ADS)

Li, Feng; Zhang, Huajian; Liu, Xiongjun; Dong, Yuecheng; Yu, Chunyan; Lu, Zhaoping

2018-02-01

The atomic structures of Cu52Zr48 and Cu45Zr48Al7 metallic glasses (MGs) have been studied by molecular dynamic simulations. The results reveal that the molar volume of the Cu45Zr48Al7 MG is smaller than that of the Cu52Zr48 MG, although the size of the Al atom is larger than that of the Cu atom, implying an enhanced atomic packing density achieved by introducing Al into the ternary MG. Bond shortening in unlike atomic pairs Zr-Al and Cu-Al is observed in the Cu45Zr48Al7 MG, which is attributed to strong interactions between Al and (Zr, Cu) atoms. Meanwhile, the atomic packing efficiency is enhanced by the minor addition of Al. Compared with the Cu52Zr48 binary MG, the potential energy of the ternary MG decreases and the glass transition temperature increases. Structural analyses indicate that more Cu- and Al-centered full icosahedral clusters emerge in the Cu45Zr48Al7 MG as some Cu atoms are substituted by Al. Furthermore, the addition of Al leads to more icosahedral medium-range orders in the ternary MG. The increase of full icosahedral clusters and the enhancement of the packing density are responsible for the improved glass-forming ability of Cu45Zr48Al7.

Dielectric properties of Ba0.6Sr0.4TiO3-La(B0.5Ti0.5)O3 (B=Mg, Zn) ceramics.

PubMed

Xu, Yebin; Liu, Ting; He, Yanyan; Yuan, Xiao

2009-11-01

Ba(0.6)Sr(0.4)TiO(3)-La(B(0.5)Ti(0.5))O(3) (B = Mg, Zn) ceramics were prepared by a solid-state reaction method, and their microwave dielectric characteristics and tunability were investigated. The ferroelectric-dielectric solid solutions with cubic perovskite structures were obtained for compositions of 10 to 60 mol% La(Mg(0.5)Ti(0.5))O(3) and 10 to 50 mol% La(Zn(0.5)Ti(0.5))O(3). With the increase of linear oxide dielectric content, the dielectric constant and tunability were decreased and Qf was increased. Ba(0.6)Sr(0.4)TiO(3)-La(Mg(0.5)Ti(0.5))O(3) has better dielectric properties than Ba(0.6)Sr(0.4)TiO(3)-La(Zn(0.5)Ti(0.5))O(3). 0.9Ba(0.6)Sr(0.4)TiO(3)-0.1La(Mg(0.5)Ti(0.5))O(3) has a dielectric constant epsilon = 338.2, Qf = 979 GHz and a tunability of was 3.7% at 100 kHz under 1.67 kV/mm. The Qf value of 0.5Ba(0.6)Sr(0.4)TiO(3)- 0.5La(Mg(0.5)Ti(0.5))O(3) reached 9367 GHz, but the tunable properties were lost.

Luminescence Properties of Self-Activated Mm(VO4)2 (M = Mg, Ca, Sr, and Ba) Phosphors Synthesized by Solid-State Reaction Method.

PubMed

Min, Xin; Huang, Zhaohui; Fang, Minghao; Liu, Yan'gai; Tang, Chao; Wu, Xiaowen

2016-04-01

In this paper, M3(VO4)2 (M = Mg, Ca, Sr, and Ba) self-activated phosphors were prepared by a solid-state reaction method at 1,000 °C for 5 h. The phase formation and micrographs were analyzed by X-ray diffraction and scanning electron microscopy. The Ca3(VO4)2 phosphor does not show any emission peaks under excitation with ultraviolet (UV) light. However, the M3(VO4)2 (M = Mg, Sr, and Ba) samples are effectively excited by UV light chips ranging from 200 nm to 400 nm and exhibit broad emission bands due to the charge transfer from the oxygen 2p orbital to the vacant 3d orbital of the vanadium in the VO4. The color of these phosphors changes from yellow to light blue via blue-green with increasing ionic radius from Mg to Sr to Ba. The luminescence lifetimes and quantum yield decrease with the increasing unit cell volume and V-V distance, in the order of Mg3(VO4)2 to Sr3(VO4)2 to Ba3(VO4)2. The emission intensity decreases with the increase of temperatures, but presents no color shift. This confirms that these self-activated M3(VO4)2 phosphors can be suggested as candidates of the single-phase phosphors for light using UV light emitting diodes (LEDs).

Properties and Degradation of Polarization Reversal of Soft BaTiO3 Ceramics for Ferroelectric Thin-Film Devices

NASA Astrophysics Data System (ADS)

Thongrueng, Jirawat; Tsuchiya, Toshio; Masuda, Yoichiro; Fujita, Shigetaka; Nagata, Kunihiro

1999-09-01

Soft BaTiO3 ceramics having a very low coercive field of 65 V/mm were prepared by substituting 9 mol% Hf Zr for the Ti-site of BaTiO3, for applications to ferroelectric thin-film devices. Electrical properties of the soft BaTiO3 ceramics were measured and compared with those of normal BaTiO3 ceramics. By substituting Hf Zr for Ti-site, the phase transition temperatures were controlled, and we could select the preferred crystal structure from the tetragonal, orthorhombic and rhombohedral phases at room temperature. In addition, the preparation and characterization of the soft BaTiO3 thin-films using a sol-gel process were carried out.

BaFe2As2/Fe Bilayers with [001]-tilt Grain Boundary on MgO and SrTiO3 Bicrystal Substrates

NASA Astrophysics Data System (ADS)

Iida, K.; Haindl, S.; Kurth, F.; Hänisch, J.; Schulz, L.; Holzapfel, B.

Co-doped BaFe2As2 (Ba-122) can be realized on both MgO and SrTiO3 bicrystal substrates with [001]-tilt grain boundary by employing Fe buffer layers. However, an additional spinel (i.e. MgAl2O4) buffer between Fe and SrTiO3 is necessary since an epitaxial, smooth surface of Fe layer can not be grown on bare SrTiO3. Both types of bicrystal films show good crystalline quality.

Annealing induced effect on the physical properties of ion-beam sputtered 0.5 Ba(Zr0.2Ti0.8)O3 - 0.5 (Ba0.7Ca0.3)TiO3-δ ferroelectric thin films

NASA Astrophysics Data System (ADS)

Oliveira, M. J. S.; Silva, J. P. B.; Veltruská, Kateřina; Matolín, V.; Sekhar, K. C.; Moreira, J. Agostinho; Pereira, M.; Gomes, M. J. M.

2018-06-01

This work reports thermal annealing induced effect on the structural, optical, chemical and ferroelectric properties of ion-beam sputtered lead-free ferroelectric 0.5 Ba(Zr0.2Ti0.8)O3 - 0.5 (Ba0.7Ca0.3)TiO3-δ (0.5BZT-0.5BCT) thin films. X-ray diffraction studies reveal that the tetragonality increases with the annealing temperature (Ta), while photoluminescence and X-ray photoelectron spectroscopy studies confirm that this effect is associated with the annihilation of the oxygen vacancies as well as changes in the Ba2+ coordination. The films annealed at 750 °C show a remarkable remnant polarization of Pr = 45.0 μC/cm2, with a coercive field of 32 kV/cm. The temperature dependence of the spontaneous polarization of the 0.5BZT-0.5BCT film reveals a mean field behavior of the polarization and the fatigue study reveals that Pr only decreases 3% after passing 109 cycles. Therefore the high remnant polarization and its high Pr stability make these films as promising candidates for memory applications.

Epitaxial YBa2Cu3O7-x nanocomposite films and coated conductors from BaMO3 (M = Zr, Hf) colloidal solutions

NASA Astrophysics Data System (ADS)

Obradors, X.; Puig, T.; Li, Z.; Pop, C.; Mundet, B.; Chamorro, N.; Vallés, F.; Coll, M.; Ricart, S.; Vallejo, B.; Pino, F.; Palau, A.; Gázquez, J.; Ros, J.; Usoskin, A.

2018-04-01

Superconducting nanocomposites are the best material choice to address the performance required in power applications and magnets working under high magnetic fields. However, it is still challenging to sort out how to achieve the highest superconducting performance using attractive and competitive manufacturing processes. Colloidal solutions have been recently developed as a novel and very promising low cost route to manufacture nanocomposite coated conductors. Well dispersed and stabilized preformance nanoparticle solutions are first prepared with high concentrations and then mixed with the YBa2Cu3O7 metalorganic precursor solutions to generate colloidal solutions to grow the nanocomposite films. Here we demonstrate, for the first time, that non-reactive BaZrO3 and BaHfO3 perovskite preformed nanoparticles are suitable for growing high quality thin and thick films, and coated conductors with a homogeneous distribution and controlled particle size using this fabrication method. Additionally, we extend the nanoparticle content of the nanocomposites up to 20%-25% mol without any degradation of the superconducting properties. Thick nanocomposite films, up to 0.8 μm, have been prepared with a single deposition of low-fluorine solutions using an ink jet printing dispenser and we demonstrate that the preformed nanoparticles display only a very limited coarsening during the growth process and so high critical current densities J c (B) under high magnetic fields. These films show the highest critical currents achieved so far based on the colloidal solution approach, I c = 220 A/cm-w at 77 K and self-field, and they still have a high potential for further increase in the film thickness. Finally, we also show that nanocomposite YBa2Cu3O7-BaZrO3 coated conductors based on an alternating beam assisted deposited YSZ buffer layer on stainless steel metallic substrates can be developed based on these novel colloidal solutions. Non-reactive preformed oxide perovskite

Effect of Halide Flux on Physicochemical Properties of MgCl2-Based Molten Salts for Accelerating Zirconium Production: Thermodynamic Assessment

NASA Astrophysics Data System (ADS)

Shin, Jae Hong; Park, Joo Hyun

2016-09-01

The effective halide flux additive for increasing the density of MgCl2 mixture and for decreasing the activity of MgCl2 was investigated in order to improve the reaction efficiency between gaseous ZrCl4 and fresh Mg melt to produce zirconium sponge. Thermochemical computation using FactSageTM software was primarily carried out, followed by the experimental confirmation. The addition of CaCl2, BaCl2, MgF2, and CaF2 to the molten MgCl2 increases the density of the melts, indicating that these halide additives can be a candidate to increase the density of the MgCl2-based molten salts. Among them, BaCl2, MgF2, and CaF2 are the useful additives. The activity of MgCl2 can be reduced by the addition of BaCl2, KCl, NaCl, MgF2, and CaF2, among which the CaF2 is the most effective additive to reduce the activity of MgCl2 with the strongest negative deviation from an ideality. Thus, the addition of CaF2 to the MgCl2, forming the MgCl2-CaF2 binary melt, is the most effective way not only to increase the density of the melt but also to decrease the activity of MgCl2, which was experimentally confirmed. Consequently, the production rate of zirconium sponge by magnesiothermic reduction process can be accelerated by the addition of CaF2.

Structural, dielectric and ferroelectric studies of BZT doped Mg0.2Cu0.3Zn0.5Fe2O4 magnetoelectric composites

NASA Astrophysics Data System (ADS)

Khader, S. Abdul; Parveez, Asiya; Giridharan, N. V.; Sankarappa, T.

2018-05-01

The composites of ferrite-ferroelectric system (x) Mg0.2Cu0.3Zn0.5Fe2O4+ (1-x) Ba0.8Zr0.2TiO3 (x=15%, 30%, 45%) were synthesized by sintering mixtures of ferroelectric Ba0.8Zr0.2TiO3 (BZT) and ferrite component Mg0.2Cu0.3Zn0.5Fe2O4 (MCZF). The presences of two phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for MCZF ferrite and tetragonal perovskite structure for BZT and, both spinel and pervoskite structures for synthesized composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). Frequency dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at RT using HIOKI LCR HI-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The ferroelectric properties of synthesized composites were analyzed using a Precision ferroelectric tester. It is observed that the composites exhibited ferroelectric hysteresis with wide loops indicating lossy nature of composites.

Crystallisation of Ba1-xSrxZn2Si2O7 from BaO/SrO/ZnO/SiO2 glass with different ZrO2 and TiO2 concentrations

NASA Astrophysics Data System (ADS)

Vladislavova, Liliya; Kracker, Michael; Zscheckel, Tilman; Thieme, Christian; Rüssel, Christian

2018-04-01

The effect of different nucleation agents such as ZrO2 and TiO2 was investigated for a first time with respect to their crystallisation behaviour in the glass system BaO-SrO-ZnO-SiO2. In all studied glasses, a Ba1-xSrxZn2Si2O7 (0.1 ≤ x ≤ 0.9) solid solution crystallized. This phase was first described in 2015 to possess a similar structure as the high temperature phase of BaZn2Si2O7 and a thermal expansion close to zero or even negative. It may find applications e.g. as cook panels, telescope mirrors, and furnace windows. Kinetic parameters of the crystallisation process were determined by supplying different heating rates in a differential scanning calorimeter (DSC). The results were evaluated using the equations of Ozawa and Kissinger with respect to the activation energies. Furthermore, the Ozawa method was used for the determination of Avrami parameters, which provides further information on the nucleation and crystallisation processes. Scanning electron microscopy including electron backscatter diffraction (EBSD) was used to characterise the microstructure, to determine the crystallite size and the crystal orientation. For the characterisation of the occurring crystalline phases, X-ray diffraction was used.

Lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 nanowires for energy harvesting.

PubMed

Zhou, Zhi; Bowland, Christopher C; Malakooti, Mohammad H; Tang, Haixiong; Sodano, Henry A

2016-03-07

Lead-free piezoelectric nanowires (NWs) show strong potential in sensing and energy harvesting applications due to their flexibility and ability to convert mechanical energy to electric energy. Currently, most lead-free piezoelectric NWs are produced through low yield synthesis methods and result in low electromechanical coupling, which limit their efficiency as energy harvesters. In order to alleviate these issues, a scalable method is developed to synthesize perovskite type 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) NWs with high piezoelectric coupling coefficient. The piezoelectric coupling coefficient of the BZT-BCT NWs is measured by a refined piezoresponse force microscopy (PFM) testing method and shows the highest reported coupling coefficient for lead-free piezoelectric nanowires of 90 ± 5 pm V(-1). Flexible nanocomposites utilizing dispersed BZT-BCT NWs are fabricated to demonstrate an energy harvesting application with an open circuit voltage of up to 6.25 V and a power density of up to 2.25 μW cm(-3). The high electromechanical coupling coefficient and high power density demonstrated with these lead-free NWs produced via a scalable synthesis method shows the potential for high performance NW-based devices.

Multi-proxy Reconstructions of the Eastern Equatorial Pacific: Measuring Sr/Ca, Ba/Ca, and Li/Mg in Modern Corals Using ICP-OES

NASA Astrophysics Data System (ADS)

Cheung, A. H.; Cole, J. E.; Vetter, L.; Jimenez, G.; Thompson, D. M.; Tudhope, A. W.

2017-12-01

Sea surface temperature (SST) in the Eastern Equatorial Pacific (EEP) exhibits large variability on multiple timescales. These variations are often related to modes of climate variability that exert significant influence on global climate, such as the El Niño Southern Oscillation. However, the short length and sparsity of instrumental data in the EEP limits our ability to discern changes in this region. Geochemical signals in corals can help extend instrumental data further back in time. While δ18O and Sr/Ca are the most commonly analyzed geochemical tracers of SST in corals, they often have site-specific complications. Several alternatives (e.g., Li/Mg) have been proposed to overcome these challenges, but have yet to be applied to long climate records, in part due to the cost and time required to measure these elements. Here, we develop a new method that uses Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) to analyze Li/Mg, Sr/Ca, and Ba/Ca ratios in coral aragonite. We apply this method to two Porites spp. corals collected from the northern Galapagos archipelago (Wolf and Darwin Islands). We specifically assess the fidelity of Li/Mg and Sr/Ca to reconstruct SST, and Ba/Ca to reconstruct upwelling conditions. Our results confirm that both Li/Mg and Sr/Ca track SST. We show that despite analytical noise, downcore reconstructions of Li/Mg have the potential to provide additional information about SST that is not present in reconstructions generated from Sr/Ca alone. Skeletal Ba/Ca shows little relationship with upwelling, perhaps because of the distance of our sites from the center of upwelling in the southern Galapagos. These results demonstrate the potential for analyzing Sr, Li, Ba, Mg simultaneously in corals with a cost- and time- efficient method, which may be applied to coral paleoclimate sites worldwide.

Investigation of structural, ferroelectric, piezoelectric and dielectric properties of Ba0.92Ca0.08TiO3-BaTi0.96Zr0.04O3 lead-free electroceramics

NASA Astrophysics Data System (ADS)

Keswani, Bhavna C.; Patil, S. I.; Kolekar, Y. D.

2018-04-01

Lead free ferroelectric with composition 0.55Ba0.92Ca0.08TiO3-0.45BaTi0.96Zr0.04O3 (BCT8-BZT4) was synthesized by solid state reaction method and investigated their structural, ferroelectric, piezoelectric and dielectric properties. X-ray diffraction analysis shows that BCT8-BZT4 ceramic possess both tetragonal (space group P4mm) and orthorhombic (space group Amm2) crystal structure which was further confirmed from Raman spectra spectroscopy. The micronized grains were observed from scanning electron micrographs while the presence of polarization-electric field hysteresis loop confirms ferroelectric nature of BCT8-BZT4 ceramic. Higher values of maximum polarization (Pmax = 22.27 μC/cm2), remnant polarization (Pr = 11.61 μC/cm2), coercive electric field (Ec = 4.77 kV/cm) and direct piezoelectric coefficient (d33) approximately 185 pC/N were observed. The real part of dielectric constant with frequency shows the usual dielectric dispersion behaviour at RT. The observed properties show that the lead free BCT8-BZT4 ceramic is suitable for ferroelectric memory device, piezoelectric sensor, capacitor, etc. applications.

Electronic structure and O vacancy formation/migration in La0.825(Mg/Ca/Ba)0.125CoO3

NASA Astrophysics Data System (ADS)

Omotayo Akande, Salawu; Gan, Li-Yong; Schwingenschlögl, Udo

2016-04-01

The effect of A-site hole doping (Mg2+, Ca2+ or Ba2+) on the electronic and magnetic properties as well as the O vacancy formation and migration in perovskite LaCoO3 is studied using first-principles calculations. All three dopants are found to facilitate O vacancy formation. Substitution of La3+ with Ba2+/Mg2+ yields the lowest O vacancy formation energy for low/intermediate spin Co, implying that not only the structure but also the spin state of Co is a key parameter. Only for low spin Co the ionic radius is correlated with the O migration barrier. Enhanced migration for intermediate spin Co is ascribed to the availability of additional space at the transition state.

In vitro degradation behavior and biocompatibility of Mg-Nd-Zn-Zr alloy by hydrofluoric acid treatment.

PubMed

Mao, Lin; Yuan, Guangyin; Niu, Jialin; Zong, Yang; Ding, Wenjiang

2013-01-01

In this paper, Mg-Nd-Zn-Zr alloy (denoted as JDBM) coated with hydrofluoric acid (HF) chemical conversion film (MgF2) was researched as a potential biodegradable cardiovascular stent material. The microstructures, in vitro degradation and biocompatibility were investigated. The field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) showed that a compact MgF2 film was formed on the surface of JDBM. The corrosion rate decreased in artificial plasma from 0.337 to 0.253 mm·y(-1) and the electrochemical measurement demonstrated that the corrosion resistance of JDBM alloy could be obviously improved due to the protective MgF2 film on the surface of the substrate. Meanwhile, the hemolysis ratio of JDBM decreased from 52.0% to 10.1% and the cytotoxicity met the requirement of cellular application after HF treatment. In addition, JDBM and MgF2 film showed good anti-platelet adhesion, which is a very favorable property for implant material in contact with blood directly. Copyright © 2012 Elsevier B.V. All rights reserved.

The Effects of Spark-Plasma Sintering (SPS) on the Microstructure and Mechanical Properties of BaTiO3/3Y-TZP Composites

PubMed Central

Li, Jing; Cui, Bencang; Wang, Huining; Lin, Yuanhua; Deng, Xuliang; Li, Ming; Nan, Cewen

2016-01-01

Composite ceramics BaTiO3/3Y-TZP containing 0 mol %, 3 mol %, 5 mol %, 7 mol %, and 10 mol % BaTiO3 have been prepared by conventional sintering and spark-plasma sintering (SPS), respectively. Analysis of the XRD patterns and Raman spectra reveal that the phase composition of t-ZrO2, m-ZrO2, and BaTiO3 has been obtained. Our results indicate that SPS can be effective for the decrease in grain size and porosity compared with conventional sintering, which results in a lower concentration of m-ZrO2 and residual stress. Therefore, the fracture toughness is enhanced by the BaTiO3 phase through the SPS technique, while the behavior was impaired by the piezoelectric second phase through conventional sintering. PMID:28773445

In vitro and in vivo corrosion, mechanical properties and biocompatibility evaluation of MgF2-coated Mg-Zn-Zr alloy as cancellous screws.

PubMed

Li, Zhen; Shizhao, Sun; Chen, Minfang; Fahlman, Bradley Dean; Debao Liu; Bi, Hongwei

2017-06-01

Magnesium (Mg) and its alloys as biodegradable materials have received much attention in the orthopedics applications; however, the corrosion behavior of these metals in vivo remains challenging. In this work, a dense and nanoscale magnesium fluoride (MgF 2 ) coating was deposited on the surface of Mg-Zn-Zr (MZZ) alloy cancellous screw. The MZZ cancellous screw with MgF 2 coating maintained an integrated shape and high yield tensile stress after 30days immersion in SBF, comparing with the bare screw. Hydrogen releasing rate of the MZZ samples was suppressed at a lower level at the initial stage, which is in favour of the adhesion of the cells. And in vivo experiments indicated that MgF 2 -coated MZZ screws presented advantages in cytocompatibility, osteoconductivity and osteogenesis of cancellous bone in rabbits. Corrosion rate in vivo perfusion environment increased very slowly with time in long-term study, which was an opposite trend in vitro static immersion test. Moreover, maximum corrosion rate (CR max ), a critical calculation method of corrosion rate was introduced to predict fracture regions of the sample. The MZZ alloy with MgF 2 coating possesses a great potential for clinical applications for internal fracture fixation repair. Copyright © 2017 Elsevier B.V. All rights reserved.

Tensile and Compressive Responses of Ceramic and Metallic Nanoparticle Reinforced Mg Composites

PubMed Central

Tun, Khin Sandar; Wong, Wai Leong Eugene; Nguyen, Quy Bau; Gupta, Manoj

2013-01-01

In the present study, room temperature mechanical properties of pure magnesium, Mg/ZrO2 and Mg/(ZrO2 + Cu) composites with various compositions are investigated. Results revealed that the use of hybrid (ZrO2 + Cu) reinforcements in Mg led to enhanced mechanical properties when compared to that of single reinforcement (ZrO2). Marginal reduction in mechanical properties of Mg/ZrO2 composites were observed mainly due to clustering of ZrO2 particles in Mg matrix and lack of matrix grain refinement. Addition of hybrid reinforcements led to grain size reduction and uniform distribution of hybrid reinforcements, globally and locally, in the hybrid composites. Macro- and micro- hardness, tensile strengths and compressive strengths were all significantly increased in the hybrid composites. With respect to unreinforced magnesium, failure strain was almost unchanged under tensile loading while it was reduced under compressive loading for both Mg/ZrO2 and Mg/(ZrO2 + Cu) composites. PMID:28809245

High waterborne Mg does not attenuate the toxic effects of Fe, Mn, and Ba on Na+ regulation of Amazonian armored catfish tamoatá (Hoplosternum litoralle).

PubMed

Duarte, Rafael M; Benaduce, Ana Paula; Garcia, Luciano; Gomes, Levy C; Gomes, Adriana Chippari; Val, Adalberto L; Baldisserotto, Bernardo

2018-04-24

Formation water (FoW) is a by-product from oil and gas production and usually has high concentrations of soluble salts and metals. Calcium (Ca) and magnesium (Mg) have been shown to reduce the toxicity of metals to aquatic animals, and previous study showed that high waterborne Ca exerts mild effect against disturbances on Na + regulation in Amazonian armored catfish tamoatá (Hoplosternum littorale) acutely exposed to high Fe, Mn, and Ba levels. Here, we hypothesized that high Mg levels might also reduce the toxic effects of these metals on Na + regulation of tamoatá. The exposure to 5% FoW promoted an increase in Na + uptake and a rapid accumulation of Na + in all tissues analyzed (kidneyMg lowered Na + efflux rates and markedly inhibited Na + uptake, and also reduced both NKA activity and newly Na + accumulation in gills of fish. High Fe levels increased Na + net losses and inhibited Na + uptake in tamoatá. The diffusive Na + losses and the newly accumulated Na + in gills were reduced in fish exposed to high Mn and Ba. High waterborne Ba also inhibited NKA in gills, while both high Mn and Ba inhibited v-type H + -ATPase in kidney of tamoatá. High Mg did not lessen the toxic effect of Fe on Na + net fluxes, and reduced even more Na + uptake and the newly Na + accumulation in gills and plasma, and did not prevent the inhibition of both NKA and v-type H + -ATPases in kidney. Furthermore, Mg did not attenuate the effect of Mn on inhibition Na + uptake, keeping the activity of v-type H + -ATPase in kidney significantly lowered. High Mg levels mildly attenuated the effects of Ba in Na + balance by increasing the new accumulation of Na + in liver, and restore the activity of both NKA and v-type H + -ATPase in gills of tamoatá. Overall, high waterborne Mg does not have a strong contribution to, or have only minor effects, in protecting

Raman-Spektren der Hexathiohypodiphosphate des NH4, Mg, Ca, Sr und Ba

NASA Astrophysics Data System (ADS)

Pätzmann, Ulrich; Brockner, Wolfgang

1987-06-01

The title compounds have been prepared and their Raman spectra recorded. The observed frequencies of (NH4)4P2S6 and Mg2P2S6 are assigned on the basis of P2S64- units with D3d symmetry. The Raman spectra of the Calcium, Strontium and Barium compounds indicate symmetry splitting, therefore the P2S64- frequencies are assigned with C2h symmetry. This assignment is supported by the correlation D3d → C2h. It is concluded that Sr2P2S6 and Ba2P2S6 crystallize in the monoclinic modification II.

Crystal orientation dependence of the dielectric properties for epitaxial BaZr0.15Ti0.85O3 thin films

NASA Astrophysics Data System (ADS)

Miao, J.; Yuan, J.; Wu, H.; Yang, S. B.; Xu, B.; Cao, L. X.; Zhao, B. R.

2007-01-01

Epitaxial Ba0.15Zr0.85TiO3 (BZT) ferroelectric thin films with (001), (011), and (111) orientations were, respectively, grown on La0.67Sr0.33MnO3 (LSMO) buffered LaAlO3 substrates by pulsed laser deposition method. The dc electric-field dependence of permittivity and dielectric loss of (001)-, (011)-, and (111)-oriented BZT/LSMO heterostructures obeys the Johnson formula, and the ac electric-field dependence of that obeys the Rayleigh law under the subswitching field region. The anisotropic dielectric properties are attributed to the higher mobility of the charge carriers, the concentration of mobile interfacial domain walls, and boundaries in the (111)-oriental films than in the (110)- and (100)-oriented films.

Why Sn doping significantly enhances the dielectric properties of Ba(Ti1-xSnx)O3

NASA Astrophysics Data System (ADS)

Shi, Tao; Xie, Lin; Gu, Lin; Zhu, Jing

2015-02-01

Through appropriate doping, the properties of BaTiO3-based ferroelectrics can be significantly enhanced. To determine the physical process induced by the doping of Sn atoms in Ba(Ti0.8Sn0.2)O3, we performed high-resolution scanning transmission electron microscopy experiments and observed that the regions with low Sn content formed polar nano regions (PNRs) embedded in the matrix in Ba(Ti0.8Sn0.2)O3. The interactions among Sn, Ti, Ba and O atoms were determined using first principles calculations. Based on the characteristics of the electronic structure and crystal lattice strain fields, the effects of doping with Sn were investigated. The Sn doping not only changed the electronic structure of the crystal but also increased the dielectric properties of the PNRs. Moreover, the Sn doping was also responsible for the diffuse phase transition of the Ba(Ti1-xSnx)O3 material. The effects mentioned in this paper are universal in lead-free ferroelectrics, and similar elements such as Sb, Mg, and Zr may have the same functions in other systems. Thus, these results provide guidance for the design of the doping process and new systems of ferroelectric or relaxor materials.

Why Sn doping significantly enhances the dielectric properties of Ba(Ti1-xSnx)O3

PubMed Central

Shi, Tao; Xie, Lin; Gu, Lin; Zhu, Jing

2015-01-01

Through appropriate doping, the properties of BaTiO3-based ferroelectrics can be significantly enhanced. To determine the physical process induced by the doping of Sn atoms in Ba(Ti0.8Sn0.2)O3, we performed high-resolution scanning transmission electron microscopy experiments and observed that the regions with low Sn content formed polar nano regions (PNRs) embedded in the matrix in Ba(Ti0.8Sn0.2)O3. The interactions among Sn, Ti, Ba and O atoms were determined using first principles calculations. Based on the characteristics of the electronic structure and crystal lattice strain fields, the effects of doping with Sn were investigated. The Sn doping not only changed the electronic structure of the crystal but also increased the dielectric properties of the PNRs. Moreover, the Sn doping was also responsible for the diffuse phase transition of the Ba(Ti1-xSnx)O3 material. The effects mentioned in this paper are universal in lead-free ferroelectrics, and similar elements such as Sb, Mg, and Zr may have the same functions in other systems. Thus, these results provide guidance for the design of the doping process and new systems of ferroelectric or relaxor materials. PMID:25721479

New FCC Mg–Zr and Mg–Zr–ti deuterides obtained by reactive milling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guzik, Matylda N., E-mail: matylda.guzik@ife.no; Deledda, Stefano; Sørby, Magnus H.

2015-03-15

Results for binary Mg–Zr and ternary Mg–Zr–Ti mixtures ball milled at room temperature under reactive deuterium atmosphere (5.6–6.7 MPa) are reported. X-ray and neutron powder diffraction combined with Rietveld refinements show that two new cubic phases were formed during milling. Mg{sub 0.40}Zr{sub 0.60}D{sub 1.78} and Mg{sub 0.40}Zr{sub 0.26}Ti{sub 0.34}D{sub 1.98} crystallize with disordered face centered cubic metal atom arrangements. Results of differential scanning calorimetry and termogravimetric measurements demonstrate that both deuterides desorb deuterium at lower temperatures than MgD{sub 2}, ZrD{sub 2} or TiD{sub 2}; 528 and 575 K in the Mg–Zr–D and Mg–Zr–Ti–D system, respectively. Interestingly, Mg{sub 0.40}Zr{sub 0.26}Ti{sub 0.34}D{submore » 1.98} stores deuterium reversibly at 673 K and 10 MPa of D{sub 2}. - Graphical abstract: High resolution SR-PXD patterns obtained for Mg{sub 0.40}Zr{sub 0.60}D{sub 1.78} and first time reported Mg{sub 0.40}Zr{sub 0.26}Ti{sub 0.34}D{sub 1.98}. - Highlights: • Synthesis and characterization of Mg{sub 0.40}Zr{sub 0.60}D{sub 1.78} and Mg{sub 0.40}Zr{sub 0.26}Ti{sub 0.34}D{sub 1.98}. • New deuterides obtained by milling under H{sub 2} gas pressure in the order of a few MPa. • Phases desorb deuterium at temperature lower than corresponding binary deuterides. • Mg{sub 0.40}Zr{sub 0.26}Ti{sub 0.34}D{sub 1.98} stores hydrogen reversibly at 673 K and 10 MPa of D{sub 2}.« less

Fluorite transition metal hydride induced destabilization of the MgH2 system in MgH2/TMH2 multilayers ( TM=Sc , Ti, V, Cr, Y, Zr, Nb, La, Hf)

NASA Astrophysics Data System (ADS)

Tao, S. X.; Notten, P. H. L.; van Santen, R. A.; Jansen, A. P. J.

2010-09-01

The structural changes in MgH2 induced by contact with fluorite transition metal hydrides ( TMH2 , TM=Sc , Ti, V, Cr, Y, Zr, Nb, La, Hf) have been studied using density-functional theory calculations. Models of MgH2(rutile)/TiH2(fluorite) and MgH2(fluorite)/TiH2(fluorite) multilayers with different Mg:TM ratios have been designed. With a fixed thickness of the TMH2 layer, structure transformation of MgH2 from rutile to fluorite occurs with a decrease in thickness of the MgH2 layer. The hydrogen desorption energy from the fluorite MgH2 layer in the multilayers is significantly lower than that of the bulk rutile MgH2 . The structural deformation of the MgH2 layer due to the strain induced by TMH2 is found to be responsible for the destabilization of the Mg-H bond: the more structural deformation, the more destabilization of the Mg-H. Our results provide an important insight for the development of new hydrogen-storage materials with desirable thermodynamic properties.

Generating mixed morphology BaZrO3 artificial pinning centers for strong and isotropic pinning in BaZrO3-Y2O3 double-doped YBCO thin films

NASA Astrophysics Data System (ADS)

Chen, Shihong; Sebastian, Mary Ann; Gautam, Bibek; Wilt, Jamie; Chen, Yanbin; Sun, Lei; Xing, Zhongwen; Haugan, Timothy; Wu, Judy

2017-12-01

High concentration artificial pinning centers (APCs), such as BaZrO3 nanorods (BZO 1D APCs) aligned along the c-axis of the high temperature superconductor YBa2Cu3O7 (YBCO) can provide strong pinning of magnetic vortices and are desirable for applications in high magnetic fields. Unfortunately, in YBCO films with single-doping (SD) of BZO 1D APCs, a monotonic decreasing superconducting T c and critical current density J c(H) with BZO doping has been observed due to strain field overlap at high-concentration perfectly c-axis aligned BZO 1D APCs. In order to resolve this issue, double-doping (DD) of 2-6 vol% BZO 1D APCs and 3.0 vol% Y2O3 nanoparticles (Y2O3-NPs) in YBCO films has been explored to promote BZO-NR orientation misalignment from the c-axis. Remarkably, a monotonic increasing J c(H) with BZO 1D APCs concentration has been obtained in the BZO DD samples. Such a microstructure change is evidenced in the much smaller c-lattice parameter expansion of 0.103% in the DD samples as opposed to 0.511% in the SD counterparts and reduced c-axis alignment of the BZO 1D APCs as revealed in TEM. This yields a mixed 1D + 2D + 3D APC morphology and enhanced isotropic pinning with respect to the orientation of the H-field in the BZO DD samples.

Phase transition behaviours near the triple point for Pb-free (1 - x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 piezoceramics

NASA Astrophysics Data System (ADS)

Gao, Jinghui; Dai, Ye; Hu, Xinghao; Ke, Xiaoqin; Zhong, Lisheng; Li, Shengtao; Zhang, Lixue; Wang, Yu; Wang, Dong; Wang, Yan; Liu, Yongbin; Xiao, Hu; Ren, Xiaobing

2016-08-01

The reason for the large electromechanical response in Pb-free piezoceramic Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 (BZT-BCT) still remains controversial, and a central issue is whether or not the multi-phase-coexisting point (triple point) in the phase diagram is a thermodynamic tricritical point. In this letter, we study the phase transition behaviour for the ferro-para transitions of BZT-BCT specimens in the vicinity of a triple point. Our results show that latent heat and thermal hysteresis approach zero, while the permittivity peak value is maximized close to the triple-point composition, which suggests that the triple point exhibits nearly tricritical transition behaviours in the BZT-BCT system. Further, the TEM result shows that the domain width is minimized with composition approaching the triple point, which indicates a reduction of the domain wall energy possibly relevant to the tricriticality of the triple point. A sixth-order Landau energy modeling shows that the triple tricritical point provides a free-energy state of near-vanishing polarization anisotropy and thus enhances the piezoelectric response for such a material system.

Dielectric studies of (x) NiFe2O4 + (1 - x) BaTi0.9Zr0.1O3 (where x = 0, 0.25, 0.50, 0.75 and 1)

NASA Astrophysics Data System (ADS)

Wadhwani, Kiran; Srivastava, Subodh; Mathur, Shubhra

2018-05-01

We present the room temperature dielectric studies of the samples in the series (x) NiFe2O4 + (1-x) BaTi0.9Zr0.1O3 (where x = 0, 0.25, 0.50, 0.75 and 1) containing nickel ferrite and Zr substituted barium titanate as the ferroelectric phase and their magnetoelectric (ME) composites in mixed in different molar ratios. Solid state diffusion has been used for the synthesis of samples. Powder X-ray diffraction (XRD) confirms the formation of ferrite and ferroelectric phases and their presence in all three composites with no impurity traces. Room temperature dielectric measurements have been made as a function of frequency (ranging from 100 Hz to 1 MHz).

CaO-MgO-Al 2O 3-SiO 2 (CMAS) corrosion of Gd 2Zr 2O 7 and Sm 2Zr 2O 7

DOE PAGES

Wang, Honglong; Bakal, Ahmet; Zhang, Xingxing; ...

2016-08-08

Ceramic thermal barrier coatings are applied to superalloys used in gas turbine engineering to increase the operating temperature and the energy conversion efficiency. However, dust consisting of CaO-MgO-Al 2O 3-SiO 2 (CMAS) from the air can be injected into the engines and corrode the thermal barrier coatings. Lanthanide zirconates are promising materials in thermal barrier coatings due to their low thermal conductivities, good phase stability and good corrosion resistance. However, the corrosion resistance mechanism of CMAS on lanthanide zirconates is still not clearly understood. In this work, the corrosion mechanism of Gd 2Zr 2O 7 and Sm 2Zr 2O 7more » in CMAS is studied. Here, the results show that the CMAS can easily react with lanthanide zirconate thermal barrier coatings to form a dense layer, which can resist further corrosion« less

In-situ study on growth units of Ba2Mg(B3O6)2 crystal

NASA Astrophysics Data System (ADS)

Lv, X. S.; Sun, Y. L.; Tang, X. L.; Wan, S. M.; Zhang, Q. L.; You, J. L.; Yin, S. T.

2013-05-01

BMBO (Ba2Mg(B3O6)2 crystal) is an excellent birefringent crystal and a potential stimulated Raman scattering (SRS) crystal. In this paper, high temperature Raman spectroscopy was used to in-situ study the melt structure near a BMBO crystal-melt interface. [B3O6]3- groups were found in this region. The result reveals that both of BaO bonds and MgO bonds are the weak bonds in the BMBO crystal structure. During the melting process, the crystal structure broke into Ba2+ ions, Mg2+ ions and [B3O6]3- groups. Our experimental results confirmed that the well-developed faces of BMBO crystals are the (001), (101) and (012) faces. Based on attachment energy theory, the crystal growth habit was discussed. The (001) (101) and (012) crystal faces linked by the weak BaO bonds and MgO bonds have smaller attachment energies and slower growth rates, and thus present in the final morphology. The (012) crystal face has a multi-terrace structure, which suggests that BMBO crystal grows with a layer-by-layer mode.

Synthesis, structural and electrical studies of Ba1-xSrxCe0.65Zr0.25Pr0.1O3-δ electrolyte materials for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Madhuri Sailaja, J.; Murali, N.; Margarette, S. J.; Mammo, Tulu Wegayehu; Veeraiah, V.

2018-03-01

This paper is discussed Sr doping effect on the microstructure, chemical stability and conductivity of Ba1-xSrxCe0.65Zr0.25Pr0.1O3-δ (0 ≤ x ≤ 0.2) electrolyte prepared by sol-gel method. The lattice constants and unit cell volumes are found to decrease as Sr atomic percentage increased in accordance with the Vegard law, confirming the formation of solid solution with orthorhombic structure. Among them all the synthesized samples are showed a conductivity with different atmosphere values at 500 °C. Ba0.92Sr0.08Ce0.65Zr0.25Pr0.1O3-δ recorded highest conductivity with a value of 3.3 × 10-6 S/cm (dry air) & 3.41 × 10-6 S/cm (wet air with 3% relative humidity) at 500 °C due to its smaller lattice volume, larger grain size and lower activation energy that led to excessive increase in conductivity. All pellets exhibited good chemical stability when exposed to air and H2O atmospheres. This study elucidates that the composition will be a promising electrolyte material for use as SOFC at intermediate temperatures if Sr doping is limited to small amounts.

Dielectric and piezoelectric properties of lead-free Ba0.85Ca0.15Ti0.9-xZr0.1CuxO3 ceramics synthesized by a hydrothermal method

NASA Astrophysics Data System (ADS)

Hunpratub, Sitchai; Phokha, Sumalin; Maensiri, Santi; Chindaprasirt, Prinya

2016-04-01

Ba0.85Ca0.15Ti0.9Zr0.1-xCuxO3 (BCTZC) nanopowders were synthesized using a hydrothermal method after which they were pressed into discs and sintered in air at 1300 °C for 3 h to form ceramic samples. The phase and microstructure of the powder and ceramic samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results indicated that the ceramic samples exhibited a tetragonal structure and that CuO, BaZrO3 or CaTiO3 impurity phases, which had been present in the powder samples, were not observed. The average grain sizes in the ceramic samples were found to be 17.0, 16.1, 20.0, 18.1 and 19.6 μm for Cu mole fractions x of 0.002, 0.004, 0.006, 0.008 and 0.01, respectively. The dielectric constants, ferroelectric hysteresis loops and piezoelectric charge coefficients of the BCZTC ceramic samples were also investigated. Optimum values for the relative dielectric constant (ɛ‧), tan δ and piezoelectric charge coefficient (d33) of the samples were 3830, 0.03 and 306 pC/N, respectively, in the Cu mole fraction samples with x = 0.002.

Continuous recrystallization during thermomechanical processing of a superplastic Al-10Mg-0.1Zr alloy

NASA Technical Reports Server (NTRS)

Hales, S. J.; Mcnelley, T. R.; Crooks, R.

1990-01-01

Microstructural evolution via static continuous recrystallization during thermomechanical processing of an Al-Mg-Zr alloy is addressed. Mechanical property data demonstrated that as-rolled material was capable of superplastic response without further treatment. Further, superplastic ductility at 300 C was enhanced by a factor of five by increasing the reheating time between rolling passes during processing also at 300 C. This enhanced ductility was associated with a Cu-texture and a microstructure consisting of predominantly high-angle boundaries. Processing to minimize recovery resulted in a strong Brass-texture component, a predominantly low-angle boundary microstructure and poorer ductility.

Dielectric properties and microstructure of nano-MgO dispersed Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} thin films prepared by sputter deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, S.-F.; Chu, Jinn P.; Lin, C.C.

2005-07-01

In this study, thin films prepared from the targets of Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} (BST), BST/5 mol % MgO, BST/10 mol % MgO, and BST/20 mol % MgO composites, using radio frequency magnetron sputtering, have been reported. As-deposited films were found to be amorphous and began to crystallize after annealing at temperatures of 650 deg. C and above. The addition of MgO in the BST films resulted in the hindrance of crystallization and inhibition of grain growth. MgO was substituted into the BST lattices to a certain degree. High-resolution transmission electron microscopy results revealed some MgO dispersed in the BSTmore » matrix. The MgO dispersed in the dense BST matrix was found to be around 25 nm in size. The dielectric constant was estimated to be 90 for the pure BST film annealed at 700 deg. C, and observed to be slightly reduced with the MgO addition. The dielectric losses of the Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} (0.006) and BST/MgO films (0.002-0.004) were much less than those of the Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}(0.013) and Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} films (0.11-0.13). The leakage current was smaller for the BST/10 mol % MgO film compared to the pure BST film and this low leakage current may be attributed to the substitution of Mg in the B sites of BST lattices which might have behaved as an electron acceptors.« less

Bizarre dielectric anomalies in magnetoelectric composites of CoFe2O4 and BaTi0.9Zr0.1O3

NASA Astrophysics Data System (ADS)

Mathur, Shubhra; Srivastava, Subodh; Surve, Sachin; Wadhwani, Kiran; Singh Rajaura, Rajveer; Dolia, S. N.

2017-12-01

The magnetoelectric (ME) composites containing cobalt ferrite as the magnetic phase and Zr substituted (10 atomic % occupancy) barium titanate as the ferroelectric counterpart having the general formula (x) CoFe2O4  +  (1  -  x) BaTi0.9Zr0.1O3 (where x  =  0, 0.25, 0.50, 0.75 and 1) have been synthesised by the conventional solid state diffusion route. Powder x-ray diffraction of thus prepared materials confirms the presence of ferrite and ferroelectric phases and their concurrent existence in all three composites without showing traces of any superfluous phase. Dielectric measurements have been recorded as a function of frequency (ranging from 100 Hz to 1 MHz) at room temperature and temperature (from 325 K up to a maximum of 825 K). In composites, relative permittivity and loss tangent curves with variable temperature show upsurge of bizarre anomalies which can be associated to the defect modes existing in the form of oxygen ion vacancies rather than ascribing it to the benchmark ferro to paraeletric transition.

Porous Ba0.85Ca0.15Zr0.1Ti0.9O3 Ceramics for Pyroelectric Applications

NASA Astrophysics Data System (ADS)

Sharma, Moolchand; Singh, V. P.; Singh, Shatrughan; Azad, Puneet; Ilahi, Bouraoui; Madhar, Niyaz Ahamad

2018-05-01

Porous Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ferroelectric ceramics were fabricated using a solid-state reaction consisting of BCZT and poly(methyl methacrylate)(PMMA) (2%, 4%, 8% and 10% by wt.%) as a pore former. By increasing the PMMA content from 0% to 10%, porosity increased from 8% to 29%. It was found that the dielectric constant (ɛ r ) decreased and the dielectric loss (tanδ) increased with increasing porosity. At 29% porosity, ɛ r of the BCZT was found to decrease more, from 3481 to 1117 at 5 kHz and at room temperature. The dielectric constant and volume-specific heat capacity decreased with the increase in porosity which ultimately improved the pyroelectric figure-of-merits (FOMs). Further, the pyroelectric FOMs were estimated and found to be improved at optimum porosity.

Local structure analysis on (La,Ba)(Ga,Mg)O3-δ by the pair distribution function method using a neutron source and density functional theory calculations

NASA Astrophysics Data System (ADS)

Kitamura, Naoto; Vogel, Sven C.; Idemoto, Yasushi

2013-06-01

In this work, we focused on La0.95Ba0.05Ga0.8Mg0.2O3-δ with the perovskite structure, and investigated the local structure around the oxygen vacancy by pair distribution function (PDF) method and density functional theory (DFT) calculation. By comparing the G(r) simulated based on the DFT calculation and the experimentally-observed G(r), it was suggested that the oxygen vacancy was trapped by Ba2+ at the La3+ site at least at room temperature. Such a defect association may be one of the reasons why the La0.95Ba0.05Ga0.8Mg0.2O3-δ showed lower oxide-ion conductivity than (La,Sr)(Ga,Mg)O3-δ which was widely-used as an electrolyte of the solid oxide fuel cell.

Superconducting transition temperature in the Y(1-x)M(x)Ba2Cu3O(y) system

NASA Astrophysics Data System (ADS)

Suzuki, Takeyuki; Yamazaki, Tsutomu; Sekine, Ryuuta; Koukitsu, Akinori; Seki, Hisashi

1989-04-01

Experimental results are presented for the inclusion of compositional additives, M, to the sintered high-temperature superconductor Y(1-x)M(x)Ba2Cu3O(y); M can be the oxides of Mg, Ce, Gd, Yb, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, and Te, as well as Li, Na, K, Ca, Sr, and La carbonates. Temperature dependence of the electrical resistance was measured down to about 80 K. Attention is given to the influence of ionic radius and the valence of the M species.

The influence of nano MgO and BaSO4 particle size additives on properties of PMMA bone cement.

PubMed

Ricker, Alyssa; Liu-Snyder, Peishan; Webster, Thomas J

2008-01-01

A common technique to aid in implant fixation into surrounding bone is to inject bone cement into the space between the implant and surrounding bone. The most common bone cement material used clinically today is poly(methyl methacrylate), or PMMA. Although promising, there are numerous disadvantages of using PMMA in bone fixation applications which has limited its wide spread use. Specifically, the PMMA polymerization reaction is highly exothermic in situ, thus, damaging surrounding bone tissue while curing. In addition, PMMA by itself is not visible using typical medical imaging techniques (such as X-rays required to assess new bone formation surrounding the implant). Lastly, although PMMA does support new bone growth, studies have highlighted decreased osteoblast (bone forming cell) functions on PMMA compared to other common orthopedic coating materials, such as calcium phosphates and hydroxyapatite. For these reasons, the goal of this study was to begin to investigate novel additives to PMMA which can enhance its cytocompatibility properties with osteoblasts, decrease its exothermic reaction when curing, and increase its radiopacity. Results of this study demonstrated that compared to conventional (or micron) equivalents, PMMA with nanoparticles of MgO and BaSO4 reduced harmful exothermic reactions of PMMA during solidification and increased radiopacity, respectively. Moreover, osteoblast adhesion increased on PMMA with nanoparticles of MgO and BaSO4 compared with PMMA alone. This study, thus, suggests that nanoparticles of MgO and BaSO4 should be further studied for improving properties of PMMA for orthopedic applications.

Bias polarization study of steam electrolysis by composite oxygen electrode Ba0.5Sr0.5Co0.8Fe0.2O3-δ/BaCe0.4Zr0.4Y0.2O3-δ

NASA Astrophysics Data System (ADS)

Yang, Tao; Shaula, Aliaksandr; Pukazhselvan, D.; Ramasamy, Devaraj; Deng, Jiguang; da Silva, E. L.; Duarte, Ricardo; Saraiva, Jorge A.

2017-12-01

The polarization behavior of Ba0.5Sr0.5Co0.8Fe0.2O3-δ-BaCe0.4Zr0.4Y0.2O3-δ (BSCF-BCZY) electrode under steam electrolysis conditions was studied in detail. The composite oxygen electrode supported by BCZY electrolyzer has been assessed as a function of temperature (T), water vapor partial pressures (pH2O), and bias polarization voltage for electrodes of comparable microstructure. The Electrochemical impedance spectra show two depressed arcs in general without bias polarization. And the electrode resistance became smaller with the increase of the bias polarization under the same water vapor partial pressures. The total resistance of the electrode was shown to be significantly affected by temperature, with the same level of pH2O and bias polarization voltage. This result highlights BSCF-BCZY as an effective oxygen electrode under moderate polarization and pH2O conditions.

Effect of Plastic Deformation on the Structure and Properties of Alloy IMV7-1 of the Mg - Y - Gd - Zr System

NASA Astrophysics Data System (ADS)

Rokhlin, L. L.; Dobatkina, T. V.; Luk'yanova, E. A.; Korol'kova, I. G.; Choporov, V. F.

2016-07-01

The microstructure and strength properties of hot-pressed alloy IMV7-1 of the Mg - Y - Gd - Zr system are studied after additional cold and hot rolling deformation. It is shown that the strength properties of the pressed alloy can be elevated by cold deformation at an admissible level of ductility.

Relaxor-like ferroelectric behaviour favoured by short-range B-site ordering in 10% Ba{sup 2+} substituted MgFe{sub 2}O{sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chithra Lekha, P.; Ramesh, G.; Revathi, V.

2014-05-01

Graphical abstract: - Highlights: • Mechanism driving polarization in MgFe{sub 2}O{sub 4} is the Maxwell–Wagner polarization. • But Raman studies confirm the existence of local P4{sub 1}22/P4{sub 3}22 symmetry in MgFe{sub 2}O{sub 4}. • Ba{sup 2+} substitution increases ferroelectric ordering, ΔT{sub m} span, and masks electronic contribution. - Abstract: Using the molten salt method, pristine and Ba{sup 2+} substituted MgFe{sub 2}O{sub 4} are prepared. The relaxor-like behaviour observed in the dielectric dispersion indicates the existence of B-site short-range ordering with the local P4{sub 1}22/P4{sub 3}22 symmetry which is confirmed by the Raman spectroscopy. The paper further analyses the origin ofmore » polarization using Maxwell–Wagner fit and Nyquist plot. This work suggests a possible way to increase the relaxor-like ferroelectric ordering, larger span of relaxation temperature (ΔT{sub m}) and the effective masking of electronic contribution by the substitution of Ba{sup 2+} ion.« less

Microstructure, mechanical properties, in vitro degradation and cytotoxicity evaluations of Mg-1.5Y-1.2Zn-0.44Zr alloys for biodegradable metallic implants.

PubMed

Fan, Jun; Qiu, Xin; Niu, Xiaodong; Tian, Zheng; Sun, Wei; Liu, Xiaojuan; Li, Yangde; Li, Weirong; Meng, Jian

2013-05-01

Mg-1.5Y-1.2Zn-0.44Zr alloys were newly developed as degradable metallic biomaterials. A comprehensive investigation of the microstructure, mechanical properties, in vitro degradation assessments and in vitro cytotoxicity evaluations of the as-cast state, as-heat treated state and as-extruded state alloys was done. The microstructure observations show that the Mg-1.5Y-1.2Zn-0.44Zr alloys are mainly composed of the matrix α-Mg phases and the Mg12ZnY secondary phases (LPS structure). The hot extrusion method significantly refined the grains and eliminated the defects of both as-cast and heat treated alloys and thereby contributed to the better mechanical properties and biodegradation resistance. The values of tensile strength and tensile yield strength of the alloy in the as-extruded condition are about 236 and 178 MPa respectively, with an excellent elongation of 28%. Meanwhile, the value of compressive strength is about 471 MPa and the value of bending strength is about 501 MPa. The superior bending strength further demonstrates the excellent ductility of the hot extruded alloys. The results of immersion tests and electrochemical measurements in the SBF indicate that a protective film precipitated on the alloy's surface with the extension of degradation. The protective film contains Mg(OH)2 and hydroxyapatite (HA) which can reinforce osteoblast activity and promote good biocompatibility. No significant cytotoxicity towards L-929 cells was detected and the immersion extracts of alloy samples could enhance the cell proliferation with time in the cytotoxicity evaluations, implying that the Mg-1.5Y-1.2Zn-0.44Zr alloys have the potential to be used for biomedical applications. Copyright © 2013 Elsevier B.V. All rights reserved.

The formation of FHA coating on biodegradable Mg-Zn-Zr alloy using a two-step chemical treatment method

NASA Astrophysics Data System (ADS)

Jiang, S. T.; Zhang, J.; Shun, S. Z.; Chen, M. F.

2016-12-01

To improve the corrosion resistance of the biomedical magnesium alloy, a two-step chemical treatment method has been employed to prepare an FHA coating on the alloy surface. Prior to forming an FHA layer, the samples of Mg-3 wt% Zn-0.5 wt% Zr alloy were soaked in HF with concentration of 20% (v/v) at 37 °C temperature for 2 h, and were then placed into an aqueous solution with 0.1 mol/L Ca(NO3).4H2O and 0.06 mol/L NH4H2PO4 at 90 °C to prepare the Ca-P coating. The concentrations of Mg2+, F- ions, and pH variation with immersing time in the solution were investigated to explore the growth mechanism of FHA. The surface morphologies and compositions of the coatings were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that the alloy surface treated with acid formed a layer of MgF2 nanoparticles with a thickness of 0.7 μm. The corrosion resistance of coatings in SBF solution was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results showed that the substrate with FHA coating had good corrosion resistance. After immersing into the calcium phosphate solution, some small spherical particles were first formed on the surface; these then cover the surface completely after 20 min. Some clusters consisting of needle-like crystal were observed in the spherical particles covering the surface, and the Ca/P ratio of the needle-like crystal was 1.46, clearly growing along the c axis preferred orientation growth. After immersion for 60 min, the FHA coating with completely uniform growth was obtained on the Mg-Zn-Zr alloy surface with its thickness reaching about 120 μm.

Effect of heat treatment on the optical properties of perovskite BaZr0.5Ce0.3Y0.2O3-δ ceramic prepared by spark plasma sintering

NASA Astrophysics Data System (ADS)

Xing, Bohang; Cheng, Zhi; Wang, Cao; Zhao, Zhe

2017-09-01

The effect of heat treatment on the in-line transmittance of BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) ceramics prepared by spark plasma sintering method was investigated. The loss of Ba in transparent BZCY532 ceramics is the key reason for the loss of transmittance during the annealing process. This problem can be effectively alleviated by using a powder bed of BZCY532. Heat treatment atmospheres, wet air and dry air, were also found to be critical for obtaining high quality transparent ceramics. A highly transparent BZCY532 ceramic with the in-line transmittance (Tin) of 71.4% at 2000 nm can be obtained by using SPS method followed by an annealing in powder bed at 1500 °C in wet air.

Quasi-2D silicon structures based on ultrathin Me2Si (Me = Mg, Ca, Sr, Ba) films

NASA Astrophysics Data System (ADS)

Migas, D. B.; Bogorodz, V. O.; Filonov, A. B.; Borisenko, V. E.; Skorodumova, N. V.

2018-04-01

By means of ab initio calculations with hybrid functionals we show a possibility for quasi-2D silicon structures originated from semiconducting Mg2Si, Ca2Si, Sr2Si and Ba2Si silicides to exist. Such a 2D structure is similar to the one of transition metal chalcogenides where silicon atoms form a layer in between of metal atoms aligned in surface layers. These metal surface atoms act as pseudo passivation species stabilizing crystal structure and providing semiconducting properties. Considered 2D Mg2Si, Ca2Si, Sr2Si and Ba2Si have band gaps of 1.14 eV, 0.69 eV, 0.33 eV and 0.19 eV, respectively, while the former one is also characterized by a direct transition with appreciable oscillator strength. Electronic states of the surface atoms are found to suppress an influence of the quantum confinement on the band gaps. Additionally, we report Sr2Si bulk in the cubic structure to have a direct band gap of 0.85 eV as well as sizable oscillator strength of the first direct transition.

Effect of solution treatment on the fatigue behavior of an as-forged Mg-Zn-Y-Zr alloy

NASA Astrophysics Data System (ADS)

Wang, S. D.; Xu, D. K.; Wang, B. J.; Han, E. H.; Dong, C.

2016-04-01

Through investigating and comparing the fatigue behavior of an as-forged Mg-6.7Zn-1.3Y-0.6Zr (wt.%) alloy before and after solid solution treatment (T4) in laboratory air, the effect of T4 treatment on fatigue crack initiation was disclosed. S-N curves illustrated that the fatigue strength of as-forged samples was 110 MPa, whereas the fatigue strength of T4 samples was only 80 MPa. Observations to fracture surfaces demonstrated that for as-forged samples, fatigue crack initiation sites were covered with a layer of oxide film. However, due to the coarse grain structure and the dissolution of MgZn2 precipitates, the activation and accumulation of {10-12} twins in T4 samples were much easier, resulting in the preferential fatigue crack initiation at cracked twin boundaries (TBs). Surface characterization demonstrated that TB cracking was mainly ascribed to the incompatible plastic deformation in the twinned area and nearby α-Mg matrix.

Over 15 MA/cm2 of critical current density in 4.8 µm thick, Zr-doped (Gd,Y)Ba2Cu3Ox superconductor at 30 K, 3T.

PubMed

Majkic, Goran; Pratap, Rudra; Xu, Aixia; Galstyan, Eduard; Selvamanickam, Venkat

2018-05-03

An Advanced MOCVD (A-MOCVD) reactor was used to deposit 4.8 µm thick (Gd,Y)BaCuO tapes with 15 mol% Zr addition in a single pass. A record-high critical current density (J c ) of 15.11 MA/cm 2 has been measured over a bridge at 30 K, 3T, corresponding to an equivalent (I c ) value of 8705 A/12 mm width. This corresponds to a lift factor in critical current of ~11 which is the highest ever reported to the best of author's knowledge. The measured critical current densities at 3T (B||c) and 30, 40 and 50 K, respectively, are 15.11, 9.70 and 6.26 MA/cm 2 , corresponding to equivalent Ic values of 8705, 5586 and 3606 A/12 mm and engineering current densities (J e ) of 7068, 4535 and 2928 A/mm 2 . The engineering current density (J e ) at 40 K, 3T is 7 times higher than that of the commercial HTS tapes available with 7.5 mol% Zr addition. Such record-high performance in thick films (>1 µm) is a clear demonstration that growing thick REBCO films with high critical current density (J c ) is possible, contrary to the usual findings of strong J c degradation with film thickness. This achievement was possible due to a combination of strong temperature control and uniform laminar flow achieved in the A-MOCVD system, coupled with optimization of BaZrO 3 nanorod growth parameters.

Electronic structure and vacancy formation in La(1 - x) B(x) CoO3 (B=Mg,Ca,Ba and x=0.125)

NASA Astrophysics Data System (ADS)

Salawu, Omotayo; Gan, Liyong; Schwingenschlogl, Udo

2015-03-01

The LaCoO3 class of materials is of interest for cathodes of solid oxide fuel cells. Spin-polarized density functional theory is applied to cubic La0.75(Mg/Ca/Ba)0.125CoO3. The effect of this cation doping on the electronic and magnetic properties as well as oxygen vacancy formation energy is studied. Oxygen vacancies with proximity to the dopant are energetically favourable in most cases. We discuss the effect of distortions of the CoO6 octahedron on the electronic structure and the formation energy of oxygen vacancies. The order of formation oxygen is found to be Mg > Ca > Ba. Cation doping incorporates holes to the Co-O network which enhances the oxygen vacancy formation.

Influence of minor combined addition of Cr and Pr on microstructure, mechanical properties and corrosion behaviors of an ultrahigh strength Al-Zn-Mg-Cu-Zr alloy.

PubMed

Wang, Ming; Huang, Lanping; Chen, Kanghua; Liu, Wensheng

2018-01-01

This work focuses on controlling grain boundary structure in an ultra-high strength Al-8.6Zn-2.5Mg-2.2Cu-0.16Zr (wt.%) alloy by the combined addition of trace Cr (0.1wt.%) and Pr (0.14wt.%), and evaluating mechanical properties and localized corrosion behaviors of the alloy in the peak aged condition. The introduction of trace Cr and Pr leads to the formation of nanoscale Cr, Pr-containing Al 3 Zr and Zr-containing PrCr 2 Al 20 dispersoids which can obviously inhibit the recrystallization and sub-grain growth of the super-high strength Al-Zn-Mg-Cu alloys, and retain the deformation-recovery microstructure dominated by low-angle grain boundaries. The nearly ellipsoidal dispersoids with a size of 10-35nm are discretely distributed and precipitate free zones are hardly formed in low-angle grain boundaries. This new alloy composition exhibits better combined properties, higher resistance to stress corrosion, exfoliation corrosion and inter-granular corrosion with the undamaged strength, ductility and fracture toughness. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural, dielectric and magnetic studies of Mn doped Y-type barium hexaferrite (Ba2Mg2Fe12O22)

NASA Astrophysics Data System (ADS)

Abdullah, Md. F.; Pal, P.; Mohapatra, S. R.; Yadav, C. S.; Kaushik, S. D.; Singh, A. K.

2018-04-01

The polycrystalline single phase Ba2Mg2Fe12O22 (BMF) and Ba2Mg2Fe11.52Mn0.48O22 (BMFM) were prepared using conventional solid state reaction route. We report the modification in structural, dielectric and magnetic properties of BMF due to 4% Mn doping at Fe site. Phase purity of both sample are confirmed by the Reitveld refinement of XRD data. Temperature dependent dielectric study shows decrease in dielectric constant (ɛ') and dielectric loss (tan δ) due to 4% Mn doping in parent sample. The ferrimagnetic to paramagnetic transition temperature (Tc) in doped sample decreases from 277°C to 150°C. Room temperature magnetization measurement shows ferrimagnetic behavior for both the samples. We have fitted the saturation magnetization data at 300 K by using least square method which confirms the enhancement of saturation magnetization and magnetic anisotropy constant in doped sample.

Surface Crystallization of a MgO/Y2O3/SiO2/Al2O3/ZrO2 Glass: Growth of an Oriented β-Y2Si2O7 Layer and Epitaxial ZrO2

PubMed Central

Wisniewski, Wolfgang; Seidel, Sabrina; Patzig, Christian; Rüssel, Christian

2017-01-01

The crystallization behavior of a glass with the composition 54.7 SiO2·10.9 Al2O3·15.0 MgO·3.4 ZrO2·16.0 Y2O3 is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD) and (scanning) transmission electron microscopy [(S)TEM] including energy-dispersive X-ray spectrometry (EDXS). This glass shows the sole surface crystallization of four different yttrium silicates of the composition Y2Si2O7 (YS). The almost simultaneous but independent nucleation of α-, β-, δ-, and ε-YS at the surface is followed by growth into the bulk, where ε-YS quickly dominates a first crystallized layer. An accumulation of Mg at the growth front probably triggers a secondary nucleation of β-YS, which forms a thin compact layer before fragmenting into a highly oriented layer of fine grained crystals occupying the remaining bulk. The residual glass between the YS growth structures allows the crystallization of indialite, yttrium stabilized ZrO2 (Y-ZrO2) and very probably μ-cordierite during cooling. Hence, this glass basically shows the inverted order of crystallization observed in other magnesium yttrium alumosilicate glasses containing less Y2O3. An epitaxial relationship between Y-ZrO2 and ε-YS is proven and multiple twinning relationships occur in the YS phases. PMID:28281661

Identification of a site involved in the block by extracellular Mg2+ and Ba2+ as well as permeation of K+ in the Kir2.1 K+ channel

PubMed Central

Murata, Yoshimichi; Fujiwara, Yuichiro; Kubo, Yoshihiro

2002-01-01

The inward rectifier potassium channel Kir2.1 is more sensitive to the weakly voltage-dependent block by extracellular Mg2+ (Mg02+) than Kir2.2 and Kir2.3. We identified Glu125 in an extracellular loop before the pore region of Kir2.1 as a site responsible for this sensitivity to M02+ block, based on the observations that the Glu125Gln (E125Q) mutation strongly decreased the sensitivity, while a mutation to Glu at the corresponding sites of Kir2.2 and 2.3 led to an increase. The negative charge proved to be crucial since the Glu125Asp (E125D) mutant showed similar properties to the wild type (WT). A similar weakly voltage-dependent block was also caused by extracellular Ca2+ and La3+ in Kir2.1 WT but not in the E125Q mutant. The sensitivity to block by extracellular Ba2+ (Ba02+) was also decreased in the E125Q mutant, although the voltage dependency of half-inhibition concentration was not changed, as reported previously. We additionally observed that the speed of Ba02+ block and recovery was decelerated by the presence of Mg02+ in WT, but not in the E125Q mutant. The sensitivity to the block by Mg02+ was increased by lowering extracellular K+ (K0+), suggesting a competitive interaction of Mg02+ and K0+. The single-channel conductance of the WT in 140 mm K+ was 39.6 pS (0 mm Mg02+) and 11.5 pS (10 mm), while that of the E125Q mutant was 26.0 pS (0 mm) and 19.6 pS (10 mm). These results demonstrate that Mg2+ competes with K+ permeation in the WT and that E125 is required for efficient K+ permeation in the absence of Mg02+. We conclude that E125 in an extracellular loop of Kir2.1 is a site which facilitates K+ permeation and entry of Ba2+ toward a deeper plugging site, and that Mg02+ competes with K0+ and Ba02+ at this site. PMID:12411513

BaZr 0.1Ce 0.7Y 0.1Yb 0.1O 3- δ electrolyte-based solid oxide fuel cells with cobalt-free PrBaFe 2O 5+ δ layered perovskite cathode

NASA Astrophysics Data System (ADS)

Ding, Hanping; Xue, Xingjian

A new anode-supported SOFC material system Ni-BZCYYb|BZCYYb|PBFO is investigated, in which a cobalt-free layered perovskite oxide, PrBaFe 2O 5+ δ (PBFO), is synthesized and employed as a novel cathode while the synthesized BZCYYb is used as an electrolyte. The cell is fabricated by a simple dry-pressing/co-sintering process. The cell is tested and characterized under intermediate temperature range from 600 to 700 °C with humified H 2 (∼3% H 2O) as fuel, ambient air as oxidant. The results show that the open-circuit potential of 1.006 V and maximal power density of 452 mW cm -2 are achieved at 700 °C. The polarization resistance of the electrodes is 0.18 Ω cm 2 at 700 °C. Compared to BaZr 0.1Ce 0.7Y 0.1O 3- δ, the conductivity of co-doped barium zirconate-cerate BZCYYb is significantly improved. The ohmic resistance of single cell is 0.37 Ω cm 2 at 700 °C. The results indicate that the developed Ni-BZCYYb|BZCYYb|PBFO cell is a promising functional material system for SOFCs.

STUDY OF BIFERROIC PROPERTIES IN THE La0.37Ca0.17Ba0.43Mn0.52Ti0.44Zr0.04O3 COMPLEX PEROVSKITE

NASA Astrophysics Data System (ADS)

Cardona-Vásquez, J. A.; Gómez, M. E.; Landínez-Téllez, D. A.; Roa-Rojas, J.

2013-10-01

In this paper, details of synthesis and structural, morphological, electrical, and magnetic characterization of the new La0.37Ca0.17Ba0.43Mn0.52Ti0.44Zr0.04O3 multiferroic complex perovskite are reported. Mixtures with 50% mass of ferromagnetic lanthanum calcium manganite La0.67Ca0.33MnO3 and ferroelectric barium-lanthanum zirconate titanate Ba0.9La0.067Ti0.91Zr0.09 O3 were prepared by the solid state reaction technique. Patterns of X-ray diffraction showed that the materials have reacted resulting in a new perovskite-like structure with tetragonal symmetry, space group P4mm(#99). The structure of the material was refined using the Rietveld method through the GSAS code. ZFC and FC magnetization curves show the occurrence of two phase transitions at 42.25 K and 203.9 K which have been associated with two different magnetic regimes. Hysteresis curves measured confirm that the relationship between the applied field and the magnetization does not evidence a linear behavior. These curves also show that in the low temperature regime the magnetic memory of the material is greater than in the high temperature region. AC impedance as a function of temperature measurements show the same two regions observed in the magnetization curves. The ferroelectric behavior with relative permittivity of 153.12 is observed by polarization curves performed at room temperature in the synthesized materials.

Three-photon absorption and nonlinear refraction of BaMgF4 in the ultraviolet region.

PubMed

Ma, Yanzhi; Chen, Junjie; Zheng, Yuanlin; Chen, Xianfeng

2012-08-01

The nonlinear refraction and nonlinear absorption phenomena are investigated in BaMgF(4) single crystal using the Z-scan technique in the ultraviolet region with a pulsed laser at 400 nm with 1 ps pulse duration. The remarkable nonlinear absorption behavior is identified to be three-photon absorption under the experimental conditions. In addition, both nonlinear refraction and nonlinear absorption have relatively large values and possess small anisotropy along three different crystallographic axes. The large values of nonlinear refractive index are demonstrated through the self-phase modulation effect.

Dielectric properties and phase transition behaviors in (1-x)PbZrO3-xPb(Mg1/2W1/2)O3 ceramics

NASA Astrophysics Data System (ADS)

Vittayakorn, Naratip; Charoonsuk, Piyanut; Kasiansin, Panisara; Wirunchit, Supamas; Boonchom, Banjong

2009-09-01

The solid solution of lead zirconate [PbZrO3 (PZ)] and lead magnesium tungstate [Pb(Mg1/2W1/2)O3 (PMW)] has been synthesized by the wolframite precursor method. The crystal structure, phase transformations, dielectric and thermal properties of (1-x)PZ-xPMW, where x =0.00-0.10, were investigated. The crystal structure of sintered ceramics was analyzed by x-ray diffraction. Phase-pure perovskite was obtained for all compositions. Furthermore, a change from orthorhombic to rhombohedral symmetry was observed as the mole fraction of increased PMW. As a result, it was found that PbZrO3-Pb(Mg1/2W1/2)O3 undergoes successive transitions from the antiferroelectric phase to the ferroelectric phase to the paraelectric state. The coexistence of orthorhombic and rhombohedral phases in this binary system is located near the composition x =0.1.

Ab initio molecular dynamics simulations of short-range order in Zr50Cu45Al5 and Cu50Zr45Al5 metallic glasses

NASA Astrophysics Data System (ADS)

Huang, Yuxiang; Huang, Li; Wang, C. Z.; Kramer, M. J.; Ho, K. M.

2016-03-01

Comparative analysis between Zr-rich Zr50Cu45Al5 and Cu-rich Cu50Zr45Al5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr50Cu45Al5 and Cu50Zr45Al5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons < 0,0,12,0> is dominant, and in the Cu-rich one the distorted icosahedral orders, especially < 0,2,8,2> and < 0,2,8,1> , are prominent. And the < 0,2,8,2> polyhedra in Cu50Zr45Al5 MG mainly originate from Al-centered clusters, while the < 0,0,12,0> in Zr50Cu45Al5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. The relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr50Cu45Al5.

[Study on Hydrothermal Preparation and Luminescence Properties of Luminescent Material BaSrMg(PO₄)₂:Eu³⁺].

PubMed

Hu, Qing-song; Zhu, Cheng-jing; Xia, Yue-yi; Wang, Li-li; Liu, Wen-han; Pan, Zai-fa

2016-02-01

Eu³⁺ doped BaSrMg (PO₄)₂ were prepared by a hydrothermal method. The crystal structure and morphology of BaSrMg(PO₄)₂:Eu³⁺ phosphor were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM). The effects of different pH values (5, 6, 7 and 8) and different reaction temperatures (120, 140, 160, 180 and 200 °C) on the crystal structure and morphology of BaSrMg(PO₄)₂:Eu³⁺ phosphor were studied in this paper. The results of XRD indicate that diffraction peaks are sharp and strong only when pH value is 6, meanwhile the FESEM shows the morphology is regular-shaped. The XRD patterns show amorphous halos superimposed with several weak sharp peaks for the samples preparing under the pH values of 5, 7 and 8. It indicates that these three samples are solid solution or mixed phases, which are in accord with the results of FESEM. From the fluorescence spectra, the peaks in the excitation spectra were assigned to the transition from ⁷F₀ to ⁵D₄, ⁵L₈, ⁵L₆ and ⁵D₂, while the peaks of emission spectra corresponding to the transition of ⁵D₁ --> ⁷F₁ and ⁵D₀-->⁷Fj (J = 0, 1, 2, 3 and 4). The strongest emission peak of the optimized phosphor located at 613 nm (⁵D0--> ⁷F₂), excited by the main excitation peak with wavelength of 394 nm. The splitting of the emission peaks changes depends on pH values and temperatures, which indicating that luminescence properties is closely related to the crystal structure and morphology of particles.

Structural, microstructural, dielectric and ferroelectric properties of lead free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic

NASA Astrophysics Data System (ADS)

Sharma, Sarita; Sharma, Hakikat; Negi, N. S.

2018-05-01

Lead free Ba0.85Ca0.15Zr0.1Ti0.9O3(BCTZ) ceramic has been synthesized by sol-gel method. Properties of material are studied at different sintering temperatures for 5 hours. Structural and microstructural properties are analyzed by using X-ray diffractrometer (XRD) and scanning electron microscopy (SEM) at annealing temperature of 850°C and 1050°C XRD pattern confirm the perovskite structure of the material without any unwanted phases crystalinity increased with increase of sintering temperature so as roughness and porosity is decreased as shown by SEM micrographs. There is large improvement in density with rise of sintering temperature which also leads to drastic change in ferroelectric and dielectric properties.

High performance fuel electrodes fabricated by electroless plating of copper on BaZr0.8Ce0.1Y0.1O3-δ proton-conducting ceramic

NASA Astrophysics Data System (ADS)

Patki, Neil S.; Way, J. Douglas; Ricote, Sandrine

2017-10-01

The stability of copper at high temperatures in reducing and hydrocarbon-containing atmospheres makes it a good candidate for fabricating fuel electrodes on proton-conducting ceramics, such as BaZr0.9-xCexY0.1O3-δ (BZCY). In this work, the electrochemical performance of Cu-based electrodes fabricated by electroless plating (ELP) on BaZr0.8Ce0.1Y0.1O3-δ is studied with impedance spectroscopy. Three activation catalysts (Pd, Ru, and Cu) are investigated and ELP is compared to a commercial Cu paste (ESL 2312-G) for electrode fabrication. The area specific resistances (ASR) for Pd, Ru, and Cu activations at 700 °C in moist 5% H2 in Ar are 2.1, 3.2, and 13.4 Ω cm2, respectively. That is a 1-2 orders of magnitude improvement over the commercial Cu paste (192 Ω cm2). Furthermore, the ASR has contributions from electrode processes and charge transfer at the electrode/electrolyte interface. Additionally, the morphology of the as-fabricated electrode is unaffected by the activation catalyst. However, heat treatment at 750 °C in H2 for 24 h leads to sintering and large reorganization of the electrode fabricated with Cu activation (micron sized pores seen in the tested sample), while Pd and Ru activations are immune to such reorganization. Thus, Pd and Ru are identified as candidates for future work with improvements to charge transfer required for the former, and better electrode processes required for the latter.

Ab initio molecular dynamics simulations of short-range order in Zr 50Cu 45Al 5 and Cu 50Zr 45Al 5 metallic glasses

DOE PAGES

Huang, Yuxiang; Huang, Li; Wang, C. Z.; ...

2016-02-01

Comparative analysis between Zr-rich Zr 50Cu 45Al 5 and Cu-rich Cu 50Zr 45Al 5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr 50Cu 45Al 5 and Cu 50Zr 45Al 5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons < 0,0,12,0 > is dominant, and in the Cu-rich one the distorted icosahedral orders, especially < 0,2,8,2 > and , are prominent. And the < 0,2,8,2 > polyhedra in Cu 50Zr 45Al 5 MG mainly originate from Al-centered clusters, while the < 0,0,12,0 > in Zr 50Cu 45Al 5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. Lastly, the relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr 50Cu 45Al 5.« less

Nonprotective Alumina Growth in Sulfur-Doped NiAl(Zr)

NASA Technical Reports Server (NTRS)

Smialek, James L.

2000-01-01

The 1200 C oxidation behavior of NiAl was examined at various levels of sulfur and zirconium dopants to test the possibility of a critical S/Zr ratio required for adhesion. Cyclic furnace testing for 200 1 -hr cycles and interrupted testing for 500 hr were used as screening tests. Pure NiAl and NiAl(Zr) with 0. 14 at.% Zr were chosen as model base compositions; they exhibited normal, slow-growing scales (3 Mg/sq cm) with excellent adhesion for the Zr-doped alloys. NiAl with about 120 ppma S exhibited a substantial weight loss (-20 Mg/sq cm) in cyclic tests and a very large weight gain (+60 Mg/sq cm) in interrupted tests. The major surface phase remained as alpha -Al2O3. Sulfur doping the NiAl(Zr) alloy caused massive weight gains of 80 - 100 Mg/sq cm, swelling, cracking, and nearly complete conversion into NiAl2O4, and alpha- Al2O3. The initial objective of determining critical S/Zr ratios for adhesion was therefore unattainable. Initiation of the catastrophic attack was examined after a 10 hr exposure, revealing a few sites of broad, raised, and cracked ridges. In cross-section, the ridges appeared as modular intrusions, with a complex, fractal, oxide-metal interface. They were primarily alumina (with occasional entrapped islands of NiAl2O4 or pure Ni metal). They possessed a unique microstructure consisting of 0.3 microns lamellae, separated by 0.1 microns open channels. This allowed for rapid growth controlled by gaseous diffusion. The microstructure is discussed in terms of SO2 evolution and a sulfur-driven de-passivation process.

Effect of the Size of Al3(Sc,Zr) Precipitates on the Structure of Multi-Directionally Isothermally Forged Al-Mg-Sc-Zr Alloy

NASA Astrophysics Data System (ADS)

Sitdikov, O. Sh.; Avtokratova, E. V.; Mukhametdinova, O. E.; Garipova, R. N.; Markushev, M. V.

2017-12-01

The effect of Al3(Sc,Zr) dispersoids on the evolution of the cast Al-Mg-Sc-Zr alloy structure under multi-directional isothermal forging (MIF) has been investigated. The alloy, which has an equiaxed grain structure with a grain size of 25 μm and contains dispersoids 5-10 and 20-50 nm in size after onestage (at 360°C for 6 h) and two-stage (360°C for 6 h + 520°C for 1 h) annealing, respectively, was deformed at 325°C ( 0.65 T m) up to cumulative strains of e = 8.4. In the initial stages of MIF, new fine (sub)grains surrounded by low-angle and high-angle boundaries (HABs) were formed near the initial grain boundaries. With increasing strain, the volume fraction and misorientation of these crystallites increased, which led to the replacement of a coarse-grained structure with a fine-grained one with a grain size of 1.5-2.0 μm. Dynamic recrystallization occurred in accordance to a continuous mechanism and was controlled by the interaction of lattice dislocations and/or (sub)grain boundaries with dispersoids that effectively inhibited the migration of boundaries, as well as the rearrangement of lattice dislocations and their annihilation. The particle size and the density of their distribution significantly affected the parameters of the evolved structure; in an alloy with smaller particles, a structure with a smaller grain size and a larger HAB fraction developed.

Seasonal Trends and Inter-Individual Heterogeneity: A multi-species record of Mg, Sr, Ba, & Mn in Planktic Foraminifera from the Modern Cariaco Basin

NASA Astrophysics Data System (ADS)

Davis, C. V.; Thunell, R.; Astor, Y. M.

2017-12-01

The trace element to calcium ratios (TE/Ca) of planktic foraminifera shells are a valuable tool for paleoceanographic reconstructions, and represent a combination of environmental, ecological and biological signals. We present here a three-year record (2010-2013) of TE/Ca (Mg, Sr, Ba, Mn) from four species of foraminifera (Orbulina universa, Globigerina ruber, Globigerinella siphonifera, and Globorotalia menardii) collected by plankton tow in the modern Cariaco basin. Each tow is paired with in situ measurements of water column properties, allowing a direct comparison between shell geochemistry and calcification environment. A combination of Laser Ablation and solution ICP-MS analyses are used to document seasonality, primarily due to the alternating influence of wind-driven coastal upwelling and riverine inputs, in shell TE/Ca. Individual shell data further allows for the quantification of trace element heterogeneity among individual shells within single tows. All TE/Ca ratios vary temporally and show inter-individual variability within single tows. The spread in TE/Ca differs between element and species, with Mg/Ca ratios being the most variable. Despite this, Mg/Ca still tracks temperature changes in G. ruber, O. universa, and G. menardii, with G. ruber most closely reproducing sea surface temperature. Some species show chamber-to-chamber differences in trace element ratios, with G. ruber Mg/Ca and Ba/Ca decreasing in younger chambers (but not other elements) and Mg/Ca, Mn/Ca and Ba/Ca decreasing in younger chambers in G. siphonifera. We find the original Mn/Ca to be variable both temporally and between species, with G. menardii in some samples having extremely high ratios (100 μmol/mol). Assessing seasonal trends and environmental drivers of TE/Ca variability and quantifying the extent of inter-individual heterogeneity in these species will inform the use of their shells as geochemical proxies.

Microstructure Evolution in Mg-Zn-Zr-Gd Biodegradable Alloy: The Decisive Bridge Between Extrusion Temperature and Performance

PubMed Central

Yao, Huai; Wen, Jiu-Ba; Xiong, Yi; Lu, Yan; Huttula, Marko

2018-01-01

Being a biocompatible metal with similar mechanical properties as bones, magnesium bears both biodegradability suitable for bone substitution and chemical reactivity detrimental in bio-ambiences. To benefit its biomaterial applications, we developed Mg-2.0Zn-0.5Zr-3.0Gd (wt%) alloy through hot extrusion and tailored its biodegradability by just varying the extrusion temperatures during alloy preparations. The as-cast alloy is composed of the α-Mg matrix, a network of the fish-bone shaped and ellipsoidal (Mg, Zn)3Gd phase, and a lamellar long period stacking ordered phase. Surface content of dynamically recrystallized (DRXed) and large deformed grains increases within 330–350°C of the extrusion temperature, and decreases within 350–370°C. Sample second phase contains the (Mg, Zn)3Gd nano-rods parallel to the extrusion direction, and Mg2Zn11 nanoprecipitation when temperature tuned above 350°C. Refining microstructures leads to different anticorrosive ability of the alloys as given by immersion and electrochemical corrosion tests in the simulated body fluids. The sample extruded at 350°C owns the best anticorrosive ability thanks to structural impacts where large DRXed portions and uniform nanosized grains reduce chemical potentials among composites, and passivate the extruded surfaces. Besides materials applications, the in vitro mechanism revealed here is hoped to inspire similar researches in biometal developments. PMID:29616216

Microstructure evolution in Mg-Zn-Zr-Gd biodegradable alloy: the decisive bridge between extrusion temperature and performance

NASA Astrophysics Data System (ADS)

Yao, Huai; Wen, Jiu-Ba; Xiong, Yi; Lu, Yan; Huttula, Marko

2018-03-01

Being a biocompatible metal with similar mechanical properties as bones, magnesium bears both biodegradability suitable for bone substitution and chemical reactivity detrimental in bio-ambiences. To benefit its biomaterial applications, we developed Mg-2.0Zn-0.5Zr-3.0Gd (wt%) alloy through hot extrusion and tailored its biodegradability by just varying the extrusion temperatures during alloy preparations. The as-cast alloy is composed of the α-Mg matrix, a network of the fish-bone shaped and ellipsoidal (Mg, Zn)3Gd phase, and a lamellar long period stacking ordered phase. Surface content of dynamically recrystallized (DRXed) and large deformed grains increases within 330-350 C of the extrusion temperature, and decreases within 350-370 C. Sample second phase contains the (Mg, Zn)3Gd nano-rods parallel to the extrusion direction, and Mg2Zn11 nanoprecipitation when temperature tuned above 350 C. Refining microstructures leads to different anticorrosive ability of the alloys as given by immersion and electrochemical corrosion tests in the simulated body fluids. The sample extruded at 350 C owns the best anticorrosive ability thanks to structural impacts where large DRXed portions and uniform nanosized grains reduce chemical potentials among composites, and passivate the extruded surfaces. Besides materials applications, the in vitro mechanism revealed here is hoped to inspire similar researches in biometal developments.

Significant increase of Curie temperature and large piezoelectric coefficient in Ba(Ti0.80Zr0.20)O3-0.5(Ba0.70Ca0.30)TiO3 nanofibers

NASA Astrophysics Data System (ADS)

Fu, Bi; Yang, Yaodong; Gao, Kun; Wang, Yaping

2015-07-01

Ba(Ti0.80Zr0.20)O3-0.5(Ba0.7Ca0.3)TiO3 (abbreviated as BTZ-0.5BCT) is a piezoelectric ceramic with a high piezoelectric coefficient d33 (˜620 pC N-1) and has been regarded as one of the most promising candidates to replace PZT-based materials (200-710 pC N-1). However, its Curie temperature TC is relatively low (93 °C) limiting its application. In this letter, we found a temperature dependent Raman spectrum in BTZ-0.5BCT nanofibers (NFs), demonstrating a diffused tetragonal-to-cubic phase transition at 300 °C. This means that the TC of the NFs is nearly 207 °C higher than that of the normal bulk material. The increased TC is considered to be associated with the size effect of BTZ-0.5BCT nanoceramic subunits and the nanoporous nature of the fiber, resulting in discontinuous physical properties. The variation of the ferro/piezoelectricity over the fiber surface is attributed to the polycrystalline structure. The d33 (173.32 pm V-1) is improved in terms of the decreased Q factor result in an increase in d33 of 236.54 pm V-1 after polarization. With a high TC and a very large d33, BTZ-0.5BCT NFs are capable of providing electromechanical behavior used in moderate temperatures.

Hysteretic Characteristics of Pulsed Laser Deposited 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3/ZnO Bilayers.

PubMed

Silva, J P B; Wang, J; Koster, G; Rijnders, G; Negrea, R F; Ghica, C; Sekhar, K C; Moreira, J Agostinho; Gomes, M J M

2018-05-02

In the present work, we study the hysteretic behavior in the electric-field-dependent capacitance and the current characteristics of 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BCZT)/ZnO bilayers deposited on 0.7 wt % Nb-doped (001)-SrTiO 3 (Nb:STO) substrates in a metal-ferroelectric-semiconductor (MFS) configuration. The X-ray diffraction measurements show that the BCZT and ZnO layers are highly oriented along the c-axis and have a single perovskite and wurtzite phases, respectively, whereas high-resolution transmission electron microscopy revealed very sharp Nb:STO/BCZT/ZnO interfaces. The capacitance-electric field ( C- E) characteristics of the bilayers exhibit a memory window of 47 kV/cm and a capacitance decrease of 22%, at a negative bias. The later result is explained by the formation of a depletion region in the ZnO layer. Moreover, an unusual resistive switching (RS) behavior is observed in the BCZT films, where the RS ratio can be 500 times enhanced in the BCZT/ZnO bilayers. The RS enhancement can be understood by the barrier potential profile modulation at the depletion region, in the BCZT/ZnO junction, via ferroelectric polarization switching of the BCZT layer. This work builds a bridge between the hysteretic behavior observed either in the C- E and current-electric field characteristics on a MFS structure.

Doped ZrO2 for future lead free piezoelectric devices

NASA Astrophysics Data System (ADS)

Starschich, S.; Böttger, U.

2018-01-01

The ferroelectric and piezoelectric properties of doped ZrO2 prepared by chemical solution deposition (CSD) are investigated. Doping with different elements such as Mg, In, La, and Y leads to a stabilization of the constricted hysteresis. As shown in a previous work, for the constricted hysteresis of ZrO2, the piezoelectric response is significantly larger compared to ZrO2 with a normal hysteresis. The Mg doped ZrO2 shows a strong temperature and cycle stability. For the piezoelectric properties, a magnesium concentration of 7% shows the largest piezoelectric response with a piezoelectric coefficient of >10 pm/V, as well as the best cycle stability. Due to thicker films, which can be realized by the CSD technique, the shown doped ZrO2 films are a promising candidate for energy related applications such as piezoelectric energy harvesting as well as for microelectromechanical systems.

Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program. II. Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Eu

NASA Astrophysics Data System (ADS)

Delgado Mena, E.; Tsantaki, M.; Adibekyan, V. Zh.; Sousa, S. G.; Santos, N. C.; González Hernández, J. I.; Israelian, G.

2017-10-01

Aims: To understand the formation and evolution of the different stellar populations within our Galaxy it is essential to combine detailed kinematical and chemical information for large samples of stars. The aim of this work is to explore the chemical abundances of neutron capture elements which are a product of different nucleosynthesis processes taking place in diverse objects in the Galaxy, such as massive stars, asymptotic giant branch (AGB) stars and supernovae (SNe) explosions. Methods: We derive chemical abundances of Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Eu for a large sample of more than 1000 FGK dwarf stars with high-resolution (R 115 000) and high-quality spectra from the HARPS-GTO program. The abundances are derived by a standard local thermodynamic equilibrium (LTE) analysis using measured equivalent widths (EWs) injected to the code MOOG and a grid of Kurucz ATLAS9 atmospheres. Results: We find that thick disc stars are chemically disjunct for Zn and Eu and also show on average higher Zr but lower Ba and Y than the thin disc stars. We also discovered that the previously identified high-α metal-rich population is also enhanced in Cu, Zn, Nd, and Eu with respect to the thin disc but presents lower Ba and Y abundances on average, following the trend of thick disc stars towards higher metallities and further supporting the different chemical composition of this population. By making a qualitative comparison of O (pure α), Mg, Eu (pure r-process), and s-process elements we can distinguish between the contribution of the more massive stars (SNe II for α and r-process elements) and the lower mass stars (AGBs) whose contribution to the enrichment of the Galaxy is delayed, due to their longer lifetimes. The ratio of heavy-s to light-s elements of thin disc stars presents the expected behaviour (increasing towards lower metallicities) and can be explained by a major contribution of low-mass AGB stars for s-process production at disc metallicities. However, the

Fluorine Kα X-Ray Emission Spectra of MgF2, CaF2, SrF2 and BaF2

NASA Astrophysics Data System (ADS)

Sugiura, Chikara; Konishi, Wataru; Shoji, Shizuko; Kojima, Shinjiro

1990-11-01

The fluorine Kα emission spectra in fluorescence from a series of alkaline-earth fluorides MF2 (M=Mg, Ca, Sr and Ba) are measured with a high-resolution two-crystal vacuum spectrometer. An anomalously low intensity of the K1L1 satellite peak arising from 1s-1(2s2p)-1 initial states is observed for SrF2. The measured emission spectra are presented along with the UPS spectra of the F- 2p valence bands obtained by Poole et al. and the fluorine K absorption-edge spectra by Oizumi et al. By using these spectra, the first peak or shoulder in the fluorine K absorption-edge spectra is identified as being due to a core exciton which is formed below the bottom of the conduction band. The binding energy of the exciton is estimated to be 1.3(± 0.3), 1.1(± 0.2), 1.0(± 0.2) and 1.7(± 0.2) eV for MgF2, CaF2, SrF2 and BaF2, respectively.

Enhanced biocorrosion resistance and biocompatibility of degradable Mg-Nd-Zn-Zr alloy by brushite coating.

PubMed

Niu, Jialin; Yuan, Guangyin; Liao, Yi; Mao, Lin; Zhang, Jian; Wang, Yongping; Huang, Feng; Jiang, Yao; He, Yaohua; Ding, Wenjiang

2013-12-01

To further improve the corrosion resistance and biocompatibility of Mg-Nd-Zn-Zr alloy (JDBM), a biodegradable calcium phosphate coating (Ca-P coating) with high bonding strength was developed using a novel chemical deposition method. The main composition of the Ca-P coating was brushite (CaHPO4·2H2O). The bonding strength between the coating and the JDBM substrate was measured to be over 10 MPa, and the thickness of the coating layer was about 10-30 μm. The in vitro corrosion tests indicated that the Ca-P treatment improved the corrosion resistance of JDBM alloy in Hank's solution. Ca-P treatment significantly reduced the hemolysis rate of JDBM alloy from 48% to 0.68%, and induced no toxicity to MC3T3-E1 cells. The in vivo implantation experiment in New Zealand's rabbit tibia showed that the degradation rate was reduced obviously by the Ca-P treatment and less gas was produced from Ca-P treated JDBM bone plates and screws in early stage of the implantation, and at least 10weeks degradation time can be prolonged by the present coating techniques. Both Ca-P treated and untreated JDBM Mg alloy induced bone growth. The primary results indicate that the present Ca-P treatment is a promising technique for the degradable Mg-based biomaterials for orthopedic applications. © 2013.

Multiple caloric effects in (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 ferroelectric ceramic

NASA Astrophysics Data System (ADS)

Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

2015-07-01

Multiple caloric effects have been investigated for Fe-doped bulk (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 (BCZTO-Fe) ferroelectric ceramic. Indirect predictions were made using Maxwell's relations in conjunction with data from experimental observations. It was revealed that bulk BCZTO-Fe has huge untapped potential for solid-state refrigeration. A peak electrocaloric effect of 0.45 K (347 K) was predicted for 0-3 kV.mm-1 electric field, significantly higher than other BCZTO based materials. A maximum elastocaloric cooling of 1.4 K (298 K) was achieved for applied stress of 0-200 MPa. Finally, an unforeseen component of electric field driven caloric effect has been reported as inverse piezocaloric effect, with a maximum temperature change of 0.28 K (298 K).

Correlative characterization of primary Al{sub 3}(Sc,Zr) phase in an Al–Zn–Mg based alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J.H., E-mail: jie-hua.li@hotmail.com; Wiessner, M.; Albu, M.

2015-04-15

Three-dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural information of primary Al{sub 3}(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (i) most primary Al{sub 3}(Sc,Zr) phases have a cubic three-dimensional morphology, with a size of about 6–10 μm, (ii) most primary Al{sub 3}(Sc,Zr) phases are located within the α-Al matrix, and exhibit a cube to cube orientation relationship with the α-Al matrix, and (iii) a layer by layer growth was observed within primary Al{sub 3}(Sc,Zr) phases.more » Al, Cu, Si and Fe are enriched in the α-Al matrix between the layers of cellular eutectic Al{sub 3}(Sc,Zr) phase, while Sc, Ti and Zr are enriched in small Al{sub 3}(Sc,Zr) phases. A peritectic reaction and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed to interpret the observed layer by layer growth. This paper demonstrates that the presence of impurities (Fe, Si, Cu, Ti) in the diffusion field surrounding the growing Al{sub 3}(Sc,Zr) particle enhances the heterogeneous nucleation of Al{sub 3}(Sc,Zr) phases. - Highlights: • Most fine cubic primary Al{sub 3}(Sc,Zr) phases were observed within the α-Al matrix. • A layer by layer growth within primary Al{sub 3}(Sc,Zr) phase was observed. • A peritectic and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed. • Impurities in diffusion fields enhance heterogeneous nucleation of Al{sub 3}(Sc,Zr)« less

Influence of fluoride treatment on surface properties, biodegradation and cytocompatibility of Mg-Nd-Zn-Zr alloy.

PubMed

Zhang, Jian; Kong, Ni; Niu, Jialin; Shi, Yongjuan; Li, Haiyan; Zhou, Yue; Yuan, Guangyin

2014-03-01

Fluoride treatment is a commonly used technique or pre-treatment to optimize the degradation kinetic and improve the biocompatibility of magnesium-based implant. The influence of changed surface properties and degradation kinetics on subsequent protein adsorption and cytocompatibility is critical to understand the biocompatibility of the implant. In this study, a patent magnesium alloy Mg-Nd-Zn-Zr alloy (JDBM) designed for cardiovascular stent application was treated by immersion in hydrofluoric acid. A 1.5 μm thick MgF2 layer was prepared. The surface roughness was increased slightly while the surface zeta potential was changed to a much more negative value after the treatment. Static contact angle test was performed, showing an increase in hydrophilicity and surface energy after the treatment. The MgF2 layer slowed down in vitro degradation rate, but lost the protection effect after 10 days. The treatment enhanced human albumin adsorption while no difference of human fibrinogen adsorption amount was observed. Direct cell adhesion test showed many more live HUVECs retained than bare magnesium alloy. Both treated and untreated JDBM showed no adverse effect on HUVEC viability and spreading morphology. The relationship between changed surface characteristics, degradation rate and protein adsorption, cytocompatibility was also discussed.

Energy storage properties and relaxor behavior of lead-free Ba1-xSm2x/3Zr0.15Ti0.85O3 ceramics.

PubMed

Sun, Zheng; Li, Lingxia; Yu, Shihui; Kang, Xinyu; Chen, Siliang

2017-10-24

Lead-free Ba 1-x Sm 2x/3 Zr 0.15 Ti 0.85 O 3 (BSZT) ceramics were synthesized by a solid state reaction route. The microstructure, dielectric relaxor behavior and energy storage properties of BSZT ceramics were studied. The growth of grain size was suppressed with the increase of Sm addition and kept in the submicrometer scale. Successive substitution of Sm 3+ for Ba 2+ disrupted the long-range dipole and promoted the increase of polar nano-region (PNR) size, resulting in the enhanced degree of relaxor behavior. The increasing PNR size also lead to the slimmer hysteresis loops and improved the energy storage efficiency. Furthermore, high saturated polarization (P max ) and low remnant polarization (P r ) were obtained due to the formation of defect dipoles, which facilitated the switch of PNRs and contributed to the enhancement of energy storage density. The x = 0.003 sample was found to exhibit a higher energy storage density of 1.15 J cm -3 and an energy storage efficiency of 92%. The result revealed that the BSZT ceramics may be a good candidate for energy storage application.

Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, a new very complex Ba-Sc phosphate mineral from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia)

NASA Astrophysics Data System (ADS)

Yakovenchuk, Victor N.; Ivanyuk, Gregory Yu.; Pakhomovsky, Yakov A.; Panikorovskii, Taras L.; Britvin, Sergei N.; Krivovichev, Sergey V.; Shilovskikh, Vladimir V.; Bocharov, Vladimir N.

2018-02-01

Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, is a new Ba-Sc phosphate from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia). It is orthorhombic, Pnma, a = 11.256(1), b = 8.512(1), c = 27.707(4) Å, V = 2654.6(3) Å3 and Z = 4 (from powder diffraction data) or a = 11.2261(9), b = 8.5039(6), c = 27.699(2) Å, V = 2644.3(3) Å3 (from single-crystal diffraction data). The mineral was found in a void within the calcite-magnetite phoscorite (enriched in hydroxylapatite and Sc-rich baddeleyite) inside the axial zone of the Kovdor phoscorite-carbonatite pipe. Kampelite forms radiated aggregates (up to 1.5 mm in diameter) of platy crystals grown on the surfaces of crystals of quintinite-2 H in close association with pyrite, bobierrite and quintinite-3 R. Kampelite is colourless, with a pearly lustre and a white streak. The cleavage is perfect on {001}, the fracture is smooth. Mohs hardness is about 1. In transmitted light, the mineral is colourless without pleochroism or dispersion. Kampelite is biaxial + (pseudouniaxial), α ≈ β = 1.607(2), γ = 1.612(2) (589 nm), and 2 V calc = 0°. The calculated and measured densities are 3.28 and 3.07(3) g·cm-3, respectively. The mean chemical composition determined by electron microprobe is: MgO 4.79, Al2O3 0.45, P2O5 31.66, K2O 0.34, Sc2O3 16.17, Mn2O3 1.62, Fe2O3 1.38, SrO 3.44, and BaO 29.81 wt%. The H2O content estimated from the crystal-structure refinement is 7.12 wt%, giving a total of 96.51 wt%. The empirical formula calculated on the basis of P = 6 apfu (atoms per formula unit) is (Ba2.62Sr0.45K0.10Ca0.06)Σ3.23Mg1.60Mn0.28(Sc3.15Fe3+ 0.23Al0.12)Σ3.50(PO4)6(OH)2.61·4.01H2O. The simplified formula is Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O. The mineral easily dissolves in 10% cold HCl. The strongest X-ray powder-diffraction lines [listed as d in Å ( I) ( hkl)] are as follows: 15.80(100)(001), 13.86(45)(002), 3.184(18)(223), 3.129(19)(026), 2.756(16)(402), 2.688(24)(10 10). The crystal structure of kampelite was

Fracture resistance and fatigue crack growth characteristics of two Al-Cu-Mg-Zr alloys

NASA Technical Reports Server (NTRS)

Sarkar, Bhaskar; Lisagor, W. B.

1992-01-01

The dependence of strength, fracture resistance, and fatigue crack growth rate on the aging conditions of two alloy compositions based on Al-3.7Cu-1.85Mg-0.2Mn is investigated. Mechanical properties were evaluated in two heat treatment conditions and in two orientations (longitudinal and transverse). Compact tension specimens were used to determine fatigue crack growth characteristics and fracture resistance. The aging response was monitored on coupons using hardness measurements determined with a standard Rockwell hardness tester. Fracture resistance is found to increase with increasing yield strength during artificial aging of age-hardenable 2124-Zr alloys processed by powder metallurgy techniques. Fatigue crack growth rate increases with increasing strength. It is argued that these changes are related to deformation modes of the alloys; a homogeneous deformation mode tends to increase fracture resistance and to decrease the resistance to the fatigue crack propagation rate.

A brief review of Ba(Ti0.8Zr0.2)O3-(Ba0.7Ca0.3)TiO3 based lead-free piezoelectric ceramics: Past, present and future perspectives

NASA Astrophysics Data System (ADS)

Zhang, Yong; Sun, Huajun; Chen, Wen

2018-03-01

As one kind of most crucial and emerging lead-free piezoelectric systems, Ba(Ti0.8Zr0.2)O3-(Ba0.7Ca0.3)TiO3 (BCZT) based lead-free piezoceramics have attracted worldwide attention in recent years. Much progress has been made, however, a summary which covers both the recent progress and the remained problems is urgently needed to further push this field forward. In this review, a brief background of the development of BCZT based lead-free piezoceramics was illustrated firstly. Then, the internal mechanism for the high piezoelectric response would be elaborated. Current research status was discussed in detail in the third section. Various strategies including: (1) Using distinct synthesis routes, (2) adopting different sintering techniques, (3) doping with foreign ions and/or second components, (4) grain size control, were exploited to improve the comprehensive performance and in turn broaden their application areas. In this part, some recently representative works were touched in detail and several existing problems were pointed out. Last, some critical comments (some thoughts related to the potential and future development of BCZT system) were given based on the current research status and existing problems. All in all, this review is devoted to summarizing the milestones in the past, classifying selected recent works and analyzing the prospects of BCZT based ceramics. It can be expected that, this first review that concentrates on BCZT based ceramics obviously would provide useful guidance for the research community.

Effect of concurrent Mg/Nb-doping on dielectric properties of Ba0.45Sr0.55TiO3 thin films

NASA Astrophysics Data System (ADS)

Alema, Fikadu; Reich, Michael; Reinholz, Aaron; Pokhodnya, Konstantin

2013-08-01

Composition, microstructure, and dielectric properties of undoped and Ba(Mg1/3Nb2/3)O3 (BMN) doped Ba0.45Sr0.55TiO3 (BST) thin films deposited via rf. magnetron sputtering on platinized alumina substrates have been investigated. The analysis of microstructure has shown that despite the sizable effect of doping on the residual stress, the latter is partially compensated by the thermal expansion coefficient mismatch, and its influence on the BST film crystal structure is insignificant. It was revealed that BMN doped film demonstrated an average (over 2000 devices) of 52.5% tunability at 640 kV/cm, which is ˜8% lower than the value for the undoped film. This drop is associated with the presence of Mg ions in BMN; however, the effect of Mg doping is partially compensated by that of Nb ions. The decrease in grain size upon doping may also contribute to the tunability drop. Doping with BMN allows achievement of a compensation concentration yielding no free carriers and resulting in significant leakage current reduction when compared with the undoped film. In addition, the presence of large amounts of empty shallow traps related to NbTi• allows localizing free carriers injected from the contacts thus extending the device control voltage substantially above 10 V.

Dielectric Properties of BST/(Y 2O 3) x(ZrO 2) 1-x/BST Trilayer Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahoo, Santosh K.; Misra, D.

2011-01-31

Thin films of Ba1-xSrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and high dielectric breakdown strength. Various approaches have been used to improve the dielectric properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in dielectric constant as well as dielectric loss. In this work the effect of Y2O3 doped ZrO2 on the dielectric properties of BST/ZrO2/BST trilayer structure ismore » studied. The structure Ba0.8Sr0.2TiO3/(Y2O3)x(ZrO2)1-x/Ba0.8Sr0.2TiO3 is deposited by a sol-gel process on platinized Si substrate. The composition (x) of the middle layer is varied while keeping the total thickness of the trilayer film constant. The dielectric constant of the multilayer film decreases with the increase of Y2O3 amount in the film whereas there is a slight variation in dielectric loss. In Y2O3 doped multilayer thin films, the dielectric loss is lower in comparison to other films and also there is good frequency stability in the loss in the measured frequency range and hence very suitable for microwave device applications.« less

Dielectric properties of BaMg1/3Nb2/3O3 doped Ba0.45Sr0.55Tio3 thin films for tunable microwave applications

NASA Astrophysics Data System (ADS)

Alema, Fikadu; Pokhodnya, Konstantin

2015-11-01

Ba(Mg1/3Nb2/3)O3 (BMN) doped and undoped Ba0.45Sr0.55TiO3 (BST) thin films were deposited via radio frequency magnetron sputtering on Pt/TiO2/SiO2/Al2O3 substrates. The surface morphology and chemical state analyses of the films have shown that the BMN doped BST film has a smoother surface with reduced oxygen vacancy, resulting in an improved insulating properties of the BST film. Dielectric tunability, loss, and leakage current (LC) of the undoped and BMN doped BST thin films were studied. The BMN dopant has remarkably reduced the dielectric loss (˜38%) with no significant effect on the tunability of the BST film, leading to an increase in figure of merit (FOM). This is attributed to the opposing behavior of large Mg2+ whose detrimental effect on tunability is partially compensated by small Nb5+ as the two substitute Ti4+ in the BST. The coupling between MgTi″ and VO•• charged defects suppresses the dielectric loss in the film by cutting electrons from hopping between Ti ions. The LC of the films was investigated in the temperature range of 300-450K. A reduced LC measured for the BMN doped BST film was correlated to the formation of defect dipoles from MgTi″, VO•• and NbTi• charged defects. The carrier transport properties of the films were analyzed in light of Schottky thermionic emission (SE) and Poole-Frenkel (PF) emission mechanisms. The result indicated that while the carrier transport mechanism in the undoped film is interface limited (SE), the conduction in the BMN doped film was dominated by bulk processes (PF). The change of the conduction mechanism from SE to PF as a result of BMN doping is attributed to the presence of uncoupled NbTi• sitting as a positive trap center at the shallow donor level of the BST.

Zr-92(d,p)Zr-93 and Zr-92(d,t)Zr-91

NASA Technical Reports Server (NTRS)

Baron, N.; Fink, C. L.; Christensen, P. R.; Nickels, J.; Torsteinsen, T.

1972-01-01

The structures of Zr-93 and Zr-91 were studied by the stripping reaction Zr-92(d,p)Zr-93 and the pick-up reaction Zr-92(d,t)Zr-91 using 13 MeV incident deuterons. The reaction product particles were detected by counter telescope. Typical spectra from the reactions were analyzed by a nonlinear least squares peak fitting program which included a background search. Spin and parity assignments to observed excited levels were made by comparing experimental angular distributions with distorted wave Born approximation calculations.

In-situ observation of recrystallization in an AlMgScZr alloy using confocal laser scanning microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taendl, J., E-mail: johannes.taendl@tugraz.atl; Nambu, S.; Orthacker, A.

2015-10-15

In this work we present a novel in-situ approach to study the recrystallization behavior of age hardening alloys. We use confocal laser scanning microscopy (CLSM) at 400 °C to investigate the static recrystallization of an AlMg4Sc0.4Zr0.12 alloy in-situ. The results are combined with electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analyses. It was found that CLSM is a powerful tool to visualize both the local initiation and temporal sequence of recrystallization. After fast nucleation and initial growth, the grain growth rate decreases and the grain boundary migration stops after some minutes due to Zener pinning from Al{sub 3}(Sc,Zr)more » precipitates produced during the heat treatment. EBSD and TEM analyses confirm both the boundary movements and the particle-boundary interactions. - Highlights: • First time that CLSM is used to study recrystallization in-situ. • The start and end of recrystallization can be directly observed. • The procedure is easy to apply and requires only simple data interpretation. • In-situ observations on the surface correlate to modifications inside the bulk. • In-situ observations correlate to EBSD and EFTEM analyses.« less

Structural and magnetic properties of spark plasma sintered Co-Mg-Zn substituted Ba-Sr hexagonal ferrite magnets

NASA Astrophysics Data System (ADS)

Harikrishnan, V.; Vizhi, R. Ezhil; Rajan Babu, D.; Saravanan, P.

2018-02-01

The effect of conventional and spark plasma sintering processes on the structural and magnetic properties of Ba0.5Sr0.5Fe12-2xCox(MgZn)x/2O19 (x = 0.2, 0.4 and 0.6) was investigated in this study. XRD patterns of both conventionally sintered (CS) and spark plasma sintered (SPS) samples with x = 0.2 and 0.4 showed the crystallization of Ba0.5Sr0.5Fe12O19-phase with space group of P63/mmc. However, in the case of SPS sample with x = 0.4, a secondary peak of α-Fe2O3 was observed. SEM analysis on the SPS samples revealed dense morphology with low porosity; while the CS samples showed the presence of aggregated particles with spherical shapes. Maximum values of saturation magnetization, MS (58 emu/g) and coercivity, HC (3.5 kOe) were obtained for the CS samples with x = 0.4; while their SPS counterparts revealed increased MS (65 emu/g) and HC (3.9 kOe) values. The observed magnetization reversal behaviour for both sintering conditions were not smooth in the case of x = 0.2, which indicated the existence of two-phase behavior. The temperature dependent magnetization studies for x = 0.2 and 0.4 were performed in order to analyze the variation in Curie temperature against Co-Mg-Zn substitution and the obtained results are discussed on the basis of crystallization of hexaferrite-phase.

Observation of extreme ultraviolet transitions in highly charged Ba{sup 16+} to Ba{sup 23+} ions with electron beam ion trap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ali, S.; Shimizu, E.; Nakamura, N.

2016-03-15

We have investigated extreme ultraviolet emission from highly charged barium using a compact electron beam ion trap at the Tokyo EBIT laboratory. The spectra were recorded for several beam energies ranging from 440 to 740 eV, while keeping the electron beam current constant at 10 mA. Radiation from charge states Zr-like Ba{sup 16+} to As-like Ba{sup 23+} were recorded and identified by varying the electron beam energy across the ionization thresholds and comparing with calculated results. The calculations were performed with a detailed relativistic configuration interaction approach using the Flexible Atomic Code. Several new lines belonging to electric dipole transitions were observedmore » and identified.« less

Infrared and TPD studies of nitrates adsorbed on Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, BaO, and MgO/{gamma}-Al{sub 2}O{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chi, Y.; Chuang, S.S.C.

2000-05-18

NO and O{sub 2} coadsorption on {gamma}-Al{sub 2}O{sub 3}-supported Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, BaO, and MgO has been investigated by in situ infrared spectroscopy coupled with temperature-programmed decomposition and desorption. BaO/{gamma}-Al{sub 2}O{sub 3} and MgO/{gamma}-Al{sub 2}O{sub 3} possess a higher NO{sub x} storage capability than Tb{sub 4}O{sub 7}/{gamma}-Al{sub 2}O{sub 3} and La{sub 2}O{sub 3}/{gamma}-Al{sub 2}O{sub 3}. NO/O{sub 2} coadsorbed on Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, and BaO in the form of bridging bidentate, chelating bidentate, and monodentate nitrates, and on MgO in the form of bridging bidentate and monodentate nitrates via the reaction of adsorbed NO withmore » adsorbed oxygen at 298 K. NO/O{sub 2} coadsorbed as a chelating bidentate nitrate on Tb{sub 4}O{sub 7} and La{sub 2}O{sub 3}, and as a distinctive bridging bidentate nitrate on BaO and MgO via the reaction of adsorbed NO with surface lattice oxygen at 523 K. These various forms of adsorbed nitrate differ in structure and reactivity from Tb(NO{sub 3}){sub 3}, La(NO{sub 3}){sub 3}, Ba(NO{sub 3}){sub 2}, and Mg(NO{sub 3}){sub 2}, the precursor used to prepare metal oxides for NO/O{sub 2} coadsorption. Temperature-programmed desorption (TPD) of chelating bidentate nitrate on Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, and BaO produced primarily NO and O{sub 2}, with maxima at 640 and 670 K, respectively. TPD of bridging bidentate nitrate and monodentate nitrate on Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, and BaO produced NO and O{sub 2} as major products and N{sub 2} and N{sub 2}O as minor products, at 320--500 K. Decomposition of bridging bidentate on MgO produced NO as a major product and N{sub 2}O as a minor product at a peak temperature of 690 K. Peak temperatures for Tb(NO{sub 3}){sub 3}, La(NO{sub 3}){sub 3}, Ba(NO{sub 3}){sub 2}, and Mg(NO{sub 3}){sub 2} decomposition occurred between those for bridging and chelating nitrates. The difference in stability between

Synthesis of BaTiO3 and Ba(ZrxTi1-X)O3 by using the soft combustion method

NASA Astrophysics Data System (ADS)

Ahmad, Atiqah; Razak, Khairunisak Abdul

2017-07-01

In this work, barium titanate, BaTiO3 (BT) and Zr doped BT, BaZrxTi1-xO3 (BZT) with powders were successfully produced using the soft combustion method. Barium nitrate and titanium (IV) isopropoxide were used as the starting materials while zirconium (IV) oxynitrate hydrate as the doping precursors, and glycine as the combustion agent. The produced powders were pressed into 12 mm diameter pellets by using 150 MPa cold press. The effect of Zr dopant in BT was studied with molar ratio of x = 0.00, 0.03, 0.05, 0.08 and 0.10. The phase presence was identified using X-ray diffractometer. Morphology of powders and sintered pellets was observed using a scanning electron microscope. Density of the sintered pellets was measured by using Archimedes' principle, while dielectric properties were analysed by using an LCR meter. Pure perovskite BT and BZT structure were obtained after sintering at 1400 °C for 5 h. BZT with x = 0.03 has grain size of 3.9 µm and shows the highest dielectric constant of 525, compared to undoped BT that has the average grain size of 4.2 µm with dielectric constant 223. The results is in agreement with microstructure observation and density of the sample.

MgO-Al2O3-ZrO2 Amorphous Ternary Composite: A Dense and Stable Optical Coating

NASA Technical Reports Server (NTRS)

Shaoo, Naba K.; Shapiro, Alan P.

1998-01-01

The process-parameter-dependent optical and structural properties of MgO-Al2O3-ZrO2 ternary mixed-composite material were investigated. Optical properties were derived from spectrophotometric measurements. The surface morphology, grain size distributions, crystallographic phases, and process- dependent material composition of films were investigated through the use of atomic force microscopy, x-ray diffraction analysis, and energy-dispersive x-ray analysis. Energy-dispersive x-ray analysis made evident the correlation between the optical constants and the process-dependent compositions in the films. It is possible to achieve environmentally stable amorphous films with high packing density under certain optimized process conditions.

Air Plasma-Sprayed La2Zr2O7-SrZrO3 Composite Thermal Barrier Coating Subjected to CaO-MgO-Al2O3-SiO2 (CMAS)

NASA Astrophysics Data System (ADS)

Cai, Lili; Ma, Wen; Ma, Bole; Guo, Feng; Chen, Weidong; Dong, Hongying; Shuang, Yingchai

2017-08-01

La2Zr2O7-SrZrO3 composite thermal barrier coatings (TBCs) were prepared by air plasma spray (APS). The La2Zr2O7-SrZrO3 composite TBCs covered with calcium-magnesium-aluminum-silicate (CMAS) powder, as well as the powder mixture of CMAS and spray-dried La2Zr2O7-SrZrO3 composite powder, were heat-treated at 1250 °C in air for 1, 4, 8, and 12 h. The phase constituents and microstructures of the reaction products were characterized by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. Experimental results showed that the La2Zr2O7-SrZrO3 composite TBCs had higher CMAS resistance than 8YSZ coating. A dense new layer developed between CMAS and La2Zr2O7-SrZrO3 composite TBCs during interaction, and this new layer consisted mostly of apatite (Ca2La8(SiO4)6O2) and c-ZrO2. The newly developed layer effectively protected the La2Zr2O7-SrZrO3 composite TBCs from further CMAS attack.

Piezoelectric properties and temperature stability of Mn-doped Pb(Mg1/3Nb2/3)-PbZrO3-PbTiO3 textured ceramics

NASA Astrophysics Data System (ADS)

Yan, Yongke; Cho, Kyung-Hoon; Priya, Shashank

2012-03-01

In this letter, we report the electromechanical properties of textured 0.4Pb(Mg1/3Nb2/3)O3-0.25PbZrO3-0.35PbTiO3 (PMN-PZT) composition which has relatively high rhombohedral to tetragonal (R-T) transition temperature (TR-T of 160 °C) and Curie temperature (TC of 234 °C) and explore the effect of Mn-doping on this composition. It was found that MnO2-doped textured PMN-PZT ceramics with 5 vol. % BaTiO3 template (T-5BT) exhibited inferior temperature stability. The coupling factor (k31) of T-5BT ceramic started to degrade from 75 °C while the random counterpart showed a very stable tendency up to 180 °C. This degradation was associated with the "interface region" formed in the vicinity of BT template. MnO2 doped PMN-PZT ceramics textured with 3 vol. % BT and subsequently poled at 140 °C (T-3BT140) exhibited very stable and high k31 (>0.53) in a wide temperature range from room temperature to 130 °C through reduction in the interface region volume. Further, the T-3BT140 ceramic exhibited excellent hard and soft combinatory piezoelectric properties of d33 = 720 pC/N, k31 = 0.53, Qm = 403, tan δ = 0.3% which are very promising for high power and magnetoelectric applications.

Magnetodielectric effect in (1 - x)(Ba0.88Ca0.12)(Ti0.88Zr0.12)O3 - xCoFe2O4

NASA Astrophysics Data System (ADS)

Pan, Pengfei; Tao, Jin; Ma, Fusheng; Zhang, Ning

2018-05-01

Magnetodielectric (MD) materials have attracted considerable attention due to their intriguing physics and potential future applications. In this work, polycrystalline (1 - x)(Ba0.88Ca0.12)(Ti0.88Zr0.12)O3 - xCoFe2O4 (x = 0.10, 0.20, 0.30, 0.40) ceramic have been prepared via sol-gel method. The room temperature magnetic and ferroelectric behaviors of the synthesized composites were investigated. For the composite with x = 0.40, a MD ratio of 5.37% was achieved under a magnetic field of 1.5 T at f = 1 kHz. The measured "butterfly hysteresis" MD curves exhibit an obvious dielectric anomaly. Theoretical analysis suggests that the observed magnetodielectric effect is attributed to the magnetoresistance effect and magnetoelectric coupling.

Controlling BaZrO3 nanostructure orientation in YBa2Cu3O{}_{7-\\delta } films for a three-dimensional pinning landscape

NASA Astrophysics Data System (ADS)

Wu, J. Z.; Shi, J. J.; Baca, F. J.; Emergo, R.; Wilt, J.; Haugan, T. J.

2015-12-01

The orientation phase diagram of self-assembled BaZrO3 (BZO) nanostructures in c-oriented YBa2Cu3O{}7-δ (YBCO) films on flat and vicinal SrTiO3 substrates was studied experimentally with different dopant concentrations and vicinal angles and theoretically using a micromechanical model based on the theory of elasticity. The organized BZO nanostructure configuration was found to be tunable, between c-axis to ab-plane alignment, by the dopant concentration in the YBCO film matrix strained via lattice mismatched substrates. The correlation between the local strain caused by the BZO doping and the global strain on the matrix provides a unique approach for controllable growth of dopant nanostructure landscapes. In particular, a mixed phase of the c-axis-aligned nanorods and the ab-plane-aligned planar nanostructures can be obtained, leading to a three-dimensional pinning landscape with single impurity doping and much improved J c in almost all directions of applied magnetic field.

Monolithic translucent BaMgAl 10O 17:Eu 2+ phosphors for laser-driven solid state lighting

DOE PAGES

Cozzan, Clayton; Brady, Michael J.; O’Dea, Nicholas; ...

2016-10-11

With high power light emitting diodes and laser diodes being explored for white light generation and visible light communication, thermally robust encapsulation schemes for color-converting inorganic phosphors are essential. In the current work, the canonical blue-emitting phosphor, high purity Eu-doped BaMgAl 10O 17, has been prepared using microwave-assisted heating (25 min) and densified into translucent ceramic phosphor monoliths using spark plasma sintering (30 min). Lastly, the resulting translucent ceramic monoliths convert UV laser light to blue light with the same efficiency as the starting powder and provide superior thermal management in comparison with silicone encapsulation.

Manganese Recovery by Silicothermic Reduction of MnO in BaO-MnO-MgO-CaF2 (-SiO2) Slags

NASA Astrophysics Data System (ADS)

Heo, Jung Ho; Park, Joo Hyun

2018-04-01

The effects of reducing agent, CaF2 content, and reaction temperature upon the silicothermic reduction of MnO in the BaO-MnO-MgO-CaF2 (-SiO2) slags were investigated. Mn recovery was proportional to Si activity in the molten alloy. Moreover, 90 pct yield of Mn recovery was obtained under 5 mass pct CaF2 content and 1873 K (1600 °C) reaction temperature. Increasing CaF2 content above 5 pct yielded little or no further increase in Mn recovery, because it was accompanied by increased slag viscosity owing to the precipitation of high melting point compounds such as Ba2SiO4.

Efficient UV-emitting X-ray phosphors: octahedral Zr(PO 4) 6 luminescence centers in potassium hafnium-zirconium phosphates K 2Hf 1- xZr x(PO 4) 2 and KHf 2(1- x) Zr 2 x(PO 4) 3

NASA Astrophysics Data System (ADS)

Torardi, C. C.; Miao, C. R.; Li, J.

2003-02-01

Potassium hafnium-zirconium phosphates, K 2Hf 1- xZr x(PO 4) 2 and KHf 2(1- x) Zr 2 x(PO 4) 3, are broad-band UV-emitting phosphors. At room temperature, they have emission peak maxima at approximately 322 and 305 nm, respectively, under 30 kV peak molybdenum X-ray excitation. Both phosphors demonstrate luminescence efficiencies that make them up to ˜60% as bright as commercially available CaWO 4 Hi-Plus. The solid-state and flux synthesis conditions, and X-ray excited UV luminescence of these two phosphors are discussed. Even though the two compounds have different atomic structures, they contain zirconium in the same active luminescence environment as that found in highly efficient UV-emitting BaHf 1- xZr x(PO 4) 2. All the three materials have hafnium and zirconium in octahedral coordination via oxygen-atom corner sharing with six separate PO 4 tetrahedra. This octahedral Zr(PO 4) 6 moiety appears to be an important structural element for efficient X-ray excited luminescence, as are the edge-sharing octahedral TaO 6 chains for tantalate emission.

Domain wall motion and electromechanical strain in lead-free piezoelectrics: Insight from the model system (1 - x)Ba(Zr 0.2Ti 0.8)O 3-x(Ba 0.7Ca 0.3)TiO 3 using in situ high-energy X-ray diffraction during application of electric fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tutuncu, Goknur; Li, Binzhi; Bowman, Keith

The piezoelectric compositions (1 - x)Ba(Zr 0.2Ti 0.8)O 3–x(Ba 0.7Ca 0.3)TiO 3 (BZT-xBCT) span a model lead-free morphotropic phase boundary (MPB) between room temperature rhombohedral and tetragonal phases at approximately x = 0.5. In the present work, in situ X-ray diffraction measurements during electric field application are used to elucidate the origin of electromechanical strain in several compositions spanning the tetragonal compositional range 0.6 ≤ x ≤ 0.9. As BCT concentration decreases towards the MPB, the tetragonal distortion (given by c/a-1) decreases concomitantly with an increase in 90° domain wall motion. The increase in observed macroscopic strain is predominantly attributedmore » to the increased contribution from 90° domain wall motion. The results demonstrate that domain wall motion is a significant factor in achieving high strain and piezoelectric coefficients in lead-free polycrystalline piezoelectrics.« less

Electrochemical performance of BaZr0.1Ce0.7Y0.1Yb0.1O3-δ electrolyte based proton-conducting SOFC solid oxide fuel cell with layered perovskite PrBaCo2O5+δ cathode

NASA Astrophysics Data System (ADS)

Ding, Hanping; Xie, Yuanyuan; Xue, Xingjian

2011-03-01

BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) exhibits adequate protonic conductivity as well as sufficient chemical and thermal stability over a wide range of SOFC operating conditions, while layered perovskite PrBaCo2O5+δ (PBCO) has advanced electrochemical properties. This research fully takes advantage of these advanced properties and develops a novel protonic ceramic membrane fuel cell (PCMFC) of Ni-BZCYYb|BZCYYb|PBCO. The performance of the button cell was tested under intermediate-temperature range from 600 to 700 °C with humified H2 (∼3% H2O) as fuel and ambient air as oxidant. The results show that the open circuit potential of 0.983 V and the maximal power density of 490 mW cm-2 were achieved at 700 °C. By co-doping barium zirconate-cerate with Y and Yb, the conductivity of electrolyte was significantly improved. The polarization processes of the button cell were characterized using the complicated electrochemical impedance spectroscopy technique. The results indicate that the polarization resistances contributed from both charge migration processes and mass transfer processes increase with decreasing cell voltage loads. However the polarization resistance induced by mass transfer processes is negligible in the studied button cell.

Enhancement of osteogenesis and biodegradation control by brushite coating on Mg-Nd-Zn-Zr alloy for mandibular bone repair.

PubMed

Guan, Xingmin; Xiong, Meiping; Zeng, Feiyue; Xu, Bin; Yang, Lingdi; Guo, Han; Niu, Jialin; Zhang, Jian; Chen, Chenxin; Pei, Jia; Huang, Hua; Yuan, Guangyin

2014-12-10

To diminish incongruity between bone regeneration and biodegradation of implant magnesium alloy applied for mandibular bone repair, a brushite coating was deposited on a matrix of a Mg-Nd-Zn-Zr (hereafter, denoted as JDBM) alloy to control the degradation rate of the implant and enhance osteogenesis of the mandible bone. Both in vitro and in vivo evaluations were carried out in the present work. Viability and adhesion assays of rabbit bone marrow mesenchyal stem cells (rBM-MSCs) were applied to determine the biocompatibility of a brushite-coated JDBM alloy. Osteogenic gene expression was characterized by quantitative real-time polymerase chain reaction (RT-PCR). Brushite-coated JDBM screws were implanted into mandible bones of rabbits for 1, 4, and 7 months, respectively, using 316L stainless steel screws as a control group. In vivo biodegradation rate was determined by synchrotron radiation X-ray microtomography, and osteogenesis was observed and evaluated using Van Gieson's picric acid-fuchsin. Both the naked JDBM and brushite-coated JDBM samples revealed adequate biosafety and biocompatibility as bone repair substitutes. In vitro results showed that brushite-coated JDBM considerably induced osteogenic differentiation of rBM-MSCs. And in vivo experiments indicated that brushite-coated JDBM screws presented advantages in osteoconductivity and osteogenesis of mandible bone of rabbits. Degradation rate was suppressed at a lower level at the initial stage of implantation when new bone tissue formed. Brushite, which can enhance oeteogenesis and partly control the degradation rate of an implant, is an appropriate coating for JDBM alloys used for mandibular repair. The Mg-Nd-Zn-Zr alloy with brushite coating possesses great potential for clinical applications for mandibular repair.

Hydration energies and structures of alkaline earth metal ions, M2+(H2O)n, n = 5-7, M = Mg, Ca, Sr, and Ba.

PubMed

Rodriguez-Cruz, S E; Jockusch, R A; Williams, E R

1999-09-29

The evaporation of water from hydrated alkaline earth metal ions, produced by electrospray ionization, was studied in a Fourier transform mass spectrometer. Zero-pressure-limit dissociation rate constants for loss of a single water molecule from the hydrated divalent metal ions, M(2+)(H(2)O)(n) (M = Mg, Ca, and Sr for n = 5-7, and M = Ba for n = 4-7), are measured as a function of temperature using blackbody infrared radiative dissociation. From these values, zero-pressure-limit Arrhenius parameters are obtained. By modeling the dissociation kinetics using a master equation formalism, threshold dissociation energies (E(o)) are determined. These reactions should have a negligible reverse activation barrier; therefore, E(o) values should be approximately equal to the binding energy or hydration enthalpy at 0 K. For the hepta- and hexahydrated ions at low temperature, binding energies follow the trend expected on the basis of ionic radii: Mg > Ca > Sr > Ba. For the hexahydrated ions at high temperature, binding energies follow the order Ca > Mg > Sr > Ba. The same order is observed for the pentahydrated ions. Collisional dissociation experiments on the tetrahydrated species result in relative dissociation rates that directly correlate with the size of the metals. These results indicate the presence of two isomers for hexahydrated magnesium ions: a low-temperature isomer in which the six water molecules are located in the first solvation shell, and a high-temperature isomer with the most likely structure corresponding to four water molecules in the inner shell and two water molecules in the second shell. These results also indicate that the pentahydrated magnesium ions have a structure with four water molecules in the first solvation shell and one in the outer shell. The dissociation kinetics for the hexa- and pentahydrated clusters of Ca(2+), Sr(2+), and Ba(2+) are consistent with structures in which all the water molecules are located in the first solvation shell.

Diffuse Phase Transitions and Giant Electrostrictive Coefficients in Lead-Free Fe3+-Doped 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 Ferroelectric Ceramics.

PubMed

Jin, Li; Huo, Renjie; Guo, Runping; Li, Fei; Wang, Dawei; Tian, Ye; Hu, Qingyuan; Wei, Xiaoyong; He, Zhanbing; Yan, Yan; Liu, Gang

2016-11-16

The electrostrictive effect has some advantages over the piezoelectric effect, including temperature stability and hysteresis-free character. In the present work, we report the diffuse phase transitions and electrostrictive properties in lead-free Fe 3+ -doped 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BZT-0.5BCT) ferroelectric ceramics. The doping concentration was set from 0.25 to 2 mol %. It is found that by introducing Fe 3+ ion into BZT-0.5BCT, the temperature corresponding to permittivity maximum T m was shifted toward lower temperature monotonically by 37 °C per mol % Fe 3+ ion. Simultaneously, the phase transitions gradually changed from classical ferroelectric-to-paraelectric phase transitions into diffuse phase transitions with a weak relaxor characteristic. Purely electrostrictive responses with giant electrostrictive coefficient Q 33 between 0.04 and 0.05 m 4 /C 2 are observed from 25 to 100 °C for the compositions doped with 1-2 mol % Fe 3+ ion. The Q 33 of Fe 3+ -doped BZT-0.5BCT ceramics is almost twice the Q 33 of other ferroelectric ceramics. These observations suggest that the present system can be considered as a potential lead-free material for the applications in electrostrictive area and that BT-based ferroelectric ceramics would have giant electrostrictive coefficient over other ferroelectric systems.

Thermal oxidation behavior of an Al-Li-Cu-Mg-Zr alloy

NASA Astrophysics Data System (ADS)

Ahmad, Maqsood

1987-04-01

The chemical composition of oxide films formed during thermal treatments of an Al-Li-Cu-Mg-Zr alloy has been studied by means of Auger electron spectroscopy and X-ray photoelectron spectroscopy. The oxide layers formed after oxidation of 2.5 minutes to 30 minutes at 530 °C in lab air have been characterized. In the early stages of oxidation the surface is composed of both the lithium rich oxides and magnesium rich oxides. However, after longer oxidation times the oxidation of lithium becomes predominant and the air/oxide interface is completely covered by lithium compounds. Oxidation products formed on the alloy surface have been studied by X-ray diffraction analysis. The following three phases, namely, Li2CO3, α-Li5AlO4, and γ-LiAlO2, were identified. During heat treatment in lab air at 530 °C and at atmospheric pressure the dominating reaction product is Li2CO3. Due to the selective oxidation of lithium a soft surface layer is developed. The width of the soft layer formed during solution heat treatments carried out in lab air and in salt bath environments has been determined by microhardness measurements. The lithium concentration profiles were calculated from a diffusion equation. The depletion of alloying elements from the near surface region during heat treatments has been investigated using energy dispersive X-ray analysis. The oxide morphology was examined using scanning electron microscopy and optical microscopy.

Thermal oxidation behavior of an Al-Li-Cu-Mg-Zr alloy

NASA Astrophysics Data System (ADS)

Ahmad, Maqsood

1987-05-01

The chemical composition of oxide films formed during thermal treatments of an Al-Li-Cu-Mg-Zr alloy has been studied by means of Auger electron spectroscopy and X-ray photoelectron spectroscopy. The oxide layers formed after oxidation of 2.5 minutes to 30 minutes at 530 °C in lab air have been characterized. In the early stages of oxidation the surface is composed of both the lithium rich oxides and magnesium rich oxides. However, after longer oxidation times the oxidation of lithium becomes predominant and the air/oxide interface is completely covered by lithium compounds. Oxidation products formed on the alloy surface have been studied by X-ray diffraction analysis. The following three phases, namely, Li2CO3, α-Li5AlO4, and γ-LiAlO2, were identified. During heat treatment in lab air at 530 °C and at atmospheric pressure the dominating reaction product is Li2CO3. Due to the selective oxidation of lithium a soft surface layer is developed. The width of the soft layer formed during solution heat treatments carried out in lab air and in salt bath environments has been determined by microhardness measurements. The lithium concentration profiles were calculated from a diffusion equation. The depletion of alloying elements from the near surface region during heat treatments has been investigated using energy dispersive X-ray analysis. The oxide morphology was examined using scanning electron microscopy and optical microscopy.

Influence of Europium Doping on Various Electrical Properties of Low-Temperature Sintered 0.5Ba0.90Ca0.10TiO3-0.5BaTi0.88Zr0.12O3-0.1%CuO- xEu Lead-Free Ceramics

NASA Astrophysics Data System (ADS)

Tian, Yongshang; Li, Shuiyun; Sun, Shulin; Gong, Yansheng; Li, Tiantian; Yu, Yongshang; Jing, Qiangshan

2018-01-01

0.5Ba0.90Ca0.10TiO3-0.5BaTi0.88Zr0.12O3-0.1%CuO- xEu (BCT-BZT-Cu- xEu; x = 0-0.90%) lead-free ceramics were sintered at 1220°C with as-synthesized nanoparticles by a modified Pechini method. The structural characteristics and electrical properties of the ceramics that were influenced by varying europium-doping were investigated. All the ceramics featured high densification (relative density: ˜ 96%). X-ray powder diffraction results indicated the samples possessed pure orthorhombic phase. The maximum relative permittivity ( ɛ r, 10869) was found at x around 0.30%. Europium ions could dope on different substitution sites in the ABO3 lattice, which evidently influenced electrical properties with various volumes of oxygen vacancy. Moreover, the formation mechanisms of oxygen vacancy and defect electron complexes were stated. The piezoelectric properties were impacted by defect electron complexes, internal stress, ionic electronegativity, etc. The optimal electrical properties, i.e., d 33 = 384 pC/N, Q m = 92, and k p = 0.36, were detected at x = 0.45%.

High-yield sol-gel synthesis of well-dispersed, colorless ZrO(2) nanocrystals.

PubMed

Mizuno, Mikihisa; Sasaki, Yuichi; Lee, Sungkil; Katakura, Hitoshi

2006-08-15

A 93% high-yield synthesis of well-dispersed, colorless zirconium dioxide (ZrO(2)) nanocrystals is reported. In this synthesis, hydrolysis and condensation reactions of zirconium(IV) tert-butoxide in the presence of oleic acid (100 degrees C) formed ZrO(2) precursors. The ZrO(2) precursors were made of -Zr-O-Zr- networks surrounded by oleic acid molecules. Annealing (280 degrees C) the precursors dispersed in dioctyl ether caused crystallization of the -Zr-O-Zr- networks, thereby generating 4 nm ZrO(2) nanocrystals stabilized with oleic acid. The particles were highly crystalline and tetragonal phase. A dense ZrO(2) nanocrystal dispersion in toluene (280 mg/mL) showed a transmittance of about 90% (3 mm optical path length) in the whole visible region.

Precipitation Behavior and Quenching Sensitivity of a Spray Deposited Al-Zn-Mg-Cu-Zr Alloy

PubMed Central

Lei, Qian; Xiao, Zhu; Wang, Mingpu

2017-01-01

Precipitation behavior and the quenching sensitivity of a spray deposited Al-Zn-Mg-Cu-Zr alloy during isothermal heat treatment have been studied systematically. Results demonstrate that both the hardness and the ultimate tensile strength of the studied alloy decreased with the isothermal treatment time at certain temperatures. More notably, the hardness decreases rapidly after the isothermal heat treatment. During isothermal heat treatment processing, precipitates readily nucleated in the medium-temperature zone (250–400 °C), while the precipitation nucleation was scarce in the low-temperature zone (<250 °C) and in the high-temperature zone (>400 °C). Precipitates with sizes of less than ten nanometers would contribute a significant increase in yield strength, while the ones with a larger size than 300 nm would contribute little strengthening effect. Quenching sensitivity is high in the medium-temperature zone (250–400 °C), and corresponding time-temperature-property (TTP) curves of the studied alloy have been established. PMID:28925964

Large Electrocaloric Effect in Lead-Free (Ba0.85Ca0.15)(Zr0.1Ti0.9)O₃ Ceramics Prepared via Citrate Route.

PubMed

Shi, Jing; Zhu, Rongfeng; Liu, Xing; Fang, Bijun; Yuan, Ningyi; Ding, Jianning; Luo, Haosu

2017-09-18

The 1 wt % Li-doped (Ba 0.85 Ca 0.15 )(Zr 0.1 Ti 0.9 )O₃ (BCZT-Li) ceramics prepared by the citrate method exhibit improved phase purity, densification and electrical properties, which provide prospective possibility to develop high-performance electrocaloric materials. The electrocaloric effect was evaluated by phenomenological method, and the BCZT-Li ceramics present large electrocaloric temperature change ∆ T , especially large electrocaloric responsibility ξ = ∆ T max /∆ E max , which can be comparable to the largest values reported in the lead-free piezoelectric ceramics. The excellent electrocaloric effect is considered as correlating with the coexistence of polymorphic ferroelectric phases, which are detected by the Raman spectroscopy. The large ξ value accompanied by decreased Curie temperature (around 73 °C) of the BCZT-Li ceramics prepared by the citrate method presents potential applications as the next-generation solid-state cooling devices.

Effect of solution treatment on stress corrosion cracking behavior of an as-forged Mg-Zn-Y-Zr alloy

PubMed Central

Wang, S. D.; Xu, D. K.; Wang, B. J.; Sheng, L. Y.; Han, E. H.; Dong, C.

2016-01-01

Effect of solid solution treatment (T4) on stress corrosion cracking (SCC) behavior of an as-forged Mg-6.7%Zn-1.3%Y-0.6%Zr (in wt.%) alloy has been investigated using slow strain rate tensile (SSRT) testing in 3.5 wt.% NaCl solution. The results demonstrated that the SCC susceptibility index (ISCC) of as-forged samples was 0.95 and its elongation-to-failure (εf) was only 1.1%. After T4 treatment, the SCC resistance was remarkably improved. The ISCC and εf values of T4 samples were 0.86 and 3.4%, respectively. Fractography and surface observation indicated that the stress corrosion cracking mode for as-forged samples was dominated by transgranular and partially intergranular morphology, whereas the cracking mode for T4 samples was transgranular. In both cases, the main cracking mechanism was associated with hydrogen embrittlement (HE). Through alleviating the corrosion attack of Mg matrix, the influence of HE on the SCC resistance of T4 samples can be greatly suppressed. PMID:27387817

Synthesis, spectroscopic characterization, thermal analysis and electrical conductivity studies of Mg(II), Ca(II), Sr(II) and Ba(II) vitamin B2 complexes

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Moussa, Mohamed A. A.; Mohamed, Soha F.

2011-05-01

Riboflavin (RF) complexes of Mg(II), Ca(II), Sr(II) and Ba(II) were successfully synthesized. Structures of metal complexes obtained were confirmed and characterized by elemental analysis, molar conductance, and infrared spectra. DC electrical conductivity measurements indicated that the alkaline earth metal (II) complexes of RF ligand are non-electrolytes. Elemental analysis of chelates suggest that the metal(II) ligand ratio is 1:2 with structure formula as [M(RF) 2( X) 2]· nH 2O. Infrared assignments clearly show that RF ligand coordinated as a bidentate feature through azomethine nitrogen of pyrazine ring and C dbnd O of pyrimidine-2,4-dione. Thermal analyses of Mg(II), Ca(II), Sr(II) and Ba(II) complexes were investigated using (TG/DSC) under atmospheric nitrogen between 30 and 800 °C. The surface morphology of the complexes was studied by SEM. The electrical conductivities of RF and its metal complexes were also measured with DC electrical conductivity in the temperature range from room to 483 K.

Fabrication of 94Zr thin target for recoil distance doppler shift method of lifetime measurement

NASA Astrophysics Data System (ADS)

Gupta, C. K.; Rohilla, Aman; Abhilash, S. R.; Kabiraj, D.; Singh, R. P.; Mehta, D.; Chamoli, S. K.

2014-11-01

A thin isotopic 94Zr target of thickness 520 μg /cm2 has been prepared for recoil distance Doppler shift method (RDM) lifetime measurement by using an electron beam deposition method on tantalum backing of 3.5 mg/cm2 thickness at Inter University Accelerator Center (IUAC), New Delhi. To meet the special requirement of smoothness of surface for RDM lifetime measurement and also to protect the outer layer of 94Zr from peeling off, a very thin layer of gold has been evaporated on a 94Zr target on a specially designed substrate holder. In all, 143 mg of 99.6% enriched 94Zr target material was utilized for the fabrication of 94Zr targets. The target has been successfully used in a recent RDM lifetime measurement experiment at IUAC.

Crystal structure and luminescence properties of silver in AgM(PO{sub 3}){sub 3} (M = Mg, Zn, Ba) polyphosphates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belharouak, I.; Parent, C.; Tanguy, B.

1999-06-01

The relationships between the crystal structures and the luminescent properties of the AgM(PO{sub 3}){sub 3} (M = Mg, Zn, Ba) polyphosphates are reported in comparison with those of AgPO{sub 3}. The structure of the magnesium and zinc phosphates is characterized by long polyphosphates chains connected to infinite chains of [AgO{sub 6}] and [MO{sub 6}] polyhedra sharing faces. The basic structural phosphate unit in AgBa(PO{sub 3}){sub 3} is a P{sub 3}O{sub 9} ring. Silver atoms are located in distorted octahedral sites. Two types of luminescent centers have been observed. The UV emission observed in all these materials is typical of isolatedmore » Ag{sup +} ions. The visible emission observed only in the zinc phosphate is probably the result of a silver-zinc association. 16 refs., 8 figs., 3 tabs.« less

Metallic glassy Zr70Ni20Pd10 powders for improving the hydrogenation/dehydrogenation behavior of MgH2

PubMed Central

El-Eskandarany, M. Sherif

2016-01-01

Because of its low density, storage of hydrogen in the gaseous and liquids states possess technical and economic challenges. One practical solution for utilizing hydrogen in vehicles with proton-exchange fuel cells membranes is storing hydrogen in metal hydrides. Magnesium hydride (MgH2) remains the best hydrogen storage material due to its high hydrogen capacity and low cost of production. Due to its high activation energy and poor hydrogen sorption/desorption kinetics at moderate temperatures, the pure form of MgH2 is usually mechanically treated by high-energy ball mills and catalyzed with different types of catalysts. These steps are necessary for destabilizing MgH2 to enhance its kinetics behaviors. In the present work, we used a small mole fractions (5 wt.%) of metallic glassy of Zr70Ni20Pd10 powders as a new enhancement agent to improve its hydrogenation/dehydrogenation behaviors of MgH2. This short-range ordered material led to lower the decomposition temperature of MgH2 and its activation energy by about 121 °C and 51 kJ/mol, respectively. Complete hydrogenation/dehydrogenation processes were successfully achieved to charge/discharge about 6 wt.%H2 at 100 °C/200 °C within 1.18 min/3.8 min, respectively. In addition, this new nanocomposite system shows high performance of achieving continuous 100 hydrogen charging/discharging cycles without degradation. PMID:27220994

Mn2+ concentration manipulated red emission in BaMg2Si2O7:Eu2+,Mn2+

NASA Astrophysics Data System (ADS)

Ye, Song; Zhang, Jiahua; Zhang, Xia; Lu, Shaozhe; Ren, Xinguang; Wang, Xiaojun

2007-02-01

The luminescent properties of concentration dependence are reported in BaMg2Si2O7:Eu2+,Mn2+ red phosphor. It is observed that the broad red emission of Mn2+ consists of two bands, located at 620 and 675 nm, respectively, which are attributed to two different Mn2+ centers [Mn2+(I) and Mn2+(II)] substituting for two nonidentical Mg2+ sites [Mg2+(I) and Mg2+(II)] in the host. It is also found that the relative emission intensity of the Mn2+(II) to the Mn2+(I) increases with increasing Mn2+ concentration, leading to a red-shift of the overall emission. A detail analysis on the energy transfer from Eu2+ to the two Mn2+ centers is presented, which indicates that the number ratio of Mn2+(II) to Mn2+(I) increases with increasing Mn2+ concentration. This result is interpreted by the preferential formation of Mn2+(I) substituting for Mg2+(I) site. Based on energy transfer, the emission intensity ratios of Mn2+(I) to Eu2+ and Mn2+(II) to Eu2+, which is Mn2+ concentration dependent, are calculated using related fluorescence lifetimes. The calculated results are in good agreement with that obtained experimentally in the emission spectra.

Hydration Energies and Structures of Alkaline Earth Metal Ions, M2+ (H2O)n, n = 5–7, M = Mg, Ca, Sr, and Ba

PubMed Central

Rodriguez-Cruz, Sandra E.; Jockusch, Rebecca A.

2005-01-01

The evaporation of water from hydrated alkaline earth metal ions, produced by electrospray ionization, was studied in a Fourier transform mass spectrometer. Zero-pressure-limit dissociation rate constants for loss of a single water molecule from the hydrated divalent metal ions, M2+(H2O)n (M = Mg, Ca, and Sr for n = 5–7, and M = Ba for n = 4–7), are measured as a function of temperature using blackbody infrared radiative dissociation. From these values, zero-pressure-limit Arrhenius parameters are obtained. By modeling the dissociation kinetics using a master equation formalism, threshold dissociation energies (Eo) are determined. These reactions should have a negligible reverse activation barrier; therefore, Eo values should be approximately equal to the binding energy or hydration enthalpy at 0 K. For the hepta- and hexahydrated ions at low temperature, binding energies follow the trend expected on the basis of ionic radii: Mg > Ca > Sr > Ba. For the hexahydrated ions at high temperature, binding energies follow the order Ca > Mg > Sr > Ba. The same order is observed for the pentahydrated ions. Collisional dissociation experiments on the tetrahydrated species result in relative dissociation rates that directly correlate with the size of the metals. These results indicate the presence of two isomers for hexahydrated magnesium ions: a low-temperature isomer in which the six water molecules are located in the first solvation shell, and a high-temperature isomer with the most likely structure corresponding to four water molecules in the inner shell and two water molecules in the second shell. These results also indicate that the pentahydrated magnesium ions have a structure with four water molecules in the first solvation shell and one in the outer shell. The dissociation kinetics for the hexa- and pentahydrated clusters of Ca2+, Sr2+, and Ba2+ are consistent with structures in which all the water molecules are located in the first solvation shell. PMID:16429612

Effect of LPSO and SFs on microstructure evolution and mechanical properties of Mg-Gd-Y-Zn-Zr alloy

NASA Astrophysics Data System (ADS)

Xu, Chao; Nakata, Taiki; Qiao, Xiaoguang; Zheng, Mingyi; Wu, Kun; Kamado, Shigeharu

2017-01-01

High performance Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy with high strength and excellent ductility has been successfully developed by hot extrusion. The effect of plate-shaped long period stacking ordered (LPSO) phases and solute-segregated stacking faults (SFs) on the dynamically recrystallization (DRX) behavior was analyzed. The plate-shaped LPSO phases stimulate the DRX by particle stimulated nucleation mechanism, leading to higher DRX ratio and weaker basal texture. While for the alloy with dense fine SFs inside the original grains, discontinuous DRX initially occurs at the original grain boundaries, and the DRX is obviously restricted. Consequently, alloy containing dense SFs exhibits higher strength but lower ductility compared with alloy with plated-shaped LPSO phases.

Effect of LPSO and SFs on microstructure evolution and mechanical properties of Mg-Gd-Y-Zn-Zr alloy

PubMed Central

Xu, Chao; Nakata, Taiki; Qiao, Xiaoguang; Zheng, Mingyi; Wu, Kun; Kamado, Shigeharu

2017-01-01

High performance Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy with high strength and excellent ductility has been successfully developed by hot extrusion. The effect of plate-shaped long period stacking ordered (LPSO) phases and solute-segregated stacking faults (SFs) on the dynamically recrystallization (DRX) behavior was analyzed. The plate-shaped LPSO phases stimulate the DRX by particle stimulated nucleation mechanism, leading to higher DRX ratio and weaker basal texture. While for the alloy with dense fine SFs inside the original grains, discontinuous DRX initially occurs at the original grain boundaries, and the DRX is obviously restricted. Consequently, alloy containing dense SFs exhibits higher strength but lower ductility compared with alloy with plated-shaped LPSO phases. PMID:28134297

Synthesis and coordination chemistry of TpC*MI complexes where M=Mg, Ca, Sr, Ba and Zn and TpC*=tris[3-(2-methoxy-1,1-dimethyl)pyrazolyl]hydroborate.

PubMed

Chisholm, Malcolm H; Gallucci, Judith C; Yaman, Gulsah

2009-01-14

Reactions involving MI2 where M=Mg, Ca, Sr, Ba or Zn and M'TpC* where M'=Na or Tl and TpC*=tris[3-methoxy-1,1-dimethyl)pyrazolyl]hydroborate in tetrahydrofuran are described leading to the isolation and characterization of the complexes TpC*MgI, , TpC*CaI, , TpC*SrI, , TpC*SrI(THF), , TpC*BaI, , TpC*BaI(pz*H), , where pz*H=3-(2-methoxyl-1,1-dimethyl)pyrazole, TpC*BaI.1/2toluene, and TpC*ZnI, . The compounds , , , , and have been characterized by single-crystal X-ray crystallography. Compounds and are isostructural and are salt-like containing kappa6-TpM+ cations and I- anions. In all other structures, the iodide is bound to the metal and TpC* is kappa6 bonded to the group 2 M(2+) ions. Reactions involving TpC*CaI, , and sodium or lithium alkoxides or amides failed to yield the amide or alkoxide calcium TpC* derivative, though related reactions involving TpC*ZnI, , and KOSiMe3 proceeded quantitatively to yield kappa3TpC*ZnOSiMe3, , which was also structurally characterized and shown to have the kappa3-TpC* bound ligand.

Architecture, microstructure and Jc anisotropy of highly oriented biaxially textured Co-doped BaFe2As2 on Fe/IBAD-MgO-buffered metal tapes

NASA Astrophysics Data System (ADS)

Trommler, S.; Hänisch, J.; Matias, V.; Hühne, R.; Reich, E.; Iida, K.; Haindl, S.; Schultz, L.; Holzapfel, B.

2012-08-01

Optimized, biaxially textured BaFe1.8Co0.2As2 thin films with an in-plane alignment of 1.7° have been realized on high-quality IBAD-textured MgO-coated technical substrates utilizing additional Fe buffer layers. High critical current densities (Jc) were achieved, comparable to films on single crystalline MgO (Jc ≥ 1 MA cm-2 at 4 K, self-field). Transmission electron microscopy investigations reveal a small number of c-axis correlated defects introduced by the MgO template. The effect of these defects on the Jc anisotropy was determined in angular-dependent electronic transport measurements.

Development of Ni-Ba(Zr,Y)O3 cermet anodes for direct ammonia-fueled solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Miyazaki, Kazunari; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

2017-10-01

In this study, the availability of Ni-Ba(Zr,Y)O3-δ (BZY) cermet for the anode of direct ammonia-fueled solid oxide fuel cells (SOFCs) is evaluated. In this device, the anodes need to be active for the catalytic ammonia decomposition as well as the electrochemical hydrogen oxidation. In the catalytic activity test, ammonia decomposes completely over Ni-BZY at ca. 600 °C, while higher temperature is required to accomplish the complete decomposition over the conventional SOFC anode of Ni-yttria-stabilized zirconia cermet. The high activity of Ni-BZY is attributed to the high basicity of BZY and the high resistance to hydrogen poisoning effect. The electrochemical property of Ni-BZY anode is also evaluated with the anode-supported cell of Ni-BZY|BZY|Pt at 600-700 °C with feeding ammonia or hydrogen as a fuel. Since the residence time of ammonia fuel in the thick Ni-BZY anode is long, the difference in the cell performance between two fuels is relatively small. Furthermore, it is proved that the steam concentration in the fuel strongly affects the cell performance. We find that this factor is important to satisfy the above mentioned requirements for the anode of direct ammonia-fueled SOFCs. Throughout this study, it is concluded that Ni-BZY cermet will be a promising anode.

Electrochemical Behavior Assessment of As-Cast Mg-Y-RE-Zr Alloy in Phosphate Buffer Solutions (X Na3PO4 + Y Na2HPO4) Using Electrochemical Impedance Spectroscopy and Mott-Schottky Techniques

NASA Astrophysics Data System (ADS)

Fattah-alhosseini, Arash; Asgari, Hamed

2018-05-01

In the present study, electrochemical behavior of as-cast Mg-Y-RE-Zr alloy (RE: rare-earth alloying elements) was investigated using electrochemical tests in phosphate buffer solutions (X Na3PO4 + Y Na2HPO4). X-ray diffraction techniques and Scanning electron microscopy equipped with energy dispersive x-ray spectroscopy were used to investigate the microstructure and phases of the experimental alloy. Different electrochemical tests such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) analysis were carried out in order to study the electrochemical behavior of the experimental alloy in phosphate buffer solutions. The PDP curves and EIS measurements indicated that the passive behavior of the as-cast Mg-Y-RE-Zr alloy in phosphate buffer solutions was weakened by an increase in the pH, which is related to formation of an imperfect and less protective passive layer on the alloy surface. The presence of the insoluble zirconium particles along with high number of intermetallic phases of RE elements mainly Mg24Y5 in the magnesium matrix can deteriorate the corrosion performance of the alloy by disrupting the protective passive layer that is formed at pH values over 11. These insoluble zirconium particles embedded in the matrix can detrimentally influence the passivation. The M-S analysis revealed that the formed passive layers on Mg-Y-RE-Zr alloy behaved as an n-type semiconductor. An increase in donor concentration accompanying solutions of higher alkalinity is thought to result in the formation of a less resistive passive layer.

Ultrasonic Vibration and Rheocasting for Refinement of Mg-Zn-Y Alloy Reinforced with LPSO Structure

NASA Astrophysics Data System (ADS)

Lü, Shulin; Yang, Xiong; Hao, Liangyan; Wu, Shusen; Fang, Xiaogang; Wang, Jing

2018-05-01

In this work, ultrasonic vibration (UV) and rheo-squeeze casting was first applied on the Mg alloy reinforced with long period stacking ordered (LPSO) structure. The semisolid slurry of Mg-Zn-Y alloy was prepared by UV and processed by rheo-squeeze casting in succession. The effects of UV, Zr addition and squeeze pressure on microstructure of semisolid Mg-Zn-Y alloy were studied. The results revealed that the synergic effect of UV and Zr addition generated a finer microstructure than either one alone when preparing the slurries. Rheo-squeeze casting could significantly refine the LPSO structure and α-Mg matrix in Mg96.9Zn1Y2Zr0.1 alloy without changing the phase compositions or the type of LPSO structure. When the squeeze pressure increased from 0 to 400 MPa, the block LPSO structure was completely eliminated and the average thickness of LPSO structure decreased from 9.8 to 4.3 μm. Under 400 MPa squeeze pressure, the tensile strength and elongation of the rheocast Mg96.9Zn1Y2Zr0.1 alloy reached the maximum values, which were 234 MPa and 17.6%, respectively, due to its fine α-Mg matrix (α1-Mg and α2-Mg grains) and LPSO structure.

Large Electrocaloric Effect in Lead-Free (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Ceramics Prepared via Citrate Route

PubMed Central

Shi, Jing; Zhu, Rongfeng; Liu, Xing; Yuan, Ningyi; Ding, Jianning; Luo, Haosu

2017-01-01

The 1 wt % Li-doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT-Li) ceramics prepared by the citrate method exhibit improved phase purity, densification and electrical properties, which provide prospective possibility to develop high-performance electrocaloric materials. The electrocaloric effect was evaluated by phenomenological method, and the BCZT-Li ceramics present large electrocaloric temperature change ∆T, especially large electrocaloric responsibility ξ = ∆Tmax/∆Emax, which can be comparable to the largest values reported in the lead-free piezoelectric ceramics. The excellent electrocaloric effect is considered as correlating with the coexistence of polymorphic ferroelectric phases, which are detected by the Raman spectroscopy. The large ξ value accompanied by decreased Curie temperature (around 73 °C) of the BCZT-Li ceramics prepared by the citrate method presents potential applications as the next-generation solid-state cooling devices. PMID:28927004

BaTiO3-based piezoelectrics: Fundamentals, current status, and perspectives

NASA Astrophysics Data System (ADS)

Acosta, M.; Novak, N.; Rojas, V.; Patel, S.; Vaish, R.; Koruza, J.; Rossetti, G. A.; Rödel, J.

2017-12-01

We present a critical review that encompasses the fundamentals and state-of-the-art knowledge of barium titanate-based piezoelectrics. First, the essential crystallography, thermodynamic relations, and concepts necessary to understand piezoelectricity and ferroelectricity in barium titanate are discussed. Strategies to optimize piezoelectric properties through microstructure control and chemical modification are also introduced. Thereafter, we systematically review the synthesis, microstructure, and phase diagrams of barium titanate-based piezoelectrics and provide a detailed compilation of their functional and mechanical properties. The most salient materials treated include the (Ba,Ca)(Zr,Ti)O3, (Ba,Ca)(Sn,Ti)O3, and (Ba,Ca)(Hf,Ti)O3 solid solution systems. The technological relevance of barium titanate-based piezoelectrics is also discussed and some potential market indicators are outlined. Finally, perspectives on productive lines of future research and promising areas for the applications of these materials are presented.

Metal-Borohydride-Modified Zr(BH4 )4 ⋅8 NH3 : Low-Temperature Dehydrogenation Yielding Highly Pure Hydrogen.

PubMed

Huang, Jianmei; Ouyang, Liuzhang; Gu, Qinfen; Yu, Xuebin; Zhu, Min

2015-10-12

Due to its high hydrogen density (14.8 wt %) and low dehydrogenation peak temperature (130 °C), Zr(BH4 )4 ⋅8 NH3 is considered to be one of the most promising hydrogen-storage materials. To further decrease its dehydrogenation temperature and suppress its ammonia release, a strategy of introducing LiBH4 and Mg(BH4 )2 was applied to this system. Zr(BH4 )4 ⋅8 NH3 -4 LiBH4 and Zr(BH4 )4 ⋅8 NH3 -2 Mg(BH4 )2 composites showed main dehydrogenation peaks centered at 81 and 106 °C as well as high hydrogen purities of 99.3 and 99.8 mol % H2 , respectively. Isothermal measurements showed that 6.6 wt % (within 60 min) and 5.5 wt % (within 360 min) of hydrogen were released at 100 °C from Zr(BH4 )4 ⋅8 NH3 -4 LiBH4 and Zr(BH4 )4 ⋅8 NH3 -2 Mg(BH4 )2 , respectively. The lower dehydrogenation temperatures and improved hydrogen purities could be attributed to the formation of the diammoniate of diborane for Zr(BH4 )4 ⋅8 NH3 -4 LiBH4 , and the partial transfer of NH3 groups from Zr(BH4 )4 ⋅8 NH3 to Mg(BH4 )2 for Zr(BH4 )4 ⋅8 NH3 -2 Mg(BH4 )2 , which result in balanced numbers of BH4 and NH3 groups and a more active H(δ+) ⋅⋅⋅(-δ) H interaction. These advanced dehydrogenation properties make these two composites promising candidates as hydrogen-storage materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microstructure Characteristics of High Lift Factor MOCVD REBCO Coated Conductors With High Zr Content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galstyan, E; Gharahcheshmeh, MH; Delgado, L

We report the microstructural characteristics of high levels of Zr-added REBa2Cu3O7-x (RE = Gd, Y rare earth) coated conductors fabricated by Metal Organic Chemical Vapor Deposition (MOCVD). The enhancements of the lift factor defined as a ratio of the in-field (3 T, B parallel to c-axis) critical current density (J(c)) at 30 K and self-field J(c) at 77 K have been achieved for Zr addition levels of 20 and 25 mol% via optimization of deposition parameters. The presence of strong flux pinning is attributed to the aligned nanocolumns of BaZrO3 and nanoprecipitates embedded in REBa2Cu3O7-x matrix with good crystal quality.more » A high density of BZO nanorods with a typical size 6-8 nm and spacing of 20 nm has been observed. Moreover, the high Zr content was found to induce a high density of intrinsic defects, including stacking faults and dislocations. The correlation between in-field performance along the c-axis and microstructure of (Gd, Y) BCO film with a high level of Zr addition is discussed.« less

Microstructure modification and performance improvement of Mg-RE alloys by friction stir processing

NASA Astrophysics Data System (ADS)

Wu, Yujuan; Peng, Liming; Zheng, Feiyan; Li, Xuewen; Li, Dejiang; Ding, Wenjiang

Friction stir processing (FSP) is a severe plastic deformation (SPD) processing, which is very useful to refine grain size and secondary phase as well as change the texture of metal materials. Many FSP research were focused on aluminum alloys, while there are few reports on FSP of magnesium alloys, esp. on precipitation-hardening Mg-RE alloys. This paper overviewed the micro structures and mechanical properties of several FSPed Mg-RE alloys, such as Mg-Gd-Zn-Zr, Mg-Gd-Ag-Zr, and Mg-Nd-Zn-Zr with or without long period stacking ordering (LPSO) structure. The effects of processing parameters, such as rotation rate and traversing speed, on microstructure and mechanical properties were evaluated. It shows that FSP can effectively lend to performance improvement by micro structure modification, including obtaining remarkable finer and more homogenized grains, changing distribution and volume percentage of secondary phase etc.

Fretting properties of biodegradable Mg-Nd-Zn-Zr alloy in air and in Hank’s solution

NASA Astrophysics Data System (ADS)

Li, Wenting; Li, Nan; Zheng, Yufeng; Yuan, Guangyin

2016-11-01

Fretting is a significant cause for the failure of orthopedic implants. Currently, since magnesium and its alloys have been developed as promising biodegradable implant materials, the fretting behavior of the Mg alloys is of great research significance. In this study, a Mg-Nd-Zn-Zr alloy (hereafter, denoted as JDBM alloy) was selected as experimental material, and its fretting behaviors were evaluated under 5 N, 10 N and 20 N normal loads with a displacement of 200 μm under the frequency of 10 Hz at 37 °C in air and in Hank’s solution, respectively. The results indicated that while the friction coefficient decreased with the increment of the normal load, the wear volume of the alloy increased with the increment of the normal load both in air and in Hank’s solution. Both the friction coefficients and the wear volume of the fretting in Hank’s solution were much lower than those in air environment. The evolution trend of friction coefficients with time had different performance in air environment and the Hank’s solution group. Although oxidation occurred during the fretting tests in Hank’s solution, the damage of JDBM alloy was still reduced due to the lubrication effects of Hank’s solution. Moreover, the addition of Fetal bovine serum (FBS) could act as lubrication and result in the reduction of the fretting damage.

First principle study of structural, elastic and electronic properties of APt3 (A=Mg, Sc, Y and Zr)

NASA Astrophysics Data System (ADS)

Benamer, A.; Roumili, A.; Medkour, Y.; Charifi, Z.

2018-02-01

We report results obtained from first principle calculations on APt3 compounds with A=Mg, Sc, Y and Zr. Our results of the lattice parameter a are in good agreement with experimental data, with deviations less than 0.8%. Single crystal elastic constants are calculated, then polycrystalline elastic moduli (bulk, shear and Young moduli, Poisson ration, anisotropy factor) are presented. Based on Debye model, Debye temperature ϴD is calculated from the sound velocities Vl, Vt and Vm. Band structure results show that the studied compounds are electrical conductors, the conduction mechanism is assured by Pt-d electrons. Different hybridisation states are observed between Pt-d and A-d orbitals. The study of the charge density distribution and the population analysis shows the coexistence of ionic, covalent and metallic bonds.

Influence of boron addition to Ti-13Zr-13Nb alloy on MG63 osteoblast cell viability and protein adsorption.

PubMed

Majumdar, P; Singh, S B; Dhara, S; Chakraborty, M

2015-01-01

Cell proliferation, cell morphology and protein adsorption on near β-type Ti-13Zr-13Nb (TZN) alloy and Ti-13Zr-13Nb-0.5B (TZNB) composite have been investigated and compared to evaluate the effect of boron addition which has been added to the Ti alloy to improve their poor tribological properties by forming in situ TiB precipitates. MG63 cell proliferation on substrates with different chemistry but the same topography was compared. The MTT assay test showed that the cell viability on the TZN alloy was higher than the boron containing TZNB composite after 36 h of incubation and the difference was pronounced after 7 days. However, both the materials showed substantially higher cell attachment than the control (polystyrene). For the same period of incubation in fetal bovine serum (FBS), the amount of protein adsorbed on the surface of boron free TZN samples was higher than that in the case of boron containing TZNB composite. The presence of boron in the TZN alloy influenced protein adsorption and cell response and they are lower in TZNB than in TZN as a result of the associated difference in chemical characteristics. Copyright © 2014. Published by Elsevier B.V.

Ferroelectricity emerging in strained (111)-textured ZrO{sub 2} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Zhen, E-mail: a0082709@u.nus.edu, E-mail: msecj@nus.edu.sg; Deng, Jinyu; Liu, Ziyan

2016-01-04

(Anti-)ferroelectricity in complementary metal-oxide-semiconductor (CMOS)-compatible binary oxides have attracted considerable research interest recently. Here, we show that by using substrate-induced strain, the orthorhombic phase and the desired ferroelectricity could be achieved in ZrO{sub 2} thin films. Our theoretical analyses suggest that the strain imposed on the ZrO{sub 2} (111) film by the TiN/MgO (001) substrate would energetically favor the tetragonal (t) and orthorhombic (o) phases over the monoclinic (m) phase of ZrO{sub 2}, and the compressive strain along certain 〈11-2〉 directions may further stabilize the o-phase. Experimentally ZrO{sub 2} thin films are sputtered onto the MgO (001) substrates buffered bymore » epitaxial TiN layers. ZrO{sub 2} thin films exhibit t- and o-phases, which are highly (111)-textured and strained, as evidenced by X-ray diffraction and transmission electron microscopy. Both polarization-electric field (P-E) loops and corresponding current responses to voltage stimulations measured with appropriate applied fields reveal the ferroelectric sub-loop behavior of the ZrO{sub 2} films at certain thicknesses, confirming that the ferroelectric o-phase has been developed in the strained (111)-textured ZrO{sub 2} films. However, further increasing the applied field leads to the disappearance of ferroelectric hysteresis, the possible reasons of which are discussed.« less

Photoluminescence and cathodoluminescence properties of Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Peng; Yu, Jae Su, E-mail: jsyu@khu.ac.kr

2015-10-15

Highlights: • Under 393 nm excitation, strong red emission located at 615 nm was observed in all the samples. • The Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest PL properties. • The CIE chromaticity coordinate of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was (0.647,0.352). • The color purity of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was 92.8%. • Strong CL properties were observed in the Eu{sup 3+}-activated CaMoO{sub 4} phosphor. - Abstract: Eu{sup 3+}-activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors were synthesized by a solid-state reaction method. Photoluminescence and cathodoluminescence (CL) spectra as well as X-ray diffraction patternsmore » were measured to characterize the fabricated samples. Under 393 nm excitation, strong red emissions located at ∼615 nm corresponding to the {sup 5}D{sub 0} → {sup 7}F{sub 2} transition of Eu{sup 3+} ions were observed in all the samples. Compared with other Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Sr, Ba) phosphors, Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest red emission intensity with better Commission Internationale de L’Eclairage chromaticity coordinate and higher color purity. Furthermore, the CL results indicated that the Eu{sup 3+}-activated CaMoO{sub 4} phosphor had excellent luminescence properties.« less

Influence of Severe Plastic Deformation on the Structure and Properties of Al-Li-Cu-Mg-Zr-Sc-Zn Alloy

NASA Astrophysics Data System (ADS)

Kaigorodova, L. I.; Rasposienko, D. Yu.; Pushin, V. G.; Pilyugin, V. P.; Smirnov, S. V.

2018-02-01

The structural and phase transformations in the Al-Li-Cu-Mg-Zr-Sc-Zn alloy have been studied by the electron microscopy after the aging for the maximum strength and in the nanostructured state after severe plastic deformation by high-pressure torsion. It has been shown that severe plastic deformation leads to the formation of a nanostructured state in the alloy, the nature of which is determined by the magnitude of deformation and the degree of completeness of the dynamic recrystallization. It has been established that deformation also causes a change in the phase composition of the alloy. The influence of the structural components of the severely deformed alloy on the level of mechanical properties, such as the hardness, plasticity, elastic modulus, and stiffness has been discussed.

Investigation of ZrO x /ZrC-ZrN/Zr thin-film structural evolution and their degradation using X-ray diffraction and Raman spectrometry

NASA Astrophysics Data System (ADS)

Usmani, B.; Vijay, V.; Chhibber, R.; Dixit, A.

2016-11-01

The thin-film structures of DC/FR magnetron-sputtered ZrO x /ZrC-ZrN/Zr tandem solar-selective coatings are investigated using X-ray diffraction and room-temperature Raman spectroscopic measurements. These studies suggest that the major contribution is coming from h-ZrN0.28, c-ZrC, h-Zr3C2 crystallographic phases in ZrN-ZrC absorber layer, in conjunction with mixed ZrO x crystallographic phases. The change in structure for thermally annealed samples has been examined and observed that cubic and hexagonal ZrO x phase converted partially into tetragonal and monoclinic ZrO x phases, whereas hexagonal and cubic ZrN phases, from absorber layer, have not been observed for these thermally treated samples in air. These studies suggest that thermal treatment may lead to the loss of ZrN phase in absorber, degrading the thermal response for the desired wavelength range in open ambient conditions in contrast to vacuum conditions.

Formation of ZrO{sub 2} in coating on Mg–3 wt.%Al–1 wt.%Zn alloy via plasma electrolytic oxidation: Phase and structure of zirconia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kang Min; Kim, Yeon Sung; Yang, Hae Woong

2015-01-15

An investigation of the coating structure formed on Mg–3 wt.%Al–1 wt.%Zn alloy sample subjected to plasma electrolytic oxidation was examined by field-emission transmission electron microscopy. The plasma electrolytic oxidation process was conducted in a phosphoric acid electrolyte containing K{sub 2}ZrF{sub 6} for 600 s. Microstructural observations showed that the coating consisting of MgO, MgF{sub 2}, and ZrO{sub 2} phases was divided into three distinctive parts, the barrier, intermediate, and outer layers. Nanocrystalline MgO and MgF{sub 2} compounds were observed mainly in the barrier layer of ~ 1 μm thick near to the substrate. From the intermediate to outer layers, variousmore » ZrO{sub 2} polymorphs appeared due to the effects of the plasma arcing temperature on the phase transition of ZrO{sub 2} compounds during the plasma electrolytic oxidation process. In the outer layer, MgO compound grew in the form of a dendrite-like structure surrounded by cubic ZrO{sub 2}. - Highlights: • The barrier layer containing MgO and MgF{sub 2} was observed near to the Mg substrate. • In the intermediate layer, m-, t-, and o-ZrO{sub 2} compounds were additionally detected. • The outer layer contained MgO with the dendrite-like structure surrounded by c-ZrO{sub 2}. • The grain sizes of compounds in oxide layer increased from barrier to outer layer.« less

Microstructure, Mechanical Properties, and Corrosion Resistance of Thermomechanically Processed AlZn6Mg0.8Zr Alloy

PubMed Central

Kowalski, Aleksander; Ozgowicz, Wojciech; Jurczak, Wojciech; Grajcar, Adam; Boczkal, Sonia; Żelechowski, Janusz

2018-01-01

The paper presents results of the investigations on the effect of low-temperature thermomechanical treatment (LTTT) on the microstructure of AlZn6Mg0.8Zr alloy (7000 series) and its mechanical properties as well as electrochemical and stress corrosion resistance. For comparison of the LTTT effect, the alloy was subjected to conventional precipitation hardening. Comparative studies were conducted in the fields of metallographic examinations and static tensile tests. It was found that mechanical properties after the LTTT were better in comparison to after conventional heat treatment (CHT). The tested alloy after low-temperature thermomechanical treatment with increasing plastic deformation shows decreased electrochemical corrosion resistance during potentiodynamic tests. The alloy after low-temperature thermomechanical treatment with deformation degree in the range of 10 to 30% is characterized by a high resistance to stress corrosion specified by the level of PSCC indices. PMID:29642448

The mineralogy of Ba- and Zr-rich alkaline pegmatites from Gordon Butte, Crazy Mountains (Montana, USA): comparisons between potassic and sodic agpaitic pegmatites

NASA Astrophysics Data System (ADS)

Chakhmouradian, Anton; Mitchell, Roger

2002-01-01

crystallize included accessory zircon and thorite. Sr-rich loparite also precipitated relatively early serving as a major repository for Sr, REE, and Nb. During the agpaitic stage, diverse titano- and zircono-silicates (barytolamprophyllite, eudialyte, wadeite, and rinkite, among others) consumed most of the Ba, Sr, Ti, Zr, and Nb still remaining in the melt. The final stage in the evolution of the pegmatites involved interaction of the earlier-formed mineral assemblages with deuteric fluids. In common with the Rocky Boy pegmatites, Sr-REE-Na-rich fluorapatite, Ba-Fe titanates and REE-bearing carbonates (ancylite, calcio-ancylite, and bastnäsite-parisite series) are chief products of the deuteric stage. The alteration of the primary mineral assemblages by deuteric fluids also produced muscovite-zeolite pseudomorphs after nepheline, replacement of wadeite and eudialyte by catapleiite-group minerals, re-deposition of Ba in the form of hyalophane, baotite, and benitoite, and cation leaching from rinkite, eudialyte, and loparite. The mineralogy of the pegmatites from Gordon Butte, other potassic complexes, and sodic agpaitic occurrences is compared in detail.

Electric-field control of electronic transport properties and enhanced magnetoresistance in La0.7Sr0.3MnO3/0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3 lead-free multiferroic structures

NASA Astrophysics Data System (ADS)

Yan, Jian-Min; Gao, Guan-Yin; Liu, Yu-Kuai; Wang, Fei-Fei; Zheng, Ren-Kui

2017-10-01

We report the fabrication of lead-free multiferroic structures by depositing ferromagnetic La0.7Sr0.3MnO3 (LSMO) polycrystalline films on polished 0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3 (BZT-BCT) piezoelectric ceramic substrates. By applying electric fields to the BZT-BCT along the thickness direction, the resistivity of LSMO films can be effectively manipulated via the piezoelectric strain of the BZT-BCT. Moreover, the LSMO polycrystalline films exhibit almost temperature independent and significantly enhanced magnetoresistance (MR) below TC. At T = 2 K and H = 8 T, the MR of polycrystalline films is approximately two orders of magnitude higher than that of LSMO epitaxial films grown on (LaAlO3)0.3(SrAl1/2Ta1/2O3)0.7 single-crystal substrates. The enhanced MR mainly results from the spin-polarized tunneling of charge carriers across grain boundaries. The LSMO/BZT-BCT structures with electric-field controllable modulation of resistivity and enhanced MR effect may have potential applications in low-energy consumption and environmentally friendly electronic devices.

Excitation-dependent local symmetry reversal in single host lattice Ba2A(BO3)2:Eu3+ [A = Mg and Ca] phosphors with tunable emission colours.

PubMed

Jayakiruba, S; Chandrasekaran, S Selva; Murugan, P; Lakshminarasimhan, N

2017-07-05

Eu 3+ activated phosphors are widely used as red emitters in various display devices and light emitting diodes (LEDs). The emission characteristics of Eu 3+ depend on the local site symmetry. The present study demonstrates the role of excitation-dependent local symmetry changes due to the structural reorganization on the emission colour tuning of Eu 3+ from orange-red to orange in single host lattices, Ba 2 Mg(BO 3 ) 2 and Ba 2 Ca(BO 3 ) 2 . The choice of these lattices was based on the difference in the extent of strain experienced by the oxygen atoms. The samples with Eu 3+ at Ba or Mg (Ca) sites were synthesized using the conventional high-temperature solid-state reaction method. The samples were characterized using powder XRD, 11 B MAS-NMR, FT-IR, and diffuse reflectance UV-Vis spectroscopic techniques. The room temperature photoluminescence (PL) recorded using different excitation wavelengths revealed a clear difference in the PL emission features due to symmetry reversal from non-inversion to inversion symmetry around Eu 3+ . The reorganization of highly strained oxygen atoms leads to such symmetry reversal. First-principles calculations were used to deduce the optimized structures of the two borate host lattices, and local geometries and their distortions upon Eu 3+ substitution. The outcomes of these calculations support the experimental findings.

Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

NASA Technical Reports Server (NTRS)

Aleksandrov, K. S.; Khrustalev, B. P.; Krivomazov, S. N.; Petrov, M. I.; Vasilyev, A. D.; Zwegintsev, S. A.

1991-01-01

After the discovery of high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides were synthesized. Here, researchers report the results of the search for superconductivity in the compounds based on tin which has a lone electron pair like Bi, Tl, and Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3O(sub x), Sn1Ba1Ca1Cu3O(sub x), Sn1Ba1Mg1Cu3O(sub x), Sn1Sr1Ca1Cu3O(sub x), Sn1Sr1Mg1Cu3O(sub x), and Sn1Ca1Mg1Cu3O(sub x). The initial components were oxides and carbonates of the appropriate elements. A standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3O(sub x) showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3O(sub x) was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperature undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3O(sub x) ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase, two-valent cations Ba and Sr were partially substituted by univalent (K) and three-valent ones (Y).

Zr/ZrC modified layer formed on AISI 440B stainless steel by plasma Zr-alloying

NASA Astrophysics Data System (ADS)

Shen, H. H.; Liu, L.; Liu, X. Z.; Guo, Q.; Meng, T. X.; Wang, Z. X.; Yang, H. J.; Liu, X. P.

2016-12-01

The surface Zr/ZrC gradient alloying layer was prepared by double glow plasma surface alloying technique to increase the surface hardness and wear resistance of AISI 440B stainless steel. The microstructure of the Zr/ZrC alloying layer formed at different alloying temperatures and times as well as its formation mechanism were discussed by using scanning electron microscopy, glow discharge optical emission spectrum, X-ray diffraction and X-ray photoelectron spectroscopy. The adhesive strength, hardness and tribological property of the Zr/ZrC alloying layer were also evaluated in the paper. The alloying surface consists of the Zr-top layer and ZrC-subsurface layer which adheres strongly to the AISI 440B steel substrate. The thickness of the Zr/ZrC alloying layer increases gradually from 16 μm to 23 μm with alloying temperature elevated from 900 °C to 1000 °C. With alloying time from 0.5 h to 4 h, the alloyed depth increases from 3 μm to 30 μm, and the ZrC-rich alloyed thickness vs time is basically parabola at temperature of 1000 °C. Both the hardness and wear resistance of the Zr/ZrC alloying layer obviously increase compared with untreated AISI 440B steel.

Microstructure, mechanical properties, biocorrosion behavior, and cytotoxicity of as-extruded Mg-Nd-Zn-Zr alloy with different extrusion ratios.

PubMed

Zhang, Xiaobo; Yuan, Guangyin; Niu, Jialin; Fu, Penghuai; Ding, Wenjiang

2012-05-01

Recently, commercial magnesium (Mg) alloys containing Al (such as AZ31 and AZ91) or Y (such as WE43) have been studied extensively for biomedical applications. However, these Mg alloys were developed as structural materials, not as biomaterials. In this study, a patented Mg-Nd-Zn-Zr (denoted as JDBM) alloy was investigated as a biomedical material. The microstructure, mechanical properties, biocorrosion behavior, and cytotoxicity of the alloy extruded at 320 °C with extrusion ratios of 8 and 25 were studied. The results show that the lower extrusion ratio results in finer grains and higher strength, but lower elongation, while the higher extrusion ratio results in coarser grains and lower strength, but higher elongation. The biocorrosion behavior of the alloy was investigated by hydrogen evolution and mass loss tests in simulated body fluid (SBF). The results show that the alloy extruded with lower extrusion ratio exhibits better corrosion resistance. The corrosion mode of the alloy is uniform corrosion, which is favorable for biomedical applications. Aging treatment on the as-extruded alloy improves the strength and decreases the elongation at room temperature, and has a small positive influence on the corrosion resistance in SBF. The cytotoxicity test indicates that the as-extruded JDBM alloy meets the requirement of cell toxicity. Copyright © 2012 Elsevier Ltd. All rights reserved.

Study of activation cross sections of deuteron induced reactions on barium. Production of 131Cs, 133Ba

NASA Astrophysics Data System (ADS)

Tárkányi, F.; Hermanne, A.; Ditrói, F.; Takács, S.; Szücs, Z.; Brezovcsik, K.

2018-01-01

In the frame of a systematic study of deuteron induced activation processes on middle mass elements, excitation functions of the natBa(d,x) 135,133,132La, 135m,133m,133mg,131mgBa, 136mg,134mg,132,129Cs reactions were measured up to 50 MeV for the first time. Cross sections were measured with the activation method using a stacked foil irradiation technique followed by HPGe γ-ray spectrometry. A comparison with the results of the nuclear model TALYS code (reported in the TENDL-2015 library) was done. The potential use of the deuteron induced reactions on Ba for applications (131Cs and 131Ba production) is discussed.

Laser emission from flash ignition of Zr/Al nanoparticles.

PubMed

Yang, Fan; Kang, Xiaoli; Luo, Jiangshan; Sun, Laixi; Xia, Handing; Yi, Zao; Tang, Yongjian

2017-10-02

We report the first laser emission from flash ignition of Zr/Al nanoparticles with the addition of strong oxidizer KClO 4 using Nd: YAG as a laser medium. The mixture Zr/Al/Kp-45 (mass ratio = 33%Zr: 33%Al: 34%KClO 4 ) has the highest brightness temperature Tb = 4615 K and the adiabatic flame temperature Tf = 4194 K with the duration of 20 ms. At 1064 nm we measured a maximum output energy of 702.5 mJ with the duration of nearly 10 ms by using only 100 mg mixture with an output coupler (transmission T = 10%). Further optimizing the concentration cavity and increasing the mixture content will yield much higher efficiency and output energy.

Fretting properties of biodegradable Mg-Nd-Zn-Zr alloy in air and in Hank’s solution

PubMed Central

Li, Wenting; Li, Nan; Zheng, Yufeng; Yuan, Guangyin

2016-01-01

Fretting is a significant cause for the failure of orthopedic implants. Currently, since magnesium and its alloys have been developed as promising biodegradable implant materials, the fretting behavior of the Mg alloys is of great research significance. In this study, a Mg-Nd-Zn-Zr alloy (hereafter, denoted as JDBM alloy) was selected as experimental material, and its fretting behaviors were evaluated under 5 N, 10 N and 20 N normal loads with a displacement of 200 μm under the frequency of 10 Hz at 37 °C in air and in Hank’s solution, respectively. The results indicated that while the friction coefficient decreased with the increment of the normal load, the wear volume of the alloy increased with the increment of the normal load both in air and in Hank’s solution. Both the friction coefficients and the wear volume of the fretting in Hank’s solution were much lower than those in air environment. The evolution trend of friction coefficients with time had different performance in air environment and the Hank’s solution group. Although oxidation occurred during the fretting tests in Hank’s solution, the damage of JDBM alloy was still reduced due to the lubrication effects of Hank’s solution. Moreover, the addition of Fetal bovine serum (FBS) could act as lubrication and result in the reduction of the fretting damage. PMID:27812007

Microstructure and Thermal Stability of A357 Alloy With and Without the Addition of Zr

NASA Astrophysics Data System (ADS)

Tzeng, Yu-Chih; Chengn, Vun-Shing; Nieh, Jo-Kuang; Bor, Hui-Yun; Lee, Sheng-Long

2017-11-01

The principal purpose of this research was to evaluate the effects of Zr on the microstructure and thermal stability of an A357 alloy that has been subjected to an aging treatment (T6) and thermal exposure (250 °C). The results show that the addition of Zr had a significant influence on the refinement of the grain size, which enhanced the hardness and tensile strength of the A357 alloy under the T6 condition. During thermal exposure at 250 °C, the rodlike metastable β'-Mg2Si precipitates transformed into coarse equilibrium phase β-Mg2Si precipitates, resulting in a significant drop in the hardness and tensile strength of the T6 heat-treated A357 alloy. However, after thermal exposure, coherent, finely dispersed Al3Zr precipitates were found to be formed in the T6 heat-treated A357 alloy. The addition of 0.1% Zr played a critical role in improving the high-temperature strength. Consequently, the A357 alloy with the addition of Zr demonstrated better mechanical properties at room temperature and high temperature than the alloy without Zr, in terms of both microstructure and thermal stability.

Crystallographic orientation of epitaxial BaTiO3 films: The role of thermal-expansion mismatch with the substrate

NASA Astrophysics Data System (ADS)

Srikant, V.; Tarsa, E. J.; Clarke, D. R.; Speck, J. S.

1995-02-01

Expitaxial ferroelectric BaTiO3 thin films have been grown on (001) MgO and MgO-buffered (001) GaAs substrates by pulsed laser deposition to explore the effect of substrate lattice parameter. X-ray-diffraction studies showed that the BaTiO3 films on both MgO single-crystal substrates and MgO-buffered (001) GaAs substrates have a cube-on-cube epitaxy; however, for the BaTiO3 films grown on MgO the spacing of the planes parallel to the substrate was close to the c-axis dimension of the unconstrained tetragonal phase, whereas the BaTiO3 films on MgO/GaAs exhibited a spacing closer to the a-axis dimension of the unconstrained tetragonal phase. The cube-on-cube epitaxy was maintained through the heterostructures even when thin epitaxial intermediate buffer layers of SrTiO3 and La(0.5)Sr(0.5)CoO3 were used. The intermediate layers had no effect on the position of the BaTiO3 peak in theta - 2 theta scans. Together, these observations indicate that, for the materials combinations studied, it is the thermal-expansion mismatch between the film and the underlying substrate that determines the crystallographic orientation of the BaTiO3 film. Preliminary measurements indicate that the BaTiO3 films are 'weakly' ferroelectric.

Effects of crystalline quality and electrode material on fatigue in Pb(Zr,Ti)O3 thin film capacitors

NASA Astrophysics Data System (ADS)

Lee, J.; Johnson, L.; Safari, A.; Ramesh, R.; Sands, T.; Gilchrist, H.; Keramidas, V. G.

1993-07-01

Pb(Zr(0.52)Ti(0.48))O3 (PZT)/Y1Ba2Cu3O(x) (YBCO) heterostructures were grown by pulsed laser deposition, in which PZT films were epitaxial, highly oriented, or polycrystalline. These PZT films were obtained by varying the deposition temperature from 550 to 760 C or by using various substrates such as SrTiO3 (100), MgO (100), and r-plane sapphire. PZT films with Pt top electrodes exhibited large fatigue with 35-50 percent loss of the remanent polarization after 10 exp 9 cycles, depending on the crystalline quality. Polycrystalline films showed better fatigue resistance than epitaxial or highly oriented films. However, PZT films with both top and bottom YBCO electrodes had significantly improved fatigue resistance for both epitaxial and polycrystalline films. Electrode material seems to be a more important parameter in fatigue than the crystalline quality of the PZT films.

Effect of CaRuO3 interlayer on the dielectric properties of Ba(Zr ,Ti)O3 thin films prepared by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Tang, X. G.; Tian, H. Y.; Wang, J.; Wong, K. H.; Chan, H. L. W.

2006-10-01

Ba(Zr0.2Ti0.8)O3 (BZT) thin films on Pt(111)/Ti /SiO2/Si(100) substrates without and with CaRuO3 (CRO) buffer layer were fabricated at 650°C in situ by pulsed laser deposition. The BZT thin films showed a dense morphology, many clusters are found on the surface images of BZT/Pt films, which are composed by nanosized grains of 25-35nm; the average grain size of BZT/CRO films is about 80nm, which lager than that of BZT/Pt thin film. The dielectric constants and dissipation factors of BZT/Pt and BZT/CRO thin films were 392 and 0.019 and 479 and 0.021 at 1MHz, respectively. The dielectric constant of BZT/Pt and BZT/CRO thin films changes significantly with applied dc bias field and has high tunabilities and figures of merit of ˜70% and 37 and 75% and 36, respectively, under an applied field of 400kV /cm. The possible microstructural background responsible for the high dielectric constant and tunability was discussed.

Metastable phase selection from undercooled Zr 77 Rh 23 liquid alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, M. L.; Gibbons, P. C.; Vogt, A. J.

2017-11-01

From measurements of X-ray and neutron scattering of electrostatically levitated Zr77Rh23 liquids, a variety of metastable crystallization behavior was observed. The metastable phase selection in deeply undercooled liquid droplets is characterized and their crystallization pathways discussed. A metastable phase previously identified as a primary devitrification product from the metallic glass formed when undercooling was maximized to near the hypercooling limit. The direct formation of α–Zr and the equilibrium C16 phase as well as a newly discovered Zr5Rh3 (Mg5Si3-type) phase are also reported.

Determination of major elements by wavelength-dispersive X-ray fluorescence spectrometry and trace elements by inductively coupled plasma mass spectrometry in igneous rocks from the same fused sample (110 mg)

NASA Astrophysics Data System (ADS)

Amosova, Alena A.; Panteeva, Svetlana V.; Chubarov, Victor M.; Finkelshtein, Alexandr L.

2016-08-01

The fusion technique is proposed for simultaneous determination of 35 elements from the same sample. Only 110 mg of rock sample was used to obtain fused glasses for quantitative determination of 10 major elements by wavelength dispersive X-ray fluorescence analysis, 16 rare earth elements and some other trace elements by inductively coupled plasma mass spectrometry analysis. Fusion was performed with 1.1 g of lithium metaborate and LiBr solution as the releasing agent in platinum crucible in electric furnace at 1100 °C. The certified reference materials of ultramafic, mafic, intermediate and felsic igneous rocks have been applied to obtain the calibration curves for rock-forming oxides (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, Fe2O3) and some trace elements (Ba, Sr, Zr) determination by X-ray fluorescence analysis. The repeatability does not exceed the allowable standard deviation for a wide range of concentrations. In the most cases the relative standard deviation was less than 5%. Obtained glasses were utilized for the further determination of rare earth (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and some other (Ba, Sr, Zr, Rb, Cs, Y, Nb, Hf, Ta, Th and U) trace elements by inductively coupled plasma mass spectrometry analysis with the same certified reference materials employed. The results could mostly be accepted as satisfactory. The proposed procedure essentially reduces the expenses in comparison with separate sample preparation for inductively coupled plasma mass spectrometry and X-ray fluorescence analysis.

Effect of a prior stretch on the aging response of an Al-Cu-Li-Ag-Mg-Zr alloy

NASA Technical Reports Server (NTRS)

Kumar, K. S.; Brown, S. A.; Pickens, J. R.

1990-01-01

The effect of a prior stretching of an aluminum alloy Al-5.3Cu-1.4Li-0.4Ag-0.4Mg-0.17Zr (in wt pct) on the microstructure that develops during aging of this alloy was investigated by comparing TEM and SAD observations and hardness curves with results for the unstretched alloy. The results suggest that stretching introduces a significant number of dislocations which may act as vacanacy sinks by sweeping vacancies away and thereby decreasing the vacancy concentration available for influencing the natural aging response. In the stretched and near-peak aged condition, a fine homogeneous distribution of T1, theta-prime, and S-prime phases were observed in an alpha solid solution matrix. Upon overaging, virtually all of the theta-prime and most of the S-prime phases were found to dissolve, leaving behind a microstructure of T1 precipitates.

Effects of Heat Treatment on Corrosion and Wear Behaviors of Mg-6Gd-2Zn-0.4Zr Alloy in Simulated Body Fluid

NASA Astrophysics Data System (ADS)

Zhao, Li; Chen, Wei; Dai, Jianwei; Wang, Zhangzhong; Zhang, Xiaobo

2017-11-01

Mg-6Gd-2Zn-0.4Zr (wt.%, GZ62K) alloy was processed by solution treatment under different temperatures. The microstructure, hardness, corrosion and wear behaviors in simulated body fluid (SBF) have been studied. The results indicate that the (Mg, Zn)3Gd phase decreases, the precipitated phases gradually increase, and the long-period stacking ordered structure disappears with the increase of solution temperature. The alloy has better corrosion resistance after solution treatment, and that solution treated at 490 °C for 12 h shows the best corrosion resistance. The friction coefficient of the alloy under dry sliding condition decreases slightly, but the mass loss increases with increasing the solution temperature. The alloy solution treated at 460 °C for 12 h exhibits the lowest friction coefficient and mass loss in SBF, and it also has the best wear resistance under dry sliding condition.

A chilled margin of komatiite and Mg-rich basaltic andesite in the western Bushveld Complex, South Africa

NASA Astrophysics Data System (ADS)

Maier, W. D.; Barnes, S.-J.; Karykowski, B. T.

2016-06-01

A chill sequence at the base of the Lower Zone of the western Bushveld Complex at Union Section, South Africa, contains aphanitic Mg-rich basaltic andesite and spinifex-textured komatiite. The basaltic andesite has an average composition of 15.2 % MgO, 52.8 % SiO2, 1205 ppm Cr, and 361 ppm Ni, whereas the komatiite has 18.7 % MgO, 1515 ppm Cr, and 410 ppm Ni. Both rock types have very low concentrations of immobile incompatible elements (0.14-0.72 ppm Nb, 7-31 ppm Zr, 0.34-0.69 ppm Th, 0.23-0.27 wt% TiO2), but high PGE contents (19-23 ppb Pt, 15-16 ppb Pd) and Pt/Pd ratios (Pt/Pd 1.4). Strontium and S isotopes show enriched signatures relative to most other Lower Zone rocks. The rocks could represent a ~20 % partial melt of subcontinental lithospheric mantle. This would match the PGE content of the rocks. However, this model is inconsistent with the high SiO2, Fe, and Na2O contents and, in particular, the low K2O, Zr, Hf, Nb, Ta, Th, LREE, Rb, and Ba contents of the rocks. Alternatively, the chills could represent a komatiitic magma derived from the asthenosphere that underwent assimilation of the quartzitic floor accompanied by crystallization of olivine and chromite. This model is consistent with the lithophile elements and the elevated Sr and S isotopic signatures of the rocks. However, in order to account for the high Pt and Pd contents of the magma, the mantle must have been twice as rich in PGE as the current estimate for PUM, possibly due to a component of incompletely equilibrated late veneer.

AC conduction of Ba1-xCaxTiO3 and BZT-BCTx

NASA Astrophysics Data System (ADS)

Khien, Nguyen Van; Huy, Than Trong; Hong, Le Van

2018-03-01

Ba1-xCaxTiO3 (BCTx), (x =0.0-0.3) and Ba0.8Zr0.2TiO3-Ba1-xCaxTiO3 (BZT-BCTx), (x=0.15-0.35) were fabricated by the solid state reaction method. Phase structure of the material samples was identified by X-ray diffraction. The impedance versus frequency in a range of 100 Hz to 2.5 MHz was measured for all the samples at room temperature. AC conductivity versus frequency of the BCTx and BZT-BCTx was evaluated and fitted by using the extended Universal Dielectric Response (UDR) equations. The fitting results were discussed in detail and shown that the localized reorientation polarization-based mechanism is most contributed in BCTx matrial samples. Basically both two the hopping polaron and polarization mechanisms play roles in BZT-BCTx material samples. In contrary the short-range polaron hopping is dominated in ac conductivity of BZT-BCTx material samples in low frequency range.

Structure and Mechanical and Corrosion Properties of a Magnesium Mg-Y-Nd-Zr Alloy after High Pressure Torsion

NASA Astrophysics Data System (ADS)

Lukyanova, E. A.; Martynenko, N. S.; Serebryany, V. N.; Belyakov, A. N.; Rokhlin, L. L.; Dobatkin, S. V.; Estrin, Yu. Z.

2017-11-01

The structure and the properties of an Mg-Y-Nd-Zr alloy (WE43) are studied after high pressure torsion (HPT) in the temperature range 20-300°C. Structure refinement proceeds mainly by deformation twinning with the formation of a partial nanocrystalline structure with a grain size of 30-100 nm inside deformation twins. The WE43 alloy is shown to be aged during heating after HPT due to the decomposition of a magnesium solid solution. HPT at room temperature and subsequent aging causes maximum hardening. It is shown that HPT significantly accelerates the decomposition of a magnesium solid solution. HPT at all temperatures considerably increases the tensile strength and the yield strength upon tensile tests and significantly decreases plasticity. Subsequent aging additionally hardens the WE43 alloy. A potentiodynamic study shows that the corrosion resistance of this alloy after HPT increases. However, subsequent aging degrades the corrosion properties of the alloy.

Fractionation of Zr and Hf during the differentiation of peralkaline magmatic system (Lovozero rare metal deposit, Kola Peninsula)

NASA Astrophysics Data System (ADS)

Kogarko, Liya

2016-04-01

Zirconium and hafnium are valuable strategic metals. We assessed principal features of the distribution of these elements in peralkaline rocks, ores and rock-forming and accessory minerals of Lovozero complex. The accumulation of these elements during the evolution of alkaline magma of Lovozero deposit up to extremely high concentrations in eudialyte ores (5-8% ZrO2 and 1200-1800 ppm Hf) has been established. These ores represent valuable complex raw material not only for Zr and Hf, but for REE as well. We evaluated partition coefficients of these elements in alkaline pyroxenes (aegirines) from porphyry-like agpaitic lujavrites of Lovozero massif which are 0.40 for zirconium and 0.58 for hafnium. We assessed variations of Zr/Hf ratio for all the rocks of Lovozero alkaline massif. The growth of this ratio in the course of the evolution of alkaline magma has been observed from 38 in the earliest magmatic phase, to 44 in the second phase and to 51-53 in the latest manifestation of alkaline magmatsm. On the basis of the obtained data and equations of equilibrium and fractional crystallization the model of the fractionation of zirconium and hafnium during the evolution of Lovozero intrusion has been constructed. We have demonstrated that the source of strongly enriched magmatic systems similar to Lovozero rare metal deposit is short-lived enriched reservoir - metasomatized and carbonatized mantle substrate. We investigated the fractionation of zirconium and hafnium in carbonatized mantle xenoliths from East Antarctica. The elevated Zr/Hf ratios (up to 125) in metasomatized xenoliths by comparison with the chondritic value have been found. The main reactions of carbonate metasomatism lead to the replacement of primary orthopyroxene by clinopyroxene 2Mg2Si2O6 + CaMg(CO3)2 = 2Mg2SiO4 + CaMgSi2O6 + 2CO2 3CaMg(CO3)2 + CaMgSi2O6 = 4CaCO3 + 2Mg2SiO4 + 2CO2 The substantial expansion of the clinopyroxene crystallization field results in increase of Zr/Hf ratio in equilibrium

High critical currents in heavily doped (Gd,Y)Ba 2Cu 3O x superconductor tapes

DOE PAGES

Selvamanickam, V.; Gharahcheshmeh, M. Heydari; Xu, A.; ...

2015-01-20

REBa 2Cu 3O x superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J c) above 20 MA/cm 2 at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba 2Cu 3O x superconductor tapes,more » which is more than three times higher than the J c typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m 3 have also been attained at 20 K. A composition map of lift factor in J c (ratio of J c at 30 K, 3 T to the J c at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO 3 (BZO) nanocolumn defect density of nearly 7 × 10 11 cm –2 as well as 2–3nm sized particles rich in Cu and Zr have been found in the high J c films.« less

Effect of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) metal ions on the antifungal activity of ZnO nanoparticles tested against Candida albicans.

PubMed

Haja Hameed, Abdulrahman Syedahamed; Karthikeyan, Chandrasekaran; Senthil Kumar, Venugopal; Kumaresan, Subramanian; Sasikumar, Seemaisamy

2015-01-01

The antifungal ability of pure and alkaline metal ion (Mg(2+), Ca(2+), Sr(2+) and Ba(2+)) doped ZnO nanoparticles (NPs) prepared by the co-precipitation method was tested against the pathogenic yeast, Candida albicans (C. albicans), and the results showed that the Mg-doped ZnO NPs possessed greater effect than the other alkaline metal ion doped ZnO NPs. The impact of the concentration of Mg doped ZnO sample on the growth of C. albicans was also studied. The Minimal Fungicidal Concentration (MFC) of the Mg doped ZnO NPs was found to be 2000 μg/ml for which the growth of C. albicans was completely inhibited. The ZnO:Mg sample (1.5mg/ml) with various concentrations of histidine reduced the fungicidal effect of the nanoparticles against C. albicans, which was deliberately explained by the role of ROS. The ZnO:Mg sample added with 5mM of histidine scavenged the ample amount of generated ROS effectively. The binding of the NPs with fungi was observed by their FESEM images and their electrostatic attraction is confirmed by the zeta potential measurement. Copyright © 2015. Published by Elsevier B.V.

Synthesis, crystal structure and spectroscopy properties of Na 3AZr(PO 4) 3 ( A=Mg, Ni) and Li 2.6Na 0.4NiZr(PO 4) 3 phosphates

NASA Astrophysics Data System (ADS)

Chakir, M.; El Jazouli, A.; de Waal, D.

2006-06-01

Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates were prepared at 750 °C by coprecipitation route. Their crystal structures have been refined at room temperature from X-ray powder diffraction data using Rietveld method. Li 2.6Na 0.4NiZr(PO 4) 3 was synthesized through ion exchange from the sodium analog. These materials belong to the Nasicon-type structure. Raman spectra of Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates present broad peaks in favor of the statistical distribution in the sites around PO 4 tetrahedra. Diffuse reflectance spectra indicate the presence of octahedrally coordinated Ni 2+ ions.

Interfacial Energy Transfer during Gamma Radiolysis of Water on the Surface of ZrO2 and Some Other Oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrik, Nikolay G.; Alexandrov, Alexandr B.; Vall, Andrey I.

Effect of oxide interface on 60Co gamma radiolysis of water molecules was studied. Based on the molecular hydrogen yield when compared with that from the radiolysis of pure gas-phase water, all tested oxides can be classified into three groups: (i) inhibitors - MnO2, Co3O4, CuO and Fe2O3; (ii) oxides with H2 yields, which are similar to or slightly greater than radiolysis of pure gas-phase water - MgO, CaO, SrO, BaO, ZnO, CdO, Cu2O, NiO, Cr2O3, Al2O3, CeO2, SiO2, TiO2, Nb2O5 and WO3; (iii) promoters - Ga2O3, Y2O3, La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Yb2O3, Er2O3, HfO2, and ZrO2. H2O radiolysis enhancementmore » for ZrO2 and other promoters is result of effective energy transfer at the oxide/water interface, presumably due to migration of excitons to the surface and their resonant coupling with the H2O adsorption complex. Plot''effective H2 yield vs. band-gap (Eg) energy'' shows a maximum near 5 eV.« less

Microwave Characterization of Ba-Substituted PZT and ZnO Thin Films.

PubMed

Tierno, Davide; Dekkers, Matthijn; Wittendorp, Paul; Sun, Xiao; Bayer, Samuel C; King, Seth T; Van Elshocht, Sven; Heyns, Marc; Radu, Iuliana P; Adelmann, Christoph

2018-05-01

The microwave dielectric properties of (Ba 0.1 Pb 0.9 )(Zr 0.52 Ti 0.48 )O 3 (BPZT) and ZnO thin films with thicknesses below were investigated. No significant dielectric relaxation was observed for both BPZT and ZnO up to 30 GHz. The intrinsic dielectric constant of BPZT was as high as 980 at 30 GHz. The absence of strong dielectric dispersion and loss peaks in the studied frequency range can be linked to the small grain diameters in these ultrathin films.

Critical current density of TlBa 2Ca 2Cu 3O 9 thin films on MgO (100) in magnetic fields

NASA Astrophysics Data System (ADS)

Piehler, A.; Ströbel, J. P.; Reschauer, N.; Löw, R.; Schönberger, R.; Renk, K. F.; Kraus, M.; Daniel, J.; Saemann-Ischenko, G.

1994-04-01

We report on the critical current density of TlBa 2Ca 2Cu 3O 9 thin films on (100) MgO substrates in magnetic fields. Single- phase and highly c-axis oriented thin films were prepared by laser ablation in combination with thermal evaporation of Tl 2O 3. Scanning electron microscope investigations indicated a flat plate-like microstructure and DC magnetization measurements showed the onset of superconductivity at ∼ 115 K. The critical current density jc was determined from magnetization cycles. Typical values of jc were 9 × 10 5 A/cm 2 at 6 K and 2.5 × 10 5 A/cm 2 at 77 K. In a magnetic field to 1 T applied parallel to the c-axis the critical current densities were 3 × 10 5 A/cm 2 at 6 K and 3 × 10 3 A/cm 2 at 77 K. The decrease of jc at higher magnetic fields is discussed and attributed to the microstructure of the TlBa 2Ca 2Cu 3O 9 thin films.

Structures and unimolecular chemistry of M(Pro2-H)(+) (M = Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn) by IRMPD spectroscopy, SORI-CID, and theoretical studies.

PubMed

Jami-Alahmadi, Yasaman; Fridgen, Travis D

2016-01-21

M(Pro2-H)(+) complexes were electrosprayed and isolated in an FTICR cell where their unimolecular chemistries and structures were explored using SORI-CID and IRMPD spectroscopy. These experiments were augmented by computational methods such as electronic structure, simulated annealing, and atoms in molecules (AIM) calculations. The unimolecular chemistries of the larger metal cation (Ca(2+), Sr(2+) and Ba(2+)) complexes predominantly involve loss of neutral proline whereas the complexes involving the smaller Mg(2+) and transition metal dications tend to lose small neutral molecules such as water and carbon dioxide. Interestingly, all complexes involving transition metal dications except for Cu(Pro2-H)(+) lose H2 upon collisional or IRMPD activation. IRMPD spectroscopy shows that the intact proline in the transition metal complexes and Cu(Pro2-H)(+) is predominantly canonical (charge solvated) while for the Ca(2+), Sr(2+), and Ba(2+) complexes, proline is in its zwitterionic form. The IRMPD spectra for both Mg(Pro2-H)(+) and Mn(Pro2-H)(+) are concluded to have contributions from both charge-solvated and canonical structures.

Novel Red-Orange Phosphors Na2BaMg(PO4)2:Pr3+: Synthesis, Crystal Structure and Photoluminescence Performance

NASA Astrophysics Data System (ADS)

Pan, Lu; Yang, Xiaozhan; Xiong, Chaoyue; Deng, Dashen; Qin, Chunlin; Feng, Wenlin

2018-01-01

A series of new red-orange emission phosphors Na2BaMg(PO4)2:Pr3+ were synthesised by a high-temperature solid-state reaction. The crystal structure and photoluminescence properties of these samples were characterised by X-ray diffraction and spectroscopic measurements. This compound holds P3̅m1 space group of the trigonal system with the lattice parameters of hexagonal cell a=0.5304(3) nm and c=0.6989(3) nm. The phosphor emits the strongest peak at 606 nm when excited by 449 nm. The average Commission Internationale de l'Eclairage chromaticity coordinates calculated for the phosphors are (0.52, 0.46). The results demonstrate the potential application of these phosphors in solid-state lighting and other fields.

Highly efficient red-emitting BaMgBO3F:Eu3+,R+ (R: Li, Na, K, Rb) phosphor for near-UV excitation synthesized via glass precursor solid-state reaction

NASA Astrophysics Data System (ADS)

Shinozaki, Kenji; Akai, Tomoko

2017-09-01

Eu3+-doped fluoroborate crystals of BaMgBO3F were synthesized by a solid-state reaction using a glassy precursor material, and their photoluminescence (PL) was investigated. To compensate for the incorporation of Eu3+ into Ba2+ sites, samples codoped with alkali ions (Li+, Na+, K+, Rb+) were also prepared. The Eu3+-doped sample showed red PL with a quantum yield (QY) of 65% caused by near-UV excitation (λ = 393 nm), and PL intensity and QY increased with the codoping of Eu3+ and alkali ions. It was found that the Eu3+,Li+-codoped sample showed the highest PL intensity and a QY of 83%.

Deformation Behavior of Ultra-Strong and Ductile Mg-Gd-Y-Zn-Zr Alloy with Bimodal Microstructure

NASA Astrophysics Data System (ADS)

Xu, C.; Fan, G. H.; Nakata, T.; Liang, X.; Chi, Y. Q.; Qiao, X. G.; Cao, G. J.; Zhang, T. T.; Huang, M.; Miao, K. S.; Zheng, M. Y.; Kamado, S.; Xie, H. L.

2018-02-01

An ultra-strong and ductile Mg-8.2Gd-3.8Y-1Zn-0.4Zr (wt pct) alloy was developed by using hot extrusion to modify the microstructure via forced-air cooling and an artificial aging treatment. A superior strength-ductility balance was obtained that had a tensile yield strength of 466 MPa and an elongation to failure of 14.5 pct. The local strain evolution during the in situ testing of the ultra-strong and ductile alloy was quantitatively analyzed with high-resolution electron backscattered diffraction and digital image correlation. The fracture behavior during the tensile test was characterized by synchrotron X-ray tomography along with SEM and STEM observations. The alloy showed a bimodal microstructure, consisting of dynamically recrystallized (DRXed) grains with random orientations and elongated hot-worked grains with < { 10{\\bar{1}}0} > parallel to the extrusion direction. The DRXed grains were deformed by the basal <;a> slip and the hot-worked grains were deformed by the prismatic slip dominantly. The strain evolution analysis indicated that the multilayered structure relaxed the strain localization via strain transfer from the DRXed to the hot-worked regions, which led to the high ductility of the alloy. Precipitation of the γ' on basal planes and the β' phases on the prismatic planes of the α-Mg generated closed volumes, which enhanced the strength by pinning dislocations effectively, and contributed to the high ductility by impeding the propagation of micro-cracks inside the grains. The deformation incompatibility between the hot-worked grains and the arched block-shaped long-period stacking ordered (LPSO) phases induced the crack initiation and propagation, which fractured the alloy.

Unexpected Ground-State Structure and Mechanical Properties of Ir₂Zr Intermetallic Compound.

PubMed

Zhang, Meiguang; Cao, Rui; Zhao, Meijie; Du, Juan; Cheng, Ke

2018-01-10

Using an unbiased structure searching method, a new orthorhombic Cmmm structure consisting of ZrIr 12 polyhedron building blocks is predicted to be the thermodynamic ground-state of stoichiometric intermetallic Ir₂Zr in Ir-Zr systems. The formation enthalpy of the Cmmm structure is considerably lower than that of the previously synthesized Cu₂Mg-type phase, by ~107 meV/atom, as demonstrated by the calculation of formation enthalpy. Meanwhile, the phonon dispersion calculations further confirmed the dynamical stability of Cmmm phase under ambient conditions. The mechanical properties, including elastic stability, rigidity, and incompressibility, as well as the elastic anisotropy of Cmmm -Ir₂Zr intermetallic, have thus been fully determined. It is found that the predicted Cmmm phase exhibits nearly elastic isotropic and great resistance to shear deformations within the (100) crystal plane. Evidence of atomic bonding related to the structural stability for Ir₂Zr were manifested by calculations of the electronic structures.

Diffuse phase ferroelectric vs. Polomska transition in (1-x) BiFeO3-(x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) solid solutions

NASA Astrophysics Data System (ADS)

Jha, Pardeep K.; Jha, Priyanka A.; Singh, Vikash; Kumar, Pawan; Asokan, K.; Dwivedi, R. K.

2015-01-01

Investigations on the solid solutions (1-x) BiFeO3 - (x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) in the temperature range 300-750 K show colossal permittivity behavior and the occurrence of diffuse phase ferroelectric transition along with frequency dependent anomaly which disappears at temperature ˜450 K. For x = 0.3, these anomalies have been verified through differential scanning calorimetry and dielectric/impedance/conductivity measurements. The occurrence of peak in pyrocurrent (dPs/dT) vs. T plots also supports phase transition. With the increasing x, transition temperature decreases and diffusivity increases. This anomaly is absent at high frequencies (>100 kHz) in conductivity plots, indicating Polomska like surface phase transition, which is supported by modulus study.

Effect of ZrO(2) additions on the crystallization, mechanical and biological properties of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics.

PubMed

Li, H C; Wang, D G; Meng, X G; Chen, C Z

2014-06-01

A series of ZrO(2) doped MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca(5)(PO4)3F (fluorapatite) and β-CaSiO(3). (β-wollastonite). m-ZrO(2) (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO(2) (tetragonal zirconia) increased the crystallization temperature of Ca(5)(PO4)(3)F and declined the crystallization temperature of β-CaSiO(3). t-ZrO(2) greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell. Copyright © 2014 Elsevier B.V. All rights reserved.

Domain wall motion and electromechanical strain in lead-free piezoelectrics: Insight from the model system (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} using in situ high-energy X-ray diffraction during application of electric fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tutuncu, Goknur; Li, Binzhi; Bowman, Keith

The piezoelectric compositions (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT-xBCT) span a model lead-free morphotropic phase boundary (MPB) between room temperature rhombohedral and tetragonal phases at approximately x = 0.5. In the present work, in situ X-ray diffraction measurements during electric field application are used to elucidate the origin of electromechanical strain in several compositions spanning the tetragonal compositional range 0.6 ≤ x ≤ 0.9. As BCT concentration decreases towards the MPB, the tetragonal distortion (given by c/a-1) decreases concomitantly with an increase in 90° domain wall motion. The increase in observed macroscopic strain is predominantly attributed to the increased contribution from 90°more » domain wall motion. The results demonstrate that domain wall motion is a significant factor in achieving high strain and piezoelectric coefficients in lead-free polycrystalline piezoelectrics.« less

Vacuum ultraviolet thin films. I - Optical constants of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 thin films. II - Vacuum ultraviolet all-dielectric narrowband filters

NASA Technical Reports Server (NTRS)

Zukic, Muamer; Torr, Douglas G.; Spann, James F.; Torr, Marsha R.

1990-01-01

An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

Physical and magnetic properties of (Ba/Sr) substituted magnesium nano ferrites

NASA Astrophysics Data System (ADS)

Ateia, Ebtesam E.; Takla, E.; Mohamed, Amira T.

2017-10-01

In the presented paper, strontium (Sr) and barium (Ba) nano ferrites were synthesized by citrate auto combustion method. The investigated samples are characterized by X-ray diffraction technique (XRD), field emission scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. The structural properties of the obtained samples were examined by XRD analysis showing that the synthesized nanoparticles are in cubic spinel structure. The average crystallite sizes are in the range of 22.66 and 21.95 nm for Mg0.7Ba0.3Fe2O4 and Mg0.7 Sr0.3Fe2O4 respectively. The VSM analysis confirms the existence of ferromagnetic nature of Sr2+/Ba2+ substituted magnesium nano particles. Exchange interaction between hard (Sr/Ba) and soft (Mg) magnetic phases improves the structural and magnetic properties of nano ferrite particles. Rigidity modulus, longitudinal and shear wave velocities are predicted theoretically from Raman spectroscopy and structural data of the investigated spinel ferrite. The magnetic and structural properties of magnesium are enhanced by doping with barium and strontium nano particles. The saturation magnetization, remanent magnetization and coercivity reported on vibrating sample magnetometer curve illustrate the promising industrial and magnetic recording applications of the prepared samples.

Average and local atomic-scale structure in BaZrxTi(1-x)O3 (x = 0. 10, 0.20, 0.40) ceramics by high-energy x-ray diffraction and Raman spectroscopy.

PubMed

Buscaglia, Vincenzo; Tripathi, Saurabh; Petkov, Valeri; Dapiaggi, Monica; Deluca, Marco; Gajović, Andreja; Ren, Yang

2014-02-12

High-resolution x-ray diffraction (XRD), Raman spectroscopy and total scattering XRD coupled to atomic pair distribution function (PDF) analysis studies of the atomic-scale structure of archetypal BaZrxTi(1-x)O3 (x = 0.10, 0.20, 0.40) ceramics are presented over a wide temperature range (100-450 K). For x = 0.1 and 0.2 the results reveal, well above the Curie temperature, the presence of Ti-rich polar clusters which are precursors of a long-range ferroelectric order observed below TC. Polar nanoregions (PNRs) and relaxor behaviour are observed over the whole temperature range for x = 0.4. Irrespective of ceramic composition, the polar clusters are due to locally correlated off-centre displacement of Zr/Ti cations compatible with local rhombohedral symmetry. Formation of Zr-rich clusters is indicated by Raman spectroscopy for all compositions. Considering the isovalent substitution of Ti with Zr in BaZrxTi1-xO3, the mechanism of formation and growth of the PNRs is not due to charge ordering and random fields, but rather to a reduction of the local strain promoted by the large difference in ion size between Zr(4+) and Ti(4+). As a result, non-polar or weakly polar Zr-rich clusters and polar Ti-rich clusters are randomly distributed in a paraelectric lattice and the long-range ferroelectric order is disrupted with increasing Zr concentration.

Structural studies of zirconium doped Ba{sub 0.70}Sr{sub 0.30}TiO{sub 3} lead free ferroelectric thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Sarita, E-mail: sss.sharmasarita@gmail.com; Ram, Mast; Thakur, Shilpa

2016-05-06

Ba{sub 0.7}Sr{sub 0.3}(Zr{sub x}Ti{sub 1-x})O{sub 3}(BSZT, x=0,0.05,0.10,0.15,0.20) thin films were prepared by using sol gel method. Structural and microstructural properties were studied by using XRD, Raman Spectroscopy and atomic force microscopy (AFM) respectively. XRD and Raman Spectroscopy show the presence of tetragonal phase in multilayer BSZT thin film. The experimental results demonstrate that structural and microstructural properties of BSZT thin film were significantly dependent on variation of Zr content.

Improved high temperature refractory. [MgCr/sub 2/O/sub 4/ composite with ZrO/sub 2/

DOEpatents

Singh, J.P.; James, J.; Picciolo, J.J.

1985-12-10

A high chromia refractory composite has been developed with improved thermal shock resistance and containing about 5 to 30 wt % of unstabilized ZrO/sub 2/ having a temperature-dependent phase change resulting in large expansion mismatch between the ZrO/sub 2/ and the chromia matrix which causes microcracks to form during cooling in the high chromia matrix. The particle size preferably is primarily between about 0.6 to 5 microns and particularly below about 3 microns with an average size in the order of 1.2 to 1.8 microns.

Process-Parameter-Dependent Optical and Structural Properties of ZrO2MgO Mixed-Composite Films Evaporated from the solid Solution

NASA Technical Reports Server (NTRS)

Sahoo, N. K.; Shapiro, A. P.

1998-01-01

The process-parameter-dependent optical and structural properties of ZrO2MgO mixed-composite material have been investigated. Optical properties were derived from spectrophotometric measurements. By use of atomic force microscopy, x-ray diffraction analysis, and energy-dispersive x-ray (EDX) analysis, the surface morphology, grain size distributions, crystallographic phases, and process-dependent material composition of films have been investigated. EDX analysis made evident the correlation between the oxygen enrichment in the films prepared at a high level of oxygen pressure and the very low refractive index. Since oxygen pressure can be dynamically varied during a deposition process, coatings constructed of suitable mixed-composite thin films can benefit from continuous modulation of the index of refraction. A step modulation approach is used to develop various multilayer-equivalent thin-film devices.

Primary fragmentation pathways of gas phase [M(uracil-H)(uracil)]+ complexes (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd , Mg, Ca, Sr, Ba, and Pb): loss of uracil versus HNCO.

PubMed

Ali, Osama Y; Randell, Nicholas M; Fridgen, Travis D

2012-04-23

Complexes formed between metal dications, the conjugate base of uracil, and uracil are investigated by sustained off-resonance irradiation collision-induced dissociation (SORI-CID) in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Positive-ion electrospray spectra show that [M(Ura-H)(Ura)](+) (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd, Mg, Ca, Sr, Ba, or Pb) is the most abundant ion even at low concentrations of uracil. SORI-CID experiments show that the main primary decomposition pathway for all [M(Ura-H)(Ura)](+) , except where M=Ca, Sr, Ba, or Pb, is the loss of HNCO. Under the same SORI-CID conditions, when M is Ca, Sr, Ba, or Pb, [M(Ura-H)(Ura)](+) are shown to lose a molecule of uracil. Similar results were observed under infrared multiple-photon dissociation excitation conditions, except that [Ca(Ura-H)(Ura)](+) was found to lose HNCO as the primary fragmentation product. The binding energies between neutral uracil and [M(Ura-H)](+) (M=Zn, Cu, Ni, Fe, Cd, Pd ,Mg, Ca, Sr Ba, or Pb) are calculated by means of electronic-structure calculations. The differences in the uracil binding energies between complexes which lose uracil and those which lose HNCO are consistent with the experimentally observed differences in fragmentation pathways. A size dependence in the binding energies suggests that the interaction between uracil and [M(Ura-H)](+) is ion-dipole complexation and the experimental evidence presented supports this. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The influence of Sr on the microstructure, degradation and stress corrosion cracking of the Mg alloys - ZK40xSr.

PubMed

Chen, Lianxi; Bin, Yuanhong; Zou, Wenqi; Wang, Xiaojian; Li, Wei

2017-02-01

In the present work, new magnesium (Mg) alloys (Mg-4Zn-0.6Zr-xSr, x=0, 0.4, 0.8, 1.2, 1.6wt%; ZK40xSr) were prepared and studied as potential biodegradable materials. The influence of strontium (Sr) addition on the properties of the new Mg alloys was investigated, which included microstructure, corrosion degradation, and the stress corrosion cracking (SCC) susceptibility. The average grain size of the ZK40Sr was approximately 100µm, which was significantly smaller than that of ZK40 alloy without Sr (402.3±40.2µm). The size of grain boundaries precipitates in the ZK40xSr alloys gradually increased with the increase of Sr content. The grain boundaries finally showed a continuously distribution and net-like shape. The degradation test showed that the average degradation rate of the ZK40xSr alloys increased with the increase of Sr addition. In the case of Mg-4Zn-0.6Zr, the degradation rate was 2.2mgcm -2 day -1 , which was lower than that of Mg-4Zn-0.6Zr-1.6Sr (4.93mgcm -2 day -1 ). When the ZK40xSr alloys were immersed in m-SBF, the rod-like Sr-contained hydroxyapatite (HA) substance was detected, which was known to enhance cell growth around bone implants. The fracture surfaces of the as-cast Mg-4Zn-0.6Zr-1.6Sr were shown intergranular stress corrosion cracking (IGSCC) patterns. The increase of SCC susceptibility of the higher Sr ZK40xSr alloys was attributed to the increase of micro-galvanic corrosion between the α-Mg and the grain boundaries precipitates. The SCC susceptibility values were ≈0.13 and ≈0.41 for the Mg-4Zn-0.6Zr-0.4Sr and the Mg-4Zn-0.6Zr-1.6Sr, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of a prior stretch on the aging response of an Al-Cu-Li-Ag-Mg-Zr alloy

NASA Technical Reports Server (NTRS)

Kumar, K. S.; Brown, S. A.; Pickens, Joseph R.

1991-01-01

Recently, a family of Al-Cu-Li alloys containing minor amounts of Ag, Mg, and Zr and having desirable combinations of strength and toughness were developed. The Weldalite (trademark) alloys exhibit a unique characteristic in that with or without a prior stretch, they obtain significant strength-ductility combinations upon natural and artificial aging. The ultra-high strength (approximately 690 MPa yield strength) in the peak-aged tempers (T6 and T8) were primarily attributed to the extremely fine T(sub 1) (Al2CuLi) or T(sub 1)-type precipitates that occur in these alloys during artificial aging, whereas the significant natural aging response observed is attributed to strengthening from delta prime (Al3Li) and GP zones. In recent work, the aging behavior of an Al-Cu-Li-Ag-Mg alloy without a prior stretch was followed microstructurally from the T4 to the T6 condition. Commercial extrusions, rolled plates, and sheets of Al-Cu-Li alloys are typically subjected to a stretching operation before artificial aging to straighten the extrusions and, more importantly, introduce dislocations to simulate precipitation of strengthening phases such as T(sub 1) by providing relatively low-energy nucleation sites. The goals of this study are to examine the microstructure that evolves during aging of an alloy that was stretch after solution treatment and to compare the observations with those for the unstretched alloy.

Synthesis, Structure, and Rigid Unit Mode-like Anisotropic Thermal Expansion of BaIr 2 In 9

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calta, Nicholas P.; Han, Fei; Kanatzidis, Mercouri G.

2015-09-08

This Article reports the synthesis of large single crystals of BaIr 2In 9 using In flux and their characterization by variable-temperature single-crystal and synchrotron powder X-ray diffraction, resistivity, and magnetization measurements. The title compound adopts the BaFe 2Al 9-type structure in the space group P6/mmm with room temperature unit cell parameters a = 8.8548(6) angstrom and c = 4.2696(4) A. BaIr 2In 9 exhibits anisotropic thermal expansion behavior with linear expansion along the c axis more than 3 times larger than expansion in the ab plane between 90 and 400 K. This anisotropic expansion originates from a rigid unit mode-likemore » mechanism similar to the mechanism of zero and negative thermal expansion observed in many anomalous thermal expansion materials such as ZrW 2O 8 and ScF 3.« less

Synthesis, Structure, and Rigid Unit Mode-like Anisotropic Thermal Expansion of BaIr2In9.

PubMed

Calta, Nicholas P; Han, Fei; Kanatzidis, Mercouri G

2015-09-08

This Article reports the synthesis of large single crystals of BaIr2In9 using In flux and their characterization by variable-temperature single-crystal and synchrotron powder X-ray diffraction, resistivity, and magnetization measurements. The title compound adopts the BaFe2Al9-type structure in the space group P6/mmm with room temperature unit cell parameters a = 8.8548(6) Å and c = 4.2696(4) Å. BaIr2In9 exhibits anisotropic thermal expansion behavior with linear expansion along the c axis more than 3 times larger than expansion in the ab plane between 90 and 400 K. This anisotropic expansion originates from a rigid unit mode-like mechanism similar to the mechanism of zero and negative thermal expansion observed in many anomalous thermal expansion materials such as ZrW2O8 and ScF3.

Genesis of Cenozoic intraplate high Mg# andesites in Northeast China

NASA Astrophysics Data System (ADS)

Liu, J. Q.; Chen, L. H.; Zhong, Y.; Wang, X. J.

2017-12-01

High-Mg# andesites (HMAs) are usually generated in the converged plate boundary and have genetic relationships with slab subduction. However, it still remained controversial about the origin of those HMAs erupted in the intra-plate setting. Here we present major, trace element, and Sr-Nd-Pb-Hf isotopic compositions for the Cenozoic intra-plate HMAs from Northeast China to constrain their origin and formation process. Cenozoic Xunke volcanic rocks are located in the northern Lesser Khingan Range, covering an area of about 3, 000 km2. These volcanic rocks are mainly basaltic andesite and basaltic trachyandesite, with only several classified as trachyandesite and andesites. They have high SiO2 contents (54.3-57.4 wt%) and Mg# (49.6-57.8), falling into the scope of high Mg# andesites. The Xunke HMAs are enriched in large ion lithophile elements but depleted in high field strength elements, with positive Ba, K, Sr and negative Zr-Hf, and Ti anomalies. Their trace element absolute concentrations are between those of potassic basalts and Wuchagou HMAs. The Xunke HMAs have relatively enriched Sr-Nd-Hf isotopes (87Sr/86Sr = 0.705398-0.705764, ɛNd=-8.8-3.8, ɛHf=0.5-11.7), and low radiogenic Pb isotopes (206Pb/204Pb = 16.701-17.198), towards to the EM1 end-member, which indicates that they are ultimately derived from ancient, recycled crustal components. Primitive silica-rich melts were generated from higher degrees of partial melting of recycled crustal materials (relative to potassic basalts) and then interacted with the peridotite to produce the Xunke HMAs.

Ferroelectric and dielectric properties of BaTi0.9Zr0.1O3 doped with Li0.5Fe2.5O4 ceramics

NASA Astrophysics Data System (ADS)

Gajula, Ganapathi Rao; Buddiga, Lakshmi Rekha; Chidambara Kumar, K. N.; Ch, Arun Kumar; Samatha, K.; Kokkiragadda, Sreeramachandra Murthy; Dasari, Madhava Prasad

2018-06-01

We have prepared a composite BaTi0.9Zr0.1O3 (BTZr) doped with Li0.5Fe2.5O4 (LF) having chemical formulae (1- x) BTZr + (x) LF (x=0, 0.05, 0.1 and 0.15) conventional solid state reaction technique. We have sintered the grown composites at 1150 °C for 3 h. We have characterized the grown composites using XRD, FESEM, P-E loop tracer and LCR meter. The XRD measurements reveal the tetragonal nature of the composites. The morphological studies reveal that the composite exhibits dense microstructure with small pores. The P-E loops confirm that the composites exhibit remnant polarization and the coercive field increases with increasing concentration of Lithium Ferrite (LF). We have studied dielectric property of the composites by varying the temperature of the sample from 30 °C to 500 °C at 1 kHz, 10 kHz and also by varying the frequency from 1 Hz to 10 MHz at 30 °C. The dielectric property of BTZr has increased after doping LF in BTZr which reveals the enhancement of electrical properties of the grown composite.

Trapped magnetic-field properties of prototype for Gd-Ba-Cu-O/MgB2 hybrid-type superconducting bulk magnet

NASA Astrophysics Data System (ADS)

Naito, Tomoyuki; Mochizuki, Hidehiko; Fujishiro, Hiroyuki; Teshima, Hidekazu

2016-03-01

We have studied experimentally and numerically the trapped magnetic-field properties of a hybrid-type superconducting bulk magnet, which comprised an inner Gd-Ba-Cu-O (GdBCO) disk-bulk and an outer MgB2 ring-bulk, under field-cooled magnetization (FCM) and pulsed-field magnetization (PFM). The trapped field by FCM at the center of the hybrid bulk was 4.5 T at 20 K, which was 0.2 T higher than that of the inner GdBCO disk-bulk without MgB2 ring-bulk. The experimental results by FCM were quantitatively reproduced by the numerical estimations for a model, which makes it possible to understand the trapped field properties of the hybrid bulk. The total magnetic flux by FCM, which was estimated numerically, was enhanced by about 1.7 times from 0.91 mWb of the single GdBCO bulk to 1.53 mWb of the hybrid bulk. We also succeeded in magnetizing the whole hybrid bulk by applying multi-pulsed-fields. The central trapped field of 1.88 T was not enhanced, but the total magnetic flux, which was obtained experimentally, was evidently increased by 2.5 times (0.25 \\to 0.62 mWb) for the hybrid bulk. The obtained results suggest that the hybridization is effective to enhance the total magnetic flux. To confirm the reinforcing effect of the MgB2 ring to the GdBCO disk during the cooling and magnetization processes, we have measured the thermal dilatation, {\\text{}}{dL}({\\text{}}T)/{\\text{}}L(300 K), of the GdBCO, MgB2 and stainless steel. As a result, the thermal dilatation of MgB2 was smaller than that of GdBCO. MgB2 ring-bulk shows no compression effect to resist the hoop stress of the GdBCO disk-bulk during the FCM process. The reinforcing material such as the stainless steel ring must be set outside the GdBCO disk-bulk.

Preliminary study of the characteristics of a high Mg containing Al-Mg-Si alloy

NASA Astrophysics Data System (ADS)

Yan, F.; McKay, B. J.; Fan, Z.; Chen, M. F.

2012-01-01

An Al-20Mg-4Si high Mg containing alloy has been produced and its characteristics investigated. The as-cast alloy revealed primary Mg2Si particles evenly distributed throughout an α-Al matrix with a β-Al3Mg2 fully divorced eutectic phase observed in interdendritic regions. The Mg2Si particles displayed octahedral, truncated octahedral, and hopper morphologies. Additions of Sb, Ti and Zr had a refining influence reducing the size of the Mg2Si from 52 ± 4 μm to 25 ± 0.1 μm, 35 ± 1 μm and 34 ± 1 μm respectively. HPDC tensile test samples could be produced with a 0.6 wt.% Mn addition which prevented die soldering. Solution heating for 1 hr was found to dissolve the majority of the Al3Mg2 eutectic phase with no evidence of any effect on the primary Mg2Si. Preliminary results indicate that the heat treatment has a beneficial effect on the elongation and the UTS.

Effects of Current Density on Microstructure and Corrosion Property of Coating on AZ31 Mg Alloy Processed via Plasma Electrolytic Oxidation

NASA Astrophysics Data System (ADS)

Lee, Kang Min; Einkhah, Feryar; Sani, Mohammad Ali Faghihi; Ko, Young Gun; Shin, Dong Hyuk

The effects of the current density on the micro structure and the corrosion property of the coating on AZ31 Mg alloy processed by the plasma electrolytic oxidation (PEO) were investigated. The present coatings were produced in an acid electrolyte containing K2ZrF6 with three different current densities, i.e., 100, 150, and 200 mA/cm2. From the microstructural observations, as the applied current density was increased, the diameter of micro-pores formed by the plasma discharges with high temperature increased. The coatings on AZ31 Mg alloy were mainly composed of MgO, ZrO2, MgF2, and Mg2Zr5O12 phases. The results of potentiodynamic polarization clearly showed that the PEO-treated AZ31 Mg alloy applied at 100 mA/cm2 of current density exhibited better corrosion properties than the others.

X-ray diffraction studies of phase transformations in heavy-metal fluoride glasses

NASA Technical Reports Server (NTRS)

Bansal, N. P.; Doremus, R. H.

1985-01-01

Powder X-ray diffraction and differential scanning calorimetry studies of the crystallization properties of five ZrF4-based glass compositions have indicated that the crystalline phase in Zr-Ba-La-Pb fluoride glass is beta-BaZrF6; no such identification of crystal phases was obtainable, however, for the other glasses. Reversible polymorphic phase transformations occur in Zr-Ba-La-Li and Zr-Ba-La-Na fluoride glasses, upon heating to higher temperatures.

White HDPE bottles as source of serious contamination of water samples with Ba and Zn.

PubMed

Reimann, Clemens; Grimstvedt, Andreas; Frengstad, Bjørn; Finne, Tor Erik

2007-03-15

During a recent study of surface water quality factory new white high-density polyethylene (HDPE) bottles were used for collecting the water samples. According to the established field protocol of the Geological Survey of Norway the bottles were twice carefully rinsed with water in the field prior to sampling. Several blank samples using milli-Q (ELGA) water (>18.2 MOmega) were also prepared. On checking the analytical results the blanks returned values of Ag, Ba, Sr, V, Zn and Zr. For Ba and Zn the values (c. 300 microg/l and 95 microg/l) were about 10 times above the concentrations that can be expected in natural waters. A laboratory test of the bottles demonstrated that the bottles contaminate the samples with significant amounts of Ba and Zn and some Sr. Simple acid washing of the bottles prior to use did not solve the contamination problem for Ba and Zn. The results suggest that there may exist "clean" and "dirty" HDPE bottles depending on manufacturer/production process. When collecting water samples it is mandatory to check bottles regularly as a possible source of contamination.

Effect of heat treatment on microstructure and mechanical properties of Mg-4Y-1.6Nd-1Sm-0.5Zr alloy

NASA Astrophysics Data System (ADS)

Jia, Guilong; Guo, Erjun; Feng, Yicheng; Wang, Liping; Wang, Changliang

2018-03-01

Microstructure and mechanical properties of Mg-4Y-1.6Nd-1Sm-0.5Zr alloy during heat treatments were investigated, while the room-temperature tensile fractographs were observed and analyzed. The results show that the eutectic phases almost dissolve into the matrix after being solutionized at 525 °C for 8 h. The ultimate tensile strength, yield strength and elongation reach 300 MPa, 219 MPa, 6.5% respectively after being under-aged at 200 °C for 16 h. The ultimate tensile strength and yield strength of the alloy decrease gradually, while the elongation increases gradually with increasing the test temperatures. The room-temperature tensile fracture modes of the as-cast alloy, solutionized alloy, aged alloy are mixed fracture of transgranular and intergranular, transgranular cleavage fracture, transgranular fracture, respectively.

Biosorption behavior and mechanism of lead (II) from aqueous solution by aerobic granules (AG) and bacterial alginate (BA)

NASA Astrophysics Data System (ADS)

Wang, Lin; Li, Yu

2012-12-01

Lead (Pb) and its compounds are common pollutants in industrial wastewaters. To develop appropriate Pb2+ treatment technologies, aerobic granules (AG) and bacterial alginates (BA) were studied as alternative biosorbents to remove Pb2+ from aqueous solutions. The biosorption mechanism of AG and BA were further analyzed to determine which functional groups in AG and BA are active in Pb2+ biosorption. In this paper, the Pb2+ biosorption behavior of AG and BA was respectively investigated in batch experiments from the perspectives of the initial pH, contact time, and initial Pb2+ concentration. The results showed that biosorption of Pb2+ by AG and BA occurred within 60min at the initial Pb2+ concentrations (0-150 mg L-1). The actual saturated Pb2+ biosorption capability of AG was 101.97 mg g-1 (dry weight of aerobic granular biomass). When the initial pH was 5, the biosorption capability of AG and BA was highest at the initial Pb2+ concentrations (0-20mg L-1). During the process of Pb2+ biosorption, K+, Ca2+, and Mg2+ were released. The Ion Chromatography (IC) and Fourier Transform Infrared Spectroscopy (FTIR) further highlighted the main role of ion exchange between Ca2+ and Pb2+ and sequestration of Pb2+ with carboxyl (-COO-) of AG and BA. This analogical analysis verifies that BA is responsible for biosorption of Pb2+ by AG. At the same optimal pH, AG cultivated with different carbon source has different Pb2+ biosorption capacity. The Pb2+ biosorption by AG with sodium acetate as the sole carbon source is higher than AG with glucose as carbon source.

The Experimental Study of Nuclear Astrophysics Reaction Rate of 93Zr(n,γ)94Zr

NASA Astrophysics Data System (ADS)

Gan, L.; Li, Z. H.; Su, J.; Yan, S. Q.; Guo, B.; Du, X. C.; Wu, Z. D.; Zeng, S.; Jin, S. J.; Wang, Y. B.; Bai, X. X.; Zhang, W. J.; Sun, H. B.; Li, E. T.

The slow neutron capture (s-) process plays a very important role in the nucleosynthesis, which produces about half of the elements heavier than iron. 94Zr is mainly from 93Zr(n,γ)94Zr in the s-process, and the direct component of the 93Zr(n,γ)94Zr capture reaction can be derived from the neutron spectroscopic factor of 94Zr. As the existing neutron spectroscopic factors of 94Zr vary from each other up to 60%, a new work should be adopted to measure it exactly. In the present work, the angular distributions of 94Zr(13C,13C)94Zr, 94Zr(12C,12C)94Zr and 94Zr(12C,13C)93Zr were obtained using the highprecision Q3D magnetic spectrograph. In addition, distorted-wave Born approximation (DWBA) calculations of the transfer differential cross sections were performed. The calculated result displays a good agreement with the experiment data, and a value of 2.60±0.20 for the neutron spectroscopic factor of 94Zr was extracted, and the direct capture cross section versus neutron energy of 93Zr(n,γ)94Zr for the ground state of 94Zr was obtained too.

The effect of glass additives on the microwave dielectric properties of Ba(Mg{sub 1/3}Ta{sub 2/3})O{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Surendran, K.P.; Mohanan, P.; Sebastian, M.T.

2004-11-01

The effect of glass additives on the densification, phase evolution, microstructure and microwave dielectric properties of Ba(Mg{sub 1/3}Ta{sub 2/3})O{sub 3} (BMT) was investigated. Different weight percentages of quenched glass such as B{sub 2}O{sub 3}, SiO{sub 2}, B{sub 2}O{sub 3}-SiO{sub 2}, ZnO-B{sub 2}O{sub 3}, 5ZnO-2B{sub 2}O{sub 3}, Al{sub 2}O{sub 3}-SiO{sub 2}, Na{sub 2}O-2B{sub 2}O{sub 3}.10H{sub 2}O, BaO-B{sub 2}O{sub 3}-SiO{sub 2}, MgO-B{sub 2}O{sub 3}-SiO{sub 2}, PbO-B{sub 2}O{sub 3}-SiO{sub 2}, ZnO-B{sub 2}O{sub 3}-SiO{sub 2} and 2MgO-Al{sub 2}O{sub 3}-5SiO{sub 2} were added to calcined BMT precursor. The sintering temperature of the glass-added BMT samples were lowered down to 1300 deg. C compared to solid-statemore » sintering where the temperature was 1650{sup o}C. The formation of high temperature satellite phases such as Ba{sub 5}Ta{sub 4}O{sub 15} and Ba{sub 7}Ta{sub 6}O{sub 22} were found to be suppressed by the glass addition. Addition of glass systems such as B{sub 2}O{sub 3}, ZnO-B{sub 2}O{sub 3}, 5ZnO-2B{sub 2}O{sub 3} and ZnO-B{sub 2}O{sub 3}-SiO{sub 2} improved the densification and microwave dielectric properties. Other glasses were found to react with BMT to form low-Q phases which prevented densification. The microwave dielectric properties of undoped BMT with a densification of 93.1% of the theoretical density were {epsilon}r=24.8, {tau}f=8ppm/{sup o}C and Q{sub u}xf=80,000GHz. The BMT doped with 1.0wt% of B{sub 2}O{sub 3} has Q{sub u}xf=124,700GHz, {epsilon}r=24.2, and {tau}f=-1.3ppm/ deg/ C. The unloaded Q factor of 0.2wt% ZnO-B{sub 2}O{sub 3}-doped BMT was 136,500GHz while that of 1.0wt% of 5ZnO-2B{sub 2}O{sub 3} added ceramic was Q{sub u}xf=141,800GHz. The best microwave quality factor was observed for ZnO-B{sub 2}O{sub 3}-SiO{sub 2} (ZBS) glass-added ceramics which can act as a perfect liquid-phase medium for the sintering of BMT. The microwave dielectric properties of 0.2wt% ZBS-added BMT dielectric was Q{sub u}xf=152,800GHz

Effect of different Zr contents on properties and microstructure of Cu-Cr-Zr alloys

NASA Astrophysics Data System (ADS)

Jinshui, Chen; Bin, Yang; Junfeng, Wang; Xiangpeng, Xiao; Huiming, Chen; Hang, Wang

2018-02-01

The crystallography and morphology of precipitate particles of Cu-Cr-Zr alloys with varying Zr contents were studied by transmission electron microscopy (TEM) after solution treatments at 950 °C for 1 h and aging treatments at 500 °C for different times ranged from 0.5 h to 24 h. The microhardness and electrical conductivity of Cu-Cr-Zr alloys after various aging process were tested. The results show that the microhardness and electrical conductivity rapidly increased at first, then the microhardness decreased slowly after reaching the peak, while the conductivity continues to increase. Nano-scaled precipitates exhibit two kinds of morphology (coffee bean and ellipse shaped). With increasing Zr content, the Zr-containing precipitation sequence of Cu-Cr-Zr alloys at peak-ageing is Heusler CrCu2Zr → Cu5Zr → Cu4Zr. The Heusler CrCu2Zr phase decomposed into fine and homogeneous Cr and Cu4Zr, resulting in improved alloy properties.

Investigation by Differential Scanning Calorimetry of Microstructure in a Superplastic Al-Mg-Zr Alloy.

DTIC Science & Technology

1987-06-01

cold-rolled zinc-copper-aluminum eutectic alloy exhibited this superplastic response. Superplasticity was initially viewed as a curious observation...limited to eutectic alloys when tested under the correct laboratory conditions. However, in 1962 Underwood [Ref. 23 reviewed Soviet work; this review...formation of a very fine dispersoid, ZrAI3. This dispersoid results in grain refinement, raises the recrystallization temperature (Ref. 7:p. 414] and gives

Fine Structure in Multi-Phase Zr8Ni21-Zr7Ni10-Zr2Ni7 Alloy Revealed by Transmission Electron Microscope

PubMed Central

Shen, Haoting; Bendersky, Leonid A.; Young, Kwo; Nei, Jean

2015-01-01

The microstructure of an annealed alloy with a Zr8Ni21 composition was studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of three phases, Zr8Ni21, Zr2Ni7, and Zr7Ni10, was confirmed by SEM/X-ray energy dispersive spectroscopy compositional mapping and TEM electron diffraction. Distribution of the phases and their morphology can be linked to a multi-phase structure formed by a sequence of reactions: (1) L → Zr2Ni7 + L’; (2) peritectic Zr2Ni7 + L’ → Zr2Ni7 + Zr8Ni21 + L”; (3) eutectic L” → Zr8Ni21 + Zr7Ni10. The effect of annealing at 960 °C, which was intended to convert a cast structure into a single-phase Zr8Ni21 structure, was only moderate and the resulting alloy was still multi-phased. TEM and crystallographic analysis of the Zr2Ni7 phase show a high density of planar (001) defects that were explained as low-energy boundaries between rotational variants and stacking faults. The crystallographic features arise from the pseudo-hexagonal structure of Zr2Ni7. This highly defective Zr2Ni7 phase was identified as the source of the broad X-ray diffraction peaks at around 38.4° and 44.6° when a Cu-K was used as the radiation source. PMID:28793460

Influence of multi-walled carbon nanotubes (MWCNTs) volume percentage on the magnetic and microwave absorbing properties of BaMg{sub 0.5}Co{sub 0.5}TiFe{sub 10}O{sub 19}/MWCNTs nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alam, Reza Shams; Moradi, Mahmood, E-mail: moradi@susc.ac.ir; Institute of Nanotechnology, Shiraz University, Shiraz 71454

2016-01-15

Graphical abstract: Reflection losses of (a) doped barium hexaferrite, BaMg{sub 0.5}Co{sub 0.5}TiFe{sub 10}O{sub 19}, sample and their nanocomposites with (b) 4 vol. (c) 8 vol. and (d) 12 vol.% of MWCNTs are presented. - Highlights: • BaMg{sub 0.5}Co{sub 0.5}TiFe{sub 10}O{sub 19}/MWCNTs nanocomposites were synthesized. • The structural, magnetic and microwave absorption properties were investigated. • The microwave absorption is strongly influenced by volume percentage of MWCNTs. • The nanocomposite with 8 vol.% of MWCNTs can be proposed as a wideband absorber. - Abstract: In this study BaMg{sub 0.5}Co{sub 0.5}TiFe{sub 10}O{sub 19}/MWCNTs nanocomposites with different amount of MWCNTs (0, 4, 8more » and 12 vol.%) were synthesized. Here, the X-ray diffraction (XRD), Fourier transform spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to demonstrate the structural and morphological characteristics of the prepared samples. XRD along with FTIR examinations exhibited that the nanocomposites were successfully synthesized. Vibrating sample magnetometer (VSM) showed the relatively strong dependence of saturation magnetization and coercivity on the volume percentage of MWCNTs. The microwave evaluation also confirmed that the complex permittivity of nanocomposites could be enhanced by adding MWCNTs. Finally, the nanocomposite with 8% vol. of MWCNTs exhibited the best microwave absorption performance among the samples.« less

Chitosan /Zeolite Y/Nano ZrO2 nanocomposite as an adsorbent for the removal of nitrate from the aqueous solution.

PubMed

Teimouri, Abbas; Nasab, Shima Ghanavati; Vahdatpoor, Niaz; Habibollahi, Saeed; Salavati, Hossein; Chermahini, Alireza Najafi

2016-12-01

In the present study, a series of chitosan/Zeolite Y/Nano Zirconium oxide (CTS/ZY/Nano ZrO 2 ) nanocomposites were made by controlling the molar ratio of chitosan (CTS) to Zeolite Y/Nano Zirconium oxide in order to remove nitrate (NO 3 - ) ions in the aqueous solution. The nanocomposite adsorbents were characterized by XRD, FTIR, BET, SEM and TEM. The influence of different molar ratios of CTS to ZY/Nano ZrO 2 , the initial pH value of the nitrate solution, contact time, temperature, the initial concentration of nitrate and adsorbent dose was studied. The adsorption isotherms and kinetics were also analyzed. It was attempted to describe the sorption processes by the Langmuir equation and the theoretical adsorption capacity (Q 0 ) was found to be 23.58mg nitrate per g of the adsorbent. The optimal conditions for nitrate removal were found to be: molar ratio of CTS/ZY/Nano ZrO 2 : 5:1; pH: 3; 0.02g of adsorbent and temperature: 35°C, for 60min. The adsorption capacities of CTS, ZY, Nano ZrO 2 , CTS/Nano ZrO 2 , CTS/ZY and CTS/ZY/Nano ZrO 2 nanocomposites for nitrate removal were compared, showing that the adsorption ability of CTS/ZY/Nano ZrO 2 nanocomposite was higher than the average values of those of CTS (1.95mg/g for nitrate removal), ZY, Nano ZrO 2 , CTS/Nano ZrO 2, and CTS/ZY. Copyright © 2016. Published by Elsevier B.V.

Microstructure and dielectric properties of BaTiO{sub 3} ceramic doped with yttrium, magnesium, gallium and silicon for AC capacitor application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Min-Jia; Yang, Hui; Zhejiang California International NanoSystems Institute, Hangzhou 310029

2014-12-15

Graphical abstract: Core–shell structure can be obtained in BaTiO{sub 3} ceramics co-doped with Y–Mg-Ga-Si. Y-Mg-Ga-Si co-dopant can obviously reduce dielectric loss, improve AC breakdown voltage and flatten temperature dependence of capacitance curve. - Highlights: • Y-Mg-Ga-Si co-doped BaTiO{sub 3} ceramics with core-shell structure were prepared. • Y{sup 3+}, Mg{sup 2+}, and Ga{sup 3+} dissolved in the lattice BaTiO{sub 3} replacing Ba{sup 2+} site or Ti{sup 4+} site. • Y{sup 3+} and Ga{sup 3+} tended to remain close to the grain boundaries as a shell maker. • Y-Mg-Ga-Si co-doped BaTiO{sub 3} ceramics show high AC breakdown voltage and low tanδ. -more » Abstract: The microstructures and dielectric properties of Y-Mg-Ga-Si co-doped barium titanate ceramics were investigated. Y{sup 3+} dissolved in the lattice of BaTiO{sub 3} replacing both Ba{sup 2+} site and Ti{sup 4+} site, and Mg{sup 2+} replaced Ti{sup 4+} site. The replacements of Y{sup 3+} and Mg{sup 2+} inhibit the grain growth, cause tetragonal-to-pseudocubic phase transition, reduce the dielectric loss, and flatten the temperature dependence of capacitance curve. The incorporation of Ga{sup 3+} can improve sintering and increase permittivity. Y{sup 3+} and Ga{sup 3+} tended to remain close to the grain boundaries, and play an important role as a shell maker in the formation of the core–shell structure in the co-doped BaTiO{sub 3} ceramics. Excellent dielectric properties: ϵ{sub r} = ∼2487, tanδ = ∼0.7% (at 1 kHz), ΔC/C{sub 25} < ∼6.56% (from −55 °C to 125 °C) and alternating current breakdown voltage E < ∼4.02 kV/mm can be achieved in the BaTiO{sub 3}–0.02Y{sub 2}O{sub 3}–0.03MgO–0.01Ga{sub 2}O{sub 3}–0.005SiO{sub 2} ceramics sintered at 1380 °C. This material has a potential application in alternating current multilayer ceramic capacitor.« less

Crystal growth of incommensurate members of 2H-hexagonal perovskite related oxides: Ba{sub 4}M{sub z}Pt{sub 3−z}O{sub 9} (M=Co, Ni, Cu, Zn, Mg, Pt)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferreira, Timothy; Morrison, Gregory; Yeon, Jeongho

2016-04-15

Millimeter sized crystals of six oxides of approximate composition Ba{sub 4}M{sub z}Pt{sub 3-z}O{sub 9} (M=Co, Ni, Cu, Zn, Mg, Pt) were grown from molten K{sub 2}CO{sub 3} fluxes and found to crystallize in a 2H hexagonal perovskite-related structure type. The compositions of these incommensurate structures, which belong to the A{sub 3n+3m}A′{sub n}B{sub 3m+n}O{sub 9m+6n} family of 2H hexagonal perovskite related oxides, were characterized by X-ray diffraction, energy dispersive spectroscopy, and magnetic susceptibility measurements. The specific synthetic considerations, crystal growth conditions, and magnetic susceptibility measurements are discussed. - Graphical abstract: SEM image and average commensurate unit cell of Ba{sub 4}Pt{sub 3}O{submore » 9.} - Highlights: • Single crystals of the series Ba{sub 4}A′{sub z}Pt{sub 3-z}O{sub 9} were grown via a molten carbonate flux. • Ba{sub 4}Pt{sub 3}O{sub 9} and all substitutional variants are incommensurate, composite structures. • All compounds have an approximate stoichiometry of Ba{sub 4}A′Pt{sub 2}O{sub 9.}.« less

Fabrication of one-transistor-capacitor structure of nonvolatile TFT ferroelectric RAM devices using Ba(Zr0.1Ti0.9)O3 gated oxide film.

PubMed

Yang, Cheng-Fu; Chen, Kai-Huang; Chen, Ying-Chung; Chang, Ting-Chang

2007-09-01

In this study, the Ba(Zr0.1Ti0.9)O3 (BZ1T9) thin films have been well deposited on the Pt/Ti/SiO2/Si substrate. The optimum radio frequency (RF) deposition parameters are developed, and the BZ1T9 thin films deposition at the optimum parameters have the maximum capacitance and dielectric constant of 4.4 nF and 190. As the applied voltage is increased to 8 V, the remnant polarization and coercive field of BZ1T9 thin films are about 4.5 microC/cm2 and 80 kV/cm. The counterclockwise current hysteresis and memory window of n-channel thin-film transistor property are observed, and that can be used to indicate the switching of ferroelectric polarization of BZ1T9 thin films. One-transistor-capacitor (1TC) structure of BZ1T9 ferroelectric random access memory device using bottom-gate amorphous silicon thin-film transistor was desirable because of the smaller size and better sensitivity. The BZ1T9 ferroelectric RAM devices with channel width = 40 microm and channel length = 8 microm has been successfully fabricated and the ID-VG transfer characteristics also are investigated in this study.

Effect of rare earth doping on optical and spectroscopic characteristics of BaZrO3:Eu3+,Tb3+ perovskites.

PubMed

Katyayan, Shambhavi; Agrawal, Sadhana

2018-04-04

This paper reports structural investigations of rare earth doped BaZrO 3 phosphors synthesized by Solid state reaction technique with varying concentrations of Eu 3+ and Tb 3+ from 0 mol% to 2 mol%. The synthesized phosphors show enhanced variable emissions in the visible region corresponding to different hypersensitive electronic transitions of Eu 3+ and Tb 3+ ions. With cubic structure confirmed in XRD analysis, the FESEM images show uniform grain connectivity and homogeneity of prepared samples. The TEM micrographs of the synthesized phosphors show agglomerated irregular structures. The synthesized phosphors were also subjected to FTIR, Raman, EDXS analysis along with studies of thermoluminescent and photoluminescent characteristics. On subjecting to 229 nm (UV) excitation, the phosphors show enhanced PL emissions corresponding to 571 nm ( 5 D 0 - 7 F 0 ), 591 nm ( 5 D 0 - 7 F 1 ), 615 nm ( 5 D 0 - 7 F 2 ) and 678 nm ( 5 D 0 - 7 F 4 ) hypersensitive transitions of Eu 3+ ions and emission peaks at 489 nm ( 5 D 4 - 7 F 6 ), 539 nm ( 5 D 4 - 7 F 5 ), 589 nm ( 5 D 4 - 7 F 4 ) and 632 nm ( 5 D 4 - 7 F 3 ) accounting for electronic transitions of Tb 3+ ions respectively. The computed average PL lifetime is 14.014 s. In the TL analysis, the second order of kinetics with the activation energy varying from 5.0 × 10 -1 eV to 6.6 × 10 -1 eV is reported. The maximum TL lifetime is estimated as 19.4985 min in the TL lifetime analysis.

Effect of rare earth doping on optical and spectroscopic characteristics of BaZrO3:Eu3+,Tb3+ perovskites

NASA Astrophysics Data System (ADS)

Katyayan, Shambhavi; Agrawal, Sadhana

2018-06-01

This paper reports structural investigations of rare earth doped BaZrO3 phosphors synthesized by Solid state reaction technique with varying concentrations of Eu3+ and Tb3+ from 0 mol% to 2 mol%. The synthesized phosphors show enhanced variable emissions in the visible region corresponding to different hypersensitive electronic transitions of Eu3+ and Tb3+ ions. With cubic structure confirmed in XRD analysis, the FESEM images show uniform grain connectivity and homogeneity of prepared samples. The TEM micrographs of the synthesized phosphors show agglomerated irregular structures. The synthesized phosphors were also subjected to FTIR, Raman, EDXS analysis along with studies of thermoluminescent and photoluminescent characteristics. On subjecting to 229 nm (UV) excitation, the phosphors show enhanced PL emissions corresponding to 571 nm (5D0-7F0), 591 nm (5D0-7F1), 615 nm (5D0-7F2) and 678 nm (5D0-7F4) hypersensitive transitions of Eu3+ ions and emission peaks at 489 nm (5D4-7F6), 539 nm (5D4-7F5), 589 nm (5D4-7F4) and 632 nm (5D4-7F3) accounting for electronic transitions of Tb3+ ions respectively. The computed average PL lifetime is 14.014 s. In the TL analysis, the second order of kinetics with the activation energy varying from 5.0 × 10‑1 eV to 6.6 × 10‑1 eV is reported. The maximum TL lifetime is estimated as 19.4985 min in the TL lifetime analysis.

Synthesis of Zr2WP2O12/ZrO2 Composites with Adjustable Thermal Expansion.

PubMed

Zhang, Zhiping; Sun, Weikang; Liu, Hongfei; Xie, Guanhua; Chen, Xiaobing; Zeng, Xianghua

2017-01-01

Zr 2 WP 2 O 12 /ZrO 2 composites were fabricated by solid state reaction with the goal of tailoring the thermal expansion coefficient. XRD, SEM and TMA were used to investigate the composition, microstructure, and thermal expansion behavior of Zr 2 WP 2 O 12 /ZrO 2 composites with different mass ratio. Relative densities of all the resulting Zr 2 WP 2 O 12 /ZrO 2 samples were also tested by Archimedes' methods. The obtained Zr 2 WP 2 O 12 /ZrO 2 composites were comprised of orthorhombic Zr 2 WP 2 O 12 and monoclinic ZrO 2 . As the increase of the Zr 2 WP 2 O 12 , the relative densities of Zr 2 WP 2 O 12 /ZrO 2 ceramic composites increased gradually. The coefficient of thermal expansion of the Zr 2 WP 2 O 12 /ZrO 2 composites can be tailored from 4.1 × 10 -6 K -1 to -3.3 × 10 -6 K -1 by changing the content of Zr 2 WP 2 O 12 . The 2:1 Zr 2 WP 2 O 12 /ZrO 2 specimen shows close to zero thermal expansion from 25 to 700°C with an average linear thermal expansion coefficient of -0.09 × 10 -6 K -1 . These adjustable and near zero expansion ceramic composites will have great potential application in many fields.

Energy band alignment of antiferroelectric (Pb,La)(Zr,Sn,Ti)O3

NASA Astrophysics Data System (ADS)

Klein, Andreas; Lohaus, Christian; Reiser, Patrick; Dimesso, Lucangelo; Wang, Xiucai; Yang, Tongqing

2017-06-01

The energy band alignment of antiferroelectric (Pb,La)(Zr,Sn,Ti)O3 is studied with photoelectron spectroscopy using interfaces with high work function RuO2 and low work function Sn-doped In2O3 (ITO). It is demonstrated how spectral deconvolution can be used to determine absolute Schottky barrier heights for insulating materials with a high accuracy. Using this approach it is found that the valence band maximum energy of (Pb,La)(Zr,Sn,Ti)O3 is found to be comparable to that of Pb- and Bi-containing ferroelectric materials, which is ∼1 eV higher than that of BaTiO3. The results provide additional evidence for the occupation of the 6s orbitals as origin of the higher valence band maximum, which is directly related to the electrical properties of such compounds. The results also verify that the energy band alignment determined by photoelectron spectroscopy of as-deposited electrodes is not influenced by polarisation. The electronic structure of (Pb,La)(Zr,Sn,Ti)O3 should enable doping of the material without strongly modifying its insulating properties, which is crucial for high energy density capacitors. Moreover, the position of the energy bands should result in a great freedom of selecting electrode materials in terms of avoiding charge injection.

Study on effects of powder and flake chemistry and morphology on the properties of Al-Cu-Mg-X-X-X powder metallurgy advanced aluminum alloys

NASA Technical Reports Server (NTRS)

Meschter, P. J.; Lederich, R. J.; Oneal, J. E.

1986-01-01

A study was conducted: (1) to develop rapid solidification processed (RSP) dispersoid-containing Al-3Cu-2Li-1Mg-0.2Zr alloys as substitutes for titanium alloys and commercial 2XXX aluminum alloys for service to at least 150 C; and (2) to develop RSP Al-4Li-Cu-Mg-Zr alloys as substitutes for high-strength commercial 7XXX alloys in ambient-temperature applications. RSP Al-3Cu-2Li-1Mg-0.2Zr alloys have density-normalized yield stresses at 150 C up to 52% larger than that of 2124-T851 and up to 30% larger than that of Ti-6Al-4V. Strength at 150 C in these alloys is provided by thermally stable delta' (Al3Li), T1 (Al2LiCu), and S' (Al2CuMg) precipitates. Density-normalized yield stresses of RSP Al-3Cu-2Li-1Mg-0.2Zr alloys are up to 100% larger than that of 2124-T851 and equivalent to that of Al-8Fe-4Ce at 260 C. Strength in the RSP alloys at 260 C is provided by incoherent dispersoids and subboundary constituent particles such as T1 and S. The RSP alloys are attractive substitutes in less than or = 100-h exposures for 2xxx and Al-4Fe-Ce alloys up to 260 C and for titanium alloys up to 150 C. RSP Al-4Li-Cu-Mg-Zr alloys have ambient-temperature yield and ultimate tensile stresses similar to that of 7050-T7651, and are 14% less dense. RSP Al-4Li-0.5Cu-1.5Mg-0.2Zr has a 20% higher specific yield stress, 40% higher specific elastic modulus, and superior corrosion resistance compared to the properties of 7050-T7651. Strength in the Al-4Li-Cu-Mg-Zr alloy class is primarily provided by the substructure and delta' precipitates and is independent of Cu:Mg ratio. Improvements in fracture toughness and transverse-orientation properties in both alloy classes depend on improved melt practices to eliminate oxide inclusions which are incorporated into the consolidated forms.

Thickness-dependent electrocaloric effect in mixed-phase Pb0.87Ba0.1 La0.02(Zr0.6Sn0.33Ti0.07)O3 thin films

PubMed Central

Correia, T. M.

2016-01-01

Full-perovskite Pb0.87Ba0.1La0.02(Zr0.6Sn0.33Ti0.07)O3 (PBLZST) thin films were fabricated by a sol–gel method. These revealed both rhombohedral and tetragonal phases, as opposed to the full-tetragonal phase previously reported in ceramics. The fractions of tetragonal and rhombohedral phases are found to be strongly dependent on film thickness. The fraction of tetragonal grains increases with increasing film thickness, as the substrate constraint throughout the film decreases with film thickness. The maximum of the dielectric constant (εm) and the corresponding temperature (Tm) are thickness-dependent and dictated by the fraction of rhombohedral and tetragonal phase, with εm reaching a minimum at 400 nm and Tm shifting to higher temperature with increasing thickness. With the thickness increase, the breakdown field decreases, but field-induced antiferroelectric–ferroelectric (EAFE−FE) and ferroelectric–antiferroelectric (EFE−AFE) switch fields increase. The electrocaloric effect increases with increasing film thickness. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’. PMID:27402937

Improved production and processing of ⁸⁹Zr using a solution target.

PubMed

Pandey, Mukesh K; Bansal, Aditya; Engelbrecht, Hendrik P; Byrne, John F; Packard, Alan B; DeGrado, Timothy R

2016-01-01

The objectives of the present work were to improve the cyclotron production yield of (89)Zr using a solution target, develop a practical synthesis of the hydroxamate resin used to process the target, and develop a biocompatible medium for (89)Zr elution from the hydroxamate resin. A new solution target (BMLT-2) with enhanced heat dissipation capabilities was designed by using helium-cooled dual foils (0.2 mm Al and 25 μ Havar) and an enhanced water-cooled, elongated solution cavity in the target insert. Irradiations were performed with 14 MeV protons on a 2M solution of yttrium nitrate in 1.25 M nitric acid at 40-μA beam current for 2 h in a closed system. Zirconium-89 was separated from Y by use of a hydroxamate resin. A one-pot synthesis of hydroxamate resin was accomplished by activating the carboxylate groups on a carboxymethyl cation exchange resin using methyl chloroformate followed by reaction with hydroxylamine hydrochloride. After trapping of (89)Zr on hydroxamate resin and rinsing the resin with HCl and water to release Y, (89)Zr was eluted with 1.2 M K2HPO4/KH2PO4 buffer (pH3.5). ICP-MS was used to measure metal contaminants in the final (89)Zr solution. The BMLT-2 target produced 349±49 MBq (9.4±1.2 mCi) of (89)Zr at the end of irradiation with a specific activity of 1.18±0.79 GBq/μg. The hydroxamate resin prepared using the new synthesis method showed a trapping efficiency of 93% with a 75 mg resin bed and 96-97% with a 100-120 mg resin bed. The elution efficiency of (89)Zr with 1.2M K2HPO4/KH2PO4 solution was found to be 91.7±3.7%, compared to >95% for 1 M oxalic acid. Elution with phosphate buffer gave very small levels of metal contaminants: Al=0.40-0.86 μg (n=2), Fe=1.22±0.71 μg (n=3), Y=0.29 μg (n=1). The BMLT-2 target allowed doubling of the beam current for production of (89)Zr, resulting in a greater than 2-fold increase in production yield in comparison with a conventional liquid target. The new one-pot synthesis of hydroxamate

Structural and compositional evolution of Al{sub 3}(Zr,Y) precipitates in Al-Zr-Y alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Haiyan, E-mail: gaohaiyan@sjtu.edu.cn

Structural and compositional evolution of Al{sub 3}(Zr,Y) precipitates in aged Al-Zr-Y alloy was investigated through atom probe tomography (APT) and transmission electron microscope (TEM) analysis and first principles calculations. The results show that short-bar-shaped D0{sub 19}-Al{sub 3}Y with some Zr atoms dissolved in precipitated at the very beginning of decomposition and worked as heterogeneous nuclei for L1{sub 2}-Al{sub 3}Zr with spherical morphology after being aged at 400 °C for 2 h. Quasi-static coarsening happened as the aging treatment lasted from 2 h to 200 h. However, distribution of Zr and Y atoms in Al{sub 3}(Zr,Y) is nearly uniform and Al{submore » 3}(Zr,Y) do not have the typical “Al{sub 3}RE core-Al{sub 3}Zr shell” structure which observed in other RE containing Al-Zr-RE alloys with L1{sub 2}-Al{sub 3}RE as nuclei. First principles calculations revealed that binding energy between Y and Zr is strong during the growth of Al{sub 3}(Zr,Y), which led to the co-precipitation of Y and Zr atoms and attribute to the evolution of Al{sub 3}(Zr,Y). - Highlights: •Al{sub 3}Y precipitated firstly and then became nuclei for Al{sub 3}Zr during aging of Al-Zr-Y. •Al{sub 3}(Zr,Y) precipitates do not have the typical “Al{sub 3}Y core-Al{sub 3}Zr shell” structure. •Strong binding between Y and Zr led to the co-precipitation of Y and Zr atoms.« less

Determination of boron in blood, urine and bone by electrothermal atomic absorption spectrometry using zirconium and citric acid as modifiers

NASA Astrophysics Data System (ADS)

Burguera, Marcela; Burguera, José Luis; Rondón, Carlos; Carrero, Pablo

2001-10-01

A comparative study of various potential chemical modifiers (Au, Ba, Be, Ca, Cr, Ir, La, Lu, Mg, Ni, Pd, Pt, Rh, Ru, Sr, V, W, and Zr), and different 'coating' treatments (Zr, W, and W+Rh) of the pyrolytic graphite platform of a longitudinally heated graphite tube atomizer for thermal stabilization and determination of boron was undertaken. The use of Au, Ba, Be, Cr, Ir, Pt, Rh, Ru, Sr and V as modifiers, and of W+Rh coating produced erratic, and noisy signals, while the addition of La, Ni and Pd as modifiers, and the W coating had positive effects, but with too high background absorption signals, rendering their use unsuitable for boron determination even in aqueous solutions. The atomic absorption signal for boron was increased and stabilized when the platform was coated with Zr, and by the addition of Ca, Mg, Lu, W or Zr as modifiers. Only the addition of 10 μg of Zr as a modifier onto Zr-treated platforms allowed the use of a higher pyrolysis temperature without analyte losses. The memory effect was minimized by incorporating a cleaning step with 10 μl of 50 g l -1 NH 4F HF after every three boron measurements. The addition of 10 μl of 15 g l -1 citric acid together with Zr onto Zr-treated platforms significantly improved the characteristic mass to m0=282 pg, which is adequate for biological samples such as urine and bone, although the sensitivity was still inadequate for the determination of boron in blood of subjects without supplementary diet. Under optimized conditions, the detection limit (3σ) was 60 μg l -1. The amount of boron found in whole blood, urine and femur head samples from patients with osteoporosis was in agreement with values previously reported in the literature.

The fracture resistance of 1420 and 1421 Al-Mg-Li alloys

NASA Technical Reports Server (NTRS)

Birt, M. J.; Hafley, R. A.; Wagner, J. A.; Lisagor, W. B.

1993-01-01

The resistance to stable crack growth in 1420-T6 (Al-5Mg-2.1Li-0.1Zr-0.01Sc, less than 0.06Fe, in wt pct) and 1421-T6 (Al-4.7Mg-1.9Li-0.09Zr-0.2Sc, less than 0.06Fe) Al-Mg-Li alloys was investigated, based on the R curves generated in accordance with ASTM E561-86 and fractography analyses. The crack resistance of 1420 and 1421 alloys was found to be comparable to that of the conventional Space Shuttle External Tank Al alloy, 2219-T87. The main differences in the fracture behaviors arose from differences in the alloys' microstructures. In the case of 1420 alloy, a slightly enhanced toughness behavior was observed, due to the T-phase precipitates, which may have promoted more homogeneous deformation and enhanced microvoid coalescence. In the case of 1421 alloy, the addition of Sc led to a refined grain size and resulted in slightly reduced toughness.

High temperature refractory of MgCr.sub.2 O.sub.4 matrix and unstabilized ZrO.sub.2 particles

DOEpatents

Singh, Jitendra P.; James, Jawana J.; Picciolo, John J.

1987-01-01

A high chromia refractory composite has been developed with improved thermal shock resistance and containing about 5-30 wt. % of unstabilized ZrO.sub.2 having a temperature-dependent phase change resulting in large expansion mismatch between the ZrO.sub.2 and the chromia matrix which causes microcracks to form during cooling in the high chromia matrix. The particle size preferably is primarily between about 0.6-5 microns and particularly below about 3 microns with an average size in the order of 1.2-1.8 microns.

Tilted BaHfO3 nanorod artificial pinning centres in REBCO films on inclined substrate deposited-MgO coated conductor templates

NASA Astrophysics Data System (ADS)

Stafford, B. H.; Sieger, M.; Ottolinger, R.; Meledin, A.; Strickland, N. M.; Wimbush, S. C.; Van Tendeloo, G.; Hühne, R.; Schultz, L.

2017-05-01

We grow BaHfO3 (BHO) nanorods in REBa2Cu3O7-x (REBCO, RE: Gd or Y) thin films on metal tapes coated with the inclined substrate deposited (ISD)-MgO template by both electron beam physical vapour deposition and pulsed laser deposition. In both cases the nanorods are inclined by an angle of 21°-29° with respect to the sample surface normal as a consequence of the tilted growth of the REBCO film resulting from the ISD-MgO layer. We present angular critical current density (J c) anisotropy as well as field- and temperature-dependant J c data of the BHO nanorod-containing GdBCO films demonstrating an increase in J c over a wide range of temperatures between 30 and 77 K and magnetic fields up to 8 T. In addition, we show that the angle of the peak in the J c anisotropy curve resulting from the nanorods is dependent both on temperature and magnetic field. The largest J c enhancement from the addition of the nanorods was found to occur at 30 K, 3 T, resulting in a J c of 3.0 MA cm-2.

New Fluoride-arsenide Diluted Magnetic Semiconductor (Ba,K)F(Zn,Mn)As with Independent Spin and Charge Doping

NASA Astrophysics Data System (ADS)

Chen, Bijuan; Deng, Zheng; Li, Wenmin; Gao, Moran; Liu, Qingqing; Gu, C. Z.; Hu, F. X.; Shen, B. G.; Frandsen, Benjamin; Cheung, Sky; Lian, Liu; Uemura, Yasutomo J.; Ding, Cui; Guo, Shengli; Ning, Fanlong; Munsie, Timothy J. S.; Wilson, Murray Neff; Cai, Yipeng; Luke, Graeme; Guguchia, Zurab; Yonezawa, Shingo; Li, Zhi; Jin, Changqing

2016-11-01

We report the discovery of a new fluoride-arsenide bulk diluted magnetic semiconductor (Ba,K)F(Zn,Mn)As with the tetragonal ZrCuSiAs-type structure which is identical to that of the “1111” iron-based superconductors. The joint hole doping via (Ba,K) substitution & spin doping via (Zn,Mn) substitution results in ferromagnetic order with Curie temperature up to 30 K and demonstrates that the ferromagnetic interactions between the localized spins are mediated by the carriers. Muon spin relaxation measurements confirm the intrinsic nature of the long range magnetic order in the entire volume in the ferromagnetic phase. This is the first time that a diluted magnetic semiconductor with decoupled spin and charge doping is achieved in a fluoride compound. Comparing to the isostructure oxide counterpart of LaOZnSb, the fluoride DMS (Ba,K)F(Zn,Mn)As shows much improved semiconductive behavior that would be benefit for further application developments.

Reproducibility of Ba/Ca variations recorded by northeast Pacific bamboo corals

NASA Astrophysics Data System (ADS)

Serrato Marks, G.; LaVigne, M.; Hill, T. M.; Sauthoff, W.; Guilderson, T. P.; Roark, E. B.; Dunbar, R. B.; Horner, T. J.

2017-09-01

Trace elemental ratios preserved in the calcitic skeleton of bamboo corals have been shown to serve as archives of past ocean conditions. The concentration of dissolved barium (BaSW), a bioactive nutrientlike element, is linked to biogeochemical processes such as the cycling and export of nutrients. Recent work has calibrated bamboo coral Ba/Ca, a new BaSW proxy, using corals spanning the oxygen minimum zone beneath the California Current System. However, it was previously unclear whether Ba/Cacoral records were internally reproducible. Here we investigate the accuracy of using laser ablation inductively coupled plasma mass spectrometry for Ba/Cacoral analyses and test the internal reproducibility of Ba/Ca among replicate radial transects in the calcite of nine bamboo corals collected from the Gulf of Alaska (643-720 m) and the California margin (870-2054 m). Data from replicate Ba/Ca transects were aligned using visible growth bands to account for nonconcentric growth; smoothed data were reproducible within 4% for eight corals (n = 3 radii/coral). This intracoral reproducibility further validates using bamboo coral Ba/Ca for BaSW reconstructions. Sections of the Ba/Ca records that were potentially influenced by noncarbonate bound Ba phases occurred in regions where elevated Mg/Ca or Pb/Ca and coincided with anomalous regions on photomicrographs. After removing these regions of the records, increased Ba/Cacoral variability was evident in corals between 800 and 1500 m. These findings support additional proxy validation to understand BaSW variability on interannual timescales, which could lead to new insights into deep sea biogeochemistry over the past several centuries.

Synthesis, characterization, and photocatalytic application of Pd/ZrO2 and Pt/ZrO2

NASA Astrophysics Data System (ADS)

Saeed, Khalid; Sadiq, Mohammad; Khan, Idrees; Ullah, Saleem; Ali, Nauman; Khan, Adnan

2018-05-01

Zirconia-supported palladium (Pd/ZrO2) and Zirconia-supported platinum (Pt/ZrO2) nanoparticles (NPs) are synthesized from their precursors via impregnation technique. The Pd/ZrO2 and Pt/ZrO2 NPs were analyzed via SEM and EDX, while the study of indigo disulfonate dye degradation was carried out by UV/VIS spectrophotometer. The SEM micrographs illustrated that the Pd and Pt NPs were well placed on ZrO2 surface. The Pd/ZrO2 and Pt/ZrO2 NPs were also employed as photocatalysts for the photodegradation of indigo disulfonate in an aqueous medium under UV-light irradiation. The photodegradation study presented that Pd/ZrO2 and Pt/ZrO2 NPs degraded 96 and 94% of indigo disulfonate in 14 h, respectively. The effect of pH of medium and catalyst dosage and efficiency of recovered Pd/ZrO2 and Pt/ZrO2 NPs on the photocatalytic degradation were also studied. It was also found that the maximum degradation of dye was found at pH 10 (95-97%) and at 0.02 g weight (40.28%).

Structural, dielectric and ferroelectric studies of (x) Mg0.25Cu0.25Zn0.5Fe2O4 + (1-x) BaTiO3 magnetoelectric nano-composites

NASA Astrophysics Data System (ADS)

Khader, S. Abdul; Muneeswaran, M.; Giridharan, N. V.; Sankarappa, T.

2016-05-01

The Particulate nano-composites of ferrite and ferroelectric phases having the general formula (x) Mg0.25Cu0.25Zn0.5Fe2O4 + (1-x) BaTiO3 (x=15%, 30% and 45%) were synthesized by sintering mixtures of highly ferroelectric BaTiO3 (BT) and highly magneto-strictive magnetic component Mg0.25Cu0.25Zn0.5Fe2O4(MCZF). The presence of constituent phases of ferrite, ferroelectric and their composites were probed and confirmed by X-ray diffraction (XRD) studies. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). The variation of dielectric constant and dissipation factor as a function of frequency from 100 Hz to 1 MHz at room temperature were carried out using a Hioki LCR Hi-Tester. The dielectric constant and dielectric loss were found to decrease rapidly in the low frequency region and became almost constant in the high frequency region. The electrical conductivity deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in these composites is in conformity with small polaron hopping model. The ferroelectric properties of synthesized magneto-electric nano-composites were measured using P-E loop tracer.

Large Energy Storage Density and High Thermal Stability in a Highly Textured (111)-Oriented Pb0.8Ba0.2ZrO3 Relaxor Thin Film with the Coexistence of Antiferroelectric and Ferroelectric Phases.

PubMed

Peng, Biaolin; Zhang, Qi; Li, Xing; Sun, Tieyu; Fan, Huiqing; Ke, Shanming; Ye, Mao; Wang, Yu; Lu, Wei; Niu, Hanben; Zeng, Xierong; Huang, Haitao

2015-06-24

A highly textured (111)-oriented Pb0.8Ba0.2ZrO3 (PBZ) relaxor thin film with the coexistence of antiferroelectric (AFE) and ferroelectric (FE) phases was prepared on a Pt/TiOx/SiO2/Si(100) substrate by using a sol-gel method. A large recoverable energy storage density of 40.18 J/cm(3) along with an efficiency of 64.1% was achieved at room temperature. Over a wide temperature range of 250 K (from room temperature to 523 K), the variation of the energy density is within 5%, indicating a high thermal stability. The high energy storage performance was endowed by a large dielectric breakdown strength, great relaxor dispersion, highly textured orientation, and the coexistence of FE and AFE phases. The PBZ thin film is believed to be an attractive material for applications in energy storage systems over a wide temperature range.

Epitaxial growth of (001)-oriented Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} thin films on a-plane sapphire with an MgO/ZnO bridge layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao Bo; Liu Hongrui; Avrutin, Vitaliy

2009-11-23

High quality (001)-oriented Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) thin films have been grown on a-plane sapphire (1120) by rf magnetron sputtering using a double bridge layer consisting of (0001)-oriented ZnO (50 nm) and (001)-oriented MgO (10 nm) prepared by plasma-assisted molecular beam epitaxy. X-ray diffraction revealed the formation of three sets of in-plane BST domains, offset from one another by 30 deg., which is consistent with the in-plane symmetry of the MgO layer observed by in situ reflective high electron energy diffraction. The in-plane epitaxial relationship of BST, MgO, and ZnO has been determined to be BST [110]//MgO [110]//ZnO [1120]more » and BST [110]/MgO [110]//ZnO [1100]. Capacitance-voltage measurements performed on BST coplanar interdigitated capacitor structures revealed a high dielectric tunability of up to 84% at 1 MHz.« less

Characterizing the residual glass in a MgO/Al2O3/SiO2/ZrO2/Y2O3 glass-ceramic

PubMed Central

Seidel, Sabrina; Patzig, Christian; Wisniewski, Wolfgang; Gawronski, Antje; Hu, Yongfeng; Höche, Thomas; Rüssel, Christian

2016-01-01

The non-isochemical crystallization of glasses leads to glass-ceramics in which the chemical composition of the amorphous matrix differs from that of the parent glass. It is challenging to solely analyse the properties of these residual glassy phases because they frequently contain finely dispersed crystals. In this study, the composition of the residual glass matrix after the crystallization of a glass with the mol% composition 50.6 SiO2 · 20.7 MgO · 20.7 Al2O3 · 5.6 ZrO2 · 2.4 Y2O3 is analysed by scanning transmission electron microscopy (STEM) including energy dispersive X-ray analysis (EDXS). A batch of the residual glass with the determined composition is subsequently melted and selected properties are analysed. Furthermore, the crystallization behaviour of this residual glass is studied by X-ray diffraction, scanning electron microscopy including electron backscatter diffraction and STEM-EDXS analyses. The residual glass shows sole surface crystallization of indialite and multiple yttrium silicates while bulk nucleation does not occur. This is in contrast to the crystallization behaviour of the parent glass, in which a predominant bulk nucleation of spinel and ZrO2 is observed. The crystallization of the residual glass probably leads to different crystalline phases when it is in contact to air, rather than when it is enclosed within the microstructure of the parent glass-ceramics. PMID:27734918

Temperature dependence of partial conductivities of the BaZr0.7Ce0.2Y0.1O3-δ proton conductor

NASA Astrophysics Data System (ADS)

Heras-Juaristi, Gemma; Pérez-Coll, Domingo; Mather, Glenn C.

2017-10-01

Partial conductivities are presented for BaZr0.7Ce0.2Y0.1O3-δ, an important proton conductor for protonic-ceramic fuel cells and membrane reactors. Atmospheric dependencies of impedance performed in humidified and dry O2, air, N2 and H2(10%)/N2(90%) in the temperature range 300-900 °C, supported by the modified emf method, confirm significant electron-hole and protonic contributions to transport. For very reducing and wet atmospheres, the conductivity is predominantly ionic, with a higher participation of protons with decreasing temperature and increasing water-vapour partial pressure (pH2O). From moderately reducing conditions of wet N2 to wet O2, however, the conductivity is considerably influenced by electron holes as revealed by a significant dependence of total conductivity on oxygen partial pressure (pO2). With higher pH2O, proton transport increases, with a concomitant decrease of holes and oxygen vacancies. However, the effect of pH2O is also influenced by temperature, with a greater protonic contribution at both lower temperature and pO2. Values of proton transport number tH ≈ 0.63 and electronic transport number th ≈ 0.37 are obtained at 600 °C for pH2O = 0.022 atm and pO2 = 0.2 atm, whereas tH ≈ 0.95 and th ≈ 0.05 for pO2 = 10-5 atm. A hydration enthalpy of -109 kJ mol-1 is obtained in the range 600-900 °C.

Research on self-propagating high temperature synthesis prepared ZrC-ZrB2 composite ceramic

NASA Astrophysics Data System (ADS)

Yong, Cheng; Xunjia, Su; Genliang, Hou; YaKun, Xing

2013-03-01

ZrC-ZrB2 composite ceramic material is prepared by self-propagating high temperature synthesis, using Zr powders, CrO2 powders and Al powders as raw materials. Samples are studied by XRD and SEM, the results show that: ZrC-ZrB2 composite ceramic is attained after self-propagating high-temperature reaction, with Zr+ B4C as the main reactive system, and which is added respectively different content (CrO3 + Al) system. The study finds that the ceramic composite products are mainly composed of ZrC and ZrB2 phase, and other subphase. Compared to the main reactive system composite ceramic, composite ceramic grains grow up obviously, after introduction of the highly exothermic system (CrO3 + Al) in the main reactive system, and with the gradual increase of the content (CrO3 + Al).

89Zr-DFO-AMG102 Immuno-PET to Determine Local Hepatocyte Growth Factor Protein Levels in Tumors for Enhanced Patient Selection.

PubMed

Price, Eric W; Carnazza, Kathryn E; Carlin, Sean D; Cho, Andrew; Edwards, Kimberly J; Sevak, Kuntal K; Glaser, Jonathan M; de Stanchina, Elisa; Janjigian, Yelena Y; Lewis, Jason S

2017-09-01

The hepatocyte growth factor (HGF) binding antibody rilotumumab (AMG102) was modified for use as a 89 Zr-based immuno-PET imaging agent to noninvasively determine the local levels of HGF protein in tumors. Because recent clinical trials of HGF-targeting therapies have been largely unsuccessful in several different cancers (e.g., gastric, brain, lung), we have synthesized and validated 89 Zr-DFO-AMG102 as a companion diagnostic for improved identification and selection of patients having high local levels of HGF in tumors. To date, patient selection has not been performed using the local levels of HGF protein in tumors. Methods: The chelator p -SCN-Bn-DFO was conjugated to AMG102, radiolabeling with 89 Zr was performed in high radiochemical yields and purity (>99%), and binding affinity of the modified antibody was confirmed using an enzyme-linked immunosorbent assay (ELISA)-type binding assay. PET imaging, biodistribution, autoradiography and immunohistochemistry, and ex vivo HGF ELISA experiments were performed on murine xenografts of U87MG (HGF-positive, MET-positive) and MKN45 (HGF-negative, MET-positive) and 4 patient-derived xenografts (MET-positive, HGF unknown). Results: Tumor uptake of 89 Zr-DFO-AMG102 at 120 h after injection in U87MG xenografts (HGF-positive) was high (36.8 ± 7.8 percentage injected dose per gram [%ID/g]), whereas uptake in MKN45 xenografts (HGF-negative) was 5.0 ± 1.3 %ID/g and a control of nonspecific human IgG 89 Zr-DFO-IgG in U87MG tumors was 11.5 ± 3.3 %ID/g, demonstrating selective uptake in HGF-positive tumors. Similar experiments performed in 4 different gastric cancer patient-derived xenograft models showed low uptake of 89 Zr-DFO-AMG102 (∼4-7 %ID/g), which corresponded with low HGF levels in these tumors (ex vivo ELISA). Autoradiography, immunohistochemical staining, and HGF ELISA assays confirmed that elevated levels of HGF protein were present only in U87MG tumors and that 89 Zr-DFO-AMG102 uptake was closely correlated

Refractory Materials of Zirconate. Part 2: Synthesis and some properties of strontium, zirconate, calcium zirconate and barium zirconate

NASA Technical Reports Server (NTRS)

Okubo, Tsutomo; Yonemochi, Osamu; Nakamura, Kazuo; Maeda, Minoru

1988-01-01

Chemical compounds SrZrO3, CaZrO3, and BaZrO3 were synthesized by solid reaction and arc fusion, and their properties examined. Results were as follows: (1) in the synthesis of CaZrO3 by solid reaction, ZrO2 solid solution with cubic form was produced, which then changed into CaZrO3; (2) the BaZrO3 was a cubic form and did not show any transformation, while SrZrO3 and CaZrO3 with an orthorhombic form transformed to a cubic form at high temperature; and (3) the solubility of BaZrO3 in acid and its vaporization rate at a high temperature were greater than those of zirconates.

Crystal structures of the new ternary stannides La3Mg4-xSn2+x and LaMg3-xSn2

NASA Astrophysics Data System (ADS)

Solokha, P.; De Negri, S.; Minetti, R.; Proserpio, D. M.; Saccone, A.

2016-01-01

Synthesis and structural characterization of the two new lanthanum-magnesium-stannides La3Mg4-xSn2+x (0.12≤x≤0.40) and LaMg3-xSn2 (0.33≤x≤0.78) are reported. The crystal structures of these intermetallics were determined by single crystal X-ray diffraction analysis and confirmed by Rietveld refinement of powder X-ray diffraction patterns of the corresponding samples. The La3Mg4-xSn2+x phase crystallizes in the hexagonal Zr3Cu4Si2 structure type (P6bar2m, hP9, Z=3, x=0.12(1), a=7.7974(7), c=4.8384(4) Å), which represents an ordered derivative of the hP9-ZrNiAl prototype, ubiquitous among equiatomic intermetallics. The LaMg3-xSn2 phase is the second representative of the trigonal LaMg3-xGe2 type, which is a superstructure of the LaLi3Sb2 structure type (P3bar1c, hP34-0.12, Z=6, x=0.35(1), a=8.3222(9), c=14.9546(16) Å). The scheme describing the symmetry reduction/coloring with respect to the parent type is reported here with the purpose to discuss the LaMg3-xSn2 off-stoichiometry from the geometrical point of view. Structural relationships between the La-Mg-Sn ternary phases, including the already known equiatomic LaMgSn compound (oP12-TiNiSi), are presented in the framework of the AlB2-related compounds family and discussed with the aid of group-subgroup relations in the Bärnighausen formalism.

Structure of zirconium-93 and zirconium-91 as shown by the reactions Zr-92(d,p)Zr-93 and Zr-92(d,t)Zr-91

NASA Technical Reports Server (NTRS)

Baron, N.; Leonard, R. F.; Stewart, W. M.; Fink, C. L.; Christensen, P. R.; Nickles, J.; Thorsteinsen, T. F.

1972-01-01

Deuterons of 13-MeV incident energy were scattered from Zr-92(d,p)Zr-93. The Zr-92(d,p)Zr-93 data analysis resulted in the location of 47 levels up to an excitation energy of 4.84 MeV, and the spins of 43 of these levels were identified. Essentially all the strength of the 2d5/2, 3s1/2, 2d3/2, and 1g7/2 shells was observed; and the excitation energy of their centroids was computed to be 0.00, 1.21, 2.23, and 2.37 MeV, respectively. Also, 43 percent of the 1h11/2 strength, 21 percent of the 2f7/2 strength, and 3 percent of the 3p3/2 strength were observed. In addition, the Zr-92(d,t)Zr-91 data analysis resulted in the location of 26 levels up to an excitation energy of 4.01 MeV, and the spins of 21 of these levels were identified. Most of the expected strength of the 2d5/2 and 1g9/2 shells was obtained, and the excitation energy of their centroids was computed to be 0.31 and 3.19 MeV, respectively. In addition, six l=1 states are populated belonging to either the 2p1/2 or 2p3/2 shells.

Developing a Basal Texture with Two Peaks Tilting Towards the Transverse Direction in Hot Rolled Mg-5.7Zn-0.5Zr Plates

NASA Astrophysics Data System (ADS)

Wang, Yannan; Xin, Yunchang; Chapuis, Adrien; Yu, Huihui; Liu, Qing

2016-08-01

Rolled Mg alloys often present a basal texture with the (0002) poles slightly tilting from the normal direction (ND) towards the rolling direction. The current work systematically studies the formation of a double-peaked basal texture tilting from the ND towards the transverse direction (TD) of Mg-5.7Zn-0.5Zr (ZK60) plates hot rolled from the as-cast condition. Our results show that a basal texture forms with the two peaks obviously tilting from the ND towards the TD after rolling to reductions over 19 pct at 673 K (400 °C), but does not appear after rolling at 293 K (20 °C). The TD-tilted double peaks of basal poles disappear after annealing, developing a stronger peak of basal poles around the ND. The microstructural examination indicates that this TD-tilted basal texture mainly results from rolling deformation rather than dynamic recrystallization. Crystal plasticity simulation using the VPSC model was used to understand the effect of slips and twinning on the formation of this TD-tilted basal texture. Simulation demonstrates that, compared to prismatic slip, pyramidal slip is more efficient to generate the basal texture tilting towards the TD. The possible mechanisms affecting the activity of non-basal slips are discussed.

Zr-ZrO2 cermet solar coatings designed by modelling calculations and deposited by dc magnetron sputtering

NASA Astrophysics Data System (ADS)

Zhang, Qi-Chu; Hadavi, M. S.; Lee, K.-D.; Shen, Y. G.

2003-03-01

High solar performance Zr-ZrO2 cermet solar coatings were designed using a numerical computer model and deposited experimentally. The layer thickness and Zr metal volume fraction for the Zr-ZrO2 cermet solar selective coatings on a Zr or Al reflector with a surface ZrO2 or Al2O3 anti-reflection layer were optimized to achieve maximum photo-thermal conversion efficiency at 80°C under concentration factors of 1-20 using the downhill simplex method in multi-dimensions in the numerical calculation. The dielectric function and the complex refractive index of Zr-ZrO2 cermet materials were calculated using Sheng's approximation. Optimization calculations show that Al2O3/Zr-ZrO2/Al solar coatings with two cermet layers and three cermet layers have nearly identical solar absorptance, emittance and photo-thermal conversion efficiency that are much better than those for films with one cermet layer. The optimized Al2O3/Zr-ZrO2/Al solar coating film with two cermet layers has a high solar absorptance value of 0.97 and low hemispherical emittance value of 0.05 at 80°C for a concentration factor of 2. The Al2O3/Zr-ZrO2/Al solar selective coatings with two cermet layers were deposited using dc magnetron sputtering technology. During the deposition of Zr-ZrO2 cermet layer, a Zr metallic target was run in a gas mixture of argon and oxygen. By control of oxygen flow rate the different metal volume fractions in the cermet layers were achieved using dc reactive sputtering. A solar absorptance of 0.96 and normal emittance of 0.05 at 80°C were achieved.

Reactions of calcium orthosilicate and barium zirconate with oxides and sulfates of various elements

NASA Technical Reports Server (NTRS)

Zaplatynsky, I.

1979-01-01

Calcium orthosilicate and barium zirconate were evaluated as the insulation layer of thermal barrier coatings for air cooled gas turbine components. Their reactions with various oxides and sulfates were studied at 1100 C and 1300 C for times ranging up to 400 and 200 hours, respectively. These oxides and sulfates represent potential impurities or additives in gas turbine fuels and in turbine combustion air, as well as elements of potential bond coat alloys. The phase compositions of the reaction products were determined by X-ray diffraction analysis. BaZrO3 and 2CaO-SiO2 both reacted with P2O5, V2O5, Cr2O3, Al2O3, and SiO2. In addition, 2CaO-SiO2 reacted with Na2O, BaO, MgO, and CoO and BaZrO3 reacted with Fe2O3.

Formation of qualified BaHfO3 doped Y0.5Gd0.5Ba2Cu3O7-δ film on CeO2 buffered IBAD-MgO tape by self-seeding pulsed laser deposition

NASA Astrophysics Data System (ADS)

Liu, Linfei; Wang, Wei; Yao, Yanjie; Wu, Xiang; Lu, Saidan; Li, Yijie

2018-05-01

Improvement in the in-filed transport properties of REBa2Cu3O7-δ (RE = rare earth elements, REBCO) coated conductor is needed to meet the performance requirements for various practical applications, which can be accomplished by introducing artificial pinning centers (APCs), such as second phase dopant. However, with increasing dopant level the critical current density Jc at 77 K in zero applied magnetic field decreases. In this paper, in order to improve Jc we propose a seed layer technique. 5 mol% BaHfO3 (BHO) doped Y0.5Gd0.5Ba2Cu3O7-δ (YGBCO) epilayer with an inserted seed layer was grown on CeO2 buffered ion beam assisted deposition MgO (IBAD-MgO) tape by pulsed laser deposition. The effect of the conditions employed to prepare the seed layer, including tape moving speed and chemical composition, on the quality of 5 mol% BHO doped YGBCO epilayer was systematically investigated by X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM) observations. It was found that all the samples with seed layer have higher Jc (77 K, self-field) than the 5 mol% BHO doped YGBCO film without seed layer. The seed layer could inhibit deterioration of the Jc at 77 K and self-filed. Especially, the self-seed layer (5 mol% BHO doped YGBCO seed layer) was more effective in improving the crystal quality, surface morphology and superconducting performance. At 4.2 K, the 5 mol% BHO doped YGBCO film with 4 nm thick self-seed layer had a very high flux pinning force density Fp of 860 GN/m3 for B//c under a 9 T field, and more importantly, the peak of the Fp curve was not observed.

Structural analysis, optical and dielectric function of [Ba{sub 0.9}Ca{sub 0.1}](Ti{sub 0.9}Zr{sub 0.1})O{sub 3} nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herrera-Pérez, G., E-mail: guillermo.herrera@cimav.edu.mx, E-mail: damasio.morales@cimav.edu.mx; Physics of Materials Department, Centro de Investigación en Materiales Avanzados; Morales, D., E-mail: guillermo.herrera@cimav.edu.mx, E-mail: damasio.morales@cimav.edu.mx

2016-09-07

This work presents the identification of inter-band transitions in the imaginary part of the dielectric function (ε{sub 2}) derived from the Kramers–Kronig analysis for [Ba{sub 0.9}Ca{sub 0.1}](Ti{sub 0.9}Zr{sub 0.1})O{sub 3} (BCZT) nanocrystals synthesized by the modified Pechini method. The analysis started with the chemical identification of the atoms that conform BCZT in the valence loss energy region of a high energy-resolution of electron energy loss spectroscopy. The indirect band energy (E{sub g}) was determined in the dielectric response function. This result is in agreement with the UV-Vis technique, and it obtained an optical band gap of 3.16 eV. The surface andmore » volume plasmon peaks were observed at 13.1 eV and 26.2 eV, respectively. The X-ray diffraction pattern and the Rietveld refinement data of powders heat treated at 700 °C for 1 h suggest a tetragonal structure with a space group (P4 mm) with the average crystal size of 35 nm. The average particle size was determined by transmission electron microscopy.« less

Contributions of intrinsic and extrinsic polarization species to energy storage properties of Ba0.95Ca0.05Zr0.2Ti0.8O3 ceramics

NASA Astrophysics Data System (ADS)

Zhan, Di; Xu, Qing; Huang, Duan-Ping; Liu, Han-Xing; Chen, Wen; Zhang, Feng

2018-03-01

Ba0.95Ca0.05Zr0.2Ti0.8O3 ceramics were prepared at different sintering temperatures by citrate precursor and solid-state reaction methods, respectively. The crystal structure and microstructure of the specimens were characterized. In view of energy storage capacitor utilizations, the dielectric properties of the specimens were investigated at room temperature as a function of frequency and applied electric field. Moreover, the nature of mobile charge carriers in the specimens was diagnosed by complex impedance spectroscopy at elevated temperatures. While the dielectric constants of the specimens prepared by different methods are quite different (4.4 × 103-2.2 × 104 at 10 kHz) at zero electric field, the energy storage densities at an identical strong electric field are similar (e.g. 0.32-0.41 J/cm3 at 120 kV/cm). The dielectric constants under bias electric field were fitted to a multipolarization mechanism model to resolve the contributions of intrinsic and extrinsic polarization mechanisms. It turned out that the extrinsic contributions fade out within low electric field range (<20 kV/cm) and thereby the intrinsic lattice polarization governs the overall dielectric responses at higher fields. Based on the fitting result, the energy storage properties of the specimens were interpreted.

Microstructure and dielectric parameters of epitaxial SrRuO3/BaTiO3/SrRuO3 heterostructures

NASA Astrophysics Data System (ADS)

Boikov, Yu. A.; Claeson, T.

2001-05-01

Epitaxial films of ferroelectric barium titanate are desirable in a number of applications but their properties are inferior to those of bulk material. Relations between microstructure and dielectric properties may give better understanding of limitations. Trilayer heterostructures SrRuO3/BaTiO3/SrRuO3 were grown by laser ablation on (100)LaAlO3 and (100)MgO substrates. The BaTiO3 layer was granular in structure. When grown on (100)SrRuO3/(100)LaAlO3, it was preferentially a-axis oriented due to tensile mechanical stress. Using (100)MgO as a substrate, on the other hand, produced a mixture of about equal value of a-axis and c-axis oriented grains of BaTiO3. The dielectric permittivity, ɛ, of the BaTiO3 layer was almost twice as large, at T>200 K and f=100 kHz, for the LaAlO3 substrate as compared to the MgO one. Its maximum value (ɛ/ɛ0≈6200) depended on temperature of growth, grain size, and electric field and compares well with optimal values commonly used for ceramic material. The maximum in the ɛ(T) shifted from about 370 to 320 K when the grain size in the BaTiO3 film decreased from 100 to 40 nm. At T<300 K, hysteresis loops in polarization versus electric field were roughly symmetric. The BaTiO3 films grown on (100)SrRuO3/(100)MgO exhibit the largest remnant polarizations and coercive fields in the temperature range 100-380 K.

Effects of oxygen vacancy on the photoconductivity in BaSnO3

NASA Astrophysics Data System (ADS)

Park, Jisung; Char, Kookrin; Institute of Applied Physics, Department of Physics; Astronomy, Seoul National University Team

We have found the photoconductive behavior of BaSnO3, especially their magnitude and time dependence, is very sensitive to the oxygen vacancy concentration. We made epitaxial BaSnO3 film with BaHfO3 buffer layer by pulsed laser deposition. As we had reported before, MgO substrate with its large band gap size about 7.8 eV was used to exclude any photoconductance from the substrate. BaHfO3 layer was used to reduce the threading dislocation density in BaSnO3 film. To control the oxygen vacancy concentration in the BaSnO3 film, we annealed the sample in Ar or O2 atmosphere with varying annealing conditions. After each annealing process, photoconductivity of BaSnO3 was measured during illumination of UV light. The result showed that the magnitude of photoconductivity of BaSnO3 increased after annealing at higher temperature in Ar atmosphere, while the changes in the dark current remains minimal. The result can be explained by a hole trap mechanism. Higher Fermi level due to the increased oxygen vacancy concentration can cause occupation of deep acceptor levels in dislocations of the BaSnO3 film. These occupied deep acceptor levels in turn trap photo-generated holes so that the recombination of electron-hole pair is deterred. Samsung Science and Technology Foundation.

Zr diffusion in titanite

NASA Astrophysics Data System (ADS)

Cherniak, D. J.

2006-11-01

Chemical diffusion of Zr under anhydrous, pO2-buffered conditions has been measured in natural titanite. The source of diffusant was either zircon powder or a ZrO2-Al2O3-titanite mixture. Experiments were run in sealed silica glass capsules with solid buffers (to buffer at NNO or QFM). Rutherford Backscattering Spectrometry (RBS) was used to measure diffusion profiles. The following Arrhenius parameters were obtained for Zr diffusion parallel to c over the temperature range 753-1,100°C under NNO-buffered conditions: D Zr = 5.33 × 10-7 exp(-325 ± 30 kJ mol-1/RT) m2 s-1 Diffusivities are similar for experiments buffered at QFM. These data suggest that titanite should be moderately retentive of Zr chemical signatures, with diffusivities slower than those for O and Pb in titanite, but faster than those for Sr and the REE. When applied in evaluation of the relative robustness of the recently developed Zr-in-titanite geothermometer (Hayden and Watson, Abstract, 16th V.M. Goldschmidt Conference 2006), these findings suggest that Zr concentrations in titanite will be less likely to be affected by later thermal disturbance than the geothermometer based on Zr concentrations in rutile (Zack et al. in Contrib Mineral Petrol 148:471-488, 2004; Watson et al. in Contrib Mineral. Petrol, 2006), but much less resistant to diffusional alteration subsequent to crystallization than the Ti-in-Zircon geothermometer (Watson and Harrison in Science 308:841-844, 2005).

High dispersibility and enhanced luminescence properties of BaMgAl10O17:Eu2+ phosphors derived from molten salt synthesis

NASA Astrophysics Data System (ADS)

Wang, Xiang; Li, Jin-hong; Shi, Ping-lu; Guan, Wei-min; Zhang, Hong-yao

2015-08-01

BaMgAl10O17:Eu2+ (BAM) phosphors were prepared via the molten salt synthesis (MSS) method. The NaCl-KCl eutectic mixture and LiF were used as the molten salt and flux, respectively. X-ray powder diffraction (XRD) patterns indicate that the BAM phase is formed above 1200 °C and that the addition of LiF leads to an obvious improvement in crystallinity. The emission intensity of the BAM phosphor with 10 wt% LiF is about 85% higher than that of the phosphor without LiF and about 200% higher than that of the phosphor without molten salt and LiF. Scanning electron microscopy (SEM) reveal that the as-prepared phosphors have good crystallinity and regular morphology, and most importantly, they are not aggregated. Li+ doping is benefit for the thermal stability and results in a slightly longer decay times of 1.17 μs.

Pressure-induced elastic, electronic and optical properties of Ba(Mg1/3Nb2/3)O3 using first principles calculations

NASA Astrophysics Data System (ADS)

Islam, A. K. M. Farid Ul; Liton, M. N. H.; Anowar, M. G. M.

2018-06-01

The pressure dependent mechanical stability, electronic structure and optical properties of Ba(Mg1/3Nb2/3)O3 (BMN) perovskite have been investigated in the framework of the density functional theory. Geometry optimization shows that the BMN possesses more compressibility along c-axis. The dependency of the elastic constants, the aggregated elastic moduli (B, G) and the elastic anisotropy on pressure has also been studied. BMN shows brittle character at ambient pressure but it becomes ductile, and also stiffer and anisotropic nature due to external pressure. Electronic structure indicates the conversion of indirect to direct band gap with increasing pressure. Dominated ionic character of BMN is confirmed from the bond population analysis. By analyzing the optical spectra, a red shift at the band edge is observed in the visible range indicating the band gap tuning. It is seen that the static dielectric constant increases with pressure.

Gigantic terahertz magnetochromism via electromagnons in the hexaferrite magnet Ba2Mg2Fe12O22

NASA Astrophysics Data System (ADS)

Kida, N.; Kumakura, S.; Ishiwata, S.; Taguchi, Y.; Tokura, Y.

2011-02-01

Effects of temperature (6-225 K) and magnetic field (0-7 T) on the low-energy (1.2-5 meV) electrodynamics of the electromagnon, the magnetic resonance driven by the light electric field, have been investigated for a hexaferrite magnet Ba2Mg2Fe12O22 by using terahertz time-domain spectroscopy. We find the gigantic terahertz magnetochromism via electromagnons; the magnetochromic change, as defined by the difference of the absorption intensity with and without magnetic field, exceeds 500% even at 0.6 T. The results arise from the fact that the spectral intensity of the electromagnon critically depends on the magnetic structure. With changing the conical spin structures in terms of the conical angle θ from the proper screw (θ=0°) to the ferrimagnetic (θ=90°) through the conical spin-ordered phases (0°<θ<90°) by external magnetic fields, we identify the maximal magnetochromism around θ≈45°. On the contrary, there is no remarkable signature of the electromagnon in the proper screw and spin-collinear (ferrimagnetic) phases, clearly indicating the important role of the conical spin order to produce the magnetically controllable electromagnons. The possible origin of this electromagnon is argued in terms of the exchange-striction mechanism.

Evolution from successive phase transitions to "morphotropic phase boundary" in BaTiO3-based ferroelectrics

NASA Astrophysics Data System (ADS)

Zhou, Chao; Ke, Xiaoqin; Yao, Yonggang; Yang, Sen; Ji, Yuanchao; Liu, Wenfeng; Yang, Yaodong; Zhang, Lixue; Hao, Yanshuang; Ren, Shuai; Zhang, Le; Ren, Xiaobing

2018-04-01

Obtaining superior physical properties for ferroic materials by manipulating the phase transitions is a key concern in solid state physics. Here, we investigated the dielectric permittivity, piezoelectric coefficient d33, storage modulus, and crystal symmetry of (1-x)Ba(Ti0.8Zr0.2)O3-x(Ba1-yCay)TiO3 (BZT-xBCyT) systems to demonstrate the gradual evolution process from successive phase transitions in BaTiO3 to the morphotropic phase boundary (MPB) regime in BZT-xBC0.3T. Furthermore, we analysed with a Landau-type theoretical model to show that the high field-sensitive response (dielectric permittivity) originates from a small polarization anisotropy and low energy barrier at the quadruple point. Together, the intermediate orthorhombic phase regime and the tetragonal-orthorhombic and orthorhombic-rhombohedral phase boundaries constitute the MPB. Our work not only reconciles the arguments regarding whether the structural state around the MPB corresponds to a single-phase regime or a multiple-phase-coexistence regime but also suggests an effective method to design high-performance functional ferroic materials by tailoring the successive phase transitions.

The preparation of Zr-deuteride and phase stability studies of the Zr-D system

NASA Astrophysics Data System (ADS)

Maimaitiyili, T.; Steuwer, A.; Bjerkén, C.; Blomqvist, J.; Hoelzel, M.; Ion, J. C.; Zanellato, O.

2017-03-01

Deuteride phases in the zirconium-deuterium system in the temperature range 25-286 °C have been studied in-situ by high resolution neutron diffraction. The study primarily focused on observations of δ→γ transformation at 180 °C, and the peritectoid reaction α + δ ↔ γ at 255 °C in commercial grade Zr powder that was deuterated to a deuterium/Zr ratio of one to one. A detailed description of the zirconium deuteride preparation route by high temperature gas loading is also described. The lattice parameters of α-Zr, δ-ZrDx and ε-ZrDx were determined by whole pattern crystal structure analysis, using Rietveld and Pawley refinements, and are in good agreement with values reported in the literature. The controversial γ-hydride phase was observed both in-situ and ex-situ in deuterated Zr powder after a heat treatment at 286 °C and slow cooling.

Trace element composition of rutile and Zr-in-rutile thermometry in meta-ophiolitic rocks from the Kazdağ Massif, NW Turkey

NASA Astrophysics Data System (ADS)

Şengün, Fırat; Zack, Thomas

2016-08-01

In northwest Turkey, ophiolitic meta-gabbros are exposed on the Kazdağ Massif located in the southern part of the Biga Peninsula. Trace element composition of rutile and Zr-in-rutile temperatures were determined for meta-gabbros from the Kazdağ Massif. The Zr content of all rutiles range from 176 to 428 ppm and rutile grains usually have a homogeneous Zr distribution. The rutile grains from studied samples in the Kazdağ Massif are dominated by subchondritic Nb/Ta (11-19) and Zr/Hf ratios (20-33). Nb/Ta and Zr/Hf show positive correlation, which is probably produced by silicate fractionation. The Nb/Ta and Zr/Hf ratios increase with a decrease in Ta and Hf contents. The core of rutile grains are generally characterized by low Nb/Ta ratios of 17-18 whereas the rims exhibit relatively high Nb/Ta ratios of 19-23. Trace element analyses in rutile suggest that these rutile grains were grown from metamorphic fluids. The P-T conditions of meta-gabbros were estimated by both Fe-Mg exchange and Zr-in-rutile thermometers, as well as by the Grt-Hb-Plg-Q geothermobarometer. The temperature range of 639 to 662 °C calculated at 9 kbar using the Zr-in-rutile thermometer is comparable with temperature estimates of the Fe-Mg exchange thermometer, which records amphibolite-facies metamorphism of intermediate P-T conditions. The P-T conditions of meta-ophiolitic rocks suggest that they occur as a different separate higher-pressure tectonic slice in the Kazdağ metamorphic sequence. Amphibolite-facies metamorphism resulted from northward subduction of the İzmir-Ankara branch of the Neo-Tethyan Ocean under the Sakarya Zone. Metamorphism was followed by internal imbrication of the Kazdağ metamorphic sequence resulting from southerly directed compression during the collision.

Purification of nuclear grade Zr scrap as the high purity dense Zr deposits from Zirlo scrap by electrorefining in LiF-KF-ZrF4 molten fluorides

NASA Astrophysics Data System (ADS)

Park, Kyoung Tae; Lee, Tae Hyuk; Jo, Nam Chan; Nersisyan, Hayk H.; Chun, Byong Sun; Lee, Hyuk Hee; Lee, Jong Hyeon

2013-05-01

Zirconium (Zr) has commonly been used as a cladding material of nuclear fuel. Moreover, it is regarded as the only material that can be used for nuclear fuel cladding because it has the lowest neutron capture cross section of any metal element and because it has high corrosion resistance and size stability. In this study, Hf-free Zr tubes (Zr-1Nb-1Sn-0.1Fe) were used as anode materials and electrorefining was performed in a LiF-KF eutectic 6 wt.% ZrF4 molten fluoride salt system. As a result of electrolysis, Zr scrap metal was recycled into pure Zr with low levels of impurities, and the size and density of the Zr deposit was controlled using applied current density.

Shield gas induced cracks during nanosecond-pulsed laser irradiation of Zr-based metallic glass

NASA Astrophysics Data System (ADS)

Huang, Hu; Noguchi, Jun; Yan, Jiwang

2016-10-01

Laser processing techniques have been given increasing attentions in the field of metallic glasses (MGs). In this work, effects of two kinds of shield gases, nitrogen and argon, on nanosecond-pulsed laser irradiation of Zr-based MG were comparatively investigated. Results showed that compared to argon gas, nitrogen gas remarkably promoted the formation of cracks during laser irradiation. Furthermore, crack formation in nitrogen gas was enhanced by increasing the peak laser power intensity or decreasing the laser scanning speed. X-ray diffraction and micro-Raman spectroscopy indicated that the reason for enhanced cracks in nitrogen gas was the formation of ZrN.

Enhanced arsenic removal from water by hierarchically porous CeO₂-ZrO₂ nanospheres: role of surface- and structure-dependent properties.

PubMed

Xu, Weihong; Wang, Jing; Wang, Lei; Sheng, Guoping; Liu, Jinhuai; Yu, Hanqing; Huang, Xing-Jiu

2013-09-15

Arsenic contaminated natural water is commonly used as drinking water source in some districts of Asia. To meet the increasingly strict drinking water standards, exploration of efficient arsenic removal methods is highly desired. In this study, hierarchically porous CeO₂-ZrO₂ nanospheres were synthesized, and their suitability as arsenic sorbents was examined. The CeO₂-ZrO₂ hollow nanospheres showed an adsorption capacity of 27.1 and 9.2 mg g(-1) for As(V) and As(III), respectively, at an equilibrium arsenic concentration of 0.01 mg L(-1) (the standard for drinking water) under neutral conditions, indicating a high arsenic removal performance of the adsorbent at low arsenic concentrations. Such a great arsenic adsorption capacity was attributed to the high surface hydroxyl density and presence of hierarchically porous network in the hollow nanospheres. The analysis of Fourier transformed infrared spectra and X-ray photoelectron spectroscopy demonstrated that the adsorption of arsenic on the CeO₂-ZrO₂ nanospheres was completed through the formation of a surface complex by substituting hydroxyl with arsenic species. In addition, the CeO₂-ZrO₂ nanospheres were able to remove over 97% arsenic in real underground water with initial arsenic concentration of 0.376 mg L(-1) to meet the guideline limit of arsenic in drinking water regulated by the World Health Organization without any pre-treatment and/or pH adjustment. Copyright © 2013 Elsevier B.V. All rights reserved.

Mass transport and crystal growth of the mixed ZrS2-ZrSe2 system

NASA Technical Reports Server (NTRS)

Wiedemeier, Heribert; Goldman, Howard

1986-01-01

The solid solubility of the ZrS2-ZrSe2 system was reinvestigated by annealing techniques to establish the relationship between composition and lattice parameters. Mixed crystals of ZrS(2x)Se2(1-x) for selected compositions of the source material were grown by chemical vapor transport and characterized by X-ray diffraction and microscopic methods. The mass transport rates and crystal growth of ZrSSe were investigated and compared with those of other compositions. The mass fluxes of the mixed system showed an increase with increasing selenium content. The transport products were richer in ZrSe2 than the residual source materials when the ZrSe2 content of the starting materials was greater than 50 mol.-pct. The mass transport rates revealed an increasing mass flux with pressure.

Metaheuristics-Assisted Combinatorial Screening of Eu2+-Doped Ca-Sr-Ba-Li-Mg-Al-Si-Ge-N Compositional Space in Search of a Narrow-Band Green Emitting Phosphor and Density Functional Theory Calculations.

PubMed

Lee, Jin-Woong; Singh, Satendra Pal; Kim, Minseuk; Hong, Sung Un; Park, Woon Bae; Sohn, Kee-Sun

2017-08-21

A metaheuristics-based design would be of great help in relieving the enormous experimental burdens faced during the combinatorial screening of a huge, multidimensional search space, while providing the same effect as total enumeration. In order to tackle the high-throughput powder processing complications and to secure practical phosphors, metaheuristics, an elitism-reinforced nondominated sorting genetic algorithm (NSGA-II), was employed in this study. The NSGA-II iteration targeted two objective functions. The first was to search for a higher emission efficacy. The second was to search for narrow-band green color emissions. The NSGA-II iteration finally converged on BaLi 2 Al 2 Si 2 N 6 :Eu 2+ phosphors in the Eu 2+ -doped Ca-Sr-Ba-Li-Mg-Al-Si-Ge-N compositional search space. The BaLi 2 Al 2 Si 2 N 6 :Eu 2+ phosphor, which was synthesized with no human intervention via the assistance of NSGA-II, was a clear single phase and gave an acceptable luminescence. The BaLi 2 Al 2 Si 2 N 6 :Eu 2+ phosphor as well as all other phosphors that appeared during the NSGA-II iterations were examined in detail by employing powder X-ray diffraction-based Rietveld refinement, X-ray absorption near edge structure, density functional theory calculation, and time-resolved photoluminescence. The thermodynamic stability and the band structure plausibility were confirmed, and more importantly a novel approach to the energy transfer analysis was also introduced for BaLi 2 Al 2 Si 2 N 6 :Eu 2+ phosphors.

Strong piezoelectric anisotropy d15/d33 in ⟨111⟩ textured Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 ceramics

NASA Astrophysics Data System (ADS)

Yan, Yongke; Priya, Shashank

2015-08-01

The shear mode piezoelectric properties of Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMN-PZT) ceramic with 72% ⟨111⟩ texture were investigated. The piezoelectric anisotropic factor d15/d33 was as high as 8.5 in ⟨111⟩ textured ceramic as compared to 2.0 in random counterpart. The high d15/d33 indicates the "rotator" ferroelectric characteristics of PMN-PZT system and suggests that the large shear piezoelectric response contributes towards the high longitudinal piezoelectric response (d33) in non-polar direction (d33 = 1100 pC/N in ⟨001⟩ textured ceramic vs. d33 = 112 pC/N in ⟨111⟩ textured ceramic).

Surface-modified Ba(Zr0.3Ti0.7)O3 nanofibers by polyvinylpyrrolidone filler for poly(vinylidene fluoride) composites with enhanced dielectric constant and energy storage density.

PubMed

Liu, Shaohui; Xue, Shuangxi; Xiu, Shaomei; Shen, Bo; Zhai, Jiwei

2016-05-17

Ferroelectric-relaxor behavior of Ba(Zr0.3Ti0.7)O3 nanofibers (BZT NF) with a large aspect ratio were prepared via electrospinning and surface modified by PVP as dielectric fillers. The nanocomposite flexible films based on surface modified BZT NF and polyvinylidene fluoride (PVDF) were fabricated via a solution casting. The results show that the surface-modified BZT NF fillers are highly dispersed and well integrated in the PVDF nanocomposites. The nanocomposites exhibit enhanced dielectric constant and reduced loss tangents at a low volume fraction of surface-modified BZT NF. The polymer nanocomposites maintain a relatively high breakdown strength, which is favorable for enhancing energy storage density in the nanocomposites. The nanocomposite containing of 2.5 vol. % of PVP modified BZT NF exhibits energy density as high as 6.3 J/cm(3) at 3800 kV/cm, which is more than doubled that of the pure PVDF of 2.8 J/cm(3) at 4000 kV/cm. Such significant enhancement could be attributed to the combined effects of the surface modification and large aspect ratio of the BZT NF. This work may provide a route for using the surface modified ferroelectric-relaxor behavior of ceramic nanofibers to enhance the dielectric energy density in ceramic-polymer nanocomposites.

Solution Treatment Effect on Tensile, Impact and Fracture Behaviour of Trace Zr Added Al-12Si-1Mg-1Cu Piston Alloy

NASA Astrophysics Data System (ADS)

Kaiser, Md. Salim

2018-04-01

The effects of T6 solution treatment on tensile, impact and fracture properties of cast Al-12Si-1Mg-1Cu piston alloys with trace of zirconium were investigated. Cast alloys were given precipitation strengthening treatment having a sequence of homogenizing, solutionizing, quenching and ageing. Both cast and solutionized samples are isochronally aged for 90 min at different temperatures up to 300 °C. Tensile and impact properties of the differently processed alloys have been studied to understand the precipitation strengthening of the alloys. Fractograpy of the alloys were observed to understand the mode of fracture. It is observed that the improvement in tensile properties in the aged alloys through heat treatment is mainly attributed to the formation of the Al2Cu and Mg2Si precipitates within the Al matrix. Solution treatment improves the tensile strength for the reason that during solution treatment some alloying elements are re-dissolved to produce a solute-rich solid solution. Impact energy decreases with ageing temperature due to formation of GP zones, β' and β precipitates. The fractography shows large and small dimple structure and broken or cracked primary Si, particles. Microstructure study of alloys revealed that the solution treatment improved distribution of silicon grains. The addition of Zr produces an improvement in the tensile properties as a result of its grain refining action and grain coarsening resistance in the matrix at a higher temperature.

Enhanced corrosion resistance and cytocompatibility of biodegradable Mg alloys by introduction of Mg(OH)2 particles into poly (L-lactic acid) coating

PubMed Central

Shi, Yong-juan; Pei, Jia; Zhang, Jian; Niu, Jia-lin; Zhang, Hua; Guo, Sheng-rong; Li, Zhong-hua; Yuan, Guang-yin

2017-01-01

A strategy of suppressing the fast degradation behaviour of Mg-based biomaterials by the introduction of one of Mg degradation products Mg(OH)2 was proposed according to the following degradation mechanism, Mg + 2H2O ⇋ Mg(OH)2 + H2↑. Specifically, Mg(OH)2 submicron particles were mixed into poly (L-lactic acid) (PLLA) to synthesize a composite coating onto hydrofluoric acid-pretreated Mg-Nd-Zn-Zr alloy. The in vitro degradation investigations showed that the addition of Mg(OH)2 particles not only slowed down the corrosion of Mg matrix, but also retarded the formation of gas pockets underneath the polymer coating. Correspondingly, cytocompatibility results exhibited significant improvement of proliferation of endothelial cells, and further insights was gained into the mechanisms how the introduction of Mg(OH)2 particles into PLLA coating affected the magnesium alloy degradation and cytocompatibility. The present study provided a promising surface modification strategy to tailor the degradation behaviour of Mg-based biomaterials. PMID:28150751

Luna 16 - Some Li, K, Rb, Sr, Ba, rare-earth, Zr, and Hf concentrations.

NASA Technical Reports Server (NTRS)

Philpotts, J. A.; Schnetzler, C. C.; Schuhmann, S.; Thomas , H. H.; Bottino, M. L.

1972-01-01

Concentrations of Li, K, Rb, Sr, Na, rare-earths, Zr and Hf have been determined for some Luna 16 core materials by mass-spectrometric isotope-dilution. Two regolith fines samples from different depths in the core, and four rock-chips, including both igneous rocks and breccias, have similar trace-element concentrations. The Luna 16 materials have general lunar trace-element characteristics but differ from other returned lunar samples in a manner that suggests the presence of excess feldspar. Unless the Luna 16 igneous rocks are fused soils, they appear to represent either partial plagioclase cumulates or the least differentiated igneous material yet returned from the moon. The similarity in trace-element concentrations of the igneous rocks and the fines would then suggest largely local derivation of the Luna 16 regolith.

Promoting effect of alkaline earth metal doping on catalytic activity of HC and NOx conversion over Pd-only three-way catalyst.

PubMed

Yang, Linyan; Lin, Siyu; Yang, Xue; Fang, Weimin; Zhou, Renxian

2014-08-30

The influence of alkaline earth metal (M=Mg, Ca, Sr and Ba) promoter on the structural/textural properties of Ce0.67Zr0.33O2 (designated as CZ) and the catalytic behavior of its supported Pd-only three-way catalyst (Pd/CZM) have been investigated. The results show that the modification with alkaline earth metal obviously improves the catalytic activity for hydrocarbon (HC) and nitrogen oxides (NOx) conversion, especially the introduction of Ba. Furthermore, the operation window of the promoted catalysts has also been widened. The doping of alkaline earth metal leads to the formation of more homogeneous Ce-Zr-M ternary solid solution with higher surface area and smaller crystallite size, and the corresponding Pd/CZM catalysts present improved reducibility of PdO species. The modification with Ca, Sr and Ba improves the thermal aging resistance, especially Ba. DRIFTS results reveal that the doping of alkaline earth metal enhances the oxygen and electron transfer ability and favors the dissociation of NO, which promotes the activation and storage capacity of the acidic atoms like NOx, and leads to enhanced catalytic activity performance. Copyright © 2014 Elsevier B.V. All rights reserved.

Fabrication and characterization of polyvinyl alcohol/metal (Ca, Mg, Ti) doped zirconium phosphate nanocomposite films for scaffold-guided tissue engineering application.

PubMed

Kalita, Himani; Pal, Pallabi; Dhara, Santanu; Pathak, Amita

2017-02-01

Nanocomposite films of polyvinyl alcohol (PVA) and zirconium phosphate (ZrP)/doped ZrP (doped with Ca, Mg, Ti) nanoparticles have been developed by solvent casting method to assess their potential as matrix material in scaffold-guided tissue engineering application. The prepared ZrP and doped ZrP nanoparticles as well as the nanocomposite films were characterized by various spectroscopic and microscopic techniques. Nanoindentation studies revealed improved nanomechanical properties in the PVA/doped ZrP nanocomposite films (highest for PVA/Ti doped ZrP: hardness=262.4MPa; elastic modulus=5800MPa) as compared to the PVA/ZrP and neat PVA films. In-vitro cell culture experiments carried out to access the cellular viability, attachment, proliferation, and migration on the substrates, using mouse fibroblast (3T3) cell lines, inferred enhanced bioactivity in the PVA/doped ZrP nanocomposite films (highest for PVA/Ca doped ZrP) in contrast to PVA/ZrP and neat PVA films. Controlled biodegradability as well as swelling behavior, superior bioactivity and improved mechanical properties of the PVA/doped ZrP nanocomposite films make them promising matrix materials for scaffold-guided tissue engineering application. Copyright © 2016 Elsevier B.V. All rights reserved.

Biocompatible Ni-free Zr-based bulk metallic glasses with high-Zr-content: compositional optimization for potential biomedical applications.

PubMed

Hua, Nengbin; Huang, Lu; Chen, Wenzhe; He, Wei; Zhang, Tao

2014-11-01

The present study designs and prepares Ni-free Zr60+xTi2.5Al10Fe12.5-xCu10Ag5 (at.%, x=0, 2.5, 5) bulk metallic glasses (BMGs) by copper mold casting for potential biomedical application. The effects of Zr content on the in vitro biocompatibility of the Zr-based BMGs are evaluated by investigating mechanical properties, bio-corrosion behavior, and cellular responses. It is found that increasing the content of Zr is favorable for the mechanical compatibility with a combination of low Young's modulus, large plasticity, and high notch toughness. Electrochemical measurements demonstrate that the Zr-based BMGs are corrosion resistant in a phosphate buffered saline solution. The bio-corrosion resistance of BMGs is improved with the increase in Zr content, which is attributed to the enrichment in Zr and decrease in Al concentration in the surface passive film of alloys. Regular cell responses of mouse MC3T3-E1 cells, including cell adhesion and proliferation, are observed on the Zr-Ti-Al-Fe-Cu-Ag BMGs, which reveals their general biosafety. The high-Zr-based BMGs exhibit a higher cell proliferation activity in comparison with that of pure Zr and Ti-6Al-4V alloy. The effects of Zr content on the in vitro biocompatibility can be used to guide the future design of biocompatible Zr-based BMGs. Copyright © 2014 Elsevier B.V. All rights reserved.

Aqueous Isolation of 17-Nuclear Zr-/Hf- Oxide Clusters during the Hydrothermal Synthesis of ZrO2/HfO2.

PubMed

Sung, Qing; Liu, Caiyun; Zhang, Guanyun; Zhang, Jian; Tung, Chen-Ho; Wang, Yifeng

2018-06-21

Novel 17-nuclear Zr-/Hf- oxide clusters ({Zr17} and {Hf17}) are isolated from aqueous systems. In the clusters, Zr/Hf ions are connected via μ3-O, μ3-OH and μ2-OH linkages into a pinwheel core which is wrapped with SO42-, HCOO- and aqua ligands. Octahedral hexanuclear Zr-/Hf- oxide clusters ({Zr6}oct and {Hf6}oct) are also isolated from the same hydrothermal system by decreasing the synthesis temperature. Structural analysis, synthetic conditions, vibrational spectra and ionic conductivity of the clusters are studied. Structural studies and synthesis inspection suggest that formation of {Zr6}oct and {Zr17} involves assembly of the same transferable building blocks, but the condensation degree and thermodynamic stability of the products increase with hydrothermal temperature. The role of {Zr6}oct and {Zr17} in the formation of ZrO2 nanocrystals are then discussed in the scenario of nonclassical nucleation theory. Besides, the Zr-oxide clusters exhibit ionic conductivity due to the mobility of protons. This study not only adds new members to the Zr-/Hf- oxide cluster family, but also establishes a connection from Zr4+ ions to ZrO2 in the hydrothermal preparation of zirconium oxide nanomaterials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physical properties of molten core materials: Zr-Ni and Zr-Cr alloys measured by electrostatic levitation

NASA Astrophysics Data System (ADS)

Ohishi, Yuji; Kondo, Toshiki; Ishikawa, Takehiko; Okada, Junpei T.; Watanabe, Yuki; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke

2017-03-01

It is important to understand the behaviors of molten core materials to investigate the progression of a core meltdown accident. In the early stages of bundle degradation, low-melting-temperature liquid phases are expected to form via the eutectic reaction between Zircaloy and stainless steel. The main component of Zircaloy is Zr and those of stainless steel are Fe, Ni, and Cr. Our group has previously reported physical property data such as viscosity, density, and surface tension for Zr-Fe liquid alloys using an electrostatic levitation technique. In this study, we report the viscosity, density, and surface tension of Zr-Ni and Zr-Cr liquid alloys (Zr1-xNix (x = 0.12 and 0.24) and Zr0.77Cr0.23) using the electrostatic levitation technique.

High Performance Proton-Conducting Solid Oxide Fuel Cells with a Layered Perovskite GdBaCuCoO5+ x Cathode

NASA Astrophysics Data System (ADS)

Zhang, Xiaozhen; Jiang, Yuhua; Hu, Xuebing; Sun, Liangliang; Ling, Yihan

2018-03-01

Proton-conducting solid oxide fuel cell (H-SOFC) based on layered perovskite type GdBaCuCoO5+x (GBCC) cathode was fabricated with in situ drop-coating BaZr0.1Ce0.7Y0.2O3-δ (BZCY) electrolyte membrane. The influences of Cu doping into Co sites of GdBaCo2O5+ x on the electrical conductivity and conduction mechanism, thermal expansion property and electrochemical performance of cathode materials and corresponding single cell were investigated. Results show that the electrical conductivity decreased and the conduction mechanism would gradually transform to the semiconductor-like behavior. A high maximum power density of 480 mW cm-2 was obtained for the anode supported NiO-BZCY/NiO-BZCY/BZCY/GBCC single cells with wet H2 fuel at 700 °C. The corresponding polarization resistance was as low as 0.17 Ω cm2. The excellent electrochemical performance of as-prepared single cell indicates that GBCC is a good candidate of cathode materials for H-SOFCs.

Liquidus Diagram of the Ba-Y-Cu-O System in the Vicinity of the Ba2YCu3O6+x Phase Field

PubMed Central

Wong-Ng, Winnie; Cook, Lawrence P.

1998-01-01

This paper describes the melting equilibria in the vicinity of the high Tc phase Ba2YCu3O6+x, including evidence for two Ba-Y-Cu-O immiscible liquids. Melting equilibria have been investigated in purified air using a combination of differential thermal analysis (DTA), thermogravimetric analysis (TGA), powder x-ray diffraction (XRD), MgO wick entrapment of liquid for analysis, scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDS), and hydrogen reduction for determination of copper oxidation state. For relatively barium-rich compositions, it was necessary to prepare the starting materials under controlled atmosphere conditions using BaO. A liquidus diagram was derived from quantitative data for the melts involved in various melting reactions. In general the 1/2(Y2O3) contents of the melts participating in these equilibria were low (mole fraction <4 %). The primary phase field of Ba2YCu3O6+x occurs at a mole fraction of <2.0 % 1/2Y2O3 and lies very close along the BaO-CuOx edge, extending from a mole fraction of ≈43 % CuO to a mole fraction of ≈76 % CuO. It is divided by a liquid miscibility gap and extends on either side about this gap. The topological sequence of melting reactions associated with the liquidus is presented as a function of temperature. Implications for the growth of Ba2YCu3O6+x crystals are discussed. PMID:28009382

Hydrogen absorption of Pd/ZrO2 composites prepared from Zr65Pd35 and Zr60Pd35Pt5 amorphous alloys

NASA Astrophysics Data System (ADS)

Ozawa, Masakuni; Katsuragawa, Naoya; Hattori, Masatomo; Yogo, Toshinobu; Yamamura, Shin-ichi

2018-01-01

Metal-dispersed composites were derived from amorphous Zr65Pd35 and Zr65Pd30Pt5 alloys and their hydrogen absorption behavior was studied. X-ray diffractograms and scanning electron micrographs indicated that mixtures containing ZrO2, the metallic phase of Pd, and PdO were formed for both amorphous alloys heat-treated in air. In the composites, micron-sized Pd-based metal precipitates were embedded in a ZrO2 matrix after heat treatment at 800 °C in air. The hydrogen temperature-programmed reduction was applied to study the reactivity of hydrogen gas with the oxidized Zr65Pd35 and Zr65Pd30Pt5 materials. Rapid hydrogen absorption and release were observed on the composite derived from the amorphous alloy below 100 °C. The hydrogen pressure-concentration isotherm showed that the absorbed amount of hydrogen in materials depended on the formation of the Pd or Pt-doped Pd phase and its large interface area to the matrix in the nanocomposites. The results indicate the importance of the composite structure for the fabrication of a new type of hydrogen storage material prepared from amorphous alloys.

Structure and transport in high pressure oxygen sputter-deposited BaSnO{sub 3−δ}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganguly, Koustav; Ambwani, Palak; Xu, Peng

BaSnO{sub 3} has recently been identified as a high mobility wide gap semiconductor with significant potential for room temperature oxide electronics. Here, a detailed study of the high pressure oxygen sputter-deposition, microstructure, morphology, and stoichiometry of epitaxial BaSnO{sub 3} on SrTiO{sub 3}(001) and MgO(001) is reported, optimized conditions resulting in single-phase, relaxed, close to stoichiometric films. Most significantly, vacuum annealing is established as a facile route to n-doped BaSnO{sub 3−δ}, leading to electron densities above 10{sup 19} cm{sup −3}, 5 mΩ cm resistivities, and room temperature mobility of 20 cm{sup 2} V{sup −1} s{sup −1} in 300-Å-thick films on MgO(001).more » Mobility limiting factors, and the substantial scope for their improvement, are discussed.« less

Mechanical properties and bio-tribological behaviors of novel beta-Zr-type Zr-Al-Fe-Nb alloys for biomedical applications.

PubMed

Hua, Nengbin; Chen, Wenzhe; Zhang, Lei; Li, Guanghui; Liao, Zhenlong; Lin, Yan

2017-07-01

The present study prepares novel Zr 70+x Al 5 Fe 15-x Nb 10 (x=0, 5) alloys by arc-melting for potential biomedical application. The mechanical properties and bio-tribological behaviors of the Zr-based alloys are evaluated and compared with biomedical pure Zr. The as-prepared alloys exhibit a microstructure containing a micrometer-sized dendritic beta-Zr phase dispersed in a Zr 2 Fe-typed matrix. It is found that increasing the content of Zr is favorable for the mechanical compatibility with a combination of low Young's modulus, large plasticity, and high compressive strength. The wear resistance of the Zr-Al-Fe-Nb alloys in air and phosphate buffer saline (PBS) solution is superior to that of pure Zr. The wear mechanism of Zr-based alloys sliding in air is controlled by oxidation and abrasive wear whereas that sliding in PBS is controlled by synergistic effects of the abrasive and corrosive wear. Electrochemical measurements demonstrate that the Zr-based alloys are corrosion resistant in PBS. Their bio-corrosion resistance is improved with the increase in Zr content, which is attributed to the enrichment in Zr and decrease in Al concentration in the surface passive film of alloys. The Zr 75 Al 5 Fe 10 Nb 10 exhibits the best corrosion resistance in PBS, which contributes to its superior wear resistance in a simulated body environment. The combination of good mechanical properties, corrosion resistance, and biotribological behaviors of the Zr-Al-Fe-Nb alloys offers them potential advantages in biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Melt inclusion evidence for the relative timing of assimilation and crystallisation in high MgO lavas, Mull, Scotland

NASA Astrophysics Data System (ADS)

Peate, D. W.; Ukstins Peate, I.; Rowe, M. C.; Thompson, J. M.; Kerr, A. C.

2010-12-01

Whole rock data on the Mull Plateau Group lavas (Scotland) show that the most primitive lavas (MgO >8 wt%) are the most crustally contaminated. One model is that hot, high-MgO magmas flow turbulently during ascent allowing more assimilation to occur than in the laminar flow regime expected for cooler, more viscous, lower-MgO magmas. We present data on rehomogenized olivine-hosted melt inclusions from four representative high-MgO flows to investigate the nature of the assimilation process in more detail. One complication on Mull is the potential effect of pervasive hydrothermal metamorphism on whole rock compositions. Melt inclusions are more protected against alteration effects within their host olivine crystal, and potentially allow more robust estimates of magmatic liquid compositions. Low sulphur contents were used to screen for degassed / breached inclusions, and the compositions of unbreached inclusions were corrected for post-entrapment crystallisation and Fe-loss. The four whole rock samples show a limited variation in Na2O (2.4-2.8 wt%) and K2O (0.23-0.29 wt%) despite a wide range in immobile element contents (e.g. Zr 62-126 ppm, Nb 2.4-4.6 ppm). In contrast, the melt inclusions show a far greater variability in Na2O (1.8-4.0 wt%) and K2O (0.02-0.35 wt%) and coherent positive correlations between K and Na. Melt inclusions from different samples show systematic correlations between alkalis (K+Na) and incompatible element ratios such as Zr/Y and La/Sm, indicating that the melt inclusions are recording magmatic values for fluid mobile elements such as K and Na. For the two most incompatible element enriched samples, the whole rock analysis is similar to the melt inclusions except for lower Na and higher Ba that are related to alteration. Therefore, any crustal assimilation in these magmas must have take place prior to the growth of the olivines in the samples. For the two more depleted samples, the melt inclusions have less contaminated compositions than the

Synthesis of 0.1% & 0.2% neodymium doped barium zirconium titanate (BaZr{sub 0.2}Ti{sub 0.8}O{sub 3}) and study of their dielectric behaviour

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Anil, E-mail: anilkantikumar@rediffmail.com; Kumar, Vipin; Gupta, Merry

2015-08-28

Efforts have been made to ease process of producing widely used multilayered ceramics of Barium Zirconium Titanium Oxides and study their dielectric behaviour and structural properties. For this purpose, adequate proportions of Barium Carbonate, Zirconium Oxide and Titanium Oxide were taken and hand milled for 2 hours. Neodymium composition of the order of 0.1% and 0.2% was used for doping to weight percentage of BaZr0.2Ti0.8O3. The samples were authenticated using raw data obtained from Bruker AXS D8 advance Copper KL alpha source XRD equipment. Further, the samples were studied for their phase transition, composition, single phase perovskite structure using XRDmore » technique. The technique has also been applied to know formation of stable homogeneous solid solution from XRD parameters. The other physical parameters like the morphology, micro structural information, crystal arrangements and topography have also been observed through SEM. The SEM has revealed information related to grain size development and composition of sample with fine agglomerates. For complete study of the compounds the atomic and weight composition has also been examined by Electron Dispersive Spectroscopy patterns. The comparison has been made with other works on ceramics at various frequencies and has yielded very interesting results.« less

Effects of extrusion and heat treatment on the mechanical properties and biocorrosion behaviors of a Mg-Nd-Zn-Zr alloy.

PubMed

Zhang, Xiaobo; Yuan, Guangyin; Mao, Lin; Niu, Jialin; Fu, Penghuai; Ding, Wenjiang

2012-03-01

Mechanical properties at room temperature and biocorrosion behaviors in simulated body fluid (SBF) at 37 °C of a new type of patented Mg-3Nd-0.2Zn-0.4Zr (hereafter, denoted as JDBM) alloy prepared at different extrusion temperatures, as well as heat treatment, were studied. The mechanical properties of this magnesium alloy at room temperature were improved significantly after extrusion and heat treatment compared to an as-cast alloy. The results of mechanical properties show that the yield strength (YS) decreases with increasing extrusion temperature. The tensile elongation decreases a little while the ultimate tensile strength (UTS) has no obvious difference. The yield strength and ultimate tensile strength were improved clearly after heat treatment at 200 °C for 10 h compared with that at the extrusion state, which can be mainly contributed to the precipitation strengthening. The biocorrosion behaviors of the JDBM alloy were studied using immersion tests and electrochemical tests. The results reveal that the extruded JDBM alloy and the aging treatment on the extruded alloy show much better biocorrosion resistance than that at solid solution state (T4 treatment), and the JDBM exhibited favorable uniform corrosion mode in SBF. Copyright © 2011 Elsevier Ltd. All rights reserved.

Electrical and Optical Properties of Nanocrystalline A8ZnNb6O24 (A = Ba, Sr, Ca, Mg) Ceramics

NASA Astrophysics Data System (ADS)

John, Fergy; Thomas, Jijimon K.; Jacob, John; Solomon, Sam

2017-08-01

Nanoparticles of A8ZnNb6O24 (A = Ba, Sr, Ca, and Mg, abbreviated as BZN, SZN, CZN, and MZN) have been synthesized by an auto-igniting combustion technique and their structural and optical properties characterized. The phase purity, crystal structure, and particle size of the prepared nanopowders were examined by x-ray diffraction (XRD) analysis and transmission electron microscopy. The XRD results revealed that all the samples crystallized with hexagonal perovskite structure in space group P6 3 cm. The Fourier-transform infrared and Raman (FT-Raman) spectra of the samples were investigated in detail. The ultraviolet-visible (UV-Vis) absorption spectra of the samples were also recorded and their optical bandgap energy values calculated. The nanopowders synthesized by the combustion technique were sintered to 95% of theoretical density at temperature of 1250°C for 2 h. The surface morphology of the sintered pellets was studied by scanning electron microscopy. The photoluminescence spectra of the samples showed intense emission in the blue-green region. Complex impedance analysis was used to determine the grain and grain boundary effects on the dielectric behavior of the ceramics.

The Introduction of substitutional and non-substitutional dopants into MgB2 in high pressure/Temperature or non-equilibrium regimes

NASA Astrophysics Data System (ADS)

Sumption, Mike

2013-03-01

In an attempt to study the effect of doping of MgB2 under conditions leading to efficient doping, we used both an high temperature/high pressure induction furnace to dope into MgB2 bulks at temperatures up to 1600 C and 1500 Psi, and thin film, PLD multilayer and mixed layer film fabrication. The high temperature/high pressure formation was used to explore the solubility at high temperatures of various dopants, and the thin film formation was an attempt to use non-equilibrium conditions to inject dopants more effectively. The dopants used were C, Ti, and Zr. C was seen to reach a maximal level at 4 at% C site substituted into MgB2, as evidenced by EPMA and XRD results. Zr, of interest as a possible Mg site substitution in MgB2 was not seen to enter into the MgB2 phase (instead segregating) in the bulk high temperature/high pressure experiments, but was seen to enter in during PLD, as evidenced by STEM and XRD results. Ti additions were attempted in the high pressures and temperature rig, with some evidence for dopant introduction. Critical field measurements on the Zr doped samples where seen to suppress Bc2 for all except very low levels of Ti addition, presumably associated with the much greater doping efficiency. This work was supported by the U.S. Department of Energy, High Energy Physics university Grant No. DE-FG02-95ER40900

First principles calculations on the influence of solute elements and chlorine adsorption on the anodic corrosion behavior of Mg (0001) surface

NASA Astrophysics Data System (ADS)

Luo, Zhe; Zhu, Hong; Ying, Tao; Li, Dejiang; Zeng, Xiaoqin

2018-06-01

The influences of solute atoms (Li, Al, Mn, Zn, Fe, Ni, Cu, Y, Zr) and Cl adsorption on the anodic corrosion performance on Mg (0001) surface have been investigated based on first-principles calculations, which might be useful for the design of corrosion-resistant Mg alloys. Work function and local electrode potential shift are chosen as descriptors since they quantify the barrier for charge transfer and anodic stability. We found that at 25% surface doping rate, Y decreased the work function of Mg, while the impact of remaining doping elements on the work function of Mg was trivial due to the small surface dipole moment change. The adsorption of Cl destabilized the Mg atoms at surface by weakening the bonding between surface Mg atoms. We find that a stronger hybridization of d orbits of alloying elements (e.g. Zr) with the orbits of Mg can greatly increase the local electrode potential,which even overbalances the negative effect introduced by Cl adsorbates and hence improves the corrosion resistance of Mg alloys.

Crystal Nucleation and Growth in Undercooled Melts of Pure Zr, Binary Zr-Based and Ternary Zr-Ni-Cu Glass-Forming Alloys

NASA Astrophysics Data System (ADS)

Herlach, Dieter M.; Kobold, Raphael; Klein, Stefan

2018-03-01

Glass formation of a liquid undercooled below its melting temperature requires the complete avoidance of crystal nucleation and subsequent crystal growth. Even though they are not part of the glass formation process, a detailed knowledge of both processes involved in crystallization is mandatory to determine the glass-forming ability of metals and metallic alloys. In the present work, methods of containerless processing of drops by electrostatic and electromagnetic levitation are applied to undercool metallic melts prior to solidification. Heterogeneous nucleation on crucible walls is completely avoided giving access to large undercoolings. A freely suspended drop offers the additional benefit of showing the rapid crystallization process of an undercooled melt in situ by proper diagnostic means. As a reference, crystal nucleation and dendrite growth in the undercooled melt of pure Zr are experimentally investigated. Equivalently, binary Zr-Cu, Zr-Ni and Zr-Pd and ternary Zr-Ni-Cu alloys are studied, whose glass-forming abilities differ. The experimental results are analyzed within classical nucleation theory and models of dendrite growth. The findings give detailed knowledge about the nucleation-undercooling statistics and the growth kinetics over a large range of undercooling.

Synthesis, spectroscopic and thermal studies of Mg(II), Ca(II), Sr(II) and Ba(II) diclofenac sodium complexes as anti-inflammatory drug and their protective effects on renal functions impairment and oxidative stress

NASA Astrophysics Data System (ADS)

El-Megharbel, Samy M.; Hamza, Reham Z.; Refat, Moamen S.

2015-01-01

The main task of our present study is the preparation of newly complexes of Mg(II), Ca(II), Sr(II) and Ba(II) with diclofenac which succeeded to great extent in alleviating the side effects of diclofenac alone and ameliorating the kidney function parameters and antioxidant capacities with respect to diclofenac treated group alone. The Mg(II), Ca(II), Sr(II) and Ba(II) with diclofenac have been synthesized and characterized using infrared, electronic and 1H NMR spectral, thermogravimetric and conductivity measurements. The diclofenac ligand has been found to act as bidentate chelating agent. Diclofenac complexes coordinate through the oxygen's of the carboxyl group. The molar ratio chelation is 1:2 (M2+-dic) with general formula [M(dic)2(H2O)2]ṡnH2O. Antibacterial screening of the alkaline earth metal complexes against Escherichia coli (Gram - ve), Bacillus subtilis (Gram + ve) and anti-fungal (Asperagillus oryzae, Asperagillus niger, Asperagillus flavus) were investigated. The kidney functions in male albino rats were ameliorated upon treatment with metal complexes of dic, which are represented by decreasing the levels of urea and uric acid to be located within normal values. The other looks bright spot in this article is the assessment of antioxidant defense system including SOD, CAT and MDA with the help of Sr2+, Mg2+ and Ca2+-dic complexes. The hormones related to kidney functions and stresses have been greatly ameliorated in groups treated with dic complexes in comparable with dic treated group.

Syntheses, crystal structure, and electronic properties of the five ABaMQ{sub 4} compounds RbBaPS{sub 4}, CsBaPS{sub 4}, CsBaVS{sub 4}, RbBaVSe{sub 4}, and CsBaVSe{sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mesbah, Adel; ICSM, UMR 5257 CEA / CNRS / UM / ENSCM, Site de Marcoule-Bâtiment 426, BP 17171, 30207 Bagnols-sur-Cèze Cedex; Prakash, Jai

Five new compounds belonging to the ABaMQ{sub 4} family were synthesized by solid-state chemistry at 1123 K. The compounds RbBaPS{sub 4}, CsBaPS{sub 4}, CsBaVS{sub 4}, RbBaVSe{sub 4}, and CsBaVSe{sub 4} are isostructural and have the TlEuPS{sub 4} structure type. They crystallize in space group D{sup 16}{sub 2h} – Pnma of the orthorhombic system. Their structure consists isolated MQ{sub 4} tetrahedra separated by A and Ba atoms to form a salt-like structure. Density Functional Theory (DFT) calculations of the electronic structures with the use of the HSE functional suggest that the compounds are semiconductors with calculated band gaps of 3.3 eVmore » (RbBaPS{sub 4}), 3.4 eV (CsBaPS{sub 4}), 2.3 eV (CsBaVS{sub 4}), and 1.6 eV (RbBaVSe{sub 4}). - Graphical abstract: General view of the ABaMQ{sub 4} structure down the a axis. - Highlights: • Five new ABaMQ{sub 4} compounds were synthesized by solid-state chemistry at 1123 K. • RbBaPS{sub 4}, CsBaPS{sub 4}, CsBaVS{sub 4}, RbBaVSe{sub 4}, and CsBaVSe{sub 4} have the TlEuPS{sub 4} structure type. • The compounds are semiconductors with calculated band gaps ranging from 1.6 to 3.4 eV.« less

In-beam studies of sup 96 Zr and sup 98 Zr: Collective excitations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henry, E.A.; Meyer, R.A.; Aprahamian, A.

1988-04-18

Nearly two decades ago signatures of deformation in the ground state bands of {sup 100}Zr and {sup 102}Zr were identified, and the rapid change in the deformation of heavy zirconium nuclei noted. It is now well accepted that the short-range proton-neutron interaction between the 1g{sub 9/2} and 1g{sub 7/2} spin-orbit partners plays an important role in producing ground state deformation in this region. Nevertheless, recent studies of zirconium nuclei, including those in the transition region, continue to refine our understanding of the interplay between single-particle and collective degrees of freedom. In this report we discuss some aspects of the levelmore » structures of {sup 96}Zr and {sup 98}Zr with emphasis on collective excitations. 18 refs., 2 tabs.« less

Arc melting and homogenization of ZrC and ZrC + B alloys

NASA Technical Reports Server (NTRS)

Darolia, R.; Archbold, T. F.

1973-01-01

A description is given of the methods used to arc-melt and to homogenize near-stoichiometric ZrC and ZrC-boron alloys, giving attention to the oxygen contamination problem. The starting material for the carbide preparation was ZrC powder with an average particle size of 4.6 micron. Pellets weighing approximately 3 g each were prepared at room temperature from the powder by the use of an isostatic press operated at 50,000 psi. These pellets were individually melted in an arc furnace containing a static atmosphere of purified argon. A graphite resistance furnace was used for the homogenization process.

Ternary semiconductors NiZrSn and CoZrBi with half-Heusler structure: A first-principles study

NASA Astrophysics Data System (ADS)

Fiedler, Gregor; Kratzer, Peter

2016-08-01

The ternary semiconductors NiZrSn and CoZrBi with C 1b crystal structure are introduced by calculating their basic structural, electronic, and phononic properties using density functional theory. Both the gradient-corrected PBE functional and the hybrid functional HSE06 are employed. While NiZrSn is found to be a small-band-gap semiconductor (Eg=0.46 eV in PBE and 0.60 eV in HSE06), CoZrBi has a band gap of 1.01 eV in PBE (1.34 eV in HSE06). Moreover, effective masses and deformation potentials are reported. In both materials A B C , the intrinsic point defects introduced by species A (Ni or Co) are calculated. The Co-induced defects in CoZrBi are found to have a higher formation energy compared to Ni-induced defects in NiZrSn. The interstitial Ni atom (Nii) as well as the VNiNii complex introduce defect states in the band gap, whereas the Ni vacancy (VNi) only reduces the size of the band gap. While Nii is electrically active and may act as a donor, the other two types of defects may compensate extrinsic doping. In CoZrBi, only the VCoCoi complex introduces a defect state in the band gap. Motivated by the reported use of NiZrSn for thermoelectric applications, the Seebeck coefficient of both materials, both in the p -type and the n -type regimes, is calculated. We find that CoZrBi displays a rather large thermopower of up to 500 μ V /K when p doped, whereas NiZrSn possesses its maximum thermopower in the n -type regime. The reported difficulties in achieving p -type doping in NiZrSn could be rationalized by the unintended formation of Nii2 + in conjunction with extrinsic acceptors, resulting in their compensation. Moreover, it is found that all types of defects considered, when present in concentrations as large as 3%, tend to reduce the thermopower compared to ideal bulk crystals at T =600 K. For NiZrSn, the calculated thermodynamic data suggest that additional Ni impurities could be removed by annealing, leading to precipitation of a metallic Ni2ZrSn phase.

Zr/ZrO2 sensors for in situ measurement of pH in high-temperature and -pressure aqueous solutions.

PubMed

Zhang, R H; Zhang, X T; Hu, S M

2008-04-15

The aim of this study is to develop new pH sensors that can be used to test and monitor hydrogen ion activity in hydrothermal conditions. A Zr/ZrO2 oxidation electrode is fabricated for in situ pH measurement of high-temperature aqueous solutions. This sensor responds rapidly and precisely to pH over a wide range of temperature and pressure. The Zr/ZrO2 electrode was made by oxidizing zirconium metal wire with Na2CO3 melt, which produced a thin film of ZrO2 on its surface. Thus, an oxidation-reduction electrode was produced. The Zr/ZrO2 electrode has a good electrochemical stability over a wide range of pH in high-temperature aqueous solutions when used with a Ag/AgCl reference electrode. Measurements of the Zr/ZrO2 sensor potential against a Ag/AgCl reference electrode is shown to vary linearly with pH between temperatures 20 and 200 degrees C. The slope of the potential versus pH at high temperature is slightly below the theoretical value indicated by the Nernst equation; such deviation is attributed to the fact that the sensor is not strictly at equilibrium with the solution to be tested in a short period of time. The Zr/ZrO2 sensor can be calibrated over the conditions that exist in the natural deep-seawater. Our studies showed that the Zr/ZrO2 electrode is a suitable pH sensor for the hydrothermal systems at midocean ridge or other geothermal systems with the high-temperature environment. Yttria-stabilized zirconia sensors have also been used to investigate the pH of hydrothermal fluids in hot springs vents at midocean ridge. These sensors, however, are not sensitive below 200 degrees C. Zr/ZrO2 sensors have wider temperature range and can be severed as good alternative sensors for measuring the pH of hydrothermal fluids.

Gd Ba Cu O bulk superconductors fabricated by a seeded infiltration growth technique under reduced oxygen partial pressure

NASA Astrophysics Data System (ADS)

Iida, K.; Babu, N. H.; Shi, Y. H.; Cardwell, D. A.; Murakami, M.

2006-06-01

Single-grain Gd-Ba-Cu-O (GdBCO) bulk superconductors have been grown by a seeded infiltration and growth (SIG) technique under a 1% O2+N2 atmosphere using a generic MgO-doped Nd-Ba-Cu-O (MgO-NdBCO) seed placed on the sample surface at room temperature (the so-called the cold-seeding method). Partial melting of the MgO-NdBCO seeds fabricated in air under notionally identical thermal processing conditions, however, limited the reliability of this bulk GdBCO single-grain process. The observed seed decomposition is attributed to the dependence of the peritectic temperature Tp of MgO-doped Nd1+xBa2-xCu3Oy solid solution (MgO-doped Nd-123ss, where ss indicates solid solution) compounds on both oxygen partial pressure during the melt process and the level of solid solution (x). The peritectic decomposition temperature of MgO-doped Nd-123ss, with x ranging from 0 to 0.5 under p(O2) = 1.00 atm, was observed to remain constant at 1120 °C. Tp was observed to decrease linearly as a function of solid solution level, on the other hand, under oxygen partial pressures of both p(O2) = 0.21 and 0.01 atm. Based on these results, MgO-doped NdBCO seed crystals should be grown under reduced oxygen partial pressure in order to obtain a stable MgO-doped NdBCO seed crystal suitable for cold-seeding processes of large-grain (RE)BCO bulk superconductors (where RE is a rare earth element).

Three-dimensional characterization of BaHfO3 precipitates in GdBa2Cu3O7-y flim using STEM tomography.

PubMed

Nishiyama, T; Kaneko, K; Yamada, K; Teranishi, R; Kato, T; Hirayama, T; Tobita, H; Izumi, T; Shiohara, Y

2014-11-01

IntroductionSince the discovery of REBa2Cu3O7-y (RE: Rare Earth element, REBCO) superconductors, they have been expected as the best candidates for the power cable application due to its high critical temperature (Tc) and critical current density (Jc). Among those REBCO superconductors, GdBa2Cu3O7-y (GdBCO) have been receiving great interest because they have higher Tc and Jc than YBa2Cu3O7-y [1].GdBCO with various types of precipitates as artificial pinning centers (APCs) have been proposed to minimize the anisotropy of Jc characteristics under the magnetic field. Among those precipitates, BaHfO3 (BHO) was found most effective precipitates as APCs in GdBCO film prepared by pulsed laser deposition (PLD) method [2]. It is therefore necessary to investigate not only the morphologies but also the dispersion of BHO precipitates within the GdBCO, to understand the role of BHO for the superconducting characteristics. In this study, morphologies and dispersions of BHO precipitates were characterized three-dimensional by scanning transmission electron tomography ExperimentalBHO dispersed GdBCO films were fabricated on Hastelloy C-276TM substrates with buffer layers of CeO2/LaMnO3/MgO/ Gd2ZrO7 by PLD method.To observe microstructure of GdBCO film with BHO precipitates, cross-section TEM specimens were prepared by FIB method using Quanta 3D-200 (FEI, USA) with acceleration voltage from 2 to 30 kV. Three-dimensional information such as morphology and dispersion, of BHO precipitates were characterized by electron tomography using STEM-HAADF. Result and discussionFigure 1 shows three-dimensional reconstructed volume of BHO precipitates in GdBCO, which revealed that fine BHO precipitates have rod- and plate-like morphologies with homogeneous dispersion in GdBCO. In addition, growth directions of these precipitates were found with wide angular distributions from growth direction of GdBCO. Anisotropy of Jc in the magnetic fields was probably enhanced by various growth directions

Characterization of hot-pressed short ZrO{sub 2} fiber toughened ZrB{sub 2}-based ultra-high temperature ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Jia, E-mail: 2013113205@xmut.edu.cn; Huang, Yu; Zhang, Houan

2014-09-15

Two different ZrB{sub 2}-based ultra-high temperature ceramics were produced by hot pressing: ZrB{sub 2} + 20 vol.% SiC particle + 15 vol.% ZrO{sub 2} fiber and ZrB{sub 2} + 20 vol.% SiC whisker + 15 vol.% ZrO{sub 2} fiber. The microstructures were analyzed by using transmission electron microscopy and high-resolution transmission electron microscopy. It was shown that a clean interface without any impurities was identified in ZrB{sub 2}-based hybrid ceramics with SiC whiskers and ZrO{sub 2} fibers, which would significantly improve the toughening mechanism. The results of high-resolution transmission electron microscopy showed that stacking faults in SiC whiskers resulted frommore » an insertion of a (111) layer, which would be one of the main reasons for material anisotropy. However, the interface between the SiC particle and ZrO{sub 2} fiber was found to be ambiguous in ZrB{sub 2}-based hybrid ceramics with SiC particles and ZrO{sub 2} fibers due to the slight reaction. The orientation relationship between t-ZrO{sub 2} and m-ZrO{sub 2} phases obeyed the classical correspondence: (100){sub m}//(100){sub t} and [001]{sub m}//〈001〉{sub t}, which further verified the feasibility of phase transformation toughening mechanism. - Highlights: • ZrB{sub 2}-based ceramics toughened by short ZrO{sub 2} fiber are characterized by TEM and HRTEM. • The orientation relationship of t- and m-ZrO{sub 2} are (100){sub m}//(100){sub t}, [001]{sub m}//〈001〉{sub t} • The clean interface without any impurities leads to improve the toughening mechanism.« less

Accelerated Discovery of Large Electrostrains in BaTiO3 -Based Piezoelectrics Using Active Learning.

PubMed

Yuan, Ruihao; Liu, Zhen; Balachandran, Prasanna V; Xue, Deqing; Zhou, Yumei; Ding, Xiangdong; Sun, Jun; Xue, Dezhen; Lookman, Turab

2018-02-01

A key challenge in guiding experiments toward materials with desired properties is to effectively navigate the vast search space comprising the chemistry and structure of allowed compounds. Here, it is shown how the use of machine learning coupled to optimization methods can accelerate the discovery of new Pb-free BaTiO 3 (BTO-) based piezoelectrics with large electrostrains. By experimentally comparing several design strategies, it is shown that the approach balancing the trade-off between exploration (using uncertainties) and exploitation (using only model predictions) gives the optimal criterion leading to the synthesis of the piezoelectric (Ba 0.84 Ca 0.16 )(Ti 0.90 Zr 0.07 Sn 0.03 )O 3 with the largest electrostrain of 0.23% in the BTO family. Using Landau theory and insights from density functional theory, it is uncovered that the observed large electrostrain is due to the presence of Sn, which allows for the ease of switching of tetragonal domains under an electric field. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Observations of a Cast Cu-Cr-Zr Alloy

NASA Technical Reports Server (NTRS)

Ellis, David L.

2006-01-01

Prior work has demonstrated that Cu-Cr-Nb alloys have considerable advantages over the copper alloys currently used in regeneratively cooled rocket engine liners. Observations indicated that Zr and Nb have similar chemical properties and form very similar compounds. Glazov and Zakharov et al. reported the presence of Cr2Zr in Cu-Cr-Zr alloys with up to 3.5 wt% Cr and Zr though Zeng et al. calculated that Cr2Zr could not exist in a ternary Cu-Cr-Zr alloy. A cast Cu-6.15 wt% Cr-5.25 wt% Zr alloy was examined to determine if the microstructure developed would be similar to GRCop-84 (Cu-6.65 wt% Cr-5.85 wt% Nb). It was observed that the Cu-Cr-Zr system did not form any Cr2Zr even after a thermal exposure at 875 C for 176.5 h. Instead the alloy consisted of three phases: Cu, Cu5Zr, and Cr.

Terahertz dielectric response of ferroelectric Ba(x)Sr(1-x)TiO3 thin films.

PubMed

Kang, Seung Beom; Kwak, Min Hwan; Choi, Muhan; Kim, Sungil; Kim, Taeyong; Cha, Eun Jong; Kang, Kwang Yong

2011-11-01

Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.

Tracing subduction zone fluid-rock interactions using trace element and Mg-Sr-Nd isotopes

NASA Astrophysics Data System (ADS)

Wang, Shui-Jiong; Teng, Fang-Zhen; Li, Shu-Guang; Zhang, Li-Fei; Du, Jin-Xue; He, Yong-Sheng; Niu, Yaoling

2017-10-01

Slab-derived fluids play a key role in mass transfer and elemental/isotopic exchanges in subduction zones. The exhumation of deeply subducted crust is achieved via a subduction channel where fluids from various sources are abundant, and thus the chemical/isotopic compositions of these rocks could have been modified by subduction-zone fluid-rock interactions. Here, we investigate the Mg isotopic systematics of eclogites from southwestern Tianshan, in conjunction with major/trace element and Sr-Nd isotopes, to characterize the source and nature of fluids and to decipher how fluid-rock interactions in subduction channel might influence the Mg isotopic systematics of exhumed eclogites. The eclogites have high LILEs (especially Ba) and Pb, high initial 87Sr/86Sr (up to 0.7117; higher than that of coeval seawater), and varying Ni and Co (mostly lower than those of oceanic basalts), suggesting that these eclogites have interacted with metamorphic fluids mainly released from subducted sediments, with minor contributions from altered oceanic crust or altered abyssal peridotites. The positive correlation between 87Sr/86Sr and Pb* (an index of Pb enrichment; Pb* = 2*PbN/[CeN + PrN]), and the decoupling relationships and bidirectional patterns in 87Sr/86Sr-Rb/Sr, Pb*-Rb/Sr and Pb*-Ba/Pb spaces imply the presence of two compositionally different components for the fluids: one enriched in LILEs, and the other enriched in Pb and 87Sr/86Sr. The systematically heavier Mg isotopic compositions (δ26Mg = - 0.37 to + 0.26) relative to oceanic basalts (- 0.25 ± 0.07) and the roughly negative correlation of δ26Mg with MgO for the southwestern Tianshan eclogites, cannot be explained by inheritance of Mg isotopic signatures from ancient seafloor alteration or prograde metamorphism. Instead, the signatures are most likely produced by fluid-rock interactions during the exhumation of eclogites. The high Rb/Sr and Ba/Pb but low Pb* eclogites generally have high bulk-rock δ26Mg values

Cooling rate dependence of simulated Cu{sub 64.5}Zr{sub 35.5} metallic glass structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryltsev, R. E.; Ural Federal University, 19 Mira Str., 620002 Ekaterinburg; L.D. Landau Institute for Theoretical Physics, Russian Academy of Sciences, 2 Kosygina Str., 119334 Moscow

Using molecular dynamics simulations with embedded atom model potential, we study structural evolution of Cu{sub 64.5}Zr{sub 35.5} alloy during the cooling in a wide range of cooling rates γ ∈ (1.5 ⋅ 10{sup 9}, 10{sup 13}) K/s. Investigating short- and medium-range orders, we show that the structure of Cu{sub 64.5}Zr{sub 35.5} metallic glass essentially depends on cooling rate. In particular, a decrease of the cooling rate leads to an increase of abundances of both the icosahedral-like clusters and Frank-Kasper Z16 polyhedra. The amounts of these clusters in the glassy state drastically increase at the γ{sub min} = 1.5 ⋅ 10{supmore » 9} K/s. Analysing the structure of the glass at γ{sub min}, we observe the formation of nano-sized crystalline grain of Cu{sub 2}Zr intermetallic compound with the structure of Cu{sub 2}Mg Laves phase. The structure of this compound is isomorphous with that for Cu{sub 5}Zr intermetallic compound. Both crystal lattices consist of two types of clusters: Cu-centered 13-atom icosahedral-like cluster and Zr-centered 17-atom Frank-Kasper polyhedron Z16. That suggests the same structural motifs for the metallic glass and intermetallic compounds of Cu–Zr system and explains the drastic increase of the abundances of these clusters observed at γ{sub min}.« less

Ca(5)Zr(3)F(22).

PubMed

Oudahmane, Abdelghani; El-Ghozzi, Malika; Avignant, Daniel

2012-04-01

Single crystals of Ca(5)Zr(3)F(22), penta-calcium trizirconium docosafluoride, were obtained unexpectedly by solid-state reaction between CaF(2) and ZrF(4) in the presence of AgF. The structure of the title compound is isotypic with that of Sr(5)Zr(3)F(22) and can be described as being composed of layers with composition [Zr(3)F(20)](8-) made up from two different [ZrF(8)](4-) square anti-prisms (one with site symmetry 2) by corner-sharing. The layers extending parallel to the (001) plane are further linked by Ca(2+) cations, forming a three-dimensional network. Amongst the four crystallographically different Ca(2+) ions, three are located on twofold rotation axes. The Ca(2+) ions exhibit coordination numbers ranging from 8 to 12, depending on the cut off, with very distorted fluorine environments. Two of the Ca(2+) ions occupy inter-stices between the layers whereas the other two are located in void spaces of the [Zr(3)F(20)](8-) layer and alternate with the two Zr atoms along [010]. The crystal under investigation was an inversion twin.

Sediment pollution in margins of the Lake Guaíba, Southern Brazil.

PubMed

de Andrade, Leonardo Capeleto; Tiecher, Tales; de Oliveira, Jessica Souza; Andreazza, Robson; Inda, Alberto Vasconcellos; de Oliveira Camargo, Flávio Anastácio

2017-12-02

Sediments are formed by deposition of organic and inorganic particles on depth of water bodies, being an important role in aquatic ecosystems, including destination and potential source of essential nutrients and heavy metals, which may be toxic for living organisms. The Lake Guaíba supplies water for approximately two million people and it is located in the metropolitan region of Porto Alegre, Rio Grande do Sul State, Brazil. Thus, the aim of this study was to evaluate the sediment pollution in the margins of Lake Guaíba in the vicinity of Porto Alegre city. Surface sediment was sampled in 12 sites to assess the concentration of several elements (C, N, P, Fe, Al, Ca, Mg, Na, K, Mn, Ba, Zn, V, Pb, Cu, Cr, Ni, Cd, Mo, and Se) and the mineralogical composition. Sediment in margins of Lake Guaíba presented predominantly (> 95%) sandy fraction in all samples, but with significant differences between evaluated sites. Sediments in the margins of Lake Guaíba showed indications of punctual water pollution with Pb, Cu, Cr, Ni, TOC, TKN, and P, mainly derived from urban streams that flow into the lake. In order to solve these environmental liabilities, public actions should not focus only on Guaíba, but also in the streams that flow into the lake.

Anode materials for lithium ion batteries

DOEpatents

Abouimrane, Ali; Amine, Khalil

2017-04-11

An electrochemical device includes a composite material of general Formula (1-x)J-(x)Q wherein: J is a metal carbon alloy of formula Sn.sub.zSi.sub.z'Met.sub.wMet'.sub.w'C.sub.t; Q is a metal oxide of formula A.sub..gamma.M.sub..alpha.M'.sub..alpha.'O.sub..beta.; and wherein: A is Li, Na, or K; M and M' are individually Ge, Mo, Al, Ga, As, Sb, Te, Ti, Ta, Zr, Ca, Mg, Sr, Ba, Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Rt, Ru or Cd; Met and Met' are individually Ge, Mo, Al, Ga, As, Sb, Te, Ti, Ta, Zr, Ca, Mg, Sr, Ba, Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Rt, Ru or Cd; 0

Optimizing Blue Persistent Luminescence in (Sr 1-δ Ba δ ) 2 MgSi 2 O 7: Eu 2+ ,Dy 3+ via Solid Solution for Use in Point-of-Care Diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Finley, Erin; Cobb, Angelica; Duke, Anna

Inorganic persistent luminescent phosphors are an excellent class of optical reporters for enabling sensitive point-of-care diagnostics, particularly with smartphone-based biosensing devices in testing formats such as the lateral flow assay (LFA). Here, the development of persistent phosphors for this application is focused on the solid solution (Sr 1-δBa δ) 2MgSi 2O 7:Eu 2+,Dy 3+ (δ = 0, 0.125, 0.25, 0.375), which is prepared using a high-temperature solid-state reaction as confirmed by synchrotron X-ray powder diffraction. The substitution of barium for strontium enables control over the Eu 2+ 5d-orbital crystal field splitting (CFS) as a tool for tuning the emission wavelengthmore » while maintaining luminescence lifetimes >9 min across the composition range. Thermoluminescence measurements of the solid solution provide evidence that trap states contribute to the persistent lifetimes with the trap depths also remaining constant as a function of composition. Time-gated luminescence images of these compounds are captured on a smartphone arranged in a layout to mimic a point-of-care test and demonstrate the viability of using these materials as optical reporters. Moreover, comparing the blue-emitting (Sr 0.625Ba 0.375) 2MgSi 2O 7:Eu 2+,Dy 3+ and the green-emitting SrAl 2O 4:Eu 2+,Dy 3+ in a single LFA-type format shows these two compounds can be detected and resolved simultaneously, thereby permitting the development of a multiplexed LFA.« less

Effects of phosphates on microstructure and bioactivity of micro-arc oxidized calcium phosphate coatings on Mg-Zn-Zr magnesium alloy.

PubMed

Pan, Y K; Chen, C Z; Wang, D G; Zhao, T G

2013-09-01

Calcium phosphate (CaP) coatings were prepared on Mg-Zn-Zr magnesium alloy by micro-arc oxidation (MAO) in electrolyte containing calcium acetate monohydrate (CH3COO)2Ca·H2O) and different phosphates (i.e. disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), sodium phosphate (Na3PO4·H2O) and sodium hexametaphosphate((NaPO3)6)). Scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS) and X-ray diffractometer (XRD) were employed to characterize the microstructure, elemental distribution and phase composition of the CaP coatings. Simulated body fluid (SBF) immersion test was used to evaluate the coating bioactivity and degradability. Systemic toxicity test was used to evaluate the coating biocompatibility. Fluoride ion selective electrode (ISE) was used to measure F(-) ions concentration during 30 days SBF immersion. The CaP coatings effectively reduced the corrosion rate and the surfaces of CaP coatings were covered by a new layer formed of numerous needle-like and scale-like apatites. The formation of these calcium phosphate apatites indicates that the coatings have excellent bioactivity. The coatings formed in (NaPO3)6-containging electrolyte exhibit thicker thickness, higher adhesive strength, slower degradation rate, better apatite-inducing ability and biocompatibility. Copyright © 2013 Elsevier B.V. All rights reserved.

The effect of lanthanum on the fabrication of ZrB{sub 2}-ZrC composites by spark plasma sintering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Kyoung Hun; Shim, Kwang Bo

2003-01-15

The effect of the addition of the rare earth element, lanthanum, on the sintering characteristics of ZrB{sub 2}-ZrC composites has been analyzed during a spark plasma sintering (SPS) process. Microscopic observation confirmed that lanthanum accelerated mass transport by the formation of the liquid phase between the particles induced by the spark plasma in the initial stage of the SPS process, and then these were recrystallized to form a lanthanum-containing secondary phase at the grain boundaries and at the grain boundary triple junctions. In spite of the strong covalent bonding characteristics of the ZrB{sub 2}-ZrC composite there are many well-developed dislocationmore » structures observed. The fracture toughness of the lanthanum-containing ZrB{sub 2}-ZrC is about 2.56 MPa m{sup 1/2}, which is comparable to that of the pure composite. Therefore, it is concluded that lanthanum is very effective as a sintering aid for the ZrB{sub 2}-ZrC composite without any degradation of the mechanical properties.« less

Self-organization during growth of ZrN/SiN{sub x} multilayers by epitaxial lateral overgrowth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fallqvist, A.; Fager, H.; Hultman, L.

ZrN/SiN{sub x} nanoscale multilayers were deposited on ZrN seed layers grown on top of MgO(001) substrates by dc magnetron sputtering with a constant ZrN thickness of 40 Å and with an intended SiN{sub x} thickness of 2, 4, 6, 8, and 15 Å at a substrate temperature of 800 °C and 6 Å at 500 °C. The films were investigated by X-ray diffraction, high-resolution scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy. The investigations show that the SiN{sub x} is amorphous and that the ZrN layers are crystalline. Growth of epitaxial cubic SiN{sub x}—known to take place on TiN(001)—onmore » ZrN(001) is excluded to the monolayer resolution of this study. During the course of SiN{sub x} deposition, the material segregates to form surface precipitates in discontinuous layers for SiN{sub x} thicknesses ≤6 Å that coalesce into continuous layers for 8 and 15 Å thickness at 800 °C, and for 6 Å at 500 °C. The SiN{sub x} precipitates are aligned vertically. The ZrN layers in turn grow by epitaxial lateral overgrowth on the discontinuous SiN{sub x} in samples deposited at 800 °C with up to 6 Å thick SiN{sub x} layers. Effectively a self-organized nanostructure can be grown consisting of strings of 1–3 nm large SiN{sub x} precipitates along apparent column boundaries in the epitaxial ZrN.« less

Solid-state NMR calculations for metal oxides and gallates: Shielding and quadrupolar parameters for perovskites and related phases

NASA Astrophysics Data System (ADS)

Middlemiss, Derek S.; Blanc, Frédéric; Pickard, Chris J.; Grey, Clare P.

2010-05-01

The NMR parameters obtained from solid-state DFT calculations within the GIPAW approach for 17O- and 69/71Ga-sites in a range of predominantly oxide-based (group II monoxides, SrTiO 3, BaZrO 3, BaSnO 3, BaTiO 3, LaAlO 3, LaGaO 3, SrZrO 3, MgSiO 3 and Ba 2In 2O 5), and gallate (α- and β-Ga 2O 3, LiGaO 2, NaGaO 2, GaPO 4 and LaGaO 3) materials are compared with experimental values, with a view to the future application of a similar approach to doped phases of interest as candidate intermediate temperature solid oxide fuel cell (ITSOFC) electrolytes. Isotropic and anisotropic chemical shift parameters, quadrupolar coupling constants, and associated asymmetries are presented and analyzed. The unusual GaO 5 site occurring in LaGaGe 2O 7 is also fully characterised. In general, it is found that the theoretical results closely track the experimental trends, though some deviations are identified and discussed, particularly in regard to quadrupolar ηQ-values. The high quality of the computed results suggests that this approach can be extended to study more complex and disordered phases.

Contributions of phase and structural transformations in multicomponent Al-Mg alloys to the linear and nonlinear mechanisms of anelasticity

NASA Astrophysics Data System (ADS)

Golovin, I. S.; Bychkov, A. S.; Mikhailovskaya, A. V.; Dobatkin, S. V.

2014-02-01

The effects of the processes of severe plastic deformation (SPD), recrystallization, and precipitation of the β phase in multicomponent alloys of the Al-5Mg-Mn-Cr and Al-(4-5%)Mg-Mn-Zn-Sc systems on the mechanisms of grain-boundary relaxation and dislocation-induced microplasticity have been studied in some detail. To stabilize the ultrafine-grained structure and prevent grain growth, dispersed Al-transition-metal particles, such as Al3Zr, Al6Mn, Al7Cr, Al6(Mn,Cr), Al18Cr2Mg3 have been used. We have special interest in alloys with additions of scandium, which forms compounds of the Al3Sc type and favors the precipitation of finer particles compared to the aluminides of other transition metals. After SPD, Al-(4-5%)Mg-Mn-Zr-Sc alloys exhibit an enhanced recrystallization temperature. The general features of the dislocation and grain-boundary anelasticity that have been established for the binary Al-Mg alloys are retained; i.e., (1) the decrease in the dislocation density in the process of recrystallization of cold-worked alloys leads to the formation of a pseudo-peak in the curves of the temperature dependences of internal friction (TDIF) and to a decrease in the critical amplitude of deformation corresponding to the onset of dislocation motion in a stress field; (2) the precipitation of the β phase suppresses the grain-boundary relaxation; (3) the dissolution of the β phase, the passage of the magnesium atoms into the solid solution, and the precipitation of the β' phase upon heating hinder the motion of dislocations; (4) the coarsening of the highly dispersed particles containing Zr and Sc increases the dislocation mobility. The grain-boundary relaxation and dislocation-impurity interaction and their temperature dependences, as well as processes of the additional alloying of the binary alloys by Mn, Cr, Zr, and Sc, have been estimated quantitatively.

The characterisation of second phases in the Zr-Nb and Zr-Nb-Sn-Fe alloys: A critical review

NASA Astrophysics Data System (ADS)

Harte, Allan; Griffiths, Malcolm; Preuss, Michael

2018-07-01

The nature and evolution of the Fe environment in Zr-Nb and Zr-Nb-Sn-Fe systems is essential to alloy performance during corrosion, hardening and irradiation-induced growth. Unfortunately, there is ambiguity in the literature regarding the characterisation of secondary phases in these systems. The presence, or not, of Fe in β-Nb phase has been a source of disagreement. In ternary ZrNbFe intermetallics, identical compositions have been designated as Zr(Nb,Fe)2 or (Zr,Nb)3Fe. We show that while Zr(Nb,Fe)2 is commonly reported, it is not always justified. The cubic phase (Zr,Nb)2Fe is easily identified, but its composition is more variable after low temperature heat treatments. We demonstrate the need for correlative approaches in the assessment of phase composition, crystallography and local Fe environment under different heat treatment regimes. Irradiation effects allow us to draw clues regarding phase designation, but there is diverse behaviour under irradiation due to initial phase composition, irradiation dose rate and temperature.

Microstructure and Properties of DCP-Derived W-ZrC Composite Using Nontoxic Sodium Alginate to Fabricate WC Preform

NASA Astrophysics Data System (ADS)

Najafzadeh Khoee, Ali Asghar; Habibolahzadeh, Ali; Qods, Fathallah; Baharvandi, Hamidreza

2015-04-01

In the present work, tungsten carbide (WC) preforms were fabricated by gel-casting process, using different nontoxic Na-alginate to tertiary calcium phosphate ratios and different loadings of WC powder in the initial slurries. The gel-cast green bodies were dried and pre-sintered at 1723 K for 4 h and then reactively infiltrated by molten Zr2Cu at 1623 K for 0.5 h, to produce W-ZrC composite via displacive compensation of porosity process. The phases, microstructures, and mechanical properties of the preforms and the W-ZrC composites were investigated by Fourier transform infrared spectroscope, x-ray diffractometer (XRD), scanning electron microscope (SEM), image analyzer, and universal mechanical testing machine. XRD results, SEM micrographs, and elemental maps indicated uniform distribution of phases (W and ZrC) and elements (W, Zr, and C). Flexural strengths and hardness of the fabricated composites were in the ranges of 429-460 MPa and 7.5-9.5 GPa, respectively. Fractography studies revealed two types of dimple rupture and cleavage fracture modes in different composite samples. The W-ZrC composite was ablated by an oxyacetylene flame for 60 s. The mean value of mass and linear ablation rates of the composite were 2.1 ± 0.1 mg/s and 3.6 ± 0.5 µm/s, respectively.

Influence of free carbon on the characteristics of ZrC and deposition of near-stoichiometric ZrC in TRISO coated particle fuel

NASA Astrophysics Data System (ADS)

Kim, Daejong; Ko, Myeong Jin; Park, Ji Yeon; Cho, Moon Sung; Kim, Weon-Ju

2014-08-01

Advanced TRISO coated particles with a ZrC coating layer as a main pressure boundary were fabricated by a fluidized-bed chemical vapor deposition (FBCVD) method using a chloride process. Experiments were performed to determine the effect of codeposition of graphitic carbon on the hardness and obtain the stoichiometric ZrC phase. The ZrC coating layer was composed of a mixture of ZrC and graphitic carbon phases at a low ZrCl4/CH4 ratio. A near-stoichiometric ZrC without the free carbon can be obtained by employing an impeller-driven ZrCl4 vaporizer. The codeposition of the graphitic carbon significantly lowered the hardness of ZrC while increasing the fraction of the carbon. The hardness reached its maximum when ZrC was in a slight carbon deficit without free carbon. As the graphitic carbon increased up to 12 vol%, the hardness was reduced by approximately 50% compared to the near-stoichiometric ZrC.

Zirconium-carbon hybrid sorbent for removal of fluoride from water: oxalic acid mediated Zr(IV) assembly and adsorption mechanism

PubMed Central

Halla, Velazquez-Jimenez Litza; Hurt Robert, H; Juan, Matos; Rene, Rangel-Mendez Jose

2014-01-01

When activated carbon (AC) is modified with zirconium(IV) by impregnation or precipitation, the fluoride adsorption capacity is typically improved. There is significant potential to improve these hybrid sorbent by controlling the impregnation conditions, which determine the assembly and dispersion of the Zr phases on carbon surfaces. Here, commercial activated carbon was modified with Zr(IV) together with oxalic acid (OA) used to maximize the zirconium dispersion and enhance fluoride adsorption. Adsorption experiments were carried out at pH 7 and 25 °C with a fluoride concentration of 40 mg L−1. The OA/Zr ratio was varied to determine the optimal conditions for subsequent fluoride adsorption. The data was analyzed using the Langmuir and Freundlich isotherm models. FTIR, XPS and the surface charge distribution were performed to elucidate the adsorption mechanism. Potentiometric titrations showed that the modified activated carbon (ZrOx-AC) possesses positive charge at pH lower than 7, and FTIR analysis demonstrated that zirconium ions interact mainly with carboxylic groups on the activated carbon surfaces. Moreover, XPS analysis demonstrated that Zr(IV) interacts with oxalate ions, and the fluoride adsorption mechanism is likely to involve –OH− exchange from zirconyl oxalate complexes. PMID:24359079